Wide-field light-combining fiber array three-degree-of-freedom heterodyne interferometer device and method

Abstract

The present application belongs to the technical field of laser interference measurement, and provides a wide-range light-combining type fiber array three-degree-of-freedom heterodyne interference device and method, which comprises a double-frequency laser, a wide-range light-combining type heterodyne interferometer, a low-noise photoelectric conversion unit, a signal output unit and an upper computer. The present application combines two beams of light with different frequencies and mutually orthogonal polarization directions into double-frequency orthogonal polarization light through a first polarization splitting device, and forms a wide-range light-combining heterodyne interference light field in the fiber array receiving plane through a wide-range interference light-combining unit, so that the fiber array can perform multi-point receiving in the same interference light field. The present application is adapted to the power of the double-frequency light source, the collimating output conditions, the light splitting ratio, the polarization plate setting and the photoelectric conversion unit according to the characteristics of low-coupling receiving of the fiber array, which is conducive to improving the signal-to-noise ratio and stability of the heterodyne signals of each channel under weak coupling conditions.

Description

Technical Field

[0001] This invention belongs to the field of laser interferometry technology, specifically relating to a wide-range optical fiber array three-degree-of-freedom heterodyne interferometry device and method. Background Technology

[0002] Heterodyne laser interferometry has advantages such as high resolution, strong anti-interference ability, easy phase demodulation and suitability for dynamic measurement, and has been widely used in fields such as precision displacement measurement, attitude detection and position feedback of ultra-precision motion platforms.

[0003] In precision motion measurement, systems often need to obtain not only axial displacement but also attitude information such as pitch and yaw angles. Traditional multi-degree-of-freedom measurement schemes typically employ multiple measurement optical paths, resulting in complex structures, difficult adjustments, and large space requirements. Single-beam three-degree-of-freedom heterodyne interferometry schemes can provide axial displacement and angular information using a single measurement beam, which helps reduce optical path complexity and is suitable for miniaturized and integrated measurement systems.

[0004] In this type of measurement scheme, fiber optic arrays can serve as multi-point receiving units. The incident end faces of each fiber channel are arranged at different positions in the interference light field to acquire the heterodyne signal at the corresponding position. Compared with area array detectors, fiber optic arrays are more compact and easier to integrate. They can transmit the light collected at the receiving end to the remote photoelectric conversion unit and keep the heat-generating devices such as the photoelectric conversion unit and signal processing circuits away from the measurement end. Therefore, they are suitable for compact, ultra-precision three-degree-of-freedom interferometric measurement devices.

[0005] However, fiber array reception is limited by both fiber coupling efficiency and optical field coverage. Due to the limited core diameter and numerical aperture of a single fiber channel, its effective receiving area for the interference optical field is small. In cases of insufficient incident light power, spot position misalignment, or large channel alignment errors, some channels are prone to decreased signal-to-noise ratio, unstable phase demodulation, or even ineffective demodulation. Simultaneously, a certain spacing is required between fiber channels to obtain angular information. Insufficient channel spacing weakens the phase difference at different sampling positions, thus reducing the angle measurement resolution; increased channel spacing requires a larger effective interference area within the receiving plane. If the spot coverage is insufficient, edge channels are prone to being in weak light regions or falling outside the effective interference area. When the target undergoes pitch or yaw motion, the position and intensity distribution of the optical field will also change, further affecting the integrity and stability of the multi-channel signal.

[0006] Existing heterodyne interferometers mostly use single-point detectors or small-area detectors as receivers, and the beam size, beam combining structure, and receiver power configuration are usually designed around the receiving conditions of a single detector. If this type of heterodyne interferometric light field is directly used for fiber optic array reception, problems such as insufficient spot coverage, large differences in received power among channels, degraded signal quality in edge channels, and limited angle measurement range can easily occur.

[0007] To overcome the aforementioned limitations, a heterodyne interference optical field with a large effective coverage area needs to be formed within the receiving plane of the fiber array, ensuring that the incident end faces of multiple fiber channels are all within the receivable and demodulation-capable interference region. Simultaneously, increasing the coverage area of ​​the optical field reduces the light intensity per unit area, and the fiber channels themselves have low coupling efficiency. Therefore, it is also necessary to match the parameters of the heterodyne source power, optical power distribution, and photoelectric conversion unit to ensure that the heterodyne signal of each channel has a sufficient signal-to-noise ratio.

