CN114942016A - Vertical laser pointing correction device and method based on interference fringe decoupling - Google Patents
Vertical laser pointing correction device and method based on interference fringe decoupling Download PDFInfo
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- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
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Abstract
The invention discloses a vertical laser pointing correction device and method based on interference fringe decoupling, which comprises the following steps: a vertical laser signal is obtained through a vertical laser generating module, the vertical laser signal is transmitted to an integrated sensing module, and a spatial interference image is generated based on the integrated sensing module; the spatial interference image is input into the signal processing module for high-precision decoupling operation, an angle deviation result of the vertical laser relative to the gravity direction is obtained, and real-time correction of the pointing direction of the vertical laser is achieved according to the angle deviation result. The vertical laser pointing correction device is completely based on the laser interference measurement principle, the measurement resolution is high, the angle measurement result can be directly traced to the laser wavelength, and the requirement of high-end equipment on ultra-precise vertical laser pointing is met. In addition, the integrated sensing module of the device is convenient to disassemble and repeatedly install, can be conveniently reused in a plurality of sets of devices, and saves cost.
Description
Technical Field
The invention belongs to the technical field of precise angle measurement, and particularly relates to a vertical laser pointing correction device and method based on interference fringe decoupling.
Background
The vertical laser taking gravity as a reference is widely used for determining a vertical reference line and measuring the tiny deviation relative to a plumb line, and has important application value in engineering construction and precision measurement. For example, the device can be used for measuring and ensuring the verticality of buildings such as buildings, elevators, dams and the like, and can also be used for precisely detecting the verticality and the straightness of mechanical structures such as guide rails and the like, measuring and correcting the torsion resistance and the like. With the rapid development of the field of precision engineering in recent years, high-end equipment has made higher requirements on the pointing accuracy of vertical laser. For example, in a quantization reference device with a mass unit of "Kg", the pointing accuracy of the vertical laser determines the overall accuracy of the device, and the pointing direction of the vertical laser must be measured and corrected ultra-precisely to ensure that it coincides with the direction of gravity.
The vertical collimator can generate vertical laser based on gravity and use the vertical laser as a plumb line, and is commonly used for construction monitoring of large buildings and installation engineering of mechanical equipment. The coaxiality of the vertical laser and the vertical axis in the vertical collimator is generally calibrated by adopting devices such as a collimator, a pentagonal prism, a right-angle coordinate plate, a steel ruler and the like. Chinese patent publication No. CN104949689A, publication date 2015, 9/30, invents a digitized calibration method and apparatus for a laser plummet based on source imaging, which images a reticle through an imaging light source, projects the image onto a target at infinity, and performs calibration comparison with a debugging reference center, thereby reducing the complexity of calibration detection and improving the accuracy to a certain extent. However, due to factors such as the levelness of the worktable, the precision of the measuring scale, and inaccurate reading of human eyes, the vertical laser generated by the plummet has the problems of low pointing precision and difficult traceability guarantee in principle, and is difficult to be used for ultra-precise measurement.
In the field of precision metrology, some scholars have also proposed vertical laser pointing measurement devices based on new principles. For example, in 2016, the article, "plane mirror horizontal adjustment method based on high-precision electronic level", published by the institute of instrumentation and instrumentation, 37 th curling chart, 4 th, proposes a method for tracing the direction of vertical laser to a level through minimum transmission links. The device finally realizes that the pointing synthetic standard of vertical laser has uncertainty of 41 mu rad, is influenced by the rotating table rotating shaft precision, the rotating table horizontal adjusting mechanism precision, the electronic level meter lead wire and the nonlinearity and the processing precision of the electronic level meter, and the precision of the horizontal reference of the device is severely limited, so that the pointing precision of the vertical light beam is directly limited, and the traceability is poor. Furthermore, the device cannot use the measurement results for feedback control to achieve real-time correction of beam pointing.
For example, in 2016, Applied Optics, 55 th publication of System for the measurement of the depth of laser beam from the vertical direction, a vertical laser beam pointing deviation measuring device based on the principle of laser auto-collimation was proposed, which uses the liquid level as a reference. The vertical laser is divided into two beams, one beam penetrates through the lens after passing through the corner reflector, the other beam penetrates through the lens after being reflected by the liquid level, the positions of two light spots are obtained by the CCD, and the angle is calculated through the distance between the light spots. The short-term stability of the device can reach 2.4 mu rad, but the measurement precision of the device is directly limited due to the processing error and the position installation error of optical elements such as a CCD (charge coupled device), a converging lens and the like, and the traceability is difficult to improve. In addition, the device can only measure the deviation angle of the laser pointing direction, and cannot correct the deviation angle to the gravity direction.
