JP2021189044A - Surface inspection device and surface inspection method - Google Patents

Abstract

To provide a surface inspection device that can detect fine defects derived from a three-dimensional shape of a surface of an inspected object hard to appear as a color characteristic, over a wide range in one shot.SOLUTION: A surface inspection device has: illumination means that projects a bright/dark pattern periodically repeating a difference between brightness and darkness to a surface of an inspected object; photographing means that takes pictures by receiving regular reflection light from the inspected object of the illumination means; and detection means that compares the image taken by the photographing means with the bright/dark pattern, and thereby detects a fine change in shape on the surface of the inspected object from the image, in which the photographing means is arranged in a position where a reflection angle θ of the regular reflection light from the illumination means falls within a range of a conditional expression (1): 45°<θ≤85°.SELECTED DRAWING: Figure 1

Description

The present invention relates to a surface inspection apparatus and a surface inspection method.

In the manufacturing industry, in order to provide high-quality, safe and secure products, it is necessary to accurately distinguish between non-defective products and defective products by the inspection process.
Generally, in defect inspection to determine defective products, the presence or absence and size of defects on the product surface are determined by performing appropriate image processing after taking a picture of the appearance of the product by combining an imaging optical system such as a camera or lighting. How to do it is known.
In particular, as a method of inspecting the unevenness of the surface of the inspected object, a method of illuminating the surface of the inspected object to take a picture and analyzing the photographed image to detect the unevenness has been widely used (for example, Patent Document). See 1-12 etc.).
However, with such a method, when the surface of the inspected object has a mirror gloss, the photographing means itself such as a camera or surrounding objects are reflected in the photographed image, and the unevenness of the surface of the inspected object is hidden. There was a problem.
In order to prevent such reflection, there is a method of attaching a diffuser to the lighting device, but since it irradiates uniform light, it is derived from a small three-dimensional shape that does not appear as a difference in color characteristics. It is difficult to detect defects that occur.

As a method of detecting a defect caused by a minute three-dimensional shape on the surface of an inspected object having a mirror gloss, for example, the surface of the inspected object is irradiated with illumination including a emission line and the reflected light is photographed by an imaging means. , A method of detecting a shape defect by detecting a distortion of a boundary between light and dark lines in a captured image has been considered (see, for example, Patent Documents 3 and 4).
However, there is a problem that it is difficult to perform wide-range detection by such a method.

The present invention has been made in view of the above problems, and is a surface capable of detecting minute defects derived from the three-dimensional shape of the surface of the object to be inspected, which are difficult to appear as color characteristics, in a wide range by one imaging. The purpose is to provide an inspection device.

In order to solve the above-mentioned problems, the surface inspection apparatus of the present invention has a lighting means for projecting a light-dark pattern that periodically repeats a difference in light and darkness onto the surface of the object to be inspected, and a positive light from the object to be inspected. Detection that detects minute shape changes on the surface of the object to be inspected from the image by comparing the image taken by the photographing means with the image taken by the photographing means and the light-dark pattern. The photographing means is characterized in that the means is arranged at a position where the angle of reflection of the specularly reflected light from the lighting means is within the range of 45 ° <θ≤85 °.

According to the present invention, it is possible to detect minute defects derived from the three-dimensional shape of the surface of the object to be inspected, which are difficult to appear as color characteristics, in a wide range by one imaging.

It is a figure which shows an example of the whole structure of the surface inspection apparatus which concerns on embodiment of this invention. It is a figure which shows an example of the composition of the light-dark pattern projected by the lighting means. It is a figure which shows an example of the positional relationship between the image pickup means and the illumination means shown in FIG. It is a figure which shows an example when the light-dark pattern shown in FIG. 3 is projected onto the surface of an inspected object. It is a figure which shows the ideal example when the light-dark pattern shown in FIG. 3 is projected onto the surface of a defect-free inspected object. It is a figure which shows an example of the photographed image in the 1st comparative example of a surface inspection apparatus. It is a figure which shows the 2nd comparative example of the surface inspection apparatus. It is a figure which shows an example of the photographed image in the 2nd comparative example shown in FIG. 7. It is a schematic diagram which shows an example of the reflection of light on the surface of an object to be inspected. It is a figure which shows another example of a light-dark pattern. It is a figure which shows an example of the structure in the case of dynamically changing a light-dark pattern.

