JPH04230886A - Speedometer - Google Patents

Abstract

PURPOSE:To obtain a speedometer which can detect speed information of a moving object highly accurately by applying Doppler effect. CONSTITUTION:On a speedometer that makes beam flux from a light source 1 come into a moving object 7 and detects speed information of the moving object to be measured, based upon frequency transition of scattered beam from the moving body, incident position information of the incident beam flux into the moving body, is detected by an irradiation position detecting measures 14, and the incident position of the beam flux to the moving body, is regulated by a regulating measures 12, based upon signal from the irradiation position detecting measures.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention relates to a speedometer, which irradiates a moving object, fluid, etc. (hereinafter referred to as a "moving object") with a laser beam, and performs a Doppler shift according to the moving speed of the moving object. This relates to a speedometer that uses the Doppler effect to measure displacement information about the displacement of a moving object and the moving speed of the moving object without contact by detecting the frequency shift of the received scattered light.

0002

2. Description of the Related Art Conventionally, a laser Doppler velocimeter has been used as a device for measuring the moving speed of a moving object in a non-contact manner with high precision. A laser Doppler velocimeter irradiates a moving object with laser light and uses the effect (Doppler effect) that the frequency of scattered light from the moving object shifts in proportion to the moving speed of the moving object. This is a device that measures the moving speed of a moving object.

FIG. 12 is an explanatory diagram showing an example of a conventional laser Doppler velocimeter.

In the figure, a laser beam emitted from a laser 1 is converted into a parallel beam 3 by a collimator lens 2.
The beam splitter 4 splits the beam into two beams, a transmitted beam 5a and a reflected beam 5b, and the beam is reflected by reflectors 6a and 6b.Then, the beam is incident on a moving object 7 moving at a speed V from a different direction at an incident angle θ. Two luminous fluxes are irradiated. Scattered light from the moving object 7 is detected by a photodetector 9 via a condensing lens 8. At this time, the frequencies of the scattered light by the two beams undergo a Doppler shift of +Δf and −Δf in proportion to the moving speed V, respectively. Here, if the wavelength of the laser beam is λ, the frequency change Δf can be expressed by the following equation (1).

Δf=V・sin(θ)/λ
‥‥‥‥(1) Scattered light that has undergone a Doppler shift of +∆f, -∆f interferes with each other, causing a change in brightness on the light receiving surface of the photodetector 9, and its frequency F
is given by the following equation (2).

F=2・Δf=2・V・sin(θ)/λ
From equations (2) and (2), the frequency F of the photodetector 9 (
By measuring the Doppler frequency (hereinafter referred to as "Doppler frequency"), the moving speed V of the moving object 7 can be determined.

In the conventional laser Doppler velocimeter, (
2) As is clear from the equation, the Doppler frequency F is inversely proportional to the wavelength λ of the laser, so it was necessary to use a laser light source with a stable wavelength as a laser Doppler velocimeter. A gas laser such as He-Ne is often used as a laser light source capable of continuous oscillation and having a stable wavelength, but the laser oscillator is large and the power source requires high voltage, which tends to make the device large and expensive.

Furthermore, laser diodes (or semiconductor lasers) used in compact discs, video discs, optical fiber communications, etc. are extremely small and easy to drive, but they have the problem of being temperature dependent.

FIG. 13 ('87 Mitsubishi Semiconductor Data Book;
(quoted from the Optical Semiconductor Device Edition) is an explanatory diagram of an example of the standard temperature dependence of a laser diode. The part where the wavelength changes continuously is mainly due to temperature changes in the refractive index of the active layer of the laser diode. It is 0.05~0.
06nm/°C.

On the other hand, the part where the wavelength changes discontinuously is called longitudinal mode hopping, and is 0.2 to 0.3 nm/°C.
It is.

[0011] In order to stabilize the wavelength, a method is generally adopted in which the laser diode is controlled to a constant temperature. This method requires temperature control components such as heaters, radiators, and temperature sensors to be attached to the laser diode with small thermal resistance for precise temperature control, making the laser Doppler velocimeter relatively large and expensive. , the instability due to longitudinal mode hopping mentioned above cannot be completely eliminated.

[0012] As a laser Doppler velocimeter that solves the above-mentioned problem, a laser beam is incident on a diffraction grating, and of the diffracted light obtained from the diffraction grating, the +nth order and -nth order other than the 0th order
A method in which two diffracted lights (n is 1, 2, etc.) of , G-LDV) was proposed by the present applicant in Japanese Patent Application No. 1-83208.

FIG. 14 shows diffracted light when a laser beam I is incident perpendicularly to the grating arrangement direction t into a transmission type diffraction grating 10 with a grating pitch d, and the diffraction angle θ0 at this time is expressed by the following equation.

sin θ0 = mλ/d where m is the diffraction order (0, 1, 2, . . . ) and λ is the wavelength of the laser beam. Among these, the ±n-order light other than the 0-order light is expressed by the following equation.

