CN114942016B - 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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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C15/00—Surveying instruments or accessories not provided for in groups G01C1/00 - G01C13/00
- G01C15/12—Instruments for setting out fixed angles, e.g. right angles
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/26—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C15/00—Surveying instruments or accessories not provided for in groups G01C1/00 - G01C13/00
- G01C15/002—Active optical surveying means
Abstract
The invention discloses a vertical laser pointing correction device and a method based on interference fringe decoupling, wherein the device comprises the following steps: the vertical laser signal is obtained through the vertical laser generating module, and is transmitted to the integrated sensing module, and a spatial interference image is generated based on the integrated sensing module; and inputting the spatial interference image into a signal processing module for high-precision decoupling operation, obtaining an angle deviation result of the vertical laser relative to the gravity direction, and realizing real-time correction of the vertical laser pointing according to the angle deviation result. The vertical laser pointing correction device is based on the laser interferometry principle completely, has high measurement resolution, can directly trace the source of angle measurement results to the laser wavelength, and meets the requirement of high-end equipment on ultra-precise vertical laser pointing. In addition, the integrated sensing module of the device is convenient to detach and repeatedly install, is convenient to reuse for multiple 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 datum line and measuring a tiny deviation relative to a plumb line, and has important application value in engineering construction and precise 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 straightness of mechanical structures such as guide rails and the like, measuring and correcting torsion resistance and the like. With the rapid development of the field of precision engineering in recent years, high-end equipment has put higher demands on the pointing precision of vertical lasers. For example, in a quantized reference device of the mass unit "Kg", the pointing accuracy of the vertical laser determines the overall accuracy of the device, and the pointing of the vertical laser must be subjected to ultra-precise measurement and correction to ensure that it coincides with the direction of gravity.
The plumb line is used for construction monitoring of large-scale buildings and installation engineering of mechanical equipment. The coaxiality of vertical laser and a vertical axis in the plumb aligner is calibrated by adopting devices such as a collimator, a pentagonal prism, a right-angle coordinate plate, a steel ruler and the like. The invention discloses a digital calibration method and device of a laser plumb aligner based on source imaging, which is disclosed in China patent publication No. CN104949689A and publication No. 2015, namely 9 and 30, wherein an imaging light source is used for imaging a reticle, then the image is projected onto a target at infinity, and compared with a debugging reference center for calibration, so that the complexity of calibration and detection is reduced, and the accuracy is improved to a certain extent. However, the vertical laser generated by the plumb aligner has the problems of lower pointing precision and difficult guarantee of traceability in principle due to factors such as levelness of a workbench, precision of a measuring ruler, inaccuracy of human eye reading and the like, and is difficult to be used for ultra-precise measurement.
In the field of precision metrology, some scholars have also proposed vertical laser pointing measuring devices based on new principles. For example, in 2016, 37 th curling chart article of the university of instruments and meters, namely, "method for adjusting level of plane mirror based on high-precision electronic level instrument", a method for tracing the vertical laser direction to the level instrument through minimum transmission links is proposed. The device finally realizes the synthesis standard uncertainty 41 mu rad of vertical laser pointing, is influenced by the rotating shaft precision of the rotating platform, the horizontal adjusting mechanism precision of the rotating platform, the lead of the electronic level and the nonlinearity and processing precision of the electronic level, the precision of the horizontal reference is severely limited, and then the pointing precision of the vertical light beam is directly limited, and the traceability is also poor. Furthermore, the device cannot use the measurement results for feedback control to achieve real-time correction of beam pointing.
For another example, in 2016, applied Optics, 55 th publication System for the measurement of the deviation of a laser beam from the vertical direction, a vertical laser pointing deviation measuring device based on the principle of laser auto-collimation was proposed, which was referenced to the liquid level. The vertical laser is divided into two beams, one beam passes through the lens after passing through the corner reflector, the other beam passes through the lens after being reflected by the liquid level, the CCD obtains the positions of two light spots, 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 accuracy of the device is limited due to the processing errors and the position installation errors of optical elements such as CCD, converging lenses and the like, and the traceability is difficult to improve. In addition, the device can only measure the deviation angle of the laser direction, and cannot correct the deviation angle to the gravity direction.
