JP2015197340A - inspection system and inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform abnormality detection with increased accuracy.SOLUTION: An inspection system according to an embodiment of the present invention comprises: an illumination unit for emitting irradiation light at a prescribed incident angle to a target surface comprising a plurality of layers; a first polarizing filter that passes a prescribed polarization component from the irradiation light; a second polarizing filter that passes a prescribed polarization component from the reflected light of the polarization component of the irradiation light with which the target surface is irradiated; an image-capturing unit for capturing an image of the target surface using the polarization component of the reflected light that has passed through the second polarizing filter; and a determination unit for determining, on the basis of the polarization component from the first polarizing filter and the polarization component from the second polarizing filter, whether the image captured by the image-capturing unit is an image of at least one of the plurality of layers.

Description

  Embodiments described herein relate generally to an inspection system and an inspection method.

  Conventionally, there has been proposed a technique for irradiating an object to be inspected, imaging reflected light from the surface of the object to be inspected as image data, and detecting an abnormality of the object to be inspected based on a change in luminance of the image data. Has been.

  In this case, a technique has been proposed in which the intensity of light applied to the object to be inspected is periodically changed and an abnormality is detected based on a change in luminance of the captured image data.

JP 2014-2125 A

  The surface to be inspected of the object to be inspected may be composed of, for example, a base, a surface coated on the base, and a plurality of layers such as a transparent layer thereon. In such a case, if it is possible to detect which layer has an abnormality, the abnormality can be detected more accurately.

  The inspection system of the embodiment includes an illumination unit that emits irradiation light at a predetermined incident angle with respect to a surface to be inspected composed of a plurality of layers, a first polarizing filter that transmits a predetermined polarization component from the irradiation light, and Imaging the surface to be inspected with a second polarization filter that transmits a predetermined polarization component from the reflected light of the polarization component of the irradiation light irradiated on the surface to be inspected, and a polarization component of the reflected light transmitted from the second polarization filter The captured image captured by the imaging unit based on the polarization component by the first polarization filter and the polarization component by the second polarization filter is an image of at least any one of the plurality of layers. And a determination unit for determining whether or not there is.

FIG. 1 is a diagram illustrating a configuration example of an inspection system according to the first embodiment. FIG. 2 is a graph showing an example of the relationship between the reflectance at the interface between air and glass and the incident angle. FIG. 3 is a diagram illustrating an example of the state of incidence of S-polarized light according to the first embodiment. FIG. 4 is a diagram illustrating an example of an observation state of a captured image in the case of S-polarized light reception in the first embodiment. FIG. 5 is a diagram illustrating an example of an observation state of a captured image in the case of receiving S-polarized light and receiving P-polarized light according to the first embodiment. FIG. 6 is a diagram illustrating an example of a P-polarized light incident state according to the first embodiment. FIG. 7 is a diagram illustrating an example of an observation state of a captured image in the case of receiving P-polarized light and receiving S-polarized light according to the first embodiment. FIG. 8 is a diagram illustrating an example of an observation state of a captured image when P-polarized light is incident and P-polarized light is received in the first embodiment. FIG. 9 is a diagram illustrating an example of a relationship between polarization information and a layer of reflected light in the first embodiment. FIG. 10 is a sequence diagram illustrating an example of a flow of inspection processing according to the first embodiment. FIG. 11 is a flowchart illustrating an example of the procedure of the image determination process according to the first embodiment. FIG. 12 is a diagram illustrating a configuration example of the inspection system according to the second embodiment. FIG. 13 is a block diagram illustrating a configuration of a time correlation camera according to the second embodiment. FIG. 14 is a conceptual diagram showing frames accumulated in time series in the time correlation camera of the second embodiment. FIG. 15 is a diagram illustrating an example of a fringe pattern irradiated by the illumination device of the second embodiment. FIG. 16 is a diagram illustrating a first detection example of abnormality of an object to be inspected by the time correlation camera of the second embodiment. FIG. 17 is a diagram illustrating an example of the amplitude of light that changes in accordance with the abnormality when the abnormality illustrated in FIG. FIG. 18 is a diagram illustrating a second example of detection of abnormality of an object to be inspected by the time correlation camera of the second embodiment. FIG. 19 is a diagram illustrating a third detection example of an abnormality of an object to be inspected by the time correlation camera according to the second embodiment. FIG. 20 is a diagram illustrating an example of a fringe pattern output from the illumination control unit according to the second embodiment to the illumination device. FIG. 21 is a diagram illustrating an example of a wave shape representing a stripe pattern after passing through the screen of the second embodiment. FIG. 22 is a flowchart illustrating a procedure of abnormality detection processing based on amplitude in the abnormality detection processing unit of the second embodiment. FIG. 23 is a flowchart illustrating a procedure of abnormality detection processing based on a phase in the abnormality detection processing unit of the second embodiment. FIG. 24 is a flowchart illustrating a procedure of abnormality detection processing based on amplitude and intensity in the abnormality detection processing unit of the second embodiment. FIG. 25 is a flowchart illustrating a procedure of an inspection process for an object to be inspected in the inspection system of the second embodiment.

(Embodiment 1)
FIG. 1 is a diagram illustrating a configuration example of an inspection system according to the first embodiment. As shown in FIG. 1, the inspection system of the first embodiment includes a PC 100, a camera 10, a lighting device 120, a screen 130, an arm 140, a first polarizing filter 160, and a second polarizing filter 170. I have.

  The arm 140 is used for fixing the object 150 to be inspected, and changes the surface of the object 150 that can be photographed by the camera 10 according to control from the PC 100.

  The illuminating device 120 is a device that irradiates the inspection object 150 with light. The screen 130 diffuses the light output from the illuminating device 120 and then irradiates the test object 150 with light in a plane. Here, the illuminating device 120 irradiates the surface to be inspected with an incident angle that does not reflect all the P-polarized light of the illumination light on the surface of the clear layer of the surface to be inspected later. Details of the incident angle will be described later.

  The screen 130 according to this embodiment irradiates the object 150 with light input from the illumination device 120 in a plane.

  The first polarizing filter 160 is provided in the vicinity of the surface of the screen 130 on the side of the object to be inspected, and transmits polarized light in a predetermined direction from the irradiation light irradiated from the screen 130. In the present embodiment, the first polarizing filter 160 switches between S-polarized light and P-polarized light as polarized light in a predetermined direction and transmits it. Here, the first polarizing filter 160 can be removed. When the illumination light is irradiated on the surface to be inspected 150 without being polarized, the inspector applies the first polarizing filter 160 to the screen 130. Remove from the front.

  The second polarizing filter 170 is provided in front of the lens of the camera 10 and transmits polarized light in a predetermined direction from the reflected light from the surface to be inspected of the inspection object 150. In the present embodiment, the second polarizing filter 170 switches between S-polarized light and P-polarized light as polarized light in a predetermined direction and transmits it. For each of the first polarizing filter 160 and the second polarizing filter 170, information indicating the S polarization transmission state and the P polarization transmission state is referred to as polarization information.

  Note that switching between the S-polarized light and the P-polarized light by the first polarizing filter 160 and the second polarizing filter 170 is performed by manually rotating the first polarizing filter 160 and the second polarizing filter 170 by the inspector. . However, the present invention is not limited to this. Means for switching between the S-polarized light and the P-polarized light by rotating each of the first polarizing filter 160 and the second polarizing filter 170 according to a command from the PC 100, etc. You may comprise so that it may provide.

  Further, an optical system component such as a condensing Fresnel lens may be provided between the illumination device 120 and the screen 130.

  In addition, although this embodiment demonstrates the example which combines the illuminating device 120 and the screen 130 and comprises a planar illumination part, it does not restrict | limit to such a combination, for example, LED is planarly formed. You may arrange | position and comprise an illumination part.

  As shown in FIG. 1, the PC 100 mainly includes an arm control unit 101, an illumination control unit 102, a determination unit 103, an abnormality detection processing unit 105, and a memory 107 as functional configurations. The hardware configuration of the PC 100 is a configuration of a normal computer including a CPU, a memory 107 such as a RAM and a ROM, an input device such as a keyboard and a mouse, a display device such as a display, and the like.

  The memory 107 stores the polarization information of each of the first polarizing filter 160 and the second polarizing filter 170, that is, the state of P polarization transmission or the state of S polarization transmission in time series. The polarization information is registered in the memory 107 manually by an inspector via an input device. When the PC 100 switches the first polarization filter 160 and the second polarization filter 170, the PC 100 registers the polarization information in the memory 107. You may comprise as follows.

