JP2025021370A - OPTICAL DEVICE, OPTICAL INSPECTION DEVICE, OPTICAL INSPECTION METHOD, AND OPTICAL INSPECTION PROGRAM - Google Patents

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

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

Non-contact inspection of objects is becoming important in various industries. Conventional methods involve using a diffraction grating or wavelength filter to separate light rays, creating a one-to-one correspondence between the color (wavelength spectrum) and the direction of the light rays, and identifying the color to identify the direction of the light rays and obtain information about the surface or inside of the object.

U.S. Pat. No. 5,675,407

W. L. Hows, “Rainbow schlieren and its application,” Applied Optics, vol. 23, No. 14, 1984 H. Ohno, “One-shot three-dimensional measurement method with the color mapping of light direction,” OSA Continuum, Vol. 4, Issue 3, 2021

The problem that the present invention aims to solve is to provide an optical device, an optical inspection device, an optical inspection method, and an optical inspection program that are capable of associating the direction of a light ray (direction of a light beam) with a wavelength spectrum.

According to an embodiment, the optical device includes an illumination optical element having a focal surface region including a focal surface or its vicinity, and a projection unit including a light source. The projection unit can emit a light beam including light of at least two different wavelength spectra from the light source. The projection unit forms a projection image that projects the light of the two different wavelength spectra at different positions in the focal surface region of the illumination optical element.

FIG. 2 is a schematic diagram showing an optical device of the optical inspection device according to the first embodiment. 2 is a diagram showing a virtual projected image of the optical device of the optical inspection device shown in FIG. 1 as viewed from the projection unit side. 10 is a diagram showing a modified example of a virtual projection image of the optical device of the optical inspection device shown in FIG. 1 as viewed from the projection unit side. 5 is a diagram showing a modified example of a virtual projection image of the optical device, different from that shown in FIG. 3, as viewed from the projection unit side. 5 is a diagram showing a modified example of a virtual projection image of the optical device, different from that shown in FIGS. 3 and 4, as viewed from the projection unit side. FIG. FIG. 13 is a schematic diagram showing a modified example of the optical device of the optical inspection device according to the first embodiment. FIG. 11 is a schematic diagram showing an optical inspection device according to a second embodiment. 10 is a flowchart of an optical inspection process for an object surface by an optical inspection device according to a second embodiment. FIG. 11 is a schematic diagram showing the imaging side from the object plane of the optical device of the optical inspection device according to the modified example of the second embodiment. FIG. 11 is a schematic diagram showing an optical device of an optical inspection device according to a third embodiment. 13 is a schematic diagram of a projected image on a projection surface directed from a projection unit of an optical device according to a first modified example of the third embodiment to an illumination lens. 13 is a schematic diagram of a projected image on a projection surface directed from a projection unit of an optical device according to a second modified example of the third embodiment to an illumination lens. FIG. 13 is a schematic diagram showing an optical device of an optical inspection device according to a fourth embodiment. FIG. 13 is a schematic diagram showing an optical device of an optical inspection device according to a first modified example of the fourth embodiment. FIG. 13 is a schematic perspective view showing an optical device of an optical inspection device according to a fifth embodiment.

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

First Embodiment
Hereinafter, the optical inspection device 10 according to this embodiment will be described in detail with reference to the drawings.

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

Figure 1 shows a schematic cross-sectional view of the optical device 12 of the optical inspection device 10 according to this embodiment, and the virtual projection image PI formed by the optical device 12. In this specification, the terms "projection" and "projection" are used interchangeably. In the optical device 12 according to this embodiment in Figure 1, the imaging unit 26 (see Figure 7 of the second embodiment) is omitted. For this reason, the optical device 12 here is described as being capable of being used primarily as an illumination device that irradiates the surface OS of an object with light of a desired color at an appropriate angle with oblique incidence or perpendicularly.

The optical device 12 in this embodiment includes a projection unit 22 and an illumination optical element 24.

The projection unit 22 is equipped with a light source 32 and can emit light of at least two different wavelength spectra at the same time. These wavelength spectra are respectively referred to as a first wavelength spectrum and a second wavelength spectrum. 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. However, this is not limited to this, and any wavelength spectrum may be emitted from the light source 32.

The projection unit 22 can form various images by focusing light beams emitted simultaneously from the light source 32 on the projection surface PP. Here, imaging means concentrating light beams from one point at another point. The point from which the image is formed is called the object point, and the point to which the image is formed is called the image point. The formation of an image by a collection of image points resulting from such imaging is called projection. A first light ray L1 having a first wavelength spectrum is projected from the projection unit 22 onto the projection surface PP, and a second light ray L2 having a second wavelength spectrum is projected onto another point on the projection surface PP. The image projected by the projection unit 22 is called the projected image PI.

The illumination optical element 24 can form an image of light. The illumination optical element 24 may be, for example, a single lens, a lens assembly consisting of multiple lenses, a concave mirror, a diffraction grating, a refractive index gradient lens (GRIN lens), etc. In other words, the illumination optical element 24 may be anything that can form an image of light. The surface on which the illumination optical element 24 forms an image of a set of points at infinity is defined as the illumination focal plane FP1. However, the illumination focal plane FP1 may also be simply called the focal plane. The illumination focal plane FP1 and its vicinity are called the illumination focal plane area FP1A or simply the focal plane area. 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 straight line is imaged again on that straight line. The illumination optical element 24 of this embodiment is, for example, a Fresnel lens. Compared to other lenses, the Fresnel lens 24 can realize a lens with a large effective diameter even if it has a short focal length. This makes it possible to increase the angle of incidence of the 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.

Object O may be either light transmitting or light reflecting. Alternatively, object O may be translucent. A point on the surface of object O or inside the object is called an object point. In the following, unless otherwise specified, object O is assumed to reflect light and object points are assumed to be on the surface of object O. The surface of object O may also be called an object surface or object surface. However, strictly speaking, an object surface is a surface that belongs to an object, whereas an object surface means a surface that is illuminated by lighting. Hereinafter, the symbol OS will be used to refer to object surface or object surface.

The light beam emitted from the projection unit 22 passes through the illumination focal plane area FP1A of the illumination optical element 24, and is irradiated onto the object plane OS through the illumination optical element 24. The divergence angle of the light beam is the maximum spread angle 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 the first divergence angle α1, and the divergence angle of the light beam immediately before entering the illumination focal plane FP1 is the second divergence angle α2. However, there are cases where the light beam from the projection unit 22 is a converging light beam (converging beam). In this case, the second divergence angle α2 is 0.

The projection unit 22 can change the light emitted from the light source 32 at the same time and instantly change (change) the virtual projection 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 an image at enlarged, reduced, or actual size is used. These projectors as the projection unit 22 can instantly switch the projection image electrically. Alternatively, the projection unit 22 may be a slide projector that projects slides, or an overhead projector (OHP) that projects an image written on a transparent sheet. However, these projection units 22 can instantly switch the projection image mechanically. In this embodiment, the projection unit 22 uses, for example, a DLP. However, the projection unit 22 is not limited to this, and various types can be used.

Next, we will describe the operation of the optical device 12 of the optical inspection device 10 according to this embodiment.

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 is also referred to as a virtual projected image. The position of the projection surface PP determined by the projection unit 22 is the focal plane area FP1A of the illumination optical element 24. In other words, the projection surface PP is located in the focal plane area FP1A. Therefore, the projection unit 22 forms an image of the light beam from the light source 32 on the focal plane FP1 or the focal plane area FP1A.

The virtual projection image PI has a first virtual area PIA1 and a second virtual area PIA2. The first virtual area PIA1 is formed by forming an image on the projection surface PP of a light flux having a first light ray L1 having a first wavelength spectrum as a principal ray. The second virtual area PIA2 is formed by forming an image on the projection surface PP of a light flux having a second light ray L2 having a second wavelength spectrum as a principal ray. The first virtual area PIA1 is formed so as to intersect with the optical axis C1 on the projection surface PP. The second virtual area PIA2 is formed so as not to intersect with the optical axis C1 on the projection surface PP. However, the virtual projection image PI is not limited to this, and any image may be used as long as the first virtual area PIA1 and the second virtual area PIA2 can be optically separated on the projection surface PP. It is preferable to form the virtual projection image PI by dividing appropriate areas PIA1 and PIA2 on the projection surface PP with light of wavelengths that can be dispersed by the imaging unit 26, such as RGB. The first virtual area PIA1 and the second virtual area PIA2 of the virtual projection image PI projected by the projection unit 22 can be formed as shown in FIG. 2 when viewed from the projection unit 22 toward the illumination optical element 24. That is, on the projection surface PP, the first virtual area PIA1 and the second virtual area PIA2 of the virtual projection image PI are adjacent to each other in a rectangular shape. However, this is not limited to this, and any virtual projection image may be used. Instantaneous change of the virtual projection image PI by the projection unit 22 also includes changing the scale of the first virtual area PIA1 and the second virtual area PIA2 of such a virtual projection image PI.

