-

1. * GB785854 (A)
Description: GB785854 (A) ? 1957-11-06
Improvements in or relating to wide-span building construction
Description of GB785854 (A)
PATENT SPECIFICATION
_ 7855854 Xff Date of Application and filing Complete Specification:
Dec23, 1955.
( iilj'> No 36876/55 Application made in Germany on Dec 29, 1954.
Complete Specification Published: Nov 6, 1957.
Index at acceptance:-Classes 20 ( 3), 11 H; and 20 ( 4), D 9,N( 1:
2:10) International Classification:-E 04 b,f.
COMPLETE SPECIFICATION
Improvements in or relating to Wide-span Building Construction I
WILHELM JOHANNES SILBERKUHL, a citizen of the Federal German Republic,
of 16, Christophstrasse, Essen-Ruhr, Germany, do hereby declare the
invention, for which I pray that a Patent may be granted to me and the
method by which it is to be performed, to be particularly described in
and by the following statement:-
This invention relates to wide-span buildings, such as factories and
assembly halls and similar single-storey constructions covered by
dog-tooth roofing of which the roofing elements proper consist of
concrete shells of wide span.
The object of the invention is to provide a building with this type of
dog-tooth roofing in which the roofing element shells may be kept to
simple form, particularly by avoiding edge reinforcement in the
shells.
According to the present invention, a dog-tooth roof, for a wide-span
building comprises roof-trusses in the form of arches, on which are
carried window frames, together with roofing elements laid on to the
top of the window frames on one truss and on to the next adjoining
truss itself, the elements being adapted to the arched form of the
trusses.
The trusses may be of rolled steel sections or of reinforced concrete.
Preferably, the arched roof-trusses are circular, parabolic, or other

2. conic sections, and the roofing elements are shells of correspondingly
generated conic section Thus, the shells may be cylindrical, or they
could even be spherical.
Particularly light trusses may be used if the haunches of the arches
are connected to each other by ties, such as steel hawsers or ropes,
which may be provided with tension devices.
In a preferred construction, in which the trusses may span either the
breadth or length of the building, there is also an upper truss
equi-distant over the span from the lower truss carrying the window
frames and either directly or obliquely over the lower truss The
glazing bars of the window frames may extend radially between the
upper and lower trusses, either as an integral structure with the
trusses or separately inserted The 50 glazing bars may then serve to
stiffen the whole truss structure Where only a lower truss is used,
arched or straight carriers may be placed on the radial window bars to
carry the roof elements 55 The roofing elements may be of
prefabricated reinforced concrete construction.
Other lightweight slabs may also be used.
Again, concrete shells may be laid in situ, and can then make
wind-bracing unnecessary, 60 since the shells may contain transverse
reinforcement In this way, a reinforced concrete truss may be reduced
virtually to the dimensions of a scaffolding that bears stresses only
during the actual building 65 operation, and in the complete structure
serves to prevent cracking of the concrete elements However, during
the actual process of construction, additional supports may be
provided if necessary The use of steel 70 binders with pre-fabricated
roofing elements makes it possible for the latter to be clamped
together, which facilitates the erection of the roof and also its
dismantling.
The invention enables the perimeter zones 75 of large buildings to be
brightened, there being a diminution of the relative lightintensity
immediately below the top of the arched roof, and this effects a more
even distribution of the light within the building 80 The fact that
light beams penetrate into the perimeter zones from only half the area
is compensated by the lesser distance of the roof windows from the
floor at those zones.
Furthermore, the illumination is influenced 85 favourably by the very
shape of the roof itself, the exterior convex form of which throws the
incidental light into the roof windows with the interior concavity
distributing the light from the windows by 90 reflection in the
lengthwise direction of the building, if the arched trusses are
transverse.
This diffusion of illumination of the area by multiple reflection from
various curved surfaces diminishes the formation of shadows, which is

3. of particular advantage when bent working positions have to be assumed
by persons within the building This arises particularly if the roofing
elements are arched spherically.
A further advantage is that the arched trusses are more suitable for
withstanding roof loading than those of the usual roof construction In
the case of horizontal trusses the dimensions required increase as the
second power of the width of the span; but in the case of the arched
trusses the extra stress arising with increased width of span can be
taken up by the tie members, so that identical truss elements having
similar curvature may be utilised for the erection of building of
various widths, with a radius of curvature appropriate for adequately
lighting the buildings, whatever their widths.
A particular advantage of the invention is that by prestressing of the
arched roof elements by the tie members, the deflection of the arch
under roof load may be anticipated and compensated Again, with the
same object, the concrete roofing elements may themselves be
prestressed, the edges of the elements or slabs being appropriately
thickened to receive carriers or anchors for the prestressing members.
One construction of building according to the invention is shown in
the accompanying drawing.
Figure 1 is a longitudinal section through the building: and Figure 2
is a transverse section.
The building 1 is provided with a roof covering 2, and windows 3
inserted in an arcuate arched truss 4 spanning the width of the
building Glazing bars 5 extend radially upwards from the truss 4 and
support curved upper window frames 6, on which rest one end of the
roofing elements 7 forming the covering 2 The elements 7 are
cylindrical sections, and their other ends are secured to the next
adjoining trusses 4 The building 1 has side and end walls 8 of
concrete construction.
Each truss 4 is of rolled H-section and its ends are connected by a
tie 9, to enable it to take the load The members 5, 6 are also of
rolled steel sections.
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* GB785855 (A)

4. Description: GB785855 (A) ? 1957-11-06
Improvements in power-operated typewriters and the like
Description of GB785855 (A)
PATENT SPECIFICATION
Date of Application and filing Complete Specification: Jan 3, 1956.
Application made in United States of America on Jan 6, 1955.
Complete Specification Publshed: Nov 6, 1957.
785,855 No 135/56.
Index at Acceptance:-Class 100 ( 4), C 20 B( 2 KL 2: 4: 8 D 2), C 20
P.
International Classification:-B 41 lj.
COMPLETE SPECIFICATION c= =-
Improvements in Power-Operated Typewriters and the like We,
INTERNATIONAL BUSINESS MACHINES CORPORATION, a corporation organized
and existing under the laws of the State of New York, United States of
America, of 590 Madison Avenue, New York 22, New York, United States
of America, do hereby declare the invention, for which we pray that a
patent may be granted to us, and the method by which it is to be
performed, to be particularly described in and by the following
statement:-
This invention relates to power-operated typewriters and the like and
more particularly to an automatic device for printing auxiliary
characters, e g underscores, therefor.
With conventional typewriters, if it is desired to underscore certain
words, phrases or paragraphs, it is necessary for the typist first to
type out the intended wording and then go back and use another key to
underscore each and every letter which she had previously typed This
is an obvious duplication of effort, and it is an object of this
invention to provide a power-driven typewriter having a device for
automatically printing such auxiliary characters.
According to the invention, we provide a power-operated typewriter or
like machine having a power driving mechanism associated with each of
a plurality of type bars and selectively operable to drive the same to
printing position, including a device automatically responsive to the
selective actuation of any type bar drive mechanism for printing an
auxiliary character, said device comprising an auxiliary type bar and

5. an associated power driving mechanism, an auxiliary actuating lever
for actuating said auxiliary power driving mechanism, means
conditioning said auxiliary type bar driving mechanism to operate
through one complete cycle only to drive said auxiliary type bar to
printing position each time said auxiliary actuating lever is operated
and connecting means responsive to the actuation of any other type bar
driving mechanism for operating said auxiliary actuating lever.
The invention may be carried into effect in lPrice 3 s 6 d l various
ways and the following description relates to one preferred embodiment
thereof, illustrated in the accompanying drawings, in which:
Fig 1 is a perspective view of components of 50 an IBM electric
typewriter embodying the invention, and Fig 2 is an end view of some
of the components of Fig 1.
Briefly, the typewriter shown includes an 55 auxiliary type bar and
its associated drive mechanism The actuating lever for the auxiliary
drive mechanism is spring biased into its operative position, and
interconnected through a linkage system to a bail that is 60 rocked
each-time any other type bar is driven to print position The rocking
of the bail lifts the auxiliary actuating lever to its inoperative
position and then lets it fall again to its operative position thus
causing its associated drive 65 mechanism to drive the auxiliary type
bar to printing position The timing of the device is such that a
carriage escapement action takes place before the auxiliary type bar
is driven to print position, and accordingly, a second 70 throat is
provided on the type bar guide to receive the auxiliary type bar in
such a position that it prints at the location of that character which
had caused the escapement.
The operations of the type bar drive mech 75 anism in an IBM
typewriter is well known and more particularly disclosed in U K
Specification No 749565.
Such a mechanism is illustrated in the drawings and comprises a
continuously rotating 80 power roll 2 is positioned for engagement
with a plurality of cams 4, each of which is pivotally supported at 6
on its respective cam lever 8 which, in turn, is mounted in a guide 9
for pivotal movement about a supporting shaft 10 85 in response to
engagement of the cam 4 with the power roll Specifically, when the
tread of the cam 4 is brought into engagement with the power roll, the
cam is rocked about its pivot 6 and the increasing radius of the cam 4
neces 90 sarily rocks the cam lever 8 about its pivot 10 until the
point of maximum lift of the cam 4 engages the power roll, whereupon,
as the cam lever 8 continues away from the power roll through its own
momentum, a spring 12 restores the cam 4 to its normal or rest
position.
The outer end 11 of cam lever 8 is connected by link 14 to the tail

