Projectors

Home and business projectors are not the same. Find out how they differ from each other.

Different technologies: LCD and DLP

There are two main types of projectors available in the modern market; LCD (Liquid Crystal Display) and DLP (Digital Light Processing). Original projectors were based on CRT (Cathode Ray Tube) technology and weighed upwards of 15 kilograms, but they have since been made obsolete by newer technology and are rare nowadays.

LCD, introduced to the market before DLP, functions in a similar way to many rear projection televisions. A small, coloured LCD panel is placed in front of the projector's bulb and the image to be displayed is imposed on the LCD from a notebook, computer or other media device (DVD player, VCR etc). The bulb shines light through the LCD projecting the image into the lens and then out onto the screen. LCD projectors typically operate with three LCD panels, one for each primary colour (red, blue and green). Each panel displays only the parts of the image in its particular colour spectrum and the three images are melded into one via a prism just before the light hits the lens.

Sanyo PLV-Z5

DLP works in a different way. Rather than projecting the light through panels, it's thrown onto the projector chip (a Digital Micromirror Device) comprised of a million tiny mirrors on tiny little hinges. Each mirror represents a different pixel on the screen, and they rotate to direct the light into or away from the lens. In a single chip DLP array -- the most common -- white light from the bulb passing through a colour wheel hits the DMD (Digital Micromirror Device) chip and is reflected out through the lens onto the screen.

InFocus Play Big IN78

The colour wheel rotates, changing the colour of the light (red-green-blue) that reaches the DMD. The DMD regulates the amount of each colour in the image at that point in time. Unlike LCD, the image is not combined before it hits the lens. Instead, it relies on the speed of the colour wheel and how quickly each colour appears on screen. If it is fast enough, it can fool the human eye into seeing only on image, which looks as though it is combined. This all continues many times per second -- the higher the speed the better the image -- resulting in a moving projected picture.

The colour wheel may also include a white light filter to boost brightness. In a three chip DLP array the colour wheel is superfluous, with each colour reflected off its own DMD. While for many people DLP projectors are excellent, some are able to see the flashes of red, green and blue across the image, known as the Rainbow Effect. This effect is caused by the alternating colours not moving fast enough to fool the eye into believing it is one image. For those unlucky viewers, watching a DLP projected image is very distracting and headache inducing. If you are looking at getting a DLP projector you should watch it running and dart your eyes across the image to see if you experience this phenomenon before making your purchase. Some single-chip DLP projectors use a six-segment colour wheel to reduce the Rainbow Effect.

The Rainbow Effect

LCoS (Liquid Crystal on Silicon) is a third technology, but as yet it has not achieved the economies of scale to make it a viable alternative. In LCoS an image is reflected off a mirror through the lens and onto the screen. LCoS projectors typically operate at a higher resolution and are more expensive.

Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Dave Jansen

Good Gear Guide

2 Comments

Hot.com.au

1

They keep getting cheaper

It's amazing to see how much projector pricing has dropped in the last few years. This article was only written in 2007, and the pricing is a little out of date - you can now get great <a href="http://www.hot.com.au/projectors/home/">Full HD home cinema projectors</a> from retailers for a mere $2,500 (as of Feb 2010). I look forward to your next update guys!

Anonymous

2

BenQ Projectors

DLP stoped working on my W5000, benQ do not have parts in stock and have had it for 4 weeks and still have not returned it to me, the Benq 2 year repair warranty is a joke.
I live in Australia.
No NOT BUY unless a REPLACEMENT Warranty is given

Comments are now closed.

Most Popular Reviews

Follow Us

Best Deals on GoodGearGuide

Shopping.com

Latest News Articles

Resources

GGG Evaluation Team

Kathy Cassidy

STYLISTIC Q702

First impression on unpacking the Q702 test unit was the solid feel and clean, minimalist styling.

Anthony Grifoni

STYLISTIC Q572

For work use, Microsoft Word and Excel programs pre-installed on the device are adequate for preparing short documents.

Steph Mundell

LIFEBOOK UH574

The Fujitsu LifeBook UH574 allowed for great mobility without being obnoxiously heavy or clunky. Its twelve hours of battery life did not disappoint.

Andrew Mitsi

STYLISTIC Q702

The screen was particularly good. It is bright and visible from most angles, however heat is an issue, particularly around the Windows button on the front, and on the back where the battery housing is located.

Simon Harriott

STYLISTIC Q702

My first impression after unboxing the Q702 is that it is a nice looking unit. Styling is somewhat minimalist but very effective. The tablet part, once detached, has a nice weight, and no buttons or switches are located in awkward or intrusive positions.

Latest Jobs

Shopping.com

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?