JP2903956B2 - Pixel defect correction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus using a solid-state image pickup device such as a CCD, and more particularly to a pixel defect correction device for detecting and correcting a pixel defect existing in the solid-state image pickup device.

[0002]

2. Description of the Related Art It is generally known that, in a solid-state imaging device formed of a semiconductor such as a CCD, image quality is deteriorated due to local crystal defects of the semiconductor. An image defect in which a constant bias voltage is always added to the imaging output according to the amount of incident light is called a white defect because if this image defect signal is processed as it is, it appears as a high-luminance white dot on the monitor screen. I have. In addition, those having low photoelectric sensitivity appear as black spots, and are called black scratches (hereinafter, pixel defects are called scratches).

[0003] Conventionally, detection of such flaws is disclosed in, for example, JP-A-61-261974. This method is a method of detecting, as a flaw, a pixel in which a target pixel has an output larger or smaller than a peripheral pixel by a certain amount or more, and takes a difference between adjacent pixels in the horizontal direction and the vertical direction to be different from the peripheral pixel This is to detect a pixel having an output.

Hereinafter, the case of detecting white flaws in the horizontal direction of the CCD will be described. Further, the present invention uses a plurality of CCDs. In this case, three CCDs are used, and R, G, and B light signals are used for these three CCDs.
A specific description will be given of a case where a conventional pixel defect correction apparatus is applied as it is to a so-called three-plate input to three CCDs. White flaws usually protrude by only one pixel from peripheral pixels. For example, the relationship between the pixel of interest and the pixels before and after the pixel of interest is represented as G input in FIG. For this reason, when the target pixel is compared with the adjacent pixels before and after the target pixel, if the target pixel is larger than the pixels before and after the certain level, it can be regarded as a flaw.

FIG. 8 shows a block diagram for realizing the above contents. The CCD output signals to which the R, G, and B light signals have been input are output through the correction circuits 14, 15, and 16 and are also input to the detection circuits 11, 12, and 13, and are output from these detection circuits. Depending on the output, the corresponding correction circuit 14,
15 and 16 are controlled.

FIG. 11 shows a block diagram of an example of the detection circuit. The input signal is a plurality of flip-flops (hereinafter F
F), the pixel value of interest sequentially transmitted through 21 and 22 and the pixel values before and after it, y _n−1 , y _n and y _{n + 1} are obtained.
Hereinafter, signals are represented by representing r, g, and b with y.
These signals are added to adders 23 and 24 and a comparison circuit 2
5, 26, the following operation is performed by the AND circuit 27.

[0007] _{y n-1 -y n> a} 1 y n + 1 -y n> a 2 a 1, a 2 is the amount of projection of the threshold for y _n-1, y _{n + 1} of the y _n In this case, it is assumed that a ₁ = a ₂ = a (> 0).

As described above, if the value of the pixel of interest protrudes by a certain level or more with respect to the values of the peripheral pixels, it is regarded as a flaw and "1" is output. Otherwise, "0" is output. The correction circuit is controlled by the detection output.

Japanese Patent Laid-Open No. Sho 62-62
Several methods are disclosed in JP 8666. For example, a method of replacing with one pixel or two pixels before, a method of replacing with the average of previous and next pixel values, a method of similarly thinking in the vertical direction, a method of replacing with one pixel higher, a method of averaging upper and lower pixel values For example.

FIG. 12 is a block diagram showing an example of the correction circuit. Here, it is assumed that the correction circuit replaces with the average of the preceding and following pixel values, and the operation is as follows. The input signal passes through the FFs 41 and 42, and extracts the value of the central target pixel and the pixel values before and after it. The average of these values is obtained from the pixel values before and after the pixel of interest and used as a correction signal. In accordance with the detection signal of the detection circuit, the value of the central target pixel is normally output, and when it is determined that the pixel is flawed, a correction signal is output.

From the above, in each of the R, G, and B paths,
Pixels projecting beyond a certain level with respect to the values of peripheral pixels can be detected as flaws, and can be corrected so as not to be noticeable.

FIG. 9 shows a first signal waveform example in the conventional pixel defect correction device. FIG. 9A shows a state in which the G flaw is corrected.

The above-described pixel defect correction operation is performed by three CCs.
A similar circuit can be used even if D performs pixel shift such that R and B are shifted by half a pixel with respect to G, for example.

FIG. 10 shows a second signal waveform example in the conventional pixel defect correction device. FIG. 10A shows a state in which the G flaw is corrected.

