CN214750381U

CN214750381U - Single-frequency laser Doppler transverse velocimeter based on grating technology

Info

Publication number: CN214750381U
Application number: CN202120571514.8U
Authority: CN
Inventors: 叶宗民
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-03-22
Filing date: 2021-03-22
Publication date: 2021-11-16
Anticipated expiration: 2031-03-22

Abstract

The utility model discloses a horizontal tachymeter of single-frequency laser Doppler based on grating technique, the test platform comprises a mounting table, the top of mount table fixed mounting respectively has laser instrument, sinusoidal grating, revolving stage, first speculum, second mirror, semi-transparent half-reflecting mirror, photoelectric detector, digital oscilloscope, signal amplifier, signal acquisition card and calculation unit are established ties mutually. The utility model discloses in, the sinusoidal grating technique of use can make whole light path have good symmetry, suppresses environmental noise effectively to can divide into two bundles of light of symmetry with a beam of light, realize the two differential mode Doppler techniques of single beam, have very high resolution ratio and precision to the small speed on solid surface, and the scheme is succinct, easily modulates, and low cost receives environmental influence factor less.

Description

Single-frequency laser Doppler transverse velocimeter based on grating technology

Technical Field

The utility model relates to a laser Doppler tests the speed technical field, especially relates to a horizontal tachymeter of single-frequency laser Doppler based on grating technique.

Background

The doppler effect was well known in the acoustic field since 1842 after being discovered by doppler in physicists. In 1964, the optical doppler effect was confirmed by komins (h.z. cummins) and leaves (y.yeh) by observing the frequency shift of scattered light from particles in a liquid, i.e. when relative motion occurs between a light source and a light receiver, a frequency shift occurs between the emitted light wave and the received light wave, the magnitude of which is related to the relative velocity between the light source and the light receiver. Since the birth of a new speed measuring technology, Laser Doppler Velocimeter, and the rapid development of the Laser Doppler Velocimeter in the next several decades, the Laser Doppler Velocimeter (Laser Doppler Velocimeter) has become a new and important speed measuring tool.

At present, the laser doppler velocity measurement technology has been widely applied to the fields of aerospace, aerodynamics, hydrodynamics, medical detection instruments and the like, and also is widely applied to the fields of industrial production and the like, and the laser doppler velocity measurement technology has been developed from experimental research in laboratories to factory sites. At present, the Laser Doppler Velocimeter (LDV) has also been slowly put into practical use in many departments in national economy of China, and has achieved good results. However, because the LDVs produced by oneself in China often use forward scattered light as signal light, the light source has to use a high-power semiconductor laser or solid laser, which has a wide frequency band and a large relative error, so that all laser doppler velocimeters used for industrial measurement are imported from abroad, and they are not only very expensive, but also have low measurement accuracy and resolution on the micro speed of the solid surface, and cannot be widely used. Therefore, the research and development of the high-precision Doppler laser velocimeter with the independent intellectual property rights of China not only can break through the monopoly of foreign technologies and save funds, but also has good market prospects in China, so that a single-frequency laser Doppler transverse velocimeter based on the grating technology is provided for solving the problems.

SUMMERY OF THE UTILITY MODEL

The utility model aims at solving the shortcoming that exists among the prior art, and the horizontal tachymeter of single-frequency laser Doppler who proposes based on grating technique.

In order to achieve the above purpose, the utility model adopts the following technical scheme:

a single-frequency laser Doppler transverse velocimeter based on a grating technology comprises an installation platform, wherein the top of the installation platform is fixedly provided with a laser, a sinusoidal grating, a rotating platform, a first reflector, a second reflector, a semi-transmitting semi-reflecting mirror, a photoelectric detector, a digital oscilloscope, a signal amplifier, a signal acquisition card and a calculation unit respectively, and the photoelectric detector, the digital oscilloscope, the signal amplifier, the signal acquisition card and the calculation unit are connected in series;

the laser comprises a supporting plate, a fixed seat is fixedly arranged on one side of the supporting plate, a laser head is rotatably connected with one side of the fixed seat, the top of the laser head is rotationally connected with a first connecting shaft, one side of the first connecting shaft, which is far away from the laser head, is rotationally connected with a movable plate, one side of the moving plate is connected with one side of the supporting plate in a sliding way, the bottom of the laser head is rotationally connected with a second connecting shaft, the bottom of the second connecting shaft is rotatably connected with a pushing plate, one side of the supporting plate is provided with a driving groove, one side of the pushing plate is connected with the inner wall of one side of the driving groove in a sliding way, a stepping motor is fixedly arranged on the inner wall of the bottom of the driving groove, the output shaft of the stepping motor is welded with a screw rod, the top of the screw rod penetrates through the pushing plate and is rotationally connected with the inner wall of the top of the driving groove, and the screw rod is in threaded connection with the pushing plate.

