Optics: measuring and testing – Range or remote distance finding – Triangulation ranging to a point with one projected beam
Reexamination Certificate
1999-09-23
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
06292256
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system for measuring a distance to an object to be measured 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 an infrared beam toward an object to be measured, and a position sensitive detector (PSD) for receiving the object-reflected infrared beam. The signal output from the PSD is a signal responsive to a position where the object-reflected infrared beam is received. A signal processing and arithmetic unit determines a distance to the object to be measured from this signal. Because a large error may occur at once measurement, averaging of multiple pieces of distance information is generally performed to obtain more accurate distance information.
In the camera contained such an active distance measurement system, when a shutter release button is half depressed, a power source voltage check and an external luminance measurement are carried out. Then, the distance measurement system starts a distance measurement. Subsequently, the shutter release button is fully depressed, it allows a shutter to open for a certain period of time for exposure film to light.
SUMMARY OF THE INVENTION
However, the aforementioned prior distance measurement system requires a sensible time not only to average the multiple pieces of distance information, but also to perform the power source voltage check and the external luminance measurement previous to the distance measurement. Accordingly, there is a problem that a long time lag may occur until the time when the exposure film to light is actually performed after half-depressing of the shutter release button. In such a case, when it is desired to shoot such as a moving subject (object to be measured), a photograph having a desired composition may not be obtained.
In order to solve the above-mentioned problems, it is an object of the present invention to provide a distance measurement system, which can measure a distance to the object with a short time lag.
To achieve this object, the present invention supplies an active distance measurement comprising: (1) a light source for emitting a predetermined series of light pulses toward the object to be measured; (2) a position sensitive detector for receiving object-reflected light pulses and outputting signals each corresponding to a position where said object-reflected light pulse is received; (3) an arithmetic unit for outputting signals each corresponding to the distance to the object in response to the signals output from said position sensitive detector; (4) an integrating capacitor set to a first reference voltage before emitting said series of pulses, said capacitor being charged or discharged in response to said signals output from said arithmetic unit; (5) a distance detection unit for detecting the distance to the object based on a charged voltage of said capacitor present after emitting said series of pulses; (6) a measuring unit for performing a predetermined measuring operation; and (7) a control unit for controlling said distance measurement system so that a distance measurement is actually performed by emitting said series of light pulses after said measuring unit has performed the predetermined measuring operation during a predetermined period after instructions to start a distance measurement operation.
According to the present invention, the light source emits the light pulses toward the object and these pulses are reflected by the object. Each reflected pulse (object-reflected pulse) is detected by the position sensitive detector (PSD). The light-receiving position where the object-reflected pulse is received changes responsive to the distance to the object. The PSD outputs a signal dependent on this light-receiving position, it is possible to determine or calculate the light-receiving position and by extension the distance to the object based on thus output signal. The arithmetic unit issues the distance signals each representative of the distance to the object through the use of the above relation. The integrating capacitor integrates the distance signals and the distance detection unit can determine, based on the results of the integration, the average value of distance-calculation results for the corresponding pulse. As the number of pulses is known, the average of the distance signals corresponding to the series of pulses can be obtained based on the results of the integration. The predetermined measuring operation is carried out during the predetermined period after the start of the distance measurement operation and before the emissions of the pulses. When the system is applied to such as a camera, the time lag of the shutter operating can be shortened.
Preferably, the integrating capacitor is charged to the first reference voltage or higher during the aforementioned predetermined period. Where the system includes the stationary-light-component removal capacitor to remove the stationary-light component of the signal output from the position sensitive detector, it is favorable to set the stationary-light-component removal capacitor to the second reference voltage during the aforementioned predetermined period. The measuring unit may perform one or more of the functions such as the power source voltage check, the external luminance measurement, and the ambient temperature measurement.
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: 5652926 (1997-07-01), Saito
patent: 5659387 (1997-08-01), Yoshida
patent: 5832324 (1998-11-01), Shimizu et al.
patent: 6026246 (2000-02-01), Yoshida et al.
Buczinski Stephen C.
Fuji Photo Optical Co., Ltd.
Leydig , Voit & Mayer, Ltd.
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