Jiahui Wang

Three-dimensional (3D) microscopic imaging is indispensable for fundamental scientific research and clinical medical diagnosis. Given that conventional widefield optical microscopy and standard confocal microscopy fail to realize high-magnification, full-color, real-time stereoscopic imaging simultaneously, we herein propose a single-optical-path 3D microscopic framework enabled by liquid crystal polarization gratings (LCPGs). The LCPG integrated at the sample plane performs polarization-dependent beam splitting to generate paired left and right viewing channels. These two disparity-bearing view channels share a unified imaging optical path compatible with commercial upright microscopes, wherein an active liquid crystal cell modulates temporal view switching for sequential camera acquisition. We further construct a white-light microscopic platform supporting integrated reflection and transmission imaging modes. Two customized LCPGs with lattice periods of 72.6 μm and 56.9 μm are fabricated, offering angular view separations of 0.84° and 1.07°, respectively. Both gratings achieve ±1st-order diffraction efficiencies above 97% with polarization crosstalk not exceeding 0.8%. The developed system acquires paired left-right images with valid binocular disparity, which can be reconstructed into intuitive stereoscopic perceptions via a 3D display monitor. This LCPG-based optical architecture upgrades standard upright microscopes to compact dual-view stereoscopic imaging systems, while fully inheriting the native merits of white-light illumination and high-magnification microscopic observation.

Corner detection is responsible for accurate camera calibration, which is an essential task for binocular three-dimensional (3D) reconstruction. In microscopic scenes, binocular 3D reconstruction has significant potential to achieve fast and accurate measurements. However, traditional corner detectors and calibration patterns (checkerboard) performed poorly in microscopic scenes due to the non-uniform illumination and the shallow depth of field of the microscope. In this paper, we present a novel method for detecting grid junction corners based on image segmentation, offering a robust alternative to the traditional checkerboard pattern. Model fitting was utilized to obtain the coordinates at a sub-pixel level. The procedures of the proposed method were elaborated, including image segmentation, corner prediction, and model fitting. The mathematical model was established to describe the grid junction. The experiment was conducted using both synthetic and real data and the experimental result shows that this method achieves high precision and is robust to image blurring, indicating this method is suitable for microscope camera calibration.

Super multi-view (SMV) display is a promising 3D display technology; however, potential frame loss due to bandwidth-limited video transmission could cause discomfort to viewers. Thus, an evaluation of the acceptable viewing experience will be valuable. This study investigates the effects of frame loss on visual fatigue in SMV display, focusing on quantified frame loss rates and varying frame loss modes. Experiments were conducted with 20 subjects, utilizing the Stroop test through an SMV display system to evaluate the visual fatigue under different frame loss conditions. The results show a rise in visual fatigue as the frame loss rate increases, with two critical thresholds identified. A 4% frame loss rate marks the threshold for significant loss-induced differences, beyond which visual fatigue begins to become significant in loss-induced modes compared to the normal loss-free mode. Subsequently, a 10% frame loss rate marks the threshold for significant mode-dependent differences, beyond which variations appear between different loss-induced modes, with monocular mode inducing more visual fatigue than binocular and dual-view more than single-view. Consequently, the findings advocate for refining the 3D video processing to maintain a frame loss rate below 4% for negligible effect and considering the interactions between different views for less visual fatigue. This research aims to provide insights and guidance for addressing potential challenges in developing and applying SMV display technology.

The densification of a point cloud is a crucial challenge in visual applications, particularly when estimating a complete and dense point cloud from a local and incomplete one. This paper introduces a point cloud completion network named FuNet to address this issue. Current point cloud completion networks adopt various methodologies, including point-based processing and convolution-based processing. Unlike traditional shape completion approaches, FuNet combines point-based processing and convolution-based processing to extract their features, and fuses them through an attention module to generate a complete point cloud from 1024 points to 16,384 points. The experimental results show that when comparing the optimal completion networks, FuNet decreases the CD by 5.17% and increases the F-score by 4.75% on the ShapeNet dataset. In addition, FuNet achieves better results in most categories on a small sample dataset.

Autostereoscopy is usually perceived at finite viewpoints that result from the separated pixel array of a display system. With directionally illuminated autostereoscopy, the separation of the illumination channel from the image channel provides extra flexibility in optimizing the performance of autostereoscopy. This work demonstrates that by taking advantage of illumination freedom, seamless viewpoints in the sweet viewing region, where the ghosting does not cause significant discomfort, are realized. This realization is based on illuminating the screen with a polyline array of light emitting diodes (LEDs), and continuous viewpoints are generated through independent variation in the radiance of each individual LED column. This new method is implemented in the directionally illuminated display for both single and multiple viewers, proving its effectiveness as a valuable technique for achieving a high-quality and high-resolution autostereoscopic display with seamless viewpoints.

Light scattering is a common physical phenomenon in nature. The scattering medium will randomly change the direction of incident light propagation, making it difficult for traditional optical imaging methods to detect objects behind the scattering body. Wiener filtering deconvolution technology based on the optical memory effect has broad application prospects by virtue of its advantages, such as fast calculation speed and low cost. However, this method requires manual parameter adjustment, which is inefficient and cannot deal with the impact of real-scene noise. This paper proposes an improved Wiener filtering deconvolution method that improves the exposure dose during the speckle collection, can quickly obtain the optimal parameter during the calculation phase, and can be completed within 41.5 ms (for a 2448 × 2048 image). In addition, a neural network denoising model was proposed to address the noise issue in the deconvolution recovery results, resulting in an average improvement of 27.3% and 186.7% in PSNR and SSIM of the images, respectively. The work of this paper will play a role in achieving real-time high-quality imaging of scattering media and be helpful in studying the physical mechanisms of scattering imaging.

Peripheral retinal imaging is a unique approach for assessing and monitoring ocular diseases. In this paper, we proposed a design for an optical coherence tomography system to accomplish ultrawide field (>120°) retinal imaging without montages. Scanning of the sample arm was achieved via two ellipsoidal mirrors. The optical design software Zemax and an eye model were used to estimate the inherent aberrations in the system and the optical performance of retinal imaging. Simulation results of the aberrations in the designed system indicated that the designed system can achieve an unprecedented imaging field of view (FOV) while maintaining acceptable resolution without sacrificing the working distance. This work suggests that ultrawide field optical coherence tomography retinal imaging is achievable, which is highly important for the diagnosis and treatment of ocular—especially peripheral—retinopathy.

We report a corrugated structure to effectively extract the surface plasmon polaritons (SPP) and waveguiding modes in organic light-emitting diodes (OLEDs). This structure is formed by nano-imprint of blazed gratings. To study the optimum extraction condition in terms of grating pitches, we compare the light extraction efficiency of corrugated OLEDs with three kinds of pitches, showing a 42.00% external quantum efficiency (EQE) enhancement ratio with this internal structure. Due to the transfer of SPP and waveguiding modes into substrate mode, the EQE enhancement ratio can be further pushed to 103.02% by attaching a macrolens. The simulation verifies the experimental results and shows the extraction mechanism of the corrugated structure towards transverse electric (TE) and transverse magnetic (TM) waves. We foresee that this method is able to enhance the optical efficiency of devices for both mass-production OLED lighting and display in a cost-effective way.

We simulate a c-Si based planar metalens which enables circularly polarized Gaussian light to efficiently focus. By assembling metalens with the optical fiber, a novel fiber optical tweezers is designed with high optical efficiency.