  The arm control unit 101 controls the arm 140 in order to change the surface of the object 150 to be imaged by the camera 10. In the present embodiment, in the PC 100, a plurality of surfaces to be imaged of the inspected object are set. Then, every time the camera 10 finishes photographing the object 150, the arm 140 moves the object 150 so that the arm controller 101 can photograph the surface on which the camera 10 is set according to the setting. . The present embodiment is not limited to repeating the movement of the arm each time shooting is completed and stopping the shooting before the shooting is started, and the arm 140 may be continuously driven. The arm 140 may also be referred to as a transport unit, a moving unit, a position changing unit, a posture changing unit, or the like.

  The illumination control unit 102 controls irradiation of the illumination device 120 in order to inspect the inspected object 150. The illumination control unit 102 according to the present embodiment controls the illumination device 120 so as to emit plain pattern illumination light.

  The determination unit 103 acquires a captured image from the camera 10 and acquires the polarization information of each of the first polarization filter 160 and the second polarization filter 170 from the memory 107. Then, the determination unit 103 determines, based on the polarization information, whether the captured image is captured by reflected light from which of a plurality of layers constituting the inspection surface, that is, which layer of the plurality of layers of the captured image It is determined whether it is an image. Hereinafter, this determination is referred to as image determination.

  The abnormality detection processing unit 105 detects a defect for each layer of the surface to be inspected from the determination result by the determination unit 103 and the captured image. In the present embodiment, a known technique can be used as the abnormality detection technique.

  Details of the image determination will be described here. The surface to be inspected is composed of a surface painted on the base and a clear layer transparently coated on the painted surface. Here, metallic particles by painting exist as a painted surface on the base. Hereinafter, the base and the metallic particles on the painted surface are collectively referred to as an inner layer.

  Based on the polarization information component of the first polarization filter 160 and the polarization information of the second polarization filter 170, the determination unit 103 is an image obtained by capturing the captured image with reflected light from the surface of the clear layer (imaging of the surface of the clear layer). Image), an image captured with reflected light from the inner layer metallic particles (captured image of the inner layer surface), or an image captured with reflected light from the ground (ground captured image).

  Hereinafter, the case where the illumination light is emitted as S-polarized light by the first polarizing filter 160 and enters the surface to be inspected is referred to as S-polarized light incidence, and the illumination light is emitted as P-polarized light by the first polarizing filter 160 and the surface to be inspected. Is incident as P-polarized light. A case where the object 150 is irradiated with illumination light without providing the first polarizing filter 160 is referred to as non-polarized incident.

  The case where the reflected light from the surface to be inspected is captured by the camera 10 as S-polarized light by the second polarizing filter 170 is called S-polarized light reception, and the reflected light from the surface to be inspected is converted to P-polarized light by the second polarizing filter 170. A case where the image is captured by the camera 10 is referred to as P-polarized light reception.

  The incident angle of the illumination light on the surface to be inspected will be described. FIG. 2 is a graph showing the relationship between the reflectance at the interface between air and glass and the incident angle. FIG. 2 shows the relationship of reflectance with respect to the incident angles of S-polarized light and P-polarized light. Although not shown, the reflectivity at the interface between air and a metal such as aluminum shows high reflectivity for both S-polarized light and P-polarized light, but the reflectivity at the interface between air and a dielectric such as glass is shown in FIG. As shown in 2. As can be seen from FIG. 2, the reflectance of S-polarized light increases as the incident angle increases from 0 ° to 90 °, while the reflectance of P-polarized light is about 5% when the incident angle is 0 °. As the angle increases, it gradually decreases. When the incident angle is about 60 °, the reflectance of P-polarized light becomes zero. Thereafter, the reflectance increases rapidly as the incident angle increases.

  In the present embodiment, the illumination device 120 is configured to irradiate the surface to be inspected with an incident angle (60 ° in the example of FIG. 2) when the reflectance of P-polarized light becomes 0. For this reason, the P-polarized light irradiated on the surface to be inspected does not reflect on the surface of the clear layer, passes through the clear layer, and reaches the inner layer.

  A case where illumination light is emitted as S-polarized light by the first polarizing filter 160 and enters the surface to be inspected (S-polarized light incidence) will be described. FIG. 3 is a diagram illustrating an example of the state of incidence of S-polarized light according to the first embodiment.

  As shown in FIG. 3, the S-polarized light of the illumination light emitted from the first polarizing filter 160 is reflected by the surface of the clear layer and transmitted to the camera 10 in the S-polarized state, and transmitted through the clear layer. Light reflected by the metallic particles on the inner layer surface and traveling toward the camera 10 in the S-polarized state, and enters the inner layer and repeats a number of reflections inside the inner layer. As a result, it becomes unpolarized and exits from the inner layer and the clear layer. The light is directed toward the camera 10.

  FIG. 4 is a diagram illustrating an example of an observation state of a captured image in the case of S-polarized light reception in the first embodiment. S-polarized light incidence and S-polarized light reception are cases where the first polarizing filter 160 transmits S-polarized light and the second polarizing filter 170 transmits S-polarized light for observation.

  In this case, since the camera 10 images the reflected light (S-polarized light) from the surface of the clear layer with the S-polarized light through the second polarizing filter 170 and observes it, as shown in FIG. Surface reflected light is observed. In addition, since the camera 10 images the reflected light (S-polarized light) from the surface of the inner layer with the S-polarized light through the second polarizing filter 170 and observes it, as shown in FIG. 4, it exists on the surface of the inner layer. Metallic particles are observed. Further, the S-polarized light transmitted to the inside of the inner layer becomes non-polarized by a large number of reflections inside, and is emitted from the inner layer and the clear layer, so that it is observed as reflected light of the base via the second polarizing filter 170.

  FIG. 5 is a diagram illustrating an example of an observation state of a captured image in the case of receiving S-polarized light and receiving P-polarized light according to the first embodiment. S-polarized light incidence and P-polarized light reception are cases where the first polarizing filter 160 transmits S-polarized light and the second polarizing filter 170 transmits P-polarized light for observation.

  In this case, as shown in FIG. 5, both the reflected light from the surface of the clear layer (S-polarized light) and the reflected light from the metallic particles present on the surface of the inner layer (S-polarized light) transmit P-polarized light. The light is blocked by the second polarizing filter 170 and is not received by the camera 10. On the other hand, the S-polarized light transmitted to the inside of the inner layer becomes non-polarized by a large number of reflections inside, and is emitted from the inner layer and the clear layer, so that it is observed as reflected light of the base via the second polarizing filter 170.

  Next, the case where illumination light is emitted as P-polarized light by the first polarizing filter 160 and enters the surface to be inspected (P-polarized light incidence) will be described. FIG. 6 is a diagram illustrating an example of a P-polarized light incident state according to the first embodiment.

  As shown in FIG. 6, the P-polarized light of the illumination light emitted from the first polarizing filter 160 is irradiated onto the surface to be inspected at an incident angle at which the reflectance of the P-polarized light becomes 0 as described above. The clear layer is transmitted without reflecting the surface. Then, the light reflected by the metallic particles on the surface of the inner layer and directed toward the camera 10 in the P-polarized state enters the inside of the inner layer and repeats a number of reflections inside the inner layer. As a result, the inner layer and the clear layer become non-polarized. The light is emitted from the light and travels toward the camera 10.

  FIG. 7 is a diagram illustrating an example of an observation state of a captured image in the case of receiving P-polarized light and receiving S-polarized light according to the first embodiment. P-polarized light incidence and S-polarized light reception are cases in which P-polarized light is transmitted through the first polarizing filter 160 and S-polarized light is transmitted through the second polarizing filter 170 for observation.

  In this case, since the P-polarized light is not reflected from the surface of the clear layer, the reflected light on the surface of the clear layer is not observed as shown in FIG. Further, since the camera 10 images the reflected light (P-polarized light) from the surface of the inner layer with the S-polarized light through the second polarizing filter 170 and observes it, as shown in FIG. 7, it exists on the surface of the inner layer. Reflected light from the metallic particles is blocked by the second polarizing filter 170, and the metallic particles cannot be observed by the camera 10. On the other hand, the P-polarized light transmitted to the inside of the inner layer becomes non-polarized by a large number of reflections inside, and is emitted from the inner layer and the clear layer, so that it is observed as reflected light of the base via the second polarizing filter 170. .

  FIG. 8 is a diagram illustrating an example of an observation state of a captured image when P-polarized light is incident and P-polarized light is received in the first embodiment. P-polarized light incidence and P-polarized light reception are cases in which P-polarized light is transmitted through the first polarizing filter 160 and P-polarized light is transmitted through the second polarizing filter 170 for observation.

