CN116953720A - Laser Doppler speed measurement method and system based on array photoelectric detector - Google Patents
Laser Doppler speed measurement method and system based on array photoelectric detector Download PDFInfo
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- CN116953720A CN116953720A CN202310687456.9A CN202310687456A CN116953720A CN 116953720 A CN116953720 A CN 116953720A CN 202310687456 A CN202310687456 A CN 202310687456A CN 116953720 A CN116953720 A CN 116953720A
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- 238000004599 local-density approximation Methods 0.000 claims description 10
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/50—Systems of measurement based on relative movement of target
- G01S17/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation
Abstract
The invention discloses a laser Doppler velocity measurement method based on an array photoelectric detector, which comprises the following steps: splitting the continuous laser beam into reference light and detection light; reflecting the signal light to the first photosurface and the second photosurface along a first direction; making the reference light incident to the first photosensitive surface and the second photosensitive surface along the second direction, wherein an included angle is formed between the first direction and the second direction; and converting interference signals on the first photosensitive surface and the second photosensitive surface into a first electric signal and a second electric signal with phase differences, and then calculating to obtain the speed and the direction of the measured moving object. The invention is applied to the field of optical measurement, can obtain the speed direction by utilizing the phase difference of the signals of the array photoelectric detector while calculating the speed of the measured moving object, and effectively solves the problems that the existing laser Doppler speed measuring system capable of distinguishing the direction has large volume and the speed measuring range is limited by the frequency shift quantity of the frequency shift device.
Description
Technical Field
The invention relates to the technical field of optical measurement, in particular to a laser Doppler velocity measurement method and system based on an array type photoelectric detector.
Background
The laser Doppler speed measurement is a novel non-contact speed measuring instrument, and is widely applied to the fields of aviation, aerospace, automobiles, industry and the like to measure parameters such as speed, acceleration, displacement, vibration and the like due to the characteristics of high precision, large measuring range, good spatial resolution and the like. However, the original laser Doppler velocimeter can only measure the speed, but cannot distinguish the direction of the speed, so that only the speed field measurement of the general known object movement direction can be satisfied.
In order to solve this problem, various frequency shifting devices are often introduced into the speed measurement system to shift the frequency of one or both of the outgoing lights. When the object to be measured is stationary, the speed measuring system can measure an offset frequency, and when the object moves, the speed direction is detected according to the measured frequency moving up or down relative to the offset frequency. Common frequency shifting devices include rotating gratings, acousto-optic frequency shifters, electro-optic phase modulators. The rotary grating has simple structure, but the frequency shift amount is limited by the number of grating lines and the mechanical rotation speed, the frequency shift amount is low, and moving parts are needed, so that the volume is larger. The electro-optic phase modulator requires high driving power and power, and the driving power has complex structure, large volume and high-frequency interference. Although the acousto-optic frequency shifter does not need high voltage, a series of complex technical measures are needed to improve the frequency shift bandwidth, which also causes the size of the device to be larger.
The frequency shift devices have complex structures and large volumes, and are not beneficial to the development of miniaturization and integration of a speed measurement system. Meanwhile, the maximum value of Doppler frequency shift quantity in a certain direction of a moving object cannot exceed the offset frequency, so that the speed measurement range of the system can be limited by the frequency shift quantity of the frequency shift device.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a laser Doppler speed measurement method and a system based on an array photoelectric detector, which can effectively solve the problems that the existing laser Doppler speed measurement system capable of distinguishing directions is large in volume and the speed measurement range is limited by the frequency shift amount of a frequency shift device.
In order to achieve the above purpose, the invention provides a laser Doppler velocity measurement method based on an array type photoelectric detector, which comprises the following steps:
splitting the continuous laser beam into reference light and detection light;
the detection light irradiates the surface of the detected moving object, and the signal light returned along the detection light source path is reflected to a first photosensitive surface and a second photosensitive surface of the photoelectric detection module along a first direction;
the reference light is made to enter a first photosurface and a second photosurface of a photoelectric detection module along a second direction, wherein an included angle 2 alpha is formed between the first direction and the second direction, and alpha is not equal to 0;
converting the interference signal on the first photosurface into a first electric signal, and converting the interference signal on the second photosurface into a second electric signal, wherein the first electric signal and the second electric signal have a phase difference;
and resolving the first electric signal or the second electric signal to obtain the speed of the measured moving object, and obtaining the speed direction of the measured moving object based on the phase difference between the first electric signal and the second electric signal.
In one embodiment, the phase difference between the first electrical signal and the second electrical signal is pi/2.
In one embodiment, the first photosurface and the second photosurface are located on the same plane, and a center-to-center distance d between the first photosurface and the second photosurface is:
where λ is the laser wavelength.
In one embodiment, the first direction is perpendicular to a plane in which the first photosurface and the second photosurface are located.
