Optical device, optical test system, and optical test method

Abstract

To provide an optical device capable of acquiring information on an object by irradiating the same irradiation field of the object with light of a plurality of wavelengths.SOLUTION: An optical device includes a light emission part for emitting light, and an imaging optical element array having first and second imaging optical elements. The first and second wavelength emitting surfaces of the optical device include a first wavelength emitting region that emits light of a first wavelength spectrum toward the imaging optical element array by the light and a second wavelength emitting region that emits light of a second wavelength spectrum different from the light of the first wavelength spectrum toward the imaging optical element array by the light when the light is emitted from the light emitting unit. The second wavelength exit surface is disposed at a position different from the first wavelength exit surface. A first wavelength exit surface is located at or near a focal plane of the first imaging optics. A second wavelength exit surface is located at or near a focal plane of the second imaging optics.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] SUMMARY OF THE INVENTION Embodiments of the present invention relate to an optical device, an optical inspection system, and an optical inspection method. [Background technology]

[0002] In various industries, it is important to acquire information about object surfaces through non-contact surface measurement and inspection. For example, there is a method of illuminating an object with color-coded light according to the direction and acquiring detailed information about the object by using an image sensor to acquire the reflected and transmitted light. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 5,675,407 [Non-patent literature]

[0004] [Non-Patent Document 1] W.L. Hows, “Rainbow schlieren and its application,” Applied Optics, vol. 23, No. 14, 1984 [Non-patent document 2] Hiroshi Ohno & Takahiro Kamikawa, “One-shot BRDF imaging system to obtain surface properties,” Optical Review volume 28, pages655-661 2021. [Non-patent document 3] S. Sorgato, et.al, “Compact etendue-preserving light-mixing optics,” OPTICS EXPRESS volume 23, No. 24, 2015. [Non-patent document 4] Hiroshi Ohno, “One-shot three-dimensional measurement method with the color mapping of light direction,” OSA Continuum Vol. 4, Issue 3, pp. 840-848, 2021. Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the present invention is to provide an optical device, an optical inspection system, and an optical inspection method that can acquire information about an object by irradiating light of multiple wavelengths onto the same irradiation field of the object. [Means for solving the problem]

[0006] According to an embodiment, an optical device includes a light output unit that emits light and an imaging optical element array having at least first and second imaging optical elements. The optical device includes first and second wavelength output surfaces having a first wavelength output region that, when light is emitted from the light output unit, causes light of a first wavelength spectrum from the light output unit to be output toward the imaging optical element array, and a second wavelength output region that, when light is emitted from the light output unit, causes light of a second wavelength spectrum different from the first wavelength spectrum to be output toward the imaging optical element array. The second wavelength output surface is located at a position different from the first wavelength output surface, and includes a second wavelength output surface that, when light is emitted from the light output unit, has a first wavelength output region and a second wavelength output region similar to the first wavelength output surface. The first wavelength output surface is located on or near the focal plane of the first imaging optical element. A second wavelength exit surface is located at or near the focal plane of the second imaging optic. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an optical device according to a first embodiment. [Figure 2] FIG. 10 is a schematic cross-sectional view showing an optical device according to a first modified example of the first embodiment. [Figure 3] FIG. 10 is a schematic cross-sectional view showing an optical device according to a second modified example of the first embodiment. [Figure 4] FIG. 10 is a schematic cross-sectional view showing an optical device according to a third modified example of the first embodiment. [Figure 5] FIG. 10 is a schematic cross-sectional view showing an optical device according to a fourth modified example of the first embodiment. [Figure 6] FIG. 10 is a schematic perspective view showing a wavelength exit surface and an imaging optical element array according to a fifth modified example of the optical device according to the first embodiment. [Figure 7] FIG. 13 is a schematic perspective view showing a wavelength exit surface and an imaging optical element array according to a sixth modified example of the optical device according to the first embodiment. [Figure 8] FIG. 10 is a schematic cross-sectional view showing an optical inspection system according to a second embodiment. [Figure 9] FIG. 9 is a diagram showing a process flow when optical inspection is performed using the optical inspection device shown in FIG. 8. [Figure 10] FIG. 10 is a schematic cross-sectional view showing an optical inspection system according to a modified example of the second embodiment. [Figure 11] FIG. 10 is a schematic cross-sectional view showing an optical inspection system according to a third embodiment. [Figure 12] FIG. 12 is a schematic perspective view showing the relationship between the illumination aperture and the imaging optical element array in FIG. 11. [Figure 13] 13 is a schematic perspective view showing the relationship between the illumination aperture and the imaging optical element array in FIG. 12 and the wavelength exit surface. DETAILED DESCRIPTION OF THE INVENTION

[0008] Each embodiment of the present invention will be described below with reference to the drawings. The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc., are not necessarily the same as those in reality. Furthermore, even when the same part is shown, the dimensions and ratios may be different depending on the drawing. In this specification and each drawing, elements similar to those previously described with reference to the previous drawings are designated by the same reference numerals, and detailed explanations will be omitted as appropriate.

[0009] In this specification, the terms "projection" and "projection" are used interchangeably, except that "projection" is used to mean projecting an image, and the two terms are used to distinguish between them.

[0010] In this specification, light is a type of electromagnetic wave, and includes X-rays, ultraviolet light, visible light, infrared light, microwaves, etc. In this embodiment, the light is considered to be visible light, with a wavelength in the range of 400 nm to 750 nm, for example.

[0011] (First embodiment) The optical device (illumination unit) 10 according to the first embodiment will be described in detail below with reference to FIG.

[0012] Fig. 1 shows a schematic cross-sectional view of an optical device 10 according to this embodiment. The cross-sectional view of Fig. 1 is assumed to be on the xz plane in an xyz Cartesian coordinate system, for example.

[0013] The optical device 10 according to this embodiment includes a light emitting section 12 and an imaging optical element array 16 .

[0014] The light emitting unit 12 emits light including a plurality of wavelengths a and b, for example, in a predetermined direction.

[0015] In this embodiment, the light emitting unit 12 has a wavelength emitting surface 14 that emits light from the light emitting unit 12. When light is irradiated from the light emitting unit 12, the wavelength emitting surface 14 according to this embodiment allows each region within the surface to be identified by the light passing through. The wavelength emitting surface 14 is formed in a surface shape that emits light having a specific wavelength spectrum that differs for each region toward the imaging optical element array 16. The positions of these regions of the wavelength emitting surface 14 are defined by the imaging optical element array 16. The wavelength emitting surface 14 has at least two surfaces: a first wavelength emitting surface 14a and a second wavelength emitting surface 14b.

[0016] The imaging optical element array 16 includes at least two imaging optical elements 16a and 16b, which are adjacent to each other along the x-axis direction.

[0017] Light from the light emitting unit 12 passes through the wavelength emitting surface 14 and the imaging optical element array 16 to illuminate the object surface S of the object O. Here, of the illuminated area on the object surface S, the irradiation fields facing the imaging optical elements 16a and 16b are referred to as irradiation fields F1 and F2, respectively. In this embodiment, the object O has an object surface S that reflects light on its surface. However, the object O is not limited to this, and may be transparent or semi-transparent to light, allowing some light to pass through.

[0018] The imaging optical elements 16a and 16b have the function of collecting a group of light rays emitted from a certain point at a conjugate image point. The imaging optical elements 16a and 16b are, for example, lenses. In FIG. 1, the imaging lenses serving as the imaging optical elements 16a and 16b are schematically depicted as a single lens, but they may also be a lens assembly consisting of multiple lenses. Alternatively, the imaging optical elements 16a and 16b may be concave mirrors, convex mirrors, or a combination thereof. In other words, the imaging optical elements 16a and 16b may be any optical elements that have the function of collecting a group of light rays emitted from a certain point at a conjugate image point.

[0019] The process of collecting (concentrating) a group of light rays emitted from an object point on the object surface onto an image point using the imaging optical elements 16a and 16b is called imaging. Alternatively, it can be said that the object point is moved to the image point (the conjugate point of the object point). The plane of conjugate points onto which a group of light rays emitted from a sufficiently distant object point are moved by the imaging optical elements 16a and 16b is called the focal plane of the imaging optical elements. The line perpendicular to the focal plane and passing through the center of the imaging optical elements 16a and 16b is called the optical axis. In this case, the conjugate image point onto which a group of light rays emitted from a sufficiently distant point on this optical axis are moved by the imaging optical elements 16a and 16b is called the focus.

[0020] As described above, the imaging optical element array 16 includes at least two imaging optical elements 16a and 16b. In particular, when the imaging optical elements 16a and 16b are lenses, the imaging optical element array 16 is called a lens array. The lens array 16 is also called a fly's eye lens or a microlens array. Since the imaging optical element array 16 includes at least two imaging optical elements 16a and 16b, it has at least two different optical axes L1 and L2. In other words, the lens array 16 has multiple optical axes L1 and L2.

[0021] In this embodiment, convex lenses are used as the imaging optical elements 16a and 16b, and the imaging optical element array 16 is a lens array. The lens array 16 in this embodiment is composed of two convex lenses arranged side by side (adjacent along the x-axis direction). These lenses are designated as the first lens element 16a and the second lens element 16b. The cross section of the optical device 10 in FIG. 1 includes the optical axes L1 and L2 of the lens elements 16a and 16b, which are parallel to the z-axis. The optical axis L1 of the first lens element 16a is designated the first optical axis, and the optical axis L2 of the second lens element 16b is designated the second optical axis.

[0022] The first wavelength emitting surface 14a is disposed on or near the focal plane of the first lens element 16a. The second wavelength emitting surface 14b is disposed on or near the focal plane of the second lens element 16b. In this embodiment, the focal planes of the first lens element 16a and the second lens element 16b are assumed to be on the same plane. Therefore, these focal planes are not distinguished from each other and are simply referred to as focal planes. However, the first lens element 16a and the second lens element 16b may have different focal planes. In this case, the first wavelength emitting surface 14a and the second wavelength emitting surface 14b are disposed on or near their respective focal planes.

[0023] The light emitting unit 12 of this embodiment may be, for example, a projector 12a, which is a projection unit that projects an image using light from the light emitting unit 12. The projector (projection unit) 12a simultaneously projects similar images (projected light as light) onto the first wavelength emitting surface 14a and the second wavelength emitting surface 14b. That is, the light emitting unit 12 may project light of wavelength spectrum a onto the wavelength emitting region 22a of the first wavelength and the wavelength emitting region 24a of the second wavelength, and may project light of wavelength spectrum b onto the wavelength emitting region 22b of the first wavelength and the wavelength emitting region 24b of the second wavelength. The projector 12a may be of the LCD (Liquid Crystal Display) type, the DLP (Digital Lighting Processing) type, or the LCOS (Liquid Crystal On Silicon) type. The LCD method splits light from a light source using a dichroic mirror, transmits each split light through an LCD panel, and then combines the light again. The DLP method uses a rotating color wheel to split the light from a light source into light with different wavelength spectra at different times, and reflects it off a DMD (Digital Micromirror Device). However, the DLP method can also be used with multiple light sources with different wavelength spectra prepared in advance, and without using a color wheel, reflects the light from each wavelength spectrum off the DMD and then combines it. The LCOS method splits light from a light source using a dichroic mirror, reflects each split light off a reflective LCD panel, and then combines the light again.

