HIGH-PRECISION DUAL-AXIS LASER INCLINOMETER BASED ON WAVEFRONT HOMODYNE INTERFERENCE AND MEASURING METHOD
20230384090 · 2023-11-30
Inventors
Cpc classification
International classification
Abstract
A high-precision dual-axis laser inclinometer based on wavefront homodyne interference and a measuring method are disclosed. The method includes: obtaining a laser signal through a laser light source module, transmitting the laser signal to an integrated sensing module, and generating a wavefront interference signal based on the integrated sensing module; and inputting the wavefront interference signal into a signal processing module for performing high-precision decoupling operation to obtain a horizontal inclination angle measurement result. The measurement resolution is high, the measurement result can be directly traced to the laser wavelength, high-precision dual-axis inclination angle measurement can be realized only by using single-beam measurement light, meanwhile, the laser inclinometer has the advantages of being simple in structure, simple in light path, easy to integrate, beneficial to engineering implementation, and high in cost performance, and the requirement of high-end equipment on the ultra-precision inclinometer is met.
Claims
1. A dual-axis laser inclinometer based on wavefront homodyne interference, comprising: a laser light source module, configured to generate a laser signal; an integrated sensing module, connected to the laser light source module, and configured to receive the laser signal and generate a wavefront interference signal based on the laser signal; and a signal processing module, connected to the integrated sensing module, and configured to perform a decoupling operation on the wavefront interference signal to obtain a horizontal inclination angle measurement result.
2. The dual-axis laser inclinometer based on wavefront homodyne interference according to claim 1, wherein the laser light source module comprises a single-frequency laser and a polarization maintaining single mode patch cable; the single-frequency laser is configured to provide linearly polarized light, and the linearly polarized light is the laser signal; the polarization maintaining single mode patch cable is connected to the single-frequency laser and is configured to transmit the linearly polarized light to an optical fiber collimator.
3. The dual-axis laser inclinometer based on wavefront homodyne interference according to claim 1, wherein the integrated sensing module comprises an optical fiber collimator, a polarization beam splitter, a reflector, a first quarter-wave plate, a second quarter-wave plate, a polarizer, a liquid container, a liquid unit, and an array detector; the optical fiber collimator is configured to receive linearly polarized light and output a linearly polarized collimated laser; the polarization beam splitter is configured to divide the linearly polarized collimated laser into first transmitted light and first reflected light, and further configured to reflect the first transmitted light having a polarization state converted to S to obtain first signal light, and transmit the first reflected light having a polarization state converted to P to obtain second signal light; the first quarter-wave plate and the reflector are configured to convert the first transmitted light having a polarization state P into the first transmitted light having the polarization state S; the second quarter-wave plate and the liquid unit are configured to convert the first reflected light having a polarization state S into the first reflected light having the polarization state P; the polarizer is configured to select components of the first signal light and the second signal light in a same polarization direction to make the first signal light and the second signal light form an interference; and the array detector is configured to detect the wavefront interference signal formed by the interference between the first signal light and the second signal light.
4. The dual-axis laser inclinometer based on wavefront homodyne interference according to claim 3, wherein the reflector is not perpendicular to the first transmitted light.
5. The dual-axis laser inclinometer based on wavefront homodyne interference according to claim 1, wherein the signal processing module comprises a master computer and a signal processing board; the signal processing board is configured to perform the decoupling operation on the wavefront interference signal through a dual-axis horizontal inclination angle decoupling algorithm, and upload the horizontal inclination angle measurement result to the master computer; and the master computer is configured to receive, display and store the horizontal inclination angle measurement result.
6. A measuring method of a dual-axis laser inclinometer based on wavefront homodyne interference, comprising: obtaining a laser signal through a laser light source module, transmitting the laser signal to an integrated sensing module, and generating a wavefront interference signal based on the integrated sensing module; and inputting the wavefront interference signal into a signal processing module to perform a decoupling operation to obtain a horizontal inclination angle measurement result.
7. The measuring method of the dual-axis laser inclinometer based on wavefront homodyne interference according to claim 6, wherein a process of the obtaining a laser signal through a laser light source module and the transmitting the laser signal to an integrated sensing module, comprises: generating the laser signal through a single-frequency laser, and transmitting the generated laser signal to an optical fiber collimator through a polarization maintaining single mode patch cable.
