JP2018084543A - Visual inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a visual inspection device that can more accurately detect the position of a bright line.SOLUTION: A visual inspection device of an embodiment is a visual inspection device calculating the height of an inspection target surface on the basis of a light section method, and comprises: a bright line image correction part that corrects a bright line image in a two-dimensional image obtained by picking up an image of the inspection target surface irradiated with the bright line; and a height calculation part that calculates the height of the inspection target surface on the basis of the amount of offset of the bright line image from a reference position in the two-dimensional image in which the bright line image is corrected. The bright line image correction part acquires the middle position of the bright line image in an offset direction, and reduces brightness values of pixels having larger brightness values than the brightness value of a pixel at the middle position in the brightness image.SELECTED DRAWING: Figure 7

Description

  The present invention relates to an appearance inspection apparatus.

  2. Description of the Related Art Conventionally, an appearance inspection apparatus that calculates the height at each position on an inspection target surface by a so-called light cutting method is known (for example, Patent Document 1). The appearance inspection apparatus 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 to the inspection target surface, and based on this offset amount, the position at the position where the bright line is irradiated Calculate the height of the inspection target surface.

JP 2011-141260 A

  In this type of technology, the detection accuracy of the bright line position affects the offset amount and thus the accuracy of the height. Therefore, it would be beneficial if an appearance inspection apparatus capable of detecting the position of the bright line with higher accuracy was obtained.

  Therefore, one of the problems of the embodiment is to obtain an appearance inspection apparatus that can detect the position of the bright line with higher accuracy, for example.

  The appearance inspection apparatus according to the embodiment is an appearance inspection apparatus that calculates the height of the inspection target surface based on the light cutting method, and in the two-dimensional image in which the inspection target surface irradiated with the bright line is captured. 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 bright line image correction unit obtains the center position of the bright 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 pixel at the center position in the bright line image.

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

  Hereinafter, exemplary embodiments of the present invention are disclosed. The configuration and control of the embodiment shown below, and the operation and result (effect) brought about by the configuration and control are examples. The present invention can be realized by other than the configurations and controls disclosed in the following embodiments. Further, the present invention can obtain various effects including derivative effects obtained by basic configuration and control.

  In addition, the X direction in FIGS. 1-3, the Y direction, and the Z direction are mutually orthogonally crossed. The X direction is a moving direction of the inspection target surface 101, a direction intersecting (orthogonal to) the direction in which the bright line L extends, and the width direction of the bright line L. The Y direction is a direction in which the bright line L extends. The Z direction is a normal direction of the inspection target surface 101 and can be referred to as a height direction.

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

  FIG. 3 shows a state where the bright line L is offset from the reference line R according to the height of the inspection target surface 101 in the appearance inspection apparatus 1. If the inspection target surface 101 is a flat surface at the position where the bright line L hits and there is no unevenness on the inspection target surface 101, the bright line L configured 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 a position where the bright line L hits, the bright line L hitting the convex portion is 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 other hand, when a concave portion is provided on the inspection target surface 101 at the position where the bright line L hits, the bright line L hitting the concave portion is on the side farther from the light source 2 from the reference line R (right side in the example of FIG. Offset in the opposite direction). Therefore, the appearance inspection apparatus 1 determines the unevenness of the inspection target surface 101 and the degree of the unevenness at each position in the Y direction of the reference line R based on the offset direction and the offset amount of the bright 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. Note that the irradiation direction of the light sheet LS and the imaging direction by the imaging device 3 are not limited to the examples of FIGS. The conditions of the irradiation direction and the imaging direction are a direction (short) that intersects the direction (longitudinal direction) in which the bright line L extends in the two-dimensional image captured by the imaging device 3 according to the height (unevenness) of the inspection target surface 101. The bright line L is offset 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 imaging direction by the imaging device 3 may be a direction inclined with respect to the normal direction.

  FIG. 4 is a block diagram of the appearance inspection apparatus 1. As shown in FIG. 4, the appearance inspection device 1 includes a light source 2, an imaging device 3, a moving device 4, and a display device 5, for example.

  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. The light source 2 may include an optical component such as a lens in addition to the lamp. Further, the light source 2 may emit the light sheet LS through a slit. In this case, the light sheet LS can be referred to as slit light.

  The imaging device 3 captures a two-dimensional image. The imaging device 3 includes a solid-state imaging element having photoelectric conversion elements (photoelectric conversion units) arranged two-dimensionally and an optical component such as a lens. The solid-state imaging device is, for example, a charge coupled device (CCD) image sensor, a complementary metal oxide semiconductor (CMOS) image sensor, or the like. The imaging device 3 can be referred to as an area sensor or a digital camera. In FIG. 1, the imaging range I by the imaging device 3 is shown, but the imaging range I only needs to include the bright line L and its periphery, and is not limited to that disclosed in FIG. 1.

  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 include, for example, a motor, a roller rotated by the motor, a belt moved by the roller, and the like. In the example 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. Note that a configuration in which the inspection target surface 101 is fixed and the light source 2, the imaging device 3, and the like move along the inspection target surface 101 (configuration that is moved by the moving device 4) may be used.

