Surface inspection method

Abstract

To provide a surface inspection device which is capable of accurately and quickly detecting the surface condition of an object, has a simple configuration, and can be manufactured at low cost, and to provide a surface inspection method using the same.SOLUTION: A surface inspection device is provided, comprising a light source for irradiating inspection light toward an inspection target, light reception means for receiving reflected light, or the inspection light reflected by the inspection target, and a displacement means for relatively changing the angle of incidence of the inspection light to the inspection target, where the light reception means is a luminance change detection device configured to output a difference in luminance of the reflected light.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a surface inspection device and a surface inspection method using the same. [Background technology]

[0002] There are various configurations of surface inspection devices in practical use for detecting surface defects on objects. A commonly known type of device detects the presence or absence and shape of surface defects on an object by irradiating an inspection light onto the object to be inspected, capturing a still image of the object's surface, and then analyzing this still image or comparing it with a defect-free reference image (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-138669 A [Patent Document 2] JP 2019-200187 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional surface inspection devices using images have a problem of high device costs because they require a high-resolution camera and a high-performance processor for handling large-sized images in order to detect minute surface defects with high accuracy. Also, large-sized images must be handled in order to detect minute surface defects with high accuracy, and a large-scale, high-cost inspection device is required when inspecting a large number of test objects in a short period of time.

[0005] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a surface inspection device that is capable of detecting the surface condition of an object quickly and with high accuracy, and that can be manufactured at low cost with a simple configuration, and a surface inspection method using the same. [Means for solving the problem]

[0006] The inventors have discovered that by irradiating inspection light towards the object being inspected while varying the irradiation angle, and using differential data of the change in brightness of the light reflected by the object being inspected, it is possible to detect the surface condition of an object with high accuracy, while still achieving a significantly smaller data volume and easier image processing compared to image data used in conventional surface inspection devices.

[0007] The present invention has been made based on the above findings, and in order to solve the above-mentioned problems, a surface inspection device according to one embodiment of the present invention proposes the following means. (1) A surface inspection device according to aspect 1 of the present invention comprises a light source which irradiates inspection light towards an object to be inspected, a light receiving means which receives light reflected from the object to be inspected, and a displacement means which relatively changes the angle of incidence of the inspection light with respect to the object to be inspected, and is characterized in that the light receiving means is a luminance change detection device which outputs the difference in luminance of the reflected light.

[0008] (2) The surface inspection device of aspect 2 of the present invention comprises a light source which irradiates inspection light towards an object under inspection, a light receiving means arranged on the opposite side of the light source across the object under inspection and which receives measurement light generated by at least one of the following: transmission, refraction, and scattering of the inspection light in the object under inspection, and a displacement means which relatively changes the angle of incidence of the inspection light with respect to the object under inspection, and the light receiving means is a luminance change detection device which outputs the difference in luminance of the measurement light.

[0009] (3) A third aspect of the present invention is characterized in that in the surface inspection device of the first aspect, the light receiving means is a luminance change detection device that outputs the polarity of the difference in luminance of the reflected light.

[0010] (4) A fourth aspect of the present invention is characterized in that in the surface inspection device of the second aspect, the light receiving means is a luminance change detection device that outputs the polarity of the difference in luminance of the measurement light.

[0011] (5) A fifth aspect of the present invention is characterized in that, in the surface inspection device of any one of the first to fourth aspects, the displacement means changes the emission angle of the inspection light emitted from the light source.

[0012] (6) A sixth aspect of the present invention is characterized in that in the surface inspection device according to any one of the first to fifth aspects, the displacement means changes the position of the object to be inspected relative to the light source.

[0013] (7) A seventh aspect of the present invention is characterized in that in the surface inspection device according to any one of the first to sixth aspects, the wavelength of the light source is in the infrared wavelength region.

[0014] (8) An eighth aspect of the present invention is characterized in that, in the surface inspection device of the third or fourth aspect, the luminance change detection device is an event-based camera.

[0015] The surface inspection method according to one embodiment of the present invention proposes the following means. (9) A surface inspection method according to aspect 9 of the present invention is characterized in that it comprises at least an irradiation step of irradiating inspection light from a light source toward an object to be inspected while continuously changing the incident angle of the inspection light relative to the object to be inspected, and a detection step of detecting surface defects of the object to be inspected based on the difference in brightness of the light reflected by the object to be inspected.

