Thickness distribution measuring device and thickness distribution measuring method

Abstract

This thickness distribution measurement device (1A) is provided with a light source unit (20), a light detection unit (30), and a control device (40). The light source unit (20) irradiates light (La) to a region extending in the width direction (D2) of the object (B) being conveyed. A light detection unit (30) detects emitted light (Lb) that has passed through an object (B). The control device (40) finds information relating to the relative thickness distribution of the object (B) in the width direction (D2) on the basis of the detection result by the light detection unit (30). The light detection unit (30) has an image sensor and a lens array. The image sensor has a plurality of pixels arranged in the width direction (D2), and detects the intensity of emitted light (Lb) at each pixel. The lens array includes a plurality of lenses arranged in a width direction (D2) and having a magnification equal to that of the lens array. The lens array condenses the emitted light (Lb) and forms an image on the image sensor.

Description

Technical Field

[0001] The present disclosure relates to a thickness distribution measuring device and a thickness distribution measuring method. Background Art

[0002] Patent document 1 discloses a film thickness measuring device. The film thickness measuring device is a device for measuring the film thickness of a measurement object. The measurement object includes a substrate having a front side and a back side, a first film formed on the front side, and a second film formed on the back side. The film thickness measuring device includes a light irradiation unit, a light detection unit, and a film thickness calculation unit. The light irradiation unit irradiates light to the front side of the measurement object. The light detection unit detects the intensity of each wavelength of the reflected light on the front side of the measurement object. The film thickness calculation unit determines the film thickness of the first film by comparing the reflectivity of each wavelength obtained based on the detection result in the light detection unit with the theoretical reflectivity of each wavelength. For the theoretical reflectivity of each wavelength, the reflectivity and transmittance on the front side and the reflectivity on the back side are considered.

[0003] Patent Documents 2 and 3 disclose sensor units of image reading devices. [Prior art literature] [Patent Document]

[0004] Patent Document 1: Japanese Patent Application Publication No. 2015-141176 Patent Document 2: Japanese Patent Application Publication No. 2020-170973 Patent Document 3: Japanese Patent Application Publication No. 2017-046241 Summary of the invention [Problems to be solved by the invention]

[0005] It is desired to check the distribution of the relative thickness of a plate-like or film-like object having a certain width in the width direction while the object is being conveyed in a direction intersecting the width direction. For example, when manufacturing a polymer film, it is desired to check and confirm that the thickness of the film is uniform after the material of the polymer film is stretched in the longitudinal and transverse directions and formed into a film.

[0006] In the past, there was a spectroscopic interference method as a method for measuring the thickness of an object. In the spectroscopic interference method, light is irradiated to the object, and the intensity of interference light between the reflected light in the light irradiation surface of the object and the reflected light in the opposite surface of the light irradiation surface of the object is measured. The thickness of the object can be calculated based on the change in the intensity of the interference light according to the wavelength. However, this method is a method for locally measuring the thickness of the object. Therefore, when it is desired to confirm the thickness distribution of the object in the middle of transportation, it is necessary to arrange a plurality of measuring units having an irradiation part for irradiating light to the object and a measuring part for measuring the interference light in parallel. In this case, the larger the width of the object, the more the number of measuring units needs to be increased, and the structure becomes complicated.

[0007] An object of the present disclosure is to provide a thickness distribution measuring device and a thickness distribution measuring method which can confirm the relative thickness distribution of an object being conveyed with a simple structure while the object is being conveyed. [Technical means to solve the problem]

[0008] [1] A thickness distribution measuring device according to one embodiment of the present disclosure includes a conveying unit, a light source unit, a light detection unit, and a computing unit. The conveying unit conveys an object having a first surface and a second surface opposite to the first surface in a conveying direction along the first surface and the second surface. The light source unit is arranged at a position facing the second surface of the object, and irradiates light to a region of the object being conveyed extending in a width direction intersecting the conveying direction. The light detection unit is arranged at a position facing the first surface of the object, and detects outgoing light that passes through the object irradiated with light. The computing unit obtains information related to the distribution of the relative thickness of the above-mentioned region of the object in the width direction based on the detection result of the light detection unit. The light detection unit includes an image sensor and a lens unit. The image sensor includes a pixel unit including at least a plurality of pixels arranged in the width direction, and detects the intensity of the outgoing light at each pixel and outputs image data. The lens unit includes a plurality of lenses having equal magnifications and arranged in the width direction, and focuses the outgoing light and forms an image on the pixel unit of the image sensor.

[0009] [2] A thickness distribution measurement method according to an embodiment of the present disclosure includes the following steps: starting to transport an object having a first surface and a second surface opposite to the first surface in a transport direction along the first surface and the second surface; starting to irradiate light to a region of the object being transported that extends in a width direction intersecting the transport direction; starting to detect emitted light that passes through the object irradiated with light; and based on the detection result in the detection step, obtaining information related to the distribution of relative thickness of the above-mentioned region of the object in the width direction. In the detection step, an image sensor and a lens unit are used, wherein the image sensor has a pixel unit that includes at least a plurality of pixels arranged in the width direction, and detects the intensity of the emitted light at each pixel and outputs image data, and the lens unit includes a plurality of lenses having equal magnifications and arranged in the width direction, and focuses and images the emitted light on the pixel unit of the image sensor.

[0010] When the light transmittance of the object is uniform, the amount of light absorbed inside the object depends on the thickness of the object. Therefore, the distribution of the relative thickness of the object in the width direction can be measured by irradiating light to an area extending in the width direction of the object and detecting the light intensity of the outgoing light from the area. According to the above-mentioned thickness distribution measuring device and thickness distribution measuring method, since an image sensor having a plurality of pixels arranged in the width direction is used to detect the light intensity of the outgoing light, the structure can be simplified compared to the spectral interference method in which a plurality of measuring units are arranged in parallel in the width direction of the object. In addition, by using a lens portion including a plurality of lenses having equal magnifications and arranged in the width direction, the outgoing light is focused and imaged on the image sensor, and the lens portion can be arranged close to the object and the collection efficiency of the outgoing light can be improved, thereby improving the detection sensitivity. Therefore, even with a simple structure, the relative thickness distribution can be measured with practical accuracy.

[0011] In the thickness distribution measuring device, the light source unit is arranged opposite to the second surface, and the light detection unit is arranged opposite to the first surface. Moreover, the outgoing light from the object is the light that passes through the object. In this way, the light source unit and the light detection unit are arranged in a manner that the object is sandwiched between them, and the light that passes through the object is detected as the outgoing light from the object, so that the light intensity of the outgoing light depends more on the thickness of the object. Therefore, the measurement accuracy of the relative thickness distribution can be further improved.

[0012] [3] In the thickness distribution measuring device of [1] and the thickness distribution measuring method of [2], the optical axis of the lens portion may be along the normal to the first surface. In this case, since the light emitted vertically from the front of the object is detected, the influence of the polarization state on the light intensity of the emitted light can be avoided, thereby further improving the measurement accuracy of the relative thickness distribution.

[0013] [4] In the thickness distribution measuring device of [1] and the thickness distribution measuring method of [2], the optical axis of the lens portion may be inclined relative to the normal line of the first surface. In this case, it is possible to easily detect damage existing on the front side of the object while measuring the relative thickness distribution. The inclination angle of the optical axis of the lens portion relative to the normal line may be greater than 5° and less than 80°.

[0014] [5] In the thickness distribution measuring device of [1], [3] or [4] and the thickness distribution measuring method of any one of [2] to [4], the image sensor may be configured to switch the gain value for amplifying the signals output from the plurality of pixels. In this case, even when the light intensity of the emitted light changes, the relative thickness distribution can be measured without replacing the image sensor.

[0015] [6] The thickness distribution measuring device of the above-mentioned [5] may further include another light source unit. The other light source unit is arranged at a position facing the first surface, and irradiates light to the above-mentioned area in the object being conveyed or another area extending in the width direction. In addition, the light detection unit may also detect the outgoing light from the object irradiated with light by the other light source unit. The gain value of the image sensor when the light is irradiated from the other light source unit may be different from the gain value of the image sensor when the light is irradiated from the light source unit. In this case, a device can be used to detect the outgoing light from the surface irradiated with light and the outgoing light from the opposite surface of the surface irradiated with light. Therefore, since information related to the relative thickness distribution can be obtained based on the detection results of these outgoing lights, the measurement accuracy of the relative thickness distribution can be further improved.

