Journal of The Optical Society of America A-optics Image Science and Vision最新文献

Following general single-channel optimization, input channels are typically treated as independent elements in the transmission matrix. This paper presents compelling evidence of a remarkable correlation between input channels due to the continuous distribution of optimal phase masks. This correlation challenges the previous notion that single-channel optimization is highly sensitive to wavefront changes, such that an obvious focal point still forms even when the optimal phase mask is completely refreshed. Further, this correlation significantly enhances the focus light intensity when the optimized wavefront is seriously impaired. The discovery of this correlation will offer new insights into the physics of a transmission matrix.

With employing strong chirality in an optical system, the direction of light propagation can be controlled and subwavelength particles can be detected. Here, we show that a different kind of chiral exceptional point (EP) with high (spatial) chirality can appear in a coupled resonator perturbed by nanoscatterers, in which both the distance and position of the scatterers can be tuned. We achieve strong chiral EP in two different distances between the resonators, with chirality around 0.99, in both cases. Besides, chiral EP associated with the higher harmonic whispering gallery mode is achieved, with chirality around 0.95. We also investigate the interaction of particles with same and different spin of light, which can mimic the spin-up and spin-down of electrons in quantum mechanics. The proposed device provides a tunable scheme to achieve high directionality of different cavity modes by incorporating one or more nanoscatterers. With incorporating more than one tunable mechanism such as nanoscatterers, nonlinearity, and time-modulation, simultaneously, the conventional limitations in chirality and sensitivity may be surpassed in the presence of unwanted imperfections of fabrication and noisy environment.

This paper presents a system for discriminating the verticality of nanohole sidewalls on dielectric substrates. The proposed system comprises optical filters and a compact neural network with only two input ports. The weak scattered field from the nanohole passes through the filters, and the neural network processes the intensity of the focused field. Numerical simulations demonstrate that this system achieves significantly lower error rates compared to conventional systems that use an optical microscope and a neural network. Additionally, we discuss the minimum aperture size of nanoholes that can be effectively discriminated.

In the assembly, launch, and on-orbit operation of satellite optical communication terminals, small deviations are difficult to avoid, which can lead to pointing errors and challenges to the establishment of optical communication links. To estimate the pointing errors of on-orbit satellite terminals, a calibration algorithm is developed based on lunar surface imagery. First, a feature extraction algorithm for low-light images is employed to process consecutive frames of low-light images to obtain a lunar surface feature map. Then, by combining the feature map and error estimation model, predictions of direction errors and zero errors were achieved. The ground validation results demonstrate the effectiveness and feasibility of the proposed on-orbit error estimation algorithm under low-signal-to-noise-ratio conditions.

Leveraging the polarization property of light to evaluate the birefringence of tissues as well as changes due to pathological conditions has been gaining interest over the past two decades with the introduction of different variants of optical coherence tomography (OCT) including polarization-sensitive OCT (PS-OCT) and cross-polarization OCT (CP-OCT). Because OCT sources are partially polarized, PS-OCT and CP-OCT generally require a linear polarizer and polarization-maintaining fibers to enable a linearly polarized input beam into the interferometer. While recent studies have suggested using an unpolarized input beam to reduce the system's complexity, the effect of unpolarized light on the point spread function (PSF) of OCT has not been fully studied. This work proposed a mathematical framework to evaluate the contribution of unpolarized light to the PSF of OCT. Simulation and experiments were performed for three OCT sources to assess the validity of the proposed model. Overall, simulations were in good agreement with experiments and revealed that unpolarized light introduced two additional reflectors into the reflectivity profile of the source, which were more pronounced in the cross-polarization configuration. This additional information can lead to misinterpretation of the birefringence of tissues in PS-OCT and CP-OCT. Their effect on image quality was evaluated in ex vivo corneal imaging of porcine eyeballs.

