Measurement equipment and programs

Abstract

To provide a measuring device capable of counting the number of rotating axles in one moving body in a non-contact manner.SOLUTION: A measuring device 100 includes: a light source 20 that emits laser light 20L0 for irradiating a side of a wheel 14 of a moving body 10 having the wheel 14 and can change a frequency of the laser light 20L0; an interference optical system 24 that separates the laser light 20L0 into reference light 20L1 and output light 20L2, in which the output light 20L2 is reflected by the side of the wheel 14, and the reflected light 20L3 is caused to interfere with the reference light 20L1 to produce interference light 20L4; a photodetector 40 that detects the interference light 20L4; and a processing circuit 60 that processes signals output from the photodetector 40. The processing circuit 60 generates data regarding the rotation speed of the wheel 14 based on the signal output from the photodetector 40.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a measurement device and a program. [Background technology]

[0002] ETC (Electronic Toll Collection) is a system that allows users to pay tolls on toll roads such as expressways without having to stop their vehicles at toll booths. There are several vehicle classifications for tolls, depending on, for example, the size and number of axles of the vehicle. Users pay the toll by setting information corresponding to their own vehicle classification in the on-board unit. There is a possibility of fraudulent passage, whereby users set information for a vehicle classification other than their own in the on-board unit in order to reduce the toll. As a countermeasure against this, ETC is equipped with a vehicle detection device containing multiple sensors.

[0003] Tolls vary greatly depending on the number of axles. Current ETC systems use tread-shaped axle detection sensors to count the number of rotating axles based on the number of wheels that come into contact with the sensors. In recent years, the number of large trucks equipped with a feature called a lift axle has been increasing. Large trucks with three or more axles can use the lift axle function to lift some axles, lifting the wheels attached to those axles. As a result, when the load is light, the pressure on the other wheels is increased, preventing the large truck from slipping. Large trucks that use the lift axle function have axles that do not rotate while driving. For this reason, ETC is required to accurately count the number of rotating axles among the vehicle's multiple axles.

[0004] In recent years, axle detection sensors that count the number of axles without contact have been developed. Patent Documents 1 to 3 disclose examples of such axle detection sensors. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5911681 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-204088 [Patent Document 3] German Patent Application Publication No. 102008037233 [Non-patent literature]

[0006] [Non-Patent Document 1] Christopher V. Poulton, et al., “Frequency-modulated Continuous-wave LIDAR Module in Silicon Photonics”, OFC2016, W4E.3, (2016). Summary of the Invention [Problem to be solved by the invention]

[0007] The present disclosure provides a measurement device that accurately counts the number of rotating axles on a single moving object without contact. [Means for solving the problem]

[0008] A measuring device according to one aspect of the present disclosure includes a light source that emits laser light to illuminate a side of a wheel of a moving body having wheels and is capable of changing the frequency of the laser light; an interference optical system that separates the laser light into reference light and output light and generates interference light by causing the reference light to interfere with reflected light generated when the output light is reflected off the side of the wheel; a photodetector that detects the interference light; and a processing circuit that processes a signal output from the photodetector, wherein the processing circuit generates data regarding the rotational speed of the wheel based on the signal output from the photodetector.

[0009] 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. A computer-readable recording medium may include 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. A "system" may include devices installed in remote locations away from other devices and connected via a communication network. [Effects of the Invention]

[0010] According to the technology of the present disclosure, it is possible to realize a measurement device that can accurately count the number of rotating axles on a single moving body without contact. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram schematically illustrating the configuration of a measurement device according to an exemplary embodiment of the present disclosure. [Figure 2A] FIG. 2A is a diagram schematically showing the time variation of the frequencies of the reference light and the reflected light when the moving object is stationary. [Figure 2B] FIG. 2B is a diagram schematically showing the time changes in the frequencies of the reference light and the reflected light when a moving object approaches the measurement device. [Figure 3A] FIG. 3A is a side view schematically illustrating an example of a moving object. [Figure 3B] FIG. 3B is a top view schematically illustrating an example of a moving object. [Figure 3C] FIG. 3C is a front view schematically illustrating an example of a moving object. [Figure 3D] FIG. 3D is an enlarged view of one of the wheels of the vehicle shown in FIG. 3A. [Figure 4] FIG. 4 is a flowchart showing an example of a measurement operation executed by the processing circuit. [Figure 5] FIG. 5 is a diagram schematically showing a first example of changes over time in the measured speed and the measured distance. [Figure 6] FIG. 6 is a diagram schematically illustrating a second example of the change over time in the measured speed. [Figure 7] FIG. 7 is a diagram schematically illustrating a third example of the change over time in the measured speed. [Figure 8A] FIG. 8A is a graph showing a first example of calculated changes in the measured velocity over time. [Figure 8B] FIG. 8B is a graph showing a second example of calculation of the change in the measured velocity over time. [Figure 8C] FIG. 8C is a graph showing a third example of calculation of the change in measurement speed over time. [Figure 9A] FIG. 9A is a graph showing the change over time in the measured speed of the moving object in Example 1. FIG. [Figure 9B] FIG. 9B is a graph showing the change over time in the measured speed of the moving object in Example 2. [Figure 10] FIG. 10 is a block diagram schematically illustrating another configuration of a measurement device according to an exemplary embodiment of the present disclosure. [Figure 11] FIG. 11 is a flowchart showing another example of the measurement operation executed by the processing circuit. [Figure 12A] FIG. 12A is a diagram schematically illustrating a first example of the installation of a measuring device in an ETC. [Figure 12B] FIG. 12B is a diagram schematically illustrating a second example of the installation of a measuring device in an ETC. DETAILED DESCRIPTION OF THE INVENTION

[0012] In this 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). An 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 programmable after LSI fabrication, or a reconfigurable logic device, which can reconfigure connections within an LSI or set up circuit partitions within an LSI, may also be used for the same purpose.

[0013] 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 performed by the processor and peripheral devices. A system or device may include one or more non-transitory recording media on which software is recorded, a processor, and necessary hardware devices, such as interfaces.

[0014] 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."

[0015] 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.

[0016] First, the findings that form the basis of this disclosure will be described.

[0017] Tread-shaped axle detection sensors that come into contact with the wheels have issues such as a high frequency of failure, high maintenance frequency, and high replacement costs. Future ETC systems will be required to allow vehicles to travel at higher speeds in order to alleviate traffic congestion, and the above issues will become even more pronounced.

