Inspection system and control method for inspection system

Abstract

To provide a system that enables the acquisition of a suitable image with minimal distortion or a highly accurate measurement.SOLUTION: An inspection system for inspecting a subject, including a substrate and a coating layer, has: a transmission part that emits terahertz waves including at least a reference pattern to the subject; and a support part that adjusts a relative position of the transmission part and the subject. Furthermore, the inspection system has: a detection part that detects terahertz waves reflected by the subject and acquires a terahertz image; and a determination part that determines whether or not an angle of incidence of the terahertz waves on the subject is a predetermined angle of incidence from the shape of the terahertz image.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an inspection system and a control method for the inspection system. [Background technology]

[0002] Camera systems using terahertz waves are being studied. Patent Document 1 discloses a camera system that acquires an image by detecting terahertz waves emitted from a transmitter and reflected by a subject. Patent Document 2 also discloses a system that inspects the surface roughness of a metal substrate through a non-metallic coating layer that covers the flat metal substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2018-087725 [Patent Document 2] Patent Publication No. 2019-158820 Summary of the Invention [Problem to be solved by the invention]

[0004] The following problems can arise in a camera system mechanism that detects terahertz waves specularly reflected from an object with multiple surfaces or curved surfaces. For example, the reflection angle of the terahertz waves from the object to each pixel of the detector changes depending on the shape of the object and the relative positions of the transmitter and detector, which can cause distortion in the object image output by the detector. Furthermore, the distribution of signal changes resulting from the object's shape is superimposed on the object image, making it difficult to perform highly accurate measurements.

[0005] Therefore, an object of the present invention is to provide a system using terahertz waves that can obtain a suitable image with little distortion or can perform highly accurate measurements. [Means for solving the problem]

[0006] One aspect of the present invention is an inspection system for inspecting an object including a substrate and a coating layer covering the substrate, the inspection system having: a transmitter that emits terahertz waves including at least a reference pattern to the object; a support that adjusts the relative position of the transmitter and the object; a detector that detects the terahertz waves reflected by the object and acquires a terahertz image; and a judgment unit that judges, from the shape of the terahertz image, whether the angle of incidence of the terahertz waves on the object is a predetermined angle.

[0007] Another aspect of the present invention is an inspection system including: a transmitter for emitting terahertz waves; a detector for detecting the terahertz waves and acquiring an image; a support unit for supporting an object having a substrate and a coating layer covering the substrate; a controller capable of performing a first operation of acquiring a first reference image and a second operation of detecting the terahertz waves reflected by the object and acquiring a second image; a determination unit that compares the first image with the second image and determines whether the angle of incidence of the terahertz waves on the object is a predetermined angle; and an attitude controller that controls the attitude of at least one of the transmitter, the detector, and the support unit based on the result of the determination unit.

[0008] Another aspect of the present invention is a control method for an inspection system having an emitter for emitting terahertz waves, a detector for detecting the terahertz waves, and a support for supporting an object, the control method for an inspection system having the steps of: emitting terahertz waves having a pattern and acquiring a first image serving as a reference; detecting the terahertz waves reflected by the object and acquiring a second image; comparing the first image with the second image; and controlling the attitude of at least one of the emitter, detector, and support based on the result of the comparison. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an inspection system using terahertz waves that enables at least highly accurate measurements, and a control method for the inspection system. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram for explaining the configuration of an inspection system according to a first embodiment. [Figure 2] FIG. 2 is a schematic diagram for explaining a pattern according to the first embodiment. [Figure 3] FIG. 3 is a flowchart for explaining the operation of the inspection system according to the first embodiment. [Figure 4] FIG. 3 is a flowchart for explaining the operation of the inspection system according to the first embodiment. [Figure 5] FIG. 3 is a flowchart for explaining the operation of the inspection system according to the first embodiment. [Figure 6] FIG. 3 is a flowchart for explaining the operation of the inspection system according to the first embodiment. [Figure 7] FIG. 1 is a schematic diagram for explaining the configuration of an inspection system according to a first embodiment. [Figure 8] FIG. 10 is a diagram for explaining an inspection system according to a second embodiment. [Figure 9] FIG. 10 is a schematic diagram illustrating a camera system according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Inspection systems and camera systems using terahertz waves will be described in detail below with reference to the drawings. In the description of each embodiment, description of configurations that are the same as those in other embodiments may be omitted. Furthermore, each embodiment can be modified as appropriate or combined with other embodiments as appropriate. The inspection system described in each embodiment below can also be used as a camera system, and the camera system described in each embodiment can also be used as an inspection system.

[0012] In the following description, terahertz waves refer to electromagnetic waves in a frequency range of 10 GHz to 100 THz, more preferably 30 GHz to 30 THz.

[0013] (Embodiment 1) The inspection system according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic diagram for explaining the configuration of the inspection system according to the first embodiment.

