JP2018163134A - Surface inspection method and apparatus for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface inspection method and an apparatus for the same capable of easily performing a surface inspection while largely changing an illumination direction to a surface of an object to be inspected.SOLUTION: A surface inspection method comprises the steps of: disposing a lighting device 13 with a linear light-emission part illuminating an object 11 to be inspected between the object 11 to be inspected and an imaging apparatus 12 in an imaging visual field of the imaging apparatus 12; obtaining a plurality of images having different illumination directions by use of the imaging apparatus 12 and including images of the same part of the object 11 to be inspected relatively moving in a direction orthogonal to a longer direction of the lighting device 13 before passing through a portion just below the lighting device and after passing through the portion just below the lighting device so as to trace the moving object 11 to be inspected on the images; and inspecting a surface of the object to be inspected on the basis of brightness information on the images having different illumination directions at the same part of the object 11 to be inspected.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a surface inspection method and apparatus for inspecting the surface of an inspection object.

  In the manufacturing process of wood building materials manufactured by processing plywood materials, appearance such as swelling caused by biting of foreign materials such as wood chips and dents caused by pressure with foreign materials, cracking of wood, peeling of surface materials, scratches, etc. Defects occur.

  As such an automatic inspection technique for the surface of an inspection object, Japanese Patent Application Laid-Open No. H10-228667 specifies a position where regular reflected light of illumination is incident while changing a relative positional relationship between the imaging device, the illumination, and the inspection object. Shows a method of measuring the surface direction of an inspection object. In this product, the inspection object such as building materials is reflected on the surface of the inspection object while taking the image with the imaging device while conveying the inspection object at a constant speed, and imaging at the same position on the inspection object surface. The position where the luminance is maximized, that is, the position where the component of the illumination light specularly reflected on the object surface is maximized, is determined, and the incident angle and the reflection angle of the illumination light obtained from the relative positions of the imaging device, the illumination and the inspection object are determined. Surface irregularities are measured by estimating the surface direction.

  In this case, in order to analyze the illumination image reflected on the surface of the inspection object by image processing, it can be applied to the inspection object having a glossy surface, such as a metal material, a building material with a glossy coating or a decorative sheet, etc. . However, it is applied to inspection objects whose surface is not glossy, such as unpainted wood, MDF (Medium Density Fiber) material, building materials with non-glossy paint or decorative sheet, because the surface of the inspection object will not be illuminated. I can't.

  It is also conceivable to perform inspection using a dedicated device such as a laser beam cutting sensor that can measure the distance. However, in the case of the above-described surface inspection of building materials, the maximum length of the target object is m, and the long side is virtually infinitely long. For example, scratches are 10 μm deep. The width is very small, less than 1 mm. A device provided with a distance measuring device having a resolution capable of clearly imaging this has a problem of enormous amounts of money.

Japanese Patent No. 3312849

  By the way, there is a known technique called “Shape from Shading” in which the surface direction of the object surface is measured using a change in shadow formed on the object surface by illumination instead of the reflection of the illumination image.

  This “Shape from Shading” method is typically used in a spacecraft that does not have a dedicated device for measuring distances. This technique is used for restoring the three-dimensional shape of the celestial body from the change in shadow in the same part of the celestial body based on the positional relationship of

  Even if the defect is shallow and small in width like a scratch, the direction of the surface changes greatly, so inspecting such a defect is a surface like the `` Shape from Shading '' method rather than measuring the distance The method of measuring the direction of this can achieve a more reliable inspection at a much lower cost.

  On the other hand, in the defect detection method for an object surface described in Patent Document 1 described above, a change in illumination direction (illumination angle) may be about several degrees in order to use a regular reflection component on a glossy surface. In the “Shape from Shading” method, it is necessary to change the shadow sufficiently, so the illumination direction must be changed at several tens of degrees. However, in the case of such a long inspection object, it is practically difficult to greatly change the illumination direction by moving the illumination.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a surface inspection method and apparatus capable of easily performing a surface inspection performed by greatly changing the illumination direction with respect to the surface of the inspection object.

  In the surface inspection method according to one aspect of the present invention, an illumination having a linear light emitting portion that illuminates an inspection object is disposed between the inspection object and an imaging device for imaging the inspection object, and the illumination is performed. It arrange | positions in the imaging visual field of the said imaging device. A portion illuminated by the illumination of the inspection object that moves relative to the imaging device and the illumination in a direction orthogonal to the longitudinal direction of the illumination is imaged by the imaging device. It moves within the imaging field of view of the imaging device by acquiring a plurality of images with different illumination directions, including an image before the same part of the inspection object passes directly under illumination and an image after passing directly under illumination. The inspection object is tracked on the image. The surface of the inspection object is inspected based on luminance information on a plurality of images having different illumination directions in the same part on the inspection object.

