Multi-wavelength simultaneous illumination multi-distance lens-free imaging method and device

Abstract

The invention discloses a multi-wavelength simultaneous illumination multi-distance lens-free imaging method and device, and belongs to the technical field of lens-free imaging. The imaging method comprises the following steps: carrying out digital focusing calibration; acquiring diffraction data of the sample and the light spot; performing image registration on the acquired diffraction data of the sample and the light spot; in each iteration, different diffraction planes are randomly selected for amplitude replacement; according to the iterative reconstruction method, emergent light fields with different wavelengths can be recovered according to the sample diffraction data, and illumination functions with different wavelengths can also be recovered according to the light spot diffraction data. According to the fact that the emergent light field is equal to the product of the illumination function and the sample transmission function, the reconstructed illumination function serves as prior information, the operation is repeated, and the transmission function of the sample is reconstructed. Redundant information of axial diffraction data is utilized, the data acquisition time is shortened, the strict requirement for light path stability is lowered, and the performance and efficiency of the whole imaging system are improved.

Description

Technical Field

[0001] The present invention belongs to the field of lensless imaging, and more specifically, relates to a multi-distance lensless imaging method and device with multi-wavelength simultaneous illumination. Background Art

[0002] With the development of coherent diffraction imaging (CDI), various schemes have emerged, such as reflective CDI, three-dimensional CDI, ptychography, and Fourier ptychography. And now we are no longer satisfied with the diffraction imaging of monochromatic light. In recent years, various broadband CDI imaging has developed rapidly.

[0003] The core problem of lensless imaging technology is how to accurately retrieve the phase information from the recorded diffraction pattern. For the missing phase information, an iterative algorithm can be applied for numerical reconstruction.

[0004] The phase retrieval algorithm originally originated from the GS algorithm, but in order to ensure the accuracy and efficiency of phase retrieval, the algorithm often needs to introduce some additional assumptions or constraints in its application. In order to solve this problem, an iterative method using more images of different diffraction distances was adopted, resulting in a multi-distance phase retrieval algorithm. This algorithm effectively improves the convergence speed and stability of the algorithm by combining image information of multiple diffraction distances, making phase retrieval more accurate and efficient. Batey et al. proposed a coherent diffraction imaging scheme, PIM, which can be used under the simultaneous action of three laser beams of different wavelengths. The biggest feature of this scheme is that the physical functions corresponding to different wavelengths do not need to be the same.

[0005] In the past, people mainly focused on using the redundancy of radial diffraction data, such as stacking technology, to achieve reconstruction of multi-mode light fields. When performing single-frame CDI, the output light field of the sample plane is the imaging result. In stacking technology, the transmission function and illumination function of the sample are the imaging results. This usually requires the collection of more diffraction data, resulting in a long data collection time and strict requirements on the stability of the optical path, making it difficult to guarantee the performance and efficiency of the overall imaging system. Summary of the invention

[0006] In view of the defects of the related art, the purpose of the present invention is to provide a multi-distance lensless imaging method and device with multi-wavelength simultaneous illumination, aiming to solve the problem in the prior art that the reconstruction of the multi-mode light field requires the collection of more diffraction data, the data collection time is long, and the requirements on the stability of the optical path are strict, making it difficult to ensure the performance and efficiency of the overall imaging system.

[0007] To achieve the above object, the present invention provides a multi-distance lensless imaging method with multi-wavelength simultaneous illumination, comprising:

[0008] S1, collimate and combine multiple laser beams and irradiate them onto the sample plane, axially move the detector to collect sample diffraction data of multiple diffraction planes, and perform image registration on the sample diffraction data;

[0009] S2, setting the initial complex amplitude distribution of the outgoing light field on the sample plane to be a random distribution;

[0010] S3, randomly selecting an untraversed diffraction plane, propagating the outgoing light field of the sample plane to the diffraction plane, and performing incoherent superposition of the diffraction light field intensities of different modes in multiple laser beams to obtain a predicted total diffraction light field intensity value;

[0011] S4. Perform amplitude replacement on the predicted total diffraction light field intensity value according to the sample diffraction data collected on the diffraction plane, and back-propagate it back to the corresponding sample plane to update the outgoing light field; determine whether all diffraction planes are traversed, if not, return to execute the diffraction light field intensity calculation module, if so, output the outgoing light field of different modes.

[0012] Optionally, before S1, it also includes:

[0013] The detector is set to an initial position, and a monochromatic laser is used to illuminate the sample to obtain a set of sample diffraction patterns;

[0014] In a preset distance range, the Sobel function is used to judge the image quality of the sample diffraction pattern at each distance, and the distance corresponding to the result with the maximum Sobel value is determined as the initial distance from the sample to the axial moving detector.

[0015] Optionally, performing image registration on the sample diffraction data includes:

[0016] In a registration interval within a preset range, calculating the autocorrelation peak center of the sample diffraction data at different diffraction planes;

[0017] The offset of each data in the sample diffraction data of different diffraction planes from the diffraction plane at the initial position is determined and aligned.

[0018] Optionally, the randomly selecting an untraversed diffraction plane and propagating the outgoing light field of the sample plane to the diffraction plane includes:

[0019] An amplitude limit is imposed on the outgoing light field at the sample plane so that the amplitude of the outgoing light field is not greater than a set constant; at the same time, a phase limit is imposed so that the phase of the transmitted light part of the outgoing light field is a constant phase;

[0020] A diffraction plane that has not been traversed is randomly selected, and the outgoing light field is propagated to the diffraction plane using the angular spectrum transfer function, which is as follows:

[0021]

[0022] in, and represents Fourier transform and inverse Fourier transform respectively, H is the angular spectrum transfer function, z is the distance between the sample and the detector, k is the wave vector, λ is the wavelength, and f x , f y is the spatial frequency.

[0023] Optionally, performing amplitude replacement on the predicted total diffraction light field intensity value according to the sample diffraction data collected on the diffraction plane, and back-propagating it back to the corresponding sample plane to update the output light field, comprises:

[0024] The following formula is used to replace the amplitude of the diffracted light field of different modes and propagate it back to the sample plane;

[0025]

[0026] in, represents the diffracted light field of each mode in the diffraction plane, I j,k (R) represents the predicted total diffraction light field intensity value at the diffraction plane, represents the diffracted light field of each mode after updating on the diffraction plane, Represents the sample diffraction data for a randomly selected diffraction plane.

