JP2023107682A - Differential type laser doppler speed meter, railroad vehicle speed measuring method, member, laser doppler speed meter, and speed measuring method - Google Patents

Abstract

To enable continuous measurement by widening a substantial measurable range for a body to be measured and thus minimizing a measurement omission against swinging in a width (lateral) direction (perpendicular to a measuring direction) during the measurement.SOLUTION: A differential type laser Doppler speed measuring device which irradiates an object with laser light and receives scattered light from the object to measure the moving speed of the object has: a laser light source; a collimator lens which collimates the laser beam from the laser light source into a parallel beam; a mirror which reflects at least one laser beam in a beam splitter splitting the parallel beam into two to irradiate the object; and an optical system which includes a lens converging the scattered light from the object, wherein the laser beam is emitted toward the object and/or a plurality of discrete places nearby the object.SELECTED DRAWING: Figure 1

Description

The present invention relates to a speedometer using the Doppler effect of laser light.

Laser Doppler velocimeters using a laser beam and the Doppler effect are used in many fields today because they can accurately measure the velocity of an object without contact. Examples of fields of application include the steel industry and railway speed measurement. In the steel industry, laser Doppler velocimeters are used for rolling control, where contact measurement is difficult in high-temperature work processes. On the other hand, when trains run at high speeds, the wheels spin and slip, making it impossible to accurately measure operating speed from wheel rotation. there is
The following methods are mainly used as conventional velocity measurement methods using laser Doppler velocimeters and the like.

In the millimeter-wave Doppler method, millimeter-waves are applied to objects at a short distance (for example, rail track surfaces and sleepers at a short distance from the vehicle), and the reflected waves from these objects are received and measured (non-contact measurement). ), there is no influence of poor contact with objects (for example, sliding or slipping). However, the wavelength is 3,000 to 1,000 µm longer than that of laser light, so the spread angle of the beam is large (it is not practical because a large antenna is required to suppress the spread), and there is the problem of unstable measurement. rice field.

In the laser Doppler method of Patent Document 1, an object to be measured is irradiated with a laser beam, and the reflected light (scattered light) is received by an optical system and photoelectrically converted to obtain a detection signal, which is based on the modulation frequency. Synchronous detection is performed to extract the Doppler frequency component, and the moving speed of the object is calculated based on the extracted value. Although this non-contact method has an advantage, it has the problem that the measurement accuracy drops due to the divergence angle on the light receiving surface because the laser beam that irradiates the ground is a single beam.

This is improved by the differential laser Doppler method of the differential method in which the laser beams irradiated to the object are collimated and the difference between the reflected beams of the two laser beams is obtained. This method has the advantage of a non-contact method and the advantage that the measurement accuracy does not deteriorate even if the light receiving surface is slightly wide by making the laser beam parallel and using a differential method, and is widely used.
However, because the optical system focuses by a differential method, the measurable width (depth of focus) is short (shallow), and the measurable area is limited to the measurable area on the object (for example, the top surface of the rail). There was a problem that the measurement was interrupted when it deviated from the measurable area. In Patent Documents 2 and 3, two sensors are arranged on the measurable area in order to improve this. , the problem remained.

To solve this problem of the differential laser Doppler method, the measurable depth (depth of focus) is lengthened (deepened) so that the measurement does not stop even if the measurable place slightly deviates from the rail surface in the height direction. is Patent Document 4. However, even this method is powerless in the width (horizontal) direction, and in railway vehicles, there is still the problem that the laser beam deviates from the rail surface at curves and the like.
When continuous measurement is difficult due to the oscillation of the object to be measured, one possible solution is to spread the laser beam in the direction of oscillation. Met.

JP-A-9-281238 JP-A-5-71929 JP-A-5-105082 JP 2017-083467 A

The object of the present invention is to expand the practical measurable range of the object to be measured, so that it , to minimize missing measurements and to enable continuous measurements.
Particularly in railways, the object is to enable highly accurate measurement of the traveling speed, traveling distance and traveling direction of a railway vehicle even with respect to swings exceeding the rail width.

