CN102628799A - Method and system of time-domain optical coherence tomography without depth scan - Google Patents

Abstract

The invention provides a method and a system of time-domain optical coherence tomography without depth scan. On the basis of a time-domain optical coherence tomography method, the method of the invention comprises substituting convex lens with cylindrical surface for focusing lens interfering with a reference arm to form linear reference light, introducing continuous light path difference in a linear length direction of the reference light through tilting a reference planar mirror of the reference arm, substituting a one-dimensional detector array for a point photoelectric detector, acquiring interference signals of a sample to be measured at continuous different depth of a same detecting point, carrying out a Hilbert transformation analysis on the interference signals in the linear length direction of the reference light after removing direct current background, and finally obtaining a tomographic profile of the sample to be measured. The method and the system of the invention can realize one-dimensional optical coherence tomography with single exposure, and have the advantages of a simple structure, a high imaging speed, no parasitic image, and insensitivity to motion blur. In a situation of not sacrificing a system signal-to-noise ratio, time-domain optical coherence tomography without depth scan can be realized.

Description

Time domain optical coherence tomography method and system without depth scanning

technical field

The present invention relates to optical coherence tomography (Optical Coherence Tomography, OCT for short), in particular to a method and system for Time-domain Optical Coherence Tomography (TD-OCT for short) without depth scanning.

Background technique

Optical coherence tomography (OCT) is an optical tomography technology developed in recent years. It can perform high-resolution non-invasive imaging of microstructures within a few millimeters in highly scattering media such as biological tissues. It has broad application prospects in the fields of living tissue imaging and medical imaging diagnosis.

The earliest OCT system was Time-Domain Optical Coherence Tomography (TD-OCT) (see prior art [1], D. Huang, E.A. Swanson, C.P. Lin, J.S. Schuman, W.G. Stinson, W. Chang, M.R. Hee , T. Flotte, K. Gregory, C.A. Puliafito and J.G. Fujimoto, "Optical coherencetomography", Science, Vol.254, pp.1178-1181, 1991). It scans the axial depth of the optical reference arm and records the interference signal intensity at different depths to obtain a one-dimensional tomogram (A-line) of the sample. The detection speed of TD-OCT is relatively low. If the measured sample moves during the detection process, motion blur will easily occur. If the axial depth scanning speed of TD-OCT is forced to increase to increase the detection speed, the system sensitivity will decrease.

Frequency domain optical coherence tomography (Fourier-domain Optical Coherence Tomography, referred to as FD-OCT) is a new type of OCT system (see prior art [2], N.Nassif, B.Cense, B.H.Park, S.H.Yun, T.C.Chen, B.E.Bouma, G.J.Tearney and J.F.de Boer, "In vivo humanretinal imaging by ultrahigh-speed spectral domain optical coherencetomography", Optics Letter, Vol.29, pp.480-482, 2004), it detects the interference spectrum and The one-dimensional tomogram (A-line) of the sample is obtained by inverse Fourier transform. Compared with the earlier time-domain optical coherence tomography system (TD-OCT), it has the advantages of no need for depth direction scanning, fast imaging speed and detection The advantage of high sensitivity can better meet the real-time requirements of biological tissue imaging and medical imaging diagnosis. However, the tomogram obtained by FD-OCT contains several parasitic images, which limits the application of FD-OCT. These spurious images are: DC background, autocoherent noise and complex conjugate image. Among them, the existence of DC background and self-coherent noise reduces the signal-to-noise ratio of FD-OCT and 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 relative to the reference optical path The optical path difference), the sample to be tested can only be placed on the side of the zero optical path difference position during measurement, resulting in a reduction of the effective detection depth range by half. In addition, the signal-to-noise ratio of FD-OCT will drop sharply as the optical path difference increases.

