Interference signal detection system and method based on light beam interference fringes and photoelectric detector group

Abstract

The invention discloses an interference signal detection system and method based on light beam interference fringes and a photoelectric detector group, and belongs to the technical field of optical measurement and photoelectric detection, the system uses interference fringes generated by overlapping two beams of coherent parallel light in space, and the fringe spacing is controlled by adjusting the included angle between the two beams of parallel light. When the fringe spacing and the spacing of a single photoelectric detector in the photoelectric detector group arranged in the overlapping interference area meet a specific relationship, the system can obtain an orthogonal interference signal. The system is compact in structure, the defects that a traditional interference signal receiving unit is large in size, large in number of optical elements, low in integration level and high in cost are overcome, the integration level of an interference measurement system is improved, and miniaturization and low-cost integration of an interference signal detection system are achieved.

Description

Technical Field

[0001] This invention belongs to the field of optical measurement and photoelectric detection technology, specifically relating to an interference signal detection system and method based on beam interference fringes and photoelectric detector groups, which is particularly suitable for high-precision interferometric measurement applications such as displacement measurement and vibration detection. Background Technology

[0002] Interferometric measurement technology is widely used in displacement measurement, vibration detection and other fields due to its advantages such as high precision, high resolution and non-contact measurement. Traditional interferometric signal detection units usually use a four-channel beam splitting and phase shifting detection module to obtain orthogonal interferometric signals. Although the common-mode DC bias can be effectively eliminated through differential operation to achieve nonlinear error compensation and noise reduction, it has the disadvantages of large size and difficulty in system integration and miniaturization. In addition, this unit mainly relies on a polarization beam splitter, which introduces two major problems: (1) polarization crosstalk: the polarization beam splitter cannot completely separate orthogonal polarized light, resulting in polarization aliasing and reducing signal quality; (2) energy imbalance: the energy imbalance between transmitted and reflected light introduces additional nonlinear errors. Moreover, obtaining orthogonal signals requires multi-channel beam splitting and additional optical components, resulting in complex assembly and high cost. In order to solve the problems of complex optical structure, high cost and difficult integration of interferometric signal detection in traditional interferometric measurement, a system with simple structure, high integration and easy realization of orthogonal interferometric signal detection is proposed. Summary of the Invention

[0003] This invention provides an interference signal detection system and method based on beam interference fringes and a photodetector array. The system forms interference fringes by overlapping two coherent beams in space and directly detects the overlapping interference field using a photodetector array to obtain orthogonal interference signals, thereby improving the system's compactness and integration and reducing costs.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides an interference signal detection system based on beam interference fringes and a photodetector array. It includes an optical interference unit and a photoelectric detection unit. The optical interference unit is used to generate two coherent parallel beams and make the two coherent parallel beams overlap in space to form interference fringes. The photoelectric detection unit adopts a photodetector group, which is arranged in the overlapping interference field where the interference fringes are located. By adjusting the angle between the two coherent parallel beams to control the interference fringe spacing, the interference fringe spacing and the spacing between adjacent photodetectors in the photodetector group satisfy a preset phase matching relationship, thereby enabling the photodetector group to output an orthogonal interference signal.

[0005] Furthermore, the optical interference unit includes a laser, a first reflecting mirror, a grating, a second reflecting mirror, a third reflecting mirror, and a beam splitter. The linearly polarized light emitted by the laser is reflected by the first reflecting mirror and then incident perpendicularly onto the grating to diffract, generating two first-order diffracted beams. The two first-order diffracted beams are reflected by the second and third reflecting mirrors, respectively, and then combined and interfered at the beam splitter.

[0006] Furthermore, the photodetector group includes at least two photodetectors arranged in a straight line, and the arrangement direction is perpendicular to the normal direction of the interference fringes.

[0007] Furthermore, the photodetector is a photodiode, photomultiplier tube, or CMOS photoelectric unit.

[0008] Furthermore, the preset phase matching relationship satisfies the following formula:

[0009] Where, Δ x 2d Δ represents the spacing between adjacent photodetectors. x The spacing between the interference fringes. N 1 is an odd number.

