Abstract
Polyimide diffractive membrane lens can be used in space optical telescope to reduce the size and mass of an imaging system. However, traditional commercial aromatic polyimide membrane is hard to meet the challenging requirements of dimensional stability and optical homogeneity for optical use. Based on molecular structure design and the optimization of fabrication process, the prepared copolyamide-imide membrane achieved the desired performance of membrane as an optical material. It showed a very low coefficient of thermal expansion (CTE), which is 0.95 ppm/°C over a temperature range of −150–100 °C and relatively low coefficient of moisture expansion (CME), which is only 13.30 ppm/% RH (0~90% RH). For the optical use, the prepared copolyamide-imide membrane (φ200 mm) achieved good thickness uniformity with wave-front error smaller than λ/30 (λ = 632 nm) in RMS (root mean square). Besides, it simultaneously meets the optical, thermal, and mechanical requirements for space telescope use. Copolyamide-imide membranes in this research with good comprehensive performance can be used as large aperture membrane optical system architectures.
Highlights
Aromatic polyimides are a kind of high performance polymer with excellent mechanical properties, thermal stability, high UV/gamma radiation resistance, and chemical resistance [1,2,3]
In MOIRE (Membrane Optical Imager Real-time Exploitation) program, patterned polyimide membrane has been used as transmissive diffractive membrane optic for space telescopes
In Falcon SAT-7 system, patterned polyimide membrane has been developed as a solar telescope
Summary
Aromatic polyimides are a kind of high performance polymer with excellent mechanical properties, thermal stability, high UV/gamma radiation resistance, and chemical resistance [1,2,3]. In the aspect of optical system design, the optical path length error of diffraction membrane optics is virtually eliminated when light passes through the membrane, so the sensitivity to surface deformation is remarkably lowered compared with the reflective optical system, which is usually built by conventional quartz lens It is difficult for traditional commercial aromatic polyimide (PI) membrane to be used as a transmissive diffractive optical lens. They are hard to simultaneously meet the challenging requirements of high dimensional stability, good optical transmission, excellent mechanical property, and high temperature resistance. Compared with traditional aromatic polyimide, the designed copolyamide-imide (co-PAI) is a good candidate for potential space optical applications
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