ACHROMATIC EXTENSION PRISM FOR MAGNETO-OPTIC DRIVE

摘要

PURPOSE: To provide a small achromatic extension prism which simplifies the matching of prisms for sending a light beam used for a magnetic optical disk driving mechanism system to a disk and a detection element in a right direction and whose component is less and miniaturized. CONSTITUTION: An achromatic extension prism 313 has a first prism 38 which has a first dispersion value and has an incident face on which the light beam is made incident and an exit face from which the light beam goes out and a constant deviation prism 40 which is fixed to the exit face of the first prism 38 and has a second dispersion value. The constant deviation prism 40 reflects the light beam to an optical disk 44 in a first direction and reflects the light beam reflected from the optical disk 44 to the detection element in the second direction. An angle between the first direction and the second direction is constant regardlress of the incident angle of the light beam to the first prism 38. Further, first and second dispersion values are selected so that the first and second directions are not related to the wavelength of the light beam.