CN100538260C - Micro-displacement high-precision real-time interferometer - Google Patents
Micro-displacement high-precision real-time interferometer Download PDFInfo
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- CN100538260C CN100538260C CNB2007100372659A CN200710037265A CN100538260C CN 100538260 C CN100538260 C CN 100538260C CN B2007100372659 A CNB2007100372659 A CN B2007100372659A CN 200710037265 A CN200710037265 A CN 200710037265A CN 100538260 C CN100538260 C CN 100538260C
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- 238000006073 displacement reaction Methods 0.000 title claims abstract description 31
- 239000004065 semiconductor Substances 0.000 claims abstract description 22
- 238000012545 processing Methods 0.000 claims abstract description 21
- 238000010606 normalization Methods 0.000 claims abstract description 12
- 238000005305 interferometry Methods 0.000 claims description 12
- 238000001914 filtration Methods 0.000 claims description 9
- 230000003287 optical effect Effects 0.000 claims description 5
- 239000004606 Fillers/Extenders Substances 0.000 claims description 4
- 238000007747 plating Methods 0.000 claims description 2
- 238000005259 measurement Methods 0.000 abstract description 14
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- 238000004364 calculation method Methods 0.000 description 1
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- 238000010586 diagram Methods 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
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Abstract
A micro-displacement high-precision real-time interferometer comprises a Tyman Green interferometer composed of a semiconductor laser, a collimation beam expander, a beam splitter, a reference flat plate, an object to be measured and a detection element, and is characterized in that: the output end of the detection element is sequentially connected with a real-time signal processing circuit normalization circuit and a single chip microcomputer in series, the single chip microcomputer is provided with phase continuous processing software, the output end of the single chip microcomputer is connected with the input end of an oscilloscope, a direct-current power supply and a signal source are connected with the semiconductor laser through a modulator, and the signal source is further connected with the real-time signal processing circuit. The invention has the advantages of improved displacement measurement precision, expanded measurement range, no need of correction during use, simple operation and high reliability.
Description
Technical field
The present invention relates to the displacement interferometer measuring technique, particularly a kind of semiconductor laser micro-displacement high accuracy real-time interferometry instrument that adopts sinusoidal phase modulation.
Background technology
In the optical precision interferometry, the sinusoidal phase modulation interfere measurement technique has higher measuring accuracy, and the displacement measurement precision can reach nanometer scale.Semiconductor laser (being designated hereinafter simply as LD) has characteristics such as volume is little, power-saving, price is low, wavelength-modulated is easy, in the interferometer that adopts light heterodyne technology, realize sinusoidal phase modulation by the injection current of direct modulation LD, not only can improve measuring accuracy, can also make the structure of interferometer more simple.Interferometer (the technology [1] formerly: Takamasa Suzuki that is used for measuring vibrations that proposes such as the Suzuki Xiaochang people such as (Takamasa Suzuki) of Japanese Niigata University, Takao Okada, Osami Sasaki, Takeo Maruyama, " Real-time vibration measurement using a feedback type of laser diodeinterferometer with an optical fiber ", Opt.Eng., 1997,36 (9), 2496-2502), it is simple in structure, and modulation accurately can be treated Measuring Object any position vibration and measure; Do not need reference surface, have the phase compensation function, feedback circuit has been eliminated the extraneous vibration interference; Can obtain vibration displacement in real time.On this basis, people such as the Song Song of Shanghai Optics and Precision Mechanics institute, Chinese Academy of Sciences have proposed another kind of semiconductor laser microvibration real-time interferometer (technology [2]: Song Song formerly, Wang Xiangchao, Wang Xuefeng, cutting edge of a knife or a sword cutting edge of a knife or a sword, Lu Hongbin, " semiconductor laser microvibration real-time interferometer ", optics journal, 2001,21 (5), 578-580; Technology [3] Song Song formerly, Wang Xiangchao, Wang Xuefeng, the cutting edge of a knife or a sword cutting edge of a knife or a sword, Chen Gaoting, " microvibration of adopting locking phase to detect is measured in real time ", and Chinese laser, 2001,28 (8), 753-756).The interference signal of this interferometer converts electric signal to by detecting element, carries out the displacement that data processing obtains vibrating by signal processing circuit.
