CN103399413B

CN103399413B - Double helix light beam-based sample axial drift detection and compensation method and device

Info

Publication number: CN103399413B
Application number: CN201310324971.7A
Authority: CN
Inventors: 匡翠方; 李帅; 杨硕; 刘旭
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2013-07-30
Filing date: 2013-07-30
Publication date: 2015-05-20
Anticipated expiration: 2033-07-30
Also published as: CN103399413A

Abstract

The invention discloses a sample axial drift detection and compensation method based on a double helical beam, comprising: phase modulation of a collimated laser beam to obtain a double helical illumination beam, and projecting the beam onto a three-dimensional nano-scanning platform to be measured sample, and get the reflected beam; the reflected beam is focused into a focused spot with two intensity peaks, and the focused spot is received by a photoelectric sensor to obtain the intensity distribution information of the spot; the connection line between the two intensity peaks is calculated according to the spot intensity distribution information The included angle with the horizontal direction; use the relationship between the included angle and the axial drift of the sample to establish a calibration function; when the axial position of the sample to be tested drifts, use the included angle measured in real time to obtain the current axial drift of the sample according to the calibration function amount, and then adjust the axial position of the three-dimensional nano-scanning platform to complete the correction of the axial position of the sample to be measured. The invention also discloses a sample axial drift detection and compensation device based on double helical light beams.

Description

Sample axial drift detection and compensation method and device based on double helical beam

技术领域technical field

本发明属于高精度、超分辨显微领域，特别涉及一种基于双螺旋光束的样品轴向漂移实时检测及补偿方法和装置。The invention belongs to the field of high-precision and super-resolution microscopy, in particular to a method and device for real-time detection and compensation of sample axial drift based on double helical light beams.

背景技术Background technique

由于热漂移、应力漂移等因素的影响，超分辨显微系统中的待测样品不可避免地会在轴向上发生位置漂移，从而发生离焦现象，影响显微成像的精度。对于需要对同一样品面进行多次重复成像的显微方法（比如基于单分子定位的超分辨显微术）来说，这种轴向漂移所带来的影响将更为明显，因为轴向漂移将导致多次重复成像的并非为同一样品面。因此，一种可以实时对样品的轴向位置漂移进行检测并进行补偿的方法在显微系统中具有十分重要的应用价值。Due to thermal drift, stress drift and other factors, the position of the sample to be tested in the super-resolution microscopy system will inevitably drift in the axial direction, resulting in defocusing and affecting the accuracy of microscopic imaging. For microscopy methods that require repeated imaging of the same sample surface (such as super-resolution microscopy based on single-molecule localization), the effect of this axial drift will be more pronounced because the axial drift It is not the same sample face that will result in multiple repeated imaging. Therefore, a method that can detect and compensate the axial position drift of the sample in real time has very important application value in the microscopic system.

近年来，研究人员们陆续提出了多种样品轴向位置校正方法。其中，基于光学的方法以其非接触、对样品影响小等优势应用最为广泛。然而，目前基于光学的样品轴向补偿方法多是基于共焦系统，虽然具有较好的测量精度，但是系统的调试与操作都较为复杂，从而在一定程度上限制了这些方法在实际中的应用。In recent years, researchers have successively proposed a variety of sample axial position correction methods. Among them, the optical-based method is the most widely used due to its advantages of non-contact and small impact on the sample. However, the current optical-based sample axial compensation methods are mostly based on confocal systems. Although they have good measurement accuracy, the debugging and operation of the system are relatively complicated, which limits the practical application of these methods to a certain extent. .

发明内容Contents of the invention

本发明提供了一种基于双螺旋光束的样品轴向漂移实时检测及补偿方法和装置，可以实现对于样品轴向位置漂移的实时高精度、大范围测量并进行校正。该种方法及装置便于搭建，操作简单，可以广泛地应用于各种光学显微系统之中，保证显微样品始终位于显微物镜的焦平面处。The invention provides a method and device for real-time detection and compensation of sample axial drift based on double helical light beams, which can realize real-time high-precision, large-scale measurement and correction of sample axial position drift. The method and device are easy to build and easy to operate, and can be widely used in various optical microscopic systems to ensure that microscopic samples are always located at the focal plane of the microscopic objective lens.