[0016] (10) A surface inspection method according to aspect 10 of the present invention is characterized by comprising at least an irradiation step of irradiating inspection light from a light source toward an object to be inspected while continuously changing the incident angle of the inspection light relative to the object to be inspected, and a detection step of detecting surface defects of the object to be inspected based on a difference in brightness of measurement light caused by at least one of transmission, refraction, and scattering in the object to be inspected.

[0017] (11) An eleventh aspect of the present invention is the surface inspection method of the ninth aspect, characterized in that in the detection step, a surface defect of the object to be inspected is detected based on the polarity of the difference in brightness of the reflected light.

[0018] (12) A twelfth aspect of the present invention is the surface inspection method of the tenth aspect, characterized in that in the detection step, a surface defect of the object to be inspected is detected based on a polarity of a difference in luminance of the measurement light.

[0019] (13) Aspect 13 of the present invention is characterized in that, in the surface inspection method of any one of aspects 9 to 12, the light source has a plurality of LEDs, and the LEDs are controlled to be turned on one by one in sequence or to be turned on multiple times simultaneously. Effect of the Invention

[0020] According to the present invention, it is possible to provide a surface inspection device that is capable of detecting the surface condition of an object quickly and with high accuracy, and that can be manufactured at low cost with a simple configuration, and a surface inspection method using the same. [Brief description of the drawings]

[0021] [Figure 1] 1 is a schematic diagram showing a basic configuration of a surface inspection device according to a first embodiment of the present invention. [Diagram 2] 4 is a schematic diagram showing how inspection light is reflected on an object under inspection. FIG. [Diagram 3] 1A and 1B are explanatory diagrams illustrating a normal distribution and reflection characteristics of reflected light from an object under inspection. [Figure 4] FIG. 4 is a schematic diagram showing the configuration of a surface inspection device according to a second embodiment of the present invention. [Diagram 5] 1 is a photograph showing the state of a surface defect formed on a specimen used for verification. [Figure 6] 1 is a photograph showing the results of detection of surface defects. [Figure 7] 1 is a schematic diagram showing a basic configuration of a surface inspection device according to a first embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] A surface inspection device and a surface inspection method according to an embodiment of the present invention will be described below with reference to the drawings. Note that the embodiment described below is specifically described to provide a better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified. Also, the drawings used in the following description may show essential parts enlarged for convenience in order to make the features of the present invention easier to understand, and the dimensional ratios of each component may not necessarily be the same as the actual ones.

[0023] (Surface inspection device: first embodiment) A surface inspection device according to a first embodiment of the present invention will be described. FIG. 1 is a schematic diagram showing the basic configuration of a surface inspection device according to the first embodiment. The surface inspection device 10 of this embodiment includes a stage 11 that supports the object to be inspected M, a light source unit (light source) 12 that emits inspection light, an event-based camera (light-receiving means) 13 which is a brightness change detection device that receives reflected light (measurement light) from the inspection light reflected by the object to be inspected M, and a control unit 14 which performs image processing and controls the operation of the light source unit 12.

[0024] The object M to be inspected for its surface condition, for example for surface defects, using the surface inspection device 10 can be made of any material capable of reflecting the inspection light L1 emitted from the light source unit 12, such as a metal material, a resin material with a smooth surface, or glass, as long as it is a light-reflecting material.

[0025] The stage 11 is a member that supports the object to be inspected M, and may have an angle adjustment mechanism that allows the surface of the object to be inspected M to be oriented in any direction.

[0026] The light source section (light source) 12 of this embodiment is configured, for example, by a ring-shaped base material 12a on which a plurality of LEDs 12b, 12b . . . are arranged in a circular shape. The control unit 14 controls the turning on and off of each of the LEDs 12b, and the LEDs 12b are turned on and off in an arbitrary lighting pattern. In this embodiment, the LEDs 12b are controlled to be turned on and off one by one in the order of their arrangement in a circle.

[0027] The light source unit 12 may be any light source capable of emitting inspection light L1 in any wavelength range, such as white light, infrared light, or ultraviolet light, in accordance with the object under inspection M. In this embodiment, LEDs 12b, 12b... capable of emitting white light are used as the light source unit 12.

[0028] The emission of the inspection light L1 from the light source unit 12 may be continuous or discontinuous. That is, in this embodiment, the LEDs 12b, 12b... may be turned on and off continuously, or may be turned on and off sequentially and discontinuously. When the emission of the inspection light L1 from the light source unit 12 is discontinuous, the control unit 14 controls the turning on and off of the light source unit 12 in conjunction with the operation of the event-based camera 13 constituting the luminance change detection device described later. When the inspection light L1 is emitted discontinuously, it is preferable to synchronize the light source unit 12 and the event-based camera (light receiving means) 13 by hardware or software.

