A displacement measurement method, apparatus and system

Abstract

The application provides a kind of measurement method, device and system, the method includes: the initial function of the outgoing wave of the first part and the second part of the object to be measured is obtained respectively, at least once the i iteration is executed respectively, in each iteration: by reciprocating propagation between object plane, modulator plane and detector plane to the outgoing wave of the i part, and the amplitude of the outgoing wave of the i part is constrained according to the actual diffraction intensity of the outgoing wave of the i part in the detector plane;Obtain the reconstruction function of the outgoing wave of the i part on the object plane;According to the reconstruction function of the outgoing wave of the first part and the second part, the displacement vector between the first part and the second part is calculated using image registration algorithm.The application can obtain the relative displacement of scanning position without positioning system, further, the relative displacement can also be used to complete diffraction imaging.

Description

Technical Field

[0001] The present application relates to the field of experimental equipment, and in particular to a displacement measurement method, device, and system. Background Art

[0002] In recent years, a variety of highly coherent radiation sources, including lasers with wavelengths ranging from terahertz to deep ultraviolet, synchrotron X-ray sources, and cold electron guns, have emerged or seen significant performance improvements. Lensless imaging methods based on lightwave coherence have gradually become important and promising technologies. Among them, coherent diffractive imaging (CDI) is the most representative lensless imaging method. CDI utilizes oversampled intensity information recorded at the far-field or near-field diffraction planes, combined with an iterative algorithm to reconstruct the complex transmittance / reflectance of the sample, thereby obtaining the absorption and refractive index distribution functions of the transmitted sample or the spatial variation and morphology of the surface reflectance of the emitted sample. Traditional CDI imaging methods require isolated samples, and image quality is heavily dependent on the complexity of the sample function. These limitations have significantly hindered its development and application, making traditional CDI a relatively mature imaging technology.

[0003] In response to the shortcomings of CDI, various improvement schemes have been proposed, among which stacked scanning imaging / scanning coherent diffraction imaging (Ptychography) is one of the most promising and excellent improvements. Scanning coherent diffraction imaging overcomes the problems faced by CDI by illuminating the sample with a light spot of limited size, recording multiple sample diffraction intensity patterns during the scanning process, and allowing adjacent sample illumination areas to overlap. After more than ten years of development, scanning coherent diffraction imaging has become an important imaging method for high-brightness and high-coherence light sources such as visible light, synchrotron X-rays, and coherent electrons. However, the existing scanning coherent diffraction imaging technology relies on precise prior knowledge of the scanning position, and the achievable image quality and resolution are limited by the accuracy of the relative displacement during multiple scans. There is still room for improvement in the existing scanning coherent diffraction imaging technology. Summary of the Invention

[0004] The present application provides a displacement measurement method, device and system, which can obtain the relative displacement of a scanning position without a positioning system.

[0005] In a first aspect, the present application provides a measurement method, comprising:

[0006] respectively obtaining initial functions of the outgoing waves of the first portion and the second portion of the object to be measured;

[0007] performing at least one first iteration with the initial function of the output wave of the first portion as input, wherein in each first iteration: the output wave of the first portion is propagated back and forth between an object plane, a modulator plane, and a detector plane, and an amplitude constraint is performed on the detector plane according to an actual diffraction intensity of the output wave of the first portion;

[0008] Obtaining a reconstruction function of the outgoing wave of the first portion on the object plane according to the at least one first iteration;

[0009] performing at least one second iteration with the initial function of the output wave of the second portion as input, wherein in each second iteration: the output wave of the second portion is propagated back and forth between the object plane, the modulator plane, and the detector plane, and an amplitude constraint is performed on the output wave of the second portion at the detector plane according to an actual diffraction intensity of the output wave of the second portion;

[0010] Obtaining a reconstruction function of the outgoing wave of the second portion on the object plane according to the at least one second iteration;

[0011] An image registration algorithm is used to calculate a displacement vector between the first portion and the second portion based on a reconstruction function of the outgoing wave of the first portion and a reconstruction function of the outgoing wave of the second portion.

[0012] Optionally, the method further includes:

[0013] According to the displacement vector, a reconstruction function of the outgoing wave of the first portion and a reconstruction function of the outgoing wave of the second portion are updated.

[0014] Optionally, the reconstruction function of the outgoing wave of the first portion is a combination function of a reconstructed illumination function of a coherent illumination light source and a reconstructed object function of the first portion;

[0015] The reconstruction function of the outgoing wave of the second part is a combination function of the reconstructed illumination function of the illumination light source and the reconstructed object function of the second part;

[0016] The updating of the reconstruction function of the outgoing wave at the first portion and / or the reconstruction function of the outgoing wave at the second portion according to the displacement vector includes:

[0017] performing at least one third iteration using the reconstruction function of the outgoing wave at the first portion and the reconstruction function of the outgoing wave at the second portion as input;

[0018] Wherein, in each of the third iterations: the outgoing waves of the first portion and the second portion are propagated back and forth between the object plane, the modulator plane and the detector plane respectively; and the displacement vector is used to impose constraints on the object plane.

[0019] Optionally, in each of said third iterations:

[0020] Separating, on the object plane, a reconstruction function of the outgoing wave of the first portion into a combination function of a reconstructed illumination function of the illumination light source and a reconstructed object function of the first portion, separating the reconstruction function of the outgoing wave of the second portion into a combination function of the reconstructed illumination function and a reconstructed object function of the second portion, and applying an object consistency constraint to the reconstructed object function of the first portion and the reconstructed object function of the second portion according to the displacement vector;

[0021] updating a reconstruction function of an outgoing wave of the first portion according to the reconstructed object function of the first portion constrained by the object consistency and the reconstructed illumination function of the illumination light source; and updating a reconstruction function of an outgoing wave of the second portion according to the reconstructed object function of the second portion constrained by the object consistency and the reconstructed illumination function of the illumination light source;

[0022] The reconstruction function of the updated output wave of the first portion propagated to the modulator plane is modulated and then propagated to the detector plane, and the actual diffraction intensity amplitude of the output wave of the first portion is constrained at the detector plane; the reconstruction function of the updated output wave of the second portion propagated to the modulator plane is modulated and then propagated to the detector plane, and the actual diffraction intensity amplitude of the output wave of the second portion is constrained at the detector plane;

[0023] The outgoing wave of the first part after the amplitude constraint and the outgoing wave of the second part after the amplitude constraint are respectively propagated back to the modulator plane for demodulation and then propagated to the object plane as input for the next third iteration.

[0024] Optionally, the method further includes:

[0025] acquiring an image of the first part and an image of the second part according to the reconstructed object function of the first part and the reconstructed object function of the second part in the last third iteration;

[0026] The image of the first part and the image of the second part are spliced ​​according to the displacement vector.

[0027] Optionally, for at least one of the first iteration, the second iteration and the third iteration, the iteration is stopped when the root mean square error between the detected diffraction intensity obtained at the detector plane and the actual diffraction intensity is less than a preset threshold, or the number of iterations reaches a preset number.

[0028] Optionally, the actual diffraction intensity of the outgoing wave at the first portion is the diffraction intensity detected when the forward wavefront of the outgoing wave obtained by irradiating the first portion on the object plane with a coherent illumination light source propagates to the modulator plane and is modulated;

[0029] The actual diffraction intensity of the outgoing wave of the second part is the diffraction intensity detected when the forward wavefront of the outgoing wave obtained by irradiating the second part on the object plane with the illumination light source propagates to the modulator plane and is modulated and then propagates to the detector plane.

[0030] Optionally, the modulator function of the modulator plane is a continuous, binary, absorption or phase modulation pattern.

[0031] Optionally, the modulator function of the modulator plane is known or unknown.

[0032] Optionally, the calculating the displacement vector between the first part and the second part using an image registration algorithm according to the reconstruction function of the outgoing wave of the first part and the reconstruction function of the outgoing wave of the second part includes:

[0033] acquiring a first image and a second image according to a reconstruction function of the outgoing wave of the first portion and a reconstruction function of the outgoing wave of the second portion;

[0034] respectively acquiring the first image and the second image after changes, wherein the changes include reduction or enlargement;

[0035] respectively calculating the change gradients of the first image and the second image;

[0036] A displacement vector between the first part and the second part is calculated according to the change gradient of the first image and the change gradient of the second image.

[0037] Optionally, calculating the displacement vector between the first part and the second part according to the change gradient of the first image and the change gradient of the second image includes:

[0038] calculating a cross-correlation spectrum of a change gradient of the first image and a change gradient of the second image;

[0039] Displacement vectors of the first image and the second image are calculated according to the cross-correlation spectrum.

[0040] Optionally, respectively acquiring the changed first image and the changed second image includes:

[0041] respectively acquiring regions of interest in the first image and the second image;

[0042] Obtaining a first sub-image and a second sub-image according to regions of interest of the first image and the second image respectively;

[0043] interpolating the first sub-image and the second sub-image respectively in Fourier space;

[0044] Perform inverse Fourier transform on the interpolated first sub-image and the second sub-image respectively to obtain the changed first image and the second image.

