Optical apparatus, optical inspection apparatus, optical inspection method, and optical inspection program

Abstract

To provide an optical device which can instantly change the correlation between the direction and the color of a beam of light according to various different applications.SOLUTION: According to an embodiment, the optical device includes: an illumination optical element having a focus surface or a focus surface region including areas in the vicinity of the focus surface; and a projection unit having a light source. The projection unit can emit a light flux which includes light with at least two different wavelength spectrums. The projection unit forms a projection image for projecting the light with two different wavelength spectrums in different positions in the focus point surface region of the illumination optical element.SELECTED DRAWING: Figure 1

Description

Technical Field

[0005] ,

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

Background Art

[0002] In various industries, non-contact inspection of objects is important. In the conventional method, there is a technique of identifying the direction of a light beam by corresponding the color (wavelength spectrum) of a light beam spectroscopically using a diffraction grating or a wavelength filter to the light beam direction one-to-one, and acquiring information on an object surface or inside the object by specifying the color.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Non-Patent Documents

[0004]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The problem that this invention aims to solve is to provide an optical device, an optical inspection device, an optical inspection method, and an optical inspection program that can associate the direction of a ray (direction of a light beam) with the wavelength spectrum. [Means for solving the problem]

[0006] According to the embodiment, the optical device comprises an illumination optical element having a focal plane region including the focal plane or its vicinity, and a projection unit equipped with a light source. The projection unit can emit a luminous beam from the light source containing light of at least two different wavelength spectra. The light beam from the light source is imaged on the projection surface, which is the focal plane or the area of ​​the focal plane. In the focal plane region of the illumination optical element, a projected image is formed by projecting light of two different wavelength spectra onto different positions. Light emitted from the same point of passage on the projection surface is given the same ray angle by the illumination optical element. When a light beam with the first ray from the light source of the projection unit as the principal ray is imaged onto the projection surface, all the rays contained in that beam become parallel light beams with the same ray angle by the illumination optical element and are irradiated onto the object surface. [Brief explanation of the drawing]

[0007] [Figure 1] A schematic diagram showing the optical apparatus of an optical inspection apparatus according to the first embodiment. [Figure 2] Figure 1 shows the virtual projected image of the optical device of the optical inspection apparatus, viewed from the projection unit side. [Figure 3] Figure 1 shows a modified example of the virtual projection image of the optical device of the optical inspection apparatus, viewed from the projection unit side. [Figure 4] A modified example of the virtual projected image, different from that shown in Figure 3 of the optical device, as seen from the projection unit side. [Figure 5] A modified example of the virtual projected image, different from that shown in Figures 3 and 4 of the optical device, as seen from the projection unit side. [Figure 6] A schematic diagram showing a modified example of the optical apparatus of the optical inspection apparatus according to the first embodiment. [Figure 7] A schematic diagram showing an optical inspection apparatus according to the second embodiment. [Figure 8] A flowchart of the optical inspection process of an object surface using an optical inspection apparatus according to the second embodiment. [Figure 9] A schematic diagram showing the imaging side from the object surface of the optical device of an optical inspection apparatus according to a modified example of the second embodiment. [Figure 10]Schematic diagram showing the optical device of the optical inspection apparatus according to the third embodiment. [Figure 11] Schematic diagram of the projected image on the projection surface from the projection unit of the optical device according to the first modification of the third embodiment towards the illumination lens. [Figure 12] Schematic diagram of the projected image on the projection surface from the projection unit of the optical device according to the second modification of the third embodiment towards the illumination lens. [Figure 13] Schematic diagram showing the optical device of the optical inspection apparatus according to the fourth embodiment. [Figure 14] Schematic diagram showing the optical device of the optical inspection apparatus according to the first modification of the fourth embodiment. [Figure 15] Schematic perspective view showing the optical device of the optical inspection apparatus according to the fifth embodiment.

Embodiments for Carrying Out the Invention

[0008] Hereinafter, each embodiment will be described with reference to the drawings. The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the ratio of the sizes between parts, etc. are not necessarily the same as the actual ones. Also, even when representing the same part, the dimensions and ratios may be represented differently depending on the drawings. In the present specification and each figure, the same reference numerals are given to the same elements as those described above with respect to the previously presented figures, and the detailed description will be omitted as appropriate.

[0009] (First Embodiment) Hereinafter, the optical inspection apparatus 10 according to the present embodiment will be described in detail with reference to the drawings.

[0010] In this specification, light is a kind of electromagnetic wave and is assumed to include gamma rays, X-rays, ultraviolet rays, visible light, infrared rays, radio waves, etc. In the present embodiment, light is assumed to be visible light, and for example, the wavelength is in the range of 400 nm to 750 nm.

[0011] FIG. 1 shows a schematic cross-sectional view of an optical device 12 of an optical inspection device 10 according to the present embodiment, and a virtual projection (projection) image PI formed by the optical device 12. In this specification, projection and projection are used in the same meaning. The optical device 12 according to the present embodiment in FIG. 1 omits the illustration of the imaging unit 26 (see FIG. 7 of the second embodiment). Therefore, the optical device 12 here will be described as a device that can be mainly used as an illumination device that irradiates the surface OS of an object with light of a desired color at an appropriate angle obliquely or perpendicularly.

[0012] The optical device 12 according to the present embodiment includes a projection (projection) unit 22 and an illumination optical element 24.

[0013] The projection unit 22 includes a light source 32 and can emit light of at least two different wavelength spectra simultaneously. These wavelength spectra are respectively referred to as the first wavelength spectrum and the second wavelength spectrum. For example, the first wavelength spectrum is blue light with a peak wavelength of 450 nm and a full width at half maximum of 100 nm. The second wavelength spectrum is, for example, red light with a peak wavelength of 650 nm and a full width at half maximum of 100 nm. However, it is not limited to this, and any wavelength spectrum emitted from the light source 32 may be used.

[0014] The projection unit 22 can form an image on the projection surface PP by imaging the light beams emitted simultaneously from the light source 32 and form various images. Here, imaging means collecting the light beams from a certain point to another point. The point of the imaging source is called the object point, and the point of the imaging destination is called the image point. Projection is to form an image by the set of image points formed by such imaging. From the projection unit 22, the first light ray L1 having the first wavelength spectrum is projected onto the projection surface PP, and the second light ray L2 having the second wavelength spectrum is projected onto another point on the projection surface PP. The image projected by the projection unit 22 is called a projection image PI.

[0015] The illumination optical element 24 is capable of imaging light. The illumination optical element 24 can be, for example, a single lens, a lens assembly composed of multiple elements, a concave mirror, a diffraction grating, a refractive index gradient lens (GRIN lens), etc. In other words, the illumination optical element 24 can be anything that can image light. The illumination focal plane FP1 is defined as the plane on which a set of points at infinity is imaged by the illumination optical element 24. However, the illumination focal plane FP1 is sometimes simply called the focal plane. The illumination focal plane FP1 and its vicinity are called the illumination focal plane region FP1A, or simply the focal plane region. The optical axis C1 of the illumination optical element 24 is a straight line perpendicular to the focal plane FP1, and light emitted from a point on that line is imaged again on that line. In this embodiment, the illumination optical element 24 is, for example, a Fresnel lens. Compared to other lenses, the Fresnel lens 24 can realize a lens with a large effective diameter even with a short focal length. This allows for a large incident angle of light rays reaching the Fresnel lens 24 from the illumination focal plane FP1. Therefore, using a Fresnel lens as the illumination optical element 24 has the effect of increasing the angle of incidence to the object surface OS. However, the illumination optical element 24 is not limited to this, and various optical elements that form an image of light can be used.

[0016] Object O may be either light-transmitting or light-reflecting. Alternatively, object O may be semi-transparent. A point on the surface of object O or within the object is called an object point. In the following, unless otherwise specified, object O is assumed to be light-reflecting, and object points are assumed to be on the surface of object O. The surface of object O is sometimes called the object surface or object plane. However, strictly speaking, the object surface is the surface belonging to the object, while the object plane refers to the surface illuminated by illumination. Hereafter, the symbol OS will be used to denote the object surface or object plane.

[0017] The light beam emitted from the projection unit 22 passes through the illumination focal plane region FP1A of the illumination optical element 24, passes through the illumination optical element 24, and irradiates the object surface OS. The divergence angle of the light beam is defined as the angle of maximum spread of the light rays contained in the light beam with respect to the optical axis C1. The divergence angle of the light beam immediately after passing through the illumination focal plane FP1 is defined as the first divergence angle α1, and the divergence angle of the light beam immediately before incidence onto the illumination focal plane FP1 is defined as the second divergence angle α2. However, the light beam from the projection unit 22 may also be a focused light beam (focused beam). In this case, the second divergence angle α2 is set to 0.

[0018] The projection unit 22 can change the light emitted from the light source 32 at the same time, and instantly change (transform) the virtual projected image PI. For example, the projection unit 22 may be a color projector. There are various types of projectors, but for example, a device that uses DLP (Digital Lighting Processing) or liquid crystal optical elements to project images at enlargement, reduction, or 1:1 scale may be used. These projectors as the projection unit 22 can electrically switch the projected image instantaneously. Alternatively, the projection unit 22 may be a slide projector that projects slides, or an overhead projector (OHP) that projects images written on a transparent sheet. However, these projection units 22 must be able to mechanically switch the projected image instantaneously. In this embodiment, the projection unit 22 is, for example, a DLP projector. However, the projection unit 22 is not limited to this, and various types can be used.

[0019] Next, the operation of the optical device 12 of the optical inspection apparatus 10 according to this embodiment will be described.

[0020] The light beam emitted from the projection unit 22 forms a projected image PI on the projection surface PP. However, the image is formed in an atmospheric environment. To emphasize this situation, the projected image PI on the projection surface PP will also be called a virtual projected image. The position of the projection surface PP determined by the projection unit 22 is the focal plane region FP1A of the illumination optical element 24. In other words, the projection surface PP is positioned in the focal plane region FP1A. Therefore, the projection unit 22 images the light beam from the light source 32 at the focal plane FP1 or the focal plane region FP1A.

[0021] The virtual projected image PI has a first virtual region PIA1 and a second virtual region PIA2. The first virtual region PIA1 is formed when a light beam with a first ray L1 having a first wavelength spectrum as its principal ray is imaged onto the projection surface PP. The second virtual region PIA2 is formed when a light beam with a second ray L2 having a second wavelength spectrum as its principal ray is imaged onto the projection surface PP. The first virtual region PIA1 is formed so as to intersect with the optical axis C1 on the projection surface PP. The second virtual region PIA2 is formed so as not to intersect with the optical axis C1 on the projection surface PP. However, the virtual projected image PI is not limited to this, and any method is acceptable as long as the first virtual region PIA1 and the second virtual region PIA2 can be optically separated on the projection surface PP. Preferably, the virtual projected image PI is formed by dividing appropriate areas PIA1 and PIA2 on the projection surface PP with light of wavelengths that can be spectrally separated by the imaging unit 26, such as RGB. The first virtual region PIA1 and the second virtual region PIA2 of the virtual projected image PI projected by the projection unit 22 may be formed as shown in Figure 2 when viewed from the projection unit 22 side towards the illumination optical element 24 side. That is, on the projection surface PP, the first virtual region PIA1 and the second virtual region PIA2 of the virtual projected image PI are adjacent to each other in a rectangular shape. However, this is not limited to this, and the virtual projected image can be anything. Instantaneously changing the virtual projected image PI by the projection unit 22 also includes changing the scale of the first virtual region PIA1 and the second virtual region PIA2 of such a virtual projected image PI.

