Effects of speckle decorrelation on motion-compensated, multi-wavelength, 3D digital holography

Abstract

Digital holography enables 3D imagery after processing frequency-diverse stacks of 2D coherent images obtained from a chirped-frequency illuminator. To compensate for object motion or vibration, a constant temporal frequency or "pilot tone" illuminator can act as a reference for each chirped frequency. This paper examines speckle decorrelation between the chirped and pilot tone illuminators and its effect on the resultant range images. We show that speckle decorrelation between the two illuminators is more severe for facets of the object's surface that are more highly sloped, relative to the optical axis, and that this decorrelation results in noise in the range images in the areas of the object that are highly sloped. We examine the severity of this noise as a function of several imaging parameters and show that post-processing apodization, effectively reducing bandwidth, in the temporal frequency domain can reduce this noise.

Speckle decorrelation effects on motion-compensated, multi-wavelength 3D digital holography: theory and simulations

“…This study is an extension of one described in Ref. 10. Here, we build on the previous study by fleshing out the theoretical details and adding some more quantitative results, including some image sharpening experiments.…”

Multiplexed, multi-wavelength 3D digital holographic imaging methods with range unwrapping

“…This scenario is not uncommon, as speckle decorrelates more readily in the pupil plane for longer propagation distances. 6,11,12 Partial speckle correlation between the 2D coherent images can induce errors in range imagery that depend on both the degree of speckle correlation between the images and the mechanism of object/platform motion. 13 However, we simulated fully uncorrelated speckle for each timestep here for two reasons: (1) simulating independent speckle realizations is the most straightforward method to model object motion/vibration, and (2) independent speckle realizations at each timestep presents a worst-case scenario for 3D imaging, against which to test the four 3D imaging modalities' motion-compensation capabilities.…”

“…( 6) offers no performance benefits or drawbacks compared to the definition in Ref. 6. This may not be the case when detector noise is taken into account.…”

“…In this case, if the object moves or vibrates between successive pulses in time, then the 3D image can experience errors in the range dimension that can severely degrade the 3D image. 6 In this paper, we examine four different 3D imaging modalities that differ in how the object is illuminated by successive pulses over the image collection time. The first method, referred to as conventional (multi-wavelength) 3D imaging, is described in Refs.…”

Optical image processing of 2-D and 3-D objects using digital holography

“…Other work has been done using holographic systems for processing holograms to manipulate the reconstructed imagery. This includes work with optical scanning holography [5], differential DH [25], algorithmic approaches to manipulate reconstructed images [26], using spatial filters within a holographic system to influence reconstruction results [27], introduction of a constant source illuminator for noise reduction in reconstructed imagery [28], etc. Each method is a unique approach to enhancing and manipulating reconstructed imagery, but they do not directly manipulate the pupil term corresponding to the real image in a digital hologram.…”