In order to solve the above problems, the differential laser Doppler velocity measurement device of the present invention includes a laser light source, a collimator lens that converts the laser beam from the laser light source into a parallel beam, a beam splitter that divides the parallel beam into two, an optical system including a mirror that reflects at least one laser beam out of the laser beams split into two by the beam splitter and irradiates it onto an object; and a lens that collects scattered light from the object;
The laser beam is radiated toward an object and/or a plurality of spaced locations near the object.

By configuring as described above, the effective measurable range is expanded, and it is possible to avoid measurement omissions when swinging due to speed monitoring of railroads and roller conveyors, speed against rails in scales, etc., movement distance, etc. became.
Moreover, compared with the case of using a plurality of conventional laser Doppler velocimetry devices, we were able to achieve an excellent effect at a low cost.

Further, the differential laser Doppler velocity measuring device of the present invention is characterized by arranging a member for branching the laser beam in an optical path from the laser light source to the object in a direction substantially perpendicular to the measurement direction. and

By configuring as described above, it is possible to effectively widen the horizontal (width) direction of the measurable area while reducing the influence on the existing optical system.

Further, in the differential laser Doppler velocity measuring device of the present invention, the branching member is a diffractive optical element.

By configuring as described above, it became small and thin and easy to install.
In addition, since the wavelength (frequency) of the light source and the crossing angle are all the same, the speed detection sensitivity is equal at each crossing angle, there is no adverse effect due to branching, and almost no adjustment work is required.
Furthermore, by selecting the grating pitch of the diffractive optical element and the wavelength to be used, the observation position interval can be made suitable for the purpose, so that the measurement width can be easily set.
In addition to the transmissive diffraction grating, a reflective diffraction grating that also serves as a beam bender can be used in the same way.

Further, the differential laser Doppler velocity measuring device of the present invention is characterized in that the branching member is arranged between the differential laser Doppler velocity measuring device and the object.

By configuring as described above, the existing optical system in the laser Doppler velocimeter can be used as it is, so it is easy to make it an optional item or an adapter for a normal item.
Moreover, it can be easily attached to a device already in use as a laser Doppler velocity measuring device.

Further, in the differential laser Doppler velocity measuring device of the present invention, the branching member is not arranged between the optical paths through which the scattered light is received from the object.

With the configuration as described above, the scattered light is received without being branched, so that it is possible to suppress the deterioration of the light receiving sensitivity at the time of swinging.

The railway vehicle speed measuring method of the present invention uses the differential laser Doppler speedometer.

With the configuration as described above, it is possible to measure even swing motion exceeding the rail width, so that the running speed, running distance and running direction of the railway vehicle can be measured with high accuracy.

The member of the present invention is a member attached to a laser Doppler velocimeter, and splits the irradiation light directed to the object from the laser Doppler velocimeter, and the irradiation light directed to the object and / or a plurality of spaced locations near the object. By doing so, the measurable range of the laser Doppler velocimeter is widened.

By configuring as described above, the effective measurable range is expanded, and it is possible to avoid measurement omissions when swinging due to speed monitoring of railroads and roller conveyors, speed against rails in scales, etc., movement distance, etc. became.
Moreover, compared with the case of using a plurality of conventional laser Doppler velocimetry devices, we were able to achieve an excellent effect at a low cost.

Further, a laser Doppler velocimeter of the present invention is characterized by using the above member.

Moreover, the velocity measurement method of the present invention is characterized by using the laser Doppler velocity meter.

According to the present invention, it is possible to avoid omission of measurement at the time of swaying, such as the speed relative to the rail and the moving distance in the speed monitoring of railroads and roller conveyors.
Moreover, the cost is low compared to the case of using a plurality of laser Doppler velocity measuring devices.

