KR20020017054A - Defect inspection method using automatized defect inspection system - Google Patents

Abstract

PURPOSE: An automatic defect inspection apparatus and an inspection method therewith are provided to examine defectiveness of an object having curved or coated surfaces regardless of interference of diffused reflection, and to improve accuracy of inspection by searching the object range automatically. CONSTITUTION: An object is distinguished from the background in deciding the object(S410). The image is obtained with a first lighting apparatus, and the inspection range is distinguished from the object to select the inspection range(S420). The object is photographed with a second lighting apparatus, and the luminosity of the inspection range is detected(S430). The defectiveness of the object is inspected with the object range stored in a memory and with inspection ranges by the lighting apparatus(S440). The image is obtained with using two lighting units, and combination image is compared with the standard image. The inspection area is automatically searched with analyzing the image within the inspection range.

Description

Defect inspection method using automatized defect inspection system

The present invention relates to a defect inspection method using an automated defect inspection apparatus.

In the production process of all products, defect inspection process is performed to evaluate the completeness of the finished product after the manufacturing process. In this case, the defects may be referred to collectively as all elements that hinder the characteristics of the product, there are defects of various sizes ranging from very small to the naked eye to the size visible to the naked eye.

Inspection of the appearance defect of a relatively large object is usually performed by randomly extracting a sample and inspecting the product with the naked eye, and a small object may also be inspected by a microscope or the like. However, in this case, since it is impossible to inspect all the produced products and subjective inspection by visual observation of the worker, objective product inspection is difficult.

In order to solve this problem, an inspection system that automates the inspection process is used, which is a standard that is pre-inputted through image analysis software to obtain an image of a product obtained through a CCD (charge-coupled device) camera. By comparing and analyzing the images and making scientific decisions, the objective is to automate objective inspection and quality control.

Such automated inspection equipment can be broadly classified into optical systems, image analysis systems, and machine control systems. The optical system illuminates the area to be measured and acquires the reflected image and transmits it to the image analysis system.The image analysis system converts the analog signal of the transmitted image into a digital signal and compares and analyzes it with the standard image inputted in advance. In this case, the defects are classified by grade and the result is output. The machine control system directly classifies defective products by type and grade according to the image analysis results.

In general, in semiconductor processes that require precise patterning techniques, fine scratches and dusts can cause fatal operating errors, requiring precise defect inspection equipment, and the appearance of relatively large objects such as glass bottles and can lids. To prevent errors, defects can be checked with relatively simple inspection equipment.

Equipment that is used for close inspection requires position correction precision down to micron units and typically analyzes local area images. Therefore, when inspection of a relatively large area is required, the entire area to be measured is analyzed by scanning, so the inspection time becomes longer in proportion to the inspection area. In addition, since all images acquired by scanning must be compared and analyzed, the time required for image analysis is much longer depending on the inspection area. For this reason, the inspection of fine defects in products such as semiconductor patterns is very precise but limited to inspection of a few randomly extracted samples.

Simple inspection equipment is used to check the appearance defects of relatively large products such as glass bottles, can lids, and goggles. Since such equipment acquires images through a simple optical system, interference is caused by diffuse reflection, which makes it difficult to make accurate measurements. In addition, in the case of a product having a curved surface or a product coated with a surface, there is a problem in that an area that cannot be inspected is generated depending on the angle or surface condition of the surface of the illumination system of the optical system and the product to be inspected.

The present invention was conceived to solve such a problem, and an object of the present invention is to provide a defect inspection method capable of eliminating the influence of interference caused by diffuse reflection.

It is another object of the present invention to provide a defect inspection method which enables defect inspection even on a test object having a curved surface or a surface coated.

1 is a schematic diagram showing the overall structure of an automated defect inspection apparatus according to a first embodiment of the present invention.

2 shows the structure of a lighting device according to a first embodiment of the present invention.

3A and 3B show areas of the inspection object to be imaged using each of the illumination devices of FIG. 2.

