Fourier transform based dynamic error modeling method for ultra-precision machine tool
Author(s):
Guoda Chen;
Yingchun Liang;
Kornel F. Ehmann;
Yazhou Sun;
Qingshun Bai
Show Abstract
In some industrial fields, the workpiece surface need to meet not only the demand of surface roughness, but the strict requirement of multi-scale frequency domain errors. Ultra-precision machine tool is the most important carrier for the ultra-precision machining of the parts, whose errors is the key factor to influence the multi-scale frequency domain errors of the machined surface. The volumetric error modeling is the important bridge to link the relationship between the machine error and machined surface error. However, the available error modeling method from the previous research is hard to use to analyze the relationship between the dynamic errors of the machine motion components and multi-scale frequency domain errors of the machined surface, which plays the important reference role in the design and accuracy improvement of the ultra-precision machine tool. In this paper, a fourier transform based dynamic error modeling method is presented, which is also on the theoretical basis of rigid body kinematics and homogeneous transformation matrix. A case study is carried out, which shows the proposed method can successfully realize the identical and regular numerical description of the machine dynamic errors and the volumetric errors. The proposed method has strong potential for the prediction of the frequency domain errors on the machined surface, extracting of the information of multi-scale frequency domain errors, and analysis of the relationship between the machine motion components and frequency domain errors of the machined surface.
Fast axis servo for the fast and precise machining of non-rotational symmetric optics
Author(s):
Fujing Tian;
Ziqiang Yin;
Shengyi Li
Show Abstract
A new long range tool servo-fast axis servo is developed, which is used for fabricating the non-rotational symmetric optics surface with millimeters’ sag. The mechanism design, motion modeling and development of FAS device were studied. The FAS consists of a linear motor, aerostatic bearings, high-resolution encoder and a motion controller. A control strategy consists of a proportional, integral and derivative (PID) feedback controller and velocity/acceleration feedforward controller is implemented to accommodate the system control performance. Experimental tests have been carried out to verify the performance of the FAS system.
A high efficiency machining method of SiC: ion-enhanced atmospheric pressure plasma machining
Author(s):
Baolu Shi;
Xuhui Xie;
Yifan Dai;
Chunde Liao
Show Abstract
An ion-enhanced atmospheric pressure plasma machining (IAPPM) method is introduced to improve the processing efficiency of SiC. The argon inductively coupled plasma is generated in designed the IAPPM machine. SF6 chosen as the reactive gas is injected into the argon plasma where SF6 is broken down into fluorine radicals. The reactive atoms are delivered onto the surface of SiC, and SiF4 is generated which is exhausted in the gaseous form. The material removal rate is increased by bringing in the energetic ions bombardment. Three linear trenches were etched onto the S-SiC sample. The etch rate is 3μm/min. The surface becomes rough after the IAPPM process.
Diamond tool wear detection method using cutting force and its power spectrum analysis in ultra-precision fly cutting
Author(s):
G. Q. Zhang;
S. To
Show Abstract
Cutting force and its power spectrum analysis was thought to be an effective method monitoring tool wear in many cutting processes and a significant body of research has been conducted on this research area. However, relative little similar research was found in ultra-precision fly cutting. In this paper, a group of experiments were carried out to investigate the cutting forces and its power spectrum characteristics under different tool wear stages. Result reveals that the cutting force increases with the progress of tool wear. The cutting force signals under different tool wear stages were analyzed using power spectrum analysis. The analysis indicates that a characteristic frequency does exist in the power spectrum of the cutting force, whose power spectral density increases with the increasing of tool wear level, this characteristic frequency could be adopted to monitor diamond tool wear in ultra-precision fly cutting.
Fabrication of micro-lens array on convex surface by meaning of micro-milling
Author(s):
Peng Zhang;
Yunlong Du;
Bo Wang;
Debin Shan
Show Abstract
In order to develop the application of the micro-milling technology, and to fabricate ultra-precision optical surface with complex microstructure, in this paper, the primary experimental research on micro-milling complex microstructure array is carried out. A complex microstructure array surface with vary parameters is designed, and the mathematic model of the surface is set up and simulated. For the fabrication of the designed microstructure array surface, a micro three-axis ultra-precision milling machine tool is developed, aerostatic guideway drove directly by linear motor is adopted in order to guarantee the enough stiffness of the machine, and novel numerical control strategy with linear encoders of 5nm resolution used as the feedback of the control system is employed to ensure the extremely high motion control accuracy. With the help of CAD/CAM technology, convex micro lens array on convex spherical surface with different scales on material of polyvinyl chloride (PVC) and pure copper is fabricated using micro tungsten carbide ball end milling tool based on the ultra-precision micro-milling machine. Excellent nanometer-level micro-movement performance of the axis is proved by motion control experiment. The fabrication is nearly as the same as the design, the characteristic scale of the microstructure is less than 200μm and the accuracy is better than 1μm. It prove that ultra-precision micro-milling technology based on micro ultra-precision machine tool is a suitable and optional method for micro manufacture of microstructure array surface on different kinds of materials, and with the development of micro milling cutter, ultraprecision micro-milling complex microstructure surface will be achieved in future.
Form control in atmospheric pressure plasma processing of ground fused silica
Author(s):
Duo Li;
Bo Wang;
Qiang Xin;
Huiliang Jin;
Jun Wang;
Wenxia Dong
Show Abstract
Atmospheric Pressure Plasma Processing (APPP) using inductively coupled plasma has demonstrated that it can achieve comparable removal rate on the optical surface of fused silica under the atmosphere pressure and has the advantage of inducing no sub-surface damage for its non-contact and chemical etching mechanism. APPP technology is a cost effective way, compared with traditional mechanical polishing, magnetorheological finishing and ion beam figuring. Thus, due to these advantages, this technology is being tested to fabricate large aperture optics of fused silica to help shorten the polishing time in optics fabrication chain. Now our group proposes to use inductively coupled plasma processing technology to fabricate ground surface of fused silica directly after the grinding stage. In this paper, form control method and several processing parameters are investigated to evaluate the removal efficiency and the surface quality, including the robustness of removal function, velocity control mode and tool path strategy. However, because of the high heat flux of inductively coupled plasma, the removal depth with time can be non-linear and the ground surface evolvement will be affected. The heat polishing phenomenon is founded. The value of surface roughness is reduced greatly, which is very helpful to reduce the time of follow-up mechanical polishing. Finally, conformal and deterministic polishing experiments are analyzed and discussed. The form error is less 3%, before and after the APPP, when 10μm depth of uniform removal is achieved on a 60×60mm ground fused silica. Also, a basin feature is fabricated to demonstrate the figuring capability and stability. Thus, APPP is a promising technology in processing the large aperture optics.
Dressing of diamond grinding wheels by abrasive water jet for freeform optical surface grinding
Author(s):
Wei Wang;
Peng Yao;
Chengwu Li;
Chuanzhen Huang;
Jun Wang;
Hongtao Zhu;
Zengwen Liu
Show Abstract
During the ultra-precision grinding of a large aperture mirror made of RB-SiC, the grinding wheel becomes dull rapidly, which will lead to an increase of grinding force and a decrease of grinding ratio. In this paper, diamond grinding sticks were dressed with micro SiC abrasive water jet and water jet. Through single factorial experiments, the influence of jet pressure on the dressing performance was investigated. To analyze and evaluate the effect of dressing quantitatively, the 3D roughness and the wheel topography were measured and compared with laser scanning confocal microscope before and after dressing. The experimental results show that the abrasive grains are well protruded from binder and the distribution of the abrasive grains becomes uniform after dressing by abrasive water jet when the dressing parameters are properly selected. The dressing performance of abrasive water jet is much better than water jet. For dressing ultra-fine grit size wheels, the abrasive size of the jet should be smaller than the wheel grit size to achieve a better result. The jet pressure is an obvious influence factor of the surface topography.
Novel MRF fluid for ultra-low roughness optical surfaces
Author(s):
Paul Dumas;
Charles McFee
Show Abstract
Over the past few years there have been an increasing number of applications calling for ultra-low roughness (ULR)
surfaces. A critical demand has been driven by EUV optics, EUV photomasks, X-Ray, and high energy laser applications. Achieving ULR results on complex shapes like aspheres and X-Ray mirrors is extremely challenging with conventional polishing techniques. To achieve both tight figure and roughness specifications, substrates typically undergo iterative global and local polishing processes. Typically the local polishing process corrects the figure or
flatness but cannot achieve the required surface roughness, whereas the global polishing process produces the required
roughness but degrades the figure. Magnetorheological Finishing (MRF) is a local polishing technique based on a
magnetically-sensitive fluid that removes material through a shearing mechanism with minimal normal load, thus removing sub-surface damage. The lowest surface roughness produced by current MRF is close to 3 Å RMS. A new
ULR MR fluid uses a nano-based cerium as the abrasive in a proprietary aqueous solution, the combination of which
reliably produces under 1.5Å RMS roughness on Fused Silica as measured by atomic force microscopy. In addition to the highly convergent figure correction achieved with MRF, we show results of our novel MR fluid achieving <1.5Å
RMS roughness on fused silica and other materials.
High performance fluoride optical coatings for DUV optics
Author(s):
Lichao Zhang;
Xikun Cai
Show Abstract
In deep ultraviolet region that typical applications are used on the ArF wavelength, coated optics should meet stringent requirements of optical systems. To meet these requirements, systematical researches are carried out on fabrication and characterization methods of fluoride coatings. First, by optimizing of deposition processes, dense coatings with the refractive index of ~1.7 for LaF3 and ~1.4 for MgF2, together with extinction coefficients of ~2×10-4 on 193nm were realized. The transmission of AR coating for 193nm achieved by using optimized deposition techniques is 99.8%. Second, a method of designing shadowing masks was developed to solve the problem of correcting coating thickness distributions for complex DUV systems. By using the method, the thickness distribution error specification of 3% PV has been achieved on substrates with ~300mm diameters and large curvatures. Finally, the laser calorimetry method is used to evaluate the laser radiation stability of fluoride coatings. It is turned out that the damage coefficients of fluoride coatings, which are defined as the values of unrecoverable increase of the absorption during the laser irradiation process, are much lower than that of fused silica substrates. The above progresses could further support the realization of high performance DUV optical systems.
Surface quality of silicon wafer improved by hydrodynamic effect polishing
Author(s):
Wenqiang Peng;
Chaoliang Guan;
Shengyi Li
Show Abstract
Differing from the traditional pad polishing, hydrodynamic effect polishing (HEP) is non-contact polishing with the wheel floated on the workpiece. A hydrodynamic lubricated film is established between the wheel and the workpiece when the wheel rotates at a certain speed in HEP. Nanoparticles mixed with deionized water are employed as the polishing slurry, and with action of the dynamic pressure, nanoparticles with high chemisorption due to the high specific surface area can easily reacted with the surface atoms forming a linkage with workpiece surface. The surface atoms are dragged away when nanoparticles are transported to separate by the flow shear stress. The development of grand scale integration put extremely high requirements on the surface quality on the silicon wafer with surface roughness at subnanometer and extremely low surface damage. In our experiment a silicon sample was processed by HEP, and the surface topography before and after polishing was observed by the atomic force microscopy. Experiment results show that plastic pits and bumpy structures on the initial surface have been removed away clearly with the removal depth of 140nm by HEP process. The processed surface roughness has been improved from 0.737nm RMS to 0.175nm RMS(10μm×10μm) and the section profile shows peaks of the process surface are almost at the same height. However, the machining ripples on the wheel surface will duplicate on the silicon surface under the action of the hydrodynamic effect. Fluid dynamic simulation demonstrated that the coarse surface on the wheel has greatly influence on the distribution of shear stress and dynamic pressure on the workpiece surface.