[0014] The inspection system includes a detection unit 101, a transmission unit 102, and a support unit 105. The detection unit 101 is, for example, a terahertz wave camera capable of detecting terahertz waves. The transmission unit 102 includes, for example, multiple generation elements 103 that emit terahertz waves. The generation element 103 is preferably a surface light source in which multiple oscillation elements that generate terahertz waves are arrayed and driven synchronously. The shape of the surface light source, which is the generation element 103, can be adjusted by arranging the oscillation elements in a lattice pattern and driving them synchronously. In other words, the size and shape of the aperture surface that generates terahertz waves are adjusted by arranging the oscillation elements. In the present invention, the shape of the surface light source preferably has at least two sides. The transmission unit 102 includes optical units 104 arranged corresponding to the multiple generation elements 103. The optical unit 104 is an optical unit that converges terahertz waves propagating from the generation element 103 at a predetermined divergence angle. Preferably, the optical unit 104 is a collimator. For example, the terahertz waves formed into a parallel beam by the optical unit 104 are irradiated onto the subject 106. If the beam width of the collimated terahertz waves is smaller than that of the terahertz image sensor constituting part of the detection unit 101, the detection unit 101 outputs the shape of the surface light source of the generating element 103 as an image via the subject 106. In other words, if there is no significant loss of light during the propagation of the terahertz waves, the shape of the surface light source of the generating element 103 is projected onto the detection unit 101. Depending on the arrangement of the pairs of the generating element 103 and the optical unit 104, a desired terahertz wave beam pattern conforming to the arrangement of the pairs can be projected onto the detection unit 101. For example, by arranging the pairs of the generating element 103 and the optical unit 104 in a checkerboard pattern, a terahertz wave beam pattern in which square light source patterns are arranged in a grid pattern can be projected onto the detection unit 101. 1, by arranging a pair of generating element 103 and optical unit 104 in a line, a rectangular terahertz wave beam pattern having different beam widths in the longitudinal and lateral directions can be projected onto detection unit 101. In the present invention, the terahertz wave beam pattern is also referred to as an irradiation pattern. In the present invention, it is preferable that the irradiation pattern has at least two sides.By having two or more sides, multiple pieces of information such as the distance between the two sides, the opening angle, the parallelism, and the difference in length can be read from the irradiation pattern, improving the ability to recognize distortions in the irradiation pattern.

[0015] The support unit 105 includes, for example, a stage, and supports the object 106 while adjusting it to a desired position. The support unit 105 may include a moving unit for moving the position of the object 106 and adjusting its position. There may be multiple moving units. The object 106 includes a substrate 107 and a coating layer 108. The object 106 may be, for example, a photosensitive drum coated with an amorphous silicon layer, a painted structure, or a bridge. The substrate 107 may be metallic or non-metallic. The coating layer 108 is disposed in close contact with the substrate 107. The coating layer 108 may be non-metallic. The coating layer 108 may be single-layer or multi-layer. The inspection surface of the object 106 may have one or more curved surfaces, multiple flat surfaces, or a combination of these curved and flat surfaces. The substrate 107 in FIG. 1 is a cylindrical member, and the coating layer 108 is an example of a resin film. The resin film has a thickness equal to or less than the wavelength of the terahertz waves, and has a thickness distribution. The resin film in FIG. 1 shows an example in which the thickness increases toward the end of the cylindrical member, and the object 106 as a whole has a recessed structure in the center. The shape of the object 106 is not limited to this. The transmitter 102 can emit terahertz waves having a specific irradiation pattern. When an imaginary plane 109 intersecting the terahertz waves emitted from the transmitter 102 is taken, the terahertz waves exhibit a specific shape. The irradiation pattern will be described later. The detector 101 detects terahertz waves 110 reflected by the object 106. For example, the inspection system inspects the thickness distribution of a coating layer 108 having a thickness of several microns to several tens of microns.

[0016] The inspection system may include a pattern determination unit 120 , a distribution measurement unit 121 , an attitude control unit 122 , a storage unit 123 , a monitoring unit 124 , an image processing unit 125 , a storage unit 126 , and an inspection unit 127 .

[0017] The monitoring unit 124 monitors the position and posture, such as the position and orientation, of the object 106 corresponding to the state of the support unit 105. For example, the monitoring unit 124 is an appearance detection device such as a visible camera, or a position detection device such as a radar or a sensor, and outputs posture information of the inspection surface of the object 106 in the measurement area of ​​the inspection system and posture information of the object 106. In the present invention, the posture information of the inspection surface of the object 106 and the posture information of the object 106 are collectively referred to as posture information of the object 106. Here, the inspection surface of the object 106 is a surface selected by the inspection system or the operator of the inspection system when the surface of the object 106 is virtually divided into multiple parts. Terahertz waves are incident on the inspection surface, and the reflected terahertz waves are detected by the detection unit 101.

[0018] The posture control unit 122 controls the state of the support unit 105. For example, the posture control unit 122 moves an inspection surface selected by the inspection system or an operator of the inspection system to a measurement area of ​​the inspection system. At this time, the posture control unit 122 refers to the posture information of the inspection surface output by the monitoring unit 124 and adjusts the posture of the inspection surface to a desired posture. As an example, the posture control unit 122 adjusts the incident angle of the terahertz waves incident on the inspection surface to a desired incident angle. Then, the posture control unit 122 refers to the posture information of the object 106 output by the monitoring unit 124 and outputs coordinate information of the measurement area of ​​the inspection system on the object 106. For example, the coordinate information is spatial coordinates virtually assigned in advance to the surface of the object 106. The spatial coordinates of the surface of the object 106 corresponding to the measurement area are output. Preferably, the pixels of the detection unit 101 are associated with the measurement area, and the pixels are linked to the spatial coordinates. Furthermore, the coordinate information is identification information of the inspection surface of the object 106. For example, as described above, consider a case where the inspection surface of the object 106 is a surface obtained by virtually dividing the surface of the object 106, and a position on the object 106 is associated with an identification number of the inspection surface in advance. In this case, the inspection location on the object 106 can be identified by specifying the identification number of the inspection surface as identification information. When the orientation of the inspection surface is adjusted by the support unit 105, it is preferable to provide the control amount of the support unit 105 along with the identification information. By providing the control amount of the support unit 105, the spatial positional relationship of multiple inspection surfaces can be estimated. Furthermore, if three-dimensional model data of the object 106 is available in advance, the control amount of the support unit 105 may be used as coordinate information. Changes in the spatial coordinates of the object 106 are predicted based on the control amount of the support unit 105, and the spatial coordinates are calculated. The coordinate information is not limited to these, and any information that can identify the terahertz image output by the detection unit 101 and the location of the measurement region of the object 106 may be used. The orientation control unit 122 may control the state of the support unit 105 in accordance with the orientation information from the monitoring unit 124.

