Enhanced Seamless Video Fusion: A Convolutional Pyramid-Based 3D Integration Algorithm.

Video fusion aims to synthesize video footage from different sources into a unified, coherent output. It plays a key role in areas such as video editing and special effects production. The challenge is to ensure the quality and naturalness of synthetic video, especially when dealing with footage of different sources and qualities. Researchers continue to strive to optimize algorithms to adapt to a variety of complex application scenarios and improve the effectiveness and applicability of video fusion. We introduce an algorithm based on a convolution pyramid and propose a 3D video fusion algorithm that looks for the potential function closest to the gradient field in the least square sense. The 3D Poisson equation is solved to realize seamless video editing. This algorithm uses a multi-scale method and wavelet transform to approximate linear time. Through numerical optimization, a small core is designed to deal with large target filters, and multi-scale transformation analysis and synthesis are realized. In terms of seamless video fusion, it shows better performance than existing algorithms. Compared with editing multiple 2D images into video after Poisson fusion, the video quality produced by this method is very close, and the computing speed of the video fusion is improved to a certain extent.

Defect detection and response non-uniformity correction of a monocentric camera based on fiber optic relay imaging.

The monocentric camera based on fiber relay imaging offers benefits of light weight, compact size envelope, vast field of view, and high resolution, which can fully fulfill the index requirements of space-based surveillance systems. However, the fiber optic plate's (FOP) defects will result in the loss of imaging data, and the FOP's discrete structural features will exacerbate the imaging's non-uniformity. A global defect detection approach based on manual threshold segmentation of saturated frames is suggested to detect FOP defect features. The suggested method's efficacy and accuracy are confirmed when compared to the classical Otsu algorithm. Additionally, through tests, the relative imaging response coefficients of each pixel are identified, the response non-uniformity of the pixels is corrected, and the whole image non-uniformity drops from 10.01% to 0.78%. The study in this paper expedites the use of fiber relay imaging-based monocentric cameras in the field of space-based surveillance, and the technique described in this paper is also appropriate for large-array optical fiber coupled relay image transmission systems.

Real-time on-orbit image quality improvement for a wide-field imaging system with detector arrays.

Wide-field imaging systems are faced with the problem of massive image information processing and transmission. Due to the limitation of data bandwidth and other factors, it is difficult for the current technology to process and transmit massive images in real-time. With the requirement for fast response, the demand for real-time on-orbit image processing is increasing. In practice, nonuniformity correction is an important preprocessing step to improve the quality of surveillance images. This paper presents a new real-time on-orbit nonuniform background correction method, which only uses the local pixels of a single row output in real-time, breaking the dependence of the traditional algorithm on the whole image information. Combined with the FPGA pipeline design, when the local pixels of a single row are read out, the processing is completed, and no cache is required at all, which saves the resource overhead in hardware design. It achieves microsecond-level ultra-low latency. The experimental results show that under the influence of strong stray light and strong dark current, our real-time algorithm has a better image quality improvement effect compared with the traditional algorithm. It will greatly help the on-orbit real-time moving target recognition and tracking.

Polarimetric calibration method for the fore-optics of a channeled spectropolarimeter.

A channeled spectropolarimeter is a powerful tool for the simultaneous measurement of the intensity, spectral, and polarization information of a target. However, the fore-optics introduce additional polarization information, which leads to inaccurate reconstruction of the Stokes parameters. In this study, we propose a simple method for polarimetric calibration and Stokes parameters reconstruction for a fieldable channeled spectropolarimeter. The polarization effects of the fore-optics and phase factors of the high-order retarders at varying view angles are considered and calibrated independently using a single reference beam. Moreover, the misalignment of the retarders is also considered. Simulation results demonstrate that the polarization effects of fore-optics can be precisely determined, enhancing the measurement accuracy of the Stokes parameters by approximately an order of magnitude. The effectiveness of the proposed method is also verified experimentally.

In-Orbit Calibration of Phase Retardance for Channeled Spectropolarimeter.

