Television – Camera – system and detail – Camera image stabilization
Reexamination Certificate
1997-12-22
2002-08-06
Ho, Tuan (Department: 2612)
Television
Camera, system and detail
Camera image stabilization
C348S352000
Reexamination Certificate
active
06429895
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an image sensing apparatus, having an image stabilization function, capable of obtaining a high-resolution image by slightly shifting an image formation position by an optical system, on an image sensing device for performing photo-electric conversion on the image, and an image synthesis apparatus for synthesizing images obtained by the image sensing apparatuses.
An electronic still camera which uses a solid-state image sensing device, such as a charge coupled device (CCD), instead of a silver-halide film has been commercialized. An electronic still camera is superior to a camera using the silver-halide film in instantaneity, however, inferior in resolution and dynamic range.
In order to improve the resolution, which is one of the above defects of an electronic still camera, an image sensing apparatus adopting pixel shifting method has been proposed. In the pixel shifting method, a plurality of images are sensed while slightly shifting the image formation position of an image, incoming through an optical system, on an image sensing device for performing photo-electric conversion on the image, and the plurality of sensed images are synthesized using a predetermined method to obtain a single high-resolution image. As the prior arts of the pixel shifting method, there are following Japanese Patent Application Laid-Opens, for example.
In the Japanese Patent Application Laid-Open No. 60-27278, a wedge-shaped prism provided in front of the lens systems is rotated about the optical axis, thereby the light path of an optical image formed on an image sensing device is shifted in parallel to the optical axis of the lens system. Then, output images are synthesized to obtain a single high-resolution image.
In the Japanese Patent Application Laid-Open No. 60-91774, in an optical system configured with a magnification optical sub-system and a master optical system, a part of the lens of the master optical system is shifted in the vertical direction with respect to the optical axis, thereby the light path of the optical image formed on an image sensing device is shifted in parallel to an optical axis of the optical system. Then the obtained output images are synthesized to obtain a single high-resolution image.
Further, in the Japanese Patent Application Laid-Open No. 61-236282, a transparent plane parallel plate provided in front of an image sensing device is rotated about an axis which is perpendicular to the optical axis of the image sensing device, thereby the light path of the optical image formed on the image sensing device is shifted in parallel to the optical axis. Then the output images are synthesized to obtain a single high-resolution image.
In the Japanese Patent Application Laid-Open No. 7-287268 (U.S. patent application Ser. No. 08/339,407), a variable apical angle prism provided in front of an optical system is operated on the basis of a vibration signal and a pixel shifting signal, thereby shifting the light path of the optical image formed on an image sensing device in parallel to the optical axis. Accordingly, compensation of vibration caused by a user as well as improvement of resolution of an image are achieved simultaneously.
Note, in this specification, any unintentional undesired movement of camera is expressed as “vibration”, and the movement is not limited to periodic motion.
However, in the aforesaid pixel shifting methods, it takes a long time from the first image signal until the last image signal are obtained, similarly to the case of performing multiple exposure in a still camera. Thus, when the electric still camera is vibrated, the quality of an image decreases, namely, a high-resolution image may not be obtained by performing pixel shifting. Thus, in order to overcome this problem, there are following Japanese Patent Application Laid-Opens, for example.
In the Japanese Patent Application Laid-Open No. 7-240932 (U.S. patent application Ser. No. 08/391,388), using a variable apical angle prism provided in front of the optical system or a moving lens system provided behind the optical system, both compensation of vibration and improvement of resolution of the image are achieved at the same time.
Further, according to the Japanese Patent Application Laid-Open No. 7-287268 (U.S. patent application Ser. No. 08/339,407), because resolution in pixel shifting operation decreases when the focal length of the optical system is larger than a predetermined value, pixel shifting is disabled in such a case.
Further, in order to widens dynamic range, which is the other defect of the electronic still camera, there are the following Japanese Patent Application Laid-Opens.
In the Japanese Patent Application Laid-Open No. 1-319370, an image sensing device is exposed a plurality of times with different luminous exposures, and a plurality of images obtained under this operation are synthesized to form a signal image of wide dynamic range.
In the Japanese Patent Application Laid-Open No. 7-264488, a plurality of image sensing devices having different sensibilities are used, and a plurality of images obtained by these image sensing devices are synthesized to form a single image of wide dynamic range.
Furthermore, as a technique for overcoming the aforesaid two problems at the same time, the Japanese Patent Application Laid-Open No. 8-37628 (U.S. patent application Ser. No. 08/505,608) discloses that at least one of a plurality of images obtained while performing pixel shifting is sensed in different luminous exposure from luminous exposure used for sensing other images, thereby obtaining an image of high resolution and wide dynamic range.
Further, in an image sensing apparatus having an image sensing device, it is possible to determine vibration of an image in advance to actually sensing the image by obtaining a movement vector of the image from time-sequential outputs from the image sensing device. Accordingly, in the Japanese Patent Application Laid-Open No. 2-57078 as a prior art in this field, a movement vector of an image is detected continuously, and, when the movement vector becomes the smallest, the image sensed at that time is decided as an image to be recorded, thereby reducing the effect of the vibration of an image sensing apparatus during exposure.
Furthermore, in the Japanese Patent Application Laid-Open No. 8-172568, movement vectors between a plurality of images sensed while performing pixel shifting are obtained, and component of vibration due to vibration of an image sensing apparatus or of an object are removed by performing interpolation, thereafter, the images are synthesized to form a single image of high resolution.
However, in the aforesaid conventional examples disclosed in the Japanese Patent Application Laid-Opens, there are following defeats.
In the methods disclosed in the Japanese Patent Application Laid-Open Nos. 60-27278, 60-91774, and 61-236282, no vibration correction mechanism is provided. Therefore, it is not possible to obtain a high-resolution image when blurring of an image caused by vibration of an image sensing apparatus is large. This is because the operation for obtaining a plurality of images in the pixel shifting method is the same as that of multiple exposure, as described above, and the time required in these operations, namely the time when the first image is sensed until the last image is sensed, is longer than the time required for performing a normal image sensing operation. As a result, effects of vibration on an image is greater when performing pixel shifting operation than when performing the normal image sensing operation vibration.
Further, according to the Japanese Patent Application Laid-Open No. 7-287268 (U.S. patent application Ser. No. 08/339,407), the variable apical angle prism, which is the light path shifting means used for vibration compensation and pixel shifting operation, is provided in front of the optical system, therefore, the coefficient (vibration compensation coefficient) for converting a vibration signal into a value for operating the variable api
Canon Kabushiki Kaisha
Ho Tuan
Morgan & Finnegan , LLP
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