Optical head apparatus

Abstract

To implement light quantity monitoring with high frequency responsivity and correction of astigmatic differences of a semiconductor laser with a simple configuration with a fewer parts. Of the light beam output from a semiconductor laser light source, a peripheral beam component is entered by a light reflection elementinto an anterior light monitoring photodetectorformed in the vicinity of a semiconductor laser light source. Furthermore, the surface of the reflection sphere of the light reflection element is formed anamorphic, and thus condensed to an appropriate size on the photodetector without being focused, providing high frequency responsivity. Furthermore, the light reflection elementis placed inclined at a predetermined angle so as to cancel out astigmatic difference of the optical semiconductor laser light source. In addition, the photodetectoris placed in the direction so that a reflected lightis bent by an inclination of the light reflection element, reducing the amount of parallel displacement during adjustment of the light reflection element