The main difference between parallel FD-OCT and traditional FD-OCT based on single-point illumination is that it realizes the parallel detection of FD-OCT two-dimensional tomogram (B-scan) by using linear light to illuminate the sample to be tested. (See prior art [3], Branislay Grajciar, Michael Pircher, Adolf F.Fercher and RainerA.Leitgeb, "Parallel Fourier domain optical coherence tomography for in vivomeasurement of the human eye", Optics Express, Vol.13, pp.1131 -1137, 2005). This method generally realizes the linear light illumination of the sample to be tested by adding a cylindrical convex mirror in the optical path, and uses a two-dimensional photodetection array to record frequency-domain interference fringes in parallel, and reconstructs a two-dimensional tomogram of the sample to be tested ( B-scan). Parallel FD-OCT has faster imaging speed and is less sensitive to motion blur because it avoids the transverse mechanical scanning of the sample to be tested. However, like traditional FD-OCT, parallel FD-OCT still has problems such as complex conjugate mirror parasitic images.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art, and provide a time-domain optical coherence tomography method and system without depth scanning. The invention can realize one-dimensional optical coherence tomography imaging with only one exposure, and has the characteristics of simple structure, fast imaging speed, no parasitic image and insensitivity to motion blur.

Technical solution of the present invention is as follows:

A time-domain optical coherence tomography method without depth scanning, the method is based on the time-domain optical coherence tomography method, using a cylindrical convex mirror to replace the focusing lens of the interference reference arm to form a linear reference light, And by tilting the reference plane reflector of the reference arm, continuous optical path difference is introduced in the direction of the reference ray-like length, and the point photodetector is replaced by a one-dimensional photodetector array to obtain the same detection point of the sample to be tested at different depths. After the interference signal is removed from the DC background, the tomogram of the sample to be tested can be obtained by performing Hilbert transformation on the interference signal along the length direction of the reference light.

The specific steps of the method for time-domain optical coherence tomography without depth scanning in the present invention are as follows:

①On the basis of the time-domain optical coherence tomography method, a cylindrical convex mirror is used to replace the focusing lens of the interference reference arm to form a linear reference light;

② Make the reference plane reflector of the reference arm tilt in the plane composed of the length direction of the linear reference light and the illumination direction of the reference light, and introduce a continuous optical path difference in the length direction of the linear reference light; the reference light is incident on the inclined plane and reflected The incident angle on the mirror is θ, where the value range of θ is -60°≤θ≤60°;

③ Replace the point photodetectors with a one-dimensional photodetector array to obtain the interference signals at the same detection point of the sample to be tested at different depths; after the system works, the interference signals recorded by the one-dimensional photodetector array are as follows: 1) as shown:

p代表所述一维光电探测器阵列的单个探测单元宽度，σ代表被测样品到所述一维光电探测器阵列的成像放大率，z₀是一个常数；R(z)是待测样品相对纵向深度位置z处的反射率或背向散射率；γ(m)是低相干光源的空间相干度函数，c是光速，

是一个相位常数，*表示卷积运算；Wherein: m is the detection unit sequence number of the one-dimensional photodetector array, and I(m) is the interference signal intensity detected by the mth detection unit of the one-dimensional photodetector array; I _sig , I _ref , I _in are the reference light signal intensity, the sample light signal intensity and the incident light signal intensity respectively; z is the relative longitudinal depth position of the sample to be measured,

p represents the width of a single detection unit of the one-dimensional photodetector array, σ represents the imaging magnification of the measured sample to the one-dimensional photodetector array, z ₀ is a constant; R(z) is the relative Reflectance or backscattering rate at longitudinal depth position z; γ(m) is the spatial coherence function of low-coherence light sources, c is the speed of light,

Is a phase constant, * means convolution operation;

④ The interference signal is averaged to obtain a DC background as shown in formula (2):

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; dc</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Wherein: M is the detection unit total number of described one-dimensional photodetector array; Subtract formula (2) from formula (1), obtain the interference signal that removes the DC background initially, as shown in formula (3):

