An interactive display that uses a planar radiation guide (such as a planar light guide) to perform display and/or imaging. The planar radiation guide has a radiation propagation portion and a radiation interface portion. The radiation propagation portion propagates the radiation by the principles of total internal reflection (with perhaps some minor leakage). The planar radiation guide also has a radiation interface portion where radiation is more apt to exit or enter the planar radiation guide. The interactive display performs both display and imaging, while the planar radiation guide is used to perform at least one (but perhaps both) of the display and imaging operations.