Huiying Zhao

Aspheric Surface Measurement Using Capacitive Sensors

This paper proposes a new method for the measurement of spherical coordinates by using capacitive sensors as a non-contact probe solution of measurement of aspheric surfaces. The measurement of the average effect of the capacitive probe and the influence of capacitive probe tilting were studied with respect to an eccentric spherical surface. Based on the tested characteristic curve of the average effect of the sphere and probe, it was found that nonlinear and linear compensation resulted in high measurement accuracy. The capacitance probe was found to be trying to fulfill a need for performing nm-level precision measurement of aspheric electromagnetic surfaces.

Multi-Repeated Projection Lithography for High-Precision Linear Scale Based on Average Homogenization Effect

A multi-repeated photolithography method for manufacturing an incremental linear scale using projection lithography is presented. The method is based on the average homogenization effect that periodically superposes the light intensity of different locations of pitches in the mask to make a consistent energy distribution at a specific wavelength, from which the accuracy of a linear scale can be improved precisely using the average pitch with different step distances. The method’s theoretical error is within 0.01 µm for a periodic mask with a 2-µm sine-wave error. The intensity error models in the focal plane include the rectangular grating error on the mask, static positioning error, and lithography lens focal plane alignment error, which affect pitch uniformity less than in the common linear scale projection lithography splicing process. It was analyzed and confirmed that increasing the repeat exposure number of a single stripe could improve accuracy, as could adjusting the exposure spacing to achieve a set proportion of black and white stripes. According to the experimental results, the effectiveness of the multi-repeated photolithography method is confirmed to easily realize a pitch accuracy of 43 nm in any 10 locations of 1 m, and the whole length accuracy of the linear scale is less than 1 µm/m.

Research and progress of rapid polishing technology for large aperture optics

In view of the ultra-precision machining for large aperture optics developing rapidly but lacking effective rapid polishing methods, the research problems worth further studying are pointed out. The current situation, removing mechanism and processing difficulties of large aperture ultra-precision machine are introduced. The quantity and diameter of plane optics are increasing year by year, but currently the rapid removing of ultra-precision machine based on deterministic control of surface shape of the meter size optical components is still a blank. The development of related field is seriously affected huge losses caused by the low precision and low processing efficiency. The research situation of the high accuracy and rapid polishing methods are introduced for the main factors in the polishing processing system, such as movement patterns, polishing pad, polishing slurry and process parameters. According to the characteristics of the polishing machining process that bad deterministic control of the surface shape and the low removal efficiency, the research emphasis should be the methods that deterministic control and rapid removing of the machine, a new generation of high precision and high efficiency rapid polishing equipment and application process suitable for the large aperture and flat optical components.

Research on the calibration method of reference flat based on gravity deformation

In high-precision vertical large-caliber flat interferometry, the gravity deformation of the reference flat will lead to a large error of the surface shape measured. Based on the analysis of the finite element method, this paper combines the three flats test method with Zernike polynomial fitting to compensate and calibrate the error of the reference flat. For the diameter of 300 mm and a thickness of 90 mm of the fused silica reference flat, the results of analysis show that the PV deformation under the T-bracing is 0.021 λ. (λ = 632.8nm). The simulation test result of the influence of deformation on the three-flats test shows that the reference flat the gravity deformation not only affects the detection of self surface, but also has a great influence on the surface detection results of the undeformed flat. And the PV of the surface shape detection results residual is close to 0.011λ. In the end, the new calibration method base on compensate reference deformation for three flats test was proposed, and the validity was verified by simulation.

Alignment Method for Linear-Scale Projection Lithography Based on CCD Image Analysis

This paper presents a method to improve the alignment accuracy of a mask in linear scale projection lithography, in which the adjacent pixel gray square variance method is applied to a charge-coupled device (CCD) image to obtain the best position of the focal length of the motherboard and then realize the alignment of the focal plane. Two image positions in the focal plane of the CCD are compared with the traits overlap according to the image splicing principle, and four typical errors are corrected on the basis of the total grating errors. Simultaneously, the rotation error of the mask is used to summarize the grayscale variation function of the CCD image. Threshold functions are employed to express the factors including the wave crests of the amplitude, period error, and phase error, which govern the rotation accuracy and weight alignment accuracy expression of the established four error factors. Finally, in the experiment, the slope of the mask is corrected and adjusted to the same direction as the slide plate with the assistance of a dual-frequency laser interferometer. The effect of the alignment error on the lithography accuracy is discussed and verified in the static case, and it is found that the CCD maximum resolution pixel is 0.1 μm and accuracy of the scale is 0.79 μm in only a 200-mm-measurement range.

