CN116182740A - Large field of view 3D phase reconstruction system and method based on coherent modulation imaging - Google Patents

Abstract

The invention discloses a large-view-field three-dimensional phase reconstruction system and method based on coherent modulation imaging, and belongs to the field of coherent modulation imaging. The diffraction patterns at different scanning positions are acquired by translating the three-dimensional sample to be detected, the imaging range is enlarged, and the three-dimensional sample to be detected is subjected to phase reconstruction by a layering slicing method, so that the method can reconstruct not only the two-dimensional non-expansile sample, but also the complex amplitude distribution of the three-dimensional expansile sample of tens to hundreds of micrometers. And in the reconstruction process, the sample function and the modulator function are updated at the same time, and the complex value field of the three-dimensional sample to be detected and the transmittance function of the modulator are reconstructed by using an iterative projection algorithm at the same time under the condition that the modulator distribution is completely unknown, and the method is independent of other imaging modes and used independently, so that the coherent modulation imaging technology is more independent and has wider application range.

Description

Large field of view three-dimensional phase reconstruction system and method based on coherent modulation imaging

Technical Field

The present invention relates to the field of coherent modulation imaging, and in particular to a large-field-of-view three-dimensional phase reconstruction system and method based on coherent modulation imaging.

Background Art

With the urgent demand for high-resolution imaging, light sources in the short-wavelength field such as X-rays, deep ultraviolet rays and electron beams are increasingly widely used. However, the optical imaging devices used in this band are difficult to manufacture and have high costs. Therefore, coherent diffraction imaging technology that does not rely on high-quality optical imaging elements plays a vital role here. Coherent modulation imaging is a new coherent diffraction imaging method. It has the advantages of simple imaging optical path and short data acquisition time. It is currently used in dynamic imaging, online wavefront diagnosis of high-power lasers and detection of optical components. Compared with the traditional coherent diffraction imaging method, coherent modulation imaging technology introduces a phase modulator in the imaging optical path to scatter the object light wave, thereby reducing the intensity of the central bright spot and reducing the requirements for the dynamic range of the detector. At the same time, due to the introduction of the modulator, the information of an object point can be distributed to many pixels of the detector, which reduces the sensitivity to detector noise during the reconstruction process, thereby significantly improving the convergence and robustness of the iterative method.

Traditional coherent modulation imaging technology requires the transmittance function of the modulator as prior information, and the modulator is usually calibrated in advance through stacked imaging. This method forces coherent modulation imaging technology to rely on other imaging methods. The imaging system is usually more complex, and the signal-to-noise ratio of the imaging results is relatively low. In addition, current research on coherent modulation imaging technology is mainly aimed at two-dimensional samples and non-extensive samples, and there is less research on three-dimensional samples and extended samples. Most samples have a certain thickness, and the measurement of three-dimensional objects is more general. Therefore, it is necessary to develop new methods to make coherent modulation imaging technology a more independent and more widely applicable diffraction imaging technology.

Summary of the invention

The purpose of the present invention is to provide a large-field-of-view three-dimensional phase reconstruction system and method based on coherent modulation imaging, which can realize phase reconstruction of three-dimensional samples and make coherent modulation imaging technology more independent and more widely applicable.

To achieve the above object, the present invention provides the following solutions:

A large-field-of-view three-dimensional phase reconstruction system based on coherent modulation imaging, comprising: a semiconductor laser source, a spatial filtering collimation system, a beam splitter, a probe, a two-dimensional translation stage, a phase modulator, a detector and a computer;

The three-dimensional sample to be tested is arranged on a two-dimensional translation stage, and the two-dimensional translation stage is used to drive the three-dimensional sample to be tested to perform two-dimensional translation;

After the two-dimensional translation stage drives the three-dimensional sample to be measured to translate each time: the laser beam emitted by the semiconductor laser source passes through the spatial filtering collimation system and outputs a plane wave; the plane wave is reflected by the beam splitter to form an incident light wave, and the incident light wave passes through the probe and the three-dimensional sample to be measured in turn, and the outgoing wave of the three-dimensional sample to be measured reaches the phase modulator; the phase modulator applies phase modulation to the outgoing wave, and transmits it to the detector, and the diffraction pattern of the scanning position of the three-dimensional sample to be measured is recorded in the detector; the scanning position is the position on the three-dimensional sample to be measured that irradiates the incident light wave;

The detector is connected to a computer, which is used to obtain diffraction patterns of different scanning positions of the three-dimensional sample to be tested recorded by the detector after multiple translations of the three-dimensional sample to be tested, and reconstruct the phase of the three-dimensional sample to be tested by using a multi-layer slicing method.