一种基于双螺旋光束的样品轴向漂移检测及补偿方法，包括以下步骤：A method for detecting and compensating axial drift of a sample based on a double helical beam, comprising the following steps:

1）将准直后的激光光束入射至空间光调制器内进行相位调制，得到双螺旋照明光束，所述的双螺旋照明光束的聚焦光斑呈现出两个强度峰值，且这两个强度峰值之间的连线在光束传播方向上具有旋转特性；1) The collimated laser beam is incident into the spatial light modulator for phase modulation to obtain a double-helix illumination beam. The focused spot of the double-helix illumination beam presents two intensity peaks, and the difference between the two intensity peaks is The connection between has a rotation characteristic in the direction of beam propagation;

2）所述的双螺旋照明光束经聚焦投射到位于三维纳米扫描平台上的待测样品，经待测样品反射并被显微物镜收集得到反射光束；2) The double helix illumination beam is focused and projected onto the sample to be tested on the three-dimensional nano-scanning platform, reflected by the sample to be tested and collected by the microscope objective lens to obtain the reflected beam;

3）所述反射光束经聚焦得到具有两个强度峰值的聚焦光斑，并利用光电感应器件接收所述的聚焦光斑，得到光斑强度分布信息；3) Focusing the reflected light beam to obtain a focused spot with two intensity peaks, and using a photoelectric sensor to receive the focused spot to obtain spot intensity distribution information;

4）根据所述的光斑强度分布信息计算两个强度峰值之间的连线与水平方向的夹角；4) Calculate the angle between the line between the two intensity peaks and the horizontal direction according to the intensity distribution information of the spots;

5）利用所述的夹角和样品轴向漂移量的关系建立标定函数；5) Establish a calibration function using the relationship between the included angle and the axial drift of the sample;

6）当待测样品发生轴向位置漂移时，重复步骤1）～4），得到实时测量的夹角，根据所述的标定函数计算当前的样品轴向漂移量，并依据当前的样品轴向漂移量调整所述三维纳米扫描平台的轴向位置，完成对待测样品的轴向位置的校正。6) When the axial position of the sample to be measured drifts, repeat steps 1) to 4) to obtain the real-time measured angle, calculate the current axial drift of the sample according to the calibration function, and calculate the current axial drift of the sample according to the current axial position of the sample. The drift amount adjusts the axial position of the three-dimensional nano-scanning platform to complete the correction of the axial position of the sample to be measured.

所述空间光调制器的相位调制函数f(ρ,φ)设置为若干种不同GL基模复光场叠加场的相位分量，即，The phase modulation function f(ρ, φ) of the spatial light modulator is set to the phase components of several different GL fundamental mode complex light field superposition fields, that is,

U(ρ,φ,z)=∑u_mn(ρ,φ,z),n=0,1,2,…,m=2n+1U(ρ,φ,z)=∑u _mn (ρ,φ,z),n=0,1,2,…,m=2n+1

f(ρ,φ)=arg[U(ρ,φ,0)]f(ρ,φ)=arg[U(ρ,φ,0)]

其中，(ρ,φ,z)为以显微物镜理想焦点为原点的柱坐标系的三个坐标分量，u_mn(ρ,φ,z)为第mn阶GL基模复光场，arg为复数的辐角函数。Among them, (ρ, φ, z) are the three coordinate components of the cylindrical coordinate system with the ideal focus of the microscopic objective lens as the origin, u _mn (ρ, φ, z) is the complex light field of the mnth order GL fundamental mode, and arg is Argument function of complex numbers.

具体地，第mn阶GL基模复光场u_mn(ρ,φ,z)的表达式为，Specifically, the expression of the complex optical field u _mn (ρ,φ,z) of the mnth order GL fundamental mode is,

${u u}_{mn mn} ((ρ ρ,, φ φ,, z z)) = = {w w}_{00} / / w w ((\overset{^^}{z z})) exp exp ((- - \overset{^^22}{ρ ρ})) exp exp ((i i \overset{^^22}{ρ ρ} \overset{^^}{z z})) exp exp [[- - i i arctan arctan ((\overset{^^}{z z}))]] \cdot \cdot {((\sqrt{22} \overset{^^}{ρ ρ}))}^{| | m m | |} {L L}_{n no}^{m m} ((22 \overset{^^22}{ρ ρ}))$

$\cdot \cdot exp exp ((imφ imφ)) exp exp [[- - i i ((22 n no + + m m)) arctan arctan ((\overset{^^}{z z}))]]$

其中，w₀为激光光束的束腰半径，i为虚数单位，λ为所用激光光束的波长，为第mn阶拉盖尔多项式。Among them, w ₀ is the beam waist radius of the laser beam, i is the imaginary number unit, λ is the wavelength of the laser beam used, is the mnth order Laguerre polynomial.

