| 摘要 |
PURPOSE:To discriminate objects different in depth by detecting the difference between the pattern of reflected light from an object on the focal surface and that from another object placed apart from the focal surface. CONSTITUTION:When a condensed optical beam 120 is irradiated to an hour hand 131, the reflected light is parallel rays of light and are made incident on a cylindrical lens 15. If a four-divided optical sensor 16 is set in such position that the refracted light has a circular beam pattern, the output of a differential amplifier 17 for photoelectric conversion of the sum and the difference among optical outputs of photodetecting surfaces A, B, C, and D is about zero. When the optical beam 120 is irradiated to a minute hand 132, the reflected light is divergent light; and when it is irradiated to a dial 130, the reflected light is a convergent light. With respect to the light refracted by a lens 15, the direction of the major axis of an ellipse for reflection from the dial 130 and that for reflection from the minute hand 132 are different by 90 deg.. Consequently, the output of the differential amplifier 17 is discriminated as a positive or negative value of the voltage to confirm positions of hands.
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