KR20050051535A - Defect inspection system - Google Patents

Abstract

The present invention relates to a defect inspection apparatus, wherein the defect inspection apparatus performs image processing by using an image pickup signal output from an imaging unit for imaging an inspection target to perform defect inspection of the inspection target, wherein the imaging unit has at least different resolutions. A defect inspection apparatus comprising two cameras, detecting defects with a high resolution camera, and detecting the defective color with a low resolution camera is provided.

Description

Fault Inspector {DEFECT INSPECTION SYSTEM}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect inspection apparatus for a member such as a display device such as a flat panel display, a color filter, and the like, and more particularly, to an improvement for high resolution in inspection of color defects and an increase in inspection time.

Background Art Conventionally, in a defect inspection apparatus of a member such as a flat panel display or a color filter, an optical signal transmitted through an inspection pattern or a color filter displayed on a display to be inspected is imaged by a CCD camera, and image data obtained by imaging. Defects were detected in some cases (see, for example, Japanese Patent Laid-Open No. 2003-61115).

1 is a configuration diagram showing an example of a conventional defect inspection apparatus.

Here, a flat panel display is used as an example as a test | inspection object.

The test | inspection object 1 is a flat panel display apparatus, such as a liquid crystal panel display and a plasma display, and displays display patterns, such as a black display and a white display, on the whole surface. An imaging unit 2 such as a CCD (charge coupled device) camera picks up the displayed image and outputs an image signal to the image processing unit 4. The signal generator 3 outputs a display pattern signal for displaying an image on the inspection target under the control of the image processor 4. The image processing unit 4 outputs the display data for generating the predetermined display pattern signal and the timing control signal for controlling the display timing to the signal generation unit 3, and also the black spot (not shown) from the captured image of the inspection target screen. Display defects, such as a light emission defect and a white point (bright point defect), are detected. The display part 5 is a display, a printer, etc. which display or print a test result. The operation part 6 consists of a keyboard, a touch panel, etc., and is a part which an operator operates this inspection apparatus.

For such an imaging unit 2 used in the defect inspection apparatus, defects are not large, such as inspection and display unevenness which require a camera of high resolution in order to detect small defects such as point defects (black spots, bright spots). However, there is an inspection that requires a camera of high resolution with respect to the luminance value in order to detect a defect in which the luminance change is minute. If these inspections are to be performed with one camera, it is necessary to be able to capture high resolution and high resolution, and an expensive camera must be used.

Therefore, some defect inspection apparatuses have been constructed at low cost by realizing high resolution with a camera array composed of a plurality of cameras having a standard resolution, detecting spot defects, and detecting other image irregularities such as luminance unevenness with another camera. For example, see Japanese Patent Laid-Open No. 1997-101236.

On the other hand, the inspection apparatus which used the 3CCD camera for the imaging part 2 is common for the inspection of a color image. In the 3CCD camera, images of R (red), G (green), and B (blue) can be acquired at once, and since there is no movable part, imaging can be performed at high speed. Moreover, since each pixel of R, G, and B image | photographs the point which is spatially the same, the inspection precision is also high.

However, due to the technical problem that the alignment of the three CCDs becomes remarkably difficult when high resolution is achieved, the 3CCD camera currently exists at a resolution of about 2 million pixels at present.

In the case of inspection of defects of relatively low spatial frequency (macro) such as color unevenness or luminance unevenness of the inspection target, it can be applied to a 3CCD camera having a resolution equal to or less than that of the inspection target. In the case of performing the defect inspection at the pixel level, the number of pixels of the inspection camera needs to be twice as wide and vertical in total and 4 times as many as the number of pixels to be measured from sampling theorem.

Therefore, the imaging part of the structure as shown in FIG. 2 using the black-and-white CCD which can implement the high resolution of 4 times or more of the inspection object is employ | adopted.

2 is a configuration diagram showing an example of an imaging unit of a conventional defect inspection apparatus.

In FIG. 2, color filters 7a, 7b, 7c (7c not shown) are mounted on the filter wheel 8, and are installed between the imaging lens 10 and the monochrome imaging device (CCD) 9. do. As the filter wheel 8 rotates, any one of the color filters is selected to switch the transmission wavelength range of the optical signal incident on the CCD. Moreover, ON / OFF control of incidence of the optical signal on the CCD is performed by opening and closing the shutter 11.