  And the surface inspection apparatus which concerns on one form of this invention is equipped with illumination, an imaging device, an image processing apparatus, and a conveying apparatus. The illumination has a linear light output part that illuminates the surface of the inspection object. The imaging device images the surface of the inspection object illuminated by the illumination. The image processing device processes an image obtained by the imaging device. The transport device moves the inspection object relative to the imaging device and the illumination in a direction orthogonal to the longitudinal direction of the illumination. The illumination is disposed within an imaging field of view of the imaging device, and the imaging device includes an image before the same portion of the inspection object passes directly under the illumination and an image after passing directly under the illumination. A plurality of images having different directions are captured. The image processing device tracks the inspection object moving within the imaging field of view of the imaging device on the image, and based on luminance information on a plurality of images having different illumination directions in the same part on the inspection object. In addition, the surface of the inspection object is inspected.

  According to an aspect of the present invention, in order to perform surface inspection from a plurality of images including an image before the inspection object passes immediately under the illumination and an image after the inspection object, an image with greatly different illumination directions is easily obtained. In addition, image processing from a plurality of images is facilitated, and a highly reliable surface inspection can be performed at a low cost.

FIG. 1 is a perspective view schematically showing an apparatus according to the first embodiment of the present invention. FIG. 2 is a schematic sectional view of the illumination. FIG. 3 is an explanatory diagram showing a change in a captured image obtained by the imaging apparatus in accordance with the movement of the inspection object in the apparatus described above. 4A to 4I are explanatory diagrams of tracking images generated from the captured images. FIG. 5 is a schematic cross-sectional view showing a difference in illumination direction for each tracking image in the same embodiment. FIG. 6 is an explanatory diagram for reconstructing the surface direction of the inspection object from a plurality of images having different illumination directions in the embodiment. FIG. 7 is a graph showing points at which the distance from directly under illumination and the imaging brightness change according to the surface direction in the embodiment. FIG. 8 is a perspective view showing an example of a calibration jig for measuring the surface direction. FIG. 9A is an explanatory diagram illustrating an example of an image showing the distribution in the surface direction generated by the embodiment described above, and FIG. 9B is an explanatory diagram illustrating an example of a luminance distribution image generated by the embodiment described above. FIG. 10 is a graph for the inspection method according to the second embodiment of the present invention. FIG. 11 is a partially transparent perspective view of the illumination according to the first modification. FIG. 12 is a sectional view of the illumination. FIG. 13 is a partial perspective view of a light guide member for illumination according to a second modification. FIG. 14 is a partial perspective view of a light guide member for illumination according to a third modification. FIG. 15 is a partial perspective view of a light guide member for illumination according to a fourth modification.

  The present invention relates to a surface inspection method and apparatus for inspecting the surface of an object to be inspected, and more particularly to a surface inspection method and apparatus for irradiating light from a linear light emitting part onto the surface of an object to be inspected. It is.

  Referring to FIG. 1 to FIG. 9 in detail, FIG. 1 shows an outline of the surface shape inspection apparatus according to the first embodiment. In FIG. A camera, which is a device, and 13 are illuminations. The camera 12 and the illumination 13 are fixed to a gantry 15, and the inspection object 11 moves at a constant linear velocity under the illumination 13 in the direction of the arrow in the drawing by the conveyance device 16.

  As shown in FIG. 2, the illumination 13 includes a rod-shaped light source 21 serving as a linear light output portion and a housing 22 whose upper half is opaque so that light from the light source 21 does not go to the camera 12 side. And emits a uniform amount of light in the circumferential direction of the lower half. Here, “linear” means that the length in one direction is longer (for example, 10 times or more in terms of the ratio) than the length (width) in the direction orthogonal to the one direction. , The width may not be zero. A thin cold cathode fluorescent tube can be suitably used as the light source 21, but is not limited thereto.

  An illumination 13 including a light source 21 having a linear light output part is located directly under the camera 12 (on the optical axis of the camera 12) between the camera 12 and the inspection object 11, and with respect to the conveyance direction of the inspection object 11. The surface of the inspection object 11 is illuminated. The illumination 13 crosses the center of the imaging field 18 of the camera 12.

  The camera 12 is, for example, an industrial area camera, and is installed so that the inspection object 11 appears to move in the vertical direction of the image within the imaging visual field 18. Data of an image photographed by the camera 12 is sent to an image processing device 14 which is a personal computer, for example, via a communication interface such as CameraLink, USB, or Gigabit Ethernet.

