CN2452005Y - Laser interferometer capable of simultaneously measuring thickness refractivity - Google Patents

Abstract

The utility model relates to a laser interferometry instrument capable of simultaneously measuring thickness and refractivity, which comprises a linear modulation light source, and a multi beam interferometer that is composed of a collimating lens, six beam splitters, two reflecting mirrors and objects to be measured on a sample rack. Four detectors are respectively connected to a signal detection and data process part which is composed of four ports on a data processor that is provided with a display panel through four phase extractors and four differentiators. The utility model can measure the thickness and the refractivity of objects in real time without scanning interference arms, and has the characteristics of high measuring accuracy and high sensitivity.

Description

Measure the laser interferometry instrument of thickness and refractive index simultaneously

The utility model relates to the laser interferometry instrument of measuring thickness and refractive index simultaneously, and all there are reflection or back in particularly suitable two surfaces to the object that scattering is arranged.

Because the thickness by the interferometer measurement object obtains is optical thickness by the optical path difference decision, so necessary searching a kind of device precision measurement physical thickness and refractive index.The device of Measuring Object physical thickness and refractive index when people such as the Tearney G.J of masschusetts, u.s.a Polytechnics provide based on optical coherence tomography system, (referring to technology [1] G.Tearney formerly, M.Brezinski, J.Southern, B.Bouma, M.Hee, and J.Fujimoto, " Determination ofthe refractive index of highscattering human tissue by optica1 coherence tomography; " Opt.Lett.20 (21), 1995,2258-2260.) as shown in Figure 1.It comprises superradiance the laser diode light source 1 and the interferometer part of (being called for short SLD).The light beam coupling that light source 1 sends is in single-mode fiber, the first via 201 as 2 * 2 road three-dB couplers 2, light beam one tunnel is divided into two-way behind coupling mechanism 2, one the tunnel 203 comes out by lens 3 collimated illumination to reference mirror 4 from optical fiber, another road 202 comes out to shine the testee 7 that places on the sample scanning support 701 through the confocal system of first lens 5 and second lens, 6 compositions from optical fiber, the two-way light light beam that reflects of the testee 7 on catoptron 4 and sample scanning support 701 respectively enters optical fiber by 203 the road and 202 the tunnel respectively and joins again coupling mechanism 2, interfere, and export from the four tunnel 204 of coupling mechanism 2.Interference signal is received element 8 and is converted to electric signal, and through restitution element 9 demodulation, analog to digital converter 10 is converted to be sent into computing machine 11 after the digital signal and carry out data processing.Measuring process is at first, makes second lens 6 focus on the front surface of testee 7, and regulating interferometer two arm optical path differences is zero.Move testee 7 along optical axis towards second lens 6 again, make second lens 6 focus on the rear surface of testee 7, testee 7 displacements are △ z.Mobile reference mirror 4 distance z,, make interferometer two arms aplanatism again.As shown in Figure 2, have according to the aplanatism principle

Nt=z+ △ z, (1) n and t are respectively the refractive index and the physical thickness of testee 7.Incident light reflects in testee 7 and air interface, by Snell's law, can get equation

Sin θ=nsin φ, (2) θ and φ are respectively the incident angle and the refraction angles of testee 7 air interface.Geometric relationship in the triangle of considering to form in refracted ray, normal and testee 7 interfaces has:

dtanφ=△ztanθ。(3) association type (2) and (3) can get, $n\sin \left[{\tan }^{-1}\left(\frac{\mathrm{nztg\θ}}{z+\mathrm{\Δz}}\right)\right]=\sin \mathrm{\θ},\left(4\right)$ Wherein sin θ is provided by the numerical aperture of first and second lens 5,6.Can obtain the refractive index of testee 7 like this according to the displacement that records from (4) formula, utilize (1) formula to obtain testee 7 physical thickness simultaneously again.Because this matching requirements scans testee 7 and reference arm, thereby need 5 to 60 seconds long Measuring Time, can't accomplish real-time measurement.And, influence measurement result accuracy because employing is that broadband SLD makes testee 7 that chromatic dispersions take place as light source 1.The SLD of light source 1 is operated in non-laser state, and its low-power output has also limited the sensitivity of device, is unfavorable for the measurement of weak reflection testee.

