Optical inspection method, optical inspection program, processing device, and optical inspection device

Abstract

To provide an optical inspection method for acquiring information on a surface of an object.SOLUTION: An optical inspection method includes: using light from a surface of an object which passes through a wavelength selection portion for selectively passing light of a plurality of predetermined wavelengths different from each other, to acquire an image by capturing the image with an image sensor having color channels that discriminate and receive the light of the plurality of predetermined wavelengths; performing, in each pixel of the image, color count estimation processing of estimating the number of channels of the color channels that have received the light as the number of colors; and performing, on the basis of the number of colors, at least one of scattered light distribution identification processing for identifying scattered light distribution (BRDF) from the surface of the object and surface state identification processing for identifying a state of the surface of the object.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] Embodiments of the present invention relate to an optical inspection method, an optical inspection program, a processing device, and an optical inspection device.

Background Art

[0002] In various industries, non-contact surface measurement of objects has become important. In the conventional method, there is a technique of splitting light rays to illuminate an object, acquiring images split by each light ray with an image sensor, and estimating each light ray direction to acquire information on the object surface.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Non-Patent Documents

[0004]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The problem to be solved by the present invention is to provide an optical inspection method, an optical inspection program, a processing device, and an optical inspection device for acquiring information on the surface of an object.

Means for Solving the Problem

[0006] According to an embodiment, an optical inspection method uses light that has passed through a wavelength selection unit that selectively passes light of a plurality of different predetermined wavelengths from the surface of an object, and images the light using an image sensor having color channels that receive the light of the plurality of predetermined wavelengths separately to obtain an image. For each pixel of the image, a color number estimation process is performed to estimate the number of channels of the color channels that have received light as the number of colors, and based on the number of colors, at least one of a scattered light distribution identification process for identifying a scattered light distribution (BRDF) from the surface of the object or a surface state identification process for identifying the state of the surface of the object is performed.

Brief Description of the Drawings

[0007]

Figure 1

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Embodiments for Carrying Out the Invention

[0008] Each embodiment will be described below with reference to the drawings. The drawings are schematic or conceptual, and the relationships between the thickness and width of each part, the ratios of the sizes between parts, etc. are not necessarily the same as those in reality. Also, even when representing the same part, the dimensions and ratios may be shown differently in the drawings. In the specification of the present application and each figure, the same reference numerals are given to the same elements as those described above with respect to the previous figures, and detailed descriptions are omitted as appropriate.

[0009] In this specification, light is a kind of electromagnetic wave, and it is assumed to include X-rays, ultraviolet rays, visible light, infrared rays, microwaves, etc. In the present embodiment, it is assumed that the light is visible light, and for example, the wavelength is in the range of 450 nm to 700 nm.

[0010] (First Embodiment) The optical inspection apparatus 10 according to the present embodiment will be described with reference to FIGS. 1 and 2.

[0011] FIG. 1 shows a schematic cross-sectional view including the optical axis L of the optical inspection apparatus 10 of the present embodiment. As shown in FIG. 1, the optical inspection apparatus 10 includes an imaging unit 12, a wavelength selection unit 14, and a processing unit 16.

[0012] The imaging unit 12 includes an imaging optical element 22 having an optical axis L and an image sensor (imaging element) 24.

[0013] The imaging optical element 22 is provided between the wavelength selection unit 14 and the image sensor 24. The imaging optical element 22 is, for example, an imaging lens. In FIG. 1, the imaging lens of the imaging optical element 22 is schematically depicted by one lens, but it may be a combination lens composed of a plurality of lenses. Alternatively, the imaging optical element 22 may be a concave mirror, a convex mirror, or a combination thereof. That is, the imaging optical element 22 may be any optical element that has the function of collecting a group of light rays emitted from a point on an object, i.e., an object point, at a conjugate image point.

[0014] The collection (condensation) of a group of light rays emitted from an object point on the surface of an object to an image point by the imaging optical element 22 is called imaging. Alternatively, having an imaging relationship means that the object point is moved to the image point (the conjugate point of the object point). The set surface of the conjugate points to which a group of light rays emitted from a sufficiently distant object point is moved by the imaging optical element 22 is called the focal plane of the imaging optical element 22. Also, a line perpendicular to the focal plane and passing through the center of the imaging optical element 22 is defined as the optical axis L. At this time, the conjugate image point of the object point moved by this light ray is called the focus.

[0015] The image sensor 24 according to this embodiment has at least one or more pixels, and each pixel is capable of receiving light rays of at least two different wavelengths, that is, a light ray of a first wavelength and a light ray of a second wavelength different from the first wavelength. The surface including the region where the image sensor 24 is disposed is defined as the image plane of the imaging optical element 22. The image sensor 24 may be an area sensor or a line sensor. An area sensor is one in which pixels are arranged in an area within the same plane. A line sensor is one in which pixels are arranged in a line. Each pixel may be provided with color channels for separately receiving light of a plurality of predetermined wavelengths, such as the three channels of R, G, and B. However, it may be provided with pixels independent of R, G, and B respectively, or the respective pixels of R, G, and B may be considered as one pixel collectively. In this embodiment, the image sensor 24 is an area sensor, and each pixel is provided with two color channels of red and blue. That is, the image sensor 24 is capable of receiving blue light with a wavelength of 450 nm and red light with a wavelength of 650 nm in independent color channels.

[0016] The wavelength selection unit 14 selectively passes light of a plurality of predetermined wavelengths. The wavelength selection unit 14 has at least two or more wavelength selection regions 32, 34, 36. The wavelength selection unit 14 in FIG. 1 has three wavelength selection regions 32, 34, 36. In the cross-section shown in FIG. 1, the wavelength selection regions 32, 34 are adjacent. Also, in the cross-section shown in FIG. 1, the wavelength selection regions 32, 36 are adjacent.