A large-field-of-view three-dimensional phase reconstruction method based on coherent modulation imaging, the large-field-of-view three-dimensional phase reconstruction method based on coherent modulation imaging using the aforementioned large-field-of-view three-dimensional phase reconstruction system based on coherent modulation imaging, the large-field-of-view three-dimensional phase reconstruction method based on coherent modulation imaging comprising:

Determining the diffraction propagation distance of the large field of view three-dimensional phase reconstruction system;

Obtaining diffraction patterns at different positions of the three-dimensional sample to be measured, and determining the scanning position of the three-dimensional sample to be measured from each diffraction pattern;

The three-dimensional sample to be tested is layered using a multi-layer slicing method;

Initialize the complex amplitude distribution of the probe, the complex amplitude distribution of each layer of the three-dimensional sample to be measured, and the transmittance function of the phase modulator;

According to the scanning position determined by each diffraction pattern, the diffraction propagation distance, the initialized probe complex amplitude distribution, the initialized complex amplitude distribution of each layer of the three-dimensional sample to be measured, and the initialized transmittance function of the phase modulator, an iterative projection algorithm is used for each diffraction pattern to reconstruct the complex value field of each layer of the three-dimensional sample to be measured at the scanning position and the transmittance function of the modulator;

According to the complex value field of each layer of the three-dimensional sample to be measured at the scanning position, the phase of each layer of the three-dimensional sample to be measured is obtained to form the three-dimensional phase of the three-dimensional sample to be measured.

Optionally, determining the diffraction propagation distance of the large field of view three-dimensional phase reconstruction system specifically includes:

The diffraction propagation distance of the large-field-of-view three-dimensional phase reconstruction system is determined from multiple diffraction pattern samples through automatic focusing and position alignment algorithms; the diffraction propagation distance includes the layer spacing of the three-dimensional sample, the diffraction propagation distance between the three-dimensional sample and the phase modulator, and the diffraction propagation distance between the phase modulator and the detector.

Optionally, the scanning position determined according to each diffraction pattern, the diffraction propagation distance, the initialized probe complex amplitude distribution, the initialized complex amplitude distribution of each layer of the three-dimensional sample to be measured, and the initialized transmittance function of the phase modulator, using an iterative projection algorithm for each diffraction pattern to reconstruct the complex value field of each layer of the three-dimensional sample to be measured at the scanning position and the transmittance function of the modulator, specifically includes:

According to the diffraction pattern, the scanning position determined by the diffraction pattern, the diffraction propagation distance, the initialized complex amplitude distribution of the probe, the initialized complex amplitude distribution of each layer of the three-dimensional sample to be measured, and the initialized transmittance function of the phase modulator, according to the propagation direction of the light wave, the exit field of each layer of the three-dimensional sample to be measured, the incident field of the phase modulator, the exit field of the phase modulator, and the plane light field of the detector are determined in sequence;

Reversely propagate the plane light field of the detector, and sequentially update the plane light field of the detector, the output field of the phase modulator, the incident field of the phase modulator, and the output fields of each layer of the three-dimensional sample to be measured;

updating the initialized transmittance function according to the updated incident field of the phase modulator;

According to the emission fields of each layer of the three-dimensional sample to be measured before and after the update, the initialized complex amplitude distribution of the probe and the initialized complex amplitude distribution of each layer of the three-dimensional sample to be measured are updated to complete one iteration;

The next iteration is performed according to the updated complex amplitude distribution of the probe, the updated complex amplitude distribution of each layer of the three-dimensional sample to be measured and the updated transmittance function until the maximum number of iterations is reached or convergence occurs, and the process ends.