[0019] The pattern determination unit 120 references the image data output from the detection unit 101 and extracts the position, area, and shape of the irradiation pattern emitted from the emission unit 102, which are included in the image data. The distribution measurement unit 121 outputs the intensity distribution of pixels corresponding to the irradiation pattern extracted by the determination unit 120. At this time, the intensity distribution image of the irradiation pattern is output with information on the intensity distribution derived from the physical properties and shape of the object 106 in the measurement area superimposed on it. For example, in this embodiment, the intensity distribution image derived from the physical properties and shape of the object 106 is an image related to the film thickness distribution of the coating layer 108 and the surface shape and scratches of the base material 107 below the coating layer 108. The intensity distribution image is not limited to this. The image processing unit 125 references the coordinate information of the measurement area, which is the coordinate information output by the attitude control unit 122 (hereinafter simply referred to as coordinate information of the measurement area), and the intensity distribution image derived from the physical properties and shape of the object 106. The image processing unit 125 can then synthesize a wide-range intensity distribution image that conforms to the shape of the object 106. At this time, the intensity distribution images may be three-dimensionally synthesized by referring to spatial coordinate information relating to the shape of the subject 106 that is stored in advance in the storage unit 123. This synthesized image is also called a synthesized intensity distribution image. The storage unit 126 can store a synthesized intensity distribution image obtained from a reference subject 106 as reference information.

[0020] The inspection unit 127 inspects the shape and physical properties of the object 106 by referring to a wide range of intensity distribution images. For example, it judges whether the shape and physical properties are good or bad by referring to reference information on the shape and physical properties of the object 106 stored in the memory unit 126. It is also possible to measure the film thickness of the coating layer 108 by using information from the surface of the substrate 107 and information from the surface of the coating layer 108. In this case, the film thickness can be output by performing a calculation in the image processing unit 125, for example, based on the output from the detection unit 101. The inspection system can also observe the surface of the substrate 107 of the object 106.

[0021] The inspection system may have a support unit for the transmitter 102 and the detector 101, and may also have a moving unit for at least one of them. That is, by moving at least one of the subject 106, the transmitter 102, and the detector 101, the measurement position of the subject 106 can be changed.

[0022] The inspection system shown in this embodiment makes it possible to safely observe the substrate 107 covered with the coating layer 108. In addition, since the inspection system refers to the posture of the object and synthesizes an intensity distribution image along the shape of the object for inspection, it is easily applicable to objects with free-form surfaces.

[0023] Each component will now be described. The detection unit 101 has a detection element capable of detecting terahertz waves. The detection element capable of detecting terahertz waves is, for example, an antenna made up of a rectifying element and a conductor. The rectifying element may be a rectifying diode such as a Schottky barrier diode or a diode using a pn junction. The detection unit 101 may also have an optical element of an imaging optical system, for example, a lens. The optical element is, for example, a lens of an imaging optical system. The optical element is, for example, a lens of an imaging optical system. The optical element is formed from a material such as high-density polyethylene (HDPE), high-resistivity silicon, or Teflon (registered trademark) (Poly Tetra Fluoro Ethylene: PTFE).

[0024] The transmitter 102 includes a plurality of generating elements 103. The transmitter 102 may further include an optical unit 104. The transmitter 102 emits terahertz waves 110. Each generating element 103 includes a plurality of oscillators capable of oscillating terahertz waves. The oscillators capable of oscillating terahertz waves include, for example, a negative resistance element and a resonator. The oscillators include, for example, a resonant tunneling diode (RTD) as a negative resistance element and an antenna. These oscillators are arranged in an array and driven synchronously to function as a single surface light source. For example, arranging the oscillators in a lattice pattern functions as a square surface light source. The optical unit 104 includes a plurality of optical elements. Here, the optical elements are collimators, and may be configured, for example, with an upward convex lens. The optical unit 104 is preferably formed of a material transparent to terahertz waves. Examples of transparent materials include high-density polyethylene, high-resistivity silicon, and Teflon. 1, three generating elements 103 are arranged in one row and three columns, with one optical element corresponding to one generating element 103. Hereinafter, the top surface of the generating element 103 will be referred to as the terahertz wave generating surface.

