A full photometric and geometric model for attached webcam/matte screen devices

• We provide a closed-form expression for the lighting emitted by an infinitely small planar light source.
• This infinitesimal model is extended to arbitrary extended planar illuminants.
• The lighting model can be used to model light emitted by a screen displaying graylevel images.
• A thorough geometrical study of webcam/screen devices is provided.
• Both photometric and geometric applications are validated in a photometric stereo application with extended sources.

We present a thorough photometric and geometric study of the multimedia devices composed of both a matte screen and an attached camera, where it is shown that the light emitted by an image displayed on the monitor can be expressed in closed-form at any point facing the screen, and that the geometric calibration of the camera attached to the screen can be simplified by introducing simple geometric constraints. These theoretical contributions are experimentally validated in a photometric stereo application with extended sources, where a colored scene is reconstructed while watching a collection of graylevel images displayed on the screen, providing a cheap and entertaining way to acquire realistic 3D-representations for, e.g., augmented reality.