CN2916623Y - Frequency domain optical coherence tomography device for full-depth detection - Google Patents

一种全深度探测的频域光学相干层析成像装置，包括低相干光源，在该低相干光源的照明方向上顺次放置准直扩束器、迈克尔逊干涉仪，该迈克尔逊干涉仪的分光器将入射光分为探测臂光路和参考臂光路，参考臂光路的末端为参考反射镜，探测臂光路的末端为被测样品，被测样品放置在一个三维精密平移台上，迈克尔逊干涉仪输出端连接一光谱仪，该光谱仪通过图像采集卡和计算机连接，该装置的特点是所述的参考反射镜连接一正弦相位调制装置。本实用新型与现有技术相比具有抗环境干扰能力强，对光源波长无关和系统结构简单的优点。

A frequency domain optical coherence tomography device for full depth detection includes a low coherence light source, a collimating beam expander and a Michelson interferometer are sequentially placed in the illumination direction of the low coherence light source, the beam splitter of the Michelson interferometer divides the incident light into a detection arm optical path and a reference arm optical path, the end of the reference arm optical path is a reference reflector, the end of the detection arm optical path is a sample to be measured, the sample to be measured is placed on a three-dimensional precision translation stage, the output end of the Michelson interferometer is connected to a spectrometer, the spectrometer is connected to a computer through an image acquisition card, and the device is characterized in that the reference reflector is connected to a sinusoidal phase modulation device. Compared with the prior art, the utility model has the advantages of strong anti-environmental interference ability, independence to the wavelength of the light source and simple system structure.

全深度探测的频域光学相干层析成像装置Frequency domain optical coherence tomography device for full depth detection

技术领域technical field

本实用新型涉及光学相干层析成像(Optical Coherence Tomography，以下简称OCT)，特别是一种利用正弦相位调制技术重建低相干光频域干涉复信号(complex interferometric signal)的全深度(full range)探测的频域光学相干层析成像(Fourier Domain Optical Coherence Tomography，简称FD-OCT)的装置。The utility model relates to optical coherence tomography (Optical Coherence Tomography, hereinafter referred to as OCT), in particular to a full-range detection using sinusoidal phase modulation technology to reconstruct a low-coherence optical frequency domain interference complex signal (complex interferometric signal) The frequency-domain optical coherence tomography (Fourier Domain Optical Coherence Tomography, referred to as FD-OCT) device.

背景技术Background technique

光学相干层析成像(OCT)基于低相干光干涉(Low CoherenceInterferometry，简称LCI)原理，能对散射介质如生物组织内部几个毫米深度范围内的微小结构进行非侵入的实时、在体的层析成像，其深度分辨率可以达到几个微米。自从1991年Huang等人第一次提出OCT概念，并将其运用到人眼视网膜和冠状动脉壁的层析成像以来，OCT技术得到了广泛研究和应用，如用于眼科、皮肤科的疾病诊断以及癌症早期诊断等，成为一种在生物成像和医学病理检测领域中具有重要应用前景的光学成像技术。Optical coherence tomography (OCT) is based on the principle of Low Coherence Interferometry (LCI), which can perform non-invasive, real-time, in-vivo tomography on tiny structures within a few millimeters of depth in scattering media such as biological tissues. imaging with a depth resolution of several microns. Since Huang et al first proposed the concept of OCT in 1991 and applied it to the tomographic imaging of the human eye retina and coronary artery wall, OCT technology has been widely studied and applied, such as for the diagnosis of diseases in ophthalmology and dermatology. As well as early diagnosis of cancer, etc., it has become an optical imaging technology with important application prospects in the fields of biological imaging and medical pathological detection.

频域光学相干层析成像系统(FD-OCT)，是一种最近发展起来的新型OCT系统，相对早先提出的时域光学相干层析成像系统(Time Domain OpticalCoherence Tomography，简称TD-OCT)，具有无需深度方向扫描、成像速度快和探测灵敏度高的优势，更适合生物组织的实时成像。Frequency Domain Optical Coherence Tomography (FD-OCT) is a recently developed new OCT system. Compared with Time Domain Optical Coherence Tomography (TD-OCT) proposed earlier, it has It has the advantages of no need for scanning in the depth direction, fast imaging speed and high detection sensitivity, and is more suitable for real-time imaging of biological tissues.