[0017] Of the wavelength selection unit 14, two wavelength selection regions are defined as a first wavelength selection region 32 and a second wavelength selection region 34. The first wavelength selection region 32 allows a light beam having a wavelength spectrum including a first wavelength to pass through. Here, allowing a light beam to pass through means directing the light beam from an object point to an image point by transmission or reflection. In this embodiment, it is assumed that the first wavelength selection region 32 transmits light beams of the first wavelength within a specific range. On the other hand, the first wavelength selection region 32 substantially blocks light beams of a second wavelength different from the first wavelength. Here, blocking means not allowing the light beam to pass through. That is, it means not directing the light beam from the object point to the image point. However, blocking includes cases where the intensity of the light beam is significantly reduced and only a small remaining component passes through. The second wavelength selection region 34 allows a wavelength spectrum including light beams of the second wavelength to pass through. On the other hand, the second wavelength selection region 34 substantially blocks light beams of the first wavelength. For example, the first wavelength is blue light of 450 nm and the second wavelength is red light of 650 nm. However, it is not limited to this, and each wavelength can be anything. Thus, the adjacent wavelength selection regions 32 and 34 have different wavelengths for passing / blocking.

[0018] Here, the directional distribution of the reflected light from an object point on the surface of the object O can be represented by a distribution function called BRDF (Bidirectional Reflectance Distribution Function). BRDF generally varies depending on the surface properties and shape of the object. For example, when the surface of the object O is rough, the reflected light spreads in various directions, so BRDF has a wide distribution. That is, when the surface of the object O is rough, there is reflected light over a wide angle. On the other hand, when the surface of the object O becomes a mirror surface, the reflected light is almost only the specular reflection component, and BRDF has a narrow distribution. Thus, BRDF reflects the surface properties and shape of the surface of the object O. Here, the surface properties and shape of the object O may be the surface roughness, for example, minute irregularities on the micron scale, the inclination of the surface, or strain, etc. That is, the surface properties and shape of the object O may be anything as long as it relates to the height distribution of the surface of the object O. When the surface properties and shape of the object O are composed of a fine structure, the typical structural scale may be on the nanoscale, the micron scale, the millimeter scale, or any scale.

[0019] The processing device 16 is composed of, for example, a computer or the like, and includes a processor (processing circuit) and a storage medium. The processor includes any one of a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), a microcomputer, an FPGA (Field Programmable Gate Array), a DSP (Digital Signal Processor), etc. The storage medium may include an auxiliary storage device in addition to a main storage device such as a memory. Examples of the storage medium include an HDD (Hard Disk Drive), an SSD (Solid State Drive), a magnetic disk, an optical disk (CD-ROM, CD-R, DVD, etc.), a magneto-optical disk (MO, etc.), and a non-volatile memory such as a semiconductor memory that can be written to and read from at any time.

[0020] In the processing device 16, only one processor and one storage medium may be provided, or a plurality of each may be provided. In the processing device 16, the processor performs processing by executing programs and the like stored in a storage medium or the like. Further, the program executed by the processor of the processing device 16 may be stored in a computer (server) connected to the processing device 16 via a network such as the Internet, or a server in a cloud environment or the like. In this case, the processor downloads the program via the network. In the processing device 16, image acquisition from the image sensor 24 and various calculation processes based on the image acquired from the image sensor 24 are executed by a processor or the like, and the storage medium functions as a data storage unit.

[0021] Further, at least a part of the processing by the processing device 16 may be executed by a cloud server configured in a cloud environment. The infrastructure of the cloud environment is configured by a virtual processor such as a virtual CPU and cloud memory. In one example, image acquisition from the image sensor 24 and various calculation processes based on the image acquired from the image sensor 24 are executed by the virtual processor, and the cloud memory functions as a data storage unit.

[0022] Note that in the present embodiment, the processing device 16 controls the image sensor 24 and performs various operations on the image data obtained from the image sensor 24.

[0023] Based on the above configuration, the operating principle of the optical inspection device 10 according to the present embodiment will be described with reference to FIGS. 1 and 2. FIG. 2 is an optical inspection processing flow for acquiring information on the surface of the object O using the processing device 16. Note that in the present embodiment, it is assumed that the third wavelength selection region 36 shown in FIG. 1 is shielded.

[0024] In FIG. 1, it is assumed that, for example, there are micron-sized uneven defects at the first object point O1 on the surface of the object O, and the second object point O2 on the surface of the object O is a mirror surface. The BRDF changes depending on the surface properties of the object O. At this time, the first BRDF indicated by reference numeral 1 at the first object point O1 has a wider distribution than the second BRDF indicated by reference numeral 2 at the second object point O2. That is, the first object point O1 and the second object point O2 have different BRDFs respectively.

[0025] The light rays belonging to the first BRDF1 from the first object point O1 include, for example, wavelengths of red light, blue light, and green light. When the first light ray B1 belonging to the first BRDF1 from the first object point O1 passes through the first wavelength selection region 32 of the wavelength selection unit 14, it becomes blue light having a spectrum from a wavelength of 430 nm to a wavelength of 480 nm, for example. The second light ray B2 belonging to the first BRDF1 from the first object point O1 passes through the second wavelength selection region 34 of the wavelength selection unit 14 and becomes red light having a spectrum from a wavelength of 620 nm to a wavelength of 680 nm, for example.

