Measurement device

Abstract

A measurement device according to the present invention comprises: a light source that emits light; an interference optical system that splits the light emitted by the light source into reference light and illumination light for illuminating an object, and that generates interference light by causing the reference light and reflected light, which is produced by the illumination light being reflected by the object, to interfere with each other; an output fiber that is connected to the interference optical system and guides the illumination light; an optical element that is connected to the output fiber and emits the illumination light; a first housing that accommodates the light source and the interference optical system; and a second housing that accommodates the first housing, wherein the output fiber is directly brought out from the first housing.

Description

Measuring equipment

[0001] The present disclosure relates to a measurement device.

[0002] Conventionally, there exists LiDAR (Light Detection and Ranging) technology, which generates measurement data related to the distance and / or velocity of an object by illuminating the object with light and detecting the light reflected from the object. A typical example of a measurement device using LiDAR technology includes a light source, a photodetector, and a processing circuit. The light source emits light to illuminate the object. The photodetector detects the wave reflected from the object and outputs a signal corresponding to the time delay of the reflected wave. The processing circuit generates measurement data related to the distance and velocity of the object based on the signal output from the photodetector, for example, using FMCW (Frequency Modulated Continuous Wave) technology. Patent Documents 1 and 2, and Non-Patent Document 1, disclose examples of measurement devices using FMCW technology.

[0003] Japanese Patent No. 6274368 JP 2019-45200 A

[0004] Christopher VP et. al., OFC2016, W4E.3

[0005] The present disclosure provides a measurement device that emits irradiation light to illuminate an object to the outside, and that can reduce the possibility of unintended light leaking to the outside.

[0006] A measurement device according to one aspect of the present disclosure includes a light source that emits light, an interference optical system that separates the light emitted from the light source into reference light and illumination light for illuminating an object, the interference optical system causing reflected light generated when the illumination light is reflected by the object to interfere with the reference light to generate interference light, an output fiber connected to the interference optical system and guiding the illumination light, an optical element connected to the output fiber and emitting the illumination light, a first housing that houses the light source and the interference optical system, and a second housing that houses the first housing, and the output fiber is pulled out directly from the first housing.

[0007] A general or specific aspect of the present disclosure may be realized as a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium such as a computer-readable recording disk, or as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium. The computer-readable recording medium may include a non-volatile recording medium such as a CD-ROM (Compact Disc-Read Only Memory). An apparatus may be composed of one or more devices. When an apparatus is composed of two or more devices, the two or more devices may be located in a single device or may be located separately in two or more separate devices. In this specification and claims, the term "apparatus" may refer not only to a single device but also to a system consisting of multiple devices.

[0008] According to the technology of the present disclosure, it is possible to realize a measurement device that emits irradiation light to illuminate an object to the outside, and that can reduce the possibility of unintended light leaking to the outside.

[0009] FIG. 1 is a block diagram schematically illustrating the configuration of a measurement apparatus according to a first exemplary embodiment of the present disclosure. FIG. 2 is a diagram schematically illustrating the temporal changes in the frequencies of reference light and reflected light when an object is stationary. FIG. 3 is a flowchart roughly illustrating an example of a measurement operation performed by a processing circuit. FIG. 4A is a diagram for explaining multiple light flows occurring within the measurement apparatus shown in FIG. 1. FIG. 4B is a diagram for explaining the optical path lengths of multiple light flows occurring within the measurement apparatus shown in FIG. 1. FIG. 5 is a block diagram schematically illustrating the configuration of a measurement apparatus according to a comparative example. FIG. 6A is a diagram for explaining multiple light flows occurring within the measurement apparatus shown in FIG. 5. FIG. 6B is a diagram for explaining the optical path lengths of multiple light flows occurring within the measurement apparatus shown in FIG. 5. FIG. 7A is a diagram schematically illustrating an example of the spectrum of a detection signal according to the first exemplary embodiment. FIG. 7B is a diagram schematically illustrating an example of the spectrum of a detection signal according to a comparative example. FIG. 8 is a block diagram schematically illustrating the configuration of a measurement apparatus according to a second exemplary embodiment of the present disclosure. FIG. 9 is a block diagram schematically illustrating the configuration of a measurement apparatus according to a third exemplary embodiment of the present disclosure. Fig. 10 is a block diagram schematically showing the configuration of a measurement apparatus according to exemplary embodiment 4 of the present disclosure. Fig. 11 is a block diagram schematically showing the configuration of a measurement apparatus according to exemplary embodiment 5 of the present disclosure. Fig. 12 is a block diagram schematically showing the configuration of a measurement apparatus according to exemplary embodiment 6 of the present disclosure. Fig. 13 is a block diagram schematically showing the configuration of a measurement apparatus according to exemplary embodiment 7 of the present disclosure.

[0010] In the present disclosure, all or part of a circuit, unit, device, component, or part, or all or part of a functional block in a block diagram, may be implemented by one or more electronic circuits, including, for example, a semiconductor device, a semiconductor integrated circuit (IC), or an LSI (large scale integration). The LSI or IC may be integrated on a single chip or may be configured by combining multiple chips. For example, functional blocks other than memory elements may be integrated on a single chip. While the terms LSI and IC are used here, the term may be changed depending on the degree of integration, and may be referred to as a system LSI, a VLSI (very large scale integration), or an ULSI (ultra large scale integration). A Field Programmable Gate Array (FPGA), which is programmed after the LSI is manufactured, or a reconfigurable logic device, which can reconfigure the connection relationships within the LSI or set up circuit sections within the LSI, can also be used for the same purpose.

[0011] Furthermore, all or part of the functions or operations of a circuit, unit, device, component, or section can be implemented by software processing. In this case, the software is recorded on one or more non-transitory recording media such as ROMs, optical disks, hard disk drives, etc., and when the software is executed by a processor, the functions specified in the software are executed by the processor and peripheral devices. A system or device may include one or more non-transitory recording media on which the software is recorded, a processor, and required hardware devices, such as interfaces.

[0012] In this disclosure, "light" refers to electromagnetic waves including not only visible light (wavelength of about 400 nm to about 700 nm), but also ultraviolet light (wavelength of about 10 nm to about 400 nm) and infrared light (wavelength of about 700 nm to about 1 mm). In this specification, ultraviolet light is also referred to as "ultraviolet light," and infrared light is also referred to as "infrared light."

[0013] Exemplary embodiments of the present disclosure will be described below. Note that the embodiments described below are all comprehensive or specific examples. The numerical values, shapes, components, component placement and connection configurations, steps, and step order shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components that are not recited in the independent claims that represent the highest concepts will be described as optional components. Furthermore, each figure is a schematic diagram and is not necessarily an exact illustration. Furthermore, in each figure, substantially identical components are assigned the same reference numerals, and duplicated descriptions may be omitted or simplified.

[0014] First, the findings that form the basis of this disclosure will be explained. Patent Document 1 discloses a laser radar device that measures the distance from the device to an object by irradiating the object with light and receiving the reflected light generated by the irradiation. Patent Document 2 discloses a distance measuring device that uses FMCW technology to accurately measure the distance from the device to an object by removing the effects of nonlinear chirp of the laser light. Non-Patent Document 1 discloses a distance measuring device that uses FMCW technology, which enables the device to be miniaturized by configuring the optical system on-chip.

[0015] In recent years, FMCW-LiDAR technology has been developed, which combines a wide dynamic range with high resolution for distance, is less susceptible to external disturbances, and can detect the speed of fast-moving objects. By using light instead of millimeter waves, the diameter of the light spot illuminating the object can be made relatively small, making it possible to obtain more accurate measurement data of the object.

[0016] A measurement device using FMCW-LiDAR technology includes a light source and an interference optical system. The interference optical system separates laser light emitted from the light source into reference light and illumination light, and generates interference light by superimposing the reference light on the reflected light generated when an object is illuminated with the illumination light. Measurement data of the object can be obtained by detecting the interference light with a photodetector.

[0017] The intensity of the laser light emitted from the measuring device to the outside is classified into classes according to, for example, JIS (Japanese Industrial Standards) C6802 "Safety Standards for Laser Products." From the viewpoint of eye safety, i.e., eye safety, it is desirable that the intensity of the laser light emitted to the outside meets Class 1.

[0018] Even if the intensity of the laser light emitted to the outside satisfies Class 1, there are cases where laser light of an intensity exceeding Class 1 is emitted from the laser light source inside the measurement device. In this case, from the viewpoint of eye safety, it is desirable that unintended light from the light source and / or interference optical system does not leak outside the measurement device. Even if laser light of an intensity that always satisfies Class 1 is emitted from the laser light source inside the measurement device, if unintended light leaks outside the measurement device, there is a possibility that accurate measurement data of the object cannot be obtained due to reflected light generated when the leaked light irradiates the object.