Study on the method to test large-aperture hyperboloid convex mirror
Author(s):
Xiaohui Meng;
Huiwen Dong;
Wen Guo;
Huijun Wang
Show Abstract
There are numerous reflecting optical system designs that call for large-aperture convex surfaces, such as secondary mirror in on-axis three mirror anastigmatic (TMA). Several methods to test high accuracy hyperboloid convex surfaces are introduced separately in this paper. A kind of arrangement is chosen to test a surface with diameter of 420mm, radius of 1371mm, and conic K -2.1229. The CGH compensator for testing is designed, which is made up of illumination lens and hologram test plate with designed residual wavefront aberration less than 0.001λ (RMS). The second transmitted method that is equipped with a technical flat surface coating by Ag film in the bottom of surface mirror under test, which form an auto-collimation optical system to eliminate the aberration. The Hindle-Simpson test that requires a larger meniscus lens to compensate the optical aberration, and the designed result of optical test system is less than 0.0016λ. Contrasting the CGH compensator and the second transmitted method, the Hindle-Simpson testing method has the advantage of it is easily to manufacture and adjust; meanwhile the test result is stable and has been less affected by the environment. It has been found that the method is rational and reliable, and it can fulfill the requirement of manufacturing and testing process for hyperboloid convex mirrors.
Study on optical polishing experiment of zerodur mirror
Author(s):
Huijun Wang;
Hang Li;
Peng Wang;
Wen Guo;
Yonggang Wang;
Yan Du;
Huiwen Dong
Show Abstract
A zerodur mirror whose aperture is 900mm is chosen to be the primary mirror of an optical system. The mirror is polished by rapid polishing and precision polishing methods relatively. The final surface figures of the mirror are as follows: the peak-to-valley value (P-V value) is 0.204λ (λ=632.8nm), and the root-mean-square value (RMS value) is 0.016λ, which meet the requirement of the optical system. The results show that the polishing process is feasible.
On-machine measurement of the grinding wheels’ 3D surface topography using a laser displacement sensor
Author(s):
Yongcheng Pan;
Qingliang Zhao;
Bing Guo
Show Abstract
A method of non-contact, on-machine measurement of three dimensional surface topography of grinding wheels’ whole surface was developed in this paper, focusing on an electroplated coarse-grained diamond grinding wheel. The measuring system consists of a Keyence laser displacement sensor, a Keyence controller and a NI PCI-6132 data acquisition card. A resolution of 0.1μm in vertical direction and 8μm in horizontal direction could be achieved. After processing the data by LabVIEW and MATLAB, the 3D topography of the grinding wheel’s whole surface could be reconstructed. When comparing the reconstructed 3D topography of the grinding wheel’s marked area to its real topography captured by a high-depth-field optical digital microscope (HDF-ODM) and scanning electron microscope (SEM), they were very similar to each other, proving that this method is accurate and effective. By a subsequent data processing, the topography of every grain could be extracted and then the active grain number, the active grain volume and the active grain’s bearing ration could be calculated. These three parameters could serve as the criterion to evaluate the grinding performance of coarse-grained diamond grinding wheels. Then the performance of the grinding wheel could be evaluated on-machine accurately and quantitatively.
Temperature field simulation on Ti6Al4V and Inconel718 heated by continuous infrared laser
Author(s):
Yanshen Wang;
Zheng Zhang;
Weiwei Feng;
Bo Wang;
Yuxian Gai
Show Abstract
Laser assisted machining technology can heat and soften metals, which can be used for improving the machinability of superalloys such as Ti6Al4V and Inconel718. Researches on temperature field simulation of Ti6Al4V and Inconel718 are conducted in this paper. A thermal differential equation is established based on Fourier’s law and energy conservation law. Then, a model using ABAQUS for simulating heat transfer process is brought out, which is then experimentally validated. Using the simulation model, detailed investigations on temperature field simulation are carried out in Ti6Al4V and Inconel718. According to simulation, surface temperature of the two superalloys eventually reaches their peak values, and the peak temperature of Ti6Al4V is much higher than that of Inconel718. To further investigate temperature heated by laser, laser parameters such as power, scanning velocity, laser spot radius and inclination angle are set to be variables separately for simulation. Simulation results show that laser power and laser spot radius are predominant factors in heating process compared with the influence of scanning velocity and inclination angle. Simulations in this paper provide valuable references for parameter optimization in the following laser heating experiments, which plays an important role in laser assisted machining.
Dwell time algorithm for multi-mode optimization in manufacturing large optical mirrors
Author(s):
Zhenyu Liu
Show Abstract
CCOS (Computer Controlled Optical Surfacing) is one of the most important method to manufacture optical surface.
By controlling the dwell time of a polishing tool on the mirror we can get the desired material removal. As the optical
surface becoming larger, traditional CCOS method can’t meet the demand that manufacturing the mirror in higher
efficiency and precision. This paper presents a new method using multi-mode optimization. By calculate the dwell time
map of different tool in one optimization cycle, the larger tool and the small one have complementary advantages and
obtain a global optimization for multi tool and multi-processing cycles. To calculate the dwell time of different tool at the
same time we use multi-mode dwell time algorithm that based on matrix calculation. With this algorithm we did
simulation experiment, the result shows using multi-mode optimization algorithm can improve the efficiency
maintaining good precision.
Numerical simulation on aspherical lens modulated by electrostatic force
Author(s):
Zhaolou Cao;
Chun Cheng;
Keyi Wang
Show Abstract
A numerical method is developed to calculate the shape of a liquid aspherical lens modulated by electrostatic force by solving a multiphysics problem that consists of electric field module and fluid flow module. The electric field module is used to calculate the electrical force on the lens surface and the fluid flow module is used to describe the velocity field inside the liquid lens by solving incompressible Navier-Stokes equation with the electrical force as a boundary condition. The arbitrary Lagrangian Eulerian (ALE) method is adopted to get the lens shape evolution since it is volume conservative. Lens shapes at different voltages and different kinds of electrodes are discussed by simulation results. Optical properties of the lens are then studied.
Multi-tool sub-aperture polishing high-slope asphere with low mid-spatial frequency errors
Author(s):
Jian Zhang;
Fei Wang;
Gaowen Wang
Show Abstract
The reasons and methods for generating and suppressing mid-spatial frequency (MSF) errors were deeply studied, and a new method of combining multiple small tools was used to smooth out MSF errors. First, an elastic tool was employed to pre-polish the aspheric surface after grinding, aiming at fast removing sub-surface damage as well as correcting surface figure. Then a second tool-self-designed smoothing tool -was mainly used to smooth the surface, which was followed by an air bonnet tool to continue figure correction until Zernike residual was not convergent. The effective combination of the three small tools was not only able to avoid the high slope fabrication difficulty of the aspheric surface, but also to suppress the MSF errors. The surface was tested by CGH, which can ensure the accuracy of the surface. This method was successfully used to polish a 150mm asphere with a maximum departure of 0.26mm. After five iterations, the surface accuracy converged to 4.05nm RMS. The result shows that this method can realize the valid polishing of high-accuracy aspheric surface.
Fabricating effect of charged ion beam on optical lenses
Author(s):
Yongqiang Gu;
Lei Dai
Show Abstract
Ion beam Figuring (IBF) is believed to be one of the best ways that can fabricate lenses to surface error less than Root Mean Square (RMS) value 1 nanometer. There are several aspects that will influence the fabricate efficiency and accuracy, for example, stability of ion beam, measuring errors of the lenses’ surfaces, dwell time algorithm, fabrication path, etc. Lots of works have been done and papers are published. Since the ion beam generated from argon plasma is electropositive, the lens’ surface will also be electropositive when it is stroked by the ion particles, so that the fabricating efficiency will be decreased because of the repelling force with the same kind electric charges. To avoid the accumulation of charges on lens’ surface, ion beam is neutralized by electrons excited by electric gun or heated tungsten filament. But sometimes the neutralization is not well done. In this paper, fabricating influence of electrified ion beam was analysed, and experiments were done. First, the shape of ion beam without neutralization was tested by Faraday cup, and its removal volumes with different sputtering time were calculated by subtracting lens’ surface error before and after it were fabricated by the ion beam. Then by adjusting the current of the tungsten filament, the excited electrons’ number was changed and the ion beam was neutralized partly, the shapes of ion beams were recorded and the corresponding removal volumes were also tested. Finally, a lens with diameter about 64mm was fabricated. The results showed that the fabrications were either excessed or not enough when using ion beams that were not neutralized perfectly. When neutralized perfectly, the convergent rate of the fabrication will be very fast, in a single iteration, the initial surface error with RMS value more than 7nm might decrease to less than 1nm.
Research on mid-frequency errors in Nd-doped glass continuous polishing
Author(s):
Jun Cao;
Aihuan Dun;
Chaoyang Wei;
Jianxun Gu;
Jianda Shao
Show Abstract
In the inertial confinement fusion (ICF) system, the mid-frequency errors of optical components will cause high-frequency modulation and nonlinear gain of laser beams. In this paper, theoretical simulations and experiments have been designed and operated, aiming at studying the effects of slotting methods on mid-frequency errors in Nd-doped glass continuous polishing. Based on Preston formula, theoretical simulations focus on the effects of slotting methods on the mid-frequency errors. The simulation results show that different slotting methods will cause different mid-frequency errors, and square and logarithmic shape grooves are easier to obtain smaller mid-frequency errors. On the basis of simulation results, two groups of experiments are carried out to do the Nd-doped glass continuous polishing. The results show that the mid-frequency error gradually decreases with the decrease of the spacing between grooves. The results also show that square shape groove is easier to get a smaller mid-frequency error than circular shape groove, which verifies the theoretical simulation results.
The real-time monitoring surface figure of optical elements in continuous polishing
Author(s):
Jun Chen;
Xueke Xu;
Chaoyang Wei;
Jianxun Gu;
Aihuan Dun;
Jianda Shao
Show Abstract
Continuous ring polishing is the key process in large aperture optical elements. The surface figure of polishing pad is inferred by the offline testing surface figure of workpiece. The defects, low processing efficiency and uncertainty processing time in traditional continuous polishing, the real-time monitoring method of polishing is proposed. The realtime monitoring system is set up based on the computer, the dynamic interferometer, a beam expanding system and a beam reflecting system. There are a workpiece and a glass monitoring plate placing in same ring. The surface figure of workpiece, monitored by the monitoring plate, synchronize with the surface of glass monitoring plate in Peak-Valley (PV) and POWER. The new method with simple structure is fast measuring and judgmental directly to the changes of surface figures. The results of real-time monitoring and surface figure converging on the workpiece are valid for continuous polishing through experimental validation.
Subsurface damage on ground fused silica surfaces
Author(s):
Jiafeng Xu;
Xueke Xu;
Wenlan Gao;
Chaoyang Wei;
Minghong Yang;
Jianda Shao
Show Abstract
The low surface laser damage threshold of fused silica components in high power laser systems such as NIF restricts the improvement of the output fluence of those systems. Once damage is initiated and grows under subsequent laser shots, the components will go unusable. Subsurface damage (SSD) introduced during manufacturing has been identified as a main damage initiator. A good knowledge of SSD and how manufacturing influences it is essential to optimize manufacturing processes for damage free optics. Using the magneto-rheological finishing (MRF) wedge technique of better accuracy attributed to a tip, we have characterized the subsurface damage on fused silica optical surfaces ground with loose Al2O3 abrasives of different sizes. Larger abrasives generates longer cracks and the number density of cracks decreases sharply with the depth for each size. Rogue particles account for the occurrence of trailing indent scratches. Addition of rogue abrasives into relatively small base abrasive extends SSD more deeply than that induced by rogue abrasives alone. The linear model, with the proportional coefficient 3.511, fits the relationship between SSD depth and surface roughness (SR) better than the quadratic polynomial one. We believe SSD depth relates to SR more statistically than following some specified physical law. The linear relationship between SSD depth and the abrasive size was also established. The abrasive size turned out not to be as a good indictor of SSD depth as SR.
