JP6775396B2 - Visual inspection equipment - Google Patents

Description

The present invention relates to a visual inspection apparatus.

Conventionally, an appearance inspection device that calculates the height of an inspection target surface at each position by a so-called optical cutting method is known (for example, Patent Document 1). The visual inspection device acquires the offset amount of the bright line from the reference line by image processing from the two-dimensional image including the bright line irradiated on the surface to be inspected, and based on this offset amount, at the position where the bright line is irradiated. Calculate the height of the surface to be inspected.

Japanese Unexamined Patent Publication No. 2011-141260

In this type of technique, the accuracy of detecting the position of the emission line affects the amount of offset and thus the accuracy of the height. Therefore, it would be beneficial if a visual inspection device capable of detecting the position of the emission line with higher accuracy could be obtained.

Therefore, one of the problems of the embodiment is to obtain, for example, an appearance inspection device capable of detecting the position of the emission line with higher accuracy.

The visual inspection device of the embodiment is a visual inspection device that calculates the height of the inspection target surface based on the optical cutting method, and is in a two-dimensional image obtained by capturing the inspection target surface irradiated with the emission line. A bright line image correction unit that corrects the bright line image and a height calculation unit that calculates the height of the inspection target surface based on the offset amount of the bright line image from the reference position in the two-dimensional image in which the bright line image is corrected. The emission line image correction unit acquires the center position of the emission line image in the offset direction, and reduces the brightness value of the pixel having a brightness value larger than the brightness value of the pixel at the center position in the emission line image.

FIG. 1 is an exemplary and schematic plan view of the visual inspection apparatus of the embodiment. FIG. 2 is an exemplary and schematic side view of the visual inspection apparatus of the embodiment. FIG. 3 is an exemplary and schematic plan view showing a state in which the emission line is offset from the reference line according to the height of the inspection target surface in the visual inspection apparatus of the embodiment. FIG. 4 is an exemplary and schematic block diagram of the visual inspection apparatus of the embodiment. FIG. 5 is an exemplary and schematic block diagram of a control unit included in the visual inspection apparatus of the embodiment. FIG. 6 is an exemplary and schematic plan view showing the emission line irradiated on the inspection target surface of the visual inspection apparatus of the embodiment and its representative position. FIG. 7 is a schematic explanatory view showing an example of correction of the luminance value by the visual inspection apparatus of the embodiment. FIG. 8 is a schematic explanatory view showing another example of correction of the luminance value by the visual inspection apparatus of the embodiment.

Hereinafter, exemplary embodiments of the present invention will be disclosed. The configurations and controls of the embodiments shown below, and the actions and results (effects) brought about by the configurations and controls, are examples. The present invention can be realized by means other than the configurations and controls disclosed in the following embodiments. In addition, the present invention can obtain various effects including derivative effects obtained by the basic configuration and control.

The X, Y, and Z directions in FIGS. 1 to 3 are orthogonal to each other. The X direction is the moving direction of the inspection target surface 101, the direction intersecting (orthogonal) with the direction in which the emission line L extends, and the width direction of the emission line L. The Y direction is the direction in which the emission line L extends. The Z direction is the normal direction of the surface 101 to be inspected, and may be referred to as the height direction.

1 and 2 are a plan view and a side view showing an example of the appearance inspection device 1 by the optical cutting method. As shown in FIGS. 1 and 2, the visual inspection device 1 has a light source 2. The light source 2 emits the light sheet LS toward the inspection target surface 101 of the inspection target surface 100 from a direction inclined with respect to the normal direction of the inspection target surface 101. A bright line L is formed on the inspection target surface 101 by the light sheet LS. The image pickup apparatus 3 photographs the inspection target surface 101 including the emission line L from the normal direction of the inspection target surface 101, and acquires a two-dimensional image including the image of the emission line L.