In summary, the conventional vertical laser pointing calibration method for the homeotropic instrument has low precision, and cannot trace the beam direction to the gravity direction in principle; the vertical laser pointing correction device based on the electronic level is limited by factors such as processing errors, the precision is limited, and the traceability is poor; the vertical laser pointing measuring device based on the auto-collimation principle is limited by the assembly error of optical elements, and the measuring result is still difficult to directly trace. Furthermore, the above-described device cannot use the measurement of the beam direction for real-time feedback and correct it to the direction of gravity. Therefore, the technical field of precise angle measurement lacks a high-precision vertical laser pointing correction device capable of directly tracing.
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 the source to the gravity direction.
In order to achieve the above object, the present invention provides the following solutions: a vertical laser pointing correction apparatus based on interference fringe decoupling, comprising:
the vertical laser generation 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 is used for receiving the vertical laser signal and generating a space interference image based on the vertical laser signal;
and the signal processing module is connected with the integrated sensing module and is used for carrying out high-precision decoupling operation on the space interference image to obtain an angle deviation result of the vertical laser relative to the gravity direction, and real-time correction of the vertical laser pointing is realized according to the angle deviation result.
Preferably, the vertical laser generating 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 turntable;
the single-frequency laser is used for providing a frequency stabilization laser signal;
the single-mode polarization maintaining optical fiber is connected with the single-frequency laser and is used for transmitting the frequency-stabilized laser signal to an optical fiber collimator;
the optical fiber collimator is connected with the single-mode polarization maintaining optical fiber and is 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 turntable 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 beam splitting pyramid prism, a spectroscope, a reflecting mirror, 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 reflecting mirror, the polarization 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 signals and reflecting part of the vertical laser signals 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 polarization spectroscope;
the polarization spectroscope is used for transmitting the transmitted light and the reflected light with the polarization state of P 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 which are used for reflecting the polarization state S are used for obtaining first signal light, second signal light, third signal light and fourth signal light which 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 states of 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 are changed into S;
the liquid container unit is used for placing the liquid in the liquid unit; a quarter wave plate for reflecting the second liquid level refracted light to the bottom surface;
the liquid unit is used for respectively dividing the transmitted light and the reflected light converted into circular polarization into first liquid level refractive light and first liquid level reflective light through liquid levels; the second liquid surface refracts light and the second liquid surface reflects light; the quarter wave plate is used for reflecting the first liquid level reflected light and the second liquid level reflected light to the quarter wave plate;
the micro pyramid array is arranged at the bottom of the liquid container unit and used for reflecting the first liquid level refraction light to the quarter wave plate;
the image sensor is used for detecting a space interference light spot formed by interference of the first signal light and the second signal light; and the space interference fringes are used for detecting the space interference fringes formed by the interference of the third signal light and the fourth signal light.
Preferably, the spatial interference 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 a feedback control signal to the two-dimensional precision angle turntable according to a measurement result, correcting and tracing the vertical laser to the gravity direction, and uploading the operation result to the upper computer;
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 the following steps,
the method comprises the steps that 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;
and inputting the spatial interference image into a signal processing module for high-precision decoupling operation, obtaining an angle deviation result of the vertical laser relative to the gravity direction, and realizing real-time correction of the vertical laser pointing according to the angle deviation result.
Preferably, the vertical laser signal is obtained through the vertical laser generating module, and the process of transmitting the vertical laser signal to the integrated sensing module comprises the steps of generating a frequency stabilization laser signal through a single-frequency laser, and transmitting the frequency stabilization 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.