As an example of the embodiment of the present invention, FIG. 1 shows a schematic configuration of the surface inspection apparatus 100.
The surface inspection device 100 according to the first embodiment of the present invention is a halogen lamp as a lighting means for irradiating a projected light 16 including a light / dark pattern having a bright portion and a dark portion toward the surface of the work P which is an inspected object. It has 10 and a camera 20 that receives the reflected light 17 reflected by the projected light 16 on the work P.
The surface inspection device 100 includes an illumination support arm 11 that supports the halogen lamp 10, a detector support arm 21 that supports the camera 20, and an immovable pedestal that supports the illumination support arm 11, the detector support arm 21, the work P, and the like. It has 1 and.
The surface inspection device 100 also has a control unit 9 which is a terminal functioning as a control means for controlling the halogen lamp 10 and the camera 20.

The control unit 9 is a computer having a CPU (Central Processing Unit), a main memory (MEM-P), a north bridge (NB), a south bridge (SB), and the like.
The control unit 9 also has an AGP (Accelerated Graphics Port) bus, an ASIC (Application Specific Integrated Circuit), and a local memory (MEM-C).
The control unit 9 also has an HD (Hard Disk), an HDD (Hard Disk Drive), a PCI bus, and a network I / F.

The CPU processes and calculates data according to a program stored in the main memory, and controls the operation of each of the above-mentioned parts. The main memory functions as a storage area of the control unit 9 and stores programs and data that realize each function of the control unit 9. Alternatively, the program may be configured to record and provide a file in an installable or executable format on a computer-readable recording medium such as a CD-ROM, FD, CD-R, or DVD. ..

The local memory (MEM-C) is used as a copy image buffer and a code buffer. The HD is a storage for accumulating image data, accumulating font data used at the time of printing, and accumulating forms. The HDD controls reading or writing of data to the HD according to the control of the CPU. The network I / F transmits / receives information to / from an external device such as an information processing device via a communication network.

The control unit 9 operates as a communication control means for controlling bidirectional communication with a host device (for example, a personal computer) via a communication network or the like.
The control unit 9 is also connected to the halogen lamp 10 and the camera 20, and as will be described later, by comparing the image taken by the camera 20 with the light-dark pattern, a minute shape change on the surface of the work P can be obtained. It functions as a detection means to detect.

The halogen lamp 10 is an illumination means for projecting a projected light 16 including a light / dark pattern as shown in FIG. 2 on the surface of the work P.
Such a light-dark pattern can be projected by providing a slit 5 or the like on the emission surface of the halogen lamp 10 as shown in FIG. 1, and a diffuser plate or a plurality of band-shaped surface illuminations are arranged side by side in the width direction. You may do so.
In the present embodiment, the light emitting portion 14 corresponding to the bright portion 12 and the shielding portion 15 corresponding to the dark portion 13 are provided in a striped pattern on the emission surface of the halogen lamp 10, as shown in FIG. It forms a light-dark pattern.
Although the halogen lamp 10 is used as the lighting means in this embodiment, various light sources such as a liquid crystal display, an LED, a fluorescent lamp, an incandescent lamp, a laser, a projector, and an organic EL element may be used as the lighting means. Further, the display may be used to turn on the portion corresponding to the bright portion 12, turn off the portion corresponding to the dark portion 13, and project the projected light 16 onto the work P.

In the present embodiment, the light-dark pattern forms a striped pattern in which arc-shaped bright portions 12 and dark portions 13 are alternately formed. Here, the bright portion 12 is a portion of the projected light 16 irradiated by the halogen lamp 10 having a high illuminance, and the dark portion 13 is a portion of the projected light 16 irradiated by the halogen lamp 10 having a low illuminance.
As described above, the light-dark pattern may have a configuration in which the bright portion 12 and the dark portion 13 having a difference in brightness in a certain direction are periodically repeated, and the shape to be irradiated is not particularly limited.
The striped configuration is not limited to this, and for example, the rectangular bright portion 12 and the dark portion 13 may have a block shape adjacent to each other.

The camera 20 includes a sensor 22 such as a CCD or CMOS that receives the reflected light 17 that is positively reflected by the projected light 16 that is applied to the surface of the work P, a zoom lens, a fixed focus lens, a lens with a tilt function, a telecentric lens, and the like. It is a digital camera provided with an image pickup optical system 23, which is a telecentric optical system configured by the use.
As shown in FIG. 3, when the incident angle θ'of the light 16 projected from the halogen lamp 10 and the reflection angle θ of the reflected light 17 are set in the camera 20, the reflection angle θ satisfies the following mathematical formula (1). do.