[0024] In this embodiment, the projection means provided in the light emitting unit 12 is a DLP-type projector 12a. However, the projector 12a is not limited to these types, and any type may be used as long as it projects light of wavelength spectrum a onto the wavelength emission region 22a of 1a and the wavelength emission region 24a of 2a, and projects light of wavelength spectrum b onto the wavelength emission region 22b of 1b and the wavelength emission region 24b of 2b. When light is projected from this projector (projection unit) 12a, the wavelength emission region 22a of 1a and the wavelength emission region 22b of 1b are formed on the first wavelength emission surface 14a, the position of which is determined by the imaging optical element 16a. The wavelength emission region 22a of 1a passes light of wavelength spectrum a, which has wavelength a as its main component (dominant wavelength). The wavelength emission region 22b of 1b passes light of wavelength spectrum b, which has wavelength b as its main wavelength. Similarly, when light is projected from the projector (projection unit) 12a, a wavelength emission region 24a (2a) and a wavelength emission region 24b (2b) are formed on the second wavelength emission surface 14b, the position of which is determined by the imaging optical element 16b. The wavelength emission region 24a (2a) passes light of wavelength spectrum a, which has wavelength a as its main component (dominant wavelength). The wavelength emission region 24b (2b) passes light of wavelength spectrum b, which has wavelength b as its main wavelength. In other words, the second wavelength emission surface 14b has the same wavelength emission region as the first wavelength emission surface 14a. However, the spatial intensity distribution of light may be slightly different from that of the first wavelength emission surface 14a. In other words, the spatial distributions of the wavelength spectra of the first wavelength emission surface 14a and the second wavelength emission surface 14b are similar.

[0025] In this embodiment, the first wavelength emitting surface 14a and the second wavelength emitting surface 14b do not have any particular structure, but are spatial regions where light is first imaged by the projector (projection unit) 12a.

[0026] In this embodiment, for example, wavelength a is 450 nm and wavelength b is 650 nm. In this case, light of wavelength spectrum a is blue light, and light of wavelength spectrum b is red light. Wavelength spectrum a and wavelength spectrum b may be anything as long as they are different from each other. For example, wavelength spectrum a may be such that the light intensity in the visible light region is considered to be substantially zero. In other words, it may be the case that visible light is blocked just before reaching wavelength emission region 22a (1a). In this case, if the light intensity of wavelength spectrum b is substantially greater than zero in the visible light region, wavelength spectrum a and wavelength spectrum b are different.

[0027] The operation of the optical device 10 according to the present embodiment described above will now be described.

[0028] Of the light emitted from the projector 12a of the light emitting unit 12, light of wavelength spectrum a is transmitted from the wavelength emission region 22a (No. 1a) and the wavelength emission region 24a (No. 2a). At the same time, light of wavelength spectrum b is transmitted from the wavelength emission region 22b (No. 1b) and the wavelength emission region 24b (No. 2b).

[0029] Light passing through first wavelength exit surface 14a illuminates object surface S via first lens elements 16a of lens array 16. The illuminated area is referred to as field F1. Similarly, a portion of light passing through second wavelength exit surface 14b illuminates the same field F1 via second lens elements 16b of lens array 16.

[0030] Of the light that has passed through first wavelength emission surface 14a, the light that has passed through wavelength emission region 22a (1a) is propagated by first lens element 16a in a direction parallel to first optical axis L1 and reaches irradiation field F1. On the other hand, the light that has passed through wavelength emission region 22b (1b) is propagated by first lens element 16a in a direction inclined to first optical axis L1 and reaches irradiation field F1.

[0031] Furthermore, of the light that passes through the second wavelength emission surface 14b, the light that passes through the 2a wavelength emission region 24a is propagated parallel to the second optical axis L2 by the second lens element 16b, reaches the object surface S, and illuminates the object surface S. The illuminated region is referred to as the irradiation field F2. The light rays that pass through the 2a wavelength emission region 24a and reach the irradiation field F2 are referred to as the 2a light rays B2a. On the other hand, the light that passes through the 2b wavelength emission region 24b is propagated by the second lens element 16b in a direction inclined to the second optical axis L2, and reaches the irradiation field F1 formed by the light that passed through the 1b wavelength emission region 22b.

[0032] Therefore, the irradiation field F1 is irradiated with at least the light of wavelength a that has passed through the wavelength emission region 22a of the first a, the light of wavelength b that has passed through the wavelength emission region 22b of the first b, and the light of wavelength b that has passed through the wavelength emission region 24b of the second b, in an overlapping manner. In other words, an area is formed where the respective lights (light of multiple wavelengths a and b) simultaneously overlap. Therefore, the optical device 10 according to this embodiment irradiates the same irradiation field F1 of the object O with multiple light of wavelengths a and b. Here, the light ray that passes through the wavelength emission region 22a of the first a and reaches the irradiation field F1 is referred to as the light ray B1a of the first a, and the light ray that passes through the wavelength emission region 22b of the first b and reaches the same irradiation field F1 is referred to as the light ray B1b of the first b. Furthermore, the light ray that passes through the wavelength emission region 24b of the second b and reaches the same irradiation field F1 is referred to as the light ray B2b of the second b.

[0033] Consider a case where the irradiation field F1 is observed from a direction (line of sight) oblique to the first optical axis L1. The object surface S is assumed to be a plane.

[0034] In this case, if the object surface S in the irradiation field F1 is a smooth surface, the 1a light ray B1a is specularly reflected along the first optical axis L1, so that the reflected light does not return to the observer, and the light having the wavelength spectrum a is not observed by the observer.

[0035] In addition, the 1b light ray B1b is also specularly reflected by the irradiation field F1 and reflected in a direction oblique to the first optical axis L1. At this time, there is a possibility that the reflected light of the 1b light ray B1b will return to the observer observing from a direction oblique to the optical axis L1 (the line of sight direction). In addition, the 2b light ray B2b is also specularly reflected by the irradiation field F1 and reflected in a direction oblique to the first optical axis L1. At this time, there is a possibility that the reflected light of the 2b light ray B2b will return to the observer observing from a direction oblique to the optical axis L1. As a result, the 1b light ray B1b and the 2b light ray B2b may be observed by the observer, but the 1a light ray B1a will not be observed. In other words, the smooth surface can be observed by the 1b light ray B1b and the 2b light ray B2b.

[0036] On the other hand, if the object surface S in the illumination field F1 has minute irregularities, the light is scattered by the minute irregularities and reflected in various directions. Such reflection characteristics can be described by a bidirectional reflectance distribution function (BRDF), which represents the light intensity for each reflection direction. For example, consider a case where the object surface S has minute irregularities. Ray 1a B1a is scattered by the minute irregularities and becomes various groups of rays, some of which travel toward the observer. The scattered group of rays also has the same wavelength spectrum a as ray 1a B1a. Therefore, each ray of the scattered group of rays is treated as ray 1a B1a. In this way, when the object surface S has minute irregularities, the observer observes ray 1a B1a. At the same time, ray 1b B1b is also scattered by the minute irregularities and travels toward the observer. Therefore, when the object surface S has minute irregularities, the observer also observes ray 1b B1b. The 2b light ray B2b is also scattered by the minute irregularities and heads toward the observer. Therefore, when there are minute irregularities on the object surface S, the 2b light ray B2b is also observed by the observer. As a result, the observer observes not only the 1a light ray B1a, but also the 1b light ray B1b and the 2b light ray B2b.

[0037] Therefore, if the object surface S is a smooth surface, the observer will not observe the 1a ray B1a. Similarly, the 2a ray B2a will not be observed either. In other words, the smooth surface cannot be observed using the 1a ray B1a and the 2a ray B2a. However, the smooth surface can be observed using the 1b ray B1b and the 2b ray B2b. However, if the object surface S has minute irregularities, not only the 1a ray B1a but also the 1b ray B1b and the 2b ray B2b will be observed. In other words, the minute irregularities can be observed not only using the 1a ray B1a but also using the 1b ray B1b and the 2b ray B2b. Therefore, if the object surface S is a smooth surface, the smooth surface cannot be observed using blue light, but can only be observed using red light. On the other hand, if the object surface S has minute irregularities, it can be observed using both blue and red light. This allows the observer to identify the presence of minute irregularities when observing, for example, blue light. As a result, by using the optical device 10 according to this embodiment, it is possible to more reliably detect the presence or absence of minute irregularities on the object surface S using color (hue) information.

[0038] The optical device 10 according to this embodiment includes a light emitting unit 12 that emits light, and an imaging optical element array 16 having at least a first imaging optical element 16a and a second imaging optical element 16b. The optical device 10 includes a first wavelength emitting surface 14a having a first wavelength emitting region (wavelength emitting region 22a of 1a) that, when light is emitted from the light emitting unit 12, causes light of a first wavelength spectrum a to be emitted toward the imaging optical element array 16 by the light from the light emitting unit 12, and a second wavelength emitting region (wavelength emitting region 22b of 1b) that causes light of a second wavelength spectrum b, different from the light of the first wavelength spectrum a, to be emitted toward the imaging optical element array 16 by the light from the light emitting unit 12. The optical device 10 also includes a second wavelength emitting surface that is disposed at a position different from the first wavelength emitting surface 14a and has a first wavelength emitting region (2a wavelength emitting region 24a) and a second wavelength emitting region (2b wavelength emitting region 24b) similar to the first wavelength emitting surface 14a, when light is emitted from the light emitting unit 12. The first wavelength emitting surface 14a is located on or near the focal plane of the first imaging optical element 16a, and the second wavelength emitting surface 14b is located on or near the focal plane of the second imaging optical element 14b.

[0039] The first imaging optical element 16a of the imaging optical element array 16 forms a first irradiation field F1 with the light of the first wavelength spectrum a emitted from the first wavelength emission region (1a wavelength emission region 22a) of the first wavelength emission surface 14a and the light of the second wavelength spectrum b emitted from the second wavelength emission region (1b wavelength emission region 22b) of the first wavelength emission surface 14a. The second imaging optical element 16b of the imaging optical element array 16 is disposed so that an overlapping region of light is formed in the first irradiation field F1 with either the light of the first wavelength spectrum a emitted from the first wavelength emission region (2a wavelength emission region 24a) of the second wavelength emission surface 14b or the light of the second wavelength spectrum b emitted from the second wavelength emission region (2b wavelength emission region 24b) of the second wavelength emission surface 14b.

[0040] Here, we have described an example in which an observer observes, but for example, the image sensor 36 (see Figure 8) described later can be used to distinguish wavelengths and receive light, and the control unit 5 described later can determine based on the color information (hue) contained in the signal received by the image sensor 36, thereby allowing the control unit 5 to obtain information about the object, such as whether the object surface S is a smooth surface or whether there are any irregularities on the object surface S.

[0041] Therefore, according to this embodiment, it is possible to provide an optical device 10 that can acquire information about an object O by irradiating the same irradiation field F1 of the object with light of a plurality of wavelengths a and b.

[0042] However, when light passing through wavelength emission region 22b (1b) passes through first lens element 16a and forms irradiation field F1, the illuminance distribution of irradiation field F1 generally becomes uneven. This means that even if the illuminance of light passing through wavelength emission region 22b (1b) is uniform within the same region, the light beams incident on first lens element 16a are deflected in different directions by lens element 16a, resulting in an uneven illuminance distribution of irradiation field F1 formed by the light beams. On the other hand, by using lens array 16 composed of multiple lens elements 16a, 16b as in this embodiment, the illuminance distribution of irradiation field F1 can be made uniform.

[0043] Here, the lens array 16 is sometimes called a fly's eye lens or a microlens array. In this embodiment, the illumination distribution is made uniform by overlapping the illumination fields F1 formed by the lens elements 16a and 16b. In other words, even if the illumination fields F1 formed by the individual lens elements 16a and 16b are non-uniform, a uniform illumination field F1 can be formed by overlapping them. Alternatively, the characteristics of the individual lens elements 16a and 16b may be intentionally made different, and the illumination distributions formed by each may be adjusted. Such adjustments cannot be made when there is only one lens element.

