| 摘要 |
PURPOSE:To curtail a large-sized half mirror, to make the title head small in size and light in weight and to execute an access at high speed by using a composite element formed by sticking a 1/2 wavelength plate having a polarizing film to a parallel plane glass plate. CONSTITUTION:A reflected light from an information recording medium 6 goes to a focusing light by a condensing lens 7 through a half mirror 4, made incident on a parallel plane glass plate 8, and from a reflected light by the surface of the plate 8, a tracking error signal is detected. A light beam which has transmitted through the plate 8 is reflected by an interface to a 1/2 wavelength plate 9 which is stuck to the plate 8, and a focus error signal is detected. Moreover, a light beam which has transmitted through the wavelength plate 9 and a polarizing film 10 provided on the plate 9 is separated into a P polarization and an S polarization, and made incident on information signal use analyzers 12, 13. In such a way, four beams for an error detection and for an information signal can be separated by one composite element, the title head can be made small in size and light in weight, and an access can be executed at a high speed. |
