CN1177193C - Double-wavelength nanometer precision real-time interferometer - Google Patents
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- CN1177193C CN1177193C CNB02112079XA CN02112079A CN1177193C CN 1177193 C CN1177193 C CN 1177193C CN B02112079X A CNB02112079X A CN B02112079XA CN 02112079 A CN02112079 A CN 02112079A CN 1177193 C CN1177193 C CN 1177193C
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Abstract
A real-time interferometer with dual-wavelength nanometer precision is suitable for measuring static displacement. Comprising two light sources with unequal wavelengths with a driving power supply and a temperature controller. The transmission path of the light beam emitted by the light source is totally performed in the optical fiber, the wave combining element and the optical fiber coupler. And a trigger controller which controls the initial phases to be the same is connected between the two driving power supplies. The photoelectric conversion element converts the received interference signal into an electric signal and inputs the electric signal into the signal processor. The other two input ports of the signal processor are respectively connected with two driving power supplies. The data processed by the signal processor is displayed on a digital display. Compared with the prior art, the method can obtain the measurement result in real time, and the measurement precision is improved by two orders of magnitude compared with the prior art and reaches less than 10 nanometers.
Description
Technical field:
The present invention relates to the real-time interferometer of double-wavelength nanometer-precision, specially refer to the double-wavelength nanometer-precision interference measuring instrument that uses the sinusoidal phase modulation interferometry.
Background technology:
In the optical precision interferometry, the sinusoidal phase modulation interferometry is a kind of high-precision measurement, and displacement measurement can reach nano-precision, but measurement range has only optical source wavelength half.In order to address this problem, the assistant assistant wood of Japan Nigata (Niigata) university repair oneself people such as (Osami Sasaki) provide in 1991 a kind of double-wavelength semiconductor laser interferometer (technology [1] formerly: " Two-wavelength sinusoidalphase-modulating laser-diode interferometer insensitive to external disturbances; " Applied Optics, Vol.30, No.28,4040-4045).In this interferometer, adopted two light sources, utilize the synthetic wavelength technology to expand the measurement range of displacement to 152 ì m, enlarged measurement range greatly.Regrettably this interferometer measurement precision is lower, only has 0.6 micron; And using the bulk optics system, volume is bigger; Measuring beam diameter big (about 1 centimetre) can not be used for the displacement of the small object of measurement size; And do not consider the temperature control measure of laser instrument, and the laser wavelength drift that temperature variation causes will cause measuring error.Use a computer simultaneously and make measurement not carry out in real time.Inventors such as Wang Xiangchao provide a kind of large range displacement measurer of full optical fiber, and (technology [2] formerly: inventor king is to court, and the step raises, Wang Xuefeng, " all-optical fiber and large range displacement measurer, " number of patent application: 01126555.8).This interferometer has significantly improved measurement range, and can be used for the measurement of small items, but measuring accuracy still only reaches micron, nor can measure in real time.
Summary of the invention:
Double-wavelength nanometer-precision real-time interferometer of the present invention comprises:
First light source, 13 emitted light beams that have first driving power 1 and first temperature controller 18 are injected in first isolator 14 by first section optical fiber 1301, after 14 outgoing of first isolator, inject by the second port b that closes ripple element 7 by second section optical fiber 1302, after the 3rd port c ejaculation of closing ripple element 7, inject by the first port P1 of the 3rd section optical fiber 1303 again by fiber coupler 8, after the 3rd port P3 ejaculation of fiber coupler 8, again by the 4th section optical fiber 1304, through collimating apparatus 15 collimations, permeation parts reflecting element 16 is mapped on the testee 17; Light beam by fiber coupler 8 second port P2 outgoing is mapped on the photo-electric conversion element 9 through the 7th section optical fiber 801.Light beam by fiber coupler 8 the 4th port P4 outgoing is mapped on the antireflection element 12 through the 8th section optical fiber 802; Wavelength X is arranged
2The wavelength X that is not equal to first light source 13
1The secondary light source 5 that has second driving power 3 and second temperature controller 4.Pass through the 5th section optical fiber 501 by secondary light source 5 emitted light beams, through second isolator 6, inject by the first port a that closes ripple element 7 through the 6th section optical fiber 502 again, after penetrating from the 3rd port c that closes ripple element 7 equally, inject by the first port P1 of the 3rd section optical fiber 1303 again, after the 3rd port P3 ejaculation of fiber coupler 8, again by the 4th section optical fiber 1304 by fiber coupler 8, through collimating apparatus 15 collimations, permeation parts reflecting element 16 is mapped on the testee 17; Be connected with between first driving power 1 and second driving power 3 and trigger controller 2; The signal processor 11 that three input port 11a, 11b, 11c and an output port 11d are arranged, the first input end mouth 11a of signal processor 11 links to each other with the output terminal of photo-electric conversion element 9, the second input port 11b of signal processor 11 links to each other with second driving power 3, the 3rd input port 11c of signal processor 11 links to each other with first driving power 1, and the output port 11d of signal processor 11 is connected on the digital indicator 10.As shown in Figure 1.