  The image processing apparatus 14 accumulates image data sent via the communication interface on a memory or storage built in the image processing apparatus 14 itself, and also for the accumulated image by the built-in arithmetic device. It has a function capable of executing arbitrary processing.

  In order to simplify the explanation, a flat inspection object 11 is arranged perpendicular to the optical axis of the camera 12, and the conveying device 16 illuminates the inspection object 11 at a right angle to the optical axis of the camera 12. It is assumed that a constant-velocity linear motion is made in a direction orthogonal to the longitudinal direction of 13.

  FIG. 3 shows an example of an image taken at every predetermined transport distance or every predetermined time while transporting the inspection object 11 at a constant speed. In the figure, 31 is an image of the illumination 13 immediately below the camera 12, and 32 is an image of a concavo-convex defect on the surface of the inspection object 11. As the inspection object 11 is transported, the photographed image sequentially moves upward as shown in FIG. That is, the image 32 at the point p1 shown in FIG. 3 has moved to the position of the point p2 that is higher by d pixels in the image taken when the target object has moved by a certain distance. Similarly, the n-th image moves to the position of the point pn moved by (n−1) d pixels from the first image, and finally the imaging field 18 of the camera 12 is removed.

  Further, the shadow of the concavo-convex defect on the surface of the inspection object 11 changes depending on the relationship between the position of the illumination 13 and the distance. 3 shows that the hatched portion of the image 32 is “shaded”, but does not show that the lower the distance from the illumination 13, the less the luminance decreases.

  The above image is processed in the image processing apparatus 14 by, for example, the procedure described below. As described above, the same part on the inspection object 11 always appears to move by d pixels on the image in which the inspection object 11 is photographed at every predetermined transport distance. Accordingly, as shown in FIGS. 4A to 4I, the regions an of the images shifted in time sequentially transmitted from the camera 12 are tracked in units of band-like regions a1 to a9 corresponding to d pixels in the vertical direction. The tracking images b1 to b9 are generated by repeatedly performing the copying process while being added to bn in a top-aligned manner. Due to the difference in the timing of addition of the upper end in the tracking images b1 to b9, the tracking image b5 shown in FIG. 4E has a plurality of images 31 of the illumination 13, and in the tracking images b1 to b4 and b6 to b9 excluding the tracking image b5. In FIG. 2, the images 32 are located at the same place. In FIG. 4, as in FIG. 3, the difference in luminance due to the difference in distance from the illumination 13 is not displayed.

  Further, the tracking images b1 to b9 are obtained by copying the same range of the inspection object 11, but are obtained by collecting images captured at the moment when the inspection object 11 is in the positions of the areas a1 to a9 in FIG. Therefore, the tracking images b1 to b9 correspond to images obtained by illuminating the inspection object 11 with parallel lights in the illumination directions L1 to L9 shown in FIG. That is, the tracking image b1 is configured by illuminating the range only with the light in the illumination direction L1, and the tracking image b2 is configured by illuminating the range with only the light in the illumination direction L2. The tracking image b9 is configured by illuminating the range with only light in the illumination direction L9. This means that the tracking images b <b> 1 to b <b> 9 are composed of images before and after passing directly under the illumination 13.

  In order to photograph a long object, the camera 12 needs to image the object from a high position as shown in FIG. 1, but the illumination 13 is installed near the inspection object 11, thereby illuminating directions L <b> 1 to L <b> 1. It is preferable to increase the range of L9. Since the illumination 13 installed near the inspection object 11 is reflected at the position a5 in the imaging visual field 18, the tracking image b5 illuminated with light in the illumination direction L5 among the generated tracking images b1 to b9 is illuminated. It becomes an invalid image in which 13 blind spots are collected. Therefore, a method for excluding the invalid tracking image b5 and estimating the surface direction from the relationship between the change in the illumination direction and the shadow will be described below.

  In FIG. 6 in which the apparatus configuration shown in FIG. 1 is viewed from the side (in the axial direction of the illumination 13), when the inspection object 11 passes under the illumination 13, the distance changes with the angle. The illumination intensity L to be performed corresponds to the square of the distance r from the illumination 13 to the point p on the inspection object 11, and can be obtained by the following equation, where α is a constant.

  Further, the angle δ formed by the specular direction of illumination and the line of sight of the camera can be obtained by the following equation, where γ is the light incident angle and β is the line of sight angle.

  The amount of reflected light V in the direction of the camera 12 is the sum of a reflection component that attenuates in proportion to the cosine of the nth power as the angle δ between the specular reflection direction and the line of sight increases and a diffusion component that is uniformly distributed in all directions. Is represented by the following equation.

