Step-scan method to enlarge the field of view of focal plane array cameras by continuously rotating optical elements

Abstract

In many applications of camera systems such as for surveillance a combination of a large field-of-view (FOV) with a high spatial resolution is desirable. Classical focal plane array (FPA) cameras can only fulfill this requirements with a very large number of pixels. We present a novel method 1 to enlarge the FOV of a camera equipped with an FPA keeping the spatial resolution of the system untouched. Four images taken at different directions of the line of sight (LOS) are stitched together to a large image resulting in a significantly enlarged FOV in both directions. For this purpose two continuously rotating scan elements are placed in front of the optics which move the LOS with a highly non-uniform scan velocity. Image exposure is triggered when the scan velocity is almost zero. The influence of the residual LOSmovement to the image blur is controllable by various parameters of the system. We present the results of the simulation for an enlarged FOV with 584 x 488 pixels obtained with a scanned infrared FPA of 384 x 288 pixels working in the 3-5µm regime. The resulting system modulation transfer function (MTF) is calculated and the correlation of system performance parameters with the design parameters of the scanner is discussed.