CN219104954U - Noise self-correction laser Doppler speed measurement system - Google Patents
Noise self-correction laser Doppler speed measurement system Download PDFInfo
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- CN219104954U CN219104954U CN202320218663.5U CN202320218663U CN219104954U CN 219104954 U CN219104954 U CN 219104954U CN 202320218663 U CN202320218663 U CN 202320218663U CN 219104954 U CN219104954 U CN 219104954U
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Abstract
The utility model discloses a noise self-correction laser Doppler velocity measurement system, which comprises: a laser for outputting continuous laser light; a beam splitter for splitting the continuous laser beam into a reference beam and a measuring beam, and reflecting scattered light in a direction opposite to that of the reference beam; the chopper is used for periodically irradiating the measuring beam on the chopper and the moving surface to be measured; the photoelectric detector is used for converting a base noise signal or a beat frequency signal generated by the reference beam and scattered light into an electric signal; and the signal processing component is used for carrying out speed calculation on the electric signals to obtain the speed of the moving surface to be measured. The utility model is applied to the fields of laser and precise measurement, a chopper is added on an emergent light path of a laser Doppler velocimeter, the cyclic measurement of the base noise and Doppler signals is realized, and the self-correction of the noise is realized by feeding back the information of the base noise to a signal processing assembly in real time, thereby being beneficial to the quality judgment and Doppler frequency identification of the Doppler signals.
Description
Technical Field
The utility model relates to the technical field of laser and precise measurement, in particular to a noise self-correction laser Doppler speed measurement system.
Background
The laser Doppler velocimeter (Laser Doppler Velocimeter, LDV) has the advantages of high speed measurement precision, non-contact measurement, high spatial resolution and the like, and is widely used in applications such as fluid speed measurement, solid surface vibration measurement, displacement measurement, vehicle-mounted integrated navigation and the like, and the accuracy of the acquisition speed of the velocimeter is directly determined by the quality of the laser Doppler signal. To determine the quality of the Doppler signal and to accurately identify the Doppler frequency, the Doppler signal and the base noise need to be acquired. The conventional laser doppler velocimetry system mainly comprises an optical path detection system and a signal processing system, as shown in fig. 1, and comprises a laser 1, a spectroscope 2, a photoelectric detector 4, a collimating lens group 5, a reflecting mirror 6, an attenuation sheet 7, a first diaphragm 8, an optical filter 9, a second diaphragm 10, a signal processing component 11, and the signal processing component 11, wherein the signal processing component 11 comprises a preamplifier 1101, a filter 1102, an AD acquisition unit 1103, a register 1104 and a doppler signal resolving unit 1105. The speed measurement flow is as follows: the measured speed is 0 before the speed measurement is started, at the moment, the laser Doppler velocimeter is self-calibrated to obtain the base noise x of the laser Doppler velocimeter, and the base noise is used as the base noise of the follow-up speed measurement process. When the speed measurement is started, beat frequency signals generated by the reference light and scattered signal light of the moving surface are converted into electric signals through the detector and then are input into the signal processing system, and AD conversion is performed after passing through the preamplifier and the filter. And inputting the Doppler signals obtained by the substrate noise x and the AD conversion obtained in the self-calibration stage into a Doppler signal resolving module for Doppler signal quality judgment and speed resolving. Because the light source of the light path detection system is continuous light, in the Doppler signal resolving process, data acquired by AD is temporarily stored in a register, and after the Doppler signal resolving system finishes the current data resolving, the data is extracted from the register to resolve the next frame. The substrate noise adopted in the speed measurement flow is the substrate noise in the self-calibration stage, and if external interference is encountered in the speed measurement process, such as electromagnetic environment change, movement surface scattering rate change and the like, the substrate noise can be changed. If the self-calibration stage is still adopted to judge the signal quality at this time, the error result is obtained, even the error Doppler frequency identification result is caused, and finally the speed accuracy of the velocimeter is reduced or the error speed information is obtained.
Disclosure of Invention
Aiming at the defects in the prior art, the utility model provides a noise self-correction laser Doppler velocimetry system, wherein a chopper is added on an emergent light path of a laser Doppler velocimetry to realize cyclic measurement of base noise and Doppler signals, and the noise self-correction is realized by feeding back information of the base noise to a signal processing assembly in real time, so that the system is beneficial to Doppler signal quality judgment and Doppler frequency identification.
