Yulei Dai

• Haiyuan 1st Road, Futian District, Shenzhen, Guangdong, P.R.C. at The University of Hong Kong - Shenzen Hospital

Ion beam polishing (IBP) is the highest precision manufacturing technology widely applied in optical, semiconductor, and other fields. This chapter systematically introduces the theoretical foundations, process mechanisms, and practical implementations of IBP. First, the material removal mechanism based on ion sputtering theory is introduced, inclu...

The mandrel parts, as the essential component of the aerostatic spindle, play a pivotal role in determining the performance of both the spindle and ultra-precision machine tools. However, the stringent precision machining requirements of these parts pose significant challenges to machining technology. In this paper, an integrated process method com...

Magnetorheological finishing (MRF) of aspherical optical elements usually requires the coordination between the translational axes and the oscillating axes of the machine tool to realize the processing. For aspheric optical elements whose steepness exceeds the machining stroke of the equipment, there is still no better method to achieve high-precis...

In a supersonic cylindrical isolator at Mach 2, the structures and frequency characteristics of shock train flow fields were experimentally studied by the schlieren measurement method. According to the design principle of parallel light through schlieren windows in a cylindrical duct, a high-precision conformal optical window pair was designed and...

A high-precision measurement machine tool faces the challenge of correlating the overall motion accuracy with the components form and positional accuracy. This study presents an innovative method for addressing this issue in ultra-precision measuring machines. A geometric error model based on multibody theory, and a weight model are established to...

X-ray mirrors, which are essential for constructing synchrotron radiation light sources, are highly required for full-range spatial wavelength errors. This paper investigated power-law non-Newtonian fluids and pointed out that both three-body removal and shear removal existed in the shear thickening polishing process. Subsequently, this paper calcu...

The on-machine measurement system can effectively improve the machining efficiency and accuracy of the optics in the grinding stage, but the common grinding machine has large geometric errors and ambient temperature errors, which are the key factors restricting the accuracy of on-machine measurement. In this paper, a high-precision error separation...

Magnetorheological finishing (MRF) is a deterministic optical processing technique based on CCOS that achieves high removal efficiency and processing accuracy while reducing subsurface damage. This technique still suffers from multiple iterations of processing due to variations in removal efficiency and the inability to fully correct mid-frequency...

The mandrel parts, as the essential component of the aerostatic spindle, play a pivotal role in determining the performance of both the spindle and ultra-precision machine tools. However, the stringent precision machining requirements of these parts pose significant challenges to machining technology. In this paper, an integrated process method com...

A dual aspheric integrated beam shaper suitable for a high-power laser situation has been designed and realized. The model for this lens was derived theoretically and the performance was evaluated using a detailed simulation. The ultrasonic vibration assisted cutting and the high-precision grinding and polishing technology were used for the process...

As a flexible grinding method with high efficiency, abrasive belt grinding has been widely used in the machining of mechanical parts. However, abrasive belt grinding has not been well applied in the field of ultra-precision optical processing, due to the lack of a stable and controllable removal function. In this paper, based on the idea of determi...

The technology of in situ measurement of cylindrical shapes is an important means of improving the surface machining accuracy of cylindrical workpieces. As a method of cylindricity measurement, the principle of the three-point method has not been fully studied and applied, so it is seldom used in the field of high-precision cylindrical topography m...

The radial error is an important parameter to evaluate the performance of ultra-precision spindles. The three-point method has not yet been well applied in nanometer-scale measurement due to its disadvantages of harmonic suppression and the complicated error separation process. In order to verify that the three-point method can realize the nanomete...

To realize the flow visualization of shock train structures by Schlieren measurements in a square-to-circular transition isolator, a high-precision conformal optical window was manufactured by fly-cutting technology. According to the light refraction principle, the window’s outer surface was iteratively optimized based on the super-elliptic curves...

To improve the material removal efficiency and surface quality of single-crystal silicon after magnetorheological finishing, a novel green chemical-mechanical magnetorheological finishing (CMMRF) fluid was developed. The main components of the CMMRF fluid are nano-Fe3O4, H2O2, CH3COOH, nanodiamond, carbonyl iron powder, and deionized water. The nov...

With the development of short wavelength optics, high requirements are put forward for the full frequency errors of optical elements, while the processing efficiency and surface quality of traditional polishing methods are difficult to meet their requirements. In this paper, a fluid lubricated polishing method is proposed by combining non-Newtonian...

Magnetorheological finishing (MRF) is a sub-aperture polishing process, which is often used to correct surface errors and remove sub-surface damage after grinding. A strong correlation exists between the material removal rate and surface roughness in MRF, but current theoretical models are incapable of predicting these two factors at the same time....

Extreme ultraviolet lithography objective lenses require surface figure accuracy of approximately sub-nanometer root mean square (RMS). As the key equipment for sub-nanometer accuracy figuring, the dynamic and static performance of ion beam figuring (IBF) machine tools are critical. However, the related research is not sufficient and comprehensive....

