Lighting device, inspection device, and inspection method for inspecting surface irregularities of an object to be inspected.

Abstract

To provide a luminaire, an inspection apparatus and an inspection method for reliably detecting micro convexoconcave of an inspection object surface.MEANS FOR SOLVING THE PROBLEM: An inspection equipment 1 for inspecting convexoconcave of an inspection object surface 13 comprises: a luminaire 2 including a planar LED light source 20 emitting white light, a first optical diffraction part 21 composed of a first holographic diffraction optical element 23 through which light emitted from the planar LED light source 20 transmits and is diffracted, and a second optical diffraction part 22 composed of a second holographic diffraction optical element 24 on which, when light emitted from the first optical diffraction part 21 transmits therethrough, the light is diffracted in a direction opposite to the first optical diffraction part 21; an inspection object table 12 the inspection object 11 is placed on a top face and third irradiation light 29 emitted from the luminaire 2 emitted to the surface 13 of the inspection object 11; and a detection part 4 for detecting reflected light 30 from the inspection object 11.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an illumination device, an inspection device, and an inspection method for inspecting unevenness on the surface of an inspection object.

Background Art

[0002] In recent years, many automation systems applying machine vision technology have been developed and used for inspecting manufactured products. In particular, a shiny surface is one of the most difficult inspection objects for machine vision. For example, Patent Document 1 discloses the following technique using a holographic diffractive optical element as a method for inspecting unevenness on the surface of an inspection object. Here, a holographic diffractive optical element is an optical element that utilizes the property of a hologram in which colors are dispersed when white light is diffracted.

[0003] As shown in FIG. 7, the emitted light from the white LED light source 210 is diffracted by the holographic diffractive optical element 230 at a predetermined angle for each color of red light 310 (dashed line), green light 320 (one-dot chain line), and blue light 330 (solid line), and made into parallel light for each color, and these are irradiated onto the surface 130 of the inspection object 110 as irradiation light 240, and the reflected light 300 is photographed by the camera 410. The region within the double arrow X on the surface 130 of the inspection object 110 is the inspection range.

[0004] At this time, for example, when there are convex portions on the surface 130 of the inspection object 110, the reflection angles of the reflected light are different between the surface other than the convex portions where the convex portions do not exist and the convex portion surfaces where the convex portions exist. Therefore, on the imaging screen of the camera 410, the convex portions are shown with their shape portions in a color different from that of the surface other than the convex portions. As a result, the presence and shape of the convex portions on the surface 130 of the inspection object 110 can be detected.

[0005] In addition, a holographic illumination unit and an appearance inspection robot equipped with the holographic illumination unit applying the technique of Patent Document 1 have been proposed (Non-Patent Document 1).

[0006] Figure 8 shows the hue profile when measuring the smooth surface of the object to be inspected 110 using the apparatus described in Non-Patent Document 1 above. The horizontal axis represents the horizontal position of the image in the direction of arrow A in Figure 7 [pixel], and the vertical axis represents the hue angle [degrees]. A hue circle is a circular arrangement of all hues in order, and complementary colors are placed at opposite positions on the hue circle. As a result, the hue angles are defined as follows: 0 to 60 degrees represents red to yellow, 60 to 120 degrees represents yellow to green, 120 to 180 degrees represents green to cyan, 180 to 240 degrees represents cyan to blue, 240 to 300 degrees represents blue to magenta, and 300 to 360 degrees represents magenta to red.

[0007] Figure 8 shows that the red, green, and blue regions, which are nearly flat, are observed as separate areas, and the intermediate colors of each color in the sloping boundary area are observed to flow smoothly and continuously. Therefore, if a convex or concave area exists within this observation area, a change in the hue angle due to the different angles of reflected light at the convex or concave area will be observed, allowing for the detection of convex or concave areas on the surface of the object being inspected. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2018-91770 [Non-patent literature]

[0009] [Non-Patent Document 1] https: / / www.maxis-inc.com / information / development / article / 138 [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] Incidentally, the methods described in Patent Document 1 and Non-Patent Document 1 use a point source white LED light source 210, so the field of view (inspection area by the holographic diffractive optical element 230) is narrow, approximately 25 mm x 25 mm, making them unsuitable for large-area inspection applications. Therefore, we considered that by combining the methods described in Patent Document 1 and Non-Patent Document 1 with a planar LED light source (sometimes called a linear light source or line-shaped light source) that has, for example, a long, narrow rectangular shape as its light-emitting area, it would be possible to apply it to large-area inspection applications. In the conventional inspection apparatus shown in Figure 7, we changed the light source to a planar LED light source that emits white light with a rectangular light-emitting area of ​​13 mm wide x 200 mm long, and also placed a holographic diffractive optical element 230 with an enlarged area capable of receiving the light irradiated from the planar LED light source between the planar LED light source and the object to be inspected, so as to be in contact with the planar LED light source, and attempted measurement. The resulting hue profile is shown in Figure 9.