[0025] As described above, the terahertz waves 110 output in a collimated state from the transmitter 102 have an irradiation pattern. The irradiation pattern is the beam pattern of the terahertz waves, which is the spatial intensity distribution of the terahertz waves. Portions of the terahertz waves emitted from the multiple generators 103 are combined to form a single irradiation pattern. The irradiation pattern is composed of terahertz wave beams. When an imaginary plane 109 perpendicular to the terahertz waves 110 is taken, the terahertz waves 110 on the imaginary plane 109 exhibit a desired shape in accordance with the arrangement of the pair of generators 103 and optical elements 104. While it is preferable that the imaginary plane 109 be perpendicular to the terahertz waves, the irradiation pattern can be verified by using a plane that intersects with the optical axis of the terahertz waves. Specifically, the irradiation pattern can be verified by placing the detector 101 on the imaginary plane 109 and observing the intensity distribution image of the terahertz waves. Alternatively, the irradiation pattern can be verified by placing a reflecting plane at the position of the object 106 and observing the intensity distribution image of the terahertz waves with the detection unit 101. The shape of this intensity distribution image is referred to as the irradiation pattern, and the irradiation pattern of the terahertz light output without passing through the object 106 or through a reference object 106 is sometimes referred to as the reference pattern. The reference pattern can also be considered a pattern parallel to the optical axis of the transmitter 102. To facilitate pattern recognition, the reference pattern preferably has two or more sides. The reference pattern may be, for example, a polygon such as a rectangle, an ellipse, or a lattice shape. The reference pattern may also have a shape having a longitudinal direction and a lateral direction. Here, it is desirable for the longitudinal direction of the reference pattern to be aligned with the direction in which the average curvature of the surface of the substrate 107 is small. Alternatively, the support unit 105, which is a stage, may move the object 106 so that the longitudinal direction of the reference pattern is aligned with the direction in which the average curvature of the surface of the substrate 107 is small. In Figure 1, a pair of generating element 103, which is a rectangular surface light source, and optical element 104 are arranged in a line with one row and three columns, so the reference pattern is a pattern of rectangular surface light sources arranged in one row and three columns. By placing multiple surface light sources close to each other, a rectangular reference pattern is created. In the following explanation, the reference pattern will be described as a rectangular reference pattern with different lengths in the long and short directions.

[0026] The inspection system performs inspection by moving either the object 106, the transmitter 102, or the terahertz waves from the transmitter 102. Here, the angle of incidence of the terahertz waves on the object 106 can be measured and further adjusted based on coordinate information from the attitude control unit 122 and monitoring information from the monitoring unit 124. In FIG. 1, the attitude control unit 122 controls the operation of the support unit 105, which is the stage, but it may also control the attitude of the detector 101 or the transmitter 102. Furthermore, the inspection system can measure the angle of incidence of the terahertz waves on the object 106 and adjust the timing of the inspection based on the output from the detector 101.

[0027] Fig. 2 is a schematic diagram for explaining a pattern according to this embodiment. Fig. 2 shows images based on information obtained by the detection unit 101. Fig. 2(a) shows image 220, Fig. 2(b) shows image 221, and Fig. 2(c) shows image 222.

[0028] The image 220 shown in FIG. 2(a) includes a reference pattern image 231. The image 220 is an image obtained when an object with a known shape and material is used as the subject. Here, for example, the reference pattern image 231 is the irradiation pattern when a metal flat plate is placed as the subject 106. If the terahertz wave generated by the transmitter 102 can be captured by the detector 101 without loss, a rectangular pattern image can be detected as a collection of multiple surface light sources. The image 220 can be acquired by irradiating the subject with terahertz waves having an irradiation pattern including the reference pattern from the transmitter 102. The image 220 can be used as a reference pattern image, and the operation for acquiring the image 220 can also be referred to as reference pattern capture. The image 220 including the reference pattern image 231 is stored, for example, in the pattern determination unit 120 of FIG. 1 and used as a reference for determining the irradiation pattern.

[0029] Image 221 shown in FIG. 2(b) includes image 232. Image 221 is an image based on information obtained when an object to be inspected, such as object 106 having substrate 107 and coating layer 108 shown in FIG. 1, is used as the subject. Specifically, image 221 simulates an image in which the longitudinal vector of the terahertz wave irradiation pattern output by transmitter 102 intersects with the longitudinal vector of cylindrical substrate 107. In this case, the longitudinal direction of rectangular terahertz waves is irradiated so as to intersect with the longitudinal direction of cylindrical substrate 107, resulting in a distorted intensity distribution image (image 232). Specifically, the intensity distribution in the longitudinal direction of cylindrical substrate 107 has a narrow distribution area due to little overlap with the terahertz waves, while the intensity distribution in the lateral direction of substrate 107 is expanded in the lateral direction due to the R-shaped cylindrical structure, resulting in image 232. The shape of the distortion in the image 232 is not limited to this, but varies depending on the shape of the subject 106 in the area overlapping with the terahertz wave irradiation pattern and the relative positional relationship between the irradiation pattern and the subject 106. Information for generating the image 221 can be acquired by irradiating the subject 106 with terahertz waves having an irradiation pattern including a reference pattern from the transmitter 102. At this time, in addition to the intensity distribution due to the physical properties of the subject 106, signals derived from the shape of the subject 106 are detected as shape distortion. The image 221 can also be considered an image in which the influence of shape distortion is significant. For example, to detect minute changes in the physical properties of the subject 106 as an intensity distribution, it is preferable to suppress these signal changes derived from the shape of the subject 106. The image 221 shows an example in which the reference pattern image 231 is superimposed on the image 232. The image 221 can be acquired by combining information acquired by the detector 101 with the image 220 stored in the pattern determination unit 120. For example, the combination is performed by the image processor 125.

[0030] The image 222 shown in FIG. 2(c) includes an image 233. The image 222 is based on information obtained when an object to be inspected, such as the object 106 having the substrate 107 and coating layer 108 shown in FIG. 1, is used as the object. Specifically, the image 222 simulates an image in which the longitudinal vector of the reference pattern and the longitudinal vector of the cylindrical substrate 107 are approximately aligned. Because the terahertz wave irradiation pattern and the longitudinal vector of the cylindrical substrate 107 are aligned, a linear intensity distribution image (image 233) similar to the reference pattern image 231 can be acquired. Information for generating the image 222 can be acquired by irradiating the object 106 with terahertz waves having an irradiation pattern including the reference pattern from the transmitter 102. The image 222 includes the reference pattern image 231 superimposed on the image 233. The image 222 can be acquired by combining information acquired by the detector 101 and the image 220 stored in the pattern determination unit 120. For example, the synthesis is performed in the image processing unit 125.

