Receiving device and method for adjusting the receiving device

Abstract

The receiving device according to this disclosure comprises a housing, a first photodetector provided inside the housing on the optical axis of terahertz waves incident from outside the housing, a mirror provided inside the housing on the optical axis and configured to reflect the terahertz waves, and a second photodetector having a plurality of pixels and configured to receive the terahertz waves reflected by the mirror inside the housing, wherein the second photodetector has more pixels than the first photodetector, and the first photodetector, the second photodetector, and the mirror are arranged in the housing such that, with the housing positioned so that the second photodetector can receive the terahertz waves reflected by the mirror, the terahertz waves obtained by removing the mirror, or the terahertz waves transmitted through the mirror, are received by the first photodetector.

Description

Technical Field

[0001] The present disclosure relates to a receiving device and a method for adjusting the receiving device.

Background Art

[0002] Patent Document 1 discloses a transmitter for positioning a transmitter and a receiver in communication using a high-frequency band such as millimeter waves or terahertz waves. This transmitter includes a transmission unit that transmits millimeter waves or terahertz radio waves via an antenna, a light source that outputs light waves of one or more wavelengths, and a reflection unit that coaxially transmits radio waves and light waves of one or more wavelengths.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] THz (terahertz) waves have a shorter wavelength than millimeter waves and have the characteristic that the beam width can be narrowed. However, in order to receive a narrow beam, the position of the light-receiving element must be accurately set at the center of the beam. Since THz waves are invisible to the eye, it has been difficult to align the position of the light-receiving element by looking only at the signal intensity. In contrast, in Patent Document 1, alignment is performed by irradiating pilot light coaxially with THz waves. However, this method has the problem that the device becomes complex and expensive.

[0005] An object of the present disclosure is to obtain a receiving device and a method for adjusting the receiving device that can be easily aligned.

Means for Solving the Problems

[0006] The receiving device according to the first disclosure comprises a housing, a first photodetector provided inside the housing on the optical axis of terahertz waves incident from outside the housing, a mirror provided inside the housing on the optical axis and configured to reflect the terahertz waves, and a second photodetector having a plurality of pixels and configured to receive the terahertz waves reflected by the mirror inside the housing, wherein the second photodetector has more pixels than the first photodetector, and the first photodetector, the second photodetector, and the mirror are arranged in the housing such that, with the housing positioned so that the second photodetector can receive the terahertz waves reflected by the mirror, the terahertz waves obtained by removing the mirror, or the terahertz waves transmitted through the mirror, are received by the first photodetector. The mirror is a movable mirror configured to achieve both a closed state that reflects the terahertz waves and an open state that transmits the terahertz waves. ru.

[0007] The receiving device according to the second disclosure comprises a substrate, a first light-receiving element provided on the substrate, and a second light-receiving element provided on the substrate having a plurality of pixels, wherein the second light-receiving element has more pixels than the first light-receiving element, and the first light-receiving element is configured to receive the terahertz waves by moving the substrate or the optical axis of the terahertz waves in a predetermined manner, starting from a state in which the substrate is positioned so that the second light-receiving element can receive the terahertz waves.

[0008] The adjustment method for the receiving device according to the third disclosure involves irradiating a terahertz wave from outside a housing that houses a first light-receiving element, a second light-receiving element having a plurality of pixels, and a mirror, causing the terahertz wave to be incident on the mirror, causing the terahertz wave reflected by the mirror to be received by the second light-receiving element, moving the housing to align the position based on the intensity of the signal obtained by the second light-receiving element receiving the terahertz wave, and in the aligned state, causing the first light-receiving element to receive the terahertz wave obtained by removing the mirror, or the terahertz wave that has passed through the mirror, wherein the second light-receiving element has more pixels than the first light-receiving element.