  In this case, as shown in FIG. 8, since the P-polarized light is not reflected from the surface of the clear layer, the reflected light on the surface of the clear layer is not observed. Further, since the camera 10 images the reflected light (P-polarized light) from the surface of the inner layer with P-polarized light through the second polarizing filter 170 and observes it, as shown in FIG. 8, it exists on the surface of the inner layer. Metallic particles are observed. Further, the P-polarized light transmitted to the inside of the inner layer becomes non-polarized by a large number of reflections inside, and is emitted from the inner layer and the clear layer, so that it is observed as the reflected light of the base via the second polarizing filter 170.

  As described above, the determination unit 103 performs polarization information on the captured image captured by the camera 10, that is, S-polarized incident and S-polarized observation, S-polarized incident and P-polarized observation, P-polarized incident and S-polarized observation, P According to polarization incident and P-polarized observation, P-polarized incident and non-polarized observation, and P-polarized incident and non-polarized observation, the captured image is an image captured by reflected light of any layer, that is, the captured image is Determine if the image is a layer.

  FIG. 9 is a diagram illustrating a relationship between polarization information and a layer of reflected light in the first embodiment. In FIG. 9, in each of the cases of S-polarized light incident, P-polarized light incident, and non-polarized light incident, the reflected light observed by the S-polarized light reception and the P-polarized light reception is reflected from which layer on the surface to be inspected. Show.

  As shown in FIG. 9, in the case of S-polarized light reception and S-polarized light reception, the determination unit 103 is an image in which a captured image is captured by reflected light from the surface of the clear layer and reflected light from the inner layer (metallic particles and the ground), that is, The image is determined to be an image of the surface of the clear layer, the metallic particles, and the base. Further, in the case of receiving S-polarized light and P-polarized light, the determination unit 103 determines that the captured image is an image captured by reflected light from the background, that is, an image of the background, as shown in FIG.

  Further, in the case of P-polarized incident and S-polarized light reception, the determination unit 103 determines that the captured image is an image captured with reflected light from the background, that is, an image of the background, as shown in FIG. Further, in the case of incident P-polarized light and P-polarized light reception, the determination unit 103 determines that the captured image is an image captured with reflected light from the background, that is, the background image, as shown in FIG.

  Further, in the case of S-polarized light reception with no polarization incident, the determination unit 103 captures the captured image with reflected light from the surface of the clear layer and reflected light from the inner layer (metallic particles and the ground) as shown in FIG. It is determined that the image is a clear layer surface, metallic particle, and background image. In the case of non-polarized incidence and P-polarized light reception, the determination unit 103, as shown in FIG. 9, is an image in which a captured image is captured with reflected light from the inner layer (metallic particles and ground), that is, metallic particles and ground. It is determined that the image is.

  Next, the inspection process of the inspected object 150 by the PC 100 of the inspection system of the present embodiment configured as described above will be described. FIG. 10 is a sequence diagram illustrating a flow of inspection processing according to the first embodiment.

  In the present embodiment, the polarization state of the first polarizing filter 160 installed in front of the screen 130 is fixed to either S-polarized light transmission or P-polarized light transmission, and the first polarizing filter 160 provided in front of the camera 10 is fixed. It is assumed that the polarization of the two-polarization filter 170 is switched.

  In addition, it is assumed that illumination light having a plain pattern is emitted from the illumination device 120 to the screen 130.

  First, the inspector switches the polarization state of the second polarizing filter on the camera 10 side (step S1011). The camera 10 receives the reflected light from the surface to be inspected of the inspection object 150 via the second polarizing filter 170, thereby imaging the surface to be inspected (step S1012). Then, the camera 10 outputs the captured image data to the PC 100 (step S1013).

  The processes from step S1011 to S1013 are executed by repeating the second polarizing filter 170 twice in different polarization states for the same region of the surface to be inspected. For example, in the first process, the second polarizing filter 170 transmits S-polarized light so as to receive S-polarized light, and in the second process, the second polarizing filter 170 is switched so as to transmit P-polarized light and receives P-polarized light. And so on. As a result, two pieces of captured image data are obtained by S-polarized light reception and P-polarized light reception, and are output to the PC 100.

  The PC 100 receives two pieces of captured image data from the camera 10 (step S1101). Then, the determination unit 103 performs an image determination process on the two captured image data (step S1002).

  FIG. 11 is a flowchart illustrating a procedure of image determination processing according to the first embodiment. The determination unit 103 acquires the polarization information of the first polarization filter 160 and the polarization information of the second polarization filter 170 set in the memory 107 (step S11). Here, with respect to the polarization information of the second polarization filter 170, the polarization information at the time of imaging of the first captured image data, and the polarization information at the time of imaging of the second captured image data are respectively acquired.

  Then, the determination unit 103 reflects reflected light from the polarization information of the first polarization filter 160 and the polarization information at the time of imaging of the first captured image data of the second polarization filter 170 with respect to the first captured image data. Is determined (step S12). That is, it is determined whether the first captured image data is an image captured by reflected light from any layer. The determination method is performed as described above based on the table of FIG. Thereby, the layer which imaged the 1st picked-up image data as a determination result is obtained.

  Next, the determination unit 103 reflects the polarization information of the first polarization filter 160 and the polarization information at the time of imaging of the second captured image data of the second polarization filter 170 with respect to the second captured image data. The light is determined (step S13). That is, it is determined whether the second captured image data is an image captured with reflected light from any layer. As a result, a layer obtained by capturing the second captured image data is obtained as a determination result.

  Next, the determination unit 103 generates a difference image that is a difference between the first captured image data and the second captured image data (step S14). And the determination part 103 determines the reflected light which imaged this difference image (step S15).

  The reason for obtaining the difference image and determining the reflected light in this way is as follows. For example, when imaging the first captured image data, the polarization information of the first polarizing filter 160 is S-polarized light transmission, and the polarization information of the second polarizing filter 170 is S-polarized light transmission, that is, S-polarized light. In the case of observing S-polarized light with incidence, as shown in the table of FIG. 2, the determination unit 103 determines that the first image is image data including a captured image of the clear layer surface, a captured image of metallic particles on the inner layer surface, and a background image. It is determined that the image is a captured image. That is, it is not possible to narrow down to a specific layer only with the first captured image data.

  On the other hand, when imaging the second captured image data obtained by imaging the same area of the surface to be inspected, the polarization information of the first polarizing filter 160 is S-polarized light transmission, and the polarization information of the second polarizing filter 170 is P-polarized light. In the case of transmission, that is, in the case of S-polarized light incidence and P-polarized light observation, the determination unit 103 determines that the image data of the second image is the background image as shown in the table of FIG.

  For this reason, when the difference between the first imaged image data and the second imaged image data is taken, the background image is removed from the difference image, and the reflected light and metallic particles from the surface of the clear layer are removed. An image by reflected light is obtained, and at least a clear layer image and a ground image can be separated. In this case, in step S15, the reflected light of the difference image is specified as the reflected light from the clear layer surface and the reflected light from the metallic particles.

  Then, the determination unit 103 outputs the first captured image data, the first captured image data, and the difference image to the abnormality determination processing unit 105 in association with the respective determination results (step S16).

  Returning to FIG. 10, when the image determination process in step S1002 is completed, the abnormality detection processing unit 105 executes an abnormality detection process for determining whether or not a defect exists on the inspection surface using the determination result of the image determination (step S1002). S1003). That is, as a result of the image determination, since the captured image is understood to be either a clear layer or an underlayer image, the abnormality detection processing unit 105 determines whether there is a defect in the clear layer of the surface to be inspected, It becomes possible to detect the presence or absence of defects. Then, the abnormality detection processing unit 105 outputs the abnormality detection result to a display device (not shown) included in the PC 1100 (step S1004).

  The arm control unit 101 determines whether or not the inspection of the object to be inspected is completed (step S1005). When it is determined that the inspection is not completed (step S1005: No), the arm control unit 101 can capture the surface of the object to be inspected with the camera 10 in accordance with a predetermined setting. Then, the movement control of the arm is performed (step S1006).

  On the other hand, when the arm control unit 101 determines that the inspection of the object to be inspected has ended (step S1005: Yes), the process ends.

  As described above, in this embodiment, the determination unit 103 of the PC 100 uses the polarization information of the first polarization filter 160 and the polarization information of the second polarization filter 170 to detect S-polarized light and S-polarized light, S-polarized light and P-polarized light, It is determined whether the pattern is P-polarized incident and S-polarized observation, P-polarized incident and P-polarized observation, P-polarized incident and non-polarized observation, or P-polarized incident and non-polarized observation. Then, the abnormality detection processing unit 105 determines whether the reflected light is reflected light from the clear layer, the inner layer, or the underlying layer that constitutes the surface to be inspected according to the pattern, and then performs defect detection. Yes. For this reason, according to this embodiment, a more accurate defect inspection can be performed.