[0011] As is clear from Figure 9, in a conventional inspection device, when the illumination light source was changed to a planar LED light source having a light-emitting area of ​​13 mm in width and 200 mm in length, and a holographic diffractive optical element 230 was placed between the white planar LED light source and the object to be inspected, the hue profile differed significantly from that in Figure 8, resulting in an analysis result with insufficient hue change. Therefore, simply changing the methods of Patent Document 1 and Non-Patent Document 1 to a combination of a planar LED light source and a holographic diffractive optical element is not sufficient to inspect a wide area of ​​the object to be inspected.

[0012] This is because, in planar LED light sources, in order to make the luminous intensity distribution within the light-emitting region uniform, for example, the light-emitting surface is roughened, or inorganic materials such as silica are incorporated into the encapsulating resin of the LED element to scatter (diffuse) the light. Therefore, when the methods of Patent Document 1 and Non-Patent Document 1 are combined with a planar LED light source, the spread of the emitted light from the planar LED light source is large, that is, the directivity of the emitted light is low, and the dispersion of the diffracted light that has passed through the holographic diffracting optical element 220 is large. [Means for solving the problem]

[0013] Therefore, the present invention provides a lighting device, an inspection device, and an inspection method for inspecting surface irregularities of an object to be inspected, which, by a new method, provides performance equivalent to or better than conventional methods and enables inspection over a wide area.

[0014] To solve the above problems, the present invention of claim 1 is: A white surface with a uniform luminosity distribution within the luminescent region. Light source and White surface When light emitted from a light source passes through , converting each of the multiple colors into parallel light at a predetermined angle for each color. A first optical diffraction section is composed of diffracting holographic diffracting optical elements, and when light emitted from the first optical diffraction section is transmitted, Convert each of the multiple colors into parallel light at a predetermined angle, It comprises a second optical diffraction section composed of a holographic diffracting optical element that diffracts in the opposite direction to the first optical diffraction section, and light is emitted from the second optical diffraction section. 、 This is a lighting device for inspecting the surface irregularities of an object being inspected.

[0015] In the present invention of claim 1, the lighting device is A white surface with a uniform luminosity distribution within the luminescent region. Light source and White surface When light emitted from a light source passes through , converting each of the multiple colors into parallel light at a predetermined angle for each color. A first optical diffraction section is composed of diffracting holographic diffracting optical elements, and when light emitted from the first optical diffraction section is transmitted, Convert each of the multiple colors into parallel light at a predetermined angle, Since the device is equipped with a second optical diffraction section composed of a holographic diffracting optical element that diffracts in the opposite direction to the first optical diffraction section, firstly, even when the directivity of the light source is low, the second optical diffraction section can suppress the dispersion of diffracted light that has passed through the first optical diffraction section, and the diffracted light can be efficiently irradiated onto the target object for inspection.

[0016] Secondly, in the second photodiffraction section, Convert each of the multiple colors into parallel light at a predetermined angle, Since the diffraction direction is reversed with respect to the first optical diffraction section, the light dispersed in the first optical diffraction section is diffracted in the reverse direction. Irradiate the object to be inspected. This makes it possible to achieve performance equivalent to or better than conventional methods, while also expanding the inspection target range compared to conventional methods.

[0017] Furthermore, by adjusting the diffraction angles of each color, such as blue, green, red, etc., of the holographic diffractive optical elements constituting the first light diffractive part and the second light diffractive part, and the distance between the holographic diffractive optical elements, the position where the lights overlap can be adjusted. Therefore, the distance between the illumination device and the inspection object can be adjusted within a wide range, and it can be applied to a wide range of uses, such as detecting scratches on a hard disk, detecting unevenness on the mold surface in a resin molding machine, and detecting unevenness on a painted surface.

