This PDF file contains the front matter associated with SPIE Proceedings Volume 11186, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists

Super-resolution optical microscopy has enabled the observation of ultra-fine structures and features beyond the diffraction limit, among which nonlinear absorption has been a useful tool to investigate physical and biological characteristics in sub-100 nanometer range. Saturation competition microscopy (SAC), based on nonlinear absorption principle, has been demonstrated to obtain high resolution in either fluorescence or non-fluorescence imaging of biological applications. Furthermore, fluorescent nanodiamonds (FNDs) have been widely researched as nitrogenvacancy centers (NVCs) in FNDs are important medium in quantum entanglement. Here, we report on the characterization of NVCs using pulse SAC (pSAC) microscopy. Resolution of λ/6 has been reached and the experimental results shows that it has better signal-to-background ratio (SBR) with lower illumination intensity in contrast to stimulated emission depletion microscopy (STED).

The segmented planar imaging detectors have attracted intensive attention because of its superior imaging performance and structural compactness. The structure of radial SPIDER is investigated and the imaging progress is mathematically analyzed according to the Van Cittert-Zernike theorem. Due to the sparse sampling density in the frequency domain resulted from restriction of the structure, the imaging quality of SPIDER is unsatisfactory. In this paper, a reconstruction algorithm based on the compressed sensing theory is proposed to reconstruct the sparse signal from far fewer sampling density than the Nyquist–Shannon sampling criterion. The objective function, measurement matrix and sparse matrix are discussed according to the physical mechanism of SPIDER. The TV/L1 minimization and alternating direction multiplier method (ADMM) are used to obtain high-resolution images. Simulation results of image reconstruction demonstrate that the imaging resolution is improved remarkably than the original image.

We propose a simple and effective method to improve the super-resolution imaging properties of a microsphere by combining plasmon coupling with the microsphere lens. Plasmon coupling can be excited when random silver nanoparticles are deposited on a self-assembled hexagonally closed-packed (hcp) SiO2 microsphere array. The electric field enhancement is found to be strongly influenced by plasmon coupling, and the enhanced near-field information of the samples can significantly affect the resolution quality. Using BaTiO3 glass (BTG) microsphere-assisted optical microscopy, we can clearly resolve a 200-nm-diameter hcp microsphere array when nanoparticle-nanoparticle plasmonic interactions and nanoparticle-thin film plasmonic interactions are excited. On the contrary, when there are no plasmon interactions excited, the 200-nm-diameter silver-coated hcp microsphere array is completely unresolved.

A single-pixel camera composed of optical coding masks, a photo detector, and a computational decoder, and therefore has very simple optical and electrical architectures. The optical coding masks are composed of holes on a substrate and are arranged on the circumference of a disk to allow mask switching by rotation of the disk. The main features are a simple structure that brings low cost in optics and electronics, no path difference in the mask, and no wavelength dependence except for a dependence on air for wideband spectral imaging.

The problem that is posed byphase-only" objects, such as epithelial cells, for brightfield microscopy has resulted in development of several specialized imaging techniques including phase-contrast and DIC. In the past decades there has been increasing research on quantitative phase imaging (QPI), which enables real-time cellular dynamics to be visualised and the 3-D morphology to be quantitatively measured. It has previously been demonstrated that the DIC and phase-contrast images can be computationally generated using the phase-image provided by QPI. Recently, we have extended this approach to include Rheinberg. Although not as popular as phase contrast or DIC, Rheinberg illumination provides a form of label-free optical staining by introducing a multi-color filter into the condenser plane of the microscope, enabling different features within the cell to be stained with different colors depending on their spatial-frequency content. We recently developed a theory for image formation with Rheinberg illumination under the conditions of Kohler illumination from which an algorithm was developed that could simulate this process using the QPI image as input. In this paper we review and further develop this approach by testing it with multiple different modalities for recording the QPI image, namely digital holographic microscopy, which uses coherent illumination and spatial light interference microscopy, which makes use of white light. We examine a variety of samples including diatom and epithelial cells using a number of microscope objectives with different numerical apertures.

