CN1129774C - Micro-displacement interferometer using semiconductor laser - Google Patents
Micro-displacement interferometer using semiconductor laser Download PDFInfo
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- CN1129774C CN1129774C CN 99113908 CN99113908A CN1129774C CN 1129774 C CN1129774 C CN 1129774C CN 99113908 CN99113908 CN 99113908 CN 99113908 A CN99113908 A CN 99113908A CN 1129774 C CN1129774 C CN 1129774C
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- 238000006073 displacement reaction Methods 0.000 title claims abstract description 25
- 239000004065 semiconductor Substances 0.000 title claims abstract description 19
- 230000010287 polarization Effects 0.000 claims abstract description 19
- 238000005305 interferometry Methods 0.000 claims description 9
- 230000003287 optical effect Effects 0.000 claims description 8
- 238000002310 reflectometry Methods 0.000 claims description 3
- 230000000694 effects Effects 0.000 abstract description 5
- 238000005259 measurement Methods 0.000 abstract description 4
- 230000003760 hair shine Effects 0.000 description 3
- 238000002347 injection Methods 0.000 description 3
- 239000007924 injection Substances 0.000 description 3
- 238000001228 spectrum Methods 0.000 description 3
- 230000003068 static effect Effects 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000002023 wood Substances 0.000 description 2
- 238000000034 method Methods 0.000 description 1
- 239000013307 optical fiber Substances 0.000 description 1
- 230000011514 reflex Effects 0.000 description 1
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- 238000005070 sampling Methods 0.000 description 1
- 230000036962 time dependent Effects 0.000 description 1
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Abstract
A micro-displacement interferometer using semiconductor laser comprises a primary light source, a first lens, a polarization beam splitter, a reference plate and an object to be measured, which are coaxially and sequentially arranged; the second lens and the modulation light source are arranged in the direction of the light beam reflected by the polarization beam splitter. The modulated light source and the primary light source are both semiconductor lasers. The wavelength of the primary light source is modulated by controlling the light intensity sinusoidal variation of the modulated light source through a sinusoidal signal generator and a driver, and the output light of the modulated light source is imposed on the primary light source and is modulated by using the photo-thermal effect. The output light intensity of the original light source does not change along with time, so that the compensation problem in the prior art is avoided, the measurement precision is improved, and the use and the operation are simple and convenient.
Description
Technical field
The present invention relates to micro-displacement interferometry apparatus, particularly relate to the micro-displacement interferometry apparatus of the semiconductor laser that uses sinusoidal phase modulation.
Background technology
Because the temperature stability of semiconductor laser (being designated hereinafter simply as LD) wavelength is solved preferably, the semiconductor laser interference instrument is is researched and developed widely.LD except that volume is little, power-saving, price low, an outstanding advantage is that wavelength-modulated is easy.This makes the light heterodyne technology that can improve measuring accuracy can realize by the injection current of direct modulation LD simply in the semiconductor laser interference instrument.The assistant assistant wood of Japan Nigata (Niigata) university is repaiied oneself (Osami Sasaki) Mr. etc. and has been proposed a kind of sinusoidal phase modulation semiconductor laser interference instrument that is used to measure micro-displacement, (referring to prior art [1] Osami Sasaki, Kazuhide Takahashi, and TakamasaSuzuki, " Sinusoidal phase modulating laser diode interferometer with a feedbackcontrol system to eliminate external disturbance; " Opt.Eng., 1990,29 (12), 1511-1515.) this interferometer as shown in Figure 1.Is parallel beam as the light beam that primary source 1 sends by first lens, 2 collimations with semiconductor laser, folded light beam f by beam splitter 3 reflections shines on the reference mirror 4, the transmitted light beam t that sees through beam splitter 3 shines on the testee 5, the interference signal that the folded light beam of reference mirror 4, testee 5 produces is converted to electric signal by receiving element 6, sends into computing machine 8 and carry out data processing after analog to digital converter 7 is converted to digital signal.The driver 9 that is connected with primary source 1 is connected with sinusoidal signal generator 11 with first direct supply 10 respectively.Inject a sinusoidal current signal to primary source 1 and make primary source 1 wavelength sinusoidal variations, thereby obtain the interference signal of sinusoidal phase modulation.But the frequency content nano-precision that obtains behind the interference signal Fourier transform is measured the micro-displacement of testee 5.
