CN101803908A - Dispersive modulation-based non-mirror image optimal frequency domain imaging system and method - Google Patents

Abstract

The invention discloses a dispersive modulation-based non-mirror image optimal frequency domain imaging system and a dispersive modulation-based non-mirror image optimal frequency domain imaging method. In the system, a transmission-type optimal scanning delay line is arranged in a reference arm for modulating dispersion so as to ensure the identity of the axial positions of a sample under different dispersion states; by changing a rotation angle of an oscillating mirror in the transmission optimal scanning delay line, the rapid modulation of dispersion is realized, and two group of interference spectrum signals of the same sample are acquired under two different dispersion states; the two group of acquired interference spectrum signals are respectively multiplied by corresponding dispersion compensation factors so as to accurately compensate the dispersion of imaginary part subjected to corresponding Fourier transform; subtraction operation is performed on the two group of interference spectrum signals subjected to dispersion compensation, then, the imaginary part of the corresponding repeated reflection signal disappears, and the real part still contains the dispersion factor; and finally, the interference spectrum signals subjected to subtraction are subjected to dispersive compensation again and then subjected to Fourier inverse transformation so as to obtain the actual reflection signal of the sample for non-mirror image reconstruction of the sample image.

Description

Based on synthetic non-mirror image optimal frequency domain imaging system of chromatic dispersion and method

Technical field

The present invention relates to optical coherent chromatographic imaging (OCT) technology, relate in particular to a kind of based on synthetic non-mirror image optimal frequency domain imaging system of chromatic dispersion and method.

Background technology

Optical coherence tomography (Optical Coherence Tomography, abbreviation OCT) imaging technique is a kind of novel optical image technology, can carry out non-intruding, noncontact, high-resolution imaging in vivo to the organizational structure and the physiological function of tested live body sample interior, at the early diagnosis of disease with in body biopsy field extensive application prospect.

Optimal frequency domain imaging system is a kind of pattern of optical coherence tomography system, by adopting high speed frequency-sweeping laser source and the axial interference spectrum signal of point probe collected specimens, reference arm is made of fixed plane mirror, do not need to carry out axial scan, by axial interference spectrum signal is carried out the axial depth information that inverse fourier transform can obtain sample, have at a high speed and highly sensitive characteristics.But also there is its inherent defect in the optimal frequency domain imaging, when the interference signal of sample depth information is carried in collection, also collect mutual interference signal between each layer of sample, each layer of sample itself from coherent interference signal, reference light itself from coherent noises such as coherent interference signals.And owing to what collect is the real part of interference spectrum signal, rather than plural interference spectrum signal, it is Hermitian conjugate that the real part of this interference spectrum signal is carried out the result that inverse fourier transform obtains, and has caused having produced in image being superimposed upon on the sample real number picture about the zero complete symmetric complex conjugate picture in light path position.

In order to differentiate the real number picture of sample, usually by regulating the reference arm light path 1 light path point is moved on to outside the sample surfaces, can make real number picture and complex conjugate picture not overlapping on image like this, but because near the fringe visibility zero light path is the highest, be that image sensitivity is the highest, the way that zero light path is removed in employing causes highly sensitive image-region can't obtain utilizing, and because zero light path is positioned at outside the sample, has caused the imaging depth of OFDI system only to utilize half.Eliminate the complex conjugate picture of Fourier domain OCT, near the high sensitivity zone can better utilization zero light path, and make imaging depth expand one times, external a lot of scientific research institutions have all carried out the research of this respect.People such as M.Wojtkowski propose to utilize piezoelectric ceramic actuator to move the method for the reflecting mirror of reference arm, the Zhongping Chen group in Irving branch school, University of California proposes to adopt the method for electro-optic phase modulator, Duke University Izatt group proposes to adopt the method for 3 * 3 fiber couplers, by between adjacent axial interference spectrum signal, introducing fixed additive phase, adopt plural interference spectrum recovery algorithms to reconstruct the plural form of interference spectrum signal, carry out inverse fourier transform again, thereby eliminate the complex conjugate picture.Medical college G.J.Tearney group of Harvard University proposes to adopt the acousto-optic phase-modulator that the interference spectrum signal is carried out the method for carrier frequency and the method for polarization encoder is removed the complex conjugate picture.People such as Hofer propose to adopt chromatic dispersion material that chromatic dispersion is provided and eliminate the method for complex conjugate picture with complicated iterative algorithm, and people such as S.Witte remove the complex conjugate picture to the elimination spike algorithm that also adopts chromatic dispersion material and carry out the chromatic dispersion coding and propose to simplify.

