Yen-Wei CHEN, Zensho NAKAO and Kouichi ARAKAKI

Department of Electrical and Electronic Engineering, Faculty of Engineering, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa, 903-01 Japan

(Received October 7, 1996; Accepted November 14, 1996)

Penumbral imaging is a technique for imaging of neutrons or other penetrating radiations. The technique uses the fact that spatial information can be recovered from the shadow or penumbra that an unknown source casts of a simple large circular aperture. The limitation is that the straightforward image reconstruction will introduce some significant distortion for a large field of view because of non-isoplanaticity of the aperture point spread function. In this paper, a genetic algorithm (GA) is proposed for reconstruction of penumbral images and the technique allows distortion-free reconstruction over a large field of view. Furthermore, because in GA the complicated a priori constraints can be easily incorporated by appropriate modification of the cost function, the algorithm is also very tolerant of the noise.

Key words : penumbral imaging, point spread function, non-isoplanatic (space-variant), genetic algorithm, constraint