Thickness distribution measuring device and thickness distribution measuring method

Abstract

A thickness-distribution measurement device 1A comprises: a light source unit 20; a light detection unit 30; and a control device 40. The light source unit 20 irradiates, with light La, a region which extends in a width direction D2 in an object B that is being conveyed. The light detection unit 30 detects emission light Lb which has passed through the object B. The control device 40 calculates information about a relative thickness distribution in the width direction D2 of the object B, on the basis of detection results from the light detection unit 30. The light detection unit 30 includes an image sensor and a lens array. The image sensor has a plurality of pixels which are arranged in the width direction D2, and detects the intensity of the emission light Lb for each pixel. The lens array has a plurality of lenses the magnification of which is equal to 1, and which are arranged in the width direction D2. The lens array condenses the emission light Lb to form an image in the image sensor.

Description

[Technical Field]

[0001] This disclosure relates to a thickness distribution measuring device and a thickness distribution measuring method. [Background technology]

[0002] Patent Document 1 discloses a film thickness measuring device. The film thickness measuring device is a device for measuring the film thickness of an object to be measured. The object to be measured comprises a substrate having a front surface and a back surface, a first film formed on the front surface, and a second film formed on the back surface. The film thickness measuring device comprises a light irradiation unit, a light detection unit, and a film thickness calculation unit. The light irradiation unit irradiates light onto the front surface of the object to be measured. The light detection unit detects the intensity of reflected light at each wavelength on the front surface of the object to be measured. The film thickness calculation unit determines the film thickness of the first film by comparing the reflectance at each wavelength obtained based on the detection results from the light detection unit with the theoretical reflectance at each wavelength. The theoretical reflectance at each wavelength takes into account the reflectance and transmittance on the front surface, as well as the reflectance on the back surface.

[0003] Patent documents 2 and 3 disclose sensor units for image reading devices. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2015-141176 [Patent Document 2] Japanese Patent Publication No. 2020-170973 [Patent Document 3] Japanese Patent Publication No. 2017-046241 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] There is a need to confirm the relative thickness distribution in the width direction of a plate-like or film-like object of a certain width while the object is being transported in a direction intersecting the width direction. For example, when manufacturing a polymer film, it is desirable to inspect and confirm that the thickness of the film is uniform after the polymer film material has been stretched in the longitudinal and transverse directions to form a film.

[0006] Conventionally, the spectral interferometry method has been used to measure the thickness of an object. In spectral interferometry, light is shone onto the object, and the intensity of the interference light between the reflected light from the light-irradiated surface of the object and the reflected light from the opposite surface is measured. The thickness of the object can be determined based on the change in interference light intensity with wavelength. However, this method measures the thickness of the object locally. Therefore, if it is necessary to check the thickness distribution of an object while it is being transported, it is necessary to arrange multiple measurement units, each having an irradiation unit that shines light on the object and a measurement unit that measures the interference light, side by side. In that case, the wider the object, the more measurement units are needed, making the configuration more complex.

[0007] The purpose of this disclosure is to provide a thickness distribution measuring device and a thickness distribution measuring method that can confirm the relative thickness distribution of an object being transported with a simple configuration while the object is being transported. [Means for solving the problem]

[0008] [1] A thickness distribution measuring device according to one embodiment of the present disclosure comprises a transport unit, a light source unit, a photodetector unit, and a calculation unit. The transport unit transports an object having a first surface and a second surface facing the opposite direction from the first surface in a transport direction along the first and second surfaces. The light source unit is positioned opposite the second surface of the object and irradiates light onto a region of the object being transported that extends in a width direction intersecting the transport direction. The photodetector unit is positioned opposite the first surface of the object and detects the emitted light that has passed through the irradiated object. The calculation unit obtains information regarding the distribution of the relative thickness of the region of the object in the width direction based on the detection result in the photodetector unit. The photodetector unit comprises an image sensor and a lens unit. The image sensor has a pixel unit including at least a plurality of pixels arranged in the width direction and detects the intensity of emitted light for each pixel to output image data. The lens unit has a plurality of lenses having equal magnification and arranged along the width direction and focuses and images the emitted light onto the pixel unit of the image sensor.

[0009] [2] A thickness distribution measurement method according to one embodiment of the present disclosure includes the steps of: starting to transport an object having a first surface and a second surface facing the opposite direction to the first surface in a transport direction along the first surface and the second surface; starting to irradiate a region of the object being transported that extends in a width direction intersecting the transport direction with light; starting to detect the emitted light that has passed through the irradiated object; and obtaining information regarding the distribution of the relative thickness of the region of the object in the width direction based on the detection result in the detection step. The detection step uses an image sensor having a pixel section including at least a plurality of pixels arranged in the width direction, which detects the intensity of emitted light for each pixel and outputs image data; and a lens section having a plurality of lenses having equal magnification and arranged along the width direction, which focuses and images the emitted light onto the pixel section of the image sensor.

[0010] When the light transmittance of an object is uniform, the amount of light absorbed inside the object depends on its thickness. Therefore, by irradiating a region extending in the width direction of the object with light and detecting the light intensity of the light emitted from that region, the relative thickness distribution of the object in the width direction can be measured. According to the above thickness distribution measuring device and thickness distribution measuring method, the light intensity of the emitted light is detected using an image sensor having multiple pixels arranged in the width direction, thus simplifying the configuration compared to a spectral interference method in which multiple measurement units are arranged in the width direction of the object. In addition, by using a lens section having multiple lenses with equal magnification arranged in the width direction to focus and image the emitted light onto the image sensor, the lens section can be placed close to the object to improve the collection efficiency of the emitted light and increase the detection sensitivity. Therefore, even with a simple configuration, the relative thickness distribution can be measured with practical accuracy.

[0011] In the thickness distribution measuring device described above, the light source is positioned facing the second surface, and the light detection unit is positioned facing the first surface. The light emitted from the object is light that has passed through the object. By positioning the light source and the light detection unit so that the object is sandwiched between them, and detecting the light that has passed through the object as the light emitted from the object, the light intensity of the emitted light becomes highly dependent 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 described in [1] and the thickness distribution measuring method described in [2], the optical axis of the lens may be aligned with the normal to the first surface. In this case, since light emitted perpendicularly from the surface of the object is detected, the influence of the polarization state on the light intensity of the emitted light can be avoided, and the accuracy of measuring the relative thickness distribution can be further improved.

[0013] [4] In the thickness distribution measuring device described in [1] and the thickness distribution measuring method described in [2], the optical axis of the lens portion may be inclined with respect to the normal of the first surface. In this case, it is possible to easily detect scratches present on the surface of the object at the same time as measuring the relative thickness distribution. The inclination angle of the optical axis of the lens portion with respect to the normal may be 5° or more and 80° or less.