[0018] The microwave Doppler sensor or spatial filter sensor disclosed in Patent Document 1 does not have sufficient spatial resolution for measuring the distance between two vehicles or two wheels. As a result, it can only measure short distances, and the sensor must be installed close to the vehicle. Furthermore, the sensor installation method disclosed in Patent Document 1 cannot detect vehicles, making it impossible to determine the extent of each vehicle.

[0019] The device disclosed in Patent Document 2 counts the number of tires based on image data obtained by irradiating the tires with laser light. This device cannot determine whether the tires are in contact with the ground or not.

[0020] The device disclosed in Patent Document 3 detects wheels using a radar. Like the sensor disclosed in Patent Document 1, this device does not have sufficient spatial resolution for detecting the distance between two vehicles and the distance between two wheels.

[0021] The present inventors have conceived a measurement device according to an embodiment of the present disclosure that can solve the problems of current ETC systems and the problems of the sensors and devices disclosed in Patent Documents 1 to 3. A measurement device according to an embodiment of the present disclosure can count the number of rotating axles on a single moving object in a non-contact manner using so-called FMCW (Frequency-Modulated Continuous-Wave)-LiDAR (Light Detecting and Ranging) technology. The measurement device according to this embodiment can accurately count the number of rotating axles with high spatial resolution, even when the distance between two vehicles is narrow, the distance between two wheels is narrow, or the vehicle is traveling at a high speed. The measurement device according to an embodiment of the present disclosure and a program used in the measurement device are described below.

[0022] A measurement device according to a first aspect of the present invention includes a light source that emits a laser beam for irradiating a side of a wheel of a vehicle having wheels and that is capable of changing the frequency of the laser beam, an interference optical system that separates the laser beam into a reference beam and an output beam and generates interference light by causing the reference beam to interfere with light reflected from the side of the wheel, a photodetector that detects the interference light, and a processing circuit that processes the signal output from the photodetector. The processing circuit generates data regarding the rotational speed of the wheel based on the signal output from the photodetector.

[0023] This measuring device can accurately count the number of rotating axles on a single moving object without contact.

[0024] The measuring device according to the second item is the measuring device according to the first item, in which the data relating to the rotational speed of the wheels is used as first data, and the processing circuit generates second data relating to at least one of the distance from the measuring device to the moving body and the traveling speed of the moving body based on the signal output from the photodetector, counts the number of rotating axles on the moving body based on the first data and the second data, and outputs data indicating the counted number.

[0025] This measuring device can accurately count the number of rotating axles on one moving object by comparing the first data with the second data.

[0026] The measuring device according to the third item is the measuring device according to the first or second item, wherein when the angle between the output light and a plane parallel to the road surface on which the moving body is traveling is defined as θ, and the angle between the output light and a plane perpendicular to the traveling direction of the moving body is defined as φ, at least one of θ and φ is not zero.

[0027] In this measuring device, the measuring speed at the vehicle body or at the non-rotating wheels and the measuring speed at the rotating wheels may differ from each other.

[0028] A measurement device according to a fourth item is the measurement device according to the third item, wherein both θ and φ are not zero.

[0029] In this measuring device, the absolute value of the difference between the measured velocity at the vehicle body or non-rotating wheel and the measured velocity at the rotating wheel can be even larger compared to when only one of the angles θ and φ is non-zero.

[0030] A measurement device according to a fifth item may be the measurement device according to the third item, wherein the absolute value of θ is equal to or greater than 0° and equal to or less than 85°.

[0031] A measurement device according to a sixth aspect is the measurement device according to the fifth aspect, wherein the absolute value of θ is equal to or greater than 0° and equal to or less than 15°.

[0032] In this measurement device, the height at which the output light scans the moving object can be easily adjusted.

[0033] A seventh aspect of the present invention relates to the measurement device according to the third, fifth, or sixth aspect, wherein the absolute value of φ is equal to or greater than 0° and equal to or less than 85°.

[0034] The measurement device according to an eighth item may be the measurement device according to the seventh item, wherein the absolute value of φ is equal to or greater than 5° and equal to or less than 30°.

[0035] The measurement device according to the ninth item is a measurement device according to any one of the first to eighth items, wherein the optical path of the output light from the interference optical system to the moving body and the optical path of the reflected light from the moving body to the interference optical system overlap each other.

[0036] In this measurement device, by adopting a coaxial optical system, the configuration of the measurement device can be simplified and stable measurements can be achieved.

[0037] A measurement device according to a tenth item is the measurement device according to any one of the first to ninth items, further comprising a beam shaper that adjusts the irradiation spot diameter of the output light to be smaller than the diameter of the wheel.

[0038] This measuring device can irradiate the vehicle body and the wheels with output light separately.

[0039] The measurement device according to an eleventh aspect is the measurement device according to the tenth aspect, wherein the wheel includes a wheel and a tire mounted on the wheel. The beam shaper adjusts the irradiation spot diameter to be smaller than the cross-sectional height of the tire.

[0040] This measuring device can irradiate only the tire of the wheel with output light.

[0041] A measurement device according to a twelfth item is the measurement device according to the tenth or eleventh item, wherein the moving body has two adjacent wheels, and the two adjacent wheels include the wheel. The beam shaper adjusts the irradiation spot diameter to be smaller than the shortest distance between the two adjacent wheels.

[0042] This measuring device can individually measure the rotational speeds of multiple wheels included in a moving object.

[0043] A thirteenth aspect of the present invention provides a measurement device according to any one of the first to twelfth aspects, further comprising a camera for capturing an image of the moving object. The processing circuit determines the direction of the output light based on image data of the moving object generated by the camera.

[0044] This measuring device can irradiate the vehicle body and wheels with output light regardless of the vehicle's running position in the lane and the size of the wheels.

[0045] The program according to the fourteenth item is a program used in a measurement device. The measurement device includes: a light source that emits a laser beam for irradiating a side of a wheel of a moving object having wheels and that is capable of changing the frequency of the laser beam; an interference optical system that separates the laser beam into a reference beam and an output beam and causes the reference beam to interfere with light reflected from the side of the wheel to generate interference light; a photodetector that detects the interference light; and a processing circuit that processes a signal output from the photodetector. The program generates data regarding the rotational speed of the wheel based on the signal output from the photodetector.

[0046] This program allows for accurate counting of the number of rotating axles on a single moving object without contact.