6. (not shown) of a type bar 18 which is pivotally mounted on the usual
wire fulcrum 20 for movement from a rest position into printing
position and return A spring such as the one 22 acting on the cam
lever 81, biases the type bar 18 normally to its rest position.
With this mechanism, when cam 4 is brought into engagement with the
power roll, the cam lever 8 is rocked about its pivot 10 to drive a
type bar 18 into the throat 19 of type bar guide 21 for printing
engagement with a platen (not shown).
In order to actuate the type bar drive mechanism, a trip latch 26 is
supported for both pivotal and transverse movement about pin 28
carried by the cam lever 8 More specifically, when a key lever 30 is
depressed, a finger 32 engages the trip latch 26 to pivot it about its
pivot point 28 and thus rocks the cam 4 about its pivot 6 and into
engagement with the power roll 2 to institute the type bar drive
action If the key lever 30 is held down, however, after it has
initiated a type bar print stroke, then, the cam lever in returning to
its rest position, causes the ear 29 of the trip latch, to engage the
side of finger 32 thus preventing the trip latch from returning to its
original position A spring 34 urges the trip latch 26 normally into
its rest position and this spring is stretched when the ear 29 comes
into engagement with the finger 32 If the key lever is again raised to
its rest position, the spring 34 will pull on the trip latch and
restore it to the position shown in the drawings, so that upon
depression of the key lever 30, a new type bar print stroke will be
brought about This nonrepeat principle is described in detail in U K.
Specification No 749,565.
In accordance with the teachings of this invention, as will be
hereinafter described, this non-repeat principle is utilized to
prevent the operation of an auxiliary type bar drive mechanism until
its actuating lever has first been restored to rest position.
ESCAPEMENT Before going farther into detail with the operation of the
underscoring mechanism, it is necessary to realize that an escapement
action takes place after every character print stroke.
The complete details of an escapement mechanism is shown in U K
Specification No.
751,170 Generally speaking, every time a type bar goes into print
position, it engages a u-bar 35 thereby moving link 37 in the
direction of the arrow to effect an escapement operation.
RIBBON FEED Still another feature of the conventional typewriter is
the mechanism for advancing an inking ribbon each time a type bar is
actuated.
The ribbon feed is described more particularly in specification No
673,064, but basically its operation is such that when the cam lever 8
is 70 rocked about its pivot 10, a tail 40 engages a vane 42 which is

7. mounted on the cross shaft 44 as shown in the aforementioned
specification.
This rocking movement imparted to the vane 42 by tail 40 of the letter
cam 8 conditions a 75 ribbon feed cam 43 (Fig 2) for operation to
advance the ribbon in a well known manner.
Actually, any slight counter-clockwise rocking of vane 42 rocks an arm
45, acting through link 47 to pivot cam release arm 49 about its
support 80 51 thereby permitting cam 43 to rotate through one
revolution The rotation of cam 43 rocks cam support 53 about pivot 55
thereby pulling on link 57 to rock a bell crank 62 about the axis of
shaft 44 85 In accordance with the teachings of this invention, the
rocking of the vane 42 is employed to actuate the ribbon feed cam 43
and thereby actuate the underscoring mechanism as will be hereinafter
described 90 UNDERSCORING MECHANISM An auxiliary, or underscore type
bar 18 ' having an underscore mark at both its upper and lower case
position is provided with its respective return spring 22, and drive
mech 95 anism comprising a cam lever 8 ', cam 4 ', trip latch 26 ' and
an auxiliary actuating lever 31, said trip latch having an ear 29 ',
finger 32 ' and spring 34 ' as conditioning means to enable the drive
mechanism to operate through one com 100 plete cycle only, each time
the auxiliary actuating lever is operated The auxiliary lever 31 is
shown as being pivotal about the usual pivot bail 46 and guided for
movement in the usual guide comb 48 The lever 31 is provided 105 with
an aperture 50 which is elongated so that a hook 52 may be freely
movable up and down within the aperture a distance equal to that
distance that the lever 31 would move from a rest to an actuating
position Hook 52 is 110 carried by a link 52 a mounted on a bell crank
54, which in turn, pivotally mounted on a rod or stud 56 The opposite
end 58 of the bell crank 54 is connected by link 60 to an arm 61 of
bell crank 62 which, as heretofore mentioned, 115 is rocked in
response to the operation of ribbon feed cam 43 The parts just
enumerated in conjunction with the ribbon feed mechanism constitute
connecting means whereby each operation of a type bar driving
mechanism 120 causes operation of the auxiliary actuating lever 31 and
hence of the underscore.
With this construction, when the tail 40 of the cam lever strikes the
vane 42, shaft 44 is rocked counter-clockwise, as shown in the 125
drawings, under the influence of the ribbon feed cam to rock bell
crank 62 and thereby push link 60 (in direction of arrow) to rock the
bell crank 54 counterclockwise about the shaft 56 thereby raising the
hook 52 If the lever 31 13 C 78 g 5,855 to raise the lever 31 to its
inactive position, thus permitting the ear 29 ' to move up under the
finger 32 ' under the influence of its spring 34 '.
Thereafter, when the bell crank 54 rocks back into its rest position,

8. the lever 31 will drop to 70 its actuating position, tripping latch 26
' to cause another print stroke of the auxiliary type bar 18 '.
In order to prevent the underscore or auxiliary type bar from being
self-actuating, it 75 is necessary to remove the tail 40 of the letter
cam lever 8 ', whereupon each time the cam lever 8 ' is rocked, to
drive the auxiliary type bar 18 ' into printing position, the vane 42
will not be rocked under the influence of the cam 80 lever and
accordingly, bell crank 62 will not be operated to rock the bell crank
54.
It is further obvious that the auxiliary type bar 18 ' should not be
operable to produce an escapement action, and accordingly, the 85
auxiliary type bar 18 ' is notched at its point of engagement with the
u-bar 35 so that the auxiliary type bar 18 ' can go into printing
position without causing an escapement operation 90 The timing of the
subject mechanism is such that as soon as the type bar 18 enters the
throat 19 of the type bar guide 21, the u-bar 35 will be moved to
start an escapement action The type bar 18 will print before the
carriage moves 95 any appreciable amount, but the carriage will have
escaped a full character space before the auxiliary lever 31 has been
raised to its inoperative position and permitted to drop again to
drive the type bar 18 ' into printing position 100 In order to
compensate for this carriage escapement and to have the auxiliary type
bar 18 ' print at the print position of the character that caused the
escapement, a second throat 19 ' is provided in the type bar guide 21,
which 105 second throat 19 ' is displaced to the left of the throat 19
of one character space The auxiliary type bar 18 ' is so shaped that
in rocking about the pivot wire 20, it will enter the second throat 19
' and accordingly, print at the character 110 location of the type bar
that had caused the escapement action.
With this structure, it is obvious that if the auxiliary lever 31 is
permitted to drop into its actuating position, the auxiliary type bar
18 '115 will enter the throat 19 ' of the type bar guide 21 for a
print stroke each time any other character has been printed It
follows, therefore, that in the operation of the automatic underscore,
the first character to be under 120 scored is first printed and then
the finger button 70 is flipped to the actuating position, thus
causing the underscore mark to print under the character which has
previously been printed and from that point on, all printed 125
characters will be automatically underscored.
While there have been shown and described and pointed out the
fundamental novel features of the invention as applied to a preferred
embodiment, it will be understood that various 130 were in its
inactive (or non-printing) position, then the hook 52 will simply move
to the upper limit 64 of the aperture 50 without moving the lever 31

9. at all However, if the lever 31 were in its actuating position, as
biased by the spring 66, then the rocking of bell crank 54 in response
to the operation of the ribbon cam 43 will cause lever 31 to be raised
from its actuating to its rest position in opposition to the force of
spring 66 This motion of lever 31, as heretofore described, will
permit the ear 29 ' on the trip latch to slide under the finger 32 '
carried by lever 31, whereupon when the bell crank 54 returns to its
rest position shown in the drawings, lever 31 will be moved again to
its actuating position under the influence of spring 66, thus tripping
its cam 4 ' into engagement with the power toll to cause the type bar
18 ' to print an underscore mark.
In order to disable the auxiliary lever 31, a lever 67 is pivotally
supported at 68 in the typewriter frame, and a button 70 extends out
for finger operation By depressing the finger button 70, the lever 67
is pivoted and acts through link 69 to raise the lever 31 from its
actuated position as biased by the spring 66 to its inactive position
A suitable detent, not shown, is provided to hold lever 67 in either
of its two positions More specifically, an aperture 72 is provided in
the lever 31, and this aperture is elongated an amount equal to the
lever movement at that position from rest to actuating position Link
69, in turn, is provided with a pin 74 passing through aperture 72,
and accordingly, if the finger 70 has been depressed to lift the lever
31 to its inactive position, the pin 74 will act on the aperture 72 to
raise lever 31 so that the hook 52 will fall to the bottom of the
aperture 50, whereupon the hook 52 is free to move in response to the
actuation of the bell crank 54 without lifting lever 31.
On the other hand, if the finger 70 has been raised to permit the
lever 31 to move to its actuating position under the influence of
spring 66, then since aperture 72 is elongated, the hook 52 acting on
the aperture 50 can raise lever 31 to its rest position and back to
its biased position without being blocked by pin 74.
OPERATION SO In the operation of this mechanism, and assuming the
power roll is rotating, then as soon as the finger 70 is raised (to
the position of Fig.
2) the lever 31 will be biased by spring 66 to its actuating position,
whereupon the finger 32 ' will press on the ear 29 ' moving the trip
latch 26 ' and, therefore, the cam 4 ' into the power roll to cause
the type bar 18 ' to print The lever 31 will then stay in its
depressed position, preventing a repeat operation of underscore until
some other type bar has been moved to print position When any other
type bar has thus been driven to print position, the tail 40 of its
cam lever 8 will act on the vane 42 to actuate the ribbon feed cam
which will rock bell crank 62, and consequently, bell crank 54
785,8,55 omissions and substitutions and changes in the form and