[0015] sinθ0 =±nλ/d
‥‥‥‥(3) (n is 1,
2, . . . ) FIG. 15 is an explanatory diagram of a Doppler velocimeter in which two beams of the ±nth-order diffracted light are irradiated onto the moving object 7 from different directions using mirrors 6a and 6b so that the incident angle is θ0. The Doppler frequency F of the photodetector 9 is (2) and (3
) From the formula F=2Vsinθ0 /λ=2nV/d
‥‥‥‥(4). That is, the moving object 7 does not depend on the laser beam I and is inversely proportional to the grating pitch d of the diffraction grating 10.
is proportional to the moving speed of Since the grating pitch d can be made sufficiently stable, the Doppler frequency F becomes a frequency proportional only to the moving speed of the moving object 7. Incidentally, the diffraction grating 10 is completely similar to a reflection type diffraction grating.

[0016]

[Problem to be Solved by the Invention] In a Doppler velocimeter, spots are incident on a moving object from two directions as shown in FIG. 15, and the scattered light from the area where the two spots overlap on the surface of the moving object is is being detected. For this reason, 2
It is important that the two spots overlap well on the moving object surface.

[0017] The present invention further improves the Doppler velocimeter previously proposed by the present applicant, and effectively deals with fluctuations in the incident positions of the two spots on the moving object plane, thereby obtaining more accurate velocity information. The purpose is to provide a speedometer that can.

[0018]

[Means for Solving the Problems] The speedometer of the present invention allows a light beam from an illumination means to enter a predetermined position of an object to be measured, detects the light beam from the object to be measured by a light detection means, and detects the light beam from the object to be measured by a light detection means. When the calculation means calculates the velocity information of the object to be measured based on the signal from the means, the irradiation position detection means detects the deviation information of the incident position of the light beam incident on the object to be measured, and detects the irradiation position. It is characterized in that the position of incidence of the light beam on the object to be measured is adjusted by the adjusting means based on a signal from the means.

[0019]

Embodiment FIG. 1 is a schematic diagram of a main part of an optical system according to a first embodiment of the present invention. In this figure, the same elements as those shown in FIG. 15 are given the same reference numerals. 1001 is a speedometer that uses the Doppler effect. Reference numeral 1 denotes a light source, which is composed of, for example, a laser diode or a semiconductor laser (hereinafter referred to as a "laser"). 2 is a collimator lens,
The light beam from the laser 1 is made into a parallel light beam 3 with a diameter of about 2 mm. Reference numeral 10 denotes a diffraction grating, which is a reflection type diffraction grating with a grating pitch d of 1.6 μm so that ±1st-order diffracted light can be extracted efficiently.

In this embodiment, the diffraction grating 10 is set so that the ±1st-order diffracted lights 5a and 5b are diffracted at a diffraction angle θ0 when they are incident perpendicularly to the grating arrangement direction.

One of the light beams 5a is reflected by a mirror 6a perpendicular to the direction of the grating arrangement, and the other light beam 5b is split into reflected light 13a and transmitted light 13b by a half mirror 15 perpendicular to the direction of the grating arrangement. The light beam 5a and the light beam 13a overlap and irradiate the moving object 7 with two light beams at an incident angle θ0 and a spot diameter of approximately 2 mm, and the scattered light from the moving object 7 is directed to the light receiving surface 9a of the photodetector 9 by the condenser lens 8. The spot is imaged and detected by the photodetector 9 to obtain a Doppler signal shown in equation (4).

Here, a Doppler signal F of the following equation (5) is obtained which is independent of the wavelength λ obtained by setting n=1 in equation (4).

F=2V/d (5) On the other hand,
The transmitted light 13b that has passed through the half mirror 15 is obliquely incident on the surface of the moving object 7 as a reference light beam for position detection, and reaches a position on the moving object 7 that is different from the irradiation position of the two light beams. A spot of about 2 mmφ is formed. This spot is imaged by the light-receiving lens 16 onto a four-division sensor 14 as an optical position sensor having four light-receiving elements 17 arranged in a line, and spot position information can be obtained from the output of each light-receiving element. . These optical systems are
The light receiving element 17 is arranged so that a spot is imaged at the center of the light receiving element 17 when the intersection position of the two light beams matches the position of the moving object.

Based on the spot position information at this time, the voice coil 12 moves the speedometer 1001 along the guides 11a and 11b in a direction perpendicular to the moving direction of the moving object 7. Determination of the spot position and driving of the voice coil 12 based on the determination are performed by a control circuit (not shown).

FIGS. 2 to 4 are schematic diagrams illustrating the method of detecting the deviation of the spots of two beams. FIG. 2 shows a state in which the moving object is closer to the speedometer than the intersection position of the two beams, and FIG. FIG. 4 shows an ideal state in which the intersection position of the two beams matches the position of the moving object, and FIG. 4 shows a state in which the moving object is farther from the speedometer than the two-beam intersection position.

The scattered light detected by the photodetector 9 is the scattered light from a region where two spots overlap. Therefore, Figure 3
The state shown in Fig. 2 and Fig. 4 has the best detection signal, and the two spots are shifted and the detection signal is small
/N ratio is poor. Furthermore, if the area where the spots overlap disappears, it becomes impossible to obtain a detection signal.

In FIGS. 2 to 4, (a) is an explanatory diagram of the optical path of the speedometer of the first embodiment, (b) is the state of the light spot on the moving object 7, and (c) is the state of the light spot on the four-split sensor 14. Luminous flux 13b
shows the imaging state of the spot.