[0047] (Embodiment) First, with reference to FIG. 1, the configuration of a measurement device according to an exemplary embodiment of the present disclosure will be described. FIG. 1 is a block diagram schematically illustrating the configuration of a measurement device according to an exemplary embodiment of the present disclosure. FIG. 1 illustrates a moving object 10 to be measured. The moving object 10 illustrated in FIG. 1 includes a body 12 having two axles and four wheels 14 attached to the axles. The wheels 14 include metal wheels and rubber tires mounted on the wheels. The measurement device 100 illustrated in FIG. 1 includes a light source 20, an interference optical system 30, a photodetector 40, a beam shaper 50, a processing circuit 60, and a memory 62. The open arrow illustrated in FIG. 1 indicates the traveling direction of the moving object 10. The thick arrow illustrated in FIG. 1 indicates the flow of light. The thin arrow illustrated in FIG. 1 indicates the transmission and reception of signals. The measurement device 100 may be installed, for example, beside a lane along which the moving object 10 travels.

[0048] The light source 20 emits laser light 20L0 whose frequency can be varied. The frequency can be modulated at a constant time period, such as a triangular wave or a sawtooth wave. The frequency modulation period can be, for example, 1 μs to 10 ms. The frequency modulation amplitude can be, for example, 100 MHz to 1 THz. The wavelength of the laser light can be, for example, within the near-infrared wavelength range of 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 can be within the visible wavelength range of 400 nm to 700 nm, or within the ultraviolet wavelength range.

[0049] The interference optical system 30 includes a first fiber splitter 32, a second fiber splitter 34, and an optical circulator 36. The first fiber splitter 32 splits the laser light 20L0 emitted from the light source 20 into a reference light 20L1 and an output light 20L2. The first fiber splitter 32 inputs the reference light 20L1 to the second fiber splitter 34 and inputs the output light 20L2 to the optical circulator 36. The optical circulator 36 inputs the output light 20L2 to the beam shaper 50. The optical circulator 36 inputs reflected light 20L3 generated by irradiating the side of the moving object 10 with the output light 20L2 to the second fiber splitter 34. The second fiber splitter 34 inputs interference light 20L4, which is obtained by superimposing and interfering with the reference light 20L1 and the reflected light 20L3, to the photodetector 40.

[0050] The photodetector 40 detects the interference light 20L4. The photodetector 40 includes one or more photodetection elements. The photodetection elements output a signal corresponding to the intensity of the detected light.

[0051] The beam shaper 50 shapes the illumination spot of the output light 20L2 and emits the output light 20L2 toward the moving body 10. The sides of the moving body 10 are illuminated with the output light 20L2 output from the beam shaper 50. The sides of the moving body 10 include the sides of the body 12 and the sides of the wheels 14. Even if the direction of the output light 20L2 is fixed, as the moving body 10 moves, the side surface of the moving body 10 is scanned across by the output light 20L2. The beam shaper 50 inputs the reflected light 20L3 generated at the side of the moving body 10 into the interference optical system 30. The beam shaper 50 is located on the optical path of the output light 20L2 and the reflected light 20L3 between the interference optical system 30 and the moving body 10.

[0052] The beam shaper 50 may include, for example, a collimating lens 52 that reduces the spread of the output light 20L2. The collimating lens 52 may adjust the illumination spot diameter of the output light 20L2 to be smaller than the diameter of the wheel 14 of the moving object 10. The output light 20L2 having such an illumination spot diameter can separately illuminate the body 12 and the wheel 14 of the moving object 10. The collimating lens 52 may also adjust the illumination spot diameter of the output light 20L2 to be smaller than the cross-sectional height of the tire. The cross-sectional height is equal to half the value obtained by subtracting the inner diameter of the tire from the outer diameter of the tire. The output light 20L2 having such an illumination spot diameter can illuminate only the tire of the wheel 14 with the output light 20L2. In some cases, a portion of the wheel of the wheel 14 may be hollowed out for design reasons. Even in such cases, if only the tire of the wheel 14 can be illuminated with the output light 20L2, effective reflected light 20L3 can be obtained, allowing the rotational speed of the wheel 14 to be accurately measured. Furthermore, the collimating lens 52 may be adjusted so that the irradiation spot diameter of the output light 20L2 is smaller than the shortest distance between two adjacent wheels 14. With output light 20L2 having such an irradiation spot diameter, it is possible to individually measure the rotational speeds of multiple wheels 14. Unlike microwaves or millimeter waves, if infrared light is used, for example, the irradiation spot diameter of the output light 20L2 can be made small as described above.

[0053] As described above, the beam shaper 50 can achieve high spatial resolution in irradiation with the output light 20L2. The output light 20L2 emitted from the beam shaper 50 is effective for irradiating two closely spaced mobile bodies 10 or two closely spaced wheels 14. The beam shaper 50 may or may not be provided as needed.

[0054] In the measurement device 100, the optical path of the output light 20L2 from the interference optical system 30 to the moving body 10 and the optical path of the reflected light 20L3 from the moving body 10 to the interference optical system 30 overlap each other. By employing such a coaxial optical system, the configuration of the measurement device 100 can be simplified and stable measurement can be achieved. Note that the above two optical paths may be designed not to overlap each other.

[0055] The processing circuit 60 controls the operations of the light source 20 and the photodetector 40. The processing circuit 60 processes the signal output from the photodetector 40 using FMCW-LiDAR technology. The processing circuit 60 counts the number of rotating axles in the moving object 10 in a non-contact manner through signal processing. The operation of the processing circuit 60 will be described in detail later.

[0056] The computer program executed by the processing circuit 60 is stored in memory 62, such as ROM or RAM (Random Access Memory). Thus, the measurement device 100 includes a processing device including the processing circuit 60 and memory 62. The processing circuit 60 and memory 62 may be integrated on a single circuit board or may be provided on separate circuit boards. The functions of the processing circuit 60 may be distributed across multiple circuits. The processing device may be installed in a remote location away from the other components and may control the operations of the light source 20 and the photodetector 40 via a wired or wireless communication network.

[0057] Next, FMCW-LiDAR technology will be briefly explained with reference to Figures 2A and 2B. FMCW-LiDAR technology makes it possible to realize a measurement device that is highly vibration-resistant, has a wide dynamic range for distance, and has high spatial resolution, and is capable of measuring the speed of a moving object. Details of FMCW-LiDAR technology are disclosed in, for example, Non-Patent Document 1.

