Off-axis diffraction based reflective stack imaging method and related apparatus

Abstract

The application discloses a reflection type laminated imaging method based on off-axis diffraction and a related device, relates to the field of laminated diffraction imaging, and comprises the following steps: acquiring diffraction images of different scanning positions in a target region of a sample; according to the diffraction images, applying an improved rPIE iterative algorithm to perform diffraction light field reconstruction to obtain the amplitude and phase of the sample reconstruction; and the improved rPIE iterative algorithm refers to replacing a diffraction propagation model in a traditional rPIE iterative algorithm with a parallel plane off-axis diffraction transmission model. In the application, the diffraction propagation model in the traditional rPIE iterative algorithm is replaced with the parallel plane off-axis diffraction transmission model, a relatively simple light field transmission model is established and applied to realize the reconstruction of the reflection type laminated imaging, no complex interpolation calculation is involved, the reconstruction method is simplified, and the reconstruction accuracy is improved from the aspects of the definition, contrast and resolution of the reconstruction result.

Description

Technical Field

[0001] This application relates to the field of stacked diffraction imaging, and in particular to a reflective stacked imaging method and related apparatus based on off-axis diffraction. Background Technology

[0002] Stacked diffraction imaging is a computational imaging technique that has emerged in recent years. It boasts advantages such as lensless operation, simple optical path, high resolution, and no need for high-quality optical components, and has been widely applied in fields such as X-ray diffraction. In industrial inspection, due to the properties of industrial samples, surface inspection generally requires reflective systems. In industrial inspection, most samples are opaque and thick, necessitating reflective optical paths for surface inspection. However, reflective optical paths involve tilting, beam distortion, and potentially complex interpolation calculations to accommodate Fourier transforms. Given the complexity of existing reflective systems, it is essential to establish a relatively accurate, simple physical model that avoids complex interpolation calculations to describe the diffraction process at large reflection angles. Summary of the Invention

[0003] The purpose of this application is to provide a reflective layered imaging method and related device based on off-axis diffraction. It is the first time that the off-axis diffraction method is used 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 solution:

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

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

[0007] Based on the diffraction image, the diffraction light field is reconstructed using an improved rPIE iterative algorithm to obtain the amplitude and phase of the reconstructed sample. 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] Secondly, this application provides a reflective stacked imaging device based on off-axis diffraction, comprising: a computer and, in order of light propagation direction, a laser, a first mirror, a second mirror, an attenuator, an objective lens, a spatial filter, a collimating convex lens, a reflective sample, and a detector;

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

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

[0011] Thirdly, this application provides a computer device, including: 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-described off-axis diffraction-based reflective stacked imaging method.

[0012] Fourthly, this application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-described off-axis diffraction-based reflective stacked imaging method.

[0013] Fifthly, this application provides a computer program product, including a computer program that, when executed by a processor, implements the above-described off-axis diffraction-based reflective stacked imaging method.

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

[0015] This application provides a reflective layered imaging method and related apparatus based on off-axis diffraction, comprising: acquiring diffraction images at different scanning positions within a target region of a sample; reconstructing the diffraction light field based on the diffraction images using an improved rPIE iterative algorithm to obtain the amplitude and phase of the reconstructed sample; 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 this invention, by replacing the diffraction propagation model in the traditional rPIE iterative algorithm with a parallel-plane off-axis diffraction transmission model, a simpler light field transmission model is established and applied to achieve reflective layered imaging reconstruction. This simplifies the reconstruction method by avoiding complex interpolation calculations and improves the reconstruction accuracy in terms of sharpness, contrast, and resolution. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 An application environment diagram for a reflective stacked imaging method based on off-axis diffraction provided in Embodiment 1 of this application;

[0018] Figure 2 This is a schematic flowchart of a reflective stacked imaging method based on off-axis diffraction provided in Embodiment 1 of this application;

[0019] Figure 3A schematic diagram illustrating the technical concept of the reflective layered imaging method based on off-axis diffraction provided in Embodiment 1 of this application;