In order to achieve the above object, the present utility model provides a noise self-correcting laser doppler velocimetry system, comprising:
a laser for outputting continuous laser light;
a beam splitter, located on the output light path of the laser, for splitting the continuous laser into a reference beam and a measuring beam, and reflecting scattered light in the opposite direction to the measuring beam;
the chopper is positioned between the spectroscope and the moving surface to be measured, and the chopper is positioned on the light path of the measuring light beam so that the measuring light beam periodically irradiates on the chopper and the moving surface to be measured;
the photoelectric detector is positioned on the light paths of the reference beam and the scattered light and is used for converting a substrate noise signal or a beat frequency signal generated by the reference beam and the scattered light into an electric signal;
and the signal processing component is electrically connected with the photoelectric detector and is used for carrying out speed calculation on the electric signals to obtain the speed of the moving surface to be detected.
In one embodiment, the chopper includes a driver and a shutter;
the driving piece is connected with the shielding piece to drive the shielding piece to displace and/or rotate, and the shielding piece periodically shields the measuring light beam in the displacement and/or rotation process.
In one embodiment, the noise self-correcting laser Doppler velocimetry system further comprises a reflector;
in the continuous laser, a part of the light beam transmitted through the beam splitter is the measuring light beam, and a part of the light beam reflected by the beam splitter is the reference light beam;
the reflecting mirror, the spectroscope and the photoelectric detector are arranged at intervals in a straight line in sequence, so that the reference beam passes through the spectroscope after being reflected by the reflecting mirror and is received by the photoelectric detector.
In one embodiment, an attenuation sheet is arranged between the reflecting mirror and the spectroscope.
In one embodiment, the noise self-correcting laser Doppler velocimetry system further comprises a first diaphragm, the first diaphragm being located in the measuring beam optical path.
In one embodiment, a collimating lens group is arranged between the laser and the spectroscope.
In one embodiment, the noise self-correction laser Doppler velocimetry system further comprises an optical filter and a second diaphragm;
the spectroscope, the optical filter, the second diaphragm and the photoelectric detector are arranged at intervals in sequence in a straight line.
The utility model has the following beneficial technical effects:
1. according to the utility model, the chopper is used for controlling the transmission and shielding of the outgoing beam of the laser Doppler velocimeter, so that the base noise and Doppler signals of the laser Doppler velocimeter can be circularly measured;
2. according to the utility model, the information of the base noise is fed back to the signal processing component in real time, so that the noise self-correction is realized, and the influence of the base noise change on the signal quality and the speed resolving precision can be reduced, namely the influence of the external environment interference on the signal quality and the speed resolving precision is reduced.
Drawings
In order to more clearly illustrate the embodiments of the present utility model or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present utility model, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural diagram of a conventional laser doppler velocimetry system;
FIG. 2 is a schematic diagram of a noise self-correcting laser Doppler velocimetry system according to an embodiment of the present utility model;
fig. 3 is a schematic view of the structure of a shutter according to an embodiment of the present utility model.
Reference numerals: the device comprises a laser 1, a spectroscope 2, a chopper 3, a driving piece 301, a shielding piece 302, a shielding area 303, a light transmission area 304, a photoelectric detector 4, a collimating lens group 5, a reflecting mirror 6, an attenuation sheet 7, a first diaphragm 8, a light filter 9, a second diaphragm 10, a signal processing component 11, a preamplifier 1101, a filter 1102, an AD acquisition unit 1103, a register 1104, a Doppler signal calculation unit 1105 and a motion surface 12 to be measured.
The achievement of the objects, functional features and advantages of the present utility model will be further described with reference to the accompanying drawings, in conjunction with the embodiments.
Detailed Description
The following description of the embodiments of the present utility model will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the utility model. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.
In addition, the technical solutions of the embodiments of the present utility model may be combined with each other, but it is necessary to be based on the fact that those skilled in the art can implement the technical solutions, and when the technical solutions are contradictory or cannot be implemented, the combination of the technical solutions should be considered as not existing, and not falling within the scope of protection claimed by the present utility model.
Fig. 2 shows a noise self-correcting laser doppler velocimetry system disclosed in this embodiment, which includes a laser 1, a beam splitter 2, a chopper 3, a photodetector 4, a collimating lens group 5, a reflecting mirror 6, an attenuation sheet 7, a first diaphragm 8, an optical filter 9, a second diaphragm 10 and a signal processing component 11. The photodetector 4 is electrically connected with the signal processing component 11, the laser 1, the collimating lens group 5, the spectroscope 2, the chopper 3, the first diaphragm 8 and the moving surface 12 to be measured are sequentially distributed at intervals along a first straight line, an outgoing direction of the laser 1 forms an included angle of 45 degrees with the spectroscope 2 along the first straight line, an included angle between the outgoing direction of the laser 1 and the moving surface 12 to be measured is θ, and θ is not equal to 90 degrees. The reflecting mirror 6, the attenuation sheet 7, the spectroscope 2, the optical filter 9, the second diaphragm 10 and the photoelectric detector 4 are sequentially distributed at intervals along a second straight line, an included angle of 45 degrees is formed between the reflecting mirror 6 and the spectroscope 2, and the first straight line and the second straight line are intersected and vertical on the spectroscope 2. The basic structure of the velocimeter is a Michelson interferometer, and the laser 1 is a single longitudinal mode solid laser. The collimating lens group 5 may be composed of a convex lens and a concave lens, or may be composed of a plurality of lenses.