Preferably, the process of generating a spatial interference image based on the integrated sensing module includes,
the vertical laser signal is reflected by the beam splitting pyramid prism and returns along the original direction, and is split into transmitted light and reflected light by the beam splitter;
the transmitted light is transmitted through a polarization spectroscope and a quarter wave plate to obtain circularly polarized light; the circularly polarized light is divided into first liquid level refraction light and first liquid level reflection light on the surface of the liquid unit;
the reflected light is reflected by a reflecting mirror and transmitted by a polarization spectroscope and a quarter wave plate to obtain circularly polarized light; the circularly polarized light is divided into second liquid level refraction light and second liquid level reflection light on the surface of the liquid unit;
the first liquid level refraction light is reflected by the micro-pyramid array at the bottom of the liquid container unit and returns in an original path, the polarization state of the first liquid level refraction light is changed into S after reversely passing through the quarter wave plate, and the first liquid level refraction light is reflected by the polarization spectroscope and then becomes first signal light to be emitted to the image sensor;
the first liquid level reflected light and the second liquid level reflected light are reflected by the liquid, the polarization state of the reflected light is changed into S after passing through the quarter wave plate reversely, and the reflected light is changed into second signal light and fourth signal light after being reflected by the polarization spectroscope and is emitted to the image sensor;
the second liquid level refraction light is reflected by the bottom surface of the liquid container, reversely passes through the quarter wave plate, becomes S in polarization state, is reflected by the polarization spectroscope, becomes 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 space interference light spot; the third signal light and the fourth signal light interfere on a detection surface of the image sensor to obtain a space interference fringe; the spatial interference light spots and the spatial interference fringes do not overlap spatially.
Preferably, the real-time correction process 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 turntable and Gaussian fitting of the space interference light spots, then performs interference fringe decoupling algorithm on the space interference fringes to realize precise measurement of vertical laser pointing, and finally sends feedback control signals to the two-dimensional precise angle turntable according to the measurement result to realize real-time correction of the vertical laser pointing, and simultaneously uploads the measurement result to the upper computer.
Preferably, the process of performing an interference image decoupling algorithm on the spatial interference image includes,
converting the space 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 space interference fringes, and calculating different space frequency components in the amplitude space of the frequency spectrum of the space interference fringes;
obtaining an amplitude maximum point and a position corresponding to the amplitude maximum point in a frequency space matrix based on the amplitude space of the spatial interference fringe frequency spectrum, and performing two-dimensional curve peak fitting by using the amplitude information of the amplitude maximum point and the adjacent matrix points to obtain a fitted accurate frequency coordinate;
and respectively obtaining X-direction horizontal inclination angles and Y-direction horizontal inclination angles according to formulas of linear relation between the angle measurement value and the spatial frequency of the spatial interference fringes according to the X-direction component and the Y-direction component of the accurate frequency coordinate obtained through fitting.
The invention discloses the following technical effects:
(1) The vertical laser pointing correction device and the method based on interference fringe decoupling are completely based on the laser interferometry principle, take the horizontal plane as a reference plane, have high measurement resolution, and can directly trace the light beam to the gravity direction.
(2) The invention ensures contrast ratio and signal-to-noise ratio of interference signals by means of conversion of laser polarization states and matching of liquid level reflectivity, liquid container bottom surface reflectivity and micropyramid array reflectivity, and angle measurement results can trace to laser wavelength.
