Hemispherical infrared focal plane arrays: a new design parameter for the instruments

摘要

In ground based astronomy, mainly all designs of sky survey telescopes are limited by the requirementthat the detecting surface is flat whereas the focal surface is curved. Two kinds of solution have beeninvestigated up to now. The first one consists in adding optical systems to flatten the image surface; however thissolution complicates the design and increases the system size. Somehow, this solution increases, in the sametime, the weight and price of the instrument. The second solution consists in curving artificially the focal surfaceby using a mosaic of several detectors, which are positioned in a spherical shape. However, this attempt isdedicated to low curvature and is limited by the technical difficulty to control the detectors alignment and tiltbetween each others.Today we would like to propose an ideal solution which is to curve the focal plane array in a spherical shape,thanks to our monolithic process developed at CEA-LETI based on thinned silicon substrates which allows a100% optical fill factor. Two infrared uncooled cameras have been performed, using 320 x 256 pixels and 25 μmpitch micro-bolometer arrays curved at a bending radius of 80 mm. These two micro-cameras illustrate theoptical system simplification and miniaturization involved by curved focal plane arrays.Moreover, the advantages of curved detectors on the optical performances (Point Spreading Function), as well ason volume and cost savings have been highlighted by the simulation of the opto-mechanical architecture of thespectrometer OptiMOS-EVE for the European Extremely Large Telescope (E-ELT).© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.