频域光学相干层析成像系统主要由低相干光源(宽光谱光源)、迈克尔逊干涉仪和光谱仪(核心元件为分光光栅、聚焦透镜和CCD探测器)三部分组成。FD-OCT基于被测物体内各层光反射或背向散射界面的深度对应频域干涉条纹的不同频率的原理，将低相干光源发出的宽光谱光经迈克尔逊干涉仪产生的干涉信号送入光谱仪(其中被测物体置于干涉仪的探测臂末端)，利用光谱仪分光特性，获取干涉信号随波长(λ)变化的强度分布，然后对其做倒数变换后得到干涉信号在频域(v域，v＝1/λ)的强度分布，即频域干涉条纹，对该信号作逆傅立叶变换得到被测物体沿探测光光轴方向的深度分辨的光反射或背向散射率分布，即层析图。但FD-OCT获得的层析图中包含着若干寄生像，限制了FD-OCT的应用。这些寄生像分别是：直流背景(DC term)，自相干噪声(autocorrelation term)和复共轭镜像(complex conjugated term ormirror image term)。其中，直流背景和自相干噪声的存在大幅度降低了FD-OCT的信噪比，影响了成像质量，而复共轭镜像的存在，使FD-OCT无法区分正负光程差(探测光路相对参考光路的光程差)，故测量时被测物体只能置于零光程差位置的一侧，导致有效深度探测范围减少了一半。The frequency-domain optical coherence tomography system is mainly composed of three parts: low-coherence light source (broad-spectrum light source), Michelson interferometer and spectrometer (the core components are spectroscopic grating, focusing lens and CCD detector). FD-OCT is based on the principle that the depth of each layer of light reflection or backscattering interface in the measured object corresponds to the different frequencies of the frequency-domain interference fringes, and the wide-spectrum light emitted by the low-coherence light source is sent into the The spectrometer (in which the measured object is placed at the end of the detection arm of the interferometer), uses the spectral characteristics of the spectrometer to obtain the intensity distribution of the interference signal changing with the wavelength (λ), and then performs an inverse transformation on it to obtain the interference signal in the frequency domain (v domain , v=1/λ), i.e. frequency-domain interference fringes, the inverse Fourier transform is performed on the signal to obtain the depth-resolved light reflection or backscattering rate distribution of the measured object along the optical axis of the probe light, i.e. tomography picture. However, the tomogram obtained by FD-OCT contains several parasitic images, which limits the application of FD-OCT. These spurious images are: DC background (DC term), autocorrelation noise (autocorrelation term) and complex conjugated term (complex conjugated term or mirror image term). Among them, the existence of DC background and self-coherence noise greatly reduces the signal-to-noise ratio of FD-OCT, which affects the imaging quality, and the existence of complex conjugate mirrors makes it impossible for FD-OCT to distinguish between positive and negative optical path differences (the detection optical path is relatively The optical path difference of the reference optical path), so the measured object can only be placed on the side of the zero optical path difference position during measurement, resulting in a reduction of the effective depth detection range by half.

为了消除FD-OCT重建的层析图中存在的复共轭镜像、自相干噪声和直流背景这些寄生像成分，A.F.Fercher等人将步进相移技术(phase shifting)引入到FD-OCT中通过重建低相干光频域干涉信号的复振幅，消除了以上寄生像，实现了全深度探测的FD-OCT(参见在先技术[1]，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，“Full range complex spectral opticalcoherence tomography technique in eye imaging”，Optics Letters，Vol.27，No.16，1415-1417，2002)。然而，步进相移算法要求每步相移准确地为一个常量，如五步相移法要求每步相移为π/2。由于FD-OCT采用的是宽光谱光源，对于不同波长，通过改变参考臂的光程引入的步进相移量会发生变化，即相移量依赖于波长，不再是一个恒定的常量，这会带来测量误差。同时，外界的微小扰动也会引起步进相移的误差，因此该系统抗干扰能力比较差。Joseph A.Izatt等人提出了一种基于N×N(N≥3)光纤耦合器的方法(参见在先技术[2]，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)。虽然可以实现瞬时或同时相移，对环境振动不敏感，但由于光纤耦合器的分束比对环境温度变化敏感，导致相移量会随温度变化产生飘移，而且该系统需要两个以上的探测器，需要保证所有探测器采集信号的同步性，系统复杂。In order to eliminate the complex conjugate image, self-coherent noise and DC background in the tomogram of FD-OCT reconstruction, A.F.Fercher et al. introduced the phase shifting technology into FD-OCT by Reconstructing the complex amplitude of the low-coherence optical frequency domain interference signal eliminates the above spurious images and realizes FD-OCT with full depth detection (see prior art [1], A.F.Fercher, R.Leitgeb, C.K.Hitzenberger, H.Sattmann and M.Wojtkowski, "Complex Spectral Interferometry OCT", Proc.SPIE, Vol 3654, 173-178, 1999; M.Wojtkowski, A.Kowalczyk, R.Leitgeb and A.F.Fercher, "Full range complex spectral optical coherence tomography technique imique agin eye" , Optics Letters, Vol.27, No.16, 1415-1417, 2002). However, the step-by-step phase-shift algorithm requires each step of the phase shift to be exactly a constant, such as the five-step phase-shift method requires each step of the phase shift to be π/2. Since FD-OCT uses a wide-spectrum light source, for different wavelengths, the step-by-step phase shift introduced by changing the optical path of the reference arm will change, that is, the phase shift depends on the wavelength and is no longer a constant. Will cause measurement error. At the same time, small external disturbances will also cause stepping phase shift errors, so the system's anti-interference ability is relatively poor. Joseph A.Izatt et al proposed a method based on N×N (N≥3) fiber couplers (see prior art [2], M.V.Sarunic, M.A.Choma, Changhuei Yang, J.A.Izatt, "Instantaneouscomplex conjugated resolved spectral domain and swept-source OCT using 3×3 fiber couplers", Optics Express, Vol.13, No.3, 957-967, 2005). Although instantaneous or simultaneous phase shift can be achieved, it is not sensitive to environmental vibrations, but because the splitting ratio of the fiber coupler is sensitive to changes in ambient temperature, the amount of phase shift will drift with temperature changes, and the system requires more than two probes It is necessary to ensure the synchronization of signals collected by all detectors, and the system is complex.

由以上分析看出，目前还没有一种具有抗环境干扰能力强，与光源波长无关，系统结构简单，而且又能够实现全深度探测的频域光学相干层析成像技术。From the above analysis, it can be seen that there is no frequency-domain optical coherence tomography technology that has strong anti-environmental interference ability, has nothing to do with the wavelength of the light source, has a simple system structure, and can realize full-depth detection.