We present a tunable experimental setup to obtain the three-dimensional refractive index distribution of microscopic biological structures. We introduce an adjustable system to change the position of the focal plane and perform stitched reconstruction. There are two main approaches for obtaining the projections of sample in optical diffraction tomography: beam scanning and rotating sample. Compared to beam scanning, the method of rotating sample allows the sample to be rotated 180° to capture uniformly distributed data, which improves the accuracy of the phase measurement and the resolution of the reconstruction result. The depth-of-field in the optical diffraction tomography setups is very small and the method of rotating sample inevitably causes the sample to deviate from the depth-of-field during the rotation, making it difficult to obtain ideal data. We divided the sample position deviation area into several ideal data acquisition areas and collected the ideal data in each area by shifting the position of the focal plane. By the combination of 180° projection method and stitched reconstruction method, we have obtained high measurement accuracy results with uniform resolution.

Differential phase contrast microscopy (DPC) provides high-resolution quantitative phase distribution of thin transparent samples under multi-axis asymmetric illuminations. Typically, illumination in DPC microscopic systems is designed with 2-axis half-circle amplitude patterns, which, however, reduce the temporal resolution of DPC, precluding observation of high-speed phenomenon. Efforts have been made to achieve video-rate DPC by using tri-mode illumination or adding multi-colored filter. However, the frequency responses of the PTFs has not been improved, leading to poor phase contrast and signal-to-noise ratio (SNR) for phase reconstruction. We present a video-rate isotropic quantitative phase imaging (QPI) method based on color-multiplexed differential phase contrast (DPC). In our method, the illumination source is modulated by an LCD into an annular color-multiplexed pattern matching the numerical aperture of the objective precisely to maximize the frequency response for both low and high frequencies (from 0 to 2NA_obj). In addition, we propose an alternating illumination scheme to provide a perfectly circularly symmetrical phase transfer function (PTF), achieving isotropic imaging resolution and signal-to-noise ratio (SNR). A color camera records the light transmitted through the specimen, and three monochromatic intensity images at each color channel are then separated and utilized to recover the phase of the specimen. We present the derivation, implementation, simulation and experimental results demonstrating that our method accomplishes high resolution, noise-robustness and reconstruction accuracy at camera-limited frame rates.

Photoacoustic imaging is an emerging optical imaging modality which provides optical absorption contrasts and high resolution in the optical diffusive regime. In photoacoustic computed tomography (PACT), often times the detection of the photoacoustic signal only covers a partial solid angle less than 4π, due to experimental or economic constraints. Incomplete spatial coverage always jeopardizes image quality and resolution, and results in significant artifacts and missing of image features. This problem is referred to as “limited view” and has remained unsolved for decades. In this work, we present a new machine-learning-based method that is specifically designed to compensate for the missing information due to limited view. The robustness and effectiveness of our method were demonstrated using numerical, phantom, and in vivo experiments.

Simultaneous localization of multiple cellular components related to the cellular activities, e.g. metabolism of small molecules, is not well understood due to the intrinsic limitations of fluorescence imaging technologies. The broad fluorescence emission often limits the available color number to ~4. Additionally, staining of small metabolic precursors is still difficult using fluorophores because the relatively large size of fluorophores will affect the regular metabolism of small molecules. Here, we apply our newly developed high-speed multicolor stimulated Raman and fluorescence imaging platform to observe and investigate lipid metabolism in live HeLa cells. Metabolic products generated from the deuterated palmitic acid were imaged in the Raman silent region using stimulated Raman scattering microscopy; meanwhile four kinds of organelles were imaged using fast-tunable confocal fluorescence microscopy. By taking advantages of both stimulated Raman imaging and fluorescence imaging, it enables the localization of multiple components up to five during cellular metabolism in live cells, which can be a helpful method to research complex biomedical processes.

Deep ultraviolet light excites many common fluorophores and is heavily absorbed by biological samples, making it ideal for facial histology of fresh biological samples. Microscopy with ultraviolet surface excitation (MUSE) provides high-resolution diagnostic images comparable to slide-based imaging. However, current implementations of MUSE are limited to the facial surface of the sample, restricting the availability of three-dimensional tissue structure. Our work extends MUSE imaging by providing inexpensive three dimensional images at resolutions comparable to confocal microscopy with the throughput of wide-field imaging. This approach allows comprehensive imaging of macro-scale samples by eliminating constraints on sample size and imaging depth. In this paper, we discuss recent advances in milling with ultraviolet excitation, with a focus on complex neurological structures such as cellular and microvascular networks.

