JP4193895B2 - Defect inspection equipment - Google Patents

Description

  The present invention processes image information obtained by processing each divided area to be inspected divided into a plurality of areas with a plurality of cameras including an area sensor composed of a lens system and a predetermined number of pixels, and is calculated feature amount The present invention relates to a defect inspection apparatus for identifying defects in the area based on the above.

  Defect inspection apparatus for inspecting luminance defects (defects in which pixels that should not shine when black display is performed) on panel-like inspection objects such as liquid crystal display elements using image information captured by an area sensor There is.

  FIG. 2 is a perspective view showing a basic system configuration of a defect inspection apparatus using two cameras including an area sensor. The inspection area of the inspection object 100 is divided into A and B, and each inspection area is imaged by the cameras 300A and 300B having the area sensors 301A and 301B via the lenses 200A and 200B, respectively. The images are transferred to the image processing apparatuses 400A and 400B, respectively.

  The image processing apparatuses 400A and 400B made up of personal computers or the like perform defect inspection by numerically processing the luminance information of the predetermined areas A and B of the inspection target 100 based on the image information captured via the image input board or the like. And each test result is integrated.

  FIG. 3 is a functional block diagram of a defect inspection apparatus that integrates inspection results based on image information captured by a plurality of cameras. Image information picked up by the cameras 300A to 300N is taken into the image processing means 400A to 400N and subjected to image processing, and defect inspection in the inspection area in charge is executed.

  The inspection results of the image processing apparatuses 400 </ b> A to 400 </ b> N are integrated with the inspection result of the entire inspection object by the coordinate conversion unit 500 and passed to the determination result output unit 600. Thus, in the inspection system that integrates a plurality of imaging systems, the characteristics of the area sensors 301A to 301N included in the cameras 300A to 300N need to match.

  For this reason, each of the cameras 300A to 300N has a gain adjustment function, and in an initial step of system operation, a preparatory operation for executing gain adjustment by an operator to match the characteristics of the respective imaging systems is performed.

  FIG. 4 is a functional block diagram illustrating a specific configuration example of the image processing apparatus. The functional configuration will be described below with the image processing apparatus 400A as a representative. Image information captured by the area sensor 301 </ b> A such as a CCD provided in the camera 300 </ b> A is taken into the image processing device 400 </ b> A by the image input board 401 and is passed to the preprocessing unit 402.

  In the pre-processing unit 402, the camera defect correction unit 402a performs correction processing of the luminance missing portion of the area sensor itself, and then the shading correction unit 402b uniformly reduces the sensitivity difference between the peripheral portion and the central portion of the area sensor. The processing to be performed is executed and passed to the detection processing means 403.

  In the detection processing unit 403, the differential enhancement filter unit 403 a processes the bright spot defect to make it conspicuous, and the binarization unit 403 b sets a filtering portion having a level higher than a preset threshold to “1”, A defect candidate is extracted by setting the low-level filtering portion to “0”, and a number is assigned to each extraction candidate by labeling 404 c and passed to the determination processing means 404.

  In the determination processing unit 404, the feature amount calculation unit 404a performs feature amount calculation for each defect candidate. The feature amount is a numerical value for determining a defect, and is, for example, average luminance, maximum luminance, luminance volume, average contrast, maximum average contrast, or the like.

  The feature amount calculated by the feature amount calculation unit 404a is output to the identification unit 404b, and a candidate exceeding the threshold value is identified as a defect by comparing this feature amount with a preset threshold value La, and a determination result output unit Pass to 405.

  FIG. 5 is a flowchart showing a signal processing procedure of each of the image processing apparatuses 400A to 400N. After the gain adjustment in step S1, when a captured image is input in step S2, camera defects are corrected in step S3, and shading correction is performed in step S4.

  Further, enhancement filter processing is performed in step S5, binarization processing is performed in step S6, and labeling is performed in step S7. Further, feature amounts are calculated in step S8, identification processing is performed in step S9, and a determination result is output in step S10.