8. The measuring method of the dual-axis laser inclinometer based on wavefront homodyne interference according to claim 6, wherein a process of the generating a wavefront interference signal based on the integrated sensing module, comprises: receiving linearly polarized light through an optical fiber collimator and outputting a linearly polarized collimated laser; dividing the linearly polarized collimated laser into first transmitted light and first reflected light after the linearly polarized collimated laser passes through a polarization beam splitter; converting a polarization state of the first transmitted light from P to S by the first transmitted light passing through a first quarter-wave plate from a front thereof, and passing through the first quarter-wave plate from a back thereof after being reflected by the reflector; obtaining first signal light based on the converted first transmitted light through the polarizer after the converted first transmitted light is reflected by the polarization beam splitter, and transmitting the first signal light to the array detector; converting a polarization state of the first reflected light from S to P by the first reflected light passing through a second quarter-wave plate from a front thereof, and passing through the second quarter-wave plate from a back thereof after being reflected by a liquid surface; obtaining second signal light based on the converted first reflected light through the polarizer after the converted first reflected light is reflected by the polarization beam splitter, and transmitting the second signal light to the array detector; and making the first signal light and the second signal light form an interference at a detection surface of the array detector to obtain the wavefront interference signal.
9. The measuring method of the dual-axis laser inclinometer based on wavefront homodyne interference according to claim 6, wherein a process of the inputting the wavefront interference signal into a signal processing module to perform a decoupling operation to obtain a horizontal inclination angle measurement result, comprises: sending the wavefront interference signal to a signal processing board; performing, by the signal processing board, the decoupling operation on the wavefront interference signal through a dual-axis horizontal inclination angle decoupling algorithm to obtain the horizontal inclination angle measurement result, and uploading the horizontal inclination angle measurement result to a master computer.
10. The measuring method of the dual-axis laser inclinometer based on wavefront homodyne interference according to claim 9, wherein a process of the performing, by the signal processing board, the decoupling operation on the wavefront interference signal through a dual-axis horizontal inclination angle decoupling algorithm, comprises: converting the wavefront interference signal into a two-dimensional light intensity matrix, performing a butterfly operation-based two-dimensional discrete Fourier transform on the two-dimensional light intensity matrix to obtain a frequency space matrix of the wavefront interference signal, and calculating different spatial frequency components in an amplitude space of a spectrum of the wavefront interference signal; obtaining an amplitude maximum value point and a corresponding position thereof in the frequency space matrix based on the amplitude space of the spectrum of the wavefront interference signal, and performing two-dimensional curve peak fitting by using amplitude information of the amplitude maximum value point and an adjacent matrix point to obtain fitted accurate frequency coordinates; and obtaining, according to an X component and a Y component of the fitted accurate frequency coordinates, included angles between a liquid surface and the reflector in a X direction and a Y direction respectively, according to formulas of linear relationships between an included angle of the liquid surface relative to the reflector and frequency of the wavefront interference signal.
Description
BRIEF DESCRIPTION OF THE DRAWING
[0046] In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the accompanying drawing that need to be used in the embodiments are briefly described below, and it is obvious that the accompanying drawing in the following description is merely some of the embodiments of the present disclosure, and those skilled in the art may obtain other drawings according to this drawing without involving any inventive effort.
[0047] A FIGURE is a schematic structural diagram of a system according to an embodiment of the disclosure.
DESCRIPTION OF REFERENCE NUMERALS
[0048] 1—master computer, 2—signal processing board, 3—array detector, 4—polarizer, 5—polarization beam splitter, 6—reflector, 7—first quarter-wave plate, 8—integrated base, 9—liquid, 10—liquid container, 11—second quarter-wave plate, 12—optical fiber collimator, 13—polarization maintaining single mode patch cable, and 14—single-frequency laser.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0049] In combination with the drawing in the embodiments of the disclosure, the technical solutions in the embodiments of the disclosure will be described clearly and completely. Apparently, the described embodiments are only some of the embodiments of the disclosure, not all of them. Based on the embodiments of the disclosure, all other embodiments obtained by those skilled in the art without creative work belong to the scope of the disclosure.
[0050] In order to make the above objects, features and advantages of the present disclosure more comprehensible, the present disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments.
