A Study of Computer Controlled Ultra-Precision Polishing of Silicon Carbide Reflecting Lenses for Enhancing Surface Roughness

2014 ◽  
Vol 625 ◽  
pp. 437-445 ◽  
Author(s):  
Zhuo Lin Li ◽  
Wing Bun Lee ◽  
Benny C.F. Cheung ◽  
L.T. Ho ◽  
Yue Gang Fu
Keyword(s):  
Surface Roughness ◽  
Silicon Carbide ◽  
Optical Quality ◽  
Optical Systems ◽  
Space Telescopes ◽  
Large Space ◽  
High Optical Quality ◽  
Ultra Precision ◽  
Important Means ◽  
Computer Controlled

Reflecting lens is an important component of optical systems, such as high-resolution cameras, large space telescopes and meteorological satellites etc. Among the lens materials, Silicon Carbide (SiC) has attracted a lot of attention as an important optical material because of its excellent mechanical and physical properties. Apart from the form accuracy, the attainment of a consistently high optical quality in polishing SiC is still of a concern. There are advanced ultra-precision polishing machines that can correct geometrical errors and surface finish of the workpiece. These include surface roughness and waviness. However, the hardness of SiC material itself put an challenge for polishing process. In this paper, A computer controlled ultra-precision polishing (CCUP) method based on mechanical polishing is used to produce the SiC lens. Experiments are being designed on a 7-axis ultra precision polishing machine (Zeeko IRP200). As it is difficult to find out slurry which is harder than SiC so that the conventional polishing slurry is be used. It provides a nice consequence that it also efficient when the polish powder is softer than the machined materials. The tool pressure, polishing head speed and the feed rate are varied and optimized to obtain the best reflectivity of the lens being polished. A pilot experiment will be conducted for the corrective polishing for the form error of the optical surface made of SiC. The result from the study will provide an important means to optimize the process for machining SiC reflective lens using the CCUP process.

scholarly journals Multifunctional contamination-resistant coatings

2019 ◽  
Vol 215 ◽  
pp. 02002
Author(s):  
Nadja Felde ◽  
Anne Gärtner ◽  
Stefan Schwinde ◽  
Sven Schröder
Keyword(s):  
Thin Film ◽  
Surface Roughness ◽  
Light Scattering ◽  
Structural Design ◽  
Optical Quality ◽  
Optical Systems ◽  
Optical Losses ◽  
High Optical Quality ◽  
Optical Surfaces ◽  
Laser Stability

Surface contaminations can critically affect the performance of optical surfaces, in particular with respect to light scattering, optical losses, and laser stability. Thus, avoiding contaminations and reducing contamination-induced effects is of particular interest in the manufacturing of optical systems. By combining a specific thin film design with a tailored structural design, contamination-resistant coatings with a high optical quality can be realized. Most important is the balance of self-cleaningand light scattering-relevant surface roughness components.

Optimising the Process Conditions in Ultra-Precision Grinding to Achieve Surface Finish of Optical Quality

2006 ◽  
Vol 304-305 ◽  
pp. 8-13 ◽  
Author(s):  
T. Jin ◽  
D.J. Stephenson
Keyword(s):  
Surface Roughness ◽  
Surface Finish ◽  
Material Removal ◽  
Removal Rate ◽  
Optical Quality ◽  
Process Conditions ◽  
Low Alloy Steel ◽  
Optical Surface ◽  
Precision Grinding ◽  
Ultra Precision

Optical surface finish below Ra 10nm can be achieved on a ‘Tetraform C’ grinder of ultra-high stiffness, when grinding a low alloy steel with or without the help of ELID (electrolytic in process dressing). Surface roughness generation modelling has been carried out to predict thepossible surface roughness values. Efforts have been made to transfer the process knowledge to different grinding mode using a rigid 5-axis Edgetek CNC grinder. The effects of material removal rate and grit size and also that of spark out passes on the surface roughness generated have been investigated.

