JP2008017246A - Inspecting method and device for solid imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent deterioration in picture quality and a decrease in yield of a product as to a solid imaging device. <P>SOLUTION: In a CCD image sensor 2, a permissible pixel area 21 smaller in size than an original effective pixel area 20 is previously set. An inspecting device 30 for the CCD image sensor 2 detects the position of a defective pixel by a defective pixel detector 31 and decides whether the defective pixel detected by the defective pixel detector 21 can be interpolated by an interpolation propriety decision unit 32. Then the inspecting device determines an effective pixel area to be finally used by an effective pixel area determining unit 33 on the basis of results input from the defective pixel detector 31 and interpolation propriety decision unit 32. When there is a defective pixel which is detected that it is outside the permissible pixel area 21 by the defective pixel detector 31 and is decided that interpolation is impossible by the interpolation propriety decision unit 32 and it is decided that interpolation is possible for other defective pixels, the permissible pixel area 21 is determined as the effective pixel area to be finally used. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method and apparatus for inspecting a solid-state imaging device incorporated in a digital camera or a video camera.

  In recent years, digital cameras using a solid-state imaging device such as a CCD (Charge Coupled Device) image sensor have been widely used. In order to obtain a finer image with a digital camera, and in conjunction with the progress of semiconductor microfabrication technology, the number of pixels of the solid-state imaging device is increasing.

  In a solid-state imaging device, defective pixels that do not operate normally may occur due to the attachment of minute dust during manufacturing or crystal defects of the semiconductor. Defective pixels cause image quality degradation such as white scratches that appear whitish when extra signal components are added to the normal output signal, and black scratches that appear black when extra signal components are subtracted from the normal output signal. Become.

  In order to prevent image quality degradation due to defective pixels, a solid-state image sensor that does not have defective pixels may be simply manufactured. However, manufacturing a solid-state image sensor that does not have defective pixels completely increases the number of pixels. At the same time, it is quite difficult at present, and even if a solid-state imaging device without defective pixels can be manufactured, the manufacturing cost increases and the yield of the product is significantly reduced.

For this reason, conventionally, on the assumption that a certain number of defective pixels always exist, the number and positions of defective pixels are inspected after the manufacture of the solid-state imaging device, and those whose inspection results are within an allowable range are assigned to the digital camera. It was incorporated as a product. When the digital camera is used, the output signal of the defective pixel is interpolated using the output signal of the normal pixel adjacent to the defective pixel (see Patent Document 1).
JP-A-5-068209

  However, with the technique described in Patent Document 1, depending on the state of the defective pixel, such as when there are several defective pixels that are tightly located in one place, there is no normal pixel used for interpolation, and interpolation can be performed. Sometimes it disappeared. If interpolation is not possible, the product is naturally discarded as a defective product, which is a cause of a decrease in product yield.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an inspection method and apparatus for a solid-state imaging device capable of preventing image quality deterioration and product yield reduction.

  In order to achieve the above object, the present invention is an inspection method for a solid-state imaging device in which a plurality of pixels having a light receiving portion that photoelectrically converts incident light and outputs a signal charge, and detects the position of a defective pixel. Based on the detection step, the determination step for determining whether or not the output signal of the defective pixel can be interpolated with the output signal of another pixel, and the results of the detection step and the determination step And a determining step for determining an effective pixel region used for generating an image.

  An allowable pixel area having a size smaller than that of the original effective pixel area is set in advance. In the determination step, it is detected that the pixel is outside the allowable pixel area in the detection step, and the interpolation is not performed in the determination step. When there is a defective pixel determined to be possible and it is determined that the interpolation is possible for other defective pixels, the allowable pixel region is finally set as an effective pixel region used for generating the image. Is preferred.

  An allowable pixel area having a size smaller than that of the original effective pixel area is set in advance. In the determination step, it is detected that the pixel is within the allowable pixel area in the detection step, and the interpolation is not performed in the determination step. When there is a defective pixel that is determined to be possible, it is preferable that the product is defective.

  It is preferable that the allowable pixel area is set so that the center thereof coincides with the original effective pixel area.