As can be seen from each figure, in the state shown in FIG. 3, the two light receiving elements at the center of the four-split sensor 14 are strongly detected, and the two light receiving elements at both ends are hardly detected. As the state of FIG. 3 changes to the state of FIG. 2, the luminous flux 13b
Since it is obliquely incident, the spot of the light beam 13b on the moving object 7 gradually moves to the left, and in the state shown in FIG.
It is strongly detected in the right two areas.

Further, as the state of FIG. 3 changes to the state of FIG. 4, the spot of the light beam 13b on the moving object 7 gradually moves to the right, and in the state of FIG. It is strongly detected in

That is, a good detection signal can always be obtained by adjusting the positional relationship between the moving object and the intersection of the two diffracted beams so that the outputs of the two central light receiving elements are maximized. This specific procedure is shown in FIG. FIG. 5 is an example of a flowchart showing a control procedure for bringing the two-beam spot into the ideal state shown in FIG. 3, and the control circuit (not shown) performs control according to the procedure in the flowchart. Here, the detection level of each light receiving element 17 of the 4-divided sensor 14 is R, CR, CL,
UP/DOWN of the G-LDV, that is, vertical movement of the speedometer, is performed by driving the voice coil 12.

Next, the control at this time will be explained based on the flowchart of FIG.

First, the power to the speedometer is turned on, and the speedometer is moved vertically upward or downward relative to the moving object using the voice coil 12, depending on the initial position of the speedometer. During the movement, the total output of the two central elements CL and CR of the light receiving section 14 exceeds that of the end elements R and L, and CL=
When CR is reached, the speedometer assumes that it has reached the proper measurement position and stops moving, and at the same time starts servo control to maintain this state. When the total output of elements CL and CR is smaller than that of elements L and R, it is determined whether the output from element L is greater than the output from element CR (or whether the output from element CL is greater than the output from element R). If so, move the speedometer downwards, otherwise move the speedometer upwards, and CL=
Movement is stopped when CR is reached. This is repeated until the measurement is completed.

With the above-described configuration and operation, it is possible to ensure that the two beam spots are superimposed on the moving object, without being affected by the surface condition of the moving object 7.

In Example 1, an example is shown in which an optical position sensor having four light-receiving elements is used as a preferred form, but the number is not limited to four, and two, three, or five or more light-receiving elements are used. A divided sensor consisting of elements may also be used.

Furthermore, in the first embodiment, position detection was performed by dividing one of the two diffracted lights, but if both of the two diffracted lights were divided and position detection was performed,
More reliable position detection becomes possible.

As described above, according to this embodiment, it is possible to achieve a speedometer that is not affected by the surface condition of a moving object and is capable of obtaining stable Doppler signals and detecting highly accurate speed information. can.

FIG. 6 is a schematic diagram of the main parts of an optical system according to a second embodiment of the present invention. In the figure, 1101 is a speedometer that uses the Doppler effect. Reference numeral 101 denotes a light source, which is comprised of, for example, a laser diode, a semiconductor laser, or the like (hereinafter referred to as a "laser"). A collimator lens 102 converts the light beam from the laser 101 into a parallel light beam 103. 110 is a diffraction grating, and the grating pitch d is 1
．． It is set to diffract 6 μm reflection type ±1st order diffracted light at a diffraction angle θ1. Reference numerals 106a and 106b each represent a reflecting mirror, and are arranged to face each other. 107 is a moving object or a moving fluid (hereinafter referred to as a "moving object"), which is moving at a moving speed V in the direction of an arrow 107a. 10
A condensing lens 8 condenses Doppler-shifted scattered light from the moving object 107 via a half mirror 113 onto a detection surface 109a of a photodetector 109 serving as a detection means. Reference numeral 111 denotes a light receiving means, for example, a CCD or the like. The surface of the moving object 107 and the detection surface 109a have a substantially conjugate relationship. Also, the moving object 107 surface and the light receiving means 1
11 also has a substantially conjugate relationship. Reference numeral 112 denotes a driving means, which is made up of, for example, a voice coil, and moves the diffraction grating 110 in a direction perpendicular to the moving direction 107a of the moving object 107, indicated by an arrow 110a, based on the output signal from the light receiving means 111.

114 is a calculation means such as a computer, which calculates and determines the moving speed V of the moving object 107 using the Doppler signal obtained by the photodetector 109.

In this embodiment, the laser beam emitted from the laser 101 is converted into a parallel beam 103 with a diameter of about 2 mm by the collimator lens 102, and is then passed through the reflection type diffraction grating 1.
10 perpendicular to the grating arrangement direction t. The diffracted lights 105a and 105b of the ±n order (n=1 in this embodiment) diffracted by the diffraction grating 110 at a diffraction angle θ1 are reflected by reflecting mirrors 106a and 106b arranged perpendicularly to the grating arrangement direction, and are moved. Figure 7(B) on the plane of the moving object 107 at the same incident angle θ1 from different directions on the object 107.
As shown in the figure, the spots L5a and L5b are incident so as to overlap and cross each other.

In this embodiment, with this configuration, the diffraction angle of the ±nth order (diffracted light) from the diffraction grating 110 changes in accordance with a change in the wavelength λ, and the incident angle θ to the moving object changes. However, an optical system including a diffraction grating, a mirror, etc. is configured so that the ratio sin θ/λ at this time is approximately constant.

