Abstract: A target is read in the presence of interference light. A photodetector generates an output signal composed of an information signal and an interference light signal. A rangefinder determines the distance of the target in a range of working distances. A controller adjusts a scan angle of a scan drive to a narrow value and adjusts an output power of a laser diode to a low power level when the target is determined to be far out in the range. The controller adjusts the scan angle to a wide value and adjusts the output power to a high power level when the target is determined to be close in the range. Signal processing circuitry processes the output signal with the information signal having a greater magnitude than that of the interference signal due to the high power level to mitigate the presence of the interference light. A power safety arrangement including dual power monitors checks the output power of the laser beam.

Abstract: Laser power control arrangements interrupt power to a laser used in electro-optical readers upon detection of an over-power condition not conforming to preestablished regulatory standards. In one embodiment, during an operational mode, a difference between laser drive currents at two operating points is compared to a difference between laser drive currents at the same two operating points during a calibration mode. The over-power condition is recognized when the difference during the operational mode exceeds the difference during the calibration mode by a predetermined amount. In another embodiment, the laser is only energized to emit the beam at a reduced power level well below regulatory standards for staring at even if a motor drive failed.

Abstract: Laser power control arrangements interrupt power to a laser used in electro-optical readers upon detection of an over-power condition not conforming to preestablished regulatory standards. In one embodiment, during an operational mode, a difference between laser drive currents at two operating points is compared to a difference between laser drive currents at the same two operating points during a calibration mode. The over-power condition is recognized when the difference during the operational mode exceeds the difference during the calibration mode by a predetermined amount. In another embodiment, the laser is only energized to emit the beam at a reduced power level well below regulatory standards for staring at even if a motor drive failed.

Abstract: Laser power control arrangements interrupt power to a laser used in electro-optical readers upon detection of operating conditions not conforming to preestablished standards, and adjust power to the laser to enhance reader performance without violating prevalent safety standards.

Abstract: Crosstalk between a drive coil and a feedback coil is eliminated by a motor drive circuit operative for generating the drive coil as a square wave, and by removing the crosstalk which occurs at zero transitions of a feedback signal. The drive coil is used to oscillate a scan mirror employed in an image projection arrangement or an electro-optical reader.

Abstract: A piezoelectric activated dither suspension system for a ring laser gyroscope has all of the transducer elements connected in parallel to simultaneously produce sustaining torque for dither motion and respond to a back component of current produced by the vibrational motion of the gyro block. The generated current, separated from drive currents from the torquer amplifier by a transformer or, in an alternative embodiment, by sensing resistors, produces the very signal used to control and sustain the oscillations. By utilizing all transducers both as torquer and pickoff elements, economies of drive efficiency, wiring simplification and circuit redundancies are achieved.

Abstract: Electro-optical apparatus for the control of the optical path length in a laser angular rate sensor. An output of a fringe detector dual photodiode and preamplifier, normally present, is processed to recover a laser intensity component present as an amplitude modulation superimposed on the phase-modulated fringe detector signal. The laser intensity component is then provided as an input to the optical path length feedback control system.