| 摘要 |
An automatic focusing apparatus for optical instruments, in particular for reflected light microscopes, wherein a measuring point is produced on the surface of an object by an eccentric measuring beam formed by blocking a portion of the path of a full beam. The measuring point is imaged onto a photoelectric device by reflecting the measuring beam along the blocked out path. When the object plane wanders from the focal plane, the photoelectric device actuates a control device which returns the object plane to the focal plane. The apparatus comprises a source of light to produce a, preferably pulsed, laser light for the full measuring beam, an optical structural element for geometrically blocking one-half of the full measuring beam to produce the eccentric measuring beam and simultaneously for geometrically blocking the reflected measuring beam from the path of the full measuring beam. A lens is positioned in the measuring beam and a photodetector device in the form of a differential photodiode pair is positioned to receive the reflected measuring beam. A divider mirror, preferably dichromatic, is provided for introducing the measuring beam into the path of the illuminating beam of the optical device and for reflecting the reflected measuring beam from the path of the illuminating beam of the optical instrument.
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