[0014] [5] In the thickness distribution measuring device described in [1], [3], or [4] above, and in any of the thickness distribution measuring methods described in [2] to [4] above, the image sensor may be configured to allow switching of the gain value for amplifying the signals output from multiple pixels. In this case, even if 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 described in [5] above may further include another light source. The other light source is positioned opposite the first surface and irradiates light onto the above region or another region extending in the width direction of the object being transported. The light detection unit may then detect the emitted light from the object irradiated by the other light source. The gain value of the image sensor when light is irradiated from the other light source may differ from the gain value of the image sensor when light is irradiated from the light source. In this case, using a single device, it is possible to detect the emitted light from the surface irradiated with light and the emitted light from the surface opposite to the surface irradiated with light. Therefore, information regarding the relative thickness distribution can be obtained based on the detection results of these emitted lights, thereby further improving the measurement accuracy of the relative thickness distribution.

[0016] [7] Any of the thickness distribution measuring devices described in [1], [3] to [6] above may further include a thickness measuring unit that locally measures the absolute thickness of an object. The calculation unit may then correct the relative thickness measurement value based on the absolute thickness measured by the thickness measuring unit. Similarly, any of the thickness distribution measuring methods described in [2] to [5], [7] above may further include a step of locally measuring the absolute thickness of an object, and in the step of obtaining information, the relative thickness measurement value may be corrected based on the absolute thickness measured in the measurement step. In the above thickness distribution measuring device, if the intensity of the light output from the light source unit fluctuates over time, the intensity of the emitted light being measured also fluctuates over time. Similarly, in the above thickness distribution measuring method, if the intensity of the light irradiated in the step of starting irradiation fluctuates over time, the intensity of the emitted light being measured also fluctuates over time. The accuracy of the measurement of the relative thickness distribution can be further improved by correction based on the absolute thickness measured by the thickness measuring unit (measurement step). The thickness measuring unit may have a spectral interference method. In the measurement step, a spectral interferometry method may be used.

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

[0018] [9] In any of the thickness distribution measuring devices described in [1], [3] to [8] above, the light detection unit may further include a first optical filter and a second optical filter. The first optical filter is provided on some of the pixels of the image sensor and has a transmission wavelength band centered on a first wavelength. The second optical filter is provided on at least some of the other pixels of the image sensor and has a transmission wavelength band centered on a second wavelength different from the first wavelength. As described above, if the intensity of the light output from the light source unit fluctuates over time, the intensity of the emitted light measured also fluctuates over time. Therefore, the measurement results of the relative thickness distribution will differ for each wavelength. This makes it possible to know that the intensity of the light output from the light source unit has fluctuated over 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 capable of confirming the thickness distribution of an object to be conveyed with a simple configuration.

Brief Description of the Drawings

[0020] [Figure 1] FIG. 1 is a diagram schematically showing the configuration of a thickness distribution measuring device according to an embodiment. [Figure 2] FIG. 2 is a perspective view showing a light source unit and a light detection unit. [Figure 3] FIG. 3 is a cutaway perspective view showing the internal structure of the light detection unit. [Figure 4] FIG. 4 is a plan view of an image sensor. [Figure 5] FIG. 5 is an example of image data obtained by the image sensor. [Figure 6] FIG. 6 is a diagram showing the configuration of the internal circuit of the image sensor. [Figure 7] FIG. 7 is a diagram showing a configuration example of each pixel. [Figure 8] FIG. 8 is a perspective view schematically showing a lens array. [Figure 9] FIG. 9 is a perspective view schematically showing a lens array. [Figure 10] FIG. 10 is a diagram schematically showing the configuration of a control device. [Figure 11] FIG. 11 is a diagram schematically showing a configuration example of the hardware of the control device. [Figure 12] FIG. 12 is a diagram schematically showing how light is attenuated when passing through an object. [Figure 13] FIG. 13 is a graph representing the relationship shown in Equation (1). [Figure 14] FIG. 14 is a flowchart showing a thickness distribution measuring method according to an embodiment. [Figure 15] FIG. 15 is a perspective view showing, as a comparative example, a form in which a plurality of measurement units of a reduction optical type are arranged side by side in the width direction of an object. [Figure 16] Part (a) of Figure 16 shows an example of an image acquired through a high-magnification lens. Part (b) of Figure 16 shows an example of an image acquired through a 1x lens. [Figure 17] Figure 17 is a cutaway perspective view showing the internal structure of the light detection unit as a first modified example. [Figure 18] Figure 18 schematically shows how light emitted from an object passes through a group of optical filters. [Figure 19] Parts (a) and (b) of Figure 19 are graphs that show the relationship shown in equation (1) for each wavelength. [Figure 20] Figure 20 is a schematic diagram showing the configuration of a thickness distribution measuring device according to the second modified example. [Figure 21] Figure 21 shows an example of the configuration of each pixel in an image sensor in a second modified example. [Figure 22] Figure 22 is a schematic diagram showing the configuration of a thickness distribution measuring device according to the third modified example. [Figure 23] Figure 23 shows an example of image data obtained by an image sensor. [Figure 24] Figure 24 is a schematic diagram showing the configuration of the thickness distribution measuring device according to the fourth modified example. [Figure 25] Figure 25 is a schematic diagram showing the configuration of the thickness distribution measuring device according to the fifth modified example. [Figure 26] Figure 26 is a perspective view showing part of the configuration of a thickness distribution measuring device. [Figure 27] Figure 27 shows the specific configuration of the thickness measurement unit. [Figure 28] Figure 28 is a diagram illustrating the principle of thickness measurement, and schematically shows a cross-section of the object. [Figure 29] Sections (a), (b), and (c) of Figure 29 are graphs showing the relationship between the intensity and wavelength of the reflected light after interference. [Figure 30] Figure 30 is a plan view showing the measurement line by the thickness measurement unit. [Figure 31]Part (a) of Figure 31 is a graph showing an example of the thickness measurement result when the calculation unit does not correct the relative thickness measurement value. Part (b) of Figure 31 is a graph showing an example of the thickness measurement result when the calculation unit corrects the relative thickness measurement value. [Modes for carrying out the invention]

[0021] Hereinafter, embodiments of the thickness distribution measuring device and thickness distribution measuring method according to this disclosure will be described in detail with reference to the attached drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant explanations are omitted.

