Photography – With exposure objective focusing means – focusing aid – or... – Having viewfinder
Reexamination Certificate
1999-09-29
2001-11-06
Perkey, W. B. (Department: 2851)
Photography
With exposure objective focusing means, focusing aid, or...
Having viewfinder
C396S384000, C396S382000
Reexamination Certificate
active
06314242
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The present invention relates to a single-lens reflex view finder which uses an electronic image pickup device such as a CCD, and more specifically a TTL view finder characterized in its focus confirming means.
b) Description of the Prior Art
A digital camera (electronic camera) has recently been attracting attention as a camera of the next generation which is to replace a silver salt 35 mm film camera (generally referred to as a Leica size camera). The digital camera has also been configured as a single-lens reflex type.
A single-lens reflex camera requires a surface having a refractive power such as a condenser lens which is disposed in the vicinity of an imaging point of a view finder system and has a function to relay a pupil, planar surface on which a fine structure such as microprisms or a mat is formed at the imaging point to permit confirming focus at the imaging point, and an optical element which is disposed on a side opposite to the fine structure and composed of a surface of a Fresnel structure having refracting function.
A CCD or the like which is used as an image pickup device in case of the digital camera has a size which is on the order of several to dozen of percent in a diagonal length of the silver salt 35 mm film. Therefore, it is necessary for the digital camera to enhance on a view finder screen, and when a Fresnel surface is to be used in the digital camera, a pitch of rings must be narrow since it is required to make the rings unnoticeable. Accordingly, the digital camera poses a problem that it makes the Fresnel hardly workable and allows it to produce an influence due to diffraction. Though the surface of the condenser lens may be configured as an ordinary refracting surface, the ordinary surface has a power weaker than that of the Fresnel surface, whereby another surface of the condenser lens must be configured as a curved surface having a refractive power. In such a case, however, the condenser lens has no focus confirming function and the curved surface must be transparent.
Furthermore, the fine structure of the microprisms or the mat surface is apt to be defective and can be worked extremely hardly.
SUMMARY OF THE INVENTION
A primary object of the present invention is to provide a single-lens reflex view finder which is free from degradation of viewing performance such as eclipse of rays even when a magnification is enhanced on a view finder screen.
Another object of the present invention is to provide a single-lens reflex view finder which makes a defect of a fine structure used as focus confirming means to be hardly noticeable.
The single-lens reflex view finder according to the present invention comprises optical path splitting means which splits at least a partial amount of a light bundle transmitting through an imaging optical system which picks up an image of an object as a view finder optical system for observing the object, a refracting surface which is disposed at an optional imaging location in the view finder optical path split by the optical path splitting means and focus confirming means which is disposed only on a central portion of the refracting surface.
REFERENCES:
patent: 2881686 (1959-04-01), Ruhle
patent: 3498198 (1970-03-01), Fujii
patent: 4027327 (1977-05-01), Harada
patent: 4119982 (1978-10-01), Imura et al.
patent: 4381521 (1983-04-01), Iida et al.
patent: 6018416 (2000-01-01), Mihara
patent: 53-125832 (1978-11-01), None
Olympus Optical Co,. Ltd.
Perkey W. B.
Pillsbury & Winthrop LLP
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