Detection device and detection method

Abstract

The present technology relates to a detection device and detection method capable of detecting even fine defects. The present invention comprises a light source having a linear or planar irradiation surface, and an imaging unit that images reflected light from an object irradiated by light from the light source, wherein the imaging unit is provided with a polarizer, and a perpendicular from the irradiation surface of the light source intersects, at a prescribed angle, the direction the imaging unit is facing. This technology can be applied to detection devices that detect defects on the surface of objects, for example.

Description

Detection device and detection method

[0001] The present technology relates to a detection device and a detection method, and more particularly to a detection device and a detection method that are capable of detecting even minute defects.

[0002] As a method for detecting defects on a glossy surface, a device has been proposed that detects abnormalities by detecting changes in polarization information and determines whether the surface is good or bad (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2017-116294

[0004] The method described in Patent Document 1 can detect defects by capturing changes in the feature amount of polarization and detecting the difference in polarization information from normal areas without defects. However, the change in polarization information is buried in the information on reflected light from normal areas, making it difficult to capture minute defects.

[0005] The present technology has been developed in view of such circumstances, and makes it possible to detect even minute defects.

[0006] A detection device according to one aspect of the present technology includes a light source having a linear or planar irradiation surface, and an imaging unit that captures reflected light from an object illuminated with light from the light source, wherein the imaging unit includes a polarizer, and a perpendicular line from the irradiation surface of the light source intersects with the direction in which the imaging unit is facing at a predetermined angle.

[0007] A detection method according to one aspect of the present technology is a detection method in which a detection device detects reflected light from an object using dark-field illumination with a polarization sensor equipped with a polarizer, and detects the surface shape of the object using the detection result.

[0008] A detection device according to one aspect of the present technology includes a light source having a linear or planar irradiation surface, and an imaging unit that captures reflected light from an object illuminated by light from the light source. The imaging unit is equipped with a polarizer, and is positioned such that a perpendicular line from the irradiation surface of the light source and the direction in which the imaging unit is facing intersect at a predetermined angle.

[0009] In a detection method according to one aspect of the present technology, a detection device detects reflected light from an object using dark-field illumination with a polarization sensor equipped with a polarizer, and uses the detection results to detect the surface shape of the object.

[0010] The detection device may be an independent device or an internal block constituting a single device.

[0011] 1 is a diagram illustrating a configuration of an embodiment of a detection device to which the present technology is applied; FIG. 2 is a diagram illustrating an example configuration of the detection device when viewed from above; FIG. 3 is a diagram illustrating an example configuration of a polarizer; FIG. 4 is a block diagram illustrating a configuration of the detection device; FIG. 5 is a diagram illustrating a method of irradiating a defect with light; FIG. 6 is a diagram illustrating a method of irradiating a defect with light; FIG. 7 is a diagram illustrating an example of a result by cosine fitting; FIG. 8 is a diagram illustrating magnification of light using blur; FIG. 9 is a diagram illustrating magnification of light using blur in a dark field and a bright field; FIG. 10 is a diagram illustrating a method of detecting a defect; FIG. 11 is a diagram illustrating a method of detecting a defect; FIG. 12 is a diagram illustrating a method of detecting a defect; FIG. 13 is a flowchart illustrating an operation of the detection device; FIG. 14 is a diagram illustrating an example configuration of a PC;

[0012] Hereinafter, modes for carrying out the present technology (hereinafter referred to as embodiments) will be described.

[0013] 1 and 2 are diagrams showing an example of the external configuration of an embodiment of a detection device 10 to which the present technology is applied. Fig. 1 is a diagram showing an example of the configuration of the detection device 10 when viewed from the side, and Fig. 2 is a diagram showing an example of the configuration when viewed from above.

[0014] The detection device 10 includes a light stand 11, a light 12, a reflector 13, a polarization sensor 14, a lens 15, a light-shielding cloth 16, and an object holder 17. The detection device 10 is a device that detects defects such as scratches and dents on the surface of an object 21 held by the object holder 17. The object 21 is an object whose reflectance characteristics are known, such as a metal or plating.

[0015] The light stand 11 holds the light 12. The light 12 may be, for example, a type of light known as a ring light or a dome light. Here, the explanation will be continued using an example in which a circular light known as a ring light is used as the light 12.

[0016] A reflector 13 having the same shape as the light source 12 is attached to the light source 12. If the light source 12 is ring-shaped, the reflector 13 is also ring-shaped (circular). Light from the light source 12 strikes the reflector 13 and is reflected by the reflector 13, and the reflected light is irradiated onto the object 21. The light source is composed of the light source 12 and the reflector 13.

[0017] The light source, which is composed of the illuminator 12 and the reflector 13, functions as a ring-shaped light source attached so as to surround the lens 15 of the polarization sensor 14, and irradiates the object 21 with light from all directions of 360 degrees. The illuminator 12 irradiates the object 21 with unpolarized light.

[0018] Here, we will continue the explanation using an example in which the light source is composed of a light 12 and a reflector 13, but this embodiment can also be applied to a light source that is configured to be able to irradiate light onto the object 21 from all directions, 360 degrees.

[0019] For example, the light source may be configured to rotate a linear light in which LEDs (Light Emitting Diodes) are arranged in a vertical row, thereby irradiating the object 21 with light from all directions, 360 degrees.