[0027] In a second aspect, the present invention further provides a multi-distance lensless imaging method with multi-wavelength simultaneous illumination, comprising:

[0028] T1, collimate and combine multiple laser beams and irradiate them onto the sample plane, move the detector axially to collect sample diffraction data of multiple diffraction planes, and perform image registration on the sample diffraction data;

[0029] T2, after collimating and combining multiple laser beams, remove the sample, axially move the detector to collect the spot diffraction data of multiple diffraction planes, and perform image registration on the spot diffraction data;

[0030] T3, setting the initial complex amplitude distribution of the outgoing light field on the sample plane to be random distribution;

[0031] T4. Randomly select an untraversed diffraction plane, propagate the outgoing light field of the sample plane to the diffraction plane, perform incoherent superposition of the diffraction light field intensities of different modes in multiple laser beams, and obtain the predicted total diffraction light field intensity value;

[0032] T5, performing amplitude replacement on the predicted total diffraction light field intensity value according to the diffraction data to be processed collected on the diffraction plane, and back-propagating it back to the corresponding sample plane to update the outgoing light field; returning to execute T4, completing one iteration after traversing all diffraction planes;

[0033] T6. Take the light spot diffraction data as the diffraction data to be processed, execute T4-T5, and obtain the illumination function probe of different modes. λi (r);

[0034] T7, setting the initial transmission functions of different modes to be randomly distributed, taking the sample diffraction data as the diffraction data to be processed, executing T4-T5, obtaining the output light fields of different modes, and updating the transmission function of the sample according to the sample transmission function update formula;

[0035] The sample transmission function update formula is:

[0036]

[0037] In the formula, is the outgoing light field at the sample plane for each wavelength, probe λi (r) represents the illumination function of different modes, O λi (r) is the transmission function of the sample;

[0038] T8. Repeat T7 until a preset number of cycles is reached, and then output the transmission function of the sample.

[0039] Optionally, the randomly selecting an untraversed diffraction plane and propagating the outgoing light field of the sample plane to the diffraction plane includes:

[0040] An amplitude limit is imposed on the outgoing light field at the sample plane so that the amplitude of the outgoing light field is not greater than a set constant; at the same time, a phase limit is imposed so that the phase of the transmitted light part of the outgoing light field is a constant phase;

[0041] A diffraction plane that has not been traversed is randomly selected, and the outgoing light field is propagated to the diffraction plane using the angular spectrum transfer function, which is as follows:

[0042]

[0043] in, and represents Fourier transform and inverse Fourier transform respectively, H is the angular spectrum transfer function, z is the distance between the sample and the detector, k is the wave vector, λ is the wavelength, and f x , f y is the spatial frequency.

[0044] Optionally, performing amplitude replacement on the predicted total diffraction light field intensity value according to the diffraction data to be processed collected on the diffraction plane, and back-propagating it back to the corresponding sample plane to update the output light field, comprises:

[0045] The following formula is used to replace the amplitude of the diffracted light field of different modes and propagate it back to the near-field plane;

[0046]

[0047] in, represents the diffracted light field of each mode in the diffraction plane, I j,k (R) represents the total diffraction light field intensity value on the diffraction plane, represents the diffracted light field of each mode after updating on the diffraction plane, represents the diffraction data to be processed for a randomly selected diffraction plane.

[0048] In a third aspect, the present invention further provides a multi-distance lensless imaging device with multi-wavelength simultaneous illumination, which is used to perform the imaging method as described in any one of the first aspects, comprising:

[0049] The sample diffraction data acquisition module is used to collimate and combine multiple laser beams and then irradiate them onto the sample plane, axially move the detector to collect sample diffraction data of multiple diffraction planes, and perform image registration on the sample diffraction data;

[0050] An initial complex amplitude setting module, used to set the initial complex amplitude distribution of the outgoing light field on the sample plane to be a random distribution;

[0051] A diffraction light field intensity calculation module is used to randomly select an untraversed diffraction plane, propagate the outgoing light field of the sample plane to the diffraction plane, and perform incoherent superposition of the diffraction light field intensities of different modes in the multiple laser beams to obtain a predicted total diffraction light field intensity value;

[0052] The iterative calculation module is used to perform amplitude replacement on the predicted total diffraction light field intensity value according to the sample diffraction data collected on the diffraction plane, and back-propagate it back to the corresponding sample plane to update the output light field; it determines whether all diffraction planes are traversed, if not, it returns to execute the diffraction light field intensity calculation module, if so, it outputs output light fields of different modes.

[0053] In a fourth aspect, the present invention further provides a multi-distance lensless imaging device with multi-wavelength simultaneous illumination, which is used to perform the imaging method as described in any one of the second aspects, comprising:

[0054] The sample diffraction data acquisition module is used to collimate and combine multiple laser beams and then irradiate them onto the sample plane, axially move the detector to collect sample diffraction data of multiple diffraction planes, and perform image registration on the sample diffraction data;

[0055] The light spot diffraction data acquisition module is used to collimate and combine multiple laser beams, move away from the sample, axially move the detector to collect light spot diffraction data of multiple diffraction planes, and perform image registration on the light spot diffraction data;

[0056] An initial complex amplitude setting module, used to set the initial complex amplitude distribution of the outgoing light field on the sample plane to be a random distribution;

[0057] The diffraction light field intensity calculation module is used to randomly select an untraversed diffraction plane, propagate the outgoing light field of the sample plane to the diffraction plane, and perform incoherent superposition of the diffraction light field intensities of different modes in multiple laser beams to obtain the predicted total diffraction light field intensity value;

[0058] An iterative calculation module is used to perform amplitude replacement on the predicted total diffraction light field intensity value according to the diffraction data to be processed collected on the diffraction plane, and back-propagate it back to the corresponding sample plane to update the outgoing light field; return to execute the diffraction light field intensity calculation module, and complete an iteration after traversing all diffraction planes;

[0059] The illumination function calculation module is used to use the light spot diffraction data as the diffraction data to be processed, execute the diffraction light field intensity calculation module and the iterative calculation module, and obtain the illumination function probe of different modes. λi (r);

[0060] A transmission function updating module, used to set the initial transmission functions of different modes to be randomly distributed, use the sample diffraction data as the diffraction data to be processed, execute the diffraction light field intensity calculation module and the iterative calculation module to obtain the output light fields of different modes, and update the transmission function of the sample according to the sample transmission function update formula;

[0061] The sample transmission function update formula is:

[0062]

[0063] In the formula, is the outgoing light field at the sample plane for each wavelength, probe λi (r) represents the illumination function of different modes, O λi (r) is the transmission function of the sample;

[0064] The transmission function output module is used to repeatedly execute the transmission function update, and after reaching a preset number of cycles, output the transmission function of the sample.

