Post-processing techniques for the reduction of range chatter in 3D holographic imaging with a pilot tone

The use of a “pilot tone” is a proven technique to compensate for object motion in 3-D holographic imaging. However, speckle decorrelation may occur between pilot-tone images and corresponding chirped-frequency images for highly sloped object facets; the speckles from these facets shift laterally across the pupil with changing optical frequency, proportional to the facet slope. This decorrelation leads to “range chatter,” where a random speckle phase corrupts the coarse depth phase, causing an incorrect range estimate. To mitigate this effect, we crop the pilot-tone and chirped-frequency pupil-plane fields to only consider regions of the speckle patterns that are shared for a given assumed facet slope. Facets of that assumed slope do not suffer from range chatter in the resultant depth image. Repeating for many different assumed facet slopes and combining the depth images using a synthetic imaging technique yields a final depth image with greatly reduced range chatter.