Structured illumination microscopy(SIM) has shown priority in bio-research field due to its low photo-toxicity and high imaging speed. In addition to sinusoidal patterns, other types of illumination patterns have been reported to applied in structured illumination microscopy. Here we propose a method based on joint Richardson-Lucy deconvolution which reconstructs both the illumination patterns and object simultaneous to extend the application of structured illumination microscopy.

We demonstrate a label-free, scan-free intensity diffraction tomography technique utilizing annular illumination (aIDT) to rapidly characterize large-volume 3D refractive index distributions in vitro. By optimally matching the illumination geometry to the microscope pupil, our technique reduces the data requirement by 60x to achieve high-speed 10 Hz volume rates. Using 8 intensity images, we recover ∼350 x 100 x 20μm³ volumes with near diffraction-limited lateral resolution of 487 nm and axial resolution of 3.4μm. Based on the 3D quantitative reconstructions of unicellular diatom microalgae, epithelial buccal cell clusters with native bacteria, and live Caenorhabditis elegans specimens, aIDT shows promise as a powerful high-speed, label-free computational microscopy technique for these applications where natural imaging is required to evaluate environmental effects on a sample in real-time.

Although the phase diversity method is an effective way to detect wave-front and restore image, it is difficult to be achieve its real time application on DSP or FPGA. The main of disadvantage of method is a great computation when it is used to estimate the wave-front phase aberration and restore the degraded images. In this paper, a parallel phase diversity method is deeply researched and the expression of the evaluation function is further clarified according the theory of Nijboer-Zernike polynomial. An outdoor image restoration verification system is established. The structure of an ordinary telescope is modified, so that it can acquire two images on the focal plane and the out-of-focus plane of the imaging system. The image objects are a chessboard at a distance of 1.1km and a worker in a construction site at a distance of 4.5km outside the laboratory window. The results indicate that the restoration image has a higher resolution. No-reference assessment methods are adopted to evaluate the quality of images. The FI value of restoration image of chessboard improved 1.478 times, and the LS value improved 2.178 times. The FI value of restoration image of worker improved 4.227 times, and the LS value improved 1.623 times.

Nonlinear focal modulation microscopy (NFOMM) is a really simple and effective super-resolution imaging method based on phase modulation with high-intensity illumination, which can extend the effective spatial-frequency bandwidth of the imaging system and achieve a transverse resolution of ~ 60 nm (~λ/10). However, multiple images under different illumination pattern is needed, which result in limited imaging speed. A novel interleaved reconstruction method is proposed to increase the frame rate without any change in the raw data of NFOMM. Since allowing easy integration with confocal microscopes, we anticipate this method will be a useful observation tool in the biological community and other research field.

Biological tissue is a kind of complex and highly scattering medium. The study of the ultrasound-modulated scattered light propagation in biological tissue is a fundamental problem that must be solved in acousto-optic tomography (AOT). Due to the action of the ultrasonic field, the optical properties of the scattering medium change with time-space, and the propagation of light in it becomes more complicated. In this paper, the finite element simulation software COMSOL Multiphysics is used to simulate the propagation of light in biological tissue under the action of different types of ultrasonic field. The effects of ultrasonic field distribution, ultrasonic intensity and frequency on the light diffusion in the scattered medium are studied. The relationship between the ultrasound-modulated scattering light and the optical properties of biological tissue is discussed. The numerical simulation results are in agreement with the experimental results.

