Difference Between Night Vision & Infrared

Infrared covers a bandwidth of light just below the visual spectrum.

The difference between infrared and night vision is a subtle, and sometimes inconsequential, distinction: One uses amplified light, the other invisible light. Most night vision devices deploy infrared technology, but not all infrared imaging is deployed in night vision. What appears in the lens of an infrared camera is a visualization of the bandwidth of light just below the visual spectrum. With night vision, the camera amplifies minute amounts of ambient light.

Light Spectrum

Infrared goggles can replicate images under low-light conditions by exploiting the light radiation emitted in the .7-to-30-micron wavelengths of light, just below wavelengths visible to the human eye. Even on a dark, cloudy and moonless night, most objects continue to emit thermal infrared, a wavelength of invisible red light between 3 and 30 microns. These are the wavelengths that appear as heat-radiated imaging.

Amplified Light

Most night vision technology deploys some type of infrared imaging when recreating scenes after dark. Infrared notwithstanding, part of night vision technology also includes amplification of barely perceptible light. Even in conditions where a human couldn't see a hand in front of his face, cats, birds of prey and other nocturnal creatures have ample light to navigate through a dark night. Light amplification intensifies imperceptible levels of visible light.

Thermal Imaging

Infrared imaging is a digital approximation of light that cannot be perceived by the human eye. Charge-coupled devices (CCDs) collect light from the infrared bandwidth, just below the visual spectrum, and then a computer processor translates those bandwidths into digital images that can be projected onto a screen. All matter emits thermal infrared, even when no visible light is present. Some of the most sensitive infrared technologies can reveal images from more than 1,000 feet away.

Light Amplification

Amplified light collects trace levels of visible light in photons. These photons then pass through a photocathode that converts them into electrons. The electrons then fire through a microchannel plate, releasing millions more electrons and amplifying the signal. A phosphor screen then converts them back into photons. These recreated photons contain the original images, only much stronger. Because light amplification uses reflected light, objects with a dull surface or dark color may be difficult to detect, even with sophisticated amplification technology.

References

• Infrared 1: Infrared Cameras and Night Vision Goggles
• Moro Vision: How Night Vision Works
• Moro Vision: How Thermal Imaging Works