Terahertz imaging device and terahertz imaging method

Abstract

A terahertz imaging device according to the present disclosure includes a terahertz light source configured to irradiate an object to be imaged with terahertz waves, an infrared sensor configured to detect the terahertz waves reflected by the object to be imaged and infrared rays from the object to be imaged, and a shutter configured to transmit the terahertz waves to the infrared sensor and block the infrared rays in a closed state, and to transmit the infrared rays to the infrared sensor in an open state.

Description

[Technical Field]

[0001] The present disclosure relates to a terahertz imaging device and a terahertz imaging method. [Background technology]

[0002] Non-Patent Document 1 describes a terahertz camera. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Development of a highly sensitive THz array sensor and camera operating at room temperature and applications of the THz camera, Naoki Oda, Journal of the Japan Society for Precision Engineering, vol.82, No.3, 2016 Summary of the Invention [Problem to be solved by the invention]

[0004] As shown in Non-Patent Document 1, there have been imaging methods using expensive imaging elements such as cooled and uncooled bolometers for terahertz waves of 0.3 to 20 THz. Also, various imaging elements such as thermopiles, bolometers, and diodes have been used for thermal infrared radiation.

[0005] Terahertz waves can penetrate fibers such as clothing, paper such as cardboard, and resin. Therefore, terahertz waves can be used to see inside fibers, paper, resin, etc. Furthermore, terahertz waves can be used to identify substances by their spectrum. This makes it possible to detect moisture content, pharmaceuticals, and dangerous substances.

[0006] On the other hand, thermal infrared light can reveal the temperature distribution of an object. For this reason, thermal infrared light imaging is widely used, and inexpensive imaging devices are widely used. For example, thermal infrared light images are being used to determine whether someone has a fever during quarantine at an airport.

[0007] Therefore, if terahertz images could be captured inexpensively, similar to conventional thermal infrared images, there would be the advantage that they could be widely used in baggage inspection, drug inspection, etc. However, there was no device that could capture both thermal infrared and terahertz waves using the same imaging element. For this reason, in order to obtain images using terahertz waves and thermal infrared, it was necessary to prepare two imaging devices, one for terahertz waves and one for thermal infrared. This not only made the devices expensive, but also required separate settings for both devices to obtain the same images using terahertz waves and thermal infrared, which was an obstacle to image acquisition.

[0008] An object of the present disclosure is to provide a terahertz imaging device and a terahertz imaging method that can capture terahertz images and thermal infrared images with a single device. [Means for solving the problem]

[0009] A terahertz imaging device according to the present disclosure includes a terahertz light source configured to irradiate an object to be imaged with terahertz waves; an infrared sensor configured to detect the terahertz waves reflected by the object to be imaged and infrared rays from the object to be imaged; and a shutter configured to transmit the terahertz waves to the infrared sensor and block the infrared rays in a closed state and to transmit the infrared rays to the infrared sensor in an open state, wherein the terahertz light source is configured to irradiate, as the terahertz waves, a first terahertz wave and a second terahertz wave having a frequency different from that of the first terahertz wave, and the shutter includes a first shutter configured to transmit the first terahertz wave to the infrared sensor and block the second terahertz wave and the infrared rays in a closed state and to transmit the infrared rays to the infrared sensor in an open state; and a second shutter configured to transmit the second terahertz wave to the infrared sensor and block the first terahertz wave and the infrared rays in a closed state and to transmit the infrared rays to the infrared sensor in an open state.