发明内容Contents of the invention

本实用新型的目的是为了克服上述在先技术的不足，提供一种全深度探测的频域光学相干层析成像装置，本实用新型既能够实现全深度探测的频域光学相干层析成像，又具有抗环境干扰能力强，与光源波长无关，系统结构简单的特点。The purpose of this utility model is to overcome the shortcomings of the above-mentioned prior art and provide a frequency-domain optical coherence tomography device for full-depth detection. The utility model can realize frequency-domain optical coherence tomography for full-depth detection and It has strong anti-environmental interference ability, has nothing to do with the wavelength of the light source, and has the characteristics of simple system structure.

本实用新型的技术原理是：The technical principle of the utility model is:

一种全深度探测的频域光学相干层析成像的方法，它是通过一正弦相位调制装置带动迈克尔逊干涉仪参考臂中的参考反射镜作正弦振动，生成一个随时间变化的正弦相位调制的低相干光频域干涉信号，然后对其作傅立叶变换，滤出其频谱的一倍频和二倍频频谱，经计算得到低相干光频域干涉复信号的实部和虚部，将实部和虚部组合得到低相干光频域按波长分布的干涉复信号，然后对该干涉复信号进行倒数变换，得到按波长倒数分布的干涉复信号，再对该干涉复信号作逆傅立叶变换，获得被测物体层析图。A frequency-domain optical coherence tomography method for full-depth detection, which uses a sinusoidal phase modulation device to drive the reference mirror in the reference arm of the Michelson interferometer to vibrate sinusoidally to generate a time-varying sinusoidal phase modulation The low-coherence optical frequency domain interference signal is then Fourier transformed to filter out the one-octave and two-octave frequency spectra of its spectrum. After calculation, the real part and imaginary part of the low-coherence optical frequency domain interference signal are obtained. The real part Combined with the imaginary part to obtain the interference complex signal distributed according to the wavelength in the low-coherence optical frequency domain, and then perform reciprocal transformation on the interference complex signal to obtain the interference complex signal distributed according to the reciprocal wavelength, and then inverse Fourier transform the interference complex signal to obtain The chromatogram of the measured object.

全深度探测的频域光学相干层析成像的方法的特点是将正弦相位调制技术用于全深度探测的频域光学相干层析成像的方法，利用正弦相位调制技术重建低相干光频域干涉复信号，以消除FD-OCT成像中存在的复共轭镜像、直流背景和自相干噪声三种寄生像，提高系统信噪比，实现全深度探测的频域光学相干层析成像。The method of frequency-domain optical coherence tomography for full-depth detection is characterized by applying sinusoidal phase modulation technology to the method of frequency-domain optical coherence tomography for full-depth detection, and using sinusoidal phase modulation technology to reconstruct low-coherence optical frequency-domain interference complex Signal to eliminate the complex conjugate image, DC background and self-coherence noise in FD-OCT imaging, improve the signal-to-noise ratio of the system, and realize frequency-domain optical coherence tomography with full depth detection.

正弦相位调制技术是一种抗干扰能力强，调制简单的相位调制技术，常用于物体表面形貌和微位移测量的激光干涉仪中(见在先技术[3]，OsamiSasaki and Hirokazu Okazaki，“Sinusoidal phase modulating interferometry forsurface profile measurement”，Applied Optics，Vol.25，No.18，3137-3140，1986)。Sinusoidal phase modulation technology is a phase modulation technology with strong anti-interference ability and simple modulation, which is often used in laser interferometers for object surface topography and micro-displacement measurement (see prior art [3], OsamiSasaki and Hirokazu Okazaki, "Sinusoidal phase modulating interferometry for surface profile measurement", Applied Optics, Vol.25, No.18, 3137-3140, 1986).

全深度探测的频域光学相干层析成像方法的具体步骤如下：The specific steps of the frequency-domain optical coherence tomography method for full-depth detection are as follows:

①通过正弦相位调制装置带动迈克尔逊干涉仪参考臂中的参考反射镜作正弦振动，引入一个调制频率为f_c的正弦相位调制，如(1)式所示：① Drive the reference mirror in the reference arm of the Michelson interferometer to vibrate sinusoidally through the sinusoidal phase modulation device, and introduce a sinusoidal phase modulation with a modulation frequency _fc , as shown in formula (1):

Z(t)＝acos(2πf_ct+θ)，                                (1)Z(t)=acos(2πf _c t+θ), (1)

其中：a为振幅，θ为初始相位，f_c为调制频率。Among them: a is the amplitude, θ is the initial phase, f _c is the modulation frequency.

光谱仪记录的对应宽光谱光源每个波长的干涉信号，如(2)式所示：The interference signal corresponding to each wavelength of the wide-spectrum light source recorded by the spectrometer is shown in formula (2):

GG (( λλ )) == GG rrrr (( λλ )) ++ ΣΣ nno GG nnn (( λλ ))

++ 22 ReRe {{ ΣΣ nno ≠≠ mm GG nmnm (( λλ )) expexp [[ -- jj 22 ππ 11 λλ (( zz nno -- zz mm )) ]] }} -- -- -- (( 22 ))

++ 22 ReRe {{ ΣΣ nno GG nrnr (( λλ )) expexp [[ -- jj 22 ππ 11 λλ (( zz nno -- zz rr )) ]] }} ,,

其中：G代表光谱密度函数，Re代表取复数的实部，z_n代表被测样品第n层反射或散射界面的光程，z_r代表参考反射镜位置的光程。Among them: G represents the spectral density function, Re represents the real part of the complex number, z _n represents the optical path of the nth reflection or scattering interface of the measured sample, and z _r represents the optical path of the reference mirror position.

