CN102853770B - Based on laser heterodyne interference measurement method and the device of little frequency difference and beam separation - Google Patents
Based on laser heterodyne interference measurement method and the device of little frequency difference and beam separation Download PDFInfo
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- CN102853770B CN102853770B CN201210347061.6A CN201210347061A CN102853770B CN 102853770 B CN102853770 B CN 102853770B CN 201210347061 A CN201210347061 A CN 201210347061A CN 102853770 B CN102853770 B CN 102853770B
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Abstract
Laser application technique field is belonged to based on the laser heterodyne interference measurement method of little frequency difference and beam separation and device; Inventive method have employed the reference light of space separation and measures light, simultaneously, the method creates the interferometry signal that two have contrary Doppler shift, and according to the direction of motion of measured target and speed, selectivity uses two measuring-signals to carry out interferometry; In contrive equipment, adopt unpolarized Amici prism to replace conventional polarization Amici prism, and add two photodetectors, two phasometers and on-off circuit in a device; The inventive method and device eliminate the frequency alias phenomenon in interferometer, improve the measuring accuracy of difference interference measuring; Solve the problem that LASER Light Source frequency difference limits measuring speed simultaneously.
Description
Technical field
The invention belongs to laser application technique field, relate generally to a kind of laser heterodyne interference measurement method based on little frequency difference and beam separation and device.
Background technology
Because it has, antijamming capability is strong, measurement range is large, signal to noise ratio (S/N ratio) is high and be easy to realize the features such as high precision and be widely used in the fields such as Ultra-precision Turning, litho machine and three coordinate measuring machine in laser heterodyne interference measurement.Along with the development of ultraprecise engineering, more and more higher requirement is proposed to machining precision and production efficiency; Simultaneously also new challenge is proposed to the measuring accuracy of difference interference measuring, resolution and speed.
In laser heterodyne interference is measured, nonlinearity erron seriously limits the further raising of measuring accuracy and resolution, and Chinese scholars has carried out large quantifier elimination to laser heterodyne interference nonlinearity erron.Nonlinearity erron comes from the optics aliasing in optical interference circuit, and traditional interferometer measuration system cannot avoid the optics aliasing in interferometry, limits the raising of its measuring accuracy and resolution.
T.L.Schmitz and J.F.Beckwith proposes the method (Ascousto-optic displacement-measureing interferometer:a new heterodyne interferometer with Anstromlevel periodic error.Journal of Modern Optics 49, pages 2105-2114) of a kind of interferometer transformation.Compared to traditional measuring method, measuring beam as spectroscope, is separated with reference beam by the method by acousto-optic frequency shifters.The method can reduce reference light and measure the frequency alias of light, is conducive to the nonlinearity erron reducing to measure, thus improves measuring accuracy and resolution.But this apparatus structure is complicated and special, in Ultra-precision Turning cannot being widely used in and measuring.
Ki-Nam Joo etc. have developed a kind of new pattern laser interferometry structure (Simple heterodyne laser interferometer with subnanometer periodic errors.Optics Letters/Vol.34, No.3/Fe bruary 1,2009).This structure is that reference beam is spatially separated with measuring beam, eliminates the frequency alias in interferometry, eliminates nonlinearity erron completely, thus improves measuring accuracy and Measurement Resolution.In addition, this apparatus structure is simple, and cost is low, compared to front a kind of measuring method, is more conducive to the application in ultra precise measurement field.But the method measuring speed still by the restriction of light source frequency difference, limits its widely using in high speed fields of measurement.
All there is the problem of measuring speed by the restriction of light source frequency difference in several interferometric method and device above.What require measuring speed along with Ultra-precision Turning improves constantly, and the frequency difference of interferometer light source also constantly increases, thus causes the structure of LASER Light Source to become increasingly complex, and cost is more and more expensive, seriously limits the widespread use of laser interferometry.And there is with measuring speed conflict in Measurement Resolution.In order to improve measuring speed and the resolution of interferometer simultaneously, Chinese scholars has been carried out large quantifier elimination to signal processing system and has been proposed corresponding solution, but the general all complex structures of existing signal processing system, cost intensive and need the chip of a lot of particular design; And by the restriction of existing semi-conductor chip level, interferometry performance boost difficulty.
In sum, existing laser heterodyne interference measurement method all cannot meet Ultra-precision Turning simultaneously and measure the high precision of interferometer and the requirement of high measurement speed, seriously limits the development of Ultra-precision Turning fields of measurement.
Summary of the invention
For the deficiency of above-mentioned existing laser heterodyne interferometer, the present invention proposes a kind of laser heterodyne interference measurement method based on little frequency difference and beam separation and device, improve the measuring accuracy of laser heterodyne interference, solve the problem that LASER Light Source frequency difference limits measuring speed.