Optionally, the exit field of each layer of the three-dimensional sample to be measured, the incident field of the phase modulator, the exit field of the phase modulator and the plane light field of the detector determined in sequence according to the propagation direction of the light wave are respectively:

式中，

表示光波经过第N层后的出射场，n表示待测三维样品的第n个扫描位置，j表示第j次迭代，符号·表示元素相乘，

表示波传播算子，z₀表示三维样品的层间距，P表示探针复振幅分布，O_N表示待测三维样品第N层的复振幅分布；The emission field of each layer of the three-dimensional sample to be measured:

In the formula,

represents the outgoing field after the light wave passes through the Nth layer, n represents the nth scanning position of the three-dimensional sample to be measured, j represents the jth iteration, and the symbol · represents element-wise multiplication.

represents the wave propagation operator, z ₀ represents the interlayer spacing of the three-dimensional sample, P represents the complex amplitude distribution of the probe, and O _N represents the complex amplitude distribution of the Nth layer of the three-dimensional sample to be tested;

式中，

表示相位调制器的入射场，z₁表示三维样品与相位调制器之间的衍射传播距离；Incident field of the phase modulator:

In the formula,

represents the incident field of the phase modulator, z ₁ represents the diffraction propagation distance between the three-dimensional sample and the phase modulator;

式中，

表示相位调制器的出射场，M表示相位调制器的透过率函数；The output field of the phase modulator:

In the formula,

represents the output field of the phase modulator, M represents the transmittance function of the phase modulator;

式中，

表示探测器的平面光场，z₂表示相位调制器与探测器之间的衍射传播距离。Planar light field of the detector:

In the formula,

represents the plane light field of the detector, and z ₂ represents the diffraction propagation distance between the phase modulator and the detector.

式中，

表示更新后的探测器的平面光场，I_n表示待测三维样品第n个扫描位置采集的衍射图案；Optionally, the updated plane light field of the detector is:

In the formula,

represents the updated plane light field of the detector, and _In represents the diffraction pattern collected at the nth scanning position of the three-dimensional sample to be measured;

式中，

表示更新后的相位调制器的出射场，

表示反向波传播算子；The output field of the updated phase modulator is:

In the formula,

represents the output field of the updated phase modulator,

represents the reverse wave propagation operator;

式中，

表示更新后的相位调制器的入射场，*表示复共轭运算，α表示第一反馈系数；The updated incident field of the phase modulator is:

In the formula,

represents the incident field of the updated phase modulator, * represents the complex conjugate operation, and α represents the first feedback coefficient;

式中，

表示更新后的待测三维样品第N层的出射场。The updated emission fields of each layer of the three-dimensional sample to be tested are:

In the formula,

Represents the updated output field of the Nth layer of the three-dimensional sample to be tested.

Optionally, the transmittance function update formula of the phase modulator is:

表示更新后的透过率函数，β表示第二反馈系数。In the formula,

represents the updated transmittance function, and β represents the second feedback coefficient.

式中，

表示待测三维样品第N层的复振幅分布；Optionally, the update formula of the complex amplitude distribution of each layer of the three-dimensional sample to be measured is:

In the formula,

represents the complex amplitude distribution of the Nth layer of the three-dimensional sample to be tested;

式中，

表示待测三维样品第N层对应的更新后的探针复振幅分布。The update formula of the probe complex amplitude distribution is:

In the formula,

It represents the updated probe complex amplitude distribution corresponding to the Nth layer of the three-dimensional sample to be tested.

According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

The present invention discloses a large-field-of-view three-dimensional phase reconstruction system and method based on coherent modulation imaging. The imaging range is increased by translating the three-dimensional sample to be tested to collect diffraction patterns at different scanning positions. The phase of the three-dimensional sample to be tested is reconstructed by a layered slicing method, so that the method can not only reconstruct two-dimensional non-expanded samples, but also reconstruct the complex amplitude distribution of three-dimensional expanded samples of tens to hundreds of microns. In addition, during reconstruction, the sample function and the modulator function are updated at the same time, and the complex value field of the three-dimensional sample to be tested and the transmittance function of the modulator are reconstructed at the same time under the condition of completely unknown modulator distribution by using an iterative projection algorithm. It is independent of other imaging methods and can be used independently, making the coherent modulation imaging technology more independent and more widely applicable.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

FIG1 is a schematic diagram of the structure of a large-field-of-view three-dimensional phase reconstruction system based on coherent modulation imaging provided by an embodiment of the present invention;

FIG2 is a flow chart of a large-field-of-view three-dimensional phase reconstruction method based on coherent modulation imaging provided by an embodiment of the present invention;

FIG. 3 is an iterative flow chart provided by an embodiment of the present invention.