[0008] Therefore, it is necessary to propose a wide-area beam-combining heterodyne interferometer adapted to fiber optic array reception. The "wide-area" in this invention refers to the effective interference region formed within the receiving plane of the fiber optic array after the measurement beam and reference beam are combined, covering the incident end faces of multiple fiber optic channels and capable of covering the range of optical field position changes caused by the pitch or yaw motion of the target under test. Through this wide-area beam-combining method, a stable multi-channel heterodyne signal can be provided for three-degree-of-freedom measurements of fiber optic arrays without increasing the number of independent measurement optical paths. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention provides a wide-area optical combining fiber array three-degree-of-freedom heterodyne interferometry device and method, thereby resolving the issues in the prior art. The technical solution adopted by this invention is as follows: A wide-range optical combining fiber array three-degree-of-freedom heterodyne interferometer includes: a dual-frequency laser, a wide-range optical combining heterodyne interferometer, a low-noise photoelectric conversion unit, a signal output unit, and a host computer; The dual-frequency laser is used to output two laser beams with a fixed frequency difference. The wide-area beam combining heterodyne interferometer includes an optical fiber array with multiple optical fiber channels; the wide-area beam combining heterodyne interferometer is used to collimate, adjust polarization, combine polarization, split reference beams, and combine interference beams of the two laser beams output by the dual-frequency laser, and form a wide-area beam combining heterodyne interference light field in the receiving plane of the optical fiber array. The low-noise photoelectric conversion unit is used to convert the optical signals output from each optical fiber channel into corresponding electrical signals. The signal output unit is used to output the electrical signal, phase information, amplitude information, and status information corresponding to each optical fiber channel; The host computer is used to receive the data output by the signal output unit and to display and record it.

[0010] Furthermore, the wide-range beam combining heterodyne interferometer includes: Collimation and polarization adjustment unit, polarization beam combining unit, adjustable reference beam splitting unit, wide-range interference beam combining unit, and fiber array; The collimation and polarization adjustment unit is used to collimate the two laser beams and adjust them into two polarized beams with mutually orthogonal polarization directions. The polarization combining unit is used to combine two beams of polarized light with mutually orthogonal polarization directions into dual-frequency orthogonal polarized light that propagates in the same direction; The adjustable reference beam splitting unit is used to split the dual-frequency orthogonal polarized light to form orthogonal polarized measurement light entering the interferometric measurement optical path and orthogonal polarized reference light used to form the reference interference signal; The wide-area interferometric combining unit is used to combine the reference beam and the measurement beam after they return, and after polarization analysis, form a wide-area combined heterodyne interference optical field in the receiving plane of the fiber array; the fiber array is used to receive heterodyne signals at different spatial locations in the wide-area combined heterodyne interference optical field.

[0011] Furthermore, the collimation and polarization adjustment unit includes a first collimator, a second collimator, and a polarization adjustment structure; In this dual-frequency laser, one of the two laser beams output is collimated by a first collimator and output as a first frequency laser beam, while the other laser beam is collimated by a second collimator and output as a second frequency laser beam. The polarization adjustment structure is used to adjust the first frequency laser beam and the second frequency laser beam into first polarized light and second polarized light with mutually orthogonal polarization directions, respectively.

[0012] Furthermore, the polarization beam combining unit includes a first polarization beam splitter; the first polarization beam splitter is used to combine the first polarized light and the second polarized light into dual-frequency orthogonal polarized light propagating in the same direction; the dual-frequency orthogonal polarized light includes two beam components with different frequencies and mutually orthogonal polarization directions.

[0013] Furthermore, the adjustable reference beam splitter unit includes a non-polarizing beam splitter, a first polarizer, and an optical fiber coupler; The non-polarization beam splitter is used to split the dual-frequency orthogonally polarized light into orthogonally polarized measurement light and orthogonally polarized reference light; the orthogonally polarized reference light enters the fiber coupler after passing through the first polarizer to form a reference interference signal.

[0014] Furthermore, the wide-area interference beam combining unit includes a second polarization beam splitter, a first quarter-wave plate, a second quarter-wave plate, a reference mirror, a target mirror, and a second polarizer; The second polarization beam splitter is used to split the orthogonally polarized measurement light into a reference beam and a measurement beam according to the polarization direction. The reference beam is incident on the reference mirror after passing through the second quarter-wave plate, and after being reflected by the reference mirror, it returns to the second polarization beam splitter after passing through the second quarter-wave plate again, and is reflected and output at the second polarization beam splitter. The measurement beam is incident on the target reflector after passing through the first quarter-wave plate, and after being reflected by the target reflector, it returns to the second polarization beam splitter after passing through the first quarter-wave plate again, and is transmitted and output at the second polarization beam splitter; the target reflector is used to reflect the measurement beam, and generates corresponding motion with the axial displacement, pitch or yaw motion of the target being measured, so that the returning measurement beam carries the motion information of the target being measured; The return reference beam and the return measurement beam are reflected and transmitted by the second polarization beam splitter and then combined and output. After being analyzed by the second polarizer, they form beam components with the same transmission direction, forming a wide-area combined heterodyne interference optical field in the receiving plane of the fiber array.