Embodiment 1
[0051] As shown in the FIGURE, the high-precision dual-axis laser inclinometer based on wavefront homodyne interference includes: a master computer 1, a signal processing board 2, an array detector 3, a polarizer 4, a polarization beam splitter 5, a reflector 6, a first quarter-wave plate 7, an integrated base 8, a liquid 9, a liquid container 10, a second quarter-wave plate 11, an optical fiber collimator 12, a polarization maintaining single mode patch cable 13, and a single-frequency laser 14. The optical fiber collimator 12, the polarization beam splitter 5, the reflector 6, the liquid container 10 and the array detector 3 are all fixed on the integrated base 8.
[0052] The liquid 9 has a viscosity value in the order of 100 centiStokes (cSt), a reflectivity of more than 1%, and a liquid surface height in the order of millimeters, which is a reference datum plane for horizontal inclination angles. The liquid container 10 is a circle with a diameter of more than 30 mm.
[0053] In the further optimized solution, the liquid 9 is silicone oil with a viscosity of 350 CS, reflectivity of about 3%, and a liquid surface height of 2 mm as a reference datum plane for horizontal inclination angles.
[0054] The reflector 6 is not perpendicular to the first transmitted light, so that the optical axis of the first signal light and the optical axis of the second signal light generate a slight angle deviation to form an inclined stripe-shaped wavefront interference signal, which is effectively detected by the array detector.
[0055] As shown in the FIGURE, the disclosure provides a high-precision dual-axis laser inclinometer based on wavefront homodyne interference, including: a laser light source module, an integrated sensing module, and a signal processing module.
[0056] The laser light source module includes a single-frequency laser 14 and a polarization maintaining single mode patch cable 13, and is configured to generate a linearly polarized laser, and an included angle between a polarization direction of the linearly polarized laser and a polarization direction of the P light is 1.77°.
[0057] The integrated sensing module includes an integrated base 8, an optical fiber collimator 12, a polarization beam splitter 5, a reflector 6, a first quarter-wave plate 7, a second quarter-wave plate 11, a liquid container 10, a liquid 9, a polarizer 4, and an array detector 3. The polarization beam splitter 5 divides the 1.77° linearly polarized light emitted by the optical fiber collimator 12 into first transmitted light and first reflected light. The first transmitted light is reflected by the reflector 6, and passes through the first quarter-wave plate 7 in front and back directions to form first signal light, that is to say, the first transmitted light passes through the first quarter-wave plate 7 from the front thereof and passes through the first quarter-wave plate 7 from the back thereof after being reflected by the reflector 6, and the first signal light can be obtained.
[0058] The first reflected light is reflected by the liquid surface, and passes through the second quarter-wave plate 11 in front and back directions to form the second signal light, that is to say, the first reflected light passes through the second quarter-wave plate 11 from the front thereof and passes through the second quarter-wave plate 11 from the back thereof after being reflected by the liquid surface, and the second signal light can be obtained. After the first signal light and the second signal light pass through the polarizer 4 together, interference occurs at the detection surface of the array detector 3 to form the wavefront interference signal.
[0059] The signal processing module includes a master computer 1 and a signal processing board 2.
[0060] The signal processing board 2 is configured to perform a high-precision decoupling operation on the wavefront interference signal through a dual-axis horizontal inclination angle decoupling algorithm, and upload an operation result (i.e., horizontal inclination angle measurement result) to the master computer 1.
[0061] The master computer 1 is configured to receive, display, and store an operation result of the horizontal inclination angle measurement.
