JPH1194696A - Ccd inspection device and method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make accurately detectable errors caused by coating unevenness of color filter. SOLUTION: Each of the elements of a CCD 1 to be inspected which has a color filter 3 is iluminated with light passed through at least two kinds of filter parts in the color filter part 3 having a colorless transparent part 3a, a red filter part 3b, a green filter 3c, and a blue filter part 3d. The outputs of each picture element corresponding to both of the filter parts are measured, one of the outputs is divided by the other, and, if the resulting maximum value exceeds a predetermined value, the CCD is determined as being defective.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to inspection of a CCD sensor, and more particularly, to inspection for defects due to uneven coating of a color filter formed on the CCD sensor.

[0002]

2. Description of the Related Art In digital copying machines, facsimile machines, image scanners, etc., CCD image sensors are used as reading elements. In particular, recently, a color CCD having a plurality of reading lines and an on-chip color filter has appeared.

[0003] However, this color CCD may cause various kinds of defects. In the on-chip process of the color filter, filters of different colors are formed in each line of the CCD, but one of the defects is unevenness in coating of the filter.

[0004] Uneven coating of the filter not only causes non-uniformity of the CCD sensitivity, but also changes the spectral sensitivity.
A phenomenon that the spectral characteristics of a document of a specific color is different from the surrounding colors appears.

[0005] Originally, CCD image sensors had PR
There is an output voltage non-uniformity called NU, which is
It can be corrected by a process called shading correction. However, if there is unevenness in the coating of the filter, the shading correction cannot correct the unevenness, and a vertical line-shaped streak is formed in the sub-scanning direction on a document of a specific color, resulting in an abnormal image. this is,
This is because the correction value of the color streak portion of the shading data obtained on the white reference plate corresponding to the white light source is an appropriate correction value for a document including a color component. Therefore, a streak-like defect does not occur in a gray document, but a color streak occurs in a colored document. For example, if the red filter has uneven coating, when reading a red document, a cyan color stripe of a complementary color appears.

[0006] Conventionally, as a CCD inspection method, PR
The NU was measured to determine the defect. However, PRN
In the case of U, in addition to the CDD sensitivity, that is, the non-uniformity of the output voltage, and the influence of the unevenness of the application of the color filter, the measurement is performed as a combination of the two. Therefore, the CCD
There was no distinction between PRNU due to its own sensitivity unevenness and PRNU due to filter coating unevenness.

For this reason, as described above, if the PRNU is caused by sensitivity unevenness, it can be considerably corrected by shading correction.
The boundary between good and bad products must be set strictly. If PRNU due to uneven sensitivity of CCD itself
If it can be distinguished from PRNU due to uneven coating of the filter, a considerable number of defective products which have been regarded as defective products will become non-defective products and the yield should be improved.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and provides a CCD inspection apparatus and an inspection method capable of accurately detecting a defect due to uneven coating of a color filter. It is an object.

[0009]

In order to achieve the above object, a CCD inspection apparatus according to the present invention is an apparatus for inspecting a CCD having a surface provided with a color filter, and a white light source for illuminating a CCD to be inspected. And a filter for changing the spectral characteristics of the light source.

Alternatively, the filter may be configured to be a chromatic color filter, the filter may include a colorless and transparent filter, or the chromatic color may be configured to include three primary colors of red, green and blue.

According to the CCD inspection method of the present invention, each element of a CCD to be inspected provided with a color filter is irradiated with light having passed through two types of filters including chromatic colors and having different spectral characteristics, and corresponding to both filters. The output of each pixel is measured, one output is divided by the other output, and when the maximum value exceeds a predetermined value, the test CCD is determined to be defective.

It is desirable that one of the two types of light having different spectral characteristics is white light. Further, the filter is a colorless transparent portion, a red filter portion, a green filter portion,
It has a blue filter unit, and calculates the ratio between the output of each pixel for white light from the colorless and transparent unit and the output of each pixel for each of the colors red, green, and blue, and calculates the value of the ratio value in any one color. If the maximum value exceeds a predetermined value, the test C
It is characterized by making the CD defective.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a view showing a schematic configuration of a CCD inspection apparatus according to the present invention. The test CCD 1 shown in FIG.
Green and blue primary color lines are arranged as a unit. The light source 2 emits white light. Also, this light source 2
Are located sufficiently distant from each other so that the light amount corresponding to the central part and the peripheral part of the CCD 1 to be inspected is almost the same. The filter 3 is used to irradiate the test CCD 1 with light of a specific wavelength band of the light from the light source 2.