1 is a configuration diagram of a laser Doppler velocity measuring device according to a first embodiment; FIG. FIG. 2 is a schematic explanatory diagram of Example 1 in a state without rocking; FIG. 2 is a schematic explanatory diagram of Example 1 in a state of swinging; FIG. 2 is a schematic explanatory diagram of Example 1 in a state of swinging; FIG. 2 is a schematic explanatory diagram of Example 1 in a state of swinging; FIG. 2 is a schematic explanatory diagram of Example 1 in a state of swinging; FIG. 11 is a schematic illustration of another embodiment with a laser Doppler velocimeter; FIG. 4 is a schematic explanatory diagram of a laser Doppler velocimeter according to a second embodiment; FIG. 5 is a schematic explanatory diagram of a laser Doppler velocimeter according to a third embodiment; It is a figure which shows the structure of the conventional laser Doppler velocimeter. It is a figure for demonstrating the operation|movement of the conventional laser Doppler velocimeter. It is a figure for demonstrating the operation|movement of the conventional laser Doppler velocimeter.

With laser Doppler velocimeters, there have been problems with fluctuations that exceed the measurable range due to various factors during measurement, resulting in missing measurements. became.

First, the principle of the laser Doppler velocimeter will be described with reference to FIG. 10 (conventional laser Doppler velocimeter). FIG. 10(a) is a view of the laser Doppler velocimeter DIV viewed from the traveling direction of the object O (from the back side of the paper surface to the front side) or from the opposite direction (from the front side of the paper surface to the back side) (hereinafter referred to as "front and back of the paper 10(b) is a view of the laser Doppler velocimeter DIV from a direction perpendicular to the moving direction of the object O (the object O moves from the left side to the right side of the paper surface). (Hereinafter, referred to as "left-to-right movement diagram on paper"). Here, the optical system, which is the basic configuration of the differential laser Doppler velocimeter, will be described below with reference to FIG.

In FIG. 10B, a laser beam emitted from a laser light source 1 is collimated by a collimator lens 2 and enters a frequency shift element (AOM) 3 . The frequency shift element 3 shifts the frequency of the incident laser beam by 40 MHz, and emits a 1st-order diffracted light 52 diffracted by a certain angle and a 0th-order diffracted light 51 which passes through as it is. These emitted lights are incident on the polarizing beam splitter 4 and split into 0th-order diffracted light 51 as P-polarized light and 1st-order diffracted light 52 as S-polarized light. The 0th-order diffracted light 51 is bent by the mirror 82, then folded back by the mirror 83, circularly polarized through the λ/4 wavelength plate 86, and then irradiated to the moving object O. FIG.

On the other hand, the first-order diffracted light 52 reflected by the polarization beam splitter 4 is reflected by the mirror 81, passes through the λ/4 wavelength plate 85, becomes circularly polarized, and irradiates the moving object O. FIG.

The 0th-order diffracted light 51 and the 1st-order diffracted light 52 are irradiated so as to intersect at the irradiation point M on the object O, and the scattered light is collected by the light receiving lens 8 and photoelectrically converted by the light receiving element 9. , Doppler shift frequency detection.
The beat signal frequency of the electrical signal output is displaced in the plus or minus direction around 40 MHz, and the displaced frequency amount is proportional to the moving speed of the object O. FIG. By processing this electrical signal, the moving speed of the object O is calculated.

As described above, the 0th-order diffracted light 51 is emitted from the frequency shift element 3, transmitted through the beam splitter 4, bent by the mirror 82, turned back by the mirror 83, passed through the λ/4 wavelength plate 86, and This is the optical path leading to the moving object O. The primary diffracted light 52 is emitted from the frequency shift element 3, reflected by the beam splitter 4 and the mirror 81, and passed through the λ/4 wavelength plate 85 to reach the moving object. This is the optical path leading to O. The 0th-order diffracted light 51 is incident from the front of the moving object, and the 1st-order diffracted light 52 is incident from the rear of the moving object. These optical systems constitute a differential laser Doppler velocimeter. ing.

