Dihedral angle optical measurement device and method

Abstract

The application discloses a dihedral angle optical measurement device and method, and belongs to the technical field of dihedral angle measurement. The dihedral angle optical measurement device is arranged to make measurement laser light pass through a laser collimator and a light splitting prism in sequence, and then split into reflected light and transmitted light according to a proportion. The reflected light and the transmitted light are reflected by a first reflector and a second reflector, and then hit the face center of a dihedral angle standard piece and return to the original path. The reflected light and the transmitted light are combined and interfered on the light splitting prism. The position and the posture of a photoelectric detector are adjusted, so that the combined signal hits the center position of the photoelectric detector, and the wavefront difference signal of the dihedral angle standard piece is read. When the wavefront difference signal of the dihedral angle standard piece is zero, the dihedral angle standard piece is replaced by a dihedral angle target piece to be measured, and the wavefront difference signal of the dihedral angle target piece to be measured is read. The wavefront difference signals of the dihedral angle standard piece and the dihedral angle target piece to be measured are used to obtain the measurement information of the dihedral angle. The designed system can improve the precision of dihedral angle measurement.

Description

Technical Field

[0001] This invention relates to the field of dihedral angle measurement technology, and more specifically to a dihedral angle optical measurement device and method based on differential wavefront sensing. Background Technology

[0002] With the continuous development of modern science and technology, many fields such as aerospace, machining, and assembly have placed urgent demands on high-precision dihedral angle measurement. Dihedral angle measurement is the foundation for establishing a coordinate reference system and has important application value for basic metrology, precision manufacturing, precision machining, and basic scientific experiments. Traditional dihedral angle measurement generally uses metrological instruments such as coordinate measuring machines (CMMs), metrological scanning probe microscopes, and multi-degree-of-freedom positioning platforms, all of which require high-precision angle measurement and positioning.

[0003] Currently, for dihedral angle measurement needs in various fields such as precision measurement, machining, and assembly, methods generally include coordinate measuring machine (CMM), combined measurement with multiple autocollimators, and large-aperture laser interferometers. Among these, the CMM is the benchmark in many precision industries; however, its measurement method is contact-based, with accuracy typically at the micrometer and arcsecond level, making it unsuitable for measuring components requiring high cleanliness or ultra-high precision. Furthermore, the high cost of CMMs limits their widespread use. While autocollimators are often used for angle measurement, they generally cannot be directly used for dihedral angle measurement and require multiple units to be used in combination, resulting in similarly high costs. Large-aperture laser interferometers are only suitable for measuring internal dihedral angles, and their algorithms are complex and their costs are also very high.

[0004] Differential wavefront sensing is an angle measurement technique based on heterodyne laser interferometry. Its basic principle is that two laser beams with a stable difference frequency are simultaneously incident on a four-quadrant detector, satisfying the coherence condition. This generates four beat frequency signals, each recording the coherent light information received in its corresponding quadrant. Signal processing yields the phase information of these four beat frequency signals. Combined with the phase-angle conversion coefficient, the angle between the two laser beams can be measured. Differential wavefront sensing offers advantages such as high measurement accuracy, strong anti-interference capability, and low coupling, and is widely used in high-precision laser interferometry applications.

[0005] Although the existing technology can achieve high measurement accuracy on the order of nrad, due to the periodic nonlinear error of heterodyne laser interferometry, when the offset angle between the signal light and the local oscillator light increases to a certain extent, the phase ambiguity of a single differential wavefront sensing device will cause it to be unable to measure when the photodetector solves the phase difference. The angle measurement range can only reach the order of mrad, resulting in inaccurate dihedral angle measurement accuracy. Summary of the Invention

[0006] To address the problems existing in the above-mentioned fields, this invention proposes a dihedral angle optical measurement device and method, which can solve the technical problem that when the offset angle between the signal light and the local oscillator light increases to a certain extent, a single differential wavefront sensing device will cause phase ambiguity and be unable to measure when the photodetector solves the phase difference, and the angle measurement range can only reach the mrad level, resulting in inaccurate dihedral angle measurement accuracy.

[0007] To address the aforementioned technical problems, this invention discloses a dihedral angle optical measurement device, comprising a laser collimator, a beam splitter, a photodetector, and a dihedral angle standard component:

[0008] The laser collimator is mounted on the measurement substrate, and its output end is optically connected to the beam splitter prism. The output end of the beam splitter prism is optically connected to a first reflector and a second reflector, and the output ends of both the first and second reflectors are optically connected to the dihedral corner standard. The photodetector is connected to the beam splitter prism.

