Television – Stereoscopic – Pseudo
Reexamination Certificate
1997-04-22
2002-09-10
Garber, Wendy R. (Department: 2612)
Television
Stereoscopic
Pseudo
C348S042000, C348S050000, C348S239000
Reexamination Certificate
active
06449004
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an electronic camera, particularly to an electronic camera which can correct an obliquely viewed object image into a photographic image viewed from front.
Electronic cameras have, as compared with conventional cameras which record images on a silver-salt film, an advantage of picking up images of satisfactory quality by suitably applying an image quality processing to the picked up images according to photographing purposes and types of objects since the quality of the photographed image can freely be processed. Thus, the electronic cameras are used as apparatus not only for usual picture taking, but also for photographing an information such as characters and graphics drawn on a white board at, e.g., a conference hall.
At the conference hall, the seats of participants are normally arranged with respect to the white board. Accordingly, if figures, characters or the like drawn on the white board are photographed without moving the seats, the photographed images are oblique images. Since the entire information such as characters drawn on the white board cannot be focused when photographing is performed obliquely with respect to the white board, a perspective geometric distortion is found in the photographed image, making it difficult to read such photographed information.
In order to avoid the problem of oblique images, the photographing position may be moved to a front position with respect to the white board. However, since it is difficult to move the photographing position during the conference, it is remarkably advantageous that the camera be provided with a function of photographing an image while correcting the geometric distortion thereof (i.e., a function of photographing while correcting an oblique image into a pseudo front image).
A variety of techniques for correcting the geometric distortion of a photographed image resulting from oblique photographing have been proposed.
For example, Japanese Unexamined Patent Publication No. 57(SHO)-129080 discloses a method for detecting or designating a specified position of an image, obtaining a normalized coefficient of this position with respect to a position on a sensing surface which this position is supposed to be located, and correcting an image distortion by applying a coordinate transformation to the input image in accordance with the obtained coefficient.
Further, Japanese Unexamined Patent Publication No. 3(HEI)-94383 discloses a method for supposing a known fixed geometry, arranging an input image within this fixed geometry, obtaining a transformation coefficient based on a deformed state of this fixed geometry, and correcting an obliquely photographed image by applying a transformation to the input image in accordance with the obtained coefficient.
Furthermore, Japanese Unexamined Patent Publication No. 5(HEI)-101221 discloses a method for superimposing an orthogonal lattice on an object surface, obtaining space coordinates of orthogonal lattice points, projecting a light while applying an orthogonal transformation to coordinate systems defined on a sensing surface, and correcting an obliquely photographed image by performing an offset calculation such that the luminance at a projection point is the luminance at the corresponding lattice points on the sensing surface.
However, according to the methods disclosed in the above publications, when the obliquely photographed image is to be corrected, a specified information needs to be input. Thus, it is difficult to perform photographing while the obliquely photographed image is corrected into a pseudo front photographed image by a simple operation.
More specifically, according to the method of the first publication, for the correction of the obliquely photographed image, a plurality of positions of the input image need to be designated to calculate a coordinate transformation coefficient. According to the method of the second publication, an image to be photographed needs to be arranged within an image of known fixed geometry. According to the method of the third publication, the two dimensional coordinates of the lattice points need to be input by superimposing the orthogonal lattice on the object surface and projecting the respective lattice points. It is extremely difficult to perform the above operations during picture taking.
Further, according to the above methods, since the obliquely photographed image is corrected into a pseudo front photographed image by coordinate transformation, the correction is complicated and it is difficult to rapidly perform it .
On the other hand, in an oblique photographic scene, the sensing surface and the object surface are normally parallel to each other along the vertical direction, but inclined to each other in a horizontal plane. Accordingly, assuming that &thgr;, S and m denote an angle of inclination, an object image and a photographing magnification, an oblique image projected on the sensing surface of the camera is m·S cos(&thgr;). Thus, if the angle of inclination &thgr; and the photographing magnification m are known, the oblique image can be corrected into a front image based thereon by a simple operation.
In view of the above, an electronic camera has been proposed which can calculate a distribution of photographing magnification m within the obliquely photographed image based on the angle of inclination &thgr; and a distance to the object and correcting the obliquely photographed image into a front image using the angle of inclination &thgr; and the distribution of photographing magnification m .
A variety of methods may be adopted to correct the distortion of an obliquely photographed image based on the angle of inclination &thgr; and the distribution of photographic magnification m. For example, the obliquely photographed image may be corrected into a pseudo front image by applying image compression to a portion of the obliquely photographed image closer than a focus position (normally, center position of the photographed image), while applying image enlargement to a portion thereof more distant that the focus position. Further, the obliquely photographed image may be corrected into a pseudo front image by using one end of the obliquely photographed image as a reference and applying image enlargement to the entire image at the other end. In such cases, the enlarged image may bulge out of the field, and a portion of the obliquely photographed image may be missing due to the correction. If a missing portion becomes larger, a necessary image cannot be photographed, with the result that the function of correcting the distortion of the obliquely photographed image may end up causing problems.
It is extremely difficult for a camera operator to predict the missing portion after correction based on the angle of inclination and an object obliquely viewed through a viewfinder. Normally, the presence or absence of the missing portion of the image and the range thereof cannot be confirmed unless the photographed image is printed out. Accordingly, an ability to confirm a range where the distortion of the obliquely photographed image is correctable before photographing is desirable for the above mentioned image distortion correcting method.
Further, according the above image distortion correcting method, unless the angle of inclination &thgr; is accurately input, the distortion of the obliquely photographed image is improperly corrected, resulting in an unnatural photographed image. Accordingly, an angle of inclination setting member of the camera needs to relatively accurately set the angle of inclination &thgr;. On the other hand, if the camera requires a complicated operation to set the angle of inclination, the operability for photographing is reduced and the image distortion correcting function cannot effectively be utilized. Therefore, the setting member should be able to easily and rapidly set the angle of inclination &thgr;.
For example, in the case that the camera operator sets the angle of inclination between the sensing surface and the object surface, there can be consi
Fujii Shinichi
Karasaki Toshihiko
Minato Shoichi
Okisu Noriyuki
Burns Doane , Swecker, Mathis LLP
Garber Wendy R.
Minolta Co. , Ltd.
White Mitchell
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