Visual inspection device

Abstract

To provide an appearance inspection device that, for an object to be inspected including a reference surface and an inclined surface inclined to a certain degree with respect to the reference surface, can inspect the reference surface and the inclined surface simultaneously with high accuracy.SOLUTION: An appearance inspection device 100 has: an LED light source 110 for irradiating an object to be inspected OB1 with light; a telecentric lens 130 that transmits reflected light from the object to be inspected OB1; a camera 120 that picks up an image of the light transmitting through the telecentric lens 130; a shielding plate 150 that changes the parallelism of incident light incident on the object to be inspected OB1; and a control unit 160. The control unit 160 has a light luminance integrated value calculation unit 163 that calculates a light luminance integrated value obtained by integrating the luminance of light received by the camera 120, and a determination unit 164 that determines a surface state of the object to be inspected OB1 from the light luminance integrated value calculated by the light luminance integrated value calculation unit 163.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The technical field of this specification relates to an appearance inspection apparatus for inspecting the presence or absence of scratches on metal parts and the like.

Background Art

[0002] Conventionally, there has been a technique for inspecting an inspection object by irradiating the inspection object with light and receiving the reflected light.

[0003] For example, Patent Document 1 discloses an inspection system 200 having a surface light source 1, a first light shielding mask M1, a second light shielding mask M2, a lens 2, a half mirror 4, and an imaging device C. The inspection system 200 detects scratches and the like based on the brightness and darkness of an image obtained by the imaging device C.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The surface of the inspection object may not be a simple flat surface, but may include a reference surface and an inclined surface that is slightly inclined with respect to the reference surface. In order to inspect the reference surface with high accuracy, it is necessary to adjust the reference surface, the light irradiation position on the reference surface, the reflected light receiving position, etc. to positions convenient for the inspection of the reference surface. As a result, it becomes difficult to inspect the inclined surface as well as the reference surface with high accuracy at the same time. Therefore, in a conventional inspection system, it is never easy to inspect the reference surface of such an inspection object and a plurality of possible inclined surfaces with high accuracy at the same time.

[0006] Therefore, for example, it may be necessary to inspect the inclined surface after inspecting the reference surface. In this case, the amount of work required to inspect the object increases. Also, in order to perform inspections with high accuracy, each surface must be aligned with high precision.

[0007] The problem that the technology described herein aims to solve is to provide a visual inspection device that can simultaneously inspect a reference surface and an inclined surface that is tilted to some extent relative to the reference surface of an object to be inspected, with high accuracy. [Means for solving the problem]

[0008] The appearance inspection apparatus in the first embodiment includes a light source for irradiating an object to be inspected with light, a telecentric lens for transmitting reflected light from the object to be inspected, an imaging unit for imaging the light transmitted through the telecentric lens, a light parallelism changing unit for changing the parallelism of the incident light incident on the object to be inspected, and a control unit. The control unit includes a light intensity integrated value calculation unit for calculating a light intensity integrated value by integrating an index of the intensity of the light received by the imaging unit, and a determination unit for determining the surface condition of the object to be inspected from the light intensity integrated value calculated by the light intensity integrated value calculation unit. The light intensity integrated value calculation unit calculates a light intensity integrated value by integrating an index of the light intensity of the reflected light from the object to be inspected for multiple parallelisms changed by the light parallelism changing unit.

[0009] This visual inspection device calculates an integrated light intensity value. This integrated light intensity value contains information about the reflected light from multiple parallel surfaces. Therefore, the visual inspection device can simultaneously inspect surfaces that are inclined at a small angle to a reference surface for the presence of scratches or dents. [Effects of the Invention]

[0010] This specification provides a visual inspection device that can simultaneously inspect, with high accuracy, both the reference surface and the inclined surface of an object to be inspected, which includes a reference surface and an inclined surface that is inclined to some extent with respect to the reference surface. [Brief explanation of the drawing]

[0011] [Figure 1] This is a plan view showing the object OB1 to be inspected by the visual inspection device of the first embodiment. [Figure 2] This is a side view of the object to be inspected, as seen from the direction of arrow K1 in Figure 1. [Figure 3] This is a schematic diagram of the visual inspection device 100 according to the first embodiment. [Figure 4] This is a block diagram showing the control unit 160 of the visual inspection device 100 according to the first embodiment. [Figure 5] This figure shows the relationship between the illumination pattern and the parallelism of the light when the illumination angle is 27°. [Figure 6] This figure shows the relationship between the illumination pattern and the parallelism of the light when the illumination angle is 1°. [Figure 7] This graph illustrates the integrated luminance values ​​in the case of scratches or dents. [Figure 8] This graph illustrates the integrated luminance value in the absence of scratches or dents. [Figure 9] This graph illustrates the relationship between the angle from the reference plane and the integrated luminance value in the visual inspection device 100 of the first embodiment. [Figure 10] This graph illustrates the luminance integration profile of the reference surface Sf0 and surfaces Sf1, Sf2, and Sf3 on the object OB1 to be inspected in the visual inspection apparatus 100 of the first embodiment. [Figure 11] This graph illustrates the relationship between the angle from the reference plane and the brightness of light when the parallelism of the light is not changed. [Figure 12] This graph illustrates the relationship between position and light intensity when the parallelism of light is not changed. [Figure 13] This is a flowchart showing the processing of the visual inspection apparatus 100 according to the first embodiment. [Figure 14] This is a flowchart showing the process in a modified example of the visual inspection apparatus 100 of the first embodiment. [Figure 15]It is a schematic configuration diagram of the appearance inspection device 200 of the second embodiment. [Figure 16] It is a diagram showing the relationship between the illumination pattern and the parallelism of the display 210 in the appearance inspection device 200 of the second embodiment. [Figure 17] It is a diagram showing the reflection of light in a metal part without liquid on its surface. [Figure 18] It is a diagram showing the reflection of light in a metal part with liquid on its surface. [Figure 19] It is a graph showing the angular dependence of the reflectance when light is incident from air into paraffin oil. [Figure 20] It is a graph showing the luminance value in the case where there is no adhesion of machining oil. [Figure 21] It is a graph showing the luminance value in the case where there is adhesion of machining oil. [Figure 22] It is a graph showing the luminance value in the case where there is no adhesion of machining oil after normalization processing. [Figure 23] It is a graph showing the luminance value in the case where there is adhesion of machining oil after normalization processing. [Figure 24] It is a graph showing the relationship between the angle of a test piece without scratches or dents and the integrated value of light luminance. [Figure 25] It is a graph showing the relationship between the angle of a test piece without scratches or dents and the luminance value. [Figure 26] It is a graph (part 1) showing the relationship between the position of a test piece with dents and the integrated value of light luminance. [Figure 27] It is a graph (part 1) showing the relationship between the position of a test piece with dents and the luminance value. [Figure 28] It is a graph (part 2) showing the relationship between the position of a test piece with dents and the integrated value of light luminance. [Figure 29] It is a graph (part 2) showing the relationship between the position of a test piece with dents and the luminance value. [Figure 30] It is a diagram conceptually decomposing the measured value of the luminance value of light. [Figure 31] It is a graph showing the maximum value, minimum value, and median value of the luminance value of light. [Figure 32] This figure shows the measurement results of test piece 1, which has processing oil residue on it. [Figure 33] This figure shows the measurement results for test piece 2, which has processing oil residue on it. [Figure 34] This figure shows the measurement results of test piece 3, which has processing oil residue on it. [Modes for carrying out the invention]