  In the present embodiment, the polarization state of the first polarizing filter 160 is fixed and not switched. However, the present invention is not limited to this, and the polarization state of the first polarizing filter 160 may be switched. .

  Further, in the present embodiment, the abnormality detection process is performed for each layer after obtaining the clear layer image by taking the difference between the two captured images of the clear layer and inner layer captured images and the ground captured image. However, the present invention is not limited to this. For example, the abnormality detection process is performed on the captured images of the clear layer and the inner layer, the abnormality detection process is performed on the captured image of the background, and the difference between the detection results is used to determine the presence or absence of defects in the clear layer and the number of defects. The unit 103 and the abnormality detection processing unit 105 may be configured.

(Embodiment 2)
In the present embodiment, in an inspection system using a time correlation camera, an abnormality such as the presence / absence of a defect is detected by determining which layer of the surface to be inspected is captured using polarization information. That is, the inspection system according to the present embodiment uses a time correlation camera instead of the camera according to the first embodiment, and irradiates the surface to be inspected with illumination light having a fringe pattern.

  FIG. 12 is a diagram illustrating a configuration example of the inspection system according to the present embodiment. As shown in FIG. 12, the inspection system of the present embodiment includes a PC 1100, a time correlation camera 110, an illumination device 120, a screen 130, an arm 140, a first polarizing filter 160, and a second polarizing filter 170. And.

  The arm 140 is used to fix the inspection object 150 and changes the position and orientation of the surface of the inspection object 150 that can be imaged by the time correlation camera 110 according to control from the PC 1100.

  The illuminating device 120 is a device that irradiates light to the object 150 to be inspected, and can control the intensity of irradiated light in units of regions in accordance with a stripe pattern from the PC 1100. Furthermore, the illuminating device 120 can control the intensity | strength of the light of the said area unit according to periodic time transition. In other words, the lighting device 120 can give a periodic temporal change and a spatial change of the light intensity. A specific light intensity control method will be described later.

  The screen 130 diffuses the light output from the illuminating device 120 and then irradiates the test object 150 with light in a plane. The screen 130 according to the present embodiment irradiates the object 150 in a surface with the light input from the illumination device 120 and subjected to periodic time change and space change. An optical system component (not shown) such as a condensing Fresnel lens may be provided between the illumination device 120 and the screen 130.

  In addition, although this embodiment demonstrates the example which comprises the planar illumination part which combines the illumination device 120 and the screen 130, and gives the periodic time change and spatial change of light intensity, such a combination is demonstrated. For example, the illumination unit may be configured by arranging LEDs in a plane.

  Similar to the first embodiment, the first polarizing filter 160 is provided in the vicinity of the surface of the screen 130 on the side of the object to be inspected, and switches between S-polarized light and P-polarized light from the irradiation light irradiated from the screen 130. To Penetrate. The second polarizing filter 170 is provided in front of the lens of the time correlation camera 110, and switches S-polarized light and P-polarized light from the reflected light from the surface to be inspected 150 and transmits the light.

  The time correlation camera 110 includes an optical system 210, an image sensor 220, a data buffer 230, a control unit 240, and a reference signal output unit 250. FIG. 13 is a block diagram showing the configuration of the time correlation camera 110 of the present embodiment.

  The optical system 210 includes a photographic lens and the like, transmits a light beam from a subject (including an object to be inspected) outside the time correlation camera 110, and forms an optical image of the subject formed by the light beam.

  The image sensor 220 is a sensor that can output the intensity of light incident through the optical system 210 as a light intensity signal at high speed for each pixel.

  The light intensity signal of the present embodiment is a signal obtained by the illumination device 120 of the inspection system irradiating a subject (including an object to be inspected) with light and the image sensor 220 receiving reflected light from the subject.

  The image sensor 220 is, for example, a sensor that can be read out at a higher speed than a conventional sensor, and has a two-dimensional planar shape in which pixels are arranged in two kinds of directions: a row direction (x direction) and a column direction (y direction). It shall be configured. Each pixel of the image sensor 220 is defined as a pixel P (1,1),..., P (i, j),..., P (X, Y) (Note that the image size in this embodiment is X X Y). Note that the reading speed of the image sensor 220 is not limited and may be the same as the conventional one.

  The image sensor 220 receives a light beam from a subject (including an object to be inspected) transmitted by the optical system 210 and photoelectrically converts the light intensity signal (photographing) indicating the intensity of light reflected from the subject. Signal) is generated and output to the control unit 240. The image sensor 220 according to the present embodiment outputs the frame for each readable unit time.

  The control unit 240 according to the present embodiment includes, for example, a CPU, a ROM, a RAM, and the like. By executing an inspection program stored in the ROM, the transfer unit 241, the reading unit 242, and the intensity image superimposing unit 243. And a first multiplier 244, a first correlation image superimposing unit 245, a second multiplier 246, a second correlation image superimposing unit 247, and an image output unit 248. Note that the present invention is not limited to implementation with a CPU or the like, and may be implemented with an FPGA or an ASIC.

  The transfer unit 241 stores the frames composed of the light intensity signals output from the image sensor 220 in the data buffer 230 in time series order.

  The data buffer 230 accumulates frames composed of light intensity signals output from the image sensor 220 in time series.

  FIG. 14 is a conceptual diagram showing frames accumulated in time series in the time correlation camera 110 of the present embodiment. As shown in FIG. 14, the data buffer 230 of this embodiment stores a plurality of light intensity signals G (1, 1, t), every time t (t = t0, t1, t2,..., Tn). .., G (i, j, t),..., G (X, Y, t) are combined into a plurality of frames Fk (k = 1, 2,..., N) in chronological order. Accumulated. Note that one frame created at time t is a light intensity signal G (1, 1, t),..., G (i, j, t), ..., G (X, Y, t). Composed.

  A light intensity signal (imaging signal) G (1,1, t),..., G (i, j, t),. Each pixel P (1,1),..., P (i, j),..., P (X, Y) constituting k = 1, 2,.

  The frame output from the image sensor 220 includes only a light intensity signal, in other words, it can be considered as monochrome image data. In this embodiment, an example in which the image sensor 220 generates monochrome image data in consideration of resolution, sensitivity, cost, and the like will be described. However, the image sensor 220 is not limited to a monochrome image sensor. Alternatively, a color image sensor may be used.

  Returning to FIG. 13, the reading unit 242 of this embodiment receives the light intensity signals G (1,1, t),..., G (i, j, t),. Y, t) are read out in frame-by-frame order, and output to the first multiplier 244, the second multiplier 246, and the intensity image superimposing unit.

  The time correlation camera 110 of the present embodiment generates image data for each output destination of the reading unit 242. In other words, the time phase camera creates three types of image data.

  The time correlation camera 110 of this embodiment generates intensity image data and two types of time correlation image data as three types of image data. Note that the present embodiment is not limited to generating three types of image data, and it may be possible to generate no intensity image data or to generate one or more types of time-correlated image data. .

  As described above, the image sensor 220 of the present embodiment outputs a frame composed of a light intensity signal every unit time. However, in order to generate normal image data, a light intensity signal corresponding to the exposure time necessary for photographing is required. Therefore, in the present embodiment, the intensity image superimposing unit 243 generates intensity image data by superimposing a plurality of frames for an exposure time necessary for photographing. In addition, each pixel value (value representing the intensity of light) G (x, y) of the intensity image data can be derived from the following equation (1). The exposure time is the time difference between t0 and tn.

  Thereby, the intensity image data in which the subject (including the object to be inspected) is photographed is generated in the same manner as the conventional camera photographing. Then, the intensity image superimposing unit 243 outputs the generated intensity image data to the image output unit 248.

  The time correlation image data is image data indicating changes in light intensity according to time transition. That is, in the present embodiment, for each frame in time series order, the light intensity signal included in the frame is multiplied by the reference signal indicating the time transition, and the reference signal, the light intensity signal, and the time that is the multiplication result Temporal correlation image data is generated by generating a temporal correlation value frame composed of correlation values and superimposing a plurality of temporal correlation value frames.

  By the way, in order to detect abnormality of the object to be inspected using the time correlation image data, it is necessary to change the light intensity signal input to the image sensor 220 in synchronization with the reference signal. For this purpose, as described above, the illumination device 120 performs planar light irradiation that periodically gives temporal changes and spatial movement of the stripes via the screen 130.