优选的技术方案中，所设置复光场为五种不同GL基模复光场的叠加，具体(m,n)取值为(1,0)，(3,1)，(5,2)，(7,3)和(9,4)。In the preferred technical solution, the set complex light field is the superposition of five different GL fundamental mode complex light fields, and the specific values of (m, n) are (1,0), (3,1), (5,2) , (7,3) and (9,4).

优选的技术方案中，所述光电感应器件为高速电荷耦合器件（CCD:Charge Couple Device）。In a preferred technical solution, the photoelectric sensing device is a high-speed charge coupled device (CCD: Charge Couple Device).

本发明还提供了一种用于实现上述方法的装置，包括：The present invention also provides a device for implementing the above method, including:

激光器，用于发出激光光束的激光器；laser, a laser for emitting a laser beam;

空间光调制器，用于对所述激光光束进行相位调制；a spatial light modulator for phase modulating the laser beam;

三维纳米扫描平台，用于放置待测样品；Three-dimensional nano-scanning platform for placing samples to be tested;

显微物镜，用于将所述空间光调制器出射的光束聚焦至待测样品，并收集经所述待测样品反射的反射光束；a microscope objective lens, used to focus the light beam emitted by the spatial light modulator to the sample to be tested, and collect the reflected light beam reflected by the sample to be tested;

场镜，用于聚焦所述的反射光束并得到聚焦光斑；A field lens, used to focus the reflected light beam and obtain a focused spot;

光电感应器件，接收所述的聚焦光斑，并得到光斑强度分布信息；a photoelectric sensing device, which receives the focused light spot and obtains the intensity distribution information of the light spot;

以及与所述三维纳米扫描平台和光电感应器件连接的计算机。And a computer connected with the three-dimensional nano-scanning platform and the photoelectric induction device.

所述的激光器和空间光调制器之间依次布置有单模光纤、准直透镜和反射镜。所述单模光纤的出射端面位于所述准直透镜的物方焦点处，所述光电感应器件位于所述场镜的像方焦点处；A single-mode optical fiber, a collimating lens and a reflecting mirror are sequentially arranged between the laser and the spatial light modulator. The exit end face of the single-mode optical fiber is located at the object focus of the collimator lens, and the photoelectric sensor is located at the image focus of the field mirror;

所述空间光调制器用于对照明光束进行相位编码，具体相位调制函数f(ρ,φ)设置为若干种不同GL基模复光场叠加场的相位分量，所述空间光调制器的相位调制函数f(ρ,φ)为The spatial light modulator is used to phase-encode the illumination light beam, and the specific phase modulation function f(ρ, φ) is set as the phase component of several different GL fundamental mode complex light field superposition fields, and the phase modulation of the spatial light modulator The function f(ρ,φ) is

f(ρ,φ)=arg[U(ρ,φ,0)]f(ρ,φ)=arg[U(ρ,φ,0)]

其中，(ρ,φ,z)为以显微物镜的焦点为原点的柱坐标系的三个坐标分量，u_mn(ρ,φ,z)为第mn阶GL基模复光场，arg为复数的辐角函数；Among them, (ρ, φ, z) are the three coordinate components of the cylindrical coordinate system with the focal point of the microscope objective lens as the origin, u _mn (ρ, φ, z) is the complex light field of the mnth order GL fundamental mode, and arg is Argument functions of complex numbers;

所述第mn阶GL基模复光场u_mn(ρ,φ,z)为：The complex optical field u _mn (ρ, φ, z) of the mnth order GL fundamental mode is:

${u u}_{mn mn} ((ρ ρ,, φ φ,, z z)) = = {w w}_{00} / / w w ((\overset{^^}{z z})) exp exp ((- - \overset{^^22}{ρ ρ})) exp exp ((i i \overset{^^22}{ρ ρ} \overset{^^}{z z})) exp exp [[- - i i arctan arctan ((\overset{^^}{z z}))]] \cdot &Center Dot; {((\sqrt{22} \overset{^^}{ρ ρ}))}^{| | m m | |} {L L}_{n no}^{m m} ((22 \overset{^^22}{ρ ρ}))$