[0009] The measuring laser beam passes sequentially through the laser collimator and beam splitter, then splits into reflected and transmitted light according to a ratio. The reflected and transmitted light are reflected by the first and second mirrors, respectively, and then return along their original paths to the face center of the dihedral standard. They are then combined and interfered with on the beam splitter. By adjusting the position and orientation of the photodetector, the combined signal hits the center of the photodetector, and the wavefront difference signal of the dihedral standard is read. When the wavefront difference signal of the dihedral standard is zero, the dihedral standard is replaced with a dihedral target object, and the wavefront difference signal of the target object is read. The measurement information of the dihedral angle is obtained through the wavefront difference signals of the dihedral standard and the target object.

[0010] Preferably, the first reflector and the second reflector are arranged in opposite parallel directions, and the emitting end of the first reflector reflects at a 90-degree angle.

[0011] Preferably, the emitting end of the second reflector reflects at a 90-degree angle.

[0012] Preferably, the beam splitting ratio of the beam splitter is set to 50:50.

[0013] Preferably, the photodetector is a four-quadrant detector.

[0014] Preferably, a measurement method for a dihedral angle optical measuring device is characterized by comprising the following steps:

[0015] The incident light generated by the measurement laser is split into reflected light and transmitted light according to a certain ratio by the beam splitting prism.

[0016] The reflected light and transmitted light are reflected by the first and second mirrors respectively, reach the face center of the dihedral standard, and return along the original path. They are combined and interfered on the beam splitter prism. By adjusting the position and orientation of the photodetector, the combined signal hits the center of the photodetector, and the wavefront differential signal of the dihedral standard is read.

[0017] When the wavefront differential signal of the dihedral standard is zero, the dihedral standard is replaced with the dihedral target to be tested, and the wavefront differential signal of the dihedral target to be tested is read.

[0018] The measurement information of the dihedral angle is obtained by reading the wavefront differential signals of the standard dihedral angle component and the target dihedral angle component to be measured.

[0019] Preferably, the method further includes calculating dihedral information based on the wavefront signals of the read dihedral standard and the dihedral target, using the dihedral measurement equation. The specific calculation formula is as follows:

[0020]

[0021] Where λ is the wavelength of the two interfering beams. The phases of the detector in the four quadrants are represented respectively, and d is the Gaussian beam with the diameter of the laser being measured.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The beam-splitting prism of this invention splits the incident laser beam proportionally into reflected and transmitted light. The reflected and transmitted light, after reflection, strike the face center of a dihedral angle standard and return along their original paths. They then combine and interfere on the beam-splitting prism. By adjusting the position and orientation of the photodetector, the wavefront differential signal of the dihedral angle standard is read. The dihedral angle standard is then replaced with a dihedral angle target object, and its wavefront differential signal is read. Based on the read wavefront differential signals of both the standard and target objects, the measurement information of the dihedral angle is obtained. This dihedral angle measurement device and method improve the accuracy of dihedral angle measurement and overcomes the phase ambiguity problem caused by a single differential wavefront sensing device when the photodetector solves for the phase difference. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall system of the present invention. Detailed Implementation

[0025] The following will refer to the appendices in the embodiments of the present invention. Figure 1The technical solutions in the embodiments of the present invention will be clearly and completely described. It should be understood that the terminology used in the present invention is only for describing particular implementation methods and is not intended to limit the present invention.

[0026] Example

[0027] like Figure 1 As shown, this embodiment of the invention provides a dihedral angle optical measurement device, including a laser collimator 1, a beam splitter prism 2, a first reflector 3, a second reflector 4, a photodetector 5, a dihedral angle standard 6, and a dihedral angle target 7. This invention presents a dihedral angle measurement optical system based on differential wavefront sensing.

[0028] Laser collimator 1: First, fix the laser collimator, connect the output fiber of the laser source to the laser collimator, and adjust the direction of the laser collimator so that the spatial light is collimated and parallel to the optical platform;

[0029] Beam splitter 2 is inserted after laser collimator 1. The orientation of beam splitter 2 is adjusted so that the reflected light and transmitted light are at 90 degrees. The reflected light is directed toward the first reflecting mirror 3 and the transmitted light is directed toward the second reflecting mirror 4.

[0030] First reflecting mirror 3 is installed after the reflected light from beam splitter 2. The orientation of reflecting mirror 3 is adjusted so that the reflected light is at a 90-degree angle to the incident light.

