Development of an off-axis TMA telescope for coastal water remote sensing

• Published in: International journal of precision engineering and manufacturing Vol. 17; no. 5; pp. 685 - 689
• Main Authors: Jeon, Min-Woo, Hyun, Sang-Won, Bae, Ji-Yong, Jeong, Byeong-Joon, Oh, Eun-Song, Kang, Hyuk-Mo, Park, Young-Je, Park, Chan-Pil, Kim, Geon-Hee
• Format: Journal Article
• Language: English
• Published: Seoul Korean Society for Precision Engineering 01.05.2016
• Subjects: Engineering; Industrial and Production Engineering; Materials Science; Short Communication; TMA telescope; Off-axis optics; Ultra-precision machining; Remote sensing
• ISSN: 2234-7593; 2005-4602
• DOI: 10.1007/s12541-016-0084-y

A proto-model of an off-axis reflective fore-optics in a new hyperspectral sensor onboard a small unmanned aerial vehicle (UAV) is developed for low-altitude coastal remote sensing. In spite of the substantial advantages of off-axis optics over refractive or on-axis reflective optics, it is difficult to fabricate and align the mirrors in off-axis systems because of their asymmetric configurations. The fore-optics is designed by Korea Institute of Ocean Science & Technology (KIOST) as a three-mirror system including aspheric primary and secondary mirrors, with an entrance pupil diameter of 70 mm and F-ratio of 5.0. The off-axis mirror is fabricated by a single point diamond turning machine (SPDTM) with a form accuracy of 89.3 nm (RMS) and surface roughness of 7.2 nm (Ra). Coarse alignment of this three-mirror off-axis optical system is accomplished by using a designated base plate and a coordinate measuring machine. The optical performance is tested using the point spread function of the returned collimated beam of a Fizeau interferometer.