We present sub-millimeter full-field depth from focus digital holography of surface topography of rough objects. For each pixel, the depth of the object is calculated from the variance of the intensity image over a set of reconstruction distances. First, we theoretically describe the axial resolution of this method and show that sub-millimeter resolution is feasible. Second, using a digital holography setup without magnifying optics or lateral scanning we experimentally demonstrate 100 μm axial

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... resolution depth ranging and surface topography imaging. This is significantly better than what has previously been reported using digital holography and could make this technique useful for rapid large-area characterization of surface topography of objects.