At this time, two diffracted lights 105a and 105b
are spots L5a and L5b each having a diameter of about 2 mm, and the surface of the moving object 107 is thereby irradiated with two light beams.

The condensing lens 108 has a Doppler shift Δf proportional to the moving speed V of the moving object 107 as shown in equation (1).
, -Δf is focused on the detection surface 109a of the photodetector 109. At this time, the two scattered lights that have undergone Doppler shifts Δf and -Δf interfere with each other on the detection surface 109a. The photodetector 109 detects the amount of light based on the brightness of the interference fringes at this time. That is, the photodetector 10
9 is a Doppler signal independent of the oscillation wavelength λ of the laser 101, which is the Doppler frequency F proportional to the moving speed V with n=1 in equation (4), F=2V/d (5) as described above. To detect. Then, the calculation means 114 detects the photodetector 109.
The moving speed V is obtained from equation (5) using the output signal from.

In this embodiment, the detection surface 109a and the moving object 1
It has a substantially conjugate relationship with the surface on the 07 plane. Therefore, if the relative positional relationship between the speedometer 1101 and the moving object 107 is set correctly, and the oscillation wavelength λ from the laser 101 remains unchanged, the two diffracted lights 105a and 105b will have their spots L5a and L5b in the figure. As shown in 7(B), moving object 1
They are incident on the 07 plane so that they intersect and overlap each other.

However, if the oscillation wavelength of the laser 101 changes, or if there is a setting error in the distance between the speedometer 1101 and the moving object 107, for example, as shown in FIG.
As shown in (C), the spots L5a and L5b of the two diffracted lights 105a and 105b do not overlap on the surface of the moving object 107, but are shifted from each other. The scattered light detected by the photodetector 109 is the scattered light from the area where the two spots L5a and L5b overlap. For this reason, two spots L5a and L5
When b shifts without overlapping, the amount of scattered light detected by the photodetector 109 decreases, and the S/N of the Doppler signal decreases.
The ratio decreases, and the measurement accuracy of the moving speed V deteriorates.

Therefore, in this embodiment, the degree of overlapping of the two spots L5a and L5b on the surface of the moving object 107 at this time is detected by a light receiving means 111 made of a CCD or the like via a half mirror 113. For example, the diffraction grating 110 is moved by the arrow 11 by the driving means 112 so that the output distribution of the output signal obtained by the light receiving means 111 is minimized.
By moving the moving object 107 in a direction perpendicular to the moving direction indicated by 0a, two spots L5a,
Adjustments are made so that L5b overlaps.

In this case, the following process is performed to determine whether the spot deviation is in the state shown in FIG. 7(A) or in the state shown in FIG. 7(C). When the light receiving means 111 detects a shift, the driving means 112 causes the diffraction grating 110 to vibrate in a direction perpendicular to the moving direction of the moving object 107.

FIG. 8 shows the relationship between the vibration direction and the distribution of the optical output signal from the light receiving means 111 in each distance relationship between the diffraction grating 110 and the moving object 107. In the figure, the movement of the diffraction grating 110 in the direction away from the moving object 107 is defined as positive, and the movement in the direction in which it approaches the moving object 107 is defined as negative.

When the moving object 107 moves away from the speedometer 1101, the optical output signal distribution increases when the moving direction is positive during vibration, and the optical signal output distribution increases when the moving direction is negative, as shown in FIG. 8(A). decreases. The moving object 107 is a speedometer 1101
As shown in FIG. 8B, when the moving direction is positive, the optical output signal distribution decreases, and when the moving direction is negative, the optical signal output distribution increases during vibration, as shown in FIG. 8(B). In other words, the phase is reversed.

When the distance between the speedometer 1101 and the moving object 107 is appropriate, that is, when the spots overlap, the value of the optical output signal distribution is the maximum and minimum of the sine wave vibration as shown in FIG. 8(C). are equal. Therefore, in order to set the distance between the diffraction grating 110 and the moving object 107 appropriately, the optical detection signal S+ when the oscillating sine wave is at its maximum is compared with the optical signal output S- when the oscillating sine wave is at its minimum, and S+>S- Now, the diffraction grating 110
approaches the moving object 7, moves it away when S+<S-, and S+=
At S-, the diffraction grating 110 may be positioned at the center of its vibration and stopped. FIG. 9 shows a flowchart at this time.

[0050] After determining only the direction in which the diffraction grating 110 is moved using the method described above and stopping the vibration, the light receiving means 1
It is also possible to move the spots in the discrimination direction while monitoring the spots in step 11 until the spots overlap.

In this way, the driving means 112 causes the two diffracted lights 105a and 105b diffracted by the diffraction grating 110 to overlap and intersect on the surface of the moving object 107 as shown in FIG. 7(B). The relative positional relationship between the irradiation position and the surface of the moving object is adjusted to maintain a good S/N ratio of the Doppler signal obtained by the photodetector 109, thereby enabling highly accurate detection of the moving speed V of the moving object 107. There is.

FIG. 10 is a schematic diagram of the main parts of an optical system according to a third embodiment of the present invention.