[0031] Image 232 has a different shape from reference pattern image 231. Image 233 has a similar shape to reference pattern image 231. The area where image 233 and reference pattern image 231 overlap is larger than the area where image 232 and reference pattern image 231 overlap. Such a difference in shape between images 232 and 233 is due to, for example, a difference in the angle of incidence of the terahertz waves on the surface of substrate 107 of object 106. Furthermore, it changes depending on the shape of object 106 in the area overlapping with the irradiation pattern of the terahertz waves and the relative positional relationship between the irradiation pattern and object 106. For example, the relative positional relationship between object 106, transmitter 102, and detector 101 is different.

[0032] By monitoring the distortion state of the terahertz image, it is possible to determine whether the incidence state of the terahertz waves on the surface of the substrate 107 is suitable. For example, it is possible to determine whether the incidence angle of the terahertz waves is suitable. For example, it is possible to determine whether the influence of the shape of the surface of the substrate 107 is suitable (whether the influence of the shape on the intensity distribution is suppressed). When the influence of the surface shape of the substrate 107 is suitable, the intensity distribution image of the terahertz waves approximates the reference pattern. This determination can be made, for example, by calculating the value of the area where the terahertz image and the reference pattern image 231 overlap, the ratio, the correlation of the shape, and the intensity distribution, and comparing these with reference values. If the determination does not satisfy the reference value, the relative positions of the subject 106, the transmitter 102, and the detector 101 are changed. Alternatively, the inspection is interrupted.

[0033] It is also possible to acquire a terahertz image of a known object that has a curved or uneven surface and determine whether the object has a curved or uneven surface. Furthermore, the curved or uneven surface of the subject may be detected by observing changes in the shape of the terahertz image.

[0034] The operation will be described below with reference to Fig. 3 to Fig. 6. Fig. 3 to Fig. 6 are flow diagrams for explaining the operation of the inspection system according to this embodiment. Note that in this flow, the order of the steps is not limited to this, and it is also possible to perform multiple steps in parallel, or to change the order of the steps as appropriate.

[0035] FIG. 3 shows the operation for acquiring the reference pattern image 231 shown in FIG. 2(a). In step S301, an object whose shape is known is used as the subject, and terahertz waves having an irradiation pattern including a reference pattern are irradiated onto the subject. The subject may be a flat plate that reflects terahertz waves, or a reference subject having the same shape as the subject to be inspected. In step S302, the detection unit 101 detects the terahertz waves reflected from the subject. Here, image information 320 including the reference pattern image 231 can be acquired. In step S303, subject information and imaging conditions are acquired. The subject information is shape information and surface shape of the subject. The subject information may also be shape information and surface information of a substrate. The imaging conditions include the shape of the reference pattern image 231, the angle of incidence of the terahertz waves on the subject, i.e., the relative positions of the transmitter 102, the detector 101, and the support 105 (which serves as a stage), and coordinate information of the support 105. In step S304, the reference pattern image 231 is stored or updated in a memory unit 323 (not shown) included in the pattern determination unit 120 shown in FIG. 1 . Here, the memory unit 323 can store object information and imaging conditions as information linked to the reference pattern image 231. The reference pattern image 231 can be acquired through this flow. Note that there may be multiple reference patterns. For example, when acquiring a reference pattern using a reference object, it is considered that the shape of the reference pattern changes depending on the irradiation position of the terahertz wave with respect to the reference object, depending on the shape of the reference object. The memory unit 323 manages and stores the irradiation position of the terahertz wave, object information at the irradiation position, and imaging conditions for multiple reference patterns. The memory unit 323 may be included in the pattern determination unit 120 or may be another memory unit.

[0036] FIG. 4 shows the operation during inspection. In step S401, terahertz waves are irradiated. The transmitter 102 irradiates the object to be inspected with terahertz waves having an irradiation pattern including a reference pattern. In step S402, an image is captured. The detector 101 detects the terahertz waves reflected from the object and acquires information 420. At this time, the information 420 may be image information. Alternatively, the information 420 may be one-dimensional intensity distribution information. In step S403, the pattern determination unit 120 performs pattern detection. In pattern detection, an image 232 based on the terahertz waves reflected from the object is acquired from the information 420 acquired in step S402. For example, threshold processing is performed on the information 420 to distinguish between the background and the intensity distribution image of the terahertz waves, and the image 232 is extracted. Furthermore, an edge extraction process is performed on the information 420 to extract the outline of the image 232. In step S404, the pattern determination unit 120 performs pattern comparison. The image 232 acquired in step S402 is compared with the reference pattern image stored in the memory unit 323 of the pattern determination unit 120. In step S405, the pattern determination unit 120 performs pattern determination. Based on the comparison result in step S404, it is determined whether a reference value or condition is satisfied. For example, the matching rate when the reference pattern image and the image 232 are superimposed, or the outer edges of the reference pattern image and the image 232 are obtained, and the similarity of the shapes of their outer edges is determined. If the matching rate or similarity meets the reference value or condition, the detection unit 101 measures or photographs the subject, and the distribution measurement unit 121 outputs the intensity distribution of the pixels corresponding to the image 232 (step S406). Alternatively, the distribution measurement unit 121 outputs the intensity distribution of the pixels corresponding to the image 232 based on the information 420 used for pattern determination. If the matching rate or similarity does not meet the reference value or condition, position control is performed in step S407. In the position control, the attitude control unit 122 in Fig. 1 controls the attitude, position, or both of the support unit 105, which is the stage, the detection unit 101, and the transmission unit 102. Then, the process returns to step S401.