[0022] Figure 1 is a schematic diagram showing the configuration of a thickness distribution measuring device 1A according to one embodiment of the present disclosure. The thickness distribution measuring device 1A is a device that obtains information regarding the relative thickness distribution of an object B. The relative thickness distribution referred to here is 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 facing opposite to the first surface Ba. In one example, the object B is a polymer film, fabric or nonwoven fabric, paper, or substrate being transported. In this embodiment, the object B consists of a single layer (single material) and does not have a structure in which multiple layers are laminated. The width direction of the object B means the direction that intersects both the transport direction D1 and the thickness direction D3. In one example, the width direction of the object B is perpendicular to both the transport direction D1 and the thickness direction D3. During transport, the thickness direction D3 is, for example, along the vertical direction.

[0023] As shown in Figure 1, the thickness distribution measuring device 1A of this embodiment comprises a transport 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 transport unit 10 transports the object B in a transport direction D1 along the first surface Ba and the second surface Bb. The transport unit 10 is, for example, a roller conveyor and has a plurality of roller pairs 11 and a drive unit (not shown) such as a motor that rotates the plurality of roller pairs 11. Each of the plurality of roller pairs 11 includes a pair of rollers 11a, 11b having a rotation axis that extends in the width direction of the object B. The object B is transported by being sandwiched between rollers 11a and 11b, with rollers 11a and 11b rotating in opposite directions to each other.

[0024] Figure 2 is a perspective view showing the light source unit 20 and the light detection unit 30. The light source unit 20 is positioned opposite one of the first surface Ba and second surface Bb of the object B. In the illustrated example, the light source unit 20 is positioned opposite the second surface Bb. The light source unit 20 irradiates a region R1 extending in the width direction D2 of the object B during transport with light La (see Figure 1). Region R1 extends from one end edge to the other edge in the width direction D2 of the object B. The light source unit 20 has a configuration in which, for example, a plurality of light-emitting elements are arranged along the width direction D2. Light-emitting diodes (LEDs) are exemplified as light-emitting elements, but are not limited to them. 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 continuous light in time. The wavelength of light La may be in the visible range or in the near-infrared range.

[0025] The light detection unit 30 is positioned opposite the other of the first surface Ba and second surface Bb of the object B. In the illustrated example, the light detection unit 30 is positioned opposite the first surface Ba. The light detection unit 30 faces the light source unit 20 with the object B in between. The light detection unit 30 detects the emitted light Lb from the object B that has been irradiated with light La. In this embodiment, the emitted light Lb from the object B is the light La that has passed through the object B.

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

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

[0028] Figure 6 shows the internal circuit configuration of the image sensor 32. As mentioned above, the image sensor 32 has a pixel section 321 in which a plurality of pixels 322 are arranged along the width direction D2. The plurality of pixels 322 have a common configuration with respect to each other. The image sensor 32 further includes a readout circuit 60 and a sensor control unit 70. The readout circuit 60 and the pixel section 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 voltage values ​​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 hold circuits 61, a plurality of switches 62, and a plurality of switches 63, each corresponding one-to-one with each pixel 322. Each hold circuit 61 is connected to the output terminal of the pixel 322 via its corresponding switch 62. Each hold circuit 61 holds the voltage value that was output from the pixel 322 immediately before its corresponding switch 62 switched from the ON state to the OFF state. Each hold circuit 61 is connected to the video line 81 via its corresponding switch 63. When its corresponding switch 63 is ON, each hold circuit 61 outputs the held voltage value to the video line 81.

[0030] Multiple switches 62 are controlled by a control signal provided by the sensor control unit 70, and are switched on / off at the same time to each other. Multiple switches 63 are controlled by another control signal provided by the sensor control unit 70, and are sequentially turned on for a certain period of time. The sensor control unit 70 controls the on / off state of each of the multiple switches 62 and multiple switches 63 of the readout circuit 60, as well as the operation of each of the multiple pixels 322.

[0031] Figure 7 shows an example configuration of each pixel 322. Each pixel 322 comprises a photodiode 64, a MOS 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 an electric charge 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., ground potential) is input. The gate of the MOS transistor 671 is connected to the cathode of the photodiode 64 via MOS transistor 65, and is also connected to a first reference potential input terminal 91 to which a first reference potential (e.g., power supply potential) is input via MOS transistor 66. The drain of the MOS transistor 671 is connected to the first reference potential input terminal 91.

[0033] An operation control switch 672 is provided between the source of the MOS transistor 671 and the connection node 674. The operation control switch 672 may be composed of a MOS transistor. A current source 673 is provided between the connection node 674 and the second reference potential input terminal 92. The current source 673 may include a MOS transistor. The current source 673 may be composed of a resistor.

[0034] The on / off states of MOS transistors 65 and 66 are controlled by control signals provided by the sensor control unit 70. When MOS transistor 66 is ON, the gate potential of MOS transistor 671 is initialized. When MOS transistors 65 and 66 are ON, the charge accumulation at the junction capacitance of photodiode 64 is initialized. When MOS transistor 65 is ON and MOS transistor 66 is OFF, the gate potential of MOS transistor 671 corresponds to the amount of light incident on photodiode 64.

[0035] The on / off state of the operation control switch 672 is also controlled by a control signal provided by the sensor control unit 70. While the operation control switch 672 is in the ON state, current flows from the first reference potential input terminal 91 through the MOS transistor 671, the operation control switch 672, and the current source 673 to the second reference potential input terminal 92. 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, while the operation control switch 672 is in the OFF state, no current flows to the source follower amplifier 67, and the source follower amplifier 67 enters a power-down state.

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

[0037] 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 amplifier 691. The inverting input terminal of amplifier 691 is connected to the connection node 674 of source follower amplifier 67 via a capacitive element 68.

[0038] The capacitance section 692 is located between the inverting input terminal and the output terminal of the amplifier 691. The capacitance section 692 stores an amount of charge corresponding to the voltage value output from the source follower amplifier 67. The capacitance section 692 is composed of a capacitance element 694.

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

[0040] Refer to Figure 3 again. The holding members 318 and 319 are fixed to the housing 31 inside the housing 31. The holding members 318 and 319 are positioned on both sides of the lens array 33 in the transport direction D1, and hold the lens array 33 by sandwiching it. The lens array 33 is an example of the lens section in this embodiment.