In this embodiment, two types of time correlation image data are generated. The reference signal may be a signal representing a time transition, but in the present embodiment, a complex sine wave e ^−jωt is used. It is assumed that the angular frequency is ω and the time is t. The angular frequency ω is such that the complex sine wave e ^−jωt representing the reference signal correlates with one period of the above-described exposure time (in other words, the time required to generate the intensity image data and the time correlation image). It shall be set. In other words, the planar and dynamic light formed by the illumination unit 120 and the illumination unit such as the screen 130 is in a first period (time period) at each position on the surface (reflection surface) of the inspection object 150. And a distribution of increase or decrease in spatial irradiation intensity in a second period (spatial period) along at least one direction along the surface. When this planar light is reflected by the surface, it is complex-modulated according to the specifications of the surface (normal vector distribution, etc.). The time correlation camera 110 receives the light complex-modulated on the surface and performs quadrature detection (orthogonal demodulation) using the reference signal of the first period, thereby obtaining time correlation image data as a complex signal. By modulation / demodulation based on such complex time correlation image data, it is possible to detect features corresponding to the surface normal vector distribution.

The complex sine wave e ^−jωt can also be expressed as e ^−jωt = cos (ωt) −j · sin (ωt). Accordingly, each pixel value C (x, y) of the time correlation image data can be derived from the following equation (2).

  In this embodiment, in the formula (2), two types of time correlation image data are divided into a pixel value C1 (x, y) representing the real part and a pixel value C2 (x, y) representing the imaginary part. Generate.

For this reason, the reference signal output unit 250 generates and outputs different reference signals for the first multiplier 244 and the second multiplier 246, respectively. Reference signal output section 250 of this embodiment outputs the first reference signal cosωt corresponding to the real part of the complex sine wave e ^-Jeiomegati the first multiplier 244, the imaginary part of the complex sine wave e ^-Jeiomegati The corresponding second reference signal sin ωt is output to the second multiplier 246. As described above, the reference signal output unit 250 according to the present embodiment describes an example in which two types of reference signals expressed as time functions of a sine wave and a cosine wave that form a Hilbert transform pair are described. Any reference signal that changes with time transition such as a function may be used.

Then, the first multiplier 244 ^calculates the real part cosωt of the complex sine wave e ^−jωt input from the reference signal output unit 250 for each light intensity signal of the frame in units of frames input from the reading unit 242. Multiply.

  The first correlation image superimposing unit 245 performs a process of superimposing the multiplication result of the first multiplier 244 on a pixel-by-pixel basis for a plurality of frames for an exposure time necessary for photographing. Thereby, each pixel value C1 (x, y) of the first time correlation image data is derived from the following equation (3).

The second multiplier 246 multiplies the light intensity signal of the frame input from the reading unit 242 by the imaginary part sin ^ωt of the complex sine wave e ^−jωt input from the reference signal output unit 250.

  The second correlation image superimposing unit 247 performs a process of superimposing the multiplication result of the second multiplier 246 on a pixel-by-pixel basis for a plurality of frames corresponding to the exposure time necessary for photographing. Thereby, each pixel value C2 (x, y) of the second time correlation image data is derived from the following equation (4).

  By performing the processing described above, two types of time correlation image data, in other words, time correlation image data having two degrees of freedom can be generated.

Further, the present embodiment does not limit the type of reference signal. For example, in this embodiment, two types of time-correlated image data of the real part and the imaginary part of the complex sine wave e ^−jωt are created, but two types of image data based on the light amplitude and the light phase are generated. May be.

  Note that the time correlation camera 110 of the present embodiment can create a plurality of systems as time correlation image data. Thereby, for example, when light in which stripes having a plurality of types of widths are combined is irradiated, two types of time correlation image data based on the real part and the imaginary part described above can be created for each stripe width. For this purpose, the time correlation camera 110 includes a combination of two multipliers and two correlation image superimposing units for a plurality of systems, and the reference signal output unit 250 has an angular frequency suitable for each system. The reference signal by ω can be output.

  Then, the image output unit 248 outputs two types of time correlation image data and intensity image data to the PC 1100. As a result, the PC 1100 detects an abnormality of the object to be inspected using the two types of time correlation image data and the intensity image data. For that purpose, it is necessary to irradiate the subject with light.

  The illuminating device 120 of this embodiment irradiates the fringe pattern which moves at high speed. FIG. 15 is a diagram illustrating an example of a fringe pattern irradiated by the illumination device 120 of the present embodiment. In the example illustrated in FIG. 15, the stripe pattern is scrolled (moved) in the x direction. A white area is a bright area corresponding to the stripe, and a black area is an interval area (dark area) corresponding to the stripe.

  In the present embodiment, the fringe pattern irradiated by the illuminating device 120 is moved by one period with the exposure time when the time correlation camera 110 captures the intensity image data and the time correlation image data. Thereby, the illuminating device 120 gives the time change of the light intensity periodically by the spatial movement of the stripe pattern of the light intensity. In this embodiment, the time during which the fringe pattern in FIG. 15 moves by one cycle corresponds to the exposure time, so that each pixel of the time-correlated image data relates to at least a light intensity signal for one cycle of the fringe pattern. Information is embedded.

  As shown in FIG. 15, in this embodiment, an example in which the illumination device 120 irradiates a stripe pattern based on a rectangular wave will be described, but other than a rectangular wave may be used. In the present embodiment, the illumination device 120 is irradiated through the screen 130, so that the bright and dark boundary region of the rectangular wave can be blurred.

  In this embodiment, the stripe pattern irradiated by the illumination device 120 is represented as A (1 + cos (ωt + kx), that is, the stripe pattern includes a plurality of stripes repeatedly (periodically). The intensity of the light applied to can be adjusted between 0 and 2 A, and is the light phase kx, where k is the wave number of the stripes, and x is the direction in which the phase changes.

  The fundamental frequency component of the light intensity signal f (x, y, t) of each pixel in the frame can be expressed as the following equation (5). As shown in Expression (5), the brightness of the stripe changes in the x direction.

f (x, y, t) = A (1 + cos (ωt + kx))
= A + A / 2 {e ^{j (ωt + kx)} + e− ^{j (ωt + kx)} } (5)

  As shown in Expression (5), the intensity signal of the fringe pattern irradiated by the illumination device 120 can be considered as a complex number.

  Then, the light from the illumination device 120 is reflected and input to the image sensor 220 from the subject (including the object to be inspected).

  Therefore, the light intensity signal G (x, y, t) input to the image sensor 220 can be used as the light intensity signal f (x, y, t) of each pixel of the frame when the illumination device 120 is irradiated. Therefore, when Expression (5) is substituted into Expression (1) for deriving intensity image data, Expression (6) can be derived. The phase is kx.

  From Expression (6), it can be confirmed that each pixel of the intensity image data is input with a value obtained by multiplying the exposure time T by the intermediate value A of the intensity of the light output from the illumination device 120. Further, when Expression (5) is substituted into Expression (2) for deriving time correlation image data, Expression (7) can be derived. Note that AT / 2 is the amplitude and kx is the phase.

  Thereby, the time correlation image data shown by the complex number shown by Formula (7) is replaceable with the two types of time correlation image data mentioned above. That is, the above-described time correlation image data composed of the real part and the imaginary part includes a phase change and an amplitude change due to a change in light intensity irradiated on the test object. In other words, the PC 1100 according to the present embodiment can detect the phase change of the light emitted from the illumination device 120 and the light amplitude change based on the two types of time correlation image data. Therefore, the PC 1100 of the present embodiment, based on the time correlation image data and the intensity image data, amplitude image data representing the amplitude of light entering each pixel and phase image data representing the phase change of light entering each pixel. And generate.

  Furthermore, the PC 1100 detects an abnormality of the object to be inspected based on the generated amplitude image data and phase image data.

  By the way, when an abnormality based on the unevenness occurs in the surface shape of the object to be inspected, a change corresponding to the abnormality occurs in the distribution of normal vectors on the surface of the object to be inspected. Further, when an abnormality that absorbs light occurs on the surface of the object to be inspected, the intensity of the reflected light changes. A change in the normal vector distribution is detected as at least one of a phase change and an amplitude change of light. Thus, in the present embodiment, using the time correlation image data and the intensity image data, at least one of the light phase change and the amplitude change corresponding to the change in the normal vector distribution is detected. Thereby, the abnormality of the surface shape can be detected. Next, the relationship between the abnormality of the inspected object, the normal vector, and the phase change or amplitude change of light will be described.

  FIG. 16 is a diagram illustrating a first detection example of abnormality of an object to be inspected by the time correlation camera 110 according to the first embodiment. In the example shown in FIG. 16, it is assumed that there is a protrusion-shaped abnormality 501 on the inspection object 500. In this situation, it can be confirmed that the normal vectors 521, 522, and 523 are in different directions in the region near the point 502 of the abnormality 501. The normal vectors 521, 522, 523 are directed in different directions, so that diffusion (for example, light 511, 512, 513) is generated in the light reflected from the anomaly 501, and the image sensor 220 of the time correlation camera 110. The width 503 of the fringe pattern entering the arbitrary pixel 531 is increased.