10. details of the device illustrated and in its operation may be made by
those skilled in the art without departing from the scope of the
invention It is the intention, therefore, to be limited only as
indicated by the scope of the following claims.
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* GB785856 (A)
Description: GB785856 (A) ? 1957-11-06
Wave-guide lens
Description of GB785856 (A)
PATENT SPECIFICATION
Inventor: EDWARD KNOX PROCTOR, JR.
Date of Application and filing Complete Specification Jan 4, 1956.
No 366/56.
Complete Specification Published Nov 6, 1957.
Index at Acceptance: -Classes 40 ( 7), AE ( 3 W: 4 A 251 A 4 P 3); and
40 ( 8), WG.
International Classification: -HO 1 b H 04 d.
COMPLETE SPECIFICATION
Wave-Guide Lens We, SPERRYRAND CORPORATION, a corporation organised
and existing under the laws of the State of Delaware, United States of
America, of 30, Rockefeller Plaza, New York, United States of America,
do hereby declare the invention, for which we pray that a patent may
be granted to us, and the method by which it is to be performed, to be
particularly described in and by the following statement:The present
invention relates to electromagnetic wave-guide lenses.
Wave-guide lenses heretofore known in the art have been subject to
excessive chromatic aberration (changes in operating characteristics

11. with alterations in frequency) because of the fact that the refractive
indices of the waveguide channels thereof vary with frequency.
The variation in refractive index of a wave guide as the operating
frequency is altered is called dispersion The shape of a microwave
lens and the refractive indices of the wave guide channels thereof are
generally predetermined to produce a required focussing action at a
single frequency Since the refractive indices vary with frequency,
such a lens cannot be operated over a wide frequency band without
being subject to chromatic aberration.
It is sometimes desirable for a wave-guide lens to be zoned (to
thereby minimize its thickness) without introducing physical impedance
discontinuities in a surface thereof This may be achieved by
constructing the lens so that its different wave-guide channels have
different effective refractive indices at the lens operating frequency
This type of lens is generally referred to as a
variable-refractiveindex lens, since different channels of the lens
have different refractive indices at a particular frequency.
Both variable-index-of-refraction wave-guide lenses and lenses where
all the wave-guide channels have the same refractive index
(constant-index-of-refraction lenses) have hitherto been subject to
chromatic aberration In a lens lPrice 3 s 6 d l of either type
designed to focus energy of one frequency at one point, energy at
other frequencies may be approximately focussed at different points,
or may not be satisfactorily focussed at all Since lenses are
frequently 50 required to perform over a relatively broad band of
frequencies without changing the position of transmitting or receiving
devices placed at the focal point and without deterioration of the
focussing properties, changes in the lens 55 operating characteristics
as described above are disadvantageous.
Furthermore if a lens is zoned as described above, it will also be
subject to chromatic aberration due to zoning, or step phase errors,
60 which occur between the adjacent zones with changes in operating
frequency For a ten per cent change in frequency in the case of a lens
having five zones from its centre to its outer edge, for example, step
phase errors cause the 65 phase fronts of the waves from the outer
zone or step to be out of phase with the phase fronts at the centre of
the lens by a half wavelength at the new frequency This occurs whether
zoning is pro 70 duced by physical steps in a face of the lens as in
constant-refractive-index lenses, or by distribution of the indices of
refraction of the wave guide channels as in variable-refractiveindex
lenses 75 Sometimes it is desirable to design the waveguide channels
of any of the aforedescribed types of lenses so that the lens design
frequency is close to the cut-off frequencies of the wave-guide
channels This increases the 80 critical angle of incidence of the lens

12. (the angle at which wave enegry incident upon an interface of the
wave-guide channeds of the lens as measured from a line perpendicular
to the interface will be subject to multiple reflections 85 and
diffraction) The critical angel is increased because the ratios of the
distance " a " between walls of each wave-guide measured in the plane
of the magnetic field therein to the free space operating wavelength
A, are decreased as 90 as the wave-guide channels are operated closer
to cut-off.
Operation of the wave-guide channels closer to cut-off, however,
causes the lens to be more frequency sensitive because the refractive
indices thereof are subject to increased dispersion This is evident
from the fact that the refractive index of any wave-guide is fc where
e is the dielectric constant of the waveguide medium, fc is the
wave-guide cut-off frequency, and f is the operating frequency.
It is therefore, an object of the present invention to provide a broad
band wave-guide lens in which chromatic aberration is reduced.
It is another object of the present invention to provide a wave-guide
lens as aforedescribed having a relatively wide critical angle of
incidence.
These and other objects are attained by providing a lens structure
comprising a plurality of ridged wave-guide channels The ridge means
of the wave-guide channels extend from the illuminated to the exit
interfaces of the lens to lower the cut-off frequencies of the
channels and reduce chromatic aberration due to dispersion of the
refractive indices of the wave-guide channels with changes in
operating frequency A predetermined critical angle of incidence can be
maintained since the distances between the wave-guide walls can be
kept relatively small with respect to the operating wavelength At In a
variable refractive index lens provided in accordance with the present
invention, the use of ridge loading means therein renders a desired
distribution of the effective indices of refraction of the ridge
loaded wave-guide channels readily obtainable because of the many ways
of varying the loading By proper proportioning, the lengths of two
differently loaded regions in each channel having different phase
velocities and different refractive indices na and 72, for example, a
required value of effective refractive index or mean phase velocity in
each channel to provide a predetermined lens focussing action can be
obtained.
Furthermore, chromatic aberration due to dispersion may be
substantially eliminated over a predetermined range of frequencies by
relating the rates of change of the refractive indices n, and n
properly in accordance with the disclosure below.
Chromatic aberration due to errors caused by zoning or stepping of the
lens is also minimized by loading groups of wave-guide end sections of

13. each lens zone in a different manner from one full zone to another The
different loading means are adapted to cause the rate of change of
refractive index with frequency of one group of end sections in one
zone to be properly different from the rate of change of the
refractive index of another group of end sections of an adjacent zone
so as to compensate for chromatic aberration due to 65 zoning errors
in phase of energy output from zone to zone with changes in frequency.
Referring to the drawings, Fig 1 is a perspective view of an antenna
system employing a variable refractive index 70 lens designed in
accordance with the present invention; Fig 2 is a plan view, partly
broken away at the top of the lens shown in Fig 1; Fig 3 is a front
view of the surface of the 75 lens illuminated by the dipole antenna:
shown in Fig 1; Fig 4 is an enlarged, longitudinal sectional view of a
lens channel taken along the line 4-4 in Fig 2; 80 Fig 5 is an
enlarged perspective view of a portion of the wave-guide channel shown
in Fig 4; Fig 5 a is a graph showing the variation with frequency of
the refractive index of the wave 85 guide channel portion shown in Fig
5, and the variations with frequency of the refractive indices of all
of the various regions in the wave-guide channel shown in Fig 4; Figs
6 through 9 are perspective views of 90 various ridge-loaded
wave-guide structures; Fig 9 a is a graph showing the variation in
index of refraction with frequency of slotted thin-ridged wave-guide
structures having different slot depths; 95 Fig 9 b is a graph showing
the variation in index of refraction with frequency of slotted
thin-ridged wave-guide structures having different slot widths; Fig 10
is a schematic view, for explanatory 100 purposes, of a variable
refractive index lens focussing section; and Fig 11 is a schematic
view, for explanatory purposes, of the lens shown in Figs 1-3 which is
compensated for chromatic aberration 109 due to dispersion and
chromatic aberration caused by zoning the lens.
Referring to Fig 1, an antenna system for a radar transmitter and
receiver 21 is shown, comprising an antenna feed line 23, a plura 110
lity of vertically aligned dipoles 25 coupled to feed line 23 and a
lens 27 The antennx feed line 23 may comprise any conventional
transmission line coupled to the radar transmitter for supplying
microwave energy to the dipoles 115 so that energy radiated therefrom
will be in the proper phase and comprise vertically polarized
electromagnetic waves having uniformly curved phase fronts in a
horizontal plane and linear phase fronts in a vertical plane The 120
feed line 23 is coupled to the radar receiver in any conventional
manner so that the system will receive as well as transmit
electromagnetic energy A line through the vertical arms of the dipole
antennx 25 comprises the focus of 125 the lens 27, the dipoles being
symmetrically arranged above and below the axis I-I of the lens.

14. 785,856 785,856 Referring to Figs 2 and 3, the lens 27 consists of a
plurality of rectangular wave-guide channels or cells of the same
cross-sectional dimensions Each channel comprises a metal tube, and
each tube includes metallic ridges 29 and 31 extending from one end to
the other along the upper and lower tube walls, respectively All of
the wave-guide channels or cells are of the same length so that the
lens interface lie in planes perpendicular to the axis I-I.
The face of the lens illuminated by the antenna 25 is shown in Fig 3
The adjacent wave-guide channels in any horizontal layer on either
side of a certival plane through the axis II-II in Fig 3 are
differently loaded thereby having different mean phase velocities and
different effective refractive indices Al of the wave-guide channels
in a vertical stack of channels shown in Fig 3 have the same effective
index of refraction depending on their spacing from the aforementioned
plane through II-II.
In the plan view of Fig 2, a part of the top is shown broken away to
illustrate the interiors of some of the wave-guide channels in the top
layer of channels in Fig 3 The view in Fig.
2 is taken along the line 2-2 in Fig 3, so only portions of the lower
ridges 31 of the wave-guide channels are seen The waveguide channels
of a first group on one side of a vertical plane through the axis I-I
in Fig 2 are designated by the numerals 41, 42, 43, 44 and 45 thereby
forming a half-zone A of the lens The channels designated by numerals
46, 47, 48 and 49 form a half-zone B of the lens, and the channels
designated by numerals 50, 51 and 52 form a half-zone C of the lens.
Corresponding, primed numerals and letters on the opposite side of the
aforementioned plane refer to corresponding wave-guide channels and
half-zones which are symmetrical about the axis I-I with the channels
and halfzones designated by the unprimed numerals and letters.
Half-zones A and A' comprise one full lens zone, half-zones B and B'
comprise a second full lens zone, and half-zones C and C' comprise a
third full lens zone The outer boundaries of zones C and C', starting
from the front face of the lens 27 at a vertical plane through III-III
in Fig 2 are spaced one wavelength further from the lens focus than
the outer boundaries of zones B and B' Likewise, the outer boundaries
of zones B and B' at the front face of lens 27 are spaced one
wavelength further from the lens focus than the outer boundaries of
zones A and A' in the same plane The outer boundaries of zones A and
A' are one wavelength further from the lens focus than a point along
the axis I-I at the front face of the lens.
The two metallic ridges 39 and 31 of each wave-guide channel are
relatively narrow and of uniform thickness and height Each ridge is
loaded by regularly spaced slots of uniform width The slots in all of
the ridges have the same width and the same spacing which width and

