Television – Special applications – Combined electronic sensing and photographic film cameras
Reexamination Certificate
1997-11-14
2001-11-20
Garber, Wendy R. (Department: 2612)
Television
Special applications
Combined electronic sensing and photographic film cameras
C348S180000, C348S187000, C348S189000
Reexamination Certificate
active
06320607
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an electronic still camera, and in particularly, to an electronic still camera wherein an image obtained through an image pickup lens is received by a solid image pickup element, and a still image thus obtained is handled as digital data.
There has been developed an electronic still camera wherein an image is converted to an electric signal by the use of a solid image pickup element to be recorded as an electric signal. An electronic still camera of this type is spreading due to its handiness that it is rapid in reproduction and image processing can also be done, thus an improvement in image quality of the electronic still camera has been desired.
In the case of an electronic still camera in prior art, there has been a big problem with regard to image quality that a false image is generated due to the relation between an interval of adjoining pixels (pixel pitch) of a solid image pickup element and a resolving power of an image pickup lens.
To solve this problem, occurrence of the false image is prevented by arranging an optical low-pass filter between an image pickup lens and a solid image pickup element as described in TOKKAIHEI 7-92430, or by giving a function of an optical low-pass filter to an image pickup lens, or by eliminating a high frequency component which is higher than a critical resolving power determined by a pixel pitch as described in TOKKAISHO 64-917.
As stated above, in the case of an electronic still camera, image quality has been improved by adding an optical low-pass filter to a conventional lens.
Though the resolution has been determined depending on the number of pixels (or pixel pitch), on the other hand, it has been difficult to obtain image quality higher than that obtained by preventing a false image, because components of a specific frequency or higher than that are eliminated as stated above.
For a recent demand for the higher image quality, the technologies mentioned above are not sufficient to obtain satisfactory images, as stated above.
SUMMARY OF THE INVENTION
An object of the invention, therefore, is to realize an electronic still camera equipped with a lens which makes it possible to obtain a high grade image when a solid image pickup element is used for image pickup.
After intensive studies about the relation between a lens and a solid image pickup element, the inventors of the invention found structures for achieving the above-mentioned object, on the point of
relationship between a type of an image pickup means (a solid image pickup element or a silver halide light-sensitive material) and a lens, and
relationship between the number of pixels of the solid image pickup element used actually and a lens, concerning conditions of the lens which is most appropriate for the solid image pickup element used in an electronic still camera.
Structures 1
An electronic still camera provided with an image pickup lens constituting an optical system which focuses a subject image on a prescribed image-focusing plane, a solid image pickup element which is provided at the position of the image-focusing plane of the image pickup lens and generates image signals by transforming photoelectrically the image obtained by the image pickup lens; and an A/D converter which converts the image signals from the solid image pickup element into digital signals, wherein the optical system satisfies the following condition:
(condition)
X≧M×N×0.8
when; I
1
represents an image formed by outputting the digital signals obtained by the electronic still camera with an outputting means, I
2
represents an image formed by outputting, with said outputting means under the same condition, what is obtained by photographing the same subject with the image pickup lens of the electronic still camera after replacing the solid image pickup element of the electronic still camera with a silver halide light-sensitive material, after reading it with a reading unit, images on plural sheets N are obtained for each of subjects in plural number M types, and an occasion where image I
1
shows higher contrast and higher sharpness for each image is represented by 1, while an occasion where image I
2
shows higher contrast and higher sharpness for each image is represented by 0, and X represents the total for all images.
In the case of this electronic still camera, it is possible to structure a lens which is suitable for a solid image pickup element and is capable of obtaining a high grade image, and thereby to realize an electronic still camera equipped with a lens capable of obtaining a high grade image when photographing with a solid image pickup element, by designing an image pickup lens which makes a solid image pickup element to obtain better evaluation when images obtained through the same image pickup lens respectively on the solid image pickup element and on a silver halide light-sensitive material are reproduced on a display to be evaluated.
Structure 2
An electronic still camera provided with an image pickup lens constituting an optical system which focuses a subject image on a prescribed image-focusing plane, a solid image pickup element having pixels in quantity A which is provided at the position of the image-focusing plane of the image pickup lens and generates image signals by transforming photoelectrically the image obtained by the image pickup lens, and an A/D converter which converts image signals from the solid image pickup element into digital signals, wherein the optical system satisfies the following conditions:
(conditions)
the total of evaluation points is not less than M×N×0.8, provided that &agr; is greater than 50000,
when;
I
1
represents an image obtained by the solid image pickup element having pixels in quantity of A,
I
2
represents an image obtained by a solid image pickup element having pixels in quantity of A+&agr; on its area identical in terms of size to the solid image pickup element having pixels in quantity of A,
images on plural sheets N are obtained for each of subjects in plural number M types, and
evaluation point 1 represents an occasion where image I
1
shows higher contrast and higher sharpness, and evaluation point 0 represents an occasion where image I
2
shows higher contrast and higher sharpness, all for evaluation.
In the case of this electronic still camera, it is possible to structure a lens which is suitable for a solid image pickup element with pixels in quantity of A, and is capable of obtaining a high grade image, by designing an image pickup lens which makes the solid image pickup element with pixels in quantity of A to obtain better evaluation when images obtained through the same image pickup lens respectively on the solid image pickup element with pixels in quantity of A and on the solid image pickup element with pixels in quantity of A+&agr; are reproduced on a display to be evaluated, resulting in realization of an electronic still camera equipped with a lens capable of obtaining a high grade image when conducting image pickup with a solid image pickup element.
Structure 3
The electronic still camera in Structure 2 wherein the solid image pickup element with pixels in quantity of A and that with pixels in quantity of A+&agr; are the same in terms of size.
In the case of this electronic still camera, it is possible to structure a lens which is suitable for a solid image pickup element with pixels in quantity of A, and is capable of obtaining a high grade image, by designing an image pickup lens which makes the solid image pickup element with pixels in quantity of A to obtain better evaluation when images obtained through the same image pickup lens respectively on the solid image pickup elements with different number of pixels (image pickup element with pixels in quantity A and that with pixels in quantity A+&agr;) are reproduced on a display to be evaluated, resulting in realization of an electronic still camera equipped with a lens capable of obtaining a high grade image when conducting image pickup with the solid image pickup ele
Bierman Jordan B.
Bierman, Muserlian and Lucas
Garber Wendy R.
Konica Corporation
White Mitchell
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