Measuring device

Abstract

This measuring device comprises: a light source; a light splitter which splits light from the light source into illuminating light for illuminating a scene and reference light; first and second optical elements from which the illuminating light is emitted and upon which reflected light from the scene is incident; first and second waveguides through which the illuminating light and the reflected light pass, the first and second waveguides being connected to the first and second optical elements, respectively; third and fourth waveguides through which the reflected light passes, the third and fourth waveguides branching from the first and second waveguides, respectively; a light detector which detects interference light between the reference light and the reflected light; a first light switch which switches a path of the illuminating light from the light splitter between the first waveguide and the second waveguide; and a second light switch which switches a path of the reflected light directed toward the light detector between the third waveguide and the fourth waveguide.

Description

Measuring equipment

[0001] The present disclosure relates to a measurement device that measures the distance and / or velocity of an object.

[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 light reflected from the object and outputs a signal corresponding to the time delay of the reflected light. The processing circuit acquires 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 disclose examples of measurement devices using FMCW technology.

[0003] International Publication No. 2023 / 145191 Specification Patent Publication No. 2019-522211

[0004] The present disclosure provides a measurement device that emits light from one of a plurality of optical elements when switched, and that alleviates restrictions on the arrangement of the plurality of optical elements.

[0005] a first optical element that emits the illumination light and receives reflected light from the scene; a first waveguide and a second optical element that transmit the illumination light and the reflected light, the first waveguide and the second waveguide being connected to the first optical element and the second optical element, respectively; a third waveguide and a fourth waveguide that transmits the reflected light, the third waveguide and the fourth waveguide being branched from the first waveguide and the second waveguide, respectively; a photodetector that detects interference light between the reference light and the reflected light; a first optical switch that switches the path of the illumination light from the optical splitter between the first waveguide and the second waveguide; and a second optical switch that switches the path of the reflected light toward the photodetector between the third waveguide and the fourth waveguide.

[0006] A comprehensive 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, for example, a non-volatile recording medium such as a CD-ROM (Compact Disc-Read Only Memory). An apparatus may consist of one or more devices. When an apparatus consists 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. The multiple devices included in a "system" may include devices installed in remote locations away from other devices and connected via a communication network.

[0007] According to the technology of the present disclosure, it is possible to realize a measurement device that emits light from one of a plurality of optical elements when switched, and that alleviates restrictions on the arrangement of the plurality of optical elements.

[0008] FIG. 1 is a block diagram schematically showing the configuration of a measurement apparatus according to a first exemplary embodiment of the present disclosure. FIG. 2 is a diagram schematically showing the time changes in the frequencies of reference light and reflected light when an object is stationary. FIG. 3 is a flowchart roughly showing an example of a measurement operation executed by a processing circuit in the measurement apparatus according to the first embodiment. FIG. 4A is a block diagram schematically showing the configuration of a measurement apparatus of a comparative example. FIG. 4B is a graph showing a signal spectrum when a distance to an object is measured using the measurement apparatus shown in FIG. 4A. FIG. 4C is a graph showing a signal spectrum when an optical element in the measurement apparatus shown in FIG. 4A is shielded from light. FIG. 5A is a block diagram schematically showing the configuration of a measurement apparatus of an example. FIG. 5B is a graph showing a signal spectrum when a distance to a first object is measured using the measurement apparatus shown in FIG. 5A. FIG. 5C is a graph showing a signal spectrum when a first optical element in the measurement apparatus shown in FIG. 5A is shielded from light. FIG. 6A is a block diagram schematically showing the configuration of a measurement apparatus of an example. FIG. 6B is a graph showing a signal spectrum when the distance to a second object is measured using the measurement device shown in FIG. 6A. FIG. 6C is a graph showing a signal spectrum when the second optical element in the measurement device shown in FIG. 6A is shielded from light. FIG. 7A is a block diagram schematically showing example 1 of components arranged outside the housing of the measurement device according to embodiment 1. FIG. 7B is a block diagram schematically showing example 2 of components arranged outside the housing of the measurement device according to embodiment 1. FIG. 7C is a block diagram schematically showing example 3 of components arranged outside the housing of the measurement device according to embodiment 1. FIG. 7D is a block diagram schematically showing example 4 of components arranged outside the housing of the measurement device according to embodiment 1. FIG. 8 is a diagram for explaining the relationship between the optical path lengths of the light flows I to V shown in FIG. 1 and the beat frequency. FIG. 9 is a block diagram schematically showing the configuration of a measurement device according to exemplary embodiment 2 of the present disclosure. FIG. 10 is a flowchart schematically showing an example of a measurement operation performed by a processing circuit in the measurement device according to embodiment 2. FIG. 11A is a block diagram schematically illustrating a first example of components arranged outside the housing of the measurement device according to the second embodiment.11B is a block diagram schematically illustrating Example 2 of components arranged outside the housing of the measurement device according to Embodiment 2. FIG. 11C is a block diagram schematically illustrating Example 3 of components arranged outside the housing of the measurement device according to Embodiment 2.

[0009] 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.

[0010] 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.

[0011] 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 may be referred to as "ultraviolet light," and infrared light may be referred to as "infrared light."

[0012] 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.

[0013] First, the findings that form the basis of this disclosure will be described.

[0014] In recent years, FMCW-LiDAR technology has been developed that combines a wide dynamic range and high resolution for distance, is less susceptible to disturbances, and can measure distance and / or 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, enabling more accurate measurement data of the object.

[0015] Patent Document 1 discloses a measurement device that uses FMCW-LiDAR technology to measure the distance to an object, i.e., distance measurement. In this measurement device, a laser beam whose frequency monotonically increases and decreases over time is emitted from a light source, and this light is separated into a reference beam and an illumination beam for illuminating the object. In this measurement device, an optical detector detects the interference light between the reflected light from the object and the reference beam. A beat signal is generated in the signal spectrum of the interference light, and the distance to the object can be measured based on the peak frequency of the beat signal, i.e., the beat frequency.

[0016] When the sum of the optical path lengths of the irradiated light and the reflected light is the same as the optical path length of the reference light, the beat frequency caused by the object is zero. As the object is farther away from the measurement device, the sum of the optical path lengths of the irradiated light and the reflected light becomes longer than the optical path length of the reference light, so the beat frequency caused by the object shifts to the higher frequency side. This principle makes it possible to measure the distance to an object.

[0017] The device disclosed in Patent Document 1 uses optical fiber to connect components. The device includes a collimator lens that converts illumination light propagating through the optical fiber into a spatial light beam, and an optical circulator that diverges the optical path of the reflected light from that of the illumination light to cause interference between the reflected light from the object and the reference light. Based on the same principle as that in which a beat signal is generated by light reflected from an object, light reflected at the lens interface of the collimator lens and internally scattered light in the optical circulator also generate beat signals as noise light. As a result, in the signal spectrum of the interference light, it becomes difficult to distinguish the beat signal generated by the reflected light from the object from that generated by the noise light. Since the object cannot be measured at or near the beat frequency of the noise light, the ranging range, which is the frequency band in which the object can be measured, becomes narrow. Even when an optical splitter is used instead of an optical circulator, a beat signal is generated due to internally scattered light in the optical splitter. The effect of noise light on ranging can be reduced by appropriately adjusting the distance between the components connected by optical fiber.