[0018] Here, in the second light diffractive part, the statement that it "diffracts in the opposite direction" to the first light diffractive part means that, for example, when light emitted from the light source is irradiated from the front side to the back side of the paper surface, and the diffraction by the holographic diffractive optical element constituting the first light diffractive part diffracts from the front side to the back side of the paper surface and in the upward direction of the paper surface, the diffraction of the light transmitted through the second light diffractive part diffracts from the front side to the back side of the paper surface and in the downward direction of the paper surface. That is, it means that the change in the diffraction angle between the first light diffractive part and the second light diffractive part when viewed from the front side to the back side of the paper surface changes by more than 90°. Considering the above effects of the present invention, it is desirable that the change in the diffraction angle between the first light diffractive part and the second light diffractive part is 180° or close to it.

[0019] The invention according to claim 2 is, in the invention according to claim 1, White surface The light source is LED (Light Emitting Diode) An illumination device for inspecting the unevenness on the surface of the inspection object.

[0020] In the invention according to claim 2, [[ID=!7]] White surface The light source is LED (Light Emitting Diode) Therefore, a light source with high output, high wavelength stability, small size, long life and low cost can be obtained.

[0021] The invention according to claim 3 includes the illumination device according to claim 1 or claim 2, an inspection object mounting table on which the inspection object is placed on the upper surface, and the light emitted from the illumination device is irradiated onto the surface of the inspection object, and a detection unit that detects the reflected light from the surface of the inspection object. 、 An inspection device for inspecting the unevenness on the surface of the inspection object.

[0022] The present invention as of claim 3 comprises a lighting device as described in claim 1 or claim 2, an inspection object mounting platform on which an object to be inspected is placed and on which light emitted from the lighting device irradiates the surface of the object to be inspected, and a detection unit for detecting reflected light from the object to be inspected. Therefore, an inspection device can be manufactured that has performance equal to or better than conventional devices and can inspect a wide area for inspecting surface irregularities of an object to be inspected. Furthermore, by using a planar light source of a white LED (white light-emitting diode), an inspection device can be manufactured that is high-output, highly wavelength-stable, compact, long-life, and inexpensive for inspecting surface irregularities of an object to be inspected.

[0023] The present invention according to claim 4 is A white surface with a uniform luminosity distribution within the luminescent region. Light emitted from a light source is used as the first irradiation light and irradiated onto a first optical diffraction section composed of holographic diffractive optical elements. The diffracted light, converted into parallel light for each of the multiple colors at predetermined angles by the first optical diffraction section, is then used as the second irradiation light and irradiated onto a second optical diffraction section composed of holographic diffractive optical elements. The light is converted into parallel light for each color at a predetermined angle, This inspection method involves irradiating the object to be inspected with light diffracted in the opposite direction to the first light diffraction unit as a third irradiation light, detecting the reflected light reflected from the surface of the object to be inspected with a detection unit, and inspecting the surface irregularities of the object to be inspected by the change in the color of the reflected light between the irregularities on the surface of the object to be inspected and the other surfaces of the object to be inspected.

[0024] In the present invention of claim 4, A white surface with a uniform luminosity distribution within the luminescent region. Light emitted from a light source is used as the first irradiation light and irradiated onto a first optical diffraction section composed of a holographic diffractive optical element. The diffracted light, converted into parallel light for each of multiple colors at predetermined angles by the first optical diffraction section, is then used as the second irradiation light and irradiated onto a second optical diffraction section composed of a holographic diffractive optical element. Firstly, even if the directivity of the light source is low, the dispersion of the diffracted light that has passed through the first optical diffraction section can be suppressed by the second optical diffraction section, and the diffracted light can be efficiently irradiated onto the target object to be inspected.

[0025] Secondly, in the second photodiffraction section, Each of the multiple colors is converted to parallel light at a predetermined angle,Since the diffraction direction is reversed with respect to the first optical diffraction section, the light dispersed in the first optical diffraction section is diffracted in the reverse direction. The third beam of light is used to illuminate the object being inspected. This makes it possible to achieve performance equivalent to or better than conventional methods, while also expanding the inspection target range compared to conventional methods.

[0026] Then, the light diffracted by the second holographic diffractive optical element is irradiated onto the object to be inspected as the third irradiation light, and the reflected light reflected from the surface of the object to be inspected is detected by the detection unit. As a result, the surface of the object to be inspected can be inspected by the color change between the uneven parts of the surface of the object to be inspected and the parts of the surface that are not uneven in the reflected light.