[0058] FIG. 2A is a diagram illustrating the temporal changes in the frequencies of the reference light 20L1 and the reflected light 20L3 when the moving object 10 is stationary. The solid line represents the reference light, and the dashed line represents the reflected light. The frequency of the reference light 20L1 shown in FIG. 2A repeats a triangular wave change over time. That is, the frequency of the reference light 20L1 increases linearly over one period and then decreases linearly by the same amount. The frequency of the reflected light 20L3 is shifted along the time axis compared to the frequency of the reference light 20L1 by the time it takes for the output light 20L2 to be emitted from the measurement device 100, reflected by the moving object 10, and returned as the reflected light 20L3. As a result, the interference light 20L4, which is the result of the superposition and interference of the reference light 20L1 and the reflected light 20L3, has a frequency corresponding to the difference between the frequency of the reflected light 20L3 and the frequency of the reference light 20L1. The double arrow in FIG. 2A indicates the difference between the two frequencies. The photodetector 40 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 difference between the above frequencies. From the beat frequency, the processing circuit 60 can generate data regarding the distance from the measurement device 100 to the moving object 10.

[0059] FIG. 2B is a diagram illustrating the time variation of the frequencies of the reference light 20L1 and the reflected light 20L3 as the moving object 10 approaches the measurement device 100. As the moving object 10 approaches, the frequency of the reflected light 20L3 shifts in an increasing direction along the frequency axis due to Doppler shift compared to when the moving object 10 is stationary. The amount of frequency shift of the reflected light 20L3 depends on the component of the velocity vector of a certain part of the moving object 10 projected in the direction of the reflected light 20L3. The beat frequency differs depending on whether the frequencies of the reference light 20L1 and the reflected light 20L3 linearly increase or decrease. In the example shown in FIG. 2B, the beat frequency when both frequencies linearly decrease is higher than the beat frequency when both frequencies linearly increase. The processing circuit 60 can generate data regarding the velocity of the moving object 10 from the difference in beat frequency.

[0060] Next, with reference to FIGS. 3A to 3D, how a moving moving object 10 is illuminated with output light 20L2 will be described. In the following description, the moving object 10 to be measured is a large truck. The moving object 10 includes a body 12 with five axles and ten wheels 14 attached to the axles. FIGS. 3A to 3C are side, top, and front views, respectively, that schematically illustrate an example of the moving object 10. FIG. 3D is an enlarged view of one of the wheels 14 of the moving object 10 shown in FIG. 3A. Of the wheels 14 shown in FIG. 3D, the inner circle represents the wheel 14a, and the outer ring represents the tire 14b.

[0061] 3A to 3D show mutually orthogonal X-, Y-, and Z-axes for ease of explanation. However, these axes do not limit the orientation of the mobile object 10 and the measurement device 100, and these orientations are arbitrary. The +X direction is the direction of the X-axis arrow, and the -X direction is the opposite direction. The same applies to the ±Y and ±Z directions. As shown in FIGS. 3A to 3D, the +X direction is the direction opposite to the traveling direction of the mobile object 10 and is parallel to the road surface on which the mobile object 10 travels. The +Y direction is perpendicular to the road surface and is a direction away from the road surface. The +Z direction is perpendicular to the traveling direction of the mobile object 10 and is parallel to the road surface and is the direction from the mobile object 10 to the measurement device 100 when the mobile object 10 and the measurement device 100 face each other.

[0062] The open arrows in FIGS. 3A and 3B represent the traveling direction of the moving object 10. The thick arrow in FIG. 3A represents the position and direction in which the moving moving object 10 is scanned by the output light 20L2. Of the two thick arrows in FIGS. 3B and 3C, the arrow pointing from the measurement device 100 to the moving object 10 represents the output light 20L2, and the arrow pointing from the moving object 10 to the measurement device 100 represents the reflected light 20L3. The angle φ in FIG. 3B represents the angle between the output light 20L2 and the YZ plane, which is perpendicular to the traveling direction of the moving object 10. The angle θ in FIG. 3C represents the angle between the output light 20L2 and the XZ plane, which is parallel to the road surface on which the moving object 10 is traveling. The open arrow in FIG. 3D represents the direction of the rotational speed of the wheel 14 at position P.

[0063] The angles φ and θ can have not only positive values ​​but also negative values. When the angle φ is positive, the output light 20L2 is emitted diagonally from the front toward the side of the moving body 10, and when the angle φ is negative, the output light 20L2 is emitted diagonally from the rear toward the side of the moving body 10. When the angle θ is positive, the output light 20L2 is emitted diagonally from above toward the side of the moving body 10, and when the angle θ is negative, the output light 20L2 is emitted diagonally from below toward the side of the moving body 10.

[0064] If the absolute value of the traveling speed of the moving object 10 is V (m / h), the traveling speed vector of the moving object 10 is (-V, 0, 0). In the example shown in FIG. 3D , the maximum radius of the wheel 14 is R (m), the distance of the straight line from the center of the wheel 14 to position P is r (m), and the angle obtained by rotating this line from the X axis is A. The X and Y components of position P in the XY coordinate system, with the center of the wheel 14 as the origin, are x = r × cosA and y = r × sinA, respectively. The absolute value of the rotational speed of the wheel 14 at position P is Vr / R, and the rotational speed vector is (-sinA × Vr / R, cosA × Vr / R, 0) = (-(y / R)V, (x / R)V, 0).

[0065] The velocity vector V1 at the vehicle body 12 or the non-rotating wheels 14 is equal to the traveling velocity vector and is expressed by the following equation (1).

number

[0066] The velocity vector V2 of the rotating wheel 14 is a composite velocity vector of the running velocity vector and the rotational velocity vector, and is expressed by the following equation (2).

number

[0067] On the other hand, a unit vector N parallel to the direction of the reflected light 20L3 is expressed by the following equation (3).

number

[0068] The X component on the right side of equation (3) can be derived by projecting the unit vector N onto the X axis in the example shown in Figure 3B. The Y component on the right side of equation (3) can be derived by projecting the unit vector N onto the Y axis in the example shown in Figure 3C. The remaining Z component on the right side of equation (3) can be derived because the magnitude of unit vector N is 1 and it is a positive component.

[0069] The velocity measured by the measurement device 100 is a component obtained by projecting a velocity vector at a certain part of the moving body 10 in the direction of the reflected light 20L3. In other words, the measured velocity is obtained by the dot product of the velocity vector at a certain part of the moving body 10 and the unit vector N.

[0070] When output light 20L2 is emitted toward body 12 or non-rotating wheels 14 of moving body 10, measured velocity v1 is obtained by the dot product of velocity vector V1 and unit vector N, and is expressed by the following equation (4).

number

[0071] Since the angle φ is known, when the angle φ≠0°, the traveling speed V of the moving body 10 can be calculated by dividing the measured speed v1 by sin φ.