(2)式中前两项分别为参考反射镜的反射光的自谱密度函数和被测样品内各层深度处反射或背向散射光的自谱密度函数叠加项，第三项为被测样品内不同深度处反射或背向散射光的互谱密度函数叠加项，第四项为参考反射镜反射光和被测样品内各层深度处反射或背向散射光的互谱密度函数叠加项。The first two items in the formula (2) are the self-spectral density function of the reflected light of the reference mirror and the self-spectral density function superposition of the reflected or backscattered light at each depth of the sample under test, and the third term is the measured The cross-spectral density function superposition item of reflected or backscattered light at different depths in the sample, and the fourth item is the cross-spectral density function superposition item of the reflected light of the reference mirror and the reflected or backscattered light at each depth of the sample under test .

生成一个随时间变化的正弦相位调制干涉信号，如(3)式所示：Generate a time-varying sinusoidal phase modulation interference signal, as shown in equation (3):

GG (( λλ ,, tt )) == GG 00 ++ 22 ReRe {{ ΣΣ nno GG nrnr (( λλ )) expexp [[ -- jj 22 ππ 11 λλ [[ (( zz nno -- zz rr )) ++ 22 ZZ (( tt )) ]] ]] }} -- -- -- (( 33 ))

其中 G 0 = G rr ( λ ) + Σ n G nn ( λ ) + 2 Re { Σ n ≠ m G nm ( λ ) exp [ - j 2 π 1 λ ( z n - z m ) ] } ，不受参考反射镜振动的调制，为一个不随时间变化的直流分量。然后对其做傅立叶变换得到(4)式，in G 0 = G rr ( λ ) + Σ no G n ( λ ) + 2 Re { Σ no ≠ m G nm ( λ ) exp [ - j 2 π 1 λ ( z no - z m ) ] } , which is not modulated by the vibration of the reference mirror, is a time-invariant DC component. Then perform Fourier transform on it to obtain formula (4),

2 Σ n G nr ( λ ) sin [ 2 π 1 λ ( z n - z r ) ] × [ Σ m = - ∞ ∞ ( - 1 ) m A 2 m - 1 σ [ ω - ( 2 m - 1 ) ω c ] ] , (4) 2 Σ no G nr ( λ ) sin [ 2 π 1 λ ( z no - z r ) ] × [ Σ m = - ∞ ∞ ( - 1 ) m A 2 m - 1 σ [ ω - ( 2 m - 1 ) ω c ] ] , (4)

其中A_m＝J_m(d)exp(j_mθ)，J_m是m阶贝塞尔函数，σ是狄拉克函数， d = 4 π α λ , ω＝2πf，ω_c＝2πf_c。Wherein A _m =J _m (d)exp(j _m θ), J _m is the m-order Bessel function, σ is the Dirac function, d = 4 π α λ , ω=2πf, ω _c =2πf _c .

从其频谱中取出一倍频F(f_c)和二倍频F(2f_c)频谱，通过(5)式计算得到干涉复信号的实部和虚部，Take the frequency spectrum of double frequency F(f _c ) and frequency double frequency F(2f _c ) from its spectrum, and calculate the real part and imaginary part of the interference complex signal through formula (5),

22 ΣΣ nno GG nrnr (( λλ )) sinsin [[ 22 ππ 11 λλ (( zz nno -- zz rr )) ]] == -- ReRe {{ Ff (( ωω CC )) }} // JJ 11 (( dd )) coscos (( θθ )) ,,

2 Σ n G nr ( λ ) cos [ 2 π 1 λ ( z n - z r ) ] = - Re { F ( 2 ω c ) } / J 2 ( d ) cos ( 2 θ ) , (5) 2 Σ no G nr ( λ ) cos [ 2 π 1 λ ( z no - z r ) ] = - Re { f ( 2 ω c ) } / J 2 ( d ) cos ( 2 θ ) , (5)

其中sin项对应干涉复信号的虚部，cos项对应干涉复信号的实部。d，θ为事先确定量，或由F(ω_c)和F(3ω_c)求得(见在先技术[3])。将实部、虚部组合得到干涉信号的复振幅如(6)式所示。其中f_c的取值由正弦相位调制频率决定，与光源波长无关。Among them, the sin term corresponds to the imaginary part of the interference complex signal, and the cos term corresponds to the real part of the interference complex signal. d, θ are predetermined quantities, or obtained from F(ω _c ) and F(3ω _c ) (see prior art [3]). The complex amplitude of the interference signal is obtained by combining the real part and the imaginary part, as shown in (6). Among them, the value of _fc is determined by the sinusoidal phase modulation frequency and has nothing to do with the wavelength of the light source.

GG ^^ (( λλ )) == 22 ΣΣ nno GG nrnr (( λλ )) coscos [[ 22 ππ 11 λλ (( zz nno -- zz rr )) ]] -- jj 22 ΣΣ nno GG nrnr (( λλ )) sinsin [[ 22 ππ 11 λλ (( zz nno -- zz rr )) ]]

= 2 Σ n G nr ( λ ) exp { - j [ 2 π 1 λ ( z n - z r ) ] } , (6) = 2 Σ no G nr ( λ ) exp { - j [ 2 π 1 λ ( z no - z r ) ] } , (6)

②对步骤①所得的按波长(λ)分布的干涉复信号(6)，做倒数变换，转换成按波长倒数(v，v＝1/λ)分布的干涉复信号，如(7)式所示：2. For the interference complex signal (6) distributed by the wavelength (λ) obtained in step 1, do reciprocal transformation, and convert it into the interference complex signal distributed by the wavelength reciprocal (v, v=1/λ), as shown in (7) formula Show:

GG ^^ (( νν )) == 22 ΣΣ nno GG nrnr (( νν )) expexp {{ -- jj [([( 22 πνπν (( zz nno -- zz rr )) ]] }} ,, -- -- -- (( 77 ))

其中 ν = 1 λ . in ν = 1 λ .