  FIG. 17 is a diagram illustrating an example of the amplitude of light that changes in accordance with the abnormality when the abnormality 501 illustrated in FIG. In the example shown in FIG. 17, the amplitude of light is divided into a real part (Re) and an imaginary part (Im) and is represented on a two-dimensional plane. In FIG. 17, the light amplitudes 611, 612, and 613 corresponding to the lights 511, 512, and 513 in FIG. The light amplitudes 611, 612, and 613 cancel each other, and light having an amplitude 621 is incident on the arbitrary pixel 531 of the image sensor 220.

  Therefore, in the situation shown in FIG. 17, it can be confirmed that the amplitude is small in the region where the abnormality 501 of the specimen 500 is imaged. In other words, when there is a region that is darker than the surroundings in the amplitude image data showing the change in amplitude, it can be assumed that there is a cancellation of the amplitude of light in the region, It can be determined that an abnormality 501 has occurred at the position of the corresponding inspection object 500.

  The inspection system according to the present embodiment is not limited to the one in which the inclination changes steeply like the abnormality 501 in FIG. 16, and can also detect an abnormality that changes gently. FIG. 18 is a diagram illustrating a second detection example of the abnormality of the inspected object by the time correlation camera 110 according to the first embodiment. In the example shown in FIG. 18, the surface of the object to be inspected is flat (in other words, the normal line is parallel) in the normal case, but a gentle gradient 701 is generated in the object 700 to be inspected. In such a situation, the normal vectors 721, 722, and 723 on the gradient 701 also change gently. Accordingly, the light beams 711, 712, and 713 input to the image sensor 220 are also shifted little by little. In the example shown in FIG. 18, since the light amplitudes do not cancel each other due to the gentle gradient 701, the light amplitudes shown in FIGS. 16 and 17 hardly change. However, although the light originally projected from the screen 130 should enter the image sensor as it is, the light projected from the screen 130 does not enter the image sensor in a parallel state because of the gentle gradient 701. A phase change occurs in the light. Therefore, by detecting the difference between the light phase change and the surroundings, an abnormality due to the gentle gradient 701 as shown in FIG. 18 can be detected.

  In addition, there may be an abnormality other than the surface shape of the inspection object (in other words, the distribution of the normal vector of the inspection object). FIG. 19 is a diagram illustrating a third example of detection of abnormality of an object to be inspected by the time correlation camera 110 according to the first embodiment. In the example shown in FIG. 19, since the dirt 801 is attached to the object 800 to be inspected, the light irradiated from the illumination device 120 is absorbed or diffusely reflected, and the dirt 801 of the time correlation camera 110 is photographed. This shows an example in which light hardly changes in intensity in an arbitrary pixel region. In other words, in an arbitrary pixel area where the dirt 801 is photographed, the light intensity causes a phase cancellation, the vibration component is canceled, and an almost DC brightness is shown.

  In such a case, in the pixel region where the dirt 801 is imaged, there is almost no light amplitude, and therefore when the amplitude image data is displayed, a region darker than the surroundings is generated. Therefore, it can be estimated that there is an abnormality 801 such as dirt at the position of the inspection object 800 corresponding to the region.

  As described above, in the present embodiment, it is possible to estimate that the object to be inspected is abnormal by detecting the change in the amplitude of the light and the change in the phase of the light based on the time correlation image data.

  Returning to FIG. 12, the PC 1100 will be described. The PC 1100 controls the entire detection system. The PC 1100 includes an arm control unit 101, an illumination control unit 102, and a control unit 1103.

  The arm control unit 101 controls the arm 140 in order to change the surface of the object 150 to be imaged by the time correlation camera 110. In the present embodiment, in the PC 1100, a plurality of surfaces to be imaged of the inspected object are set. Then, every time the time correlation camera 110 finishes photographing the object to be inspected 150, the arm control unit 101 can photograph the surface on which the time correlation camera 110 is set according to the setting. Move 150. The present embodiment is not limited to repeating the movement of the arm each time shooting is completed and stopping the shooting before the shooting is started, and the arm 140 may be continuously driven. The arm 140 may also be referred to as a transport unit, a moving unit, a position changing unit, a posture changing unit, or the like.

  The illumination control unit 102 outputs a fringe pattern irradiated by the illumination device 120 in order to inspect the inspected object 150. The illumination control unit 102 of this embodiment transfers at least three or more stripe patterns to the illumination device 120 and instructs the illumination device 120 to switch and display the stripe patterns during the exposure time.

  FIG. 20 is a diagram illustrating an example of a fringe pattern output from the illumination control unit 102 to the illumination device 120. In accordance with the rectangular wave shown in FIG. 20B, the illumination control unit 102 performs control so that the stripe pattern in which the black region and the white region shown in FIG. 20A are set is output.

  In this embodiment, the stripe interval for each stripe pattern to be irradiated is set according to the size of the abnormality (defect) to be detected, and detailed description thereof is omitted here.

  In addition, the angular frequency ω of the rectangular wave for outputting the fringe pattern is set to the same value as the angular frequency ω of the reference signal.

  As shown in FIG. 20, the fringe pattern output from the illumination control unit 102 can be shown as a rectangular wave, but the border area of the fringe pattern is blurred through the screen 130, that is, the bright area in the fringe pattern. By making the intensity change of light at the boundary between the (stripe region) and the dark region (interval region) gentle (dull), it can be approximated to a sine wave. FIG. 21 is a diagram illustrating an example of a wave shape representing a stripe pattern after passing through the screen 130. As shown in FIG. 21, the measurement accuracy can be improved when the wave shape approaches a sine wave. Further, a gray region in which the brightness changes in multiple steps may be added to the stripe, or a gradation may be given. Further, a stripe pattern including color stripes may be used.

  Returning to FIG. 12, the control unit 1103 includes an amplitude-phase image generation unit 104, an abnormality detection processing unit 105, and a determination unit 1104. The control unit 1103 determines that the intensity image data and the time correlation image data input from the time correlation camera 110 from the polarization information of the first polarization filter 160 and the second polarization filter 170 are the clear layer of the surface to be inspected and the background. It is a feature corresponding to the distribution of normal vectors on the surface to be inspected 150 of the object 150 to be inspected based on the intensity image data and the time correlation image data. A process for calculating the feature to be detected is performed. In the present embodiment, in order to perform the inspection, two types of real number and imaginary part of complex number correlation image data are used instead of time correlation image data (referred to as complex time correlation image data) indicated by complex numbers. Are received from the time correlation camera 110.

  The amplitude-phase image generation unit 104 generates amplitude image data and phase image data based on the intensity image data input from the time correlation camera 110 and the time correlation image data.

  The amplitude image data is image data representing the amplitude of light entering each pixel. The phase image data is image data representing the phase of light entering each pixel.

  Although the present embodiment does not limit the calculation method of the amplitude image data, for example, the amplitude-phase image generation unit 104 has pixel values C1 (x, y) and C2 (x, From y), each pixel value F (x, y) of the amplitude image data can be derived using Equation (8).

  In the present embodiment, it is possible to determine whether there is a region where an abnormality has occurred based on the pixel value (amplitude) of the amplitude image data and the pixel value of the intensity image data. For example, an abnormality occurs in a region where the value obtained by dividing the pixel value (AT) of the intensity image data by 2 and the amplitude of the amplitude image data (which is AT / 2 when cancellation does not occur) to some extent I can guess that it is not. On the other hand, it can be presumed that the amplitude cancellation occurs in the non-matching region. A specific method will be described later.

  Similarly, the amplitude-phase image generation unit 104 uses the pixel values C1 (x, y) and C2 (x, y) to calculate each pixel value P (x, y) of the phase image data using Equation (9). Can be derived.

  The determination unit 1104 acquires the polarization information of each of the first polarization filter 160 and the second polarization filter 170 from the memory 107, and each image acquired from the time correlation camera 110 configures the surface to be inspected based on the polarization information. An image is determined as to which of the plurality of layers is captured with reflected light, that is, which of the plurality of layers is the captured image. Here, details of the image determination are performed in the same manner as in the first embodiment, and thus the description thereof is omitted.

  The abnormality detection processing unit 105 is a feature corresponding to the distribution of the normal vector on the inspection symmetry plane based on the amplitude image data and the phase image data generated by the amplitude-phase image generation unit 104, and is based on a difference from the surroundings. Then, a feature related to the abnormality of the inspection object 150 is detected. In the present embodiment, an example in which the amplitude distribution of the complex time correlation image is used as the feature corresponding to the distribution of the normal vector will be described. The amplitude distribution of the complex time correlation image is data indicating the amplitude distribution of each pixel of the complex time correlation image, and corresponds to amplitude image data. In the present embodiment, abnormality detection is performed for each clear layer and background, which is a determination result by the determination unit 1104.

