Presented by-REHAN FAZAL

Projectors

(1) Introduction to projectors

(2) Types of projectors

(3) Advantages and disadvantages

(4) conclusion

Table of contents

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

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

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 or WXGA. 4). A very key point is contrast ration.above 300:1 blacks look dark grey. 1000:1 + is excellent.

CRT

The Cathode Ray Tube 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.

. 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

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.

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.

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 

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.

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.

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.

ADVANTAGE OF LCD

-Higher contrast ratio in specific projector models 

-Sharper image in specific projector models

 LCD projector disadvantages - LCD panel degradation 

-Low contrast ratio the design of equipment, equipping them with high quality optics. 

-High-weight 

-Dust blobsImpurities in panels (dust blobs).. LCD structure projector should be cleaned every 300 hours of use. 

-Color decay-Limited lifetime 

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.

DLP

LCD

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.

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