FIG. 3 shows a state in which the emission line L is offset from the reference line R according to the height of the inspection target surface 101 in the visual inspection device 1. If the inspection target surface 101 is flat and there is no unevenness on the inspection target surface 101 at the position where the emission line L hits, the emission line L formed on the inspection target surface 101 is linear. The bright line L in this case is the reference line R (straight line, reference position). On the other hand, when a convex portion is provided on the inspection target surface 101 at the position where the bright line L hits, the bright line L hitting the convex portion is on the side closer to the light source 2 from the reference line R (in the example of FIG. 3). Offset to the left (X direction). On the contrary, when the inspection target surface 101 is provided with a recess at the position where the emission line L hits, the emission line L hitting the recess is on the side far from the light source 2 from the reference line R (right side in the example of FIG. 3, X). Offset in the opposite direction). Therefore, the visual inspection device 1 has the unevenness of the inspection target surface 101 and the degree of the unevenness at each position of the reference line R in the Y direction based on the offset direction and the offset amount of the emission line L with respect to the reference line R in the X direction. (The height of the convex portion, the depth of the concave portion, and the height position of the inspection target surface 101 in the normal direction) can be calculated. The irradiation direction of the light sheet LS and the image pickup direction by the image pickup device 3 are not limited to the examples of FIGS. 1 and 2, and can be set in various ways. The conditions of the irradiation direction and the imaging direction are the direction (short) intersecting the direction in which the emission line L extends (longitudinal direction) according to the height (unevenness) of the inspection target surface 101 in the two-dimensional image captured by the imaging device 3. An offset of the emission line L occurs in the hand direction). Therefore, for example, the irradiation direction of the light sheet LS may be the normal direction of the inspection target surface 101, and the image pickup direction by the image pickup apparatus 3 may be a direction inclined with respect to the normal direction.

FIG. 4 is a block diagram of the visual inspection device 1. As shown in FIG. 4, the visual inspection device 1 includes, for example, a light source 2, an image pickup device 3, a mobile device 4, and a display device 5.

The light source 2 emits a light sheet LS (for example, a laser light sheet). The light source 2 is shown in a simplified manner in FIGS. 1 and 2. The light source 2 may have an optical component such as a lens in addition to the lamp. Further, the light source 2 may emit the light sheet LS through the slit. In this case, the light sheet LS can be referred to as slit light.

The image pickup apparatus 3 captures a two-dimensional image. The image pickup device 3 includes a solid-state image pickup device having a photoelectric conversion element (photoelectric conversion unit) arranged in two dimensions, and an optical component such as a lens. The solid-state image sensor is, for example, a CCD (charge coupled device) image sensor, a CMOS (complementary metal oxide semiconductor) image sensor, or the like. The image pickup device 3 may be referred to as an area sensor or a digital camera. Although the imaging range I by the imaging device 3 is shown in FIG. 1, the imaging range I may include the emission line L and its surroundings, and is not limited to the one disclosed in FIG.

The moving device 4 moves the inspection object 100 so that the imaging position (inspection position) by the imaging device 3 on the inspection target surface 101 changes with time. The moving device 4 can have, for example, a motor, a roller rotated by the motor, a belt moved by the roller, and the like. In the examples of FIGS. 1 and 2, the inspection target surface 101 is moved in the X direction by the moving device 4. As the inspection target surface 101 moves, the imaging position on the inspection target surface 101, that is, the inspection target area A (inspection target position, see FIG. 3) moves. As shown in FIG. 3, the inspection target area A is a position on the reference line R. The inspection target surface 101 may be fixed, and the light source 2, the image pickup device 3, and the like may be moved along the inspection target surface 101 (a configuration in which the inspection target surface 101 is moved by the moving device 4).

The display device 5 outputs an image showing an inspection result or the like. The display device 5 is, for example, an LCD (liquid crystal display) or the like.

FIG. 4 is a block diagram of the visual inspection device 1. As shown in FIG. 4, the visual inspection device 1 includes a control unit 40, a ROM 41 (read only memory), a RAM 42 (random access memory), an NVRAM 43 (non-volatile RAM), a light irradiation controller 44, and an imaging controller 45. It includes a mobile controller 46, a display controller 47, and the like. The light irradiation controller 44 controls the light emission (on, off, etc.) of the light source 2 based on the control signal from the control unit 40. The image pickup controller 45 controls the image pickup by the image pickup apparatus 3 based on the control signal from the control unit 40. The mobile controller 46 controls the mobile device 4 based on the control signal received from the control unit 40, and controls the transportation (start, stop, speed, etc.) of the inspection object 100. The display controller 47 controls the display device 5 based on the control signal from the control unit 40. Further, the control unit 40 reads and executes a (stored) program (application) installed in a ROM 41, an NVRAM 43, or the like as a non-volatile storage unit. The RAM 42 temporarily stores various data used when the control unit 40 executes a program to execute various arithmetic processes. The hardware configuration shown in FIG. 4 is merely an example, and can be variously modified and implemented, for example, by making a chip or a package. Further, various arithmetic processes can be processed in parallel, and the control unit 40 and the like can have a hardware configuration capable of parallel processing.

FIG. 5 is a block diagram of the control unit 40. As shown in FIG. 5, the control unit 40 includes a light irradiation control unit 40a, an image pickup control unit 40b, a movement control unit 40c, and an image processing unit 40d (image acquisition unit 40d1, emission line image correction unit 40d2, height calculation unit). It has 40d3, an abnormality detection unit 40d4), a display control unit 40e, and the like.