(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 detach and repeatedly install, is convenient to reuse for multiple 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 that are 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 other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a system architecture according to an embodiment of the present invention;
the device comprises a 1-upper computer, a 2-image sensor, a 3-light splitting pyramid prism, a 4-integrated sensing base, a 5-spectroscope, a 6-reflecting mirror, a 7-polarization spectroscope, an 8-quarter wave plate, a 9-micro pyramid array, a 10-liquid container, 11-liquid, a 12-two-dimensional precise angle turntable, a 13-pentagonal prism, a 14-integrated light source base, a 15-optical fiber collimator, a 16-single-frequency laser, a 17-single-mode polarization maintaining optical fiber and an 18-signal processing card.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. 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 order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
The vertical laser pointing correction device based on interference fringe decoupling as shown in fig. 1 comprises an upper computer 1, an image sensor 2, a beam splitting pyramid prism 3, an integrated sensing base 4, a beam splitter 5, a reflecting mirror 6, a polarization beam splitter 7, a quarter wave plate 8, a micropyramid array 9, a liquid container 10, a liquid 11, a two-dimensional precise angle turntable 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;
the optical fiber collimator 15 and the pentagonal prism 13 are fixed on the integrated light source base 14, and the light splitting pyramid prism 3, the spectroscope 5, the reflecting mirror 6, the polarizing spectroscope 7, the quarter wave plate 8, the liquid container 10 and the image sensor 2 are 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 turntable 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 circular with a diameter of 50mm, and is made of transparent material and coated with light absorbing material; the bottom surface of the integrated base 4 is provided with a slope, the angles of the slope in the X direction and the Y direction relative to the integrated base are in milliradian magnitude, one side of the slope with lower height is plated with a part of reflecting film, and the reflectivity is equivalent to the liquid reflectivity in the laser wave band, namely 3% for the laser reflectivity in the wave band of 633 nm; the micro pyramid array 9 is arranged on the side with higher height, and the reflectivity of the plated reflecting film is equivalent to the reflectivity of liquid in the laser wave band, namely 3% for the laser wave band of 633 nm; the liquid 11 is silicone oil, and has a viscosity of 350CS, a reflectivity of about 3%, a refractive index of 1.4, and a liquid level of 2mm, and serves as a reference surface for directing the light beam.
As shown in fig. 1, the vertical laser pointing correction apparatus based on interference fringe decoupling provided by the present invention includes: the system comprises a vertical laser generating module, an integrated sensing module and a signal processing module;
the vertical laser generating 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 turntable, and generates a vertical laser signal with a polarization state P and finely adjusts the direction of the vertical laser signal;
the integrated sensing module comprises an integrated sensing base, a light splitting pyramid prism, a spectroscope, a reflecting mirror, 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: the 633nm single-frequency helium-neon laser 16 provides a frequency-stabilized laser signal, the laser signal is linearly polarized light, the linearly polarized light is conducted to the optical fiber collimator 15 through the single-mode polarization maintaining fiber 17, the optical fiber collimator 15 outputs collimated laser with the polarization state P, and the collimated laser signal becomes a vertical laser signal after passing through the pentagonal prism 13;
part of the vertical laser signals are reflected by the beam splitting pyramid prism 3 and then return along the original direction, and are split 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 beam splitter 7 and the quarter wave plate 8, and is divided into first liquid level refraction light and first liquid level 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, becomes circularly polarized light, and is divided into second liquid level refraction light and second liquid level reflection light on the surface of the liquid 11; the first liquid level refraction light is reflected by the micro-pyramid array 9 at the bottom of the liquid container 10 and returns in the original path, the polarization state of the first liquid level refraction light is changed into S after reversely passing through the quarter wave plate 8, and the first liquid level refraction light is reflected by the polarization spectroscope 7 and then becomes first signal light to be emitted to the image sensor 2; the first liquid surface reflected light is reflected by the liquid 11, reversely passes through the quarter wave plate 8, becomes S in polarization state, and then becomes second signal light after being reflected by the polarization spectroscope 7 and is emitted to the image sensor 2; the second liquid level refraction light is reflected by the bottom surface of the liquid container 10, reversely passes through the quarter wave plate 8, becomes S in polarization state, is reflected by the polarization spectroscope 7, becomes third signal light and is emitted to the image sensor 2; the second liquid level reflected light is reflected by the liquid 11, reversely passes through the quarter wave plate 8, becomes S in polarization state, and becomes 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 the detection surface of the image sensor 2 to form a space interference light spot; the third signal light and the fourth signal light interfere on the detection surface of the image sensor 2 to form a space 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 carried out on interference signals, a feedback control signal is sent to the two-dimensional precision angle turntable 12 according to a measurement result, vertical laser is directed to correct and trace to the gravity direction, and the measurement result is sent to the upper computer 1.