4 is a flowchart of a defect inspection method according to a first embodiment of the present invention.

5A to 5C are graphs showing brightness of an image of a test target object obtained according to each lighting apparatus used.

6 shows the structure of a lighting device according to a second embodiment of the present invention.

7 shows the structure of a lighting device according to a third embodiment of the present invention.

8A to 8C are graphs showing brightness of an image of an object to be inspected acquired according to each lighting apparatus used in the third embodiment of the present invention.

In order to solve the above problems, in the present invention, by using two or more lighting devices to separate the area of the object to be divided into two or more to obtain a separate image and then analyze the combination, the sample inspection before the defect inspection of the produced product Using the target object, each lighting device is automatically determined to determine each inspection target area for the image. The determination of the inspection target area is performed by obtaining an image of the inspection target object using a corresponding illumination device, analyzing the brightness, and designating the inspection target area according to the change of the brightness.

That is, in the defect inspection method according to the present invention, illuminating the inspection object with a first lighting device and receiving the reflected light as an image pickup means to obtain a first image of the inspection object, the brightness of the first image. Searching for and identifying a first inspectable area using the first lighting device, and storing information about the first inspectable area.

In this case, the second illumination device is used to illuminate the inspection object to receive the reflected light as an image pickup means to obtain a second image of the inspection object, and to search for the brightness of the second image to use the second illumination device. The method may further include identifying a second inspectable region and storing information on the second inspectable region, and before the obtaining of the first image, light reflected by illuminating a predetermined region to be inspected. Acquiring a third image of a certain region to be examined by the image pickup means, identifying a background and an object to be inspected by searching the brightness of the third image, and storing information about the region of the object to be inspected. It may further comprise a step.

The identification of the first or second inspectable area is preferably performed by selecting a portion having a brightness within a predetermined range of the first or second image, and the boundary of the first or second inspectable area is the first or second. 2 Brightness changes rapidly in the image.

After storing the information on the first inspectable area, the light reflected by illuminating the other inspected object by using the first lighting device is received as the image pickup means, and the other inspected object on the first inspectable area is received. Acquiring a third image of the target image; illuminating the other inspection target object using the third illumination device, and receiving the reflected light as the image pickup means, to obtain a second image of the remaining inspection region of the other inspection target object except for the first inspectable region; The method may further include obtaining a fourth image and comparing and analyzing the third and fourth images with the standard image.

After storing the information about the first and second inspectable areas, the light reflected by illuminating another object to be inspected by using the first lighting device is received as the image pickup means, and the other Acquiring a fifth image of the object to be inspected, illuminating the other object to be inspected using the second illumination device, and receiving the reflected light as an image pickup means, thereby obtaining a sixth image of the other object to be inspected for the second inspectable area; The method may further include acquiring an image and comparing and analyzing the fifth and sixth images with the standard image, wherein comparing and analyzing the fifth and sixth images with the standard image may include the fifth and sixth images. Obtaining a seventh image of the entire other object to be inspected using the image and comparing and analyzing the seventh image with the standard image, or the fifth image corresponds to the first inspectable area. It may comprise the step of comparison with the second standard image corresponding to the comparison stage and the sixth image to the first standard image in the second inspection area.

Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

1 is a schematic diagram showing the overall configuration of an automated defect inspection apparatus according to a first embodiment of the present invention.

The automated defect inspection apparatus 100 according to the present invention may be largely divided into the measurement optical system 200 and the image analysis system 300. The measuring optical system 200 includes an image capturing unit 230 including a CCD camera and lighting units 210 and 220 divided into two upper and lower parts, and acquires an image reflected by illuminating an area to be measured to obtain an image analysis system ( 300). That is, the object 400 to be inspected sequentially moves through the belt 500 to pass through a predetermined position under the measuring optical system 200. In this case, the image of the object 400 to be inspected is measured by the measuring optical system 200. Obtained.

