JP2024073929A - Imaging device, inspection device using said imaging device, and imaging method - Google Patents

Abstract

[Problem] To provide an imaging device capable of obtaining a tomographic image having a resolution in the depth direction of an object to be measured, an inspection device using said imaging device, and an imaging method. [Solution] The imaging device includes a light source 20 that irradiates the object to be measured W with emitted light in a wavelength range that can transmit through the object to be measured W at a constant incident angle, an imaging optical system 31 that acquires reflected light from the object to be measured W irradiated with the emitted light from the light source 20, a light receiver 32 that photoelectrically converts the reflected light acquired by the imaging optical system 31 at a plurality of pixels to continuously generate image data of the object to be measured W, a partial image generating unit 62 that extracts data of a specific pixel from the plurality of image data generated by the light receiver 32 to generate a partial image made of the data of the specific pixel, and a tomographic image generating unit 63 that synthesizes the plurality of partial images to generate a tomographic image of a depth corresponding to the specific pixel, and the object to be measured W moves relative to the light source 20, the combined optical system 31, and the light receiver 32. [Selected Figure] Figure 1

Description

The present invention relates to an imaging device, an inspection device using the imaging device, and an imaging method, and in particular to an imaging device for inspecting the sealing portion of an object to be measured for adhesion defects and foreign matter contamination, an inspection device using the imaging device, and an imaging method.

For products in which food or other contents are packed in a bag- or tube-shaped packaging material, the opening is sealed after the contents are placed in the packaging material. At that time, there may be gaps in the sealed part of the packaging material, or the contents or their debris may become trapped inside. Products with such poor sealing must be rejected as defective goods.

Therefore, there is a demand for an inspection device that can image sealing defects on products that have been sealed with this type of packaging material as the test object.

Conventionally, diffuse optical spectroscopy (DOS), diffuse optical tomography (DOT), optical coherence tomography (OCT), etc. are known as technologies for imaging information inside living organisms.

However, these techniques have the drawback that they require expensive equipment and are not suitable for imaging the inside of packaging materials made of paper, metal, plastic, or resin.

On the other hand, a technology is known that uses a relatively inexpensive projector-camera system to extract the signal amplitude of light reflected from specific three-dimensional positions on the surface and inside of an object, based on digital image signals of multiple composite images that change sequentially over time and correspond respectively to multiple spatial frequencies in a pattern image projected from a projector onto an object and multiple spatial frequencies output from an imaging device, and calculate the optical characteristics inside the object (see, for example, Patent Document 1).

In addition, in a projector-camera system that uses illumination from a laser scanning projector and photography with a rolling shutter camera, a technique is known in which a slight delay of less than 1 millisecond is intentionally inserted between the timing of illumination and photography to reduce the effect of reflected light on the subject's surface and measure the scattered light that passes through the interior of the subject (see, for example, Non-Patent Document 1).

JP 2020-85618 A

H. Kubo, S. Jayasuriya T.Iwaguchi, T. Funatomi, Y. Mukaigawa, S. Narasimhan, "Programmable Non-Epipolar Indirect Light Transport: Capture and Analysis", IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS, VOL. 27, NO. 4, APRIL 2021, Pages 2421-2436

However, the technology disclosed in Patent Document 1 does not directly capture images of the inside of an object, but estimates information about the inside of an object through information processing. As a result, the technology disclosed in Patent Document 1 has problems in that it requires a large amount of processing and cannot be applied to inspection equipment in which objects to be measured are transported one after another, and there is also a problem in that the surface reflection component and the deep scattering component cannot be sufficiently separated spatially.

In addition, as can be seen from the fact that the images acquired using the technology disclosed in Non-Patent Document 1 reflect not only the interior of the subject but also the subject's surface (surfaces of the face, arms, etc.), the technology disclosed in Non-Patent Document 1 also has the problem of being unable to sufficiently separate spatially the surface reflection component and the deep scattering component.

The present invention has been made to solve these problems in the past, and aims to provide an imaging device capable of obtaining a tomographic image with resolution in the depth direction of an object to be measured, an inspection device using the imaging device, and an imaging method.

In order to solve the above problem, the imaging device according to the present invention is an imaging device including an imaging system that moves relative to the object to be measured, and an image processing unit that generates a tomographic image of the object to be measured. The imaging system includes a light source that irradiates the object to be measured with outgoing light in a wavelength range that can transmit the object to be measured at a certain angle of incidence, an imaging optical system that acquires reflected light or transmitted light from the object to be measured irradiated with the outgoing light from the light source, and a photoreceiver that photoelectrically converts the reflected light or transmitted light acquired by the imaging optical system at multiple pixels to continuously generate image data of the object to be measured. The image processing unit includes a partial image generating unit that extracts data of a specific pixel from each of the image data generated by the photoreceiver and generates a partial image consisting of the data of the specific pixel, and a tomographic image generating unit that synthesizes the multiple partial images and generates the tomographic image at a depth corresponding to the specific pixel.

With this configuration, the imaging device according to the present invention continuously generates image data of the object to be measured by the photoreceiver while irradiating the object to be measured, which is moving relative to the imaging system, with light at a constant angle of incidence, and further generates a tomographic image by synthesizing partial images at depths corresponding to specific pixels of the photoreceiver. In other words, the imaging device according to the present invention can directly capture a tomographic image with resolution in the depth direction of the object to be measured. Furthermore, the imaging device according to the present invention can provide the user with a tomographic image that includes information such as poor adhesion of the seal of the object to be measured or the presence of foreign matter.

In addition, in the imaging device according to the present invention, the depth of field of the imaging optical system may be set to a range that includes the desired observation position of the object to be measured.

With this configuration, the imaging device of the present invention can generate a tomographic image of the desired observation position of the object to be measured by appropriately setting the depth of field of the imaging optical system to a range that includes the desired observation position of the object to be measured.