Further, the correction method of the vertical laser pointing comprises the following steps:
step one, vertical laser pointing pre-adjustment: the signal processing card drives the two-dimensional precise angle turntable to rotate around the X axis and the Y axis respectively, so that the space interference light spots are approximate to a circle;
step two, adjusting an initial value of an angle in the X direction: the signal processing card drives the two-dimensional precise angle turntable to reciprocally rotate around the Y axis, and carries out sinusoidal modulation on the pointing direction of the vertical laser along the X direction, wherein the modulation frequency is f m The method comprises the steps of carrying out a first treatment on the surface of the Meanwhile, carrying out real-time Gaussian fitting on the intensity distribution of the space interference light spots along the X direction, and recording the half-width d of a fitting curve x The method comprises the steps of carrying out a first treatment on the surface of the Adjusting the central angle value of the two-dimensional precise angle turntable around the Y axis to enable d x The curve becomes a frequency of 2f m Sinusoidal curve of (d) at this time x Reaching a maximum d when the turret is at a central angle value x-max ；
Step three, adjusting an initial value of the angle in the Y direction: signal processing cardDriving a two-dimensional precise angle turntable to reciprocally rotate around an X axis, and performing sinusoidal modulation on the direction of vertical laser along the Y direction, wherein the modulation frequency is f m The method comprises the steps of carrying out a first treatment on the surface of the Meanwhile, carrying out real-time Gaussian fitting on the intensity distribution of the space interference light spots along the Y direction, and recording the half-width d of a fitting curve y The method comprises the steps of carrying out a first treatment on the surface of the Adjusting the central angle value of the two-dimensional precise angle turntable around the X axis to enable d y The curve becomes a frequency of 2f m Sinusoidal curve of (d) at this time y Reaching a maximum d when the turret is at a central angle value y-max ；
Correcting the initial value of the vertical laser pointing: stopping the angle modulation of the two-dimensional precise angle turntable to ensure that the angle modulation is at the central angle value in the X direction and the Y direction, and simultaneously the half-width of the space interference light spot in the X direction and the Y direction reaches the maximum value d x-max And d y-max The method comprises the steps of carrying out a first treatment on the surface of the Meanwhile, a spatial interference fringe decoupling algorithm is executed on the spatial interference fringes, and the initial values theta of the horizontal dip angles of the X direction and the Y direction of the spatial interference fringes are recorded X0 And theta Y0 ；
Step five, vertical laser pointing monitoring and real-time correction: executing a spatial interference fringe decoupling algorithm on the spatial interference fringes, and measuring an angle result theta in real time X And theta Y The angular deviations of the vertical laser light in the X direction and the Y direction relative to the gravity direction are respectively theta' X ＝θ X -θ X0 And theta Y ′＝θ Y -θ Y0 The method comprises the steps of carrying out a first treatment on the surface of the Meanwhile, the signal processing card performs closed-loop feedback control on the gesture of the two-dimensional precise angle turntable according to the measured angle deviation, so that theta 'is achieved' X And theta Y ' are all zero.
The spatial interference fringe decoupling algorithm of (1) tracing the angle measurement to the laser wavelength, the algorithm comprising:
converting a space interference fringe into a two-dimensional gray matrix, performing butterfly operation-based two-dimensional discrete Fourier transform on the matrix to obtain a frequency space matrix of the space interference fringe, and calculating different space frequency components of the space interference fringe in the amplitude space of a space interference fringe frequency spectrum;
step two, obtaining an amplitude maximum point and a position corresponding to the amplitude maximum point in a frequency space matrix in an amplitude space of a spatial interference fringe frequency spectrum, and performing two-dimensional curve peak fitting by using amplitude information of the amplitude maximum point and adjacent matrix points to obtain a fitted accurate frequency coordinate;
step three, angle measurement θ X And theta Y The linear relation is formed between the X-direction component and the Y-direction component of the accurate frequency coordinate obtained by fitting, and the X-direction horizontal inclination angle theta and the Y-direction horizontal inclination angle theta can be respectively obtained according to the formula 1 and the formula 2 X And theta Y 。
Wherein f X And f Y X-direction and Y-direction components of the spatial fringe frequency, respectively, lambda being the laser wavelength, n liquid Is a liquid refractive index. Because the liquid level is always vertical to the gravity direction, the method can calculate and monitor the change of the laser pointing direction relative to the gravity direction in real time.