Preferably, a driving motor is fixedly mounted at the top of the mounting table, and an output shaft of the driving motor is welded with the circle center of the bottom of the rotating table.

Preferably, the laser is a single longitudinal mode He — Ne laser.

Preferably, the calculation unit comprises a comparator, a counter and a calculator, and the comparator, the counter and the calculator are connected in series.

Preferably, a spring is fixedly mounted at the top of the moving plate, and the top of the spring is fixedly connected with one side of the supporting plate.

Preferably, a sliding block is fixedly mounted on one side of the pushing plate, a sliding rail is fixedly mounted on the inner wall of one side of the driving groove, and the sliding block is connected with the sliding rail in a sliding manner.

Compared with the prior art, the beneficial effects of the utility model are that: the utility model discloses utilize sinusoidal grating to diffract incident light, the effectual laser utilization ratio that has improved does not need expensive photoelectric detector and the signal analysis processing system of complicacy also can accurately detect the signal beat frequency, uses the He-Ne laser as the light source simultaneously, and the light source frequency band is narrower, and measurement accuracy is higher, adopts the differential Doppler measurement system of forward scattering of double optical paths, can restrain the influence of ambient noise to the signal effectively, is favorable to improving measuring resolution ratio and precision.

The utility model discloses in, the sinusoidal grating technique of use can make whole light path have good symmetry, suppresses environmental noise effectively to can divide into two bundles of light of symmetry with a beam of light, realize the two differential mode Doppler techniques of single beam, have very high resolution ratio and precision to the small speed on solid surface, and the scheme is succinct, easily modulates, and low cost receives environmental influence factor less.

Drawings

Fig. 1 is a schematic structural view of a single-frequency laser doppler lateral velocity meter based on a grating technology according to the present invention;

fig. 2 is a schematic structural diagram of a laser of a single-frequency laser doppler lateral velocity meter based on a grating technology according to the present invention;

fig. 3 is a schematic diagram of the schematic structure of a single-frequency laser doppler lateral velocity meter based on the grating technology according to the present invention;

fig. 4 is a schematic structural diagram of a computing unit of a single-frequency laser doppler lateral velocity meter based on a grating technology according to the present invention;

fig. 5 is the utility model provides a relative error accuracy measurement result chart of horizontal tachymeter of single-frequency laser doppler based on grating technique.

In the figure: the laser device comprises a laser 1, a supporting plate 1.1, a fixed seat 1.2, a laser head 1.3, a first connecting shaft 1.4, a movable plate 1.5, a spring 1.6, a second connecting shaft 1.7, a pushing plate 1.8, a driving groove 1.9, a stepping motor 1.10, a screw 1.11, a rotating table 2, a sinusoidal grating 3, a first reflector 4, a second reflector 5, a half-transmitting and half-reflecting mirror 6, a photodetector 7, a digital oscilloscope 8, a signal amplifier 9, a signal acquisition card 10, a computing unit 11, a comparator 12, a counter 13, a calculator 14, a mounting table 15 and a driving motor 16.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments.

Referring to fig. 1-5, a single-frequency laser doppler lateral velocity measuring instrument based on a grating technology comprises an installation table 5, wherein the top of the installation table 5 is fixedly provided with a laser 1, a sinusoidal grating 3, a rotating table 2, a first reflecting mirror 4, a second reflecting mirror 5, a semi-transparent semi-reflecting mirror 6, a photoelectric detector 7, a digital oscilloscope 8, a signal amplifier 9, a signal acquisition card 10 and a calculating unit 11 respectively, and the photoelectric detector 7, the digital oscilloscope 8, the signal amplifier 9, the signal acquisition card 10 and the calculating unit 11 are connected in series;

