JPH06284346A - Automatic defect detector for solid-state image pickup device - Google Patents

Abstract

PURPOSE:To accurately detect defective picture elements by relatively simple constitution. CONSTITUTION:This detector is provided with a level difference detection circuit 21 for detecting the level difference of a first picture signal from the first picture element of a solid-state image pickup element 3 and a second picture signal from a second picture element around the first picture element, a comparator 22 for comparing the output signal of the level difference signal circuit 21 with a prescribed threshold value Vr and a memory 11 for storing the compared results of the comparator 22 for plural fields and the defective picture elements are decided by the stored information of the memory 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic defect detecting apparatus for a solid-state image pickup device capable of automatically detecting a local crystal defect of a solid-state image pickup device such as a CCD.

[0002]

2. Description of the Related Art Generally, in a solid-state image pickup device formed of a semiconductor such as a CCD, a defective pixel in which excessive charge is generated due to a local crystal defect of the semiconductor may occur. Is known to cause deterioration. Conventionally, in order to eliminate image quality deterioration due to this defective pixel, in a solid-state imaging device using a CCD or the like, this defective pixel is detected and defect correction is performed.

A solid-state image pickup device having an automatic defect detection function as shown in FIG. 3 has been proposed. Referring to FIG. 3, reference numeral 1 in FIG. 3 denotes an image pickup lens, and the image pickup lens 1 guides incident light from a subject to an image pickup surface of a CCD solid-state image pickup device 3 via an optical filter 2.

As the CCD solid-state image pickup device 3, for example, a color CCD solid-state image pickup device having a color filter of complementary color mosaic arrangement as shown in FIG. 4 is used. The color filters of this complementary color mosaic array are Mg (magenta), G
(Green), Ye (yellow), and Cy (cyan) are arranged in a repeating pattern of [2 columns in the horizontal scanning direction] × [4 rows in the vertical scanning direction].

The color CCD solid-state image pickup device 3 employs, for example, an interline transfer system as a charge transfer system. Based on various timing signals generated by the timing generation circuit 4, the drive circuit 5 performs the readout of the signal charge of each pixel of the color CCD solid-state image sensor 3 and the drive control of vertical and horizontal transfer. The image pickup output signal (CCD
The output signal) is sampled and held by the sample and hold circuit 6 and digitized by the AD converter 7,
It is supplied to the defect detection circuit 8.

The spatial arrangement obtained from the color CCD solid-state image pickup device 3 is shown in FIG. Here, a signal of one field when the color CCD solid-state imaging device of the complementary color mosaic array is field-accumulated is shown as an example, and each pixel signal is defined as follows for simplification.

(Mg + Ye) = A (G + Cy) = B (G + Ye) = C (Mg + Cy) = D

Therefore, in the nth line, A ₁₁ , B ₁₂ , A ₁₃
Pixel signals of the combination ... are obtained in dot sequence. n
In the + 1st line, pixel signals of a combination of C ₂₁ , D ₂₂ , C _23, ... Are obtained dot-sequentially, and in the (n + 2) th line, A ₃₁ , B ₃₂ , A _33, ... And again the same as the nth line. Image signals of color combinations are obtained in dot sequence. The above is sequentially repeated.

When an image of a subject with little change in brightness is taken,
The following equation is locally established between pixel signals. A ₁₁ ≈ A ₁₃ ≈ A ₁₅ ≒ ‥‥‥, A ₁₃ ≈ A ₃₃ B ₁₂ ≈ B ₁₄ ≈ B ₁₆ ≈ ‥‥‥‥, B ₁₄ ≈ B ₃₄ C ₂₁ ≈ C ₂₃ ≈ C ₂₅ ≈ ‥‥‥‥, C ₂₃ ≈ C ₄₃ D ₂₂ ≈ D ₂₄ ≈ D ₂₆ ≈ ..., D ₂₄ ≈ D ₄₄ That is, the level difference of the output signals between the adjacent pixels of the same color is small.

Here, the defect detection circuit 8 will be described. It is assumed that the pixel corresponding to the pixel signal B ₃₄ is a defective pixel as shown by the hatching in FIG. In this case, an output level difference occurs between adjacent same-color pixel signals, and B ₃₂ ≠ B ₃₄ ≠ B ₃₆ , B
₁₄ ≠ B ₃₄ . In the defect detection circuit 8, paying attention to the spatial correlation of the output signal, the defective pixel is detected.