I _nodc (m)=I(m) _-Idc ; (3)

5. the formula (3) of step 4. gained is done the Fourier transform with m as variable and obtains formula (4):

代表以m为变量的傅里叶变换；将式(4)信号先乘上一个区间大小为2π的矩形窗函数 $W\left(f_m\right)=\left\{\begin{array}{c}0,\left|f_m\right|\&le;\mathrm{\&pi;}\\ 1,\left|f_m\right|>\mathrm{\&pi;}\end{array}\right.$ 进行高通滤波，得到式(5)：Among them: f _m represents the Fourier transform spectrum corresponding to m,

Represents the Fourier transform with m as the variable; multiply the signal of formula (4) by a rectangular window function with an interval size of 2π $W\left(f_m\right)=\left\{\begin{array}{c}0,\left|f_m\right|\&le;\mathrm{\&pi;}\\ 1,\left|f_m\right|>\mathrm{\&pi;}\end{array}\right.$ Perform high-pass filtering to obtain formula (5):

E' _nodc (f _m ) = E _nodc (f _m )·W(f _m ); (5)

Then, the signal of formula (5) is subjected to inverse Fourier transform with f _m as a variable to obtain the interference signal that completely removes the DC background, as shown in formula (6):

代表以f_m为变量的逆傅里叶变换；in

Represents the inverse Fourier transform with f _m as a variable;

6. To the background interference signal (6) obtained in step 5., do Hilbert transform with m as a variable to obtain formula (7):

代表以m为变量的希尔伯特变换；将信号式(6)和式(7)合成得到式(8)，in

Represents the Hilbert transform with m as a variable; the signal formula (6) and formula (7) are synthesized to obtain formula (8),

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; Hilbert</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; nodc</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 4</span>}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; ref</span>}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; *</span><span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; \&gamma;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; ;</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

⑦ Convert the independent variable m of the signal formula (8) obtained in step ⑥ into the independent variable z, that is, obtain the one-dimensional chromatogram of the sample to be tested, as shown in the formula (9):

I ₀ (z)=4I _ref I _in R(z)*|γ(z)|. (9)

⑧ Scan the sample to be tested in two dimensions along the plane perpendicular to the optical axis of the illumination light through the precision translation stage, and repeat the above steps ② to ⑦ to obtain the three-dimensional tomogram of the sample to be tested.

A time-domain optical coherence tomography system without depth scanning for realizing the above method, including 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, and the Michelson interferometer The beam splitter divides the incident light into a transmitted beam and a reflected beam. Its characteristics are: in the direction of the transmitted beam, a cylindrical lens and a plane mirror placed obliquely are arranged in sequence to form a reference arm optical path, and in the direction of the reflected beam The first focusing lens and the sample to be tested are arranged in sequence to form the optical path of the detection arm, and the sample to be tested is placed on a precision mobile platform; the second focusing lens and the one-dimensional photodetector are sequentially placed at the output end of the Michelson interferometer device array; the one-dimensional photodetector array is connected to the computer through the image data acquisition card; the cylindrical lens converges the incident parallel light into a linear light to generate a linear reference light; the tilted pendulum of the plane reflector put, introduce continuous optical path difference in the reference ray-like length direction; the focal length of the cylindrical lens is the same as the focal length of the first focusing lens; The one-dimensional photodetector array constitutes a conjugate relationship of the object image; the direction of the detection unit array of the one-dimensional photodetector array and the length direction of the linear illumination light in the light path of the reference arm are in the same plane.

The low-coherence light source is a broadband light source with a typical full width at half maximum of its spectrum ranging from tens of nanometers to hundreds of nanometers, such as light-emitting diodes or superluminescent light-emitting diodes or femtosecond lasers or supercontinuum light sources.

The collimating beam expander is composed of an objective lens and several lenses.

The one-dimensional photodetector array is a linear CCD or linear CMOS or linear InGaAs or other one-dimensional detector array with photoelectric signal conversion function.