  Next, the abnormality detection process based on the amplitude in the abnormality detection processing unit 105 of the present embodiment will be described. FIG. 22 is a flowchart showing a procedure of the processing in the abnormality detection processing unit 105 of the present embodiment.

  First, the abnormality detection processing unit 105 determines the average amplitude of the N × N region from the light amplitude value (representing pixel value) stored in each pixel of the amplitude image data, with the pixel as a reference (for example, the center). The value is subtracted (step S1101), and average difference image data of amplitude is generated. The average difference image data of the amplitude corresponds to the gradient of the amplitude. The integer N is set to an appropriate value depending on the embodiment.

  Next, the abnormality detection processing unit 105 performs a mask process using a predetermined amplitude threshold value on the average difference image data of the amplitude generated by the subtraction (step S1102).

  Further, the abnormality detection processing unit 105 calculates a standard deviation for each pixel within the mask area of the average difference image data (step S1103). In the present embodiment, a method based on the standard deviation will be described. However, the method is not limited to the case where the standard deviation is used. For example, an average value or the like may be used.

  Then, the abnormality detection processing unit 105 detects a pixel having an amplitude pixel value obtained by subtracting an average smaller than −4.5δ (δ: standard deviation) as a region having an abnormality (defect) (step S1104).

  By the processing procedure described above, an abnormality of the object to be inspected can be detected from the amplitude value of each pixel (in other words, the amplitude distribution). However, the present embodiment is not limited to detecting an abnormality from the amplitude distribution of the complex time correlation image. The gradient of the phase distribution may be used as a feature corresponding to the distribution of normal vectors on the inspection symmetry plane. An example using the gradient of the phase distribution will be described next.

  Next, the abnormality detection process based on the phase in the abnormality detection processing unit 105 of the present embodiment will be described. FIG. 23 is a flowchart showing a procedure of the processing in the abnormality detection processing unit 105 of the present embodiment.

  First, the abnormality detection processing unit 105 subtracts the average phase value of the N × N region from the phase value of the light of each pixel of the phase image data (a pixel value representing the pixel value) using the pixel as a reference (for example, the center). (Step S1201), phase average difference image data is generated. The phase average difference image data corresponds to the phase gradient.

  Next, the abnormality detection processing unit 105 compares the magnitude (absolute value) of the average difference image data of the phase generated by the subtraction with a threshold value, and determines pixels whose average difference image data size is equal to or greater than the threshold value. Then, it is detected as an abnormal (defect) pixel (step S1202).

  Based on the detection result of S1202, the abnormality detection processing unit 105 can determine the unevenness based on the sign of the average difference image data, that is, the magnitude relationship between the phase value of the pixel and the average phase value (step S1203). Which of the pixel phase value and the average phase value is convex depends on the setting of each part, but the unevenness differs if the magnitude relationship is different.

  An abnormality can be detected from the gradient of the phase distribution obtained by another method. For example, as another method, the abnormality detection processing unit 105 determines whether the difference between the average vector of the N × N region of the normalized time correlation image data and the normalized vector of each pixel is a threshold value. If it is larger than that, it can be detected as a pixel having an abnormality (defect). Further, the abnormality of the object to be inspected may be detected based on information corresponding to the phase distribution, not limited to the gradient of the phase distribution.

  Next, the abnormality detection process based on the amplitude and intensity in the abnormality detection processing unit 105 of the present embodiment will be described. FIG. 24 is a flowchart showing a procedure of the processing in the abnormality detection processing unit 105 of the present embodiment.

  First, the abnormality detection processing unit 105 uses the following equation (10) for each pixel from the time correlation image data and the intensity image data, and uses the following equation (10) to indicate the amplitude (representing pixel value) C (x, y) (equation ( 7)) and intensity (a pixel value representing) G (x, y) (see equation (6)) R (x, y) is calculated (step S1301).

R (x, y) = C (x, y) / G (x, y) (10)

  Next, the abnormality detection processing unit 105 compares the ratio R (x, y) with a threshold value, and sets a pixel having a ratio R (x, y) value equal to or less than the corresponding threshold value to a pixel having an abnormality (defect). (Step S1302). In addition, the abnormality detection processing unit 105 compares the ratio R (x, y) with a threshold value, and determines that a pixel whose ratio R (x, y) is equal to or greater than another corresponding threshold value is uneven (dirt or the like). A pixel is detected (step S1303). When the cancellation of the amplitude (attenuation) becomes noticeable due to the abnormal distribution of the normal vector, the amplitude is greatly reduced compared to the strength. On the other hand, although there is not so much abnormality in the normal vector distribution, when the light absorption becomes significant due to dirt on the surface of the object 150 to be inspected, the intensity is greatly reduced compared to the amplitude. Therefore, the abnormality detection processing unit 105 can detect the abnormality type in steps S1302 and S1303.

  Next, an inspection process for an object to be inspected in the inspection system of the present embodiment will be described. FIG. 25 is a flowchart showing a procedure of the above-described processing in the inspection system of the present embodiment. It is assumed that the device under test 150 is already fixed to the arm 140 and arranged at the initial position of the inspection.

  Also in this embodiment, the polarization state of the first polarizing filter 160 installed in front of the screen 130 is fixed to either S-polarized light transmission or P-polarized light transmission, and is provided in front of the time correlation camera 110. The polarization of the second polarizing filter 170 is switched.

  The PC 1100 of the present embodiment outputs a fringe pattern for inspecting the object to be inspected to the illumination device 120 (step S1401).

  The illuminating device 120 stores the fringe pattern input from the PC 1100 (step S1421). And the illuminating device 120 displays the stored fringe pattern so that it may change according to a time transition (step S1422). Note that the conditions under which the illuminating device 120 starts display are not limited when the fringe pattern is stored, and may be, for example, when the inspector performs a start operation on the illuminating device 120.

  Then, the inspector switches the polarization state of the second polarizing filter 170 on the time correlation camera 110 side (step S1011).

  Then, the control unit 1103 of the PC 1100 transmits a shooting start instruction to the time correlation camera 110 (step S1402).

  Next, the time correlation camera 110 starts imaging for an area including the inspection object 150 in accordance with the transmitted imaging instruction (step S1411). Next, the control unit 240 of the time correlation camera 110 generates intensity image data and time correlation image data (step S1412). Then, the control unit 240 of the time correlation camera 110 outputs the intensity image data and the time correlation image data to the PC 1100 (step S1413).

  The processes in steps S1011 and S1411 to S1413 are executed by repeating the second polarizing filter 170 twice in different polarization states for the same region of the surface to be inspected. For example, in the first process, the second polarizing filter 170 transmits S-polarized light so as to receive S-polarized light, and in the second process, the second polarizing filter 170 is switched so as to transmit P-polarized light and receives P-polarized light. And so on.

  The control unit 1103 of the PC 1100 receives the intensity image data and the time correlation image data (step S1403). Then, the amplitude-phase image generation unit 104 generates amplitude image data and phase image data from the received intensity image data and time correlation image data (step S1404).

  The determination unit 103 performs image determination processing on the two intensity images (step S1002). The image determination process is performed in the same manner as in the first embodiment.

  Then, the abnormality detection processing unit 105 performs abnormality detection control of the inspected object based on the determination result of the determination unit 1104, the amplitude image data, and the phase image data (step S1405). That is, as a result of the image determination, since each image is understood to be either a clear layer or an underlayer image, the abnormality detection processing unit 105 determines whether there is a defect in the clear layer of the surface to be inspected, It becomes possible to detect the presence or absence of defects. Then, the abnormality detection processing unit 105 outputs the abnormality detection result to a display device (not shown) included in the PC 1100 (step S1406).

  As an output example of the abnormality detection result, the intensity image data is displayed, and an area of the intensity image data corresponding to the area where the abnormality is detected based on the amplitude image data and the phase image data is displayed. For example, it is possible to display the decoration so that it can be recognized. Further, the output is not limited to visual output, and it may be output that an abnormality has been detected by voice or the like.

  The control unit 1103 determines whether or not the inspection of the object to be inspected is completed (step S1407). When it is determined that the inspection has not been completed (step S1407: No), the arm control unit 101 can photograph the surface of the inspection object to be inspected with the time correlation camera 110 according to a predetermined setting. In this manner, arm movement control is performed (step S1408). After the arm movement control is completed, the control unit 1103 transmits an imaging start instruction to the time correlation camera 110 again (step S1402).