The Effect of Up-Cutting and Down-Cutting Directions on Materials Swelling in Ultra-Precision Raster Milling

2006 ◽  
Vol 532-533 ◽  
pp. 697-700 ◽  
Author(s):  
Ming Chu Kong ◽  
Wing Bun Lee ◽  
Chi Fai Cheung ◽  
Suet To
Keyword(s):  
Surface Roughness ◽  
Spectral Density ◽  
Power Spectral Density ◽  
Surface Finish ◽  
Copper Alloys ◽  
Cutting Conditions ◽  
Power Spectral ◽  
Ultra Precision ◽  
Important Means ◽  
Cutting Direction

The influence of materials swelling across the steps on surface roughness under up-cutting and down-cutting direction in ultra-precision raster milling was investigated. The normalized extent of swelling is characterized by a swelling significance index, defined based on the power spectral density of the roughness profile. Materials swelling was found to be significant in ultra-precision raster milling, especially when copper alloys machined in the up-cutting direction. The findings in the present study provide an important means for improving the surface finish of the raster-milled surfaces and optimizing the cutting conditions.

Influence of Machining Characteristics on Ultra-Precision Cutting of Aluminum Alloys

2014 ◽  
Vol 625 ◽  
pp. 201-206
Author(s):  
Daisuke Hirase ◽  
Yukio Maeda ◽  
Kenichi Iwatsuka ◽  
Takanori Yazawa
Keyword(s):  
Surface Roughness ◽  
Cutting Force ◽  
Edge Length ◽  
Optical Quality ◽  
Al Alloys ◽  
Cutting Edge ◽  
Al Alloy ◽  
Ultra Precision ◽  
The Relationship ◽  
Geometric Surface

In this study, we investigated ultra-precision cutting technology used in the production of Al alloy polygon mirrors. We compared characteristics of three Al alloys (Al–Mg, Al–Cu, and Al–Si) when cut with a straight diamond tool. When cutting Al alloys, it is desirable to reduce geometric surface roughness and remove tear-out marks and scratch marks. We investigated the relationship between end cutting edge length, surface roughness, and cutting force of straight diamond tools. In addition, we compared surface roughness and cutting force produced by double facet tools with microfacets at the end cutting edge and on the rake-face side. It was found that both tools have similar cutting characteristics and that Al–Mg has the best optical quality, followed by Al–Cu and Al–Si.

Design of optical systems for large space telescopes

1995 ◽  
Author(s):  
Yevgeny R. Malamed ◽  
M. N. Sokolsky
Keyword(s):  
Optical Systems ◽  
Space Telescopes ◽  
Large Space

scholarly journals A Nanoscale Photonic Crystal Cavity Optomechanical System for Ultrasensitive Motion Sensing

Crystals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 462
Author(s):  
Ji Xia ◽  
Fuyin Wang ◽  
Chunyan Cao ◽  
Zhengliang Hu ◽  
Heng Yang ◽  
...  
Keyword(s):  
Photonic Crystal ◽  
Optical Cavity ◽  
Optical Quality ◽  
Optical Force ◽  
Mechanical Oscillator ◽  
Maximum Displacement ◽  
Optomechanical System ◽  
High Optical Quality ◽  
Hybrid Platform ◽  
Optomechanical Coupling

Optomechanical nanocavities open a new hybrid platform such that the interaction between an optical cavity and mechanical oscillator can be achieved on a nanophotonic scale. Owing to attractive advantages such as ultrasmall mass, high optical quality, small mode volume and flexible mechanics, a pair of coupled photonic crystal nanobeam (PCN) cavities are utilized in this paper to establish an optomechanical nanosystem, thus enabling strong optomechanical coupling effects. In coupled PCN cavities, one nanobeam with a mass meff~3 pg works as an in-plane movable mechanical oscillator at a fundamental frequency of . The other nanobeam couples light to excite optical fundamental supermodes at and 1554.464 nm with a larger than 4 × 104. Because of the optomechanical backaction arising from an optical force, abundant optomechanical phenomena in the unresolved sideband are observed in the movable nanobeam. Moreover, benefiting from the in-plane movement of the flexible nanobeam, we achieved a maximum displacement of the movable nanobeam as 1468 . These characteristics indicate that this optomechanical nanocavity is capable of ultrasensitive motion measurements.

