The technology of computationally adaptive plenoptic imaging system (CAPIS) can simultaneously record the position and direction of a signal, obtain the distorted wavefront slope from the light field information, and thus perform the wavefront reconstruction. This study investigates the optical wavefront distortion detected by the CAPIS technology, and provides a numerical calculation model for simulation analysis. The results denote that the CAPIS technology can accurately detect a low-order aberration wavefront. Furthermore, the root mean square value of the wavefront residual is less than 0.1λ. The experimental light path is established, and the detection of the low-order aberration wavefront is realized and the root mean square value of the wavefront residual is less than 0.5λ. The simulation and experimental results denote that the CAPIS technology can effectively detect a low-order aberration wavefront, which is considerably significant for exploring one large-field wavefront detection method.

Frequency stability is an important indicator to evaluate the performance of a coherent population trapping (CPT) atomic clock, and the type and pressure ratios of the buffer gas compositions inside an atomic vapor cell are main factors influencing frequency stability. In this study, the temperature frequency shift caused by buffer gas compositions, i.e., Ar and N2, was simulated and analyzed theoretically, and the temperature shifts caused by different pressure ratios of buffer gas compositions were tested experimentally. The optimal ratio of buffer gas compositions in the atomic vapor cell was determined based on the theoretical and experimental results, and the corresponding operation point for the minimum temperature frequency shift was found. The research results provide a valuable reference for selecting the pressure ratio of buffer gas compositions and the operation temperature of the atomic vapor cell for a CPT atomic clock.

Using the strong field approximation method combined with the time window function, the two-dimensional (2D) momentum spectra of hydrogen atoms for above-threshold ionization by a few-cycle intense laser field were calculated and compared with the results obtained by the Coulomb-Volkov approximation combined with the time window function. It is found that the fanlike structures in the 2D momentum spectra are formed as a result of the interplay of intracycle and intercycle interferences under the action of a long-range Coulomb potential. In addition, the 2D momentum spectra of hydrogen atoms under different pulse durations were calculated by solving the time-dependent Schr dinger equation and it is found that some special fringe structures appear in the 2D momentum spectra beyond the intracycle and intercycle interference fringes. These structures are formed by the rescattered electron wave packets.

In this study, the micro-nano composite structures having multiple morphologies and periods were fabricated via conventional ultraviolet photolithography combined with two-beam laser interference lithography and two-step exposure via two-beam laser interference lithography. The micro-nano composite structure could overcome the shortages imposed by conventional laser photolithography, which yields the microstructures with single morphology and period. By optimizing the experimental parameters, the micro-nano composite structures having different nano-gratings, such as micro-strip gratings, rectangular lattices, circular lattices, and hexagonal lattices, were fabricated. By incorporating the micro-nano composite grating in glass/Ag film/CH3NH3PbI3, the absorption of CH3NH3PbI3 is enhanced in the visible range. This enhancement is mainly attributed to the coaction of light scattering of micro-grating and electric field enhancement of surface plasmon polaritons at the Ag film/CH3NH3PbI3 interface.

To address the problems of human-computer interaction, poor separation, low efficiency, and difficulty in seed selection in the traditional image foreground-background separation algorithms, we propose an automatic image-foreground-background separation algorithm based on the texture features extracted in the Lab color space. First, we segment the image into blocks and convert it into a CIE-Lab color space established by the international commission on illumination (CIE). Then, we extract the color and texture features of each image block and select seeds. Finally, we use a region growing algorithm for image separation and region merging to reduce over separation. The experimental results show that the proposed algorithm is superior to the traditional algorithm in terms of the separation results, processing time, and algorithmic complexity.

Herein, a method for unsharp masking (USM) sharpening detection is proposed. First, the local binary pattern (LBP) method is used to detect the edge features in an image. Then, a support vector machine is used for classification to detect whether the image is sharpened. Subsequently, the different LBP detection modes are compared in terms of the resulting sharpening intensity to select the optimal detection method. The experimental results show that the LBP method can achieve a relatively good USM sharpening detection effect. The rotation-invariant mode provides the best detection performance, providing a detection rate of up to 90% under the condition of weak sharpening, which is better than those achieved by the existing methods.

