Potassium dihydrogen phosphate (KDP) crystal is a classic electro-optical material and is the only nolinear optical material used in the Inertial Confinement Fusion(ICF) program. The growth method and seed have a considerable effect on the quality of KDP crystal. In this study, KDP crystals were grown using both conventional and point-seed rapid-growth methods. By changing the directions of seeds, the regeneration sector was decreased and the length of the growth period was reduced. In addition, the grown crystals were made highly transparent and had no visible defect. Optical transmittance performance, crystalline perfection, and the laser damage threshold were measured. The results show that the crystals have high transmittance in the visible and infrared wavebands, and strong diffraction intensity in (001) face with a sharp peak; the damage thresholds of KDP crystals are improved by 1.7~2.1 with R -on-1 method as compared with 1-on-1 method. The grown crystals exhibit excellent optical performance, and the seeds have a considerable effect on the growth and quality of KDP crystal.

To solve the problem of free placement of different materials at any location on a part during selective laser melting, the manufacturing technology of selective laser melting of heterogeneous material parts was studied. This method is based on supplying powder through multiple funnels and cleaning and recovering of powder using a flexible scraper. The processing mechanism, the prevention mechanism of powder cross contamination, and the data processing method of heterogeneous material parts were discussed in detail. Two materials, namely, a CuSn10 alloy and 4340 steel, were used to verify the technology. Experiments show that this method can effectively solve the difficult problem of heterogeneous material placement during selective laser melting and can realize the formation of heterogeneous material parts. Specific results of the study are as follows: (1)Heterogeneous materials can be arranged freely in different layers or in different zones of a single layer. (2) For a bulk heterogeneous material part, the average mass percentages of Fe in the copper alloy region and of Cu in the steel region can be controlled to less than 2% and less than 1%, respectively. (3) A heterogeneous material gear part with a complex shape and the characteristics of a narrow material region is successfully formed. The heterogeneous material distribution of the part is not limited by the complex shape, and the materials can be arranged freely as needed. The heterogeneous material region in one layer with a 0.5 mm width can also be well expressed, and the dimensional error does not exceed ± 0.1 mm.

To obtain a high-performance ultraviolet laser thin film, developing one that achieves accurate measurement of absorption loss is essential. In this study, Ta2O5 thin films with different absorptivities were deposited on fused quartz substrates using an ion-beam sputtering technique and by changing the oxygen flow. Ta2O5 thin films were used as high refractive index materials, and UV high reflectance absorption thin films of 355 nm were developed. Two types of 355-nm absorption thin films were prepared on fused quartz substrates using an ion-beam sputtering deposition technique. The transmissivity, reflectivity, and absorptivity at a wavelength of 355 nm were 0.1%, 95.0%, and 4.9% for 5% UV absorption spectra, respectively, whereas those at the wavelength of 355 nm were 0.1%, 87.4% and 12.5% for 12% UV absorption spectra, respectively. The experimental results show that the preparation of high reflectance thin films of 355 nm with different absorptivity can be prepared by ion-beam sputtering deposition. This is of great significance to the calibration of UV thin film weak absorption measuring instruments based on photothermal deflection measurement technology.

To meet the application demands of a wide field of view and fast focal ratio for an aerospace imaging spectrometer, a three-mirror folded Schmidt telescope using a freeform Offner convex grating spectrometer was designed to obtain a field of view 5°, focal ratio of 2, spectral range of 400-1 000 nm, and spectral resolution of 5 nm for a space hyperspectral imager. The expression of an axisymmetric anamorphic asphere Schmidt surface was given and calculated, and a manufacturing method was introduced. The optical system for a Schmidt spectrometer was designed and optimized using software Zemax. Results show that spectral distortion is less than 0.88%, the spectral smile is smaller than 1/3 pixel size, and the optical module transfer function is greater than 0.8. These imaging characteristics can meet the requirements of a space imager. The Schmidt system shows a simple configuration and uses only a single aspherical mirror. Because it possesses excellent imaging specifications, small distortion, small central obscuration, and a compact size, Schmidt is the best candidate for a space instrument with a large aperture, large field of view, and fast focal ratio.