scholarly journals An Elementary Approximation of Dwell Time Algorithm for Ultra-Precision Computer-Controlled Optical Surfacing

Micromachines ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 471
Author(s):  
Yajun Wang ◽  
Yunfei Zhang ◽  
Renke Kang ◽  
Fang Ji
Keyword(s):  
Dwell Time ◽  
Convergence Rates ◽  
Rotational Symmetry ◽  
Time Algorithm ◽  
Two Dimensions ◽  
Efficient Computation ◽  
Deconvolution Problem ◽  
Ultra Precision ◽  
Computer Controlled Optical Surfacing ◽  
Computer Controlled

The dwell time algorithm is one of the key technologies that determines the accuracy of a workpiece in the field of ultra-precision computer-controlled optical surfacing. Existing algorithms mainly consider meticulous mathematics theory and high convergence rates, making the computation process more uneven, and the flatness cannot be further improved. In this paper, a reasonable elementary approximation algorithm of dwell time is proposed on the basis of the theoretical requirement of a removal function in the subaperture polishing and single-peak rotational symmetry character of its practical distribution. Then, the algorithm is well discussed with theoretical analysis and numerical simulation in cases of one-dimension and two-dimensions. In contrast to conventional dwell time algorithms, this proposed algorithm transforms superposition and coupling features of the deconvolution problem into an elementary approximation issue of function value. Compared with the conventional methods, it has obvious advantages for improving calculation efficiency and flatness, and is of great significance for the efficient computation of large-aperture optical polishing. The flatness of φ150 mm and φ100 mm workpieces have achieved PVr150 = 0.028 λ and PVcr100 = 0.014 λ respectively.

High optical quality GaN nanopillar arrays

2005 ◽  
Vol 86 (7) ◽  
pp. 071917 ◽  
Author(s):  
Y. D. Wang ◽  
S. J. Chua ◽  
S. Tripathy ◽  
M. S. Sander ◽  
P. Chen ◽  
...  
Keyword(s):  
Optical Quality ◽  
High Optical Quality ◽  
Nanopillar Arrays

Recent advances in reaction bonded silicon carbide optics and optical systems

2005 ◽  
Author(s):  
Joseph Robichaud ◽  
Jay Schwartz ◽  
David Landry ◽  
William Glenn ◽  
Brian Rider ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Optical Systems ◽  
Recent Advances

scholarly journals An Investigation of the High-Frequency Ultrasonic Vibration-Assisted Cutting of Steel Optical Moulds

Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 460
Author(s):  
Canbin Zhang ◽  
Chifai Cheung ◽  
Benjamin Bulla ◽  
Chenyang Zhao
Keyword(s):  
Surface Roughness ◽  
Ultrasonic Vibration ◽  
High Frequency ◽  
Optical Glass ◽  
Contact Point ◽  
Cutting Speed ◽  
Optical Quality ◽  
Machining Parameters ◽  
Nose Radius ◽  
Cutting Geometry

Ultrasonic vibration-assisted cutting (UVAC) has been regarded as a promising technology to machine difficult-to-machine materials such as tungsten carbide, optical glass, and hardened steel in order to achieve superfinished surfaces. To increase vibration stability to achieve optical surface quality of a workpiece, a high-frequency ultrasonic vibration-assisted cutting system with a vibration frequency of about 104 kHz is used to machine spherical optical steel moulds. A series of experiments are conducted to investigate the effect of machining parameters on the surface roughness of the workpiece including nominal cutting speed, feed rate, tool nose radius, vibration amplitude, and cutting geometry. This research takes into account the effects of the constantly changing contact point on the tool edge with the workpiece induced by the cutting geometry when machining a spherical steel mould. The surface morphology and surface roughness at different regions on the machined mould, with slope degrees (SDs) of 0°, 5°, 10°, and 15°, were measured and analysed. The experimental results show that the arithmetic roughness Sa of the workpiece increases gradually with increasing slope degree. By using optimised cutting parameters, a constant surface roughness Sa of 3 nm to 4 nm at different slope degrees was achieved by the applied high-frequency UVAC technique. This study provides guidance for ultra-precision machining of steel moulds with great variation in slope degree in the pursuit of optical quality on the whole surface.

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