[0065] Compared with the prior art, the above technical solution conceived by the present invention can achieve the following beneficial effects:

[0066] 1. The present invention provides a multi-distance lensless imaging method with simultaneous multi-wavelength illumination. By moving the axial distance multiple times, a small amount of sample diffraction data is collected. According to the sample diffraction data corresponding to different diffraction planes, it is iterated to reconstruct the outgoing light field of different modes to obtain sample information of multiple modes. By utilizing the redundant information of the axial diffraction data, multiple modes can be separated from multiple beams of light using less diffraction data. Not only does it take less time to collect, but the reconstructed multi-mode wavelength light field is almost the same as the reconstruction effect of a single beam of light. This significantly reduces the data collection time and reduces the stringent requirements for the stability of the optical path, thereby improving the performance and efficiency of the overall imaging system.

[0067] 2. The present invention provides a multi-distance lensless imaging method with multi-wavelength simultaneous illumination. A small amount of sample and spot diffraction data is collected, and the sample's outgoing light field for different wavelengths is first reconstructed. Then, based on the reconstructed outgoing light field, which is actually the product of the illumination function and the object's transmission function, a similar method is used to reconstruct the illumination function, and the illumination function is used as prior information to further extract the object's transmission function. When the illumination function is restored, the sample function is reconstructed separately to obtain better experimental results. This significantly reduces the data acquisition time and reduces the stringent requirements for optical path stability, thereby improving the performance and efficiency of the overall imaging system.

[0068] 3. The present invention provides a multi-distance lensless imaging method with simultaneous multi-wavelength illumination. Data collection requires axial movement of the detector, so the optical path collimation requirement is high. In order to reduce the experimental error caused by collection in this case, the collected diffraction information is realigned and then reconstructed, thereby improving the performance and efficiency of the overall imaging system.

[0069] 4. The present invention provides a multi-distance lensless imaging method with multi-wavelength simultaneous illumination. This scheme can effectively distinguish the different absorption characteristics of the morphology, tissue structure and macromolecular components of biological samples to different wavelengths of light without using dyes. This method is expected to be widely used in many fields such as biology, medicine and material science. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 A schematic flow chart of a multi-distance lensless imaging method with multi-wavelength simultaneous illumination provided by an embodiment of the present invention;

[0071] Figure 2 A schematic diagram of a multi-distance lensless imaging experiment optical path for multi-wavelength simultaneous illumination provided by an embodiment of the present invention;

[0072] Figure 3 A phase iteration algorithm flow chart of a multi-distance lensless imaging method for multi-wavelength simultaneous illumination provided by an embodiment of the present invention;

[0073] Figure 4 A comparison diagram of the reconstruction results of biological samples used in the method of the present invention for multi-distance lensless imaging applied to multi-wavelength simultaneous illumination provided by an embodiment of the present invention and the monochromatic light results; wherein (a) is the amplitude distribution of the output wave of 532nm monochromatic light, (b) is the amplitude distribution of the output wave of 532nm mode, (c) is the amplitude distribution of the output wave of 632nm monochromatic light, and (d) is the amplitude distribution of the output wave of 632nm mode;

[0074] Figure 5 A schematic flow chart of a multi-distance lensless imaging method with multi-wavelength simultaneous illumination provided by an embodiment of the present invention;

[0075] Figure 6 A test target for multi-distance lensless imaging for multi-wavelength simultaneous illumination provided in an embodiment of the present invention and used in the method of the present invention is provided, in which a reconstruction diagram of a sample function is reconstructed separately when an illumination function has been reconstructed; wherein, (a) is the reconstructed illumination function, (b) is the 532nm mode reconstruction diagram, (c) is the 532nm mode sample amplitude distribution diagram, (d) is the amplitude distribution of the 632nm mode illumination function, (e) is the 632nm mode reconstruction diagram, and (f) is the 632nm mode sample amplitude distribution diagram. DETAILED DESCRIPTION

[0076] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0077] The contents involved in the above embodiment are described below in conjunction with a preferred embodiment.

[0078] Embodiment 1

[0079] like Figure 1 As shown, the present invention provides a multi-distance lensless imaging method with multi-wavelength simultaneous illumination, comprising:

[0080] S1, collimate and combine multiple laser beams and irradiate them onto the sample plane, axially move the detector to collect sample diffraction data of multiple diffraction planes, and perform image registration on the sample diffraction data;

[0081] S2, setting the initial complex amplitude distribution of the outgoing light field on the sample plane to be a random distribution;

[0082] S3, randomly selecting an untraversed diffraction plane, propagating the outgoing light field of the sample plane to the diffraction plane, and performing incoherent superposition on the diffraction light field intensities of different modes in the multiple laser beams to obtain a predicted total diffraction light field intensity value;

[0083] S4. Perform amplitude replacement on the predicted total diffraction light field intensity value according to the sample diffraction data collected on the diffraction plane, and back-propagate it back to the corresponding sample plane to update the outgoing light field; determine whether all diffraction planes are traversed, if not, return to execute S3, if yes, output outgoing light fields of different modes.

