CN110132180B - Mirror-surface type laser self-mixing micro-angle measuring system and method with any included angle - Google Patents

Mirror-surface type laser self-mixing micro-angle measuring system and method with any included angle Download PDF

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CN110132180B
CN110132180B CN201910492083.3A CN201910492083A CN110132180B CN 110132180 B CN110132180 B CN 110132180B CN 201910492083 A CN201910492083 A CN 201910492083A CN 110132180 B CN110132180 B CN 110132180B
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laser
plane mirror
mirror
angle
turntable
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CN110132180A (en
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吕亮
王晨辰
陈由泽
毕铁柱
周俊峰
王志平
俞本立
王焕钦
桂华侨
刘建国
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Anhui University
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Anhui University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/26—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes

Abstract

The invention relates to the technical field of optical angle measurement, in particular to a mirror laser self-mixing micro-angle measurement system with any included angle and a measurement method.

Description

Mirror-surface type laser self-mixing micro-angle measuring system and method with any included angle
Technical Field
The invention relates to the technical field of optical angle measurement, in particular to a mirror surface type laser self-mixing micro-angle measurement system and method based on an intersecting mirror and with any included angle.
Background
The angle measurement technology is an important component of the metering technology, and with the continuous development of the scientific technology, the angle measurement technology is widely applied to the technical fields of optical-mechanical-electrical integration, aerospace, military, national defense and the like.
In the angle measurement technology, the measurement principle is mainly divided into three categories: the mechanical angle measurement technology, the electromagnetic angle measurement technology and the optical angle measurement technology were first researched and started, wherein the mechanical angle measurement technology is represented by a multi-tooth dividing disc, and the electromagnetic angle measurement technology is represented by a circular magnetic grid angle measurement technology and an induction synchronizer angle measurement technology. Both the mechanical angle measurement technology and the electromagnetic angle measurement technology have the defects of manual operation and contact measurement, and are not beneficial to realizing the automation of angle measurement. Compared with mechanical angle measurement technology and electromagnetic angle measurement technology, the optical angle measurement technology has the advantages of non-contact measurement, high measurement precision, high measurement resolution and the like.
At present, the optical angle measurement technology at home and abroad mainly comprises the following steps according to different measurement principles: circular grating method, ring laser method, optical internal reflection method, auto-collimation method, laser interference method, etc.
The optical internal reflection method measures the change of the incident angle by measuring the change of the reflected light intensity by utilizing the relation between the change of the incident angle and the change of the reflected light intensity under the full-emission condition; the auto-collimation method is characterized in that an optical auto-collimation principle is utilized, a rotation angle of an emission environment on a measured object is converted into a linear quantity change on an auto-collimation receiver, and the change of a micro angle of a reflecting surface is indirectly measured by measuring the linear quantity change.
The laser interferometry is to use the phase change caused by the angle change and then measure the angle through a phase detection mechanism, and the typical laser interferometry is based on the basic principle of the michelson interferometer, and the angle change is represented by the change of the optical path difference of the two beams, and finally the angle to be measured is obtained by observing interference fringes. Although the angle measurement method based on the double-beam laser interference has improved measurement accuracy and measurement range to a certain extent compared with the angle measurement method based on the measurement of the light intensity change, the measurement device has a relatively complex structure, the volume and the cost of the system are increased, and the light path auto-collimation is difficult to realize in the actual measurement.
In recent years, laser interference angle measurement technology based on the laser self-mixing principle is becoming a research hotspot of angle measurement technology. Compared with the traditional angle measurement technology by a laser double-beam interference method, the angle measurement technology based on the laser self-mixing principle gradually becomes an important research direction of the laser interference angle measurement technology due to the advantages of single-light path design, auto-collimation and the like. Various micro-angle measurement schemes based on the laser self-mixing principle have been designed and tried by a plurality of research groups at home and abroad, and preliminary experimental results are obtained. In 2008, the schneiderian et al of Chinese university designed and researched a micro-angle measuring system by using a method of rotating a plane mirror, the plane mirror can generate angle change along with the rotation of a turntable, so that the length of an external cavity is changed, the rotation angle of the turntable can be obtained by measuring laser self-mixing interference signals formed by feedback light and combining a fringe counting method, and the angle measuring range is +/-2.41'.
According to the research scheme, the existing angle measuring device based on the laser self-mixing principle still simply adopts a plane reflector, the incidence position of a laser beam is strictly limited, meanwhile, the feedback light intensity fluctuates along with the change of the angle in the rotation process, the signal to noise ratio of a signal to be measured is further influenced, and the measurement range and the resolution ratio of the system are greatly reduced. There are also some documents that disclose the solution of using a single reflection prism, although it is not limited by the incident position of the laser, the measurement range is still limited by the rotation angle, when the rotation angle is too large, the light cannot be detected, and there is still the problem of low resolution.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a laser self-mixing micro-angle measuring system and a laser self-mixing micro-angle measuring method based on an intersecting mirror, which can effectively overcome the problems of the existing angle measuring method based on the laser self-mixing principle and can realize the measurement of a large angle range under the condition of high resolution.
In order to achieve the above technical objects, a first technical solution of the present invention is:
a laser self-mixing micro-angle measuring system comprises a first rotary table, a second rotary table, a T-shaped transmission support, a first intersecting plane mirror, a second intersecting plane mirror, an orthogonal reflector, a third reflector, a reflector transmission support, a laser, a beam splitter, a photoelectric detector and a computer;
the first turntable and the second turntable synchronously rotate through the T-shaped transmission bracket;
the T-shaped transmission support comprises a first transmission rod and a support rod which are horizontally arranged and are perpendicular to each other, a first connecting column and a second connecting column are connected to two ends of the first transmission rod respectively, the bottom of the first connecting column and the bottom of the second connecting column are arranged on a first rotary table and a second rotary table respectively through bearings, the first transmission rod is parallel to a connecting line between the circle center of the first rotary table and the circle center of the second rotary table, and the middle part of the support rod is connected to the second connecting column;
the first intersected plane mirror comprises a first plane mirror and a second plane mirror, one side of the first plane mirror is connected with one side of the second plane mirror, and the included angle between the mirror surface of the first plane mirror and the mirror surface of the second plane mirror is 90 degrees;
the second intersecting plane mirror comprises a third plane mirror and a fourth plane mirror, one side of the third plane mirror is connected with one side of the fourth plane mirror, and the included angle between the third plane mirror and the fourth plane mirror is 90 degrees;
the connecting edge of the first plane mirror and the second plane mirror and the connecting edge of the third plane mirror and the fourth plane mirror are respectively connected with the lower half parts of the two ends of the supporting rod, the angular bisector of the included angle between the first plane mirror surface and the second plane mirror surface and the angular bisector of the included angle between the third plane mirror surface and the fourth plane mirror surface are both vertical to the supporting rod, and the mirror surfaces of the first plane mirror, the second plane mirror, the third plane mirror and the fourth plane mirror are all deviated from the first transmission rod;
the orthogonal reflector comprises a first reflector and a second reflector, one side of the first reflector is connected with one side of the second reflector, the included angle between the mirror surface of the first reflector and the mirror surface of the second reflector is 90 degrees, and the bisector of the included angle of the orthogonal reflector and the first transmission rod are positioned on the same straight line;
the reflector transmission bracket comprises a second transmission rod and a third transmission rod which are symmetrically arranged, the bottom of one end of the second transmission rod is connected to the upper half part of one end of the support rod, the bottom of one end of the third transmission rod is connected to the upper half part of the other end of the support rod, the other end of the second transmission rod is connected with the other end of the third transmission rod, and the bottom of the joint of the first transmission rod and the third transmission rod is connected to the top of the joint of the first reflector and the second reflector;
the third reflector is arranged in front of the fourth plane mirror, and the included angle between the third reflector and the fourth plane mirror is 45 degrees;
the laser emits a laser beam onto the first plane mirror, and the included angle between the laser beam and the first plane mirror is 45 degrees;
the beam splitter is arranged between the laser and the first plane mirror and is used for splitting a laser beam onto the photoelectric detector;
the photoelectric detector converts the received laser signal into an electric signal and sends the electric signal to a computer;
and the computer processes and analyzes the received electric signal to obtain the rotation angle of the first turntable to be tested.
