High-precision Photogrammetric Surface Figure Measurements under Cryogenic Environment
Abstract
Limited by the working temperature of the measurement equipments, most of the high-precision surface figure measurement techniques cannot be applied under a cryogenic environment. This paper reports the first attempt to measure the surface figure of a high-precision terahertz reflector panel under low temperatures based on photogrammetry. The measurement employs a high resolution industrial camera sitting on an automatic experimental platform which enables photos been taken in an automatic fashion inside a climate chamber. A repeatable accuracy of 2.1 μm rms is achieved under the cryogenic environment. Furthermore, surface figure measured by a three-coordinate measuring machine under room temperature is used to calibrate the thickness variation of the paper targets. By this technique, the surface figure of an aluminum prototype panel of the 5 meter Dome A Terahertz Telescope (DATE5) is measured from room temperature down to -55°C.
- Publication:
-
Acta Astronomica Sinica
- Pub Date:
- January 2016
- Bibcode:
- 2016AcASn..57..115L
- Keywords:
-
- THz telescopes;
- techniques: surface figure measurements;
- photogrammetry;
- panels;
- cryogenic environment