[0009] The adjustment method for the receiving device according to the fourth disclosure is as follows: a substrate is provided on which a first photodetector and a second photodetector having a plurality of pixels are provided, the second photodetector receives a terahertz wave, the optical axis of the terahertz wave is aligned based on the intensity of the signal obtained by receiving the terahertz wave with the second photodetector, and after the alignment, the substrate or the optical axis of the terahertz wave is moved in a predetermined manner so that the first photodetector receives the terahertz wave, the second photodetector has more pixels than the first photodetector. [Effects of the Invention]

[0010] In the receiving device and adjustment method for the receiving device described in the first to fourth disclosures, alignment can be performed using terahertz waves and a second photodetector having more pixels than the first photodetector. Therefore, alignment can be easily performed. [Brief explanation of the drawing]

[0011] [Figure 1] This is a diagram illustrating the configuration of the receiving device according to Embodiment 1. [Figure 2] This is a cross-sectional view of the second light-receiving element according to Embodiment 1. [Figure 3] This is a flowchart showing the adjustment method for the receiving device according to Embodiment 1. [Figure 4] This is a diagram illustrating the configuration of the receiving device according to Embodiment 2. [Figure 5] This is a diagram illustrating the configuration of the receiving device according to Embodiment 3. [Modes for carrying out the invention]

[0012] The receiving device and the adjustment method for the receiving device according to each embodiment will be described with reference to the drawings. The same or corresponding components are denoted by the same reference numerals, and repetition of the description may be omitted.

[0013] Embodiment 1. Figure 1 is a diagram illustrating the configuration of a receiving device 100 according to Embodiment 1. The receiving device 100 comprises a housing 30, a first photodetector 10, a second photodetector 20, and a mirror 40 housed in the housing 30. A THz wave 51 is incident on the receiving device 100 from an external THz light source 50. Hereinafter, the frequency f1 of the THz wave 51 is set to 0.3 THz ≤ f1 ≤ 20 THz, and the wavelength λ1 is set to 15 μm ≤ λ1 ≤ 1 mm. The first photodetector 10 and the second photodetector 20 are sensitive to the THz wave 51.

[0014] The first photodetector 10 is located inside the housing 30, on the optical axis L1 of the terahertz wave incident from outside the housing 30. The first photodetector 10 is an element capable of receiving signals for high-speed communication using THz waves. The first photodetector 10 is, for example, a Resonant Tunneling Diode (RTD) capable of high-speed response. The first photodetector 10 may also be a heterodyne receiver or detection diode using CMOS (Complementary Metal Oxide Semiconductor), InP HBT (Heterojunction Bipolar Transistor), etc.

[0015] The first photodetector 10 is more efficient than the second photodetector 20, which will be described later. The first photodetector 10 should have at least one of the following characteristics: faster response speed, higher sensitivity, and lower noise than the second photodetector 20. The first photodetector 10 is generally difficult to integrate from a cost standpoint. The first photodetector 10 may have only one pixel as the pixel that receives the THz wave 51.

[0016] The second light-receiving element 20 is configured to receive the THz wave 51 reflected by the mirror 40 inside the housing 30. The second light-receiving element 20 is used for the alignment of the optical axis L1. The second light-receiving element 20 has a plurality of pixels. The second light-receiving element 20 has more pixels than the first light-receiving element 10. The second light-receiving element 20 is, for example, a thermal imaging device. Since thermal imaging devices are generally inexpensive, the cost can be reduced by using a thermal imaging device. Although it is more expensive than a thermal imaging device, the second light-receiving element 20 may be an RTD having a plurality of pixels.

[0017] FIG. 2 is a cross-sectional view of the second light-receiving element 20 according to Embodiment 1. Here, an example in which the second light-receiving element 20 is a thermal imaging device will be described. The second light-receiving element 20 has an imaging chip 22 made of, for example, a silicon IC (Integrated Circuit). The imaging chip 22 is bonded onto a ceramic substrate 21.

[0018] The imaging chip 22 is provided with a plurality of pixels 23. A plurality of the pixels 23 are arranged along the X-axis and the Y-axis orthogonal to each other on the surface of the imaging chip 22, respectively. The second light-receiving element 20 detects the temperature rise of the pixel 23 due to the THz wave 51 by a diode or the like and outputs a signal. In order to detect a minute temperature rise due to the THz wave 51, a vacuum sealing region 25 is provided to thermally isolate the pixel 23 from the outside.