③对步骤②得到的按波长倒数(v，v＝1/λ)分布的干涉复信号作逆傅立叶变换得到被测物体的层析图如(8)式所示：3. the interference complex signal distributed by the reciprocal wavelength (v, v=1/λ) to step 2. obtained is done inverse Fourier transform to obtain the tomogram of the measured object as shown in (8) formula:

其中：Γ_nr为一阶互相关函数，其包含着被测物体的沿探测光光轴方向的深度分辨的光反射或背向散射信息，即层析图。Among them: Γ _nr is the first-order cross-correlation function, which contains the depth-resolved light reflection or backscattering information of the measured object along the optical axis of the probe light, that is, the tomogram.

本实用新型方法与不采用正弦相位调制，直接对(2)式作逆傅立叶变换得到的层析图(9)式相比，消除了FD-OCT成像中存在的复共轭镜像(I₂)、直流背景(I₀)和自相干噪声(I₁)三种寄生像，提高了信噪比，实现了全深度探测的频域光学相干层析成像。Compared with the tomogram (9) formula obtained by directly doing inverse Fourier transform to (2) formula without using sinusoidal phase modulation, the method of the utility model eliminates the complex conjugate image (I ₂ ) existing in FD-OCT imaging , DC background (I ₀ ) and self-coherent noise (I ₁ ) three kinds of spurious images, which improve the signal-to-noise ratio and realize the frequency-domain optical coherence tomography of full-depth detection.

== ΓΓ rrrr (( zz )) ++ ΣΣ nno ΓΓ nnn (( zz )) ++ ΣΣ nno ≠≠ mm ΓΓ nmnm [[ zz ++ (( zz nno -- zz mm )) ]] ++ ΣΣ nno ≠≠ mm ΓΓ nmnm [[ zz -- (( zz nno -- zz mm )) ]]

++ ΣΣ nno ΓΓ nrnr [[ zz ++ (( zz nno -- zz rr )) ]] ++ ΣΣ nno ΓΓ nrnr [[ zz -- (( zz nno -- zz rr )) ]]

== II 00 ++ II 11 ++ II 22 ++ ΣΣ nno ΓΓ nrnr [[ zz -- (( zz nno -- zz rr )) ]] ,,

其中： I 0 = Γ rr ( z ) + Σ n Γ nn ( z ) 为直流背景分量，in: I 0 = Γ rr ( z ) + Σ no Γ n ( z ) is the DC background component,

I 1 = Σ n ≠ m Γ nm [ z + ( z n - z m ) ] + Σ n ≠ m Γ nm [ z - ( z n - z m ) ] 为自相干噪声分量， I 1 = Σ no ≠ m Γ nm [ z + ( z no - z m ) ] + Σ no ≠ m Γ nm [ z - ( z no - z m ) ] is the self-coherent noise component,

I 2 = Σ n Γ nr [ z + ( z n - z r ) ] 为复共轭镜像分量。 I 2 = Σ no Γ nr [ z + ( z no - z r ) ] is the complex conjugate mirror component.

本实用新型的技术解决方案如下：The technical solution of the utility model is as follows:

一种全深度探测的频域光学相干层析成像装置，包括低相干光源，在该低相干光源的照明方向上顺次放置准直扩束器、迈克尔逊干涉仪，该迈克尔逊干涉仪的分光器将入射光分为探测臂光路和参考臂光路，参考臂光路的末端为参考反射镜，探测臂光路的末端为被测样品，被测样品放置在一个三维精密平移台上；迈克尔逊干涉仪输出端连接一光谱仪，该光谱仪通过图像采集卡和计算机连接，该装置的特点是所述的参考反射镜连接一正弦相位调制装置，该正弦相位调制装置驱动所述的参考反射镜作正弦振动。A frequency-domain optical coherence tomography device for full-depth detection, including a low-coherence light source, a collimated beam expander and a Michelson interferometer are sequentially placed in the illumination direction of the low-coherence light source, and the light splitter of the Michelson interferometer The device divides the incident light into the detection arm optical path and the reference arm optical path. The end of the reference arm optical path is the reference mirror, and the end of the detection arm optical path is the measured sample. The measured sample is placed on a three-dimensional precision translation stage; Michelson interferometer The output end is connected with a spectrometer, and the spectrometer is connected with a computer through an image acquisition card. The feature of the device is that the reference mirror is connected with a sinusoidal phase modulation device, and the sinusoidal phase modulation device drives the reference mirror to perform sinusoidal vibration.

所述的正弦相位调制装置由正弦函数电信号发生器和固定在所述的参考反射镜上的压电陶瓷驱动器组成，所述的正弦函数电信号发生器发出的时间正弦函数驱动电信号通过压电陶瓷驱动器驱动所述的参考反射镜作正弦振动。The sinusoidal phase modulation device is composed of a sinusoidal function electrical signal generator and a piezoelectric ceramic driver fixed on the reference mirror, and the time sinusoidal function driving electrical signal sent by the sinusoidal function electrical signal generator passes through the piezoelectric ceramic driver. An electroceramic driver drives the reference mirror to vibrate sinusoidally.

