CN100520361C - Full-range frequency domain optical coherence tomography method and system thereof - Google Patents

Abstract

Disclosed are a method and a system for in frequency domain optical coherent tomography imaging. The method employs sine phase modulation to recreate complex amplitude of the coherent frequency interference signal; and then performs inverse Fourier transform to the complex amplitude to get the tomographic images of the tested objects and eliminate the complex conjugate image, direct current background and self-coherent noise three spurious images, which enlarges the imaging depth of frequency domain optical coherent tomography imaging is two times larger than the original depth and realizes full depth finding of frequency domain optical coherent tomography imaging.

Description

The method and the system thereof of the domain optical coherence tomography of full depth finding

Technical field

The present invention relates to optical coherent chromatographic imaging (Optical Coherence Tomography, hereinafter to be referred as OCT), particularly a kind of sinusoidal phase modulation technology of utilizing is rebuild method and system thereof that the low-coherent light frequency domain is interfered the domain optical coherence tomography of the full degree of depth (full range) detection of complex signal (complex interferometric signal) (Fourier Domain Optical Coherence Tomography, abbreviation FD-OCT).

Background technology

Optical coherent chromatographic imaging (OCT) is interfered (Low CoherenceInterferometry based on low-coherent light, be called for short LCI) principle, can carry out the micro-structure in the several mm depth scopes of scattering medium such as biological tissue inside non-invasive in real time, at the tomography of body, its depth resolution can reach several microns.Since people such as Huang in 1991 propose the OCT notion for the first time, and since it is applied to the tomography of human eye retina and coronary arterial wall, the OCT technology has obtained broad research and application, as be used for the medical diagnosis on disease of ophthalmology, dept. of dermatology and early diagnosis of cancer etc., become a kind of optical image technology that in bio-imaging and medical pathologies detection range, has the important application prospect.

Domain optical coherence tomography system (FD-OCT), it is the New O CT system that a kind of latest developments are got up, previous relatively time domain optical coherence tomography system (the Time Domain OpticalCoherence Tomography that proposes, be called for short TD-OCT), have and need not depth direction scanning, image taking speed is fast and detection sensitivity is high advantage, be more suitable for the real time imagery of biological tissue.

The domain optical coherence tomography system mainly is made up of low-coherence light source (broad spectrum light source), Michelson interferometer and spectrometer (core parts are spectro-grating, condenser lens and ccd detector) three parts.FD-OCT is based on the principle of the different frequency of the corresponding frequency domain interference fringe of the degree of depth at reflection of each layer light or backscattering interface in the testee, the wide spectral light that low-coherence light source sends is sent into spectrometer (wherein testee places the feeler arm end of interferometer) through the interference signal that Michelson interferometer produces, utilize the spectrometer dichroism, obtain the intensity distributions that interference signal changes with wavelength (λ), obtain interference signal in frequency domain (ν territory after then it being done conversion reciprocal, ν=1/ λ) intensity distributions, it is the frequency domain interference fringe, this signal is obtained light reflection or backscattering rate distribution, the i.e. tomographic map of testee along the depth resolution of surveying the light optical axis direction as inverse Fourier transform.But comprising some parasitic images in the tomographic map that FD-OCT obtains, limiting the application of FD-OCT.These parasitic images are respectively: direct current background (DC term), and from coherent noise (autocorrelation term) and complex conjugate mirror image (complex conjugated term ormirror image term).Wherein, direct current background and reduced the signal to noise ratio (S/N ratio) of FD-OCT from the existence of coherent noise significantly, influenced image quality, and the existence of complex conjugate mirror image, make FD-OCT can't distinguish positive and negative optical path difference (surveying the optical path difference of light path relative reference light path), so testee can only place a side of zero optical path difference position when measuring, and causes the significant depth investigative range to reduce half.