[0026] The light ray B belonging to the second BRDF2 from the second object point O2 includes, for example, wavelengths of red light, blue light, and green light. The light ray B belonging to the second BRDF2 from the second object point O2 is parallel or substantially parallel to the optical axis L, passes through the second wavelength selection region 34 of the wavelength selection unit 14, and becomes red light having a spectrum from a wavelength of 620 nm to a wavelength of 680 nm.

[0027] Here, the first object point O1 is transferred to the first image point I1 on the image sensor 24 by the imaging optical element 22. The second object point O2 is transferred to the second image point I2 on the image sensor 24 by the imaging optical element 22. Thereby, the processing device 16 controls the image sensor (area sensor) 24 and performs an image acquisition process of acquiring an image with the image sensor 24 (step S101). That is, the image acquired by the image sensor 24 is sent to the processing device 16 as an electrical signal.

[0028] Note that the image data of the image point I1 and the image data of the image point I2 captured by the image sensor 24 are colored according to the scattering angle (including specularly reflected light) from the surface of the object O. Therefore, the colors of the obtained image points I1 and I2 depend not on the color of the surface of the object O itself, but on the wavelength selectively passed by the setting of the wavelength selection unit 14. For this reason, the image data of the image points I1 and I2 acquired by the imaging unit 12 in the present embodiment may be considered to be different from the colors of the images of a normal camera without using the wavelength selection unit 14, even for images of the same surface of the object O, by appropriately setting the wavelength selection unit 14.

[0029] In the present embodiment, at the first image point I1 on the image sensor 24, at least blue light and red light are received. That is, the pixel corresponding to the first image point I1 on the image sensor 24 receives blue light and red light. Therefore, the processing device 16 recognizes that the light from the first object point O1 has passed through at least two types of wavelength selection regions 32 and 34. On the other hand, at the second image point I2, only red light is received by the image sensor 24. That is, the pixel corresponding to the second image point I2 on the image sensor 24 receives red light. Therefore, the processing device 16 recognizes that the light from the second object point O2 has passed through only one type of wavelength selection region 34. In this way, the process of outputting the number of color channels in which light is received at each pixel of the image sensor 24 by the processing device 16 is called the color number estimation process (received light color number estimation process). That is, the processing device 16 can acquire the number of colors of the light received by the pixels corresponding to the image points I1 and I2 by the color number estimation process performed by the processing device 16 (step S102).

[0030] However, there are various ways of counting the number of colors, depending on how the background noise (such as dark current noise, the spectroscopic performance of the image sensor 24 and the wavelength selection unit 14, etc.) is set. For example, depending on the spectroscopic performance of the image sensor 24, even though green light has not reached the image sensor 24, the electrical signal corresponding to green light may react to red light. Therefore, the processing device 16 performs calibration to associate the number of colors with the number of wavelength selection regions 32, 34 through which the light beam has passed, such as offsetting the background noise. Through such calibration, the processing device 16 can obtain the accurate number of colors.

[0031] It is considered that the wider the BRDF (scattered light distribution) at the object point O1 of the object O is as the number of colors received by each pixel is larger, and the narrower the BRDF (scattered light distribution) at the object point O2 of the object O is as the number of colors received by each pixel is smaller. Therefore, the processing device 16 can identify the difference in BRDF at each object point O1, O2 by obtaining the number of colors at each image point I1, I2 through the color number estimation process for each image point I1, I2 (step S103).

[0032] As described above, the processing device 16 causes the image sensor 24 to image the light from the object O that has passed through the wavelength selection unit 14 having at least two different wavelength selection regions 32, 34, obtains images corresponding to two different wavelength spectra each including at least two different wavelengths, and performs a color number estimation process for estimating the number of channels of the color channels that have received light as the number of colors at each pixel of the images corresponding to those at least two different wavelength spectra, and can perform a scattered light distribution identification process for identifying the scattered light distribution (BRDF) from the surface of the object O based on the number of colors.

[0033] The BRDF is correlated with the surface properties and shape of the object O. Therefore, the processing device 16 can identify the differences in the surface properties of each object point O1, O2 on the surface of the object O based on the image data acquired by the imaging unit 12 using the light that has passed through the wavelength selection unit 14 (step S104). Note that the processing device 16 can directly perform a surface state identification process of identifying the differences in the surface properties and shape of the object O without recognizing the differences in the BRDF at each object point O1, O2 based on the number of colors received at each pixel. Here, the surface properties and shape can be rephrased as the surface state. That is, it is also preferable for the processing device 16 to perform at least one of a scattered light distribution identification process of identifying the scattered light distribution (BRDF) from the surface of the object O based on the number of colors, or a surface state identification process of identifying the surface state of the object O. Therefore, after performing the surface state identification process, the scattered light distribution identification process can also be performed.

[0034] And by using the optical inspection device 10 according to the present embodiment, it is possible to acquire information (surface state) on the surface of the object O non-contact without splitting the illumination into R, G, B, etc. Further, when the surface of the object O is a mirror surface, since the color is assigned according to the scattering angle (including specular reflection light) from the surface of the object O, if the BRDF can be acquired, the three-dimensional shape of the surface can be acquired (see Non-Patent Document 2). For example, the uneven defect at the object point O1 can be acquired as a three-dimensional shape.

[0035] Also, the wavelength selection unit 14 of the optical inspection device 10 according to the present embodiment can be disposed between the imaging unit 12 and the object O, that is, in front of the imaging unit 12. Therefore, the optical inspection device 10 according to the present embodiment can incorporate this optical system for any imaging unit (that is, camera) 12. That is, the selection range of the imaging unit 12 can be widened by the optical inspection device 10 according to the present embodiment. That is, with the configuration in which the light that has passed through the wavelength selection unit 14 passes through the imaging optical element (imaging lens) 22 for imaging, the wavelength selection unit 14 can be easily disposed.