Super-resolution hyperspectral imaging is a key technology for many applications, especially in the fields of remote sensing, military, agriculture, and geological exploration. Recovering a high resolution image needs enormous data, which puts forward very high requirements on image system hardware. Compressed sampling spectral imaging technology could well solve this problem and achieve high-resolution objects with low-resolution compressed data. In this paper, the method of a compressed sampling spectral imaging based on push-broom coded aperture and dispersion prism is proposed. A spectral aliasing image is formed when the object passing through the dispersive prism. According to the prism dispersion condition and the CCD pixel size, the visible spectrum can be divided into N spectral bands, and the measurement matrix of the coded aperture is respectively calibrated for the center wavelength of each spectral band. By controlling a stepper to implement the push broom of the coded aperture to change the measurement matrix, multiple spectral aliasing images can be obtained. The pixel size of the coded aperture becomes half of the CCD by a relay lens, which means the pixel of CCD is low-resolution for the coded aperture. The super-resolution hyperspectral image of the object is obtained by the improved LS reconstruction algorithm. Simulation results show that, the recovered hyperspectral image has twice resolution compared with the low-resolution CCD image, and the peak signal-to-noise ratio (PSNR) and structural similarity (SSIM) increase with the increasing compressed sampling hyperspectral images. For N=31, the average PSNR and SSIM recovered from six aliasing images is 22.019 and 0.235, respectively. The average PSNR and SSIM of the recovered 31 bands are also increasing with increasing aliasing images. While the aliasing imaging is 156, The average PSNR and SSIM exceeds 38 and 0.9. This method proves that super-resolution hyperspectral imaging can be achieved by capturing less low-resolution object images.

By iteratively stitching together the series of low-resolution (LR) images captured by either various small-aperture illuminations or angle-varied illuminations, the Fourier ptychography (FP) can recover large space-bandwidth- product (SBP) and high-resolution (HR) object images. The FP has been considered to be promising in various computational imaging fields. However, the illumination-based FP is limited by strict requirements of the objects which must be thin and satisfy the one-to-one mapping relationship in the Fourier plane, and the aperture-scanning Fourier ptychography is also limited by the long-time scanning and stable scanning mechanical structures requirements even though it can achieve super-resolution macroscopic imaging. Furthermore, the position and shape of the scanning aperture must be accurately modeled for the reconstruction, otherwise false object images may be output. Herein, based on the 4-f optical correlator structure, we proposed a novel method, termed variable-aperture Fourier ptychography, for reconstructing HR images from series of LR images. The numerical simulations illustrated that the variable-aperture Fourier ptychography can use a small number of LR images to reconstruct the object images, The experiments demonstrated that a high-quality object image with better resolution and contrast than other schemes, include direct imaging based on 4-f system and aperture scanning FP, can be obtained by our method. Two additional experiments proved that it is almost unaffected by the position and shape of the apertures.

With a piece of far-field diffraction image, the purpose of reconstruction an object can be achieved by the Coherent Diffraction Imaging (CDI) method under some certain conditions. Practically, the far-field diffraction images captured by the optical system are not always matched well with the phase retrieval algorithms, which frequently leads to lower resolution of the reconstructed object image. However, we find that the gray distortion of the power spectrum has a great impact on the object reconstruction, and even a good phase retrieve algorithm can not reconstruct the object. Based on experiment and simulation results, we find that the spatial power spectrum pattern gray-level distortion has much influence on the CDI reconstruction, and the acquired pattern distortion rate should be less than 0.1. When the gray-level distortion is less than 0.1, clear object can be reconstructed in fewer iterations. The reconstruction algorithm is fault-tolerant to the distortion of power spectrum. The convergence speed of the algorithm can be accelerated through giving an upper bound of gray-level distortion. This result provides a reference for other researches in CDI to avoid the convergence stagnation caused by the distortion of spatial power spectrum collected by experiments.

Light sheet fluorescence microscopy (LSFM) is widely used in biological imaging because of its low photobleaching and phototoxicity. The axial resolution of LSFM is determined and also limited by the thickness of the light sheet and the numerical aperture (NA) of the detection objective. We propose a novel method, light sheet modulation fluorescence microscopy (LSMFM) which is able to achieve a promising axial resolution enhancement of light sheet microscopy.