The phase retardance of the optical system (PROS) is a crucial factor limiting the accuracy of the Stokes vector reconstruction for the channeled spectropolarimeter. The dependence on reference light with a specific angle of polarization (AOP) and the sensitivity to environmental disturbance brings challenges to the in-orbit calibration of PROS. In this work, we propose an instant calibration scheme with a simple program. A function with a monitoring role is constructed to precisely acquire a reference beam with a specific AOP. Combined with numerical analysis, high-precision calibration without the onboard calibrator is realized. The simulation and experiments prove the effectiveness and anti-interference characteristics of the scheme. Our research under the framework of fieldable channeled spectropolarimeter shows that the reconstruction accuracy of S2 and S3 in the whole wavenumber domain are 7.2 × 10-3 and 3.3 × 10-3, respectively. The highlight of the scheme is to simplify the calibration program and ensure that the PROS high-precision calibration is not disturbed by the orbital environment.

Channeled spectropolarimeter with arbitrary retarder orientation settings.

A channeled spectropolarimeter can simultaneously obtain intensity, spectral, and polarization information. In the traditional model, the retarders must be oriented at specific angles. However, misalignments of the retarders are inevitable during assembly, and the status of the retarders is sensitive to environmental perturbations, which affects the performance of the channeled spectropolarimeter. In this study, a general channeled spectropolarimeter model was derived, in which the retarder orientations can be arbitrary and unknown. Meanwhile, the system is unaffected by environmental perturbation because it can self-calibrate to avoid fluctuations in the retarder orientations and phase retardations. The effectiveness and robustness of the model were verified through simulations and experiments.

Torque Ripple Suppression of Brushless DC Motor Drive System Based on Improved Harmonic Injection Active Disturbance Rejection Control.

The positioning accuracy and speed stability of the brushless DC motor (BLDC motor), as the drive element of the optomechanically scanned system (OMSS), are closely interrelated to the final imaging quality of the system. Active disturbance rejection control (ADRC) with strong anti-interference ability, fast response and good robustness is one of the extensively used control strategies. However, the performance of ADRC working in a complicated environment will be limited due to the controller structure, parameter tuning and the influence of multi-source nonlinear disturbance. Therefore, an improved ADRC method is proposed, which can switch between 'point-to-point control mode' and 'stable speed control mode' according to the system requirements. To further suppress the torque ripple and improve the control performance of the system, an improved harmonic injection scheme is added, and the parameters of improved ADRC are tuned by a slime mould algorithm based on a Levy flight operator (LF-SMA). The stability of the proposed ADRC is proved by Lyapunov stability theory. The experimental results show that the proposed control scheme could be available to reduce the torque ripple of the system.

Spatially modulated snapshot computed tomographic polarization imaging spectrometer.

Herein, a spatially modulated snapshot computed tomographic polarization imaging spectrometer (SMSCTPIS) is proposed. This instrument can obtain spatial, intensity, and polarization information of different wavelengths of a target simultaneously. It can also alleviate certain limitations of the spatially modulated snapshot imaging polarimeter (SMSIP) based on a Savart polarizer, which cannot obtain information of different wavelengths in a single measurement. Further, it can also mitigate the need to frequently replace the filters of SMSIPs for different detection wavelengths. The paper introduces the structure and principle of the SMCTPIS first, followed by experiments confirming its accuracy. Finally, the experimental results are analyzed, and conclusions are drawn.

Postoperative hydrocephalus is a high-risk lethal factor for patients with low-grade optic pathway glioma.