[0031] The second reflecting mirror 4 is installed after the transmitted light from the beam splitter 2. The orientation of the reflecting mirror 4 is adjusted so that the reflected light is at a 90-degree angle to the incident light.

[0032] Dihedral standard component 6 is placed at the intersection of the light emitted from the first reflector 3 and the light emitted from the second reflector 4. The orientation of the dihedral standard component 6 is adjusted so that the light emitted from the first reflector 3 hits one side of the dihedral standard component 6 and then returns along the original path.

[0033] Adjust the orientation of the second reflector 4 so that the emitted light hits the other vertical side of the dihedral standard part 6 perpendicularly and then returns along the original path.

[0034] Adjust the orientation of beam splitter 2 so that the two beams of light returning from the first reflecting mirror 3 and the second reflecting mirror 4 can re-interfere on beam splitter 2.

[0035] Photodetector 5 is installed at the reflection and beam combining end of the beam splitter 2. By observing the detector response, the position and orientation of photodetector 5 are adjusted so that the beam combining signal hits the center position of the four-quadrant detector 5.

[0036] Adjust to achieve maximum interference signal contrast. Adjust the orientation of the first reflector 3 and the second reflector 4, and observe the response of the photodetector 5 to make the interference signal contrast reach its maximum value, and the dihedral angle measurement differential signal in the four quadrants is zero.

[0037] The dihedral angle test target 7 is removed, the dihedral angle standard 6 is removed, and the dihedral angle test target 7 is replaced; the attitude of the dihedral angle test target 7 is adjusted so that interference signals appear simultaneously in the four quadrants of the photodetector 5; the dihedral angle of the dihedral angle test target 7 is measured, the phase signals of the four quadrants of the photodetector 5 are read, and the dihedral angle is measured according to the above dihedral angle measurement equation.

[0038] The optical system developed in this application has the advantages of simple structure and high measurement accuracy, and can be widely used for the detection and calibration of dihedral angles such as pyramids.

[0039] Based on a dihedral angle measurement optical system based on differential wavefront sensing, this invention also proposes a measurement method for the dihedral angle measurement optical system based on differential wavefront sensing, comprising the following steps:

[0040] The laser beam is converted from fiber light into incident collimated spatial light by the laser collimator 1 and enters the optical measurement device. The incident collimated spatial light enters the beam splitter prism 2 with normal incidence and is split in a 50:50 ratio. The beam splitter prism 2 emits two spatially collimated laser beams that are perpendicular to each other. The transmitted light has the same direction, and the reflected light is perpendicular to the transmitted light. The reflected light is directed towards the first reflector 3, and the transmitted light is directed towards the second reflector 4.

[0041] The reflected light is reflected at a 90-degree angle by the center of the first reflecting mirror 3, aligning with the direction of the incident collimated spatial light. The transmitted reflected light is reflected at a 90-degree angle by the center of the second reflecting mirror 4, perpendicular to the direction of the incident collimated spatial light. The light emitted from the first reflecting mirror 3 strikes the center of the dihedral standard 6 or the dihedral target 7 with normal incidence, and is reflected back along the same path, becoming the first retroreflected light. The first retroreflected light is reflected again at a 90-degree angle by the first reflecting mirror 3 and strikes one side of the beam splitter prism 2. The light emitted from the second reflecting mirror 4 strikes the other perpendicular surface of the dihedral standard 6 or the dihedral target 7 with normal incidence. The first and second backscattered beams are reflected back along the original path to form the second backscattered beam. The second backscattered beam is reflected again by the second reflecting mirror 4 at a 90-degree angle and is directed towards the other vertical surface of the beam splitter 2. The first and second backscattered beams are combined at the center of the beam splitter 2. After passing through the beam splitter 2, the transmitted light of the first backscattered beam strikes the photodetector 5 with normal incidence. After passing through the beam splitter 2, the reflected light of the second backscattered beam strikes the photodetector 5 with normal incidence. The transmitted and reflected light are combined at the center of the surface of the photodetector 5 to generate an interference signal. The interference signal is measured by the photodetector 5 to extract the wavefront difference signal.

[0042] This invention presents the measurement principle of a dihedral angle measurement optical system based on differential wavefront sensing.

[0043] First, the beam direction of the interferometric measuring device is adjusted using the dihedral standard 6. According to the design of the optical path measuring device, after adjusting the interference signal, the angle between the two reflected beams is zero, which is used as the reference for dihedral angle measurement. Then, the dihedral target 7 is replaced to perform dihedral angle measurement.

