2. (1) Introduction to projectors
(2)Types of projectors
(3) Advantages and disadvantages
(4) conclusion
Table of contents
3. A video projector is an image projector that
receives a video signal and projects the corresponding
image on a projection screen using a lens system..
Video projectors are widely used for many
applications such as, conference room
presentations, classroom training, home theatre and
concerts
INTRODUCTION
4. The history of projectors is not really that
long, going back only as far as the 1970s, when
the first projectors came out in the form of CRT
(cathode ray tube or Braun tube) projectors. While
having the advantage of displaying smoothly
flowing movement, CRT projectors had
drawbacks including image distortion and issues
in reducing the size of the projectors
5. Four Main things to look for:
1).The type of projector - LCD, DLP, CRT
2).The Lumens output (brightness) of lamp - 800-1000 is
good for LCD, DLP at 1000 is good. Dont get it to high or
colours will look poor, less than 1500 is really needed for
good colour reproduction.
3).The Resolution. For optimal picture make sure to get
XGA orWXGA.
4). A very key point is contrast ration.above 300:1 blacks
look dark grey. 1000:1 + is excellent.
6. CRT
The Cathode RayTube Projector was one of the first digital
projectors that was put out on the market.The Cathode Ray
Tube is a vacuum tube where an electron beam comes into
contact with a phosphorescent surface .The CRT uses those
tubes to project an image. In the most of the projectors
there were three tubes on red, one blue, and one green .
When video signal were processed they would go to their
specific tube.The tubes all had lens that would project the
image giving the projection.The technology was developed
in the late 1800s, was not utilized until the 1930s.These
tubes were being used to project images inside of the
televisions.
7. .These projectors are generally used in fixed installations
because of their size. CRTs are typically not as bright as the other
technologies, but the refined picture quality of a properly
calibrated CRT is tough to beat
8. There are two main competing projector structures
in the market - DLP (Digital Light Processing) and
LCD (Liquid Chrystal Display). It would be hard to
say that any of this technology is better but you
may need to consider advantages and
disadvantages of each before you buy a projector.
There are also the projectors using LEDs as a light
source instead of traditional lamps. Out of these 3
technologies currently used in projectors' market
at home and office, only two can be regarded as
highly used - LCD and DLP.
9. DLP
DLP ("Digital Light Processing") technology is developed by
Texas Instruments. It has completely different structure
compared to LCD: the DLP chip is a reflective surface made
up of thousands (or millions) of microscopic mirrors. Each
mirror represents a single pixel. Light from the projector's
lamp is goes to the surface of the DLP chip.The mirrors turn
on or off so the pixel is on or off.The colors are generated
through color wheel.
Alse there are DLP projector which use three DLP chips.
Each of it represents three colors - red, green and blue.
Usually 3 DLP chip technology is used in proffesional or
home theater projectors and is much more expensive
compared to 1 chip technology.
10.
11. ADVANTAGE OF DLP
Filter-free design
Sealed projection system. New DLP projectors usually have
sealed and filter-free projection system, so you will never
need to clean or change air filter nor experience problems
related to failed air-filter.
Higher contrast
Less pixelation
Lighter and smaller
12. DISADVANTAGE OF DLP
Rainbow effect
Color wheels can produce rainbow effect. Rainbow
effect (sometimes referred to as color separation
artifacts) are momentary flashes of banded color
that look like rainbows.They occur at random, and
they only last for an instant.This problem tend to
appear only in slower color wheel projectors..
Also, rainbow artifacts problem never appears in 3-
DLP chip projectors thanks to it’s 3 single DLP
chips technology.
13. LCD
Construction of optical system in LCD projectors us
based on an image created using three liquid crystal
matrix LCD panels. How it works? Lamp produces a
powerful light.Then a series of colorful reflections of
light are passed through filters, and lamp creates white
and multicolored reflections on the streams of light
representing the three primary colors - red, green and
blue. Each of these streams is concentrated at one of
the liquid crystal panels. Images from individual LCD
panels are then passed through the lens. In this way the
signal of the video source (PC, DVD, etc.) is displayed on
the screen placed in front of the projector.
14. Until recently, LCD projectors can generate an image with a contrast
ratio of 1500:1,. Latest LCD projectors (home cinema) produce Full
HD 1920 x 1080 pixels resolution as a standard and offers contrast
ratios almost as high as DLP structure projectors.
15. ADVANTAGE OF LCD
-Higher contrast ratio in specific projector models
-Sharper image in specific projector models
16. LCD projector disadvantages
- LCD panel degradation
-Low contrast ratio
the design of equipment, equipping them with high
quality optics.
-High-weight
-Dust blobs
Impurities in panels (dust blobs).. LCD structure
projector should be cleaned every 300 hours of use.
-Color decay
-Limited lifetime
17. Other disadvantages:
Screen-door effect. it is when the lines between pixels
become visible (and as a result seperate pixels become
visible), and this effect becomes distracting.
Dust issues. Due to dust accumulation contrast ratio might be
reduced up to 50% over time.
Dead pixels.You might heard about it while talking about LCD
monitors.The same issue comes to LCD projectors.This
happen when one pixel becomes permanently off or on. If it is
only a single pixel - you might even not notice it.
20. CONCLUSION
If you want the best money can buy, a three chip DLP
projection is the best you can get. From our experience
we tend to think that there are more LCD disadvantages
than advantages. But mainly we sell and work with data
projectors which usually display static views and in those
cases all LCD disadvantages just appear in all of it's glory.
Turning into home cinema market it would be harder to
tell if LCD structure projectors have more disadvantages
or advantages over DLP structure projectors. We
recommend reading about both LCD and DLP
technologies, trying them (if possible) and only then
make decisions.