The traditional multi-feature fusion change detection does not consider the fact that different features contribute differently toward the change detection results. Furthermore, the traditional Markov random field (MRF) change detection quality is affected by the spatial information weight. This study proposes a novel change detection method based on density attraction and multi-scale and multi-feature fusion. First, the texture difference image is obtained by local similarity measurement and information entropy on the basis of extracting Gabor texture features, and the spectral difference image is calculated by change vector analysis. Then, the adaptive method is used to fuse the spectral and texture differences. Finally, the density attraction model is combined with the traditional MRF to construct an adaptive weighted MRF model and obtain the change map of a difference image. The experimental results show that the proposed method can not only make full use of different features, but also well maintain the image edge details and improve the change detection accuracy.

To address the fusion problem of time sequence features in video classification, this paper proposes a new three-dimensional (3D) squeezing excitation (SE) network structure module that is constructed by combining the SE network in a two-dimensional convolutional neural network (CNN) with a 3D convolutional residual network. The new module adds an extra time-dimension coefficient to the coefficient set of a directly transformed 3D SE module, allowing it to record the changes in the motion trajectories of the research objects on time trajectories. The proposed module can not only record the characteristics of a specific time point, but also strengthen the relevance of multiple time points. To assess the effectiveness of the module, an SE network with a spatial and temporal latitude was used to perform character-action-behavior recognition. The experimental results indicate that the module can accelerate the loss convergence and effectively improve the accuracy of video classification.

In order to extract the reliable phases from fringe patterns with large phase variation, the corresponding fringes are analyzed by Paul wavelet transform. Under the condition of different Paul wavelet parameters, the phase extraction process from fringe patterns with large phase variation under noise is analyzed. The method for the selection of scaling factor, wavelet order, and other parameters in the phase extraction process is presented. The results of the simulation experiment indicate that the speed and reliability level of phase extraction from fringe patterns with large phase variation can be effectively improved by adjustment of the parameters for Paul wavelet transform.

Based on the background continuity priori knowledge, we propose a new saliency-detection method. In this method, an image is first abstracted as a set of super-pixels. We then search the shortest path and calculate the foreground weight of each super-pixel in the path according to its color difference with those at two ends of the path. We also integrate the color-difference-based foreground weight correction with the boundary priori knowledge based saliency optimization to obtain the final saliency detection results. The proposed method is extensively evaluated on several public datasets and the experimental results confirm its state-of-the-art performance.

A stripe skeleton-level sub-calibration algorithm was used for interference fringe detection. The experimental samples of laser interference fringe were processed. An adaptive window was used to filter the interference fringes of different shapes, and the experimental samples were denoised to obtain the interference images with high contrast. The interference fringe extraction was performed according to the perfect sample images, and the teal-time stripe calibration and detection were then performed. The results show that the proposed multi-noise-based interference fringe detection model can realize the real-time detection of optical components and effectively improve their detection efficiency. Moreover it can realize the industrial automation detection based on the C++ platform.

Fourier ptychography imaging is a new type of super-resolution microscopic imaging technology, capable of achieving a large field of view. The physical and mathematical models for macroscopic Fourier ptychography imaging are constructed and the corresponding reconstruction algorithm is provided. An experimental system is constructed, and the Fourier ptychography imaging technology is applied to the field of macro-imaging. Several experiments are performed and the results denote that macroscopic Fourier ptychography imaging can significantly improve the resolution of an imaging system. This technique can be potentially applied in the fields of aerospace reconnaissance and long-range imaging.

A method for precision-adjustable optical paths is proposed to measure the central thickness of a lens based on low-coherence interference with transmitted illumination. A pair of wedge prisms are used to translate the movement that is nearly perpendicular to the optical axis with low accuracy into movement along the optical axis with high accuracy, and thus the optical path along the optical axis can be precisely adjusted. The accuracy for adjusting the optical-path difference (OPD) is related to the wedge angle. The smaller the wedge angle, the more accurate the adjustable OPD. A pair of prisms with a wedge angle of 5°30' and a linear stage with 5 μm accuracy are used to realize the movement along the optical axis with an accuracy below 0.5 μm, and the central thickness accuracy of the tested lens is less than 0.9 μm. The proposed method is employed to improve the contrast of interference fringes. Moreover, the central thicknesses of lenses with different shapes can be measured by the proposed method and the thickness-measuring scope can be extended easily.