The image analysis system 300 includes an image processing processor 310, a memory device 320, a display unit 330, and the like, which converts an analog signal of an image transmitted from the measurement optical system 200 into a digital signal and is input in advance. The result is displayed on the display unit 330 by comparing and analyzing the standard image and classifying defects by type and grade. In addition, although not shown in the drawings, the results may be used to directly classify defective items by type and grade.

Now, the lighting unit of the automated defect inspection apparatus according to the first embodiment of the present invention will be described in more detail. FIG. 2 is a view illustrating in detail the lighting units 210 and 220 of FIG. 1.

As shown in Fig. 1 and Fig. 2, the lighting device of the present invention is composed of two parts, the first lighting device 210 on the upper side and the second lighting device 220 on the lower side.

The first lighting device 210 has a support 213 having an opening 211 for allowing the image capturing unit 230 to image the object 400 to be inspected, and is attached to the inside of the support 213. It consists of a plurality of light emitting diodes 212. As described above, the first lighting device 210 that irradiates light from the upper side to the object to be inspected emits light at an angle that is almost perpendicular to the object to be inspected 400.

Meanwhile, the lower second lighting device 220 also has a support having an opening 221 for allowing the imaging unit 230 to capture the inspection object 400 similarly to the first lighting device 210. 223 and a plurality of light emitting diodes 222 attached to the inside of the support 223. In the case of the second lighting device 220, the light emitting diodes 222 are attached to the inner side of the support 223. have. Therefore, the second lighting device 220 is irradiated with light to the object to be inspected 400 at a substantially inclined angle compared with the first lighting device (210).

The reason why the lighting unit composed of two different lighting devices is used is that the surface of the object to be inspected is curved or the coating is not able to inspect the entire object to be inspected by only one lighting device. For example, when a test object to be coated with a donut-shaped surface having a hole in the center is to be inspected, an area that can be inspected using each lighting device is as shown in FIGS. 3A and 3B.

When the donut-shaped inspection object 400 is irradiated using the first lighting device 210, an area where an accurate image for defect inspection can be obtained is a boundary portion indicated by hatching in FIG. 3A, that is, a donut-shaped inspection. It will be around the outer periphery of the object and a hole in the center of the donut shape. The middle part, which is not marked by hatching, is the part where diffuse reflection occurs, making it difficult to obtain an accurate image of the surface condition and appearing bright overall.

On the contrary, when the second lighting device 220 is used, the image of the center portion except for the outline portion of the donut-shaped inspection target object which cannot be inspected by the first lighting device 210 can be obtained accurately. A portion indicated by hatching in FIG. 3B is a portion where an accurate image can be obtained using the second lighting device 220.

Therefore, in order to obtain an accurate image of the entire inspection object, an embodiment of the present invention captures an image of the entire inspection object by capturing twice once each using two lighting apparatuses. The images obtained by two sequential imaging are sent to the image analysis system and combined into one to form the image of the whole object to be inspected.The image analysis system compares and analyzes it with the standard image and classifies the defects by type and grade. Is displayed through the display unit. Alternatively, the defect inspection may be performed by comparing the images of the respective portions obtained through the respective imaging with the standard images of the corresponding portions, without combining the images obtained by the two imaging as described above.

On the other hand, in the automated defect inspection apparatus according to an embodiment of the present invention, the area to be inspected through the respective imaging by the two illumination devices is automatically input by the automated defect inspection apparatus through the brightness measurement, rather than inputting a predetermined value. Is determined.

Now, the process of determining the inspection area in the automated defect inspection apparatus according to the first embodiment of the present invention will be described in detail. 4 is a flowchart illustrating a defect inspection method according to a first embodiment of the present invention, and FIGS. 5A to 5C are graphs showing brightness of an image obtained to determine an inspection region.

First, when the object to be selected is selected, the background and the object to be inspected must be identified (S410).

