On-line nonuniformity and temperature compensation of uncooled IRFPAs using embedded digital hardware

摘要

We present a model and a signal-processing algorithm for compensating the nonuniformity (NU) noise and surrounding temperature self-heating e ects on the response of uncooled microbolometer-based infrared cameras. The model for the NU noise considers pixelwise gain and o set parameters. The representation for the self-heating dynamics of the camera is an autoregressive moving average (ARMA) model for camera's internal temperature. The algorithm performs initially a two-point calibration at a known surrounding temperature. Next, without modifying the NU parameters, we dynamically compensate variations in the camera readout using both estimates of the ARMA model and measurements of the surrounding temperature taken by a simple sensor embedded in the camera. Tested on a CEDIP Jade UC33 camera, our system compensates reference black-body images at 30 degrees Celsius, with a peak error below 1.3 and a mean error below 0.3 degrees Celsius, in scenarios where the room temperature varied up to 14 degrees Celsius. Moreover, the regularity and simplicity of the algorithm enables us to implement it on embedded digital hardware, thereby reducing its cost, size, and power consumption. We implemented the algorithm on a Xilinx XC6SLX45 FPGA using fixed-point arithmetic. The circuit exhibits an arithmetic error of 0.06 degrees compared to a software double-precision implementation. It compensates 320×240-pixel video at up to 1,437 fps and 640×480-pixel video at up to 360 fps, using 1% of the logic resources of the FPGA, and less than 1 mW of dynamic power at 110 MHz. Adding Gigabit Ethernet communication, HDMI display, and a pseudocolor map on the chip uses 10% of the resources and consumes 915 mW.