Large-size reflective grating is the core element for improving both the resolution of astronomical spectrometers and the output energy of chirp-pulse amplification systems. With the development of astronomy and laser fusion, the fabrication of large-size reflective gratings has become a hot topic for scholars both domestically and internationally. Compared to the fabrication of a single large-size reflective grating, the mosaic method has become the primary method of fabricating large-size reflective gratings, as it has the advantages of a low difficulty coefficient, low production cost, easy fabrication, and high quality of small gratings to be mosaicked. In this study, the basic principles of large-size reflective grating mosaic technology are introduced, and the research progress of grating mosaic technology is summarized in detail. More specifically, this study considers the theory of grating mosaic error detection, the separation of grating mosaic error, the phase correction of the wavefront of mosaic grating, the reduction of the dimension of grating mosaic error, and the grating mosaic device. Finally, the advantages and disadvantages of grating mosaic technology and directions for future development are summarized.

An optical system simulation and design methods for large-area divergent solar simulators were studied to achieve uniform illumination of a large irradiation area of solar simulators. First, the working principles of fly-eye lens array groups and examine divergent projection systems as well as the production mechanism of the sidelobe effect was analyzed. Subsequently, using nesting modeling combined with the polynomial fitting method, the intensity distribution curve of the xenon lamp axis was obtained. Then a luminous intensity distribution simulation of the xenon lamp was conduct based on the luminous energy symmetry of the xenon lamp. Considering the boundary conditions and parameters for the optical system designly, a beam-shaping system, a fly-eye lens array group, and a divergent projection system were designed. The experimental results show that when the working distance is 20 000 mm and the irradiation surface diameter is 1 500 mm, the irradiation uniformity is 92.8%, which meets the uniform illumination requirement for large-area divergent solar simulators.

To dynamically measure a two-dimensional rotation angle and overcome the shortcomings of a complicated structure and high costs, a method based on laser collimation was proposed and a measurement system was established. First, a method was proposed based on the key measurement requirements. A collimated laser was used as a measurement datum and a remote position detector as a detection device. Second, a measurement system was developed, each module was designed, and the main modules were optimized. Third, the model was established completely after an algorithm was produced. Finally, tests were performed and the obtained data were analyzed within ± 2°. The experimental results show that the stability of the system is positive, the measurement repeatability error is 1 μrad, the X-and Y-axis nonlinearity errors are 1.8% and 1.7%, respectively, and the dynamic band response frequency is better than 200 Hz within ± 0.01°. The study confirms that the system basically offers high precision, high repeatability, high stability, and a dynamic measurement of a two-dimensional rotation angle.

To improve the accuracy of the atmospheric inversion of an ozone observation instrument and to overcome the effects of thermal distortion and satellite attitude error on the orbit for the accuracy of limb pointing, an error correction method for the limb pointing of an ozone detector on the orbit was established. First, through the analysis of low-magnitude star energy and based on observations, an appropriate star observation window and integration time were designed. The blur spot of a star was obtained using flat glass. An image motion compensation technique was then used to ensure the blur spot was stable. The position of the star in the image plane was calculated using a threshold centroid. Subsequently, based on the satellite orbit and detector geometry, a pointing correction method was designed and the pointing accuracy was analyzed after being modified. The results of star observation experiments on the ground show that with this method, the error of stellar positioning is less than ±1.83″ and the pointing error of the visual axe is less than ±3.08″. When the encoder repeats accuracy is ±2.47″, the positioning error of the scanning mirror in the limb observation axis is within ±3.95″, and the accuracy of limb pointing of the ozone detector is better than ±7.9″, which fully meets the inversion accuracy requirement of ±12.4″.

