Search

Underwater imaging is a crucial and challenging problem. The backscattering caused by particles in turbid water can severely degrade the image. In this paper, A novel image dehazing method is devised, which combines optics with image processing technology. This method can directly remove part of the backscattering through polarization technology, and then quickly solve the dehazing image through our algorithm. Experimental results show that our method is valid and robust for targets of diverse materials, grayscale images and color images in diverse scattering environments. Furthermore, our method takes only 2 percent of the time of the fast dark channel prior (DCP) method when processing 1 K resolution images, which meets the requirements of real-time.

Daytime use of Shack–Hartmann wavefront sensor (SHWS)-based adaptive optics (AO) at a telescope is hindered by the fluctuating bright sky background. Therefore, we propose a Gaussian modeling centroid extraction algorithm that performs real-time daylight AO closed-loop corrections. The algorithm is executed in the process of modeling and updating each pixel of the consecutive SHWS images. The simulation results show that our method can provide a lower centroid estimation error (CEE) for bright sky background conditions. We also performed a field experiment on a 2 m ground-based telescope and achieved a daylight AO correction of 2.1 times diffraction limit for a star with a visual magnitude of 4.7 (HIP113116) when the elevation angle of the sun was 7.7°. This represents the first publicly reported daylight natural guide star AO correction result on a 2 m class telescope.

As a continuation of our previous work [Optics Express.25, 15229(2017)] in which we have verified the performance of a coherent free space optical communication (FSOC) system with a 97-element adaptive optics (AO) system, in this paper, we evaluated the performance improvement of the coherent FSOC system using a large-scale high-speed AO system with a 349-element continuous surface deformable mirror. The mixing efficiency (ME) and bit-error-rate (BER) under different Greenwood frequency (GF) were calculated as the performance metric of coherent FSOC system. The performance of FSOC system using such a large-scale AO system was quantitatively verified for the first time. The obtained results showed that the performance was obviously improved when a larger-scale high-speed AO system is employed in coherent FSOC system. This analysis result provides a performance verification for large-scale high-speed AO systems used in FSOC system which is beneficial for coherent FSOC system parameters design.

Idiopathic pulmonary fibrosis (IPF) is a refractory disease. Therefore, developing effective therapies for IPF is the need of the hour.Yiqi Huoxue Formula (YQHX) is an herbal formula comprising three herbal medicines: Ligusticum chuanxiong Hort. (Chuanxiong Rhizoma, CR), Panax notoginseng (Burk.) F. H. Chen (Notoginseng Radix Et Rhizoma, NR) and Panax ginseng C. A. Mey. (Ginseng Radix Et Rhizoma, GR). This study aims to determine the anti-pulmonary fibrosis effect of YQHX and explore its mechanism of action.Design and Methods: The chemical components in the GR, CR and NR extracts were identified by High Performance Liquid Chromatography. A TGF-β1-induced myofibroblast cell model was used to test the anti-fibrosis effect of GR, CR, NR and YQHX. RNA-sequencing was used to identify the differentially expressed genes (DEGs) after YQHX treatment. Subsequently, gene enrichment analysis and key transcription factors (TFs) prediction for YQHX-regulated DEGs was performed. The active constituents of GR, CR and NR were obtained from the Traditional Chinese Medicine Database and Analysis Platform. Targets of the active constituents were predicted using the similarity ensemble approach search server and Swiss Target Prediction tool. YQHX-targeted key TFs that transcribed the DEGs were screened out. Then, the effect of YQHX on the bleomycin-induced pulmonary fibrosis mouse model was studied. Finally, one of the predicted TFs, STAT3, was selected to validate the prediction accuracy.Seven, two, and five compounds were identified in the GR, CR, and NR extracts, respectively. YQHX and its constituents-GR, CR and NR-inhibited the expression of fibrotic markers, including α -SMA and fibronectin, indicating that YQHX inhibited TGF-β1-induced myofibroblast activation. RNA-sequencing identified 291 genes that were up-regulated in the TGF-β1 group but down-regulated after YQHX treatment. In total, 55 key TFs that transcribed YQHX-regulated targets were predicted. A regulatory network of 24 active ingredients and 232 corresponding targets for YQHX was established. Among YQHX's predicted targets, 20 were TFs. On overlapping YQHX-targeted TFs and DEGs' key TFs, six key TFs, including HIF1A, STAT6, STAT3, PPARA, DDIT3 and AR, were identified as the targets of YQHX. Additionally, YQHX alleviated bleomycin-induced pulmonary fibrosis in a mouse model by inhibiting the phosphorylation of STAT3 in the lungs of pulmonary fibrosis mice.This study provides pharmacological support for the use of YQHX in the treatment of IPF. The potential mechanism of action of YQHX is speculated to involve the modulation of core TFs and inhibition of pathogenetic gene expressions in IPF.