When inspecting an inspection target (not shown), for example, R, G, and the like are formed while the image of the inspection target is imaged on the CCD 9 by the imaging lens 10 and the color filters 7a, 7b, and 7c are changed. The images transmitted through three color gamuts of B are acquired, respectively. By performing the image processing alone or after calculating these three images, it is possible to measure the color of the pixel defect, the unevenness of the luminance, and the unevenness of the color at one pixel level.

However, in the conventional defect inspection apparatus using the imaging unit shown in Fig. 2, when performing defect inspection of a color image, a filter with a rotating mechanism must be provided in the imaging unit, which makes the structure complicated.

In addition, since the time required for the rotation of the filter at the time of imaging and the relatively low spatial frequency inspection such as color unevenness and luminance unevenness should be used, a high-resolution CCD should be used, so that imaging and transmission of image data for obtaining one color image is required. You need to repeat this three times. Therefore, there existed a problem that a test takes time.

The present invention is intended to solve the problems of such a conventional defect inspection apparatus, and by eliminating the rotation mechanism of the color filter inside the camera, eliminating the waiting time for rotation of the filter, It is an object of the present invention to provide a defect inspection apparatus which minimizes the image pickup data transmission and shortens the inspection time.

Hereinafter, the present invention will be described in detail with reference to the drawings.

3 is a configuration diagram showing an embodiment of a defect inspection apparatus of the present invention. In addition, the same code | symbol is attached | subjected to the part equivalent to the said figure, and the description is abbreviate | omitted.

Here, a flat panel display is used as an inspection object as an example, and when inspecting a color filter or the like, an optical signal transmitted through illumination from the rear of the color filter is imaged.

In FIG. 3, the inspection target 20 is a flat panel display. The 3CCD color camera 21 is equipped with an imaging lens 22 for a 3CCD color camera. The high resolution camera 23 is equipped with an imaging lens 24 for a high resolution camera. The 3CCD color camera 21 and the high resolution camera 23 are provided so that the whole display part of the inspection object 20 can be picked up.

The optical axis of the 3CCD color camera 21 or the high resolution camera 23 is installed to coincide with the center line 25 of the inspection object, but any one camera (the high resolution camera 23 in FIG. 3) cannot be installed on the center line.

In that case, it is preferable to move the imaging lens so that the main point of the imaging lens is approximately coincident on the straight line connecting the center of the CCD and the display. In this embodiment, the high resolution camera imaging lens 24 is shifted.

The imaging signal of each camera is received and processed by the image processing part 4a. The image processing unit 4a outputs display data for generating a predetermined display pattern signal and a timing control signal for controlling the display timing to the signal generation unit 3, and simultaneously generates black spots (not shown) from the captured image of the inspection target screen. Display defects such as light emission defects) and white point (brightness defects) are detected, and the color of the defects is specified. In addition, the position, size, brightness, and the like of the defect are measured.

And this image processing part 4a may be comprised by at least 1 computer which inputs the signal of a camera via an image input board.

Here, in the present embodiment, a case where the resolution of the inspection target 20 is XGA (horizontal 1024 x 768 pixels in height) is considered.

In the case of a color display, three display units of RGB are contained in one pixel, but the RGB set is defined here as one pixel.

In this case, the high resolution camera 23 is preferably a camera having a vertical and horizontal resolution twice the pixel number of the inspected display and having a margin of a few pixels, that is, a camera having a resolution of around 2150 × 1600 pixels. The 3CCD color camera 3 selects a resolution of about 1075 x 800 pixels with a slight margin to the same degree as the display under test.

These cameras are installed as shown in FIG. At this time, it is difficult to completely match one pixel of the inspection object with four pixels of the CCD of the high resolution camera because of an error in positioning of the inspection object and the high resolution camera or an aberration of the imaging lens for the high resolution camera. The same applies to the 3CCD color camera, and one pixel of the inspection object 20 and one pixel of the 3CCD color camera cannot be completely matched.

Accordingly, there is a shift in the pixel position of the high resolution camera and the 3CCD color camera.

