Papers by Keyword: Aspheric Surface

Abstract: Previous researches have confirmed that MCF (magnetic compound fluid) slurry shows outstanding performance in the nanoprecision polishing of flat surfaces and V-grooves. However, no investigations have been conducted on the polishing of aspheric surfaces using MCF slurry. In this work, a novel method employing a doughnut-shaped MCF polishing tool and a 6-DOF manipulator has been proposed for the aspheric surface polishing. The time consumption for forming stable polishing tool and its final appearance are investigated. Flat aluminum alloy workpieces that can be considered as a kind of aspheric elements with infinite curve radius were adopted in the investigation of the polished forces under variable parameters. As a typical experimental result, with MCF3 slurry, 2.5ml volume of supplied slurry and work gap 3.5 mm, the surface roughness Ra decreases from 125nm to almost 10nm after 90 min polishing, confirming that the proposed method has the potential to polish aspheric surfaces.

Abstract: A novel principle of cup wheel grinding of rotating concave quadric surface was proposed. The mathematical model of machining process was established to prove the feasibility of precision grinding of rotating concave paraboloid based on the introduced principle. The conditions of non-interference grinding of concave paraboloid were mathematically derived. The processing range and its influence factors were discussed. The trajectory equation of abrasive particle was concluded. Finally, the math expressions of numerical controlled parameters was put forward in the process of grinding of the concave paraboloid.

Abstract: Aspheric lens of Zinc sulfide is widely used in infrared, but it is always formed by polishing with low efficiency, ductile regime grinding aspheric surface of hot-pressed zinc sulfide is studied to reduce time-consuming of polishing. The results of orthogonal grinding experiments demonstrate that the depth of grinding is the main influencing factor on ductile regime removal mechanisms and surface roughness Ra values which decrease with decreasing depth of grinding, and the optimal value is 7.6nm, the steady ductile regime removal mechanisms appears when depth of grinding is below 0.4μm. With diamond wheel by grain size of D20/30, machining parameters on the basis of orthogonal grinding experiments, the aspheric surface cross grinding experiments show that ductile regime removal is obtained only in little center areas of aspheric surface, most of aspheric surface is in brittle regime. Then, the ductile regime aspheric surface with roughness of 20.1nm is observed by cross grinding of diamond wheel with grain size of D4/8.

Abstract: An analyzing rotating error method has presented based on grinding aspheric optical component. A coordinate transform has been done between the new and original coordinates system in view of the rotating error in installing parts, further, the rotating angle error model has deduced between actual curve and theoretical curve. The surface error formulas can be used for variety of rotary conic aspheric curve, depending on the requirements of the parts surface accuracy, quantitative adjustment target can be given in installation and adjustment process before grinding. Based on the rotating error formulas, the calculating example shows that installation angle bas various different influence to surface shape error, the error decreases with the θ decreasing, the surface error is reduced a magnitude accordingly when the angle is reduced to a magnitude. The parts surface error is up from-0.0030mm to-0.0448mm when the rotating angle increasing from 0.1° to 1°. When θ is constant, the surface shape error increases with steepness increasing, installing rotating angle requirement is more stringent for all the large steepness parts.

Abstract: A new method of processing optical aspheric parts by of bending and forming is presented, and the processing is line contact. The grinding principle is given of the bending and forming method. Based on the Preston equation, the grinding conditions is put forward to the bending and forming method. The function of the pressure and the relative velocity on the any point of at the processing surface are made. The material removal function is deduced about the bending and forming method. The experiments shows the grinding average error is 0.0272mm using solid abrasive on parabolic parts, and the maximum error is 1.0038μm using abrasive belt on hyperboloid parts.

Abstract: This paper introduces a new devices and technology of large-aperture quadratic optical components rapid powerful NC polishing, it has greatly improved the efficiency and precision of aspheric polishing. Through self-designed five-axis CNC polishing machine, to achieve the controlling of rotation, revolution integral rapid powerful polishing head. By optimizing the process parameters, determine a reasonable polishing path and polishing mode structure, to obtain good experimental results. Size 340mm × 340mm aspheric optical glass, surface shape accuracy PV λ / 5, surface roughness Rq 1.2nm, processing efficiency has been effectively improved, surface shape convergence stable.

Abstract: Based on MTTSD (Magneto-rheological Torque Transmission Servo Devices) and force-position decoupling control technology, an aspheric surface NC polishing project is put forward. The aspheric surface polishing fundamental theory is researched. Under the condition of a constant material removal rate, a new aspheric surface polishing model is brought forward. In addition, under the condition of a constant material removal rate, this paper brought up a polishing force control model and a workpiece rotating speed control model, according to witch, force and rotating speed change with the coordinates of working points, and variation curves are drawn.CLC Number: TH166 Document Identifier: A

Abstract: A new method is proposed that high speed lapping aspheric surface workpiece using lapping tool by means of bending because there processing difficult, In this study, the principle of high speed lapping has been presented, the mathematical model for the lapping tool has been established, and the equidistance curve error of the lapping tool has been analyzed. The results of the experiment indicate that the forming precision of the lapping tool is high using this method, the surface precision of the workpiece reaches micron grade, furthermore, the aspheric surface workpiece can been machined using this method in lapping, and that it can meet the need of medium precision of machining the aspheric surface workpiece. The experiment result indicates that the the lapping tool shape precision is high, the lapping error of the workpiece is 0.0108mm, and lapping efficiency is high and the cost is low. This aspheric lapping method has incomparable superiority of other processing methods.

Abstract: In order to meet the requirement of tank sight and improve the ability of Joint Transform Correlator(JTC) in target detection and recognition, the infrared telephoto system with high image quality and high performance-price ratio is designed for wavelength 8μm～12μm. Initial structure is composed of four refractive lenses. The focal length is 200 mm, the relative aperture is 1:2.6 and image field of view is 1 inch (CCD). Considering the fabrication process, production cost and other factors, the system structure is further improved. First the telephoto which is composed of four lenses is designed with normal spherical surface. Then on the basis of the original spherical structure, an aspheric surface is introduced. The optical system can be reduced into three lenses. The image quality of the whole system becomes much better. The optical system image quality is evaluated with ZEMAX optical design software. The result shows that MTF of each field is close to the diffraction-limited curve at the cut-off frequency 17lp/mm. The spot diagram RMS radiuses are smaller than the radius of Airy disk 25.35μm. The wave front aberrations for all the fields are less than 0.25λ. The telephoto can meet the requirement of target detection. Combining JTC with this infrared telephoto lens, the infrared target at longer distance can be detected and recognized.

Abstract: A method of symmetric distortion correction is described and successfully applied to correct the distortion mapping errors caused by CGH as well as internal imaging optics. The aspheric surface is 160 mm in diameter and has a maximum departure of 145 μm. According to the model established by the fiducial spots on the aspheric surface, we show experimental results after direct measurement and distortion-corrected error map respectively. The results show that the method of symmetric distortion correction is useful and effective.