Projection television takes home cinema to its ultimate limits. No longer is the viewing experience restricted by the physical constraints imposed by a TV tube. With a front projector system an entire wall of your lounge becomes your TV screen. Movies appear as they would in the auditorium of a cinema. You view in total darkness for the best effect. Although there are some models which incorporate a tuner and audio amplifier, this is rare. To casually watch TV you must use the tuner in your VCR for video and your AV amplifier for sound.
Video projectors fall into two categories. Tubed and LCP (liquid crystal projection). Both have unique advantages that affect installation and performance. The tubed projector is a box sporting three lenses. They focus separate red, green and blue images on to the screen to build a TV image as large as you like. It is this type of projector that is commonly used in cinemas and at public displays. On these models, there's more to the optics than meets the eye. As each lens is on a different axis, the pictures don't naturally overlap. An electronic means for converging the picture is therefore provided and a pattern generator produces a grid which has to be focused and aligned so the squares are geometrically true. The process is repeated for all three tubes. If you're inexperienced it can take many hours and if you move the projector you must start again from scratch.
Consequently, tubed projectors are fixed assets usually installed by experts then rarely touched. As the lenses are wide angle, they provide big pictures close to the screen - typically a 60in picture at 2.5m. Typical mountings include ceiling fixing or even floor mounting in the middle of the room.
Your other projection option is more user-friendly. An LCP can be moved from room to room and requires no more set-up than a slide projector. At the heart of the LCP are a number (usually three) of liquid crystal panels. All are illuminated by a single high-wattage metal halide lamp. A complex series of dichroic reflectors and filters split the spectrally pure white light into rays of red, green and blue. Each of these beams illuminates a liquid crystal panel. The images from the panels converge at the focal point of a single lens. Focus and zoom are provided and on many models are controlled via an IR handset.
The disadvantage of LCP has been the so-called 'chicken-wire' effect. Superimposed upon the image is a criss-cross network of pixels or image elements. It is these individual cells that form the picture and, when magnified by the lens, they can become rather obvious.
more infomation you can see>>
http://www.projectorbuyingguide.com
An Introduction to Projection Technology
Hitachi CP-RS55 LCD projector
CNET editors' review
Reviewed by: Rich Malloy
Edited by: Felisa YangReviewed on 4/5/05
Release date: 12/1/04
Hitachi positions its Performa CP-RS55 as a dual-use projector, best applied to business situations but quite handy in the living room, as well. We might go a step further: in view of its compact size (11.2 by 8.0 by 3.2 inches)--not much larger than a cigar box--this 4.8-pound model is also well suited for mobile applications. Add to that a record-low price tag that occasionally dips below $800, and we might just call the CP-RS55 a basic, one-size-fits-all business projector.
Inside the stylish but understated silver-gray case is an LCD imaging engine, part of the reason for the projector's low price. Hitachi has upgraded this venerable technology with what it calls Progressive Scan Technology, which promises reduced flicker. Nevertheless, CNET Labs' tests revealed the typical trademarks of LCD technology: superior color handling (particularly with blues, in this case), a significant screen-door-like grid effect on projected images, and a lower-than-average contrast ratio (only 192:1).
Another traditional LCD drawback inherited by the Hitachi is the need for regular cleaning of the cooling fan's air filter. In other words, this model is better for tabletop use than for ceiling installations with limited access.
The CP-RS55 comes with a decent but spartan set of connectors and cables. The standard connectors (VGA, S-Video, composite video, and audio) are all present and accounted for, though the projector ships with only one VGA cable and an AC cable. The only surprise is an RS-232 port labeled Control, which, with an optional cable, enables you to control the projector either locally or via a network.
As you might have guessed by now, the old adage still stands: you get what you pay for, or in this case, you don't get what you don't pay for. The CP-RS55 lacks many of the features you would normally expect with projectors, such as a carrying case, a laser pointer, or optical zoom. The top panel of the projector has only three buttons, one of which toggles in four directions for menu navigation. This button deficiency is compensated for by the oversize remote control, which bristles with no fewer than 24 buttons. But unlike the remotes that come with the BenQ PB6110 or the InFocus X2 budget projectors, not one of these many buttons can page through a PowerPoint presentation, which is an egregious oversight for a business projector, budget or otherwise. Instead, they are dedicated to dubious features such as digital zooming and image freezing. You'll have to rely on your laptop or a mouse to page through presentations.