[0084] like Figure 2 The figure shows the optical path diagram corresponding to this method. The multiple laser beams include lasers of at least two wavelengths. In this scheme, lasers of two wavelengths are taken as an example. The two light sources passing through the precision pinhole are collimated and then combined by a beam splitter. After passing through the aperture, they reach the sample plane. The axially moving detector collects a series of sample diffraction data. Among them, the combined beam spot formed on the detector plane after the light source passes through the precision pinhole should be intercepted by the aperture to prevent some external stray light from interfering with the experimental results.

[0085] Optionally, before S1, it also includes:

[0086] The detector is set to an initial position, and a monochromatic laser is used to illuminate the sample to obtain a set of sample diffraction patterns;

[0087] In a preset distance range, the Sobel function is used to judge the image quality of the sample diffraction pattern at each distance, and the distance corresponding to the result with the maximum Sobel value is determined as the initial distance from the sample to the axial moving detector.

[0088] After obtaining the initial distance from the sample to the axial moving detector, the axial moving detector collects the sample diffraction data of multiple diffraction planes. According to the distance of the moving detector and the initial distance, the distance between each diffraction plane and the sample can be obtained. The outgoing light field propagates and the diffracted light field propagates through different distances to the corresponding diffraction plane / sample plane.

[0089] Optionally, performing image registration on the sample diffraction data includes:

[0090] In a registration interval within a preset range, calculating the autocorrelation peak center of the sample diffraction data at different diffraction planes;

[0091] The offset of each data in the sample diffraction data of different diffraction planes from the diffraction plane at the initial position is determined and aligned.

[0092] The outgoing light field is reconstructed after the sample diffraction data is aligned, thereby improving the performance and efficiency of the overall imaging system.

[0093] The process of reconstructing the outgoing light field on the sample plane is as follows: Figure 3 As shown in the figure, in each iteration, a different diffraction plane is randomly selected, and the outgoing light field of different modes is propagated to a certain diffraction plane. The diffraction light field intensity of different modes is incoherently superimposed to obtain the predicted total diffraction light field intensity value. The amplitude of the diffraction light field of different modes is replaced by the collected sample diffraction data, and it is reversely propagated back to the near-field plane. This step is repeated until the set number of cycles is reached to obtain the outgoing light field data of different modes.

[0094] In each iteration of previous multi-distance phase retrieval algorithms, diffraction data at different distances are usually used in turn to impose amplitude constraints, which may lead to slow iterative convergence or even failure to converge when the illumination light source is partially coherent. Some existing algorithms usually adopt the strategy of collecting diffraction data at a specific distance to avoid this problem. In contrast, in our experiment, we still collect data at different distances at equal intervals, but randomly select data for amplitude replacement in the algorithm, which greatly facilitates iterative convergence. In this scheme, different diffraction planes are randomly selected at each iteration to effectively suppress the semi-convergence problem of the phase retrieval algorithm.

[0095] Optionally, the randomly selecting an untraversed diffraction plane and propagating the outgoing light field of the sample plane to the diffraction plane includes:

[0096] An amplitude limit is imposed on the outgoing light field at the sample plane so that the amplitude of the outgoing light field is not greater than a set constant; at the same time, a phase limit is imposed so that the phase of the transmitted light part of the outgoing light field is a constant phase;

[0097] A diffraction plane that has not been traversed is randomly selected, and the outgoing light field is propagated to the diffraction plane using the angular spectrum transfer function, which is as follows:

[0098]

[0099] in, and represents Fourier transform and inverse Fourier transform respectively, H is the angular spectrum transfer function, z is the distance between the sample and the detector, k is the wave vector, λ is the wavelength, and f x , f y is the spatial frequency.

[0100] The outgoing light field corresponding to the wavelength of each laser beam is selected for propagation. In order to replace the amplitude of the light field function of the diffraction plane, the light field intensity value of the diffraction plane needs to be calculated and summed in each iteration:

[0101]

[0102] in, represents the light field function of each mode in the diffraction plane, I j,k (R) represents the total light field intensity value calculated on the diffraction plane.

[0103] Optionally, performing amplitude replacement on the predicted total diffraction light field intensity value according to the sample diffraction data collected on the diffraction plane, and back-propagating it back to the corresponding sample plane to update the output light field, comprises:

[0104] The following formula is used to replace the amplitude of the diffracted light fields of different modes and propagate them back to the sample plane;

[0105]

[0106] in, represents the diffraction light field of each mode calculated on the diffraction plane, I j,k (R) represents the predicted total diffraction light field intensity value calculated on the diffraction plane, represents the diffracted light field of each mode after updating on the diffraction plane, represents the sample diffraction data of a randomly selected diffraction plane, H λi represents the angular spectrum transfer function corresponding to each wavelength, is the outgoing light field of each mode at the sample plane.

[0107] After traversing all planes, an iteration is completed to obtain output light fields of different modes; the imaging result can be obtained according to the obtained output light fields.

[0108] The embodiment of the present invention uses a 532nm laser beam and a 632nm laser beam as the incident light for imaging, and the diameter of the precision pinhole is 50μm. The pixel size of the detector is 6.5μm, and the number of pixels is 1024. Propagation is performed in two modes. The field of view of the reconstructed image is 6656μm*6656μm. The samples used are USAF1951 resolution test targets and biological samples.

[0109] The imaging results are as follows Figure 4 As shown, Figure 4 (a) and (c) represent the amplitude distribution of the outgoing wave reconstructed by red light and green light respectively, (a) is the amplitude distribution of the 532nm outgoing wave, (c) is the amplitude distribution of the 632nm outgoing wave; Figure 4In (b) and (d), the illuminated sample after the red light and green light are combined, and the amplitude distribution of the output wave obtained is synchronously reconstructed using this method. (b) is the amplitude distribution of the 532nm mode output wave, and (d) is the amplitude distribution of the 632nm mode output wave. When reconstructing biological samples of different colors, the conditions of samples of different modes can be clearly distinguished.

[0110] Furthermore, the present invention is applicable to both multi-beam laser beam combination and monochromatic light source. The experimental optical path is simple and convenient to construct, and the experimental data collection operation is simple and fast. It can well reconstruct an image with good effect using two wavelength modes.