[0019] In light of the above, it is desirable to reduce the possibility of unintended light leaking to the outside from a measurement device that emits illumination light to illuminate an object. The inventor has conceived a measurement device according to an embodiment of the present disclosure that can reduce such possibility. A measurement device according to this embodiment that uses FMCW-LiDAR technology includes a light source, an interference optical system, a first housing that houses the light source and the interference optical system, and a second housing that houses the first housing. The measurement device according to this embodiment can reduce the possibility of unintended light from the light source and the interference optical system leaking to the outside of the measurement device compared to a configuration that does not include a first housing that houses the light source and the interference optical system. A measurement device according to an embodiment of the present disclosure will be described below.

[0020] A measurement device according to a first aspect of the present invention includes a light source that emits light, an interference optical system that separates the light emitted from the light source into reference light and illumination light for illuminating an object, the interference optical system causing reflected light generated when the illumination light is reflected from the object to interfere with the reference light to generate interference light, an output fiber connected to the interference optical system and guiding the illumination light, an optical element connected to the output fiber and emitting the illumination light, a first housing that houses the light source and the interference optical system, and a second housing that houses the first housing. The output fiber is directly drawn out from the first housing.

[0021] In this measurement device, the possibility of unintended light leakage to the outside can be reduced. Furthermore, since the output fiber is directly drawn out from the first housing, noise in the spectrum of the detection signal can be reduced.

[0022] A measurement device according to a second aspect of the present invention is the measurement device according to the first aspect of the present invention, wherein the output fiber is drawn out from the first housing and the second housing, and the optical element is disposed outside the second housing.

[0023] In this measurement device, even if the optical element is disposed outside the second housing, noise can be reduced in the spectrum of the detection signal.

[0024] A third aspect of the present invention relates to the measurement device of the first aspect, wherein the output fiber is drawn out from the first housing, the optical element is disposed outside the first housing and inside the second housing, and the second housing includes a light-transmitting window that transmits the irradiation light.

[0025] In this measurement device, even if the optical element is disposed outside the first housing and inside the second housing, noise can be reduced in the spectrum of the detection signal.

[0026] A measurement apparatus according to a fourth item is the measurement apparatus according to any one of the first to third items, wherein the optical element emits the irradiation light and receives the reflected light. The interference optical system includes a first optical splitter, a second optical splitter, and a circulator or a third optical splitter. The first optical splitter separates the reference light and the irradiation light and outputs them, inputs the output reference light to the second optical splitter, and inputs the output irradiation light to the circulator or the third optical splitter. The circulator or the third optical splitter outputs the irradiation light from the first optical splitter and inputs it to the optical element, and outputs the reflected light from the optical element and inputs it to the second optical splitter. The second optical splitter generates the interference light by causing the reflected light from the circulator or the third optical splitter to interfere with the reference light from the first optical splitter.

[0027] In this measurement device, interference light can be generated by using a first optical splitter, a second optical splitter, and a circulator, or by using a first optical splitter, a second optical splitter, and a third optical splitter.

[0028] The measurement apparatus according to the fifth item is the measurement apparatus according to the fourth item, wherein the optical path length of a first path from the first optical splitter to a photodetector that detects the interference light is d １ , the optical path length of the second path from the second optical splitter to the optical element is d ２ , the optical path length of the third path from the optical element to the photodetector is d ３ The optical path length of a fourth path from the first optical splitter to the photodetector via the noise optical path of the circulator or the third optical splitter is d ４ When |d ２ +d ３ -d １ |≦|d ４ -d １ The relationship is satisfied.

[0029] This measurement device can accurately obtain measurement data of an object without narrowing the distance range in which distance and / or velocity of the object can be measured.

[0030] The measurement device according to the sixth item is the measurement device according to any one of the first to fifth items, further comprising a signal fiber that guides the interference light from the interference optical system, and a photodetector connected to the signal fiber that detects the interference light.

[0031] In this measurement device, the interference light can be detected by the photodetector.

[0032] A seventh aspect of the present invention relates to the measurement device of the sixth aspect, wherein the photodetector is disposed outside the first housing and inside the second housing.

[0033] In this measurement device, the photodetector is disposed outside the first housing, making maintenance of the photodetector easy.

[0034] The measuring device according to an eighth aspect is the measuring device according to the seventh aspect, wherein the signal fiber includes two connectors and a receptacle for connecting the two connectors, and the receptacle is attached to the first housing.

[0035] In this measuring device, the photodetector can be attached and detached.

[0036] A measurement device according to a ninth item is the measurement device according to the sixth item, wherein the photodetector is disposed inside the first housing.

[0037] In this measurement device, the signal fiber connecting the photodetector and the interference optical system does not need to be equipped with a connector and a receptacle, so the components of the measurement device can be simplified and the cost of parts can be kept low.

[0038] A measurement device according to a tenth aspect is the measurement device according to the ninth aspect, wherein the interference optical system and the photodetector are configured on-chip.

[0039] This measurement device allows for miniaturization of the measurement device.

[0040] The measuring device according to the eleventh item is the measuring device according to the sixth item, further comprising a processing circuit that controls the operation of the light source and the operation of the photodetector and processes the signal output from the photodetector, the processing circuit being located outside the first housing and inside the second housing.

[0041] In this measuring device, heat generated from the processing circuit can be effectively dissipated to the outside via the second housing.

[0042] A measurement device according to a twelfth item is the measurement device according to the eleventh item, wherein the light source is capable of changing the frequency of the light over time.

[0043] This measurement device uses FMCW-LiDAR technology to enable distance and / or velocity measurement of objects.

[0044] The measuring device according to the thirteenth item comprises a light source that emits light, an interference optical system that separates the light emitted from the light source into reference light and illumination light for illuminating an object, the interference optical system causing reflected light generated when the illumination light is reflected by the object to interfere with the reference light to generate interference light, an output fiber connected to the interference optical system and guiding the illumination light, an optical element connected to the output fiber and emitting the illumination light, a photodetector that detects the interference light, a first housing that houses the light source and the interference optical system, a second housing that houses the first housing, and a processing circuit that controls the operation of the light source and the operation of the photodetector and processes a signal output from the photodetector, the processing circuit being arranged outside the first housing and inside the second housing.

[0045] This measurement device can reduce the possibility of unintended light leakage to the outside, and can also effectively dissipate heat generated by the processing circuit to the outside via the second housing.

[0046] A measuring device according to a fourteenth item is the measuring device according to the thirteenth item, wherein the output fiber is a single continuous optical fiber.

[0047] In this measurement device, a single continuous optical fiber can reduce noise in the spectrum of the detection signal.

[0048] A measurement device according to a fifteenth item is the measurement device according to the thirteenth or fourteenth item, wherein the light source is capable of changing the frequency of the light over time.

[0049] This measurement device uses FMCW-LiDAR technology to enable distance and / or velocity measurement of objects.

[0050] The measurement device according to the sixteenth item includes a light source that emits light, an interference optical system that separates the light emitted from the light source into reference light and illumination light for illuminating an object, the interference optical system causing reflected light generated when the illumination light is reflected by the object to interfere with the reference light to generate interference light, an output fiber connected to the interference optical system and guiding the illumination light, an optical element connected to the output fiber and emitting the illumination light, a first housing that accommodates the light source and the interference optical system, and a second housing that accommodates the first housing. The output fiber is disposed inside the first housing. The optical element is disposed inside the first housing. The first housing includes a first optically transmissive window that transmits the illumination light. The second housing includes a second optically transmissive window that transmits the illumination light.

[0051] This measurement device reduces the possibility of unintended light leakage to the outside. Furthermore, because it does not require a fiber extraction section for extracting the output fiber, the components of the measurement device can be simplified and the cost of parts can be kept low.

[0052] First Embodiment [Measurement Apparatus] First, an example configuration of a measurement apparatus according to a first embodiment of the present disclosure will be described with reference to Fig. 1. Fig. 1 is a block diagram schematically illustrating the configuration of a measurement apparatus according to the first exemplary embodiment of the present disclosure. Fig. 1 illustrates a person as an object 10 to be measured. The object 10 may be any object other than a person, such as a vehicle or a building.

[0053] The measurement device 100A shown in FIG. 1 includes a light source 20, an interference optical system 30, an optical element 40, an output fiber 42, a photodetector 50, two signal fibers 52, a processing circuit 60, and a memory 62. The measurement device 100A further includes a first housing 70a that houses the light source 20, the interference optical system 30, the photodetector 50, the processing circuit 60, and the memory 62, and a second housing 70b that houses the first housing 70a. The thick lines in FIG. 1 represent optical fibers connecting two components to each other. The solid lines with arrows in FIG. 1 represent signal transmission and reception. The dashed lines with arrows in FIG. 1 represent the flow of light. Some components of the measurement device 100A according to the first embodiment may be manufactured and / or sold separately from the remaining components. The some components may be, for example, at least one of the photodetector 50, the processing circuit 60, and the memory 62.

[0054] The measurement device 100A according to the first embodiment emits illumination light 20L2 for irradiating the object 10 and receives reflected light 20L3 resulting from irradiating the object 10 with the illumination light 20L2, thereby making it possible to acquire measurement data relating to the distance and / or speed of the object 10. Compared to a configuration that does not include the first housing 70a that houses the light source 20 and the interference optical system 30, the measurement device 100A according to the first embodiment can reduce the possibility that unintended light from the light source 20 and the interference optical system 30 will leak outside the measurement device 100A.