15. spacing are appreciably less than the wavelength of energy of the
opearting frequency of the lens Each wave-guide channel is further 70
loaded by a predetermined length of dielectric element 33 supported
between its two ridges as illustrated in Figs 3, 4 and 5.
The depth of the slots in the ridges 29 and 31 of the symmetrical
half-zones A and A' is 75 constant and of a first value from the front
face of the lens 27 illuminated by the antenna 25 to the ends of
dielectric elements 33 at a vertical plane through lines WT-TV in Fig
2.
Beyond this plane the slot depth in the ridges 80 of the wave-guide of
half-zones A and A' is constant and of a second value larger than the
first In half-zones B and B' the slot depth is also constant and of
the aforementioned first value as one progresses from the aforemen 85
tioned illuminated face toward the exit face of the lens, and changes
to a depth of said second value at the ends of the dielectric elements
33 closest to the exit face of the lens In halfzones C and C', the
slot depth is constant and 90 of said first value from the illuminated
to the exit faces of the lens Fig 4 is a longitudinal sectional view
which illustrates the variations in slot depth and dielectric loading
in the lens channel 49, for example 95 Referring to Figs 2 and 4, the
regions of the wave-guide channels where there are no portions of
dielectric elements 33 and where the depth of the slots in the ridges
is equal to the aforementioned first value of depth have an 100 index
of refraction designated by n,, and lengths D, The regions of the
wave-guide channels on one side of a vertical plane through TV-TV
closer to the illuminated face of the lens which include portions of
dielectric ele 105 ments 33 have refractive index designated by n and
lengths D_ The regions of the waveguide channels on O the other side
of the vertical plane through IV-IV which include portions of
dielectric elements 33 have a refrac 110 tive index designated by n,
and lengths D, The refractive indices n, and n, are made equal in the
illustrated structure for reasons which become apparent below The
regions of the wave-guide 115 channels having no dielectric loading
elements 33 and where the depth of the slots in the ridges is equal to
the aforementioned second value have a refractive index designated by
n, and lengths D 1, The terminations of the 120 regions of different
refractive index in each wave-guide channel are schematically
indicated in Fig 2 by the heavy dashed lines.
The lens shown in Figs 1-3 is hypotheti 125 cally divided into a
focussing section 35 and a zoning or step phase compensating section
37.
Once particular values for n, and n, in the focussing section 35 are
assigned for a particular frequency (n being larger and n,), the 130
785,856 focussing section may be adapted to convert incident wave

16. energy from antennx 25 having curved phase fronts in a horizontal
plane into wave energy having plane phase fronts at a vertical plane
through IV-IV.
The proper conversion of energy is achieved by correctly proportioning
the lengths D, and D, of the regions of refractive index n, and n,
respectively, in each channel so that the effective refractive indices
of the symmetrical channels are properly different from the
symmetrical Pair of channels to another The step phase compensating
section 37 is included for reasons which will become more clear below,
although it need not necessarily form part of the lens 27.
A large value of (r-n,) is desired in the focusing section 35 of the
lens as aforedescribed to minimize the lens thickness In a lens
employing non-ridged wave-s ide channels this could be obtained for
example, by partially filling the wave-guide channels with dielectric
material However, if the wave-guide channels are totally filled in
cross section, but only partially filled axially, the refractive
indices of the non-loaded air-filled regions will be subject to
excessive dispersion when orerated at wavelengths close to the cut-off
dimensions of the air-filled wave-guide sections.
It may be desirable for the wave-ide channels of the lens to be
dimensioned close to cutoff for the operating frequency so that the
critical angle of incidence for the lens will be maximized If energy
is incident upon a lens interface at an angle with respect to the
normal to the interface which is larger than the aforementioned
critical angle, the nower transmitted into the lens is greatly reduced
The critical angle of incidence is propotricnal to the ratio of a/Ar,
where " a" is the distance between the walls of a wave-guide as
measured in the magnetic plane of electormagnetic wave propagation
therein along the interface of the lens, and Ak is the operating
wavelength in free space It has bee-n found that as the aforementioned
ratio descreases from a value of the order of 1 O to a value of the
order of 0 5, the critical angle of incidence increases up to a
maximum value of the order of 90 degrees.
This can be established from theorv based on an article entitled "
Reflection of an Electromagnetic Plane Wave by an Infinite Set of
Planes I " by Carlson and Heins, ptiblished in the Quarterly of
Applied Mathernatics, Vol.
IV, No 4, January 1947, pages 313-329.
Therefore, if unloaded air-filled wave-guide sections are employed in
the lens, the rates of variation in refractive indices thereof with
frequency will be excessive if the guides are operated close to
cut-off to attain a larzre critical angle of incidence for the lens As
the ratio of a/Xa is decreased, the refractive index of a wave-guide
decreases, with the slope of the curve of index of refraction becoming

17. increasingly steep as the wave-guide is operated closer to cut-off and
the critical angle of incidence becomes larger.
Both a large critical angle of incidence and relatively low rates of
variaion with frequency of the refractive indices of the wave-guide 70
channels of a variable-refractive-index lens could be obtained by
filling the entire axial lengths of non-ridged wave-guide channels
with -dielectric materials of first and second different dielectric
constants Therefore, 75 the distance " a " between the walls of a
wave-guide channel could be made small enough relative to the
operating wavelength to permit relatively wide angles of incidence and
the electrical distance between 80 such walls would be effectively
increased.
Thus, the cut-off frequencies of the wave-guide channels would be
lowered, thereby decreasing the rates of variation of the refractive
indices of the channels 85 with changes in frequency However, such a
lens would be impractical because of excessive weight and the lens
would still be subject to chromatic aberration due to the fact that
the different regions of different di 90 electric materials would have
incorrectly related rates of variation in refractive index with
frequency changes.
Some of the aforementioned difficulties may be overcome by using
ridged wave-guide lens 95 channels as described above Placinm a
metallic ridge in a wave-guide as is shown in Figs 6, 7 and K, for
example, has the efce or reducing the cut-off frequency of the
wave-guide without alteration of the " a " dimension there l Op of The
"a" dimension (in the plane of the magnetic field for the dominant
mede of operation) of each wave-guide in Figs 6-8 can thereby be
independently specified by selecting a ridge of the proper size In
general, for 105 a fixed " a " dimension, the cut-off frequency of a
ridged wave-guide is progressively reduced for the dominant mode of
opeartion as the ridge height "h" is increased.
Therefore if ridge wave-guides are used for 110 the lens channels from
the front to the back lens faces, as in the lens shown in Figs 1-3,
all of the guides may be operated at frequencies wovell above cut-off
te reduce the rates of variation of the refractive indices thereof
Aith fre 115 quencv Furthermore the ratio of a/A, can be maitained
relatively small, even at a value equal to 0 5 to provide a maximum
critical angle of incidence for the lens.
The required variations in refractive index 120 in the different
regions of the ridged waveguide channels can also be readlyr effected
in many different ways Where the " a" and " b " dimensions of a
wave-guide are constant 5 a guide having a ridge of one cross section
125 would have a different refractive index thar the same guide having
a ridge of another cross section, for example Furthermore, the ridges

18. could be loaded with a plurality of loading means such as slots, for
example, having rela 130 785,856 tively small dimensions and spacings
with respect to the operating wavelength c A slot-loaded thin-ridged
wave-guide is shown in Fig 9 The refractive index can be i changed by
varying either the depth dimension " d " of the series of slots, the
width " W " X thereof, or the repetition distance " 1 " shown I in Fig
9.
Figs 9 a and 9 b are graphs which illustrate the variation of
refractive index N for a slotloaded, thin-ridged wave-guide as a
function of f/f l In both of these figures f, refers to the cut-off
frequency of the wave-guide in the the absence of a ridge, f ' refers
to the cut-off frequency with a non-slotted ridge in place, and f is
the operating frequency The frequency axis, f/fi', is thus normalized
to the cut-off frequency of a non-loaded ridge waveguide The curve in
Fig 9 a illustrates the effects of loading the ridge with slots of
different depth, all other dimensions being constant at the relative
values illustrated in the graph In Fig 9 d the various curves shown
illustrate the effects of loading the ridge with slots of different
width all other dimensions being constant at the relative values
illustrated.
The refractive index of aridged wave-guide can also be changed by
providing loading means comprising a dielectric element such as
element 33 in Figs 2, 3 and 5, for example.
The width of the dielectric element and its dielectric constant are
factors which determine how much the loading and refractive index are
varied.
In the lens structure 27 shown in Figs 1-5, of which Fig 5 is a
perspective view of a portion of one of the lens channel 49, it will
be noted that each lens channel comprises, in effect, two rectangular
wave-guides joined together with their common wall removed.
All of the channels of lens 27 are of similar construction, thereby
reducing the weight of the lens Such a lens channel is substantially
equivalent electrically to a wave-guide structure comprising two
rectangular wave-guides including a common wall therebetween.
Fig 5 a shows the effect on refractive index n of changing the slot
depth in the thin-ridge wave-guide of Fig 5, and the effect of placing
a dielectric loading element between the two ridges 29 and 31 The
curve designated by n 2 and n, is for the wave-guide of rig 5
including the dielectric element 33 having a dielectric constant O = 2
55 The curve designated by n, is for the same guide with the same
ridge and slots therein, but without the dielectric element 33 The
curve designated by n, is for the same guide as that employed to
obtain the curve n,, but with a different slot depth The various
relative dimensions of the different wave-guide sections and elements

