A Phase Comparison Cross-Modulation Test Instrument

Abstract

While the methods for measuring and controlling cross-modulation distortion have been practiced for many years, the costs of these tests preclude their use as frequently as one would desire for best quality control. This paper describes a new test instrument that permits the laboratory to exercise control for each individual printer and for each print. The instrument requires only an inch (2 ½ cm) of film rather than the several hundred feet (hundred or more meters) of film normally required for such a test. A special and unique feature of the instrument is the phase comparison test which indicates to the operator the direction and magnitude by which the print density should be changed for minimum distortion (i.e. the amount of increase or decrease in density required). In addition, the instrument provides a direct measure of the level of distortion that is present, and also an indication of printer performance (e.g. slippage contact, etc.). Since the test is obtained by simply inserting the test section into the instrument aperture, only a few seconds are required to make the analysis. All of the presently used cross-modulation tone-pairs are accepted by the instrument.