The encoding aperture errors with different types and different degrees occurred during the process of encoding aperture by micro-Nano technology. The encoding aperture is a key component of the CSSI, and the analysis of errors in encoding aperture processing provides an important evidence for the CSSI. In this paper, based on the error occurring in the process of encoding aperture, the simulation is established by commercial software FDTD by which the optical field modulation of incident light in the CSSI system is analyzed by comparing the ideal encoding aperture and the error encoding aperture. The simulation results show that there is a significant difference in the optical intensity distribution of incident light modulated by a single error aperture and a single ideal aperture, the optical intensity distribution modulated by the ideal aperture has two distinct peaks at the aperture surface, and the optical intensity distribution modulated by the error aperture is approximately twice as large as by the ideal aperture; the optical intensity distribution modulated by the two type aperture has obvious peaks while leaving the aperture surface, and the optical intensity distribution modulated by the ideal aperture is approximately twice as large as by the error aperture; changing the number of pixels of the encoding aperture, the ideal encoding aperture and the error encoding aperture have little difference in modulation of the incident light; comparing the ideal aperture, as the increasing of the rounded radius of error aperture, the influence of the optical field distribution modulation becomes more obvious.

Outdoor imaging often suffers from the negative effects of the rain streaks, which would lead to the distortion of image contents. Most of the existing deraining approaches propose to build prior models to formulate the appearance of rain streaks and image features. However, these works deal with the rain streaks removal on the whole image regions. This may lead to the image regions without rain streaks distorted. In this paper, we proposed a new method for simultaneously investigating the candidates of rain streaks and image restoration. We use the L0 sparsity regularization for rain region estimation , and apply the framelet with L0 norm to protect the sharpen images. Our method only processes the regions with rain streaks and leaves other regions free. Experimental results demonstrate the effectiveness of our approach on rain streak removal and image restoration.

The optical integrated aperture imaging system arranges several small aperture optical elements according to a certain regular spatial position, and achieves common phase precision on the same focal plane by adjusting the optical path and matching the phase. It is 0.1λ precision. As a high-precision displacement adjustment device, stacked piezoelectric ceramics can realize displacement deformation in the micrometer direction in the longitudinal direction. In this paper, a piezoelectric ceramic tube is stacked and filled with a transparent liquid medium. A compact optical phase modulator is designed and the output is prepared. Using interferometer to detect phase and combined with optimized image processing technology, an optical phase detection method with an accuracy of 0.1λ is obtained, which provides a feasible reference scheme for optical synthetic aperture common phase adjustment.

A new frequency-shifting confocal microscopy (FSCM) illuminated by an azimuthally polarized Bessel-Gaussian (BG) beam is investigated. The solid excitation spot is produced by the BG beam modulated by a spiral phase plate, and the donut excitation spot is directly obtained by the same BG beam. Through vector diffraction theory and two-view RL reconstruction algorithm, the optical transfer functions of two confocal imaging modes and the simulation imaging of FSCM are presented. The results show that, two illumination modes produced by the azimuthally polarized BG beam can enhance the spatial resolution of FSCM, the spatial resolution of reconstructed image is mainly depended on the illumination mode with higher frequency transfer efficiency, the small pinhole is helpful to improve the contrast and spatial resolution of image. When the iterations number is about 100, the reconstructed image has good quality. This FSCM is helpful to quickly realize super resolution and high contrast in cell imaging.

Optical coherence tomography (OCT) is a new medical imaging technology that developed at the end of the 20th century after X-ray, computed tomography (CT), magnetic resonance imaging (MRI), and intravascular ultrasound (IVUS). It is called “optical biopsy” technology with the advantages of no radiation, simple structure and high resolution that can reach ten times that of IVUS. However, OCT also has the disadvantage of insufficient depth of detection that only a few millimeters and imaging speed. Even so, OCT can be used in combination with microscopes, medical catheters and endoscopes; therefore, it has broad application prospects in the field of biomedicine. The OCT system is simple in structure, mainly Michelson interferometer. Using the principle of optical coherence imaging, it detects the back-reflecting or scattering signals of incident light at different depths of biological tissue to obtain the surface and subsurface imaging of transparent or opaque substances. The combination of OCT and endoscopy extends the use of OCT to the diagnosis of cardiovascular diseases, which is called intravascular optical coherence tomography (IVOCT). It enables rapid visualization of microscopic images of vascular cross sections and is a powerful tool for clinical detection of coronary atherosclerosis, in which coronary artery calcification is a common problem in the clinic and is closely related to cardiovascular diseases. This review will briefly introduce the principle of OCT technology and its application in cardiovascular diseases, and focus on the research progress of detection of coronary artery calcification based on OCT technology.

