Freeform Wide Field-of-View Spaceborne Imaging Telescope: From Design to Demonstrator.

Wide field-of-view imaging optics offer a huge potential for space-based Earth observation enabling the capture of global data. Reflective imaging telescopes are often favored, as they do not show chromatic aberrations and are less susceptible to radiation darkening than their refractive counterparts. However, the main drawback of reflective telescopes is that they are limited with respect to field-of-view while featuring large dimensions. We propose the use of freeform optics to maximize the field of view while maintaining diffraction-limited image quality and minimizing system dimensions. In this paper, we present a novel freeform wide field-of-view reflective telescope, starting from the optical design, and continuing to tolerancing analysis and manufacture, towards a proof-of-concept demonstrator. The novel telescope features a full field-of-view of 120° while showing an exceptional spatial resolution of 2.6 km and fitting within 1 CubeSat unit. To the best of our knowledge, this is the widest field-of-view that has ever been realized for a space-based telescope, nearly reaching Earth observation from limb to limb from an altitude of about 700 km. We hope this design paves the way for future space missions enabling improved Earth observation and leading to enhanced monitoring of climate and climate change.

Miniature freeform flow-line lightguide for sensing: from design to fabrication.

We present the development of a compact (about 1.3 × 2.0 × 20 mm3) freeform optical lightguide for sensing applications, from the conceptual design to the fabrication through injection molding. The design of the optic is based on the flow-line method from Nonimaging Optics, which allows the desired optical functionalities (45° half-acceptance and 40° beam steering) while meeting particularly tight mechanical and geometrical constraints. An extensive analysis of the effects of fabrication parameters on the performances demonstrates the importance of minimizing the fillet radius. This requisite inspired a special procedure for designing the mold, which is built as a "3D puzzle" assembly of separate pieces, each one dedicated to one specific side surface of the lightguide. This technique enables uniform optical quality on all the optic's surfaces and removes the need of a fillet radius in the mold. At present, the first lightguide prototypes have been fabricated; after the coating phase, they will be ready for the validation stage.