In summary, the conventional vertical laser pointing calibration method for the plummet is low in precision, and cannot trace the light beam direction to the gravity direction in principle; the electronic level meter-based vertical laser pointing correction device is limited by factors such as processing errors and the like, the precision is limited, and the traceability is poor; the vertical laser pointing measurement device based on the auto-collimation principle is limited by the assembly error of an optical element, and the measurement result is still difficult to directly trace the source. Furthermore, the above-described device cannot use the measurement result of the beam pointing for real-time feedback and correct it to the direction of gravity. Therefore, a high-precision vertical laser pointing correction device capable of directly tracing is absent in the technical field of precision angle measurement.
Disclosure of Invention
The invention aims to provide a vertical laser pointing correction device and method based on interference fringe decoupling, which can realize high-precision measurement and correction of vertical laser pointing and directly trace to the gravity direction.
In order to achieve the purpose, the invention provides the following scheme: a vertical laser pointing correction device based on interference fringe decoupling comprises:
the vertical laser generating module is used for generating a vertical laser signal and finely adjusting the direction of the vertical laser signal;
the integrated sensing module is connected with the vertical laser generating module and used for receiving the vertical laser signal and generating a spatial interference image based on the vertical laser signal;
and the signal processing module is connected with the integrated sensing module and used for carrying out high-precision decoupling operation on the spatial interference image to obtain an angle deviation result of the vertical laser relative to the gravity direction, and realizing real-time correction of the pointing direction of the vertical laser according to the angle deviation result.
Preferably, the vertical laser generation module comprises a single-frequency laser, a single-mode polarization maintaining fiber, a fiber collimator, a pentagonal prism, an integrated light source base and a two-dimensional precise angle rotary table;
the single-frequency laser is used for providing a frequency-stabilized laser signal;
the single-mode polarization maintaining fiber is connected with the single-frequency laser and used for transmitting the frequency stabilized laser signal to the fiber collimator;
the optical fiber collimator is connected with the single-mode polarization maintaining optical fiber and used for receiving the frequency stabilized laser signal and outputting collimated laser;
the pentagonal prism is used for receiving the collimated laser and outputting a vertical laser signal;
the integrated light source base is used for fixing the optical fiber collimator and the pentagonal prism;
the two-dimensional precise angle rotary table is used for placing the integrated sensing base and the integrated light source base.
Preferably, the integrated sensing module comprises an integrated sensing base, a light splitting pyramid prism, a spectroscope, a reflector, a polarization spectroscope, a quarter-wave plate, a liquid container unit, a liquid unit, a micro-pyramid array and an image sensor;
the integrated sensing base is used for fixing the light-splitting pyramid prism, the spectroscope, the reflector, the polarizing spectroscope, the quarter-wave plate, the liquid container unit, the liquid unit and the image sensor;
the beam splitting pyramid prism is used for transmitting the vertical laser signal and reflecting part of the vertical laser signal to the first spectroscope;
the spectroscope is used for dividing the vertical laser signal into transmitted light and reflected light;
the reflecting mirror is used for reflecting the reflected light to the polarizing beam splitter;
the polarization spectroscope is used for transmitting the transmission light with the polarization state P and the reflection light to the quarter-wave plate; the first liquid level refraction light, the first liquid level reflection light, the second liquid level refraction light and the second liquid level reflection light with the polarization state of S are reflected to obtain first signal light, second signal light, third signal light and fourth signal light, and the first signal light, the second signal light, the third signal light and the fourth signal light are emitted to the image sensor;
the quarter-wave plate is used for transmitting the transmitted light and the reflected light and converting the transmitted light and the reflected light into circularly polarized light; the polarization state of the first liquid surface refraction light, the first liquid surface reflection light, the second liquid surface refraction light and the second liquid surface reflection light is changed into S;
the liquid container unit is used for placing liquid in the liquid unit; the second liquid surface is used for reflecting the light to the quarter-wave plate;
the liquid unit is used for dividing the transmitted light and the reflected light which are converted into circular polarization into first liquid surface refraction light and first liquid surface reflected light through liquid surfaces respectively; the second liquid surface refracts light and reflects light; the quarter-wave plate is used for reflecting the first liquid surface reflected light and the second liquid surface reflected light;
the micro-pyramid array is arranged at the bottom of the liquid container unit and used for reflecting the first liquid level refracted light to the quarter-wave plate;
the image sensor is used for detecting a spatial interference light spot formed by interference of the first signal light and the second signal light; and the optical detector is used for detecting a spatial interference fringe formed by the interference of the third signal light and the fourth signal light.