[0010] A terahertz imaging method according to the present disclosure includes: a shutter that, in a closed state, transmits terahertz waves to an infrared sensor and blocks infrared rays, and that, in an open state, transmits the infrared rays to the infrared sensor; in a state in which the terahertz waves are irradiated onto an object to be imaged, the terahertz waves reflected from the object are detected by the infrared sensor via the shutter, thereby capturing a terahertz image; in a state in which the shutter is open and the terahertz waves are not irradiated onto the object to be imaged, the infrared sensor detects the infrared rays from the object to be imaged, thereby capturing an infrared image; and, ... the shutters include a first shutter configured to transmit a first terahertz wave to the infrared sensor and block a second terahertz wave and the infrared ray in a closed state, and to transmit the infrared ray to the infrared sensor in an open state; and a second shutter configured to transmit the second terahertz wave to the infrared sensor and block the first terahertz wave and the infrared ray in a closed state, and to transmit the infrared ray to the infrared sensor in an open state; and in capturing the terahertz image, one of the first shutter and the second shutter is closed and the other of the first shutter and the second shutter is opened, and the first terahertz wave and the second terahertz wave having a frequency different from that of the first terahertz wave are irradiated as the terahertz wave, and in capturing the infrared image, the first shutter and the second shutter are opened. do. [Effects of the Invention]

[0011] The terahertz imaging device and terahertz imaging method according to the present disclosure can capture terahertz images and thermal infrared images with a single device. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram illustrating a terahertz imaging device according to a first embodiment. [Figure 2] 1A to 1C are diagrams illustrating a terahertz imaging method according to the first embodiment. [Figure 3] 10 is a diagram illustrating a terahertz imaging device according to a second embodiment. FIG. [Figure 4] 10 is a diagram illustrating a terahertz imaging device according to a third embodiment. FIG. [Figure 5] FIG. 10 is a cross-sectional view of an infrared sensor according to a fourth embodiment. [Figure 6] 10 is a diagram illustrating a terahertz imaging device according to a fifth embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] A terahertz imaging device and a terahertz imaging method according to each embodiment will be described with reference to the drawings. The same or corresponding components may be denoted by the same reference numerals, and repeated descriptions may be omitted.

[0014] Embodiment 1. FIG. 1 is a diagram for explaining a terahertz imaging device 100 according to Embodiment 1. The terahertz imaging device 100 includes a terahertz light source 5, a signal processing circuit 4, a lens 3, a shutter 2, and an infrared sensor 1.

[0015] The terahertz light source 5 irradiates the object 50 to be imaged with terahertz waves 7. The terahertz waves have a lower frequency than infrared rays. Hereinafter, the frequency f1 of the terahertz waves is set to 0.3 THz ≤ f1 ≤ 20 THz, and the wavelength λ1 is set to 15 μm ≤ λ1 ≤ 1 mm. Also, the frequency f2 of the infrared rays is set to 20 THz ≤ f2 ≤ 37 THz, and the wavelength λ2 is set to 8 μm ≤ λ2 ≤ 15 μm. The frequency f1 of the terahertz waves may be defined as 0.3 THz ≤ f1 < 20 THz, or 0.1 THz < f1 ≤ 10 THz. Also, infrared rays may be referred to as thermal infrared rays. The terahertz light source 5 irradiates the object 50 to be imaged during the imaging of a terahertz image, and does not irradiate the object 50 to be imaged during the imaging of an infrared image.

[0016] The lens 3 causes the terahertz waves L1 and the infrared rays L2 from the object 50 to be imaged to enter the infrared sensor 1. That is, the lens 3 condenses the light fluxes of the terahertz waves L1 and the infrared rays L2 onto the pixels of the infrared sensor 1.

[0017] The terahertz waves L1 reflected by the object 50 to be imaged and the infrared rays L2 from the object 50 to be imaged enter the infrared sensor 1 via the lens 3 and the shutter 2. The infrared sensor​​​The openable shutter 2 allows terahertz waves L1 to pass through to the infrared sensor 1 and blocks infrared rays L2 when closed. When the shutter 2 is open, it allows infrared rays L2 and terahertz waves L1 to pass through to the infrared sensor 1. The shutter 2 is configured to be in a closed state when capturing a terahertz image using terahertz waves L1, and to be in an open state when capturing an infrared image using infrared rays L2.

[0019] The shutter 2 is, for example, a bandpass filter or lowpass filter that, when closed, passes the terahertz wave L1 and blocks the infrared light L2. The bandpass filter or lowpass filter is, for example, a metal mesh. The metal mesh is a member with multiple openings formed on a metal surface. The metal mesh is designed to obtain the desired frequency characteristics. In other words, the metal mesh is designed to transmit the terahertz wave but not the thermal infrared light. The metal mesh can be easily manufactured, for example, by an etching process using a pattern formed by exposure. Therefore, the shutter 2 can be manufactured inexpensively. The shutter 2 may be part of the infrared sensor 1.