[0037] In step S405, if the reference values ​​or conditions for the matching rate or similarity are met, the information on the subject, the obtained image 232, and posture information such as coordinates acquired by the posture control unit 122 may be stored in the memory unit 323 of the pattern determination unit 120. This can be used to improve the accuracy of determination by machine learning or the like.

[0038] In step S408, the image processing unit 125 generates information (inspection information) to be used for the inspection. For example, the posture information of the object output by the posture control unit 122 may be referenced to identify a measurement region of the object, and the terahertz wave intensity distribution image may be superimposed on a 3D model image of the object or a visible image output by the monitoring unit 124. At this time, the posture information of the posture control unit 122 may be linked to shape information of the object pre-stored in the memory unit 123, and the position and posture of the terahertz wave intensity distribution image may be adjusted. Alternatively, the posture information (coordinate information) of the posture control unit 122 may be linked to shape information of the object pre-stored in the memory unit 123 (spatial coordinate information). Then, the intensity signals of each pixel constituting the terahertz wave intensity distribution image may be reassigned to the corresponding coordinates of the 3D model image or visible image of the object. Alternatively, when multiple terahertz wave intensity distribution images are acquired, the terahertz wave intensity signals may be sequentially assigned to the 3D model image or visible image of the object, and the resulting images may be combined to generate a single piece of inspection information. In other words, information on the intensity distribution of the entire subject is created from information on the intensity distribution of the terahertz waves measured locally.

[0039] Furthermore, intensity distribution information can be generated based on a reference pattern image using a reference subject, and the generated inspection information can be stored in the storage unit 126 as reference inspection information.

[0040] In step S409, the inspection unit 127 inspects the subject by referring to the inspection information output by the image processing unit 125. For example, the inspection unit 127 compares the reference inspection information stored in the storage unit 126 with the inspection information output by the image processing unit 125, checks for differences, and performs a pass / fail judgment.

[0041] 5 is a diagram simply illustrating a flow for correcting an image, i.e., performing image processing, as an example of image processing in the pattern determination unit 120. The inspection system can perform, for example, steps S501 to S503 in S402 and S403, which are the pattern detection steps in FIG.

[0042] Step S501 is a terahertz image acquisition step. Step S501 is a so-called imaging step, and corresponds to, for example, step S402 in FIG. 4. The acquired terahertz image is an image obtained by detecting the reflected terahertz waves emitted by the transmitter 102 in FIG. 1 after the terahertz waves are reflected by the object 106 and detected by the detector 101. The acquired terahertz image can also be referred to as image information 510. As described above, the image information 510 is an intensity distribution image 511 including a reference irradiation pattern (reference pattern image) and information derived from the physical properties and shape of the object. In the present invention, the terahertz waves generated from the generator 103 are coherent because their phases are adjusted and synchronized by the oscillators constituting the generator 103. Therefore, some of the terahertz waves generated from the multiple generators 103 may interfere with each other. Furthermore, when the terahertz waves pass through the optical element 104, interference derived from the external shape of the optical element 104 may be superimposed on the terahertz waves. Furthermore, a lens or aperture at the terahertz wave input stage of the detection unit 101 may cause a portion of the terahertz wave to interfere with and be superimposed on the terahertz wave signal. Signals resulting from such interference may be superimposed on the image information 510. In the present invention, signals resulting from this interference are sometimes referred to as light source unevenness. For example, if light source unevenness is superimposed on the reference pattern, there is a possibility that the light source unevenness pattern may be erroneously detected as a pattern resulting from the subject during pattern detection in step S403 or the like. Therefore, it is preferable to suppress light source unevenness. Misdetection of a pattern may, for example, induce a decrease in the inspection performance in the subsequent inspection step (step S409). The process of FIG. 5 illustrates an example of a process for suppressing this light source unevenness.

[0043] In step S501, when a flat plate that reflects terahertz waves or a reference object having the same shape as the object to be inspected is used as the object, the intensity distribution image 511 of the image information 510 is an image that includes a reference pattern and a light source unevenness pattern. For example, intensity correction data for suppressing the light source unevenness pattern is set for each pixel based on the reference pattern and the intensity distribution image 511 resulting from the light source unevenness. In the present invention, this intensity correction data for each pixel is also referred to as pixel correction data. For example, pixel correction data is created so that the intensity of the intensity distribution image 511 becomes uniform. This correction data may be stored in the memory unit 323 of the pattern determination unit 120.

[0044] Step S502 is an intensity correction step. In step S502, the image information 510 is corrected using pixel correction data, which is intensity correction information stored in the storage unit 323. A process is performed to remove information about light source unevenness from the intensity distribution image 511 of the image information 510. The removal process may be, for example, a differential process that adjusts the base of the intensity signal, a division process that adjusts the amplitude of the intensity signal, or a combination of differential and division processes. The removal process is not limited to this. For example, if the intensity signal of light source unevenness varies nonlinearly with the terahertz waves input to the detection unit 101, correction may be performed according to an approximate formula, or multiple pixel correction data may be prepared in stages to match the intensity of the input terahertz waves. Here, intensity correction is performed on pixels included in the intensity distribution image 511 of step S501. The area where intensity correction is performed is also referred to as the correction area.

[0045] Step S503 is a terahertz image output step. In step S503, the image information corrected in step S502 is output. The image information is, for example, an intensity distribution image 511. In the intensity distribution image 511, the correction area 523 is corrected by the correction, and an object image can be obtained in which the influence of the light source unevenness caused by the transmitting unit 102 is reduced.

[0046] Fig. 6 shows a modified example of the image processing in the pattern determination unit 120 described in Fig. 5, and simply illustrates a flow for updating information for image processing. The inspection system can perform the operations of steps S601 to S605.

