CN202096197U - Full range frequency-sweeping OCT imaging system based on phase multiplexing - Google Patents

Abstract

The utility model discloses a full range frequency-sweeping OCT (Optical Coherence Tomography) imaging system based on phase multiplexing. An electrooptical modulator is arranged in a reference arm in a frequency-sweeping OCT system, thereby realizing high-speed phase modulation for interference spectrums; preset phase change between adjacent sampling points of the collected interference spectrums is maintained by synchronously triggering a data collecting card and the electrooptical modulator, thereby realizing phase multiplexing collecting for the interference spectrums within a single frequency-sweeping period; data collecting points for the collected interference spectrums are grouped according to corresponding additional phases thereof and then are respectively mapped into a same wave number space corresponding to equidistance sampling points, thereby forming phase shift interference spectrum data subsets for the wave number space; and the phase shift interference spectrum data subsets can be used for reconstructing an interference spectrum data and reconstructing a full range frequency-sweeping OCT image. On the basis of phase modulation and multiplexing of electrooptical modulated interference spectrums within a single frequency-sweeping period, the phase shifting speed is high, the precision is high, the mirror image suppression ratio is high, and high-sensitivity imaging for an interested deep area can be realized.

Description

A kind of based on the mutually multiplexing gamut frequency sweep OCT imaging system in position

Technical field

This utility model relates to optical coherent chromatographic imaging (OCT) technology and frequency sweep Optical Coherence Tomography Imaging Technology, relates in particular to a kind of based on the mutually multiplexing gamut frequency sweep OCT imaging system in position.

Background technology

Optical coherence tomography (Optical Coherence Tomography; Abbreviation OCT) imaging technique is a kind of promising optical image technology; Can non-intruding, noncontact, high-resolution ground carry out imaging in vivo to tested living body biological sample tissue inner structure and physiological function, the early diagnosis of disease and in body biopsy field the extensive application prospect.

Frequency sweep optical coherence tomography system belongs to a kind of fourier-domain optical coherence chromatographic imaging system.The fourier-domain optical coherence tomographic system has two kinds of ways of realization, is based on the wideband light source and the quick spectral coverage OCT system of multi-channel spectrometer based respectively, and based on the frequency sweep OCT system of fast tunable laser instrument and point probe.The fourier-domain optical coherence tomographic system need not to carry out the mechanical type axial scan; Through quick collection interference spectrum signal; The interference spectrum signal is carried out based on the signal processing of FFT to obtain the axial depth information of sample, compare with time domain OCT system and have at a high speed and highly sensitive advantage.But also there is its inherent defect in the fourier-domain optical coherence tomography; 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; This is done solid work relate to spectral signal to carry out the result that FFT obtains be Hermitian conjugate, caused in image, having produced being superimposed upon on the actual picture of sample about the zero complete symmetric conjugate lens picture in light path position.

Coherent noises such as the conjugate lens picture in the fourier-domain optical coherence tomographic map and sample image are overlapping; Usually the light path official post zero light path face that needs to regulate between sample arm and the reference arm moves on to beyond the sample surface; Can make actual picture and conjugate image not overlapping on image like this; But because near the fringe visibility the zero light path face is the highest; Be that image sensitivity is the highest, each spectral component in the light source is introduced same optical path difference, cause the sample image signal to noise ratio along with descending rapidly away from zero light path face.The way that zero light path face is removed in employing causes highly sensitive image-region can't obtain utilizing, and because zero light path face is positioned at outside the sample, has caused the imaging depth of fourier-domain optical coherence tomographic system only to utilize half the.Eliminate the conjugate image mirror 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.It is phase-shifting method that people such as M.Wojtkowski propose to utilize the method for the reflecting mirror in the piezoelectric ceramic actuator stepping 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; Through 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 acousto-optic frequency shifters 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.Thereby the two-way interference signal that people such as the J.P.Rolland of Rochester University propose to utilize two balance detection devices to survey respectively and have 90 degree phase contrasts is eliminated the complex conjugate mirror image in order to make up plural interference spectrum signal.

