US 6,188,842 B1Granted

Rangefinder apparatus

AssigneeFuji Photo Optical Co., Ltd.

InventorHideo Yoshida

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Abstract

In a rangefinder apparatus where the external light luminance is relatively high, the period of each accumulating operation in an integrating circuit, the light-emitting period of an infrared emitting diode (IRED), and the light-emitting interval of the IRED are set to 26 microseconds, 52 microseconds, and 360 microseconds, respectively. When the external light luminance is relative low, on the other hand, the period of each accumulating operation in the integrating circuit, the light-emitting period of the IRED, and the light-emitting interval of the IRED are set to 50 microseconds, 76 microseconds, and 526 microseconds, respectively. Further, the number of accumulating operations in the integrating circuit is also adjusted such that the product of the period of light pulses projected by the IRED and the number of accumulating operations is substantially constant among distance measurements. Alternatively, the number of accumulating operations in the integrating circuit is adjusted such that the sum of the respective periods of accumulating operations becomes substantially constant among distance measurements.

Claims8

Dependent claims

A rangefinder apparatus comprising:

luminance measuring means for measuring an external light luminance;
light-projecting means for projecting a luminous flux in pulses toward an object at a distance to be measured;
light-receiving means for storing a steady-state light component received by a position sensitive detector when the luminous flux is not projected from said light-projecting means, detecting reflected light of the luminous flux projected toward the object at a light-detecting position on said position sensitive detector corresponding to the distance to the object, and eliminating the stored steady-state light component, to out-put a signal corresponding to the light-detecting position;
arithmetic means for carrying out an arithmetic operation according to the signal output from said light-receiving means, and outputting an output ratio signal corresponding to the distance to the object;
integrating means for accumulating and integrating the output ratio signal, and outputting an integrated signal corresponding to integration of the output ratio signal;
adjusting means for adjusting a period of each accumulating operation in said integrating means according to an external light luminance measured by said luminance measuring means;
and
detecting means for detecting the distance to the object according to the integrated signal output from said integrating means.

5 more elements

Dependencies are inferred from the claim text.