When the contrast of the bright spot defect is high and the number of defects is small, even if there is a misalignment between the pixel positions of the high resolution camera and the 3CCD color camera, the detection of the bright spot position and color is not very difficult, but the contrast of the defect is low and the number of defects is large. In this case, matching of pixel positions of a high resolution camera and a 3CCD color camera becomes important.

Hereinafter, matching of pixel positions will be described with reference to the drawings.

4 is a display example showing bright spot defects in a display region to be inspected. The bright spot defect 30 is a defect (bright spot defect) of a bright shining point in black display occurring in the display region 31 of the inspection object 20.

As shown in FIG. 5, the inspection target 20 displays bright spots (markers) having a size of 1 pixel at regular intervals, for example, 10 pixels.

5 is a display example in which a marker is displayed on the display area of the inspection object.

The bright point 32 and the bright point 33 indicated by the bright point 32 are bright point defects. In this example, it can be seen that the bright point defect exists between the third and fourth rows from the right side and the second and third rows from above. Therefore, the schematic diagram of the image at the time of imaging the part with the high resolution camera is shown in FIG. 6, and the schematic diagram of the image at the time of imaging with the 3CCD color camera is shown in FIG.

6 and 7 show pixels of the CCDs of the respective cameras.

In FIG. 6, each point of A, B, C, and D is a bright point displayed on the inspection object 20, and P point is a bright point defect. Each point of A, B, C, and D is displayed at a size of 1 pixel at 10 pixel intervals on the inspection object 20, but is 4 pixels at about 20 pixel intervals on the high resolution CCD. Moreover, it does not necessarily correspond to the pixel position of CCD.

In FIG. 7, each point of A1, B1, C1, D1 is a bright point displayed on the inspection object 20. In FIG. Although P1 point is a position of a bright point defect, it cannot suppose that it is clear as a bright point in the image of a 3CCD color camera. In this case, each point of A, B, C, and D is the same as the display on the inspection object 20, and is displayed at a size of about 1 pixel at intervals of about 10 pixels.

Since FIG. 6 and FIG. 7 are in a relationship of projection, when the position of point P in FIG. 6 is calculated | required as a relative position from A, B, C, and D point, the position of P1 point in FIG. 7 is A1, B1, C1, It can obtain | require as a relative position from D1 point. At this time, the position of each point of FIG. 6, FIG. 7 can be calculated | required with the resolution of 1 pixel or less by obtaining the center position of a bright point. In this way, the color of the bright spot defect detected by the high resolution camera can be obtained from the image of the 3CCD color camera.

The specific processing sequence is as follows.

In the image of Fig. 6, the coordinates of P are represented by the coordinates on the CCD of the high resolution camera. This coordinate is called (xp, yp). Here, the coordinate system of the image on the CCD has the upper left as the origin (0,0), the right direction as the positive direction of x, the lower direction as the positive direction of y, and the xy coordinate system in units of pixels.

In Fig. 6, ABCD (represents a rectangle with points A, B, C, and D as a normal point) is a unit square, and a coordinate system with A as the origin is (l, m), and the above (x, y) Find the relationship with the coordinate system.

If we get the conversion matrix K

It can be represented as.

The coordinates (l p, mp) in the (l, m) coordinate system of the bright spot defect P can be obtained using the formula (1).

Similarly, in the image of Fig. 7, the relationship between the coordinates (x1, y1) on the CCD of the 3CCD color camera and? A1B1C1D1 as the unit square is determined, and the coordinate system (11, m1) with A1 as the origin is obtained. Suppose that the obtained transformation matrix is K1

It can be represented as.

If you transform (2)

By substituting the coordinates (l p, mp) of the bright spot defect obtained in the formula (1) into the formula (3), the coordinates (xp1, yp1) on the 3CCD color camera CCD of the bright spot defect can be obtained. The color of the bright spot defect can be specified by irradiating the color of (xp1, yp1) in the image of FIG. At this time, when a bright spot defect overlaps with the bright spot to display, it can substitute by another display bright spot which adjoins.

This will be described with reference to the drawings.

