In recent years, white LED light source technology has been rapidly promoted and applied in film and television lighting. This provides a new generation of energy-saving, high-efficiency, long-life lamps for TV studios. As a form of TV studio, the virtual studio has a special aspect in addition to the generality of the general studio. This article takes CCTV's 18th virtual studio lighting system as a case to discuss the design of the LED studio virtual studio lighting system. CCTV's 18th studio area is 250m2. The studio is a rectangular parallelepiped structure with a long side of about 17m, a short side of about 14m, and a device layer about 6m high. A U-shaped blue box with a short side, a depth of about 10 m and a height of about 4.5 m is placed in the studio. Lighting system design includes: lighting hanging system, dimming control system, DMX512 signal control system, LED lamps and other parts. First, the technical characteristics of the virtual studio A virtual studio is a form of production that synthesizes a television picture through a virtual scene and a real person or thing. The essence is to digitally synthesize the virtual three-dimensional scene made by the computer and the live action image of the person photographed by the TV camera, so that the character and the virtual background can be synchronized and changed, thereby achieving seamless integration of the two to obtain a perfect composite picture. In the virtual studio, the TV program does not need to set up the actual background, so it does not occupy the studio scene and the time of the scene, saves the huge props warehouse, shortens the program production cycle, saves manpower, material resources, financial resources, and the production cost. reduce. Prospective characters in the virtual studio need a special performance venue. Actors generally perform a variety of performances in a "U" or "L" box (see Figure 1). The cabinet is a semi-open "blue box" consisting of several blue (green) panels. It is also required that the intersection of the blue plates on each side is connected by a circular arc surface, and there is no obvious joint at the joints of the plates in the box. Virtual studio technologies include color key technology, computer virtual scene design and blue background technology, lighting technology and camera tracking technology. The video chromatograph processes the foreground signal obtained by the camera and the background signal generated by the virtual studio system, thereby realizing the synthesis of the foreground character and the virtual scene. The actual foreground camera captures the foreground characters. The background images (picture decorations, props, and scenery scenes) are mostly three-dimensional maps, which are generated by the production staff in advance by computer, and the foreground and background images are mixed during transmission or recording. In contrast to the traditional blue screen color key technology, the real camera (foreground image) and the "virtual camera" (the background image) in the virtual studio technology are always in sync interlock. For this reason, it is necessary to determine the various real cameras. Motion parameters, including zoom, focus, pan, tilt, and XYZ information of the camera body. The methods for transmitting this information mainly include several methods such as mechanical sensing, mesh recognition, infrared sensing, and auxiliary cameras. Second, the virtual studio lighting features The illuminance of the virtual studio is different from that of the general studio. It requires the foreground to match the illumination of the blue box background and pursue the consistency of illumination. In addition, the flexibility of the virtual studio column and the diversity of the electronic background also require that the illumination must meet the needs of different columns and different electronic backgrounds. Therefore, the lighting of the virtual studio should meet the requirements of most programming. 1. Lighting layout features The first is to have suitable luminaires and reasonable lighting layout; the second is to properly align the lights, to ensure that the foreground and the virtual background lighting brightness and direction match, the actual and virtual light source synchronization changes; and that hot lamps can not affect the virtual tracking The normal operation of technology is especially important in studios that use infrared sensing. The arrangement of the lights determines the realism of the virtual background, and it is necessary to ensure the precise regulation of the lamps at any time. Any change in actual light can be detected by a computer-generated background to trigger a change in the virtual light, and vice versa. The shadows cast by actors and real props must also enter the virtual space together. In order to better capture the shadows, the lighting should be set so that the blue level of the shadow is significantly different from the blue level of the background blue screen. According to the requirements of the "blue box" lighting of the virtual studio video technology, the illumination of the light in the active area is generally required to be uniform, the light should be soft, and there should be no obvious spots and shadows of the lights, that is, the four sides of the blue box. The illuminance values ​​should be basically the same. The requirements for the light of the characters are basically the same as those of the traditional studio. Generally, the light is arranged according to the principle of three-point lighting. The difference is that the light and shadow relationship of the characters should be consistent with the virtual background. 2. Requirements for lamps Virtual studio lighting is basically the same as a traditional studio, but there are some differences. Based on the general studio lighting system design, the proportion of soft light should be appropriately increased. The soft light has uniform illumination, small shadow and high luminous efficiency, which makes the lighting effect more natural and realistic. 3. Lighting characteristics The virtual studio lighting is basically the same as the traditional lighting method, but pay attention to the following points. The area of ​​the light is large. In the virtual studio, in order to enhance the authenticity and liveliness of the program, the host will have a certain activity area. Therefore, the foreground (host) lighting cannot use the positioning method of the spot lighting like the news program, but must Perform large area lighting. Stereoscopic lighting is the key. Traditional news studios generally use three-point lighting to meet the requirements, while virtual studios use the color keyer blue technology for indigo processing. Therefore, in order to eliminate the influence of blue on the foreground (host), it is necessary to have the concept of three-dimensional lighting. The order of the blue boxes in the foreground. The soft light is scattered and not well controlled, and the foreground light will have a certain influence on the blue box. When lighting, first meet the requirements of the foreground lighting, and then properly fill the blue box to meet the requirements of computer indigo. The key to the perfect integration of the future and the electronic background is the reasonable layout of the foreground and the blue box. The blue box should be evenly distributed. The layout of the blue box should be uniform and not too strong. It should be carefully adjusted according to the actual situation of the virtual scene. 4. Light characteristics Face light: The surface of the virtual studio is generally low-level, and the primary projection of the foreground person should be avoided when lighting. Because the blue box reflects light on the shadow, after being processed by the computer, the shadow will be eliminated by the blue cancel circuit of the color key, thereby affecting the image quality of the foreground of the output. The virtual studio does not recommend adding a primary light source, because if it is used improperly, a logical error in the projection environment may occur, and an inconsistency between the actual light source and the virtual light source may occur. In addition, the secondary projection produced by the primary source on the blue box can also affect the image processing of the computer. Backlighting: The traditional principle of lighting is that the backlight is stronger than the main light, which highlights the host's distinctive outline and enhances the spatial stereo. Virtual studios must pay attention to the proper use of backlighting. Too strong backlighting will make the blue box floor appear too bright and white to destroy the consistency of the blue box color, which will affect the computer indigo effect; the secondary projection of the foreground on the blue box ground will also affect the computer image processing. Without backlighting or backlighting, the foreground (host) is stuck on an electronic background, which is very rigid. Therefore, the rational use of backlighting can well reflect the relationship between people and scenes, thus enhancing the sense of depth and enhancing the three-dimensional effect. Too strong or too weak backlighting will have a great adverse effect on the picture. 