| 摘要 |
PURPOSE:To attain a high-speed access with an optical head by forming a plane vertical to an optical axis at the light input side of an objective lens and cutting a plane at the light output side with a slight degree of tilt secured against the plane at the input side. CONSTITUTION:A light source 1 is provided to deliver the light beam to an objective lens 2 vertically to the incident light to the lens 2 and to read the information recorded on an optical disk. A plane 4a is formed to the lens 2 at the side of the source 1 to prevent the dispersion of the light beam. While the 2nd plane 4b having a slight angle against the light beam is formed at the outer circumferential part of the lens 2 at the side opposite to the source 1 so that the light beam of the source 1 entering the lens 2 is slightly refracted. A position sensor 3 is set vertical to the light beam given from the source 1 in order to receive the refracted light beam. Then the transmitted light T refracted by the plane 4b is received by the sensor 3, and the size of the position signal given from the sensor 3 is detected. Thus a degree of deviation of the lens 2 can be detected to a normal position.
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