FIGS. 11 and 12 show a case where the differential laser Doppler velocimeter shown in FIG. 10 is used to measure the speed of a railcar, for example. Here, FIGS. 11 and 12 show a state in which the laser Doppler velocimeter DIV is attached to a vehicle (not shown). , that is, the moving speed of the vehicle, is an explanatory diagram of a configuration for measuring.
11(a) and 12(a) are diagrams showing the movement of the vehicle (laser Doppler velocimeter DIV) with respect to the railroad rail R, and FIGS. 1 is a diagram of a laser irradiation area directed to a rail R on a railroad rail R viewed from the laser Doppler velocimeter DIV side (upper side).

As shown in FIGS. 11 and 12, the upper surface (head) of the rail R is the measurement surface, but since it is R-shaped (rounded shape), the effective width W of the upper surface total width L of the rail R has an allowable error. It is the range of the surface that can be measured by
Generally, the rail R has an upper surface full width L of 62 to 65 mm and a width W of 40 to 50 mm.
Here, laser irradiation is normally performed from the laser Doppler velocimeter DIV using the center M of the width W as a reference position (see FIG. 11).
Also, the limit of the measurable laser irradiation area is, for example, an irradiation area M' from the irradiation light of the laser Doppler velocimeter DIV as shown in FIG.
As a result, if the laser Doppler velocimeter moves beyond W/2 (±W/2) in the lateral width direction of the rail R from the reference position, the irradiation area on the measurement surface cannot be properly measured.

The present invention has improved this, and embodiments of the present invention will be described below with reference to the drawings.
It should be noted that the present invention is not limited to the following embodiments, but includes configurations that can achieve the same technical idea as the present embodiment.

FIG. 1 is a configuration diagram of the optical part of the laser Doppler velocimeter of the first embodiment. In FIG. 10 (conventional laser Doppler velocimeter), a laser It is configured to perform beam irradiation.
Specifically, a diffractive optical element (DOE) was arranged as a member 100 for branching the laser beam in the optical path from the laser light source of the laser Doppler velocimeter to the object in a direction substantially perpendicular to the measurement direction.
Here, a diffractive optical element is an element in which a substrate is periodically provided with slits or irregularities. or phase distribution light.
The member 100 is not necessarily limited to a diffractive optical element, but in the case of a diffractive optical element, as shown in FIG. It is possible to easily irradiate (irradiation area n), 0th-order light to a measurement target portion (irradiation area m) of the object O, and 1st-order light to a measurement target portion (irradiation area p) of the object O, respectively.
Here, in the conventional laser Doppler velocimeter (FIG. 10), the 0th-order diffracted light 51 and the 1st-order diffracted light 52 intersect at the object and/or in the vicinity of the object, so that only one irradiation point M on the object O is irradiated. being irradiated.
On the other hand, in the laser Doppler velocimeter of the first embodiment (FIG. 1), the 0th-order diffracted light 51 and the 1st-order diffracted light 52 cross each other at three points (n, m and p) are irradiated.
Symbols and numbers used in the drawings can be interpreted as the same unless otherwise explained.
In this specification, in order to distinguish the diffracted light from the member 100 (diffractive optical element) from the "zero-order diffracted light 51" and the "first-order diffracted light 52" from the frequency shift element 3, "first-order light" and " The terms 0 order light" and "-1 order light" are used.

Specifically, the 0th-order diffracted light 51 (and the 1st-order diffracted light 52) emitted from the laser Doppler velocimeter becomes circularly polarized through the λ/4 wave plate 86 (and the λ/4 wave plate 85). After that, as shown in FIG. 1(a), the member 100 (diffractive optical element) splits into at least three of −1st-order light, 0th-order light, and +1st-order light, and n ( The irradiation range of -1st order light), m (irradiation range of 0th order light), and p (irradiation range of +1st order light) are irradiated respectively.