[0022] The first virtual region PIA1 and the second virtual region PIA2 of the virtual projected image PI projected by the projection unit 22 may, when viewed from the projection unit 22 side towards the illumination optical element 24 side, be rotationally symmetric with respect to the optical axis C1 of the illumination optical element 24 as shown in Figure 3, or they may be arranged in a stripe pattern as shown in Figure 4, or they may be formed radially as shown in Figure 5. In other words, the virtual projected image PI can have any shape as long as at least the first virtual region PIA1 and the second virtual region PIA2 can be partitioned. Furthermore, the projection unit 22 can change these virtual projected images PI shown in Figures 2 to 5 over time. The projection unit 22 projects, for example, predetermined projected images PI over time, either sequentially or randomly, at an appropriate frame rate of the image sensor 56 of the imaging unit 26. For this reason, the number of projected images PI per unit time that the projection unit 22 projects over time onto the projection surface PP can be set as appropriate. In this way, the image acquired by the imaging unit 26 changes according to the projected image PI onto the projection surface PP. In other words, the imaging unit 26 can obtain one or more images for inspecting the presence or absence of defects on the object surface OS, depending on the projected image PI.

[0023] In the example shown in Figure 3, the optical axis C1 of the illumination optical element 24 intersects with the first virtual region PIA1, while in the examples shown in Figures 4 and 5, the optical axis C1 of the illumination optical element 24 intersects with, for example, one of the three first virtual regions PIA1 and one of the three second virtual regions PIA2.

[0024] In this embodiment, the virtual projected image PI shown in Figures 1 and 2 is projected onto the projection surface PP.

[0025] The divergence angle of the light beam immediately after passing through the focal plane region FP1A is larger than that of the light beam immediately before. This is because the projection unit 22 forms an image of the projected image PI in the focal plane region FP1A. In other words, the projection unit 22 can make the divergence angle immediately after the light beam from the light source 32 passes through the focal plane FP1 or the focal plane region FP1A larger than the divergence angle immediately before passing through the focal plane FP1 or the focal plane region FP1A. As a result, the first divergence angle α1 is larger than the second divergence angle α2. This allows the light beam reaching the illumination optical element 24 to reach a wider area rather than just a local area of ​​the illumination optical element 24. Therefore, when using the optical device 12 according to this embodiment, there is an effect of widening the illumination field irradiated from the illumination optical element 24 onto the object surface OS.

[0026] The illumination optical element 24 irradiates the object surface OS with light that passes through any point on the illumination focal plane FP1. Here, based on geometrical optics (see Non-Patent Literature 2), the angle of the illumination optical element 24 with respect to the optical axis C1 is determined according to the point of passage on the illumination focal plane FP1. In other words, light emitted from the same point of passage on the projection surface PP or the illumination focal plane FP1 all have the same ray angle due to the illumination optical element 24. As a result, when a light beam with the first ray L1 as the principal ray is imaged on the projection surface PP, all the rays contained in that light beam become parallel light beams with the same ray angle due to the illumination optical element 24 and irradiate the object surface OS. As a result, the first ray L1 is incident on the object surface OS with an angle of first ray angle β1 with respect to the optical axis C1. Similarly, when a light beam with the second ray L2 as the principal ray is imaged onto the projection plane PP, all the rays contained in that beam are illuminated by the illumination optical element 24 as parallel beams with the same ray angle, illuminating the object plane OS. As a result, the second ray L2 is incident on the object plane OS with an angle β2 relative to the optical axis C1.

[0027] The first divergence angle α1 is larger than the second divergence angle α2. On the other hand, as the projection image PI is changed and the first divergence angle α1 is gradually reduced, bringing the outer edge of the second virtual region PIA2, which is far from the optical axis C1, closer to the optical axis C1, the number of points on the illumination field irradiated from the illumination optical element 24 onto the object surface OS that have a reduced variety of incident ray angles increases. In other words, by making the first divergence angle α1 larger than the second divergence angle α2, it is possible to increase the variety of incident ray angles at points on the illumination field irradiated from the illumination optical element 24 onto the object surface OS.

[0028] Furthermore, the light from the first wavelength spectrum and the light from the second wavelength spectrum have different colors. This allows the optical device 12 to irradiate the object surface OS with beams of light with different ray angles for each color. In other words, the optical device 12 can irradiate the object surface OS with light rays at different incident angles for each color.

[0029] The directional distribution of reflected light from an object's surface OS changes depending on the surface properties and shape of the object's surface OS. This directional distribution is described by the Bidirectional Reflectance Distribution Function (BRDF). Generally, the BRDF can be used to estimate the surface properties and shape of an object's surface OS, i.e., object surface information. This BRDF significantly influences the image captured by the imaging unit 26 (see Figure 7). Conversely, the image captured by the imaging unit 26 contains information about the BRDF.

[0030] The BRDF of the surface OS of an object changes depending on the angle of incidence of the incident light. In other words, two BRDFs for two different incident angles contain more information than a BRDF for a single incident angle. The more information available about the BRDF, the more detailed the state of the surface OS of the object can be estimated. The projection unit 22 of the optical device 12 according to this embodiment can change the virtual projected image PI in various ways, thereby instantaneously changing the angle of incidence to the surface OS of the object. Then, by observing the reflected light with, for example, the imaging unit 26 each time, it is possible to obtain a more detailed surface state of the object.

[0031] Furthermore, for example, the imaging unit 26 projects images PI of different colors onto multiple virtual regions PIA1 and PIA2, appropriately partitioned on the projection surface PP, and when light rays with different incidence angles for each color are incident on the surface OS of an object, the reflected light corresponding to each incidence angle can be distinguished by color and acquired simultaneously. In other words, the optical device 12 according to this embodiment can convert at least two different wavelength spectra into light rays with different incidence angles. Therefore, for example, the imaging unit 26 has the effect of being able to distinguish by color and acquire reflected light corresponding to each incidence angle simultaneously. As a result, for example, the imaging unit 26 has the effect of being able to acquire more detailed BRDF information of the surface OS of an object. This is particularly useful in optical inspection, as it contributes to improving both the inspection speed and accuracy of the surface OS of an object.

[0032] According to this embodiment, in the image captured by the image sensor 56 of the imaging unit 26, which will be described later, the flat portion of the object surface OS is expected to be predominantly colored by light at the first ray angle β1 (blue light). On the other hand, in the image captured by the image sensor 56 of the imaging unit 26, the color of the defective portion of the object surface OS changes depending on the tilt angle of the defect, but may be predominantly colored by light at the second ray angle β2 (red light), or a mixture of the light at the first ray angle β1 and the light at the second ray angle β2. For example, the smaller the tilt angle of the defect, the more the image is acquired as the color of the optical axis C1 or a region close to the optical axis C1 in the virtual projection image PI projected onto the focal plane FP1 of the illumination optical element 24, and the larger the tilt angle, the more the image is acquired as the color of a region farther from the optical axis C1 in the virtual projection image PI projected onto the focal plane FP1 of the illumination optical element 24.

[0033] In particular, in optical inspection, it is necessary to select the optimal direction of light rays illuminating the surface OS of an object depending on the type of object O. Conventionally, this required, for example, the preparation of various types of ring illumination (oblique incidence illumination). However, using the optical device (illumination device) 12 according to this embodiment has the effect of changing the incident angle of the light rays by instantly changing the virtual projection image PI. In other words, by using one optical device 12 according to this embodiment, it becomes possible to selectively use various types of illumination devices of various sizes with a single device.

[0034] The optical device 12 according to this embodiment can be fitted with various projection units 22. Therefore, the optical device 12 has the advantage of being able to select a wide range of commercially available projection units 22 that can form a virtual projected image PI in a predetermined area FP1A (including the projection surface PP and the illumination focal plane FP1). In addition, the optical device 12 has the advantage of being able to use commercially available projection units 22 without modification.

[0035] The optical device 12 according to this embodiment comprises an illumination optical element 24 having a focal plane FP1 or a focal plane region FP1A including its vicinity, and a projection unit 22 equipped with a light source 32. The projection unit 22 can emit a light beam containing at least two different wavelength spectra from the light source 32 onto the illumination optical element 24. The projection unit 22 also projects the two different wavelength spectra of light onto different positions on the focal plane FP1 or focal plane region FP1A of the illumination optical element 24, forming a projected image PI. Therefore, the optical device 12 of the optical inspection device 10 according to this embodiment makes it possible to associate the direction of a light ray (direction of the light beam) with the wavelength spectrum. Wavelength spectrum can be considered synonymous with the color of a light ray. Therefore, it can also be said that the optical device 12 makes it possible to associate the direction of a light ray with the color of a light ray.

[0036] Furthermore, the projection unit 22 of the optical device 12 of the optical inspection apparatus 10 according to this embodiment can instantly change the virtual projected image PI. Therefore, the optical device 12 according to this embodiment has the effect of instantly changing the correspondence between the direction of the light rays and the color of the light rays according to various applications.

[0037] (modified version) A modified example of the first embodiment will be described with reference to Figure 6.

[0038] In a modified example of this embodiment shown in Figure 6, a schematic cross-sectional view of the optical device 12 of the optical inspection apparatus 10 and the virtual projected image PI formed by the optical device 12 is shown. The virtual projected image PI shown in Figure 6 is perpendicular to the optical axis C1. In this modified example, the first wavelength spectrum and the second wavelength spectrum are the same as those described in the third embodiment.

[0039] In this modified example, a black light-shielding region PIA0 is formed on the optical axis C1 of the illumination optical element 24, at and near the illumination focal plane FP1. The light-shielding region PIA0 may be actual or virtual. If it is virtual, it is preferable that light from the light source 32 does not illuminate the light-shielding region PIA0. If it is virtual, the size and shape of the light-shielding region PIA0 can be electrically changed.

[0040] Next, the operation of the optical device 12 of the optical inspection apparatus 10 according to this modified example will be described.

[0041] The light beam emitted from the projection unit 22 forms a virtual projection image PI on the projection surface PP.

[0042] The virtual projection image PI has a 0th virtual region (light-shielding region) PIA0, a 1st virtual region PIA1, and a 2nd virtual region PIA2.

[0043] The first virtual region (light-shielding region) PIA0 is formed so as to intersect with the optical axis C1 of the illumination optical element 24 on the projection plane PP.

[0044] The first virtual region PIA1 is formed when a light beam with a first ray L1 having a first wavelength spectrum as its principal ray is imaged onto the projection surface PP. The first virtual region PIA1 is formed so as not to intersect with the optical axis C1 on the projection surface PP. The second virtual region PIA2 is formed when a light beam with a second ray L2 having a second wavelength spectrum as its principal ray is imaged onto the projection surface PP. The second virtual region PIA2 is formed so as not to intersect with the optical axis C1 on the projection surface PP.