Explanation of symbols: 1- semiconductor laser source, 2- spatial filtering and collimation system, 3- beam splitter, 4- probe, 5- three-dimensional sample to be measured, 6- phase modulator, 7- detector, 8- computer.

DETAILED DESCRIPTION

The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

The present invention proposes a large-field-of-view three-dimensional phase reconstruction system and method based on coherent modulation imaging. A two-dimensional electric translation stage is used to move the three-dimensional sample to be measured (extended sample), and multiple diffraction patterns at different positions are recorded on the detector. Each diffraction pattern corresponds to the same distribution of the same modulator. During translation, two adjacent positions will have a certain overlap, and the overlapping part remains unchanged in two measurements. In addition, the method can use an iterative projection algorithm to simultaneously reconstruct the complex value field of the three-dimensional extended sample and the transmittance function of the modulator in the case of completely unknown modulator distribution. During reconstruction, a layered slicing method is used to perform phase reconstruction on the three-dimensional extended sample. It is necessary to simultaneously update the sample function and modulator function of each layer in each step of the iterative process, and bring the updated results into the next iterative calculation. Finally, the algorithm converges and reconstructs the sample complex amplitude and modulator function. The introduction of this new method will make coherent modulation imaging technology a more independent and practical diffraction imaging technology, broadening its application in the fields of material science, biomedicine, engineering measurement, etc.

Example 1

As shown in Figure 1, an embodiment of the present invention provides a large field of view three-dimensional phase reconstruction system based on coherent modulation imaging, including: a semiconductor laser source 1, a spatial filtering and collimation system 2, a beam splitter 3, a probe 4, a two-dimensional translation stage, a phase modulator 6, a detector 7 and a computer 8.

The three-dimensional sample 5 to be tested is set on a two-dimensional translation stage, and the two-dimensional translation stage is used to drive the three-dimensional sample 5 to be tested to perform two-dimensional translation. After the two-dimensional translation stage drives the three-dimensional sample 5 to be tested to translate each time: the laser beam emitted by the semiconductor laser source 1 passes through the spatial filtering collimation system 2 and outputs a plane wave; after the plane wave is reflected by the beam splitter 3, an incident light wave is formed, and the incident light wave passes through the probe 4 and the three-dimensional sample 5 to be tested in turn, and the outgoing wave of the three-dimensional sample 5 to be tested reaches the phase modulator 6; after the phase modulator 6 applies phase modulation to the outgoing wave, it is transmitted to the detector 7, and the diffraction pattern of the scanning position of the three-dimensional sample 5 to be tested is recorded in the detector 7; the scanning position is the position on the three-dimensional sample 5 to be tested where the incident light wave is irradiated. The detector 7 is connected to a computer 8, and the computer 8 is used to obtain the diffraction patterns of different scanning positions of the three-dimensional sample 5 to be tested recorded by the detector 7 after the three-dimensional sample 5 to be tested is translated multiple times, and the phase of the three-dimensional sample 5 to be tested is reconstructed by a multi-layer slicing method.

The computer 8 is connected to the two-dimensional translation stage, and the computer 8 controls the moving track of the two-dimensional translation stage.

Exemplarily, the computer 8 can control the exposure time of the detector 7, thereby controlling the sampling frequency and sampling time (including the sampling end time). The detector 7 is preferably a CCD camera.