[0055] The components of the measuring device 100A will be described below.

[0056] <Light Source 20> The light source 20 emits laser light 20L0. The light source 20 is capable of changing the frequency of the laser light 20L0. The frequency can be changed over time in a constant time period, for example, in a triangular or sawtooth wave shape. The time period can be, for example, 1 μsec or more and 10 ms or less. The time period may vary. The frequency change width can be, for example, 100 MHz or more and 1 THz or less.

[0057] The wavelength of the laser light 20L0 may be, for example, within the wavelength range of near-infrared light, from 700 nm to 2000 nm. Sunlight contains near-infrared light and visible light, and the amount of near-infrared light is less than the amount of visible light. Therefore, using near-infrared light as the laser light 20L0 can reduce the influence of sunlight as noise. The wavelength of the laser light 20L0 does not necessarily have to be within the wavelength range of near-infrared light. The wavelength of the laser light 20L0 may be within the wavelength range of visible light, from 400 nm to 700 nm, or may be within the wavelength range of ultraviolet light.

[0058] The light source 20 may include, for example, a distributed feedback (DFB) laser diode or an external cavity (EC) laser diode. These laser diodes are inexpensive and compact, capable of single-mode oscillation, and capable of modulating the frequency of the laser light 20L0 according to the amount of current applied. If a laser diode capable of emitting high-intensity laser light exceeding Class 1 is used as the light source 20, the frequency of the laser light 20L0 can be stably modulated. However, the intensity of the laser light 20L0 emitted from the light source 20 is adjusted so that the intensity of the laser light emitted to the outside satisfies Class 1.

[0059] The light source 20 is connected to the first optical splitter 32a. An attenuator for adjusting the intensity of the laser light 20L0 may be disposed between the light source 20 and the first optical splitter 32a.

[0060] <Interference Optical System 30> The interference optical system 30 includes a first optical splitter 32a, a second optical splitter 32b, and an optical circulator 34. The first optical splitter 32a separates the laser beam 20L0 emitted from the light source 20 into a reference beam 20L1 and an irradiation beam 20L2 for irradiating the object 10, and outputs the separated beams. The intensity of the reference beam 20L1 may be, for example, 1% to 10% of the intensity of the laser beam 20L0 input to the first optical splitter 32a. The first optical splitter 32a inputs the output reference beam 20L1 to the second optical splitter 32b and the output irradiation beam 20L2 to the optical circulator 34. The first optical splitter 32a is connected to the second optical splitter 32b and the optical circulator 34.

[0061] The optical circulator 34 outputs the illumination light 20L2 from the first optical splitter 32a and inputs the illumination light 20L2 to the optical element 40 via an output fiber 42. The optical circulator 34 further outputs reflected light 20L3 generated when the illumination light 20L2 is reflected by the object 10 and inputs the reflected light 20L3 to the second optical splitter 32b. The optical circulator 34 is connected to the first optical splitter 32a, the second optical splitter 32b, and the optical element 40.

[0062] The second optical splitter 32b inputs interference light 20L4, which is obtained by superimposing and interfering the reference light 20L1 and the reflected light 20L3, to the photodetector 50 via two signal fibers 52. The second optical splitter 32b is connected to the first optical splitter 32a, the optical circulator 34, and the photodetector 50.

[0063] <Optical Element 40> The optical element 40 outputs the irradiation light 20L2 from the optical circulator 34 to the outside via the output fiber 42. The optical element 40 further receives the reflected light 20L3 and inputs the reflected light 20L3 to the optical circulator 34 via the output fiber 42. The optical element 40 may be, for example, a collimator lens that collimates the irradiation light 20L2. In this specification, the term "collimate" refers not only to the case where the irradiation light 20L2 is made into parallel light, but also to the case where the spread of the irradiation light 20L2 is reduced.

[0064] The optical element 40 may be a condenser lens that focuses the illumination light 20L2, or a diffusing lens that diffuses the illumination light 20L2. The optical element 40 may be a diffraction grating that outputs the illumination light 20L2 to the outside as zeroth-order diffracted light and / or ±Nth-order diffracted light (N is a natural number). By measuring the distance and / or speed of the object 10 using multiple diffracted lights emitted in different directions, the angular range for measuring the distance and / or speed of the object 10 can be expanded. The optical element 40 may be configured by combining at least two of a collimator lens, a condenser lens, a diffusing lens, and a diffraction grating.

[0065] The measurement apparatus 100A may further include an optical deflector that changes the direction of the illumination light 20L2 emitted from the optical element 40. The optical deflector may be, for example, one selected from the group consisting of a galvanometer scanner, a polygon mirror, a MEMS scanner, a phase modulation scanner, a refractive index modulation scanner, and a wavelength modulation scanner.

[0066] In the measurement apparatus 100A, the path of the illumination light 20L2 from the interference optical system 30 to the object 10 overlaps with the path of the reflected light 20L3 from the object 10 to the interference optical system 30. By employing such a coaxial optical system, the configuration of the measurement apparatus 100A can be simplified and stable measurements can be achieved.

[0067] <Output Fiber 42> The output fiber 42 is a single continuous optical fiber, and guides the irradiation light 20L2 from the optical circulator 34 and the reflected light 20L3 from the optical element 40. The output fiber 42 is connected to the interference optical system 30, more specifically, the optical circulator 34, and the optical element 40 is connected to the output fiber 42.

[0068] The output fiber 42 has a connector 42a at one of two ends located opposite each other. The optical element 40 has a receptacle 40a for connecting the connector 42a of the output fiber 42. The optical element 40 and the output fiber 42 are detachable, which facilitates manufacturing and maintenance of the measurement device 100A. Alternatively, the output fiber 42 may be directly connected to the optical element 40, for example, by a coupling lens. A type in which the output fiber 42 is connected to the optical element 40 in such a manner is called a pigtail type.

[0069] <Photodetector 50> The photodetector 50 detects the interference light 20L4 from the second optical splitter 32b via two signal fibers 52 and outputs a signal corresponding to the intensity of the interference light 20L4. The photodetector 50 includes one or more photodiodes. The photodiodes output signals corresponding to the intensity of the interference light 20L4. The photodetector 50 may include a preamplifier that amplifies the signal.

[0070] 1, the photodetector 50 is a balanced photodiode with two ports. The photodetector 50 detects the difference between the light input from the two ports, and therefore can reduce common-mode noise. Note that the photodetector 50 may also be a photodiode with one port other than a balanced photodiode.

[0071] <Signal Fibers 52> The two signal fibers 52 equally separate and guide the interference light 20L4 from the second optical splitter 32b. Each signal fiber 52 is connected to the second optical splitter 32b, and the photodetector 50 is connected to the two signal fibers 52. Each signal fiber 52 has a connector 52a at one of two ends located opposite each other. The photodetector 50 has two receptacles 50a for connecting the connectors 52a of the two signal fibers 52, respectively.

[0072] Each signal fiber 52 has two connectors 52b and a receptacle 52c between the two ends. The receptacle 52c is located between the two connectors 52b and serves to connect the two connectors 52b. The receptacle 52c is attached to the first housing 70a. The two connectors 52b and the receptacle 52c allow the portion of each signal fiber 52 connected to the photodetector 50 and the portion connected to the second optical splitter 32b to be detachable. This simplifies the manufacture and maintenance of the measurement device 100A. Alternatively, each signal fiber 52 may be directly connected to the photodetector 50, for example, by a coupling lens. Like the output fiber 42, each signal fiber 52 may be a single continuous optical fiber. If the photodetector 50 is a photodiode with one port, the number of signal fibers 52 is one.

[0073] <Processing Circuit 60> The processing circuit 60 includes a control circuit 60a, a drive circuit 60b, and a signal processing circuit 60c. The control circuit 60a controls the operations of the drive circuit 60b, the signal processing circuit 60c, and the photodetector 50. In this specification, the operations of the control circuit 60a, the drive circuit 60b, and the signal processing circuit 60c may be described as the operation of the processing circuit 60. The drive circuit 60b drives the light source 20. It can also be said that the control circuit 60a controls the operation of the light source 20 via the drive circuit 60b.

[0074] The signal processing circuit 60c uses FMCW-LiDAR technology to process the signal output from the photodetector 50. Based on the signal, the processing circuit 60 generates and outputs measurement data related to the distance and / or speed of the object 10. Specifically, the signal processing circuit 60c performs a Fourier transform on the time waveform of the detection signal to generate data indicating its frequency spectrum, and generates and outputs measurement data based on the data.

[0075] The signal processing circuit 60c may input the output measurement data to a display (not shown), which may display information about the distance and / or speed of the object 10. Alternatively, the signal processing circuit 60c may input the output measurement data to another device, which may perform a specific operation based on the measurement data. The other device may be, for example, a vehicle or an industrial robot.

