JP3243703B2 - Defect detection method for color filter for viewfinder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for automatically inspecting a color filter for a viewfinder for appearance defects such as dirt and scratches.

[0002]

2. Description of the Related Art Heretofore, as a method for inspecting the appearance of a color filter for a viewfinder, a method of visual observation by a human using a light projector and a method of using a microscope for fine defects which are difficult to visually inspect have been adopted. . However, in recent years, there has been an increasing demand for miniaturization and mass production of viewfinder-color filters. With higher definition, it has become increasingly required to detect fine defects as well.
As for the conventional visual inspection using a light projector or a microscope, there is a difference between humans and a problem in reproducibility. Therefore, an automated inspection method that is not manually performed has been required. In addition, an automated inspection method has been required for mass production. However, in the case of a viewfinder color filter, the entire front and back surfaces of the product are to be inspected, and the transmission and / or transmission over the entire front and back surfaces of the product is performed.
In addition, it is necessary to inspect for defects with reflected illumination, and the transmittance and / or reflectance of the colored pixel portion, outer peripheral light-shielding portion, and outermost transparent portion are different from each other, making automatic appearance inspection difficult and corresponding. Was required.

[0003]

Under these circumstances, the entire front and back surfaces of the color filter for the viewfinder can be inspected using transmitted illumination and / or reflected illumination.
In addition, there has been a demand for an automatic appearance inspection method that can respond to mass production. The present invention intends to provide an automatic appearance inspection method for a viewfinder color filter, and more particularly, to an automatic appearance inspection method for a viewfinder color filter having different transmittances and / or reflectances depending on places (parts). .

[0004]

According to a method of detecting a defect in a color filter for a viewfinder according to the present invention, an image of the entire surface of the color filter for a viewfinder is obtained by using transmitted illumination light and / or reflected illumination light. The signal is subjected to image processing to automatically inspect appearance defects such as dirt and scratches. The inspection area of the color filter is divided into a plurality of areas according to differences in transmittance and / or reflectance. The image signal level of the imaging means is adjusted according to the exposure condition corresponding to each area, the entire inspection area is imaged, and the defect is detected by the video signal obtained by the imaging. The entire inspection area is inspected. Normally, in order to image under the exposure conditions corresponding to each area, the entire inspection area is imaged under a plurality of different exposure conditions, and a defect in each area is detected from a video signal obtained under each condition. To inspect the entire inspection area. It is necessary to detect the appearance defects such as dirt and scratches of the viewfinder color filter on the entire front and back surfaces. However, the viewfinder color filter usually has transmittance and / or reflectance depending on its location (part). Therefore, if the signal obtained by imaging is subjected to image processing under the same conditions for the entire front and back surfaces, the level of the video signal obtained by imaging greatly differs depending on the location (part), and appropriate defect detection is performed. Can not. Normally, the surface of the colored portion of the viewfinder color filter has a low reflectance, the outer light-shielding portion has a high reflectance, the colored portion and the outer light-shielding portion have a low light transmittance, and the outermost transparent portion has a high light transmittance. Therefore, the area (area) on the front and back of the color filter for the viewfinder
Is used to adjust the video signal level of the imaging means so that the video signal level is appropriate for defect detection. The adjustment is performed by the photoelectric conversion function of the imaging means with a variable imaging exposure time. Adjusting with the exposure time, or adjusting the illumination light intensity of the transmitted light and / or reflected light from the viewfinder color filter,
Alternatively, the adjustment is performed using both of them. The entire inspection area is exposed and imaged corresponding to each area, and a signal of a level suitable for detecting defects in only a specific area is extracted from the video signal obtained under the exposure conditions corresponding to the specific area. If necessary, the signal components in other areas are removed or processed so that they can be excluded. For example, at the time of imaging for defect detection, the reflected illumination light intensity is increased in the colored portion having a low reflectance, the video signal level is increased, and the reflected illumination intensity is reduced in the peripheral light shielding portion having a high reflectance. Lower the video signal level,
The imaging is performed by adjusting the video signal level. Also, during imaging for defect detection, the transmitted light intensity is increased in the colored portion and the outer light-shielding portion with low transmittance, the video signal level is increased, and the transmitted light intensity is increased in the outermost transparent portion with high transmittance. Is small,
The video signal level is lowered, the video signal level is adjusted, and imaging is performed. In addition, for example, in imaging for defect detection, a colored portion having a low reflectance has a longer imaging exposure time and is subjected to photoelectric conversion to increase a video signal level, thereby providing an outer peripheral light shielding portion having a high reflectance. In the Japanese Patent Application Laid-Open No. H11-260, an image pickup exposure time is shortened, photoelectric conversion is performed, thereby lowering a video signal level, and adjusting a video signal level to perform imaging. In imaging for defect detection, the imaging exposure time is lengthened and the photoelectric conversion is performed on the colored portion and the outer peripheral light-shielding portion with low transmittance to increase the video signal level, thereby increasing the outermost peripheral portion with high transmittance. In the transparent portion, the image pickup exposure time is shortened, and the photoelectric conversion is performed to lower the video signal level, adjust the video signal level, and perform imaging.