For the complex conjugate mirror image that exists in the tomographic map of eliminating the FD-OCT reconstruction, from coherent noise and these parasitic image compositions of direct current background, people such as A.F.Fercher are incorporated among the FD-OCT stepping phase-shifting technique (phase shifting) by rebuilding the complex amplitude of low-coherent light frequency domain interference signal, eliminated above parasitic image, the FD-OCT that has realized full depth finding is (referring to technology [1] formerly, A.F.Fercher, R.Leitgeb, C.K.Hitzenberger, H.Sattmann and M.Wojtkowski, " Complex SpectralInterferometry OCT ", Proc.SPIE, Vol 3654,173-178,1999; M.Wojtkowski, A.Kowalczyk, R.Leitgeb and A.F.Fercher, " Fullrange complex spectral opticalcoherence tomography technique in eye imaging ", Optics Letters, Vol.27, No.16,1415-1417,2002).Yet it is a constant exactly that the stepping phase shift algorithm requires per step phase shift, and requiring per step phase shift as five step phase-shift methods is pi/2.Because what FD-OCT adopted is broad spectrum light source, for different wave length, the stepping phase-shift phase of introducing by the light path that changes reference arm can change, and promptly phase-shift phase depends on wavelength, no longer is a constant constant, and this can bring measuring error.Simultaneously, extraneous small sample perturbations also can cause the error of stepping phase shift, so this system's antijamming capability is poor.People such as JosephA.Izatt have proposed a kind of method based on N * N (N ≧ 3) fiber coupler (referring to technology [2] formerly, M.V.Sarunic, M.A.Choma, Changhuei Yang, J.A.Izatt, " Instantaneouscomplex conjugated resolved spectral domain and swept-source OCT using 3 * 3fiber couplers ", Optics Express, Vol.13, No.3,957-967,2005).Though can realize instantaneous or phase shift simultaneously, insensitive to ambient vibration, but because the splitting ratio of fiber coupler is to the variation of ambient temperature sensitivity, cause phase-shift phase can vary with temperature the generation drift, and this system needs plural detector, need to guarantee the synchronism of all detector acquired signal, system complex.

Found out do not have also at present that a kind of to have anti-environmental interference ability strong by above analysis, irrelevant with optical source wavelength, system architecture is simple, and can realize the domain optical coherence tomography technology of full depth finding again.

Summary of the invention

The objective of the invention is in order to overcome the deficiency of above-mentioned technology formerly, a kind of method and system thereof of domain optical coherence tomography of full depth finding are provided, the present invention can either realize the domain optical coherence tomography of full depth finding, it is strong to have anti-environmental interference ability again, irrelevant with optical source wavelength, the system architecture characteristic of simple.

Technical solution of the present invention is as follows:

A kind of method of domain optical coherence tomography of full depth finding, it is to do sinusoidal vibration by the reference mirror that a sinusoidal phase modulation device drives in the Michelson interferometer reference arm, generate the low-coherent light frequency domain interference signal of a time dependent sinusoidal phase modulation, then it is made Fourier transform, leach a frequency multiplication and the two frequency multiplication frequency spectrums of its frequency spectrum, calculate the low-coherent light frequency domain and interfere the real part and the imaginary part of complex signal, real part and imaginary part combination are obtained the interference complex signal of low-coherent light frequency domain by Wavelength distribution, then this interference complex signal is carried out conversion reciprocal, obtain by the wavelength interference complex signal that distributes reciprocal, again this interference complex signal is made inverse Fourier transform, obtain the testee tomographic map.

The characteristics of the method for the domain optical coherence tomography of the full depth finding of the present invention are the methods that the sinusoidal phase modulation technology is used for the domain optical coherence tomography of full depth finding, utilize the sinusoidal phase modulation technology to rebuild the low-coherent light frequency domain and interfere complex signal, to eliminate the complex conjugate mirror image that exists in the FD-OCT imaging, direct current background and from three kinds of parasitic images of coherent noise, improve system signal noise ratio, realize the domain optical coherence tomography of full depth finding.

The sinusoidal phase modulation technology is that a kind of antijamming capability is strong, modulate simple phase modulation technique, be usually used in (seeing technology [3] formerly in the laser interferometer of object surface appearance and microdisplacement measurement, OsamiSasaki and Hirokazu Okazaki, " Sinusoidal phase modulating interferometry forsurface profile measurement ", Applied Optics, Vol.25, No.18,3137-3140,1986).

