  Birefringence, an inherent characteristic of optically anisotropic materials,
is widely utilized in various imaging applications ranging from material
characterizations to clinical diagnosis. Polarized light microscopy enables
high-resolution, high-contrast imaging of optically anisotropic specimens, but
it is associated with mechanical rotations of polarizer/analyzer and relatively
complex optical designs. Here, we present a novel form of
polarization-sensitive microscopy capable of birefringence imaging of
transparent objects without an optical lens and any moving parts. Our method
exploits an optical mask-modulated polarization image sensor and
single-input-state LED illumination design to obtain complex and birefringence
images of the object via ptychographic phase retrieval. Using a camera with a
pixel resolution of 3.45 um, the method achieves birefringence imaging with a
half-pitch resolution of 2.46 um over a 59.74 mm^2 field-of-view, which
corresponds to a space-bandwidth product of 9.9 megapixels. We demonstrate the
high-resolution, large-area birefringence imaging capability of our method by
presenting the birefringence images of various anisotropic objects, including a
birefringent resolution target, liquid crystal polymer depolarizer, monosodium
urate crystal, and excised mouse eye and heart tissues.