The reason for dividing the inspection area into a plurality of images and imaging with a plurality of cameras is that the resolution of an area sensor such as a CCD mounted on the cameras is limited. The resolution of a liquid crystal display element (hereinafter, LCD) to be inspected is 1980 × 1080 × RGB = 6,220,800 in full high-definition.

  If the pixel ratio of the LCD and CCD is at least 1: 3 × 3 for defect identification, the resolution required for the CCD will be 55,987,200, nine times the resolution of the LCD, even with a camera equipped with a 10,000,000 pixel CCD. A stand is required.

  In order to identify even a minute defect, it is necessary to further increase the pixel ratio of the LCD and the CCD, and accordingly, the number of cameras increases.

  There is known a technique for increasing the pixel ratio between the LCD and the CCD by increasing the apparent resolution of the CCD without increasing the number of cameras. This is a technique called “image shifting”. In the case of a black and white CCD, four times of imaging is performed while shifting the image vertically and horizontally by 1/2 of the pixel pitch of the CCD. An image having a resolution can be obtained.

  Patent Document 1 discloses the principle of apparent resolution improvement by “image shifting” in an image pickup apparatus using a CCD as an image sensor, and image shifting means by an optical system (lens shift) and a mechanical system (piezoelectric element). .

JP-A-6-261236

A defect inspection apparatus using a plurality of cameras incorporating an image shifting mechanism has the following problems.
(1) The apparatus becomes larger. A camera equipped with an image shifting mechanism is heavier and larger because a piezo XY stage is built in the camera. An XY stage driver is also required for each camera. Along with this, the rigidity of the stage holding the camera is also required, leading to an increase in the size of the inspection apparatus.

(2) The apparatus becomes expensive. Piezo XY stages are required for the number of cameras, and drivers for the XY stages are also required, which is expensive.

(3) When a cooling CCD is mounted, the size and the cost are further increased. The S / N ratio of the CCD is remarkably improved by cooling. In order to increase the accuracy of inspection, the CCD may be cooled by a Peltier element or the like. When an XY stage with a built-in cooling unit is installed, the camera becomes very large, leading to further increase in size and cost of the device.

(4) The amount of image shift is not the same between cameras. When using a plurality of cameras, it is necessary to match the image shift amounts of the cameras so that the same image processing can be applied to the images of all the cameras. It is cumbersome to adjust this shift amount with a plurality of cameras, and it is not possible to match them completely.

(5) It is necessary to use a camera having an image shifting mechanism. Since the types of cameras provided with the image shifting mechanism are limited, the cameras that can be used are limited.

  The present invention has been made in order to solve the above-described problems. Even if a plurality of cameras are used, the apparatus does not increase in size, and a defect inspection apparatus capable of realizing the same image shift amount with all the cameras is realized. It is an object.

In order to achieve such a subject, the present invention has the following configuration.
(1) Image information obtained by imaging each divided area to be inspected divided into a plurality of areas with a plurality of cameras including an area sensor composed of a lens system and a predetermined number of pixels is processed into a calculated feature amount. In a defect inspection apparatus for identifying defects in the area based on
A camera board for fixedly arranging the plurality of cameras;
Actuator means for periodically moving the camera board in a predetermined range in the X and Y directions;
A defect inspection apparatus comprising:

(2) The actuator means periodically moves the camera board in the X and Y directions within a range of m · δ / 2, where m is the imaging magnification of the lens system and δ is the pixel pitch. The defect inspection apparatus according to (1), wherein the defect inspection apparatus is operated.

(3) Position restriction means for setting the amount of movement of the camera board based on the imaging magnification and pixel pitch information, and the actuator means is a cylinder for moving the camera board with respect to the position restriction means. The defect inspection apparatus according to (1) or (2), wherein the defect inspection apparatus includes a motor.

(4) The defect inspection according to (1) or (2), wherein the actuator means is composed of a piezoelectric element whose vibration amplitude is regulated based on the imaging magnification and pixel pitch information. apparatus.