[0012] The following describes specific embodiments, using a visual inspection apparatus as an example. However, the technology described herein is not limited to these embodiments.

[0013] (First embodiment) 1. Items to be inspected Figure 1 is a plan view showing the object OB1 to be inspected by the visual inspection apparatus of the first embodiment. Figure 2 is a side view of the object to be inspected as seen from the direction of arrow K1 in Figure 1. The object to be inspected OB1 is a metal part that is close to a plate shape.

[0014] As shown in Figures 1 and 2, the object under inspection OB1 has a reference plane Sf0 and surfaces Sf1, Sf2, and Sf3. The reference plane Sf0 and surfaces Sf1, Sf2, and Sf3 are reflective surfaces that reflect light. The reference plane Sf0 and surfaces Sf1, Sf2, and Sf3 are nearly parallel planes. Surface Sf1 is an inclined surface tilted at an angle of 1° with respect to the reference plane Sf0. Surface Sf2 is tilted at an angle of 2° with respect to the reference plane Sf0. Surface Sf3 is tilted at an angle of 3° with respect to the reference plane Sf0.

[0015] Thus, the object OB1 to be inspected has multiple reflective surfaces, and these surfaces are slightly inclined relative to each other. When performing a visual inspection of such an object OB1 using light, it is generally difficult to inspect surfaces Sf1 and Sf2 simultaneously.

[0016] 2. Visual Inspection Device 2-1.Each part Figure 3 is a schematic diagram of the appearance inspection device 100 according to the first embodiment. The appearance inspection device 100 includes an LED light source 110, a camera 120, a telecentric lens 130, a half mirror 140, a shielding plate 150, and a control unit 160. The appearance inspection device 100 irradiates the object to be inspected OB1 with light and inspects the object to be inspected OB1 for the presence or absence of scratches from the reflected light.

[0017] The LED light source 110 is a light source for illuminating the object OB1 to be inspected. The LED light source 110 is preferably a surface light source.

[0018] Camera 120 is an imaging unit that captures light reflected by the object OB1 being inspected. Camera 120 captures light that has passed through the telecentric lens 130.

[0019] The telecentric lens 130 aligns the principal ray parallel to the lens optical axis. The telecentric lens 130 transmits reflected light from the object being inspected OB1. The telecentric lens 130 is attached to the camera 120. Light from the half mirror 140 enters the camera 120 after passing through the telecentric lens 130.

[0020] The half mirror 140 directs light from the LED light source 110 toward the object OB1 to be inspected and also directs the reflected light from the object OB1 toward the camera 120. The half mirror 140 is positioned between the location of the object OB1 to be inspected and the LED light source 110. The half mirror 140 is positioned at an angle with respect to the direction of light propagation from the LED light source 110. For example, the half mirror 140 is tilted at a 45° angle with respect to the light from the LED light source 110.

[0021] The shielding plate 150 can block a portion of the light from the LED light source 110. The shielding plate 150 has an opening, and the size of this opening can be changed. Therefore, the shielding plate 150 is part of a light parallelism changing unit that can change the parallelism of the incident light that enters the object OB1 from the LED light source 110. In other words, the light parallelism changing unit includes the shielding plate 150.

[0022] The control unit 160 controls each component. For example, the control unit 160 controls the size of the opening in the shielding plate 150. This allows the control unit 160 to control the parallelism of the light from the LED light source 110. The control unit 160 also has a calculation unit that processes the light received by the camera 120.

[0023] 2-2. Arrangement of each part and the path of light The LED light source 110 faces the location of the object to be inspected OB1, with a half mirror 140 in between. The half mirror 140 is positioned between the LED light source 110 and the object to be inspected OB1. The half mirror 140 illuminates the object to be inspected OB1 with light from the LED light source 110 and illuminates the telecentric lens 130 with reflected light from the object to be inspected OB1.

[0024] Light emitted from the LED light source 110 is adjusted for parallelism by the shielding plate 150, then passes through the half mirror 140 and is reflected by the object under inspection OB1. The light reflected by the object under inspection OB1 is reflected again by the half mirror 140 and travels toward the camera 120. The light reflected by the half mirror 140 passes through the telecentric lens 130 and enters the camera 120.

[0025] 3. Control Unit Figure 4 is a block diagram showing the control unit 160 of the visual inspection device 100 according to the first embodiment. As shown in Figure 4, the control unit 160 includes a shielding plate control unit 161, a light intensity detection unit 162, a light luminance integrated value calculation unit 163, and a judgment unit 164.