The light irradiation control unit 40a controls the light irradiation controller 44. The image pickup control unit 40b controls the image pickup controller 45. The movement control unit 40c controls the movement controller 46. The image processing unit 40d executes image processing. The display control unit 40e controls the display device 5. Further, the image acquisition unit 40d1 acquires a two-dimensional image captured by the image pickup device 3. The bright line image correction unit 40d2 corrects the bright line image included in the two-dimensional image. The height calculation unit 40d3 calculates the height of the inspection target surface 101 at each position in the Y direction on the reference line R based on the offset amount of the emission line L from the reference line R in the X direction. The abnormality detection unit 40d4 acquires the height of the inspection target surface 101 in the two-dimensional region based on the height of the inspection target surface 101 at each position in the Y direction on the plurality of reference lines R. The height data in the two-dimensional region may be referred to as a height image or a pseudo image. The abnormality detection unit 40d4 can detect an abnormality by executing image processing on a height image (pseudo image).

The control unit 40 is, for example, a CPU (central processing unit). The control unit 40 operates according to a program stored (installed) in the ROM 41, NVRAM 43, or the like and read during operation. By operating according to the program, the control unit 40 includes a light irradiation control unit 40a, an image pickup control unit 40b, a movement control unit 40c, an image processing unit 40d, an image acquisition unit 40d1, an emission line image correction unit 40d2, and a height calculation unit 40d3. , Abnormality detection unit 40d4, and display control unit 40e. The program includes a light irradiation control unit 40a, an imaging control unit 40b, a movement control unit 40c, an image processing unit 40d, an image acquisition unit 40d1, a bright line image correction unit 40d2, a height calculation unit 40d3, an abnormality detection unit 40d4, and display control. A module corresponding to the part 40e is included. At least a part of the control unit 40 may be configured by hardware. In that case, the control unit 40 may include an ASIC (application specific integrated circuit), an FPGA (field programmable gate array), a CPLD (complex programmable logic device), and the like.

FIG. 6 is an enlarged view of the emission line L irradiated on the inspection target surface 101. As shown in FIG. 6, the emission line L has a width W on the inspection target surface 101. Therefore, the height calculation unit 40d3 calculates the offset amount of the bright line L in the X direction at each position of the bright line L in the Y direction as the offset amount of the representative position Rp of the bright line L in the X direction from the reference line R.

Further, the height calculation unit 40d3 can calculate the representative position Rp at each position of the emission line L in the Y direction by, for example, a weighted average value (weighted average value) of the luminance values of the pixels constituting the width W. The height calculation unit 40d3 can obtain the height of the inspection target surface 101 as a value obtained by multiplying the offset amount by a predetermined coefficient.

7 and 8 are schematic explanatory views showing an example of correction of the luminance value by the visual inspection apparatus 1. 7 and 8 are diagrams showing the distribution of the luminance values in the X direction in the pixels in the vicinity of the region corresponding to the emission line L at a predetermined position in the Y direction of the reference line R. In FIGS. 7 and 8, _{n-2 to n + 3} are codes for identifying a plurality of pixels adjacent to each other in the X direction, and D _{n-2 to} D _{n + 3} are symbols in the X direction at a predetermined position in the Y direction in the two-dimensional image. It is the distribution of the brightness value of each pixel. In the examples of FIGS. 7 and 8, the image processing unit 40d defines the region where the luminance values D _{n-2 to} D _{n + 3} exceed the second threshold value Th2 as the emission line L.

Here, according to the diligent research of the inventors, when speckle noise is included in the emission line L, the X is more than the center C (center position of the emission line image) in the X direction (width direction) of the emission line L. It was found that a region having a luminance value larger than the luminance value at the center C was detected on one side of the direction. Speckle noise is noise with a brightness value based on the interference of scattered light due to minute irregularities on the surface to be inspected 101.

The broken lines in FIGS. 7 and 8 show the case where speckle noise is included. Figures 7 and 8 illustrate the case where speckle noise does not affect the second threshold Th2. The solid line is the correction value of the luminance value by the logic of this embodiment.