To improve the security of a rotary piezoelectric generator and broaden the effective frequency band, a rotating piezoelectric generator with tunable frequency was studied and its performance was evaluated through theoretical analysis, simulations, and experiments. Natural frequency offset and stiffness offset models were first established, and the effects of stiffness and the number of rotating magnets on the response performance of a generator were determined through a simulation. The analytical results show that the stiffness of the generator linearly increased with axial tension and linearly decreased with axial compression. In addition, the natural frequency increased and became steady with axial tension but decreased at a fast rate with axial compression. Based on the fact that the number of rotating magnets affects the number of resonant peaks as well as the amplitude ratio of the generator, a prototype rotating piezoelectric generator was fabricated and tested. The test results reveal that the natural frequency of the generator increases and that generated voltage decreases depending on whether the piezoelectric beam is stretched or compressed, with the latter having a greater influence on voltage reduction. In addition, the number of rotating magnets affects the natural frequency of the generator. By changing the number of rotating magnets and conducting pre-stretching and pre-compression, the natural frequency of the generator can be adjusted to within a range of 39.2-112 Hz with a maximum frequency shift of 185.7%.

"Sketch and Peel" lithography (SPL) has demonstrated the potential to improve the efficiency of electron beam direct writing. However, it is time-consuming to design exposure layouts for complex patterns. In this study, we proposed a method to generate SPL layouts for complex patterns using an edge tracing algorithm to extract digital image contours. First, the color image was converted to a binary image by image graying and the Otsu adaptive threshold segmentation algorithm. Then, the boundary of the binary image was traced by the MATLAB bwboundaries function. Finally, the MATLAB GDS toolbox was utilized to transform the traced boundary to layouts for exposure. The experiments confirmed that the proposed method is effective for extracting the boundaries of images and converting them to layouts. As shown by fabricating a maple leaf-like pattern, the generated layout still maintains its high graphic fidelity when applied to SPL. The versatility of the proposed method for micro-nanomanufacturing was also verified by fabricating other complex patterns of different sizes and different geometries.

To investigate the interactive effects of micro-cracks on the surfaces and subsurfaces of BK7 optical glass materials during ultrasonic vibration assisted grinding, a group of twice-indentation experiments using Vickers diamond indenters were conducted on BK7 optical glass to simulate the multi-indention effect of single abrasive grit on optical glass under ultrasonic vibration. In addition, the bonded interface technique was performed on the specimens to determine the morphologies of the indentations and micro-cracks on the surface and subsurface of the optical glass. The experimental results show that the maximum depth of subsurface cracks produced by the second indentation is affected by the previous lateral cracks and is reduced by 30 μm under the same loading conditions. Furthermore, the optical glass materials will be broken after lateral crack are closed on the surface or inside of the optical glass. Based on indentation fracture mechanics, a model of elastic/plastic stress fields in the BK7 optical glass under indention loading was established to analyze the mechanism of micro-cracks propagation and the shield effect. The analysis of the interaction of micro-cracks as influenced by ultrasonic vibration reveals that the depth of subsurface cracks decreases and the material removal efficiency is improved with ultrasonic vibration assistance.

Focusing mechanism is a key part of space cameras. Its dynamic performance greatly affects camera reliability. To analysis the dynamic characteristics, the focusing mechanism platform of a space camera was researched in simulation, where its entry point was the guide, and the model of the guide joint was built with the optimized tandem spring damping element in the finite element model of the focusing mechanism platform. The research obtained dynamic parameters based on the Hertzian contact theory and equalizes the rigidity of the ball screw and the coupling on the guide, and formulates the relation expression and corrected parameter. The corrected parameter was confirmed by a comparative experiment based on the variable of the coupling stiffness, thereby completing the dynamic analysis of the space camera focusing platform. Finally, the research accomplishes the dynamic simulation analysis of the focusing platform with the stated analysis method under different conditions, with a deviation of under 2%, thus demonstrating high accuracy and reliability of the analysis method.