(5) According to (1) or (2), the actuator means is moved by a position servo control device that controls a moving amount of the camera board based on the imaging magnification and pixel pitch information. Defect inspection apparatus as described.

(6) A saddle that is periodically moved in the X direction by the first actuator means with respect to the fixed frame is provided, and the camera board is periodically moved in the Y direction by the second actuator means with respect to the saddle. The defect inspection apparatus according to any one of (1) to (5), wherein the defect inspection apparatus is moved.

According to the present invention, the following effects can be expected.
(1) Since all the cameras are displaced by the same actuator means, the same pixel shift amount can be realized by all the cameras.

(2) Since a camera without an image shifting mechanism can be mounted, camera options can be expanded and cost performance can be improved.

(3) Even if the number of cameras increases, it is possible to shift images with the same structure (actuator means in the X and Y2 directions).

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a plan view showing an embodiment of a camera stage in a defect inspection apparatus to which the present invention is applied.

  Two cameras 2A and 2B are fixedly arranged on a camera board 1 that is periodically moved in the X and Y directions by actuator means described later.

  A frame-type saddle 3 is disposed surrounding the camera board 1 with a predetermined gap therebetween. The relative position of the camera board 1 with respect to the saddle 3 is restricted by the leaf springs 4a to 4d that can be finely moved only in the Y direction arranged in the gap, and are restricted to the neutral position shown in the figure.

  A frame-shaped fixed frame 5 is disposed so as to surround the saddle 3 with a predetermined gap therebetween. The relative position of the saddle 3 with respect to the fixed frame 5 is restricted by the leaf springs 6a to 6d that can be finely moved only in the X direction arranged in the gap, and is restricted to the neutral position shown in the figure.

  A cylinder motor 7 constituting the first actuator means is fixedly disposed on the fixed frame 5, and the cylinder 7a periodically moves the saddle 3 to a predetermined range in the X direction against the leaf springs 6a to 6d.

  A cylinder motor 8 constituting the second actuator means is fixedly disposed on the saddle 3, and the cylinder 8a periodically moves the camera board 1 to a predetermined range in the Y direction against the leaf springs 4a to 4d.

  The amount of movement of the camera board 1 relative to the saddle 3 in the Y direction is set by a stopper 9a to 9d that protrudes from the saddle 3 side and forms a position restricting means in a gap where the saddle 3 and the camera board 1 face each other. The amount of protrusion of these stoppers can be adjusted by a screw mechanism or the like.

  Similarly, the amount of movement of the saddle 3 in the X direction relative to the fixed frame 5 is set by a stopper 10a to 10d that protrudes from the fixed frame 5 side and forms a position restricting means in a gap where the fixed frame 5 and the saddle 3 face each other. . The amount of protrusion of these stoppers can be adjusted by a screw mechanism or the like.

  The operation polarity and operation cycle in the X direction of the cylinder 7 a of the cylinder motor 7 are sequence-controlled by the controller 12 via the driver 11. Similarly, the operation polarity and operation cycle in the Y direction of the cylinder 8 a of the cylinder motor 8 are sequence-controlled by the controller 12 via the driver 13.

Next, the procedure for setting the smoothing amount will be described. FIG. 6 shows an optical system showing the imaging relationship of the camera. When the distance between the principal points of the inspection object 100 and the lens 200 is b, the distance between the lens principal point and the area sensor (CCD) 301 is a, and the focal length of the lens is f.
1 / a + 1 / b = 1 / f
Holds. At this time, the image magnification m is m = b / a.

  Assuming that the pixel pitch of the CCD is δ, when performing pixel shifting, conventionally, the camera body and the lens to be inspected are fixed, and the CCD is moved by δ / 2 in the X and Y directions, and imaging is performed four times. This is equivalent to fixing the inspection object 100 and simultaneously moving the camera, lens and CCD by m · δ / 2.

  Since the values of a, b, and f are known when the inspection apparatus is set, m can be easily calculated, and the camera movement amount m · δ / 2 can be set.