[0076] The operation of the processing circuit 60 will be described in detail below. Computer programs executed by the control circuit 60a and the signal processing circuit 60c are stored in a memory 62, such as a ROM or a RAM (Random Access Memory). Thus, the measurement device 100A includes a processing device including the processing circuit 60 and the memory 62. The processing circuit 60 and the memory 62 may be integrated on a single circuit board or provided on separate circuit boards. The control circuit 60a, the drive circuit 60b, and the signal processing circuit 60c included in the processing circuit 60 may be distributed across multiple circuits. The processing device, or a portion thereof, may be installed in a remote location away from the other components and control the operation of the light source 20 and the photodetector 50 via a wired or wireless communication network.

[0077] <First Housing 70a and Second Housing 70b> The first housing 70a houses the light source 20 and the interference optical system 30 for the following reasons. The light source 20 and the first optical splitter 32a are connected by an optical fiber. The same applies to the first optical splitter 32a and the second optical splitter 32b, the first optical splitter 32a and the optical circulator 34, and the second optical splitter 32b and the optical circulator 34. If the optical fiber connecting the two components is broken, for example, light may leak from the broken portion. As described above, from the viewpoint of stably modulating the frequency of the laser light 20L0, a laser diode capable of emitting high-intensity laser light may be used as the light source 20. If the light source 20 emits laser light with an intensity exceeding Class 1, it is undesirable from the viewpoint of eye safety if the laser light leaks outside the measurement device 100A from a broken portion of the optical fiber. Even if the light source 20 always emits laser light with an intensity that satisfies Class 1, if unintended light leaks to the outside, the object is irradiated with the leaked light and the resulting reflected light may prevent accurate acquisition of measurement data of the object. ｏｕｔ and the intensity of the irradiation light 20L2 output from the optical circulator 32a is I ｒａｄ１The light intensity lost due to loss and reflection in the optical element 40 is expressed as L ｅｌｅ If the loss of the optical fiber is negligibly small, then I ｏｕｔ I ｏｕｔ =I ｒａｄ１ -L ｅｌｅ Since a part of the optical path of the irradiation light 20L2 output from the optical circulator 32a exists outside the first housing 70a, I ｒａｄ１ It is desirable that the upper limit of the light intensity that satisfies Class 1 is I ｌｉｍｉｔ Then, I ｌｉｍｉｔ ≧I ｒａｄ１ =I ｏｕｔ +L ｅｌｅ Therefore, I ｏｕｔ I ｏｕｔ ≦I ｌｉｍｉｔ -L ｅｌｅ The strength is usually L ｅｌｅ I ｏｕｔ Therefore, the optical element 40 can emit the irradiation light 20L2 at an intensity close to the upper limit that satisfies Class 1.

[0078] The measurement device 100A according to the first embodiment can reduce the possibility that unintended light from the light source 20 and the interference optical system 30 will leak outside the measurement device 100A, compared to a configuration that does not include the first housing 70a that houses the light source 20 and the interference optical system 30. When the first housing 70a houses the light source 20 and the interference optical system 30 in a tightly sealed state, the possibility that unintended light will leak outside the measurement device 100A can be effectively reduced.

[0079] The first housing 70a and the second housing 70b each include a first fiber lead-out portion 72a and a second fiber lead-out portion 72b for leading out the output fiber 42. The continuous output fiber 42 is led out of the first housing 70a and the second housing 70b via the first fiber lead-out portion 72a and the second fiber lead-out portion 72b. The first fiber lead-out portion 72a and the second fiber lead-out portion 72b are configured to allow the continuous output fiber 42 to be led directly out of the first housing 70a and the second housing 70b, respectively. The first fiber lead-out portion 72a and the second fiber lead-out portion 72b do not include a connector or receptacle for detachably attaching the output fiber 42. Therefore, the output fiber 42 hardly reflects the irradiation light 20L2 when guiding the irradiation light 20L2. The effect of hardly reflecting the irradiation light 20L2 will be described later.

[0080] The fiber pull-out portions 72a, 72b may be, for example, rubber bushings. When a hole is drilled in the rubber bushing and the output fiber 42 is passed through the hole, the elasticity of the rubber fills the gap between the outer coating of the output fiber 42 and the hole in the rubber bushing. In addition to being rubber bushings, the fiber pull-out portions 72a, 72b may also be, for example, covers that close the gap between holes drilled in the housings 70a, 70b and the outer coating of the output fiber that has passed through the hole.

[0081] The optical element 40 is connected to the output fiber 42 drawn from the housings 70a, 70b via the fiber drawing sections 72a, 72b. Therefore, the optical element 40 is disposed outside the second housing 70b. With this configuration, the direction of the irradiation light 20L2 emitted from the optical element 40 can be easily adjusted according to the position of the object 10, independently of the installation direction of the measurement device 100A.

[0082] The first housing 70a further includes a wiring lead-out portion 74 for leading out wiring that transmits signals from the drive circuit 60b to the light source 20. The drive circuit 60b and the light source 20 are electrically connected by wiring. The wiring lead-out portion 74 may be, for example, an electrical connector. By drilling a hole in the first housing 70a and providing a cover that closes the gap between the hole and the electrical connector, the possibility of unintended light leakage can be reduced.

[0083] As described above, the first housing 70a can house the light source 20 and the interference optical system 30 in a sealed state with no gaps. Furthermore, the first housing 70a and the second housing 70b can extract the irradiation light 20L2 to the outside via the output fiber 42. In this way, it is possible to both block leakage light from the light source 20 and the interference optical system 30 and extract the irradiation light 20L2 to the outside. Because the output fiber 42 is an optical fiber that is directly drawn out from the first housing 70a and the second housing 70b, the irradiation light 20L2 is guided within the output fiber 42 with almost no reflection.

[0084] The photodetector 50 and the processing circuit 60 are disposed outside the first housing 70 a and inside the second housing 70 b. The photodetector 50 may include components that do not generate much heat, such as a photodiode and a preamplifier. In contrast, the processing circuit 60 may include a processing element that generates a relatively large amount of heat, such as a CPU or FPGA.

[0085] Unlike the measurement device 100A according to the first embodiment, in a configuration in which the processing circuit 60 is hermetically housed in the first housing 70a, heat generated by the processing circuit 60 cannot be effectively dissipated to the outside, which may cause the operation of the processing circuit 60 to become unstable. Furthermore, when the temperature inside the first housing 70a rises, the length of the optical fiber inside the first housing 70a fluctuates on the order of micrometers. As a result, depending on the distance range and distance resolution in which the distance and / or velocity of the object 10 can be measured, errors may occur in the measurement data of the object 10.

[0086] In contrast, in the measurement device 100A according to the first embodiment, the processing circuit 60 is disposed outside the first housing 70a, so that heat generated by the processing circuit 60 during operation can be effectively dissipated to the outside via the second housing 70b. The second housing 70b may be provided with a ventilation port or fan for heat dissipation. Because the heat generated by the processing circuit 60 can be effectively dissipated to the outside, the processing circuit 60 can operate more stably, and fluctuations in the length of the optical fiber within the first housing 70a can be suppressed, enabling accurate acquisition of measurement data of the object 10. Furthermore, because the photodetector 50 and the processing circuit 60 are disposed outside the first housing 70a, maintenance of the photodetector 50 and the processing circuit 60 is easy.

[0087] [FMCW-LiDAR Technology] Next, the FMCW-LiDAR technology will be briefly described with reference to Fig. 2. Details of the FMCW-LiDAR technology are disclosed in, for example, Non-Patent Document 1.

[0088] FIG. 2 is a diagram schematically illustrating the temporal changes in the frequencies of the reference light 20L1 and the reflected light 20L3 when the object 10 is stationary. The solid line represents the reference light 20L1, and the dashed line represents the reflected light 20L3. The frequency of the reference light 20L1 shown in FIG. 2 repeatedly changes over time in a triangular waveform. That is, the frequency of the reference light 20L1 alternates between up-chirp and down-chirp. The frequency increase during the up-chirp period and the frequency decrease during the down-chirp period are equal to each other. The frequency of the reflected light 20L3 is shifted in the positive direction along the time axis compared to the frequency of the reference light 20L1. The amount of time shift of the reflected light 20L3 is equal to the time it takes for the illumination light 20L2 to be emitted from the measurement device 100A to the outside, reflected by the object 10, and returned as the reflected light 20L3. As a result, the reference light 20L1 and the reflected light 20L3 are superimposed and interfere with each other to produce interference light 20L4, which has a frequency corresponding to the frequency difference between the frequency of the reflected light 20L3 and the frequency of the reference light 20L1. The double-headed arrow in FIG. 2 represents the frequency difference between the two. The photodetector 50 outputs a signal indicating the intensity of the interference light 20L4. This signal is called a beat signal. The frequency of the beat signal, i.e., the beat frequency, is equal to the frequency difference. The processing circuit 60 can generate measurement data related to the distance and / or velocity of the object 10 from the beat frequency.

[0089] When the object 10 is stationary, the beat frequency during the up-chirp period is equal to the beat frequency during the down-chirp period. If the increase or decrease in the frequency of light during the up-chirp period or the down-chirp period is Δf, the time required for the change in Δf is Δt, the speed of light is c, and the difference between the optical path length of the reference light 20L1 and the sum of the optical path lengths of the illumination light 20L2 and the reflected light 20L3 is 2d, then the beat frequency during the up-chirp period or the down-chirp period is ｂｅａｔ is expressed by the following equation (1).

