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The optical microstructure on the roller surface is the key for manufacturing microstructures on optical film. In this context, the fabrication of optical microstructures on the cylindrical roller surface is more difficult than that on the planar surface. This Letter starts with a machinability of microstructure arrays on a cylindrical surface, and studies the restriction influences of the tool geometry and process parameters on the characteristics of the microstructure. Then a suitable flexible hinge holder for the fast tool servo is designed based on finite element analysis, and the influential factors to the machining precision of microstructure arrays are investigated. Finally, a machining test of spherical arrays on an aluminium cylindrical surface is carried out, and the high quality of the microstructure indicates that the proposed method is appropriate for the fabrication of optical microstructures.

The classification of esophageal disease based on gastroscopic images is important in the clinical treatment, and is also helpful in providing patients with follow-up treatment plans and preventing lesion deterioration. In recent years, deep learning has achieved many satisfactory results in gastroscopic image classification tasks. However, most of them need a training set that consists of large numbers of images labeled by experienced experts. To reduce the image annotation burdens and improve the classification ability on small labeled gastroscopic image datasets, this study proposed a novel semi-supervised efficient contrastive learning (SSECL) classification method for esophageal disease. First, an efficient contrastive pair generation (ECPG) module was proposed to generate efficient contrastive pairs (ECPs), which took advantage of the high similarity features of images from the same lesion. Then, an unsupervised visual feature representation containing the general feature of esophageal gastroscopic images is learned by unsupervised efficient contrastive learning (UECL). At last, the feature representation will be transferred to the down-stream esophageal disease classification task. The experimental results have demonstrated that the classification accuracy of SSECL is 92.57%, which is better than that of the other state-of-the-art semi-supervised methods and is also higher than the classification method based on transfer learning (TL) by 2.28%. Thus, SSECL has solved the challenging problem of improving the classification result on small gastroscopic image dataset by fully utilizing the unlabeled gastroscopic images and the high similarity information among images from the same lesion. It also brings new insights into medical image classification tasks.

Weak-stiffness mirrors are widely used in various fields such as aerospace and optoelectronic information. However, it is difficult to achieve micron-level precision machining because weak-stiffness mirrors are hard to clamp and are prone to deformation. The machining errors of these mirrors are randomly distributed and non-rotationally symmetric, which is difficult to overcome by common machining methods. Based on the fast tool servo system, this paper proposes a high-precision machining method for weak-stiffness mirrors. Firstly, the clamping error and cutting error compensation strategy is obtained by analyzing the changing process of the mirror surface morphology. Then, by combining real-time monitoring and theoretical simulation, the elastic deformation of the weak-stiffness mirror is accurately extracted to achieve the compensation of the clamping error, and the compensation of the cutting error is achieved by iterative machining. Finally, a weak-stiffness mirror with a thickness of 2.5 mm was machined twice, and the experimental process produced a clamping error with a peak to valley (PV) value of 5.2 µm and a cutting error with a PV value of 1.6 µm. The final machined surface after compensation had a PV value of 0.7 µm. The experimental results showed that the compensation strategy proposed in this paper overcomes the clamping error of the weak-stiffness mirror and significantly reduces cutting errors during the machining process, achieving the high precision machining of a weak-stiffness mirror.

The development of free-form surface optical system makes the design and manufacture of optical components with integrated function and structure more and more important. This paper introduces the evolution and development trend of optical components with integrated functional structure; and analyzes the reasons of high order freeform surface mirror machining prone to astigmatism surface error, it is concluded that forced displacement is the main reason for this phenomenon; the research on the mechanical and thermal performance of optical components with integrated functional structure provides theoretical support for their design and manufacture.

To overcome the loss of the working stroke caused by large stiffness flexible hinge in the single piezoelectric actuator Fast Tool Servo System (FTS), this paper presents a design method of large stroke FTS driven by two-way piezoelectric ceramics. First, the mechanical system is modelled and analysed to get the effect of mechanical parameters on the system response. Then based on the effect and guide means for stiffness requirements of compliant guide mechanism, we use compensating the flexibility matrix method to design a double parallelogram mechanism. Finite element simulation results show that the compensation method can significantly reduce parasitic displacement (reduced from 33.250mm to 4.545mm). The double parallelogram mechanism is completed based on the method of parallel symmetrical design. The results show that the stiffness in function direction is the small, the ratio of the stiffness in non- function direction to function direction is large, which ensure high accuracy and large stroke linear movement of the tool.