The micro-angle measurement method based on the measurement system comprises the following steps:
A. the first turntable and the second turntable can synchronously rotate based on the arrangement of the T-shaped transmission support, when any one turntable rotates, the T-shaped transmission support drives the other turntable to synchronously rotate, and further drives the first intersecting plane mirror and the second intersecting plane mirror to horizontally move;
B. the carousel rotates in-process laser instrument outgoing laser beam, and laser beam's the light path of marcing does:
a. the laser emits laser beams, the laser beams enter the first plane mirror at an angle of 45 degrees and are reflected to the first reflecting mirror through the second plane mirror;
b. the first reflector reflects the laser beam to the second reflector and then reflects the laser beam to the third plane mirror through the second reflector, the direction of the laser beam incident to the third plane mirror is the same as the direction of the laser beam emitted by the laser, and the included angle between the laser beam and the third plane mirror is 45 degrees;
c. laser beams are reflected by a third plane mirror and a fourth plane mirror which are vertical to each other in sequence and then enter the third reflecting mirror at an angle of 90 degrees, and the direction of the laser beams entering the third reflecting mirror is opposite to the direction of laser beams emitted by a laser;
d. the third reflector reflects the incident laser beam, and the reflected laser beam returns to the laser cavity along the original path to form a laser self-mixing signal;
C. feeding back the laser self-mixing signal to a photoelectric detector through a beam splitter;
D. the photoelectric detector converts the received laser signal into an electric signal and sends the electric signal to a computer;
E. the computer processes and analyzes the received signals, obtains the external cavity optical path difference of the laser self-mixing signals before and after the rotation of the turntable by utilizing the laser self-mixing interference principle, and obtains the rotation angle of the turntable by utilizing the relation between the external cavity optical path difference and the rotation angle of the turntable.
As can be seen from the above description, the measurement system and the measurement method thereof have the following advantages: (1) when a laser beam is incident on the first intersecting plane mirror, the laser beam is firstly incident on the first plane mirror at the outer side, namely, an external incidence mode is adopted, and compared with a traditional heterodyne interference system, the system structure is simpler; (2) through the reflection unit that first crossing plane mirror, first speculum, second crossing plane mirror and third speculum constitute, not only realized the auto-collimation of laser self-mixing signal but also compare in the reflection unit that reflection unit or right-angle prism that traditional level mirror constitutes constitute and constitute, under same turned angle, before and after the rotation, the optical path difference grow of laser self-mixing signal to the measurement resolution ratio and the measuring range of system have been improved.
In order to achieve the above technical object, a second technical solution of the present invention is:
a laser self-mixing micro-angle measuring system comprises a first rotary table, a second rotary table, a T-shaped transmission support, a first intersecting plane mirror, a second intersecting plane mirror, a first reflecting mirror, a second reflecting mirror, a third reflecting mirror, a second transmission rod, a third transmission rod, a laser, a beam splitter, a photoelectric detector and a computer;
the first turntable and the second turntable synchronously rotate through the T-shaped transmission bracket;
the T-shaped transmission support comprises a first transmission rod and a support rod which are horizontally arranged and are perpendicular to each other, a first connecting column and a second connecting column are connected to two ends of the first transmission rod respectively, the bottom of the first connecting column and the bottom of the second connecting column are arranged on a first rotary table and a second rotary table respectively through bearings, the first transmission rod is parallel to a connecting line between the circle center of the first rotary table and the circle center of the second rotary table, and the middle part of the support rod is connected to the second connecting column;
the first intersected plane mirror comprises a first plane mirror and a second plane mirror, one side of the first plane mirror is connected with one side of the second plane mirror, and the included angle between the mirror surface of the first plane mirror and the mirror surface of the second plane mirror is 90 degrees;
the second intersecting plane mirror comprises a third plane mirror and a fourth plane mirror, one side of the third plane mirror is connected with one side of the fourth plane mirror, and the included angle between the third plane mirror and the fourth plane mirror is 90 degrees;
the connecting edge of the first plane mirror and the second plane mirror and the connecting edge of the third plane mirror and the fourth plane mirror are respectively connected with two ends of the supporting rod, an angular bisector of an included angle between the first plane mirror surface and the second plane mirror surface and an angular bisector of an included angle between the third plane mirror surface and the fourth plane mirror surface are both perpendicular to the supporting rod, and the mirror surfaces of the first plane mirror, the second plane mirror, the third plane mirror and the fourth plane mirror are all deviated from the first transmission rod;
the first reflector is arranged in front of the first plane mirror, the included angle between the first reflector and the first plane mirror is 90 degrees, and the first reflector is fixedly connected with the first plane mirror through a second transmission rod;
the second reflecting mirror is arranged in front of the fourth plane mirror, the included angle between the mirror surfaces of the second reflecting mirror and the fourth plane mirror is 90 degrees, and the second reflecting mirror is fixedly connected with the fourth plane mirror through a third transmission rod;
the third reflector is arranged in front of the third plane mirror, and the included angle between the third reflector and the third plane mirror is 45 degrees;
the laser emits a laser beam onto the second plane mirror, and the included angle between the laser beam and the mirror surface of the second plane mirror is 45 degrees;
the beam splitter is arranged between the laser and the second plane mirror and is used for splitting the laser beam to the photoelectric detector;
the photoelectric detector converts the received laser signal into an electric signal and sends the electric signal to a computer;
and the computer processes and analyzes the received electric signal to obtain the rotation angle of the first turntable to be tested.