The relationship between the extinction ratio and the stress birefringence phase difference is identified based on a Jones matrix. The extinction ratio of a crystal is measured by the rotating sample method, its expression is also derived, and the errors are analyzed theoretically. A light source with power instability lower than 0.2% and a polarizer with an extinction ratio higher than 50 dB are used to build the test system. This test system is suitable for testing the samples with phase differences in the range of (π/2, π), and the test accuracy is less than -55 dB. The measured extinction ratio of a 1/2 wave plate is -41.66 dB, and the comprehensive error is less than 1%.

This study proposes a novel subpixel edge extraction algorithm for the detection of defects in workpieces, which is based on Zernike moments. First, the target image is decomposed using a wavelet transform, and the decomposed frequency information is preprocessed by employing different algorithms. After reconstruction, the image noise can be effectively filtered out and the target information can be enhanced. Then, the proposed subpixel edge extraction algorithm is applied to locate the image edges and extract their feature information with the aim to reduce the edge information error and segment the target contour more accurately. Finally, the geometric parameters of the surrounding region and the global information entropy are calculated to determine whether there are defects. The algorithm is verified with an experiment, and the experimental results show that the proposed algorithm can reduce the metal high-light noise and extract the defect edges effectively. Moreover, the algorithm is robust even when the ambient light illumination changes, and thus improves the accuracy of metal-defect detection.

Based on a large amount of test data, the variations of the output gray value and the calibration background bias of an infrared measurement system with ambient temperature were analyzed. Further, the influence of background bias on the precision of the surface target-radiance measurements was assessed. Based on the results, a new method for calculating the surface target radiance based on background offset cancelling is proposed. This method can improve the measurement accuracy of the infrared radiation characteristics of dynamic targets by eliminating the influence of background bias, which is influenced by ambient temperature. The dynamic characteristics of a particular type of aircraft were calculated and compared using both the traditional and the proposed methods. The results verify the effectivity of the newly proposed method.

A sawtooth resonant-cavity-coupled metal-waveguide structure is proposed. It is found that adding a sawtooth resonator improves the signal output frequency of the waveguide structure. In addition, the output signal frequency of the logic-gate light source can be controlled by adjusting the length and width of the sawtooth resonator. Moreover, the increase of logic signal output ports by increasing the number of output waveguides can help to realize the two- and three-channel signal outputs. This logic gate output light source, constructed by coupling a sawtooth resonator with a metal waveguide structure, has a broad working bandwidth and a high transmission efficiency. With a suitable adjustment of the length and width of the sawtooth resonator one can get a transmission efficiency of 60% and an average working range of 1000 nm.

Herein, Fe-based cladding coatings are prepared on Q235 carbon steels using a pulsed laser. The effects of heat treatment temperatures of 600 ℃, 750 ℃, and 900 ℃ on these coatings are investigated. In addition, the microstructures, phase compositions, and mechanical properties of these coatings are characterized. Moreover, the corrosion behaviors of these coatings before and after heat treatment are examined. The results show that after heat treatment, the coatings were observed to consist of both crystalline and amorphous structures. The content of the crystalline phase increases with the increase of heat treatment temperature, and heat treatment can increase the near surface hardness of cladding layers, specifically, the average hardness of cladding layers is the highest at approximately 1100 HV0.1 under the heat treatment of 900 ℃ for 2 h. The anti-corrosion performance of coatings improves with the increase of heat treatment temperature, and the Fe-based cladding layers after heat treatment of 900 ℃ for 2 h show the highest corrosion potential of -0.52500 V, the lowest corrosion current density of 2.2810×10-6 A/cm2, implying the highest anti-corrosion performance.

Since the establishment of the B-integral criterion, it has been a basic design criterion for the nonlinear effect control in large laser drivers. Through an overview of the experimental and simulation processes for establishing two B-integral criteria in the national ignition facility, we explain the principle and the creation conditions of the B-integral criteria, and point out the applicability and the existing problems of the B integral criteria. It is concluded that the two B-integral criteria are imperfect. In order to accurately determine the B-integral criteria applicable to the current large high power solid-state laser devices, the actual conditions of the current laser devices should be comprehensively considered and the corresponding experiments and simulations should be conducted.

A motion model is used to overcome the shortcoming of the low tracking accuracy of a kernelized correlation filter (KCF) based only on a target appearance model. The intersection-over-union (IOU) between the detection target bounding box and the predicted target bounding box was calculated. The optimal correlation among the targets was determined using the Hungarian algorithm. Both the KCF and IOU models are characterized by fast responses; therefore, the algorithm has the ability to process data online. The experiments were conducted on the public 2DMOT2015 and MOT16 datasets. Compared with the other state-of-the-art method, the tracking accuracy of the proposed method is higher than 10% while ensuring a processing speed of 30 frame/s or faster.