[0020] The irradiation surface of the light source is a reflector 13 in the example shown in Fig. 1, but the shape of this reflector 13 may be a linear shape in cross section as shown in Fig. 1, or may be a curved shape (a shape having a curved portion). In this case, the irradiation surface of the light source is formed in a planar shape.

[0021] The polarization sensor 14 has a pixel array section in which pixels are arranged two-dimensionally, and a polarizer 31 shown in Fig. 3 is provided on the pixel array section. The polarizer 31 is an optical element that has the property of transmitting only light that vibrates in one specific direction and blocking light that vibrates in other directions. If four 2x2 pixels in the pixel array section are considered to be one unit, each of the four pixels is provided with a polarizer 31 that transmits light that vibrates in a different direction.

[0022] Of the four 2x2 pixels, the pixel located at the bottom right is provided with a polarizer 31a that transmits light vibrating in the 0-degree direction, and the pixel located at the top right is provided with a polarizer 31b that transmits light vibrating in the 45-degree direction.Furthermore, of the four 2x2 pixels, the pixel located at the top left is provided with a polarizer 31c that transmits light vibrating in the 90-degree direction, and the pixel located at the bottom left is provided with a polarizer 31d that transmits light vibrating in the 135-degree direction.

[0023] As shown in Figure 2, polarization sensor 14 having polarizer 31 is provided at the center of ring-shaped illumination 12 and captures an image of light reflected from object 21. Lens 15 is attached to polarization sensor 14. Object 21 is located in the direction in which lens 15 is pointed. As will be described in detail below, object 21 is held by object holder 17 so that the defect-free surface of object 21, hereinafter referred to as the normal surface, faces lens 15 and faces the normal surface in a substantially parallel relationship.

[0024] The object holder 17 holds the object 21 so that the normal surface of the object 21 is positioned directly opposite the polarization sensor 14. The object holder 17 is provided so as to be movable in the up, down, left, and right directions so that the object 21 can be held at a desired position.

[0025] 1, the reflector 13 is provided from the light 12 to (slightly above) the surface on which the object 21 is located. The reflector 13 functions as a light source together with the light 12.

[0026] A light-shielding cloth 16 is provided above the polarization sensor 14. The light-shielding cloth 16 is provided to prevent excess light from entering the space where the light reflected by the reflector 13 is present. A configuration without the light-shielding cloth 16 is also possible.

[0027] 4 is a diagram showing the configuration of the detection device 10. The detection device 10 is configured to include a lens 15 and a polarization sensor 14 that receives reflected light from an object 21 that has passed through the lens 15. The detection device 10 also includes an information processing device 25 that processes a signal of the reflected light received by the polarization sensor 14.

[0028] The information processing device 25 includes a polarization signal processing unit 41 and a surface shape calculation unit 42. Of the light reflected by the object 21, the lens-transmitted light that passes through the lens 15 and is received by the polarization sensor 14 is converted by the polarization sensor 14 into four-directional polarization images, classified, and supplied to the polarization signal processing unit 41 of the information processing device 25.

[0029] The polarization signal processing unit 41 calculates the degree of polarization and the elliptical azimuth angle using a technique called curve fitting, which fits the measurement results to a predetermined curve. Here, we will explain an example in which cosine fitting, which fits to a curve based on a cosine function, is applied.

[0030] The degree of polarization and ellipse azimuth angle obtained by the polarization signal processing unit 41 are supplied to a surface shape calculation unit 42. If the object 21 has a defect such as a scratch or dent (hereinafter referred to as a defective portion), the position, size, depth, etc. of the defective portion can be calculated from the degree of polarization and the ellipse azimuth angle. The surface shape calculation unit 42 detects the shape of the surface of the object 21.

[0031] The surface shape calculation unit 42 calculates the surface angle of the defect. By representing the surface angle of the defect, for example, with a color according to the angle, the defect of the object 21 can be presented to the user as an image. The surface shape calculation unit 42 is provided with information on the reflectance of the object 21 from an external source, generates a table (described below) using the reflectance, and calculates the surface angle based on the table.

[0032] 8, if the polarization signal processing unit 41 determines that only one pixel out of four 2×2 pixels receives reflected light, it instructs the lens focus control unit 51 to adjust the lens 15 to create blur. By adjusting the lens 15 to create blur, the reflected light passing through the lens 15 is magnified, and the light passing through the lens is made incident on four pixels of the polarization sensor 14.

[0033] <Light Irradiation Related to Defect Detection> With reference to Figures 5 and 6, the principles of defect detection in the object 21 will be explained. The detection device 10 observes (detects) defects in the object 21 using dark-field observation. Dark-field observation is an observation method that uses oblique illumination to enhance the contrast of a specimen that is difficult to image well under normal lighting conditions. While bright-field observation is an alternative to dark-field observation, bright-field observation is an observation method in which the entire sample is illuminated with direct light and observed using transmitted or reflected light.

[0034] The detection device 10 irradiates light onto the object 21 from an oblique direction to observe (detect) defects using dark-field observation. The light source of the detection device 10, which is composed of the illumination 12 and the reflector 13, is arranged to surround the object 21 and is configured to be able to irradiate light from all directions of 360 degrees. Since FIG. 5 shows a cross section, it is shown as if there are light sources on the left and right of the object 21. The arrows in FIG. 5 represent, for example, light emitted from the light source located on the left side of the figure and the reflected light that strikes the object 21 and is reflected. The configuration is such that light is irradiated onto the object 21 from an oblique direction.