The concrete steps of the domain optical coherence tomography method of the full depth finding of the present invention are as follows:

1. the reference mirror that drives in the Michelson interferometer reference arm by the sinusoidal phase modulation device is done sinusoidal vibration, and introducing a modulating frequency is f _cSinusoidal phase modulation, shown in (1) formula:

Z(t)＝acos(2πf _ct+θ)， (1)

Wherein: a is an amplitude, and θ is an initial phase, f _cBe modulating frequency.

The interference signal of corresponding each wavelength of broad spectrum light source of spectrometer record, shown in (2) formula:

$G\left(\mathrm{\λ}\right)=G_{\mathrm{rr}}\left(\mathrm{\λ}\right)+\underset{n}{\mathrm{\Σ}}{G}_{\mathrm{nn}}\left(\mathrm{\λ}\right)$

$+2\mathrm{Re}\left\{\underset{n\&NotEqual;m}{\mathrm{\&Sigma;}}{G}_{\mathrm{nm}}\left(\mathrm{\&lambda;}\right)\exp [-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C200610028629E00141.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}(z_n-z_m)]\right\}---\left(2\right)$

$+2\mathrm{Re}\left\{\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nr}}\left(\mathrm{\&lambda;}\right)\exp [-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C200610028629E00141.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}(z_n-z_r)]\right\},$

Wherein: G represents the spectral concentration function, and real, z are got in the Re representative _nRepresent the light path at reflection of detected sample position n layer or scattering interface, z _rRepresent the light path of reference mirror position.

(2) the auto spectral density function stack of each layer depth place reflection or back-scattering light in preceding two catoptrical auto spectral density functions that are respectively reference mirror and the sample in the formula, the 3rd is the mutual spectral density function stack of the reflection of different depth place or back-scattering light in the sample, and the 4th be the mutual spectral density function stack item of each layer depth place reflection or back-scattering light in reference mirror reflected light and the sample.

Generate a time dependent sinusoidal phase modulation interference signal, shown in (3) formula:

$G(\mathrm{\&lambda;},t)=G_0+2\mathrm{Re}\left\{\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nr}}\left(\mathrm{\&lambda;}\right)\exp [-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C200610028629E00141.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}[(z_n-z_r)+2Z\left(t\right)]]\right\},---\left(3\right)$

Wherein $G_0=G_{\mathrm{rr}}\left(\mathrm{\&lambda;}\right)+\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nn}}\left(\mathrm{\&lambda;}\right)+2\mathrm{Re}\left\{\underset{n\&NotEqual;m}{\mathrm{\&Sigma;}}{G}_{\mathrm{nm}}\left(\mathrm{\&lambda;}\right)\exp [-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C200610028629E00141.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}(z_n-z_m)]\right\},$ Not being subjected to the modulation of reference mirror vibration, is a time-independent DC component.Then it is done Fourier transform and obtains (4) formula,

(4)

$2\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nr}}\left(\mathrm{\&lambda;}\right)\sin \left[2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}(z_n-z_r)\right]\&times;\left[\underset{m=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{(-1)}^m{A}_{2m-1}\mathrm{\&sigma;}[\mathrm{\&omega;}-(2m-1){\mathrm{\&omega;}}_c]\right],$

A wherein _m=J _m(d) exp (jm θ), J _mBe m rank Bessel's functions, σ is a Dirac function, $d=4\mathrm{\&pi;}\frac{a}{\mathrm{\&lambda;}},$ ω＝2πf，ω _c＝2πf _c。

From its frequency spectrum, take out a frequency multiplication F (f _c) and two frequency multiplication F (2f _c) frequency spectrum, calculate the real part and the imaginary part of interfering complex signal by (5) formula,

$2\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nr}}\left(\mathrm{\&lambda;}\right)\sin \left[2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}(z_n-z_r)\right]=-\mathrm{Re}\left\{F\left({\mathrm{\&omega;}}_c\right)\right\}/J_1\left(d\right)\cos \left(\mathrm{\&theta;}\right),$

(5)

$2\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nr}}\left(\mathrm{\&lambda;}\right)\sin \left[2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}(z_n-z_r)\right]=-\mathrm{Re}\left\{F\left({2\mathrm{\&omega;}}_c\right)\right\}/J_2\left(d\right)\cos \left(2\mathrm{\&theta;}\right),$