Daytime application of the pyramid wavefront sensor (PyWFS) is greatly challenged by a bright and fluctuating sky background, especially in the visible. A daytime-Py approach to apply visible pyramid wavefront sensing for real-time daylight AO is described in this paper. A field stop (FS) and a lenslet array are applied in the daylight AO system based on a visible PyWFS to separate the object signal from the background signal and improve the signal-to-noise ratio (SNR). A background elimination algorithm is proposed to extract the effective object signal. Closed-loop experiment using the daytime-Py approach is performed, which presents the first laboratory real-time daylight natural guide star AO correction of a faint object based on a visible PyWFS. SNR ranges for both the daytime-Py approach and PyWFS are reported. Furthermore, the correction results in different SNRs using both methods and with various pupil samplings using the daytime-Py approach are presented to prove that our proposal has the advantages over the PyWFS and Shack-Hartmann wavefront sensor (SHWFS) for daylight AO. This study demonstrates that the daytime-Py approach can realize the real-time object tracking and closed-loop correction in the daylight natural guide star adaptive optics (AO) system based on the visible PyWFS.

An approach to measure a high-dynamic two-dimensional (2D) temperature field using a high-speed quadriwave lateral shearing interferometer (QWLSI) is proposed. The detailed theoretical derivation to express the wavefront reconstruct principle of the proposed method is presented. The comparison experiment with thermocouples shows that the temperature field measurement using QWLSI has a precision of ±0.5 °C. An experiment for measuring the highdynamic temperature field generated by an electrical heater is carried out. A 200 frame rate temperature field video with 512 × 512 resolution is obtained finally. Experimental results show that the temperature field measurement system using a QWLSI has the advantage of high sensitivity and high resolution.

Based-on the previous study on the theory of the sequential pyramid wavefront sensor (SPWFS), in this paper, the SPWFS is first applied to the coherent free space optical communications (FSOC) with more flexible spatial resolution and higher sensitivity than the Shack-Hartmann wavefront sensor, and with higher uniformity of intensity distribution and much simpler than the pyramid wavefront sensor. Then, the mixing efficiency (ME) and the bit error rate (BER) of the coherent FSOC are analyzed during the aberrations correction through numerical simulation with binary phase shift keying (BPSK) modulation. Finally, an experimental AO system based-on SPWFS is setup, and the experimental data is used to analyze the ME and BER of homodyne detection with BPSK modulation. The results show that the AO system based-on SPWFS can increase ME and decrease BER effectively. The conclusions of this paper provide a new method of wavefront sensing for designing the AO system for a coherent FSOC system.

A phase-shifting iterative algorithm is proposed to calibrate the wavefront phase image demodulated from an interferogram generated by quadriwave lateral shearing interferometer. It reduces the error of the residual slope to RMS < 1.5×10 −4λ after calibration. A favorable result was obtained in the present experiment. We measured a certain wavefront provided by a deformable mirror using the quadriwave lateral shearing interferometer after calibration. The deviation between the wavefront graph of the deformable mirror and the wavefront constructed by quadriwave later shearing interferometer was 2.63%. Our method increases the accuracy and reliability of the reconstructed wavefront data and has a high practical value, all of which meets the requirement of high-precision wavefront sensing.