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 the stability requirement to phase place is high, receives the influence of various environmental perturbations to phase place easily; Utilize the method for electro-optic phase modulator and acousto-optic frequency shifters 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 receive 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 mirror method that disappears that utilizes chromatic dispersion that proposes need rely on complicated iterative algorithm, and the simplification of algorithm has also been reduced the complex conjugate suppression ratio; Utilize the method for two balance detections to increase system complexity, and the phase contrast of introducing has higher requirement to environmental stability, be not suitable for the optical-fiber type system.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

It is a kind of based on position mutually multiplexing gamut frequency sweep OCT formation method and system that the purpose of this utility model is to provide.In the reference arm of frequency sweep OCT imaging system, electrooptic modulator is set, comes the conjugate lens picture in the removal of images, obtain the gamut OCT image of high sensitivity zone through the mutually multiplexing collection in interference spectrum position.

The purpose of this utility model realizes through following technical scheme:

One, a kind of based on the mutually multiplexing gamut frequency sweep OCT formation method in position:

In the reference arm of frequency sweep optical coherence tomography system, electrooptic modulator is set, in reference light, introduces additive phase, realize the high-speed phase modulation of interference spectrum signal; Through the synchronous triggering between data collecting card and the electrooptic modulator, make to have preset phase change between the adjacent interference spectrum sampled point, realize the spectrographic mutually multiplexing collection in position of single wavelength sweep cycle internal interference; The interference spectrum data that collect are divided into groups by its pairing additive phase; Obtain some groups of interference spectrum data subsets corresponding to same additive phase; Respectively the interference spectrum data subset corresponding to same additive phase of every group of time domain collection is mapped to wave number such as the preset wave number space of coordinate at interval then, promptly utilize these etc. wave number phase shift interference spectroscopic data subclass spaced apart make up multiple interference spectrum data; According to multiple interference spectrum data, rebuild the high sensitivity gamut frequency sweep OCT imaging of depth areas interested; The concrete steps of this method are following:

1) adjustment function generator produces one tunnel phase modulated and drives signal, is input to the electrooptic modulator in the reference arm, and reference light is introduced additive phase, and the phase place of the interference spectrum that forms after reference light and sample light converge is modulated by this additive phase promptly;

2) system's each several part hardware synchronization work is set; Make the triggering signal of swept light source output trigger functional generator generation waveform and data collecting card image data simultaneously; And the data collecting card frequency acquisition is set to 3～5 times of phase modulated signal frequency that functional generator produces, makes to have preset phase change between the consecutive number strong point that collects;

3) the interference spectrum signal that collects by data collecting card; Because having preset additive phase between the consecutive number strong point changes; The data point that will have same additive phase is divided into one group; Can form 3～5 groups of interference spectrum data subsets corresponding to different additive phases; Respectively the interference spectrum data subset corresponding to same additive phase of every group of time domain collection is mapped to wave number such as the preset wave number space of coordinate at interval, utilize these etc. wave number phase shift interference spectral signal subclass spaced apart make up multiple interference spectrum signal, rebuild the high sensitivity gamut frequency sweep OCT imaging of area-of-interest.

Two, a kind of based on the mutually multiplexing gamut frequency sweep OCT imaging system in position:

Comprise light source, broadband optical fiber coupler, sample arm, reference arm and OCT interference spectrum signal detecting device; The low-coherent light that sends from light source gets into broadband optical fiber coupler; After beam split, get into reference arm and sample arm respectively, the interference spectrum signal of generation gets into OCT interference spectrum signal detecting device and gathers; It is characterized in that: said light source is the low-coherent light that scanning light source sends, and gets into first end of first broadband optical fiber coupler; The light of second end of first broadband optical fiber coupler is incident upon on the sample through the sample arm circulator; The light of the 3rd end of first broadband optical fiber coupler gets into the electro-optic phase modulator of reference arm; At second broadband optical fiber coupler and formation OCT interference spectrum signal after the sample light that sample arm is returned converges; Survey through the balance detection device through second broadband optical fiber coupler the 3rd end and the 4th end, after the data collecting card in the computer gather; The triggering signal of scanning light source output is divided into two-way, and one road and function generator connects, and produces phase modulated signal and is connected with electrooptic modulator, realizes reference light is introduced additive phase; Another road directly is connected with data collecting card, is used to gather the interference spectrum data; The data that data collecting card collects input to computer and carry out date processing and image reconstruction; Data collecting card produces one road galvanometer driving signal and is connected with the sample arm scanning galvanometer, realizes the transversal scanning to sample.