The profile and concentricity of hemispherical shells affect the frequency split and quality factor of hemispherical resonators. To compensate for machining errors caused by tool wear and tool setting, an on-machine measurement (OMM) method for the profile and concentricity of hemispherical shells in ultra-precision grinding was developed without t...

The surface figure accuracy requirement of cylindrical surfaces widely used in rotors of gyroscope, spindles of ultra-precision machine tools and high-energy laser systems is nearly 0.1 µm. Cylindricity measuring instrument that obtains 1-D profile result cannot be utilized for deterministic figuring methods. Interferometric stitching test for cyli...

X ray mirrors are symmetrical workpieces along the length and width and are widely used in various optical systems. Unlike the center-symmetric circular mirror, it is more difficult to suppress the edge effect of the x ray mirror during the polishing process, which greatly limits the polishing accuracy and polishing efficiency. Based on this, the u...

The geometric accuracy of a hemispherical shell resonator (HSR) affects the assembly accuracy and final performance of a hemispherical resonant gyroscope in many ways. During the precision grinding of a resonator, the tool-setting error and wear error affect the form and positional accuracy of the inner and outer spherical surfaces. In this study,...

In order to perform the flow visualization of a shock train structure by the schlieren imaging method in the cylindrical isolator, to the best of our knowledge, a novel integrative design and processing scheme of an aluminum alloy pipe with an acrylic conformal optical window pair are proposed. The optical ray tracing and wavefront correction metho...

Objective Smooth polishing has a good improvement on the medium and high frequency errors of the workpiece, but the surface accuracy of the workpiece will be damaged subsequently. Methods Therefore, a nonlinear compensation method is proposed. The realization mechanism, mathematical model and compensation effect of nonlinear compensated smooth pol...

A three-step quasi-absolute testing method for optical cylinders is proposed in this Letter. Three measurements are taken at the so-called cat's eye position and confocal null testing positions with a computer-generated hologram (CGH) rotated around the axis parallel to that of the cylinder. The quasi-absolute surface error of the cylinder is obtai...

With the application spectrum moving from infrared to visible light, aluminum optics with complex forms are difficult to fabricate by the majority of existing processing methods. Possessing the highest machining precision and low processing contamination, ion beam figuring (IBF) is a better method for fabrication of aluminum optics. However, the su...

Micro-jet is an effective ultra-smooth polishing method, but its polishing effect is affected by many factors. In this paper, the effects of different distributions of nozzles on the workpiece were investigated by finite element software, including uniform distribution, from large to small (with the edge as the starting point) and from small to lar...

Ion beam figuring (IBF) provides a deterministic figuring method for fabricating ultra-high precision optical components such as lithographic objective lenses. But in the previous IBF process, the convergence of surface accuracy is often uncertain. Therefore, the iterative processing methods are mostly adopted. In the iterative process, the converg...

With the development of optoelectronic information technology, high-performance optical systems require an increasingly higher surface accuracy of optical mirrors. The fast tool servo (FTS) based on the piezoelectric actuator is widely used in the compensation machining of high-precision optical mirrors. However, with the low natural frequency of m...

The computer-controlled optical surface (CCOS) can process good optical surfaces, but its edge effect greatly affects its development and application range. In this paper, based on the two fundamental causes of the CCOS’s edge effect—namely the nonlinear variation of edge pressure and the unreachable edge removal—a combined polishing method of doub...

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 machinabi...

Benefiting from high specific stiffness and high reflectance, aluminum optics with a complex surface profile are widely used in aerospace optical systems which have strict requirements for volume of the systems. Contact figuring polishing process provides highly deterministic technology for the fabrication of high precision aluminum optics. However...

The surface quality and subsurface damage (SSD) distribution achieved with a fine-grained grinding wheel under different depth-of-cut and cutting speed is experimentally studied. The ground surface roughness (SR) is investigated via white light interferometry and expressed in terms of four typical roughness values (PV, RMS, Rz, and Ra). The SSD is...

Aluminum optics are widely used in modern optical systems because of their high specific stiffness and high reflectance. With the applied optical frequency band moving to visible, traditional processing technology cannot meet the processing precision. Ion beam sputtering (IBS) provides a highly deterministic technology for high-precision aluminum o...

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,...

Aluminum optics are widely used in modern optical systems because of high specific stiffness and high reflectance. Magnetorheological finishing (MRF) provides a highly deterministic technology for high precision aluminum optics fabrication. However, the contamination layer will generate on the surface and bring difficulties for the subsequent proce...

We investigate the nanoscale damage precursors that will cause laser damage initiation on fused silica surface during KOH-based wet etching. Some nanoscale damage precursors, like impurity contamination and chemical structure defects on different etched surface with a KOH solution, are explored through a variety of testing methods at nanoscale spat...

To realize low-damage ultra-precision grinding on fused silica, the surface quality and subsurface damage (SSD) distribution with fine-grained grinding wheel under different depth-of-cut and cutting speed are experimentally studied. The material removal mechanism under different grinding parameters is revealed by calculating undeformed chip thickne...