  It is preferable that the permissible pixel area is set so that the aspect ratio matches the original effective pixel area.

  The allowable pixel area is preferably set to 50% or more and 90% or less of the original effective pixel area.

  In the determination step, when it is determined in the determination step that the interpolation is possible for all defective pixels, it is preferable that the original effective pixel region is finally used as the effective pixel region used for generating the image. .

  Further, the present invention is a solid-state image sensor inspection device in which a plurality of pixels having a light receiving unit that photoelectrically converts incident light and outputs a signal charge, the detection unit detecting a position of a defective pixel, A determination unit that determines whether or not an output signal of a defective pixel can be interpolated with an output signal of another pixel, and is finally used to generate an image based on the results of the detection unit and the determination unit And a determining unit that determines an effective pixel region.

  An allowable pixel area having a size smaller than the original effective pixel area is set in advance, and the determination unit detects that the detection unit is outside the allowable pixel area, and the determination unit does not perform the interpolation. When there is a defective pixel determined to be possible and it is determined that the interpolation is possible for other defective pixels, the allowable pixel region is finally set as an effective pixel region used for generating the image. Is preferred.

  An allowable pixel area having a size smaller than the original effective pixel area is set in advance, and the determination unit detects that the detection unit is within the allowable pixel area, and the determination unit does not perform the interpolation. When there is a defective pixel that is determined to be possible, it is preferable that the product is defective.

  It is preferable that the allowable pixel area is set so that the center thereof coincides with the original effective pixel area.

  It is preferable that the permissible pixel area is set so that the aspect ratio matches the original effective pixel area.

  The allowable pixel area is preferably set to 50% or more and 90% or less of the original effective pixel area.

  When the determination unit determines that the interpolation is possible for all defective pixels, the determination unit preferably uses the original effective pixel region as the effective pixel region that is finally used for image generation. .

  According to the inspection method and apparatus for a solid-state imaging device of the present invention, the position of a defective pixel is detected, and it is determined whether or not the output signal of the defective pixel can be interpolated with the output signal of another pixel. Based on these results, the effective pixel region to be finally used for image generation is determined, so that it is possible to prevent image quality degradation and product yield reduction.

  In FIG. 1, a CCD image sensor (hereinafter abbreviated as CCD) 2 is incorporated in an imaging device such as a digital camera or a video camera, and captures a subject image and outputs an imaging signal for use in generating the image. A light receiving unit 11, a readout transfer gate (hereinafter abbreviated as TG) 12, a vertical CCD (hereinafter abbreviated as VCCD) 13, a horizontal CCD (hereinafter abbreviated as HCCD) 14, and an output amplifier 15 that constitute the pixel 10. Consists of

  The light receiving units 11 are arranged in a matrix at a predetermined pitch in the vertical direction (arrow A direction) and the horizontal direction (arrow B direction) (for example, 4000 × 2000 × 8 million pixels, see FIG. 2). . A color filter and a microlens (not shown) are stacked on the light receiving unit 11. The light receiving unit 11 receives light incident through the microlens and the color filter, performs photoelectric conversion, and generates and accumulates signal charges corresponding to the amount of incident light. The TG 12 is provided in each light receiving unit 11 and transfers signal charges accumulated in the light receiving unit 11 to the VCCD 13.

  The VCCD 13 is provided between the vertical columns of the light receiving unit 11. The VCCD 13 transfers the signal charges transferred from the light receiving unit 11 via the TG 12 to the HCCD 14 line by line in the vertical direction. The last end of each VCCD 13 is connected to the HCCD 14. The HCCD 14 receives the signal charges output from the last end of the VCCD 13 line by line, and transfers the signal charges to the output amplifier 15 each time the signal charge for one line is received. The output amplifier 15 converts the signal charge for one row from the HCCD 14 into a signal voltage corresponding to the charge amount, and outputs the signal voltage to the outside of the CCD image sensor 2 as an imaging signal.