In general, by increasing the reflection angle θ, the distortion of the light-dark pattern with respect to the inclination direction of the defect on the surface of the work P is emphasized, and the defect can be easily detected. The defect on the surface of the work P as used herein refers to, for example, a change in the three-dimensional shape of the surface that is not present in the ideal work P, but includes, for example, minute irregularities, distortions, and scratches on the surface.
When the reflection angle θ of the reflected light 17 is 45 ° or less, it becomes difficult to detect minute irregularities. On the other hand, when the reflection angle θ is larger than 85 °, the detection sensitivity of minute irregularities is improved, while the length of the orthogonal projection of the work P on the captured image surface in the depth direction is larger than the actual size of the work P. Since it is displayed at a magnification of cos 85 ° (≈0.087) or less, the shooting range is excessively crushed. That is, the resolution of the work P when viewed from the camera 20 is insufficient, and it becomes difficult to perform a sufficient surface inspection.
Further, at an angle equal to or greater than the Brewster angle represented by Fresnel's equation, the reflectance of both s-polarized light and p-polarized light increases. Therefore, even when the mirror surface of the work P is low, there is an advantage that reflection is easily obtained and the contrast of the light-dark pattern is improved.

When viewed from the sensor 21 through the image pickup optical system 23, the work P is arranged diagonally with respect to the optical axis, and the focus is on any part of the light / dark pattern projected on the surface of the work P. desirable. That is, it is more preferable that the imaging optical system 23 has a long depth of field so as to form an image on the light receiving surface of the sensor 21. However, in a configuration in which the work P is viewed from an angle as in the present invention, a telecentric optical system is particularly preferable in order to reduce the perspective difference between the back side and the front side of the work P.
By using the telecentric optical system as the imaging optical system 23, the magnifying powers on the images taken on the front side and the back side of the work P become equal, and the entire shooting range of the work P can be inspected with the same quality. ..
Further, if the imaging optical system 23 is a telecentric lens, only the light incident on the telecentric lens surface (in other words, parallel to the optical axis of the lens) is captured, and the entire imaging range of the work P is covered. Surface inspection can be performed with the same reflection angle θ.

The captured image Q captured by the camera 20 is captured, for example, as shown in FIG. 4 when the cylindrical work P is irradiated.
At this time, since the irradiation light 16 emitted by the halogen lamp 10 is irradiated as a light-dark pattern in which bright portions 12 and dark portions 13 are alternately formed, it is ideal without any surface defects such as distortion and scratches. The reflected light 17'from the work P'should be photographed by the camera 20 in a form in which the light and dark patterns are not distorted as in the image shown in FIG. 5, for example.
However, as shown in FIG. 4, when the surface of the work P is distorted or scratched, it is detected in the captured image Q as a distortion of a light-dark pattern as shown by the broken line A and the broken line B.

The control unit 9 has a reference image R when the ideal work P'as shown in FIG. 5 is irradiated with the irradiation light 16 including a light and dark pattern, and an image taken by the camera 20 as shown in FIG. By comparing with the image Q, it is possible to detect whether or not the surface of the work P is distorted or scratched.
The reference image R may be, for example, image data taken by placing an ideal work P'as reference data in advance at the time of shipment of the surface inspection apparatus 100, or may be an image data taken as shown in FIG. 2. The projected light 16 may be data representing the shape of a light-dark pattern when projected onto a work P'having a certain three-dimensional shape.
At this time, even if the halogen lamp 10 or surrounding objects are reflected on the surface of the work P, since the light and dark patterns are reflected on the surface of the work P, the light and dark patterns included in the captured image Q can be obtained. ..
Further, since it is possible to capture even a slight change in the surface of the work P by the light / dark pattern, it is possible to reliably detect even minute irregularities on the surface of the work P.
With such a configuration, defects in the surface shape such as distortion and scratches of the work P can be detected more accurately than the conventional method of detecting from the color information of the image such as brightness and saturation.

Further, even when the surface of the work P is mirror-finished, the camera 20 can shoot a bright and dark pattern with high accuracy by focusing on the halogen lamp 10 reflected on the surface of the work P. Since it is possible to obtain an image of a light-dark pattern with good image quality, it is possible to improve the detection accuracy of defects on the surface of the work P.
As described above, even when the surface of the work P has a mirror gloss, it is possible to detect a defect in the three-dimensional shape of the surface of the work P.