[0018] The device disclosed in Patent Document 1 further includes an optical splitter connected to an optical circulator and multiple collimating lenses connected to the splitter. The optical splitter splits illumination light emitted from a light source via the optical circulator into multiple collimating lenses, which then output the light as multiple beams to the outside of the device. The distances from the optical splitter to the multiple collimating lenses are designed to be different. Therefore, although multiple beams are input to the photodetector at the same time, the frequency band in the signal spectrum of the interference light is divided into multiple sub-frequency bands corresponding to the multiple collimating lenses. Focusing on the sub-frequency band corresponding to a certain collimating lens reveals that it is a beat signal generated by the beam emitted from that collimating lens.

[0019] On the other hand, since the frequency band is divided by the number of beam branches, the ranging range becomes narrower. Furthermore, skirt-like phase noise occurs around the beat frequency of the beat signal. When the peak intensity of the beat signal is high, large phase noise occurs in a wide band around the beat frequency. Therefore, the phase noise of the beat signal in a certain sub-frequency band can affect not only that sub-frequency band but also other sub-frequency bands.

[0020] Patent Literature 2 discloses a measurement device that measures the distance to an object using FMCW technology. In the device disclosed in Patent Literature 2, multiple optical heads are each connected to a housing via multiple waveguides. The housing contains a light source, a light receiver, a controller, and an optical router. In this device, the optical router switches the path of illumination light emitted from the light source to one of the multiple optical heads. As a result, illumination light is emitted from that one of the multiple optical heads, and reflected light from the object that returns to the same optical head is input to the light receiver. Therefore, it is possible to emit light from the selected one of the multiple optical heads.

[0021] In such a configuration, unlike the device disclosed in Patent Document 1, it is not necessary to divide the frequency band into multiple sub-frequency bands, and therefore it is possible to avoid narrowing the ranging range. Furthermore, since it is not necessary to divide the frequency band into multiple sub-frequency bands, phase noise of the beat signal in one sub-frequency band does not affect other sub-frequency bands.

[0022] Meanwhile, the irradiated light and reflected light pass through the same waveguide connecting the optical router and the optical head. The waveguide may be, for example, an optical fiber. The optical fiber located between the optical router and the optical head generates fiber noise. The optical fiber generates Rayleigh scattering due to particles sufficiently small compared to the wavelength of the light propagating through it, or fluctuations in density, stress, or composition. Therefore, when the irradiated light propagates through the optical fiber between the optical router and the optical head, backscattered light is generated throughout the optical fiber. Since the backscattered light is detected by the photodetector in the same way as the reflected light, fiber noise is generated due to the backscattered light. The longer the optical fiber, the wider the frequency band of the fiber noise, resulting in a narrower ranging range. For this reason, in the device disclosed in Patent Document 2, the optical fiber between the optical router and the optical head cannot be made very long, which limits the arrangement of multiple optical heads.

[0023] Based on the above considerations, the inventors have conceived of a measurement device using FMCW-LiDAR technology according to an embodiment of the present disclosure. Details of the measurement device according to this embodiment will be described below.

[0024] 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 one or more objects 10 to be measured. The measurement apparatus 100A illustrated in Fig. 1 illuminates a scene with illumination light and measures the distance to one or more objects 10 included in the scene.

[0025] The measurement device 100A shown in FIG. 1 includes a light source 20, an interference optical system 30, an optical switch 40, a plurality of optical elements 50, a photodetector 60, a processing circuit 70, and a memory 72. The measurement device 100A further includes a housing (not shown) that houses at least some of these components. The thick lines shown in FIG. 1 represent optical fibers connecting two components to each other. The solid lines with arrows shown in FIG. 1 represent signal transmission and reception. Note that if the user separately prepares the processing circuit 70 and memory 72, the measurement device 100 may be provided to the user with a configuration excluding the processing circuit 70 and memory 72.

[0026] In the example shown in Fig. 1 , the one or more objects 10 include a first object 10a and a second object 10b, but the number of objects 10 is not limited to two. The number of objects 10 may be one, or three or more. Similarly, in the example shown in Fig. 1 , the multiple optical elements 50 include a first optical element 50a and a second optical element 50b, but the number of optical elements 50 is not limited to two. The number of optical elements 50 may be three or more. The multiple optical elements 50 include at least a first optical element 50a and a second optical element 50b.

[0027] As will be explained in detail later, in the measurement device 100A according to embodiment 1, the optical switch 40 switches the path of light from the interference optical system 30 to one of the multiple optical elements 50, and the light is emitted from that one of the multiple optical elements 50. Furthermore, in the measurement device 100A according to embodiment 1, by appropriately arranging the components, it is possible to narrow the frequency band of fiber noise and widen the ranging range. Furthermore, in the measurement device 100A according to embodiment 1, by appropriately arranging the components, there is no limit to the distance between specific components, and restrictions on the arrangement of the multiple optical elements 50 can be relaxed.

[0028] Each component of the measurement apparatus 100A according to the first embodiment will be described below.

[0029] <Light Source 20> The light source 20 emits laser light 20L0 whose frequency can be varied. The frequency can be varied over time at a constant time period, for example, in a triangular or sawtooth waveform. The time period of the frequency change may vary. The time period of the frequency can be, for example, 1 μsec or more and 10 ms or less. The frequency width can be, for example, 100 MHz or more and 1 THz or less. The wavelength of the laser light 20L0 can be included in the near-infrared wavelength range, for example, from 700 nm to 2000 nm. Since the amount of near-infrared light in sunlight is less than the amount of visible light, using near-infrared light as the laser light 20L0 can reduce the influence of sunlight as noise. Alternatively, the wavelength of the laser light 20L0 may be included in the visible light wavelength range, from 400 nm to 700 nm or less, or in the ultraviolet light wavelength range.

[0030] The light source 20 may include, for example, a distributed feedback laser diode or an external cavity laser diode. These laser diodes are inexpensive and compact, capable of single-mode oscillation, and capable of changing the frequency of the laser light depending on the amount of current applied. The relationship between the applied current value and the frequency of the laser light will be described later.

[0031] <Interference Optical System 30> The interference optical system 30 includes a first optical splitter 32a, a first optical splitter 32a, and an optical circulator 34. The first optical splitter 32a splits the laser beam 20L0 emitted from the light source 20 into a reference beam 20L1 and an irradiation beam 20L2 for irradiating a scene. The first optical splitter 32a inputs the reference beam 20L1 to the second optical splitter 32b and inputs the irradiation beam 20L2 to the optical circulator 34. The optical circulator 34 inputs the irradiation beam 20L2 to the optical switch 40. The optical circulator 34 further inputs reflected beam 20L3 from the scene, which is generated by irradiating the scene with the irradiation beam 20L2 via one of the plurality of optical elements 50, to the second optical splitter 32b. The second optical splitter 32b inputs the interference light 20L4, which is obtained by superimposing and interfering the reference light 20L1 and the reflected light 20L3, into the photodetector.

[0032] In this specification, the first optical splitter 32a is also simply referred to as the "optical splitter," and the second optical splitter 32b is also referred to as the "other optical splitter."

[0033] The optical circulator 34 is an example of an optical branching element. If it is acceptable for the irradiation light 20L2 and the reflected light 20L3 to be branched and their intensities to be reduced, an optical splitter may be used instead of the optical circulator 34 as another example of an optical branching element.

[0034] <Optical Switch 40> The optical switch 40 is connected to the interference optical system 30, more specifically, to the optical circulator 34 included in the interference optical system 30. The optical switch 40 switches the path of the irradiation light 20L2. More specifically, the optical switch 40 switches the path of the irradiation light 20L2 from the optical circulator 34 to one of a plurality of optical elements in time series, and inputs the irradiation light 20L2 to that one of the plurality of optical elements. When the number of optical elements 50 is N, the path of the irradiation light 20L2 is sequentially switched from the first optical element 50 to the second optical element 50, ..., the Nth optical element 50. Switching from the first optical element 50 to the Nth optical element 50 constitutes one operation, and this operation is repeated multiple times. The path of the irradiation light 20L2 being switched is also the path of the reflected light 20L3.