[0072] When output light 20L2 is emitted toward rotating wheel 14, measured velocity v2 is obtained by the dot product of velocity vector V2 and unit vector N, and is expressed by the following equation (5).

number

[0073] The measured velocity v2 has a first term on the right-hand side due to the rotational velocity, compared to the measured velocity v1, which depends on the X and Y components of the position P.

[0074] When the emission angles of the output light 20L2 are θ = 0° and φ = 0°, the measurement velocities v1 and v2 are zero. This is because the velocity vector V1 or V2 is orthogonal to the unit vector N. If at least one of the emission angles θ and φ of the output light 20L2 is non-zero, the measurement velocities v1 and v2 may differ from each other. If both the emission angles θ and φ of the output light 20L2 are non-zero, the absolute value of the difference between the measurement velocities v1 and v2 may be larger than when only one of the emission angles θ and φ is non-zero. Note that even if at least one of the emission angles θ and φ of the output light 20L2 is non-zero, the measurement velocities v1 and v2 may coincide depending on the X and Y components of the position P. An angle φ ≠ 0° corresponds to a state in which the output light 20L2 intersects the YZ plane. An angle θ ≠ 0° corresponds to a state in which the output light 20L2 intersects the XZ plane.

[0075] When θ=0°, if output light 20L2 scans at a height where it passes through the center of wheel 14 (i.e., y=0), measured speed v2 will be the same as measured speed v1, as shown in equations (4) and (5). For this reason, it will be impossible to distinguish between the measured speed at vehicle body 12 or non-rotating wheel 14 and the measured speed at rotating wheel 14. When θ=0°, if output light 20L2 scans at a height that is somewhat separated from the height of y=0, these measured speeds can be clearly distinguished. This is because measured speed v2 differs from measured speed v1 by V(y / R)sinφ.

[0076] In contrast, when θ≠0°, even if output light 20L2 scans at a height of y=0, measurement speed v2 differs from measurement speed v1 by V(x / R)sinθ. When θ≠0°, the component of V(x / R)sinθ makes it possible to clearly distinguish between the measurement speed at the vehicle body 12 or non-rotating wheel 14 and the measurement speed at the rotating wheel 14, even if output light 20L2 scans at a height near y=0. From the above, when θ≠0°, the degree of freedom in the height at which output light 20L2 scans can be increased.

[0077] In this embodiment, the absolute value of the angle φ may be, for example, 0° or greater and 85° or less. A more desirable absolute value of the angle φ may be 5° or greater and 30° or less. In this embodiment, the absolute value of the angle θ may be, for example, 0° or greater and 85° or less, except when the angles θ and φ are both 0°. When the absolute value of the angle θ is large, the height at which the output light 20L2 scans the moving object 10 varies significantly depending on the traveling position of the moving object 10 in the ETC lane. When the absolute value of the angle θ is small, the height at which the output light 20L2 scans the moving object 10 can be easily adjusted. The absolute value of such an angle θ may be, for example, 0° or greater and 15° or less.

[0078] Next, an example of the measurement operation performed by the processing circuit 60 will be described with reference to Fig. 4. Fig. 4 is a flowchart showing an example of the measurement operation performed by the processing circuit 60. The processing circuit 60 performs the following operations from steps S101 to S104.

[0079] <Step S101> The processing circuit 60 causes the light source 20 to emit the laser beam 20L0 while changing the frequency of the laser beam 20L0. The frequency may be changed at a constant time period. The time period of the frequency change may also be variable.

[0080] <Step S102> The processing circuit 60 causes the photodetector 40 to detect the interference light 20L4. The photodetector 40 outputs a signal corresponding to the intensity of the interference light 20L4.

[0081] <Step S103> The processing circuit 60 generates data on the distance from the measuring device 100 to the moving body 10, and data on the measured speed of the body 12 and wheels 14 of the moving body 10, based on the signal output from the photodetector 40. The data on the measured speed of the body 12 or the non-rotating wheels 14 includes data on the traveling speed of the moving body 10. The data on the measured speed of the rotating wheels 14 includes data on the rotational speed of the wheels 14.

[0082] In this specification, data regarding the rotational speed of the wheels 14 is also referred to as "first data," and data regarding at least one of the distance from the measuring device 100 to the moving body 10 and the traveling speed of the moving body 10 is also referred to as "second data."

[0083] <Step S104> Based on the data generated in step S103, the processing circuit 60 counts the number of rotating wheels 14 on the side of the moving object 10 and outputs data indicating the counted number. The number of rotating wheels 14 on the side of the moving object 10 is equal to the number of rotating axles on the moving object 10. In other words, counting the number of rotating wheels 14 on the side of the moving object 10 is the same as counting the number of rotating axles on the moving object 10. The output data is input to, for example, a display device, and the display device displays the number of rotating wheels 14 on the side of the moving object 10.

[0084] As described above, by using the measurement device 100 according to this embodiment, it is possible to count the number of rotating axles in the moving body 10 in a non-contact manner.

[0085] Next, examples of time-dependent changes in the measurement speed and measurement distance will be described with reference to FIGS. 5 to 7. A moving body 10 is shown in FIGS. 5 to 7. The illustration of the moving body 10 clarifies the relationship between the time-dependent changes in the measurement speed and measurement distance and the scanning position of the moving body 10 scanned by the output light 20L2. The thick arrows crossing the moving body 10 shown in FIGS. 5 to 7 are as described with reference to FIG. 3A. The dashed-dotted lines shown in FIGS. 5 to 7 represent the front and rear ends of the moving body 10. The dashed lines shown in FIGS. 5 to 7 represent both ends of the portion of the wheels 14 scanned by the output light 20L2. In the moving body 10 shown in FIGS. 5 to 7, the fourth axle from the front of the five axles is elevated by a lift axle function. Therefore, the wheel 14 attached to the fourth axle is suspended and does not rotate while the moving body is traveling.

[0086] 5 is a diagram schematically illustrating a first example of time-varying measured speed and measured distance. In the example shown in FIG. 5, the emission angle of output light 20L2 is θ=30° and φ=0°, and output light 20L2 passes through the center of wheel 14. The traveling speed of moving object 10 is V=30 km / h. Output light 20L2 intersects the road surface obliquely and perpendicularly to the traveling direction of moving object 10.

