Reflective laminated imaging method based on off-axis diffraction and related device

Abstract

The invention discloses a reflective laminated imaging method based on off-axis diffraction and a related device, and relates to the field of laminated diffraction imaging, and the method comprises the steps: obtaining diffraction images of different scanning positions in a sample target area; according to the diffraction image, performing diffraction light field reconstruction by using an improved rPIE iterative algorithm to obtain the amplitude and phase of sample reconstruction; according to the improved rPIE iterative algorithm, a diffraction propagation model in a traditional rPIE iterative algorithm is replaced with a parallel plane off-axis diffraction transmission model. According to the method, a diffraction propagation model in a traditional rPIE iterative algorithm is replaced by a parallel plane off-axis diffraction transmission model, a relatively simple light field transmission model is established and applied to realize the reconstruction of reflective laminated imaging, complicated interpolation calculation is not involved, the reconstruction method is simplified, and the resolution of a reconstruction result is improved. And the reconstruction accuracy is improved in the aspects of contrast, resolution and the like.

Description

Technical Field

[0001] The present application relates to the field of stacked diffraction imaging, and in particular to a reflective stacked imaging method based on off-axis diffraction and related devices. Background Art

[0002] Layered diffraction imaging is a computational imaging technology that has emerged in recent years. It has the advantages of no lenses, simple optical path, high resolution, and no need for high-quality optical components. It has been widely used in fields such as X-ray diffraction. In industrial detection, based on the nature of industrial detection samples, industrial sample surface detection generally requires the use of a reflective system. In industrial detection, most of the samples to be tested are thick and opaque samples, and a reflective optical path is required for surface detection. The reflective optical path involves tilting, and the light beam will be deformed, which may involve complex interpolation operations to adapt to Fourier transforms. Due to the complexity of existing reflective systems, it is necessary to establish a more accurate, simple, and non-complex interpolation physical model to describe the diffraction process at larger reflection angles. Summary of the invention

[0003] The purpose of this application is to provide a reflective stack imaging method and related devices based on off-axis diffraction. The off-axis diffraction method is used for the first time to describe the reflective diffraction process between parallel planes. The model is relatively simple and does not involve complex interpolation calculations.

[0004] To achieve the above objectives, this application provides the following solutions:

[0005] In a first aspect, the present application provides a reflective stack imaging method based on off-axis diffraction, comprising:

[0006] Acquire diffraction images at different scanning positions within the target area of ​​the sample;

[0007] According to the diffraction image, an improved rPIE iterative algorithm is applied to reconstruct the diffraction light field to obtain the amplitude and phase of the sample reconstruction; the improved rPIE iterative algorithm refers to replacing the diffraction propagation model in the traditional rPIE iterative algorithm with a parallel plane off-axis diffraction transmission model.

[0008] In a second aspect, the present application provides a reflective stack imaging device based on off-axis diffraction, comprising: a computer and, in order according to the propagation direction of light, a laser, a first reflector, a second reflector, an attenuation plate, an objective lens, a spatial filter, a collimating convex lens, a reflective sample and a detector;

[0009] The detector is used to collect diffraction images at different scanning positions within the sample target area;

[0010] The computer is used to execute the above-mentioned off-axis diffraction-based reflective stacking imaging method.

[0011] In a third aspect, the present application provides a computer device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the above-mentioned off-axis diffraction-based reflective stacking imaging method.

[0012] In a fourth aspect, the present application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-mentioned off-axis diffraction-based reflective stacking imaging method.

[0013] In a fifth aspect, the present application provides a computer program product, including a computer program, which, when executed by a processor, implements the above-mentioned off-axis diffraction-based reflective stacking imaging method.

[0014] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0015] The present application provides a reflective stack imaging method based on off-axis diffraction and related devices, including: obtaining diffraction images at different scanning positions in the target area of ​​the sample; according to the diffraction images, applying an improved rPIE iterative algorithm to reconstruct the diffraction light field to obtain the amplitude and phase of the sample reconstruction; the improved rPIE iterative algorithm refers to replacing the diffraction propagation model in the traditional rPIE iterative algorithm with a parallel plane off-axis diffraction transmission model. In the present invention, the diffraction propagation model in the traditional rPIE iterative algorithm is replaced with a parallel plane off-axis diffraction transmission model, and a relatively simple light field transmission model is established and used to realize the reconstruction of reflective stack imaging, which does not involve complex interpolation calculations, simplifies the reconstruction method, and improves the reconstruction accuracy in terms of clarity, contrast and resolution of the reconstruction results. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application 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 application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 A diagram of the application environment of a reflective stacking imaging method based on off-axis diffraction provided in Example 1 of the present application;

