Analysis and Prospect of the hottest DLP projectio

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Analysis and Prospect of DLP projection technology

Abstract: This paper introduces the application of DLP (digital light processing) technology in projection equipment, deeply analyzes its advantages and disadvantages, and prospects the development of this technology

key words: DLP DMD MEMS projection


dlp (digital light processing) lead screw and nut as performance parts. This technology, originally developed under the auspices of the U.S. military for weapons manufacturing, was introduced into the manufacturing of civilian projection equipment at the end of the last century. The principle of this technology is not complicated. The difficulty lies in the complex manufacturing process of DMD (digital micromirror device), the core component of this technology. This kind of MEMS (micro electro mechanical systems) device produced based on semiconductor process is currently only mastered by TI company, so the cost is high. However, the advantages of using DLP technology to manufacture projection equipment are its high light utilization, simple light path design and better imaging quality. Therefore, although DLP projection technology entered the market later than CRT and LCD projection technology, it has achieved amazing growth. In 2004, more than 2million DLP based projectors were sold, and the growth momentum has not stopped. It can be predicted that DLP will occupy an important position in projection technology and gradually dominate this market. Figure 1 shows the demand analysis of rear projection TVs of various technologies

dlp projection technology

the success of a projection technology depends on the design and manufacture of display panels, optics and driving circuits. So, does DLP projection technology have advantages or disadvantages in these three aspects

first of all, in terms of display panel, it can be said that DLP has no advantage in cost. In addition to the difficulty of DMD growth, which limits its yield and integration, its packaging, storage and transportation need special treatment, so the high cost can be imagined. The complexity of other display technologies is much lower. Changhong in China has long mastered the manufacturing of CRT projection guns, and the manufacturing of LCD display panels is no secret to Japan, South Korea and Taiwan. Although the production technology of LCD micro display panels is more difficult than that of ordinary TFT LCD panels, it is just around the corner for domestic manufacturers to master this technology

how about the performance of DMD panel? In terms of resolution, DMD is currently difficult to achieve high resolution. The integration of mainstream products is about 500000 pixels, while lcd/lcos is relatively easy to achieve high resolution. In order to meet the display requirements of high-definition images, Ti adopts smooth picture technology to improve the resolution. To be exact, smooth picture does not improve the physical resolution of the panel, but allows an image to be displayed in two times, and then by setting a dithering mirror on the optical path, the two pictures are staggered, time-sharing and superimposed together, as shown in Figure 3. For example, CRT imaging is actually the result of a point that is high-speed and convenient to detect movement. From the actual effect, the image quality of using smooth picture is good, and the production cost is greatly reduced. Therefore, this technology is used in all panels after hd3, and the physical resolution of these panels is half of the nominal, but you can't say this is fake, because you can't say that the resolution of CRT is 1

Figure 3 smooth picture doubles the resolution by time-sharing interleaving and superposition of images.

from the perspective of light modulation method, DMD is a passive reflective light intensity modulation, which produces the difference between light and darkness by different angles of light reflection from the pixel mirror, and then produces different gray levels by controlling the length of light and darkness. Compared with the transmission panel, this modulation method can produce higher contrast and light utilization. In addition, the response time of the digital micro mirror is faster, it can rotate thousands of times per second, and the moving image will not appear smear, so the imaging quality of DMD is high. From the perspective of cost performance, DLP technology is equivalent to LCD but higher than other technologies

secondly, DLP is the most concise optical design. Most DLP projectors adopt single panel imaging design, as shown in Figure 4. This design based on the principle of time mixing color should not be a boastful technology, because the use of color wheel to produce red, green and blue primary colors in sequence, which are modulated by the panel, and then high-speed mixed imaging greatly wastes light energy. Its theoretical value of light efficiency is only one third, which is not as good as Philips LCOS prism design, It is not as good as the common use of three panel LCD projector light splitting and combining design. But its advantage is that the design is simple, the cost of using only one panel is low, and the volume can be designed to be very small. From the performance analysis, the optical design of color wheel mode not only has low light utilization, but also has problems such as flicker, edge dispersion of high-speed moving objects and so on. However, ti will adopt technologies such as multi primary color display and improving video refresh rate to reduce the above problems. In addition, there is no convergence problem in single panel imaging, so the optical mechanical cost performance of DLP projector has great advantages

Figure 4: DLP projector with single DMD panel using color wheel

finally, analyze the driving technology of DLP projection. Due to the complexity of the panel and the imaging process, the DLP driving technology has also become complex. In addition to the fact that DMD driving requires two different driving chips, analog and digital, the control and synchronization of the color wheel, the control of smooth picture, Rambus or reduced latency DRAM high-speed frame cache, the connection between the surface board and the circuit board all require more complex hardware design, such as the high dependence on the import of raw materials and even software programming control, This undoubtedly increases the cost and difficulty for projector manufacturers. In contrast, the drive of other types of projectors is relatively simple, and it is less difficult to produce, assemble and debug. However, the drive part accounts for a low proportion of the total cost of the system, so the DLP drive puts forward higher requirements for the technical strength of manufacturers to a large extent

Figure 5 Schematic diagram of DLP projection drive board


through the analysis of DLP projection technology, we conclude that DLP is the best projection technology at present in terms of performance, but due to the complexity of the technology, its cost has always been the main problem perplexing its development. It can be predicted that DLP projection will develop in two directions. First, new technologies will be adopted to continue to reduce costs. For example, Zhao Ping, director of the International Trade Research Department of the Research Institute of the China Council for the promotion of international trade, said that the current gold shell packaging process and similar smooth picture technology will be adopted, so that it can compete with other projection technologies and even large screen display technologies such as PDP; On the other hand, DLP will enter more non price sensitive projection equipment, such as digital cinema, meteorology, disaster relief command and other fields that need super large screen display. In these fields, DLP projection technology can give full play to the characteristics of high-quality display. (end)

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