[0035] The object 21 has a defect-free portion, hereinafter referred to as the normal surface. The explanation will be continued using an example in which the object 21 shown in Figure 5 has a concave defect that is recessed downward from the normal surface and a convex defect that protrudes upward from the normal surface.

[0036] Object 21 is positioned so that its normal surface (a surface assumed to be the normal surface) faces the surface onto which light from polarization sensor 14 is incident, in other words, the surface onto which lens 15 is attached. As shown in Figure 5, when incident light L1 emitted from the light source on the left strikes the normal surface of object 21, its specularly reflected light L1' (hereinafter simply referred to as reflected light L1') does not proceed toward lens 15 and is not received by polarization sensor 14. Reflected light L3', reflected light L4', and reflected light L6' of incident light L3, incident light L4, and incident light L6 that strike the normal surface also do not proceed toward lens 15 and are not received by polarization sensor 14.

[0037] When the incident light L2 emitted from the light source on the left side strikes a defect (concave portion) in the object 21, the reflected light L2' travels toward the lens 15 and is received by the polarization sensor 14. When the incident light L5 emitted from the light source on the left side strikes a defect (convex portion) in the object 21, the reflected light L5' does not travel toward the lens 15 and is not received by the polarization sensor 14. As shown in FIG. 6 , the reflected light of the light emitted from below the light source is received by the defect (convex portion) by the polarization sensor 14.

[0038] Like FIG. 5 , FIG. 6 also illustrates the relationship between the incident light emitted from the light source and the reflected light. The incident light illustrated in FIG. 6 represents light emitted from the light source approximately halfway down from the center of the figure. Incident light L11 and incident light L13 strike the normal surface of object 21 and travel in directions different from the lens 15 as reflected light L11' and reflected light L13', respectively, and are not received by polarization sensor 14. Incident light L12 strikes a defect (concave portion), and its reflected light L12' travels toward lens 15 and is received by polarization sensor 14. Incident light L14 strikes a defect (convex portion), and its reflected light L14' travels toward lens 15 and is received by polarization sensor 14.

[0039] Of the light emitted from the light source, the reflected light that hits a normal surface and is reflected does not proceed toward the lens 15, and is therefore not received by the polarization sensor 14. On the other hand, of the light emitted from the light source, the reflected light that hits a defective portion proceeds toward the lens 15, and is therefore received by the polarization sensor 14. The polarization sensor 14 receives the light reflected from the defective portion.

[0040] The position at which the defect is struck differs between the light irradiated from the upper side of the light source shown in Fig. 5 and the light irradiated from the lower side of the light source shown in Fig. 6. By adjusting the vertical length of the light source in the figure, it is possible to appropriately adjust the detection of shallow or deep defects, in other words, to adjust the sensitivity. As shown in Figs. 5 and 6, by providing the light source close to the object 21, in other words, by providing a light source (reflector 13) that is long in the vertical direction, it is possible to detect deep defects and even minute defects, thereby increasing the sensitivity for defect detection.

[0041] The light source (illumination 12 and reflector 13) may be configured to be movable in the vertical direction, and observation may be performed while moving it in the vertical direction. In the configurations shown in Figures 5 and 6, the normal surface (including the surface) of the object 21 and the surface illuminated by the light source are described as being perpendicular to each other, but they may have a positional relationship other than perpendicular. The light source may be provided at an angle so that it can illuminate the object 21 with light from an oblique direction.

[0042] The positional relationship between the polarization sensor 14 (lens 15) and the object 21 will now be explained. When the reflected light incident on the polarization sensor 14 is traced from the polarization sensor 14 side, it travels from the polarization sensor 14 to the defect and then from the defect to the light source. When the light incident on the polarization sensor 14 is traced in the reverse direction, it eventually travels to the light source (reflector 13). When such a light path is obtained, there is a defect on that path.

[0043] Light from the normal surface does not follow this path because it does not enter polarization sensor 14. If we assume that light that hits the normal surface is received by polarization sensor 14, when the light that has entered polarization sensor 14 is traced from the polarization sensor 14 side, it will not ultimately hit the light source (reflector 13).

[0044] The object 21, the light source (lighting 12 and reflector 13), and the polarization sensor 14 are arranged so that this relationship is satisfied.

[0045] This positional relationship will be further explained using the positional relationship shown in Figure 6 as an example. Consider a line perpendicular to the surface illuminated by the light source (reflector 13). This line perpendicular to reflector 13 and the direction in which polarization sensor 14 is facing intersect perpendicularly.

[0046] 6, the reflectors 13 are positioned so that their irradiation surfaces face each other. A line connecting the opposing irradiation surfaces of the reflectors 13 is perpendicular to the direction in which the polarization sensor 14 faces.

[0047] The irradiation surface of the reflector 13 may have a shape that includes a curved shape in part. Furthermore, the irradiation surface of the reflector 13 may be in a slightly inclined position relative to the normal surface of the object 21, rather than being perpendicular to it. For example, the reflector 13 may be provided in a V-shape relative to the object 21.

[0048] In such a case, the polarization sensor 14 is positioned at a predetermined angle to the perpendicular to the irradiation surface of the reflector 13 and the direction in which the polarization sensor 14 faces.

