CN117685906A - A dihedral angle optical measurement device and method - Google Patents

Abstract

The invention discloses a dihedral angle optical measurement device and method, which belongs to the technical field of dihedral angle measurement. Through the dihedral angle optical measurement device, the measurement laser passes through a laser collimator and a spectroscopic prism in sequence and then is split according to proportions. It is divided into reflected light and transmitted light; the reflected light and the transmitted light are respectively reflected by the first reflector and the second reflector and then return to the center of the face of the dihedral standard part. They are combined and interfered on the dichroic prism. By adjusting the photoelectric The position and attitude of the detector are such that the combined signal hits the center of the photodetector and the wavefront differential signal of the dihedral standard is read; when the wavefront differential signal of the dihedral standard is zero, the two Replace the dihedral angle standard part with the dihedral angle target part to be measured, and read the wavefront differential signal of the dihedral angle target part to be measured; through the wavefront differential signal of the dihedral angle standard part and the dihedral angle target part to be measured, Obtain measurement information for dihedral angles. The system is designed to improve the accuracy of dihedral angle measurement.

Description

A dihedral angle optical measurement device and method

Technical field

The present invention relates to the technical field of dihedral angle measurement, and more specifically to a dihedral angle optical measurement device and method based on differential wavefront sensing.

Background technique

With the continuous development of modern science and technology, many fields such as aerospace, mechanical processing and assembly have put forward urgent requirements for high-precision dihedral angle measurement. Dihedral angle measurement is the basis for establishing a coordinate reference system and has important application value for basic metrology, precision manufacturing and precision processing, and basic scientific experiments. Traditional dihedral angle measurement generally uses measuring instruments such as three-coordinate CMM, metrological scanning probe microscope, and multi-degree-of-freedom positioning platform, all of which require high-precision angle measurement and positioning.

At present, to meet the needs of dihedral angle measurement in many fields such as precision measurement, processing and assembly, three-coordinate measurement, joint measurement of multiple autocollimators, and large-diameter laser interferometer are generally used to measure dihedral angle. Among them, the three-dimensional coordinate measuring machine is the benchmark for many precision industries. However, its measurement method is contact measurement, and the accuracy is generally in the micron and arc second levels. It is not suitable for measuring high-cleanliness and ultra-high-precision components. In addition, the three-dimensional coordinate measuring machine The machine is very expensive, which limits its widespread use. Although autocollimators are often used for angle measurement, they generally cannot be used directly for dihedral angle measurement. Multiple units need to be used in conjunction, and the cost is also relatively high. Large-aperture laser interferometer is only suitable for internal dihedral angle measurement, the algorithm is complex and the cost is also very high.

Differential wavefront sensing measurement is an angle measurement technology based on heterodyne laser interference. The basic principle is that two laser beams with stable difference frequencies are incident on the four-quadrant detector at the same time, and if the coherence conditions are met, four-way beat frequencies will be generated. The four beat frequency signals record the coherent light information received by the corresponding quadrant respectively. Through signal processing, the phase information of the four beat frequency signals can be obtained. Combined with the phase angle conversion coefficient, the angle measurement of the two laser beams can be achieved. Differential wavefront sensing has the advantages of high measurement accuracy, strong anti-interference ability, and small coupling, and is widely used in high-precision laser interference applications.

Although this existing technology can achieve high measurement accuracy of nrad level, due to the periodic nonlinear error in heterodyne laser interference, when the offset angle of the signal light and the local oscillator light increases to a certain extent, the single differential wavefront sensing When the photoelectric detector solves the phase difference, the device will cause phase blur and cannot be measured. The angle measurement range can only reach the mrad level, resulting in inaccurate dihedral angle measurement accuracy.

Contents of the invention

In view of the problems existing in the above fields, the present invention proposes a dihedral angle optical measurement device and method, which can solve the problem of a single differential wavefront sensing device when the offset angle of the signal light and the local oscillator light increases to a certain extent. When the photoelectric detector solves the phase difference, it will cause phase blur and cannot be measured, and the angle measurement range can only reach the mrad level, resulting in technical problems such as inaccurate dihedral angle measurement accuracy.

