Patent ID: 8167208
Filing Date: 2012-05-01
Classification: G06K

Abstract:
1. An arrangement for controlling a laser that has an internal semiconductor laser chip and an internal semiconductor monitor photodiode, in an electro-optical reader for reading indicia, comprising: a controller for deenergizing the laser chip in a deenergized state, and for energizing the laser chip to emit a laser beam with an output power in an energized state; a positive voltage power supply connected to an anode of the monitor photodiode, for forward biasing the monitor photodiode at a substantially constant positive voltage below a threshold voltage of the monitor photodiode, and for maintaining said substantially constant positive voltage at the anode to support a substantially constant photodiode leakage current in both states; and a signal processor for supporting a total current comprised of a main photodiode current indicative of the output power of the laser beam in the energized state and of the substantially constant photodiode leakage current which flows opposite to the main photodiode current, and for removing the substantially constant photodiode leakage current from the total current to output only the main photodiode current in the energized state.