Polarization as Texture: Microscale 3D Shape from Polarized Light Focus

Defocus is a crucial cue for image-based microscale depth estimation, yet its measurement depends on spatial appearance changes, such as texture. We show that passively observed polarization is responsive to small irregularities of the surface visible in the microscopic world and can be leveraged for focus measure as a strong texture. Our key idea is to leverage texture from polarization for blur analysis and accurately estimate the focus level of microscopic polarization images. We further utilize normal cues from polarization to create a prior distribution of the focus level between neighboring pixels. We then interpolatively propagate the focus level of discrete image slices at different focus depths while denoising. We implement our method with a single polarization camera with a microscope and recover the per-pixel depth from the multi-focus images. The reconstructed results demonstrate the effectiveness of our method for various microscale objects regardless of the surface texture.