[0045] In a second aspect, the present application provides a measurement method, the method comprising:

[0046] Using a coherent illumination light source to illuminate at least a first portion and a second portion of the object to be measured, respectively, to obtain an outgoing wave from the first portion and an outgoing wave from the second portion;

[0047] Using a modulator, modulate the outgoing wave of the first portion and the outgoing wave of the second portion that propagate forward to the modulator plane, respectively, to obtain a modulated outgoing wave of the first portion and a modulated outgoing wave of the second portion;

[0048] Using a detector, respectively, detect the modulated outgoing wave of the first portion and the modulated outgoing wave of the second portion that propagate forward to the detector plane to obtain actual diffraction intensity of the outgoing wave of the first portion and actual diffraction intensity of the outgoing wave of the second portion;

[0049] The method further comprises:

[0050] The object to be measured is measured according to the actual diffraction intensity of the outgoing wave at the first portion and the actual diffraction intensity of the outgoing wave at the second portion, and any one of the measurement methods.

[0051] In a third aspect, the present application provides a measuring device, comprising:

[0052] A first acquisition module is used to respectively acquire initial functions of the outgoing waves of the first portion and the second portion of the object to be measured;

[0053] a first iteration module, configured to perform at least one first iteration using an initial function of the output wave of the first portion as input, wherein in each first iteration: the output wave of the first portion is propagated back and forth between an object plane, a modulator plane, and a detector plane, and an amplitude constraint is performed on the detector plane based on an actual diffraction intensity of the output wave of the first portion;

[0054] A first reconstruction module, configured to obtain a reconstruction function of the outgoing wave of the first portion on the object plane according to the at least one first iteration;

[0055] a second iteration module, configured to perform at least one second iteration using the initial function of the output wave of the second portion as input, wherein in each second iteration: the output wave of the second portion is propagated back and forth between the object plane, the modulator plane, and the detector plane, and an amplitude constraint is performed on the output wave of the second portion at the detector plane according to an actual diffraction intensity of the output wave of the second portion;

[0056] a second reconstruction module, configured to obtain a reconstruction function of the outgoing wave of the second portion on the object plane according to the at least one second iteration;

[0057] A calculation module is used to calculate the displacement vector between the first part and the second part using an image registration algorithm based on the reconstruction function of the outgoing wave of the first part and the reconstruction function of the outgoing wave of the second part.

[0058] Optionally, the measuring device further includes:

[0059] An updating module is used to update the reconstruction function of the outgoing wave of the first part and the reconstruction function of the outgoing wave of the second part according to the displacement vector.

[0060] Optionally, the reconstruction function of the outgoing wave of the first portion is a combination function of a reconstructed illumination function of a coherent illumination light source and a reconstructed object function of the first portion;

[0061] The reconstruction function of the outgoing wave of the second part is a combination function of the reconstructed illumination function of the illumination light source and the reconstructed object function of the second part;

[0062] When the updating module updates the reconstruction function of the outgoing wave at the first portion and / or the reconstruction function of the outgoing wave at the second portion according to the displacement vector, the updating module is specifically configured to:

[0063] performing at least one third iteration using the reconstruction function of the outgoing wave at the first portion and the reconstruction function of the outgoing wave at the second portion as input;

[0064] Wherein, in each of the third iterations: the outgoing waves of the first portion and the second portion are propagated back and forth between the object plane, the modulator plane and the detector plane respectively; and the displacement vector is used to impose constraints on the object plane.

[0065] Optionally, in each of the third iterations, the update module is specifically configured to:

[0066] Separating, on the object plane, a reconstruction function of the outgoing wave of the first portion into a combination function of a reconstructed illumination function of the illumination light source and a reconstructed object function of the first portion, separating the reconstruction function of the outgoing wave of the second portion into a combination function of the reconstructed illumination function and a reconstructed object function of the second portion, and applying an object consistency constraint to the reconstructed object function of the first portion and the reconstructed object function of the second portion according to the displacement vector;

[0067] updating a reconstruction function of an outgoing wave of the first portion according to the reconstructed object function of the first portion constrained by the object consistency and the reconstructed illumination function of the illumination light source; and updating a reconstruction function of an outgoing wave of the second portion according to the reconstructed object function of the second portion constrained by the object consistency and the reconstructed illumination function of the illumination light source;

[0068] The reconstruction function of the updated output wave of the first portion propagated to the modulator plane is modulated and then propagated to the detector plane, and the actual diffraction intensity amplitude of the output wave of the first portion is constrained at the detector plane; the reconstruction function of the updated output wave of the second portion propagated to the modulator plane is modulated and then propagated to the detector plane, and the actual diffraction intensity amplitude of the output wave of the second portion is constrained at the detector plane;

[0069] The outgoing wave of the first part after the amplitude constraint and the outgoing wave of the second part after the amplitude constraint are respectively propagated back to the modulator plane for demodulation and then propagated to the object plane as input for the next third iteration.

[0070] Optionally, the device further comprises:

[0071] a second acquisition module, configured to acquire an image of the first part and an image of the second part according to the reconstructed object function of the first part and the reconstructed object function of the second part in the last third iteration;

[0072] A stitching module is used to stitch the image of the first part and the image of the second part according to the displacement vector.

[0073] In a third aspect, the present application provides a measurement system, comprising:

[0074] A coherent illumination light source is used to illuminate at least a first portion and a second portion of the object to be measured, respectively, to obtain an outgoing wave from the first portion and an outgoing wave from the second portion;

[0075] a modulator, configured to modulate the outgoing wave of the first portion and the outgoing wave of the second portion that propagate forward to the modulator plane, respectively, to obtain a modulated outgoing wave of the first portion and a modulated outgoing wave of the second portion;

[0076] a detector, configured to respectively detect the modulated outgoing wave of the first portion and the modulated outgoing wave of the second portion that propagate forward to a detector plane, and obtain an actual diffraction intensity of the outgoing wave of the first portion and an actual diffraction intensity of the outgoing wave of the second portion;

[0077] A measuring device is used to perform any one of the measurement methods according to the actual diffraction intensity of the outgoing wave at the first portion and the actual diffraction intensity of the outgoing wave at the second portion.

[0078] In an embodiment of the present application, a modulator is used to change the wavefront. In the far-field detector plane, since the wavefront function of the object to be measured in real space and the function of the modulator are in a product relationship, it is equivalent to the convolution of the two functions in the reciprocal space. Therefore, the wavefront function of the object to be measured will be convolved and randomly distributed in various areas of the diffraction pattern; when the camera size is limited, it may not be possible to obtain a complete diffraction pattern, but the convolution relationship can be used to use only a part of the diffraction pattern to restore the unmeasured part, and the algorithm can be used to achieve the effect of deconvolution to find the wavefront function of the object to be measured. Therefore, in an embodiment of the present application, the displacement vector of the first part and the second part can be accurately estimated only by a single diffraction pattern of the first part and the second part and an algorithm. Optionally, the object function of the first part and the second part can be further optimized based on the displacement vector to obtain a more accurate object function of each part. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] Figure 1A is a schematic diagram of an embodiment of the measurement method of the present application;

[0080] Figure 1B is a schematic diagram of an embodiment of the first iteration or the second iteration of the measurement method of the present application;

[0081] Figure 2 is a schematic diagram of an embodiment of an image registration method in the measurement method of the present application;

[0082] Figure 3is a schematic diagram of an embodiment of the third iteration of the measurement method of the present application;

[0083] Figure 4 is a schematic diagram of an embodiment of the measurement method of the present application;

[0084] Figure 5 is a schematic diagram of an embodiment of a measurement system of the present application;

[0085] Figure 6 The left figure is the amplitude distribution diagram of the transmittance function of the object, and the right figure is the phase function distribution diagram of the object;

[0086] Figure 7 Comparison of the object amplitude and phase images reconstructed by the existing method at a known position and the method in the embodiment of the present application at an unknown position;

[0087] Figure 8 is the position measurement result diagram;

[0088] Figure 9 This is a diagram showing the effect of reconstructing the vortex light wavefront using the measurement method of an embodiment of the present application;

[0089] Figure 10 Schematic diagram of wavefront reconstruction;

[0090] Figure 11 This is a schematic diagram of experimental results of an embodiment of the measurement method of the present application;

[0091] Figure 12 This is a schematic diagram of experimental results in one embodiment of the measurement method of the present application;

[0092] Figure 13 is a schematic diagram of an embodiment of a measuring device of the present application;

[0093] Figure 14 Schematic diagram of an embodiment of a measurement system of the present application. DETAILED DESCRIPTION

[0094] The following describes embodiments of the present application in more detail with reference to the accompanying drawings. Although the accompanying drawings illustrate embodiments of the present application, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. Rather, these embodiments are provided to make the present application more thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

[0095] The terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application. As used in this application and the appended claims, the singular forms "a," "an," "the," and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0096] It should be understood that although the terms "first", "second", "third", etc. may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of this application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0097] A key requirement for existing scanning coherent diffraction imaging reconstruction is accurate a priori scanning position information, which is typically obtained using complex interferometric positioning systems. This application proposes a new method for obtaining scanning position information, which can be applied to scanning coherent diffraction imaging. This method eliminates the need for any a priori position information from the positioning system to complete imaging. This method is described below with examples in conjunction with the accompanying figures.