Described sample arm comprises the sample arm circulator, sample arm collimating mirror, sample arm scanning galvanometer and sample 7 arm condenser lenses; The light process sample arm circulator of second end of first broadband optical fiber coupler, the sample arm collimating mirror, the sample arm scanning galvanometer, the sample arm condenser lens is incident upon on the sample, and the former road of reflected light is back to second broadband optical fiber coupler.

Compare with background technology, the beneficial effect that the utlity model has is:

1, realizes the mutually multiplexing collection in position of interference spectrum signal through in a frequency sweep cycle, introducing different additive phases.Compare with the method for multistep phase shift; Need not to stop the time of several axial scans in same transversal scanning position; Realize the spectrographic mutually multiplexing collection in position of single wavelength sweep cycle internal interference a lateral attitude, just can rebuild the no mirror image of high sensitivity zone, image taking speed is fast.

2, this method is employed in the scheme of introducing different additive phases in the frequency sweep cycle.Because the time cycle of axial scan is very short; Need between different frequency sweep cycles, introduce the method for different additive phases with respect to the multistep phase-moving method; Position phase stability between each interference spectrum signal subclass of this method is higher; The complex conjugate rejection ratio is higher, can realize the no mirror image imaging of high complex conjugate rejection ratio.

3, can introduce the accurately additive phase corresponding through electrooptic modulator with each spectral component.Introduce the method for additive phase than stepping reference plane mirror; Can have coupling because the ability of the phase shift aberration that each spectral component amount of phase shift is forbidden to cause; Realize dispersionless phase shift, further improve the complex conjugate rejection ratio, guarantee high speed, the imaging of high sensitivity gamut.

Description of drawings

Fig. 1 is the frequency sweep optical coherence tomography system sketch map of this utility model;

Fig. 2 is the interference spectrum signal schematic representation based on the collection of staircase waveform bits of modulation phase multiplexing method of this utility model;

Among the figure: 1, swept light source, 2, broadband optical fiber coupler, 3, the sample arm circulator; 4, sample arm collimating mirror, 5, the sample arm scanning galvanometer, 6, the sample arm condenser lens; 7, sample, 8, electrooptic modulator, 9, the balance detection device; 10, computer, 11, data collecting card, 12, functional generator.

The specific embodiment

Below in conjunction with accompanying drawing and embodiment this utility model is further described.

As shown in Figure 1; This utility model comprises light source, broadband optical fiber coupler, sample arm, reference arm and OCT interference spectrum signal detecting device; The low-coherent light that sends from light source gets into broadband optical fiber coupler; After beam split, get into reference arm and sample arm respectively, the interference spectrum signal of generation gets into OCT interference spectrum signal detecting device and gathers; Said light source is the low-coherent light that scanning light source 1 sends, and gets into first end of first broadband optical fiber coupler 2; The light of second end of first broadband optical fiber coupler 2 is incident upon on the sample 7 through sample arm circulator 3; The light of the 3rd end of first broadband optical fiber coupler 2 gets into the electro-optic phase modulator 8 of reference arm; At second broadband optical fiber coupler 2 and formation OCT interference spectrum signal after the sample light that sample arm is returned converges; Survey through balance detection device 9 through second broadband optical fiber coupler 2 the 3rd end and the 4th end, after the data collecting card 11 in the computer 10 gather; The triggering signal of scanning light source 1 output is divided into two-way, and one road and function generator 12 connects, and produces phase modulated signal and is connected with electrooptic modulator 8, realizes reference light is introduced additive phase; Another road directly is connected with data collecting card 11, is used to gather the interference spectrum data; The data that data collecting card 11 collects input to computer 10 and carry out date processing and image reconstruction; Data collecting card 11 produces one road galvanometer driving signal and is connected with sample arm scanning galvanometer 5, realizes the transversal scanning to sample.Among the figure, the high-speed wideband electro-optic phase modulator that electrooptic modulator 8 adopts Uniphase company to produce can be introduced an additive phase to reference optical signal through input voltage wherein, can realize the phase modulated of interference spectrum signal after converging with sample light; Line is defined as among the figure: the broken line of band arrow is that the signal of telecommunication connects, and the curve with arrow is not that optical fiber connects.