[0016] [7] The thickness distribution measuring device of any one of [1], [3] to [6] may further include a thickness measuring unit for locally measuring the absolute thickness of the object. Furthermore, the calculation unit may correct the relative thickness measurement value based on the absolute thickness measured by the thickness measuring unit. Similarly, the thickness distribution measuring method of any one of [2] to [5] and [7] may further include a step of locally measuring the absolute thickness of the object, and in the step of obtaining information, the relative thickness measurement value is corrected based on the absolute thickness measured by the measuring step. In the thickness distribution measuring device, when the intensity of the light output from the light source unit varies with time, the intensity of the measured emitted light also varies with time. Similarly, in the thickness distribution measuring method, when the intensity of the irradiated light varies with time in the step of starting irradiation, the intensity of the measured emitted light also varies with time. By making a correction based on the absolute thickness measured by the thickness measuring unit (the measuring step), the measurement accuracy of the relative thickness distribution can be further improved. The thickness measuring unit may have a spectral interference method. In the measuring step, a spectral interference method can be used.

[0017] [8] In the thickness distribution measuring device of any one of [1], [3] to [7] above, the image sensor may be a line scan sensor.

[0018] [9] In the thickness distribution measuring device of any one of [1], [3] to [8] above, the light detection unit may further have a first optical filter and a second optical filter. The first optical filter is disposed on a portion of the pixels among the multiple pixels of the image sensor, and has a transmission wavelength band centered on the first wavelength. The second optical filter is disposed on at least another portion of the pixels among the multiple pixels of the image sensor, and has a transmission wavelength band centered on a second wavelength different from the first wavelength. As described above, when the intensity of the light output from the light source unit varies with time, the measured intensity of the emitted light also varies with time. Therefore, the measurement result of the relative thickness distribution becomes a result that varies depending on the wavelength. Therefore, it can be known that the intensity of the light output from the light source unit varies with time. [Effects of the Invention]

[0019] According to the present disclosure, it is possible to provide a thickness distribution measuring device and a thickness distribution measuring method that can confirm the thickness distribution of a conveyed object with a simple structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The figure schematically shows the structure of a thickness distribution measuring device according to one embodiment. Figure 2 It is a three-dimensional diagram showing the light source unit and the light detection unit. Figure 3 A cutaway perspective view showing the internal structure of the light detection unit. Figure 4 A top view of the image sensor. Figure 5 This is an example of image data obtained by an image sensor. Figure 6 A diagram showing the structure of the internal circuit of an image sensor. Figure 7 A diagram showing a structural example of each pixel. Figure 8 The figure schematically shows a stereoscopic view of a lens array. Fig. 9 The figure schematically shows a stereoscopic view of a lens array. Fig.10 This is a diagram schematically showing the structure of a control device. Fig.11 This is a diagram schematically showing an example of the hardware configuration of a control device. Fig.12 This diagram schematically shows how light attenuates when passing through an object. Fig.13This is a graph showing the relationship shown in equation (1). Fig.14 FIG. 4 is a flow chart showing a thickness distribution measurement method according to an embodiment. Fig.15 This is a perspective view showing a state in which a plurality of optical reduction type measurement units are arranged in parallel in the width direction of an object as a comparative example. Fig.16 Part (a) shows an example of an image obtained through a high-magnification lens. Fig.16 Part (b) shows an example of an image obtained through an equal magnification lens. Fig.17 A cutaway perspective view showing the internal structure of the light detection unit as a first modification. Fig.18 This diagram schematically shows how light emitted from an object passes through an optical filter group. Fig.19 Parts (a) and (b) of FIG. 1 are graphs showing the relationship represented by equation (1) for each wavelength. Fig. 20 A diagram schematically showing the structure of a thickness distribution measuring device according to a second modification. Fig.21 A diagram showing the structure of each pixel of an image sensor according to a second variation. Fig. 22 A diagram schematically showing the structure of a thickness distribution measuring device according to a third modified example. Fig.23 This is an example of image data obtained by an image sensor. Fig.24 A diagram schematically showing the structure of a thickness distribution measuring device according to a fourth modified example. Fig.25 A diagram schematically showing the structure of a thickness distribution measuring device according to a fifth modification. Fig.26 It is a perspective view showing a part of the structure of the thickness distribution measuring device. Fig. 27 It is a figure which shows the specific structure of a thickness measuring part. Fig.28 This is a diagram for explaining the principle of thickness measurement, schematically showing a cross section of an object. Fig.29 Parts (a), (b), and (c) are graphs showing the relationship between the intensity of reflected light after interference and the wavelength. Fig.30 It is a top view showing the measurement line of the thickness measurement part. Fig.31 Part (a) is a graph showing an example of the thickness measurement result when the calculation unit does not correct the measured value of the relative thickness. Fig.31 Part (b) is a graph showing an example of the thickness measurement result when the calculation unit corrects the measured value of the relative thickness. DETAILED DESCRIPTION

[0021] Hereinafter, embodiments of the thickness distribution measuring device and the thickness distribution measuring method disclosed herein will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and repeated descriptions are omitted.

[0022] Figure 1 The figure schematically shows the structure of a thickness distribution measuring device 1A according to an embodiment of the present disclosure. The thickness distribution measuring device 1A is a device for obtaining information related to the relative thickness distribution of an object B. The relative thickness distribution described here refers to the relative thickness distribution of the object B in the width direction of the object B. The object B is a plate-like or sheet-like object having a first surface Ba and a second surface Bb opposite to the first surface Ba. In one example, the object B is a cloth such as a polymer film, a cloth or a nonwoven fabric, a paper or a substrate being conveyed. The object B of this embodiment is composed of a single layer (single material) and does not have a structure of stacking multiple layers. The width direction of the object B refers to a direction that intersects both the conveying direction D1 and the thickness direction D3. In one example, the width direction of the object B is orthogonal to both the conveying direction D1 and the thickness direction D3. In the middle of conveying, the thickness direction D3 is, for example, along the vertical direction.

[0023] like Figure 1 As shown, the thickness distribution measuring device 1A of the present embodiment includes a conveying unit 10, a light source unit 20, a light detection unit 30, a control device 40, an input device 54, and a monitor 55. The conveying unit 10 conveys the object B in the conveying direction D1 along the first surface Ba and the second surface Bb. The conveying unit 10 is, for example, a roller conveyor, and has a plurality of roller pairs 11 and a driving unit (not shown) such as a motor for rotating and driving the plurality of roller pairs 11. The plurality of roller pairs 11 each include a pair of rollers 11a and 11b having a rotation axis extending in the width direction of the object B. The object B is conveyed by causing the rollers 11a and 11b to rotate in opposite directions to each other while being sandwiched between the rollers 11a and 11b.

[0024] Figure 2 30. The light source unit 20 is disposed at a position facing one of the first surface Ba and the second surface Bb of the object B. In the example shown in the figure, the light source unit 20 is disposed at a position facing the second surface Bb. The light source unit 20 irradiates the area R1 extending in the width direction D2 of the object B being conveyed with light La (see FIG. 3 ). Figure 1). The region R1 extends from one end edge in the width direction D2 of the object B to the other end edge. The light source unit 20, for example, has a structure in which a plurality of light emitting elements are arranged along the width direction D2. As the light emitting element, a light emitting diode (LED: Light Emitting Diode) is exemplified, but not limited to this. The emission wavelength and emission intensity of the plurality of light emitting elements are consistent among the plurality of light emitting elements. The light La output from the light source unit 20 is temporally continuous light. The wavelength of the light La may be included in the visible range or in the near-infrared range.