19. included therein are illustrated in Fig 5 a.
In Fig 5 a, the index of refraction N is the ordinate and the ratio of
f/fol is the abcissa.
lhe frequency axis flf,' is normalized to the cut-off frequency of a
non-loaded ridge waveguide for the dominant mode of operation havng
the relative dimensions illustrated in the graph The curve of
refractive index n,, n,, 70 ni and N 4 showing the variations in N
with frequency changes are for the regions of the wave-guide channels
shown in Fig 2 and 4 having correspondingly designated refractive
indices Although many different curves could 75 be obtained by
changing the size and/or dielectric constant of the loading element
33, and/or by changing the various dimensions of the slots and ridges,
the particular relative dimensions illustrated in Fig 5 a were chosen
80 for the lens shown in Figs 1-3 for reasons which will be more
apparent below.
Referring now to Fig 10 a lens 53 is schematically shown having a
predetermined thickness at its centre and a curved illuminated sur 85
face 55 and a plane exit surface 57 The shape of the surfaces may be
arbitrarily chosen The lens 53 is divided into six half-zones A, B, C,
A, B' and CU symmetrically disposed about the axis V-V as illustrated
Each half-zone is 90 divided into regions of different refractive
indices in, and n, The horizontal dashed lines within the lens
configuration define the lens half-zones the curved dashed lines
within each half-zone indicating the divisions between the 95 regions
of different refractive index The letter F indicates the position of a
source of electromagnetic wave energy at the focus of the lens.
The source of focus F produces vertically polarized waves having
curved phase fronts in a 100 horizontal plane with the E vectors of
the waves perpendicular to the plane of the drawings.
Each half-zone of the lens shown in Fig 10 is comprised of a plurality
of wave-guide chan 105 nels or paths Each path within any particular
half-zone of the lens has a different effective refractive index N
determined by the proportions of lengths D, and D, of in, and in,,
respectively, therein It will be assumed that the 110 refractive index
n, is greater than in, at any frequency.
Suppose, for example, that the exit face 57 of the lens 53 lies in a
plane and the face 55 illuminated by the source at F is curved as 115
shown For a lens designed to produce a plane phase front, every point
on the lens face 57 should be connected to the energy source at the
lens focus F by a transmission or ray path I=K+D K is the free space
portion, and D 120 the lens portion of the ray path, where D=D, +D, in
any path The phase shift along all of the ray paths I must be equal or
differ only by integral multiples of 360 degrees to produce the
desired plane phase fronts 125 The phase shift 0, along a ray path may

20. be 27 r expressed as p=-=/l, where A is the wavelength in the medium
in which the waves 27 r are propagating and /3-is the phase constant
of the medium The ray paths I are partially in free space having
lengths K, for which 2.r the phase constant is /3 =-and partially in A
O the lens having lengths D, for which the phase 2 vr constant is
AI,=- The wavelength A, is in Al free space and AL is the wavelength
in the lens portion Since I=K-I-D, the lens 53 must be designed so
that for any two rays from the focus F following along two arbitrary
paths p and q the following equation is satisfied:13 o Kp+BL Dp=/o
Kq+BL Dq 2-r N ( 1) In equation ( 1) K, and D, are the free space and
lens portions, respectively of a -ray path 4, from the focus F through
an arbitrary lens path p to the exit surface 57 of the lens, and K,
and D, have the same meanings for a ray path Iq through a different
lens path q /3 o is the phase constant for electromagnetic waves of
wavelength A in free space P)L is the mean phase constant for
electromagnetic wave within the lens, the term 13 L differing from one
path in the lens to another because of the different effective
refractive indices thereof The term 2 r-N expresses the fact that the
ray paths 4, and 4, may differ by integral multiples of 360 degrees
(depending on which lens zones the path l, and Iq pass through) If a
particular path considered through the lens of Fig 10 extends through
either zone A or zone A 1, N=O; if the path is through either zone B
or BW, N= 1; and if the path is through either zone C or C', N= 2.
Equation ( 1) may be divided by P,, to yield: PLDP 8 D, K, I -K,±+ N,
( 2) The effective index of refraction of the lens portion of a ray
path is n=- Therefore,equation ( 2) may be rewritten as:K, +n
DD,=K,+iq Dq NA ( 3) Equation ( 3) is applicable to a lens of any
shape, and is employed to determine the electrical distances along the
ray paths from the focus of the lens shown in Figs 1-3 to the vertical
plane through IV-IV in Fig 2.
Once a lens is designed, n D is fixed for each channel However, in a
double media lens comprising the focussing section 35 of the lens
shown in Figs 1-3, and the lens shown in Fig 10, for example, n D=n D,
+n D,, where N is the effective refractive index of the lens channel
considered There are many combinations of,, it,, D, and D which may
produce the required values of n D There are some combinations which
are better than others from the standpoint of chromatic aberration due
to variations of the refractive indices with frequency.
In a double media lens as shown in Figs.
1-3 Fig 10, equation ( 3) for lens channels such as p and q in
different zones becomes: (K,+n,'D, n 1 D,)-(Kq+fl'D 1 +n,'DD)+NA 01 =
O p p i I ( 4) where n,' and n,' are particular values of A 01 At a
new wavelength A 01 ', the correspondrefractive indices it, and n, at
a wavelength ing equation is: (Kp+nl,"Dl'+n" 2 D,)-(K,+n,' D, +n,

21. 'D)-+NA 11 = 8 p p q q ( 5) where n,' and n," are new values of the
refractive indices n, and N 2, respectively, at a new wave length A 1
' and 6 is the path length error caused by changing the wavelength.
Subtracting equation ( 4) from equation ( 5) gives:a= l(D 1 D,) (n," N
1 _t)+(D -D 2) (t Z 21 ' -t?-1)1 +lN(A 1 ' ')l Equation ( 6) is
composed of two parts Let ad= r(Dp-1) (n 11)+(D,-D,) (n 21 '-pn 2 q) 1
L D O and 8,=N(Aoll Al) ( 8) Therefore, 8 = 8 d+ as The error 6 d is
produced solely by dispersion of the refractive indices nz, and n, of
the wave-guide channels when the operating wavelength varies, and the
error (, is Droduced by step phase errors with frequency variations
due to the zoning of the lens.
In order for no error to occur because of dispersion of the refractive
indices, equation ( 7) may be set equal to zero Letting An, = (n,
''-nl) and Aen -(nj' il) gives:/D' D 2 p q IfN A=n C ( 9) D, D, If
wave-guide channel (p) is in the region of the centre of the lens
where D, = O and D,= p p D., where D is the lens thickness at the
centre, equation ( 9) reduces to:( 6) ( 7) 785,856 785,856 (Do -D)
An,=An, ( 10) D, For a lens of constant thickness where both the
illuminated and exit surfaces are planar, as shown in Figs 1-3, D
-D,=D,, so equaq q 1 tion ( 10) reduces to:Anl=LAn 2 =(n,"l
-n,'l)=(n'01 ' _ n,') ( 11) Equations ( 9), ( 10), and ( 11) specify
the relative slopes of a line between n,' and N 1 " on a refractive
index curve ni, and a line between N 2 ' and n,1 ' on a refractive
index curve n, which will substantially eliminate chromatic aberration
due to dispersion errors ad over a band of wavelengths from A ' to AJ
11 Equation ( 9) is the general equtaion which is applicable to a lens
of any shape, and should be satisfied to minimize dispersion errors ad
over a wide frequency band.
In order to properly design the chromatic focussing section 35 of the
lens 27 shown in Figs 1 and 2, which section has a constant thickness,
the slope of the line between ai' and nl' should be equal to the slope
of the line between n,' and N 21 ' on the curves of the refractive
indices nl and N 2 Therefore, once the values of n,' and N 2, at a
particular design frequency are determined, two curves of refractive
index versus frequency for the wave-guide regions D, and D 2 in each
channel must be found where n,1-nl 11 =n,-n," 1 The curves for n, and
n 2 shown in Fig 5 a have regions therealong which have the same
slopes between wavelengths A O ' and A 01 ' as illustrated Therefore,
if the operating wavelength is changed from Aol to a larger wavelength
A 01 ', there could be substantially no chromatic aberration errors
produced in the focussing section 35 of the lens 27 due to dispersion
Obviously, since the curves of i, and n, over a corresponding
wavelength band to the right of A O ' in Fig 5 a have equal slopes
compensation would also be produced if the operating wavelength were

22. to decrease.
If one of the lens faces were curved, as in Fig 10 for example, An,
would not be equal to An Therefore, to minimize dispersion errors,
curves of refractive index having the proper relative slopes over the
required frequency band as determined by equation ( 9) must be
obtained For any particular lens having a predetermined shape for
operation over a predetermined frequency band the curves of refractive
index of ridge wave-guide regions of refractive index n, and n, may be
determined empirically in order to satisfy equation ( 9) A wide
variety of curves of refractive index versus frequency having various
slopes may be obtained by suitable variations of 1, w, or d in a
slot-loaded ridge 7.
wave-guide as shown in rig 5, and/or by 60 suitable variations in e,,
e, or the dielectric constant of elements 33 Some of these curves have
been shown in Fig 5 a, Fig 9 a and Fig.
9 o, for example.
The plane phase fronts of the waves of wave 65 length A ' at the
outputs of the axis half-zones of the lens 53 are schematically shown
in Fig.
by the solid lines to the right of the lens.
At a wavelength A 01, the phase fronts are dispiaced oy one wavelength
from one zone to 70 another as illustrated If the focussing section of
the constant thickness lens of Figs 1-3 were designed on the same
principles as above for wavelength A 01, the phase fronts at the
output of the focussing section 35 would also be 75 similar to those
shown in Fig 10 It the frequency charges to establish a new wavelength
A O ", the phase fronts will all shift by equal increments, assuming
there is no error due to dispersion of the refractive indices of the
lens 80 if the frequency is decreased and the wavelength increased to
A,11, for example, the phase fronts at the outputs of the lens
half-zones would be displaced to the right in Fig 10.
The phase fronts of the waves at a wavelength 85 A 01 ' are indicated
in Fig 10 by the dot-dashed lines at the outputs of zones B, B' C and
C' and the dashed lines at the outputs of zones A and A' These phase
fronts are all shifted by equal increments, so that the spacings 90
between the phase fronts are still integral multiples of the
wavelength A O ' from one zone to another However, it is desired that
the difference between the phase fronts from one zone to another of
the new wavelengths A,,' 95 be equal to integral multiples of A 011
Therefore, the phase fronts of the waves at the outputs of zones B,
B', C and C' should be shifted to the positions of the dashed lines
opposite these zones 100 The aforementioned zoning phase errors may be
substantially reduced by including a compensating section of fixed
lengths S at the end of the lens In the lens 27 shown in Figs.