[0027] Furthermore, by adjusting the diffraction angles of each color of the holographic diffractive optical elements constituting the first and second optical diffraction sections, such as blue, green, and red, and the distance between the holographic diffractive optical elements, the position where the light overlaps can be adjusted. This allows for adjustment of the distance between the illumination device and the object being inspected over a wide range, making it applicable to a wide range of uses, such as detecting scratches on hard disks, detecting irregularities on mold surfaces in resin molding machines, and detecting irregularities on painted surfaces. [Effects of the Invention]

[0028] The lighting equipment is A white surface with a uniform luminosity distribution within the luminescent region. Light source and White surface When light emitted from a light source passes through , converting each of the multiple colors into parallel light at a predetermined angle for each color. A first optical diffraction section is composed of diffracting holographic diffracting optical elements, and when light emitted from the first optical diffraction section is transmitted, Convert each of the multiple colors into parallel light at a predetermined angle, Since the device is equipped with a second optical diffraction section composed of a holographic diffracting optical element that diffracts in the opposite direction to the first optical diffraction section, firstly, even when the directivity of the light source is low, the second optical diffraction section can suppress the dispersion of diffracted light that has passed through the first optical diffraction section, and the diffracted light can be efficiently irradiated onto the target object for inspection.

[0029] Secondly, in the second photodiffraction section, Convert each of the multiple colors into parallel light at a predetermined angle, Since the diffraction direction is reversed with respect to the first optical diffraction section, the light dispersed in the first optical diffraction section is diffracted in the reverse direction. Irradiate the object to be inspected. This makes it possible to achieve performance equivalent to or better than conventional methods, while also expanding the inspection target range compared to conventional methods.

[0030] Furthermore, by adjusting the diffraction angles of each color of the holographic diffractive optical elements constituting the first and second optical diffraction sections, such as blue, green, and red light, and the distance between the holographic diffractive optical elements, the position where the light overlaps can be adjusted. This allows for adjustment of the distance between the illumination device and the object being inspected over a wide range, making it applicable to a wide range of uses, such as detecting scratches on hard disks, detecting irregularities on mold surfaces in resin molding machines, and detecting irregularities on painted surfaces. [Brief explanation of the drawing]

[0031] [Figure 1] This is a schematic diagram showing the overall configuration of the inspection apparatus according to the first embodiment of the present invention. [Figure 2] This is a hue profile showing the relationship between the measurement position and the hue angle when inspecting a smooth surface of an object using the inspection device shown in Figure 1. [Figure 3] This is a schematic diagram illustrating the presence of scratches on a hard drive. [Figure 4] (a) is a hue profile showing the relationship between the measurement position and the hue angle when inspecting scratches on the hard disk shown in Figure 3 using the inspection apparatus of the first embodiment of the present invention, and (b) is a hue profile showing the relationship between the measurement position and the hue angle when inspecting scratches on the hard disk shown in Figure 3 using the inspection apparatus of Non-Patent Literature 1. [Figure 5] Figure 4 is a graph showing the relationship between the measurement position and the signal-to-noise ratio, where (a) is the case of the inspection apparatus according to the first embodiment of the present invention, and (b) is the case of the inspection apparatus according to Non-Patent Document 1. [Figure 6] This is a schematic diagram showing the overall configuration of a surface inspection apparatus according to a second embodiment of the present invention. [Figure 7] This is a schematic diagram showing the overall configuration of a conventional surface inspection device (Patent Document 1). [Figure 8]This is the hue profile obtained when inspecting a smooth surface of an object using a conventional surface inspection device (Non-Patent Literature 1). [Figure 9] This is the hue profile when inspecting a smooth surface of an object using a surface inspection device with a planar LED light source that emits white light, replacing the light source of a conventional surface inspection device. [Modes for carrying out the invention]

[0032] The overall configuration of the inspection apparatus 1 of the first embodiment of the present invention will be described with reference to Figure 1. As shown in Figure 1, the inspection apparatus 1 for inspecting the unevenness of the surface 13 of an object to be inspected 11 consists of an illumination device 2 for inspecting the unevenness of the surface 13 of the object to be inspected 11, an inspection object placement table 12 on which the object to be inspected 11 is placed and on which light emitted from the illumination device 2 is irradiated onto the surface 13 of the object to be inspected 11 as a third irradiation light 29, and a detection unit 4 for detecting reflected light 30 from the surface 13 of the object to be inspected 11.