[0036] As described above, according to the present embodiment, it is possible to provide an optical inspection method, an optical inspection program, a processing device 16, and an optical inspection device 10 for acquiring information on the surface of an object O.

[0037] Further, the wavelength selection unit 14 is supported by the support unit 15 between the object O and the imaging unit 12. The support unit 15 can rotate the wavelength selection unit 14, for example, around the axis of the optical axis L. When the BRDF has a special anisotropy, the processing device 16 can acquire an accurate BRDF distribution by imaging the surface of the object O with the image sensor 24 while rotating the wavelength selection unit 14 by the support unit 15.

[0038] (First Modification Example) The optical inspection device 10 according to the first modification example of the first embodiment will be described.

[0039] In this modification example, each pixel of the image sensor 24 includes three color channels of red, blue, and green. That is, the image sensor 24 can receive blue light with a wavelength of 450 nm, red light with a wavelength of 650 nm, and green light with a wavelength of 530 nm in independent color channels.

[0040] Also, as shown in FIG. 1, the wavelength selection unit 14 includes a first wavelength selection region 32, a second wavelength selection region 34, and a third wavelength selection region 36. The third wavelength selection region 36 passes a wavelength spectrum including light rays of the third wavelength. On the other hand, the third wavelength selection region 36 substantially shields the light rays of the first wavelength and the second wavelength. For example, the first wavelength is blue light with a wavelength of 450 nm, the second wavelength is red light with a wavelength of 650 nm, and the third wavelength is green light with a wavelength of 530 nm. However, it is not limited to this, and each wavelength may be any. The third wavelength selection region 36 of the wavelength selection unit 14 in the first embodiment was described as a shielding unit, but in this modification example, it is used as a wavelength selection region that passes the third wavelength.

[0041] The third light ray B3 belonging to the first BRDF1 from the first object point O1 passes through the third wavelength selection region 36 of the wavelength selection unit 14 and becomes green light having a spectrum from a wavelength of 520 nm to a wavelength of 580 nm, for example. The green light is transferred from the first object point O1 to the first image point I1. As a result, the image sensor 24 receives light of three colors, red light, blue light, and green light, at the first image point I1. The processing device 16 determines that the number of colors at the first image point I1 is 3 by color number estimation processing. As a result, the number of colors at the first image point I1 where the image of the first object point O1 is transferred is 3, while the number of colors at the second image point I2 where the image of the second object point O2 is transferred is 1, and the difference in the number of colors between the first object point O1 and the second object point O2 becomes clearer.

[0042] Therefore, according to this modification, it is possible to provide an optical inspection method, an optical inspection program, the processing device 16, and the optical inspection device 10 that can acquire information on the surface of the object O with higher accuracy and perform a more accurate optical inspection.

[0043] (Second Modification) The optical inspection device 10 according to the second modification of the first embodiment will be described with reference to FIG. 3. The optical inspection device 10 according to this modification is basically the same as the optical inspection device 10 according to the first embodiment. The differences will be described below.

[0044] In the example of the wavelength selection unit 14 shown in FIG. 3, instead of the second wavelength selection region 34 shown in FIG. 1, the third wavelength selection region 36 is used. As shown in FIG. 3, for example, the third wavelength selection region 36 is arranged at two locations in the wavelength selection unit 14. In this way, the wavelength selection unit 14 can repeatedly use a region that allows light of the same wavelength spectrum, such as the wavelength selection region 36, to pass through and blocks light of different wavelength spectra. For this reason, for example, the third wavelength selection region 36 may be arranged at three locations in the wavelength selection unit 14.

[0045] Even if the wavelength selection unit 14 is configured in this way, the processing device 16 outputs such that the number of colors at the first image point I1 corresponding to the first object point O1 is 2, and the number of colors at the second image point I2 corresponding to the second object point O2 is 1. For this reason, there can be a difference in the number of colors at the first image point I1 and the second image point I2. Therefore, the processing device 16 can identify the difference between the first BRDF1 of the first object point O1 corresponding to the first image point I1 and the second BRDF2 of the second object point O2 corresponding to the second image point I2.

[0046] By repeatedly using the same type of wavelength selection region 36, the wavelength selection unit 14 can reduce the types of wavelength spectra to be distinguished by the image sensor 24. That is, by arranging the wavelength selection regions 36 of the wavelength selection unit 14 at least two or more times repeatedly, there is an advantage that sufficient effects can be obtained even if the number of color channels of the image sensor 24 is reduced, the optical performance of the wavelength selection unit 14 is lowered, or for example, it is made inexpensive.

[0047] However, when the wavelength selection regions 36 are arranged repeatedly, the two adjacent wavelength selection regions 32, 34 of the wavelength selection unit 14 have different predetermined wavelengths for passing light. That is, since the predetermined wavelengths for passing light are different between the two adjacent wavelength selection regions 32, 36, it is possible to identify whether the BRDF has spread and passed through those two wavelength selection regions 32, 36 simultaneously, or whether the BRDF has narrowed and passed through one of those two wavelength selection regions 32, 36.

[0048] As described above, according to this modification example, it is possible to provide an optical inspection method, an optical inspection program, a processing device 16, and an optical inspection device 10 for acquiring information on the surface of the object O.

[0049] (Second Embodiment) The optical inspection device 10 according to this embodiment will be described in detail with reference to FIGS. 4 and 5. The optical inspection device 10 according to this embodiment is basically the same as the optical inspection device 10 according to the first embodiment. The differences will be described below.