[0020] The signal processing circuit 4 performs arithmetic processing on the output signals of each pixel of the infrared sensor 1 to form a terahertz image and an infrared image.

[0021] The signal processing circuit 4, lens 3, shutter 2, and infrared sensor 1 are housed, for example, in the same housing. The terahertz light source 5 may be housed in the same housing as the infrared sensor 1, etc., or in a separate housing. If it is desired to irradiate a wide area with terahertz waves, it is advisable to house the terahertz light source 5 in a separate housing from the infrared sensor 1, etc.

[0022] FIG. 2 is a diagram illustrating a terahertz imaging method according to the first embodiment. A method for acquiring an infrared image and a terahertz image will be described with reference to FIG. 2. First, prior to capturing an infrared image, shutter 2 is closed and infrared sensor 1 is calibrated (step 1). When shutter 2 is closed, thermal infrared rays do not pass through infrared sensor 1. In this state, infrared sensor 1 is calibrated. Calibration allows the zero point of the thermal infrared signal to be corrected. Therefore, an accurate infrared image can be captured.

[0023] Next, an infrared image is captured. First, the terahertz light source 5 is turned off and the shutter 2 is opened (step 2). Next, the infrared light L2 incident on the infrared sensor 1 is measured. Then, the output signal of each pixel of the infrared sensor 1 is processed by the signal processing circuit 4 to capture an infrared image (step 3). That is, the infrared image is captured by detecting the infrared light L2 from the object 50 to be captured with the infrared sensor 1 in the open state and with the terahertz wave 7 not being irradiated onto the object 50. Note that infrared light has a high level of blackbody radiation, and is therefore sufficiently radiated from any object with a temperature. For this reason, an infrared light source is not required.

[0024] Next, a terahertz image is captured. First, terahertz waves 7 are irradiated onto the object 50 from the terahertz light source 5, and the shutter 2 is closed (step 4). Next, the terahertz waves L1 incident on the infrared sensor 1 are measured. Then, the output signals of each pixel of the infrared sensor 1 are processed by the signal processing circuit 4 to capture a terahertz image (step 5). Since the shutter 2 transmits only terahertz waves in the closed state, a terahertz image can be captured. In other words, the terahertz image is captured by closing the shutter 2, irradiating the object 50 with terahertz waves 7, and detecting the terahertz waves L1 reflected by the object 50 via the shutter 2 with the infrared sensor 1. Note that the order of steps 2 and 3 and steps 4 and 5 may be reversed.

[0025] Next, a conventional infrared imaging device will be described as a comparative example. Conventional infrared imaging devices have optimized sensitivity and focus for thermal infrared rays. As a result, conventional infrared imaging devices have almost no sensitivity to terahertz waves, which are weaker than thermal infrared rays. Furthermore, conventional shutters are made of resin materials that do not transmit infrared rays. As such, conventional devices have not been able to capture terahertz images and thermal infrared images.

[0026] For this reason, in the past, to obtain images using terahertz waves and thermal infrared rays, it was necessary to prepare two imaging devices, one for terahertz waves and one for thermal infrared rays. Capturing images separately using two imaging devices increases costs and the effort required for imaging. Furthermore, to overlay two types of images, the imaging areas of the two imaging devices must be set so that they overlap as much as possible. This requires a significant amount of time for imaging preparation. Furthermore, in the past, the pixels of image data obtained using terahertz waves and thermal infrared rays do not match. For this reason, it was necessary to generate new image data by interpolating the two image data using arithmetic processing to make the pixels identical. This resulted in significant time and cost required for arithmetic processing.

[0027] In contrast, this embodiment allows both infrared and terahertz images to be captured using the same device. The cost of the imaging device can be reduced by using only one imaging device, instead of the two that were previously required. Furthermore, the calculation process required for setting up the imaging device and superimposing the captured images can be simplified.