Formerly in the technology [2], inventors such as the king Xiang Chao of Shanghai precision optical machinery research institute of the Chinese Academy of Sciences provide a kind of semiconductor laser interferometric instrument of micro-displacement in patent 2L99239062.1, as shown in Figure 3.It comprises light source and the interferometer part that places in the shell 16.Laser diode (LD) as primary source 12 is driven by first direct supply 21, makes the light intensity of primary source 12 not change in time, and the wavelength of primary source 12 is by modulated light source 25 sinusoidal photo-thermal modulation.The light that primary source 12 sends sees through the transmitted light beam t of polarization beam apparatus 13 and beam splitter 14 by first lens, 5 collimations ₁Shine on the reference plate 15, see through the transmitted light beam t of reference plate 15 ₂Shine on the testee 7, the interference signal that reference plate 15 and testee 7 beam reflected produce is converted to electric signal by receiving element 8, sends into computing machine 11 through analog to digital converter 10 and handles.The signal of sinusoidal signal generator 18 enters the driver 22 of modulated light source 23 behind phase shifter 19, controller 17 produces the sampling trigger pulse and sampled signal is sent into analog to digital converter 10.The light that modulated light source 23 is sent, is focused on the primary source 12 by first lens 5 after polarization beam apparatus 13 reflections by second lens, 6 collimations.Primary source 12 is vertical mutually with the polarisation of light direction that modulated light source 23 is sent, polarization beam apparatus 13 makes the light transmission of primary source 12 and does not reflex on the modulated light source 23, the light of modulated light source 23 is incided on the primary source 12, and wherein the segment beam that is reflected by primary source 12 can not see through polarization beam apparatus 13.Sinusoidal signal generator 18 adds the output intensity sinusoidal variations that sinusoidal signal makes modulated light source 23 by phase shifter 19 to driver 22, after this light intensity shines on the primary source 12, because photo-thermal effect, the corresponding sinusoidal variations of the light intensity of primary source 12 makes the wavelength of interferometer primary source 12 by sinusoidal variations.The phase place of the interference signal that receiving element 8 receives is by Sine Modulated.Because the injection current of primary source 12 is a direct current, the output intensity of primary source 12 does not change in time, so the interference signal that receives of receiving element 8

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 15 optical path difference when static.R (t) is a micro-displacement to be measured.Formula (5) is carried out Fourier transform tries to achieve α (t),

r(t)=λ ₀α(t)/4π。(6) measuring accuracy of α (t) reaches 0.01rad and is easier to realize.If adopting wavelength commonly used is the laser diode (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.What but this measuring instrument was measured is the short space displacement of testee, can not measure the refractive index and the thickness of testee in real time.

The purpose of this utility model is the deficiency that overcomes in the above-mentioned technology formerly, providing a kind of need not to scan testee 7 and reference arm and measures the measuring instrument of testee refractive index and physical thickness simultaneously, measuring instrument will have high sensitivity, and will eliminate the influence of testee chromatic dispersion.