In order to solve the above technical problems, the present invention discloses a dihedral angle optical measurement device, which includes a laser collimator, a spectroscopic prism, a photodetector and a dihedral angle standard part:

The laser collimator is installed on the measurement base, and the exit end of the laser collimator is optically connected to the dichroic prism; the exit end of the dichroic prism is optically connected to a first reflector and a second reflector, so The exit ends of the first reflector and the second reflector are optically connected to the dihedral standard; the photodetector is connected to the dichroic prism;

Wherein, the measurement laser passes through the laser collimator and the dichroic prism in sequence and then splits the light according to the proportion, and is divided into reflected light and transmitted light; the reflected light and the transmitted light correspond to each other after being reflected by the first reflector and the second reflector. Return to the center of the face of the dihedral standard, and combine the beams for interference on the dichroic prism. By adjusting the position and attitude of the photodetector, the combined signal hits the center of the photodetector. position, read the wavefront differential signal of the dihedral standard part; when the wavefront differential signal of the dihedral standard part is zero, replace the dihedral standard part with the dihedral target to be measured The component reads the wavefront differential signal of the dihedral angle target component to be measured; and obtains the dihedral angle measurement information through the wavefront differential signal of the dihedral angle standard component and the dihedral angle target component to be measured.

Preferably, the first reflector and the second reflector are arranged anti-parallel, and the emission end of the first reflector reflects at 90 degrees.

Preferably, the emitting end of the second mirror reflects at 90 degrees.

Preferably, the light splitting ratio of the dichroic prism is set to 50:50.

Preferably, the photodetector is a four-quadrant detector.

Preferably, a method of measuring a dihedral angle optical measuring device is characterized by including the following steps:

The incident light generated by the measurement laser is split according to the proportion through the dichroic prism, and divided into reflected light and transmitted light;

The reflected light and the transmitted light are correspondingly reflected by the first reflector and the second reflector, respectively, after reaching the face-center reflection of the dihedral standard, and then return to the original path, and then combine and interfere on the dichroic prism. And by adjusting the position and attitude of the photodetector, the combined signal reaches the center position of the photodetector, and the wavefront differential signal of the dihedral standard is read;

When the wavefront differential signal of the dihedral angle standard part is zero, replace the dihedral angle standard part with the dihedral angle target part to be measured, and read the wavefront differential signal of the dihedral angle target part to be measured. ;

According to the read wavefront differential signals of the dihedral angle standard part and the dihedral angle target part to be measured, the dihedral angle measurement information is obtained.

Preferably, it also includes calculating the dihedral angle information through the dihedral angle measurement equation based on the read wavefront signals of the dihedral angle standard part and the dihedral angle target part to be measured. The specific calculation formula is:

Among them, λ is the wavelength of the two interference beams, represent the phases of the four quadrants of the detector respectively, and d is the Gaussian beam used to measure the diameter of the laser.

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

The dichroic prism provided in the present invention splits the incident laser light in proportion and divides it into reflected light and transmitted light. After reflection, the reflected light and the transmitted light hit the center of the face of the dihedral standard part and return to the original path, and are combined on the dichroic prism. Beam interference, and by adjusting the position and attitude of the photodetector, read the wavefront differential signal of the dihedral standard part; replace the dihedral standard part with the dihedral angle target part to be measured, and the read dihedral angle is to be measured Measure the wavefront differential signal of the target part; obtain the dihedral angle measurement information based on the read wavefront differential signal of the dihedral angle standard part and the dihedral angle target part to be measured. The dihedral angle measurement device and the measurement method provided improve the accuracy of dihedral angle measurement, and can overcome the phase ambiguity problem caused by a single differential wavefront sensing device when the photoelectric detector solves the phase difference.

Description of the drawings

Figure 1 is a schematic diagram of the overall system of the present invention.

Detailed ways

The technical solution in the embodiment of the present invention will be clearly and completely described below with reference to Figure 1 in the embodiment of the present invention. It should be understood that the terms used in the present invention are only used to describe particular embodiments and are not intended to limit the present invention.

Example

As shown in Figure 1, an embodiment of the present 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 Angle standard part 6, dihedral angle target part to be measured 7. The invention provides a dihedral angle measurement optical system based on differential wavefront sensing.