Lightening techniques applied in reflect mirror
Author(s):
Wen Guo;
Xiao-hui Meng;
Yonggang Wang;
Ling-di Xu
Show Abstract
Based on Zerdour, quartzs, developing Experimental process by ultrasonic drilling and milling, analyse the results of the
Process Parameters of various . With a lightweight plane mirror as an example, The processing results show that the
lightening ratio of plane mirror is as high as 45%, the roughness is higher than 2 μm.
Active deformation and engineering analysis of CFRP mirror of various lay-up sequences within quasi-isotropic laminates
Author(s):
Chunmei Zeng;
Xia Yu;
Peiji Guo
Show Abstract
A regularization stiffness coefficient method was verified further to optimize lay-up sequences of quasi-isotropic
laminates for carbon fiber reinforced polymer (CFRP) composite mirrors. Firstly, the deformation due to gravity of 1G
and temperature difference of 20-100°C and the modal were analyzed by finite element method (FEM). Secondly, the
influence of angle error of ply stacking on quasi-isotropic of bending stiffness was evaluated. Finally, an active support
system of 49 actuators in circular arrangement is designed for a 500mm CFRP mirror, and its goal is to deform the
spherical CFRP mirror to a parabolic. Therefore, the response functions of the actuators were gotten, and the surface
form errors and stresses were calculated and analyzed. The results show that the CFRP mirrors designed by the method
have a better symmetrical bending deformation under gravity and thermal load and a higher fundamental frequency, and
the larger n the better symmetry (for π/n quasi-isotropic laminates); the method reduces the sensitivity to misalignment of
ply orientation for symmetric bending, and the mirror’s maximum von Mises stress and maximum shear stress are less
compared to those laminates not optimized in lay-up sequence.
Research on the low speed stability control technology of fly-cutting machine for KDP crystals
Author(s):
Dongsheng Chen;
Fang Ji;
Hua Chen
Show Abstract
In the paper, The problem about stability in low speed of the air bearing stage driven by a linear motor was investigated to satisfy the ultra-precision fly-cutting of KDP crystals. First of all, the modal of the servo system with the permanent magnet synchronous linear motor was analyzed. In the system of the low speed linear motor driver, the main interferences came from cutting force f Load , the friction of chain and cable f n , the ripple thrust f ripp , and motor friction f fric . Secondly, the factors about low speed stability were analyzed: the key to improve the system’s stability is to control the interference forces; Another important issue is to develop an advanced control strategy. Thirdly, some optimization experiments about low speed stability were developed as follows: the influence of feedback element, the influence of Power converter, speed optimization of damping feed-forward control, speed optimization of Spindle vibration, speed optimization based on disturbance observer. Finally the experimental results: the lowest speed of the stage can reach 0.2 mm/min; the error of the speed is less than 0.06mm/min when running between 1mm/min and 10 mm/min. The cutting experiment of KDP with the size of 330mm × 330mm × 10mm, was proceeded on the Fly-cutting machine by the feeding velocity of 1mm/min. The results about the surface roughness show that the value of Rq is 3.3nm and the value of Ra is 2.6nm.
Freeform manufacturing of a progressive addition lens by use of a voice coil fast tool servo
Author(s):
Yi Yu Li;
Jiao Jie Chen;
Hai Hua Feng;
Chaohong Li;
Jia Qu;
Hao Chen
Show Abstract
The back surface of progressive addition lens (PAL) is a non-rotationally symmetric freeform surface. The local radius varies progressively from the far zone to the near zone along the intermediate zone to give the addition power. Numerical simulation method is performed to calculate the discrete points on the freeform surface in polar coordinate and generate the data files containing the trajectory of diamond tool tip for surface machining. The fabrication of PAL is accomplished by using self-developed single-point diamond turning machine with voice coil fast tool servo. The polished freeform surface profile measured by a 3-axes coordinate measuring machine shows little deviation to the simulation result. Surface power and cylinder of the fabricated PAL is also measured for comparison with theoretical design.
Influences of grinding and polishing parameters on the quality of super smooth surface
Author(s):
Yuzhu Jin;
Yi Tong;
Lingyan Jiao;
Dongxu Wu;
Weijin Guo
Show Abstract
Firstly, in this paper, a reasonable process flow is designed and the surface roughness of each procedure is tested. Secondly, the influences of particle size distribution of slurry on the quality of super smooth surface are studied, and then the conclusions are obtained that large span distribution of slurry will lead to surface scratches. Lastly, the effects of aging and ratios of polishing pad on the quality of super smooth surface are researched, and then some specific process parameters are gained such as shaving cycle and asphalt ratios in different environments.
Optimal design of segmented quasi-phase-matching SHG+DFG wavelength conversion structure based on hybrid genetic algorithm
Author(s):
Tao Liu;
Jie Cui
Show Abstract
A hybrid genetic algorithm is proposed to optimal design the wavelength converter which using segmented grating
structure and cascaded second-harmonic generation and difference-frequency generation process. Investigation of the
influences of the structure parameters on conversion bandwidth and conversion response are carried out. High conversion
efficiency, flat response and broad conversion bandwidth can be obtained simultaneously, by adding the segment number
of QPM grating and optimizing the poling period of each segment. The utilizing of the hybrid genetic algorithm can not
only make one obtain precise optimal results, but also shorten the simulation time significantly, so it is helpful to the
practical design of the wavelength converters.
Theoretical and experimental investigation of grinding marks in sphere NC grinding process
Author(s):
Peng Wang;
Hao Zhang;
Changshun Hui
Show Abstract
Sphere ultra-precision NC grinding process with diamond cup wheel is widely used as an indispensable working procedure for manufacturing spherical, most aspherical, and some freeform surfaces. This paper presents a mathematic model of sphere grinding with cup diamond wheel based on homogeneous transformation method to simulate grinding marks. Different kinds of grinding marks are obtained by changing the geometrical parameters including the shift in axis X and Y axis and inclination angle deviation. Form accuracy and dimensional errors caused by geometrical parameters are also analyzed, and hence a three-step method utilizing grinding marks is proposed to correct these errors. A series of experiments are conducted and the results show that the proposed method is very efficient and effective in actual spherical surface generating process.
Effect of the inflated-pressure to the tool influence function for polishing using SR bonnet
Author(s):
Chunjin Wang;
Xu Yang;
Bo Zhong;
Zhenzhong Wang;
Yinbiao Guo;
Qiao Xu
Show Abstract
The purpose of this paper is to study the effect of the inner pressure to the tool influence function (TIF) for polishing using a semi-rigid (SR) bonnet tool. The simulation model of a Semi-rigid (SR) bonnet polishing tool polishing BK7 is demonstrated and the pressure distribution data under different inflated-pressures in the contact area has been extracted. It’s observed that the inflated-pressure has few effects to the polishing pressure, and their shapes are also Gaussian-like. Hence, we made a hypothesis that the effect of inflated-pressure to the TIF is rather small. To verify this hypothesis, a group of experiments to generate TIFs under different inflated-pressure are conducted, and the hypothesis has been proved to be correct through comparing these TIFs.
Study on mechanism and process of ion beam machining on high-precision large optical surfaces
Author(s):
Xiao Liang;
Yongqiang Gu;
Xiang Wang;
Zhanlong Ma;
Yongxin Sui;
Jinjin Zheng
Show Abstract
Ion beam machining has become an important means adopted to high-precision large optical mirror processing. This study has conducted a bitmap-style model, calculation and analysis on low-energy Ar+ ion beam sputtering optical surface, based on Sigmund Theory and the CCOS principle. We have obtained the relationship of the removal function and the removal rate with major technological parameters of ion beam machining (e.g. dwell time, work distance, ion energy, etc.) also via orthogonal experiments of single point removal. Results indicated that the removal rate of amorphous SiO2 (fused silica) by Ar+ ions with 600~1200 electron volts increases with the increase of ion energy and dwell time at different extents, decreases exponentially with the increase in work distance. On the basis of computational analysis and experimental investigations, we optimized process conditions and further figured the plane mirror with the clear aperture of 130 millimeters, utilizing technologically optimized low-energy Ar+ ion beam machining. Eventually we obtained the high-precision figure shape with the post-machined surface roughness of 0.43~0.44 nm rms and the post-machined figure error of 1 nm rms.
Stressed mirror polishing: finite element simulation of mirror blank deformation
Author(s):
Yu Han;
Lihong Lu
Show Abstract
The theoretical principle of Stressed Mirror Polishing (SMP) is introduced, including the representation method of elastic deformation, the formulations of discrete bending moment and shearing force. A Finite Element Analysis (FEA) simulation model of has been set up by ANSYS software. The warping facility in this model is consisted of 36 aluminum alloy arms equally distribute on the ambit of mirror blank. Two forces are applied on each arm to provide bending moment and shearing force. Taking type 82 segment of Thirty Meters Telescope (TMT) primary mirror for example, a FEA simulation of mirror blank deformation has been performed. Simulation result shows that, the deformation error is 33μm PV. The theoretical deformation PV value is 205μm and the simulation deformation PV value is 172μm, converging rate reaches to 0.84 in a single warping cycle. After three or four warping cycles, the residue error may converge into 1μm.
Design and realization of comb filter based on fiber grating with new structure
Author(s):
Ming-zhu Li;
Yu-ye Zhang;
Guo-feng Xu
Show Abstract
Based on Mach-Zehnder interferometer and the Fiber Bragg Grating Sagnac Loop, a new structure of photo-fiber combfilter is designed which can obtain high reflectivity and big reverberation bandwidth. This filter has the advantage of low insertion loss and the equal intervals passband. The quantity and interval of passband can be changed through the length difference of optical fiber and without having to redesign and produce the fiber grating again. Within the range of the craft allows, the reverberation bandwidth of the filter amounts to 5 nm and the reflectivity nears to the 100% which can be widely applied in optical fiber sensors and optical fiber communication fields.
Fused silica fine grinding with low roughness
Author(s):
Lei Dai;
Yongqiang Gu;
Di Wu
Show Abstract
Lithography-optics is one of the most complex optical systems. The fine grinding process is the most important step before polishing. Roughness and sub-surface damage (SSD) are essential outputs of fine grinding. We demonstrate the method that use fix abrasive cup tool with CNC grinding machine to complete the fine grinding process, even instead of lapping process. And experiment sample roughness can reach 23.40nm rms and Ra 18.554nm. The SSD estimate is about 2 μm which is also smaller than commercial lapping process. The fine grinding output can satisfy the lithography optic fabrication demands and efficiently reduce the polishing time.
Design of MWIR step-zoom detection imaging system with a large FPA
Author(s):
Yu Bai;
Tingwen Xing;
Wumei Lin;
Yadong Jiang
Show Abstract
For novel cooled 640×512 large focal plane array staring focal plane array (FPA) infrared detector with the picture clement size of 15 μm×15 μm,a mid-wave infrared step-zoom detection imaging system with a large FPA was presented in the paper.The manner of variational fov was accomplished by switching two lenses into the narrow fov system layout with mechanism framework.The parameters of the novel system are 4.0 f/number, 800mm/400mm effective focal length (EFL) and 3.7-4.8 μm spectrum region,100% cold shield efficiency.Image quality and thermal Analysis was evaluated by Code-v optical design software.At the spatial frequency 33lp/mm,the Modulation Transfer Function(MTF) was above 0.15 both the long EFL and short EFL in the working temperature range -35°C~55°C.
Dynamic fracture characteristics of brass foil subjected to laser shock loading
Author(s):
Chao Zheng;
Zhong Ji;
Jie Fu;
Yunhu Zhu;
Libin Song;
Jianhua Zhang
Show Abstract
Micro scale laser shock punching is a high strain rate micro forming method which uses the high-amplitude shock wave pressure induced by pulsed laser irradiation. The process can serve as a rapidly established and high precision technique to impress micro features on thin sheet metals. The response of brass foil under different ratio of laser beam diameter (d) to die hole diameter (D) in micro scale laser shock punching was investigated. The typical fracture surface morphologies were observed using scanning electron microscope. The influence of the ratio d/D on dynamic deformation and fracture of the brass foil was characterized. The results show that the dynamic fracture behavior of the brass foil is sensitive to the ratio d/D. According to the general mechanical analysis, the specimen fails in a shear fracture mode at d/D=1.75 due to the existence of shear stresses, while the fracture occurs in a tensile fracture mode at d/D=0.47 under the effect of bidirectional tensile stresses. In the case of d/D=0.70, the specimen fails in a mixed fracture mode under the co-action of tensile and shear stresses.