[0028] The functions of the signal processing circuit 4 are realized by one or more control circuits, such as the processor 4a shown in Fig. 1. Each control circuit may be dedicated hardware. Alternatively, the control circuit may be a CPU (Central Processing Unit) that executes a program stored in the memory 4b. The CPU may be a central processing unit, processing unit, microprocessor, microcomputer, processor, or DSP (Digital Signal Processor).

[0029] When the control circuit is dedicated hardware, the control circuit may be, for example, a single circuit, a composite circuit, a programmed processor, or a parallel programmed processor. The control circuit may also be an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array). The control circuit may also be a combination of these. The functions of each part of the signal processing circuit 4 may each be realized by a separate control circuit. The functions of each part may also be realized together by a single control circuit.

[0030] When the control circuit is a CPU, the functions of the signal processing circuit 4 are realized by software, firmware, or a combination of software and firmware. The software and firmware are written as programs and stored in memory 4b. The control circuit realizes the functions of each part by reading and executing the programs stored in memory 4b.

[0031] That is, memory 4b stores programs for forming terahertz images and infrared images by performing arithmetic processing on the output signals of each pixel of infrared sensor 1. These programs can also be said to cause a computer to execute the procedures or methods in signal processing circuit 4.

[0032] Here, the memory 4b in which the program is stored may be a non-volatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, or EEPROM. The memory may be a magnetic disk, flexible disk, optical disk, compact disk, minidisk, DVD, or the like. RAM is an abbreviation for Random Access Memory. ROM is an abbreviation for Read Only Memory. EPROM is an abbreviation for Erasable Programmable Read Only Memory. EEPROM is an abbreviation for Electrically Erasable Programmable Read-Only Memory. Multiple memories 4b may be provided.

[0033] It is also possible to realize some of the functions of the signal processing circuit 4 with dedicated hardware and some with software or firmware. In this way, the control circuit can realize each of the above-mentioned functions with hardware, software, firmware, or a combination of these.

[0034] The above-described modifications can be applied as appropriate to the terahertz imaging devices and terahertz imaging methods according to the following embodiments. Note that the terahertz imaging devices and terahertz imaging methods according to the following embodiments have much in common with the first embodiment, so the following description will focus on the differences from the first embodiment.

[0035] Embodiment 2 3 is a diagram illustrating a terahertz imaging device 200 according to a second embodiment. The terahertz light source 5 of this embodiment can irradiate terahertz waves of multiple frequencies. The terahertz light source 5 simultaneously irradiates, as terahertz waves, for example, a first terahertz wave 7a and a second terahertz wave 7b having a different frequency from the first terahertz wave 7a. Hereinafter, the frequency of the first terahertz wave 7a will be referred to as the first frequency, and the frequency of the second terahertz wave 7b will be referred to as the second frequency.

[0036] The shutter of this embodiment includes a first shutter 2a and a second shutter 2b. When the first shutter 2a is closed, it transmits the first terahertz wave 7a to the infrared sensor 1 and blocks the second terahertz wave 7b and the infrared light L2. When the first shutter 2a is open, it transmits the infrared light L2, the first terahertz wave 7a, and the second terahertz wave 7b to the infrared sensor 1.

[0037] When the second shutter 2b is closed, it transmits the second terahertz wave 7b to the infrared sensor 1 and blocks the first terahertz wave 7a and the infrared light L2. When the second shutter 2b is open, it transmits the infrared light L2, the first terahertz wave 7a, and the second terahertz wave 7b to the infrared sensor 1. The other configurations are the same as those in the first embodiment.

[0038] In this embodiment, when capturing a terahertz image of a first frequency, the first shutter 2a is closed, the second shutter 2b is open, and the terahertz light source 5 is turned on. In this state, the terahertz wave L1 incident on the infrared sensor 1 is measured. When capturing a terahertz image of a second frequency, the second shutter 2b is closed, the first shutter 2a is open, and the terahertz light source 5 is turned on. In this state, the terahertz wave L1 incident on the infrared sensor 1 is measured.

