CN114383538B - Device and method for accurately measuring angle through line quantity modulation - Google Patents

Abstract

The invention provides a device and a method for accurately measuring an angle through line quantity modulation. The device comprises: a laser for generating a gaussian laser beam; the first light modulation module is used for converting the Gaussian laser beam into an LG (light-emitting diode) beam; the second light modulation module is used for carrying out phase modulation on the LG light beam to obtain a modulated light beam; the notch beam generation module is used for converting the modulated beam into a rectangular beam, filtering the rectangular beam and applying a transverse linear barrier to obtain a rectangular beam with a notch; the beam splitting module is used for splitting the rectangular light beam with the notch into quasi-signal light and quasi-reference light, and performing inverse Fourier transform on the quasi-signal light to obtain an annular light beam with the notch; and the angle measurement module is used for respectively aligning the notched annular light beams with the two edges of the measured angle to obtain the measured angle.

Description

A device and method for accurately measuring angle quantity through line quantity modulation

Technical field

The invention belongs to the field of laser technology, and specifically relates to a device and method for accurately measuring angle quantity through line quantity modulation.

Background technique

The statements in this section merely provide background technical information related to the present invention and do not necessarily constitute prior art.

Optical angle measurement has attracted much attention due to its non-contact, high accuracy and high sensitivity characteristics.

In particular, the development of stable laser light sources has made industrial on-site measurements possible. Therefore, the application of optical angle measurement methods has become more and more widespread, and various new optical angle measurement methods have also emerged.

Angle measurement technology can determine the inclination angle of the measured object to the horizontal plane or its movement attitude. It has important applications in military and civilian fields, such as the measurement of inclination angle in mechanical processing and construction, and the navigation attitude angle of unmanned aerial vehicles. Motion posture control of intelligent robots, and motion rehabilitation instruments in medical treatment, etc.

At present, in addition to the well-known optical dividing head method and polyhedral prism method, optical angle measurement methods are commonly used including photoelectric encoder method, diffraction method, self-collimation method, optical fiber method, acousto-optic modulation method, circular grating method, Optical internal reflection method, laser interference method, parallel interference pattern method, ring laser method and laser triangulation method, etc. However, these methods have significant drawbacks. For example, the circular grating method requires high centering accuracy between the grating and the turntable, and it is difficult to manufacture and process high-accuracy gratings; the optical internal reflection method has a small measurement range and can only be used for small angle measurements; laser interference angle measurement technology The effect of measuring the entire circumferential angle is not ideal, the measurement accuracy is not high, the volume is large, and it is not suitable for on-site use; the ring laser angle measurement method can only achieve dynamic measurement and has high requirements on measurement conditions; the laser triangulation method has a small measurement range, It can only be used for small angle measurement; the photoelectric encoder has high requirements on the machining accuracy and installation accuracy of the mechanical shaft system; the electronic circuit of the rotary transformer combined with the induction synchronizer system is complex, and the error mechanism analysis and error separation technology are difficult.

In order to make non-contact angle measurement simpler and faster, Qikun Jia et al. realized an effective way to measure the small angle of the wedge with very high accuracy by converting the linear motion of the optical wedge into the rotational frequency shift in the orbital angular momentum interferometer. Methods: Song Qiu et al. observed the energy flow by capturing the intensity section of the incomplete vortex field; achieving direct measurement of the tilt angle of the Poynting vector. However, existing non-contact measurement inventions can still only achieve accurate measurement of small angles. Therefore, it is necessary to find an effective and simple non-contact method for measuring large angles.

Contents of the invention

In order to solve the above problems, the present invention proposes a device and method for accurately measuring angle through line amount modulation. The present invention realizes line amount modulation to accurately measure angle, and can realize the measurement of the entire circumferential angle, with a measurement resolution of 0.0001°. , and can achieve contact-free angle measurement.

According to some embodiments, the present invention adopts the following technical solutions:

In a first aspect, the present invention provides a device for accurately measuring angle quantity through line quantity modulation.

