Night-vision glasses work by capturing tiny amounts of light, some of it from the infrared portion of the light spectrum, and amplifying it in order to create an image that is more easily observed. Some systems may also utilize thermal imaging technology, either alone or in concert with light amplification.
Night vision devices capture a minute quantities of visible light through a special component known as an image intensifier tube. This tube utilizes both a conventional lens and a photocathode to convert photons into electrons which are then amplified through the use of a microchannel plate. The amplified electrons that exit the image intensifier tube strike a plate that has been coated with phosphors in order to create a visual image. This image is then viewed through an ocular lens which provides additional magnification and focus.
Thermal imaging devices make use of a lens which collects light from within the infrared spectrum. Once this light has been focused, it is scanned by a phased array of infrared-detector elements. These elements are able to create a detailed pattern based called a thermogram which is then translated into electrical signals. A signal processing unit is then used to create an observable image that is based on the information contained within the thermogram.