[0098] like Figure 1A As stated, Figure 1A 1 is a schematic diagram of an embodiment of the measurement method of the present application. The measurement method 100 includes:

[0099] In step S101 , a coherent light source is used to illuminate at least a first portion and a second portion of the object to be measured, respectively, to obtain an outgoing wave from the first portion and an outgoing wave from the second portion.

[0100] The coherent light source can be any illumination light source that can emit a light beam with a certain degree of coherence. The emitted light beam illuminates the first portion of the object to be measured and forms an output wave of the first portion after diffraction by the object. Assume that the illumination function of the light source is ψ(x P ,y P ), the function of the first part is ψ(x S1 ,y S1 ), then the function of the outgoing wave calculated on the object plane in real space is ψ(x O1 ,y O1 )According to ψ(x P ,y P ) and ψ(x S1 ,yS1 ) is obtained by multiplying; where (x i ,y i ) represents the coordinates of the position where the object to be measured is illuminated by the outgoing light beam. The same is true for the second part. Assume that the function of the second part is ψ(x S2 ,y S2 ), then the function of the outgoing wave calculated on the object plane in real space is ψ(x O2 ,y O2 )According to ψ(x P ,y P ) and ψ(x S2 ,y S2 ) is obtained by multiplying .

[0101] Step S102 : using a modulator to modulate the outgoing wave of the first portion and the outgoing wave of the second portion that propagate forward to the modulator plane, respectively, to obtain a modulated outgoing wave of the first portion and a modulated outgoing wave of the second portion.

[0102] The outgoing waves formed by diffraction from the first and second parts of the object to be measured propagate forward for a certain distance and then reach the modulator, where they are modulated and emitted. Let P1(·} represent the propagation operator from the actual object plane to the actual modulator plane. Then the function of the outgoing wave from the first part of the modulator front surface is ψ modulator_front (x M1 ,y M1 )=P1{ψ(x O1 ,y O1 )}, the function of the outgoing wave at the second position on the front surface of the modulator is ψ modulator_front (x M2 ,y M2 )=P1{ψ(x O2 ,y O2 )}.

[0103] Let M{·} represent the modulation operator, then the function of the outgoing wave at the first position of the rear surface of the actual modulator is ψ modulator_rear (x M1 ,y M1 )=M{ψ modulator_front (x M1 ,y M1 )}, the function of the outgoing wave at the second position of the rear surface of the actual modulator is ψ modulator_rear (x M2 ,y M2 )=M{ψ modulator_front (x M2 ,y M2 )}.

[0104] In step S103, a detector is used to detect the modulated outgoing wave of the first portion and the modulated outgoing wave of the second portion that propagate forward to the detector plane, respectively, to obtain the actual diffraction intensity of the outgoing wave of the first portion and the actual diffraction intensity of the outgoing wave of the second portion.

[0105] The modulated outgoing wave propagates forward a certain distance before reaching the detector, where it detects the actual diffraction intensity. Let P2{·} represent the propagation operator from the actual modulator plane to the actual detector plane. At the actual detector plane, the wavefront function ψ of the first part of the object to be measured is detector (x D1 ,y D1 )=P2{ψ mod u lator_rear (x M1 ,y M1 )}, the wavefront function of the second part ψ detector (x D2 ,y D2 )=P2{ψ modulator_rear (x M2 ,y M2 )}.

[0106] Optionally, the coherent light source, modulator, and detector can be fixed to each other within a detection device (e.g., a microscope system). Optionally, a detection platform is provided between the coherent light source and the modulator for placing the object to be detected. By adjusting the position and posture of the object to be detected on the detection platform, the part of the object to be detected illuminated by the coherent light source can be adjusted.

[0107] Steps S101-103 are used to experimentally obtain the actual diffraction intensity of at least the first and second portions of the object to be measured. Steps S104-120 estimate the illumination function of the light source and the object function of the scanned portion of the object to be measured and / or the illumination function of the illumination light source. An iterative algorithm is then used to repeatedly estimate the first object function of the scanned portion of the object to be measured and / or the illumination function of the illumination light source. The amplitude of the estimated wavefront of the outgoing wave is constrained by the actual diffraction intensity, so that the estimated function approaches or equals the actual function. This iterative algorithm is further described below.

[0108] Step S104 , respectively obtaining initial functions of the outgoing waves of the first portion and the second portion of the object to be measured.

[0109] The initial function of the outgoing wave is a combination of the initial illumination function of the coherent illumination light source and the initial object function of the scanned portion of the object to be measured. For example, the initial function of the outgoing wave at the first portion is ψ(x i O ,y iO ) is a combination function of the initial illumination function of the illumination light source and the initial object function of the first part, for example, equal to ψ object (x P ,y P )ψ object (x iS ,y i s ), where ψ object (x P ,y P ) and ψ object (x i S ,y i s ) are the initial guesses of the first object function and the initial guess of the illumination function, respectively, and i represents the i-th location. Similarly, the initial function of the outgoing wave of the second location is a combination of the initial illumination function of the illumination light source and the initial object function of the second location.

[0110] Optionally, the initial guess of the object function of the scanned portion of the object to be measured and / or the initial guess of the illumination function of the light source may be an all-one matrix, or may be a random matrix.

[0111] In the iterative algorithm, the initial function of the outgoing wave of the first part is used as input as the initial guess of the outgoing wave of the first part, and at least one first iteration is performed, wherein in each of the first iterations: the outgoing wave of the first part is propagated back and forth between the object plane, the modulator plane and the detector plane, and the amplitude of the outgoing wave of the first part is constrained at the detector plane according to the actual diffraction intensity of the outgoing wave of the first part.

[0112] The same is true for the second part. Taking the initial function of the outgoing wave of the second part as input, at least one second iteration is performed, wherein in each of the second iterations: the outgoing wave of the second part is propagated back and forth between the object plane, the modulator plane and the detector plane, and the amplitude of the outgoing wave of the second part is constrained at the detector plane according to the actual diffraction intensity of the outgoing wave of the second part.

[0113] The initial guess can be started from the object plane or the detector plane. Figure 1B The first and second iterations are explained with examples in steps S105-S107. Figure 1B is a schematic diagram of an embodiment of the first iteration or the second iteration.

[0114] Step S105, propagating the outgoing wave of the i-th part forward from the object plane to the modulator plane, modulating the outgoing wave of the i-th part using a modulator on the modulator plane to obtain the modulated outgoing wave of the i-th part, where i is equal to one or two.

[0115] According to the forward propagation operator P1{·} from the object plane to the modulator plane in step S102, the function of the outgoing wave at the i-th position on the front surface of the modulator is ψ modulator_front (x i M ,y i M )=P1{ψ(x i o ,y i O In some examples, the propagation operator P1{·} can be obtained by the angular spectrum method.

[0116] In the algorithm, the same modulation function as in step S102 is used to modulate the outgoing wave on the modulation plane. According to the modulation operator M{·} in step S102, the function of the outgoing wave at the i-th position on the rear surface of the modulation plane is ψ modulator_rear (x i M,y i M )=M×ψ modulator_front (x i M,y i M ).

[0117] Step S106 , performing amplitude constraint on the diffraction intensity of the modulated outgoing wave at the i-th position on the detector plane according to the actual diffraction intensity.

[0118] According to the propagation operator P2{·} from the modulator plane to the detector plane in step S103, the wavefront ψ of the outgoing wave at the detector plane is detector (x i D,y i D )=P2{ψ modulator-rear (x i M ,y i M )}. In some examples, the propagation operator P2{·} is usually Fourier transform, (x D ,y D ) represents the coordinates of the detector plane space.

[0119] The amplitude of the outgoing wave on the detector plane in the algorithm is constrained according to the actual diffraction intensity obtained in step S103, and the amplitude-constrained wavefront

[0120] Among them, I(x i D ,y i D ) represents the data intensity received by the detector in step S103, and abs{·} represents the amplitude operator.

[0121] Step S107 , propagating the amplitude-constrained outgoing wave back to the modulation plane for demodulation and then continuing to propagate back to the object plane.

[0122] Among them, represents the back propagation operator from the modulation plane to the detector plane, then the amplitude-constrained outgoing wave on the rear surface of the modulator is

[0123] There are many ways to perform demodulation on the modulation plane. For example, demodulation can be achieved by simple division, or demodulation can be achieved by using a demodulation operator, which can reduce noise compared to simple division. In one example, the demodulated outgoing wave Where α is the update coefficient, usually set to 0.9.