[0087] The measured speed shown in FIG. 5 is zero for the vehicle body 12 and the fourth non-rotating wheel 14 from the front, and increases linearly from negative to positive for the wheels 14 other than the fourth. This change in measured speed over time can be explained by equations (4) and (5). According to equation (4), the measured speed for the vehicle body 12 and the non-rotating wheels 14 of the moving body 10 is zero. According to equation (5), the measured speed for the rotating wheels 14 is V(x / R)sinθ. In the example shown in FIG. 5, x / R increases linearly from -1 to 1 over time. The rotational speed of the front part of the wheels 14 is measured as a negative value, and the rotational speed of the rear part is measured as a positive value. The rotational speed of the wheels 14 varies from a minimum speed of -15 km / h to a maximum speed of 15 km / h. There is a clear difference between the measured speed for the rotating wheels 14 and the measured speed for the vehicle body 12 or the non-rotating wheels 14. Therefore, the number of rotating wheels can be accurately counted.

[0088] The measurement distance shown in Fig. 5 is the distance from the measurement device 100 to the moving body 10 when the moving body 10 is illuminated with the output light 20L2, and is the distance from the measurement device 100 to an object located far away when the moving body 10 is not illuminated with the output light 20L2. In reality, the measurement distances for the vehicle body 12 and the wheels 14 are different, but in the example shown in Fig. 5, for simplicity, the measurement distances for the vehicle body 12 and the wheels 14 are set to be constant.

[0089] As shown in FIG. 5, there is a clear difference in the measured distance between when the moving body 10 is irradiated with the output light 20L2 and when it is not. Therefore, the number of moving bodies 10 can be counted based on the measured distances shown in FIG. 5. When multiple moving bodies 10 are traveling in a narrow space, it may be impossible to distinguish whether the rotating wheels 14 correspond to one moving body 10 or two moving bodies 10 based on the measured speed alone. Even in such cases, the number of rotating axles in one moving body 10 can be accurately counted from the measured speed and measured distance. In step S104 of the measurement operation shown in FIG. 4, the processing circuit 60 counts the number of rotating axles in one moving body 10 based on data related to the distance from the measurement device 100 to the moving body 10 and data related to the rotational speed of the rotating wheels 14.

[0090] The size of the wheels 14 may vary depending on the vehicle 10. Furthermore, if the ETC lane is wide, the vehicle 10 may not travel in the center of the lane, but may travel to the right or left of the center of the lane. Therefore, the output light 20L2 may not necessarily pass through the center of the wheel 14, but may pass through the top or bottom of the wheel 14.

[0091] FIG. 6 is a diagram schematically illustrating a second example of the change in the measured speed over time. In the example shown in FIG. 6, the emission angle of the output light 20L2 is θ=30° and φ=0°, and the output light 20L2 passes above the wheel 14. The traveling speed of the moving body 10 shown in FIG. 6 is equal to the traveling speed of the moving body 10 shown in FIG. 5, V=30 km / h. The measured speed shown in FIG. 6 differs from the measured speed shown in FIG. 5 in that the change width of the measured speed of the rotating wheel 14 from negative to positive is small. According to equation (5), the measured speed of the rotating wheel 14 is V(x / R) sin θ. In the example shown in FIG. 6, x / R linearly increases over time from a value greater than −1 to a value less than 1, so the change width of x / R is small. Therefore, the difference between the measured speed of the rotating wheel 14 and the measured speed of the vehicle body 12 or the non-rotating wheels 14 is unclear, and it may not be easy to accurately count the number of rotating axles.

[0092] If the output light 20L2 not only intersects the road surface obliquely but also intersects the traveling direction of the moving body 10 obliquely, the difference in the measured speed can be made clear even if the output light 20L2 passes over the top of the wheel 14.

[0093] FIG. 7 is a diagram schematically illustrating a third example of the change in the measured speed over time. In the example shown in FIG. 7, the emission angles of the output light 20L2 are θ=15° and φ=15°, and the output light 20L2 passes over the upper part of the wheel 14, as in the example shown in FIG. 6. The traveling speed of the moving body 10 shown in FIG. 7 is equal to the traveling speed of the moving body 10 shown in FIG. 6, that is, V=30 km / h. The measured speed shown in FIG. 7 differs from the measured speed shown in FIG. 6 in that the measured speed at the car body 12 and the non-rotating wheels 14 is greater than zero, and the minimum value of the measured speed at the rotating wheels 14 is greater than the measured speed at the car body 12 and the non-rotating wheels 14. This change in the measured speed over time can be explained by equations (4) and (5). According to equation (4), the measured speed at the car body 12 and the non-rotating wheels 14 is Vsinφ, which is greater than zero. According to equation (5), the measured velocity at the rotating wheel 14 is V[(x / R)sinθ+(y / R)sinφ]+Vsinφ. The difference between the measured velocity at the rotating wheel 14 and the measured velocity at the vehicle body 12 or the non-rotating wheel 14 is V[(x / R)sinθ+(y / R)sinφ]. In the example shown in FIG. 7, x / R increases linearly over time from a value greater than −1 to a value less than 1, while y / R has a constant value greater than zero and less than 1. In the example shown in FIG. 7, since sinθ=sinφ, if (x / R)+(y / R) is always positive, the minimum measured velocity at the rotating wheel 14 will be greater than the measured velocities at the vehicle body 12 and the non-rotating wheel 14. In the example shown in FIG. 7, the difference between the measured velocities is clear, allowing the number of rotating axles to be accurately counted.

[0094] 5 and 6, when the moving body 10 is irradiated with output light 20L2, the measured speed is greater than zero. That is, from the measured speed, it is possible to count not only the number of rotating wheels 14 but also the number of moving bodies 10. In step S104 of the measurement operation shown in FIG. 4, the processing circuit 60 counts the number of rotating axles in one moving body 10 based on data related to the traveling speed of the moving body 10 and data related to the rotational speed of the rotating wheels 14.

[0095] Next, with reference to FIGS. 8A to 8C, we will explain how the time change in the measurement speed varies depending on the scanning position of the output light 20L2 when the emission angles φ and θ of the output light 20L2 are fixed. FIGS. 8A to 8C are graphs showing an example of calculating the time change in the measurement speed. FIGS. 8A to 8C show a wheel 14 rotating in the direction indicated by the curved arrow. The illustration of the wheel 14 clarifies the relationship between the time change in the measurement speed and the scanning position of the wheel 14 by the output light 20L2. The thick arrows crossing the wheel 14 in FIGS. 8A to 8C represent the position and direction of the moving object 10 scanned by the output light 20L2. The parts other than the wheel 14 are considered to be part of the vehicle body 12. In the example shown in FIGS. 8A to 8C, the emission angles of the output light 20L2 are θ = 15° and φ = 15°, the traveling speed of the moving object 10 is 30 km / h, and the diameter of the wheel 14 is 1 m. In the examples shown in FIGS. 8A to 8C, the heights of the scanning position of output light 20L2 from the road surface are 0.9 m, 0.5 m, and 0.1 m, respectively.