Behind the semiconductor laser injection current as primary source 1, its intensity and wavelength are respectively:
g(t)＝β
1[i
0+Δi(t)] (1)
λ(t)＝λ
0+β
2Δi(t)， (2)
i
0Be respectively the direct current and the AC compounent of drive current, β with Δ i (t)
1, β
2Be proportionality constant, λ
0For corresponding to DC component i
0Centre wavelength.AC compounent
Δi(t)＝αcos(ω
ct+θ)。(3)
Receiving element 6 detected interference signals are:
I(t)＝I
0(t)+S
0(t)cos[zcos(ω
ct+θ)+α
0+α(t)]， (4)
I wherein
0(t) and S
0(t) be the modulated time dependent function that produces of output intensity owing to primary source 1, z is the amplitude of interference signal phase modulation (PM), α
0=2 π r
0/ λ
0, α (t)=4 π r (t)/λ
0, r
0Be testee 5 optical path difference when static, r (t) is a micro-displacement to be measured.Formula (4) is carried out Fourier transform (referring to prior art [2] Osami Sasaki and Hirokazu Okazaki, " Sinusoidal phase modulating interferometerusing optical fibers for displacement measurement; " Appl.Opt.1988,27 (19), 4139-4142.) try to achieve α (t), and then try to achieve micro-displacement r (t).
Because the light intensity g (t) of primary source 1 is modulated, make I
0(t) and S
0(t) change in time, the spectrum component that this will influence behind formula (4) Fourier transform causes measuring error.For eliminating this error, assistant assistant wood is repaiied own Mr. and is adopted the method for software to compensate the variation of primary source 1 output intensity, and this compensation is after obtaining interference signal, realizes during data processing, only be rough compensation, and need at any time software to be revised according to the variation of external condition.If this interferometer instrumentation, the user is according to the variation of external condition fixed software at any time, and this causes difficulty to correct measurement.
Summary of the invention
Purpose of the present invention is the compensation problem of the intensity variation that fundamentally solves the direct modulation light wavelength and cause, and easy to operate for making, the measuring accuracy height provides a kind of micro-displacement interferometry apparatus with semiconductor laser.
Micro-displacement interferometry apparatus with semiconductor laser of the present invention, as shown in Figure 2.It comprises on the emission light beam working direction that places the primary source that has first direct supply 10 1 in the casing 19 and is equipped with first lens 2 successively with optical axis ground, beam splitter 3 and testee 5; Folded light beam f at beam splitter 3
2On the receiving element 6 that is connected of analog to digital converter 7 on being equipped with output and being connected to casing 19 computing machine 8 outward, be characterized in: between first lens 2 and beam splitter 3 with optical axis be provided with polarization beam apparatus 17, between beam splitter 3 and testee 5, be provided with reference plate 18; Folded light beam f at polarization beam apparatus 17
1Working direction on, be equipped with second lens 16 and modulated light source 15 successively; Modulated light source 15 has driver 9, and driver 9 is connected with second direct supply 14 and phase shifter 13, and phase shifter 13 links to each other with controller 12 through sinusoidal signal generator 11, and controller 12 is connected on the analog to digital converter 7 that places outside the casing 19.
Above said primary source 1 and modulated light source 15 all are semiconductor laser (also claim laser diode, abbreviate LD as).
Said receiving element 6 is electrooptical devices such as photodiode, or photoelectric cell.
Said polarization beam apparatus 17 is to be made of the beam splitter that the orthogonal two-beam in polarization direction can be separated.That is to say, allow a branch of light transmission, the beam splitter that allows another perpendicular Shu Guang of polarization direction be reflected constitutes.Polarization splitting prism in this way, or be coated with parallel flat of rete etc.
Said beam splitter 3 is meant the beam splitter that incident light can be divided into two-beam by the beam intensity ratio that approached 1: 1.Be coated with the parallel flat of analysing the light film etc. as Amici prism or one side
Said reference plate 18 is one facing to being coated with anti-reflection film on the surface of beam splitter 3 one sides, and another is coated with the parallel flat that increases anti-film facing on the surface of testee 5 one sides.Its reflectivity R satisfies 0.08＜R＜0.73, and correspondingly transmissivity T satisfies 0.27＜T＜0.92.