The inherent rate-dependent hysteresis non-linearity of a piezoelectric micro-positioning station seriously limits its micro-positioning accuracy. To solve this problem, the Hammerstein rate-dependent hysteresis nonlinear model based on Backlash-Like hysteresis and its modeling method were investigated in this study. An improved Backlash-Like piece-wise identification model was first utilized to describe the static nonlinear characteristics of the piezoelectric micro-positioning station. Combined with the Auto Regressive eXogenous(ARX) model, a rate-dependent dynamic hysteresis model was then established to describe the piezoelectric micro-positioning station. In addition, to solve the problem in which the traditional Particle Swarm Optimization (PSO) method easily falls into a local optimum, an improved PSO method using a cross-mutation strategy was proposed to identify the parameters of the model. The experimental results show that, compared to the traditional Backlash-Like model, the maximum error of model identification is reduced from 0.68 μm to 0.104 μm and the maximum relative error is reduced from 2.69% to 0.35% when the input voltage is 60 V and the voltage frequency is a single-frequency signal of 2 Hz. In addition, when the input voltage of the piezoelectric micro-positioning station is 60 V and the voltage frequency is a single-frequency signal of 30, 60, and 90 Hz, as compared with the Backlash-Like piece-wise identification model, the root mean square error of the Hammerstein rate-dependent hysteresis model decrease from 0.338 7-0.700 6 to 0.035 1-0.190 4, and the relative error decrease from 1.478%-3.087% to 0.153%-0.831%. It was verified that the rate-dependent hysteresis model based on the improved Backlash-Like model could more accurately describe the rate-dependent dynamic hysteresis characteristics of a piezoelectric micro-positioning station as compared with the traditional Backlash-Like static hysteresis model. In addition, the model showed better frequency generalization, and the positioning accuracy of the piezoelectric micro-positioning platform was improved.

Permanent Magnet Linear Synchronous Motors (PMLSMs) with discontinuous stators are used in long-distance transport systems. Control performance degradation of PMLSMs is generally caused by the inability to install position sensors and by the fact that electromagnetic parameters between different movers and stators are not fixed. To solve this problem, a control system was implemented in a section of the stator in this study. First, the electromagnetic parameters of the motor were calibrated during the entry of the mover, and the controller parameters were adjusted based on the calibration parameters to achieve a better control effect. Then, the control system without a position sensor was used to enable the mover to reach a set speed quickly and run stably. Experimental results show that the calibration accuracy of the parameters of the entering process are 0.002 Wb and 0.000 4 H, the position estimation accuracy is 0.63 mm, the speed of the sensorless control can reach the set value within 0.45 s, and the steady state error is 0.02 m/s. The study thus shows that the implemented control system can satisfy the system requirements of high speed and stability.

To meet the requirement of step accuracy for the scanning mirror of a Differential Optical Absorption Spectroscopy (DOAS) mounted on a geosynchronous orbit satellite, the design of a scanning mirror control system with high accuracy is proposed that specifically considers structural and circuit design aspects. In this scheme, the scanning mirror system was controlled by the master controller that received instructions and sended back information about the current position of the scanning mirror. The scanning mirror controled circuit outputs power through the LMD18200 driver chip. Then, the driver consisting of a stepping motor and harmonic reducer drived the scanning mirror to rotate, and the encoder readed the position information of the scanning mirror. In this study, a method of setting the duty cycle of the PWM was proposed, and the control and elimination methods of the harmonic gear transmission hysteresis were studied. Experimental results show that the mean deviation of the step angle of the system is less than 1″, the maximum deviation is less than 5″, and the standard deviation is less than 2″. This control system design satisfies the requirements of step accuracy for the scanning mirror and provides a reference for related applications on subsequent satellite payload.

To meet the high-precision and lightweight requirements of a space optical mirror pointing mechanism, a type of space parallel mechanism based on a spherical 5R mechanism was proposed. Load mounting with traditional 5R parallel mechanisms was difficult. To solve this problem, asymmetrical branches and specific linkages were designed. Workspace, dexterity and carrying capacity were used as optimal indices, and structural parameter optimization design was conducted based on performance atlases. Model analysis of the optimized mechanism was conducted by using the finite element method. Optimization results show that the asymmetrical branched-chain mechanism has a better index of dexterity. The barycenter of the pointing mirror load was designed at the center of the spherical mechanism, which makes the mechanism more compact and increases its natural frequency. The proposed parallel pointing mechanism was shown to have good integrated performance. This study provides a basis for high-precision space optical pointing applications.

