Comparative study on thermal image enhancement of transmission line joints using different histogram transformation methods

The thermal images directly obtained from infrared imaging system are usually blurred and contrast is low because of several external factors. So image enhancement is important in fault diagnosis. External factors affecting detection accuracy are summarized. The basic features of thermal images of transmission line joints are analyzed. The thermal images are enhanced using histogram modification based on the square root transformation function and global histogram equalization. In analyzing the merits of the two methods mentioned, a local area histogram equalization algorithm based on linear smoothing filter is presented. Finally, results show that it is a more efficient method for enhancing thermal images of transmission line joints.