[0044] For laser interferometric measurement signals, the yaw angles of the two lasers can be measured using four-quadrant wavefront difference, thus extracting the dihedral angle information of the two reflecting surfaces. Assume the phases of the detector in the four quadrants are represented as follows: If the measuring laser is a Gaussian beam with diameter d, then the equation for measuring the dihedral angle can be expressed as:

[0045]

[0046] Where λ is the wavelength of the two interfering beams.

[0047] This invention discloses an optical system design for dihedral angle measurement based on differential wavefront sensing. The design includes an optical path system design and a measurement principle. The optical path system design includes a differential wavefront sensing interferometric optical path design; the measurement principle explains the basic principles of dihedral angle measurement and its theoretical measurement accuracy; and the measurement steps provide the operational procedures for dihedral angle measurement.

[0048] This invention presents a design for a dihedral angle measurement optical system based on differential wavefront sensing, enabling high-precision measurement and calibration of dihedral angles. This design offers advantages such as non-contact measurement, simple structure, portability, and high precision, and can be widely applied in industrial production, metrology, and experimental calibration.

[0049] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0050] Furthermore, unless otherwise stated, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. All references to this specification are incorporated by way of citation to disclose and describe methods relating to those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

Claims

1. A dihedral angle optical measuring device, characterized in that, Includes a laser collimator (1), a beam splitter (2), a photodetector (5), and a dihedral standard component (6): The laser collimator (1) is mounted on the measurement substrate, and the output end of the laser collimator (1) is optically connected to the beam splitter (2); the output end of the beam splitter (2) is optically connected to a first reflector (3) and a second reflector (4), and the output ends of the first reflector (3) and the second reflector (4) are both optically connected to the dihedral standard (6); the photodetector (5) is connected to the beam splitter (2); The measuring laser passes sequentially through the laser collimator (1) and the beam splitter (2) and is then split proportionally into reflected light and transmitted light. The reflected light and transmitted light are reflected by the first reflector (3) and the second reflector (4) respectively and then hit the face center of the dihedral standard (6) and return along the original path. They are combined and interfered on the beam splitter (2). By adjusting the position and orientation of the photodetector (5), the combined signal hits the center position of the photodetector (5) and the wavefront difference signal of the dihedral standard (6) is read. When the wavefront difference signal of the dihedral standard (6) is zero, the dihedral standard (6) is replaced with the dihedral target (7) to be measured, and the wavefront difference signal of the dihedral target (7) to be measured is read. The measurement information of the dihedral is obtained through the wavefront difference signals of the dihedral standard (6) and the dihedral target (7).

2. The dihedral angle optical measuring device according to claim 1, characterized in that, The first reflector (3) and the second reflector (4) are arranged in opposite parallel directions, and the emitting end of the first reflector (3) reflects at 90 degrees.

3. The dihedral angle optical measuring device according to claim 2, characterized in that, The emitting end of the second reflector (4) reflects at a 90-degree angle.

4. The dihedral angle optical measuring device according to claim 3, characterized in that, The beam splitting ratio of the beam splitter prism (2) is set to 50:

50.

5. The dihedral angle optical measuring device according to claim 4, characterized in that, The photodetector (5) is a four-quadrant detector.

6. The measurement method of the dihedral angle optical measuring device according to claim 1, characterized in that, Includes the following steps: The incident light generated by the measurement laser is split into reflected light and transmitted light according to the ratio by the beam splitter prism (2); The reflected light and transmitted light are reflected by the first reflector (3) and the second reflector (4) respectively, and then reflected by the face center of the dihedral standard (6) and return along the original path. They are combined and interfered on the beam splitter (2). By adjusting the position and orientation of the photodetector (5), the combined signal hits the center position of the photodetector (5) and the wavefront differential signal of the dihedral standard (6) is read. When the wavefront differential signal of the dihedral standard (6) is zero, the dihedral standard (6) is replaced with the dihedral target (7) to be tested, and the wavefront differential signal of the dihedral target (7) to be tested is read. The measurement information of the dihedral is obtained by reading the wavefront differential signals of the standard dihedral part (6) and the target dihedral part (7).

7. The measurement method of the dihedral angle optical measuring device according to claim 6, characterized in that, It also includes calculating dihedral information based on the wavefront signals of the dihedral standard part (6) and the dihedral target part (7) being measured, using the dihedral measurement equation. The specific calculation formula is as follows: in, λ Let be the wavelength of the two interfering beams. φ 1. φ 2. φ 3. φ 4 represents the phase of the detector in each of the four quadrants. d A Gaussian beam for measuring the diameter of a laser.

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