OBJECTIVES: To explore the prognostic factors of patients with low-grade optic pathway glioma (OPG) and the optimal treatment to reduce the incidence of postoperative hydrocephalus. PATIENTS AND METHODS: This single-center study retrospectively analyzed data from 66 patients with OPGs who underwent surgery. The patients were followed, and overall survival (OS) and progression-free survival (PFS) were determined. The effects of different treatments on the hydrocephalus of patients were compared. RESULTS: Postoperative hydrocephalus was identified as a factor to increase the risk of mortality by 1.99-fold (p = .028). And, 5-year survival rate was significantly lower among patients with postoperative hydrocephalus (p = .027). The main factors leading to preoperative hydrocephalus in patients are large tumor volume and invasion into the third ventricle. Gross total resections (GTR) could reduce the risk of long-term hydrocephalus (p = .046). Age younger than 4 years (p = .046) and tumor invasion range/classification (p = .029) are the main factors to reduce the five-year survival rate. Postoperative radiotherapy (RT) and chemotherapy (CT) had no significant effects on OS. Extraventricular drainage (EVD) was not associated with perioperative infection (p = .798 > .05) and bleeding (p = .09 > .05). Compared with 2 stage surgery (external ventricular drainage or ventriculoperitoneal shunt (VPS) was first placed, followed by tumor resection), 1 stage surgery (direct resection of tumor) had no complication increase. CONCLUSIONS: Postoperative hydrocephalus is mostly obstructive hydrocephalus, and it is an important factor that reduces the OS of patients with low-grade OPGs. Surgery to remove the tumor to the greatest extent improves cerebrospinal fluid circulation is effective at reducing the incidence postoperative hydrocephalus. For patients whose ventricles are still dilated after surgery, in addition to considering poor ventricular compliance, they need to be aware of the persistence and progression of hydrocephalus.

LTBP1 plays a potential bridge between depressive disorder and glioblastoma.

BACKGROUND: Glioblastoma multiforme (GBM) is the most malignant tumor in human brain. Diagnosis and treatment of GBM may lead to psychological disorders such as depressive and anxiety disorders. There was no research focusing on the correlation between depressive/anxiety disorder and the outcome of GBM. Thus, the aim of this study was to investigate the possibility of depressive/anxiety disorder correlated with the outcome of GBM patients, as well as the overlapped mechanism bridge which could link depressive/anxiety disorders and GBM. METHODS: Patient Health Questionnaire (PHQ-9) and Generalized Anxiety Disorder (GAD-7) were used to investigate the psychological condition of GBM patients in our department. To further explore the potential mechanism, bioinformatic methods were used to screen out genes that could be indicators of outcome in GBM, followed by gene ontology (GO) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, and protein-protein interaction (PPI) analysis. Further, cellular experiments were conducted to evaluate the proliferation, migration capacity of primary GBM cells from the patients. RESULTS: It was revealed that patients with higher PHQ-9 and GAD-7 scores had significantly worse prognosis than their lower-scored counterparts. Bioinformatic mining revealed that LTBP1 could be a potential genetic mechanism in both depressive/anxiety disorder and GBM. Primary GBM cells with different expression level of LTBP1 should significantly different proliferation and migration capacity. GO, KEGG analysis confirmed that extracellular matrix (ECM) was the most enriched function of LTBP1. PPI network showed the interaction of proteins altered by LTBP1. Hub genes COL1A2, COL5A1 and COL10A1, as well as mesenchymal marker CD44 and Vimentin were statistically higher expressed in LTBP1 high group; while proneural marker E-cadherin was significantly higher expressed in low LTBP1 group. CONCLUSION: There is closely correlation between depressive/anxiety disorders and GBM. LTBP1 could be a potential bridge linking the two diseases through the regulation of ECM.

Correction to: LTBP1 plays a potential bridge between depressive disorder and glioblastoma.

An amendment to this paper has been published and can be accessed via the original article.

Optical system optimization method for as-built performance based on nodal aberration theory.

The traditional optical design process isolates the two steps of system performance optimization and tolerance allocation, making it difficult to achieve optimal design of as-built performance. To solve this problem, this paper proposes an analytical method for optimizing the as-built performance of optical systems. The method uses the nodal aberration theory to derive the wavefront aberration estimated value under the given surface decenter and tilt tolerance, and establishes the optical system as-built performance evaluation model. The as-built performance evaluation does not require a large amount of ray tracing, which can be completed only by tracking the paraxial marginal ray and the principal ray, and the calculation amount is small. The as-built performance evaluation model can be directly used as error function in optical design software for optical system optimization. A Cooke triplet system is taken as an example to compare the as-built performance optimization method, Code V and Zemax OpticStudio's built-in optimization methods and the traditional method which optimizes only nominal performance by Monte-Carlo tolerance analysis.

Spatially modulated snapshot imaging polarimeter using two Savart polariscopes.