[0035] 1 , the optical switch 40 switches the path of the irradiation light 20L2 to one of the first optical element 50a and the second optical element 50b and inputs the irradiation light 20L2 to that one. The optical switch 40 also inputs the reflected light 20L3 that has returned to that one into the optical circulator 34. Thereafter, the optical switch 40 switches the path of the irradiation light 20L2 to the other of the first optical element 50a and the second optical element 50b and performs the same operation.

[0036] The path of the irradiated light 20L2 may be switched using, for example, an electro-optic effect, or may be switched using, for example, a micro electro mechanical systems (MEMS) mirror.

[0037] <Optical Elements 50> The optical elements 50 are connected to the optical switch 40. Irradiation light 20L2 is emitted from the optical elements 50, and reflected light 20L3 is incident on the optical elements 50. The positions of the optical elements 50 are different from one another. The optical elements 50 may be arranged, for example, along an imaginary straight line or curve. The straight line may be parallel to the vertical direction, for example. Alternatively, the straight line or curve may be parallel to a horizontal plane. When the number of optical elements 50 is three or more, the optical elements 50 may be arranged side by side at equal intervals or at different intervals.

[0038] As a result of the optical switch 40 switching the path of the irradiated light 20L2, one of the optical elements 50 emits the irradiated light 20L2 to the outside and receives the reflected light 20L3. None of the remaining optical elements 50 emit the irradiated light 20L2 to the outside. From the one of the optical elements 50 that emits the irradiated light 20L2, the direction and / or height at which the object 10 is located can be determined. In this specification, the direction in which the irradiated light 20L2 is emitted from the optical element 50 is also referred to as "forward."

[0039] The optical element 50 may be, for example, a collimator lens that collimates the illumination light 20L2. In this specification, "collimate" refers not only to converting the illumination light 20L2 into parallel light, but also to reducing the spread of the illumination light 20L2. Alternatively, the optical element 50 may be a diffraction grating that outputs the illumination light 20L2 to the outside as zeroth-order diffracted light and / or ±Mth-order diffracted light (M is a natural number). By measuring the distance to the object 10 using multiple diffracted lights emitted in different directions, the angular range of distance measurement for the object 10 can be expanded. In the following description, the optical element 50 is assumed to be a collimator lens.

[0040] <Photodetector 60> The photodetector 60 detects the interference light 20L4. The photodetector includes one or more photodetection elements. The photodetection elements output signals corresponding to the intensity of the interference light 20L4.

[0041] In the measurement apparatus 100A, the optical path of the illumination light 20L2 from the interference optical system 30 to the object 10 overlaps with the optical 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.

[0042] <Processing Circuit 70> The processing circuit 70 controls the operations of the light source 20, the optical switch 40, and the photodetector 60. Note that, when the processing circuit 70 samples the signal output from the photodetector 60 at a predetermined timing while the photodetector 60 is constantly detecting the interference light 20L4, the processing circuit 70 does not need to control the operation of the photodetector 60.

[0043] The processing circuit 70 processes the signal output from the photodetector using FMCW-LiDAR technology. Based on the signal, the processing circuit 70 generates and outputs measurement data related to the distance and / or velocity of the object. The operation of the processing circuit will be described in detail below.

[0044] The computer program executed by the processing circuit 70 is stored in memory 72, such as ROM or RAM (Random Access Memory). Thus, the measurement device 100A includes a processing device including the processing circuit 70 and memory 72. The processing circuit 70 and memory may be integrated on a single circuit board, or may be provided on separate circuit boards. The control and signal processing functions of the processing circuit 70 may be distributed across multiple circuits. The processing device may be installed in a remote location away from the other components and control the operations of the light source 20, the optical switch 40, and the photodetector 60 via a wired or wireless communication network.

[0045] [FMCW-LiDAR Technology] Next, the FMCW-LiDAR technology will be briefly described with reference to FIG.

[0046] 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 60 outputs a signal indicating the intensity of the interference light 20L4. A beat signal caused by the object 10 appears in the signal spectrum of the interference light 20L4. The beat frequency is equal to the frequency difference. The processing circuit 70 can generate measurement data regarding the distance to the object 10 from the beat frequency.

[0047] 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).

[0048] The beat frequency f in equation (1) ｂｅａｔ is 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.

[0049] 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 circuitry 70 can generate measurement data regarding the velocity and distance of the object 10 from the frequency difference and average of these beat frequencies, respectively.

[0050] [Operations Executed by Processing Circuitry 70] Next, an example of operations executed by the processing circuitry 70 in the measurement device 100A according to embodiment 1 will be described with reference to Fig. 3. Fig. 3 is a flowchart that schematically shows an example of measurement operations executed by the processing circuitry 70 in the measurement device 100A according to embodiment 1. The processing circuitry 70 executes the operations of steps S101 to S106 shown in Fig. 3.

[0051] <Step S101> The processing circuitry 70 causes the light source 20 to emit laser light 20L0 whose frequency changes over time.

[0052] <Step S102> The processing circuit 70 causes the optical switch 40 to switch the path of the irradiation light 20L2 to one of the plurality of optical elements 50.

[0053] <Step S103> The processing circuitry 70 causes the photodetector 60 to detect the interference light 20L4. The photodetector 60 outputs a signal corresponding to the intensity of the interference light 20L4. Note that the processing circuitry 70 may sample the photodetection signal at a predetermined timing while the photodetector 60 is constantly detecting the interference light 20L4.

[0054] <Step S104 > The processing circuit 70 generates measurement data relating to the distance and / or speed of the object 10 based on the signal output from the photodetector 60 .

[0055] <Step S105> The processing circuit 70 determines whether or not all of the optical elements 50 have been selected. If the determination is Yes, the processing circuit 70 executes the operation of step S106. If the determination is No, the processing circuit 70 executes the operations of steps S102 to S104 again. In this case, in step S102, the processing circuit 70 causes the optical switch 40 to switch the path of the illumination light 20L2 to one of the multiple optical elements 50 that has not been selected so far.

[0056] <Step S106> The processing circuit 70 determines whether or not to end the measurement operation. If the determination is Yes, the processing circuit 70 ends the measurement operation. If the determination is No, the processing circuit 70 executes the operations of steps S102 to S105 again.

[0057] By the above operation, it becomes possible to measure the distance and / or speed of the object 10 by determining the direction and / or height at which the object 10 is located from one of the multiple optical elements 50 that emits the irradiation light 20L2.

[0058] [Example] Next, with reference to Figs. 4A to 6C, an example in which the distance to the object 10 is measured by the measurement device 100A according to this embodiment will be described together with a comparative example.

[0059] <Explanation of Figs. 4A to 6C> Fig. 4A is a block diagram schematically showing the configuration of a measurement device of a comparative example. The triangles in Fig. 4A represent connectors. In the measurement device 90 shown in Fig. 4A, unlike the measurement device 100A shown in Fig. 1, a single optical element 50 is connected to the interference optical system 30 without via the optical switch 40. The housing 80 included in the measurement device 90 shown in Fig. 4A houses the light source 20, the interference optical system 30, the photodetector 60, the processing circuit 70, and the memory 72 shown in Fig. 1. The optical element 50 is disposed outside the housing 80.