Preferably, the spatial interference light spot and the spatial interference fringe do not spatially overlap.
Preferably, the signal processing module comprises an upper computer and a signal processing card;
the signal processing card is used for carrying out high-precision decoupling operation on interference signals through a spatial interference fringe decoupling algorithm, sending feedback control signals to the two-dimensional precision angle rotary table according to measurement results, correcting and tracing the vertical laser pointing direction to the gravity direction, and uploading the operation results to an upper computer;
and the upper computer is used for receiving, displaying and storing the measurement result of the vertical laser pointing correction.
A vertical laser pointing correction method based on interference fringe decoupling comprises,
obtaining a vertical laser signal through a vertical laser generating module, transmitting the vertical laser signal to an integrated sensing module, and generating a spatial interference image based on the integrated sensing module;
and inputting the spatial interference image into a signal processing module for high-precision decoupling operation to obtain an angle deviation result of the vertical laser relative to the gravity direction, and realizing real-time correction of the pointing direction of the vertical laser according to the angle deviation result.
Preferably, the process of obtaining a vertical laser signal through the vertical laser generating module and transmitting the vertical laser signal to the integrated sensing module includes generating a frequency stabilized laser signal through a single-frequency laser and transmitting the frequency stabilized laser signal to an optical fiber collimator through a single-mode polarization maintaining optical fiber; the optical fiber collimator outputs collimated laser, and the collimated laser transmits a vertical laser signal to the integrated sensing module after obtaining the vertical laser signal through the pentagonal prism.
Preferably, the process of generating the spatial interference image based on the integrated sensing module comprises,
the vertical laser signal returns along the original direction after being reflected by the beam splitting pyramid prism and is divided into transmitted light and reflected light by the beam splitter;
the transmission light is transmitted by the polarization spectroscope and the quarter-wave plate to obtain circularly polarized light; the circularly polarized light is divided into first liquid surface refraction light and first liquid surface reflection light on the surface of the liquid unit;
the reflected light is reflected by the reflecting mirror and then transmitted by the polarization beam splitter and the quarter wave plate to obtain circularly polarized light; the circularly polarized light is divided into second liquid surface refraction light and second liquid surface reflection light on the surface of the liquid unit;
the first liquid level refraction light is reflected by the micro-angle cone array at the bottom of the liquid container unit and returns to the original path, the first liquid level refraction light reversely passes through the quarter-wave plate, the polarization state is changed into S, and the first liquid level refraction light is reflected by the polarization spectroscope to become first signal light and is emitted to the image sensor;
the first liquid surface reflected light and the second liquid surface reflected light are reflected by liquid, the polarization state is changed into S after the first liquid surface reflected light and the second liquid surface reflected light reversely pass through the quarter-wave plate, and the first liquid surface reflected light and the second liquid surface reflected light are changed into second signal light and fourth signal light after being reflected by the polarization spectroscope and emitted to the image sensor;
the second liquid surface refracted light is reflected by the bottom surface of the liquid container, reversely passes through the quarter-wave plate, then is changed into S in a polarization state, is reflected by the polarization spectroscope, then is changed into third signal light and is emitted to the image sensor;
the first signal light and the second signal light interfere on a detection surface of the image sensor to obtain a spatial interference light spot; the third signal light and the fourth signal light interfere with each other on a detection surface of the image sensor to obtain a spatial interference fringe; the spatial interference light spot and the spatial interference fringe are not overlapped in space.
Preferably, the real-time correction process of the vertical laser pointing direction comprises,
and the signal processing card traces the vertical laser signal to the absolute gravity direction through angle modulation of the two-dimensional precise angle rotary table and Gaussian fitting of a spatial interference light spot, executes an interference fringe decoupling algorithm on the spatial interference fringes to realize precise measurement pointed by the vertical laser, and finally sends a feedback control signal to the two-dimensional precise angle rotary table according to the measurement result to realize real-time correction pointed by the vertical laser and simultaneously uploads the measurement result to an upper computer.