[0050] FIG. 4 shows a cross-sectional view along the optical axis L of the imaging optical element 22 of the optical inspection apparatus 10 according to the present embodiment. The optical axis L is orthogonal to the image sensor 26.

[0051] The optical inspection apparatus 10 according to the present embodiment further includes an illumination unit 18 and a beam splitter 20.

[0052] The wavelength selection unit 14 according to the present embodiment includes a plurality (here, three) of wavelength selection regions 32, 34, and 36. Each of the wavelength selection regions 32, 34, and 36 is, for example, stripe-shaped or linear in a plane orthogonal to the optical axis L of the imaging optical element 22. That is, it is assumed that each of the wavelength selection regions 32, 34, and 36 of the wavelength selection unit 14 extends in a direction orthogonal to the plane of FIG. 4.

[0053] In the cross-section shown in FIG. 4, a plurality of wavelength selection regions 32, 34, and 36 are arranged. That is, the cross-section shown in FIG. 4 includes the direction in which the plurality of wavelength selection regions 32, 34, and 36 are arranged side by side. On the other hand, it is assumed that the plurality of wavelength selection regions 32, 34, and 36 do not change with respect to the direction orthogonal to the cross-section shown in FIG. 4 (that is, the direction orthogonal to the plane of FIG. 4).

[0054] The illumination unit 18 irradiates light onto the surface of the object O. The illumination unit 18 includes a light source 42, an aperture 44, and an illumination lens 46. It is assumed that the aperture 44 is slit-shaped. That is, for example, the longitudinal direction is 200 mm and the short-side direction is 0.8 mm. The light passing through the aperture 44 becomes stripe-shaped. The aperture 44 in FIG. 4 shows a cross-sectional view in the short-side direction.

[0055] The illumination lens 46 is, for example, a cylindrical lens, the longitudinal direction is 200 mm, and the focal length is, for example, 50 mm. FIG. 4 shows a cross-sectional view including the short-side direction. The slit-shaped aperture 44 is disposed on the focal plane of the illumination lens (cylindrical lens) 46.

[0056] As the light source 42, for example, an LED is used. A plurality of surface-emitting type LEDs as the light source 42 having, for example, a size of 3 mm × 3 mm are arranged in a direction orthogonal to the plane of FIG. 4.

[0057] With the above configuration, in the cross-section shown in FIG. 4, the illumination unit 18 can generate parallel light. The illumination unit 18 irradiates parallel light within the same cross-section shown in FIG. 4. The parallel light is irradiated onto the surface of the object O along the optical axis L of the imaging optical element (lens) 22 by the beam splitter 20. Such an illumination method is called coaxial epi-illumination.

[0058] Hereinafter, the operating principle of the optical inspection apparatus 10 according to the present embodiment will be described with reference to FIGS. 4 and 5.

[0059] FIG. 5 omits the illustration of the illumination unit 18. Assume that the surface of the object O shown in FIG. 5 is a mirror surface, and the surface of the object O is orthogonal to the optical axis L of the imaging optical element (imaging lens) 22. At this time, the parallel light incident on the surface of the object O from the illumination unit 18 is reflected by the surface of the object O and travels toward the imaging unit 12 along the optical axis L. At this time, depending on the wavelength selection regions 32, 34, 36 of the wavelength selection unit 14, the regions of the surface of the object O are imaged in different colors.

[0060] That is, among the surface of the object O, the region that reflects the parallel light between the fourth light ray B4 and the fifth light ray B5 passes through the first wavelength selection region 32 and becomes blue light. Among the surface of the object O, the region that reflects the parallel light between the fifth light ray B5 and the sixth light ray B6 passes through the second wavelength selection region 34 and becomes red light. Among the surface of the object O, the region that reflects the parallel light between the seventh light ray B7 and the fourth light ray B4 passes through the third wavelength selection region 36 and becomes green light. That is, when the surface of the object O is a mirror-like flat surface, for example, when there are no irregularities, the processing device 16 can estimate that the number of colors of the acquired image of the image sensor 24 is 1 over the entire region to be imaged.

[0061] At this time, assume that there are uneven defects at the first object point O1 in FIGS. 4 and 5. When parallel light from the illumination unit 18 irradiates the first object point O1, the BRDF at the first object point O1 spreads compared to the case where the surface of the object O is a mirror-like plane without unevenness. The light rays from the object point O1 pass through, for example, all of the first wavelength selection region 32, the second wavelength selection region 34, and the third wavelength selection region 36 and are imaged as a first image point I1 on the image sensor 24. That is, the number of colors of the first image point I1 corresponding to the first object point O1 is 3. Thereby, the processing device 16 can immediately recognize that the BRDF has a wide distribution at the first object point O1. That is, the processing device 16 can absolutely evaluate the magnitude of the BRDF distribution according to the absolute value of the number of colors without relatively comparing the number of colors at each object point.

[0062] As described above, according to the present embodiment, an optical inspection method, an optical inspection program, the processing device 16, and the optical inspection device 10 for acquiring information on the surface of the object O can be provided.

[0063] (Third Embodiment) The optical inspection device 10 according to the present embodiment will be described in detail with reference to FIG. 6. The optical inspection device 10 according to the present embodiment is basically the same as the optical inspection device 10 according to the second embodiment. The differences will be described below.

[0064] FIG. 6 shows a cross-sectional view of the optical inspection device 10 of the present embodiment. As shown in FIG. 6, let the BRDFs of the first object point O1 and the second object point O2 be the first BRDF1 and the second BRDF2, respectively. Assume that the first BRDF1 spreads and distributes more widely than the second BRDF2.