[0060] Fig. 4B is a graph showing a signal spectrum when the distance to the object 10 is measured by the measurement device 90 shown in Fig. 4A. Fig. 4C is a graph showing a signal spectrum when the optical element 50 in the measurement device 90 shown in Fig. 4A is shielded from light.

[0061] Fig. 5A is a block diagram schematically illustrating the configuration of a measurement apparatus according to an embodiment. A housing 80 included in a measurement apparatus 100A shown in Fig. 5A houses the light source 20, interference optical system 30, photodetector 60, processing circuit 70, and memory 72 shown in Fig. 1. An optical switch 40, a first optical element 50a, and a second optical element 50b are disposed outside the housing 80. In the example shown in Fig. 5A, the optical switch 40 switches the path of the illumination light 20L2 to the first optical element 50a, as indicated by the thick line.

[0062] Fig. 5B is a graph showing a signal spectrum when the distance to the first object 10a is measured by the measurement device 100A shown in Fig. 5A. Fig. 5C is a graph showing a signal spectrum when the first optical element 50a in the measurement device 100A shown in Fig. 5A is shielded from light.

[0063] 6A is a block diagram showing a schematic configuration of a measurement device according to an embodiment of the present invention, which is the same as the example shown in FIG. 5A except that the path of the illumination light 20L2 is switched to the second optical element 50b by the optical switch 40.

[0064] Fig. 6B is a graph showing a signal spectrum when the distance to the second object 10b is measured by the measurement device 100A shown in Fig. 6A. Fig. 6C is a graph showing a signal spectrum when the second optical element 50b in the measurement device 100A shown in Fig. 6A is shielded.

[0065] 4A, 5A, and 6A, the optical elements 50, 50a, and 50b are collimator lenses with a focal length f=20 mm. The objects 10, 10a, and 10b are pieces of Kent paper placed 1 m away from the incident surface of the irradiation light 20L2 of the optical elements 50, 50a, and 50b.

[0066] The signal spectra shown in Figures 4B, 4C, 5B, 5C, 6B, and 6C show overlapping beat signals during the up-chirp and down-chirp periods (i.e., T1 and T2). The vertical and horizontal axes in these figures represent signal strength and frequency, respectively. Frequency correlates with distance. The frequency is expressed in arbitrary units. Zero frequency corresponds to the exit surface of the first optical splitter 32a from which the illumination light 20L2 exits, as shown in Figure 1.

[0067] In the comparative example, the irradiation light 20L2 emitted from the interference optical system 30 was directly input to the optical element 50 and emitted from the optical element 50 as a beam of spatial light toward the object 10. In contrast, in the example, the irradiation light 20L2 emitted from the interference optical system 30 was input to the first optical element 50a or the second optical element 50b by the optical switch 40. The irradiation light 20L2 was emitted from the first optical element 50a or the second optical element 50b as a beam of spatial light toward the first object 10a or the second object 10b.

[0068] <Beat Signals Caused by Objects 10, 10a, and 10b> Reflected light 20L3 from the objects 10, 10a, and 10b generates beat signals caused by the objects 10, 10a, and 10b. In the examples shown in Figures 4B, 5B, and 6B, the clearest beat signals caused by the objects 10, 10a, and 10b appeared at the same frequency around 100. The peak intensities of the beat signals caused by the objects 10a and 10b in the example were similar to the peak intensity of the beat signal caused by the object 10 in the comparative example.

[0069] In the example, the irradiation light 20L2 emitted from the interference optical system 30 is input to either the first optical element 50a or the second optical element 50b without being branched to either the first optical element 50a or the second optical element 50b. Therefore, in the example, with the simple configuration of using the optical switch 40, it is possible to emit irradiation light 20L2 of relatively high intensity from the selected one of the first optical element 50a and the second optical element 50b. The intensity of the irradiation light 20L2 in the example is approximately the same as the intensity of the irradiation light 20L2 in the comparative example.

[0070] The reflected light 20L3 from the first object 10a or the second object 10b passes through the first optical element 50a or the second optical element 50b from which the irradiation light 20L2 is emitted and enters the photodetector 60 at high intensity without being branched. Therefore, the peak intensity of the beat signal caused by the objects 10a and 10b in the example is approximately the same as the peak intensity of the beat signal caused by the object 10 in the comparative example.

[0071] Since the illumination light 20L2 is not branched into the first optical element 50a and the second optical element 50b, unlike the device disclosed in Patent Document 1, the frequency band is not divided into multiple sub-frequency bands, and the ranging range is not narrowed.

[0072] <Various Beat Signals> The multiple light flows in the measurement apparatus 100A generate various beat signals. Here, referring again to FIG. 1 , the multiple light flows in the measurement apparatus 100A will be described. The dashed lines with arrows in FIG. 1 represent the light flows. Light flow I is the flow of the reference light 20L1 from the first optical splitter 32a to the photodetector 60. Light flow II is the flow of the illumination light 20L2 from the first optical splitter 32a to the object 10, and the reflected light 20L3 from the object 10 to the photodetector 60. Light flow III is the flow of a portion of the illumination light 20L2 from the first optical splitter 32a to be reflected by the optical element 50 and reach the photodetector 60. Light flow IV is the flow of another portion of the illumination light 20L2 from the first optical splitter 32a to the photodetector 60 via the optical circulator 34 without heading to the optical switch 40. It has been experimentally confirmed that the optical path length of light flow IV can be longer than the optical path length of light flow II. Light flow V is the flow of yet another part of the illumination light 20L2 from the first optical splitter 32a to the photodetector 60 after being reflected by the optical switch 40.

[0073] 5B represent beat signals generated by the light flows II to V, respectively. The beat frequencies of the beat signals II to V are proportional to the absolute value of the difference between the optical path length of the light flows II to V and the optical path length of the light flow I.

[0074] Beat signal II is caused by reflected light 20L3 from the first object 10a. Beat signal III is noise caused by a portion of the illumination light 20L2 reflected by the interface between the incident surface of the first optical element 50a and the exit surface of the optical fiber. This portion of the illumination light 20L2 is detected by the photodetector 60, just like the reflected light 20L3. Because the first object 10a is located in front of the incident surface of the first optical element 50a, beat signal III serves as an indicator of zero distance for the first object 10a. Because beat signal III appears at a lower frequency than beat signal II, beat signal III can be distinguished from beat signal II.

[0075] Beat signal IV is noise caused by another portion of irradiated light 20L2 that does not travel toward optical switch 40 but enters photodetector 60 via optical circulator 34. This other portion of irradiated light 20L2 is detected by photodetector 60, similar to reflected light 20L3. Depending on the optical path lengths of light flows III and IV, beat signal IV appears on the lower or higher frequency side than beat signal III. In the example shown in FIG. 5B , beat signal IV appears on the lower frequency side than beat signal III, so beat signal IV can be distinguished from beat signal II. In contrast, if beat signal IV appears on the higher frequency side than beat signal III, it becomes difficult to distinguish beat signal IV from beat signal II.

[0076] Beat signal V is noise resulting from a further portion of the irradiated light 20L2 reflected by the interface between the optical switch 40 and the optical fiber, which has a different refractive index. This further portion of the irradiated light 20L2 is detected by the photodetector 60, similar to the reflected light 20L3. Depending on the optical path lengths of the light flows III and V, beat signal V appears at a lower or higher frequency than beat signal III. In the example shown in FIG. 5 , beat signal V appears at a lower frequency than beat signal III, so beat signal V can be distinguished from beat signal II. However, because the intensity of the reflected light from the optical switch 40 is high, the tail-like phase noise of beat signal V also increases, increasing the noise level in the short-distance range. As a result, it becomes difficult to obtain a low-intensity signal in the short-distance range. If beat signal V appears at a higher frequency than beat signal III, it becomes difficult to distinguish beat signal V from beat signal II.