We used a microwave gyro resonance ion source to study the etching effects on the surfaces of rotating sapphire samples under different Kr+-ion beam parameters. We used the four-factor and three-level orthogonal experiments to analyze the influences of the incident angle, energy, ion flux density, and action time of a Kr+-ion beam on the sapphire surface structures after irradiation. We also studied the relationship between ion beam parameters and sapphire surface roughness and etching rates. The experimental results demonstrate that when an ion beam has an incident angle of 60°, an energy of 600 eV, an ion flux density of 239 μA·cm-2, and action time of 90 min, the sample surface roughness after etching is the greatest and the dot-like structures are formed on the sample surface. In contrast, under the same incident angle, energy, and ion flux density of the ion beam, but a shorter etching time of 30 min, the etching rate reaches its maximum value and the dot-like structures on the surface are dense. Therefore, one can obtain good dot-like nanostructures, optimal roughness and etching rate using the optimal combination of parameters.

This study investigates the four-wave mixing (FWM) processes from two channels in an inverted Y-type four-level atomic system driven by a periodic phase-modulation field using the density matrix equation. The numerical analysis results denote that the FWM signals from the two channels can be controlled to overlap or separate by the probe field with periodic phase modulation. The suppression, enhancement, and splitting of the FWM signals can be observed by selecting different modulation frequencies, modulation coefficients, and dressing field strengths. This FWM control with a periodically driven field can be probably used in the optimization of optical nonlinear processes and the optical information processing.

In this paper, based on deformable mirrors and the stochastic parallel-gradient-descent (SPGD) algorithm, an adaptive optics system (AOS) without wavefront detection is theoretically simulated. In order to improve the convergence speed of the AOS without reducing its accuracy, this paper optimizes the relationship between the amplitude of random perturbation and the gain coefficient in the SPGD algorithm. The experiment conducted in this study shows that the AOS has a parameter preference area, which is related to the initial distortion magnitude. Furthermore, the results of the theoretical verification and the comparison with that by the simulated annealing algorithm reveal that the convergence accuracy of the SPGD algorithm is 6.32% higher than that of the SA algorithm and the SPGD algorithm has a larger convergence speed.

In this paper, we propose and verify a calculation and analysis model of shading and blocking in a linear Fresnel reflector system. Specifically, 16 mirrors are arranged at an equal spacing and the aiming line height is 9056 mm. For this setup, we compare the shading calculation results from the proposed model with those from SolTrace at a mirror spacing of 100 mm. Then, we present one example of how to determine the best mirror field spacing for the proposed model under the above conditions, and it is found that the ideal spacing is 331.91 mm, close to the 330 mm obtained via the traditional shadow-less layout method. Finally, we verify the accuracy of the proposed calculation model. The proposed model can be used to analyze shading and blocking in the field of a linear Fresnel reflector, and it is helpful to guide the design of a linear Fresnel reflector system.

A telecentric ultraviolet warning optical system with a large relative aperture and a long focal length is designed using ZEMAX. This optical system contains six pieces of spherical lenses and has a total length of 154 mm. The system has a focal length of 100 mm, a relative aperture of 1∶2, and a field of view angle of 10°. CaF2 with a negative temperature coefficient of the refractive index is used as a concave lens for thermal compensation. The result shows that the average light modulation transfer function of each field of view is >0.4 at 10 lp/mm. Further, the biggest root-mean-square radius of the spot diagrams is smaller than 50 μm. With the advantages of excellent imaging quality, compact configuration, and wide temperature adaptability, the system is suitable for ultraviolet warning cameras.

This study proposes a blue-green light-emitting diode light source system for jaundice phototherapy instrument. Based on the process of light transmission through skin and tissues and the process of conversion between bilirubin and phosgene, a light spectrum with a higher matching degree to the target spectrum is established via the spectral matching method. In addition, the light source array is designed and simulated, followed by the fabrication and illumination test of the corresponding light source system. The results indicate that the system achieves an average illumination of 32.9 μW·cm -2·nm-1 with 81% uniformity. The uniformity is further improved by adding a Fresnel lens array to the light source system. When the ring distance of the Fresnel lens is 1 mm and the distance from the lens to the light source is 1 cm, the uniformity is increased to 85% and the illuminance is 31 μW·cm -2·nm-1 , which are in accordance with the design requirements.