The precision mobile platform can perform translation with micron-level precision along three mutually perpendicular directions.

The system works as follows:

The light emitted by the low-coherence light source is expanded by the collimator and split into two beams in the Michelson interferometer. One beam of light passes through the reference arm and is focused in the converging plane of the cylindrical convex mirror to produce a linear illumination light. , incident on the inclined plane mirror, another beam of light is incident on the sample to be tested through the detection arm, the reflected light from the plane mirror and the sample light reflected or backscattered from different depths in the sample to be tested Return along the reference arm and the detection arm respectively, and meet in the Michelson interferometer for interference. The interference signal is recorded by the one-dimensional photodetector array after being focused by the focusing lens, and sent to the computer for data processing after digital-to-analog conversion by the image data acquisition card. , to obtain a one-dimensional tomogram of the sample to be tested along the optical axis of the illumination light. The sample to be tested is scanned two-dimensionally along a plane perpendicular to the optical axis of the illumination light through a precision translation stage to obtain a three-dimensional tomogram of the sample to be tested.

Compared with prior art, the beneficial effect of the present invention is:

The feature of the method of time-domain optical coherence tomography without depth scanning in the present invention is to introduce a continuous optical path difference in the length direction of the linear reference light by using a linear reference light and an obliquely placed plane reference mirror, using spatial filtering and Hill The Burt transform analysis method obtains the one-dimensional tomographic information of the sample to be tested at one time, improves the imaging speed without sacrificing the signal-to-noise ratio of the system, and realizes time-domain optical coherence tomography without deep scanning.

Compared with the prior art 1, the present invention does not require axial depth scanning, has fast imaging speed, is insensitive to motion blur, and has low requirements on the stability of the interferometer and the sample.

Compared with the prior art 2 and 3, the system structure of the present invention is simple, there is no problem of parasitic images, and the image signal-to-noise ratio does not decrease with the increase of the optical path difference.

Description of drawings

FIG. 1 is a schematic diagram of the optical path and structure of the time-domain optical coherence tomography system without depth scanning according to the present invention.

Detailed ways

The present invention will be further described below in conjunction with the embodiments and accompanying drawings, but the protection scope of the present invention should not be limited thereby.

See Figure 1. FIG. 1 is a schematic diagram of the optical path and structure of the time-domain optical coherence tomography system without depth scanning according to the present invention. It can be seen from Fig. 1 that the time-domain optical coherence tomography system without depth scanning of the present invention includes a low-coherence light source 1, and a collimating beam expander 2 and a Michelson interferometer 3 are sequentially placed in the illumination direction of the low-coherence light source 1, The dichroic prism 31 of this 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 32 is a cylindrical convex mirror 36 and a plane mirror 33 placed obliquely. The end of the optical path 34 is a focusing lens 37 and a sample to be tested 35, and the sample to be tested 35 is placed on a precision mobile platform (not shown in the figure); the output end of the Michelson interferometer 3 is sequentially placed with a focusing lens 4 and a linear array CCD detection device 5; the linear array CCD detector 5 is connected to the computer 7 through the image data acquisition card 6. The feature of this system is that the cylindrical convex mirror 36 at the end of the reference arm optical path 32 converges the incident parallel light into a linear light to generate a linear reference light; the inclined plane mirror 33 at the end of the reference arm optical path 32 is at the reference A continuous optical path difference is introduced along the light-like length direction.

The focal length of the cylindrical convex mirror 36 in front of the plane reflector 33 and the focus lens 37 before the test sample 35 in the described Michelson interferometer 3 are the same; The array CCD detector 5 is object-image conjugate relationship on the system optical path; the detection unit array direction of the linear array CCD detector 5 and the linear illumination light length direction in the reference arm optical path 32 are on the same plane Inside.

