<title>Ballistic imaging of biomedical samples using picosecond optical Kerr gate</title>

Abstract

Imaging with ultrashort exposure times is generally achieved with a crossed-beam geometry. In the usual arrangement, an off-axis gating pulse induces birefringence in a medium exhibiting a strong Kerr response (commonly carbon disulfide) which is followed by a polarizer aligned to fully attenuate the on-axis imaging beam. By properly timing the gate pulse, imaging light experiences a polarization change allowing time-dependent transmission through the polarizer to form an ultrashort image. The crossed-beam system is effective in generating short gate times, however, signal transmission through the system is complicated by the crossing angle of the gate and imaging beams. This work presents a robust ultrafast time-gated imaging scheme based on a combination of type-I frequency doubling and a collinear optical arrangement in carbon disulfide. We discuss spatial effects arising from crossed-beam Kerr gating, and examine the imaging spatial resolution and transmission timing affected by collinear activation of the Kerr medium, which eliminates crossing angle spatial effects and produces gate times on the order of 1 ps. In addition, the collinear, two-color system is applied to image structure in an optical fiber and a gasoline fuel spray, in order to demonstrate image formation utilizing ballistic or refracted light, selected on the basis of its transmission time.

Automatic Differentiation for All Photons Imaging to See Inside Volumetric Scattering Media

“…Optical coherence tomography [1], confocal microscopy [2], and two-photon imaging [3] optically reject scattered photons to capture only ballistic photons. Time-of-flight measurements enable the time-gating of ballistic photons [4], so that the measurement only relies upon the first photon to hit the sensor. Methods to measure ballistic photons have been used to solve remote sensing problems in computer vision and robotics applications [5,6,7].…”

Time-resolved imaging with OKE-based time-gate: enhancement in spatial resolution using low-coherence ultra-short illumination

“…However, many real-world applications and phenomena of interest are intrinsically linked to turbid environments where light scattering and attenuation strongly limit the interpretation of optical signals. In a wide range of applications, from imaging in biological tissues [1,2], to measurements of high-pressure multiphase flows involving cavitation or turbulent breakup [3], key information is scrambled by the distortion imparted to the light signal as it transits the measurement volume [4]. Informative optical diagnostics in such media require detailed understanding of the light source, propagation and scattering in the measurement volume, and a detection arrangement tailored to collect the meaningful parts of the transmitted light signal.…”

Efficient optical Kerr gate of Bi2O3–B2O3–SiO2glass for acquiring high contrast ballistic imaging in turbid medium

“…So, it is difficult to observe a target hidden in a turbid medium because of the strongly scattered photons, which will degrade the image contrast. Generally, using the method of ballistic imaging [6,7], transillumination images can clearly be improved by limiting the scattered photons. In order to preferentially select photons based on their propagation direction [8,9], a direct method introduces a spatial filter.…”