Night vision devices work on a technology that enhances available light from environment many times to enable the user visualize in complete darkness or night. It allows vision at night. These devices are highly sensitive to light and the slightest amount of light is sufficient to make vision possible.
Photons that are available in light enter the cathode and as they pass through the tube get multiplied many folds and thereby eliminating huge amount of photons that makes visibility possible. Hence some amount of light is completely mandatory to visualize objects in complete darkness. Generation 1 night vision devices needed more light however with time technology has upgraded night vision devices to a level where vision is possible with bare minimum light source.
As an answer to the above direct question as direct answer would be NO! It is not effective to use a night vision device in complete darkness. But what seems to be complete darkness may not be a retarding factor in using night vision device. Generation 3 night vision devices are highly sensitive to light and are capable of detecting minimum available light. Light energy from natural sources such as moonlight, starlight or infrared light can be sufficient in enabling vision by use of a night vision device. Infrared light is invisible to human eyes and hence its presence can only be detected with a camera. So what seems to be complete darkness may also allow possibility of vision through a night vision device.
Technology has developed devices and solutions to enable vision in complete darkness in jungles, canyons and cloudy nights. Today many night vision devices today are coupled with infrared illuminator that makes it possible to see even in complete darkness. Infrared light is invisible to human eyes however camera lenses are capable of detecting infrared radiations in complete darkness.
Use of infrared or IR illuminators in dark is a very good solution for viewing objects in complete darkness. In closed environments it is usually completely dark and an illuminator can ease visibility with night vision devices. Illuminators provide enough light for clear and sharp objects and images and thereby clarity in vision. Many night vision goggles come with inbuilt infrared illuminators for closer focus and large distance viewing. When light is less the quality of picture or image produced is also of low quality. So an illuminator comes in handy in complete darkness and at places where light is less and a low quality night vision is used for viewing.