[0111] The embodiment of the present invention collects a small amount of sample diffraction data by moving the axial distance multiple times, and iterates according to the sample diffraction data corresponding to different diffraction planes to reconstruct the outgoing light field of different modes to obtain sample information of multiple modes. By utilizing the redundant information of the axial diffraction data, multiple modes can be separated from multiple beams of light using less diffraction data. Not only does it take less time to collect, but the reconstructed multi-mode wavelength light field has almost the same reconstruction effect as a single beam of light. The technical problem that the reconstruction of the multi-mode light field in the prior art requires the collection of more diffraction data, has a long data collection time, and has strict requirements on the stability of the optical path, making it difficult to ensure the performance and efficiency of the overall imaging system is solved. The data collection time is significantly reduced, and the strict requirements on the stability of the optical path are reduced, thereby improving the performance and efficiency of the overall imaging system.

[0112] Embodiment 2

[0113] like Figure 5 As shown, the present invention also provides a multi-distance lensless imaging method with multi-wavelength simultaneous illumination, comprising:

[0114] T1, collimate and combine multiple laser beams and irradiate them onto the sample plane, move the detector axially to collect sample diffraction data of multiple diffraction planes, and perform image registration on the sample diffraction data;

[0115] T2, after collimating and combining multiple laser beams, remove the sample, axially move the detector to collect the spot diffraction data of multiple diffraction planes, and perform image registration on the spot diffraction data;

[0116] T3, setting the initial complex amplitude distribution of the outgoing light field on the sample plane to be random distribution;

[0117] T4. Randomly select an untraversed diffraction plane, propagate the outgoing light field of the sample plane to the diffraction plane, perform incoherent superposition of the diffraction light field intensities of different modes in multiple laser beams, and obtain the predicted total diffraction light field intensity value;

[0118] T5, performing amplitude replacement on the predicted total diffraction light field intensity value according to the diffraction data to be processed collected on the diffraction plane, and back-propagating it back to the corresponding sample plane to update the outgoing light field; returning to execute T4, completing one iteration after traversing all diffraction planes;

[0119] T6. Take the light spot diffraction data as the diffraction data to be processed, execute T4-T5, and obtain the illumination function probe of different modes. λi (r);

[0120] T7, setting the initial transmission functions of different modes to be randomly distributed, taking the sample diffraction data as the diffraction data to be processed, executing T4-T5, obtaining the output light fields of different modes, and updating the transmission function of the sample according to the sample transmission function update formula;

[0121] The sample transmission function update formula is:

[0122]

[0123] In the formula, is the outgoing light field at the sample plane for each wavelength, probe λi (r) represents the illumination function of different modes, O λi (r) is the transmission function of the sample;

[0124] T8. Repeat T7 until a preset number of cycles is reached, and then output the transmission function of the sample.

[0125] like Figure 2 The figure shows the optical path diagram corresponding to this method. The multiple laser beams include lasers of at least two wavelengths. In this scheme, lasers of two wavelengths are taken as an example. The two light sources passing through the precision pinhole are collimated and then combined by a beam splitter. After passing through the aperture, they reach the sample plane. The axially moving detector collects a series of sample diffraction data. Among them, the combined beam spot formed on the detector plane after the light source passes through the precision pinhole should be intercepted by the aperture to prevent some external stray light from interfering with the experimental results.

[0126] When collecting spot diffraction data, it is similar to collecting multiple sets of sample diffraction data. The only difference is that the sample needs to be removed. The two light sources passing through the precision pinhole are collimated and combined through the beam splitter. After passing through the aperture, they reach the detector plane. The detector is moved axially to collect a series of diffraction data. Among them, the combined beam spot formed in the far field after the light source passes through the precision pinhole should be intercepted through the aperture to prevent some external stray light from interfering with the experimental results.

[0127] Optionally, before T1, it also includes:

[0128] The detector is set to an initial position, and a monochromatic laser is used to illuminate the sample to obtain a set of sample diffraction patterns;

[0129] In a preset distance range, the Sobel function is used to judge the image quality of the sample diffraction pattern at each distance, and the distance corresponding to the result with the maximum Sobel value is determined as the initial distance from the sample to the axial moving detector.

[0130] As can be seen from the first embodiment, after obtaining the initial distance from the sample to the axially moving detector, the distance between each diffraction plane and the sample can be obtained.

[0131] On the basis of the above-mentioned embodiment, image registration is performed on the sample diffraction data and the spot diffraction data. The specific method is as described in the first embodiment.

[0132] In each iteration of the existing multi-distance phase retrieval algorithm, diffraction data at different distances are usually extracted sequentially to meet the amplitude constraint. This may lead to slow iterative convergence or even failure to converge when the illumination source is partially coherent. To this end, this scheme adopts the method of randomly selecting different diffraction planes to effectively suppress the semi-convergence problem of the phase retrieval algorithm.

[0133] The process of reconstructing the illumination function of different modes and the transmission function of the sample is as follows: Figure 3 As shown, in each iteration, a different diffraction plane is randomly selected, and the outgoing light fields of different modes are propagated to a certain diffraction plane. The diffraction light field intensities of different modes are incoherently superimposed to obtain the predicted total diffraction light field intensity value. The collected sample diffraction data is used to replace the amplitude of the diffraction light field of different modes, and it is back-propagated back to the near-field plane. This step is repeated until the set number of cycles to obtain the outgoing light field data of different modes. The collected spot diffraction data is then used for cyclic iteration to reconstruct the illumination functions of different modes. Specifically, the initial transmission functions of different wavelength modes are set to be randomly distributed, and according to the fact that the outgoing light field is equal to the product of the illumination function and the sample transmission function, it is expressed as: Taking the reconstructed illumination function as prior information and using the collected sample diffraction data, the steps of reconstructing illumination functions of different modes are performed according to the above-mentioned iterative reconstruction method to obtain output light fields of different modes, and the transmission function of the sample is updated according to the sample transmission function update formula. The above process is repeated to reconstruct and output the transmission function of the sample.

[0134] In each iteration of previous multi-distance phase retrieval algorithms, diffraction data at different distances are usually used in turn to impose amplitude constraints, which may lead to slow iterative convergence or even failure to converge when the illumination source is partially coherent. Some existing algorithms usually adopt the strategy of collecting diffraction data at a specific distance to avoid this problem. In contrast, in our experiment, we still collect data at different distances at equal intervals, but randomly select data for amplitude replacement in the algorithm, which greatly facilitates iterative convergence. In each iteration, a different diffraction plane is randomly selected for iteration to solve the semi-convergence problem.