Object of the present invention is achieved through the following technical solutions:
1, based on a high speed ultra-precise laser difference interference measuring method for little frequency difference and beam separation, the method step is as follows:
(1) frequency stabilized laser exports two bundle frequencies and is respectively f
1, f
2parallel beam;
(2) two parts of restrainting parallel beams that frequency stabilized laser exports directly are converted to the reference signal that laser heterodyne interference is measured after detection, and its frequency difference value is f
b=f
1-f
2, be expressed as I
r∝ cos (2 π f
bt);
(3) two another part restrainting parallel beams that frequency stabilized laser exports are divided into reference beam and measuring beam by unpolarized Amici prism;
(4), in reference beam, frequency is respectively f
1, f
2the referenced prismatic reflection of two light beams return unpolarized Amici prism;
(5), in measuring beam, frequency is respectively f
1, f
2two light beams be reflected back unpolarized Amici prism by the corner cube reflector of measured target end, make frequency be f by regulating reference prism and corner cube reflector
1measuring beam and frequency be f
2reference beam interfere, produce a road measuring-signal, be expressed as I
m1∝ cos [2 π (f
b+ Δ f) t]; Frequency is f
2measuring beam and frequency be f
1reference beam interfere, produce another road measuring-signal, be expressed as I
m2∝ cos [2 π (f
b-Δ f) t];
(6) two measuring-signals have the Doppler shift that size is identical, symbol is contrary, and its frequency is respectively f
b+ Δ f and f
b-Δ f;
(7) two measuring-signals send into two identical phasometer A and phasometer B respectively after photodetector detection, and wherein, phasometer A is f for the treatment of frequency
bthe measuring-signal of+Δ f, phasometer B is f for the treatment of frequency
bthe measuring-signal of-Δ f;
(8) according to direction of motion and the movement velocity of measured target end corner cube reflector, on-off circuit is used to select between phasometer A and phasometer B;
(9) according to selected phasometer A or phasometer B, the displacement of measured target is calculated.
Described phasometer use on-off circuit select time, when measured target end corner cube reflector positive movement speed is higher than setting value V
1time, selected phase meter B; When measured target end corner cube reflector negative movement speed is higher than setting value V
2time, selected phase meter A; Wherein, if measured target end corner cube reflector is positive dirction away from the direction of unpolarized Amici prism.
A kind of laser heterodyne interference measurement mechanism based on little frequency difference and beam separation, this device comprises frequency stabilized laser, unpolarized Amici prism, corner cube reflector, reference prism, photodetector A, photodetector B, this device also comprise phasometer A, phasometer B, on-off circuit, metering circuit, wherein, unpolarized Amici prism is positioned at frequency stabilized laser output terminal; Corner cube reflector is positioned at the transmitted light output terminal of unpolarized Amici prism, and reference prism is positioned at unpolarized Amici prism reflected light output terminal; Unpolarized Amici prism exports two-way interferometric beams, and wherein a road meets photodetector A, and another road meets photodetector B; The output termination phasometer B input end of photodetector A, photodetector B exports termination phasometer A input end; The reference signal output terminal of frequency stabilized laser is connected with the input end of phasometer A and phasometer B respectively, and phasometer A and phasometer B output terminal connect on-off circuit input end simultaneously; On-off circuit is connected with measurement of output end circuit.
Described reference prism is made up of two prism of corner cubes.
The present invention has following characteristics and good result:
(1) in the present invention, reference light is spatially separated with measurement light, does not occur lap over before reaching the detector, the root that the nonlinearity erron eliminating interferometer produces.
(2) adopt polarization splitting prism to carry out beam separation in conventional dry interferometer, interference mirror group adjustment difficulty is high and cost is high; Use common unpolarized Amici prism in the present invention instead and replace polarization splitting prism, because the change of its polarization state to LASER Light Source is insensitive, thus greatly reduce the adjustment difficulty of interference mirror group, meanwhile, use unpolarized Amici prism can reduce interferometer cost.
(3), in the present invention, two measuring-signals that interferometer produces have the Doppler shift that size is identical, symbol is contrary, select, can ensure that Doppler shift makes frequency difference increase all the time according to movement direction of object to two measuring-signals.Compared to traditional interferometer, the interferometer in the present invention makes the restriction of measuring speed no longer Stimulated Light light source frequency difference, during traditional little frequency difference laser instrument also can be applied to and measure at a high speed.
(4) in the present invention, because laser frequency difference is less, signal processing system can utilize common clock signal to obtain high resolving power, simplifies the design of Signal Measurement System, reduces the cost of system.