Above-mentioned these methods, all there is its inherent defect, as utilizes piezoelectric ceramic actuator to carry out the multistep phase-moving method need to take multiple measurements same position, reduce image taking speed, and, be subjected to of the influence of various environmental perturbations easily to phase place to the stability requirement height of phase place; Utilize the method for electro-optic phase modulator harmony optical phase modulator need introduce more complicated and expensive instrument and equipment, and the system data picking rate has been proposed harsh requirement; Utilizing the method for 3 * 3 fiber couplers to be subjected to temperature easily causes and recovers the inaccurate of plural interference spectrum, the complex conjugate suppression ratio that influence is whole the influence of the coefficient of coup; The existing method of utilizing chromatic dispersion to remove the complex conjugate picture that proposes need rely on complicated iterative algorithm, and the simplification of algorithm has also been reduced the complex conjugate suppression ratio.Therefore be necessary to study and be easy to realize and the mirror method that disappears that the complex conjugate suppression ratio is high.

Summary of the invention

The objective of the invention is at the deficiencies in the prior art, provide a kind of based on synthetic non-mirror image optimal frequency domain imaging system of chromatic dispersion and method.Reference arm at optimal frequency domain imaging system is provided with the transmission-type optical scan delay-line, realizes that the synthetic light path of keeping reference arm simultaneously of chromatic dispersion is constant, guarantees the homogeneity of sample axial location under different chromatic dispersion states.By the anglec of rotation of galvanometer in the quick change transmission-type optical scan delay-line, obtain two groups of interference spectrum signals of same sample under two kinds of chromatic dispersion states.By the multiplied by corresponding dispersion compensation factor chromatic dispersion of corresponding imaginary part is compensated, implement dispersion compensation once more after two groups of interference spectrums behind the dispersion compensation are subtracted each other, carry out inverse fourier transform then, just can obtain the real reflected signal of sample, the no mirror image that is used for sample image is rebuild, and makes one times of system imaging degree of depth expansion.

The objective of the invention is to be achieved through the following technical solutions:

A kind of based on the synthetic non-mirror image optimal frequency domain imaging system of chromatic dispersion, it comprises: swept light source, first broadband optical fiber coupler, second broadband optical fiber coupler, sample ami light circulator, reference arm light circulator, sample arm Polarization Controller, sample arm collimating mirror, reference arm Polarization Controller, reference arm collimating mirror, reference arm condenser lens, reference arm plane mirror, sample arm scanning galvanometer, sample arm condenser lens, the 3rd broadband optical fiber coupler, transmission-type optical scan delay-line, balance detection device, Mach-Zehnder interferometers, data collecting card, computer.Wherein, swept light source links to each other with first broadband optical fiber coupler; First broadband optical fiber coupler connects second broadband optical fiber coupler and Mach-Zehnder interferometers respectively; Second broadband optical fiber coupler connects sample ami light circulator and reference arm light circulator respectively; The sample ami light circulator links to each other successively with sample arm Polarization Controller, sample arm collimating mirror; The collimated light beam degree of being of sample arm scanning galvanometer and the outgoing of sample arm collimating mirror is placed, and the light beam of turning back is radiated on the sample by the sample arm condenser lens; The reference arm light circulator links to each other successively with reference arm Polarization Controller, reference arm collimating mirror, reference arm condenser lens, reference arm plane mirror; The output port of reference arm light circulator is connected with the transmission-type optical scan delay-line again, the output port of transmission-type optical scan delay-line and sample ami light circulator links to each other with the 3rd broadband optical fiber coupler respectively, and two output ports of the 3rd broadband optical fiber coupler link to each other with two input ports of balance detection device; The output port of balance detection device, Mach-Zehnder interferometers links to each other with data collecting card respectively, and data collecting card links to each other with computer.

