| 摘要 |
A method and apparatus for an improved autofocus in an optical system is presented. The improved autofocus system uses distinct optics from those of the primary optical system. Although optically distinct, physically, the autofocus optics are mechanically linked to the optical output stage of the primary optical system. The optical separation of the autofocus optics from those of the primary optical system overcomes the trade-offs associated with trying to combine the primary optical function and focus in the same beam. In particular, the autofocus beam is not blinded by a more powerful write beam. The physical integration of the autofocusing optics with the optical output stage of the primary optical system overcomes the difficulties associated with using external distance sensors. In particular, the autofocusing system is not susceptible to steady state error because the autofocus sensor is a true null detector.
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