The structure of said signal processor 11 comprises that the first input end mouth 11a of signal processor 11 links to each other with the 4th multiplier 1111 with first multiplier 1101, second multiplier 1121, the 3rd multiplier 1110 respectively.Insert in the first memory 1105 after wherein first multiplier 1101 is connected with first low-pass filter 1103 and first analog to digital converter 1104.Second multiplier 1121 is connected with second low-pass filter 1120 and second analog to digital converter 1119 in the back access first memory 1105.The 3rd multiplier 1110 is connected with the 3rd low-pass filter 1108 and the 3rd analog to digital converter 1107 in the back access second memory 1106.The 4th multiplier 1111 is connected with the 4th low-pass filter 1112 and the 4th analog to digital converter 1113 in the back access second memory 1106; The second input port 11b of signal processor 11 links to each other with the 6th multiplier 1109 with the 4th multiplier 1111 respectively, and wherein the 6th multiplier 1109 links to each other with the 3rd multiplier 1110; The 3rd input port 11c of signal processor 11 links to each other with the 5th multiplier 1102 with second multiplier 1121 respectively, and wherein the 5th multiplier 1102 links to each other with first multiplier 1101; The output of first memory 1105 through the 7th multiplier 1118 to totalizer 1116 and pass through subtracter 1114, divider 1115 and the 8th multiplier 1117 successively to totalizer 1116; The output of second memory 1106 is passed through subtracter 1114, divider 1115 and the 8th multiplier 1117 successively to totalizer 1116; The output of totalizer 1116 inserts in the digital indicator 10.As shown in Figure 2.
Double-wavelength nanometer-precision real-time interferometer of the present invention, its structure such as above-mentioned shown in Figure 1.First light source 13 that has first driving power 1 and first temperature controller 18 links to each other by the input end of the first section optical fiber 1301 and first isolator 14.The output terminal of first isolator 14 links to each other with the second port b that closes ripple element 7 by second section optical fiber 1302.First driving power 1 links to each other by triggering controller 2 with second driving power 3.The secondary light source 5 that has second driving power 3 and second temperature controller 4 links to each other by the input end of the 5th section optical fiber 501 and second isolator 6.The output terminal of second isolator 6 links to each other with the first port a that closes ripple element 7 by the 6th section optical fiber 502.The 3rd port c that closes ripple element 7 links to each other by the first port P1 of the 3rd section optical fiber 1303 and fiber coupler 8.The 3rd port P3 of fiber coupler 8 is connected to collimating apparatus 15 by the 4th section optical fiber 1304.The light beam directive and partial reflection element 16 and the testee 17 of collimating apparatus 15 that penetrate by collimating apparatus 15 with the optical axis placement.The second port P2, the 4th port P4 of fiber coupler 8 are connected to photo-electric conversion element 9 and antireflection element 12 by the 7th, eight section optical fiber 801,802 respectively.The output of photo-electric conversion element 9 is connected with the first input end mouth 11a of signal processor 11.The output of first driving power 1 and second driving power 3 is connected with the second input port 11b with the 3rd input port 11c of signal processor 11 respectively.The output of signal processor 11 is shown by digital indicator 10.