It should be noted that, in the specific application, the angle between the outgoing direction of the laser 1 and the beam splitter 2 is not limited to 45 °, but may be other angles other than 90 ° such as 30 °, 60 °. The angle between the reflecting mirror 6 and the beam splitter 2 is not limited to 45 °, and the reflecting mirror 6 only needs to be perpendicular to the reference beam direction. The first straight line and the second straight line are not limited to be perpendicular.
In this embodiment, the chopper 3 includes a driver 301 and a shutter 302. The driver 301 is connected to the shutter 302, and the shutter 302 is displaceable and/or rotatable under the driving of the driver 301, and the shutter 302 periodically blocks the measuring beam during the displacement and/or rotation.
The working process of the speed measuring system in the embodiment is as follows:
the laser 1 outputs continuous laser along the first straight line direction, the continuous laser irradiates the spectroscope 2 after the collimation degree is improved by the collimation lens group 5, the continuous laser is split into a reference beam and a measuring beam by the spectroscope 2, wherein part of the beam transmitted by the spectroscope 2 is the measuring beam, and part of the beam reflected by the spectroscope 2 is the reference beam;
for the reference beam, the reference beam is reflected by the spectroscope 2, then is emitted to the attenuation sheet 7 and the reflecting mirror 6 along the reflecting direction of the second straight line, and sequentially passes through the attenuation sheet 7, the spectroscope 2, the optical filter 9 and the second diaphragm 10 along the direction of the second straight line after being reflected by the reflecting mirror 6, and then irradiates on the detection surface of the photoelectric detector 4;
as for the measuring beam, since the chopper 3 can periodically block the measuring beam, the measuring beam has two cases, respectively:
when the chopper 3 blocks the measuring beam, the measuring beam irradiates the chopper 3 directly along the direction of the first straight line, the scattered light reflected by the chopper 3 along the opposite direction of the first straight line passes through the optical filter 9 and the second diaphragm 10 after being reflected by the spectroscope 2, and finally falls on the detection surface of the photoelectric detector 4, at this time, the reference beam and the measuring beam reflected light on the detection surface of the photoelectric detector 4 can not generate beat frequency signals because the measuring beam is perpendicular to the plane of the chopper 3, at this time, the signal obtained by the detector is a substrate noise signal, and the amplitude of the substrate noise can be obtained by converting the substrate noise signal into an electrical signal and inputting the electrical signal into the signal processing component 11. The specific implementation process of calculating the base noise is a conventional means in the art, so this embodiment will not be repeated here.
When the chopper 3 does not block the measuring beam, the measuring beam passes through the chopper 3 and the first diaphragm 8 along the first straight line direction and then enters the moving surface 12 to be measured at an angle θ, and diffuse reflection of the moving surface 12 to be measured generates scattered light along all directions, wherein the scattered light along the opposite direction of the first straight line is reflected by the spectroscope 2, stray light is filtered by the optical filter 9, and then passes through the second diaphragm 10 and then falls on the detection surface of the photodetector 4. From the doppler effect, scattering of moving particles will cause the frequency of the incident light to change. Therefore, the reference light and the signal light generate beat frequency signals on the surface of the detector, the beat frequency signals are converted into electric signals and then input into the signal processing component 11, and the Doppler frequency f of the beat frequency signals can be obtained by calculating the base noise obtained by the last calculation D The Doppler frequency of the beat signal is proportional to the velocity of the moving surface 12 to be measured, i.e.:
the speed of the moving surface can thus be expressed as:
wherein K is D Is a scale factor, V is the running speed of the moving surface 12 to be measured, λ is the wavelength of incident light, and θ is the angle between the direction of incident light and the speed direction.