Described sample arm comprises sample arm circulator 3, sample arm collimating mirror 4, sample arm scanning galvanometer 5 and sample arm condenser lens 6; The light process sample arm circulator 3 of second end of first broadband optical fiber coupler, sample arm collimating mirror 4, sample arm scanning galvanometer 5, sample arm condenser lens 6 are incident upon on the sample 7, and the former road of reflected light is back to second broadband optical fiber coupler.

Shown in Figure 2 is the interference spectrum signal schematic representation based on the collection of staircase waveform bits of modulation phase multiplexing method of this utility model.Describe in the face of the curve among Fig. 2 down.

$I\left(k\right)=S\left(k\right)R_R+S\left(k\right){\∫}_{-\∞}^{+\∞}{\∫}_{-\∞}^{+\∞}{\left[R_S\left(\mathrm{\Δz}\right)R_S\left({\mathrm{\Δz}}^{\′}\right)\right]}^{1/2}\×\exp \left\{i\right[k(\mathrm{\Δz}-{\mathrm{\Δz}}^{\′})+\mathrm{\φ}\left(\mathrm{\Δz}\right)-\mathrm{\φ}\left({\mathrm{\Δz}}^{\′}\right)\left]\right\}\mathrm{d\Δzd}{\mathrm{\Δz}}^{\′}$

$+2S\left(k\right){\∫}_{-\∞}^{+\∞}\sqrt{R_R{R}_S\left(\mathrm{\Δz}\right)}\cos [\mathrm{k\Δz}+\mathrm{\φ}\left(\mathrm{\Δz}\right)+{\mathrm{\φ}}^{\left(1\right)}]\mathrm{d\Δz},i=\mathrm{1,2,3,4,5}$

Wherein, φ ⁽¹⁾=-π,

φ ⁽³⁾=0, φ ⁽⁵⁾=π puts into five groups of new data sets, i.e. I respectively with interference spectrum signal I (t) consecutive points that collect ⁽¹⁾(t), I ⁽²⁾(t), I ⁽³⁾(t), I ⁽⁴⁾(t), I ⁽⁵⁾(t), through the k spatial mappings and be interpolated into after the calculating process of corresponding wave number value, obtain I ⁽¹⁾(k), I ⁽²⁾(k), I ⁽³⁾(k), I ⁽⁴⁾(k), I ⁽⁵⁾(k).The amplitude that utilizes five step phase shift formula calculated complex interference spectrums commonly used with mutually, expression formula is respectively:

$\mathrm{\Ψ}\left(k\right)=\frac{1}{4}{({\left\{2\right[I^{\left(2\right)}\left(k\right)-I^{\left(4\right)}\left(k\right)\left]\right\}}^2+{[{2I}^{\left(3\right)}\left(k\right)-I^{\left(5\right)}\left(k\right)-I^{\left(1\right)}\left(k\right)]}^2)}^{0.5}$

$\mathrm{\Φ}\left(k\right)=\arctan \frac{2[I^{\left(2\right)}\left(k\right)-I^{\left(4\right)}\left(k\right)]}{2I^{\left(3\right)}\left(k\right)-I^{\left(5\right)}\left(k\right)-I^{\left(1\right)}\left(k\right)}$

The amplitude and the phase place of trying to achieve with following formula make up plural interference spectrum, and its expression formula does,

$\tilde{I}\left(k\right)=\mathrm{\Ψ}\left(k\right)\·\exp \left(\mathrm{j\Φ}\left(k\right)\right)$

Through the image reconstruction of Fourier transform, can obtain not having the gamut picture signal of mirror image:

${\mathrm{FT}}^{-1}\left\{\tilde{I}\left(k\right)\right\}=\underset{n}{\mathrm{\Σ}}\mathrm{\Γ}[\mathrm{\τ}-({\mathrm{\τ}}_r-{\mathrm{\τ}}_n)]$