8 shows an example of an image obtained by photographing the periphery of the bright spot defect P when the black uniform screen is displayed on the inspection target 20 with a high resolution camera. The grid represents one pixel of the CCD of the high resolution camera. FIG. 9 shows an example of the image when the same part as FIG. 8 is imaged with a low resolution 3CCD color camera. The grid represents one pixel of the CCD of the 3CCD camera.

Next, the bright point is displayed on the display under test at equal intervals (for example, at intervals of 10 pixels). FIG. 10 shows an example of an image obtained by capturing the same portion as that in FIG. 8 with a high resolution camera. FIG. 11 shows an example of an image when the same portion as that in FIG. 9 is captured by a low resolution 3CCD color camera.

In this example, the bright spot defect P is overlapped in the substantially same part as the bright spot D displayed. The superposition of the bright spot to be displayed and the bright spot defect can be determined according to the coordinates on the CCD. In such a case, instead of the ABDC normally used for matching the pixel position of the high resolution camera and the 3CCD color camera, AEIG is used. Change to

The selection of the four points of the display bright point is not limited to AEIG, but is four points arranged so as to surround the defect, such as BCHF, and a defect may be present in the rectangle connecting the four points.

In addition, when defect inspection of a member such as a color filter is carried out, a marker is printed at a known position of a colorless transparent sheet, and the like is superimposed with a color filter for imaging. Do it.

In addition, luminance unevenness, line defect, color unevenness, etc. are examined using the image of a 3CCD camera.

12 shows the results of simulation of inspection time according to the present embodiment. The time of imaging was compared with respect to the case of the camera for a conventional inspection apparatus, and the case of the defect inspection apparatus of this invention.

The inspection camera of the prior art is configured to perform defect inspection and color image inspection such as color unevenness and luminance unevenness with the same camera using a monochrome 3.34 million pixel camera and an RGB color filter. On the other hand, the present invention uses a monochrome 3.34 million pixel camera for defect inspection, and uses a 3CCD camera of 860,000 pixels for color unevenness and luminance unevenness inspection.

Here, assuming that 10 imagings are required for inspection, at least three high-resolution images and color images are required, and four other images may be taken by either camera, so as to be as short as possible. Assign. Therefore, in the conventional example, seven black and white images are shot in three color images, and in the present invention, three black and white images are shot in seven color images.

The camera's data transfer clock is 10MHz, allowing parallel data transfer. The exposure time is made constant at 100 msec.

As a result, the total time required for inspection is 8390 msec in the conventional example, 2622 msec in the present invention, and is 1/3 or less of the conventional example. In reality, the image processing time is added to this, but since the image processing time is proportional to the number of pixels, it is considered that the ratio is the same as in the conventional example and the present invention.

In the embodiment, the high resolution camera is shifted from the optical axis and used. However, the 3CCD color camera can be shifted and used with the high resolution camera as the axis.

In this embodiment, the display of the bright point in Fig. 5 is used only to match the relationship between the pixels of the two cameras. However, when the luminance indicates a known bright point, the ratio of the brightness level of the bright spot defect to the brightness level of the display bright point is shown. Accordingly, the luminance of the bright spot defect can be obtained. Therefore, it can also be used as a reference of luminance.

In this embodiment, the inspection system is composed of a combination of a high resolution black and white camera and a lower resolution 3CC D color camera, but a combination of color cameras having different resolutions or black and white cameras having different resolutions is used to determine the inspection system. Therefore, it is also possible to select and use a camera appropriately. It is further effective when defect inspections such as minute scratches and relatively large defect inspections such as color unevenness and luminance unevenness are mixed.

In the present embodiment, the bright point is displayed on the inspection object each time to match the pixel coordinates of the CCDs of the two cameras, but the relative positions of the two cameras and the imaging magnification of the inspection object and the camera do not change. If the inspection apparatus is installed, the pixel coordinates of the two cameras are matched over the entire surface to be inspected, the data is retained as the inherent data of the apparatus, and the data is used to match the pixels during inspection. It may be.

For example, the manufacturing line of the liquid crystal display not only produces a single variety, but also produces liquid crystal panels of various sizes and resolutions according to the demand at that time, and when the items change, the area of the area to be inspected. It is required to be able to change quickly.

In response to such a request, when high resolution is realized by the camera array described in the prior art, the following adjustment is necessary.

