A Bayes-spectral-entropy-based measure of camera focus using a discrete cosine transform

作者：Kristan Matej^*; Pers Janez; Perse Matej; Kovacic Stanislav

来源：Pattern Recognition Letters, 2006, 27(13): 1431-1439.

DOI：10.1016/j.patrec.2006.01.016

• camera focusing
• spectral methods
• DCT
• Bayes entropy

In this paper we present a novel measure of camera focus based on the Bayes spectral entropy of an image spectrum. In order to estimate the degree of focus, the image is divided into non-overlapping sub-images of 8 x 8 pixels. Next, sharpness values are calculated separately for each sub-image and their mean is taken as a measure of the overall focus. The sub-image spectra are obtained by an 8 x 8 discrete cosine transform (DCT). Comparisons were made against four well-known measures that were chosen as reference, on images captured with a standard visible-light camera and a thermal camera. The proposed measure outperformed the reference measures by exhibiting a wider working range and a smaller failure rate. To assess its robustness to noise, additional tests were conducted with noisy images.

• 出版日期2006-10-1