[0019] The vacuum sealing region 25 can be formed by bonding and hermetically sealing the window chip 24 in a vacuum. That is, the window chip 24 covers the plurality of pixels 23 on the imaging chip 22 so as to vacuum-seal them. The window chip 24 is provided with an antireflection film for preventing the reflection of the THz wave 51. Thereby, it is possible to suppress a decrease in the incident light amount of the THz wave 51 to the pixel 23 due to reflection. The window chip 24 can be made of a silicon substrate or the like.

[0020] The second light-receiving element 20 has a function of detecting the THz wave 51 and outputting a DC or low-frequency electrical signal in proportion to the intensity of the THz wave 51. Since a plurality of pixels 23 are arranged in the second light-receiving element 20, for example, the intensity distribution of the THz wave 51 can be obtained as an image.

[0021] The mirror 40 is provided on the optical axis L1 inside the housing 30 and is configured to reflect the THz wave 51. The mirror 40 of the present embodiment is a movable mirror configured to be able to realize, for example, a closed state in which the THz wave 51 is reflected and an open state in which the THz wave 51 is transmitted. The mirror 40 may be an openable and closable shutter.

[0022] Next, the arrangement of each component in the housing 30 will be described. Assume a state in which the housing 30 is arranged at a position where the second light-receiving element 20 can receive the THz wave 51 reflected by the mirror 40. In the state after this alignment, the first light-receiving element 10, the second light-receiving element 20, and the mirror 40 are arranged in the housing 30 in advance so that the THz wave 51 obtained by removing the mirror 40 is received by the first light-receiving element 10. That is, if the mirror 40 is removed in the state where alignment is performed using the second light-receiving element 20, the positions of each component are preset so that the THz wave 51 can be received by the first light-receiving element 10. The THz wave 51 obtained by removing the mirror 40 means, in the present embodiment, the THz wave 51 obtained with the mirror 40 in the open state.

[0023] Next, a method for adjusting the receiving device 100 will be described. FIG. 3 is a flowchart showing a method for adjusting the receiving device 100 according to Embodiment 1. First, with the mirror 40 in the closed state, the THz wave 51 is irradiated from the outside of the housing 30 to make the THz wave 51 incident on the mirror 40. As a result, the THz wave 51 reflected by the mirror 40 is received by the second light-receiving element 20 (step 1).

[0024] At this time, an image showing the intensity distribution of the THz wave 51 is obtained by multiple pixels 23. In other words, the direction of the THz light source 50 can be detected by the intensity of the image (Step 2). Next, the position of the housing 30 is adjusted to the direction detected in Step 2 (Step 3). Thus, in this embodiment, the housing 30 is moved and adjusted based on the intensity of the signal obtained by receiving the THz wave 51 with the second photodetector 20.

[0025] If alignment is complete (Yes in step 4), the mirror 40 is opened and the THz wave 51 is shone onto the first photodetector 10 (step 5). In other words, the first photodetector 10 receives the THz wave 51 obtained by removing the mirror 40 or the THz wave 51 that has passed through the mirror 40. If the center of the first photodetector 10 and the optical axis L1 are not aligned in step 4, the process returns to step 1.

[0026] In this embodiment, optical axis alignment can be performed with a simple configuration using only THz light, without the need for pilot light such as laser light. Therefore, positioning can be easily performed. Furthermore, when laser light is used for positioning, positioning could not be performed in areas where people were present due to human safety concerns. In this embodiment, since laser light is not used, optical axis alignment can be performed frequently even in environments where people are present. Therefore, the optical axis L1 can be corrected at any time, even if the THz light source 50 or the receiving device 100 moves.

[0027] Furthermore, with THz waves, which have a narrow beam width, it is crucial to accurately align the position of the first photodetector 10 with the optical axis L1. However, it is generally difficult to integrate multiple pixels into a high-performance first photodetector 10. Moreover, THz waves are invisible to the human eye. Therefore, it is not possible to determine the direction in which to move the optical axis L1 by only looking at the signal intensity of the first photodetector 10. In addition, if the optical axis L1 deviates from the first photodetector 10, which has a small number of pixels and a small light-receiving area, it becomes difficult to find the optical axis L1. Thus, it is difficult to perform alignment using the first photodetector 10.

