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.
All parts of a good projection system are centered on its optical axis.
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