the laser device 1 comprises a supporting plate 1.1, a fixed seat 1.2 is fixedly installed on one side of the supporting plate 1.1, a laser head 1.3 is rotatably connected to one side of the fixed seat 1.2, a first connecting shaft 1.4 is rotatably connected to the top of the laser head 1.3, a movable plate 1.5 is rotatably connected to one side of the first connecting shaft 1.4, one side of the movable plate 1.5 is slidably connected to one side of the supporting plate 1.1, a second connecting shaft 1.7 is rotatably connected to the bottom of the laser head 1.3, a pushing plate 1.8 is rotatably connected to the bottom of the second connecting shaft 1.7, a driving groove 1.9 is formed in one side of the supporting plate 1.1, one side of the pushing plate 1.8 is slidably connected to the inner wall on one side of the driving groove 1.9, a stepping motor 1.10 is fixedly installed on the inner wall on the bottom of the driving groove 1.9, a screw rod 1.11 is welded on the output shaft of the stepping motor 1.10, the top of the screw rod 1.11 penetrates through the pushing plate 1.8 and is rotatably connected to the inner wall on the top of the driving groove 1.11, and the screw rod 1.11 is in threaded connection with the pushing plate 1.8, the sinusoidal grating 3 is used to diffract the incident light, which effectively improves the laser utilization rate, can accurately detect the beat frequency of the signal without an expensive photoelectric detector and a complex signal analysis processing system, simultaneously uses a He-Ne laser as a light source, has narrow light source frequency band and high measurement precision, adopts a dual-light path forward scattering differential Doppler measurement system, can effectively inhibit the influence of environmental noise on the signal, and is beneficial to improving the measurement resolution and precision. Low cost and less environmental influence factors.

The utility model discloses in, the top fixed mounting of mount table 15 has driving motor 16, and driving motor 16's output shaft welds with the bottom centre of a circle position of revolving stage 2 mutually.

In the present invention, the laser 1 is a single longitudinal mode He-Ne laser.

In the present invention, the calculating unit 11 includes a comparator 12, a counter 13 and a calculator 14, and the comparator 12, the counter 13 and the calculator 14 are connected in series.

The utility model discloses in, movable plate 1.5's top fixed mounting has spring 1.6, spring 1.6's top and backup pad 1.1 one side fixed connection.

The utility model discloses in, one side fixed mounting of slurcam 1.8 has the slider, and fixed mounting has the slide rail on one side inner wall of drive groove 1.9, and slider and slide rail sliding connection.

In the utility model, the laser 1 is used for outputting single longitudinal mode linear polarized light with stable frequency and narrow frequency band, and directly making the light beam normally incident on the grating surface, the rotating platform 2 can be used as an excitation source with adjustable speed, as the true value of the speed, the sinusoidal grating 3 is used for being fixed on the edge of the rotating platform 2, as the speed information of the rotating platform 2 is carried as the speed target, and the incident light can be diffracted to make the incident light exit to two first reflecting

mirrors

4 and 5 about the normal line of the grating surface, the first reflecting mirror 4 and the second reflecting mirror 5 are used for adjusting the direction of the diffracted light and making two beams of +/-1 grade diffracted light intersect at the half-transmitting half-reflecting mirror, the half-transmitting half-reflecting mirror 6 is used for combining two beams of +/-1 grade diffracted light into one beam and interfering in space to generate mixing frequency, the photoelectric detector 7 is used for converting the optical signal into electric signal and outputting the electric signal to the digital oscilloscope 8 and the signal amplifier 9 respectively, a digital oscilloscope 8 for visually detecting the amplitude change of the beat frequency signals of the two beams of diffraction light to conveniently and slightly adjust the system, a signal amplifier 9, is used for amplifying beat frequency alternating current signals of the two beams of diffracted light and outputting the beat frequency alternating current signals to a signal acquisition card 10, is used for collecting and outputting the alternating current signals to the computing unit 11, the computing unit 11 is used for measuring and analyzing the collected signals, and finally calculating the grating transverse speed on the surface of the rotating platform 2 according to the Doppler formula, wherein the comparator 12 is arranged to provide a threshold comparison on the ac signal, thereby converting the ac sinusoidal signal into a square wave pulse signal, and outputs to the counter 13, the counter 13 is used for calculating the number of pulses appearing in a period of time, the calculator 14 is used for firstly calculating the frequency of the signal, and then calculating the moving speed of the object according to the Doppler formula.

