Television – Camera – system and detail – Combined image signal generator and general image signal...
Reexamination Certificate
1998-10-02
2003-09-02
Garber, Wendy R. (Department: 2612)
Television
Camera, system and detail
Combined image signal generator and general image signal...
C348S241000, C348S608000, C375S240250, C375S240260
Reexamination Certificate
active
06614473
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to the processing of output of an effective pixel region and an optical black area of a solid-state image sensor used in a camera.
(2) Description of the Related Art
As shown in
FIG. 5
, in a conventional photovoltaic surface of a CCD, which is a solid-state image sensor applicable to, for example, a digital camera, there are provided an effective area
50
a
serving as an effective pixel region in which image signals of pixels (cells) can be read, and an optical black area (OB)
50
b
in which reference black level signals for correction of the image output signals with regard to the above-mentioned pixels can be read.
Further, output signals from each pixel array of the CCD are sampled-and-held by a correlated double sample-and-hold circuit, subjected to an A/D conversion, temporarily stored in a DRAM, subjected to a compressing process by a compressing/decompressing circuit, and then, stored as image signals in a recording medium such as a memory card.
The compressing process is carried out in such a manner that all the pixel arrays which include the effective area.
50
a
and the OB area
50
b
are divided into a predetermined unit block of n (number of pixels) by m (number of pixels), such that output of each pixel is read by the unit block, and subjected to a DCT, and then, Huffman coding processing is conducted. At regeneration, the compressed data in each block is inversely transformed by a decompressing process and image signals are obtained. Incidentally, the compressing process is irreversible, so that the image signals processed by the irreversible compressing process are not exactly the same as the image signals before the compressing process, even if the compressed image signals are decompressed.
With regard to the conventional imaging apparatus described above, the compressing process is conducted in such a manner that the pixel arrays of the CCD are divided into blocks of n by m as described above. However, when all the pixels of the CCD are divided into the blocks, a boundary line L
0
between the effective area
50
a
and the OB area
50
b
may run through the divided blocks described above like a boundary block
50
c
, as shown in
FIG. 6
, owing to the relationship between the number of all the pixels and the number of pixels in divided blocks. When the image signals of the boundary blocks
50
c
are compressed and regenerated by the decompressing process, the regenerated image of the boundary blocks
50
c
is not exactly the same as the original image owing to the irreversibility of the compressing process. Therefore, the optical black area affects the effective area, so that the boundary line L
0
becomes irregularly fuzzy causing poor quality of the image output.
As shown in
FIG. 6
, showing an enlarged arrangement of the photovoltaic surface, when all the pixels of the CCD are divided into the blocks
50
c
, the boundary line L
0
may be coincident with a dividing line L
1
of the divided blocks. Pixel output signals around the dividing line L
1
, which lies in the transition area to the optical black area may include noise. When the output signals of the effective area have the noise described above, an imaging signal level in the edge portion of the area may fluctuate, so that the regenerated image has poor quality.
Additionally, in the conventional compressing process, only the effective area is recorded and a black level is determined by a clamping process at the time of recording, so that a stable accuracy of the black level is hardly obtained. Further, it is capable of correcting the black level at the time of recording, but there is a problem that the period of the recording process becomes long.
SUMMARY OF THE INVENTION
The present invention is intended to address the problems described above. An object of the present invention is to provide a camera that uses a solid-state image sensor in which fluctuations at a boundary region between an effective pixel region and an optical black area are removed so as to obtain picture signals with high quality; and further, in which a highly accurate black level can be detected and correction is conducted at regeneration.
A first camera in accordance with the present invention includes: a solid-state image sensor having an optical black area at a predetermined region other than an effective pixel region; a correlated double sample-and-hold circuit provided with the solid-state image sensor for sampling-and-holding pixel output of the solid-state image sensor; and a compressing unit for irreversibly compressing output signals of the correlated double sample-and-hold circuit corresponding to the effective pixel region and the optical black area of the solid-state image sensor, respectively; and wherein the solid-state image sensor has a margin area which is provided at a boundary area between the effective pixel region and the optical black area, and the margin area does not contribute to regeneration of an image.
A second camera in accordance with the present invention includes: a solid-state image sensor having an optical black area at a predetermined region other than an effective pixel region; a correlated double sample-and-hold circuit provided with the solid-state image sensor for sampling-and-holding pixel outputs of the solid-state image sensor; and a compressing unit for irreversibly compressing output signals of the correlated double sample-and-hold circuit corresponding to the effective pixel region and the optical black area of the solid-state image sensor, respectively; and wherein the solid-state image sensor has a margin area which is provided at a boundary area between the effective pixel region and the optical black area, and the margin area does not contribute to regeneration of an image, and the width in the line direction of the optical black area is set to 2 times or more by integer the width of the block area as a processing unit in the irreversible compressing process by the compressing unit.
A third camera in accordance with the present invention includes: a solid-state image sensor having an optical black area at a predetermined region other than an effective pixel region; a correlated double sample-and-hold circuit provided with the solid-state image sensor for sampling-and-holding pixel outputs of the solid-state image sensor; and a compressing unit for irreversibly compressing output signals of the correlated double sample-and-hold circuit corresponding to the effective pixel region and the optical black area of the solid-state image sensor, respectively.
REFERENCES:
patent: 5486859 (1996-01-01), Matsuda
patent: 5608455 (1997-03-01), Oda
patent: 5719624 (1998-02-01), Sasaki et al.
patent: 6011583 (2000-01-01), Hieda et al.
patent: 6061092 (2000-05-01), Bakhle et al.
patent: 6072527 (2000-06-01), Iwai
patent: 6323900 (2001-11-01), Kobayashi
patent: 6426771 (2002-07-01), Kosugi
Garber Wendy R.
Volpe and Koenig P.C.
Ye Lin
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