Here, as a first comparative example with respect to the present invention, FIG. 6 shows a photographed image Q1 when the projected light 161 having no light / dark pattern is irradiated. In the first comparative example, the camera 20 is diagonally arranged so as to have a reflection angle of 70 ° with respect to the work P, and the surface of the work P is mirror-finished.
That is, the first comparative example is different from the embodiment of the present invention in that the projected light 161 has no light / dark pattern.
As is clear from FIG. 6, if the camera 20 is simply installed within the range of the mathematical formula (1), the defective portion that is near the boundary portion of the reflection of the projected light 161 as shown by the alternate long and short dash line is not included. Although it can be detected, there is a problem that the detectable area is narrow.

Further, as a second comparative example, the light and dark patterns shown in FIGS. 7 and 8 are the cases where the projected light 162 including the same as that of the embodiment of the present invention is irradiated, and the position of the camera 40 is arranged directly above the work P. The photographed image Q2 in the above configuration is shown.
As for the light-dark pattern, it is assumed that the light-dark pattern as shown in FIGS. 2 and 4 is formed as in the embodiment of the present invention, and the work P having the same shape is used.

As is clear from FIG. 8, in the photographed image Q2 taken by the camera 40 from above the work P, although the light-dark pattern is irradiated on the work P, a defect is found by using the distortion of the light-dark pattern. Difficult to detect.

This point will be described in more detail with reference to FIGS. 9A and 9B. In FIGS. 9A and 9B, the irradiation light 16 emitted from the halogen lamp 10 and the specularly reflected light reflected on the surface of the work P having no defects are shown by solid lines, and the specularly reflected light when there is a defect. Is indicated by a one-dot chain line.
Further, in the embodiment of the present invention in FIG. 9 (a), the vicinity of the defect portion A surrounded by a circle is enlarged and a schematic diagram of a light beam is added, which is a work P and a halogen lamp. The camera 20 is arranged diagonally with respect to the 10 at a position satisfying the formula (1), and the work P is irradiated with the projected light 16 including the light / dark pattern from the halogen lamp 10.
As described above, when the work P is irradiated with the projected light 16 including the light and dark pattern and the reflected angle θ of the reflected light 17 directed to the camera 20 arranged in the direction of the specular reflection of the projected light 16 is set, the reflected angle θ is set. If the equation (1) is satisfied, it is possible to detect minute irregularities from the distortion of the light-dark pattern, and it is possible to secure a sufficient length of specular projection on the image surface with respect to the actual size of the work P. The resolution of the image can be ensured.

Further, the distortion of the light-dark pattern is caused by the deviation of the specular reflection of light due to the presence or absence of defects such as minute irregularities and scratches on the surface shape. The deviation between the specularly reflected light on the flat surface without defects in the work P and the specularly reflected light on the defective portion increases as the distance from the defective portion increases.
That is, it is shown that the distortion of the light / dark pattern is gradually emphasized by moving the camera 20 away from the work P. Further, since the positional relationship between the halogen lamp 10, the work P, and the camera 20 is uniquely determined in order to receive the specularly reflected light, the longer the optical path length of the projected light 16, which is the incident light, the more the influence of distortion. Becomes larger.
That is, the halogen lamp 10, the work P, and the camera 20 can have a distance between the halogen lamp 10 and the work P, which are lighting means, while the angle at which they are arranged with each other is defined within the range of the mathematical formula (1). The farther away it is, the greater the distortion of the light-dark pattern can be detected.

Specifically, as a minute defect portion A having a three-dimensional shape on the surface of the work P, the displacement in the direction perpendicular to the normal in the specular reflection of the light-dark pattern projected on the surface of the work P by the halogen lamp 10 is x. , The displacement in the normal direction with respect to x is defined as y, the resolution of the surface of the work P in the captured image Q captured by the camera 20 is δ, and the optical path length L of the projected light 16 as the incident light is defined as δ. At this time, since the defects on the surface of the work P are minute irregularities, y is sufficiently small with respect to x (y << x).