[0090] The beat frequency f in equation (1) ｂｅａｔis obtained by multiplying the time rate of change of frequency Δf / Δt by the time (2d / c) it takes for the irradiated light 20L2 to be emitted from the measuring device 100A to the outside, reflected by the object 10, and returned as reflected light 20L3.

[0091] When the object 10 moves, the frequency of the reflected light 20L3 undergoes a Doppler shift in the positive or negative direction along the frequency axis compared to the frequency of the reference light 20L1. In this case, the beat frequency during the up-chirp period differs from the beat frequency during the down-chirp period. The processing circuit 60 can generate measurement data regarding the velocity and distance of the object 10 from the frequency difference and average of these beat frequencies, respectively.

[0092] [Measurement Operation Executed by Processing Circuitry 60] Next, an example of the measurement operation executed by the processing circuitry 60 in embodiment 1 will be described with reference to Fig. 3. Fig. 3 is a flowchart that schematically shows an example of the measurement operation executed by the processing circuitry 60. The processing circuitry 60 executes the operations of steps S101 to S103 shown in Fig. 3.

[0093] <Step S101> The processing circuit 60 causes the light source 20 to emit laser light 20L0 whose frequency varies over time. Specifically, the control circuit 60a causes the drive circuit 60b to drive the light source 20, causing the light source 20 to emit laser light 20L0 whose frequency varies over time.

[0094] <Step S102> The processing circuitry 60 causes the photodetector 50 to detect the interference light 20L4. The photodetector 50 outputs a signal corresponding to the intensity of the interference light 20L4. Specifically, the control circuit 60a causes the photodetector 50 to detect the interference light 20L4.

[0095] <Step S103> The processing circuit 60 generates measurement data related to the distance and / or speed of the object 10 based on the signal output from the photodetector 50. Specifically, the control circuit 60a causes the signal processing circuit 60c to generate measurement data based on the signal output from the photodetector 50.

[0096] The above-described operation of the processing circuit 60 enables the distance and / or velocity of the object 10 to be measured.

[0097] [Light Flow in Measurement Apparatus 100A] Next, multiple light flows occurring within the measurement apparatus 100A shown in FIG. 1 and their optical path lengths will be described with reference to FIGS. 4A and 4B. FIG. 4A is a diagram for explaining multiple light flows occurring within the measurement apparatus 100A shown in FIG. 1. For simplicity, FIG. 4A shows the signal fiber 52 connecting the second optical splitter 32b and the photodetector 50 as a single optical fiber. In other figures, the optical fiber connecting the two may also be shown as a single optical fiber. The dashed lines with arrows shown in FIG. 4A represent the light flows. As shown in FIG. 4A, multiple light flows α to δ occur within the measurement apparatus 100A.

[0098] The light flow α is the flow of the reference light 20L1 from the first optical splitter 32a to the photodetector 50. The light flow β is the flow of the illumination light 20L2 from the first optical splitter 32a to the object 10, and the flow of the reflected light 20L3 from the object 10 to the photodetector 50.

[0099] On the other hand, the light flows γ and δ cause noise in the detection signal. The light flow γ is the flow of a portion of the illumination light 20L2 from the first optical splitter 32a to the photodetector 50 after being reflected by the optical element 40. Such reflection occurs at the receptacle 40a of the optical element 40 shown in FIG. 1. The light flow δ is the flow of another portion of the illumination light 20L2 from the first optical splitter 32a to the photodetector 50 via a noise light path inside the optical circulator 34. The noise light path is considered to be the path through the optical circulator 34, or more specifically, the path along which leakage light of the illumination light 20L2 heading toward the optical element 40 in the optical circulator 34 travels while being multiple-scattered inside.

[0100] As described above, part of the irradiated light 20L2 is reflected by the optical element 40, and the other part is multiple-scattered inside the optical circulator 34, so it is the remaining part of the irradiated light 20L2 that is actually emitted to the outside from the optical element 40. However, in this specification, unless there is any misunderstanding, it will be stated that "the optical element 40 emits the irradiated light 20L2 to the outside."

[0101] 4B is a diagram for explaining the optical path lengths of the multiple light flows α to δ occurring in the measurement device 100A shown in FIG. The first optical path length of the first path from the first optical splitter 32a to the photodetector 50 is denoted by d. １ The second optical path length of the second path from the first optical splitter 32a to the optical element 40 is d ２ The third optical path length of the third path from the optical element 40 to the photodetector 50 is d ３ The optical path length of the fourth path from the first optical splitter 32a through the noise light path inside the interference optical system 30, more specifically, inside the optical circulator 34, to the photodetector 50 is defined as a fourth optical path length d ４ The round-trip distance between the optical element 40 and the object 10 is set to 2L. The distance L is the distance from the receptacle 40a of the optical element 40 shown in FIG. 1 to the point on the object 10 where the irradiation light 20L2 is irradiated. Therefore, when the object 10 contacts the optical element 40, the distance L corresponds to the length of the optical element 40. The optical path length of the light flow α is d １ , the optical path length of the light flow β is d ２ +d ３ +2L, the optical path length of the light flow γ is d ２ +d ３ , the optical path length of the light flow δ is d ４ is.

[0102] The frequency of the beat signal caused by the reflected light 20L3 reflected by the object 10 is expressed by the following equation (2). ２ +d ３ +2L-d １ | is the optical path length difference between the light flow β and the light flow α.

[0103] The frequency f of the beat signal caused by the light reflected by the optical element 40 in the irradiation light 20L2 ｏｐｔ is expressed by the following formula (3). ２ +d ３ -d １ | is the optical path length difference between the light flow γ and the light flow α.

[0104] The frequency f of the beat signal caused by the multiple scattered light generated inside the optical circulator 34ｃｉｒ is expressed by the following formula (4). ４ -d １ | is the optical path length difference between the light flow δ and the light flow α.

[0105] The influence of the optical path length of the paths of the light flows α to δ in the measurement device 100A on the distance range in which distance and / or velocity of the object 10 can be measured is explained in detail in Japanese Patent Application No. 2022-010910 (filing date: January 27, 2022). The entire disclosure of Japanese Patent Application No. 2022-010910 is incorporated herein by reference.

[0106] 5 to 6B, a problem that arises when an output fiber having a connector and a receptacle between two ends located on opposite sides is used, instead of the output fiber 42 that is directly drawn out from the first housing 70a and the second housing 70b, will be described using a measurement device according to a comparative example.

[0107] FIG. 5 is a block diagram schematically illustrating the configuration of a measurement device according to a comparative example. The measurement device 90 illustrated in FIG. 5 differs from the measurement device 100A illustrated in FIG. 1 in that the measurement device 90 includes an output fiber 43 illustrated in FIG. 5 instead of the output fiber 42 illustrated in FIG. 1. The output fiber 43 includes a first connector 43a at one of two opposite ends. The first connector 43a is connected to the receptacle 40a of the optical element 40. The output fiber 43 further includes two second connectors 43b and a first receptacle 43c between the two ends. The first receptacle 43c is located between the two second connectors 43b and is a component for connecting the two second connectors 43b. The first receptacle 43c is attached to the first housing 70a. The output fiber 43 further includes two third connectors 43d and a second receptacle 43e between the two ends. The second receptacle 43e is a component located between the two third connectors 43d and used to connect the two third connectors 43d. The second receptacle 43e is attached to the second housing 70b.

[0108] Of the output fiber 43, the portion connected to the optical element 40, the portion connected to the optical circulator 34, and the portion located between these two portions are detachable, which facilitates the manufacture and maintenance of the measurement device 90. On the other hand, because the output fiber 43 is not an optical fiber that is directly drawn out from the first housing 70a and the second housing 70b, reflection of the irradiation light 20L2 occurs at the first receptacle 43c and the second receptacle 43e when the irradiation light 20L2 is guided.

[0109] FIG. 6A is a diagram illustrating multiple light flows that occur within the measurement device 90 shown in FIG. 5. As shown in FIG. 6A, in addition to light flows α to δ, light flows γ' and γ'' that cause noise in the detection signal occur in the measurement device 90. As described above, the light flows γ and δ are caused by a part and another part of the illumination light 20L2, respectively. The light flow γ' is the flow of yet another part of the illumination light 20L2 from the first optical splitter 32a, reflected by the first receptacle 43c, and reaching the photodetector 50. The light flow γ'' is the flow of yet another part of the illumination light 20L2 from the first optical splitter 32a, reflected by the second receptacle 43e, and reaching the photodetector 50.

[0110] 6B is a diagram for explaining the optical path lengths of a plurality of light flows occurring within the measurement device 90 shown in FIG. The fifth optical path length of the fifth path from the first optical splitter 32a to the first receptacle 43c is denoted by d ２１ The sixth optical path length of the sixth path from the first receptacle 43c to the photodetector 50 is defined as d ３１ The seventh optical path length of the seventh path from the first optical splitter 32a to the second receptacle 43e is defined as d ２２ The eighth optical path length of the eighth path from the second receptacle 43e to the photodetector 50 is defined as d ３２ The optical path length of the light flow γ' is d ２１ +d ３１ , the optical path length of the light flow γ″ is d ２２ +d ３２ is.