[0044] When the optical device 10 according to this embodiment is used, an irradiation field F1 formed by light having the wavelength spectrum b that has passed through the wavelength emission region 22b of the first b can be superimposed on an irradiation field F1 formed by light having the same wavelength spectrum b that has passed through the wavelength emission region 24b of the second b. In other words, the optical device 10 according to this embodiment has the advantage of being able to homogenize the illuminance distribution of light having the same wavelength spectrum b from multiple directions by using the lens array 16.

[0045] Uniformity of the illuminance distribution in the irradiation field F1 can suppress large fluctuations in the intensity of reflected light from each object point on the object surface S, for example, when the object surface S is a smooth surface. Furthermore, when minute irregularities exist on the smooth surface, the intensity and color of light from the minute irregularities simultaneously change significantly. This increases the difference in the intensity of reflected light between when the object surface S is a smooth surface and when minute irregularities exist. On the other hand, when the illuminance distribution is non-uniform and the intensity of reflected light fluctuates significantly on a smooth surface, it becomes difficult to distinguish this from changes in the intensity of reflected light due to the presence of minute irregularities. In other words, compared to when the illuminance distribution in the irradiation field F1 is non-uniform, when the illuminance distribution in the irradiation field F1 is uniformed using the optical device 10 according to this embodiment, the intensity of reflected light from minute irregularities can be identified, making it easier to identify the presence or absence of minute irregularities. Here, when minute irregularities exist, not only the light intensity but also the color (hue) can be significantly changed at the same time compared to when the surface is smooth.

[0046] As described above, when the optical device 10 according to this embodiment is used, it is possible to obtain more accurately the surface information of the object (object surface) S in the irradiation field F1 from the light intensity or color (hue) information. Furthermore, when the optical device 10 according to this embodiment is used, it is possible to form the irradiation field F1 with a more uniform illuminance distribution.

[0047] The optical inspection method according to this embodiment includes emitting light of a first wavelength spectrum a from the wavelength emission region 22a of 1a toward the first imaging optical element 16a of the imaging optical element array 16, emitting light of a second wavelength spectrum b different from the first wavelength spectrum a from the wavelength emission region 22b of 1b toward the first imaging optical element 16a of the imaging optical element array 16, and emitting light of the first wavelength spectrum b from the wavelength emission region 24a of 2a different from the wavelength emission region 22a of 1a and the wavelength emission region 22b of 1b toward the first imaging optical element 16a of the imaging optical element array 16. the light a and the light b of the second wavelength spectrum having passed through the first imaging optical element 16a and the light b of the second wavelength spectrum having passed through the second imaging optical element 16b, and emitting the light of the second wavelength spectrum b from the wavelength emission region 22a of the first wavelength, the wavelength emission region 22b of the first wavelength, and the wavelength emission region 24b of the second wavelength that is different from the wavelength emission region 24a of the second wavelength toward the second imaging optical element 16b of the imaging optical element array 16; and illuminating an object surface S of the object O with the light a and the light b of the first wavelength spectrum having passed through the first imaging optical element 16a and the light a and the light b of the second wavelength spectrum having passed through the second imaging optical element 16b. Illuminating the object surface S of the object O includes irradiating the same first illumination field F1 with the light a and the light b of the first wavelength spectrum having passed through the first imaging optical element 16a. For example, by using light illuminating the object surface S of the object O, an observer can grasp the color (wavelength spectrum a, b) from the first illumination field F1 that illuminates the object surface S of the object O, thereby obtaining information about the object surface S of the object.

[0048] Furthermore, illuminating the object surface S of the object O includes forming an area where light overlaps with the first irradiation field F1 using either the light of the first wavelength spectrum a emitted from the wavelength emission region 24a (2a) or the light of the second wavelength spectrum b emitted from the wavelength emission region 24b (2b). According to the optical inspection method of this embodiment, by using the lens array 16 (imaging optical elements 16a, 16b), it is possible to irradiate the first irradiation field F1 with light from multiple directions having the same wavelength spectrum b, thereby achieving a uniform illuminance distribution.

[0049] Therefore, according to this embodiment, it is possible to provide an optical device 10 and an optical inspection method that can acquire information about an object O by irradiating the same irradiation field F1 of the object O with light of multiple wavelengths a and b.

[0050] In the above example, the projector 12a is used as the light output unit 12. The light output unit 12 may be, for example, one described in the following modified example.

[0051] (First Modification) As shown in FIG. 2, the light emitting unit 12 may be a combination of a projector 12a and a light diffusion unit (a light diffusion plate or a light diffusion sheet) 12b. That is, the light diffusion unit 12b may be disposed on the focal plane of each lens element 16a, 16b of the lens array 16, and the projector 12a may project an image toward the light diffusion unit 12b. In this way, the light diffusion unit 12b spreads the light in various directions. This allows the light to reach the entire area of ​​the lens elements 16a, 16b, thereby widening the illumination field F1. However, the light emitting unit 12 is not limited to the projector 12a, but may be any unit that allows light of wavelength spectrum a to pass through the wavelength emission region 22a of 1a and the wavelength emission region 24a of 2a, and allows light of wavelength spectrum b to pass through the wavelength emission region 22b of 1b and the wavelength emission region 24b of 2b.

[0052] (Second Modification) 3, the light emitting unit 12 may use, for example, light sources 12aa and 12ab that emit light (e.g., white light) including wavelength spectrum a and wavelength spectrum b. Therefore, white LEDs (Light-Emitting Diodes) can be used as the light sources 12aa and 12ab. The light emitting unit 12 according to this modification includes wavelength emitting surfaces 14 (first wavelength emitting surface 14a and second wavelength emitting surface 14b). The first wavelength emitting surface 14a and the second wavelength emitting surface 14b are configured so that their actual surfaces can be confirmed without projecting light from the light emitting unit 12.

[0053] Furthermore, the first wavelength emitting surface 14a has a first filter 22a and a second filter 22b arranged in the wavelength emitting region 1a and the wavelength emitting region 1b. The first filter 22a passes light of a wavelength spectrum having wavelength a as its main component (dominant wavelength). This wavelength spectrum is referred to as wavelength spectrum a. The first filter 22a blocks light of wavelength b. The second filter 22b passes light of a wavelength spectrum having wavelength b as its main wavelength. This wavelength spectrum is referred to as wavelength spectrum b. The second filter 22b blocks light of wavelength a. However, the first filter 22a and the second filter 22b are not limited to this, and any filters may be used as long as the wavelength emitting region 22a of 1a and the wavelength emitting region 22b of 1b pass light of different wavelength spectrums. That is, color filters that transmit light of different wavelength spectrums are arranged on the first wavelength emitting surface 14a and the second wavelength emitting surface 14b, respectively.

[0054] Furthermore, the second wavelength emitting surface 14b has a first filter 24a and a second filter 24b arranged in the wavelength emitting region 2a and the wavelength emitting region 2b. The wavelength emitting region 24a of the second wavelength passes light of wavelength spectrum a, which has wavelength a as its main component (dominant wavelength), and blocks light of wavelength b. The wavelength emitting region 24b of the second wavelength passes light of wavelength spectrum b, which has wavelength b as its main wavelength, and blocks light of wavelength a. However, the second wavelength emitting surface 14a is not limited to this, and any filter may be used as long as the wavelength emitting region 24a of the second wavelength and the wavelength emitting region 24b of the second wavelength pass light of different wavelength spectra.

[0055] The light source 12aa may be arranged on or near the first wavelength emitting surface 14a so that light rays including wavelength spectra a and b from the light source 12aa are irradiated onto the color filters arranged in the wavelength emitting regions 22a and 22b of the first wavelength emitting surface 14a, and the light source 12ab may be arranged on or near the second wavelength emitting surface 14b so that light rays including wavelength spectra a and b from the light source 12ab are irradiated onto the color filters arranged in the wavelength emitting regions 24a and 24b of the second wavelength emitting surface 14b.

[0056] In this modification, an example has been described in which the light sources 12aa and 12ab that emit light (e.g., white light) including wavelength spectrum a and wavelength spectrum b are used as the light output unit 12. Instead of these light sources 12aa and 12ab, the projector 12a described in the first embodiment can also be used.

[0057] The optical device 10 according to this embodiment includes a light emitting unit 12 that emits light, and an imaging optical element array 16 having at least two imaging optical elements, a first imaging optical element 16a and a second imaging optical element 16b. The optical device 10 includes a first wavelength emitting surface 14a having a first wavelength emitting region (wavelength emitting region 22a of 1a) that, when light is emitted from the light emitting unit 12, causes light of a first wavelength spectrum a to be emitted toward the imaging optical element array 16 by the light from the light emitting unit 12, and a second wavelength emitting region (wavelength emitting region 22b of 1b) that causes light of a second wavelength spectrum b, different from the light of the first wavelength spectrum a, to be emitted toward the imaging optical element array 16 by the light from the light emitting unit 12. The optical device 10 also includes a second wavelength emitting surface 14a, which is disposed at a position different from the first wavelength emitting surface 14a and has a first wavelength emitting region (2a wavelength emitting region 24a) and a second wavelength emitting region (2b wavelength emitting region 24b) similar to the first wavelength emitting surface 14a. The first wavelength emitting surface 14a is located on or near the focal plane of the first imaging optical element 16a, and the second wavelength emitting surface 14b is located on or near the focal plane of the second imaging optical element 14b.

[0058] The first wavelength emission regions (1a wavelength emission region 22a, 2a wavelength emission region 24a) are respectively provided with first filters 22a, 24a that transmit light of the first wavelength spectrum a. The second wavelength emission regions (2b wavelength emission region 24a, 2b wavelength emission region 24a) are respectively provided with second filters 22b, 24b that transmit light of the second wavelength spectrum b.

[0059] (Third Modification) The light emitting unit 12 according to this modification includes wavelength emitting surfaces 14 (first wavelength emitting surface 14a and second wavelength emitting surface 14b). The first wavelength emitting surface 14a and second wavelength emitting surface 14b are configured so that their actual entities can be confirmed without projecting light from the light emitting unit 12.

[0060] As shown in Fig. 4, instead of arranging color filters in the wavelength emission region 22a of the first wavelength emission surface 14a and the wavelength emission region 24a of the second wavelength emission surface 14b, a phosphor (first phosphor) that emits light of wavelength spectrum a when irradiated with excitation light may be arranged in or near the wavelength emission region 22a or the wavelength emission region 24a. In this case, the light source of the light emitting unit 12 serving as the source of excitation light may be an LED or LD (Laser-diode) having a wavelength spectrum that excites the phosphors (first phosphors) 22a and 24a, and irradiate the phosphors 22a and 24a with light from the LED or LD (Laser-diode) having a wavelength spectrum that excites the phosphors (first phosphors) 22a and 24a. For example, an LED or LD denoted by reference numeral 12a1 is used as the light source that causes the phosphor 22a to emit light of wavelength spectrum a, and an LED or LD denoted by reference numeral 12a2 is used as the light source that causes the phosphor 24a to emit light of wavelength spectrum a. The wavelength of the light emitted from light sources 12a1 and 12a2 that excite phosphors 22a and 24a that emit light of wavelength spectrum a is shorter than that of wavelength spectrum a, but this is not a limitation and the wavelength may be longer.

[0061] Similarly, instead of arranging color filters in the wavelength emission region 22b of the first wavelength emission surface 14a and the wavelength emission region 24b of the second wavelength emission surface 14b, a phosphor (second phosphor) that emits light of wavelength spectrum b when irradiated with excitation light may be arranged in or near the wavelength emission region 22b or the wavelength emission region 24b. In this case, the light source of the light emitting unit 12 serving as the source of excitation light may be an LED or LD (Laser-diode) having a wavelength spectrum that excites the phosphors (second phosphors) 22b and 24b, and irradiate the phosphors 22b and 24b with light from the LED or LD (Laser-diode) having a wavelength spectrum that excites the phosphors (second phosphors) 22b and 24b. For example, an LED or LD denoted by reference symbol 12b1 is used as the light source that causes the phosphor 22b to emit light of wavelength spectrum b, and an LED or LD denoted by reference symbol 12b2 is used as the light source that causes the phosphor 24b to emit light of wavelength spectrum b. The wavelength of the light emitted from light sources 12b1 and 12b2 that excite phosphors 22b and 24b that emit light of wavelength spectrum b is shorter than that of wavelength spectrum b, but this is not a limitation and the wavelength may be longer.

[0062] For this reason, phosphors are disposed on each of the first wavelength emitting surface 14a and the second wavelength emitting surface 14b.

[0063] In other words, in this embodiment, the illumination device that directs light into the imaging optical element array 16 to illuminate an appropriate irradiation field F1 may be any device that emits light of wavelength spectrum a from wavelength emission region 22a no. 1a and wavelength emission region 24a no. 2a, and emits light of wavelength spectrum b from wavelength emission region 22b no. 1b and wavelength emission region 24b no. 2b.

[0064] (Fourth Modification) 5, the light emitting unit 12 includes light sources (two pairs of light sources are shown here) 13a1, 13b1, 13a2, and 13b2, and wavelength emitting surfaces 14 (first wavelength emitting surface 14a and second wavelength emitting surface 14b). The optical device 10 according to this modification includes multiple pairs of light sources 13a1, 13b1, 13a2, and 13b2, each of which has a wavelength emitting surface 14 integrated with the light emitting unit 12.

[0065] For example, light sources 13a1 and 13a2 each emit light of wavelength spectrum a. Light sources 13b1 and 13b2 each emit light of wavelength spectrum b. For example, a micro LED, a micro LED array, an LED, an LED array, or an LD that emits light of wavelength spectrum a can be used as light sources 13a1 and 13a2. For example, a micro LED, a micro LED array, an LED, an LED array, or an LD that emits light of wavelength spectrum b can be used as light sources b1 and 13b2.

[0066] The light emission position of the light source 13a1 is preferably the position of the 1a wavelength emission region 22a (on or near the first wavelength emission surface 14a) described with reference to Figures 1 to 4, and the light emission position of the light source 13b1 is preferably the position of the 1b wavelength emission region 22b (on or near the first wavelength emission surface 14a) described with reference to Figures 1 to 4. The light emission position of the light source 13a2 is preferably the position of the 2a wavelength emission region 24a (on or near the second wavelength emission surface 14b) described with reference to Figures 1 to 4, and the light emission position of the light source 13b2 is preferably the position of the 2b wavelength emission region 24b (on or near the second wavelength emission surface 14b) described with reference to Figures 1 to 4.

[0067] That is, the light emitting unit 12 includes first light sources 13a1 and 13a2 that emit light of a first wavelength spectrum a and second light sources 13b1 and 13b2 that emit light of a second wavelength spectrum b. The first light sources 13a1 and 13a2 are disposed in wavelength emission regions 22a and 24a of the first wavelength emitting surface 14a and the second wavelength emitting surface 14b, respectively. The second light sources 13b1 and 13b2 are disposed in wavelength emission regions 22b and 24b of the first wavelength emitting surface 14a and the second wavelength emitting surface 14b, respectively.

[0068] In other words, in this embodiment, the illumination device that directs light into the imaging optical element array 16 to illuminate an appropriate irradiation field F1 may be any device that emits light of the first wavelength spectrum a from the wavelength emission region 22a of 1a and the wavelength emission region 24a of 2a, and emits light of the second wavelength spectrum b from the wavelength emission region 22b of 1b and the wavelength emission region 24b of 2b.

[0069] (Fifth Modification) Below, a modified example of the wavelength exit surface 14 and the imaging optical element array 16 of the optical device 10 will be described with reference to FIG.

[0070] 6 shows a perspective view of the wavelength exit surface 14 of the optical device 10 according to a fifth modified example of this embodiment and the imaging optical element array 16. In FIG. 6, the light exit unit 12 and the irradiation fields F1 and F2 are not shown.

[0071] The lens array 16 shown in FIG. 6 includes axisymmetric lens elements 16a and 16b. That is, the first lens element 16a is axisymmetric about the first optical axis L1, and the second lens element 16b is axisymmetric about the second optical axis L2. The optical axes L1 and L2 are assumed to be parallel to the z-axis, and the xy plane is perpendicular thereto. The first lens element 16a and the second lens element 16b are assumed to be identical. The focal planes of the first lens element 16a and the second lens element 16b are assumed to be coplanar. The focal planes are assumed to be parallel to the xy plane. The first wavelength emitting surface 14a and the second wavelength emitting surface 14b may be formed by a projector (projection unit) 12a (see FIG. 1) to project images that are concentric with the first optical axis L1 and the second optical axis L2, respectively. Alternatively, wavelength emission regions 22a, 22b, 24a, and 24b may be arranged as color filters (see FIG. 3) or phosphors (see FIG. 4), etc. Therefore, the center of wavelength emission region 22a of 1a intersects with the first optical axis L1, and the center of wavelength emission region 24a of 2a intersects with the second optical axis L2.

[0072] Consider a case where an image of the irradiation field F1 illuminated by the optical device 10 according to this modification is acquired by an image sensor 36 (see FIGS. 8, 10, and 11) instead of an observer. When the image acquired by the image sensor 36 is processed by a control unit 5 (see FIGS. 8 and 9) including a processor, the spread of the BRDF in the x-axis and y-axis directions in the irradiation field F1 (see FIGS. 1 to 4) can be simultaneously acquired (observed) as color information (see Non-Patent Document 2). Thus, when an object (object surface S) is illuminated using the optical device 10 according to this modification and the illuminated irradiation field F1 is acquired as an image, the surface condition can be identified from the spread of the BRDF in various directions. Furthermore, by using the optical device 10 according to this modification, the irradiation field F1 formed by the first lens element 16a and the irradiation field F1 formed by the second lens element 16b can be overlapped, as described in the first embodiment, thereby reducing uneven illuminance in the irradiation field F1.

[0073] Therefore, according to this modified example, it is possible to provide an optical device 10 and an optical inspection method that can acquire information about an object O by irradiating the same irradiation field F1 of the object O with light of multiple wavelengths a and b.

[0074] (Sixth Modification) An optical device 10 as a further modification of the fifth modification will be described below with reference to FIG.

[0075] 7 shows a perspective view of the wavelength exit surface 14 and the imaging optical element array 16 of the optical device 10 according to a modified example of this embodiment. In FIG. 7, the light exit unit 12 and the irradiation fields F1 and F2 are not shown.

[0076] In FIG. 7, the lens array 16 includes lens elements 16a and 16b that have translational symmetry. That is, for example, the first lens element 16a and the second lens element 16b have translational symmetry in the y-axis direction. Such a lens is called a lenticular lens. The optical axes L1 and L2 of the lens elements 16a and 16b are assumed to be parallel to the z-axis, and the xy plane is perpendicular to the z-axis. The first lens element 16a and the second lens element 16b are assumed to be identical. The focal planes of the first lens element 16a and the second lens element 16b are assumed to be on the same plane. The focal planes are assumed to be parallel to the xy plane. The first wavelength emitting surface 14a and the second wavelength emitting surface 14b are assumed to have translational symmetry along the y-axis, and wavelength emitting regions 22a, 22b, 22c, 24a, 24b, and 24c are formed on the first wavelength emitting surface 14a and the second wavelength emitting surface 14b, respectively, by projected images formed by light from a projector (projection unit). Alternatively, the wavelength emitting regions 22a, 22b, 22c, 24a, 24b, and 24c may be formed by color filters or phosphors. In other words, the first wavelength emitting surface 14a has three different wavelength emitting regions 22a, 22b, and 22c, which are referred to as wavelength emitting region 22a, wavelength emitting region 22b, and wavelength emitting region 22c. The second wavelength emitting surface 14b is similarly assumed to have wavelength emitting region 24a, wavelength emitting region 24b, and wavelength emitting region 24c. Here, wavelength emission regions 22a and 24a pass light of wavelength spectrum a, whose dominant wavelength is wavelength a, and wavelength emission regions 22b and 24b pass light of wavelength spectrum b, whose dominant wavelength is wavelength b. Furthermore, wavelength emission regions 22c and 24c pass light of wavelength spectrum c, whose dominant wavelength is wavelength c. Here, wavelength c is 550 nm, and is green light.

[0077] In FIG. 7, the center of the 1a wavelength emission region 22a intersects with the first optical axis L1, and the center of the 2a wavelength emission region 24a intersects with the second optical axis L2.

[0078] When an imaging image that can be obtained when an object O is illuminated using the optical device 10 according to this modification as an illumination unit is processed using a control unit including a processor (see FIGS. 8 and 9), the spread of the BRDF in the x-axis direction in the irradiation field F1 (see FIGS. 1 to 4) can be acquired (observed) as color (hue) information. Therefore, the control unit 5 acquires information about the BRDF of the object O based on the hue of the light from the object O. Meanwhile, the spread in the y-axis direction can be acquired (observed) as a change in light intensity. This allows various surface conditions to be identified as changes in color (hue) and light intensity. Furthermore, by using the optical device 10 according to this modification, the irradiation field F1 formed by the first lens element 16a and the irradiation field F1 formed by the second lens element 16b can be overlapped, as described in the first embodiment, thereby reducing uneven illuminance in the irradiation field F1.

[0079] Therefore, the optical inspection method according to this modified example includes acquiring the hue of light from the object surface S of the object O by illuminating the object surface S of the object O as described above, and acquiring information about the BRDF of the object O based on the acquired hue of the light.

[0080] Therefore, according to this modification, it is possible to provide an optical device 10 and an optical inspection method that can acquire information about the object O by irradiating the same irradiation field F1 of the object O with light of a plurality of wavelengths a and b.

[0081] (Second embodiment) The optical inspection system 1 according to this embodiment will be described in detail below with reference to Figures 8 and 9. This embodiment is a further modification of the first embodiment, including various modifications. Components that are the same as or have the same functions as those described in the first embodiment will be assigned the same reference numerals as much as possible, and detailed descriptions will be omitted.

[0082] Fig. 8 shows a schematic cross-sectional view of the optical inspection system 1 according to this embodiment. The cross-sectional view shown in Fig. 8 is assumed to be on the xz plane, for example.

[0083] The optical inspection system 1 according to this embodiment includes an optical inspection device 3 and a control unit 5.

[0084] The optical inspection device 3 includes an illumination unit (optical device) 10 and an imaging unit 30. The illumination unit 10 includes a light emitting unit 12 and an imaging optical element array 16. The light emitting unit 12 and the imaging optical element array 16 may be the same as those described in the first embodiment.

[0085] The imaging unit 30 includes an imaging optical element 32, an imaging aperture 34, and an image sensor 36. The imaging optical element 32 is an imaging optical element 32 provided in the imaging unit 30. The focal plane of the imaging optical element 32 is the imaging focal plane. The imaging aperture 34 is disposed between the imaging optical element 32 and the image sensor 36, at or near the imaging focal plane of the imaging optical element 32.

[0086] In Figure 8, the illumination side is depicted schematically above the object surface S, and the imaging side is depicted schematically below the object surface S. In particular, if the object O transmits light, the actual positional relationship between the illumination side and the imaging side will be the same as in this figure. On the other hand, if the object O reflects light from its surface, the actual positional relationship between the illumination side and the imaging side will be the mirror image of Figure 8 reflected with respect to the object surface S. However, in this case, structural interference between the illumination unit 10 and the imaging unit 30 may occur. This can be easily avoided by placing a non-polarizing beam splitter (not shown) or a polarizing beam splitter (not shown) in the optical path of the light reflected from the object surface S. In this way, partially overlapping the optical path from the illumination unit 10 to the imaging unit 30 via the beam splitter has the advantage of avoiding structural interference between the illumination unit 10 and the imaging unit 30 while also making the entire optical inspection device 3 more compact. In particular, aligning the optical axis L1 of the illumination unit 10 with the imaging optical axis L of the imaging unit 30 is called coaxial epi-illumination.

[0087] Furthermore, when a polarizing beam splitter is used to return the optical path, it is possible to extract light scattered by minute irregularities on the object surface S, which has the advantage of enabling the acquisition of surface information about the object O. This is because when light is scattered by minute irregularities, the polarization of the reflected light generally rotates relative to the incident light.

[0088] In this embodiment, the object O reflects light, and the optical path on the imaging side in FIG. 8 is actually reflected mirror-symmetrically at the object surface S. At this time, the object surface S of the object O is illuminated by light from the light emitting unit 12 of the illumination unit 10. Here, the illuminated areas on the object surface S are called illumination fields F1 and F2. However, the object O is not limited to this, and may be transparent or translucent to light.

[0089] The imaging optical elements 16a and 16b of the imaging optical element array 16 have the function of collecting a group of light rays emitted from a certain point onto a conjugate image point. In this embodiment, the imaging optical element array 16 is a lens array, and the two aligned imaging optical elements 16a and 16b that make up the lens array 16 are, for example, Fresnel lenses.

[0090] The optical axes L1 and L2 of the lens elements 16a and 16b are included in the cross section of Figure 8 and are parallel to the z-axis. The optical axis L1 of the first lens element 16a and the optical axis L2 of the second lens element 16b are defined as the first optical axis L1 and the second optical axis L2, respectively.

[0091] The first wavelength exit surface 14a and the second wavelength exit surface 14b are formed on or near the focal planes of the first lens element 16a and the second lens element 16b, respectively. In this embodiment, the focal planes of the first lens element 16a and the second lens element 16b are assumed to be on the same plane.

[0092] The first wavelength emitting surface 14a forms a wavelength emitting region 22a (1a) and a wavelength emitting region 22b (1b). The wavelength emitting region 22a (1a) transmits light of a wavelength spectrum having wavelength a as its main component (dominant wavelength). This wavelength spectrum is wavelength spectrum a. The wavelength emitting region 22b (1b) transmits light of a wavelength spectrum having wavelength b as its main component. This wavelength spectrum is wavelength spectrum b. In this embodiment, for example, wavelength a is 450 nm and wavelength b is 650 nm. In this case, light of wavelength spectrum a is blue light, and light of wavelength spectrum b is red light. However, this is not limited to this, and wavelength spectrum a and wavelength spectrum b may be any spectrums different from each other. For example, wavelength spectrum a may be such that the light intensity in the visible light range is considered to be substantially zero. In this case, wavelength spectrum b includes light in the visible light range whose light intensity is substantially greater than zero. In this case, wavelength spectrum a and wavelength spectrum b are different.

[0093] The imaging optical element 32 for capturing images is a lens assembly made up of multiple lenses. However, the imaging optical element 32 is not limited to this, and may be a concave mirror, a convex mirror, or a combination thereof. In other words, the imaging optical element 32 may be any optical element that has the function of collecting a group of light rays emitted from a certain point onto a conjugate image point.

[0094] The imaging aperture 34 of the imaging unit 30 is, for example, a color filter having a region that passes a specific wavelength spectrum. The imaging aperture 34 is further assumed to have a first wavelength selection region 41 and a second wavelength selection region 42. The first wavelength selection region 41 passes light of wavelength spectrum b. On the other hand, the first wavelength selection region 41 blocks light of wavelength a. The second wavelength selection region 42 passes light of wavelength spectrum a. On the other hand, the second wavelength selection region 42 blocks light of wavelength b. However, this is not limited to this, and the imaging aperture 34 may be a through-hole or an annular opening. In other words, anything having a region that passes a specific wavelength spectrum may be used.

[0095] As shown in Fig. 3, the light output unit 12 of this embodiment has two types of color filters 22a, 22b, 24a, and 24b that transmit light of wavelength spectrum a and wavelength spectrum b, respectively, arranged on or near the wavelength output surfaces 14a and 14b. Light from, for example, white LEDs (light-emitting diodes) serving as light sources 12aa and 12ab is irradiated onto the color filters 22a, 22b, 24a, and 24b, selectively transmitting light of wavelength spectrum a and wavelength spectrum b. However, the light source of the light output unit 12 is not limited to this, and any of the light sources described with reference to Figs. 1 to 4 can be used as appropriate. Furthermore, any of the light sources described with reference to Figs. 1 to 7 can be used as appropriate for the wavelength output surfaces 14a and 14b of the wavelength output surface 14.

[0096] The image sensor 36 of the imaging unit 30 has at least one pixel, and each pixel can receive light of at least two different wavelengths, i.e., light of wavelength a and light of wavelength b, as independent signals. The surface including the image sensor 36 is the imaging surface (or image plane) of the imaging optical element 32. The image sensor 36 may be an area sensor or a line sensor. An area sensor has pixels arranged in an area on the same surface. A line sensor has pixels arranged in a line. Each pixel may have three color channels: R, G, and B. In other words, it may be capable of receiving light through independent color channels. However, each color channel does not need to be completely independent; in fact, each color channel may have slight sensitivity to the same wavelength. In this embodiment, the image sensor 36 is an area sensor that can distinguish at least two different wavelengths included in wavelength spectrum a and wavelength spectrum b.

[0097] The control unit 5 is, for example, a computer that controls the light emission unit 12 and the image sensor 36 of the imaging unit 30. The control unit 5 includes a processor, a ROM (storage unit), a RAM, an auxiliary storage device (storage unit), a communication interface (communication unit), and the like.

[0098] The processor corresponds to the central part of a computer that performs processes such as calculations and controls required for the processing of the control unit 5, and comprehensively controls the entire control unit 5. The processor executes control to realize various functions of the control unit 5 based on programs such as system software, application software, or firmware stored in a storage unit such as a ROM or an auxiliary storage device. The processor includes, for example, a central processing unit (CPU), a micro processing unit (MPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), or a field programmable gate array (FPGA). Alternatively, the processor may be a combination of two or more of these. The control unit 5 may be provided with one or more processors.

[0099] The ROM corresponds to the main memory of a computer with a processor at its core. The ROM is a non-volatile memory used exclusively for reading data. For example, the ROM stores an optical inspection program based on the flow shown in FIG. 9. The ROM also stores data or various setting values ​​used by the processor when it performs various processes.

[0100] RAM is equivalent to the main memory of a computer, which is centered around a processor. RAM is memory used for reading and writing data. RAM is used as a so-called work area, where data is temporarily stored when the processor performs various processes.

[0101] The auxiliary storage device corresponds to the auxiliary storage device of a processor-based computer. Examples of the auxiliary storage device include an EEPROM (electrically erasable programmable read-only memory) (registered trademark), an HDD (hard disk drive), or an SSD (solid state drive). The auxiliary storage device may also store an optical inspection program based on the flow shown in FIG. 9 above. The auxiliary storage device may also store data used by the processor when performing various processes, data generated by the processor's processes, various setting values, etc.

[0102] The programs stored in the ROM or the auxiliary storage device include a program for controlling the control unit 5. For example, an optical inspection program based on the flow shown in Fig. 9 is preferably stored in the ROM or the auxiliary storage device.

[0103] The communication interface is an interface for communicating with other devices via a network or the like, either wired or wirelessly, receiving various types of information transmitted from other devices, and transmitting various types of information to other devices. The optical inspection program of the optical inspection system 1 may be executed on a server or cloud of various systems remote from the optical inspection device 3 via the communication interface of the control unit 5. For this reason, it is also preferable that the optical inspection program is stored on a server or cloud rather than stored in a ROM or an auxiliary storage device, and is executed while communicating with, for example, the control unit 5 of the optical inspection system 1 via the communication interface.

[0104] The operation of the optical inspection system 1 according to the present embodiment described above will be described with reference to FIG.

[0105] Light from a white LED light source provided in the light emitting unit 12 is transmitted through the color filters 22a, 22b, 24a, and 24b, so that light of wavelength spectrum a passes through the wavelength emission region 1a 22a and the wavelength emission region 24a of the second a. At the same time, light of wavelength spectrum b passes through the wavelength emission region 1b 22b and the wavelength emission region 24b of the first b.

[0106] The light passing through the first wavelength emitting surface 14a illuminates the object surface S by the first lens element 16a of the lens array 16, and the illuminated area is defined as the irradiation field F1. Similarly, the light passing through the second wavelength emitting surface 14b illuminates the object surface S by the second lens element 16b of the lens array 16. At this time, a portion of the light passing through the second wavelength emitting surface 14b illuminates the irradiation field F1. However, the irradiation field F1 formed by the first lens element 16a and the irradiation field F1 formed by the second lens 16b do not completely overlap, and there are areas where they do not overlap. As a result, the optical inspection system 1 according to this embodiment has the advantage of being able to illuminate a wider area of ​​the object surface S by using the imaging optical element array 16 rather than using a single lens element 16a.

[0107] Of the light that has passed through first wavelength emission surface 14a, the light that has passed through wavelength emission region 22a (1a) is propagated by first lens element 16a in a direction parallel to first optical axis L1 and reaches irradiation field F1. On the other hand, the light that has passed through wavelength emission region 22b (1b) is propagated by first lens element 16a in a direction inclined to first optical axis L1 and reaches irradiation field F1.

[0108] Furthermore, of the light that has passed through the second wavelength emission surface 14b, the light that has passed through the 2a wavelength emission region 24a is propagated by the second lens element 16b in parallel along the second optical axis L2, reaches the object surface S, and illuminates the object surface S. On the other hand, the light that has passed through the 2b wavelength emission region 24b is propagated by the second lens element 16b in a direction inclined to the first optical axis L1, and reaches the irradiation field F1 formed by the light that has passed through the 1b wavelength emission region 22b (step S1).

[0109] Here, the light ray that passes through the wavelength emission region 22a of 1a and reaches the irradiation field F1 is referred to as the ray B1a of 1a, the light ray that passes through the wavelength emission region 22b of 1b and reaches the irradiation field F1 is referred to as the ray B1b of 1b, and the light ray that passes through the wavelength emission region 24b of 2b and reaches the irradiation field F1 is referred to as the ray B2b of 2b.

[0110] The imaging unit 30 is used to image an object surface S within the irradiation field F1. The object surface S is assumed to be flat. If the object surface S in the irradiation field F1 is a smooth surface, the 1a light ray B1a is specularly reflected along the first optical axis L1. This reflected light is designated the 3a light ray B3a. Note that in FIG. 8, for convenience, the imaging side is depicted as mirror-symmetric with respect to the object surface S. The 3a light ray B3a is directed toward an image point on the image sensor 36 by the imaging optical element 32. However, the light of wavelength a is blocked by the first wavelength selection region 41 of the imaging aperture 34 located on the imaging focal plane. In other words, because the light of wavelength a, which is the dominant wavelength of wavelength spectrum a, is blocked, the 3a light ray B3a is imaged on the image sensor 36 with weak light intensity (dark) (step S2).

[0111] Meanwhile, the 1b light ray B1b and the 2b light ray B2b are also specularly reflected by the object surface S and reflected in a direction oblique to the first optical axis L1. These reflected lights are referred to as the 4b light ray B4b and the 5b light ray B5b, respectively. These light rays B4b and B5b are directed toward an image point on the image plane on the image sensor 36 by the imaging optical element 32 for imaging of the imaging unit 30. However, the light of wavelength b is blocked by the second wavelength selection region 42 of the imaging aperture 34 arranged on the imaging focal plane. In other words, because the light of wavelength b, which is the dominant wavelength of wavelength spectrum b, is blocked, the 4b light ray B4b and the 5b light ray B5b are imaged on the image sensor 36 with weak intensity (dark).

[0112] From the above, if the object surface S is a smooth surface, the image of the irradiation field F1 will be dark. In other words, the object surface S will not be imaged by the image sensor .

[0113] The control unit 5 analyzes the light reception signal (image) of the image sensor 36 (step S3).

[0114] Here, the control unit 5 outputs that the object surface S is a smooth surface because the object surface S is not imaged by the image sensor 36 due to the irradiation of light from the light emitting unit 12 (step S4).

[0115] Next, consider a case where minute irregularities exist on the smooth surface of the object surface S. In this case, the 1a light ray B1a is scattered by the minute irregularities and reflected obliquely with respect to the first optical axis L1. It then reaches the second wavelength selection region 42 of the imaging aperture 34, which is disposed in the imaging focal plane of the imaging optical element 32. Because the second wavelength selection region 42 transmits light of wavelength spectrum a, the scattered light of the 1a light ray B1a is imaged with high light intensity (bright) on the image sensor 36. Meanwhile, the 1b light ray B1b and the 2b light ray B2b are also scattered by the minute irregularities on the object surface S and reflected in a direction oblique to the first optical axis L1. It then reaches the first wavelength selection region 41 of the imaging aperture 34, which is disposed in the imaging focal plane of the imaging optical element 32. Because the first wavelength selection region 41 transmits light of wavelength spectrum b, the 4b light ray B4b and the 5b light ray B5b are imaged with high intensity (bright) on the image sensor 36.

[0116] From the above, when there are minute irregularities on the object surface S, the minute irregularities are captured clearly and brightly by the image sensor 36 (step S2). Furthermore, the smooth surface and the minute irregularities have different colors (hues).

[0117] The control unit 5 analyzes the light reception signal (image) of the image sensor 36 (step S3).

[0118] Here, the control unit 5 outputs (step S4) that minute irregularities exist on the object surface S (that is, a part of the part of the irradiation field F1 whose image is obtained by the image sensor 36 is not simply a smooth surface) because the object surface S is imaged by the image sensor 36 due to the irradiation of light from the light emitting unit 12. This has the effect of enabling minute irregularities to be reliably detected when the optical inspection system 1 according to this embodiment is used.

[0119] 9, the control unit 5 controls the light emitting unit 12 to emit illumination light containing wavelengths a and b toward the wavelength emitting surface 14, and the illumination light containing wavelengths a and b illuminates the irradiation field F1 of the object surface S through the wavelength emitting surface 14 and the imaging optical element array 16 (step S1). The control unit 5 then controls the image sensor 36 to acquire light (reflected light, transmitted light, etc.) from the irradiation field F1 (step S2). The control unit 5 then analyzes whether the image sensor 36 acquired at least one of the wavelengths a and b of light, or whether it acquired neither (step S3). The control unit 5 then uses the analysis results to output the surface texture of the irradiation field F1 of the object surface S (step S4). Therefore, the control unit 5 acquires information about the object based on the light reception signal captured by the image sensor 36 of the imaging unit 30.

[0120] However, when light passing through wavelength emission region 22b (1b) passes through first lens element 16a and forms irradiation field F1, the illuminance distribution of irradiation field F1 generally becomes uneven. This means that even if the illuminance of light passing through wavelength emission region 22b (1b) is uniform within the same region, the illuminance distribution of the irradiation field formed by the light beams is uneven because the light beams incident on first lens element 16a are deflected in different directions. Therefore, the illuminance distribution of irradiation field F1 is made uniform by using lens array 16, which is composed of multiple lens elements 16a and 16b.

[0121] Here, the lens array 16 is sometimes called a fly's eye lens or a microlens array. The illumination distribution is made uniform by overlapping the irradiation field F1 formed by each lens element 16a, 16b. In this way, even if the irradiation field F1 formed by each lens element 16a, 16b is non-uniform, a uniform irradiation field F1 can be formed by overlapping them.

[0122] When the optical inspection system 1 according to this embodiment is used, an irradiation field F1 formed by light having the wavelength spectrum b that has passed through the wavelength emission region 22b of the first b can be superimposed on an irradiation field F1 formed by light having the same wavelength spectrum b that has passed through the wavelength emission region 24b of the second b. In other words, the optical inspection system 1 according to this embodiment has the advantage of being able to homogenize the illuminance distribution of light having the same wavelength spectrum b from multiple directions by using the lens array 16.

[0123] In this embodiment, if the illuminance distribution in the irradiation field F1 can be made uniform, it is possible to reduce fluctuations in the intensity of reflected light from each object point on a smooth surface due to illuminance unevenness, for example. Furthermore, when there are minute irregularities on the smooth surface, the light intensity and color (hue) from the minute irregularities can be simultaneously changed more significantly than in the case of a smooth surface. This increases the difference in the intensity of reflected light between when the object surface S is a smooth surface and when minute irregularities exist. In other words, compared to when the illuminance distribution in the irradiation field F1 is uneven, when the illuminance distribution is made uniform using the optical inspection system 1 according to this embodiment, the intensity of the reflected light can more clearly highlight the minute irregularities. In other words, using the optical inspection system 1 according to this embodiment makes it possible to uniformize the illuminance distribution, which has the effect of making it easier to detect the presence of minute irregularities.

[0124] In the present embodiment, the light emitting unit 12 is described as using a white LED as the light source, but the light source may have other configurations.

[0125] As a result, by using the optical inspection system 1 according to this embodiment, it is possible to form an irradiation field F1 with a more uniform illuminance distribution, and it is possible to more accurately obtain surface information of objects within the irradiation field F1 from light intensity or color (hue) information.

[0126] Therefore, according to this embodiment, an optical device 10, an optical inspection system 1, and an optical inspection method can be provided that can obtain information about an object O by irradiating light of multiple wavelengths a and b onto the same irradiation field F1 of the object O.

[0127] (Variation) 10 shows a cross-sectional view of the optical inspection system 1 according to a modification of this embodiment. In this modification, an example will be described in which the imaging aperture 34 of the imaging unit 30 is changed from the imaging aperture 34 shown in FIG.

[0128] The imaging aperture 34 of the imaging unit 30 of this modified example has a central through-hole 35a, surrounded by a light-shielding plate with a light-shielding area 35b that blocks visible light. Wavelength spectrum a has substantially zero light intensity in the visible light range and cannot be detected by the image sensor 36 of the imaging unit 30. The dominant wavelength of wavelength spectrum b is 650 nm, which is referred to as wavelength b. In other words, the light of wavelength spectrum b is red light.

[0129] The central through-hole 35a of the imaging aperture 34 is defined as a first wavelength-selective region, which allows visible light to pass through. In other words, it allows at least light of wavelength spectrum b to pass through. On the other hand, the surrounding light-blocking region 35b is defined as a second wavelength-selective region, which does not allow light of wavelength spectrum b, including light of wavelength b, to pass through. In other words, it blocks light of wavelength spectrum b.

[0130] Assume that the object surface S in the irradiation field F1 is a smooth plane. The object surface S in the irradiation field F1 is imaged by the image sensor 36. At this time, the light of wavelength spectrum b emitted from the 1b wavelength emission region 22b and the 2b wavelength emission region 24b is specularly reflected by the object surface S, and then blocked by the second wavelength selection region (light-blocking region) 35b of the imaging opening 34. Therefore, the image of the object surface S is not captured by the image sensor 36 (the light intensity becomes sufficiently dark).

[0131] On the other hand, if minute irregularities exist on the object surface S within the irradiation field F1, the light of wavelength spectrum b is scattered by the irregularities, and the BRDF spreads. As a result, the light of wavelength spectrum b reaches the first wavelength selection region (central through hole) 35a of the imaging aperture 34, and then passes through this region 35a to reach the image sensor 36. Therefore, using the optical inspection system 1 according to this modification has the effect of allowing only the minute irregularities to be captured brightly and clearly by the image sensor 36.

[0132] Therefore, according to this modified example, it is possible to provide an optical device 10, an optical inspection system 1, and an optical inspection method that can obtain information about an object O by irradiating light of multiple wavelengths a and b onto the same irradiation field F1 of the object O.

[0133] (Third embodiment) The optical inspection system 1 according to this embodiment will be described in detail below with reference to Fig. 11 to Fig. 13. This embodiment is a modified example of the first and second embodiments. Components that are the same as or have the same functions as those described in the first and / or second embodiments are denoted by the same reference numerals as much as possible, and detailed descriptions thereof will be omitted.

[0134] A cross-sectional view of the optical inspection system 1 according to this embodiment is shown in Fig. 11. This cross-section is a yz cross-section, unlike the zx cross-sections in Figs. 1 to 4, 8, and 10. The optical inspection system 1 according to this embodiment includes an optical inspection device 3, a control unit 5, and a transport unit 7.

[0135] The control unit 5 only needs to be able to control at least one of the light emitting unit 12 of the optical device 10, the image sensor 36 of the imaging unit 30, and the transport unit .

[0136] As described in the second embodiment, the optical inspection device 3 includes an illumination unit 10 and an imaging unit 30. The illumination unit 10 includes a light emitting unit 12 and an imaging optical element array 16. The light emitting unit 12 and the imaging optical element array 16 may be those described in the first and second embodiments as appropriate.

[0137] The specific configuration of the transport unit 7 is not shown in Fig. 11. The transport unit 7 transports the object O by, for example, an appropriate conveyor or the like. The direction in which the object O is transported by the transport unit 7 is the y-axis direction.

[0138] In FIG. 11, it is assumed that object O is being transported in the transport direction. The transport direction is the positive direction of the y-axis. However, this is not limited to this, and object O may be fixed, and the illumination unit 10 and the imaging unit 30 may be transported simultaneously. That is, instead of transporting object O to be inspected, transport unit 7 may transport optical inspection device 3, for example, in the y-axis direction. In this embodiment, it is sufficient for transport unit 7 to be able to move object O to be inspected and optical inspection device 3 relatively in the y-axis direction. In other words, it is sufficient for transport unit 7 to be able to transport object O and at least one of optical device 10 and imaging unit 30. FIG. 11 is a schematic diagram showing the instantaneous positional relationship of each component at a certain time.

[0139] In this embodiment, it is assumed that the object points of object O move together with object O due to the transport of object O by the transport unit 7. In other words, the positions of the object points are defined as relative positions with respect to object O. In this case, it is assumed that the image points corresponding to the object points move together with the transport on the image captured by the imaging unit 30.

[0140] The illumination unit 10 of the optical inspection device 3 includes a light emitting unit 12, an imaging optical element array 16, and an illumination aperture 18.

[0141] A first light ray B1 is emitted from the light source of the light emitting unit 12 toward the first wavelength emitting surface 14a, and simultaneously a second light ray B2 is emitted toward the second wavelength emitting surface 14b. The imaging optical element array 16 is a lenticular lens composed of a plurality of cylindrical lenses (including at least imaging optical elements 16a and 16b arranged in the x-axis direction). Each of the lenticular lenses 16a and 16b has translational symmetry in the y-axis direction.

[0142] The light source of the light emitting unit 12 is a series arrangement of multiple white LEDs in the direction perpendicular to the cross section (x-axis direction). The light from the light source is then collimated by a cylindrical lens. Note, however, that the light beams projected onto the cross section shown in FIG. 11 become collimated light.

[0143] Furthermore, color filters that selectively transmit light of wavelength spectrum a and light of wavelength spectrum b are arranged in the wavelength emission regions 22a, 24a and wavelength emission regions 22b, 24b of the first wavelength emission surface 14a and the second wavelength emission surface 14b described in the first embodiment, respectively. Collimated light from the light source of the light emitting unit 12 passes through the color filters 22a, 22b, 24a, and 24b. The light that reaches the first wavelength emission surface 14a after passing through the color filters 22a, 22b, 24a, and 24b is referred to as a first light ray B1, and the light that reaches the second wavelength emission surface 14b is referred to as a second light ray B2.

[0144] By using the light emitting section 12 and the wavelength emitting surface 14, light of wavelength spectrum a is emitted from the wavelength emitting regions 22a and 24a of the first wavelength emitting surface 14a and the second wavelength emitting surface 14b, and light of wavelength spectrum b is emitted from the wavelength emitting regions 22b and 24b of the first wavelength emitting surface 14a and the second wavelength emitting surface 14b.

[0145] As shown in Figures 12 and 13, the imaging optical elements 16a and 16b of the imaging optical element array 16 are lenticular lenses. The optical axis of each lens element 16a and 16b is assumed to be parallel to the z-axis, and the xy plane is assumed to be perpendicular thereto. The first lens element 16a and the second lens element 16b are assumed to be identical. The focal planes of the first lens element 16a and the second lens element 16b are assumed to be on the same plane. The focal planes are assumed to be parallel to the xy plane.

[0146] In this embodiment, the illumination aperture 18 is assumed to be a slit-like shape extending in the x-axis direction and narrow in the y-axis direction. The illumination aperture 18 has the same shape in at least two mutually parallel reference planes (cross sections) 19a and 19b, which are parallel to the y-z plane. That is, the reference cross sections 19a and 19b in FIG. 12 have the same aperture width (gap) 18a in the y-axis direction. Furthermore, the aperture width 18a along the y-axis direction in these reference planes 19a and 19b is assumed to be sufficiently smaller than the width of the field of view captured by the image sensor 36 of the imaging unit 30. As a result, the light beams projected onto the reference cross sections 19a and 19b are generated by the illumination aperture 18 in this optical system as a substantially fan-shaped light beam group. Fan beams refer to light beams that spread radially (in a fan shape) from a light source (or secondary light source) that can be regarded as a substantially point. The fan-shaped group of light rays formed by the illumination aperture 18 is called a fan-shaped group of light rays. Because the illumination aperture 18 has the same shape on the first reference plane 19a and the second reference plane 19b parallel to the yz plane, a first fan-shaped group of light rays Ba and a second fan-shaped group of light rays Bb are formed, each with equivalent spread, regardless of the position along the x-axis. That is, the light from the light output unit 12 is formed by the illumination aperture 18 into a fan-shaped group of light rays that spreads toward the object O on the reference plane 19a including the optical axis L1 of the first imaging optical element 16a and the reference plane 19b including the optical axis L2 of the second imaging optical element 16b. Note, however, that the fan-shaped groups of light rays Ba and Bb are light rays obtained by projecting the light from the light output unit 12 onto the respective reference cross sections 19a and 19b.

[0147] 11 and 13, the direction in which the first wavelength emitting surface 14a and the second wavelength emitting surface 14 are arranged side by side is perpendicular to the conveying direction of the conveying unit 7. As shown in FIG. 13, the first wavelength emitting surface 14a and the second wavelength emitting surface 14b each have wavelength emitting regions 22a, 22b, 22c, 24a, 24b, and 24c, for example, as color filters or phosphors, that have translational symmetry about the y-axis. That is, the first wavelength emitting surface 14a has three different wavelength emitting regions 22a, 22b, and 22c, which are referred to as the wavelength emitting region 22a, the wavelength emitting region 22b, and the wavelength emitting region 22c. The second wavelength emitting surface 14b similarly has three different wavelength emitting regions 24a, 24b, and 24c, which are referred to as the wavelength emitting region 24a, the wavelength emitting region 24b, and the wavelength emitting region 24c. Here, the wavelength emission region 22a of the first wavelength emission surface 14a and the wavelength emission region 24a of the second wavelength emission surface 14b pass light of wavelength spectrum a, with wavelength a as the dominant wavelength. The wavelength emission region 22b of the first wavelength emission surface 14a and the wavelength emission region 24b of the second wavelength emission surface 14b pass light of wavelength spectrum b, with wavelength b as the dominant wavelength. Furthermore, the wavelength emission region 22c of the first wavelength emission surface 14a and the wavelength emission region 24c of the second wavelength emission surface 14b pass light of wavelength spectrum c, with wavelength c as the dominant wavelength. Here, wavelength a is 450 nm blue light, wavelength b is 650 nm red light, and wavelength c is 550 nm green light. This allows the control unit 5 to acquire (observe) the spread of the BRDF of light from object O in the x-axis direction as a change in color (hue) based on the flow described in FIG. 9. Furthermore, since the irradiation fields F1 formed by the first lens element 16a and the second lens element 16b can be overlapped, there is an effect of reducing unevenness in illuminance.

[0148] The directional distribution of reflected light from an object point on an object surface (object surface) S can be expressed by a distribution function called BRDF. BRDF generally changes depending on the surface condition (surface texture and surface shape). For example, if the surface is rough, the reflected light spreads in various directions, resulting in a wide BRDF distribution. In other words, reflected light is present over a wide range of angles. On the other hand, if the surface is specular, the reflected light will consist almost entirely of specular reflection components, resulting in a narrow BRDF distribution. In this way, BRDF reflects the surface condition of the object surface (object surface S). In particular, BRDF generally changes significantly due to minute irregularities that are 10 times the wavelength of light or smaller.

[0149] BRDF depends on the angle of incidence of light on the object surface S and the angle of reflection (scattering angle) of light from the object surface S. Not only does the dependence of the intensity distribution on the angle of reflection when the angle of incidence of light on the object surface S is constant, but the dependence of the intensity distribution on the angle of incidence when the angle of reflection of light from the object surface S is constant is also important information that reflects the state (information) of the object surface.

[0150] When illumination light from the illumination unit 10 is reflected by or transmitted through an object point within the object O, the imaging unit 30 forms an image of the light from the object on the image sensor 36. This allows an image of the object to be acquired. In other words, the object is imaged using light.

[0151] In this embodiment, the object is opaque and reflects light from the object surface S. However, the object is not limited to this, and may be transparent or transmissive. In this case, the imaging means is disposed on the side where light from the illumination passes through the object.

[0152] Based on the above configuration, the operating principle of the optical inspection system 1 according to this embodiment will be described.

[0153] On the surface of object O (object surface S) shown in Figure 11, the first object point P1 is assumed to be a smooth surface. In this case, the reflected light from the first object point P1 is almost specular, and its BRDF has only a narrow distribution of specular components (specular reflection components). On the other hand, the second object point P2 has a minute defect, and its BRDF has a wide distribution.

[0154] If the xy plane in the coordinate system in Figure 11 is used as the reference plane (the horizontal plane relative to the ground), then the object surface S will have various inclinations relative to that reference plane. In this case, in the yz cross section in Figure 11, the inclination of the object surface S relative to the y axis is Θ, with the counterclockwise direction being the positive direction. This Θ is called the inclination angle of the object surface S. Unless otherwise specified below, the counterclockwise direction is the positive direction for angles in the yz cross section.

[0155] Furthermore, the angle formed by the direction of the first illumination light R1 from the illumination unit 10 and the negative direction of the z axis is defined as α. In this embodiment, α is called the angle of incidence. If the object surface S is a specular surface at the first object point P1, the light incident on the object surface S is specularly reflected.

[0156] The imaging unit 30 captures an image by focusing a light beam having an intensity distribution represented by a BRDF at each object point P1, P2 onto an image point on the image sensor 36. Here, the ray of light along a straight line passing through both the first object point P1 and the image point is defined as the principal ray Pr1. The angle that the principal ray Pr1 makes with the negative direction of the z-axis is defined as θ. In this embodiment, θ is called the reflection angle. It is assumed that the optical axis of the imaging unit 30 is parallel to the z-axis.

[0157] In this case, the tilt angle Θ of the object that can be imaged with the first illumination light R1 can be expressed as the following equation (1). Θ = (θ + α) / 2 (1)

[0158] This relationship is not limited to the first object point P1, but is similar for the second object point P2 and other object points. For the second object point P2, the second illumination light R2 and chief ray Pr2 can be shown in Figure 11. In this case, the angle of incidence α and angle of reflection θ can also be set.

[0159] In the group of light rays projected onto the y-z cross section in Figure 11, the illumination light becomes fan rays with various incident directions. That is, the illumination unit 10 can irradiate the object O with illumination light from various angles within the range of the angle α that the illumination light can take. Therefore, the control unit 5 can gradually move, for example, the object O in the conveying direction (+y-axis direction) using the conveying unit 7 while continuously acquiring images (at an appropriate frame rate) using the illumination unit 10 and the imaging unit 30, thereby making illumination light from various angles incident on each object point and capturing images. That is, the optical inspection device 3 can irradiate each object point on the object surface S with incident light from various directions and capture an image of the object surface S each time. As a result, even if the object point is tilted and the reflected light at one moment does not head toward the imaging unit 30 but deviates, by conveying the object O using the conveying unit 7, it is possible to irradiate light with an incident direction that reflects toward the imaging unit 30 at another moment. In other words, even for an object O having an object surface S with various inclinations, it is possible to capture an image of the object surface S of the object O by repeatedly irradiating the object O with illumination light in an appropriate direction while transporting the object O in a predetermined direction.

[0160] For example, let us consider a first object point P1. The angle of incidence α of the first object point P1 changes over time while it is being transported by the transport section 7. In other words, the angle of incidence changes in various ways. At the same time, the angle of reflection θ also changes in various ways. As a result, as is clear from equation (1), the tilt angle Θ to be imaged also changes in various ways. In other words, the optical inspection device 3 of the optical inspection system 1 can image objects O with various tilts.

[0161] Because the first object point P1 is on a specular surface, the angular distribution of its BRDF is narrow, and the light reflected from the first object point P1 in response to the illumination light from the fan rays is almost entirely specular. In other words, in equation (1), the reflection angle θ corresponding to the incident angle α is uniquely determined. Therefore, the optical inspection system 1 according to this embodiment can image the first object point P1 only when the incident angle α and the reflection angle θ, which is uniquely determined by the incident angle α, satisfy the relationship in equation (1) for the tilt angle Θ at the first object point P1. In other words, the first object point P1 is imaged while the incident angle α satisfies equation (1).

[0162] On the other hand, because the second object point P2 is located on a micro defect, its BRDF is broad and the reflected light contains a large amount of scattered light. Therefore, there are various reflection angles θ corresponding to the angle of incidence α. Therefore, even if the angle of incidence α takes various values ​​relative to the inclination angle Θ at the second object point P2, the relationship of Equation (1) is satisfied. Therefore, for example, if the conveying speed of the conveying unit 7 is constant, in the optical inspection system 1, the second object point P2 will be imaged brightly on the image sensor 36 of the imaging unit 30 for a longer period of time than the first object point P1. This allows the control unit 5 to detect a micro defect (second object point P2) on the object O based on the intensity and duration of light on the image sensor 36.

[0163] The optical inspection system 1 according to this embodiment performs steps S3 and S4 of the flow shown in FIG. 9 using multiple images of the object O being transported by the transport unit 7, acquired by the imaging unit 30. This allows for easy and accurate identification of minute defects in the transported object O. For example, when the control unit 5 analyzes the received light signals obtained from each image (see step S3 in FIG. 9), if multiple images captured by the imaging unit 30 at regular time intervals during transport are superimposed so that object points P1 and P2 coincide with each other, the angular distribution of the BRDF of the minute defect is broad, resulting in the defect being captured (detected) in more images than in a smooth surface. This increases the pixel value in the images obtained by superimposing object points P1 and P2 of each image, thereby making the minute defect brighter and clearer. This also allows for easy and highly accurate identification of minute defects.

[0164] If the object O is appropriately long in the conveying direction, the object O can be divided into appropriate lengths by the conveying unit 7 and the processes of steps S3 and S4 shown in Fig. 9 can be performed. In this case, by acquiring images of some areas overlapping in the conveying direction, it is possible to output the surface texture of the object surface S over the entire length of the object O.

[0165] The BRDF at object points P1 and P2 of object O changes depending on the angle of incidence. By understanding the dependency of this BRDF on the angle of incidence, the control unit 5 can output details of the surface texture (object surface condition) of object O at object points P1 and P2. Therefore, the optical inspection system 1 according to this embodiment can obtain BRDFs for various angles of incidence, which has the effect of enabling detailed information about object points P1 and P2 to be obtained.

[0166] In Figure 13, consider the projection of a ray of light incident on an object point of object O onto the xz plane. The angle of incidence of the ray of light relative to the z-axis can be identified from the wavelength spectrum. That is, in the image captured on the image sensor 36 of the imaging unit 30, the dominant wavelengths (i.e., wavelengths a, b, and c) of each wavelength spectrum can be distinguished based on the pixel values ​​of each color channel of the pixels at the image points where the ray of light is reflected by object points P1 and P2. This allows the control unit 5 to identify the angle of incidence of the ray of light projected onto the xz plane. Therefore, the control unit 5 can simultaneously acquire BRDF information for various angles of incidence of the ray of light incident on the object point projected onto the xz plane, distinguishing them by color (hue). In this way, the optical inspection system 1 can acquire more detailed BRDF information of object O based on the color (hue) information acquired by the image sensor 36.

[0167] When an object point is on a smooth surface, the illumination light reflected from that object point is specularly reflected light. In this case, the direction of the specularly reflected light can be identified by the pixel position when it is imaged on the image sensor 36. The light reflected from an object point generally has a high light intensity of the specular reflection component, even if it is scattered light with a widened BRDF. Therefore, by selecting the image with the highest light intensity (e.g., pixel value) at the object point from multiple images captured while the object O is being transported, it can be estimated that the image was formed by the specular reflection component. This allows the control unit 5 to identify the specular reflection direction of the object point on the object from the pixel position of the image.

[0168] As mentioned above, when a ray of light incident on an object point of object O is projected onto the xz plane, the angle of incidence with respect to the z axis can be identified by the wavelength spectrum.

[0169] Meanwhile, in FIG. 13, consider the projection onto the yz plane of a ray of light incident on an object point of object O. In this case, the angle of incidence of the ray of light with respect to the z-axis can be limited (identified within a certain range) by the pixel position and intensity when the ray of light is specularly reflected from the object point and imaged on the image sensor 36. This is because, in the ray of light projected onto the yz plane, the incident ray can be considered as a fan-shaped ray emanating from a single point, and therefore its end point (starting point) is fixed. The other end point (object point) exists on a line along the direction of the specularly reflected light determined by the pixel position. Furthermore, the z position of the object point exists within the range in which an image can be formed on the image sensor 36 by the imaging unit 30. As a result, the angle of incidence of the ray of light incident on the object point, projected onto the yz plane, with respect to the z-axis can also be identified within a certain range.

[0170] From the above, the direction of the specular reflection component of light reflected from an object point (specular reflection direction) can be obtained from the pixel position of the image, and the direction of the light ray incident on the object point can be limited from the color (hue) and pixel position of the image. It is known that if the specular reflection direction can be identified and the incident direction can be limited, the three-dimensional shape of the object can be limited by reconstruction (see Non-Patent Document 4). Therefore, by using the optical inspection system 1 according to this embodiment, it is possible to have the effect of limiting the three-dimensional shape of the object (identifying it within a certain range).

[0171] Therefore, according to this embodiment, an optical device 10, an optical inspection system 1, and an optical inspection method can be provided that can obtain information about an object O by irradiating light of multiple wavelengths a and b onto the same irradiation field F1 of the object O.

[0172] According to at least one of the embodiments described above, an optical device 10, an optical inspection system 1, and an optical inspection method can be provided that can obtain information about an object O by irradiating light of multiple wavelengths a and b onto the same irradiation field F1 of the object O.

[0173] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0174] 1...optical inspection system, 3...optical inspection device, 5...control unit, 7...transport unit, 10...optical device (illumination unit), 12...light emitting unit, 12a...projector, 12b...light diffusion unit, 12a1, 12a2, 12b1, 12b2...light source, 12aa, 12ab...light source, 14...wavelength emitting surface, 14a...first wavelength emitting surface, 14b...second wavelength emitting surface, 16...imaging optical element array, 16a, 16b...imaging optical element, 18...illumination aperture, 18a...aperture width, 22a...1a wavelength emitting region, 22b...1b wavelength emitting region , 24a...2a wavelength emission region, 24b...2b wavelength emission region, 30...imaging unit, 32...imaging optical element, 34...imaging aperture, 36...image sensor, 41...first wavelength selection region, 42...second wavelength selection region, F1, F2...illumination field, B1a...1a light ray, B1b...1b light ray, B2a...2a light ray, B2b...2b light ray, B3a...3a light ray, B4b...4b light ray, B5b...5b light ray, L1, L2...optical axis, O...object, S...object surface, P1...first object point, P2...second object point.

Claims

1. a light emitting unit that emits light; an imaging optical element array having at least a first imaging optical element and a second imaging optical element; Equipped with When light is emitted from the light emitting portion, a first wavelength emission region that emits light of a first wavelength spectrum toward the imaging optical element array using the light; a second wavelength emission region that emits light of a second wavelength spectrum different from the light of the first wavelength spectrum toward the imaging optical element array using the light; a first wavelength exit surface having a second wavelength emitting surface disposed at a position different from the first wavelength emitting surface and having the first wavelength emitting region and the second wavelength emitting region similar to the first wavelength emitting surface; Assume that it is equipped with the first wavelength exit surface is located at or near a focal plane of the first imaging optical element, and the second wavelength exit surface is located at or near a focal plane of the second imaging optical element; optical equipment.

2. the first imaging optical element of the imaging optical element array forms a first illumination field by the light of the first wavelength spectrum emitted from the first wavelength emission region of the first wavelength emission surface and the light of the second wavelength spectrum emitted from the second wavelength emission region of the first wavelength emission surface; the second imaging optical element of the imaging optical element array is arranged so that a region where light overlaps with the first irradiation field is formed by either the light of the first wavelength spectrum emitted from the first wavelength emission region of the second wavelength emission surface or the light of the second wavelength spectrum emitted from the second wavelength emission region of the second wavelength emission surface; The optical device according to claim 1 .

3. the light emitting unit is a projection unit that projects an image using light from the light emitting unit, the projection unit simultaneously projects similar images onto the first wavelength emission surface and the second wavelength emission surface, respectively; 3. The optical device according to claim 1.

4. the light output unit includes a first light source that emits light of the first wavelength spectrum and a second light source that emits light of the second wavelength spectrum; The first light source is disposed in the first wavelength emission region of each of the first wavelength emission surface and the second wavelength emission surface, The second light source is disposed in the second wavelength emission region of each of the first wavelength emission surface and the second wavelength emission surface.

3. The optical device according to claim 1.

5. a first filter disposed in each of the first wavelength emission regions and configured to pass light of the first wavelength spectrum; a second filter disposed in each of the second wavelength emission regions and passing light of the second wavelength spectrum; Equipped with 3. The optical device according to claim 1.

6. a first phosphor disposed in each of the first wavelength emission regions and configured to emit light of the first wavelength spectrum in response to excitation light from the light emitting portion; a second phosphor disposed in each of the second wavelength emission regions and configured to emit light of the second wavelength spectrum in response to excitation light from the light emitting portion; Equipped with 3. The optical device according to claim 1.

7. The optical device according to claim 1 or 2; an imaging unit having an imaging optical element and an image sensor; a control unit that controls the image sensor; Assume that it is equipped with the control unit acquires information about the object based on a light reception signal captured by the image sensor of the imaging unit. Optical inspection systems.

8. the image sensor of the imaging unit can distinguish at least two different wavelengths included in the first wavelength spectrum and the second wavelength spectrum, respectively; the control unit acquires information about the object based on the hue of the light reception signal captured by the image sensor of the imaging unit. The optical inspection system of claim 7 .

9. an imaging aperture provided on a focal plane of the imaging optical element between the imaging optical element and the image sensor; The optical inspection system of claim 7 .

10. a transport unit capable of transporting the object and at least one of the optical device and the imaging unit; The optical inspection system of claim 7 , comprising:

11. the first wavelength emission surface and the second wavelength emission surface are arranged side by side in a direction perpendicular to a conveying direction by the conveying unit; The optical inspection system of claim 10.

12. the light from the light emitting unit is formed into a fan-shaped group of rays that spreads out toward the object by an illumination aperture on a reference plane including an optical axis of the first imaging optical element and a reference plane including an optical axis of the second imaging optical element; the control unit illuminates the object with the fan-shaped light beam group and acquires information about the object based on a light reception signal captured by the image sensor of the imaging unit. The optical inspection system of claim 7 .

13. Illuminating the object using the optical device as an illumination unit; The control unit acquires information about the BRDF of the object based on the hue of the light from the object. The optical inspection system of claim 7 .

14. the control unit controls at least one of the light emitting unit, the imaging unit, and the transport unit of the optical device. The optical inspection system of claim 10.

15. emitting light of a first wavelength spectrum from a wavelength emission region 1a toward a first imaging optical element of an imaging optical element array; emitting light of a second wavelength spectrum different from the first wavelength spectrum from a wavelength emission region 1b toward the first imaging optical element of the imaging optical element array; emitting the light of the first wavelength spectrum from a second a wavelength emission region different from the first a wavelength emission region and the first b wavelength emission region toward a second imaging optical element different from the first imaging optical element of the imaging optical element array; emitting the light of the second wavelength spectrum from the first wavelength emission region, the first wavelength emission region, and a second wavelength emission region different from the second wavelength emission region toward the second imaging optical element of the imaging optical element array; illuminating an object plane of an object with the light of the first and second wavelength spectra that has passed through the first imaging optical element and the light of the first and second wavelength spectra that has passed through the second imaging optical element; Including, An optical inspection method, wherein illuminating the object surface of the object includes irradiating the same first illumination field with light of the first and second wavelength spectra that have passed through the first imaging optical element.

16. illuminating the object surface of the object includes forming a region where light overlaps with the first illumination field by either the light of the first wavelength spectrum emitted from the second wavelength emission region a or the light of the second wavelength spectrum emitted from the second wavelength emission region b. The optical inspection method according to claim 15.

17. obtaining a hue of light from the object surface of the object by illuminating the object surface of the object; obtaining information about the BRDF of the object based on the hue of the light; The optical inspection method according to claim 15 or 16, further comprising:

Images