Algorithms and Hardware Implementation of Real Time Automatic Gain Control Feature for Thermal Imager

Thermal imagers operating in the 3-5 micron and 8-12 micron spectral bands require Automatic Gain Control (AGC) to enhance the visual detection and identification of targets against varying atmospheric conditions. In this paper, two algorithms viz., plateau equalization and adaptive plateau equalization algorithms are discussed for implementing AGC. The MATLAB simulation results show the effectiveness of these algorithms in controlling the levels of contrast. The plateau parameter selected for a scene renders targets easily recognizable and also provides contextual information about the surrounding regions. Results of the AGC algorithms on the IR images obtained by the 3-5 micron hand held thermal imager are discussed. The simulation results calls for hardware implementation using Xilinx SPARTAN-II FPGAs. The uniqueness of this paper lies in two features: one is the improvement suggested on the adaptive plateau equalization algorithm and the other is the hardware implementation approach.