This study involved the Metasequoia glyptostroboides, Salix babylonica, Ligustrum lucidum, bamboo, and Malus pumila Mill. from the Qianjiang new town forest park of the Hangzhou city and the Hongqipo farm of the Aksu city in the Xinjiang Uygur Autonomous Region. The structural, textural, and crown features were proposed based on high-resolution point cloud data acquired by the airborne LiDAR and a support vector machine classifier. The experimental results demonstrate that the overall accuracy of the classification is 85%, with a Kappa coefficient of 0.81. The proposed method derives promising features for a tree based on the LiDAR data and demonstrates an effective framework for improving the classification performance of the tree species.

When compared with the traditional edge-emitting semiconductor lasers, the vertical-cavity surface-emitting lasers (VCSELs) offer several advantageous properties, including a narrow line width, superior beam quality, high reliability, and low manufacturing cost. Recently, with an increase in the output power and power conversion efficiency of the 808 nm VCSEL arrays, they have become an attractive alternative for the pumping sources of solid-state lasers. In this study, we introduce the performance advantages, applications, and status of the VCSELs. As for the VCSEL-array-pumped solid-state lasers, the research progress is reviewed, and the development prospect as well as their technical shortcomings are discussed.

Light-emitting diodes (LEDs) are incoherent light sources with limited bandwidths, and the discovery of biological effects of LED light sources promotes its application in biomedicine. Based on the phenomenon that tissue penetration depths of lights with different wavelengths are different, this work introduces the target tissue specificity and biological effects of LED light sources at each band. This article also reviews the current application of these LED light sources in a clinical setting for the treatment of dominant diseases. Finally, the application of LED light sources in the biomedical field is prospected herein to help guide their clinical application together with instrument research and development.

The target attribute scattering center is parametrically modeled for automatic identification of the radar targets. Before generating the model, high-precision geometric modeling is applied based on the decomposition of the solid parts, and a set of ray tracing methods exhibiting spatial ray diversity is proposed. Based on this ray tracing step, a set of parametric forward-modeling methods is developed for estimating the center of scattering based on the spatial ray diversity. Further, the center of the strong scattering source with respect to the target edge is added on the basis of the already extracted surface scattering source. The model parameters are also derived during this additive process. The results obtained using this method are compared with those obtained using the typically used high-frequency method, confirming the effectiveness of the parametric model. Thus, the proposed method for parametric modeling provides a new auxiliary mechanism for compiling the radar target features.

We measured the terahertz time-domain electric fields of alumina and aluminum hydroxide samples in the range of 0.5-1.5 THz using terahertz time-domain spectroscopy. The frequency-domain spectra of sample and reference signals containing the amplitude and phase information were obtained by the fast Fourier transform of the measured time-domain signals. Compared with the frequency-domain spectrum of a reference signal, one can find that the aluminum hydroxide sample has obvious characteristic peaks at 1.20 THz and 1.33 THz; however, the alumina samples have the same characteristic peaks as the reference signal. The near-field enhancement via the surface plasmon polaritons of graphene was used to enhance resonant stretching of the hydroxyl groups in a molecule by doping a certain proportion of graphene and aluminum hydroxide, and thereby the enhanced regulation of characteristic peaks of aluminum hydroxide is achieved. This study not only offers effective nondestructive test and identification of aluminum hydroxide, but also increases the detection sensitivity of aluminum hydroxide using graphene. Moreover, it has reference significance for further study of spectral information for other hydroxides using terahertz time-domain spectroscopy.

We designed and modeled a short-magnetic-focusing pulse-dilation framing camera. Based on the principle of pulse dilation and the equation of photoelectron motion, we studied the fs-photoelectron acceleration, transmission, and imaging characteristics in a pulse-dilation system. In addition, we analyzed the temporal-spatial dispersion and discussed the methods for its reduction. The simulated results show that when the pulse-dilation system has a length of 500 mm, a gradient of dilation pulse of 10 V·ps-1, and an accelerating field of 2 kV·mm-1, the total physical-temporal resolution resulting from temporal dispersion is 1.62 ps, which is 70% of the temporal resolution of the camera. The spatial dispersion is 62.87 μm, and the image contrast is reduced by 13.58%. Thus, the influence of temporal-spatial dispersion on physical-temporal resolution and imaging contrast can be effectively reduced by enhancing the accelerating field.