[0124] by represents the back propagation operator from the modulation plane to the object plane, then the amplitude-constrained outgoing wave

[0125] After step S107, the reconstruction function of the outgoing wave at the first portion and the reconstruction function of the outgoing wave at the second portion are obtained on the object plane. Then, the reconstruction function of the outgoing wave at the first portion is used as the input of a new round of first iteration, and a new round of first iteration is performed (i.e., steps S105 to S107 are re-executed). After performing at least one first iteration, the reconstruction function of the outgoing wave at the first portion output by the last first iteration is obtained. Similarly, for the second portion, after performing at least one second iteration, the reconstruction function of the outgoing wave at the second portion output by the last second iteration is obtained.

[0126] When it is detected that the preset stop condition is met, the first and second iterations are stopped, and the reconstruction function of the outgoing wave of the first part is obtained in the last first iteration, and the reconstruction function of the outgoing wave of the second part is obtained in the last second iteration.

[0127] Step S108 : calculating the displacement vector between the first part and the second part using an image registration algorithm according to the reconstruction function of the outgoing wave of the first part and the reconstruction function of the outgoing wave of the second part.

[0128] Specifically, POS{·} represents the image registration operator, then the scanning position (x D ,y D ) and (x T ,y T ) relative displacement between D-T =POS{ψ object (x D ,y D ), ψ object (x T ,y T Optionally, the image registration operator is based on an image registration method, including SIFT, SURF, ORB or AKAZE based on key point and feature description, or RANSAC or LMEDS based on image transformation, or a method based on deep learning and reinforcement learning, or an image registration method based on grayscale, intensity, or phase cross-correlation, etc., which are not limited here.

[0129] Traditional gradient-based image registration algorithms usually calculate the gradients along the X and Y axes without considering the gradient information along other directions. This application also provides a new sub-pixel image registration algorithm that can utilize gradient information in all directions.

[0130] like Figure 2 As shown, Figure 2 FIG. 2 is a schematic diagram of an embodiment of an image registration method in the measurement method of the present application. The image registration method 200 includes:

[0131] Step S201 : acquiring a first image and a second image according to a reconstruction function of the first part and a reconstruction function of the second part.

[0132] Step S202 : acquiring the first image and the second image after changes, respectively. The changes include reduction or enlargement.

[0133] Optionally, the first image and the second image can be directly reduced or enlarged. Alternatively, the region of interest of the first image and the region of interest in the second image can be obtained respectively. Based on the region of interest of the first image and the region of interest in the second image, the first sub-image and the second sub-image are respectively determined. For example, the region of interest of the first image can be directly used as the first sub-image, or the region of interest of the second image can be directly used as the second sub-image. In some examples, in order to speed up calculations, the regions of interest of the first image and the second image can be cropped respectively, and the first sub-image and the second sub-image can be obtained based on the cropped regions of interest.

[0134] The first sub-image and the second sub-image are interpolated in Fourier space, and inverse Fourier transform is performed on the interpolated first sub-image and the second sub-image to obtain the changed first image and the second image.

[0135] Specifically, in an example, suppose A and B are two M×M images to be registered, K is the interpolation kernel, and R is the mask of the region of interest. Then the region of interest A R =A×R,B R = B × R. According to the size of the region of interest and the requirements of discrete Fourier transform, the image is cropped to speed up the calculation, and A is obtained. C =Crop{A R}, B C =Crop{B R}. Use the predefined interpolation kernel K to interpolate the image in Fourier space and get A I =Int{F{A C}, K}, B I =Int{F{B C}, K}. Perform inverse Fourier transform to obtain the scaled image, i.e. A S =IFFT{A I}, B S =IFFT{B I}.

[0136] Step S203 : Calculate the change gradients of the first image and the second image respectively.

[0137] For example, the change gradient G of the first image A =A S -A, the change gradient G of the second image B =B S -B.

[0138] Step S204 : calculating the displacement vectors of the first image and the second image according to the change gradient of the first image and the change gradient of the second image.

[0139] In one example, the cross-correlation spectrum of the change gradient of the first image and the change gradient of the second image is calculated; and the displacement vector of the first image and the second image is calculated based on the cross-correlation spectrum. Specifically, the cross-correlation spectrum CS=F{G A}×F{G B} * , the displacement of the two images is calculated by iterative integral inverse Fourier transform. Optionally, other relative displacement measurement methods other than cross-correlation spectrum can be used to obtain the displacement vectors of the first image and the second image, which is not limited here.

[0140] After the displacement vectors of the first image and the second image are obtained, a similar method may be used to obtain reconstruction functions of other parts of the object to be measured and the displacement vectors between the parts.

[0141] Optionally, in the measurement method of the present application, after obtaining the displacement vector between the first portion and the second portion, the displacement vector can also be used to update the reconstruction function of the outgoing wave of the first portion and the reconstruction function of the outgoing wave of the second portion, so that the outgoing waves of the first portion and the second portion are more accurate. Optionally, after obtaining the displacement vector, since the reconstruction functions of the outgoing waves of the first portion and the second portion are combined functions of the reconstructed illumination function of the coherent illumination light source and the reconstructed object function of the first portion and the reconstructed object function of the second portion, respectively, the displacement vector can also be used to separate the outgoing wave of the first portion into the object function and the illumination function of the first portion, and to separate the outgoing wave of the second portion into the object function and the illumination function of the second portion.

[0142] At least one third iteration is performed using the reconstruction function of the outgoing wave at the first location and the reconstruction function of the outgoing wave at the second location as input. In each third iteration, the outgoing waves at the first location and the second location are propagated back and forth between an object plane, a modulator plane, and a detector plane, respectively, and a constraint is imposed on the object plane using the displacement vector.

[0143] The third iteration process can be similar to the first and second iteration processes, but the initial input of the third iteration is the reconstruction function of the outgoing waves of the first and second locations. Figure 3 As shown, Figure 3 FIG2 is a schematic diagram of an embodiment of the third iteration of the measurement method of the present application. In the third iteration, in the object plane, the reconstruction function of the outgoing wave of the first portion is separated into a combination of the reconstructed illumination function of the illumination light source and the reconstructed object function of the first portion; the reconstruction function of the outgoing wave of the second portion is separated into a combination of the reconstructed illumination function of the illumination light source and the reconstructed object function of the second portion; and an object consistency constraint is applied to the reconstructed object functions of the first portion and the second portion based on the displacement vector.

[0144] In the object plane, a reconstruction function of the outgoing wave of the first part is updated according to the reconstructed object function of the first part after being constrained by the object consistency and the reconstructed illumination function of the illumination light source; and a reconstruction function of the outgoing wave of the second part is updated according to the reconstructed object function of the second part after being constrained by the object consistency and the reconstructed illumination function of the illumination light source.

[0145] The updated outgoing waves of the first and second parts are forwardly propagated to the modulator plane for modulation and then propagated to the detector plane. At the detector plane, the amplitude is constrained by the actual diffraction intensity of the outgoing wave of the first part and the actual diffraction intensity of the outgoing wave of the second part respectively.

[0146] The outgoing wave of the first part after the amplitude constraint and the outgoing wave of the second part after the amplitude constraint are respectively propagated back to the modulator plane for demodulation and then propagated to the object plane as input for the next third iteration.

[0147] In the final third iteration, the reconstructed object function of the first part after the object consistency constraint is used as the object function of the first part, the reconstructed object function of the second part after the object consistency constraint is used as the object function of the second part, and the reconstructed illumination function of the illumination light source is used as the illumination function.

[0148] There may be various stopping conditions for the first, second, and third iterations, and the stopping conditions for the three iterations may be the same or different, without limitation herein. For example, the iterations may be stopped when the root mean square error between the diffraction intensity detected by the detector plane and the actual diffraction intensity is less than a preset threshold, or when the number of iterations reaches a preset value.

[0149] In an embodiment of the present application, a modulator is used to change the wavefront. In the far-field detector plane, because the wavefront function of the object to be measured in real space and the function of the modulator are in a product relationship, it is equivalent to the convolution of the two functions in the reciprocal space. Therefore, the object function of the object to be measured will be convolved and randomly distributed in various areas of the diffraction pattern; when the camera size is limited, it may not be possible to obtain a complete diffraction pattern. The convolution relationship can be used to use only a part of the diffraction pattern to restore the unmeasured part; since the function of the modulator and the convolution result are known, the deconvolution effect can be achieved through the algorithm to find the object function of the object to be measured, and the same is true for the illumination function of the illumination light source; therefore, in an embodiment of the present application, the displacement vector of the first part and the second part can be accurately estimated only by a single diffraction pattern and an algorithm, and the object function of the first part and the second part can be further optimized according to the displacement vector to obtain a more accurate object function of each part.

[0150] In some examples, the modulator can use a phase-type modulator with a continuous random modulation pattern, which can cause the low-frequency and high-frequency information in the wavefront of the modulator plane to overlap, helping to achieve high-resolution imaging. In traditional methods, the low-frequency information in the diffraction pattern is distributed in the middle and has a particularly high intensity, which may burn out the detector. By using a modulator with a random modulation function, the high and low frequencies are randomly distributed, which has a certain protective effect on the detector. And because continuous functions are convenient for sampling, using a modulator with a continuous modulation function can facilitate calibration. Optionally, the modulation function of the modulator can also be binary.

