A control system for an optical sheet sensor device, including at least one light emitter and at least one light detector associated therewith for sensing a sheet in a sheet travel path, having a control system for automatically adjusting the intensity of said light from said light emitter. The control system stores a light emitter current level corresponding to a known valid operating condition where, when a sheet is absent from the sheet travel path, light detected at a light detector beyond a threshold level. A current level at a preset amount off-set from said stored current level is determined. A current is applied to a light emitter, the applied current rising toward a level at which the threshold level for the light detector is reached. The instantaneous applied current level is compared with the determined current level, and an error signal is provided when the applied current level reaches the determined current level. If the determined current level is not reached by the applied current level, the light emitter is operated at the applied current level, and if the determined level is reached, such error signal is provided.