Combined fabrication process for high-precision aspheric surface based on smoothing polishing and magnetorheological finishing
Author(s):
Xuqing Nie;
Shengyi Li;
Ci Song;
Hao Hu
Show Abstract
Due to the different curvature everywhere, the aspheric surface is hard to achieve high-precision accuracy by the traditional polishing process. Controlling of the mid-spatial frequency errors (MSFR), in particular, is almost unapproachable. In this paper, the combined fabrication process based on the smoothing polishing (SP) and magnetorheological finishing (MRF) is proposed. The pressure distribution of the rigid polishing lap and semi-flexible polishing lap is calculated. The shape preserving capacity and smoothing effect are compared. The feasibility of smoothing aspheric surface with the semi-flexible polishing lap is verified, and the key technologies in the SP process are discussed. Then, A K4 parabolic surface with the diameter of 500mm is fabricated based on the combined fabrication process. A Φ150 mm semi-flexible lap is used in the SP process to control the MSFR, and the deterministic MRF process is applied to figure the surface error. The root mean square (RMS) error of the aspheric surface converges from 0.083λ (λ=632.8 nm) to 0.008λ. The power spectral density (PSD) result shows that the MSFR are well restrained while the surface error has a great convergence.
Research on ultrasonic cleaning technology of optical components
Author(s):
Lingyan Jiao;
Yi Tong;
Ying Cui;
Jianhua Chen;
Qingguang Bai
Show Abstract
Along with the higher demand of super smooth optical surface, the cleaning technique that is the critical process to obtain super smooth surface has to meet even higher standards. In virtue of higher efficiency and better effect, the ultrasonic cleaning technology has been widely used in cleaning high-end optical lenses. This paper introduced the process, principle and method of the ultrasonic cleaning technology for a super smooth surface. The basis of determining the main technical parameters, such as the power and frequency of ultrasonic wave, the ultrasonic time, the components of cleaning agent and its operating temperature, were also discussed. In addition, the progress situations of ultrasonic cleaning technologies including the characteristics of complex frequency ultrasonic and megasonics cleaning technology and the removal mechanism of different granularity of dirt were analyzed. The mechanism of complex frequency ultrasound produces chemical process and the relationship between megasonics boundary layer and the particles removing were studied. Results showed that the chemical functions of complex frequency ultrasound and megasonics were better than that of single frequency ultrasound for the particles removal effect. Therefore, the new complex frequency ultrasonic and megasonic cleaning technologies are very necessary for cleaning optical components.
Preparation and optimization of the laser thin film filter
Author(s):
Jun-hong Su;
Wei Wang;
Jun-qi Xu;
Yao-jin Cheng;
Tao Wang
Show Abstract
A co-colored thin film device for laser-induced damage threshold test system is presented in this paper, to make the
laser-induced damage threshold tester operating at 532nm and 1064nm band. Through TFC simulation software, a film
system of high-reflection, high -transmittance, resistance to laser damage membrane is designed and optimized. Using
thermal evaporation technique to plate film, the optical properties of the coating and performance of the laser-induced
damage are tested, and the reflectance and transmittance and damage threshold are measured. The results show that, the
measured parameters, the reflectance R ≥ 98%@532nm, the transmittance T ≥ 98%@1064nm, the laser-induced damage
threshold LIDT ≥ 4.5J/cm2 , meet the design requirements, which lays the foundation of achieving laser-induced damage threshold multifunction tester.
Design of dual band imaging system for space debris
Author(s):
Hu Wang;
Jianjun Luo;
Xin Lu;
Chunyan Li
Show Abstract
In order to detect the space debris, a dual band imaging system for space debris was proposed. The dual band imaging
system was consisted of visible imaging system and long-wave imaging system. The dual band imaging system used the
primary mirror and secondary mirror together, including correction lens in every imaging system in order to balance
aberration. The focal length was 1000 mm and field of view was 1. 2° for visible imaging system, and the focal length was 250 mm and field of view was 2.75° for LWIR imaging system. Some measures were taken to make sure the less
degradation of MTF for thermal distortion, such as a kind of material with good thermal property as mirror substrate to reduce surface distortion. The modulation transfer function (MTF) of dual band imaging system in condition of 20± 5°C
was analyzed, which showed a good result for user’s requirement.
Evaluate error correction ability of magnetorheological finishing by smoothing spectral function
Author(s):
Jia Wang;
Bin Fan;
Yongjian Wan;
Chunyan Shi;
Bin Zhuo
Show Abstract
Power Spectral Density (PSD) has been entrenched in optics design and manufacturing as a characterization of mid-high spatial frequency (MHSF) errors. Smoothing Spectral Function (SSF) is a newly proposed parameter that based on PSD to evaluate error correction ability of computer controlled optical surfacing (CCOS) technologies. As a typical deterministic and sub-aperture finishing technology based on CCOS, magnetorheological finishing (MRF) leads to MHSF errors inevitably. SSF is employed to research different spatial frequency error correction ability of MRF process. The surface figures and PSD curves of work-piece machined by MRF are presented. By calculating SSF curve, the correction ability of MRF for different spatial frequency errors will be indicated as a normalized numerical value.
Experiment study on the cutting property of hot press Zinc Sulfide by single point diamond turning
Author(s):
Weihao Li;
Yi Tong;
Weiyan Lian;
Dandan Liu;
Hao Zhang
Show Abstract
Microscopic morphology and XRD spectra of Hot Press(HP) ZnS powders and fractrues were tested. Preliminary analysis of the turning characters of HP ZnS was got by associating with the characters of HP ZnS and the processing mechanism of hard and brittle materials. Orthogonal experiment of 3 factors and 3 levers was taken by setting roughness Ra value index of the turning surface, and more analyses of the ultra-precision turning characters of HP ZnS were got by associating with the 3D microscopic morphology of CVD ZnSe ultra-precision turning surface and HP ZnS polishing surface. How to get the lower Ra value was discussed at last. The research shows: the primary removal mechanism of HP ZnS is powder removal; HP ZnS can get good ultra-precision turning surface which Ra value is lower than 10nm; to get the Ra value of the turning surface lower than 4nm, speed of main spindle, blunt edge radius, and the corner radius must be optimized because of the polycrystalline structure of the HP ZnS.
The method test of transition mirror method to process sphere output mirror with large radius curvature
Author(s):
Dongxu Wu;
Yi Tong;
Weijin Guo;
Lingyan Jiao;
Yuzhu Jin
Show Abstract
This paper introduces the general requirements of parameter indexes about sphere output mirror with large radius curvature mainly including: sphere radius,spherical area,coaxiality,surface defect disease,RMS value and so on. The difficulties that ultra-smooth machining for sphere output mirror were indicated. A “plano-convex” structure has been designed for transition chip to solving the problem that roughcast and tool pad can’t directly processed by the matrix angles using optical cement method. Based on the sphere output mirror’s process feature, the processing plan to polish sphere surface and then to process platform was laid down. The purpose of this article is to control the test process to get to the target of the “transition chip” method by using “the design and produce of transition chip”,“the conservation of super smooth” and the “control process”, after testing on relative indicators of sphere output mirror, it prove that “transition chip” method can be applied to sipper smooth polish in sphere output mirror with large radius of curvature.
Research on optical surface quality online monitoring based on support vector machine
Author(s):
Guo Bi;
Zhiji Sun;
Dongxu Zhang
Show Abstract
The interference of grinding wheel and optic surface during grinding process causes numerous acoustic emission (AE)
phenomena. AE signals are competent for monitoring the quality of the ground surface. A quality prediction model of
grinding optics is established based on support vector machine (SVM). Some time domain characteristics of AE signals
are chosen as the input vectors. And surface roughness (Ra) and surface shape accuracy (P-V) are the output vectors,
respectively. The experiment results show that the model can accurately predict the surface quality of the optics during
grinding.
Simulation research on cutting brittle optical material with diamond wire saw based on LS-DYNA
Author(s):
Jian Wang;
Jianbo Liu;
Yonghao Xiao;
Shicao Zhao
Show Abstract
The quality of optical material cutting affects the efficiency and quality of follow-up polishing processing directly. Among various ways of cutting, the diamond wire saw cutting of fixed abrasive has advantages of narrow cutting seam, efficient cutting, high chip quality, little pollution to environment, ability to process bigger diameter workpiece, etc. So it has been used widely in optical material processing. In this paper, the coupled algorithm of FEM/SPH has been used to simulate deformation, fracture of brittle optical material in diamond grain cutting. The influence of workpiece feeding rate, cutting speed and cutting depth on the surface roughness are then analyzed in detail. Numerical simulation results show that the coupled algorithm efficiently explains the mechanism of material removal. From these results, we can not only determine optimum technology parameters for the manufacture of diamond wire saw, but also provide basis for improving the wire cutting efficiency and finished-product rate of optical material.
The research and realization of digital management platform for ultra-precision optical elements within life-cycle
Author(s):
Juan Wang;
Jian Wang;
Lijuan Li;
Kun Zhou
Show Abstract
In order to solve the information fusion, process integration, collaborative design and manufacturing for ultra-precision optical elements within life-cycle management, this paper presents a digital management platform which is based on product data and business processes by adopting the modern manufacturing technique, information technique and modern management technique. The architecture and system integration of the digital management platform are discussed in this paper. The digital management platform can realize information sharing and interaction for information-flow, control-flow and value-stream from user's needs to offline in life-cycle, and it can also enhance process control, collaborative research and service ability of ultra-precision optical elements.
A detail enhancement and dynamic range adjustment algorithm for high dynamic range images
Author(s):
Bo Xu;
Huachuang Wang;
Mingtao Liang;
Cong Yu;
Jinlong Hu;
Hua Cheng
Show Abstract
Although high dynamic range (HDR) images contain large amounts of information, they have weak texture and low contrast. What's more, these images are difficult to be reproduced on low dynamic range displaying mediums. If much more information is to be acquired when these images are displayed on PCs, some specific transforms, such as compressing the dynamic range, enhancing the portions of little difference in original contrast and highlighting the texture details on the premise of keeping the parts of large contrast, are needed. To this ends, a multi-scale guided filter enhancement algorithm which derives from the single-scale guided filter based on the analysis of non-physical model is proposed in this paper. Firstly, this algorithm decomposes the original HDR images into base image and detail images of different scales, and then it adaptively selects a transform function which acts on the enhanced detail images and original images. By comparing the treatment effects of HDR images and low dynamic range (LDR) images of different scene features, it proves that this algorithm, on the basis of maintaining the hierarchy and texture details of images, not only improves the contrast and enhances the details of images, but also adjusts the dynamic range well. Thus, it is much suitable for human observation or analytical processing of machines.
Study on machining mechanism of nanotwinned CBN cutting tool
Author(s):
Junyun Chen;
Tianye Jin;
Jinhu Wang;
Qingliang Zhao;
Ling Lu
Show Abstract
The latest developed nanotwinned cubic boron nitride (nt-CBN) with isotropic nano-sized microstructure possesses an extremely high hardness (~100GPa Hv), very large fracture toughness (>12Mpa m1/2) and excellent high temperature stability. Thus nt-CBN is a promising tool material to realize ultra-precision cutting of hardened steel which is widely used in mold insert of optical and opto-electrical mass products. In view of its hard machinability, the machining mechanism is studied in this paper. Three feasible methods of mechanical lapping, laser machining as well as ion beam sputtering are applied to process nt-CBN. The results indicate that among the three kinds of methods, mechanical lapping not only can achieve the highest machining accuracy because of material removing at ductile mode completely, but also has satisfactory high material removal rate. Thus mechanical lapping method is appropriate to finish machining of nt-CBN cutting tool. Moreover, laser machining method can be only used in contour machining or rough machining of cutting tool as worse machined surface quality. With regard to ion beam sputtering method, the material remove rate is too low in spite of high machining accuracy. Additionally, no phase transition was found in any machining process of nt-CBN.