[0025] The light detection unit 30 is arranged at a position facing the other of the first surface Ba and the second surface Bb of the object B. In the illustrated example, the light detection unit 30 is arranged at a position facing the first surface Ba. The light detection unit 30 faces the light source unit 20 across the object B. The light detection unit 30 detects the outgoing light Lb from the object B irradiated with the light La. In the present embodiment, the outgoing light Lb from the object B is the light La that passes through the object B.

[0026] Figure 3 3 is a cutaway perspective view showing the internal structure of the light detection unit 30. Figure 3 As shown, the light detection unit 30 includes a housing 31, an image sensor 32, a lens array 33, a circuit substrate 34, and holding members 318 and 319. The housing 31 is a hollow container having a rectangular parallelepiped appearance extending in the width direction D2. The housing 31 includes a top plate 311, a bottom plate 312, and side plates 313 and 314. The top plate 311 and the bottom plate 312 are opposite to each other in the thickness direction D3. The side plate 313 extends in the thickness direction D3, connecting the end edge of one side of the top plate 311 in the conveying direction D1 to the end edge of one side of the bottom plate 312 in the conveying direction D1. The side plate 314 extends in the thickness direction D3, connecting the end edge of the other side of the top plate 311 in the conveying direction D1 to the end edge of the other side of the bottom plate 312 in the conveying direction D1. The housing 31 accommodates the image sensor 32, the lens array 33, the circuit substrate 34, and the holding members 318 and 319. A slit 315 extending in the width direction D2 is formed in the bottom plate 312 of the housing 31 . The outgoing light Lb from the object B passes through the slit 315 and reaches the inside of the housing 31 .

[0027] Figure 4 : is a top view of the image sensor 32. The image sensor 32 is, for example, a line scan sensor, and has a pixel unit 321 with the width direction D2 as the long side direction. The pixel unit 321 includes at least a plurality of pixels 322 arranged along the width direction D2. Each pixel 322 includes a photodiode. The image sensor 32 detects the intensity of the emitted light Lb at each pixel 322 and generates image data. The image sensor 32 repeatedly generates such image data at a predetermined time period. Figure 5is an example of image data obtained by the image sensor 32. The image sensor 32 outputs the generated image data to the control device 40. Figure 3 As shown, the image sensor 32 is mounted on the circuit board 34. The circuit board 34 is mounted and fixed to the top board 311 in such a manner that a mounting surface 34a on which the image sensor 32 is mounted faces the bottom board 312 and a surface opposite to the mounting surface 34a faces the top board 311.

[0028] Figure 6 3 is a diagram showing the structure of the internal circuit of the image sensor 32. As described above, the image sensor 32 has a pixel portion 321 in which a plurality of pixels 322 are arranged along the width direction D2. The plurality of pixels 322 have a common structure. The image sensor 32 further has a readout circuit 60 and a sensor control unit 70. The readout circuit 60 and the pixel portion 321 of the image sensor 32 are controlled by the control device 40 and the sensor control unit 70. The image sensor 32 sequentially outputs a voltage value corresponding to the amount of incident light on each pixel 322 from the readout circuit 60 to the control device 40 via the video line 81.

[0029] The readout circuit 60 includes a plurality of holding circuits 61, a plurality of switches 62, and a plurality of switches 63 that correspond one-to-one to each pixel 322. Each holding circuit 61 is connected to the output terminal of the pixel 322 via the corresponding switch 62. Each holding circuit 61 holds the voltage value output from the pixel 322 before the corresponding switch 62 is turned from the on state to the off state. Each holding circuit 61 is connected to the video line 81 via the corresponding switch 63. Each holding circuit 61 outputs the held voltage value to the video line 81 when the corresponding switch 63 is in the on state.

[0030] The multiple switches 62 are controlled by a control signal given from the sensor control unit 70, and are switched on / off at the same timing. The multiple switches 63 are controlled by another control signal given from the sensor control unit 70, and are sequentially turned on only for a fixed period. In addition to controlling the on / off of each of the multiple switches 62 and each of the multiple switches 63 of the readout circuit 60, the sensor control unit 70 also controls the operation of each of the multiple pixels 322.

[0031] Figure 7 3 is a diagram showing a configuration example of each pixel 322. Each pixel 322 includes a photodiode 64, a MOS (Metal-Oxide-Semiconductor) transistor 65, a MOS transistor 66, and a source follower amplifier 67. The source follower amplifier 67 includes a MOS transistor 671, an operation control switch 672, and a current source 673.

[0032] The photodiode 64 generates charges in response to incident light. The anode of the photodiode 64 is connected to a second reference potential input terminal 92 to which a second reference potential (e.g., a ground potential) is input. The gate of the MOS transistor 671 is connected to the cathode of the photodiode 64 via the MOS transistor 65, and is connected to a first reference potential input terminal 91 to which a first reference potential (e.g., a power supply potential) is input via the MOS transistor 66. The drain of the MOS transistor 671 is connected to the first reference potential input terminal 91.

[0033] The action control switch 672 is provided between the source of the MOS transistor 671 and the connection node 674. The action control switch 672 can be formed by a MOS transistor. The current source 673 is provided between the connection node 674 and the second reference potential input terminal 92. The current source 673 can be formed by including a MOS transistor. The current source 673 can also be formed by a resistor.

[0034] The on / off of each of the MOS transistors 65 and 66 is controlled by a control signal given from the sensor control unit 70. When the MOS transistor 66 is in the on state, the gate potential of the MOS transistor 671 is initialized. When the MOS transistors 65 and 66 are in the on state, the accumulation of charge in the junction capacitance of the photodiode 64 is initialized. When the MOS transistor 65 is in the on state and the MOS transistor 66 is in the off state, the gate potential of the MOS transistor 671 becomes a potential corresponding to the amount of incident light on the photodiode 64.

[0035] The on / off of the action control switch 672 is also controlled by the control signal given from the sensor control unit 70. During the period when the action control switch 672 is in the on state, the current flows from the first reference potential input terminal 91 to the second reference potential input terminal 92 via the MOS transistor 671, the action control switch 672 and the current source 673. As a result, a voltage value corresponding to the gate potential of the MOS transistor 671 is output from the connection node 674. On the other hand, during the period when the action control switch 672 is in the off state, the current does not flow through the source follower amplifier 67, and the source follower amplifier 67 is in the off state.

[0036] Each pixel 322 further includes a capacitor 68 and a charge amplifier 69 . The charge amplifier 69 includes an amplifier 691 , a capacitor 692 , and a reset switch 693 .

[0037] The amplifier 691 has an inverting input terminal, a non-inverting input terminal, and an output terminal. A fixed bias potential is input to the non-inverting input terminal of the amplifier 691. The inverting input terminal of the amplifier 691 is connected to the connection node 674 of the source follower amplifier 67 via the capacitor 68.

[0038] The capacitor section 692 is provided between the inverting input terminal and the output terminal of the amplifier 691. The capacitor section 692 accumulates electric charge of an amount corresponding to the voltage value output from the source follower amplifier 67. The capacitor section 692 includes a capacitor element 694.

[0039] The reset switch 693 is provided between the inverting input terminal and the output terminal of the amplifier 691, in parallel with the capacitor section 692. When the reset switch 693 is in the on state, the charge accumulation in the capacitor section 692 is reset. When the reset switch 693 is in the off state, a voltage value corresponding to the charge accumulation amount in the capacitor section 692 and the capacitance value of the capacitor section 692 is output from the output terminal of the amplifier 691. The on / off of the reset switch 693 is controlled by a control signal given from the sensor control section 70.

[0040] Reference again Figure 3 The holding members 318 and 319 are fixed to the housing 31 inside the housing 31. The holding members 318 and 319 are arranged on both side surfaces of the lens array 33 in the conveying direction D1, and hold the lens array 33 therebetween. The lens array 33 is an example of a lens unit in the present embodiment.