A kind of formation method of using above-mentioned based on the synthetic non-mirror image optimal frequency domain imaging system of chromatic dispersion may further comprise the steps:

(1) the transmission-type optical scan delay-line is set in the reference arm of optimal frequency domain imaging system, looses in order to color to be provided;

(2) regulate the transmission-type optical scan delay-line, produce the chromatic dispersion that changes with galvanometer 15 anglecs of rotation, and it is constant to keep the reference arm light path;

(3) gather interference spectrum signal under two kinds of chromatic dispersion states, eliminate mirror image with dispersion compensation and the algorithm that subtracts each other, the acquisition gamut does not have the sample image of mirror image.

Compare with background technology, the present invention has following technique effect:

1, quick image cancellation algorithm.In the transmission-type optical scan delay-line, by changing the anglec of rotation of galvanometer, realize fast modulation to chromatic dispersion, obtain two groups of interference spectrum signals of same sample under two kinds of chromatic dispersion states thus.By these two groups of interference spectrum signal dispersion are compensated, reduce the imaginary part of common interflection signal, then the dispersion compensation second time is carried out in the residual dispersion of the interference spectrum signal of corresponding real part, can obtain plural interference spectrum signal, at last this plural interference spectrum signal is carried out inverse fourier transform, promptly obtain the optical coherence tomography image that gamut does not have mirror image.

2, can guarantee to realize under the constant condition of reference arm light path the fast modulation of chromatic dispersion.By the transversal displacement y between galvanometer rotating shaft and the fourier transform lens optical axis in the adjusting transmission-type optical scan delay-line ₀, keep the reference arm light path constant in the time of can being implemented in the galvanometer anglec of rotation change in the transmission-type scanning delay line; Regulate the angle theta between grating normal and the optical axis _g, can realize the fast modulation of chromatic dispersion by changing the anglec of rotation of galvanometer in the transmission-type optical scan delay-line, the light path of keeping reference arm is constant, guarantees the homogeneity of sample axial location under different chromatic dispersion states.Realize zero group delay and chromatic dispersion modulation simultaneously by introducing the transmission-type optical scan delay-line, be easy to realize, and guaranteed the compactedness and the reliability of optimal frequency domain imaging system.

Description of drawings

Fig. 1 is the system schematic of the specific embodiment based on the synthetic non-mirror image optimal frequency domain formation method of chromatic dispersion of the present invention;

Fig. 2 is the structural representation based on the transmission-type optical scan delay-line in the synthetic non-mirror image optimal frequency domain imaging system of chromatic dispersion of the present invention;

Fig. 3 is the sequencing contro figure based on the synthetic non-mirror image optimal frequency domain imaging system of chromatic dispersion of the present invention;

Fig. 4 is the algorithm flow chart based on the synthetic non-mirror image optimal frequency domain imaging system of chromatic dispersion of the present invention;

Among the figure: 1, swept light source, 2, broadband optical fiber coupler, 3, optical circulator, 4, Polarization Controller, 5, the sample arm collimating mirror, 6, the sample arm scanning galvanometer, 7, condenser lens, 8, sample, 9, the reference arm collimating mirror, 10, condenser lens, 11, plane mirror, 12, collimating mirror, 13, balzed grating,, 14, fourier transform lens, 15, galvanometer, 16, corner cube prism, 17, receive reflecting mirror, 18, receive collimating mirror, 19, the balance detection device, 20, Mach-Zehnder interferometers, 21, data collecting card, 22, computer, 23, the transmission-type optical scan delay-line.

The specific embodiment

The present invention is based on the synthetic non-mirror image optimal frequency domain formation method of chromatic dispersion, reference arm at optimal frequency domain imaging system is provided with the transmission-type optical scan delay-line, realize that the synthetic light path of keeping reference arm simultaneously of chromatic dispersion is constant, guarantee the homogeneity of sample axial location under different chromatic dispersion states.By the anglec of rotation of galvanometer in the quick change transmission-type optical scan delay-line, obtain two groups of interference spectrum signals of same sample under two kinds of chromatic dispersion states.By the multiplied by corresponding dispersion compensation factor chromatic dispersion of corresponding imaginary part is compensated, implement dispersion compensation once more after two groups of interference spectrums behind the dispersion compensation are subtracted each other, carry out inverse fourier transform then, just can obtain the real reflected signal of sample, rebuild with the no mirror image that is used for sample image, make one times of system imaging degree of depth expansion.Its concrete steps are as follows:

1, by the galvanometer in the transmission-type optical scan delay-line in the synchronizing sequential circuit control reference arm, the scanheads of sample arm and the collection of data collecting card are synchronous, gather the interference spectrum signal of determining sequential.