[0015] Furthermore, the fiber array includes multiple fiber channels; the incident end face of the fiber channel is disposed within the effective interference region of the wide-area combined heterodyne interference optical field.

[0016] Furthermore, the low-noise photoelectric conversion unit includes a multi-channel low-noise photodetector group; each low-noise photodetector is connected to a corresponding optical fiber channel to convert the optical signal output by each optical fiber channel into a corresponding electrical signal. The low-noise photoelectric conversion unit includes a reference detection channel for receiving a reference interference signal formed by the orthogonally polarized reference light and outputting an electrical reference signal.

[0017] A three-degree-of-freedom heterodyne interferometry method for wide-area optical combining fiber arrays includes: A dual-frequency laser outputs two laser beams with a fixed frequency difference; The collimation and polarization adjustment unit collimates two laser beams with a fixed frequency difference and adjusts them into first polarized light and second polarized light with mutually orthogonal polarization directions. The polarization combining unit combines the first polarized light and the second polarized light into dual-frequency orthogonally polarized light. The adjustable reference beam splitter splits the dual-frequency orthogonally polarized light into orthogonally polarized reference light and orthogonally polarized measurement light. The orthogonally polarized reference light enters the fiber coupler after passing through the first polarizer to form a reference interference signal. The second polarization beam splitter in the wide-area interferometric beam combining unit splits the orthogonally polarized measurement beam into a reference beam and a measurement beam; The reference beam passes through the second quarter-wave plate and is incident on the reference mirror. After being reflected by the reference mirror, it passes through the second quarter-wave plate again and returns to the second polarization beam splitter, and is reflected and output by the second polarization beam splitter. The measurement beam passes through the first quarter-wave plate and is incident on the target mirror. After being reflected by the target mirror, it passes through the first quarter-wave plate again and returns to the second polarization beam splitter, and is then transmitted and output by the second polarization beam splitter. The return reference beam and the return measurement beam are reflected and transmitted by the second polarization beam splitter and then combined and output. After being analyzed by the second polarizer, they form beam components with the same transmission direction, forming a wide-area combined heterodyne interference optical field in the receiving plane of the fiber array. Multiple fiber channels of the fiber array receive heterodyne signals at different spatial locations in the wide-area combined heterodyne interference optical field; The low-noise photoelectric conversion unit converts the optical signals output from each fiber optic channel into corresponding electrical signals. The signal output unit outputs the electrical signal, phase information, amplitude information, and status information corresponding to each optical fiber channel; The host computer receives the data output by the signal output unit and displays and records it.

[0018] The present invention has the following beneficial effects: (1) The present invention combines two beams of light with different frequencies and orthogonal polarization directions into dual-frequency orthogonal polarized light through a first polarization beam splitter, and forms a wide-domain combined heterodyne interference light field in the receiving plane of the fiber array through a wide-domain interference beam combining unit, so that the fiber array can perform multi-point reception in the same interference light field.

[0019] (2) By setting up a second polarization beam splitter, a first quarter-wave plate, a second quarter-wave plate, a reference mirror, a target mirror, and a second polarizer, the present invention enables the returned reference beam and the measurement beam to be combined and output, and after being polarized by the second polarizer, beam components with the same transmission direction are formed, thereby forming a receivable and demodulated heterodyne interference light field on the receiving plane of the fiber array.

[0020] (3) By setting an adjustable reference beam splitter, the optical power entering the interferometric measurement optical path and the optical power forming the reference interference signal can be allocated according to a predetermined ratio. When the optical fiber array requires a large optical power, the optical power entering the interferometric measurement optical path can be increased, which is beneficial to improving the received signal quality of each optical fiber channel under low coupling conditions.

[0021] (4) The present invention enables the effective interference region of the wide-area combined heterodyne interference optical field to cover the incident end face of multiple optical fiber channels, and can cover the range of optical field position changes caused by the pitch or yaw motion of the target under test; while the optical fiber channels maintain a predetermined spatial spacing, each channel can still receive an effective heterodyne signal, which is beneficial to balance the angle measurement resolution and the angle measurement range.

[0022] (5) In view of the characteristics of low coupling reception of fiber array, the present invention adapts the power of dual frequency light source, collimation output conditions, beam splitting ratio, polarizer setting and photoelectric conversion unit, which is beneficial to improve the signal-to-noise ratio and stability of heterodyne signals of each channel under weak coupling conditions.