A device for accurately measuring angular quantities through line quantity modulation, including:

Lasers for generating Gaussian-shaped laser beams;

The first light modulation module is used to convert Gaussian laser beam into LG beam;

The second light modulation module is used to phase modulate the LG beam to obtain a modulated beam;

Notched beam generation module, used to convert the modulated beam into a rectangular beam, filter the rectangular beam and apply transverse linear obstacles to obtain a notched rectangular beam;

The beam splitting module is used to divide the rectangular beam with a notch into a quasi-signal light and a quasi-reference light, and perform inverse Fourier transform on the quasi-signal light to obtain a notched annular beam;

An angle measurement module is used to align the notched annular beam with the two sides of the measured angle respectively to obtain the measured angle.

In a second aspect, the present invention provides a method for accurately measuring angle quantity through line quantity modulation.

A method for accurately measuring angular quantity through line quantity modulation, using the device for accurately measuring angular quantity through line quantity modulation described in the first aspect, including:

Convert Gaussian laser beam into LG beam;

Phase modulate the LG beam to obtain a modulated beam;

Convert the modulated beam into a rectangular beam, filter the rectangular beam and apply a transverse linear obstacle to obtain a notched rectangular beam;

The notched rectangular beam is divided into quasi-signal light and quasi-reference light, and the quasi-signal light is subjected to inverse Fourier transform to obtain a notched annular beam;

Aim the notched annular beam at the two sides of the measured angle respectively to obtain the measured angle.

In a third aspect, the present invention provides a method for accurately measuring angle quantity through line quantity modulation.

A method for accurately measuring angular quantities through line quantity modulation, characterized by adopting the device for accurately measuring angular quantities through line quantity modulation described in the first aspect, including:

Adjust the height of the obstacle so that the notched annular beam is aligned with the two sides of the angle to be measured, record the position difference of the transverse notch of the rectangular beam through the charge-coupled element, and obtain the angle to be measured through calculation.

Compared with the prior art, the beneficial effects of the present invention are:

The invention effectively solves the problem of too small non-contact measurement angle range. By modulating the angle into a linear quantity, the angle measurement is more convenient and faster, and the measurement resolution is 0.0001°.

Description of drawings

The description and drawings that constitute a part of the present invention are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

Figure 1 is a schematic structural diagram of a device for accurately measuring angle quantity through line quantity modulation as described in Embodiment 1 of the present invention;

Figure 2(a) shows the calibrated 0° notched rectangular beam one;

Figure 2(b) shows the calibrated 0° notched annular beam 2;

Figure 2(c) shows the calibrated 180° rectangular beam with a notch;

Figure 2(d) shows the calibrated 180° notched annular beam 2;

Figure 3(a) is a schematic diagram of aligning the notch with a corner edge;

Figure 3(b) is an example of the measured angle;

Figure 3(c) shows a notched annular beam aimed at the upper corner of the measured angle;

Figure 3(d) shows a notched annular beam aimed at the lower corner of the angle being measured;

Among them, 1. Helium-neon laser; 2. Attenuation plate; 3, 4. Beam expander; 5. First spatial light modulator; 6. First diaphragm; 7. First reflector; 8. Second reflector ; 9. The second spatial light modulator; 10. The first lens; 11. The second diaphragm; 12. The beam splitter; 13. The second lens; 14. The third lens; 15. The fourth lens; 16. Angle measurement; 17. Charge coupled element.

Detailed ways:

The present invention will be further described below in conjunction with the accompanying drawings and examples.

It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It should be noted that the terms used herein are for the purpose of describing specific embodiments only, and are not intended to limit the exemplary embodiments according to the present invention. As used herein, the singular forms are also intended to include the plural forms unless the context clearly indicates otherwise. Furthermore, it will be understood that when the terms "comprises" and/or "includes" are used in this specification, they indicate There are features, steps, operations, means, components and/or combinations thereof.

In the present invention, terms such as "connection" should be understood in a broad sense, indicating that it can be a fixed connection, an integral connection or a detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. For relevant scientific researchers or technicians in the field, the specific meanings of the above terms in the present invention can be determined according to specific circumstances, and should not be understood as limitations of the present invention.

Embodiment 1

This embodiment provides a device for accurately measuring angle quantity through line quantity modulation.

A device for accurately measuring angular quantities through line quantity modulation, including:

Lasers for generating Gaussian-shaped laser beams;

The first light modulation module is used to convert Gaussian laser beam into LG beam;

The second light modulation module is used to phase modulate the LG beam to obtain a modulated beam;

Notched beam generation module, used to convert the modulated beam into a rectangular beam, filter the rectangular beam and apply transverse linear obstacles to obtain a notched rectangular beam;

The beam splitting module is used to divide the rectangular beam with a notch into a quasi-signal light and a quasi-reference light, and perform inverse Fourier transform on the quasi-signal light to obtain a notched annular beam;

An angle measurement module is used to align the notched annular beam with the two sides of the measured angle respectively to obtain the measured angle.