  In the above formula, ρ is the reflectance of the reflection component, and ε is the reflectance of the diffusion component. The greater the multiplier n in this equation, the stronger the reflection in the regular reflection direction, and the higher the gloss.

  The amount of reflected light V ′ at the point p ′ whose surface direction is inclined by θ is expressed by the following equation using the angle δ ′ formed between the specular reflection direction and the line of sight because the specular reflection direction changes by 2θ.

  FIG. 7 shows a graph of the change of the reflected light amount V ′ obtained by the above formula depending on the inclination θ in the surface direction. In the figure, “a” is the case of −20 °, “b” is −10 °, “c” is 0 °, “d” is 10 °, and “e” is an inclined surface of 20 °. As is clear from FIG. 7, the reflected light amount V ′ is brightest immediately below the illumination 13 if it is a horizontal plane, and the luminance decreases evenly as it moves away from the illumination 13 to the left and right, but the surface direction is opposite to the illumination on an inclined surface. During the period, it is darker than the flat surface due to the shadow, and when the surface direction is directed toward the illumination after passing directly under the illumination, it becomes brighter than the flat surface.

  Therefore, if the luminance values where the luminance is higher than the surroundings are obtained from the respective tracking images b1 to b4 and b6 to b9, and each luminance value is approximated to an upward convex function as shown in FIG. Even if the actual maximum luminance cannot be measured due to being shielded by the illumination 13, the peak position dp and the peak luminance at which the reflected light amount V ′ is maximum can be obtained.

  Since the change of V ′ is a nonlinear function including a trigonometric function as shown in the equation (4), in order to accurately approximate the constant n representing the glossiness of the surface, the reflectance of the reflection component and the diffusion component, Ρ and ε to be shown must be known, and nonlinear regression approximation requires an iterative method, which requires processing time and is not practical for actual inspection applications.

  Therefore, a linear expression having a similar curve shape, for example, the following expression can be used.

  By using this equation, approximation by the method of least squares is possible, and a unique solution can be obtained at high speed. Note that I (d) is the luminance of the tracking image at the distance d from the position directly below the camera. If the parameters a, b, and c in the equation are obtained by the method of least squares, the peak position dp at which the reflected light amount V ′ is maximum may be obtained as the position where the derivative on the right side of the above equation is 0. It is expressed by the following formula.

  As another method, approximation may be made to a Gaussian function expressed by the following equation.

  When the Gaussian function is used, the luminance I (d) is regarded as a probability density function with respect to the distance d, and the expected value of the probability density function may be obtained as the peak position dp by the following equation. However, the accuracy is inferior, but the processing can be performed at high speed.

  A theoretical formula for obtaining the plane direction from the peak position dp is shown by the following formula.

  Also in this case, it is necessary that the constant n representing the glossiness of the surface and ρ and ε representing the reflectance of the reflection component and the diffusion component are known. Therefore, when it is desired to derive the surface direction, dp is used by using the calibration jig 4 which is a polyhedral test piece having a shape as shown in FIG. If the relationship between the surface direction is obtained, the surface direction information can be acquired at high speed.

  In addition, if you want to detect local irregularities in the surface direction such as flat bulges and dents as defective, it is only necessary to detect the part that is greatly deviated from the surface direction distribution of the non-defective part. There is no need to ask. In such a case, the dp value itself may be used as a feature representing the surface direction. FIG. 9A is an image showing a distribution of dp obtained by imaging a dent portion on the surface of a non-glossy MDF plate.

  In FIG. 9A, if the surface direction is perpendicular to the screen, it is an intermediate color, dark if it is tilted downward on the screen, and bright if tilted upward on the screen. It can be seen that the shape of the recessed portion can be clearly distinguished, and is sufficiently practical for inspection of surface defects.

  Furthermore, since the peak value of the approximate function corresponds to the luminance value when the inspection object 11 is illuminated from the front, the luminance at the position directly below the illumination 13 that is not covered by the illumination 13 and is not visible in the flat part is restored. Can do. Since this corresponds to an image that does not include a shadow imaged using coaxial epi-illumination, this luminance information can be used to detect defects associated with the density of the surface of the inspection object 11 such as dirt and scratches. Incidentally, FIG. 9B is an image showing the distribution of luminance information acquired simultaneously with FIG. 9A. It can be seen that although the dent portion is present, the dent portion and the flat portion look the same, and an image including no shadow can be generated. For this reason, it is possible to detect a defect associated with the density of the surface of the inspection object 11 without being affected by the dent.

