Image Number 4 for United States Patent #6103177.
A mastering apparatus for recording optical information onto a glass master 6, includes an objective lens 3, a slider 5 for controlling the movement of the objective lens 3 in the tracking direction, a turn table 7 for rotating the glass master 6, a spindle motor 8 for controlling the rotation of the turn table 7, a positioning beam generator 9, a positioning beam detector 10 for detecting a positioning beam reflected and/or diffracted by positioning units 16 and 17 and a slider controller 11 for moving the slider 5 based on the result of reception of a beam at the positioning beam detector 10. The positioning unit 16 is mounted on the vicinity of the objective lens 3, and the positioning unit 17 is mounted on the upper surface of a spindle stationary portion 13. Since the position of the positioning unit 17 is always stable, relative positional deviation between the positioning units 16 and 17 can be accurately detected by detecting the beam diffracted by the positioning units 16 and 17.
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