[0041] Figure 8 Schematically shows a stereoscopic diagram of the lens array 33. The lens array 33 has a plurality of lenses 331 arranged along the width direction D2. The magnification of each of the plurality of lenses 331 is equal, and in one example is 1. When the magnification of each of the plurality of lenses 331 is equal, it does not need to be strictly 1, for example, as long as it is greater than 0.9 times and less than 1.1 times, it is allowed to be equal. Each of the plurality of lenses 331 is, for example, a cylindrical lens made of glass. The light incident end face 332 of each lens 331 passes through the slit 315 of the bottom plate 312 (refer to Figure 3 ), and the first surface Ba of the object B (reference Figure 2 ) opposite. The distance between the light incident end surface 332 and the first surface Ba is, for example, 5 mm or more and 20 mm or less, and is 12 mm in one example. The light emitting end surface 333 of each lens 331 is opposite to the pixel portion 321 of the image sensor 32 (reference Figure 4 ) opposite. Each lens 331 does not necessarily have to correspond one-to-one to each pixel 322 of the pixel unit 321. The lens array 33 focuses the emitted light Lb and forms an image on the pixel unit 321 of the image sensor 32. The magnification of the image presented on the image sensor 32 is the same as or smaller than the magnification of the subject, i.e., the object B. Therefore, the light collection efficiency can be improved compared to a high-magnification lens. In particular, compared to Figure 8 A lens array 33 of such a row, such as Fig. 9The lens array 33 having multiple rows (for example, 2 rows or 3 rows) can further improve the light collection efficiency compared with a high-magnification lens. The optical axis of the lens array 33 is along the normal of the surface Ba and the surface Bb of the object B that are opposite to the light detection unit 30. In the example shown in the figure, the optical axis of the lens array 33 is along the normal of the first surface Ba. In other words, the optical axis of the lens array 33 is perpendicular to the surface Ba and the surface Bb of the object B that are opposite to the light detection unit 30.

[0042] The control device 40 is electrically connected to the conveying unit 10 , the light source unit 20 , and the light detection unit 30 . Fig.10 This is a diagram schematically showing the structure of the control device 40. The control device 40 has a transport control unit 41 that controls the movement of the transport unit 10 such as the transport speed, a light source control unit 42 that controls the movement of the light source unit 20, a detection control unit 43 that controls the movement of the light detection unit 30, and a calculation unit 44. The calculation unit 44 receives image data as a result of detecting the emitted light Lb from the light detection unit 30. Based on the image data, the calculation unit 44 obtains information related to the distribution of the relative thickness of the region R1 of the object B in the width direction D2. The control device 40 can be, for example, a smart device such as a personal computer, a smart phone, a tablet terminal, or a computer having a processor such as a cloud server. At least one of the transport control unit 41, the light source control unit 42, and the detection control unit 43 can also be composed of a computer different from the calculation unit 44.

[0043] Fig.11 FIG. 4 is a diagram schematically showing an example of the hardware configuration of the control device 40. Fig.11 As shown, the control device 40 can be physically constituted as a common computer including a processor (CPU: Central Processing Unit) 401, a main storage device such as a ROM (Read Only Memory) 402 and a RAM (Random Access Memory) 403, and an auxiliary storage device 404 such as a hard disk. The processor 401 of the computer can realize the various functions of the above-mentioned control device 40 by reading out the program stored in the ROM 402 or the auxiliary storage device 404. Therefore, the program causes the processor 401 of the computer to act as the transport control unit 41, the light source control unit 42, the detection control unit 43, and the calculation unit 44 in the control device 40. The storage device storing the program can also be a non-temporary recording medium. As the recording medium, a recording medium such as a floppy disk, a CD (Compact Disc), or a DVD (Digital Versatile Disc), a recording medium such as a ROM, a semiconductor memory, or a cloud server, etc. are exemplified.

[0044] The input device 54 is electrically connected to the control device 40. The operator inputs various settings related to the transport control unit 41, the light source control unit 42, the detection control unit 43 and the operation unit 44 through the input device 54. The input device 54 can be, for example, a keyboard, a mouse or a touch panel. The monitor 55 is electrically connected to the control device 40. The monitor 55 displays information related to the relative thickness distribution obtained by the operation unit 44. The monitor 55 can also be a touch screen including a touch panel, i.e., the input device 54.

[0045] Fig.10 The calculation unit 44 shown obtains information related to the distribution of the relative thickness of the region R1 of the object B in the width direction D2 based on the image data. The information related to the relative thickness distribution may be the relative thickness distribution or a group of numerical values ​​associated with the relative thickness distribution. For example, the information related to the relative thickness distribution may also be the image data itself. The reason is that the light intensity of the emitted light Lb shown in the image data is correlated with the thickness of the object B. The relative thickness means the relative value of other positions when the value of a certain position in the width direction D2 is used as a reference. Therefore, the calculation unit 44 does not have to correctly obtain the absolute thickness at each position in the width direction D2.

[0046] Fig.12 This is a diagram schematically showing the attenuation of light La when passing through object B. The thickness of the arrow in the figure indicates the light intensity. As described above, light La emitted from the light source unit 20 passes through object B to become emitted light Lb. The emitted light Lb is detected by the image sensor 32. Here, if the light intensity of light La is set to I0, the light intensity of emitted light Lb is set to I, the absorption coefficient of object B is set to α, and the thickness of object B is set to x, the following formula (1) holds. [Number 1] I=I0·exp(-αx)...(1) Since the absorption coefficient α is a value inherent in the material of the object B, it can be easily found. Fig.13 This is a graph showing the relationship shown in equation (1). Fig.13 In FIG. 1 , the vertical axis represents the ratio (I / I0) of the light intensity I of the emitted light Lb to the light intensity I0 of the light La, and the horizontal axis represents the thickness x of the object B. Based on this relationship, for example, when the value of the ratio (I / I0) is P1, the thickness x of the object B is x1, and when the value of the ratio (I / I0) is P2, the thickness x of the object B is x2, and the thickness x is uniformly calculated based on the size of the ratio (I / I0). If the light intensity I0 of the light La is known, the thickness x is calculated based on the light intensity I of the emitted light Lb. Even if the light intensity I0 of the light La is unknown, as long as the irradiation intensity of the plurality of light emitting elements from the light source unit 20 is uniform, the relative thickness distribution in the width direction D2 can be calculated.

[0047] Fig.14 The flowchart of the thickness distribution measurement method of the present embodiment is shown. The thickness distribution measurement method can be implemented using the above-mentioned thickness distribution measurement device 1A. In the thickness distribution measurement method, in step ST1, the object B having a first surface Ba and a second surface Bb opposite to the first surface Ba is started to be transported in the transport direction D1 along the first surface Ba and the second surface Bb. In step ST2, the area R1 extending along the width direction D2 intersecting the transport direction D1 in the object B being transported is irradiated with light La. In step ST3, the detection of the emitted light Lb from the object B irradiated with the light La is started. In step ST3, an image sensor 32 and a lens array 33 are used. As described above, the image sensor 32 has a pixel portion 321 including at least a plurality of pixels 322 arranged in the width direction D2, and detects the intensity of the emitted light Lb in each pixel 322 and outputs image data. The lens array 33 has a plurality of lenses 331 arranged in the width direction D2, and focuses the emitted light Lb and forms an image on the pixel unit 321 of the image sensor 32. In step ST4, based on the detection result in step ST3, information on the distribution of the relative thickness of the region R1 of the object B in the width direction D2 is obtained.

[0048] The effects obtained by the thickness distribution measuring device 1A and the thickness distribution measuring method of the present embodiment described above will be described. When the light transmittance of the object B is uniform, the amount of light absorbed inside the object B depends on the thickness of the object B. Therefore, the distribution of the relative thickness of the object B in the width direction D2 of the object B can be measured by irradiating the region R1 extending in the width direction D2 of the object B with light La and detecting the light intensity I of the emitted light Lb from the region R1. In addition, according to the thickness distribution measuring device 1A and the thickness distribution measuring method of the present embodiment, since the image sensor 32 having a plurality of pixels 322 arranged in the width direction D2 is used to detect the light intensity I of the emitted light Lb, the structure can be simplified compared to the spectral interference method in which a plurality of measuring units are arranged in parallel in the width direction D2 of the object B.

