Optical Head Controlled by Double Diffraction Patterns

Abstract

An optical head with 10 mm in height and 10 g in weight for practical use of optical mass storage systems, applied a thin lens-actuator, has been successfully developed by employing double diffraction patterns for focusing and tracking error detection. The first diffraction pattern for the focusing error detection is derived from a particular detecting lens, and by a so-called push-pull method the second for the tracking error detection is also used. The lens for the focusing error detection consists of some decentered surfaces and also has a short detecting distance. An objective lens is supported by four thin springs. Therefore the height of this lens-actuator becomes less than 10 mm. The thin optical head and a method for the focusing error detection of the optical head with a single-beam optical system are described.