[0096] In the examples shown in Figures 8A to 8C, the measured speed at the vehicle body 12 is 30 sin 15° (km / h) = 7.76 (km / h). In the examples shown in Figures 8A to 8C, the measured speed at the wheel 14 increases linearly over time. In the example shown in Figure 8A, the minimum value of the measured speed at the wheel 14 is higher than the measured speed at the vehicle body 12. In the example shown in Figure 8B, the minimum value of the measured speed at the wheel 14 is lower than the measured speed at the vehicle body 12, and the maximum value of the measured speed at the wheel 14 is higher than the measured speed at the vehicle body 12. In the example shown in Figure 8C, the maximum value of the measured speed at the wheel 14 is lower than the measured speed at the vehicle body 12.

[0097] According to equation (5), the measurement speed of the rotating wheel 14 increases linearly due to the component V(x / R) sinθ. The rate of change of the measurement speed over time does not depend on the height of the scanning position of the output light 20L2. On the other hand, the range of change of the measurement speed depends on the height of the scanning position. This is because the range of change of x / R decreases as the distance from the center of the wheel 14 increases. When the output light 20L2 passes through the center of the wheel 14, the minimum value of (x / R) is −1 and the maximum value of (x / R) is 1. When the output light 20L2 passes through the top or bottom of the wheel 14, the minimum value of (x / R) is greater than −1 and the maximum value of (x / R) is less than 1.

[0098] Furthermore, according to equation (5), the measured velocity of the rotating wheel 14 shifts in an increasing or decreasing direction depending on the height of the irradiation position of output light 20L2 due to the component of V(y / R)sinφ. When output light 20L2 passes over the upper part of the wheel 14, the measured velocity shifts in an increasing direction compared to when output light 20L2 passes through the center of the wheel 14. When output light 20L2 passes under the wheel 14, the measured velocity shifts in a decreasing direction compared to when output light 20L2 passes through the center of the wheel 14.

[0099] The criterion for counting the number of rotating axles is based on the difference between the measured speed at the vehicle body 12 and the measured speed at the wheels 14. The criterion differs depending on the scanning position of the output light 20L2, such as the relationship between the minimum and maximum measured speeds at the wheels 14 and the measured speed at the vehicle body 12.

[0100] 8A to 8C show similar behavior regardless of whether the traveling speed V of the moving body 10 is high or low. Therefore, the measurement device 100 according to this embodiment can count the number of rotating axles in one moving body 10 regardless of whether the traveling speed V of the moving body 10 is high or low.

[0101] Next, with reference to FIGS. 9A and 9B , an example in which the speed of the vehicle body 12 and the wheels 14 of a moving body 10 was measured using the measurement device 100 according to this embodiment will be described. FIGS. 9A and 9B are graphs showing the time change in the measured speed of the moving body 10 in Examples 1 and 2, respectively. The open circles in FIGS. 9A and 9B represent measured values, and the closed circles represent calculated values ​​obtained using Equations (4) and (5). Similar to FIGS. 5 to 7 , FIGS. 9A and 9B show the moving body 10. The illustration of the moving body 10 clarifies the relationship between the time change in the measured speed and the scanning position of the output light of the moving body 10. The moving body 10 in Examples 1 and 2 was a passenger car. The frequency of the laser light 20L0 emitted from the light source 20 was modulated to form a triangular wave. The wavelength of the laser light 20L0 was 1550 nm. The modulation period was 20 μs, and the frequency modulation amplitude was 5 GHz.

[0102] In Example 1 shown in Figure 9A, the emission angles of output light 20L2 were θ = 0° and φ = 30°, the traveling speed of moving body 10 was 5.5 km / h, the diameter of wheel 14 was 55 cm, and the height of the scanning position of output light 20L2 from the road surface was approximately 45 cm. As shown in Figure 9A, the measurement speed at vehicle body 12 and the measurement speed at wheel 14 were almost constant over time. The measurement speed at wheel 14 was higher than the measurement speed at vehicle body 12, and the measurement speed changed significantly when the measurement location was changed from vehicle body 12 to wheel 14. The measured values ​​and calculated values ​​matched well.

[0103] In Example 2 shown in Figure 9B, the emission angles of output light 20L2 were θ = 7° and φ = 15°, the traveling speed of moving body 10 was 5.7 km / h, the diameter of wheel 14 was 55 cm, and the height of the scanning position of output light from the road surface was approximately 42 cm. As shown in Figure 9B, the measured speed at vehicle body 12 remained almost constant over time, while the measured speed at wheel 14 increased over time. The minimum measured speed at wheel 14 was higher than the measured speed at vehicle body 12. The measured values ​​and calculated values ​​matched well.

[0104] According to the first and second embodiments, it is possible to count the number of rotating axles in one moving body 10 from the difference between the measured speed at the body 12 and the measured speed at the wheels 14.

[0105] As described above, the measurement device 100 according to this embodiment can count the number of rotating axles of one moving body 10 by irradiating the body 12 and wheels 14 of the moving body 10 with output light 20L2. On the other hand, if the direction and irradiation spot diameter of output light 20L2 emitted from the measurement device 100 are fixed, it may not be possible to irradiate the body 12 and / or wheels 14 with output light 20L2, depending on the running position of the moving body 10 in the lane and the size of the wheels 14. Furthermore, if the height from the road surface of the scanning position of output light 20L2 from the road surface is smaller than the minimum distance between the body 12 and the road surface, it is possible to irradiate the wheels 14 with output light 20L2, but it is not possible to irradiate the body 12 with output light 20L2.

[0106] Another example of the measurement device 100 according to this embodiment, which can solve the above-described problems, will be described below with reference to FIG. 10. FIG. 10 is a block diagram schematically showing another configuration of the measurement device according to the exemplary embodiment of the present disclosure. The measurement device 100 shown in FIG. 10 includes a camera 70 and an optical deflector 80 in addition to the components of the measurement device 100 shown in FIG. 1. The processing circuit 60 controls the camera 70 and the optical deflector 80 in addition to the light source 20 and the photodetector 40.

