Automatic focusing device

Abstract

Abstract PURPOSE: To make a pin hole unnecessary and to increase the strength against the external vibrations by using the light emitting portion itself of a semiconductor laser as the pin hole. CONSTITUTION: The laser beam 12 from a semiconductor laser 11 is reflected on the surface of a disc 14, in which video signals are recorded, and is reversed through a lens 13 so that it enters the p-n junction 15 of the light emitting portion of the semiconductor laser 11. Since the terminal voltage of the laser 11 is varied, the varied output 16 is applied to a phase detector 19 and is subjected to phase detection while using as reference signals the oscillatory output of an oscillator 17 which is operative to drive a vibrator 18 for vibrating the laser 11 in the direction of the optical axis in a preset frequency. The output of the phase detector 19 is applied to an actuator 20 which is operative to control the position of the lens 13 in the optical axis direction. On the other hand, 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