所述的低相干光源为宽光谱光源，其光谱典型半宽度为几十个nm到几百个nm，如发光二极管(LED)或超辐射发光二极管(SLD)或飞秒激光器等。The low-coherence light source is a broad-spectrum light source, and its typical half-width of the spectrum is tens to hundreds of nm, such as light-emitting diodes (LEDs) or superluminescent light-emitting diodes (SLDs) or femtosecond lasers.

所述的准直扩束器由物镜和若干透镜组成。The collimating beam expander is composed of an objective lens and several lenses.

所述的迈克逊干涉仪，其特征在于具有两个接近等光程的干涉光路，一路为参考臂光路，另一路为探测臂光路。它可以是体光学系统，如由分光棱镜分光构成参考臂和探测臂两路光路；也可以是光纤光学系统，如由2×2光纤耦合器的两个输出光纤光路分别作为参考臂和探测臂光路。The Michelson interferometer is characterized in that it has two interference optical paths close to equal optical paths, one is the optical path of the reference arm, and the other is the optical path of the detection arm. It can be a bulk optical system, such as the two optical paths of the reference arm and the detection arm composed of beam splitting prisms; it can also be a fiber optic system, such as the two output fiber optical paths of the 2×2 fiber coupler as the reference arm and the detection arm respectively light path.

所述的光谱仪由分光光栅，聚焦透镜和光电探测器阵列组成。The spectrometer is composed of a spectroscopic grating, a focusing lens and a photodetector array.

所述的光电探测器阵列是CCD或光电二极管阵列或其他具有光电信号转换功能的探测器阵列。The photodetector array is a CCD or photodiode array or other detector arrays with photoelectric signal conversion function.

所述的三维精密平移台，可以沿三个相互垂直方向作微米级精度的平移。The three-dimensional precision translation platform can perform translation with micron-level precision along three mutually perpendicular directions.

该系统的工作情况如下：The system works as follows:

低相干光源发出的光经准直扩束器准直扩束后，在迈克尔逊干涉仪中被分成两束，一束光经参考臂入射到参考反射镜表面，另外一束光经探测臂入射到被测样品内，从参考反射镜表面反射回来的光和从被测样品内不同深度处反射或背向散射回来的光被收集并沿参考臂和探测臂返回，在迈克逊干涉仪中汇合发生干涉，再送入光谱仪分光并记录，经图像采集卡数模转换后送入计算机进行数据处理，得到被测样品沿探测光光轴方向的层析图。通过三维精密平移台对被测样品沿与探测光光轴方向垂直的平面做横向扫描，得到被测样品的二维或三维层析图。其中正弦相位调制装置与迈克尔逊干涉仪参考臂中的参考反射镜相连，该装置在一个正弦变化的电信号驱动下，带动参考反射镜作正弦振动，在光谱仪采集的干涉信号中引入正弦相位调制。The light emitted by the low-coherence light source is collimated and expanded by the collimator beam expander, and then divided into two beams in the Michelson interferometer. One beam is incident on the surface of the reference mirror through the reference arm, and the other beam is incident on the detection arm. Into the measured sample, the light reflected from the surface of the reference mirror and the light reflected or backscattered from different depths in the measured sample are collected and returned along the reference arm and the detection arm, and merged in the Michelson interferometer Interference occurs, and then sent to the spectrometer to split and record. After digital-to-analog conversion by the image acquisition card, it is sent to the computer for data processing, and the tomogram of the measured sample along the optical axis of the probe light is obtained. Through the three-dimensional precision translation stage, the measured sample is scanned horizontally along the plane perpendicular to the optical axis of the probe light, and the two-dimensional or three-dimensional tomogram of the measured sample is obtained. The sinusoidal phase modulation device is connected to the reference mirror in the reference arm of the Michelson interferometer. Driven by a sinusoidally changing electrical signal, the device drives the reference mirror to vibrate sinusoidally, and introduces sinusoidal phase modulation into the interference signal collected by the spectrometer. .

本实用新型的技术效果是：The technical effect of the utility model is:

与在先技术1相比，本实用新型由于采用正弦相位调制技术，通过对正弦相位调制的频域干涉信号作傅立叶变换，取出其一倍频和二倍频的频谱信息重建低相干光的频域干涉复信号，对环境噪声不敏感，故抗环境干扰能力强，而且一倍频和二倍频的取值由正弦相位调制频率决定，不随波长变化而改变，故对光源波长无关。Compared with the prior art 1, the utility model adopts the sinusoidal phase modulation technology, by performing Fourier transform on the frequency-domain interference signal modulated by the sinusoidal phase, and extracting the spectrum information of its double frequency and double frequency to reconstruct the frequency of low coherent light. Domain interference complex signal is not sensitive to environmental noise, so it has strong anti-environmental interference ability, and the value of double frequency and double frequency is determined by the sinusoidal phase modulation frequency, which does not change with the wavelength change, so it has nothing to do with the wavelength of the light source.

与在先技术2相比，本实用新型只需一个探测器，避免了多探测器的同步性校准，系统结构简单。Compared with the prior art 2, the utility model only needs one detector, avoids the synchronous calibration of multiple detectors, and has a simple system structure.

附图说明Description of drawings

图1为本实用新型全深度探测的频域光学相干层析成像装置的体光学系统结构示意图。FIG. 1 is a schematic structural diagram of the volume optical system of the frequency-domain optical coherence tomography imaging device for full-depth detection of the present invention.

具体实施方式Detailed ways

下面结合实施例和附图对本实用新型作进一步说明，但不应以此限制本实用新型的保护范围。Below in conjunction with embodiment and accompanying drawing, the utility model will be further described, but should not limit the protection scope of the utility model with this.

