Light path alignment for computed tomography of scattering material

We aim to estimate internal slice of the scattering material by Computed Tomography (CT). In the scattering material, the light path is disturbed and is spread. Conventional CT cannot measure the scattering material because they rely on the assumption that rays are straight and parallel. We propose light path alignment to deal with scattering rays. Each path of disturbed scattering light is approximated with a straight line. Then the light path in the object corresponding to a single incident ray is modeled as straight paths spreading from incident point. These spreading paths are aligned to be parallel, so that they can be used directly by conventional reconstruction algorithm

Programmable Non-Epipolar Indirect Light Transport: Capture and Analysis

The decomposition of light transport into direct and global components, diffuse and specular interreflections, and subsurface scattering allows for new visualizations of light in everyday scenes. In particular, indirect light contains a myriad of information about the complex appearance of materials useful for computer vision and inverse rendering applications. In this paper, we present a new imaging technique that captures and analyzes components of indirect light via light transport using a synchronized projector-camera system. The rectified system illuminates the scene with epipolar planes corresponding to projector rows, and we vary two key parameters to capture plane-to-ray light transport between projector row and camera pixel: (1)the offset between projector row and camera row in the rolling shutter, and (2)the exposure of the camera row. We describe how this synchronized rolling shutter performs illumination multiplexing, and develop a nonlinear optimization algorithm to demultiplex the resulting 3D light transport operator. Using our system, we are able to capture live short and long-range indirect light transport, disambiguate subsurface scattering, diffuse and specular interreflections, and distinguish materials according to their subsurface scattering properties. In particular, we show the utility of indirect imaging for capturing and analyzing the hidden structure of veins in human skin

Acquiring and Characterizing Plane-to-Ray Indirect Light Transport

2018 IEEE International Conference on Computational Photography (ICCP) 4-6 May 2018 ,Pittsburgh, PA, USASeparation of light transport into direct and indirect paths has enabled new visualizations of light in everyday scenes. However, indirect light itself contains a variety of components from subsurface scattering to diffuse and specular interreflections, all of which contribute to complex visual appearance. In this paper, we present a new imaging technique that captures and analyzes these components of indirect light via light transport between epipolar planes of illumination and rays of received light. This plane-to-ray light transport is captured using a rectified projector-camera system where we vary the offset between projector and camera rows (implemented as synchronization delay) as well as the exposure of each camera row. The resulting delay-exposure stack of images can capture live short and long-range indirect light transport, disambiguate subsurface scattering, diffuse and specular interreflections, and distinguish materials according to their subsurface scattering properties