23. 1-3, the compensating section comprises pro, 105 perly loaded
continuations of the ridged waveguide channels at the output of the
focussing section 35 of the lens For explanatory purposes, the lens 27
is schematically shown in Fig 11 110 Referring to Fig 11, let S be
divided into lengths D, and D 4 (having refractive indices n, and N 4)
in various zones such that: S=DI,+D 4 ( 12) The lengths D, and D 4 may
vary from zone 115 to zone but not within a zone If n, equals n, at
the wavelength A 01, as is the case in the lens of Figs 1-3 (see Fig 5
a), the net effect of the added section at the wavelength A O ' is to
advance the phase fronts of all the zones of 120 the lens by a uniform
amount, if n, =n 4 > 1, or retard the phase fronts of all the zones by
a uniform amount if n, =n 4 < 1 The amount of the advancement or delay
of the phase fronts 7 85,856 is n,1 S=n,'S at the wavelength Aio
However, if n, +n 4 at a new wavelength A ', the phase fronts of the
waves from a given zone will be altered by an amount depending on the
relative lengths of D, and D 4 therein, and compensation for zoning
errors can be effected.
For zero step-phase error at a new wavelength AJ 1, n 411 S-(n 3 ' D,+
+ iz," 'D 4)+ d 6 = O ( 13) Substituting from equations ( 8) and (
12), n 41 ll S -(-,"D, +it DS _ n"D,)+N (Ao 10-Aol)=O ( 14) Equation (
14) can be solved to yield: A 01 -Ao'0 D,=N @ ( 15) f 24 lN,"l 1 For
half-zones A and A' of the lens, where N= 0, equation ( 15) gives D,=
O For N=N max, where N max is the largest value of N for which
compensation is desired (N= 2 in the illustrated lens of Figs 1-3), J
A ' t 11 D,=N max -S ( 16) ( lln 3 I 11 It is not essential that N 3
=n, at Al ', provided the slopes of the n,, and ag, curves versus
frequency are different I However, in a constant thickness
compensating section as illustrated in Figs 1-3 and Fig 11, n, should
preferably equal n, at A O ' in order to avoid complications in design
of the focussing section 35 of the lens of Figs 1-3 Therefore, the
curves of refractive index in the waveguide regions having refractive
indices n, and n, in the compensating section 37 of the lens shown in
Figs 1-3, cross each other at the wavelength A O ' as shown in Fig 5 a
The curve of n,> may be the same as the curve of 12, so the ridged
wave-guide lengths D, of the compensating section of the lens 27 in
Figs.
1-3 may be loaded the same as the lengths da therein Therefore, the
loading of the ridged wave-guide sections of the compensating section
having refractive indices N 4 are preferably chosen so that the curve
of refractive index of n, has a different slope from n, in the proper
direction for compensation, and crosses ni, at the operating
wavelength A 01, where f/fl is 1 8, for example Other suitable curves
to satisfy equation ( 16) for any particular lens design may be
obtained empirically.

24. Although the particular lens illustrated in Figs 1-3 comprises a
constant thickness lens in the form of a parallelepiped excited by a
line source of microwaves, it should be apparent that the present
invention is equally applicable to any generally similar wave-guide
lens regardless of the shape thereof, the type source of microwaves
employed therewith, or the particular type phase front desired to be
produced from the incident lens energy.
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* GB785857 (A)
Description: GB785857 (A) ? 1957-11-06
A device for indicating depth of focus in photographic cameras
Description of GB785857 (A)
PATENT SPECIFICATION
785,857 Date of Application and filing Complete Specification: Jan 10,
1956.
No 839/56 Application made in Germany on Feb 10, 1955.
Complete Specification Published: Nov 6, 1957.
Index at acceptance:-Class 98 ( 1), A 12 A( 1: 4: 6: X).
International Classification:-G 03 b.
COMPLETE SPECIFICATION
A Device for Indicating Depth of Focus in Photographic Cameras We,
HANS DECKEL of Waakirchnerstrasse 7-13, Mfunich 25 Germany, and
FRIEDRICH WILHELM DECKEL, of Hans Lorettoh 6 he Zug Switzerland, both
of German nationality, do hereby declare the invention, for which we
pray that a patent may be granted to us, and the method by which it is
to be performed, to be particularly described in and by the following
statement:-

25. The present invention relates to a device for indicating the depth of
focus in photographic cameras.
An object of the invention is to devise a depth of focus indicating
device affording a very large angle of displacement of the indicating
elements thereby making possible the use of a widely-divided and
easily visible scale of distances to be used in conjunction with such
indicating elements Another object is to provide a form of
construction which will be simple to manufacture Still another object
is to produce a compact arrangement suitable for being adapted without
difficulty to cameras of all forms including the compact form of
construction of lens system and shutter arrangements.
To the attainment of these objects the invention provides a device for
indicating the depth of focus in a photographic camera characterised
in that indicating elements are incorporated each of which is
individually mnovable by means of a rocking element and that the
individual rocking elements are operable by a common driving element
actuated, through a cam slot, by the lens stop setting element.
The foregoing and subsidiary features of the invention will be fully
understood from the following description aided by the accompanying
drawings which show an exemplary form or embodiment.
Fig 1 is a diagrammatic sketch of the view of the depth of focus
indicating device; and lPrice 3 s & AM Fig 2 to 5 show the structural
arrangement of the device in an interchangeable photographic lens.
The device for indicating the depth of focus comprises two pointers
10, 12 working 50 in conjunction with a distance scale 14 and
delimiting thereon the actual range of the depth of focus The pointers
10, 12 are attached on rings 16, 18 which are arranged close to eacfh
other and coaxially to the 55 optical axis of the camera These two
rings are coupled together in such manner that upon one ring being
moved in a particular direction the other ring is caused to move in
the opposite direction This effect is 60 obtained by transmission
means which comprises a pair of cranked rocking levers and 22 These
rocking levers are respectively pivoted on trunnions 24 and 26 carried
on a fixed ring 28 which is likewise 65 coaxial with the optical axis
of the camera.
The free ends of the rocking levers carry drive pins 30 and 32 which
engage in slots 34 and 36 of the pointer rings 16 and 19 One end of a
follower pin 38 arranged laterally 70 parallel to the optical axis of
the camera is fixed at 40 in the rocking lever 20, passes through a
slot 42 of the other rocking lever 22 and slides with its other end 44
in a cam slot 46 of a setting ring 48 which is coaxial 75 with the
optical axis of the camera.
This setting ring 48 is linked with the lens stop setting element, in
particular by means of a bent driving lug 50 The lens stop device and

26. its setting element are for 80 the sake of simplicity not shown in Fig
1; only a linearly-graduated stop-setting scale 52 is diagrammatically
indicated there in conjunction with the driving lug 50 The cam slot 46
already mentioned is incorporated 85 in the transmission linkage
between the setting ring 48, 50 and the pointers 10, 12 for the
purpose of performing the motion of the lens stop setting element into
a correctly co-related motion of the pointers The cam 90 motion This
axial connection permitting relative rotation is furnished by the ring
28 shown in Fig 1 which, as particularly shown in Fig 4 is seated on
an end face 108 of the part 102 and is attached to the bush 106 by 70
means of a number of screws 110 and spacing tubes 112 A ring 114 of
Z-cross-section is attached by a number of screws 116 to said bush
106.
The inside of the bush 106 receives the 75 mount 118 of the lens
components 121) and 122 The lens tube of the shutter easing, 72
further contains a fixed lens component 124.
Upon rotating the setting ring 100) 102, consequently the parts 106,
114, 118 with 80 the lens elements 120 122 are moved axiall-, i.e in
the direction of the optical axis.
forwards or backwards The rotation of these parts is prevented by a
guide-pin 126 on the ring 114, which engages in a guiding 85 hole 128
of the immovable bayonet joint element 92.
The space 130 between the parts 106 and 114 accomodates an iris
diaphragm stop of known kind and action comprising a number 90 of
diaphragm blades 132 The corresponding setting ring 134 is connected
by means of the drive pin 136 passing through a curved slot 138 in the
bush 106, with the setting ring 45 of the indicating device The arm 50
on the 95 setting ring 48 is at the same time in engagement with a
coupling ring 140 located between the two mounting parts 92, 93 and
one edge of which 142 projects through a peripheral slot 144 in these
parts, to the 100 inside The arm 50 of the ring 48 further engages in
a slot 146 of the coupling flange 142.
The coupling ring 140 further possesses a coupling tooth 148 which
when the interchangeable photographic lens is placed in 105 front of
the shutter engages in one of the coupling notches 150 on the end face
of the setting ring 82 The coupling ring 140 itself is axially loaded
by a corrugated spring 152 by which means the engagement of the 110
coupling is assured This coupling ring consequently provides a linkage
between the time-setting ring 50 of the shutter and the setting ring
134 of the lens stop device in the interchangeable photographic lens
115 The coupling ring 140 itself can ibe moved axially against the
force of the spring and thus set for a new relative coupling position
of the setting elements.
The depth of focus indicating device 120 shown diagrammatically in Fig

