Abstract

We present confocal stereo, a new method for computing 3D shape by controlling the focus and aperture of a lens. The method is specifically designed for reconstructing scenes with high geometric com- plexity or fine-scale texture. To achieve this, we introduce the confocal constancy property, which states that as the lens aperture varies, the pixel intensity of a visible in-focus scene point will vary in a scene- independent way, that can be predicted by prior radiometric lens cali- bration. The only requirement is that incoming radiance within the cone subtended by the largest aperture is nearly constant. First, we develop a detailed lens model that factors out the distortions in high resolution SLR cameras (12MP or more) with large-aperture lenses (e.g., f1.2). This allows us to assemble an A × F aperture-focus image (AFI) for each pixel, that collects the undistorted measurements over all A aper- tures and F focus settings. In the AFI representation, confocal constancy reduces to color comparisons within regions of the AFI, and leads to fo- cus metrics that can be evaluated separately for each pixel. We propose two such metrics and present initial reconstruction results for complex scenes.