[0023] (6) Unlike heterodyne interferometers designed for small-area detectors, this invention configures the effective interference region, beam splitting ratio, polarization combining structure and low-noise photoelectric conversion unit with the receiving requirements of fiber array as constraints, so that the heterodyne interferometer light field can adapt to the receiving requirements of multi-channel fiber array. Attached Figure Description

[0024] Figure 1 This is a structural diagram of the present invention; Figure 2 A schematic diagram of the mechanical mounting structure of a wide-area beam combining heterodyne interferometer; Figure 3 This is a schematic diagram of the optical path of a wide-area beam combining heterodyne interferometer; Figure 4 A schematic diagram illustrating the matching relationship between the wide-area combined heterodyne interference optical field and the receiving region of the fiber array; Explanation of reference numerals in the attached figures: Figure 1 In the middle section: 1. Dual-frequency laser; 2. Wide-range beam combining heterodyne interferometer; 3. Low-noise photoelectric conversion unit; 4. Signal output unit; 5. Host computer; Figure 2 In the middle: 21 Collimator mounting bracket; 22 Beam splitter mounting bracket; 23 Waveplate mounting bracket; 24 Optical component mounting ring; 25 Mirror mounting bracket; 26 Fiber optic coupler mounting bracket; 27 Fiber optic array mounting bracket; 28 Polarizer mounting bracket; 29 Integrated mounting substrate; Figure 3 In the middle: 31 First collimator; 32 Second collimator; 33 First polarization beam splitter; 34 Unpolarization beam splitter; 35 Second polarization beam splitter; 36 First polarizer; 37 Second polarizer; 38 Fiber coupler; 39 Fiber array; 40 First quarter-wave plate; 41 Second quarter-wave plate; 42 Target mirror; 43 Reference mirror; 44 First frequency laser beam; 45 Second frequency laser beam; 46 First polarized light; 47 Second polarized light; 48 Dual-frequency orthogonal polarized light; 49 Orthogonal polarization measurement light; 50 Orthogonal polarization reference light; 51 Reference beam; 52 Returning reference beam; 53 Measurement beam; 54 Returning measurement beam; 55 Wide-range combined heterodyne interference field; Figure 4 D: Effective coverage size; P: Fiber array receiving area size; S: Spacing between adjacent fiber channels. Detailed Implementation

[0025] The following will be described in conjunction with embodiments of the present invention. Figures 1-4 The technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0026] like Figure 1 , Figure 3 This invention proposes a wide-area beam-combining fiber array three-degree-of-freedom heterodyne interferometry device, which enables the measurement beam 53 and the reference beam 51 to form a wide-area beam-combining heterodyne interferometry optical field 55 in the receiving plane of the fiber array 39. The wide-area beam-combining heterodyne interferometry optical field 55 can cover the incident end faces of multiple fiber channels; including: 1. Dual-frequency laser, 2. Wide-range beam combining heterodyne interferometer, 3. Low-noise photoelectric conversion unit, 4. Signal output unit, and 5. Host computer.

[0027] The dual-frequency laser 1 is used to output two laser beams with a fixed frequency difference.

[0028] The wide-range beam combining heterodyne interferometer 2 includes a collimation and polarization adjustment unit, a polarization beam combining unit, an adjustable reference beam splitting unit, a wide-range interference beam combining unit, and an optical fiber array 39. The wide-range beam combining heterodyne interferometer 2 is used to collimate, adjust, combine, reference-split, and interfere with the two laser beams with a fixed frequency difference, forming a wide-range beam combining heterodyne interference light field 55 within the receiving plane of the optical fiber array 39.

[0029] The collimation and polarization adjustment unit includes a first collimator 31, a second collimator 32, and a polarization adjustment structure. The first collimator 31 is used to collimate the output of a first frequency laser beam 44, and the second collimator 32 is used to collimate the output of a second frequency laser beam 45. The polarization adjustment structure is used to adjust the first frequency laser beam 44 and the second frequency laser beam 45 into first polarized light 46 and second polarized light 47 with mutually orthogonal polarization directions, respectively. In one embodiment, the first polarized light 46 is p-polarized light, and the second polarized light 47 is s-polarized light.

[0030] The polarization beam combining unit includes a first polarization beam splitter 33. The first polarization beam splitter 33 is used to combine the first polarized light 46 and the second polarized light 47 into a dual-frequency orthogonal polarized light 48 that propagates in the same direction. The dual-frequency orthogonal polarized light 48 includes two beam components with different frequencies and mutually orthogonal polarization directions.

