Alternating projection-based phase optimization for arbitrary glare suppression through multimode fiber

Abstract

Wavefront shaping for glare suppression helps to reduce the speckle background through scattering media and enables imaging, sensing, and some speckle-related advanced applications through customizing the speckle light field. For glare suppression in a target region, current methods are either slow or not sufficiently generic. Here, an alternating projection method that fully exploits the transmission matrix of the scattering medium is proposed for fast and arbitrary glare suppression. Parallelly, multiple phase masks corresponding to different target regions can be computationally optimized without iterative hardware feedback. Numerical simulation shows that under phase-only modulation, a suppression factor of ∼10−3 can be realized for a large target region with only 30 iterations. With the use of a graphics processing unit and a digital micromirror device, fast and effective glare suppression for target regions of various shapes and sizes was demonstrated at the distal end of a multimode fiber. This technique could be promising for applications like multimode fiber-based speckle optical tweezer or endoscopy with speckle illumination inside complex environments.