[0049] The reflector 13 and the polarization sensor 14 are arranged in a state where a perpendicular to the irradiation surface of the reflector 13 forms a predetermined angle with the direction in which the polarization sensor 14 faces. In other words, the reflector 13 and the polarization sensor 14 are arranged in a state where the perpendicular to the irradiation surface of the reflector 13 and the direction in which the polarization sensor 14 faces are not parallel (the predetermined angle is 0 degrees).

[0050] By arranging the polarization sensor 14 and the light source so as to satisfy this positional relationship, it is possible to create a situation in which the polarization sensor 14 receives the light reflected from the defective portion, but does not receive the light reflected from the normal surface, as described with reference to Figures 5 and 6.

[0051] By applying dark field observation to defect observation in the detection device 10, it is possible to ensure that only light from the defective portion is received by the polarization sensor 14, and that specularly reflected light from the normal surface is not received. Dark field observation makes it possible to observe polarization information of finer defects than bright field observation.

[0052] <Information Obtained by Cosine Fitting> The graph shown in Fig. 7 can be created from the information received by polarization sensor 14. As described with reference to Fig. 3, polarization sensor 14 is provided with four pixels to which polarizers 31a to 31d at 0 degrees, 45 degrees, 90 degrees, and 135 degrees are respectively attached, and four measurement values ​​are obtained from these polarizers 31. When the four measurement values ​​are fitted to a sine wave by cosine fitting, the graph shown in Fig. 7 is obtained.

[0053] The vertical axis of the graph shown in Figure 7 represents brightness, and the horizontal axis represents polarization angle. As shown in Figure 7, a sine wave can be identified by using measurements at 0 degrees, 45 degrees, 90 degrees, and 135 degrees. If four measurements are obtained, such a sine wave can be identified, but if four measurements are not obtained, it is difficult to obtain an accurate sine wave.

[0054] For example, as shown in the left diagram of Figure 8, if reflected light is received only by the pixel where polarizer 31b of polarizers 31a to 31d is provided, only a 45-degree measurement value can be obtained, making it difficult to obtain a sine wave by cosine fitting. This situation can occur, for example, when the defect is very small. In such a case, even if a defect exists, it may not be possible to detect the defect.

[0055] The lens focus control unit 51 ( FIG. 4 ) controls the lens 15 to perform focus control that intentionally blurs the image. When the lens 15 is controlled to obtain a blurred image, the light is expanded, as shown in the right diagram of FIG. 8 , and a state in which light is input evenly to each of the four pixels can be created. The light input to the polarizer 31b shown in the left diagram of FIG. 8 is expanded by blurring, and is input with equal intensity to each pixel equipped with the polarizers 31a, 31b, 31c, and 31d. In the situation shown in the right diagram of FIG. 8 , measurement values ​​of 0 degrees, 45 degrees, 90 degrees, and 135 degrees can be obtained, and a sine wave like that shown in FIG. 7 can be obtained by cosine fitting.

[0056] When the polarization signal processing unit 41 (FIG. 4) determines from the four-directional polarization image obtained from the polarization sensor 14 that only one pixel is receiving light, as shown in the left diagram of FIG. 8, it supplies a blur control amount to the lens focus control unit 51 (FIG. 4) so ​​that the lens 15 is controlled to obtain a blurred image. As a result, when reflected light is received by four pixels and four measurement values ​​are obtained, a sine wave such as that shown in FIG. 7 is acquired, and the surface angle of the defect can be calculated by analyzing this sine wave.

[0057] The fact that dark-field observation is more suitable than bright-field observation for observing defects by utilizing such blur and magnifying light will be described with reference to Fig. 9. The upper diagram of Fig. 9 is a diagram for explaining the situation when the blur of lens 15 is utilized to magnify light in dark-field observation, and is the same as Fig. 8. As described with reference to Fig. 8, in the case of dark-field observation, for example, when reflected light from a defect is incident only on polarizer 31b, magnifying the reflected light by utilizing the blur of lens 15 magnifies the reflected light from the defect, and a situation can be created in which the reflected light is incident on four pixels of polarizers 31a to 31d.

[0058] 9 is a diagram for explaining the situation when light is magnified in bright-field observation by utilizing the blur of the lens 15. In the case of dark-field observation, for example, even when reflected light from the defective portion is incident only on the polarizer 31b, reflected light from the normal portion (normal surface of the object 21) is also incident on each of the polarizers 31a to 31d.

[0059] In this situation, if the blur of lens 15 is used to magnify the reflected light, the reflected light from the defective portion and the reflected light from the normal portion will be magnified. As a result, a mixture of the reflected light from the defective portion and the reflected light from the normal portion will be incident on the four pixels of polarizers 31a to 31d. In this case, the polarization information obtained from each of polarizers 31a to 31d will be polarization information obtained from the mixture of the reflected light from the defective portion and the reflected light from the normal portion.

[0060] In dark-field observation, the blur of the lens is used to magnify only the light reflected from the defect, making it possible to obtain polarization information. However, in bright-field observation, the blur of the lens magnifies the light reflected from both the defect and normal areas, making it difficult to obtain polarization information from the defect.

[0061] In this way, even when the incidence of reflected light on four pixels is controlled by utilizing the blur of lens 15, it is possible to generate polarization information based on the reflected light from the defective portion by observing the defective portion using dark-field observation. By utilizing the blur of the lens, it becomes possible to observe light that exceeds the resolution limit, and it becomes possible to observe (detect) even minute defects.