In order to achieve the above purpose, the invention also provides a laser Doppler velocity measurement system based on the array photoelectric detector, which adopts the method to measure the velocity and direction of the measured moving object.
In one embodiment, the laser doppler velocity measurement system comprises a laser, a first light splitting device, a second light splitting device, a third light splitting device, a reflecting mirror, a photoelectric detection module and a signal processing module;
the laser, the first light-splitting device, the second light-splitting device and a third direction parallel to a first direction of the measured moving object are sequentially arranged at intervals, the third light-splitting device is positioned below the second light-splitting device, and the third light-splitting device and the photoelectric detection module are arranged at intervals along the first direction;
the photoelectric detection module is provided with a first photosensitive surface and a second photosensitive surface which are positioned on the same plane, the reflecting mirror is positioned at the rear of the third light splitting device, and an included angle pi/4+alpha is formed between the reflecting plane of the reflecting mirror and the first direction;
the signal processing module is electrically connected with the photoelectric detection module.
In one embodiment, two photoelectric devices are arranged on the photoelectric detection module in parallel, the first photosensitive surface is an input end of one photoelectric device, and the second photosensitive surface is an input end of the other photoelectric device;
the two photoelectric devices are integrated on the same integrated circuit and are used for capturing phase information of light spot movement so as to distinguish the movement direction of interference fringes;
the photoelectric device can be a photoelectric diode, an avalanche diode and other photovoltaic detectors, the photosensitive surface of the detector can be circular, rectangular or other customized shapes, and the avalanche diode with the circular photosensitive surface is selected.
Compared with the prior art, the invention has the following beneficial technical effects:
the invention can obtain the Doppler frequency based on the optical heterodyne technology, thereby solving the speed of the measured moving object, and simultaneously obtaining the speed direction by utilizing the phase difference of the signals of the array type photoelectric detector. Compared with the traditional frequency shift type laser Doppler velocity measurement system, the system has smaller volume and can measure velocity without being limited by the frequency shift amount of the frequency shifter.
Drawings
In order to more clearly illustrate the embodiments of the present invention 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 invention, 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 flow chart of a laser Doppler velocimetry method in an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a laser doppler velocimetry system according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a conventional laser Doppler velocimetry system;
FIG. 4 is a schematic view of incident directions of reference light and signal light with respect to a photosensitive surface according to an embodiment of the present invention;
fig. 5 is a schematic diagram illustrating positions of a first photosurface and a second photosurface on an array photoelectric detection module according to an embodiment of the invention.
Reference numerals: the device comprises a laser 1, a first light-splitting device 2, a second light-splitting device 3, a reflecting mirror 4, a third light-splitting device 5, a photoelectric detection module 6, a first photosurface 601, a second photosurface 602 and a measured moving object 7.
The achievement of the objects, functional features and advantages of the present invention 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 invention 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 invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In addition, the technical solutions of the embodiments of the present invention 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 invention.
Fig. 1 shows a laser doppler velocity measurement method based on an array type photoelectric detector, which includes the following steps:
the first light splitting device splits the continuous laser into reference light and detection light;
the method comprises the steps that detection light irradiates the surface of a detected moving object, and signal light returned along a detection light source path is reflected to a first photosensitive surface and a second photosensitive surface of a photoelectric detection module along a first direction based on a second light splitting device and a third light splitting device;
making the reference light incident to the first photosensitive surface and the second photosensitive surface of the photoelectric detection module along the second direction, wherein an included angle 2 alpha is formed between the first direction and the second direction, and alpha is not equal to 0;
converting the interference signal on the first photosurface into a first electric signal, and converting the interference signal on the second photosurface into a second electric signal, wherein a phase difference exists between the first electric signal and the second electric signal;
and resolving the first electric signal or the second electric signal to obtain the speed of the measured moving object, and obtaining the speed direction of the measured moving object based on the phase difference between the first electric signal and the second electric signal.
Referring to fig. 2, a laser doppler velocimetry system for implementing the laser doppler velocimetry method in this embodiment includes a laser 1, a first beam splitter 2, a second beam splitter 3, a reflector 4, a third beam splitter 5, a photoelectric detection module 6 and a signal processing module. The laser 1, the first light-splitting device 2 and the second light-splitting device 3 are sequentially arranged at intervals along a third direction parallel to the first direction, the third light-splitting device 5 is located below the second light-splitting device 3, the third light-splitting device 5 and the photoelectric detection module 6 are arranged along the first direction, the photoelectric detection module 6 is provided with a first photosensitive surface 601 and a second photosensitive surface 602 which are located on the same plane, the reflecting mirror 4 is located behind the third light-splitting device 5, and an included angle pi/4+alpha is formed between the reflecting plane of the reflecting mirror 4 and the first direction, so that an angle 2 alpha exists between the first direction and the second direction. The signal processing module is electrically connected with the photoelectric detection module 6. It should be noted that, in specific applications, the method of adjusting the reflecting mirror 4 in the optical path structure shown in fig. 2 is not limited to realizing that an included angle is formed between the first direction and the second direction, and the same effect can be achieved by adjusting the angle of the second light splitting device 2 and/or the third light splitting device 3.