[0062] The disclosure further provides a measuring method of a high-precision dual-axis laser inclinometer based on wavefront homodyne interference, and a measuring process based on the laser inclinometer is as follows: the single-frequency laser 14 of the embodiment adopts a 633 nanometers (nm) single-frequency helium-neon laser for providing a frequency-stabilized laser signal, the laser signal is linearly polarized light and is transmitted to the optical fiber collimator 12 through the polarization maintaining single mode patch cable 13, the optical fiber collimator 12 outputs linearly polarized collimated laser, and the included angle between the polarization direction of the linearly polarized collimated laser and the polarization direction of the P-light is 1.77°. The 1.77° linearly polarized collimated laser passes through the polarization beam splitter 5 and then is divided into first transmitted light and first reflected light; the first transmitted light with the polarization state P is successively transmitted by the first quarter-wave plate 7, reflected by the reflector 6, and returned after the reverse transmission of the first quarter-wave plate 7, its polarization state is changed into S, and then the first transmitted light becomes the first signal light through the polarizer 4 after being reflected by the polarization beam splitter 5, and the polarization state is 45°. Meanwhile, the first reflected light with the polarization state S is successively transmitted by the second quarter-wave plate 11, reflected by the liquid surface of the liquid 9, and returned after the reverse transmission of the second quarter-wave plate 11, its polarization state is changed into P, and then the first reflected light becomes second signal light through the polarizer 4 after being transmitted through the polarization beam splitter 5, and the polarization state is 45°; and the reflector 6 is not perpendicular to the first transmitted light, the optical axis of the first signal light and the optical axis of the second signal light are caused to generate a tiny angle deviation, so that an inclined stripe-shaped wavefront interference signal is formed on the detection surface of the array detector 3, and is detected by the array detector 3. The wavefront interference signal is sent to the signal processing board 2 in a digital quantity form, a dual-axis horizontal inclination angle decoupling algorithm is integrated in the signal processing board 2, the high-precision decoupling operation is performed on the wavefront interference signal, and an operation result is uploaded to the master computer 1; and the dual-axis horizontal inclination angle decoupling algorithm of the laser inclinometer can perform the high-precision decoupling operation on the wavefront interference signal and trace the horizontal inclination angle measurement to the laser wavelength.
[0063] The process of tracing the horizontal inclination angle by the dual-axis horizontal inclination angle decoupling algorithm to the laser wavelength includes: [0064] step 1: converting the wavefront interference signal into a two-dimensional grayscale matrix (i.e., two-dimensional light intensity matrix), performing a butterfly operation-based two-dimensional discrete Fourier transform on the two-dimensional grayscale matrix to obtain a frequency space matrix thereof, and calculating different spatial frequency components thereof in an amplitude space of a spectrum thereof; [0065] step 2, obtaining an amplitude maximum point and the corresponding position thereof in the frequency space matrix in the amplitude space of the two-dimensional frequency spectrum of the wavefront interference signal, and performing two-dimensional curve peak fitting by using amplitude information of the amplitude maximum amplitude point and the adjacent matrix point to obtain the fitted accurate frequency coordinates; [0066] step 3: the angle of the liquid surface relative to the reflector is in a linear relationship with the frequency of the wavefront interference signal, and according to the X component and the Y component of the accurate frequency coordinate obtained by fitting, the included angle between the liquid surface and the reflector in the X direction and the Y direction may be respectively obtained according to formula 1 and formula 2. Due to the fact that the liquid surface is always perpendicular to the gravity direction, the method can calculate and monitor the dual-axis horizontal inclination angle of the plane in real time.
[0067] In the formulas, θ.sub.X and θ.sub.Y represent horizontal inclination angles in the x and y directions, respectively; f.sub.X and f.sub.Y represent x and y components of the spatial frequency of the wavefront interference signal, respectively; λ represent the laser wavelength, and n.sub.air represent the air refractive index.
[0068] In the measuring method of the high-precision dual-axis laser inclinometer based on wavefront homodyne interference provided by the disclosure, the horizontal plane is taken as the reference datum plane, a wavefront homodyne interference principle of linear polarization laser is utilized, a to-be-measured horizontal inclination angle is converted into a wavefront interference signal through a liquid surface and attitude inclined reflector, high-precision decoupling calculation is conducted on the wavefront interference signal, and finally high-precision double-axis measurement of the horizontal inclination angle is achieved. In addition, by converting the laser polarization state and cooperating with the polarization beam splitter, the energy utilization efficiency is improved, the requirement for the laser power is reduced, and the virtual reflection in the optical path and the periodic nonlinear error caused thereby are also reduced. The laser inclinometer of the disclosure is completely based on the principle of laser interference measurement, the measurement resolution is high, the measurement result can be directly traced to the laser wavelength, and the laser inclinometer has the advantages of simple structure, concise optical path, easy integration, facilitation of engineering implementation, high cost performance and the like, and meets the requirements of high-end equipment on the ultra-precision inclinometer.
[0069] The above embodiments are only described in the preferred manner of the present disclosure, and are not limited to the scope of the present disclosure, and various modifications and improvements made by those of ordinary skill in the art on the technical solutions of the present disclosure shall fall within the scope of protection determined by the claims of the present disclosure without departing from the spirit of the present disclosure.