At this time, if the angle φ is y / x = tanφ, then y / x = tanφ ≈φ (rad) from y << x. As is clear from FIG. 9B, this y / x or tanφ represents the inclination in the defect portion A.
That is, in the defect portion A, the angle of the normal line deviates by φ from the normal line direction of the surface of the ideal work P. At this time, the reflection angle θ of the specularly reflected light on a flat surface without defects is the reflection angle θ, and since the camera 20 is installed in the direction of the reflection angle θ, when there is a defect portion A, from the same position of the halogen lamp 10. The irradiated light beam is reflected in a direction different from that of the camera 20 due to the inclination of the normal line. If the camera 20 is a telecentric optical system, the light rays incident on the camera 20 when the defect portion A is present are light rays having a reflection angle θ + φ. That is, the difference in angle between the ideal incident light and the incident light such that the specularly reflected light at the defect portion A is received by the camera 20 is represented by 2φ.
In other words, in order to enter the camera 20, the light needs to have a deviation of 2φ on the incident light side. Since φ is sufficiently smaller than y << x, the length of the arc created by two rays of the same length L is 2Ltanφ = 2Lφ as shown in FIG. 9C.

According to the above description, the specularly reflected light reflected by the defect portion A incident on the camera 20 receives the projected light 16 from a position deviated by the arc length of 2 Lφ with respect to the specularly reflected light on the ideal surface. It will be. As described above, since the halogen lamp 10 projects a light-dark pattern in which the bright part 12 and the dark part 13 periodically repeat as shown in FIG. 2, such a deviation in the incident position is photographed by the camera 20. It will be measured as distortion and deviation of the light and dark pattern as illustrated in FIG. 4 in the captured image.
In order to emphasize the distortion of the light-dark pattern due to the defect, it is desirable that the arc length 2Lφ is at least twice the resolution δ. That is, it is preferable to satisfy the mathematical formulas (2) and (3).

By the way, as the distance from the halogen lamp 10 to the work P increases, the luminance contrast between the bright portion 12 and the dark portion 13 irradiated on the work P decreases due to the influence of the diffusion of light.
In particular, in the captured image Q captured by the camera 20, under the condition that the brightness of the bright portion 12 is less than 1.3 times the brightness of the dark portion 13, the bright portion 12 and the dark portion 13 of the light-dark pattern are distinguished. Will be difficult, and it will be difficult to detect defects.
Therefore, it is preferable that the halogen lamp 10, the work P, and the camera 20 are arranged at positions such that the brightness of the bright portion 12 is 1.3 times or more the brightness of the dark portion 13.
Regarding the difference in brightness between the bright portion 12 and the dark portion 13, the distances between the halogen lamp 10, the work P, and the camera 20, as well as the transmissive portion 14 of the halogen lamp 10 and the shielding portion 15. It is more preferable to use the difference in brightness between the bright portion 12 and the dark portion 13 in the captured image Q as a condition because it is also caused by a difference in transmittance between the two.

Further, in the light-dark pattern, it is preferable that the bright part 12 and the dark part 13 are periodically repeated.
As for the light / dark pattern, it is preferable that the light / dark pattern is set on the halogen lamp 10 side according to the three-dimensional shape of the work P so that the light / dark pattern is uniformly projected on the surface of the work P. Specifically, for example, for a cylindrical work P as shown in FIG. 4, an anamorphosis technique is performed so that the bright portion 12 and the dark portion 13 are alternately projected as striped lines when irradiated. It is preferable to set by the pattern design with reference to.
It should be noted that such a "pattern according to the three-dimensional shape" is not limited to such a configuration, and can be freely deformed according to the shape and position of the halogen lamp 10, the position of the camera 20, and the scanning method for inspection. You can do it.

Further, the width of the light-dark pattern between the bright portion 12 and the dark portion 13 in the direction having periodicity (for example, the width in the direction along the Y direction shown in FIG. 4) is not more than 1 times the width of the defect. It is preferable from the viewpoint of detection sensitivity.
That is, it is preferable that the bright portion 12 and the dark portion 13 are set so that the width of the bright portion 12 and the width of the dark portion 13 are smaller than the width of the defect to be detected.
According to this configuration, when there is a defect at the boundary portion between the bright portion 12 and the dark portion 13, the distortion of the light / dark pattern is detected from the reflected light. Therefore, the purpose is to further improve the detection accuracy of defects due to distortion of the light / dark pattern.
At this time, in addition to the change in the width design between the bright portion 12 and the dark portion 13, for example, the distortion of the bright / dark pattern is projected by moving the phase of either the bright portion 12 or the dark portion 13 by an arbitrary value. However, the defect can be detected at a gap narrower than the width of the original bright portion 12 and the dark portion 13.

