Improving distance imaging accuracy through temporal position correction with phase difference compensation.

This study introduces a time-domain-based phase compensation method to address decoherence effects in optical heterodyne detection, which is critical for remote sensing and distance imaging. The numerical simulations demonstrate a substantial reduction in localization bias (6.56-2.85) and an increased probability of bias values below 2 (21.6%-70.5%). The experiments show significant improvement in whiteboard distance imaging accuracy at 10 m from the detector, with 91.7% of the data falling within 10-12 m, compared to a mere 2.3% accuracy before compensation. The method effectively enhances intensity image quality, mitigates decoherence phenomena, and improves detection accuracy and reliability without additional hardware.

Optical heterodyne detection system for a high-speed camera based on the HSA phase compensation method.

This study proposes an innovative active optical heterodyne detection system to address the limitations of existing swarm intelligence algorithms in resolving phase compensation issues within coherent detection systems. The design incorporates a high-speed camera array detector, offering improved practicality and a simplified structure. Employing a heuristic search algorithm (HSA) transforms the high-dimensional problem into multiple one-dimensional optimization problems, significantly enhancing algorithmic running speed. The HSA maintains excellent performance even with increased array elements, allowing for real-time phase correction in large arrays. Experimental results using shot peening comparison samples reveal a substantial amplification of the heterodyne signal spectrum amplitude peak, approximately 60 times greater than the original signal. This innovative approach holds great potential for active optical heterodyne detection of dim targets, paving the way for further research in the field.

Investigation polarimetric scattering of light from the randomly rough surface based on the calculation of the Mueller matrix.

As the transmission matrix of scattering and incident light, the Mueller matrix reflects the polarimetric scattering characteristics of the rough surface, providing a significant reference for the study of light scattering. Currently, few calculations of the Mueller matrix for a two-dimensional randomly rough surface have been carried out by numerical methods. In this paper, we use six polarization states of incident light and calculate their scattering polarization states numerically by finite-difference time-domain method and obtain the rough surface Mueller matrix by combination. To verify the accuracy of the calculated Mueller matrix, the polarization state of the scattering light obtained by simulation is compared with the predicted result, and the maximum relative error is 0.0635, yielding a good result. In addition, we use this method to obtain the Mueller matrix at different incidence angles and investigate the polarization scattering characteristics. The results show that the derived parameters of the Mueller matrix of different media at different incidence angles have distinct trends. This polarization scattering property obtained from the Mueller matrix can be effectively applied to target recognition, material detection, and other fields.

Photonic integrated interferometric imaging based on main and auxiliary nested microlens arrays.

The traditional microlens array imager lacks content information and has low imaging quality when restoring the image of the target, which limits the development of photon integrated detection and imaging technology. Therefore, this paper proposes a new structure of the microlens array optical frequency detection imager, wherein the main microlens array is embedded into the auxiliary microlens array to achieve high-quality restoration of the target. The simulation results show that the proposed structure increased the peak signal-to-noise ratio (PSNR) of the restored image by 21.05% and reduced the mean square error (MSE) by 29.39%. The microlens array with the main and auxiliary nested structure can achieve high-quality imaging of the target and has great application potential in the field of target detection.

Spatial decoherence compensation algorithm for a target speckle field in heterodyne detection based on frequency analysis and time translation.

The decoherence effect of a laser caused by a speckle field seriously restricts the development of heterodyne lidar. To address this problem, we proposed a spatial decoherence compensation algorithm, whose feasibility was proved by experiments with a system featuring simple structure and convenient operation. The results demonstrated that the speed of the proposed algorithm was several orders higher than that of other algorithms and the system SNR was increased by a maximum of 1464 times after the algorithm processing. The proposed algorithm can process the signal in real time and effectively, having great application potential in long-distance weak target detection.

Filterless radio-over-fiber system that generates 80 and 160 GHz millimeter waves based on two MZMs.

In this paper, we propose a radio-over-fiber system with no filters and generate 80 and 160 GHz millimeter (mm) waves via two Mach-Zehnder modulators (MZMs). The two MZMs, biased at the maximum transmission point, are used to suppress odd-order sidebands. By controlling the phase difference between the RF driving signal of the two MZMs, the $\pm({4}{n - 2})$-order is canceled. By adjusting the optical attenuator and phase shifter, the 0-order sideband is canceled, so only the $\pm 4{n}$-order sidebands are left. The simulation results show that using a 10 GHz RF signal to drive the MZMs, we obtain an 80 GHz mm wave signal with a 36.59 dB optical sideband suppression ratio (OSSR), a 30.27 dB radio frequency sideband suppression ratio (RFSSR), and a 160 GHz mm wave signal with a 30.34 dB OSSR and 24.77 dB RFSSR. The results are consistent with the theoretical analysis. Because no optical filter is employed and only two MZMs are used, the system exhibits a simple structure, good performance and is low cost.

