DLP projector color wheel and color processing tec

DLP projector color wheel and color processing technology

I. The basic principle of DLP color wheel technology

as we all know, because DLP adopts DMD micro lens reflection technology, in color processing, single-chip and two-piece DMD methods use color wheel to complete the separation and processing of color

generally speaking, the color wheel is a combination of red, green, blue, white and other color separation filters, which can separate the transmitted white light and rotate it through a high-speed motor, then sequentially separate different monochromatic light on the specified optical path, and finally synthesize 2010 through other optical and mechanical elements and project a full-color image

from the physical structure, the surface of the color wheel is a very thin metal layer. The metal layer adopts vacuum film plating technology. The coating thickness corresponds to the spectral wavelength of red, green and blue. When white light passes through the metal coating layer, the color of the corresponding spectral wavelength will pass through the color wheel, while other colors will be blocked and absorbed, so as to complete the separation and filtration of white light

in the single-chip DMD projection system, the input signal is converted into RGB data, and the data is written into the SRAM of the DMD in sequence. The white light source is focused on the color wheel through the focusing lens, The light passing through the color wheel is then imaged on the surface of the DMD. If the sample is to be destroyed (such as stretching). When the color wheel rotates, the red, green and blue light are shot on the DMD in sequence. The color wheel and video image are carried out in sequence, so when the red light shines on the DMD, the lens is tilted to "on" according to the position and intensity of the red information , green and blue lights and video signals work the same way. The human visual system concentrates red, green and blue information and sees a full-color image. Through the projection lens, the image formed on the DMD surface can be projected onto a large screen

in the two-piece DMD projection system, in order to improve the brightness and make up for the lack of red of metal halide, the color wheel adopts two auxiliary colors - magenta and yellow.; Magenta segments allow red and blue light to pass through, while yellow segments can pass through red and green. The three DMDs use color separation prism without color separation wheel

below, we mainly discuss several color wheel technologies of single-chip DMD mainly used in DLP rear projection unit

II. Several commonly used color wheel processing technologies and characteristics

because the color wheel of a single DMD projector can only process one color at a time, it will bring some loss of brightness. At the same time, due to the difference in the inherent characteristics of the spectral wavelength of different color light, there will be different color restoration, and the picture color often shows that the red is not bright enough. Therefore, how to make the projector not only have sufficient display brightness, but also fully ensure the true restoration of color is a key problem for each projector manufacturer in product design, and one of the most important factors is the design solution of color wheel technology

the following are several commonly used DLP color wheel technologies:

1. Three segment color wheel RGB

is composed of red R, green G and blue B. the design of red, green and blue opening angles of products from different manufacturers are different. Generally speaking, the red opening angle is large, which can make up for the deficiency of image red. The premise of adopting the color wheel technology is that the optical machine part of the projector has sufficient brightness, otherwise it may bring the brightness problem of the image. At the same time, the color restoration of the three-stage color wheel technology is relatively good

2. Four segment color wheel RGBW

is composed of red R, green G, blue B and white W. The purpose of adding white segment color is mainly for researchers to try to develop degradable PUR and further improve the brightness of projectors, which can generally be increased by about 20% compared with three segment color wheel. But at the same time, this color wheel technology will also bring the problem of insufficient color restoration of the projector, distort the image color and reduce the image quality. In addition, in the design, the pulse signal can be synchronously locked in the w segment, and the pulse width corresponds to the w segment width, which can reduce the flicker of the picture to a certain extent. This technology is mainly used in conference rooms and teaching projectors

3, six segment color wheel rgbrgbrgb

because DLP technology is more and more widely used in home theater projection and rear projection TV with great market potential, people put forward higher requirements for the color embodiment and continuous dynamic video picture effect of DLP

six segment color wheel is a color wheel composed of six colors in rgbrgb. With the corresponding increase of color wheel speed (180hz) and more pictures processed per unit time, this design effectively reduces the rainbow effect of moving image and edge, has better video dynamic effect, and the color of image is richer and more gorgeous. However, due to the large separation of six color sections and the large time loss of the light collecting column passing through various color sections, the brightness of the projector is often relatively low. Therefore, a few projector manufacturers began to design and adopt the 7-segment color wheel rgbrggbw technology to improve the brightness of the projector and reduce the flicker of the picture surface. This technology is mainly used for applications with high requirements for household consumption and video

4. Gain color wheel SCR

SCR (sequential color recovery) is also called continuous color compensation technology. Its basic principle is similar to the above color wheel technology. The difference is that the surface of the color wheel adopts Archimedes principle spiral optical coating, and the light collecting column (light channel) adopts special gain technology, which can compensate part of the reflected light and greatly improve the brightness of the system (about 40%). However, the processing technology of the color wheel is relatively complex. At present, only a few projector manufacturers adopt it in their products. From the perspective of technology development direction, this technology has great market potential

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