The use of ABCD (ray-transfer) matrices to analyze wave propagation through paraxial optical systems, with emphasis on imaging systems, is described. It is shown how to find the image, Fourier transform, and exit pupil planes. Different forms of the propagation integrals are given. The propagation integral for an imaging system, which includes an aperture stop, is derived. The relationships between the aperture stop and the exit pupil and the impulse response of a paraxial imaging system are derived.

The visualization and tracking of adipocytes and their lipid droplets (LDs) during differentiation are pivotal in developmental biology and regenerative medicine studies. Traditional staining or labeling methods, however, pose significant challenges due to their labor-intensive sample preparation, potential disruption of intrinsic cellular physiology, and limited observation timeframe. This study introduces a novel method for long-term visualization and quantification of biophysical parameters of LDs in unlabeled adipocytes, utilizing the refractive index (RI) distributions of LDs and cells. We employ low-coherence holotomography (HT) to systematically investigate and quantitatively analyze the 42-day redifferentiation process of fat cells into adipocytes. This technique yields three-dimensional, high-resolution refractive tomograms of adipocytes, enabling precise segmentation of LDs based on their elevated RI values. Subsequent automated analysis quantifies the mean concentration, volume, projected area, and dry mass of individual LDs, revealing a gradual increase corresponding with adipocyte maturation. Our findings demonstrate that HT is a potent tool for non-invasively monitoring live adipocyte differentiation and analyzing LD accumulation. This study, therefore, offers valuable insights into adipogenesis and lipid research, establishing HT and image-based analysis as a promising approach in these fields.

We developed a new method to enhance the resolution of blood platelet aggregates imaged via quantitative phase imaging (QPI) using a Pix2Pix generative adversarial network (GAN). First, 1 µm polystyrene beads were imaged with low- and high-resolution QPI, to train the GAN model and validate its applicability. Testing on the polystyrene beads demonstrated a mean error of 4.14% in the generated high-resolution optical-path-delay values compared to the optically acquired ones. Next, blood platelets were collected with low- and high-resolution QPI, and a deep neural network was trained to predict the high-resolution platelet optical-path-delay profiles using the low-resolution profiles, achieving a mean error of 7.01% in the generated high-resolution optical-path-delay values compared to the optically acquired ones. These results highlight the potential of the method in enhancing QPI resolution of cell aggregates without the need for sophisticated optical equipment and optical system modifications for high-resolution microscopy, allowing for better understanding of platelet-related disorders and conditions such as thrombocytopenia and thrombocytosis.

This paper serves as part II of a two-part tutorial on "aero-optical effects." In part I, we provide introductory material with an emphasis on system-level considerations, particularly for those who are new to the field of aero-optics. In part II, we move on to survey several sources of aberrations. For example, we cover foundational sources like boundary layers and shear layers, as well as miscellaneous sources like mechanical contamination, shock waves, and aero acoustics. Throughout part II, we emphasize drivers for system-level performance, which appropriately builds on the system-level considerations covered in part I. This emphasis will inform future efforts looking to develop airborne-laser systems flying at subsonic, supersonic, and hypersonic speeds.

Quantitative phase imaging (QPI) has emerged as a powerful tool in label-free bioimaging, in situ microstructure characterization for advanced manufacturing, and high-speed imaging of material property changes. Among various QPI methods, quadri-wave lateral shearing interferometry (QWLSI) stands out for its unique advantages in compactness, robustness, and high temporal resolution, making it an ideal choice for a wide range of applications. The compact design of QWLSI allows for easy integration with existing microscopy systems, while its robustness is manifested in the ability to maintain precise interferometric sensitivity even in high-vibration environments. Moreover, QWLSI also enables single-shot measurements that facilitate the capture of fast dynamic processes. This paper provides an in-depth exploration of the technical aspects of QWLSI, focusing on the evolution of its optical system and the primary algorithms used in wavefront reconstruction. The review also showcases significant applications of QWLSI, with a particular emphasis on its contributions to biomedical imaging. By discussing the advantages, limitations, and potential future developments of QWLSI, this paper aims to provide a comprehensive overview of this powerful QPI technique and its impact on various research fields.