[0020] Figure 4 This is a schematic diagram of the parallel plane reflection propagation coordinate system provided in Embodiment 1 of this application;

[0021] Figure 5 This is a schematic diagram of the amplitude and phase recovery and reconstruction results provided in Embodiment 1 of this application;

[0022] Figure 6 This is a schematic diagram of the structure of the reflective stacked imaging device based on off-axis diffraction provided in Embodiment 2 of this application;

[0023] Figure 7 This is a schematic diagram of the structure of a computer device provided in Embodiment 3 of this application. Detailed Implementation

[0024] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Example 1

[0027] The off-axis diffraction-based reflective stacked imaging method provided in this application can be applied to, for example... Figure 1In the application environment shown, the terminal communicates with the server via a network. The data storage system stores the data the server needs to process. The data storage system can be set up independently, integrated into the server, or placed in the cloud or on another server. The terminal can send diffraction images from different scanning positions within the sample target area to the server. After receiving the images, the server reconstructs the diffraction field using an improved rPIE iterative algorithm based on the diffraction images, obtaining the amplitude and phase of the reconstructed sample. The improved rPIE iterative algorithm replaces the diffraction propagation model in the traditional rPIE iterative algorithm with a parallel-plane off-axis diffraction transmission model. The server can then feed back the obtained amplitude and phase of the reconstructed sample to the terminal. Furthermore, in some embodiments, the off-axis diffraction-based reflective stacked imaging method can also be implemented independently by the server or the terminal. For example, the terminal can directly apply the improved rPIE iterative algorithm to reconstruct the diffraction field from the diffraction images at different scanning positions within the sample target area, or the server can obtain diffraction images from the data storage system at different scanning positions within the sample target area and apply the improved rPIE iterative algorithm to reconstruct the diffraction field.

[0028] The terminals can be, but are not limited to, various desktop computers, laptops, smartphones, tablets, IoT devices, and portable wearable devices. IoT devices can include smart speakers, smart TVs, smart air conditioners, and smart in-vehicle systems. Portable wearable devices can include smartwatches, smart bracelets, and head-mounted devices. Servers can be implemented using independent servers, server clusters composed of multiple servers, or cloud servers.

[0029] In an exemplary embodiment, a parallel-plane scheme based on off-axis diffraction is used to study reflective stacked imaging. Stacked imaging, as a type of computational imaging, is widely known in the field of image phase retrieval. A coherent beam (such as a laser) interacts with the sample, and the resulting diffraction pattern is received and recorded by a detector. The sample and 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. Stacked imaging technology is widely used due to its advantages such as lensless operation, scalable imaging range, and fast convergence speed. However, in industrial inspection, most samples are opaque, making transmission-based stacked imaging unsuitable. Therefore, extending stacked imaging technology to the reflective field is necessary. However, due to the complexity of reflective systems, establishing and applying a relatively simple light field transmission model to reconstruct reflective stacked imaging is of profound significance. Therefore, a parallel-plane reflective stacked imaging scheme based on off-axis diffraction has a positive impact on the inspection of reflective industrial samples. Figure 2 and Figure 3As shown, this invention provides a reflective layered imaging method based on off-axis diffraction. This method is executed by a computer device, specifically a terminal or server, or both. In this embodiment, the method is applied to... Figure 1 Taking the server in the example, the explanation includes the following steps 101 to 102. Wherein:

[0030] Step 101: Obtain diffraction images at different scanning positions within the target area of ​​the sample.

[0031] As an example, a parallel-plane reflective stacked imaging system can be built, with the surface of the sample to be tested parallel to the surface of the detector, and each pixel of the detector being 5.5 μm in size; a 532 nm green laser is selected as the laser; the distance from the surface of the sample to be tested to the CCD camera that acquires the diffraction pattern is 90 mm, and a series of sample diffraction patterns with a certain degree of overlap are acquired to reconstruct and restore the amplitude and phase information distribution of the sample.

