Focused image creation approaches for macroscopic objects encoded in digital holograms

Abstract

When a digital hologram is reconstructed only points on objects within the depth of focus at the reconstruction distance are in focus. For complex scenes, scenes containing multiple objects or multiple object features located at different depths, this can lead to a reconstruction with large blurred regions. Using a depth-from-focus algorithm we have developed an approach to extract an objects depth information in the form of a depth map from volumes of reconstructions, where each reconstruction in the volume is a reconstruction at a different focal plane. By combining the depth map with the volume of reconstructions used to calculate the depth map we can create an image, an extended focus image, where the full scene is in focus. To our knowledge, this is the first technique which creates extended focused images of digital holograms encoding macroscopic objects. We present results for digital holograms containing low and high contrast macroscopic objects.