Study of femtosecond laser-induced structural changes in lithium niobate crystal
Author(s):
Liang Zhang;
Jie Feng;
Zhongxue Fan;
Xinrui Wei;
Changliang Shan;
Qing Wu;
Zigang Zhou
Show Abstract
In recent years, the microfabrication of Lithium Niobate (LiNbO3) based optical integrated devices by using femtosecond laser pulses has been attracting increasing attention. One key current challenge is to understand the mechanism of the interaction of femtosecond laser pulses on LiNbO3 crystal, which is still elusive. Here we demonstrate the etching of LiNbO3 crystal surface by using tightly focused femtosecond laser pulses with repetition rate 75 MHz, pulse duration 50 fs, and single pulse energy 3nJ. The morphology of the etched area is observed by a scanning electron microscope (SEM) which shows the laser illuminated area has obvious thermal damage. When the etching time is 30 seconds and the etched area is 42μm in diameter, thermal damage is observed within the area with 28μm diameter, redeposition is observed in between 28-34μm diameter, and modification is observed in between 34-42μm diameter. A theoretical thermal diffusion model is built to simulate the temperature distribution in the area etched by laser pulses with repetition rates 1 kHz, 1 MHz, and 75 MHz, respectively. The simulation result from 75 MHz repetition rate matches experimental observation very well. The results show that there is thermal damage when LiNbO3 crystal is illuminated with high repetition rate femtosecond laser pulses.
Calibration technology research of force sensor in the manufacture of large optics
Author(s):
Si Li;
Hongshen Zhao;
Xiaojin Li;
Wei Gu
Show Abstract
Active lap technology is usually used in the manufacture of large optics. As the feedback element, force sensor plays an
important role in the lap control system. With regard to the condition that the calibration of pulling force sensor is completed manually and inefficiently then the process of calibration data is complicated, a new automatic calibration
technology of force sensor is developed. In which the method of data acquisition, computer control, curve fitting and
error analysis are integrated in the calibration process, so the efficiency and reliability of force calibration is improved
observably. The result of calibration can satisfy the requirement of the control system of active lap.
Selection of the compensation quantity to the lens deformation caused by gravity
Author(s):
Lijuan Yang;
Tingwen Xing
Show Abstract
With the development of optical processing and manufacturing technology and the needs of scientific research and equipment manufacturing, now the design and manufacture of optical lens mainly consider the influence of gravity on the deformation of optical system. Advanced compensation is a method which uses finite element analysis software to calculate the gravitational deformation, thus compensating it in the processing stage and making the lens surface after deforming as the desired shape in order to reduce the deformation. The relationship between gravity deformation and compensation quantity is analyzed in this paper and an effectively method of selecting the compensation quantity is presented. The surface shape variation caused by gravity deformation before and after the compensation are compared though the ANSYS and it proves that this method can effectively reduce the influence of gravity deformation.
A path planning method used in fluid jet polishing eliminating lightweight mirror imprinting effect
Author(s):
Wenzong Li;
Bin Fan;
Chunyan Shi;
Jia Wang;
Bin Zhuo
Show Abstract
With the development of space technology, the design of optical system tends to large aperture lightweight mirror with high dimension-thickness ratio. However, when the lightweight mirror PV value is less than λ/10 , the surface will show wavy imprinting effect obviously. Imprinting effect introduced by head-tool pressure has become a technological barrier in high-precision lightweight mirror manufacturing. Fluid jet polishing can exclude outside pressure. Presently, machining tracks often used are grating type path, screw type path and pseudo-random path. On the edge of imprinting error, the speed of adjacent path points changes too fast, which causes the machine hard to reflect quickly, brings about new path error, and increases the polishing time due to superfluous path. This paper presents a new planning path method to eliminate imprinting effect. Simulation results show that the path of the improved grating path can better eliminate imprinting effect compared to the general path.
Ultra-precision process of CaF2 single crystal
Author(s):
Guoju Yin;
Shengyi Li;
Xuhui Xie;
Lin Zhou
Show Abstract
This paper proposes a new chemical mechanical polishing (CMP) process method for CaF2 single crystal to get ultraprecision surface. The CMP processes are improving polishing pad and using alkaline SiO2 polishing slurry with PH=8, PH=11 two phases to polish, respectively, and the roughness can be 0.181nm Rq (10μm×10μm). The CMP process can’t get high surface figure, so we use ion beam figuring (IBF) technology to obtain high surface figure. However, IBF is difficult to improve the CaF2 surface roughness. We optimize IBF process to improve surface figure and keep good surface roughness too. Different IBF incident ion energy from 400ev to 800ev does not affect on the surface roughness obviously but the depth of material removal is reverse. CaF2 single crystal can get high precision surface figure (RMS=2.251nm) and still keep ultra-smooth surface (Rq=0.207nm) by IBF when removal depth is less than 200nm. The researches above provide important information for CaF2 single crystal to realize ultra-precision manufacture.
Research on the processing technology of elongated holes based on rotary ultrasonic drilling
Author(s):
Yi Tong;
Jianhua Chen;
Lipeng Sun;
Xin Yu;
Xin Wang
Show Abstract
The optical glass is hard, brittle and difficult to process. Based on the method of rotating ultrasonic drilling, the study of single factor on drilling elongated holes was made in optical glass. The processing equipment was DAMA ultrasonic machine, and the machining tools were electroplated with diamond. Through the detection and analysis on the processing quality and surface roughness, the process parameters (the spindle speed, amplitude, feed rate) of rotary ultrasonic drilling were researched, and the influence of processing parameters on surface roughness was obtained, which will provide reference and basis for the actual processing.
Study on grinding of free-form optics surface in three-axis CNC machine
Author(s):
Haicheng Yang;
Yun-long Zhang;
Feng Zhang;
Zhibin Wang;
Long-xiang Bao;
Ying Su;
Rui Guo;
Xuan-min Liu
Show Abstract
Due to the glass is a type of brittle material, so the high-precision free-form optics of glass material is usually machined
by the technical of grinding. In this paper, for the characteristics of the diamond grinding wheel, analyzing the grinding
path of free-form optics and mathematical model of the path is established based on the three-axis CNC grinding device.
Moreover, the cause of the interference in the process of grinding is analyzed and the methods of avoiding. Finally, based
on the above analysis results, through the experiment, the free-form optics surface accuracy was reached to 3.6um,
realize the machining of the free-form optics.
New fabrication technology in single point diamond turning for IR aspheric optical parts
Author(s):
Ying Su;
Xianhe Chen;
Xiaogang Guo;
Guo Rui;
Xuanmin Liu;
Feng Zhang;
Chao Yang;
Yingyu Xiao;
Zengqi Xu
Show Abstract
With the development of IR imaging technology, IR aspheric optical parts become more and more widely used in IR optical systems, the precision requirements are also becoming more and more rigorous. The precision of parts directly influences the image quality and optical efficiency of IR optical systems. However, the surface shape precision and surface inclination with high quality and high efficiency machining have been a challenge for the precision optics process. This paper focuses on the surface shape precision, surface roughness and surface inclination which affect the precision of IR aspheric parts, new fabrication technology for optimization parameters in turning process of different IR materials, surface inclination machining and accurate measurement of aspheric surface is proposed. By adopting the proposed technology, high precision aspheric parts with surface shape precision PV≤0.3μm (Φ ≤80mm), surface roughness Ra≤5nm and surface inclination≤30″ (Φ ≤30mm) can be manufactured.
Research on precision grinding processing and compensation finishing experiment for mid-large- aperture square aspheric optical element
Author(s):
Fengming Nie;
Zhanguo Li;
Dasen Wang;
Guangping Zhang;
Chengjun Guo;
Ning Pei;
Yupeng Li
Show Abstract
This paper analyzes dot-line envelope grinding principle, which is applicable to mid-large- aperture square aspheric
optical element, determines the mathematical process control model based on X/Y/C three-axis aspheric grinding
machine, We develop the appropriate high-precision aspheric grinding manufacturing and measurement systems
software, using the plane grinding wheel to do the grinding experiments and the repeated compensation processing
experiment. The experiments show that: high-precision aspheric grinding manufacturing and measurement systems
software can be realized axisymmetric aspheric high-precision machining control and measurement; using compensation
processing of the X/Y/C three-axis aspheric grinding machine which can effectively improve the precision PV value,
surface error from the initial processing of the PV value :12 μm to the compensation processing of the PV value :3 μm .
Simulation analysis of grinding wheel motion trajectory on SiC ceramics aspheric surface grinding
Author(s):
Feihu Zhang;
Lifei Liu;
Chunhui Li
Show Abstract
In grinding process of SiC ceramics aspheric surface, the motion trajectory of grinding wheel has great influence on the
surface forming. The paper provides mathematical models of grinding wheel movements; analytical simulation was done
to describe the trajectories of the grinding wheel in manufacturing an aspherical workpiece. The effect of grinding
parameters (including the rotation speed of the workpiece, the feed rate of grinding wheel etc.) on the aspheric surface
coverage rate was conducted and discussed in detail. An experimental study was done according to the simulation results
and an aspheric surface with form error less than 10μm was gained.
Analysis of composite flow field characteristics in fluid jet polishing
Author(s):
Rongzhu Zhang;
Yinchuan Luo;
Xiulong Li;
Yang Zhang
Show Abstract
Fluid jet polishing is an effective ultra-smooth surface processing technology. It can be targeted to remove high-frequency surface defects. Removal efficiency is directly related to the speed of flow field, therefore it is necessary to further analyze the composite flow field distribution characteristics. Aiming at the characteristics of composite flow field, theoretical and modeling research was conducted. FLUENT is used to simulate composite jet flow field. The fluid jet velocity and pressure distribution curve on the workpiece wall have been obtained.
Process optimization for ultrasonic vibration assisted polishing of micro-structured surfaces on super hard material
Author(s):
Zhiyuan Sun;
Bing Guo;
Zhimin Rao;
Qingliang Zhao
Show Abstract
In consideration of the excellent property of SiC, the ground micro-structured surface quality is hard to meet the requirement,consequently the ultrasonic vibration assisted polishing (UVAP) of micro-structures of molds is proposed in this paper. Through the orthogonal experiment, the parameters of UVAP of micro-structures were optimized. The experimental results show that, abrasive polishing process, the effect of the workpiece feed rate on the surface roughness (Ra), groove tip radius (R) and material removal rate (MRR) of micro-structures is significant. While, the UVAP, the most significant effect factor for Ra, R and MRR is the ultrasonic amplitude of the ultrasonic vibration. In addition, within the scope of the polishing process parameters selected by preliminary experiments, ultrasonic amplitude of 2.5μm, polishing force of 0.5N, workpiece feed rate of 5 mm·min-1, polishing wheel rotational speed of 50rpm, polishing time of 35min, abrasive size of 100nm and the polishing liquid concentration of 15% is the best technology of UVAP of micro-structures. Under the optimal parameters, the ground traces on the micro-structured surface were removed efficiently and the integrity of the edges of the micro-structure after grinding was maintained efficiently.
