There are several types of projectors that can be used for presentations or entertainment. A front projection projector is good for large audiences but makes interaction difficult. A rear projection TV projects an image through lenses and mirrors to create a large screen image in a shallow depth. CRT projectors use small color CRT tubes to focus and enlarge the image onto the screen, while LCD projectors send light through a prism to separate colors and display the image. DLP projectors use a digital micro-mirror device to project images. The brightness level in lumens is an important factor, as is the throw distance between the projector and screen. Projector lamps are a key component that transfers the image to the larger screen.

1. PROJECTOR'S

2. FRONT VIEW
From an entertainment point of view there is probably nothing more impressive than
going to a first run cinema (front projection) and being enveloped by the large screen
and catchy plot. That's great if the purpose is for entertainment or large scale
audiences. However, if the purpose is to explain a project topic or concept, a different
system may be desired. When we are giving lectures or presentations we tend to move
around and interact with our slides and graphics

3. REAR VIEW
A large-screen TV set that uses one of several technologies for generating the
image. All methods yield larger screens than the one-tube, direct view CRT
TV, which reached a practical limit of 36". The depth of rear screen sets is
reasonably shallow because the image is projected through a series of lenses
and mirrors that flip it back toward the screen.

4. CRT
A CRT projector is a video projector that uses a small, high-brightness CRT
(or picture tube) as the image generating element. The image is then focused
and enlarged onto a screen using a lens kept in front of the CRT face. Most
modern CRT projectors are color and have three separate CRTs (instead of a
single, color CRT), and their own lenses to achieve color images.
The red, green and blue portions of the incoming video signal are processed
and sent to the respective CRTs whose images are focused by their lenses to
achieve the overall picture on the screen.

5. LCD
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. To display images, LCD (liquid-
crystal display) projectors typically send light from a metal-halide lamp
through a prism or series of dichroic filters that separates light to

6. DLP
Digital Light Processing is a brand of projector technology that uses
a digital micro mirror device. It was originally developed in 1987 by Dr. Larry
Hornbeck of Texas Instruments. DLP is used in a variety of display
applications from traditional static displays to interactive displays and also
non-traditional embedded applications including medical, security, and
industrial uses.

7. LUMENS
A major factor in choosing a projector for a particular audiovisual
presentation application is the level of brightness that the projector is capable
of outputting. You may have seen brightness specifications quoted in ANSI
lumens and wondered what these are and how they are defined. This Bamboo
AV advice article should enable to you to make accurate comparisons between
multimedia projectors of varying levels of brightness.

8. THROW
In film terminology, throw is the distance of a movie projector from the
screen. It is the distance the image is thrown onto the screen, and it has a large
effect on screen size. Often in home theatre individuals lack the correct throw
distance in the room but can buy a short throw lens. There are also "long
throw" lenses available. A related term, throw ratio, refers to the ratio of the
distance to the screen (throw) to the screen width. A larger throw ratio
corresponds to a more tightly focused optical system.

9. LAMP
A projector lamp is used to transfer an image from a multimedia projector
onto a larger screen for an audience to view. The projector lamp has been
used in businesses and educational organizations for many years in order to
help convey information to an audience. The projector lamp is also used for
movie or home theaters, where it sends DVD or film images to a large screen
for all to see. The technical description of a projector lamp is that it is an
ultra-high pressure mercury vapor ARC lamp.
Projector lamps are scientifically
categorized as metal halide lamps and
Philips has trademarked the name
"UHP lamp" for their projector lamps.

10. WERE I GOT THINGS
http://www.ta-inc.com/newshtml/frontvsrear.htm
http://en.wikipedia.org/wiki/CRT_projector
http://en.wikipedia.org/wiki/LCD_projector
http://en.wikipedia.org/wiki/Digital_Light_Processing
http://en.wikipedia.org/wiki/Throw_(projector)
http://www.bambooav.com/explaining-brightness-and-ansi-lumens.html
http://www.hd-tv1.com/wp-content/uploads/2011/01/projectors-for-home-
theaters.jpg
http://www.princetonlighting.com/news/what-is-a-projector-lamp-68.html
http://www.projectorlampexperts.ca/images/site/Ple/major-components-04.png
http://www.pcmag.com/encyclopedia_term/0,1237,t=rear-
projection+TV&i=50285,00.asp
http://static.ddmcdn.com/gif/projection-tv-rear-projection.jpg