Measuring instrument of the present utility model as shown in Figure 4.The concrete structure that it comprises is: the linear modulation light source 24 emitted laser bundles that are made of the laser diode 2403 that has direct supply 2401 and signal generator 2402 on the direction that laser beam is advanced, are equipped with center O successively behind collimation lens 5 collimations ₁, O ₄All first beam splitter, 25, the four beam splitters 44 on linear modulated light source 24 emission beam optical axis OO are until the testee 7 that places on the specimen holder 34; In the center O of passing first beam splitter 25 ₁The first perpendicular line O perpendicular to linear modulation light source 24 emission beam optical axis OO ⁰O ⁰On, place the two ends of first beam splitter 25 that first catoptron 25 and the 4th detector 47 are arranged respectively, between first beam splitter 25 and first catoptron 29, center O is arranged ₂Place the first perpendicular line O ⁰O ⁰On second beam splitter 27, between second beam splitter 27 and first catoptron 29, center O is arranged ₃Place the first perpendicular line O ⁰O ⁰On the 3rd beam splitter 28; In the center O of passing second beam splitter 27 ₂With the first perpendicular line O ⁰O ⁰Vertically, on first just parallel parallel lines O ' O ' with linear modulation light source 24 emission beam optical axis OO, the output that is equipped with second catoptron 26 and first detector, 37, the first detectors 37 at the two ends of second beam splitter respectively is connected to first port 3501 of data processor 35 by first phase extractor 38 and first differentiator 39; In the center O of passing the 4th beam splitter 44 ₄On the second perpendicular line O O perpendicular to linear modulation light source 24 emission beam optical axis OO center O is arranged ₅The 5th beam splitter 40 on the second perpendicular line O O has receiving plane to face toward second detector 41 of the reflecting surface of the 5th beam splitter 40.The output of second detector 41 is connected to second port 3502 of data processor 35 by second phase extractor 42 and second differentiator 43; In the center O of passing the 3rd beam splitter 28 ₃The intersection point O of second parallel lines O " O " parallel and the second above-mentioned perpendicular line O O with linear modulation light source 24 emission beam optical axis OO ₆Be equipped with center O ₆With intersection point O ₆The 6th beam splitter 30 that overlaps.Go up have three detector 31 of receiving plane at the second parallel lines O " O " facing to the 6th beam splitter 30 reflectings surface.The output of the 3rd detector 31 is connected to the 3rd port 3503 of data processor 35 by third phase position extraction apparatus 32 and the 3rd differentiator 33; The above-mentioned first perpendicular line O that places ⁰O ⁰On the output of the 4th detector 47 be connected to the 4th port 3504 of data processor 35 by the 4th phase extractor 46 and the 4th differentiator 45.

The length scanning interferometer of the linear modulation semiconductor laser that the utility model uses is measured testee thickness and refractive index simultaneously, as above-mentioned structure and shown in Figure 4.It comprises the Lights section, multiple-beam interferometer, input and data processing section.The Lights section comprises linear modulation light source 24, and linear modulation light source 24 is by direct supply 2401, and signal generator 2402, laser diode 2403 (being called for short LD) are formed.Interferometer partly comprises collimation lens 5, first beam splitter 25, second beam splitter, 27, the three beam splitters, 28, the four beam splitters, 44, the five beam splitters, 40, the six beam splitters, 30, the first catoptrons 29, second catoptron 26 and places testee 7 on the specimen holder 34.The signal detecting part branch comprises first detector 37, second detector, 41, the three detectors, 31, the four detectors 47, first phase extractor 38, second phase extractor 42, third phase position extraction apparatus 32, the four phase extractors 46, first differentiator 39, second differentiator, 43, the three differentiators, 33, the four differentiators 45.Data processing section comprises data processor 35 and display panel 36.

Above laser diode 2403 in the said linear modulation light source 24 are semiconductor laser (being called for short LD).Signal generator 2402 is to produce the device of frequency from several hertz to hundreds of KHz triangular wave.

Said first beam splitter 25, second beam splitter, 27, the three beam splitters, 28, the four beam splitters, 44, the five beam splitters, 40, the six beam splitters 30 are respectively the beam splitters that incident beam is divided into two-beam in certain penetration ratio.Be that Amici prism or one side are coated with the parallel flat of analysing optical mode etc.

Said first catoptron 29, second catoptron 26 are meant parallel flat or the angle vertebra prism that is coated with high reflection mould.

Said specimen holder 34 is to put the three-dimensional adjustable platform with reflection or backscattering characteristic testee 7.