[0041] Figure 8 is a schematic perspective view 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, in one example it is 1x. When the magnification of each of the plurality of lenses 331 is equal, it does not have to be exactly 1x; for example, a magnification of 0.9x or more and 1.1x or less is acceptable as equal magnification. Each of the plurality of lenses 331 is, for example, a glass rod lens. The light incident end face 332 of each lens 331 faces the first surface Ba of the object B (see Figure 2) through a slit 315 in the bottom plate 312 (see Figure 3). The distance between the light incident end face 332 and the first surface Ba is, for example, 5 mm or more and 20 mm or less, in one example it is 12 mm. The light output end face 333 of each lens 331 faces the pixel portion 321 of the image sensor 32 (see Figure 4). Each lens 331 does not necessarily have to correspond one-to-one with each pixel 322 of the pixel section 321. The lens array 33 focuses and images the emitted light Lb onto the pixel section 321 of the image sensor 32. The magnification of the image captured by the image sensor 32 is the same as or less than the magnification of the object B, which is the subject. Therefore, the light collection efficiency can be increased compared to a high-magnification lens. In particular, a multi-row lens array 33 (for example, two or three rows) as shown in Figure 9 can achieve a higher light collection efficiency compared to a high-magnification lens than a single-row lens array 33 as shown in Figure 8. The optical axis of the lens array 33 is along the normal to the surface of the first surface Ba and second surface Bb of the object B that faces the light detection unit 30. In the illustrated example, the optical axis of the lens array 33 is along the normal to the first surface Ba. In other words, the optical axis of the lens array 33 is perpendicular to the surface of the first surface Ba and second surface Bb of the object B that faces the light detection unit 30.

[0042] The control device 40 is electrically connected to the transport unit 10, the light source unit 20, and the photodetection unit 30. Figure 10 is a schematic diagram showing the configuration of the control device 40. The control device 40 includes a transport control unit 41 that controls the operation of the transport unit 10, such as the transport speed, a light source control unit 42 that controls the operation of the light source unit 20, a detection control unit 43 that controls the operation of the photodetection unit 30, and a calculation unit 44. The calculation unit 44 receives image data from the photodetection unit 30 as a result of detecting the emitted light Lb. Based on the image data, the calculation unit 44 obtains information regarding the distribution of the relative thickness of region R1 of the object B in the width direction D2. The control device 40 may be, for example, a personal computer; a smart device such as a smartphone or tablet terminal; or a computer with 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 may be configured by a computer separate from the calculation unit 44.

[0043] Figure 11 is a schematic diagram showing an example of the hardware configuration of the control device 40. As shown in Figure 11, the control device 40 can be physically configured as a normal computer, including a processor (CPU) 401, main memory such as ROM 402 and RAM 403, and auxiliary storage 404 such as a hard disk. The computer's processor 401 can realize each of the above functions of the control device 40 by reading programs stored in the ROM 402 or auxiliary storage 404. Therefore, the program causes the computer's processor 401 to operate as the transport control unit 41, light source control unit 42, detection control unit 43, and arithmetic unit 44 of the control device 40. The storage device that stores the program may be a non-temporary recording medium. Examples of recording media include flexible disks, CDs or DVDs, ROMs, semiconductor memory, or cloud servers.

[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, light source control unit 42, detection control unit 43, and calculation unit 44 through the input device 54. The input device 54 can be, for example, a keyboard, mouse, or touch panel. The monitor 55 is electrically connected to the control device 40. The monitor 55 displays information regarding the relative thickness distribution determined by the calculation unit 44. The monitor 55 may be a touchscreen that includes the input device 54, which is a touch panel.

[0045] The calculation unit 44 shown in Figure 10 obtains information regarding the distribution of the relative thickness of region R1 of object B in the width direction D2 based on the image data. The information regarding the relative thickness distribution may be the relative thickness distribution itself, or it may be some set of numerical values ​​related to the relative thickness distribution. For example, the information regarding the relative thickness distribution may be the image data itself, because the light intensity of the emitted light Lb appearing in the image data is correlated with the thickness of object B. Relative thickness refers to the relative value of other positions in the width direction D2 with respect to the value at a certain position. Therefore, the calculation unit 44 does not necessarily have to accurately determine the absolute thickness at each position in the width direction D2.

[0046] Figure 12 schematically shows how light La is attenuated when it passes through object B. The thickness of the arrows in the figure represents the light intensity. As described above, light La emitted from the light source 20 passes through object B and becomes emitted light Lb. Emitted light Lb is detected by the image sensor 32. Here, if the light intensity of light La is I0, the light intensity of emitted light Lb is I, the absorption coefficient of object B is α, and the thickness of object B is x, then the following equation (1) holds.

number

[0047] Figure 14 is a flowchart illustrating the thickness distribution measurement method according to this embodiment. This thickness distribution measurement method can be performed using the thickness distribution measurement device 1A described above. In this thickness distribution measurement method, in step ST1, the transport of an object B having a first surface Ba and a second surface Bb facing the opposite direction to the first surface Ba is started in the transport direction D1 along the first surface Ba and the second surface Bb. In step ST2, the irradiation of light La onto a region R1 of the transported object B that extends in the width direction D2 intersecting the transport direction D1 is started. In step ST3, the detection of emitted light Lb from the object B irradiated with 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 section 321 including at least a plurality of pixels 322 arranged in the width direction D2, and detects the intensity of emitted light Lb for 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 and images the emitted light Lb onto the pixel portion 321 of the image sensor 32. In step ST4, based on the detection results in step ST3, information is obtained regarding the distribution of the relative thickness of region R1 of object B in the width direction D2.

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

[0049] Here, Figure 15 is a perspective view showing a configuration in which multiple reduction-optical type measurement units 101 are arranged in the width direction D2 of the object B, as a comparative example. The reduction-optical type measurement unit 101 has a high-magnification lens (i.e., a magnification greater than 1x). In this case, the measurement unit 101 is placed at a large distance from the object B, so the collection efficiency of the emitted light Lb is kept low. Part (a) of Figure 16 shows an example of an image acquired through a high-magnification lens with low collection efficiency of emitted light Lb. In addition, with a high-magnification lens, the distortion between the center and the periphery is large, so the variation in the collection efficiency of emitted light Lb within each measurement unit 101 becomes large. In contrast, in this embodiment, the emitted light Lb is focused and imaged onto the image sensor 32 using a lens array 33 having multiple 1x lenses 331 arranged in the width direction D2. This makes it possible to place the lens array 33 close to the object B to increase the collection efficiency of emitted light Lb and improve the detection sensitivity. Part (b) of Figure 16 shows an example of an image with high collection efficiency of emitted light Lb, acquired through a 1:1 lens. This image is significantly clearer than the image shown in Part (a) of Figure 16. In addition, since the distortion between the center and periphery of each lens 331 is small, the variation in the collection efficiency of emitted light Lb can be kept to a minimum. From the above, according to this embodiment, even with a simple configuration, the relative thickness distribution can be measured with practical accuracy.

[0050] As in this embodiment, the light source unit 20 may be positioned facing one of the first surface Ba and the second surface Bb, and the light detection unit 30 may be positioned facing the other of the first surface Ba and the second surface Bb. The light Lb emitted from the object B may be light that has passed through the object B. By positioning the light source unit 20 and the light detection unit 30 so that the object B is sandwiched between them, and detecting the light that has passed through the object B as the light Lb emitted from the object B, the light intensity I of the emitted light Lb becomes highly dependent on the thickness of the object B. Therefore, the measurement accuracy of the relative thickness distribution can be further improved.

