Design Simulation of Czerny–Turner Configuration-Based Raman Spectrometer Using Physical Optics Propagation Algorithm

We report the design simulation of the Raman spectrometer using Zemax optical system design software. The design is based on the Czerny–Turner configuration, which includes an optical system consisting of an entrance slit, two concave mirrors, reflecting type diffraction grating and an image detector. The system’s modeling approach is suggested by introducing the corresponding relationship between detector pixels and wavelength, linear CCD receiving surface length and image surface dimension. The simulations were carried out using the POP (physical optics propagation) algorithm. Spot diagram, relative illumination, irradiance plot, modulation transfer function (MTF), geometric and encircled energy were simulated for designing the Raman spectrometer. The simulation results of the Raman spectrometer using a 527 nm wavelength laser as an excitation light source are presented. The present optical system was designed in sequential mode and a Raman spectrum was observed from 530 nm to 630 nm. The analysis shows that the system’s image efficiency was quite good, predicting that it could build an efficient and cost-effective Raman spectrometer for optical diagnostics.

FL-MISR: fast large-scale multi-image super-resolution for computed tomography based on multi-GPU acceleration

Multi-image super-resolution (MISR) usually outperforms single-image super-resolution (SISR) under a proper inter-image alignment by explicitly exploiting the inter-image correlation. However, the large computational demand encumbers the deployment of MISR in practice. In this work, we propose a distributed optimization framework based on data parallelism for fast large-scale MISR using multi-GPU acceleration named FL-MISR. The scaled conjugate gradient (SCG) algorithm is applied to the distributed subfunctions and the local SCG variables are communicated to synchronize the convergence rate over multi-GPU systems towards a consistent convergence. Furthermore, an inner-outer border exchange scheme is performed to obviate the border effect between neighboring GPUs. The proposed FL-MISR is applied to the computed tomography (CT) system by super-resolving the projections acquired by subpixel detector shift. The SR reconstruction is performed on the fly during the CT acquisition such that no additional computation time is introduced. FL-MISR is extensively evaluated from different aspects and experimental results demonstrate that FL-MISR effectively improves the spatial resolution of CT systems in modulation transfer function (MTF) and visual perception. Comparing to a multi-core CPU implementation, FL-MISR achieves a more than 50$$\times$$ × speedup on an off-the-shelf 4-GPU system.

Evaluation of optical quality in pterygium patients with a new modified sutureless and glue-free method

Background Modified sutureless and glue-free method is an effective and novel surgical approach for pterygium. We aim to evaluate optical quality in pterygium treated with the new method and investigate the clinical application of the Optical Quality Analysis System (OQAS) and Anterior segment optical coherence tomography (AS-OCT) to evaluate the pterygium surgery. Methods A total of 52 eyes of 52 patients with pterygium were randomly divided into 2 groups. After surgical excision, the bare sclera was placed with a tight fit limbal conjunctival autograft fixed via the modified sutureless and glue-free method in group 1 (26 eyes) and conventional sutures in group 2 (26 eyes). Objective scattering index (OSI), modulation transfer function (MTF) and Strehl ratio (SR) were measured using OQAS in both groups during the perioperative period. Pterygium diameter was measured on AS-OCT. Ocular surface disease index (OSDI) questionnaire also was used. Results The group 1 had significantly lower mean OSI, higher mean MTF, and higher mean SR at 1 month and 3 months after surgery (p < 0.05). The group 1 had significantly lower mean OSDI at 1 month (p < 0.05), while was similar to group 2 at 3 months (p > 0.05). Pterygium diameter positively correlated with OSI (r = 0.528, p < 0.001), while it negatively correlated with MTF (r = − 0.501, p < 0.001) and SR (r = − 0.174, p = 0.217) before operation. Conclusions The modified sutureless and glue-free method might be more advantageous in improving the optical quality during early postoperative recovery times and pterygium diameter affected optical quality. OQAS can be reliably used to evaluate postoperative outcomes.

2D perovskite-based high spatial resolution X-ray detectors

X-ray radiography is the most widely used imaging technique with applications encompassing medical and industrial imaging, homeland security, and materials research. Although a significant amount of research and development has gone into improving the spatial resolution of the current state-of-the-art indirect X-ray detectors, it is still limited by the detector thickness and microcolumnar structure quality. This paper demonstrates high spatial resolution X-ray imaging with solution-processable two-dimensional hybrid perovskite single-crystal scintillators grown inside microcapillary channels as small as 20 µm. These highly scalable non-hygroscopic detectors demonstrate excellent spatial resolution similar to the direct X-ray detectors. X-ray imaging results of a camera constructed using this scintillator show Modulation Transfer Function values significantly better than the current state-of-the-art X-ray detectors. These structured detectors open up a new era of low-cost large-area ultrahigh spatial resolution high frame rate X-ray imaging with numerous applications.

Comparison of Objective and Subjective Visual Quality Following LASEK, FS-LASIK and SMILE for Different Myopic Corrections: A Prospective Study

Background: To investigate the differences in visual quality after laser epithelial keratomileusis (LASEK), femtosecond laser in situ keratomileusis (FS-LASIK) and small-incision lenticule extraction (SMILE) in different degrees of myopia.Methods: This prospective study incorporated 200 consecutive myopic subjects (200 eyes). Myopia was subdivided into 3 levels based on the preoperative spherical equivalent (SE) value: low myopia (SE ≥ -3.0 D), moderate myopia (−3.0 D > SE ≥ −6.0 D), and high myopia (SE < −6.0 D). Visual quality was recorded and analyzed both objectively using the Optical Quality Analysis System II (OQAS II), and subjectively with uncorrected distance visual acuity (UDVA) and a questionnaire, preoperatively, 1 month and 6 months postoperatively. Results: Six months after LASEK, FS-LASIK and SMILE in myopia, the logarithm of the minimum angle of resolution (LogMAR) UDVA statistically decreased compared with preoperative values (all P < 0.001). While preoperatively, in three surgical procedure groups, objective visual quality parameters demonstrated no significant difference among three degrees of myopia (all P > 0.05), at 6 months postoperatively, after FS-LASIK and SMILE, the modulation transfer function (MTF) cutoff frequency in low myopia was significantly higher than that in high myopia (both P < 0.05). Moreover, intergroup differences in LASEK, FS-LASIK and SMILE groups were not statistically significant, before and 6 months after surgery (all P > 0.05), except that FS-LASIK provided a significantly higher preoperative LogMAR UDVA than SMILE in high myopia (P < 0.05).Conclusion: LASEK, FS-LASIK and SMILE could achieve similar improvement in visual quality to each other after myopia correction. Low myopic patients may achieve better postoperative visual quality after FS-LASIK and SMILE than high myopic patients.Trial registration: This is a prospective study. The study followed the Declaration of Helsinki and was approved by the Institutional Review Board of the Second People’s Hospital of Yunnan Province.