Studio background screen with LED small pitch and DLP splicing screen comparison analysis

First, LED display

LED is the abbreviation of LightEmittingDiode. Chinese means LED, which is a solid-state semiconductor device that can directly convert electrical energy into light energy. LED display is an advanced digital information product. It successfully combines computer technology, network communication technology, image processing technology, embedded control technology, etc. It has flexible display area and resolution (modular can be assembled at will), high Brightness, low power consumption, long life, low heat, environmental protection and durability, etc., comprehensively use sound, light, electricity, graphics, text, is a terminal product that displays information in all directions and perfectly.

LED displays are increasingly being used in large-scale events in television studios and television broadcasts. As a stage backdrop, it provides a variety of vivid, dazzling background images and more interactive features to make the background image To make the performance and the background blend together, let people feel immersive. It brings a larger space for imagining the beauty of the dance, designing a modern and visually striking stage, perfectly blending the atmosphere of the scene and the show, and realizing the functions and effects that are difficult to achieve in other stage art equipment.

The viewer's viewing effect and feeling on the LED display screen is very intuitive. As long as the screen size and pixel pitch and viewing distance are appropriate, this direct-view display can achieve excellent results. However, the number of viewers in front of the TV is much larger than the number of viewers in the audience. Therefore, the viewing effect of the viewers in front of the TV is the focus of research and discussion by TV technicians. Many Taiwanese use LED display screens, but the TV screens have different effects. Some of them are colorful, clear and stable from beginning to end. Some are small and invisible when they are in the distant view. They are either highlights of some activities during close-up, or The erratic stripes interfere with the appearance of reticulated interference in some people's close-ups, which disturbs the viewer's line of sight.

Pay attention to the following aspects in the selection and use of LED display:

1. The spacing should be as small as possible

The dot pitch is the distance between the center points of adjacent pixels of the LED display. The smaller the dot pitch, the more pixels per unit area, the higher the resolution, the closer the shooting distance can be, and of course the more expensive it is. At present, the dot spacing of the LED display screen used in the domestic TV studio is 6-8 mm. In order to achieve excellent results, the relationship between the resolution of the signal source and the dot pitch should be carefully studied, and the resolution must be consistent. Achieve a point-to-point display for optimal results.

2. The fill factor should be high

The fill factor of the LED display (FillFactor) is also called the bright area ratio, that is, the ratio of the light-emitting area of ​​each pixel to the physical surface area occupied by the pixel. The LED display is arranged by discrete pixels, and there are obvious black areas that are not illuminated between the pixels. When viewed at close range, the picture is incoherent and incomplete, and uneven brightness produces graininess. If the light source is confined to a small pixel surface area, so that the brightness of a single pixel is several times or even more than ten times the brightness of the whole screen, Causes a more serious glare. The flat panel display industry recognized TCO'99 standard stipulates that the fill factor should not be lower than 50%. At present, the filling factor of many LED displays on the market does not reach this target. The cut-off characteristics of the low-pass filter of the TV also directly affect the appropriate shooting distance of the LED display with different fill coefficients.

LED display screens with the same dot pitch have a smaller fill factor than the fill factor, so the shooting distance needs to be increased. If the low-pass filter passband of the system is 4MHz and the high-frequency attenuation characteristic is 12db/octave, then the shooting distance of 25% of the fill factor is 1.15db more than the fill factor of 50%, and the shooting distance needs to increase by about 10%. . The increase of the fill factor makes the display angle of the display wider, the color mixing effect is more ideal, overcomes the glare problem of the pixel, and creates conditions for appropriately improving the brightness of the whole screen to obtain better effects. The Jiangsu Education Desk chose an LED display with a 60% fill factor. It has moderately soft brightness, evenly bright colors, clear and delicate expressiveness, and guarantees the high quality of the display.

3. Color temperature can be adjusted

ColorTemperature is the temperature determined by comparing the shape of the emission spectrum of the emitter with the shape of the best fit blackbody emission spectrum. When the studio uses the LED display as the background, its color temperature should be consistent with the color temperature of the studio, in order to get accurate color reproduction during shooting. The lighting of the studio is sometimes based on the demand of the program, sometimes using 3200K low color temperature lamps, sometimes using 5600K high color temperature lamps, and the LED display screen needs to be adjusted to the corresponding color temperature to obtain satisfactory shooting results.

4. The shooting distance should be appropriate

As mentioned in the previous discussion about dot pitch and fill factor, LED display with different dot pitch and different fill factor, the suitable shooting distance is different. The distance between the person being photographed and the screen is suitable for 4-10 meters, so that when shooting a character, a better background image can be obtained. If the character is too close to the screen, the background will appear grainy when shooting close-ups, and it will also be prone to texture interference.