[0010] Secondly, the present invention provides a method for detecting interference signals based on beam interference fringes and a photodetector array, which, based on the detection system described in the first aspect, includes the following steps: S1. Generate two coherent parallel beams and make the two coherent parallel beams overlap in space to form interference fringes; S2. The photodetector group is placed in the overlapping interference field where the interference fringes are located, and the photodetector group includes at least two photodetectors arranged along a preset direction; S3. Adjust the angle between the propagation directions of the two coherent parallel beams to control the spacing of the interference fringes; make the spacing of the interference fringes satisfy a preset phase matching relationship with the spacing of adjacent photodetectors in the photodetector group, so that the photodetector group outputs two or more orthogonal interference signals.

[0011] Furthermore, in step S1, a combination of a single-frequency laser and optical elements generates a dual-beam structure to form interference fringes.

[0012] Furthermore, in step S1, interference fringes are formed by heterodyne interference through a combination of dual-frequency lasers and optical elements.

[0013] Furthermore, in step S3, the angle between the two coherent parallel beams is adjusted by adjusting the angle of the reflector.

[0014] Furthermore, the preset phase matching relationship satisfies the following formula:

[0015] Where, Δ x 2d Δ represents the spacing between adjacent photodetectors. x The spacing between the interference fringes. N 1 is an odd number.

[0016] Compared with the prior art, the present invention has at least the following beneficial technical effects: 1) This invention utilizes the interference fringes formed by the spatial overlap of two coherent beams to place the photodetector group in the overlapping interference field. By adjusting the spacing of the interference fringes, the spacing between adjacent detectors in the photodetector group is matched with the spacing of the interference fringes, thereby realizing the detection of orthogonal interference signals without the need for complex beam splitting and phase shifting optical structures. This invention has a simple structure, significantly simplifies system design, and is easy to integrate and miniaturize.

[0017] 2) This invention is low-cost and reduces the number of optical components and the requirements for optical path alignment. Traditional four-channel beam-splitting phase-shifting detection modules utilize optical components such as polarizing beam splitters and waveplates to naturally generate four orthogonal interference signals by controlling the polarization state of light. This invention, however, achieves π / 2 phase shift separation without relying on polarizing optical components, significantly reducing the number of optical components. Traditional four-channel beam-splitting phase-shifting detection modules require high consistency in intensity, polarization state, and spatial overlap of the four optical signals, placing high demands on assembly. This invention, however, only requires adjusting the interference fringe spacing to match the spacing of adjacent detectors, significantly reducing assembly requirements. This invention reduces manufacturing and assembly costs and facilitates system miniaturization and integration. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the system of the present invention; Figure 2 This is a schematic diagram showing the relative positions of the beam interference fringes and the photodetector array. Figure 3 This is a schematic diagram of the orthogonal interference signal output by the photodetector group.

[0019] In the attached diagram: 1-Laser; 2-First reflector; 3-Grate; 4-Second reflector; 5-Third reflector; 6-Beam splitter; 7-Photodetector group; 8-First beam; 9-Second beam; 10-Incident angle of the second beam i 2; 11 - First beam incident angle i 1; 12 - Angle between the two beams α ; 13-Optical interferometer unit; 71-First photodetector; 72-Second photodetector; Δ x 2d - Spacing between adjacent detectors; Δ x- Spacing of interference fringes. Figure 3 The dashed line represents the output signal of the first photodetector; the solid line represents the output signal of the second photodetector. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0021] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0022] It should be noted that when an element is referred to as being "set on" another element, it can be directly on the other element or may be interposed with another element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or may be interposed with another element. The terms "upper," "lower," "front," "rear," "left," "right," "top," "bottom," "inner," and "outer," etc., used herein to indicate orientation or positional relationships are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention.

[0023] Unless otherwise defined, 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 pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0024] An interference signal detection system based on beam interference fringes and a photodetector array includes an optical interference unit and a photodetector unit.