Technology [2,3] formerly, the wavelength and the intensity of semiconductor laser are respectively:
λ(t)=λ
0+β
1Δi(t), (1)
g(t)=β
2[i
0+Δi(t)], (2)
i
0Be the DC component of drive current, Δ i (t) is the AC compounent of drive current, β
1Be wavelength-modulated coefficient, β
2Be intensity modulation coefficient, λ
0Be DC component i
0Corresponding centre wavelength.Modulating current is
Δi(t)=acos(ω
0t+θ) (3)
In the formula: a is the modulating current amplitude.
The detected interference signal of detecting element is
S(t)=S
0(t)+S
1(t)cos[z?cos(ω
0t+θ)+α
0+α
r(t)], (4)
S
0(t) and S
1(t) changed z=4 π β in time by intensity modulation
1β
2AD
0/ λ
0 2Be the sinusoidal phase modulation degree of depth.α in the formula (t) is α
0With α
r(t) and.Obtaining detectable signal P (t) after interference signal is handled through signal processing circuit is:
P(t)=KaJ
1(z)sin?α(t), (5)
In the formula: K is the enlargement factor of signal processing circuit, J
1(z) be the 1st rank Bessel's function.
From the above, interference signal obtains phase place α (t) after signal processing circuit is handled, thereby can obtain micro-displacement r (t).Because the light intensity of semiconductor laser is modulated, make S
0(t), S
1(t) change in time, cause measuring error.Simultaneously, the displacement in (5) formula is with initial light path difference 2D
0, circuit enlargement factor K, depth of modulation z be relevant with the Bessel's function value, they are influential to measuring accuracy, will proofread and correct before the test.Formerly technology [1] does not solve the modulated problem of light intensity yet, and intensity modulation causes that the flip-flop of interference signal and AC amplitude composition change in time, have bigger influence to measuring accuracy.
Summary of the invention
The technical problem to be solved in the present invention is to overcome the defective of above-mentioned prior art, and a kind of micro-displacement high accuracy real-time interferometry instrument is provided, and to solve the light intensity variation and interferometer parameter that the directly modulated laser wavelength causes, comprises initial light path difference 2D
0, circuit enlargement factor K, depth of modulation z and Bessel's function value make microdisplacement measurement not need correction, easy to operate to the influence of measuring accuracy, and reliable test result.
Technical solution of the present invention is as follows:
A kind of micro-displacement high accuracy real-time interferometry instrument, comprise by semiconductor laser, the collimator and extender mirror, beam splitter, reference plate, safe graceful Green's interferometer that object to be measured and detecting element are formed, be characterized in: the output termination real time signal processing circuit input end of described detecting element, this real time signal processing circuit output end connects the normalization circuit input end, this normalization circuit output terminal connects the single-chip microcomputer input end, this single-chip microcomputer has the continuous phase process software, the output terminal of this single-chip microcomputer links to each other with oscillographic input end, direct supply is connected with described semiconductor laser by modulator with signal source, and described signal source also is connected with described real time signal processing circuit.
Described beam splitter is that incident light is divided into the element of two-beam by 1: 1 light intensity, and the parallel flat of being analysed the light film by Amici prism or one side plating constitutes.
Described reference plate is an optical flat, and its one side near beam splitter is coated with highly reflecting films.
Described detecting element is photodiode or photoelectric cell or photomultiplier.
Described real time signal processing circuit is by two amplifiers, a multiplier), wave filter constitutes.
Described normalization circuit is made of power operation circuit, filtering circuit, extracting operation circuit and division arithmetic circuit polyphone.
The function that described single-chip microcomputer calculates and oscillograph shows is finished by a computing machine.
Advantage of the present invention:
1), eliminated the influence of light intensity.In the prior art, during the wavelength of directly modulated laser, the output intensity of semiconductor laser changes in time, and measured displacement is obtained according to this light intensity, so measuring error has been introduced in the variation of output intensity.The present invention utilizes normalization circuit to eliminate the influence of light intensity to measuring accuracy.
2), technology [2] formerly, can't accurately measure initial light path difference 2D
0, therefore can not accurately obtain the Bessel's function value.Need during use to proofread and correct, this correctly uses this instrument to bring difficulty for the user.The present invention has eliminated initial light path difference 2D
0Influence, make the operation of interferometer more simple.