The micro-angle measurement method based on the measurement system comprises the following steps:
A. the first turntable and the second turntable can synchronously rotate based on the arrangement of the T-shaped transmission support, when any one turntable rotates, the T-shaped transmission support drives the other turntable to synchronously rotate, and further drives the first intersecting plane mirror and the second intersecting plane mirror to horizontally move;
B. the carousel rotates in-process laser instrument outgoing laser beam, and laser beam's the light path of marcing does:
a. the laser emits laser beams, the laser beams enter the second plane mirror at an angle of 45 degrees and are reflected to the first reflecting mirror through the first plane mirror;
b. the first reflector reflects the laser beam to the second reflector and then reflects the laser beam to the fourth plane mirror through the second reflector, the direction of the laser beam incident to the fourth plane mirror is the same as the direction of the laser beam emitted by the laser, and the included angle between the laser beam and the fourth plane mirror is 45 degrees;
c. laser beams are reflected by a fourth plane mirror and a third plane mirror which are vertical to each other in sequence and then enter a third reflecting mirror at an angle of 90 degrees, and the direction of the laser beams entering the third reflecting mirror is opposite to the direction of laser beams emitted by a laser;
d. the third reflector reflects the incident laser beam, and the reflected laser beam returns to the laser cavity along the original path to form a laser self-mixing signal;
C. feeding back the laser self-mixing signal to a photoelectric detector through a beam splitter;
D. the photoelectric detector converts the received laser signal into an electric signal and sends the electric signal to a computer;
E. the computer processes and analyzes the received signals, obtains the external cavity optical path difference of the laser self-mixing signals before and after the rotation of the turntable by utilizing the laser self-mixing interference principle, and obtains the rotation angle of the turntable by utilizing the relation between the external cavity optical path difference and the rotation angle of the turntable.
As can be seen from the above description, the measurement system and the measurement method thereof have the following advantages: (1) when laser beams are incident to the first intersecting plane mirror, the laser beams are firstly incident to the second plane mirror at the inner side, namely, an internal incidence mode is adopted, so that the whole structure of the measuring system is compact; (2) through the reflection unit formed by the first orthogonal plane mirror, the first reflection mirror, the second orthogonal plane mirror and the third reflection mirror, the auto-collimation of the laser self-mixing signal is realized, and compared with the reflection unit formed by the traditional plane mirror or the reflection unit formed by a right-angle prism, the optical path difference of the laser self-mixing signal is increased before and after rotation under the same rotation angle, so that the measurement resolution and the measurement range of the system are improved; (3) the measuring system linkage device is simple and easy to realize; the two external reflectors are separately linked and can be independently controlled, so that the machining error is reduced, and the light path is more easily collimated.
In order to achieve the above technical object, a third technical solution of the present invention is:
the utility model provides a laser is from little angle measurement system of mixing which characterized in that: comprises a first rotary table, a second rotary table, a transmission rod, an intersecting plane mirror, a reflector, a laser, a beam splitter and a photoelectric probeA detector and a computer; the first turntable and the second turntable synchronously rotate through the transmission rod; the end parts of the two ends of the transmission rod are respectively connected with a first connecting column and a second connecting column, the bottom of the first connecting column and the bottom of the second connecting column are respectively arranged on the first rotary table and the second rotary table through bearings, and the transmission rod is parallel to a connecting line between the circle center of the first rotary table and the circle center of the second rotary table; the intersecting plane mirror comprises a first plane mirror and a second plane mirror, wherein the mirror surfaces of the first plane mirror and the second plane mirror are opposite, one side of the first plane mirror is connected with one side of the second plane mirror, the connecting edges of the first plane mirror and the second plane mirror are connected onto a second connecting column, the mirror surfaces of the first plane mirror and the second plane mirror are deviated from the transmission rod, the angular bisector of the included angle between the first plane mirror and the second plane mirror and the transmission rod are positioned on the same straight line, the included angle between the first plane mirror and the second plane mirror is recorded as alpha, and the value range of the alpha is as follows: 0 degree<α<180 degrees; the reflector is arranged at the outer side of the second plane mirror, and the included angle between the mirror surface and the first plane mirror surface is equal to
Figure GDA0002614901860000071
The laser emits laser beams to the second plane mirror, an included angle formed by the laser beams emitted by the laser and the laser beams reflected by the second plane mirror is equal to alpha, and an included angle formed by the laser beams emitted by the laser and the mirror surface of the reflecting mirror is equal to alpha
Figure GDA0002614901860000072
The beam splitter is arranged between the laser and the second plane mirror and is used for splitting the laser beam to the photoelectric detector; the photoelectric detector converts the received laser signal into an electric signal and sends the electric signal to a computer; and the computer processes and analyzes the received electric signal to obtain the rotation angle of the first turntable to be tested.
The micro-angle measurement method based on the measurement system comprises the following steps:
A. the first turntable and the second turntable can synchronously rotate based on the arrangement of the transmission rod, and when any one turntable rotates, the transmission rod drives the other turntable to synchronously rotate so as to drive the intersecting plane mirror to horizontally move;
B. the carousel rotates in-process laser instrument outgoing laser beam, and laser beam's the light path of marcing does:
a. the laser emits laser beams to the second plane mirror, then the laser beams are reflected to the first plane mirror and then reflected to the reflecting mirror;
b. the third reflector reflects the incident laser beam, and the reflected laser beam returns to the laser cavity along the original path to form a laser self-mixing signal;
C. feeding back the laser self-mixing signal to a photoelectric detector through a beam splitter;
D. the photoelectric detector converts the received laser signal into an electric signal and sends the electric signal to a computer;
E. the computer processes and analyzes the received signals, obtains the external cavity optical path difference of the laser self-mixing signals before and after the rotation of the turntable by utilizing the laser self-mixing interference principle, and obtains the rotation angle of the turntable by utilizing the relation between the external cavity optical path difference and the rotation angle of the turntable.
As can be seen from the above description, the measurement system and the measurement method thereof have the following advantages: (1) when laser beams are incident to the intersecting plane mirrors, the laser beams are firstly incident to the second plane mirror on the inner side, namely, an internal incidence mode is adopted, so that the overall structure of the measuring system is compact; (2) through the reflection unit formed by the crossed plane mirror and the reflection mirror, the auto-collimation of the laser self-mixing signal is realized, and compared with the reflection unit formed by the traditional plane mirror or the reflection unit formed by a right-angle prism, the optical path difference of the laser self-mixing signal is increased before and after rotation under the same rotation angle, so that the measurement resolution and the measurement range of the system are improved; (3) the whole structure of the measuring system is simple and easy to realize, the mechanical error is small, the included angle between the first plane mirror and the second plane mirror is adjustable, different angles correspond to different system measurement resolutions, and the included angle can be selected according to actual requirements.
As an improvement, the device also comprises a transmission belt which is sleeved on the first rotating disc and the second rotating disc; the synchronization of the first turntable and the second turntable is further ensured by a transmission belt.
As an improvement, an optical attenuator is also arranged between the laser and the beam splitter; the optical attenuator is used for adjusting the intensity of feedback light received by the laser to prevent the feedback light from being too strong or exceeding a laser damage threshold.
Preferably, the laser is a semiconductor laser, a he-ne laser, a microchip laser or a fiber laser.