Research on the method of spherical optical fairing edge width tolerances
Author(s):
Fang Wang;
Yuzhu Jin;
Jianmin An;
Tao Liu;
Yi Tong
Show Abstract
Optical fairing is one of the key components of the missile , which can improve the aerodynamic characteristics of the missile , and can play a role in protection of its internal optical system . Precision connection between the fairing and the shell structure can ensure the tightness of the optical compartment . In the fairing manufacturing process, due to the limitations of process design , some of the fairing reference size may tighten the tolerance zone or offset , which will bring a series of manufacturing and inspection issues . This paper first outlines the optical fairing shape structure, explained the significance of the edge width control precision. Secondly, Manufacturing process for the fairing is made a brief introduction. On this basis , analyzes the relationship between the relevant linear dimensions , and uses the formula defines the numerical relationship between the main parameters . Finally , the various sources of error are analyzed, and a method to determine the width of the edge of the tolerance range is put forward. This method can effectively achieve spherical fairing edge width tolerance, its findings apply equally meniscus lens with the platform structure.
Design and preparation of laser film on sapphire substrate
Author(s):
Shao-kun Dang;
Jun-qi Xu;
Jun-hong Su;
Fang Guo;
Yao-jin Cheng
Show Abstract
Sapphire crystal as a kind of good material has a good transmittance in the ultraviolet, visible, infrared, which was widely used in the high-intensity laser system as the window material. Anti-reflection thin films on sapphire substrate were commonly used in high-energy laser system in the middle infrared bands 3~5μm and these thin films are very easily damaged for high energy laser system. In this paper, we adopt thermal evaporation technique on the sapphire substrate was prepared by design of single layer and multilayer anti-reflection coatings system so that the infrared transmittance satisfy the design requirements. The results of transmittance and laser damage performance tests show that the anti-reflection coating of 3~5μm transmittance is more than 97% on average, Laser-induced damage threshold (LIDT) is more than 5J/cm2 (1064nm), which means that this method could obtain a high-quality laser film.
Finite element simulation of laser shock peening on bulk metallic glass
Author(s):
Jie Fu;
Huigang Shi;
Chao Zheng;
Ren Liu;
Zhong Ji
Show Abstract
Laser shock peening (LSP) can be used to induce compressive residual stresses on the surface of a material, then to improve the mechanical properties such as performance of plasticity and fatigue. However, the residual stresses and their exact spatial distribution are very difficult to measure by experiment, especially for very small workpieces. In this paper, a finite-element model has been developed to numerically simulate the LSP process of bulk metallic glass (BMG) Zr41.2 Ti13.8Cu12.5Ni10Be22.5, and predict the stress distribution. The constitutive equation established in this work is hydrostatic-pressure sensitive and strain-rate dependent, it is based on the free volume model and Coulomb-Mohr yield criterion, and can describe such special deformation behaviors of BMG as strain softening. The simulated results show that, for one-side peening, along depth direction, the compressive residual stress gradually reduced to zero, then change to the tensile residual stress, but for two-side peening, the residual stress is from compressive to tensile and then to compressive along depth direction. These simulation results have a great significance to study the application of LSP in strengthening brittle amorphous alloys.
Research on the magnetorheological finishing (MRF) technology with dual polishing heads
Author(s):
Wen Huang;
Yunfei Zhang;
Jianguo He;
Yongcheng Zheng;
Qing Luo;
Jing Hou;
Zhigang Yuan
Show Abstract
Magnetorheological finishing (MRF) is a key polishing technique capable of rapidly converging to the required surface figure. Due to the deficiency of general one-polishing-head MRF technology, a dual polishing heads MRF technology was studied and a dual polishing heads MRF machine with 8 axes was developed. The machine has the ability to manufacture large aperture optics with high figure accuracy. The large polishing head is suitable for polishing large aperture optics, controlling large spatial length’s wave structures, correcting low-medium frequency errors with high removal rates. While the small polishing head has more advantages in manufacturing small aperture optics, controlling small spatial wavelength’s wave structures, correcting mid-high frequency and removing nanoscale materials. Material removal characteristic and figure correction ability for each of large and small polishing head was studied. Each of two polishing heads respectively acquired stable and valid polishing removal function and ultra-precision flat sample. After a single polishing iteration using small polishing head, the figure error in 45mm diameter of a 50 mm diameter plano optics was significantly improved from 0.21λ to 0.08λ by PV (RMS 0.053λ to 0.015λ). After three polishing iterations using large polishing head , the figure error in 410mm×410mm of a 430mm×430mm large plano optics was significantly improved from 0.40λ to 0.10λ by PV (RMS 0.068λ to 0.013λ) .This results show that the dual polishing heads MRF machine not only have good material removal stability, but also excellent figure correction capability.
3D microstructure of optical fiber based on femtosecond laser and temperature characteristic
Author(s):
Qiancheng Zhao;
Yutang Dai;
Tao Li;
Bin Liu;
Guanglin Yin
Show Abstract
Different novel kinds of 3D microstructure manufactured in the cladding of FBG are proposed. Femtosecond laser and special rotary are used to fabricate microstructure such as single thread, double thread and annulus. The thread pitch is 60μm, 80μm controlled by feed and rotary speed. In addition, a thickness of 300nm copper film is coated in the microgrooves by magnetron sputtering technology. Temperature experiment has also been set up and done. Experiment result shows that the FBG sensor with double thread of 80μm is the most sensitive one responding to temperature change. It is approximately five times higher than the standard FBG sensor .This new type of FBG sensor shows great prospect in temperature sensing.
The thin mirror deformation and stress distribution analysis based on different influence functions
Author(s):
Hongqiao Wang;
Bin Fan;
Yongqian Wu;
Haitao Liu;
Rong Liu
Show Abstract
The active support technique can be applied in the fabrication of large thin meniscus mirror. It can reduce the grinding and polishing difficulty for thin mirror. Compare between two kinds of influence function, we correct the Zernike 5th, 6th, 10th and 11th mode deformation. The low-order Zernike modes which are prone to appearing during large primary mirror processing are revised with active support technology. Influence functions are expressed with Z coordinate value and Zernike coefficient of surface shape. This paper reports that respectively adopting different influence functions to solve correction forces and the correction forces compensates specific Zernike modes of mirror deformation. After comparing the PV and RMS values of amendatory residual of surface shape, we analyze the effect of different correction forces to the biggest stress on the underside of the primary mirror. We compare the two methods based on the PV and RMS values of the residual error and the Max-stress. Gain a conclusion that correction forces obtained from Z coordinate value of surface shape is superior to the one obtained from the Zernike coefficient of surface shape.
Research on the 2-axis cup-wheel dressing technology of arc-diamond grinding wheel
Author(s):
X. L. Chang;
H. Y. Wu;
Y. F. Peng
Show Abstract
The precision dressing of arc-diamond wheel is very hard, expensive and time-consuming because of the super-hard diamond particles and complicated geometrical shape. This paper aims to investigate the cup-wheel dressing technology to realize the high-efficiency regeneration of the arc-diamond wheel. A two-axis cup-wheel dressing technique for precision dressing arc-diamond wheel was suggested and tested. The dressing mechanism of 2-axis cup-wheel was studied. The dressing algorithm and error compensation method were further investigated to improve the dressing precision and efficiency. The experimental results show that the 2-axis cup-wheel dressing technique is valid and applicable to realize the precision dressing of arc-diamond wheel. The machined optical surface condition was apparently improved with the cup-wheel dressed diamond wheel and even became much better when the error compensation algorithm was performed on the arc-diamond wheel.
Influence factors of optical surface roughness in traditional polishing process
Author(s):
Li-Jun Shen;
Yong-Jian Wan;
Kai Meng
Show Abstract
Reducing the optical surface roughness is the key to improve the polishing quality of optical mirrors. Traditional
polishing technology in ultra-smooth polishing glass has been used widely for a long time. In this paper, the theories of
traditional polishing in polishing process were summarized. The problems in polishing procedure were analyzed and the
influence factors of optical surface roughness were provided according to the polishing procedure of optical mirrors, and
the relative measurements were pointed out. During the factors, polishing slurry and polishing pad are the important ones.
Contrasting with former traditional polishing technology, roughness factors of new polishing slurry and polishing pad
were analyzed and used in polishing process. The optical mirror of Ø246mm was polished in traditional technology with
new polishing slurry and polishing pad, the obtained testing results were surface roughness 3.421nm before polishing
and 0.613nm after polishing.
A study on the diamond lapping direction determination
Author(s):
Ning Yang;
WenJun Zong;
ZengQiang Li;
Tao Sun
Show Abstract
The anisotropy of material removal rate for diamond gives a method to control the lapping rate of diamond specimen, i.e. changing the lapping direction. This requires comprehension on the relationship of the material removal rate and the lapping direction for diamond. This paper provides a method to figure out the diamond lapping direction. By preprocessing a straight edge formed by lapping a surface intersects with the required machining surface, the diamond lapping direction can be figured out under the Confocal Scanning Laser Microscope only if the crystal directions of the two surfaces are determined at first. The advantage of our method is that there is no need to consider the position and posture of the diamond specimen fixed on the holder.
Study on algorithm of dwell time in ion beam figuring based on RBF neural network
Author(s):
Dasen Wang;
Guoxu Ding;
Chunyang Wang;
Qiang Wang
Show Abstract
Give the figures, which describe the relation between Ion Beam Figuring parameters(Ion beam density, energy, incident angle) and removal features based on SRIM software, the beam removal function model is built and proposed an algorithm of dwell time using RBF neural network optical controlling removal function and processing route. Then, Analyzed the error of algorithm and did some related compensation researches. Results showed that under a certain accuracy, the proposed algorithm can greatly speed up, control more optimization, make the IBF technology more practical, promoting the further development of the super precision optical surface processing technology.
The effect of machining error on the diffraction efficiency of refraction and diffractive optical element
Author(s):
Long Gao;
Changxi Xue;
Hongfang Yang;
Xin Nie
Show Abstract
According to the expression of the phase delay and diffraction efficiency of the diffractive optical elements(DOEs), the expression of diffraction efficiency of refraction and diffractive optical element with the tilt and decenter error in fabrication process was presented in this paper. Analysis results show, in the wavelength band of 501nm-554nm, the cycle of 500μm, the center wavelength of 521nm, when the tilt angleα increases form 0° to9.8° , the diffraction efficiency is above 99%; when the tilt angleα increases form 9.8° to 29.7° , diffraction efficiency is above 92.5%; when the tilt angleα is above 29.7° , the diffraction efficiency declines rapidly, diffraction efficiency is 0 when the tilt angleα is above 58° . When the decenter Δ increases form 0nm to 21.6μm,the diffraction efficiency is above 98%; when the decenter Δ increases form 21.6nm to 63.3μm, the diffraction efficiency is above 90%; when the decenter Δ is above 63.3μm, the diffraction efficiency declines rapidly, diffraction efficiency is 0 when the he decenter Δ is above 241.7μm. To sum up the results of analysis,mathematical analysis model of the relationship between the decenter and tilt error of diffractive optical element in processing and the diffraction efficiency can be used to guide the design of the refraction and diffractive hybrid optical system comprising the diffractive optical element.
Modeling and analysis of ductility of brittle materials using indentation method
Author(s):
Guoyan Sun;
Zhe Lu;
Jianming Bai;
Fangsu Yu
Show Abstract
Nowadays, many optical elements are fabricated by means of glass molding using hard and brittle inserts such as Silicon Carbide (SiC) and Silicon Nitride (Si3N4). However, for those hard-to-machine materials, the most feasible solution is still with ultra-precision grinding and following polishing. Hence, it is necessary and meaningful to study their plastic properties for the development of optical fabrication and ultra-precision manufacturing process. However, the conventional methods including compression test and indentation fracture mechanics are not sufficient to obtain the accurate parameters and still lack of reliable supporting of the machining process. To solve this problem, this paper presents a novel way to correlate the plastic properties to the indentation data using dimensional analysis for the two sorts of hard and brittle materials of SiC and Si3N4. Through integrating the data obtained by the indentation tests and the modeling method presented in this paper, stress-strain behavior, yield stress σy, yield strain epsilony and strain hardening exponent n could be determined. The processing performance of these two materials reflected by the above parameters are consistent with the conclusions drawing from the indentation crack development under varying loads during the indentation test, which verifies the effectiveness and feasibility of the presented modeling method.