The wide-spectrum light emitted by the low-coherence light source 1 is expanded by the collimator 2, and then split into two beams by the dichroic prism 31 in the Michelson interferometer 3, and a beam of transmitted light is generated by a cylindrical convex mirror 36 in the reference arm optical path 32 A linear illuminating light is reflected by the inclined plane reflector 33 and returns backward; another beam of reflected light enters the sample to be measured 35 placed on the precision translation stage (not shown in the figure) through the detection arm optical path 34, from The light reflected by the plane mirror 33 and the light reflected or backscattered from different depths in the sample 35 to be measured return along the reference arm optical path 32 and the detection arm optical path 34 respectively, and converge in the Michelson interferometer 3 to interfere. Then it is focused by the focusing lens 4, imaged on the line array CCD detector 5, converted into electrical signals, and then sent to the computer 7 for data processing after digital-to-analog conversion by the image data acquisition card 6, and the sample 35 to be tested along the optical axis of the illumination light is obtained. A one-dimensional tomogram of the orientation.

The reference plane reflector 33 in the reference arm optical path 32 is inclined in the plane composed of the linear reference light length direction and the reference light illumination direction, and the incident angle of the reference light incident on the inclined plane reflector 33 is θ.

The interference signals recorded by the linear array CCD detector 5 at the same detection point of the sample to be tested 35 at different depths are:

p代表线阵CCD探测器5的单个探测单元宽度，σ＝F₂/F₁代表一维成像系统的横向放大率，F₁代表聚焦透镜37和柱面凸镜36的焦距，F₂代表聚焦透镜4的焦距，z₀是一个常数；R(z)是待测样品35相对纵向深度位置z处的反射率或背向散射率；γ(m)是所述低相干光源1的空间相干度函数，c是光速，是一个相位常数，*表示卷积运算。Wherein: m is the detection unit serial number of described linear array CCD detector 5, and I (m) is the interference signal intensity that the mth detection unit of linear array CCD detector 5 detects; I _sig , I _ref , I _in respectively is the reference optical signal intensity, the sample optical signal intensity and the incident optical signal intensity; z is the relative longitudinal depth position of the sample to be measured 35,

p represents the width of a single detection unit of the line array CCD detector 5, σ=F ₂ /F ₁ represents the lateral magnification of the one-dimensional imaging system, F ₁ represents the focal length of the focusing lens 37 and the cylindrical convex mirror 36, and F ₂ represents the focus The focal length of the lens 4, z ₀ is a constant; R (z) is the reflectivity or backscattering rate at the relative longitudinal depth position z of the sample to be measured 35; γ (m) is the spatial coherence of the low coherent light source 1 function, c is the speed of light, is a phase constant, * means convolution operation.

First, the interference signal formula (10) is averaged, and the DC background is obtained as shown in formula (11):

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; dc</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 11</span>}<span\; class="notranslate">\; )</span>$

Wherein: M is the total number of detection units of the linear array CCD detector 5; Subtract formula (11) from formula (10) to obtain the interference signal that initially removes the DC background, as shown in formula (12):

I _nodc (m)=I(m) _-Idc ; (12)

Then do the Fourier transform of the signal formula (12) with m as a variable to obtain the formula (13):

Among them: f _m represents the Fourier transform spectrum corresponding to m, Represents the Fourier transform with m as the variable; multiply the signal formula (13) by a rectangular window function with an interval size of 2π $W\left(f_m\right)=\left\{\begin{array}{c}0,\left|f_m\right|\&le;\mathrm{\&pi;}\\ 1,\left|f_m\right|>\mathrm{\&pi;}\end{array}\right.$ Perform high-pass filtering to obtain formula (14):

E' _nodc (f _m ) = E _nodc (f _m )·W(f _m ); (14)

Then take the signal formula (14) as the inverse Fourier transform with f _m as the variable to obtain the interference signal that completely removes the DC background, as shown in formula (15):

代表以f_m为变量的逆傅里叶变换。in

Represents the inverse Fourier transform with f _m as the variable.