In addition, in the imaging device according to the present invention, the angle of incidence is set at an angle at which an illumination area on the surface of the object to be measured, on which the light emitted from the light source is irradiated, is separated from an exit position on at least a portion of the surface of the object to be measured from which the light emitted from the light source that entered the interior of the object to be measured exits, in a plan view, and the partial image may be an image of the reflected light or the transmitted light from the exit position of the object to be measured.

With this configuration, the imaging device of the present invention can spatially separate the surface reflection components and deep scattering components of the object to be measured by appropriately setting the angle of incidence of the light emitted from the light source on the surface of the object to be measured, so that it is possible to generate a tomographic image by eliminating or spatially separating the light reflected from the surface of the object to be measured.

The imaging device according to the present invention may further include a scatterer between the light source and the object to be measured on the optical path of the light emitted from the light source.

With this configuration, the imaging device of the present invention can effectively irradiate the light emitted from the light source into the inside of the object to be measured by spreading the light emitted from the light source onto a spherical surface using a scatterer and making the light incident on the object to be measured.

The imaging device according to the present invention may further include a convex lens between the light source and the object to be measured on the optical path of the light emitted from the light source.

With this configuration, the imaging device of the present invention can use the convex lens to adjust the spread and incident angle of the wavefront of the light emitted from the light source, allowing the light emitted from the light source to be effectively irradiated into the inside of the object to be measured.

The imaging device according to the present invention may further include a polarizer between the light source and the imaging optical system on the optical path of the light emitted from the light source.

With this configuration, the imaging device according to the present invention can use the polarizer to adjust the polarization state of the light emitted from the light source to either linear polarization, elliptical polarization, or circular polarization, and can effectively irradiate the light emitted from the light source into the inside of the object to be measured. In particular, for objects to be measured that are highly scattering, it is effective to use circular polarization or random polarization as the polarization state of the light emitted from the light source.

The imaging device according to the present invention may further include an optical slit between the light receiver and the object to be measured on the optical path of the light emitted from the light source, which selects the reflected light from a specific depth position of the object to be measured, or the transmitted light that is not reflected at a specific depth position of the object to be measured and is transmitted therethrough, and causes it to enter the light receiver.

With this configuration, the imaging device according to the present invention can generate a tomographic image with improved depth resolution by determining the depth of the slice to be imaged in advance using an optical slit.

The imaging device according to the present invention may further include a drive mechanism for periodically translating the optical slit.

With this configuration, the imaging device of the present invention can generate a tomographic image with no blind spots in the depth direction while improving the depth resolution by periodically translating the optical slit using a drive mechanism to continuously change the depth of the slice to be imaged.

The inspection device according to the present invention is configured to include any of the imaging devices described above and an inspection unit that inspects the object to be measured based on the tomographic image generated by the imaging device.

With this configuration, the inspection device according to the present invention can provide the user with inspection results for defects such as poor adhesion or foreign matter contamination in the object being measured, enabling highly sensitive inspection of defects.

The imaging method according to the present invention is an imaging method using an imaging device including an imaging system that moves relative to the object to be measured, the imaging system including a light source that irradiates the object to be measured with outgoing light in a wavelength range that can be transmitted through the object to be measured at a constant angle of incidence, an imaging optical system that acquires reflected light or transmitted light from the object to be measured irradiated with the outgoing light from the light source, and a photoreceiver that photoelectrically converts the reflected light or transmitted light acquired by the imaging optical system at multiple pixels to continuously generate image data of the object to be measured, and includes a partial image generation step of extracting data of a specific pixel from each of the image data generated by the photoreceiver to generate a partial image consisting of the data of the specific pixel, and a tomographic image generation step of synthesizing the multiple partial images to generate the tomographic image at a depth corresponding to the specific pixel.

The present invention provides an imaging device capable of obtaining a tomographic image with resolution in the depth direction of an object to be measured, an inspection device using the imaging device, and an imaging method.

1 is a configuration diagram of an imaging device and an inspection device according to a first embodiment of the present invention. 2 is a diagram showing a configuration example in which a scatterer is disposed between a light source and an object to be measured of the imaging device shown in FIG. 1 ; 2 is a diagram showing the depth of field of the imaging optical system of the image pickup apparatus shown in FIG. 1 . 1A shows a cross-sectional view of a model of an object to be measured taken along a plane parallel to the conveying direction, and FIG. 1B shows a plan view of the model of an object to be measured. 11A to 11C are diagrams showing how the positions of the irradiation area and the imaging line shift relative to the object to be measured as the object to be measured is transported. 2 is a diagram showing a configuration example in which an optical slit is disposed between a light receiver and a measured object of the imaging device shown in FIG. 1 . FIG. 1 is a diagram showing the incident angle of light emitted from a light source to an object to be measured, the irradiation area on the surface of the object to be measured onto which the light emitted from the light source is irradiated, and the exit position on the upper surface of the object to be measured from which the light emitted from the light source that entered the inside of the object to be measured exits. FIG. 4 is a diagram showing an example of a tomographic image generated by an image processing unit. 4A to 4C are diagrams illustrating the direction of light emitted from a measurement object when the incident angle of light emitted from a light source to the measurement object is set to various values. FIG. 11 is a configuration diagram of an imaging device and an inspection device according to a second embodiment of the present invention. FIG. 1 is a diagram showing the angle of incidence of light emitted from a light source to an object to be measured, the irradiation area on the surface of the object to be measured onto which the light emitted from the light source is irradiated, and the exit position on the lower surface of the object to be measured from which the light emitted from the light source that entered inside the object to be measured exits. FIG. 1A is a diagram showing an example of a tomographic image generated by the image processing unit based on reflected light from the object to be measured, and FIG. 1B to FIG. 1D are diagrams showing examples of tomographic images generated by the image processing unit based on transmitted light from the object to be measured. 4 is a flowchart showing the process of an imaging method using the imaging device according to the embodiment of the present invention.