Research on aspheric focusing lens processing and testing technology in the high-energy laser test system
Author(s):
Dan Liu;
Xiu-hua Fu;
Zong-he Jia;
Zhe Wang;
Huan Dong
Show Abstract
In the high-energy laser test system, surface profile and finish of the optical element are put forward higher request. Taking a focusing aspherical zerodur lens with a diameter of 100mm as example, using CNC and classical machining method of combining surface profile and surface quality of the lens were investigated. Taking profilometer and high power microscope measurement results as a guide, by testing and simulation analysis, process parameters were improved constantly in the process of manufacturing. Mid and high frequency error were trimmed and improved so that the surface form gradually converged to the required accuracy. The experimental results show that the final accuracy of the surface is less than 0.5μm and the surface finish is □, which fulfils the accuracy requirement of aspherical focusing lens in optical system.
Precision truing of diamond wheel with sharp edge
Author(s):
Cheng Ge;
Bing Guo;
QIngliang Zhao;
Bing Chen;
Jinhu Wang
Show Abstract
Diamond wheel with sharp edge has small contour structures, which can lead to fast wear of wheel in the grinding process. Traditional truing methods are hard to apply to this kind of wheels. Therefore, as for the difficulty of precision truing of diamond wheel with sharp edge, the novel methods for resin and metal bonded diamond wheels with sharp edge are presented, respectively. In this experiment, a conditioning procedure with rare metal alloy block Ta was used to true the resin bonded diamond grinding wheel and in the same way Nb alloy block was utilized to complete rough truing of metal bonded diamond grinding wheel. Then a CNC truing technique with rotational green carbide (GC) truing stick was applied to precise truing of metal bonded diamond grinding wheel. Methods mentioned above were measured in order to evaluate the performance of truing. Geometric features of the wheel sharp edge were duplicated on the organic glass (PMMA) in order to measure and calculate the radius of the sharp edge. The edge radius of trued resin bonded wheel and metal bonded wheel is perceived as an important assessment. The experiments results revealed that the edge radius of 12.45μm for the resin bonded wheel and the edge radius of 30.17μm for the metal bonded wheel could be achieved.
Design of optical system for spectrometer involving a volume phase holographic transmission grating
Author(s):
Zhong Ren;
Guodong Liu;
Zhen Huang
Show Abstract
At present, spectrometer has popularly being used into varieties of fields including environment, food, medical health monitoring and metal industry because it has the advantages of noninvasive, high efficient and convenient etc. The performance of the spectrometer is determined by its optical system. Normally, according to the apparatus and principle of splitting-light, optical system of spectrometer can be classified into several categories, for example, filter-typed, dispersion typed, Fourier transform typed and acousto-optic tunable typed. The grating typed optical system has been popularly used into the spectrometer due to the features of higher diffraction efficiency, resolution and dispersion rate etc. In the grating-typed optical system, although the traditional plane and concave grating have usually been used into some spectrometers, some disadvantages of them still limit their applications, such as, large aberration, worse spectral flatness and low deficiency, etc. In this paper, to overcome these disadvantages of the traditional plane and concave grating, a novel optical system for spectrometer (OSS) based on volume phase holographic transmission (VPHT) grating was designed. For this novel grating, its manufacture and theories were investigated, and its diffraction efficiency was firstly numerically simulated according to different parameters. In order to prove the feasibility of this designed OSS, the spectral calibration experiment was performed and the spectral resolution reached 2nm.
Stray light analysis for optical splitting system of micro-biochemical analyzer
Author(s):
Zhen Huang;
Guodong Liu;
Zhong Ren;
Lvming Zeng
Show Abstract
In this paper, the stray light for an optical splitting system of micro biochemical analyzer is ray tracing by using software FRED and actually measured respectively. The generation and propagation of stray light is simulated and the measures of restraining stray light, such as setting baffle structure, coating critical surface and optimizing light source path are put forward. The results of experiment for improved system show that the stray light coefficient is reduced from 4.6% to 1.2%.
Manufacture of PMMA triangular pyramid microstructure film
Author(s):
Boqi Wu;
Lianhe Dong;
Da Mu;
Yanbing Leng;
Meixuan Li;
Hang Yin
Show Abstract
Triangular Pyramid Microstructure Array has the obvious effect that the light can be emitted uniformly. We use hot embossing technology to produce the Triangular Pyramid Array on PMMA, which the period of microstructure is 50μm and the height is 20μm. The film can replace spherical micromirror array film, and then the transmission of light can be improved by 2.2%. The results showed that under certain temperature conditions there is a matching relation between PMMA and mold about the thermal expansion coefficient, and the pressing temperature has great influence on the roughness of the microstructure surface.
Design and fabrication of visible and infrared laser HR coating
Author(s):
Meixuan Li;
Lianhe Dong;
Lei Zhang;
Boqi Wu;
Jun Ma
Show Abstract
In view of the special requirements of the high power laser spectral bands and the incident angle, plate dual wavelength laser high reflecting membrane on the K9 optical glass by using electron beam evaporation deposition. Under the condition of vertical incidence, the reflectivity of 532 nm wavelength is higher than 90%; Under the condition of plus or minus 45 ° incident angle, the reflectivity of 1064 nm wavelength at near infrared band is higher than 99.9%. Through material selection, optimization of process parameters and the method of the ion source assisted deposition to improve the membrane layer density and membrane base binding strength, laser-damaged threshold and meet the requirements of the use of optical instruments under certain environmental conditions.
Design of a vertical ultra-precision linear axis modular driven by dual linear motors
Author(s):
Enbing Qi;
Zhenyong Fang;
Tao Sun;
Bo Wang
Show Abstract
Non-rotational symmetric surface machining requires at least three numerically controlled axes, so there exists a desperately need of an ultra-precision vertical linear axis for ultra-precision machine tools. Based on the above consideration, a vertical ultra-precision linear axis has been developed to satisfy the need for non-rotational symmetric surface ultra-precision machining. The paper discusses the design challenges of the vertical ultra-precision linear axis and presents the mechanical structure designed with dual linear motor drive. A guide component and a gravity compensation mechanism have been designed. Finite element models for the vertical ultra-precision were established to evaluate the dynamic performance of the vertical ultra-precision linear axis. Analysis results show that the configuration of the vertical ultra-precision linear axis is reasonable with good dynamic performance.
Simulation on turning aspheric surface method via oscillating feed
Author(s):
Fanxing Kong;
Zengqiang Li;
Tao Sun
Show Abstract
It is quite difficult to manufacturing optical components, the combination of high gradient ellipsoid and hyperboloid,
with high machining surface requirements. To solve the problem, in this paper we present a turning and forming method
via oscillating feed of R-θ layout lathe, analyze machining ellipsoid segment and hyperboloid segment separately through
oscillating feed. Also calculate parameters on each trajectory during processing respectively and obtain displacement,
velocity, acceleration and other parameters. The simulation result shows that this rotary turning method is capable of
ensuring that the cutter is on the equidistance line of meridian cross section curve of work piece during processing high
gradient aspheric surface, which helps getting high quality surface. Also the method provides a new approach and a
theory basis for manufacturing high quality aspheric surface and extending function of the available twin-spindle lathe as
well.
Research on beam splitting prism in laser heterodyne interferometer
Author(s):
Xiu-hua Fu;
Shi-fu Xiong;
Yang Kou;
Yong-gang Pan;
Heng Chen;
Zeng-yu Li;
Chuan-xin Zhang
Show Abstract
With the rapid development of optical testing technology, laser heterodyne interferometer has been used more and more widely. As the testing precision requirements continue to increase, the technical prism is an important component of heterodyne interference. The research utilizing thin film technology to improve optical performance of interferometer has been a new focus. In the article, based on the use requirements of interferometer beam splitting prism, select Ta2O5 and SiO2 as high and low refractive index materials respectively, deposit on substrate K9. With the help of TFCalc design software and Needle method, adopting electron gun evaporation and ion assisted deposition, the beam splitting prism is prepared successfully and the ratio of transmittance and reflectance for this beam splitting prism in 500~850 nm band, incident angle 45 degree is 8:2. After repeated tests, solved the difference problem of film deposition process parameters ,controlled thickness monitoring precision effectively and finally prepared the ideal beam splitting prism which is high adhesion and stable optics properties. The film the laser induced damage threshold and it meet the requirements of heterodyne interferometer for use.
Research on the polishing technology of high-precision aspherical cylindrical lens
Author(s):
Xiu-hua Fu;
Zhe Wang;
Zong-he Jia;
Huan Dong;
Dan Liu;
Chuan-xin Zhang
Show Abstract
Aspherical cylindrical lens compared with the cylindrical lens, they improved image quality and optical properties, simplified the system architecture. They applied in many fields, such as high power laser system, fax machines and typographical scan imaging system, as well as bar code scanning, lighting and other aspects of holography. Aspherical cylindrical lens are centrosymmetric. It is difficult to process. Parallel with the side line and bus bar line is difficult to ensure. Machining accuracy is low. It is usually about 15 μm, that not sufficient to meet the needs of modern highprecision laser systems. These have become a major problem restricting its development. Combining traditional and modern polishing techniques, a new technique for polishing aspherical cylindrical lens is proposed-- longitudinal feedback compensation technology. With dimensions of 15 × 5 × 5 mm quartz aspherical cylindrical lens as an example, the surface profilometer results of detection of the workpiece usually, modify the shape of the polishing surface of the mold, to control the size of the area of the polishing, the surface of the workpiece to achieve the effect of the type of compensation. After repeated testing and feedback compensation, gradually improve the accuracy of the workpiece surface type. The results show that this technique can effectively improve the precision aspherical cylindrical lens. After detection the workpiece surface accuracy is 0.8μm, the surface finish is Class II. It has the actual production of a certain application value.
Research on processing technology of odd-form off-axis aspherical lens
Author(s):
Xiu-hua Fu;
Huan Dong;
Zong-he Jia;
Zhe Wang;
Dan Liu;
Chuan-xin Zhang
Show Abstract
With the development of advanced optical processing technology, the off-axis aspherical lens are the vital optical device for the high precision measurement and machining system. Off-axis aspherical lens can not only reduce the complexity of the system, but also increase the breadth of coverage to get closer to the ideal image. In order to get high efficiency and high surface accuracy, the off-axis aspherical lens processing and testing methods are deeply researched. The processing of traditional off-axis aspherical lens process coaxial aspherical lens first, then cut it to off-axis aspherical lens. This method is prone to edge spliting and on the surface of the secondary damage. This article presents a novel processing technology - splicing processing technology. The technology can guarantee the accuracy of polishing the surface type, and to avoid secondary damage to the surface, to achieve high-precision off-axis aspherical lens machining. The off-axis aspherical lens are tested by Taylor Hobson profilometer. The off-axis aspheric surface figure can get 0.715 μm, the surface polish can achieve the Grade II. Therefore, a high efficiency, reproducible off-axis aspherical polishing method were summarized. The off-axis aspherical lens to achieve mass production.
Nearly arc-length tool path generation and tool radius compensation algorithm research in FTS turning
Author(s):
Minghui Zhao;
Xuesen Zhao;
Zengqiang Li;
Tao Sun
Show Abstract
In the non-rotational symmetrical microstrcture surfaces generation using turning method with Fast Tool Servo(FTS), non-uniform distribution of the interpolation data points will lead to long processing cycle and poor surface quality. To improve this situation, nearly arc-length tool path generation algorithm is proposed, which generates tool tip trajectory points in nearly arc-length instead of the traditional interpolation rule of equal angle and adds tool radius compensation. All the interpolation points are equidistant in radial distribution because of the constant feeding speed in X slider, the high frequency tool radius compensation components are in both X direction and Z direction, which makes X slider difficult to follow the input orders due to its large mass. Newton iterative method is used to calculate the neighboring contour tangent point coordinate value with the interpolation point X position as initial value, in this way, the new Z coordinate value is gotten, and the high frequency motion components in X direction is decomposed into Z direction. Taking a typical microstructure with 4μm PV value for test, which is mixed with two 70μm wave length sine-waves, the max profile error at the angle of fifteen is less than 0.01μm turning by a diamond tool with big radius of 80μm. The sinusoidal grid is machined on a ultra-precision lathe succesfully, the wavelength is 70.2278μm the Ra value is 22.81nm evaluated by data points generated by filtering out the first five harmonics.