Further, between the bright portion 12 and the dark portion 13, the ratio of the dark portion 13 to the bright portion 12 in the above-mentioned width direction is in the range of 0.5 to 2.0 from the viewpoint of maintaining the contrast between the bright portion and the dark portion 13. It is advantageous from the above, and is preferable in ensuring the detection sensitivity.

In the captured image Q in which the light / dark pattern is captured, the shape of the light / dark pattern may be various shapes such as vertical, horizontal, diagonal, cross, and multidimensional function, but the shape of the light / dark pattern is most preferably a striped shape.
This is because the boundary portion between the bright portion 12 and the dark portion 13 is clear, and the defect can be easily detected by increasing the frequency and frequency of intersection with the defect.

Further, the block shape as shown in FIG. 10 may have a rectangular shape in which the bright portions 12 and the dark portions 13 are alternately adjacent to each other. According to such a block shape, the area occupied by the light-dark boundary per unit area increases, so that the frequency and number of times the defect and the light-dark boundary intersect are ensured to facilitate detection. Because.

Further, the light-dark pattern may be such that the bright portion 12 and the dark portion 13 are statically formed by the transmission portion 14 and the shielding portion 15 of the slit 5, and the slit 5, the liquid crystal element, and other optical members may be formed. It may be used to dynamically change the positions of the transparent portion 14 and the shielding portion 15 to dynamically change the arrangement of the bright portion 12 and the dark portion 13.
Further, in such a case, as shown in FIG. 11, one set of the bright portion 12 and the dark portion 13 adjacent to each other is defined as one cycle and fluctuates according to the phase table of FIG. 11 (b). It may be. In FIG. 11B, white corresponds to the bright portion 12 and black corresponds to the dark portion 13, and "moving the phase by π" indicates that the bright portion 12 and the dark portion 13 are inverted from each other. .. At this time, the slit 5 functions as a phase changing means capable of moving the phase of the light / dark pattern by an arbitrary value.
Further, when a liquid crystal display or the like is used as the lighting means instead of the halogen lamp 10, the bright part 12 and the dark part 13 can be arbitrarily switched by turning on and off, and the lighting means can be used as the phase changing means. It will also have a function.

Further, in order to quantitatively perform the comparison by the control unit 9, the boundary portion between the bright portion 12 and the dark portion 13 is formed in parallel or substantially parallel to the horizontal direction of the observation field of view of the captured image Q. preferable.
As described above, when the shapes of the light and dark patterns are captured in parallel or substantially parallel to the captured image Q, there is an effect that the distortion of the light and dark patterns by the image processing can be easily quantified.

The camera 20 focuses on the light-dark pattern projected on the halogen lamp 10 reflected on the surface of the work P, not on the surface of the work P itself.
In this way, focusing on the reflected halogen lamp 10 is equivalent to focusing on the light-dark pattern projected on the surface of the work P.
By adjusting the focus of the camera 20 in this way, it becomes easier to detect the distortion of the light / dark pattern, which contributes to the improvement of the SN ratio of the inspection.

The surface inspection device 100 according to the present invention may divide the captured image Q into a plurality of regions for inspection.
By dividing into each region in this way, the threshold value for inspection can be set for each region, so that the three-dimensional shape of the surface of the more subdivided work P can be evaluated.
It is preferable to individually set the division of the region of the captured image Q according to the size of the work P, the three-dimensional shape, and the period and shape of the projected light / dark pattern.
Further, the comparison between the captured image Q and the reference image R performed by the control unit 9 or the evaluation of the three-dimensional shape is performed by image processing using frequency filtering, a time change method, a phase shift method, or another rule-based image processing method. Image processing methods such as general, machine learning, and deep learning may be used.
By detecting the distortion of the light-dark pattern caused by the defect of the work P from the light-dark pattern captured in the captured image Q by using these image processing methods, it is possible to detect defects such as unevenness on the surface of the work P.
Further, the surface inspection apparatus 100 according to the present invention can easily and accurately detect minute film thickness steps on the coating film and irregularities due to foreign substances, which are difficult to detect with the conventional apparatus.
Further, the work P inspected by the surface inspection device 100 may have reflected light for the projected light and dark pattern, and may be applied to various work Ps such as a glossy painted surface, a metal surface, and a glass surface. Can be done.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to such a specific embodiment, and unless otherwise specified in the above description, the present invention described in the claims. Various modifications and changes are possible within the scope of the above.