The following describes an embodiment of an imaging device, an inspection device using the imaging device, and an imaging method according to the present invention, with reference to the drawings.

First Embodiment
As shown in FIG. 1, the imaging device 1 according to the first embodiment of the present invention includes a conveying unit 10, a light source 20, an imaging unit 30, an operation unit 40, a display unit 50, and an image processing unit 61. Here, the light source 20 and the imaging unit 30 constitute an imaging system that moves relative to the object (article) W. The imaging device 1 irradiates the object W with light from the light source 20 in a wavelength range that appropriately transmits the object W, and generates a tomographic image of the object W based on the light transmitted or reflected by the object W at that time. Here, the object W is, for example, a packaging material or a container that contains a resin material and has a sealing portion. In addition, it is desirable that the transmittance of the object W to the light irradiated from the light source 20 is 10% or more.

The inspection device 100 according to the first embodiment of the present invention includes an imaging device 1 and an inspection unit 64. The inspection device 100 performs various inspections of the object W to be measured, such as checking for the presence of foreign matter and for defective seals, based on the tomographic images generated by the imaging device 1.

The transport unit 10 is composed of, for example, a belt conveyor arranged horizontally relative to the main body of the imaging device 1, and includes a transport belt 11 made of a material that easily transmits light emitted from the light source 20. The transport unit 10 transports multiple objects W to be measured sequentially along a predetermined transport direction (direction indicated by arrow X) to the inspection area R within a transport path formed by the transport belt 11. The transport belt 11 has a transport surface 11a on which the objects W to be measured are placed and transported in the transport direction. When inspecting the objects W to be measured, the transport unit 10 drives the transport belt 11 at a transport speed that is set in advance by the rotation of a drive motor based on the control of a transport control unit (not shown).

The light source 20 is composed of a laser or an LED (Light Emitting Diode), and is configured to irradiate the object W being measured transported by the transport unit 10 with emitted light having a wavelength range of 380 nm to 2500 nm that can be transmitted through the object W. For example, the light source 20 may be configured as a line light source perpendicular to the transport direction of the object W being measured by the transport unit 10.

The imaging device 1 of this embodiment may include a convex lens 21 between the light source 20 and the object to be measured W on the optical path of the light emitted from the light source 20. By providing the convex lens 21 in this manner, the spread of the wavefront of the light emitted from the light source 20 and the incident angle θ can be adjusted, and the light emitted from the light source 20 can be effectively irradiated inside the object to be measured W. Note that a further convex lens may be disposed between the object to be measured W and the imaging unit 30 on the optical path of the light emitted from the light source 20.

The imaging device 1 of this embodiment may also include a polarizer between the light source 20 and the imaging optical system 31 described later on the optical path of the light emitted from the light source 20. For example, by providing a polarizer 22 between the light source 20 and the object to be measured W, the polarization state of the light emitted from the light source 20 can be adjusted to be linearly polarized, elliptically polarized, or circularly polarized, so that the light emitted from the light source 20 can be effectively irradiated inside the object to be measured W. Furthermore, by providing a polarizer 23 between the object to be measured W and the imaging unit 30, the combination of the polarizer 22 and the polarizer 23 can be configured to select only a specific polarized component of the emitted light and prevent reflected light from the surface of the object to be measured W from entering the imaging unit 30.

As shown in FIG. 2, the imaging device 1 of this embodiment may also include a scatterer 24, such as frosted glass or a resin plate, between the light source 20 and the object to be measured W on the optical path of the light emitted from the light source 20. By providing the scatterer 24 in this manner, the light emitted from the light source 20 spreads spherically and enters the object to be measured W, so that the light emitted from the light source 20 can be effectively irradiated into the inside of the object to be measured W.

As shown in FIG. 1, the imaging unit 30 has an imaging optical system 31 that acquires reflected light from the object to be measured W irradiated with light emitted from the light source 20, and a light receiver 32 that receives the reflected light acquired by the imaging optical system 31 and continuously generates image data of the object to be measured W being transported by the transport unit 10.

The imaging optical system 31 is composed of at least one imaging lens 33, and is arranged between the object to be measured W and the light receiver 32 on the optical path of the light emitted from the light source 20, so that the light reflected from the object to be measured W is imaged on the light receiver 32. In addition, it is preferable that the imaging optical system 31 has an aperture 34 between the light receiver 32 and the imaging lens 33 to block light reflected on the surface of the object to be measured W and scattered components whose optical path has been significantly shifted.

The depth of field D of the imaging optical system 31 is set to a range that includes the desired observation position of the object to be measured W. For example, as shown in FIG. 3, the depth of field D of the imaging optical system 31 is set to cover the entire thickness of the object to be measured W. Alternatively, the depth of field D of the imaging optical system 31 may be set to be narrower than the thickness of the object to be measured W so as to include only the desired depth position of the object to be measured W.

When the convex lens 21 is placed between the object to be measured W and the imaging unit 30 on the optical path of the light emitted from the light source 20, the position of the imaging optical system 31 is adjusted appropriately so that the depth of field can be set to the desired area of the object to be measured W, including this convex lens 21.

As shown in FIG. 1, the light receiver 32 includes an image sensor 32a, such as an area sensor or line sensor, in which a plurality of photoelectric conversion elements are arranged in an array to photoelectrically convert the reflected light from the object W to be measured via the imaging optical system 31, and an image data output unit 32b that converts the photoelectrically converted electrical signal output from the image sensor 32a into image data in a predetermined output format and outputs it. Here, each photoelectric conversion element possessed by the light receiver 32 constitutes one pixel. The image data output from the image data output unit 32b is a one-dimensional image when the image sensor 32a is a line sensor, and is a two-dimensional image when the image sensor 32a is an area sensor.