Preferably, the process of performing an interference image decoupling algorithm on the spatial interference image comprises,
converting the spatial interference fringes into a two-dimensional gray matrix, performing two-dimensional discrete Fourier transform based on butterfly operation on the two-dimensional gray matrix to obtain a frequency space matrix of the spatial interference fringes, and calculating different spatial frequency components in the amplitude space of a spatial interference fringe frequency spectrum;
obtaining a maximum amplitude value point and a corresponding position of the maximum amplitude value point in a frequency space matrix based on the amplitude space of the spatial interference fringe frequency spectrum, and performing two-dimensional curve peak value fitting by using amplitude information of the maximum amplitude value point and adjacent matrix points to obtain a fitted accurate frequency coordinate;
and respectively obtaining an X-direction horizontal inclination angle and a Y-direction horizontal inclination angle according to the X-direction component and the Y-direction component of the accurate frequency coordinate obtained by fitting and a formula in which the angle measurement value and the spatial frequency of the spatial interference fringe are in a linear relation.
The invention discloses the following technical effects:
(1) the vertical laser pointing correction device and method based on interference fringe decoupling are completely based on the laser interference measurement principle, the horizontal plane is taken as a reference datum plane, the measurement resolution is high, and light beams can be pointed to the direction of gravity directly.
(2) By means of conversion of the polarization state of the laser and matching of the liquid surface reflectivity, the liquid container bottom surface reflectivity and the micro-angle cone array reflectivity, the contrast ratio and the signal-to-noise ratio of interference signals are guaranteed, and angle measurement results can be traced to laser wavelengths.
(3) The invention further realizes real-time feedback precision correction of the beam direction on the basis of precision measurement of the vertical laser direction.
(4) The integrated sensing module of the device is convenient to disassemble and repeatedly install, can be conveniently reused in a plurality of sets of devices, and saves cost.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a schematic diagram of a system configuration according to an embodiment of the present invention;
the system comprises a host computer 1, an image sensor 2, a light splitting pyramid prism 3, an integrated sensing base 4, a spectroscope 5, a reflector 6, a polarizing spectroscope 7, a quarter wave plate 8, a micro pyramid array 9, a liquid container 10, liquid 11, a two-dimensional precise angle rotary table 12, a pentagonal prism 13, an integrated light source base 14, an optical fiber collimator 15, a single-frequency laser 16, a single-mode polarization maintaining optical fiber 17 and a signal processing card 18.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
In order to make the aforementioned objects, features and advantages of the present invention more comprehensible, the present invention is described in detail with reference to the accompanying drawings and the detailed description thereof.
The vertical laser pointing correction device based on interference fringe decoupling shown in fig. 1 comprises an upper computer 1, an image sensor 2, a light-splitting pyramid prism 3, an integrated sensing base 4, a spectroscope 5, a reflector 6, a polarizing spectroscope 7, a quarter wave plate 8, a micro-pyramid array 9, a liquid container 10, liquid 11, a two-dimensional precise angle rotary table 12, a pentagon prism 13, an integrated light source base 14, an optical fiber collimator 15, a single-frequency laser 16, a single-mode polarization-maintaining optical fiber 17 and a signal processing card 18;
the optical fiber collimator 15 and the pentagon prism 13 are fixed on the integrated light source base 14, and the light-splitting pyramid prism 3, the spectroscope 5, the reflector 6, the polarization spectroscope 7, the quarter-wave plate 8, the liquid container 10 and the image sensor 2 are all fixed on the integrated sensing base 4; the integrated sensing base 4 and the integrated light source base 14 are both positioned on the two-dimensional precise angle rotary table 12; the integrated sensing module can be detached or installed at any time and is positioned on the same plane with the integrated light source base.
The liquid container 10 is a round shape with a diameter of 50mm, and is made of transparent material and coated with light absorption material; the bottom surface of the integrated base is a slope, the angles in the X direction and the Y direction relative to the integrated base 4 are all milliradian magnitude, a partial reflecting film is plated on one side with lower height of the slope, the reflectivity is equivalent to the liquid reflectivity in the used laser wave band, namely the reflectivity to laser with wave band of 633nm is 3%; the micro-pyramid array 9 is arranged on the higher side, and the reflectivity of the plated reflecting film is equivalent to that of liquid in the used laser wave band, namely the reflectivity of laser on the 633nm wave band is 3 percent; the liquid 11 is silicone oil, the viscosity of which is 350CS, the reflectivity is about 3%, the refractive index is 1.4, the liquid level height is 2mm, and the liquid serves as a reference surface for the light beam to point.