[0029] In addition, with regard to the emission of the inspection light L1 here, "continuous" or "discontinuous" refers not only to the temporal continuity as described above, but also to spatial continuity or discontinuity, such as whether the emitted light uniformly illuminates the space or illuminates the space by changing the irradiation position locally, depending on whether the LEDs 12b, 12b... are formed intermittently or continuously.

[0030] The event-based camera 13 is an example of a luminance change detection device that is a light receiving means, and includes an event-based sensor, a memory that stores and updates, and the like. The event-based camera 13 detects luminance changes for each pixel as events. That is, when the luminance change of the received light exceeds a preset threshold, the event-based camera 13 outputs an event (coordinates, polarity, time) as an event signal. This operation is performed independently and asynchronously for each pixel.

[0031] Based on such event signals, the event-based camera 13 asynchronously outputs the pixel coordinates where the brightness has changed, the degree of brightness change (difference) and polarity (whether the brightness has changed to a higher or lower level) to the control unit 14 as brightness change information at any timing.

[0032] The brightness change information output from the event-based camera 13 contains only information about pixels in which a brightness change has occurred. Therefore, the data volume is extremely small compared to image information that contains the brightness, color tone, and so on of all pixels, which is obtained, for example, by imaging an object under test with a CMOS camera, and this facilitates data transfer and image processing.

[0033] That is, the event-based camera 13 records only the time when an event occurred and its pixel position. The pixel position where such an event occurred is the position of a surface defect (scratch) in the surface inspection method described later, so no calculation processing is required to identify the position.

[0034] The event-based camera 13 has a high time resolution that enables it to process input light in a short time, a wide dynamic range, which is the ratio of the maximum and minimum values ​​of the signal that can be processed, and consumes less power than a typical CMOS camera, etc. Therefore, by using the event-based camera 13, it is possible to shorten the calculation time and greatly reduce the data storage capacity. This makes it possible to configure the surface inspection device 10 at low cost by using an inexpensive notebook computer, etc. as the control unit 14.

[0035] In this embodiment, event-based camera 13 is used as a luminance change detection device, which is a light receiving means, and the difference in luminance and polarity of incident light are output as luminance change information, but the luminance change detection device is not limited to event-based camera 13. For example, when a luminance difference camera is used as the luminance change detection device, the difference in luminance of incident light is output as luminance change information. In this way, any configuration of sensor device can be applied as long as it is capable of detecting at least pixel positions and the difference in luminance change therebetween.

[0036] The event-based camera (light receiving means) 13 may further include a low-pass filter (LPF). When the lighting of the light source unit 12 is controlled by pulse modulation, events due to noise components of the pulse modulation can be removed by removing high-frequency signals above a certain level using a low-pass filter. Note that such removal of noise components of the pulse modulation can also be performed by software installed in the control unit 14, without relying on hardware such as a low-pass filter.

[0037] The control unit 14 constitutes a displacement means for continuously changing the angle of incidence of the inspection light L1 from the light source unit 12 to the object under inspection M by controlling the turning on and off of the multiple LEDs 12b, 12b.... The control unit 14 also constitutes an image processing means for imaging the portion where the luminance has changed based on the luminance change information output from the event-based camera 13, and outputting the image as a surface defect image to a display or the like. The control unit 14 also constitutes a storage means (memory). The storage means stores, for example, information output from the event-based camera 13.

[0038] The control unit 14 that performs such processing may be composed of, for example, a computer (PC) on which image processing software capable of processing luminance information is installed, an interface, a display, etc. The control unit 14 may also be composed of an FPGA (Field Programmable Gate Array) or the like.

[0039] In this embodiment, the control of the light source unit 12 as the displacement means of the control unit 14 is to first light any one of the LEDs 12b for a certain period of time after the start of the inspection, and then turn it off. Next, the LED 12b adjacent to the turned on LED 12b is turned on for a certain period of time and then turned off. In this manner, the multiple LEDs 12b, 12b... arranged in a ring are controlled to be turned on one by one for a certain period of time in a clockwise direction, for example, and then turned off. The lighting of the LEDs 12b can be achieved by lighting the multiple LEDs 12b, 12b... arranged in a ring in sequence for one revolution.

[0040] By controlling the plurality of LEDs 12b, 12b... constituting the light source unit 12 by the control unit 14 as described above, it is possible to change the emission angle of the inspection light L1 emitted from the light source unit 12 with respect to the object under inspection M. As a result, the incidence angle of the inspection light L1 incident on the object under inspection M changes continuously by 360°.

