A second-order theory of texture for depth from focus

We present a theory of textured appearance of optically roughsurfaces based on wave optics, emphasizing the role of texture for passivedepth from focus. Our theory shows that even surfaces that traditionalcomputer vision would consider textureless can produce textured appear-ance, due to subjective speckle from surface microgeometry. We analyzethe properties of this second-order texture, and show that we can enhanceits contrast under natural ambient lighting by simply using a narrowbandspectral filter. Doing so results in dramatic improvements in passive depthreconstruction of seemingly textureless scenes, as we demonstrate throughextensive theory, simulations, and real-world experiments.