Said first detector, 37, the second detectors, 41, the three detectors, 31, the four detectors 47 are electrooptical devices such as photodiode, or photomultiplier.

Said first phase extractor, 38, the second phase extractors 42, third phase position extraction apparatus 32, the four phase extractors 46 are that lock-in amplifier or other extract the interference signal device of variation phase in time.

Said first differentiator, 39, the second differentiators, 43, the three differentiators, 33, the four differentiators 45 are that simple differentiating circuit element or other can be realized the device of the differential function of time dependent electric signal.

Said data processor 35 mainly is by first, the second, the three amplifier 3505,3506,3510, the first, the data processor that contains four ports 3501,3502,3503,3504 that the second, the three plus-minus method hybrid arithmetic unit 3507,3508,3509 and divider 3511 constitute.Be to realize obtaining different interference surface optical path differences and calculating the device of testee 7 thickness and refractive index from the angular frequency of four detectors outputs.

Said display panel 36 is common liquid crystals displays.

As above-mentioned structure shown in Figure 4, add direct current biasing as the laser diode 2403 (LD) of linear modulation light source 24 by direct supply 2401, wavelength adds linear modulation by signal generator 2402.The light beam that is sent by linear modulation light source 24 is behind collimation lens 5 collimations, be divided into two bundles by first beam splitter 25, a branch of smooth directive second beam splitter 27 is divided into two bundles once more by second beam splitter 27, by second beam splitter, 27 transmitted light beam directives the 3rd beam splitter 28, see through light beam directive first catoptron 29 of the 3rd beam splitter 28, by folded light beam directive second catoptron 26 of second beam splitter 27.Light transmission the 3rd beam splitter 28 that first catoptron 29 reflects is also interfered and is received at first detector 37 by the light beam that the light beam that second beam splitter, 27 beam reflected and second catoptron 26 reflect sees through second beam splitter 27, obtained its phase information by first phase extractor 38, obtain the function of time of angular frequency again through first differentiator 39, be input to first port 3501 of data processor 35.The testee 7 of the light beam irradiates that sees through first beam splitter 25 to the specimen holder 34.Reflected by fourth, fifth beam splitter 44,40 from testee 7 front and rear surfaces beam reflected, interfere and be received at second detector 41, second phase extractor 42 obtains its phase information, obtain the function of time of angular frequency again through second differentiator 43, be input to second port 3502 of data processor 35.The light beam that first catoptron 29 reflects reflects through 44 reflections of the 4th beam splitter by the light beam of 28 reflections of the 3rd beam splitter and 30 transmissions of the 6th beam splitter and from testee 7 front and rear surfaces, 40 transmissions of the 5th beam splitter and the 6th beam splitter 30 beam reflected interfere, received by the 3rd detector 31, obtain its phase information by third phase position extraction apparatus 32, obtain the function of time of angular frequency again through the 3rd differentiator 33, be input to the 3rd port 3503 of data processor 35.The light beam that reflects from first transmitting mirror 29 sees through the 3rd beam splitter 28, the light beam of second beam splitter 27 and first beam splitter 25 is interfered by first beam splitter, 25 beam reflected through the 4th beam splitter 44 by 27 reflections of second beam splitter and through the light beam of first beam splitter 25 and the reflected light of testee 7 front and rear surfaces with the light beam that reflects from second catoptron 26, interference signal is received by the 4th detector 47, obtain its phase information by the 4th phase extractor 46, obtain the function of time of angular frequency again through the 4th differentiator 45, be input to the 4th port 3504 of data processor 35.

