Transmissive diffractive membrane optic can be used in space optical telescope to reduce the size and mass of imaging system. Based on the international research results about transmissive diffractive membrane, a 4-level diffractive substrate with 100mm apertures was designed and transmissive diffractive membrane was fabricated by spin coating. High-precision support structure for diffractive membrane with surface precision 0.12λ RMS (λ=632.8nm) was introduced, and that can meet the diffractive imaging requirements. Diffraction efficiency of the diffractive membrane supported by support structure was tested, and the test results showed that diffraction efficiency was >50%. The step figure test results illustrated the etched deep precision was less the 10nm. The imaging wavefront test result demonstrated a wavefront error of about 38 nm RMS. The transmissive diffractive membrane optic can be very useful for large aperture imaging system to realize low mass and low cost.
Asteroid detection is of great significance for studying the origin and evolution of the solar system, collision warning, space resource development, etc. through the networking of micro-satellite constellation, large-scale and high-frequency observations of asteroids can be achieved. Aiming at the above requirements, through the collaborative optimization of imaging chains, this paper develops a 5kg high-performance visible camera for weak space target detection, which has the detection ability better than 13 Mv, which is equivalent to detecting a target with a diameter of 10cm at a distance of 1000km, and can be carried on a 10kg micro-satellite. Through the networking of micro-satellites, give play to the advantages of cluster detection, realize the high-sensitivity and high-frequency detection of asteroids, and provide high real-time data support for asteroid research and early warning.
ABSTRACT:Diffractive optical imaging technology provides a new way to realize high resolution earth observation on geostationary orbit. There are a lot of benefits to use the membrane-based diffractive optical element in ultra-large aperture optical imaging system, including loose tolerance, light weight, easy folding and unfolding, which make it easy to realize high resolution earth observation on geostationary orbit. The implementation of this technology also faces some challenges, including the configuration of the diffractive primary lens, the development of high diffraction efficiency membrane-based diffractive optical elements, and the correction of the chromatic aberration of the diffractive optical elements. Aiming at the configuration of the diffractive primary lens, the "6+1" petaltype unfold scheme is proposed, which consider the compression ratio, the blocking rate and the development complexity. For high diffraction efficiency membrane-based diffractive optical element, a self-collimating method is proposed. The diffraction efficiency is more than 90% of the theoretical value. For the chromatic aberration correction problem, an optimization method based on schupmann is proposed to make the imaging spectral bandwidth in visible light band reach 100nm. The above conclusions have reference significance for the development of ultra-large aperture diffractive optical imaging system.
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