Title: Coherence measurements of scattered incoherent light for lensless identification of an object's location and size,
Abstract: In absence of a lens to form an image, incoherent or partially coherent light
scattering off an obstructive or reflective object forms a broad intensity
distribution in the far field with only feeble spatial features. We show here
that measuring the complex spatial coherence function can help in the
identification of the size and location of a one-dimensional object placed in
the path of a partially coherent light source. The complex coherence function
is measured in the far field through wavefront sampling, which is performed via
dynamically reconfigurable slits implemented on a digital micromirror device
(DMD). The impact of an object -- parameterized by size and location -- that
either intercepts or reflects incoherent light is studied. The experimental
results show that measuring the spatial coherence function as a function of the
separation between two slits located symmetrically around the optical axis can
identify the object transverse location and angle subtended from the detection
plane (the ratio of the object width to the axial distance from the detector).
The measurements are in good agreement with numerical simulations of a forward
model based on Fresnel propagators. The rapid refresh rate of DMDs may enable
real-time operation of such a lensless coherency imaging scheme.