[0018] Figure 2 A schematic flow chart of a reflective stacking imaging method based on off-axis diffraction provided in Example 1 of the present application;

[0019] Figure 3A schematic diagram of the technical concept of a reflective stack imaging method based on off-axis diffraction provided in Example 1 of the present application;

[0020] Figure 4 A schematic diagram of a parallel plane reflection propagation coordinate system provided in Example 1 of the present application;

[0021] Figure 5 A schematic diagram of the amplitude and phase recovery and reconstruction results provided in Example 1 of the present application;

[0022] Figure 6 A schematic structural diagram of a reflective stacked imaging device based on off-axis diffraction provided in Example 2 of the present application;

[0023] Figure 7 A schematic diagram of the structure of a computer device provided in Example 3 of the present application. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0025] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0026] Example 1

[0027] The off-axis diffraction based reflective stacking imaging method provided in the embodiment of the present application can be applied to Figure 1In the application environment shown. Among them, the terminal communicates with the server through the network. The data storage system can store the data that the server needs to process. The data storage system can be set up separately, integrated on the server, or placed on the cloud or other servers. The terminal can send the diffraction images of different scanning positions in the sample target area to the server. After the server receives it, the server applies the improved rPIE iterative algorithm to reconstruct the diffraction light field according to the diffraction image, and obtains the amplitude and phase of the sample reconstruction; the improved rPIE iterative algorithm refers to replacing the diffraction propagation model in the traditional rPIE iterative algorithm with the parallel plane off-axis diffraction transmission model. The server can feed back the obtained amplitude and phase of the sample reconstruction to the terminal. In addition, in some embodiments, the reflective stacking imaging method based on off-axis diffraction can also be implemented by a server or a terminal alone, such as the terminal can directly target the diffraction images of different scanning positions in the sample target area, and apply the improved rPIE iterative algorithm to reconstruct the diffraction light field, or the server can obtain the diffraction images of different scanning positions in the sample target area from the data storage system, and apply the improved rPIE iterative algorithm to reconstruct the diffraction light field.

[0028] The terminals may be, but are not limited to, various desktop computers, laptops, smart phones, tablet computers, IoT devices and portable wearable devices. IoT devices may be smart speakers, smart TVs, smart air conditioners, smart car-mounted devices, etc. Portable wearable devices may be smart watches, smart bracelets, head-mounted devices, etc. The server may be implemented as an independent server or a server cluster consisting of multiple servers, or a cloud server.

[0029] In an exemplary embodiment, based on off-axis diffraction, a parallel plane scheme is used to study reflective stack imaging. Stack imaging, as a type of computational imaging, is widely known in the field of image phase recovery. After a coherent light beam (such as a laser) interacts with a sample to be tested, the propagated diffraction pattern is received and recorded by a detector, and the sample and the probe are moved relative to each other to obtain a coherent diffraction pattern with a certain overlap rate. Finally, a reconstruction algorithm is used to reconstruct the amplitude and phase distribution information of the sample to be tested. Stack imaging technology is widely used due to its advantages such as no lens, expandable imaging range, and fast convergence speed. In industrial inspection, most of the samples to be tested cannot transmit light, and transmissive stack imaging cannot be used. It is necessary to extend the stack imaging technology to the reflection field. However, due to the complexity of the reflection system, it is of profound significance to establish and use a relatively simple light field transmission model to realize the reconstruction of reflective stack imaging. Therefore, the parallel plane reflective stack imaging scheme based on off-axis diffraction has a positive impact on the detection of reflective industrial samples. Figure 2 and Figure 3As shown, the present invention provides a reflective stack imaging method based on off-axis diffraction, which is executed by a computer device, specifically, it can be executed by a computer device such as a terminal or a server alone, or it can be executed by a terminal and a server together. In the embodiment of the present application, the method is applied to Figure 1 The server in the example is used to illustrate, including the following steps 101 to 102. Among them:

[0030] Step 101, obtaining diffraction images at different scanning positions within a target area of ​​a sample.

[0031] As an example, a parallel plane reflective stack imaging system can be built. The surface of the sample to be tested is parallel to the detector surface, and the size of each pixel of the detector is 5.5μm. The laser uses a 532nm green light laser. The distance from the surface of the sample to be tested to the CCD camera for collecting diffraction patterns is 90mm. A series of sample diffraction patterns with a certain overlap are collected to reconstruct and restore the sample amplitude and phase information distribution.

