Diffuse Reflective Screen: A common screen for film and slide projection. There are cloth curtains, rubber screens, plastic screens and screens coated with coatings such as barium sulfate, matt paint and zinc oxide on the above surfaces. The feature is that the surface of the screen can uniformly and uniformly reflect the light flow on the screen to all directions. When viewing the screen image at any different angle in front of the screen, the brightness does not change with direction and angle, and is suitable for a wider place. Suitable for black and white and color images.
Directional diffuse reflection screen: Its optical characteristic is that the light flow on the screen can be concentrated in a certain direction after being redistributed by reflection. The disadvantage is that the diffusion angle is small, and there are two kinds of metal screens and glass bead screens. The metal screen is coated with a layer of white metal powder such as aluminum powder that reflects various colors on the base surface. The glass bead screen is coated with a layer of white paint on the surface of a fibrous material, and a transparent spherical glass bead is evenly applied to the white paint.
Honeycomb Screen: The honeycomb on the screen is a number of small, smooth, convex or concave mirrors or lenses made by molding or rolling processes, arranged in a certain order. Some are made of small flat plates, and some are made of small concave mirrors with small steel balls pressed into a concave surface.
The transmissive screen is used for indoor projection of movies, projections, and slides without shading equipment. The audience is watching on the back of the screen. The brightness of the screen depends entirely on the amount of light transmitted from the back of the screen. Therefore, this screen has a large number of transmissions. Since the audience is on the back, it will not be disturbed and can reduce the visual fatigue of the human eye; because the interior is bright, the audience can take notes while watching. Therefore, the screen is officially used for the elective teaching of schools.
Perforated screen: Evenly put a lot of small holes on the screen. When using a normal screen, the speakers are usually on both sides of the screen, but in order to coordinate the sound and the action of the picture, the speaker is preferably placed in the center of the screen. However, the texture of the ordinary screen is dense, and it is not easy to transmit sound, which affects the quality of the ring. To compensate for this shortcoming, cinemas or clubs use perforated screens.
[page] The four main steps to properly select the screen:
(1) Select screen type
Casting the curtain: There are manual hanging screen and electric hanging screen type; two-legged bracket screen; triangular bracket screen, metal plane curtain, arc screen.
Rear projection screen: a variety of hard rear projection screens (divided into double curved screen and diffused screen) and soft rear projection screen (diffused screen); the effect of hard screen is better than soft screen.
(2) Choose the best screen size
The choice of the best screen size depends mainly on the size of the space used and the number of seats and the arrangement of the seats. The first rule is to choose the screen that is right for the viewer -- not the screen that fits the projector, which means putting the viewer's visual experience first.
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Here are some references to choosing a screen size:
1. The height of the screen should allow the viewers of each row to clearly see the contents of the projected picture;
2. The distance from the screen to the first row of seats should be greater than 2 times the height of the screen;
3. The bottom edge of the screen is about 1.5 meters away from the ground.
(3) Select the format (screen scale) that suits the needs of the projection device you are using. The common format is as follows:
Image format screen ratio (width: height)
VGA signal 4:3/ projector 1:1/ NTSC system 4:3/ PAL system 4:3/ HDTV (high resolution TV) 16:9/ wide screen 1.85
(4) Selection of screen materials
The screen fabric you choose should suit the needs of your projector and audience. However, if a screen needs to be used by multiple projectors, the screen fabric should be selected for the projector that requires a higher screen.
For example, when you have both a slide projector and a projector, because the projector's light output is lower than the projector, you should choose the reflectance (gain) parameter that fits the projector's fabric.
However, since most projectors now have a relatively high brightness, a better projection effect can be obtained by using a Matte White screen having a lower reflectance (gain) than a Glass Beaded screen.
Maintenance of the projection screen:
1. The glass bead screen can't be folded. You can't touch the screen with your fingers or hard objects to avoid contamination.
2, the curtain area dust should be wiped with feather duster, the stain is heavy, can be gently scrubbed with cotton balls and water.
3. If the bucky white plastic screen is stained, wipe it gently with a damp cloth.
4. The spring reel curtain should be handled with care to avoid collision deformation and affect the service life.
5. If an abnormal phenomenon occurs during use, it must be stopped immediately to eliminate the malfunction.
6. Do not disassemble the electric teaching screen yourself, so as to avoid unnecessary losses.
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