As shown in fig. 1, the vertical laser pointing correction device based on interference fringe decoupling provided by the present invention includes: the device comprises a vertical laser generation module, an integrated sensing module and a signal processing module;
the vertical laser generation module comprises a single-frequency laser, a single-mode polarization maintaining optical fiber, an optical fiber collimator, a pentagonal prism, an integrated light source base and a two-dimensional precise angle rotary table, and is used for generating a vertical laser signal with a polarization state P and finely adjusting the direction of the vertical laser signal;
the integrated sensing module comprises an integrated sensing base, a light splitting pyramid prism, a spectroscope, a reflector, a polarizing spectroscope, a quarter-wave plate, a liquid container, liquid, a micro-pyramid array and an image sensor;
the working principle of the vertical laser pointing correction device is as follows: a single-frequency helium-neon laser 16 with the wavelength of 633nm provides a frequency stabilization laser signal, the laser signal is linearly polarized light and is conducted to an optical fiber collimator 15 through a single-mode polarization maintaining optical fiber 17, the optical fiber collimator 15 outputs collimated laser with the polarization state of P, and the collimated laser becomes a vertical laser signal after passing through a pentagonal prism 13;
part of vertical laser signals return along the original direction after being reflected by the beam splitting pyramid prism 3 and are divided into transmitted light and reflected light by the spectroscope 5; the transmitted light is changed into circularly polarized light after being transmitted by the polarization spectroscope 7 and the quarter-wave plate 8 and is divided into first liquid surface refraction light and first liquid surface reflection light on the surface of the liquid 11; the reflected light is reflected by the reflecting mirror 6, is transmitted by the polarization beam splitter 7 and the quarter-wave plate 8, is changed into circularly polarized light, and is divided into second liquid surface refraction light and second liquid surface reflection light on the surface of the liquid 11; the first liquid level refracted light is reflected by the micro-angle cone array 9 at the bottom of the liquid container 10 and returns to the original path, the first liquid level refracted light reversely passes through the quarter-wave plate 8, the polarization state is changed into S, the first liquid level refracted light is reflected by the polarization spectroscope 7 to become first signal light and the first signal light is emitted to the image sensor 2; the first liquid surface reflected light is reflected by the liquid 11, the polarization state is changed into S after reversely passing through the quarter-wave plate 8, and the second liquid surface reflected light is changed into second signal light after being reflected by the polarization spectroscope 7 and is emitted to the image sensor 2; the second liquid surface refracted light is reflected by the bottom surface of the liquid container 10, passes through the quarter-wave plate 8 in the reverse direction, changes the polarization state into S, is reflected by the polarization beam splitter 7 to become third signal light and is emitted to the image sensor 2; the second liquid surface reflected light is reflected by the liquid 11, the polarization state is changed into S after the second liquid surface reflected light reversely passes through the quarter-wave plate 8, and the second liquid surface reflected light is changed into fourth signal light after being reflected by the polarization spectroscope 7 and is emitted to the image sensor 2; the first signal light and the second signal light interfere on a detection surface of the image sensor 2 to form a spatial interference light spot; the third signal light and the fourth signal light interfere with each other on the detection surface of the image sensor 2 to form a spatial interference fringe; the space interference light spots are not overlapped with the space interference fringes; the spatial interference light spots and the spatial interference fringes are sent to the signal processing card 18 in a digital quantity mode, a spatial interference fringe decoupling algorithm is integrated in the signal processing card 18, high-precision decoupling operation is conducted on interference signals, feedback control signals are sent to the two-dimensional precision angle rotary table 12 according to measurement results, vertical laser pointing is corrected and traced to the gravity direction, and meanwhile the measurement results are sent to the upper computer 1.