When such speckle noise is included, for example, when the representative position Rp (see FIG. 6) of the emission line L is calculated by the weighted average of the luminance values, the emission line L is on the side where the luminance value is increased by the speckle noise. Since the representative position Rp of the above is deviated, the detection accuracy of the offset amount and the detection accuracy of the height of the inspection target surface 101 at each position are lowered. In the example of FIG. 7, there is a pixel n + 1 having a brightness value larger than the brightness value of the center C on the right side of the center C, that is, in the X direction, and in the example of FIG. 8, the pixel n + 1 is on the right side of the brightness value of the center C, that is, In the X direction, pixels n + 1 and n + 2 having a luminance value larger than the luminance value of the center C exist. In this case, when the representative position Rp of the emission line L is calculated as the weighted average value (weighted average value) of the luminance value, the representative position Rp is shifted to the right side of the center C, that is, in the X direction in FIGS. It ends up. In the example of FIG. 8, the image processing unit 40d sets the brightness value of the center C to the brightness of the two pixels n, n + 1 closest to the center C among the plurality of pixels n-1 to n + 2 included in the emission line L. It is calculated as the average value of the values.

Therefore, in the present embodiment, when the emission line image correction unit 40d2 detects a region (pixel, pixel group) having a brightness value larger than the brightness value in the center C on one side in the width direction of the emission line L in the width direction. The brightness value of the region is reduced. In the example of FIG. 7, the brightness value D _{n + 1} of the pixel n + 1 having a brightness value larger than the brightness value of the center C is corrected to a brightness value B _{n + 1} smaller than the brightness value D _{n + 1} , and in the example of FIG. 8, the center C is corrected. The brightness values D _{n + 1} and D _{n + 2} of the pixels n + 1, n + 2 having a brightness value larger than the brightness value of D _{n + 1} are corrected to the brightness values B _{n + 1} and B _{n + 2} smaller than the brightness values D _{n + 1} and D _{n + 2} . In the examples of FIGS. 7 and 8, the brightness value of the center C is set to the first threshold value Th1, and the emission line image correction unit 40d2 corrects the brightness value of the pixel having a brightness value larger than the first threshold value Th1 to be lower. ing. As a result, the increase (bias) in the luminance value due to speckle noise is reduced, and the deviation of the representative position Rp due to the increase in the luminance value is reduced. Therefore, according to the present embodiment, a decrease in the detection accuracy of the offset amount due to speckle noise, and eventually a decrease in the detection accuracy of the height of the inspection target surface 101 at each position can be suppressed.

Further, as is clear from FIGS. 7 and 8, in the present embodiment, the luminance line image correction unit 40d2 sets the luminance value in the region where the luminance value is larger than the luminance value in the center C, and the luminance value becomes farther from the center C. It is corrected so that it becomes smaller. Specifically, for example, the emission line image correction unit 40d2 executes correction by multiplying the luminance value by a correction coefficient, and the correction coefficient is reduced as the pixel moves away from the center C in the X direction. For example, for pixels one distance from the center C in the X direction (adjacent pixels), the brightness value is multiplied by a correction coefficient of 0.8, and for pixels two distances from the center C in the X direction, the brightness value is calculated. , The correction coefficient 0.5, which is smaller than the correction coefficient 0.8 of the pixel one away from the center C in the X direction, is multiplied. As a result, the corrected luminance value becomes larger as it is closer to the center C, and the distribution of the luminance value in the emission line L including the corrected luminance value is the brightness value assumed when there is no influence by speckle noise. You can get closer to the distribution.

Further, as is clear from FIGS. 7 and 8, in the present embodiment, the luminance line image correction unit 40d2 centers on the luminance value in the region where the luminance value is larger than the luminance value (first threshold value Th1) in the center C. It is corrected so that it is equal to or less than the luminance value of C (first threshold value Th1). As a result, the corrected luminance value becomes the largest at the center C, and the distribution of the luminance value in the emission line L including the corrected luminance value is the distribution of the luminance value assumed when there is no influence by speckle noise. Can be approached to. When the luminance value obtained by multiplying the luminance value in the two-dimensional image by the correction coefficient is larger than the luminance value in the center C, the emission line image correction unit 40d2 has the luminance value in the two-dimensional image. May be corrected so as to have the same value as the brightness value at the center C.

As described above, in the present embodiment, the emission line image correction unit 40d2 sets the luminance value of the pixel whose luminance value is larger than the first threshold Th1 in the luminance image to the center C (center position of the emission line image). ) To the X direction (offset direction), the correction is made so that the image becomes smaller. Therefore, according to the present embodiment, the distribution of the luminance value affected by the speckle noise can be brought close to the distribution of the luminance value expected when there is no influence by the speckle noise. Therefore, a decrease in the detection accuracy of the offset amount due to speckle noise, and eventually a decrease in the detection accuracy of the height of the inspection target surface 101 at each position can be suppressed.