[0032] Step 102, according to the diffraction image, apply the improved rPIE iterative algorithm to reconstruct the diffraction light field to obtain the amplitude and phase of the sample reconstruction; the improved rPIE iterative algorithm refers to replacing the diffraction propagation model in the traditional rPIE iterative algorithm with a parallel plane off-axis diffraction transmission model.

[0033] Implement the above-mentioned steps 101 to 102 to obtain diffraction images at different scanning positions in the target area of ​​the sample; according to the diffraction image, apply the improved rPIE iterative algorithm to reconstruct the diffraction light field to obtain the amplitude and phase of the sample reconstruction; the improved rPIE iterative algorithm refers to replacing the diffraction propagation model in the traditional rPIE iterative algorithm with a parallel plane off-axis diffraction transmission model. In the present invention, the diffraction propagation model in the traditional rPIE iterative algorithm is replaced with a parallel plane off-axis diffraction transmission model, and a relatively simple light field transmission model is established and used to realize the reconstruction of reflective stacked imaging, which does not involve complex interpolation calculations, simplifies the reconstruction method, and improves the reconstruction accuracy in terms of clarity, contrast and resolution of the reconstruction results.

[0034] In another exemplary embodiment of the present application, in step 102, the collected sample diffraction pattern data and the experimental parameters of the parallel plane reflective stack imaging system are input into the rPIE iterative algorithm for reconstruction and recovery, and the diffraction transmission model in the rPIE iterative algorithm is replaced with the parallel plane off-axis diffraction transmission model. The formula derivation process of the parallel plane off-axis diffraction transmission model is as follows:

[0035] like Figure 4 As shown, it is a parallel plane reflection propagation coordinate system, and the wave vector is The incident beam (solid arrow, related to the laser wavelength λ, known quantity, size is ) is reflected by the sample surface and transmitted to the detector surface parallel to the sample surface. This process can make the incident light beam equivalent. The wave vector size of the equivalent inclined incident light beam is k0, and the direction of the equivalent inclined incident light beam is the same as the displacement vector The transmitted beam in the same direction ( Figure 4 The dashed arrow in the figure shows the direction of incidence, where is the direction of the principal ray of the reflected beam. The input field is extracted from the integral using the parallel plane angular spectrum method. The separation of the input field and the lateral modulation can effectively simulate the propagation of light at any angle along the tilted axis. The sampling window is laterally shifted (x0, y0) due to the oblique incident light. Define the displacement vector is the direction vector from the input surface to the output surface.

[0036]

[0037] Among them, θ x With θ y is the angle between the equivalent inclined incident wave vector and the x-axis and y-axis, which is known from the experimental measurement. is the unit vector in the x, y, and z directions; Z is the vertical distance from the sample plane to the detector plane, which is known in the experiment.

[0038] Define the shift wave vector:

[0039]

[0040] in, is the wave vector after rotation. The magnitude of the shifted wave vector is 2π / f, where f is the spatial frequency corresponding to the corresponding position on the detector plane.

[0041] The off-axis diffraction transfer function is expressed as:

[0042]

[0043] The relationship between the wave vectors is: Use K x and K y To represent K z . K x , K y and K z represents the shifted wave vector Components in the x, y, and z directions; k 0x , k 0y and k 0z represents the incident beam wave vector Components in the x, y, and z directions.

[0044] The off-axis transfer function expression is further derived as:

[0045]

[0046] in, is the tilt factor, is the displacement vector and The cosine of the angle is

[0047] In another exemplary embodiment of the present application, in step 102, after introducing the parallel plane off-axis diffraction transmission model, the improved rPIE iterative algorithm is applied to reconstruct the diffraction light field according to the diffraction image to obtain the amplitude and phase of the sample reconstruction, which specifically includes:

[0048] (1) Randomly determine the initial complex amplitude distribution diagram of the sample, and determine the initial complex amplitude distribution diagram of the probe based on the collected probe.

[0049] (2) A target scanning position is randomly selected, and the complex amplitude distributions in the current sample complex amplitude distribution map and the current probe complex amplitude distribution map at the current target scanning position are determined respectively, so as to obtain the sample target scanning position complex amplitude distribution map and the probe target scanning position complex amplitude distribution map; initially, the current sample complex amplitude distribution map and the current probe complex amplitude distribution map refer to the sample initial complex amplitude distribution map and the probe initial complex amplitude distribution map.