[0151] In some examples, the modulator's modulation function can also be phase-dependent. In some cases, when the temporal coherence of the light source is poor, an amplitude-dependent, or absorption-dependent, modulator can be used. This is because a phase-dependent modulator responds differently to different wavelengths, making experimental manipulation difficult. An absorption-dependent modulator only modulates the amplitude of the wavefront, allowing all wavelengths to share the same modulator, making experiments much more convenient. Traditional methods produce a blurred diffraction pattern; in this example, the diffraction pattern is a convolution of the blurred diffraction pattern with the modulator function.

[0152] In the embodiment of the present application, the modulation function of the modulator can be known or unknown. The calculated diffraction pattern and the measured value gap are large. By arranging a modulator between the outgoing wave and the detector, the convergence of the iterative algorithm can be enhanced. Moreover, due to the conjugate image, that is, the amplitude of the Fourier transform of an outgoing wave and its conjugate is the same, the algorithm cannot distinguish whether the calculated object function corresponds to the outgoing wave or the conjugate of the outgoing wave. In this application, the propagation process between the object and the detector is changed by adding a modulator, which solves the problem that the conjugate image and the true solution have the same diffraction intensity. Therefore, the information of the part of the object to be measured corresponding to the diffraction pattern can be restored by using a diffraction pattern. Moreover, the analytical ability of the information of the object to be measured can be enhanced by adding a modulator. In the object to be measured with a strong phase change (for example, a sample with strong strain), the phase jump is too large to cause the object to be measured to be unable to be analyzed. By adding a modulator, since the function of the modulator is known and the light propagation mode is also known, the analytical difficulty of the object to be measured is greatly reduced. For low-light scenes, the modulator can also play a role in signal enhancement. The existence of the convolution relationship allows the diffraction signal to be received by more pixels. In traditional methods, the information is distributed in a small area in the middle. In low-light scenes, the signal will be interfered with by Poisson noise. By adding a modulator, the information is encoded into a larger area with the convolution relationship, and the influence of Poisson noise will be weakened.

[0153] In some examples, the light beam emitted by the coherent illumination source can be visible light, or short-wavelength beams such as X-rays and EUV. In the embodiments of the present application, both far-field diffraction and near-field diffraction are applicable. However, the advantage of far-field diffraction is that the object plane and the detector plane have a scaling relationship, which allows for nm-level sampling of the object plane, while the detector pixel size only needs to be at the μm level.

[0154] Optionally, a lens is further provided between the actual modulator plane and the actual detector plane. After the modulator modulates the output wave using a known modulation function, the output wave is Fourier transformed by the lens before being incident on the actual detector plane. Alternatively, the detector can be placed at a longer distance without placing a lens to achieve Fourier transform. Optionally, in the example where the coherent light source emits a short-wavelength light beam, a lens can be omitted. In the example where the coherent light source emits visible light, a lens is placed between the actual modulator plane and the actual detector plane to achieve Fourier transform within a short distance in the visible light band, so that the sampling pixel of the object is smaller than that of the detector.

[0155] Optionally, in an embodiment of the present application, the first image and the second image can be spliced ​​into one image based on the displacement vector and the object consistency constraint. Similarly, different parts of the object to be measured can be illuminated multiple times by an illumination light source, and the object functions and images corresponding to the different parts can be obtained according to steps S102 to S109. Then, an image registration algorithm is applied to the images corresponding to the different parts to calculate the displacement vectors between the different parts, and the images are spliced ​​into an image corresponding to the object to be measured based on the displacement vectors and the object consistency constraint.

[0156] like Figure 4 As stated, Figure 4 It is a schematic diagram of an embodiment of the measurement method of the present application. Figure 4 The measurement method shown in FIG4 is the algorithm part of the measurement method shown in FIG1 . The measurement method 400 includes:

[0157] Step S401 : obtaining initial functions of the outgoing waves of the first portion and the second portion of the object to be measured respectively.

[0158] Step S402, taking the initial function of the outgoing wave of the first part as input, performing at least one first iteration, wherein in each of the first iterations: the outgoing wave of the first part is propagated back and forth between the object plane, the modulator plane and the detector plane, and the amplitude of the outgoing wave of the first part is constrained on the detector plane according to the actual diffraction intensity of the outgoing wave of the first part.

[0159] Step S403 : obtaining a reconstruction function of the outgoing wave of the first portion on the object plane according to the at least one first iteration.

[0160] Step S404, performing at least one second iteration with the initial function of the outgoing wave of the second part as input, wherein in each second iteration: the outgoing wave of the second part is propagated back and forth between the object plane, the modulator plane and the detector plane, and the amplitude of the outgoing wave of the second part is constrained at the detector plane according to the actual diffraction intensity of the outgoing wave of the second part.

[0161] Step S405 : obtaining a reconstruction function of the outgoing wave of the second portion on the object plane according to the at least one second iteration.

[0162] Step S406 : Calculate the displacement vector between the first part and the second part using an image registration algorithm according to the reconstruction function of the outgoing wave of the first part and the reconstruction function of the outgoing wave of the second part.

[0163] Optionally, the actual diffraction intensities of the outgoing waves at the first and second locations are the diffraction intensities of the forward wavefront of the outgoing wave propagating to the detector plane after being modulated by the modulator when the forward wavefront propagates to the modulator plane, respectively, using an illumination light source to illuminate the first and second locations of the object to be measured at the object plane. A detailed explanation of these actual diffraction intensities can be found in the embodiment shown in FIG1 and will not be repeated here. Alternatively, the actual diffraction intensities may be obtained using other methods, which are not limited here.

[0164] For the explanation of each step, please refer to the explanation in the embodiment shown in FIG1 , which will not be repeated here.

[0165] In the theory of scanning coherent diffraction imaging, resolution is determined by the wavelength of the illumination light and the maximum diffraction angle of the recorded data. However, in existing practical experiments, the image quality and resolution achievable by scanning coherent diffraction imaging are also limited by the position uncertainty of the sample translation stage. The most important influencing factor is the accuracy of the relative displacement during multiple scans. Hardware-based improvements to the feedback position accuracy of the sample translation stage are mainly achieved through closed-loop feedback and integrated interferometer systems, which will affect the data acquisition rate and increase costs. To this end, a variety of algorithm-based position acquisition and correction methods have been proposed in recent years, including: serial correlation algorithm, annealing algorithm, conjugate gradient algorithm, similar structure method, and many other position calibration algorithms.

[0166] However, the above-mentioned position correction algorithms all require known rough position information and are suitable for applications with small relative position errors, such as correcting the feedback position error of the sample displacement stage in visible light imaging systems or the positioning error caused by thermal drift of the sample displacement stage. In application scenarios such as electron microscopy and X-ray microscopy, even with a high-precision closed-loop translation stage system, there is still a large relative error in the position, and the existing position correction method cannot work. In addition, the use of a closed-loop sample stage will lead to a decrease in data acquisition rate and an increase in the complexity and cost of the hardware device, which will compress the sample working distance and limit the possible sample working environment. There is currently no method to implement scanning diffraction imaging that does not require position information. In addition, there is also an application demand for high-precision measurement of the relative lateral displacement of distant light waves and objects.

[0167] The measurement method and the required system provided in the embodiments of the present application are simple, compact, have low detector requirements, and are independent of the accuracy of the sample displacement stage. Therefore, they can be widely used in microscopy systems. Traditional scanning coherent diffraction imaging devices rely on high-precision sample displacement stages, which are relatively expensive. The system in the embodiments of the present application does not require a high-precision displacement stage and can reconstruct sample information without any position information, and realize displacement measurement, diffraction imaging, and wavefront reconstruction. The system in the embodiments of the present application is simple, low-cost, high-resolution, and highly scalable, which is of great significance to the scientific and engineering applications of diffraction imaging. When achieving high-resolution imaging at the atomic level and below, the feedback accuracy of the sample displacement stage is highly correlated with the imaging quality and resolution. The method in the embodiments of the present application can greatly relax the requirements for the feedback accuracy of the sample displacement stage, thereby achieving higher-resolution imaging. In the field of biomedical imaging, the method in the embodiments of the present application can be used for in-situ, large-field-of-view, high-resolution imaging of unstained biological cells / tissues. In the field of mechanical processing, the method in the embodiments of the present application provides the ability to perform quantitative, high-resolution, rapid, and large-scale imaging of the surface morphology of a workpiece, and can be applied to online, in-service detection, etc.

[0168] Optionally, in this application, the light source can be used to repeatedly detect different parts of the object to be measured to reconstruct the object functions of different parts, and then a sub-pixel image registration algorithm can be used to extract scanning trajectory information from the overlapping areas of the reconstructed multiple object functions. Optionally, the object functions can be assembled into a complete object function based on the scanning trajectory information.

[0169] like Figure 5 As shown, Figure 5is a schematic diagram of an embodiment of a measurement system of the present application. The measurement system 500 includes an illumination source 501, a modulator 503, a lens 504, a detector 505, and a reconstruction device (not shown). In some examples, the reconstruction device and the detector may be integrated into a single device, or may be separate devices from the detector, without limitation.