  Next, a second embodiment will be described based on FIG.

  A portion where the change in the surface direction is large may be extracted by utilizing the fact that the shadow changes greatly as the change in the surface direction increases. In the apparatus configuration of the second embodiment, since the distance between the illumination 13 and the inspection object 11 gradually changes, the imaging luminance is multiplied by a multiplier that is inversely proportional to the light source light intensity represented by the expression of “Equation 1”. As a result, a luminance change as shown in FIG. 10 is obtained. In the figure, (a) indicates the surface direction inclination θ is -20 °, (b) indicates the surface direction inclination θ is -10 °, (c) indicates the surface direction inclination θ is 0 °, (d) indicates the surface direction inclination θ is 10 °, This is a case where the inclination θ in the surface direction is 20 °.

  In FIG. 10, by using the difference between the maximum value and the minimum value of the luminance as a feature amount representing the surface direction, it is possible to detect the uneven defect on the surface of the inspection object 11. According to the method of the second embodiment, since it is not necessary to perform an approximation process to a function in order to obtain a luminance peak, high-speed processing is possible.

  In the second embodiment, the inspection object 11 is moved by the transport device 16 because the inspection object 11 is long, but when the inspection object 11 is not so long, the imaging device 12 is moved. Of course, the illumination 13 may be moved relative to the inspection object 11. Further, the illumination 13 may be located at a position shifted by about several degrees from the optical axis of the imaging device 12, and does not need to be strictly below the imaging device 12. In short, the illumination 13 is in the imaging field 18 of the imaging device 12, and it is only necessary that the imaging device 12 can capture both images before and after the inspection object 11 passes directly under the illumination 13.

  Next, as a first modification, a modification of the illumination 13 used in the first embodiment and the second embodiment will be described with reference to FIGS.

  As described in the first embodiment, the illumination 13 is located in the imaging field 18 of the imaging device 12 as shown by the image 31 in FIG. 3, and the image 31 of the illumination 13 is inspected in the captured image. It is invalid without contributing to. For this reason, it is preferable to shorten the width of the illumination 13 so that the area of the image 31 is as small as possible. Further, as shown in FIG. 6, the distance and angle used in the above-described theoretical formula are determined as a length on a straight line starting from one point of illumination 13 (center in FIG. 6) or an angle formed with this straight line. Yes. However, since there is actually a width in the light output part of the illumination 13, the actual value may cause an error from the theoretical value obtained from the theoretical formula. Also from this viewpoint, it is preferable that the width of the illumination 13 is short.

  Moreover, it is preferable that the illumination 13 does not have unevenness in the amount of light (illuminance) in the longitudinal direction, that is, the amount of light is uniform in the longitudinal direction.

  As described above, in the first modified example, as shown in FIGS. 11 and 12, the light guide member 6 whose one side surface is a linear light output part 62 and the light incident on the light guide member 6 are emitted. An illumination 13 having a light emitting unit 5 is used.

  The light guide member 6 has a plate shape with translucency having a rectangular cross section. As a material of the light guide member 6, acrylic or the like that not only has translucency but also light 500 traveling in the light guide member 6 is easily totally reflected at the interface between the light guide member 6 and the surrounding air. However, the resin is not particularly limited as long as it has translucency.

  One side surface (end surface) located at the end portion of the light guide member 6 in the longitudinal direction is the light output portion 62. Further, the side surface (end surface) located at the end of the light guide member 6 on the opposite side to the light exit part 62 in the longitudinal direction becomes the light incident part 61 on which the light from the light emitting part 5 enters.

  The light emitting unit 5 is made of a light emitting diode and is mounted on the substrate 50. The substrate 50 has a long shape whose longitudinal direction is the direction along the longitudinal direction of the light incident portion 61, and a plurality of light emitting portions 5 are arranged at intervals in the longitudinal direction.

  The light emitting unit 5 and the light guide member 6 are housed in a case 7 and unitized. The case 7 includes a first pressing piece 71 that holds the edge of one plate surface of the plate-shaped light guide member 6 and a second pressing piece that holds most of the other plate surface of the light guide member 6. 72, and a connecting piece 73 that connects the first pressing piece 71 and the second pressing piece 72.

  The substrate 50 on which the light emitting unit 5 is mounted has the first pressing piece 71 and the second pressing piece in a portion between the first pressing piece 71 and the second pressing piece 72 by adhesive, screwing or fitting. It is fixed to at least one of the piece 72 and the connecting piece 73.

  The light guide member 6 is inserted between the first pressing piece 71 and the second pressing piece 72 and is sandwiched between the first pressing piece 71 and the second pressing piece 72. An adhesive is applied to a portion of the light guide member 6 that is in contact with the first pressing piece 71 or the second pressing piece 72 to prevent the light guide member 6 from coming off from the case 7.