[0031] The adjustable reference beam splitter unit includes a non-polarized beam splitter 34, a first polarizer 36, and an optical fiber coupler 38. The non-polarized beam splitter 34 splits the dual-frequency orthogonally polarized light 48 into orthogonally polarized measurement light 49 and orthogonally polarized reference light 50. The orthogonally polarized reference light 50 enters the optical fiber coupler 38 after passing through the first polarizer 36 to form a reference interference signal.

[0032] The non-polarized beam splitter 34 has a predetermined transmission-to-reflection ratio. This predetermined ratio is determined based on the optical power required by the fiber array 39 and the optical power required by the reference interference signal. In one embodiment, the transmission ratio of the non-polarized beam splitter 34 is greater than its reflection ratio, allowing more optical power to enter the subsequent interferometric measurement optical path to meet the low-coupling reception requirements of the fiber array for incident light power. The non-polarized beam splitter 34 can be a non-polarized beam splitter prism, a non-polarized beam splitter, or other optical devices capable of splitting light according to the predetermined transmission-to-reflection ratio.

[0033] The wide-area interference beam combining unit includes a second polarization beam splitter 35, a first quarter-wave plate 40, a second quarter-wave plate 41, a reference mirror 43, a target mirror 42, and a second polarizer 37. The second polarization beam splitter 35 is used to split the orthogonally polarized measurement light 49 into a reference beam 51 and a measurement beam 53 according to the polarization direction.

[0034] The reference beam 51 passes through the second quarter-wave plate 41 and is incident on the reference mirror 43. After being reflected by the reference mirror 43, it passes through the second quarter-wave plate 41 again and returns to the second polarization beam splitter 35. Since the reference beam 51 passes through the second quarter-wave plate 41 twice, its polarization direction is reversed when it returns to the second polarization beam splitter 35, and it is reflected and output at the second polarization beam splitter 35.

[0035] The measurement beam 53, after passing through the first quarter-wave plate 40, is incident on the target reflector 42, and after being reflected by the target reflector 42, returns to the second polarization beam splitter 35 via the first quarter-wave plate 40 again. The target reflector 42 reflects the measurement beam and moves accordingly with the axial displacement, pitch, or yaw motion of the target being measured, causing the returning measurement beam 54 to carry the motion information of the target being measured. After being reflected by the target reflector 42, the measurement beam 53 carries the phase change caused by the motion of the target being measured. Because the measurement beam 53 passes through the first quarter-wave plate 40 twice, its polarization direction is reversed when it returns to the second polarization beam splitter 35, and it is transmitted and output at the second polarization beam splitter 35.

[0036] The returning reference beam 52 and the returning measurement beam 54 are reflected and transmitted by the second polarization beam splitter 35, respectively, and then combined. After being analyzed by the second polarizer 37, they form beam components with the same transmission direction, creating a wide-area combined heterodyne interference optical field 55 within the receiving plane of the fiber array 39. This wide-area combined heterodyne interference optical field 55 has an effective interference region covering the incident end faces of multiple fiber channels and can cover the range of optical field position changes caused by the pitch or yaw motion of the target being measured. The effective interference region is jointly determined by the output beam size and divergence angle of the first collimator 31 and the second collimator 32, the beam combining position of the second polarization beam splitter 35, the position of the second polarizer 37, and the position of the receiving plane of the fiber array 39.

[0037] like Figure 4 As shown, the wide-area combined heterodyne interference optical field 55 has an effective coverage size D within the receiving plane of the fiber array, the receiving area of ​​the fiber array has a receiving area size P, and there is a spacing S between adjacent fiber channels. The effective coverage size D is set to cover the receiving area of ​​the fiber array. Preferably, the effective coverage size D is determined based on the receiving area size P of the fiber array and the range of optical field position changes caused by the change in the angle of the target under test, so that when the target under test moves within a predetermined pitch or yaw range, the incident end face of each fiber channel remains within the effective interference area.

[0038] The receiving unit of the fiber array 39 includes multiple fiber channels. The incident end faces of the multiple fiber channels are disposed within the effective interference region of the wide-area combined heterodyne interference optical field 55, and are distributed according to a predetermined two-dimensional spatial position relationship, for receiving heterodyne signals at different spatial positions respectively.

[0039] The low-noise photoelectric conversion unit 3 includes a multi-channel low-noise photodetector group. Each low-noise photodetector is connected to a corresponding optical fiber channel to convert the optical signal output from each optical fiber channel into a corresponding electrical signal. The low-noise photoelectric conversion unit 3 may also include a reference detection channel for receiving the reference interference signal formed by the orthogonally polarized reference light 50 and outputting an electrical reference signal.