In this embodiment, a driving means 11 comprising a voice coil, a motor, etc. is used as an adjustment means for adjusting the relative positional relationship between the irradiation position of the diffracted light beam onto the moving object surface and the moving object surface.
speedometer 11 via control means 115 using
01 along the guides 117a, 117b with the arrow 112a.
The moving object 107 is vibrated in a direction perpendicular to the moving direction 107a. The other configurations are basically the same as the second embodiment shown in FIG.

That is, in this embodiment, two spots L5a
, L5b on the surface of the moving object 107 through a half mirror 113.
11, and the speedometer 1101 is moved by the driving means 112 in a direction perpendicular to the moving direction of the moving object 107 shown by the arrow 112a so that the output distribution of the output signal obtained by the light receiving means 111 is minimized (FIG. 7). Adjustments are made so that the two spots L5a and L5b overlap as shown in B).

In addition, in Examples 2 and 3, two diffracted lights 1
05a and 105b on the surface of the moving object 107 without using the light receiving means 111.
09 (in this case, half mirror 1
13 becomes unnecessary).

For example, the driving means 112 drives the diffraction grating 11.
Alternatively, the position where the detection signal from the photodetector 109 is the largest (the spot diameter is the smallest) may be determined by slightly vibrating the speedometer 1101 in the direction of the arrow 110a. At this time, depending on whether the phase of the detection signal frequency obtained by the photodetector 109 and the phase of the drive signal frequency are in phase or out of phase, whether the distance between the moving object 107 and the speedometer 1101 or the diffraction grating 110 is too close or too far. is determined electrically.

Although a reflection type diffraction grating was used in the above-described embodiment, a transmission type diffraction grating may also be used. In addition to the ±1st-order diffracted light, second-order or higher-order diffracted light may be used as the diffracted light.

Furthermore, the angle of incidence of the laser light onto the diffraction grating 110 does not have to be perpendicular, but may be made at a constant angle. At this time, 2 of the ±n-order diffracted light generated by the diffraction grating 110
The two diffracted lights of the ±n-order diffracted lights may be made incident on the moving object while maintaining the same intersection angle as that of the two diffracted lights.

Note that if the light beams emitted from the same light source are used, if at least one of the two diffracted lights incident on the moving object is the nth-order diffracted light, the other diffracted light may be of the n-th order, e.g. It may be of any order such as 0th order, n+1st order, n+2nd order, etc.

[0060] Also, one of the two light beams emitted from the same light source to be input to the light receiving element is converted into n-order diffracted light and is made to enter the moving object, and the other light beam is directly transmitted to the light receiving element without passing through the moving object. Alternatively, the Doppler signal may be obtained by making the light incident on the light beam and causing it to interfere with the scattered light from the moving object. In this case, the illumination position of the light beam on the moving object must be adjusted to an appropriate position.

FIG. 11 is a schematic diagram of the main parts of an optical system according to a fourth embodiment of the present invention. In the figure, 2101 is a speedometer that utilizes the Doppler effect. A light source 201 is composed of, for example, a wavelength tunable laser diode whose oscillation wavelength is variable. As the wavelength tunable laser diode 201, for example, a wavelength tunable DBR-DC-PBH semiconductor laser, etc., whose oscillation wavelength can be changed by controlling the current injected into a phase control region and a distributed reflection (DBR) region, can be applied. .

A controller 212 controls the current injected into the laser diode 201 according to an output signal from the light receiving means 211, which will be described later.
The oscillation wavelength from 01 is changed. The laser diode 201 will be referred to as a "laser" hereinafter.

A collimator lens 202 converts the light beam from the laser 201 into a parallel light beam 203. 2
Reference numeral 10 denotes a diffraction grating, which is a reflection type diffraction grating with a grating pitch d of 1.6 μm, and is set to diffract ±1st-order diffracted light having a wavelength λ at a diffraction angle θ1. 206a,
206b are reflecting mirrors, which are arranged to face each other. 2
07 is a moving object or a moving fluid (hereinafter referred to as a "moving object"), which is moving at a moving speed V in the direction of an arrow 207a. 208 is a condensing lens that converts the scattered light that has undergone Doppler shift from the moving object 207 to the half mirror 2.
13 to the detection surface 2 of the photodetector 209 as a detection means.
The light is focused on 09a. 211 is a light receiving means, for example C
It consists of CDs etc. Moving object 207 surface and detection surface 2
09a has a substantially conjugate relationship. Furthermore, the surface of the moving object 207 and the light receiving means 211 also have a substantially conjugate relationship.

214 is a calculation means, and a photodetector 209
The moving speed V of the moving object 207 is calculated and determined using the Doppler signal obtained in the above.

In this embodiment, the laser beam emitted from the laser 201 is converted into a parallel beam 203 with a diameter of about 2 mm by the collimator lens 202, and is then passed through the reflection type diffraction grating 2.
10 perpendicular to the grating arrangement direction t. Then, ± of the wavelength λ diffracted by the diffraction grating 210 at a diffraction angle θ1
N-th order (n=1 in this example) diffracted light 205a, 205
b is a reflecting mirror 206a, 2 arranged perpendicularly to the grating arrangement direction;
06b, and a spot L5a appears on the surface of the moving object 207 from different directions at the same incident angle θ1 as in Example 2, as shown in FIG. 7(B).
, L5b are incident so as to overlap and intersect with each other.