[0051] As in this embodiment, the optical axis of the lens array 33 may be aligned with the normal to the surface of the first surface Ba and the second surface Bb that faces the light detection unit 30. In this case, the emitted light Lb that is emitted perpendicularly from the surface of the object B is detected. Therefore, the influence of the polarization state on the light intensity I of the emitted light Lb can be avoided, and the measurement accuracy of the relative thickness distribution can be further improved. In this case, the multiple light-emitting elements of the light source unit 20 should preferably be highly directional so that the light La is incident perpendicularly to the surface of the object B as much as possible. [First variation]

[0052] Figure 17 is a cutaway perspective view showing the internal structure of the light detection unit 30A as a first modified example. In this modified example, the light detection unit 30A further includes an optical filter unit 35 in addition to the configuration of the light detection unit 30 of the above embodiment. The optical filter unit 35 is provided on the pixel unit 321 of the image sensor 32. Light Lb emitted from the object B passes through the optical filter unit 35 before entering the pixel unit 321 of the image sensor 32.

[0053] Figure 18 schematically shows how the light Lb emitted from object B passes through the optical filter section 35. As schematically shown in this figure, the optical filter section 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 modified example, and the other of the optical filters 37 to 39 is an example of the second optical filter in this modified example. Optical filter 37 is provided on some of the pixels 322 of the plurality of pixels 322 of the image sensor 32. Optical filter 38 is provided on some of the other pixels 322 of the plurality of pixels 322 of the image sensor 32. Optical filter 39 is provided on the remaining pixels 322 of the plurality of pixels 322 of the image sensor 32. Optical filter 37 has a transmission wavelength band centered on wavelength λ1. Optical filter 38 has a transmission wavelength band centered on wavelength λ2, which is greater than wavelength λ1. Optical filter 39 has a transmission wavelength band centered on wavelength λ3, which is greater than wavelengths λ1 and λ2. Wavelength λ1 is not included in the transmission wavelength band of optical filters 38 and 39. Wavelength λ2 is not included in the transmission wavelength band of optical filters 37 and 39. Wavelength λ3 is not included in the transmission wavelength band of optical filters 37 and 38.

[0054] Of the light Lb emitted from object B, the wavelength component centered on wavelength λ1 passes through optical filter 37 and is incident on pixel 322. The wavelength component centered on wavelength λ2 passes through optical filter 38 and is incident on another pixel 322. The wavelength component centered on wavelength λ3 passes through optical filter 39 and is incident on yet another pixel 322. In this way, the light intensity I of the emitted light Lb is detected for each wavelength.

[0055] The (a) part and (b) part of FIG. 19 are graphs representing the relationship shown in Equation (1) for each wavelength. In the figure, curve G1 corresponds to wavelength λ1, curve G2 corresponds to wavelength λ2, and curve G3 corresponds to wavelength λ3. The curves G1 to G3 in the (b) part of FIG. 19 are the same as the curves G1 to G3 in the (a) part of FIG. 19. Since the absorption coefficient α depends on the wavelength, the curves are different for each wavelength in this way. In this example, it is assumed that the larger the wavelength, the smaller the absorption coefficient α, that is, the larger the light transmittance. Now, assume that the light intensity of light La is a predetermined magnitude I0 and is known. At this time, as shown in the (a) part of FIG. 19, for a certain thickness x1 of the object B, the value of the ratio (I / I0) is P 11 at wavelength λ1 and P 12 at wavelength λ2 and P 13 at wavelength λ3. And the calculation unit 44 calculates the thickness of the object B as x1 regardless of which wavelength's ratio (I / I0) value is used. Then, assume that the light intensity of light La has changed from the predetermined magnitude I0. At this time, since the light intensity I of the emitted light Lb changes, as shown in the (b) part of FIG. 19, the value of the ratio (I / I0) changes from P 11 to P 21 at wavelength λ1, from P 12 to P 22 at wavelength λ2, and from P 13 to P 23 at wavelength λ3. Then, the calculation result of the thickness of the object B by the calculation unit is x 11 at wavelength λ1, x 12 at wavelength λ2, x 13 at wavelength λ3, and the results are different for each wavelength. From this, the operator can know that the light intensity of the light La output from the light source unit 20 has changed over time, and can know the timing to adjust the light intensity of the light La or the parameters of the formula.

[0056] In the above explanation, an example was given where each optical filter group 36 contains three optical filters 37 to 39, but the number of optical filters in each optical filter group 36 may be two or four or more. If each optical filter group 36 contains only two optical filters 37 and 38, optical filter 37 is provided on some of the pixels 322 of the image sensor 32, and optical filter 38 is provided on the remaining pixels 322 of the image sensor 32. [Second variation]

[0057] Figure 20 is a schematic diagram showing the configuration of the thickness distribution measuring device 1B according to the second modified example. The thickness distribution measuring device 1B of this modified example further includes a light source unit 21 separate from the light source unit 20, in addition to the configuration of the thickness distribution measuring device 1A of the above embodiment. The light source unit 21 is positioned opposite the surface (first surface Ba in the illustrated example) of the object B, which is opposite to the surface facing the light source unit 20, among the first surface Ba and second surface Bb. The light source unit 21 irradiates light Lc onto the object B being transported, either region R1 or another region extending in the width direction D2 (see Figure 2). This other region, like region R1, extends from one end edge to the other edge in the width direction D2 of the object B. The light source unit 21 has a configuration in which, for example, a plurality of light-emitting elements are arranged along the width direction D2. Light-emitting diodes (LEDs) are exemplified as light-emitting elements, but are not limited to them. The emission wavelength and emission intensity of the plurality of light-emitting elements are aligned among the plurality of light-emitting elements. The light source unit 21 outputs continuous light, which is light Lc. The wavelength of light Lc may be in the visible region or in the near-infrared region. The light intensity of light Lc may be equal to or different from the light intensity of light La. The wavelength of light Lc may be equal to or different from the wavelength of 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 embodiment. The light detection unit 30B differs from the light detection unit 30 of the above embodiment in that the image sensor 32 is configured to allow switching of the gain value for amplifying the signals output from multiple pixels, and is otherwise identical to the light detection unit 30 of the above embodiment. The light detection unit 30B detects the emitted light Lb from the object B irradiated with light La by the light source unit 20, and in addition, detects the emitted light Lb from the object B irradiated with light Lc by the light source unit 21. The irradiation timing of light La and the irradiation timing of light Lc are controlled by the light source control unit 42 of the control device 40 (see Figure 10) and are different from each other.