In the first embodiment of the present invention, in this step, an image of the object to be inspected is first obtained by using the first lighting device 210. In the case of the donut-shaped test object shown in FIG. 3A, the brightness of the image obtained when the line is shown along the dotted line in FIG. 3A is as shown in FIG. 5A. That is, the brightness sharply changes at the boundary between the background and the object to be inspected, where the area of the object to be inspected is darker than the background part. On the other hand, the ab area and the a'-b 'area of the center of the object to be inspected appear bright as the background area under the influence of the reflected light, but since the shape of the object to be inspected is known as the donut shape in advance, the ab area and the a'-b' area are It can be seen that 'the area is not the background area but the area of the object to be inspected, and the area of the object and the background area of the object to be inspected can be identified using the boundary points at which the four brightnesses of A, B, A' and B 'change rapidly. Can be. Information about the identified area is stored in the storage of the image analyzer.

Now, the inspectable area using each lighting device is identified with respect to the area of the object to be inspected. First, the inspection target region is identified within the object region by using an image obtained by using the first lighting device 210 to identify the inspection target region (S420). As described above, the ab area and the a'-b 'area in the object areas AB and A'-B' are the remaining areas Aa, bB, B'-b 'and a'-A' under the influence of the reflected light. It appears brighter than, and the brightness rapidly changes between the two regions (FIG. 5B). Therefore, the areas in which defects can be inspected using the first lighting device 210 are A-a, b-B, B'-b ', and a'-A' areas which are not affected by the reflected light.

Searching of the inspection target region may use a method of searching by drawing a circle from the outline of the inspection target object. However, there is no limitation in the method for searching the inspection subject region, and the inspection subject region can be obtained by arbitrarily searching for the brightness of the entire inspection object starting from one point on the inspection subject. However, since the boundary of the region to be inspected is often the same shape as the outline of the object to be inspected, it is possible to shorten the search time by using a method of searching by drawing a circle from the outline as in the embodiment of the present invention. That's how it can be.

An area within the object to be inspected having a brightness within a predetermined predetermined range may be determined as the testable area. That is, the remaining portion except for a portion having the highest and lowest brightness is determined as the inspectionable region. For example, if the brightness of each pixel can be recognized by dividing it into 256 levels, except for the part having the brightness of 0 to 50 and the part of the brightness of 205 to 255 in the upper and lower 20% ranges. The remaining part can be determined as an inspectable area.

The area determined as the testable area through the search as described above is stored in the storage of the image analysis system.

Next, the brightness of the inspection object region is identified by capturing the inspection object 400 using the second lighting device 220 (S430). When the second lighting device is used, most of the light is irradiated at an inclined angle with respect to the object to be inspected unlike the first lighting device. The brightness of the image obtained at this time is as shown in Fig. 5c. That is, as shown in FIG. 5B, the ab area and the a'-b 'area appear dark in the inspection object area AB and A'-B', and the remaining areas Aa, bB, B'-b 'and a' are dark. A ') appears bright under the influence of reflected light. Therefore, the areas where defects can be inspected using the second lighting device are a-b areas and a'-b 'areas that are not affected by the reflected light. The area determined as a testable area through retrieval is also stored in the storage of the image analyzer.

At this time, it is preferable that the object to be inspected used to determine the inspectable area is a product of a complete form without defects.

Now, defect inspection may be performed on the object to be inspected using an area corresponding to the object to be inspected stored in the storage device and an inspectable area that may be inspected using each lighting apparatus (S440). In the defect inspection, as described above, when the object 400 to be inspected sequentially moves through the belt 500 and comes to a predetermined position under the measuring optical system 200, the region to be measured by the first and second lighting apparatuses in order In this case, the image capturing unit acquires an image of the object to be inspected and transmits the image to the image analyzer 300. In the image analyzer, the analog signal of the transmitted image is converted into a digital signal, compared and analyzed with a standard input image, and the defect is classified by type and grade, and the result is displayed.

In the first embodiment described above, two inspection devices are used to determine the inspection target area for accurate determination of the inspection area. However, in some cases, the inspection area using the lighting device is obtained from an image acquired using only one lighting device. It is also possible to designate the remaining area as an area using another lighting device.