$\cdot &Center Dot; exp exp ((imφ imφ)) exp exp [[- - i i ((22 n no + + m m)) arctan arctan ((\overset{^^}{z z}))]]$

本发明原理如下：Principle of the present invention is as follows:

GL模光束是亥姆赫兹方程在近轴条件下的解。任意的空间光场总是可以分解成若干个不同的GL基模的复光场的叠加。当若干个特定的GL基模叠加时可以产生双螺旋光束。所谓双螺旋光束是旋转光束的一种，在一定的空间范围内，光束的光场能量保持不变，光场分布情况不变，变化的仅仅是位相、以及光场分布的一种趋向。特别地，双螺旋光束经过透镜聚焦之后，所成聚焦光斑会呈现出两个强度峰值，并且这两个强度峰值之间连线在光束传播方向上具有旋转特性，即在不同的轴向位置，两个强度峰值之间连线与水平方向的夹角是不同的。The GL mode beam is the solution of the Helmhertz equation under the paraxial condition. Any spatial light field can always be decomposed into the superposition of complex light fields of several different GL fundamental modes. Double helical beams can be generated when several specific GL fundamental modes are superimposed. The so-called double helix beam is a kind of rotating beam. Within a certain space range, the light field energy of the beam remains unchanged, and the distribution of the light field remains unchanged. The only changes are the phase and a tendency of the light field distribution. In particular, after the double helical beam is focused by the lens, the resulting focused spot will show two intensity peaks, and the line between the two intensity peaks has a rotation characteristic in the direction of beam propagation, that is, at different axial positions, The angle between the line connecting the two intensity peaks and the horizontal direction is different.

基于双螺旋光束的这一特性，本发明利用空间光调制器对照明光束进行相位调制，从而形成双螺旋照明光束。当待测样品在轴向上发生漂移时，所述双螺旋照明光束在样品面上所成聚焦光斑中两个强度峰值的连线指向角会发生改变，相应的监控光束聚焦后在光电感应器件上所成光斑中两个强度峰值的连线指向角也会发生改变。通过标定监控光束在光电感应器件上所成光斑的指向角与样品轴向漂移量的关系，便可以实现对于样品轴向漂移的实时检测与补偿。Based on this characteristic of the double helical light beam, the present invention utilizes a spatial light modulator to perform phase modulation on the illumination light beam, thereby forming a double helical light beam. When the sample to be measured drifts in the axial direction, the pointing angle of the line connecting the two intensity peaks in the focused spot formed by the double helical illumination beam on the sample surface will change, and the corresponding monitoring beam will be focused on the photoelectric sensor The pointing angle of the line connecting the two intensity peaks in the formed spot will also change. By calibrating the relationship between the pointing angle of the light spot formed by the monitoring beam on the photoelectric sensor device and the axial drift of the sample, the real-time detection and compensation of the axial drift of the sample can be realized.

相对于现有技术，本发明具有以下有益的技术效果：Compared with the prior art, the present invention has the following beneficial technical effects:

（1）装置结构简单，调试与操作方便；(1) The structure of the device is simple, and it is convenient to debug and operate;

（2）具有较高的测量灵敏度和较大的测量范围；(2) High measurement sensitivity and large measurement range;

（3）便于引入显微系统中进行应用。(3) It is easy to introduce into the microscopic system for application.

附图说明Description of drawings

图1为本发明中基于双螺旋光束的样品轴向漂移检测及补偿装置的示意图；1 is a schematic diagram of a sample axial drift detection and compensation device based on a double helical beam in the present invention;

图2为本发明中所用空间光调制器的相位调制函数分布示意图；2 is a schematic diagram of the phase modulation function distribution of the spatial light modulator used in the present invention;

图3为本发明中样品不同离焦位置时光电感应器件上所得光斑的强度分布图。Fig. 3 is an intensity distribution diagram of the light spot obtained on the photoelectric sensor device at different defocus positions of the sample in the present invention.

具体实施方式Detailed ways

下面结合实施例和附图来详细说明本发明，但本发明并不仅限于此。The present invention will be described in detail below in conjunction with the embodiments and accompanying drawings, but the present invention is not limited thereto.