[0049] Here, Fig.15 This is a perspective view showing a state in which a plurality of measurement units 101 of the reduction optical type are arranged in parallel in the width direction D2 of the object B as a comparative example. The measurement unit 101 of the reduction optical type has a lens with a high magnification (i.e., a magnification greater than the same magnification). In this case, since the measurement unit 101 is arranged at a large distance from the object B, the collection efficiency of the emitted light Lb is suppressed to be low. Fig.16Part (a) shows an example of an image obtained through a high-magnification lens with a low collection efficiency of the outgoing light Lb. In addition, in a high-magnification lens, since the distortion between the center and the peripheral portion is large, the deviation of the collection efficiency of the outgoing light Lb in each measurement unit 101 becomes larger. In this regard, in the present embodiment, a lens array 33 having a plurality of lenses 331 of equal magnification arranged in the width direction D2 is used to focus the outgoing light Lb and image it on the image sensor 32. As a result, the lens array 33 can be arranged close to the object B to improve the collection efficiency of the outgoing light Lb and improve the detection sensitivity. Fig.16 Part (b) of FIG. 1 shows an example of an image obtained by an equal-magnification lens with a high collection efficiency of the outgoing light Lb. Fig.16 The image shown in part (a) is much clearer. In addition, since the deformation between the center and the peripheral portion of each lens 331 is small, the deviation of the collection efficiency of the emitted light Lb can be suppressed to a small extent. Based on the above, according to this embodiment, even with a simple structure, the relative thickness distribution can be measured with practical accuracy.

[0050] As in the present embodiment, the light source unit 20 may be arranged to face one of the first surface Ba and the second surface Bb, and the light detection unit 30 may be arranged to face the other of the first surface Ba and the second surface Bb. Furthermore, the outgoing light Lb from the object B may be light that passes through the object B. In this way, by arranging the light source unit 20 and the light detection unit 30 in such a manner that the object B is sandwiched between the light source unit 20 and the light detection unit 30, the light that passes through the object B is detected as the outgoing light Lb from the object B, and the light intensity I of the outgoing light Lb is more dependent on the thickness of the object B. Therefore, the measurement accuracy of the relative thickness distribution can be further improved.

[0051] As in the present embodiment, the optical axis of the lens array 33 may also be along the normal of the surface of the first surface Ba and the second surface Bb that is opposite to the light detection unit 30. In this case, the outgoing light Lb vertically emitted from the front of the object B is detected. Therefore, the influence of the polarization state on the light intensity I of the outgoing light Lb can be avoided, thereby further improving the measurement accuracy of the relative thickness distribution. In this case, as a plurality of light-emitting elements of the light source unit 20, an element with high directivity can be used to make the light La incident on the surface of the object B as vertically as possible. [First Modification]

[0052] Fig.171 is a cutaway perspective view showing the internal structure of the light detection unit 30A as a first modification. The light detection unit 30A of this modification further includes an optical filter unit 35 in addition to the structure of the light detection unit 30 of the above-mentioned embodiment. The optical filter unit 35 is provided on the pixel unit 321 of the image sensor 32. The outgoing light Lb from the object B passes through the optical filter unit 35 and enters the pixel unit 321 of the image sensor 32.

[0053] Fig.18 : This is a diagram schematically showing a state in which the outgoing light Lb from the object B passes through the optical filter unit 35. As schematically shown in the figure, the optical filter unit 35 has a plurality of optical filter groups 36 arranged along the width direction D2. Each optical filter group 36 includes a plurality of optical filters 37 to 39. One of the optical filters 37 to 39 is an example of the first optical filter in this modification, and the other of the optical filters 37 to 39 is an example of the second optical filter in this modification. The optical filter 37 is provided on a portion of the pixels 322 of the plurality of pixels 322 of the image sensor 32. The optical filter 38 is provided on another portion of the pixels 322 of the plurality of pixels 322 of the image sensor 32. The optical filter 39 is provided on the remaining pixels 322 of the plurality of pixels 322 of the image sensor 32. The optical filter 37 has a transmission wavelength band centered on the wavelength λ1. The optical filter 38 has a transmission wavelength band centered around a wavelength λ2 that is larger than the wavelength λ1. The optical filter 39 has a transmission wavelength band centered around a wavelength λ3 that is larger than the wavelengths λ1 and λ2. The wavelength λ1 is not included in the transmission wavelength bands of the optical filters 38 and 39. The wavelength λ2 is not included in the transmission wavelength bands of the optical filters 37 and 39. The wavelength λ3 is not included in the transmission wavelength bands of the optical filters 37 and 38.

[0054] Of the outgoing light Lb from the object B, the wavelength component centered around the wavelength λ1 enters the pixel 322 through the optical filter 37. The wavelength component centered around the wavelength λ2 enters another pixel 322 through the optical filter 38. The wavelength component centered around the wavelength λ3 enters yet another pixel 322 through the optical filter 39. In this way, the light intensity I of the outgoing light Lb is detected by wavelength.

[0055] Fig.19 Parts (a) and (b) of FIG. 1 are graphs showing the relationship shown in equation (1) for each wavelength. In the graph, curve G1 corresponds to wavelength λ1, curve G2 corresponds to wavelength λ2, and curve G3 corresponds to wavelength λ3. Fig.19 The curves G1 to G3 in part (b) and Fig.19The curves G1 to G3 in part (a) are the same. Since the absorption coefficient α depends on the wavelength, the curves vary depending on the wavelength. In this example, the absorption coefficient α is smaller as the wavelength increases, that is, the light transmittance is greater. Now, the light intensity of the light La is assumed to be a predetermined value I0 and is known. At this time, if Fig.19 As shown in part (a), for a certain thickness x1 of the object B, the value of the ratio (I / I0) at the wavelength λ1 is P 11 , at wavelength λ2 is P 12 , at wavelength λ3 is P 13 . And, regardless of the value of the ratio (I / I0) at which wavelength the calculation unit 44 uses, the thickness of the object B calculated is always x1. Then, it is assumed that the light intensity of the light La changes from a predetermined value I0. At this time, since the light intensity I of the emitted light Lb changes, Fig.19 As shown in part (b), the value of the ratio (I / I0) changes from P to 11 Change to P 21 , at wavelength λ2 from P 12 Change to P 22 , at wavelength λ3 from P 13 Change to P 23 Thus, the calculation result of the thickness of the object B by the calculation unit 44 becomes x 11 , at wavelength λ2 is x 12 , at wavelength λ3 is x 13 Thus, the operator can know that the light intensity of the light La output from the light source unit 20 changes with time, and can know the timing of adjusting the light intensity of the light La or the parameters of the equation.

[0056] In the above description, the case where each optical filter group 36 includes three optical filters 37 to 39 is exemplified, but the number of optical filters in each optical filter group 36 may be two, or may be four or more. When each optical filter group 36 includes only two optical filters 37 and 38, the optical filter 37 is provided on a portion of the pixels 322 of the plurality of pixels 322 of the image sensor 32, and the optical filter 38 is provided on the remaining pixels 322 of the plurality of pixels 322 of the image sensor 32. [Second Modification]

[0057] Fig. 201 is a diagram schematically showing the structure of a thickness distribution measuring device 1B of a second variant. In addition to the structure of the thickness distribution measuring device 1A of the above-mentioned embodiment, the thickness distribution measuring device 1B of this variant further includes a light source unit 21 that is different from the light source unit 20. The light source unit 21 is arranged at a position opposite to the surface opposite to the surface facing the light source unit 20 (the first surface Ba in the example shown) of the first surface Ba and the second surface Bb of the object B. The light source unit 21 is directed to a region R1 of the object B being conveyed, or to a region R2 along the width direction D2 (reference Figure 2 ) is irradiated with light Lc to another area extending in the width direction D2 of the object B. The other area, like the area R1, extends from one end edge in the width direction D2 of the object B to the other end edge. The light source unit 21, for example, has a structure in which a plurality of light-emitting elements are arranged along the width direction D2. As the light-emitting element, a light-emitting diode (LED) is exemplified, but not limited to this. The emission wavelength and emission intensity of the plurality of light-emitting elements are consistent among the plurality of light-emitting elements. The light source unit 21 outputs continuous light, namely, light Lc. The wavelength of the light Lc may be included in the visible range or in the near-infrared range. The light intensity of the light Lc may be equal to or different from the light intensity of the light La. The wavelength of the light Lc may be equal to or different from the wavelength of the light La.