[0033] The lighting device 2 uses a planar LED light source 20 that emits white light as its light source. The first light diffraction section 21 is composed of a first holographic diffracting optical element 23, and the second light diffraction section 22 is composed of a second holographic diffracting optical element 24. In this first embodiment, light emitted from the planar LED light source 20 is irradiated onto the first holographic diffracting optical element 23 as the first irradiation light 27, and light emitted from the first holographic diffracting optical element 23 is irradiated onto the second holographic diffracting optical element 24 as the second irradiation light 28. Therefore, the light emitted from the second holographic diffracting optical element 24 becomes the light emitted from the lighting device 2 toward the object to be inspected 11, i.e., the third irradiation light 29.

[0034] The light source is a planar LED light source 20 that emits white light, and therefore has the characteristics of high output, high wavelength stability, small size, long lifespan, and low cost. The white LED is an LED light source that emits white light by mixing the blue light emitted from the LED element with the yellow light emitted from the phosphor, which is excited by the blue light and contains a resin around the LED element. The planar LED light source 20 uses a line lighting system (Leimac IDBBL-LSR200w-S) with a light-emitting area of ​​13 mm width x 200 mm length, where the luminous intensity distribution within the light-emitting area is uniform. Figure 1 is a view of the planar LED light source 20 from the short side (13 mm width).

[0035] Furthermore, the planar LED light source 20 is not limited to the above dimensions in terms of width and length, nor is its shape limited to a rectangle. Also, the planar LED light source 20 emitting white light may be an LED light source in which a resin containing an LED element that emits blue light and a phosphor that is excited by the blue light and emits green and red light is sealed around the LED element, and white light is emitted by mixing the blue light emitted from the LED element with the green and red light emitted from the phosphor. Alternatively, the LED light source may be an LED element that emits ultraviolet light and a resin containing a phosphor that is excited by the ultraviolet light and emits blue, green, and red light is sealed around the LED element, and white light is emitted by mixing the blue, green, and red light emitted from the phosphor. Furthermore, a planar LED light source 20 that emits white light may be used, in which multiple sets of LED elements emitting blue, green, and red light (the number of each is adjusted according to brightness and color mixing) are arranged on a printed circuit board and treated to equalize the luminous intensity distribution within the light-emitting area. Furthermore, the light source emitting white light is not limited to LED light sources; xenon light, halogen light, laser light, etc., can also be used.

[0036] In this first embodiment, the first holographic diffractive optical element 23 constituting the first optical diffraction section 21 is such that, as shown in Figure 1, when the first irradiation light 27, which is white light incident perpendicularly from above onto the first holographic diffractive optical element 23, passes through the first holographic diffractive optical element 23, the red light 31 (dashed line) with a wavelength of 635 nm is diffracted to the left at an angle of 16°, the green light 32 (dotted line) with a wavelength of 532 nm is diffracted at an angle of 13°, and the blue light 33 (solid line) with a wavelength of 450 nm is diffracted at an angle of 11°. As a result, the red light 31, green light 32, and blue light 33 are emitted downward as parallel light for each color, as the second irradiation light 28. Note that the diffraction angles are not limited to those shown above.

[0037] In this first embodiment, the second holographic diffractive optical element 24 constituting the second light diffraction section 22 is such that, in Figure 1, red light 31 incident on the second holographic diffractive optical element 24 from above and vertically at an angle of 16° is diffracted to the right at an angle of 16°. Similarly, green light 32 incident on the second holographic diffractive optical element 24 from above and vertically at an angle of 13° is diffracted to the right at an angle of 13°, and blue light 33 incident on the second holographic diffractive optical element 24 from above and vertically at an angle of 11° is diffracted to the right at an angle of 11°. As a result, the red light 31, green light 32, and blue light 33 are emitted downward as parallel light for each color, as the third irradiation light 29. Note that the diffraction angle is not limited to the above. Figure 1 also shows the light path for light emitted from both ends of the planar LED light source 20.