[0062] Polarization information is obtained from the measurement values ​​of the reflected light from the defect obtained from four 2 x 2 pixels. The polarization information is the degree of polarization and the ellipse azimuth angle, and is calculated based on the following equations (1) and (2). Polarization degree (ρ) = polarized component / (polarized component + unpolarized component) ... (1) Ellipse azimuth angle (φ) = angle at which the maximum value of polarization is expected ... (2)

[0063] Referring again to FIG. 7, the degree of polarization is the ratio of the polarized component to the unpolarized component, and is calculated by dividing the polarized component by (polarized component + unpolarized component) as shown in Equation (1). Referring to FIG. 7, the polarized component is the difference between the maximum and minimum intensity values, and the unpolarized component is the difference between the minimum intensity value and zero intensity. The elliptical azimuth angle is the angle at which the maximum value of the polarization is assumed, and can be the amount of shift of the sine wave, as will be described later with reference to FIG. 12.

[0064] <Regarding how to determine the surface angle of a defect from polarization information> The following describes the process of calculating the surface angle of a defect using polarization information. With reference to Fig. 10 , the principle of detecting the degree to which a defect in an object 21 is tilted in the pitch direction and / or roll direction will be described.

[0065] Light from a light source that emits unpolarized light including a reflector 13 is irradiated onto an object 21 from the upper left diagonal direction in the figure. The light reflected by the object 21 is received by a polarization sensor 14 located on the right side of the figure. Consider a plane P that contains the incident light emitted from the reflector 13 (light source) and the reflected light received by the polarization sensor 14. This plane P intersects perpendicularly with a surface Q (a normal surface or a surface of a defective part) on the object 21.

[0066] The roll direction is the direction of rotation while maintaining the state in which the plane P and the surface Q on the object 21 intersect at a right angle. The pitch direction is the direction of rotation around the axis of the line where the plane P and the surface Q on the object 21 intersect. Note that the following description will be given using an example in which the roll direction and pitch direction are set in such directions, but the present technology can also be applied and falls within the scope of application of the present technology even if directions other than those exemplified here are set.

[0067] The calculation results obtained by cosine fitting when the object 21 is tilted in the roll direction will be described with reference to Fig. 11. Fig. 11A is a diagram for explaining the results of cosine fitting obtained when the object 21 and the polarization sensor 14 are directly facing each other.

[0068] When object 21 and polarization sensor 14 are facing each other and light is being irradiated from the polarization sensor 14 side, in other words, when incident light is incident on object 21 at an incident angle of 0 degrees, the intensities of the reflected waves that pass through the 0-degree polarizer 31a, the 45-degree polarizer 31b, the 90-degree polarizer 31c, and the 135-degree polarizer 31d will be equal. That is, in this case, the 0-degree measurement value, the 45-degree measurement value, the 90-degree measurement value, and the 135-degree measurement value will be equal. The result (graph) of cosine fitting obtained when the incident angle is 0 degrees is a straight line at a predetermined intensity, as shown in the lower diagram of FIG. 11A.

[0069] 11B is a diagram illustrating the results of cosine fitting obtained when the object 21 is tilted in the roll direction. When the object 21 is tilted in the roll direction with respect to the polarization sensor 14 and incident light is incident on the object 21 at an incident angle of A degrees, the degree of polarization changes, and the intensities of the reflected waves transmitted through the 0-degree polarizer 31a, the 45-degree polarizer 31b, the 90-degree polarizer 31c, and the 135-degree polarizer 31d each have different values.

[0070] In the case shown in Figure 11B, the light transmitted through the 90-degree polarizer 31c, which transmits light that oscillates in the roll direction (polarization angle direction), has the strongest intensity, and the light transmitted through the 0-degree polarizer 31a, which transmits light that oscillates in a direction perpendicular to the polarization angle direction, has the weakest intensity. The light transmitted through the 45-degree polarizer 31c and the 135-degree polarizer 31d, which transmit light that oscillates in a direction oblique to the polarization angle direction, have approximately the same intensity. The result (graph) of cosine fitting obtained at an incident angle of A degrees is a sine wave as shown in the lower diagram of Figure 11B.

[0071] 11C is a diagram illustrating the results of cosine fitting obtained when the object 21 is tilted in the roll direction with respect to the polarization sensor 14 and the incident light is incident on the object 21 at an incident angle B degrees, which is larger than the incident angle A degrees. In this case, the intensity obtained changes more than when the degree of polarization is at an incident angle of A degrees.

[0072] In the case shown in Figure 11C, the light transmitted through the 90-degree polarizer 31c has the strongest intensity, the light transmitted through the 0-degree polarizer 31a has the weakest intensity, and the intensities of the light transmitted through the 45-degree polarizer 31c and the 135-degree polarizer 31d are approximately the same.

[0073] The intensity of light transmitted through the 90-degree polarizer 31c is greater when the incident angle is B degrees than when the incident angle is A degrees. Also, the intensity of light transmitted through the 0-degree polarizer 31c is smaller when the incident angle is B degrees than when the incident angle is A degrees. The difference between the intensity of light transmitted through the 0-degree polarizer 31c and the intensity of light transmitted through the 45-degree polarizer 31c is greater when the incident angle is B degrees than when the incident angle is A degrees.