[0032] Step 102: Based on 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; 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] By performing steps 101 and 102 above, diffraction images at different scanning positions within the target area of ​​the sample are acquired. Based on the diffraction images, an improved rPIE iterative algorithm is applied to reconstruct the diffraction light field, yielding the amplitude and phase of the reconstructed sample. The improved rPIE iterative algorithm replaces the diffraction propagation model in the traditional rPIE iterative algorithm with a parallel-plane off-axis diffraction transmission model. In this invention, the diffraction propagation model in the traditional rPIE iterative algorithm is replaced with a parallel-plane off-axis diffraction transmission model. A simpler light field transmission model is established and used to achieve the reconstruction of reflective layered imaging. This simplifies the reconstruction method by avoiding complex interpolation calculations and improves the reconstruction accuracy in terms of sharpness, contrast, and resolution.

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

[0035] like Figure 4 As shown, this is a parallel-plane reflection propagation coordinate system, with the wave vector being... The incident beam (solid arrow, related to the laser wavelength λ, a known quantity, magnitude is) After being reflected by the sample surface, the incident beam is transmitted to the detector surface parallel to the sample surface. This process can be represented by an equivalent incident beam, with the wave vector magnitude of the equivalent tilted incident beam being k0, and the direction of the equivalent tilted incident beam being the same as the displacement vector. Same direction transmitted beam ( Figure 4 The direction of incidence (indicated by the dashed arrow in the image), where The direction of the principal ray of the reflected beam is shown. The input field is extracted from the integral using the parallel plane angular spectrum method. This separation of the input field from the transverse modulation effectively simulates light propagating at arbitrary angles along the tilt axis. The sampling window undergoes a transverse translation (x0, y0) due to the tilted incident light. The displacement vector is defined. This is the direction vector from the input surface to the output surface.

[0036]

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

[0038] Define the shift wave vector:

[0039]

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

[0041] If we express the rotated wave vector using the shifted wave vector and the incident beam wave vector, then the off-axis diffraction transfer function is expressed as:

[0042]

[0043] The relationship between the wave vectors is as follows: 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, z directions; k 0x k 0y and k 0z Represents the incident beam wave vector Components in the x, y, and z directions.

[0044] Further derivation of the expression for the off-axis transfer function is as follows:

[0045]

[0046] in, Here is the tilt factor, and here is the displacement vector. and The cosine of the included angle has a value of

[0047] In another exemplary embodiment of this 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 field based on the diffraction image to obtain the amplitude and phase of the sample reconstruction, specifically including:

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

[0049] (2) Randomly select a target scanning position, and determine the complex amplitude distribution at the current target scanning position in the current sample complex amplitude distribution map and the current probe complex amplitude distribution map respectively, so as to obtain the complex amplitude distribution map of the sample target scanning position and the complex amplitude distribution map of the probe target scanning position; initially, the current sample complex amplitude distribution map and the current probe complex amplitude distribution map refer to the initial complex amplitude distribution map of the sample and the initial complex amplitude distribution map of the probe.

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

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

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

[0053] (6) Based on the parallel plane off-axis diffraction transmission model, the new diffraction light field is backpropagated to the sample surface to obtain a new emission field.

[0054] (7) Based on the emission field at the current target scanning position and the new emission field, update the current sample complex amplitude distribution map and the current probe complex amplitude distribution map respectively, and obtain the updated sample complex amplitude distribution map and the updated probe complex amplitude distribution map.

[0055] The update formula is as follows:

[0056]

[0057] Among them, R C The coordinates of the scan position C; For scanning position C, the emitted wave function after the probe interacts with the sample; The outgoing wavefunction is the light field transmitted to the observation plane according to the derived parallel plane off-axis diffraction model. The new complex amplitude is obtained by replacing the amplitude with the measured diffraction pattern. Finally, the new complex amplitude field is backpropagated to the sample surface according to the transmission model, thus obtaining the new outgoing wavefunction. O(r) represents the sample complex amplitude distribution map before the update at scanning position C; O'(r) represents the sample complex amplitude distribution map after the update; P(r) represents the probe complex amplitude distribution map before the update at scanning position C; P'(r) represents the probe complex amplitude distribution map after the update; * indicates the complex conjugate calculation of the matrix. This represents the square of the maximum modulus of the complex amplitude of the sample at scanning position C; α represents the square of the maximum modulus of the probe complex amplitude at scanning position C; O With α P These are the tuning parameters for the sample and probe, respectively, β O With β P , respectively, represent the update step size for the sample and probe. r represents the spatial coordinates of the guessed region.