The effects described in the embodiments of the present invention merely list the most suitable effects resulting from the present invention, and the effects according to the present invention are limited to those described in the embodiments of the present invention. is not it.

9 Detection means (control unit)
10 Lighting means (halogen lamp)
12 Bright part (part of bright and dark pattern)
13 Dark part (part of light / dark pattern)
20 Shooting means (camera)
100 Surface inspection device P Inspected body (work)
Q Photographed image R Reference image

Japanese Unexamined Patent Publication No. 11-132964 Japanese Patent No. 4685971 Japanese Unexamined Patent Publication No. 2005-337857 Japanese Patent No. 5895733 Japanese Patent No. 5182833 Japanese Patent No. 6420131 Japanese Unexamined Patent Publication No. 2009-168454 Japanese Unexamined Patent Publication No. 2007-071562 Japanese Unexamined Patent Publication No. 2010-230648 Japanese Unexamined Patent Publication No. 2006-017481 Japanese Unexamined Patent Publication No. 2012-063190 Japanese Unexamined Patent Publication No. 2002-148209

Claims (10)

Illumination means that project a light-dark pattern that periodically repeats the difference between light and dark onto the surface of the object to be inspected.
An imaging means for receiving and photographing specularly reflected light from the object to be inspected by the lighting means, and an imaging means.
It has a detecting means for detecting a minute shape change on the surface of the object to be inspected from the image by comparing the image taken by the photographing means with the light and dark pattern.
In the photographing means, the reflection angle θ of the specularly reflected light from the lighting means is the conditional expression (1):
45 ° <θ ≤ 85 °
A surface inspection device characterized by being placed in a position within the range of. In the surface inspection apparatus according to claim 1,
The shape change on the surface of the inspected object is a displacement in the direction perpendicular to the normal in the specular reflection of the light and dark pattern projected on the surface of the inspected object by the illumination means, and the method with respect to the x. Conditional expression (2): When the displacement in the linear direction is y, the resolution of the surface of the object to be inspected in the image taken by the photographing means is δ, and the length of the incident light is L.
L ≧ δx / y
A surface inspection device characterized by satisfying. In the surface inspection apparatus according to claim 1 or 2.
The light-dark pattern is a surface inspection apparatus characterized in that the brightness of a bright portion in an image captured by the photographing means is 1.3 times or more the brightness of a dark portion. The surface inspection apparatus according to any one of claims 1 to 3.
A surface inspection apparatus characterized in that the shape of the light-dark pattern is a striped shape in which bright parts and dark parts are alternately repeated. The surface inspection apparatus according to any one of claims 1 to 3.
A surface inspection apparatus characterized in that the shape of the light-dark pattern is a block shape in which a bright part and a dark part are adjacent to each other. The surface inspection apparatus according to any one of claims 1 to 5.
The lighting means is a surface inspection device comprising a phase changing means capable of moving the phase of the light / dark pattern by an arbitrary value. In the surface inspection apparatus according to any one of claims 1 to 6.
A surface inspection device characterized in that the object to be inspected has a cylindrical shape. In the surface inspection apparatus according to any one of claims 1 to 7.
The photographing means is a surface inspection apparatus characterized in that it focuses on the lighting means reflected on the surface of the object to be inspected and photographs the image. The surface inspection apparatus according to any one of claims 1 to 8.
The detection means divides an image captured by the photographing means into a plurality of regions based on the light / dark pattern in the image and the magnitude of the shape change to be detected, and divides the image into a plurality of regions and divides the image into the bright / dark patterns included in each region. A surface inspection apparatus for detecting minute changes in shape on the surface of the object to be inspected for each region based on the above. A lighting means including a light source portion that gives illuminance to the surface of the inspected object, and a bright portion and a dark portion that project a periodic light / dark pattern according to the three-dimensional shape of the inspected object onto the surface of the inspected object. ,
An imaging means for receiving and photographing the specularly reflected light from the light-dark pattern at a position where the reflection angle θ satisfies 45 ° <θ≤85 °.
It is possible to use a detection means for detecting a defect derived from a minute three-dimensional shape on the surface of the object to be inspected by detecting a distortion with respect to the periodicity of the light / dark pattern from an image taken by the photographing means. Characteristic surface inspection method.

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