Abstract: There is provided a time variant defect correcting method in an infrared thermal imaging system. Digital video signals representing a frame are received and it is determined whether a first pixel from the frame is likely to be a defect. If the first pixel is likely to be a defect, the number of defect determinations for the first pixel is counted and the count value is compared with a threshold count. If the count value is equal to or less than the threshold count, digital video signals representing a next frame are received and it is determined whether the first pixel in the next frame is likely to be a defect. If the count value exceeds the threshold count, the first pixel is registered as a defect and corrected.