27. 1 is in the form or embodiment according to Fig 2 arranged around the
part 102 and between the rings 28 and 48 It would be superflous again
to describe the details of this device 125 The pointers 10 and 12 pass
through a peripheral slot 154 in the part 93 outwards.
The depth of focus indicating device is consqeuently moved axially
together with the setting ring 100 102, but is not rotate-l 130 slot
46 and with it the degree of transformation of the motion between the
stop-setting action and the depth of focus indication can be
selectively adjusted or preset.
The practieal embodiment of the device for indicating depth of focus
is shown in Figs 2 to 5 In this illustrated form a retaining element
is provided in the form of a bayonet ring 60 which is attached by
means of a number of screws 62 to the front plate of the camera 64 A
cylindrical collar 66 (Fig 3) on the camera 64 enters into a
cylindrical recess 6 S of the bayonet ring 60 and serves to centre the
latter with reference to the optical axis of the camera The bayonet
slots of the bayonet ring 60 are denoted by 70 The cylindrical shutter
housing 72, only partially shown, is of usual form and provided
circumferentially with a number of flanged eyes 74 which pass through
corresponding openings 76 in the front plate of the camera 64 and
enter the cylindrical recess 68 of the bayonet ring 60 where they are
secured thereto by screws 78 By these means, the shutter casing 72 is
attached to the bayonet ring 60 and simultaneously held joined to the
camera 64.
The inside of the shutter casing 72 contains the shutter blades (not
shown) with their actuating and controlling means of known kind and
action The operation of the shutter (setting and releasing) is
effected by means likewise not shown The setting of the exposure time
or shutter speed is performed on the shutter by means of the
time-setting ring 50 which is rotatably attached on the front face of
the shutter.
This time-setting ring 80, situated inside the camera 64 and the
bayonet ring 60, is connected with an external setting ring 82,
specifically in such manner that a bent tongue 86 on the time-setting
ring 80 projects into an opening 84 in the aforesaid setting ring 52,
and at the same time passes through 4.5 a curved slot 88 in the
bayonet ring 60 A packing ring 90 is attached by screws 91 to the
bayonet ring 60 and locks the setting ring 52 in the axial direction.
The bayonet ring 60 detachably secures a photographic lens system in
front of the camera shutter assembly This interchangeable photographic
lens system has a twopiece mounting 92, 93 provided with bayonet lugs
94 which engage in the bayonet slots 70 of the bayonet ring 60 The
parts 92, 93 of the mounting are held together by means not shown The
complete mounting has the form of a hollow cap and is provided in

28. front on its inner rim with a number of turns of a screw thread 98,
receiving a screwed-in, two-part setting ring 100, 102 The parts 100,
102 are secured together by a number of screws 104 The part 102
receives internally a rotatable bush 106 of tee cross-section and is
linked with this part in regard to axial 785,857 The arrangement of
the graduated scales is most clearly apparent from Fig 5 The distance
scale 14 is arranged on the periphery of the axially movable and
rotatable setting ring 100 and works past a reference mark 160 on the
fixed mounting part 93 The ends of the pointers 10, 12 projecting
through the slot 134 move over this distance scale 14 and delimit
thereon the range of focus in depth corresponding to the preset
distance and lens stop aperture The stop aperture scale 58 is arranged
on the periphery of the coupling ring 140 and works past a principal
reference mark 156 on the fixed bayonet ring 60 Since the stop
aperture setting is already determined by the indicating depth of
focus during the act of setting, the stop aperture scale 52 may be
omitted if preferred.
The time or shutter speed scale 158 on the periphery of the setting
ring 82 also works past the principal reference mark 156 and the
relative coupling positions of the timesetting ring 80 and the
stop-setting ring 134 are adjustable for instance by means of a scale
162 graduated in summary exposure values on the setting ring 82 in
conjunction with a reference mark 164 on the coupling ring 140.
It has already been mentioned earlier that the form or embodiment of
the depth of focus indicating device according to the invention
presents substantial advantages.
Firstly, it allows of a very wide setting angle between the pointers
10 and 12 actuated by the stop-setting element in such manner that the
distance scale 14, as clearly shown in Fig 5, can be graduated with
widely spaced and easily visible scale divisions; which appreciably
facilitates the setting operation.
Furthermore, the arrangement gives a simple and compact form of
construction enabling such a depth of focus indicating device to be
employed in all cases without difficulty; i.e, not only, as shown, on
a photographic lens system but also, if preferred, on a 45 shutter or
on the camera itself Similarly, the depth of focus indicating device
can equally well be fitted in some other part of the lens system or
its mounting than that shown 50 The invention is likewise not
dependent on the presence of coupling means between the time-setting
element and the stop-setting element.
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* GB785858 (A)
Description: GB785858 (A) ? 1957-11-06
Photosensitive element and process for preparing printing relief images
Description of GB785858 (A)
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The EPO does not accept any responsibility for the accuracy of data
and information originating from other authorities than the EPO; in
particular, the EPO does not guarantee that they are complete,
up-to-date or fit for specific purposes.
PATENT SPECIFICATION
Inventor: LOUIS PLAMBECK JR.
785858 Date of Application and filing Complete Specification Jan 11,
1956.
e No 1027/56.
(Patent of Addition to No 741,294 dated Aug 20, 1952).
Complete Specification Published Nov 6, 1957.
Index at Acceptance: -lass 98 ( 2), M.
International Classification: -GO 3 f.
COMPLETE SPECIFICATION
Photosensitive Elemnent and Process' for preparing Printing Relief
Images We, E I Du PONT DE NEMOURS AND COMPm Y, a Corporation organised
and existing under the laws of the State of Delaware, United States of
America, of Wilmington, D Qlaware, United States of America, do hereby
declare the invention, for which we pray that a patent may be granted
to us, and the method by which it is to be performed, to be
particularly described in and by the following statement: -
This invention relates to photopolymerisable sheet elements suitable

30. for making relief printing forms.
In the specification of our Application No.
20946/52 (Serial No 741,294) we have described a process of preparing
a printing relief image which comprises photopolymerising with actinic
light through a process transparency a layer at least 3 mils thick of
ethylenically unsaturated photopolymerisable composition contaning a
catalyst for such photopolymerisation carried on a permanent support
therefor having a continuous surface, continuing such exposure until
the exposed material is substantially completely polymerised to the
insoluble state in the lightexposed areas throughout its entire
thickness without any substantial polymerisation in the unexposed
areas, removing said transparency and removing the unexposed and
therefor not insolubilised areas of the photopolymerisable layer to
leave a relief image in photopolymerised material adherent to said
support.
The term " process transparency " is defined as a transparency
carrying an image made up solely of areas, e g lines and dots, of high
and substantially uniform density, e g a line or half-tone diapositive
or dianegative The catalysts are defined as substances capable of
initiating the photopolymerisation under the influence of light and
which are not active to polymerise the material under the action of
heat alone at temperatures below 80 C.
In the said specification it is further disclosed that there may be
provided between the photopolymerisable layer and the support a layer
absorptive of actinic light which serves to suppress reflection of
actinic light from the support Such a layer absorptive of actinic
light can be described as an antihalation layer and is so referred to
herein.
Various modifications of the aforesaid processes are described in the
Specification of our Application No 12197/53 (Serial No.
741 L 441) and Application No 20708/54 (Serial No 741,470).
The present invention is concerned with an alternative form of
photopolymerisable element suitable for use in the aforesaid
processes.
According to the present invention there is provided an improvement in
or modification of the invention claimed in the Specification of
Application No 20946/52 (Serial No.
741,294) being a photopolymerisable element comprising a layer at
least 3 mils thick of ethylenically unsaturated photopolymerisable
composition containing a catalyst for such photopolymerisation (as
herein defined) and capable of undergoing, on exposure to actinic
light, transformation throughout its thickness to a high molecular
weight addition polymer, the said layer being carried on one side of a
permanent sheet support which is transparent to actinic light, the

31. said support carrying on its other side a layer containing an
antihalation material.
According to a further feature of the present invention an improvement
in or relating to the process claimed in the Specification of
Application No 20946/52 (Serial No.
741294) comprises effecting the process steps therein described using
a photopolymerisable element as defined' in the last preceding
paragraph.
The photopolymerisable layer can vary from a Iiluid state to, a solid
state, including a gel state It may be superposed directly on lPr Adi,
785,858 the surface of the support or on a sublayer which provides
enhanced anchorage between the photopolymerisable layer and the
support.
In general, the thickness of the photopolymerisable layer will vary
between 3 and 250 mils, depending on the nature of the particular
subject to be reproduced For half-tone printing reliefs, the thickness
will vary between 3 and 30 mils whereas layers from 10 to 60 mils in
thickness will usually be used for line printing plates.
The photopolymerisable layer can be composed of any
addition-polymerisable monomer (viz an ethylenically unsaturated
monomer) which, on exposure of the layer to actinic light and in the
presence of a photopolymerisation initiator or catalyst, necessarily
contained in the layer is converted throughout its thickness to a high
molecular weight additimn polymer The photopolymerisable layer can
also contain added preformed compatible condensation or addition
polymers, as well as immiscible polymeric or non-polymeric organic or
inorganic fillers or reinforcing agents, which are essentially
transparent e g, the organophilic silicas, bentonites silica and
powdered glass, having a particle size less than 0.4 mil and in
amounts varying with the desired properties of the photopolymerisable
layer, which can be liquid or solid, including gel, in nature.
Any of the photopolymerisable monomers described in the Specifications
of Applications
Nos 20946/52 (Serial No 741,294) and its patents of addition Nos
12197/53 (Serial No.
741,441) and 20708/54 (Serial No 741,470) can be used The preferred
monomers are the ethylenically unsaturated, addition-polymerisable
monomers, particularly those wherein the said ethylenic linkages are
terminal i e, those monomers having the characteristic CH = C< group,
i e, the vinylidene monomers Because of the greater speed with which
such compositions polymerise to rigid materials, it is preferred that
the photopolymerisable layer contain appreciable proportions of
ethylenically unsaturated polymerisable materials containing a
plurality of said polymerisable linkages per molecule These types of