Increase the spacing of each camera in the camera array. The entire camera array is away from the panel under test so that the field of view of each camera overlaps slightly to cover the entire display area of the panel. Or a zoom lens is mounted in each camera, and each zoom is adjusted so that the above conditions may be satisfied. Adjust the focus of each camera individually. Depending on the number of cameras constituting the camera array, manual adjustments like this require a great deal of time.

Moreover, when performing it automatically, it is necessary to prepare an XYZ stage and an automatic focus adjustment mechanism for each camera, and even if a camera is low price, cost will be raised rather than preparing the high resolution camera of this invention.

On the other hand, since the present invention performs point defect inspection using a high resolution camera, it is sufficient to work away from the camera and adjust the focus, which does not cause the complexity of adjustment by increasing the number of cameras such as a camera array. And the adjustment time does not increase. Similarly, in the case of automatic adjustment, only one stage and one focus adjustment mechanism are required, so the cost is lower than that of the camera array.

In addition, since the liquid crystal display to be inspected has a viewing angle characteristic, in order to separate the unevenness and unevenness of the brightness due to the viewing angle characteristic, the viewing angle of the camera for spot inspection should be as small as possible as the camera for spot defect inspection. Therefore, a camera for spot inspection must be installed on the central axis of the display.

Therefore, in the case of using a camera array, it is difficult to install a far-flung spot inspection camera on a central axis of the display without disturbing the field of view of the camera array provided near the display. As described above, it is easy to install the 3CCD camera for spot inspection on the central axis of the display.

In addition, this invention is not limited to the said Example, A change and a deformation | transformation are included also in the range which does not deviate from the essence.

As described above, the present invention has the following effects.

By detecting a small point defect with a high resolution camera and specifying the color of the defect with a low resolution color camera, the structure becomes simple, the imaging time is short, and the inspection time can be shortened.

In the case of an inspection object having a viewing angle characteristic such as a liquid crystal display, by providing a camera on the central axis of the inspection object, the inspection can be performed without being affected by the viewing angle characteristic.

In addition, by displaying the marker for position detection on the inspection object, the position of the defect picked up by the high resolution camera and the position of the defect picked up by the low resolution camera can be matched.

In addition, even when the marker and the defect overlap, the position of the defect can be detected.

In addition, by displaying the marker for position detection at a known luminance, the luminance of the bright spot defect can be obtained using this marker as a luminance reference.

1 is a configuration diagram showing an example of a conventional defect inspection apparatus.

2 is a configuration diagram showing an example of an imaging unit of a conventional defect inspection apparatus.

3 is a configuration diagram showing an embodiment of a defect inspection apparatus of the present invention.

4 is a display example showing bright spot defects in a display region to be inspected.

5 is a display example in which a marker is displayed on a display area of an inspection object.

6 is an explanatory diagram showing positions of pixels and bright spot defects of a high resolution CCD;

7 is an explanatory diagram showing positions of pixels and bright spot defects of a CCD of a 3CCD camera.

It is a figure which shows the example of the image which image | photographed the periphery of the bright spot defect in the case of displaying a black uniform screen on a test object with a high resolution camera.

FIG. 9 is a diagram illustrating an example of an image when a portion substantially the same as that in FIG. 8 is captured by a low resolution 3CCD color camera.

FIG. 10 is a diagram showing an example of an image obtained by capturing the same portion as that of FIG. 8 with a high resolution camera when a marker is displayed.

FIG. 11 is a diagram showing an example of an image obtained by capturing the same portion as FIG. 9 with a 3CCD camera when displaying a marker. FIG.

12 is a diagram showing the results of simulation of inspection time according to the present embodiment.