如图1所示，一种基于双螺旋光束的样品轴向漂移检测及补偿装置，包括：激光器1，单模光纤2，准直透镜3，反射镜4，空间光调制器5，分光棱镜6，显微物镜7，三维纳米扫描平台8，场镜9，光电感应器件10，计算机11。As shown in Figure 1, a sample axial drift detection and compensation device based on a double helical beam includes: a laser 1, a single-mode fiber 2, a collimator lens 3, a mirror 4, a spatial light modulator 5, and a beam splitting prism 6 , a microscope objective lens 7, a three-dimensional nano-scanning platform 8, a field lens 9, a photoelectric sensing device 10, and a computer 11.

其中，单模光纤2、准直透镜3、反射镜4、空间光调制器5、分光棱镜6、显微物镜7和三维纳米扫描平台8依次位于激光器1的出射光光路的光轴上，显微物镜7将光线聚焦到位于三维纳米扫描平台8的待测样品上。Among them, the single-mode optical fiber 2, the collimating lens 3, the reflector 4, the spatial light modulator 5, the beam splitting prism 6, the microscopic objective lens 7 and the three-dimensional nano-scanning platform 8 are sequentially located on the optical axis of the outgoing light path of the laser 1, showing The micro-objective lens 7 focuses the light onto the sample to be measured located on the three-dimensional nano-scanning platform 8 .

场镜9和光电感应器件10依次位于监控光束光路的光轴上，监控光束光路的光轴与激光器1出射的照明光束的光轴垂直，监控光束为待测样品反射回来的照明光束经分光棱镜6分光后的反射光线。The field lens 9 and the photoelectric induction device 10 are sequentially located on the optical axis of the optical path of the monitoring beam, the optical axis of the optical path of the monitoring beam is perpendicular to the optical axis of the illuminating beam emitted by the laser 1, and the monitoring beam is the illuminating beam reflected back from the sample to be measured through the beam splitter 6 reflected light after splitting.

计算机11同时连接光电感应器件10和三维纳米扫描平台8。The computer 11 is connected to the photoelectric sensing device 10 and the three-dimensional nano-scanning platform 8 at the same time.

其中，单模光纤2的出射端面位于准直透镜3的物方焦点处，光电感应器件10位于监控光束聚焦透镜11的像方焦点处。Wherein, the exit end face of the single-mode optical fiber 2 is located at the object focal point of the collimator lens 3 , and the photoelectric sensor 10 is positioned at the image focal point of the monitoring beam focusing lens 11 .

其中，空间光调制器5的相位调制函数f(ρ,φ)设置为五种不同GL基模复光场叠加场的相位分量，即，Wherein, the phase modulation function f(ρ, φ) of the spatial light modulator 5 is set to be the phase components of the superposition field of five different GL fundamental mode complex light fields, namely,

U(ρ,φ,z)=∑u_mn(ρ,φ,z);(m,n)=(1,0),(3,1),(5,2),(7,3),(9,4)U(ρ,φ,z)=∑u _mn (ρ,φ,z);(m,n)=(1,0),(3,1),(5,2),(7,3), (9,4)

f(ρ,φ)=arg[U(ρ,φ,0)]f(ρ,φ)=arg[U(ρ,φ,0)]

${u u}_{mn mn} ((ρ ρ,, φ φ,, z z)) = = {w w}_{00} / / w w ((\overset{^^}{z z})) exp exp ((- - \overset{^^22}{ρ ρ})) exp exp ((i i \overset{^^22}{ρ ρ} \overset{^^}{z z})) exp exp [[- - i i arctan arctan ((\overset{^^}{z z}))]] \cdot \cdot {((\sqrt{22} \overset{^^}{ρ ρ}))}^{| | m m | |} {L L}_{n no}^{m m} ((22 \overset{^^22}{ρ ρ}))$ $\cdot \cdot exp exp ((imφ imφ)) exp exp [[- - i i ((22 n no + + m m)) arctan arctan ((\overset{^^}{z z}))]]$

其中，w₀为所用激光光束的束腰半径，i为虚数单位，λ为所用激光光束的波长，为第mn阶拉盖尔多项式。Among them, w ₀ is the beam waist radius of the laser beam used, i is the imaginary unit, λ is the wavelength of the laser beam used, is the mnth order Laguerre polynomial.

上述装置中，光电感应器件为高速电荷耦合器件（CCD:Charge CoupleDevice）。In the above device, the photoelectric sensing device is a high-speed charge coupled device (CCD: Charge Couple Device).