32. monomers are conventionally referred to as cross-linking agents.
This cross-linking facility can be incorporated in the
photopolymerisable layer by the use of polymers containing the
indicated plurality of polymerisable unsaturated linkages in which
instance such materials serve a duel function of both increasing the
viscosity of the photopolymerisable layer to the desired level and
making available the desired cross-linking facility for the
photopolymerisation.
The introduction of cross-links into a polymer increases its
insolubility in selected solvents at a much more rapid rate than
merely increasing the extent of linear polymerisation.
In addition, cross-linking causes the early development of a gel
structure in the polymerising body with a resulting net increase in
polymerisation rate, presumably by reducing the rate of the chain
termination reaction For these reasons, it is desirable that from 55 O
to 100 % by weight of the polymerisable mono 70 mers in the
photopolymerisable composition be cross-linking materials A useful
class of such materials are the polymerisable monomers containing two
ethylenic unsaturations, preferably terminal, conjugated or not, e g,
75 methacrylic and acrylic acid diesters of ethylene glycol and the
polyethylene glycols, such as diethylene glycol, triethylene glycol
and tetraethyene glycol or mixtures of these etheralcohols;
methacrylic and acrylic diesters of 80 polymethylene glycols such as
trimethylene glycol and hexamethylene glycol; divinylacetylene,
divinylbenzene, diisopropenyl-diphenyl, crotyl methacrylate, diallyl
phthalate, diallyl maleate and trillvl cyanurate Suitable poly 85 mers
containing an ethylenically unsaturated group, capable of further
polymerisation, are those made by reacting an
ethylene-s:,-dicarboxylic acid or anhydride e g maleic, furnaric, or
itaconic acid or anhydride with a glycol 90 e.g ethylene glycol,
diethylene glycol, triethylene glycol and propylene glycol Such
polymers have a low acid number, e g 20 (or below) to 50 Suitable
polymers are described in Ellis U S Patent 2,255313 95 Suitable
photopolymerisation initiators or catalysts include vicinal ketaldonyl
compounds such as diacetyl and benzil, alpha-ketaldonyl alcohols such
as benzoin and pivaloin; acyloin ethers such as benzoin methyl or
ethyl ethers; 100 alpha-hydrocarbon substituted aromatic acyloins
including x-methylbenzoin, Adallylbenzoin, and 9 -nhenylbenzoin.
The transparent support may be flexible or rigid, depending upon
ultimate use to which 105 the printing relief is to be put Suitable
supports are glass; superpolymers, e g, nylon, polymethylene
terephthalates, e g, polyethylene terephthalate, polyethylene,
polystyrene, polyvinyl chloride, poly(vinyl chloride co 110 vinyl
acetate) and polymethyl methacrylate; cellulose derivatives, e g,

33. cellulose nitrate, cellulose acetate, cellulose acetate propionate,
cellulose acetate butyrate and ethyl cellulose, which organic polymer
film supports are 115 hydrophobic in character.
The antihalation layer may contain any dye or finely divided inorganic
or organic pigment which is absorptive of actinic light of wavelengths
to which the photopolymerisable layer 120 is sensitive These dyes or
pigments may be dispersed in any suitable binding agent, e g, gelatin,
polyvinyl alcohol polyvinyl acetals such as sodium
o-sulpho-benzaldehyde polyvinyl acetal, cellulose glycollate, ethyl
cellulose 125 or any of the organic materials used for the supports
These layers can be coated onto the supports in the same manner as
antihalation layers are coated onto a transparent film base used in
the manufacture of photographic film 130 cury vapour lamp until the
layer had polymerised This provided a solvent resistant layer adapted
to anchor the subsequently formed image.
A layer of the above syrup was applied on the photopolymerised anchor
layer and spacers mils thick were disposed around the periphery A line
negative on thin glass was then placed on the syrup with the glass
side in contact with the syrup and resting on the spacers The assembly
was then exposed for minutes to the light from a transformerless
mercury vapour sunlamp located 13 inches above the plane of the
negative The lamp with its integral reflector and frosted glass bulb
furnished a light source approximately S inches in diameter-somewhat
larger than the negative used Upon completion of the exposure the
negative was removed and the unpolymerised areas, which were still
liquid, were removed by washing the plate in a tray of acetone A
relief image of the exposed areas was then present on the plate The
image obtained was sharper than when the procedure was carried out in
the same way except that the black coating on the base was omitted.
EXAMPLE II.
A sheet of cellulose triacetate film base having a thickness of O 0055
inch was coated on its back surface with a solution made by admixing
four parts (by volume) of the following binder solution with one part
(by volume) of the following activator solution, the percentages given
being by weight.
For example, an aqueous dispersion or an organic solvent dispersion of
the dye or pigment and the binding agent is coated onto a surface of
the transparent support and dried.
Desirably the antihalation layer may contain carbon black particles,
but various other pigments, e g, manganese dioxide may also be used
Instead of pigments dyes may be used, e g Auramine (C I 655),
Helianthin (C I 142, 146), Brilliant yellow S (C I 144), Chrysoin (C I
148), Acid blue black (C I.
246), Rhodamine (C I 749, 750, 751, 746, 753, 761, 763), Fuchsin (C I

34. 677), Safranie G (C I 841), Ponceau 6 R (C I 186), Crocein scarlet (C
I 277, 251, 286, 252, 291, 183), Azorubin (C L 179), Safranine O (C I
841), Ponceau 2 R (C I 79), Spirit soluble nigrosine (C.I 864) Metanil
yellow (C I 138), Acid magenta O (C I 692) The reference Nos.
given are to Rowe's Colour Index.
The photopolymerisable elements of this invention can be used for the
preparation of printing reliefs by any of the procedures described in
the aforesaid applications They are also useful in producing
ornamental reliefs.
The printing reliefs when on thin films can be tacked onto printing
blocks.
The following examples will serve to illustrate the invention.
EXAMPLE I.
A dough was prepared by mixing 400 parts of medium viscosity polyvinyl
alcohol ( 75 % hydrolysed polyvinyl acetate) with 300 parts of boric
acid and 2250 Darts of ethanol By means of a sigma blade mixer
approximately one-half of this dough was combined over a period of one
hour with a paste of 400 parts of carbon black and 1600 parts of
ethanol.
The black concentrate obtained was milled for half an hour in a
Banbury mixer to disperse the carbon Darticles thoroughly, then
returned to the sigma blade mixer and combined with the remainder of
the polyvinyl alcohol dough.
The mixture was diluted with ethanol to give a composition containing
approximately 1 % by weight carbon black A sheet of transparent
polymethyl methacrylate approximately 265 mils thick was coated on one
side with the above solution and allowed to dry A black opaque film
was present on the polymer sheet.
The other surface of the sheet was coated with a photopolymerisable
composition prepared by mixing 90 parts of a methyl methacrylate
monomer-polymer syrup (viscosity 10 to 12 poises) with 1 0 part
benzoin, O 0025 parts of hydroquinone, and 10 parts of the monomeric
polyethylene glycol dimethacrylate mixture described in Example I of U
S Patent No 2,468,094 Spacers 20 mills in thickness and 4 inch wide
were then disposed around the periphery of the coated sheet and a
plain glass plate lowered onto the syrup and allowed to rest on the
spacers This assembly was exposed to ultra violet radiation from a
merBINDER SOLUTION Polyvinyl butyral resin Zinc tetroxy-chromate Zn Cr
O 4 4 (n((H):,) Lamp black Asbestos fibres Methyl isobutyl ketone
Isopropyl alcohol 8.9 % 8.5 % 0.1 % 1.3 % 17.8 % 63.4 % ACTIVATOR
SOLUTION Water -16 4 % Isopropyl alcohol 65 1 % 110 Phosphoric acid 18
5 % The above sheet with its coated surface downwards was lowered into
contact with the upper surface of a glass plate Thirty-mil thick
spacing strips about 4 inch wide were 115 disposed about the periphery

35. of the sheet.
Between the spacing strips, the sheet was coated with a
photopolymerisable resin consisting of a 70 % by weight solution of
propylene glycol phthalate/maleate ( 3:1) and 120 having unesterified
carboxyl groups corresponding to an acid number of 46 2, and 1 03
unesterified hydroxyl, dissolved in monomeric styrene, and 1 % by
weight of benzoin methyl ether A negative consisting of lines and half
125 tone dots mounted on a glass plate was lowered with its gelatin
emulsion surface into 785,858 contact with the photopolymerisable
layer.
The layer was exposed for 15 minutes at a distance of 8 inches from a
bank of 20 ( 30 watt) fluorescent lamps in a plane parallel to the
film, the lamps being coated on their inner surfaces with a calcium
phosphate phosphor emitting light in the range 3200 to 4500 A with a
peak at 3600 A The unpolymerised material was removed by gentle
brushing with isopropyl acetate A second similarly prepared sheet free
from the antihalation layer was exposed and processed in like manner
The image formed in the first element was sharply outlined and had
good relief, while the second element was less sharp The depth of the
relief in the half-tone areas of the first element was 4 2 to 4 5 mils
and in the second was 1.1 mils.
In place of the particular binding solution described in Example II,
there can be substituted the solution described in Exam Ple II of U S
Patent No 2525,107.
The photopolymerisable elements of this invention avoid the production
of undesirable halation effects in the relief images Since the
anti-halation layer is remote from the photopolymerisable layer, it
can not have any effect on the light-sensitivity of the latter layer A
further advantage is that the coating of the antihalation layer can be
carried out without regard to the nature of the particular
photopolymerisable layer being coated on the obverse side, thus
affording the manufacturer greater latitude in making the final
elements.
In our Application Serial No 780,218 we have claimed a process for
preparing intaglio and relief images which comprises exposing to
actinic light of wave lengths between 1800 and 7000 A, through an
image-bearing transparency, a solid layer comprising essentially a
synthetic organic macromolecular addition polymer, and optionally
having a liquid surface layer thereon, said solid polymer andlor said
surface layer, or a separate layer intercalated therebetween,
containing a photo-polymerisation catalyst activatable by actinic
light of such wave lengths, continuing the said exposure until
substantial degradation of the polymer to substantially lower
molecular weight products takes place in the light exposed areas at

36. least in the surface of said solid layer, and physically removing the
degradation products in the light-exposed areas of the said solid
layer substantially without affecting the polymer in the non-exposed
areas.
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