[0077] From the above, if beat signals IV and V appear on the lower frequency side than beat signal III, the higher frequency side than beat signal III can be used as the distance measurement range. Furthermore, if beat signal V is sufficiently far from beat signal III, the tail-like phase noise of beat signal V has almost no effect on beat signal II.

[0078] In addition to the noise beat signals III to V, fiber noise also appears in the signal spectrum. This fiber noise is noise caused by yet another portion of the illumination light 20L2 that is backscattered throughout the optical fiber located between the optical circulator 34 and the optical elements 50, 50a, and 50b. This yet another portion of the illumination light 20L2 is detected by the photodetector 60, just like the reflected light 20L3.

[0079] Fiber noise appears even when the optical elements 50, 50a, and 50b are shielded from light. In the examples shown in Figures 4C, 5C, and 6C, noise resulting from the addition of fiber noise to the shot noise of the photodetector 60 appears in the low-frequency band, while the shot noise of the photodetector 60 appears in other frequency ranges. Because fiber noise appears over a wide band, it narrows the ranging range. The frequency band of the fiber noise can be narrowed by appropriately adjusting the arrangement of the optical circulator 34, the optical switch 40, the first optical element 50a, and the second optical element 50b, as described below.

[0080] As described above, what is actually emitted from the optical element 50 is the remaining portion of the irradiation light 20L2, excluding the portion that causes the noise. However, in this specification, unless there is any misunderstanding, it will be stated that "the optical element 50 emits the irradiation light 20L2."

[0081] [Components Arranged Outside the Housing 80] Next, examples of components arranged outside the housing 80 in the measurement device 100A according to embodiment 1 will be described with reference to Figures 7A to 7D. Figures 7A to 7D are block diagrams that schematically show examples 1 to 4 of components arranged outside the housing 80 in the measurement device 100A according to this embodiment, respectively. However, in Figures 7A to 7D, the light source 20, the processing circuit 70, and the memory 72 shown in Figure 1 are omitted.

[0082] The example shown in Fig. 7A corresponds to the examples shown in Fig. 5A and Fig. 6A. In the example shown in Fig. 7A, the first optical splitter 32a, the second optical splitter 32b, the optical circulator 34, the photodetector 60, and the light source 20, the processing circuit 70, and the memory 72 shown in Fig. 1 are housed in a housing 80. The optical switch 40, the first optical element 50a, and the second optical element 50b are disposed outside the housing 80. The housing 80 can reduce the influence of the external environment, such as temperature and humidity, on the components inside the housing 80. If a temperature adjustment element is provided in the housing 80, stable measurement is possible even if temperature-sensitive components are present.

[0083] 7B, unlike the example shown in Fig. 7A, the optical switch 40 is disposed inside the housing 80. In this case, the influence of the external environment on the optical switch 40 can be reduced.

[0084] 7A , in the example shown in Fig. 7C , in addition to the optical switch 40, the first optical element 50a, and the second optical element 50b, the optical circulator 34 is also arranged outside the housing 80. Therefore, in the example shown in Fig. 7C , unlike the examples shown in Figs. 7A and 7B in which the optical circulator 34 is housed in the housing 80, it is easy to shorten the fiber noise section between the optical circulator 34 and the first optical element 50a and the fiber noise section between the optical circulator 34 and the second optical element 50b. Because the fiber noise section is shortened, it is possible to narrow the frequency band of the fiber noise and widen the ranging range.

[0085] Furthermore, backscattered light generated in the optical fiber between the first optical splitter 32a and the optical circulator 34 and in the optical fiber between the optical circulator 34 and the second optical splitter 32b does not reach the photodetector 60, so these optical fibers do not generate fiber noise. Since the length of these optical fibers does not affect the distance measurement range, there is no limit to the length of these optical fibers, making it easy to arrange the multiple optical elements 50 in desired locations away from the first optical splitter 32a and the second optical splitter 32b. In this way, restrictions on the arrangement of the multiple optical elements 50 are alleviated.

[0086] 7D differs from the example shown in Fig. 7C in that the measurement device 100 further includes another housing 82 that houses the optical circulator 34 and the optical switch 40. The other housing 82 may be provided with, for example, a temperature adjustment element, similar to the housing 80. Such another housing 82 can reduce the influence of the external environment on the optical circulator 34 and the optical switch 40.

[0087] In addition to the housing 80, the measurement apparatus 100A may further include at least one optical head that houses the plurality of optical elements 50 shown in FIG. 1 . The optical head helps to protect the optical element 50. The at least one optical head may include, for example, a plurality of optical heads that each house a plurality of optical elements 50.

[0088] 7A to 7D, the optical path length between the components shown in Fig. 7A to 7D is as follows: The optical path length from the first optical splitter 32a to the optical circulator 34 is d １ , the optical path length from the first optical splitter 32a to the second optical splitter 32b is d ２ , the optical path length from the optical circulator 34 to the optical switch 40 is d ３ , the optical path length from the optical circulator 34 to the second optical splitter 32b is d ４ , the optical path length inside the optical circulator 34 from the optical circulator 34 to the second optical splitter 32b is d ｃ , the optical path length from the optical switch 40 to the first optical element 50a is d ５１ , the optical path length from the optical switch 40 to the second optical element 50b is d ５２ , the optical path length from the first optical element 50a to the first object 10a is d ６１ , the optical path length from the second optical element 50b to the second object 10b is d ６２ In the examples shown in FIGS. 7A to 7D, d ５１ <d ５２ is.

[0089] Next, the relationship between the optical path lengths of the light flows I to V shown in FIG. 1 and the beat frequency will be described with reference to FIG. 8 . FIG. 8 is a diagram for explaining the relationship between the optical path lengths of the light flows I to V shown in FIG. 1 and the beat frequency. "(I)," "(IV)," and "(V)" in FIG. 8 represent the optical path lengths of the light flows I, IV, and V, respectively. "(IIa)" and "(IIb)" in FIG. 8 represent the optical path lengths of the light flow II via the first optical element 50a and the second optical element 50b, respectively. "(IIIa)" and "(IIIb)" in FIG. 8 represent the optical path lengths of the light flow III reflected by the incident surfaces of the first optical element 50a and the second optical element 50b, respectively. The "first beam" and "second beam" in FIG. 8 refer to the irradiation light 20L2 emitted as a beam of spatial light from the first optical element 50a and the second optical element 50b, respectively.

[0090] The optical path length of the light flow I is d ２ The optical path length of the light flow IIa is d １ +2d ３ +2d ５１ +2d ６１ +d ４ The optical path length of the light flow IIb is d １ +2d ３ +2d ５２ +2d ６２ +d ４ The optical path length of the light flow IIIa is d １ +2d ３ +2d ５１ +d ４ The optical path length of the light flow IIIb is d １ +2d ３ +2d ５２ +d ４ The optical path length of the light flow IV is d １ +d ４ +d ｃ The optical path length of the light flow V is d １ +2d ３ +d ４ The fiber noise is d １ +d ４ The optical path length of the light flows IIIa and IIIb is in the range from the optical path length of the light flows IIIa and IIIb.

