A night-vision gear (NVG), also known as night optical/observation device (NOD) and night-vision goggles (NVG), is an optoelectronic device that allows images be produced in levels of light approaching total darkness. The image may be a conversion to visible light of both visible light and near-infrared, while by convention detection of thermal infrared is denoted thermal imaging. The image produced is typically monochrome, e.g. shades of green. NVDs are most often used by the military and law enforcementagencies, but are available to civilian users.