Drawings
FIG. 1 is a schematic structural view of embodiment 1 of the present invention;
FIG. 2 is a schematic structural view of embodiment 1 of the present invention;
FIG. 3 is a schematic diagram of the optical path structure of a single orthogonal plane mirror in example 1 of the present invention;
FIG. 4 is a schematic diagram of the optical path structure of a bi-orthogonal plane mirror in example 1 of the present invention;
FIG. 5 is a schematic view of a three-mirror cavity model;
FIG. 6 is a schematic structural view of embodiment 2 of the present invention;
FIG. 7 is a schematic structural view of embodiment 2 of the present invention;
FIG. 8 is a schematic diagram of the optical path structure of a single orthogonal plane mirror in example 2 of the present invention;
FIG. 9 is a schematic diagram of the optical path structure of a bi-orthogonal plane mirror in example 2 of the present invention;
FIG. 10 is a schematic structural view of embodiment 3 of the present invention;
FIG. 11 is a schematic structural view of embodiment 3 of the present invention;
fig. 12 is a schematic diagram of the optical path structure of an arbitrary-angle intersecting plane mirror in example 3 of the present invention.
Detailed Description
Embodiment 1 of the present invention is described in detail with reference to fig. 1 to 5, but the present invention is not limited to the claims.
As shown in fig. 1, a laser self-mixing micro-angle measurement system includes a first turntable 101 and a second turntable 102, a T-shaped transmission support 103, a first intersecting plane mirror 104, a second intersecting plane mirror 105, an orthogonal mirror 106, a third mirror 107, a mirror transmission support 108, a laser 109, a beam splitter 110, a photodetector 111, and a computer 112, which are arranged side by side;
the first rotary table 101 and the second rotary table 102 synchronously rotate through a T-shaped transmission bracket 103; the T-shaped transmission bracket 103 comprises a first transmission rod 1031 and a support rod 1032 which are horizontally arranged and vertical to each other, two ends of the first transmission rod 1031 are respectively connected with a first connecting column 113 and a second connecting column 114, the bottoms of the first connecting column 113 and the second connecting column 114 are respectively arranged on the first rotary table 101 and the second rotary table 102 through bearings, the first transmission rod 1031 is parallel to a connecting line between the circle center of the first rotary table 101 and the circle center of the second rotary table 102, and the middle part of the support rod 1032 is connected to the second connecting column 114; the first intersecting plane mirror 104 comprises a first plane mirror 1041 and a second plane mirror 1042, one side of the first plane mirror 1041 is connected with one side of the second plane mirror 1042, and the included angle between the mirror surface of the first plane mirror 1041 and the mirror surface of the second plane mirror 1041 is 90 degrees; the second intersecting plane mirror 105 comprises a third plane mirror 1051 and a fourth plane mirror 1052, one side of the third plane mirror 1051 is connected with one side of the fourth plane mirror 1052, and the included angle between the mirror surface of the third plane mirror 1051 and the mirror surface of the fourth plane mirror 1052 is 90 degrees; the connecting edge of the first flat mirror 1041 and the second flat mirror 1042 and the connecting edge of the third flat mirror 1051 and the fourth flat mirror 1052 are respectively connected with the lower half parts of the two ends of the supporting rod 1032, the angular bisector of the included angle between the mirror surface of the first flat mirror 1041 and the second flat mirror 1042 and the angular bisector of the included angle between the mirror surface of the third flat mirror 1051 and the fourth flat mirror 1052 are both perpendicular to the supporting rod 1032, and the mirror surfaces of the first flat mirror 1041, the second flat mirror 1042, the third flat mirror 1051 and the fourth flat mirror 1052 all deviate from the first transmission rod 1031; the orthogonal mirror 106 comprises a first mirror 1061 and a second mirror 1062, one side of the first mirror 1061 is connected with one side of the second mirror 1062, and an included angle between the mirror surface of the first mirror 1061 and the mirror surface of the second mirror 1062 is 90 degrees, and the bisector of the included angle and the first transmission rod 1031 are located on the same straight line; the mirror driving bracket 108 includes a second driving rod 1081 and a third driving rod 1082 symmetrically disposed, wherein the second driving rod 1081 is connected to the upper half of one end of the supporting rod 1032 at the bottom of one end thereof, the third driving rod 1082 is connected to the upper half of the other end of the supporting rod 1032 at the bottom of one end thereof, the second driving rod 1081 is connected to the other end of the third driving rod 1082 at the bottom of the connection between the two driving rods, and the connection between the two driving rods is connected to the top of the connection between the first mirror 1061 and the second mirror 1062; the third reflector 107 is arranged in front of the fourth plane mirror 1052, and the included angle between the two mirror surfaces is 45 degrees; the laser 109 emits a laser beam onto the first plane mirror 1041, and an included angle between the laser beam and the mirror surface of the first plane mirror 1041 is 45 degrees; the beam splitter 110 is disposed between the laser 109 and the first plane mirror 1041, and is configured to split the laser beam onto the photodetector 111; the photoelectric detector 111 converts the received laser signal into an electric signal and sends the electric signal to the computer 112; the computer 112 processes and analyzes the received electrical signal to obtain the rotation angle of the first turntable to be measured.
The micro-angle measurement method based on the measurement system comprises the following steps:
A. the first turntable and the second turntable can synchronously rotate based on the arrangement of the T-shaped transmission support, when any one turntable rotates, the T-shaped transmission support drives the other turntable to synchronously rotate, and further drives the first intersecting plane mirror and the second intersecting plane mirror to horizontally move;
B. the carousel rotates in-process laser instrument outgoing laser beam, and laser beam's the light path of marcing does:
a. the laser emits laser beams, the laser beams enter the first plane mirror at an angle of 45 degrees and are reflected to the first reflecting mirror through the second plane mirror;
b. the first reflector reflects the laser beam to the second reflector and then reflects the laser beam to the third plane mirror through the second reflector, the direction of the laser beam incident to the third plane mirror is the same as the direction of the laser beam emitted by the laser, and the included angle between the laser beam and the third plane mirror is 45 degrees;
c. laser beams are reflected by a third plane mirror and a fourth plane mirror which are vertical to each other in sequence and then enter the third reflecting mirror at an angle of 90 degrees, and the direction of the laser beams entering the third reflecting mirror is opposite to the direction of laser beams emitted by a laser;
d. the third reflector reflects the incident laser beam, and the reflected laser beam returns to the laser cavity along the original path to form a laser self-mixing signal;
C. feeding back the laser self-mixing signal to a photoelectric detector through a beam splitter;
D. the photoelectric detector converts the received laser signal into an electric signal and sends the electric signal to a computer;
E. the computer processes and analyzes the received signals, obtains the external cavity optical path difference of the laser self-mixing signals before and after the rotation of the turntable by utilizing the laser self-mixing interference principle, and obtains the rotation angle of the turntable by utilizing the relation between the external cavity optical path difference and the rotation angle of the turntable.
Wherein, the theory of the basis of the processing and analyzing process in the step E is as follows:
as shown in fig. 2, a start position P1P2(first intersecting plane mirror vertex P1Vertex P of plane mirror intersecting with second phase2Is parallel to the y-axis, when the first rotation angle is theta
Figure GDA0002614901860000101
The second turntable 2 rotates by the same angle, and the T-shaped transmission support is always parallel to the x axis to ensure that the first intersected plane mirror and the second intersected plane mirror do not deviate in the vertical direction and only generate translation in the xy plane. After the rotation, the first plane mirror, the second plane mirror, the third plane mirror and the fourth plane mirror are all kept orthogonal and generate offset, the laser 1 emits laser light through the point A, in the whole rotation process, the position of the laser 1 is always kept at the point A, the light returns from the point H along the original path after being reflected by the plane mirrors and the reflectors for multiple times, and the radiuses of the first rotary disc and the second rotary disc are both R. The first intersecting plane mirror and the second intersecting plane mirror are orthogonal plane mirrors due to the fact that the included angle is 90 degrees.
