The large screen display technology development and application outlined
With network technology, computer information technology, automatic control technology in the coal production enterprises rapidly growing popularity, the mine automation equipment level rapidly rising, local and the whole mine automation system in a growing number of mine applications. As a whole mine production safety and the command center dispatch room, the entire mine is the pooling of information, processing, control centers, various subsystems such as safe production monitoring, industrial television, on the ground of production control, safety monitoring, pump control, tape control, main fan control, closed orbit transportation systems such as letter sets the screen needs command center in real-time scheduling, multi-screen display. Large-screen digital mosaic wall display system can signal will be all types of computers, large screen video signal in the digital mosaic wall that formed a perfect functions, technologically advanced information display management control system, the provision of an interactive human-machine interface , mine scheduling command center fully satisfy the real-time, multi-screen display needs. In this paper, the three generations of mainstream big-screen digital mosaic wall display technology and application for a brief introduction.
CRT large screen display wall system
CRT (Cathode Ray Tube) denote that cathode ray tubes, is the first application of a kind of display technology. CRT projector display color images better, reducing Yes, the geometric distortion with strong adjustment capacity, lower brightness shortcomings is complicated to operate, huge in size and environmental requirements on the installation of high and difficult to 40 m2 area shown above. CRT technology is the early simulation technology, a few years ago had quit the stitching on the big screen walls market, there are only occasionally in some low-end market to see.
PDP large screen display wall system
PDP (Plasma Display Panel) display is a use of gas discharge display devices. PDP display technology advantages: Contrast and brightness are higher than other large-screen display technology box to thin, installed and tested a simpler. Its shortcomings are more obvious: low resolution, and can not be superimposed splicing slot, even with the edge of the latest technology splicing slot also 3 mm, and can only be done 2 x 2 splicing at the middle part of the splicing slot achieve this Stitching the big screen, the frame 5 cm wide splicing slot still not eliminated and the average life expectancy very short time without fault, if a 24 x 7 x 365 work will be running more to shorten their very limited lifespan; large power consumption , the heat also great, so how backplane tops Group fan for heat dissipation, this has also led to greater fan noise. In summary, the PDP display technology as a home big-screen television and small-area flat-panel demonstration equipment have greater development potential, but the product attributes its decision not suitable for use in the need for 24 x 7 x 365 such work running control Room Scheduling.
LCD large screen display wall system
LCD (Liquid Crystal Display) LCD projectors are generally referred to as liquid crystal plate imaging devices, the use of liquid crystal perspective effect, that is, in the liquid crystal molecules with the electric field changes, the impact of LCD modules reflectance or transmittance rate, thus affecting optical properties, have generated different gray level and color images. The current market common LCD projector plate is three-PLCD projector.
The core principle of display technology
LCD technology use analog control, its board by simulating the changes in voltage-controlled valve opening and closing time of the formation of different length gray. Analog signal interference and poor, serious distortion, analog voltage in the accuracy of control there is always unstable and less accurate factors exist.
LCD is a transmission light processing technology, there is a congenital deficiency problem: the brightness loss, optical efficiency generally only about 30 percent.
As LCD technology gap between the very components, resulting image will have a very significant effect of the pixels, thus causing "ScreenDoor".
LCD technology in the liquid crystal molecules response time normally only 15ms, digital micromirror than the response time faster 1,000 times liquid crystal molecules. Because the liquid crystal molecules reaction time is longer, so in the fast dynamic display images in the LCD projector images have Smearing, ghosting effects.
Uniformity of color
Three PLCD projectors use three PLCD plates, each plate PLCD corresponding red, green and blue color in kind. The white light bulbs are divided into red, green and blue color, each color is not the same as the optical path, which led to the distribution of the brightness of each different light, and have the uniformity of color. Uniformity of color measurement is the level of large-screen mosaic wall an important technical level indicators, the use of LCD technology Construction of the large-screen display system splicing wall there are bound to be in the "big Erhualian" phenomenon, which seriously affected the mosaic wall visual effects .
Shade LCD projector three different optical paths, multiple optical spectroscopy and the first mirror, then launched into vertical LCD panels. LCD display three matrix is fixed or through sophisticated screwdriver to adjust, but this arrangement and adjustment of certain errors. After much reflection of light to complete vertical LCD panels actual radio people it is impossible, which would enable the imaging should be a point of red, green and blue color can not be completely displayed on the same point. But poor results gathered through the optical lens was doubled to enlarge.
Optical current structure of most LCD projector used three LCD panels imaging structure, the three board structure clearly need more optical devices, lenses, filters and micromirror to guide the light source to LCD panel. And we must use three panels and data formatting electronic. Therefore, the relative complexity of the optical system, to reduce the volume and weight system, causing a certain obstacles.
Long-term reliability with the passage of time, LCD projector images in the optical performance and reliability are a significant change:
LCD optical modulators caused by the deterioration of the image quality defects, but also appeared in the early operation of this phenomenon;
See LCD screen in the performance change is not gradual. In the normal observation conditions. It is the emergence of sudden and unacceptable. Even if the image is faint yellowing, the naked eye is also very obvious, therefore pale yellow change is unacceptable.
LCD performance degradation, the only solution is to repair or replace the light modulator, which will require users to return the projector manufacturers, and related costs will be expensive.
Prices for LCD system, in addition to replacing light bulbs, but also the need for regular replacement of three PLCD matrix (life around about 3000 h) and the corresponding filter and a series of annexes, otherwise the whole wall color and brightness uniformity can not be adjusted. These expensive LCD panels costs and the complex After-sales Services costs must be added, such as the replacement of the lamp is a series of expenditure users unbearable. LCD projector used earlier, is a relatively mature technology of transmission. Therefore price reduction has been a very small space.
