A calibration-free, high-precision pointing adjustment device and method for dual optical wedges

Abstract

This invention relates to a calibration-free, high-precision pointing adjustment device and method using dual optical wedges. The device includes a first optical wedge adjustment mechanism, a second optical wedge adjustment mechanism, a beam expander, a corner-reflecting light guide prism, a diffraction beam splitting module, a pointing monitoring lens, a pointing monitoring focal plane, and a processing and control module. Laser light sequentially enters the first optical wedge adjustment mechanism, the second optical wedge adjustment mechanism, the beam expander, the corner-reflecting light guide prism, the diffraction beam splitting module, the pointing monitoring lens, and the pointing monitoring focal plane. A detector on the pointing monitoring focal plane records the focal plane spot information. Finally, the processing and control module calculates the laser pointing information based on the focal plane spot and controls the rotation of the two optical wedge adjustment mechanisms to bring the laser pointing to the target value. This invention eliminates the need for absolute calibration of the optical wedges and scale calibration, significantly improving pointing monitoring accuracy through diffraction beam splitting, and enhancing environmental adaptability and reliability.

Description

Technical Field

[0001] This invention belongs to the field of laser remote sensing technology and relates to a calibration-free dual-wedge high-precision pointing adjustment device and method. Background Technology

[0002] In laser remote sensing technology, using dual optical wedges for laser pointing adjustment is a common technique. After determining the target direction, the dual optical wedge adjustment mechanisms need to each adjust their rotation angle to align the synthesized laser with the target.

[0003] Currently, adjustments using dual optical wedges often require absolute calibration of the wedge rotation angle. After installing the dual optical wedges, scales are marked on the structure of the two wedges using absolute calibration, and then the rotation angle is calculated from the calibrated scales based on the target direction. While this method is simple to calculate, it places high demands on calibration accuracy and structural stability in many operating conditions requiring high pointing precision and subject to mechanical shock and vibration. When the hardware parameters of the optical wedges change due to shock, vibration, or variations in gravity, the rotation angle calculated from the absolute calibration parameters will have significant errors, potentially even preventing the target direction from being reached.

[0004] Furthermore, the adjustment angular resolution of the dual optical wedges is closely related to their apex angle and rotation angle resolution. High-precision pointing angle adjustment often requires high rotation angle resolution and high-precision rotation angle control. High rotation angle control accuracy places extremely high demands on the precision and cost of the control mechanism, increasing the cost and reliability requirements of the solution implementation. Summary of the Invention

[0005] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a calibration-free double optical wedge high-precision pointing adjustment device and method, which eliminates the need for absolute calibration of the optical wedges and improves environmental adaptability and reliability.

[0006] The solution of the present invention is: a calibration-free double optical wedge high-precision pointing adjustment device, which emits a single-wavelength collimated laser from a laser, and includes a first optical wedge adjustment mechanism, a second optical wedge adjustment mechanism, a beam expander, a corner reflection light guide prism, a diffraction beam splitter module, a pointing monitoring lens, a pointing monitoring focal plane, and a processing and control module;

[0007] The first and second optical wedge adjustment mechanisms have the same structure. Through refraction and rotation, the direction of the collimated laser is deflected around the output optical axis of the laser in three-dimensional space.

[0008] Beam expanders are used to thicken laser beams and compress the divergence angle;

[0009] An angle-reflecting light guide prism is used to flip a laser beam in completely opposite directions;

[0010] A diffraction beam splitter is used to split a laser beam into multiple laser beams distributed at a specific angle.

[0011] A pointing monitoring lens is used to image and focus multiple laser beams from different directions onto the pointing monitoring focal plane;

[0012] The pointing monitoring focal plane is an area array detector mounted on the focal plane of the pointing monitoring lens, which can detect the laser spot image corresponding to the laser beam;

[0013] The processing and control module extracts the centroid of the laser spot on the focal plane of the beam expander and calculates the pointing data of the laser emitted from the beam expander. Based on the pointing adjustment target input to the processing and control module, it calculates the deviation between the pointing data and the target, and then calculates the adjustment amount of the rotation of the first and second optical wedge adjustment mechanisms. It controls the rotation of the first and second optical wedge adjustment mechanisms to make the laser pointing reach the adjustment target value.

[0014] Furthermore, the aforementioned angle-reflecting light guide prism supports full-aperture or partial light extraction.

[0015] Furthermore, both the first optical wedge adjustment mechanism and the second optical wedge pointing adjustment mechanism can be replaced with pointing scanning mirrors.

[0016] Furthermore, the beam expander is a transmission beam expander or a reflection beam expander.