[0111] The frequency f of the beat signal caused by the light reflected by the first receptacle 43c in the irradiated light 20L2 isｒ１ is expressed by the following formula (5). ２１ +d ３１ -d １ | is the optical path length difference between the light flow γ' and the light flow α.

[0112] The frequency f of the beat signal caused by the light reflected by the second receptacle 43e in the irradiated light 20L2 is ｒ２ is expressed by the following formula (6). ２２ +d ３２ -d １ | is the optical path length difference between the light flow γ″ and the light flow α.

[0113] In the measurement device 90 according to the comparative example, the first housing 70a can house the light source 20 and the interference optical system 30 in a tightly sealed state. Furthermore, the first housing 70a and the second housing 70b can extract the irradiation light 20L2 to the outside via the output fiber 43. In this way, it is possible to both block leakage light from the light source 20 and the interference optical system 30 and extract the irradiation light 20L2 to the outside. However, since the output fiber 43 is not an optical fiber directly drawn out from the first housing 70a and the second housing 70b but includes connectors 43b and 43d and receptacles 43c and 43e, when the irradiation light 20L2 is guided, a portion of the irradiation light 20L2 may be reflected by the receptacles 43c and 43e.

[0114] Next, examples of the spectrum of the detection signal in the first embodiment and the comparative example will be described with reference to Figures 7A and 7B. Figures 7A and 7B are diagrams that schematically show examples of the spectrum of the detection signal in the first embodiment and the comparative example, respectively. The vertical axis represents the intensity of the detection signal, and the horizontal axis represents the frequency. The frequency is equal to or greater than zero and corresponds to the distance from the optical element 40 to the object 10. In the examples shown in Figures 7A and 7B, the second optical path length d ２ and the third optical path length d ３ The sum of the first optical path length d １ That is, d ２ +d ３ = d １and from equation (3) f ｏｐｔ = 0 Hz. The distance from the optical element 40 to the object 10 can be measured by setting the receptacle 40a of the optical element 40 shown in Fig. 1 as 0 m. Even when the object 10 is in contact with the optical element 40, the distance from the optical element 40 to the object 10 corresponds to the length of the optical element 40, so the peaks β and γ do not overlap with each other.

[0115] f ｏｐｔ If the frequency is f ｏｐｔ The frequency range lower than f is not used as a frequency range corresponding to the distance range in which the distance and / or velocity of the object 10 can be measured. ｏｐｔ = 0 Hz, there is no unused frequency range, so the distance range in which the distance and / or velocity of the object 10 can be measured can be maximized.

[0116] In the example shown in Figure 7A, peaks β, γ, and δ appear in the spectrum of the detection signal due to the light flows β, γ, and δ, respectively. The peak frequency of peak β is f ｏｂｊ and the peak frequency of peak γ is f ｏｐｔ and the peak frequency of peak δ is f ｃｉｒ The difference in the optical path length between the light flow β and δ causes the frequency f ｏｂｊ , f ｏｐｔ , and f ｃｉｒ are different from each other. Peaks γ and δ are noise. Frequency f ｏｂｊ is the frequency f ｃｉｒ If the frequency f is not in the vicinity of ｃｉｒ The frequency range other than the vicinity of frequency f corresponds to the distance range in which the distance and / or velocity of the object 10 can be measured. ｃｉｒ The frequency range around the frequency f may vary depending on the environment in which the distance and / or velocity of the object 10 is measured. ｃｉｒ The frequency range around the frequency f ｃｉｒ This corresponds to a distance range of 1 m, 10 cm, or within 1 cm of the distance equivalent to the distance.

[0117] In contrast, in the example shown in FIG. 7B, not only peaks β, γ, and δ appear in the spectrum of the detection signal, but also peaks γ and γ″ due to the light flows γ′ and γ″, respectively. The peak frequency of peak γ′ is f ｒ１ and the peak frequency of peak γ″ is f ｒ２ The difference in the optical path lengths of the light flows β, γ, γ', γ'', and δ causes the frequency f ｏｂｊ , f ｏｐｔ , f ｒ１ , f ｒ２ , and f ｃｉｒ In the example shown in FIG. ｒ２ <f ｒ１ And f ｒ１ <f ｃｉｒ The peaks γ and γ'' are noise. ｏｂｊ is the frequency f ｃｉｒ Even if it is not in the vicinity of ｒ１ or f ｒ２ 7B, when the frequency f ｏｂｊ is the frequency f ｒ１ or f ｒ２ In this way, the peaks γ and γ″ narrow the distance range in which the distance and / or velocity of the object 10 can be measured.

[0118] In the above example, ２ +d ３ = d １ However, d ２ +d ３ ≠d １ However, the same argument as above applies even if the frequency f ｏｂｊ、 f ｏｐｔ , f ｒ１ , f ｒ２ , and f ｃｉｒ When the condition of the following formula (7) is satisfied, if the output fiber 43 in the comparative example is used, the frequency f ｏｂｊ , f ｒ１ , f ｒ２ , and f ｃｉｒ is the frequency f ｏｐｔ Therefore, the frequency fｏｂｊ is the frequency f ｒ１ or f ｒ２ may overlap.

[0119] When the condition of formula (7) is satisfied, if the output fiber 42 in the first embodiment is used, the frequency f ｏｂｊ is the frequency f ｃｉｒ , measurement data of the object 10 can be accurately acquired without narrowing the distance range in which distance and / or velocity measurement of the object 10 can be performed. Note that the condition of formula (7) is not essential for the measurement device 100A according to embodiment 1.

[0120] From the above, the measurement device 100A according to the first embodiment can achieve the following advantages (1) to (3). (1) By housing the light source 20 and the interference optical system 30 in the first housing 70a, the possibility of unintended light leakage to the outside can be reduced. (2) By arranging the processing circuit 60 outside the first housing 70a and inside the second housing 70b, heat generated by the processing circuit 60 can be effectively dissipated to the outside. As a result, the processing circuit 60 can operate more stably and fluctuations in the length of the optical fiber within the first housing 70a can be suppressed, thereby enabling accurate acquisition of measurement data of the object 10. (3) By using the output fiber 42 drawn directly from the first housing 70a and the second housing 70b, noise in the detection signal spectrum can be reduced. As a result, accurate acquisition of measurement data of the object 10 can be achieved without narrowing the distance range in which distance and / or velocity measurement of the object 10 can be performed.

[0121] The housing of the light source 20 and the interference optical system 30 in the first housing 70a for the purpose of reducing the possibility of unintended light leakage to the outside is not described in Patent Documents 1 and 2 and Non-Patent Document 1. Similarly, the placement of the processing circuit 60 outside the first housing 70a and inside the second housing 70b, and the use of output fibers 42 drawn directly from the first housing 70a and the second housing 70b are not described in Patent Documents 1 and 2 and Non-Patent Document 1.

[0122] Note that, if the amount of heat generated by the processing circuit 60 is not particularly large, effect (2) of effects (1) to (3) does not need to be emphasized. In that case, the processing circuit 60 may be disposed inside the first housing 70a. Furthermore, if the amount of light reflected by the receptacles 43c and 43e of the output fiber 43 including the connectors 43b and 43d and the receptacles 43c and 43e of the irradiation light 20L2 is not particularly large, effect (3) of effects (1) to (3) does not need to be emphasized. In that case, instead of the output fiber 42 directly drawn out from the first housing 70a and the second housing 70b, the output fiber 43 including the connectors 43b and 43d and the receptacles 43c and 43e may be used.

[0123] Second Embodiment Next, with reference to FIG. 8 , an exemplary configuration of a measurement device according to a second embodiment of the present disclosure will be described, focusing on differences from the measurement device according to the first embodiment. FIG. 8 is a block diagram schematically illustrating the configuration of a measurement device according to the second exemplary embodiment of the present disclosure. The measurement device 100B illustrated in FIG. 8 differs from the measurement device 100A illustrated in FIG. 1 in the following two respects. First, the first housing 70a accommodates not only the light source 20 and the interference optical system 30 but also the photodetector 50. Second, the first housing 70a includes not only a first wiring lead-out portion 74a but also a second wiring lead-out portion 74b. The first wiring lead-out portion 74a is a portion for leading out wiring that transmits signals from the drive circuit 60b to the light source 20. The second wiring lead-out portion 74b is a portion for leading out wiring that transmits signals from the control circuit 60a to the photodetector 50 and wiring that transmits signals from the photodetector 50 to the signal processing circuit 60c. The first wiring lead-out portion 74a and the second wiring lead-out portion 74b may be, for example, the electrical connectors described above.

[0124] The photodetector 50 may include components such as a photodiode and a preamplifier. These components do not generate much heat. Therefore, even if the photodetector 50 is disposed inside the first housing 70a, problems such as unstable operation of the photodetector 50 or errors in the measurement data of the object 10 due to fluctuations in the length of the optical fiber inside the first housing 70a do not occur.