In addition, in the first embodiment of the present invention, the first lighting device is used in the background and the step of identifying the object to be inspected, but it may be desirable to use the second lighting device depending on the shape or surface condition of the object to be inspected. In addition, images may be obtained by simultaneously illuminating an object under inspection with two lighting devices. However, if you obtain an image by illuminating the object under test with two lighting devices at the same time, you can take an image once to distinguish the object area from the object area and the background area, and use each light device to distinguish the area under test from the object area. In this case, three imagings are required, so that three imagings are required. As shown in the first embodiment, when the inspection target object region and the background region are distinguished from each other, the same image is used to illuminate the first imaging unit. By setting the inspection target area, the inspection time can be shortened.

For more accurate surface inspection, other types of lighting devices using light emitting diodes and curved reflectors may be used. 6 shows an example of an illumination device used in an automated inspection device according to a second embodiment of the present invention.

The lighting device of the second embodiment is also divided into two parts, the first lighting device 610 and the second lighting device 620, and the second lighting device 620 is the second lighting device used in the first embodiment of the present invention. Similar to 220).

The upper first lighting device 610 is attached to the support 613 and the plurality of light emitting diodes 612 and the support 613 attached to the inside of the support 613, and an opening 611 in the center thereof. Is formed and consists of a curved reflector 614 for reflecting light emitted from the light emitting diode 612. When the first lighting device 610 is used, the light emitted from each light emitting diode 612 of the first lighting device is reflected by the curved reflector 614 to irradiate the object 400 to be inspected.

In this case, the light directed to the object 400 is not directly irradiated from the light emitting diode 612 to the object 400, but is reflected by the curved reflector 614 toward the object 400 to be irradiated. The reflected light is also uniformly irradiated with other portions on the area of the inspection object 400 positioned below the opening 611. Therefore, more uniform illumination can be obtained than the first lighting device 210 used in the first embodiment of the present invention, and the type (concave, convex) and curvature of the curved reflector 614, the light emitting diode 612 and The angle of inclination of the light can be adjusted by appropriately adjusting parameters such as the distance between the curved reflectors 614, the direction in which the light emitting diodes 612 are disposed, and the distance between the curved reflectors 614 and the object 400 to be inspected. Even when the target object 400 has a thickness of a certain degree or more, the shadow effect can be prevented from appearing, and an accurate image can be obtained even when the inspection target object 400 has a groove or an opening.

In the present invention, the portion of the image obtained by using the first lighting device and the second lighting device may vary according to the characteristics of the object to be inspected. In particular, the influence of the diffuse reflection depends on the curved state of the surface of the object to be inspected or the surface treatment state (coating treatment, etc.). Therefore, the inspection area of the inspection object must be divided differently according to the shape or surface characteristics of the inspection object, which can be easily achieved by using the inspection area search method of the present invention.

On the other hand, the structure of the lighting device used in the first and second embodiments of the present invention is provided with a first lighting device having a light emitting diode installed on the upper surface of the first lighting device or the support including a curved reflector on the upper side, Although the second lighting device provided with the light emitting diode is installed on the inner side, the positions of the two lighting devices may be changed as necessary. In addition, if necessary, three or more imaging may be performed using three or more lighting devices, or a back lighting device may be used in combination.

Now, a third embodiment of the present invention using the back lighting device will be described.

7 illustrates a structure of a lighting apparatus according to a third embodiment of the present invention, and FIGS. 8A to 8C are graphs showing brightness of an image of an object to be inspected acquired according to each lighting apparatus used in a third embodiment of the present invention. to be.

As shown in FIG. 7, first and second lighting devices 710 and 720 similar to those of the first embodiment are installed between the inspection target object 400 and the imaging unit 230 and are based on the inspection target object. When viewed from the opposite side of the imaging unit 230, the back lighting device 730 is provided.