Based on the micro-angle measurement system with the double-orthogonal plane mirror, the optical path change of the micro-angle measurement system is theoretically calculated, the experimental device is simplified, and the structure diagram of the single-orthogonal plane mirror shown in fig. 3 is established.
As shown in FIG. 3, the vertex V of the orthogonal plane mirror1Reaches V after rotating2Primary light path AB1C1D1Become AB2C2D2The optical path difference can be derived from the geometrical relationship as follows:
Figure GDA0002614901860000111
the optical path difference caused by the angle change can be expressed as:
Figure GDA0002614901860000112
therefore, for the micro-angle measurement system with the bi-orthogonal plane mirrors described in this embodiment, as shown in fig. 4, the optical path difference can be calculated as:
Figure GDA0002614901860000113
when the optical path of the feedback light changes one wavelength each time the laser changes one stripe from the mixed waveform, the following can be obtained:
ΔL＝4R(2cosθ-2sinθ-1)＝Nλ(4)
in the formula (3), N is the number of stripes.
Combining the laser self-mixing theory, as shown in FIG. 5, n0Is the effective refractive index, r, of the working substance of the laser at the signal light wavelength1And r2Is two end faces M of the laser1And M2Reflection coefficient of electric field amplitude of (1), feedback end face M3Has an electric field amplitude reflection coefficient of r3D represents the lumen length, LextLength of the external cavity, thus, the initial electric field E in the laser cavity0(t) the electric field e (t) after one round trip can be expressed as:
Figure GDA0002614901860000121
in the formula (5), v is the frequency of the optical wave, R2Indicating the laser rear facet M2Wherein R is2＝|r2|2，r2Where c is the light velocity in vacuum, g is the linear gain of the gain medium per unit length of the laser to the signal light, and γ is the total loss of the signal light per unit distance in the laser cavityAnd (4) consuming. Further from the steady state laser oscillation conditions, an expression of the angular variation of the output power of the laser can be obtained as follows:
Figure GDA0002614901860000122
in equation (6), ζ is the modulation factor, λ is the laser wavelength, P0Output intensity of the laser, L, without light feedback0Indicating the initial external cavity length.
It can be seen from the derivation process that, compared with the conventional laser self-mixing angle measurement method, the system and the method for measuring the external incidence type laser self-mixing micro-angle of the dual-orthogonal plane mirror described in this embodiment have the advantages of unlimited angle measurement range and high system resolution.
As can be seen from the above description, the present embodiment has the following advantages: (1) when a laser beam is incident on the first intersecting plane mirror, the laser beam is firstly incident on the first plane mirror at the outer side, namely, an external incidence mode is adopted, and compared with a traditional heterodyne interference system, the system structure is simpler; (2) through the reflection unit that first crossing plane mirror, first speculum, second crossing plane mirror and third speculum constitute, not only realized the auto-collimation of laser self-mixing signal but also compare in the reflection unit that reflection unit or right-angle prism that traditional level mirror constitutes constitute and constitute, under same turned angle, before and after the rotation, the optical path difference grow of laser self-mixing signal to the measurement resolution ratio and the measuring range of system have been improved.
The measurement system described in this embodiment can be further improved as follows:
(1) the measuring system further comprises a transmission belt 115 which is sleeved on the first rotating disc and the second rotating disc, so that the synchronism of the first rotating disc and the second rotating disc is further improved, and the accuracy of the measuring result is improved.
(2) An optical attenuator 116 is additionally arranged between the laser and the beam splitter, the optical attenuator 116 is used for adjusting the light intensity of the feedback light received by the laser, and the feedback light is prevented from being too strong or exceeding the damage threshold of the laser, so that the accuracy of the measurement result is further ensured.
(3) The laser type in the system is not limited, can be various types such as a semiconductor laser, a helium-neon laser, a microchip laser or a fiber laser, and can be selected according to application requirements.
Embodiment 2 of the present invention is described in detail with reference to fig. 5 to 9, but the present invention is not limited to the claims.
As shown in fig. 6, a laser self-mixing micro-angle measuring system comprises a first rotating disk 201, a second rotating disk 202, a T-shaped transmission bracket 203, a first intersecting plane mirror 204, a second intersecting plane mirror 205, a first reflecting mirror 206, a second reflecting mirror 207, a third reflecting mirror 208, a second transmission rod 209, a third transmission rod 210, a laser 211, a beam splitter 212, a photoelectric detector 213 and a computer 214;
the first rotating disc 201 and the second rotating disc 202 synchronously rotate through a T-shaped transmission bracket 203; the T-shaped transmission bracket 203 comprises a first transmission rod 2031 and a support rod 2032 which are horizontally arranged and are perpendicular to each other, two ends of the transmission rod 2031 are respectively connected with a first connecting post 215 and a second connecting post 216, the bottoms of the first connecting post 216 and the bottom of the second connecting post 216 are respectively arranged on the first turntable 201 and the second turntable 202 through bearings, the first transmission rod 2031 is parallel to a connecting line between the circle center of the first turntable 201 and the circle center of the second turntable 202, and the middle part of the support rod 2032 is connected on the second connecting post 216; the first intersecting plane mirror 204 includes a first plane mirror 2041 and a second plane mirror 2042, one side of the first plane mirror 2041 is connected to one side of the second plane mirror 2042, and an included angle between the first plane mirror 2041 and the second plane mirror 2042 is 90 °; the second intersecting plane mirror 205 comprises a third plane mirror 2051 and a fourth plane mirror 2052, one side of the third plane mirror 2051 is connected with one side of the fourth plane mirror 2052, and the included angle between the mirror surface of the third plane mirror 2051 and the mirror surface of the fourth plane mirror 2052 is 90 degrees; the connecting edge of the first flat mirror 2041 and the second flat mirror 2042 and the connecting edge of the third flat mirror 2051 and the fourth flat mirror 2052 are respectively connected with two ends of the supporting rod 2032, the angular bisector of the included angle between the mirror surface of the first flat mirror 2041 and the second flat mirror 2042 and the angular bisector of the included angle between the mirror surface of the third flat mirror 2051 and the mirror surface of the fourth flat mirror 2052 are both perpendicular to the supporting rod 2032, and the mirror surfaces of the first flat mirror 2041, the second flat mirror 2042, the third flat mirror 2051 and the fourth flat mirror 2052 are all deviated from the first transmission rod 2031; the first reflecting mirror 206 is arranged in front of the first plane mirror 2041, and the included angle between the two mirror surfaces is 90 degrees, and the first reflecting mirror 206 is fixedly connected with the first plane mirror 2041 through the second transmission rod 209; the second reflecting mirror 207 is arranged in front of the fourth plane mirror 2052, the included angle between the two mirror surfaces is 90 degrees, and the second reflecting mirror 207 is fixedly connected with the fourth plane mirror 2052 through a third transmission rod 210; the third reflector 208 is disposed in front of the third flat mirror 2051, and the included angle between the two mirror surfaces is 45 degrees; the laser 211 emits a laser beam onto the second flat mirror 2042, and an included angle between the laser beam and the mirror surface of the second flat mirror 2042 is 45 degrees; the beam splitter 212 is disposed between the laser 211 and the second flat mirror 2042, and is configured to split the laser beam onto the photodetector 213; the photodetector 213 converts the received laser signal into an electrical signal and sends the electrical signal to the computer 214; the computer 214 processes and analyzes the received electrical signal to obtain the rotation angle of the first turntable.