3), technology [2] formerly, the circuit enlargement factor can't accurately be measured, and the circuit enlargement factor will change with variation of ambient temperature.The present invention has eliminated the influence of circuit enlargement factor to measuring accuracy.
4), the anti-external interference ability of method of the present invention is strong.
5), measurement range of the present invention exceeds half wavelength, enlarged measurement range.
Description of drawings
Fig. 1 is micro-displacement high accuracy real time interferometer example structure figure of the present invention.
Fig. 2 is the signal flow graph of real time signal processing circuit of the present invention and normalization circuit.
Embodiment
The invention will be further described below in conjunction with embodiment and accompanying drawing, but should not limit protection scope of the present invention with this.
See also Fig. 1 earlier, Fig. 1 is a micro-displacement high accuracy real time interferometer embodiment structural representation of the present invention.As seen from the figure, micro-displacement high accuracy real time interferometer of the present invention has on the semiconductor laser 1 emission light beam working direction of direct supply 11 and is placed with lens 2 successively with optical axis, beam splitter 3, object 5 to be measured; Place reference plate 4 on the folded light beam f1 working direction of this beam splitter 3.Light beam f1 is placed with detecting element 6 on reference plate 4 beam reflected f2 working direction, constitute safe graceful Green's interferometer, what contact successively with detecting element 6 is real time signal processing circuit 7, normalization circuit 8, single-chip microcomputer 9, shows measurement results by oscillograph 10 at last.Direct supply 11, signal source 12 are connected with modulator 13.Signal source 12 also is connected with real time signal processing circuit 7.Semiconductor laser 1 is connected with modulator 13.
In the present embodiment, described semiconductor laser 1 is that centre wavelength is the semiconductor laser of 785nm.Described beam splitter 3 is by the Amici prism that is divided into two-beam at 1: 1 with light intensity.Described reference plate 4 is gold-plated level crossings.Described detecting element 6 is photodiodes.
Described real time signal processing circuit 7 is by first amplifying circuit 701, second amplifying circuit 702, mlultiplying circuit 703, and filtering circuit 704 constitutes.First amplifying circuit 701 is made of chip LM232, and second amplifying circuit 702 is made of chip LM232.Mlultiplying circuit 703 is made of chip AD532, and filtered electrical router chip LF356 and follower BC108 constitute.
Described normalization circuit 8 is made of power circuit 801, filtering circuit 802, evolution circuit 803, division circuit 804.Power circuit 801 is made of the identical chip AD532 of two-way input.Filtering circuit 802 is pi type filters.Evolution circuit 803 is made of chip LM232.Division circuit 804 is made of chip AD538.
Described single-chip microcomputer 9 is that a model is the single-chip microcomputer of ADuc812.Described oscillograph 10 is one to have the digital oscilloscope of memory function.Described signal source 12 is signal generators.Described modulator 13 is laser current modulators.
The course of work of micro-displacement high accuracy real time interferometer of the present invention is: semiconductor laser 1 is driven by direct supply 11, the sinusoidal signal modulation that the wavelength of semiconductor laser 1 is exported by signal generator 12.The light beam that semiconductor laser 1 sends shines on the Amici prism 3 behind collimator and extender mirror 2 collimator and extenders, and a branch of light is divided into two-beam, and folded light beam f1 shines on the reference plate 4, and another transmitted light beam t1 shines on the object 5 to be measured.The interference signal that reference planes mirror 4 and object to be measured 5 beam reflected f2 and t2 produce converts electric signal to by detecting element 6, and this interference signal is
S(t)=S
0(t)+S
1(t)cos[z?cos(ω
0t+θ)+α
0+α(t)], (6)
α
0=4πD
0/λ
0, (7)
α(t)=4πr(t)/λ
0, (8)
2D
0Be two optical path differences of interfering between the arm of the graceful interferometer of described Thailand, the micro-displacement of r (t) expression object 5 to be measured.In Fig. 2, above-said current signal S (t) and modulation signal α cos (ω
cT+ θ) (gain is respectively K to amplify the back through first amplifier 701, second amplifier 702 in the signal processing circuit 7 respectively
1, K
2), (coefficient is K to carry out multiplying by computing and filtering circuit 703
c) (gain is K with low-pass filtering
L) after obtain detectable signal P (t)
P
s(t)=K
1K
2K
cK
LS
1AJ
1(z)sin?α(t)=K
ssin?α(t), (9)
K wherein
s=K
1K
2K
cK
LS
0AJ
1(z); A is the amplitude of the sinusoidal phase modulation voltage signal of signal generator 12 outputs.