When the illumination optical element 24 side is viewed from the projection unit 22 side, the first virtual area PIA1 and the second virtual area PIA2 of the virtual projection image PI projected by the projection unit 22 may be rotationally symmetric with respect to the optical axis C1 of the illumination optical element 24 as shown in FIG. 3, may be arranged in a stripe pattern as shown in FIG. 4, or may be formed radially as shown in FIG. 5. In other words, the virtual projection image PI may have any shape as long as at least the first virtual area PIA1 and the second virtual area PIA2 can be partitioned. In addition, the projection unit 22 can change the virtual projection image PI shown in FIG. 2 to FIG. 5 in a time series. The projection unit 22 projects, for example, a predetermined projection image PI in a time series at an appropriate frame rate of the imaging element 56 of the imaging unit 26, for example, in order or randomly. For this reason, the number of projection images PI per unit time that the projection unit 22 projects in a time series onto the projection surface PP can be appropriately set. In this way, the image that can be acquired by the imaging unit 26 changes depending on the projection image PI onto the projection surface PP. In other words, the imaging unit 26 can obtain one or more types of images for inspecting the presence or absence of defects on the object surface OS depending on the projection image PI.

In the example shown in FIG. 3, the optical axis C1 of the illumination optical element 24 intersects with the first virtual area PIA1, and in the examples shown in FIG. 4 and FIG. 5, the optical axis C1 of the illumination optical element 24 intersects with, for example, one of the three first virtual areas PIA1 and one of the three second virtual areas PIA2.

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

The divergence angle of the light beam immediately after passing through the focal plane area FP1A is larger than that of the light beam immediately before passing through the focal plane area FP1A. This is because the projection unit 22 forms an image of the projected image PI on the focal plane area FP1A. In other words, the projection unit 22 can make the divergence angle of the light beam from the light source 32 immediately after passing through the focal plane FP1 or the focal plane area FP1A larger than that (divergence angle) immediately before passing through the focal plane FP1 or the focal plane area FP1A. This makes the first divergence angle α1 larger than the second divergence angle α2. This allows the light beam that reaches the illumination optical element 24 to reach a wider area rather than a local area of the illumination optical element 24. Therefore, when the optical device 12 according to this embodiment is used, there is an effect that the irradiation field irradiated from the illumination optical element 24 to the object surface OS is wider.

The illumination optical element 24 irradiates the light incident through any point on the illumination focal plane FP1 onto the object plane OS. Here, based on geometric optics (see Non-Patent Document 2), the angle of the light passing through the illumination optical element 24 with respect to the optical axis C1 of the illumination optical element 24 is determined according to the passing point on the illumination focal plane FP1. In other words, the light emitted from the same passing point on the projection plane PP or the illumination focal plane FP1 all has the same light ray angle by the illumination optical element 24. As a result, when a light beam with the first light ray L1 as the principal ray is imaged on the projection plane PP, all the light rays contained in the light beam are made into parallel light beams having the same light ray angle by the illumination optical element 24 and irradiated onto the object plane OS. As a result, the first light ray L1 is incident on the object plane OS with an angle with respect to the optical axis C1 being the first light ray angle β1. Similarly, when a light beam with the second light ray L2 as the principal ray is imaged on the projection plane PP, all of the light rays contained in the light beam are converted by the illumination optical element 24 into parallel light beams with the same light ray angle and irradiated onto the object plane OS. As a result, the second light ray L2 is incident on the object plane OS at an angle of β2 with respect to the optical axis C1.

The first divergence angle α1 is larger than the second divergence angle α2. On the other hand, by gradually decreasing the first divergence angle α1 while changing the projected image PI and bringing the outer edge of the second virtual area PIA2 away from the optical axis C1 closer to the optical axis C1, the number of points on the irradiation field irradiated from the illumination optical element 24 to the object surface OS at which the types of light ray angles incident on those points will decrease. In other words, by making the first divergence angle α1 larger than the second divergence angle α2, there is an effect of increasing the types of light ray angles incident on points on the irradiation field irradiated from the illumination optical element 24 to the object surface OS.

In addition, the light of the first wavelength spectrum and the light of the second wavelength spectrum are different colors. This allows the optical device 12 to irradiate the object surface OS with a bundle of rays with different ray angles for each color. In other words, the optical device 12 can irradiate the object surface OS with rays with different angles of incidence for each color.

The directional distribution of reflected light from the surface OS of an object changes depending on the surface properties and surface shape of the object's surface OS. The directional distribution of reflected light is described by a Bidirectional Reflectance Distribution Function (BRDF). In general, the surface properties and surface shape of the object's surface OS, that is, the object surface information, can be estimated using the BRDF. This BRDF has a significant effect on the image captured by the imaging unit 26 (see Figure 7). In other words, conversely, the image captured by the imaging unit 26 contains information related to the BRDF.

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 angles of incidence contain more information than a BRDF for one angle of incidence. The more information there is about the BRDF, the more detailed the condition 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 projection image PI in various ways, thereby instantly changing the angle of incidence with respect to the surface OS of the object. Then, by observing the reflected light each time, for example with the imaging unit 26, it is possible to obtain a more detailed surface condition of the object.

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

According to this embodiment, in an image captured by the image sensor 56 of the image capture unit 26 described later, it is assumed that the color of light (blue light) due to the first light ray angle β1 will be predominant in the flat portion of the object surface OS. On the other hand, in an image captured by the image sensor 56 of the image capture unit 26, the color of the defective portion of the object surface OS changes depending on the inclination angle of the defect, but the color of light (red light) due to the second light ray angle β2 may be predominant, or the color of light due to the first light ray angle β1 may be mixed with the color of light due to the second light ray angle β2. For example, the smaller the inclination 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 on the focal plane FP1 of the illumination optical element 24, and the larger the inclination angle, the more the image is acquired as the color of the region farther from the optical axis C1 in the virtual projection image PI projected on the focal plane FP1 of the illumination optical element 24.

In particular, in optical inspection, it is necessary to select the optimal direction of the light beam to be irradiated onto the surface OS of the object depending on the type of object O. In the past, this required the preparation of various types of ring illumination (oblique incidence illumination), for example. However, by using the optical device (illumination device) 12 according to this embodiment, it is possible to instantly change the virtual projection image PI to change the angle of incidence of the light beam. In other words, by using one optical device 12 according to this embodiment, it is possible to selectively use a variety of illumination devices of various sizes with a single device.

The optical device 12 according to this embodiment can be applied to a variety of projection units 22. Therefore, the optical device 12 has the advantage that it is possible to select from a wide range of commercially available projection units 22 capable of forming a virtual projection image PI in a predetermined area FP1A (including the projection plane PP and the illumination focal plane FP1). In addition, the optical device 12 has the advantage that it is possible to use commercially available projection units 22 without modifying them.

The optical device 12 according to this embodiment includes an illumination optical element 24 having a focal plane area FP1A including the focal plane FP1 or its vicinity, and a projection unit 22 including a light source 32. The projection unit 22 can emit a light beam including light of at least two different wavelength spectra from the light source 32 to the illumination optical element 24. The projection unit 22 also projects light of two different wavelength spectra at different positions on the focal plane FP1 or focal plane area FP1A of the illumination optical element 24 to form a projection image PI. Therefore, the optical device 12 of the optical inspection device 10 according to this embodiment can associate the direction of the light beam (direction of the light beam) with the wavelength spectrum. The wavelength spectrum can be considered to be synonymous with the color of the light beam. Therefore, it can be said that the optical device 12 can associate the direction of the light beam with the color of the light beam.

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

(Modification)
A modification of the first embodiment will be described with reference to FIG.

In a modified example of this embodiment shown in FIG. 6, a schematic cross-sectional view of the optical device 12 of the optical inspection device 10 and the virtual projection image PI formed by the optical device 12 is shown. The virtual projection image PI shown in FIG. 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.

In this modified example, a black light-shielding area 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 area PIA0 may actually exist or may be virtual. If it is virtual, it is preferable that the light-shielding area PIA0 is not irradiated with light from the light source 32. If it is virtual, the size and shape of the light-shielding area PIA0 can be electrically changed.

Next, we will describe the operation of the optical device 12 of the optical inspection device 10 according to this modified example.

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

The virtual projection image PI has a zeroth virtual area (light-shielded area) PIA0, a first virtual area PIA1, and a second virtual area PIA2.

The zeroth virtual area (light-shielded area) PIA0 is formed so as to intersect with the optical axis C1 of the illumination optical element 24 on the projection plane PP.