In this embodiment, the light source 20 and the imaging unit 30 that constitute the imaging system are installed at fixed positions, and the measured object W is transported by the transport unit 10, but the present invention is not limited to this, and the imaging device 1 may be configured so long as the measured object W and the imaging system move relative to each other. For example, the imaging device 1 may be configured so that the imaging system moves to one-dimensionally or two-dimensionally scan multiple measured objects W that are arranged one-dimensionally or two-dimensionally. Alternatively, the imaging device 1 may be configured so that the multiple measured objects W and the imaging system move together.

The operation unit 40 is for accepting operation input by the user, and is composed of, for example, a touch panel equipped with a touch sensor for detecting the contact position by a touch operation on an input surface corresponding to the display screen of the display unit 50. When the user touches the position of a specific item displayed on the display screen with a finger, a stylus, or the like, the operation unit 40 recognizes that the position detected by the touch sensor on the display screen matches the position of the item, and outputs a signal for executing a function assigned to each item to the image processing unit 61 or the inspection unit 64. Alternatively, the operation unit 40 may be composed of an input device such as a keyboard or a mouse.

The display unit 50 is composed of display devices such as an LCD display or a CRT, and displays various display contents such as the tomographic image of the object W to be measured generated by the tomographic image generating unit 63 based on display control by the image processing unit 61 and the inspection unit 64. Furthermore, the display unit 50 displays operation objects such as buttons, soft keys, pull-down menus, and text boxes for setting various conditions.

The image processing unit 61 and the inspection unit 64 are configured by a control device including, for example, a CPU, a GPU, an FPGA, a ROM, a RAM, a HDD, and the like. For example, the image processing unit 61 and the inspection unit 64 can be configured in software by the execution of a predetermined program by the CPU or the GPU. The above program is stored in the ROM or the HDD in advance. Alternatively, the above program may be provided or distributed in an installable or executable format recorded on a computer-readable recording medium such as a compact disc or a DVD. Alternatively, the above program may be stored in a computer connected to a network such as the Internet, and provided or distributed by downloading via the network.

The image processing unit 61 is configured to generate a tomographic image of the object W to be measured based on multiple image data output from the image data output unit 32b, and includes a partial image generating unit 62 and a tomographic image generating unit 63.

The partial image generating unit 62 extracts data of specific pixels from each image data generated at different times by the photoreceiver 32, and generates a partial image consisting of the data of the specific pixels. For example, a specific pixel refers to a pixel row corresponding to a desired imaging line for the measured object W. Here, in a configuration in which the light source 20 and the imaging unit 30 constituting the imaging system are installed at fixed positions, the position of the imaging line is determined in the inspection region R.

The tomographic image generating unit 63 arranges and synthesizes multiple partial images generated at different times in chronological order to generate a tomographic image at a depth corresponding to a specific pixel of the image sensor 32a of the light receiver 32. In other words, the tomographic image generating unit 63 outputs information equivalent to tomographic imaging of a deep part of the object W to be measured by stitching together multiple partial images in which different parts are captured at a specific depth position of the object W to be measured.

Figures 4(a) and (b) show a model of the object W to be measured to explain the operation of the image processing unit 61. Figure 4(a) shows a cross-sectional view parallel to the transport direction of the object W to be measured. Figure 4(b) shows a plan view of the object W to be measured. This object W to be measured is composed of five layers, from the first layer to the fifth layer, from the top, and internal structure patterns P1 and P2 simulating foreign objects are formed on the second and fourth layers. In Figures 4(a) and (b), the irradiation area of the object W to be measured of the light emitted from the light source 20 at a certain point in time is indicated by the symbol Rw.

For example, as shown in Figs. 4(a) and (b), the partial image generating unit 62 generates three one-dimensional images as partial images based on the reflected light emitted from the positions of the imaging lines A, B, and C on the measured object W and received by three pixel rows of the image sensor 32a of the receiver 32. Here, the position of each imaging line in the inspection region R and the correspondence between each imaging line and the pixel rows of the receiver 32 can be set in advance according to the type of measured object W. Figs. 5(a) to (c) show how the positions of the irradiation region Rw and the imaging lines A, B, and C shift relative to the measured object W as the measured object W is transported. That is, the partial image generating unit 62 sequentially generates three one-dimensional images as partial images based on the reflected light emitted from the positions of the imaging lines A, B, and C that move relative to the measured object W.

As shown in FIG. 6, the imaging device 1 of this embodiment may have an optical slit 25 between the light receiver 32 and the object to be measured W on the optical path of the light emitted from the light source 20, which selects reflected light from a specific depth position of the object to be measured W and allows it to enter the image sensor 32a of the light receiver 32.

Figure 6 shows an example in which, of the reflected light from the first layer at depth d1, the second layer at depth d2, and the third layer at depth d3 of the object W, the reflected light from the first and second layers and other scattered light are blocked by the optical slit 25, and only the reflected light from the third layer is selected by the optical slit 25 and enters the light receiver 32. By providing the imaging device 1 with such an optical slit 25, it is possible to determine in advance the depth of the tomography in the object W to be imaged by the image processing unit 61, and to generate a tomography image of the object W with increased depth resolution. Note that the descriptions of the first layer at depth d1, the second layer at depth d2, and the third layer at depth d3 are for convenience, and the object W does not necessarily have a layered structure.

Furthermore, the imaging device 1 of this embodiment may include a drive mechanism 26 that periodically translates the optical slit 25 in a plane parallel to the transport surface 11a. For example, the drive mechanism 26 translates the opening of the optical slit 25 once to scan the reflected light from the object W while the object W is transported a predetermined distance. This causes the depth of the slice imaged by the image processing unit 61 to change continuously. Thereafter, the drive mechanism 26 repeats the translation of the optical slit 25, allowing the image processing unit 61 to generate a slice image without blind spots in the depth direction while increasing the depth resolution.

