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

Ren Matsumoto, Takahiro Okabe, Ryo Kawahara

Abstract:

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