[0026] The shielding plate control unit 161 controls the opening width of the shielding plate 150. This adjusts the parallelism of the light from the LED light source 110. The parallelism of the light is represented by the irradiation angle θ in Figure 3. The smaller the opening width of the shielding plate 150, the smaller the irradiation angle θ becomes. The shielding plate control unit 161 can change the light irradiation angle θ in 1° increments, for example, from 1° to 15°.

[0027] The light intensity detection unit 162 controls the shielding plate 150 to change the parallelism of the light from the LED light source 110 and irradiates the object to be inspected OB1 with light. The camera 120 receives the reflected light and detects the brightness of the received light.

[0028] The light luminance integrated value calculation unit 163 calculates a light luminance integrated value by integrating the luminance of the light received by the camera 120. In practice, the light luminance integrated value calculation unit 163 calculates the light luminance integrated value by integrating the luminance of the light detected by the light intensity detection unit 162. This light luminance integrated value is, for example, the integrated value of the luminance of the reflected light from the object under inspection OB1 when light with an irradiation angle θ from 1° to 15° is irradiated. In other words, the light luminance integrated value is, for example, the value obtained by sequentially adding the reflected light when light with an irradiation angle θ of 1° is incident, and the reflected light when light with an irradiation angle θ of 2° is incident.

[0029] The judgment unit 164 determines the surface condition of the object OB1 to be inspected from the integrated luminance value calculated by the luminance integrated value calculation unit 163. For example, the judgment unit 164 determines whether or not there are scratches or dents on the object OB1 to be inspected.

[0030] 4. Integrated luminance value 4-1. Irradiation angle and parallelism of light Figure 5 shows the relationship between the illumination pattern and the parallelism of the light when the illumination angle is 27°. The illumination angle θ is shown in Figure 5. The illumination angle θ is the largest angle formed on the surface of the object OB1 being inspected by light from two points opposite each other on either side of the center of the illumination pattern. As shown in Figure 5, a larger illumination pattern results in a larger illumination angle θ and lower parallelism. Low parallelism means a large illumination angle θ.

[0031] Figure 6 shows the relationship between the illumination pattern and the parallelism of the light when the illumination angle is 1°. As shown in Figure 6, when the illumination pattern is small, the illumination angle θ is small and the parallelism is high.

[0032] As described later, the visual inspection device 100 irradiates the object to be inspected OB1 with light while changing the size of the illumination pattern of the light source, and calculates a light luminance integrated value by accumulating the luminance of light with different parallelisms. Based on this light luminance integrated value, the visual inspection device 100 determines whether or not there are scratches or dents on the object to be inspected OB1.

[0033] 4-2. Calculation of Integrated Luminance Value For example, let's consider the case where the illumination angle is changed in 1° increments from 1° to 27°. In this case, the luminance values ​​for the illumination angle of 1°, 2°, ..., up to 27° are added together sequentially. The integrated luminance value is the sum of the luminances from the illumination angle of 1° to the illumination angle of 27°. Therefore, the visual inspection device 100 observes the light from the object OB1 to be inspected while changing the size of the illumination pattern in 1° increments. The visual inspection device 100 calculates the integrated luminance value.

[0034] 5. Integrated luminance value and presence of scratches, etc. 5-1. Determining whether there are any scratches or other damage. Figure 7 is a graph illustrating the integrated luminance values ​​in the case of scratches or dents. As shown in Figure 7, the integrated luminance values ​​change relatively significantly around the area with scratches or dents.

[0035] Figure 8 is a graph illustrating the integrated luminance value in the absence of scratches or dents. As shown in Figure 8, the integrated luminance value remains almost constant when there are no scratches or dents.

[0036] The judgment unit 164 determines that there are scratches or dents on the object OB1 if the integrated light luminance value changes significantly locally, as shown in Figure 7. The judgment unit 164 determines that there are no scratches or dents on the object OB1 if the integrated light luminance value does not change much depending on the location, as shown in Figure 8.

[0037] 5-2. Relationship between integrated luminance value and inclined surface The integrated luminance value is the sum of the reflected light after irradiating the object under inspection OB1 with light while varying the parallelism. Therefore, the integrated luminance value includes information not only from the reflected light from the reference surface Sf0, but also from the reflected light from surfaces Sf1, Sf2, and Sf3.

[0038] 5-3. Measurement of reference planes and inclined planes Figure 9 is a graph illustrating the relationship between the angle from the reference plane and the integrated luminance value in the visual inspection apparatus 100 of the first embodiment. The horizontal axis of Figure 9 represents the angle (°) from the reference plane Sf0. The vertical axis of Figure 9 represents the integrated luminance value.

[0039] As shown in Figure 9, when the angle from the reference plane Sf0 is 0°, the integrated luminance value is a0. When the angle from the reference plane Sf0 is 1°, the integrated luminance value is a1. When the angle from the reference plane Sf0 is 2°, the integrated luminance value is a2. When the angle from the reference plane Sf0 is 3°, the integrated luminance value is a3.

[0040] As mentioned above, the integrated luminance value includes information on reflected light from surfaces other than the reference surface Sf0. For example, in the case of the visual inspection device 100 where the relationship between the angle from the reference surface and the integrated luminance value is as shown in Figure 9, it is possible to detect reflected light from inclined surfaces with an angle of 0° to 5° relative to the reference surface Sf0. In this way, even when inspecting an object OB1 where the surface angle varies depending on the part, the visual inspection device 100 can inspect multiple parts simultaneously.

[0041] Figure 10 is a graph illustrating the integrated luminance profile of the reference surface Sf0 and surfaces Sf1, Sf2, and Sf3 on the object OB1 of the inspection object OB1 in the visual inspection apparatus 100 of the first embodiment. The horizontal axis of Figure 10 represents the position on the object OB1 of the inspection object. The vertical axis of Figure 10 represents the integrated luminance value.