The angle of incidence θ of the light emitted from the light source 20 on the object to be measured W is set to a constant value. As shown in FIG. 7, it is desirable that the angle of incidence θ is set so that the irradiation area Rw on the surface of the object to be measured W, on which the light emitted from the light source 20 is irradiated, is separated from the exit position x (for example, the positions of the arbitrarily set imaging lines A, B, and C in FIG. 7) of at least a portion of the upper surface of the object to be measured W from which the light emitted from the light source 20 that has entered the inside of the object to be measured W is emitted, in a plan view.

That is, if the width of the irradiation region Rw along the transport direction of the object W is 2r, and the emission positions x of the reflected light from the first layer, the second layer, and the third layer from the outermost surface of the object W on the light source 20 side when the center of the irradiation region Rw is used as a reference are expressed as _x1 , _x2 , and _x3 , respectively, it is desirable that r< _xn is satisfied. Here, the maximum value of n is 3, but the maximum value of n can take any positive integer value depending on the desired depth resolution. If r is larger than _xn , the reflected light from the inside of the object W and the reflected light from the outermost surface of the object W on the light source 20 side are superimposed, and the information in the depth direction and the information on the surface are mixed. Therefore, by setting the incident angle θ so that r< _xn is satisfied, it is possible to prevent the spread of the incident light from the light source 20 to the object W from affecting the detection at each pixel of the light receiver 32 corresponding to the imaging lines A, B, and C. The partial image generated by the partial image generating unit 62 is preferably an image obtained by capturing reflected light from within the object W that is emitted from an emission position _xn of the object W and satisfies r< _xn .

Here, in FIG. 7, an example is shown in which arbitrarily settable imaging lines A, B, and C are set for the structural model of the top three layers of the measured object W, but imaging lines A, B, and C may also be set for any layer in a five-layer model such as that in FIG. 4. Also, while the examples of the measured object W shown in FIG. 4 and FIG. 7 are both represented by multi-layer models, imaging lines can be set at any position in the same way for any continuous model that is not divided into layers.

Figure 8 shows an example of a tomographic image generated by the image processing unit 61 when the angle of incidence θ of the light emitted from the light source 20 on the object to be measured W is set in various ways. The imaging lines A, B, and C are set for a five-layer model as shown in Figure 4. Figures 9 (a) to (c) are diagrams that show the direction of the light emitted from the object to be measured W when the angle of incidence θ of the light emitted from the light source 20 on the object to be measured W is set in various ways. This object to be measured W is composed of five layers, from the first layer to the fifth layer, in order from the top, and internal structure patterns P1 and P2 simulating foreign objects are formed in the second and fourth layers.

When the incident angle θ is 0°, the internal structure pattern P1 of the second layer is imaged dimly in the tomographic image of the second layer based on the reflected light at the position of the imaging line B in FIG. 9(a). This is thought to be because, as shown in FIG. 9(a), the emission angle of the light emitted from the object W increases the farther away from the irradiation position of the light emitted from the light source 20 on the object W, but the power density of the light emitted from the light source 20 decreases significantly inside the object W.

When the incident angle θ was 4.1°, the internal structure pattern P1 of the second layer was clearly imaged in the tomographic image of the second layer based on the reflected light at the position of imaging line B in FIG. 9(b). The internal structure pattern P1 of the second layer was faintly reflected in the tomographic image of the first layer based on the reflected light at the position of imaging line A in FIG. 9(b). The internal structure pattern P2 of the third layer was dimly imaged in the tomographic image of the third layer based on the reflected light at the position of imaging line C in FIG. 9(b). It is believed that these tomographic images enable information derived from the internal shape and structure of the object W to be measured to be extracted while maintaining the power density of the light emitted from the light source 20, compared to when the incident angle θ was 0°.

When the incident angle θ is 8.8°, the internal structure pattern P1 of the second layer is relatively clearly imaged in the tomographic image of the second layer based on the reflected light at the position of the imaging line B in FIG. 9(c). Also, the internal structure pattern P2 of the third layer is relatively clearly imaged in the tomographic image of the third layer based on the reflected light at the position of the imaging line C in FIG. 9(c). On the other hand, the internal structure pattern P1 of the second layer is dimly imaged in the tomographic image of the first layer based on the reflected light at the position of the imaging line A in FIG. 9(c). From these tomographic images, it is considered that information derived from the shape and structure inside the measured object W can be extracted while maintaining the power density of the light emitted from the light source 20, compared to the case where the incident angle θ is 0°. Furthermore, from these tomographic images, it can be seen that information derived from the shape and structure at a deeper position inside the measured object W can be extracted, compared to the case where the incident angle θ is 4.1°.

That is, as can be seen from the example of the tomographic image shown in FIG. 8, the imaging device 1 of this embodiment can extract information on different depth positions of the object W to be measured, depending on the angle of incidence θ of the light emitted from the light source 20 to the object W to be measured. For example, as shown in the above examples where the angle of incidence θ is 0°, 4.1°, and 8.8°, it can be seen that the depth position of the object W from which information can be extracted becomes deeper when the angle of incidence θ is increased.

The inspection unit 64 of the inspection device 100 of this embodiment inspects the object W for defects such as poor adhesion of the seal based on the tomographic image generated by the image processing unit 61, and outputs the inspection results to the display unit 50. The tomographic image generated by the image processing unit 61 captures reflected light due to differences in refractive index distributed in the depth direction of the object W. For example, the inspection unit 64 detects locations where the refractive index change is relatively large due to poor adhesion or foreign matter contamination of the seal of food, cosmetic, or pharmaceutical containers that are compressed by thermocompression or the like, and outputs the detection results to the display unit 50. This allows the inspection unit 64 to provide the user with inspection results such as poor adhesion or foreign matter contamination of the object W, thereby realizing highly sensitive defect inspection.

