Optical information signal reproducing device

Abstract

Abstract PURPOSE:To simplify the constitution of an optical system and reduce the cost by holding the oscillation wavelength of a semiconductor laser constant by a waveform control loop which uses an optical filter having such a transmission characteristic that light varies sharply in transmittivity to the optical wavelength. CONSTITUTION:When the oscillation wavelength of the semiconductor laser 2 is made smaller than a specific value lambda1 owing to, for example, a drop in room temperature, the mode of projection light from a filter PF1 which has transmission characteristics as shown by a curve A is asymmetric about a horizontal axis as shown by a curve 5. A filter PF2, on the other hand, has modulation characteristics as shown by a curve B. Therefore, the synthetic modulation mode of the filters PF1 and PF2 to laser light is asymmetric on a horizontal axis as well. Such a signal is extracted by a filter 14 and detected by a detecting circuit 15 to generate a DC component. The DC component is supplied to a Peltier element 13, which is heated, so that the wavelength of the laser light returns to lambda1. Thus, the oscillation wavelength of the laser is held constant by the simple constitution of the optical system.

Inventors

• 👤 Osamu Tajima
• 👤 修 田島

Bibliographic Details