  In FIG. 2, the CCD 2 has a preset allowable pixel area 21 (shown by hatching) smaller than the original effective pixel area (width 4000 × length 2000 = 8 million pixels, aspect ratio 2: 1) 20. ing. As shown in the figure, the horizontal axis of the pixel 10 array is the X axis and the vertical axis is the Y axis. (2, 1),..., And the coordinates of the pixel 10 at the lower right corner are (4000, 2000), the allowable pixel area 21 is the pixel 10 at the coordinates (251, 126) and the lower right corner is the upper right corner. The coordinate (3750, 1875) has a size of horizontal 3500 × longitudinal 1750≈6 million pixels. The allowable pixel area 21 has the same aspect ratio 2: 1 as the original effective pixel area 20, and the center thereof coincides with the original effective pixel area 20.

  In FIG. 3, the CCD 2 inspection device 30 inspects the CCD 2 before shipping the imaging device incorporating the CCD 2, and includes a defective pixel detection unit 31, an interpolation enable / disable determination unit 32, and an effective pixel region determination unit 33. Is done.

  Here, the manufacturer of the CCD 2 inspects the defective pixels of the CCD 2 before shipping the CCD 2 to the manufacturer of the image pickup apparatus, and based on the inspection result, information on the position of the defective pixels, for example, the electronic information representing the coordinates of the defective pixels. Data is created, and this data is provided to the manufacturer of the imaging device together with the CCD 2. Data provided from the manufacturer of the CCD 2 is input to the defective pixel detection unit 31. The defective pixel detection unit 31 analyzes the input data to detect the position of the defective pixel, and outputs the detection result to the interpolation availability determination unit 32 and the effective pixel region determination unit 33.

  The interpolation enable / disable determining unit 32 determines whether or not the defective pixel detected by the defective pixel detecting unit 31 can be interpolated with the output signal of the adjacent pixel 10 when the defective pixel is mounted on the imaging apparatus.

  Specifically, it is examined from the information on the position of the defective pixel whether there is a normal pixel 10 that can be used for interpolation around the defective pixel. When there is a normal pixel 10 that can be used for interpolation (for example, one defective pixel surrounded by the normal pixel 10), it is determined that interpolation is possible, and conversely, it is used for interpolation. If there is no normal pixel 10 that can perform (for example, when four or more defective pixels are present together), it is determined that interpolation is impossible. The interpolation enable / disable determining unit 32 outputs the determination result to the effective pixel region determining unit 33.

  The effective pixel region determination unit 33 determines an effective pixel region to be finally used based on the results input from the defective pixel detection unit 31 and the interpolation availability determination unit 33.

  Specifically, there is a defective pixel 22a (see FIG. 2) that is detected by the defective pixel detection unit 31 to be outside the allowable pixel region 21 and is determined to be incapable of interpolation by the interpolation availability determination unit 32. When it is determined that interpolation is possible for other defective pixels, the allowable pixel area 21 is finally set as an effective pixel area to be used. On the other hand, when there is a defective pixel 22b (see FIG. 2) that is detected by the defective pixel detection unit 31 to be within the allowable pixel region 21 and is determined to be incapable of interpolation by the interpolation availability determination unit 32, The product is defective. If the interpolation enable / disable determining unit 32 determines that all defective pixels can be interpolated, the original effective pixel region 21 is finally used as an effective pixel region.

  Next, the inspection procedure of the CCD 2 by the inspection apparatus 30 having the above configuration will be described with reference to the flowchart of FIG. First, data representing the position of the defective pixel provided from the manufacturer of the CCD 2 is input to the defective pixel detection unit 31. The defective pixel detection unit 31 analyzes the input data and thereby detects the position of the defective pixel. The detection result by the defective pixel detection unit 31 is output to the interpolation availability determination unit 32 and the effective pixel region determination unit 33.

  The interpolability determination unit 32 determines whether the output signal of the defective pixel detected by the defective pixel detection unit 31 can be interpolated by the output signal of the adjacent pixel 10. The determination result by the interpolation availability determination unit 32 is output to the effective pixel region determination unit 33.

