We propose image processing algorithms for measuring two-dimensional distributions of
linear birefringence using a pair of variable retarders. Several algorithms that use between
two and five recorded frames allow us to optimize measurements for speed, sensitivity, and
accuracy. We show images of asters, which consist of radial arrays of microtubule polymers
recorded with a polarized light microscope equipped with a universal compensator. Our
experimental results confirm our theoretical expectations. The lowest noise level of 0.036 nm …