Photography – Having variable focal length of camera objective – Having focus operation
Reexamination Certificate
2001-08-29
2003-04-29
Perkey, W. B. (Department: 2851)
Photography
Having variable focal length of camera objective
Having focus operation
C396S104000, C396S106000, C396S109000, C396S123000, C396S096000, C396S091000
Reexamination Certificate
active
06556785
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
There have generally been, roughly classified, two methods for an auto focus (AF) apparatus of a conventional camera.
2. Description of the Related Art
One of the methods is called a passive method which is based on an image signal of a subject. The other one is called an active method for focusing on the basis of reflected signal light of light projected from a camera to a subject.
In the passive method, the image signal is used, which makes it difficult to focus in a dark scene. Even in a bright scene, it is not possible to focus on a subject having no contrast, in principle. To deal with this, a technique of switching the aforementioned two methods for use as disclosed in Japan Patent Application KOKAI Publication No. 11-83474.
In general, there are many cases where an important object is located in the center of a finder in a camera. When another object located in an ambient portion in the finder is brought into focus, the important object located in the center cannot be focused on. More specifically, a case has arises in that, in the scene as shown in
FIG. 10
, when a camera is focused on a beer bottle
101
, a face of the person
102
, an essential part, becomes blurred.
However, if either of the two methods is used while switching one to the other between the two methods as like in a conventional technique, a problem of misjudgment has not been able to be avoided such that one method, not the selected one, should have been selected, in fact.
BRIEF SUMMARY OF THE INVENTION
In view of the above-depicted status, it is an object of the present invention to provide a range finder which makes it possible to accurately focus on a person in such scenes, and sufficiently considers shutter time lag or energy conservation by combining the two methods.
To achieve the above object, a range finder of the invention is characterized by comprising first focus means for focusing by using an image signal of a subject, light-projection means for projecting light, second focus means for focusing on the basis of reflected signal light of light projected from the light-projection means, and determination means for determining, on the basis of an output result from one of the first or second focus means and a zoom position of a zoom lens, whether or not to operate the other one of the first or second focus means.
The range finder includes a plurality of ranging points having different precedence from each other, is characterized by comprising determination means for determining whether or not to re-range on the basis of reliability in ranging the plurality of points of high precedence.
In addition, the range finder is characterized by comprising switching means for switching the plurality of points of high precedence on the basis of an angle of view in shooting, in that integral time during A/D conversion of an image signal of a subject is switched in performing the re-ranging.
Moreover, the range finder is characterized in that presence/absence of projecting light for range finding during A/D conversion of an image signal of a subject is switched in performing the re-ranging.
According to a range finder having the above-described mechanism, it is possible to provide a range finder which considers energy conservation or shutter time lag, and furthermore, makes it possible to focus accurately without having a weak point in any scenes.
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: 5293194 (1994-03-01), Akashi
Nakata Koichi
Nonaka Osamu
Perkey W. B.
Pokotylo John C.
Straub & Pokotylo
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