JP2001337041A - Defect-inspection apparatus and defect inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a defect-inspection apparatus and a defect inspection method whereby the apparatus can be made compact and inspection can be sped up. SOLUTION: To this defect-inspection apparatus are set a line sensor 4 with sensor elements arranged for detecting a concentration level of an object 1 to be inspected, a moving device for moving the line sensor or the object in a direction intersecting a direction in which the sensor elements of the line sensor are arranged, a threshold storage device 8 for storing one threshold value for each pixel, a binarization circuit 6 for binarizing the concentration level with the use of threshold values, a run length device 7 for holding the concentration level only when binary data have a predetermined value and generating one-dimensional defect information from the held concentration level, and a link process device 9 for linking each of the one-dimensional defect information and generating two-dimensional defect information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect inspection apparatus and a defect inspection method for detecting a defect existing on an inspection object using a line sensor and determining the type of the defect based on the size and density of the detected defect. About.

[0002]

2. Description of the Related Art In a conventional defect inspection apparatus using a line sensor, when defects having different densities are detected separately,
The output of the sensor is binarized using a plurality of threshold values for each pixel.

In order to measure the density of a detected defect, an image of the entire inspection object having the defect is recorded in a frame memory or the like at the same time as the process of detecting the defect, and position information of the detected defect is obtained. First, the inside of the frame memory or the like is searched, and the density data of the defect is obtained from a corresponding portion in the image of the entire inspection object.

[0004]

However, in the above prior art, a plurality of thresholds are required for each pixel in order to distinguish defects having different densities. Therefore, a storage device for storing these thresholds, However, there is a problem that a binarization circuit for performing binarization using the threshold value becomes large, and thus the entire defect inspection apparatus also becomes large.

[0005] When a plurality of thresholds are used as described above,
There is also a problem that, when large defects having a low density include small defects having a high density, each of them is detected as an independent defect.

Further, in order to finely classify the density of defects to be detected, thresholds are required by the number of classifications, and a storage device for storing these thresholds, and a binarization for performing binarization using these thresholds. There is a problem that the size of the circuit is further increased, and thus the entire defect detection device is also increased in size.

Further, in order to measure the density of a detected defect, the inside of a frame memory or the like is searched based on the position information of the defect, and when a corresponding portion in the image of the entire inspection object is referred to, the inspection object is inspected. There is a problem in that it takes time to search for a corresponding portion from the entire image, and as a result, the throughput of the entire inspection process including this process does not increase.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a defect inspection apparatus and a defect inspection method capable of reducing the size of an apparatus and increasing the speed of inspection.

[0009]

SUMMARY OF THE INVENTION The gist of the present invention is that sensor elements for detecting the density level of each point on an inspection object are arranged in a straight line, and the density in a region of one line on the inspection object is determined. A line sensor for detecting and outputting a level, a moving device for moving the line sensor or the inspection object in a direction intersecting the direction in which the sensor elements of the line sensor are arranged, and a threshold value for each pixel. , A binarization circuit for binarizing the density level output by the line sensor using the threshold value stored in the threshold storage unit, and outputting binary data, and a binarization circuit Only when the binary data output by the line sensor is a predetermined value, the density level output by the line sensor is held, and from the held density level, the density level of one line on the inspection object is held. And run length apparatus for generating a one-dimensional defect information which is information of a defect existing in the range, and connecting each one-dimensional defect information the run length of device generates,
A connection processing device that generates two-dimensional defect information that is information of a defect that spreads in a two-dimensional direction on the inspection object.

Further, the gist of the present invention is characterized in that it has a judgment processing device for judging the type of a defect present on the inspection object based on the two-dimensional defect information generated by the connection processing device. It is a defect inspection device.

Further, the gist of the present invention is that the line sensor outputs a density level as analog data, and the analog data output from the line sensor is converted into a multi-valued digital signal between the line sensor and a binarization circuit. A defect inspection apparatus having a line sensor interface for converting data into data and sending the converted digital data to the binarization circuit.

Further, the gist of the present invention is a defect inspection apparatus having an illumination device for illuminating the inspection object.