Here, the pixel signal B₃₄Determine the pixels that correspond to
If the pixel is a pixel, the adjacent same-color pixel signal is the pixel signal B.
₃₂, B₃₆, B₁₄And B₅₄4 pixel signals. Pixel signal
B₃₂And B₃₄Taking the level difference between
When capturing a screen with few changes, it is the adjacent pixels.
B₃₂≒ B₃₄Should hold, but the pixel signal B₃₄To
When the corresponding pixel is a defective pixel B₃₂≠ B₃₄Therefore,
This pixel signal B₃₂And B ₃₄And measure the level difference with
If the threshold value is exceeded, the pixel signal B₃₄Pixels corresponding to
It can be estimated that it is a fall pixel.

The CCD output signal from the defect detection circuit 8 is supplied to the signal processing circuit 9, and various signal processing such as defect correction is performed in this signal processing circuit 9 to obtain a predetermined color video signal at the output terminal 10. It is done like this.

[0013]

However, the pixel signal B
When pixels corresponding to ₃₄ images of the edge components is input between the pixel signal B ₃₂ and B ₃₄ as shown in FIG. 6 without a defect it will be also become B ₃₂ ≠ B _34, the pixel signal B ₃₄
There is an inconvenience that a pixel corresponding to is erroneously detected as a defective pixel.

Therefore, when the defective pixel is detected in the same field as described above, further peripheral pixel signals B ₃₆ , B
The respective level differences between ₁₄ and B ₅₄ and this pixel signal B ₃₄ must be determined to eliminate the effects as shown in FIG.

Further, although the color of the judgment pixel signal is B, the pixel signals of colors other than B in the periphery, for example, the level difference between D ₂₂ and D ₂₄ and the level difference between D ₄₂ and D ₄₄ are detected. There is an inconvenience that it becomes necessary to detect an edge whether or not an edge component exists between B ₃₂ and B ₃₄ .

Similarly, B₃₄And B₃₆To detect the edge between
D_{twenty four}And D₂₆Level difference judgment and D ₄₄And D₄₆Level with
Difference judgment is required, and B₃₄And B₁₄Edge detection between
A to get out₁₃And A₃₃Level difference judgment and A₁₅And A₃₅With
Level difference judgment is required. From these level difference information
Pixel signal B₃₄Whether the pixel corresponding to is a defective pixel
Assuming all input image patterns to make a decision
And the need for extremely complex detection algorithms.
There was a match.

In view of the above problems, an object of the present invention is to enable a defective pixel to be accurately detected with a relatively simple structure.

[0018]

An automatic defect detecting apparatus for a solid-state image pickup device according to the present invention is, for example, as shown in FIGS. 1 and 2, a first pixel signal from a first pixel of a solid-state image pickup device 3 and the periphery of the first pixel. Level difference detection circuit 21 for detecting the level difference from the second pixel signal from the second pixel of
It has a comparator 22 for comparing the output signal of 1 with a predetermined threshold value Vr, and a memory 11 for storing the comparison result of the comparator 22 for a plurality of fields. The defective pixel is determined based on the information stored in the memory 11. It was done like this.

In the automatic defect detecting apparatus of the solid-state image pickup device of the present invention, for example, as shown in FIGS. 1 and 4, the solid-state image pickup device 3 is provided with color filters of complementary color mosaic arrangement.

As shown in FIGS. 1 and 4, the automatic defect detecting device of the solid-state image pickup device of the present invention has the complementary color mosaic array color filters of Mg (magenta) and G as described above.
It is composed of a repeating pattern of (green), Ye (yellow), and Cy (cyan) [2 columns in the horizontal scanning direction] × [4 rows in the vertical scanning direction].

As shown in FIGS. 1 and 5, for example, the automatic defect detection device of the solid-state image pickup device of the present invention is such that, in the above description, the odd-numbered lines are pixel signals A and G (green) in which Mg (magenta) and Ye (yellow) are mixed. And the pixel signal B mixed with Cy (cyan) is a dot-sequential signal, and the even line has a pixel signal C mixed with G (green) and Ye (yellow) and a mixture of Mg (magenta) and Cy (cyan). The pixel signal D is a dot-sequential signal.

