Multibounce light transport analysis using ultrafast imaging for material acquisition

Abstract

This thesis introduces a novel framework for analysis of multibounce light transport using time-of-flight imaging for the applications of ultrafast reflectance acquisition and imaging through scattering media. Using ultrafast imaging and ultrafast illumination, we analyze light indirectly scattered off materials to provide new insights into the important problem of material acquisition. We use an elegant matrix based representation of light transport, which enables scene reconstruction using standard optimization techniques. We demonstrate the accuracy and efficiency of our methods using various simulations as well as an experimental setup. In particular, we develop the concept of 'in the wild' reflectance estimation using ultrafast imaging. We demonstrate a new technique that allows a camera to rapidly acquire reflectance properties of objects from a single viewpoint, over relatively long distances and without encircling equipment. We measure material properties by indirectly illuminating an object by a laser source, and observing its reflected light indirectly using a time-of-fight camera. As compared to lengthy or highly calibrated reflectance acquisition techniques, we demonstrate a device that can rapidly and simultaneously capture meaningful reflectance information of multiple materials. Furthermore, we use this framework to develop a method for imaging through scattering media using ultrafast imaging. We capture the diffuse scattering in the scene with a time-of- flight camera and analyze the multibounce light transport to recover albedo and depth information of planar objects hidden behind a diffuser. The methods developed in this thesis using ultrafast imaging can spur research with novel real-time applications in computer graphics, medical imaging and industrial photography.