8/13/2023 0 Comments Homemade projector![]() ![]() This filter will absorb the IR, converting it to heat which must be removed by air circulation.Ī better solution is to install a cold mirror (dichroic filter) at the above position. The infrared is picked up by the collection system and passed along to the slide unless special precautions are taken.Ī “low tech” solution to this problem is to install a heat filter of IR blocking glass in the optical chain just before the slide. The heated air must be exhausted either by convection or forced ventilation. These special mirrors can also be made of dichroic material (see Handling Heat below).Īny incandescent source powerful enough to be useful in scenic projection will produce a large amount of heat, part of it as heated air and the rest as infrared (IR) light. These gather and direct the light with greater efficiency than the lens train method. Adaptations of the ellipsoidal reflector system may be more efficient overall than the lens system above. Furthermore an additional lens, sometimes called a “collector,” may be installed just in front of the slide to converge the light passing through the slide into the rear element of the objective lens.Ģ. A conventional spherical mirror, plano-convex lens arrangement upgraded by the use of the best quality mirror and one or more high-quality lenses designed to converge the cone of light to a diameter equal to the diagonal of the slide. In general, two approaches are to be found:ġ. The object of the system is to gather as much of the light output of the lamp as possible and direct it through the slide and into the rear element of the objective lens. However collecting light for projection is more demanding. The principle of collecting light in a projector is the same as collecting light in a spotlights. In the case of theatrical projectors, it often fitted with mounting equipment such as a yoke and “C” clamp or a base that allows accurate tilting and panning. It may also carry the aperture apparatus and the objective lens.Ī lamp house is much like the housing of a high-powered spotlight it must withstand heat, contain dangerous radiation, withstand occasional rough handling, and may have to be engineered to contain the violent explosion of a high-pressure lamp. The lamp house is the enclosure around the light gathering apparatus that contains spill light from the lamp and supports the lamp and its electrical leads. ![]() Under these conditions, there will be no distortion due to misalignment, but optical distortion from lens or reflector faults may still exist. Not only should all parts be centered on the optical axis, their optical planes should also be at right angles to it. This is a line through the center of each optical element and, ideally, extending to the center of the screen. This article was taken directly from: indepthinfo.All parts of a good projection system are centered on its optical axis. So to what uses can we put these amazing machines? Most modern DLP projectors have overcome this problem with multiple chips and higher rotation rates for the color wheel. Small shadows of red, blue, or green may be seen. This can happen when white objects move on a dark background. Some DLP projectors, have been known to manifest a rainbow effect. DLP, with its more vivid colors, is thought to be better for video. Knowing the difference between these two types of projectors can be important, as LCD is considered better for static or high-contrast images. This technology was developed by Texas Instruments and is based on an older technology that was used for color television in the 1950s. The image appears to be constantly lit, when in fact small parts of it are constantly flickering. Even though only one color is shown at a time, one color follows another so quickly that the primary colors seem to blend into the appropriate color. The mirrors are turned off or on by electronic impulses according to the need for the color at that moment. This time the light is shined through a spinning color wheel onto a chip that is mounted with hundreds of thousands of tiny mirrors. DLP, or Digital Light Processing is a bit more complex. The light is then beamed through a lens onto a screen where the images can be seen by the human eye. The screens themselves are sent signals to allow just so much of the light through at specific pixel locations. ![]() The prism splits the light into its component colors and these are sent through small LCD screens. A bulb is set up to shine a fairly powerful light through a prism. The way this places an image on a screen is fascinating and not nearly as complex as you might imagine. ![]() LCD is the older technology, but this does not mean that it is becoming obsolete by any means. Projectors come with many features, strengths, or weaknesses, but most will run on either LCD or DLP technology. There are two major types of projectors in use as of this writing (things change pretty fast in the field). ![]()
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