[0059] The gain value of the image sensor 32 is controlled to be different when light La is irradiated from the light source unit 20 and when light Lc is irradiated from the light source unit 21. That is, if the light intensity I of the emitted light Lb when light La is irradiated is greater than the light intensity I of the emitted light Lb when light Lc is irradiated, the gain value of the image sensor 32 when 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 light Lc is irradiated. If the light intensity I of the emitted light Lb when light La is irradiated is less than the light intensity I of the emitted light Lb when light Lc is irradiated, the gain value of the image sensor 32 when 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 light Lc is irradiated. This makes it possible to reduce the range of fluctuation in the magnitude of the signal output from the image sensor 32.

[0060] Figure 21 shows an example of the configuration of each pixel 322A of the image sensor 32 in this modified example. Pixel 322A has the same configuration and function as pixel 322 in the above embodiment, except for the following points. That is, pixel 322A in this modified example has a capacitor 692A instead of the capacitor 692 (see Figure 7) in the above embodiment. Capacitor 692A is provided between the inverting input terminal and the output terminal of amplifier 691. Capacitor 692A stores an amount of charge corresponding to the voltage value output from source follower amplifier 67. The capacitance value of capacitor 692A is variable. Capacitor 692A can have a variable capacitance value by including a capacitor element 694, a capacitor element 695, and a switch 696. Capacitor element 695 and switch 696 are connected in series with each other. The series circuit consisting of capacitor element 695 and switch 696 and capacitor element 694 are provided in parallel with each other. The capacitance value of the capacitive section 692A and the gain (gain value) of the charge amplifier 69 differ depending on whether the switch 696 is in the on or off state. The on / off state of the switch 696 is controlled by a control signal provided by the sensor control unit 70.

[0061] As shown in this modified example, the image sensor 32 may be configured to allow switching of the gain value for amplifying the signals output from multiple 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 signal-to-noise ratio (S / N) is improved, and the measurement accuracy of the relative thickness distribution is improved.

[0062] As shown in this modified example, a separate light source unit 21 is provided in addition to the light source unit 20. The light source unit 21 is positioned opposite the surface of the object B opposite to the surface facing the light source unit 20, and may irradiate a region of the object B extending along the width direction D2 during transport with light Lc. The light detection unit 30B may further detect not only the light Lb emitted from the object B irradiated with light La by the light source unit 20, but also the light Lb emitted from the object B irradiated with light Lc by the light source unit 21. In this case, a single thickness distribution measuring device 1B can be used to detect the light Lb emitted from the surface that was irradiated with light and the light Lb emitted from the surface opposite to the surface that was irradiated with light. Therefore, information regarding the relative thickness distribution can be obtained based on the detection results of these emitted light Lb, thereby further improving the measurement accuracy of the relative thickness distribution. [Third variation]

[0063] Figure 22 is a schematic diagram showing the configuration of the thickness distribution measuring device 1C according to the third modified example. The thickness distribution measuring device 1C of this modified example differs from the thickness distribution measuring device 1A of the above embodiment in that the optical axis of the lens array 33 of the light detection unit 30 is inclined. Furthermore, the thickness distribution measuring device 1C of this modified example is equipped with a control device 40A instead of the control device 40 of the above embodiment. In addition to the transport control unit 41, light source control unit 42, detection control unit 43, and calculation unit 44 of the control device 40 of the above embodiment, the control device 40A further includes a scratch detection unit 45 for detecting scratches occurring on the surface of the object B.

[0064] Specifically, in this modified example, the optical axis of the lens array 33 is inclined with respect to the normal of the surface of the object B facing the light detection unit 30 (the first surface Ba in the illustrated example), among the first surface Ba and second surface Bb of the object B. The inclination angle of the optical axis of the lens array 33 with respect to that normal is, for example, 5° or more, and may be 45° or more. The inclination angle may be 80° or less. The larger the inclination angle of the optical axis of the lens array 33 with respect to that normal, the easier it is to detect scratches, as described later. Similar to the above embodiment, the light detection unit 30 detects the emitted light Lb from the object B irradiated with light La. Since the direction of light emission 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 with respect to the direction of light emission from the light source unit 20. Similar to the above embodiment, the calculation unit 44 obtains information regarding 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] In addition, in this modified example, the scratch detection unit 45 detects scratches on the surface of object B based on image data obtained by the image sensor 32. Figure 23 is an example of image data obtained by the image sensor 32. This image data includes an image of a scratch E on the surface of object B. The scratch E on the surface of object B appears more clearly in the image data by tilting the optical axis of the lens array 33 with respect to the normal to the surface of object B facing the light detection unit 30 and detecting scattered light. Therefore, according to this modified example, scratches present on the surface of object B can be detected simultaneously with the measurement of the relative thickness distribution. The thickness distribution measuring device 1C may be equipped with a control device 40 without a scratch detection unit 45 instead of the control device 40A having a scratch detection unit 45. That is, even if the purpose is not to detect scratches E and is only to obtain information on the distribution of the relative thickness of object B in the width direction D2, the optical axis of the lens array 33 may be tilted.

[0066] In this modified example, information regarding the relative thickness distribution and the detection of scratches E on the surface of object B are performed using a single optical detection unit 30, but separate optical detection units 30 may be used for each. In that case, the optical axis of the lens array 33 of the optical detection unit 30 for acquiring information regarding the relative thickness distribution may be set parallel to the normal to the surface of object B, and the optical axis of the lens array 33 of the optical detection unit 30 for detecting scratches E may be tilted with respect to the normal to the surface of object B. [Fourth variation]

[0067] Figure 24 is a schematic diagram showing the configuration of the thickness distribution measuring device 1D according to the fourth modified example. The thickness distribution measuring device 1D of this modified example differs from the above embodiment in that the light detection unit 30 is positioned opposite the same surface (second surface Bb in the illustrated example) of the object B that is opposite the light source unit 20, but is otherwise consistent with the above embodiment. In this case, the light Lb emitted from the object B detected by the light detection unit 30 is light emitted from the same surface on which the light La was incident. This emitted light Lb includes light reflected from the surface opposite to the surface on which the light La was incident, that is, light that has passed through the interior of the object B. Therefore, the light intensity of the emitted light Lb changes according to the thickness of the object B.

[0068] As in this modified example, even when the light detection unit 30 is positioned facing the same surface as the surface of the object B facing the light source unit 20, information regarding 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 modified example as well, the optical axis of the lens array 33 may be inclined with respect to the normal of the surface of the object B facing the light detection unit 30, similar to the third modified example. [Fifth variation]

[0069] Figure 25 is a schematic diagram showing the configuration of the thickness distribution measuring device 1E according to the fifth modified example. Figure 26 is a perspective view showing a part of the configuration of the thickness distribution measuring device 1E. The thickness distribution measuring device 1E of this modified example further includes a thickness measuring unit 50 in addition to the configuration of the thickness distribution measuring device 1A of the above 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 positioned facing the first surface Ba, the second surface Bb, or both of them of the object B.