The light applied to n on the moving object surface becomes scattered light, and when it passes through the member 100 again, it is split into at least three of −1st order light, 0th order light, and +1st order light, of which , −1st-order light or +1st-order light is collected by the light receiving lens 8, photoelectrically converted by the light receiving element 9, and the Doppler shift frequency is detected.
Similarly, the light irradiated to m on the moving object plane becomes scattered light, and when it passes through the member 100 again, it is split into at least three of -1st order light, 0th order light, and +1st order light, Among them, the 0th order light is condensed by the light receiving lens 8 and photoelectrically converted by the light receiving element 9 to detect the Doppler shift frequency.
Similarly, the light irradiated to p on the moving object plane becomes scattered light, and when it passes through the member 100 again, it is divided into at least three of −1st-order light, 0th-order light, and +1st-order light. Among them, the −1st order light or +1st order light is collected by the light receiving lens 8 and photoelectrically converted by the light receiving element 9 to detect the Doppler shift frequency.
Normally, these values are summed up by the light receiving element 9 and detected.

Therefore, if any of n, m, or p on the object plane is properly illuminated, the object velocity can be measured.

[Example 1]
A case of measuring the speed of a vehicle on a railroad will be described as a first embodiment with reference to FIGS. 2 to 6. FIG. In particular, FIGS. 2 and 3 correspond to conventional FIGS. 11 and 12, respectively.

That is, at the reference position, as shown in FIG. 2 corresponding to FIG. 11, n (−1st-order light irradiation range), m (0th-order light irradiation range), m (0th-order light irradiation range), and Locations of p (irradiation range of +1st-order light) are respectively irradiated.

At the position moved by W/2 due to the rocking motion, as shown in FIG. 3 corresponding to FIG. irradiation range) are irradiated.

Furthermore, at the position moved by W due to the swing, as shown in FIG. 4, a point p (+1st-order light irradiation range) within the range of the upper surface W of the rail R is irradiated.

That is, by using the member 100, even if the laser Doppler velocimeter moves W from the reference position, it is possible to irradiate the point p, so that the irradiation area is widened and the speed of the vehicle can be measured. become.

Furthermore, if up to the second order light is used, even at a position moved by W+W/2 due to the swing, as shown in FIG. ) can be irradiated.

In this case, by using the secondary light of the member 100, even if the laser Doppler velocimeter moves W+W/2 from the reference position, q (+secondary light irradiation range) outside p (+1st order light irradiation range) Since it is possible to irradiate a portion of the irradiation range), the irradiable region is further expanded, making it possible to measure the speed of the vehicle.

In FIG. 6(c), by setting the interval between the −1st order light, the 0th order light and the 1st order light to be W, which is the measurement range considering the error of the rail R, up to the 2nd order light can be used as shown in FIG. FIG. 10 is a diagram showing that the laser Doppler velocimeter can cope with a movement of W+W/2 from the reference position even with −1st order light, 0th order light and 1st order light.

FIG. 6(d) shows the 0th-order light reduced. In this case, by allocating the 0th-order light irradiation to the -1st-order light and the +1st-order light, it is possible to effectively irradiate only two places, so that waste can be eliminated and electricity consumption can be reduced. Also, as shown in the figure, by setting the distance between the two to be W, it is possible to cope with the movement of the distance of W.

As described above, the member 100 (diffractive optical element) of Example 1 is of a transmissive type, but the diffractive optical element of the present invention is not limited to a transmissive type. For example, even if it is a reflective type, the same effect can be obtained and it can be included in the present invention.
In addition, the phase-type diffractive optical element converts the phase distribution of incident light into a phase distribution that forms a desired pattern on the image plane. is very energy efficient. Therefore, it is applied not only to a diffractive optical element with a simple shape such as a uniform intensity distribution, but also to a diffractive optical element that generates a diffraction pattern with a complicated shape, and a phase-type diffractive optical element is preferable.
Note that the member 100 is not limited to a diffractive optical element and may be other optical elements (for example, a prism, a mirror, a beam splitter, a lens, etc.) as long as it can irradiate a plurality of locations with laser light.

