Dual image coincidence type finder system

Details Dual image coincidence type finder system Dual image coincidence type finder system

1997-12-29

2001-08-14

Perkey, W. B. (Department: 2851)

Photography

Having variable focal length of camera objective

Having direct viewfinder

C396S148000, C396S147000

Reexamination Certificate

active

06275657

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a finder system for a camera, and particularly to a finder system which is provided separate from a taking (photographing) optical system.
Recently, an autofocusing function is generally employed in cameras, not only SLR (single lens reflex cameras) but also so-called compact cameras. In SLRs, degree of blur on a focusing plate changes in accordance with a focusing condition of a photographing lens, an operator can confirm whether an intended object is focused or not through a finder.
In cameras which have a finder system separately from the photographing optical system, however, the operator may know whether an object is focused from an indicator such as a small lamp inside the finder. That is, when the lamp is ON, the photographing lens is focused on the object. In this type of cameras, the operator only knows whether the photographing lens is focused on an object or not, and the operator cannot confirm whether the intended object is correctly focuses or not in advance when the exposure is performed. That is, if the autofocusing is executed with the intended object being out of a focusing zone (which is, for example, at a central part of a finder field), or it is difficult to execute auto-focusing (e.g., the object is a flame, or the object is a scenery through a window glass), the intended object may not be focused even though the indicator indicates the in-focus condition.
SUMMARY OF THE INVENTION
It is therefore an object of the invention is to provide a finder system which enables an operator to confirm, in advance, whether an intended object will be photographed in in-focus state.
Another object of the invention is to provide a dual image coincidence type finder system in which the size of the optical path composing element such as the half mirror can be made relatively small, with suppressing the manufacturing cost.
For the above object, according to the invention, there is provided a dual image coincidence type finder system for a camera, said finder system having a first window and a second window through which light from an object being entered, said first window and said second window being apart from each other by a predetermined base length, comprising: a image combining system which generates a superimposed image by superimposing a first image corresponding to said first window and a second image corresponding to said second window; a distance-related information input system which obtains information corresponding to a distance to said object; and a controller which controls said image combining system to vary relative position of said first image and said second image in accordance with said information corresponding to said distance to said object.
According to another aspect of the invention, there is provided a dual image coincidence type finder system for a camera, said finder system having a first window and a second window through which light from an object being entered, said first window and said second window being apart from each other by a predetermined base length, comprising: an eyepiece optical system used for observing an object image within a finder field; a deflecting system which deflects light entered from said second window, a beam combining element, which combines light entered from said first window, and light entered through said second window and deflected by said deflecting system, said object image observed within said finder field including a dual image area showing superimposed two images respectively corresponding to light entered through said first window and said second window, said deflecting system changing degree of relative displacement between said superimposed two images; a distance-related information input system which obtains information corresponding to a distance to said object; and a controller which controls said deflecting system, in accordance with said information corresponding to said distance to said object, to change a deflecting condition so that said superimposed two images coincide.
Thus, the operator of the camera can confirm whether the object is currently focused on or not by observing the object through the finder system.
According to furthermore-aspect of the invention, there is provided a dual image coincidence type finder system for a camera, said finder system having a first window and a second window through which light from an object being entered, said first window and said second window being apart from each other by a predetermined base length, comprising: a deflecting system which deflects light entered from said second window; a beam combining element, which combines light entered from said first window, and light entered through said second window and deflected by said deflecting system; a real image type objective optical system, light combined by said beam combining element entering said objective optical system, a real image of said object being formed by said objective optical system on an image plane; and an eyepiece optical system used for observing said real image formed by said objective optical system, wherein said real image includes a dual image composed of superimposed two images respectively corresponding to light entered through said first window and said second window, and wherein said deflecting system is capable of changing degree of relative displacement between said superimposed two images.
Since the objective lens is provided on the eyepiece optical system side with respect to the beam combining element, only a single objective optical system is required. Accordingly, the number of elements of the finder system is reduced, and further, the structure thereof is made simple.
Optionally, the finder system may be further provided with a distance-related information input system which obtains information corresponding to a distance to said object, and a controller which controls said deflecting system, in accordance with said information corresponding to said distance to said object, to change a deflecting condition so that said superimposed two images coincide with each other.
Since the status of the dual image is changed in accordance with the object distance, the operator can recognize the object currently focused.
Optionally, said distance-related information input system may be a distance measuring device which independently detects said distance to said object.
Further, said deflecting system may include a rotatable mirror rotatable about an axis which is perpendicular to said base length direction.
In this case, it may be advantageous that said deflecting system includes a driving mechanism which drives said rotatable mirror. The driving mechanism may be a mechanism which drives the rotatable mirror in response to movement of focusing lens of the camera.
Still optionally, the finder system may include a dual image area defining system which defines an area of said dual image within a finder field. By restricting the area of the dual image within the finder field, it is easy to recognize whether the two image of the dual image area coincide.
The dual image area defining system may have an aperture plate located between said second window and said beam combining element. Alternatively, said dual image area defining system comprises a mirror surface between said second window and said beam combining element, said mirror surface reflects a predetermined part of light entered through said second window corresponding to an area of said dual image.
Still alternatively, said deflecting system comprises a rotatable mirror rotatable about an axis which is perpendicular to said base length direction, and said dual image area defining system may have a reflection surface of said rotatable mirror, said reflection surface reflects a predetermined part, corresponding to an area of said dual image, of light entered through said second window.
Further optionally, the beam combining element may include a transparent plate having a half mirror portion, light entered through said finder window passing through said transparent pla

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