Plasmonic electromagnetic wave absorbers based on metal-dielectric-metal nanostructures can achieve single and multi-band absorption. Their multiplex absorption spectra depend on the pattern and dimensions of the nanostructures rather than the materials they are made of. In this progress report, an overview of this field was provided, first summarizing the absorption mechanism from the perspective of materials and the nanostructure, and subsequently discussing a selection of examples focusing on their extreme performance flexibility. The already developed and potential applications, including selective thermal radiator, biosensor, and photoelectric detector were introduced. Finally, we explore the expectations in this rapidly developing field and the future challenges, including dynamic tunability and energy conversion.

A calibration method for the robotic Tool Center Frame (TCF) was proposed, and a calibration sensor system and experimental platform are constructed in this study. The calibration speed and accuracy of the system were measured and studied. This calibration method involved robot movement along the trajectory of a predetermined circle and a straight line. The photoelectric calibration sensor records the time while the system was moving. The position of the deviation of the tool coordinate system was obtained. In this study the error caused by the photoelectric calibration sensor was analyzed, which may not achieve a rectangular coordinate system due to the cause of the assembly. Experimental results reveal the calibration accuracy of a robot tool coordinate system at ±0.5 mm, and a calibration and recovery time of 15 s. These values meet the requirements for accuracy and efficiency in vehicle production, indicating that our method is capable of calibrating the robot tool coordinate system quickly and effectively.

A Singular Value Decomposition (SVD) based turbulence velocity structure function construction method was proposed. The velocity structure function constructed by the method was fitted with a turbulence model to realize the turbulence identification of a laser radar. First, the spatial data of lidar scanning was divided into distance gate sectors. Singular value decomposition was then performed on the turbulent wind field in each subsector, and the characteristic velocity reference value and turbulent pulsation velocity of each distance gate were obtained to construct the velocity structure function. The standard von Kármán turbulence model function was selected as the fitting constraint, and the cube root of the eddy current dissipation rate was obtained to assess the intensity of the turbulence. Finally, through measured data obtained from Lanzhou Airport, the performance of the velocity structure function and local average method of the SVD method under different turbulence intensities were compared and analyzed. The turbulence data reported by the crew were compared and analyzed, and the SVD method was used to predict the turbulence warning, which could reach 85.2%. This method is of great significance for improving airport turbulence detection and identification.

Hyperspectral image classification comprises the classification of every pixel in an image by applying the combination of hyperspectral data atlas and rich spectral information, which can be employed for achieving high-precision classification and automatic recognition of ground objects. Hyperspectral image classification plays an important role in earth observation. Based on the analysis of the characteristics of hyperspectral images with respect to two aspects of general machine learning and deep learning, the progress in associated research and comparison of the effects of pixel-level classification of hyperspectral images are summarized and discussed in this study. The advantages and disadvantages of various algorithms were visually illustrated by comparing the corresponding results. Research objectives and development prospects of hyperspectral image classification are analyzed with respect to two aspects. Firstly, various algorithms need to be studied. A hyperspectral classification algorithm can guarantee classification accuracy required for reducing the algorithm complexity by incorporating multi-source remote sensing data with multi-feature and multi-scale composites. Such an algorithm can improve the classification accuracy of a small sample of the classification model with few parameters, and it can adapt to the intelligent and rapid development requirements of earth observation. Secondly, market applications need to be closely integrated. Practical applications of hyperspectral images should be considered and efficient classification algorithms with marketable competency should be investigated for enhancing the applicability of hyperspectral image classification in remote sensing applications.

