  Superposing multiple plane waves can generate helicity lattices in which the
optical helicity varies regularly in space. Here we propose an inverse design
method for constructing arbitrary helicity structures based on placing a
digital object of dielectric inclusions in three-dimensional space. We apply
the method to design structures that reproduce two-dimensional lattices
embedded within a three-dimensional region using only a single plane wave as an
input. In order to demonstrate the power and flexibility of our method, we go
beyond the paradigm of a regular lattice and propose structures that can create
arbitrary images consisting of regions of varying helicity, again using only a
single plane wave as an input.