[0074] The result (graph) of cosine fitting obtained when the incident angle is B degrees is a sine wave as shown in the lower diagram of FIG. 11C.

[0075] When comparing the polarization component a at an incident angle of A degrees shown in FIG. 11B with the polarization component b at an incident angle of B degrees shown in FIG. 11C, the relationship polarization component a < polarization component b holds. In other words, it can be seen that the polarization component increases as the incident angle increases. The magnitude of the polarization component also depends on the reflectivity of the object 21, and if the object 21 has a high reflectivity, the polarization component is likely to increase. The polarization component is the value used in the above-mentioned formula (1), which is the formula for calculating the degree of polarization. The incidence angle in the roll direction can be calculated from the magnitude of the degree of polarization.

[0076] Light reflected from a defect in object 21 is incident on polarization sensor 14, and the degree to which the defect is tilted with respect to the normal surface can be detected from the polarization information obtained by polarization sensor 14. If the defect is tilted in the roll direction, as described with reference to Figure 11, it is possible to determine from the value of the degree of polarization whether or not there is a defect, the angle of incidence with respect to the defect, and the estimated surface angle of the defect from the angle of incidence.

[0077] A method for determining the surface angle of the defect in the pitch direction will now be described with reference to FIG.

[0078] 12A is a diagram for explaining the results of cosine fitting obtained when the object 21 is tilted in the pitch direction. The pitch direction is a direction perpendicular to the roll direction.

[0079] When the object 21 is tilted in the pitch direction relative to the polarization sensor 14 and incident light is incident on the object 21 at an incident angle of C degrees, the degree of polarization changes, and the intensities of the reflected waves transmitted through the 0-degree polarizer 31a, the 45-degree polarizer 31b, the 90-degree polarizer 31c, and the 135-degree polarizer 31d each have different values.

[0080] In the case shown in Figure 12A, the light transmitted through the 135-degree polarizer 31d, which transmits light that oscillates in the pitch direction (polarization angle direction), has the strongest intensity, and the light transmitted through the 45-degree polarizer 31b, which transmits light that oscillates in a direction perpendicular to the polarization angle direction, has the weakest intensity. The light transmitted through the 0-degree polarizer 31a and the 90-degree polarizer 31c, which transmit light that oscillates in a direction oblique to the polarization angle direction, have approximately the same intensity. The result (graph) of cosine fitting obtained at an incident angle of C degrees is a sine wave as shown in the lower diagram of Figure 12A.

[0081] Comparing the graph shown in Fig. 11B (referred to as graph 11B) with the graph shown in Fig. 12A (referred to as graph 12A), graph 12A is shifted to the right more than graph 11B. Whether or not there is a slope in the pitch direction can be detected by whether or not the graph is shifted.

[0082] FIG. 12B is a diagram illustrating the results of cosine fitting obtained when the object 21 is tilted in the pitch direction relative to the polarization sensor 14 and the incident light is incident on the object 21 at an incident angle D degrees, which is larger than the incident angle C degrees.

[0083] In the case shown in Fig. 12B, the light transmitted through the 135-degree polarizer 31d has the strongest intensity, the light transmitted through the 45-degree polarizer 31b has the weakest intensity, and the light transmitted through the 0-degree polarizer 31a and the 90-degree polarizer 31c has approximately the same intensity. The result (graph) of cosine fitting obtained at an incident angle of D degrees is a sine wave as shown in the lower diagram of Fig. 12B.

[0084] Comparing graph 12A shown in Fig. 12A with graph 12B shown in Fig. 12B, graph 12B is shifted further to the right than graph 12A. Whether or not there is a slope in the pitch direction can be detected by whether or not the graph is shifted, and the magnitude of the slope can be calculated from the amount of shift.

[0085] When the shift amount c at the incident angle C degrees shown in Fig. 12A is compared with the shift amount d at the incident angle D degrees shown in Fig. 12B, the relationship of shift amount c<shift amount d holds. In other words, it can be seen that the shift amount increases as the incident angle increases. The shift amount can be calculated as the magnitude of the ellipse azimuth angle obtained by the above-mentioned equation (2).

[0086] Because light reflected from a defect in object 21 is incident on polarization sensor 14, it is possible to detect the degree to which the defect is tilted with respect to the normal surface from the polarization information obtained by polarization sensor 14. If the defect is tilted in the pitch direction, as described with reference to Fig. 12, it is possible to determine from the value of the degree of polarization whether or not there is a defect, the angle of incidence with respect to the defect, and the estimated surface angle of the defect from the angle of incidence.

[0087] As described with reference to Figures 11 and 12, the angle of the defect in the roll direction and the angle in the pitch direction can be found from the degree of polarization and the elliptical azimuth angle, which are determined by cosine fitting using the intensity of the reflected light that has passed through the polarizer 31. That is, the surface angle of the defect can be found. Since the surface angle can be found, it becomes possible to find the shape of the surface of the object 21. The shape of the surface can be the shape of the detected defect, even if it is a minute defect.

[0088] <Operation of the Detection Apparatus> The operation of the detection apparatus 10 shown in FIG. 4 will be described with reference to the flowchart shown in FIG.

[0089] In step S11, the surface shape calculation unit 42 acquires information about the reflectance of the object 21 to be inspected.

[0090] In step S12, the surface shape calculation unit 42 creates and stores a table. The table may be a table in which the roll direction angle and the pitch direction angle are written as columns and records, and the polarization degree and ellipse azimuth angle are written as fields.