Hilbert transform the interference signal (15) with m as the variable to get the formula (16):

代表以m为变量的希尔伯特变换；将信号式(15)和式(16)合成得到式(17)，in

Represents the Hilbert transform with m as a variable; the signal formula (15) and formula (16) are synthesized to obtain formula (17),

I ₀ (m)＝|I _Hilbert (m)| ² +|I′ _nodc (m)| ² ＝4I _ref I _in R(z)*|γ(m)|; (17)

Finally, the independent variable m of the signal formula (18) is converted into the independent variable z, that is, the one-dimensional chromatogram of the sample 35 to be tested is obtained, as shown in the formula (18):

I ₀ (z)=4I _ref I _in R(z)*|γ(z)|. (18)

The sample 35 to be tested is scanned two-dimensionally along a plane perpendicular to the optical axis of the illumination light by a precision translation stage (not shown in the figure), and the above process is repeated to obtain a three-dimensional tomogram of the sample 35 to be tested.

Claims (4)

1. A time domain optical coherence tomography method without depth scanning is characterized in that on the basis of a time domain optical coherence tomography method, a cylindrical convex lens is used for replacing a focusing lens of an interference reference arm to form linear reference light, continuous optical path difference is introduced in the linear length direction of the reference light through a reference plane reflecting mirror of an inclined reference arm, a one-dimensional photoelectric detector array is used for replacing a point photoelectric detector to obtain interference signals of a sample to be detected at continuous different depths of the same detection point, and after a direct current background is removed, Hilbert conversion is carried out on the interference signals along the linear length direction of the reference light to obtain a chromatogram of the sample to be detected.

2. The method for time-domain optical coherence tomography without depth scanning of claim 1, wherein the method comprises the following steps:

on the basis of a time domain optical coherence tomography method, a cylindrical convex lens is used for replacing a focusing lens of an interference reference arm to form linear reference light;

inclining a reference plane reflector of the reference arm in a plane formed by the linear reference light length direction and the reference light illumination direction, and introducing continuous optical path difference in the linear reference light length direction; the incident angle of the reference light incident on the inclined plane reflector is theta, wherein the theta is in a value range of between 60 degrees below zero and 60 degrees below zero;

replacing a point photoelectric detector with a one-dimensional photoelectric detector array to obtain interference signals of the same detection point of the sample to be detected at different continuous depths:

wherein: m is the serial number of the detection unit of the one-dimensional photoelectric detector array, and I (m) is the intensity of the interference signal detected by the mth detection unit of the one-dimensional photoelectric detector array; i is_sig、I_ref、I_inReference light signal intensity, sample light signal intensity and incident light signal intensity, respectively; z is the relative longitudinal depth position of the sample to be measured,

p represents the width of a single detection unit of the one-dimensional photoelectric detector array, sigma represents the imaging magnification of the detected sample to the one-dimensional photoelectric detector array, and z₀Is a constant; r (z) is the reflectivity or backscattering rate of the sample to be measured at the position z relative to the longitudinal depth; gamma (m) is the spatial coherence function of the low coherence light source, c is the speed of light,

is a phase constant, representing a convolution operation;

fourthly, averaging the interference signals I (m) to obtain a direct current background:

<math> <mrow> <msub> <mi>I</mi> <mi>dc</mi> </msub> <mo>=</mo> <mfrac> <mn>1</mn> <mi>M</mi> </mfrac> <munderover> <mi>&Sigma;</mi> <mrow> <mi>m</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>M</mi> </munderover> <msub> <mi>I</mi> <mi>m</mi> </msub> <mo>,</mo> </mrow> </math>

wherein: m is the total number of detection units of the one-dimensional photodetector array; subtracting the DC background I from the interference signal I (m)_dcObtaining an interference signal I for preliminarily removing the DC background_nodc(m) is:

I_nodc(m)＝I(m)-I_dc；

fifthly, removing the interference signal I of the DC background preliminarily_nodc(m) performing a Fourier transform with m as a variable to obtain:

wherein: f. of_mRepresenting the fourier transform spectrum corresponding to m,

representing a fourier transform with m as a variable; will E_nodc(f_m) Multiplying a rectangular window function with the interval size of 2 pi to perform high-pass filtering to obtain:

E′_nodc(f_m)＝E_nodc(f_m)·W(f_m)，

wherein the rectangular window function is <math> <mrow> <mi>W</mi> <mrow> <mo>(</mo> <msub> <mi>f</mi> <mi>m</mi> </msub> <mo>)</mo> </mrow> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <mn>0</mn> <mo>,</mo> <mo>|</mo> <msub> <mi>f</mi> <mi>m</mi> </msub> <mo>|</mo> <mo>&le;</mo> <mi>&pi;</mi> </mtd> </mtr> <mtr> <mtd> <mn>1</mn> <mo>,</mo> <mo>|</mo> <msub> <mi>f</mi> <mi>m</mi> </msub> <mo>|</mo> <mo>></mo> <mi>&pi;</mi> </mtd> </mtr> </mtable> </mfenced> <mo>;</mo> </mrow> </math> Then E 'is prepared'_nodc(f_m) Is made of f_mIs an inverse Fourier transform of a variable to obtain an interference signal I 'with a completely removed DC background'_nodc(m)：

WhereinIs represented by f_mIs the inverse Fourier transform of the variable;

'interference signal to completely remove background'_nodc(m) obtaining by performing a Hilbert transform with m as a variable:

wherein,represents a Hilbert transform with m as a variable; will signal I'_nodc(m) and I_Hilbert(m) Synthesis to yield:

I₀(m)＝|I_Hilbert(m)|²+|I′_nodc(m)|²＝4I_refI_inR(z)*|γ(m)|；

seventhly, obtaining a signal I₀(m) converting the independent variable m into the independent variable z to obtain the one-dimensional chromatogram of the sample to be detected:

I₀(z)＝4I_refI_inR(z)*|γ(z)|。

3. the method of claim 2, further comprising the steps of:

and (b) enabling the sample (35) to be measured to perform two-dimensional scanning along a plane vertical to the direction of the optical axis of the illumination light by a precise translation platform, and repeating the steps from (c) to obtain a three-dimensional chromatographic chart of the sample (35) to be measured.

4. A time-domain optical coherence tomography system without depth scanning, implementing the method according to any one of claims 1 to 3, comprising a low coherence light source (1), a collimating beam expander (2) and a michelson interferometer (3) placed in sequence in the direction of illumination of the low coherence light source (1), the optical splitter (31) of which splits the incident light into a transmitted beam and a reflected beam, characterized in that: a cylindrical lens (36) and a plane reflector (33) which is obliquely arranged are sequentially arranged in the direction of the transmitted light beam to form a reference arm light path (32), a first focusing lens (37) and a sample to be detected (35) are sequentially arranged in the direction of the reflected light beam to form a detection arm light path (34), and the sample to be detected (35) is placed on a precise moving platform; a second focusing lens (4) and a one-dimensional photoelectric detector array (5) are sequentially arranged at the output end of the Michelson interferometer (3); the one-dimensional photoelectric detector array (5) is connected with a computer (7) through an image data acquisition card (6); the cylindrical lens (36) converges the incident parallel light into linear light to generate linear reference light; the plane reflector (33) is obliquely arranged, and continuous optical path difference is introduced in the linear length direction of the reference light; the focal length of the cylindrical lens (36) is the same as that of the first focusing lens (37); the sample to be measured (35) and the plane reflector (33) respectively form an object-image conjugate relation with the one-dimensional photoelectric detector array (5); the array direction of the detection units of the one-dimensional photoelectric detector array (5) and the length direction of the linear illumination light in the reference arm light path (32) are in the same plane.

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