[0058] The thickness distribution measuring device 1B of this modified example includes a light detection unit 30B instead of the light detection unit 30 of the above-mentioned embodiment. The light detection unit 30B is different from the light detection unit 30 of the above-mentioned embodiment in that the image sensor 32 can be configured to switch the gain value for amplifying the signals output from a plurality of pixels, but is consistent with the light detection unit 30 of the above-mentioned embodiment in other points. The light detection unit 30B detects the outgoing light Lb from the object B irradiated with the light La by the light source unit 20, and further detects the outgoing light Lb from the object B irradiated with the light Lc by the light source unit 21. The irradiation timing of the light La and the irradiation timing of the light Lc are controlled by the light source control unit 42 of the control device 40 (refer to Fig.10 ) are controlled and are different from each other.

[0059] The gain value of the image sensor 32 is controlled to be different when the light La is irradiated from the light source unit 20 and when the light Lc is irradiated from the light source unit 21. That is, when the light intensity I of the emitted light Lb when the light La is irradiated is greater than the light intensity I of the emitted light Lb when the light Lc is irradiated, the gain value of the image sensor 32 when the light La is irradiated from the light source unit 20 is controlled to be smaller than the gain value of the image sensor 32 when the light Lc is irradiated. When the light intensity I of the emitted light Lb when the light La is irradiated is smaller than the light intensity I of the emitted light Lb when the light Lc is irradiated, the gain value of the image sensor 32 when the light La is irradiated from the light source unit 20 is controlled to be larger than the gain value of the image sensor 32 when the light Lc is irradiated. In this way, the fluctuation range of the magnitude of the signal output from the image sensor 32 can be reduced.

[0060] Fig.21 322A of the image sensor 32 of this modification. The pixel 322A has the same structure and function as the pixel 322 of the above embodiment except for the following points. That is, the pixel 322A of this modification replaces the capacitor section 692 (refer to Figure 7 ), having a capacitor section 692A. The capacitor section 692A is arranged between the inverting input terminal and the output terminal of the amplifier 691. The capacitor section 692A accumulates an amount of charge corresponding to the voltage value output from the source follower amplifier 67. The capacitance value of the capacitor section 692A is variable. The capacitor section 692A can make the capacitance value variable by being configured to include a capacitor element 694, a capacitor element 695 and a switch 696. The capacitor element 695 and the switch 696 are connected in series with each other. The serial circuit including the capacitor element 695 and the switch 696 is arranged in parallel with the capacitor element 694. Depending on the state of the switch 696 being on / off, the capacitance value of the capacitor section 692A is different, and the gain (gain value) of the charge amplifier 69 is different. The on / off of the switch 696 is controlled by a control signal given from the sensor control section 70.

[0061] As in this modification, the image sensor 32 may be configured to switch the gain value for amplifying the signals output from the plurality of pixels 322A. In this case, even when the light intensity I of the emitted light Lb changes, the relative thickness distribution can be measured without replacing the image sensor 32. By setting the gain value to an appropriate value, the S / N (Signal / Noise) is improved, and the measurement accuracy of the relative thickness distribution is improved.

[0062] As in this modified example, a light source unit 21 different from the light source unit 20 may be provided, and the light source unit 21 may be arranged at a position facing the opposite surface of the surface facing the light source unit 20 in the first surface Ba and the second surface Bb of the object B, so as to irradiate the light Lc to the area extending along the width direction D2 of the object B being conveyed. In addition, the light detection unit 30B may further detect the irradiated light Lb from the object B irradiated with the light La by the light source unit 20, and the irradiated light Lb from the object B irradiated with the light Lc by the light source unit 21. In this case, one thickness distribution measuring device 1B may be used to detect the irradiated light Lb from the surface irradiated with light and the irradiated light Lb from the opposite surface of the surface irradiated with light. Therefore, since information related to the relative thickness distribution can be obtained based on the detection results of these irradiated lights Lb, the measurement accuracy of the relative thickness distribution can be further improved. [Third Modification]

[0063] Fig. 22This is a diagram schematically showing the structure of a thickness distribution measuring device 1C of the third variant. The difference between the thickness distribution measuring device 1C of this variant and the thickness distribution measuring device 1A of the above embodiment is that the optical axis of the lens array 33 of the light detection unit 30 is tilted. Furthermore, the thickness distribution measuring device 1C of this variant is provided with a control device 40A instead of the control device 40 of the above embodiment. The control device 40A has a damage detection unit 45 for detecting damage generated on the front surface of the object B in addition to the conveying control unit 41, the light source control unit 42, the detection control unit 43 and the calculation unit 44 of the control device 40 of the above embodiment.

[0064] Specifically, the optical axis of the lens array 33 in this modified example is inclined relative to the normal of the surface (the first surface Ba in the illustrated example) of the first surface Ba and the second surface Bb of the object B that is opposite to the light detection unit 30. The inclination angle of the optical axis of the lens array 33 relative to the normal is, for example, greater than 5°, and may also be greater than 45°. The inclination angle may also be less than 80°. The greater the inclination angle of the optical axis of the lens array 33 relative to the normal, the easier it is to detect damage described later. Similar to the above-mentioned embodiment, the light detection unit 30 detects the outgoing light Lb from the object B irradiated with light La. Since the light emission direction from the light source unit 20 is perpendicular to the second surface Bb of the object B, the optical axis of the lens array 33 is also inclined relative to the light emission direction of the light source unit 20. The calculation unit 44 is the same as the above-mentioned embodiment, and obtains information related to the distribution of the relative thickness of the object B in the width direction D2 based on the image data obtained by the image sensor 32.

[0065] Furthermore, in the present modification, the damage detection unit 45 detects damage generated on the front surface of the object B based on the image data obtained by the image sensor 32 . Fig.23 is an example of image data obtained by the image sensor 32. The image data includes an image of damage E generated on the front side of the object B. The damage E generated on the front side of the object B is detected by tilting the optical axis of the lens array 33 relative to the normal of the surface of the object B opposite to the light detection unit 30, and the scattered light is detected, so that it appears more clearly in the image data. Therefore, according to this modification, the damage existing on the front side of the object B can be detected while measuring the relative thickness distribution. The thickness distribution measuring device 1C can also replace the control device 40A having the damage detection unit 45, and include a control device 40 without the damage detection unit 45. That is, even if the damage E is not detected, and only for obtaining information related to the distribution of the relative thickness of the object B in the width direction D2, the optical axis of the lens array 33 can be tilted.

[0066] In this modification, one light detection unit 30 is used to obtain information related to the relative thickness distribution and to detect the damage E generated on the front surface of the object B, but separate light detection units 30 may be used for each. In this case, the optical axis of the lens array 33 of the light detection unit 30 used to obtain information related to the relative thickness distribution may be parallel to the normal line of the surface of the object B, and the optical axis of the lens array 33 of the light detection unit 30 used to detect the damage E may be inclined relative to the normal line of the surface of the object B. [Fourth Modification]

[0067] Fig.24 This is a diagram schematically showing the structure of the thickness distribution measuring device 1D of the fourth variant. The thickness distribution measuring device 1D of this variant is different from the above-mentioned embodiment in that the light detection unit 30 and the light source unit 20 are arranged opposite to each other on the same surface of the surface of the object B (the second surface Bb in the example shown), but is consistent with the above-mentioned embodiment in other points. In this case, the outgoing light Lb from the object B detected by the light detection unit 30 is the light emitted from the same surface as the surface on which the light La is incident. The outgoing light Lb includes light reflected from the opposite surface of the surface on which the light La is incident, that is, light passing through the interior of the object B. Therefore, the light intensity of the outgoing light Lb varies according to the thickness of the object B.