[0065] In the wavelength selection unit 14, a first wavelength selection region 32, a second wavelength selection region 34, and a third wavelength selection region 36 are formed. However, it is assumed that the second wavelength selection region 34 and the third wavelength selection region 36 are of the same type. That is, when the same light is incident on the second wavelength selection region 34 and the third wavelength selection region 36 respectively, light of the same wavelength spectrum passes through and the rest is blocked. Here, for example, it is assumed that the first wavelength selection region 32 passes blue light, and the second wavelength selection region 34 and the third wavelength selection region 36 pass red light.

[0066] The light rays included in the first BRDF1 are, for example, a first light ray B1, a second light ray B2, and a third light ray B3. The first light ray B1 passes through the first wavelength selection region 32. The second light ray B2 passes through the second wavelength selection region 34. The third light ray B3 passes through the third wavelength selection region 36. As a result, two colors, red light and blue light, are imaged at the image point I1 on the image sensor 24.

[0067] On the other hand, the light rays included in the second BRDF2 are, for example, an eighth light ray B8, a ninth light ray B9, and a tenth light ray B10. The eighth light ray B8 passes through the boundary between the first wavelength selection region 32 and the second wavelength selection region 34. The ninth light ray B9 passes through the second wavelength selection region 34. The tenth light ray B10 passes through the first wavelength selection region 32. As a result, two colors, blue light and red light, are imaged at the image point I2 on the image sensor 24. At this time, the processing device 16 identifies that the number of colors corresponding to the first object point O1 and the second object point O2 is both 2. Although the first BRDF1 is more spread out and distributed than the second BRDF2, in terms of the number of colors, the difference in BRDF, that is, the difference in the surface properties of the object O, may not be distinguishable.

[0068] To distinguish this, the third wavelength selection region 36 may be made different from the first wavelength selection region 32 and the second wavelength selection region 34. For example, assume that the light passing through the second wavelength selection region 34 becomes red light and the light passing through the third wavelength selection region 36 becomes green light. In this way, the number of colors imaged at the image point I1 of the first object point O1 is 3, and the number of colors for the second object point O2 is 2. Thereby, the difference in BRDF can be identified.

[0069] That is, the processing device 16 uses the light that has passed through the wavelength selection unit 14 having the wavelength selection regions 32, 34, and 36 that selectively pass light of at least three different predetermined wavelengths, images the light from the object O, obtains images corresponding to at least three different wavelength spectra, and estimates the number of wavelength selection regions 32, 34, 36 through which the light has passed (the number of colors received by the image sensor 24) from the images corresponding to at least three different wavelength spectra, thereby being able to identify the scattered light (BRDF) from the surface of the object O.

[0070] Here, since the eighth light ray B8 passes through the boundary between the first wavelength selection region 32 and the second wavelength selection region 34, the number of colors at the image point I2 can be 2. Thus, the light passing through the boundary between the first wavelength selection region 32 and the second wavelength selection region 34 can have 2 colors. Therefore, considering the light passing through the boundary between such wavelength selection regions 32 and 34 or the boundary between wavelength selection regions 32 and 36, it is advisable for the wavelength selection unit 14 to prepare at least three wavelength selection regions 32, 34, and 36. That is, by making the number of colors acquired at each pixel 3 or more at maximum, it is possible to identify the BRDF including the light passing through the boundary between the wavelength selection regions 32 and 34 or the boundary between the wavelength selection regions 32 and 36.

[0071] As described above, according to the present embodiment, it is possible to provide an optical inspection method, an optical inspection program, the processing device 16, and the optical inspection device 10 for acquiring information on the surface of the object O.

[0072] (Fourth Embodiment) The optical inspection apparatus 10 according to this embodiment will be described in detail with reference to FIG. 7. The optical inspection apparatus 10 according to this embodiment is basically the same as the optical inspection apparatus 10 according to the second embodiment. The following describes the differences.

[0073] FIG. 7 shows a perspective view of the optical inspection apparatus 10 according to this embodiment.

[0074] The illumination unit 18 of the optical inspection apparatus 10 according to this embodiment is different from the illumination unit 18 of the optical inspection apparatus 10 according to the second embodiment.

[0075] In the optical inspection apparatus 10 shown in FIG. 7, in a cross section including the optical axis L and including the arrangement direction of the wavelength selection unit 14, the light from the illumination unit 18 is parallel light. The direction of the optical axis L coincides with the direction orthogonal to the image sensor 24. Therefore, the same cross section can be rephrased as a cross section including the direction orthogonal to the image sensor 24 and including the arrangement direction of the wavelength selection unit 14. This is defined as the first cross section S1. Also, in the light rays orthogonally projected (orthographically projected) onto the first cross section S1, the light from the illumination unit 18 is parallel light. On the other hand, a cross section orthogonal to the first cross section S1 is defined as the second cross section S2. In the light rays orthogonally projected onto the second cross section S2, the light from the illumination unit 18 is not parallel light but diffused light. For this reason, the illumination unit 18 illuminates the surface of the object O with illumination light that is parallel light within the cross section S1 spanned by the optical axis L of the imaging optical element 22 and the direction in which the first wavelength selection region 32 and the second wavelength selection region 34 are arranged in the wavelength selection unit 14, and is diffused light in a cross section orthogonal to the first cross section S1.