Degradation of bit-error-rate (BER), caused by atmospheric turbulence, seriously hinders the performance of coherent Free Space Optical (FSO) communication systems. An adaptive optics system proves to be effective in suppressing the atmospheric turbulence. The holographic modal wavefront sensor (HMWFS) proposed in our previous work, noted for its fast detecting rates and insensitivity to beam scintillation, is applied to the coherent FSO communication systems. In this paper, based on our previous work, we first introduce the principle of the HMWFS in brief and give the BER of the coherent FSO with homodyne detection in theory, and then analyze the improvement of BER for a coherent FSO system based on our previous simulation works. The results show that the wavefront sensor we propose is better for weak atmospheric turbulence. The most obvious advantages of HMWFS are fast detecting rates and insensitivity to beam scintillation.

For a coherent lidar, the efficiency of homodyne detection is a significant factor. Adaptive optics (AO) is an effective way to correct the turbulence-induced wavefront distortions. Based on our previous works, an expression for the homodyne detection efficiency is given. The results of the numerical simulation show that the atmospheric coherent length has an influence on the homodyne detection efficiency for a fixed atmospheric Greenwood frequency and a closed-loop control bandwidth. In addition, an experimental AO system is employed to verify the effect of the AO on the coherent lidar. The results show that the homodyne detection efficiency is obviously improved after aberrations are corrected. The conclusion of this paper provides a reference for designing an AO system for a coherent lidar.

We describe a sequential operation approach for a three-sided pyramid wavefront sensor (PWFS) based on a micromirror array with hexagonal geometry. The geometrical optics analysis and numerical simulations show that a linear relationship exists between the signals calculated by the sensing data and the local tilt of the wavefront. We discuss the selection of parameter index that is used in our experiment and build a closed-loop system with this wavefront sensor and a 21-element deformable mirror as a wavefront corrector. The experimental results confirm the feasibility of using a nonmodulated sequential three-sided PWFS in adaptive optics systems.

We describe a closed-loop holographic laser adaptive optics system (HLAOS) based on a holographic wavefront sensor (HWFS) and 21-element continuous-surface piezoelectric deformable mirror (DM). The principle behind HWFSs is described, and then the response sensitivity and crosstalk effect on the lowest 12 Zernike modes of aberration are analyzed. Next, the wavefront-correction capability of the 21-element DM is analyzed. The closed-loop correction of the HLAOS to a static aberration is then numerically simulated. We report a practical implementation of the HLAOS and compare the aberration-compensation effect with a traditional adaptive optics system based on a 37-unit Shark–Hartmann sensor. The practically relevant parameters are analyzed and the experimental results show that an HLAOS using a piezoelectric DM can achieve a correction capability comparable to that of a traditional adaptive optics system.

Degradation of fiber coupling efficiency, caused by atmospheric turbulence, seriously hinders the performance of free space optical (FSO) communication systems. Holographic modal wave-front sensor (HMWFS), noted for its fast detecting rates and insensitivity to beam scintillation, is creatively applied to FSO communication systems in this paper. We analyze the principle of HMWFS and the relationship between fiber coupling efficiency and Strehl rate in theory, then simulate wave-front aberrations detection and correction in FSO communication systems. Additionally, the impact on fiber coupling efficiency of the FSO communication systems before and after aberrations correction based on HMWFS is fully discussed. The results show that HMWFS cater for weak atmospheric turbulence with the root-mean-square (RMS) value of residual aberrations less than 0.04 lambda and the peak-to-valley (PV) value less than 0.25 lambda, while the fiber coupling efficiency is increased from nearly 30% to more than 70%. (C) 2014 Elsevier Ltd. All rights reserved.

Pointing errors caused by the atmospheric turbulence will degrade the performance of free space optical (FSO) communication systems, especially the bit error rate (BER). In this paper, we innovatively analyze the relationship between BER and pointing errors by the probability density functions (PDFs) and intensky displacement in focal plane under the On-Off Keying (OOK) modulation conditions. The closed-loop experimental system is set up in laboratory, where the fast steering mirror (FSM) is real-time controlled by embedded controller with the parallel processing technology and the atmospheric turbulence is simulated by a turbulence simulation box. The results of repeated experiments show that the method of pointing errors correction we proposed is efficient under the conditions of atmospheric turbulence. By utilizing our method, the BER can decrease from nearly 10(-3) to nearly or even below 10(-9), thus improving the performance of FSO communication systems significantly. (C) 2013 Elsevier GmbH. All rights reserved.

