Effects Of Rectification On Image Correlation
Stephen M. Jaffey, Mitchell W. Millman · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1980
Many situations arise in which it is desired to combine several undersampled images of a scene to provide improved resolution or signal to noise ratio. For example, one technique to reduce the bandwidth of a real time tactical air vehicle video link to overcome jamming is to subsample each frame. Since there is generally a substantial frame to frame overlap, the received data could potentially be combined to approximate the original resolution if the pixels are adequately aligned. Prior workl showed the alignment accuracy requirement to be approximately 0.15 pixels, so that the received undersampled (aliased) frames would have to be rectified and correlated to this precision. Changes in perspective in the sequence of frames can prevent such precise alignment for two reasons. (1) Resampling, during rectification, and changes in ground resolution between images both degrade correlation accuracy. (2) Small correlation windows are required to minimize the effect of scene relief; thus, reducing potential averaging out of (1) by numerous pixels. This paper reports on experiments done to deter-mine over what range of perspective changes, small windows from video frames can be aligned well enough to permit resolution improvement. The results show that the goal of .15 pixel registration precision is achievable for images down to 8 x 8 pixels in size for scale changes between images of up to 30%.