We present a spatially modulated snapshot imaging polarimeter using two Savart polariscopes (SMSIPTS). Not only can it avoid alignment angle errors and additional phase errors of a half-wave plate (HWP), it can also avoid changing the HWP frequently when we want the target polarization state at different wavelengths and can increase some channel bandwidth to improve image quality, compared with a spatially modulated snapshot imaging polarimeter (SMSIP). The alignment angle error and additional phase errors of SMSIP and the optical layout and principle of SMSIPTS are derived first. The full Stokes polarization images can be obtained by processing the interferogram. Based on SMSIPTS, we determine the filtering method by simulation. We proved the feasibility of SMSIPTS, and the effect of SMSIPTS and SMSIP on reconstruction is compared by simulation. Last, we experimentally verified the feasibility of the theory of SMSIPTS.

Stray light nonuniform background correction for a wide-field surveillance system.

Wide field and a long exposure time can effectively improve the ability of a space surveillance telescope to detect faint space targets. However, such systems are very susceptible to stray light. A stray light nonuniform background will cause great interference to subsequent target recognition, resulting in a large number of false alarms. This study presents an accurate and robust correction algorithm, called the improved new top-hat transformation (INTHT), for a stray light nonuniform background. First, we analyzed the formation mechanism and influence of the stray light nonuniform background. Then, to retrieve the lost targets, the size relationship of the two different, but related, structural operators is changed so the sizes of two structural operators are not equal. Finally, before comparing to the original image to take the minimum value, we added an expansion operation to restore the background size transformation caused by the different sizes of the structural operators in the previous step. This will ensure that there is no residual stray light nonuniform background. We believe, to the best of our knowledge, that the experimental results for the real captured image datasets demonstrate that, compared to other algorithms, the proposed INTHT algorithm has a higher accuracy and effectiveness in correcting a stray light nonuniform background.

Optical axis maladjustment sensitivity in a triangular ring resonator.

This paper estimates and measures the influences of mismatch and misalignment on continuous-wave cavity ring-down spectroscopy. We describe the theoretical differences in maladjustment effects on power transfer under different resonant cavity configurations and present a method for reducing the impact of maladjustment. Finally, we demonstrate a method for measuring the effect of maladjustment on power transfer when a Gaussian beam is matched to a triangular ring resonator.

Development of space active optics for a whiffletree supported mirror.

The requirements of a lightweight primary mirror for large-aperture space telescopes include a precise mirror figure and high reliability. However, lightweight mirrors are easily affected by environmental disturbances, as they lack structural stability and rigidity. Active optics can be used to compensate for the gravity-induced deformation and correct low-order aberrations due to thermal changes and gravity relief during observing periods. Due to their complexity, active optics have been rarely used in space. To validate the technology of space active optics, an active optics system based on a passive, whiffletree-supported mirror is developed. During integration and testing on ground and under normal conditions in space, the surface accuracy is guaranteed by passive support. Within this hybrid support, the active optics system only serves to assist support. This paper focuses on the compatibility between a passive multisupporting system and active optics. We present the prototype of a 0.676 m diameter passive supported lightweight mirror and active support with nine axial force actuators. The passive support includes a 9-point axial support and three A-frame lateral support. The active actuator distribution has been optimized with finite element analysis and its experimental performance characterized in representative conditions. The effectiveness of the hybrid passive-active support developed has been verified.

Comparative toxicity and contrast enhancing assessments of Gd2O3@BSA and MnO2@BSA nanoparticles for MR imaging of brain glioma.

The albumin-templated Gd2O3 and MnO2 nanoparticles (NPs) have been developed as a new type of magnetic resonance (MR) T1 contrast agents. However, their potential toxicity and applicability for MR imaging of brain gliomas has not been fully explored so far. In this study, we prepared Gd2O3@BSA and MnO2@BSA nanoparticles (NPs) and investigated their toxicity comprehensively and comparatively by H&E staining, blood biochemical analysis, and adverse outcome pathways testing. It is revealed that both Gd2O3@BSA and MnO2@BSA NPs are biocompatible at a rational dose level. Although the relaxivity of MnO2@BSA NPs is less than that of Gd2O3@BSA NPs, the MnO2@BSA NPs lead to a greater contrast enhancement in the brain glioma due to the controlled release of Mn ions under the acidic tumor microenvironmental conditions. These comparative toxicity and contrast enhancement data are of fundamental importance for the clinical translation of Gd2O3@BSA and MnO2@BSA NPs as MR contrast agents for brain glioma diagnosis.