FIG. 2 is an enlarged view of the filter 3. As shown in the figure, the filter 3 has a circular plate shape,
There are two round transparent parts. That is, a transparent portion or a colorless and transparent portion 3a having nothing, and a red filter portion 3
b, a green filter portion 3c, and a blue filter portion 3d. The filter 3 is rotatably supported at the center O. With such a configuration, the light of the light source 2 irradiates the test CCD through a filter of an arbitrary color.

FIG. 3 is a diagram showing output data of specific pixels of the CCD 1 to be inspected. The line connecting the x represents the output Xw (i) when irradiating white light, and the line connecting x represents the output Xr (i) when irradiating red light. Since red light is a part of white light, the output Xr (i) of the pixel is always lower than the output Xw (i) of white light.

FIG. 4 is a diagram obtained by calculation from FIG. First, Kr is obtained from the following equation. Kr = Xr (i) / Xw (i) (1)

This value is obtained for all the pixels, normalized with the average value of all the pixels being 100%, and the change with respect to it is shown in FIG.

In FIG. 4, the maximum value of all pixels is ΔKrm.
ax. Then, the maximum value is compared with the actual image, and the value of ΔKrmax at the time of occurrence of an abnormality in the image is set as a limit value for the inspection standard.

The above is the description of red color.
Similarly, for the green and blue colors, Xg (i) and Xb (i)
Is measured, and Kg and Kb can be obtained by the following equations. Kg = Xg (i) / Xw (i) (2) Kb = Xb (i) / Xw (i) (3)

Then, this value is obtained for all pixels, and Δ
Determine limit values for Kgmax and ΔKbmax,
Make inspection standard. Once the inspection standards for the three primary colors are determined, if any one of them exceeds the limit value, the CCD to be inspected can be determined to be defective.

After eliminating defects due to coating unevenness as described above,
By performing the PRNU inspection, it is possible to eliminate the influence of the coating unevenness, reduce the pass line of the PRNU, and improve the yield.

In the above embodiment, the CCD to be inspected is
The inspection was performed on a line in which red, green, and blue were lined up one by one. However, the arrangement of elements of each color is not limited to this, and even if red, green, and blue were alternately lined up on one line, The present invention can be applied to any object such as one in which one CCD is entirely one of red, green, and blue. In the above equations 1 to 3, Xw (i) is used as the denominator.
Conversely, the quality can be similarly determined by using this as a numerator.

[0023]

According to the present invention as described above,
In the CCD inspection, only the coating unevenness inspection can be independently performed.

In addition, the CCD inspection is performed by using P for measuring the sensitivity.
Since it is possible to inspect only the coating unevenness independently of the RNU, it is possible to prevent a conventionally good product from being erroneously determined as a defective product. Therefore, CC
The yield of D can be improved.

The filter has a transparent portion, a red filter portion, a green filter portion, and a blue filter portion, and divides an output for white light from the transparent portion by an output for each of red, green, and blue. If the maximum value of the color exceeds a predetermined value, the CCD is determined to be defective.
Even if a streak is formed in only one color, it can be reliably excluded as a defective product.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a CCD inspection apparatus of the present invention.

FIG. 2 is an enlarged view showing a configuration of a filter.

FIG. 3 is a diagram showing an output state of a pixel in the case of white light and red light.

FIG. 4 is a diagram in which the output ratio of FIG. 3 is normalized.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Test CCD 2 Light source 3 Filter 3a Transparent part 3b Red filter part 3c Green filter part 3d Blue filter part

Claims (7)

[Claims] 1. An apparatus for inspecting a CCD having a color filter formed on a surface thereof, comprising: a white light source for illuminating a CCD to be inspected; and a filter for changing a spectral characteristic of the light source. apparatus. 2. The CCD inspection apparatus according to claim 1, wherein said filter is a chromatic color filter. 3. The CCD inspection apparatus according to claim 2, wherein said filter includes a colorless and transparent filter. 4. The CCD inspection apparatus according to claim 2, wherein the chromatic colors are three primary colors of red, green, and blue. 5. An element of a CCD to be inspected having a color filter is irradiated with light having passed through two types of filters having different spectral characteristics including chromatic colors, and the output of each pixel corresponding to both filters is measured. Divides one output by the other output, and when the maximum value exceeds a predetermined value, the CCD to be tested
A method for inspecting a CCD. 6. The CC according to claim 5, wherein one of the two types of light having different spectral characteristics is white light.
D inspection method. 7. The filter has a colorless transparent portion, a red filter portion, a green filter portion, and a blue filter portion,
The output of each pixel for white light from the colorless and transparent part,
The ratio between the output of each pixel with respect to each of the green and blue colors is determined, and when the maximum value of the ratio in any one color exceeds a predetermined value, the test CCD is determined to be defective. CCD inspection method.