Abstract
This paper addresses computer numerical control (CNC) polishing of aspheric or freeform optics. Prior CNC grinding of the asphere tends to produce mid-spatial frequencies (MSFs) at some level. Precessions polishing can rectify these, but the very ability of the bonnet tooling to adapt to the local asphere enables it to do so, at least in part, to similar spatial frequencies in the MSFs. To accelerate smoothing, hard tools can, in principle, be used, but aspheric misfit is often assumed to preclude this. In this paper, we explore new insight into the role of abrasive particle size in accommodating misfit. First, we report on a glass-bending rig to produce a continuous range of complex surfaces, while withstanding process forces. Then, we describe how this was used to evaluate the triangle of misfit, abrasive size, and MSFs produced for hard rotating tools. This has revealed a regime in which such tools can be used without introducing significant new MSFs, as evidenced by manufacture of prototype off-axis aspheric segments for the European Extremely Large Telescope project.
| Language | English |
|---|---|
| Pages | 9925-9931 |
| Number of pages | 7 |
| Journal | Applied Optics |
| Volume | 56 |
| Issue number | 36 |
| DOIs | |
| Publication status | Published - 13 Dec 2017 |
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Insight into aspheric misfit with hard tools : Mapping the island of low mid-spatial frequencies. / Walker, David; Hsing-Yu, Wu; Yu, Guoyu; Li, Hongyu; Zhang, Wang; Lu, Chunlian.
In: Applied Optics, Vol. 56, No. 36, 13.12.2017, p. 9925-9931.Research output: Contribution to journal › Article
TY - JOUR
T1 - Insight into aspheric misfit with hard tools
T2 - Applied Optics
AU - Walker, David
AU - Hsing-Yu, Wu
AU - Yu, Guoyu
AU - Li, Hongyu
AU - Zhang, Wang
AU - Lu, Chunlian
PY - 2017/12/13
Y1 - 2017/12/13
N2 - This paper addresses computer numerical control (CNC) polishing of aspheric or freeform optics. Prior CNC grinding of the asphere tends to produce mid-spatial frequencies (MSFs) at some level. Precessions polishing can rectify these, but the very ability of the bonnet tooling to adapt to the local asphere enables it to do so, at least in part, to similar spatial frequencies in the MSFs. To accelerate smoothing, hard tools can, in principle, be used, but aspheric misfit is often assumed to preclude this. In this paper, we explore new insight into the role of abrasive particle size in accommodating misfit. First, we report on a glass-bending rig to produce a continuous range of complex surfaces, while withstanding process forces. Then, we describe how this was used to evaluate the triangle of misfit, abrasive size, and MSFs produced for hard rotating tools. This has revealed a regime in which such tools can be used without introducing significant new MSFs, as evidenced by manufacture of prototype off-axis aspheric segments for the European Extremely Large Telescope project.
AB - This paper addresses computer numerical control (CNC) polishing of aspheric or freeform optics. Prior CNC grinding of the asphere tends to produce mid-spatial frequencies (MSFs) at some level. Precessions polishing can rectify these, but the very ability of the bonnet tooling to adapt to the local asphere enables it to do so, at least in part, to similar spatial frequencies in the MSFs. To accelerate smoothing, hard tools can, in principle, be used, but aspheric misfit is often assumed to preclude this. In this paper, we explore new insight into the role of abrasive particle size in accommodating misfit. First, we report on a glass-bending rig to produce a continuous range of complex surfaces, while withstanding process forces. Then, we describe how this was used to evaluate the triangle of misfit, abrasive size, and MSFs produced for hard rotating tools. This has revealed a regime in which such tools can be used without introducing significant new MSFs, as evidenced by manufacture of prototype off-axis aspheric segments for the European Extremely Large Telescope project.
UR - http://www.scopus.com/inward/record.url?scp=85038392540&partnerID=8YFLogxK
U2 - 10.1364/AO.56.009925
DO - 10.1364/AO.56.009925
M3 - Article
VL - 56
SP - 9925
EP - 9931
JO - Applied Optics
JF - Applied Optics
SN - 1559-128X
IS - 36
ER -