5. Guarantee a good use environment

The product has a low failure rate under the right working conditions only during the service life. As an integrated electronic product, the LED display is mainly composed of a control board equipped with electronic components, a switching power supply, a light-emitting device, etc., and the life and stability of all of these components are closely related to the operating temperature. If the actual working temperature exceeds the scope of use specified by the product, not only will its life be shortened, but the product itself will also be severely damaged. In addition, the threat of dust cannot be ignored. Working in a dusty environment, because the PCB absorbs dust, and the deposition of dust will affect the heat dissipation of the electronic components, the temperature of the components will rise, and then the thermal stability will decrease or even cause leakage, which will lead to burning. Dust also absorbs moisture, which can corrode electronic circuits, causing short-circuit problems that are difficult to check. Be careful to keep the studio clean. The studio transformation will generate a lot of dust, and it is necessary to protect the LED display in advance.

The use of the LED display greatly enriches the display form of the program background, and the LED display screen serves as a background for large-scale variety shows of large scenes and large studios.

Second, DLP splicing screen

DLP is the abbreviation of DigitalLightProcessing. Chinese means digital light processing. This technique first processes the image signal digitally and then projects the light. From the technical principle of DLP, it has the advantages of minimum signal noise, accurate gray level, high reflectivity, seamless image display, and high reliability. DLP splicing screen is made up of multiple rear projection display units. Its main feature is that the seam is small and can be controlled to within 0.5 mm. Everyone calls it “seamless” splicing. This is also the other two technologies LCD and PDP. Unreachable. Due to its advantages, in recent years, TV stations have popularly used DLP splicing screens as the background of the studio. CNN, BBC, SKY, CCTV and other well-known big TV stations have achieved very good program effects after use.

DLP splicing screens also have disadvantages. Since the light source of the DLP splicing is from the bulb, it consumes a large amount of power, has a high heat dissipation, and the brightness is lowered after a period of use, and the user must constantly change the bulb to maintain the original display effect. With the development of technology, thanks to the addition of LED light sources, DLP splicing screens have solved a series of problems such as frequent lamp replacement, high power consumption and high heat dissipation. The DLP splicing screen after adopting the LED light source not only has a great breakthrough in the service life and power consumption, but also has revolutionized the color, so that the DLP splicing screen continues to maintain the market leading advantage.

In order to achieve a satisfactory TV effect, we should pay attention to the following aspects in the selection and use of DLP splicing screen:

1. The stitching gap should be as small as possible

The background display we want is seamless on the TV, which requires the stitching gap to be small enough to see no gaps in the lens. At present, the use of titanium alloy needle stitching technology can reduce the stitching gap to within 0.2 mm, and the connection plate design can ensure that the screen does not deform during thermal expansion and contraction, providing high quality image geometry and sharpness for the entire screen.

2. High uniformity

The DLP splicing screen is made up of multiple screens, which creates individual differences for each screen, and we want them to look like a large display with matching colors and brightness, which requires technical improvements. Uniformity. At present, this technology is relatively mature, and the advanced technology manufacturers have been able to operate in the background silent mode without the operator's participation. It integrates the proprietary brightness and color sensor to continuously measure the color and brightness of the screen wall and between the projection modules. Communication, automatically match all white, black and all gray level brightness and all display module colors, and keep the gray level of the entire display the same, thus achieving long-term consistency of images under multi-screen stitching.

3. Color temperature needs to be adjustable

Like the LED display, the color temperature of the DLP splicing screen needs to be consistent with the color temperature of the lighting in the studio to ensure the true reproduction of the image color.

4. Studio lighting should be well controlled

Compared with other display screens, DLP splicing screens have lower brightness, which requires controlling the lighting of the studio to avoid direct lighting to the screen. After groping and researching, we used a cold light source with a 20° grille to effectively control the illumination of the light on the screen to within 100 lux, and ensure that the illuminance of the host's surface light can reach 800-1000 lux, which is satisfactory. Effect.

5. The light source needs high security

The interactive nature of TV live broadcast is getting stronger and stronger, and the security requirements for background are getting higher and higher. The single screen size of DLP splicing screen is larger. If there is a problem with the light source, it will lead to black screen, which is negative for this program and even one station. The impact will be great. Therefore, it is necessary to use a dual-lamp hot backup or a redundant LED module as a light source.

6. Ensure good heat dissipation and control noise

UHP bulbs and LED light sources generate a lot of heat during operation. Its heat dissipation is an important part of ensuring the life and normal operation of the light source. Advanced liquid cooling technology can make the cooling efficiency higher, the noise is smaller, and still pay attention to keep good. The ambient temperature, when shutting down, can not immediately cut off the power supply, let the cooling system continue to run for a period of time, so that the light source is fully cooled and then cut off the power supply, which has a good protection for the light source, so that it can work optimally. which performed.

DLP splicing screen is a major change in the studio background, but because it has high requirements for lighting, it is not suitable for use in large-scale variety shows. It is suitable for news, interviews, on-site connection, weather forecast, etc. in small and medium-sized studios. Type of program.

With the development of technology, more new technologies and new methods will be applied to the studio background. We need to understand their characteristics in depth, choose technology products as the background for different studio conditions, program forms and requirements, let these new technologies maximize their advantages, serve the programs better, and serve the audience.