[0025] The optical interference unit is used to generate two coherent parallel beams, a first beam 8 and a second beam 9 (the first beam 8 and the second beam 9 have the same polarization direction), and to make them overlap in space to form stable interference fringes; in one embodiment, the optical interference unit includes a combination of a laser and optical elements, such as... Figure 1As shown, the optical components include a first reflecting mirror 2, a grating 3, a second reflecting mirror 4, a third reflecting mirror 5, and a beam splitter 6. Linearly polarized light emitted from the laser 1 is reflected by the first reflecting mirror 2 and then incident perpendicularly onto the grating 3, where it undergoes diffraction, producing two first-order diffracted beams. These two beams are reflected by the second reflecting mirror 4 and the third reflecting mirror 5, respectively, and then combined and interfered at the beam splitter 6. Finally, the beams are incident on the photodetector group 7, where the interference signal is acquired.

[0026] The photoelectric detection unit is used to receive the light intensity signal in the interference fringes. The photoelectric detector group is arranged in the overlapping interference field where the interference fringes are located, and its direction is as perpendicular as possible to the perpendicular bisector direction of the two light beams. The photoelectric detector group includes several photoelectric detectors, and the direction of the line connecting adjacent photoelectric detectors is basically perpendicular to the normal direction of the interference fringes. The photoelectric detection unit is fixed by a 3D printed bracket, and the structural parameters of the 3D printed bracket are set by the size specifications of the photoelectric detection unit.

[0027] By adjusting the angle between the first beam 8 and the second beam 9 α Controlling the interference fringe spacing, when the interference fringe spacing Δ x When the spacing between the photodetectors in the photodetector group satisfies a predetermined phase matching relationship, the photodetector group outputs mutually orthogonal interference signals.

[0028] This system utilizes the interference fringes generated by the spatial overlap of two coherent parallel beams. The fringe spacing is controlled by adjusting the angle between the two beams. When the fringe spacing satisfies a specific relationship with the spacing between adjacent photodetectors in the photodetector array arranged in the overlapping interference region, the system can obtain orthogonal interference signals. This system has a compact structure, overcoming the shortcomings of traditional interference signal receiving units, such as large size, numerous optical components, low integration, and high cost. It improves the integration of interferometric measurement systems and achieves miniaturization and low-cost integration of interference signal detection systems.

[0029] This system is applicable to a variety of interferometric measurement scenarios, including displacement measurement, angle measurement, vibration detection, and surface morphology measurement.

[0030] Two beams of light interfere to form interference fringes. A photodetector array is placed in the overlapping interference (fringe) region. By adjusting the angle between the beams, the interference fringes rotate, and the fringe spacing changes. For example, when the displacement stage carrying the grating moves, the interference fringes move accordingly. The photodetectors receive the light intensity signals, generating sinusoidal signals. Due to phase matching, one detector outputs a sinusoidal signal, and the other outputs a cosine signal. Through subsequent demodulation circuitry, the displacement and its direction can be determined.

[0031] A method for detecting interference signals based on beam interference fringes and a photodetector array includes the following steps: Step 1: The optical interference unit generates two coherent parallel beams, the first beam 8 and the second beam 9, and makes them overlap in space to form stable interference fringes; Step 2: The photoelectric detection unit receives the interference signal; by adjusting the angle between the first beam 8 and the second beam 9... α By controlling the interference fringe spacing, while keeping the photodetector spacing constant, when the interference fringe spacing Δ x When the spacing between the photodetectors and the adjacent photodetectors satisfies a predetermined phase matching relationship, the photodetector group outputs mutually orthogonal interference signals.

[0032] The two coherent beams in step 1 can be formed in either of the following ways: one is by generating two beams from a combination of a single-frequency laser and optical elements to form interference fringes; the other is by forming interference fringes from a combination of a dual-frequency laser and optical elements through heterodyne interference technology.

[0033] The optical interference unit in step 1 is a combination of a laser and optical elements. These optical elements include, but are not limited to, beam splitters, mirrors, collimating lenses, and diffractive optical elements. Depending on the optical measurement principle, one or more of these optical elements are selected and combined with the laser to form the optical interference unit.

[0034] The photodetector group in step 2 consists of several (greater than or equal to 2) photodiodes, photomultiplier tubes, CMOS photodetectors or other types of photodetectors. The photodetectors are arranged in a straight line or planar array, and the spacing between adjacent detection units is designed according to the interference fringe spacing to achieve the acquisition of two or more phase-orthogonal signals. The number of signals is determined by the number of photodetectors in the detector group. One photodetector outputs one signal, two photodetectors output two signals, and four photodetectors output four signals.

