Until recently projectors were mostly based on LCD (liquid crystal display) technology. With LCD technology, light from the projector lamp is filtered through red, blue and yellow LCD panels to produce a full colour image. Because of the three panels, the projector casing needs to be larger in order to accommodate more room for the electronics.

More recently Texas Instruments developed DLP ("Digital Light Processing") technology. The DLP chip surface is made up of tiny mirrors. Light is reflected from the surface of the chip, into the projector lens, and straight into a full colour image. This allows manufacturers to make much smaller projectors.

The downside of DLP is that the accuracy of the colours produced is not as accurate as many LCD projectors. In some cases green can look close to yellow.

Q. What is an LCD panel?

A translucent glass panel that shows a computer or video image using a matrix of tiny liquid crystal displays, each creating one pixel ("picture element," or dot) that makes up the image. Used with an overhead projector for a light source, an LCD panel can make an economical and very effective computer projection device. It also refers to the smaller panels used internally in todays LCD video projectors.

Q. Are there different kinds of lamps for projectors?

Up to now, most projectors used metal halide lamps. With the introduction of the UHP (Ultra High Pressure) lamp, which uses less power, lasts longer, has a noticeably less light output drop-off, and actually produces more light, there are more reasons to select UHP over metal halide.

Q. How long does a projector lamp last?

Metal halide and Ultra High Pressure (UHP) lamps are the two light sources for projectors and offer a life of 750 - 4,000 hours or longer. Typically, the longer a lamp lasts, the more expensive it is.

Good question. It all comes down to your eyes. Projector brightness, measured in ANSI Lumens, refers to an average of total brightness on a 40" diagonal standard size screen. Although one projector may offer higher lumens than another, your eye will be the best judge.

Q. What is the difference between an active-matrix versus the passive type LCD projection system?

An active-matrix system offers sharper, cleaner, higher contract and deeper color images. Overall, this type of system offers faster response speeds and is suitable for multimedia, animation and video. The price is now as affordable as the older passive type LCD projection systems.
Active-matrix systems use either Amorphous Silicon (A-Si) or Poly Silicon (P-Si) in the liquid crystal formulations; the newer P-Si material offers brighter images.

Q. What is horizontal and vertical resolution?

Computer and video images are made up of horizontal and vertical rows of Picture Elements (pixels). Resolution is limited by the number of distinguishable rows that the monitor or LCD device can form. Horizontal resolution refers to the number of distinct lines that you can count going across the image. Vertical resolution measures the number lines you can count from the top to the bottom of the image.

Q. What is pixel mapping?

Pixel mapping is a form of compression that uses computer algorithms to map high resolution computer images to a lower resolution LCD. Pixel mapping offers the best results when lowering resolution by one step i.e. 1024x768 to 800x600 delivers a very clear image through an LCD.

Q. What is keystoning?

Keystoning is when the image you are projecting appears wider at the top or bottom as a result of the projector being positioned somewhere other than the center of the screen. Many projectors allow you to adjust keystoning and some offer fixed keystone factor (allows you to place the projector at about 8 degree angle lower or higher than the center of the screen).

Because your desktop computer monitor does not have the internal circuitry to output to both a screen and the monitor itself, a loopthrough output is often used to operate a desktop computer monitor at the same time the computer image is being projected onto a large screen. Another way to loopthrough is to use a projector specific, Y-cable with the projector, which splits the signal between the monitor and your large-screen device.

Q. Why isn't my projector starting up?

Often, your projector will behave this way when the filter door of your system has not been shut completely. A safety switch will prevent the projector from starting up. So, check that your filter door is properly secured.

A wireless mouse control generally works off the same controls that operate the other functions on your projector. The advantages of having a wireless mouse make it a useful device for presenters as it allows you to operate at a distance from your computer and gives you both flexibility and control during your presentation.

First, make sure that your laptop is turned off and you have connected everything correctly.

Second, turn on everything else and save the laptop for last. Third, if your laptop allows simultaneous display via the projector and on the laptop screen, disable the internal display and make sure everything is working correctly. Sometimes, the simultaneous display capability can affect the workings of the whole system depending on the type of laptop and projector being used.