[0039] When capturing an infrared image, the first shutter 2a and the second shutter 2b are opened and the terahertz light source 5 is turned off. In this state, the infrared light L2 incident on the infrared sensor 1 is measured. Note that the infrared sensor 1 is calibrated with the first shutter 2a or the second shutter 2b closed so that no infrared light passes through.

[0040] In this embodiment, each shutter transmits only the desired terahertz waves. This makes it easy to capture terahertz images of different frequencies. This allows the frequency dependence of terahertz wave intensity, i.e., the spectrum, to be obtained. This makes it possible to identify substances within the imaged object 50. This makes it easy to detect dangerous substances such as drugs and explosives. Furthermore, information from the infrared image may be added to the terahertz wave spectrum to identify substances.

[0041] The terahertz waves may have three or more frequencies. Such a configuration can be achieved by increasing the number of filters constituting the shutter. The terahertz waves may have multiple continuous frequencies, and the terahertz light source 5 may emit a spectrum of a wide continuous frequency range including the desired frequency.

[0042] Embodiment 3 FIG. 4 is a diagram illustrating a terahertz imaging device 300 according to a third embodiment. This embodiment differs from the first embodiment in that the terahertz light source 5 is configured to be able to switch the frequency of the terahertz wave 7. The other configurations are the same as those of the first embodiment. The terahertz light source 5 can irradiate, as terahertz waves, a first terahertz wave 7a and a second terahertz wave 7b having a different frequency from the first terahertz wave 7a. The terahertz light source 5 can be externally controlled to achieve a state in which it irradiates only the first terahertz wave 7a and a state in which it irradiates only the second terahertz wave 7b.

[0043] Shutter 2, which is provided on the incident surface of infrared sensor 1, transmits both the first frequency band of first terahertz wave 7a and the second frequency band of second terahertz wave 7b in the closed state, and does not transmit thermal infrared rays in the closed state.

[0044] In this embodiment, when capturing a terahertz image of a first frequency, shutter 2 is closed and first terahertz wave 7a is emitted from terahertz light source 5. In this state, terahertz wave L1 incident on infrared sensor 1 is measured. When capturing a terahertz image of a second frequency, shutter 2 is closed and second terahertz wave 7b is emitted from terahertz light source 5. In this state, terahertz wave L1 incident on infrared sensor 1 is measured. In this way, when capturing a terahertz image, shutter 2 is closed and the frequency of the terahertz wave is switched, and then imaging is performed.

[0045] When capturing an infrared image, the shutter 2 is opened and the terahertz light source 5 is turned off. In this state, the infrared light L2 incident on the infrared sensor 1 is measured. Note that the infrared sensor 1 is calibrated with the shutter 2 closed so that no infrared light passes through.

[0046] In this embodiment, terahertz images of multiple frequencies can also be easily captured. Therefore, the frequency dependence of terahertz wave intensity, i.e., the spectrum, can be obtained, making it possible to identify a substance. Furthermore, information from an infrared image may be added to the terahertz wave spectrum to identify a substance.

[0047] The terahertz waves may have three or more frequency bands, and may have a plurality of continuous frequencies.

[0048] Embodiment 4 5 is a cross-sectional view of an infrared sensor 401 according to the fourth embodiment. The infrared sensor 401 has an imaging chip 25 made of, for example, a silicon IC (Integrated Circuit). The imaging chip 25 is die-bonded onto a ceramic substrate 21 with solder 24. Wires 27 connect electrodes 23 on the ceramic substrate 21 to pads 26 provided on the imaging chip 25. The ceramic substrate 21 has through-holes that connect the upper electrodes 23 to the lower leads 22. The signal lines of the terahertz imaging device and the electrical wiring of the power supply are connected to external circuits via the leads 22.

[0049] The imaging chip 25 has a plurality of pixels 20. The infrared sensor 401 detects the temperature rise of the pixels 20 due to the terahertz waves L1 and infrared rays L2 using a diode or the like and outputs a signal. In order to detect the minute temperature rise due to the terahertz waves L1 and infrared rays L2, a vacuum sealed region 11 is provided to thermally isolate the pixels 20 from the outside. The vacuum sealed region 11 creates a vacuum around the pixels 20.