As described above, the imaging device 1 according to this embodiment continuously generates image data of the object W to be measured by the photoreceiver 32 while irradiating the transported object W with light at a constant angle of incidence, and further generates a tomographic image by synthesizing partial images at depths corresponding to specific pixels of the photoreceiver 32. In other words, the imaging device 1 according to this embodiment can directly capture a tomographic image having resolution in the depth direction of the object W to be measured. Furthermore, the imaging device 1 according to this embodiment can provide the user with a tomographic image that includes information such as poor adhesion of the seal of the object W to be measured and the presence of foreign matter.

In addition, the imaging device 1 according to this embodiment can generate a tomographic image of the desired observation position of the object W by appropriately setting the depth of field of the imaging optical system to a range that includes the desired observation position of the object W.

In addition, the imaging device 1 according to this embodiment can spatially separate the surface reflection components and deep scattering components of the object W by appropriately setting the angle of incidence of the light emitted from the light source 20 on the surface of the object W, and can therefore generate a tomographic image by eliminating or spatially separating the light reflected from the surface of the object W.

In addition, the imaging device 1 according to this embodiment can effectively irradiate the light emitted from the light source 20 into the inside of the object to be measured W by spreading the light emitted from the light source 20 onto a spherical surface using the scatterer 24 and making it incident on the object to be measured W.

In addition, the imaging device 1 according to this embodiment can adjust the spread of the wavefront and the angle of incidence of the light emitted from the light source 20 using the convex lens 21, so that the light emitted from the light source 20 can be effectively irradiated into the inside of the object to be measured W.

In addition, the imaging device 1 according to this embodiment can adjust the polarization state of the light emitted from the light source 20 to either linearly polarized, elliptically polarized, or circularly polarized light using the polarizer 22, and can effectively irradiate the light emitted from the light source 20 into the inside of the object to be measured W. In particular, for an object to be measured W that has high scattering properties, it is effective to use circularly polarized or randomly polarized light as the polarization state of the light emitted from the light source 20. Furthermore, by providing a polarizer 23 between the object to be measured W and the imaging unit 30, the combination of the polarizer 22 and the polarizer 23 can be used to select only a specific polarization component of the emitted light, and it can be configured to prevent reflected light from the surface of the object to be measured W from entering the imaging unit 30.

In addition, the imaging device 1 according to this embodiment can generate a tomographic image with improved depth resolution by determining the depth of the slice to be imaged in advance using the optical slit 25.

In addition, the imaging device 1 according to this embodiment can generate a tomographic image without blind spots in the depth direction while improving the depth resolution by periodically translating the optical slit 25 using the driving mechanism 26 to continuously change the depth of the slice to be imaged.

Second Embodiment
Next, an imaging device 2 according to a second embodiment of the present invention will be described with reference to the drawings. Note that descriptions of configurations and operations similar to those of the first embodiment will be omitted as appropriate.

In the first embodiment, the process of generating a tomographic image based on reflected light from the object to be measured W irradiated with light emitted from the light source 20 has been described as an example, but the present invention is not limited to this. For example, even if a configuration is used in which a tomographic image is generated based on transmitted light from the object to be measured W irradiated with light emitted from the light source 20, the same effect as that of the imaging device 1 of the first embodiment can be obtained.

As shown in FIG. 10, the imaging device 2 of this embodiment has a configuration for measuring the reflected light from the object to be measured W, as well as a configuration for measuring the transmitted light from the object to be measured W.

That is, in addition to the configuration of the imaging device 1 of the first embodiment, the imaging device 2 of this embodiment further includes one imaging unit 30', a prism 27a that irradiates the light emitted from the light source 20 onto the object to be measured W, a prism 27b that causes the reflected light from the object to be measured W to enter the imaging optical system 31 of the imaging unit 30, and a prism 27c that causes the transmitted light from the object to be measured W to enter the imaging optical system 31' of the imaging unit 30'.

The configuration of the imaging unit 30' is the same as that of the imaging unit 30 in the first embodiment. Furthermore, if it is not necessary to perform measurements using two imaging units 30 and 30' simultaneously, one imaging device can be used as the imaging unit 30 or imaging unit 30' as appropriate.

The imaging unit 30' has an imaging optical system 31' that acquires transmitted light from the object to be measured W irradiated with the light emitted from the light source 20, and a photoreceiver 32' that photoelectrically converts the transmitted light acquired by the imaging optical system 31' at multiple pixels to continuously generate image data of the object to be measured W being transported by the transport unit 10.

The imaging optical system 31' of the imaging unit 30' consists of at least one imaging lens 33', and is arranged between the object to be measured W and the light receiver 32' on the optical path of the light emitted from the light source 20, so that the light transmitted through the object to be measured W is imaged on the light receiver 32'. The depth of field of the imaging optical system 31' is set to a range that includes the desired observation position of the object to be measured W. In addition, it is preferable that the imaging optical system 31' has an aperture (not shown) between the light receiver 32' and the imaging lens 33' to block light reflected on the surface of the object to be measured W.

The optical receiver 32' has the same configuration as the optical receiver 32 in the first embodiment, except that it generates image data of transmitted light from the object to be measured W, rather than image data of reflected light from the object to be measured W.

The imaging device 2 may also include a convex lens 21' on the optical path of the light emitted from the light source 20, between the light source 20 and the object to be measured W, or between the object to be measured W and the imaging unit 30, 30'.

The imaging device 2 may also include polarizers 22', 23' between the light source 20 and the imaging optical systems 31, 31' on the optical path of the light emitted from the light source 20.

The imaging device 2 may also include a scatterer (not shown) between the light source 20 and the object to be measured W on the optical path of the light emitted from the light source 20.

