  Angular filter refractometry is an optical diagnostic that measures absolute
contours of line-integrated density gradient by placing a filter with
alternating opaque and transparent zones in the focal plane of a probe beam,
which produce corresponding alternating light and dark regions in the image
plane. Identifying transitions between these regions with specific zones on the
angular filter (AF) allows the line-integrated density to be determined, but
the sign of the density gradient at each transition is degenerate and must be
broken using other information about the object plasma. Additional features
from diffraction in the filter plane often complicate data analysis. In this
paper, we present an improved AF design that uses a stochastic pixel pattern
with a sinusoidal radial profile to minimize unwanted diffraction effects in
the image caused by the sharp edges of the filter bands. We also present a
technique in which a pair of AFs with different patterns on two branches of the
same probe beam can be used to break the density gradient degeneracy. Both
techniques are demonstrated using a synthetic diagnostic and data collected on
the OMEGA EP laser.