[0013] The gist of the present invention is that the run-length generating device includes: a start point register for storing a start point position of a defect existing in an area of one line on the inspection object; An end point register for storing an end point position of a defect existing in the line area, an integration register for storing an integrated value of the density level of each pixel of the defect area existing in the one line area on the inspection object, A peak register for storing a peak value of a density level of each pixel of a defective area existing in an area of one line on the inspection object;
The one-dimensional defect information generated by the run-length generating device is:
The start point position of the defect stored in the start point register, the end point position of the defect stored in the end point register, the integrated value of the density level stored in the integration register, and the peak value of the density level stored in the peak register A defect inspection apparatus characterized by including:

[0014] The gist of the present invention is that the two-dimensional defect information generated by the connection processing device includes a position, a width, a height, and an area of each defect extending in a two-dimensional direction of the inspection object, and each defect area. And an average value of the density level of each defect obtained by dividing the integrated value of the density level by the area of the defect.

Further, the gist of the present invention is the defect inspection apparatus, wherein the threshold storage device stores a threshold value individually determined for each point on the inspection object.

Further, the gist of the present invention is to provide a method for detecting an object on an inspection object.
Detecting the density level in the area of the line, moving the area to be detected in the direction intersecting the line, using one threshold for each pixel, binarizing the density level into binary data, Only when the binary data is a predetermined value, the density level is held, and from the held density level, one-dimensional defect information which is information of a defect existing in an area of one line on the inspection object. Is generated, and the generated one-dimensional defect information is connected to generate two-dimensional defect information which is information of a defect extending in a two-dimensional direction on the inspection object.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of a defect inspection apparatus according to an embodiment of the present invention will be described below with reference to FIG. Reference numeral 1 denotes an inspection object whose defect is inspected by the defect inspection apparatus of the present invention. A lighting device 2 for illuminating the inspection target 1 from below is disposed below the inspection target 1. In the present invention, in addition to using transmitted light as in the present embodiment, reflected light, scattered light, or the like may be used. Further, a plurality of lighting devices can be used.

A camera 3 for picking up an image of the inspection object 1 is arranged above the inspection object 1. A line sensor 4 that converts a captured image into an image signal is built in the camera 3. This line sensor 4
Is a linear arrangement of sensor elements for detecting the brightness of each pixel of the image, that is, the density level. The line sensor 4 detects the density level in an area of one line on the inspection target 1 by one imaging, and outputs a detection result as an image signal. The image signal output from the line sensor 4 is an analog signal.
As another embodiment, a line sensor that outputs an image signal in the form of a digital signal may be used.

The inspection object 1 can be moved by a moving device (not shown) in the longitudinal direction of the line sensor 4 in the camera 3, that is, in the direction orthogonal to the direction in which the sensor elements are arranged. By using this moving device, the entire surface of the inspection object 1 is imaged by imaging the inspection object 1 line by line while moving the inspection object 1. In the present invention, the camera 3 may be moved instead of the inspection object 1, or both may be moved.

An image signal output from the line sensor 4 is input to a line sensor interface 5. The line sensor interface 5 A / D converts an image signal, which is an analog signal, input from the line sensor 4, converts the image signal into multi-value data, which is a multi-value digital signal, and outputs the converted multi-value data. This multi-value data is output for each density level in each pixel obtained from each sensor element of the line sensor 4. The multi-value data output from the line sensor interface 5 is input to a binarization circuit 6 and a run-length conversion device 7.

Prior to the inspection of the inspection object 1, one predetermined threshold is stored for each pixel in the threshold storage device 8. Among the pixels on the inspection object 1, a portion corresponding to a pixel from which density data exceeding this threshold is obtained is recognized as a defect. The threshold storage device 8 sends the stored predetermined threshold to the binarization circuit 6.

The binarization circuit 6 sends multi-value data of each pixel based on density data obtained from each sensor element of the line sensor 4 input from the line sensor interface 5 from the threshold storage device 8. Compare to the threshold,
If the multi-value data of each pixel exceeds the threshold, 1 is output,
If the multi-value data of each pixel is equal to or smaller than the threshold value, the multi-value data sent from the line sensor interface 5 is converted into binary data by outputting 0. Here, the threshold value sent from the threshold value storage device 8 may be a constant value common to all pixels or a different value for each pixel. Also, 2
The value data may be set to 1 if the multi-valued data is smaller than the threshold, and may be set to 0 if the multi-valued data is equal to or larger than the threshold.

Based on the binary data sent from the binarizing circuit 6, the run length converting device 7
Is detected, that is, the start point position of the defect on the inspection object 1 and the position where the binary data changes from 1 to 0, that is, the end point position of the defect on the inspection object 1 are detected.

At the same time, the run length converting device 7
While the binary data is 1, that is, at the position where the defect exists, the peak value of the multi-valued data while the binary data is 1 is detected based on the multi-valued data output by the line sensor interface 5, Further, an integrated value of the multi-value data while the binary data is 1 is calculated.

