Optics: measuring and testing – Range or remote distance finding – Triangulation ranging to a point with one projected beam
Reexamination Certificate
1999-09-28
2001-09-18
Buczinski, Stephen C. (Department: 3662)
Optics: measuring and testing
Range or remote distance finding
Triangulation ranging to a point with one projected beam
C396S106000, C396S120000
Reexamination Certificate
active
06292257
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system for measuring a distance to an object of distance measurement and more particularly to an active distance measurement system favorably applied to various types of cameras.
2. Related Background Art
Such an active distance measurement system applied to cameras generally includes an infrared-emitting diode (IRED) for emitting a beam of light toward an object of distance measurement, and a position sensitive detector (PSD) for receiving the emitted and reflected light beam. The signal outputted from the PSD is processed in signal processing and arithmetic circuits to be inputted therefrom as distance information into a central processing unit (CPU), by which a distance to the object of distance measurement is determined. Because an error may occur in distance measured based on one-shot light emission alone, multi-shot light emissions are generally performed thereby to obtain multiple pieces of distance information. The obtained information is typically integrated and averaged in an integrating circuit.
SUMMARY OF THE INVENTION
However, as in the distance measurement system described above, the pieces of distance information must be integrated and averaged in the integrating circuit, a considerable time may be required until the distance measurement is completed, because a time consumed during each emission is accumulated each time pulse light is emitted. More specifically, as shown in timing charts
79
to
82
of
FIG. 1
, the integration starts when an INT signal comes to “high” after the output from the integrating circuit in the above distance measurement system has been stabilized enough, that is, after a sufficient time (26 &mgr;s) has lapsed from a time point at which a HOLD signal reaches “high”. This causes the emission period of time of the IRED to be extended to 60 &mgr;s and accordingly a period of time necessary to pass through each cycle of emission noticeably increases to (60 &mgr;s+415 &mgr;s). This results in that a considerable time is necessary to end the distance measurement.
Accordingly, a time difference occurring between half-depressing of a release button and light exposure increases, so that when it is desired to shoot such as a moving object (subject of distance measurement), a photograph having a desired composition may not be obtained.
Therefore, it is an object of the present invention to provide a distance measurement system, which can measure an object distance with a little time difference while maintaining high accuracy.
With this object in view, according to the present invention, a distance measurement system is provided, which comprises means for emitting a beam of light toward an object of distance measurement; means including a position sensitive detector for receiving the beam of light emitted toward and reflected from the object at a receiving position on said position sensitive detector corresponding to a distance to the object, said light receiving means outputting a signal corresponding to the receiving position; arithmetic means for carrying out a calculation based on the signal outputted from said light receiving means to output a signal corresponding to the distance to the object; means including an integrating capacitor charged to a reference voltage for integrating the signal outputted from said arithmetic means over time by charging or discharging said integrating capacitor by an amount corresponding to the signal outputted from said arithmetic means, said integrating means outputting a signal corresponding to the results of the integration; means for determining the distance to the object based on the signal outputted from said integrating means; and said signal outputted from said arithmetic means being integrated by said integrating means immediately after the distance signal outputted from said arithmetic means is stabilized.
According to this distance measurement system, immediately after the output representative of the distance signal from the arithmetic means is stabilized, the integrating means starts the integration of the signal outputted from the arithmetic means. Accordingly, the emission period of time required for the emission means can be decreased while maintaining the same integration time, i.e., the same distance measurement accuracy as the prior art. This enables a time difference possibly occurring until light exposure ends after the half-depression of a release button to be decreased.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
REFERENCES:
patent: 5493362 (1996-02-01), Nonaka
patent: 5659387 (1997-08-01), Yoshida
patent: 5832324 (1998-11-01), Shimizu et al.
patent: 7181038 (1995-07-01), None
Buczinski Stephen C.
Fuji Photo Optical Co., Ltd.
Leydig , Voit & Mayer, Ltd.
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