Wherein sin item correspondence is interfered the imaginary part of complex signal, the corresponding real part of interfering complex signal of cos item.D, θ are the amount of determining in advance, or by F (ω _c) and F (3 ω _c) try to achieve (seeing technology [3] formerly), wherein F (3 ω _c) be three rank frequency multiplication frequency spectrums.Real part, imaginary part combination are obtained the complex amplitude of interference signal shown in (6) formula.F wherein _cValue by sinusoidal phase modulation frequency decision, irrelevant with optical source wavelength.

$\hat{G}\left(\mathrm{\&lambda;}\right)=2\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nr}}\left(\mathrm{\&lambda;}\right)\cos \left[2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}(z_n-z_r)\right]-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C200610028629E00141.png"\; state="\{\{state\}\}">j</figure-callout>}2\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nr}}\left(\mathrm{\&lambda;}\right)\sin \left[2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}(z_n-z_r)\right]$

(6)

$=2\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nr}}\left(\mathrm{\&lambda;}\right)\exp \{-j\left[2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}(z_n-z_r)\right]\},$

2. to step 1. gained press the interference complex signal (6) that wavelength (λ) distributes, do conversion reciprocal, convert the interference complex signal that distributes by wavelength inverse (ν, ν=1/ λ) to, shown in (7) formula:

$\hat{G}\left(v\right)=2\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nr}}\left(v\right)\exp \{-j\left[2\mathrm{\&pi;v}(z_n-z_r)\right]\},---\left(7\right)$

Wherein $v=\frac{1}{\mathrm{\&lambda;}}.$

3. the interference complex signal that distributes by wavelength inverse (ν, ν=1/ λ) that 2. step is obtained obtain testee as inverse Fourier transform tomographic map shown in (8) formula:

Wherein: Γ n _rBe the single order cross correlation function, it is comprising light reflection or backscattering information, the i.e. tomographic map along the depth resolution of surveying the light optical axis direction of testee.

The inventive method with do not adopt sinusoidal phase modulation, directly tomographic map (9) formula that (2) formula obtains as inverse Fourier transform is compared, eliminated the complex conjugate mirror image (I that exists in the FD-OCT imaging ₂), direct current background (I ₀) and from coherent noise (I ₁) three kinds of parasitic images, improved signal to noise ratio (S/N ratio), realized the domain optical coherence tomography of full depth finding.

(9)

$={\mathrm{\&Gamma;}}_{\mathrm{rr}}\left(z\right)+\underset{n}{\mathrm{\&Sigma;}}{\mathrm{\&Gamma;}}_{\mathrm{nn}}\left(z\right)+\underset{n\&NotEqual;m}{\mathrm{\&Sigma;}}{\mathrm{\&Gamma;}}_{\mathrm{nm}}[z+(z_n-z_m)]+\underset{n\&NotEqual;m}{\mathrm{\&Sigma;}}{\mathrm{\&Gamma;}}_{\mathrm{nm}}[z-(z_n-z_m)]$

$+\underset{n}{\mathrm{\&Sigma;}}{\mathrm{\&Gamma;}}_{\mathrm{nr}}[z+(z_n-z_r)]+\underset{n}{\mathrm{\&Sigma;}}{\mathrm{\&Gamma;}}_{\mathrm{nr}}[z-(z_n-z_r)]$

$=I_0+{\mathrm{<figure-callout\; id="1"\; label="I"\; filenames="C200610028629E00141.png"\; state="\{\{state\}\}">I</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="C200610028629E00141.png"\; state="\{\{state\}\}">I</figure-callout>}}_2+\underset{n}{\mathrm{\&Sigma;}}{\mathrm{\&Gamma;}}_{\mathrm{nr}}[z-(z_n-z_r)],$

Wherein: $I_0={\mathrm{\&Gamma;}}_{\mathrm{rr}}\left(z\right)+\underset{n}{\mathrm{\&Sigma;}}{\mathrm{\&Gamma;}}_{\mathrm{nn}}\left(z\right)$ Be the direct current background component,