[0170] Optionally, measurement system 500 further includes a probe (not shown), which can be formed by a pinhole of limited diameter and located on the side of the outgoing light from illumination source 501. Object 502 to be measured is placed between the probe and modulator 503. Lens 504 is located between modulator 503 and detector 505 and is used to perform a Fourier transform. In some examples where the illumination source is configured to emit converging light, the probe may not be required.

[0171] The diffraction intensity dataset collected by detector 505 is used as input to an iterative algorithm to obtain displacement vectors between scanned portions of the object 506 to be measured. Optionally, an object function for each scanned portion is further obtained based on the displacement vectors and the iterative algorithm. Optionally, the iterative algorithm uses a shared probe for measurements of different portions of the object to be measured, and reconstruction is performed on each portion in parallel. Optionally, the images corresponding to each portion are spliced ​​together based on the displacement vectors between the portions to form a single image of the object to be measured.

[0172] The following Figures 6 to 10 The experimental results shown in the figure illustrate the effect of the measurement method in the embodiment of the present application. Figure 6 and Figure 7 shown. Figure 6 The left image shows the distribution of the object's amplitude function, and the right image shows the distribution of the object's phase transmittance function. The image size is 669*669 pixels. Figure 7 The comparison of the object amplitude and phase images reconstructed by the existing method at a known position and the method in the embodiment of the present application at an unknown position is shown. Figure 7 The above figure shows the object absorption and phase diagram reconstructed by the existing method when the position is known. Figure 7 The following figure shows the object absorption and phase diagram reconstructed by the method in the embodiment of the present application under the condition of unknown position. Figure 7 The figure below shows the results obtained after 300 iterations of the iterative algorithm. The average grid spacing of the object scan is 30 pixels, with 6*6 = 36 points. It can be seen that the reconstruction quality of the method in this embodiment at unknown locations is the same as the image quality of the existing method at known locations. Figure 7 The figure below effectively verifies the imaging effect of this method when the position is unknown.

[0173] In Experimental Example 2, Figure 8This experiment was used to verify the displacement measurement capabilities of the measurement method in the embodiments of this application. In this experimental example, the sample was raster scanned with a spacing of 20 pixels between each scanning point, for a total of 64 points. The displacement between each scanning point was calculated using an image cross-correlation position calibration algorithm. Figure 8 is the position measurement result diagram, where Figure 8 The middle figure is the scanning position error diagram, Figure 8 The left picture is the Y-axis position error diagram. Figure 8 The figure below shows the X-axis position error. It can be seen that the reconstructed path has almost no error with the true path.

[0174] Experimental Example 3 is used to verify the wavefront measurement effect of the measurement method in the embodiment of the present application. Figure 9 This is a diagram showing the effect of reconstructing the vortex light wavefront using the measurement method of an embodiment of the present application. Figure 9 The upper left picture is a schematic diagram of the wavefront amplitude, the upper right picture is a schematic diagram of the wavefront phase, the middle left picture is a schematic diagram of the reconstructed wavefront amplitude, and the middle right picture is a schematic diagram of the reconstructed wavefront phase. The lower left picture is a schematic diagram of the normalized wavefront amplitude difference, and the lower right picture is a schematic diagram of the wavefront phase difference. Amplitude normalization is because the existence of the number of photons will cause the light intensity to be non-constant, and the subtraction morphology will be the same but the value will be very different. The phase is originally in the range of -pi to pi and does not need to be normalized. Figure 9 It can be seen that the amplitude and phase of the reconstructed vortex light wavefront are almost consistent with the generated vortex light wavefront.

[0175] Experimental Example 4 is an optical verification experiment used to demonstrate the ability to measure wavefronts. Figure 10 Schematic diagram of wavefront reconstruction, wherein the upper left figure is a schematic diagram of the wavefront amplitude reconstructed by conventional stacked scanning imaging, the upper right figure is a schematic diagram of the wavefront phase reconstructed by conventional stacked scanning imaging, the left middle figure is a schematic diagram of the reconstructed wavefront amplitude in the measurement method of the embodiment of the present application, the right middle figure is a schematic diagram of the reconstructed wavefront phase in the measurement method of the embodiment of the present application, the left lower figure is a schematic diagram of the normalized wavefront amplitude difference, and the right lower figure is a schematic diagram of the phase difference. Figure 10 The error between the wavefront reconstructed by traditional stack scanning imaging and the reconstructed wavefront by the measurement method of the embodiment of the present application verifies the ability of the proposed method to measure the wavefront.

[0176] Experimental Example 5 is an optical verification experiment. In this experiment, Figure 4The measurement system shown in this experimental example uses a stabilized HeNe laser with a wavelength of 632.8 nm as the illumination source. A 0.85 mm diameter aperture is used to shape the beam and is positioned 0.2 mm upstream of the sample. The object to be measured is a fig, and a continuous-wave phase modulator with a scattering angle of 5 degrees is positioned 12.5 mm downstream of the sample. A Fourier lens with a focal length of 30 mm is positioned between the modulator and the detector. The detector is a Dhyana V3 camera with a pixel size of 6.5 μm. Figure 11 Schematic diagram of experimental results, where Figure 11 The upper left and upper right images are the amplitude and phase of a fig fruit reconstructed using prior position information. The lower left and lower right images are the amplitude and phase of a fly wing reconstructed using the measurement method of the present application without prior position information. Figure 12 are the position errors along the Y and X axes, respectively.

[0177] like Figure 11 As shown, the amplitude and phase reconstructed without position information are consistent with the amplitude and phase obtained using position information. Figure 12 The reconstructed positions in the image match well with the actual positions. Figure 12 The position error along the Y and X axes was analyzed separately. In this experiment, the pixel size in the sample plane was 2.9 μm. Notably, the average position error along both axes was less than 0.01 pixel, and the maximum position error was less than 0.05 pixel, demonstrating the effectiveness and robustness of the proposed method.

[0178] like Figure 13 As stated, Figure 13 1 is a schematic diagram of an embodiment of a measuring device of the present application. The measuring device 1300 includes:

[0179] A first acquisition module 1301 is used to respectively acquire initial functions of the outgoing waves of the first portion and the second portion of the object to be measured;

[0180] A first iteration module 1302 is configured to perform at least one first iteration using an initial function of the output wave of the first portion as input, wherein in each first iteration: the output wave of the first portion is propagated back and forth between an object plane, a modulator plane, and a detector plane, and an amplitude constraint is performed on the detector plane based on an actual diffraction intensity of the output wave of the first portion;

[0181] A first reconstruction module 1303 is configured to obtain a reconstruction function of the outgoing wave of the first portion on the object plane according to the at least one first iteration;

[0182] A second iteration module 1304 is configured to perform at least one second iteration using the initial function of the output wave of the second portion as input, wherein in each second iteration: the output wave of the second portion is propagated back and forth between the object plane, the modulator plane, and the detector plane, and an amplitude constraint is performed on the output wave of the second portion at the detector plane according to an actual diffraction intensity of the output wave of the second portion;

[0183] A second reconstruction module 1305 is configured to obtain a reconstruction function of the outgoing wave of the second portion on the object plane according to the at least one second iteration;

[0184] The calculation module 1306 is configured to calculate the displacement vector between the first portion and the second portion using an image registration algorithm according to the reconstruction function of the outgoing wave of the first portion and the reconstruction function of the outgoing wave of the second portion.

[0185] Optionally, the measuring device further includes:

[0186] An updating module is used to update the reconstruction function of the outgoing wave of the first part and the reconstruction function of the outgoing wave of the second part according to the displacement vector.

[0187] Optionally, the reconstruction function of the outgoing wave of the first portion is a combination function of a reconstructed illumination function of a coherent illumination light source and a reconstructed object function of the first portion;

[0188] The reconstruction function of the outgoing wave of the second part is a combination function of the reconstructed illumination function of the illumination light source and the reconstructed object function of the second part;

[0189] When the updating module updates the reconstruction function of the outgoing wave at the first portion and / or the reconstruction function of the outgoing wave at the second portion according to the displacement vector, the updating module is specifically configured to:

[0190] performing at least one third iteration with the reconstruction function of the outgoing wave at the first portion and the reconstruction function of the outgoing wave at the second portion as input;

[0191] Wherein, in each of the third iterations: the outgoing waves of the first portion and the second portion are propagated back and forth between the object plane, the modulator plane and the detector plane respectively; and the displacement vector is used to impose constraints on the object plane.

