Power control system for a semiconductor laser

Details Power control system for a semiconductor laser Power control system for a semiconductor laser

G - Physics

11

B

352/32.2

G11B 7/125 (2006.01) G11B 19/02 (2006.01) H01S 5/0683 (2006.01)

Patent

CA 1255386

6082-216 ABSTRACT OF THE DISCLOSURE In an optical recording system using a semiconductor diode laser and having both read and write capabilities, the laser power must be carefully controlled at appropriate different levels for reading and writing. A continuous read beam is emitted by the laser while write pulses at a higher power level are generated. The laser power control loop of the present disclosure maintains both the read and write output power levels of the laser within predetermined limits. A light sensing diode is used to determine laser output power and operate the control circuit by adjusting the read and write current to the laser. The sensing diode vol- tage is passed through a read/write switch which is controlled by write pulses, which also control the laser. In read mode a DC signal is sent to a quad comparator circuit for read power control. In write mode a pulsed signal is sent to a sample and hold circuit whose output goes through an amplifier to another quad comparator circuit for write power control. The outputs of the comparators update the read and write power control circuits which determine the current levels to be provided to the laser diode during these operations. The power control circuits are counters which step up or down after every power measurement, if necessary, and a D/A converter controlled by the counter which drives the current sources. When the counters reach the end of the range limit this signals that the laser is close to a failing condition and at this time a warning signal is emitted. Error status signals are emit- ted if the read or write power signals indicate the absence of, or an improper signal. OSI 814-CA

511083

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