[0040] The signal output unit 4 includes a phase processing board or a multi-channel signal output interface, used to output electrical signals, phase information, amplitude information or status information corresponding to each channel.

[0041] The host computer 5 is used to receive the data output by the signal output unit 4, and to display, record or provide it to the subsequent processing unit.

[0042] Furthermore, the first polarization beam splitter 33 and the second polarization beam splitter 35 may be polarization beam splitters, polarization beam splitters, or other polarization beam splitters that can split or combine beams according to the polarization direction.

[0043] Furthermore, the non-polarized beam splitter 34 can be a non-polarized beam splitter prism, a non-polarized beam splitter plate, or other optical devices capable of splitting light according to a predetermined transmission-to-reflection ratio. Preferably, the transmission ratio of the non-polarized beam splitter 34 is greater than the reflection ratio, in order to increase the optical power entering the interferometric measurement optical path and meet the low coupling efficiency requirements of the fiber array 39 for incident optical power.

[0044] Furthermore, the transmittance-to-reflection ratio of the non-polarized beam splitter 34 can be determined based on the number of fiber channels in the receiving unit of the fiber array 39, the fiber coupling efficiency, the coverage size of the effective interference region, the detection sensitivity of the low-noise photoelectric conversion unit 3, and the optical power required for the reference interference signal.

[0045] Furthermore, the first polarizer 36 is used to allow the two orthogonal polarization components in the reference interference signal light to pass through the same transmission direction, thereby forming a detectable reference interference signal. The second polarizer 37 is used to allow the combined reference beam 51 and the measurement beam 53 to pass through the same transmission direction, thereby forming a heterodyne interference light field that can be received by the fiber array 39 within the receiving plane of the fiber array 39.

[0046] Furthermore, the output beam size and divergence angle of the first collimator 31 and the second collimator 32 are determined based on the receiving area size of the fiber array 39, the fiber channel spacing, the allowable angle variation range of the target reflector 42, and the required effective interference area at the receiving plane.

[0047] Furthermore, the effective coverage size of the wide-area combined heterodyne interference optical field 55 within the receiving plane of the fiber array 39 is set to cover the receiving area of ​​the fiber array 39 formed by the incident end faces of multiple fiber channels. Preferably, the effective coverage size is determined based on the receiving area size of the fiber array 39 and the range of optical field position changes caused by the angle change of the target under test, so that when the target under test moves within a predetermined pitch or yaw range, the incident end face of each fiber channel remains within the effective interference area.

[0048] Furthermore, the plurality of fiber optic channels can be distributed in a cross array, rectangular array, ring array, triangular array, or other non-collinear two-dimensional spatial positional relationship suitable for three-degree-of-freedom measurements. The spacing between the plurality of fiber optic channels is determined based on the angle measurement resolution requirements, angle measurement range, coverage size of the effective interference region, and channel reception signal-to-noise ratio.

[0049] Furthermore, the low-noise photoelectric conversion unit 3 has a low-noise amplifier circuit suitable for detecting weak fiber-coupled signals, which is used to improve the signal-to-noise ratio of heterodyne signals in each channel under low coupling efficiency conditions.

[0050] Furthermore, the signal output unit 4 is used to provide multi-channel heterodyne signal output and output the heterodyne signal, phase information, amplitude information or status information of each channel to the subsequent processing unit; like Figure 2 As shown, the wide-area beam combining heterodyne interferometer 2 adopts an integrated mechanical mounting structure. The optical components in the wide-area beam combining heterodyne interferometer 2 are mounted and maintain a predetermined relative positional relationship through corresponding fixing structures. The collimator mounting bracket 21, beam splitter mounting bracket 22, waveplate mounting bracket 23, optical component fixing ring 24, mirror mounting bracket 25, fiber coupler mounting bracket 26, fiber array mounting bracket 27, and polarizer mounting bracket 28 are all mounted on the integrated mounting substrate 29.

[0051] Specifically, the first collimator 31 and the second collimator 32 are fixed by the collimator mounting bracket 21; the first polarization beam splitter 33, the unpolarization beam splitter 34 and the second polarization beam splitter 35 are fixed by the beam splitter mounting bracket 22; the first quarter-wave plate 40 and the second quarter-wave plate 41 are fixed by the wave plate mounting bracket 23; the first polarizer 36 and the second polarizer 37 are fixed by the polarizer mounting bracket 28 and the optical device mounting ring 24; the target reflector 42 and the reference reflector 43 are fixed by the reflector mounting bracket 25; the fiber optic coupler 38 is fixed by the fiber optic coupler mounting bracket 26; and the fiber optic array 39 is fixed by the fiber optic array mounting bracket 27.