Specifically, the device described in this embodiment includes: 1 helium-neon laser, 2 attenuator, 3.4 beam expander, 5 first spatial light modulator, 6 first diaphragm, 7 first reflector, 8 second reflector Mirror, 9 second spatial light modulator, 10 first lens, 11 second diaphragm, 12 beam splitter, 13 second lens, 14 third lens, 15 fourth lens, 16 measured angle, 17 charge coupled element . As shown in Figure 1.

The Gaussian beam emitted by the helium-neon laser 1 first passes through the attenuator 2, which adjusts the laser power passing through it. After the beam expanders 3 and 4 expand the Gaussian laser spot, The expanded light spot is vertically incident on the first spatial light modulator 5. The LG beam output by the first spatial light modulator 5 passes through the first aperture 6. The first aperture 6 selects the first-order diffracted LG beam. , the first-order diffracted LG beam is vertically incident on the second spatial light modulator 9 through the first reflector 7 and the second reflector 8 to achieve phase modulation. The phase modulated beam output by the second spatial light modulator 9 is Through the first lens 10, the first lens 10 implements Fourier transformation of the modulated light beam to turn it into a rectangular light beam. The rectangular light beam passes through the second aperture 11, and the second aperture 11 selects the first-order diffraction. A rectangular beam and applying transverse linear obstacles to it generate a notched rectangular beam. The notched rectangular beam is divided into a quasi-signal light and a quasi-reference light through the beam splitter 12. The quasi-signal light passes through the fourth lens 15. The fourth lens 15 implements the inverse Fourier transform of the quasi-signal light to restore it to a notched annular beam. The quasi-reference light passes through the 4f system composed of the second lens 13 and the third lens 14. The 4f system will The quasi-reference light becomes a notched rectangular beam, and the quasi-reference light becomes a reference light. Therefore, the measured angle 16 placed at the back focal plane of the fourth lens can be measured with a notched ring beam, which is a non-contact measurement; the horizontally oriented beam has a charge-coupled element placed at the back focal plane of the third lens 17 can be used to shoot and record the rectangular beam after loading obstacles.

The specific calculation process is as follows:

The phase hologram of the LG vortex beam is loaded on the first spatial light modulator. The expression of the LG beam is:

Among them, p is the radial index, which describes the change of the phase in the radial direction; l is the azimuthal index, which describes the change of the phase in the angular direction; is the beam width after propagation distance z, where w(0) is the beam width at z=0, z _R is the Rayleigh distance;/> is an associated Laguerre polynomial, which can be expressed as:

Among them, the coordinate transformation that needs to be realized from the LG beam to the rectangular beam is:

v＝aarctan(y/x)

Among them, (x, y) is the input plane, (u, v) is the spectrum plane, and a, b are constants.

Among them, the phase that needs to be loaded from the LG beam to the rectangular beam is:

The specific angle measurement is implemented as follows:

Determine the special angles of the two annular beam notches to the vertical axis clamp: 0° and 180°. The width of the obstacle corresponding to these two angles is 10 pixels, and the angle difference is:

Δφ＝180°-0°＝180°

The difference (in pixels) between the ordinates of obstacles is:

Δy＝2008-994＝1014

Therefore, we can divide 180° into 1014 parts, and the angle corresponding to each part is θ=180°/1014≈0.1775°

Align the annular beam gap with the two sides of the angle being measured, then use a charge-coupled element to take a picture of the rectangular beam gap position, and then use MATLAB to identify the center of the gap, and then read the ordinate pixel difference between the two angles to calculate the angle. out.

Among them, the angle calculation formula is:

φ=Δn×θ

Among them, Δn is the pixel point difference value of the two sides of the measured angle, and θ is the angle value corresponding to the pixel point.

Embodiment 2

This embodiment provides a method for accurately measuring angle quantity through line quantity modulation.