Because linear modulation light source 24 is by linear modulation, output wavelength t in time changes

△ λ=α t, in (7) formula, α is the linear modulation proportionality constant.If participating in the optical path difference of the two-beam of interference is △ L, then time delay is

△ t=2 △ L/c, (8) wherein c are the light velocity.The two-beam of participating in interference forms optical beat, and interference signal is with beat frequency

F=2 △ ff _m△ L/c (9) f changes in the cycle.△ f is that laser diode (LD) is injected into the frequency displacement that the electric current linear modulation produces, f in the formula _mBe modulating frequency.Multiple-beam interference produces the interference signal with a series of beat frequencies

G (t)=a (t)+∑ b _Mn(t) cos[2 π f _MnT+ φ _Mn], (10) wherein, m, n=1,2,3,4, represent the front and rear surfaces of the testee 7 on first catoptron 29, second catoptron 26 and the specimen holder 34 and m ≠ n respectively.A (t) is the total intensity of several Shu Guang, b _Mn(t) be the range value of interference fringe between two-beam m and the n.Have simultaneously

φ=φmn+2πfmnt,(11) ${\mathrm{\&phi;}}_{\mathrm{mn}}=\frac{2\mathrm{\&pi;}{L}_{\mathrm{mn}}}{\mathrm{\&lambda;}},\left(12\right)$ $f_{\mathrm{mn}}=\frac{{\mathrm{\&alpha;}}_0{L}_{\mathrm{mn}}}{{\mathrm{\&lambda;}}^2},\left(13\right)$ $\mathrm{\&omega;mn}=\frac{\mathrm{d\&phi;}}{\mathrm{dt}},\left(14\right)$ L in the formula _MnIt is the optical path difference that participates in two light beams of interference.Phase place to interference signal is differentiated, and obtains beat frequency.Suppose the optical path difference L of 26 of first catoptron, 29, the second catoptrons ₁₂Known, its corresponding angular frequency ₁₂By 39 outputs of first differentiator, then $\mathrm{Lmn}=\frac{{\mathrm{\&omega;}}_{\mathrm{mn}}}{{\mathrm{\&omega;}}_{12}}{\mathrm{<figure-callout\; id="12"\; label="L"\; filenames="Y0025951700121.png"\; state="\{\{state\}\}">L</figure-callout>}}_{12},\left(15\right)$ Make subscript r1, r2 represent first catoptron 29, second catoptron 26 respectively, sf, sr represent the front and rear surfaces of testee 7 respectively.Second detector 41 detects and exports ω from second differentiator 43 _Sfsr, the 3rd differentiator 33 output ω _Sfsr, ω _R1sf, ω _R1sr, the 4th differentiator 45 output ω _Sfsr, ω r _2sf, ω _R2sr, ω _R1sr, ω _R1sf, ω ₁₂The output of the 3rd differentiator 33 deducts the output of second differentiator 43, remaining ω _R2sf, ω _R2sr, the two has following relation:

ω r1sf+ ω sfsr=ω r1sr, (16) are so ω _R1sfBe half of the output of the 3rd differentiator 33 output that deducts 2 times of second differentiator 43.The output of the 4th differentiator 45 deducts the remaining ω of output of the 3rd and first differentiator 33 and 39 _Sfsr, ω _R2sf, ω _R2sr, the three has following relation:

ωr2sf-ωsfsr=ωr2sr,(17)

So ω r _2srBe half of the output of the 4th differentiator 45 difference that deducts the output that deducts 2 times of second differentiator 43 after the output of the 3rd and first differentiator 33 and 39 again.Can get ω by (13) formula again _Sfsr, ω _R1sf, ω _R2srCorresponding optical path difference L _R1r2, L _R1sf, L _R2srBecause first catoptron 29 and second catoptron 26, first catoptron 29 and testee 7 front surfaces, and the medium between testee 7 rear surfaces and second catoptron 26 is air, so optical path difference just directly equals two times of its physical thickness, so testee 7 physical thickness d=(L _R1r2-L _R1sf-L _R2sr)/2.Its optical thickness L _S1s2Be the product of refractive index n and physical thickness d, then refractive index is

n=Ls1s2/d。(18) thus record the physical thickness and the refractive index of testee 7 simultaneously.Measurement result is presented on the display panel 36.Fig. 5 is the structural representation of the utility model data processor 35.Because the identification of each optical path difference and calculate all and realize, thereby realized not scanning interferometer and measured testee 7 physical thickness and refractive index in real time by adder-subtractor and amplifier.And eliminated the influence of testee 7 chromatic dispersions owing to the use of the LD of narrow-band light source.