In this embodiment, with this configuration, the diffraction angle of the ±nth order (diffracted light) from the diffraction grating 210 changes in accordance with a change in the wavelength λ, and the incident angle θ to the moving object changes. However, an optical system including a diffraction grating, a mirror, etc. is configured so that the ratio sin θ/λ at this time is approximately constant.

[0067] Also, at this time, two diffracted lights 205a and 20
5b are spots L5a and L5b with a diameter of about 2 mm,
As a result, two beams of light are irradiated onto the surface of the moving object 207.

The condensing lens 208 has a Doppler shift Δf proportional to the moving speed V of the moving object 207 as shown in equation (1).
, -Δf is focused on the detection surface 209a of the photodetector 209. At this time, the two scattered lights that have undergone Doppler shifts Δf and −Δf interfere with each other on the detection surface 209a. The photodetector 209 detects the amount of light based on the brightness of the interference fringes at this time. That is, the photodetector 20
9 is the Doppler frequency F proportional to the moving speed V with n=1 in equation (4) as above, F=2V/d (
5) Detecting a Doppler signal independent of the oscillation wavelength λ of the laser 201. Then, the calculation means 214 uses the output signal from the photodetector 209 to calculate the moving speed V (5
) is calculated from the formula.

In this embodiment, the detection surface 209a and the moving object 2
It has a substantially conjugate relationship with the surface on the 07 plane. Therefore, if the relative positional relationship between the speedometer 2101 and the moving object 207 is set correctly, the two diffracted lights 205a and 205b will be
The spots L5a and L5b are incident on the surface of the moving object 207 so as to intersect and overlap with each other, as shown in FIG. 7(B).

However, the speedometer 2101 and the moving object 2
If there is a setting error in the distance from 07, for example, Fig. 7
As shown in (A) and (C), two diffracted lights 205a and 2
Spots L5a and L5b of 05b do not overlap on the surface of the moving object 207 and are shifted from each other. The scattered light detected by the photodetector 209 is the scattered light from the area where the two spots L5a and L5b overlap. For this reason, two spots L5
When a and L5b shift without overlapping, the amount of scattered light detected by the photodetector 209 decreases, the S/N ratio of the Doppler signal decreases, and the measurement accuracy of the moving speed V deteriorates. come.

For example, as shown in FIG. 7B, when the spots L5a and L5b of the two diffracted lights 205a and 205b completely overlap on the surface of the moving object 207, the distance h between the diffraction grating 210 and the moving object 207 is Mirrors 206a, 206b
Let the distance between them be L and the grating interval of the diffraction grating be d.

Here, L=50mm, λ=0.78μm,
When d=1.6 μm, h=89.5 mm. At this time, when the distance h changes by 1 mm, the two spots L5a
, L5b can be completely overlapped by changing the oscillation wavelength λ from the laser 201 by about 6 nm, for example, according to equation (6).

Therefore, in this embodiment, the degree of overlapping of the two spots L5a and L5b on the surface of the moving object 207 at this time is detected by the light receiving means 211 made of a CCD or the like via a half mirror 213. For example, suppose that the output distribution of the output signal obtained by the light receiving means 211 is the smallest when the two spots L5a and L5b completely overlap, and the oscillation wavelength from the laser 201 is adjusted so that such an output signal is obtained. are being varied in various ways.

That is, as is clear from equation (3), the present invention changes the wavelength λ and changes the diffraction angle θ1 from the diffraction grating to produce two diffracted lights 205a and 205 onto the surface of the moving object 207.
By adjusting the incident angle θ1 of b, the spot L5a
, L5b is characterized by adjusting the degree of overlap.

Specifically, using the output signal from the light receiving means 211, the controller 212 changes the current injected into the laser 201, thereby changing the oscillation wavelength λ from the laser 201. Then, the diffraction angle θ1 of the diffracted light of a predetermined order (±1st order) of wavelength λ diffracted from the diffraction grating 210
At the same time as changing the angle of incidence θ1 on the surface of the moving object 207
is changed so that the two spots L5a and L5b intersect and overlap well on the surface of the moving object 207, as shown in FIG. 7(B), for example.

Is the spot shift as shown in FIG. 7(A)?
To determine whether the state is in (C), instead of vibrating the diffraction grating in the method shown in Figures 8 and 9, the wavelength λ of the laser beam is lengthened or shortened to vibrate it, and the same judgment is made from the phase.・Perform processing. In this case, the operation of moving the diffraction grating in the direction of separating it and the operation of lengthening the wavelength are equivalent. As a result, in this embodiment, the S/N ratio of the Doppler signal obtained by the photodetector 209 is maintained at a good level, and the moving speed V of the moving object 207 can be detected with high accuracy.

In this embodiment, the change in the oscillation wavelength from the laser 201 corresponding to the change in the current injected into the laser 201 is at a high speed and can sufficiently follow the speed of mechanical fluctuations, so the spot L5a can be quickly adjusted. , L5b can be adjusted.

Although a reflection type diffraction grating is used in this embodiment, it is also possible to use a transmission type diffraction grating. In addition to the ±1st-order diffracted light, second-order or higher-order diffracted light may be used as the diffracted light.