[0042] Figure 10 shows that there are no scratches or dents on the reference surface Sf0, and surfaces Sf1, Sf2, and Sf3 of the object under inspection OB1. If a lot of object OB1 with scratches or dents is measured, one of the lines in Figure 10 will fluctuate significantly, as shown in Figure 7. For example, if there is a scratch or dent on surface Sf1, the line outputting the integrated luminance value a1 will fluctuate significantly. In this way, by calculating the integrated luminance value, it is possible to identify which surface has scratches or dents.

[0043] 5-4. When parallelism is not changed The visual inspection device 100 of the first embodiment calculates the integrated light luminance value while changing the parallelism. Therefore, for comparison with the first embodiment, a case in which the light luminance is detected without changing the parallelism will be described.

[0044] Figure 11 is a graph illustrating the relationship between the angle from the reference plane and the brightness of the light when the parallelism of the light is not changed. The horizontal axis of Figure 11 represents the angle (°) from the reference plane Sf0. The vertical axis of Figure 11 represents the brightness of the light.

[0045] As shown in Figure 11, the light intensity is high at an angle of 0° from the reference plane Sf0, but at other angles, the light intensity is almost zero. Therefore, in this case, the visual inspection device can only detect light at angles near 0° from the reference plane Sf0.

[0046] Figure 12 is a graph illustrating the relationship between position and light intensity when the parallelism of light is not changed. The horizontal axis of Figure 12 represents the position of the object OB1 being inspected. The vertical axis of Figure 12 represents the light intensity.

[0047] As shown in Figure 12, the luminance of the reflected light from the reference surface Sf0 is a positive value. However, the luminance of the reflected light from surfaces Sf1, Sf2, and Sf3 is almost zero. In other words, in a device that does not change the parallelism of light, the reference surface Sf0 can be inspected, but surfaces Sf1, Sf2, and Sf3 cannot be inspected simultaneously.

[0048] In a visual inspection system that does not change the parallelism of light, each surface must be inspected sequentially. Furthermore, if the surface is even slightly tilted relative to the reference surface Sf0, it becomes difficult for the camera 120 to receive the reflected light. In other words, the object to be inspected OB1 must be aligned with very high precision each time. Thus, in a visual inspection system that does not change the parallelism of light, the surface of the object to be measured on OB1 must be aligned with high precision each time it is measured. Therefore, in this type of visual inspection system, if the alignment accuracy decreases, there is a risk of failing to detect scratches or dents. In addition, the man-hours required for inspection will increase.

[0049] 6. Inspection Flow Figure 13 is a flowchart showing the processing of the visual inspection apparatus 100 according to the first embodiment.

[0050] First, the shielding plate control unit 161 sets the opening width of the shielding plate 150 (S101). Then, the LED light source 110 emits light. The shielding plate 150 changes the parallelism of this light. The half mirror 140 transmits the light from the LED light source 110 toward the object to be inspected OB1. The reflected light from the object to be inspected OB1 is reflected by the half mirror 140, enters the telecentric lens 130, and then enters the camera 120. Then, the process proceeds to S102.

[0051] Next, the light intensity detection unit 162 of the control unit 160 detects the intensity of the light incident on the camera 120 (S102). The light intensity detection unit 162 stores the detected light intensity information. Then, the process proceeds to S103.

[0052] In S103, it is determined whether the number of parallel light beams is greater than or equal to a predetermined threshold n. If the number of parallel light beams is greater than or equal to the predetermined threshold n (S103: Yes), proceed to S104. If the number of parallel light beams is less than the predetermined threshold n (S103: No), return to S101.

[0053] In S104, the light luminance integrated value calculation unit 163 acquires luminance information for multiple parallelisms of light detected and held by the light intensity detection unit 162. The light luminance integrated value calculation unit 163 then calculates the light luminance integrated value at each position of the object OB1 under inspection. This light luminance integrated value is the value obtained by integrating the luminance of the reflected light from the object OB1 under inspection for multiple parallelisms.

[0054] 7. Effects of the First Embodiment In the first embodiment, the visual inspection apparatus 100 irradiates the object to be inspected OB1 with light from the LED light source 110 and directs the reflected light into the camera 120. At the same time, the parallelism of the light from the LED light source 110 is gradually changed while irradiating the object to be inspected OB1, and the integrated value of the luminance of the reflected light is calculated.

[0055] The integrated luminance value is the sum of the reflected light after irradiating the object OB1 under inspection with light of different parallelisms. Therefore, the integrated luminance value includes not only information from the reference plane Sf0, but also information from reflected light from surfaces that are inclined at a relatively small angle with respect to the reference plane Sf0. Consequently, the visual inspection device 100 can simultaneously inspect not only surfaces at 0° with respect to the reference plane Sf0, but also inclined surfaces that are slightly inclined with respect to the reference plane Sf0.

[0056] The visual inspection device 100 can inspect the object OB1 even if the observation surface is slightly tilted. Therefore, the visual inspection device 100 can accurately detect scratches or dents. In addition, the visual inspection device 100 can reduce the man-hours required for inspection.

[0057] 8. Variations 8-1. Light Intensity Integrated Value Calculation Unit In the first embodiment of the visual inspection apparatus 100, the presence or absence of scratches on the object to be inspected OB1 is inspected by the integrated light luminance value. Instead of light luminance, an integrated value obtained by integrating other indicators related to light intensity may be used. For example, instead of the integrated light luminance value calculation unit 163, there is an integrated light intensity value calculation unit. The integrated light intensity value calculation unit calculates an integrated light intensity value by integrating indicators related to the light intensity of reflected light from the object to be inspected OB1 for multiple parallelisms changed by the light parallelism change unit.

[0058] 8-2. When the object to be inspected is large Figure 14 is a flowchart showing the process in a modified version of the visual inspection device 100 of the first embodiment. If the object to be inspected OB1 is large, the position of the object to be inspected OB1 can be shifted and the inspection can be performed multiple times.

