Rear Projection Tv

Introduction To Dlp Rear Projection Tv

DLP stands for Digital light Processing and it is technology that is used in projectors and video projectors. It was first introduced by Dr. Larry Hornbeck in 1987 at Texas Instruments. DLP applications are used in DLP front projectors which are small standalone projection units. In today's HDTV market, the rear-projection technologies compete against LCD and Plasma flat panel displays.

DLP technique

The actual video image is displayed on a semiconductor chip called Digital Micromirror Device (DMD). Every pixel on a DMD chip is a reflective mirror. The micro mirrors on the chip tilt very rapidly as the image changes. As a result, the grayscale foundation is produced for the image. Then the color is added as light passes through a high-speed color wheel and is reflected off the micro mirrors present on the chip as they rapidly tilt towards or away from the light source.

The degree of tilt of each micro mirror combined with the rapidly spinning color wheel gives the color structure of the projected image. As the amplified light bounces off the micro mirrors, it is sent through the lens, reflected off a large single mirror, and onto the screen.

Other key elements involved in DLP

1. Projection lenses - These lenses are used to magnify the projected image. Four to five lenses are used in rear-projection TVs to maintain shape and brightness integrity of the image. Single lens makes things look good in the center of the image, but as the light and image content is scattered across the screen area, additional lens elements are required to maintain the overall image shape. The benefit of using combination of several lenses is to manage and control the high temperature variations from both internal and external factors.

2. Mirrors - Even though the surface is large, but the space provided to project an image is relatively small. So, a mirror is placed in the path of the projection element, magnifying lenses and the screen to be placed at the bottom of the projection television cabinet. This makes the projected image larger on the screen to view it correctly.

3. The Screen - The screen is made up of two elements: the inner Fresnel surface that magnifies and scatters the brightness of the image along the screen; and the outer lenticular surface that helps in the final shape integrity of the image and also contrast and the wideness of viewing angle.

4. The Box - The box is used to seal all the elements. Its size depends on the size of the screen surface itself.

Merits

- Smooth, jitter-free images. - Perfect picture and excellent grayscale linearity can be achievable. - Smaller, thinner, and lighter than CRT projectors. - Cost is considerably less than LCD or plasma flat-panel displays.

Demerits

- Some devices may create fan noise. - Silk screen effect. - Screen door effect. - Dithering noise may be created, especially in dark image areas.