[0028] In contrast, in this embodiment, alignment is performed using a second photodetector 20, which has multiple pixels 23 integrated to ensure a large light-receiving area. This makes it possible to detect the direction in which the housing 30 should be moved based on the intensity of the image caused by the THz wave 51. Therefore, alignment becomes easy. Furthermore, thermal image sensors with multiple pixels 23 integrated are generally inexpensive. Therefore, the optical axis of the THz wave can be aligned easily and inexpensively. However, although thermal image sensors are inexpensive, their response speed is slow, making them unsuitable for receiving high-speed communications. For this reason, it is preferable to switch to the first photodetector 10 when actually receiving high-speed communication signals. Thus, in this embodiment, a receiving device that allows for easy alignment can be realized by combining the first photodetector 10 and the second photodetector 20.

[0029] This embodiment can also be applied to communication that avoids people, that is, communication in an environment where people can freely enter between the THz light source 50 and the first photodetector 10. If a person is in the propagation path of the THz wave, the THz wave will be blocked by the person. In communication that avoids people, multiple transmitting and receiving devices are arranged, and when a person is detected, the communication path is switched to perform communication. For example, this embodiment can be applied to communication across a room where people are freely coming and going.

[0030] Any mirror that can be removed from the optical axis L1 can be used as the mirror 40, not limited to those that can be opened and closed. Furthermore, the mirror 40 may be a half-mirror that transmits a portion of the THz wave 51. In this case, opening or removing the mirror 40 is unnecessary. Specifically, in step 5, the THz wave 51 transmitted through the mirror 40 is irradiated onto the first photodetector 10 without moving the mirror 40. Using a half-mirror eliminates the movable mechanism of the mirror 40, allowing the receiving device 100 to be manufactured at an even lower cost and reducing mechanical failures.

[0031] The modifications described above can be appropriately applied to the receiving device and adjustment method of the receiving device according to the following embodiments. Since the receiving device and adjustment method of the receiving device according to the following embodiments have many similarities with Embodiment 1, the explanation will focus on the differences from Embodiment 1.

[0032] Embodiment 2. Figure 4 is a diagram illustrating the configuration of the receiving device 200 according to Embodiment 2. The receiving device 200 comprises a housing 30 and a circuit board 260 housed in the housing 30. A first light-receiving element 10 and a second light-receiving element 20 are provided on the circuit board 260. The same light-receiving elements as in Embodiment 1 can be used as the first light-receiving element 10 and the second light-receiving element 20.

[0033] The substrate 260 is an electronic circuit board made of glass epoxy, alumina, or the like. The first light-receiving element 10 and the second light-receiving element 20 are mounted on the substrate 260 with their light-receiving surfaces facing the same direction.

[0034] Next, the arrangement of each component in the housing 30 will be described. Assume that the substrate 260 is positioned so that the second photodetector 20 can receive the THz wave 51. The receiving device 200 configures the first photodetector 10 to receive the THz wave 51 by moving the optical axis L1 of the substrate 260 or the THz wave 51 as predetermined from this positioned state. In other words, the positions of each component are predetermined so that the first photodetector 10 can receive the THz wave 51 by moving the optical axis L1 of the substrate 260 or the THz wave 51 as predetermined after aligning the second photodetector 20 so that its optical axis is at a desired pixel such as the central pixel of the second photodetector 20. For example, in this embodiment, the first light-receiving element 10 is configured to receive THz waves 51 by moving the substrate 260 by a predetermined distance in the direction D1 where the first light-receiving element 10 and the second light-receiving element 20 are aligned, starting from the position after alignment. At this time, for example, the position of the housing 30 is fixed, and the substrate 260 moves relative to the housing 30.

[0035] Next, the adjustment method for the receiving device 200 will be explained using Figure 3. First, the second photodetector 20 receives the THz wave 51 (Step 1). This provides an image showing the intensity distribution of the THz wave 51 using multiple pixels 23. In other words, the direction of the THz light source 50 can be detected by the intensity of the image (Step 2). Next, the housing 30 is positioned to match the direction detected in Step 2, so that the optical axis aligns with a desired pixel, such as the central pixel of the second photodetector 20 (Step 3). In other words, the housing 30 is moved to align the optical axis L1 of the THz wave 51 based on the intensity of the signal obtained by receiving the THz wave 51 with the second photodetector 20.