The micro-angle measurement method based on the measurement system comprises the following steps:
A. the first turntable and the second turntable can synchronously rotate based on the arrangement of the T-shaped transmission support, when any one turntable rotates, the T-shaped transmission support drives the other turntable to synchronously rotate, and further drives the first intersecting plane mirror and the second intersecting plane mirror to horizontally move;
B. the carousel rotates in-process laser instrument outgoing laser beam, and laser beam's the light path of marcing does:
a. the laser emits laser beams, the laser beams enter the second plane mirror at an angle of 45 degrees and are reflected to the first reflecting mirror through the first plane mirror;
b. the first reflector reflects the laser beam to the second reflector and then reflects the laser beam to the fourth plane mirror through the second reflector, the direction of the laser beam incident to the fourth plane mirror is the same as the direction of the laser beam emitted by the laser, and the included angle between the laser beam and the fourth plane mirror is 45 degrees;
c. laser beams are reflected by a fourth plane mirror and a third plane mirror which are vertical to each other in sequence and then enter a third reflecting mirror at an angle of 90 degrees, and the direction of the laser beams entering the third reflecting mirror is opposite to the direction of laser beams emitted by a laser;
d. the third reflector reflects the incident laser beam, and the reflected laser beam returns to the laser cavity along the original path to form a laser self-mixing signal;
C. feeding back the laser self-mixing signal to a photoelectric detector through a beam splitter;
D. the photoelectric detector converts the received laser signal into an electric signal and sends the electric signal to a computer;
E. the computer processes and analyzes the received signals, obtains the external cavity optical path difference of the laser self-mixing signals before and after the rotation of the turntable by utilizing the laser self-mixing interference principle, and obtains the rotation angle of the turntable by utilizing the relation between the external cavity optical path difference and the rotation angle of the turntable.
Wherein, the theory of the basis of the processing and analyzing process in the step E is as follows:
as shown in FIG. 7, a start position P1P2(first orthogonal plane mirror 4 vertex P1And the vertex P of the second orthogonal plane mirror 52Is parallel to the y-axis, when the first turntable 1 rotates by an angle theta
Figure GDA0002614901860000141
The second turntable 2 rotates by the same angle, and the T-shaped transmission bracket 3 is always parallel to the x axis to ensure that the first orthogonal plane mirror 4 and the second orthogonal plane mirror 5 do not deviate in the vertical direction and only generate translation in the xy plane. After rotation, the first plane mirror 41, the second plane mirror 42, the third plane mirror 51 and the fourth plane mirror 52 are all kept orthogonal and generate deviation, the laser 1 emits laser light from point a, in the whole rotation process, the position of the laser 1 is always kept at point a, the light returns from point H along the original path after being reflected by the plane mirrors and the reflecting mirrors for multiple times, and the radiuses of the first rotating disc and the second rotating disc are both R. The first intersecting plane mirror and the second intersecting plane mirror are orthogonal plane mirrors due to the fact that the included angle is 90 degrees.
Based on the micro-angle measurement system with the double-orthogonal plane mirror, the optical path change of the micro-angle measurement system is theoretically calculated, the experimental device is simplified, and the structure diagram of the single-orthogonal plane mirror shown in fig. 8 is established.
As shown in FIG. 8, the vertex V of the orthogonal plane mirror1Reaches V after rotating2Primary light path AB1C1D1Become AB2C2D2The optical path difference can be derived as follows:
Δl＝2(AB1C1D1-AB2C2D2) (7)
by geometric derivation, the optical path difference caused by the angle change can be represented as:
Δl＝-4Rsinθ(8)
therefore, for the micro-angle measurement system with the bi-orthogonal plane mirrors described in this embodiment, as shown in fig. 9, the optical path difference can be calculated as:
Figure GDA0002614901860000151
when the optical path of the feedback light changes one wavelength each time the laser changes one stripe from the mixed waveform, the following can be obtained:
ΔL＝4R(2cosθ-2sinθ-1)＝Nλ (10)
in the formula (10), N is the number of stripes.
Combining the laser self-mixing theory, as shown in FIG. 5, n0Is the effective refractive index, r, of the working substance of the laser at the signal light wavelength1And r2Is two end faces M of the laser1And M2Reflection coefficient of electric field amplitude of (1), feedback end face M3Has an electric field amplitude reflection coefficient of r3D represents the lumen length, LextLength of the external cavity, thus, the initial electric field E in the laser cavity0(t) the electric field e (t) after one round trip can be expressed as:
Figure GDA0002614901860000152
in formula (11), v is the frequency of the optical wave, R2Indicating the laser rear facet M2Wherein R is2＝|r2|2，r2For the reflection coefficient, c is the optical speed in vacuum, g represents the linear gain of the gain medium per unit length of the laser to the signal light, and γ is the total loss of the signal light per unit distance in the laser cavity. Further from the steady state laser oscillation conditions, an approximate expression of the angular variation of the output power of the laser can be obtained as follows:
Figure GDA0002614901860000161
in equation (12), ζ is the modulation factor, λ is the laser wavelength, P0Output intensity of the laser, L, without light feedback0Indicating the initial external cavity length.
It can be seen from the derivation process that, compared with the conventional laser self-mixing angle measurement method, the incident type laser self-mixing micro-angle measurement system and measurement method in the dual-orthogonal plane mirror described in this embodiment have the advantages of unlimited angle measurement range and high system resolution.
As can be seen from the above description, the present embodiment has the following advantages: (1) when laser beams are incident to the first intersecting plane mirror, the laser beams are firstly incident to the second plane mirror at the inner side, namely, an internal incidence mode is adopted, so that the whole structure of the measuring system is compact; (2) through the reflection unit formed by the first orthogonal plane mirror, the first reflection mirror, the second orthogonal plane mirror and the third reflection mirror, the auto-collimation of the laser self-mixing signal is realized, and compared with the reflection unit formed by the traditional plane mirror or the reflection unit formed by a right-angle prism, the optical path difference of the laser self-mixing signal is increased before and after rotation under the same rotation angle, so that the measurement resolution and the measurement range of the system are improved; (3) the measuring system linkage device is simple and easy to realize; the two external reflectors are separately linked and can be independently controlled, so that the machining error is reduced, and the light path is more easily collimated.
The measurement system described in this embodiment can be further improved as follows:
(1) the measuring system further comprises a transmission belt 217, and the transmission belt is sleeved on the first rotating disc and the second rotating disc, so that the synchronism of the first rotating disc and the second rotating disc is further improved, and the accuracy of the measuring result is improved.
(2) An optical attenuator 218 is additionally arranged between the laser and the beam splitter, the optical attenuator 218 is used for adjusting the light intensity of feedback light received by the laser, and the feedback light is prevented from being too strong or exceeding a laser damage threshold, so that the accuracy of a measurement result is further ensured.