[0091] The f shown in FIG.ｃｏｌ , f ｃｉｒ , f ｓｗ , f ＰＤ , and f ｎｏｉｓ The following is true for f ｃｏｌ represents the beat frequency of the beat signals IIIa and IIIb caused by the optical elements 50a and 50b. ｃｏｌ corresponds to the zero distance between the first and second beams. ｃｉｒ represents the beat frequency of the beat signal IV caused by the optical circulator 34. ｓｗ represents the beat frequency of the beat signal V caused by the optical switch 40. ＰＤ represents the cutoff frequency of the photodetector 60. ｎｏｉｓｅ represents the frequency band of fiber noise in the signal spectrum. ｃｏｌ From f ＰＤ The frequency band is up to

[0092] In the example shown in FIG. 8, the optical path length of the light flow V is equal to the optical path length of the light flow I, so the beat frequency f ｓｗ In the example shown in FIG. 8, the optical path length of the light flow I is d １ +d ４ and the optical path length d of the optical flow IIIa １ +2d ３ +2d ５１ +d ４ The average of (d １ +d ４ ) + (d １ +2d ３ +2d ５１ +d ４ ) )] / 2=(d １ +d ３ +d ５１ +d ４ ) and d １ +d ４ and the optical path length d of the optical flow IIIb １ +2d ３ +2d ５2 +d ４ The average of (d １ +d ４ ) + (d １ +2d ３ +2d ５２ +d４ ) )] / 2=(d １ +d ３ +d ５２ +d ４ ) is shorter than

[0093] Optical path length d of light flow I ２ Even if d is less than the optical path length of the light flows IIIa and IIIb, １ +d ４ and the optical path lengths of the optical flows IIIa and IIIb are longer than the above average, the fiber noise is ｃｏｌ appears in the higher frequency range than

[0094] On the other hand, the optical path length d ２ d １ +d ４ longer than the optical path length of d １ +d ４ and the optical path lengths of the light flows IIIa and IIIb are less than the above average, the fiber noise is narrow-banded and varies from zero frequency to the beat frequency f of the beat signals IIIa and IIIb. ｃｏｌ It falls within the range of.

[0095] As described above, the measurement device 100A according to the first embodiment can emit the irradiation light 20L2 from a selected one of the plurality of optical elements 50. Therefore, unlike the device disclosed in Patent Document 1, there is no need to divide the frequency band into a plurality of sub-frequency bands, and therefore it is possible to avoid narrowing the ranging range due to division of the frequency band.

[0096] Furthermore, in the measurement device 100A according to the first embodiment, the optical circulator 34, the optical switch 40, and the optical element 50 are disposed outside the housing 80, thereby shortening the fiber noise section between the optical circulator 34 and the optical element 50. As a result, the frequency band of the fiber noise can be narrowed, and the ranging range can be broadened.

[0097] Furthermore, in the measurement device 100A according to the first embodiment, the length of the optical fiber between the first optical splitter 32a and the optical circulator 34 and the optical fiber between the optical circulator 34 and the second optical splitter 32b does not affect the distance measurement range. Therefore, there is no limit to the length of these optical fibers, and restrictions on the arrangement of the multiple optical elements 50 are relaxed.

[0098] Second Embodiment Hereinafter, an exemplary configuration of a measurement device according to a second embodiment of the present disclosure will be described with reference to Fig. 9 . Fig. 9 is a block diagram schematically illustrating the configuration of a measurement device according to an exemplary second embodiment of the present disclosure. The measurement device 100B illustrated in Fig. 9 differs from the measurement device 100A illustrated in Fig. 1 in that the measurement device 100B includes a first optical switch 40a, a second optical switch 40b, and a plurality of optical circulators 34 instead of the optical switch 40 and the optical circulator 34 illustrated in Fig. 1 . Note that in the measurement device 100B, as in the measurement device 100A, the optical circulator 34 is an example of an optical branching element.

[0099] 9, the multiple optical circulators 34 include a first optical circulator 34a and a second optical circulator 34b, but the number of optical circulators 34 is not limited to two. The number of optical circulators 34 may be three or more. Since the multiple optical elements 50 correspond to the multiple optical circulators 34, the number of optical elements 50 is the same as the number of optical circulators 34. The multiple optical circulators 34 include at least a first optical circulator 34a and a second optical circulator 34b. The multiple optical elements 50 include at least a first optical element 50a and a second optical element 50b.

[0100] As will be explained in detail later, in the measurement device 100B according to the second embodiment, the first optical switch 40a switches the path of light from the first optical splitter 32a to one of the multiple optical elements 50, and the light is emitted from that one of the multiple optical elements 50. Furthermore, in the measurement device 100B according to the second embodiment, by appropriately arranging the components, it is possible to narrow the frequency band of the fiber noise and widen the ranging range. Furthermore, in the measurement device 100B according to the second embodiment, there is no restriction on the distance between specific components, and restrictions on the arrangement of the multiple optical elements 50 can be relaxed.

[0101] The measuring apparatus 100B according to the second embodiment will be described in detail below.

[0102] The measurement apparatus 100B further includes a first waveguide 12a, a second waveguide 12b, a third waveguide 12c, and a fourth waveguide 12d. The first waveguide 12a is connected to the first optical element 50a. The first waveguide 12a is also connected to the first optical circulator 34a. The second waveguide 12b is connected to the second optical element 50b. The second waveguide 12b is also connected to the second optical circulator 34b. The third waveguide 12c branches off from the first waveguide 12a. The third waveguide 12c is further connected to the second optical switch 40b. The fourth waveguide 12d branches off from the second waveguide 12b. The fourth waveguide 12d is further connected to the second optical switch 40b.

[0103] The irradiated light 20L2 and the reflected light 20L3 pass through one of the first waveguide 12a and the second waveguide 12b, and the reflected light 20L3 passes through one of the third waveguide 12c and the fourth waveguide 12d.

[0104] The first optical switch 40a switches the path of the illumination light 20L2 from the first optical splitter 32a to either the first optical circulator 34a or the second optical circulator 34b. The first optical circulator 34a inputs the illumination light 20L2 to the first optical element 50a via the first waveguide 12a. The second optical circulator 34b inputs the illumination light 20L2 to the second optical element 50b via the second waveguide 12b.

[0105] In addition, with regard to switching of the path of the illumination light 20L2 by the first optical switch 40a, the first optical circulator 34a and the second optical circulator 34b may be rephrased as the first waveguide 12a and the second waveguide 12b, respectively, because the first optical circulator 34a and the second optical circulator 34b correspond to the first waveguide 12a and the second waveguide 12b, respectively. Alternatively, the first optical circulator 34a and the second optical circulator 34b may be rephrased as the first optical element 50a and the second optical element 50b, respectively, because the first optical circulator 34a and the second optical circulator 34b correspond to the first optical element 50a and the second optical element 50b, respectively.

[0106] When the path of the illumination light 20L2 is switched to the first optical circulator 34a, the first optical element 50a emits the illumination light 20L2 and receives the reflected light 20L3. The second optical switch 40b switches the path of the reflected light 20L3 to the first optical circulator 34a in synchronization with the first optical switch 40a. The first optical circulator 34a inputs the reflected light 20L3 passing through the first waveguide 12a into the third waveguide 12c. The reflected light 20L3 passes through the third waveguide 12c and reaches the second optical switch 40b.

[0107] When the path of the irradiation light 20L2 is switched to the second optical circulator 34b, the second optical element 50b emits the irradiation light 20L2 and receives the reflected light 20L3. The second optical switch 40b switches the path of the reflected light 20L3 to the second optical circulator 34b in synchronization with the first optical switch 40a. The second optical circulator 34b inputs the reflected light 20L3, which is incident on the second optical element 50b and passes through the second waveguide 12b, into the fourth waveguide 12d. The reflected light 20L3 passes through the fourth waveguide 12d and reaches the second optical switch 40b.

