Beam controller for magneto-optical disc memory system

Claim 1

A beam controller for controlling a semiconductor laser provided in an optical recording and reproducing apparatus comprising: first current source means for generating a first current to drive the semiconductor laser at a low level necessary for reproducing data stored on an optical memory device; second current source means for generating a second current to be used in driving the semiconductor laser at a high level necessary for recording data onto said optical memory device and/or erasing data stored on said optical memory device; a sample-hold circuit including, switching circuit having first and second input terminals and one output terminal, a low-pass filter connected to said output terminal of said switching circuit, and memory means for storing an output signal from said low-pass filter; said first input terminal of said switching circuit being connected so as to input data corresponding to an intensity of the beam from the semiconductor laser; said second input terminal of said switching circuit being connected to an output of said memory means; said switching circuit being controlled so as to connect said first input terminal to said low-pass filter when a reproducing mode is selected; said switching circuit connecting said second input to said low-pass filter when a recording or erasing mode is selected; and control means, in response to said sample-hold circuit, for controlling said first current source to generate said first current.