  At this time, most of the other plate surface of the light guide member 6 is bonded to the second pressing piece 72 by an adhesive, but the refractive index of the adhesive is made of acrylic or the like rather than the refractive index of air. Since the refractive index is close to 6, the light 500 traveling in the light guide member 6 is easily emitted from the adhesive surface without being totally reflected. Therefore, a reflective film 63 in which a metal such as aluminum is laminated by vapor deposition or the like is formed on the plate surface of the light guide member 6 on the side in contact with the second pressing piece 72. Such a reflective film 63 may be formed on the plate surface on the side in contact with the first pressing piece 71.

  In the first modification, since the light guide member 6 having the linear light output part 62 is used for the illumination 13, the width of the illumination 13 is made shorter (thinner) than the illumination 13 using the cold cathode fluorescent tube. Is possible. Thereby, the area of the image 31 of the illumination 13 that is wasted in the captured image can be made as small as possible.

  Further, a plurality of light emitting units 5 made of light emitting diodes are arranged along the longitudinal direction of the light incident part 61, but the light 500 emitted from the light emitting part 5 and incident on the light incident part 61 of the light guide member 6 is The light advances to the light exiting part 62 while being reflected by a plate surface or the like. At this time, since the light 500 traveling in the light guide member 6 is made uniform in the longitudinal direction, the amount of light from the light output part 62 becomes uniform in the longitudinal direction. In addition, since a light emitting diode is used for the light emitting unit 5, a large amount of light can be maintained with a short start-up time and stable for a long period of time.

  Next, a second modification derived from the first modification will be described with reference to FIG.

  In the second modified example, diffusion that diffuses the light emitted from the illumination 13 in the light emitting part 62 of the light guide member 6 in the same way as in the first modified example in the transport direction of the inspection object 11 (left and right direction in FIG. 6). As a part, a lot of scratches 64 made of dents are formed. The scratches 64 have a depth of 1 mm or less occupying more than half, but the specific numerical values are not particularly limited. Further, the scratch 64 is formed so that its longitudinal direction is along the longitudinal direction of the light output portion 62, but the longitudinal direction of the scratch 64 and the shape and size of the scratch 64 are not limited.

  When the light guide member 6 is made of acrylic, the critical angle at the interface with the surrounding air is 42.2 degrees, and the light emitted from the light emitting section 62 is a maximum of ± 47.8 degrees light distribution centered on the optical axis. Has only corners. In addition, since the light distribution of the light emitting diode itself which is the light emitting unit 5 is also biased in the optical axis direction, if the light output unit 62 is a smooth surface, the light 500 is stirred even when the light 500 is agitated while traveling in the light guide member 6. The light distribution is such that the vicinity of the axis is bright and the light decreases as it moves away in the circumferential direction. There is provided a diffusing portion made of a scratch 64 made of a dent that further uniformizes the emitted light from the light emitting portion 62 in the conveying direction of the inspection object 11 and gives a wide light distribution angle.

  The scratches 64 made of dents are formed by manually sanding the light output portion 62 of the light guide member 6.

  By providing such a diffusing portion composed of the scratches 64, the light emitted from the light exiting portion 62 can be made more uniform in the transport direction of the inspection object 11, and a wide light distribution angle can be given.

  Further, the scratch 64 made of a dent can be easily formed by a file or the like.

  Next, a third modification derived from the first modification will be described with reference to FIG.

  In the third modification, a plurality of grooves 65 are formed as diffusion parts in the light output part 62 of the light guide member 6 similar to that in the first modification. The groove 65 is preferably deeper than the scratch 64 of the second modified example, such as 1 mm, 2 mm, etc., and may be more than 2 mm or less than 1 mm, and specific numerical values are not particularly limited.

  The groove 65 has a V-shaped cross section, and a plurality of grooves 65 are arranged in parallel to the longitudinal direction of the light emitting portion 62. The groove 65 functions as a lens that refracts and expands the light emitted from the light output portion 62 in the direction in which the inspection object 11 is conveyed.

  By providing such a diffusing portion composed of the groove 65, the emitted light from the light emitting portion 62 can be further uniformized in the transport direction of the inspection object 11, and a wide light distribution angle can be given.

  Also, compared with the second modification, in the second modification, oil or the like enters the scratches 64 and the function as the diffusing portion is likely to deteriorate. However, even if oil enters the groove 65, the function as the diffusing portion is unlikely to decrease. .