[0050] (3) Calculating the exit field after the probe interacts with the sample based on the complex amplitude distribution diagram of the current sample target scanning position and the complex amplitude distribution diagram of the current probe target scanning position.

[0051] (4) Calculate the diffraction light field of the current output field on the observation plane according to the parallel plane off-axis diffraction transmission model.

[0052] (5) Using the measured diffraction light intensity to replace the amplitude of the current diffraction light field to obtain a new diffraction light field; the measured diffraction light intensity is determined based on the diffraction image at the corresponding scanning position.

[0053] (6) According to the parallel plane off-axis diffraction transmission model, the new diffraction light field is propagated back to the sample surface to obtain a new output field.

[0054] (7) According to the exit field at the current target scanning position and the new exit field, the current sample complex amplitude distribution map and the current probe complex amplitude distribution map are updated respectively to obtain an updated sample complex amplitude distribution map and an updated probe complex amplitude distribution map.

[0055] The update formula is:

[0056]

[0057] Among them, R C is the coordinate of the scanning position C; is the outgoing wave function after the probe interacts with the sample at the scanning position C; The output wave function is transmitted to the light field of the observation plane according to the derived parallel plane off-axis diffraction model, and then the new complex amplitude is replaced by the amplitude using the measured diffraction pattern. Finally, the new complex amplitude field is back-propagated to the sample surface according to the transmission model, thereby obtaining a new output wave function; O(r) represents the sample complex amplitude distribution map before update corresponding to the scanning position C; O'(r) represents the sample complex amplitude distribution map after update; P(r) represents the probe complex amplitude distribution map before update corresponding to the scanning position C; P'(r) represents the probe complex amplitude distribution map after update; * represents the complex conjugate calculation of the matrix; represents the square of the maximum modulus of the sample complex amplitude at the scanning position C; represents the square of the maximum modulus of the probe complex amplitude at the scanning position C; α O With α P are the tuning parameters of the sample and the probe, β O With β P are the update steps of the sample and probe respectively. r represents the spatial coordinates of the guessed region.

[0058] (8) Using the updated sample complex amplitude distribution map as the current sample complex amplitude distribution map, using the updated probe complex amplitude distribution map as the current probe complex amplitude distribution map, and selecting a target scanning position from the unselected scanning positions as the current target scanning position, returning to the step of "respectively determining the complex amplitude distributions at the current target scanning position in the current sample complex amplitude distribution map and the current probe complex amplitude distribution map, and obtaining the sample target scanning position complex amplitude distribution map and the probe target scanning position complex amplitude distribution map", until all scanning positions are traversed, and the reconstructed sample complex amplitude distribution map and the reconstructed probe complex amplitude distribution map are obtained.

[0059] (9) Using the currently reconstructed sample complex amplitude distribution map as the current sample complex amplitude distribution map, and using the currently reconstructed probe complex amplitude distribution map as the current probe complex amplitude distribution map, return to the step of "randomly selecting a target scanning position, and respectively determining the complex amplitude distributions in the current sample complex amplitude distribution map and the current probe complex amplitude distribution map at the current target scanning position", until the number of reconstruction iterations reaches the preset number of iterations.

[0060] (10) Obtaining the amplitude and phase of sample reconstruction based on the complex amplitude distribution diagram of the reconstructed sample obtained in the last iteration.

[0061] In another exemplary embodiment of the present application, considering that there is a certain amount of noise in the reconstructed complex amplitude distribution map, the present invention traverses all diffraction patterns once and completes TV denoising of the updated probe and sample complex amplitudes. Therefore, before executing step (9) "using the currently reconstructed sample complex amplitude distribution map as the current sample complex amplitude distribution map, and using the currently reconstructed probe complex amplitude distribution map as the current probe complex amplitude distribution map", the off-axis diffraction based reflective stack imaging method includes:

[0062] Apply the TV denoising algorithm to denoise the current reconstructed sample complex amplitude distribution map and the current reconstructed probe complex amplitude distribution map, respectively, to obtain a new reconstructed sample complex amplitude distribution map and a new reconstructed probe complex amplitude distribution map; the new reconstructed sample complex amplitude distribution map is used as the current reconstructed sample complex amplitude distribution map; the new reconstructed probe complex amplitude distribution map is used as the current reconstructed probe complex amplitude distribution map.