[0045] When a light beam with the first ray L1 as the principal ray is imaged onto the projection surface PP, all the rays contained in that light beam are converted into parallel beams with the same ray angle by the illumination optical element 24, depending on the position on the projection surface PP, and illuminate the object surface OS. As a result, the first ray L1 is incident on the object surface OS with an angle of first ray angle β1 with respect to the optical axis C1. Similarly, when a light beam with the second ray L2 as the principal ray is imaged onto the projection surface PP, all the rays contained in that light beam are converted into parallel beams with the same ray angle by the illumination optical element 24, depending on the position on the projection surface PP, and illuminate the object surface OS. As a result, the second ray L2 is incident on the object surface OS with an angle of second ray angle β2 with respect to the optical axis C1.

[0046] In this case, only the light beam with the first ray L1 as the principal ray and the light beam with the second ray L2 as the principal ray can be incident on the object surface OS. In other words, only the oblique incidence component can be incident. To put it another way, by forming a light-shielding region PIA0 with the 0th virtual region (light-shielding region) PIA0, oblique incidence illumination can be achieved with the light beam with the first ray L1 as the principal ray and the light beam with the second ray L2 as the principal ray. As a result, only the component scattered by the object surface OS can be imaged, enabling dark-field imaging.

[0047] However, the virtual projected image PI is not limited to this and can be anything. The virtual projected image PI projected by the projection unit 22 may be, for example, rotationally symmetric with respect to the optical axis C1 of the illumination optical element 24, may be striped, or may be radial. In other words, the virtual projected image PI can have any shape.

[0048] From the above, the optical device 12 of the optical inspection apparatus 10 according to this modified example makes it possible to associate the direction of the light ray (direction of the light beam) with the wavelength spectrum. Furthermore, the projection unit 22 of the optical device 12 can instantly change the virtual projected image PI. For example, on the projection surface PP, each region PIA0, PIA1, and PIA2 can be stretched or contracted in an appropriate direction. Therefore, the optical device 12 according to this modified example has the effect of instantly changing the association between the direction of the light ray and the color of the light ray according to various applications.

[0049] (Second Embodiment) Figure 7 shows a schematic cross-sectional view of the optical device 12 and the virtual projection image PI formed by the optical device 12 of the optical inspection apparatus 10 according to the second embodiment. The optical inspection apparatus 10 according to this embodiment includes the optical device 12 and the processing device 14.

[0050] The optical device 12 of the optical inspection apparatus 10 according to this embodiment comprises a projection unit 22, an illumination optical element 24, and an imaging unit 26. Of the optical device 12 of the optical inspection apparatus 10 according to this embodiment, the projection unit 22 and the illumination optical element 24 have the same configuration as the projection unit 22 and illumination optical element 24 of the optical device 12 described in the first embodiment. For this reason, the description of the projection unit 22 and the illumination optical element 24 of the optical device 12 will be omitted as appropriate.

[0051] The projection unit 22 can instantly change (transform) the virtual projected image PI. Object O is opaque and reflects light on its surface. However, it is not limited to this; the object may be transparent or semi-transparent. The surface of the object is referred to as the object surface OS.

[0052] In Figure 7, the illumination system, which illuminates the object surface OS using the projection unit 22, is depicted to the left of the object surface OS, and the imaging system, which uses the light reflected from the object surface OS to capture images using the imaging unit 26, is depicted simultaneously to the right of the object surface OS. In other words, the optical device 12 in Figure 7 is depicted with the illumination side (illumination system) and imaging side (imaging system) simultaneously on the left and right sides, with the object surface OS as the boundary. However, in reality, the light reflected from the object surface OS returns in the direction of the projection unit 22. Therefore, it is necessary to place a beam splitter 26a, shown by a dashed line, between the illumination optical element 24 and the object surface OS to guide the light reflected from the object surface OS to the imaging unit 26, also shown by a dashed line in Figure 7. That is, in Figure 7, the imaging unit 26, shown by a dashed line, is schematically depicted to the right of the object surface OS. Note that the object O in Figure 7 also has a suitable thickness, but the thickness is ignored in the depiction.

[0053] The first wavelength spectrum emitted from the light source 32 of the projection unit 22 is blue light with a peak at 450 nm and a full width at half maximum (FMAX) of 100 nm. That is, the first wavelength is included in the first wavelength spectrum and is the peak of the first wavelength spectrum. The second wavelength spectrum emitted from the light source 32 is red light with a peak at 650 nm and a full width at half maximum (FMAX) of 200 nm. That is, the second wavelength is included in the second wavelength spectrum and is the peak of the second wavelength spectrum. However, the first and second wavelengths are different from each other and can be any wavelengths included in the first and second wavelength spectra, respectively. Furthermore, the wavelength spectrum generated from the light source 32 is not limited to these and can be any. Here, it is assumed that the FMAX of the second wavelength spectrum is 200 nm and overlaps with the first wavelength spectrum. Thus, the first and second wavelength spectra may overlap. As explained in the first embodiment, if the full width at half maximum of the second wavelength spectrum is 100 nm, the region overlapping with the first wavelength spectrum becomes small. Therefore, the first wavelength spectrum and the second wavelength spectrum may or may not overlap.

[0054] The imaging unit 26 includes an imaging optical element 52, an imaging aperture 54, and an image sensor 56.

[0055] The imaging optical element 52 is capable of forming an image of light. The imaging optical element 52 can be, for example, a single lens, a lens assembly composed of multiple elements, a concave mirror, a diffraction grating, a refractive index gradient lens (GRIN lens), etc. In other words, the imaging optical element 52 can be anything that can form an image of light. The imaging focal plane FP2 is defined as the plane on which a set of points at infinity is imaged by the imaging optical element 52. However, the imaging focal plane FP2 is sometimes simply called the focal plane. The imaging focal plane FP2 and its vicinity are called the imaging focal plane region FP2A or simply the focal plane region. The optical axis C2 of the imaging optical element 52 is a straight line perpendicular to the imaging focal plane FP2, and light emitted from a point on that line is imaged again on that line. In this embodiment, the imaging optical element 52 is a lens assembly. However, the imaging optical element 52 is not limited to this, and various optical elements that form an image of light can be used.

[0056] The imaging aperture 54 is positioned in the focal plane region FP2A of the imaging optical element 52. The imaging aperture 54 is, for example, ring-shaped, and a through-hole 54a is provided near the optical axis C2 of the imaging aperture 54, allowing light of a first wavelength and a second wavelength to pass through. On the other hand, a medium (light-shielding body) 54b is provided around the through-hole 54a of the imaging aperture 54 to shield light of the first wavelength and the second wavelength. In this case, based on geometrical optics, the imaging unit 26 will have object-side telecentricity with respect to the first wavelength and the second wavelength. In other words, the imaging unit 26 of the optical device 12 of the optical inspection device 10 will have object-side telecentricity with respect to at least one wavelength of light from the light source 32.

[0057] The image sensor 56 has pixels that can spectrally separate at least a first wavelength and a second wavelength of light and independently acquire a received light signal for each. Therefore, the imaging unit 26 is capable of spectrally separating at least two different wavelengths contained in at least two different wavelength spectra of light from the light source 32. The image sensor 56 may be an area sensor or a line sensor. The image sensor 56 may also be a single pixel. In other words, the image sensor 56 can be anything that can spectrally separate at least two wavelengths and convert light into a received light signal. The received light signal of the image sensor 56 is also sometimes simply called the signal, signal value, or pixel value.

[0058] Furthermore, the image sensor 56 of the imaging unit 26 is connected to the processing unit 14 by wire or wireless connection. Preferably, the processing unit 14 controls not only the image sensor 56 of the imaging unit 26 but also the light source 32 of the projection unit 22.

[0059] The processing unit 14 includes a processor 62 for acquiring images captured by the imaging unit 26 and performing image processing on the acquired images, and a storage device 64 for saving the images, for example.

[0060] The processor 62 may be a CPU or GPU, but it can be any element capable of performing calculations (such as the inspection process of the object surface OS shown in Figure 8), as described later. The processor 62 corresponds to the central part of the computer that performs calculations and control necessary for the processing of the processing unit 14, and comprehensively controls the entire processing unit 14. The processor 62 executes control to realize various functions of the processing unit 14 based on programs such as system software, application software, or firmware stored in a storage device 64, such as a ROM or auxiliary storage device. The processor 62 may include, for example, a CPU (central processing unit), an MPU (micro processing unit), a DSP (digital signal processor), an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a GPU (graphics processing unit). Alternatively, the processor 62 may be a combination of several of these. The processing unit 14 may have one processor 62 or multiple processors 62.

[0061] The processing unit 14 performs various functions by causing the processor 62 to execute programs stored in the storage device 64. The control program for the processing unit 14 is not stored in the processing unit 14's storage device 64, but is preferably located on an appropriate server or cloud. In this case, the control program is executed while communicating with the processor 62, for example, of the optical inspection device 10, via a communication interface. That is, the processing unit 14 according to this embodiment may be located in the optical inspection device 10, or it may be located on a server or cloud of a system in various inspection facilities, separate from the optical inspection device 10. Therefore, it is also preferable that the optical inspection program resides on a server or cloud rather than being stored in the storage device 64, and that the program is executed while communicating with the processor 62, for example, of the optical inspection device 10, via a communication interface. Consequently, the processor 62 (processing unit 14) can execute the optical inspection program (optical inspection algorithm) described later.

[0062] The processor 62 (processing unit 14) controls the light emission timing of the light source 32 of the projection unit 22, the timing of image data acquisition by the image sensor 56, and the acquisition of image data from the image sensor 56, and can also perform appropriate image processing on a given image.

[0063] Furthermore, the storage device 64 can be, for example, an HDD or SSD, but anything that can store (save) images will do.

[0064] Next, the operation of the optical inspection apparatus 10 according to this embodiment will be described.

[0065] Assume that the standard plane of an object's surface OS is planar and smooth. In this case, light incident on the standard plane is specularly reflected. According to geometrical optics, specular reflection means that the angle of incidence and the angle of reflection are equal within the incident plane, and the incident ray and the reflected ray can be correlated one-to-one. On the other hand, assume that the object's surface OS has defects such as irregularities, dirt, or scratches. Then, light incident on the defects is scattered and reflected in various directions. In other words, for a single incident ray, reflected rays in various directions are generated. The directional distribution of such reflected rays can be described by BRDF.

[0066] The processor 62 of the processing unit 14 controls the light source 32 of the projection unit 22, causing the light source 32 of the projection unit 22 to emit light in a predetermined direction. The light beam emitted from the projection unit 22 forms a projected image PI on the projection surface PP.

[0067] As described above, the virtual projection image PI has a first virtual region PIA1 and a second virtual region PIA2 that are adjacent to each other. The first virtual region PIA1 is formed when a light beam whose principal ray is a first ray L1 having a first wavelength spectrum is imaged onto the projection surface PP. The second virtual region PIA2 is formed when a light beam whose principal ray is a second ray L2 having a second wavelength spectrum is imaged onto the projection surface PP. When the light beam whose principal ray is the first ray L1 is imaged onto the projection surface PP, all the rays contained in that light beam are irradiated onto the object surface OS as parallel light beams with the same ray angle by the illumination optical element 24. As a result, the first ray L1 is incident on the object surface OS with an angle β1 with respect to the optical axis C1. Similarly, when a light beam with the second ray L2 as the principal ray is imaged onto the projection plane PP, all the rays contained in that beam are illuminated by the illumination optical element 24 as parallel beams with the same ray angle, illuminating the object plane OS. As a result, the second ray L2 is incident on the object plane OS with the angle of the illumination optical element 24 with respect to the optical axis C1 being the second ray angle β2.