The inner structure of signal processor 11 such as above-mentioned shown in Figure 2, first input end mouth 11a links 1101, second multiplier 1121, the 3rd multiplier 1110 and the 4th multiplier 1111 of first multiplier respectively.The 3rd input port 11c is connected to the 5th multiplier 1102 and second multiplier 1121.The output of the 5th multiplier 1102 is connected to first multiplier 1101.Input is connected to first analog to digital converter 1104 with the output of first low-pass filter 1103 that 1101 outputs of first multiplier link to each other.Input is connected to second analog to digital converter 1119 with the output of second low-pass filter 1120 that 1121 outputs of second multiplier link to each other.The output of the first memory 1105 that two inputs are connected with the output of first analog to digital converter 1104 and second analog to digital converter 1119 respectively is connected respectively to the 7th multiplier 1118 and subtracter 1114.The output of the 7th multiplier 1118 is connected to the input of totalizer 1116.The second input port 11b of signal processor is connected respectively to the 6th multiplier 1109 and the 4th multiplier 1111.Another input port of the 3rd multiplier 1110 links to each other with the 6th multiplier 1109.Input is connected to the 3rd analog to digital converter 1107 with the output of the 3rd low-pass filter 1108 that 1110 outputs of the 3rd multiplier link to each other.Input is connected to the 4th analog to digital converter 1113 with the output of the 4th low-pass filter 1112 that 1111 outputs of the 4th multiplier link to each other.The output of the second memory 1106 that two inputs are connected with the output of the 3rd analog to digital converter 1107 and the 4th analog to digital converter 1113 respectively is connected to subtracter 1114.The output of subtracter 1114 is input to divider 1115, and the output that divider 1115 is input to the 8th multiplier 1117, the eight multipliers 1117 is input to totalizer 1116.
Above said first light source 13, secondary light source 5 all are semiconductor laser (also claim laser diode, abbreviate LD as), all as measurement light source usefulness, and two light emitted wavelength X
1, λ
2Unequal, i.e. λ
1≠ λ
2
Said first driving power 1 provides direct current, sinusoidal ac signal to first light source 13.
Said second driving power 3 provides direct current, sinusoidal ac signal to secondary light source 5.
The temperature of said first temperature controller, 18 controls, first light source 13 only changes the temperature of first light source 13 in ± 0.05 ℃ scope.
The temperature of said second temperature controller, 4 control secondary light sources 5 only changes the temperature of secondary light source 5 in ± 0.05 ℃ scope.
Said first, second isolator the 14, the 6th light of light source 13,5 emission is passed through, and the light beam that returns from light path can not pass through, and that is to say that the light beam that returns from light path penetrates less than on the former transmitting illuminant 13,5.
The said ripple element 7 that closes is to be used for realizing that light beam closes the fiber optic component on road, can be fiber coupler, sonet multiplexer etc.
Said collimating apparatus 15 is that to instigate its emergent light be the optical element of directional light.
Said partial reflection element 16 is meant and can makes a part of incident light transmission, the element that a part of incident light reflects back.Wherein one side does not reflect, or reflectivity very low (reflectivity R＜0.005), or its reflected light can not reflex in the optical fiber.The reflected light of another side can reflect back in the optical fiber simultaneously, and its reflectivity satisfies (0.05＜R＜0.45).
Said photo-electric conversion element 9 is photodiodes, or photoelectric cell etc.
Said antireflection element 12 is meant that its beam intensity ratio that reflects back into fiber coupler 8 reflects back into the little fiber optic component more than 100 times of light intensity of fiber coupler 8 from partial reflection element 16, as optical fiber collimator, end face for the joints of optical fibre at approximate 8 degree angles or directly optical fiber connector is immersed in the matching fluid.
Said digital indicator 10 can show the numerical value of input signal with numeral.
The sinusoidal signal frequency that said triggering controller 2 produces first driving power 1 is the integral multiple of second driving power 3, makes the AC signal of second driving power 3 and the initial phase of first driving power 1 be zero simultaneously.
Said signal processor 11 is meant by handling the output signal of photo-electric conversion element 9, first driving power 1 and second driving power 3, obtains the signal processing circuit of optical path difference between partial reflection element 16 and the testee 17.As shown in Figure 2.
Said first multiplier 1101, second multiplier 1121, the 3rd multiplier 1110, the 4th multiplier 1111, the 5th multiplier 1102 and the 6th multiplier 1109 are analog multiplier in the signal processor 11.
Said subtracter 1114, the 7th multiplier 1118, the 8th multiplier 1117, divider 1115 are digital circuit blocks (commercialization) with totalizer 1116 in the signal processor 11.