[0063] In another exemplary embodiment of the present application, the TV denoising algorithm is applied to the currently reconstructed sample complex amplitude distribution map and the currently reconstructed probe complex amplitude distribution map for denoising, specifically including:

[0064] (91) Constructing a denoising objective function; the objective function includes a regularization term and a fitting term; the regularization term is used to extract the original characteristic structure in the current complex amplitude distribution image to be denoised to remove the noise points of the image features; the fitting term is used to reduce the difference between the current denoised complex amplitude distribution image and the current complex amplitude distribution image to be denoised to ensure that the image is not distorted.

[0065] Among them, the expression of the denoising objective function is:

[0066]

[0067] Among them, ||·||1 and ||·||2 represent norms; represents gradient difference; u is the complex amplitude distribution image after denoising; g is the complex amplitude distribution image to be denoised; λ′ represents the regularization parameter.

[0068] The denoising objective function consists of two parts: the regularization term and the fitting term, which realize different processing functions. The regularization term is also called the prior term. The prior term in the TV denoising algorithm is the TV norm, which is a differential operator inside. In the image denoising process, the original characteristic structure of the complex amplitude distribution image to be denoised is extracted to remove noise points that do not belong to the image features. The fitting term is used to continuously reduce the difference between the complex amplitude distribution image after denoising and the complex amplitude distribution image to be denoised, so that the two images are infinitely close to ensure that the image is not distorted. There is a regularization term parameter between the prior term and the fitting term. In the flat area of ​​the image, the regularization term needs to have a strong denoising effect, and in the edge area of ​​the image, more texture information needs to be retained. The regularization term parameter plays a balancing role.

[0069] (92) According to the current complex amplitude distribution map to be denoised, the denoising objective function is solved to obtain the current complex amplitude distribution image after denoising; initially, the current complex amplitude distribution map to be denoised is the current reconstructed sample complex amplitude distribution map or the current reconstructed probe complex amplitude distribution map.

[0070] (93) Taking the current denoised complex amplitude distribution image as the current complex amplitude distribution image to be denoised, return to the step of "solving the denoising objective function according to the current complex amplitude distribution image to be denoised" until the number of denoising iterations reaches the preset number of denoising iterations, and obtain the final denoised sample complex amplitude distribution image or the final denoised probe complex amplitude distribution image.

[0071] (94) The final denoised sample complex amplitude distribution image is used as the new reconstructed sample complex amplitude distribution map, and the final denoised probe complex amplitude distribution image is used as the new reconstructed probe complex amplitude distribution map.

[0072] In order to verify the effectiveness of the method of the present invention, a reconstruction experiment was conducted. The rPIE algorithm was set to α O =α P =1,β O =β P =0.1, which can be adjusted as needed. The complex amplitude distribution of the probe initial guess is set to a full 1 matrix, and the complex amplitude distribution of the sample initial guess is set to a full 1 matrix. The vertical distance Z from the object plane to the detector plane is 90 mm, the sample inclination angle in the x direction is 20 degrees, and the inclination in the y direction is 0 degrees. Set the number of rPIE iterations to 300 times. After each rPIE iteration update, perform 10 denoising iterations. If the number of iterations is not reached, return to the rPIE iteration and denoising process to reach the set number of iterations and output the reconstruction results.

[0073] The following are the advantages of the method of the present invention:

[0074] (A) Consider the clarity, contrast and resolution of the restored and reconstructed sample. Specifically: (1) Clarity: The result after restoration and reconstruction is as follows: Figure 5 (a) is the amplitude image, Figure 5 (b) is the phase image. It can be concluded that due to the accuracy of the parallel plane off-axis diffraction transmission model and the introduction of the denoising algorithm, the entire restored result is very clear to the naked eye and there is no obvious noise. (2) Contrast: Figure 5 (c) and Figure 5As shown in (d) of FIG. 1 , it is the intensity-pixel contrast diagram of the corresponding line position. The contrast of the third line pair of the fifth group of the resolution plate is very good, and the relative difference between the peak and the valley is obvious, which illustrates the effectiveness of the parallel plane off-axis diffraction transmission model established by the present invention. (3) Resolution: The results of the restoration using the method proposed in the present application are shown in FIG. Figure 5 As shown, the fourth line pair of the fifth group of the resolution plate can still be resolved, which corresponds to the fact that the resolution of the reconstruction result is better than 22 microns. The resolution of the reconstruction method of the present invention is strong.