  On the other hand, if the control unit 1103 determines that the inspection of the object to be inspected has ended (step S1407: Yes), the control unit 1103 outputs an end instruction to the time correlation camera 110 (step S1409), and ends the process.

  Then, the time correlation camera 110 determines whether an end instruction has been received (step S1414). If an end instruction has not been received (step S1414: NO), the processing is performed again from step S1011. On the other hand, if an end instruction has been received (step S1414: YES), the process ends.

  Note that the inspecting process of the illumination device 120 may be performed by an inspector, or may be ended in accordance with an instruction from another configuration.

  As described above, in this embodiment, in the inspection system using the time correlation camera, when detecting abnormality such as the presence / absence of a defect using the time correlation image, any layer of the surface to be inspected using the polarization information. Since abnormality detection is performed after judging whether the image is an image, even when inspection processing is performed in an environment with a lot of ambient light, stable defect inspection can be performed with minimal influence of ambient light. Defect detection can be performed.

  In the present embodiment, an example in which intensity image data generated using the time correlation camera 110 and time correlation image data are generated has been described. However, the present invention is not limited to using the time correlation camera 110 to generate the intensity image data and the time correlation image data, and an imaging system that performs an equivalent operation may be used. For example, image data generated by a normal digital still camera is output, and the information processing apparatus superimposes a reference signal using the image data generated by the digital still camera as frame image data, thereby generating time-correlated image data. The time correlation image data may be generated using a digital camera that superimposes the reference signal on the light intensity signal in the image sensor.

  In this embodiment, an example in which a feature related to an abnormality is detected based on a difference from the surroundings has been described, but the present invention is not limited to detecting the feature based on a difference from the surroundings. The feature may be detected based on a difference from data (reference data such as time correlation data, amplitude image data, phase image data, etc.). In this case, it is necessary to align and synchronize the spatial phase modulation illumination (stripe pattern) with the reference data.

  In the present embodiment, the example in which the abnormality (defect) of the object to be inspected is detected by moving the stripe pattern in the x direction has been described, but the present invention is not limited to this. For example, when an abnormality (defect) in which the normal distribution changes steeply in the y direction perpendicular to the x direction occurs in the object to be inspected, the stripe pattern is moved in the y direction rather than in the x direction. In some cases, it may be easier to detect the defect. In such a case, the stripe pattern moving in the x direction and the stripe pattern moving in the y direction may be switched alternately. You may comprise so that the fringe pattern which the illumination control part 102 outputs to the illuminating device 120 may be simultaneously moved to ax direction and ay direction.

  Moreover, although this embodiment demonstrated the example which the illuminating device 120 displays the stripe width | variety with one width | variety of a stripe width | variety in x direction, it is not limited to this. For example, you may comprise so that the width | variety of the stripe of an x direction may be made into multiple types.

  In this embodiment, the S-polarized light incidence and the P-polarized light incidence are performed separately. However, the present invention is not limited to this, and the S-polarized light incidence and the P-polarized light incident on the object 150 are performed simultaneously. It may be configured. For example, the irradiation light from the illumination device 120 is separated into two light beams by a half mirror or the like, and each light beam is projected onto a separate screen. Then, the inspected object 150 is irradiated with the light flux from one screen as S-polarized light by the polarizing filter, and the inspected object 150 is irradiated with the light flux from the other screen as S-polarized light by the polarizing filter. It can be configured to perform P-polarized light incidence simultaneously. In this case, the S-polarized light frequency and the P-polarized light frequency can be different from each other. This eliminates the need to switch between S-polarized light incidence and P-polarized light incidence, thereby improving inspection efficiency.

  The inspection program executed by the PC 100 of the above-described embodiment is a file in an installable format or an executable format, and is a computer such as a CD-ROM, a flexible disk (FD), a CD-R, a DVD (Digital Versatile Disk). It is recorded on a readable recording medium and provided.

  In addition, the inspection program executed by the PC 100 according to the above-described embodiment may be provided by being stored on a computer connected to a network such as the Internet and downloaded via the network. The inspection program executed on the PC according to the above-described embodiment may be provided or distributed via a network such as the Internet.

  Although some embodiments and modifications of the present invention have been described, these embodiments and modifications are presented as examples and are not intended to limit the scope of the invention. These novel embodiments and modifications can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and equivalents thereof.

  DESCRIPTION OF SYMBOLS 10 ... Camera, 100, 1100 ... PC, 110 ... Time correlation camera, 101 ... Arm control part, 102 ... Illumination control part, 103, 1104 ... Determination part, 104 ... Phase image generation part, 105 ... Abnormality detection process part, 110 ... time correlation camera, 120 ... lighting device, 130 ... screen, 140 ... arm, 160 ... first polarizing filter, 170 ... second polarizing filter, 210 ... optical system, 220 ... image sensor, 230 ... data buffer, 240 ... control 241 ... Transfer unit, 242 ... Reading unit, 243 ... Intensity image superimposing unit, 244 ... First multiplier, 245 ... First correlation image superimposing unit, 246 ... Second multiplier, 247 ... No. 2 correlation image superimposing units, 248... Image output unit, 250... Reference signal output unit, 1103.

Claims (10)

An illumination unit that emits irradiation light at a predetermined incident angle with respect to a surface to be inspected composed of a plurality of layers;
A first polarizing filter that transmits a predetermined polarization component from the irradiation light;
A second polarizing filter that transmits a predetermined polarization component from the reflected light of the polarization component of the irradiation light irradiated on the surface to be inspected;
An imaging unit that images the surface to be inspected with a polarization component of reflected light transmitted from the second polarizing filter;
Based on the polarization component by the first polarization filter and the polarization component by the second polarization filter, it is determined whether the captured image captured by the imaging unit is an image of at least one of the plurality of layers. A determination unit;
Inspection system equipped with. The surface to be inspected comprises a base, a painted surface painted on the ground, and a clear layer transparent on the painted surface,
The predetermined incident angle is an angle at which not all of the P-polarized light of the illumination light is reflected by the surface of the clear layer,
The determination unit determines whether the captured image is an image of the surface of the clear layer, an image of the painted surface, or the base based on a polarization component by the first polarization filter and a polarization component by the second polarization filter. Determine at least one of the images
The inspection system according to claim 1. In the determination unit, when the polarization component by the first polarization filter is S-polarized light and the polarization component by the second polarization filter is S-polarization, the captured image is the surface of the clear layer, the painted surface, and the It is determined that the image is a background image.
The inspection system according to claim 2. The determination unit determines that the captured image is the background image when the polarization component by the first polarization filter is S polarization and the polarization component by the second polarization filter is P polarization.
The inspection system according to claim 2 or 3. The determination unit determines that the captured image is the background image when the polarization component by the first polarization filter is P polarization and the polarization component by the second polarization filter is S polarization.
The inspection system according to any one of claims 2 to 4. When the polarization component by the first polarizing filter is P-polarized light and the polarization component by the second polarizing filter is P-polarized light, the determination unit determines that the captured image is an image of the painted surface and the background. judge,
The inspection system according to any one of claims 2 to 5. The illuminating unit is a planar illuminating unit that gives a periodic temporal change and a spatial change of light intensity,
The inspection system includes:
A time correlation image generating unit that generates a time correlation image by a time correlation camera or an imaging system that performs an equivalent operation;
An arithmetic processing unit that calculates, from the time correlation image, a feature corresponding to the distribution of the normal vector on the surface to be inspected and detecting an abnormality by at least one of a difference from the surroundings and a difference from the reference surface When,
An abnormality detection processing unit that detects an abnormality of the inspection target surface based on the determination result by the determination unit and the feature calculated by the arithmetic processing unit;
The inspection system according to any one of claims 1 to 6, further comprising: The time correlation image generation unit generates a complex time correlation image,
The inspection system according to claim 1, wherein the feature corresponds to a phase distribution of the complex time correlation image. The time correlation image generation unit generates a complex time correlation image,
The feature corresponds to the amplitude distribution of the complex time correlation image;
The inspection system according to claim 7 or 8. Irradiation light is emitted at a predetermined incident angle to the surface to be inspected consisting of a plurality of layers
The first polarizing filter transmits a predetermined polarization component from the irradiation light,
The second polarizing filter transmits a predetermined polarization component from the reflected light of the polarization component of the irradiation light irradiated on the surface to be inspected,
Imaging the surface to be inspected by the polarization component of the reflected light transmitted from the second polarizing filter;
Determining whether a captured image captured by the imaging unit is an image of at least one of the plurality of layers, based on a polarization component by the first polarization filter and a polarization component by the second polarization filter;
Inspection method including that.

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