Nonlinear friction caused by the flexible link and the transmission process in the harmonic drive leads to complex hysteresis characteristics of harmonic transmission that inevitably affect the transmission accuracy. To describe the hysteresis characteristics of the harmonic drive, a concise neural network hysteresis hybrid model, comprising hysteresis-like characteristic preconditioning in series with a dynamic neural network, was presented in this study. It was executed in two steps: the input signal was preprocessed to produce hysteresis-like behavior; the dynamic Radial Basis Function (RBF) neural network was fully utilized to achieve high-precision approximation of hysteresis-like to hysteresis characteristics of the harmonic drive. Moreover, an experimental platform was constructed in this study, and the data obtained under different experimental conditions were modeled and verified. Both at a constant input accuracy and the accuracy with different input signals and loads, the verification accuracy obtained by the neural network hysteresis hybrid model is 0.449 6 (Mean Square Error (MSE)), which is much higher than the 3.0321 (MSE) accuracy of the classical neural network model. This proves the effectiveness and adaptability of the proposed neural network hysteresis hybrid model.

In the binary description algorithm (Oriented Fast and Rotated Brief, ORB), scale and rotation cause a great error in the registration, and the registration rate is low. Meanwhile, the RANdom Sample Consensus (RANSAC) algorithm has an instability issue. Therefore, in this study, a fast feature matching algorithm was presented based on ORB with RANSAC. First, the feature point extraction method was optimized to eliminate the influence of feature edges. After constructing a simplified pyramid scale-space model, the scale-space structure of the layered image was improved by reducing the number of generated image layers. Subsequently, the gradient direction was used to improve the main direction extraction mode of the traditional ORB algorithm, and the accuracy of the main direction of the feature angular point was improved. Finally, the RANSAC algorithm was improved by applying block random sampling, which improved the stability and accuracy of image registration. Experimental results reveal that the improved ORB and RANSAC fusion algorithm performance greatly improved in terms of scale and rotation registration, and higher registration precision is exhibited in comparison with traditional ORB. The scale registration accuracy is improved by 55.41%, and the rotational registration accuracy is improved by 26.66%. These results indicate that the proposed algorithm basically meets the accuracy and real-time requirements for fast and accurate registration of complex images.

To solve the problems of lost details and added noise in the previous sparse representation image super-resolution, an improved feature extraction algorithm was proposed to improve the image Super-Resolution Reconstruction (SRR) effect. The Gaussian filter was replaced by a symmetric nearest neighbor filter to speed up image super-resolution, and the problem of dictionary learning in the feature space was solved. First, sample training images were generated based on the remote sensing image degradation model, and high-low resolution images were divided into image patches sized 7×7. Then, a high-low resolution joint dictionary mapping matrix was generated after the dictionary was trained and updated. Finally, image super-resolution reconstruction was performed in sparse representation. Experimental results revealed that the proposed method reconstructed a higher-quality super-resolution image in less time. Simultaneously, as compared with the image obtained with the most advanced sparse representation super-resolution algorithm, the SRR resulting image contained more texture details of ground objects. In addition, the peak signal-to-noise ratio and structural similarity index measure were increased by approximately 1.7 dB and 0.016, respectively. Conclusion: The improved sparse representation SRR algorithm can effectively improve the SRR effect of remote sensing images and reduce the super-resolution reconstruction time.

The traditional Dimensionality Reduction (DR) methods consider the spectral features but ignores useful spatial information in HSI. To overcome this problem, this paper proposed a new dimensionality reduction method called Multi-Feature Manifold Discriminant Embedding (MFDE). First, the MFDE method extracted the features of the local binary pattern from HSI data. Next, the with-class and between-class graphs were constructed using sample labels to exploit the local manifold structure. Then, an optimal object function was designed to learn the combined spatial-spectral features by compacting the intra-class samples and simultaneously separating the inter-class samples. Thus, the discriminative ability of embedding features was improved. Experimental results in the Indian Pines and Heihe hyperspectral data sets show that the proposed MFDE method performs better than some state-of-the-art DR methods in most cases and achieves an overall classification accuracy of 95.05% and 96.20%, respectively. Its advantage is more significant for less training samples, making it more conducive to practical applications.