[0050] The vacuum sealing region 11 can be formed by joining the window chip 28 with solder 10 in a vacuum and hermetically sealing it. That is, the window chip 28 covers the multiple pixels 20 on the imaging chip 25 in a vacuum-sealing manner. The window chip 28 is provided with an anti-reflection film 9 that prevents reflection of the terahertz wave L1 and infrared light L2. This makes it possible to prevent a reduction in the amount of incident light of the terahertz wave L1 and infrared light L2 on the pixels 20 due to reflection.

[0051] The window chip 28 can be made of a silicon substrate or the like. In particular, the window chip 28 of this embodiment is made of non-doped silicon. The window chip 28 may also be a non-doped high-resistivity silicon substrate that does not use a dopant.

[0052] Conventional window chips use doped silicon substrates, which are generally available at low cost. However, in the terahertz band, dopants in the silicon substrate can cause unwanted absorption of terahertz waves. This reduces the transmittance of terahertz waves and reduces the sensitivity of the pixel 20.

[0053] In contrast, in this embodiment, the window chip 28 is made of non-doped silicon, which can suppress the absorption of terahertz waves by dopants in the silicon substrate, thereby improving the sensitivity of the terahertz imaging device.

[0054] Furthermore, a silicon substrate is used for the imaging chip 25. By using silicon, which has the same linear expansion coefficient, for the window chip 28, damage to the window chip 28 and breaking of the vacuum seal due to thermal expansion can be prevented.

[0055] It is also possible to use a terahertz-transmitting material other than silicon, such as PTFE (polytetrafluoroethylene), for the window chip 28. In this case, in addition to the problem of the linear expansion coefficient, it is difficult to seal the silicon imaging chip 25 to maintain a vacuum. For this reason, a silicon substrate that can be easily vacuum-sealed with solder 10 is suitable for the window chip 28.

[0056] Therefore, to capture both terahertz and thermal infrared radiation using the same imaging device, it is necessary to select a material that is transparent to both infrared and terahertz waves while taking into consideration the linear expansion coefficient and sealing. Therefore, it is optimal to use non-doped, high-resistivity silicon for the window chip 28. The thickness of the window chip 28 is adjusted to accommodate terahertz waves.

[0057] The infrared sensor 401 of this embodiment may be applied to any of the embodiments.

[0058] Embodiment 5. 6 is a diagram illustrating a terahertz imaging device 500 according to a fifth embodiment. A signal processing circuit 4 according to this embodiment is configured to correct a misalignment between a terahertz image and an infrared image due to a difference in the refractive index of a lens 3 between the terahertz wave L1 and the infrared wave L2, or due to the influence of a shutter 2. The other configurations are the same as those of the first embodiment.

[0059] As described in the first embodiment, the terahertz waves and thermal infrared rays are condensed by the lens 3. Therefore, as shown in FIG. 6, a slight difference in the refractive index of the lens 3 can cause the image incident on the infrared sensor 1 to be shifted. Furthermore, the infrared sensor 1 receives the terahertz waves L1 that have passed through the filter of the shutter 2. Therefore, the image incident on the infrared sensor 1 can also be shifted due to the influence of the filter.

[0060] In this embodiment, image misalignment caused by the lens 3 or shutter 2 can be corrected by calculations in the signal processing circuit 4. Therefore, the terahertz image and the infrared image can be accurately superimposed.

[0061] If the image correction of this embodiment is not performed, errors will be large, especially in the peripheral areas of the image. However, correction is not necessary for applications that do not require precision in the peripheral areas of the image. On the other hand, correction of this embodiment is essential for applications that require accurate terahertz and infrared images that match across the entire image. An example of an application requiring precision is when there is a heating element at the edge of the image and the material of that heating element needs to be identified.