[0035] In step 2, the angle between the first beam 8 and the second beam 9 is controlled by adjusting the angles of the second reflector 4 and the third reflector 5. α .

[0036] In step 2, the predetermined phase matching relationship is as follows:

[0037] The spacing between adjacent detectors in the detector group is Δ. x 2d , N 1 is an odd number. x 1 represents the coordinates of the geometric center of the photosensitive surface of a photodetector. x 2 represents the coordinates of the geometric center of the photosensitive surface of another photodetector.

[0038] Example This embodiment provides a method for detecting interferometric signals, such as Figure 1 As shown. Linearly polarized light emitted from laser 1 is reflected by the first reflecting mirror 2 and then incident perpendicularly on the grating 3, where it undergoes diffraction, generating two first-order diffracted beams (first beam 8 and second beam 9). The first beam 8 and second beam 9 are reflected by the second reflecting mirror 4 and the third reflecting mirror 5, respectively, and then combined and interfered by the beam splitter 6. Finally, they are incident on the photodetector group 7, where the interference signal is acquired. Two coherent parallel beams—the first beam 8 and the second beam 9—are generated by the optical interference unit 13 at incident angles of [missing information]. i 1 and i 2. The light is incident on the photodetector group 7, which includes a first photodetector 71 and a second photodetector 72. The angle between the two beams can be controlled by adjusting the angles of the second reflector 4 and the third reflector 5. α Because the interfering beams overlap, they form an overlapping interference field. The original wavefronts of both beams have the same shape, both being circular. Assume that the two beams have the same polarization direction and equal initial phase. f If 0 = 0, then the wavefront functions of the first beam 8 and the second beam 9 can be expressed as follows: (1) (2) in, This represents the wavefront function of the first beam 8. This represents the wavefront function of the second beam 9. x Let t represent the coordinate variable and t represent the time variable. π Represents pi (π). A 1 and A 2 represents the amplitude of the wavefront function of the first beam 8 and the second beam 9, respectively; f 0 represents the frequency of the light beam; Δ f This indicates the frequency difference between the second beam 9 and the first beam 8; k The wave vector of the beam.

[0039] From the two-beam interference intensity formula (3), the beam interference intensity in the overlapping interference region can be obtained. I Expression (4): (3) (4) Since the fringe spacing is determined by the wave vector difference between the two beams and is independent of time, the fringe spacing Δ x The expression (5) is: (5) in, lThe wavelength of the light beam is the wavelength of the light beam. The light beam is a collective term for the first and second light beams.

[0040] A dual photodetector array is arranged along the normal direction of the interference fringes within the interference overlap region, such as... Figure 2 As shown. Considering the finite size of the detector's photosensitive surface, the signal detected by the detector is essentially the spatial integral of the light intensity within the detection region. Since the interference field exhibits a uniform distribution along the fringe direction, this two-dimensional integral can be simplified to a one-dimensional integral along the fringe normal direction. Let the detector along... x The effective half-width in the axial direction is Δ l (theoretically Δ) l (The value should be as small as possible to approximate a point detection), then the coordinates of the geometric center of the effective photosensitive surface of the photodetector are... x Detection light intensity at the location S ( x This can be represented as: (6) During the i-th period of the interference fringes, according to the phase matching condition: When the phase satisfies k (sin i 1+sin i 2) x When 1 = 2iπ, i is an integer. The geometric center of the overlapping interference field of the detection plane is taken as the origin of the coordinate system. At this time, the coordinate position of the geometric center of the photosensitive surface of the first photodetector 71 is... x The mathematical expression for 1 is (7) When the phase satisfies k (sin i 1+sin i 2) x When 2 = 2iπ + π / 2, the coordinates of the geometric center of the photosensitive surface of the second photodetector 72 are as follows: x The mathematical expression for 2 is: (8) To achieve orthogonal detection, let the distance between the two detectors in the array be Δ. x 2d When the spacing satisfies the following relationship: (9) in N Since 1 is an odd number, according to formulas 6 and 9, the interference light intensity formed at the first photodetector 71 and the second photodetector 72 at this time is... S ( x 1) and S ( x 2) It can be written in the following form: (10) (11) At this time, the photodetector can detect the two paths with a phase difference of . The interference signal, that is, the acquisition of orthogonal interference signal.