Said first low-pass filter 1103, second low-pass filter 1120, the 3rd low-pass filter 1108, the 4th low-pass filter 1112 are the above low-pass filter of quadravalence in the signal processor 11.
Said first memory 1105 is ROM (read-only memory) (ROM) or random access memory (RAM) with second memory 1106 in the signal processor 11.
As above-mentioned structure shown in Figure 1, have the light that first light source 13 of first driving power 1 and first temperature controller 18 sends and incide first isolator 14 by optical fiber 1301.Emergent light by first isolator 14 incides the second port b that closes ripple element 7 by optical fiber 1302.By triggering controller 2 controls second driving power 3, have the light that the secondary light source 5 of second driving power 3 and second temperature controller 4 sends and incide second isolator 6 by optical fiber 501.Emergent light by second isolator 6 incides the first port a that closes ripple element 7 by optical fiber 502.After the 3rd port c outgoing of ECDC ripple element 7, incide the first port P1 of fiber coupler 8 again by optical fiber 1303.Incide the 12 back ejaculations of antireflection element from the 4th port P4 emergent light of fiber coupler 8 by optical fiber 1303.The effect of antireflection element 12 is exactly to prevent to have the light reflection to turn back in the light path herein.Incide collimating apparatus 15 from the 3rd port P3 emergent light of fiber coupler 8 by optical fiber 1304.Emergent light behind collimating apparatus 15 collimations incides on the partial reflection element 16, be mapped on the testee 17 by the light of partial reflection element 16 transmissions and reflect again, the reflected light that does not see through on light that it reflects and the partial reflection element 16 produces interferes, interference signal light enters fiber coupler 8 by collimating apparatus 15 and optical fiber 1304 again, from the second port P2 outgoing of fiber coupler 8, by 801 converting the first input end mouth 11a that electric signal is input to signal processor 11 to behind the optical fiber by photo-electric conversion element 9.The output of first driving power 1 and second driving power 3 is input to the 3rd input port 11c and the second input port 11b of signal processor 11 respectively.Signal processor 11 processing section reflecting elements 16 and the interference signal that testee 17 produces obtain optical path difference, and optical path difference is shown by digital indicator 10, can obtain the displacement that testee 17 moves according to the optical path difference on the digital indicator 10.
Concrete process prescription is: behind first light source 13 and secondary light source 5 injection currents, its wavelength is respectively:
λ
1(t)＝λ
01+β
1Δi
1(t)， (1)
λ
2(t)＝λ
02+β
2Δi
2(t)， (2)
β
1, β
2Be proportionality constant, λ
01, λ
02Be centre wavelength corresponding to the drive current DC component.Δ i
1(t), Δ i
2(t) be the AC compounent of drive current, be expressed as
Δi
1(t)＝a
1cos(ω
c1t+θ
1)， (3)
Δi
2(t)＝a
2cos(ω
c2t+θ
2)， (4)
ω wherein
C1, ω
C2Be respectively the angular frequency of the sinusoidal phase modulation of first light source 13 and secondary light source 5, t is the time of modulation of source, θ
1, θ
2Be the initial phase of the sinusoidal phase modulation of first light source 13 and secondary light source 5, a
1, a
2Amplitude for the drive current AC compounent.
Photo-electric conversion element 9 detected interference signals are:
S(t)＝I
B(t)+I
M1(t)cos[z
1cos(ω
c1t+θ
1)+α
01]
+I
M2(t)cos[z
2cos(ω
c2t+θ
2)+α
02]， (5)
I wherein
B(t) be the background intensity of interference signal, I
M1(t), I
M2(t) be respectively the modulate intensity of two light sources 13,5.z
1, z
2Be the interference signal phase modulation (PM) degree of depth, according to technology [1] formerly, the optical path difference between partial reflection element 16 and the testee 17 is:
Δl＝(α
01-α
02)λ
e/2π， (6)
In the formula
λ
e＝|λ
01λ
02/(λ
01-λ
02)| (7)
Be synthetic wavelength.