请参阅图1，图1为本实用新型全深度探测的频域光学相干层析成像装置实施例--体光学系统的结构示意图。由图可见，本实用新型全深度探测的频域光学相干层析成像装置，包括低相干光源1，在该低相干光源1的照明方向上顺次放置准直扩束器2、迈克尔逊干涉仪3，该迈克尔逊干涉仪3的分光器31将入射光分为探测臂光路34和参考臂光路32，参考臂光路的末端为参考反射镜33，探测臂光路的末端为被测样品35，被测样品35放置在一个三维精密平移台(图中未示)上；迈克尔逊干涉仪3输出端连接一光谱仪5，该光谱仪5通过图像采集卡6和计算机7连接，其特征在于所述的参考反射镜33连接一正弦相位调制装置4，所述的正弦相位调制装置4由正弦函数电信号发生器和固定在所述的参考反射镜33上的压电陶瓷驱动器组成，所述的正弦函数电信号发生器发出的时间正弦函数驱动电信号通过压电陶瓷驱动器驱动所述的参考反射镜33作正弦振动。Please refer to FIG. 1 . FIG. 1 is a schematic structural diagram of a volume optical system, an embodiment of a frequency-domain optical coherence tomography device for full-depth detection of the present invention. It can be seen from the figure that the frequency-domain optical coherence tomography device for full-depth detection of the utility model includes a low-coherence light source 1, and a collimating beam expander 2 and a Michelson interferometer are placed in sequence in the illumination direction of the low-coherence light source 1 3. The beam splitter 31 of the Michelson interferometer 3 divides the incident light into a detection arm optical path 34 and a reference arm optical path 32, the end of the reference arm optical path is a reference mirror 33, and the end of the detection arm optical path is a measured sample 35, which is The test sample 35 is placed on a three-dimensional precision translation stage (not shown in the figure); the output end of the Michelson interferometer 3 is connected to a spectrometer 5, and the spectrometer 5 is connected with a computer 7 through an image acquisition card 6, and is characterized in that the reference Mirror 33 is connected with a sinusoidal phase modulation device 4, and described sinusoidal phase modulation device 4 is made up of a sinusoidal function electrical signal generator and a piezoelectric ceramic driver fixed on the reference mirror 33, and the sinusoidal function electrical signal The time sinusoidal function driving electrical signal sent by the signal generator drives the reference mirror 33 to vibrate sinusoidally through the piezoelectric ceramic driver.

低相干光源1发出的宽光谱光经准直扩束器2准直扩束后，在迈克尔逊干涉仪3中被分光棱镜31分成两束，一束经参考臂光路32入射到一个参考反射镜33表面，另一束经探测臂光路34入射到放置在三维精密平移台上的被测样品35内，从参考反射镜33表面反射回来的光和从被测样品35内不同深度处反射或背向散射回来的光被收集并沿参考臂光路32和探测臂光路34返回，在迈克逊干涉仪3中31处汇合发生干涉，再送入光谱仪5被光栅51分光，经会聚透镜52，成像在CCD探测器53，转换成电信号后，经图像采集卡6数模转换送入计算机7进行数据处理，得到被测样品35沿探测光光轴方向的层析图。通过三维精密平移台(图中未示)对被测样品35沿与探测光光轴方向垂直的平面做横向扫描，得到被测样品35的二维或三维层析图。其中正弦相位调制装置4与迈克尔逊干涉仪参考臂中的参考反射镜33相连，该装置在正弦变化电信号的驱动下，带动参考反射镜作正弦振动，在光谱仪采集的干涉信号中引入正弦相位调制。The wide-spectrum light emitted by the low-coherence light source 1 is collimated and expanded by the collimator beam expander 2, and then split into two beams by the beam splitter 31 in the Michelson interferometer 3, and one beam enters a reference mirror through the reference arm optical path 32 33 surface, another beam is incident on the measured sample 35 placed on the three-dimensional precision translation stage through the detection arm optical path 34, the light reflected from the surface of the reference mirror 33 and the reflection or backlight from different depths in the measured sample 35 The light scattered back is collected and returned along the reference arm optical path 32 and the detection arm optical path 34, where it converges at 31 in the Michelson interferometer 3 and undergoes interference, then is sent to the spectrometer 5 and is split by the grating 51, and is imaged on the CCD through the converging lens 52 The detector 53 is converted into an electrical signal, which is converted into an electrical signal by the image acquisition card 6 and sent to the computer 7 for data processing to obtain a tomogram of the measured sample 35 along the optical axis of the probe light. A three-dimensional precision translation stage (not shown in the figure) scans the measured sample 35 horizontally along a plane perpendicular to the optical axis direction of the probe light to obtain a two-dimensional or three-dimensional tomogram of the measured sample 35. Wherein the sinusoidal phase modulation device 4 is connected with the reference reflector 33 in the reference arm of the Michelson interferometer, the device drives the reference reflector to vibrate sinusoidally under the drive of the sinusoidally varying electrical signal, and introduces the sinusoidal phase into the interference signal collected by the spectrometer modulation.

所述的参考反射镜33作如下正弦振动：Described reference reflector 33 makes following sinusoidal vibration:

Z(t)＝acos(2πf_ct+θ)，                               (10)Z(t)=acos(2πf _c t+θ), (10)

其中：a为振幅，θ为初始相位，f_c为调制频率。Among them: a is the amplitude, θ is the initial phase, f _c is the modulation frequency.