[0075] (B) The parallel plane off-axis diffraction transmission model derived by the present invention takes into account the tilt angles in two directions (x and y directions), providing an optimizable path for more complex scenarios.

[0076] In this embodiment, a receiving scheme in which the CCD detection plane is parallel to the sample plane is selected, and based on the assumption of oblique incident plane waves, the paraxial approximation is abandoned, and the parallel plane off-axis diffraction transfer function of near-field diffraction is derived and applied to reflective stacked diffraction imaging. In the reconstruction and recovery process, a restoration and reconstruction algorithm based on the rPIE algorithm combined with total variation denoising is used. The effectiveness of the method was verified in the experiment, and excellent resolution was obtained. In addition, the model takes into account tilts at multiple angles, providing a direction for the optimization of the application of more complex scenes.

[0077] The present application also provides an application scenario, which applies the above-mentioned reflective stacking imaging method based on off-axis diffraction. Specifically: The reflective stacking imaging method based on off-axis diffraction provided in this embodiment can be applied in the scene of non-transparent, reflective object surface detection. The scenario includes experimental platform construction, diffraction image acquisition and reconstruction and recovery. The reconstruction and recovery link of the reflective stacking imaging method based on off-axis diffraction provided in this embodiment.

[0078] Example 2

[0079] like Figure 6 As shown, this embodiment provides a reflective stack imaging device based on off-axis diffraction, including: a computer (corresponding to Figure 6 PC in the figure) and includes a laser, a first reflector (corresponding to Figure 6 M1 in), the second reflector (corresponding to Figure 6 M2 in), attenuation plate, microscope objective (corresponding to Figure 6 L1 in), spatial filter, collimating convex lens (corresponding to Figure 6L2 in the figure), reflective sample (mounted on a GCM-1641M three-dimensional translation stage that can move along the x and y directions, with a GCM-1108M rotating stage as the base, which can read the tilt angle of the sample surface relative to the light beam. The sample uses the Edmund 1951 USAF resolution test target plate, negative film) and detector (corresponding to the CCD camera in Figure 6). For the CCD camera, the pixel size of IMPERX's CCD (model IGV-B4020M-KF000) is 5.5μm. In the algorithm reconstruction and restoration, the actual array size used is 800×800 pixels. A 3×3 (3 rows and 3 columns) scanning method is used, with a distance of Z=90mm; the computer PC is connected to and controls the CCD camera.

[0080] The detector is used to collect diffraction images at different scanning positions within the sample target area;

[0081] The computer is used to execute the off-axis diffraction-based reflective stacking imaging method described in Example 1.

[0082] Among them, the process of collecting diffraction images by the reflective stack imaging device based on off-axis diffraction is as follows: the laser emitted by the solid laser passes through the reflectors M1 and M2, and the optical path can be collimated by adjusting the up, down, left and right knobs of the reflectors. The minimum output power of the laser used is 0.01W. An attenuation plate is placed behind the collimated laser to adjust the intensity of the output light to ensure that the image received by the CCD camera is not overexposed. The laser is expanded and collimated through a microscope objective, a spatial filter and a collimating convex lens to ensure that the laser beam is uniformly amplified. The collimated and expanded laser is irradiated onto the tilted reflective resolution board test sample, and the reflected light beam is diffracted and irradiated onto the CCD camera, received by the CCD camera, and transmitted to the computer PC for processing. There is a certain overlap between each two consecutive collected images.

[0083] Requirements for stacking imaging experiments using a reflective stacking imaging device based on off-axis diffraction: The parallel plane reflective stacking imaging optical path system belongs to a diffraction imaging system, which does not require high overall shock resistance and stability, and can be integrated and portable. The use of reflective resolution test samples is to effectively and intuitively verify the effectiveness of the solution. In order to obtain the best reconstruction effect, the sample's tilt angle and diffraction distance need to be obtained more accurately, and the overlapping area of ​​two consecutively collected images must be more than 60%.

[0084] In this embodiment, the sample to be tested is first placed parallel to the detector receiving plane, and then the expanded and collimated laser is incident on the relatively tilted sample to be tested, and the sample to be tested is moved to collect the diffraction image. The reconstruction of the amplitude and phase information of the sample to be tested requires the knowledge of the wavelength of light in the stacked optical path, the diffraction distance, and the tilt angle of the sample relative to the incident light in the x and y directions, and then the stacked imaging iterative algorithm is used for reconstruction, and the TV denoiser is introduced in the reconstruction iterative process for denoising.