Despite cost-cutting, the Hitachi did well in our Labs tests, falling only a little short of its impressive advertised brightness of 1,500 ANSI lumens. In fact, even in its low-power, lamp-friendly Whisper mode, the CP-RS55 was able to outshine the Toshiba TDP-S20U. We also appreciated the CP-RS55's surprisingly short warm-up and cool-down times of only 22 seconds and 1 minute, 16 seconds, respectively. This model also runs quite cool; we noticed some warm areas near its fan exhaust, but nothing that was uncomfortably hot. In our tests, the greens produced by this projector seemed a bit yellowish, but our colorimeter showed that it handles reds and blues remarkably well. Contrary to what Hitachi claims, we did see a small amount of flicker, but nothing beyond the ordinary.
The Hitachi Performa CP-RS55's replacement lamp is rated for 2,000 hours of use, half that of other projectors. Hitachi charges $199 for the lamp, which works out to about 10 cents per hour--not exactly cheap, but better than average. Changing the lamp is fairly simple: you only need to remove three screws. Hitachi bundles the projector with a two-year warranty, but the lamp is covered for only 90 days or a surprisingly short 180 hours of use. The company's Web site lists only limited support services, such as replacement parts and accessories for the projector, but it does not indicate how to purchase them or what they cost. To get more information, you must fill out an electronic form or send an e-mail message to one of the tech-support mailboxes listed there. Toll-free phone technical support is provided seven days a week, from 8 a.m. to 8:30 p.m. CT.
Sony VPL-VW50 "Pearl" (LCOS)
Sony VPL-VW50 "Pearl" (LCOS)
Advantages:
Excellent black level and contrast.
Excellent color saturation.
Pixel-free (feature of LCOS technology)
Quiet fan
Powered 1.72x zoom and 2-picture height lens shift allows for reasonably good installation flexibility
Powered zoom enables 2.35 CIH image management without needing an anamorphic lens.
Good connectivity: 2 HDMI, one VGA (RGB/component), one component
Issues:In most cases, rear-shelf mounting will be preferred. Since vertical lens shift is limited to two picture heights, most ceiling mount installations will require an extension tube drop unless it is a low ceiling to begin with. This is the largest of the 1080p projectors in the group, and suspending it mid-air may prompt aesthetic objections from others in the household.
Not one of the brightest 1080p models in the group—about 400 lumens in optimal video calibration with lamp on high, and zoom lens set to wide angle. Loses 25% of its light potential when the lens is set to maximum telephoto position. Loses another 35% in low lamp mode, which most users won't want to lose, so plan to run in full lamp power mode.
In this group of 1080p projectors, the Sony has the softest image with HD content. Some people call this a "film-like" image. Others prefer a sharper picture. This is a matter of personal taste and preference.
Summary:The Sony Pearl is capable of producing a dazzling, rich, dynamic image with black level, contrast, and color saturation as particularly strong characteristics. In these aspects it outperforms the LCD competition. Weaknesses include HD image softness, limited lumen output in some video-optimized operating modes, and limited vertical lens shift which limits options for ceiling mounting.
Panasonic PT-AE1000U (3LCD)
.jpg)
Panasonic PT-AE1000U (3LCD)Editor's Choice
Advantages:
Excellent sharpness/detail with HD material (among the best)
Outstanding, clear, noise free DVD and other SD sources
Pixel-free due to "Smooth Screen" technology
Powered 2x zoom provides maximum installation flexibility
Powered zoom enables 2.35 Constant Image Height image management without needing an anamorphic lens.
Good connectivity: 2 HDMI, 2 component
Very low fan noise.
Low street prices. Only the Epson Home 1080 is less expensive.
Three year warranty effective as of 4/18/07--matches the longest warranty in the group.
Issues:Brightness is a very ample 500 lumens with the zoom lens set to wide angle. However, it loses 45% of its brightness at maximum telephoto. Caution should be used in designing the layout. The AE1000 will easily illuminate a 120" screen from 12 feet, but not from 24 feet.
Black level and shadow detail are comparable to the other 1080p LCD offerings. Performance in these areas is very good by historical standards, but falls short of what is being achieved by the DLP and LCOS competition.