[0058] (8) Use the updated sample complex amplitude distribution map as the current sample complex amplitude distribution map, use the updated probe complex amplitude distribution map as the current probe complex amplitude distribution map, and select a target scanning position from the unselected scanning positions as the current target scanning position. Return to the step "determine the complex amplitude distribution at the current target scanning position in the current sample complex amplitude distribution map and the current probe complex amplitude distribution map respectively, and obtain the sample target scanning position complex amplitude distribution map and the probe target scanning position complex amplitude distribution map", until all scanning positions have been traversed, and obtain the reconstructed sample complex amplitude distribution map and the reconstructed probe complex amplitude distribution map.

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

[0060] (10) The amplitude and phase of the reconstructed sample are obtained from the complex amplitude distribution map of the reconstructed sample obtained from the last iteration.

[0061] In another exemplary embodiment of this application, considering the presence of noise in the reconstructed complex amplitude distribution map, the present invention performs TV denoising on all diffraction patterns once and completes 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 the currently reconstructed probe complex amplitude distribution map as the current probe complex amplitude distribution map", the off-axis diffraction-based reflective stacked imaging method includes:

[0062] The TV denoising algorithm is applied to the reconstructed sample complex amplitude distribution map and the reconstructed probe complex amplitude distribution map to denoise them respectively, resulting in 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 this application, the TV denoising algorithm is applied to both the reconstructed sample complex amplitude distribution map and the reconstructed probe complex amplitude distribution map for denoising, specifically including:

[0064] (91) Construct a denoising objective function; the objective function includes a regularization term and a fitting term; the regularization term is used to extract the original feature structure in the current complex amplitude distribution map to be denoised in order to remove noise points in 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 map to be denoised in order to ensure that the image is not distorted.

[0065] The expression for the denoising objective function is:

[0066]

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

[0068] The denoising objective function consists of two parts: a regularization term and a fitting term, which perform different processing functions. The regularization term, also known as the prior term, is the TV norm in the TV denoising algorithm. Internally, it's a difference operator that extracts the original feature structure of the complex amplitude distribution image to be denoised during image denoising, removing noise points that are not part of the image features. The fitting term continuously reduces the difference between the denoised complex amplitude distribution image and the original complex amplitude distribution image, making the two images infinitely close and ensuring the image remains undistorted. A regularization parameter exists between the prior and fitting terms. In flat areas of the image, a strong regularization effect is needed, while in edge areas, more texture information needs to be preserved. The regularization parameter plays a balancing role.

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

[0070] (93) Using the current denoised complex amplitude distribution image as the current denoised complex amplitude distribution image, return to the step "Solve the denoising objective function according to the current denoised complex amplitude distribution image" 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 image, and the final denoised probe complex amplitude distribution image is used as the new reconstructed probe complex amplitude distribution image.

[0072] To verify the effectiveness of the method of the present invention, a reconstruction experiment was conducted. The rPIE algorithm was set to α in the experiment. O =α P =1,β O =β P =0.1, which can be adjusted as needed. The initial guessed complex amplitude distribution of the probe is set to a matrix of all 1s, and the initial guessed complex amplitude distribution of the sample is also set to a matrix of all 1s. The vertical distance Z from the object plane to the detector plane is 90mm, the sample tilt angle in the x-direction is 20 degrees, and the tilt angle in the y-direction is 0 degrees. The rPIE iteration count is set to 300 times. After each rPIE iteration update, 10 denoising iterations are performed. If the number of iterations is not reached, the rPIE iteration and denoising process is returned to the previous iteration. Once the set number of iterations is reached, the reconstruction result is output.