2, by regulating the angle of grating normal and optical axis in the transmission-type optical scan delay-line, generation can be with the chromatic dispersion of galvanometer anglec of rotation change, by regulating the transversal displacement of galvanometer rotating shaft and optical axis, the light path that guarantees reference arm when the galvanometer anglec of rotation changes is constant, guarantees the homogeneity of sample axial location under different chromatic dispersion states.

3, in the transmission-type optical scan delay-line in the one-period of vibration mirror scanning, gather the interference spectrum signal of two groups of corresponding different galvanometer anglecs of rotation by synchronizing sequential circuit control data capture card, obtain two groups of interference spectrum signals of same sample under two kinds of chromatic dispersion states thus, by implementing the interference spectrum behind the dispersion compensation is subtracted each other and carries out once more the algorithm of dispersion compensation, reconstruct the complex expression of interference spectrum signal, by inverse fourier transform, can reconstruct the gamut optical coherence tomography image of no mirror image at last.

The present invention is based on the synthetic non-mirror image optimal frequency domain imaging system of chromatic dispersion, comprise swept light source, broadband optical fiber coupler, optical circulator, Polarization Controller, the sample arm that constitutes by collimating mirror, scanning galvanometer, two gummed achromat, sample, the reference arm that constitutes by collimating mirror, two gummed achromat, plane mirror, transmission-type optical scan delay-line, by the demarcation light path that Mach-Zehnder interferometers constitutes, balance detection device, data collecting card, computer.The low-coherent light that comes out from swept light source, enter demarcation light path and main interference instrument light path respectively through broadband optical fiber coupler, the light that enters the demarcation light path produces a road sign through Mach-Zehnder interferometers and decides signal, the light that enters main interference instrument light path enters reference arm and sample arm respectively after the broadband optical fiber coupler beam split, the coherent light of two arms interferes back formation interference signal to be surveyed through the balance detection device at the broadband optical fiber coupler place, interference signal and demarcation signal are through the data collecting card collection, handle at computer at last, produce the interference signal of plural form, by the inverse fourier transform reconstructed image.

The transmission-type optical scan delay-line is made up of collimating mirror, balzed grating,, fourier transform lens, galvanometer, corner cube prism, reception reflecting mirror, reception collimating mirror, and wherein there is an adjustable angle theta in the optical axis of the normal of balzed grating, and fourier transform lens _g, balzed grating, is positioned on the front focal plane of fourier transform lens, and galvanometer is positioned on the back focal plane of fourier transform lens, and the rotating shaft of galvanometer and the spacing of optical axis are an adjustable side-play amount y ₀

The present invention is further illustrated below in conjunction with drawings and Examples, and it is more obvious that purpose of the present invention and effect will become.

Figure 1 shows that based on the structure chart of a specific embodiment of the synthetic non-mirror image optimal frequency domain imaging system of chromatic dispersion, comprise swept light source 1, first broadband optical fiber coupler 2, second broadband optical fiber coupler 3, sample ami light circulator 4, reference arm light circulator 5, sample arm Polarization Controller 6, sample arm collimating mirror 7, reference arm Polarization Controller 8, reference arm collimating mirror 9, reference arm condenser lens 10, reference arm plane mirror 11, sample arm scanning galvanometer 19, sample arm condenser lens 20, sample 21, the 3rd broadband optical fiber coupler 22, transmission-type optical scan delay-line 23, balance detection device 24, Mach-Zehnder interferometers 25, data collecting card 26, computer 27.