[0070] Figure 27 shows the specific configuration of the thickness measuring unit 50. The thickness measuring unit 50 comprises a light irradiation unit 51, a light detection unit 52, and a calculation unit 53. The light irradiation unit 51 irradiates light onto 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 emission unit 513. The light source 511 generates non-coherent (incoherent) light L1. The wavelength band of light L1 may be in the visible wavelength range, in which case a lamp-type light source emitting white light or a white LED may be used as the light source 511. The wavelength band of light L1 may also be in the wavelength range from the visible wavelength range to the near-infrared wavelength range. The wavelength band of light L1 may have a substantially flat (broad) spectrum in the infrared wavelength range. In particular, if the wavelength band of light L1 includes the near-infrared wavelength range, light L1 can be transmitted even if object B has color, thus reducing the influence of the color of object B on the measurement results. In that case, various light-emitting elements such as ASE (Amplified Spontaneous Emission) light sources, LEDs, and SLDs (Super Luminescent Diodes) can be applied as the light source 511. A white light source and optical components such as optical films may also be combined with each other.

[0071] The light guide member 512 has one end optically coupled to the light source 511 and guides the light L1 emitted from the light source 511. Suitable examples of the light guide member 512 include a light guide and an optical fiber. The light emitter 513 is optically coupled to the other end of the light guide member 512 and irradiates the object B with the light L1 guided by the light guide member 512. The light emitter 513 is housed in the measurement unit 56 and positioned opposite 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 light L2 emitted from the object B. The light detection unit 52 is composed of a light incident unit 521, a light guide member 522, and a spectral detection unit 523. Light L2 emitted 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 positioned facing the same surface of the object B that is facing the light emission unit 513. Alternatively, the light incident unit 521 may be positioned facing the opposite surface of the object B that is facing the light emission unit 513. The optical axis of the light emission unit 513 and the optical axis of the light incident unit 521 may be parallel to each other, or they may intersect each other at the object B. Alternatively, the optical axis of the light emission unit 513 and the optical axis of the light incident unit 521 may coincide with each other. The light guide member 522 is optically coupled to the light incident section 521 at one end and guides the emitted light L2 incident on the light incident section 521. For example, a light guide or an optical fiber can be used as the light guide member 522. The spectral detection unit 523 is optically coupled to the other end of the light guide member 522 and spectrally analyzes the emitted light L2 guided by the light guide member 522 for each wavelength, detecting the intensity of the light for each spectrally analyzed wavelength. The spectral detection unit 523 is preferably configured, for example, by a combination of a spectroscopic optical element and an image sensor. The spectral 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 image sensor is, for example, a line sensor, an area image sensor, a photomultiplier tube, or a photodiode.

[0073] The calculation unit 53 determines the absolute thickness of object B based on the detection results from the photodetector 52. Specifically, the calculation unit 53 compares the measured spectral reflectance, which is the reflectance for each wavelength obtained based on the detection results from the photodetector 52, with the theoretical spectral reflectance, which is the reflectance for each wavelength, and fits these together to determine the absolute thickness of object B. The data regarding the absolute thickness of object B thus obtained 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 explained in detail. Figure 28 is a diagram illustrating the principle of thickness measurement and schematically shows a cross-section of object B. When incoherent light L1 is incident on object B, the reflected light from the first surface Ba of object B and the reflected light from the second surface Bb of object B interfere with each other. If 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 within object B. Therefore, a phase difference corresponding to the thickness of object B occurs between these reflected lights.

[0075] Sections (a), (b), and (c) of Figure 29 are graphs showing the relationship between the intensity and wavelength of the reflected light after interference. Section (a) of Figure 29 shows the case where the thickness of object B is thinner than that of sections (b) and (c). Section (c) of Figure 29 shows the case where the thickness of object B is thicker than that of sections (a) and (b). As shown in Figure 29, the spectrum of the reflected light after interference (reflection spectrum) is wavy due to interference. The interval between these waves, i.e., the period, becomes smaller as the thickness of object B increases.

[0076] By utilizing the relationship between the reflection spectrum and the thickness of object B as described above, the absolute thickness of object B can be determined. Specific methods include the Fast Fourier Transform (FFT) method and the curve fitting method. The FFT method involves performing a FFT on the reflection spectrum and determining the film thickness from its peak frequency. The curve fitting method involves fitting the measured spectral reflectance (i.e., the actual spectral reflectance) obtained from the measured reflection spectrum with the theoretical spectral reflectance calculated from a theoretical formula, and determining the film thickness from the fitted theoretical spectral reflectance. The curve fitting method allows for accurate measurement even when the thickness of object B is 1 μm or less.

[0077] As described above, the information regarding the relative thickness distribution of object B calculated by the calculation unit 44 is affected by the temporal fluctuations in the light intensity La irradiated onto object B. In this modified example, the calculation unit 44 corrects the measured value of the relative thickness distribution based on the absolute thickness measured by the thickness measurement unit 50. Specifically, at the point where the absolute thickness is measured by the thickness measurement unit 50, the calculation unit 44 corrects the magnitude of the parameters in equation (1), such as light intensity I0, so that the relative thickness x obtained by equation (1) matches the absolute thickness.

[0078] As shown by the double arrow F in Figure 26, the measurement unit 56 may irradiate light L1 and detect emitted light L2 while moving along the width direction D2 of the object B. Figure 30 is a plan view showing the measurement line Q1 by the thickness measurement unit 50 in that case. The object B is transported at a constant speed along the transport direction D1. Therefore, when the measurement unit 56 moves back and forth at a constant speed along the width direction D2, as shown in Figure 30, the trajectory of the measurement points by the thickness measurement unit 50 forms a zigzag measurement line Q1. The absolute thickness of the object B is measured only at the measurement line Q1. On the other hand, the position of the measurement point where the relative thickness of the object B is measured by the detection result of a certain pixel 322 of the image sensor 32 is constant in the width direction D2. Therefore, the trajectory of the measurement point where the relative thickness is measured by a certain pixel 322 forms a measurement line Q2 extending along the transport direction D1. The calculation unit 44 can correct the relative thickness measurement value obtained from the detection result at one pixel 322 at point S where measurement line Q1 and measurement line Q2 intersect.