[0015]

However, according to the above-described method, a signal such as a point light source is erroneously determined to be flawed because it protrudes despite being a signal. For example, FIG.
(B) is input, the signal at the center is erroneously determined to be flawed and erroneously corrected. As a result, as in the output shown on the left side of FIG. As described above, when there is a signal such as a point light source, there is a problem that the image quality is deteriorated and a good image cannot be obtained.

A similar problem occurs even if the three CCDs perform pixel shift such that R and B are shifted by half a pixel with respect to G, for example. For example, when a signal as shown in FIG. 10B is input in which only one point is bright in the dark surroundings, the signal at the center is erroneously determined to be flawed and erroneously corrected. As a result, as in the output shown on the left side of FIG.

As described above, when there is a signal such as a point light source, there is a problem that the image quality is deteriorated and a good image cannot be obtained.

The present invention is intended to solve such a conventional problem. A simple structure is used to accurately discriminate a signal and a flaw, correct only the flaw, and perform processing on an image including a signal such as a point light source. Another object of the present invention is to provide a pixel defect correction device capable of obtaining a good image without deteriorating the original image quality.

[0019]

According to the present invention, there is provided a pixel defect correcting apparatus comprising: a plurality of solid-state imaging devices; a detection circuit for detecting protrusion from a value of a pixel of the solid-state imaging device output from the solid-state imaging devices; It comprises a correlation detection circuit for detecting the correlation between the outputs of these detection circuits, and a correction circuit controlled by the output signal of the correlation detection circuit.

Further, the pixel defect correcting device of the present invention has a first
A plurality of solid-state imaging devices in which the second solid-state imaging device is arranged at a position shifted by a half pixel with respect to the solid-state imaging device, and the first solid-state imaging device and the first pixel of the first solid-state imaging device project from the values of the pixels before and after the first solid-state imaging device A first detection circuit for detecting, and a second and a second solid-state imaging devices around a half pixel of the first pixel of the first solid-state imaging device
A second detection circuit that detects the protrusion of the value of the second and third pixels from the value of the third pixel and the values of pixels before and after the third pixel, and a correlation between outputs of the first and second detection circuits. It comprises a correlation detection circuit and a correction circuit controlled by an output signal of the correlation detection circuit.

[0021]

According to the present invention, even for a signal such as a point light source, erroneous detection and erroneous correction are not performed as in the prior art, the signal and the flaw can be distinguished, and the flaw can be detected with high accuracy. As a result, a good image can be obtained without deteriorating the original image quality.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of a first embodiment of the present invention. The output signals of the CCDs 1, 2, and 3 to which the R, G, and B light signals have been input are respectively corrected by the correction circuits 14, 15,
16 and output from the detection circuits 11, 1
2, 13 and by the outputs of these detection circuits,
Control the corresponding correction circuit.

An example of the detection circuit is the same as the block diagram shown in FIG. That is, the input signal passes through a plurality of flip-flops (hereinafter abbreviated as FF) 21 and 22,
The pixel value of interest sequentially sent and the pixel values before and after it, y
_n-1, y _n, obtain y _{n + 1.} Thereafter, the signals are denoted by r, g,
b is represented by y. The following calculations are performed on these signals by the adders 23 and 24, the comparison circuits 25 and 26, and the AND circuit 27.

[0024] _{y n-1 -y n> a} 1 y n + 1 -y n> a 2 a 1, a 2 is an amount of protrusion of the threshold for y _n-1, y _{n + 1} of the y _n Here, it is assumed that a ₁ = a ₂ = a (> 0).

As described above, if the value of the pixel of interest protrudes by more than a certain level with respect to the value of the peripheral pixels, it is regarded as a defect and "1" is output. Otherwise, "0" is output.

FIG. 2 shows a circuit diagram of an example of the correlation detection circuit. The operation of this circuit will be described focusing on the path of G. When the G input is “1” and both R and B are “0”, the G output of the correlation detection circuit is regarded as having no correlation with G and other signals, and the possibility of scratches is high. Judge that "1"
Is output. When the G input is “1” and both or one of R and B is “1”, it is determined that there is a correlation between G and other signals, and it is determined that the possibility of a point light source is high.
Outputs "0".

FIG. 12 is a block diagram showing an example of the correction circuit. The correction circuit is controlled by the correlation detection output. In the correction operation, similarly to the conventional example, when it is determined that a defect is present, the pixel value is replaced with the average of previous and subsequent pixel values. That is, the input signal passes through the FFs 31 and 32, extracts the value of the center pixel of interest and the pixel values before and after it, and obtains an average value of these values from the pixel values before and after the pixel of interest to obtain a correction signal. In accordance with the detection signal of the correlation detection circuit 17, the value of the central target pixel is normally output, and when it is determined that the pixel is flawed, a correction signal is output.

