Laser driver and control circuit

Abstract

A control apparatus for a pumped rod-type laser includes an arc lamp disposed to illuminate the lasing medium, such as a NdYAG crystalline rod. The apparatus includes a full wave rectifier to power the arc lamp, and a MOSFET switching circuit to turn on and off the arc lamp power at controlled times during each half cycle of the power waveform so that the laser medium is pumped and optically discharged once during each half cycle of the power supply. The laser power output is measured by a photodetector during each half cycle, and the photodetector output is integrated and compared with a manually set, variable laser output power level. When the actual laser power reaches the preset power level, the comparator initiates turning off the MOSFET switching circuit power for that respective half cycle of the power waveform. The full wave rectified power supply also permits the use of 110 VAC utility power. The apparatus also includes safety circuits that permit laser operation only when the internal cooling system is operating, when the current to the arc lamp is below a maximum level, and when the temperature created by the laser illumination on a target is below a variable preset level, and the like. A further safety circuit detects the presence of laser radiation in the area surrounding the laser to shut it off when laser light escapes from the system. For medical uses, this feature obviates the need for laser safety goggles for operational personnel.