| 摘要 |
PURPOSE:To keep the interval of two laser beams on a disk with high accuracy by detecting the error of relative position of the two laser beams and controlling one optical axis of the two laser beams based on the error signal obtained from the detection. CONSTITUTION:A laser beam radiated from an Ar<+> laser device 21 is guided by a mirror 23 and split into two beams such as an information signal recording beam and a tracking signal recording beam. The information signal beam is led to a beam synthesizer 40 via an optical modulator 28a and the 1st collimator optical system 37. On the other hand, the tracking signal recording beam is led to a synthesizer 40 via an optical modulator 28b and the 2nd collimator system 53. Both the beams synthesized by the synthesizer 40 are formed on a half mirror 66 and picked up by an ITV camera 68. The error of the relative position of both the beams is detected based on the output signal of the camera 68 to move either of convex lenses 34, 50 in collimator systems 37, 53 in a prescribed direction orthogonal to the optical axis based thereupon.
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