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

  FIG. 4 is a block diagram of the appearance inspection apparatus 1. As shown in FIG. 4, the appearance inspection apparatus 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, an imaging controller 45, A movement controller 46, a display controller 47, and the like are provided. The light irradiation controller 44 controls light emission (ON, OFF, etc.) of the light source 2 based on a control signal from the control unit 40. The imaging controller 45 controls imaging by the imaging device 3 based on a control signal from the control unit 40. The movement controller 46 controls the moving device 4 based on the control signal received from the control unit 40 and controls the conveyance (start, stop, speed, etc.) of the inspection object 100. The display controller 47 controls the display device 5 based on a control signal from the control unit 40. Further, the control unit 40 reads and executes a program (application) installed (stored) in the ROM 41, the NVRAM 43, or the like as a nonvolatile storage unit. The RAM 42 temporarily stores various data used when the control unit 40 executes programs and executes various arithmetic processes. Note that the hardware configuration shown in FIG. 4 is merely an example, and can be implemented with various modifications such as a chip or a package. Various arithmetic processes can be performed 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. 5, the control unit 40 includes a light irradiation control unit 40a, an imaging control unit 40b, a movement control unit 40c, an image processing unit 40d (image acquisition unit 40d1, bright line image correction unit 40d2, height calculation unit). 40d3, an abnormality detection unit 40d4), a display control unit 40e, and the like.

  The light irradiation control unit 40 a controls the light irradiation controller 44. The imaging control unit 40b controls the imaging controller 45. The movement control unit 40 c controls the movement controller 46. The image processing unit 40d executes image processing. The display control unit 40 e controls the display device 5. The image acquisition unit 40d1 acquires a two-dimensional image captured by the imaging 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 in the X direction of the bright line L from the reference line R. 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 can be referred to as a height image or a pseudo image. The abnormality detection unit 40d4 can detect an abnormality by performing image processing on the 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, the NVRAM 43 or the like and read out during operation. By operating according to the program, the control unit 40 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, and a height calculation unit 40d3. , Function as an abnormality detection unit 40d4 and a 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 a display control. A module corresponding to the unit 40e is included. Note that at least a part of the control unit 40 may be configured by hardware. In that case, the control unit 40 may include an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a complex programmable logic device (CPLD), and the like.

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

  In addition, the height calculation unit 40d3 can calculate the representative position Rp at each position in the Y direction of the bright line L, for example, by a weighted average value (weighted average value) of luminance values in 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 diagrams illustrating an example of luminance value correction performed by the appearance inspection apparatus 1. FIGS. 7 and 8 are diagrams showing the distribution of luminance values in the X direction in pixels in the vicinity of the region corresponding to the bright line L at a predetermined position in the Y direction of the reference line R. FIG. 7 and 8, _{n−2 to n + 3} are codes for identifying a plurality of adjacent pixels in the X direction, and D _{n−2 to} D _{n + 3} are X-directions at predetermined positions in the Y direction in the two-dimensional image. It is distribution of the luminance value of each pixel. In the example of FIGS. 7 and 8, the image processing unit 40 d sets a region where the luminance values D _{n−2 to} D _{n + 3} exceed the second threshold Th _{< b > 2} as the bright line L.

  Here, when the speckle noise is included in the bright line L by the inventors' diligent research, the X is more than the center C (the center position of the bright line image) of the bright line L in the X direction (width direction). It has been found that a region having a luminance value larger than the luminance value at the center C is detected on one side of the direction. Speckle noise is noise with a luminance value based on the fact that scattered light interferes due to minute unevenness on the inspection target surface 101.

  The broken lines in FIGS. 7 and 8 both show the case where speckle noise is included. 7 and 8 illustrate a case where speckle noise does not affect the second threshold Th2. A solid line is a correction value of the luminance value according to the logic of the present embodiment.

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

Therefore, in the present embodiment, the bright line image correction unit 40d2 detects a region (pixel, pixel group) having a luminance value larger than the luminance value at the center C on one side in the width direction from the center C of the bright line L. First, the luminance value of the area is reduced. In the example of FIG. 7, the luminance value D _{n + 1} of the pixel n + 1 having a luminance value larger than the luminance value of the center C is corrected to the luminance value B _{n + 1} smaller than the luminance value D _{n + 1. In} the example of FIG. The luminance values D _{n + 1} and D _{n + 2} of the pixels n + 1 and n + 2 whose luminance values are larger than the luminance values D _{n + 1} and D _{n + 2} are corrected to the luminance values B _{n + 1} and B _{n + 2} smaller than the luminance values D _{n + 1} and D _{n + 2} . In the example of FIGS. 7 and 8, the luminance value of the center C is set to the first threshold Th1, and the bright line image correction unit 40d2 corrects the luminance value of the pixel whose luminance value is larger than the first threshold Th1 to be low. ing. Thereby, the increase (bias) of the luminance value due to speckle noise is reduced, and the shift of the representative position Rp due to the increase of the luminance value is reduced. Therefore, according to the present embodiment, it is possible to suppress a decrease in the detection accuracy of the offset amount due to speckle noise, and a decrease in the detection accuracy of the height of the inspection target surface 101 at each position.