  In the embodiment of FIG. 1, the protrusion amounts of the stoppers 9 a to 9 d and 10 a to 10 d are adjusted based on the movement amount m · δ / 2 calculated according to the distance b between the inspection object 100 and the lens 200. When the inspection object and the camera are fixedly arranged and the imaging magnification is fixed, the protrusion amount of the stopper can be fixed to a constant value.

  In the embodiment of FIG. 1, when the movement amounts of the respective cylinders 7a and 8a can be controlled by the cylinder motors 7 and 8, the movement amount m is set to the controller 12 from the setting means 14 for obtaining the values of m and δ. The position of the cylinders 7a and 8a of the cylinder motors 7 and 8 can be controlled from the controller 12 via the drivers 11 and 13 by setting δ / 2.

  In the embodiment of FIG. 1, the cylinder motors 7 and 8 are exemplified as the actuator means. However, the cylinder motors 7 and 8 are configured by piezoelectric elements (piezo actuators or the like) whose vibration amplitude is regulated based on the values of the imaging magnification m and the pixel pitch δ. You can also.

  In the case of more accurate position control, the movement distance from the reference position of the camera board 1 and the saddle 3 is measured by a high-precision optical distance sensor, and this measured value and the movement amount setting value from the setting means 14 are measured. It is also possible to configure a position control servo system that inputs m · δ / 2 to the controller 12 and operates the cylinder motors 7 and 8 via the drivers 11 and 13 based on the deviation.

  In the embodiment of FIG. 1, the case where there are two turtles fixedly arranged on the camera board 1 is exemplified, but any number of three or more turtles can be mounted. The larger the number of mounted units, the more the pixel ratio of LCD (Liquid Crystal Display) and CCD can be increased.

It is a top view which shows one Embodiment of the camera stage in the defect inspection apparatus to which this invention is applied. It is a perspective view which shows the basic system structure of the defect inspection apparatus by two cameras provided with an area sensor. It is a functional block diagram of a defect inspection apparatus that integrates inspection results based on image information captured by a plurality of cameras. It is a functional block diagram which shows the specific structural example of an image processing apparatus. It is a flowchart which shows the signal processing procedure of an image processing apparatus. It is an optical system showing the imaging relationship of the camera.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Camera board 2A, 2B Camera 3 Saddle 4a-4d Leaf spring 5 Fixed frame 6a-6d Leaf spring 7 Cylinder motor 7a Cylinder 8 Cylinder motor 8a Cylinder 9a-9d Stopper 10a-10d Stopper 11 Driver 12 Controller 13 Driver 14 Setting means

Claims (6)

The image information obtained by imaging each divided area to be inspected divided into a plurality of areas by a plurality of cameras including an area sensor composed of a lens system and a predetermined number of pixels is processed, and based on the calculated feature amount In defect inspection equipment that identifies defects in areas,
A camera board for fixedly arranging the plurality of cameras;
Actuator means for periodically moving the camera board in a predetermined range in the X and Y directions;
A defect inspection apparatus comprising:   The actuator means periodically moves the camera board in the X and Y directions within a range of m · δ / 2, where m is the imaging magnification of the lens system and δ is the pitch of the pixels. The defect inspection apparatus according to claim 1.   Position restriction means for setting the amount of movement of the camera board based on the imaging magnification and pixel pitch information is provided, and the actuator means is constituted by a cylinder motor that moves the camera board with respect to the position restriction means. The defect inspection apparatus according to claim 1, wherein the defect inspection apparatus is provided.   The defect inspection apparatus according to claim 1, wherein the actuator unit is configured by a piezoelectric element whose vibration amplitude is regulated based on the imaging magnification and pixel pitch information.   3. The defect inspection apparatus according to claim 1, wherein the actuator unit is moved by a position control unit that controls a moving amount of the camera board based on the imaging magnification and pixel pitch information.   A saddle that is periodically moved in the X direction by a first actuator means with respect to a fixed frame is provided, and the camera board is periodically moved in the Y direction by a second actuator means with respect to the saddle. The defect inspection apparatus according to claim 1, wherein:

Images