[0041] As another control of the light source unit 12 as the displacement means of the control unit 14, two or more LEDs arranged in a ring shape may be simultaneously turned on and then turned off by the control unit 14. For example, among the LEDs 12b, 12b arranged in a ring shape, two LEDs 12b positioned opposite each other (0 degree or 180 degree positional relationship) may be simultaneously turned on, and two LEDs 12b facing each other but shifted sequentially clockwise or counterclockwise may be simultaneously turned on and off.

[0042] Alternatively, among the LEDs 12b, 12b arranged in a ring shape, three LEDs 12b located at positions of 0 degrees, 120 degrees, and 360 degrees can be turned on simultaneously and then turned off, and three LEDs 12b located at positions shifted by 60 degrees in a clockwise or counterclockwise direction can be turned on simultaneously and then turned off. In this way, the method of controlling the turning on and off of the plurality of LEDs 12b constituting the light source unit 12 is not limited, and the plurality of LEDs 12b can be turned on and off in any lighting pattern.

[0043] The surface inspection device 10 configured as described above may be positioned, for example, so that the center of the inspection surface of the object to be inspected M, the center of the ring of the substrate 12a of the light source unit 12, and the optical axis of the event-based camera 13 are aligned on a single optical axis S.

[0044] (Surface inspection method) Next, the operation of the surface inspection apparatus 10 of the first embodiment and a surface inspection method of this embodiment using the surface inspection apparatus 10 will be described. FIG. 2 is a schematic diagram showing how the inspection light is reflected by the object under inspection. When using the surface inspection device 10 to inspect the surface of an arbitrary object M to be inspected, for example to detect surface defects, the object M to be inspected is first supported on the stage 11 so that the inspection surface of the object M faces the event-based camera 13. In this embodiment, a mirror-finished aluminum plate is used as the object M to be inspected for surface defects.

[0045] Next, the control unit 14 is operated to control the light source unit 12, and the multiple LEDs 12b, 12b... arranged in a ring are sequentially turned on one by one in a clockwise direction for a certain period of time and then turned off (irradiation process). At this time, inspection light L1, which is white light, is emitted from each of the turned-on LEDs 12b and enters the inspection object M. Then, the inspection light L1 that has entered the inspection object M is reflected in accordance with the surface condition of the inspection object M, and enters the event-based camera 13 as reflected light L2.

[0046] The control unit 14, which is a displacement means for relatively changing the angle of incidence of the inspection light L1 with respect to the object under inspection M, may be set so that the displacement is a periodic movement. In this case, the period is T. For example, in the case of the light source unit 12 having a plurality of LEDs 12b arranged in a ring shape, when the LEDs 12b are turned on and off one by one in sequence, the period T is the time required for one rotation. Alternatively, a single light source may be moved periodically along a certain locus in free space, and in this case, the time required for the light source to move from the start point to the end point is the period T.

[0047] Then, only when the luminance of the reflected light L2 from each of the LEDs 12b, 12b . . . changes, the event-based camera 13 records the pixel position of the event-based sensor and the amount of change (difference) in luminance as an event.

[0048] 2(a), when the inspection surface of the inspection object M is smooth and has no surface defects such as unevenness, inspection light L11 emitted from LED 12b1 is reflected at a reflection angle θ and enters the event-based camera 13 as reflected light L21. In addition, inspection light L12 emitted from LED 12b2 arranged at a different position from LED 12b1 shown in FIG. 2(a) is reflected at a reflection angle θ and enters the event-based camera 13 as reflected light L22.

[0049] In other words, if the inspection surface of the inspection object M is smooth and free of surface defects such as unevenness, the inspection light L1 emitted from any of the multiple LEDs 12b, 12b... is reflected at the same reflection angle θ and enters the event-based camera 13 as reflected light L2 of the same luminance. The event-based camera 13 does not record it as an event while the luminance of the incident reflected light L2 is the same.

[0050] That is, when there are no surface defects on the entire inspection surface of the inspection object M, even if the multiple LEDs 12b, 12b... arranged in a ring are sequentially turned on to change the angle of incidence of the inspection light L1 with respect to the inspection object M, no change in luminance occurs, and therefore no luminance change information is output from the event-based camera 13. Therefore, when no luminance change information is output from the event-based camera 13 even when all the LEDs 12b, 12b... are sequentially turned on, the control unit 14 outputs that there are no surface defects.