Wherein, swept light source 1 links to each other with first broadband optical fiber coupler 2; First broadband optical fiber coupler 2 connects second broadband optical fiber coupler 3 and Mach-Zehnder interferometers 25 respectively; Second broadband optical fiber coupler 3 connects sample ami light circulator 4 and reference arm light circulator 5 respectively; Sample ami light circulator 4 links to each other successively with sample arm Polarization Controller 6, sample arm collimating mirror 7; Sample arm scanning galvanometer 19 is 45 degree placements with the collimated light beam of sample arm collimating mirror 7 outgoing, and the light beam of turning back is radiated on the sample 21 by sample arm condenser lens 20; Reference arm light circulator 5 links to each other successively with reference arm Polarization Controller 8, reference arm collimating mirror 9, reference arm condenser lens 10, reference arm plane mirror 11; The output port of reference arm light circulator 5 is connected with transmission-type optical scan delay-line 23 again, the output port of transmission-type optical scan delay-line 23 and sample ami light circulator 4 links to each other with the 3rd broadband optical fiber coupler 22 respectively, and two output ports of the 3rd broadband optical fiber coupler 22 link to each other with two input ports of balance detection device 24; The output port of balance detection device 24, Mach-Zehnder interferometers 25 links to each other with data collecting card 26 respectively, and data collecting card 26 links to each other with computer 27.

As shown in Figure 1, the low-coherent light that sends from swept light source 1, enter demarcation light path and main interference instrument light path respectively through first broadband optical fiber coupler 2, enter the light of demarcating light path and decide signal through Mach-Zehnder interferometers 25 generations one road sign, the light that enters main interference instrument light path enters reference arm and sample arm respectively after 3 beam split of second broadband optical fiber coupler, light in the reference arm enters transmission-type optical scan delay-line 23 after collimating through collimating mirror 12, reaching sample light that the 3rd broadband optical fiber coupler 22 and sample arm return converges the back and interferes, enter balance detection device 24, the demarcation signal that OCT interference spectrum signal that forms and Mach-Zehnder interferometers 25 produce is gathered by data collecting card 26 simultaneously, and these interference spectrum signals import into and carry out date processing and image reconstruction in the computer 27 at last.

Of the present invention based on the synthetic non-mirror image optimal frequency domain formation method of chromatic dispersion, may further comprise the steps:

1, the transmission-type optical scan delay-line is set in the reference arm of optimal frequency domain imaging system, in order to chromatic dispersion to be provided.

The light path that light among Fig. 1 in the sample arm is walked is a constant, uses L in the following derivation of equation _SamExpression, the light path that the light in the reference arm is walked can be divided into two parts: the light path L except that transmission-type optical scan delay-line 23 _RefExpression, the light path L in the transmission-type optical scan delay-line 23 _RsodExpression, then the phase contrast of interference spectrum signal can be expressed as:

Φ＝kL _sam-kL _ref-kL _rsod (1)

Wherein k is light wave number and k=2 π/λ.Light is by transmission-type optical scan delay-line 23, and its phase change amount can be expressed as:

k·L _rsod＝φ _R+k·l (2)

Wherein, l is galvanometer anglec of rotation γ in the transmission-type optical scan delay-line 23 and grating defocusing amount (L-f) light path when being zero.φ _RAdditional phase place, then this additive phase φ under the non-vanishing state of galvanometer anglec of rotation γ in the transmission-type optical scan delay-line 23 and grating defocusing amount (L-f) _RExpression is:

${\mathrm{\φ}}_R\left(\mathrm{\ω}\right)=\frac{4y_0\mathrm{\ω\γ}}{c}+\frac{4\mathrm{L\ω\γ}\sin \mathrm{\α}}{c\cos \mathrm{\α}}+\frac{4\mathrm{L\ω}\cos \mathrm{\α}}{c}+\frac{4\mathrm{f\ω}}{c\cos \mathrm{\α}}+\frac{8\mathrm{\πm}(L-f)\sin \mathrm{\α}}{p\cos \mathrm{\β}}-\frac{8\mathrm{f\ω}}{c}---\left(3\right)$

Wherein ω is light frequency and ω=kc, y ₀Be the transversal displacements of galvanometer 15 rotating shafts apart from optical axis, γ is the anglec of rotation of galvanometer 15, and L is the distance between balzed grating, 13 and the fourier transform lens 14, and f is the focal length of fourier transform lens 14, and β is by p sin β=m (λ-λ ₀) decision, p is a grating constant, m is that the order of diffraction is inferior, λ ₀Be centre wavelength, α is by α=β+θ _gDecision, θ _gBe the angle that is become between the normal of balzed grating, 13 and the optical axis.φ _R(ω) Taylor expansion is:

