The design of a lens for long-range oblique aerial reconnaissance demonstrates how lightweight reflective optics are effective in producing an optical system which can detect, recognize, and identify distant ground objects from an airborne platform. The lens herein described transforms an object space filled with low-contrast targets of small angular subtense to an image space having the spatial and optical characteristics best suited to an electro-optical detector designed for this application. The lens incorporates two key reflective elements: a lightweight primary mirror which provides all the optical power of the lens, and a scan mirror of cellular construction which directs light into the lens. Although the nominal design is diffraction limited, the scan mirror deflections caused by gravity induce notable wavefront errors. Finite element techniques were used to predict the deflections. The deflections were then used to predict lens performance. The lens has been built and tested, and test results agree with predictions. The lens/detector-system combination allows intelligence gathering from an airborne platform at standoff ranges up to 150 nmi.

Date Published: 11 October 1989
PDF: 10 pages
Proc. SPIE 1113, Reflective Optics II, (11 October 1989); doi: 10.1117/12.955579

Published in SPIE Proceedings Vol. 1113:
Reflective Optics II
Dietrich G. Korsch, Editor(s)