Referring to fig. 3, there is shown an embodiment of a shield 302 in which the shield 302 is equally divided into a number of sections, where the black areas are light-blocking areas 303 and the white areas are light-transmitting areas 304. The driver 301 is now a motor for driving the shutter 302 in rotation. When the shade is coveredWhen the shutter 302 rotates, the position where the measuring beam irradiates the shutter 302 is shown by a circular dotted line in fig. 3. Let the AD sampling frequency in the signal processing component 11 be f s The number of data points for each frame base noise calculation and Doppler signal calculation is N, and the sampling time T s The method comprises the following steps:
therefore, the light transmission time and the light shielding time of the chopper 3 should satisfy:
where r is the radius of the circular dotted line in fig. 3, s is the arc length of the measuring beam passing through each of the light-transmitting region 304 and the light-shielding region 303, α is the radian corresponding to each of the light-transmitting region 304 and the light-shielding region 303, and v is the rotation angular velocity of the chopper 3. The design of the shield 302 should therefore be such that:
the shielding member 302 is designed according to the parameters, and is rotated at the angular speed omega under the control of the driving member 301 to realize the on-off control of the measuring beam, so that the base noise signal and the beat frequency signal can be obtained at intervals in sequence. When the speed is calculated, the amplitude distribution of the base noise is calculated, and then the amplitude distribution of the base noise is used for calculating the beat frequency signal acquired next time, so that the cyclic reciprocation is realized, the noise self-correction in the speed measuring process is realized, and the influence of external interference on signal quality judgment and Doppler frequency identification is avoided.
It should be noted that, although the shutter 302 in the present embodiment is configured to rotate to control the on/off of the measuring beam, the present utility model is not limited to the specific application, and may be configured to move. For example, a baffle is directly adopted as the shielding member 302, a telescopic cylinder is adopted as the driving member 301, the shielding member 302 is driven by a telescopic rod to do linear reciprocating motion, and the effect of controlling the on-off of the measuring beam can be achieved.
The foregoing description is only of the preferred embodiments of the present utility model and is not intended to limit the scope of the utility model, and all equivalent structural changes made by the description of the present utility model and the accompanying drawings or direct/indirect application in other related technical fields are included in the scope of the utility model.
Claims (7)
1. A noise self-correcting laser doppler velocimetry system, comprising:
a laser for outputting continuous laser light;
a beam splitter, located on the output light path of the laser, for splitting the continuous laser into a reference beam and a measuring beam, and reflecting scattered light in the opposite direction to the measuring beam;
the chopper is positioned between the spectroscope and the moving surface to be measured, and the chopper is positioned on the light path of the measuring light beam so that the measuring light beam periodically irradiates on the chopper and the moving surface to be measured;
the photoelectric detector is positioned on the light paths of the reference beam and the scattered light and is used for converting a substrate noise signal or a beat frequency signal generated by the reference beam and the scattered light into an electric signal;
and the signal processing component is electrically connected with the photoelectric detector and is used for carrying out speed calculation on the electric signals to obtain the speed of the moving surface to be detected.
2. The noise self-correcting laser doppler velocimetry system of claim 1, wherein the chopper comprises a driver and a shutter;
the driving piece is connected with the shielding piece to drive the shielding piece to displace and/or rotate, and the shielding piece periodically shields the measuring light beam in the displacement and/or rotation process.
3. The noise self-correcting laser doppler velocimetry system of claim 1 or 2, further comprising a mirror;
in the continuous laser, a part of the light beam transmitted through the beam splitter is the measuring light beam, and a part of the light beam reflected by the beam splitter is the reference light beam;
the reflecting mirror, the spectroscope and the photoelectric detector are arranged at intervals in a straight line in sequence, so that the reference beam passes through the spectroscope after being reflected by the reflecting mirror and is received by the photoelectric detector.
4. The noise self-correcting laser Doppler velocimetry system of claim 3, wherein an attenuation sheet is provided between the reflecting mirror and the spectroscope.
5. The noise self-correcting laser doppler velocimetry system of claim 1 or 2, further comprising a first diaphragm located in the measuring beam optical path.
6. The noise self-correcting laser doppler velocimetry system according to claim 1 or 2, wherein a collimating lens group is arranged between the laser and the spectroscope.
7. The noise self-correcting laser doppler velocimetry system of claim 1 or 2, further comprising a filter and a second diaphragm;
the spectroscope, the optical filter, the second diaphragm and the photoelectric detector are arranged at intervals in sequence in a straight line.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202320218663.5U CN219104954U (en) | 2023-02-15 | 2023-02-15 | Noise self-correction laser Doppler speed measurement system |
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| CN202320218663.5U CN219104954U (en) | 2023-02-15 | 2023-02-15 | Noise self-correction laser Doppler speed measurement system |
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| CN219104954U true CN219104954U (en) | 2023-05-30 |
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