OPTICAL HEAD AND FOCUSING SERVO MEANS

摘要

PURPOSE:To provide a microminiature and light-weight movable head by omitting a movable part and a focus actuator from a separation type optical head of an optical memory device. CONSTITUTION:A diffraction element 105 which is used for detection a focus error signal is set between a collimator lens 109 and a semiconductor laser 101 or between the focus error detecting photodiodes 102 and 103 of a separation type optical. head. In such a constitution, the lens 109 is moved on its optical axis for a focusing servo operation. Thus a mobile heed 113 consists of only a reflecting mirror 110 and a fixed objective lens 11. Then a microminiature and light-weight movable heed is obtained.