Optical head

DETAILED DESCRIPTION The present invention has for its object to provide a novel and useful optical head in which an incident angle to an optical surface of the critical angle prism can be adjusted precisely and easily without moving the light source.
It is another object of the invention to provide an optical head in which the required accuracy of the angle adjustment of the prism can be maintained for a long time without being influenced by temperature variations.
It is another object of the invention to provide an optical head in which the angle adjustment of the prism can be carried out using a simple construction.
It is still another object of the invention to provide an optical head which is small in size, particularly in the optical direction of the objective lens and in the radial direction.
According to the invention, an optical head for recording and/or reproducing a signal on and/or from an optical record medium, comprises: a light source for emitting a light beam; a beam splitter for splitting the light beam into a transmitted light beam and a reflected light beam; an objective lens for projecting the transmitted or reflected light beam onto the record medium as a fine light spot and for directing the light beam reflected by the record medium toward said beam splitter; a prism integrally coupled with said beam splitter and having an optical surface upon which the light beam reflected from or transmitted through the beam splitter is made incident substantially at the critical angle of total reflection; means for supporting an assembly of the beam splitter and prism rotatably about an axis such that the incident angle of the light beam to the optical surface of the prism is adjustable; and a light detector arranged to receive a light beam totally reflected by the optical surface of prism.