[0076] The wavelength selection unit 14 includes a plurality of wavelength selection regions 32, 34, 36. Each of the wavelength selection regions 32, 34, 36 is assumed to be strip-shaped. The wavelength selection unit 14 has a plurality of wavelength selection regions 32, 34, 36 that cross the first cross-section S1. That is, the first cross-section S1 shown in FIG. 7 includes the direction in which the wavelength selection regions 32, 34, 36 are arranged. On the other hand, in the second cross-section S2 orthogonal to the first cross-section S1 shown in FIG. 7, each wavelength selection region 32, 34, 36 does not change. For example, when the second cross-section S2 crosses the first wavelength selection region 32, the second cross-section S2 does not cross the second wavelength selection region 34 and the third wavelength selection region 36. Similarly, when the second cross-section S2 crosses the second wavelength selection region 34, the second cross-section S2 does not cross the first wavelength selection region 32 and the third wavelength selection region 36. When the second cross-section S2 crosses the third wavelength selection region 36, the second cross-section S2 does not cross the first wavelength selection region 32 and the second wavelength selection region 34.

[0077] The illumination unit 18 irradiates the surface of the object O to form an irradiation field F on the surface of the object O. The first object point O1 in the irradiation field F is imaged as a first image point I1 on the image sensor 24 by an imaging optical element (imaging lens) 22. At the first object point O1, the BRDF is the first BRDF1. The first light ray B1 is included in the first BRDF1.

[0078] In the light ray orthogonally projected onto the first cross-section S1, the spread of the distribution of the first BRDF1 passes through the wavelength selection regions 32, 34, 36 of the wavelength selection unit 14 and can be identified by the number of colors of the light received by the pixel corresponding to the image point I1 on the image sensor 24. That is, the processing device 16 identifies the spread of the BRDF at the object point O1 based on the number of colors of the light received by the image sensor 24 based on the image received by the image sensor 24.

[0079] However, since the light irradiated from the illumination unit 18 to the surface of the object O is parallel light, in the light ray orthogonally projected onto the first cross-section S1, the imaging angle becomes narrow in the imaging unit 12. That is, in the light ray orthogonally projected onto the first cross-section S1, the imaging range of the imaging unit 12 is narrow.

[0080] On the other hand, in the second cross-section S2 or a cross-section parallel thereto, the number of wavelengths (number of colors) incident on the image sensor 24 is constant. This is because in the second cross-section S2 or a cross-section parallel thereto, the wavelength selection region of the wavelength selection unit 14 does not change. However, in the light rays orthogonally projected onto the second cross-section S2, since the light from the illumination unit 18 is diffused light, the angle of view at the imaging unit 12 becomes wider.

[0081] As described above, in the acquired image of the image sensor 24, for two directions orthogonal to the optical axis L, the angle of view is narrow in the first direction (the direction along the first cross-section S1), but the angle of view can be widened in the second direction (the direction along the second cross-section S2) orthogonal to the first direction. Also, the number of colors at the first image point I1 is the number of colors in the light rays orthogonally projected onto the first cross-section S1.

[0082] As a result, the optical inspection apparatus 10 according to the present embodiment has an effect that the overall angle of view can be widened as compared with the case where the light from the illumination unit 18 is made completely parallel light. Also, by forming the wavelength selection regions 32, 34, 36 in a stripe shape, there is an effect that the overall angle of view can be widened as compared with the case where it is not so.

[0083] Therefore, according to the present embodiment, it is possible to provide an optical inspection method, an optical inspection program, a processing device 16, and an optical inspection apparatus 10 that can acquire information on the surface of the object O with higher accuracy and perform a more accurate optical inspection.

[0084] (Example of the wavelength selection unit 14) Figures 8 to 11 show examples of various wavelength selection units 14. The wavelength selection unit 14 shown in Figures 8 to 11 is arranged orthogonal to the optical axis L. The wavelength selection unit 14 shown in Figures 8 to 11 can be appropriately rotated around the axis of the optical axis L by, for example, a support unit 15 (see Figure 1 etc.) and used.

[0085] The wavelength selection unit 14 shown in FIG. 8, in addition to the wavelength selection region 32 that passes blue, the wavelength selection region 34 that passes red, and the wavelength selection region 36 that passes green described above, at the boundary between the blue and green wavelength selection regions, for example, a cyan wavelength selection region 38 is disposed. Further, at the boundary between the red and green wavelength selection regions, for example, a yellow wavelength selection region 40 is disposed. In the example of the wavelength selection unit 14 shown in FIG. 8, the wavelength selection regions 32, 34, 36 for blue, red, and green are in a stripe shape and are formed with substantially the same width. The cyan wavelength selection region 38 and the yellow wavelength selection region 40 are formed with a width narrower than that of the wavelength selection regions 32, 34, 36 for blue, red, and green. Note that the cyan wavelength selection region 38 and the yellow wavelength selection region 40 are formed with substantially the same width.

[0086] The wavelength selection unit 14 shown in FIG. 9 has a first region 52 and a second region 54. The first region 52 and the second region 54 are arranged in the left - right direction in FIG. 9. The first region 52 is formed in the same manner as the wavelength selection unit 14 shown in FIG. 8. In the second region 54, each wavelength selection region is formed wider than the width of the wavelength selection unit 14 shown in FIG. 8.

[0087] The wavelength selection unit 14 shown in FIG. 10 has a wavelength selection region 32 that passes blue and a wavelength selection region 34 that passes red. The wavelength selection region 32 and the wavelength selection region 34 are repeated in the left - right direction of the paper surface of FIG. 10. The width of each of the wavelength selection regions 32, 34 is, for example, constant.