[0005]

In the method for detecting a defect of a color filter for a viewfinder according to the present invention, the inspection area of the color filter is divided into a plurality of areas, and the defect detection of each area is obtained by imaging under exposure conditions corresponding to each area. Since the image processing is performed by performing image processing on the obtained video signal, the exposure condition can be adjusted according to the light transmittance and / or light reflection of the area so that the video signal level is easily detected. In this case, it is possible to reliably detect a defect in the area. Then, imaging the entire inspection area under the exposure conditions corresponding to each area, detecting defects in each inspection area from video signals obtained under each condition, and detecting defects on the entire inspection area. It can detect defects on the entire surface of the color filter. The adjustment of the video signal level can be relatively easily performed by adjusting the imaging exposure time of the imaging unit by the photoelectric conversion function of varying the imaging exposure time, or by adjusting the illumination light intensity of the transmitted light and / or the reflected light, or by adjusting both. It is possible to automate the inspection of appearance defects such as dirt and scratches on the entire front and back surfaces of the viewfinder color filter having different transmittances and / or reflectances depending on locations (parts).

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a color filter defect detecting method for a viewfinder according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view of an apparatus for detecting a defect in a color filter for a viewfinder according to the first embodiment.
FIG. 3 is a diagram showing an apparatus for performing an automatic inspection by reflecting and illuminating the surface of a sample using an area sensor. In the figure, 1 is an imaging camera, 2 is a light source, 3 is a color filter for a viewfinder, 4 is a holding plate, 5 is an image processing device, 6 is a half mirror, and the imaging camera 1 is a CCD area sensor having an electronic shutter function. (C3077-50 manufactured by Hamamatsu Photonics KK), and the exposure time is variable. As the light source, a xenon light source having a fiber shape was used.
The light from the light source 2 is reflected by the half mirror 6 and the holding plate 4
The entire surface of the sample viewfinder color filter 3 placed on the sample is illuminated. The entire surface of the image of the color filter 3 is formed on the CCD area sensor of the imaging camera 1 by the lens by the reflected light from the color filter 3 for the sample viewfinder, and the image is captured. Then, the video signal obtained by the imaging is subjected to image processing, and a defect is detected.
Here, an area sensor of 512 pixels × 480 pixels is used, and 40 μm is provided at the center of the 15 mm × 13 mm viewfinder color filter shown in FIG. 11 on the substrate.
Using a color filter for a viewfinder in which three colors of R, G, and B were repeatedly arranged at a pitch of mx20 μm as a sample, the entire surface of the sample was photographed through a lens. First, prior to detection of a defect in the viewfinder color filter, a predetermined defect sample is placed on the holding plate 4 since the reflectance of the viewfinder color filter is different between the colored pixel portion and the outer peripheral light shielding portion. Department,
The exposure time of the electronic shutter is adjusted so that an appropriate defect can be detected at each location of the outer peripheral light-shielding portion, and an appropriate exposure time of 1/60 sec, 1/1200 s is applied to each location.
ec was obtained. Next, the viewfinder color filter 3 as a sample is placed on the holding plate 4 by the imaging camera 1, and the entire surface of the viewfinder color filter 3 is exposed to an exposure time 1 / An image was taken at an exposure time of 1/1200 sec appropriate for detecting a defect in the outer peripheral light-shielding portion at 60 sec, and image signals obtained by the imaging at each exposure time were subjected to image processing, and a defect was detected for each image processing. . From the imaging at an exposure time of 1/60 sec suitable for detecting a defect of the colored pixel portion, a defect due to reflected illumination of the colored portion is detected, and an exposure time of 1/1200 sec suitable for detecting a defect of the outer peripheral light shielding portion.
A defect in the outer peripheral light-shielding portion was detected from the imaging in the above.