  The effective pixel region determination unit 33 determines the effective pixel region to be finally used based on the results input from the defective pixel detection unit 31 and the interpolation availability determination unit 33. That is, there is a defective pixel 22a that is detected by the defective pixel detection unit 31 to be outside the allowable pixel region 21 and that is determined to be incapable of interpolation by the interpolation availability determination unit 32, and interpolation is performed for other defective pixels. If it is determined that it is possible, the allowable pixel area 21 is finally determined as an effective pixel area to be used. On the other hand, if there is a defective pixel that is detected by the defective pixel detection unit 31 to be within the allowable pixel region 21 and that is determined to be incapable of interpolation by the interpolation availability determination unit 32, it is determined as a product defect, Discarded. If the interpolation enable / disable determining unit 32 determines that all defective pixels can be interpolated, the original effective pixel region 21 is finally determined as the effective pixel region to be used.

  Then, the CCDs 2 other than those discarded as product defects are mounted on the imaging device and shipped as products. When the image pickup apparatus is used, the CCD 2 is operated in the effective pixel area determined by the effective pixel area determining unit 33. When the allowable pixel area 21 is finally determined as an effective pixel area to be used, the pixel 10 of the original effective pixel area 20 that is not included in the allowable pixel area 21 is treated as an optical black (OP) area. Is called.

  As described above, the effective pixel region determination unit 33 finally uses the effective pixel area determination unit 33 based on the defective pixel position detection result by the defective pixel detection unit 31 and the interpolation availability determination unit 32 by the interpolation availability determination unit 32. Since the pixel area is determined, even a CCD having a defective pixel that cannot be interpolated, which has been discarded as a defective product in the past, may be shipped as a product if it is outside the allowable pixel area 21. it can. Also, defective pixels that cannot be interpolated outside the allowable pixel area 21 are treated as optical black areas and do not contribute to image generation, so there is no risk of image quality deterioration.

  In the above embodiment, an example in which the original effective pixel area 20 is 8 million pixels and the allowable pixel area 21 is about 75% 6 million pixels has been described. However, the allowable pixel area 21 is the original effective pixel area 20. It may be set to 50% or more and 90% or less. If the allowable pixel area 21 of 50% or less is used at the same focal length as when the original effective pixel area 20 is used, the captured image is originally set to 50% or more. This is because it is the same as the case where the effective pixel region 20 is used, and the wide-angle side is difficult to use, and the usability is deteriorated. If 90% or less, the possibility that defective pixels that cannot be interpolated is included in the allowable pixel region 21 is low (the probability is 10% or less when the probability is calculated from the area). This is because the effect of suppressing the decrease in product yield cannot be expected so much.

  Further, the allowable pixel area may be set in a plurality of stages, for example, 7 million pixels, 6 million pixels, 5 million pixels,. In this case, if there are defective pixels that cannot be interpolated within the allowable pixel area of 7 million pixels and outside the allowable pixel area of 6 million pixels, the allowable pixel area of 6 million pixels is finally used. If there is a defective pixel that cannot be interpolated within the allowable pixel area of 6 million pixels and outside the allowable pixel area of 5 million pixels, the final allowable pixel area is 5 million pixels. The effective pixel area to be finally used is gradually narrowed, such as the effective pixel area to be used. In this way, it is possible to further suppress a decrease in product yield.

  In the above embodiment, the position of the defective pixel is detected by the defective pixel detection unit 31 based on the data provided from the manufacturer of the CCD 2, but without using the data provided from the manufacturer of the CCD 2, the semiconductor The position of the defective pixel may be detected using a tester. In this case, the comparator compares the output signal of each pixel 10 with a preset threshold value (a value for detecting white or black flaws) input from the semiconductor tester, and based on the comparison result, the defective pixel is compared. Detection is performed.

  The determination of whether or not interpolation is possible differs depending on the interpolation method and the performance of the interpolation circuit. Therefore, the example related to the determination of whether or not interpolation is possible is merely an example, and the present invention is not particularly limited.

It is a schematic plan view which shows the structure of a CCD image sensor. It is a figure for demonstrating the relationship between the original effective pixel area | region and an allowable pixel area | region. It is a block diagram which shows the structure of an inspection apparatus. It is a flowchart which shows the test | inspection procedure by a test | inspection apparatus.

