| 摘要 |
A distance measuring device for a camera, emits 10 a pulsed distance measuring beam to an object and receives 3 reflected light from the subject. The device integrates 50 the outputs of position sensitive detector 3 in turn, and measures the number Nf, Nn of pulses of emitted light required for the integround Vi to reach a first threshold; the range is then given by Nf/(Nf+Nn). In order to improve precision without inordinately increasing integration times, the output of PSD 3 is integrated with normal precision until the integround Vi reaches a second predetermined value (lower than the first predetermined value) during which time each pulse counts as 10, then, integrated from the second predetermined value to the first predetermined value with a higher precision by switching input resistance 52, 53 of the integration circuit 50, during which time each pulse counts as 1. As a result the integround Vi quickly and accurately reaches the first predetermined value. Alternatively (fig 8) the time for which integration occurs is preset but controllable, and the amplification of amplifier 40 is variable. <IMAGE>
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