[0017] Furthermore, the corner-reflecting light guide prism is a corner-reflecting or irregularly shaped corner-reflecting mirror with its apex cut off.

[0018] Furthermore, the diffraction beam splitting module is any one of a DOE element, a birefringent beam splitting element, or a metasurface lens element.

[0019] A method for high-precision pointing adjustment of a calibration-free dual optical wedge includes the following steps:

[0020] The processing and control module (8) extracts the initial average position of the laser spot on the pointing monitoring focal plane (7) as A(x). mA ,y mA The principal optical axes of the two optical wedge rotating mechanisms are located at corresponding positions Z(x) on the monitoring focal plane (7). Z ,y Z The target for adjusting the laser spot on the focal plane (7) is O(x) (unknown). O ,y O );

[0021] The first optical wedge adjustment mechanism (1) and the second optical wedge adjustment mechanism (2) are rotated 180° clockwise to emit a laser. At this time, the processing and control module (8) extracts the average position of the laser spot on the focal plane (7) as B(x). mB ,ymB According to A(x) mA ,y mA ) and B(x mB ,y mB The positions Z(x) of the principal optical axes of the two optical wedge rotating mechanisms on the monitoring focal plane (7) were calculated. Z ,y Z );

[0022] Rotate the first optical wedge adjustment mechanism (1) clockwise. At the same time, the second optical wedge adjustment mechanism (2) rotates counterclockwise. When a laser is emitted, the processing and control module (8) extracts the average position of the laser spot on the focal plane (7) as C(x). mC ,y mC );

[0023] Calculate the rotation angle required to adjust B to Z. The required rotation angle from B to O The rotation angle required from Z to O

[0024] Calculate the following judgment criteria:

[0025]

[0026] x O ′=x O (y mB -y Z )+y O (x Z -x mB )+x mB y Z -x Z y mB

[0027] Calculate the clockwise rotation angle of the first optical wedge adjustment mechanism (1) Second optical wedge adjustment mechanism (2) rotates clockwise. Rotate the two optical wedge adjustment mechanisms to move the center of the laser spot pointing in the monitoring focal plane (7) to the target position O(x). O ,y O ):

[0028]

[0029] Furthermore, the aforementioned

[0030] Furthermore, Z(x) Z ,y Z The calculation formula is:

[0031]

[0032] Furthermore, rotation angle The calculation method is as follows:

[0033]

[0034] Where n is the refractive index of the optical wedge, α is the apex angle of the optical wedge, K is the beam expansion factor, F is the focal length of the pointing monitoring lens (6), and L AB L OZ L BZ L OB The straight-line distance between the centers of the light spots pointing to the monitoring focal plane (7) is expressed as follows:

[0035]

[0036] The beneficial effects of this invention compared to the prior art are:

[0037] (1) The present invention does not require absolute calibration of the optical wedge, and does not require calibration of the scale, thus improving environmental adaptability and reliability;

[0038] (2) This invention improves the pointing monitoring accuracy by multiple times through diffraction beam splitting and reduces the pointing recording error. The value is M, where M is the number of laser beams split by the diffraction beam splitting module, thereby reducing the difficulty and cost of monitoring cameras.

[0039] (3) The present invention improves the pointing accuracy by a factor of two with low rotation resolution, thereby reducing the difficulty of developing a high-precision pointing adjustment system and the cost of the mechanism. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of a calibration-free double optical wedge high-precision pointing adjustment device according to the present invention;

[0041] Figure 2 A schematic diagram of the three-dimensional coordinates formed by the optical axis z pointing to the monitoring lens and the focal plane pointing to the monitoring lens;

[0042] Figure 3 This is a schematic diagram showing the positional relationship of each point in step one;

[0043] Figure 4 This is a schematic diagram showing the positional relationship of each point in step two;

[0044] Figure 5 This is a schematic diagram of the uncalibrated double optical wedge high-precision pointing adjustment device in Example 1;

[0045] Figure 6 Example 1 illustrates the diffraction beam splitting and monitoring of the light spot distribution on the focal plane. Detailed Implementation

[0046] like Figure 1 As shown, the present invention proposes a calibration-free dual-wedge high-precision pointing adjustment device, which includes a first wedge adjustment mechanism 1, a second wedge adjustment mechanism 2, a beam expander 3, a corner reflection light guide prism 4, a diffraction beam splitter module 5, a pointing monitoring lens 6, a pointing monitoring focal plane 7, and a processing and control module 8; a single-wavelength collimated laser is emitted by a laser.

