PURPOSE: To decrease noise without producing radiation by monitoring a laser light of a laser element in an optical pickup device of an optical video disc device so as to apply negative feedback to an applied current of the laser element.
CONSTITUTION: A laser light 2 irradiated from a semiconductor laser element 1 is separated into three laser lights by a diffraction grating 4 and made incident to a half mirror 5. The laser light 12 reflected on an optical disc 11 is collected into three points on a 3-spot photodetector 16, where the light is converted into an information signal for a video signal or a sound signal or the like, a focusing signal and a track signal. An electric signal proportional to the luminous amount of the laser light 6 incident to a photodiode 8 is fed back to the applied current of the laser element 1 via an inverse amplifier 9 and a capacitor C so as to keep the luminous amount of the laser light 6 to a constant value thereby decreasing an SCOOP noise.
NAKAJIMA MITSUYOSHI
KONDOU TAKAHIKO
HITACHI LTD
HITACHI MICROCUMPUTER ENG