There are three categories of night vision cameras. Passive night vision cameras rely on ambient infrared radiation, such as that coming from the moon, stars, or other sources. These cameras use photons from that light to produce an intensified visible image. Even a dimly lit scene can be viewed by the naked eye via visual output, or stored as data for later analysis. These cameras don’t function as well in complete darkness.
Active illumination cameras solve the problem of use in complete darkness. These night vision cameras generally combine imaging intensification technology with an active source of illumination in the near infrared or shortwave infrared band (infrared illuminators). In other words, they come with their own light source via a built-in infrared illuminator.