--- ADVERTISEMENT ---
Summary:Wins Editor's Choice Award due to a combination of four compelling competitive advantages: (1) low price, (2) excellent installation flexibility, (3) a sharp, competitive HD image, and (4) a uniquely outstanding, noise-free image with DVD and other SD sources that clearly beats the competition. Of these, the AE1000's performance in SD was the deciding factor for us. However, if you are primarily concerned with HD performance and don't care as much about SD, then other models in this list have as much or more to offer than this one.
Optoma HD81 (DLP)
.jpg)
Optoma HD81 (DLP)
Advantages:
Very bright in video optimized mode, excellent for very large screen theaters.
Maintains excellent black level and contrast despite high lumen output.
Very sharp image
Subtle pixelation, but not visible at normal viewing distances.
Outstanding connectivity, best in the group, due to separate video processor
No air filter to clean or replace, significantly reduces maintenance.
Excellent standard three year warranty—longest in the group.
Street prices have dropped, and it is a superb value for the money.
Issues:The only serious limitations on the HD81 are the short 1.2x manual zoom lens and no lens shift. But the short, bright lens is part of the trade off to get the very bright lumen output. Nevertheless, the lens configuration virtually mandates a ceiling mount installation. The projector must be located with precision relative to the screen in order to avoid tilt and keystone correction.
Fan noise in full lamp mode is higher than average, and heat output is higher as well due to a 300W lamp. Both of these factors argue for installation in a larger room with a larger than normal screen, say up to 150" diagonal. However, if operating in low lamp mode, fan noise and heat are non-issues
Summary:With the recent street price reductions, the Optoma HD81 is now a highly competitive option in the group, much more so than it was when first released. Accordingly, we have just re-rated it, giving it the full 5 stars for Value. Picture quality in general is first rate, with excellent sharpness and color dynamics. If you are planning to ceiling mount your projector, give this one strong consideration. If you want a rear shelf mount, look elsewhere.
Mitsubishi HC5000 (3LCD)
.jpg)
Mitsubishi HC5000 (3LCD)
Advantages
Sharpest HD image we've seen on a 1080p projector under $10K
Excellent color saturation
Flawless deinterlacing
Brighter than average lumen output in the group.
Powered 1.6x zoom/focus and 2.5 picture heights of vertical lens shift for very good installation flexibility
Powered lens allows optional 2.35 CIH image management without anamorphic lens
Can be ceiling mounted or rear shelf mounted with ease.
5,000 hour lamp life in eco mode, and bright enough to fill a 120" screen in eco-mode.
Almost silent fan, even in full power mode.
Available in either black or white case to match your room décor.
Minimal pixelation, not visible at normal viewing distances.
Issues:Black level and shadow detail are comparable to the other 1080p LCD offerings. Performance in these areas is very good by historical standards, but falls short of what is being achieved by the DLP and LCOS competition.
Summary:The finest home theater projector yet produced by Mitsubishi, and an exceptionally competitive offering with the sharpest HD image in the group. For most theaters there will be ample lumen output to run in eco-mode to gain the advantage of the 5000-hour lamp. While black levels are not as deep as the DLP and LCOS competition, this only becomes apparent in side by side viewing. Standing alone, the HC5000 produces a beautiful, thoroughly absorbing image.
See current dealer prices on the Mitsubishi HC5000BL
JVC DLA-RS1 ("D-ILA" LCOS)
JVC DLA-RS1 ("D-ILA" LCOS)Editor's Choice
Advantages: 
Outstanding contrast and black level, the best in the group
Outstanding color accuracy and saturation, the best in the group
Excellent sharpness/detail with HD material (comparable to DLP competition, and just shy of the razor sharp Mitsubishi HC5000)
Very high lumen output potential, among the brightest in the group in video-optimized operation
Manual 2.0x zoom lens and 2.67 picture heights of vertical lens shift provides excellent installation flexibility
D-ILA technology delivers pixel-free image
Almost perfectly calibrated to D65 out of the box.
Good connectivity: two HDMI, one component
Issues:The most expensive of the 1080p models in this group, but with premium price comes premium performance.
No powered zoom/focus/shift like some of the competition. A non-issue unless you have a 4:3 or 2.35 screen and want to control the size of different aspect ratio materials with zoom lens adjustment.
Summary: