Optical apparatus, optical test apparatus, optical test system, and optical test method

Abstract

To provide an optical device capable of illuminating an object by changing the direction of at least a part of a light beam emitted from a light emission part to a light beam in a direction different from the direction of the light beam.SOLUTION: According to an embodiment, an optical device includes a light emission part, a light direction selection part, and an imaging optical element. The light emission part emits a first light beam of a first wavelength spectrum including a first wavelength. The light direction selection section includes a first light direction selection region and a second light direction selection region on a focal plane of the imaging optical element or in the vicinity thereof. A first light beam incident on the first light direction selection region or the second light direction selection region is emitted as a light beam having different optical characteristics depending on the region, and at least one of the regions includes a light direction modifier that modifies a direction of an incident light beam into a different direction and emits the light beam.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to an optical device, an optical inspection device using the optical device, an optical inspection system using the optical inspection device, and an optical inspection method. [Background technology]

[0002] Non-contact inspection of objects is becoming increasingly important in various industries. Conventional methods involve using a diffraction grating or wavelength filter to separate light beams, creating a one-to-one correspondence between the color (wavelength spectrum) and the direction of the beam, and identifying the color to identify the direction of the beam, thereby obtaining information about the surface or interior of the object. [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] H. Ohno and T. Kamikawa, “One-shot BRDF imaging system to obtain surface properties,” Optical Review 28, p.655-661 2021 [Non-patent document 3] H. Ohno, “One-shot colored reflectance direction field imaging system for optical inspection,” Applied Optics Vol. 62, Issue 18, 2023 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem that the present invention aims to solve is to provide an optical device that can change the direction of at least a portion of the light beam emitted from a light emitting section to a light beam in a different direction to illuminate an object, an optical inspection device that includes the optical device, an optical inspection system that includes the optical inspection device, and an optical inspection method. [Means for solving the problem]

[0006] According to an embodiment, an optical device includes a light output unit, a light direction selecting unit, and an imaging optical element. The light output unit outputs a first light ray of a first wavelength spectrum including a first wavelength. The light direction selecting unit includes a first light direction selecting region and a second light direction selecting region at or near a focal plane of the imaging optical element. The first light ray incident on the first light direction selecting region or the second light direction selecting region is output as a light ray with different optical properties depending on the region, and at least one of the regions includes a light redirecting body that changes the direction of the incident light ray and outputs it. [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] 10 is a schematic cross-sectional view of a portion of the optical device, with the viewer's line of sight aligned with the direction in which the second light ray is specularly reflected by the smooth surface. [Figure 3] 3 is a schematic cross-sectional view showing a part of an optical inspection device of an optical inspection system in which the observer shown in FIG. 2 is used as an imaging unit. [Figure 4] FIG. 4 is a diagram showing a processing flow of the optical inspection system shown in FIG. 3. [Figure 5] 10 is a schematic cross-sectional view showing a part of the optical device when the line of sight of an observer V is in a direction different from the direction in which the second light ray is specularly reflected when the object surface is a smooth surface. [Figure 6] 6 is a schematic cross-sectional view showing a part of an optical inspection device of an optical inspection system in which the observer shown in FIG. 5 is used as an imaging unit. [Figure 7] FIG. 7 is a diagram showing a processing flow of the optical inspection system shown in FIG. 6. [Figure 8] FIG. 10 is a schematic cross-sectional view showing an optical device according to a first modification of the first embodiment. [Figure 9] FIG. 10 is a schematic cross-sectional view showing an optical device according to a second modification of the first embodiment. [Figure 10] FIG. 10 is a schematic cross-sectional view showing an optical device according to a third modification of the first embodiment. [Figure 11] FIG. 10 is a schematic cross-sectional view showing an optical device according to a second embodiment. [Figure 12] FIG. 10 is a schematic perspective view showing a phosphor of an optical device according to a first modified example of the second embodiment. [Figure 13] FIG. 10 is a schematic perspective view showing a phosphor of an optical device according to a further modified example of the first modified example of the second embodiment. [Figure 14] FIG. 10 is a schematic perspective view showing a phosphor of an optical device according to Modification 2 of the second embodiment. [Figure 15] FIG. 10 is a schematic cross-sectional view showing a phosphor of an optical device according to a third modification of the second embodiment. [Figure 16] FIG. 11 is a schematic cross-sectional view showing a light emitting portion and a phosphor of an optical device according to a fourth modification of the second embodiment. [Figure 17] FIG. 10 is a schematic cross-sectional view showing a light emitting section and a light direction selecting section of an optical device according to a third embodiment. [Figure 18] FIG. 11 is a schematic cross-sectional view showing a light emitting section, a light direction selecting section, and an imaging optical element of an optical device according to a modified example of the third embodiment. [Figure 19] FIG. 10 is a schematic cross-sectional view showing an optical inspection device according to a fourth embodiment. [Figure 20] FIG. 11 is a schematic cross-sectional view showing a modified example of the imaging unit of the optical inspection device according to the fourth embodiment. [Figure 21] FIG. 11 is a schematic perspective view of an optical inspection device according to a fifth embodiment, with a light exit unit omitted. 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, light is a type of electromagnetic wave, and includes gamma rays, X-rays, ultraviolet rays, visible light, infrared rays, radio waves, etc. In this embodiment, light is considered to be visible light, with a wavelength in the range of 400 nm to 750 nm, for example.

[0010] (First embodiment) An optical device 10 according to this embodiment will be described below with reference to FIGS.

[0011] 1 is a schematic cross-sectional view of an optical device 10 according to this embodiment. The optical device 10 according to this embodiment includes a light emitting unit 12, an imaging optical element 14, and a light direction selecting unit 16.

[0012] The light emitting unit 12 includes a light source 120, which emits a first light ray B1 having a first wavelength spectrum including at least a first wavelength. For example, the first wavelength is 405 nm, and the first wavelength spectrum has a peak at the first wavelength. Light having such a first wavelength spectrum is referred to as blue light. However, this is not limiting, and the wavelength spectrum of the light source may be any. For example, it may be white light.

[0013] The light source is an LED (Light-Emitting Diode) that emits blue light. However, this is not a limitation and any light-emitting device can be used, including an LD (Laser Diode). Alternatively, sunlight, a plasma light source, or a thermal radiation light source (such as an incandescent bulb, halogen lamp, or xenon lamp) can be used.

[0014] In this embodiment, the light source 120 has a light-emitting surface that is small enough to be considered a point light source. However, this is not limiting, and a light source with a large light-emitting surface may also be used. When considered as a point light source, light is emitted radially from a single point. In particular, thermal radiation light sources can often be considered as point light sources because they can be made very small.

[0015] The imaging optical element 14 can form an image of light. The imaging optical element 14 may be, for example, a single lens, a compound lens consisting of multiple lenses, a concave mirror, a Fresnel lens, a diffraction grating, a gradient index lens (GRIN lens), or the like. In other words, the imaging optical element 14 may be anything that can form an image of light. The plane on which a set of points at infinity are imaged by the imaging optical element 14 is defined as the focal plane f. The focal plane f and its vicinity are called the focal plane region Rf. The optical axis L of the imaging optical element 14 is a straight line perpendicular to the focal plane f. Light emitted from a sufficiently distant point on the optical axis L is imaged at the point where the optical axis L and the focal plane f intersect. This point is called the focus.

[0016] The imaging optical element 14 of this embodiment is a compound lens made up of multiple lenses. Here, this is referred to as an imaging lens. However, in FIG. 1, for simplicity, the imaging lens, which is a compound lens, is schematically depicted as a single lens. However, the imaging optical element 14 is not limited to this, and any element that can image light may be used. In the cross-sectional view of FIG. 1, the optical axis of the imaging optical element is included in this cross section.

[0017] The light direction selecting unit 16 has a first light direction selecting region R1 and a second light direction selecting region R2 on or near the focal plane f of the imaging optical element 14. That is, the light direction selecting unit 16 has the first light direction selecting region R1 and the second light direction selecting region R2 in the focal plane region Rf.

[0018] The first light direction selection region R1 either changes (modifies) the optical characteristics of the first light ray B1 of a first wavelength included in the first wavelength spectrum and passes the first light ray B1, or passes the first light ray B1 without changing (modifying) the optical characteristics of the first light ray B1. In this embodiment, the first light direction selection region R1 passes the first light ray B1 without changing the optical characteristics of the first light ray B1. In this case, a collection of the first light ray B1 pointing in various different directions from a point in the first light direction selection region R1 is defined as a first light direction group G1.

[0019] The second light direction selection region R2 changes the optical properties of the first light ray B1, including the direction, wavelength, wavelength spectrum, polarization, brightness, illuminance, and luminous flux (amount of light).

[0020] The light direction selecting unit 16 includes a light redirector 16a in the second light direction selecting region R2. The light redirector 16a changes the direction of incident light rays, redirecting them into rays in a different direction. The light redirector 16a may be a light diffuser that diffuses light and directs it, such as frosted glass, a holographic diffuser, a diffraction grating, or a phosphor. Alternatively, the light redirector 16a may be a transparent resin with dispersed light-scattering particles, silk screen printing, paper, or any other material that changes the direction of light. Alternatively, the light redirector 16a may be a microlens array, a fly's eye lens, or any other material that changes the direction of light.

[0021] When light is diffused, at least two light rays are generated, including one traveling in a direction different from the incident direction. In other words, at least one new light ray different from the incident light ray is branched and generated. Furthermore, even when light is diffused by the diffuser 16a, the light quantity (total luminous flux) of the light before and after diffusion can be maintained. In other words, the diffuser 16a can diffuse light without changing the light quantity.

[0022] In this embodiment, the light diffuser 16a is a holographic diffuser. When light of a first wavelength spectrum passes through the light diffuser 16a, the wavelength spectrum does not change.

[0023] Object O may be either light-transmitting or light-reflecting, or it may be translucent. A point on the surface of object O or inside object O is called an object point. In the following, unless otherwise specified, object O is assumed to reflect light, and object points are assumed to be on the surface of the object. The surface of object O may also be called object surface or object plane S.

[0024] Next, the operation of the optical device 10 of this embodiment will be described.

[0025] 1, light of a first wavelength spectrum is radially emitted from the point light source 120 of the light emitting unit 12. A first light ray B1 is light of a first wavelength included in the first wavelength spectrum. The first light ray B1 travels toward the light direction selecting unit 16 and reaches the first light direction selecting region R1, the second light direction selecting region R2, or both.

[0026] The first light ray B1 that reaches the first light direction selection region R1 passes through it as is. Here, at a point in the first light direction selection region R1, a collection of the first light rays B1 that pass through that point is defined as a first light direction group G1. Meanwhile, a second light ray B2 that has a different direction from the first light ray B1 is generated by the diffuser 16a provided in the second light direction selection region R2. Here, at a point in the second light direction selection region R2, a collection of the second light rays B2 that pass through that point is defined as a second light direction group G2.

[0027] The first light direction selection region R1 and the second light direction selection region R2 are arranged on or near the focal plane f of the imaging optical element 14, and are positioned differently from each other. Therefore, as shown in Fig. 2, a first light ray B1, which is one light ray in the first light direction group G1, and a second light ray B2, which is one light ray in the second light direction group G2, have different inclination angles with respect to the optical axis L when they pass through the imaging optical element 14. In other words, based on geometric optics, the inclination angle with respect to the optical axis L is determined depending on the position where the light ray B1 passes through the focal plane f.

[0028] The illumination field F is defined as a region of the object surface S illuminated by the first light ray B1, the second light ray B2, or both the light rays B1 and B2. In this embodiment, since the diffuser 16a is present in the second light direction selection region R2, there may be at least two points illuminated by both the first light ray B1 and the second light ray B2 within the illumination field F. These points are defined as the first object point P1 and the second object point P2.

[0029] Now, consider the case where the diffuser 16a is not provided in the second light direction selection region R2. In this case, the light rays emitted from the point light source 120 are all condensed to a single point by the imaging optical element 14. That is, the light rays emitted from the point light source 120 are imaged at a single point, which is the image of the point light source. Here, since the point light source 120 can be regarded as a point, its image can also be regarded as a point. Therefore, regardless of the distance (working distance) between the imaging optical element 14 and the object surface S, the number of points simultaneously illuminated by the first light ray B1 and the second light ray B2 is at most one, and this is the image point. In other words, if the diffuser 16a is not provided in the second light direction selection region R2, it is not possible to simultaneously illuminate the first object point P1 and the second object point P2 with both the first light ray B1 and the second light ray B2.

[0030] On the other hand, in this embodiment, the diffuser 16a is provided in the second light direction selection region R2, so that the first light ray B1 and the second light ray B2 can simultaneously illuminate two different object points P1 and P2, even if the light source is a point light source 120. As a result, in this embodiment, compared to when the diffuser 16a is not provided, a wide irradiation field F including at least two object points P1 and P2 can be simultaneously illuminated with the first light ray B1 and the second light ray B2.

[0031] As shown in Figure 2, consider the case where the irradiation field F is observed from a direction oblique to the optical axis L. Also, the object surface S is assumed to be flat. In the irradiation field F, the first object point P1 on the object surface S is assumed to be on a smooth surface. On the other hand, the second object point P2 has a minute defect (minute irregularity) that widely scatters light. The observer's line of sight is assumed to be along the direction in which the second light ray B2 is specularly reflected by the smooth surface.

[0032] The second light ray B2 is generated by diffusing the first light ray B1 by the diffuser 16a in the second light direction selection region R2. In other words, the first light ray B1 is branched by the diffuser 16a. Therefore, the brightness of the second light ray B2 is lower than that of the first light ray B1.

[0033] First, consider the light reflected from the first object point P1. At the first object point P1, the first light ray B1 is specularly reflected along the optical axis L. Therefore, the reflected light does not return to the observer V and is not observed. Meanwhile, the second light ray B2 is also specularly reflected at the first object point P1 and is reflected in a direction oblique to the optical axis L. Because the line of sight of the observer V is set along this oblique direction, this reflected light B21 is observed. In other words, at the first object point P1 on the smooth surface, the observer V observes the specularly reflected light B21 from the second light ray B2.

[0034] Next, consider the light reflected from the second object point P2. Because a micro-defect exists at the second object point P2, both the first ray B1 and the second ray B2 are scattered by the micro-defect and diffused (reflected) in various directions. In other words, the light rays B1 and B2 incident on the micro-defect branch off in various directions. These reflection characteristics can be described by a bidirectional reflectance distribution function (BRDF), which represents the light intensity for each reflection direction. The angular distribution of light described by the BRDF is a narrow distribution dominated by specular reflection components for smooth surfaces, but a broad distribution for micro-defects. Generally, the BRDF of a micro-defect has a broad distribution centered on the specular reflection direction. Furthermore, the brightness of the light rays B1a and B2a in each direction is lower than that at the time of incidence due to branching caused by scattering by the micro-defect. In other words, the brightness of the second scattered light B2a, which is the scattered light from the second ray B2, is lower. Therefore, if observer V observes only the second scattered light B2a, the second object point P2 appears dark. Meanwhile, observer V simultaneously observes not only second scattered light B2a resulting from scattering of second light ray B2 at second object point P2, but also first scattered light B1a resulting from scattering of first light ray B1 at second object point P2. That is, observer V observes a combined component B12 of first scattered light B1a and second scattered light B2a. Because the luminance of first light ray B1 is greater than that of second light ray B2, the luminance of first scattered light B1a is accordingly greater than that of second scattered light B2a. Therefore, scattered light (first scattered light B1a) with a greater intensity than the second scattered light B2a reaches observer V. That is, observer V can clearly observe a minute defect at second object point P2.

[0035] On the other hand, when the luminance of the first light ray B1 is equal to or lower than the luminance of the second light ray B2, the intensity of the scattered light from the second object point is reduced, and the second object point P2 appears dark to the observer V. This makes it difficult to clearly identify the second object point P2. In other words, the optical device 10 according to this embodiment has the effect of brightening and sharpening the second object point P2.

[0036] As a result, when the object surface S is a smooth surface, the object points P1 and P2 can be observed using the second light ray B2. Furthermore, when the object surface S has a minute defect, the observer V simultaneously observes not only the second scattered light B2a caused by the second light ray B2 but also the first scattered light B1a caused by the first light ray B1. The first light ray B1 has a greater luminance than the second light ray B2. Therefore, the scattered light B1a caused by the first light ray B1 can brighten and clarify the minute defect. As a result, when the optical device 10 is used, both the smooth surface and the minute defect become bright and can be clearly observed.

[0037] As a result, by using the optical device 10 of this embodiment, it is possible to more reliably detect the surface condition of the object O using light intensity information in a wide irradiation field F that includes at least two different object points P1 and P2.

[0038] Fig. 3 shows a diagram in which the observer V shown in Fig. 2 is replaced with an imaging unit 18. An optical inspection device 1 is configured including an optical device 10 and an imaging unit 18 that captures an image illuminated by the optical device 10. A control unit 20 is connected to the image sensor 18a of the imaging unit 18, and an optical inspection system 100 is configured that includes the control unit 20 and the optical inspection device 1. Fig. 4 shows a process flow of optical inspection using the control unit 20.

[0039] 3, the optical device 10 can be observed using an imaging unit 18 including an image sensor 18a, instead of by an observer V. That is, the optical axis direction of the imaging unit 18 is set to be the direction in which the second light ray B2 is specularly reflected by the smooth surface. A control unit 20 is connected to the image sensor 18a of the imaging unit 18 via a wired or wireless connection.

[0040] The control unit 20 is, for example, a computer that controls the light emission unit 12 and the image sensor 18a of the imaging unit 18. The control unit 20 includes a processor, a ROM (storage unit), a RAM, an auxiliary storage device (storage unit), a communication interface (communication unit), and the like.

[0041] 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 20, and comprehensively controls the entire control unit 20. The processor executes control to realize various functions of the control unit 20 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 may include, 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 20 may be provided with one or more processors.

[0042] 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. The ROM stores an optical inspection program based on the flow shown in Figures 4 and 7, for example. The ROM also stores data and various setting values ​​used by the processor when it performs various processes.

[0043] 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.

[0044] 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 Figures 4 and 7 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.

[0045] The programs stored in the ROM or the auxiliary storage device include a program for controlling the control unit 20. For example, an optical inspection program based on the flows shown in Figures 4 and 7 is preferably stored in the ROM or the auxiliary storage device.

[0046] 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 100 may be executed on a server or cloud of various systems remote from the optical inspection device 1 via the communication interface of the control unit 20. 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 20 of the optical inspection system 100 via the communication interface.

[0047] The image sensor 18a has at least two different color channels and is capable of, for example, separating RGB and detecting luminance values ​​(pixel values). Note that the imaging unit 18 is assumed to be provided with an imaging optical element (not shown) that forms an image on the image sensor 18a.

[0048] As described above, consider the light reflected from the first object point P1. At the first object point P1, the first light ray B1 is specularly reflected along the optical axis L. Therefore, the reflected light does not return to the imaging unit 18 and is not observed. Meanwhile, the second light ray B2 is also specularly reflected at the first object point P1 and is reflected in a direction oblique to the optical axis L. Because the optical axis direction of the imaging unit 18 is set to be along this oblique direction, this reflected light B21 is acquired by the image sensor 18a. In other words, the specularly reflected light B21 from the second light ray B2 can be obtained as an image at the first object point P1 on the smooth surface.

[0049] Next, consider the light reflected from a second object point P2 where a micro-defect exists. As described above, the brightness of the second scattered light B2a resulting from scattering of the second light ray B2 is reduced. Therefore, if the imaging unit 18 only observed the second scattered light B2a, the second object point P2 would be captured as a dark image. Meanwhile, the imaging unit 18 simultaneously captures not only the second scattered light B2a resulting from scattering of the second light ray B2 at the second object point P2, but also the first scattered light B1a resulting from scattering of the first light ray B1 at the second object point P2. In other words, the imaging unit 18 captures an image of the combined component B12 of the first scattered light B1a and the second scattered light B2a. Because the brightness of the first light ray B1 is greater than that of the second light ray B2, the brightness of the first scattered light B1a is also greater than that of the second scattered light B2a. Therefore, scattered light (first scattered light B1a) having a greater intensity than the second scattered light B2a reaches image sensor 18a of imaging unit 18. That is, in the image obtained by image sensor 18a, the minute defect at second object point P2 can be clearly observed.

[0050] On the other hand, when the brightness of the first light ray B1 is equal to or lower than the brightness of the second light ray B2, the intensity of the scattered light from the second object point P2 is reduced, and the image sensor 18a captures a dark image of the second object point P2. This makes it difficult to clearly identify the second object point P2. In other words, the optical device 10 according to this embodiment has the effect of brightening and sharpening the second object point P2.

[0051] As a result, when the object surface S is a smooth surface, the image sensor 18a can capture images of the object points P1 and P2 using the second light ray B2. Furthermore, when the object surface S has a small defect, the imaging unit 18 simultaneously captures not only the second scattered light B2a caused by the second light ray B2 but also the first scattered light B1a caused by the first light ray B1. The first light ray B1 has a higher brightness than the second light ray B2. Therefore, the scattered light B1a caused by the first light ray B1 can brighten and clarify the small defect. Therefore, when the imaging unit 18 of the optical device 10 is used, both the smooth surface and the small defect become bright and can be clearly observed.

[0052] 4, the optical device 10 according to this embodiment emits light from the light emitting unit 12 (step S11), illuminates the object surface S, acquires an image of the light reflected from the object surface S with the image sensor 18a of the imaging unit 18, and outputs the luminance value (pixel value) of the received light signal (step S12). A defect such as the second object point P2 is extracted from the degree of change in luminance value between adjacent pixels in the acquired image (step S13). Therefore, by using the optical inspection system 100 according to this embodiment, it is possible to determine the presence or absence of a defect on the object surface S.

[0053] As shown in Figure 5, consider the case where the irradiation field F is observed from a direction oblique to the optical axis L. Also, assume that the object surface S is flat. In the irradiation field F, there is a third object point P3 (see Figure 1) that is illuminated only by the second light ray B2. The line of sight of the observer V is set to a direction different from the direction of the light ray B23 that is specularly reflected from the second light ray B2 at the third object point P3 when the object surface S is a smooth surface.

[0054] The second light ray B2, which is light from the second light direction selection region R2, can reach the third object point P3 only after the first light ray B1 has been redirected by the light redirector 16a. In this embodiment, the light redirector 16a is a diffuser, but the light redirector 16a does not necessarily have to be a diffuser and can be anything that redirects light, such as a microlens array.

[0055] On the other hand, without the light direction changing body 16a, the light from the second light direction selection region R2 cannot reach the third object point P3. In other words, this embodiment has the effect of widening the irradiation field F of the second light ray B2.

[0056] Assume that the third object point P3 is on a smooth surface. In this case, the second light ray B2 is specularly reflected at the third object point P3 and is reflected in a direction oblique to the optical axis L. The line of sight of the observer V is different from the direction of the specularly reflected light ray B23. As a result, the specularly reflected light ray B23 is not observed. In other words, when the third object point P3 is on a smooth surface, it is not observed.

[0057] On the other hand, suppose that the third object point P3 is located on a micro defect. At this time, the second light ray B2 is scattered by the micro defect and diffused (reflected) in various directions. At this time, the observer V observes scattered light B2b due to the second light ray B2. As a result, when the third object point P3 is located on a smooth surface, the third object point P3 is not observed. In other words, the third object point P3 is not observed by the illumination light. However, when there is a micro defect on the object surface S, the observer V can observe the third object point P3 by scattered light B2b resulting from the second light ray B2 being scattered (reflected). As a result, when the third object point P3 is located on a micro defect, a larger change in light intensity can be observed compared to when the third object point P3 is located on a smooth surface. In other words, the presence or absence of a micro defect can be detected by the change in light intensity. Therefore, by using this embodiment, the presence or absence of a micro defect in a wide field of view including the third object point P3 can be more reliably detected using light intensity information.

[0058] FIG. 6 shows a diagram in which the observer V shown in FIG. 5 is replaced with an imaging unit 18 (see FIG. 3). An optical inspection device 1 is configured that includes the optical device 10 and the imaging unit 18. A control unit 20 is connected to the image sensor 18a of the imaging unit 18, and an optical inspection system 100 is configured that includes the control unit 20 and the optical inspection device 1. FIG. 7 shows a process flow of optical inspection using the control unit 20.

[0059] Assume that a third object point P3 is located on a smooth surface. In this case, the second light ray B2 is specularly reflected at the third object point P3 and is reflected in a direction oblique to the optical axis L. The optical axis direction of the image capture unit 18 differs from the direction of this specularly reflected anti-oblique light ray B23. As a result, an image of the light in this specular reflection direction cannot be obtained. In other words, when the third object point P3 is located on a smooth surface, no image is captured by the image capture unit 18.

[0060] Meanwhile, suppose that the third object point P3 is located on a small defect. At this time, the second light ray B2 is scattered by the small defect and diffused (reflected) in various directions. When a small defect is present on the object surface S, the image sensor 18a of the imaging unit 18 can capture an image of the third object point P3 as scattered light B2b resulting from the scattering (reflection) of the second light ray B2. As a result, when the third object point P3 is located on a small defect, the image sensor 18a can capture an image that exhibits a larger change in light intensity than when the third object point P3 is located on a smooth surface. In other words, the image sensor 18a can detect the presence or absence of a small defect based on the change in light intensity. Therefore, by using this embodiment, the presence or absence of a small defect in a wide field of view including the third object point P3 can be more reliably detected using light intensity information.

[0061] 7, the optical device 10 according to this embodiment emits light from the light emitting unit 12 (step S21), illuminates the object surface S, acquires an image of the light reflected from the object surface S with the image sensor 18a of the imaging unit 18, and outputs the luminance value (pixel value) of the received light signal (step S22). A defect such as the third object point P3 is extracted from the degree of change in luminance value between adjacent pixels in the acquired image (step S23). Therefore, by using the optical inspection system 100 according to this embodiment, it is possible to determine the presence or absence of a defect on the object surface S.

[0062] In the light direction changer 16a according to this embodiment, a first light ray B1 incident on the first light direction selection region R1 or the second light direction selection region R2 is emitted as a light ray with different optical properties depending on the region. That is, in addition to being emitted as the first light ray B1, it is also emitted as a second light ray B2 with optical properties different from the first light ray B1. Then, one of the light direction selection regions R1, R2 changes the direction of the incident light ray B1 to a light ray B2 in a different direction and emits it. Therefore, according to this embodiment, there are provided an optical device 10 capable of illuminating an object O as a light ray B2 obtained by changing the direction of at least a part of the light ray B1 emitted from the light emitting unit 12 in a different direction, an optical inspection device 1 including the optical device 10, and an optical inspection system 100 including the optical inspection device 1. At this time, at least a portion of the light ray B1 emitted from the light emitting portion 12 can be emitted as a light ray B2 having optical properties different from those of the light ray B1 depending on the first light direction selection region R1 or the second light direction selection region R2.

[0063] The optical inspection method also includes emitting a first light ray B1 of a first wavelength spectrum including a first wavelength toward the imaging optical element 14, and changing the first light ray B1 incident on a first light direction selection region R1 or a second light direction selection region R2 of the light direction selection unit 16 provided on the focal plane f of the imaging optical element 14 or a focal plane region Rf nearby the first light ray B1 into a light ray B2 having different optical properties depending on the region, and emitting the first light ray B1 in a direction different from the incident direction, to illuminate the object O. According to this embodiment, an optical inspection method is provided that can change the direction of at least a part of the light ray B1 emitted from the light emitting unit 12 to a light ray B2 in a different direction to illuminate the object O.

[0064] The optical inspection method also includes acquiring information about the surface S of the object O using light from the object O by illuminating the object O. At this time, at least a part of the light ray B1 emitted from the light emitting unit 12 can be emitted as a light ray B2 having optical properties different from those of the light ray B1 according to the first light direction selection region R1 or the second light direction selection region R2.

[0065] The light direction selection unit 16 has a diffuser 16a disposed in at least one of the first light direction selection region R1 or the second light direction selection region R2, which generates at least two light rays B1 and B2 including a direction (the direction of the light ray B2) different from the direction of the incident light (the light ray B1) and diffuses the light. Therefore, a wide irradiation field F can be simultaneously illuminated with the light rays B1 and B2.

[0066] (Variation 1) FIG. 8 shows a cross-sectional view of a modified example of the optical device 10. This cross-sectional view includes the optical axis L. In the first embodiment, the light source of the light emitting unit 12 is a point light source 120, but in this modified example, the light source is a surface light source 120a. The surface light source 120a is, for example, an LED. The LED emits a first light ray B1 of a first wavelength spectrum. Generally, the light-emitting surface of an LED is not uniform, and there is illuminance unevenness. In other words, there is unevenness in the distribution of brightness on the light-emitting surface.

[0067] Two different points on the light-emitting surface of the surface light source 120a are designated as a first light source point 121 and a second light source point 122. A first light ray B1 of a first wavelength spectrum is emitted from these light source points 121 and 122. However, due to unevenness in the brightness distribution of the light-emitting surface, the luminance of the light rays from the first light source point 121 and the second light source point 122 differs.

[0068] Consider a case where the light diffuser 16a is not present in the second light direction selection region R2. In this case, a first virtual rectilinear light 1211 and a second virtual rectilinear light 1221 are emitted from the first light source point 121 and the second light source point 122, respectively, and travel straight through the second light direction selection region R2. Here, due to uneven illuminance on the light-emitting surface, the first virtual rectilinear light 1211 and the second virtual rectilinear light 1221 have different luminances. These light rays (the first virtual rectilinear light 1211 and the second virtual rectilinear light 1221) form a second light direction group G2 at points within the second light direction selection region R2. A light ray belonging to the second light direction group G2 is referred to as a second light ray B2. Furthermore, the first virtual rectilinear light 1211 and the second virtual rectilinear light 1221 reach a first object point P1 and a second object point P2, respectively, via the imaging optical element 14. Here, the second light ray B2 is incident on the first object point P1 and the second object point P2 at the same angle of incidence but with different intensities. As a result, when attempting to detect the presence or absence of a micro defect at the first object point P1 and the second object point P2, the brightness of the incident second light ray B2 is different. Therefore, for example, even if the first object point P1 and the second object point P2 are on a smooth surface, the intensities of the reflected light will be different. Similarly, even if the first object point P1 and the second object point P2 are on a micro defect, the intensities of the reflected light will be different. In other words, it becomes difficult to determine the presence or absence of a micro defect at both object points P1 and P2 using light intensity information.

[0069] On the other hand, this modification includes a light diffuser 16a in the second light direction selection region R2. This uniformizes the luminance of the light beams B2 directed in each direction in the second light direction group G2 formed at points within the second light direction selection region R2. This is a general feature of the light diffuser 16a, and it is known that the greater the degree to which the light diffuser 16a diffuses light, the more uniform the luminance becomes. In other words, the directional distribution of light intensity approaches a Lambertian distribution. This uniformization makes it possible to uniformize the luminance of the second light direction group G2 even when the luminances from the points 121 and 122 on the light-emitting surface are different. This has the effect of equalizing the luminance of the second light beam B2 incident on the first object point P1 and the second object point P2. This effect can only be achieved by a device capable of changing the direction of incident light, such as the light diffuser 16a. In other words, the light diffuser 16a's function as a light direction changer makes it possible to adjust the luminance of the two light beams in the second light direction group G2. This has the effect that when detecting the presence or absence of a micro defect at the first object point P1 and the second object point P2, the brightness of the second light ray B2, which is the incident light, is approximately equal, so that the presence or absence of a micro defect can be determined at both object points P1 and P2 using light intensity information, i.e., the relationship between the light intensities.

[0070] (Variation 2) FIG. 9 shows a cross-sectional view of Modification 2 of the optical device 10. This cross-sectional view includes the optical axis L. In the first embodiment, the light source of the light emitting unit 12 is a point light source 120, but in this modification, a laser light source 124 is used. The laser light source 124 emits light that is highly rectilinear and close to parallel light. The laser light source 124 also emits light with a narrow wavelength spectrum width. The peak wavelength of this wavelength spectrum is defined as the first wavelength.

[0071] In the first light direction selection region R1 and the second light direction selection region R2 of the light direction selecting unit 16, a first light diffuser 160a and a second light diffuser 160b are arranged, respectively.

[0072] Laser light source 124 irradiates at least light beam B1 having a wavelength spectrum with a first wavelength as a peak wavelength onto first light diffuser 160a and second light diffuser 160b.

[0073] These light diffusers 160a and 160b can each diffuse light, but the degree to which they diffuse light differs. That is, when a first light ray B1 is incident on each of the light diffusers 160a and 160b, the brightness of the light ray in the first light direction group G1 and the second light direction group G2 is different. That is, here, one of the light diffusers 160a and 160b is arranged as an attenuator that attenuates light of a first wavelength. If both the light diffusers 160a and 160b are attenuators, the attenuation degrees of the two are different.

[0074] The end faces of the light diffusers 160a and 160b serving as attenuators may be tapered as appropriate along the optical axis L. In this case, the cross sections of the light diffusers 160a and 160b shown in Fig. 9 are trapezoidal, for example, and either the upper base (the position indicated by the leading lines of the reference symbols 160a and 160b) or the lower base (the position of the focal plane f) may be longer. The amount of light reflected by the end faces of the light diffusers 160a and 160b serving as attenuators can be adjusted by the taper, which has the effect of adjusting the intensity distribution of the first light direction group G1 or the second light direction group G2.

[0075] As shown in FIG. 2 or 3 of the first embodiment described above, consider the case where the irradiation field F is observed from a direction oblique to the optical axis L. Also, assume that the object surface S is flat. In the irradiation field F, a first object point P1 on the object surface S is on a smooth surface. On the other hand, a minute defect exists at a second object point P2, and this minute defect scatters light. The line of sight of the observer V is assumed to be along the direction in which the second light ray B2 is specularly reflected by the smooth surface.

[0076] The second light ray B2 is generated by diffusing the first light ray B1 by the diffuser 160b. In other words, the second light ray B2 is generated by branching the first light ray B1. Therefore, the brightness of the second light ray B2 is lower than the brightness of the first light ray B1.

[0077] First, consider the light reflected from the first object point P1. At the first object point P1, the first light ray B1 is specularly reflected along the optical axis L. Therefore, the reflected light does not return to the observer V and is not observed. On the other hand, the second light ray B2 is also specularly reflected at the first object point P1 and is reflected in a direction oblique to the optical axis L. Because the line of sight of the observer V is set along this oblique direction (see Figure 2), this reflected light B21 (see Figure 2) is observed. In other words, the first object point P1 on the smooth surface can be observed by the specularly reflected light B21 from the second light ray B2.

[0078] Next, consider the light reflected from the second object point P2. Because a microdefect exists at the second object point P2, both the first light ray B1 and the second light ray B2 are scattered by the microdefect and diffused (reflected) in various directions. Generally, the BRDF of a microdefect has a wide distribution centered on the specular reflection direction. In this case, the observer V simultaneously observes not only the first scattered light B1a (see FIG. 2) from the first light ray B1 but also the second scattered light B2a (see FIG. 2) from the second light ray B2. In other words, the observer V observes the combined component B12 of the first scattered light B1a and the second scattered light B2a. Here, the ratio of the luminance of the first light ray B1 and the luminance of the second light ray B2 can be adjusted by changing the type of the first light diffuser 160a and the second light diffuser 160b. Therefore, for example, the brightness of the microdefect can be adjusted by adjusting the degree of diffusion of the first light diffuser 160a. This adjustment makes it possible to increase the difference in the intensity of reflected light (or scattered light), i.e., the difference in brightness, between the first object point P1 on the smooth surface and the second object point P2 on the minute defect, making it possible to distinguish between them based on the difference in light intensity, i.e., the difference in brightness.

[0079] As a result, when the object surface S is a smooth surface, the object points P1 and P2 can be observed using the second light ray B2. On the other hand, when the object surface S has a microdefect, the observer V simultaneously observes not only the second scattered light B2a due to the second light ray B2 but also the first scattered light B1a due to the first light ray B1. The ratio between the luminance of the first light ray B1 and the luminance of the second light ray B2 can be adjusted by the first light diffuser 160a and the second light diffuser 160b. Therefore, for example, by adjusting the diffusion degree of the first light diffuser 160a, the brightness of the microdefect can be adjusted. This allows appropriate changes in light intensity to be observed when a microdefect is present on a smooth surface and when it is not. In other words, by using the optical device 10 according to this modification, the presence or absence of a microdefect can be more reliably detected using light intensity information.

[0080] (Variation 3) FIG. 10 shows a cross-sectional view of a third modification of the optical device (illumination unit) 10. As shown in FIG.

[0081] In this modification, the imaging optical element 14 of the illumination unit 10 is an imaging optical element array. The imaging optical element array 14 includes at least two imaging optical element elements 14a, 14b, which are adjacent to each other along the x-axis direction. The imaging optical element array 14 preferably includes a plurality of imaging optical element elements 14a, 14b, ... arranged in an array.

[0082] The light direction selecting unit 16 includes a first light direction selecting region R1, a second light direction selecting region R2, a third light direction selecting region R3, and a fourth light direction selecting region R4. The first light direction selecting region R1 and the second light direction selecting region R2 face the first imaging optical element 14a. The second imaging optical element 14b faces the third light direction selecting region R3 and the fourth light direction selecting region R4.

[0083] It should be noted that a first light direction selection region R1 is provided on the optical axis La of the first imaging optical element element 14a. The second light direction selection region R2 is adjacent to the first light direction selection region R1. A third light direction selection region R3 is provided on the optical axis Lb of the second imaging optical element element 14b. The fourth light direction selection region R4 is adjacent to the third light direction selection region R3. It is preferable that the configurations of the first light direction selection region R1 and the second light direction selection region R2 for the first imaging optical element element 14a are the same as the configurations of the third light direction selection region R3 and the fourth light direction selection region R4 for the second imaging optical element element 14b.

[0084] The imaging optical element elements 14a and 14b of the imaging optical element array 14 have the function of collecting a group of light rays emitted from a certain point at a conjugate image point. In this modification, the imaging optical element array 14 is a lens array, and the two aligned imaging optical element elements 14a and 14b that make up the lens array 14 are, for example, Fresnel lenses.

[0085] 10 includes the optical axes La and Lb of the lens element elements 14a and 14b, which are parallel to the z-axis. The optical axis La of the first lens element element 14a and the optical axis Lb of the second lens element element 14b are defined as the first optical axis La and the second optical axis Lb, respectively.

[0086] The first light direction selection region R1 and the second light direction selection region R2 are formed on or near the focal plane f of the first lens element element 14a. The third light direction selection region R3 and the fourth light direction selection region R4 are formed on or near the focal plane f of the second lens element element 14b. In this modification, the focal planes f of the first lens element element 14a and the second lens element element 14b are assumed to be on the same plane.

[0087] As described in the first embodiment, the first light ray B1 that reaches the first light direction selection region R1 and the third light direction selection region R3 from the light output unit 12 passes through as is as the light ray B1. Also, the first light ray B1 that reaches the second light direction selection region R2 and the fourth light direction selection region R4 from the light output unit 12 generates a new second light ray B2 that travels in a direction different from that of the first light ray B1.

[0088] The operation of the optical device 10 according to the above-described modified example will now be described.

[0089] In this modification, the object O reflects light. 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, this is not limiting, and the object O may be transparent or translucent to light.

[0090] The light that has passed through the first light direction selection region R1 is propagated by the first lens element element 14a in a direction parallel to the first optical axis La and reaches the irradiation field F1. On the other hand, the light that has passed through the second light direction selection region R2 is propagated by the first lens element element 14a in a direction inclined to the first optical axis La and reaches the irradiation field F1.

[0091] Furthermore, the light that has passed through the third light direction selection region R3 is propagated by the second lens element element 14b in parallel along the second optical axis Lb, reaches the object surface S, and illuminates the object surface S. The illuminated region is called an illumination field F2. On the other hand, the light that has passed through the fourth light direction selection region R4 is propagated by the second lens element element 14b in a direction inclined to the second optical axis Lb, and reaches an illumination field F1 formed by the light that has passed through the first light direction selection region R1 and the second light direction selection region R2.

[0092] Therefore, the irradiation field F1 is irradiated with at least the first light ray B1 that passed through the first light direction selection region R1, the second light ray B2 that passed through the second light direction selection region R2, and the second light ray B2 that passed through the fourth light direction selection region R4, all overlapping. In other words, an area is formed where the light rays B1 and B2 from different directions simultaneously overlap. Therefore, the optical device 10 according to this modification irradiates the same irradiation field F1 of the object O with light rays B1 and B2 from multiple directions. Furthermore, since the light of the second light ray B2 that passed through the second light direction selection region R2 and the light of the second light ray B2 that passed through the fourth light direction selection region R4 are irradiated with overlapping light, the illuminance unevenness of the irradiation field F1 is more uniform than when only one of these light beams is used. This is because the more light beams with various illuminance unevennesses are overlapped, the more the illuminance unevenness is reduced.

[0093] Consider a case where an observer observes the irradiation field F1 from a direction (line of sight) oblique to the first optical axis L1. The object surface S is assumed to be a plane.

[0094] At this time, if the object surface S in the irradiation field F1 is a smooth surface, the light ray B1 that passes through the first light direction selection region R1 is specularly reflected and reflected along the first optical axis L1. Therefore, the reflected light does not return to the observer, and the light having the wavelength spectrum a is not observed by the observer.

[0095] Note that the light ray B2 that passes through the second light direction selection region R2 is specularly reflected by the irradiation field F1 and reflected in a direction oblique to the first optical axis La. At this time, there is a possibility that the reflected light of the light ray B2 will return to the observer observing from a direction oblique to the optical axis La (the line of sight direction). In addition, the light ray B2 that passes through the fourth light direction selection region R4 is also specularly reflected by the irradiation field F1 and reflected in a direction oblique to the first optical axis La. At this time, there is a possibility that the reflected light of the light ray B2 that passes through the fourth light direction selection region R4 will return to the observer observing from a direction oblique to the optical axis La. As a result, the light ray B2 may be observed by the observer, but the light ray B1 will not be observed. In other words, the observer can observe the light ray B2 when the surface is smooth.

[0096] On the other hand, if there is a minute defect (minute unevenness) on the object surface S in the irradiation field F1, the minute defect scatters light and widens the angular distribution, so that not only the light ray B2 but also the light ray B1 are observed at the same time. This has the effect of making the defect appear brighter. Furthermore, in this embodiment, the illuminance unevenness of the smooth surface within the irradiation field F1 is reduced. Therefore, to the observer, the change in light intensity due to the minute defect has a greater intensity contrast than the intensity contrast of the smooth surface area caused by the illuminance unevenness. In other words, there is the effect of making it possible to more clearly identify the minute defect.

[0097] (Second embodiment) The optical inspection device according to this embodiment will be described below with reference to FIG.

[0098] In this specification, light is a type of electromagnetic wave, and includes gamma rays, X-rays, ultraviolet rays, visible light, infrared rays, radio waves, etc. In this embodiment, light is considered to be visible light, with a wavelength in the range of 400 nm to 750 nm, for example.

[0099] 11 is a schematic cross-sectional view of an optical device 10 according to this embodiment. The optical device 10 according to this embodiment includes a light emitting section 12, an imaging optical element 14, and a light direction selecting section 16.

[0100] The light emitting unit 12 includes a light source 120b, which emits a first light ray B1 having a first wavelength spectrum including at least a first wavelength. For example, the first wavelength is 405 nm, and the first wavelength spectrum has a peak at the first wavelength. Light having such a first wavelength spectrum is referred to as blue light. However, this is not limiting, and the wavelength spectrum of the light source 120b may be any. For example, it may be white light.

[0101] Light source 120b is a surface-emitting light-emitting diode (LED) that emits blue light. However, this is not a limitation and any light-emitting device, such as a laser diode (LD), may be used. Light source 120b may also be sunlight, a plasma light source, or a thermal radiation light source (such as an incandescent lamp, halogen lamp, or xenon lamp).

[0102] The imaging optical element 14 can form an image of light. For example, it can be a single lens, a compound lens consisting of multiple lenses, a concave mirror, a Fresnel lens, a diffraction grating, a gradient index lens (GRIN lens), etc. In other words, the imaging optical element 14 can be anything that can form an image of light. The plane on which the imaging optical element 14 forms an image of a set of points at infinity is called the focal plane f. The focal plane f and its vicinity are called the focal plane region Rf. The optical axis L of the imaging optical element 14 is a straight line perpendicular to the focal plane f. Light emitted from a sufficiently distant point on the optical axis L is imaged at the point where the optical axis and the focal plane f intersect. This point is called the focus.

[0103] The imaging optical element 14 of this embodiment is a compound lens made up of multiple lenses. Here, this is referred to as an imaging lens. However, in FIG. 11, for simplicity, the imaging lens, which is a compound lens, is schematically depicted as a single lens. However, the imaging optical element is not limited to this, and any element that can image light may be used. In the cross-sectional view of FIG. 11, the optical axis L of the imaging optical element 14 is included in this cross section.

[0104] The light direction selecting unit 16 has a first light direction selecting region R1 and a second light direction selecting region R2 on or near the focal plane f of the imaging optical element 14. That is, the first light direction selecting region R1 and the second light direction selecting region R2 are located in the focal plane region Rf. The first light direction selecting region R1 either changes the optical properties of a first light ray B1 of a first wavelength included in a first wavelength spectrum and passes the first light ray B1 therethrough, or passes the first light ray B1 therethrough without changing the optical properties. In this embodiment, the first light direction selecting region R1 passes the first light ray B1 therethrough without changing the optical properties. In this case, a set of first light rays B1 pointing in various different directions from a point in the first light direction selecting region R1 is referred to as a first light direction group G1. The second light direction selecting region R2 changes the optical properties of the first light ray B1. Here, the optical properties include the direction, wavelength, wavelength spectrum, polarization, brightness, illuminance, and luminous flux (amount of light) of the light ray.

[0105] The light direction selection unit 16 includes a light direction changer 16a in the second light direction selection region R2. The light direction changer 16a may be, for example, a phosphor, frosted glass, a holographic diffuser, a diffraction grating, a transparent resin dispersed with light-scattering particles, silk printing, or paper. Light diffusion generates at least two light rays, including a light ray traveling in a direction different from the incident direction. That is, at least one new light ray B2 is generated, which has at least some optical properties different from the incident light ray B1. Furthermore, the light quantity (total luminous flux) can be maintained before and after light diffusion. In other words, light can be diffused without changing the light quantity. However, diffusion may also change the light quantity.

[0106] In this embodiment, light redirector 16a is a phosphor (wavelength converting diffuser) 16b. Phosphor 16b converts a first wavelength to a second wavelength. For example, the second wavelength is 650 nm. The light of the second wavelength spectrum has the second wavelength as its peak wavelength. In other words, the light of the second wavelength spectrum is red light. However, the second wavelength is not limited to this and can be any wavelength different from the first wavelength. Furthermore, when phosphor 16b absorbs light and emits light of a different wavelength, it emits at least one light beam in a direction different from the incident direction of the light. Therefore, phosphor 16b is used as a wavelength converting diffuser that converts the wavelength of incident light and diffuses outgoing light.

[0107] Next, the operation of the optical device 10 according to this embodiment will be described.

[0108] 11, light of a first wavelength spectrum is emitted from the surface-emitting LED 120b of the light emitting unit 12. A first light ray B1 is light of a first wavelength included in the first wavelength spectrum. The first light ray B1 travels toward the light direction selecting unit 16 and reaches the first light direction selecting region R1, the second light direction selecting region R2, or both.

[0109] The first light ray B1 that reaches the first light direction selection region R1 passes through as is. Here, at a point in the first light direction selection region R1, a collection of the first light rays B1 that pass through that point is defined as a first light direction group G1. Meanwhile, a second light ray B2 that has a different direction and wavelength from the first light ray B1 is newly generated by the phosphor 16b provided in the second light direction selection region R2. Here, at a point in the second light direction selection region R2, a collection of the second light rays B2 that pass through that point is defined as a second light direction group G2. The phosphor 16b causes the wavelength of the second light ray B2 to become a second wavelength that is different from the first wavelength.

[0110] The first light direction selection region R1 and the second light direction selection region R2 are located on or near the focal plane f of the imaging optical element 14, but are at different positions. Therefore, as shown in Fig. 11, a first light ray B1, which is one light ray in the first light direction group G1, and a second light ray B2, which is one light ray in the second light direction group G2, have different inclination angles with respect to the optical axis L when they pass through the imaging optical element 14. In other words, based on geometric optics, the inclination angle with respect to the optical axis L is determined depending on the position where the light ray B1 passes through the focal plane f.

[0111] The illumination field F is defined as a region of the object surface S illuminated by the first light ray B1, the second light ray B2, or both B1 and B2. In this embodiment, there are two different points illuminated by both the first light ray B1 and the second light ray B2 within the illumination field F. These points are defined as the first object point P1 and the second object point P2.

[0112] As shown in FIG. 2 of the first embodiment, consider the case where an observer V observes an irradiation field F from a direction oblique to the optical axis L. Also, assume that the object surface S is flat. In the irradiation field F, a first object point P1 on the object surface S is on a smooth surface. On the other hand, a second object point P2 has a minute defect (minute irregularity), which scatters light. The line of sight of the observer V is assumed to be along the direction in which the second light ray B2 is specularly reflected by the smooth surface. The second light ray B2 is the first light ray B1 converted into light of a second wavelength by a phosphor.

[0113] First, consider the light reflected from the first object point P1. At the first object point P1, the first light ray B1 is specularly reflected along the optical axis L. Therefore, the reflected light of the first light ray B1 reflected at the first object point P1 does not return to the observer V, and the observer V cannot observe it.

[0114] Meanwhile, the second light ray B2 is also specularly reflected at the first object point P1, and is reflected in a direction oblique to the optical axis L. Because the line of sight of the observer V is set along this oblique direction, this reflected light is observed. In other words, the first object point P1 on the smooth surface can be observed by the specularly reflected light from the second light ray B2. In this case, the second light ray B2 is light of the second wavelength, which is red light. In other words, the first object point P1 on the smooth surface is observed by the red light.

[0115] Next, consider the light reflected from a second object point P2. Because a micro-defect exists at the second object point P2, both the first ray B1 and the second ray B2 are scattered by the micro-defect and diffused (reflected) in various directions. These reflection characteristics can be described by a bidirectional reflectance distribution function (BRDF), which represents the light intensity for each reflection direction. The angular distribution of light described by the BRDF is a narrow distribution dominated by the specular reflection component for a smooth surface, but a broad distribution for a micro-defect. Generally, the BRDF of a micro-defect has a broad distribution centered on the specular reflection direction. In this case, the observer simultaneously observes not only the first scattered light from the first ray but also the second scattered light from the second ray. In other words, the observer observes the combined component of the first scattered light and the second scattered light. Therefore, the second object point is observed not only by light of the first wavelength but also by light of the second wavelength. In other words, the second object point is observed by both blue and red light.

[0116] As a result, the smooth surface on the object surface is observed with red light, and the micro-defects are observed with blue and red light. In other words, by using this embodiment, it is possible to more reliably detect the presence or absence of micro-defects using light color (hue) information.

[0117] In the light direction changer 16a according to this embodiment, a first light ray B1 incident on the first light direction selection region R1 or the second light direction selection region R2 is emitted as a light ray with different optical properties depending on the region. That is, in addition to being emitted as the first light ray B1, it is also emitted as a second light ray B2 with optical properties different from the first light ray B1. Then, one of the regions R1 and R2 changes the direction of the incident light ray B1 to a light ray B2 in a different direction and emits it. Therefore, according to this embodiment, there are provided an optical device 10 capable of changing the direction of at least a part of the light ray B1 emitted from the light emitting unit 12 to a light ray B2 in a different direction to illuminate an object O, an optical inspection device 1 including the optical device 10, and an optical inspection system 100 including the optical inspection device 1. At this time, at least a portion of the light ray B1 emitted from the light emitting unit 12 can be emitted as light ray B2 having optical properties different from that of the light ray B1, depending on the first light direction selection region R1 or the second light direction selection region R2. Furthermore, according to this embodiment, an optical inspection method is provided in which the direction of at least a portion of the light ray B1 emitted from the light emitting unit 12 is changed to light ray B2 having a different direction, that is, the object O can be illuminated with light ray B2 obtained by changing the direction of at least a portion of the light ray B1 to a different direction. At this time, at least a portion of the light ray B1 emitted from the light emitting unit 12 can be emitted as light ray B2 having optical properties different from that of the light ray B1, depending on the first light direction selection region R1 or the second light direction selection region R2.

[0118] Phosphor 16b of diffuser 16a is a wavelength converting diffuser that converts light of a first wavelength into light of a second wavelength, which is different from the first wavelength. Wavelength converting diffuser 16b is disposed in second light direction selection region R2. Wavelength converting diffuser 16b emits light of a second wavelength spectrum (light beam B2) that is different from the light of the first wavelength spectrum and includes the second wavelength, from second light direction selection region R2. Therefore, optical device 10 according to this embodiment can emit light beams B1 and B2, which have different direction and optical properties other than the direction, from light direction selection unit 16 toward imaging optical element 14 and object O.

[0119] Furthermore, by using this embodiment, it is possible to detect the presence or absence of a micro defect and the BRDF of the micro defect without using a color filter on the focal plane f.

[0120] (Variation 1) In this embodiment, the phosphor 16b of the light direction selection unit 16 may be as shown in FIG. 12. In FIG. 12, the z-axis is the optical axis. Two axes perpendicular to the z-axis are the x-axis and y-axis, respectively. The phosphor 16b is created by providing a through-hole 17 in a thick phosphor plate (phosphor plate). The thickness is, for example, 0.5 mm to 3 mm. However, this is not limited and any thickness is acceptable. The phosphor plate 16b may be made by dispersing phosphor inside a transparent resin, glass, or the like. The side surface 165 of the through-hole 17 is a glossy surface. However, this is not limited and the side surface 165 of the through-hole 17 may be a diffusing surface.

[0121] The region where the through-hole 17 exists is defined as a first light direction selection region R1, and the region where the phosphor plate (phosphor plate) exists is defined as a second light direction selection region R2.

[0122] Because the side surface 165 of the through-hole 17 is a glossy surface, light incident on the phosphor plate 16b is totally reflected by the side surface 165 and does not leak to the outside. Therefore, the light is confined within the phosphor plate 16b until just before it is emitted from the second light direction selection region R2, and is emitted to the outside immediately after reaching the second light direction selection region R2. This ensures that the first light ray B1, which passes through the through-hole 17 and is emitted from the first light direction selection region R1, and the light ray B2, which is emitted from the second light direction selection region R2, are clearly separated without intersecting with each other. Based on geometric optics, the directions of the light rays B1 and B2 emitted from the imaging optical element 14 are determined by the positions at which the light rays B1 and B2 pass through the focal plane f. In other words, this modification, in which the side surface 165 of the phosphor plate 16b arranged on the focal plane f is a glossy surface, allows the light rays to be clearly distinguished between the first light ray B1 and the second light ray B2. Since the first light ray B1 and the second light ray B2 have different wavelengths, there is an effect that the directions of the light rays B1 and B2 can be clearly distinguished by color (hue).

[0123] 12 shows an example in which phosphor plate 16b has a disk-like appearance and through-holes 17 have a circular shape. As shown in FIG. 13, it is also preferable that phosphor plate 16b has a substantially rectangular plate-like appearance and through-holes 17 are formed in the shape of slits. In this case, through-holes 17 also form side surfaces 165.

[0124] (Variation 2) In this embodiment, the phosphor may be as shown in FIG. 14. In FIG. 14, the z-axis is the optical axis. Two axes perpendicular to the z-axis are the x-axis and y-axis, respectively. The phosphor 16b may be a coating layer 168 of phosphor applied to an aperture substrate 167 formed by providing through-holes 170 in a thick transparent substrate plate. The thickness of the aperture substrate 167 is, for example, 0.5 mm to 3 mm. However, this is not a limitation and any thickness is acceptable. The coating layer 168 is thin, approximately several hundred μm. However, this is not a limitation. This modification allows the light beam directions to be clearly distinguished between the first light beam B1 and the second light beam B2. Because the first light beam B1 and the second light beam B2 have different wavelengths, the directions of the light beams B1 and B2 can be clearly distinguished by color (hue).

[0125] (Variation 3) In this embodiment, the phosphor may be that shown in FIG. 15. FIG. 15 is a cross section including the optical axis L. The first light direction selection region R1 is provided with a light blocking body 17a that blocks light. In other words, the first light ray B1 emitted from the light source 120b (see FIG. 11) does not pass through the first light direction selection region R1. Therefore, the first light direction group G1 is not formed. Alternatively, the light intensity of the first light direction group G1 becomes zero. As a result, the intensity of the first light ray B1 also becomes zero. As a result, since the first light ray B1 and the second light ray B2 have different wavelengths and intensities, there is an effect that the directions of the light rays B1 and B2 can be clearly distinguished not only by color (hue) but also by light intensity.

[0126] (Variation 4) In this modified example, the phosphor 16b may be that shown in FIG. 16. FIG. 16 is a cross section including the optical axis L. A diffuser 16c that diffuses light is provided in the first light direction selection region R1. That is, the first light ray B1 emitted from the light source 120c of the light emitting unit 12 is diffused in the first light direction selection region R1. Therefore, the first light direction group G1 has a wide angular distribution. In addition, a diffuser 16c is also provided in the second light direction selection region R2. And, due to the light diffuser 16c, the second light direction group G2 also has a wide angular distribution. These have the effect of widening the irradiation field F.

[0127] The light emitting unit 12 also includes a projection unit 120c that can project an image onto the focal plane f or near the focal plane. The projection unit 120c is, for example, a projector. The projector 120c has the effect of being able to switch the intensity and wavelength of the first light beam B1 and the second light beam B2 to desired ones. In particular, if an electrically controlled projector is used as the projector 120c, the light beam B1 can be instantly switched.

[0128] The projector 120c may be an LCD (Liquid Crystal Display) type, a DLP (Digital Lighting Processing) type, or an LCOS (Liquid Crystal On Silicon) type. The LCD type projector 120c splits light from a light source using a dichroic mirror, transmits each split light through an LCD panel, and then combines the split light again. The DLP type projector 120c uses a rotating color wheel to convert light from a light source into light with different wavelength spectra at different times, and reflects the light with a DMD (Digital Micromirror Device). However, the DLP type projector 120c may also use a system in which multiple light sources with different wavelength spectra are prepared in advance, and the light from each wavelength spectrum is reflected by the DMD and then combined without using a color wheel. The LCOS type projector 120c splits light from a light source using a dichroic mirror, reflects each split light on a reflective LCD panel, and then combines the light again. It is assumed that the projection unit 120c provided in the light emission unit 12 in this embodiment is a DLP type projector.

[0129] However, the projector 120c is not limited to these types, and may project light of various wavelengths and intensities toward the focal plane f where the light direction selection unit 16 is located. In other words, the projector 120c may project light of a different wavelength spectrum or a different intensity in addition to light of the first wavelength spectrum.

[0130] (Third embodiment) 17 is a schematic cross-sectional view of the light emitting unit 12 and the light direction selecting unit 16 of the optical device 10 according to this embodiment. In FIG. 17, the imaging optical element 14, the object plane O, etc. (see FIG. 11) are not shown.

[0131] The light emitting unit includes a first light source 121, a second light source 122, and a third light source 123. The first light source 121, the second light source 122, and the third light source 123 are blue LEDs that emit light of a first wavelength spectrum that includes a first wavelength. However, they may emit light of different wavelength spectrums. In other words, any material that emits light is acceptable. The light sources 121, 122, and 123 are sealed by transparent sealants 121a, 122a, and 123a, respectively. The sealants 121a, 122a, and 123a may be made of, for example, silicone. However, the material is not limited to this, and any transparent material that transmits light from the light sources 121, 122, and 123 may be used.

[0132] A diffuser 161 is disposed opposite the first light source 121 .

[0133] Phosphor 162 is disposed facing second light source 122, and phosphor 163 is disposed facing third light source 123. Phosphor 162 is a quantum dot that converts light of a first wavelength into light of a second wavelength. The light of the second wavelength is red light with a wavelength of 650 nm. Phosphor 163 is a quantum dot that converts light of the first wavelength into light of a third wavelength. The light of the third wavelength is green light with a wavelength of 550 nm.

[0134] The light of the second wavelength spectrum includes a second wavelength, and the light of the third wavelength spectrum includes a third wavelength, and the first wavelength spectrum, the second wavelength spectrum, and the third wavelength spectrum are different from each other.

[0135] The first light direction selection region R1, the second light direction selection region R2, and the third light direction selection region R3 form a first light direction group G1, a second light direction group G2, and a third light direction group G3, respectively.

[0136] Next, the operation of the optical device 10 according to this embodiment will be described.

[0137] The divergence angle of the light beam immediately after passing through each of the light direction selection regions R1, R2, and R3 on the focal plane f is larger than that of the light beam immediately before that. This allows the light beam that reaches the imaging optical element 14 to reach a wider area rather than a localized area of ​​the imaging optical element 14. This has the effect of widening the irradiation field F irradiated from the imaging optical element 14 onto the object plane O.

[0138] Furthermore, by using this embodiment, it is possible to instantly change the intensities of the first light source 121, the second light source 122, and the third light source 123 independently. That is, light of different wavelengths can be emitted from the first light direction selection region R1, the second light direction selection region R2, and the third light direction selection region R3, respectively, and the intensity ratio between them can be instantly adjusted. This has the effect of enabling the direction of light formed by the imaging optical element 14 to be distinguished by wavelength spectrum, and simultaneously enabling the intensity ratio between them to be instantly switched to a desired one.

[0139] As described above, the optical device 10 according to this embodiment makes it possible to associate a wavelength spectrum with a light intensity in relation to the direction of the light. The wavelength spectrum can be considered synonymous with the color of the light. Therefore, it can also be said that it is possible to associate a color with the direction of the light. This has the effect of enabling the association of color and intensity to be instantly changed in relation to the direction of the light according to various applications.

[0140] According to the present embodiment, there are provided an optical device 10 capable of changing the direction of at least a portion of light beam B1 emitted from the light emitting unit 12 to light beam B2 in a different direction to illuminate an object O, an optical inspection device 1 including the optical device 10, and an optical inspection system 100 including the optical inspection device 1. At this time, at least a portion of light beam B1 emitted from the light emitting unit 12 can be emitted as light beam B2 having optical properties different from that of light beam B1 according to a first light direction selection region R1 or a second light direction selection region R2. Furthermore, according to the present embodiment, there is provided an optical inspection method capable of changing the direction of at least a portion of light beam B1 emitted from the light emitting unit 12 to light beam B2 in a different direction to illuminate an object O. At this time, at least a portion of light beam B1 emitted from the light emitting unit 12 can be emitted as light beam B2 having optical properties different from that of light beam B1 according to the first light direction selection region R1 or the second light direction selection region R2.

[0141] (Variation) FIG. 18 shows a cross-sectional view of the optical device 10 according to this modified example, including the optical axis L. Light from the first light source 121, the second light source 122, and the third light source 123 is combined by a dichroic mirror 19. The dichroic mirror 19 may be a polarizing beam splitter or a non-polarizing beam splitter. Any device capable of combining two or more light beams may be used. When using a polarizing beam splitter, if a polarization camera capable of detecting polarization direction is used in the imaging unit 18 (see FIGS. 3, 6, and 19), polarization information can be used in the same way as color information, thereby obtaining a wealth of information regarding the directional distribution of light at an object point. By using two or more light sources, such as light sources 121, 122, and 123, a new wavelength spectrum with two spaced peaks can be generated after combining. This allows, for example, the first wavelength spectrum and the second wavelength spectrum to be significantly different, allowing accurate color distinction and more accurate and rapid acquisition of information regarding the directional distribution of light. Alternatively, the light intensities of two or more light sources 121, 122, and 123 can be adjusted independently and appropriately.

[0142] (Fourth embodiment) FIG. 19 shows a schematic cross-sectional view of the optical inspection device 1 according to this embodiment. The optical inspection device 1 according to this embodiment includes an optical device 10 and an imaging unit 18. Although not shown in FIG. 19, it is preferable that the image sensor 18a be connected to a control unit 20 (see FIGS. 3 and 6) of the optical inspection system 100. The control unit 20 can output color information for each pixel of the image acquired by the image sensor 18a.

[0143] The imaging unit 18 includes an image sensor 18a, an imaging optical element 18b, and an imaging aperture 18c. The imaging aperture 18c is disposed on or near the focal plane of the imaging optical element 18b.

[0144] The light emitting unit 12 includes an LD light source 120d and emits light of a first wavelength spectrum including at least a first wavelength. The light of the first wavelength is referred to as a first light ray B1. For example, the first wavelength spectrum is blue light having a peak at a wavelength of 450 nm and a full width at half maximum of 100 nm.

[0145] The light direction selecting unit 16 includes a diffuser 16a in the first light direction selecting region R1 and a phosphor 166a in the second light direction selecting region R2. The phosphor 166a converts light of a first wavelength into light of a second wavelength. A first light ray B1 having a first wavelength spectrum is emitted from the first light direction selecting region R1, and a second light ray B2 having a second wavelength spectrum different from the light of the first wavelength spectrum is emitted from the second light direction selecting region R2. That is, the light redirecting body 16a emits light of a first wavelength and light of a second wavelength different from the light of the first wavelength. The second wavelength spectrum has a peak at the second wavelength. The second wavelength is 650 nm, and the second light ray B2 is red light. However, this is not limited to this, and any wavelength spectrum may be used.

[0146] Furthermore, the second light direction selection region R2 of the light direction selecting unit 16 includes a phosphor 166b sandwiching the phosphor 166a between it and the first light direction selection region R1. The phosphor 166b converts light of the first wavelength into light of a third wavelength. As a result, in addition to a second light ray B2 having a second wavelength spectrum, a third light ray B3 having a third wavelength spectrum is emitted from the second light direction selection region R2. The third wavelength spectrum has a peak at a third wavelength. The third wavelength is 550 nm, and the third light ray B3 is green light. However, this is not a limitation, and any wavelength spectrum may be used.

[0147] The imaging optical element 14 is a Fresnel lens. Compared to other lenses, a Fresnel lens can achieve a large effective diameter even with a short focal length. This allows the angle of incidence of light rays reaching the Fresnel lens 14 from the focal plane f to be increased. Therefore, the Fresnel lens 14 has the effect of increasing the angle of incidence on the object plane S.

[0148] The light beam emitted from the light emitting unit 12 passes through the focal plane region Rf of the imaging optical element 14 and is irradiated onto the object surface S. At this time, the divergence angle of the light beam is set to the maximum inclination angle of the light rays B1 and B2 contained in the light beam with respect to the optical axis L. The wider the range that the light beam reaches on the Fresnel lens, which is the imaging optical element 14, the wider the irradiation field F. In other words, the phosphors 166a and 166b provided in the second light direction selection region R2 have the effect of widening the irradiation field F.

[0149] Hereinafter, the imaging optical element 18b for image pickup will also be referred to as the imaging optical element.

[0150] The imaging optical element 18b can form an image of light. The imaging optical element 18b may be, for example, a single lens, a compound lens composed of multiple lenses, a concave mirror, a diffraction grating, a gradient index lens (GRIN lens), or the like. In other words, anything that can form an image of light is acceptable. The plane on which a set of points at infinity are imaged by the imaging optical element 18b is referred to as the imaging focal plane f1. However, the imaging focal plane f1 may also be simply referred to as the focal plane. The imaging focal plane f1 and its vicinity are referred to as the imaging focal plane region or simply the focal plane region. The optical axis of the imaging optical element 18b is a straight line perpendicular to the imaging focal plane f1, and light emitted from a sufficiently distant point on this line is again imaged on this straight line. This image-forming point is referred to as the imaging focus. In this embodiment, the imaging optical element 18b is a compound lens. However, this is not limited to this.

[0151] The imaging aperture 18c is disposed on the imaging focal plane f1 of the imaging optical element 18b or in an imaging focal plane region nearby. A through-hole 18c1 is provided near the optical axis of the imaging aperture 18c, allowing light of the first wavelength, the second wavelength, and the third wavelength to pass through. Meanwhile, a medium that blocks light of the first wavelength, the second wavelength, and the third wavelength is provided around the through-hole of the imaging aperture 18c. In this case, based on geometric optics, the imaging unit 18 has object-side telecentricity for light of the first wavelength, the second wavelength, and the third wavelength. In other words, the imaging unit 18 has object-side telecentricity for light of at least one wavelength from the light source 120d.

[0152] The image sensor 18a is configured with pixels that can separate light of, for example, at least the first wavelength and the second wavelength out of light of a first wavelength, a second wavelength, and a third wavelength, and acquire light reception signals independently from each other. The image sensor 18a can distinguish between light of at least two wavelengths (the first wavelength, the second wavelength, and the third wavelength) and receive them as independent signals. For example, the image sensor 18a may be an area sensor or a line sensor. It may also be a single pixel. In other words, any sensor that has at least one color channel that can separate at least two wavelengths and can convert light into a light reception signal may be used. The light reception signal may also be simply referred to as a signal, a signal value, or a pixel value.

[0153] Next, the operation of the optical inspection device 1 according to this embodiment will be described.

[0154] Basically, the irradiation of light from the optical device 10 onto the object surface S is the same as that described in the fourth modified example of the second embodiment (FIG. 16), and therefore the description will be omitted where appropriate.

[0155] Assume that the standard surface of object O is flat and smooth. In this case, light incident on the standard surface is specularly reflected. Based on geometric optics, specular reflection occurs when the angle of incidence and the angle of reflection within the plane of incidence are equal, and there is a one-to-one correspondence between incident light rays and reflected light rays. On the other hand, assume that the object surface S has defects such as unevenness, dirt, or scratches. In this case, light incident on the defects is scattered and reflected in various directions. In other words, for one incident ray, reflected light rays are generated in various directions. The directional distribution of such reflected light rays can be described by BRDF.

[0156] The imaging optical element 14 in the optical device (illumination unit) 10 irradiates incident light that passes through an arbitrary point on the illumination focal plane f onto the object plane S. Here, based on geometric optics (Non-Patent Document 2), the angle of the light ray passing through the imaging optical element 14 with respect to the optical axis L is determined depending on the passing point on the focal plane f. In other words, all light emitted from the same passing point on the illumination focal plane f will have the same ray angle on the object plane S side. As a result, the first light ray B1 is incident on the object plane S at an angle θ with respect to the optical axis L, which is a first ray angle. Meanwhile, the second light ray B2 is incident on the object plane S at an angle θ with respect to the optical axis L, which is a second ray angle. The third light ray B3 is incident on the object plane S at an angle θ with respect to the optical axis L, which is a third ray angle. Here, the first ray angle < the second ray angle < the third ray angle. Here, the light of the first wavelength spectrum, the second wavelength spectrum, and the third wavelength spectrum are different colors. As a result, the optical device 10 can irradiate the object surface S with a bundle of rays having different angles for each color. In other words, the optical device 10 can irradiate the object surface S with rays having different angles of incidence for each color.

[0157] In this embodiment, the object surface S is illuminated using the optical device (illumination unit) 10 of the optical inspection device 1, and then the object surface S is imaged using the imaging unit 18 of the optical inspection device 1.

[0158] First, consider the case where the object surface S is a standard surface. In this case, as shown in Figure 19, a first light ray B1 is specularly reflected by the object surface S, passes through the beam splitter 19a and mirror 19b, passes through the through-hole of the imaging aperture 18c on the focal plane f1 of the imaging optical element 18b, and is imaged by the image sensor 18a. Here, the angle that the reflected light of the first light ray B1 makes with respect to the imaging optical axis L1 is defined as the first reflected ray angle. Furthermore, the mirror 19b may be any material that reflects light, and may be a beam splitter.

[0159] The second light ray B2 is specularly reflected from the object surface S, passes through beam splitter 19a and mirror 19b, and is intercepted by the medium of imaging aperture 18c on focal plane f1 of imaging optical element 18b. Here, the angle that the reflected light of second light ray B2 makes with respect to imaging optical axis L1 is defined as the second reflected ray angle. Similarly, the third light ray B3 is specularly reflected from the object surface S, passes through beam splitter 19a and mirror 19b, and is intercepted by the medium of imaging aperture 18c on focal plane f1 of imaging optical element 18b. Here, the angle that the reflected light of third light ray B3 makes with respect to imaging optical axis L1 is defined as the third reflected ray angle.

[0160] As a result, the second light ray B2 and the third light ray B3 do not reach the image sensor 18a of the imaging unit 18, and are not imaged. In other words, if the object surface S is a standard surface, an image is captured using only the light of the first wavelength, and not using the light of the second wavelength or the light of the third wavelength. In other words, the standard surface is captured using only blue light, and not using red or green light.

[0161] The image sensor 18a includes at least one color channel that can receive and convert light of a predetermined wavelength spectrum into a signal, where a first wavelength is included in the predetermined wavelength spectrum and a second wavelength is not included in the predetermined wavelength spectrum.

[0162] Next, consider the case where a defect exists on the object surface S. In particular, assume that a defect exists on the surface S where the first light ray B1 and the second light ray B2 reach. In this case, the first light ray B1 is scattered by the defect on the object surface S, causing the BRDF to spread. As a result, part of the scattered light passes through the beam splitter 19a and mirror 19b, passes through the through-hole of the imaging aperture 18c on the focal plane f1 of the imaging optical element 18b, and is then imaged by the image sensor 18a.

[0163] Meanwhile, the second light ray B2 is also scattered by a defect on the object surface S, causing the BRDF to spread. As a result, some of the scattered light passes through the beam splitter 19a and mirror 19b, passes through the through-hole of the imaging aperture 18c on the focal plane f1 of the imaging optical element 18b, and is then imaged by the image sensor 18a. In other words, if there is a defect on the object surface S, the defect will be imaged using light of the first wavelength and light of the second wavelength. In other words, the defect will be imaged using both blue and red light.

[0164] The image sensor 18a includes at least one color channel that can receive and convert light of a predetermined wavelength spectrum into a signal, where a first wavelength is included in the predetermined wavelength spectrum and a second wavelength is included in the predetermined wavelength spectrum.

[0165] Although detailed description is omitted, in this embodiment, it is assumed that not only the first light ray B1 and the second light ray B2 but also the third light ray B3 reach the surface S on which a defect exists. In this case, the image sensor 18a also images the defect using not only the light of the first wavelength and the light of the second wavelength but also the light of the third wavelength. In other words, the defect is imaged using blue light, red light, and green light.

[0166] The control unit 20 of the optical inspection system 100 can analyze the color information of the image acquired by the image sensor 18a to determine the presence or absence of defects on the object surface S based on the color of the captured image. Therefore, the control unit 20 of the optical inspection system 100 outputs the state of the surface S of the object O based on the image acquired by the image sensor 18a. On the other hand, if the imaging unit 18 does not have an imaging aperture 18c, it will be impossible to identify the presence or absence of such defects by color. This is because, without the imaging aperture 18c, light of all colors is captured by the image sensor 18a, regardless of the presence or absence of defects on the object O. Therefore, the optical inspection device 1 has object-side telecentricity for at least one wavelength of light from the light source 120d, thereby having the effect of being able to identify the presence or absence of defects.

[0167] In this embodiment, the imaging aperture 18c of the imaging unit 18 has a through-hole on the imaging optical axis L1, and a medium surrounding the through-hole. For example, FIG. 20 shows a modified example of the imaging unit 18. The optical device 10 is not shown in FIG. 20. Contrary to the example shown in FIG. 19, the imaging aperture 18c of the imaging unit 18 has a medium on the imaging optical axis L1 of the imaging unit 18, and a through-hole (space) surrounding the through-hole. The first wavelength is not included in a predetermined wavelength spectrum, and the second wavelength is included in the predetermined wavelength spectrum. That is, when the object surface S is a standard surface, the first light ray B1 is specularly reflected by the object surface S and blocked by the medium on the imaging optical axis L1 of the imaging aperture 18c at the focal plane f1 of the imaging optical element 18b. The second light ray B2 is specularly reflected by the object surface S and passes through the through-hole off the imaging optical axis L1 of the imaging aperture 18c to be imaged by the image sensor 18a. This means that the third light ray B3 is also imaged by the image sensor 18a in the same manner as the second light ray B2.

[0168] Therefore, by configuring the imaging aperture 18c as shown in the examples in Figures 19 and 20, for example, when the object plane S is a standard plane, the image sensor 18a can selectively receive light of the desired wavelength.

[0169] 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. A first light ray B1 passing through the first light direction selection region R1 is scattered by the minute irregularities into various light ray groups, some of which travel toward the observer. The scattered light ray group also has the same wavelength spectrum as the first light ray B1. Therefore, each ray of the scattered light ray group is treated as the first light ray B1. In this way, when the object surface S has minute irregularities, the observer observes the first light ray B1. At the same time, the second light ray B2 passing through the second light direction selection region R2 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 the second light ray B2. The second light ray B2 passing through the fourth light direction selection region R4 is also scattered by the minute asperities and heads toward the observer. Therefore, when there are minute asperities on the object surface S, the observer also observes the second light ray B2b. As a result, the observer observes not only the first light ray B1 but also the second light ray B2.

[0170] As a result of the above, if the object surface S is a smooth surface, the first light ray B1 passing through the first light direction selection region R1 will not be observed by the observer. Similarly, the first light ray B1 passing through the third light direction selection region R3 will not be observed by the observer. In other words, the smooth surface cannot be observed by the first light ray B1. However, the smooth surface can be observed by the second light ray B2 passing through the second light direction selection region R2 and the fourth light direction selection region R4.

[0171] However, if there are minute irregularities on the object surface S, not only the first light ray B1 passing through the first light direction selection region R1 but also the second light ray B2 passing through the second light direction selection region R2 and the second light ray B2 passing through the fourth light direction selection region R4 are observed. In other words, the minute irregularities can be observed not only by the first light ray B1 but also by the second light ray B2.

[0172] According to the present embodiment, there are provided an optical device 10 capable of changing the direction of at least a portion of light beam B1 emitted from the light emitting unit 12 to light beam B2 in a different direction to illuminate an object O, an optical inspection device 1 including the optical device 10, and an optical inspection system 100 including the optical inspection device 1. At this time, at least a portion of light beam B1 emitted from the light emitting unit 12 can be emitted as light beam B2 having optical properties different from that of light beam B1 according to a first light direction selection region R1 or a second light direction selection region R2. Furthermore, according to the present embodiment, there is provided an optical inspection method capable of changing the direction of at least a portion of light beam B1 emitted from the light emitting unit 12 to light beam B2 in a different direction to illuminate an object O. At this time, at least a portion of light beam B1 emitted from the light emitting unit 12 can be emitted as light beam B2 having optical properties different from that of light beam B1 according to the first light direction selection region R1 or the second light direction selection region R2.

[0173] (Fifth embodiment) The optical inspection device 1 according to this embodiment will be described in detail below with reference to FIG.

[0174] FIG. 21 shows a perspective view of this embodiment. The optical inspection device 1 according to this embodiment includes an illumination unit (optical device) 10 and an imaging unit 18. However, in FIG. 21, the light emission unit 12 of the illumination unit 10 is not shown. The first cross section C1 includes the optical axis L of the imaging optical element 14 of the illumination unit 10 and the imaging optical axis L1. The second cross section C2 is perpendicular to the first cross section C1. The basic configuration is the same as that of the fourth embodiment. The differences will be described below.

[0175] Hereinafter, the imaging optical element 14 of the illumination unit 10 will be referred to as an illumination optical element.

[0176] The illumination optical element 14 has translational symmetry in a direction perpendicular to the first cross section C1. This direction is defined as the longitudinal direction of the illumination optical element 14. The illumination optical element 14 is, for example, a cylindrical lens. The illumination optical axis L of the cylindrical lens 14 is on the first cross section C1.

[0177] The light output unit 12 includes a DLP projector 120c (see FIG. 16) which is a projection unit, and projects an image onto the focal plane region Rf of the illumination optical element 14. This illuminates the object surface S, forming an illumination field F. When this illumination light is projected onto the second cross section C2, it becomes divergent light.

[0178] The imaging unit 18 includes an imaging optical element 18b, an imaging aperture 18c, and an imaging element 18a. The imaging element 18a is an image sensor and is a line sensor. However, this is not limiting, and the imaging element 18a may also be an area sensor. The longitudinal direction of the line sensor 18a coincides with the longitudinal direction of the illumination optical element 14.

[0179] The imaging aperture 18c has a wavelength selection section. The wavelength selection section 18c has at least two (here, three) wavelength selection regions 180a, 180b, and 180c. The wavelength selection regions 180a, 180b, and 180c have translational symmetry in a direction perpendicular to the first cross section C1. This direction is defined as the longitudinal direction of the wavelength selection regions 180a, 180b, and 180c. The wavelength selection section 18c is composed of multiple wavelength selection regions 180a, 180b, and 180c arranged in a stripe pattern. The direction along which the wavelength selection regions 180a, 180b, and 180c change on the wavelength selection regions 180a, 180b, and 180c is defined as the arrangement direction. This arrangement direction is parallel to the first cross section C1. That is, the arrangement direction of the wavelength selection regions 180a, 180b, and 180c is perpendicular to the longitudinal direction of the line sensor 18a.

[0180] The object O is transported in a direction perpendicular to the longitudinal direction of the line sensor 18a. The line sensor 18a continuously captures images of the object O being transported in this manner, thereby obtaining a two-dimensional image.

[0181] The light beam emitted from the projection unit 120c passes through the light direction selection unit 16 and illuminates the object surface S, forming an illumination field F. Furthermore, if the first object point P has a micro defect, the BRDF spreads, and some of the light rays pass through the imaging aperture 18c to form an image of the first object point P on the line sensor 18a. On the other hand, if the first object point P is on a standard surface, the first light ray B1 having the first wavelength is specularly reflected by the standard surface. In this case, by appropriately forming the projection image from the projector 120c, the first light ray B1 can be made to reach the center of the imaging aperture 18c of the imaging unit 18. In other words, the first light ray B1 can be made to reach the area including the imaging optical axis L1. The wavelength selection region 180a, located at the center of the imaging aperture 18c, is designed to block light of the first wavelength. As a result, if the first object point P does not have a micro defect, the first object point P will not be imaged with light of the first wavelength.

[0182] On the other hand, if a micro defect exists at the first object point P, the first object point P is imaged with light of the first wavelength that passes through the wavelength selection regions 180b and 180c. This has the effect of making it possible to identify the presence or absence of a micro defect. In addition, information regarding the spread of the directional distribution of light (i.e., the BRDF) at the object point P can be obtained.

[0183] Furthermore, when the first object point P is located on a standard surface, a second light ray having a second wavelength different from the first wavelength is also specularly reflected by the standard surface. In this case, by appropriately forming a projected image using the projector 120c, the reflection direction of the second light ray B2 can be aligned with the reflection direction of the first light ray B1. As a result, the light ray having the second wavelength reaches the center of the imaging aperture 18c of the imaging unit 18. That is, it reaches the wavelength selection region 180a on the imaging aperture 18c, which includes the imaging optical axis L1. The wavelength selection region 180a, located at the center of the imaging aperture 18c, is designed to transmit light having the second wavelength. In this case, based on geometric optics, the imaging unit 18 has object-side telecentricity for the second wavelength. That is, it has object-side telecentricity for at least one wavelength of light from the light source 120c. This has the effect of enabling a bright-field telecentric image to be acquired using the second wavelength. That is, detailed information about the object surface S can be obtained in combination with the image captured using the first light ray B1.

[0184] Consider a light ray projected onto the first cross section C1. In this case, the distribution of the first BRDF expands, resulting in light reaching and passing through the wavelength-selective regions 180b and 180c that would not have been reached in the standard surface. Here, depending on the direction of the reflected light, it can be seen that the reflected light reaches different regions of the wavelength-selective regions 180b and 180c in the imaging aperture 18c. However, light rays that reach outside the medium of the imaging aperture 18c, outside the range of the imaging aperture 18c, are not incident on the imaging optical element 18b and are not imaged. In other words, the range of light ray directions that can be imaged is limited by the imaging aperture 18c. Meanwhile, consider a light ray projected onto the second cross section C2. Because the light from the illumination unit 10 is diffused light, the angle of view at the imaging unit 18 widens depending on the divergence angle of the diffused light. Furthermore, because the wavelength-selective regions 180a, 180b, and 180c are striped, it can be seen that the color of the light ray does not depend on the angle of view. Furthermore, by making the longitudinal direction of the stripe sufficiently long, there is an effect that the angle of view in the longitudinal direction of the line sensor 18a can be widely and effectively used. Furthermore, by arranging the wavelength selecting unit 18c in front of the line sensor 18a and the imaging optical element 18b of the imaging unit 18, this optical system including the line sensor 18a, the imaging optical element 18b, and the wavelength selecting unit 18c can be easily assembled for any imaging unit 18.

[0185] This embodiment provides information about the spread of the directional distribution of light at object point P. Another advantage is that the imaging field of view of imaging unit 18 can be widened as the longitudinal direction of line sensor 18a is increased. This makes it possible to inspect the properties or shape of object surface S.

[0186] According to the present embodiment, there are provided an optical device 10 capable of changing the direction of at least a portion of light beam B1 emitted from the light emitting unit 12 to light beam B2 in a different direction to illuminate an object O, an optical inspection device 1 including the optical device 10, and an optical inspection system 100 including the optical inspection device 1. At this time, at least a portion of light beam B1 emitted from the light emitting unit 12 can be emitted as light beam B2 having optical properties different from that of light beam B1 according to a first light direction selection region R1 or a second light direction selection region R2. Furthermore, according to the present embodiment, there is provided an optical inspection method capable of changing the direction of at least a portion of light beam B1 emitted from the light emitting unit 12 to light beam B2 in a different direction to illuminate an object O. At this time, at least a portion of light beam B1 emitted from the light emitting unit 12 can be emitted as light beam B2 having optical properties different from that of light beam B1 according to the first light direction selection region R1 or the second light direction selection region R2.

[0187] According to at least one of these embodiments, an optical device 10 can be provided that can change the direction of at least a portion of the light ray B1 emitted from the light emitting section 12 to a light ray in a different direction to illuminate an object O, an optical inspection system 100 that has the optical device 10, and an optical inspection method.

[0188] 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]

[0189] 1...optical inspection device, 10...optical device (illumination unit), 12...light emission unit, 120...point light source, 120a...surface light source, 120b...light source, 120c...projection unit (projector), 120d...LD light source, 121...light source (light source point), 121a...sealant, 122...light source (light source point), 122a...sealant, 123...light source, 123a...sealant, 124...laser light source, 1211...virtual rectilinear light, 1221...virtual rectilinear light, 14...imaging optical element, 16...light direction selection unit, 16a...light direction changer (light diffuser), 160a, 160b...light diffuser, 161...diffuser, 162, 163...phosphor, 165...side, 166a, 166b...phosphor, 167...aperture substrate, 168...coating layer, 17, 170...through hole, 17a...light shield, 18...imaging unit, 18a...image sensor, 18b...imaging optical element, 18c...imaging aperture, 180a, 180b, 180c...wavelength selection region, 20...control unit, 100...optical inspection system.

Claims

1. a light emitting portion; a light direction selection unit; and an imaging optical element, the light emitting unit emits a first light ray having a first wavelength spectrum including a first wavelength; The light direction selection unit includes a first light direction selection area and a second light direction selection area on or near a focal plane of the imaging optical element, The first light ray incident on the first light direction selection area or the second light direction selection area is emitted as a light ray with different optical properties depending on the area, and at least one of the areas is provided with a light direction changer that changes the direction of the incident light ray to a different one and emits it. optical equipment.

2. In claim 1, The light direction selecting unit has a diffuser disposed in at least one of the first light direction selecting area or the second light direction selecting area, which generates at least two light rays including a direction different from the direction of incident light and diffuses the light. optical equipment.

3. In claim 2, the diffuser is a wavelength-converting diffuser that converts light of the first wavelength into light of a second wavelength different from the first wavelength; The wavelength converting diffuser is disposed in the second light direction selective region, light of a second wavelength spectrum that is different from the light of the first wavelength spectrum and that includes the second wavelength is emitted from the second light direction selection region; optical equipment.

4. The light direction selection unit includes a phosphor plate having a through hole formed therein, a region where the through hole exists is defined as the first light direction selection region, and a region where the phosphor plate exists is defined as the second light direction selection region; 3. The optical device according to claim 1.

5. In claim 1 or claim 2, a light attenuator that attenuates light of a first wavelength is disposed in either the first light direction selection region or the second light direction selection region; optical equipment.

6. In claim 1, The imaging optical element is configured in an array of first imaging optical element elements and second imaging optical element elements, The light direction selecting unit includes a third light direction selecting area and a fourth light direction selecting area in addition to the first light direction selecting area and the second light direction selecting area, The first light direction selection area and the second light direction selection area are arranged opposite to the first imaging optical element, The third light direction selection area and the fourth light direction selection area are arranged facing the second imaging optical element. optical equipment.

7. The optical device according to claim 1 or 2; an imaging unit that captures an image illuminated by the optical device; Assume that it is equipped with The imaging unit An image sensor and an imaging optical element for imaging; an imaging aperture; Optical inspection equipment.

8. In claim 7, the light redirector emits light of the first wavelength and light of a second wavelength different from the light of the first wavelength; The image sensor has at least one color channel, and the color channel can receive light of a predetermined wavelength spectrum and convert it into a signal; the first wavelength is included in the predetermined wavelength spectrum; the second wavelength is not included in the predetermined wavelength spectrum; Optical inspection equipment.

9. In claim 7, the light redirector emits light of the first wavelength and light of a second wavelength different from the light of the first wavelength; The image sensor has at least one color channel, and the color channel can receive light of a predetermined wavelength spectrum and convert it into a signal; the first wavelength is included in the predetermined wavelength spectrum; the second wavelength is included in the predetermined wavelength spectrum; Optical inspection equipment.

10. In claim 7, the light redirector emits light of the first wavelength and light of a second wavelength different from the light of the first wavelength; The image sensor has at least one color channel, and the color channel can receive light of a predetermined wavelength spectrum and convert it into a signal; the first wavelength is not included in the predetermined wavelength spectrum; the second wavelength is included in the predetermined wavelength spectrum; Optical inspection equipment.

11. In claim 7, illuminating an object using the optical device; The image sensor has at least two different color channels, each of which can distinguish between light of a first wavelength and light of a second wavelength and receive the light as an independent signal. Optical inspection equipment.

12. The optical inspection device according to claim 7; a control unit that outputs the state of the surface of the object based on the image acquired by the image sensor; An optical inspection system comprising:

13. directing a first light beam of a first wavelength spectrum including a first wavelength toward an imaging optic; The first light ray incident on a first light direction selection region or a second light direction selection region of a light direction selection unit provided on the focal plane of the imaging optical element or a focal plane region nearby the focal plane is converted into a light ray with different optical properties depending on the region, and emitted in a direction different from the incident direction of the first light ray to illuminate an object. An optical inspection method comprising:

14. Obtaining information about the surface of the object from light emitted from the object by illuminating the object. The optical inspection method of claim 13 , comprising:

Images