OPTICAL HEAD

PURPOSE:To attain the geometric separation of multiplex laser beams even at a place near a condensing surface by refracting the traveling direction of at least one of multiplex laser beams reflected by the surface of an information storage medium. CONSTITUTION:The optical axes (r), (w) and (p) are slightly tilted to each other for a read beam 17, a record beam 14 and a preceding beam 18 respectively which are reflected by the surface of an information storage medium and passed through an objective lens. A prism 52 is set at the condensing point of a projection lens 51 of at a place near the lend 51. The beams 17 and 18 transmit through the prism 52 and are projected to detection cells 53a-53d and 53e of a photodetector 53 respectively. These beams are used for reading of signals, detection of a track shift and an out-of-focus state and detection of the reflected light quantity respectively. The beam 14 is cut off in a light cut-off area 54 on the prism 52. Thus the information on both beams 17 and 18 can be detected without receiving any effect of the cut-off beam 14. The detection is possible just at a small part of a photodetector 53. This attains a compact design of an optical head with reduction of the cost.