Advantage of the present utility model has:

1. need not the scanning interferometer arm.The utility model need not the scanning interferometer arm owing to the use of the linear modulation light source of said structure.Formerly in the technology [1], utilize light path matching principle and refractive index abrupt interface Snell's law to obtain the relation of testee 7 physical thickness and refractive index and reference arm, testee 7 arm displacements, and the numerical aperture of utilizing confocal system is obtained testee 7 physical thickness and refractive index, need scan reference arm and testee 7 arms respectively, thereby Measuring Time is from several seconds to tens seconds, and influences the accuracy of measurement result.And the utility model just need not anyly scan.

2. can measure in real time.Formerly technology [1] needs scan reference arm and testee 7 arms respectively, thereby Measuring Time can not be done in real time and measure from several seconds to tens seconds.And the utility model need not anyly scan, the utility model is by each beam splitter in light path for the acquisition and the identification of beat frequency and corresponding light path difference, detector, phase extractor, differentiator and data processor processes interference signal have realized measuring simultaneously and in real time testee 7 physical thickness and refractive index

3. testee 7 dispersive influence have been avoided.Formerly to adopt half-power bandwidth be wideband light source SLD about 20 nanometers to technology [1], and reaching micron-sized spatial resolution, but wideband light source causes testee 7 chromatic dispersions, thereby each wavelength testee 7 refractive index difference in the light source bandwidth influence measurement result.The utility model uses linear modulation light source 24, and wherein LD modulates through linearity, and wavelength modulation range only be zero several nanometers at zero point, and the order of magnitude of refraction index changing is 10-7, and is can the refractive index measurement result not influential, thereby makes the measuring accuracy height.

4. has high sensitivity.Formerly technology [1] adopts SLD to make light source, output power from the hundreds of microwatt to several milliwatts.The utility model uses LD to do light source, than SLD bigger incident power is arranged, and reaches tens milliwatts, helps the detection of interference signal.Therefore measure sensitivity and improved, thereby the scope of application expands to the measurement of the more weak testee 7 of reflection or back scattering.

Description of drawings:

Fig. 1 makes light source 1 for technology [1] formerly based on the super luminescence diode laser instrument, measures the structural representation of thickness and refractive index device simultaneously with optical coherence tomography system.

Fig. 2 is that formerly technology [1] is measured the synoptic diagram that carries out testee 7 scannings causing focal position variation simultaneously for realizing thickness and refractive index.

Fig. 3 is that formerly technology [2] is the semiconductor laser interferometric device structural representation of realization micro-displacement.

Fig. 4 is the structural representation that use linear modulation light source 24 of the present utility model is realized thickness and refractive index while and the real-time laser interferometry instrument of measuring.

Fig. 5 is the structural representation of the utility model data processor 35.

Embodiment:

Structure as shown in Figure 4.Testee 7 is a glass plate.Wherein linear modulation light source 24 adopts the laser diode 2403 (LD) of centre wavelength 785nm, the direct current biasing 72mA of direct supply 2401 outputs, and the ac modulation of signal generator 2402 outputs is the triangular wave of frequency 100Hz.Detector 37,41,31,47 is photodiode.First beam splitter 25, second beam splitter, 27, the three beam splitters, 28, the four beam splitters 44, the 5th beam splitter 40, the six beam splitters 30 are to be coated with the parallel flat of analysing optical mode.The central point O of first catoptron, 29 to second beam splitters 27 is set ₂Light path and the central point O of second catoptron, 26 to second beam splitters 27 ₂Optical path difference be 15.527 millimeters.Phase extractor 38,42,32,46th, lock-in amplifier.Differentiator 39,43,33,45th, simple differentiating circuit element.Data processor 35 as above-mentioned structure shown in Figure 5.Through triangular signal generator based 2402 and the output wavelength linear change of the linear modulated light source 24 of direct supply 2401 control, as the interferometer light source, the physical thickness that utilizes measuring instrument of the present utility model to record testee 7 glass is 3.003 millimeters, optical thickness is 4.394 millimeters, and drawing refractive index is 1.4619.

