Automatic reference background monitoring network for a film processor

摘要

A film processor having film transport rollers driven by a drive motor, a sensor for generating a signal representative of roller transport speed and a film density detector arrangement that includes a photodetector responsive to the intensity of a light source for generating a reference background level signal against which processed film is compared is characterized by a monitoring arrangement which periodically samples the photodetector output signal and adjusts a reference background level signal in accordance with fluctuations in the output of the scanner arrangement. To prevent the system from reacting to momentary perturbations in background level a moving weighted averaging technique is employed. The rate at which the reference background level signal is sampled is determined by the transport roller speed.