[0068] As in this modification, even when the light detection unit 30 and the light source unit 20 are arranged facing each other on the same surface of the surface of the object B, information on the distribution of the relative thickness of the object B in the width direction D2 can be obtained based on the image data obtained by the image sensor 32. In this modification, as in the third modification, the optical axis of the lens array 33 can be tilted relative to the normal line of the surface of the object B facing the light detection unit 30. [Fifth Modification]

[0069] Fig.25 It is a diagram schematically showing the structure of a thickness distribution measurement device 1E according to a fifth modification. Fig.26 1 is a perspective view showing a part of the structure of the thickness distribution measuring device 1E. The thickness distribution measuring device 1E of this modified example is provided with a thickness measuring unit 50 in addition to the structure of the thickness distribution measuring device 1A of the above-mentioned embodiment. The thickness measuring unit 50 locally measures the absolute thickness of the object B. The thickness measuring unit 50 measures the absolute thickness of the object B using, for example, a spectral interference method. Specifically, the thickness measuring unit 50 has a measuring unit 56 and a control unit 57. The measuring unit 56 is arranged opposite to the first surface Ba, the second surface Bb or both of the object B.

[0070] Fig. 27: This is a diagram showing the specific structure of the thickness measuring unit 50. The thickness measuring unit 50 includes a light irradiation unit 51, a light detection unit 52, and a calculation unit 53. The light irradiation unit 51 irradiates light to the first surface Ba or the second surface Bb of the object B. The light irradiation unit 51 is composed of a light source 511, a light guide member 512, and a light emitting unit 513. The light source 511 generates incoherent light L1. The wavelength band of the light L1 may also be a visible wavelength range. In this case, as the light source 511, a lamp-based light source or a white LED that emits white light may be used. The wavelength band of the light L1 may also be a band spanning from the visible wavelength range to the near-infrared wavelength range. The wavelength band of the light L1 may have a substantially flat (wide) spectrum in the infrared wavelength range. In particular, when the wavelength band of the light L1 includes the near-infrared wavelength range, even if the object B has a color, the light L1 can be transmitted, thereby reducing the influence of the color of the object B on the measurement result. In this case, various light emitting elements such as ASE (Amplified Spontaneous Emission), LED, SLD (Super Luminescent Diode) can be used as the light source 511. A white light source and optical components such as an optical film can also be combined with each other.

[0071] One end of the light guide member 512 is optically coupled to the light source 511, and guides the light L1 emitted from the light source 511. As the light guide member 512, for example, a light guide or an optical fiber is preferably used. The light emitting portion 513 is optically coupled to the other end of the light guide member 512, and irradiates the light L1 guided by the light guide member 512 to the object B. The light emitting portion 513 is housed in the measurement unit 56, and is arranged at a position opposite to the first surface Ba or the second surface Bb of the object B.

[0072] The light detection unit 52 detects the intensity (spectrum) of each wavelength of the outgoing light L2 from the object B. The light detection unit 52 is composed of a light incident unit 521, a light guide member 522, and a spectroscopic detection unit 523. The outgoing light L2 from the object B is incident on the light incident unit 521. The light incident unit 521 is housed in the measurement unit 56, and is arranged to face the same surface as the surface of the object B that the light exit unit 513 faces. Alternatively, the light incident unit 521 may be arranged to face the opposite surface of the surface of the object B that the light exit unit 513 faces. The optical axis of the light exit unit 513 and the optical axis of the light incident unit 521 may be parallel to each other, or may intersect with each other in the object B. Alternatively, the optical axis of the light exit unit 513 and the optical axis of the light incident unit 521 may be consistent with each other. One end of the light-guiding member 522 is optically coupled to the light incident portion 521, and guides the outgoing light L2 incident to the light incident portion 521. As the light-guiding member 522, for example, a light guide or an optical fiber is used. The spectroscopic detection unit 523 is optically coupled to the other end of the light-guiding member 522, and splits the outgoing light L2 guided by the light-guiding member 522 according to the wavelength, and detects the intensity of the light of each wavelength after the splitting. The spectroscopic detection unit 523 is preferably constructed by, for example, a combination of a spectroscopic optical element and an imaging element. The spectroscopic detection unit 523 outputs the detected light intensity as an electrical signal. The spectroscopic optical element is, for example, a prism or a grating element. The imaging element is, for example, a linear sensor, an area image sensor, a photomultiplier tube, or a photodiode.

[0073] The calculation unit 53 obtains the absolute thickness of the object B based on the detection result of the light detection unit 52. That is, the calculation unit 53 compares the reflectivity of each wavelength obtained based on the detection result of the light detection unit 52, that is, the measured spectral reflectivity, and the theoretical reflectivity of each wavelength, that is, the theoretical spectral reflectivity, and fits them to each other, thereby obtaining the absolute thickness of the object B. Data related to the absolute thickness of the object B obtained in this way is provided to the calculation unit 44. The light source 511, the spectral detection unit 523, and the calculation unit 53 are included in the control unit 57.

[0074] Here, the thickness measurement method using the thickness measurement unit 50 will be described in detail. Fig.28 This is a diagram for explaining the principle of thickness measurement, schematically showing a cross section of an object B. Now, when incoherent light L1 is incident on the object B, the reflected light from the first surface Ba of the object B and the reflected light from the second surface Bb of the object B interfere with each other. When the first surface Ba is the light incident surface, the optical path length of the reflected light from the second surface Bb is longer than the optical path length of the reflected light from the first surface Ba by the amount of the optical path in the object B. Therefore, a phase difference corresponding to the thickness of the object B is generated between these reflected lights.

[0075] Fig.29 Parts (a), (b), and (c) are graphs showing the relationship between the intensity of reflected light after interference and the wavelength. Fig.29 Part (a) shows a situation where the thickness of the object B is thinner than that of parts (b) and (c). Fig.29 Part (c) of FIG. 1 shows that the thickness of object B is thicker than that of parts (a) and (b). Fig.29 As shown in FIG. 1 , the spectrum of the reflected light after interference (reflection spectrum) fluctuates due to the interference. The interval between the waves, that is, the period, becomes smaller as the thickness of the object B becomes thicker.

[0076] The absolute thickness of the object B can be obtained by using the relationship between the reflection spectrum and the thickness of the object B as described above. As specific methods, there are fast Fourier transform method and curve fitting method. Fast Fourier transform method is a method for performing fast Fourier transform on the reflection spectrum and obtaining the film thickness from its peak frequency. Curve fitting method is a method for fitting the spectral reflectance obtained from the measured reflection spectrum, that is, the measured spectral reflectance, with the theoretical spectral reflectance calculated from the theoretical formula, and obtaining the film thickness from the suitable theoretical spectral reflectance. According to the curve fitting method, even if the thickness of the object B is less than 1μm, it can be measured with high precision.

[0077] As described above, the information related to the relative thickness distribution of the object B calculated by the calculation unit 44 is affected by the temporal variation of the light intensity of the light La irradiated to the object B. The calculation unit 44 of this modification corrects the measured value of the relative thickness distribution based on the absolute thickness measured by the thickness measuring unit 50. Specifically, at the point where the absolute thickness is measured by the thickness measuring unit 50, the magnitude of the parameters of the formula (1), such as the light intensity I0, is corrected so that the relative thickness x calculated by the formula (1) is consistent with the absolute thickness.

[0078] like Fig.26 As shown by the double arrow F, the measurement unit 56 can move along the width direction D2 of the object B while irradiating the light L1 and detecting the emitted light L2. Fig.30 FIG. 5 is a top view showing the measurement line Q1 of the thickness measuring unit 50 in this case. The object B is transported at a constant speed along the transport direction D1. Therefore, when the measuring unit 56 reciprocates at a constant speed along the width direction D2, as shown in FIG. Fig.30 As shown, the trajectory of the measurement points of the thickness measuring unit 50 forms a sawtooth measurement line Q1. And, the absolute thickness of the object B is measured only in the measurement line Q1. On the other hand, the position of the measurement point for measuring the relative thickness of the object B based on the detection result in a certain pixel 322 of the image sensor 32 does not change in the width direction D2. Therefore, the trajectory of the measurement point for measuring the relative thickness through a certain pixel 322 forms a measurement line Q2 extending along the conveying direction D1. The calculation unit 44 can correct the relative thickness measurement value obtained from the detection result in the one pixel 322 at the point S where the measurement line Q1 intersects the measurement line Q2.