[0051] On the other hand, as shown in Figure 2(b), if a surface defect Q such as unevenness is present on the inspection surface of the inspected object M, the inspection light L11 emitted from the LED 12b1 shown in Figure 2(b) is diffusely reflected by the surface defect Q, and the reflected light L21 entering the event-based camera 13 has a reduced brightness compared to the light reflected from a smooth surface.

[0052] 2(b), the inspection light L12 emitted from the LED 12b2 arranged at a different position from the LED 12b1 is diffusely reflected by the surface defect Q, but because the incident angle with respect to the inspection object M is different from that of the inspection light L11, the diffuse reflection occurs with a scattering pattern different from that of the diffuse reflection by the LED 12b1. As a result, the reflected light L22 incident on the event-based camera 13 has a luminance different from that of the reflected light from a smooth surface and the reflected light L21.

[0053] In this way, when a surface defect Q is present on the inspection surface of the object to be inspected M, when the multiple LEDs 12b, 12b... arranged in a ring shape are sequentially turned on and then turned off, diffuse reflection occurs in different patterns depending on the difference in the incident angle of the inspection light L1 onto the object to be inspected M, and a brightness change occurs in the reflected light L2 that is continuously incident on the event-based camera 13.

[0054] That is, as shown in Figure 3, the normal distribution of reflected light differs between a normal portion of the inspection object M, which has no surface defects, and an abnormal portion, which has surface defects and irregularities. Therefore, the reflection characteristics of the reflected light differ between the normal portion and the abnormal portion due to the difference in normal distribution. The difference in reflection characteristics is detected as the difference in brightness and polarity.

[0055] The event-based camera 13 detects a luminance change for each pixel as an event. The event-based camera 13 detects a luminance change of the reflected light L2 due to the surface defect Q as an event. That is, when the luminance change of the received light exceeds a preset threshold, the event-based camera 13 records the pixel position of the event-based camera 13 and the amount of change (difference) in luminance and polarity as an event, and outputs it to the control unit 14 as an event signal. The pixel position included in this event signal is data corresponding to the position (coordinates) where the surface defect Q exists on the inspection surface of the object M to be inspected, and the amount of change (difference) in luminance is data corresponding to the shape (depth of unevenness, etc.) of the surface defect Q. Note that such operations of the event-based camera 13 are performed independently and asynchronously for each pixel.

[0056] When the control unit 14 sequentially lights up all the LEDs 12b, 12b... and receives brightness change information, it uses image processing software to generate an enlarged image of the surface defect Q present on the object M based on the brightness change information, and outputs the image as a surface defect image, for example, on a display (detection process).

[0057] In this detection process, surface defects are detected from an event group consisting of one or more stored events. For example, this event group is divided in time into an event cycle group with a cycle T, and then divided in space into a grid based on the xy coordinates. This divides the event group into spatial and temporal rectangular parallelepipeds (voxels). The number of events in each voxel is counted, and if the count value reaches or exceeds a certain value, the voxel is defined as a surface defect voxel.

[0058] If other voxels spatially adjacent to the voxel in question are surface defect voxels, they are linked as surface defect voxels related to the same surface defect. This linking process is repeated until it becomes impossible to link spatially adjacent voxels. Within the period T, spatial detection is performed for each surface defect. After the detection process, tracking of the surface defect can also be performed (tracking process).

[0059] In this tracking process, if a surface defect detected at a certain time is a surface defect detected before that time, they are tracked as the same surface defect. For the above-mentioned connected surface defect voxel group, surface defect voxels that are temporally nearby are searched for, and the surface defect voxels are connected in the time axis direction. This makes it possible to track the above-mentioned surface defect in space and time.

[0060] In addition, when the object to be inspected moves at a constant speed on a belt conveyor or the like, it is also preferable to execute a correction process as a pre-processing process for the detection process. In this correction process, the coordinates (pixel positions) of all events stored in the storage means of the control unit 14 are corrected based on the known moving speed. Then, based on an arbitrary time as a reference, a coordinate correction amount is calculated using the difference time and the moving speed according to the difference between the occurrence time of each event. The coordinates are corrected by subtracting this coordinate correction amount from the coordinates of the event. This correction process makes it possible to process an object to be inspected that moves at a constant speed in the same way as if it were stationary. With the above-described configuration, surface inspection can be performed by the surface inspection method using the surface inspection apparatus of this embodiment.

[0061] As described above, the surface inspection apparatus and method of this embodiment make it possible to easily detect surface defects on an object to be inspected with a simple configuration in which inspection light is incident on the object to be inspected at a number of different angles of incidence and the luminance change in the resulting reflected light is detected by a luminance change detection device.