[0079] Part (a) of Figure 31 is a graph showing an example of the measurement result of thickness x when the calculation unit 44 does not correct the relative thickness measurement value. Part (b) of Figure 31 is a graph showing an example of the measurement result of thickness x when the calculation unit 44 corrects the relative thickness measurement value. In parts (a) and (b) of Figure 31, the vertical axis represents the relative thickness of object B at the measurement line Q2, and the horizontal axis represents the position of object B in the transport direction D1. As shown in part (a) of Figure 31, when the calculation unit 44 does not correct the relative thickness measurement value, the relative thickness measurement value gradually increases or decreases due to the temporal fluctuation of the light intensity of light La and the temporal change in the characteristics of the light source unit 20. In contrast, as shown in part (b) of Figure 31, when the calculation unit 44 corrects the relative thickness measurement value, the parameters for calculating the relative thickness measurement value are corrected at point S. Therefore, regardless of the temporal fluctuation of the light intensity of light La, the increase or decrease in the relative thickness measurement value can be suppressed.

[0080] The thickness distribution measuring device and thickness distribution measuring method according to this disclosure are not limited to the embodiments described above, and various other modifications are possible. For example, the first to fifth modifications described above may be combined with each other depending on the required purpose and effect. In the above embodiments, the case in which each of the multiple lenses 331 is a rod lens was illustrated, but each of the multiple lenses 331 may be a lens of another form, such as a convex lens.

[0081] While the principles of the present invention have been illustrated and described in preferred embodiments, it will be recognized by those skilled in the art that the present invention can be modified in arrangement and detail without departing from such principles. The present invention is not limited to the specific configurations disclosed in these embodiments. Accordingly, all modifications and changes arising from the scope of the claims and their spirit are claimed. [Explanation of Symbols]

[0082] 1A, 1B, 1C, 1D, 1E... Thickness distribution measuring device, 10... Transport unit, 11... Roller pair, 11a, 11b... Rollers, 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, 37~39... Optical filters, 40, 40A... Control device, 41... Transport control unit, 42... Light source control unit, 43... Detection control unit, 44...Calculation unit, 45...Scratch detection unit, 50...Thickness measurement unit, 51...Light irradiation unit, 52...Light detection unit, 53...Calculation unit, 54...Input device, 55...Monitor, 56...Measurement unit, 57...Control unit, 60...Readout circuit, 61...Hold circuit, 62,63...Switch, 64...Photodiode, 65,66...MOS transistor, 67...Source follower amplifier, 68...Capacitance element, 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 section, 322...Pixel, 331...Lens, 332...Light incident end face, 333...Light emission end face, 401...Processor, 402...ROM, 403...RAM, 404...Auxiliary storage device, 511...Light source, 512...Light guide member, 513...Light emission section, 521...Light incident section, 522...Light guide member, 523...Spectroscopic detection section, 671... MOS transistor, 672...operation control switch, 673...current source, 674...connection node, 691...amplifier, 692...capacitance section, 693...reset switch, 694, 695...capacitance element, 696...switch, B...object, Ba...first surface, Bb...second surface, D1...transport direction, D2...width direction, D3...direction, E...scratch, F...double arrow, G1~G3...curve, L1, La, Lc...light, L2, Lb...emitted light, Q1, Q2...measurement line, R1...area, S...point.

Claims

1. A conveying unit that conveys an object having a first surface and a second surface facing the opposite direction from the first surface in a conveying direction along the first surface and the second surface, A light source unit is positioned opposite the second surface of the object and irradiates light onto a region of the object being transported that extends in a width direction intersecting the transport direction, A light detection unit is positioned opposite the first surface of the object and detects the emitted light that has passed through the object irradiated with light, A calculation unit that obtains information regarding the distribution of the relative thickness of the region of the object in the width direction based on the detection results of the light detection unit, Equipped with, The aforementioned light detection unit is An image sensor having a pixel section including at least a plurality of pixels arranged in the transport direction, which detects the intensity of the emitted light for each pixel and outputs image data, The image sensor has a lens section that collects and forms an image of the emitted light in the pixel section, and has a plurality of lenses arranged along the width direction having a magnification of 1x, A thickness distribution measuring device having the following features.

2. The thickness distribution measuring device according to claim 1, wherein the optical axis of the lens portion is aligned with the normal to the first surface.

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

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

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

6. The system further comprises another light source unit positioned opposite the first surface, which irradiates light onto the object being transported, either in the aforementioned area or another area extending in the width direction, The light detection unit detects the emitted light reflected from the object that has been illuminated by the other light source unit, The thickness distribution measuring device according to claim 5, wherein the gain value of the image sensor when the light is irradiated from the other light source is different from the gain value of the image sensor when the light is irradiated from the light source.

7. The object further comprises a thickness measuring unit for locally measuring the absolute thickness of the object, The thickness distribution measuring device according to any one of claims 1 to 4, wherein the calculation unit corrects the measured value of the relative thickness based on the absolute thickness measured by the thickness measuring unit.

8. The thickness distribution measuring device according to any one of claims 1 to 4, wherein the image sensor is a line scan sensor.

9. The aforementioned light detection unit is A first optical filter is provided on some of the pixels of the plurality of pixels of the image sensor and has a transmission wavelength band centered on a first wavelength, A second optical filter is provided on at least some of the other pixels among the plurality of pixels of the image sensor, and has a transmission wavelength band centered on a second wavelength different from the first wavelength. A thickness distribution measuring device according to any one of claims 1 to 4, further comprising the above.

10. A step of starting the transport of an object having a first surface and a second surface facing the opposite direction from the first surface, in a transport direction along the first surface and the second surface, The steps include: starting to irradiate a region of the object being transported that extends in a width direction intersecting the transport direction with light; The steps include: starting the detection of emitted light that has passed through the object irradiated with the aforementioned light; A step of obtaining information regarding the distribution of the relative thickness of the region of the object in the width direction based on the detection result of the emitted light, Includes, In the step of initiating the detection, An image sensor having a pixel section containing at least a plurality of pixels arranged in the width direction, detecting the intensity of the emitted light for each pixel and outputting image data, The image sensor has a lens section that collects and forms an image of the emitted light in the pixel section, and has a plurality of lenses arranged along the width direction having a magnification of 1x, A method for measuring thickness distribution using [a specific method / tool].

11. The thickness distribution measurement method according to claim 10, wherein the optical axis of the lens portion is aligned with the normal to the first surface.

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

13. The thickness distribution measurement method according to claim 12, wherein the inclination angle of the optical axis of the lens portion with respect to the normal is 5° or more and 80° or less.

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

15. The method further includes the step of locally measuring the absolute thickness of the object, The thickness distribution measurement method according to any one of claims 10 to 13, wherein in the step of obtaining the aforementioned information, the measurement value of the relative thickness is corrected based on the absolute thickness measured in the measurement step.

Images