[0022]

According to the present invention, the result of comparison between the output signal of the level difference detection circuit 21 and the threshold value Vr is stored in the memory 11 over a plurality of fields, and the defective pixel is determined based on the information stored in the memory 11. Therefore, even if there is an edge component, the defective pixel can be accurately detected.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an automatic defect detecting apparatus for a solid-state image pickup device according to the present invention will be described below with reference to the drawings. In FIG. 1, parts that react with FIG.
Detailed description thereof will be omitted. Also in this example, the subject image from the imaging lens 1 is guided to the imaging surface of the CCD solid-state imaging device 3 via the optical filter 2.

As the CCD solid-state image pickup device 3, for example, a color CCD solid-state image pickup device having a color filter of complementary color mosaic arrangement as shown in FIG. 4 is used. The color filter of this complementary color mosaic arrangement has a repeating pattern configuration of [2 columns in the horizontal scanning direction] × [4 rows in the vertical scanning direction] of Mg (magenta), G (green), Ye (yellow), and Cy (cyan). It is a thing.

The color CCD solid-state image pickup device 3 employs, for example, an interline transfer system as a charge transfer system. Based on various timing signals generated by the timing generation circuit 4, the drive circuit 5 performs the readout of the signal charge of each pixel of the color CCD solid-state image pickup device 3 and the drive control of vertical and horizontal transfer.

The image pickup output signal (CCD output signal) of the color CCD solid-state image pickup device 3 is sampled and held by the sample and hold circuit 6, digitized by the AD converter 7, and then supplied to the defect detection circuit 8a. It

The spatial arrangement obtained from the color CCD solid-state image pickup device 3 is as shown in FIG. 5, and here, a signal of one field when the color CCD solid-state image pickup device of the complementary color mosaic arrangement is field-accumulated is taken as an example. Shows,
For simplification, as described above, (Mg + Ye) = A (G + Cy) = B (G + Ye) = C (Mg + Cy) = D.

Therefore, in the nth line, A ₁₁ , B ₁₂ , A ₁₃
Pixel signals of the combination ... are obtained in dot sequence. n
In the + 1st line, pixel signals of a combination of C ₂₁ , D ₂₂ , C _23, ... Are obtained dot-sequentially, and in the (n + 2) th line, A ₃₁ , B ₃₂ , A _33, ... And again the same as the nth line. Pixel signals of color combinations are obtained in dot sequence. The above is sequentially repeated.

When an image of a subject with little change in brightness is taken,
The following equation is locally established between the pixel signals, similarly to the above.

[0030] _{A 11 ≒ A 13 ≒ A 15} ≒ ‥‥‥, A 13 ≒ A 33 B 12 ≒ B 14 ≒ B 16 ≒ ‥‥‥, B 14 ≒ B 34 C 21 ≒ C 23 ≒ C 25 ≒ ‥‥ _{‥, C 23 ≒ C 43 D} 22 ≒ D 24 ≒ D 26 ≒ ‥‥‥, D 24 ≒ D 44

That is, the level difference of the output signals between the adjacent pixels of the same color is small.

As shown in FIG. 2, the defect detection circuit 8a according to the present example detects the level difference between adjacent pixel signals of the same color supplied from the input terminal 21a by the level difference detection circuit 21, and this level difference is the threshold value Vr. It is judged by the comparator 22 whether or not the above, and the output terminal 2 of this comparator 22
When the level difference obtained in 2a is equal to or larger than the threshold value Vr, the pixel which responds to this pixel signal is determined to be a defective pixel and the address information is stored in the memory 11.

As the memory 11, defective pixel address information over several fields, for example, 6 fields can be sequentially stored. As the memory 11, a field memory or a RAM that stores only address data can be used.

For example, as indicated by hatching in FIG. 5, the pixel signal B
₃₄It is assumed that the pixel corresponding to is a defective pixel. in this case
A level difference between adjacent same-color pixel signals occurs, and B₃₂≠ B₃₄
≠ B ₃₆Becomes The level difference between the same color pixel signals is
When the value is Vr or more, this B ₃₄Memory address information
Store in 11.