Detectable signal P (t) through the power circuit 801 of normalization circuit 8 as power is
If the frequency of α (t) is ω, selecting cutoff frequency for use is that the low-pass filtering 802 of 1.5 ω gets as filtering operation,
With 803 couples of P of evolution circuit
2(t) get as extracting operation
P
3(t)=K
s, (12)
To (9) formula and (12) formula division arithmetic, obtain measured signal P (t) by division circuit 804
P(t)=sinα(t)。(13)
Its signal Processing block diagram is as shown in Figure 2.
With measured signal P (t) input single-chip microcomputer 9, this single-chip microcomputer 9 has continuous phase to be handled (referring to technology [4] Wang Xuefeng formerly, Wang Xiangchao etc., be used for the semiconductor laser interference instrument that the nano-precision large range displacement is measured, Chinese laser, 2001,28 (5)) software of computing method establishment, handle to calculate phase place α (t) through continuous phase, calculate measured displacement again and be
r(t)=mπ/4+λ
0α(t)/(4π)。(14)
Wherein m is an integer.The measuring accuracy of phase place can reach 0.001rad, and the resolution of measurement is 0.1nm, and has enlarged range of displacement measurement.
By (13) formula as can be seen, the light intensity of measuring-signal P (t) and semiconductor laser 1 output changes irrelevant, and light intensity changed the influence to measurement result when wavelength-modulated had fundamentally been eliminated in the displacement that obtains from (14) formula.Measuring-signal P (t) and measurement parameter are as the two initial light path difference 2D that interfere between the arm
0, circuit enlargement factor K
1, K
2, K
c, K
L, depth of modulation z and Bessel's function value be irrelevant.
This shows that the present invention has improved the displacement measurement precision, its measurement range surpasses one more than the wavelength, does not need during use to proofread and correct, and is easy and simple to handle, the reliability height.
Claims (7)
1, a kind of micro-displacement high accuracy real-time interferometry instrument, comprise safe graceful Green's interferometer of forming by semiconductor laser (1), collimator and extender mirror (2), beam splitter (3), reference plate (4), object to be measured (5) and detecting element (6), it is characterized in that:
Output termination real time signal processing circuit (7) input end of described detecting element (6), this real time signal processing circuit (7) output termination normalization circuit (8) input end, this normalization circuit (8) output terminal connects single-chip microcomputer (9) input end, this single-chip microcomputer (9) has the continuous phase process software, the output terminal of this single-chip microcomputer (9) links to each other with the input end of oscillograph (10), direct supply (11) is connected with described semiconductor laser (1) by modulator (13) with signal source (12), and described signal source (12) also is connected with described real time signal processing circuit (7).
2, micro-displacement high accuracy real-time interferometry instrument according to claim 1 is characterized in that described beam splitter (3) is that incident light is divided into the element of two-beam by 1: 1 light intensity, and the parallel flat of being analysed the light film by Amici prism or one side plating constitutes.
3, micro-displacement high accuracy real-time interferometry instrument according to claim 1 is characterized in that described reference plate (4) is an optical flat, and its one side near beam splitter is coated with highly reflecting films.
4, micro-displacement high accuracy real-time interferometry instrument according to claim 1 is characterized in that described detecting element (6) is photodiode or photoelectric cell or photomultiplier.
5, micro-displacement high accuracy real-time interferometry instrument according to claim 1 is characterized in that described real time signal processing circuit (7) is made of two amplifiers (701,702), a multiplier (703) and a wave filter (704).
6, micro-displacement high accuracy real-time interferometry instrument according to claim 1 is characterized in that described normalization circuit (8) is made of power operation circuit (801), filtering circuit (802), extracting operation circuit (803) and division arithmetic circuit (804) polyphone.
7, micro-displacement high accuracy real-time interferometry instrument according to claim 1 is characterized in that described single-chip microcomputer (9) calculates and the function of oscillograph (10) demonstration is finished by a computing machine.
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