[0059] Let's explain the differences from Figure 13. In S103, if the number of parallelisms of light is greater than or equal to a predetermined threshold n (S103: Yes), proceed to S211.

[0060] In S211, if the number of positions of the inspected object OB1 that have been irradiated with light is equal to or greater than the predetermined threshold m (S211: Yes), proceed to S104. If the number of positions of the inspected object OB1 that have been irradiated with light is less than the predetermined threshold m (S211: No), return to S101. To do this, the position of the inspected object OB1 should be moved.

[0061] 8-3. Angle of the surface of the object to be inspected In the object under inspection OB1, surfaces Sf1, Sf2, and Sf3 are inclined at 1°, 2°, and 3°, respectively, with respect to the reference plane Sf0. Of course, these inclination angles may be other than those specified above.

[0062] 8-4. Shape of the object to be inspected The object to be inspected, OB1, has a reference surface Sf0 and surfaces Sf1, Sf2, and Sf3. There may be one or more surfaces inclined with respect to the reference surface Sf0. Alternatively, there may be no surfaces inclined with respect to the reference surface Sf0.

[0063] 8-5. Parallelism of light In the first embodiment, the parallelism of the light is set to 15 different values ​​from 1° to 15° in 1° increments. The increment size of the parallelism may be different from that set. Also, the lower and upper limits of the parallelism of the light may be different from those set.

[0064] 8-6. Combinations You may freely combine the above variations.

[0065] (Second embodiment) A second embodiment will be described.

[0066] 1. Visual inspection device Figure 15 is a schematic diagram of the appearance inspection device 200 according to the second embodiment. The appearance inspection device 200 includes a display 210, a camera 120, a telecentric lens 130, a half mirror 140, a plano-convex lens 250, and a control unit 160.

[0067] The display 210 is a light source for illuminating the object OB1 under inspection. The display 210 can emit light from all or part of its screen. In other words, the display 210 can set the area that emits light.

[0068] The plano-convex lens 250 and the display 210 are light parallelism changing units that can change the parallelism of light.

[0069] Figure 16 shows the relationship between the illumination pattern and parallelism of the display 210 in the visual inspection apparatus 200 of the second embodiment. As shown in Figure 16, the larger the diameter of the illuminated area, the lower the parallelism of the light. Conversely, the smaller the diameter of the illuminated area, the higher the parallelism of the light.

[0070] 2. Effects of the second embodiment By using a combination of a display 210 that emits light from all or part of a flat screen and a plano-convex lens 250, the parallelism of the light can be adjusted. Therefore, similar to the first embodiment, the luminance integration value calculation unit 163 can calculate the luminance integration value.

[0071] 3. Variant 3-1. Projector A projector and screen may be used as the light source. Light from the projector passes through the screen, and the transmitted light enters the half mirror 140. The light that has passed through the half mirror 140 enters the object OB1 to be inspected.

[0072] (Third embodiment) A third embodiment will now be described. The hardware configuration of the visual inspection apparatus in the third embodiment is the same as that of the first embodiment.

[0073] 1. Pressed parts 1-1. Pressing and Inspection In the third embodiment, the object to be inspected, OB1, is a press-formed part. The press-formed part is covered with processing oil for lubrication within the press die. When inspecting a press-formed part after press forming, it is sufficient to inspect the press-formed part after the processing oil has been removed. However, if problems such as the adhesion of foreign matter occur in the press die, scratches or dents may similarly occur in a large number of processed parts produced in succession. Therefore, by inspecting the press-formed part immediately after press forming, i.e., before the processing oil is removed, abnormalities can be detected early, allowing for the early resolution of problems in the processing line and improving yield.

[0074] 1-2. Problems when machining oil is present Figure 17 shows the reflection of light on a metal part with no liquid on its surface. Here, the surface of the metal part is assumed to be an ideal mirror surface. Light is incident on the metal part and reflected by the mirror surface. In this case, the intensity of the incident light I0 is equal to the intensity of the reflected light I1.

[0075] Figure 18 shows the reflection of light on a metal part with a liquid on its surface. Here, the surface of the metal part is assumed to be an ideal mirror surface. The liquid is not perfectly transparent. Light enters the liquid, is reflected by the mirror surface of the metal part, and then travels back into the liquid. In this case, light is reflected when it enters the liquid from the air and when it enters the air from the liquid. Also, the light intensity is attenuated because it is absorbed by the liquid. In this case, the reflected light I2 is less than the incident light I0.

[0076] Therefore, in the case of machined parts whose surfaces are covered with machining oil, reflection and absorption of light occur due to the machining oil. When machining oil is present on the machined part, the intensity of light is relatively low. For this reason, it is not easy to measure scratches or dents on the surface of a machined part.

[0077] Figure 19 is a graph showing the angle dependence of reflectance when light is incident on paraffin oil from air. Here, the refractive index of air is set to 1 and the refractive index of paraffin oil is set to 1.67. In Figure 19, the horizontal axis represents the angle of incidence of light (°), and the vertical axis represents the reflectance (%).

[0078] When the angle of incidence is approximately 50° or less, the reflectance hardly changes, but when the angle of incidence is approximately 60° or more, the reflectance increases sharply. The difference between the reflectance at an angle of incidence of 0° and the reflectance at an angle of incidence of 15° is approximately 0.15%.

[0079] Therefore, if the pressed part has a relatively small angle with respect to the reference plane, it can be assumed that the effects of light reflection and absorption by the processing oil are constant regardless of the irradiation angle.

[0080] 2. Standardization Processing Section The control unit 160 has a scaling processing unit that scales an index relating to the intensity of light with respect to the parallelism of light to a numerical range between a predetermined maximum and minimum value. At this time, the light intensity integrated value calculation unit 163 calculates the light intensity integrated value by integrating the index relating to the intensity of light after it has been scaled by the scaling processing unit.

