Radiant energy – Photocells; circuits and apparatus – With circuit for evaluating a web – strand – strip – or sheet
Reexamination Certificate
1998-10-14
2001-01-09
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
With circuit for evaluating a web, strand, strip, or sheet
C250S201500, C396S121000
Reexamination Certificate
active
06172375
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a distance measurement apparatus for automatically performing focus control of a camera in accordance with the distance to an object to be photographed. More particularly, the present invention relates to a method that can cope when distance measurement is impossible in a distance measurement apparatus for detecting object distance by obtaining the relative image distance between the first and second object images formed by a pair of lenses spaced apart at a predetermined interval.
In a conventional camera using a passive AF (Auto Focus) function, when distance measurement is impossible, the shutter is locked (kept inoperative) or the focusing lens is extended to a predetermined position regardless of the object distance, and then the shutter is operated (actuated).
As disclosed in Jpn. Pat. Appln. KOKAI Publication No. 64-84231, there is also known a method of extending the focusing lens to infinity for a bright object not requiring use of an electronic flash, and to the position to which light from the electronic flash can reach for a dark object requiring use of the electronic flash.
Jpn. Pat. Appln. KOKAI Publication Nos. 64-78205 and 64-78206 disclose techniques for measuring the distance to a low-luminance, low-contrast object by phase difference detection using CCD output data of only auxiliary light.
The conventional techniques except lock processing in all the prior arts described above extend the focusing lens regardless of the object distance and photograph, thereby resulting in a large number of out-of-focus photographs. These prior arts were primarily devised to eliminate the confusion and dissatisfaction experienced when the user cannot take photographs. A large number of out-of-focus photographs, however, do not mean that this objective has satisfactorily been achieved. How to reduce this large number of out-of-focus photographs is still left unsolved.
The techniques disclosed in Jpn. Pat. Appln. KOKAI Publication Nos. 64-78205 and 64-78206 take a long time to acquire (integrate) data enough to operate correlation for CCD sensor elements in the ON state of auxiliary light. In addition, the complexity of distance measurement operation requires a high-speed arithmetic means (CPU), resulting in a high-cost apparatus.
BRIEF SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a distance measurement apparatus capable of photography even when distance measurement cannot be done, reducing the number of out-of-focus photographs, and preventing an increase in apparatus cost.
It is the first object of the present invention is to provide a distance measurement apparatus comprising:
auxiliary light means for illuminating an object to be photographed;
a pair of optical means placed at a predetermined interval;
light-receiving means for receiving light from the object through the optical means and outputting two image signals;
first distance measurement means for calculating an object distance on the basis of a relative image distance between the two image signals; and
second distance measurement means for calculating the object distance on the basis of a difference between light amounts from the object in illuminated and non-illuminated states with the auxiliary light means.
It is the second object of the present invention to provide a distance measurement apparatus comprising:
an auxiliary light unit for illuminating an object to be photographed;
a pair of optical units placed at a predetermined interval;
a light-receiving unit for receiving light from the object through the optical units and outputting two image signals;
a first distance measurement unit for calculating an object distance on the basis of a relative image distance between the two image signals;
a second distance measurement unit for calculating the object distance on the basis of a difference between light amounts from the object in illuminated and non-illuminated states with the auxiliary light unit; and
a control unit for determining reliability of the object distance calculated by the first distance measurement unit, and operating the second distance measurement unit upon determining that the object distance calculated by the first distance measurement unit is not reliable.
It is the third object of the present invention to provide a distance measurement apparatus comprising:
auxiliary light means for illuminating an object to be photographed;
a pair of optical means placed at a predetermined interval;
light-receiving means for receiving light from the object through the optical means and outputting two image signals;
first distance measurement mode arithmetic means for calculating a first distance measurement mode, the first distance measurement mode arithmetic means including first arithmetic means for obtaining a relative image distance of the two image signals on the basis of outputs from the optical means and second arithmetic means for calculating the object distance on the basis of the relative image distance;
second distance measurement mode arithmetic means for calculating a second distance measurement mode, the second distance measurement mode arithmetic means including third arithmetic means for obtaining a light amount from the object, when only the auxiliary light means is used as an illumination light source for the object, in accordance with a difference of light amounts from the object in illuminated and non-illuminated states with the auxiliary light means, and fourth arithmetic means for obtaining the object distance on the basis of the light amount obtained by the third arithmetic means; and
control means for performing distance measurement in the first distance measurement mode, and performing distance measurement in the second distance measurement mode when the first distance measurement mode is incapable of distance measurement.
It is the fourth object of the present invention to provide a distance measurement apparatus comprising:
first distance measurement means for obtaining an object distance by a phase difference detection method;
second distance measurement means for obtaining an object distance upon detection of an auxiliary light amount; and
control means for actuating the second distance measurement means when the first distance measurement means is incapable of distance measurement.
It is the fifth object of the present invention to provide a distance measurement apparatus comprising:
auxiliary light means for illuminating an object to be photographed;
a pair of optical means placed at a predetermined interval;
light-receiving means for receiving light from the object through the optical means and outputting two image signals;
first distance measurement means for calculating an object distance on the basis of a relative image distance between the two image signals;
second distance measurement means for calculating the object distance on the basis of a reflected light amount from the object upon illumination by the auxiliary light means; and
control means for determining reliability of the object distance calculated by the first distance measurement means, and operating the second distance measurement means upon determining that the object distance calculated by the first distance measurement means is not reliable.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
REFERENCES:
patent: 4853731 (1989-08-01), Tsujimura et al.
patent: 5939705 (1999-08-01), Nakamura
patent: 64-78205 (1989-03-01), None
patent: 64-78206 (1989-03-01), None
patent: 64-84231 (1989-03-01), None
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Le Que T.
Olympus Optical Co,. Ltd.
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