Further, the method for correcting the vertical laser pointing direction comprises the following steps:
step one, vertical laser pointing preconditioning: the signal processing card drives the two-dimensional precise angle rotary table to rotate around an X axis and a Y axis respectively, so that the spatial interference light spot is approximately circular;
step two, adjusting the initial value of the angle in the X direction: the signal processing card drives the two-dimensional precise angle rotary table to rotate around the Y axis in a reciprocating manner, the pointing direction of the vertical laser is subjected to sine modulation along the X direction, and the modulation frequency is f m (ii) a Meanwhile, carrying out real-time Gaussian fitting on the intensity distribution of the spatial interference light spots along the X direction, and recording the full width at half maximum d of a fitting curve x (ii) a Adjusting the central angle value of the two-dimensional precision angle rotary table around the Y axis so that d x The curve becomes a frequency of 2f m At this time d x Reaches a maximum value d when the turntable is at the central angle value x-max ；
Step three, adjusting the initial value of the angle in the Y direction: the signal processing card drives the two-dimensional precise angle rotary table to rotate around the X axis in a reciprocating manner, the pointing direction of the vertical laser is subjected to sine modulation along the Y direction, and the modulation frequency is f m (ii) a Meanwhile, carrying out real-time Gaussian fitting on the intensity distribution of the spatial interference light spots along the Y direction, and recording the full width at half maximum d of a fitting curve y (ii) a Adjusting the central angle value of the two-dimensional precision angle rotary table around the X axis so that d y The curve becomes a frequency of 2f m At this time d y Reaches a maximum value d when the turntable is at the central angle value y-max ；
Step four, correcting the initial value of the vertical laser pointing direction: stopping the angle modulation of the two-dimensional precise angle rotary table to enable the two-dimensional precise angle rotary table to be at the central angle value in the X direction and the Y direction, and simultaneously enabling the half-height width of the spatial interference light spot in the X direction and the half-height width of the spatial interference light spot in the Y direction to reach the maximum value d x-max And d y-max (ii) a Meanwhile, a spatial interference fringe decoupling algorithm is executed on the spatial interference fringes, and initial values theta of horizontal dip angles in the X direction and the Y direction are recorded X0 And theta Y0 ；
Step five, monitoring and real-time correcting the vertical laser pointing direction: executing space interference fringe decoupling algorithm to space interference fringes and measuring angle result in real timeθ X And theta Y The angle deviations of the vertical laser light in the X direction and the Y direction with respect to the gravity direction are θ' X ＝θ X -θ X0 And theta Y ′＝θ Y -θ Y0 (ii) a Meanwhile, the signal processing card carries out closed-loop feedback control on the attitude of the two-dimensional precise angle rotary table according to the measured angle deviation so as to enable theta' X And theta Y ' are all zero.
The spatial interference fringe decoupling algorithm traces the angle measurement value to the laser wavelength, and the algorithm comprises the following steps:
converting the spatial interference fringes into a two-dimensional gray matrix, performing two-dimensional discrete Fourier transform based on butterfly operation on the matrix to obtain a frequency space matrix of the spatial interference fringes, and calculating different spatial frequency components of the spatial interference fringes in an amplitude space of a frequency spectrum of the spatial interference fringes;
step two, obtaining an amplitude maximum value point and a corresponding position of the amplitude maximum value point in a frequency space matrix in the amplitude space of the spatial interference fringe frequency spectrum, and performing two-dimensional curve peak value fitting by using the amplitude information of the amplitude maximum value point and the adjacent matrix point to obtain a fitted accurate frequency coordinate;
step three, measuring the angle theta X And theta Y The linear relation is formed between the X-direction component and the spatial frequency of the spatial interference fringe, and the X-direction horizontal inclination angle theta and the Y-direction horizontal inclination angle theta can be respectively obtained according to a formula 1 and a formula 2 according to the X-direction component and the Y-direction component of the precise frequency coordinate obtained by fitting X And theta Y 。
In the formula (f) X And f Y X-and Y-components of the spatial interference fringe frequency, λ being the laser wavelength, n liquid Is the refractive index of the liquid. Since the liquid level is always perpendicular to the gravity direction, the method canThe change of the laser pointing direction relative to the gravity direction is calculated and monitored in real time.
The invention also provides a method for the vertical laser pointing correction device based on interference fringe decoupling, which comprises the steps of utilizing the reflection and refraction effects of a liquid level on laser, taking a horizontal plane as a reference datum plane, pointing a light beam to a tracing direction to a gravity direction by virtue of a space interference light spot, converting a light beam inclination angle into a space interference fringe of linearly polarized laser by utilizing slope reflection at the bottom of a liquid container, and accurately measuring the angle deviation of the light beam pointing relative to the gravity direction by calculating the frequency of the space interference fringe in the X direction and the Y direction; meanwhile, by means of conversion of the polarization state of the laser and matching of the reflectivity, the contrast ratio and the signal-to-noise ratio of interference signals are ensured; finally, the posture of the vertical laser generating module is subjected to feedback control, so that precise real-time correction of the pointing direction of the vertical laser is realized. The vertical laser pointing correction device is completely based on the laser interference measurement principle, the measurement resolution is high, the angle measurement result can be directly traced to the laser wavelength, and the requirement of high-end equipment on ultra-precise vertical laser pointing is met. In addition, the integrated sensing module of the device is convenient to disassemble and repeatedly install, can be conveniently reused in a plurality of sets of devices, and saves cost.
The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.