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

[0074] (A) Considerations include the sharpness, contrast, and resolution of the reconstructed sample. Specifically: (1) Sharpness: The reconstructed result is as follows: Figure 5 (a) in the image 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, with no obvious noise. (2) Contrast: such as Figure 5 (c) and Figure 5As shown in (d) in the figure, the intensity-pixel contrast map is shown at the corresponding line position. The contrast of the third line pair in the fifth group of the resolution panel is very good, and the difference between the peak and valley values ​​is obvious, which shows the effectiveness of the parallel plane off-axis diffraction transmission model established in this invention. (3) Resolution: The recovery result using the method proposed in this application is as follows Figure 5 As shown, the fourth line pair in the fifth group of the resolution panel is still resolvable, indicating that the resolution of the reconstructed result is better than 22 micrometers. The method of this invention reconstructs a high resolution.

[0075] (B) The parallel plane off-axis diffraction transmission model derived in this 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 detector plane is parallel to the sample plane is selected. Based on the assumption of obliquely incident plane waves, the paraxial approximation is abandoned, and the off-axis diffraction transfer function of the parallel plane for near-field diffraction is derived and applied to reflection-based stacked diffraction imaging. During the reconstruction process, a reconstruction algorithm based on the rPIE algorithm combined with total variation denoising is used. Experiments verify the effectiveness of the method, achieving excellent resolution. Furthermore, the model considers tilt at multiple angles, providing direction for optimization in more complex scenarios.

[0077] This application also provides an application scenario in which the above-described off-axis diffraction-based reflective layered imaging method is used. Specifically, the off-axis diffraction-based reflective layered imaging method provided in this embodiment can be applied to the detection of opaque, reflective object surfaces. This scenario includes experimental platform construction, diffraction image acquisition, and reconstruction. The reconstruction stage of the off-axis diffraction-based reflective layered imaging method provided in this embodiment is also described.

[0078] Example 2

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

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

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

[0082] The process of acquiring diffraction images using an off-axis diffraction-based reflective stacked imaging device is as follows: The laser emitted from a solid-state laser passes through mirrors M1 and M2. The optical path is collimated by adjusting the up, down, left, and right knobs of the mirrors. The minimum output power of the laser used is 0.01W. An attenuator is placed behind the collimated laser to adjust the intensity of the output light, ensuring that the image received by the CCD camera is not overexposed. The laser beam is then expanded and collimated by a microscope objective, a spatial filter, and a collimating convex lens to ensure uniform magnification. The collimated and expanded laser beam illuminates the tilted reflective resolution plate test sample. The reflected beam diffracts and illuminates the CCD camera, which receives the image and transmits it to a computer (PC) for processing. There is a certain overlap between each consecutive image acquisition.

[0083] Requirements for using an off-axis diffraction-based reflective stacked imaging device in stacked imaging experiments: The parallel-plane reflective stacked imaging optical path system belongs to the diffraction imaging system, and its overall vibration resistance and stability requirements are not high, allowing for integration and portability. Using reflective resolution test samples is for effective and intuitive verification of the scheme's effectiveness. To obtain the best reconstruction results, the sample's tilt angle and diffraction distance need to be obtained with high precision, and the overlap area of ​​two consecutively acquired images should be above 60%.

[0084] In this embodiment, the sample to be tested is first placed parallel to the detector receiving plane. Then, a beam-expanded and collimated laser is incident on the relatively tilted sample, and the sample is moved to acquire diffraction images. Reconstructing the amplitude and phase information of the sample requires 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. Then, a stacked imaging iterative algorithm is used for reconstruction, and a TV denoiser is introduced during the reconstruction iteration process.

[0085] Example 3

[0086] This embodiment provides a computer device, which may be a server or a terminal, and its internal structure diagram may be as follows. Figure 7 As shown, this computer device includes a processor, memory, input / output (I / O) interfaces, and a communication interface. The processor, memory, and I / O interfaces are connected via a system bus, and the communication interface is also connected to the system bus via the I / O interfaces. The processor provides computational and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system, computer programs, and a database. The internal memory provides the environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The database stores the amplitude and phase of the reconstructed samples. The I / O interfaces are used for exchanging information between the processor and external devices. The communication interface is used for communication with external terminals via a network connection. When executed by the processor, the computer program implements a reflective layered imaging method based on off-axis diffraction.