[0108] In addition, with regard to the switching of the path of reflected light 20L3 by second optical switch 40b, first optical circulator 34a and second optical circulator 34b may be rephrased as third waveguide 12c and fourth waveguide 12d, respectively, because first optical circulator 34a and second optical circulator 34b correspond to third waveguide 12c and fourth waveguide 12d, respectively. Alternatively, first optical circulator 34a and second optical circulator 34b may be rephrased as first optical element 50a and second optical element 50b, respectively, because first optical circulator 34a and second optical circulator 34b correspond to first optical element 50a and second optical element 50b, respectively.

[0109] [Operations Executed by Processing Circuitry 70] Next, an example of operations executed by the processing circuitry 70 in the measurement device 100B according to embodiment 2 will be described with reference to Fig. 10. Fig. 10 is a flowchart that schematically shows an example of measurement operations executed by the processing circuitry 70 in the measurement device 100B according to embodiment 2. The processing circuitry 70 executes the operations of steps S201 to S206 shown in Fig. 10. The operations of steps S201 and S203 to S206 are the same as the operations of steps S101 and S103 to S106 shown in Fig. 3, respectively.

[0110] <Step S202> The processing circuit 70 causes the first optical switch 40a and the second optical switch 40b to respectively switch the paths of the irradiated light 20L2 and the reflected light 20L3 to one of the plurality of optical elements 50. The first optical switch 40a and the second optical switch 40b are synchronized.

[0111] By the above operation, it becomes possible to measure the distance and / or speed of the object 10 by determining the direction and / or height at which the object 10 is located from one of the multiple optical elements 50 that emits the irradiation light 20L2.

[0112] 11A to 11C, examples of components arranged outside the housing 80 in the measurement device 100B according to embodiment 2 will be described. FIGS. 11A to 11C are block diagrams schematically showing examples 1 to 3 of components arranged outside the housing 80 in the measurement device 100B according to this embodiment, respectively. However, in FIGS. 11A to 11C, the light source 20, the processing circuit 70, and the memory 72 shown in FIG. 1 are omitted.

[0113] 11A , the first optical splitter 32 a, the second optical splitter 32 b, the first optical switch 40 a, the second optical switch 40 b, the photodetector 60, as well as the light source 20, the processing circuit 70, and the memory 72 shown in FIG. 1 are housed in a housing 80. The first optical circulator 34 a, the second optical circulator 34 b, the first optical element 50 a, and the second optical element 50 b are disposed outside the housing 80.

[0114] Neither the first optical switch 40a nor the second optical switch 40b is located between the first optical circulator 34a and the first optical element 50a, nor between the second optical circulator 34b and the second optical element 50b. Therefore, it is easy to sufficiently shorten the fiber noise section between the first optical circulator 34a and the first optical element 50a and the fiber noise section between the second optical circulator 34b and the second optical element 50b. Because the fiber noise section is sufficiently short, it is possible to further narrow the frequency band of the fiber noise.

[0115] Furthermore, backscattered light generated in the optical fiber between the first optical switch 40a and the first optical circulator 34a, the optical fiber between the first optical circulator 34a and the second optical switch 40b, the optical fiber between the first optical switch 40a and the second optical circulator 34b, and the optical fiber between the second optical circulator 34b and the second optical switch 40b does not reach the photodetector 60, so these optical fibers do not generate fiber noise. Since the length of these optical fibers does not affect the ranging range, there is no limit to the length of these optical fibers, making it easy to arrange the multiple optical elements 50 at desired locations away from the first optical switch 40a and the second optical switch 40b. In this way, restrictions on the arrangement of the multiple optical elements 50 are alleviated.

[0116] Furthermore, the portion of the illumination light 20L2 that is reflected by the first optical switch 40a does not reach the photodetector 60, so no beat signal is generated due to the first optical switch 40a. Similarly, the portion of the reflected light 20L3 that is reflected by the second optical switch 40b does not reach the photodetector 60, so no beat signal is generated due to the second optical switch 40b. Therefore, the first optical switch 40a and the second optical switch 40b do not affect the ranging range.

[0117] 11A, measurement device 100B further includes another housing 82a that houses first optical circulator 34a and another housing 82b that houses second optical circulator 34b. Instead of the other housings 82a and 82b, a single other housing that houses first optical circulator 34a and second optical circulator 34b may be used.

[0118] Thus, measurement device 100B further includes at least one other housing that houses first optical circulator 34 a and second optical circulator 34 b. The at least one other housing may include, for example, other housing 82 a and other housing 82 b. If a temperature adjustment element is provided in at least one other housing, the influence of the external environment on first optical circulator 34 a and second optical circulator 34 b can be reduced.

[0119] In the example shown in Figure 11C, unlike the example shown in Figure 11B, the other housing 82a houses not only the first optical circulator 34a but also the first optical element 50a, and the other housing 82b houses not only the second optical circulator 34b but also the second optical element 50b.

[0120] The measurement apparatus 100B may further include at least one optical head that houses a plurality of optical elements 50 shown in Fig. 9. The at least one optical head may include, for example, a plurality of optical heads that each house a plurality of optical elements 50. The other housings 82a and 82b shown in Fig. 11C may also be optical heads.

[0121] The optical path lengths between the components shown in FIGS. 11A to 11C are the optical path lengths d １ , d ２ , d ４ , d ６１ , d ６２ The optical path length from the first optical switch 40a to the first optical circulator 34a is d ３１ , the optical path length from the first optical switch 40a to the second optical circulator 34b is d ３２ , the optical path length from the first optical circulator 34a to the first optical element 50a is d ５１ , the optical path length from the second optical circulator 34b to the second optical element 50b is d ５２ , the optical path length from the first optical circulator 34a to the second optical switch 40b is d ７１ , the optical path length from the second optical circulator 34b to the second optical switch 40b is d ７２ It is defined as:

[0122] The optical path length d from the first optical circulator 34a to the first optical element 50a ５１ corresponds to the optical path length of the first waveguide 12a shown in FIG. 9. The optical path length d from the second optical circulator 34b to the second optical element 50b ５２ corresponds to the optical path length of the second waveguide 12b shown in Figure 9. The optical path length d from the first optical circulator 34a to the second optical switch 40b ７１ corresponds to the optical path length of the third waveguide 12c shown in Figure 9. The optical path length d from the second optical circulator 34b to the second optical switch 40b ７２corresponds to the optical path length of the fourth waveguide 12d shown in FIG.

[0123] When the zero distance of the first beam emitted from the first optical element 50a and the zero distance of the second beam emitted from the second optical element 50b coincide, it is easy to evaluate the distance between the first object 10a and the second object 10b. When the following formula (2) is satisfied, the zero distance of the first beam and the zero distance of the second beam coincide.

[0124] From the above, the measurement device 100B according to the second embodiment can emit the irradiation light 20L2 from one switched optical element 50 among the plurality of optical elements 50. Therefore, unlike the device disclosed in Patent Document 1, there is no need to divide the frequency band into a plurality of sub-frequency bands, and therefore it is possible to avoid narrowing the ranging range due to division of the frequency band.

[0125] Furthermore, in the measurement device 100B according to the second embodiment, the first optical circulator 34a, the second optical circulator 34b, the first optical element 50a, and the second optical element 50b are disposed outside the housing 80, thereby making it possible to sufficiently shorten the fiber noise section between the first optical circulator 34a and the first optical element 50a and the fiber noise section between the second optical circulator 34b and the first optical element 50a. As a result, the frequency band of the fiber noise can be further narrowed, and the ranging range can be further broadened.