Next, a second embodiment will be described. FIG. 2 shows the second embodiment.
Inspection of color filters for viewfinders in Japan
The schematic diagram of the device when
Using a CCD area sensor, the
A device that illuminates from the back and performs an automatic inspection based on the transmitted light of the sample
FIG. In the figure, 11 is an imaging camera, 12 is light
Source 13, color filter for viewfinder, 1
4 is a transparent holding plate, 15 is an image processing device,
3 is imaged on the CCD area sensor by the lens
The light source 12 that is adjusted to
The illumination light source intensity is variable and the color for the viewfinder
The entire surface of the filter 13 is transmitted and illuminated. In addition, CC
Use the same D area sensor and light source as in Example 1.
Was. Light from the light source 12 is placed on a transparent holding plate 14.
Of the sample viewfinder color filter 13
The entire surface is illuminated through the back. Sample viewfinder
Color filter by the transmitted light from the color filter
The entire surface of the image of the luter 13 is
An image is formed on a CD area sensor and imaged. And
The video signal obtained by imaging is subjected to image processing and defects are detected
Is done. First, the color filter for the viewfinder
Prior to detecting defects, the color filter for the viewfinder
Luther has a high transmittance with a colored pixel part and a peripheral light-shielding part with low transmittance.
In the outermost transparent portion of the transmittance, the transmittance of the illumination light greatly differs.
Therefore, a predetermined defect sample is placed on the transparent holding plate 14.
The colored pixel area, the outer peripheral light-shielding area, and the outermost transparent area.
The light source 13 is used so that appropriate defect detection can be performed at each location.
Adjust the illumination light intensity of the
2 million cd / m intensity brightness^Two50,000 cd / m ^TwoI got
Next, the view camera as a sample is
The color filter 13 for the underlayer on the transparent holding plate 14.
Of the viewfinder color filter 13
When the whole surface is illuminated by transmission from the back, colored pixels with low transmittance
Illumination brightness 2 million c suitable for detecting defects in the outer and outer light-shielding parts
d / m^TwoAnd illumination suitable for detecting defects in the outermost transparent part
50,000 cd / m^TwoAt each lighting intensity
Image processing of the video signal obtained by
Defects were detected for each image processing. Defects in the above colored pixel section
Illumination luminance 2 million cd / m suitable for detection^TwoFrom imaging with
Indicates that a defect caused by transmitted illumination of the
50,000 cd luminance suitable for detecting defects in the outermost transparent part
/ M^TwoDefects in the outermost transparent part are detected
Was.

In the above-described first and second embodiments, a method for extracting only a defect in a predetermined region by excluding a region other than a predetermined region portion, that is, a method for extracting a defect only in a region of interest will be described below. Note that, here, for simplicity, the description will be limited to a case where the colored pixel area is inspected by transmitted illumination. The whole surface of the sample is imaged under an exposure condition suitable for detecting a defect in the colored pixel region by the transmitted illumination, and an enhancement process is performed on the image signal obtained by the imaging. Here, the image signal is differentiated in the x direction. This emphasis process emphasizes a change in the signal in the x direction. When the colored pixel area is inspected by transmitted illumination, the entire surface of the sample is imaged, and when the obtained image signal is subjected to an emphasis process, as shown in FIG. Other than the colored pixel portion region such as the boundary of the pixel portion, the outer peripheral light shielding portion, and the outermost transparent portion are also extracted as defects, but only the region of interest (colored pixel portion region) is extracted as shown in FIG. The AND of the binarized image and the masking image of the area to be detected is calculated. This masking image is obtained by, for example, setting an area to be detected in the memory to all bits 1 and other areas to 0, and performing an emphasis process 2
By taking an AND with the digitized value image, it is possible to leave the binarized value of only the region of interest (colored pixel portion region) and exclude other regions. Next, a case in which a masking image of the colored portion area is created will be described. As shown in FIG. 5A, first, the entire surface of a sample having no defect is imaged, and an image signal obtained by imaging corresponding to the luminance level of each region of the sample is binarized to a predetermined slice level. The colored pixel portion region image a is extracted as in 5 (2). In order to reduce the image a in FIG. 5 (2), the image a is shifted left and right (or up and down when the enhancement process is a differentiation process in the y direction), and as shown in FIG. Create Since the masking image is created smaller than the actual colored pixel portion area, even if the boundary line due to the signal change between the colored portion and the outer peripheral light shielding portion as shown in FIG. 3 is extracted, as shown in FIG.
Only the defect in the colored pixel area is extracted by ANDing with the masking image. Here, the shift amount in the processing of FIG. 6 will be described. An image signal obtained by imaging is as shown in FIG. 7 in the x direction. FIG. 9 shows a case where filtering is performed on the image signal of FIG. 7 using the element filter shown in FIG. So in this case,
In the inspection area, two pixels on the left side and three pixels on the right side appear as boundaries and must be excluded, so the shift amount of the image a is 2 pixels on the right side and 3 pixels on the left side. The image obtained by shifting the image a in this way and taking the AND is a masking image corresponding to the colored pixel area, but the other areas of the sample are imaged by adjusting the exposure conditions and the slice level. By binarizing and shifting, a masking image corresponding to each area can be created.