In the first embodiment, the case of measuring the speed of a vehicle on a railroad has been shown, but another application is shown in FIG.
FIG. 7(e) shows an irradiation point by a laser Doppler velocimeter when the width is not so limited and the movement direction is not so strict, for example, the speed control of the rolling process in the steel industry. .
In this case, the reference position of the laser Doppler velocimeter (for example, the position irradiated when there is 0th order light) is set to C, and the positions corresponding to the vertices of an equilateral triangle (X1, X2 in FIG. 7E) and X3, and C in some cases) are used as the irradiation point.

FIG. 7(f) shows an area irradiated by a laser Doppler velocimeter for an object whose moving direction is not constant, for example, an ocean current.
In this case, a diffractive optical element designed so that the irradiation points from the laser Doppler velocimeter correspond to the vertices and the center of a regular hexagon (Y1 to Y7 in FIG. 7(f)) is used.

In order to reduce the size of the differential laser Doppler velocimeter, the frequency shift element 3 and the λ/4 wavelength plates 85 and 86 in FIG. 1 may be removed. In this case, since the frequency shift element 3 is removed, the laser Doppler velocimeter is small and inexpensive, but the movement direction (polarity of movement) of the moving object O cannot be detected.
This form will be described in detail in a second embodiment (Example 2) described later.

Further, a simplified optical system of the differential laser Doppler velocimeter will be described in detail in a third embodiment (Example 3).

Although the 0th-order diffracted light 51 is reflected by the mirror 83 and the 1st-order diffracted light 52 is reflected by the mirror 81, the forms may be different. For example, the 1st-order diffracted light may be reflected by the mirror 83 and the 0th-order diffracted light may be reflected by the mirror 81 .

(Specification value example of Example 1)
Laser light wavelength: 690 nm
Measurement distance: 500mm
Rail head effective measurable width W: 40 mm
Corresponding oscillation width (± 1st order light): 116mm
Corresponding oscillation width (±secondary light): 192mm
Member 100 (diffractive optical element): 110 lines/mm diffraction grating)

[Example 2]
FIG. 8 is a configuration diagram of the optical portion of the laser Doppler velocimeter of Example 2. FIG. Example 2 is a form in which the frequency shift element 3 and the λ/4 wavelength plates 85 and 86 in Example 1 (FIG. 1) are removed in order to reduce the size of the differential laser Doppler velocimeter of Example 1. is. Since the frequency shift element 3 is removed, the laser Doppler velocimeter of FIG. 8 is small and inexpensive, but cannot detect the movement direction (polarity of movement) of the moving object O.

In FIG. 8, a laser beam emitted from a laser light source 1 is converted into a parallel beam by a collimator lens 2, and this emitted light is incident on a non-polarizing beam splitter 121 and reflected 90 degrees with a first beam 122 traveling straight. is separated into a second beam 123 pointing in the direction.
Here, unlike the first embodiment, the first beam 122 and the second beam 123 in FIG. 8 are beams of the same optical frequency with no frequency shift. The first beam 122 and the second beam 123 are reflected by the mirror 83 and the mirror 81, respectively, and split into at least three of −1st order light, 0th order light, and +1st order light by the member 100 (diffractive optical element). , and irradiates respective locations of n (-1st order light irradiation range), m (0th order light irradiation range), and p (+1st order light irradiation range) on the object O surface.