[0047] The first optical wedge adjustment mechanism 1 and the second optical wedge adjustment mechanism 2 have the same structure. Through refraction and rotation, the direction of the collimated laser is deflected around the output optical axis of the laser in three-dimensional space.

[0048] Beam expander 3 is used to thicken the laser beam and compress the divergence angle;

[0049] The corner-reflecting light guide prism 4 is used to flip a laser beam in completely opposite directions;

[0050] The diffraction beam splitter module 5 is used to split a laser beam into multiple laser beams according to a specific angle distribution.

[0051] The pointing monitoring lens 6 is used to image and focus multiple laser beams from different directions onto the pointing monitoring focal plane 7;

[0052] The pointing monitoring focal plane 7 is an area array detector mounted on the focal plane of the pointing monitoring lens 6, which can detect the laser spot image corresponding to the laser beam;

[0053] The processing and control module 8 extracts the centroid based on the laser spot on the focal plane 7 and calculates the pointing data of the laser emitted from the beam expander 3. Based on the pointing adjustment target input to the processing and control module 8, it calculates the deviation between the pointing data and the target, and then calculates the adjustment amount of the rotation of the first optical wedge adjustment mechanism 1 and the second optical wedge adjustment mechanism 2. It controls the rotation of the first optical wedge adjustment mechanism 1 and the second optical wedge adjustment mechanism 2 so that the laser pointing reaches the adjustment target value.

[0054] The optical path process is as follows:

[0055] The laser sequentially enters the first optical wedge adjustment mechanism 1, the second optical wedge adjustment mechanism 2, the beam expander 3, the corner reflection light guide prism 4, the diffraction beam splitter module 5, the pointing monitoring lens 6, and the pointing monitoring focal plane 7. The detector of the pointing monitoring focal plane 7 records the focal plane spot information, and finally the processing and control module 8 calculates the laser pointing information based on the focal plane spot.

[0056] After passing through the fixed optical wedge adjustment mechanism 1 and optical wedge adjustment mechanism 2, the laser enters the subsequent optical path, and finally obtains a pointing monitoring image containing M light spots distributed on the pointing monitoring focal plane 7. The processing and control module 8 extracts the positions of the M light spots {(x1,y1), (x2,y2)…(x...y1)} from the pointing monitoring focal plane 7. M ,y M Then calculate the average spot position (x) m ,y m The calculation formula is:

[0057]

[0058] Let the three-dimensional coordinates formed by the optical axis z of the pointing monitoring lens 6 and the pointing monitoring focal plane 7 be as follows: Figure 2 As shown, the three-dimensional coordinate system is established as follows: the optical axis z pointing towards the monitoring lens 6 is aligned with the optical axis of the laser, and the x-direction is any direction within the plane perpendicular to the optical axis z, determined by the right-hand rule. Let the focal length of the monitoring lens 6 be F, then the angle θ between the laser beam emitted through the beam expander 3 and the z-axis is... z The calculation formula is:

[0059]

[0060] The laser emitted after beam expander 3 points to the azimuth angle θ on the xy projection plane. x The calculation formula is:

[0061]

[0062] Let the pointing measurement error of a single light spot be Δθ, then the pointing jitter measurement error measured by M light spots is:

[0063]

[0064] Therefore, the laser pointing measurement range of the processing and control module 8 is θ. z ±Δθ m The jitter measurement error is reduced to that of the existing adjustment mechanism. M represents the number of laser beams split by the diffraction beam splitting module.

[0065] In the device of the present invention, the corner reflector light guide prism 4 can capture light at full aperture, in which case a semi-reflective and semi-transparent film needs to be deposited; or it can capture light partially, in which case a semi-reflective and semi-transparent film is not required.

[0066] Both the first beam wedge adjustment mechanism 1 and the second beam wedge pointing adjustment mechanism 2 can be replaced by other mechanisms that can adjust the beam pointing, such as a pointing scanning mirror.

[0067] The beam expander 3 can be a transmission beam expander or a reflection beam expander.

[0068] The corner-reflecting light guide prism 4 is a corner-reflecting or irregularly shaped corner-reflecting mirror with its apex cut off.

[0069] The diffraction beam splitting module 5 can be a DOE element, a birefringent beam splitting element, a metasurface lens element, or other beam splitting element capable of splitting a single beam of light into multiple beams with overlapping exit beams.

[0070] This invention proposes a high-precision pointing adjustment method for calibration-free dual optical wedges, comprising the following steps:

[0071] Step 1, as follows Figure 3 As shown, the processing and control module 8 extracts the initial average position of the laser spot on the pointing monitoring focal plane 7 as A(x). mA ,y mA The principal optical axes of the two optical wedge rotating mechanisms are at corresponding positions Z(x) on the monitoring focal plane 7. Z ,y Z The target for adjusting the laser spot on the monitoring focal plane 7 is unknown, and is O(x). O ,y O ).

