Abstract: A beam-of-light (BOL) sensor having means for regulating the intensity of the sensor light source to compensate for extraneous factors in its operating environment, e.g., dust accumulation, component aging, misalignment, etc., that may affect consistent sensor operation. The BOL sensor includes a photosensor whose output signal is compared against a reference signal to determine if the light source intensity is of the proper level. The comparison signal is used to gate clock pulses to a counter to adjust its stored count upward or downward, dependent on whether the light source intensity is low or high, respectively. A filter is provided to override interruptions in the photosensor output signal below a predetermined minimum time duration.

Abstract: A beam-of-light (BOL) sensor having means for regulating the intensity of the sensor light source to compensate for extraneous factors in the operating environment, e.g. dust accumulation, that may affect consistent sensor operation. The BOL sensor includes a photosensor whose output signal is compared against a reference signal to determine if the light source intensity is of the proper level. The comparison signal is transformed into a digital pulse that adjusts the stored count of a counter upward or downward in accordance with the comparison of the photosensor signal and reference signal. The adjusted count is converted to analog form and fed back to drive the light source.A trailing edge detector enables the counter to count up or down when an object is in the sensing station defined by the light source and photosensor.