Accompanying drawing explanation
Fig. 1 is apparatus of the present invention structural representation
Fig. 2 adopts two prism of corner cubes as the interference mirror group structural representation with reference to prism in Fig. 1
In figure, 1 frequency stabilized laser, 2 unpolarized Amici prisms, 3 corner cube reflectors, 4 reference prisms, 5 photodetector A, 6 photodetector B, 7 phasometer A, 8 phasometer B, 9 on-off circuits, 10 metering circuits, 11 prism of corner cube A, 12 prism of corner cube B.
Embodiment
Below in conjunction with accompanying drawing, example of the present invention is described in detail.
A kind of high speed ultra-precise laser difference interference measuring device based on little frequency difference and beam separation, this device comprises frequency stabilized laser 1, unpolarized Amici prism 2, corner cube reflector 3, reference prism 4, photodetector A 5, photodetector B 6, this device also comprise phasometer A 7, phasometer B 8, on-off circuit 9, metering circuit 10, wherein, unpolarized Amici prism 2 is positioned at frequency stabilized laser 1 output terminal; Corner cube reflector 3 is positioned at the transmitted light output terminal of unpolarized Amici prism 2, and reference prism 4 is positioned at unpolarized Amici prism 2 reflected light output terminal; Unpolarized Amici prism 2 exports two-way interferometric beams, and wherein a road meets photodetector A 5, and another road meets photodetector B 6; Output termination phasometer B 8 input end of photodetector A 5, photodetector B 6 exports termination phasometer A 7 input end; The reference signal output terminal of frequency stabilized laser 1 is connected with the input end of phasometer A7 and phasometer B8 respectively, and phasometer A 7, phasometer B 8 output terminal connect on-off circuit 9 input end simultaneously; On-off circuit 9 is connected with measurement of output end circuit 10.
Based on a high speed ultra-precise laser difference interference measuring method for little frequency difference and beam separation, the method step is as follows:
(1) frequency stabilized laser 1 exports two bundle frequencies and is respectively f
1, f
2parallel beam;
(2) two parts of restrainting parallel beams that frequency stabilized laser 1 exports directly are converted to the reference signal that laser heterodyne interference is measured after detection, and its frequency difference value is f
b=f
1-f
2, be expressed as I
r∝ cos (2 π f
bt);
(3) two light beams that frequency stabilized laser 1 exports are divided into reference beam and measuring beam by unpolarized Amici prism 2 respectively;
(4), in reference beam, frequency is respectively f
1, f
2the referenced prism of two light beams 4 be reflected back unpolarized Amici prism;
(5), in measuring beam, frequency is respectively f
1, f
2two light beams be reflected back unpolarized Amici prism by the corner cube reflector 3 of measured target end, make frequency be f by regulating reference prism and corner cube reflector
1measuring beam and frequency be f
2reference beam interfere, produce a road measuring-signal, be expressed as I
m1∝ cos [2 π (f
b+ Δ f) t]; Frequency is f
2measuring beam and frequency be f
1reference beam interfere, produce another road measuring-signal, be expressed as I
m2∝ cos [2 π (f
b-Δ f) t];
(6) two measuring-signals have the Doppler shift that size is identical, symbol is contrary, and its frequency is respectively f
b+ Δ f and f
b-Δ f;
(7) two measuring-signals are detected by photodetector A 5 and photodetector B 6 respectively;
(8) photodetector A 5 output frequency is f
bthe measuring-signal of-Δ f, and signal is sent in phasometer B 8 process;
(9) photodetector B 6 output frequency is f
bthe measuring-signal of+Δ f, and signal is sent in phasometer A 7 process;
(10) processing signals of phasometer A 7 and phasometer B 8 sends into on-off circuit 9 simultaneously, selects between two phase place meter according to the direction of motion of measured target end corner cube reflector 3 and movement velocity; There is part overlap in the measurement range of phasometer A and phasometer B.By " hysteresis district " that this lap switches as phasometer, when measured target end corner cube reflector 3 movement velocity is higher than the upper limit V in " hysteresis district "
1time, switch to phasometer B by phasometer A, phasometer B exports and is admitted to phase accumulator.In like manner, when measured target end corner cube reflector 3 movement velocity is lower than the lower limit-V in " hysteresis district "
2time, switch back phasometer A by phasometer B.When measured target speed is in " hysteresis district ", do not carry out phasometer blocked operation, thus eliminate circuit noise and speed noise to the impact of blocked operation, wherein, if measured target end corner cube reflector 3 is positive dirction away from the direction of unpolarized Amici prism 2.
(11) process in the signal feeding metering circuit 10 after on-off circuit 9 is selected, thus obtain the movable information of measured target.