${\mathrm{\φ}}_R\left(\mathrm{\ω}\right)={\mathrm{\φ}}_R\left({\mathrm{\ω}}_0\right)+{\mathrm{\φ}}_R^{\′}\left({\mathrm{\ω}}_0\right)\·(\mathrm{\ω}-{\mathrm{\ω}}_0)+\frac{1}{2!}{{\mathrm{\φ}}_R}^{\′\′}\left({\mathrm{\ω}}_0\right)\·{(\mathrm{\ω}-{\mathrm{\ω}}_0)}^2+\·\·\·---\left(4\right)$

Wherein, φ _R(ω ₀) be phase retardation, φ _R' (ω ₀) be group delay, φ _R ^"(ω ₀) be GVD.Its expression formula is respectively:

${\mathrm{\φ}}_R\left({\mathrm{\ω}}_0\right)=\frac{4{\mathrm{\ω}}_0{y}_0\mathrm{\γ}}{c}+\frac{4{\mathrm{\ω}}_0(L-f)}{c}---\left(5\right)$

${{\mathrm{\φ}}_R}^{\′}\left({\mathrm{\ω}}_0\right)=\frac{4y_0\mathrm{\γ}}{c}-\frac{8\mathrm{\πmL\γ}}{p{\mathrm{\ω}}_0\cos {\mathrm{\θ}}_g}+\frac{4(L-f)}{c}---\left(6\right)$

${{\mathrm{\&phi;}}_R}^{\&prime;\&prime;}\left({\mathrm{\&omega;}}_0\right)=\frac{16{\mathrm{\&pi;}}^2{m}^{2}c\sin {\mathrm{\&theta;}}_g\mathrm{L\&gamma;}}{{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="HSA00000045388900011.png"\; state="\{\{state\}\}">p</figure-callout>}}^2{\mathrm{\&omega;}}_0^3{\mathrm{<figure-callout\; id="3"\; label="cos"\; filenames="HSA00000045388900011.png"\; state="\{\{state\}\}">cos</figure-callout>}}^3{\mathrm{\&theta;}}_g}+\frac{16{\mathrm{\&pi;}}^2{m}^{2}c(L-f)}{{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="HSA00000045388900011.png"\; state="\{\{state\}\}">p</figure-callout>}}^2{\mathrm{\&omega;}}_0^3{\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000045388900011.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2{\mathrm{\&theta;}}_g}---\left(7\right)$

Only consider φ _R(ω) second order term of Taylor expansion can get interference spectrum phase contrast expression formula to (2), (4) formula substitution (1) formula and is:

$\mathrm{\&Phi;}=\frac{\mathrm{\&omega;}}{c}\&CenterDot;[L_{\mathrm{sam}}-L_{\mathrm{ref}}-l-{\mathrm{\&phi;}}_R^{\&prime;}\left({\mathrm{\&omega;}}_0\right)\&CenterDot;c]-[{\mathrm{\&phi;}}_R\left({\mathrm{\&omega;}}_0\right)-{\mathrm{\&phi;}}_R^{\&prime;}\left({\mathrm{\&omega;}}_0\right)\&CenterDot;{\mathrm{\&omega;}}_0+\frac{1}{2}{\mathrm{\&phi;}}_R^{\&prime;\&prime;}\left({\mathrm{\&omega;}}_0\right)\&CenterDot;{(\mathrm{\&omega;}-{\mathrm{\&omega;}}_0)}^2]---\left(8\right)$

2, regulate the transmission-type optical scan delay-line, produce the chromatic dispersion that changes with galvanometer 15 anglecs of rotation, and it is constant to keep the reference arm light path.

The transversal displacement of regulating between galvanometer 15 rotating shafts and optical axis is a following expression:

$y_0=\frac{m{\mathrm{\&lambda;}}_{0}L}{P\&CenterDot;\cos {\mathrm{\&theta;}}_g}---\left(9\right)$ Group delay φ then _R' (ω ₀) not the anglec of rotation γ with galvanometer 15 change.Again because when the light path l of the defocusing amount (L-f) of the anglec of rotation γ of the galvanometer in the transmission-type optical scan delay-line 23 15 and balzed grating, 13 when all being zero be constant, and the light path L except that transmission-type optical scan delay-line 23 in the reference arm _RefBe constant,, be made as so first in (8) formula is only relevant with the sample depth z:

z＝L _sam-L _ref-l-φ _R′(ω ₀)·c (10)