采用图1所示的装置，其工作过程为：Using the device shown in Figure 1, its working process is:

从激光器1发出的照明光束，首先被导入单模光纤2，从单模光纤2出射的照明光束，经过准直透镜3完成准直。The illuminating beam emitted from the laser 1 is first introduced into the single-mode fiber 2 , and the illuminating beam emitted from the single-mode optical fiber 2 is collimated through the collimating lens 3 .

经过准直后的照明光束经反射镜4反射后，入射到空间光调制器5中接受相位调制，形成双螺旋照明光束；空间光调制器5的相位调制函数分布如图2所示。The collimated illumination beam is reflected by the reflector 4, and then enters the spatial light modulator 5 for phase modulation to form a double helical illumination beam; the distribution of the phase modulation function of the spatial light modulator 5 is shown in FIG. 2 .

双螺旋照明光束透过分光棱镜6，之后经显微物镜7聚焦投射到位于三维纳米扫描平台8上的待测样品之上。The double helical illumination beam passes through the dichroic prism 6 , and then is focused and projected onto the sample to be measured on the three-dimensional nano-scanning platform 8 through the microscope objective lens 7 .

经待测样品反射的照明光束经显微物镜7收集后，经分光棱镜6反射作为监控光束。The illuminating light beam reflected by the sample to be measured is collected by the microscope objective lens 7 and then reflected by the beam splitting prism 6 as the monitoring light beam.

监控光束由场镜9聚焦之后，形成双螺旋聚焦光斑由光电感应器件10接收，并将光斑强度分布信息传送至计算机11。After the monitoring light beam is focused by the field lens 9 , a double helical focusing spot is formed, which is received by the photoelectric sensor 10 , and the intensity distribution information of the spot is sent to the computer 11 .

计算机11根据所得到的光斑强度分布信息计算得出双螺旋光斑的光斑指向与水平方向的夹角（双螺旋聚焦光斑具有两个强度峰值，两个强度峰值之间的连线与水平方向的夹角，即为双螺旋光斑的光斑指向与水平方向的夹角），并标定该夹角（也称为聚焦光斑指向角）与样品轴向漂移量的关系，将此关系式作为系统的标定函数。The computer 11 calculates the angle between the direction of the double helix spot and the horizontal direction according to the obtained light spot intensity distribution information (the double helix focus spot has two intensity peaks, and the angle between the line between the two intensity peaks and the horizontal direction Angle, which is the angle between the spot pointing of the double helix spot and the horizontal direction), and calibrate the relationship between the angle (also called the pointing angle of the focusing spot) and the axial drift of the sample, and use this relationship as the calibration function of the system .

当待测样品发生轴向位置漂移时，计算机11根据所测得的监控光束聚焦光斑指向角在标定好的系统内跟踪查询到相应的待测样品的轴向位置漂移量，并据此发出指令调整三维纳米扫描平台8的轴向位置，实现对待测样品的轴向位置的校正。When the axial position drift of the sample to be measured occurs, the computer 11 tracks and inquires the corresponding axial position drift of the sample to be measured in the calibrated system according to the measured pointing angle of the focused spot of the monitoring beam, and issues instructions accordingly Adjust the axial position of the three-dimensional nano-scanning platform 8 to realize the correction of the axial position of the sample to be measured.

具体来说：Specifically:

本实施例采用CCD作为光电感应器件10，此时根据CCD上聚焦光斑的强度分布，可以计算得出监控光束的聚焦光斑指向角。将待测样品放在三维纳米扫描平台8上，通过调整三维纳米扫描平台8的轴向位置，并实时记录CCD上监控光束聚焦光斑的强度分布，计算出监控光束聚焦光斑指向角，从而得到光斑指向角与待测样品的轴向位置漂移量的关系，把这个关系式作为系统标定函数输入计算机11，完成系统的标定。In this embodiment, a CCD is used as the photoelectric sensing device 10. At this time, according to the intensity distribution of the focused spot on the CCD, the pointing angle of the focused spot of the monitoring beam can be calculated. Put the sample to be tested on the three-dimensional nano-scanning platform 8, adjust the axial position of the three-dimensional nano-scanning platform 8, and record the intensity distribution of the focused spot of the monitoring beam on the CCD in real time, calculate the pointing angle of the focused spot of the monitoring beam, and obtain the spot The relationship between the pointing angle and the axial position drift of the sample to be measured is input into the computer 11 as a system calibration function to complete the system calibration.