Furthermore, the incident angle of the laser beam 203 onto the diffraction grating 210 does not have to be perpendicular, but may be made incident at a constant angle. At this time, the two diffracted lights of the ±nth order may be made incident on the moving object while maintaining the same intersection angle as the intersection angle of the two diffracted lights of the ±nth order generated by the diffraction grating 210.

[0080] If light fluxes emitted from the same light source are used, if at least one of the two diffracted lights incident on the moving object is an n-th order diffracted light, the other diffracted light may be of an order other than the n-th order, e.g. It may be of any order such as 0th order, n+1st order, n+2nd order, etc.

[0081] Also, one of the two light beams emitted from the same light source to be input to the light receiving element is converted into n-order diffracted light and is made to enter the moving object, and the other light beam is directly transmitted to the light receiving element without passing through the moving object. Alternatively, the Doppler signal may be obtained by making the light incident on the light beam and causing it to interfere with the scattered light from the moving object. In this case, the irradiation position of the light beam on the moving object must be adjusted to an appropriate position.

In addition, in this embodiment, the laser 201 is
The oscillation wavelength is swept from several nanometers to several tens of nanometers, and the wavelength is fixed at the point where the Doppler signal detected by the photodetector 209 becomes the largest (the state shown in FIG. 7(B)). After that, the speedometer 210 is detected using a known distance detection means such as a triangular distance measurement method or an image shift detection method used in a camera.
1 from a predetermined position (for example, the diffraction grating 210) to the moving object 2
Detect the distance to 07. Then, the oscillation wavelength λ from the laser 201 may be changed in accordance with the difference from the design value to adjust the degree of overlap between the spots L5a and L5b on the surface of the moving object 207.

Furthermore, in this embodiment, two diffracted lights 205
A photodetector 209 for detecting the moving speed of the moving object 207 without using the light receiving means 211 detects the degree of overlapping of the objects a and 205b on the surface of the moving object 207.
(In this case, the half mirror 213
is no longer necessary).

For example, the oscillation wavelength from the laser 201 may be changed by the controller 212 so that the detection signal from the photodetector 209 becomes the largest, that is, the spot diameter may be the smallest.

Furthermore, in this embodiment, instead of a laser diode that changes the oscillation wavelength by changing the injection current, a normal laser diode whose oscillation wavelength changes depending on the temperature change is used as the laser 201, and the oscillation can be performed by adjusting the temperature. The wavelength may also be changed.

[0086] Further, the overlap of the spots L5a and L5b, which are shifted due to the oscillation wavelength changed due to the temperature change, may be adjusted by changing the injection current.

[0087]

Effects of the Invention According to the present invention, by setting each element as described above, a speedometer is capable of correcting deviations in the incident position of a light beam onto a moving object and detecting stable and highly accurate movement information. can be achieved.

Furthermore, according to the present invention, it is possible to adjust the spots of two diffracted lights so that they overlap well on the moving object surface, so that the distance to the moving object surface is not displaced due to assembly errors or setting errors. , even if the intersection position of the two diffracted lights deviates from the moving object plane, the overlap of the spots can be easily corrected, a signal with a high S/N ratio can be obtained, and the moving speed of the moving object can be increased. It is possible to achieve a speedometer using the Doppler effect with high reliability and high accuracy.

Furthermore, since the speedometer of the present invention can reduce the overlapping diameter of two diffracted lights on the surface of a moving object, it is possible to determine the moving speed with high accuracy even when the moving object is small. It has the following characteristics.

[Brief explanation of the drawing]

[Figure 1] Schematic diagram of main parts of Example 1 of the present invention

[Figure 2]
An explanatory diagram showing the relationship between the incident position of the light beam on the moving object in Figure 1 and the optical position sensor

[Figure 3] An explanatory diagram showing the relationship between the incident position of the light beam on the moving object in Figure 1 and the optical position sensor

[Figure 4] An explanatory diagram showing the relationship between the incident position of the light beam on the moving object in Figure 1 and the optical position sensor.

[Figure 5] Flowchart showing the control in Figure 1

[Figure 6]
A schematic diagram of the main parts of Embodiment 2 of the present invention

[Figure 7] An explanatory diagram showing the state of incidence of two light beams on the moving object surface in Figure 6

[Fig. 8] Explanatory diagram of the method for determining the direction of deviation in Example 2

[Figure 9] Flowchart showing control of Example 2

[
Figure 10: Schematic diagram of main parts of Embodiment 3 of the present invention

[Figure 11]
Schematic diagram of main parts of Embodiment 4 of the present invention

[Figure 12] Schematic diagram of the main parts of a conventional Doppler velocimeter

[Figure 13] Explanatory diagram showing the temperature characteristics of the oscillation wavelength of a laser diode

[Figure 14] Explanatory diagram of each order of diffracted light diffracted by a diffraction grating

[Figure 15] Schematic diagram of main parts of Doppler velocimeter using G-LDV

[Explanation of symbols]

1001, 1101, 2101 Speedometer 1, 101,
201 Laser 2, 102, 202 Collimator lens 3, 103
, 203 Parallel light beam 10, 110, 210 Diffraction grating 7, 107, 207 Moving object 8, 108, 208 Condensing lens 9, 109, 209 Photodetector 14 Optical position sensor 111 Light receiving means 114 Computing means