(8) second GVD φ in the formula _R" (ω ₀) change with the anglec of rotation γ of scanning galvanometer 15, promptly form the quantitative variable phase of the chromatic dispersion generation that causes by transmission-type optical scan delay-line 23 _d, its expression formula is:

${\mathrm{\&phi;}}_d=-[{\mathrm{\&phi;}}_R\left({\mathrm{\&omega;}}_0\right)-{\mathrm{\&phi;}}_R^{\&prime;}\left({\mathrm{\&omega;}}_0\right)\&CenterDot;{\mathrm{\&omega;}}_0+\frac{1}{2}{\mathrm{\&phi;}}_R^{\&prime;\&prime;}\left({\mathrm{\&omega;}}_0\right)\&CenterDot;{(\mathrm{\&omega;}-{\mathrm{\&omega;}}_0)}^2]---\left(11\right)$

The OCT interference signal that the reference light that sample light that sample arm is returned and reference arm return interferes the back to form, the interference spectrum signal expression that is collected by data collecting card 21 is:

3, gather interference spectrum signal under two kinds of chromatic dispersion states, eliminate mirror image with dispersion compensation and the algorithm that subtracts each other, the acquisition gamut does not have the sample image of mirror image.

By the galvanometer 15 in the synchronous sequence signal control transmission-type optical scan delay-line 23, corresponding to galvanometer 15 different rotary angles, transmission-type optical scan delay-line 23 provides two kinds of different chromatic dispersions respectively, computer 21 produces two trigger collection signal triggering data collecting cards 20 respectively and carries out data acquisition, and two interference spectrum signals that collect are:

Because chromatic dispersion phase place

Can separate the parcel algorithm by phase place and try to achieve by place plane mirror in sample arm, each layer of sample relevant certainly

Since intensity very I to ignore reference arm intensity | E _r| ²Can remove DC terms by the balance detection device.To the interference spectrum signal times with dispersion compensation factors

Can be compensated the interference spectrum signal I of chromatic dispersion _c(ω):

The processing that subtracts of (6) formula that dispersion compensation is obtained and (7) formula, the interference spectrum signal of the corresponding interflection signal imaginary part that can be eliminated:

To (8) formula poor divided by twice dispersion compensation factors square

The interference spectrum signal that can obtain plural form is:

At last resulting plural interference spectrum signal is carried out just can be eliminated an axial scan depth information of mirror image of Fourier transform, can realize the more good utilisation of zero light path place high sensitivity zone and make investigation depth enlarge one times.

Figure 2 shows that the sketch map of transmission-type optical scan delay-line.Wherein the optical axis of the normal of balzed grating, 13 and fourier transform lens 14 forms a θ _gAngle, the light of reference arm enters the transmission-type optical scan delay-line after collimating through collimating mirror 12, collimated beam is via 13 beam split of reflection-type balzed grating,, each spectral components after the beam split focuses on the galvanometer 15 by fourier transform lens 14, after galvanometer 15 reflections, turn back to balzed grating, 13 by fourier transform lens 14, and merged into a branch of collimated light behind the diffraction once more by balzed grating, 13 and project on the corner cube prism 16, the light of process corner cube prism 16 is after staggering with the vertical direction in plane, optical table place, turn back to balzed grating, 13 along former direction, pass through fourier transform lens 14 and galvanometer 15 again, passed through fourier transform lens 14 and balzed grating, 13 once more after galvanometer 15 reflections, again merge into emergent light behind 13 4 diffraction of balzed grating,, the outgoing beam that is received reflecting mirror 17 reflections at last enters and receives collimating mirror 18.

Figure 3 shows that sequencing contro figure based on the synthetic non-mirror image optimal frequency domain imaging system of chromatic dispersion.Computer 27 produces synchronous sequence signals and controls galvanometer 15 in the transmission-type optical scan delay-line 23 and the scanning galvanometer 19 in the sample arm.Computer 27 produces the scanning galvanometer 19 in one road triangular signal driving sample arm, and computer 27 produces the galvanometer 15 in one road square-wave signal driving transmission-type optical scan delay-line 23.Low level in the transmission-type optical scan delay-line in the square wave driving signal of 23 galvanometer 15 and the respectively corresponding two kinds of different chromatic dispersion states of high level.Utilize computer 27 to produce synchronous sequence, the ascent stage correspondence that the triangular wave of the scanning galvanometer 19 in sample arm drives signal in the transmission-type optical scan delay-line low level section in the square wave driving signal of 23 galvanometer 15, and the descending branch correspondence that the triangular wave of the scanning galvanometer 19 in sample arm drives signal in the transmission-type optical scan delay-line high level section in the square wave driving signal of 23 galvanometer 15.Computer 27 produces one tunnel trigger collection signal, is used for trigger data acquisition card 26 and carries out data acquisition, collects under two kinds of chromatic dispersion states corresponding to two groups of interference spectrum signals of same sample, imports at last and carries out date processing in the computer 27.