[0125] The measuring device 100B according to embodiment 2 can achieve the above-described effects (1) to (3) in the same way as the measuring device 100A according to embodiment 1. Furthermore, unlike the measuring device 100A according to embodiment 1, the measuring device 100B according to embodiment 2 does not require the signal fiber 52 to include two connectors 52b and two receptacles 52c. This allows for simplification of the components of the measuring device 100B, and reduces the cost of the components.

[0126] Third Embodiment Next, with reference to FIG. 9 , an example configuration of a measurement device according to a third embodiment of the present disclosure will be described, focusing on differences from the measurement device according to the second embodiment. FIG. 9 is a block diagram schematically illustrating the configuration of a measurement device according to the third exemplary embodiment of the present disclosure. The measurement device 100C illustrated in FIG. 9 differs from the measurement device 100B illustrated in FIG. 8 in that the measurement device 100C further includes a chip 80 that supports the interference optical system 30 and the photodetector 50. That is, the interference optical system 30 and the photodetector 50 are configured on-chip. The chip 80 uses optical waveguides instead of optical fibers connecting components. The thick lines within the chip 80 illustrated in FIG. 9 represent optical waveguides.

[0127] The chip 80 includes a first optical coupling unit 82a, a second optical coupling unit 82b, and a signal electrode 84. The first optical coupling unit 82a inputs the laser light 20L0 emitted from the light source 20 to the first optical splitter 32a. The second optical coupling unit 82b inputs the irradiation light 20L2 from the optical circulator 34 to the optical element 40 via the output fiber 42, and inputs the reflected light 20L3 from the optical element 40 to the optical circulator 34 via the output fiber 42. The first optical coupling unit 82a and the second optical coupling unit 82b may be, for example, end faces of optical waveguides or grating couplers. The signal electrode 84 inputs a signal output from the control circuit 60a to the photodetector 50 and inputs a signal output from the photodetector 50 to the signal processing circuit 60c.

[0128] The measurement apparatus 100C according to embodiment 3 can obtain the above-described effects (1) to (3) in the same way as the measurement apparatus 100A according to embodiment 1. Furthermore, unlike the measurement apparatus 100B according to embodiment 2, the measurement apparatus 100C according to embodiment 3 has the interference optical system 30 and the photodetector 50 configured on-chip, which allows the measurement apparatus 100C to be miniaturized.

[0129] Fourth Embodiment Next, with reference to Fig. 10 , an example configuration of a measurement device according to a fourth embodiment of the present disclosure will be described, focusing on differences from the measurement device according to the first embodiment. Fig. 10 is a block diagram schematically illustrating the configuration of a measurement device according to the fourth exemplary embodiment of the present disclosure. The measurement device 100D illustrated in Fig. 10 differs from the measurement device 100A illustrated in Fig. 1 in that the measurement device 100D includes a third optical splitter 32c illustrated in Fig. 10 instead of the optical circulator 34 illustrated in Fig. 1 .

[0130] The intensity of the reflected light 20L3 input to the second optical splitter 32b by the third optical splitter 32c is lower than the intensity of the reflected light 20L3 input to the second optical splitter 32b by the optical circulator 34. When the branching ratio of the third optical splitter 32c is 50:50, the intensity of the reflected light 20L3 output from the third optical splitter 32c is half the intensity of the reflected light 20L3 input to the third optical splitter 32c. Therefore, the intensity of the beat signal caused by the object 10 is lower. On the other hand, because the third optical splitter 32c is cheaper than the optical circulator 34, component costs can be kept low.

[0131] When the third optical splitter 32c is used instead of the optical circulator 34, there is a possibility that a portion of the reflected light 20L3 returns to the light source 20 via the first optical splitter 32a. Such returning light may be removed by providing an optical isolator between the light source 20 and the first optical splitter 32a.

[0132] The measuring device 100D according to embodiment 4 can obtain the above-described effects (1) to (3) in the same way as the measuring device 100A according to embodiment 1. Furthermore, the measuring device 100D according to embodiment 4 uses the third optical splitter 32c instead of the optical circulator 34, and therefore can keep component costs low.

[0133] Fifth Embodiment Next, with reference to FIG. 11 , an exemplary configuration of a measurement device according to a fifth embodiment of the present disclosure will be described, focusing on differences from the measurement device according to the first embodiment. FIG. 11 is a block diagram schematically illustrating the configuration of a measurement device according to the fifth exemplary embodiment of the present disclosure. The measurement device 100E illustrated in FIG. 11 differs from the measurement device 100A illustrated in FIG. 1 in the following two respects. First, the optical element 40 is located outside the first housing 70a and inside the second housing 70b. Second, the second housing 70b includes a light-transmitting window 76 that transmits the irradiation light 20L2 emitted from the optical element 40 and the reflected light 20L3 reflected by the object 10. The light-transmitting window 76 may be an optical substrate that is transmissive to the irradiation light 20L2 and the reflected light 20L3, or may be an opening. The optical substrate may have a transmittance of 60% or more, more preferably 80% or more, for the irradiation light 20L2 and the reflected light 20L3, for example.

[0134] In the measurement device 100E, the output fiber 42 is drawn only from the fiber drawing section 72 of the first housing 70a. The fiber drawing section 72 has the same configuration as the first fiber drawing section 72a shown in FIG. 1 . In the measurement device 100E, the output fiber 42 can be made shorter than in the measurement device 100A. When the output fiber 42 guides the irradiation light 20L2, slight unintended reflections may occur due to defects within the fiber. As a result, noise may occur in the spectrum of the detection signal. The longer the output fiber 42, the wider the frequency band in which noise may occur. In the measurement device 100E, the output fiber 42 can be made shorter, thereby reducing the possibility of noise occurring in the spectrum of the detection signal.

[0135] The measuring device 100E according to the fifth embodiment can achieve the aforementioned advantages (1) to (3) in the same way as the measuring device 100A according to the first embodiment. However, advantage (3) is achieved by the output fiber 42 being directly drawn from the first housing 70a but not from the second housing 70b. Furthermore, unlike the measuring device 100A according to the first embodiment, the measuring device 100E according to the fifth embodiment does not require the second fiber drawing section 72b. Therefore, the components of the measuring device 100E can be simplified and the cost of the parts can be kept low. Furthermore, because the output fiber 42 is short, the possibility of noise occurring in the spectrum of the detection signal can be reduced.

[0136] Sixth Embodiment Next, with reference to FIG. 12 , an example configuration of a measurement device according to a sixth embodiment of the present disclosure will be described, focusing on differences from the measurement device according to the first embodiment. FIG. 12 is a block diagram schematically illustrating the configuration of a measurement device according to the sixth exemplary embodiment of the present disclosure. The measurement device 100F shown in FIG. 12 differs from the measurement device 100A shown in FIG. 1 in the following two respects. First, the optical element 40 is located inside the first housing 70a. Second, the first housing 70a includes a first light-transmitting window 76a, and the second housing 70b includes a second light-transmitting window 76b. The first light-transmitting window 76a and the second light-transmitting window 76b have the same configuration as the light-transmitting window 76 shown in FIG. 11 .

[0137] In the measurement device 100F, there is no point where the output fiber 42 is drawn out. Therefore, in the measurement device 100F, the output fiber 42 can be made even shorter than in the measurement device 100E, and the possibility of noise occurring in the spectrum of the detection signal can be further reduced.

[0138] 12, the optical element 40 is directly fixed to the first light-transmitting window 76a, which reduces the possibility that light other than the irradiation light 20L2 emitted from the optical element 40 will leak from the first housing 70a. Note that the optical element 40 may be disposed away from the first light-transmitting window 76a.

[0139] The measuring device 100F according to the sixth embodiment can achieve the aforementioned advantages (1) to (3) in the same way as the measuring device 100A according to the first embodiment. However, advantage (3) can be achieved by using a single continuous output fiber 42 that is not drawn out from the first housing 70a or the second housing 70b. Furthermore, unlike the measuring device 100A according to the first embodiment, the measuring device 100F according to the sixth embodiment does not require the first fiber drawing section 72a or the second fiber drawing section 72b. This simplifies the components of the measuring device 100E and reduces the cost of the components. Furthermore, the short length of the output fiber 42 reduces the possibility of noise occurring in the spectrum of the detection signal.

[0140] Seventh Embodiment Next, with reference to FIG. 13 , an example configuration of a measurement device according to a seventh embodiment of the present disclosure will be described, focusing on differences from the measurement device according to the first embodiment. FIG. 13 is a block diagram schematically illustrating the configuration of a measurement device according to an exemplary seventh embodiment of the present disclosure. The measurement device 100G illustrated in FIG. 13 differs from the measurement device 100A illustrated in FIG. 1 in the following respects. In the measurement device 100G according to this embodiment, the second optical splitter 32b and the optical circulator 34 that constitute the interference optical system 30 are located outside the first housing 70a and inside the second housing 70b. In this embodiment, a fiber that guides the reference light 20L1 output from the first optical splitter 32a and a fiber that guides the irradiation light 20L2 are drawn to the outside of the first housing 70a. The fiber that guides the reference light 20L1 and the fiber that guides the illumination light 20L2 are each directly pulled out from the third fiber pulling section 72c of the first housing 70a, but instead of the third fiber pulling section 72c, a connector and receptacle may be provided to pull out the fibers.

