Digital enhancement of night vision and thermal images
C. K. Teo · Defense Technical Information Center (DTIC) · 2003
Low image contrast limits the amount of information conveyed to the user With the proliferation of digital imagery and computer interface between man-and-machine, it is now viable to consider digitally enhancing the image before presenting it to the user, thus increasing the information throughput. This thesis explores the effect of the Contrast Limited Adaptive Histogram Equalization (CLAHE) process on night vision and thermal images With better contrast, target detection and discrimination can be improved. The contrast enhancement by CLAHE is visually significant and details are easier to detect with the higher image contrast. Analyzing the image frequency response reveals increases in the higher spatial frequencies. As higher frequencies correspond to image edges, the power increase is viewed as corresponding to edge enhancement and hence, an increase in visible image details. This edge enhancement is perceived as improvement in image quality. This is further substantiated by a subjective testing, where a majority of human subjects agreed that CLAHE-enhanced images are more informative than the original night vision images.