Optical components with complex surfaces are widely applied. Ultra-precision diamond turning technology can fabricate these complex surfaces efficiently and accurately. Fast axis servo (FAS) system has the characteristics of large stroke and high frequency response. In this paper, Fast axis servo system based on linear rolling guide rail was used t...

Single point diamond turning (SPDT) is highly versatile in fabricating axially symmetric form, non-axially-symmetric form and free form surfaces. However, inevitable microstructure known as turning marks left on the surface have limited the mirror’s optical performance. Based on chemical mechanical polishing (CMP) mechanism, smoothing polishing (SP...

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...

In recent years, monolithic multisurface optics with high-order aspheric surfaces and free-form surfaces have become a research hotspot. However, the high-precision shape and position error detection and high-efficiency compensation processing are the challenges faced by monolithic multisurface optics. In this paper, the shape and position error de...

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...

Ultra-smooth surfaces with low contamination and little damage are a great challenge for aluminum optical fabrication. Ion beam sputtering (IBS) has obvious advantages of low contamination and non-contact that make it a perfect method for processing aluminum optics. However, the evolution laws of aluminum surface morphology are quite different from...

An aerostatic spindle is a core component in ultra-precision machine tools. The rotor of the spindle has extremely high manufacturing accuracy, which cannot be directly achieved via traditional machining, but always via manual grinding. The deterministic figuring theory is introduced into the machining of shaft parts, which overcomes many shortcomi...

At present, aluminum-based optical payloads are widely used in the aviation and aerospace field, and the demand for aluminum mirrors has become increasingly urgent in the visible light region. The main processing of an aluminum alloy mirror involves single-point diamond turning followed by a combined polishing process. Among these processes, magnet...

The application of ultra-precision shaft parts is widely used, such as the spindle core of the air bearing spindle in ultra-precision machine tools. The precision of the spindle core is extremely high, and it is very difficult to obtain directly by traditional Computer Numerical Control (CNC) machine tools but is mostly obtained by manual grinding,...

Nanoscale laser damage precursors generated from fabrication have emerged as a new bottleneck that limits the laser damage resistance improvement of fused silica optics. In this paper, ion beam etching (IBE) technology is performed to investigate the evolutions of some nanoscale damage precursors (such as contamination and chemical structural defec...

Ultra-precision shaft components are widely used, such as the shaft core of air-floating spindle, etc. At present, the final precision of such workpieces are difficult to reach through CNC machining tools, but often with the help of manual grinding, of which the machining precision and efficiency are greatly limited. Based on the deterministic figu...

The installation tilt causes the actual measured circular contour to be an elliptical contour [1], and the installation eccentricity causes the sampled points uneven [2], which can both affect the measurement accuracy of the roundness error [3, 4]. The tilt and eccentricity error must be separate from the measured data when measuring the cylindrica...

A deterministic figuring method for cylindrical surface based on abrasive belt polishing is proposed in this study in order to improve the geometric accuracy of metal shaft parts. The principal motion of material removal is performed through the axial oscillation of the abrasive belt, and the different material removal at different positions can be...

Metallic elements can contaminate single crystal silicon mirror during ion beam etching (IBE) and other postprocessing methods, which can affect the performance of components in an infrared laser system. In this work, scanning electron microscope (SEM) and atomic force microscope (AFM) were used to characterize the distribution of contaminant repre...

To improve the effective deformation of the unimorph deformable mirror (DM), ion beam figuring (IBF) is applied for manufacturing the initial surface figure. However, heat produced during IBF can cause comparable internal stress and thermal deformation on the adhesive layer, which causes the mirror's figure to be unsatisfactory. Consequently, the w...

All-reflective coaxial visible/infrared imaging systems based on monolithic multisurface optics have been a hot point of research in recent years. Since multiple surfaces share a single substrate, their relative positions are fundamentally guaranteed as fabricated without any alignment. In this paper, the coaxial system is designed with multifolded...

The correction accuracy of a pint-sized unimorph deformable mirror (DM) is significantly influenced by the nonlinear hysteresis error of piezoelectric ceramics, especially in an open-loop state. Moreover, the control bandwidth is also reduced by the nonlinearity. In this paper, we fabricated a three-unit pint-sized unimorph DM with strain gauges in...

Ultrasmooth surfaces with sub-nanometer roughness and low damage are a great challenge for optical fabrication. Ion beam sputtering (IBS) has obvious advantages on the improvement of surface quality and the removal of surface defects. However, surface defects with different properties and structures display different evolution laws during the IBS p...

As the main device to correct optical aberrations, the unimorph or bimorph deformable mirror (DM) is widely used in adaptive optics. The Shack-Hartmann Wave-front sensor et al. obtains the surface figure through the mirror's reflected light. However, it does not directly receive the motion state of the piezoelectric ceramic, and the wave-front sens...

As the thickness of the adhesive layer between the mirror and the actuator decreases and the performance requirements of the unimorph deformable mirror (DM) increase, stricter control on the adhesive layer thickness and Young’s modulus is necessary. In this paper, a finite element model (FEM) for the unimorph DM with an adhesive layer is obtained....