Digital image processing in high resolution infrared camera with use ofprogrammable logic device

摘要

In article a digital system for high resolution infrared camera control and image processing is described. The camera is built with use of bolometric focal plane array of size 640 by 480 detectors. Single detector in array has size of 25 gm and can detect incident radiation from the spectral range of 8+12 gm thanks to the special filter installed in specially designed entrance window. The most important tasks of infrared image processing system are array readout and correction of detectors offset and responsivity variations. The next tasks of the system are conversion of analog voltage signals from microbolometers in array to digital form and then composition of a thermal image. Microbolometer array needs to be controlled via several signals. The signal generator for readout circuit is capable of changing various timing parameters like frame rate or integration time of the detector array. The changes in these parameters can be done via special set of memory mapped registers. The infrared data received from detector array is transferred via data bus to modules performing image processing, for example techniques for image enhancement. Image processing algorithms necessary for infrared image generation are nonuniformity correction, bad pixel replacement and radiometric calibration. Optionally an additional image processing techniques can be performed like edge enhancement, dynamic range compression or object identification. The elaborated architecture of the system allowed easy change of parameters of the system and to adopt many new algorithms without significant hardware changes. Scientific work funded from science fund for years 2009-2011 as a development project.