[0085] Example 3

[0086] This embodiment provides a computer device, which may be a server or a terminal. Its internal structure diagram may be as follows: Figure 7 As shown. The computer device includes a processor, a memory, an input / output interface (Input / Output, referred to as I / O) and a communication interface. The processor, the memory and the input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store the amplitude and phase of sample reconstruction. The input / output interface of the computer device is used to exchange information between the processor and an external device. The communication interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, a reflective stack imaging method based on off-axis diffraction is implemented.

[0087] Those skilled in the art will understand that Figure 7 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components. In an exemplary embodiment, a computer device is provided, including a memory and a processor, wherein a computer program is stored in the memory, and the processor implements the steps in the above-mentioned method embodiments when executing the computer program.

[0088] In an exemplary embodiment, a computer-readable storage medium is provided, storing a computer program, and when the computer program is executed by a processor, the steps in the above method embodiments are implemented.

[0089] In an exemplary embodiment, a computer program product is provided, including a computer program, and when the computer program is executed by a processor, the steps in the above method embodiments are implemented.

[0090] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with relevant regulations.

[0091] Those of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM may be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0092] The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. The non-relational database may include a distributed database based on blockchain, etc., but is not limited thereto. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., but is not limited thereto.

[0093] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0094] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, 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 this application.

Claims

1. A reflective stack imaging method based on off-axis diffraction, characterized in that: The off-axis diffraction-based reflective stacking imaging method comprises: Acquire diffraction images at different scanning positions within the target area of ​​the sample; According to the diffraction image, an improved rPIE iterative algorithm is applied to reconstruct the diffraction light field to obtain the amplitude and phase of the sample reconstruction; the improved rPIE iterative algorithm refers to replacing the diffraction propagation model in the traditional rPIE iterative algorithm with a parallel plane off-axis diffraction transmission model.

2. The reflective stacking imaging method based on off-axis diffraction according to claim 1, characterized in that: The expression of the parallel plane off-axis diffraction transmission model is: in, In the formula, i represents the imaginary unit; is the tilt factor; θ x With θ y is the angle between the wave vector of the equivalent oblique incident beam and the x-axis and y-axis. The wave vector of the equivalent oblique incident beam has a magnitude of k0 and a direction that is the same as the displacement vector The incident direction of the transmitted light beam in the same direction, the displacement vector is the unit vector in the x, y, and z directions; k0 is the incident beam wave vector The size of Z is the vertical distance from the sample plane to the detector plane; K x and K y represents the shifted wave vector The components in the x and y directions, is the wave vector after rotation.

3. The off-axis diffraction based reflective stacking imaging method according to claim 1, characterized in that: According to the diffraction image, the improved rPIE iterative algorithm is applied to reconstruct the diffraction light field to obtain the amplitude and phase of the sample reconstruction, specifically including: Randomly determine the sample initial complex amplitude distribution map, and determine the probe initial complex amplitude distribution map based on the collected probe; A target scanning position is randomly selected, and the complex amplitude distributions at the current target scanning position in the current sample complex amplitude distribution map and the current probe complex amplitude distribution map are determined respectively, to obtain the sample target scanning position complex amplitude distribution map and the probe target scanning position complex amplitude distribution map; initially, the current sample complex amplitude distribution map and the current probe complex amplitude distribution map refer to the sample initial complex amplitude distribution map and the probe initial complex amplitude distribution map; Calculate the exit field after the probe interacts with the sample according to the complex amplitude distribution diagram of the current sample target scanning position and the complex amplitude distribution diagram of the current probe target scanning position; Calculating the diffraction light field of the current output field on the observation plane according to the parallel plane off-axis diffraction transmission model; Using the measured diffraction light intensity to replace the amplitude of the current diffraction light field to obtain a new diffraction light field; the measured diffraction light intensity is determined according to the diffraction image at the corresponding scanning position; According to the parallel plane off-axis diffraction transmission model, the new diffracted light field is propagated back to the sample surface to obtain a new output field; According to the exit field at the current target scanning position and the new exit field, the current sample complex amplitude distribution map and the current probe complex amplitude distribution map are updated respectively to obtain an updated sample complex amplitude distribution map and an updated probe complex amplitude distribution map; Using the updated sample complex amplitude distribution map as the current sample complex amplitude distribution map, using the updated probe complex amplitude distribution map as the current probe complex amplitude distribution map, and selecting a target scanning position from the unselected scanning positions as the current target scanning position, returning to step "respectively determining the complex amplitude distributions at the current target scanning position in the current sample complex amplitude distribution map and the current probe complex amplitude distribution map, and obtaining the sample target scanning position complex amplitude distribution map and the probe target scanning position complex amplitude distribution map", until all scanning positions are traversed, and the reconstructed sample complex amplitude distribution map and the reconstructed probe complex amplitude distribution map are obtained; Using the currently reconstructed sample complex amplitude distribution map as the current sample complex amplitude distribution map, using the currently reconstructed probe complex amplitude distribution map as the current probe complex amplitude distribution map, returning to step "randomly selecting a target scanning position, and respectively determining the complex amplitude distributions at the current target scanning position in the current sample complex amplitude distribution map and the current probe complex amplitude distribution map", until the number of reconstruction iterations reaches a preset number of iterations; The amplitude and phase of sample reconstruction are obtained according to the reconstructed sample complex amplitude distribution diagram obtained in the last iteration.