In a specific implementation process, two avalanche diodes are arranged in parallel on the photoelectric detection module 6 as photoelectric devices, the first photosurface 601 is an input end of one avalanche diode, and the second photosurface 602 is an input end of the other avalanche diode. The two avalanche diodes are integrated on the same integrated circuit for capturing the phase information of the spot movement, thereby distinguishing the movement direction of the interference fringes.
The process of measuring the speed of the measured moving object 7 in this embodiment is:
the light emitted by the laser 1 is divided into two beams perpendicular to each other through the first light splitting device 2, one beam is transmitted detection light, the detection light irradiates the surface of the detected moving object 7 through the second light splitting device 3, the detection light is changed into signal light through scattering of particles on the surface of the detected moving object 7, and the signal light returns to the first photosurface 601 and the second photosurface 602 of the photoelectric detection module 6 after being reflected by the second light splitting device 3 and the third light splitting device 5 along the reverse direction of the detection light. The other beam is the reflected reference light, and the reference light passes through the third light splitting device 5 and reaches the first photosensitive surface 601 and the second photosensitive surface 602 of the photoelectric detection module 6 after being reflected by the reflecting mirror 4. The reference light and the signal light are mixed on the first photosurface 601 and the second photosurface 602 of the photoelectric detection module 6, and photocurrents, namely the first electric signal and the second electric signal, are obtained. The frequency of the alternating current component in the first electric signal or the second electric signal can be calculated through corresponding signal processing by the signal processing module, and the Doppler frequency shift quantity caused by the movement of the measured moving object 7 can be obtained, so that the movement speed of the measured moving object 7 can be calculated.
In this embodiment, the relationship between the doppler frequency and the motion speed of the optical path structure of the laser doppler velocity measurement system is:
wherein v is the speed of the measured moving object 7, θ is the included angle between the signal light and the moving direction of the measured moving object 7, and λ is the laser wavelength.
Referring to fig. 3, ideally, the reference light and the signal light should be completely parallel and perpendicularly incident to the surface of the photodetection module 6, where the angle between the reflecting mirror 4 and the first direction is pi/4. However, in practice, the reference light and the signal light cannot be completely parallel, and a certain included angle exists between the reference light and the signal light. As shown in fig. 4, the x-plane is the plane in which the photosensitive surface of the photodetector module 6 is located,is the wave vector of the reference light,/>Is the wave vector of the signal light, θ 1 And theta 2 The incident angles of the reference light and the signal light, respectively.
Assume complex amplitudes E of reference light and signal light incident on the photodetector module 6 r 、E s The method comprises the following steps of:
wherein E is 1 And E is 2 Respectively are referred to asAmplitude of light and signal light, f 0 For the laser 1 exit frequency, f D In order to be a doppler frequency,and->The initial phases of the reference light and the signal light, respectively, k is +.>And->K=2pi/λ. The light intensity distribution at the surface of the photodetector module 6 can be expressed as:
wherein, the liquid crystal display device comprises a liquid crystal display device,
from the above formula (4), it is known that f when the measured moving object 7 is stationary D =0, the interference fringes remain stable. When the measured moving object 7 moves, the stripes move, and the moving speed is proportional to the speed of the measured moving object 7. F when the movement directions of the measured moving objects 7 are different D The sign of the stripe is changed and the moving direction of the corresponding stripe is also different, so that the direction can be distinguished by detecting the moving direction of the stripe.
For this purpose, the present embodiment employs an array type photodetector module 6, and two parallel avalanche diodes are integrated on one integrated circuit for capturing phase information of the spot movement, thereby discriminating the movement direction of the fringes.
As shown in fig. 5, the photodetection module 6 used in the present embodiment has a center-to-center distance d between the first photosurface 601 and the second photosurface 602.
At some point, when the condition is satisfiedWhen n=0, ±1, ±2, …, the light intensity on the surface of the photodetection module 6 reaches the maximum value, and bright streaks appear. The stripe pitch p between two adjacent intensity maxima is:
because of theta 1 、θ 2 The fringe spacing p between two adjacent intensity maxima can be reduced to:
the most identifiable phase difference between the two electrical signals is pi/2, and the center-to-center distance d of the two avalanche diodes must be p/4 in order to obtain pi/2 phase difference. The first current i obtained by the two avalanche diodes at this time 1 And a second current i 2 The method comprises the following steps of:
according to the first current i 1 And a second current i 2 The relationship of the advance or retard of the signal phase allows direction discrimination, e.g. by passing the first current i 1 Signal phase advance of second current i 2 The moving direction of the measured moving object 6 is defined as positive direction when the signal phase of the (B) is lagged, the first current i is calculated 1 Signal phase lag of (2) second current i 2 The moving direction of the measured moving object 6 is specified as a negative direction when the signal phase of (a) is advanced.
