How Night Vision Works

Night Vision is an imaging technology designed to improve visibility in minimal or no light by amplifying or creating light. This imaging technology utilizes the upper or lower portion of the light spectrum to create a clearer and more detailed picture of the target. In essence, night vision devices utilize the portion of the light spectrum that is invisible to the human eye in order to create a clearer picture. Unlike the visible portion, which depends wholly on light reflection, garnering image data from the infrared spectrum means that the night vision device uses the target’s emitted thermal energy. The target’s photon particle emission causes thermal energy emission because of atomic energy release after excitation.

Components of a Night Vision Device

A night vision device uses a special lens to focus on all the infrared light that the target and other objects in view emit. The phased array that scans the focused infrared light creates a thermogram temperature pattern. This thermogram temperature pattern is converted to electrical impulses and sent to the unit’s computers for processing and is translated into an image that the user can understand.

How Light Works
To truly understand how night vision technology works, the reader needs to know how light works. The light spectrum ranges from infrared to ultraviolet, with visible light ranging from red to violet. Though the human eye cannot see either infrared or ultaviolet light, it can see the range of colors that make up visible light. The light wave’s wavelength determines the lights’ colors. The smaller the light’s wavelength, the more energy present. Night vision devices that use image enhancement rely on this principle to allow light that the human eye cannot detect to become detectable.

While most light that we see is simply reflected off of objects, some objects actually produce light. This is the principle behind thermal imaging and heat signatures. When energy excites an atom, the atom’s electrons move to a higher orbit around its nucleus. By doing so, the electrons gain more potential energy. As the electrons come back to their original orbit around the nucleus, the additional energy is ejected from the electron as a photon – a particle of light.

Image Enhancement
Some night vision devices use a technology known as image enhancement. Image enhancement is based on the fact that all objects reflect light, whether the light can be seen or not.

Image enhancement night vision devices use an image intensifier tube that gathers and magnifies visible and infrared light. They use an objective or conventional lens to collect light and infrared. These collected photon particles are passed through the image intensifier tube, which batteries power. Inside, a photocathode converts the photons into electrons. The number of electrons is multiplied in the order of thousands with an MCP or Micro Channel Plate. A phosphor coated screen at the image intensifier’s end catches the electrons and emits photons upon electron impact. These phosphors produce the characteristic green color of night vision images that are viewed through the ocular lens.

Thermal Imaging
Other night vision devices use a technology known as thermal imaging. Thermal imaging collects traces of light from the upper light spectrum rather than the lower. In this range of light, the night vision device can detect heat. Because different objects give off varying degrees of heat, a solider using a thermal imaging night vision device can easily distinguish between a person, a building, or a nearby tree. While thermal imaging and image enhancement are quite different, they are often included in the same night vision device.

Thermal devices can either be uncooled or cryogenically cooled. Although cryogenically cooled thermal imaging devices produce a much better picture than an uncooled one (because of its greater temperature scanning range), these devices are a lot more expensive and prone to damage. Moreover, the uncooled thermal imaging device operates at room temperature, is faster, and much quieter.

Applications
Night vision technology has existed since World War II. It is currently used in goggles, scopes, and cameras. Law enforcement agencies, military, wildlife researchers, hunting parties, navigators, private investigators, entertainment companies, surveillance and security systems, and even everyday people use this technology.