Color astrophotography with a 100 mm-diameter f/2 polymer flat lens

Abstract

We demonstrate a 100 mm-diameter, 2.4 μm-thick multilevel diffractive lens (MDL) with a 200 mm focal length, optimized for the 400 to 800 nm wavelength range—specifications that are difficult to achieve even with complex multi-element refractive systems. Created using an inverse-design approach and grayscale lithography, the MDL achieves achromatic focusing, confirmed through hyperspectral point-spread function (PSF) characterization. Imaging experiments resolved spatial frequencies up to 181 lp/mm and demonstrated the MDL's capability in capturing high-quality, full-color images of the moon, sun, and distant terrestrial scenes. Color-enhanced lunar images revealed key geological features, while solar imaging identified visible sunspots. Additionally, the MDL was integrated with a refractive achromatic lens to form a hybrid telescope, significantly reducing weight for airborne and space-based imaging applications. Simulations and experimental results reported here underscore the potential of large-area achromatic flat lenses as lightweight alternatives to conventional refractive systems for astrophotography and other long-range imaging tasks.