Claims (10)
1. The utility model provides a vertical laser pointing correcting unit based on interference fringe decoupling zero which characterized in that includes:
the vertical laser generating module is used for generating a vertical laser signal and finely adjusting the direction of the vertical laser signal;
the integrated sensing module is connected with the vertical laser generating module and used for receiving the vertical laser signal and generating a spatial interference image based on the vertical laser signal;
and the signal processing module is connected with the integrated sensing module and used for carrying out high-precision decoupling operation on the spatial interference image to obtain an angle deviation result of the vertical laser relative to the gravity direction, and realizing real-time correction of the pointing direction of the vertical laser according to the angle deviation result.
2. The vertical laser pointing correction device based on interference fringe decoupling according to claim 1,
the vertical laser generation module comprises a single-frequency laser, a single-mode polarization maintaining optical fiber, an optical fiber collimator, a pentagonal prism, an integrated light source base and a two-dimensional precise angle rotary table;
the single-frequency laser is used for providing a frequency stabilization laser signal;
the single-mode polarization maintaining fiber is connected with the single-frequency laser and used for transmitting the frequency stabilized laser signal to the fiber collimator;
the optical fiber collimator is connected with the single-mode polarization maintaining optical fiber and used for receiving the frequency stabilized laser signal and outputting collimated laser;
the pentagonal prism is used for receiving the collimated laser and outputting a vertical laser signal;
the integrated light source base is used for fixing the optical fiber collimator and the pentagonal prism;
the two-dimensional precise angle rotary table is used for placing the integrated sensing base and the integrated light source base.
3. The vertical laser pointing correction device based on interference fringe decoupling according to claim 1,
the integrated sensing module comprises an integrated sensing base, a light splitting pyramid prism, a spectroscope, a reflector, a polarizing spectroscope, a quarter-wave plate, a liquid container unit, a liquid unit, a micro-pyramid array and an image sensor;
the integrated sensing base is used for fixing the light-splitting pyramid prism, the spectroscope, the reflector, the polarizing spectroscope, the quarter-wave plate, the liquid container unit, the liquid unit and the image sensor;
the beam splitting pyramid prism is used for transmitting the vertical laser signal and reflecting part of the vertical laser signal to the first spectroscope;
the spectroscope is used for dividing the vertical laser signal into transmitted light and reflected light;
the reflecting mirror is used for reflecting the reflected light to the polarizing beam splitter;
the polarization spectroscope is used for transmitting the transmission light with the polarization state P and the reflection light to the quarter-wave plate; the first liquid level refraction light, the first liquid level reflection light, the second liquid level refraction light and the second liquid level reflection light with the polarization state of S are reflected to obtain first signal light, second signal light, third signal light and fourth signal light, and the first signal light, the second signal light, the third signal light and the fourth signal light are emitted to the image sensor;
the quarter-wave plate is used for transmitting the transmitted light and the reflected light and converting the transmitted light and the reflected light into circularly polarized light; the polarization state of the first liquid surface refraction light, the first liquid surface reflection light, the second liquid surface refraction light and the second liquid surface reflection light is changed into S;
the liquid container unit is used for placing liquid in the liquid unit; the second liquid surface is used for reflecting the light to the quarter-wave plate;
the liquid unit is used for dividing the transmitted light and the reflected light which are converted into circular polarization into first liquid surface refraction light, first liquid surface reflected light, second liquid surface refraction light and second liquid surface reflected light through liquid surfaces respectively; the quarter-wave plate is used for reflecting the first liquid surface reflected light and the second liquid surface reflected light;
the micro-pyramid array is arranged at the bottom of the liquid container unit and used for reflecting the first liquid level refracted light to the quarter-wave plate;
the image sensor is used for detecting a spatial interference light spot formed by interference of the first signal light and the second signal light; and the optical detector is used for detecting a spatial interference fringe formed by the interference of the third signal light and the fourth signal light.
4. The vertical laser pointing correction device based on interference fringe decoupling according to claim 3,
the spatial interference light spot and the spatial interference fringe are not overlapped in space.
5. The vertical laser pointing correction device based on interference fringe decoupling according to claim 1,
the signal processing module comprises an upper computer and a signal processing card;
the signal processing card is used for performing high-precision decoupling operation on interference signals through a spatial interference fringe decoupling algorithm, sending feedback control signals to the two-dimensional precision angle rotary table according to measurement results, correcting and tracing the orientation of the vertical laser to the gravity direction, and uploading the operation results to an upper computer;
and the upper computer is used for receiving, displaying and storing the measurement result of the vertical laser pointing correction.