[0047] Step S601 is a terahertz image acquisition step. Step S601 is a so-called imaging step, and corresponds to, for example, step S402 in FIG. 4. The acquired terahertz image is an image obtained by detecting the reflected terahertz waves emitted by the transmitter 102 in FIG. 1 after the terahertz waves are reflected by the object 106 using the detector 101. The acquired terahertz image can also be referred to as image information 610. The image information 610 is an intensity distribution image 611 that includes a reference pattern, information derived from the physical properties and shape of the object, and light source unevenness. Here, as described with reference to FIG. 5, in the image information 610, a correction region derived from intensity correction information pre-stored in the memory unit 323 of the pattern determination unit 120 is indicated as a correction region 624. In other words, the correction region 624 indicates an area where the pattern determination unit 120 plans to perform light source unevenness correction.

[0048] Step S602 is a correction region acquisition step. In step S602, a correction region 625 is acquired from the intensity distribution image 610, which is image information. For example, the boundary of the correction region 625 is obtained by performing threshold processing or edge extraction processing on the intensity distribution image 611. Then, position information of the correction region 625 is acquired, and the amount of deviation of the position and tilt with respect to the correction region 624 is obtained. Preferably, the amount of deviation is obtained for each pixel.

[0049] Step S603 is a process for updating the lookup table stored in the storage unit 323 of the pattern determination unit 120. The lookup table stores the positions of pixels to be corrected and pixel correction data for each pixel position. Based on the deviation amount obtained in step S602, at least the position information of the pixels to be corrected in the intensity correction information of the lookup table is updated. In other words, the correction area 624 is moved to the correction area 625. If the deviation amount is zero, the position information of the intensity correction information of the lookup table does not need to be updated.

[0050] Step S604 is an intensity correction step. The image information 610 is corrected using the pixel correction data in the updated lookup table. Here, since the position information of the pixel correction data has been updated, the positions of the correction area 625 and the correction area 623 indicated in the image information correspond to each other.

[0051] Step S605 is a terahertz image output step. In step S605, image information 612 corrected in step S604 is output. In the image information 612, the correction area 623 is corrected, and a preferable subject image with reduced light source unevenness can be obtained.

[0052] Next, a method for measuring film thickness using the measurement device of this embodiment will be described with reference to FIG. 7. FIG. 7 shows the angle at which terahertz waves are incident on the object 106 and the reflectance at the surface of the substrate 107 at that time. Here, the terahertz waves are incident on the object 106 as P-polarized waves. The reflectance can also be considered the intensity of the reflected terahertz waves detected by the detection unit 101. The values ​​in FIG. 7 are values ​​obtained when the angle of incidence and reflectance of the terahertz waves are measured using a reference object 106. The reference object 106 refers to an object from which information on the shape of the substrate 107 and the material and thickness of the coating layer 108 has been acquired. Here, the angle of incidence and intensity distribution information can be obtained from the image information acquired in the measurement or imaging in step S406 of FIG. 4 and the positional information at that time. The film thickness of the coating layer 108 can be estimated from the obtained angle of incidence and intensity distribution information based on the information in FIG. 7.

[0053] 1 shows a signal path that directly connects the attitude control unit 122 and the memory unit 123, but it may also be a signal path in which a processing unit or the like is disposed between the attitude control unit 122 and the memory unit 123. Furthermore, the attitude control unit 122, the image processing unit 125, and the like may be configured on the same processing chip or processing board.

[0054] Although the present embodiment has been described using two-dimensional image information, one-dimensional image information or an image of one-dimensional intensity distribution may also be used.

[0055] With the configuration of this embodiment, for example, the surface shape and position of the subject 106 can be detected and corrected to a suitable angle. In addition, a suitable terahertz image can be obtained by correcting the intensity distribution using a reference pattern image.

[0056] (Embodiment 2) The inspection system according to this embodiment will be described with reference to FIG. 8. FIG. 8 is a schematic diagram illustrating the configuration of the inspection system. FIG. 8 corresponds to FIG. 1, and description of the same configuration as in FIG. 1 will be omitted. The inspection system according to this embodiment has a half mirror 840 between the transmitter 102 and the object 106 or between the object 106 and the detector 101. The half mirror 840 makes the angle of incidence of the terahertz waves including the reference pattern with respect to the surface of the object 106 approximately 0 degrees, and the angle of incidence of the terahertz waves including the reference pattern reflected from the surface of the object 106 to the detector 101 approximately 0 degrees. Such an angle of incidence improves the detection accuracy of the reference pattern, enabling more accurate inspection.

[0057] (Embodiment 3) The camera system according to this embodiment will be described with reference to Fig. 9. Fig. 9 is a schematic diagram for explaining the configuration of a camera system 900 using terahertz waves. Individual components such as a transmitter, detector, and processor have been described in other embodiments, so a description thereof will be omitted.

[0058] The camera system 900 has a transmitter 901, a detector 902, and a processor 903. The terahertz waves emitted from the transmitter 901 are reflected by an object 905 and detected by the detector 902. The processor 903 processes the signal detected by the detector 902. The image data generated by the processor 903 is output from the output unit 904. With this configuration, a terahertz image can be acquired.

[0059] Even in this configuration, an image that is not dependent on the surface shape of the object 905 can be acquired by irradiating the object with terahertz waves that include a reference pattern.

[0060] (Other embodiments) The optical unit in each embodiment can have any configuration, such as a Fresnel lens, a cylindrical lens, an elliptical lens, a convex lens, a concave lens, or a biconvex lens. The optical unit 104 may also be an optical element such as a prism. The optical unit may be composed of multiple layers containing at least one material transparent to terahertz waves, such as polyethylene, Teflon, high-resistivity silicon, or polyolefin resin. The optical unit may also be composed of multiple integrated optical elements or independent optical elements. Having such an optical unit can improve the accuracy of detecting a reference pattern when emitting or detecting terahertz waves containing the reference pattern.