The imaging device 2 may also have an optical slit 25' between the light receiver 32' and the object to be measured W on the optical path of the light emitted from the light source 20, which selects transmitted light that is not reflected at a specific depth position of the object to be measured W and allows it to enter the image sensor of the light receiver 32'.

The imaging device 2 may also include a drive mechanism 26' that periodically translates the optical slits 25, 25'. For example, the drive mechanism 26' translates the openings of the optical slits 25, 25' once while the object to be measured W is transported a predetermined distance so as to scan the transmitted light from the object to be measured W. Thereafter, the drive mechanism 26' repeats the translation of the optical slits 25, 25' in the same manner.

As in the first embodiment, the angle of incidence θ of the light emitted from the light source 20 on the object W is set to a constant value. As shown in FIG. 11, it is desirable to set the angle of incidence θ so that the irradiation area Rw on the surface of the object W irradiated with the light emitted from the light source 20 is separated from the emission position x (for example, the position of the imaging lines A', B', C' in FIG. 11) on the lower surface of the object W from which the light emitted from the light source 20 that entered the inside of the object W is emitted, in a plan view.

The object to be measured W shown in FIG. 11 has a three-layer structure, and an internal structure pattern P1 consisting of an air layer is formed in the second layer. That is, the refractive indexes of the first and third layers, and the area of the second layer where the internal structure pattern P1 is not formed, are greater than the refractive index of the internal structure pattern P1. For this reason, the behavior of the light emitted from the light source 20 that passes through the internal structure pattern P1 is, for example, as described below.

The transmitted light, whose emission position x is x ₁ ' from the outermost surface of the object W opposite the light source 20 and based on the center of the irradiation area Rw, has an emission angle (refraction angle) smaller than the incidence angle at the interface between the internal structure pattern P1 in the second layer and the third layer.

Furthermore, the transmitted light whose emission position x from the outermost surface of the object W opposite the light source 20 is _x2 ' based on the center of the irradiation area Rw is not significantly affected by the change in refractive index in the internal structure pattern P1 in the second layer, and the emission angle (refraction angle) is approximately equal to the incidence angle at the interface between the internal structure pattern P1 in the first layer and the internal structure pattern P1 in the second layer and at the interface between the internal structure pattern P1 in the second layer and the third layer.

In addition, the transmitted light whose emission position x from the outermost surface of the object W opposite the light source 20 is _x3 ' based on the center of the irradiation area Rw has an emission angle (refraction angle) larger than the incidence angle at the interface between the internal structure pattern P1 in the first layer and the second layer.

For any transmitted light, it is desirable that r<x _n ' holds true, as in the case of reflected light.

In this embodiment, the partial image generating section 62 of the image processing section 61 sequentially generates one-dimensional images as partial images based on reflected light or transmitted light that is emitted from the position of the imaging line on the measured object W and received by the pixel rows of the image sensor of the light receiver 32 or 32'. It is desirable that the partial images generated by the partial image generating section 62 are images obtained by capturing transmitted light inside the measured object W that is emitted from the emission position x _n ' of the measured object W and satisfies r < x _n '.

Figure 12(a) shows an example of a tomographic image of the object W to be measured, generated by the image processing unit 61 based on image data obtained by the imaging unit 30, which captures reflected light from the object W to be measured. Figures 12(b) to (d) show examples of tomographic images of the object W to be measured, generated by the image processing unit 61 based on image data obtained by the imaging unit 30', which captures transmitted light from the object W to be measured, as shown diagrammatically in Figure 11.

As shown in FIG. 12(a), the internal structure pattern P1 was captured relatively clearly in the tomographic image of the second layer based on the reflected light emitted from the position of the imaging line A' shown in FIG. 11.

As shown in FIG. 12(b), the internal structure pattern P1 was captured relatively clearly in the tomographic image of the second layer based on the transmitted light emitted from the imaging line A' position shown in FIG. 11. This tomographic image in the imaging line A' is based on transmitted light that contains many components refracted after passing through the air layer of the internal structure pattern P1, so the brightness of the tomographic image of the second layer based on the reflected light emitted from the imaging line A' position shown in FIG. 12(a) is inverted. Note that in FIGS. 12(a) and (b), since the thickness of the measured object W is relatively thin, the reflected light and transmitted light emitted from the imaging line A' position are shown at the same emission position x and inverted in brightness, but depending on the configuration of the measured object, a tomographic image based on reflected light and a tomographic image based on transmitted light with inverted brightness may be obtained on different imaging lines.

On the other hand, as shown in Figures 12(b) and (c), the internal structure pattern P1 was not clearly captured in the tomographic images based on the transmitted light emitted from the positions of the imaging lines B' and C' shown in Figure 11.

In this way, the imaging device 2 of this embodiment, which captures transmitted light from the object to be measured W, can also generate a tomographic image containing information on the desired depth position of the object to be measured W by selecting an appropriate imaging line.

In addition, the imaging device 2 of this embodiment may be configured so that the user can select whether to use the imaging unit 30 that captures reflected light from the object to be measured W, or the imaging unit 30' that captures transmitted light from the object to be measured W, depending on the type of object to be measured W and the purpose of the inspection.

The inspection unit 64 provided in the inspection device 110 of this embodiment inspects the object W for defects such as poor adhesion of the seal portion based on a tomographic image generated by the image processing unit 61 that captures reflected light or transmitted light due to differences in refractive index distributed in the depth direction of the object W, and outputs the inspection results to the display unit 50. As in the first embodiment, the inspection unit 64 detects areas in the object W where the change in refractive index is relatively large, and outputs the detection results to the display unit 50.

(Imaging method)
Hereinafter, an example of the process of an imaging method using the imaging device 1 according to the first embodiment or the imaging device 2 according to the second embodiment will be described with reference to the flowchart of FIG.