DLP large screen display wall system
DLP (Digital Light Processing) is using all-digital image processing technology, relying on the same resolution the same number of DMD (Digital Micromirror Device) digital micromirror integrity of the reflected light generated images. Because the process is all-digital, so DLP projector functions produce high-brightness, high-contrast, the perfect rich color images. DLP projection technology to the emergence of the times leap from analogue to the digital age, is a major technological breakthrough. In recent years through the extensive application of mosaic wall in the area of large-screen (84 "display unit below) basically replaced the original CRT and PLCD market, as the vast majority of manufacturers and users have adopted the technology and products.
Figures Advantage DLP
Technology is all-digital, digital information can be captured directly from external signal source without going through several Die (D/A) converter, direct modulation imaging, so that the signal attenuation is kept to the minimum so that the noise disappeared. DMD micromirror can flip 50000 times per second and above (0/1 between), and by controlling the number of turns per overturned at the time to produce different levels of grayscale image, showing a clear, sharp, level rich screen display.
Optical Efficiency DLP
Full use of specular reflection imaging principle, there are two light sources working methods, or through a lens of hitting on the screen, or directly into an absorption people, light utilization efficiency of 85 percent or more. TI has introduced the fourth generation deflection angle of 12 °. 7 "DDR DMD progressive scan chips, reflective micromirror structure from 10 ° to 120, to capture more light from the lamp, effectively increase the brightness of more than 20%; micromirror internal adopted Light Eating technology, the Ministry of reducing dark picture the scattering light, again with CRlo. high reflection mirror manufacturing process, the contrast can be promoted to more than 5%.
Digital Micromirror DeviceTM is the core of DLPTM technology. The 0.7-inch semiconductor integrates 786,432 (1024 x 768, XGA) digital micromirror, every pixel DMD chip small size to 14 microns, which used to show that an effective display area of 13.68 microns, the two pixels interval is 0.32 micron. DLP TM Image display technology is very smooth, but more similar to the film results. This is due to the pixel gap between very small and therefore feel that the resolution will be higher than the actual resolution.
DLP TM DMD digital micromirror the reaction time is generally 15-10 cents between Fanny and PLCD technology in the liquid crystal molecules reaction time in 15 ms general, the digital micromirror reaction time faster than the liquid crystal molecules 1000 times.
Uniformity of Color
In the single-chip DLP projector, the three have the same optical light path, so to have better color uniformity. The level of uniformity of color measurement splicing technology is an important indicator for the level of use of DLP technology Construction of the large-screen mosaic wall system to avoid the "Big Erhualian" phenomenon of the generation, continued to maintain color consistency.
The single-chip DLP projector Shade three have the same optical path, there is no convergence problems, not monolithic DlP projection convergence issue, in color on the convergence always better than PLCD projector.
Stitching current DLP big-screen wall projector used by most of the structure using a single-chip imaging than three board structure PLCD projectors require less optical devices, its relatively simple optical system, the miniaturization of the system a great deal advantage.
DMD chip has been tested more than IG cycles, equivalent to 20 consecutive life. But the current DMD has been qualified by all standards semiconductor testing and the actual operating environment simulation conditions DMD obstacles tests, including thermal shock, temperature cycle, tolerance and humid, mechanical shock, vibration and acceleration experiments. With the passage of time, DMD projector images in the optical performance and reliability there was no significant difference.
(1) DMD light modulator in the whole test period, and its image quality noticeably remain unchanged.
(2) DMD performance or with the passage of time remained stable, or as a replacement of the lamp and volatility, which is manifested in evenness area. The current mainstream DLP big-screen mosaic wall lamp manufacturers have a replacement after the automatic adjustment of brightness and color uniformity technology, makes large-screen display system replacing light bulbs in the future will continue to maintain the excellent state factory.
(3) The DLP digital optical processing technology, and we only require users regular replacement bulbs, this can be resumed image quality, the replacement of the lamp in lmin work to be completed within, and the cost of the entire system, the light bulbs cost only a small part.
The DLP digital optical processing technology, the system's consumables only part of the lamp. Early effects of DLP projection technology is the main reason for the popularity DMD chip prices. Along with the fast-growing market capacity, DMD chip production technology matures, the yield increase, DLP projector prices to the annual 20 percent above the speed of decline. DLP continuously improve performance, the price is very stable, we can see that its cost-effective advantages brought about by the strong market position.
In a word, Several mainstream of the above analysis shows that technology is not difficult to see, CRT display technology because of the low brightness, size, installed and tested withdrawal also has been complicated by market competition; PDP technology because of their technical characteristics and could not overcome a wide slot and short life expectancy problem can not Stitching in the large-screen display system application market applications; LCD as a mature second-generation display technologies, but also because of its low-efficiency, long-term use of the reasons for the severe attenuation caused the rapid decline in market share; current DLP technology the market has occupied the leading position in the international field of large-splicing have been used in all the mainstream manufacturers of the technology.
The current DLP technology very much in line with the use of the coal industry user demand for coal mine monitoring dispatch center 24 x 7 x 365 uninterrupted job requirements. First, the DLP technology is the pure digital technology, in line with today's digital technology in the trend of the times and second. The use of the mosaic wall DLP technology with a high degree of brightness and color consistency. Guarantee users in the coal industry shows that some mining information will not chart a result of the deviation of the judgment of the operator error; Finally, the use of large-screen DLP technology mosaic wall display system is cost-effective, low maintenance costs characteristics, protection users invest long-term interests. To believe that the future DLP big-screen Mosaic wall as the mainstream big-screen display system is bound to become the products of choice for the coal industry.