[0062] Furthermore, since the brightness change difference data used in this embodiment has a significantly smaller data volume than high-definition image data capturing the entire surface of the object to be inspected, image processing and image output of surface defects can be performed using an inexpensive personal computer equipped with a processor, without using an expensive image processing device, and a surface inspection device capable of detecting surface conditions such as surface defects can be realized with a simple configuration and at low cost.

[0063] It should be noted that the luminance change of reflected light used in this embodiment is not limited to macroscopic luminance changes across multiple pixels of the luminance change detection sensor, which are caused by surface defects (e.g., dents) due to relatively large unevenness on the object under inspection, as described above.

[0064] For example, if the reflection due to minute unevenness is isotropic and the brightness changes cancel each other out within one pixel of the brightness change detection sensor, this is treated as no brightness change, and if the reflection due to unevenness is anisotropic and a brightness change occurs within one pixel of the brightness change detection sensor, this is treated as a brightness change.This makes it possible to detect surface defects with minute unevenness, such as scratches, with high accuracy.

[0065] (Surface Inspection Apparatus: Modification of the First Embodiment) As a modified example of the surface inspection apparatus of the first embodiment described above, the stage can be configured to be rotatable by a rotating device (displacement means) or the like. In this case, the light source may be fixed at one location. Even with this configuration, the angle of incidence of the inspection light with respect to any region of the object under inspection except the center point can be changed by rotating the object under inspection supported by the stage with respect to the inspection light emitted at a uniform emission angle.

[0066] As a result, if a surface defect exists on the object to be inspected, the brightness of the reflected light from that area will change. By detecting the difference in brightness change with a brightness change detection device, for example, an event-based camera, it becomes possible to inspect the surface condition of the object to be inspected, such as the surface defects, as in the first embodiment described above. Such a modification of the first embodiment is suitable as a low-cost surface inspection device for inspecting an object to be inspected which is a light-reflective disk, for example, a metal wafer.

[0067] (Surface inspection device: second embodiment) FIG. 4 is a schematic diagram showing the configuration of a surface inspection device according to the second embodiment of the present invention. The surface inspection device 20 of the second embodiment includes a conveyor 21 on which multiple inspection objects M are placed in one direction, a light source unit (light source) 22 that emits inspection light, an event-based camera (light-receiving means) 23 which is a brightness change detection device that receives reflected light (measurement light) from the inspection light L1 reflected by the inspection object M, a control unit 24 that performs image processing and controls the operation of the light source unit 12, and a displacement means 25 that drives the conveyor 21 to move the inspection objects M placed thereon in one direction X.

[0068] The light source section (light source) 22 is composed of one light source, and irradiates one inspection object M on the conveyor 21 with inspection light L1. The event-based camera 23 receives reflected light L2 from the object under inspection M irradiated with the inspection light L1. The control unit 24 controls the displacement means 25 to move the object to be inspected M in one direction X at a preset arbitrary moving speed.

[0069] In the surface inspection device 20 configured as described above, while a single object to be inspected M moves within the irradiation range of the inspection light L1 along one direction X, the incident angle of the inspection light L1 with respect to the object to be inspected M changes. However, if there are no surface defects such as unevenness on the surface of the object to be inspected M, the brightness of the reflected light L2 reflected from the surface of the object to be inspected M becomes uniform and does not change.

[0070] On the other hand, if there is a surface defect such as unevenness on the surface of the inspection object M, while a single inspection object M moves in one direction X through the irradiation range of the inspection light L1, the inspection light L1 is diffusely reflected by the crystal defect, and the brightness of the reflected light L2 changes. By detecting such a change in brightness with the event-based camera 23, the surface of the object to be inspected M can be inspected.

[0071] The surface inspection device 20 of this embodiment can be suitably used, for example, in a manufacturing line for parts having glossy surfaces, for continuously inspecting the surface conditions of the manufactured parts.

[0072] (Surface inspection device: third embodiment) A surface inspection device according to a second embodiment of the present invention will be described below. Note that the same components as those in the first embodiment are given the same reference numerals, and duplicated explanations will be omitted. FIG. 7 is a schematic diagram showing the basic configuration of a surface inspection device according to the second embodiment. The surface inspection device 30 of this embodiment includes a light-transmitting stage 31 that supports the object to be inspected M, a light source unit (light source) 12 that emits inspection light L11, an event-based camera (light-receiving means) 13 which is a brightness change detection device that receives measurement light L12 generated by at least one of transmission, refraction, and scattering of the inspection light L11 by the object to be inspected M2, and a control unit 14 which performs image processing and controls the operation of the light source unit 12.