FIG. 3 shows a signal waveform in the first embodiment of the present invention. The relationship between the input and output of R, G, B in the case of a flaw and the case of a point light source in the above circuit will be described. R, G, B in the case of a scratch and a point light source in the above circuit
Shows the relationship between the input and output of. When there is a flaw in G as in this example, only G protrudes and is corrected. In the case of a normal white point light source, since there is a correlation between R, G, and B, the signal is determined to be a signal, and an original signal is output without being erroneously corrected.

Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. FIG. 4 shows a block diagram of a second embodiment of the present invention. This figure shows a case where detection and correction are performed for two paths of G and R for simplicity. Hereinafter, a case where the two paths are detected and corrected will be described.

Here, the R and B CCs are set with respect to the G CCD 1.
D2 and D3 are arranged at positions shifted by half a pixel.

CCDs 1 and 2 to which G and R optical signals are input
Are output via the correction circuits 14 and 15, and the detection circuit 11, the detection circuit 61, and the detection circuit 62
Is input to the detection circuit 12. Here, the detection circuit 11
And the detection circuit 62, and the detection circuit 61 and the detection circuit 12 are the same circuit.

The outputs of the detection circuits 11 and 12 are input to the correlation detection circuit 18, and the output of the correlation detection circuit 18 controls the G path correction circuit 14.

The outputs of the detection circuits 61 and 62 are input to the correlation detection circuit 19, and the output of the correlation detection circuit 19 controls the R path correction circuit 15.

Hereinafter, the case of detecting and correcting the G signal, that is, the outputs of the detection circuits 11 and 12 are input to the correlation detection circuit 18,
The case where the correction circuit 14 of the G path is controlled by the following will be described.

An example of the detection circuit is the same as the block diagram shown in FIG. This operation is basically the same as that described in the first embodiment. The following calculation is performed on the sequentially transmitted pixel value of interest and the pixel values g _n−1 , g _n , and g _{n + 1} before and after it.

[0036] _{g n-1 -g n> a} g n + 1 -g n> a a is the amount of projection of the threshold for _{g n-1, g n +} 1 of g _n. Detecting a projected against _{g n-1, g n +} 1 of g _n This operation, if projecting a certain level or higher outputs "1", and outputs the otherwise "0".

FIG. 5 is a block diagram showing an example of the detection circuit. The detection circuit 12 performs an auxiliary operation on the detection circuit 11 in detecting a G defect. In the case of a normal white point light source and the center is g _n , the point light source has a spread due to the influence of the optical LPF, and in addition to g _n , the surrounding pixels, ie, r
Light also _hits portions corresponding to _{n - 0.5} and rn _{- 0.5} , and a signal is generated. In the case of a flaw, only g _n protrudes, and no protruding occurs in other paths. For this reason, the detection circuit 12 detects the value of the surrounding pixels, that is, rn _{- 0.5} , and the protrusion of the pixels before and after _{rn - 0.5} , so that it is possible to determine whether the light source is a point light source or a flaw. .

The operation of the detection circuit 12 will be described below. The input signal passes through a plurality of flip-flops 71 to 74, and sequentially transmits a target pixel value and pixel values r before and after the target pixel value.
_{n-1. 5, r n-} 0 .5, r n- 0 .5, obtain r _{n + 1. 5.} For these signals, adders 75 to 77, comparison circuits 78 and 79,
The following operation is performed by the AND circuit 80.

[0039] _{(r n- 0 .5 + r n-} 0 .5) / 2 = r n 'r n' -r n-1. 5> b 1 r n '-r n + 1. 5> b 2 b _1, b ₂ is _{r n-1. 5, r} n + 1. threshold amount of projection for ₅ r _n ', where b ₁ = b ₂ = considered as b (> 0).

As described above, if the value of the pixel of interest protrudes by more than a certain level with respect to the values of the peripheral pixels, it is regarded as a flaw and "1" is output. Otherwise, "0" is output.

The detection circuit 11 and the detection circuit 12 are input to the correlation detection circuit 18. FIG. 6 shows an example of the correlation detection circuit 18. Here, the correlation detection circuit 18 and the correlation detection circuit 19
Are the same circuit. The output of the correlation detection circuit 18 is G
When the input is “1” and the R input is “0”, it is considered that there is no correlation between the G input and the R input, it is determined that the possibility of the scratch is high, and “1” is output. Also, even if the G input is "1",
When both or one of R and B is “1”, it is considered that there is a correlation between G and other signals, it is determined that the possibility of a point light source is high, and “0” is output.