[0072] Step 2: Rotate the first optical wedge adjustment mechanism 1 and the second optical wedge adjustment mechanism 2 clockwise by 180° to emit a laser. At this time, the processing and control module 8 extracts the average position of the laser spot pointing on the monitoring focal plane 7 as B(x). mB ,y mB ).like Figure 4 As shown, at this time, the principal optical axes of the two optical wedge rotating mechanisms are at the corresponding positions Z(x) on the monitoring focal plane 7. Z ,y Z The calculation formula is:

[0073]

[0074] Step 3: Rotate the first optical wedge adjustment mechanism 1 clockwise. Simultaneously, the second optical wedge adjustment mechanism 2 rotates counterclockwise. When a laser is emitted, the processing and control module 8 extracts the average position of the laser spot on the monitoring focal plane 7 as C(x). mC ,y mC ).

[0075] Step 4: Calculate the angles according to formulas (6), (7), and (8).

[0076]

[0077] in, These represent the rotation angles required to adjust from B to Z, from B to O, and from Z to O, respectively; n is the refractive index of the optical wedge; α is the apex angle of the optical wedge; K is the beam expansion factor; F is the focal length of the pointing monitoring lens 6; and L... AB L OZ L BZ L OB The straight-line distance between the centers of the light spots pointing to the monitoring focal plane 7 is expressed as follows:

[0078]

[0079] Step 5: Calculate the following judgment criteria:

[0080]

[0081] x O ′=x O (y mB -y Z )+y O (x Z -x mB )+x mB y Z -x Z y mB (11)

[0082] Step 6: Calculate the clockwise rotation angle of the first optical wedge adjustment mechanism 1 according to formulas (12) and (13). Second optical wedge adjustment mechanism 2 rotates clockwise. Rotate the two optical wedge adjustment mechanisms to move the center of the laser spot pointing in the monitoring focal plane 7 to the target position O(x). O ,y O ).

[0083]

[0084] The present invention will be further described below with reference to the embodiments.

[0085] Example 1

[0086] like Figure 5 As shown, the calibration-free dual-wedge high-precision pointing adjustment device in this embodiment consists of a first wedge adjustment mechanism 1, a second wedge adjustment mechanism 2, a beam expander 3, a corner reflection light guide prism 4, a diffraction beam splitter module 5, a pointing monitoring lens 6, a pointing monitoring focal plane 7, and a processing and control module 8.

[0087] The laser operates at a wavelength of 1064 nm. The emitted laser light sequentially passes through optical wedge adjustment mechanism 1, optical wedge adjustment mechanism 2, beam expander 3, corner reflection light guide prism 4, diffraction beam splitting module 5, and pointing monitoring lens 6 before reaching pointing monitoring focal plane 7, where a laser spot is formed. The diffraction beam splitting module 5 splits the single laser beam into nine beams with an angle of 0.1° between each other. The pointing monitoring lens 6 has a focal length of 350 mm. The angular distribution of the nine laser beams and their spot distribution on the area array detector 7 are shown below. Figure 6 .

[0088] According to formula (1), the centroid distribution of the monitoring focal spot is extracted, and the pointing information of the laser to be tested can be obtained from formulas (2) and (3). If the laser pointing angle error corresponding to the centroid of a single spot is Δθ, then according to formula (4), the laser pointing angle error corresponding to the centroids of 9 spots is Δθ / 3.

[0089] The apex angles of both the first and second optical wedge adjustment mechanisms 1 and 2 are 1.2°, and their refractive index for a wavelength of 1064nm is 1.45. The beam expander 3 has a beam expansion factor K = 10. Given that the rotation angle controls the resolution by 0.5°, the dual-wedge adjustment resolution can be better than 200urad, while the system's adjustment accuracy is better than 20urad.

[0090] At this point, the position O(x) of target O on the monitoring focal plane 7 is given. O ,y O Then, according to steps 1 to 6 of the present invention, the laser spot can be adjusted to the target position O(x). O ,y O ).

