Noise insensitive focus value operator for digital imaging systems

Most auto-focusing algorhythms based on focus values which are calculated with high frequency image components are very sensitive to noise factor. The noise under low illumaination conditions generally degrades the auto-focusing performance. In this paper, we propose an operator to determine the noise insensitive focus value for digital imaging systems. The proposed algorhithm uses spatially adapted weights based on the local statistics of the image and the noise factors. Experiments conducted with and without noise factors demonstrate the high performance of the proposed method.