| 摘要 |
PURPOSE:To make the adjustment of focal distance unnecessary and to improve the sensitivity of focus detection by projecting reflected light from the disk of an optical disk device to a spherical lens and providing a focus detector at exit position of the spherical lens. CONSTITUTION:Reflected light from the disk 1 of the optical disk device is deflected by a deflecting mirror 3 through a diaphragm lens 2, divided by a mirror 4, and one is led to a groove detector 5 and another is projected to a focus detector 7 through a spherical lens 6. When the disk 1 and lens 2 are just focused, light coming out from the lens 2 becomes parallel light, and projected to the spherical lens 6 and focused on the surface of the spherical lens 6. The focus detector 7 is placed at the position of focus of the spherical lens 6. Thus, adjustment of focal distance of the spherical lens 6 becomes unnecessary, and high focus detection sensitivity is obtained. |