Claims (4)
1., based on a laser heterodyne interference measurement method for little frequency difference and beam separation, the method step is as follows:
(1) frequency stabilized laser exports two bundle frequencies and is respectively f
1, f
2parallel beam;
(2) two parts of restrainting parallel beams that frequency stabilized laser exports directly are converted to the reference signal that laser heterodyne interference is measured after detection, and its frequency difference value is f
b=f
1-f
2, be expressed as I
r∝ cos (2 π f
bt);
(3) two another part restrainting parallel beams that frequency stabilized laser exports are divided into reference beam and measuring beam by unpolarized Amici prism;
(4), in reference beam, frequency is respectively f
1, f
2the referenced prismatic reflection of two light beams return unpolarized Amici prism;
(5), in measuring beam, frequency is respectively f
1, f
2two light beams be reflected back unpolarized Amici prism by the corner cube reflector of measured target end, make frequency be f by regulating reference prism and corner cube reflector
1measuring beam and frequency be f
2reference beam interfere, produce a road measuring-signal, be expressed as I
m1∝ cos [2 π (f
b+ Δ f) t]; Frequency is f
2measuring beam and frequency be f
1reference beam interfere, produce another road measuring-signal, be expressed as I
m2∝ cos [2 π (f
b-Δ f) t];
(6) two measuring-signals have the Doppler shift that size is identical, symbol is contrary, and its frequency is respectively f
b+ Δ f and f
b-Δ f;
It is characterized in that:
(7) two measuring-signals send into two identical phasometer A and phasometer B respectively after photodetector detection, and wherein, phasometer A is f for the treatment of frequency
bthe measuring-signal of+Δ f, phasometer B is f for the treatment of frequency
bthe measuring-signal of-Δ f;
(8) according to direction of motion and the movement velocity of measured target end corner cube reflector, on-off circuit is used to select between phasometer A and phasometer B;
(9) according to selected phasometer A or phasometer B, the displacement to measured target calculates.
2. the laser heterodyne interference measurement method based on little frequency difference and beam separation according to claim 1, when it is characterized in that using on-off circuit to select, when measured target end corner cube reflector positive movement speed is higher than setting value V
1time, selected phase meter B; When measured target end corner cube reflector negative movement speed is higher than setting value V
2time, selected phase meter A; Wherein, if measured target end corner cube reflector is positive dirction away from the direction of unpolarized Amici prism.
3. the laser heterodyne interference measurement mechanism based on little frequency difference and beam separation, this device comprises frequency stabilized laser (1), unpolarized Amici prism (2), corner cube reflector (3), reference prism (4), photodetector A (5), photodetector B (6), wherein, unpolarized Amici prism (2) is positioned at frequency stabilized laser (1) output terminal; Corner cube reflector (3) is positioned at the transmitted light output terminal of unpolarized Amici prism (2), and reference prism (4) is positioned at unpolarized Amici prism (2) reflected light output terminal; Unpolarized Amici prism (2) exports two-way interferometric beams, and wherein a road meets photodetector A (5), and another road meets photodetector B (6); It is characterized in that this device also comprises phasometer A (7), phasometer B (8), on-off circuit (9), metering circuit (10); Wherein, output termination phasometer B (8) input end of photodetector A (5), photodetector B (6) exports termination phasometer A (7) input end, the reference signal output terminal of frequency stabilized laser (1) is connected with the input end of phasometer A (7) and phasometer B (8) respectively, and phasometer A (7) and phasometer B (8) output terminal connect on-off circuit (9) input end simultaneously; On-off circuit (9) is connected with measurement of output end circuit (10).
4. the laser heterodyne interference measurement mechanism based on little frequency difference and beam separation according to claim 3, is characterized by reference prism (4) and is made up of prism of corner cube A (11) and prism of corner cube B (12).
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| CN104296678B (en) * | 2014-09-29 | 2017-02-22 | 中国科学院光电研究院 | Heterodyne interferometer based on phase shift of low-frequency-difference acousto-optic frequency shifter |
| CN104990619B (en) * | 2015-06-12 | 2016-06-29 | 哈尔滨工业大学 | Michelson heterodyne laser vialog based on dual-acousto-optic modulation and depolarization light splitting |
| CN104931124B (en) * | 2015-06-12 | 2016-04-27 | 哈尔滨工业大学 | Based on dual-acousto-optic modulation and the Michelson heterodyne laser vialog of polarization spectro |
| CN104880244B (en) * | 2015-06-12 | 2017-11-10 | 哈尔滨工业大学 | The Michelson heterodyne laser vialog being divided based on monophone light modulation and depolarization |
| CN112393746B (en) * | 2020-11-20 | 2021-09-07 | 北京控制工程研究所 | Interference angle measuring system in vacuum cryogenic environment |
| CN114812534B (en) * | 2022-04-28 | 2023-04-04 | 中国科学院精密测量科学与技术创新研究院 | Device and method for high-precision adjustment and separation of laser beam parallelism |
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