The specific experimental parameters are as follows: The laser beam emitted from the semiconductor laser source 1 (COHERENT, OBIS 532LS) with a wavelength of 532nm outputs a plane wave through the spatial filtering collimation system 2, and is reflected by the beam splitter 3BS (Beam Splitter) to irradiate the three-dimensional sample 5 to be tested (the dashed box in Figure 1 indicates that the three-dimensional sample is sliced by multi-layer slicing method, and each grid represents a slice layer). The three-dimensional sample 5 to be tested is placed on an x-y translation stage (DAHENG, GCD0401M), placed downstream of a 1mm probe 4, and the phase modulator 6 processed by the quartz substrate is placed at a certain distance behind the three-dimensional sample 5 to be tested. In the experiment, the phase modulator 6 is made of silicon glass and photolithography technology, and different etching depths on the substrate will bring different phase delays. It roughly has a binary structure of 0 and π, which can produce a random phase delay of 0/π for the incident light field of the working wavelength, and is designed to be randomly distributed, with the size of each pixel being 16μm×16μm. The final diffraction pattern is recorded by a CCD (Charge Coupled Device) camera (IMPERX IGV 6620B), and its pixel size is 5.5 μm × 5.5 μm. The CCD camera and the x-y translation stage (two-dimensional translation stage) are controlled by a computer 8. The function of the probe 4 is to limit the size of the light spot, play a constraining role in the spatial domain, and accelerate the convergence of the algorithm.

Example 2

A large-field-of-view three-dimensional phase reconstruction system (imaging optical path system) based on coherent modulation imaging of Example 1 is built on an experimental platform. Based on the built imaging optical path system, an embodiment of the present invention provides a large-field-of-view three-dimensional phase reconstruction method based on coherent modulation imaging, as shown in FIG2 , comprising:

Step 1: Determine the diffraction propagation distance of the large field of view 3D phase reconstruction system.

The diffraction propagation distance of the large field of view three-dimensional phase reconstruction system is determined from multiple diffraction pattern samples by automatic focusing and position registration algorithms. The diffraction propagation distance includes the layer spacing z ₀ of the three-dimensional sample, the diffraction propagation distance z ₁ between the three-dimensional sample and the phase modulator 6, and the diffraction propagation distance z ₂ between the phase modulator 6 and the detector.

Step 2: Obtain diffraction patterns at different positions of the three-dimensional sample 5 to be tested, and determine the scanning position of the three-dimensional sample 5 to be tested from each diffraction pattern.

A plurality of diffraction patterns are recorded by moving the three-dimensional sample 5 to be measured multiple times, and then experimental parameters such as the scanning position are pre-acquired from the measurement data through automatic focusing and position registration algorithms.

Step 3: Use a multi-layer slicing method to layer the three-dimensional sample 5 to be tested.

Slicing is performed along a direction parallel to the two-dimensional translation stage, and it is assumed that the distances between adjacent layers of all three-dimensional samples are equal, and the interlayer spacing of the three-dimensional samples is z ₀ .

Step 4: Initialize the complex amplitude distribution of the probe 4 , the complex amplitude distribution of each layer of the three-dimensional sample 5 to be measured, and the transmittance function of the phase modulator 6 .

Step 5: Based on the scanning position, diffraction propagation distance, initialized complex amplitude distribution of the probe 4, initialized complex amplitude distribution of each layer of the three-dimensional sample 5 to be tested, and initialized transmittance function of the phase modulator 6 determined for each diffraction pattern, an iterative projection algorithm is used for each diffraction pattern to reconstruct the complex value field of each layer of the three-dimensional sample 5 to be tested at the scanning position and the transmittance function of the modulator.

Exemplarily, the specific reconstruction process is:

According to the diffraction pattern, the scanning position determined by the diffraction pattern, the diffraction propagation distance, the initialized complex amplitude distribution of the probe 4, the initialized complex amplitude distribution of each layer of the three-dimensional sample 5 to be tested, and the initialized transmittance function of the phase modulator 6, according to the propagation direction of the light wave, the exit field of each layer of the three-dimensional sample 5 to be tested, the incident field of the phase modulator 6, the exit field of the phase modulator 6, and the plane light field of the detector 7 are determined in sequence;

The plane light field of the detector 7 is propagated in reverse order, and the plane light field of the detector 7, the output field of the phase modulator 6, the incident field of the phase modulator 6 and the output fields of each layer of the three-dimensional sample 5 to be measured are updated in sequence;

updating the initialized transmittance function according to the updated incident field of the phase modulator 6;

According to the exit fields of each layer of the three-dimensional sample 5 to be tested before and after the update, the initialized complex amplitude distribution of the probe 4 and the initialized complex amplitude distribution of each layer of the three-dimensional sample 5 to be tested are updated to complete one iteration;

The next iteration is performed according to the updated complex amplitude distribution of the probe 4 , the updated complex amplitude distribution of each layer of the three-dimensional sample 5 to be measured and the updated transmittance function until the maximum number of iterations is reached or convergence occurs.

