Temperature-Sensitive Phosphors for the Evaluation of Air Jets Designed to Cool Motion-Picture Film

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.