Prostate cancer is one of the most common malignant tumors threatening male health. The important reason for high mortality rate of prostate cancer is the difficulty in early diagnosis. The nano-mechanical property of cells has been used as a useful index for early cancer diagnosis at single cell level. In this study, atomic force microscopy (AFM) was implemented to measure and compare the morphology and elasticity of different prostate cell lines, including normal cells (PZ-HPV-7) and cancer cells (PC-3). The results showed that the morphology of PZ-HPV-7 cell has a multiple-angle or other irregular shape and the cellular surface is smooth with fewer protrusions. While PC-3 cell has a spindle or spherical shape with more protrusions on the membrane. The average values of elasticity of PZ-HPV-7 and PC-3 cells were 2206.85±1084.99 Pa and 1226.19±520.36 Pa, respectively. And the average values of viscosity were 20.21 ± 4.96 Pa.s and 13.24 ± 4.52 Pa.s, respectively. We found that the elasticity and viscosity of PC-3 were significantly lower than those of PZ-HPV-7, suggesting that the prostate cancer cells are softer than the normal counterpart. It shows that the nanomechanical properties of cells may provide an early index at single cell level for prostate cancer early detection.

Space-time adaptive methods, and their expansion of the aspects of application and operation platform, are extending from the traditional space-time system design to the structured devices, augmented reality, virtual reality, artificial intelligence and open Internet and so on,based on the holographic beam tracing technology, the core technology system on real scene was built, which can not only provide realistic reappearance effect, but also confirmed a practical application.

Photonic nanojet (PNJ) is a tightly focused, non-resonant and spatially highly confined light beam that emerging on the shadow side surface of a light-illuminated lossless dielectric microparticle with a diameter comparable or slightly larger than the wavelength of the incident light. PNJ’s significant properties of subwavelength transverse beamwidth, high light intensity and propagation capability of extending evanescent field region make it get a lot of applications in a broad range of areas, such as optical signals enhancement, optical imaging, optical tweezers, optical data storage, optical waveguide, optical sensing, optical nanofabrication, optical switching, etc. The formation characteristics of the PNJ are depended on the geometrical morphologies and dielectric properties of the microparticles, the surrounding medium and the natures of illumination light. Over the past 15 years, PNJs generated from different structures (cylinder, sphere, ellipsoid, disk, cuboid, core-shell, multilayer, assembled nanofibles, etc.) were investigated. In this paper, a unique structure of D-shaped microfibers in terms of height (h_D), width of D-sector (w_D) and curvature radius (r_D), which can be fabricated through optical fiber polishing and optical fiber tapering techniques, was presented and studied with a finite-element- based numerical method. Three different cases of h_D < r_D, h_D = r_D, and h_D < r_D were chosen as typical research models. The PNJ parameters of focal distance, full-width at half-maximum, decay length and maximum light intensity with respect to the variations of widths of D-sector and rotation angles were systematically analyzed. The research results provide a good insight to develop optical microprobes and optical microlenses with long working distance.

We present a single-shot quantitative phase imaging (QPI) method based on color-multiplexed Fourier ptychographic microscopy (FPM). Three light-emitting diode (LED) elements with respective R/G/B channels in a programmable LED array illuminate the specimen simultaneously, providing triangle oblique illuminations matching the numerical aperture (NA) of the objective lens precisely. A single color image sensor records the light transmitted through the specimen, and three monochromatic intensity images at each color channel are then separated and utilized to recover the phase of the specimen. After one-step deconvolution based on the phase contrast transfer function, the obtained initial phase map is further refined by the FPM-based iterative recovery algorithm to overcome pixel-aliasing and improve the phase recovery accuracy. The high-speed, high- throughput QPI capabilities of the proposed approach are demonstrated by achieving a half-pitch resolution of 345 nm across a wide FOV of 1.33 mm² at camera-limited frame rates (50 fps).