Claims (11)

[Claims] Claim 1: A light beam from an illumination means is made incident on a predetermined position of an object to be measured, a light beam from the object to be measured is detected by a light detection means, and a light beam from the object to be measured is detected based on a signal from the light detection means. When the calculation means calculates the velocity information of the object to be measured, the irradiation position detection means detects the deviation information of the incident position of the light beam incident on the object to be measured, and the position of the light beam is detected based on the signal from the irradiation position detection means. A speedometer characterized in that the position of incidence on an object to be measured is adjusted by an adjusting means. 2. A speedometer that makes a light beam from a light source incident on a moving object and detects speed information of the moving object based on a shift in the frequency of scattered light from the moving object, wherein the light beam is incident on the moving object. A speedometer characterized in that information on the incident position of the luminous flux is detected by an irradiation position detection means, and the incidence position of the luminous flux on the moving object is adjusted by an adjustment means based on a signal from the irradiation position detection means. 3. A light beam with a wavelength λ is made incident on a moving object at an incident angle θ, and the light beam is adjusted such that the incident angle θ changes in accordance with a change in the wavelength λ of the light beam, and sin θ/λ is approximately constant. In a speedometer that has an optical system that makes light incident on a moving object and detects speed information of the moving object based on a shift in the frequency of scattered light from the moving object, the direction perpendicular to the plane of incidence of the moving object A speedometer characterized in that it has means for detecting the relative positional relationship of the moving object with respect to a predetermined reference position. 4. Means for diffracting a light beam from a light source by a diffraction grating to form a diffracted light, and causing two different emitted diffracted lights to be superimposed on the moving object, and a means for making the two light beams incident on the moving object. means for receiving scattered light from an object and detecting movement information of the moving object; means for detecting a relative positional relationship between the intersecting position of the two diffracted lights and the surface of the moving object; and based on the detection result. and means for adjusting the relative positional relationship so that the intersection position and the moving object plane match, and the means for detecting the relative positional relationship,
means for splitting at least one of the two diffracted beams to form a reference beam, and making the reference beam incident obliquely at different positions on the moving object surface; and detecting the incident position of the reference beam. A speedometer comprising means for detecting a relative positional relationship between the intersection position of the two diffracted lights and the moving object surface. 5. A speedometer that detects speed information of a moving object based on a frequency shift of scattered light from the moving object by making an irradiation light beam with a wavelength λ incident on the moving object at a predetermined angle of incidence θ. , an optical system that makes the irradiation light beam incident on the moving object such that the incident angle θ changes according to a change in the wavelength λ of the irradiation light beam, and sin θ/λ is approximately constant; A speedometer characterized by having an adjusting means for detecting the relative positional relationship between the irradiation position and the moving object surface in a direction perpendicular to the moving direction, and adjusting the relative positional relationship based on the detection result. . 6. A light beam from a light source is made incident on a diffraction grating, and the +nth and -nth orders (n=1, 2, 3, etc.) from the diffraction grating are
) are irradiated onto the moving object surface from different directions at the same angle of incidence so that the two diffracted lights intersect near the moving object surface, and are subjected to Doppler shift from the moving object surface. In a speedometer that detects the two scattered lights with a detection means and uses the signal obtained by the detection means to detect the moving speed of the moving object, the intersection position of the two diffracted lights and the surface of the moving object are determined. 1. A speedometer characterized in that the diffraction grating is moved in a direction perpendicular to the moving direction of the moving object by a driving means based on the detection result. 7. The speed according to claim 6, wherein the relative positional relationship between the intersecting position of the two diffracted lights and the moving object surface is determined using a signal obtained by the detecting means. Total. 8. A speedometer that detects speed information of a moving object based on a frequency shift of scattered light from the moving object by making an irradiation light beam with a wavelength λ incident on the moving object at a predetermined angle of incidence θ. , an optical system that makes the irradiation light beam incident on the moving object such that the incident angle θ changes in accordance with a change in the wavelength λ of the irradiation light beam, and sin θ/λ is approximately constant; A speedometer comprising means for changing the wavelength λ of the irradiation light beam based on the relative positional relationship between the irradiation position and the moving object surface in a direction perpendicular to the moving direction. 9. The speed according to claim 8, wherein the relative positional relationship between the intersecting position of the two diffracted lights and the moving object surface is determined using a signal obtained by the detecting means. Total. 10. The speedometer according to claim 8, wherein the relative positional relationship between the intersecting position of the two diffracted lights and the moving object surface is determined using distance detecting means. 11. The light flux from the light source is made incident on a diffraction grating, and the +nth and -nth orders (n=1, 2, 3) from the diffraction grating are
) are irradiated onto the moving object surface from different directions at the same angle of incidence so that the two diffracted lights intersect near the moving object surface, and the Doppler shift from the moving object surface is In a speedometer that detects two received scattered lights with a detection means and uses a signal obtained by the detection means to detect the moving speed of the moving object, the intersection position of the two diffracted lights and the surface of the moving object are determined. A speedometer characterized in that the oscillation wavelength from the light source is changed based on the relative positional relationship with the light source.