As above-mentioned shown in Figure 2, after the signal of photo-electric conversion element 9 is input to signal processor 11, enter first multiplier 1101, second multiplier 1121, the 3rd multiplier 1110 and the 4th multiplier 1111 respectively.Signal from first driving power 1 enters the 5th multiplier 1102 and second multiplier 1121.The output signal of first multiplier 1101 obtains digitized cos α after through first low-pass filter 1103 and first analog to digital converter 1104
01, similarly, obtain digitized sin α from the output of second analog to digital converter 1119
01, according to corresponding cos α
01With sin α
01Value obtains λ from first memory 1105
eα
01The value of/2 π.Similarly, the output from second memory 1106 obtains λ
eα
02The value of/2 π.The output of first memory 1105 and second memory 1106 is input to subtracter 1114 subtracts each other, and obtains the coarse value of optical path difference Δ l.The output of first memory 1105 obtains λ after through the 7th multiplier 1118
01α
01/ 2 π.The output of subtracter 1114 is met m λ through behind the divider 1115
01The λ of≤Δ l＜(m+1)
01Integer m value, obtain m λ through the 8th multiplier 1117 again
01, the optical path difference of the output of the 7th multiplier 1118 and the 8th multiplier 1117 through obtaining after the totalizer 1116 being asked,
Δl＝mλ
01+λ
01α
01/2π， (8)
And by digital indicator 10 its numerical value of demonstration, since first precision that can be less than 1nm on equal sign the right in the following formula, second precision that can reach several nanometers, so the measuring accuracy of optical path difference is several nanometers.
If object moves to position two along optical axis by position one, the optical path difference that records is respectively Δ l
1, Δ l
2, then the displacement of testee 17 just can be according to showing that the difference of numerical value obtains, promptly twice of digital indicator 10
d
12＝(Δl
2-Δl
1)/2 (9)
We have just obtained the displacement of object with the precision of several nanometers like this.
If the employing wavelength is respectively the LD of 785nm and 780nm, synthetic wavelength λ
eBe 122.46 μ m, the measurement range of displacement is 61.23 μ m; If adopt wavelength to be respectively the LD of 1305.0nm and 1308.0nm, the measurement range of displacement is 284.49 μ m, and measuring accuracy is several nanometers.Compare with technology [1] formerly, under the prerequisite that measurement range also enlarges, measuring accuracy has improved greatly.And measurement no longer needs computing machine.
The present invention compares with technology formerly, has outstanding feature:
1), compare with technology formerly, double-wavelength nanometer-precision real-time interferometer of the present invention, under the identical situation of measurement range, measuring accuracy has improved two orders of magnitude, is less than 10 nanometers.
2), compare with technology formerly, double-wavelength nanometer-precision real-time interferometer of the present invention adopts signal processor 11 to realize all computings, has save computing machine, can obtain measurement result in real time.
3), compare with technology formerly, double-wavelength nanometer-precision real-time interferometer of the present invention adopts and triggers controller 2 and realize that the Sine Modulated of two light sources has identical initial phase, guarantees phase place α
01And α
02Measuring accuracy.
Description of drawings:
Fig. 1 is the structural representation of double-wavelength nanometer-precision real-time interferometer of the present invention.
Fig. 2 is the structural representation of signal processor 11 in the double-wavelength nanometer-precision real-time interferometer of the present invention.
Embodiment:
Structure as shown in Figure 1.Trigger the ratio ω that controller 2 makes first light source 13 and secondary light source 5 sinusoidal phase modulation angular frequencies by control
C1/ ω
C2=10.Wherein first light source 13 and secondary light source 5 adopt wavelength to be respectively λ
1=1305.0nm and λ
2The distributed feedback semiconductor laser of=1308.0nm (DFB-LD), synthetic wavelength λ
eBe 568.98 ì m.Photo-electric conversion element 9 is a photodiode.Antireflection element 12 is the joints of optical fibre.Close ripple element 7 and be fiber coupler.The splitting ratio of fiber coupler 8 is 1: 1.The reflectivity of partial reflection element 12 is 27%.When beginning to measure, at first open first light source 13 and secondary light source 5, and make the temperature stabilization of first light source 13 and secondary light source 5 with first temperature controller 18 and second temperature controller 4 respectively.The amplitude of the sinusoidal ac signal by regulating first driving power 1 and second driving power 3 makes z
1=z
2During=2.34rad, the precision of the displacement of trying to achieve is the highest.When testee 17 during in position 1, the numerical value on the digital indicator 10 is Δ l
1=2128nm, when testee 17 during in position 2, the numerical value on the digital indicator 10 is Δ l
2=2543nm is 207.5nm according to the displacement that above-mentioned formula (9) can be obtained testee 17 then.