The light irradiated to n, m, and p on the surface of the object O becomes scattered light, but unlike the first embodiment, the scattered light does not pass through the member 100 and is condensed by the light receiving lens 8 .
Therefore, the scattered light is not split into −1st-order light, 0th-order light, +1st-order light, etc. by the member 100 (diffractive optical element), thereby reducing light loss and increasing measurement efficiency.
The light passing through the light-receiving lens 8 is bent by the mirror 84, photoelectrically converted by the light-receiving element 9, and the Doppler shift frequency is detected. deviates from 0 Hz in proportion to the absolute value of The moving speed of the object O is calculated by processing the electric signal having the frequency of this beat signal.

The light-receiving element 9 at this time has a wide light-receiving area so that all of the irradiation points n, m, and p on the object plane are imaged, or scattered light is incident on the light-receiving element 9. It is desirable that the image forming position is in one place, such as by arranging a toric lens between them.

In this embodiment, a linearly polarized laser Doppler velocimeter is configured for miniaturization. It is also possible to deal with an object O having a polarization dependence by using a circularly polarized wave.

[Example 3]
FIG. 9 is a configuration diagram of the optical portion of the laser Doppler velocimeter of Example 3. FIG. Example 3 is a simplified optical system of the differential laser Doppler velocimeter of Example 1, and has a simple configuration.

In FIG. 9, a laser beam emitted from a laser light source 1 is collimated by a collimator lens 2 and enters a frequency shift element (AOM) 3 . As in Example 1, the frequency shift element 3 shifts the frequency of the incident laser beam by 40 MHz, and emits the 1st-order diffracted light 52 diffracted by a certain angle and the 0th-order diffracted light 51 which passes through as it is. The emitted light (1st-order diffracted light 52 and 0th-order diffracted light 51) is split into at least three of −1st-order light, 0th-order light, and +1st-order light by the member 100 (diffractive optical element), and enters the polarization beam splitter 4. 0th order diffracted light 51 (−1st order light, 0th order light, +1st order light) which is P-polarized and 1st order diffracted light 52 (−1st order light, 0th order light, +1st order light) which is S polarization. bisected.

Then, the 0th-order diffracted light 51 (-1st-order light, 0th-order light, +1st-order light) travels straight to the transmission side, is converted into S-polarized light by the λ/2 wavelength plate 5, and then faces the moving object O, The first-order diffracted light 52 (−1st order light, 0th order light, +1st order light) travels toward the moving object O through the mirror 7, and is irradiated with n (−1st order light irradiation range) on the surface of the object O. ), m (irradiation range of 0th-order light), and p (irradiation range of +1st-order light) are irradiated.
Here, the 0th-order diffracted light 51 (-1st order light, 0th-order light, +1st-order light) is incident from the front of the moving object, and the 1st-order diffracted light 52 (-1st-order light, 0th-order light, +1st-order light ) is incident from the rear of the moving object, and these optical systems constitute a differential laser Doppler velocimeter.
There is a slight optical path difference length between these two optical paths (between the 0th order diffracted light 51 and the 1st order diffracted light 52) (see FIG. 9).
The lights irradiated to n, m, and p on the surface of the object O become scattered lights, but unlike the first embodiment, the scattered lights do not pass through the member 100 and are directly condensed by the light receiving lens 8 .
Therefore, the scattered light is not split into −1st-order light, 0th-order light, +1st-order light, etc. by the member 100 (diffractive optical element), thereby reducing light loss and increasing measurement efficiency.
The light that has passed through the light receiving lens 8 is photoelectrically converted by the light receiving element 9, the Doppler shift frequency is detected, and the moving speed of the object O is calculated.

The light-receiving element 9 at this time has a wide light-receiving area so that all of the irradiation points n, m, and p on the object plane are imaged, or scattered light is incident on the light-receiving element 9. It is desirable that the image formation position is one, such as by disposing a toric lens between the two.