First, the image processing unit 61 sets the position of a specific pixel of the image sensor of the photoreceiver 32 or 32' that corresponds to the desired imaging line in response to a user's operation on the operation unit 40 (step S1).

Next, the transport unit 10 starts transporting the object to be measured W (step S2).

Next, the light source 20 irradiates the measured object W transported to the inspection area R by the transport unit 10 with emitted light in a wavelength range that can transmit through the measured object W (step S3).

Next, the photoreceiver 32 or 32' photoelectrically converts the reflected or transmitted light from the object W acquired by the imaging optical system 31 or 31' at multiple pixels to generate image data of the object W being transported by the transport unit 10 (step S4).

Next, the image processing unit 61 extracts data of the specific pixel set in step S1 from the image data generated by the photodetector 32 or 32' in step S4, and executes a process of generating a partial image consisting of the data of the specific pixel (partial image generation step S5).

Next, the image processing unit 61 determines whether the object W being measured has left the inspection area R (step S6). If the object W being measured has left the inspection area R, the image processing unit 61 executes the process of step S7. On the other hand, if the object W being measured has not left the inspection area R, the image processing unit 61 executes the processes from step S4 onwards again.

In step S7, the image processing unit 61 performs a process of synthesizing the partial images obtained at different times in the partial image generation step S5 and generating a tomographic image at a depth corresponding to a specific pixel of the image sensor of the optical receiver 32 or 32' (tomographic image generation step S7).

Next, the display unit 50 displays the tomographic image generated in the tomographic image generation step S7 (step S8).

Next, the image processing unit 61 determines whether or not tomographic images of all the objects W to be measured have been generated in the tomographic image generation step S7 (step S9). If tomographic images of all the objects W to be measured have been generated, the image processing unit 61 ends the process. On the other hand, if tomographic images of all the objects W to be measured have not been generated, the image processing unit 61 executes the processes from step S3 onwards again.

REFERENCE SIGNS LIST 1, 2 Imaging device 10 Conveyor section 11 Conveyor belt 11a Conveyor surface 20 Light source 21 Convex lens 22, 23 Polarizer 24 Scatterer 25, 25' Optical slit 26, 26' Driving mechanism 27a, 27b, 27c Prism 30, 30' Imaging section 31, 31' Imaging optical system 32, 32' Light receiver 32a Image sensor 32b Image data output section 33 Imaging lens 40 Operation section 50 Display section 60 Control device 61 Image processing section 62 Partial image generating section 63 Tomographic image generating section 100, 110 Inspection device W Object to be measured

Claims (10)

An imaging device (1, 2) including an imaging system that moves relatively to a measured object (W) and an image processing unit (61) that generates a tomographic image of the measured object,
The imaging system includes:
a light source (20) that irradiates the object to be measured with emitted light having a wavelength range that can transmit the object to be measured at a constant incident angle;
an imaging optical system (31, 31′) for acquiring reflected light or transmitted light from the object to be measured irradiated with light emitted from the light source;
a light receiver (32, 32') that photoelectrically converts the reflected light or the transmitted light acquired by the imaging optical system at a plurality of pixels to continuously generate image data of the object to be measured,
The image processing unit includes:
a partial image generating unit (62) for extracting data of a specific pixel from each of the image data generated by the light receiver and generating a partial image consisting of the data of the specific pixel;
a tomographic image generating unit (63) that combines a plurality of the partial images to generate the tomographic image at a depth corresponding to the specific pixel. The imaging device according to claim 1, characterized in that the depth of field of the imaging optical system is set to a range that includes the desired observation position of the object to be measured. the incidence angle is set to an angle at which an illumination area on the surface of the object to be measured, on which the light emitted from the light source is irradiated, is separated from an emission position of at least a part of the surface of the object to be measured, from which the light emitted from the light source having entered the inside of the object to be measured is emitted, in a plan view;
3. The imaging device according to claim 1, wherein the partial image is an image obtained by capturing the reflected light or the transmitted light from the emission position of the object to be measured. The imaging device according to claim 1 or 2, further comprising a scatterer (24) between the light source and the object to be measured on the optical path of the light emitted from the light source. The imaging device according to claim 1 or 2, further comprising a convex lens (21, 21') between the light source and the object to be measured on the optical path of the light emitted from the light source. The imaging device according to claim 1 or 2, further comprising a polarizer (22, 23, 22', 23') between the light source and the imaging optical system on the optical path of the light emitted from the light source. The imaging device according to claim 1 or 2, further comprising an optical slit (25, 25') between the light receiver and the object to be measured on the optical path of the light emitted from the light source, which selects the reflected light from a specific depth position of the object to be measured, or the transmitted light that is not reflected at a specific depth position of the object to be measured and is transmitted therethrough, and causes it to enter the light receiver. The imaging device according to claim 7, further comprising a driving mechanism (26, 26') for periodically translating the optical slit. The imaging device according to claim 1 or 2,
and an inspection section (64) that inspects the object to be measured based on the tomographic image generated by the imaging device. An imaging system that moves relative to the object to be measured (W),
The imaging system includes:
a light source (20) that irradiates the object to be measured with emitted light having a wavelength range that can transmit the object to be measured at a constant incident angle;
an imaging optical system (31, 31′) for acquiring reflected light or transmitted light from the object to be measured irradiated with light emitted from the light source;
a light receiver (32, 32') that photoelectrically converts the reflected light or the transmitted light acquired by the imaging optical system at a plurality of pixels to continuously generate image data of the object to be measured,
a partial image generating step (S5) of extracting data of a specific pixel from each of the image data generated by the light receiver and generating a partial image consisting of the data of the specific pixel;
and a tomographic image generating step (S7) of synthesizing a plurality of the partial images to generate the tomographic image at the depth corresponding to the specific pixel.

Images