[0036] If alignment is complete (Yes in Step 4), the first photodetector 10 receives the THz wave 51 by moving the optical axis L1 of the substrate 260 or the THz wave 51 as predetermined (Step 5). Specifically, the first photodetector 10 is irradiated with the THz wave 51 by moving the substrate 260 by a predetermined distance in the direction D1 where the first photodetector 10 and the second photodetector 20 are aligned. The distance to which the substrate 260 is moved is assumed to be predetermined and known. If the center of the first photodetector 10 and the optical axis L1 are not aligned in Step 4, the process returns to Step 1.

[0037] In this embodiment as well, optical axis alignment can be performed with a simple configuration using only THz light, without using pilot light such as laser light. Therefore, the same effects as in Embodiment 1 can be obtained. Furthermore, by integrally configuring the first photodetector 10 and the second photodetector 20 on the substrate 260 and moving the substrate 260 as predetermined after alignment, the first photodetector 10 can receive the THz wave 51. Therefore, the THz wave 51 incident on the receiving device 200 can be configured to be received by the first photodetector 10 or the second photodetector 20 without the need for a mirror. Thus, a mirror is unnecessary, and the receiving device 200 can be constructed at an even lower cost.

[0038] Embodiment 3. Figure 5 is a diagram illustrating the configuration of the receiving device 300 according to Embodiment 3. The receiving device 300 of this embodiment differs from the receiving device 200 of Embodiment 3 in that a direction adjustment mirror 345 is provided inside the housing 30. The direction adjustment mirror 345 is, for example, a three-axis movable mirror that allows for fine positioning. The direction adjustment mirror 345 reflects the THz wave 51 incident on the receiving device 300 and receives the light with the first light receiving element 10 or the second light receiving element 20.

[0039] Next, the adjustment method for the receiving device 300 will be explained using Figure 3. First, the second photodetector 20 receives the THz wave 51 (Step 1). At this time, the THz wave 51 is reflected by the direction adjustment mirror 345 and incident on the second photodetector. As a result, an image showing the intensity distribution of the THz wave 51 is obtained by multiple pixels 23. In other words, the direction of the THz light source 50 can be detected by the intensity of the image (Step 2). Next, based on the intensity of the signal obtained by receiving the THz wave 51 with the second photodetector 20, the direction adjustment mirror 345 is moved to align the optical axis L1 of the THz wave 51 (Step 3). In this embodiment, the optical axis L1 is aligned by moving the direction adjustment mirror 345 without changing the position of the housing 30.

[0040] If alignment is complete (Yes in Step 4), the substrate 260 is moved by a predetermined distance in the direction D1 where the first photodetector 10 and the second photodetector 20 are aligned, thereby irradiating the first photodetector 10 with a THz wave 51 (Step 5). If the center of the first photodetector 10 and the optical axis L1 are not aligned in Step 4, the process returns to Step 1.

[0041] In this embodiment, the optical axis L1 can be aligned while the position of the housing 30 remains fixed.

[0042] Alternatively, in step 5, the THz wave 51 may be irradiated onto the first photodetector 10 by moving the direction adjustment mirror 345 as predetermined, without moving the substrate 260. In other words, after alignment, the THz wave 51 is received by the first photodetector 10 by moving the direction adjustment mirror 345 to move the optical axis L1 as predetermined. In this case, alignment of the optical axis L1 and irradiation of the first photodetector 10 with the THz wave 51 can be achieved by adjusting only the direction adjustment mirror 345. It is assumed that the method of moving the direction adjustment mirror 345 after alignment so that the THz wave 51 is irradiated onto the first photodetector 10 is known in advance.