Explanation of symbols

2 CCD image sensor (CCD)
DESCRIPTION OF SYMBOLS 10 Pixel 11 Light-receiving part 20 Original effective pixel area 21 Permissible pixel area 22a, 22b Defective pixel 30 Inspection apparatus 31 Defective pixel detection part 32 Interpolation possibility determination part 33 Effective pixel area determination part

Claims (14)

A method for inspecting a solid-state imaging device in which a plurality of pixels having a light receiving unit that photoelectrically converts incident light and outputs a signal charge,
A detection step of detecting the position of the defective pixel;
A determination step of determining whether or not the output signal of the defective pixel can be interpolated with an output signal of another pixel;
And a determination step of finally determining an effective pixel region used for generating an image based on the results of the detection step and the determination step. An allowable pixel area that is smaller in size than the original effective pixel area is preset,
In the determination step, there is a defective pixel that is detected to be outside the allowable pixel region in the detection step and determined to be incapable of interpolation in the determination step, and the interpolation is performed for other defective pixels. The method for inspecting a solid-state imaging device according to claim 1, wherein, when it is determined that the allowable pixel area is possible, the allowable pixel area is an effective pixel area that is finally used for generating an image. An allowable pixel area that is smaller in size than the original effective pixel area is preset,
In the determining step, if there is a defective pixel that is detected in the detection step and is determined to be incapable of interpolation in the determination step, a defective product is determined. The method for inspecting a solid-state imaging device according to claim 1 or 2.   4. The inspection method for a solid-state imaging device according to claim 2, wherein the permissible pixel region is set so that a center thereof coincides with the original effective pixel region.   5. The method for inspecting a solid-state imaging device according to claim 2, wherein the permissible pixel area is set so that an aspect ratio thereof matches that of the original effective pixel area.   6. The inspection method for a solid-state imaging device according to claim 2, wherein the permissible pixel area is set to 50% or more and 90% or less of the original effective pixel area.   In the determination step, when it is determined in the determination step that the interpolation is possible for all defective pixels, the original effective pixel region is finally used as the effective pixel region used for generating the image. A method for inspecting a solid-state imaging device according to claim 1. An inspection apparatus for a solid-state imaging device in which a plurality of pixels having a light receiving unit that photoelectrically converts incident light and outputs a signal charge,
A detection unit for detecting the position of the defective pixel;
A determination unit that determines whether or not the output signal of the defective pixel can be interpolated with an output signal of another pixel;
An inspection device for a solid-state imaging device, comprising: a determination unit that finally determines an effective pixel region to be used for generating an image based on the results of the detection unit and the determination unit. An allowable pixel area that is smaller in size than the original effective pixel area is preset,
The determination unit includes a defective pixel that is detected by the detection unit to be outside the allowable pixel region and is determined to be impossible to be interpolated by the determination unit, and the interpolation is performed on other defective pixels. 9. The inspection apparatus for a solid-state imaging device according to claim 8, wherein if it is determined that the allowable pixel area is possible, the allowable pixel area is an effective pixel area that is finally used for generating an image. An allowable pixel area that is smaller in size than the original effective pixel area is preset,
The determining unit determines that the product is defective when there is a defective pixel that is detected by the detecting unit to be within the allowable pixel region and the determining unit determines that the interpolation is impossible. The inspection apparatus for a solid-state imaging device according to claim 8 or 9.   11. The inspection device for a solid-state imaging device according to claim 9, wherein the permissible pixel region is set so that a center thereof coincides with the original effective pixel region.   12. The inspection apparatus for a solid-state image pickup device according to claim 9, wherein the allowable pixel area is set so that an aspect ratio thereof coincides with the original effective pixel area.   13. The inspection apparatus for a solid-state imaging device according to claim 9, wherein the allowable pixel area is set to 50% or more and 90% or less of the original effective pixel area.   When the determination unit determines that the interpolation is possible for all defective pixels, the determination unit sets an original effective pixel region as an effective pixel region that is finally used for image generation. An inspection apparatus for a solid-state imaging device according to claim 8.

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