Research of the wavefront detection method based on the scanning pentaprism

With the rapid developing of science and technology, large aperture optical system plays an important role in the hightech fields including space optics, astronomical optics, inertial confinement fusion, the detecting and recognizing of space target. However, the problems of the wavefront sensing about large aperture optical system has been totally solved because of the equipment expenses and long manufacturing periods. In order to test the large aperture elements in optical system with cheaper costs and higher resolution, more and more attentions are paid into the wavefront sensing of large aperture optical systems. The scanning pentaprism system is introduced to divide the wavefront of the interferometer into a series of sub-wavefront, and the relative positions of the spot centroid accroding to every sub-wavefront are recorded on the CCD camera. The normal directions of every sub-wavefront are obtained to reconstruct the tested wavefront. Experimental results are accord with the interferometer measure results. The feasibility of the pentaprism scanning method has been validated. Finally the influences of measurement apparatus and environment on the measuring precision is discussed. Which is useful to expand the measuring range to keep high spatial resolution and reduce cost.

Mechanism and experimental research on ultra-precision grinding of ferrite

Ultra-precision grinding of ferrite is conducted to investigate the removal mechanism. Effect of the accuracy of machine tool key components on grinding surface quality is analyzed. The surface generation model of ferrite ultra-precision grinding machining is established. In order to reveal the surface formation mechanism of ferrite in the process of ultraprecision grinding, furthermore, the scientific and accurate of the calculation model are taken into account to verify the grinding surface roughness, which is proposed. Orthogonal experiment is designed using the high precision aerostatic turntable and aerostatic spindle for ferrite which is a typical hard brittle materials. Based on the experimental results, the influence factors and laws of ultra-precision grinding surface of ferrite are discussed through the analysis of the surface roughness. The results show that the quality of ferrite grinding surface is the optimal parameters, when the wheel speed of 20000r/mm, feed rate of 10mm/min, grinding depth of 0.005mm, and turntable rotary speed of 5r/min, the surface roughness Ra can up to 75nm.

Design of an ultra-precision CNC chemical mechanical polishing machine and its implementation

The chemical mechanical polishing (CMP) is a key process during the machining route of plane optics. To improve the polishing efficiency and accuracy, a new CMP model and machine tool were developed. Based on the Preston equation and the axial run-out error measurement results of the m circles on the tin plate, a CMP model that could simulate the material removal at any point on the workpiece was presented. An analysis of the model indicated that lower axial run-out error led lower material removal but better polishing efficiency and accuracy. Based on this conlusion, the new CMP machine was designed, and the ultra-precision gas hydrostatic guideway and rotary table as well as the Siemens 840Dsl numerical control system were incorporated in the new CMP machine. To verify the design principles of new machine, a series of detection and machining experiments were conducted. The LK-G5000 laser sensor was employed for detecting the straightness error of the gas hydrostatic guideway and the axial run-out error of the gas hydrostatic rotary table. A 300-mm-diameter optic was chosen for the surface profile machining experiments performed to determine the CMP efficiency and accuracy.

On-line measurement of diameter of hot-rolled steel tube

In order to design a online diameter measurement system for Hot-rolled seamless steel tube production line. On one hand, it can play a stimulate part in the domestic pipe measuring technique. On the other hand, it can also make our domestic hot rolled seamless steel tube enterprises gain a strong product competitiveness with low input. Through the analysis of various detection methods and techniques contrast, this paper choose a CCD camera-based online caliper system design. The system mainly includes the hardware measurement portion and the image processing section, combining with software control technology and image processing technology, which can complete online measurement of heat tube diameter. Taking into account the complexity of the actual job site situation, it can choose a relatively simple and reasonable layout. The image processing section mainly to solve the camera calibration and the application of a function in Matlab, to achieve the diameter size display directly through the algorithm to calculate the image. I build a simulation platform in the design last phase, successfully, collect images for processing, to prove the feasibility and rationality of the design and make error in less than 2%. The design successfully using photoelectric detection technology to solve real work problems