OPTICAL HEAD

摘要

PURPOSE:To economize the time required for designing an optical system and to economize the time and cost required for development of an optical head by adding a beam splitter to a condenser lens and diaphragm lens, considering the optical system constituted thereof as one object to be designed and correcting an aberration over the entire part of the optical system. CONSTITUTION:The wave surface 10 of the light which is emitted from a semiconductor laser 1 and is past the 1st group optical system constituted of the condenser lens 9 consisting of a single lens having positive power and the beam splitter 3 contains the wave front aberration symmetrical with the optical axis. However, the wave surface can be approximated to the ideal plane wave by designing adequately the optical system. The diaphragm lens 4 which is the 2nd group optical system is designed to form a satisfactory spherical wave 11 after correcting the aberration remaining slightly in the surface 10 and making the light incident on a transparent parallel plate 5 for protecting the recording surface. Said lens forms the light spot of a satisfactory microdiameter on the recording surface 6. The diaphragm lens satisfying such performance is realized by a combination lens of three pieces. The number of the lenses required for the entire part of the optical head is made four pieces and is reduced by approximately half as compared to the conventional head.