当待测样品发生轴向位置漂移时，CCD将监控光束的聚焦光斑强度分布传送给计算机11，计算机11计算出相应的光斑指向角后，在标定好的系统内跟踪查询到相应的待测样品的轴向位置漂移量，并据此发出指令调整三维纳米扫描平台8的轴向位置，即可实现待测样品轴向位置的校正。When the axial position of the sample to be tested drifts, the CCD transmits the focused spot intensity distribution of the monitoring beam to the computer 11, and the computer 11 calculates the corresponding spot pointing angle, and tracks and inquires the corresponding sample to be tested in the calibrated system The axial position drift of the 3D nano-scanning platform 8 can be adjusted according to the axial position of the three-dimensional nano-scanning platform 8, so as to realize the correction of the axial position of the sample to be measured.

为了进一步检验上述装置和方法的实际效果，本实施例分别记载了待测样品不同轴向位置漂移量下，相应的监控光束聚焦光斑的光强分布情况，具体如图3所示，其中z₀为所用激光光束的瑞利长度。在图3中，a图为z=-2.5z₀形成的聚焦光斑的光强分布图，b图为z=-z₀形成的聚焦光斑的光强分布图，c图为z=0形成的聚焦光斑的光强分布图，d图为z=z₀形成的聚焦光斑的光强分布图，e图为z=2.5z₀形成的聚焦光斑的光强分布图，由此可知，通过测量监控光束聚焦光斑的光强分布，可以简单有效地完成对于待测样品轴向漂移的实时检测与补偿。In order to further test the actual effect of the above-mentioned device and method, this embodiment records the light intensity distribution of the corresponding monitoring beam focus spot under different axial position drifts of the sample to be tested, as shown in Figure 3, where z ₀ is the Rayleigh length of the laser beam used. In Figure 3, picture a is the light intensity distribution diagram of the focused spot formed by z=-2.5z ₀ , picture b is the light intensity distribution picture of the focused spot formed by z=-z ₀ , and picture c is the light intensity distribution picture formed by z=0 The light intensity distribution diagram of the focused spot, the picture d is the light intensity distribution picture of the focused spot formed by z=z ₀ , and the picture e is the light intensity distribution picture of the focused spot formed by z=2.5z ₀ . The light intensity distribution of the focused spot of the beam can simply and effectively complete the real-time detection and compensation of the axial drift of the sample to be measured.

Claims

1. A sample axial drift detection and compensation method based on a double helical light beam, characterized in that, comprising the following steps:

1) The collimated laser beam is incident into the spatial light modulator for phase modulation to obtain a double helical illumination beam. The focused spot of the double helix illumination beam presents two intensity peaks, and the difference between the two intensity peaks is The line between them has a rotation characteristic in the beam propagation direction, that is, at different axial positions, the angle between the line between the two intensity peaks and the horizontal direction is different;

2) The double-helix illumination beam is focused and projected onto the sample to be measured on the three-dimensional nano-scanning platform, reflected by the sample to be tested and collected by a microscopic objective lens to obtain a reflected beam;

3) The reflected light beam is focused to obtain a focused spot with two intensity peaks, and a photoelectric sensor device is used to receive the focused spot to obtain spot intensity distribution information;

4) Calculate the angle between the line between the two intensity peaks and the horizontal direction according to the intensity distribution information of the facula;

5) Establish a calibration function using the relationship between the included angle and the axial drift of the sample;

6) When the axial position of the sample to be measured drifts, repeat steps 1) to 4) to obtain the real-time measured angle, calculate the current axial drift of the sample according to the calibration function, and calculate the current axial drift of the sample according to the current axial position of the sample. The drift amount adjusts the axial position of the three-dimensional nano-scanning platform to complete the correction of the axial position of the sample to be measured.

2. the sample axial drift detection and compensation method based on double helical light beam as claimed in claim 1, is characterized in that, the phase modulation function f (ρ, φ) of described spatial light modulator is

f(ρ,φ)=arg[U(ρ,φ,0)]

U(ρ,φ,z)=Σu _mn (ρ,φ,z),n=0,1,2,…,m=2n+1

Among them, (ρ, φ, z) are the three coordinate components of the cylindrical coordinate system with the focal point of the microscope objective lens as the origin, u _mn (ρ, φ, z) is the complex light field of the mnth order GL fundamental mode, and arg is Argument function of complex numbers.

