Fig. 1

Epi-GLIM enables phase imaging of opaque structures. a The epi-GLIM module intercepts the sheared beams in reflected light DIC (blue/red) before they are recombined at the output analyzer (P2). Specifically, we focus light from an IR source through a diffuser (Dif.) by way of lenses L1, L2, beam splitter and objective (L1, L2, BS OBJ). To achieve differential interference contrast, the light is polarized by an input polarizer (P1) and split with a Nomarski prism into two laterally sheared polarizations (NP). The backscattered field is then collected by the objective and tube lens (TL). By using a liquid crystal variable retarder (LVR), we control the relative phase shifts between these polarizations. Rendering performed in Blender. b We reconstruct a relief style phase map using a sequence of DIC intensity frames acquired at 0°, 90°, 180°, 270° phase shift, as indicated. c To validate our approach, we imaged a 1.9 μm bead on a reflective surface. Upon integration, we recover the expected phase profile for a polystyrene bead blurred by the impulse response of the system (40×/0.75 490 nm), which is twice the value as expected in a transmission geometry. The slight mismatch on the right lobe motivates the use of a measured impulse response in later portions of this work