Computer vision systems in a variety of applications operate by projecting light onto an object and then detecting the light reflected back from the object. For example, three-dimensional (3D) mapping systems commonly project a pattern of structured light or short pulses of light onto an object and then extract 3D contours from an image of the patterned or pulsed light.
One system of this sort is described, for example, in U.S. Patent Application Publication 2008/0240502, whose disclosure is incorporated herein by reference. This publication describes apparatus for mapping an object using an illumination assembly, which includes a transparency containing a fixed pattern of spots. A light source transilluminates the transparency with optical radiation so as to project the pattern onto the object. An image capture assembly captures an image of the pattern that is projected onto the object. A processor processes the image captured by the image capture assembly so as to reconstruct a 3D map of the object. The image capture assembly may comprise a bandpass filter, which is chosen and positioned so that the image sensor receives light in the emission band of the light source, while filtering out ambient light that might otherwise reduce the contrast of the image of the projected pattern that is captured by the sensor.