[0073] The object M2 to be inspected for its surface condition, for example for surface defects, by the surface inspection device 30 can be made of any material that can transmit, refract, or scatter the inspection light L11 emitted from the light source unit 12, such as transparent or translucent glass, resin material, or other material that has light transmittance, light refraction, or light scattering properties. In this embodiment, a transparent resin material having light transmittance is used as the object M2 to be inspected.

[0074] In addition, the light transmittance, light refraction, and light scattering referred to here are states in which at least a portion or all of the wavelength range of the inspection light is transmitted, refracted, or scattered, respectively, and are not limited to states in which the entire wavelength range of the inspection light is transmitted, refracted, or scattered.

[0075] The stage 31 is a member that supports the object M2 under inspection. The stage 31 may be a stage that supports the entire surface of the object M2 under inspection, or a frame-like stage that supports the peripheral portion of the object M2 under inspection. When a stage that supports the entire surface of the object M2 under inspection is used as the stage 31, the stage 31 may be made of a material that can transmit the measurement light L12.

[0076] The light source section (light source) 12 of this embodiment is configured, for example, by a ring-shaped base material 12a on which a plurality of LEDs 12b, 12b . . . are arranged in a circular shape. The control unit 14 controls the turning on and off of each of the LEDs 12b, and the LEDs 12b are turned on and off in an arbitrary lighting pattern. In this embodiment, the LEDs 12b are controlled to be turned on and off one by one in the order of their arrangement in a circle.

[0077] The multiple LEDs 12b, 12b... of the light source unit (light source) 12 are arranged so as to be located outside the viewing area (angle of view) E of the event-based camera (light-receiving means) 13. This prevents the event-based camera (light-receiving means) 13 from detecting an event other than a luminance change due to a surface defect of the object M2 to be inspected, that is, from detecting an event due to the turning on and off of the LEDs 12b, 12b....

[0078] The event-based camera 13 has a viewing area (angle of view) E adjusted by an installation position or a filter so that the multiple LEDs 12b, 12b . . . of the light source unit (light source) 12 do not enter the viewing area (angle of view).

[0079] A surface inspection method using the surface inspection device 30 configured as above will be described. When using the surface inspection device 30 to inspect the surface of, for example, a light-transmitting inspection object M2, for example to detect surface defects, the control unit 14 is operated to control the light source unit 12, and the multiple LEDs 12b, 12b... arranged in a ring are sequentially turned on one by one in a clockwise direction for a fixed period of time and then turned off.

[0080] At this time, inspection light L1, which is white light, is emitted from each of the lit LEDs 12b and enters the object under inspection M2. Then, the inspection light L1 that enters the object under inspection M2 is transmitted, refracted, or scattered depending on the surface condition of the object under inspection M2, and enters the event-based camera 13, which is disposed on the opposite side to the light source unit 12, via the object under inspection M2 as measurement light L12.

[0081] The event-based camera 13 records the pixel position and the amount of change (difference) in luminance of the event-based sensor as an event only when the luminance of the measurement light L12 generated by each LED 12b, 12b... due to transmission, refraction, or scattering by a surface defect of the object to be inspected M2 changes.

[0082] When event-based camera 13 detects a luminance change for each pixel as an event, it records the pixel position and the amount (difference) of change in luminance and polarity as an event, and outputs it to control unit 14 as an event signal.

[0083] When the control unit 14 sequentially turns on and off all the LEDs 12b, 12b... and receives brightness change information, it uses image processing software to generate an enlarged image of the surface defect Q present on the inspection object M2 based on the brightness change information, and outputs the image as a surface defect image, for example, to a display. With the above-described configuration, surface inspection can be performed by the surface inspection method using the surface inspection apparatus 30 of the third embodiment.

[0084] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents described in the claims, as well as in the scope and spirit of the invention. EXAMPLES

[0085] The effect of the present invention was verified. (Verification example 1) For the verification, a surface inspection device with the configuration shown in Figure 1 was used. Event-based camera: EVK, manufactured by Prophesee Corporation (equipped with a 25 mm objective lens) was used. Light source: 60 white light LEDs arranged in a ring. Test piece: A stainless steel plate with a mirror-finished surface (white light reflectance 95%) was used. Control unit: A laptop computer with luminance image processing software installed was used.

[0086] As shown in Figure 5, dents, line scratches, and abrasion scratches were created as surface defects on the stainless steel plate to be inspected. Then, 60 white light LEDs were sequentially illuminated toward this inspection object, and the reflected light was input to the event-based camera. The event-based camera then output information on luminance changes. Figure 5 shows a photograph of the inspection result, in which pixels that had an event output of a luminance change are displayed in white.

