| 摘要 |
A focus detecting device has an objective lens, a pair of re-imaging lenses for receiving the light imaged by the objective lens to form a first and a second image, respectively, a pair of focus detecting photoelectric converters disposed near the focal planes of the pair of re-imaging lenses, respectively, the pair of photoelectric converters being adapted to produce photoelectric outputs corresponding to the position changes of the first and second images caused on the photoelectric converters by movement of the objective lens in the direction of the optical axis, and detecting means for receiving the outputs from the pair of photoelectric converters and detecting whether or not the objective lens is in its in-focus condition. The pair of re-imaging lenses are provided so that the F-number thereof in a direction perpendicular to the direction of movement of the images is smaller than the F-number thereof in the direction of movement of the images position-changed on the photoelectric converters.
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