[0038] In this first embodiment, the first holographic diffractive optical element 23 constituting the first light diffraction section 21 is positioned in contact with the planar LED light source 20. In Figure 1, the first holographic diffractive optical element 23 is depicted separately below the planar LED light source 20; this is to explain the first irradiated light 27 from the planar LED light source 20 and the diffraction related to the first holographic diffractive optical element 23. Of course, the first holographic diffractive optical element 23 may also be positioned away from the planar LED light source 20, as shown in Figure 1.

[0039] Furthermore, a second holographic diffractive optical element 24, which constitutes the second light diffraction section, is positioned parallel to the first holographic diffractive optical element 23 at a position (f1) 100 mm below it. The area of ​​the second holographic diffractive optical element 24 has been enlarged to 70 mm × 200 mm in order to enable it to receive the second irradiated light 28 from the first holographic diffractive optical element 23. Also, in Figure 1, when viewed from above the planar LED light source 20, the second holographic diffractive optical element 24 is positioned such that the angle of diffraction changes by 180° relative to the first holographic diffractive optical element 23.

[0040] In this first embodiment, since the first holographic diffractive optical element 23 and the second holographic diffractive optical element 24 use the same absolute value of the angle of diffraction downward as described above, the inspection object placement table 12 was adjusted so that the second holographic diffractive optical element 24 and the surface 13 of the inspection object 11 were parallel at a position (f2) 100 mm below the second holographic diffractive optical element 24. By placing the surface 13 of the inspection object 11 in this position, the red light 31, green light 32, and blue light 33 diffracted by the second holographic diffractive optical element 24 Irradiate the object to be inspected 11. It is possible.

[0041] The detection unit 4 of this first embodiment consists of a camera 41 that captures reflected light 30 from the surface 13 of the object to be inspected 11, a monitor 42 that displays the image (image) captured by the camera 41, an image data analysis unit that analyzes and stores the image data from the camera 41, and a control unit 43 that controls the positions of the object to be inspected 11 and the camera 41, and the image capture on the monitor 42. The camera 41 used is a GigE color camera BG302LMCF (manufactured by Toshiba Terry Corporation). The distance fc from the surface 13 of the object to be inspected 11 to the camera 41 is 50 mm.

[0042] As is clear from Figure 1, by using the inspection device 1 described above, the inspection target area (double arrow Y), which is the part where each color is mixed, is wider than the conventional inspection target area (double arrow X), and it can be seen that the inspection target area is also wider in the width direction. Therefore, the inspection area can be expanded not only in the direction of the long side of the rectangular planar LED light source 20, but also in the direction of the short side.

[0043] Figure 2 is a hue profile showing the relationship between the measurement position in the direction of arrow A in Figure 1 and the hue angle when the inspection device 1 in Figure 1 is used, an object to be inspected 11 with a smooth surface 13 is prepared on the object to be inspected 12, and the object to be inspected 11 is placed with the smooth surface facing upwards and measured.

[0044] As is clear from Figure 2, there is a gradual change from the red to the blue region, indicating a significant improvement compared to Figure 9.

[0045] Furthermore, when comparing the hue profile obtained by measuring a smooth surface using the apparatus described in Non-Patent Document 1 (Figure 7) shown in Figure 8, it can be seen that the colors are blended, the flat areas disappear in Figure 2, and the hue characteristics in the central part become more linear.

[0046] Therefore, by adding the second holographic diffracting optical element 24, which is the second light diffraction section 22, it became possible to realize an illumination device 2 that suppresses excessive color dispersion even when using a planar LED light source 20 that emits white light with low directivity, has performance equal to or better than conventional devices, and can also expand the inspection target area, as well as an inspection device 1 equipped with the above illumination device 2.

[0047] Next, the measurement results of the unevenness of the object to be inspected will be explained using the inspection apparatus of the first embodiment of the present invention, based on Figures 3 to 5. As shown in Figure 3, this measurement measures scratches, i.e., recesses, formed on the surface of the object to be inspected. The object to be inspected is a scratch 52 on the magnetic disk 51 of the storage device 50. The scratch 52 is a recess with a width W of 0.3 mm and a length L of 0.5 mm.

[0048] Figure 4 shows the results when measuring the area of ​​scratch 52. (a) is the measurement result when using the inspection device 1 of the present invention described above, and is the hue profile in the direction of arrow A in Figure 1. (b) is the hue profile in the direction of arrow A in Figure 7 when using the device described in Non-Patent Literature 1. Here, "Hue" (solid line) in Figure 4 represents the measurement result of the area of ​​scratch 52, and "Noise" (dashed line) represents the measurement result of the area other than scratch 52, i.e., the background.

