An auto-focusing algorithm for accurate axial location of particle

摘要

Resolution of particle axial position is lower and uncertainty due to the impact of zero-order image, twin image and depth of focus,which is tens of times more than particle diameter in digital in-line Fresnel holography system. An auto-focusing algorithm based on the most gradient for accurate location of particle was proposed. Because the real gradient direction for the edge of particle may not be the appointed direction, hence the gradients in all possible directions is calculated and chosen the largest gradient as the result. At the same time, in order to improve the precision and stability of auto-focusing algorithm, another threshold parameter is introduced. Through experiments, we find out that the algorithm has the characteristics such as strong single peak feature and good stability.