The back lighting device 730 is formed of a support 733 and a plurality of light emitting diodes 732 attached to the inner surface of the support 733.

In the third embodiment of the present invention, first, the object to be inspected 400 is irradiated from the opposite side of the image capturing unit 230 when the object to be inspected 400 is used as the back illumination device 730. In the case of the opaque inspection object, when the light is irradiated from the rear side using the back lighting device 730, the light does not pass through the inspection object region, and thus the background region and the inspection region are clearly distinguished as shown in FIG. 8A.

Next, the first illumination device 710 and the second illumination device 720 are sequentially photographed, and then the image is analyzed to set the inspection target region. The procedure for setting the inspection subject area is similar to that of the first embodiment of the present invention.

Although the present invention has been described in detail with reference to preferred embodiments, this embodiment has been presented for the purpose of understanding the present invention, and the scope of the present invention is not limited to this embodiment. It will be understood by those skilled in the art that various modifications can be made without departing from the scope of the technical idea of the present invention, and the scope of the present invention should be interpreted by the appended claims.

In the automated defect inspection apparatus according to the present invention, by using two or more lighting devices for irradiating light to the object to be inspected in different ways, images of different parts of the object to be inspected are obtained and combined with each other to compare with the standard image, By automatically searching and obtaining the inspection target area that can be inspected by using two or more lighting devices, there is no need to designate the inspection target area for each object to be inspected, and use the exact inspection area obtained as a result of the measurement. The defect inspection can be performed to increase the accuracy of the defect inspection.

Claims (9)

Illuminating the object to be inspected using a first lighting device to receive the reflected light as an image pickup means to obtain a first image of the object to be inspected; Searching for brightness of the first image to identify a first inspectable area using the first lighting device; And storing information about the first inspectable area. The method of claim 1, Illuminating the object to be inspected using a second lighting device to receive the reflected light into the imaging means to obtain a second image of the object to be inspected; Identifying a second inspectable area using the second lighting device by searching the brightness of the second image; And storing information about the second inspectable area. The method of claim 1, Prior to acquiring the first image, Illuminating a predetermined area to be examined and receiving light reflected by the image pickup means to obtain a third image of the predetermined area; Identifying a background and the object to be inspected by searching the brightness of the third image; And storing information on the area of the object to be inspected. The method according to claim 1 or 2, And identifying the first or second inspectable area by selecting a portion of the first or second image having brightness within a predetermined predetermined range. The method according to claim 1 or 2, And a boundary of the first or second inspectable area is a portion in which the brightness is rapidly changed in the first or second image. The method of claim 1, After storing information about the first inspectable region, Receiving a light reflected by illuminating another inspection object by using the first lighting device as the image pickup means, and obtaining a third image of the another inspection object with respect to the first inspectable area; The light reflected by illuminating the other inspected object by using a third lighting device is received by the imaging means, and the other inspected object of the other inspected object except for the first inspectable region of the inspected object is Acquiring a fourth image; And comparing and analyzing the third and fourth images with a standard image. The method of claim 2, After storing information about the first inspectable region and storing information about the second inspectable region, Receiving light reflected by illuminating another inspection object using the first lighting device as the image pickup means, and acquiring a fifth image of the other inspection object with respect to the first inspectable area; Receiving light reflected by illuminating the other inspection object using the second lighting device as the image pickup means, and obtaining a sixth image of the other inspection object with respect to the second inspectable area; And comparing and analyzing the fifth and sixth images with a standard image. The method of claim 7, wherein Comparing and analyzing the fifth and sixth image with the standard image, Obtaining a seventh image of the whole other object to be inspected using the fifth and sixth images; And comparing and analyzing the seventh image with a standard image. The method of claim 7, wherein Comparing and analyzing the fifth and sixth image with the standard image, Comparing and analyzing the fifth image with a first standard image corresponding to the first inspectable area; And comparing and analyzing the sixth image with a second standard image corresponding to the second inspectable area.