Referring to the iterative flow chart shown in FIG3 , the detailed steps of one iteration are as follows:

Step 1: guess the complex amplitude distribution P of the probe and the complex amplitude distribution o ₁ , o ₂ . . . o _N of each layer of the three-dimensional sample and the transmittance function M of the phase modulator 6 , where N is the number of layers of the three-dimensional sample divided by the multi-layer slicing method.

Step 2: After the incident light wave passes through the probe P, it passes through each layer of the sample in turn. The output field of the Nth layer is

表示光波经过第N层后的出射场，n表示样品的第n个区域，j表示第j次迭代，·表示对应元素相乘，

表示波传播算子，可以是角谱传播算子或者傅里叶变换，z₀表示样品的层间距，我们假设每层样品之间的距离都是相等的。In the formula,

represents the outgoing field after the light wave passes through the Nth layer, n represents the nth region of the sample, j represents the jth iteration, and · represents the multiplication of the corresponding elements.

represents the wave propagation operator, which can be the angular spectrum propagation operator or the Fourier transform, z ₀ represents the interlayer spacing of the sample, and we assume that the distance between each layer of the sample is equal.

Step 3: The sample outgoing wave reaches the modulator plane after diffraction at a distance of z _1. The modulator incident light field distribution is

Step 4: Phase modulator 6 applies phase modulation to the light field, and the modulator emits a field

Step 5: The modulated light field continues to diffract and propagate forward a certain distance z ₂ to reach the detector 7 plane, and its light field distribution is

Step 6: In the detector 7 plane, an intensity constraint is imposed on the light field. The iteratively estimated detector 7 plane light field amplitude is replaced by the square root of the collected diffraction pattern, and the phase is kept unchanged to obtain the updated detector 7 plane light field distribution.

表示更新后探测器7平面的光场分布，I_n表示样品第n个区域采集的衍射图案。In the formula,

It represents the light field distribution of the detector 7 plane after updating, and _In represents the diffraction pattern collected from the nth area of the sample.

Step 7: Back propagate the light field obtained above to obtain the updated modulator output field

表示反向波传播算子。In the formula,

represents the reverse wave propagation operator.

Step 8: Update the modulator's transmittance function

In the formula, * represents the complex conjugate operation, α and β are feedback coefficients, and generally take the value of 1.

Step 9: Inverse diffract the updated modulator incident field to obtain the updated Nth layer output field

Step 10: Continue to backpropagate the updated output field of the Nth layer and update it layer by layer until it reaches the first layer, so as to obtain the updated material function and probe 4 distribution of each layer.

Repeat steps 2 to 10 until all recorded diffraction patterns are used up, and it is considered that one iteration is completed. When the predetermined number of iterations is completed or convergence occurs, the algorithm can be considered to be finished. When the mean square error between the restored diffraction pattern and the recorded diffraction pattern is small enough or the correlation between the two is high enough, the algorithm can be considered to have reached convergence.

Step 6: According to the complex value field of each layer of the three-dimensional sample 5 to be measured at the scanning position, the phase of each layer of the three-dimensional sample 5 to be measured is obtained to form the three-dimensional phase of the three-dimensional sample 5 to be measured.

The present invention has the following technical effects:

1. Strong independence: During reconstruction, the sample function and the modulator function are updated simultaneously, and the iterative projection algorithm is used to reconstruct the complex value field of the object and the transmittance function of the modulator at the same time when the modulator distribution is completely unknown. The proposed method does not require prior information and is completely independent of other imaging methods. Under plane wave illumination, this method has a higher signal-to-noise ratio than traditional coherent modulation imaging.

2. Large field of view: By translating the three-dimensional sample to be tested to collect diffraction patterns at different positions, the imaging range is increased, overcoming the problem of small field of view of single exposure of coherent modulation imaging. At the same time, due to the redundancy of data, the imaging resolution is also improved.

3. High adaptability: The phase of three-dimensional thick samples is reconstructed by layered slicing, so that this method can not only reconstruct two-dimensional non-expanded samples, but also reconstruct the complex amplitude distribution of three-dimensional expanded samples of tens to hundreds of microns.