A method for accurately measuring angular quantities through line quantity modulation, including:

Perform beam expansion and collimation on the generated Gaussian laser beam and convert the expanded Gaussian beam into an LG beam;

Filter the LG beam to obtain a first-order diffracted LG beam;

Phase modulate the first-order LG beam to obtain a modulated beam;

Fourier transform is performed on the modulated beam to obtain a rectangular beam;

Filter the rectangular beam and apply transverse linear obstacles to obtain a notched rectangular beam;

Split the notched rectangular beam to obtain quasi-signal light and quasi-reference light respectively;

Let the quasi-reference light pass through a 4f system composed of two identical lenses to obtain a rectangular beam with a notch;

Perform inverse Fourier transform on the quasi-signal light to obtain a notched annular beam;

The measured angle can be calculated by aligning the notched annular beam with the two sides of the measured angle respectively.

Using the device for accurately measuring angle quantity through line quantity modulation in Embodiment 1, the specific process is as follows:

Step 1: The laser generated by laser 1 passes through the attenuator 2, and the laser power transmitted through it is adjusted;

Step 2: The laser beam obtained in step 1 is expanded through beam expanders 3 and 4;

Step 3: The beam obtained in Step 2 is vertically incident on the first spatial light modulator 5 to complete the modulation from Gaussian light to LG vortex beam;

Step 4: The beam obtained in step 3 is filtered through the first aperture 6 to select the first-order diffracted LG beam;

Step 5: The light beam obtained in Step 4 passes through the first reflector 7 and the second reflector 8 and is vertically incident on the second spatial light modulator 9 to achieve phase modulation;

Step 6: The light beam obtained in step 5 passes through the first lens 10 to implement Fourier transformation, turning it into a rectangular light beam;

Step 7: The beam obtained in step 6 passes through the second aperture 11, selects the first-order diffracted rectangular beam and applies a transverse linear obstacle to it to generate a notched rectangular beam;

Step 8: The light beam obtained in step 7 is divided into two beams of light through the beam splitter 12, which are: quasi-signal light and quasi-reference light;

Step 9: The quasi-signal light obtained in step 8 passes through the fourth lens 15 to realize the inverse Fourier transform of the quasi-signal light and restores it to a notched ring beam; the quasi-reference light obtained in step 8 passes through the second and third lenses The 4f system composed of 13 and 14 changes the quasi-reference light into a notched rectangular beam.

Step 10: Align the notch of the signal light obtained in step 9 with the two sides of the measured angle 16 respectively, take a picture of the rectangular beam with the notch corresponding to the two sides through the charge coupled device 17, import it into MATLAB, and calculate The gap pixel difference corresponding to the two sides is obtained, and the measured angle can be calculated through the calculation formula.

The specific calculation process is as follows:

The phase hologram of the LG vortex beam is loaded on the first spatial light modulator. The expression of the LG beam is:

Among them, p is the radial index, which describes the change of the phase in the radial direction; l is the azimuthal index, which describes the change of the phase in the angular direction; is the beam width after propagation distance z, where w(0) is the beam width at z=0, z _R is the Rayleigh distance;/> is an associated Laguerre polynomial, which can be expressed as:

Among them, the coordinate transformation that needs to be realized from the LG beam to the rectangular beam is:

v＝aarctan(y/x)

Among them, (x, y) is the input plane, (u, v) is the spectrum plane, and a, b are constants.

Among them, the phase that needs to be loaded from the LG beam to the rectangular beam is:

The specific angle measurement is implemented as follows:

Determine the special angles of the two annular beam notches to the vertical axis clamp: 0° and 180°. As shown in Figure 2(a), (b), (c), (d). The width of the obstacle corresponding to these two angles is 10 pixels, and the angle difference is:

Δφ＝180°-0°＝180°

The difference (in pixels) between the ordinates of obstacles is:

Δy＝2008-994＝1014

Therefore, we can divide 180° into 1014 parts, and the angle corresponding to each part is θ=180°/1014≈0.1775°

Align the annular beam notch with the two sides of the measured angle, as shown in Figure 3(a), (b), (c), and (d). Then use a charge-coupled element to take a picture of the rectangular beam gap position, and then use MATLAB to identify the center of the gap. The angle can be calculated by reading the ordinate pixel difference between the two angles.

Among them, the angle calculation formula is:

φ=Δn×θ

Among them, Δn is the pixel point difference value of the two sides of the measured angle, and θ is the angle value corresponding to the pixel point.

Embodiment 3

This embodiment provides a method for accurately measuring angle quantity through line quantity modulation.

