High-brightness laser imaging with tunable speckle reduction enabled by electroactive micro-optic diffusers

Abstract

High coherence of lasers is desirable in high-speed, high-resolution, and wide-field imaging. However, it also causes unavoidable background speckle noise thus degrades the image quality in traditional microscopy and more significantly in interferometric quantitative phase imaging (QPI). QPI utilizes optical interference for high-precision measurement of the optical properties where the speckle can severely distort the information. To overcome this, we demonstrated a light source system having a wide tunability in the spatial coherence over 43% by controlling the illumination angle, scatterer’s size, and the rotational speed of an electroactive-polymer rotational micro-optic diffuser. Spatially random phase modulation was implemented for the lower speckle imaging with over a 50% speckle reduction without a significant degradation in the temporal coherence. Our coherence control technique will provide a unique solution for a low-speckle, full-field, and coherent imaging in optically scattering media in the fields of healthcare sciences, material sciences and high-precision engineering.

Scattering‐Based Light‐Sheet Microscopy for Rapid Cellular Imaging of Fresh Tissue

“…In future, we will improve the image quality through the following approaches: We will further reduce the speckle noise using the angular‐diverse illumination [30] or implementing the moving diffuser [31,32], which will help analyze the cellular details. Although the imaging depth demonstrated in this preliminary study, ~200 µm, might be sufficient for examining the epithelial layer, where many of the disease‐associated cellular changes are present, a larger imaging depth will be desirable for imaging deeper regions.…”

Coherence‐Tailored Multiwavelength High‐Speed Quantitative Phase Imaging with a High Phase Stability via a Frequency Comb

“…High‐brightness and high‐coherence continuous‐wave (CW) lasers have been utilized in QPI for efficient light–specimen interaction and phase‐sensitive interferometric imaging. [ 15,16 ] However, the high coherence inevitably superimposes unexpected coherent noise (e.g., speckle, diffraction, and parasitic interferogram) to the target interferograms, which significantly hampers sensitive phase detection and successful phase reconstruction. [ 17,18 ] The coherent noise gets even more severe when imaging through the scattering media, e.g., biological tissues, plasmonic nanoparticles, and nonideal optics with surface roughness or contamination.…”

Tailoring of spatial coherence in a multimode fiber by selectively exciting groups of eigenmodes

“…Therefore, speckle formation can be changed by controlling the coherence of light. A number of techniques have been proposed to generate partially coherent or totally incoherent light [6][7][8]. One of the attractive methods is to use a multimode fiber (MMF) since it supports hundreds of waveguide modes which could effectively reduce the spatial coherence when light is propagating through MMF [9][10][11].…”