[0192] Optionally, in each of the third iterations, the update module is specifically configured to:

[0193] Separating, on the object plane, a reconstruction function of the outgoing wave of the first portion into a combination function of a reconstructed illumination function of the illumination light source and a reconstructed object function of the first portion, separating the reconstruction function of the outgoing wave of the second portion into a combination function of the reconstructed illumination function and a reconstructed object function of the second portion, and applying an object consistency constraint to the reconstructed object function of the first portion and the reconstructed object function of the second portion according to the displacement vector;

[0194] updating a reconstruction function of an outgoing wave of the first portion according to the reconstructed object function of the first portion constrained by the object consistency and the reconstructed illumination function of the illumination light source; and updating a reconstruction function of an outgoing wave of the second portion according to the reconstructed object function of the second portion constrained by the object consistency and the reconstructed illumination function of the illumination light source;

[0195] The reconstruction function of the updated output wave of the first portion propagated to the modulator plane is modulated and then propagated to the detector plane, and the actual diffraction intensity amplitude of the output wave of the first portion is constrained at the detector plane; the reconstruction function of the updated output wave of the second portion propagated to the modulator plane is modulated and then propagated to the detector plane, and the actual diffraction intensity amplitude of the output wave of the second portion is constrained at the detector plane;

[0196] The outgoing wave of the first part after the amplitude constraint and the outgoing wave of the second part after the amplitude constraint are respectively propagated back to the modulator plane for demodulation and then propagated to the object plane as input for the next third iteration.

[0197] Optionally, the measuring device further includes:

[0198] a second acquisition module, configured to acquire an image of the first part and an image of the second part according to the reconstructed object function of the first part and the reconstructed object function of the second part in the last third iteration;

[0199] A stitching module is used to stitch the image of the first part and the image of the second part according to the displacement vector.

[0200] Optionally, for at least one of the first iteration, the second iteration and the third iteration, the iteration is stopped when the root mean square error between the detected diffraction intensity obtained at the detector plane and the actual diffraction intensity is less than a preset threshold, or the number of iterations reaches a preset number.

[0201] Optionally, the actual diffraction intensity of the outgoing wave at the first portion is the diffraction intensity detected when the forward wavefront of the outgoing wave obtained by irradiating the first portion on the object plane with a coherent illumination light source propagates to the modulator plane and is modulated;

[0202] The actual diffraction intensity of the outgoing wave of the second part is the diffraction intensity detected when the forward wavefront of the outgoing wave obtained by irradiating the second part on the object plane with the illumination light source propagates to the modulator plane and is modulated and then propagates to the detector plane.

[0203] Optionally, the modulator function of the modulator plane is a continuous, binary, absorption or phase modulation pattern.

[0204] Optionally, the modulator function of the modulator plane is known or unknown.

[0205] Optionally, when the calculation module calculates the displacement vector between the first part and the second part using an image registration algorithm based on the reconstruction function of the outgoing wave of the first part and the reconstruction function of the outgoing wave of the second part, the calculation module is specifically configured to:

[0206] acquiring a first image and a second image according to a reconstruction function of the outgoing wave of the first portion and a reconstruction function of the outgoing wave of the second portion;

[0207] respectively acquiring the first image and the second image after changes, wherein the changes include reduction or enlargement;

[0208] respectively calculating the change gradients of the first image and the second image;

[0209] A displacement vector between the first part and the second part is calculated according to the change gradient of the first image and the change gradient of the second image.

[0210] Optionally, when calculating the displacement vector between the first part and the second part according to the change gradient of the first image and the change gradient of the second image, the calculation module is specifically configured to:

[0211] calculating a cross-correlation spectrum of a change gradient of the first image and a change gradient of the second image;

[0212] Displacement vectors of the first image and the second image are calculated according to the cross-correlation spectrum.

[0213] Optionally, when respectively acquiring the changed first image and the changed second image, the calculation module is specifically configured to:

[0214] respectively acquiring regions of interest in the first image and the second image;

[0215] Obtaining a first sub-image and a second sub-image according to regions of interest of the first image and the second image respectively;

[0216] interpolating the first sub-image and the second sub-image respectively in Fourier space;

[0217] Perform inverse Fourier transform on the interpolated first sub-image and the second sub-image respectively to obtain the changed first image and the second image.

[0218] like Figure 14 As shown, Figure 14 1400 is a schematic diagram of an embodiment of a measurement system of the present application. The measurement system 1400 includes:

[0219] A coherent illumination light source 1401 is used to illuminate at least a first portion and a second portion of the object to be measured, respectively, to obtain an outgoing wave from the first portion and an outgoing wave from the second portion;

[0220] A modulator 1402 is configured to modulate the outgoing wave at the first portion and the outgoing wave at the second portion that propagate forward to the modulator plane, respectively, to obtain a modulated outgoing wave at the first portion and a modulated outgoing wave at the second portion;

[0221] a detector 1403, configured to respectively detect the modulated outgoing wave from the first portion and the modulated outgoing wave from the second portion that propagate forward to the detector plane, and obtain actual diffraction intensity of the outgoing wave from the first portion and actual diffraction intensity of the outgoing wave from the second portion;

[0222] The measuring device 1404 is configured to execute the above-mentioned measuring method according to the actual diffraction intensity of the outgoing wave at the first portion and the actual diffraction intensity of the outgoing wave at the second portion.

[0223] The measuring device 1404 may be Figure 13 The description of the measurement system 1400 can refer to the description of the measurement method above, which will not be repeated here.

[0224] The present application also provides a measuring device, including a processor and a memory, wherein the memory stores an executable code, and when the executable code is executed by the processor, the processor executes the above Figure 2 Measurement method shown.

[0225] Alternatively, the present application can also be implemented as a computer-readable storage medium (or non-transitory machine-readable storage medium or machine-readable storage medium) on which executable code (or computer program or computer instruction code) is stored. When the executable code (or computer program or computer instruction code) is executed by a processor of an electronic device (or server, etc.), the processor executes part or all of the steps of the above-mentioned method according to the present application.

[0226] The embodiments of the present application have been described above. The above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or improvements to the technology in the market, or to enable other persons skilled in the art to understand the embodiments disclosed herein.

Claims

1. A displacement measurement method, characterized in that: include: respectively obtaining initial functions of the outgoing waves of the first portion and the second portion of the object to be measured; performing at least one first iteration with the initial function of the output wave of the first portion as input, wherein in each first iteration: the output wave of the first portion is propagated back and forth between an object plane, a modulator plane, and a detector plane, and an amplitude constraint is performed on the detector plane according to an actual diffraction intensity of the output wave of the first portion; Obtaining a reconstruction function of the outgoing wave of the first portion on the object plane according to the at least one first iteration; performing at least one second iteration with the initial function of the output wave of the second portion as input, wherein in each second iteration: the output wave of the second portion is propagated back and forth between the object plane, the modulator plane, and the detector plane, and an amplitude constraint is performed on the output wave of the second portion at the detector plane according to an actual diffraction intensity of the output wave of the second portion; Obtaining a reconstruction function of the outgoing wave of the second portion on the object plane according to the at least one second iteration; An image registration algorithm is used to calculate a displacement vector between the first portion and the second portion based on a reconstruction function of the outgoing wave of the first portion and a reconstruction function of the outgoing wave of the second portion.

2. The displacement measurement method according to claim 1, characterized in that: The method further comprises: According to the displacement vector, a reconstruction function of the outgoing wave of the first portion and a reconstruction function of the outgoing wave of the second portion are updated.

3. The displacement measurement method according to claim 2, characterized in that: The reconstruction function of the output wave of the first part is a combination function of the reconstructed illumination function of the coherent illumination light source and the reconstructed object function of the first part; The reconstruction function of the outgoing wave of the second part is a combination function of the reconstructed illumination function of the illumination light source and the reconstructed object function of the second part; The updating of the reconstruction function of the outgoing wave at the first portion and the reconstruction function of the outgoing wave at the second portion according to the displacement vector includes: performing at least one third iteration using the reconstruction function of the outgoing wave at the first portion and the reconstruction function of the outgoing wave at the second portion as input; Wherein, in each of the third iterations: the outgoing waves of the first portion and the second portion are propagated back and forth between the object plane, the modulator plane and the detector plane respectively; and the displacement vector is used to impose constraints on the object plane.

4. The displacement measurement method according to claim 3, characterized in that: In each of said third iterations: Separating, on the object plane, a reconstruction function of the outgoing wave of the first portion into a combination function of a reconstructed illumination function of the illumination light source and a reconstructed object function of the first portion, separating the reconstruction function of the outgoing wave of the second portion into a combination function of the reconstructed illumination function and a reconstructed object function of the second portion, and applying an object consistency constraint to the reconstructed object function of the first portion and the reconstructed object function of the second portion according to the displacement vector; updating a reconstruction function of an outgoing wave of the first portion according to the reconstructed object function of the first portion constrained by the object consistency and the reconstructed illumination function of the illumination light source; and updating a reconstruction function of an outgoing wave of the second portion according to the reconstructed object function of the second portion constrained by the object consistency and the reconstructed illumination function of the illumination light source; The reconstruction function of the updated output wave of the first portion propagated to the modulator plane is modulated and then propagated to the detector plane, and the actual diffraction intensity amplitude of the output wave of the first portion is constrained at the detector plane; the reconstruction function of the updated output wave of the second portion propagated to the modulator plane is modulated and then propagated to the detector plane, and the actual diffraction intensity amplitude of the output wave of the second portion is constrained at the detector plane; The outgoing wave of the first part after the amplitude constraint and the outgoing wave of the second part after the amplitude constraint are respectively propagated back to the modulator plane for demodulation and then propagated to the object plane as input for the next third iteration.

