title: Digital focusing of OCT images based on scalar diffraction theory and information entropy.
abstract: This paper describes a digital method that is capable of automatically focusing optical coherence tomography (OCT) en face images without prior knowledge of the point spread function of the imaging system. The method utilizes a scalar diffraction model to simulate wave propagation from out-of-focus scatter to the focal plane, from which the propagation distance between the out-of-focus plane and the focal plane is determined automatically via an image-definition-evaluation criterion based on information entropy theory. By use of the proposed approach, we demonstrate that the lateral resolution close to that at the focal plane can be recovered from the imaging planes outside the depth of field region with minimal loss of resolution. Fresh onion tissues and mouse fat tissues are used in the experiments to show the performance of the proposed method.
authors.affiliation: Department of Bioengineering, University of Washington, 3720 15th Avenue Northeast, Seattle, Washington 98195,  USA ; Department of Photo-electronic Information and Communication Engineering, Beijing Information Science and Technology University, Beijing 100192,  China.
authors.forename: Guozhong
authors.initials: G
authors.lastname: Liu
authors.forename: Zhongwei
authors.initials: Z
authors.lastname: Zhi
authors.forename: Ruikang K
authors.initials: RK
authors.lastname: Wang