[0061] The optical unit may have an anti-reflection film or structure on at least one of its upper and lower outer edges to reduce reflection of terahertz waves. The upper outer edge can also be called the outer edge on the output side, and the lower outer edge can also be called the outer edge on the input side.

[0062] The image processing in each embodiment may be performed by AI processing (artificial intelligence processing). Also, the image processing in each embodiment can be modified as appropriate, such as performing part of the AI ​​processing in a processing circuit or the like and performing the remaining processing in the cloud.

[0063] In each embodiment, the operation of the transmitting unit may be controlled according to the measured intensity distribution result. The operating conditions, such as the power of each transmitting unit or each generating element, may be controlled individually so that the intensity distribution becomes the desired distribution.

[0064] The camera systems described in the respective embodiments are merely examples, and other configurations may be used. In particular, the information acquired by the system is not limited to image information, and may be a detection system that detects signals.

[0065] The embodiments are merely examples of specific implementations of the present invention, and should not be construed as limiting the technical scope of the present invention. In other words, the present invention can be implemented in various forms without departing from its technical concept or main features. [Explanation of symbols]

[0066] 101 Detector 102 Transmission Department 103 Generator 104 Optics Department 105 Support part 106 Subject 107 Base material 108 Covering layer 109 Virtual Surface 110 Terahertz waves

Claims

1. 1. An inspection system for inspecting an object including a substrate and a coating layer overlying the substrate, comprising: a transmitter that emits terahertz waves including at least a reference pattern to the subject; a support unit for adjusting the relative positions of the transmitter and the subject; a detection unit for detecting the terahertz wave reflected by the subject and acquiring a terahertz image; and a determination unit that determines, from the shape of the terahertz image, whether or not the angle of incidence of the terahertz wave on the subject is a predetermined angle of incidence.

2. The inspection system of claim 1 , wherein the reference pattern includes a shape having at least two sides.

3. the transmitting unit has one or more generating elements and an optical unit that is paired with the one or more generating elements and collimates the terahertz wave, 3. The inspection system according to claim 1, wherein the generating element is a surface light source in which a plurality of oscillation elements that oscillate terahertz waves are arrayed.

4. the reference pattern is a pattern conforming to the arrangement of a pair of the generating element and the optical unit, 4. The inspection system according to claim 3, wherein the inspection system is configured by a light beam parallel to the optical axis of the transmitting unit, and has an arbitrary shape when a plane perpendicular to the optical axis is taken.

5. The inspection system according to claim 1 , wherein the determining unit estimates the angle of incidence from a correlation between the shapes of the reference pattern and the terahertz image.

6. 6. The inspection system according to claim 1, further comprising a distribution measurement unit that acquires an intensity distribution image of the terahertz wave from the terahertz image acquired by the detection unit when the judgment unit determines that the incident angle is a predetermined incident angle.

7. 7. The inspection system according to claim 1, further comprising a posture control unit that outputs a signal for controlling the position of the support unit and outputs coordinate information of the support unit.

8. The inspection system according to claim 7 , further comprising a monitoring unit for acquiring coordinate information of the support unit.

9. a storage unit in which shape information of the subject is stored, 9. The inspection system according to claim 7, wherein the posture control unit outputs the coordinate information for controlling the position of the support unit by referring to the shape information.

10. an attitude control unit that outputs a signal for controlling the position of the support unit and outputs coordinate information of the support unit; a monitoring unit for acquiring coordinate information of the support unit; a distribution measurement unit that acquires an intensity distribution image of the terahertz wave from the terahertz image acquired by the detection unit when the determination unit determines that the incident angle is a predetermined incident angle; 10. The inspection system according to claim 1, further comprising: an image processing unit that outputs the intensity distribution image and a composite intensity distribution image in which the intensity distribution image is assigned to the shape of the subject based on the coordinate information.

11. 11. The inspection system according to claim 10, further comprising an inspection unit that inspects the film thickness of the coating layer from the intensity distribution of the composite intensity distribution image.

12. a storage unit for storing the reference information generated by the inspection unit; The inspection system according to claim 11 , wherein the inspection unit determines whether the film thickness distribution is good or bad by referring to the reference information.

13. The inspection system according to claim 12 , wherein the reference information is a detected terahertz intensity distribution image of the coating layer.

14. The inspection system of claim 1 , wherein the reference pattern is rectangular.

15. The inspection system according to claim 1 , wherein the reference pattern is a grid pattern.

16. an emitter for emitting terahertz waves; a detection unit for detecting the terahertz wave and acquiring an image; a support portion for supporting an object having a substrate and a coating layer covering the substrate; a control unit capable of performing a first operation of acquiring a first image serving as a reference and a second operation of detecting the terahertz wave reflected by the subject and acquiring a second image; a determination unit that compares the first image with the second image and determines whether an incident angle of the terahertz wave on the subject is a predetermined incident angle; An inspection system having a posture control unit that controls the posture of at least one of the transmitter, detector, and support unit based on the result of the determination unit.

17. an emitter for emitting terahertz waves; a detection unit for detecting the terahertz wave; A control method for an inspection system having a support unit that supports an object, the method comprising: a step of emitting terahertz waves having a pattern and acquiring a first image as a reference; detecting the terahertz waves reflected by the object to obtain a second image; comparing the first image and the second image; and controlling the attitude of at least one of the transmitter, the detector, and the support based on the result of the comparison.

Images