[0135] Optionally, the randomly selecting an untraversed diffraction plane and propagating the outgoing light field of the sample plane to the diffraction plane includes:

[0136] An amplitude limit is imposed on the outgoing light field at the sample plane so that the amplitude of the outgoing light field is not greater than a set constant; at the same time, a phase limit is imposed so that the phase of the transmitted light part of the outgoing light field is a constant phase;

[0137] A diffraction plane that has not been traversed is randomly selected, and the outgoing light field is propagated to the diffraction plane using the angular spectrum transfer function, which is as follows:

[0138]

[0139] in, and represents Fourier transform and inverse Fourier transform respectively, H is the angular spectrum transfer function, z is the distance between the sample and the detector, k is the wave vector, λ is the wavelength, and f x , f y is the spatial frequency.

[0140] The outgoing light field corresponding to the wavelength of each laser beam is selected for propagation. In order to replace the amplitude of the light field function of the diffraction plane, the light field intensity value of the diffraction plane needs to be calculated and summed in each iteration:

[0141]

[0142] in, represents the calculated light field function of the diffraction plane for each wavelength, I j,k (R) is the total light field intensity value calculated on the diffraction plane.

[0143] Optionally, performing amplitude replacement on the predicted total diffraction light field intensity value according to the diffraction data to be processed collected on the diffraction plane, and back-propagating it back to the corresponding sample plane to update the output light field, comprises:

[0144] The following formula is used to replace the amplitude of the diffracted light field of different modes and propagate it back to the sample plane;

[0145]

[0146] in, represents the diffraction light field of each mode calculated on the diffraction plane, I j,k (R) represents the total diffraction light field intensity value calculated on the diffraction plane, represents the diffracted light field of each mode after updating on the diffraction plane, represents the diffraction data to be processed at a randomly selected diffraction plane, H λi represents the angular spectrum transfer function corresponding to each wavelength, is the outgoing light field of each mode at the sample plane.

[0147] After traversing all planes using the light spot diffraction data, an iteration is completed to obtain illumination functions of different modes; according to the fact that the emergent light field is equal to the product of the illumination function and the sample transmission function, after traversing all planes using the sample diffraction data, an iteration is completed to obtain emergent light fields of different modes; according to the emergent light fields of different modes obtained each time, the transmission function of the sample is updated, and this step is repeated. After reaching a preset number of cycles, the transmission function of the sample is output.

[0148] The embodiment of the present invention uses a 532nm laser beam and a 632nm laser beam as the incident light for imaging, and the diameter of the precision pinhole is 50μm. The pixel size of the detector is 6.5μm, and the number of pixels is 1024. Propagation is performed in two modes. The field of view of the reconstructed image is 6656μm*6656μm. The samples used are USAF1951 resolution test targets and biological samples.

[0149] The imaging results are as follows Figure 6 As shown, Figure 6 In order to use the method in this paper to reconstruct the sample transmission function alone when the illumination function has been reconstructed, Figure 6 (a) and (d) are the reconstructed illumination functions, (a) is the amplitude distribution of the 532nm mode illumination function, (d) is the amplitude distribution of the 632nm mode illumination function; Figure 6 (b) and (e) show that the sample is placed in the optical path to reconstruct the amplitude distribution of the outgoing wave. (b) is the 532nm mode reconstruction image, and (e) is the 632nm mode reconstruction image. Figure 6 (c) and (f) are sample functions of separated illumination functions, (c) is the amplitude distribution diagram of the sample in 532nm mode, and (f) is the amplitude distribution diagram of the sample in 632nm mode.

[0150] Furthermore, the present invention is applicable to both multi-beam laser beam combination and monochromatic light source. The experimental optical path is simple and convenient to construct, and the experimental data collection operation is simple and fast. It can well reconstruct an image with good effect using two wavelength modes.

[0151] The embodiment of the present invention collects a small amount of diffraction data of samples and light spots by moving the axial distance multiple times, iterates according to the diffraction data corresponding to different diffraction planes, reconstructs illumination functions of different modes, and then reconstructs the transmission function of the sample separately, and finally obtains sample information of multiple modes. By utilizing the redundant information of the axial diffraction data, multiple modes can be separated from multiple beams of light using less diffraction data. Not only does it take less time to collect, but the reconstructed multi-mode wavelength light field has almost the same reconstruction effect as a single beam of light. It solves the technical problem in the prior art that the reconstruction of the multi-mode light field requires the collection of more diffraction data, the data collection time is long, and the requirements for the stability of the optical path are strict, making it difficult to ensure the performance and efficiency of the overall imaging system. It significantly reduces the data collection time and reduces the strict requirements for the stability of the optical path, thereby improving the performance and efficiency of the overall imaging system.

[0152] Embodiment 3

[0153] On the basis of the above embodiments, the present invention further provides a multi-distance lensless imaging device with multi-wavelength simultaneous illumination, which is used to perform the imaging method described in any one of the embodiments, including:

[0154] The sample diffraction data acquisition module is used to collimate and combine multiple laser beams and then irradiate them onto the sample plane, axially move the detector to collect sample diffraction data of multiple diffraction planes, and perform image registration on the sample diffraction data;

[0155] An initial complex amplitude setting module, used to set the initial complex amplitude distribution of the outgoing light field on the sample plane to be a random distribution;

[0156] A diffraction light field intensity calculation module is used to randomly select an untraversed diffraction plane, propagate the outgoing light field of the sample plane to the diffraction plane, and perform incoherent superposition of the diffraction light field intensities of different modes in the multiple laser beams to obtain a predicted total diffraction light field intensity value;

[0157] The iterative calculation module is used to perform amplitude replacement on the predicted total diffraction light field intensity value according to the sample diffraction data collected on the diffraction plane, and back-propagate it back to the corresponding sample plane to update the output light field; it determines whether all diffraction planes are traversed, if not, it returns to execute the diffraction light field intensity calculation module, if so, it outputs output light fields of different modes.