[0141] The second housing 70b includes a second fiber lead-out portion 72b for leading out the output fiber 42. The single continuous output fiber 42 is led out of the second housing 70b via the second fiber lead-out portion 72b. The second fiber lead-out portion 72b has a structure that allows the continuous output fiber 42 to be directly led out of the second housing 70b. The second fiber lead-out portion 72b does not include a connector or receptacle for detachably connecting or disconnecting the output fiber 42. Therefore, the output fiber 42 hardly reflects the illumination light 20L2 when guiding the illumination light 20L2.

[0142] In the measuring device 100G according to the seventh embodiment, the intensity of the irradiation light 20L2 emitted from the optical element 40 is I ｏｕｔ The intensity of the irradiation light 20L2 output from the first optical splitter 32a is I ｒａｄ２ The light intensities lost in the optical element 40 and the optical circulator 34 and due to reflection are respectively represented by L ｅｌｅ and L ｃｉｒ If the loss of the optical fiber is negligibly small, then I ｏｕｔ I ｏｕｔ =I ｒａｄ２ -L ｃｉｒ -L ｅｌｅ Since a part of the optical path of the illumination light 20L2 output from the first optical splitter 32a exists outside the first housing 70a, I ｒａｄ２ must satisfy Class 1. The upper limit of the light intensity that satisfies Class 1 is I ｌｉｍｉｔ Then, I ｌｉｍｉｔ ≧I ｒａｄ２ =I ｏｕｔ +L ｅｌｅ +L ｃｉｒ Therefore, I ｏｕｔ I ｏｕｔ ≦I ｌｉｍｉｔ -L ｅｌｅ -L ｃｉｒ The strength is usually L ｅｌｅ and L ｃｉｒ I ｏｕｔ Therefore, even in this embodiment, it is possible to emit the irradiation light 20L2 from the optical element 40 at an intensity close to the upper limit that satisfies Class 1.

[0143] A feature of the configuration of this embodiment is that the light source 20 and the first optical splitter 32a are housed in the first housing 70a. The measurement device 100G according to embodiment 7 can achieve the above-described effects (1) and (2) in the same manner as the measurement device 100A according to embodiment 1. Furthermore, by providing the output fiber 42 outside the first housing 70a and using the output fiber 42 drawn directly from the second housing 70b, noise in the spectrum of the detection signal can be reduced. Furthermore, this embodiment allows fewer optical components to be housed in the first housing 70a, which allows the first housing 70a to be made more compact, which has the advantage of enabling the first housing 70a to be manufactured at low cost.

[0144] The components of the measurement devices 100A to 100F described above may be combined in any manner as long as there are no contradictions. For example, the configuration of the measurement device 100B in which the first housing 70a accommodates not only the light source 20 and the interference optical system 30 but also the photodetector 50 may be applied to the measurement devices 100D to 100F. Alternatively, the configuration of the measurement device 100C in which the interference optical system 30 and the photodetector 50 are supported by the chip 80 may be applied to the measurement devices 100D to 100F. Alternatively, the configuration of the measurement device 100D in which the interference optical system 30 includes the third optical splitter 32c instead of the optical circulator 34 may be applied to the measurement devices 100E and 100F.

[0145] The measurement device according to the embodiment of the present disclosure can be used, for example, as a ranging system mounted on a vehicle such as an automobile, a UAV (Unmanned Aerial Vehicle), or an AGV (Automated Guided Vehicle), or as a security system installed on an infrastructure side. The security system can detect, for example, a person or a vehicle.

[0146] 10 Object 20 Light source 20L0 Laser light 20L1 Reference light 20L2 Irradiation light 20L3 Reflected light 20L4 Interference light 30 Interference optical system 32a First optical splitter 32b Second optical splitter 32c Third optical splitter 34 Optical circulator 40 Optical element 42 Output fiber 50 Photodetector 52 Signal fiber 60 Processing circuit 60a Control circuit 60b Drive circuit 60c Signal processing circuit 62 Memory 70a First housing 70b Second housing 80 Chip 90, 100A to 100G Measurement device

Claims

1. A light source that emits light; an interference optical system that separates the light emitted from the light source into a reference light and an illumination light for illuminating an object, the interference optical system causing a reflected light generated by the illumination light being reflected by the object to interfere with the reference light, thereby generating an interference light; an output fiber connected to the interference optical system and guiding the illumination light; an optical element connected to the output fiber and configured to emit the irradiation light; a first housing that houses the light source and the interference optical system; a second housing that houses the first housing; Equipped with The output fiber is directly drawn out from the first housing. Measuring equipment.

2. the output fiber is drawn out from the first housing and the second housing, The optical element is disposed outside the second housing. The measurement device according to claim 1 .

3. the output fiber is drawn out from the first housing, the optical element is disposed outside the first housing and inside the second housing, The second housing includes a light-transmitting window that transmits the irradiation light. The measurement device according to claim 1 .

4. The optical element emits the irradiated light and receives the reflected light, the interference optical system includes a first optical splitter, a second optical splitter, and a circulator or a third optical splitter; the first optical splitter separates the reference light and the irradiation light and outputs the separated light, inputs the output reference light to the second optical splitter, and inputs the output irradiation light to the circulator or the third optical splitter; the circulator or the third optical splitter outputs the irradiated light from the first optical splitter and inputs the irradiated light to the optical element, outputs the reflected light from the optical element and inputs the reflected light to the second optical splitter; the second optical splitter generates the interference light by causing the reflected light from the circulator or the third optical splitter to interfere with the reference light from the first optical splitter; The measuring device according to any one of claims 1 to 3.

5. The optical path length of the first path from the first optical splitter to the photodetector that detects the interference light is d １ , The optical path length of the second path from the first optical splitter to the optical element is d ２ , The optical path length of the third path from the optical element to the photodetector is d ３ , The optical path length of a fourth path from the first optical splitter to the photodetector via the noise optical path of the circulator or the third optical splitter is d ４ When |d ２ +d ３ -d １ |≦|d ４ -d １ | The relationship is satisfied, The measurement device according to claim 4.

6. a signal fiber that guides the interference light from the interference optical system; a photodetector connected to the signal fiber and detecting the interference light; Further comprising: The measuring device according to any one of claims 1 to 3.

7. The photodetector is disposed outside the first housing and inside the second housing. The measurement device according to claim 6.

8. the signal fiber includes two connectors and a receptacle for connecting the two connectors, the receptacle being attached to the first housing; The measurement device according to claim 7.

9. The photodetector is disposed inside the first housing. The measurement device according to claim 6.

10. The interference optical system and the photodetector are configured on-chip. The measurement device according to claim 9.

11. a processing circuit for controlling an operation of the light source and an operation of the photodetector and for processing a signal output from the photodetector, the processing circuit being located outside the first housing and inside the second housing; The measurement device according to claim 6.

12. The light source is capable of changing the frequency of the light over time. The measurement device according to claim 11.

13. A light source that emits light; an interference optical system that separates the light emitted from the light source into a reference light and an illumination light for illuminating an object, the interference optical system causing a reflected light generated by the illumination light being reflected by the object to interfere with the reference light, thereby generating an interference light; an output fiber connected to the interference optical system and guiding the illumination light; an optical element connected to the output fiber and configured to emit the irradiation light; a photodetector for detecting the interference light; a first housing that houses the light source and the interference optical system; a second housing that houses the first housing; a processing circuit that controls an operation of the light source and an operation of the photodetector and processes a signal output from the photodetector, the processing circuit being disposed outside the first housing and inside the second housing; Equipped with Measuring equipment.

14. the output fiber is a continuous optical fiber; The measurement device according to claim 13.

15. The light source is capable of changing the frequency of the light over time. The measuring device according to claim 13 or 14.

16. A light source that emits light; an interference optical system that separates the light emitted from the light source into a reference light and an illumination light for illuminating an object, the interference optical system causing a reflected light generated by the illumination light being reflected by the object to interfere with the reference light, thereby generating an interference light; an output fiber connected to the interference optical system and guiding the illumination light; an optical element connected to the output fiber and configured to emit the irradiation light; a first housing that houses the light source and the interference optical system; a second housing that houses the first housing; Equipped with the output fiber is disposed inside the first housing; The optical element is disposed inside the first housing, the first housing includes a first light-transmitting window that transmits the irradiation light; The second housing includes a second light-transmitting window that transmits the irradiation light. Measuring equipment.

17. A light source that emits light; an interference optical system including a splitter that separates the light emitted from the light source into a reference light and an illumination light for illuminating an object, the interference optical system causing a reflected light generated by the illumination light being reflected by the object to interfere with the reference light, thereby generating an interference light; an output fiber connected to the interference optical system and guiding the illumination light; an optical element connected to the output fiber and configured to emit the irradiation light; a first housing that houses the light source and the splitter; a second housing that houses the first housing, The output fiber is directly drawn out from the second housing. Measuring equipment.

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