Complex surface optical components have been widely used in the forefront of aerospace, space exploration, military reconnaissance and modern information technology due to their advantages in improving aberrations, improving imaging quality, reducing system unit quantity and weight, reducing power loss, improving accuracy and stability. As one of the main methods to process high precision optical component, Computer controlled optical surfacing (CCOS) has also been applied in the processing of complex surfaces. However, due to the incompletely contact between the polishing pad and the surface of the workpiece especially the high-steepness and large curvature area during processing, the phenomenon of unstable removal function is generated, which leads to deterioration of surface accuracy and even flaws..In this paper, the elastic fiber modeling theory derivation, ABAQUS finite element simulation and experimental verification method are used to study the contact problem between the polishing disc and the workpiece surface and the stress distribution when processing complex curved surfaces, and the deformation layer of the polishing pad is optimized. An improved semiflexible polishing disc was used to machine a complex curved aluminum alloy mirror, which improved the surface quality while controlling the change in surface accuracy (PV value) within 10%, verifying the improved polishing disc processing. The effectiveness of complex surfaces.

Various items of roll molds are popularly used to fabricate different kinds of optical films for optoelectronic information and other new and high-tech fields, while the fabrication and evaluation of optical microstructures on the cylindrical roller surface is more difficult than ecumenic manufactured products. This paper investigates the machinability of microstructures on the roll based on a fast tool servo (FTS) system. First, the flexible hinge holder for FTS is designed and its structure parameters are optimized with finite element analysis and fatigue reliability theory. Then the tool radius compensation algorithm for complicated microstructures is deduced based on the surface fitting and bilinear interpolation algorithm of discrete data. Meanwhile, the evaluation index and method are proposed by the medium section method. Finally, a machining test of aspheric arrays on aluminum cylindrical surface is carried out, and the high quality of the microstructure indicates that the proposed method is able to fabricate optical microstructures.

Various items of roll molds are popularly used to fabricate different kinds of optical films for optoelectronic information and other new and high-tech fields, while the fabrication and evaluation of optical microstructures on a cylindrical roller surface is more difficult than ecumenically manufactured products. In this study, the machinability of microstructures on the roll based on a fast tool servo (FTS) system is investigated. First, the flexible hinge holder for a FTS is designed and its structural parameters are optimized with finite-element analysis and fatigue reliability theory. The tool radius compensation algorithm for complicated microstructures is then deduced based on the surface fitting and bilinear interpolation algorithm of discrete data. Meanwhile, the evaluation index and method are proposed by the medium section method. Finally, a machining test of aspheric arrays on a cylindrical aluminum surface is carried out, and the high quality of the microstructure indicates that the proposed method is able to be used to fabricate optical microstructures.

Advanced optical systems have brought forward higher requirements for aspheric processing of hard brittle materials, which put forward higher request to the dynamic performances of optical grinding spindles. Due to the integration of the spindle and the tool of optical machine systems, the dynamic behaviors of the spindle system are more complicated than that of other spindles. An integrated model dynamic model of optical grinding motorized spindles which consists of a bearing model, a thermal model and a spindle-tool dynamic model is proposed. The bearing model takes the effect of the thermal displacement into account, and the rotor dynamic model with the effects of the tool and damp is established by the finite element method (FEM). An example calculation on a grinding motorized spindle is preformed and the correlative test is carried out. In the process, the dynamic model is modified by the free excitation test. The mathematical results agree well with the experimental data, which indicates that the proposed model is able to analyse the bearing-spindle-tool assembly dynamics of optical grinding motorized spindles. Meanwhile, the influences of the thermo-mechanical coupled factor (TMCF) and the tool on the dynamic behaviors of the system are obtained. The conclusions are available to the dynamic analysis and design of various high speed and precision spindles.

Owing to its material properties, aluminum-based optical loads are widely used in the aerospace field. At present, the main processing of an aluminum alloy mirror is single-point diamond turning followed by the combined polishing process. The surface will generate some white crystals during the chemical mechanical polishing process (CMP). These crystals can affect the improvement of surface quality and seriously reduce the processing efficiency of the whole process. In view of the above problems, four main factors of crystallization are obtained by interface theoretical analysis, Visual MINTEQ simulation of chemical morphological distribution, and experimental analysis. They are temperature, PH value of polishing fluid, solid-liquid contact angle, and impurity content of aluminum alloy. The crystallization phenomenon in the polishing process is successfully suppressed by improving the polishing process and selecting new materials. The experimental results showed that the surface roughness decreased from 7.21 to 2.98 nm without crystallization using the new method.