As shown in Figure 2, driven by first direct supply 10 as the LD of primary source 1, make the light intensity of primary source 1 not change in time, the wavelength of primary source 1 is by modulated light source 15 sinusoidal photo-thermal effects modulation.The light that primary source 1 sends sees through the transmitted light beam t of polarization beam apparatus 17 and beam splitter 3 by first lens, 2 collimations
1Shine on the reference plate 18, see through the transmitted light beam t of reference plate 18
2Shine on the testee 5, the interference signal that reference plate 18 and testee 5 both beam reflected produce is converted to electric signal by receiving element 6, sends into computing machine 8 through analog to digital converter 7 and handles.The signal of sinusoidal signal generator 11 enters the driver 9 of modulation primary source 15 behind phase shifter 13, controller 12 produces the sampling trigger pulse and sampled signal is sent into analog to digital converter 7.The light that modulated light source 15 is sent, is focused on the primary source 1 by first lens 2 after polarization beam apparatus 17 reflections by second lens, 16 collimations.Primary source 1 is vertical mutually with the polarisation of light direction that modulated light source 15 is sent, polarization beam apparatus 17 makes the light transmission of primary source 1 and does not reflex on the modulated light source 15, the light of modulated light source 15 is incided on the primary source 1, and wherein the segment beam that is reflected by primary source 1 can not pass through polarization beam apparatus 17 again.Sinusoidal signal generator 11 adds the output intensity sinusoidal variations that sinusoidal signal makes modulated light source 15 by phase shifter 13 to driver 9, after this light intensity shines on the primary source 1, because photo-thermal effect, the junction temperature of primary source 1 is sinusoidal variations correspondingly, makes the wavelength of primary source 1 by sinusoidal variations.The phase place of the interference signal that receiving element 6 receives is by Sine Modulated.Because the injection current of primary source 1 is a direct current, the output intensity of primary source 1 does not change in time, so the interference signal that receiving element 6 receives is
I(t)＝I
0+S
0cos[zcos(ω
ct+θ)+α
0+α(t)]， (5)
Wherein, I
0With S
0Be respectively the amplitude of interference signal DC component and AC compounent, z is the amplitude of interference signal phase modulation (PM), α
0=2 π r
0/ λ
0, α (t)=4 π r (t)/λ
0, r
0Be testee 5 optical path difference when static.R (t) is a micro-displacement to be measured.Formula (5) is carried out Fourier transform (referring to documents [2] Osami Sasaki andHirokazu Okazaki, " Sinusoidal phase modulating interferometer using optical fibersfor displacement measurement; " Appl.Opt.1988,27 (19), 4139-4142.) try to achieve α (t)
r(t)＝λ
0α(t)/4π。(6)
The measuring accuracy of α (t) reaches 0.01rad and is easier to realize.If adopt wavelength X commonly used
0Be the LD of 785nm, the resolution of displacement is 0.62nm.If the measuring accuracy of α is brought up to 0.001rad, then resolution is brought up to 0.062nm.
Because of the variation in time of output light intensity of primary source 1, the I in the formula (5)
0, S
0Be constant, thereby light intensity changes influence to measuring when fundamentally having solved modulation wavelength.
Advantage of the present invention has:
1. improved measuring accuracy.In the prior art, when directly modulating the wavelength of primary source 1, the output intensity of primary source 1 changes in time, has influenced interference signal is carried out the spectrum distribution that obtains behind the Fourier transform.Because displacement is to obtain according to the frequency content of this frequency spectrum, so measuring error has been introduced in the variation of output intensity.The present invention contains modulated light source 15, utilizes the wavelength of photo-thermal effect modulation primary source 1, and the output intensity of primary source 1 does not change in time, has avoided this measuring error, has improved measuring accuracy.
2. the variation of the output intensity of prior art is to adopt the software approach compensation.This compensation is after obtaining interference signal, realizes during data processing, only is rough compensation, has residual error, and needs at any time software to be revised according to the variation of external condition.The present invention has avoided this compensation problem.
3. directly modulate the interference measuring instrument of primary source 1 wavelength with regard to prior art, behind the instrumentation, the user must according to the variation of external condition at any time fixed software change with the compensation light intensity, this correctly uses this instrument to bring difficulty for the user.Behind the interference measuring instrument instrumentation of the present invention, do not need the user to compensate, use easy and simple to handle.
Description of drawings
Fig. 1 directly modulates the interference measuring instrument synoptic diagram of primary source 1 wavelength for prior art;
Fig. 2 is the interference measuring instrument synoptic diagram that utilizes photo-thermal effect modulation primary source 1 wavelength that contains modulated light source 15 of the present invention.
