|Sunday, 15 October 2006|
A digital light projector (DLP) includes a digital mirror device (DMD) that receives a demanded image to produce a video image that is projected onto a screen. Different from the liquid crystal display technology, in the digital light processing technology, the light is reflected by the digital light processing chip to form an image on a surface. The key element of this technology is a semiconductor device controlled by a binary impulse adjustment, and this device is called digital micromirror device (DMD). This type of projectors is sometimes referred to as DMD projectors. In a DLP projector, a digital control method and a reflection principle are adopted. A DLP light engine directs white light from a lamp onto a color wheel producing red, green, blue and white light. The color wheel mainly includes a motor, a color filter and a washer. The washer and the color filter are mounted on the motor. The motor includes a housing and a motor body, which rotates together with the housing. Light rays from the light source are collected and focused by the lens to pass through three color filters. The light rays are then projected onto a digital micro-mirror device. Since the DMD includes several movable micro mirrors, driving electrodes may control the tilt angle and deflection time of each movable mirror. Then, the light rays are projected to form an image by switching the direction of the light ray reflections. Each mirror corresponds to a pixel of the projected image. To turn a pixel on, the respective mirror reflects the light into the engine's optics. To turn a pixel off, the mirror reflects the light away from the optics. When the DLP projection system is under a light state, light beams projected onto the micro-mirrors are reflected into a projection lens by these micromirrors and then focused on a screen. When the DLP projection system is under a dark state, these micromirrors are driven by applying a voltage to the driving electrodes and tilted to a specific angle, so that light beams projected onto the mirrors are reflected to other directions instead of reflected into the projection lens. The DMD chip, which is used as a rapid reflective digital optical switch, precisely controls the light in the projector. In the DLP projector, different clamping mechanisms are used to fix the color wheel and the light integration rod in the DLP projector so that the relative position between the color wheel and the light integration rod may be controlled.
A DMD comprising a number of mirror elements with variable light reflection angles adapted to change reflection angles of illumination light according to image signals so as to reflect only the signal light required for forming an image toward a projection lens system is used as image display means (light valve). DMD chips are silicon based chips having movable microelectromechanical mirrors constructed thereon that act as the image forming device. The deformable mirror device is a monolithic single-chip integrated circuit spatial light modulator (SLM), comprised of a high density array of micron square movable micromirrors on micron centers. These mirrors are fabricated over address circuitry including an array of SRAM cells and address electrodes. These rectangular minute mirrors have a high reflectance adapted to change their inclinations within a predetermined angle range according to image signals, which are formed on a silicon memory chip by using the CMOS semiconductor technology. Each mirror of the array is individually controlled to either direct incident light into the projector lens, or to the light absorber. The projection type image display apparatus using the DMD is configured so as to regulate the reflecting direction of light from the light source by changing the angles of mirror elements, such that only desirable reflected light is converged onto a screen. The projector lens ultimately focuses and magnifies the modulated light from the pixel mirrors onto a display screen and produces an image in the case of a display. In a digital micromirror device, light to become signal light is emitted toward the projection lens whereas light (unnecessary light) not to become signal light is emitted into a direction not oriented to the projection lens. In order to eliminate influences of scattering light and improve the contrast, projection type image display apparatus using the DMD are usually provided with a diaphragm member by which the passing area of a luminous flux which can be made incident on the projection lens is restricted to a predetermined range.
Digital light processing (DLP) is a widely used projection technology. The DLP projector is the mainstream portable projector because it enjoys several advantages over other methods including, high brightness, accurate tone reproduction, quick response time, noise-free operation, thin and light composition. A digital light processing (DLP) projector eliminates the pixel mosaic problem of a liquid crystal display (LCD) projector and delivers a higher contrast ratio so as to enhance original color reproducibility, thereby enabling highly bright, clear, and large color images to be obtained in presentations for use in businesses, schools, and advertisements, or in entertainment fields such as movies. The digital micromirror device is a reflective-type optical device with high filling ratio. This property provides a higher luminous efficiency, so that the digital light processing projector can be used in areas which require high brightness and high resolution. Because the DMD can reflect light with a high fill ratio, DMD holds to potential to provide a higher luminous efficiency than other technologies. Digital light processing technology is therefore commonly used in applications needing high brightness and high resolution. The DLP technology typically has better heat dissipation capability than CRTs or flat panel displays so that it can use a light source with higher wattage without reducing the design lifetime of a DMD. The improved heat dissipation ability allows the use of a light source with high watts while not decreasing the lifetime of the digital micromirror device. Unlike the older cathode ray tube projectors, the DLP projectors do not include coated tubes, but instead generate images by beaming light from a lamp to a surface of a digital micromirror device. The DLP projectors are relatively compact in comparison with their CRT counterparts and can produce high quality images without grainy scan lines when images from a standard video source are enlarged to fill a large screen. Moreover, because DLP technology is an entirely digital design, the images produced are more stable and precise than those generated by other technologies.