Laser collimator 1, first fix the laser collimator, connect the emitting fiber of the laser light source to the laser collimator, and adjust the direction of the laser collimator to make the spatial light collimated and parallel to the optical platform;

The dichroic prism 2 is inserted after the laser collimator 1, and the posture of the dichroic prism 2 is adjusted so that the reflected light and the transmitted light are at 90 degrees. The reflected light is directed to the first reflecting mirror 3, and the transmitted light is directed to the second reflecting mirror 3. Two reflectors 4;

The first reflector 3 is installed after the reflected light from the dichroic prism 2, and the posture of the reflector 3 is adjusted so that the reflected light is 90 degrees from the incident light;

The second reflector 4 is installed after the transmitted light of the dichroic prism 2, and the posture of the reflector 4 is adjusted so that the reflected light is 90 degrees from the incident light;

The dihedral standard part 6 is placed at the intersection of the emitted light of the first reflector 3 and the emitted light of the second reflector 4, and the posture of the dihedral standard part 6 is adjusted so that the first reflection The emitted light from the mirror 3 hits one side of the dihedral standard part 6 and then returns along the original path;

Adjust the attitude of the second reflector 4 so that the emitted light vertically hits the other vertical side of the dihedral standard piece 6 and then returns along the original path;

Adjust the attitude of the dichroic prism 2, and adjust the dichroic prism 2 so that the two beams of light returning from the first reflecting mirror 3 and the second reflecting mirror 4 recombine and interfere on the dichroic prism 2;

The photodetector 5 is installed at the reflection combining end of the adjusting beam splitter prism 2. By observing the detector response, the position and attitude of the photodetector 5 are adjusted so that the combining signal hits the center of the four-quadrant detector 5. Location;

Adjust to achieve the maximum interference signal contrast, adjust the postures of the first reflector 3 and the second reflector 4, and observe the response of the photodetector 5, so that the contrast of the interference signal reaches the maximum value, and the four quadrant dihedral angles measure the differential signal is zero;

For the dihedral angle target piece 7, remove the dihedral standard piece 6 and replace it with the dihedral target piece 7; adjust the posture of the dihedral target piece 7 and adjust the dihedral target piece 7. Make interference signals appear in the four quadrants of the photodetector 5 at the same time, measure the dihedral angle of the target object 7 to be measured, read the phase signals of the four quadrants of the photodetector 5, and measure the dihedral angle according to the above dihedral angle measurement equation. horn.

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

Based on a dihedral angle measurement optical system based on differential wavefront sensing, the present invention also proposes a measurement method of a dihedral angle measurement optical system based on differential wavefront sensing, which includes the following steps:

The laser is converted from fiber light into incident collimated space light through the laser collimator 1 and enters the optical measurement device; the incident collimated space light enters the dichroic prism 2 at normal incidence and is split 50:50; the dichroic prism 2 emits two beams pointing vertically Two spatially collimated laser beams, in which the direction of the transmitted light remains unchanged and the reflected light is perpendicular to the transmitted light; the reflected light is directed to the first reflector 3, and the transmitted light is directed to the second reflector 4;

The reflected light is reflected at 90 degrees through the center of the face of the first reflector 3, pointing in the same direction as the incident collimated space light; the transmitted reflected light is reflected at 90 degrees through the center of the face of the second reflecting mirror 4, and is perpendicular to the direction of the incident collimated space light; The light emitted from the first reflector 3 hits the center of the dihedral standard part 6 or the dihedral angle target part to be measured 7 at normal incidence, and is reflected by the original path, becoming the first retroreflected light; the first retroreflected light passes through the first reflection again The mirror 3 reflects at 90 degrees and shoots towards one side of the dichroic prism 2; the light emitted from the second reflecting mirror 4 hits the face center of the other vertical surface of the dihedral standard part 6 or the dihedral angle target part 7 to be measured at normal incidence. It is reflected by the original path and becomes the second retroreflected light; the second retroreflected light is reflected again at 90 degrees by the second reflecting mirror 4 and shoots to the other vertical surface of the dichroic prism 2; the first retroreflected light and the second retroreflected light pass through the dichroic prism 2 center beam combining; after the first retroreflected light passes through the dichroic prism 2, the transmitted light hits the photodetector 5 with normal incidence; after the second retroreflected light passes through the dichroic prism 2, the reflected light hits the photodetector 5 with normal incidence; transmission The light 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 differential signal;

The invention provides a measurement principle of a dihedral angle measurement optical system based on differential wavefront sensing.

First, use the dihedral angle standard piece 6 to adjust the beam direction of the interference measurement device. According to the design of the above-mentioned optical path measurement device, after adjusting the interference signal, the angle between the two reflected beams is zero, which is used as the reference standard for dihedral angle measurement. Then switch to the dihedral angle target piece 7 to measure the dihedral angle.