[0087] 6, when the surface inspection device of this embodiment is used, dent scratches, line scratches, and abrasion scratches formed on the stainless steel plate are all clearly detected. This confirmed the effectiveness of the surface inspection device of this embodiment.

[0088] (Verification example 2) For the verification, a surface inspection device with the configuration shown in Figure 7 was used. Event-based camera: EVK, manufactured by Prophesee Inc. (with 25 mm objective lens attached) was used. The detection angle was adjusted so that the white light LED of the light source did not enter the field of view. Light source: 60 white light LEDs arranged in a ring. Test piece: A hollow box made of acrylic resin (white light transmittance 95%). Scratches were formed on the surface. Control unit: A laptop computer with luminance image processing software installed was used.

[0089] Sixty white light LEDs were sequentially illuminated toward the test object, and the measurement light that had passed through the test object was input to an event-based camera. The event-based camera then output luminance change information. As a result, scratches formed on the hollow box-shaped body made of acrylic resin were clearly detected. This confirmed the effectiveness of the surface inspection device of this embodiment. [Industrial Applicability]

[0090] According to the surface inspection device and surface inspection method of the present invention, by inspecting the surface condition of an object to be inspected based on luminance change information, which has a smaller capacity and allows faster data processing compared to conventional image inspection devices, it is possible to realize a surface inspection device capable of high-speed inspection with a simple configuration and at low cost. Therefore, the present invention has industrial applicability. [Explanation of symbols]

[0091] 10. Surface inspection device 11. Stage 12...Light source section (light source) 13...Event-based camera (light receiving means) 14...Control section (displacement means)

Claims

1. a light source that irradiates an inspection light toward an object under inspection, a light receiving means that receives light reflected from the inspection light by the object under inspection, and a displacement means that relatively changes an incident angle of the inspection light with respect to the object under inspection, A surface inspection apparatus according to claim 1, wherein said light receiving means is a luminance change detection device that outputs a difference in luminance of said reflected light.

2. a light source which irradiates an inspection light to an object under inspection; a light receiving means which is disposed on the opposite side of the object under inspection from the light source and receives measurement light which is generated by at least one of the following means: transmission, refraction, and scattering of the inspection light in the object under inspection; and a displacement means which relatively changes an incident angle of the inspection light with respect to the object under inspection; A surface inspection apparatus according to claim 1, wherein the light receiving means is a luminance change detection device that outputs a difference in luminance of the measurement light.

3. 2. A surface inspection apparatus according to claim 1, wherein said light receiving means is a luminance change detection device that outputs a polarity of a difference in luminance of said reflected light.

4. 3. A surface inspection apparatus according to claim 2, wherein said light receiving means is a luminance change detection device that outputs a polarity of a difference in luminance of said measurement light.

5. 5. The surface inspection device according to claim 1, wherein the displacement means changes an emission angle of the inspection light emitted from the light source.

6. 5. The surface inspection apparatus according to claim 1, wherein the displacement means changes a position of the object to be inspected relative to the light source.

7. 5. The surface inspection device according to claim 1, wherein the wavelength of the light source is in the infrared wavelength region.

8. 5. The surface inspection apparatus according to claim 3, wherein the luminance change detection device is an event-based camera.

9. A surface inspection method comprising at least an irradiation step of irradiating an object to be inspected with inspection light from a light source while continuously changing the incident angle of the inspection light relative to the object to be inspected, and a detection step of detecting surface defects of the object to be inspected based on the difference in brightness of the light reflected by the object to be inspected.

10. A surface inspection method comprising at least an irradiation step of irradiating an inspection light from a light source toward an object to be inspected while continuously changing the incident angle of the inspection light relative to the object to be inspected, and a detection step of detecting surface defects of the object to be inspected based on a difference in brightness of the measurement light caused by at least one of transmission, refraction, and scattering in the object to be inspected.

11. 10. The surface inspection method according to claim 9, wherein in the detection step, a surface defect of the object to be inspected is detected based on a polarity of a difference in luminance of the reflected light.

12. 11. The surface inspection method according to claim 10, wherein in the detection step, a surface defect of the object to be inspected is detected based on a polarity of a difference in luminance of the measurement light.

13. 13. The surface inspection method according to claim 9, wherein the light source includes a plurality of LEDs, and the LEDs are controlled to be turned on one by one in sequence or to be turned on simultaneously.

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