Claims (2)
1. double-wavelength nanometer-precision real-time interferometer comprises:
＜1〉first light source (13) emitted light beams that has first driving power (1) and first temperature controller (18) is injected in first isolator (14) by first section optical fiber (1301), after first isolator (14) outgoing, inject by second port (b) that closes ripple element (7) by second section optical fiber (1302), after the 3rd port (c) ejaculation of closing ripple element (7), inject by first port (P1) of fiber coupler (8) by the 3rd section optical fiber (1303) again, after the 3rd port (P3) ejaculation of fiber coupler (8), again by the 4th section optical fiber (1304), through collimating apparatus (15) collimation, permeation parts reflecting element (16) is mapped on the testee (17);
＜2〉light beam by fiber coupler (8) second port (P2) outgoing is mapped on the photo-electric conversion element (9) through the 7th section optical fiber (801), is mapped on the antireflection element (12) through the 8th section optical fiber (802) by the light beam of fiber coupler (8) the 4th port (P4) outgoing;
It is characterized in that:
＜3〉wavelength X is arranged
2The wavelength X that is not equal to first light source (13)
1The secondary light source (5) that has second driving power (3) and second temperature controller (4), pass through the 5th section optical fiber (501) by secondary light source (5) emitted light beams, through second isolator (6), inject by first port (a) that closes ripple element (7) through the 6th section optical fiber (502) again, after penetrating from the 3rd port (c) that closes ripple element (7) equally, inject by first port (P1) of fiber coupler (8) by the 3rd section optical fiber (1303) again, after the 3rd port (P3) ejaculation of fiber coupler (8), again by the 4th section optical fiber (1304), through collimating apparatus (15) collimation, permeation parts reflecting element (16) is mapped on the testee (17);
＜4〉be connected with triggering controller (2) between first driving power (1) and second driving power (3);
＜5〉signal processor (11) that comprises three input ports (11a, 11b, 11c) and an output port (11d) is arranged, the first input end mouth (11a) of signal processor (11) links to each other with the output terminal of photo-electric conversion element (9), second input port (11b) of signal processor (11) links to each other with second driving power (3), the 3rd input port (11c) of signal processor (11) links to each other with first driving power (1), and the output port (11d) of signal processor (11) is connected on the digital indicator (10).
2. double-wavelength nanometer-precision real-time interferometer according to claim 1, the structure that it is characterized in that said signal processor (11) comprises, the first input end mouth (11a) of signal processor (11) respectively with first multiplier (1101), second multiplier (1121), the 3rd multiplier (1110) links to each other with the 4th multiplier (1111), insert in the first memory (1105) after wherein first multiplier (1101) is connected with first low-pass filter (1103) and first analog to digital converter (1104), second multiplier (1121) is connected with second low-pass filter (1120) and second analog to digital converter (1119) in the back access first memory (1105), insert after the 3rd multiplier (1110) is connected with the 3rd low-pass filter (1108) and the 3rd analog to digital converter (1107) in the second memory (1106), the 4th multiplier (1111) is connected with the 4th low-pass filter (1112) and the 4th analog to digital converter (1113) in the back access second memory (1106); Second input port (11b) of signal processor (11) links to each other with the 6th multiplier (1109) with the 4th multiplier (1111) respectively, and wherein the 6th multiplier (1109) links to each other with the 3rd multiplier (1110); The 3rd input port (11c) of signal processor (11) links to each other with the 5th multiplier (1102) with second multiplier (1121) respectively, and wherein the 5th multiplier (1102) links to each other with first multiplier (1101); The output of first memory (1105) and second memory (1106) is input to subtracter (1114) and subtracts each other, obtain the coarse value of optical path difference Δ l, the output of first memory (1105) is met m λ through the 7th multiplier (1118) behind the output of subtracter (1114) the process divider (1115)
01The λ of≤Δ l＜(m+1)
01Integer m value, again through the 8th multiplier (1117), the output of the 7th multiplier (1118) and the 8th multiplier (1117) obtains the optical path difference asked through totalizer (1116); The output of totalizer (1116) inserts in the digital indicator (10).
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