[0062] The present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure. The present disclosure also includes all combinations of the configurations shown in the above-described embodiments. [Explanation of symbols]

[0063] REFERENCE SIGNS LIST 1 infrared sensor, 2 shutter, 2a first shutter, 2b second shutter, 3 lens, 4 signal processing circuit, 4a processor, 4b memory, 5 terahertz light source, 7 terahertz wave, 7a first terahertz wave, 7b second terahertz wave, 9 anti-reflection coating, 10 solder, 11 vacuum sealing area, 20 pixel, 21 ceramic substrate, 22 lead, 23 electrode, 24 solder, 25 imaging chip, 26 pad, 27 wire, 28 window chip, 50 imaged object, 100 terahertz imaging device, 200 terahertz imaging device, 300 terahertz imaging device, 401 infrared sensor, 500 terahertz imaging device

Claims

1. a terahertz light source configured to irradiate the object to be imaged with terahertz waves; an infrared sensor configured to detect the terahertz wave reflected by the object to be imaged and infrared rays from the object to be imaged; a shutter configured to transmit the terahertz wave to the infrared sensor and block the infrared light when in a closed state, and to transmit the infrared light to the infrared sensor when in an open state; Equipped with the terahertz light source is configured to irradiate, as the terahertz waves, a first terahertz wave and a second terahertz wave having a frequency different from that of the first terahertz wave; The shutter is a first shutter configured to transmit the first terahertz wave to the infrared sensor and block the second terahertz wave and the infrared ray in a closed state, and to transmit the infrared ray to the infrared sensor in an open state; a second shutter configured to transmit the second terahertz wave to the infrared sensor and block the first terahertz wave and the infrared ray in a closed state, and to transmit the infrared ray to the infrared sensor in an open state; A terahertz imaging device comprising:

2. The terahertz imaging device described in Claim 1, characterized in that the shutter is a band-pass filter or a low-pass filter.

3. The infrared sensor An imaging chip; a plurality of pixels provided on the imaging chip; a window chip provided on the imaging chip and covering the plurality of pixels in a vacuum-sealed manner; and 3. The terahertz imaging device according to claim 1, wherein the window chip is made of non-doped silicon.

4. a lens that causes the terahertz wave and the infrared light from the object to be imaged to be incident on the infrared sensor; a signal processing circuit configured to correct a deviation between a terahertz image generated by the terahertz wave and an infrared image generated by the infrared light due to a difference in refractive index of the lens between the terahertz wave and the infrared light or due to an influence of the shutter; 3. The terahertz imaging device according to claim 1, further comprising:

5. 3. The terahertz imaging device according to claim 1, wherein the shutter is a metal mesh.

6. a shutter that, in a closed state, transmits terahertz waves to an infrared sensor and blocks infrared rays, and that, in an open state, transmits the infrared rays to the infrared sensor, is set in the closed state, and in a state in which the terahertz waves are irradiated onto an object to be imaged, the terahertz waves reflected by the object to be imaged are detected by the infrared sensor via the shutter, thereby capturing a terahertz image; With the shutter in the open state and without irradiating the terahertz wave onto the object to be imaged, the infrared sensor detects the infrared ray from the object to be imaged, thereby capturing an infrared image; overlaying the terahertz image and the infrared image; The shutter is a first shutter configured to transmit a first terahertz wave to the infrared sensor in a closed state, block a second terahertz wave and the infrared ray, and transmit the infrared ray to the infrared sensor in an open state; a second shutter configured to transmit the second terahertz wave to the infrared sensor and block the first terahertz wave and the infrared ray in a closed state, and to transmit the infrared ray to the infrared sensor in an open state; Including, In capturing the terahertz image, one of the first shutter and the second shutter is closed, and the other of the first shutter and the second shutter is opened, and the first terahertz wave and the second terahertz wave having a frequency different from that of the first terahertz wave are irradiated as the terahertz wave; The terahertz imaging method is characterized in that, when capturing the infrared image, the first shutter and the second shutter are in an open state.

7. 7. The terahertz imaging method according to claim 6, wherein the shutter is closed and the infrared sensor is calibrated before capturing the infrared image.

Images