[0091] The processes of steps S11 and S12 need only be performed once when the detection device 10 starts observing defects in a new object 21. The processes of steps S11 and S12 are performed when the object to be inspected is changed to an object 21 with a different reflectance.

[0092] In step S13, light starts to be irradiated onto the object 21. By irradiating the object 21 with light, observation of the defect portion starts.

[0093] In step S14, it is determined whether the reflected wave has been input to four pixels. As described with reference to Fig. 8, this process is a process for determining whether reflected light from a defect has been input to one pixel of the four 2x2 pixels. If it is determined in step S14 that the reflected wave has been input to four pixels, step S15 is omitted and the process proceeds to step S16.

[0094] On the other hand, if it is determined in step S14 that the reflected wave has not been input to four pixels, in other words, that it has been input to only one pixel, the process proceeds to step S15. In step S15, the blur of the lens 15 is controlled by the lens focus control unit 51 to create a blurred state. Once the blurred state has been created, the process returns to step S13, and the subsequent processes are repeated.

[0095] In step S16, the polarization signal processing unit 41 creates the graphs described with reference to Figures 7, 11, and 12 using the polarization images in four directions obtained from the polarization sensor 14. By creating the graphs, the degree of polarization and the azimuth angle of the ellipse are calculated. Although it is stated that a graph is created, data required to calculate the degree of polarization and the azimuth angle of the ellipse may be generated instead of actually creating a graph.

[0096] In step S17, the table is referenced and the surface angle of the defect is calculated. The field in which the degree of polarization and ellipse azimuth calculated in step S16 are recorded is detected, and the roll direction angle and pitch direction angle written in the column and record of that field are read out, thereby calculating the angle of the defect.

[0097] Here, we have explained an example in which a table is created and the angle of the defect is calculated by referring to the table, but it is also possible to configure the system so that the angle is calculated by performing a specified calculation using the obtained measurement values ​​or a graph obtained from the obtained measurement values.

[0098] By executing such processing, the presence or absence of defects in the object 21, as well as the position, size, depth, etc. of the defects, are detected.

[0099] This technology allows simultaneous surface defect inspection and shape estimation for shiny metal inspection surfaces. By using dark-field illumination, even minute defects and their shapes can be detected and classified. It can detect defects that cannot be detected using existing defect detection methods such as zebra lighting. By combining dark-field and polarization sensors, it is possible to observe finer shapes than when using only an RGB sensor or when using a polarization sensor with bright-field illumination.

[0100] This technology can be used to inspect plated parts, such as those found on automobiles. It can also be used to inspect shiny surfaces, such as semiconductor wafers, to detect minute changes in the surface. Applying this technology to measure the minute shapes of objects makes it possible to build accurate 3D models in the Metaverse.

[0101] <Regarding the Recording Medium> The above-described series of processes can be executed by hardware or software. When the series of processes is executed by software, the programs that make up the software are installed on a computer. Here, the term "computer" includes computers built into dedicated hardware, and general-purpose personal computers, for example, that can execute various functions by installing various programs.

[0102] 14 is a block diagram showing an example of the hardware configuration of a computer that executes the above-mentioned series of processes using a program. In the computer, a CPU (Central Processing Unit) 2001, a ROM (Read Only Memory) 2002, and a RAM (Random Access Memory) 2003 are interconnected by a bus 2004. An input / output interface 2005 is also connected to the bus 2004. An input unit 2006, an output unit 2007, a storage unit 2008, a communication unit 2009, and a drive 2010 are connected to the input / output interface 2005.

[0103] The input unit 2006 includes a keyboard, a mouse, a microphone, etc. The output unit 2007 includes a display, a speaker, etc. The storage unit 2008 includes a hard disk, a non-volatile memory, etc. The communication unit 2009 includes a network interface, etc. The drive 2010 drives removable media 2011 such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory.

[0104] In a computer configured as described above, the CPU 2001 performs the above-described series of processes by, for example, loading a program stored in the memory unit 2008 into the RAM 2003 via the input / output interface 2005 and the bus 2004 and executing it.

[0105] The program executed by the computer (CPU 2001) can be provided by being recorded on, for example, a removable medium 2011 such as a package medium. The program can also be provided via a wired or wireless transmission medium such as a local area network, the Internet, or digital satellite broadcasting.

[0106] In the computer, the program can be installed in the storage unit 2008 via the input / output interface 2005 by inserting the removable medium 2011 into the drive 2010. The program can also be received by the communication unit 2009 via a wired or wireless transmission medium and installed in the storage unit 2008. Alternatively, the program can be installed in advance in the ROM 2002 or the storage unit 2008.

[0107] The program executed by the computer may be a program that processes in chronological order according to the order described in this specification, or may be a program that processes in parallel or at the required timing, such as when called.

[0108] In this specification, a system refers to an entire device made up of multiple devices.

[0109] The effects described in this specification are merely examples and are not limiting, and other effects may also be present.

[0110] It should be noted that the embodiments of the present technology are not limited to the above-described embodiments, and various modifications are possible within the scope of the present technology.