[0107] The camera 70 captures an image of the moving object 10 and generates and outputs image data of the moving object 10. The image data is useful for identifying the positions of the body 12 and wheels 14 of the moving object 10. The camera 70 may be, for example, a monochrome camera or a color camera.

[0108] The optical deflector 80 can change the direction of the output light 20L2 emitted from the beam shaper 50. The optical deflector 80 can include, for example, a MEMS (Micromechanical Electrosystem) mirror or a galvanometer mirror. The optical deflector 80 may have a function of adjusting the irradiation spot diameter of the output light 20L2.

[0109] Next, another example of the measurement operation executed by the processing circuit 60 will be described with reference to Fig. 11. Fig. 11 is a flowchart showing another example of the measurement operation executed by the processing circuit 60. The processing circuit 60 executes the following operations from steps S201 to S206.

[0110] <Step S201> The processing circuit 60 causes the camera 70 to capture an image of the moving object 10. The camera 70 generates and outputs image data of the moving object 10.

[0111] <Step S202> The processing circuit 60 determines the emission direction and irradiation spot diameter of the output light 20L2 based on the image data output from the camera 70. The processing circuit 60 controls the optical deflector 80 so that the output light 20L2 is emitted in the determined emission direction and irradiation spot diameter.

[0112] <Steps S203 to S206> The operations in steps S203 to S206 are the same as the operations in steps S101 to S104 shown in FIG.

[0113] From the above, by using the measuring device 100 shown in Figure 10, the body 12 and wheels 14 of the moving body 10 can be illuminated with output light 20L2 regardless of the moving position of the moving body 10 in the lane and the size of the wheels 14.

[0114] Next, an example of installation of the measuring device 100 in ETC will be described with reference to Figures 12A and 12B. Figures 12A and 12B are diagrams that schematically show an example of installation of the measuring device 100 in ETC. Figures 12A and 12B show a moving object 10, which is a large truck, traveling in an ETC lane.

[0115] In the example shown in FIG. 12A, the measurement device 100 is installed beside a lane. In the example shown in FIG. 12A, the measurement device 100 emits output light 20L2 from the side of the moving object 10 toward the side of the moving object 10. In the example shown in FIG. 12A, the angle φ can be, for example, not less than −60° and not more than +60°, and the angle θ can be, for example, not less than −30° and not more than +30°. In the example shown in FIG. 12B, the measurement device 100 is installed at a gate of the lane. The moving object 10 passes through the gate. In the example shown in FIG. 12B, the measurement device 100 emits output light 20L2 from above the moving object 10 toward the side of the moving object 10. In the example shown in FIG. 12B, the angle φ can be, for example, not less than 0° and not more than 80°, and the angle θ can be, for example, not less than 60° and not more than 90°.

[0116] The measuring device 100 is not limited to the examples shown in FIGS. 12A and 12B, and may be installed at any position in the ETC as long as the side of the moving object 10 can be illuminated with the output light 20L2. [Industrial Applicability]

[0117] The measurement device of the present disclosure can be used, for example, as an axle detection sensor in ETC. [Explanation of symbols]

[0118] 10 Mobile 12 Body 14 wheels 14a wheels 14b tires 20 light source 20L0 laser light 20L1 reference light 20L2 output light 20L3 reflected light 20L4 interference light 30 Interference Optical System 40 Photodetector 50 Beam Shaper 52 Collimating Lens 60 Processing circuit 62 memory 70 Camera 80 Optical deflector

Claims

1. a light source that emits a laser beam for irradiating a side portion of a wheel of a moving object having a wheel, the laser beam being frequency-modulated; an interference optical system that separates the laser light into a reference light and an output light, and generates interference light by causing the reference light to interfere with reflected light generated when the output light is reflected by a side portion of the wheel; a photodetector for detecting the interference light; a processing circuit for processing a signal output from the photodetector; A measuring device comprising: The processing circuit, based on the signal output from the photodetector, generating first data relating to a rotational speed of the wheel and second data relating to a distance from the measurement device to the moving object; counting the number of rotating axles in one of the moving bodies, distinguished from the plurality of moving bodies, based on the first data and the second data, and outputting data indicating the counted number; Measuring equipment.

2. When an angle between the output light and a plane parallel to a road surface on which the moving body is traveling is defined as θ, and an angle between the output light and a plane perpendicular to a traveling direction of the moving body is defined as φ, at least one of θ and φ is not zero. The measurement device according to claim 1 .

3. The θ and the φ are not both zero. The measurement device according to claim 2 .

4. The absolute value of θ is equal to or greater than 0° and equal to or less than 85°. The measurement device according to claim 2 .

5. The absolute value of θ is 0° or more and 15° or less. The measurement device according to claim 4.

6. The absolute value of the angle φ is equal to or greater than 0° and equal to or less than 85°.

6. The measuring device according to claim 2, 4 or 5.

7. The absolute value of the angle φ is 5° or more and 30° or less. The measurement device according to claim 6.

8. an optical path of the output light from the interference optical system to the moving body and an optical path of the reflected light from the moving body to the interference optical system overlap each other; The measuring device according to any one of claims 1 to 7.

9. a beam shaper that adjusts the irradiation spot diameter of the output light to be smaller than the diameter of the wheel; The measuring device according to any one of claims 1 to 8.

10. The wheel includes a wheel and a tire mounted on the wheel, The beam shaper adjusts the irradiation spot diameter to be smaller than the cross-sectional height of the tire. The measurement device according to claim 9.

11. the moving body has two adjacent wheels, and the two adjacent wheels include the wheel; The beam shaper adjusts the irradiation spot diameter to be smaller than the shortest distance between the two adjacent wheels. The measuring device according to claim 9 or 10.

12. a camera for capturing an image of the moving object; the processing circuit determines the direction of the output light based on image data of the moving object generated by the camera. The measuring device according to any one of claims 1 to 11.

13. A program used in a measurement device, The measuring device is a light source that emits a laser beam for irradiating a side portion of a wheel of a moving object having a wheel, the laser beam being frequency-modulated; an interference optical system that separates the laser light into a reference light and an output light, and generates interference light by causing the reference light to interfere with reflected light generated when the output light is reflected by a side portion of the wheel; a photodetector for detecting the interference light; a processing circuit for processing a signal output from the photodetector; Equipped with The program generating first data relating to a rotational speed of the wheel and second data relating to a distance from the measuring device to the moving object based on the signal output from the photodetector; counting the number of rotating axles in one of the moving bodies, distinguished from the plurality of moving bodies, based on the first data and the second data, and outputting data indicating the counted number; program.

Images