Aperture size imposes, by way of diffraction, a fundamental limit on the spatial resolution that can be attained with an imaging system that operates at a given distance from a target. It is therefore natural to seek to improve image resolution by increasing the size of the collection aperture of a remote sensing system. On the other hand, as aperture size increases it becomes technically more difficult, and financially much more expensive, to maintain a figure quality that holds geometrical aberrations to a level that is negligible compared to diffraction effects. This paper presents an analysis of an approach that combines active optics with what has been called a post-detection phase diversity technique [R. A. Gonsalves, "Phase retrieval and diversity in adaptive optics," Opt. Eng. 21, 829-832 (1982)]. The basic concept is to allow for variable focus as an inherent system capability, in order to acquire multiple defocused images, each one of which has slightly different, and complementary, spatial frequency content. The proper deconvolution and merging of these images produces a composite image that is superior to the image that can be acquired at any single focal setting. This paper presents the theoretical basis of this approach, and numerical simulations that include the effects of noise and various levels of third order spherical aberration.

Date Published: 6 November 2003
PDF: 9 pages
Proc. SPIE 5174, Novel Optical Systems Design and Optimization VI, (6 November 2003); doi: 10.1117/12.509524

Published in SPIE Proceedings Vol. 5174:
Novel Optical Systems Design and Optimization VI
Jose M. Sasian; R. John Koshel; Paul K. Manhart, Editor(s)