"infrared imaging is to see varying degrees of 'heat'"
Actually you are getting terms confused. Infrared imaging can only see intense infrared light cast from an infrared light source. Such light sources include many motion detector alarm systems (thus infrared goggles are very useful for avoiding security systems.) Meanwhile, if you want to be able to see in the dark, you need an infrared "flashlight" to cast infrared light on your surroundings. Infrared imaging systems commonly include a light attached to the goggles.
What you are describing is thermo-imaging. Thermo-imaging sees heat, hence the name.
Actually you are getting terms confused. Infrared imaging can only see intense infrared light cast from an infrared light source. Such light sources include many motion detector alarm systems (thus infrared goggles are very useful for avoiding security systems.) Meanwhile, if you want to be able to see in the dark, you need an infrared "flashlight" to cast infrared light on your surroundings. Infrared imaging systems commonly include a light attached to the goggles.
What you are describing is thermo-imaging. Thermo-imaging sees heat, hence the name.