${\mathrm{<figure-callout\; id="1"\; label="I"\; filenames="C200610028629E00141.png"\; state="\{\{state\}\}">I</figure-callout>}}_1=\underset{n\&NotEqual;m}{\mathrm{\&Sigma;}}{\mathrm{\&Gamma;}}_{\mathrm{nm}}[z+(z_n-z_m)]+\underset{n\&NotEqual;m}{\mathrm{\&Sigma;}}{\mathrm{\&Gamma;}}_{\mathrm{nm}}[z-(z_n-z_m)]$ For from the coherent noise component,

${\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="C200610028629E00141.png"\; state="\{\{state\}\}">I</figure-callout>}}_2=\underset{n}{\mathrm{\&Sigma;}}{\mathrm{\&Gamma;}}_{\mathrm{nr}}[z+(z_n-z_r)]$ Be the complex conjugate image component.

Implement the domain optical coherence tomography system of the full depth finding of said method, comprise low-coherence light source, on the illumination direction of this low-coherence light source, place collimator and extender device, Michelson interferometer in turn, the optical splitter of this Michelson interferometer is divided into feeler arm light path and reference arm light path with incident light, the end of reference arm light path is a reference mirror, the end of feeler arm light path is a sample, and sample is placed on the accurate translation stage of three-dimensional; The Michelson interferometer output terminal connects a spectrometer, this spectrometer is connected with computing machine by image pick-up card, the characteristics of this system are that described reference mirror connects a sinusoidal phase modulation device, and this sinusoidal phase modulation device drives described reference mirror and does sinusoidal vibration.

Described sinusoidal phase modulation device is made up of sine function electric signal generator and the piezoelectric ceramic actuator that is fixed on the described reference mirror, and the time sine function driving electric signal that described sine function electric signal generator sends drives described reference mirror by piezoelectric ceramic actuator and does sinusoidal vibration.

Described low-coherence light source is a broad spectrum light source, and its spectrum typical case half width is that tens nm are to a hundreds of nm, as light emitting diode (LED) or super-radiance light emitting diode (SLD) or femto-second laser etc.

Described collimator and extender device is made up of object lens and some lens.

Described Michelson steller interferometer, the one tunnel is the reference arm light path near aplanatic optical interference circuit to it is characterized in that having two, another road is the feeler arm light path.It can be the bulk optics system, as be made of reference arm and feeler arm two-way light path the Amici prism beam split; Also can be fiber optic system, as by two output optical fibre light paths of 2 * 2 fiber couplers respectively as with reference to arm and feeler arm light path.

Described spectrometer is by spectro-grating, and condenser lens and photodetector array are formed.

Described photodetector array is that CCD or photodiode array or other have the detector array of photosignal translation function.

The accurate translation stage of described three-dimensional can be done the translation of micron order precision along three mutually perpendicular directions.

The working condition of this system is as follows:

The light that low-coherence light source sends is behind collimator and extender device collimator and extender, in Michelson interferometer, be divided into two bundles, a branch of light incides the reference mirror surface through reference arm, a branch of in addition light is in feeler arm incides sample, light of returning from the reference mirror surface reflection and the light that different depth reflection or backscattering are returned in the sample are collected and return along reference arm and feeler arm, in Michelson steller interferometer, converge and interfere, send into spectrometer beam split and record again, after the image pick-up card digital-to-analog conversion, send into computing machine and carry out data processing, obtain sample along the tomographic map of surveying the light optical axis direction.By the accurate translation stage of three-dimensional sample is done transversal scanning along the plane vertical with surveying the light optical axis direction, obtain the two dimension or the three-dimensional tomographic map of sample.Wherein the sinusoidal phase modulation device links to each other with reference mirror in the Michelson interferometer reference arm, this device is under the electric signal of a sinusoidal variations drives, drive reference mirror and do sinusoidal vibration, in the interference signal of spectrometer collection, introduce sinusoidal phase modulation.