6. A vertical laser pointing correction method based on interference fringe decoupling is characterized by comprising the following steps,
obtaining a vertical laser signal through a vertical laser generating module, transmitting the vertical laser signal to an integrated sensing module, and generating a spatial interference image based on the integrated sensing module;
and inputting the spatial interference image into a signal processing module for high-precision decoupling operation to obtain an angle deviation result of the vertical laser relative to the gravity direction, and realizing real-time correction of the pointing direction of the vertical laser according to the angle deviation result.
7. The method of claim 6, wherein the vertical laser signal is obtained by a vertical laser generation module, and the transmitting the vertical laser signal to the integrated sensing module comprises,
generating a frequency stabilized laser signal through a single-frequency laser, and conducting the frequency stabilized laser signal to an optical fiber collimator through a single-mode polarization maintaining optical fiber; the optical fiber collimator outputs collimated laser, and the collimated laser obtains a vertical laser signal through the pentagonal prism and then transmits the vertical laser signal to the integrated sensing module.
8. The method of claim 6, wherein the process of generating the spatial interference image based on the integrated sensing module comprises,
the vertical laser signal returns along the original direction after being reflected by the beam splitting pyramid prism and is divided into transmitted light and reflected light by the beam splitter;
the transmission light is transmitted by the polarization spectroscope and the quarter-wave plate to obtain circularly polarized light; the circularly polarized light is divided into first liquid surface refraction light and first liquid surface reflection light on the surface of the liquid unit;
the reflected light is reflected by the reflecting mirror and then transmitted by the polarization beam splitter and the quarter wave plate to obtain circularly polarized light; the circularly polarized light is divided into second liquid surface refraction light and second liquid surface reflection light on the surface of the liquid unit;
the first liquid level refraction light is reflected by the micro-angle cone array at the bottom of the liquid container unit and returns to the original path, the first liquid level refraction light reversely passes through the quarter-wave plate, the polarization state is changed into S, and the first liquid level refraction light is reflected by the polarization spectroscope to become first signal light and is emitted to the image sensor;
the first liquid surface reflected light and the second liquid surface reflected light are reflected by liquid, the polarization state is changed into S after the first liquid surface reflected light and the second liquid surface reflected light reversely pass through the quarter-wave plate, and the first liquid surface reflected light and the second liquid surface reflected light are changed into second signal light and fourth signal light after being reflected by the polarization spectroscope and emitted to the image sensor;
the second liquid surface refracted light is reflected by the bottom surface of the liquid container, reversely passes through the quarter-wave plate, then is changed into S in a polarization state, is reflected by the polarization spectroscope, then is changed into third signal light and is emitted to the image sensor;
the first signal light and the second signal light interfere on a detection surface of the image sensor to obtain a spatial interference light spot; the third signal light and the fourth signal light interfere with each other on a detection surface of the image sensor to obtain a spatial interference fringe; the spatial interference light spot and the spatial interference fringe are not overlapped in space.
9. The method of claim 6, wherein the real-time correction of the vertical laser pointing comprises,
and the signal processing card traces the vertical laser signal to the absolute gravity direction through angle modulation of the two-dimensional precise angle rotary table and Gaussian fitting of a spatial interference light spot, executes an interference fringe decoupling algorithm on the spatial interference fringes to realize precise measurement pointed by the vertical laser, and finally sends a feedback control signal to the two-dimensional precise angle rotary table according to the measurement result to realize real-time correction pointed by the vertical laser and simultaneously uploads the measurement result to an upper computer.
10. The method of claim 9, wherein the step of performing an interference pattern decoupling algorithm on the spatial interference pattern comprises,
the process of sending the space interference image to a signal processing card, and the signal processing card carrying out high-precision decoupling operation on the wavefront space interference image through an interference image decoupling algorithm comprises the following steps,
converting the spatial interference fringes into a two-dimensional gray matrix, performing two-dimensional discrete Fourier transform based on butterfly operation on the two-dimensional gray matrix to obtain a frequency space matrix of the spatial interference fringes, and calculating different spatial frequency components in the amplitude space of a spatial interference fringe frequency spectrum;
obtaining a maximum amplitude value point and a corresponding position of the maximum amplitude value point in a frequency space matrix based on the amplitude space of the spatial interference fringe frequency spectrum, and performing two-dimensional curve peak value fitting by using amplitude information of the maximum amplitude value point and adjacent matrix points to obtain a fitted accurate frequency coordinate;
and respectively obtaining the X-direction horizontal inclination angle and the Y-direction horizontal inclination angle according to the X-direction component and the Y-direction component of the accurate frequency coordinate obtained by fitting and a formula in which the angle measurement value and the spatial frequency of the spatial interference fringes are in a linear relation.
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