| 摘要 |
PURPOSE:To reduce the size of an optical head optical system and simplify it by detecting a focus error by using a specified optical device and an ordinary and an extraordinary light beam which are reflected by an information recording medium and separated in an anisotropic medium while one of the beams is given aberration. CONSTITUTION:The optical device is constituted by joining a prism member 4 made of the anisotropic medium with a prism member 6 made of an isotropic medium and a light reflecting and transmitting layer 10 is formed on the surface except the joined surface. A semiconductor laser 2 emits a light beam to the light reflecting and transmitting layer 10 and the light beam which is reflected by the light reflecting and transmitting layer 10 is converged on an optical disk 12 for magneto-optical storage. Light beams corresponding to the ordinary and extraordinary light beams which are reflected by the optical disk 12, transmitted through the light reflecting and transmitting layer 10, and separated in the anisotropic medium of the optical element 14 while one of the beams is given aberration are processed by a signal processing circuit 24 to generate a focus error signal. |