[0041] The system structure of this invention is simple, the number of optical components is reduced, it is suitable for interferometric measurement scenarios such as high-precision displacement measurement, and it has good integration potential.

[0042] Although embodiments of the present invention have been described above in conjunction with the accompanying drawings, the invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art, guided by this specification, can make many other forms without departing from the scope of the claims of the present invention, and all of these are within the scope of protection of the present invention.

Claims

1. An interferometric signal detection system based on beam interference fringes and a photodetector array, characterized in that, It includes an optical interference unit and a photoelectric detection unit. The optical interference unit is used to generate two coherent parallel beams and make the two coherent parallel beams overlap in space to form interference fringes. The photoelectric detection unit adopts a photodetector group, which is arranged in the overlapping interference field where the interference fringes are located. By adjusting the angle between the two coherent parallel beams to control the interference fringe spacing, the interference fringe spacing and the spacing between adjacent photodetectors in the photodetector group satisfy a preset phase matching relationship, thereby enabling the photodetector group to output an orthogonal interference signal.

2. The interference signal detection system based on beam interference fringes and photodetector array according to claim 1, characterized in that, The optical interference unit includes a laser (1), a first mirror (2), a grating (3), a second mirror (4), a third mirror (5), and a beam splitter (6). The linearly polarized light emitted by the laser (1) is reflected by the first mirror (2) and then incident perpendicularly on the grating (3) to diffract, generating two first-order diffracted beams. The two first-order diffracted beams are reflected by the second mirror (4) and the third mirror (5), respectively, and then combined and interfered at the beam splitter (6).

3. The interference signal detection system based on beam interference fringes and photodetector array according to claim 1, characterized in that, The photodetector group includes at least two photodetectors arranged in a straight line, and the arrangement direction is perpendicular to the normal direction of the interference fringes.

4. The interference signal detection system based on beam interference fringes and photodetector array according to claim 3, characterized in that, The photodetector is a photodiode, a photomultiplier tube, or a CMOS photoelectric unit.

5. The interference signal detection system based on beam interference fringes and photodetector array according to claim 1, characterized in that, The preset phase matching relationship satisfies the following formula: Where, Δ x 2d Δ represents the spacing between adjacent photodetectors. x The spacing between the interference fringes. N 1 is an odd number.

6. A method for detecting interference signals based on beam interference fringes and a photodetector array, based on the system described in claim 1, characterized in that, Includes the following steps: S1. Generate two coherent parallel beams and make the two coherent parallel beams overlap in space to form interference fringes; S2. The photodetector group is placed in the overlapping interference field where the interference fringes are located, and the photodetector group includes at least two photodetectors arranged along a preset direction; S3. Adjust the angle between the propagation directions of the two coherent parallel beams to control the spacing of the interference fringes; make the spacing of the interference fringes satisfy a preset phase matching relationship with the spacing of adjacent photodetectors in the photodetector group, so that the photodetector group outputs two or more orthogonal interference signals.

7. The method for detecting interference signals based on beam interference fringes and a photodetector array according to claim 6, characterized in that, In step S1, a combination of a single-frequency laser and optical elements generates a dual-beam structure, forming interference fringes.

8. The method for detecting interference signals based on beam interference fringes and a photodetector array according to claim 6, characterized in that, In step S1, interference fringes are formed by heterodyne interference through a combination of dual-frequency lasers and optical elements.

9. The method for detecting interference signals based on beam interference fringes and a photodetector array according to claim 6, characterized in that, In step S3, the angle between the two coherent parallel beams is adjusted by adjusting the angle of the reflector.

10. The method for detecting interference signals based on beam interference fringes and a photodetector array according to claim 6, characterized in that, The preset phase matching relationship satisfies the following formula: Where, Δ x 2d Δ represents the spacing between adjacent photodetectors. x The spacing between the interference fringes. N 1 is an odd number.

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