Technique effect of the present invention is:

Compare with technology 1 formerly, the present invention is owing to adopt the sinusoidal phase modulation technology, frequency domain interference signal by the offset of sinusoidal phase modulation (PM) is made Fourier transform, the spectrum information that takes out one frequency multiplication and two frequencys multiplication is rebuild the frequency domain interference complex signal of low-coherent light, insensitive to neighbourhood noise, so anti-environmental interference ability is strong, and the value of a frequency multiplication and two frequencys multiplication is determined by the sinusoidal phase modulation frequency, do not change, so irrelevant optical source wavelength with wavelength variations.

Compare with technology 2 formerly, the present invention only needs a detector, has avoided the synchronism calibration of multidetector, and system architecture is simple.

Description of drawings

Fig. 1 is the bulk optics system architecture synoptic diagram of the domain optical coherence tomography system of the full depth finding of the present invention.

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, Fig. 1 is domain optical coherence tomography system embodiment---the structural representation of bulk optics system of the full depth finding of the present invention.As seen from the figure, the domain optical coherence tomography system of the full depth finding of the present invention, comprise low-coherence light source 1, on the illumination direction of this low-coherence light source 1, place collimator and extender device 2, Michelson interferometer 3 in turn, the optical splitter 31 of this Michelson interferometer 3 is divided into feeler arm light path 34 and reference arm light path 32 with incident light, the end of reference arm light path is a reference mirror 33, the end of feeler arm light path is a sample 35, and sample 35 is placed on the accurate translation stage (not shown) of three-dimensional; Michelson interferometer 3 output terminals connect a spectrometer 5, this spectrometer 5 is connected with computing machine 7 by image pick-up card 6, it is characterized in that described reference mirror 33 connects a sinusoidal phase modulation device 4, described sinusoidal phase modulation device 4 is made up of sine function electric signal generator and the piezoelectric ceramic actuator that is fixed on the described reference mirror 33, and the time sine function driving electric signal that described sine function electric signal generator sends drives described reference mirror 33 by piezoelectric ceramic actuator and does sinusoidal vibration.

The wide spectral light that low-coherence light source 1 sends is behind collimator and extender device 2 collimator and extenders, in Michelson interferometer 3, be divided into two bundles by Amici prism 31, a branch ofly incide reference mirror 33 surfaces through reference arm light path 32, another bundle is in feeler arm light path 34 incides the sample 35 that is placed on the three-dimensional accurate translation stage, light of returning from reference mirror 33 surface reflections and the light that different depth reflection or backscattering are returned in the sample 35 are collected and return along reference arm light path 32 and feeler arm light path 34,31 places converge and interfere in Michelson steller interferometer 3, send into spectrometer 5 again by grating 51 beam split, through convergent lens 52, be imaged on ccd detector 53, after converting electric signal to, send into computing machine 7 through image pick-up card 6 digital-to-analog conversions and carry out data processing, obtain sample 35 along the tomographic map of surveying the light optical axis direction.By the accurate translation stage (not shown) of three-dimensional sample 35 is done transversal scanning along the plane vertical with surveying the light optical axis direction, obtain the two dimension or the three-dimensional tomographic map of sample 35.Wherein sinusoidal phase modulation device 4 links to each other with reference mirror 33 in the Michelson interferometer reference arm, this device is under the driving of sinusoidal variations electric signal, drive reference mirror and do sinusoidal vibration, in the interference signal of spectrometer collection, introduce sinusoidal phase modulation.

Described reference mirror 33 is done following sinusoidal vibration:

Z(t)＝acos(2πf _ct+θ)， (10)

Wherein: a is an amplitude, and θ is an initial phase, f _cBe modulating frequency.

The signal of described ccd detector 53 records is:

$G(\mathrm{\&lambda;},t)=G_0+2\mathrm{Re}\left\{\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nr}}\left(\mathrm{\&lambda;}\right)\exp [-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C200610028629E00141.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}[(z_n-z_r)+2Z\left(t\right)]]\right\},---\left(11\right)$

Wherein: G represents the spectral concentration function, and real, z are got in the Re representative _nRepresent the light path at reflection of detected sample position n layer or scattering interface, z _rRepresent the light path of reference mirror position.And $G_0=G_{\mathrm{rr}}\left(\mathrm{\&lambda;}\right)+\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nn}}\left(\mathrm{\&lambda;}\right)+2\mathrm{Re}\left\{\underset{n\&NotEqual;m}{\mathrm{\&Sigma;}}{G}_{\mathrm{nm}}\left(\mathrm{\&lambda;}\right)\exp [-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C200610028629E00141.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}(z_n-z_m)]\right\},$ It is a time-independent DC component.