In this example, the address information of the defective pixel is stored in the memory 11 over the above-mentioned several fields, for example, 6 fields. Also, this memory 1
1 is provided with an algorithm for determining only the pixels which are always determined to be defective pixels as defective pixels over these several fields, for example, 6 fields.

The CCD output signal from the defect detection circuit 8a is supplied to the signal processing circuit 9, and various signal processing such as defect correction is performed in this signal processing circuit 9 to obtain a predetermined color video signal at the output terminal 10. I will do it.

According to this example, the level difference between the same-color pixel signals adjacent to each other for detecting the defective pixel is obtained, and when this level difference is equal to or more than the threshold value Vr, each field of the pixel corresponding to this pixel signal is detected. Since the address information is stored in the memory 11 and only the pixels determined to be defective pixels are always determined to be defective pixels over several fields, for example, 6 fields, the edge component of the moving image is generated by the time integration effect. Can be eliminated.

Therefore, according to this example, the risk of erroneous detection is greatly reduced and the detection accuracy is improved. Further, there is an advantage that the defect detection algorithm is simplified as compared with the case of processing only in the same field.

Further, in the above embodiment, the defect detection circuit 8
Although the threshold value Vr of the comparator 22 for comparing the level difference between the adjacent same-color pixel signals in a is relatively lowered and the pixel which is always determined as the defective pixel over several fields is determined to be the defective pixel. Raise the threshold value Vr,
Even if the edge component is erroneously detected even if it is wrong and the pixel determined to be the defective pixel even once over several fields is determined to be the defective pixel, the same effect as described above cannot be obtained. Easy to understand.

The present invention is not limited to the above-described embodiments, and it goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

[0041]

According to the present invention, the result of comparison between the output signal of the level difference detection circuit and the threshold value Vr is stored in the memory 11 over a plurality of fields, and the defective pixel is determined based on the information stored in the memory 11. Therefore, even if there is an edge component, there is an advantage that a defective pixel can be accurately detected with a simple configuration.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an automatic defect detection device of a solid-state image pickup device of the present invention.

FIG. 2 is a block diagram showing an example of a main part of FIG.

FIG. 3 is a block diagram showing an example of a conventional automatic defect detection device for a solid-state imaging device.

FIG. 4 is a diagram showing an example of a color filter having a complementary color mosaic arrangement.

FIG. 5 is a diagram showing an example of a spatial arrangement of pixel signals.

FIG. 6 is a diagram used for explaining the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Imaging lens 3 CCD solid-state imaging device 8a Defect detection circuit 9 Signal processing circuit 11 Memory 21 Level difference detection circuit 22 Comparator

Claims (4)

[Claims] 1. A level difference detection circuit for detecting a level difference between a first pixel signal from a first pixel of a solid-state image sensor and a second pixel signal from a second pixel around the first pixel, and the level difference detection circuit. A comparator for comparing the output signal of the difference detection circuit with a predetermined threshold value and a memory for storing the comparison result of the comparator for a plurality of fields are provided, and the defective pixel is determined based on the information stored in the memory. An automatic defect detection device for a solid-state imaging device, which is characterized in that 2. The automatic defect detection device for a solid-state imaging device according to claim 1, wherein the solid-state imaging device is provided with a color filter having a complementary color mosaic arrangement. 3. The automatic defect detection device for a solid-state image pickup device according to claim 2, wherein the color filters of the complementary color mosaic array are Mg (magenta), G (green), Ye (yellow), and Cy (cyan) [horizontal]. An automatic defect detection device for a solid-state image pickup device, which is constituted by a repeating pattern of [2 columns in scanning direction] × [4 lines in vertical scanning direction]. 4. The automatic defect detection device for a solid-state image pickup device according to claim 3, wherein the odd-numbered lines are pixel signals mixed with Mg (magenta) and Ye (yellow) and G (green).
And Cy (cyan) mixed pixel signals and dot-sequential signals, and even lines are G (green) and Ye.
An automatic defect detection device for a solid-state imaging device, which is a dot-sequential signal of a pixel signal mixed with (yellow) and a pixel signal mixed with Mg (magenta) and Cy (cyan).