3. the sample axial drift detection and compensation method based on double helical light beam as claimed in claim 2, is characterized in that, described mnth order GL fundamental mode complex optical field u _mn (ρ, φ, z) is:

\begin{matrix} {u u}_{mn mn} ((ρ ρ,, φ φ,, z z)) = = {w w}_{00} / / w w ((\overset{^^}{z z})) exp exp ((- - {\overset{^^}{ρ ρ}}^{22})) exp exp ((i i {\overset{^^}{ρ ρ}}^{22} \overset{^^}{z z})) exp exp [[- - i i arctan arctan ((\overset{^^}{z z}))]] \cdot &Center Dot; {((\sqrt{22} \overset{^^}{ρ ρ}))}^{| | m m | |} {L L}_{n no}^{m m} ((22 {\overset{^^}{ρ ρ}}^{22})) \\ \cdot \cdot exp exp ((imφ imφ)) exp exp [[- - i i ((22 n no + + m m)) arctan arctan ((\overset{^^}{z z}))]] \end{matrix}

Among them, w ₀ is the beam waist radius of the laser beam, i is the imaginary number unit, λ is the wavelength of the laser beam used, is the mnth order Laguerre polynomial.

4. the sample axial drift detection and compensation method based on double helical light beam as claimed in claim 3, is characterized in that, described (m, n) take the value of (1,0), (3,1), ( 5,2), (7,3) and (9,4).

5 . The method for detecting and compensating axial drift of a sample based on a double helical beam according to claim 1 , wherein the photoelectric sensing device is a high-speed charge-coupled device. 6 .

6. A device for realizing the sample axial drift detection and compensation method according to any one of claims 1 to 5, characterized in that it comprises:

laser, a laser for emitting a laser beam;

a spatial light modulator for phase modulating the laser beam;

Three-dimensional nano-scanning platform for placing samples to be tested;

a microscope objective lens, used to focus the light beam emitted by the spatial light modulator to the sample to be tested, and collect the reflected light beam emitted by the sample to be tested;

A field lens, used to focus the reflected light beam and obtain a focused spot;

a photoelectric sensing device, which receives the focused light spot and obtains the intensity distribution information of the light spot;

And a computer connected with the three-dimensional nano-scanning platform and the photoelectric induction device.

7. The device according to claim 6, wherein a single-mode optical fiber, a collimating lens and a reflecting mirror are sequentially arranged between the laser and the spatial light modulator.

8. The device according to claim 6, wherein the phase modulation function f (ρ, φ) of the spatial light modulator is

f(ρ,φ)=arg[U(ρ,φ,0)]

U(ρ,φ,z)=Σu _mn (ρ,φ,z),n=0,1,2,…,m=2n+1

Among them, (ρ, φ, z) are the three coordinate components of the cylindrical coordinate system with the focal point of the microscope objective lens as the origin, u _mn (ρ, φ, z) is the complex light field of the mnth order GL fundamental mode, and arg is Argument functions of complex numbers;

The complex optical field u _mn (ρ, φ, z) of the mnth order GL fundamental mode is:

\begin{matrix} {u u}_{mn mn} ((ρ ρ,, φ φ,, z z)) = = {w w}_{00} / / w w ((\overset{^^}{z z})) exp exp ((- - {\overset{^^}{ρ ρ}}^{22})) exp exp ((i i {\overset{^^}{ρ ρ}}^{22} \overset{^^}{z z})) exp exp [[- - i i arctan arctan ((\overset{^^}{z z}))]] \cdot &Center Dot; {((\sqrt{22} \overset{^^}{ρ ρ}))}^{| | m m | |} {L L}_{n no}^{m m} ((22 {\overset{^^}{ρ ρ}}^{22})) \\ \cdot &Center Dot; exp exp ((imφ imφ)) exp exp [[- - i i ((22 n no + + m m)) arctan arctan ((\overset{^^}{z z}))]] \end{matrix}

Among them, w ₀ is the beam waist radius of the laser beam, i is the imaginary number unit, λ is the wavelength of the laser beam used,

w (\hat{z}) = w_{0} {(1 + {\hat{z}}^{2})}^{1 / 2},

\hat{ρ} = ρ / w (\hat{z}),

is the mnth order Laguerre polynomial.

9. The device according to claim 8, wherein the values of (m, n) are (1,0), (3,1), (5,2), (7,3) and ( 9,4).

10. The device according to claim 6, wherein the photoelectric sensing device is a high-speed charge-coupled device.