Testee 7 of the present utility model is that two surfaces all have reflection or backward scattered transparent substance.

Claims (2)

1. laser interferometry instrument of measuring thickness and refractive index simultaneously comprises: light source, and collimation lens (5), beam splitter, catoptron, detector, the output of data processor (35) is connected with display panel (36), it is characterized in that concrete structure is:

＜1〉linear modulation light source (24) the emitted laser bundle that is made of the laser diode (2403) that has direct supply (2401) and signal generator (2402) on the direction that laser beam is advanced, is equipped with center (O successively behind collimation lens (5) collimation ₁, O ₄) first beam splitters (25) on the optical axis (OO) of linear modulated light source (24) emission light beam all, the 4th beam splitter (44) is until the testee (7) that places on the specimen holder (34);

＜2〉at the center (O that passes first beam splitter (25) ₁) perpendicular to the first perpendicular line (O of linear modulation light source (24) emission beam optical axis (OO) ⁰O ⁰) on, place the two ends of first beam splitter (25) that first catoptron (29) and the 4th detector (47) are arranged respectively, between first beam splitter (25) and first catoptron (29), center (O is arranged ₂) place the first perpendicular line (O ⁰O ⁰) on second beam splitter (27), between second beam splitter (27) and first catoptron (29), center (O is arranged ₃) place the first perpendicular line (O ⁰O ⁰) on the 3rd beam splitter (28);

＜3〉at the center (O that passes second beam splitter (27) ₂) launch on parallel first parallel lines (O ' O ') of beam optical axis (OO) with linear modulation light source (24), be equipped with second catoptron (26) and first detector (37) respectively at the two ends of second beam splitter (27), the output of first detector (37) is connected to first port (3501) of data processor (35) by first phase extractor (38) and first differentiator (39);

＜4〉at the center (O that passes the 4th beam splitter (44) ₄) five beam splitter (40) of center (O5) on second perpendicular line (O O ) arranged on second perpendicular line (O O ) perpendicular to linear modulation light source (24) emission beam optical axis (OO), have receiving plane to face toward second detector (41) of the 5th beam splitter (40) reflecting surface, the output of second detector (41) is connected to second port (3502) of data processor (35) by second phase extractor (42) and second differentiator (43);

＜5〉center (O of the 6th beam splitter (30) is arranged ₆) just with the center (O that passes the 3rd beam splitter (28) ₃) launch parallel second parallel lines (O " O ") of beam optical axis (OO) and the intersection point (O of above-mentioned second perpendicular line (O O ) with linear modulation light source (24) ₆) overlap, second parallel lines (O " O ") go up receiving plane facing to the 6th beam splitter (30) reflecting surface the 3rd detector (31) arranged, the output of the 3rd detector (31) is connected to the 3rd port (3503) of data processor (35) by third phase position extraction apparatus (32) and the 3rd differentiator (33);

＜6〉the above-mentioned first perpendicular line (O that places ⁰O ⁰) on the output of the 4th detector (47) be connected to the 4th port (3504) of data processor (35) by the 4th phase extractor (46) and the 4th differentiator (45).

2. the laser interferometry instrument of measuring thickness and refractive index simultaneously according to claim 1, it is characterized in that said data processor (35) mainly is by first amplifier (3505), second amplifier (3506), the 3rd amplifier (3510), the first plus-minus method hybrid arithmetic unit (3507), the second plus-minus method hybrid arithmetic unit (3508), the 3rd plus-minus method hybrid arithmetic unit (3509) and divider (3511) constitute contains four ports (3501,3502,3503,3504) data processor.

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