[0068] The first divergence angle α1 is larger than the second divergence angle α2. On the other hand, as the first divergence angle α1 is gradually reduced, the number of points on the illumination field of the object surface OS where the variety of incident ray angles decreases increases. In other words, by making the first divergence angle α1 larger than the second divergence angle α2, it is possible to increase the variety of incident ray angles at points on the illumination field irradiated from the illumination optical element 24 onto the object surface OS. Furthermore, the light of the first wavelength spectrum and the light of the second wavelength spectrum have different colors. As a result, the optical device 12 can irradiate the object surface OS with beams of light with different ray angles for each color. That is, the optical device 12 can irradiate the object surface OS with rays of light with different incident angles for each color.

[0069] From the above, the optical device 12 of the optical inspection apparatus 10 according to this embodiment makes it possible to associate the direction of the light ray (direction of the light beam) with the wavelength spectrum. Furthermore, the projection unit 22 of the optical device 12 can instantly change the virtual projected image PI. Therefore, the optical device 12 according to this embodiment has the effect of being able to instantly change the association between the direction of the light ray and the color of the light ray according to various applications.

[0070] The optical inspection device 10 illuminates the object surface OS using the projection unit 22 of the optical device 12, captures an image of the object surface OS using the imaging unit 26, and acquires an image of the object surface OS corresponding to the virtual projected image PI using the processor 62 of the processing device 14 (step S1 in Figure 8).

[0071] First, let's consider the case where the object surface OS is a standard surface. In this case, as shown in Figure 7, the first ray L1 is specularly reflected by the object surface OS, passes through the imaging aperture 54, and is imaged by the image sensor 56. Here, the angle that the reflected light makes with respect to the imaging optical axis C2 when the first ray L1 is reflected is defined as the first reflected ray angle γ1. On the other hand, the second ray L2 is specularly reflected by the object surface OS and is shielded by the imaging aperture 54. Here, the angle that the reflected light makes with respect to the imaging optical axis C2 when the second ray L2 is reflected is defined as the second reflected ray angle γ2. As a result, the second ray L2 is not imaged by the imaging unit 26. In other words, when the object surface OS is a standard surface, the imaging unit 26 images only at the first wavelength and not at the second wavelength. To put it another way, a standard surface of the object surface OS is imaged only at blue light and not at red light.

[0072] Next, let's consider the case where there is a defect on the object surface OS. In particular, let's assume that there is a defect on the surface reached by the first ray L1 and the second ray L2. Then, the first ray L1 is scattered by the defect on the object surface OS, and the BRDF spreads. As a result, some of the scattered light passes through the imaging optical element 52 and the imaging aperture 54 and is imaged by the image sensor 56. On the other hand, the second ray L2 is also scattered by the defect on the object surface OS, and the BRDF spreads. As a result, some of the scattered light passes through the imaging optical element 52 and the imaging aperture 54 and is imaged by the image sensor 56. In other words, if there is a defect on the object surface OS, that defect is imaged with light of the first wavelength and the second wavelength. To put it another way, defects on the object surface OS are imaged with both blue light and red light.

[0073] As a result, the processing unit 14 (specifically its processor 62) can determine the presence or absence of defects in the object surface OS based on the color of the captured image acquired by the image sensor 56 of the imaging unit 26. That is, as shown in Figure 8, the processing unit 14 inspects the object surface OS for defects based on the image acquired by the imaging unit 26 (step S2).

[0074] As shown in Figure 8, in this embodiment, the processing unit 14 can output that there are no defects on the surface OS of the object being examined when it determines, based on the light received signals from all pixels of the image sensor 56, that one color of light (blue light) has been incident. Furthermore, the processing unit 14 can output that there are defects on the surface OS of the object being examined when it determines, based on the light received signals from all pixels of the image sensor 56, that two colors (blue light and red light) have been incident on the light received signals of some pixels. In this way, the processing unit 14 can output whether or not there are defects on the surface OS of the object being examined (step S3). Therefore, when performing an optical inspection, the processing unit 14 (processor 62) outputs the state of the object's surface OS based on the number of colors emitted from the light source 32 and the number of colors acquired by each pixel of the image sensor 56 of the imaging unit 26.

[0075] The optical inspection device 10, using the processing device 14, can perform the inspection process of the object surface OS shown in Figure 8 each time the virtual projected image PI projected onto the projection surface PP is changed. For example, the optical inspection device 10 can perform an optical inspection of the object surface OS based on the color information of the image captured by the imaging unit 26 each time a plurality of different virtual projected images PI are projected onto the projection surface PP, using the processor 62 of the processing device 14, and output whether or not there are defects. The processing device 14 can perform an optical inspection of the object surface OS at an appropriate speed using various illumination methods by synchronizing the image capture by the image sensor 56 when the projection unit 22 electrically or mechanically switches to project different virtual projected images PI onto the projection surface PP. When a typical projection unit 22 electrically or mechanically switches to project different virtual projected images PI onto the projection surface PP, for example, if it has a performance of approximately 60 fps or more, the projection unit 22 can project 60 or more images per second. Furthermore, by acquiring the image synchronously with the image sensor 56, optical inspection of the object surface OS can be performed in a relatively short time using light from various different directions and light of various colors. For this reason, the optical inspection apparatus 10 according to this embodiment can improve the accuracy of optical inspection compared to performing optical inspection of the object surface OS using a single type of conventional illumination device.

[0076] Furthermore, if the imaging unit 26 does not have an imaging aperture 54, that is, if there is no imaging aperture 54 at the focal plane FP2 of the imaging optical element 52 between the imaging optical element 52 and the image sensor 56, it becomes impossible to distinguish the presence or absence of defects on the object surface O by color, as described above. This is because, in the absence of an imaging aperture 54, all colors of light emitted from the light source 32 are captured by the image sensor 56, regardless of whether or not there are defects on the object surface OS. Therefore, the imaging unit 26 of the optical inspection device 10 has the effect of being able to distinguish the presence or absence of defects on the object surface OS by having object-side telecentricity for at least one wavelength of light from the light source 32.

[0077] Furthermore, the processing unit 14 of the optical inspection apparatus 10 described in this embodiment can be used together with the optical apparatus 12 according to the third, fourth, and fifth embodiments described later.

[0078] (modified version) A modified example of the imaging unit 26 of the optical device 12 of the optical inspection apparatus 10 of the second embodiment will be explained with reference to Figure 9. In this modified example, all parts except the imaging aperture 54 of the imaging unit 26 are the same as the imaging unit 26 of the optical device 12 of the optical inspection apparatus 10 described in the second embodiment. That is, the projection unit 22 and illumination optical element 24 of the optical device 12 have the same configuration as described in the first and second embodiments, so their explanation here will be omitted.

[0079] Figure 9 shows a schematic cross-sectional view of the optical device 12 of the optical inspection apparatus 10 according to this modified example, on the side of the imaging unit 26 that is closer to the object surface OS. The cross-sectional view shown in Figure 9 includes the imaging optical axis C2 of the imaging unit 26.

[0080] The imaging aperture 54 in this modified example has a first wavelength-selective region 55a and a second wavelength-selective region 55b. The imaging aperture 54 in this modified example is not a virtual one formed by projection, but is an actual entity. The first wavelength-selective region 55a allows light of a first wavelength (e.g., blue light) to pass through. However, the first wavelength-selective region 55a blocks light of a second wavelength (e.g., red light). The second wavelength-selective region 55b allows light of a second wavelength to pass through. However, the second wavelength-selective region 55b blocks light of a first wavelength. The first wavelength-selective region 55a is positioned so as to intersect the optical axis C2 of the imaging unit 26 at the imaging focal plane FP2 of the imaging optical element 52. The second wavelength-selective region 55b is positioned so as not to intersect the optical axis C2 of the imaging unit 26 at the imaging focal plane FP2 of the imaging optical element 52.

[0081] The operation of the optical inspection device 10 in this modified example will be explained.

[0082] In this modified example, the virtual projected image PI by the projection unit 22 has a first virtual region PIA1 and a second virtual region PIA2 (see Figure 7).

[0083] First, the first virtual region PIA1 is formed when a light beam with a first ray L1 having a first wavelength spectrum as its principal ray is imaged onto the projection surface PP. The second virtual region IA2 is formed when a light beam with a second ray L2 having a second wavelength spectrum as its principal ray is imaged onto the projection surface PP. At this time, the first ray L1 passes through the first wavelength selection region 55a. The second ray L2 passes through the second wavelength selection region 55b. That is, both the first ray L1 and the second ray L2 pass through the imaging aperture 54 and are imaged by the image sensor 56. This is independent of whether or not there are defects on the surface OS of the object. In other words, the surface OS of the object is imaged by the image sensor 56 at a first wavelength (e.g., blue light) and a second wavelength (e.g., red light), regardless of whether or not there are defects. In other words, the image sensor 56 of the optical device 12 according to this modified example can acquire a normal color image. In other words, the image sensor 56 of the optical device 12 according to this modified example can acquire a bright-field image of the surface OS of an object that may contain defects.

[0084] Next, the first virtual region PIA1 is formed when a light beam with a second ray L2 having a second wavelength spectrum as its principal ray is imaged onto the projection surface PP. The second virtual region is formed when a light beam with a first ray L1 having a first wavelength spectrum as its principal ray is imaged onto the projection surface PP. This is different from the example described above, where the blue light and red light are swapped. That is, the processing device 14 controls the light source 32 to swap the emission of blue light and red light compared to the example described above.

[0085] In this case, if the surface OS of the object is a standard surface, both the first ray L1 and the second ray L2 are blocked by the imaging aperture 54. In other words, light does not enter the image sensor 56 from the surface OS of the object, which is a standard surface, and therefore it is not imaged by the image sensor 56.

[0086] On the other hand, let's assume that a defect exists on the surface OS of the object, and that the defect is located in the region reached by the first ray L1 and the second ray L2. In this case, both the first ray L1 and the second ray L2 are scattered, and their respective BRDFs spread out. As a result, a portion of the scattered light from each passes through the imaging aperture 54. Consequently, the image sensor 56 images the defect with the first ray L1 and / or the second ray L2. In other words, the image sensor 56 of the optical device 12 according to this modified example can acquire a dark-field image with enhanced defect contrast relative to a standard plane.

[0087] As described above, the optical device 12 according to this modified example has the effect of changing the projected image PI by the projection unit 22 by having at least two wavelength selection regions 55a and 55b in the imaging aperture 54, and the image sensor 56 can acquire both bright-field and dark-field images. As a result, the optical inspection device 10 can acquire detailed information of the object surface OS.

[0088] Furthermore, in this modified example, the processing unit 14 can identify that the projected image PI from the projection unit 22 is different. That is, in this modified example, the processing unit 14 can recognize the switching between a mode for acquiring a bright-field image and a mode for acquiring a dark-field image, and acquires an image for each (see step S1 in Figure 8). In the mode for acquiring a dark-field image, the processing unit 14 can determine whether two colors (blue light and red light) have been incident on the light-receiving signal of some pixels based on the light-receiving signal of all pixels of the image sensor 56 (see step S2 in Figure 8). The processing unit 14 can then output whether or not there is a defect on the surface OS of the object being inspected (see step S3 in Figure 8). In this way, the optical inspection device 10 can use the processing unit 14 to perform the inspection process of the object surface OS shown in Figure 8 and output whether or not there is a defect on the surface OS of the object being inspected.

[0089] The imaging unit 26 according to this modified example can be used in the optical device 12 according to the third and fourth embodiments described later.

[0090] (Third embodiment) Figure 10 shows a schematic cross-sectional view of the optical device 12 and the virtual projection image PI formed by the optical device 12 of the optical inspection apparatus 10 according to the third embodiment. This embodiment is a modified version of the optical inspection apparatus 10 described in the first embodiment, including modified versions, and the second embodiment, including modified versions. The same reference numerals are used for members that are the same as those described in the first embodiment, including modified versions, and the second embodiment, including modified versions, or members that have the same function as those described in the first embodiment, including modified versions, and their descriptions are omitted.

[0091] The optical device 12 according to this embodiment includes a projection unit 22, an illumination optical element 24, and a light diffusion plate (light diffusion unit) 28. Here, the imaging unit 26, which was described in the second embodiment (including modified examples), is not shown.

[0092] The projection unit 22 can instantly change (transform) the virtual projected image PI. In this embodiment, the projection unit 22 uses, for example, a liquid crystal display. However, the projection unit 22 is not limited to this, and as described above, a DLP display can also be used.

[0093] The projection unit 22 is equipped with, for example, two light sources 32, each capable of emitting light with two different wavelength spectra. In Figure 6, for convenience, the light sources 32 are depicted as a single entity. The light from the two light sources 32 can be combined using a dichroic mirror or the like just before reaching the projection lens 36. These wavelength spectra are referred to as the first wavelength spectrum, the second wavelength spectrum, and the third wavelength spectrum, respectively. For example, the first wavelength spectrum is blue light with a peak at 450 nm and a full width at half maximum of 100 nm. The second wavelength spectrum is red light with a peak at 650 nm and a full width at half maximum of 100 nm. The third wavelength spectrum is the same as the second wavelength spectrum. However, the wavelength spectra are not limited to these examples and can be any wavelengths.

[0094] The projection unit 22 includes a liquid crystal spatial modulator 34 and a projection lens 36. The projection lens 36 images the light beam emitted from the light source 32 and passed through the spatial modulator 34 onto the projection surface PP. The spatial modulator 34 has multiple pixels, and various images can be formed by independently modulating each pixel. In Figure 6, the spatial modulator 34 is depicted as a single unit for convenience. In reality, two spatial modulators 34 through which light with different wavelength spectra from two light sources 32 pass independently spatially modulate these lights, and then combine them using a dichroic mirror or the like. After combination, the combined light is incident on the projection lens 36. The projection unit 22 projects a first ray L1 with a first wavelength spectrum, a second ray L2 with a second wavelength spectrum, and a third ray L3 with a third wavelength spectrum onto different points on the projection surface PP.

[0095] In this embodiment, the illumination optical element 24 is a lens assembly consisting of multiple lenses. However, in Figure 6, for convenience, the lens assembly is schematically depicted as a single lens.

[0096] The light beam emitted from the projection unit 22 passes through the illumination focal plane region FP1A of the illumination optical element 24, passes through the illumination optical element 24, and irradiates the object surface OS. The divergence angle of the light beam immediately after passing through the illumination focal plane FP1 is defined as the first divergence angle α1, and the divergence angle of the light beam immediately before incident on the illumination focal plane FP1 is defined as the second divergence angle α2. However, the light beam from the projection unit 22 may also be a focused beam. In this case, the second divergence angle α2 is set to 0.

[0097] The light diffuser 28 is placed on the illumination focal plane FP1 or the illumination focal plane region FP1A. The light diffuser 28 is assumed to be a physical entity, not a virtual entity like a projected image. The light diffuser 28 increases the divergence angle of the light beam as it passes through the focal plane FP1 or the focal plane region FP1A. In other words, the divergence angle of the light that has passed through the light diffuser 28 is larger than the divergence angle before passing through. In Figure 10, for convenience, a virtual projected image PI is placed on the illumination focal plane FP1, and the light diffuser 28 is depicted as being placed adjacent to the downstream side of the virtual projected image PI. For example, it is also preferable to place the virtual projected image PI on the illumination focal plane FP1 and to place the light diffuser 28 there as well.

[0098] Next, the operation of the optical inspection apparatus 10 according to this embodiment will be described.

[0099] The processing unit 14 emits light from the light source 32 of the projection unit 22. The light beam emitted from the projection unit 22 forms a projected image PI on the projection surface PP. The position of the projection surface PP, determined by the projection unit 22, is located in the focal plane region FP1A of the illumination optical element 24.

[0100] In the cross-section of Figure 6, the virtual projected image PI has a first virtual region PIA1, a second virtual region PIA2, and a third virtual region PIA3. The first virtual region PIA1 is formed when a light beam with a first ray L1 having a first wavelength spectrum as its principal ray is imaged onto the projection surface PP. The second virtual region PIA2 is formed when a light beam with a second ray L2 having a second wavelength spectrum as its principal ray is imaged onto the projection surface. The third virtual region PIA3 is formed when a light beam with a third ray L3 having a third wavelength spectrum as its principal ray is imaged onto the projection surface PP. The first virtual region PIA1 intersects the optical axis C1. In Figure 10, the virtual projected image PI is assumed to be concentric with respect to the optical axis C1. In this case, the first virtual region PIA1 and the third virtual region PIA3 are symmetrical with respect to the optical axis C2. However, this does not apply to the virtual projection image PI; anything is acceptable.

[0101] The divergence angle α1 of the luminous beam immediately after passing through the illumination focal plane region FP1A is larger than the divergence angle α2 of the luminous beam immediately before. One reason for this is that the projection unit 22 forms an image of the projected image PI in the focal plane region FP1A. In other words, the first divergence angle α1 is larger than the second divergence angle α2. As a result, the luminous beam reaching the illumination optical element 24 can reach a wider area rather than just a local area of ​​the illumination optical element 24. Therefore, when using the optical device 12 according to this embodiment, there is an effect of widening the illumination field irradiated from the illumination optical element 24 onto the object surface OS.

[0102] Furthermore, in this embodiment, a light diffuser 28 is placed in the illumination focal plane region FP1A. This allows for an even greater divergence angle of light passing through the focal plane region FP1A compared to the case where the diffuser is not placed. In other words, the light beam reaching the illumination optical element 24 can reach a wider area, rather than just a local area of ​​the illumination optical element 24. As a result, the illumination field irradiated from the illumination optical element 24 onto the object surface OS is further widened.

[0103] The illumination optical element 24 irradiates the object surface OS with light that passes through any point on the illumination focal plane FP1. Here, based on geometrical optics (see Non-Patent Literature 2), the angle of the illumination optical element 24 with respect to the optical axis C1 is determined according to the point of passage on the illumination focal plane FP1. In other words, light emitted from the same point of passage on the projection surface PP or the illumination focal plane FP1 will all have the same ray angle due to the illumination optical element 24. As a result, when a light beam with the first ray L1 as the principal ray is imaged on the projection surface PP, all the rays contained in that light beam become parallel light beams with the same ray angle due to the illumination optical element 24 and irradiate the object surface OS. As a result, the first ray L1 is incident on the object surface OS with an angle of first ray angle β1 with respect to the optical axis C1. Similarly, when a light beam with the second ray L2 as the principal ray is imaged onto the projection plane PP, all the rays contained in that beam are illuminated by the illumination optical element 24 as parallel beams with the same ray angle and irradiate the object surface. When a light beam with the third ray L3 as the principal ray is imaged onto the projection plane PP, all the rays contained in that beam are illuminated by the illumination optical element 24 as parallel beams with the same ray angle and irradiate the object surface OS. As a result, the second ray L2 and the third ray L3 are incident on the object surface OS at an angle β2 relative to the optical axis C1.

[0104] The first divergence angle α1 is larger than the second divergence angle α2. On the other hand, as the first divergence angle α1 is gradually reduced, the number of points on the illumination field irradiated from the illumination optical element 24 onto the object surface OS that have a reduced variety of incident ray angles increases. In other words, by making the first divergence angle α1 larger than the second divergence angle α2, it is possible to increase the variety of incident ray angles at points on the illumination field irradiated from the illumination optical element 24 onto the object surface OS. In particular, the light diffuser plate 28 can greatly enhance this effect.

[0105] Furthermore, the light from the first wavelength spectrum and the light from the second wavelength spectrum have different colors. This allows the optical device 12 to irradiate the object surface OS with beams of light with different ray angles for each color. In other words, the optical device 12 can irradiate the object surface OS with light rays at different incident angles for each color.

[0106] The BRDF of the surface OS of an object changes depending on the angle of incidence of the incident light. In other words, two BRDFs for two incident angles provide more information about the surface OS of an object than a BRDF for one incident angle. The more information there is about the BRDF, the more detailed the state of the surface OS of the object can be estimated (see Second Embodiment (including modifications)). The optical device 12 according to this embodiment can change the virtual projection image PI in various ways, thereby instantaneously changing the angle of incidence to the surface OS of an object. And, as described in the Second Embodiment (including modifications), by observing the reflected light with, for example, the imaging unit 26 each time, it is possible to obtain a more detailed surface state of the object.

[0107] Furthermore, by appropriately dividing the projection surface PI into one virtual region PIA1 and two virtual regions PIA2 and PIA3, and projecting images PI of different colors onto each of these regions, and irradiating the surface OS of an object with light rays at different incidence angles for each color, the imaging unit 26, as described in the second embodiment (including modified examples), can simultaneously acquire the reflected light corresponding to each incidence angle, distinguishing it by color. In other words, the optical device 12 according to this embodiment can convert at least two different wavelength spectra into light rays at different incidence angles. Therefore, for example, the imaging unit 26 can simultaneously acquire the reflected light corresponding to each incidence angle, distinguishing it by color. This has the effect of enabling the imaging unit 26 to acquire more detailed BRDF information. This is particularly useful in optical inspection, as it contributes to improving the inspection accuracy of the surface OS of an object.

[0108] In optical inspection, it is necessary to select the optimal direction of light rays illuminating the surface OS of an object depending on the type of object O. Conventionally, this required, for example, preparing various types of ring illumination (oblique incidence illumination). However, using the optical device (illumination device) 12 according to this embodiment has the effect of changing the incident angle of the light rays by instantly changing the virtual projection image PI. In other words, by using one optical device 12 according to this embodiment, it is possible to selectively realize various types of illumination of various sizes without having to prepare multiple conventional illumination devices.

[0109] From the above, the optical device 12 of the optical inspection apparatus 10 according to this embodiment makes it possible to associate the direction of a light ray (direction of the light beam) with the wavelength spectrum. The wavelength spectrum can be considered synonymous with the color of the light ray. Therefore, it can also be said that it is possible to associate the direction of a light ray with the color of the light ray. Furthermore, the projection unit 22 can instantly change the virtual projected image PI. Therefore, the optical device 12 according to this embodiment has the effect of being able to instantly change the association between the direction of a light ray and the color of the light ray according to various applications.

[0110] (Variation 1) A first modified example of the third embodiment will be described with reference to Figure 11.

[0111] In the first modified example of this embodiment shown in Figure 11, a virtual projected image PI is shown. The virtual projected image PI shown in Figure 11 is perpendicular to the optical axis C1. In this modified example, the first and second wavelength spectra are the same as those described in the third embodiment. On the other hand, the third, fourth, and fifth wavelength spectra are all different. For example, the peak of the third wavelength spectrum is 550 nm, and the peaks of the fourth and fifth wavelength spectra are 500 nm and 600 nm, respectively. The full width at half maximum of these wavelength spectra is 100 nm. The light source 32 of the projection unit 22 is provided with five light sources, each emitting light of these five wavelength spectra. The projection unit 22 is also provided with five spatial modulators 34 corresponding to the five light sources 32. These five types of light are combined using a dichroic mirror or the like just before they enter the projection lens 36.

[0112] In this modified example, the virtual projection image PI is assumed to have a concentric circle at its center and a 120° rotationally symmetrical outer region. In other words, the center is axially symmetrical, and the outer region changes in the azimuthal direction. The virtual projection image PI is composed of a first wavelength selection region PI1 and a second wavelength selection region PI2 located outside the first wavelength selection region PI1, forming the central part of the concentric circle. The virtual projection image PI is composed of a third wavelength selection region PI3, a fourth wavelength selection region PI4, and a fifth wavelength selection region PI5, forming the 120° rotationally symmetrical outer region. The first wavelength selection region PI1 intersects the optical axis C1 of the illumination optical element 24.

[0113] Furthermore, there is a virtual black border between adjacent areas. This is formed, for example, by not projecting light onto the projection surface PP. Such a black border can be formed virtually, or it may be formed by an actual barrier rather than virtually.

[0114] By using such a virtual projection image PI, the optical device 12 of the optical inspection device 10 according to this modified example can not only associate the angle of the light ray with respect to the optical axis C1 as the direction of incidence of the light ray onto the object surface OS with the color of the light ray, but also associate the azimuth angle direction of the light ray with the color of the light ray. As a result, by using the optical inspection device 10 according to this modified example to distinguish and observe reflected light from the object surface OS by color, the optical inspection device 10 can simultaneously acquire detailed BRDF information not only regarding the angle of the light ray with respect to the optical axis C1 but also regarding the azimuth angle. As a result, using the optical inspection device 10 according to this modified example improves the accuracy and speed of inspection for defects on the object surface OS.

[0115] (Modification 2) A second modified example of the third embodiment will be described with reference to Figure 12.

[0116] In the second modified example of this embodiment shown in Figure 12, a virtual projected image PI is shown. The virtual projected image PI shown in Figure 12 is perpendicular to the optical axis C1. In this modified example, the first and second wavelength spectra are the same as those described in the third embodiment. On the other hand, the third spectrum is different from them. For example, the peak of the third wavelength spectrum is 550 nm, and the full width at half maximum of the wavelength spectrum is 100 nm. The light source 32 of the projection unit 22 is provided with three light sources, each emitting light of these three wavelength spectra. The projection unit 22 is also provided with three spatial modulators 34 corresponding to the three light sources 32. These three types of light are combined using a dichroic mirror or the like just before they enter the projection lens 36.

[0117] In this modified example, the virtual projected image PI has a fan-shaped first virtual region PIA1, a second virtual region PIA2, and a third virtual region PIA3. The projection unit 22, under control, for example by the processing unit 14, changes the inclination of the virtual projected image PI on the projection surface PP in a time series, from left to right in Figure 12, while maintaining the same shape and size. The first virtual region PIA1 intersects the optical axis C1 of the illumination optical element 24, for example. This virtual projected image PI is in the same state as being rotated around the axis of the optical axis C1. The optical axis C1 may be at the vertex of the fan shape of the virtual projected image PI.

[0118] The optical device 12, by using the virtual projected image PI in this way, can not only associate the angle of the light ray with the optical axis C1 (direction of the light ray) and the color of the light ray as the direction of incidence of the light ray onto the object surface OS, but also has the effect of being able to change the azimuth angle direction of the light ray in a time series. As a result, the imaging unit 26 can observe the reflected light from the object surface OS by distinguishing it by color, and the imaging unit 26 can simultaneously acquire BRDF information for different incidence angles. As a result, by using the optical inspection device 10 according to this modified example, the accuracy and speed of inspection for defects on the object surface OS are improved. Furthermore, by changing the azimuth angle direction of the virtual projected image PI in a time series, the optical device 12 can incident light with different incidence azimuth angles onto the object surface OS. Therefore, it has the effect of being able to acquire BRDF information for different incidence azimuth angles. In other words, more detailed BRDF information can be acquired. As a result, by using the optical inspection device 10 according to this modified example, the accuracy of inspection for defects on the object surface OS is improved.

[0119] (Fourth Embodiment) Figure 13 shows a schematic cross-sectional view of the optical device 12 of the optical inspection apparatus 10 according to the fourth embodiment, and the virtual projection image PI formed by the optical device 12. This embodiment is a modified version of the optical inspection apparatus 10 described in the first embodiment, the second embodiment, and the third embodiment, including modified versions. The same reference numerals are used for members that are the same as those described in the first embodiment, the second embodiment, and the third embodiment, including modified versions, or members that have the same function as those described in the first embodiment, the second embodiment, and the third embodiment, including modified versions, and their descriptions are omitted.

[0120] The optical device 12 according to this embodiment includes a projection unit 22 and an illumination optical element 24. The projection unit 22 can instantly change (transform) the virtual projected image PI. In this embodiment, the light source 32 of the projection unit 22 uses a light-emitting unit 33 composed of multiple LEDs (Light-Emitting Diodes) that can electrically and instantaneously switch between emitting light at a first wavelength (e.g., blue light) and a second wavelength (e.g., red light). However, the light source 32 is not limited to this, and various types can be used.

[0121] The light source 32 of the projection unit 22 has a plurality of LED light-emitting units 33. Each light-emitting unit 33 can simultaneously or selectively emit light of two different wavelength spectra. These two different wavelength spectra are referred to as the first wavelength spectrum and the second wavelength spectrum, respectively. For example, the first wavelength spectrum is blue light with a peak at a wavelength of 450 nm and a full width at half maximum of 100 nm. The second wavelength spectrum is red light with a peak at a wavelength of 650 nm and a full width at half maximum of 100 nm.

[0122] In this embodiment, the illumination optical element 24 is a lens assembly consisting of multiple lenses. However, in Figure 13, for convenience, the lens assembly is schematically depicted as a single lens.

[0123] The light-emitting surface of the light source 32 is positioned on the illumination focal plane FP1 or illumination focal plane region FP1A of the illumination optical element 24. In this embodiment, the projection surface PP coincides with the light-emitting surface of the light source 32.

[0124] The light beam emitted from the projection unit 22 immediately passes through the illumination focal plane region FP1A of the illumination optical element 24, passes through the illumination optical element 24, and irradiates the object surface OS. The divergence angle of the light beam immediately after passing through the illumination focal plane FP1 is defined as the first divergence angle α1, and the divergence angle of the light beam before it is incident on the illumination focal plane FP1 is defined as the second divergence angle α2. However, here, since the light-emitting surface of the light source 32 is positioned on the illumination focal plane FP1, there is no light beam before it is incident on the illumination focal plane FP1. Therefore, the second divergence angle α2 is set to 0.

[0125] Next, the operation of the optical inspection apparatus 10 according to this embodiment will be described.

[0126] The light beam emitted from the projection unit 22 forms a projected image PI on the projection surface PP. The position of the projection surface PP, determined by the projection unit 22, is located in the focal plane region FP1A of the illumination optical element 24.

[0127] In the cross-section shown in Figure 13, the projected image PI has a first virtual region PIA1, a second virtual region PIA2, and a third virtual region PIA3. In Figure 13, the projected image PI is assumed to be concentric with respect to the optical axis C1. In this case, the first virtual region PIA1 and the third virtual region PIA3 are symmetrical with respect to the optical axis C1.

[0128] The divergence angle α1 of the luminous beam immediately after passing through the focal plane region FP1A is larger than the divergence angle α2 of the luminous beam immediately before that (not shown in Figure 13; see Figures 1, 7, and 10). As a result, the luminous beam reaching the illumination optical element 24 can reach a wider area rather than just a local area of ​​the illumination optical element 24. Therefore, when using the optical device 12 according to this embodiment, there is an effect of widening the illumination field irradiated from the illumination optical element 24 onto the object surface OS.

[0129] The illumination optical element 24 irradiates the object surface OS with light that passes through any point on the illumination focal plane FP1. Here, based on geometrical optics (see Non-Patent Literature 2), the angle of the illumination optical element 24 with respect to the optical axis C1 is determined according to the point of passage on the illumination focal plane FP1. In other words, light emitted from the same point of passage on the projection plane PP or the illumination focal plane FP1 all have the same ray angle due to the illumination optical element 24. As a result, when a light beam with the first ray L1 as the principal ray is imaged on the projection plane PP, all the rays contained in that light beam become parallel light beams with the same ray angle due to the illumination optical element 24 and irradiate the object surface OS. As a result, the first ray L1 is incident on the object surface OS with an angle of first ray angle β1 with respect to the optical axis C1. Similarly, when a light beam with the second ray L2 as the principal ray is imaged onto the projection plane PP, all the rays contained in that beam are converted into parallel beams with the same ray angle by the illumination optical element 24 and irradiate the object surface OS. When a light beam with the third ray L3 as the principal ray is imaged onto the projection plane PP, all the rays contained in that beam are converted into parallel beams with the same ray angle by the illumination optical element 24 and irradiate the object surface OS. As a result, the second ray L2 and the third ray L3 are incident on the object surface OS at an angle of the second ray angle β2 with respect to the optical axis C1.

[0130] The BRDF of the surface OS of an object changes depending on the angle of incidence of the incident light. In other words, two BRDFs for two different incident angles provide more information about the surface OS of an object than a BRDF for a single incident angle. The more information available in the BRDF, the more detailed the state of the surface OS of the object can be estimated (see Second Embodiment (including modifications)). Therefore, the optical device 12 according to this embodiment can change the projected image PI in various ways, thereby instantaneously changing the angle of incidence to the surface OS of the object. And, as described in the Second Embodiment (including modifications), by observing the reflected light with, for example, the imaging unit 26 each time, it is possible to obtain a more detailed surface state of the object.

[0131] Furthermore, for example, the imaging unit 26 projects images PI of different colors onto one virtual region PIA1 and two virtual regions PIA2 and PIA3, respectively, by appropriately dividing the projection surface PI into sections. When light rays with different incidence angles for each color are incident on the surface OS of an object, the imaging unit 26, as described in the second embodiment (including modified examples), can simultaneously acquire reflected light corresponding to each incidence angle, distinguishing it by color. In other words, the optical device 12 according to this embodiment can convert at least two different wavelength spectra into light rays with different incidence angles. Therefore, for example, the imaging unit 26 has the effect of simultaneously acquiring reflected light corresponding to each incidence angle, distinguishing it by color. As a result, for example, the imaging unit 26 has the effect of acquiring more detailed BRDF information. This is particularly useful in optical inspection, where it contributes to improving the inspection accuracy of the surface OS of an object.

[0132] In optical inspection, it is necessary to select the optimal direction of light rays illuminating the surface OS of an object depending on the type of object O. Conventionally, this required, for example, preparing various types of ring illumination (oblique incidence illumination). However, using the optical device (illumination device) 12 according to this embodiment has the effect of changing the incident angle of the light rays by instantly changing the projected image PI. In other words, by using one optical device 12 according to this embodiment, it is possible to selectively use various types of illumination of various sizes without having to prepare multiple conventional illumination devices.

[0133] From the above, the optical device 12 of the optical inspection apparatus 10 according to this embodiment makes it possible to associate the direction of a light ray with its wavelength spectrum. The wavelength spectrum can be considered synonymous with the color of a light ray. Therefore, it can also be said that it is possible to associate the direction of a light ray with its color. Furthermore, the projection unit 22 can instantly change the projected image PI. Therefore, the optical device 12 according to this embodiment has the effect of being able to instantly change the association between the direction of a light ray and its color according to various applications.

[0134] (modified version) Figure 14 shows a schematic cross-sectional view of the optical device 12 of the optical inspection apparatus 10 according to a modified example of the fourth embodiment.

[0135] The optical device 12 according to this modified example includes a first light source 32a and a second light source 32b having different wavelength spectra as the light source 32. The first light source 32a has a plurality of first light-emitting units 33a. The second light source 32b has a plurality of second light-emitting units 33b. Each of the first light-emitting units 33a emits light of a first wavelength spectrum simultaneously or selectively. Each of the second light-emitting units 33b emits light of a second wavelength spectrum. The light from the first light source 32a and the second light source 32b is combined by a dichroic mirror 38. The dichroic mirror 38 may be a polarizing beam splitter or an unpolarizing beam splitter. The dichroic mirror 38 is not limited to these, and can be anything that can combine two lights. When a polarizing beam splitter is used as the dichroic mirror 38, if a polarization camera capable of sensing the polarization direction is used in the image sensor 56 of the imaging unit 26, polarization information can be used in the same way as color information, thereby acquiring more information about the directional distribution of light at an object point. By using two light sources 32a and 32b, a new wavelength spectrum with two spaced-apart peaks can be generated after the combined wave. This makes it possible to make, for example, the first wavelength spectrum and the second wavelength spectrum significantly different, allowing for accurate color distinction and more accurate and rapid acquisition of information about the directional distribution of light. Alternatively, the light intensity of the two light sources 32a and 32b can be adjusted independently and appropriately.

[0136] From the above, the optical device 12 of the optical inspection apparatus 10 according to this modified example makes it possible to associate the direction of light rays with the wavelength spectrum. Furthermore, the projection unit 22 can instantly change the projected image PI. Therefore, the optical device 12 according to this modified example has the effect of instantly changing the association between the direction of light rays and color according to various applications.

[0137] (Fifth embodiment) The optical device 12 according to the fifth embodiment will be described below with reference to Figure 15.

[0138] Figure 15 shows a schematic perspective view of the optical device 12 of the optical inspection apparatus 10 according to this embodiment, and the virtual projection image PI formed by the optical device 12. This embodiment comprises a projection unit 22, an illumination optical element 24, and an imaging unit 26. However, the projection unit 22 of the optical device 12 is not shown in Figure 15. Various types of projection units 22 as described in the first to fourth embodiments can be used. The basic configuration of the optical device 12 is the same as that of the optical device 12 described in the first to fourth embodiments. The differences will be described below.

[0139] The first cross-section S1 in Figure 15 includes the illumination optical axis C1 and the imaging optical axis C2. The second cross-section S2 is perpendicular to the first cross-section S1.

[0140] The illumination optical element 24 has translational symmetry in a direction perpendicular to the first cross-section S1. This direction is defined as the longitudinal direction of the illumination optical element 24. The illumination optical element 24 is, for example, a cylindrical lens. The illumination optical axis C1 of the cylindrical lens lies on the first cross-section S1.

[0141] The projection unit 22 uses the light beam B from the light source 32 to project a virtual projection image PI onto the focal plane region FP1A of the illumination optical element 24. For example, the virtual projection image PI may have a first virtual region PIA1, a second virtual region PIA2, and a first virtual region PIA3. On the virtual projection image PI, the direction along the direction in which the virtual projection image PI changes is defined as the array direction. This array direction is parallel to the first cross section S1. In other words, the array direction of the virtual projection image PI is perpendicular to the longitudinal direction of the line sensor 56. The first virtual region PIA1 intersects the optical axis C1. As a result, the object surface OS is illuminated, and the illumination field F is formed. When this illumination light is projected onto the second cross section S2, it becomes divergent light. However, this is not limited to this, and the virtual projection image PI may change in any way.

[0142] Although the projected image PI from the projection unit 22 using the light beam B can be changed instantaneously, as an example, light of a first wavelength projected onto the first virtual region PIA1 is shielded by the first wavelength selection region 55a of the wavelength selection unit 55 (described later), and passes through the second wavelength selection region 55b and the third wavelength selection region 55c. Light of a second wavelength projected onto the second virtual region PIA2 passes through the first wavelength selection region 55a of the wavelength selection unit 55 (described later), is shielded by the second wavelength selection region 55b, and passes through the third wavelength selection region 55c. Light of a third wavelength projected onto the third virtual region PIA3 passes through the first wavelength selection region 55a and the second wavelength selection region 55b of the wavelength selection unit 55 (described later), and is shielded by the third wavelength selection region 55c.

[0143] The imaging unit 26 includes an imaging optical element 52, an imaging aperture 54, and an image sensor 56. The optical axis C2 of the imaging optical element 52 intersects with the wavelength selection unit 55 of the imaging aperture 54, which will be described later. The image sensor 56 is an image sensor, and in this embodiment, it is a line sensor. The longitudinal direction of the line sensor 56 coincides with the longitudinal direction of the illumination optical element 24.

[0144] The imaging aperture 54 has a wavelength selection section 55 instead of the through hole 54a described in the first embodiment (Figure 7). In Figure 15, the illustration of the medium 54b of the imaging aperture 54 is omitted. In this embodiment, it is preferable that the through hole 54a is formed in a rectangular shape that is long in the longitudinal direction of the line sensor 56. The wavelength selection section 55 of the imaging aperture 54 has translational symmetry in a direction perpendicular to the first cross-section S1. This direction is defined as the longitudinal direction of the wavelength selection section 55. The wavelength selection section 55 has a plurality of regions 55a, 55b, 55c arranged in a stripe pattern. On the wavelength selection section 55, the direction along the direction in which the wavelength selection section 55 changes is defined as the arrangement direction. This arrangement direction is parallel to the first cross-section S1. In other words, the arrangement direction of the wavelength selection section 55 is perpendicular to the longitudinal direction of the line sensor 56.

[0145] Furthermore, it is preferable that the imaging aperture 54, similar to the imaging aperture 54 described in the first embodiment (Figure 7), has the area outside the wavelength selection section 55 formed as a medium 54b to shield the line sensor 56 from light.

[0146] The object O is transported in the direction indicated by the arrow FD, which is perpendicular to the longitudinal direction of the line sensor 56. The line sensor 56 can acquire a two-dimensional image by continuously imaging the object O as it is transported in this manner.

[0147] The light beam emitted from the projection unit 22 (see the first to fourth embodiments) passes through the virtual projected image (illumination-side wavelength selection unit) PI and irradiates the object surface OS, forming an irradiation field F on the object surface OS.

[0148] If there is a minute defect at the first object point O1 on the object surface OS, the BRDF will spread, and some of the light rays will selectively pass through the respective regions 55a, 55b, and 55c of the wavelength selection section 55 of the imaging aperture 54, imaging the first object point O1 onto the line sensor 56.

[0149] On the other hand, when the first object point O1 is on the standard plane, the first ray L1 having the first wavelength is specularly reflected by the standard plane. At this time, by appropriately forming a virtual projection image PI, the first ray L1 can be made to reach the center of the imaging aperture 54 of the imaging unit 26. In other words, the first ray L1 can be made to reach the region including the imaging optical axis C2. The first wavelength selection region 55a of the wavelength selection unit 55, which is located at the center of the imaging aperture 54, is created to block light of the first wavelength. As a result, if there are no minute defects at the first object point O1, the first object point O1 is not imaged with light of the first wavelength. On the other hand, if there are minute defects at the first object point O1, the first object point O1 is imaged with light of the first wavelength. This has the effect that the presence or absence of minute defects can be identified using the optical inspection device 10 according to this embodiment. In addition, information regarding the spread of the directional distribution of light (i.e., BRDF) at the object point can be obtained using the optical inspection device 10 according to this embodiment.

[0150] Furthermore, if the first object point O1 is on the standard plane, the second ray L2, which has a second wavelength different from the first wavelength, is similarly specularly reflected by the standard plane. The first wavelength selection region 55b of the wavelength selection unit 55, located at the center of the imaging aperture 54, is created to block light of the second wavelength. As a result, if there are no minute defects at the first object point O1, the first object point O1 is not imaged with light of the second wavelength. On the other hand, if there are minute defects at the first object point O1, the first object point O1 is imaged with light of the second wavelength. However, even if the first object point O1 is on the standard plane, the projection unit 22 instantaneously changes the virtual projection image PI and appropriately forms the virtual projection image PI, so that the reflection direction of the second ray L2 is made to coincide with the imaging optical axis C2. As a result, the ray of the second wavelength reaches the center of the imaging aperture 54 of the imaging unit 26. That is, it reaches the region on the imaging aperture 54 that includes the imaging optical axis C2. The first wavelength selection region 55a of the wavelength selection unit 55, located at the center of the imaging aperture 54, is designed to transmit light of the second wavelength and be imaged by the line sensor 56. In this case, based on geometrical optics, the imaging unit 26 will have telecentricity toward the object with respect to the second wavelength. In other words, the optical device 12 according to this embodiment will have telecentricity toward the object with respect to at least one wavelength of light from the light source 32. As a result, the optical device 12 of the optical inspection apparatus 10 according to this embodiment has the effect of being able to acquire a bright-field telecentric image with respect to the second wavelength. In other words, the optical device 12 of the optical inspection apparatus 10 according to this embodiment can acquire detailed information of the object surface in combination with the image acquired using the first ray.

[0151] Furthermore, the third wavelength, like the second wavelength, is specularly reflected by the standard plane when the first object point O1 is on the standard plane. The first wavelength selection region 55c of the wavelength selection unit 55, located at the center of the imaging aperture 54, is created to shield the light of the third wavelength. As a result, if there are no minute defects at the first object point O1, the first object point O1 is not imaged with light of the third wavelength. On the other hand, if there are minute defects at the first object point O1, the first object point O1 is imaged with light of the third wavelength. However, even when the first object point O1 is on the standard plane, the projection unit 22 instantaneously changes the virtual projection image PI and appropriately forms the virtual projection image PI, so that the third ray passes through the first wavelength selection region 55a and is imaged by the line sensor 56. At this time, based on geometrical optics, the imaging unit 26 has telecentricity toward the object with respect to the third wavelength. In other words, the optical device 12 according to this embodiment has object-side telecentricity with respect to at least one wavelength of light from the light source 32.

[0152] Consider the case where a light ray is projected onto the first cross-section S1. In this case, as shown in Figure 15, the distribution of the BRDF of the first object point O1 broadens, causing light to reach the wavelength selection area 55, which was not reached in the case of a standard plane, and to pass through it. Here, it can be seen that depending on the direction of the reflected light, the reflected light reaches different regions 55b and 55c of the wavelength selection area 55 in the imaging aperture 54. However, light rays that reach outside the range of the imaging aperture 54 are not captured. In other words, the range of light ray directions that can be captured is limited by the imaging aperture 54.

[0153] On the other hand, consider the case where light rays are projected onto the second cross-section S2. In this case, since the light from the projection unit 22 is diffuse light, it can be seen that the field of view in the imaging unit 26 widens according to the divergence angle of the diffuse light. Furthermore, since the wavelength selection unit 55 is striped, it can be seen that the color of the light rays does not depend on the field of view. In addition, by making the longitudinal direction of the stripes sufficiently long, it is possible to effectively use a wide field of view in the longitudinal direction of the line sensor 56. Moreover, by arranging the wavelength selection unit 55 in front of the imaging optical element 52 and the image sensor 56, this optical system can be easily assembled for any combination of imaging optical element 52 and image sensor 56.

[0154] The optical inspection apparatus 10 according to this embodiment provides information regarding the spread of the directional distribution of light at object point O1. Furthermore, the imaging field of the optical device 12 of the optical inspection apparatus 10 according to this embodiment can be widened as the longitudinal direction of the line sensor 56 is increased. As a result, the optical inspection apparatus 10 according to this embodiment can inspect the properties or shape of the object surface OS.

[0155] From the above, the optical device 12 of the optical inspection apparatus 10 according to this embodiment makes it possible to associate the direction of light rays (direction of the light beam) with the wavelength spectrum. Furthermore, the projection unit 22 of the optical device 12 can instantly change the virtual projected image PI. For example, on the projection surface PP, each region PIA1, PIA2, and PIA3 can be stretched or contracted in an appropriate direction. Therefore, the optical device 12 according to this embodiment has the effect of instantly changing the association between the direction of light rays and the color of light rays according to various applications.

[0156] According to at least one embodiment described above, it is possible to provide an optical device 12, an optical inspection device 10, an optical inspection method, and an optical inspection program stored in a non-temporary storage medium such as a storage device 64, which are capable of associating the direction of a ray (direction of a light beam) with the wavelength spectrum.

[0157] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. The claims of this application as they were at the time of filing are included below. [Note 1] An illumination optical element having a focal plane region including the focal plane or its vicinity, A projection unit equipped with a light source Equipped with, The projection unit is capable of emitting a light beam containing at least two different wavelength spectra from the light source to the illumination optical element. The projection unit forms projected images at different positions using light of two different wavelength spectra within the focal plane or focal plane region of the illumination optical element. optical equipment. [Note 2] The optical apparatus as described in Appendix 1, wherein the projection unit emits a light beam containing at least two different wavelength spectra from the light source at the same time. [Note 3] The optical apparatus according to Appendix 1 or Appendix 2, wherein the projection unit is capable of changing the projected image over time using light of two different wavelength spectra. [Note 4] The projection unit increases the divergence angle immediately after the light beam from the light source passes the focal plane or the focal plane region compared to the angle immediately before passing through. The optical device described in Appendix 1 or Appendix 2. [Note 5] The projection unit forms an image of the light beam from the light source on the focal plane or the focal plane region. The optical device described in Appendix 1 or Appendix 2. [Note 6] The light-emitting surface of the light source is positioned on the focal plane or the focal plane region. The light source is capable of independently emitting light of the two different wavelength spectra in different regions. The optical device described in Appendix 1 or Appendix 2. [Note 7] Furthermore, it is equipped with a light-diffusing section, The light diffusing section increases the divergence angle of the light beam as the light beam passes through the focal plane or the focal plane region. The optical device described in Appendix 1 or Appendix 2. [Note 8] Furthermore, it is equipped with an imaging unit, The imaging unit is capable of spectrally separating at least two different wavelengths from the light source, each of which is included in the at least two different wavelength spectra of the light. The optical device described in Appendix 1 or Appendix 2. [Note 9] Furthermore, it is equipped with an imaging unit, The imaging unit has object-side telecentricity with respect to at least one wavelength of light from the light source. The optical device described in Appendix 1 or Appendix 2. [Note 10] The aforementioned illumination optical element is a lens. The optical device described in Appendix 1 or Appendix 2. [Note 11] The optical device described in Appendix 9, A processor controls the imaging unit, causes the imaging unit to acquire an image, and performs optical inspection of the object surface based on the color information of the image acquired by the imaging unit. An optical inspection device equipped with the following features. [Note 12] The optical inspection apparatus according to Appendix 11, wherein the processor outputs the state of the object surface based on the number of colors emitted from the light source and the number of colors acquired by each pixel of the imaging unit when performing the optical inspection. [Note 13] An optical inspection method using the optical apparatus described in Appendix 9, The imaging unit acquires an image of the object surface. An optical inspection is performed based on the color information of the image captured by the imaging unit. Optical inspection methods, including those mentioned above. [Note 14] The optical inspection method described in Appendix 13, wherein the optical inspection is performed by outputting the state of the object surface based on the number of colors emitted from the light source and the number of colors acquired by each pixel of the imaging unit. [Note 15] An optical inspection program using the optical device described in Appendix 9, The imaging unit acquires an image of the surface of an object. An optical inspection of the surface of the object is performed based on the color information of the image captured by the imaging unit. An optical inspection program that causes a computer to perform an inspection of the surface condition of an object. [Note 16] The optical inspection program described in Appendix 15 includes causing the computer to output the state of the surface of the object based on the number of colors emitted from the light source and the number of colors acquired by each pixel of the imaging unit. [Explanation of Symbols]

[0158] 10…Optical inspection device, 12…Optical device, 14…Processing device, 22…Projection unit, 24…Illumination optical element, 26…Imaging unit, 26a…Beam splitter, 28…Light diffusion plate, 32…Light source, 52…Imaging optical element, 54…Imaging aperture, 54a…Through hole, 54b…Medium, 56…Imaging sensor, 62…Processor, 64…Memory device, C1…Illumination optical axis, C2…Imaging optical axis, FP1…Illumination focal plane, FP1 A... Illumination focal plane region, FP2... Imaging focal plane, FP2A... Imaging focal plane region, PIA1... First virtual region, PIA2... Second virtual region, L1... First ray, L2... Second ray, PI1... First wavelength selection region, PI2... Second wavelength selection region, α1... First divergence angle, α2... Second divergence angle, β1... First ray angle, β2... Second ray angle, γ1... First reflected ray angle, γ2... Second reflected ray angle.

Claims

1. An illumination optical element having a focal plane region including the focal plane or its vicinity, A projection unit equipped with a light source Equipped with, The projection unit is capable of emitting a light beam containing at least two different wavelength spectra from the light source to the illumination optical element. The projection unit forms an image of the light beam from the light source on the projection surface which is the focal plane or the focal plane region, and forms projected images at different positions using the two different wavelength spectra of light on the focal plane or the focal plane region of the illumination optical element. Light emitted from the same point of passage on the projection surface is all given the same ray angle by the illumination optical element. When a light beam with the first ray from the light source of the projection unit as the principal ray is imaged onto the projection surface, all the rays contained in that light beam are converted into parallel light beams with the same ray angle by the illumination optical element and irradiated onto the object surface. optical equipment.

2. The optical apparatus according to claim 1, wherein the projection unit simultaneously emits a beam of light containing at least two different wavelength spectra from the light source.

3. An illumination optical element having a focal plane region including the focal plane or its vicinity, A projection unit equipped with a light source Equipped with, The projection unit is capable of emitting a light beam containing at least two different wavelength spectra from the light source to the illumination optical element. The projection unit forms projected images at different positions using light of two different wavelength spectra within the focal plane or focal plane region of the illumination optical element. The projection unit is capable of changing the projected image over time using light of two different wavelength spectra. optical equipment.

4. The projection unit increases the divergence angle immediately after the light beam from the light source passes the focal plane or the focal plane region compared to the angle immediately before passing through. The optical apparatus according to any one of claims 1 to 3.

5. The light-emitting surface of the light source is positioned on the focal plane or the focal plane region. The light source is capable of independently emitting light of the two different wavelength spectra in different regions. The optical apparatus according to any one of claims 1 to 3.

6. Furthermore, it is equipped with a light-diffusing section, The light diffusing section increases the divergence angle of the light beam as the light beam passes through the focal plane or the focal plane region. The optical apparatus according to any one of claims 1 to 3.

7. Furthermore, it is equipped with an imaging unit, The imaging unit is capable of spectrally separating at least two different wavelengths from the light source, each of which is included in the at least two different wavelength spectra of the light. The optical apparatus according to any one of claims 1 to 3.

8. Furthermore, it is equipped with an imaging unit, The imaging unit has object-side telecentricity with respect to at least one wavelength of light from the light source. The optical apparatus according to any one of claims 1 to 3.

9. The aforementioned illumination optical element is a lens. The optical apparatus according to any one of claims 1 to 3.

10. The optical apparatus according to claim 8, A processor controls the imaging unit, causes the imaging unit to acquire an image, and performs optical inspection of the object surface based on the color information of the image acquired by the imaging unit. An optical inspection device equipped with the following features.

11. The processor, when performing the optical inspection, outputs the state of the object surface based on the number of colors emitted from the light source and the number of colors acquired by each pixel of the imaging unit. The optical inspection apparatus according to claim 10.

12. An optical inspection method using the optical apparatus described in Claim 8, The imaging unit acquires an image of the object surface. An optical inspection is performed based on the color information of the image captured by the imaging unit. Optical inspection methods, including those mentioned above.

13. Performing the aforementioned optical inspection includes outputting the state of the object surface based on the number of colors emitted from the light source and the number of colors acquired by each pixel of the imaging unit. The optical inspection method according to claim 12.

14. An optical inspection program using the optical device described in Claim 8, The imaging unit acquires an image of the object surface. An optical inspection of the object surface is performed based on the color information of the image captured by the imaging unit. An optical inspection program that causes a computer to perform an inspection of the surface condition of an object.

15. Performing the optical inspection includes causing the computer to output the state of the object surface based on the number of colors emitted from the light source and the number of colors acquired by each pixel of the imaging unit. The optical inspection program according to claim 14.

16. An illumination optical element having a focal plane region including the focal plane or its vicinity, A projection unit equipped with a light source Equipped with, The projection unit is capable of emitting a light beam containing at least two different wavelength spectra from the light source to the illumination optical element. The projection unit forms projected images at different positions using light of two different wavelength spectra within the focal plane or focal plane region of the illumination optical element. The light-emitting surface of the light source is positioned on the focal plane or the focal plane region. The light source is capable of independently emitting light from two different wavelength spectra in different regions, combining them, and then incident them onto the illumination optical element. optical equipment.

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