A method for accurately measuring angle quantity through line quantity modulation, using the device for accurately measuring angle quantity through line quantity modulation described in Embodiment 1, including:

Adjust the height of the obstacle so that the notched annular beam is aligned with the two sides of the angle to be measured, record the position difference of the transverse notch of the rectangular beam through the charge-coupled element, and obtain the angle to be measured through calculation.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims (9)

1. A device for accurately measuring angular quantities through line quantity modulation, which is characterized in that it includes: Lasers for generating Gaussian-shaped laser beams; The first light modulation module is used to convert Gaussian laser beam into LG beam; The second light modulation module is used to phase modulate the LG beam to obtain a modulated beam; Notched beam generation module, used to convert the modulated beam into a rectangular beam, filter the rectangular beam and apply transverse linear obstacles to obtain a notched rectangular beam; The beam splitting module is used to divide the rectangular beam with a notch into a quasi-signal light and a quasi-reference light, and perform inverse Fourier transform on the quasi-signal light to obtain a notched annular beam; An angle measurement module is used to align the notched annular beam with the two sides of the measured angle to obtain the measured angle; The notched beam generating module includes a first lens and a second aperture. The first lens implements Fourier transformation of the modulated beam, turning the modulated beam into a rectangular beam. The rectangular beam passes through the second aperture, and is selected. First-order diffracted rectangular beam and applying transverse linear obstacles to it generate a notched rectangular beam; The notched annular beam means that when the notched rectangular beam is divided into quasi-signal light and quasi-reference light through a beam splitter, the quasi-signal light passes through the fourth lens, and the fourth lens realizes quasi-signal light. The inverse Fourier transform is used to restore it to the notched ring beam. 2. The device for accurately measuring angle quantity through line quantity modulation according to claim 1, characterized in that the laser is a helium-neon laser. 3. The device for accurately measuring angle quantity through line quantity modulation according to claim 1, characterized in that the first light modulation module includes an attenuator, a first beam expander, a second beam expander and a first space Optical modulator, the attenuator adjusts the laser power passing through it; the first beam expander and the second beam expander expand the Gaussian laser spot, and the expanded spot is vertically incident on the first and a spatial light modulator, the first spatial light modulator outputs an LG beam. 4. The device for accurately measuring angle quantity through line quantity modulation according to claim 1, characterized in that the second light modulation module includes: a first diaphragm, a first reflector, a second reflector and a second light modulation module. Spatial light modulator, the first aperture selects the first-order diffracted LG beam passing through it, and the first-order diffracted LG beam passes through the first reflecting mirror and the second reflecting mirror and is vertically incident on the second spatial light modulator. Realize phase modulation and obtain modulated beam. 5. The device for accurately measuring angular quantity through line quantity modulation according to claim 1, characterized in that the quasi-reference light passes through a 4f system composed of a second lens and a third lens and becomes a notched rectangular light beam, Turn the quasi-reference light into a reference light. 6. The device for accurately measuring angular quantity through line quantity modulation according to claim 5, characterized in that when measuring the measured angle, the notched annular beam is located at the rear focal plane of the fourth lens . 7. The device for accurately measuring angular quantity through linear quantity modulation according to claim 5, characterized in that the device further includes a charge coupled element, the charge coupled element is located at the rear focal plane of the third lens, Used to record the rectangular beam after loading obstacles. 8. A method for accurately measuring angular amount through line amount modulation, characterized in that the device for accurately measuring angular amount through line amount modulation according to any one of claims 1-7 is used, including: Convert Gaussian laser beam into LG beam; Phase modulate the LG beam to obtain a modulated beam; Convert the modulated beam into a rectangular beam, filter the rectangular beam and apply a transverse linear obstacle to obtain a notched rectangular beam; The notched rectangular beam is divided into quasi-signal light and quasi-reference light, and the quasi-signal light is subjected to inverse Fourier transform to obtain a notched annular beam; Aim the notched annular beam at the two sides of the measured angle respectively to obtain the measured angle. 9. A method for accurately measuring angular amount through line amount modulation, characterized in that the device for accurately measuring angular amount through line amount modulation according to any one of claims 1-7 is used, including: Adjust the height of the obstacle so that the notched annular beam is aligned with the two sides of the angle to be measured, record the position difference of the transverse notch of the rectangular beam through the charge-coupled element, and obtain the angle to be measured through calculation.