最新刊期
期 6 ， 2023
- 摘要：The field of view （FOV） and spatial resolution of conventional optical microscopes are mutually constrained， how to break through this limit， and how to simultaneously obtain high resolution and large FOV for high throughput imaging is one of the main research directions in the field of microscopy. Solving this scientific problem will help to accelerate scientific research， improve manufacturing capabilities， and provide new tools for medically assisted diagnosis. This paper introduces and compares five cutting-edge high-throughput microscopy techniques， including large-aperture objective fabrication and curved detectors， scanning stitching method， Fourier ptychographic microscopy （FPM）， wide-field structured light illumination microscopy （SIM） and lens-free on-chip microscopy. The current status， challenge and future trends of high-throughput microscopy techniques are also analyzed and reported. The analysis points out that computational imaging is gradually becoming the main means of high-throughput microscopy， which breaks or bypasses the physical limit of optical microscopy and will open up a new era of high-throughput microscopy imaging.关键词：microscopy imaging;high throughput;Computational Imaging
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发布时间：2023-06-12 - 摘要：Fourier ptychographic microscopy （FPM） enables wide-field and high-resolution quantitative complex amplitude imaging by stitching low-resolution intensity images captured under angle-varied illuminations via synthetic aperture and phase retrieval techniques. The spectrum position of each captured image is crucial prior knowledge for reconstructing the high-quality image. Therefore， calibration of the light source pose， which determines the position of the spectrum， is a key to achieving robust FPM systems. Recently， various methods have been proposed to calibrate the misalignment of the light source， including mechanical calibration methods with multi-degree-of-freedom precision mechanical stages， data-driven calibration methods based on the intensity or spectrum information of the captured images， and imaging mechanism calibration methods based on the optical principle of microscope. This paper briefly introduces the basic principle of FPM and the pose deviation of light sources， then reviews the principles and characteristics of three calibration methods. The mechanical methods can eliminate the pose deviation essentially， but it is time-consuming and laborious. The data-driven methods can automatically calibrate the pose deviation， but long calibration time and coupling of parameters limit its application. The imaging mechanism method not only has high robustness， but also can decouple the accurate pose parameters from various systematic errors， which is a promising method with great potential for development and application.关键词：fourier ptychographic microscopy;computational optical imaging;phase retrieval;pose calibration
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发布时间：2023-06-12 - 摘要：3D shape measurement based on fringe projection profilometry （FPP） has been extensively studied in terms of improving measurement accuracy， accelerating the measurement speed， expanding the measurement depth， and increasing the adaptability of the measurement scene. However， due to the principle limitation of FPP， it is difficult to achieve accurate matching of corresponding points using the traditional FPP method. The deformation measurement and strain analysis relying on the corresponding point tracking can be further performed to analyze the motion state of the object， material properties and structural mechanics parameters， which plays an indispensable role in many fields such as motion bionics， material mechanics， and structural mechanics. Therefore， this paper reviews a series of newly developed 3D shape and deformation measurement techniques based on FPP in recent years， and discusses how scholars have gradually realized the measurement from simple rigid body displacement measurement to complex and fine structure deformation measurement and strain analysis based on a FPP system. Finally， the advantages of this technique in measurement integrity， resolution and computational efficiency compared with the existing deformation measurement technique are analyzed， and the challenges and potential development trends of this technique are given.关键词：three-dimensional measurement;fringe projection;digital image correlation;dynamic three-dimensional shape measurement;three-dimensional deformation measurement;strain analysis
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发布时间：2023-06-12 - 摘要：Three-dimensional （3D） shape measurement plays an important role in advanced manufacturing， aerospace， biomedicine and other fields. With the advantages of high precision， full field of view， and non-contact， fringe projection profilometry is currently the most widely used optical three-dimensional measurement method. In order to obtain 360° global three-dimensional information， it is usually necessary to place the object to be measured on the turntable， and obtain the global information of the object by continuous scanning and stitching. However， the traditional scanning and stitching are performed offline， resulting in slow reconstruction of the entire 3D model. Although the existing real-time point cloud registration methods can effectively improve the speed of point cloud scanning and stitching， the accuracy of real-time point cloud stitching is still limited by the motion state of the object under test. This paper optimizes and improves the above problems， and proposes a real-time high-precision model reconstruction method based on global optimization. Firstly， a fast point cloud registration algorithm from coarse to fine registration is introduced， and a point cloud initialization algorithm based on point cloud normal vector constraints is proposed on this basis， which can improve the stability and accuracy of the point cloud initial pose calculated during the rough registration process. Secondly， a graph optimization algorithm is introduced in the fine registration stage to obtain the optimal solution of the global point cloud pose， which further improves the accuracy of global point cloud registration. The experimental results show that the proposed method can achieve higher precision and stable global point cloud registration than the current real-time point cloud registration method. In particular， this method can still robustly complete the reconstruction of the 3D model， and the accuracy of the omni-directional model reconstruction reaches 84 μm， especially for situations such as sudden changes in the speed of the measured object caused by factors such as jitter in the dynamic scene.关键词：Fringe Projection Profilometry;Graph optimization;real-time;3D reconstruction;point cloud registration
