Laser intensity gain control for detecting oscillation in the feedback circuit

摘要

In laser feedback systems of an optical memory the most suitable feedback gain value depends on the type of optical disks used. According to the invention a system and a method is provided which finds by way of an iteration a suitable maximum feedback gain value so that the feedback system does not oscillate. The method consists in starting with a low gain value for driving a laser diode, increasing the gain value by small amounts until an oscillation detecting unit detects that the laser feedback system is oscillating. Then the gain value is reset to the previous value or a little bit more. Then the laser feedback system is again in a non-oscillating area with a suitable maximum gain value. This iteration is performed by a system consisting mainly of a laser diode, a photodiode for detecting the reflected light, and an oscillation detecting unit which controls a gain controller. This gain controller sets the gain on a multiplier which drives the laser driver for the laser diode.