The first virtual area PIA1 is formed by focusing a light beam having a first light ray L1 with a first wavelength spectrum as its principal ray on the projection surface PP. The first virtual area PIA1 is formed so as not to intersect with the optical axis C1 on the projection surface PP. The second virtual area PIA2 is formed by focusing a light beam having a second light ray L2 with a second wavelength spectrum as its principal ray on the projection surface PP. The second virtual area PIA2 is formed so as not to intersect with the optical axis C1 on the projection surface PP.

When a light beam having a first light ray L1 as a principal ray is focused on the projection plane PP, all of the light rays contained in the light beam are converted by the illumination optical element 24 into parallel light beams having the same light ray angle and irradiated onto the object plane OS depending on the position of the projection plane PP. As a result, the first light ray L1 is incident on the object plane OS at a first light ray angle β1 relative to the optical axis C1. Similarly, when a light beam having a second light ray L2 as a principal ray is focused on the projection plane PP, all of the light rays contained in the light beam are converted by the illumination optical element 24 into parallel light beams having the same light ray angle and irradiated onto the object plane OS depending on the position of the projection plane PP. As a result, the second light ray L2 is incident on the object plane OS at a second light ray angle β2 relative to the optical axis C1.

At this time, only the light beam whose principal ray is the first light ray L1 and the light beam whose principal ray is the second light ray L2 can be incident on the object surface OS. In other words, only oblique incidence components can be incident. In other words, by forming the light-shielding area PIA0 using the 0th virtual area (light-shielding area) PIA0, it is possible to realize oblique incidence illumination using the light beam whose principal ray is the first light ray L1 and the light beam whose principal ray is the second light ray L2. This makes it possible to image only the components scattered at the object surface OS, enabling dark-field imaging.

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

As described above, the optical device 12 of the optical inspection device 10 according to this modified example makes it possible to associate the direction of light rays (direction of light beams) with wavelength spectra. In addition, the projection unit 22 of the optical device 12 makes it possible to instantly change the virtual projection image PI. For example, on the projection surface PP, each of the areas PIA0, PIA1, and PIA2 can be expanded or contracted in an appropriate direction. Therefore, the optical device 12 according to this modified example has the effect of being able to instantly change the correspondence between the direction of light rays and the color of light rays according to various applications.

Second Embodiment
7 shows a schematic cross-sectional view of the optical device 12 of the optical inspection device 10 according to the second embodiment and a virtual projected image PI formed by the optical device 12. The optical inspection device 10 according to the present embodiment has the optical device 12 and a processing device 14.

The optical device 12 of the optical inspection device 10 according to this embodiment includes a projection unit 22, an illumination optical element 24, and an imaging unit 26. Of the optical device 12 of the optical inspection device 10 according to this embodiment, the projection unit 22 and the illumination optical element 24 are configured similarly to the projection unit 22 and the 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.

The projection unit 22 can instantly change (vary) the virtual projection image PI. The object O is opaque and reflects light on its surface. However, this is not limited to this, and the object may be transparent or translucent. The surface of the object is referred to as the object surface OS.

In FIG. 7, an illumination system that illuminates the object surface OS by the projection unit 22 is drawn on the left side of the object surface OS, and an imaging system that captures an image using light reflected from the object surface OS by the imaging unit 26 is drawn on the right side of the object surface OS. In other words, the optical device 12 in FIG. 7 is drawn with the illumination side (illumination system) and the imaging side (imaging system) on the left and right sides at the boundary of the object surface OS. However, in reality, the light reflected by the object surface OS returns toward 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 and guide the light reflected by the object surface OS to the imaging unit 26 shown by a dashed line in FIG. 7. In other words, in FIG. 7, the imaging unit 26 shown by a dashed line is drawn diagrammatically on the right side of the object surface OS. Note that the object O in FIG. 7 also has an appropriate thickness, but the thickness is ignored when drawing.

The first wavelength spectrum emitted from the light source 32 of the projection unit 22 is blue light with a peak at a wavelength of 450 nm and a full width at half maximum of 100 nm. That is, the first wavelength is a wavelength 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 a wavelength of 650 nm and a full width at half maximum of 200 nm. That is, the second wavelength is a wavelength included in the second wavelength spectrum and is the peak of the second wavelength spectrum. However, the first wavelength and the second wavelength are different from each other, and may be anything as long as they are included in the first wavelength spectrum and the second wavelength spectrum, respectively. The wavelength spectrum generated from the light source 32 is not limited to this, and may be anything. Here, it is assumed that the full width at half maximum of the second wavelength spectrum is 200 nm and overlaps with the first wavelength spectrum. In this way, the first wavelength spectrum and the second wavelength spectrum may overlap. As described in the first embodiment, if the full width at half maximum of the second wavelength spectrum is 100 nm, the area that overlaps with the first wavelength spectrum is small. Therefore, the first wavelength spectrum and the second wavelength spectrum may or may not have an overlapping portion.

The imaging unit 26 has an imaging optical element 52, an imaging aperture 54, and an imaging element (image sensor) 56.

The imaging optical element 52 can form an image of light. The imaging optical element 52 may be, for example, a single lens, a lens assembly consisting of multiple lenses, a concave mirror, a diffraction grating, a refractive index gradient lens (GRIN lens), etc. In other words, the imaging optical element 52 may be anything that can form an image of light. The surface on which the imaging optical element 52 forms an image of a set of points at infinity is defined as the imaging focal plane FP2. However, the imaging focal plane FP2 may also be simply called the focal plane. The imaging focal plane FP2 and its vicinity are referred to as the imaging focal plane area FP2A or simply as the focal plane area. 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 straight line is imaged again on that straight line. The imaging optical element 52 of this embodiment 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.

The imaging aperture 54 is disposed 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 the first wavelength and the second wavelength to pass through. Meanwhile, a medium (light shield) 54b that blocks light of the first wavelength and the second wavelength is provided around the through hole 54a of the imaging aperture 54. At this time, based on geometric optics, the imaging unit 26 has telecentricity on the object side for 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 has object-side telecentricity for at least one wavelength of light from the light source 32.

The image sensor 56 has pixels that can separate at least the first wavelength and the second wavelength and obtain light reception signals independently. Therefore, the imaging unit 26 can separate at least two different wavelengths contained in light of at least two different wavelength spectra 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 may be anything that can separate at least two wavelengths and convert light into a light reception signal. The light reception signal of the image sensor 56 may also be simply called a signal, a signal value, or a pixel value.

The processing device 14 is connected to the imaging element 56 of the imaging unit 26 by wire or wirelessly. The processing device 14 not only controls the imaging element 56 of the imaging unit 26, but also preferably controls the light source 32 of the projection unit 22.

The processing device 14 has 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, for example, storing the images.

The processor 62 is, for example, a CPU or a GPU, but may be any element capable of performing the calculations described below (inspection processing of the object surface OS shown in FIG. 8). The processor 62 corresponds to the central part of a computer that performs processing such as calculations and control required for the processing of the processing device 14, and controls the entire processing device 14 in an integrated manner. The processor 62 executes control to realize various functions of the processing device 14 based on programs such as system software, application software, or firmware stored in a storage device 64 such as a ROM or an auxiliary storage device. The processor 62 includes, 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 is a combination of two or more of these. The processor 62 provided in the processing device 14 may be one or more.

The processing device 14 executes processes to perform various functions by having the processor 62 execute programs stored in the storage device 64. It is also preferable that the control program of the processing device 14 is not stored in the storage device 64 of the processing device 14, but is placed on an appropriate server or cloud. In this case, the control program is executed while communicating with, for example, the processor 62 of the optical inspection device 10 via a communication interface. That is, the processing device 14 according to this embodiment may be included in the optical inspection device 10, or may be located on a server or cloud of various inspection site systems away from the optical inspection device 10. For this reason, it is also preferable that the optical inspection program is not stored in the storage device 64, but is on a server or cloud, and the program is executed while communicating with, for example, the processor 62 of the optical inspection device 10 via a communication interface. Therefore, the processor 62 (processing device 14) can execute the optical inspection program (optical inspection algorithm) described later.

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

The storage device 64 may be, for example, a HDD or SSD, but may be anything that can store (save) images.

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

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

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

As described above, the virtual projection image PI has a first virtual area PIA1 and a second virtual area PIA2 adjacent to each other. The first virtual area PIA1 is formed by forming an image on the projection surface PP of a light flux having a first light ray L1 having a first wavelength spectrum as a principal ray. The second virtual area PIA2 is formed by forming an image on the projection surface PP of a light flux having a second light ray L2 having a second wavelength spectrum as a principal ray. Then, when the light flux having the first light ray L1 as a principal ray is formed on the projection surface PP, all the light rays contained in the light flux are made into parallel light fluxes having the same light ray angle by the illumination optical element 24 and irradiated onto the object surface OS. As a result, the first light ray L1 is incident on the object surface OS at an angle of the first light ray angle β1 with respect to the optical axis C1. Similarly, when a light beam with the second light ray L2 as the principal ray is imaged on the projection plane PP, all of the light rays contained in the light beam are converted by the illumination optical element 24 into parallel light beams with the same light ray angle and irradiated onto the object plane OS. As a result, the angle of the second light ray L2 with respect to the optical axis C1 of the illumination optical element 24 becomes the second light ray angle β2 and is incident on the object plane OS.

The first divergence angle α1 is larger than the second divergence angle α2. On the other hand, if the first divergence angle α1 is gradually reduced, the number of points on the irradiation field of the object surface OS at which the types of light ray angles incident on the points will decrease will increase. In other words, by making the first divergence angle α1 larger than the second divergence angle α2, it is possible to increase the types of light ray angles incident on points on the irradiation field irradiated from the illumination optical element 24 to the object surface OS. In addition, the light of the first wavelength spectrum and the second wavelength spectrum are different colors. This allows the optical device 12 to irradiate the object surface OS with light beams with different light ray angles for each color. In other words, the optical device 12 can irradiate the object surface OS with light beams with different incident angles for each color.

From the above, 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 a light beam) with a wavelength spectrum. In addition, the projection unit 22 of the optical device 12 can instantly change the virtual projection image PI. Therefore, the optical device 12 according to this embodiment has the effect of being able to instantly change the correspondence between the direction of a light ray and the color of the light ray according to various applications.

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 obtains an image of the object surface OS corresponding to the virtual projection image PI using the processor 62 of the processing device 14 (step S1 in Figure 8).

First, consider the case where the object surface OS is a standard surface. In this case, as shown in FIG. 7, the first light ray L1 is specularly reflected by the object surface OS, passes through the imaging aperture 54, and is imaged by the imaging element 56. Here, the angle of the reflected light of the first light ray L1 relative to the imaging optical axis C2 when it is reflected is defined as the first reflected light ray angle γ1. On the other hand, the second light ray L2 is specularly reflected by the object surface OS and is blocked by the imaging aperture 54. Here, the angle of the reflected light of the second light ray L2 relative to the imaging optical axis C2 when it is reflected is defined as the second reflected light ray angle γ2. As a result, the second light 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 it only with the first wavelength, and not with the second wavelength. In other words, the standard surface of the object surface OS is imaged only with blue light, and not with red light.

Next, consider the case where a defect exists on the object surface OS. In particular, assume that a defect exists on the surface where the first light ray L1 and the second light ray L2 reach. Then, the first light ray L1 is scattered by the defect on the object surface OS, and the BRDF spreads. As a result, a part of the scattered light passes through the imaging optical element 52 and the imaging aperture 54 and is imaged by the imaging element 56. On the other hand, the second light ray L2 is also scattered by the defect on the object surface OS, and the BRDF spreads. As a result, a part of the scattered light passes through the imaging optical element 52 and the imaging aperture 54 and is imaged by the imaging element 56. In other words, if there is a defect on the object surface OS, the defect is imaged with light of the first wavelength and the second wavelength. In other words, the defect on the object surface OS is imaged with both blue light and red light.

As a result, the processing device 14 (processor 62) can determine whether or not there is a defect on the object surface OS based on the color of the image captured by the imaging element 56 of the imaging unit 26. That is, as shown in FIG. 8, the processing device 14 inspects the object surface OS for defects based on the image captured by the imaging unit 26 (step S2).

As shown in FIG. 8, in this embodiment, when the processing device 14 determines that one color of light (blue light) is incident based on the light receiving signals of all pixels of the image sensor 56, it can output that there is no defect on the surface OS of the object to be the subject. Also, when the processing device 14 determines that two colors (blue light and red light) are incident on the light receiving signals of some pixels based on the light receiving signals of all pixels of the image sensor 56, it can output that there is a defect on the surface OS of the object to be the subject. In this way, the processing device 14 can output whether or not there is a defect on the surface OS of the object to be the subject (step S3). Therefore, when performing optical inspection, the processing device 14 (processor 62) outputs the state of the object surface OS based on the number of colors emitted from the light source 32 and the number of colors acquired at each pixel of the image sensor 56 of the imaging unit 26.

The optical inspection device 10 can perform the inspection process of the object surface OS shown in FIG. 8 by the processing device 14 every time the virtual projection image PI projected on the projection surface PP is changed. For this reason, 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 every time a plurality of different virtual projection images PI are projected on the projection surface PP by the processor 62 of the processing device 14, and output the presence or absence of defects for each. The processing device 14 can perform optical inspection of the object surface OS at an appropriate speed and with various illumination methods by synchronizing the imaging by the imaging element 56 when the projection unit 22 electrically or mechanically switches to project different virtual projection images PI on the projection surface PP. When a general projection unit 22 electrically or mechanically switches to project different virtual projection images PI on the projection surface PP, for example, if the projection unit 22 has a performance of approximately 60 fps or more, the projection unit 22 can project 60 images or more per second. In addition, by synchronously acquiring the image using the imaging element 56, optical inspection of the object surface OS can be performed in a relatively short time using light from various different directions and various colors of light. Therefore, the optical inspection device 10 according to this embodiment can improve the optical inspection accuracy compared to optical inspection of the object surface OS using one type of conventional lighting device.

If the imaging section 26 does not have an imaging aperture 54, i.e., if the imaging aperture 54 does not exist on the focal plane FP2 of the imaging optical element 52 between the imaging optical element 52 and the imaging element 56, it becomes impossible to identify the presence or absence of defects on the object surface O by color as described above. This is because, if there is no imaging aperture 54, light of all colors emitted from the light source 32 is imaged by the imaging element 56 regardless of the presence or absence of defects on the object surface OS. For this reason, the imaging section 26 of the optical inspection device 10 has object-side telecentricity for at least one wavelength of light from the light source 32, thereby having the effect of being able to identify the presence or absence of defects on the object surface OS.

The processing device 14 of the optical inspection device 10 described in this embodiment can be used together with the optical device 12 according to the third, fourth, and fifth embodiments described below.

(Modification)
A modified example of the imaging section 26 of the optical device 12 of the optical inspection device 10 of the second embodiment will be described with reference to Fig. 9. In this modified example, the imaging section 26 is the same as the imaging section 26 of the optical device 12 of the optical inspection device 10 described in the second embodiment, except for the imaging opening 54 of the imaging section 26. That is, the projection section 22 and the illumination optical element 24 of the optical device 12 have the same configuration as those described in the first and second embodiments, and therefore will not be described here.

Figure 9 shows a schematic cross-sectional view of the optical device 12 of the optical inspection device 10 according to this modified example, on the imaging unit 26 side from the object plane OS. The cross-sectional view shown in Figure 9 includes the imaging optical axis C2 of the imaging unit 26.

The imaging aperture 54 according to this modification has a first wavelength selection region 55a and a second wavelength selection region 55b. The imaging aperture 54 according to this modification is not a virtual one formed by projection, but an actual one. The first wavelength selection region 55a passes light of a first wavelength (e.g., blue light). However, the first wavelength selection region 55a blocks light of a second wavelength (e.g., red light). The second wavelength selection region 55b passes light of a second wavelength. However, the second wavelength selection region 55b blocks light of the first wavelength. The first wavelength selection region 55a is arranged so as to intersect with the optical axis C2 of the imaging unit 26 on the imaging focal plane FP2 of the imaging optical element 52. The second wavelength selection region 55b is arranged so as not to intersect with the optical axis C2 of the imaging unit 26 on the imaging focal plane FP2 of the imaging optical element 52.

The operation of the optical inspection device 10 of this modified example will be described.

In this modified example, the virtual projected image PI by the projection unit 22 has a first virtual area PIA1 and a second virtual area PIA2 (see FIG. 7).

First, the first virtual area PIA1 is formed by forming an image on the projection surface PP of a light flux having a first light ray L1 having a first wavelength spectrum as a principal ray. The second virtual area IA2 is formed by forming an image on the projection surface PP of a light flux having a second light ray L2 having a second wavelength spectrum as a principal ray. At this time, the first light ray L1 passes through the first wavelength selection area 55a. The second light ray L2 passes through the second wavelength selection area 55b. That is, both the first light ray L1 and the second light ray L2 pass through the imaging aperture 54 and are imaged by the imaging element 56. This does not depend on the presence or absence of defects on the surface OS of the object. That is, the object surface OS is imaged by the imaging element 56 at a first wavelength (e.g., blue light) and a second wavelength (e.g., red light) regardless of the presence or absence of defects. That is, the imaging element 56 of the optical device 12 according to this modified example can acquire a normal color image. In other words, the imaging element 56 of the optical device 12 in this modified example can acquire a bright-field image of the surface OS of an object that may contain defects.

Next, the first virtual area PIA1 is formed by focusing a light flux having a second light ray L2 with a second wavelength spectrum as its principal ray on the projection surface PP. The second virtual area is formed by focusing a light flux having a first light ray L1 with a first wavelength spectrum as its principal ray on the projection surface PP. In this case, the blue light and red light are swapped compared to the above example. That is, the processing device 14 controls the light source 32 to swap the emission of blue light and red light with the above example.

At this time, if the surface OS of the object is a standard surface, both the first light ray L1 and the second light ray L2 are blocked by the imaging aperture 54. In other words, if the surface OS of the object is a standard surface, no light is incident on the imaging element 56, and the surface is not imaged by the imaging element 56.

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

As described above, according to the optical device 12 of this modified example, by having the imaging aperture 54 with at least two wavelength selection regions 55a, 55b, the projection image PI by the projection unit 22 is changed, and the imaging element 56 can acquire both a bright field image and a dark field image. This allows the optical inspection device 10 to acquire detailed information about the object surface OS.

In this modified example, the processing device 14 can identify that the projected image PI by the projection unit 22 is different. That is, in this modified example, the processing device 14 can recognize switching between a mode for acquiring a bright field image and a mode for acquiring a dark field image, and acquire an image for each mode (see step S1 in FIG. 8). In the mode for acquiring a dark field image, the processing device 14 can determine whether two colors (blue light and red light) are incident on the light receiving signals of some pixels based on the light receiving signals of all pixels of the image sensor 56 (see step S2 in FIG. 8). Then, the processing device 14 can output whether or not there is a defect on the surface OS of the object to be the subject (see step S3 in FIG. 8). In this way, the optical inspection device 10 can use the processing device 14 to perform the inspection process of the object surface OS shown in FIG. 8, and output whether or not there is a defect on the surface OS of the object to be the subject.

The imaging section 26 of this modified example can be used in the optical device 12 according to the third and fourth embodiments described below.

Third Embodiment
10 shows a schematic cross-sectional view of the optical device 12 of the optical inspection device 10 according to the third embodiment, and the virtual projected image PI formed by the optical device 12. This embodiment is a modified example of the optical inspection device 10 described in the first embodiment including the modified example and the second embodiment including the modified example, and the same members or members having the same functions as the members described in the first embodiment including the modified example and the second embodiment including the modified example are given the same reference numerals, and description thereof will be omitted.

The optical device 12 according to this embodiment has a projection section 22, an illumination optical element 24, and a light diffusion plate (light diffusion section) 28. Here, the imaging section 26 described in the second embodiment (including the modified example) is not shown.

The projection unit 22 can instantly change (alter) the virtual projection image PI. In this embodiment, the projection unit 22 uses, for example, a liquid crystal. However, the projection unit 22 is not limited to this, and can also use a DLP as described above.

The projection unit 22 is equipped with, for example, two light sources 32 capable of emitting light of two different wavelength spectra. In FIG. 6, for convenience, the light source 32 is depicted as one. 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 respectively referred to as the first wavelength spectrum, the second wavelength spectrum, and the third wavelength spectrum. 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. The third wavelength spectrum is the same as the second wavelength spectrum. However, this is not limited to this, and any wavelength spectrum may be used.

The projection unit 22 includes a liquid crystal spatial modulator 34 and a projection lens 36. The projection lens 36 forms an image on the projection surface PP of the light beam emitted from the light source 32 and passing through the spatial modulator 34. The spatial modulator 34 has a plurality of pixels, and various images can be formed by independently modulating each pixel. For convenience, the spatial modulator 34 is depicted as being one in FIG. 6. In reality, the light beams having different wavelength spectra from the two light sources 32 are spatially modulated independently by the two spatial modulators 34 through which the light beams pass, and are combined using a dichroic mirror or the like. After the combination, the combined light beams are made incident on the projection lens 36. The projection unit 22 projects the first light beam L1 having the first wavelength spectrum, the second light beam L2 having the second wavelength spectrum, and the third light beam L3 having the third wavelength spectrum onto different points on the projection surface PP.

In this embodiment, the illumination optical element 24 is a lens assembly made up of multiple lenses. However, for convenience, in FIG. 6, the lens assembly is depicted as a single lens.

The light beam emitted from the projection unit 22 passes through the illumination focal plane area FP1A of the illumination optical element 24, and is then irradiated onto the object plane OS through the illumination optical element 24. 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 entering the illumination focal plane FP1 is defined as the second divergence angle α2. However, there are also cases where the light beam from the projection unit 22 is a converging beam. In this case, the second divergence angle α2 is defined as 0.

The light diffuser 28 is disposed on the illumination focal plane FP1 or the illumination focal plane area FP1A. The light diffuser 28 is not a virtual one like a projected image, but has a real entity. The light diffuser 28 increases the divergence angle of the light beam when it passes through the focal plane FP1 or the focal plane area 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. For convenience, in FIG. 10, the virtual projected image PI is disposed on the illumination focal plane FP1, and the light diffuser 28 is depicted as being disposed adjacent to the virtual projected image PI on the downstream side. For example, it is also preferable to dispose the virtual projected image PI on the illumination focal plane FP1 and the light diffuser 28.

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

The processing device 14 emits light from the light source 32 of the projection unit 22. The light beam emitted from the projection unit 22 forms a projection image PI on the projection plane PP. The position of the projection plane PP determined by the projection unit 22 is located in the focal plane area FP1A of the illumination optical element 24.

In the cross section of FIG. 6, the virtual projection image PI has a first virtual area PIA1, a second virtual area PIA2, and a third virtual area PIA3. The first virtual area PIA1 is formed by forming an image on the projection surface PP of a light beam having a first light ray L1 having a first wavelength spectrum as a principal ray. The second virtual area PIA2 is formed by forming an image on the projection surface PP of a light beam having a second light ray L2 having a second wavelength spectrum as a principal ray. The third virtual area PIA3 is formed by forming an image on the projection surface PP of a light beam having a third light ray L3 having a third wavelength spectrum as a principal ray. The first virtual area PIA1 intersects with the optical axis C1. In FIG. 10, the virtual projection image PI is assumed to be concentric with the optical axis C1. In this case, the first virtual area PIA1 and the third virtual area PIA3 are symmetrical with respect to the optical axis C2. However, the virtual projected image PI is not limited to this and can be anything.

The divergence angle α1 of the light beam immediately after passing through the illumination focal plane area FP1A is larger than the divergence angle α2 of the light beam immediately before that. One reason for this is that the projection image PI is imaged on the focal plane area FP1A by the projection unit 22. In other words, the first divergence angle α1 is larger than the second divergence angle α2. This allows the light beam that reaches the illumination optical element 24 to reach a wider area rather than a localized area of the illumination optical element 24. Therefore, when the optical device 12 according to this embodiment is used, there is an effect that the irradiation field irradiated from the illumination optical element 24 to the object surface OS is wider.

Furthermore, in this embodiment, an optical diffuser 28 is disposed in the illumination focal plane area FP1A. This allows the divergence angle of the light passing through the focal plane area FP1A to be further increased compared to when the optical diffuser 28 is not disposed. In other words, the light flux reaching the illumination optical element 24 can reach a wider area rather than a localized area of the illumination optical element 24. This has the effect of further widening the irradiation field irradiated from the illumination optical element 24 to the object surface OS.

The illumination optical element 24 irradiates the light incident through any point on the illumination focal plane FP1 onto the object plane OS. Here, based on geometric optics (see Non-Patent Document 2), the angle of the light passing through the illumination optical element 24 with respect to the optical axis C1 of the illumination optical element 24 is determined according to the passing point on the illumination focal plane FP1. In other words, the light emitted from the same passing point on the projection plane PP or the illumination focal plane FP1 all has the same light ray angle by the illumination optical element 24. As a result, when a light beam with the first light ray L1 as the principal ray is imaged on the projection plane PP, all the light rays contained in the light beam are made into parallel light beams having the same light ray angle by the illumination optical element 24 and irradiated onto the object plane OS. As a result, the first light ray L1 is incident on the object plane OS with an angle with respect to the optical axis C1 being the first light ray angle β1. Similarly, when a light beam having the second light ray L2 as its chief ray is imaged on the projection plane PP, all of the light rays contained in the light beam are converted by the illumination optical element 24 into a parallel light beam having the same light ray angle and irradiated onto the object plane. When a light beam having the third light ray L3 as its chief ray is imaged on the projection plane PP, all of the light rays contained in the light beam are converted by the illumination optical element 24 into a parallel light beam having the same light ray angle and irradiated onto the object plane OS. As a result, the second light ray L2 and the third light ray L3 are incident on the object plane OS at an angle of the second light ray angle β2 with respect to the optical axis C1.

The first divergence angle α1 is larger than the second divergence angle α2. On the other hand, if the first divergence angle α1 is gradually reduced, the number of points on the irradiation field irradiated from the illumination optical element 24 to the object surface OS at which the types of light ray angles incident on those points will decrease. In other words, by making the first divergence angle α1 larger than the second divergence angle α2, there is an effect of increasing the types of light ray angles incident on points on the irradiation field irradiated from the illumination optical element 24 to the object surface OS. In particular, the light diffuser 28 can enhance such an effect.

In addition, the light of the first wavelength spectrum and the light of the second wavelength spectrum are different colors. This allows the optical device 12 to irradiate the object surface OS with a bundle of rays with different ray angles for each color. In other words, the optical device 12 can irradiate the object surface OS with rays with different angles of incidence for each color.

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 angles of incidence provide more information about the surface OS of an object than a BRDF for one angle of incidence. The more information about the BRDF, the more detailed the state of the surface OS of the object can be estimated (see the second embodiment (including modifications)). The optical device 12 according to this embodiment can change the virtual projection image PI in various ways, thereby instantly changing the angle of incidence with respect to the surface OS of the object. As explained in the second embodiment (including modifications), there is an effect that a more detailed surface state of the object can be obtained by observing the reflected light each time, for example, with the imaging unit 26.

Furthermore, by appropriately dividing the projection surface PI into one virtual area PIA1 and two virtual areas PIA2 and PIA3, and projecting different colored projection images PI onto each of the virtual areas PIA1 and PIA2 and PIA3, and irradiating light rays with different angles of incidence for each color onto the surface OS of the object, the imaging unit 26 described in the second embodiment (including modifications) can simultaneously acquire the reflected light corresponding to each angle of incidence while distinguishing it by color. In other words, the optical device 12 according to this embodiment can convert light rays with at least two different wavelength spectra into light rays with different angles of incidence. Therefore, for example, the imaging unit 26 has the effect of being able to simultaneously acquire the reflected light corresponding to each angle of incidence while distinguishing it by color. This has the effect of allowing the imaging unit 26 to acquire more detailed BRDF information, for example. This contributes to improving the inspection accuracy of the surface OS of an object, particularly in optical inspection.

In optical inspection, it is necessary to select the optimal direction of the light beam to be irradiated onto the surface OS of the object depending on the type of object O. Conventionally, this required the preparation of various types of ring illumination (oblique incidence illumination), for example. However, by using the optical device (illumination device) 12 according to this embodiment, it is possible to instantly change the virtual projection image PI to change the angle of incidence of the light beam. In other words, by using one optical device 12 according to this embodiment, it is possible to selectively realize a variety of illuminations in various sizes without the need to prepare multiple conventional illumination devices.

From the above, 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 a light beam) with a 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 the color of a light ray. In addition, the projection unit 22 can instantly change the virtual projection 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 a light ray according to various applications.

(Variation 1)
A first modification of the third embodiment will be described with reference to FIG.

In the first modified example of this embodiment shown in FIG. 11, a virtual projection image PI is shown. The virtual projection image PI shown in FIG. 11 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. On the other hand, the third wavelength spectrum, the fourth wavelength spectrum, and the fifth wavelength spectrum are all different. For example, the peak of the third wavelength spectrum is 550 nm, and the peaks of the fourth wavelength spectrum and the fifth wavelength spectrum 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 that emit light of these five wavelength spectra. In addition, the projection unit 22 is 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 entering the projection lens 36.

In this modified example, the virtual projection image PI has a concentric center and an outer side that is rotationally symmetric by 120°. In other words, the center is axially symmetric and the outer side changes in the azimuth direction. The central part of the concentric circle of the virtual projection image PI is made up of a first wavelength selection region PI1 and a second wavelength selection region PI2 outside the first wavelength selection region PI1. The outer regions of the virtual projection image PI that are rotationally symmetric by 120° are made up of a third wavelength selection region PI3, a fourth wavelength selection region PI4, and a fifth wavelength selection region PI5. The first wavelength selection region PI1 intersects with the optical axis C1 of the illumination optical element 24.

Note that there is a virtual black frame between adjacent regions. This is formed, for example, by not projecting light on the projection surface PP. Such a black frame can be formed virtually. Alternatively, it may be formed by an actual obstruction rather than being virtual.

By using such a virtual projection image PI, the optical device 12 of the optical inspection device 10 according to this modified example has the effect of not only being able to match the angle of the light ray relative to the optical axis C1 as the direction of incidence of the light ray on the object surface OS with the color of the light ray, but also being able to match 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 observe the reflected light from the object surface OS by distinguishing it by color, the optical inspection device 10 has the effect of simultaneously obtaining detailed BRDF information not only regarding the angle of the light ray relative to the optical axis C1, but also regarding the azimuth angle. As a result, by using the optical inspection device 10 according to this modified example, the accuracy and speed of inspection for the presence or absence of defects on the object surface OS is improved.

(Variation 2)
A second modification of the third embodiment will be described with reference to FIG.

In the second modified example of this embodiment shown in FIG. 12, a virtual projection image PI is shown. The virtual projection image PI shown in FIG. 12 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. 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 equipped with three light sources that emit light of these three wavelength spectra. In addition, the projection unit 22 is equipped 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 entering the projection lens 36.

In this modified example, the virtual projection image PI has a fan-shaped first virtual area PIA1, a second virtual area PIA2, and a third virtual area PIA3. The projection unit 22, for example, under the control of the processing device 14, changes the inclination of the virtual projection image PI on the projection plane PP from left to right in FIG. 12 along a time series while maintaining the same shape and size. Note that the first virtual area PIA1, for example, intersects with the optical axis C1 of the illumination optical element 24. This virtual projection image PI is in the same state as if it were rotated around the optical axis C1. The optical axis C1 may be at the apex of the fan-shaped virtual projection image PI.

By using the virtual projection image PI in this way, the optical device 12 has the effect of not only being able to correspond the angle of the light ray relative to the optical axis C1 (direction of the light ray) and the color of the light ray as the incident direction of the light ray to the object surface OS, but also being able to change the azimuth angle direction of the light ray in time. As a result, the imaging unit 26 can simultaneously obtain BRDF information for different incident angles by observing the reflected light from the object surface OS by distinguishing them by color. As a result, by using the optical inspection device 10 according to this modified example, the accuracy and speed of inspection for the presence or absence of defects on the object surface OS can be improved. In addition, the optical device 12 can make incident light with different incident azimuth angles incident on the object surface OS by changing the azimuth angle direction of the virtual projection image PI in time. Therefore, there is an effect that BRDF information for different incident azimuth angles can be obtained. In other words, more detailed BRDF information can be obtained. As a result, using the optical inspection device 10 according to this modified example has the effect of improving the accuracy of inspection for the presence or absence of defects on the object surface OS.

Fourth Embodiment
13 shows a schematic cross-sectional view of the optical device 12 of the optical inspection device 10 according to the fourth embodiment, and the virtual projected image PI formed by the optical device 12. This embodiment is a modification of the optical inspection device 10 described in the first embodiment including a modification, the second embodiment including a modification, and the third embodiment including a modification, and the same members or members having the same functions as the members described in the first embodiment including a modification, the second embodiment including a modification, and the third embodiment including a modification are given the same reference numerals, and description thereof will be omitted.

The optical device 12 according to this embodiment has a projection unit 22 and an illumination optical element 24. The projection unit 22 can instantly change (alter) the virtual projection 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 instantly electrically switch between emitting light of 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 light sources can be used.

The light source 32 of the projection unit 22 has multiple LED light-emitting units 33. Each light-emitting unit 33 can emit light of two different wavelength spectra simultaneously or selectively. These two different wavelength spectra are called 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.

In this embodiment, the illumination optical element 24 is a lens assembly made up of multiple lenses. However, for convenience, in FIG. 13, the lens assembly is depicted as a single lens.

The light emitting surface of the light source 32 is disposed in the illumination focal plane FP1 or illumination focal plane area FP1A of the illumination optical element 24. In this embodiment, the projection plane PP coincides with the light emitting surface of the light source 32.

The light beam emitted from the projection unit 22 immediately passes through the illumination focal plane area FP1A of the illumination optical element 24, and is irradiated onto the object plane OS through the illumination optical element 24. The divergence angle of the light beam immediately after passing through the illumination focal plane FP1 is set to the first divergence angle α1, and the divergence angle of the light beam before entering the illumination focal plane FP1 is set to the second divergence angle α2. However, since the light emitting surface of the light source 32 is disposed on the illumination focal plane FP1, there is no light beam before entering the illumination focal plane FP1. Therefore, the second divergence angle α2 is set to 0.

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

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 area FP1A of the illumination optical element 24.

In the cross section of FIG. 13, the projected image PI has a first virtual area PIA1, a second virtual area PIA2, and a third virtual area PIA3. In FIG. 13, the projected image PI is concentric with respect to the optical axis C1. In this case, the first virtual area PIA1 and the third virtual area PIA3 are symmetrical with respect to the optical axis C1.

The divergence angle α1 of the light beam immediately after passing through the focal plane area FP1A is larger than the divergence angle α2 of the light beam immediately before that (not shown in FIG. 13, see FIGS. 1, 7, and 10). This allows the light beam that reaches the illumination optical element 24 to reach a wider area rather than a localized area of the illumination optical element 24. Therefore, when the optical device 12 according to this embodiment is used, there is an effect that the irradiation field irradiated from the illumination optical element 24 to the object surface OS is wider.

The illumination optical element 24 irradiates the light incident through any point on the illumination focal plane FP1 onto the object plane OS. Here, based on geometric optics (see Non-Patent Document 2), the angle of the light passing through the illumination optical element 24 with respect to the optical axis C1 of the illumination optical element 24 is determined according to the passing point on the illumination focal plane FP1. In other words, the light emitted from the same passing point on the projection plane PP or the illumination focal plane FP1 all has the same light ray angle by the illumination optical element 24. As a result, when a light beam with the first light ray L1 as the principal ray is imaged on the projection plane PP, all the light rays contained in the light beam are made into a parallel light beam having the same light ray angle by the illumination optical element 24 and irradiated onto the object plane OS. As a result, the first light ray L1 is incident on the object plane OS with an angle with respect to the optical axis C1 being the first light ray angle β1. Similarly, when a light beam having the second light ray L2 as its chief ray is imaged on the projection plane PP, all of the light rays contained in the light beam are converted by the illumination optical element 24 into parallel light beams having the same light ray angle and irradiated onto the object plane OS. When a light beam having the third light ray L3 as its chief ray is imaged on the projection plane PP, all of the light rays contained in the light beam are converted by the illumination optical element 24 into parallel light beams having the same light ray angle and irradiated onto the object plane OS. As a result, the second light ray L2 and the third light ray L3 are incident on the object plane OS at an angle of the second light ray angle β2 with respect to the optical axis C1.

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 angles of incidence provide more information about the surface OS of an object than a BRDF for one angle of incidence. The more information about the BRDF, the more detailed the state of the surface OS of the object can be estimated (see the 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 with respect to the surface OS of the object. As explained in the second embodiment (including modifications), the reflected light can be observed each time, for example, by the imaging unit 26, which has the effect of allowing more detailed surface conditions of the object to be obtained.

Furthermore, for example, the imaging unit 26 appropriately divides the projection surface PI into one virtual area PIA1 and two virtual areas PIA2 and PIA3, and projects projection images PI of different colors onto each of the virtual areas PIA1 and PIA2 and PIA3. When light rays with different angles of incidence for each color are incident on the surface OS of the object, the imaging unit 26 described in the second embodiment (including the modified example) can distinguish the reflected light according to each angle of incidence by color and simultaneously acquire it. In other words, the optical device 12 according to this embodiment can make light rays with at least two different wavelength spectra into light rays with different angles of incidence. Therefore, for example, the imaging unit 26 has the effect of distinguishing the reflected light according to each angle of incidence by color and simultaneously acquiring it. This has the effect of, for example, allowing the imaging unit 26 to acquire more detailed BRDF information. This particularly contributes to improving the inspection accuracy of the surface OS of the object in optical inspection.

In optical inspection, it is necessary to select the optimal direction of the light beam to be irradiated onto the surface OS of the object depending on the type of object O. Conventionally, this required the preparation of various types of ring illumination (oblique incidence illumination), for example. However, by using the optical device (illumination device) 12 according to this embodiment, it is possible to instantly change the projected image PI to change the angle of incidence of the light beam. In other words, by using one optical device 12 according to this embodiment, it is possible to selectively use a variety of illuminations in various sizes without having to prepare multiple conventional illumination devices.

From the above, the optical device 12 of the optical inspection device 10 according to this embodiment makes it possible to associate the direction of light rays with a wavelength spectrum. The wavelength spectrum can be considered synonymous with the color of light rays. Therefore, it can also be said that it is possible to associate the direction of light rays with a color. In addition, 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 correspondence between the direction of light rays and colors according to various applications.

(Modification)
FIG. 14 shows a schematic cross-sectional view of the optical device 12 of the optical inspection device 10 according to a modified example of the fourth embodiment.

The optical device 12 according to this modification shows 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. The first light-emitting units 33a each emit light of a first wavelength spectrum simultaneously or selectively. The second light-emitting units 33b each emit 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 a non-polarizing beam splitter. The dichroic mirror 38 is not limited to this, and may be anything that can combine two lights. When a polarizing beam splitter is used as the dichroic mirror 38, if a polarizing camera capable of sensing the polarization direction is used for the image sensor 56 of the image capture unit 26, the polarization information can be used in the same way as the color information, and a lot of information about the directional distribution of light at the object point can be obtained. By using two light sources 32a and 32b, a new wavelength spectrum having two separated peaks can be generated after combining. This allows, for example, the first wavelength spectrum and the second wavelength spectrum to be significantly different, and the colors can be accurately distinguished to obtain information about the directional distribution of light more accurately and quickly. Alternatively, the light intensity of the two light sources 32a and 32b can be adjusted independently and appropriately.

As described above, the optical device 12 of the optical inspection device 10 according to this modified example makes it possible to associate the direction of light rays with the wavelength spectrum. In addition, 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 being able to instantly change the correspondence between the direction of light rays and colors according to various applications.

Fifth Embodiment
Hereinafter, an optical device 12 according to the fifth embodiment will be described with reference to FIG.

Figure 15 shows a schematic perspective view of the optical device 12 of the optical inspection device 10 according to this embodiment, and the virtual projection image PI formed by the optical device 12. This embodiment includes a projection unit 22, an illumination optical element 24, and an imaging unit 26. However, in Figure 15, the projection unit 22 of the optical device 12 is not shown. The projection unit 22 can be any of the various projection units described in the first to fourth embodiments. 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.

The first cross section S1 in FIG. 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.

The illumination optical element 24 has translational symmetry in a direction perpendicular to the first cross section S1. This direction is 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 is on the first cross section S1.

The projection unit 22 uses the light beam B from the light source 32 to project the virtual projection image PI onto the focal plane area FP1A of the illumination optical element 24. For example, the virtual projection image PI has a first virtual area PIA1, a second virtual area PIA2, and a first virtual area PIA3. The direction along the direction in which the virtual projection image PI changes on the virtual projection image PI is the arrangement direction. This arrangement direction is parallel to the first cross section S1. In other words, the arrangement direction of the virtual projection image PI is perpendicular to the longitudinal direction of the line sensor 56. Then, the first virtual area PIA1 is assumed to intersect with the optical axis C1. This illuminates the object surface OS, and an irradiation 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.

The projected image PI by the light beam B from the projection unit 22 can be changed instantly. As an example, the light of the first wavelength projected on the first virtual area PIA1 is blocked by the first wavelength selection area 55a of the wavelength selection unit 55 described later, and passes through the second wavelength selection area 55b and the third wavelength selection area 55c. The light of the second wavelength projected on the second virtual area PIA2 passes through the first wavelength selection area 55a of the wavelength selection unit 55 described later, is blocked by the second wavelength selection area 55b, and passes through the third wavelength selection area 55c. The light of the third wavelength projected on the third virtual area PIA3 passes through the first wavelength selection area 55a and the second wavelength selection area 55b of the wavelength selection unit 55 described later, and is blocked by the third wavelength selection area 55c.

The imaging section 26 has an imaging optical element 52, an imaging aperture 54, and an imaging element 56. The optical axis C2 of the imaging optical element 52 intersects with a wavelength selection section 55 (described later) of the imaging aperture 54. The imaging element 56 is an image sensor, and in this embodiment is a line sensor. The longitudinal direction of the line sensor 56 coincides with the longitudinal direction of the illumination optical element 24.

The imaging aperture 54 has a wavelength selection section 55 instead of the through hole 54a described in the first embodiment (FIG. 7). In FIG. 15, the medium 54b of the imaging aperture 54 is omitted. In this embodiment, the through hole 54a is preferably 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 the longitudinal direction of the wavelength selection section 55. The wavelength selection section 55 has a plurality of regions 55a, 55b, and 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 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.

As with the imaging aperture 54 described in the first embodiment (Figure 7), it is preferable that the outside of the wavelength selection section 55 is formed as a medium 54b that blocks light from the line sensor 56.

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 obtain a two-dimensional image by continuously capturing images of the object O being transported in this manner.

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

When there is a minute defect at the first object point O1 on the object surface OS, the BRDF spreads, and some of the light rays selectively pass through the areas 55a, 55b, and 55c of the wavelength selection section 55 of the imaging aperture 54 to form an image of the first object point O1 on the line sensor 56.

On the other hand, when the first object point O1 is on the standard surface, the first light ray L1 having the first wavelength is specularly reflected by the standard surface. At this time, by appropriately forming the virtual projection image PI, the first light ray L1 can be made to reach the center of the imaging aperture 54 of the imaging unit 26. That is, the first light ray L1 can be made to reach the area including the imaging optical axis C2. The first wavelength selection area 55a of the wavelength selection unit 55 arranged at the center of the imaging aperture 54 is created so as to block the light of the first wavelength. As a result, if there is no micro defect in the first object point O1, the first object point O1 is not imaged with the light of the first wavelength. On the other hand, if there is a micro defect in the first object point O1, the first object point O1 is imaged with the light of the first wavelength. This has the effect of being able to identify the presence or absence of a micro defect 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.

In addition, when the first object point O1 is on the standard surface, the second light ray L2 having a second wavelength different from the first wavelength is also regularly reflected by the standard surface. The first wavelength selection area 55b of the wavelength selection unit 55 arranged at the center of the imaging aperture 54 is created to block the light of the second wavelength. As a result, when the first object point O1 does not have a micro defect, the first object point O1 is not imaged with the light of the second wavelength. On the other hand, when the first object point O1 has a micro defect, the first object point O1 is imaged with the light of the second wavelength. However, even when the first object point O1 is on the standard surface, the reflection direction of the second light ray L2 can be made to coincide with the imaging optical axis C2 by instantly changing the virtual projection image PI by the projection unit 22 and appropriately forming the virtual projection image PI. As a result, the light ray of the second wavelength reaches the center of the imaging aperture 54 of the imaging unit 26. That is, it reaches the area on the imaging aperture 54 that includes the imaging optical axis C2. The first wavelength selection region 55a of the wavelength selection unit 55 arranged at the center of the imaging aperture 54 is created to transmit light of the second wavelength and be imaged by the line sensor 56. At this time, based on geometric optics, the imaging unit 26 has telecentricity on the object side for the second wavelength. In other words, the optical device 12 according to this embodiment has object-side telecentricity for at least one wavelength of light from the light source 32. As a result, the optical device 12 of the optical inspection device 10 according to this embodiment has the effect of being able to acquire a bright field telecentric image using the second wavelength. In other words, the optical device 12 of the optical inspection device 10 according to this embodiment can acquire detailed information of the object surface in addition to the image captured using the first light ray.

The third wavelength, like the second wavelength, is specularly reflected by the standard surface when the first object point O1 is on the standard surface. The first wavelength selection area 55c of the wavelength selection unit 55 arranged at the center of the imaging aperture 54 is created to block the light of the third wavelength. As a result, if there is no micro defect in the first object point O1, the first object point O1 is not imaged with the light of the third wavelength. On the other hand, if there is a micro defect in the first object point O1, the first object point O1 is imaged with the light of the third wavelength. However, even if the first object point O1 is on the standard surface, the third light ray passes through the first wavelength selection area 55a and is imaged by the line sensor 56 by instantly changing the virtual projection image PI by the projection unit 22 and appropriately forming the virtual projection image PI. At this time, based on geometric optics, the imaging unit 26 has telecentricity on the object side for the third wavelength. In other words, the optical device 12 according to this embodiment has object-side telecentricity for at least one wavelength of light from the light source 32.

Consider a ray of light projected onto the first cross section S1. In this case, as shown in FIG. 15, the distribution of the BRDF of the first object point O1 spreads, resulting in light reaching and passing through the wavelength selection section 55 that would not have been reached in the case of the standard surface. Here, it can be seen that depending on the direction of the reflected light, the reflected light reaches different regions 55b, 55c of the wavelength selection section 55 in the imaging aperture 54. However, light rays that reach outside the range of the imaging aperture 54 are not imaged. In other words, the range of light directions that can be imaged is limited by the imaging aperture 54.

On the other hand, consider a light ray 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 angle of view at the imaging unit 26 becomes wider according to the divergence angle of the diffuse light. And since the wavelength selection unit 55 is striped, it can be seen that the color of the light does not depend on the angle of view. Also, by making the longitudinal direction of the stripe sufficiently long, it is possible to achieve the effect of widely and effectively using the longitudinal angle of view of the line sensor 56. Also, by arranging the wavelength selection unit 55 in front of the imaging optical element 52 and the imaging element 56, this optical system can be easily assembled for any combination of imaging optical element 52 and imaging element 56.

The optical inspection device 10 according to this embodiment provides information regarding the spread of the directional distribution of light at the object point O1. In addition, the optical device 12 of the optical inspection device 10 according to this embodiment has the advantage that the imaging field of view can be made wider as the longitudinal direction of the line sensor 56 is made longer. This makes it possible for the optical inspection device 10 according to this embodiment to inspect the properties or shape of the object surface OS.

From the above, the optical device 12 of the optical inspection device 10 according to this embodiment makes it possible to associate the direction of light rays (direction of the light beam) with the wavelength spectrum. In addition, the projection unit 22 of the optical device 12 can instantly change the virtual projection image PI. For example, on the projection surface PP, each of the areas PIA1, PIA2, and PIA3 can be expanded or contracted in an appropriate direction. Therefore, the optical device 12 according to this embodiment has the effect of being able to instantly change the correspondence between the direction of light rays and the color of light rays according to various applications.

According to at least one of the embodiments 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-transitory storage medium such as a storage device 64, which are capable of associating the direction of a light ray (direction of a light beam) with a wavelength spectrum.

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

10...optical inspection device, 12...optical device, 14...processing device, 22...projection unit (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 element, 62...processor, 64...storage device, C1...illumination optical axis, C2...imaging optical axis, FP1...illumination focal plane, FP1 A...illumination focal plane area, FP2...imaging focal plane, FP2A...imaging focal plane area, PIA1...first virtual area, PIA2...second virtual area, L1...first light ray, L2...second light ray, PI1...first wavelength selection area, PI2...second wavelength selection area, α1...first divergence angle, α2...second divergence angle, β1...first light ray angle, β2...second light ray angle, γ1...first reflected light ray angle, γ2...second reflected light ray angle.

Claims (16)

an illumination optical element having a focal plane region including a focal plane or a vicinity thereof;
A projection unit having a light source;
The projection unit can emit a light beam including light of at least two different wavelength spectra from the light source to the illumination optical element,
the projection unit forms projection images at different positions on the focal plane or the focal plane area of the illumination optical element using the light of the two different wavelength spectra.
Optical device. The optical device according to claim 1, wherein the projection unit simultaneously emits a light beam including light of at least two different wavelength spectra from the light source. The optical device according to claim 1 or 2, wherein the projection unit is capable of changing the projection image produced by the light of the two different wavelength spectra in a time series manner. the projection unit makes a divergence angle of the light beam from the light source immediately after passing through the focal plane or the focal plane area larger than that immediately before passing through the focal plane or the focal plane area,
3. The optical device according to claim 1 or 2. The projection unit forms an image of the light beam from the light source on the focal plane or the focal plane area.
3. The optical device according to claim 1 or 2. The light emitting surface of the light source is arranged at the focal plane or at the focal plane region,
The light source is capable of independently emitting light of the two different wavelength spectrums in different regions.
3. The optical device according to claim 1 or 2. Further, a light diffusion section is provided,
The light diffusion section increases a divergence angle of the light beam when the light beam passes through the focal plane or the focal plane area.
3. The optical device according to claim 1 or 2. It also has an imaging unit,
The imaging unit is capable of separating light from the light source into at least two different wavelengths each of which is included in the at least two different wavelength spectra.
3. The optical device according to claim 1 or 2. It also has an imaging unit,
the imaging unit has object-side telecentricity with respect to light having at least one wavelength among the light from the light source;
3. The optical device according to claim 1 or 2. The illumination optical element is a lens.
3. The optical device according to claim 1 or 2. An optical device according to claim 9 ;
and a processor that controls the imaging unit, causes the imaging unit to acquire an image, and performs optical inspection of an object surface based on color information of the image captured by the imaging unit. The optical inspection device according to claim 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. An optical inspection method using the optical device according to claim 9,
acquiring an image of a surface of an object with the imaging unit;
performing an optical inspection based on color information of the image captured by the imaging unit;
An optical inspection method comprising: The optical inspection method according to claim 13, wherein performing the 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. An optical inspection program using the optical device according to claim 9,
acquiring an image of a surface of an object with the imaging unit;
performing an optical inspection of a surface of the object based on color information of the image captured by the imaging unit;
An optical inspection program for inspecting the surface condition of an object, the program causing a computer to execute the above steps. The optical inspection program of claim 15, wherein performing the optical inspection includes causing the computer to execute a process of outputting a surface condition of the object based on the number of colors emitted from the light source and the number of colors acquired at each pixel of the imaging unit.