Television – Camera – system and detail – Combined image signal generator and general image signal...
Reexamination Certificate
1999-08-03
2004-07-20
Garber, Wendy R. (Department: 2612)
Television
Camera, system and detail
Combined image signal generator and general image signal...
Reexamination Certificate
active
06765614
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pixel defect compensating apparatus and a method of compensating pixel defect, particularly, relates to an apparatus and a method of compensating pixel defect of a solid-state image sensor by means of signal processing in an image pickup apparatus utilizing a solid-state image sensor of all-pixel readout system.
2. Description of the Related Art
Generally, it is well known that a pixel is deteriorated by sectional defect of semiconductor such as crystal defect in a solid-state image sensor such as a CCD (Charge-Coupled Device), which is produced from semiconductor. Such pixel defect as always adding a certain bias voltage to an image output in response to an amount of incident light appears on a monitor screen as a white spot in high intensity if a signal of the pixel defect is processed as it is. The white spot is called as a pixel of white defect.
FIG. 1
is a diagram of depicting a method of compensating pixel defect by a pixel defect compensating apparatus, which compensates a pixel of white defect of an interline solid-state image sensor, hereinafter called an interline CCD (IT-CCD), of the prior art. An IT-CCD reads out pixel signals in the interline transfer system. CCD signals, which are outputted from an IT-CCD, are processed to eliminate noise components prior to compensating pixels of white defect and adjusted to a predetermined signal level, and then converted into digital signals.
CCD signals, which are obtained from 2 pixels in horizontal direction and converted into a digital configuration, are mixed and called a luminance signal. The luminance signal is written in plurality of line memories by each line and compensates a pixel of white defect.
FIG. 1
is an example of compensating pixels of white defect included in luminance signals for 3 lines with providing line memories for 2 lines. Pixels of white defect in luminance signals for 3 lines are compensated by utilizing luminance signals for total 3 lines, which are composed of luminance signals for 2 lines read out from the line memories and a luminance signal for one line to be inputted succeeding to the 2 lines.
In
FIG. 1
, each 3 pixels continuing in horizontal direction are arranged in continuing 3 lines, that is, a first line L
0
, a second line L
1
, and a third line L
2
respectively. In other words, 3 pixels “a” through “c” are arranged in the line L
0
, and 3 pixels “d” through “f” are arranged in the line L
1
, and 3 pixels “g” through “i” are arranged in the line L
2
.
According to the method of compensating pixel defect of the prior art, a pixel of white defect at the pixels “b”, “e”, and “h” shown in
FIG. 1
is compensated by utilizing luminance signals of total 9 pixels forming a matrix of 3 pixels horizontally and 3 pixels vertically. In addition thereto, the compensation is applied to luminance signals for 3 lines together and not for each line so as to prevent a vertical aperture signal from a pixel of white defect, which may be included in the vertical aperture signal.
Compensation of a pixel of white defect in the pixel “e” is depicted first. Luminance signals of the pixels “d” and “f” are compared with each other and a lower signal level of them is defined “Y
1
L” as a representative value. Luminance signals of 6 pixels including pixels “a” through “c” and “g” through “i” are compared with each other and a highest signal level of them is defined “Y
1
H” as a representative value. Then, with comparing the representative values “Y
1
L” and “Y
1
H”, a larger value of them is defined “Y
1
”. In case that a value of subtracting the value “Y
1
” from a luminance signal value of the pixel “e” exceeds a predetermined threshold value, it is discriminated that a pixel of white defect is presented in the pixel “e”.
In the case of being discriminated that a pixel of white defect is presented in the pixel “e” as mentioned above, the pixel of white defect is compensated by replacing the luminance signal value of the pixel “e” with the value “Y
1
”. On the other hand, in case that a value of subtracting the value “Y
1
” from a luminance signal value of the pixel “e” does not exceed a predetermined threshold value, it is discriminated that a pixel of white defect is not presented in the pixel “e”. Then, the luminance signal value of the pixel “e” is utilized as it is.
In case that a pixel of white defect in the pixel “b” is compensated, luminance signals of the pixels “a” and “c” are compared with each other and a lower signal level of them is defined “Y
0
L” as a representative value. Luminance signals of pixels “d” through “f” are compared with each other and a highest signal level of them is defined “Y
0
H” as a representative value. Then, with comparing the representative values “Y
0
L” and “Y
0
H”, a larger value of them is defined “Y
0
”. In case that a value of subtracting the value “Y
0
” from a luminance signal value of the pixel “b” exceeds a predetermined threshold value, it is discriminated that a pixel of white defect is presented in the pixel “b”.
In the case of being discriminated that a pixel of white defect is presented in the pixel “b” as mentioned above, the pixel of white defect is compensated by replacing the luminance signal value of the pixel “b” with the value “Y
0
”. On the other hand, in case that a value of subtracting the value “Y
0
” from a luminance signal value of the pixel “b” does not exceed a predetermined threshold value, it is discriminated that a pixel of white defect is not presented in the pixel “b”. Then, the luminance signal value of the pixel “b” is utilized as it is.
In addition thereto, in case that a pixel of white defect in the pixel “h” is compensated, luminance signals of the pixels “g” and “i” are compared with each other and a lower signal level of them is defined “Y
2
L” as a representative value. Luminance signals of pixels “d” through “f” are compared with each other and a highest signal level of them is defined “Y
2
H” as a representative value.
Then, with comparing the representative values “Y
2
L” and “Y
2
H”, a larger value of them is defined “Y
2
”. In case that a value of subtracting the value “Y
2
” from a luminance signal value of the pixel “h” exceeds a predetermined threshold value, it is discriminated that a pixel of white defect is presented in the pixel “h”.
In the case of being discriminated that a pixel of white defect is presented in the pixel “h” as mentioned above, the pixel of white defect is compensated by replacing the luminance signal value of the pixel “h” with the value “Y
2
”. On the other hand, in case that a value of subtracting the value “Y
2
” from a luminance signal value of the pixel “h” does not exceed a predetermined threshold value, it is discriminated that a pixel of white defect is not presented in the pixel “h”. Then, the luminance signal value of the pixel “h” is utilized as it is.
Accordingly, in case that a luminance signal level of one pixel is extremely higher than those of adjacent pixels, the pixel is discriminated as a pixel of white defect and compensated as mentioned above.
However, with respect to a recent single-unit video camera-recorder utilizing a solid-state image sensor such as a CCD, a need for obtaining one blur-free still picture signal composed of moving picture signals including even and odd fields is increasing in conjunction with promoting higher image quality. In some cases, a progressive scan CCD, hereinafter called a PS-CCD, of all-pixel readout system is utilized for such a single-unit video camera-recorder not an IT-CCD, which reads out a pixel signal in the interline transfer system.
In case that a pixel of white defect in a CCD signal obtained from such a PS-CCD is compensated by a pixel defect compensating apparatus of the prior art with a luminance signal, which is obtained by mixing 2 pixels in horizontal direction, it causes a problem of deteriorating resolution. Further, in case that a pixel of white defect is compensated by a CCD signal, prior to mixing 2 pixels in horizontal direction, with
Anderson Kill & Olick P.C.
Garber Wendy R.
Lieberstein Eugene
Meller Michael N.
Tillery Rashawn N
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