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发布时间：2023-06-12 - 摘要：In order to realize more accurate 3D reconstruction of featureless and featureless objects， this paper studies the automatic splicing algorithm of 3D point cloud under multi-view sensor. Firstly， the axis data was calibrated by the binocular calibration of sensors from different perspectives， and then multiple axis data were analyzed in three-dimensional space. A point cloud splicing method based on the axis fusion of sensors from multiple perspectives was proposed， so as to calculate the optimal axis data with the minimum error. Finally， the fitted axis data was used as the axis center to splice the three-dimensional point cloud in the world coordinate system. The experimental results show that the error of the proposed method is less than 0.037 mm in the measurement range of 1.3~1.9 m for the standard ball with a diameter of 144.954 2 mm， and the reconstruction of objects without and with feature points can have a good stitching effect， and the stitching time is not limited by the size of the total point cloud. This method basically meets the requirements of good stability， fast efficiency and high precision of 3D reconstruction.关键词：three-dimensional reconstruction;point cloud splicing;axis
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发布时间：2023-06-12 - 摘要：The existing target analysis through scattering media is mainly aimed at stationary targets. At the same time， ambient or external luminance conditions have a critical impact on the target analysis results. This paper puts forward extremely high requirements for the dynamic range and time resolution of the image acquisition equipment. Due to its high dynamic range， high temporal resolution and low latency， event cameras provide new solutions to the above problems. Aiming at the problem of poor detection effect of moving targets through thin scattering medium under low illumination， event camera is adopted to carry out target detection research through thin scattering medium. V2E network is used to prepare the “event speckle” dataset by grayscale speckle， and ResNet classification network is adopted for target classification. The ten-class accuracy of 94.27% is obtained. Experimental results show that the applicaiton of event streams has great potential for analyzing target information passing through scattering media.关键词：speckle imaging;event camera;Neural networks
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发布时间：2023-06-12 - 摘要：The defects and heterogenous structures which are far beyond the molecular scale always exist on the film surfaces or inside the films， such as surface defects， phase separation， crystallization， microbubbles and other impurity particles， resulting in the significant decline of their performance. Until now， in-situ characterization of these defects and structures is still challenging. Herein， we explore the applications of the digital holographic microscope （DHM）， an in-situ， nondestructive and high-precision optical 3D imaging technique， in the 3D characterizations of both the surface and internal defects of polymer films. Examples include 3D distribution characterization of 100 nm polystyrene nanoparticles in a thin liquid layer， morphology of the surface of the polyurethane coated wafer， phase separation process of polymethacrylate film from water， edge crystallization monitoring during the drying of polyethylene glycol film， and characterization of micro-nano bubbles in the polyvinyl alcohol film. Obviously， DHM has unique advantages and is promising for future applications in polymer film characterization.关键词：polymer films;digital holography;three-dimensional imaging
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发布时间：2023-06-12 - 摘要：When the compressive sensoring is used in wavefront measurement， classic methods of slopes’ restoration has a relatively low precision， which make it difficult to measure the atmospheric turbulence wavefront. In the paper， a deep neural network is presented to improve the slopes’ restoration precision. The traditional compressive sensing technology does not take into account the relatively small slopes， which increases the wavefront measurement errors. To measure the complex wavefront induced by atmospheric turbulence with a high speed， the paper presents an improved deep neural network to restore the slopes from sparse ones with high precision， which improves the precision of wavefront reconstruction. When the compression ratio is ranged from 0.1 to 0.9， the wavefront error PV （Peak to valley） of the compressed wavefront detection algorithm based on depth neural network （DNNCWS） proposed in this paper is better than 0.014 μm， and the running time of the algorithm is 4.4 ms. In the case of low signal-to-noise ratio， the residual wavefront PV is better than 0.011 μm. In addition， the simulation results indicate that it has good anti-noise performance. The DNNCWS improves the detection accuracy of compressive sensing and overcomes the problem of low accuracy for complex aberration induced by atmospheric turbulence. It can also be used in other adaptive optical applications， such as laser communication and retinal imaging.关键词：compressed wavefront sensing;adaptive optics;atmospheric turbulence
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发布时间：2023-06-12 - 摘要：The dynamically changing atmospheric turbulence and the reduced brightness of the observed target severely affect the accuracy of the Shack-Hartmann wavefront sensor （SHWFS） to detect wavefronts. Under these two complicated observational conditions， this paper proposes a neural network model based on Transformer structure，which has excellent global modelling capabilities and could reconstruct wavefronts from light spot array images from SHWFS with high accuracy. The residual wavefront RMS error of the presented network model can be stabilized between 0.010 μm and 0.024 μm by simulating for dynamically varying typical atmospheric turbulence coherence length r0. Comparing with reported methods， the wavefront aberrations can be reconstructed more accurately. In addition， the reconstruction accuracy of the method is robust to the magnitude variation of guide stars or detection targets. Therefore， the reconstruction accuracy of this method has strong stability to the changes of two observation conditions， and provides a promising way for high-resolution imaging for large-aperture astronomical optical telescopes.关键词：adaptive optics;deep learning;Shack-Hartmann Wavefront Sensor;Transformer;Wavefront reconstruction