[0081] 3. Image processing method 3-1. Processing Method In the third embodiment, the reduction in light intensity due to machining oil is corrected by normalization. Here, normalization is a process that normalizes the light intensity measured from a single machined part so that the maximum value is set to 1 and the minimum value is set to 0. By performing this normalization, the same effect as multiplying the measured light intensity by a constant is obtained.

[0082] First, create a data array M(Xi, Yj, Am, In). Here, Xi and Yj are the X and Y coordinates of the captured image. Am is the illumination angle. In is the light intensity value.

[0083] Next, the maximum and minimum values ​​of the luminance value In are extracted for each coordinate (Xi, Yj). In most cases, the maximum value is taken when the illumination angle Am is large, and the minimum value is taken when the illumination angle Am is small. For example, if an illumination angle Am ranging from 1° to 27° is used, the luminance value In will almost always be at its minimum when the illumination angle is 1°, and at its maximum when the illumination angle is 27°.

[0084] Next, the luminance value In is scaled for each coordinate (Xi, Yj) so that the minimum value is 0 and the maximum value is 1. This scales the luminance value for each coordinate (Xi, Yj). For example, at coordinate (X1, Y2), the luminance value In for all illumination angles Am is multiplied by 1.2, and at coordinate (X3, Y4), the luminance value In for all illumination angles Am is multiplied by 1.6. Thus, the magnitude of the factor applied during normalization differs for each coordinate.

[0085] Next, the integrated luminance value is calculated for each coordinate (Xi, Yj) using the scaled luminance value In. That is, the luminance values ​​In for different illumination angles Am are added together.

[0086] 3-2. Processing Results Figure 20 is a graph showing the brightness value when there is no machining oil present. Figure 21 is a graph showing the brightness value when machining oil is present. As shown in Figures 20 and 21, in regions where the irradiation angle is large above a certain level, the brightness value when machining oil is present is smaller than the brightness value when machining oil is absent.

[0087] Figure 22 is a graph showing the brightness values ​​when there is no machining oil residue after normalization. Figure 23 is a graph showing the brightness values ​​when there is machining oil residue after normalization. By performing normalization, the maximum value of the measured light brightness is normalized to 1, regardless of the presence or absence of machining oil.

[0088] In this way, by performing normalization, the brightness value of light can be evaluated regardless of the presence or absence of machining oil. This is because the magnitude of the factors applied during normalization differs for each coordinate.

[0089] 4. Effects of the Third Embodiment The third visual inspection device normalizes the measured light luminance values. This makes the maximum luminance value when no processing oil is present equal to the maximum luminance value when processing oil is present. Therefore, the visual inspection device can determine the presence or absence of scratches or dents on the press-formed part, regardless of the presence or absence of processing oil.

[0090] 5. Variations 5-1. Maximum and Minimum Values After normalization, the maximum value of the luminance value is 1 and the minimum value is 0. However, the maximum value may be a number other than 1, and the minimum value may be a number other than 0. In this case, the scaling processing unit rescales the index of light intensity after scaling. For example, the maximum value may be 255 and the minimum value may be 0. Also, for example, the maximum value may be 100 and the minimum value may be -100. Any other numbers are acceptable as long as the maximum and minimum values ​​are determined and the proportional relationship between the maximum and minimum values ​​is maintained.

[0091] 5-2. Combinations The above modifications and modifications from the first to the second embodiment may be combined.

[0092] (Combination of embodiments) The first to third embodiments may be combined, including variations.

[0093] (Evaluation test) 1. Integrated luminance value The visual inspection apparatus 100 of the first embodiment was used. A metal plate free of scratches or dents was used as the object to be inspected OB1. Images were acquired by the camera 120 while changing the angle of the metal plate relative to the light source. The parallelism of the light was also changed at that time.

[0094] Figure 24 is a graph showing the relationship between the angle of a test specimen without scratches or dents and the integrated luminance value. The horizontal axis of Figure 24 represents the angle of the test specimen (°). The vertical axis of Figure 24 represents the integrated luminance value.

[0095] As shown in Figure 24, when the angle of the surface (reference plane) of the test specimen with respect to the optical axis is small from 0°, the integrated luminance value will be a non-zero value. For example, when the angle of the surface (reference plane) of the test specimen is between 1° and 5°, the integrated luminance value will be a non-zero value. Therefore, the visual inspection device can inspect for the presence or absence of scratches on surfaces that are inclined with respect to the reference plane.

[0096] Figure 25 is a graph showing the relationship between the angle and brightness value of a test specimen without scratches or dents. The horizontal axis of Figure 25 represents the angle (°) of the test specimen. The vertical axis of Figure 25 represents the brightness value.

[0097] As shown in Figure 25, when the angle of the surface (reference plane) of the test specimen with respect to the optical axis deviates from 0°, the luminance value is almost zero. For example, when the angle of the surface (reference plane) of the test specimen is between 1° and 5°, the luminance value is almost zero. For this reason, it is difficult for the visual inspection device to inspect for scratches on surfaces that are inclined with respect to the reference plane.

[0098] 2. Presence or absence of scratches or dents The second embodiment of the visual inspection apparatus 200 was used. A metal plate with scratches or dents was used as the object to be inspected OB1. Images were acquired by the camera 120 while changing the angle of the metal plate relative to the light source. The parallelism of the light was also changed at that time.

[0099] 2-1. When the test specimen is not angled (reference plane Sf0) First, let's explain the case where the test specimen is not angled. This corresponds to the case where the reference plane Sf0 is measured in the first embodiment.

[0100] Figure 26 is a graph (part 1) showing the relationship between the location of the indentation on the test specimen and the integrated luminance value. The horizontal axis of Figure 26 represents the location of the test specimen. The vertical axis of Figure 26 represents the integrated luminance value.

[0101] As shown in Figure 26, the integrated luminance value fluctuates significantly near the center. The integrated luminance value has two depressions. These depressions are thought to point to the left and right edges of the dent. Therefore, in this case, it is possible to determine whether or not there is a dent.

