An improved nonuniformity correction algorithm for IRFPA
To improve nonuniformity correction real-time performance of infrared focal plane arrays (IRFPA), a novel compression nonuniformity correction algorithm is proposed. In this paper the basic principle of the proposed algorithm are expounded, and its real-time performance is tested by hardware. Experimental results show that the proposed algorithm has the less calculation and the higher speed than traditional nonuniformity correction algorithm based on blackbody, and this helps to realization of real-time nonuniformity correction of IRFPA.
Two-point nonuniformity correction based on LMS
In real-time system, the Infrared Focal Plane Array (IRFPA) should be compensated in traditional method of two-point temperature non-uniformity correction (NUC) before system was used every time, which make the system complex. Based on discussion of traditional two-point temperature NUC algorithm, Two-point temperature NUC based on least mean square (LMS) algorithm was proposed in the paper. In the view of the LMS algorithm theory, the correction gain and offset coefficients were iterated one by one during image processing, so that the expected correction result were obtained in little time. At the same time, the correction and coefficients iteration processes were completed in FPGA and DSP respectively, and make the arithmetic structure simple. The simplified structure, low cost and out-door suitable operation-systems are the merits of the system.
Nonuniformity compensation for IR focal plane array sensors
Recent reports indicate that cooled and uncooled IR focal plane array sensors are progressing to a field-worthy level for commercial and defense applications. They offer higher sensitivity, amenability to signal processing and mechanical simplicity. However these sensors contain large detector-to- detector dark current (offset) and responsivity (gain) variations. These variations result in a severe problem called fixed pattern noise that can mask/distort the image obtained from the sensor. The correction process is generally termed as nonuniformity compensation. Conventional two-point compensation techniques are accurate enough, but require built-in controllable temperature references along with mechanical and electro-optical shutters. Therefore this compensation technique detracts the mechanical simplicity of using IR focal plane arrays. Scene-based nonuniformity techniques dispenses with the requirement of temperature references and shutters, but are not accurate enough for certain applications. This paper discusses two-point and scene-based nonuniformity compensation algorithms and proposes an empirical formula to automatically calculate the scene constants, which is an essential step towards practical applications. This paper reports the analyzed results of testing the algorithms on a number of IR images. A practical problem of 'artifacts' which arise when using scene-based nonuniformity compensation is also discussed. A common hardware scheme to implement both the algorithms is also presented in this paper.