[0091] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

[0092] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A calibration-free dual-wedge high-precision pointing adjustment device, comprising a laser emitting a single-wavelength collimated laser, characterized in that, The first optical wedge adjustment mechanism (1), the second optical wedge adjustment mechanism (2), the beam expander (3), the corner cube reflector (4), the diffraction beam splitting module (5), the pointing monitoring lens (6), the pointing monitoring focal plane (7) and the processing and control module (8); The first optical wedge adjustment mechanism (1) and the second optical wedge adjustment mechanism (2) are the same in structure, and deflect the direction of the collimated laser around the light-emitting optical axis of the laser in three-dimensional space through refraction and rotation; The beam expander (3) is used for thickening the laser beam and compressing the divergence angle; The corner cube reflector (4) is used for turning a laser beam in the completely opposite direction; The diffraction beam splitting module (5) is used for splitting a laser beam into multiple laser beams according to a specific included angle distribution; The pointing monitoring lens (6) is used for imaging and focusing multiple laser beams in different directions on the pointing monitoring focal plane (7); The pointing monitoring focal plane (7) is a surface array detector installed on the focal plane of the pointing monitoring lens (6) and can detect a laser spot image corresponding to the laser beam; The processing and control module (8) extracts the centroid according to the laser spot on the pointing monitoring focal plane (7), calculates the pointing data of the laser emitted from the beam expander (3), calculates the deviation of the pointing data from the pointing adjustment target input to the processing and control module (8), and then calculates the adjustment amount of the rotation of the first optical wedge adjustment mechanism (1) and the second optical wedge adjustment mechanism (2), so as to control the rotation of the first optical wedge adjustment mechanism (1) and the second optical wedge adjustment mechanism (2) and make the pointing of the laser reach the adjustment target value.

2. The no-scale dual-optical-wedge high-precision pointing adjustment device according to claim 1, characterized in that, The corner cube reflector (4) supports full-aperture light collection or partial light collection.

3. The no-scale dual-optical-wedge high-precision pointing adjustment device according to claim 1, characterized in that, The beam expander (3) is a transmissive beam expander or a reflective beam expander.

4. The no-scale dual-optical-wedge high-precision pointing adjustment device according to claim 1, characterized in that, The corner cube reflector (4) is an angular reflector or a special-shaped angular reflector with a cut-off top corner.

5. The no-scale dual-optical-wedge high-precision pointing adjustment device according to claim 1, characterized in that, The diffraction beam splitting module (5) is any one of a DOE element, a birefringent light splitting element and a metasurface lens element.

6. A non-calibrated dual-wedge high-precision pointing adjustment method based on the device according to any one of claims 1 to 5, characterized in that, The method comprises the following steps: The processing and control module (8) extracts the initial average position of the laser spot on the monitoring focal plane (7) as A(x mA ,y mA ), the corresponding positions of the main optical axes of the two optical wedge rotating mechanisms on the monitoring focal plane (7) are unknown as Z(x Z ,y Z ), and the adjustment target of the laser spot on the monitoring focal plane (7) is O(x O ,y O ). Rotate the first optical wedge adjustment mechanism (1) and the second optical wedge adjustment mechanism (2) clockwise by 180°, emit laser light, at this time, the processing and control module (8) extracts the average position of the laser light spot on the pointing monitoring focal plane (7) as B(x mB ,y mB ), and calculates the corresponding positions Z(x Z ,y Z ) of the main optical axes of the two optical wedge rotating mechanisms on the pointing monitoring focal plane (7) according to A(x mA ,y mA ) and B(x mB ,y mB ). Rotate the first optical wedge adjustment mechanism (1) clockwise At the same time, rotate the second optical wedge adjustment mechanism (2) counterclockwise Emit laser light, at this time, the processing and control module (8) extracts the average position of the laser spot on the pointing monitoring focal plane (7) as C(x mC ,y mC ) Rotation angle required for B to rotate to Z Rotation angle required for B to rotate to O Rotation angle required for Z to rotate to O The following judgment criteria are calculated: x O ′= x O (y mB -y Z )+y O (x Z -x mB )+x mB y Z -x Z y mB Calculate the clockwise rotation angle of the first optical wedge adjustment mechanism (1) and the clockwise rotation angle of the second optical wedge adjustment mechanism (2) Rotate both optical wedge adjustment mechanisms to move the pointing monitor focal plane (7) in the center of the laser spot to the target position O(x O ,y O ) 7. The method of claim 6, wherein, The 8. The method of claim 6, wherein, Z(x Z ,y Z The calculation formula is:

9. The method of claim 6, wherein, Rotation angle is calculated as follows: where n is the refractive index of the wedge, a is the apex angle of the wedge, K is the beam expansion factor, F is the focal length of the pointing monitor lens (6), L AB , L OZ , L BZ , L OB is the straight-line distance between the centers of the spots in the pointing monitor focal plane (7), and is given by:

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