Then, the run-length conversion device 7 has an end point register for recording a position where the binary data changes from 0 to 1 on one line, that is, a defect start position, and 1 to 0.
The end point register records the position at which the defect changes, that is, the end point position of the defect, the peak register records the peak value of the multi-valued data in the defect, and the integration register records the integrated value of the multi-valued data in the defect. Output run-length data including. The run length data is one line of data for one line. At this time, the maximum value and the integrated value generated from the multi-value data may be used as the maximum value and the integrated value of the difference between the multi-value data and the threshold. The run length data output from the run length generating device 7 is input to the link processing device 9.

The connection processing device 9 includes a run length converting device 7
Is input, and a defect existing on the inspection object 1 is detected in a direction orthogonal to the longitudinal direction of the line sensor 4 based on the input run-length data. It is determined whether or not it has spread, and if it has spread, the run-length data are linked together as information relating to the same defect, and a two-dimensional defect as information relating to one defect extending in the two-dimensional direction of the inspection object 1 is determined. Output information.

That is, the connection processing device 9 calculates the total integrated value of the multi-value data of all the pixels included in one defect extending in the two-dimensional direction of the inspection object 1. Specifically, the integrated value for each line included in each run length data is totaled. Further, the peak values of the multi-value data included in each run-length data are compared with each other, the maximum value of the peak values is extracted, and the peak values of the density data of all the pixels included in one defect extending in the two-dimensional direction are extracted. I do.

Further, the link processing device 9 calculates a defect starting point position and an end point position included in each run length data,
The position, width, height, and area of the defect in the two-dimensional direction of the inspection object 1 are calculated. Here, the position of the defect is 1
Center position of one defect. The width of a defect is the length of one defect in the longitudinal direction of the line sensor 4. The height of a defect is the length of one defect in a direction orthogonal to the longitudinal direction of the line sensor 4.

The link processing device 9 divides the total integrated value of the multi-value data by the area of the defect to calculate an average value of the multi-value data for one defect. And the connection processing device 9
Outputs two-dimensional defect information including the position, width, height, area of the defect and the maximum value, integrated value, and average value of the multi-valued data.

The judgment processing device 10 includes the connection processing device 9
The type of each defect is determined based on the size and density of each defect included in the two-dimensional defect information output by, and appropriate processing is performed based on the determination result.

[0031]

An embodiment of the present invention will be described with reference to FIG.
The inspection object 1 is illuminated by the illumination device 2. The camera 3 captures an image of the inspection target 1. The line sensor 4 in the camera 3 is driven at 50 MHz. That is, the line sensor 4 detects the value (analog value) of each sensor element in the line sensor 4 at a frequency of 50 MHz.
Are sequentially output. A sequence of these detection values is an image signal.

The inspection object 1 is moved by the moving device in a direction orthogonal to the longitudinal direction of the line sensor 4 in the camera 3, and the camera 3 captures an image for each line. Thereby, the line sensor 4 in the camera 3 captures an image of the entire surface of the inspection target 1.

The image signal, which is an analog signal output from the line sensor 4, is sent to an A / D converter 5a, where it is A / D converted in synchronization with the driving frequency of the line sensor 4 of 50 MHz, and is converted into one pixel. The data is 8-bit multivalued data.

The binarizing circuit 6 also compares the multi-value data of each pixel with the threshold value of each pixel stored in advance in the threshold value memory 8a in synchronization with the driving frequency of the line sensor 4 of 50 MHz. By outputting 1 when the value data exceeds the threshold and outputting 0 when the multi-value data is equal to or less than the threshold, the multi-value data is converted into binary data.

The threshold memory 8a stores one threshold for each pixel. This threshold is determined in advance for each pixel and stored in the threshold memory 8a prior to the inspection. The threshold value stored in the threshold value memory 8a may be a constant value common to each pixel in one line or a different value for each pixel.

The run-length generating device 7 includes an AND circuit 7a
And a run length conversion circuit 7b. AND
The circuit 7a calculates the logical product of the multi-level data output from the A / D converter 5a and the binary data output from the binarization circuit 6, and masks the multi-level data using the binary data. That is, in the mask data output by the AND circuit 7a,
Only the multi-value data of the pixel determined to exceed the threshold by the binarization circuit 6 remains, and the multi-value data of the pixel determined to be equal to or less than the threshold is set to 0. That is, only the multi-value data of the pixel where the defect is detected remains, and the multi-value data of the pixel where the defect is not detected is discarded. The mask data output from the AND circuit 7a is input to the run-length conversion circuit 7b.