[0102] Figure 27 is a graph (part 1) showing the relationship between the location of the dent on the test specimen and the brightness value. The horizontal axis of Figure 27 represents the location of the test specimen. The vertical axis of Figure 27 represents the brightness value.

[0103] As shown in Figure 27, the brightness value fluctuates significantly near the center. The brightness value has two peaks near the center. Therefore, in this case, it is possible to determine whether or not there is a dent.

[0104] 2-2. When the test specimen is angled (Surface Sf1) Next, we will describe the case where the test specimen is angled. The angle of the test specimen is 1°. This corresponds to the case where surface Sf1 is measured in the first embodiment.

[0105] Figure 28 is a graph (part 2) showing the relationship between the location of the indentation on the test specimen and the integrated luminance value. The horizontal axis of Figure 28 represents the location of the test specimen. The vertical axis of Figure 28 represents the integrated luminance value.

[0106] As shown in Figure 28, the integrated luminance value fluctuates significantly near the center. The integrated luminance value has two depressions. These depressions are thought to point to the left and right edges of the dent. Therefore, in this case, it is possible to determine whether or not there is a dent.

[0107] Figure 29 is a graph (part 2) showing the relationship between the location of the dent in the test specimen and the brightness value. The horizontal axis of Figure 29 represents the location of the test specimen. The vertical axis of Figure 29 represents the brightness value.

[0108] As shown in Figure 29, the luminance value has a single peak near the center. This peak is very small. Therefore, in this case, it is difficult to determine whether or not there is a dent.

[0109] 3. If processing oil is present 3-1. Evaluation Method Figure 30 shows a conceptual decomposition of the measured light intensity value. As shown in Figure 30, the measured value includes baseline, signal, and noise. However, in practice, it is difficult to separate these three.

[0110] Figure 31 is a graph showing the maximum, minimum, and median values ​​of light intensity. The median is the value that is in the middle when the intensity values ​​within a certain interval are arranged in ascending or descending order.

[0111] The evaluation index EI shown below will be used. EI = (Imedian-Imin) / (Imax-Imedian) Imax: Maximum value Imin: Minimum value Median: Median

[0112] The above evaluation index EI is used for evaluation purposes and is not a processing item handled by the visual inspection device. A higher evaluation index EI tends to indicate stronger contrast in luminance values.

[0113] The luminance integration value was standardized to 8 bits. That is, the minimum value of the luminance integration value was set to 0, and the maximum value to 255.

[0114] Then, several test pieces were prepared by intentionally creating scratches on flat metal plates, and these test pieces were coated with processing oil.

[0115] 3-2. Test Results Figure 32 shows the measurement results for test specimen 1 with processing oil residue. Figure 32(a) is an image of test specimen 1 before normalization. Figure 32(b) is the luminance integrated value profile of test specimen 1 before normalization. Figure 32(c) is an image of test specimen 1 after normalization. Figure 32(d) is the luminance integrated value profile of test specimen 1 after normalization. In Figures 32(b) and (d), the horizontal axis represents the position on the surface of the test specimen, and the vertical axis represents the luminance integrated value. The dashed lines in Figures 32(a) and (c) indicate the measurement positions of the luminance integrated value profiles in Figures 32(b) and (d), respectively.

[0116] As shown in Figure 32(a), the scratch on test piece 1 is a slightly irregular annular shape, which can be seen in the image. There are two scratches at the measurement positions indicated by the dashed lines in Figure 32(a). In Figure 32(b), the scratch at the 2mm position can be detected, but the scratch at the 1mm position is difficult to detect due to noise. In Figure 32(d), noise that is thought to be caused by machining oil has been removed. The scratches at the 1mm and 2mm positions are clearly visible. In addition, the evaluation index EI has increased from 1.9 to 3.5 due to the normalization process. The increase in the evaluation index EI suggests that the contrast has become stronger.

[0117] Figure 33 shows the measurement results for test piece 2, which has machining oil residue. Figures 33(a), (b), (c), and (d) correspond to Figures 32(a), (b), (c), and (d). That is, the vertical and horizontal axes of the graph in Figure 33 are the same as in Figure 32.

[0118] As shown in Figure 33, the normalization process increased the evaluation index EI from 1.7 to 3.8, and the contrast improved. As shown in Figures 33(a) and 33(c), it is difficult to see the scratches in the image. In other words, the scratches on test piece 2 are sufficiently small. As shown in Figure 33(b), the noise has a significant impact before the normalization process. However, as shown in Figure 33(d), it is clear that scratches have occurred at the two measurement locations after the normalization process.

[0119] Figure 34 shows the measurement results for test piece 3, which has machining oil residue. Figures 34(a), (b), (c), and (d) correspond to Figures 32(a), (b), (c), and (d). That is, the vertical and horizontal axes of the graph in Figure 34 are the same as in Figure 32.

[0120] As shown in Figure 34, the normalization process increases the evaluation index EI from 1.2 to 2.9, and the contrast is enhanced. As shown in Figures 34(a) and (c), it is difficult to see the scratches in the image. In other words, the scratches on test piece 3 are sufficiently small. As shown in Figure 34(b), before the normalization process, the influence of noise is significant, making it very difficult to determine whether or not there are scratches. However, as shown in Figure 34(d), after the normalization process, it is clear that scratches have occurred.

[0121] 4. Summary of the experiment When using integrated luminance values, it is possible to simultaneously detect defects on both the reference surface Sf0 and the surface Sf1, as shown in Figures 26 and 28.

[0122] When using non-integrated luminance values, scratches on the reference surface Sf0 can be detected, as shown in Figures 27 and 29, but scratches on the surface Sf1 are difficult to detect. In the experiment, larger scratches or dents were formed on the test specimen, so small peaks were observed even when using non-integrated luminance values. However, if the scratches or dents are small, there is a risk that no peaks will be observed when using non-integrated luminance values.