An example of the correction circuit is the same as the block diagram of FIG. The correction circuit is controlled by the correlation detection output. The correction operation is the same as in the conventional example.
It is assumed that the pixel value is replaced with the average of the preceding and following pixel values. The input signal passes through the FFs 41 and 42, and extracts the value of the central target pixel and the pixel values before and after the central pixel, and obtains an average value of these values from the pixel values before and after the target pixel as a correction signal. According to the detection signal of the correlation detection circuit, the value of the central target pixel is normally output, and when it is determined that the pixel is flawed, a correction signal is output.

FIG. 7 shows a signal waveform in the second embodiment of the present invention. The relationship between the input and output of R, G, B in the case of a flaw and the case of a point light source in the above circuit will be described. When there is a flaw in G as in this example, only G protrudes and is corrected. In the case of a normal white point light source, since there is a correlation between R, G, and B, the signal is determined to be a signal, and an original signal is output without being erroneously corrected. In this example, since the circuit is for two paths of G and R, the B signal does not directly contribute to the output.

As described above, the case of detecting and correcting the two paths G and R has been described.
Similar to the processing for R, it can be realized by performing the same processing for R, B, B, and G. In the detection, for example, for G, the output of the G detection circuit and R,
A method is also conceivable in which the correlation detection circuit obtains a correlation from a total of three outputs of both the detection circuit B.

In the first and second embodiments described above, only the white flaws have been described. However, regarding the black flaws, a ₁ and a ₂ are considered in consideration of the fact that the directions of the flaws are opposite.
By changing the sign and the direction of the inequality sign, the detection can be performed in the same manner.

Although the above embodiment has been described only in the horizontal direction, the same applies to the vertical direction, and processing combining both the horizontal direction and the vertical direction is also possible.

[0047]

As is apparent from the above description, according to the present invention, signals such as point light sources are not erroneously detected and erroneously corrected as in the prior art. Since the detection can be performed with high accuracy, it is possible to correct only the flaw and obtain a good image without deteriorating the original image quality.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a pixel defect correction device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing an example of the internal configuration of a correlation detection circuit according to the first embodiment;

FIG. 3 is a signal waveform diagram for explaining the operation of the first embodiment.

FIG. 4 is a block diagram illustrating a configuration of a pixel defect correction device according to a second embodiment of the present invention.

FIG. 5 is a block diagram showing an example of the internal configuration of a detection circuit according to the second embodiment.

FIG. 6 is a block diagram showing an example of the internal configuration of a correlation detection circuit according to the second embodiment;

FIG. 7 is a signal waveform diagram for explaining the operation of the second embodiment.

FIG. 8 is a block diagram showing a configuration of a conventional pixel defect correction device.

FIG. 9 is a signal waveform diagram for explaining the operation of the conventional pixel defect correction device.

FIG. 10 is a signal waveform diagram for explaining the operation of the conventional pixel defect correction device.

FIG. 11 is a block diagram showing an example of the internal configuration of a detection circuit in the conventional example.

FIG. 12 is a block diagram showing an example of the internal configuration of a correction circuit in the conventional example.

[Explanation of symbols]

 1-3 CCD 11-13 Detection circuit 14-16 Correction circuit 17 Correlation detection circuit

Claims (2)

(57) [Claims] A plurality of solid-state imaging devices; a plurality of detection circuits for detecting a protrusion from a pixel value of an output of the solid-state imaging device; a correlation detection circuit for detecting a correlation between outputs of the detection circuits; A correction circuit controlled by an output signal of the correlation detection circuit. 2. A plurality of solid-state imaging devices in which a second solid-state imaging device is displaced by a half pixel with respect to the first solid-state imaging device; and a first pixel of the first solid-state imaging device and the first solid-state imaging device. A first detection circuit for detecting protrusion from values of preceding and succeeding pixels, and second and third pixels of the second solid-state imaging device located before and after half a pixel of the first pixel of the first solid-state imaging device A second detection circuit for detecting the protrusion of the values of the second and third pixels from the value of the pixel and the values of the pixels before and after the second detection circuit, and a correlation detection circuit for detecting the correlation between the outputs of the first and second detection circuits. And a correction circuit controlled by an output signal of the correlation detection circuit.