Further, in the present embodiment, the first threshold value Th1 is a luminance value at the center C (center position of the emission line image). When there is no influence of speckle noise, the brightness value at the center C tends to be the highest. Therefore, with such a setting, the distribution of the luminance value affected by the speckle noise can be brought closer to the distribution of the luminance value expected when there is no influence of the speckle noise. Therefore, a decrease in the detection accuracy of the offset amount due to speckle noise, and eventually a decrease in the detection accuracy of the height of the inspection target surface 101 at each position can be suppressed. In addition, the first threshold Th1 can be set relatively easily.

Further, in the present embodiment, the emission line image correction unit 40d2 corrects, for example, the brightness value of a pixel having a brightness value larger than the first threshold value Th1 so as to be smaller than the first threshold value Th1. Therefore, according to the present embodiment, the distribution of the luminance value affected by the speckle noise can be brought close to the distribution of the luminance value expected when there is no influence by the speckle noise. Therefore, a decrease in the detection accuracy of the offset amount due to speckle noise, and eventually a decrease in the detection accuracy of the height of the inspection target surface 101 at each position can be suppressed.

Further, in the present embodiment, the emission line image correction unit 40d2 sets the center C (center position of the emission line image) in the X direction (offset direction) in which the brightness value is larger than the second threshold value Th2 (predetermined threshold value). Calculated as the center position of the pixel sequence along the line. Therefore, according to the present embodiment, the center C can be set relatively easily. Further, for example, by setting the luminance value of the pixel whose luminance value is equal to or less than the second threshold value Th2 to 0, it can be used as a filtering threshold value, and the calculation load in the image processing unit 40d can be further reduced. ..

Further, in the present embodiment, the offset amount is an offset amount between the representative position Rp and the reference line R (reference position) calculated by the weighted average of the brightness values of the pixels included in the emission line image. In this embodiment, since the luminance value of the pixels in the emission line image is corrected by the emission line image correction unit 40d2, the representative position Rp of the emission line L is calculated by the weighted average of the brightness values of the pixels included in the emission line image. That is, in the case of calculation based on the luminance value, the representative position Rp of the emission line L is calculated based on the luminance value of more pixels, and the out-of-order pixels can be absorbed, which is more effective. It can be said that there is.

Although the embodiments of the present invention have been illustrated above, the above embodiments are merely examples. The embodiment can be implemented in various other forms, and various omissions, replacements, combinations, and changes can be made without departing from the gist of the invention. Further, the configuration and shape of the embodiment can be implemented by partially replacing the configuration and shape with other configurations and shapes. In addition, specifications such as each configuration and shape (structure, type, direction, angle, shape, size, length, width, thickness, height, number, arrangement, position, material, etc.) are changed as appropriate. Can be carried out.

For example, in the above embodiment, the configuration in which the surface to be inspected moves with respect to the light source and the imaging device has been exemplified, but the present invention is applicable even in the configuration in which the light source and the imaging device move with respect to the surface to be inspected. It is possible. Further, the relative moving direction of the surface to be inspected does not have to be a linear direction such as a circumferential direction. Further, the representative position of the emission line may be calculated by a method other than the weighted average.

1 ... Appearance inspection device, 40d2 ... Bright line image correction unit, 40d3 ... Height calculation unit, 101 ... Inspection target surface, C ... Center (center position), L ... Bright line, R ... Reference line (reference position), Rp ... Representative Position, Th1 ... first threshold value (luminance value at the center position), Th2 ... second threshold value (predetermined threshold value).

Claims (5)

An visual inspection device that calculates the height of the surface to be inspected based on the optical cutting method.
A bright line image correction unit that corrects the bright line image in the two-dimensional image in which the inspection target surface irradiated with the bright line is captured,
A height calculation unit that calculates the height of the inspection target surface based on the offset amount of the bright line image from the reference position in the two-dimensional image in which the bright line image is corrected.
With
The emission line image correction unit acquires the center position of the emission line image in the offset direction, and reduces the brightness value of a pixel having a brightness value larger than the brightness value of the center position in the emission line image. The bright line image correction unit corrects the luminance value of a pixel whose luminance value is larger than the luminance value at the central position in the luminance image so that it becomes smaller as the distance from the central position increases in the offset direction. The visual inspection apparatus according to 1. The bright line image correction unit corrects the luminance value of a pixel having a luminance value larger than the luminance value at the center position in the luminance image so as to be smaller than the luminance value at the central position. 2. The visual inspection apparatus according to 2. The bright line image correction unit according to any one of claims 1 to 3, which calculates the center position as the center position of a pixel array along the offset direction in which the brightness value is larger than a predetermined threshold value. Visual inspection equipment. The offset amount is the offset amount between the representative position and the reference position calculated by the weighted average of the brightness values of the pixels included in the emission line image, according to any one of claims 1 to 4. Visual inspection equipment.

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