The method comprises the following steps: speed measurement scheme:

keeping the rotating platform 2 still, fixing the sinusoidal grating 3 at the edge of the rotating platform 2, ensuring that the grating surface is parallel to the tangential direction of the edge of the rotating platform 2, outputting single-frequency linear polarized light with the wavelength lambda of 632.8nm by the laser 1, and normally irradiating the surface of the sinusoidal grating 3 fixed on the rotating platform 2, adjusting each optical element, ensuring that the incident light, the grating and the axis of the rotating platform 2 are in the z-axis direction at the same time, and adjusting the angular velocity omega of the rotating platform by using the rotating platform 2 as a velocity excitation source through a driving motor 16, thereby achieving the purpose of changing the transverse velocity v of the rotating platform, wherein the radius r (namely the distance between the grating surface and the axis of the rotating platform) of the rotating platform is 13.6mm, which is the real velocity of the surface of the rotating platform 2.

According to the grating equation, d, sin and theta are lambda, the grating diffracts incident light which perpendicularly enters the surface of the grating, diffracted plus or minus 1-order diffraction light exits in the direction with the diffraction angle theta being 49 degrees and is symmetrically distributed on two sides of the normal line of the grating surface, two beams of plus or minus 1-order diffraction light respectively pass through the first reflecting mirror 4 and the second reflecting mirror 5 to reach the half-transmitting mirror 6, the two beams of light are combined into one beam of light after passing through the half-transmitting mirror and interfere in space to generate mixing frequency, and signals are converted into electric signals by the photoelectric detector 7.

The turntable 2 is driven to rotate at an angular velocity ω according to: the magnitude of the lateral velocity v of the grating surface is known as ω · r. According to the optical Doppler effect, the original frequency f of the diffracted + 1-order light is changed into f1, wherein v is the lateral velocity of the turntable 2, c is the speed of light in vacuum, and θ is the included angle of diffraction:

similarly, the frequency of diffracted-1 order light becomes f 2:

the beat frequency fD can be detected by the photodetector 7, and can be known from the above two doppler formulas:

the signal can be monitored in real time through the digital oscilloscope 8, and meanwhile, the electric signal finally enters the computing unit through the signal amplifier 9 and the signal acquisition card 10.

The calculating unit 11 can calculate the speed by using the LabVIEW program, which includes a comparator 12 that sets a threshold value to compare the ac analog signal with the ac analog signal, so as to convert the analog signal into a digital signal, and input the digital signal into a counter 13, wherein the counter 13 can collect the number of pulses N within a period Δ t to more accurately calculate the beat frequency fD of the diffracted light within the period Δ t, as shown in the following formula:

f_D＝N/Δt

the counter 13 finally outputs the result to the calculator 14, which calculates the speed v of the surface of the turntable 2 according to the following formula:

step two: and (5) calibrating the relative error of the measuring speed.

By varying the speed vr of the rotating table 2, a series of measurements vm are obtained, the relative error Er being calculated according to the following formula:

the relative error measurement results are shown in FIG. 5

The working principle is as follows: when the velocimeter body needs to be used, firstly, the irradiation angle of the laser head 1.3 needs to be adjusted, so that a light beam emitted by the laser head 1.3 is absorbed on the sinusoidal grating 3, the stepping motor 1.10 is started, the stepping motor 1.10 can drive the screw rod 1.11 to rotate, the screw rod 1.11 is in threaded connection with the push plate 1.8, so that the rotary motion can be converted into linear motion, at the moment, the push plate 1.8 can move, the push plate 1.8 can drive the laser head 1.3 to rotate, the laser head 1.3 can drive the first connecting shaft 1.4 to move, the spring 1.6 can be deformed, at the moment, under the traction force of the spring 1.6, the rotation speed of the laser head 1.3 can be reduced, the position of the laser head 1.3 can be accurately adjusted, the stepping motor 1.10 can be stopped when the position of the laser head 1.3 is adjusted to the emitted light speed, the emitted light can be positively emitted on the sinusoidal grating 3, and the output wavelength lambda of the laser head 1 can be single-frequency 632, the normal incidence is on the surface of a sinusoidal grating 3 fixed on a rotary table 2, each optical element is adjusted, the incident light, the sinusoidal grating 3 and the axis of the rotary table 2 are ensured to be in the z-axis direction at the same time, the rotary table 2 is used as a speed excitation source, the angular speed omega of the rotary table can be adjusted through a driving motor 16, and the purpose of changing the transverse speed v of the rotary table is achieved, the radius r of the rotary table (namely the distance between the grating surface and the axis of the rotary table) is 13.6mm, namely the real speed of the surface of the rotary table 2, two beams of +/-1 diffraction light respectively pass through a first reflecting mirror 4 and a second reflecting mirror 5 to reach a semi-transparent semi-reflecting mirror 6, the two beams of light are combined into one beam of light after passing through the semi-transparent semi-reflecting mirror 6 and are interfered in space to generate mixing, the signal is converted into an electric signal by a photoelectric detector 7 to drive the rotary table 2 to rotate at the angular speed omega, the signal can be monitored in real time through a digital oscilloscope 8, and the electric signal passes through a signal amplifier 9, The signal acquisition card 10 finally enters the calculation unit 11, so that the calculation unit 11 can realize the speed calculation through a LabVIEW program.