In the above-described first and second embodiments, the image signal obtained by imaging is input to an image processing device and subjected to an emphasis process or the like to detect a defect. This will be described with reference to FIG. First,
A plurality of images are picked up by the image pickup means at the same place on the sample, image signals are obtained, and the obtained image signals are integrated and averaged. This means that the light transmittance distribution as shown in FIG. 10A is obtained for the portion including the defective portion, but the video signal from the image pickup device has the pattern illumination unevenness and the image pickup surface as shown in FIG. A signal that responds to a signal that includes a gradual signal change (shading) due to uneven sensitivity, random noise generated in a video signal circuit, and a local change in the signal due to dust or the like attached to an optical system. In the same place, an image signal is obtained a plurality of times by the imaging means, an image signal is obtained, and the obtained image signal is integrated and averaged for a plurality of times, whereby the number of additions is reduced as shown in (c). If N, the ratio of random noise is 1 / ^N1 / ² . Here, A1, B
1, A2 and B2 indicate defective portions, and C indicates a local change of a signal due to dust or the like adhering to the optical system. Next, by slightly shifting the position to be imaged and similarly integrating and averaging, a signal (d) obtained by slightly displacing the signal (c) can be obtained. When the difference signal is obtained, the signal becomes as shown in (e), and a signal component that does not change due to a gradual signal change (shading) or a movement of the imaging position is removed. Here, only the signal component due to the change in light transmittance and the reduced random noise component remain, and when this signal (e) is further subjected to a subtraction or differentiation process of the neighborhood average value, as shown in FIG. It can be seen that the gradual signal change (shading) component is also removed, and as a result, the obtained signal (f) is locally changed only in a portion corresponding to the defective portion, and is emphasized. In the binarization by the slice processing, the signal (f) is processed at a predetermined slice level SL, and only the defective portion is determined and binarized. It should be noted that the type of defect (white defect, black defect) can be identified by the order of signal inversion at the defective portion in FIG.
Note that, here, the white defect refers to a pinhole or a missing pattern in the colored pattern portion, and the black defect refers to an extra colored portion or a light-shielded portion other than a predetermined pattern in the colored pattern portion. Scratches in the glass part are also detected as black defects.

[0010]

According to the above configuration, the method for detecting a defect in a color filter for a viewfinder according to the present invention enables a reliable automatic inspection of appearance defects such as dirt and scratches on the front and back of the color filter for a viewfinder. And

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic view of an apparatus according to a second embodiment of the present invention.

FIG. 3 is an emphasis processing diagram.

FIG. 4 is a masking diagram of a binarized image.

FIG. 5 is a process chart for creating a masking image.

FIG. 6 is a shift processing diagram for creating a masking image.

FIG. 7 is an x-direction image signal diagram.

FIG. 8 is an element filter diagram.

FIG. 9 is an image signal diagram after the factoring.

FIG. 10 illustrates an example of image processing.

FIG. 11 is a schematic view of a color filter for a viewfinder.

[Explanation of symbols]

Reference Signs List 1, 11 imaging camera 2, 12, light source 3, 13, color filter for viewfinder 4 holding plate 5, 15, image processing device 6, half mirror 14, transparent holding plate

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-3-160350 (JP, A) JP-A-4-158249 (JP, A) JP-A-1-313743 (JP, A) JP-A-5-305 281147 (JP, A) JP-A-1-222381 (JP, A) JP-A-6-174652 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 21/84-21 / 958 G06T 1/00-9/40

Claims (4)

(57) [Claims] 1. An image pickup device using a transmitted illumination light and / or a reflected illumination light to image an entire surface of a viewfinder color filter having different transmittances and / or reflectances depending on locations, and obtains a signal obtained. A method for automatically inspecting appearance defects by performing image processing, wherein an inspection area of the color filter is formed with a transmittance and / or
Alternatively, the area is divided into a plurality of areas according to the difference in reflectance, and the defect inspection of each area is performed by adjusting the video signal level of the imaging unit according to the exposure condition corresponding to each area, imaging the entire inspection area, and obtaining an image obtained by imaging. A defect detection method for a color filter for a view finder, wherein a defect is detected by a signal, and the entire inspection area is inspected together with the defect detection for each area. 2. The method according to claim 1, wherein the adjustment of the video signal level of the image pickup means according to the exposure condition is performed by the image pickup exposure time of the electronic shutter of the image pickup means. 3. The viewfinder color filter according to claim 1, wherein the adjustment of the video signal level of the imaging means according to the exposure condition is performed by adjusting the intensity of the illumination light of the transmitted light and / or the reflected light. Defect detection method. 4. The method according to claim 1, wherein the adjustment of the video signal level of the image pickup means according to the exposure condition includes adjusting the image signal exposure time of the electronic shutter of the image pickup means and adjusting the illumination light intensity of the transmitted light and / or the reflected light. A defect detection method for a color filter for a viewfinder, wherein the defect detection method is performed by adjustment and combined use.