  Next, a fourth modification derived from the first modification will be described with reference to FIG.

  In the fourth modification, a concave cylindrical lens processing part 66 is formed as a diffusion part in the light output part 62 of the light guide member 6 similar to that in the first modification. The concave cylindrical lens processing section 66 is a concave surface whose shape in a cross section perpendicular to the longitudinal direction of the light exit section 62 is concave in the exit direction, and refracts the light emitted from the light exit section 62 in the transport direction of the inspection object 11. Functions as an expanding lens.

  By providing such a diffusing unit including the concave cylindrical lens processing unit 66, the emitted light from the light emitting unit 62 can be further uniformized in the transport direction of the inspection object 11, and a wide light distribution angle can be given.

  In addition, an arbitrary orientation angle can be obtained by changing the curvature of the concave cylindrical lens processing portion 66.

  As is apparent from the first embodiment, the second embodiment, and the first to fourth modifications described above, the surface inspection method of the first aspect is a linear pattern that illuminates the inspection object 11. The illumination 13 having the light emitting part is arranged between the inspection object 11 and the imaging device 12 for photographing the inspection object 11, and the illumination 13 is arranged in the imaging visual field 18 of the imaging device 12. A portion illuminated by the illumination 13 of the inspection object 11 that moves relative to the imaging device 12 and the illumination 13 in a direction orthogonal to the longitudinal direction of the illumination 13 is imaged by the imaging device 12. By acquiring a plurality of images having different illumination directions including an image before the same portion of the inspection object 11 passes directly under the illumination 13 and an image after passing through the illumination 13, the imaging field of the imaging device 12 is acquired. The moving inspection object 11 is tracked on the image. The surface of the inspection object 11 is inspected based on luminance information on a plurality of images having different illumination directions in the same part on the inspection object 11.

  According to the first aspect, in order to perform surface inspection from a plurality of images including an image before the inspection object 11 passes immediately under the illumination 13 and an image after the inspection object 11 passes, images with greatly different illumination directions can be easily obtained. It can be obtained, and image processing from a plurality of images is facilitated, and a highly reliable surface inspection can be performed at low cost.

  The second aspect is realized by a combination with the first aspect. In the second aspect, in a plurality of images having different illumination directions, the luminance change in the same portion of the surface of the inspection object 11 is approximated to a function that becomes a convex curve, and the inspection is performed based on the peak position of the function. An image representing the surface direction distribution of the surface of the object 11 is acquired.

  According to the 2nd aspect, based on the peak position of the said function, the image showing the surface direction distribution of the surface of the test object 11 can be acquired, and the surface of the test object 11 can be test | inspected.

  The third aspect is realized by a combination with the first aspect. In the third aspect, in a plurality of images having different illumination directions, the luminance change in the same portion of the surface of the inspection object 11 is approximated to a function that becomes a convex curve, and the inspection is performed based on the peak position of the function. An image representing the reflectance distribution on the surface of the object 11 is acquired.

  According to the 3rd aspect, based on the peak position of the said function, the image showing the reflectance distribution of the surface of the test object 11 can be acquired, and the surface of the test object 11 can be test | inspected.

  The fourth aspect is realized by a combination with the first aspect. In the fourth aspect, in a plurality of images having different illumination directions, a luminance change accompanying a change in the distance to the illumination 13 is estimated to normalize the luminance change in the same portion of the surface of the inspection object 11 and change the illumination direction. An image representing the surface direction distribution on the surface of the inspection object 11 is acquired based on the amount of change in luminance associated with.

  According to the fourth aspect, by estimating the luminance change amount, an image representing the surface direction distribution of the surface of the inspection object 11 is acquired based on the amount of change in luminance, and the surface of the inspection object 11 is inspected. can do.

  The surface inspection apparatus according to the fifth aspect includes an illumination 13, an imaging device 12, an image processing device 14, and a transport device 16. The illumination 13 has a linear light output part that illuminates the surface of the inspection object 11. The imaging device 12 images the surface of the inspection object 11 illuminated by the illumination 13. The image processing device 14 processes the image obtained by the imaging device 12. The transport device 16 moves the inspection object 11 relative to the imaging device 12 and the illumination 13 in a direction orthogonal to the longitudinal direction of the illumination 13. The illumination 13 is disposed in the imaging field 18 of the imaging device 12, and the imaging device 12 includes an image before the same portion of the inspection object 11 passes immediately below the illumination 13 and an image after passing immediately below the illumination 13. A plurality of images including different illumination directions are captured. The image processing device 14 tracks the inspection object 11 moving within the imaging field of the imaging device 12 on the image, and based on luminance information on a plurality of images with different illumination directions in the same part on the inspection object 11. In addition, the surface of the inspection object 11 is inspected.