[0158] A multi-distance lensless imaging device with simultaneous multi-wavelength illumination provided by an embodiment of the present invention is used to execute a multi-distance lensless imaging method with simultaneous multi-wavelength illumination provided by any embodiment 1 of the present invention, and has corresponding functional modules and beneficial effects.

[0159] Embodiment 4

[0160] On the basis of the above embodiments, the present invention further provides a multi-distance lensless imaging device with multi-wavelength simultaneous illumination, which is used to perform the imaging method described in any one of the second embodiments, including:

[0161] The sample diffraction data acquisition module is used to collimate and combine multiple laser beams and then irradiate them onto the sample plane, axially move the detector to collect sample diffraction data of multiple diffraction planes, and perform image registration on the sample diffraction data;

[0162] The light spot diffraction data acquisition module is used to collimate and combine multiple laser beams, move away from the sample, axially move the detector to collect light spot diffraction data of multiple diffraction planes, and perform image registration on the light spot diffraction data;

[0163] An initial complex amplitude setting module, used to set the initial complex amplitude distribution of the outgoing light field on the sample plane to be a random distribution;

[0164] The diffraction light field intensity calculation module is used to randomly select an untraversed diffraction plane, propagate the outgoing light field of the sample plane to the diffraction plane, and perform incoherent superposition of the diffraction light field intensities of different modes in multiple laser beams to obtain the predicted total diffraction light field intensity value;

[0165] An iterative calculation module is used to perform amplitude replacement on the predicted total diffraction light field intensity value according to the diffraction data to be processed collected on the diffraction plane, and back-propagate it back to the corresponding sample plane to update the outgoing light field; return to execute the diffraction light field intensity calculation module, and complete an iteration after traversing all diffraction planes;

[0166] The illumination function calculation module is used to use the light spot diffraction data as the diffraction data to be processed, execute the diffraction light field intensity calculation module and the iterative calculation module, and obtain the illumination function probe of different modes. λi (r);

[0167] A transmission function updating module, used to set the initial transmission functions of different modes to be randomly distributed, use the sample diffraction data as the diffraction data to be processed, execute the diffraction light field intensity calculation module and the iterative calculation module to obtain the output light fields of different modes, and update the transmission function of the sample according to the sample transmission function update formula;

[0168] The sample transmission function update formula is:

[0169]

[0170] In the formula, is the outgoing light field at the sample plane for each wavelength, probe λi (r) represents the illumination function of different modes, O λi (r) is the transmission function of the sample; a transmission function output module is used to repeatedly execute the transmission function update, and after reaching a preset number of cycles, output the transmission function of the sample.

[0171] A multi-distance lensless imaging device with simultaneous multi-wavelength illumination provided by an embodiment of the present invention is used to execute a multi-distance lensless imaging method with simultaneous multi-wavelength illumination provided by any third embodiment of the present invention, and has corresponding functional modules and beneficial effects.

[0172] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A multi-distance lensless imaging method with multi-wavelength simultaneous illumination, characterized in that: include: S1, collimate and combine multiple laser beams and irradiate them onto the sample plane, axially move the detector to collect sample diffraction data of multiple diffraction planes, and perform image registration on the sample diffraction data; S2, setting the initial complex amplitude distribution of the outgoing light field on the sample plane to be a random distribution; S3, randomly selecting an untraversed diffraction plane, propagating the outgoing light field of the sample plane to the diffraction plane, and performing incoherent superposition on the diffraction light field intensities of different modes in the multiple laser beams to obtain a predicted total diffraction light field intensity value; S4. Perform amplitude replacement on the predicted total diffraction light field intensity value according to the sample diffraction data collected on the diffraction plane, and back-propagate it back to the corresponding sample plane to update the outgoing light field; determine whether all diffraction planes are traversed, if not, return to execute S3, if yes, output outgoing light fields of different modes.

2. The imaging method according to claim 1, characterized in that Prior to S1, it also included: The detector is set to an initial position, and a monochromatic laser is used to illuminate the sample to obtain a set of sample diffraction patterns; In a preset distance range, the Sobel function is used to judge the image quality of the sample diffraction pattern at each distance, and the distance corresponding to the result with the maximum Sobel value is determined as the initial distance from the sample to the axial moving detector.

3. The imaging method according to claim 2, characterized in that: The image registration of the sample diffraction data comprises: In a registration interval within a preset range, calculating the autocorrelation peak center of the sample diffraction data at different diffraction planes; The offset of each data in the sample diffraction data of different diffraction planes from the diffraction plane at the initial position is determined and aligned.

4. The imaging method according to claim 1, wherein: The randomly selecting an untraversed diffraction plane and propagating the outgoing light field of the sample plane to the diffraction plane comprises: An amplitude limit is imposed on the outgoing light field at the sample plane so that the amplitude of the outgoing light field is not greater than a set constant; at the same time, a phase limit is imposed so that the phase of the transmitted light part of the outgoing light field is a constant phase; A diffraction plane that has not been traversed is randomly selected, and the outgoing light field is propagated to the diffraction plane using the angular spectrum transfer function, which is as follows: in, and represents Fourier transform and inverse Fourier transform respectively, H is the angular spectrum transfer function, z is the distance between the sample and the detector, k is the wave vector, λ is the wavelength, and f x , f y is the spatial frequency.

5. The imaging method according to claim 1, characterized in that: The step of performing amplitude replacement on the predicted total diffraction light field intensity value according to the sample diffraction data collected on the diffraction plane, and back-propagating it back to the corresponding sample plane to update the output light field comprises: The following formula is used to replace the amplitude of the diffracted light field of different modes and propagate it back to the sample plane; in, represents the diffraction light field of each mode calculated on the diffraction plane, I j,k (R) represents the predicted total diffraction light field intensity value at the diffraction plane, represents the diffracted light field of each mode after updating on the diffraction plane, Represents the sample diffraction data for a randomly selected diffraction plane.

