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Fig. 2. Schematic of RCA Ultra-Speed Projection System.
which may be of interest to applications engineers and exhibitors.
Nature and Performance of the UltraSpeed System
The RCA Ultra-Speed Theater Television Optics (Fig. 1 ) are currently being built in a focal length of 15.515 in. and an effective optical speed of //0.82. * This is a suitable focal length for a large number of theater installations where pictures up to 15 X 20 ft are to be projected from a 7-in., 80-kv kinescope. The system is capable of delivering a 2-ft-c highlight level to the screen under these conditions, from kinescopes of present design.
The optical system has two basic
* A System that gathers a cone of light 90 ° in diameter has a speed of//0.71. In a theater television projection system, the mirror must be masked out at the center to prevent reflection of light directly back to the face of the kinescope. Taking this into account, the Ultra-Speed System has a net optical speed of//0.82.
optical parts: a concave spherical mirror; and a low-power ogee lens at its center of curvature. In its meridian section the curved surface of the lens is seen to have a generating curve in the form of an S or ogee, hence the name. These parts are shown, respectively, at A and B of Fig. 2. The focal length of the ogee lens is of the order of 20 times that of the entire optical system. If the ogee lens is not made of a suitable flint glass, a radiation filter must be mounted approximately in contact with it as shown at C of the figure. Such a filter becomes, of necessity, a part of the optical system and its surfaces must be made sufficiently flat and parallel to have the minimum possible effect upon the image. The kinescope tube is located at D on the axis of symmetry of the optical system, with its face, E, directed toward the mirror. When the radius of curvature of the kinescope face or screen is equal to the focal length of the optical system (of the order of one-half the radius of curvature of the spherical mirror), the
Sachtleben and Alice: Theater Television Optics
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