(3) The laser type in the system is not limited, can be various types such as a semiconductor laser, a helium-neon laser, a microchip laser or a fiber laser, and can be selected according to application requirements.
Embodiment 3 of the present invention is described in detail with reference to fig. 5 and fig. 10 to 12, but the present invention is not limited to the claims.
As shown in fig. 10, a laser self-mixing micro-angle measuring system includes a first rotating disk 301, a second rotating disk 302, a transmission rod 303, an intersecting plane mirror 304, a reflecting mirror 305, a laser 306, a beam splitter 307, a photodetector 308, and a computer 309; the first turntable 301 and the second turntable 302 synchronously rotate through a transmission rod 303; the end parts of the two ends of the transmission rod 303 are respectively connected with a first connecting column 310 and a second connecting column 311, the bottom of the first connecting column 310 and the bottom of the second connecting column 311 are respectively arranged on the first turntable 301 and the second turntable 302 through bearings, and the transmission rod 303 is parallel to a connecting line between the circle center of the first turntable 301 and the circle center of the second turntable 302; the intersecting plane mirror 304 comprises a first plane mirror 3041 and a second plane mirror 3042, the mirror surfaces of which are opposite to each other, one side of the first plane mirror 3041 is connected with one side of the second plane mirror 3042, the connecting edges of the first plane mirror 3041 and the second plane mirror 3042 are connected to the second connecting column 311, the mirror surfaces of the first plane mirror 3041 and the second plane mirror 3042 are both deviated from the transmission rod 303, and the angle bisector of the included angle between the mirror surfaces of the first plane mirror 3041 and the second plane mirror 3042 is positioned on the same straight line with the transmission rod 303; an included angle between the first plane mirror 3041 and the second plane mirror 3042 is recorded as α, and a value range of α is: 0°<α<180 degrees; the reflecting mirror 305 is disposed outside the second plane mirror 3042 and the angle between the mirror surface and the first plane mirror 3041 is equal to
Figure GDA0002614901860000171
306 laser emits laser beams to the second plane mirror 3042, an included angle formed by the laser beams emitted by the laser 306 and the laser beams reflected by the second plane mirror 3042 is equal to alpha, and an included angle formed by the laser beams emitted by the laser 306 and the mirror surface of the reflecting mirror 305 is equal to alpha
Figure GDA0002614901860000172
The beam splitter 307 is disposed between the laser 306 and the second flat mirror 3042, and is configured to split the laser beam onto the photodetector 308; the photodetector 308 converts the received laser signal into an electrical signal and sends the electrical signal to the computer 309; the computer 309 processes and analyzes the received electrical signal to obtain the rotation angle of the first turntable.
The micro-angle measurement method based on the measurement system comprises the following steps:
A. the first turntable and the second turntable can synchronously rotate based on the arrangement of the transmission rod, and when any one turntable rotates, the transmission rod drives the other turntable to synchronously rotate so as to drive the intersecting plane mirror to horizontally move;
B. the carousel rotates in-process laser instrument outgoing laser beam, and laser beam's the light path of marcing does:
a. the laser emits laser beams to the second plane mirror, then the laser beams are reflected to the first plane mirror and then reflected to the reflecting mirror;
b. the third reflector reflects the incident laser beam, and the reflected laser beam returns to the laser cavity along the original path to form a laser self-mixing signal;
C. feeding back the laser self-mixing signal to a photoelectric detector through a beam splitter;
D. the photoelectric detector converts the received laser signal into an electric signal and sends the electric signal to a computer;
E. the computer processes and analyzes the received signals, obtains the external cavity optical path difference of the laser self-mixing signals before and after the rotation of the turntable by utilizing the laser self-mixing interference principle, and obtains the rotation angle of the turntable by utilizing the relation between the external cavity optical path difference and the rotation angle of the turntable.
Wherein, the theory of the basis of the processing and analyzing process in the step E is as follows:
as shown in fig. 11, the starting position O2V (center O of second turntable)2A line connecting the fixed points V of the intersecting plane mirrors) is parallel to the y-axis, and when the rotation angle of the first rotating disc 1 is theta
Figure GDA0002614901860000181
The second turntable 2 rotates by the same angle, and the transmission rod is always parallel to the x axis to ensure that the intersecting plane mirror does not deviate in the vertical direction and only generates translation in the xy plane. After the rotation, the first plane mirror and the second plane mirror are both crossed and shifted, the laser 1 emits laser through the point A, in the whole rotation process, the position of the laser 1 is always kept at the point A, light rays are reflected by the plane mirror and the reflector for multiple times and then return from the point D along the original path, and the radiuses of the first rotary disc and the second rotary disc are both R.
Based on the micro-angle measurement system with the single-intersection plane mirror, the optical path change of the micro-angle measurement system is theoretically calculated, a single intersection plane mirror structure diagram with any included angle as shown in figure 12 is established, and the vertex V of the intersection plane mirror is1Reaches V after rotating2Primary light path AB1C1D1Become AB2C2D2The optical path difference can be derived as follows:
Figure GDA0002614901860000182
wherein the content of the first and second substances,
Figure GDA0002614901860000183
geometrically derived:
Figure GDA0002614901860000184
the optical path difference caused by the angle change can be expressed as:
Figure GDA0002614901860000191
when the optical path of the feedback light changes one wavelength each time the laser changes one stripe from the mixed waveform, the following can be obtained:
ΔL＝Nλ (16)
in the formula (16), N is the number of stripes.
Combining the formula (15), it can be known that the optical path difference is related to the included angle α between the two mirror surfaces and the rotation angle θ of the turntable, and the included angle between the special mirror surfaces is simplified as follows for the simplified equation:
(1) when the included angle alpha of the two mirror surfaces is 90 degrees, namely the two mirror surfaces are vertical, the optical path difference can be obtained:
ΔL＝-4Rsinθ (17)
from equation (16), when Δ L is equal to the wavelength, i.e., when N is equal to 1, the minimum measurable angle is obtained:
Figure GDA0002614901860000192
taking he-ne laser as an example, when R is 3cm, the resolution of angle measurement can reach 2.64 × 10-6rad。
(2) When the included angle α of the mirror surface is 60 °, the optical path difference can be obtained:
Figure GDA0002614901860000193
from equation (16), when Δ L is equal to the wavelength, i.e., when N is equal to 1, the minimum measurable angle is obtained:
Figure GDA0002614901860000194
taking he-ne laser as an example, when R is 3cm, the resolution of angle measurement can reach 5.90 × 10-6rad。
From the above special angle calculation results in combination with the optical path difference relationship diagram, it can be obtained that the optical path difference corresponding to the same rotation angle is increased along with the increase of the mirror included angle α, that is, when the mirror included angle is gradually increased, the resolution of angle measurement is gradually increased.