6. A multi-distance lensless imaging method with multi-wavelength simultaneous illumination, characterized in that: include: T1, collimate and combine multiple laser beams and irradiate them onto the sample plane, move the detector axially to collect sample diffraction data of multiple diffraction planes, and perform image registration on the sample diffraction data; T2, after collimating and combining multiple laser beams, remove the sample, axially move the detector to collect the spot diffraction data of multiple diffraction planes, and perform image registration on the spot diffraction data; T3, setting the initial complex amplitude distribution of the outgoing light field on the sample plane to be random distribution; T4. Randomly select an untraversed diffraction plane, propagate the outgoing light field of the sample plane to the diffraction plane, perform incoherent superposition of the diffraction light field intensities of different modes in multiple laser beams, and obtain the predicted total diffraction light field intensity value; T5, performing amplitude replacement on the predicted total diffraction light field intensity value according to the diffraction data to be processed collected on the diffraction plane, and back-propagating it back to the corresponding sample plane to update the outgoing light field; Return to execute T4 and complete one iteration after traversing all diffraction planes; T6. Take the light spot diffraction data as the diffraction data to be processed, execute T4-T5, and obtain the illumination function probe of different modes. λi (r); T7, setting the initial transmission functions of different modes to be randomly distributed, taking the sample diffraction data as the diffraction data to be processed, executing T4-T5, obtaining the output light fields of different modes, and updating the transmission function of the sample according to the sample transmission function update formula; The sample transmission function update formula is: In the formula, is the outgoing light field at the sample plane for each wavelength, probe λi (r) represents the illumination function of different modes, O λi (r) is the transmission function of the sample; T8. Repeat T7 until a preset number of cycles is reached, and then output the transmission function of the sample.

7. The imaging method according to claim 1, characterized in that: The randomly selecting an untraversed diffraction plane and propagating the outgoing light field of the sample plane to the diffraction plane comprises: An amplitude limit is imposed on the outgoing light field at the sample plane so that the amplitude of the outgoing light field is not greater than a set constant; at the same time, a phase limit is imposed so that the phase of the transmitted light part of the outgoing light field is a constant phase; A diffraction plane that has not been traversed is randomly selected, and the outgoing light field is propagated to the diffraction plane using the angular spectrum transfer function, which is as follows: in, and represents Fourier transform and inverse Fourier transform respectively, H is the angular spectrum transfer function, z is the distance between the sample and the detector, k is the wave vector, λ is the wavelength, and f x , f y is the spatial frequency.

8. The imaging method according to claim 1, wherein: The step of performing amplitude replacement on the predicted total diffraction light field intensity value according to the diffraction data to be processed collected on the diffraction plane, and back-propagating it back to the corresponding sample plane to update the outgoing light field comprises: The following formula is used to replace the amplitude of the diffracted light field of different modes and propagate it back to the near-field plane; in, represents the diffraction light field of each mode calculated on the diffraction plane, I j,k (R) represents the total diffraction light field intensity value on the diffraction plane, represents the diffracted light field of each mode after updating on the diffraction plane, represents the diffraction data to be processed for a randomly selected diffraction plane.

9. A multi-distance lensless imaging device with multi-wavelength simultaneous illumination, used to perform the imaging method according to any one of claims 1 to 5, characterized in that: include: The sample diffraction data acquisition module is used to collimate and combine multiple laser beams and then irradiate them onto the sample plane, axially move the detector to collect sample diffraction data of multiple diffraction planes, and perform image registration on the sample diffraction data; An initial complex amplitude setting module, used to set the initial complex amplitude distribution of the outgoing light field on the sample plane to be a random distribution; A diffraction light field intensity calculation module is used to randomly select an untraversed diffraction plane, propagate the outgoing light field of the sample plane to the diffraction plane, and perform incoherent superposition of the diffraction light field intensities of different modes in the multiple laser beams to obtain a predicted total diffraction light field intensity value; The iterative calculation module is used to perform amplitude replacement on the predicted total diffraction light field intensity value according to the sample diffraction data collected on the diffraction plane, and back-propagate it back to the corresponding sample plane to update the output light field; it determines whether all diffraction planes are traversed, if not, it returns to execute the diffraction light field intensity calculation module, if so, it outputs output light fields of different modes.

10. A multi-distance lensless imaging device with multi-wavelength simultaneous illumination, used to perform the imaging method according to any one of claims 6 to 8, characterized in that: include: The sample diffraction data acquisition module is used to collimate and combine multiple laser beams and then irradiate them onto the sample plane, axially move the detector to collect sample diffraction data of multiple diffraction planes, and perform image registration on the sample diffraction data; The light spot diffraction data acquisition module is used to collimate and combine multiple laser beams, move away from the sample, axially move the detector to collect light spot diffraction data of multiple diffraction planes, and perform image registration on the light spot diffraction data; An initial complex amplitude setting module, used to set the initial complex amplitude distribution of the outgoing light field on the sample plane to be a random distribution; The diffraction light field intensity calculation module is used to randomly select an untraversed diffraction plane, propagate the outgoing light field of the sample plane to the diffraction plane, and perform incoherent superposition of the diffraction light field intensities of different modes in multiple laser beams to obtain the predicted total diffraction light field intensity value; An iterative calculation module, used for performing amplitude replacement on the predicted total diffraction light field intensity value according to the diffraction data to be processed collected on the diffraction plane, and back-propagating it back to the corresponding sample plane to update the output light field; Return to execute the diffraction light field intensity calculation module, and complete one iteration after traversing all diffraction planes; The illumination function calculation module is used to use the light spot diffraction data as the diffraction data to be processed, execute the diffraction light field intensity calculation module and the iterative calculation module, and obtain the illumination function probe of different modes. λi (r); A transmission function updating module, used to set the initial transmission functions of different modes to be randomly distributed, use the sample diffraction data as the diffraction data to be processed, execute the diffraction light field intensity calculation module and the iterative calculation module to obtain the output light fields of different modes, and update the transmission function of the sample according to the sample transmission function update formula; The sample transmission function update formula is: In the formula, is the outgoing light field at the sample plane for each wavelength, probe λi (r) represents the illumination function of different modes, O λi (r) is the transmission function of the sample; a transmission function output module is used to repeatedly execute the transmission function update, and after reaching a preset number of cycles, output the transmission function of the sample.

Images