Research of multi-band laser high reflection mirror
Author(s):
Xiu-hua Fu;
Yong-gang Pan;
Fei Wang;
Dong-mei Liu;
Jing Zhang
Show Abstract
Through the method of nonlinear optical frequency conversion method, 532nm, 355nm and 266nm laser wavelength can be attained by YAG1064nm laser. Mirror that works in this system must satisfy the requirements of high reflection in four bands. Based on the film design system to choose appropriate coating materials, adopting electron beam vacuum ion assisted deposition technique, through optimizing the parameters of the process, the film that reflectance is 99.8% at 1064nm , 99.6% at 532nm ,97.9% at 355nm and 96.8% at 266nm is prepared on the substrate of JGS1. Additionally, the laser induce damage threshold in the ultraviolet wave band is 1.432J/cm2 at 355nm , 0.923J/cm2 at 266nm. The results show that all the preparation of mirror meets the requirements well.
The research on conformal acid etching process of glass ceramic
Author(s):
Kepeng Wang;
Peiji Guo
Show Abstract
A series of experiments have been done to explore the effect of different conditions on the hydrofluoric acid etching. The hydrofluoric acid was used to etch the glass ceramic called “ZERODUR”, which is invented by SCHOTT in Germany. The glass ceramic was processed into cylindrical samples. The hydrofluoric acid etching was done in a plastic beaker. The concentration of hydrofluoric acid and the etching time were changed to measure the changes of geometric tolerance and I observed the surface using a microscope in order to find an appropriate condition of hydrofluoric acid etching.
Research of the residual stress in grinding surface of glass-ceramics
Author(s):
Peng Zhou;
Peiji Guo
Show Abstract
We simulated the process of grinding glass-ceramics with the finite element simulation method. During the simulation, we considered the impact of changes in various process parameters on the grinding and analysis the simulation results of the residual stress at last. The target of this research is to provide some basic reference for the choice of the glass-ceramics grinding process parameters.
Simulation of surface topography of big aspheric fabrication by ultra-precision diamond turning based on tool swing feeding
Author(s):
Honghui Yao;
Zengqiang Li;
Tao Sun
Show Abstract
In the respect of ultra-precision manufacturing of axisymmetric surface, the machine tool with tool swing feeding which has less interpolation error sources compared to the conventional ultra-precision diamond turning machine tool with T-structureis worth studying.Therefore,based on the dynamic simulation modeling and multi-body dynamics theory,in this paper, we establish the control model,and tool path for Ultra-precision machine.Then we got the model for surface topography with differentinput parameters like spindle speed, feedrate, tool parameters and so on. Taking the spherical optics part with diameter of 300 mm, for example, we input the process parameters and get its surface topography, then evaluate its surface quality by surface roughness value (Ra) and surface shape accuracy(PV) .
Study on the auto-leveling adjustment vibration isolation system for the ultra-precision machine tool
Author(s):
XiCong Zou;
ZengQiang Li;
XueSen Zhao;
Tao Sun;
KunPeng Zhang
Show Abstract
The requirement of the vibration isolation system for ultra-precision machine tool was extremely stringent. However, most of the isolation systems currently cannot meet the requirement. Therefore, it is urgently needed to design a new vibration isolation system to fulfill the strict vibration capability required by ultra-precision machine tool. In this paper the structure and principle of the conventional vibration isolation systems composed of air springs were first elucidated thoroughly. Based on these knowledge, we have designed a vibration isolation system with the function of auto-leveling adjustment for a home-made ultra-precision machine tool. The capability of vibration isolation system was validated by an experimental method, in which acceleration-frequency curves were recorded. And post data processing including the analyzing the cut-off frequency and amplitude attenuation were followed. The experimental results demonstrated that the air spring vibration isolation system designed in this paper has the capability to effectively isolate the vibration from the ground: it has a higher attenuation ratio for vibration with a frequency beyond 3 Hz, which preferably meet the vibration isolation requirement of the ultra-precision machine tool.
20 W passive mode-locked picosecond oscillator
Author(s):
Zhen-ao Bai;
Zhong-wei Fan;
Fu-qiang Lian;
Zhen-xu Bai;
Zhi-jun Kan;
Jing Zhang
Show Abstract
Detail studies on the 888 nm laser diode (LD) pumped Nd:YVO4 crystal was reported to reduce the absorption coefficient
and improve thermal performance of the laser, which could generate high power mode-locked pulses output easily. The
mode-locking operation was induced by a semiconductor saturable absorber mirror (SESAM). When pumping power is
65 W, the maximum output power of 20 W is obtained at repetition rate of 63.5 MHz with the optical-optical conversion
efficiency of 30.8% and pulse width of 45 ps.
Towards fusion technique for astronomical images with high dynamic range
Author(s):
Lin Du;
Huayan Sun;
Zhaofei Hou;
Yingying Qi
Show Abstract
Astronomical detection always need high dynamic range image, but there are problems such as underexposure or overexposure in astronomical images taken by commercial camera, this paper proposed the technique that combine establishing the first order difference quotient curve of each pixel with data feature positioning to calculate optimal exposure value of each pixel, which achieves high dynamic range fusion. In this paper, data feature positioning method was firstly utilized to establish mathematical model to calculate optimal exposure point in the first order difference quotient curve of each pixel in the target scene. Correlate optimal exposure point and camera response function to calculate optimal brightness value of each pixel, the fused high dynamic range image will be achieved. Finally, take a series of low dynamic range images with different exposure value by commercial camera, establish mathematical model and calculate to achieve high dynamic range fusion, which verifies the fusion technique proposed in this paper can obtain high dynamic range astronomical images effectively.
Boundary marking by three-dimensional coordinate machine in the field of optical manufacturing
Author(s):
Xi Chen;
Peiji Guo
Show Abstract
This paper presents a method for automatic marking of optical components for processing area. Using testing equipment, such as wave surface interferometer or coordinate contour measuring machine, we get the two dimensional maps of surface error. According to the positional relationship between the surface error distribution and the corresponding position on the optical surface, we get the X, Y coordinates of the boundary waiting for further milling, grinding or polishing in the workpiece coordinate system. The workpiece coordinate system of optical element is established and the boundary waiting for further processing is marked with points or line by using three-dimensional coordinate machine, so as to realize marking automatically. Experiments show that the processing method of marking is useful in optical manufacturing, and this method is particularly suitable for marking the optical elements that difficult to mark directly in interference testing.
Correction of the removal function of lap in manufacturing large aspherical mirror
Author(s):
Wei Zhang;
Zhige Zeng;
Fan Wu;
Liang Feng
Show Abstract
The pendulum type processing technique is a manufacture way that the workpiece is rotating actively and the lap is slave
drive from the workpiece under its gravity force and the pressure which comes from the pressure head. The rotational
speed of lap is varied. Because the aperture size of the lap can be selected in the processing. So the processing efficiency
is high. And this technique is commonly used in the grinding stage to remove a large margin, sub-surface damage layer and to smooth the mirror surface in the stage of polishing. Shown in the Preston equation, the removal function of lap is
connected to the relative speed of lap_workpiece. Based on moment-equilibrium principle, a theoretical model is
established about the lap which associated with the coherent parameters. Under the condition of the lap and the workpiece at different relative positions, the rotational speed of the lap and correspondence between the parameters is summarized and derived. The speed ratio of lap_workpiece increases with the increment of the eccentricity, and the
actual rotational speed is determined by the workpiece’s rotational speed, the size of lap and the force acting on the lap. The relationship of speed ratio between the lap and workpiece which impacts on the removal function is given at the last
of the paper.
Research on the fluid jet polishing in advanced optical fabrication
Author(s):
Tianxiang Sun;
Long Sun;
Yuqi Jin;
Feng Wang;
Dianxian Sun
Show Abstract
Based on the principle of fluid mechanics, this paper presents the technological process of Fluid Jet Polishing. According
to the Preston hypothesis, the Fluid Jet Polishing removal amount could be described as a linearity function. The material
is removed by the collision and shear action between slurry and work-piece. Comparing to other optical method, kind of
abrasive slurry, average diameter of abrasive particle, pressure of abrasive particle, working time, incidence distance and
angle of incidence influence the surface figure result and quality of fluid jet polishing. The paper mainly focuses on the
influence of abrasive slurry and incidence distance.
In the experiment, we take the diameter of Φ120mm, thickness of 20mm, fused silica for example to examine the
exactitude principle of the fluid jet polishing. After the final process of fluid jet polishing, the surface figure PV(Peak
and Valley) is about 0.046λ(λ=633nm), the RMS (Root-Mean-Square)is about 0.007λ. The result of experiment testifies
fluid jet polishing could get high precision.
Digital calibration method for defects evaluation of large fine optical surfaces
Author(s):
Xiaoyu Chen;
Dong Liu;
Yongying Yang;
Lu Yan;
Lu Li;
Pin Cao;
Shitong Wang;
Yibing Shen
Show Abstract
The digital calibration method, which is employed in the Surface Defects Evaluation System (SDES) for the defects evaluation of large fine optical surfaces, is presented in this paper. A criterion board, which comes from special design and careful fabrication, is employed to relate the dimensions of the defects and those of their images. The calibration procedure, including collecting of calibration images, digital image processing and calibration function fitting, is described in detail in this paper. Calibration experiments on scratch width and dig diameter were carried out at three different microscope magnification conditions. Experiment results show that following the proposed digital calibration method, micron-sized defects distributed sparsely on a large-aperture fine optical surface can be evaluated with micron accuracy and high efficiency.
Stray light analysis in the TV system for tracking and measuring
Author(s):
Lei Cao;
Hong-bin Chen;
Qi Qiu;
Ge Ren;
Yang Jiang;
Bo Qi
Show Abstract
According to the technical features and requirements of the television imaging system for tracking and measuring, we
designed a TV system with focal length of 2800mm, F/11.7 and 2ω(FOV) of 14.2′. The system is compact and easy to
fabricate and align, with good image quality. Meanwhile, we performed stray light analysis with ASAP optical software,
described stray light suppression techniques used in the TV for tracking and measuring, proposed a method to determine
optical properties of the system components and parameters of the scattering model reasonably. We calculated the PST
curve of the system for incident angle from -45° to 45°. The results show that when the off-axis angle is larger than the
critical incident angle of the sun, PST value is less than 10-8.
Research on the design of surface acquisition system of active lap based on FPGA and FX2LP
Author(s):
Hongshen Zhao;
Xiaojin Li;
Bin Fan;
Zhige Zeng
Show Abstract
In order to research the dynamic surface shape changes of active lap during the processing, this paper introduces a
dynamic surface shape acquisition system of active lap using FPGA and USB communication. This system consists of
high-precision micro-displacement sensor array, acquisition board, PC computer composition, and acquisition circuit
board includes six sub-boards based on FPGA, a hub-board based on FPGA and USB communication. A sub-board is
responsible for a number of independent channel sensors’ data acquisition; hub-board is responsible for creating encoder
simulation tools to active lap deformation control system with location information, sending synchronization information
to latch the sensor data in all of the sub-boards for a time, while addressing the sub-boards to gather the sensor data in
each sub-board one by one and transmitting all the sensor data together with location information via the USB chip
FX2LP to the host computer. Experimental results show that the system is capable of fixing the location and speed of
active lap, meanwhile the control of surface transforming and dynamic surface data acquisition at a certain location in the
processing is implemented.