[0126] Furthermore, in the measurement device 100B according to the second embodiment, the lengths of the optical fibers between the first optical switch 40a and the first optical circulator 34a, the first optical circulator 34a and the second optical switch 40b, the first optical switch 40a and the second optical circulator 34b, and the second optical switch 40b do not affect the distance measurement range. Therefore, there is no limit to the lengths of these optical fibers, and restrictions on the arrangement of the multiple optical elements 50 are relaxed.

[0127] In the above example, the two components are connected by an optical fiber, but the present invention is not limited to this example. At least some of the components included in the measurement device 100 may be integrated on a chip by a semiconductor process, and the two components may be connected by a waveguide on the chip.

[0128] [Additional Notes] The above description of the embodiments discloses the following techniques.

[0129] a first optical element and a second optical element that emit the illumination light and receive reflected light from the scene; a first waveguide and a second waveguide through which the illumination light and the reflected light pass, the first waveguide and the second waveguide being connected to the first optical element and the second optical element, respectively; a third waveguide and a fourth waveguide through which the reflected light passes, the third waveguide and the fourth waveguide being branched from the first waveguide and the second waveguide, respectively; a photodetector that detects interference light between the reference light and the reflected light; a first optical switch that switches a path of the illumination light from the optical splitter between the first waveguide and the second waveguide; and a second optical switch that switches a path of the reflected light toward the photodetector between the third waveguide and the fourth waveguide.

[0130] In this measurement device, light is emitted from one of the multiple optical elements when selected, which alleviates restrictions on the arrangement of the multiple optical elements.

[0131] [Technology 2] The measurement device according to Technology 1, further comprising a housing that houses the light source, the optical splitter, the first optical switch, the second optical switch, and the photodetector, wherein the first optical element and the second optical element are disposed outside the housing.

[0132] In this measurement device, the housing can reduce the influence of the external environment, such as temperature and humidity, on the optical splitter, the first optical switch, the second optical switch, and the photodetector.

[0133] [Technology 3] The measurement device according to Technology 1 or 2, further comprising: a first optical branching element that inputs the illumination light from the optical splitter into the first waveguide and the reflected light from the first optical element into the third waveguide; and a second optical branching element that inputs the illumination light from the optical splitter into the second waveguide and the reflected light from the second optical element into the fourth waveguide.

[0134] In this measurement device, the first and second optical branching elements allow the irradiated light and reflected light to be input into the waveguide without reducing their intensities.

[0135] [Technology 4] The optical switch further includes another optical splitter that superimposes the reflected light and the reference light and inputs the superimposed light as the interference light to the photodetector, and the optical path length between the optical splitter and the first optical switch is set to d １ , the optical path length between the first optical switch and the first optical branching element is d ３１ , the optical path length between the first optical switch and the second optical branching element is d ３２ , the optical path length between the first optical branching element and the first optical element is d ５１ , the optical path length between the second optical branching element and the second optical element is d ５２ , the optical path length between the first optical branching element and the second optical switch is d ７１ , the optical path length between the second optical branching element and the second optical switch is d ７２ , the optical path length between the second optical switch and the other optical splitter is d ４ When this is the case, d １ +d ３１ +2d ５１ +d ７１ +d ４ = d １ +d ３２ +2d ５２ +d ７２ +d ４ The measuring device according to Technology 3,

[0136] In this measurement device, the zero distance of the irradiated light emitted from the first optical element and the zero distance of the irradiated light emitted from the second optical element coincide with each other.

[0137] [Technology 5] The measurement device according to Technology 3, further comprising at least one other housing that houses the first optical branching element and the second optical branching element.

[0138] In this measurement device, at least the other housing can reduce the influence of the external environment on the first and second optical branching elements.

[0139] [Technology 6] The measurement device according to Technology 5, wherein the at least one other housing accommodates the first optical element and the second optical element.

[0140] In this measurement device, the first and second optical elements can be protected by at least one other housing.

[0141] [Technology 7] The measurement device described in Technology 6, wherein the at least one other housing includes two other housings that are a first optical head and a second optical head, the first optical head housing the first light branching element and the first optical element, and the second optical head housing the second light branching element and the second optical element.

[0142] In this measurement device, the first optical head can protect the first light branching element and the first optical element, and the second optical head can protect the second light branching element and the second optical element.

[0143] The measurement device according to the embodiment of the present disclosure can be used, for example, in a ranging system mounted on a vehicle such as an automobile, an unmanned aerial vehicle (UAV), or an automated guided vehicle (AGV), or for vehicle detection purposes.

[0144] 10 Object 10a First object 10b Second object 12a First waveguide 12b Second waveguide 12c Third waveguide 12d Fourth waveguide 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 34 Optical circulator 40 Optical switch 40a First optical switch 40b Second optical switch 50 Optical element 50a First optical element 50b Second optical element 60 Photodetector 70 Processing circuit 72 Memory 80 Housing 82, 82a, 82b Other housings 90, 100 Measurement device

Claims

1. A measuring device comprising: a light source; an optical splitter that separates light from the light source into illumination light for irradiating a scene and reference light; a first optical element and a second optical element through which the illumination light is emitted and to which reflected light from the scene is incident; a first waveguide and a second waveguide through which the illumination light and the reflected light pass, the first waveguide and the second waveguide being connected to the first optical element and the second optical element respectively; a third waveguide and a fourth waveguide through which the reflected light passes, the third waveguide and the fourth waveguide being branched from the first waveguide and the second waveguide respectively; a photodetector that detects interference light between the reference light and the reflected light; a first optical switch that switches the path of the illumination light from the optical splitter between the first waveguide and the second waveguide; and a second optical switch that switches the path of the reflected light toward the photodetector between the third waveguide and the fourth waveguide.

2. The measuring device according to claim 1, further comprising a housing that houses the light source, the optical splitter, the first optical switch, the second optical switch, and the photodetector, wherein the first optical element and the second optical element are disposed outside the housing.

3. The measuring device according to claim 1 or 2, further comprising: a first optical branching element that inputs the illumination light from the optical splitter into the first waveguide and inputs the reflected light from the first optical element into the third waveguide; and a second optical branching element that inputs the illumination light from the optical splitter into the second waveguide and inputs the reflected light from the second optical element into the fourth waveguide.

4. Further comprising another optical splitter for superimposing the reflected light and the reference light and inputting the result as the interference light to the photodetector, wherein the optical path length between the optical splitter and the first optical switch is d １ , the optical path length between the first optical switch and the first optical branching element is d ３１ , the optical path length between the first optical switch and the second optical branching element is d ３２ , the optical path length between the first optical branching element and the first optical element is d ５１ , the optical path length between the second optical branching element and the second optical element is d ５２ , the optical path length between the first optical branching element and the second optical switch is d ７１ , the optical path length between the second optical branching element and the second optical switch is d ７２ , the optical path length between the second optical switch and the other optical splitter is d ４ When this is the case, d １ + d ３１ + 2d ５１ + d ７１ + d ４ = d １ + d ３２ + 2d ５２ + d ７２ + d ４ That is, the measuring device according to claim 3.

5. The measuring device according to claim 3, further comprising at least one other housing that houses the first optical branching element and the second optical branching element.

6. The measuring device according to claim 5, wherein the at least one other housing houses the first optical element and the second optical element.

7. The measuring device according to claim 6, wherein the at least one other housing includes two other housings that are a first optical head and a second optical head, the first optical head houses the first optical branching element and the first optical element, and the second optical head houses the second optical branching element and the second optical element.

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