Application of DBN and GWO-SVM in analog circuit fault diagnosis.

For large-scale integrated electronic equipment, the complex operating mechanisms make fault detection very difficult. Therefore, it is important to accurately identify analog circuit faults in a timely manner. To overcome this problem, this paper proposes a novel fault diagnosis method based on the deep belief network (DBN) and restricted Boltzmann machine (RBM) optimized by the gray wolf optimization (GWO) algorithm. First, DBN is used to extract the deep features of the analog circuit output signal. Then, GWO is used to optimize the penalty factor c and kernel parameter g of support vector machine (SVM). Finally, GWO-SVM is used to diagnose the signal features extracted by the DBN. Fault diagnosis simulation was conducted for the Sallen-Key band-pass filter and a four-opamp biquad highpass filter. The experimental results show that compared with the existing algorithms, the algorithm proposed in this paper improves the accuracy of Sallen-Key bandpass filter circuit to 100% and shortens the fault diagnosis time by about 90%; for four-opamp biquad highpass filter, the accuracy rate has increased to 99.68%, and the fault diagnosis time has been shortened by approximately 75%, and reduce hundreds of iterations. Moreover, the experimental results reveal that the proposed fault diagnosis method greatly improves the accuracy of analog circuit fault diagnosis, which solves a major problem in analog circuitry and has great significance for the future development of relevant applications.

Low-complexity carrier phase estimation for M-ary quadrature amplitude modulation optical communication based on dichotomy.

In high-speed optical communication, the blind phase search (BPS) algorithm performs carrier phase estimation better but with higher computational complexity (CC), bringing a larger computational burden to the digital signal processing unit. In this paper, a new low-complexity CPE algorithm (DBPS) is proposed for M-ary quadrature amplitude modulation (M-QAM) formats. It uses the BPS algorithm to estimate the compensation phase interval, before using dichotomy to quickly and accurately determine the compensation phase value. Simulation results show the CC (multiplication / addition) of DBPS is reduced by 2.79 / 2.84 (16-QAM), 5.35 / 5.45 (64-QAM), and 2.98 / 3.01 (128-QAM) than that of BPS, and DBPS has a smaller phase tracking error variance. DBPS can relax the limitation of optical communication rate caused by high-speed data operations.

Filterless radio-over-fiber system based on polarization multiplexing to generate an 80 GHz millimeter wave.

We propose a filterless full-duplex radio-over-fiber system based on polarization multiplexing and demonstrate the generation of an 80 GHz millimeter wave using two Mach-Zehnder modulators. By adjusting the polarization direction, we could generate an 80 GHz frequency millimeter-wave signal and restore the original pure light carrier, providing a light source for the uplink. The simulation results show that the 80 GHz millimeter-wave signal was obtained with a 23.48 dB radio-frequency sideband suppression ratio. Furthermore, we showed that the proposed scheme is relatively flexible and free from the limitation of filter fixed bandwidth in addition to being simple and economical.

Research on Airplane and Ship Detection of Aerial Remote Sensing Images Based on Convolutional Neural Network.

The wide range, complex background, and small target size of aerial remote sensing images results in the low detection accuracy of remote sensing target detection algorithms. Traditional detection algorithms have low accuracy and slow speed, making it difficult to achieve the precise positioning of small targets. This paper proposes an improved algorithm based on You Only Look Once (YOLO)-v3 for target detection of remote sensing images. Due to the difficulty in obtaining the datasets, research on small targets for complex images, such as airplanes and ships, is the focus of research. To make up for the problem of insufficient data, we screen specific types of training samples from the DOTA (Dataset of Object Detection in Aerial Images) dataset and select small targets in two different complex backgrounds of airplanes and ships to jointly evaluate the optimization degree of the improved network. We compare the improved algorithm with other state-of-the-art target detection algorithms. The results show that the performance indexes of both datasets are ameliorated by 1-3%, effectively verifying the superiority of the improved algorithm.

[Effects of Naoyaojia on structural mechanical properties of femur in rats].

OBJECTIVE: To study the effect of long term Naoyaojia administration on the structural mechanical properties of rat femurs. METHOD: Young wistar rats were treated orally with Naoyaojia at doses of 3, 6, and 12 mg/kg body weight every 2 weeks for 1 year. Beary's bending test was used for determining physical properties of the femur. RESULT: The thickness of the cortex and cross-sectional area of femur increased significantly in animals treated with 3 mg/kg dose of Naoyaojia (P<0.01), significant increase in maximum bending load was also found in this group compared with the control group (P<0.01). But an opposite change was found in animals treated with 12 mg/kg dose of Naoyaojia. CONCLUSION: Stimulation on the thickness of the cortex along the axis as well as the maximum bending load of femurs are found in animals treated with 3 mg/kg dose of Naoyaojia, but negative effects were observed at higher dose level.