  According to the fifth aspect, in order to perform surface inspection from a plurality of images including an image before the inspection object 11 passes directly under the illumination 13 and an image after the inspection object 11 passes, images with greatly different illumination directions can be easily obtained. It can be obtained, and image processing from a plurality of images is facilitated, and a highly reliable surface inspection can be performed at low cost.

  The sixth aspect is realized by a combination with the fifth aspect. In the sixth aspect, the illuminator 13 includes the light guide member 6 that has a linear light output part 62 on one side surface, and the light emitting part 5 that emits light incident on the light guide member 6.

  According to the sixth aspect, since the light guide member 6 is used, the illumination 13 that is wasted in the captured image is used as compared with, for example, a cold cathode fluorescent tube in which the light guide member 6 is not used. The area of the image 31 can be reduced.

  The seventh aspect is realized by a combination with the sixth aspect. In the seventh aspect, in the light guide member 6, another side surface having a longitudinal direction along the longitudinal direction of the light exiting portion 62 becomes the light incident portion 61 into which light from the light emitting portion is incident, and the light emitting portion 5 made of a light emitting diode. However, a plurality of light incident portions 61 are arranged along the longitudinal direction.

  According to the 7th aspect, the light quantity from the light emission part 62 becomes uniform in a longitudinal direction, the starting time of the light emission part 5 is short, and it can maintain the big light quantity stabilized for a long period of time.

11 Inspection object 12 Camera (imaging device)
DESCRIPTION OF SYMBOLS 13 Illumination 14 Image processing apparatus 16 Conveyance apparatus 18 Imaging visual field 5 Light emission part 6 Light guide member 61 Light incident part 62 Light emission part

Claims (7)

  An illumination having a linear light emitting part for illuminating the inspection object is arranged between the inspection object and the imaging device for imaging the inspection object, and the illumination is arranged in an imaging field of view of the imaging device, A portion illuminated by the illumination of the inspection object that moves relative to the imaging device and the illumination in a direction orthogonal to the longitudinal direction of the illumination is imaged by the imaging device, and the inspection object By acquiring a plurality of images having different illumination directions including an image before the same portion passes directly under the illumination and an image after passing directly under the illumination, the inspection object moving within the imaging field of view of the imaging device is obtained. A surface inspection method characterized in that the surface of an inspection object is inspected based on luminance information on a plurality of images that are tracked on the image and have different illumination directions in the same part on the inspection object.   In a plurality of images with different illumination directions, the luminance change in the same part of the surface of the inspection object is approximated to a function that becomes a convex curve, and the surface direction of the surface of the inspection object based on the peak position of the function The surface inspection method according to claim 1, wherein an image representing a distribution is acquired.   In multiple images with different illumination directions, the luminance change at the same part of the surface of the inspection object is approximated to a function that becomes a convex curve, and the reflectance of the surface of the inspection object based on the peak position of the function The surface inspection method according to claim 1, wherein an image representing a distribution is acquired.   In multiple images with different illumination directions, the luminance change accompanying the change in the distance to the illumination is estimated to normalize the luminance change in the same part of the surface of the object to be examined, and the amount of change in luminance accompanying the change in the illumination direction is also obtained. 2. The surface inspection method according to claim 1, wherein an image representing a surface direction distribution on the surface of the inspection object is acquired. Illumination having a linear light emitting part that illuminates the surface of the inspection object, an imaging device that images the surface of the inspection object illuminated by the illumination, and an image processing device that processes an image obtained by the imaging device The inspection object consists of the imaging device and a transport device that moves relative to the illumination in a direction perpendicular to the longitudinal direction of the illumination,
The illumination is arranged in the imaging field of the imaging device,
The imaging device captures a plurality of images having different illumination directions including an image before the same part of the inspection object passes directly under illumination and an image after passing directly under illumination,
The image processing device tracks the inspection object moving within the imaging field of view of the imaging device on the image, and based on luminance information on a plurality of images having different illumination directions in the same part on the inspection object. A surface inspection apparatus for inspecting the surface of an inspection object.   The surface inspection apparatus according to claim 5, wherein the illumination includes a light guide member that forms the light output portion having a linear side surface, and a light emitting portion that emits light incident on the light guide member. In the light guide member, another side surface having a longitudinal direction along the longitudinal direction of the light output portion serves as a light incident portion on which light from the light emitting portion is incident,
The surface inspection apparatus according to claim 6, wherein a plurality of the light emitting units made of light emitting diodes are arranged along a longitudinal direction of the light incident unit.