Lcd projector

1. LCD Projector
Definition:
​ ​An LCD projector is a type of video projector for displaying video, images or
computer data on a screen or other flat surface. It is a modern equivalent of the
slide projector or overhead projector.
Working Principle
LCD projectors are rapidly becoming popular as useful presentation tools for business and
entertainment at home on large screens as home theaters.
LCD (liquid crystal display) projectors contain three separate LCD glass panels, one for red, green, and
blue components of the image signal being transferred to the projector. As the light passes through the
LCD panels, individual pixels can be opened to allow light to pass or closed to block the light. This
activity modulates the light and produces the image that is projected onto the screen.
The lamp provides white light that passes through a polarizing filter. Polarizing works by accepting
light that is traveling on the same plane. All other light will be blocked.
From the polarizing filter the light is then passed through a series of dichroic mirrors. Dichroic mirrors
work by only allowing certain colors in the light spectrum to be reflected, while others pass through.
The dichroic mirrors in LCD projectors separate the light into the three primary colors: green, red and
blue.
These three colors are then sent to a separate LCD panel: remember there are three of them. From there
the LCD panels send the light through the dichroic prism which recombines the light and sends it out
the main lens in the LCD projector to the surface against which it is projected. Each LCD is only
capable of controlling one color. So if you were to see a picture of a red plane against a blue sky, the
green LCD would block the light from passing to the dichroic prism and out the lens.
LCD panels in LCD projectors work by allowing the polarized light to travel through a pane of glass
Green Blue

2. into the liquid crystal inside the display. The liquid crystals bend the light, and it is traveling on a
different plane then when it entered through the polarizing filter. If you apply an electrical current to the
liquid crystal they will align, allowing the light to pass through on the same plane as when it entered. If
you add a second polarizing filter at the other end of the liquid crystal you can then effectively block all
light from passing through. Each LCD panel has a separate system to control the electrical current that
passes through the liquid crystal, allowing each to be controlled individually.
The resolution, or how sharp the image is, of each LCD is determined by the number of cells which are
called pixels, with the higher the number of pixels meaning more clarity to the image. Each LCD panel
also has the ability to control what color each pixel will be in that particular panel so that when all the
light is recombined at the dichroic prism, it will be the right color.
What are the components of LCD projectors?
A bulb, a LCD panel, a lens, a control panel, a main circuit board, a cooling fan, an input panel, a
power supply and a case.
Advantages of LCD projector
Enable a lot of people to be able to see something even from a distance
They produce sharper images
They have an edge in light efficiency
They generate largest possible image size
Low cost
Space saving
Easy to install
Disadvantages of LCD projector
Image quality may not be as good as projected
Dark room often required
Maintenance required
Installation can be more involved
Separate audio system required
If one pixel on the chip burns out, whole chip is required to be replaced