Design and performance evaluation of sensors and actuators for advanced optical systems

Abstract

Current state-of-the-art commercial sensors and actuators do not meet many of NASA's next generation spacecraft and instrument needs. Nor do they satisfy the DoD needs for satellite missions, especially micro/nano satellite missions. In an effort to develop advanced optical devices and instruments that meet mission requirements, NASA Langley recently completed construction of a new cleanroom housing equipment capable of fabricating high performance active optic and adaptive optic technologies including deformable mirrors, reconfigurable lenses (both refractive and diffractive), spectrometers, spectro-polarimeters, tunable filters and many other active optic devices. In addition to performance, these advanced optic technologies offer advantages in speed, size, weight, power consumption, and radiation tolerance. The active optic devices described in this paper rely on birefringent liquid crystal materials to alter either the phase or the polarization of the incoming light. Design considerations and performance evaluation results for various NASA applications are presented. Applications presented will include large space telescopes, optical communications, spacecraft windows, coronagraphs, and star trackers.

Intelligent Optical Systems Using Adaptive Optics

“…A sequence of phase maps for each pixel at each gray level was acquired. The non-uniformity was less than 1/10 of a wavelength (lambda); hence, a simple polynomial interpolation of the phase, Y, can be used to represent the pixel controller plant model: Y = p1*x^4 + p2*x^3+p3*x^2+p4*x+p5 (1) For our LCOS device p 1 = -82.521; p 2 = 425.35; p 3 = -484.04; p 4 = -49.964 and p 5 =213. Any requirement for increased wavefront accuracy is beyond the capability of commercial interferometers and new more sophisticated wavefront sensors would need to be developed.…”

“…Liquid crystals arise under certain conditions in organic (hydrocarbon) chemicals so that the molecules are sharply anisotropic, that is, they have highly elongated (rod-like) molecules or flattened (disc-like) molecules. A direct consequence of the ordering of the anisotropic molecules is the anisotropy of the mechanical, electric, magnetic, and optical properties [1][2][3][4][5] .…”

Polarization compensation of Fresnel aberrations in telescopes

“…Each one of these will have degraded performance because of Fresnel polarization apodization. This paper addresses the modeling, and mitigation of Fresnel polarization effects in space-based coronagraphic telescopes using an innovative device that incorporates birefringent nanolayers 6 to control the amplitude and phase of polychromatic white light wavefronts. The SVRP device provides control of the broadband white-light optical polarization and retardation to maximize coronagraph system transmittance, contrast, and to minimize losses to scattered light.…”

Adaptive liquid-crystal phase-only passive devices

“…Tunable filter based on both Solc and Lyot can simultaneously accommodate an extremely narrow bandwidth and a wide field of view. The NASA Langley Research Center has developed large aperture Solc prisms with LC filled cavity [48].…”