Thermal imaging cameras, also known as infrared cameras, detect the heat given off by an object or person. Thermal imaging cameras have lenses which focus waves from the infrared energy present in all objects onto an infrared sensor array. These sensors on the array convert the infrared energy into electrical signals, which create a video image. The infrared camera measures and displays a “thermal profile” of objects in relation to the temperature of surrounding objects. A person warmer than the surrounding air appears “white” while the cooler surrounding air or buildings will appear in varying shades of gray.

Thermal imaging cameras can only “see” heat as it radiates off of an object. It can’t see into the house because the camera picks up the house’s exterior thermal image first. Glass is also insulated from Thermal imaging. Thermal imaging has also been used to improve energy conservation in houses and buildings by monitoring homes for heat loss from gaps.

Thermal imaging cameras can help in law enforcement in many ways. It helps police officers stay safe by spotting suspects hiding in bushes or in dark alleys — in fact it can “see” someone hiding behind an object like a box or trash can if that person radiates enough heat to cast a thermal image around the object.

It assists police in pursuit. Thermal cameras can see people running in the night, even through the cover of trees. These cameras are also used to identify a recently driven car (by the warmth of the hood), or in some cases even the warmth of the skid marks left by a fleeing car.

Evidence collection can be assisted through Thermal imaging cameras. The technology can help police officers spot an object a suspect has discarded while being pursued, or gather evidence or uncover situations of evidence tampering at a crime scene.

After a search warrant is executed, police may sometimes use these cameras to look for objects hidden in interior walls, like drugs or money. These objects act like insulation in the walls and may produce a different thermal image in that section of the wall compared with the surrounding wall space and studs.