25 September 2013 Freeform mirror polishing for compensation on non-symmetry system aberrations of remote sensing instrument
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Cassegrain optical systems are widely used in remote sensing instrument. Cassegrain telescope is composed of a primary mirror (M1), a secondary mirror (M2), and a set of correction lenses. The system aberrations of telescope could be corrected and balanced by M1 and M2. In the event of deformation of telescope assembly, the non-symmetry aberrations will be induced to the optical system and reduce the optical performance. The non-symmetry aberrations can be measured after completing M1 and M2 assembly and alignment processes. Compensating this identified error to M1 or M2 can improve the optical performance of the telescope system. The error compensation on M2 is more efficient due to its smaller aperture and quickly assembly and de-assembly processes. In this study, we map the system wavefront error caused by deformation of mirror supporting and gravity onto the designed aspheric surface of M2. The surface of M2 becomes a freeform from aspheric. The polishing process combines the techniques of conventional lapping and CNC polishing. We apply the conventional spherical lapping process to quick remove the sub-surface damage (SSD) layer and to get the accurate radius of best fit sphere of the designed aspheric surface with fine surface texture simultaneously. The polishing and metrology processes were performed by using Zeeko IRP1000 polisher and QED ASI. A Φ 150 mm mirror with freeform surface was completed.
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Ching-Hsiang Kuo, Ching-Hsiang Kuo, Zong-Ru Yu, Zong-Ru Yu, Cheng-Fang Ho, Cheng-Fang Ho, Wei-Yao Hsu, Wei-Yao Hsu, Fong-Zhi Chen, Fong-Zhi Chen, "Freeform mirror polishing for compensation on non-symmetry system aberrations of remote sensing instrument", Proc. SPIE 8841, Current Developments in Lens Design and Optical Engineering XIV, 88410Z (25 September 2013); doi: 10.1117/12.2023124; https://doi.org/10.1117/12.2023124


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