[0111] The present technology may also be configured as follows. (1) A detection device comprising: a light source having a linear or planar irradiation surface; and an imaging unit that captures reflected light from an object irradiated with light from the light source, wherein the imaging unit includes a polarizer, and a perpendicular line from the irradiation surface of the light source intersects with a predetermined angle in a direction in which the imaging unit faces. (2) The detection device according to (1), wherein the light source is circular, and the perpendicular line is a line connecting the opposing irradiation surfaces in a cross-sectional view. (3) The detection device according to (1) or (2), wherein the perpendicular line intersects with a direction in which the imaging unit faces perpendicularly. (4) The detection device according to any of (1) to (3), wherein the light source is composed of an illuminator and a reflector that reflects light irradiated from the illuminator. (5) The detection device according to any of (1) to (4), wherein the light source irradiates light onto the object from an oblique direction. (6) The detection device according to any of (1) to (5), wherein the imaging unit further comprises: a pixel array unit in which four polarizers that transmit light vibrating in four different directions are arranged in a 2 x 2 matrix of four pixels; and a focus control unit that controls the focus of the imaging unit when the pixel receiving the reflected light from the object is one of the four pixels so that the reflected light received by the one pixel is received by the four pixels. (7) The detection device according to (6), wherein the focus control unit controls the imaging unit to defocus so that the reflected light is increased. (8) The detection device according to any of (1) to (7), further comprising: a holding unit that holds the object in a position where a normal surface of the object directly faces the imaging unit. (9) The detection device according to any of (1) to (8), further comprising: a calculation unit that calculates a degree of polarization and an elliptical azimuth angle from the intensity of the reflected light from the object received via the polarizer. (10) The detection device according to (9), wherein a table in which the degree of polarization and the elliptical azimuth angle are associated for each tilt angle of the object is referenced, and the angle corresponding to the degree of polarization and the elliptical azimuth angle calculated by the calculation unit is read out.(11) The detection device according to (10), which acquires the reflectance of the object and creates the table using the acquired reflectance. (12) A detection method, in which a detection device detects reflected light from an object using dark-field illumination with a polarization sensor equipped with a polarizer, and detects a surface shape of the object using the detection result. (13) The detection method according to (12), which calculates a degree of polarization and an elliptical azimuth angle from the detection result, refers to a table in which the degree of polarization and the elliptical azimuth angle are associated for each tilt angle of the object, and reads out the tilt angle corresponding to the precalculated degree of polarization and the elliptical azimuth angle. (14) The detection method according to (13), which calculates the degree of polarization and the elliptical azimuth angle using a result obtained by applying cosine fitting to the detection result.

[0112] REFERENCE SIGNS LIST 10 Detection device, 11 Light stand, 12 Lighting, 13 Reflector, 14 Polarization sensor, 15 Lens, 16 Shading cloth, 17 Object holder, 21 Object, 25 Information processing device, 31 Polarizer, 41 Polarization signal processing unit, 42 Surface shape calculation unit, 51 Lens focus control unit

Claims

1. A detection device comprising: a light source having a linear or planar illumination surface; and an imaging unit that images reflected light from an object illuminated with light from the light source, wherein the imaging unit has a polarizer, and a perpendicular line from the illumination surface of the light source intersects with a direction in which the imaging unit is facing at a predetermined angle.

2. The detection device according to claim 1, wherein the light source is circular, and the perpendicular line is a line connecting the opposing irradiation surfaces in a cross-sectional view.

3. The detection device according to claim 1, wherein the perpendicular line and the direction in which the imaging unit faces intersect perpendicularly.

4. The detection device according to claim 1, wherein the light source is composed of an illumination and a reflector that reflects the light emitted from the illumination.

5. The detection device according to claim 1, wherein the light source irradiates the object with light from an oblique direction.

6. The detection device according to claim 1, further comprising: a pixel array section in which the imaging section has four polarizers that transmit light vibrating in four different directions, each arranged in a 2 x 2 matrix of four pixels; and a focus control section that controls the focus of the imaging section when the pixel receiving the reflected light from the object is one of the four pixels, so that the reflected light received by the one pixel is received by the four pixels.

7. The detection device according to claim 6, wherein the focus control unit controls the imaging unit to be out of focus and controls the reflected light to be increased.

8. The detection device according to claim 1, further comprising a holding section for holding the object in a position where the normal surface of the object faces directly opposite the imaging section.

9. The detection device according to claim 1, further comprising a calculation unit that calculates a degree of polarization and an elliptical azimuth angle from the intensity of the reflected light from the object received through the polarizer.

10. The detection device according to claim 9, further comprising: a table in which the degree of polarization and the azimuth angle of the ellipse are associated with each tilt angle of the object; and the angle corresponding to the degree of polarization and the azimuth angle of the ellipse calculated by the calculation unit is read out.

11. The detection device according to claim 10, further comprising: acquiring a reflectance of the object; and creating the table using the acquired reflectance.

12. A detection method, comprising: a detection device detecting reflected light from an object using a dark-field illumination method with a polarization sensor equipped with a polarizer; and detecting the surface shape of the object using the detection result.

13. The detection method according to claim 12, further comprising: calculating a degree of polarization and an azimuth angle of an ellipse from the detection result; referring to a table in which the degree of polarization and the azimuth angle of an ellipse are associated with each tilt angle of the object; and reading out the tilt angle to which the previously calculated degree of polarization and azimuth angle of the ellipse correspond.

14. The detection method according to claim 13, further comprising the step of calculating the degree of polarization and the ellipse azimuth angle using a result of applying cosine fitting to the detection result.

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