[0043] The technical features described in each embodiment may be used in combination as appropriate. [Explanation of symbols]

[0044] 10 First photodetector, 20 Second photodetector, 21 Ceramic substrate, 22 Imaging chip, 23 Pixel, 24 Window chip, 25 Vacuum sealed area, 30 Housing, 40 Mirror, 50 THz light source, 51 THz wave, 100 Receiver, 200 Receiver, 260 Substrate, 300 Receiver, 345 Directional adjustment mirror

Claims

1. The casing and Inside the housing, a first photodetector is provided on the optical axis of terahertz waves incident from outside the housing, A mirror is provided inside the housing on the optical axis and configured to reflect the terahertz waves, A second photodetector having multiple pixels and configured to receive the terahertz waves reflected by the mirror inside the housing, Equipped with, The second light-receiving element has more pixels than the first light-receiving element. With the housing positioned so that the second photodetector can receive the terahertz waves reflected by the mirror, the first photodetector, the second photodetector, and the mirror are arranged in the housing such that the terahertz waves obtained by removing the mirror, or the terahertz waves transmitted through the mirror, are received by the first photodetector. The receiving device is characterized in that the mirror is a movable mirror configured to achieve both a closed state that reflects the terahertz waves and an open state that transmits the terahertz waves.

2. The receiving device according to claim 1, characterized in that the first light-receiving element has a faster response speed than the second light-receiving element.

3. The receiving device according to claim 1 or 2, characterized in that the first light-receiving element has higher sensitivity than the second light-receiving element.

4. The receiving device according to claim 1 or 2, characterized in that the first light-receiving element has less noise than the second light-receiving element.

5. The receiving device according to claim 1 or 2, characterized in that the second light-receiving element is a thermal image sensor.

6. circuit board and A first light-receiving element provided on the substrate, A second light-receiving element having multiple pixels and provided on the substrate, Equipped with, The second light-receiving element has more pixels than the first light-receiving element. A receiving device characterized in that, from a state in which the substrate is positioned so that the second photodetector can receive terahertz waves, the first photodetector is configured to receive the terahertz waves by moving the substrate or the optical axis of the terahertz waves in a predetermined manner.

7. The receiving device according to claim 6, characterized in that the first light-receiving element has a faster response speed than the second light-receiving element.

8. The receiving device according to claim 6 or 7, characterized in that the first light-receiving element has higher sensitivity than the second light-receiving element.

9. The receiving device according to claim 6 or 7, characterized in that the first light-receiving element has less noise than the second light-receiving element.

10. The receiving device according to claim 6 or 7, characterized in that the second light-receiving element is a thermal image sensor.

11. The receiving device according to claim 6 or 7, characterized in that the first light-receiving element is configured to receive the terahertz waves by moving the substrate by a predetermined distance in the direction in which the first light-receiving element and the second light-receiving element are aligned, starting from a state in which the substrate is positioned so that the second light-receiving element can receive the terahertz waves.

12. The receiving device according to claim 11, characterized in that the terahertz waves incident on the receiving device are received by the first photodetector or the second photodetector without the need for a mirror.

13. The receiving device according to claim 6 or 7, further comprising a mirror that reflects the terahertz waves incident on the receiving device and receives them with the first or second light-receiving element.

14. A terahertz wave is irradiated from outside a housing that houses a first light-receiving element, a second light-receiving element having multiple pixels, and a mirror, causing the terahertz wave to enter the mirror, and the terahertz wave reflected by the mirror is received by the second light-receiving element. Based on the intensity of the signal obtained by receiving the terahertz wave with the second photodetector, the housing is moved to perform positioning. In the state where the alignment is performed, the terahertz wave obtained by removing the mirror, or the terahertz wave transmitted through the mirror, is made to be received by the first light-receiving element. A method for adjusting a receiving device, characterized in that the second light-receiving element has more pixels than the first light-receiving element.

15. A substrate is provided with a first light-receiving element and a second light-receiving element having multiple pixels, and the second light-receiving element is made to receive terahertz waves. Based on the intensity of the signal obtained by receiving the terahertz wave with the second photodetector, the optical axis of the terahertz wave is aligned. After the alignment, the first light-receiving element receives the terahertz wave by moving the substrate or the optical axis of the terahertz wave as predetermined. A method for adjusting a receiving device, characterized in that the second light-receiving element has more pixels than the first light-receiving element.

Images