[0079] Fig.31 Part (a) of FIG. 4 is a graph showing an example of the measurement result of the thickness x when the calculation unit 44 does not correct the measured value of the relative thickness. Fig.31 Part (b) of FIG. 4 is a graph showing an example of the measurement result of the thickness x when the calculation unit 44 corrects the measured value of the relative thickness. Fig.31 In parts (a) and (b) of FIG. 1 , the vertical axis represents the relative thickness of the object B in the measurement line Q2, and the horizontal axis represents the position of the object B in the conveying direction D1. Fig.31 As shown in part (a) of FIG. 1 , when the operation unit 44 does not correct the measured value of the relative thickness, the measured value of the relative thickness gradually increases or decreases according to the time-dependent change in the characteristics of the light source unit 20 due to the temporal change in the light intensity of the light La. Fig.31 As shown in part (b) of FIG. 1 , when the operation unit 44 corrects the measured value of the relative thickness, the parameter for calculating the measured value of the relative thickness is corrected at point S. Therefore, the increase or decrease of the measured value of the relative thickness can be suppressed regardless of the temporal variation of the light intensity of the light La.

[0080] The thickness distribution measuring device and thickness distribution measuring method disclosed in the present invention are not limited to the above-mentioned embodiments, and various other variations can be made. For example, the above-mentioned first to fifth variations can be combined with each other according to the necessary purpose and effect. The above-mentioned embodiments have illustrated the case where each of the multiple lenses 331 is a cylindrical lens, but each of the multiple lenses 331 can also be a lens of other shapes, such as a convex lens.

[0081] The principles of the present invention are illustrated and described in appropriate embodiments, but those skilled in the art will recognize that the present invention may be changed in configuration and detail without departing from such principles. The present invention is not limited to the prescribed structure disclosed in this embodiment. Therefore, all amendments and changes from the scope of the patent application and its spirit are claimed.

Explanation of symbols

[0082] 1A, 1B, 1C, 1D, 1E: thickness distribution measuring device, 10... conveying unit, 11... roller pair, 11a, 11b... roller, 20, 21... light source unit, 30, 30A, 30B... light detection unit, 31... housing, 32... image sensor, 33... lens array (lens unit), 34... circuit board, 34a... mounting surface, 35... optical filter unit, 36... optical filter group, 37 to 39... optical filter, 40, 40A... control device, 41... conveying control unit, 42... light source control unit, 43... Detection control unit, 44... operation unit, 45... damage detection unit, 50... thickness measurement unit, 51... light irradiation unit, 52... light detection unit, 53... operation unit, 54... input device, 55... monitor, 56... measurement unit, 57... control unit, 60... readout circuit, 61... holding circuit, 62, 63... switch, 64... photodiode, 65, 66... ​​MOS transistor, 67... source follower amplifier, 68... capacitor, 69... charge amplifier, 70... sensor control unit, 81... video line, 101... measurement unit, 311…top plate, 312…bottom plate, 313, 314…side plates, 315…slit, 318, 319…holding member, 321…pixel unit, 322…pixel, 331…lens, 332…light incident end face, 333…light emitting end face, 401…processor, 402…ROM, 403…RAM, 404…auxiliary storage device, 511…light source, 512…light guide member, 513…light emitting unit, 521…light incident unit, 522…light guide member, 523…spectroscopic detection unit, 671… MOS transistor, 672…action control switch, 673…current source, 674…connection node, 691…amplifier, 692…capacitor section, 693…reset switch, 694, 695…capacitor element, 696…switch, B…object, Ba…first surface, Bb…second surface, D1…conveying direction, D2…width direction, D3…direction, E…damage, F…double arrow, G1 to G3…curves, L1, La, Lc…light, L2, Lb…outgoing light, Q1, Q2…measurement line, R1…area, S…point

Claims

1. A thickness distribution measuring device, comprising: a conveying section that conveys an object having a first surface and a second surface opposite to the first surface in a conveying direction along the first surface and the second surface; a light source unit disposed at a position facing the second surface of the object and irradiating light to a region of the object being conveyed extending in a width direction intersecting the conveying direction; a light detection unit disposed at a position facing the first surface of the object and detecting outgoing light transmitted through the object irradiated with the light; and a calculation unit for obtaining information related to a distribution of a relative thickness of the region of the object in the width direction based on a detection result of the light detection unit, The light detection unit comprises: An image sensor having a pixel portion including at least a plurality of pixels arranged in the conveying direction, and detecting the intensity of the emitted light at each pixel and outputting image data; and The lens unit includes a plurality of lenses having the same magnification and arranged along the width direction, and focuses the emitted light and forms an image on the pixel unit of the image sensor.

2. The thickness distribution measuring device according to claim 1, in, The optical axis of the lens portion is along a normal line of the first surface.

3. The thickness distribution measuring device according to claim 1, in, The optical axis of the lens portion is inclined with respect to a normal line of the first surface.

4. The thickness distribution measuring device according to claim 3, in, The inclination angle of the optical axis of the lens portion with respect to the normal line is greater than or equal to 5° and less than or equal to 80°.

5. The thickness distribution measuring device according to any one of claims 1 to 4, in, The image sensor is configured to be capable of switching a gain value for amplifying signals output from the plurality of pixels.

6. The thickness distribution measuring device according to claim 5, further comprising: another light source unit is disposed at a position facing the first surface and irradiates light to the region of the object being conveyed or another region extending in the width direction. The light detection unit detects the outgoing light reflected from the object irradiated with the light by the other light source unit; The gain value of the image sensor when the light is irradiated from the other light source section is different from the gain value of the image sensor when the light is irradiated from the light source section.

7. The thickness distribution measuring device according to any one of claims 1 to 6, further comprising: a thickness measuring unit for locally measuring the absolute thickness of the object, The calculation unit corrects the measured value of the relative thickness based on the absolute thickness measured by the thickness measurement unit.

8. The thickness distribution measuring device according to any one of claims 1 to 7, in, The image sensor is a line scan sensor.

9. The thickness distribution measuring device according to any one of claims 1 to 8, in, The light detection unit further comprises: a first optical filter disposed on a portion of the plurality of pixels of the image sensor and having a transmission wavelength band centered on a first wavelength; and The second optical filter is provided on at least another part of the plurality of pixels of the image sensor and has a transmission wavelength band centered around a second wavelength different from the first wavelength.

10. A thickness distribution measurement method comprising the following steps: causing an object having a first surface and a second surface opposite to the first surface to start being conveyed in a conveying direction along the first surface and the second surface; starting to irradiate light onto a region of the object being conveyed extending in a width direction intersecting the conveying direction; Starting to detect the outgoing light that has passed through the object irradiated with the light; and Based on the detection result in the detecting step, information related to the distribution of the relative thickness of the region of the object in the width direction is obtained, In the detection step, use: An image sensor having a pixel portion including at least a plurality of pixels arranged in the width direction, and detecting the intensity of the emitted light at each pixel and outputting image data; and The lens unit includes a plurality of lenses having the same magnification and arranged along the width direction, and focuses the emitted light and forms an image on the pixel unit of the image sensor.

11. The thickness distribution measuring method according to claim 10, in, The optical axis of the lens portion is along a normal line of the first surface.

12. The thickness distribution measuring method according to claim 10, in, The optical axis of the lens portion is inclined with respect to a normal line of the first surface.

13. The thickness distribution measuring method according to claim 12, in, The inclination angle of the optical axis of the lens portion with respect to the normal line is greater than or equal to 5° and less than or equal to 80°.

14. The thickness distribution measurement method according to any one of claims 10 to 13, in, The image sensor is configured to be capable of switching a gain value for amplifying signals output from the plurality of pixels.

15. The thickness distribution measurement method according to any one of claims 10 to 14, further comprising the following steps: locally measuring the absolute thickness of the object; In the step of obtaining the information, the measured value of the relative thickness is corrected based on the absolute thickness measured in the step of measuring.

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