(11) formula is made Fourier transform, obtain

$F\left(\mathrm{\&omega;}\right)=G_0\mathrm{\&sigma;}\left(\mathrm{\&omega;}\right)+2\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nr}}\left(\mathrm{\&lambda;}\right)\cos \left[2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}(z_n-z_r)\right]\&times;\left[\underset{m=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{(-1)}^m{A}_{2m}\mathrm{\&sigma;}(\mathrm{\&omega;}-2m{\mathrm{\&omega;}}_c)\right]$

(12)

$2\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nr}}\left(\mathrm{\&lambda;}\right)\sin \left[2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}(z_n-z_r)\right]\&times;\left[\underset{m=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{(-1)}^m{A}_{2m-1}\mathrm{\&sigma;}[\mathrm{\&omega;}-(2m-1){\mathrm{\&omega;}}_c]\right],$

A wherein _m=J _m(d) exp (jm θ), J _mBe m rank Bessel's functions, σ is a Dirac function, $d=4\mathrm{\&pi;}\frac{a}{\mathrm{\&lambda;}},$ ω＝2πf，ω _c＝2πf _c。By (12) formula, can push away

$2\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nr}}\left(\mathrm{\&lambda;}\right)\sin \left[2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}(z_n-z_r)\right]=-\mathrm{Re}\left\{F\left({\mathrm{\&omega;}}_c\right)\right\}/\left[J_1\left(d\right)\cos \left(\mathrm{\&theta;}\right)\right],$

(13)

$2\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nr}}\left(\mathrm{\&lambda;}\right)\cos \left[2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}(z_n-z_r)\right]=-\mathrm{Re}\left\{F\left({2\mathrm{\&omega;}}_c\right)\right\}/\left[J_2\left(d\right)\cos \left(2\mathrm{\&theta;}\right)\right],$

Wherein: the corresponding imaginary part of interfering complex signal of sin item, the corresponding real part of interfering complex signal of cos item.D, θ are the amount of determining in advance, or by F (ω _c) and F (3 ω _c) try to achieve (seeing technology [3] formerly).

Two combinations by in (13) formula can obtain complex signal

$\hat{G}\left(\mathrm{\&lambda;}\right)=2\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nr}}\left(\mathrm{\&lambda;}\right)\cos \left[2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}(z_n-z_r)\right]-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C200610028629E00141.png"\; state="\{\{state\}\}">j</figure-callout>}2\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nr}}\left(\mathrm{\&lambda;}\right)\sin \left[2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}(z_n-z_r)\right]$

(14)

$=2\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nr}}\left(\mathrm{\&lambda;}\right)\exp \{-j\left[2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}(z_n-z_r)\right]\},$

(14) are done conversion reciprocal, obtain the complex signal of frequency domain (ν territory, ν=1/ λ)

$\hat{G}\left(v\right)=2\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nr}}\left(v\right)\exp \{-j\left[2\mathrm{\&pi;v}(z_n-z_r)\right]\},---\left(15\right)$

(15) formula is made inverse Fourier transform, obtain the tomographic map of testee

Wherein: Γ _NrBe the single order cross correlation function, comprising light reflection or backscattering information, the i.e. tomographic map along the depth resolution of surveying the light optical axis direction of testee.Drive testee by the accurate translation stage of three-dimensional and do transversal scanning, repeat two dimension or three-dimensional tomographic map that above computation process can obtain testee.