Embodiment
Structure as shown in Figure 2.Wherein primary source 1 and modulated light source 15 all adopt wavelength X
0LD for 785nm.Receiving element 6 is a photodiode.Beam splitter 3 is that one side is coated with the parallel flat of analysing the light film.Polarization beam apparatus 17 is polarization splitting prisms.Reference plate 18 is transmissivity T=0.62, reflectivity R=0.38.When beginning to measure, control the amplitude of the output intensity sinusoidal variations of modulated light source 15, make that the z value in the above-mentioned formula (5) is about 2.34 by sinusoidal signal generator 11 and driver 9.Make that by regulating phase shifter 13 θ value in the above-mentioned formula (5) is 0 or π.When z=2.34 and θ=0 or π, the precision of the displacement r (t) that tries to achieve is the highest.R (t)=62.47 α (t) nm, as α (t)=1.0, r (t)=62.47nm.
Can measuring amplitude be no more than the displacement of half optical source wavelength with interference measuring instrument of the present invention, this displacement can be static displacement or the displacement of random variation in time.
Claims (4)
1. micro-displacement interferometry apparatus with semiconductor laser comprises:
＜1〉be equipped with first lens (2), beam splitter (3) and testee (5) successively with optical axis ground on the direction of advancing with the primary source (1) of first direct supply (10) emission light beam, above-mentioned each parts all place in the casing (19) except that testee (5);
＜2〉on the folded light beam (f2) of beam splitter (3), be equipped with output and be connected to casing (19) outside computing machine (8) on the receiving element (6) that is connected of analog to digital converter (7);
It is characterized in that:
＜3〉between first lens (2) and beam splitter (3) with optical axis be equipped with polarization beam apparatus (17); Between beam splitter (3) and testee (5), be provided with reference plate (18);
＜4〉on the direction of polarization beam apparatus (17) folded light beam (f1), be equipped with second lens (16) and modulated light source (15) successively;
＜5〉modulated light source (15) has the driver (9) that is connected with second direct supply (14) and phase shifter (13), and wherein phase shifter (13) links to each other through the controller (12) of sinusoidal signal generator (11) analog to digital converter (7) outer with being connected to casing (19).
2. the micro-displacement interferometry apparatus with semiconductor laser according to claim 1 is characterized in that said primary source (1) and modulated light source (15) all are semiconductor lasers.
3. the micro-displacement interferometry apparatus with semiconductor laser according to claim 1, it is characterized in that said polarization beam apparatus (17) is to be made of the beam splitter that the orthogonal two-beam in polarization direction can be separated, polarization splitting prism in this way, or be coated with the parallel flat of rete.
4. the micro-displacement interferometry apparatus with semiconductor laser according to claim 1, it is characterized in that said reference plate (18) is to be coated with anti-reflection film facing on the surface of beam splitter (3) one sides, and another is coated with the parallel flat that increases anti-film facing on the surface of testee (5) one sides, its reflectivity R satisfies 0.08＜R＜0.73, and correspondingly transmissivity T satisfies 0.27＜T＜0.92.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 99113908 CN1129774C (en) | 1999-07-23 | 1999-07-23 | Micro-displacement interferometer using semiconductor laser |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 99113908 CN1129774C (en) | 1999-07-23 | 1999-07-23 | Micro-displacement interferometer using semiconductor laser |
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| Publication Number | Publication Date |
|---|---|
| CN1281970A CN1281970A (en) | 2001-01-31 |
| CN1129774C true CN1129774C (en) | 2003-12-03 |
Family
ID=5277047
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 99113908 Expired - Fee Related CN1129774C (en) | 1999-07-23 | 1999-07-23 | Micro-displacement interferometer using semiconductor laser |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100547344C (en) * | 2007-02-07 | 2009-10-07 | 中国科学院上海光学精密机械研究所 | Sine phase modulation interferometer for real-time measurement of surface topography |
| CN100538260C (en) * | 2007-02-07 | 2009-09-09 | 中国科学院上海光学精密机械研究所 | Micro-displacement high-precision real-time interferometer |
| CN101625233B (en) * | 2009-08-05 | 2010-12-29 | 富美科技有限公司 | Installation detecting system of cleaning scraper blade |
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1999
- 1999-07-23 CN CN 99113908 patent/CN1129774C/en not_active Expired - Fee Related
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Granted publication date: 20031203 Termination date: 20110723 |