[0052] Through the aforementioned mechanical mounting structure, the collimator, beam splitter, waveplate, polarizer, mirror, fiber coupler, and fiber array can be integrated into the wide-area beam combining heterodyne interferometer 2, thereby improving the compactness of the optical path structure and the stability of their relative positions. The specific shape, connection method, and installation position of each mounting bracket can be adjusted according to the actual optical path layout, as long as the corresponding optical components are fixed and their relative positions are maintained.

[0053] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications, alterations, alterations, or substitutions made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A wide-range optical combining fiber array three-degree-of-freedom heterodyne interferometer, characterized in that, include: Dual-frequency laser (1), wide-range beam combining heterodyne interferometer (2), low-noise photoelectric conversion unit (3), signal output unit (4), and host computer (5); The dual-frequency laser (1) is used to output two laser beams with a fixed frequency difference; The wide-area beam combining heterodyne interferometer (2) includes an optical fiber array (39) with multiple optical fiber channels; the wide-area beam combining heterodyne interferometer (2) is used to collimate, adjust polarization, combine polarization, split reference beams and combine interference beams of the two laser beams output by the dual-frequency laser (1), and form a wide-area beam combining heterodyne interference light field (55) in the receiving plane of the optical fiber array (39). The low-noise photoelectric conversion unit (3) is used to convert the optical signals output by each optical fiber channel into corresponding electrical signals; The signal output unit (4) is used to output the electrical signal, phase information, amplitude information and status information corresponding to each optical fiber channel; The host computer (5) is used to receive the data output by the signal output unit (4) and to display and record it.

2. The wide-area optical combining fiber array three-degree-of-freedom heterodyne interferometer according to claim 1, characterized in that, The wide-range beam combining heterodyne interferometer (2) includes: Collimation and polarization adjustment unit, polarization beam combining unit, adjustable reference beam splitting unit, wide-area interference beam combining unit and fiber array (39). The collimation and polarization adjustment unit is used to collimate the two laser beams and adjust them into two polarized beams with mutually orthogonal polarization directions. The polarization combining unit is used to combine two beams of polarized light with mutually orthogonal polarization directions into dual-frequency orthogonal polarized light that propagates in the same direction; The adjustable reference beam splitting unit is used to split the dual-frequency orthogonal polarized light to form orthogonal polarized measurement light entering the interferometric measurement optical path and orthogonal polarized reference light used to form the reference interference signal; The wide-area interference beam combining unit is used to combine the reference beam and the measurement beam after they return, and after polarization analysis, form a wide-area beam combining heterodyne interference field (55) in the receiving plane of the fiber array (39); the fiber array (39) is used to receive heterodyne signals at different spatial positions in the wide-area beam combining heterodyne interference field (55).

3. The wide-area optical combining fiber array three-degree-of-freedom heterodyne interferometer according to claim 2, characterized in that, The collimation and polarization adjustment unit includes a first collimator (31), a second collimator (32), and a polarization adjustment structure; Among them, one of the two laser beams output by the dual-frequency laser (1) is collimated by the first collimator (31) and output as the first frequency laser beam (44), and the other laser beam is collimated by the second collimator (32) and output as the second frequency laser beam (45). The polarization adjustment structure is used to adjust the first frequency laser beam (44) and the second frequency laser beam (45) into first polarized light (46) and second polarized light (47) with mutually orthogonal polarization directions, respectively.

4. The wide-range optical combining fiber array three-degree-of-freedom heterodyne interferometer according to claim 3, characterized in that, The polarization beam combining unit includes a first polarization beam splitter (33); the first polarization beam splitter (33) is used to combine the first polarized light (46) and the second polarized light (47) into a dual-frequency orthogonal polarized light (48) that propagates in the same direction; the dual-frequency orthogonal polarized light (48) includes two beam components with different frequencies and mutually orthogonal polarization directions.

5. A wide-area optical combining fiber array three-degree-of-freedom heterodyne interferometer according to claim 4, characterized in that, The adjustable reference beam splitter unit includes a non-polarized beam splitter (34), a first polarizer (36), and an optical fiber coupler (38). The non-polarized beam splitter (34) is used to split the dual-frequency orthogonally polarized light (48) into orthogonally polarized measurement light (49) and orthogonally polarized reference light (50); the orthogonally polarized reference light (50) enters the fiber coupler (38) after passing through the first polarizer (36) to form a reference interference signal.