[0049] Furthermore, Figure 5 is a graph with the signal-to-noise ratio (SN) difference in the measurement shown in Figure 4 on the vertical axis, where (a) is the measurement result when using the inspection device 1 of the present invention, and (b) is the result when using the device described in Non-Patent Document 1. Note that the SN difference is 20log 10 It can be calculated from (S / N).

[0050] Comparing Figure 5(a) and Figure 5(b), it can be seen that the range of the defect 52 where the SN difference is detected (double arrow Z) is wider in Figure 5(a). Therefore, by using the inspection device 1 of the present invention, the location and size of the defect 52 can be detected more accurately than in the conventional method. The same applies to protrusions; in the case of protrusions, the shape of the protrusion is displayed in a different color from the rest of the surface, so the presence and shape of the protrusion on the surface 13 of the object to be inspected 11 can be detected more accurately than in the conventional method.

[0051] Next, a second embodiment of the present invention will be described with reference to Figure 6. In this second embodiment, the second holographic diffracting optical element 24 constituting the second light diffraction section 22 used in the illumination device 2 of Figure 1 is replaced with a third holographic diffracting optical element 25 and a fourth holographic diffracting optical element 26. The first holographic diffracting optical element 23 constituting the first light diffraction section 21 is the same as that used in the first embodiment.

[0052] The third holographic diffractive optical element 25, which constitutes the second optical diffraction section 22, diffracts red light 31 that has been diffracted by the first holographic diffractive optical element 23, which constitutes the first optical diffraction section 21, and is incident on the third holographic diffractive optical element 25 from above and at an angle of 16° from the vertical, perpendicularly downwards to the third holographic diffractive optical element 25. Similarly, for green light 32, green light 32 that has been incident on the third holographic diffractive optical element 25 from above and at an angle of 13° from the vertical is diffracted perpendicularly downwards to the third holographic diffractive optical element 25. For blue light 33, blue light 33 that has been incident on the third holographic diffractive optical element 25 from above and at an angle of 11° from the vertical is diffracted perpendicularly downwards to the third holographic diffractive optical element 25. In other words, the red light 31, green light 32, and blue light 33 that pass through the third holographic diffractive optical element 25 are irradiated onto the fourth holographic diffractive optical element 26, which is positioned below, as light parallel to the vertical direction.

[0053] Furthermore, the fourth holographic diffractive optical element 26, which together with the third holographic diffractive optical element 25 constitutes the second optical diffraction section 22, diffracts red light 31 incident perpendicularly from above to the fourth holographic diffractive optical element 26 to the right by 16°; green light 32 incident perpendicularly from above to the fourth holographic diffractive optical element 26 to the right by 13°; and blue light 33 incident perpendicularly from above to the fourth holographic diffractive optical element 26 to the right by 11°. Therefore, the second optical diffraction section 22 is positioned such that the angle of diffraction changes by 180° with respect to the first optical diffraction section 21.

[0054] The distance f1 between the first holographic diffracting optical element 23 and the third holographic diffracting optical element 25 constituting the first optical diffraction section 21 is 100 mm, the same as the distance between the first holographic diffracting optical element 23 and the second holographic diffracting optical element 24 in Figure 1. The distance f2 between the fourth holographic diffracting optical element 26 constituting the second optical diffraction section 22 and the surface 13 of the object to be inspected 11 is 100 mm, the same as the distance between the second holographic diffracting optical element 24 and the surface 13 of the object to be inspected 11 in Figure 1. This is based on the fact that the diffraction angles of the first holographic diffracting optical element 23 and the fourth holographic diffracting optical element 26 are the same.

[0055] As is clear from Figure 6, by using the inspection device 1 of this second embodiment, the inspection target area (double arrow Y), which is the part where each color is mixed, is wider than the conventional inspection target area (double arrow X), and it can be seen that the inspection target area is also wider in the width direction. Therefore, the inspection area can be expanded not only in the direction of the long side of the rectangular planar LED light source 20, but also in the direction of the short side.