[0123] Thus, the visual inspection device 100 of the first embodiment and the visual inspection device 200 of the second embodiment can simultaneously inspect both the reference surface and the inclined surface of an object to be inspected that has a surface inclined with respect to the reference surface.

[0124] The visual inspection device of the third embodiment can inspect with high accuracy for scratches or dents on press-formed parts to which processing oil is attached.

[0125] (Note) The appearance inspection apparatus in the first embodiment includes a light source for irradiating an object to be inspected with light, a telecentric lens for transmitting reflected light from the object to be inspected, an imaging unit for imaging the light transmitted through the telecentric lens, a light parallelism changing unit for changing the parallelism of the incident light incident on the object to be inspected, and a control unit. The control unit includes a light intensity integrated value calculation unit for calculating a light intensity integrated value by integrating an index of the intensity of the light received by the imaging unit, and a determination unit for determining the surface condition of the object to be inspected from the light intensity integrated value calculated by the light intensity integrated value calculation unit. The light intensity integrated value calculation unit calculates a light intensity integrated value by integrating an index of the light intensity of the reflected light from the object to be inspected for multiple parallelisms changed by the light parallelism changing unit.

[0126] In the visual inspection apparatus of the second embodiment, in addition to the first embodiment, the light intensity integrated value calculation unit calculates a light luminance integrated value as the light intensity integrated value, which is obtained by integrating the luminance of the reflected light from the object to be inspected.

[0127] In the third embodiment, the visual inspection apparatus, in addition to the first or second embodiment, allows the light source to set a region to emit light.

[0128] In the visual inspection apparatus of the fourth embodiment, in addition to the first or second embodiment, the light parallelism changing unit has a shielding plate that shields light from the light source. The control unit has a shielding plate control unit that controls the opening width of the shielding plate.

[0129] The visual inspection apparatus in the fifth embodiment, in addition to the features of the first to fourth embodiments, includes a half-mirror positioned between the light source and the object to be inspected. The half-mirror illuminates the object to be inspected with light from the light source and illuminates the telecentric lens with reflected light from the object to be inspected.

[0130] In the visual inspection apparatus of the sixth embodiment, in addition to the embodiments of the first to fifth embodiments, the object to be inspected has a reference surface and an inclined surface that is inclined with respect to the reference surface.

[0131] In the seventh aspect of the visual inspection apparatus, in addition to the aspects of the first to sixth aspects, the control unit has a scaling processing unit that scales an index relating to the intensity of light with respect to the parallelism of light to a numerical range between a predetermined maximum and minimum value.

[0132] In the visual inspection apparatus of the eighth embodiment, in addition to the seventh embodiment, the light intensity integrated value calculation unit calculates the light intensity integrated value by integrating an index relating to the light intensity after it has been scaled by the scaling processing unit.

[0133] In the visual inspection apparatus of the ninth embodiment, in addition to the eighth embodiment, the scaling processing unit scales the index relating to the light intensity after scaling again. [Explanation of symbols]

[0134] 100…Visual inspection device 110...LED light source 120... Camera 130... Telecentric lens 140... Half mirror 150...shielding plate 160... Control Unit 161...Shielding plate control unit 162...Light intensity detection unit 163... Luminance integrated value calculation unit 164...judgment department

Claims

1. A light source for illuminating the object to be inspected, A telecentric lens that transmits reflected light from the object to be inspected, An imaging unit that captures light transmitted through the telecentric lens, A light parallelism changing unit that changes the parallelism of the incident light incident on the object to be inspected, Control unit and It has, The control unit, A light intensity integrated value calculation unit calculates a light intensity integrated value by accumulating an index related to the intensity of light received by the imaging unit, The system includes a determination unit that determines the surface condition of the object to be inspected from the integrated light intensity value calculated by the integrated light intensity value calculation unit, The aforementioned light intensity integrated value calculation unit is: The integrated light intensity value is calculated by accumulating an index relating to the light intensity of reflected light from the object being inspected for multiple parallelisms changed by the light parallelism changing unit. A visual inspection device that includes [specific components / features].

2. In the visual inspection apparatus according to claim 1, The aforementioned light intensity integrated value calculation unit is: The integrated light intensity value is calculated by integrating the luminance of the reflected light from the object being inspected. A visual inspection device that includes [specific components / features].

3. In the visual inspection apparatus according to claim 1 or claim 2, The aforementioned light source is It is possible to set the area that emits light. A visual inspection device that includes [specific components / features].

4. In the visual inspection apparatus according to claim 1 or claim 2, The optical parallelism changing unit is, It has a shielding plate that blocks light from the aforementioned light source, The control unit, The shielding plate has a control unit that controls the opening width of the shielding plate. A visual inspection device that includes [specific components / features].

5. In the visual inspection apparatus according to claim 1 or claim 2, It has a half-mirror positioned between the light source and the object to be inspected, The aforementioned half mirror is The light from the light source is irradiated onto the object to be inspected. Irradiating the telecentric lens with reflected light from the object to be inspected. A visual inspection device that includes [specific components / features].

6. In the visual inspection apparatus according to claim 1 or claim 2, The aforementioned visual inspection device is a device for inspecting an object to be inspected, which includes a reference surface and an inclined surface that is inclined with respect to the reference surface.

7. In the visual inspection apparatus according to claim 1 or claim 2, The control unit, The system includes a scaling processing unit that scales an index relating to the intensity of the light with respect to the parallelism of the light to a numerical range between a predetermined maximum and minimum value. A visual inspection device that includes [specific components / features].

8. In the visual inspection apparatus according to claim 7, The aforementioned light intensity integrated value calculation unit is: The integrated light intensity value is calculated by accumulating the indicators related to the light intensity after they have been scaled by the scaling processing unit. A visual inspection device that includes [specific components / features].

9. In the visual inspection apparatus according to claim 8, The scaling processing unit, Re-scaling the indicator of light intensity after it has been scaled. A visual inspection device that includes [specific components / features].

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