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Temperature-Sensitive Phosphors for the Evaluation of Air Jets Designed to Cool Motion-Picture Film
By F. J. KOLB, JR., and F. URBACH
In the projection of motion-picture film at high intensities for maximum screen illumination, it is sometimes desirable to cool the film and control its position with a blast of high velocity air. This paper presents a method for evaluating the design, placement, and operation of the jet which provides the cooling air. The heart of the method is the fact that the brightness of certain phosphors depends strongly on temperature. Such phosphors provide an immediate visual indication of the temperature distribution over the film face. Examples of several air flow patterns revealed by the use of phosphors are discussed. Test results obtained by projection of film are compared with predictions.
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EMANDS for higher light output from motion-picture projectors to supply the requirements of both the outdoor theaters and the larger indoor theaters, have emphasized the existence of limiting values of radiant flux beyond which film performance becomes unsatisfactory, and have focused attention upon means for increasing screen illumination without making additional demands upon the film. This situation has been reviewed more fully in a previous article1 which discussed the behavior of motion-picture film under high radiant-flux densities, and considered several general ap
Presented on May 2, 1951, at the Society's Convention at New York by F. J. Kolb, Jr. (who read the paper), Manufacturing Experiments Div., and F. Urbach, Kodak Research Laboratories, Eastman Kodak Co., Rochester 4, N.Y. (This paper was received on February 19, 1954.)
preaches to the problem of keeping actual film temperatures below the critical threshold. This earlier paper pointed out that cooling the film in the aperture by streams of high-velocity air is one method of increasing the safe permissible maximum flux density, and ; therefore increasing total screen light.
In order to take advantage of air-cooling it is necessary to design jets which provide high-velocity air over the entire film surface exposed in the gate. It is the purpose of this paper to consider the problems of proper jet design, placement and operation.
Film in the aperture is able to lose some heat by radiation to cooler surroundings, by conduction to solid surfaces in direct contact with it, and by conduction into the air — which latter heat is carried away from the film sur
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May 1954 Journal of the SMPTE Vol. 62