An academic lecture hall is designed as 380 (person), with a building area of ​​880m2, a height of 12m, a stage width of 22m, a depth of 9m, and a width of 16m. The design needs to meet the requirements of use. The main functions include: academic report, graduation ceremony, large-scale Conferences, small art performances, film screenings, etc. In order to meet the requirements of multi-functionality, the design scheme adapts to various application requirements of users, and the video and audio are all required to meet the high-definition requirements. The effect of the video display system is particularly important. There are many kinds of current display technologies, and the following is how to determine the final selection. A discussion. At present, the mainstream large-size video high-definition display technology mainly includes: small-pitch LED screen, DLP splicing screen, liquid crystal splicing screen, projection fusion screen, large-size liquid crystal display, etc. , each of which has advantages and disadvantages, and is suitable for different environments. The comparison of its main technical performance indicators is shown in Figure 1. 1. Visual seam problem Both LCD and PDP have physical and optical seams. The LCD seam is currently at a minimum of 3.5mm (Editor's Note: The current LCD minimum seam is 1.4mm), DLP is slightly better, can reach 0.5~1mm, multi-screen projection is processed. When properly used, the splicing area can be disposed of; the small-pitch LED display technology can realize optical stitch-free stitching. Although the large-size LCD screen has no physical and optical seams, the large-area display size is limited. 2. Display effect From the indicators of grayscale, contrast, brightness, refresh rate, etc., DLP rear projection and projection fusion technology display the worst effect (the worst attribute determined by the physical properties of the projection), LCD display is better, but after long-term use, due to The brightness is attenuated and dark edges and black corners appear. In addition, brightness and color difference will appear between the screen and the screen, while the human eye is sensitive to the difference. The gray scale, contrast, refresh rate and other indicators of the small pitch LED display technology are very good. Well, you can solve the light fade problem by point-by-point correction, but there are two problems: (1) Dead light: The standard of the death rate of LED display is generally one ten thousandth to three ten thousandths, but the small pitch LED standard needs to be greatly improved. Take the P2.5 size small pitch LED display as an example. There are 160,000 lamp beads per square meter; if the distance is further up to 1mm, there are 1 million lamp beads per square meter. At this time, if you press the LCD "no more than 3 bad points" standard requirements, LED The display screen is almost impossible to reduce the dead light rate to three parts per million, but since the general screen area is at least tens of square meters, the viewing distance is generally about ten meters, and the effect can be appropriately relaxed. (2) Contradiction between brightness and gradation: Since it is often necessary to watch the display for a long time, and the indoor illumination is low, the brightness of the LED display should be greatly reduced. The brightness of the reference TV is 350cd/m2~500cd/m2; DLP stitching brightness It is 250 cd/m2 to 400 cd/m2; the brightness of liquid crystal splicing is 450 cd/m2 to 700 cd/m2. LED as a self-luminous display technology, unlike passive illuminating, the human eye is more sensitive, so it requires a lower brightness to be comfortable for the human eye. Generally, the level below 300 cd/m2 can achieve the best viewing effect of the human eye. Grayscale loss occurs in the picture, and as the brightness decreases, the gradation loss becomes more and more serious. When the brightness is reduced to less than 200 cd/m2, the gradation loss of most of the display screen is extremely large, and the image quality is almost "unsightly". How to achieve the minimum loss of gray level at the brightness level of 300cd/m2 is a bottleneck for LED display manufacturers, which is the key to adopting this technology. 3. Resolution DLP and LCD all have higher resolution, while small-pitch LED technology is composed of lamp beads because of the pixel points. Therefore, the resolution may be lower than other technologies under the same cost. Unless the small-pitch LED size is large enough, such as command, control, monitoring, etc., the display often needs to match the standard resolution signal output by each subsystem, such as the 1080P signal of the HD camera, and within the specified size, the standard LED The display cabinet may not be stitched out to the required standard resolution. 4. Cost issues Among all indoor large-screen display solutions, the lowest cost is LCD splicing and multi-screen projection fusion, followed by PDP splicing. At present, the small pitch LED display has many technical advantages compared with the DLP rear projection splicing, but the high cost is a major problem plaguing the small pitch LED. (Editor's note: At present, the small spacing and DLP prices are already comparable, and even some brands have a slightly lower price.) 5. Service life In terms of the length of use, LED display technology has the longest service life, while in indoor applications, LED display brightness requirements are very low, and the maximum output power of 20% can meet the requirements. The indoor high-end display market is dominated by DLP rear projection display, but DLP technology has natural defects. First, it is a 1mm patchwork between display units that cannot be eliminated at all, and at least one display pixel is swallowed. Secondly, in terms of color expression, it is also inferior to the direct-emitting LED display. What is particularly lacking is that due to the difference between the DLP display units, the uniformity of color and brightness of the entire display screen is difficult to control. As the running time of the product increases, the difference between the units will increase. The seams are difficult to keep consistent and will become more and more obvious. The difference in color between the units and the adjustment of the seams, even in the later maintenance and repair, is a difficult task. Combining the above factors, combined with the actual application of the project, taking into account the characteristics of multiple functions (Table 2), the video display system uses a small-pitch LED splicing screen as the main display screen, taking into account the best projection effect, taking into account the daily application mode, the screen size According to the 2.35:1 design, it supports up to 4K ultra-high definition projection mode. The screen display area size is 11.2mx 4.8m (28 x 12 groups), the border width is 100mm, and the bottom is 900mm away from the ground (stage), which can meet various application scenarios and high definition. Pictures and 720P, 1080P, Blu-ray DVD, 1.3K, 2K, 4K HD and other video formats. Meet the requirements of various applications for video display, the specific parameters are shown in Table 3. From project demonstration to technical and economic comparison of design schemes, comparative analysis of alternative equipment selection, the final selection of P2.5LED splicing screen is the main display, the full-screen display pixels can reach 8.6 million, meet the 4K standard, and determine the most cost-effective P2.5LED. The splicing screen is the main display of the project. Meet the current various applications and future HD playback standards, to achieve complete seamless and natural color of display colors. At the same time, in the aspect of post-maintenance, the mature point-by-point correction technology is used, and the display can be used for one-time correction of the whole screen by using the display for more than one year, so as to ensure the maximum investment value of the user. The mud pump Valve Box material is alloy steel forgings, straight-through type valve box has serrated thread on the top, small volume, high volume efficiency. 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