The run-length generating circuit 7b has a built-in pixel counter, starting point register, integrating register, and peak register (not shown).

The pixel counter is a 16-bit up counter for specifying a pixel position being processed. The value of this pixel counter is initialized to 1 at the start of scanning of the inspection object 1, and is counted up one by one with a clock of 50 MHz, which is the driving frequency of the line sensor 4.

The start point register is a 16-bit register, and holds a pixel counter value of a pixel immediately before the head pixel position of one defect. If the mask data is 0, the starting point register value is updated to the value of the pixel counter at that time, and if the mask data is not 0, the value held before is kept as it is.

The accumulation register is a 24-bit register and holds an accumulation value obtained by sequentially adding multi-value data in one defect. This integration register value is such that the mask data is 0
If the mask data is not 0, the value is obtained by adding the value of the mask data to the integrated value at that time.

The peak register is an 8-bit register and holds a peak value of multi-value data in one defect. If the mask data is 0, the peak register value is set to 0. If the mask data is not 0, the peak register value at that time is compared with the mask data value, and the peak register value at that time is masked. If the value is less than the data value, the value is updated to the value of the mask data. If the peak register value at that time is equal to or more than the mask data value, the value held previously is retained.

When the mask data changes from non-zero to zero, that is, at the end point of the defect, the run-length conversion circuit 7b determines the pixel counter value immediately after the mask data has changed to zero (the end point of the defect) and , The start register value, the integration register value, and the peak register value immediately before the mask data changes to 0 are output as run-length data. The pixel counter is 16 bits, the starting point register is 16 bits, the accumulation register is 24 bits, and the peak register is 8 bits.
Since the bits are bits, the run length data is 64 bits in total.

FIG. 3 shows an example of run length data generation. In this case, when the pixel counter value reaches 7, the run-length generating circuit 7b outputs run-length data. In this run-length data, the pixel counter value is 7, the starting point register value is 3, the integration register value is 353, and the peak register value is 132.

The link processing device 9 determines whether or not the defect continues in a direction orthogonal to the longitudinal direction of the line sensor 4 based on the information on the start point position and the end point position of the defect included in each run length data. to decide. Then, information on one defect continuous in the two-dimensional direction is output as one two-dimensional defect information. The two-dimensional defect information includes the position, width, height, area of the defect, and the integrated value, average value, and maximum value of the density levels of the pixels included in the defect. Here, the position of the defect is a central position of one defect in the longitudinal direction of the line sensor 4 and a direction orthogonal to the longitudinal direction. Also,
The width of the defect is 1 in the longitudinal direction of the line sensor 4.
Is the length of one defect. The height of a defect is the length of one defect in a direction orthogonal to the longitudinal direction of the line sensor 4.

FIG. 4 shows an example of the two-dimensional defect information output by the connection processing device 9. The position in the x-axis direction refers to the central position of one defect in the longitudinal direction of the line sensor 4, that is, the minimum value of the defect start point position (start point coordinate value) (in the start point register value) in each connected individual run-length data. It is intermediate between the minimum value) and the maximum value (maximum pixel counter value) of the end point position (end point coordinates). The y-axis direction position is a center position of one defect in a direction orthogonal to the longitudinal direction of the line sensor 4, that is, a center position of a line from which run-length data is output.

The width is the length of one defect in the x-axis direction,
That is, it is a value obtained by subtracting 1 from the difference between the maximum value of the defect end point position (pixel counter value) and the minimum value of the start point position (start point register value) in each linked run-length data. Height is the length of one defect in the y-axis direction,
That is, the number of lines from which run-length data is output continuously.

The area is the area of one defect, that is, the value obtained by subtracting 1 from the difference between the end point position (pixel counter value) and the start point position (start point register value) of each connected run-length data. Is the integrated value of

The integrated value of the density level is a value obtained by integrating multi-value data of all pixels included in one defect. Specifically, it is a value obtained by totalizing the integration register values included in the run length data in each line. The average value of the density levels is a value obtained by dividing the integrated value of the density levels by the area of the defect, that is, the total number of pixels included in one defect. The maximum value of the density level is the maximum multilevel data among all the pixels included in one defect. Specifically, it is the largest of the peak values of the run length data in each line. Based on the two-dimensional defect information output from the link processing device 9, the type of each defect is determined by the determination processing device.