[0087] Those skilled in the art will understand that Figure 7 The structures shown are merely block diagrams of some structures related to the present application and do not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than shown in the figures, or combine certain components, or have different component arrangements. In an exemplary embodiment, a computer device is provided, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps in the above-described method embodiments.

[0088] In one exemplary embodiment, a computer-readable storage medium is provided storing a computer program that, when executed by a processor, implements the steps in the above-described method embodiments.

[0089] In one exemplary embodiment, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps in the above-described method embodiments.

[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, data stored, data displayed, 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 the relevant data must comply with relevant regulations.

[0091] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, databases, or other media used in the embodiments provided in this 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 can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM).

[0092] The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0093] The technical features of the above embodiments can be combined in any way. For the sake of brevity, 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 document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A reflection type lamination imaging method based on off-axis diffraction, characterized by, The reflection type stack imaging method based on off-axis diffraction comprises: acquiring diffraction images of different scanning positions in a target region of a sample; applying an improved rPIE iterative algorithm to reconstruct a diffraction light field according to the diffraction images to obtain reconstructed amplitude and phase of the sample; the improved rPIE iterative algorithm refers to replacing a diffraction propagation model in a traditional rPIE iterative algorithm with a parallel plane off-axis diffraction transmission model; wherein an expression of the parallel plane off-axis diffraction transmission model is: wherein ; where i represents an imaginary unit; With the wave vector of the equivalent oblique incident light beam and the axis, the included angle between the wave vector of the equivalent oblique incident light beam and the axis, the size of the wave vector of the equivalent oblique incident light beam is , the direction of the incident direction of the transmitted light beam is the same as the direction of the displacement vector , the direction of the direction of the chief ray of the reflected light beam is the direction of the direction of the displacement vector , , , is a unit vector in the x, y, z direction; is the size of the wave vector of the incident light beam ; Z is the vertical distance from the sample plane to the detector plane; and represent the components of the displacement wave vector in the x, y direction, , is the wave vector after rotation; is the tilt factor, and is the cosine value of the included angle between the displacement vector and the axis. wherein applying the improved rPIE iterative algorithm to reconstruct the diffraction light field according to the diffraction images to obtain the reconstructed amplitude and phase of the sample specifically comprises: randomly determining an initial complex amplitude distribution map of the sample and an initial complex amplitude distribution map of a probe according to a collected probe; randomly selecting a target scanning position, determining complex amplitude distributions in the current target scanning position in a current sample complex amplitude distribution map and a current probe complex amplitude distribution map respectively to obtain a sample target scanning position complex amplitude distribution map and a 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 initial complex amplitude distribution map of the sample and the initial complex amplitude distribution map of the probe; calculating an exit field after the probe and the sample interact according to the current sample target scanning position complex amplitude distribution map and the current probe target scanning position complex amplitude distribution map; calculating a diffraction light field of the current exit field on an observation plane according to the parallel plane off-axis diffraction transmission model; replacing an amplitude of the current diffraction light field with a measured diffraction light intensity to obtain a new diffraction light field; the measured diffraction light intensity is determined according to the diffraction image of the corresponding scanning position; propagating the new diffraction light field to the sample surface in reverse according to the parallel plane off-axis diffraction transmission model to obtain a new exit field; updating the current sample complex amplitude distribution map and the current probe complex amplitude distribution map respectively according to the exit field in the current target scanning position and the new exit field to obtain an updated sample complex amplitude distribution map and an updated probe complex amplitude distribution map; taking the updated sample complex amplitude distribution map as the current sample complex amplitude distribution map, taking the updated probe complex amplitude distribution map as the current probe complex amplitude distribution map, and selecting a target scanning position from unselected scanning positions as the current target scanning position, returning to the step of "determining the complex amplitude distributions in the current target scanning position in the current sample complex amplitude distribution map and the current probe complex amplitude distribution map respectively to obtain 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 to obtain a reconstructed sample complex amplitude distribution map and a reconstructed probe complex amplitude distribution map; taking the current reconstructed sample complex amplitude distribution map as the current sample complex amplitude distribution map and taking the current reconstructed probe complex amplitude distribution map as the current probe complex amplitude distribution map, and returning to the step of "randomly selecting a target scanning position, determining the complex amplitude distributions in the current target scanning position in the current sample complex amplitude distribution map and the current probe complex amplitude distribution map respectively", until a reconstruction iteration number reaches a preset iteration number. The reconstructed sample complex amplitude distribution is obtained according to the reconstructed sample complex amplitude distribution of the last iteration.