Above, only be the concrete implementation of the preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto, and any person skilled in the art is in the technical scope of the present invention, according to the technical solution of the present invention and the design of the present invention, equivalent replacement or change should be covered within the protection scope of the present invention.

Claims

1. A single-frequency laser Doppler transverse velocimeter based on a grating technology comprises an installation platform (15) and is characterized in that a laser (1), a sinusoidal grating (3), a rotating platform (2), a first reflecting mirror (4), a second reflecting mirror (5), a semi-transmitting semi-reflecting mirror (6), a photoelectric detector (7), a digital oscilloscope (8), a signal amplifier (9), a signal acquisition card (10) and a calculating unit (11) are fixedly installed at the top of the installation platform (15) respectively, and the photoelectric detector (7), the digital oscilloscope (8), the signal amplifier (9), the signal acquisition card (10) and the calculating unit (11) are connected in series;

the laser device (1) comprises a supporting plate (1.1), a fixing seat (1.2) is fixedly installed on one side of the supporting plate (1.1), a laser head (1.3) is rotatably connected to one side of the fixing seat (1.2), a first connecting shaft (1.4) is rotatably connected to the top of the laser head (1.3), a movable plate (1.5) is rotatably connected to one side of the first connecting shaft (1.4) far away from the laser head (1.3), one side of the movable plate (1.5) is slidably connected with one side of the supporting plate (1.1), the bottom of the laser head (1.3) is rotatably connected with a second connecting shaft (1.7), the bottom of the second connecting shaft (1.7) is rotatably connected with a pushing plate (1.8), a driving groove (1.9) is formed in one side of the supporting plate (1.1), one side of the pushing plate (1.8) is slidably connected with the inner wall of one side of the driving groove (1.9), and a stepping motor (1.10) is fixedly installed on the inner wall of the bottom of the driving groove (1.9), the screw rod (1.11) is welded on the output shaft of the stepping motor (1.10), the top of the screw rod (1.11) penetrates through the push plate (1.8) and is rotationally connected with the inner wall of the top of the driving groove (1.11), and the screw rod (1.11) is in threaded connection with the push plate (1.8).

2. The single-frequency laser Doppler lateral velocity meter based on the grating technology as claimed in claim 1, wherein a driving motor (16) is fixedly installed at the top of the installation table (15), and an output shaft of the driving motor (16) is welded with the bottom center of a circle of the rotating table (2).

3. A single frequency laser doppler lateral velocimeter based on grating technology according to claim 1, characterized in that the laser (1) is a single longitudinal mode He-Ne laser.

4. Single frequency laser doppler lateral velocimeter according to claim 1, characterised in that the calculation unit (11) comprises a comparator (12), a counter (13) and a calculator (14), and the comparator (12), the counter (13) and the calculator (14) are connected in series.

5. Single frequency laser doppler lateral velocimeter according to claim 1, characterised in that the top of the moving plate (1.5) is fixedly mounted with a spring (1.6), and the top of the spring (1.6) is fixedly connected with one side of the support plate (1.1).

6. The single-frequency laser Doppler lateral velocity meter based on the grating technology as claimed in claim 1, wherein a sliding block is fixedly mounted on one side of the pushing plate (1.8), a sliding rail is fixedly mounted on the inner wall of one side of the driving groove (1.9), and the sliding block and the sliding rail are connected in a sliding manner.