In order to decrease the Bit Error Rate (BER) and increase coupling efficiency of free space optical (FSO) communication system, we compute and compensate the wavefront aberrations of the laser signal with the wavefront measurement method based on the focal plane proposed in this paper. The aberrations of laser signal are calculated based on the two images which are respectively generated from focal plane (PF) channel and the defocused plane (DF) channel. Assuming the On-Off Keying (OOK) modulation is used under the condition of weak turbulence, the fundamental of wavefront measurement method based on focal plane is introduced. By numerical simulation, we analyze the variation trend of coupling efficiency and BER, using the method we proposed to measure and compensate the wavefront aberrations for the FSO communication system. The experiment results show that the wavefront measurement error can reach nearly 0.004 wavelengths, the average coupling efficiency increases from 10.32% to 63.82%, and the average BER of FSO communication system decreases from 10-5 to 10-13. 2013 Elsevier B.V.

The Greenwood frequency (GF) is influential in performance improvement for the coherent free space optical communications (CFSOC) system with a closed-loop adaptive optics (AO) unit. We analyze the impact of tilt and high-order aberrations on the mixing efficiency (ME) and bit-error-rate (BER) under different GF. The root-mean-square value (RMS) of the ME related to the RMS of the tilt aberrations, and the GF is derived to estimate the volatility of the ME. Furthermore, a numerical simulation is applied to verify the theoretical analysis, and an experimental correction system is designed with a double-stage fast-steering-mirror and a 97-element continuous surface deformable mirror. The conclusions of this paper provide a reference for designing the AO system for the CFSOC system.

We propose a sequential three-sided pyramid wavefront sensor based on a micromirror array with hexagonal geometry. It can provide a simplified optical relay and be applied to a broadband optical system easily and without a specific achromatic design.

In this paper, we describe a sequential operating method which can be realized using a micromirror array. Geometrical optics calculations are described first to illustrate principle of the method. Then, numerical simulations verify the feasibility of using a non-modulation method into closed loop system.

Attention deficit hyperactivity disorder (ADHD) is the most common childhood onset neurodevelopment disorder. The etiology is unclear, but is suspected to involve the dopamine system. In this study we used the haplotype-based haplotype relative risk (HHRR) analysis and the transmission disequilibrium test (TDT) to investigate the potential contribution of dopamine transporter (DAT1) gene variants to ADHD. DAT1 gene polymorphisms were assessed in 54 ADHD Chinese Han children and all 108 of their parents and 66 normal child controls. No differences were found in either genotype or allele distributions. The HHRR analysis of the DAT1 polymorphisms suggests that the transmission of this polymorphism is not significantly associated with ADHD. And the TDT result showed that ADHD was not in linkage with the DAT1 gene. These findings do not support the hypothesis that DAT1 gene variants contribute to the pathogenesis of ADHD in Chinese Han population.

The pyramid wavefront sensor is a novel slope wavefront sensor that is similar to the Foucault knife-edge test. In this paper, we describe a sequential operation method that can be realized using a micromirror array. The goal of this paper is to discuss the possibility and analyze the features of the method. Geometrical optics calculations are described first to illustrate the principle of the method. Then, more exact diffraction calculations are provided that illustrate the method being equivalent to the pyramid sensor in principle but with a weak diffraction effect. Numerical simulations are also provided to verify the feasibility of using a nonmodulation method in the closed-loop system.

We describe a closed-loop dynamic holographic adaptive optics system. This system can be realized via one liquid crystal spatial light modulator and one CCD camera. The liquid crystal spatial light modulator is used as the wavefront sensor and corrector, as well as imaging element. CCD detects the spots at holographic image plane and at focal plane of imaging channel simultaneously. The basic principle of the system is introduced first, and then the numerical analysis is presented. On this basis, we report a practical implementation of the dynamic holographic adaptive optics system. The results show that a rapid increase of Strehl ratio and improved image quality at focal plane for deliberately introduced aberrations can be achieved, verifying the feasibility of the system.