Figure 4 shows that algorithm flow chart based on the synthetic non-mirror image optimal frequency domain imaging system of chromatic dispersion.Interference spectrum signal 1 and the interference spectrum signal 2 that collects be multiply by corresponding dispersion compensation factors respectively, make the imaginary part chromatic dispersion fine compensation behind the corresponding Fourier transform, obtain interference spectrum signal 1 behind the dispersion compensation and the interference spectrum signal 2 behind the dispersion compensation, with two groups of interference spectrum signal subtractions behind the above-mentioned dispersion compensation, the imaginary part of then corresponding interflection signal disappears, and real part still includes the chromatic dispersion factor.Interference spectrum signal after subtracting each other is implemented dispersion compensation once more, promptly obtain plural interference spectrum signal, carry out the real reflected signal that Fourier transform just can obtain sample at last, can be used for rebuilding the gamut optical coherence tomography image of no mirror image.

Claims (2)

1. one kind based on the synthetic non-mirror image optimal frequency domain imaging system of chromatic dispersion, it is characterized in that it comprises: swept light source (1), first broadband optical fiber coupler (2), second broadband optical fiber coupler (3), sample ami light circulator (4), reference arm light circulator (5), sample arm Polarization Controller (6), sample arm collimating mirror (7), reference arm Polarization Controller (8), reference arm collimating mirror (9), reference arm condenser lens (10), reference arm plane mirror (11), sample arm scanning galvanometer (19), sample arm condenser lens (20), the 3rd broadband optical fiber coupler (22), transmission-type optical scan delay-line (23), balance detection device (24), Mach-Zehnder interferometers (25), data collecting card (26), computer (27).Wherein, swept light source (1) links to each other with first broadband optical fiber coupler (2); First broadband optical fiber coupler (2) connects second broadband optical fiber coupler (3) and Mach-Zehnder interferometers (25) respectively; Second broadband optical fiber coupler (3) connects sample ami light circulator (4) and reference arm light circulator (5) respectively; Sample ami light circulator (4) links to each other successively with sample arm Polarization Controller (6), sample arm collimating mirror (7); Sample arm scanning galvanometer (19) is the placement of (45) degree with the collimated light beam of sample arm collimating mirror (7) outgoing, and the light beam of turning back is radiated on the sample (21) by sample arm condenser lens (20); Reference arm light circulator (5) links to each other successively with reference arm Polarization Controller (8), reference arm collimating mirror (9), reference arm condenser lens (10), reference arm plane mirror (11); The output port of reference arm light circulator (5) is connected with transmission-type optical scan delay-line (23) again, the output port of transmission-type optical scan delay-line (23) and sample ami light circulator (4) links to each other with the 3rd broadband optical fiber coupler (22) respectively, and two output ports of the 3rd broadband optical fiber coupler (22) link to each other with two input ports of balance detection device (24); The output port of balance detection device (24), Mach-Zehnder interferometers (25) links to each other with data collecting card (26) respectively, and data collecting card (26) links to each other with computer (27).

2. an application rights requires 1 described formation method based on the synthetic non-mirror image optimal frequency domain imaging system of chromatic dispersion, may further comprise the steps:

(1) the transmission-type optical scan delay-line is set in the reference arm of optimal frequency domain imaging system, in order to chromatic dispersion to be provided.

(2) regulate the transmission-type optical scan delay-line, produce the chromatic dispersion that changes with galvanometer 15 anglecs of rotation, and it is constant to keep the reference arm light path.

(3) gather interference spectrum signal under two kinds of chromatic dispersion states, eliminate mirror image with dispersion compensation and the algorithm that subtracts each other, the acquisition gamut does not have the sample image of mirror image.

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