The invention also provides a vertical laser pointing correction device based on interference fringe decoupling, which uses the reflection and refraction effects of liquid level on laser, uses a horizontal plane as a reference datum plane, points a light beam to trace the source to the gravity direction by means of a space interference light spot, converts the inclination angle of the light beam into a space interference fringe of linear polarization laser by using slope reflection at the bottom of a liquid container, and accurately measures 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 laser polarization states and matching of reflectivity, contrast ratio and signal-to-noise ratio of interference signals are guaranteed; finally, the precise real-time correction of the vertical laser pointing is realized by carrying out feedback control on the gesture of the vertical laser generating module. The vertical laser pointing correction device is based on the laser interferometry principle completely, has high measurement resolution, can directly trace the source of angle measurement results to the laser wavelength, and meets the requirement of high-end equipment on ultra-precise vertical laser pointing. In addition, the integrated sensing module of the device is convenient to detach and repeatedly install, is convenient to reuse for multiple sets of devices, and saves cost.
The above embodiments are only illustrative of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention, and various modifications and improvements made by those skilled in the art to the technical solutions of the present invention should fall within the protection scope defined by the claims of the present invention without departing from the design spirit of the present invention.
Claims (7)
1. Vertical laser directional correction device based on interference fringe decoupling, characterized by comprising:
the vertical laser generation 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 is used for receiving the vertical laser signal and generating a space interference image based on the vertical laser signal;
the signal processing module is connected with the integrated sensing module and is 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 real-time correction of the vertical laser pointing is realized according to the angle deviation result;
the integrated sensing module comprises an integrated sensing base, a beam splitting pyramid prism, a spectroscope, a reflecting mirror, 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 reflecting mirror, the polarization 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 signals and reflecting part of the vertical laser signals to the 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 polarization spectroscope;
the polarization spectroscope is used for transmitting the transmitted light and the reflected light with the polarization state of P 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 which are used for reflecting the polarization state S are used for obtaining first signal light, second signal light, third signal light and fourth signal light which 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 states of 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 are changed into S;
the liquid container unit is used for placing the liquid in the liquid unit; a quarter wave plate for reflecting the second liquid level refracted light to the bottom surface; the bottom surface of the liquid container unit is an inclined surface;
the liquid unit is used for respectively dividing the transmitted light and the reflected light converted into circular polarization into first liquid level refractive light, first liquid level reflective light, second liquid level refractive light and second liquid level reflective light through liquid levels; the quarter wave plate is used for reflecting the first liquid level reflected light and the second liquid level reflected light to the quarter wave plate;
the micro pyramid array is arranged at the bottom of the liquid container unit and used for reflecting the first liquid level refraction light to the quarter wave plate;
the image sensor is used for detecting a space interference light spot formed by interference of the first signal light and the second signal light; the spatial interference fringes are used for detecting the spatial interference fringes formed by the interference of the third signal light and the fourth signal light;
the spatial interference light spot and the spatial interference fringe are not overlapped in space.
2. The vertical laser pointing correction apparatus based on interference fringe decoupling as claimed in claim 1, wherein,
the vertical laser generating 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 turntable;
the single-frequency laser is used for providing a frequency stabilization laser signal;
the single-mode polarization maintaining optical fiber is connected with the single-frequency laser and is used for transmitting the frequency-stabilized laser signal to an optical fiber collimator;
the optical fiber collimator is connected with the single-mode polarization maintaining optical fiber and is 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 turntable is used for placing the integrated sensing base and the integrated light source base.