The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims (10)

1. A large field of view three-dimensional phase reconstruction system based on coherent modulation imaging, characterized in that it includes: a semiconductor laser source, a spatial filtering collimation system, a beam splitter, a probe, a two-dimensional translation stage, a phase modulator, a detector and a computer; The three-dimensional sample to be tested is arranged on a two-dimensional translation stage, and the two-dimensional translation stage is used to drive the three-dimensional sample to be tested to perform two-dimensional translation; After the two-dimensional translation stage drives the three-dimensional sample to be measured to translate each time: the laser beam emitted by the semiconductor laser source passes through the spatial filtering collimation system and outputs a plane wave; the plane wave is reflected by the beam splitter to form an incident light wave, which passes through the probe and the three-dimensional sample to be measured in turn, and the outgoing wave of the three-dimensional sample to be measured reaches the phase modulator; the phase modulator applies phase modulation to the outgoing wave, and transmits it to the detector, and the diffraction pattern of the scanning position of the three-dimensional sample to be measured is recorded in the detector; the scanning position is the position on the three-dimensional sample to be measured that irradiates the incident light wave; The detector is connected to a computer, which is used to obtain the diffraction patterns of the three-dimensional sample at different scanning positions recorded by the detector after the three-dimensional sample is translated multiple times, and reconstruct the phase of the three-dimensional sample by using a multi-layer slicing method. 2. The large field of view three-dimensional phase reconstruction system based on coherent modulation imaging according to claim 1, characterized in that the computer is connected to a two-dimensional translation stage; The computer is used to control the moving track of the two-dimensional translation stage. 3. The large-field-of-view three-dimensional phase reconstruction system based on coherent modulation imaging according to claim 1, characterized in that the detector is a CCD camera. 4. A method for large-field-of-view three-dimensional phase reconstruction based on coherent modulation imaging, characterized in that the method for large-field-of-view three-dimensional phase reconstruction based on coherent modulation imaging applies the large-field-of-view three-dimensional phase reconstruction system based on coherent modulation imaging according to any one of claims 1 to 3, and the method for large-field-of-view three-dimensional phase reconstruction based on coherent modulation imaging comprises: Determining the diffraction propagation distance of the large field of view three-dimensional phase reconstruction system; Obtaining diffraction patterns at different positions of the three-dimensional sample to be measured, and determining the scanning position of the three-dimensional sample to be measured from each diffraction pattern; The three-dimensional sample to be tested is layered using a multi-layer slicing method; Initialize the complex amplitude distribution of the probe, the complex amplitude distribution of each layer of the three-dimensional sample to be measured, and the transmittance function of the phase modulator; According to the scanning position determined by each diffraction pattern, the diffraction propagation distance, the initialized probe complex amplitude distribution, the initialized complex amplitude distribution of each layer of the three-dimensional sample to be measured, and the initialized transmittance function of the phase modulator, an iterative projection algorithm is used for each diffraction pattern to reconstruct the complex value field of each layer of the three-dimensional sample to be measured at the scanning position and the transmittance function of the modulator; According to the complex value field of each layer of the three-dimensional sample to be measured at the scanning position, the phase of each layer of the three-dimensional sample to be measured is obtained to form the three-dimensional phase of the three-dimensional sample to be measured. 5. The method for large-field-of-view three-dimensional phase reconstruction based on coherent modulation imaging according to claim 4, characterized in that determining the diffraction propagation distance of the large-field-of-view three-dimensional phase reconstruction system specifically comprises: The diffraction propagation distance of the large-field-of-view three-dimensional phase reconstruction system is determined from multiple diffraction pattern samples by automatic focusing and position alignment algorithms; the diffraction propagation distance includes the layer spacing of the three-dimensional sample, the diffraction propagation distance between the three-dimensional sample and the phase modulator, and the diffraction propagation distance between the phase modulator and the detector. 6. The method for large-field three-dimensional phase reconstruction based on coherent modulation imaging according to claim 4 is characterized in that, according to the scanning position determined for each diffraction pattern, the diffraction propagation distance, the initialized probe complex amplitude distribution, the initialized complex amplitude distribution of each layer of the three-dimensional sample to be measured, and the transmittance function of the initialized phase modulator, an iterative projection algorithm is used for each diffraction pattern to reconstruct the complex value field of each layer of the three-dimensional sample to be measured at the scanning position and the transmittance function of the modulator, specifically comprising: According to the diffraction pattern, the scanning position determined by the diffraction pattern, the diffraction propagation distance, the initialized complex amplitude distribution of the probe, the initialized complex amplitude distribution of each layer of the three-dimensional sample to be measured, and the initialized transmittance function of the phase modulator, according to the propagation direction of the light wave, the exit field of each layer of the three-dimensional sample to be measured, the incident field of the phase modulator, the exit field of the phase modulator, and the plane light field of the detector are determined in sequence; Reversely propagate the plane light field of the detector, and sequentially update the plane light field of the detector, the output field of the phase modulator, the incident field of the phase modulator, and the output fields of each layer of the three-dimensional sample to be measured; updating the initialized transmittance function according to the updated incident field of the phase modulator; According to the emission fields of each layer of the three-dimensional sample to be measured before and after the update, the initialized complex amplitude distribution of the probe and the initialized complex amplitude distribution of each layer of the three-dimensional sample to be measured are updated to complete one iteration; The next iteration is performed according to the updated complex amplitude distribution of the probe, the updated complex amplitude distribution of each layer of the three-dimensional sample to be measured and the updated transmittance function until the maximum number of iterations is reached or convergence occurs, and the process ends. 7. The method for large-field three-dimensional phase reconstruction based on coherent modulation imaging according to claim 6 is characterized in that the exit field of each layer of the three-dimensional sample to be measured, the incident field of the phase modulator, the exit field of the phase modulator, and the plane light field of the detector determined in sequence according to the propagation direction of the light wave are respectively: The emission field of each layer of the three-dimensional sample to be measured:

In the formula,

represents the outgoing field after the light wave passes through the Nth layer, n represents the nth scanning position of the three-dimensional sample to be measured, j represents the jth iteration, and the symbol · represents element-wise multiplication.

represents the wave propagation operator, z ₀ represents the interlayer spacing of the three-dimensional sample, P represents the complex amplitude distribution of the probe, and O _N represents the complex amplitude distribution of the Nth layer of the three-dimensional sample to be tested; Incident field of the phase modulator:

In the formula,

represents the incident field of the phase modulator, z ₁ represents the diffraction propagation distance between the three-dimensional sample and the phase modulator; The output field of the phase modulator:

In the formula,

represents the output field of the phase modulator, M represents the transmittance function of the phase modulator; Planar light field of the detector:

In the formula,

represents the plane light field of the detector, and z ₂ represents the diffraction propagation distance between the phase modulator and the detector. 8. The method for large field of view three-dimensional phase reconstruction based on coherent modulation imaging according to claim 7, characterized in that: The updated plane light field of the detector is:

In the formula,

represents the updated plane light field of the detector, and _In represents the diffraction pattern collected at the nth scanning position of the three-dimensional sample to be measured; The output field of the updated phase modulator is:

In the formula,

represents the output field of the updated phase modulator,

represents the reverse wave propagation operator; The updated incident field of the phase modulator is:

In the formula,

represents the incident field of the updated phase modulator, * represents the complex conjugate operation, and α represents the first feedback coefficient; The updated emission fields of each layer of the three-dimensional sample to be tested are:

In the formula,

Represents the updated output field of the Nth layer of the three-dimensional sample to be tested. 9. The large field of view three-dimensional phase reconstruction method based on coherent modulation imaging according to claim 8, characterized in that the transmittance function update formula of the phase modulator is:

In the formula,

represents the updated transmittance function, and β represents the second feedback coefficient. 10. The method for large field of view three-dimensional phase reconstruction based on coherent modulation imaging according to claim 9, characterized in that: The update formula of the complex amplitude distribution of each layer of the three-dimensional sample to be tested is:

In the formula,

represents the complex amplitude distribution of the Nth layer of the three-dimensional sample to be tested; The update formula of the probe complex amplitude distribution is:

In the formula,

It represents the updated probe complex amplitude distribution corresponding to the Nth layer of the three-dimensional sample to be tested.

Images