Claims (28)

In the defect inspection apparatus which performs the image processing using the imaging signal output from the imaging part which image | photographs an inspection object, and performs the defect inspection of the said inspection object, The imaging unit has at least two cameras having different resolutions, The defect inspection apparatus detects a defect with a high resolution camera, and detects the color of the said defect with a low resolution camera. The method of claim 1, The high resolution camera is a monochrome camera, and the low resolution camera is a color inspection device, characterized in that the color camera. The method of claim 1, The defect inspection apparatus characterized by installing any one of the said cameras so that an optical axis may match with the centerline of the said inspection object. The method of claim 2, The defect inspection apparatus characterized by installing any one of the said cameras so that an optical axis may match with the centerline of the said inspection object. The method of claim 1, A marker as a reference of the position is displayed on the inspection object, and according to the positional information of the marker, the position of the defect photographed by the high resolution camera and the position of the defect photographed by the low resolution camera ( The defect inspection apparatus characterized by the above-mentioned. The method of claim 2, The marker which becomes a reference | standard of a position is displayed on the said inspection object, and the position of the defect image | photographed by the said high resolution camera is matched with the position of the defect image | photographed by the said low resolution camera according to the positional information of this marker. Defect inspection apparatus. The method of claim 3, The marker which becomes a reference | standard of a position is displayed on the said inspection object, and the position of the defect image | photographed by the said high resolution camera is matched with the position of the defect image | photographed by the said low resolution camera according to the positional information of this marker. Defect inspection apparatus. The method of claim 4, wherein The marker which becomes a reference | standard of a position is displayed on the said inspection object, and the position of the defect image | photographed by the said high resolution camera is matched with the position of the defect image | photographed by the said low resolution camera according to the positional information of this marker. Defect inspection apparatus. The method of claim 5, The markers are displayed at predetermined intervals, and the position of a defect picked up by each camera is obtained as a relative position with respect to four markers surrounding the defect. The method of claim 6, The markers are displayed at predetermined intervals, and the position of a defect picked up by each camera is obtained as a relative position with respect to four markers surrounding the defect. The method of claim 7, wherein The markers are displayed at predetermined intervals, and the position of a defect picked up by each camera is obtained as a relative position with respect to four markers surrounding the defect. The method of claim 8, The markers are displayed at predetermined intervals, and the position of a defect picked up by each camera is obtained as a relative position with respect to four markers surrounding the defect. The method of claim 9, When the marker and the defect overlap, the defect inspection apparatus is characterized in that the position of the defect is obtained by substituting adjacent markers. The method of claim 10, When the marker and the defect overlap, the defect inspection apparatus is characterized in that the position of the defect is obtained by substituting adjacent markers. The method of claim 11, When the marker and the defect overlap, the defect inspection apparatus is characterized in that the position of the defect is obtained by substituting adjacent markers. The method of claim 12, When the marker and the defect overlap, the defect inspection apparatus is characterized in that the position of the defect is obtained by substituting adjacent markers. The method of claim 5, The defect inspection apparatus characterized by displaying the said marker by a known brightness | luminance and making a reference when detecting a defect of a brightness | luminance. The method of claim 6, The defect inspection apparatus characterized by displaying the said marker by a known brightness | luminance and making a reference when detecting a defect of a brightness | luminance. The method of claim 7, wherein The defect inspection apparatus characterized by displaying the said marker by a known brightness | luminance and making a reference when detecting a defect of a brightness | luminance. The method of claim 8, The defect inspection apparatus characterized by displaying the said marker by a known brightness | luminance and making a reference when detecting a defect of a brightness | luminance. The method of claim 9, The defect inspection apparatus characterized by displaying the said marker by a known brightness | luminance and making a reference when detecting a defect of a brightness | luminance. The method of claim 10, The defect inspection apparatus characterized by displaying the said marker by a known brightness | luminance and making a reference when detecting a defect of a brightness | luminance. The method of claim 11, The defect inspection apparatus characterized by displaying the said marker by a known brightness | luminance and making a reference when detecting a defect of a brightness | luminance. The method of claim 12, The defect inspection apparatus characterized by displaying the said marker by a known brightness | luminance and making a reference when detecting a defect of a brightness | luminance. The method of claim 13, The defect inspection apparatus characterized by displaying the said marker by a known brightness | luminance and making a reference when detecting a defect of a brightness | luminance. The method of claim 14, The defect inspection apparatus characterized by displaying the said marker by a known brightness | luminance and making a reference when detecting a defect of a brightness | luminance. The method of claim 15, The defect inspection apparatus characterized by displaying the said marker by a known brightness | luminance and making a reference when detecting a defect of a brightness | luminance. The method of claim 16, The defect inspection apparatus characterized by displaying the said marker by a known brightness | luminance and making a reference when detecting a defect of a brightness | luminance.