3. The vertical laser pointing correction apparatus based on interference fringe decoupling as claimed in claim 1, wherein,
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 a feedback control signal to the two-dimensional precision angle turntable according to a measurement result, correcting and tracing the vertical laser to the gravity direction, and uploading the operation result to the upper computer;
the upper computer is used for receiving, displaying and storing the measurement result of the vertical laser pointing correction.
4. A vertical laser pointing correction method based on interference fringe decoupling is characterized by comprising the following steps of,
the method comprises the steps that 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;
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 vertical laser pointing according to the angle deviation result;
the process of generating a spatial interference image based on the integrated sensing module includes,
the vertical laser signal is reflected by the beam splitting pyramid prism and returns along the original direction, and is split into transmitted light and reflected light by the beam splitter;
the transmitted light is transmitted through a polarization spectroscope and a quarter wave plate to obtain circularly polarized light; the circularly polarized light is divided into first liquid level refraction light and first liquid level reflection light on the surface of the liquid unit;
the reflected light is reflected by a reflecting mirror and transmitted by a polarization spectroscope and a quarter wave plate to obtain circularly polarized light; the circularly polarized light is divided into second liquid level refraction light and second liquid level reflection light on the surface of the liquid unit; wherein the bottom surface of the liquid container unit is an inclined surface;
the first liquid level refraction light is reflected by the micro-pyramid array at the bottom of the liquid container unit and returns in an original path, the polarization state of the first liquid level refraction light is changed into S after reversely passing through the quarter wave plate, and the first liquid level refraction light is reflected by the polarization spectroscope and then becomes first signal light to be emitted to the image sensor;
the first liquid level reflected light and the second liquid level reflected light are reflected by the liquid, the polarization state of the reflected light is changed into S after passing through the quarter wave plate reversely, and the reflected light is changed into second signal light and fourth signal light after being reflected by the polarization spectroscope and is emitted to the image sensor;
the second liquid level refraction light is reflected by the bottom surface of the liquid container, reversely passes through the quarter wave plate, becomes S in polarization state, is reflected by the polarization spectroscope, becomes 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 space interference light spot; the third signal light and the fourth signal light interfere on a detection surface of the image sensor to obtain a space interference fringe; the spatial interference light spots and the spatial interference fringes do not overlap spatially.
5. The vertical laser pointing correction method based on interference fringe decoupling as recited in claim 4, wherein the process of obtaining a vertical laser signal by a vertical laser generating module, transmitting the vertical laser signal to an integrated sensing module comprises,
generating a frequency-stabilized laser signal by a single-frequency laser, and transmitting the frequency-stabilized laser signal to an optical fiber collimator by 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.
6. The method for correcting vertical laser pointing based on interference fringe decoupling as claimed in claim 4, wherein the real-time correction process of 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 turntable and Gaussian fitting of the space interference light spots, then executes an interference fringe decoupling algorithm on the space interference fringes to realize precise measurement of vertical laser pointing, and finally sends a feedback control signal to the two-dimensional precise angle turntable according to a measurement result to realize real-time correction of the vertical laser pointing and upload the measurement result to an upper computer.
7. The method of vertical laser pointing correction based on interference fringe decoupling as recited in claim 6, wherein performing an interference image decoupling algorithm on said spatial interference image comprises,
the space interference image is sent to a signal processing card, the signal processing card performs high-precision decoupling operation on the wave front space interference image through an interference image decoupling algorithm,
converting the space 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 space interference fringes, and calculating different space frequency components in the amplitude space of the frequency spectrum of the space interference fringes;
obtaining an amplitude maximum point and a position corresponding to the amplitude maximum point in a frequency space matrix based on the amplitude space of the spatial interference fringe frequency spectrum, and performing two-dimensional curve peak fitting by using the amplitude information of the amplitude maximum point and the adjacent matrix points to obtain a fitted accurate frequency coordinate;
and according to the X-direction component and the Y-direction component of the accurate frequency coordinate obtained by fitting, obtaining the horizontal inclination angles of the X-direction and the Y-direction according to the linear relation between the angle measurement value and the spatial frequency of the spatial interference fringe.
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