[0056] Using the inspection apparatus 1 of this second embodiment, the hue profile showing the relationship between the measurement position in the direction of arrow A in Figure 6 and the hue angle when measuring an inspection object 11 with a smooth surface 13 was the same as in Figure 2, and the hue profile showing the relationship between the measurement position and the hue angle of the scratch 62 in Figure 3 was the same as in Figure 4(a).

[0057] Therefore, even when the second holographic diffraction optical element 24, which is the second light diffraction unit 22 of the first embodiment, is changed to the third holographic diffraction optical element 25 and the fourth holographic diffraction optical element 26, or when a surface LED light source 20 that emits white light with low directivity of the light source is used, excessive color dispersion can be suppressed, and the illumination device 2 having performance equivalent to or better than that of the conventional one and capable of expanding the inspection target area, and the inspection device 1 including the above-described illumination device 2 can be realized.

[0058] In the implementation of the present invention, it is not limited to the above-described embodiments, and various changes can be made without departing from the object of the present invention.

[0059] For example, in the above-described second embodiment, the first holographic diffraction optical element 23 is used as the first light diffraction unit 21, and the third holographic diffraction optical element 25 and the fourth holographic diffraction optical element 26 are used as the second light diffraction unit 22. However, the first holographic diffraction optical element 23 and the third holographic diffraction optical element 25 may be used as the first light diffraction unit 21, and the fourth holographic diffraction optical element 26 may be used as the second light diffraction unit 22.

[0060] In the above-described first and second embodiments, the diffraction angles are 16° for the red light 31, 13° for the green light 32, and 11° for the blue light 33. However, the diffraction angles may be set differently. For example, by making the diffraction angle of the second light diffraction unit 22 smaller than the diffraction angle of the first light diffraction unit 21, f1 < f2 can be achieved, and conversely, it is also possible to set them in the reverse way.

Explanation of Reference Numerals

[0061] 1 Inspection device 2 Illumination device 4 Detection unit 11 Object to be inspected 12 Object-to-be-inspected mounting table 13 Surface 20 Surface LED light source 21 First photodiffraction section 22 Second photodiffraction section 23. First Holographic Diffraction Optical Element 24. Second Holographic Diffractive Optical Element 25. Third Holographic Diffractive Optical Element 26. Fourth Holographic Diffractive Optical Element 27 First illumination light 28 Second illumination light 29 Third irradiation light 30 Reflected light 31 Red light 32 Green light 33 blue light 41 Cameras 51 Magnetic disks 52 wounds

Claims

1. A white planar light source in which the luminous intensity distribution within the light-emitting region is uniform, A first optical diffraction unit is composed of a holographic diffracting optical element that, when light emitted from the white planar light source passes through, converts it into parallel light at predetermined angles for each of multiple colors and for each color, and diffracts it. The device comprises a second optical diffraction section composed of a holographic diffracting optical element that, when light emitted from the first optical diffraction section is transmitted, converts it into parallel light at a predetermined angle for each of the multiple colors and for each color, and diffracts it in the opposite direction to the first optical diffraction section. A lighting device for inspecting surface irregularities of an object to be inspected, from which light is emitted by the second light diffraction section.

2. The lighting device for inspecting surface irregularities of an object to be inspected, according to claim 1, wherein the white planar light source is an LED (light-emitting diode).

3. A lighting device according to claim 1 or claim 2, An inspection object placement platform on which an object to be inspected is placed, and on which light emitted from the illumination device is shone onto the surface of the object to be inspected, An inspection device for inspecting the surface irregularities of an object to be inspected, comprising a detection unit for detecting reflected light from the surface of the object to be inspected.

4. Light emitted from a white planar light source with a uniform luminescence distribution within the light-emitting region is used as the first irradiation light to irradiate a first light diffraction section composed of a holographic diffractive optical element, The first light diffraction unit converts the diffracted light, which has been converted into parallel light for each of the multiple colors at a predetermined angle, into a second light diffraction unit composed of a holographic diffracting optical element, as the second irradiation light. The second light diffraction unit converts the light into parallel light for each of the multiple colors at a predetermined angle, and the light diffracted in the opposite direction to that of the first light diffraction unit is irradiated onto the object to be inspected as the third irradiation light. The detection unit detects the reflected light reflected from the surface of the object being inspected. An inspection method for inspecting the surface irregularities of an object to be inspected by observing the change in the color of the reflected light between the irregularities on the surface of the object to be inspected and other surfaces of the object to be inspected.

Images