6. The wide-area optical combining fiber array three-degree-of-freedom heterodyne interferometer according to claim 5, characterized in that, The wide-area interference beam combining unit includes a second polarization beam splitter (35), a first quarter-wave plate (40), a second quarter-wave plate (41), a reference mirror (43), a target mirror (42), and a second polarizer (37). The second polarization beam splitter (35) is used to split the orthogonally polarized measurement light (49) into a reference beam (51) and a measurement beam (53) according to the polarization direction. The reference beam (51) is incident on the reference mirror (43) after passing through the second quarter-wave plate (41), and after being reflected by the reference mirror (43), it returns to the second polarization beam splitter (35) through the second quarter-wave plate (41) and is reflected and output at the second polarization beam splitter (35); The measurement beam (53) is incident on the target reflector (42) after passing through the first quarter-wave plate (40), and after being reflected by the target reflector (42), it returns to the second polarization beam splitter (35) through the first quarter-wave plate (40) and is transmitted and output at the second polarization beam splitter (35); the target reflector (42) is used to reflect the measurement beam and generates corresponding motion with the axial displacement, pitch or yaw motion of the target being measured, so that the returning measurement beam (54) carries the motion information of the target being measured; The return reference beam (52) and the return measurement beam (54) are reflected and transmitted by the second polarization beam splitter (35) respectively, and then combined and output. After being analyzed by the second polarizer (37), they form beam components with the same transmission direction, forming a wide-area combined heterodyne interference optical field (55) in the receiving plane of the fiber array (39).

7. A wide-area optical combining fiber array three-degree-of-freedom heterodyne interferometer according to any one of claims 1-6, characterized in that, The fiber array (39) includes multiple fiber channels; the incident end face of the fiber channel is located within the effective interference region of the wide-area combined heterodyne interference field (55).

8. A wide-range optical combining fiber array three-degree-of-freedom heterodyne interferometer according to claim 5, characterized in that, The low-noise photoelectric conversion unit (3) includes a multi-channel low-noise photodetector group; each low-noise photodetector is connected to a corresponding optical fiber channel to convert the optical signal output by each optical fiber channel into a corresponding electrical signal. The low-noise photoelectric conversion unit (3) includes a reference detection channel for receiving a reference interference signal formed by the orthogonally polarized reference light (50) and outputting an electrical reference signal.

9. A three-degree-of-freedom heterodyne interferometry method for wide-area optical combining fiber arrays, characterized in that, A wide-area optical combining fiber array three-degree-of-freedom heterodyne interferometer based on any one of claims 1-8 comprises: The dual-frequency laser (1) outputs two laser beams with a fixed frequency difference; The collimation and polarization adjustment unit collimates two laser beams with a fixed frequency difference and adjusts them into first polarized light (46) and second polarized light (47) with mutually orthogonal polarization directions. The polarization combining unit combines the first polarized light (46) and the second polarized light (47) into dual-frequency orthogonal polarized light (48). The adjustable reference beam splitter splits the dual-frequency orthogonally polarized light (48) into orthogonally polarized reference light (50) and orthogonally polarized measurement light (49). The orthogonally polarized reference light (50) enters the fiber coupler (38) after passing through the first polarizer (36) to form a reference interference signal. The second polarization beam splitter (35) in the wide-area interference beam combining unit splits the orthogonally polarized measurement beam (49) into a reference beam (51) and a measurement beam (53). The reference beam (51) is incident on the reference mirror (43) after passing through the second quarter-wave plate (41), and after being reflected by the reference mirror (43), it passes through the second quarter-wave plate (41) again and returns to the second polarization beam splitter (35), and is reflected and output by the second polarization beam splitter (35); The measurement beam (53) is incident on the target mirror (42) after passing through the first quarter-wave plate (40), and after being reflected by the target mirror (42), it passes through the first quarter-wave plate (40) again and returns to the second polarization beam splitter (35), and is transmitted and output by the second polarization beam splitter (35); The return reference beam (52) and the return measurement beam (54) are reflected and transmitted by the second polarization beam splitter (35) respectively, and then combined and output. After being analyzed by the second polarizer (37), they form beam components with the same transmission direction, forming a wide-area combined heterodyne interference optical field (55) in the receiving plane of the fiber array (39). Multiple fiber channels of the fiber array (39) respectively receive heterodyne signals at different spatial locations in the wide-area combined heterodyne interference optical field (55); The low-noise photoelectric conversion unit (3) converts the optical signals output from each optical fiber channel into corresponding electrical signals; The signal output unit (4) outputs the electrical signal, phase information, amplitude information, and status information corresponding to each optical fiber channel; The host computer (5) receives the data output by the signal output unit (4) and displays and records it.

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