5. The displacement measurement method according to claim 4, characterized in that: The method further comprises: acquiring an image of the first part and an image of the second part according to the reconstructed object function of the first part and the reconstructed object function of the second part in the last third iteration; The image of the first part and the image of the second part are spliced ​​according to the displacement vector.

6. The displacement measurement method according to any one of claims 3 to 5, characterized in that: For at least one of the first iteration, the second iteration and the third iteration, the iteration is stopped when the root mean square error between the detected diffraction intensity obtained at the detector plane and the actual diffraction intensity is less than a preset threshold, or the number of iterations reaches a preset number.

7. The displacement measurement method according to any one of claims 1 to 5, characterized in that: The actual diffraction intensity of the outgoing wave at the first portion is the diffraction intensity of the outgoing wave obtained by illuminating the first portion at the object plane with a coherent illumination light source, which is modulated when the forward wavefront propagates to the modulator plane and is then detected when the forward wavefront propagates to the detector plane; The actual diffraction intensity of the outgoing wave of the second part is the diffraction intensity detected when the forward wavefront of the outgoing wave obtained by irradiating the second part on the object plane with the illumination light source propagates to the modulator plane and is modulated and then propagates to the detector plane.

8. The displacement measurement method according to any one of claims 1 to 5, characterized in that: The modulator function of the modulator plane is a continuous, binary, absorption or phase modulation pattern.

9. The displacement measurement method according to any one of claims 1 to 5, characterized in that: The modulator function of the modulator plane is known or unknown.

10. The displacement measurement method according to any one of claims 1 to 5, characterized in that: The calculating the displacement vector between the first part and the second part using an image registration algorithm according to the reconstruction function of the outgoing wave of the first part and the reconstruction function of the outgoing wave of the second part comprises: acquiring a first image and a second image according to a reconstruction function of the outgoing wave of the first portion and a reconstruction function of the outgoing wave of the second portion; respectively acquiring the first image and the second image after changes, wherein the changes include reduction or enlargement; respectively calculating the change gradients of the first image and the second image; A displacement vector between the first part and the second part is calculated according to the change gradient of the first image and the change gradient of the second image.

11. The displacement measurement method according to claim 10, characterized in that: The calculating the displacement vector between the first part and the second part according to the change gradient of the first image and the change gradient of the second image includes: calculating a cross-correlation spectrum of a change gradient of the first image and a change gradient of the second image; Displacement vectors of the first image and the second image are calculated according to the cross-correlation spectrum.

12. The displacement measurement method according to claim 10, characterized in that: The respectively acquiring the changed first image and the changed second image includes: respectively acquiring regions of interest in the first image and the second image; Obtaining a first sub-image and a second sub-image according to regions of interest of the first image and the second image respectively; interpolating the first sub-image and the second sub-image respectively in Fourier space; Perform inverse Fourier transform on the interpolated first sub-image and the second sub-image respectively to obtain the changed first image and the second image.

13. A displacement measurement method, characterized in that: The method comprises: Using a coherent illumination light source to illuminate at least a first portion and a second portion of the object to be measured, respectively, to obtain an outgoing wave from the first portion and an outgoing wave from the second portion; Using a modulator, modulate the outgoing wave of the first portion and the outgoing wave of the second portion that propagate forward to the modulator plane, respectively, to obtain a modulated outgoing wave of the first portion and a modulated outgoing wave of the second portion; Using a detector, respectively, detect the modulated outgoing wave of the first portion and the modulated outgoing wave of the second portion that propagate forward to the detector plane to obtain actual diffraction intensity of the outgoing wave of the first portion and actual diffraction intensity of the outgoing wave of the second portion; The method further comprises: The object to be measured is measured according to the actual diffraction intensity of the outgoing wave at the first portion and the actual diffraction intensity of the outgoing wave at the second portion, and the displacement measurement method according to any one of claims 1 to 12.

14. A displacement measuring device, characterized in that: include: A first acquisition module is used to respectively acquire initial functions of the outgoing waves of the first portion and the second portion of the object to be measured; a first iteration module, configured to perform at least one first iteration using an initial function of the output wave of the first portion as input, wherein in each first iteration: the output wave of the first portion is propagated back and forth between an object plane, a modulator plane, and a detector plane, and an amplitude constraint is performed on the detector plane based on an actual diffraction intensity of the output wave of the first portion; A first reconstruction module, configured to obtain a reconstruction function of the outgoing wave of the first portion on the object plane according to the at least one first iteration; a second iteration module, configured to perform at least one second iteration using the initial function of the output wave of the second portion as input, wherein in each second iteration: the output wave of the second portion is propagated back and forth between the object plane, the modulator plane, and the detector plane, and an amplitude constraint is performed on the output wave of the second portion at the detector plane according to an actual diffraction intensity of the output wave of the second portion; a second reconstruction module, configured to obtain a reconstruction function of the outgoing wave of the second portion on the object plane according to the at least one second iteration; A calculation module is used to calculate the displacement vector between the first part and the second part using an image registration algorithm based on the reconstruction function of the outgoing wave of the first part and the reconstruction function of the outgoing wave of the second part.

15. The displacement measuring device according to claim 14, characterized in that: The device further comprises: An updating module is used to update the reconstruction function of the outgoing wave of the first part and the reconstruction function of the outgoing wave of the second part according to the displacement vector.

16. The displacement measuring device according to claim 15, characterized in that: The reconstruction function of the output wave of the first part is a combination function of the reconstructed illumination function of the coherent illumination light source and the reconstructed object function of the first part; The reconstruction function of the outgoing wave of the second part is a combination function of the reconstructed illumination function of the illumination light source and the reconstructed object function of the second part; When the updating module updates the reconstruction function of the outgoing wave at the first portion and the reconstruction function of the outgoing wave at the second portion according to the displacement vector, the updating module is specifically configured to: performing at least one third iteration using the reconstruction function of the outgoing wave at the first portion and the reconstruction function of the outgoing wave at the second portion as input; Wherein, in each of the third iterations: the outgoing waves of the first portion and the second portion are propagated back and forth between the object plane, the modulator plane and the detector plane respectively; and the displacement vector is used to impose constraints on the object plane.

17. The displacement measuring device according to claim 16, characterized in that: In each of the third iterations, the update module is specifically configured to: Separating, on the object plane, a reconstruction function of the outgoing wave of the first portion into a combination function of a reconstructed illumination function of the illumination light source and a reconstructed object function of the first portion, separating the reconstruction function of the outgoing wave of the second portion into a combination function of the reconstructed illumination function and a reconstructed object function of the second portion, and applying an object consistency constraint to the reconstructed object function of the first portion and the reconstructed object function of the second portion according to the displacement vector; updating a reconstruction function of an outgoing wave of the first portion according to the reconstructed object function of the first portion constrained by the object consistency and the reconstructed illumination function of the illumination light source; and updating a reconstruction function of an outgoing wave of the second portion according to the reconstructed object function of the second portion constrained by the object consistency and the reconstructed illumination function of the illumination light source; The reconstruction function of the updated output wave of the first portion propagated to the modulator plane is modulated and then propagated to the detector plane, and the actual diffraction intensity amplitude of the output wave of the first portion is constrained at the detector plane; the reconstruction function of the updated output wave of the second portion propagated to the modulator plane is modulated and then propagated to the detector plane, and the actual diffraction intensity amplitude of the output wave of the second portion is constrained at the detector plane; The outgoing wave of the first part after the amplitude constraint and the outgoing wave of the second part after the amplitude constraint are respectively propagated back to the modulator plane for demodulation and then propagated to the object plane as input for the next third iteration.

18. The displacement measuring device according to claim 17, characterized in that: The device further comprises: a second acquisition module, configured to acquire an image of the first part and an image of the second part according to the reconstructed object function of the first part and the reconstructed object function of the second part in the last third iteration; A stitching module is used to stitch the image of the first part and the image of the second part according to the displacement vector.

19. A displacement measurement system, characterized in that: include: A coherent illumination light source is used to illuminate at least a first portion and a second portion of the object to be measured, respectively, to obtain an outgoing wave from the first portion and an outgoing wave from the second portion; a modulator, configured to modulate the outgoing wave of the first portion and the outgoing wave of the second portion that propagate forward to the modulator plane, respectively, to obtain a modulated outgoing wave of the first portion and a modulated outgoing wave of the second portion; a detector, configured to respectively detect the modulated outgoing wave of the first portion and the modulated outgoing wave of the second portion that propagate forward to a detector plane, and obtain an actual diffraction intensity of the outgoing wave of the first portion and an actual diffraction intensity of the outgoing wave of the second portion; A displacement measuring device, configured to perform the displacement measuring method according to any one of claims 1 to 13 based on the actual diffraction intensity of the outgoing wave at the first portion and the actual diffraction intensity of the outgoing wave at the second portion.

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