Claims (4)

1, a kind of method of domain optical coherence tomography of full depth finding, it is characterized in that: do sinusoidal vibration by the reference mirror that the sinusoidal phase modulation device drives in the Michelson interferometer reference arm, generate the low-coherent light frequency domain interference signal of a time dependent sinusoidal phase modulation, be shown below:

$G(\mathrm{\&lambda;},t)=G_0+2\mathrm{Re}\left\{\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nr}}\left(\mathrm{\&lambda;}\right)\exp [-j2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}[(z_n-z_r)+2Z\left(t\right)]]\right\},$

Wherein: z (t)=acos (2 π f _cT+ θ),

$G_0=G_{\mathrm{rr}}\left(\text{\&lambda;}\right)+\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nn}}\left(\mathrm{\&lambda;}\right)+2\mathrm{Re}\left\{\underset{n\&NotEqual;m}{\mathrm{\&Sigma;}}{G}_{\mathrm{nm}}\left(\mathrm{\&lambda;}\right)\exp [-j2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}(z_n-z_m)]\right\}$ λ is a wavelength, and a is an amplitude, and θ is an initial phase, f _cBe modulating frequency, G represents the spectral concentration function, and real, z are got in the Re representative _nRepresent the light path at reflection of detected sample position n layer or scattering interface, z _rRepresent the light path of reference mirror position; (λ t) makes Fourier transform, takes out a frequency multiplication F (ω of its frequency spectrum to G then _c) and two frequency multiplication frequency spectrum F (2 ω _c), calculate real part and imaginary part that the low-coherent light frequency domain is interfered complex signal, be shown below

$2\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nr}}\left(\mathrm{\&lambda;}\right)\sin \left[2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}(z_n-z_r)\right]=-\mathrm{Re}\left\{F\left({\mathrm{\&omega;}}_c\right)\right\}/\left[J_1\left(d\right)\cos \left(\mathrm{\&theta;}\right)\right],$

$2\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nr}}\left(\mathrm{\&lambda;}\right)\sin \left[2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}(z_n-z_r)\right]=-\mathrm{Re}\left\{F\left({2\mathrm{\&omega;}}_c\right)\right\}/\left[J_2\left(d\right)\cos \left(2\mathrm{\&theta;}\right)\right],$

Wherein sin item correspondence is interfered the imaginary part of complex signal, the corresponding real part of interfering complex signal of cos item, J ₁And J ₂Be respectively and be single order and second order Bessel's function, d=4 π a/ λ obtains the interference complex signal of low-coherent light frequency domain by Wavelength distribution with real part and imaginary part combination, is shown below

$\hat{G}\left(\mathrm{\&lambda;}\right)=2\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nr}}\left(\mathrm{\&lambda;}\right)\cos \left[2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}(z_n-z_r)\right]-j2\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nr}}\left(\mathrm{\&lambda;}\right)\sin \left[2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}(z_n-z_r)\right]$

$=2\underset{n}{\mathrm{\&Sigma;}}{G}_{\mathrm{nr}}\left(\mathrm{\&lambda;}\right)\exp \{-j\left[2\mathrm{\&pi;}\frac{1}{\mathrm{\&lambda;}}(z_n-z_r)\right]\},$

Then this interference complex signal is carried out conversion reciprocal, obtain again this interference complex signal being obtained the testee tomographic map as inverse Fourier transform by the wavelength interference complex signal that distributes reciprocal.

2, a kind of domain optical coherence tomography system that realizes the full depth finding of the described method of claim 1, comprise low-coherence light source (1), on the illumination direction of this low-coherence light source (1), place collimator and extender device (2), Michelson interferometer (3) in turn, the optical splitter (31) of this Michelson interferometer (3) is divided into incident light surveys light path (34) and reference path (32), the end of reference path is reference mirror (33), the end of surveying light path is sample (35), and sample (35) is placed on the accurate translation stage of three-dimensional; Michelson interferometer (3) output terminal connects a spectrometer (5), this spectrometer (5) is connected with computing machine (7) by image pick-up card (6), it is characterized in that described reference mirror (33) connects a sinusoidal phase modulation device (4), this sinusoidal phase modulation device (4) drives described reference mirror (33) and does sinusoidal vibration.

3, the domain optical coherence tomography system of full depth finding according to claim 2 is characterized in that described sinusoidal phase modulation device (4) is made up of sine function electric signal generator and the piezoelectric ceramic actuator that is fixed on the described reference mirror (33).

4, the domain optical coherence tomography system of full depth finding according to claim 2 is characterized in that described low-coherence light source is a broad spectrum light source.

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