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发布时间：2023-06-12
Intelligent Imaging
- 摘要：In the naked eye 3D video viewing， due to the contradiction of convergence adjustment， viewers will have visual fatigue symptoms such as dizziness and vomiting. Especially in medical， A/VR and other scenes， 3D video viewing is usually driven by special task. As eye movement behavior is subjectively controlled， it is difficult to accurately assess visual fatigue with a single eye movement feature， let alone obtain the visual fatigue level， resulting in visual fatigue not being detected in time and causing unpredictable losses. To solve the above problems， this paper proposes a 3D visual fatigue rating model based on a variety of eye movements， aiming to obtain the real-time visual fatigue rating by modeling and analyzing the eye movements such as fixation， scanning and blinking when viewing 3D content. The method combining subjective and objective is used to carry out the experiment： the subjects watch 3D content， the experimenters record subjective scores of the subjects， and extract the objective eye movement behavior of the subjects with an eye tracker. Through correlation analysis， the various objective eye movement behaviors that can represent 3D visual fatigue under task driving are explored. A four grade evaluation model of visual fatigue based on 16 eye movements is established by using neural network. The prediction accuracy of the model for 3D visual fatigue level reaches 82%， proving the effectiveness of the model.关键词：Naked eye 3D display;eye fatigue;eye movements;task driving;neural network
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发布时间：2023-06-12 - 摘要：As a three-dimensional （3D） display method， computer-generated holography （CGH） can achieve accurate reconstructions of the target light fields based on diffractive optics. It has broad applications in the metaverse， head-mounted display， head-up display， etc. High-speed calculation and high-quality reconstruction of phase-only holograms （POHs） are key issues that should be emphasized in this field. In recent years， the leapfrog development of deep learning has provided a novel path to address this challenge. In this review， the basic principles and classifications of CGH are briefly introduced. Then， the existing CGH methods based on deep learning are summarized. The advantages and disadvantages of various methods are compared. Finally， the possible research directions and challenges of this field are prospected.关键词：computer-generated holography;deep learning;3D display;convolutional neural network;Liquid crystal spatial light modulator
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发布时间：2023-06-12 - 摘要：The microlens image may serve deviations from the true projected centers and shape irregularities when the light field imaging system is used in narrow space. This paper analyzed and proposed the distortionless condition for microlens images. The narrow space is modeled as an additional aperture in the light field imaging system， whose pupil size and position in the light field imaging system were related to the distortionless condition. The distortionless condition was studied from three aspects and the experiments were designed including microlens image deviation and arithmetic aperture-shift. Experimental results show the correlation coefficient between the experimental and theoretical result is more than 99%， and aperture-shift measurement is （9.97±1.5） mm. The distortionless condition is proved by experimental results， which can be used to guide the design of light field imaging system and analyze the microlens image distortion parameters quantitatively.关键词：light field imaging;stop aperture;microlens image distortion;microlens image deviation
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发布时间：2023-06-12 - 摘要：Since an integral imaging display system has limited depth of field， the reconstruction depth of 3D image should be considered in the acquisition and generation processes to make sure that the reconstructed 3D image is within the depth of field of the integral imaging display system. When the reconstruction depth of 3D image does not match the depth of field of the display system， the capture parameters need to be adjusted to display clear 3D images. In order to avoid re-acquisition of 3D scene and improve the utilization efficiency of elemental image array， this paper proposed a generation method of elemental image array for different reconstruction depths. This method can change the sampling interval of light field by adjusting the pitch of elemental image and the parallax value between adjacent elemental image， so that the elemental image array can be adapted to integral imaging display systems with different depth of field and improve the practicability of elemental image array. Experimental results show that the proposed method can achieve 3D image reconstruction with different reconstruction depths and verify the correctness and feasibility of the proposed method.关键词：elemental image scaling;integral imaging;parallax of homonymous point;3D image point reconstruction depth
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发布时间：2023-06-12 - 摘要：In order to apply two-dimensional （2D）/three-dimensional （3D） compatible display technology into augmented reality display devices， this paper proposed an augmented reality 2D/3D compatible display system based on lens array holographic optical element and reflective polarizer. By using reflective polarizer to reflect or transmit the projection light， the reflected light loaded with 2D image source is used to realize 2D display， and the transmitted light loaded with 3D image source is used to realize 3D display after being modulated by lens array holographic optical element. Both reflective polarizer and lens array holographic optical element have good ambient transmittance， which makes the display system own optical see-through property for augmented reality application. The experimental results indicate that the proposed augmented reality 2D/3D compatible display system can switch freely between 2D and 3D display modes， and the ambient contrast ratio of the system is higher than 3∶1， which is the standard value of display.关键词：2D/3D compatible display;augmented reality;reflective polarizer;Holographic optical element;ambient contrast ratio
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发布时间：2023-06-12
Intelligent Displays
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