  7 and 8, in the present embodiment, the bright line image correction unit 40d2 has a luminance value in a region having a luminance value larger than the luminance value at the center C, and the luminance value increases as the distance from the center C increases. Corrections are made to make it smaller. Specifically, for example, the bright line image correction unit 40d2 performs the correction by multiplying the luminance value by the correction coefficient, and the correction coefficient is decreased as the pixel moves away from the center C in the X direction. For example, for a pixel that is one distance away from the center C in the X direction (adjacent pixels), the luminance value is multiplied by the correction coefficient 0.8, and for a pixel that is two distances away from the center C in the X direction, The correction coefficient 0.5, which is smaller than the correction coefficient 0.8 of the pixel one distance away from the center C in the X direction, is multiplied. Thereby, the corrected luminance value becomes larger as it is closer to the center C, and the distribution of the luminance value in the bright line L including the corrected luminance value is the luminance value assumed when there is no influence of speckle noise. Can approach the distribution.

  7 and 8, in the present embodiment, the bright line image correction unit 40d2 uses the luminance value of the region having the luminance value larger than the luminance value at the center C (first threshold Th1) as the center. Correction is made so as to be equal to or less than the luminance value of C (first threshold value Th1). Accordingly, the corrected luminance value is the largest at the center C, and the luminance value distribution in the bright line L including the corrected luminance value is assumed to be a luminance value distribution assumed when there is no influence of speckle noise. Can approach. Note that the bright line image correction unit 40d2 determines that the luminance value in the two-dimensional image is the luminance value obtained by multiplying the luminance value in the two-dimensional image by the correction coefficient is greater than the luminance value at the center C. May be corrected so as to be the same value as the luminance value at the center C.

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

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

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

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

  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 a weighted average of luminance values of pixels included in the bright line image. In this embodiment, since the luminance value of the pixel in the bright line image is corrected by the bright line image correcting unit 40d2, the representative position Rp of the bright line L is calculated by the weighted average of the luminance values of the pixels included in the bright line image. That is, in the case where the calculation is based on the luminance value, the representative position Rp of the bright line L is calculated based on the luminance values of more pixels, and the extraneous pixels can be absorbed. It can be said that there is.

  As mentioned above, although embodiment of this invention was illustrated, the said embodiment is an example to the last. The embodiment can be implemented in various other forms, and various omissions, replacements, combinations, and changes can be made without departing from the scope of the invention. In addition, the configuration and shape of the embodiment can be partially replaced with other configurations and shapes. In addition, specifications (structure, type, direction, angle, shape, size, length, width, thickness, height, number, arrangement, position, material, etc.) of each configuration, shape, etc. are changed as appropriate. Can be implemented.

  For example, in the above-described embodiment, the configuration in which the inspection target surface moves with respect to the light source and the imaging device is illustrated, but the present invention is applied even in a configuration in which the light source and imaging device move with respect to the inspection target surface. Is possible. Further, the relative movement direction of the inspection target surface may not be a linear direction such as a circumferential direction. Further, the representative position of the bright line may be calculated by a method other than the weighted average.

  DESCRIPTION OF SYMBOLS 1 ... Appearance inspection apparatus, 40d2 ... Bright line image correction part, 40d3 ... Height calculation part, 101 ... Inspection object surface, C ... Center (center position), L ... Bright line, R ... Reference line (reference position), Rp ... Representative Position, Th1... First threshold (luminance value at the center position), Th2... Second threshold (predetermined threshold).

Claims (5)

An appearance inspection apparatus that calculates the height of a surface to be inspected based on a light cutting method,
A bright line image correction unit that corrects a bright line image in a two-dimensional image obtained by imaging the inspection target surface irradiated with the bright line;
A height calculating unit that calculates the height of the inspection target surface based on an offset amount of the bright line image from a reference position in the two-dimensional image in which the bright line image is corrected;
With
The bright line image correcting unit is an appearance inspection apparatus that acquires a center position of the bright line image in an offset direction and reduces the luminance value of a pixel having a luminance value larger than the luminance value of the central position in the bright line image.   The bright line image correcting unit corrects the luminance value of a pixel having a luminance value larger than the luminance value at the central position in the bright line image so as to decrease as the distance from the central position in the offset direction increases. 1. An appearance inspection apparatus according to 1.   The bright line image correction unit corrects the luminance value of a pixel having a larger luminance value than the luminance value at the central position in the bright line image so as to be smaller than the luminance value at the central position. 2. An appearance inspection apparatus according to 2.   4. The bright line image correction unit according to claim 1, wherein the bright line image correction unit calculates the center position as a center position of a pixel row along the offset direction having a luminance value larger than a predetermined threshold value. Appearance inspection device.   5. The offset amount according to claim 1, wherein the offset amount is an offset amount between a representative position calculated by a weighted average of luminance values of pixels included in the bright line image and the reference position. Appearance inspection device.

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