In the embodiment of the present invention, examples of operation at wavelengths of 690 nm and 785 nm were shown, but the wavelengths used in the present invention are not limited to these. Wavelengths include 405 nm blue-violet, 460 nm blue, 530 nm green, 660 nm, high-power 1000 nm, 1300 nm, and 1550 nm wavelength bands for optical communication, or other wavelength bands such as lasers and Operation is possible as long as the photodetector is operable.
In the embodiment, the distance from the laser Doppler velocimeter to the rail is preferably 250 to 350 mm when mounted on a truck, and 500 to 700 mm when mounted on a vehicle body. ~50 mm, but the invention is not limited to these numerical ranges.
The distance projected by the member 100 (the distance between adjacent irradiation points on the object) is preferably 20 to 50 mm, preferably 30 to 45 mm.

The present invention can accurately measure the speed, length, and distance of an object to be measured without contact. Therefore, the present invention can be used for measuring the dimensions of billets in the rolling process of the steel industry, controlling the speed of the rolling process, etc., accurately measuring the speed and travel distance of moving objects such as trains in railways, and accurately measuring the speed and length of rails and the like. Accurate measurement of speed and travel distance of moving objects such as inspection vehicles for road infrastructure Accurate measurement of speed and travel trajectory of vehicles related to automobiles Accurate measurement of moving objects such as engines, windows, and doors Speed and distance measurement, accurate speed measurement of rotating objects such as engines and generators in the electric power industry, aviation industry, and ship industry, development in industrial equipment such as the chemical industry, construction industry, manufacturing industry, food industry, medical industry, etc. It can be applied to accurately measure the velocity and length of substances and materials in equipment, manufactured products, and manufacturing equipment. It can also be applied to measurement of fluid flow velocity and blood flow velocity.

1 laser light source 2 collimator lens 3 frequency shift element 4 polarizing beam splitter 5 λ/2 wavelength plate 6 non-polarizing beam splitter 7 mirror 8 lens 9 light receiving element 10 amplifier 51 0th order diffracted light 52 1st order diffracted light 81, 82, 83, 84 mirror 85, 86 λ/4 wavelength plate 91 Oscillator 92 High-frequency current superimposition circuit O Object R Railway rail L Upper surface width of railway rail W Measurable width of upper surface of railway rail n Area irradiated with −1st order light m Area irradiated with 0th order light p Region irradiated with primary light q Region irradiated with secondary light M Reference position DIV Laser Doppler velocimeter

Claims (9)

In a differential laser Doppler velocity measurement device that irradiates an object with laser light and measures the moving speed of the object by receiving scattered light from the object, a laser light source and a collimator that converts the laser beam from the laser light source into a parallel beam a lens, a beam splitter that divides the parallel beam into two, a mirror that reflects at least one of the laser beams divided into two by the beam splitter to irradiate an object, and a mirror that collects scattered light from the object. an optical system including a lens;
A differential laser Doppler velocity measurement device, wherein the laser beam is directed toward an object and/or a plurality of spaced locations near the object. 2. The differential laser Doppler velocity according to claim 1, wherein a member for branching the laser beam in a direction substantially perpendicular to the measurement direction is arranged in the optical path from the laser light source to the object. measuring device. 3. A differential laser Doppler velocity measuring apparatus according to claim 2, wherein said branching member is a diffractive optical element. 4. The differential laser Doppler velocity measuring device according to claim 2, wherein said branching member is arranged between said differential laser Doppler velocity measuring device and an object. 5. The differential laser Doppler velocity measuring device according to claim 2, wherein said branching member is not arranged between said object and an optical path through which said scattered light is received. A railway vehicle speed measuring method using the differential laser Doppler speed measuring device according to any one of claims 1 to 5. A member attached to a laser Doppler velocimeter, which splits the irradiation light directed toward the object from the laser Doppler velocimeter and makes the irradiation light directed to the object and / or a plurality of locations spaced apart in the vicinity of the object. A member characterized by widening the measurable range of a laser Doppler velocimeter. 8. A laser Doppler velocimeter according to claim 7, wherein said member is used. A velocity measurement method using the laser Doppler velocity meter.