[0088] The wavelength selection unit 14 shown in FIG. 11 has a first region 62, a second region 64, and a third region 66. The first region 62, the second region 64, and the third region 66 are arranged in the left - right direction in FIG. 11. In the first region 62, each of the wavelength selection regions 32, 34, 36 is formed wider than in the second region 64. In the second region 64, each of the wavelength selection regions 32, 34, 36 is formed narrower than in the third region 66. In the third region 66, each of the wavelength selection regions 32, 34, 36 is formed wider than in the second region 64.

[0089] According to at least one of the above-described embodiments, it is possible to provide an optical inspection method for acquiring information on the surface of an object, an optical inspection program, a processing device 16, and an optical inspection device 10.

[0090] Although some embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalent scope thereof.

Description of Reference Numerals

[0091] 10... optical inspection device, 12... imaging unit, 14... wavelength selection unit, 15... support unit, 16... processing device, 22... imaging optical element, 24... image sensor, 32... first wavelength selection region, 34... second wavelength selection region, 36... third wavelength selection region, B1, B2, B3... light rays, I1, I2... image points, O1, O2... object points.

Claims

1. An image is acquired by imaging with an image sensor having color channels that receive light by distinguishing the light of a plurality of predetermined wavelengths that have passed through a wavelength selection unit that selectively passes light of a plurality of different predetermined wavelengths from the surface of an object, At each pixel of the image, a color number estimation process is performed to estimate the number of channels of the color channels that have received light as the number of colors, Based on the number of colors, at least one of a scattered light distribution identification process for identifying a scattered light distribution (BRDF) from the surface of the object or a surface state identification process for identifying the state of the surface of the object is performed, An optical inspection method.

2. The wavelength selection unit is In a first region, light of a first wavelength from the surface of the object is passed through, and light of a second wavelength and a third wavelength different from the first wavelength is blocked, In a second region, light of the second wavelength from the surface of the object is passed through, and light of the first wavelength and the third wavelength is blocked, In a third region, light of the third wavelength from the surface of the object is passed through, and light of the first wavelength and the second wavelength is blocked, The color channels of the image sensor receive light by distinguishing the light of the first wavelength, the light of the second wavelength, and the light of the third wavelength, respectively, The color number estimation process estimates the number of channels of the color channels that have received light as the number of colors at each pixel of the image acquired by the image sensor, The optical inspection method according to claim 1.

3. The wavelength selection unit is In a first region, light of a first wavelength from the surface of the object is passed through, and light of a second wavelength different from the first wavelength is blocked, In a second region, light of the second wavelength from the surface of the object is passed through, and light of the first wavelength is blocked, The illumination light is parallel light in a cross section that is stretched in a direction orthogonal to the image sensor and in which the first region and the second region are arranged in the wavelength selection unit, and is diffused light in a cross section orthogonal to that cross section, and illuminates the surface of the object. The optical inspection method according to claim 1.

4. An image acquisition process of passing light of a first wavelength from the surface of an object, using light that has passed through a wavelength selection unit having a first region that blocks light of a second wavelength different from the first wavelength, a second region that passes light of the second wavelength and blocks light of the first wavelength, and imaging with an image sensor having color channels that distinguish and receive light of the first wavelength and light of the second wavelength to obtain an image; A color number estimation process of estimating, as the number of colors, the number of channels of the color channels that have received light for each pixel of the image; Based on the number of colors, at least one of a scattered light distribution identification process for identifying a scattered light distribution (BRDF) from the surface of the object or a surface state identification process for identifying the state of the surface of the object An optical inspection program that causes a processor to execute.

5. Using light that has passed through a wavelength selection unit that selectively passes light of a plurality of different predetermined wavelengths from the surface of an object, imaging with an image sensor having color channels that distinguish and receive light of the plurality of predetermined wavelengths to obtain an image, In each pixel of the image corresponding to the wavelength spectrum of the plurality of predetermined wavelengths, performing a color number estimation process of estimating, as the number of colors, the number of channels of the color channels that have received light; Based on the number of colors, performing at least one of a scattered light distribution identification process for identifying a scattered light distribution (BRDF) from the surface of the object or a surface state identification process for identifying the state of the surface of the object. A processing device including a processor.

6. A wavelength selection unit that allows light of a first wavelength from the surface of the object to pass through and blocks light of a second wavelength different from the first wavelength, and a second region that allows light of the second wavelength from the surface of the object to pass through and blocks light of the first wavelength, An image sensor having color channels that receive the light of the first wavelength and the light of the second wavelength that have passed through the wavelength selection unit separately, An imaging optical element that converges a group of light rays emitted from a point on the surface of the object to an image point on the image sensor, The processing device according to claim 5 and An optical inspection device having the same.

7. The imaging optical element is provided between the wavelength selection unit and the image sensor. The optical inspection device according to claim 6.

8. The first region and the second region of the wavelength selection unit are stripe-shaped in a plane orthogonal to the optical axis of the imaging optical element. The optical inspection device according to claim 6 or claim 7.

9. The second region is arranged at at least two positions in the wavelength selection unit. The optical inspection device according to any one of claims 6 to 8.

10. Having an illumination unit that irradiates light onto the surface of the object. The optical inspection device according to any one of claims 6 to 9.

11. The illumination unit irradiates parallel light within the same cross-section. The optical inspection device according to claim 10.

12. The illumination unit irradiates illumination light that is parallel light in a cross-section formed by the direction in which the first region and the second region are arranged and the optical axis of the imaging optical element, and is diffused light in a cross-section formed by the direction orthogonal to the direction in which the first region and the second region are arranged and the optical axis. The optical inspection apparatus according to claim 10.

13. A support unit that supports the wavelength selection unit and rotates the wavelength selection unit around the axis of the optical axis of the imaging optical element. The optical inspection apparatus according to any one of claims 6 to 12.

Images