Preferably as a result ofIn the embodiment, the signal light is vertically incident on the photoelectric detection module 6, namely, the incident angle theta of the signal light 2 =0. By rotating the mirror 4 by an angle alpha with respect to the first direction, the reference beam reflected by the mirror 4 will be rotated by 2 alpha in the same rotation direction. And can be obtained according to the refraction law, the propagation direction of the reference light after passing through the third light splitting device 5 is unchanged, and the incident angle theta of the reference light relative to the photosensitive surface of the photoelectric detection module 6 1 ＝2α。
The fringe spacing p between two adjacent intensity maxima at this point can be expressed as:
the center-to-center distance between the first photosurface 601 and the second photosurface 602 is as follows:
in summary, in the laser doppler velocity measurement method based on the array photoelectric detector in this embodiment, the size of the doppler frequency is obtained based on the optical heterodyne technology, so that the velocity of the measured moving object 7 is calculated, and the velocity direction can be obtained by using the array photoelectric detector. Compared with the traditional frequency shift type laser Doppler velocity measurement system, the system has smaller volume and the velocity measurement size is not limited by the frequency shift amount of the frequency shifter.
The foregoing description is only of the preferred embodiments of the present invention and is not intended to limit the scope of the invention, and all equivalent structural changes made by the description of the present invention and the accompanying drawings or direct/indirect application in other related technical fields are included in the scope of the invention.
Claims (7)
1. The laser Doppler speed measurement method based on the array type photoelectric detector is characterized by comprising the following steps of:
splitting the continuous laser beam into reference light and detection light;
the detection light irradiates the surface of the detected moving object, and the signal light returned along the detection light source path is reflected to a first photosensitive surface and a second photosensitive surface of the photoelectric detection module along a first direction;
the reference light is made to enter a first photosurface and a second photosurface of a photoelectric detection module along a second direction, wherein an included angle 2 alpha is formed between the first direction and the second direction, and alpha is not equal to 0;
converting the interference signal on the first photosurface into a first electric signal, and converting the interference signal on the second photosurface into a second electric signal, wherein the first electric signal and the second electric signal have a phase difference;
and resolving the first electric signal or the second electric signal to obtain the speed of the measured moving object, and obtaining the speed direction of the measured moving object based on the phase difference between the first electric signal and the second electric signal.
2. The laser doppler velocimetry method based on the array type photoelectric detector according to claim 1, wherein a phase difference between the first electric signal and the second electric signal is pi/2.
3. The laser doppler velocimetry method based on the array photoelectric detector according to claim 2, wherein the first photosurface and the second photosurface are located on the same plane, and a center-to-center distance d between the first photosurface and the second photosurface is:
where λ is the laser wavelength.
4. A laser doppler velocimetry method based on an array photo detector according to claim 1 or 2 or 3, wherein the first direction is perpendicular to the first photosurface and the second photosurface.
5. A laser doppler velocity measurement system based on an array type photoelectric detector, characterized in that the method of any one of claims 1 to 4 is adopted to measure the velocity and direction of a measured moving object.
6. The laser Doppler velocimetry system based on the array photoelectric detector according to claim 6, wherein the laser Doppler velocimetry system comprises a laser, a first light splitting device, a second light splitting device, a third light splitting device, a reflecting mirror, a photoelectric detection module and a signal processing module;
the laser, the first light-splitting device, the second light-splitting device and the measured moving object are sequentially arranged at intervals along a third direction parallel to the first direction, the third light-splitting device is positioned below the second light-splitting device, and the third light-splitting device and the photoelectric detection module are sequentially arranged at intervals along the first direction;
the photoelectric detection module is provided with a first photosensitive surface and a second photosensitive surface which are positioned on the same plane, the reflecting mirror is positioned at the rear of the third light splitting device, and an included angle pi/4+alpha is formed between the reflecting plane of the reflecting mirror and the first direction;
the signal processing module is electrically connected with the photoelectric detection module.
7. The laser Doppler speed measurement method based on the array photoelectric detector according to claim 6, wherein two photoelectric devices are arranged on the photoelectric detection module in parallel, the first photosensitive surface is an input end of one photoelectric device, and the second photosensitive surface is an input end of the other photoelectric device;
the two photoelectric devices are integrated on the same integrated circuit and are used for capturing phase information of light spot movement so as to distinguish the movement direction of the interference fringes.
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