1. HOW DOES
PROJECTORS WORK?
By-PRADEEP Kr. SHARMA

2. WHAT IS A PROJECTOR ?
 It’s an electronic device used to project rays
of light, esp. an apparatus with a system of
lenses for projecting images or film onto a
screen.

3. TYPES OF PROJECTORS
 There are three main types of projectors:-
1. CRT(Cathode Ray Tube)
2. LCD(Liquid Cristal Display)
3. DLP(Digital Light Processing)
*NOTE- A latest technology LCOS (Liquid Crystal On
Silicon) has entered into the picture which is
considered as a more recent variant of the LCD
technology.

4. HOW DOES A PROJECTOR WORK
 CRT Projectors-:
 A CRT, fires a beam of electrons at a phosphor-
coated screen.
 Every time an electron comes into contact with the
screen, that point, called a pixel, glows.
 Color CRT use three electron beams and separate
phosphors for red, green and blue.
 Traditional CRT TV sets are called direct-view
displays as When you watch, you're looking directly
at the surface that the TV uses to create the picture

5. A CRT

6. LCD Projectors
 At the centre of the projector is a halogen bulb,
which is surrounded by three LCD panels.
 These panels produce light.
 As the halogen bulb heats up, the crystals melt
and allow more light to pass through.
 Images travel to the tube present inside the
projector from the DVD player or the satellite box.
 These images hit a surface coated with phosphor.
Contd…

7. LCD Projectors
 Every fragment of light hitting the screen is called
as , PIXEL.
 On hitting the screen, the pixel breaks down into
its color component, ie- is red, blue or green.
 The heat produced by the halogen bulb is
controlled by the voltage that flows into the LCD
video projector.
 The 3 LCD panels can produce more than sixteen
million colors, depending upon the voltage, that
flows into the LCD video projector, this is what
enables us to view all the subtle colors of a sunset.

8. LCD Projectors
 A single panel is for a single color, meaning one
panel handles all the pixels that are created by the
red color,
 The second for blue and the third for green.
 The color images travel as three separate beams
of light and hit the wall. Here the colors fall on
each other to produce the true color.

10. An LCD Projectors
Ricoh PJ X3241 LCD

11. DLP Projectors
 It works with a different technology than LCD.
 In place of glass panels through which light is
passed as in LCD, the DLP chip is a reflective
surface made up of thousands of tiny mirrors.
 Each mirror represents a single pixel.
 In Case of DLP light from the projector's lamp is
directed onto the surface of the DLP chip.
 The mirrors wobble back and forth, directing light
either into the lens path to turn the pixel on, or
away from the lens path to turn it off.

12. DLP Projectors

13. DLP Projector
RICOH PJWX4130N DLP PROJECTOR

14. LCOS Projector
 Just like LCD the LCOS also uses 3 panels of
Red, Blue & Green;
 However, However, Lcos uses reflexive
technology as opposed to transmissive;
 LCOS ,allows the pixel structure of LCoS
projectors to be much less visible than the
competition (virtually invisible at normal
seating distance).
 This provides a remedy for "screen door" and
"rainbow" effects.

15. LCOS Projectors
AN LCOS PROJECTOR

16. LCOS Prolectors
A JVC LCOS PROJECTOR