Thermoptics is the shorthand term for converting the heat signatures of hot and cold objects into a viewable image. It was originally used offensively, to spy on the enemy at night and launch attacks when visible light wasn't available. Very quickly though, defensive techniques evolved, such as heat shielding and thermal decoys.
There has been a virtual revolution in the science and engineering of thermoptic technology in recent years. The latest development is a sophisticated counter-measure called Thermoptic Shielding.
The principal of Thermoptic Shielding is to envelop a target area in layers of electrically charged shielding. A computer program then generates a simulated thermal signal based on the user's design. The simulated heat signature is projected outward, while the true signature remains concealed.
The result is that anyone spying on a Thermoptically Shielded target could just as easily confuse an empty room for a room full of agents, and vice versa.