The document discusses laser interferometry, which uses lasers to make highly accurate length measurements. It describes how a laser produces coherent, monochromatic light and can be used as the light source in interferometry. Interferometry works by superimposing laser light waves to extract information about the waves. Specifically, it uses the frequency difference between two laser beams to precisely measure displacements down to 0.1mm over distances of 100m. Key components of a laser interferometer system include a dual frequency laser source, optical elements like beam splitters, and a measurement receiver and display.

1. BY
Kaviyarasan.S

2.  LASER
 (light amplification by
Stimulated emission of
Radiation)
 It is the powerful ,Monochromatic light
source
 The advantage of laser is production of
coherent light which is very intense at small
point

3.  Stimulated emission
 Population inversion
 Incident photon is equal to the emission
photon
 EG : when xenon flash tube excites the
atom of ruby rod ,it produce photon, where
incident photon of flash tube is equal to
emitted photon of ruby rod.
 photon is packs of charge.

4.  Interferometry :
 It is used to understand nature of light
 It is a family of techniques in which waves,
usually electromagnetic, are superimposed
in order to extract information about the
waves

5.  Interferometry means the complete study
about the frequency signals of light.
 In other words , interferometry is
investigation of wave signals of light.
 The highest point of the wave is called
crest ,lowest point of the wave is called
trough.
 The distance between two crest or trough
is called wavelength(l).

6.  The maximum disturbance of wave is called
amplitude(A),either it may be in crest or
trough.
 Light is allowed to interfere where it
produce dark band of waves corresponding
to the frequency of light.
 Only monochromatic lights are used to
investigate waves of light.
 Monochromatic lights are used in measuring
flatness and determining length of slip
gauges.

7.  The laser in interferometry is used to find
accurate measurements of length.
 The accuracy of laser measurement is in
order of 0.1mm in 100m.
 In modified laser design ,a single frequency
is selected from coherent beam and used
for interferometric measurement.
 Time consumption is less.

8.  parts involved in interferometry ;
I. Two frequency laser source
II. Optical element
III. Laser head measurement receiver
IV. Measurement display

9.  The two frequency laser source becomes
HE-NE type that generates stable
coherent light beam of two frequency.
 Laser is oscillated at two frequency by
placing the laser in cylindrial permanent
magnet.
 In two frequency one is polarised
horizontally and other is polarised
vertically.

10.  Two frequency waves allowed to pass
through quarter and half wave plate that
seperates two frequency in two
perpendicular direction.
 So we get two frequency of laser.

11.  various optical element are ,
1. Beam splitter
2. Beam bender
3. Retro reflector
 BEAM SPLITTER:

12.  It is used to split laser into separate beams
along different axes
 The output intensity can be adjusted by the
reflectivity of beam.

13.  It is used to deflect the light beam around
corners of object from laser to each axis

14.  This type of reflectors are found in cube
corners prism that reflect parallel light
rays of incident ray.

15.  Laser head measurement receiver:
It is used to detect part of
returning beam as f1-f2 ie, difference
between frequency.
 Measurement display:
The measurement display has
a microcomputer to compute and display
results.

16. STANDARD INTERFEROMETER:
The displacement is
between cube corner and ,it is least
expensive used where ever it is possible
SINGLE BEAM INTERFEROMETER:
Here the out going and
returning beam are super imposed on
eachother having parallel light rays.

18.  Introduction:
Interferometer uses ac laser
as light source and thus used to measure
large distance ,the laser beam wavelength
is exact and pure for highly accurate
measurements.
Principle:
1. optical technique
2. digital electronics.

19. 1. Two frequency zeeman laser
2. Beam splitter
3. Fixed internal cube corners
4. External cube corners
5. Photo detector
6. Amplifiers
7. Pulse converter

20.  Two frequency laser: Two frequency laser
one is polarised vertically and other is
polarised horizontally.
 Beam splitter: splits beam
 Cube corners: 2 cube corners are required
one is placed externally and other is placed
internally, both are used to reflect laser
beam.
 Photo detectors: receives signal from
splitter and change into electrical signals.

21.  Amplifiers: it is used to separate frequency
difference
 Pulse converter: It is used to extract
information as pulse signal
 Working: