Optical apparatus, optical inspection system, and method for imaging object

Abstract

To provide an optical apparatus capable of imaging a surface of an object (a flat surface or an inclined surface having an appropriate inclination).SOLUTION: According to one embodiment, an optical apparatus includes at least two light sources, illumination opening portions, and an imaging portion for imaging an object. The illumination opening portions are configured to partially block light emitted from the two or more light sources, respectively, to form illumination light. The two or more light sources are disposed at positions facing each other with an optical axis of the imaging portion interposed between the two or more light sources. The illumination light from the two or more light sources is formed to spread like a fan shape toward the object respectively by the illumination opening portions. The fan shape is defined on a reference plane including the optical axis of the imaging portion and on another plane parallel to the reference plane. The imaging portion is configured to image an object using the illumination light.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] SUMMARY OF THE DISCLOSURE Embodiments of the present invention relate to optical devices, optical inspection systems, and methods for imaging objects. [Background technology]

[0002] In various industries, it is important to obtain information on the surface of an object without contact. Conventional methods include, for example, illuminating an object with a ring light and acquiring a dark-field image with an imaging unit to obtain information on the object's surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] “Color ranging method for high speed low-cost 3D surface profile measurement” US patent 5,675,407 [Non-patent literature]

[0004] [Non-Patent Document 1] W.L. Hows, “Rainbow schlieren and its application,” Applied Optics, vol. 23, No. 14, 1984. [Non-Patent Document 2] Hiroshi Ohno & Takahiro Kamikawa, “One-shot BRDF imaging system to obtain surface properties,” Optical Review volume 28, pages655-661 (2021). Summary of the Invention [Problem to be solved by the invention]

[0005] The problem that the present invention aims to solve is to provide an optical device capable of imaging the surface of an object (flat surfaces and appropriately inclined surfaces), an optical inspection system that optically inspects an object using an image acquired by the optical device, and an imaging method for an object capable of imaging the surface of an object (flat surfaces and appropriately inclined surfaces). [Means for solving the problem]

[0006] According to an embodiment, an optical device includes at least two light sources, an illumination opening that forms illumination light by partially blocking light from the at least two light sources, and an imaging unit that images an object. The at least two light sources are disposed at positions facing each other across the optical axis of the imaging unit. The illumination light from each of the at least two light sources is formed by the illumination opening so as to spread in a fan shape toward the object on a reference plane including the optical axis of the imaging unit and another plane parallel to the reference plane. The imaging unit images the object using the illumination light. [Brief description of the drawings]

[0007] [Figure 1] 1 is a schematic block diagram of an optical inspection system according to an embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing an optical device of the optical inspection system according to the first embodiment. [Diagram 3] 3 is a schematic perspective view showing a first illumination opening of a first illumination section of the optical device shown in FIG. 2 and illumination light irradiated onto an object. FIG. [Figure 4] An example of an optical inspection algorithm flow. [Diagram 5] 5 is an example of a flow of the optical inspection process in FIG. 4 . [Figure 6] FIG. 11 is a schematic cross-sectional view showing an optical device of an optical inspection system according to a second embodiment. [Figure 7] FIG. 11 is a schematic cross-sectional view showing an optical device of an optical inspection system according to a third embodiment. [Figure 8] FIG. 13 is a schematic cross-sectional view showing an optical device of an optical inspection system according to a modified example of the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The optical inspection system 1 according to 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. 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 are omitted as appropriate.

[0009] (First embodiment) Hereinafter, an optical inspection system 1 according to this embodiment will be described with reference to FIGS.

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

[0011] FIG. 1 shows a schematic block diagram of an optical inspection system 1 according to this embodiment. FIG. 2 shows a schematic cross-sectional view of an optical device (optical inspection device) 10 of the optical inspection system 1 according to this embodiment. This cross-sectional view is assumed to be on the xz plane of an XYZ orthogonal coordinate system. The cross-section shown in FIG. 2 may be referred to as a reference plane S1. FIG. 3 shows a schematic perspective view showing a first illumination opening 312 of a first illumination unit 31 of the optical device 10 shown in FIG. 2 and illumination light L1 irradiated to an object.

[0012] As shown in FIG. 1, the optical inspection system 1 according to this embodiment includes an optical device 10 and a control unit 100.

[0013] As shown in FIG. 1 and FIG. 2, the optical device 10 according to the present embodiment includes an imaging unit 20 and an illumination unit 30. The illumination unit 30 includes at least two independent illumination units. However, these two illumination units may function in conjunction with each other. In the present embodiment, the illumination unit 30 includes a first illumination unit 31 and a second illumination unit 32. The optical device 10 also includes a transport unit 40 that transports the object S in a predetermined direction, for example. The predetermined direction in which the object S is transported is defined as the transport direction. The transport direction may be any direction, but here, the direction along the x-axis is defined as the transport direction. However, the transport unit 40 may transport the imaging unit 20, and any means may be used as long as the relative positional relationship between the imaging unit 20 and the object S changes. These are collectively referred to as transport. When the imaging unit 20 is transported, it is preferable that the illumination unit 30 is also transported in the same direction together with the imaging unit 20 while maintaining its positional relationship with the imaging unit 20.

[0014] The imaging unit 20 includes an imaging optical element 21 and an image sensor 22 .

[0015] The imaging optical element 21 is, for example, an imaging lens. In FIG. 2, the imaging lens is typically depicted as one lens, but may be a lens assembly consisting of a plurality of lenses. Alternatively, the imaging optical element 21 may be a concave mirror, a convex mirror, or a combination of them. In other words, the imaging optical element 21 may be any optical element that has a function of collecting a group of rays emitted from a point on an object, that is, an object point, at a conjugate image point. The imaging optical element 21 is a process in which a group of rays emitted from an object point on the surface of the object S is collected (concentrated) at an image point. Alternatively, it is also called that the object point is moved to an image point (a conjugate point of the object point). The collection plane of the conjugate points to which the group of rays emitted from a sufficiently distant object point is moved by the imaging optical element 21 is called the focal plane of the imaging optical element 21. In addition, a line perpendicular to the focal plane and passing through the center of the imaging optical element 21 is defined as an optical axis Oa. In this case, the conjugate image point of the object point transferred by the light beam is called a focal point. In this embodiment, the imaging optical element 21 may be simply called a lens.

[0016] In the cross section shown in Figure 2, the optical axis Oa coincides with the z-axis. The z-axis, i.e., the optical axis Oa, is included in the cross section.

[0017] The image sensor 22 has at least one pixel, and each pixel can receive light of at least two different wavelengths, that is, light of a first wavelength and light of a second wavelength. A surface including the image sensor 22 is the image surface of the imaging optical element 21. The image sensor 22 may be an area sensor or a line sensor. An area sensor is a sensor in which pixels are arranged in an area on the same surface. A line sensor is a sensor in which pixels are arranged in a line. Each pixel may have three color channels of R, G, and B. In other words, the image sensor 22 may be a sensor that can receive light in independent color channels. However, each color channel does not need to be completely independent, and in reality, the color channels may have slight sensitivity to the same wavelengths.

[0018] The illumination units 30 are preferably disposed at positions facing each other across the imaging optical axis Oa of the imaging unit 20, for example. The illumination units 30 are more preferably disposed at positions mirror-symmetrical to each other across the imaging optical axis Oa of the imaging unit 20. The illumination unit 30 includes, for example, two light sources 311 and 321 and two illumination openings 312 and 322. That is, the first illumination unit 31 includes a first light source 311 and a first illumination opening 312, and the second illumination unit 32 includes a second light source 321 and a second illumination opening 322. The light flux emitted from the first illumination unit 31 is defined as a first illumination light L1, and the light flux emitted from the second illumination unit 32 is defined as a second illumination light L2.

[0019] Both the first light source 311 and the second light source 321 emit white light. However, the present invention is not limited to this, and the first light source 311 and the second light source 321 may emit any type of light. In this embodiment, the wavelength spectrum of the white light has a significant intensity distribution between 400 nm and 750 nm. Therefore, the first light source 311 and the second light source 321 each emit light having at least two different wavelengths. Furthermore, each of the light sources 311 and 321 may be one or more.

[0020] A part of the light beam from the first light source 311 is blocked by the first illumination opening 312. A part of the light beam from the second light source 321 is blocked by the second illumination opening 322. The illumination lights L1 and L2 of the optical device 10 are formed by the light beams that have passed through the first illumination opening 312 and the second illumination opening 322. That is, the illumination unit 30 forms the desired illumination lights L1 and L2 by partially blocking the light from the two light sources 311 and 321.

[0021] FIG. 3 shows a perspective view of the first illumination aperture 312 of the first illumination unit 31. As shown in FIG. 3, the first illumination aperture 312 has the same size and shape in at least two mutually parallel planes (sections) S1 and S2, for example, parallel to the xz plane. Furthermore, in these planes S1 and S2, the aperture width W is sufficiently smaller than the field width imaged by the image sensor 22 of the imaging unit 20. As a result, the illumination aperture 312 creates a substantial fan ray as the first illumination light L1 in the optical system of the optical device 10. The fan ray means a ray of light that spreads radially (in a fan shape) from the light source. Here, the fan ray is generated from the light source 311 that can be regarded as a substantial point, or the illumination aperture 312 that is a secondary light source that can be regarded as a substantial point. In this embodiment, the illumination aperture 312 has a slit 3120. That is, the slit 3120 of the first illumination opening 312 has the same opening width (gap) W in the cross section (reference plane parallel to the xz plane) S1 shown in FIG. 2 and in another plane S2 parallel to the cross section (reference plane). That is, the size and shape of the first illumination opening 312 are the same in the reference plane S1 including the optical axis Oa of the imaging unit 20 and in another plane S2 parallel to the reference plane. In this embodiment, the first illumination light L1, which can be regarded as a point light source formed from the light source 311 along the y axis through the slit 3120 of the first illumination opening 312, becomes a group of light rays that spread in a fan shape (approximately sector shape) along the zx plane (propagating parallel to the zx plane) toward a transport surface 401 of the transport unit 40, which will be described later. It is preferable to consider another plane S2 parallel to the reference plane S1 not only as one plane, but as a group of planes having a width at least approximately equal to the width of the object S or the width of the transport path 401 of the object S. For this reason, the illumination light L1 is irradiated along the zx plane from each point light source regarded as a line light source as a collection of point light sources having a length at least approximately equal to the width of the object S or the width of the transport path 401 of the object S. For this reason, when the object S has an appropriate width along the y-axis direction, it is preferable that the first illumination unit 31 emits illumination light from a plurality of light sources 311 arranged in the y-axis direction.

[0022] Moreover, it is preferable that the illuminance of the first light source 311 on the transport surface 401 in the direction along the y-axis within the illuminated region on the transport surface 401 is substantially constant.

[0023] The slit 3120 of the first illumination opening 312 with a width W is formed, for example, between a pair of light-shielding surfaces 312a, 312b extending in the y-axis direction in a plane parallel to the xy plane. These light-shielding surfaces 312a, 312b are provided outside the field of view of the imaging unit 20. Therefore, the field of view of the imaging unit 20 is not obstructed by the first illumination opening 312 and is appropriately secured. The second illumination unit 32 is mirror-symmetric with respect to the first illumination unit 31 with respect to the optical axis Oa of the optical device 10, and therefore a description thereof will be omitted here.

[0024] The illumination lights L1 and L2, which can be regarded as point light sources, are formed in relation to the conveying section 40 so as to spread in a fan shape toward the object S by the illumination opening 312, at a cross section S1 shown in FIG. 1 (a reference plane parallel to the xz plane and including the conveying direction of the conveying section 40) and at another plane S2 parallel to the cross section (reference plane) S1.

[0025] The directional distribution of reflected light from object points on the surface (object surface) OS of an object S can be expressed by a distribution function called BRDF (Bidirectional Reflectance Distribution Function). BRDF generally changes depending on the surface condition (surface texture and surface shape) of the object surface OS. For example, if the surface is rough, the reflected light spreads in various directions, so the BRDF has a wide distribution. In other words, reflected light is present over a wide range of angles. On the other hand, if the surface is mirror-finished, the reflected light will consist almost entirely of regular reflection components, and the BRDF will have a narrow distribution. In this way, the BRDF reflects the surface condition of the object surface. In particular, the BRDF generally changes significantly due to tiny irregularities that are 10 times the wavelength of light or less.

[0026] As shown in FIG. 1 and FIG. 2, the conveying unit 40 places an object S on a conveying surface 401 parallel to the xy plane, for example, and conveys the object S in a predetermined direction. The conveying direction in this embodiment is along the x-axis. The conveying surface 401 of the conveying unit 40 is formed by, for example, a belt of a belt conveyor. However, the conveying unit 40 may be configured as a linear actuator, one driven by a stepping motor, or the like. In other words, the conveying unit 40 may be anything that can convey the object S. The conveying direction of the conveying unit 40 is along the reference plane S1 (see FIG. 3) of the illumination lights L1 and L2 from the two light sources 311 and 321, respectively. In other words, the conveying direction of the conveying unit 40 is along and parallel to the reference plane S1.

[0027] As shown in FIG. 1, the optical device 10 is connected to a control unit 100. The control unit 100 controls at least one of the image sensor 22 of the imaging unit 20, the two light sources 311 and 321 of the illumination unit 30, and the transport unit 40. In this embodiment, the control unit 100 controls the image sensor 22 of the imaging unit 20, the two light sources 311 and 321 of the illumination unit 30, and the transport unit 40. The control unit 100 is connected to the imaging unit 20, the two illumination units 30, and the transport unit 40 by wire or wirelessly. When the control unit 100 is connected to the imaging unit 20, the illumination unit 30 having the two light sources 311 and 321, and the transport unit 40 by wireless, the control unit 100 may be located adjacent to the imaging unit 20, the illumination unit 30, and the transport unit 40, or may be located remotely.

[0028] The control unit 100 has a processor 101 for acquiring an image captured by the imaging unit 20 and calculating the BRDF of each object point from the acquired image, and a storage device 102 for, for example, storing the image. That is, the control unit 100 can acquire detailed information of each object point from the BRDF of the object point. In other words, the control unit 100 acquires information of the object S based on the image captured by the imaging unit 20. Note that the control unit 100 that acquires detailed information of the object point based on the image acquired by the imaging unit 20 may be separate from the control unit that controls the two illumination units 30 and the transport unit 40.

[0029] The processor 101 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. 1).

[0030] The processor 101 corresponds to the central part of a computer that performs processes such as calculations and controls required for the processing of the control unit 100, and controls the entire control unit 100 in an integrated manner. The processor 101 executes control to realize various functions of the control unit 100 based on programs such as system software, application software, or firmware stored in a storage device 102 such as a ROM or an auxiliary storage device. The processor 101 includes, for example, a central processing unit (CPU), a micro processing unit (MPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or a graphics processing unit (GPU). Alternatively, the processor 101 is a combination of a plurality of these. The processor 101 provided in the control unit 100 may be one or more.

[0031] The control unit 100 executes processes to exert various functions by making the processor 101 execute programs and the like stored in the storage device 102. It is preferable that the control program of the control unit 100 is not stored in the storage device 102 of the control unit 100, but is placed on an appropriate server or cloud. In this case, the control program is executed while communicating with, for example, the processor 101 of the optical inspection system 1 via a communication interface. The control unit 100 according to the present embodiment may be disposed near the imaging unit 20, the illumination unit 30, and the transport unit 40 of the optical device 10, or may be located on a server or cloud of a system of various inspection sites away from the imaging unit 20, the illumination unit 30, and the transport unit 40. For this reason, it is also preferable that the optical inspection program is not stored in the storage device 102, but is on a server or cloud, and the program is executed while communicating with, for example, the processor 101 of the optical inspection system 1 via a communication interface. Therefore, the processor 101 (control unit 100) can execute an optical inspection program (optical inspection algorithm) (see FIG. 4 and FIG. 5) described later.

[0032] The processor 101 (control unit 100) controls the transport speed of the transport unit 40 along the transport direction of the object surface OS, the light emission timing of the light sources 311, 321 of the illumination unit 30, the imaging timing of the imaging unit 20, the frame rate, the acquisition of image data from the image sensor 22, etc., and can perform appropriate image processing on the acquired images.

[0033] Furthermore, the storage device 102 is, for example, a HDD or SSD, but may be anything that can store (save) images.

[0034] In this embodiment, the object S is opaque and is reflected by the object surface OS. In this case, the imaging optical axis Oa of the imaging unit 20 is disposed, for example, directly above the transport surface 401 so as to be perpendicular to the transport surface 401. The first illumination unit 31 and the second illumination unit 32 are also disposed, for example, directly above the transport surface 401. The longitudinal directions of the slit 3120 of the first illumination opening 312 and the slit of the second illumination opening 322 coincide with the y-axis direction of the transport surface 401.

[0035] However, the object S is not limited to this, and may be transparent or transmissive. In this case, the imaging unit 20 is disposed on the side of the object S where the light from the illumination passes through.

[0036] With the above configuration, the operation principle of the optical inspection system 1 according to this embodiment will be described.

[0037] The control unit 100 causes the first light source 311 of the first illumination unit 31 and the second light source 321 of the second illumination unit 32 to emit light at the same time, and irradiates fan rays L1, L2 (see FIGS. 2 and 3) toward the object surface of the object S through the illumination openings 312, 322. At this time, the control unit 100 irradiates the illumination lights L1, L2 from the light sources 311, 321 to the object S so as to spread in a fan shape toward the object S through the illumination openings 312, 322 on a reference plane S1 including the optical axis Oa and another plane S2 parallel to the reference plane S1. In this embodiment, the illumination lights L1, L2 are irradiated from the light sources 311, 321 from positions mirror-symmetrical to the optical axis Oa of the imaging unit 20, and illuminate the object S.

[0038] In Figure 1, the object surface OS is assumed to be a specular surface. In this case, at every point on the object surface OS, the reflected light is specular, and the BRDF has only a narrow distribution of specular components (specular reflection components).

[0039] The object surface OS has various inclinations relative to the reference plane, assuming that the xy plane (transport surface 401) is the reference plane. In this case, in the xz cross section in FIG. 2, the inclination of the object surface OS from the x axis is Θ, and the counterclockwise direction is the positive direction. This inclination Θ is called the inclination angle of the object surface OS. In the following, unless otherwise specified, the positive direction of the angle in the plane (including the inclination angle Θ) is the counterclockwise direction. However, the clockwise direction may be the positive direction, and the positive and negative directions of the angles may be defined in any way. When the positive and negative directions of the angles in the plane are not specifically mentioned, two cases are considered: the positive direction of the angle is counterclockwise, or the positive direction of the angle is clockwise. In this case, the definition of positive and negative is not changed for each angle in the same plane, and one of the two ways is defined consistently. In addition, the angle in the plane is in the range of -90° to +90°. In other words, the angle is defined to be 90° at maximum and -90° at minimum.

[0040] Regarding the illumination light from the illumination unit 30, consider a light beam (first illumination light L1) that has passed through the illumination opening 312 from the first light source 311. In the reference plane S1, the angle that the direction of the light rays in this light beam makes with the z-axis is defined as α. In other words, the angle that the first illumination light L1 makes with the optical axis Oa is defined as α. Similarly, consider a light beam (second illumination light L2) that has passed through the illumination opening 322 from the second light source 321. In the reference plane S1, the angle that the direction of the light rays in this light beam makes with the z-axis is defined as β. In other words, the angle that the second illumination light L2 makes with the optical axis Oa is defined as β.

[0041] When illumination light from the illumination unit 30 is reflected or transmitted by an object point within the object O, the imaging unit 20 forms an image of the light from the object S on the image sensor 22. This allows the control unit 100 to acquire an image of the object S using the imaging unit 20 (image sensor 22). That is, the imaging unit 20 captures an image of the object S, and an image of the surface of the object S is acquired. In particular, if the object is opaque, the illumination light L1, L2 is reflected by the object surface, and an image of the object on the object surface is acquired (captured).

[0042] The imaging unit 20 captures an image by converging a light beam having an intensity distribution represented by a BRDF at an object point onto an image point on the image sensor 22. Here, a light ray along a straight line passing through both the object point and the image point is defined as a principal ray. On the reference plane S1, the angle that the principal ray makes with the z axis is defined as θ. In other words, the angle that the principal ray makes with the optical axis Oa is defined as θ.

[0043] When the object surface OS is a mirror surface and the first illumination light L1 (incident light) is specularly reflected onto the object surface OS, the inclination angle Θ of the object that can be imaged with the first illumination light L1 on the reference plane S1 is given by Θ = (θ + α) / 2 (1) From this formula, it can be seen that the greater the absolute value of the incidence angle α of the first illumination light L1, the greater the absolute value of the tilt angle Θ that can be imaged. Similarly, when the second illumination light L2 (incident light) is specularly reflected on the object surface OS, the tilt angle Θ of the object that can be imaged with the second illumination light L2 on the reference plane S1 is given by Θ = (θ + β) / 2 (2) From this formula, it can be seen that the greater the absolute value of the incident angle β of the second illumination light L2, the greater the absolute value of the tilt angle Θ at which imaging can be performed.

[0044] In the cross-sectional view (reference plane S1) of FIG. 2, the maximum angle of incidence of the illumination lights L1 and L2 is the angle of incidence of the first illumination light L1, which is designated as αmax. The minimum angle of incidence of the first illumination light L1 is designated as αmin. On the other hand, the minimum angle of incidence of the illumination lights L1 and L2 is the angle of incidence of the second illumination light L2, which is designated as βmin. The maximum angle of incidence of the second illumination light L2 is designated as βmax. At this time, the range of the tilt angle Θ that can be imaged is: βmin / 2 ≦ Θ - θ / 2 ≦ αmax / 2 (3) That is, the range of the tilt angle Θ (maximum width of the angle) is αmax / 2 - βmin / 2. This is larger than the range given by only formula (1) or formula (2). That is, the range of the tilt angle Θ that can be imaged using only the first illumination light L1 is αmax / 2 - αmin / 2, and the range of the tilt angle Θ that can be imaged using only the second illumination light L1 is βmax / 2 - βmin / 2. On the other hand, the range of the tilt angle Θ that can be imaged using both the first illumination light L1 and the second illumination light L2 is αmax / 2 - βmin / 2 as shown in formula (3), which is larger than the range of the tilt angle Θ when only one of the illuminations is used. Therefore, the range of the tilt angle Θ that can be imaged is larger than the range of the tilt angle Θ that can be imaged using only the first illumination light L1, and is larger than the range of the tilt angle Θ that can be imaged using only the second illumination light L2.

[0045] If there is only one illumination light in the optical device 10 according to this embodiment, that is, for example, if there is only the first illumination light L1, the range of inclination angles Θ that can be captured is smaller than the range that can be captured by the above-mentioned two illumination lights L1 and L2 (that is, formula (3)). As a result, by providing at least two illumination units 31 and 32 (illumination lights L1 and L2) at positions facing each other across the optical axis Oa, the optical device 10 according to this embodiment has the effect of making the range of inclination angles that can be captured by the imaging unit 20 larger than when there is only one illumination light.

[0046] The control unit 100 connected to the optical device 10 according to this embodiment operates according to an optical inspection program (optical inspection algorithm) shown in FIGS. 4 and 5, for example.

[0047] 4, the control unit 100 controls the conveying unit 40 to move the conveying surface 401 in a predetermined conveying direction at a predetermined speed (step S1). At this time, it is preferable to continue moving the conveying surface 401 of the conveying unit 40 at the predetermined speed and to continue to convey the object S in the predetermined conveying direction (x-axis direction) at the predetermined speed until the end of the processing.

[0048] Then, the control unit 100 performs an optical inspection process on the object S being transported on the transport surface 401 (step S2).

[0049] As shown in FIG. 5, in the optical inspection process, the control unit 100 controls the first light source 311 and the second light source 321 of the illumination unit 30 to irradiate the first illumination light L1 and the second illumination light L2 onto the object surface OS of the object S (see FIG. 2) (step S21). However, such an operation is not necessarily required, and it is sufficient that the first light source 311 and the second light source 321 of the illumination unit 30 are continuously turned on. In other words, it does not matter if the illumination light is always irradiated onto the object surface OS. On the other hand, controlling the first light source 311 and the second light source 321 of the illumination unit 30 may have the effect of reducing power consumption.

[0050] The control unit 100 controls the image sensor 22 to capture an image of the object surface OS and obtain the captured image (information of the object surface) (step S22).

[0051] Then, the control unit 100 determines the object plane OS based on the information (image) of the object plane OS acquired in step S22 (step S23). The determination of the object plane OS here can be performed using various types of image processing.

[0052] 4, the control unit 100 determines whether or not the object S has passed through the field of view of the imaging unit 20 (step S3). If the object S has completely passed through the field of view of the imaging unit 20 (S3-Yes), the optical inspection process for the object S is terminated.

[0053] Furthermore, if the object S has not yet passed through the field of view of the imaging unit 20 (S3-No), the optical inspection process is performed again on the object S. In this case, the virtual intersection position between the object S and the optical axis Oa is different from the intersection position between the object S and the optical axis Oa in the previous optical inspection process. For example, the intersection position between the object S and the optical axis Oa, which changes over time, becomes a position further downstream of the object S on the conveying surface 401.

[0054] 5, even if the determination of the object surface for one acquired image is not completed, the object S may continue to be transported by the transport surface 401 of the transport unit 40. During this time, the intersection position of the object S with the optical axis Oa of the imaging unit 20 changes. That is, the control unit 100 may simultaneously perform, for example, determination of the object surface at different positions on the same object S in the optical inspection process. For example, in the optical inspection process, for an object S that is longer than the field of view of the imaging unit 20 in the transport direction, the entire surface of the object S is imaged at least once by multiple imaging, and then the quality of the multiple images acquired by imaging is determined.

[0055] It is preferable that the control unit 100 stops the conveyance of the conveying unit 40 at an appropriate timing after all the objects to be inspected have passed through the field of view of the imaging unit 20, regardless of whether the object S is one or multiple objects.

[0056] Here, consider the illumination light generated by a conventional ring illumination. In a cross section including the symmetric axis of the ring illumination, the range of tilt angles that can be imaged is set as the reference range. In this case, in any plane (zx plane where y ≠ 0) that is parallel to the cross section including the symmetric axis of the ring illumination (zx plane where y = 0 in FIG. 2; reference plane) and different from the cross section, the range of tilt angles is always smaller than the reference range. This can be derived based on geometric optics. That is, the ring illumination is arranged in an annular shape around the axis of the z axis, and the tilt angle range in the zx plane when y = 0 in FIG. 2 is maximum, and as y becomes larger or smaller than 0, the tilt angle range in the cross section parallel to the zx plane becomes smaller, and finally the tilt angle range becomes 0. In a cross section (reference plane) including the imaging optical axis Oa of the optical device 10 of this embodiment, the range of tilt angles that can be imaged is set as the reference range. The range of the tilt angle in at least one plane (zx plane of y≠0) that is parallel to the cross section (reference plane) including the imaging optical axis Oa of the optical device 10 and different from the cross section is the same as the reference range of the reference plane. The reason for this is that in the reference plane S1 (see FIG. 3) and another plane S2 (see FIG. 3) parallel to the reference plane S1, the illumination light L1 regarded as a point light source is formed to spread in a fan shape with the same size and shape toward the object S, and the illumination light L2 is formed to spread in a fan shape with the same size and shape toward the object S from the opposite side across the optical axis Oa. In other words, compared to the ring illumination, the optical device 10 according to this embodiment has the effect of being able to keep the range of the tilt angle that can be imaged constant in a parallel plane (zx plane of y≠0) different from the reference plane. Furthermore, compared to the ring illumination, the optical device 10 according to this embodiment has the effect of being able to make the range of the tilt angle that can be imaged large in at least two parallel planes (zx plane of y≠0) in the same way as in the case of the reference plane.

[0057] In the cross section of FIG. 2, the first illumination light L1 and the second illumination light L2 become fan rays with various incident directions. That is, all the incident rays of the illumination lights L1 and L2 with irradiation angles in the range of βmin to αmax can be irradiated onto the object S. Therefore, by continuously acquiring images by the imaging unit 20 while gradually moving the object S in the conveying direction, it is possible to make all the incident rays with irradiation angles in the range of βmin to αmax incident onto an arbitrary object point and to image the object surface OS. That is, there is an effect that incident light in various directions can be irradiated onto an arbitrary object point and the object surface OS can be imaged each time. As a result, even if the object surface OS is inclined and the reflected light is directed in various directions, it is possible to irradiate light with an incident direction that reflects toward the imaging unit 20. That is, even if the object surface OS of the object S has various inclinations, it is possible to irradiate illumination light in an appropriate direction and image the object surface OS with the imaging unit 20.

[0058] The BRDF at an object point of the object S changes depending on the incidence angle of the illumination light. By understanding the dependency of this BRDF on the incidence angle of the illumination light, the state at the object point can be known in detail. Therefore, the optical device 10 according to the present embodiment can obtain the BRDF for various incidence angles, and therefore has the effect of obtaining detailed information about the object point.

[0059] As an example of the optical device 10 of the optical inspection system 1 according to this embodiment, the distance between the object S and the image sensor 22 is, for example, about 500 mm, depending on the selection of the imaging optical element (imaging lens) 21, the width of the image sensor 22, etc. The field of view of such an optical device 10 is, for example, about 200 mm, depending on the selection of the imaging optical element (imaging lens) 21, the width of the image sensor 22, etc. When optical device 10 according to this embodiment is used, light sources 311, 321 are arranged at opposing positions across optical axis Oa, and fan beams L1, L2 are incident on the field of view of imaging unit 20, the angular range at which reflected light from object S within the field of view is incident on image sensor 22 can be expanded to approximately ±30°, for example. Therefore, optical device 10 according to this embodiment can obtain an image of object plane OS with a larger inclination angle.

[0060] Incidentally, as an optical device different from the optical device 10 according to the present embodiment, there is a method of irradiating, for example, white light from one light source in the direction of the optical axis Oa, and causing the illumination light to enter the field of view through a half mirror or the like intersecting the optical axis Oa to obtain an image of the object surface. When such light is incident into the field of view, it is assumed that it is difficult to image the object S having a large tilt angle due to problems such as the size, performance, and arrangement of the half mirror and the arrangement space of the entire optical device. In such an optical device, when the distance between the object S and the image sensor is, for example, about 500 mm, and the field of view range of the optical device is, for example, about 200 mm, it is assumed that the tilt angle range in which the reflected light from the object S reaches the image sensor (i.e., the tilt angle range in which the object S can be imaged) is, for example, about ±10°.

[0061] In the optical device 10 according to this embodiment, illumination light can be irradiated onto the object surface OS from a first illumination unit 31 and a second illumination unit 32 that are arranged opposite each other across the optical axis Oa of the imaging unit 20 and are outside the field of view. This eliminates the need for a half mirror that intersects with the optical axis Oa, and makes it possible to obtain an image of the object surface OS, including a flat, curved, or inclined surface, by making reflected light from the object surface OS, including a flat, curved, or inclined surface, incident on the imaging unit 20 without depending on space constraints or the performance of the half mirror.

[0062] In this way, the optical device 10 of this embodiment can obtain an image of the surface of the object S, which has not only flat surfaces but also curved surfaces and inclined surfaces with appropriate angles, making it easier to use the control unit 100 of the optical inspection system 1 to inspect various surfaces, such as whether the object surface OS is good or bad.

[0063] The optical device 10 according to this embodiment includes at least two light sources 311, 321, illumination openings 312, 322 that form illumination lights L1, L2 by partially blocking light from the at least two light sources 311, 321, respectively, and an imaging unit 20 that captures an object S. The at least two light sources 311, 321 are disposed at positions facing each other across the optical axis Oa of the imaging unit 20. The illumination lights L1, L2 from the at least two light sources 311, 321 are formed to spread in a fan shape toward the object S by the illumination openings 312, 322 on a reference plane S1 including the optical axis Oa of the imaging unit 20 and another plane S2 parallel to the reference plane S1. The imaging unit 20 captures an image of the object S using the illumination lights L1, L2. In addition, the method for imaging an object according to this embodiment includes irradiating illumination light L1, L2 onto the object S so that it spreads in a fan shape from at least two light sources 311, 321 toward the object S on a reference plane S1 including the optical axis Oa of the imaging unit 20 and another plane S2 parallel to the reference plane S1 from at least two light sources 311, 321 arranged at opposing positions across the optical axis Oa of the imaging unit 20, imaging the object S with the imaging unit 20, and acquiring an image of the surface of the object S.

[0064] As described above, according to this embodiment, it is possible to provide an optical device 10 capable of imaging the surface OS of an object (flat surface and appropriately inclined surface), an optical inspection system 1 that optically inspects an object using an image acquired by the optical device 10, and an imaging method capable of imaging the surface OS of an object (flat surface and appropriately inclined surface).

[0065] Second embodiment Hereinafter, the optical device (optical inspection device) 10 of the optical inspection system 1 according to this embodiment will be described with reference to Fig. 6. The optical inspection system 1 according to the second embodiment is a modified example of the optical inspection system 1 according to the first embodiment, and the same members as those described in the first embodiment or members having the same functions are denoted by the same reference numerals as much as possible, and detailed descriptions thereof will be omitted.

[0066] 6 shows a schematic cross-sectional view of the optical device 10 of the optical inspection system 1 according to this embodiment. This cross-sectional view is taken to be on the xz plane.

[0067] The optical device 10 according to this embodiment includes an imaging section 20 including a wavelength selection section 23 and an illumination section 30 including at least two light sources 311 and 321.

[0068] The illumination unit 30 is similar to the illumination unit 30 described in the first embodiment, and therefore a description thereof will be omitted here.

[0069] In addition, in this embodiment, the optical device 10 includes a transport unit 40 that transports the image capture unit 20 and the illumination unit 30 together instead of transporting the object S. The image capture unit 20 and the illumination unit 30 may be transported in any direction, but here, the transport direction is the negative direction of the x-axis. However, the transport unit 40 may also transport the object S, and any means may be used as long as it changes the relative positional relationship between the image capture unit 20 and the illumination unit 30 and the object S. These are collectively referred to as transport.

[0070] In this embodiment, the object S is placed on a placement surface FL formed as a flat surface, for example.

[0071] The image sensor 22 of the imaging unit 20 of this embodiment has at least one pixel, and each pixel can receive at least two different wavelengths of light, that is, light of a first wavelength and light of a second wavelength. A surface including the image sensor 22 is the image surface of the imaging optical element 21. The image sensor 22 may be an area sensor or a line sensor. An area sensor is a sensor in which pixels are arranged in an area on the same surface. A line sensor is a sensor in which pixels are arranged in a line. The image sensor 22 may have three color channels of R, G, and B for each pixel. That is, the image sensor 22 may be capable of receiving light in independent color channels. However, each color channel of the image sensor 22 does not need to be completely independent, and each color channel may have a slight sensitivity to the same wavelength. In this embodiment, the image sensor 22 has at least two channels of R and B. That is, the image sensor 22 can separate red light (R) and blue light (B). In other words, the imaging section 20 can separate light into at least two different wavelengths.

[0072] The blue light has a wavelength spectrum from 400 nm to 500 nm, with a peak wavelength of 450 nm. The first wavelength is this peak wavelength of 450 nm. The red light has a wavelength spectrum from 580 nm to 700 nm, with a peak wavelength of 650 nm. The second wavelength is this peak wavelength of 650 nm. However, the wavelength spectrum, first wavelength, and second wavelength are not limited to this.

[0073] The wavelength selection unit 23 includes a first wavelength selection region 231, a second wavelength selection region 232, and a third wavelength selection region 233. The optical axis Oa intersects with the first wavelength selection region 231. The second wavelength selection region 232 and the third wavelength selection region 233 pass red light and block blue light. The first wavelength selection region 231 passes blue light and blocks red light. That is, the first wavelength selection region 231 passes at least a first wavelength and blocks a second wavelength different from the first wavelength, and the second wavelength selection region 232 passes at least the second wavelength and blocks the first wavelength.

[0074] In this embodiment, the object S is opaque and reflects light from the object surface. However, the object is not limited to this, and may be transparent or transmissive. In this case, the imaging unit 20 is disposed on the side where the light from the illumination passes through the object.

[0075] With the above configuration, the operation principle of the optical inspection system 1 according to this embodiment will be described.

[0076] In Figure 6, the first object point P1 on the object surface OS is assumed to be a standard surface. The standard surface is a mirror surface, the reflected light is regular, and its BRDF has only a narrowly distributed specular component (regular reflection component). Meanwhile, the second object point P2 on the object surface OS has a minute defect with a height difference of about a few microns. In this case, the light is scattered and spreads widely at the second object point P2. In other words, the BRDF has a wide angular distribution. In this case, the BRDF has not only a specular component (regular reflection component) but also a diffuse component.

[0077] Regarding the illumination light from the illumination unit 30, consider a light beam from the first light source 311. The angle that the direction of the light rays in this light beam forms with the z-axis (optical axis Oa) is defined as α. Similarly, consider a light beam from the second light source 321. The angle that the direction of the light rays in this light beam forms with the z-axis (optical axis Oa) is defined as β.

[0078] When illumination light from the illumination unit 30 is reflected by or transmitted through object points P1, P2 within the object S, the imaging unit 20 forms an image of the light from the object S on the image sensor 22. This makes it possible to acquire an image of the object S. In other words, the object S is imaged.

[0079] The imaging unit 20 captures an image by converging a light flux having an intensity distribution represented by a BRDF at object points P1 and P2 onto an image forming point on the image sensor 22. Here, a ray of light along a straight line passing through both the object point P1 or object point P2 and the image forming point is defined as a principal ray. The angle that the principal ray makes with the negative direction of the z axis is defined as θ.

[0080] In the cross-sectional view of Fig. 6, the maximum (positive) angle of incidence of the illumination lights L1 and L2 is the angle of incidence of the first illumination light L1, which is designated as αmax. If there is only one illumination light, that is, for example, if there is only the first illumination light L1, the range of tilt angles Θ that can be captured is smaller than the range of images that can be captured by the two illumination lights L1 and L2 described above. As a result, the optical device 10 according to this embodiment has at least two illumination lights L1 and L2, which has the effect of increasing the range of tilt angles that can be captured by the imaging unit 20.

[0081] In the cross section of the optical device 10 shown in FIG. 6, the first illumination light L1 and the second illumination light L2 become fan rays having various incident directions. That is, all the incident rays of the illumination lights L1 and L2 whose irradiation angles are in the range of βmin to αmax can be irradiated onto the object S. Therefore, by continuously acquiring images by the imaging unit 20 while gradually moving the object S relatively in the conveying direction, it is possible to make all the incident rays whose irradiation angles are in the range of βmin to αmax incident onto an arbitrary object point and to image the object. That is, there is an effect that incident light in various directions can be irradiated onto an arbitrary object point and an image can be taken each time. As a result, even if the object surface OS is inclined and the reflected light is directed in various directions, it is possible to irradiate light with an incident direction that reflects toward the imaging unit 20. That is, even if the object surface OS has various inclinations, it is possible to irradiate illumination light in an appropriate direction and image the object surface OS with the imaging unit 20.

[0082] The BRDF at an object point of the object S changes depending on the incidence angle of the illumination light. By understanding the dependency of this BRDF on the incidence angle of the illumination light, the state at the object point can be known in detail. Therefore, the optical device 10 according to the present embodiment can obtain the BRDF for various incidence angles, and therefore has the effect of obtaining detailed information about the object point.

[0083] The wavelength selection unit 23 includes at least two wavelength selection regions 231, 232, and 233.

[0084] The reflected light from the first object point P1 has a narrow angular distribution according to the first BRDF. Therefore, it reaches only the first wavelength selection region 231 of the wavelength selection unit 23, and blue light is received by the image sensor 22. On the other hand, the reflected light from the second object point P2 has a wide angular distribution according to the second BRDF. Therefore, it reaches all the wavelength selection regions of the wavelength selection unit 23, that is, the first wavelength selection region 231, the second wavelength selection region 232, and the third wavelength selection region 233, and blue light and red light are received by the image sensor 22.

[0085] The image sensor 22 of the imaging unit 20 can distinguish between blue light and red light at each pixel. As a result, when determining the object surface OS (S23) shown in FIG. 5, the control unit 100 acquires information about the object S based on the color (hue) of the image captured by the imaging unit 20. This has the effect that the control unit 100 can distinguish the difference in BRDF by color (hue). If the difference in BRDF can be distinguished, the control unit 100 can determine whether the object surface OS is a standard surface or whether a micro defect is present. Therefore, the optical inspection system 1 according to this embodiment has the advantage of enabling micro defect inspection.

[0086] As described above, this embodiment is capable of imaging object surfaces OS with various inclinations. Also, for various inclined surfaces, the number of passing wavelength selection regions 231, 232, and 233 of the wavelength selection unit 23 differs depending on the spread of the BRDF. In other words, the color differs depending on the spread of the BRDF. Therefore, there is an effect that it is possible to inspect minute defects on object surfaces with various inclinations.

[0087] According to this embodiment, it is possible to provide an optical device 10 capable of imaging the surface OS of an object S (flat surface and appropriately inclined surface), an optical inspection system 1 that optically inspects the object S using an image acquired by the optical device 10, and an imaging method capable of imaging the surface OS of an object (flat surface and appropriately inclined surface).

[0088] In the present embodiment, an example has been described in which the optical device 10 is transported without transporting the object S. The object S may be transported, and the imaging unit 20 and the illumination unit 30 of the optical device 10 may not move. Alternatively, the imaging unit 20 and the illumination unit 30 of the optical device 10 may be moved in the -x-axis direction while the object S is transported in the x-axis direction.

[0089] Third embodiment Hereinafter, the optical device (optical inspection device) 10 of the optical inspection system 1 according to this embodiment will be described with reference to Fig. 7. The optical inspection system 1 according to the third embodiment is a modified example of the optical inspection system 1 according to the first and second embodiments, and the same members or members having the same functions as those described in the first and second embodiments are denoted by the same reference numerals as much as possible, and detailed descriptions thereof will be omitted.

[0090] 7 shows a schematic cross-sectional view of the optical device 10 of the optical inspection system 1 of this embodiment. This cross-sectional view is taken to be on the xz plane.

[0091] The optical device 10 according to this embodiment includes an imaging unit 20 and at least two illumination units 30. The illumination units 30 include a first illumination unit 31 and a second illumination unit 32. The optical device 10 also includes a transport unit 40 that moves the object S and the imaging unit 20 relatively, that is, transports the object S. The transport direction may be any direction, but here, the object S is transported in the positive direction of the x-axis. However, the transport may be any means that changes the relative positional relationship between the imaging unit 20 and the object S. These are collectively referred to as transport.

[0092] In this embodiment, six light sources 311a-311c, 321a-321c are used. In this embodiment, the first light source 311 of the first illumination unit 31 includes a light emitting unit having a light source 1a 311a, a light source 1b 311b, and a light source 1c 311c. These emit blue light, red light, and green light, respectively. The peak wavelength of the blue light is 450 nm, which is the first wavelength. The peak wavelength of the red light is 650 nm, which is the second wavelength. The peak wavelength of the green light is 550 nm, which is the third wavelength. That is, the light source 1a 311a, the light source 1b 311b, and the light source 1c 311c of the light emitting unit of the first light source 311 emit wavelength spectra different from each other. The second light source 321 of the second illumination unit 32 includes a light emitting unit having a 2a light source 321a, a 2b light source 321b, and a 2c light source 321c. These light sources 321a, 321b, and 321c emit blue light, red light, and green light, respectively. The peak wavelengths of the blue light, red light, and green light of the second light source 321 are the same as those of the first light source 311. That is, the 2a light source 321a, the 2b light source 321b, and the 2c light source 321c of the light emitting unit of the second light source 321 emit wavelength spectra different from each other.

[0093] Here, the 1a light source 311a of the first light source 311 and the 2a light source 321a of the second light source 321 are equidistant in the xz plane with respect to the imaging optical axis Oa. The 1b light source 311b of the first light source 311 and the 2b light source 321b of the second light source 321 are equidistant in the xz plane with respect to the imaging optical axis Oa. The 1c light source 311c of the first light source 311 and the 2c light source 321c of the second light source 321 are equidistant in the xz plane with respect to the imaging optical axis Oa. This is true not only for the cross section (plane S1) in FIG. 7, but also for the plane S2 in FIG. 3. Therefore, the light emitting unit of the first light source 311 and the light emitting unit of the second light source 321 are arranged so as to be mirror symmetrical with respect to the optical axis Oa of the imaging unit 20. It is preferable that the light sources 311 and 321 are mirror-symmetric with respect to the optical axis Oa not only in terms of their arrangement but also in terms of the light irradiation direction.

[0094] The image sensor 22 has at least one pixel, and each pixel can receive light beams of at least two different wavelengths, that is, light beams of a first wavelength and light beams of a second wavelength. The surface including the image sensor 22 is the image surface of the imaging optical element 21. The image sensor 22 may be an area sensor or a line sensor. The area sensor is a sensor in which pixels are arranged in an area on the same surface. The line sensor is a sensor in which pixels are arranged in a line. The image sensor 22 may have three color channels of R, G, and B for each pixel. That is, the image sensor 22 may be a sensor that can receive light in independent color channels. However, each color channel of the image sensor 22 does not need to be completely independent, and each color channel may have a slight sensitivity to the same wavelength. In this embodiment, the image sensor 22 has at least three channels of R, B, and G. That is, the image sensor 22 can separate red light (R), blue light (B), and green light (G).

[0095] With the above configuration, the operation principle of the optical inspection system 1 according to this embodiment will be described.

[0096] In Figure 7, as in Figure 6, the first object point P1 on the object surface OS is assumed to be a standard surface. The standard surface is a mirror surface, the reflected light is regular, and its BRDF has only a narrowly distributed specular component (regular reflection component). Meanwhile, as in Figure 6, the second object point P2 on the object surface OS has a minute defect with a height difference of about a few microns. In this case, the light is scattered and spreads widely at the second object point P2. In other words, the BRDF has a wide angular distribution. In this case, the BRDF has not only a specular component (regular reflection component) but also a diffuse component.

[0097] The reflected light from the first object point P1 has a narrow angular distribution according to the first BRDF. Therefore, the reflected light from the first object point P1 passes through the imaging optical element (imaging lens) 21, including blue light, red light, and green light. Therefore, when they reach the image sensor 22 of the imaging unit 20, the image sensor 22 receives all colors of blue light, red light, and green light. On the other hand, the reflected light from the second object point P2 has a wide angular distribution according to the second BRDF. Therefore, when the reflected light from the second object point P2 reaches the image sensor 22 of the imaging unit 20, the green light at the center (center) in the x-axis direction of the light-emitting unit of the first light source 311 or the green light at the center (center) in the x-axis direction of the light-emitting unit of the second light source 321 is received more strongly than the blue light and red light. This is because the light source 311a (blue light) and light source 311b (red light) around the light source 311c (green light) of the light-emitting unit of the first light source 311, and the light source 321a (blue light) and light source 321b (red light) around the light source 321c (green light) of the light-emitting unit of the second light source 321 tend to fall outside the imaging optical element (imaging lens) 21 due to the spread of the BRDF.

[0098] The image sensor 22 can not only separate blue light, red light, and green light at each pixel, but also obtain the pixel values ​​of each color. The ratio of pixel values ​​of each color of light (e.g., the ratio of green light to blue light (red light)) acquired at the image point of the image sensor 22 for the first object point P1 having a narrow angle distribution according to the first BRDF (e.g., the ratio of green light to blue light (red light)) is different from the ratio of pixel values ​​of each color of light acquired at the image point of the image sensor 22 for the second object point P2 having a relatively wide angle distribution according to the second BRDF. For example, if the ratio is the ratio of green light to blue light (red light), the second BRDF is larger than the first BRDF. As a result, when determining the object surface OS shown in FIG. 5 (S23), the control unit 100 can identify the difference in BRDF by using the magnitude relationship of the pixel value ratio at each pixel, etc., based on the image captured by the imaging unit 20 and acquired from the imaging unit 20. If the control unit 100 can identify the difference in BRDF, it can determine whether the object surface OS is a standard surface or whether a micro defect is present. Therefore, the optical inspection system 1 according to this embodiment has the advantage of enabling micro defect inspection.

[0099] The image sensor 22 of the imaging unit 20 can distinguish (disperse) blue light, red light, and green light at each pixel. Therefore, the image captured by the imaging unit 20 contains color (hue) information. As a result, when determining the object surface OS (S23) shown in FIG. 5, the control unit 100 can distinguish the difference in BRDF by color (hue) from the image captured by and acquired from the imaging unit 20. If the control unit 100 can distinguish the difference in BRDF, it can determine whether the object surface OS is a standard surface or whether a micro defect is present. Therefore, the optical inspection system 1 according to this embodiment has the advantage of enabling micro defect inspection.

[0100] As described above, the optical device 10 according to this embodiment is capable of capturing images of object surfaces OS having various inclinations by using the illumination units 30 disposed to face each other across the imaging optical axis Oa.

[0101] According to this embodiment, it is possible to provide an optical device 10 capable of imaging the surface OS of an object S (flat surface and appropriately inclined surface), an optical inspection system 1 that optically inspects the object S using an image acquired by the optical device 10, and an imaging method capable of imaging the surface OS of an object (flat surface and appropriately inclined surface).

[0102] (Modification) Fig. 8 shows an optical device 10 according to a modified example of the third embodiment. As shown in Fig. 8, the imaging unit 20 of the optical device 10 shown in Fig. 7 may include the wavelength selection unit 23 described in the second embodiment.

[0103] For example, the wavelength selection unit 23 includes a first wavelength selection region 231, a second wavelength selection region 232, and a third wavelength selection region 233. The optical axis Oa intersects with the first wavelength selection region 231. In this embodiment, the first wavelength selection region 231 passes green light and blocks red light and blue light. The second wavelength selection region 232 passes blue light and blocks red light and green light. The third wavelength selection region 233 passes red light and blocks blue light and green light.

[0104] The reflected light from the first object point P1 has a narrow angular distribution according to the first BRDF. Therefore, it reaches only the first wavelength selection region 231 of the wavelength selection unit 23, and green light is received by the image sensor 22. On the other hand, the reflected light from the second object point P2 has a wide angular distribution according to the second BRDF. Therefore, it reaches all the wavelength selection regions of the wavelength selection unit 23, that is, the first wavelength selection region 231, the second wavelength selection region 232, and the third wavelength selection region 233, and green light, blue light, and red light are received by the image sensor 22.

[0105] In this case, there is an advantage that more precise control of color discrimination is possible.

[0106] Furthermore, even on flat surfaces and / or various inclined surfaces (curved surfaces), the number of light passing through the wavelength selection regions 231, 232, and 233 of the wavelength selection unit 23 varies depending on the spread of the BRDF. In other words, the color incident on the image sensor 22 varies depending on the spread of the BRDF. Therefore, the control unit 100 has the effect of being able to inspect the presence or absence of minute defects on object surfaces with various inclinations based on the information on the incident color.

[0107] According to at least one of the embodiments described above, it is possible to provide an optical device 10 capable of imaging the surface OS of an object S (flat surface and appropriately inclined surface), an optical inspection system 1 that optically inspects the object S using an image acquired by the optical device 10, and an imaging method capable of imaging the surface OS of an object (flat surface and appropriately inclined surface).

[0108] Although some 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 implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0109] 1...optical inspection system, 10...optical device, 20...imaging section, 21...imaging optical element, 22...image sensor, 23...wavelength selection section, 231...first wavelength selection region, 232...second wavelength selection region, 233...third wavelength selection region, 30...illumination section, 31...first illumination section, 311...first light source, 312...first illumination opening, 312a, 312b...light-shielding surface, 312b...light-shielding surface, 3120...slit, 32...second illumination section, 321...second light source, 322...second illumination opening, 40...transport section, 401...transport surface, 100...control section, 101...processor, 102...storage device, L1...first illumination light (fan light), L2...second illumination light (fan light).

Claims

1. At least two light sources; an illumination aperture that partially blocks light from the at least two light sources to form illumination light; An imaging unit that captures an image of an object; It is assumed that The at least two light sources are disposed at positions facing each other across an optical axis of the imaging unit, The illumination light from each of the at least two light sources is formed by the illumination opening so as to spread in a fan shape toward the object on a reference plane including the optical axis of the imaging unit and another plane parallel to the reference plane, The imaging unit images the object using the illumination light. optical equipment.

2. The imaging device further includes a conveying unit that changes a relative positional relationship between the object and the imaging unit, The conveying direction of the conveying unit is along the reference plane.

2. The optical device of claim 1.

3. the illumination aperture has the same size and shape on the reference plane including the optical axis of the imaging unit and another plane parallel to the reference plane; 3. The optical device according to claim 1 or 2.

4. the illumination opening has a slit having the same width in the reference plane including the conveying direction of the conveying section and another plane parallel thereto; 3. The optical device according to claim 2.

5. On the reference plane, an angle formed between a first illumination light, which spreads in a fan shape from a first light source of the at least two light sources through the illumination opening, and the optical axis is defined as α; In the reference plane, an angle formed between the optical axis and second illumination light that spreads in a fan shape through the illumination opening from a second light source that faces the first light source across the optical axis among the at least two light sources is defined as β, On the reference plane, an angle between a principal ray along a straight line passing through both an object point of the object and an image forming point on an image sensor of the imaging unit and the optical axis is defined as θ; When the first illumination light is specularly reflected on the object surface of the object on the reference plane, the inclination angle Θ of the object that can be imaged by the imaging unit using the first illumination light is expressed as follows: Θ = (θ + α) / 2 (1) and When the second illumination light from the second light source is specularly reflected onto the object surface, the inclination angle Θ of the object that can be imaged by the imaging unit using the second illumination light is expressed as follows: Θ = (θ + β) / 2 (2) That is, 3. The optical device according to claim 1 or 2.

6. In the reference plane, The range of the tilt angle Θ that can be captured by the image sensor of the imaging unit using both the first illumination light and the second illumination light is is larger than the range of tilt angles Θ that can be imaged using only the first illumination light, is larger than the range of tilt angles Θ that can be imaged using only the second illumination light, 6. The optical device according to claim 5.

7. On the reference plane, a maximum value of the incidence angle of the first illumination light is αmax, and a minimum value of the incidence angle of the second illumination light is βmin, The range of the tilt angle Θ that can be captured by the image sensor of the imaging unit is βmin / 2 ≦ Θ - θ / 2 ≦ αmax / 2 (3) This means that 6. The optical device according to claim 5.

8. At least a portion of the light sources comprises a light emitting unit; The light-emitting units emit different wavelength spectra in the reference plane; each of the different wavelength spectrums includes either a first wavelength or a second wavelength different from the first wavelength; The imaging unit is capable of separating light into the first wavelength and the second wavelength.

3. The optical device according to claim 1 or 2.

9. The light emitting units of the light source are arranged in mirror symmetry with respect to the optical axis of the imaging unit.

9. The optical device according to claim 8.

10. The imaging unit includes a wavelength selection unit, The wavelength selection unit includes a first wavelength selection region that passes at least a first wavelength and blocks a second wavelength different from the first wavelength, and a second wavelength selection region that passes at least the second wavelength and blocks the first wavelength.

3. The optical device according to claim 1 or 2.

11. A control unit is provided that controls at least one of the imaging unit, the light source, and the transport unit of the optical device according to claim 2. Optical inspection systems.

12. a control unit that controls at least one of the imaging unit and the light source of the optical device according to claim 1 or 2, The control unit acquires information of the object based on the image captured by the imaging unit. Optical inspection systems.

13. The light source emits light having at least two different wavelengths; The imaging unit is capable of separating light into at least two different wavelengths, The control unit acquires information about the object based on a hue of an image captured by the imaging unit. The optical inspection system of claim 12.

14. Illuminating the object with illumination light from at least two light sources arranged at positions facing each other across an optical axis of an imaging unit, in a reference plane including the optical axis of the imaging unit and another plane parallel to the reference plane, so that the illumination light spreads in a fan shape from the at least two light sources toward the object; The object is imaged by the imaging unit to obtain an image of a surface of the object. A method for imaging an object, comprising:

15. On the reference plane, an angle formed between a first illumination light, which spreads in a fan shape from a first light source through a first illumination opening, and the optical axis is defined as α, In the reference plane, an angle formed between the optical axis and second illumination light that spreads in a fan shape through a second illumination opening from a second light source that faces the first light source across the optical axis among the at least two light sources is defined as β; On the reference plane, an angle between a principal ray along a straight line passing through both an object point of the object and an image forming point on an image sensor of the imaging unit and the optical axis is defined as θ; When the first illumination light from the first light source is specularly reflected onto an object surface of the object on the reference plane, the inclination angle Θ of the object that can be imaged by the imaging unit using the first illumination light is expressed as follows: Θ = (θ + α) / 2 (1) and When the second illumination light from the second light source is specularly reflected onto the object surface, the inclination angle Θ of the object that can be imaged by the imaging unit using the second illumination light is expressed as follows: Θ = (θ + β) / 2 (2) Let us say, The imaging method according to claim 14.

16. Irradiating the object with the illumination light includes irradiating the object with the light from the at least two light sources from positions that are mirror symmetric with respect to the optical axis of the imaging unit, thereby illuminating the object. The imaging method according to claim 14 or 15.

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