Combining the laser self-mixing theory, as shown in FIG. 5, n0Is the effective refractive index, r, of the working substance of the laser at the signal light wavelength1And r2Is two end faces M of the laser1And M2Reflection coefficient of electric field amplitude of (1), feedback end face M3Has an electric field amplitude reflection coefficient of r3D represents the lumen length, LextLength of the external cavity, thus, the initial electric field E in the laser cavity0(t) the electric field e (t) after one round trip can be expressed as:
Figure GDA0002614901860000201
in the formula (21), v is the frequency of the optical wave, R2Indicating the laser rear facet M2Wherein R is2＝|r2|2，r2For the reflection coefficient, c is the optical speed in vacuum, g represents the linear gain of the gain medium per unit length of the laser to the signal light, and γ is the total loss of the signal light per unit distance in the laser cavity. Further from the steady state laser oscillation conditions, an approximate expression of the angular variation of the output power of the laser can be obtained as follows:
Figure GDA0002614901860000202
in the formula (22), ζ is the modulation factor, λ is the laser wavelength, and P0Output intensity of the laser, L, without light feedback0Indicating the initial external cavity length.
It can be seen from the derivation process that, compared with the conventional laser self-mixing angle measurement method, the incident type self-mixing micro-angle measurement system and measurement method in the single arbitrary angle intersection plane mirror described in this embodiment have the advantages of unlimited angle measurement range and high system resolution.
As can be seen from the above description, the present embodiment has the following advantages: (1) when laser beams are incident to the intersecting plane mirrors, the laser beams are firstly incident to the second plane mirror on the inner side, namely, an internal incidence mode is adopted, so that the overall structure of the measuring system is compact; (2) through the reflection unit formed by the crossed plane mirror and the reflection mirror, the auto-collimation of the laser self-mixing signal is realized, and compared with the reflection unit formed by the traditional plane mirror or the reflection unit formed by a right-angle prism, the optical path difference of the laser self-mixing signal is increased before and after rotation under the same rotation angle, so that the measurement resolution and the measurement range of the system are improved; (3) the whole structure of the measuring system is simple and easy to realize, the mechanical error is small, the included angle between the first plane mirror and the second plane mirror is adjustable, different angles correspond to different system measurement resolutions, and the included angle can be selected according to actual requirements.
The measurement system described in this embodiment can be further improved as follows:
(1) the measuring system further comprises a transmission belt 312, and the transmission belt is sleeved on the first rotating disc and the second rotating disc, so that the synchronization degree of the first rotating disc and the second rotating disc is further improved, and the accuracy of the measuring result is improved.
(2) An optical attenuator 313 is additionally arranged between the laser and the beam splitter, the optical attenuator 313 is used for adjusting the light intensity of feedback light received by the laser, and the feedback light is prevented from being too strong or exceeding the damage threshold of the laser, so that the accuracy of the measurement result is further ensured.
(3) The laser type in the system is not limited, can be various types such as a semiconductor laser, a helium-neon laser, a microchip laser or a fiber laser, and can be selected according to application requirements.
It should be understood that the detailed description of the invention is merely illustrative of the invention and is not intended to limit the invention to the specific embodiments described. It will be appreciated by those skilled in the art that the present invention may be modified or substituted equally as well to achieve the same technical result; as long as the use requirements are met, the method is within the protection scope of the invention.

Claims (6)

1. The utility model provides an arbitrary contained angle mirror surface formula laser is from mixing little angle measurement system which characterized in that: the device comprises a first turntable, a second turntable, a transmission rod, an intersecting plane mirror, a reflecting mirror, a laser, a beam splitter, a photoelectric detector and a computer;
the first turntable and the second turntable synchronously rotate through the transmission rod;
the end parts of the two ends of the transmission rod are respectively connected with a first connecting column and a second connecting column, the bottom of the first connecting column and the bottom of the second connecting column are respectively arranged on the first rotary table and the second rotary table through bearings, and the transmission rod is parallel to a connecting line between the circle center of the first rotary table and the circle center of the second rotary table;
the intersecting plane mirror comprises a first plane mirror and a second plane mirror, wherein the mirror surfaces of the first plane mirror and the second plane mirror are opposite, one side of the first plane mirror is connected with one side of the second plane mirror, the connecting edges of the first plane mirror and the second plane mirror are connected onto a second connecting column, the mirror surfaces of the first plane mirror and the second plane mirror are deviated from the transmission rod, the angular bisector of the included angle between the first plane mirror and the second plane mirror and the transmission rod are positioned on the same straight line, the included angle between the first plane mirror and the second plane mirror is recorded as alpha, and the value range of the alpha is as follows: 0 ° < α <180 °;
the reflector is arranged at the outer side of the second plane mirror, and the included angle between the mirror surface and the first plane mirror surface is equal to
Figure FDA0002087358910000011
The laser emits laser beams to the second plane mirror, an included angle formed by the laser beams emitted by the laser and the laser beams reflected by the second plane mirror is equal to alpha, and an included angle formed by the laser beams emitted by the laser and the mirror surface of the reflecting mirror is equal to alpha
Figure FDA0002087358910000012
The beam splitter is arranged between the laser and the second plane mirror and is used for splitting the laser beam to the photoelectric detector;
the photoelectric detector converts the received laser signal into an electric signal and sends the electric signal to a computer;
and the computer processes and analyzes the received electric signal to obtain the rotation angle of the first turntable to be tested.
2. The arbitrary angle mirrored laser self-mixing micro angle measurement system of claim 1, wherein: the transmission belt is sleeved on the first rotating disc and the second rotating disc.
3. The arbitrary angle mirrored laser self-mixing micro angle measurement system of claim 1, wherein: and an optical attenuator is also arranged between the laser and the beam splitter.
4. The arbitrary angle mirrored laser self-mixing micro angle measurement system of claim 1, wherein: the laser is a semiconductor laser, a helium-neon laser, a microchip laser or a fiber laser.
5. The micro-angle measurement method based on the arbitrary-angle mirrored laser self-mixing micro-angle measurement system of claim 1, comprising the steps of:
A. the first turntable and the second turntable can synchronously rotate based on the arrangement of the transmission rod, and when any one turntable rotates, the transmission rod drives the other turntable to synchronously rotate so as to drive the intersecting plane mirror to horizontally move;
B. the carousel rotates in-process laser instrument outgoing laser beam, and laser beam's the light path of marcing does:
a. the laser emits laser beams to the second plane mirror, then the laser beams are reflected to the first plane mirror and then reflected to the reflecting mirror;
b. the third reflector reflects the incident laser beam, and the reflected laser beam returns to the laser cavity along the original path to form a laser self-mixing signal;
C. feeding back the laser self-mixing signal to a photoelectric detector through a beam splitter;
D. the photoelectric detector converts the received laser signal into an electric signal and sends the electric signal to a computer;
E. the computer processes and analyzes the received signals, obtains the external cavity optical path difference of the laser self-mixing signals before and after the rotation of the turntable by utilizing the laser self-mixing interference principle, and obtains the rotation angle of the turntable by utilizing the relation between the external cavity optical path difference and the rotation angle of the turntable.
6. The micro-angle measurement method of the any-included-angle mirrored laser self-mixing micro-angle measurement system according to claim 5, wherein: an optical attenuator is arranged between the laser and the plane mirror on which the laser beam emitted by the laser firstly enters, and the optical attenuator is used for adjusting the light intensity of the feedback light received by the laser to prevent the feedback light from being too strong or exceeding the damage threshold of the laser.
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