Photography – Flash system responsive to focal length or distance – Illumination angle responds to focal length or distance
Reexamination Certificate
2000-03-02
2001-12-04
Perkey, W. B. (Department: 2851)
Photography
Flash system responsive to focal length or distance
Illumination angle responds to focal length or distance
C396S106000, C396S157000, C396S175000
Reexamination Certificate
active
06327434
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-066370, filed Mar. 12, 1999; the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a camera having an electronic flash equipment which can be used as an auxiliary light source for auto-focusing (to be called as AF hereinafter), and having a function in which the AF auxiliary light covers a range area regardless of its shooting view angle.
Conventionally, for an AF operation, AF detection auxiliary light is used when the brightness of an object to be photographed is low or the contrast is low.
Examples of the technique for emitting AF detection auxiliary light while an AF operation of a camera, are as follows. First, a technique in which an LED or light bulb serving as exclusive light emitting means is provided for an electronic flash equipment or camera body so as to emit AF detection auxiliary light, is known. Second, a technique in which the electronic flash equipment is appropriated, and a very small amount of light emission is created by utilizing its light adjustment function, is known.
Further, these days, as the usage rate of the zoom lens increases, an electronic flash equipment capable of controlling the flash irradiation angle, has been put into practical use.
More specifically, for example, Jpn. Pat. Appln. KOKAI Publication No. 9-61896 discloses a technique regarding an electronic flash equipment of a camera, including the first light emitting means for irradiating light at the first light distribution angle and the second light emitting means for irradiating light at a light distribution angle narrower than the first light distribution angle, characterized in that either one of the first and second light emitting means is selected to perform preliminary light emission which is carried out before an exposure to a film, thereby optimizing the amount of light emission in the preliminary irradiation of light.
However, in the case where there are a plurality of ways in the light emission by the flash equipment, it suffices if the AF auxiliary light covers an AF detection area only.
Further, with the technique disclosed in the above Jpn. Pat. Appln. KOKAI Publication No. 9-61896, where auxiliary light is necessary, the reliability of subject distance data obtained without using auxiliary light is low, and therefore it is not appropriate to control the irradiation angle based on such data. Further, the focal point detection area is situated at a center of the image or in its vicinity, whereas the flashing light for imaging covers the image in its entirety. Therefore, in the case where auxiliary light is used, the light is irradiated also onto the area other than the focal point detection area, thus wasting energy.
BRIEF SUMMARY OF THE INVENTION
The present invention has been proposed in consideration of the above-described drawbacks of the prior art technique, and the object thereof is to enhance the auxiliary light usage efficiency by appropriately controlling the flashing light irradiation range in the case of a flash equipment whose irradiation angle can be set at a plurality of ways, and at the same time, to reduce the energy consumption by avoiding wasteful use of energy.
In order to achieve the above-described object, there is provided according to the first aspect of the present invention, a camera comprising: a zoom lens, detection means for detecting a focal length of the zoom lens, electronic flash means for irradiating electronic flash onto an object to be photographed, capable of setting a first irradiation angle to cover an image view angle of a wide angle side of the zoom lens, and a second irradiation angle which is narrower than the first irradiation angle; first selection means for selecting either one of the first and second irradiation angles in accordance with the focal length detected by the detection means; distance measurement means for measuring a distance to the object to be photographed, located in a distance measurement area within an imaging view angle, by operating the electronic flash means on the basis of object conditions; and second selection means for selecting the second irradiation angle regardless of the selection made by the first selection means, when the distance to the object is measured with use of the electronic flash means.
Further, there is provided according to the second aspect of the present invention, a camera comprising: a zoom lens; detection means for detecting a focal length of the zoom lens; electronic flash means for irradiating electronic flash onto an object to be photographed, capable of changing its irradiation angle; first irradiation angle setting means for setting an irradiation angle of the electronic flash means; distance measurement means for measuring a distance to the object to be photographed, located in a distance measurement area within an imaging view angle, by operating the electronic flash means on the basis of object conditions; and second irradiation angle setting means for setting an irradiation angle of the electronic flash means when the distance to the object is measured with use of the electronic flash means.
Further, there is provided according to the second aspect of the present invention, a camera comprising: a zoom lens; detection means for detecting a focal length of the zoom lens; electronic flash means for irradiating electronic flash onto an object to be photographed, capable of changing its irradiation angle; first irradiation angle setting means for setting an irradiation angle of the electronic flash means; distance measurement means for measuring a distance to the object to be photographed, located in a distance measurement area within an imaging view angle, by operating the electronic flash means on the basis of object conditions; and second irradiation angle setting means for setting an irradiation angle of the electronic flash means when the distance to the object is measured with use of the electronic flash means.
Further, there is provided according to the third aspect of the present invention, a camera comprising: an imaging lens capable of varying a focal length; electronic flash means for irradiating electronic flash onto an object to be photographed; imaging means for executing an imaging operation with use of the electronic flash means when the object to be photographed has a low brightness; distance measurement means for measuring a distance to the object to be photographed, located in a distance measurement area within an image plane, by operating the electronic flash means to emit light on the basis of object conditions; and irradiation angle setting means for setting an irradiation angle of the electronic flash means in accordance with the focal distance of the imaging lens in the imaging operation, and for setting the irradiation angle of the electronic flash means at a predetermined angle when the measurement distance is measured with use of the electronic flash means.
Further, there is provided according to the fourth aspect of the present invention, a camera comprising: an imaging lens capable of varying a focal length; electronic flash means for irradiating electronic flash onto an object to be photographed; imaging means for executing an imaging operation; distance measurement means for measuring a distance to the object to be photographed, located in a distance measurement area within an image plane; and control unit for setting an irradiation angle of the electronic flash means at an appropriate angle for the distance measurement area when the measurement distance is measured with use of the electronic flash means to emit light, and setting the irradiation angle of the electronic flash means in accordance with the focal distance of the imaging lens in the imaging operation.
Further, there is provided according to the fifth aspect of the present invention, a camera comprising: imaging angle changing means; a electronic flash unit for
Okumura Yoichiro
Watanabe Yoji
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Olympus Optical Co,. Ltd.
Perkey W. B.
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