For laser interferometry signals, the four-quadrant wavefront difference can be used to measure the yaw angles of two lasers, and the information on the dihedral angles of the two reflecting surfaces can be extracted. Assume that the phases of the four quadrants of the detector are expressed as The measuring laser is a Gaussian beam with diameter d, then the measurement equation of the dihedral angle can be expressed as:

Among them, λ is the wavelength of the two interference beams.

The invention discloses a dihedral angle measurement optical system design based on differential wavefront sensing. The design includes optical path system design and measurement principles. The optical path system design includes a set of differential wavefront sensing interference optical path design; the measurement principle explains the basic principles of dihedral angle measurement and its theoretical measurement accuracy; the measurement steps provide the operating steps of dihedral angle measurement.

The design of the dihedral angle measurement optical system based on differential wavefront sensing provided by the present invention can achieve high-precision measurement and calibration of dihedral angles. This design can achieve the advantages of non-contact measurement, simple structure, portability, and high precision, and can be widely used in industrial production, metrological testing, and experimental calibration.

The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person familiar with the technical field can, within the technical scope disclosed in the present invention, implement the technical solutions of the present invention. Equivalent substitutions or changes of the inventive concept thereof shall be included in the protection scope of the present invention.

In addition, unless defined otherwise, all technical and scientific terms used herein have the same meanings commonly understood by one of ordinary skill in the art to which this invention belongs. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods in connection with which the documents relate. In the event of conflict with any incorporated document, the contents of this specification shall prevail.

Claims (7)

1. A dihedral angle optical measurement device, characterized in that it comprises a laser collimator (1), a beam splitter prism (2), a photodetector (5) and a dihedral angle standard component (6): The laser collimator (1) is mounted on a measurement substrate, the output end of the laser collimator (1) is optically connected to the beam splitter prism (2); the output end of the beam splitter prism (2) is optically connected to a first reflector (3) and a second reflector (4), the output ends of the first reflector (3) and the second reflector (4) are both optically connected to the dihedral angle standard component (6); the photoelectric detector (5) is connected to the beam splitter prism (2); The measuring laser passes through the laser collimator (1) and the beam splitter prism (2) in sequence and then is split according to a ratio into reflected light and transmitted light; the reflected light and the transmitted light are respectively reflected by the first reflector (3) and the second reflector (4) and then hit the center of the dihedral angle standard component (6) and return along the original path, and are combined and interfered on the beam splitter prism (2); the position and posture of the photodetector (5) are adjusted so that the combined signal hits the center position of the photodetector (5), and the wavefront difference signal of the dihedral angle standard component (6) is read; when the wavefront difference signal of the dihedral angle standard component (6) is zero, the dihedral angle standard component (6) is replaced with a dihedral angle target component (7) to read the wavefront difference signal of the dihedral angle target component (7); and the measurement information of the dihedral angle is obtained through the wavefront difference signals of the dihedral angle standard component (6) and the dihedral angle target component (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 anti-parallel, 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 90 degrees. 4. The dihedral angle optical measurement device according to claim 3, characterized in that the light splitting ratio of the light splitting 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. A method for measuring a dihedral angle optical measurement device, characterized in that it comprises the following steps: The incident light generated by the measuring laser is split into reflected light and transmitted light in proportion by the beam splitting prism (2); The reflected light and the transmitted light are respectively reflected by the first reflector (3) and the second reflector (4) and then return along the original path after being reflected at the center of the dihedral angle standard component (6), and are combined and interfered on the beam splitter prism (2). The position and posture of the photodetector (5) are adjusted so that the combined beam signal hits the center position of the photodetector (5), and the wavefront difference signal of the dihedral angle standard component (6) is read; When the wavefront differential signal of the dihedral angle standard component (6) is zero, the dihedral angle standard component (6) is replaced with a dihedral angle target component (7) to be measured, and the wavefront differential signal of the dihedral angle target component (7) to be measured is read; The measurement information of the dihedral angle is obtained based on the read wavefront difference signals of the dihedral angle standard component (6) and the dihedral angle target component (7). 7. The measuring method of the dihedral angle optical measuring device according to claim 6 is characterized in that it also includes calculating the dihedral angle information through the dihedral angle measurement equation according to the wavefront signals of the read dihedral angle standard component (6) and the dihedral angle target component (7), and the specific calculation formula is: Where λ is the wavelength of the two interfering beams, They represent the phases of the four quadrants of the detector, and d is the diameter of the Gaussian beam measuring the laser.