CVPR 2011 Computational imaging

Structured Light 3D Scanning in the Presence of Global Illumination

Mohit Gupta, Amit Agrawal, Ashok Veeraraghavan, and Srinivasa G. Narasimhan

Measuring shape in the presence of inter-reflections, subsurface scattering, and defocus

Seeing beyond global illumination

The scene has significant inter-reflections and subsurface scattering. Conventional Gray codes and phase-shifting produce errors at points receiving inter-reflections; modulated phase-shifting produces errors on translucent fruits. In contrast, the depth map computed using our techniques is nearly error free.

Overview

The goal of this work is to build an end-to-end system for structured light 3D scanning under a broad range of global illumination effects, such as inter-reflections, diffusion and sub-surface scattering. We have designed structured light patterns that are resilient to individual global illumination effects using simple logical operations and tools from combinatorial mathematics.

Scenes exhibiting multiple phenomena are handled by combining results from a small ensemble of such patterns. Our methods can be readily incorporated into existing scanning systems without a significant overhead in terms of capture time or hardware.

Projection
patterns

Conventional Gray codes perform poorly in the presence of global illumination. The proposed patterns use logical operations and stripe-width design to address different light transport effects. Select any pattern to view it at full resolution.

Logical XOR-02 and XOR-04: good for handling inter-reflections.
Max min-stripe width Gray codes: good for handling inter-reflections, subsurface scattering, and defocus.