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Extraction of three-dimensional shape information from a digital hologram

We present a technique to convert a digital hologram of a three-dimensional (3D) object into a cloud of surface points in 3D space. Two depth-from-defocus techniques are used to generate a depth map for a particular reconstructed perspective of the object encoded in the digital hologram. The Fresnel transform is used to effect defocus, and a histogram-based approach is used to determine the degree of defocus for each neighborhood of pixels. Our experiments involve simulated and real-world objects (captured using phase-shift digital interferometry). The technique could be used in registration and 3D object recognition applications.