Different Projectors Technology Explained

At present, projectors can be classified into two categories: Liquid Crystal Display (LCD) and Digital Light Processing (DLP). There are a few technical differences between the two projection technologies.
A new projection technology, jointly developed by several vendors particularly JVC and Hitachi, is LCOS (Liquid Crystal On Silicon).

LCD PROJECTION TECHNOLOGY is used by many manufacturers such as Epson, Sanyo, Sony and Hitachi. It contains three separate LCD glass panels, one for red, green and blue components of the image signal being transferred to the projector. As the light passes through the LCD panels, individual pixels can be opened to allow light to pass or closed to block the light. This activity modulates the light and produces the image that is projected onto the screen.

LCD technology is "transmissive".

Advantages:

• LCD is typically brighter than DLP for the same lamp white light intensity.
• The picture is sharper when compared to a DLP projection, however may be offset by the screen door effect.  
• Better color saturation than DLP. No color wheels.

Disadvantages of LCD

• Suffers from the "screen door" effect, meaning, if you are viewing the image through a screen door because of the black space between pixels, as resolutions improves, the "screen door" pixelization effect becomes less of a problem.
• Being transmissive in nature, not all white light is blocked; blacks are not as black as they could be.
• LCD panel may degrade time, particularly for the blue colorant, it may cause color balance problems and loss of contrast over time.

DLP PROJECTION TECHNOLOGY can be found in projectors from manufacturers such as BenQ, InFocus and Optoma. The world's only all-digital display solution uses an optical semiconductor, known as the Digital Micro mirror Device, or DMD chip to recreate source material.

DLP projection technology is "reflective".

Advantages of DLP

• Blacker blacks than LCD, meaning great contrast ratios. Mirrors can reflect light away from the path of projection, not allowing white light to pass through as in LCD.
• Compact. One array of mirrors for all colorants rather than one array for each colorant (like LCD). Great for mobile projectors.
• "Screen door" effect not as evident. As resolutions improve, the "screen door" pixelization effect becomes less of a problem.

Disadvantages of DLP

• Rainbow effect. Color wheels spin quickly between the primary colorants to create a color, with each primary color remaining for a fraction of a second. This is usually fast enough for the human eye not to notice, however some do and it can be very irritating.

LCOS PROJECTION TECHNOLOGY, a newer technology, used mostly by Canon, is similar to both DLP and LCD designs. Liquid crystal is placed on a mirror substrate that is used to reflect incident light. Like LCD projectors and high end DLP projectors, there is one LCOS chip for each colorant.

Advantages:

• Smoother image. The pixel edges are not as sharp as DLP pixel edges.
• Little "screen door" effect. Mostly due to the higher resolutions and smaller dot pitch.
• No rainbow effect because there is no color wheel.

Disadvantages:

• Limited lamp life
• Not so good contrast ratios
• Expensive