所述的CCD探测器53记录的信号为：The signal recorded by the CCD detector 53 is:

GG (( λλ ,, tt )) == GG 00 ++ 22 ReRe {{ ΣΣ nno GG nrnr (( λλ )) expexp [[ -- jj 22 ππ 11 λλ [[ (( zz nno -- zz rr )) ++ 22 ZZ (( tt )) ]] ]] }} ,, -- -- -- (( 1111 ))

其中：G代表光谱密度函数，Re代表取复数的实部，z_n代表被测样品第n层反射或散射界面的光程，z_r代表参考反射镜位置的光程。而 G 0 = G rr ( λ ) + Σ n G nn ( λ ) + 2 Re { Σ n ≠ m G nm ( λ ) exp [ - j 2 π 1 λ ( z n - z m ) ] } ，为一个不随时间变化的直流分量。Among them: G represents the spectral density function, Re represents the real part of the complex number, z _n represents the optical path of the nth reflection or scattering interface of the measured sample, and z _r represents the optical path of the reference mirror position. and G 0 = G rr ( λ ) + Σ no G n ( λ ) + 2 Re { Σ no ≠ m G nm ( λ ) exp [ - j 2 π 1 λ ( z no - z m ) ] } , is a DC component that does not vary with time.

对(11)式作傅立叶变换，得到Taking Fourier transform of (11), we get

Ff (( ωω )) == GG 00 σσ (( ωω )) ++ 22 ΣΣ nno GG nrnr (( λλ )) coscos [[ 22 ππ 11 λλ (( zz nno -- zz rr )) ]] ×× [[ ΣΣ mm == -- ∞∞ ∞∞ (( -- 11 )) mm AA 22 mm σσ (( ωω -- 22 mm ωω cc )) ]]

2 Σ n G nr ( λ ) sin [ 2 π 1 λ ( z n - z r ) ] × [ Σ m = - ∞ ∞ ( - 1 ) m A 2 m - 1 σ [ ω - ( 2 m - 1 ) ω c ] ] , (12) 2 Σ no G nr ( λ ) sin [ 2 π 1 λ ( z no - z r ) ] × [ Σ m = - ∞ ∞ ( - 1 ) m A 2 m - 1 σ [ ω - ( 2 m - 1 ) ω c ] ] , (12)

其中A_m＝J_m(d)exp(jmθ)，J_m是m阶贝塞尔函数，σ是狄拉克函数， d = 4 α λ , ω＝2πf，ω_c＝2πf_c。由(12)式，可推得Wherein A _m =J _m (d)exp(jmθ), J _m is the m-order Bessel function, σ is the Dirac function, d = 4 α λ , ω=2πf, ω _c =2πf _c . From (12), it can be deduced that

22 ΣΣ nno GG nrnr (( λλ )) sinsin [[ 22 ππ 11 λλ (( zz nno -- zz rr )) ]] == -- ReRe {{ Ff (( ωω cc )) }} // JJ 11 (( dd )) coscos (( θθ )) ,,

2 Σ n G nr ( λ ) cos [ 2 π 1 λ ( z n - z r ) ] = - Re { F ( 2 ω c ) } / J 2 ( d ) cos ( 2 θ ) , (131) 2 Σ no G nr ( λ ) cos [ 2 π 1 λ ( z no - z r ) ] = - Re { f ( 2 ω c ) } / J 2 ( d ) cos ( 2 θ ) , (131)

其中：sin项对应干涉复信号的虚部，cos项对应干涉复信号的实部。d，θ为事先确定量，或由F(ω_c)和F(3ω_c)求得(见在先技术[3])。Among them: the sin term corresponds to the imaginary part of the interference complex signal, and the cos term corresponds to the real part of the interference complex signal. d, θ are predetermined quantities, or obtained from F(ω _c ) and F(3ω _c ) (see prior art [3]).

由(13)式中的两项组合，可得到复信号From the combination of the two terms in (13), the complex signal can be obtained

GG ^^ (( λλ )) 22 ΣΣ nno GG nrnr (( λλ )) coscos [[ 22 ππ 11 λλ (( zz nno -- zz rr )) ]] -- jj 22 ΣΣ nno GG nrnr (( λλ )) sinsin [[ 22 ππ 11 λλ (( zz nno -- zz rr )) ]]

= 2 Σ n G nr ( λ ) exp { - j [ 2 π 1 λ ( z n - z r ) ] } , (14) = 2 Σ no G nr ( λ ) exp { - j [ 2 π 1 λ ( z no - z r ) ] } , (14)

对(14)做倒数变换，得到频域(v域，v＝1/λ)的复信号Perform reciprocal transformation on (14) to get complex signal in frequency domain (v domain, v=1/λ)

GG ^^ (( νν )) == 22 ΣΣ nno GG nrnr (( νν )) expexp {{ -- jj [[ 22 πνπν 11 λλ (( zz nno -- zz rr )) ]] }} ,,

对(15)式作逆傅立叶变换，得到被测物体的层析图Perform inverse Fourier transform on formula (15) to obtain the tomogram of the measured object

其中：Γ_nr为一阶互相关函数，包含着被测物体的沿探测光光轴方向的深度分辨的光反射或背向散射信息，即层析图。通过三维精密平移台带动被测物体作横向扫描，重复以上计算过程即可得到被测物体的二维或三维层析图。Among them: Γ _nr is the first-order cross-correlation function, which contains the depth-resolved light reflection or backscattering information of the measured object along the optical axis of the probe light, that is, the tomogram. The object under test is scanned horizontally by the three-dimensional precision translation stage, and the two-dimensional or three-dimensional tomogram of the object under test can be obtained by repeating the above calculation process.