Automatic focusing device

Abstract

Abstract PURPOSE: To make a pin hole unnecessary and to improve the strength against the external vibrations by using the p-n junction itself or a light emitting portion of a semiconductor laser as the pin hole. CONSTITUTION: The laser beam 12 from a semiconductor laser 11 is reflected upon the surface of a disc 14 and is reversed through a lens 13 so that it enters the light emitting portion 15 of the laser 11. As a result, since the terminal voltage of the semiconductor laser 11 is varied, the varied output 16 is applied a phase detector 19 so that it may be subjected to phase detection while using as the reference signals the oscillatory output of an oscillator 17 which is operative to drive an actuator 20 for vibrating the lens 13 in the direction of the optical axis in a preset frequency. Since the terminal voltage varied output 16 contains the signal component recorded in the disc 14, it is introduced into a signal processing circuit 21 for the reproducing purpose. COPYRIGHT: (C)1979,JPO&Japio

Inventors

• 👤 Kazuo Okada
• 👤 Mitsushige Kondo

Bibliographic Details