In the formula: the real number interference spectrum signal intensity that I (k) representative is gathered, k represents light wave number, R _RRepresent the reference arm reflectance, R _S(Δ z) and R _S(Δ z ') each layer of representative sample reflectance, the coordinate of the inner different depth of Δ z and Δ z ' representative sample, the additive phase that inner each layer of φ (Δ z) and φ (Δ z ') representative sample introduced the interference spectrum signal, φ ⁽ⁱ⁾The additive phase that representative is introduced by electrooptic modulator, the amplitude of the plural interference spectrum that ψ (k) representative is rebuild, the phase place of the plural interference spectrum that Φ (k) representative is rebuild,

The plural interference spectrum signal that representative is rebuild, Γ represents the auto-correlation function of light source, the time delay coordinate that the τ representative is rebuild, τ _rRepresent the time delay of reference arm, τ _nThe time delay of each layer of representative sample.

The step signal of demonstrating in the foregoing description carries out synthetic situation, and each cycle that is used for the phase modulation step signal comprises five kinds of different phase states, utilizes the phase multiplexing acquisition technique of this method to obtain five groups of interference spectrum signal subclass I ⁽¹⁾(k), I ⁽²⁾(k), I ⁽³⁾(k), I ⁽⁴⁾(k), I ⁽⁵⁾(k) come reconstruct complex interference spectrum signal to recover gamut OCT image.In the process of utilizing the actual enforcement of this method; Can adopt each cycle by three kinds of phase states or four kinds of staircase waveform phase modulated signals that phase state is formed equally; Phase multiplexing acquisition technique with this method obtains corresponding three groups or four groups of interference spectrum signal subclass; Algorithm through based on method of least square gets final product reconstruct complex interference spectrum signal, recovers gamut OCT image.

This utility model obtains several groups of synthetic interference spectrum signals of out of phase by same group of interference spectrum data that collect, and has realized that the position of interference spectrum is mutually multiplexing.Through these several groups of interference spectrum signal reconstruction plural number interference spectrum signals, implement image reconstruction based on FFT, guaranteed effectively to realize the gamut imaging of frequency sweep optical coherence tomography in the highest zero light path zone of sensitivity.

Claims (2)

1. one kind based on the mutually multiplexing gamut frequency sweep OCT imaging system in position; Comprise light source, broadband optical fiber coupler, sample arm, reference arm and OCT interference spectrum signal detecting device; The low-coherent light that sends from light source gets into broadband optical fiber coupler; After beam split, get into reference arm and sample arm respectively, the interference spectrum signal of generation gets into OCT interference spectrum signal detecting device and gathers; It is characterized in that: said light source is the low-coherent light that scanning light source (1) sends, and gets into first end of first broadband optical fiber coupler; The light of second end of first broadband optical fiber coupler is incident upon on the sample (7) through sample arm circulator (3); The light of the 3rd end of first broadband optical fiber coupler gets into the electro-optic phase modulator (8) of reference arm; At second broadband optical fiber coupler and formation OCT interference spectrum signal after the sample light that sample arm is returned converges; Survey through balance detection device (9) through second broadband optical fiber coupler the 3rd end and the 4th end, after the data collecting card (11) in the computer (10) gather; The triggering signal of scanning light source (1) output is divided into two-way, and one road and function generator (12) connects, and produces phase modulated signal and is connected with electrooptic modulator (8), realizes reference light is introduced additive phase; Another road directly is connected with data collecting card (11), is used to gather the interference spectrum data; The data that data collecting card (11) collects input to computer (10) and carry out date processing and image reconstruction; Data collecting card (11) produces one road galvanometer driving signal and is connected with sample arm scanning galvanometer (5), realizes the transversal scanning to sample.

2. according to claim 1 a kind of it is characterized in that: described sample arm comprises sample arm circulator (3) based on the mutually multiplexing gamut frequency sweep OCT imaging system in position, sample arm collimating mirror (4), sample arm scanning galvanometer (5) and sample arm condenser lens (6); The light process sample arm circulator (3) of second end of first broadband optical fiber coupler, sample arm collimating mirror (4), sample arm scanning galvanometer (5), sample arm condenser lens (6) are incident upon on the sample (7), and the former road of reflected light is back to second broadband optical fiber coupler.

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