2. The off-axis diffraction based reflective lamination imaging method of claim 1, wherein, Before the step of "taking the reconstructed sample complex amplitude distribution as the current sample complex amplitude distribution and taking the reconstructed probe complex amplitude distribution as the current probe complex amplitude distribution", the reflection type layered imaging method based on off-axis diffraction comprises the following steps: TV denoising algorithms are applied to the current reconstructed sample complex amplitude distribution and the current reconstructed probe complex amplitude distribution respectively to obtain a new reconstructed sample complex amplitude distribution and a new reconstructed probe complex amplitude distribution; The new reconstructed sample complex amplitude distribution is taken as the current reconstructed sample complex amplitude distribution, and the new reconstructed probe complex amplitude distribution is taken as the current reconstructed probe complex amplitude distribution.

3. The off-axis diffraction based reflective lamination imaging method of claim 2, wherein, The TV denoising algorithms are applied to the current reconstructed sample complex amplitude distribution and the current reconstructed probe complex amplitude distribution respectively, and specifically comprising the following steps: A denoising objective function is constructed; the objective function comprises a regularization term and a fitting term; the regularization term is used to extract the original feature structure in the current to-be-denoised complex amplitude distribution to remove the noise points of the image features; and the fitting term is used to reduce the difference between the current denoised complex amplitude distribution image and the current to-be-denoised complex amplitude distribution to ensure that the image is not distorted; The denoising objective function is solved according to the current to-be-denoised complex amplitude distribution to obtain a current denoised complex amplitude distribution image; initially, the current to-be-denoised complex amplitude distribution is the current reconstructed sample complex amplitude distribution or the current reconstructed probe complex amplitude distribution; The current denoised complex amplitude distribution image is taken as the current to-be-denoised complex amplitude distribution, and the step of "solving the denoising objective function according to the current to-be-denoised complex amplitude distribution" is returned until the denoising iteration number reaches the preset denoising iteration number to obtain a final denoised sample complex amplitude distribution image or a final denoised probe complex amplitude distribution image; The final denoised sample complex amplitude distribution image is taken as the new reconstructed sample complex amplitude distribution, and the final denoised probe complex amplitude distribution image is taken as the new reconstructed probe complex amplitude distribution.

4. The off-axis, diffraction-based, reflective, laminated imaging method of claim 3, wherein, The expression of the denoising objective function is as follows: ； wherein, and denotes a norm; denotes a gradient difference; is a denoised complex amplitude distribution image; is a complex amplitude distribution image to be denoised; denotes a regularization parameter.

5. A reflection type laminated imaging device based on off-axis diffraction, characterized by, The reflection type layered imaging device based on off-axis diffraction comprises a computer and a laser, a first mirror, a second mirror, an attenuation sheet, an objective lens, a spatial filter, a collimating convex lens, a reflection type sample and a detector arranged in sequence according to the light propagation direction; The detector is used to collect diffraction images at different scanning positions in a target region of the sample; The computer is used to execute the reflection type layered imaging method based on off-axis diffraction according to any one of claims 1 to 4.

6. 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 reflection type layered imaging method based on off-axis diffraction according to any one of claims 1 to 4.

7. A computer-readable storage medium having stored thereon a computer program, characterized in that The computer program is executed by the processor to implement the reflection type layered imaging method based on off-axis diffraction according to any one of claims 1 to 4.

8. A computer program product comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the reflective stacked imaging method based on off-axis diffraction as described in any one of claims 1-4.

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