| 摘要 |
PURPOSE:To make the titled head small in size remarkably by constituting the head for irradiating focusing light to an information storage medium and reading the information by using a generated reflected light, of a projecting means on which an out-of-focus detecting reflecting surface and a track shift detecting reflecting surface is provided, and a photodetector for detecting these reflected lights. CONSTITUTION:A divergent laser beam originating from a semiconductor laser 21 is changed to a parallel luminous flux by a collimating lens 23, and irradiated and recorded to an information storage medium 22 through a polarized beam splitter 24, a 1/4 wavelength plate 25 and an objective lens 26. Subsequently, read-out reflected light from the medium 22 is returned to the splitter 24, and this reflected light is detected by a photodetector 29 through a projecting means 27 and a condenser lens 28, but in the projecting means 27 of the optical head consisting of them, one fan-type out-of-focus detecting light reflecting surface 27a and two track shift detecting light reflecting surfaces 27b, 27c of a fan type in the same way are provided, and also in the photodetector 29, as well, out-of-focus detecting cells 29a, 29b and track shift photodetecting cells 29c, 29d corresponding to them are provided, and the focal displacement is detected. |
