Fabrication and correction of freeform surface based on Zernike polynomials by slow tool servo
16 Oct 2017-Vol. 10448, pp 1044813
TL;DR: In this paper, the free-form surface using multi-axis ultra-precision manufacturing could be upgraded with Zernike polynomial fitting to improve the form accuracy of freeform.
Abstract: Recently, freeform surface widely using to the optical system; because it is have advance of optical image and freedom available to improve the optical performance. For freeform optical fabrication by integrating freeform optical design, precision freeform manufacture, metrology freeform optics and freeform compensate method, to modify the form deviation of surface, due to production process of freeform lens ,compared and provides more flexibilities and better performance. This paper focuses on the fabrication and correction of the free-form surface. In this study, optical freeform surface using multi-axis ultra-precision manufacturing could be upgrading the quality of freeform. It is a machine equipped with a positioning C-axis and has the CXZ machining function which is also called slow tool servo (STS) function. The freeform compensate method of Zernike polynomials results successfully verified; it is correction the form deviation of freeform surface. Finally, the freeform surface are measured experimentally by Ultrahigh Accurate 3D Profilometer (UA3P), compensate the freeform form error with Zernike polynomial fitting to improve the form accuracy of freeform.
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TL;DR: A recently introduced method for characterizing the shape of rotationally symmetric aspheres is generalized here for application to a wide class of freeform optics.
Abstract: A recently introduced method for characterizing the shape of rotationally symmetric aspheres is generalized here for application to a wide class of freeform optics. New sets of orthogonal polynomials are introduced along with robust and efficient algorithms for computing the surface shape as well as its derivatives of any order. By construction, the associated characterization offers a rough interpretation of shape at a glance and it facilitates a range of estimates of manufacturability.
161 citations
TL;DR: In this article, a long-stroke fast tool servo is proposed and installed on the Z-axis of a diamond turning machine as an additional synchronized axis to obtain a tool motion with large amplitude and high bandwidth.
Abstract: Fabrication of free-form surfaces that are frequently demanded for the construction of optical imaging systems is described. To obtain a tool motion with large amplitude and high bandwidth, a novel long-stroke fast tool servo is proposed and installed on the Z-axis of a diamond turning machine as an additional synchronized axis. In addition, a special on-machine measurement device is used to measure the optical parameters of the machined surface and to compensate for the residual form of errors that are commonly produced in the diamond turning process. Actual machining test results show that the proposed procedures are capable of generating the copper free-form mirrors of 50 mm diameter to a form accuracy of 0.15 μm in peak-to-valley value error.
89 citations
"Fabrication and correction of freef..." refers background in this paper
...Freeform surfaces can be machined by fast tool servo (FTS) [7][8], micro-milling [9], fly-cutting or raster milling [10][11], and slow tool servo (STS) [12]-[14]....
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TL;DR: In this paper, a theoretical and experimental analysis of nano-surface generation in ultra-precision raster milling is presented, where an optimization system is established based on the theoretical models for the optimization of cutting conditions and cutting strategy.
Abstract: The fabrication of high-quality freeform surfaces is based on ultra-precision raster milling, which allows direct machining of the freeform surfaces with sub-micrometric form accuracy and nanometric surface finish. Ultra-precision raster milling is an emerging manufacturing technology for the fabrication of high-precision and high-quality components with a surface roughness of less than 10 nm and a form error of less than 0.2 μm without the need for any additional post-processing. Moreover, the quality of a raster milled surface is based on a proper selection of cutting conditions and cutting strategies. Due to different cutting mechanics, the process factors affecting the surface quality are more complicated, as compared with ultra-precision diamond turning and conventional milling, such as swing distance and step distance. This paper presents a theoretical and experimental analysis of nano-surface generation in ultra-precision raster milling. Theoretical models for the prediction of surface roughness are built. An optimization system is established based on the theoretical models for the optimization of cutting conditions and cutting strategy in ultra-precision raster milling. A series of experiments have conducted and the results show that the theoretical models predict well the trend of the variation of surface roughness under different cutting conditions and cutting strategies.
70 citations
"Fabrication and correction of freef..." refers background in this paper
...Freeform surfaces can be machined by fast tool servo (FTS) [7][8], micro-milling [9], fly-cutting or raster milling [10][11], and slow tool servo (STS) [12]-[14]....
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TL;DR: In this article, the authors presented a theoretical and experimental investigation on the 3D surface generation in single point diamond tuning using slow tool servo, and the form error of off-axis paraboloid caused by tool centering error was analyzed and verified by cutting experiment.
Abstract: Off-axis aspheric surfaces have been widely applied in optical systems, but it is difficult to fabricate this kind of optical surface with high quality. Slow tool servo is one of the methods for turning off-axis aspheric surfaces on-axis, which have a large travel range without an additional device. This paper presents a theoretical and experimental investigation on the 3D surface generation in single point diamond tuning using slow tool servo. The form error of off-axis paraboloid caused by tool centering error is analyzed and verified by cutting experiment.
64 citations
"Fabrication and correction of freef..." refers background in this paper
...1 with the basic configuration of the STS function [16]....
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...Fig.6. shows the PAL mold freeform surface before and after fine finishing by STS machining Proc. of SPIE Vol. 10448 1044813-3 2.3 Freeform Surface Measurement We use UA3P-4 with User-Defined function to measure the PAL surface....
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...Then, a PAL freeform surface, which was machined with STS technology, was fabricated....
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...Keywords: freeform surface, ultra-precision manufacturing, slow tool servo (STS), Zernike polynomials...
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...Freeform surfaces can be machined by fast tool servo (FTS) [7][8], micro-milling [9], fly-cutting or raster milling [10][11], and slow tool servo (STS) [12]-[14]....
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TL;DR: In this article, a cylindrical coordinate micromachining method is studied for the ultra-precision cutting of sinusoidal surfaces in a three-axis turning machine, whose NC path is generated in a spiral curve considering the workpiece surface and tool geometry.
Abstract: Micro- and ultra-precision machining is an effective approach to achieving a nanometric surface finish, which is important for the sinusoidal surface as the calibrator of multi-axis precision machines. A cylindrical coordinate micromachining method is studied for the ultra-precision cutting of sinusoidal surfaces in this paper. The three-axis (X, Z, C) turning machine is used, whose NC path is generated in a spiral curve considering the workpiece surface and tool geometry. The avoiding interference technique is proposed, including the optimal selection of tool geometry and simulation of the cutting process. The tool geometry is optimized by using a sectional curve method. The cutting simulation is implemented using a constrained B-spline path fitting and a pipe model of the cutting face. With the method developed, sinusoidal surfaces with a nanometric finish of 5.54 nm in Ra are achieved effectively.
59 citations