INFORMATION RECORDING AND REPRODUCING APPARATUS USING LIGHT BEAM MODULATION ON A SPIRAL GUIDE GROOVE DISK

摘要

An information recording and reproducing apparatus comprises anoptical device for causing a light beam to impinge upon a disc having aspiral guide groove along which a control signal is substantiallyrecorded for scanning the spiral guide groove; a light beam modulatingportion operative to intensity-modulate the light beam incident upon thedisc in response to an information signal so that the informationsignal is intermittently recorded on the disc and operative further tocause the light beam to keep a relatively small intensity during aperiod in which the recording of the information signal is temporarilyinterrupted; a photo-detecting portion for detecting the light beamcoming from the disc; a read signal processing portion operative toobtain, based on a detection output from the photo-detecting portion, aread output signal containing a read output of the control signal and atotal amount signal corresponding to momentary total light amount of thelight beam received by the photo-detecting portion; a variable gaincontrol portion operative to perform a gain-control to the read outputsignal in response to the total amount signal when the light beam comingfrom the disc is detected by the photo-detecting portion; and a signalreproducing portion for obtaining a reproduced output of the controlsignal on the strength of the read output signal having been subjectedto the gain-control performed by the variable gain control portion.