A holographic imager is a device capable of playing back footage in a two-dimensional format, without the use of cathode-ray tube techonlogy.
The imager is comprised of a enclosed wide cylinder, with the image projected within this cylinder.
Commander Cain has such an imager in his quarters aboard Pegasus, which he uses to introduce Sheba to Apollo and Starbuck, and later introduce the fact that Cassiopeia once knew Cain prior to the fall of the Twelve Colonies (The Living Legend, Part I).
Notes
- The device is never actually given a name in the episode. "Holographic imager" is the term used to describe this device and should not be considered the canonical term.