Molecular and clinical characterization of PTPN2 expression from RNA-seq data of 996 brain gliomas.

BACKGROUND: Immune checkpoint inhibitors have been shown to promote antitumor immunity and achieve durable tumor remissions. However, certain tumors are refractory to current immunotherapy. These negative results encouraged us to uncover other therapeutic targets and strategies. PTPN2 (protein tyrosine phosphatase, non-receptor type 2) has been newly identified as an immunotherapy target. Loss of PTPN2 sensitizes the tumor to immunotherapy via IFNγ signaling. METHODS: Here, we investigated the relationship between PTPN2 mRNA levels and clinical characteristics in gliomas. RNA-seq data of a cohort of 325 patients with glioma were available from the Chinese Glioma Genome Atlas and 671 from The Cancer Genome Atlas. R language, GraphPad Prism 5, and SPSS 22.0 were used to analyze data and draw figures. RESULTS: PTPN2 transcript levels increased significantly with higher grades of glioma and in isocitrate dehydrogenase (IDH) wild-type and mesenchymal subtype gliomas. A comprehensive biological analysis was conducted, which indicated a crucial role of PTPN2 in the immune and inflammation responses in gliomas. Specifically, PTPN2 was positively associated with HCK, LCK, MHC II, and STAT1 but negatively related to IgG and interferon. Moreover, canonical correlation analysis showed a positive correlation of PTPN2 with infiltrating immune cells, such as macrophages, neutrophils, and CD8+ T cells. Clinically, higher levels of PTPN2 were associated with a worse overall survival both in patients with gliomas and glioblastomas. CONCLUSION: PTPN2 expression level was increased in glioblastomas and associated with gliomas of the IDH wild-type and mesenchymal subtype. There was a close correlation between PTPN2 and the immune response and inflammatory activity in gliomas. Our results show that PTPN2 is a promising immunotherapy target and may provide additional treatment strategies.

Aberration fields of off-axis astronomical telescopes induced by rotational misalignments.

Due to the absence of rotational symmetry, off-axis astronomical telescopes with off-set pupil become subject to rotational misalignments. Rotational misalignments of large off-axis mirrors with reference to their geometric center can greatly degrade the imaging quality. This paper presents an in-depth discussion on the net aberration fields of off-axis astronomical telescopes induced by rotational misalignments. Aberration function of off-axis telescopes with rotational misalignments is derived based on the framework of nodal aberration theory. Expressions of several important aberrations are obtained under some approximations. Then the specific field characteristics of these aberrations are presented and explicated. Meanwhile, we demonstrate that rotational misalignments can be converted to a kind of surface decenters; on the other hand, the effects of rotational misalignments have their special features which are different from the effects of general surface decenters. Besides, some other insightful discussions are further presented. This work is also applicable to the rotational misalignments of the off-axis segments of primary mirror in segmented mirror astronomical telescopes.

Feature-based phase retrieval wavefront sensing approach using machine learning.

A feature-based phase retrieval wavefront sensing approach using machine learning is proposed in contrast to the conventional intensity-based approaches. Specifically, the Tchebichef moments which are orthogonal in the discrete domain of the image coordinate space are introduced to represent the features of the point spread functions (PSFs) at the in-focus and defocus image planes. The back-propagation artificial neural network, which is one of most wide applied machine learning tool, is utilized to establish the nonlinear mapping between the Tchebichef moment features and the corresponding aberration coefficients of the optical system. The Tchebichef moments can effectively characterize the intensity distribution of the PSFs. Once well trained, the neural network can directly output the aberration coefficients of the optical system to a good precision with these image features serving as the input. Adequate experiments are implemented to demonstrate the effectiveness and accuracy of proposed approach. This work presents a feasible and easy-implemented way to improve the efficiency and robustness of the phase retrieval wavefront sensing.