| 摘要 |
A closed loop automatic focusing system suitable for use in a camera is disclosed which has a beam producing means producing a narrow beam of light radiation directed toward an object to be focused. Having been reflected by the object, the beam is received by an afocal objective lens group which refracts the beam in collimated form when the object is in focus and refracts the beam in divergent or convergent form when the object is not in focus. The beam is then directed to a double photocell upon which the beam impinges equally when in collimated form and unequally when in divergent or convergent form. If the double photocell senses any divergence or convergence, a servo system is directed to correct the focusing error. Alternatively, the objective lens group refracts the beam in constant divergent or convergent form when the object is in focus and non-constant divergent or convergent form when the object is not in focus.
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