Acquiring multispectral light transport using multi-primary DLP projector

Acquiring the light transport (LT) of a scene is important for various applications such as radiometric analysis, image-based relighting, and controlling appearance of the scene. The multispectral LT, i.e. the LT in multiple primary colors enables us not only to enhance the color gamut but also to investigate wavelength-dependent interactions between light and a scene. In this paper, we propose a method for acquiring the multispectral LT by using a single off-the-shelf multi-primary DLP (Digital Light Processing) projector; it does not require any self-built equipment, geometric registration, and temporal synchronization. Specifically, based on the rapid color switch due to a rotating color wheel in the projector, we present a method for estimating the spectral properties of the projector in a non-destructive manner, and a method for acquiring the images of a scene illuminated only by one of the primary colors. We conducted a number of experiments by using real images, and confirmed that our method works well and the acquired multispectral LT is effective for radiometric analysis and image-based relighting.