[0049]

According to the present invention, since binarization is performed for each pixel using only one threshold value, a storage device for storing the threshold value, and binarization for performing binarization using the threshold value. The circuit can be miniaturized, and therefore the entire defect inspection apparatus can be miniaturized.

Further, according to the present invention, when measuring the density of a detected defect, it is only necessary to search for the corresponding portion from the density data of only the defective portion, so that the corresponding portion can be searched at high speed. As a result, it is possible to speed up the entire inspection process including this search process.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a defect inspection apparatus according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a defect inspection apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram showing an example of run length data generation.

FIG. 4 is a diagram showing an example of two-dimensional defect information output by the connection processing device 9;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Inspection object 2 Illumination device 3 Camera 4 Line sensor 5 Line sensor interface 5a A / D converter 6 Binarization circuit 7 Run-length conversion device 7a AND circuit 7b Run-length conversion circuit 8 Threshold storage device 8a Threshold memory 9 Connection processing Apparatus 10 Judgment processing device

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Fumio Kadozawa 4-1-1 Ushikawa-dori, Toyohashi-shi, Aichi F-term (reference) 2M051 AA31 AB07 CA03 CB01 CB02 CB05 DA06 EA11 EB01 EC01 ED09 5B057 BA02 CA08 CA12 CB06 CB12 CC01 CE12 CG04 CH11 DA08 DB02 DB05 DB09

Claims (8)

[Claims] 1. A line sensor for detecting a density level at each point on an inspection target in a straight line, detecting and outputting a density level in an area of one line on the inspection target. A movement device for moving the line sensor or the inspection object in a direction intersecting the direction in which the sensor elements of the line sensor are arranged; a threshold storage device for storing one threshold for each pixel; A binarization circuit that binarizes the density level output by the line sensor using a threshold value stored in the storage device and outputs binary data; and a binary data output by the binarization circuit is a predetermined value. Only when is the density level output from the line sensor is held, and from the held density level, the information on the defect existing in the area of one line on the inspection object is obtained. A run-length generating device that generates one-dimensional defect information; and two-dimensional defect information that is information of a defect that extends in a two-dimensional direction on the inspection object by connecting each one-dimensional defect information generated by the run-length generating device. And a consolidation processing device for generating a defect. 2. The apparatus according to claim 1, further comprising a determination processing device that determines a type of a defect existing on the inspection target based on two-dimensional defect information generated by the connection processing device. Defect inspection equipment. 3. The line sensor outputs a density level as analog data, and converts the analog data output by the line sensor into multi-value digital data between the line sensor and a binarization circuit. The defect inspection apparatus according to claim 1, further comprising a line sensor interface for sending the digital data obtained to the binarization circuit. 4. The defect inspection apparatus according to claim 1, further comprising an illumination device that illuminates the inspection object. 5. A run-length generating apparatus, comprising: a start-point register for storing a start-point position of a defect existing in an area of one line on the inspection object; An end point register for storing an end point position of a defect to be inspected; an integration register for storing an integrated value of a density level of each pixel in a defective area existing in an area of one line on the inspection object; A peak register for storing a peak value of a density level of each pixel in a defect area existing in an area of one line, wherein the one-dimensional defect information generated by the run-length generating apparatus includes:
The start point position of the defect stored in the start point register, the end point position of the defect stored in the end point register, the integrated value of the density level stored in the integration register, and the peak value of the density level stored in the peak register The defect inspection apparatus according to claim 1, further comprising: 6. The two-dimensional defect information generated by the connection processing device includes a position, a width, a height, and an area of each defect extending in a two-dimensional direction of the inspection object, and a density level of each pixel in each defect area. The defect inspection apparatus according to claim 5, further comprising: an integrated value and a peak value, and an average value of density levels of each defect obtained by dividing the integrated value of the density level by an area of the defect. 7. The defect inspection apparatus according to claim 1, wherein the threshold storage device stores a threshold value individually determined for each point on the inspection object. 8. A method for detecting a density level in an area of one line on an inspection object, moving an area to be detected in a direction intersecting with the line, and using one threshold for each pixel, The level is binarized into binary data. Only when the binary data is a predetermined value, the density level is held, and from the held density level, an area for one line on the inspection object is stored. Generating one-dimensional defect information that is information on existing defects, linking each of the generated one-dimensional defect information, and generating two-dimensional defect information that is information on a defect extending in a two-dimensional direction on the inspection object. A defect inspection method characterized by the above-mentioned.