4. The off-axis diffraction based reflective stacking imaging method according to claim 3, characterized in that: Before executing the step of "using the currently reconstructed sample complex amplitude distribution map as the current sample complex amplitude distribution map, and using the currently reconstructed probe complex amplitude distribution map as the current probe complex amplitude distribution map", the off-axis diffraction-based reflective stack imaging method includes: Applying a TV denoising algorithm to the currently reconstructed sample complex amplitude distribution map and the currently reconstructed probe complex amplitude distribution map to denoise them respectively, to obtain a new reconstructed sample complex amplitude distribution map and a new reconstructed probe complex amplitude distribution map; The new reconstructed sample complex amplitude distribution map is used as the current reconstructed sample complex amplitude distribution map; the new reconstructed probe complex amplitude distribution map is used as the current reconstructed probe complex amplitude distribution map.

5. The off-axis diffraction based reflective stacking imaging method according to claim 4, characterized in that: Applying a TV denoising algorithm to the currently reconstructed sample complex amplitude distribution map and the currently reconstructed probe complex amplitude distribution map respectively for denoising, specifically comprising: Constructing a denoising objective function; the objective function includes a regularization term and a fitting term; the regularization term is used to extract the original characteristic structure in the current complex amplitude distribution image to be denoised to remove the noise points of the image characteristics; the fitting term is used to reduce the difference between the current denoised complex amplitude distribution image and the current complex amplitude distribution image to be denoised to ensure that the image is not distorted; According to the current complex amplitude distribution map to be denoised, the denoising objective function is solved to obtain the current complex amplitude distribution image after denoising; initially, the current complex amplitude distribution map to be denoised is the current reconstructed sample complex amplitude distribution map or the current reconstructed probe complex amplitude distribution map; Taking the current denoised complex amplitude distribution image as the current complex amplitude distribution image to be denoised, returning to the step of "solving the denoising objective function according to the current complex amplitude distribution image to be denoised", until the number of denoising iterations reaches the preset number of denoising iterations, and obtaining the final denoised sample complex amplitude distribution image or the final denoised probe complex amplitude distribution image; The final denoised sample complex amplitude distribution image is used as the new reconstructed sample complex amplitude distribution map, and the final denoised probe complex amplitude distribution image is used as the new reconstructed probe complex amplitude distribution map.

6. The off-axis diffraction based reflective stacking imaging method according to claim 5, characterized in that: The expression of the denoising objective function is: Among them, ||·||1 and ||·||2 represent norms; represents gradient difference; u is the complex amplitude distribution image after denoising; g is the complex amplitude distribution image to be denoised; λ′ represents the regularization parameter.

7. A reflective stack imaging device based on off-axis diffraction, characterized in that: The reflective stack imaging device based on off-axis diffraction comprises: a computer and, in order according to the propagation direction of light, a laser, a first reflector, a second reflector, an attenuation plate, an objective lens, a spatial filter, a collimating convex lens, a reflective sample and a detector; The detector is used to collect diffraction images at different scanning positions within the sample target area; The computer is used to execute the off-axis diffraction based reflective stacking imaging method according to any one of claims 1 to 6.

8. A computer device comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the off-axis diffraction-based reflective stacking imaging method according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the off-axis diffraction-based reflective stacking imaging method according to any one of claims 1 to 6 is implemented.

10. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the off-axis diffraction-based reflective stacking imaging method according to any one of claims 1 to 6 is implemented.

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