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Introduction
Night vision is used to locate an object which is 200 yards away even in moonless, cloudy night.
Night vision can work into two different ways, depending on the technology used.
They are image enhancement and thermal imaging. Image enhancement works by collecting lower portion of infrared light spectrum.
Thermal imaging operates by capturing the upper portion of the infrared light spectrum.
Image enhancement
This works by collecting the tiny amounts of light, including the lower portion of the infrared light spectrum, that are present but may be imperceptible to our eyes, and amplifying it to the point that we can easily observe the image.
Thermal imaging
This technology operates by capturing the upper portion of the infrared light spectrum, which is emitted as heat by objects instead of simply reflected as light. Hotter objects, such as warm bodies, emit more of this light than cooler objects like trees or buildings.
The Basics
In order to understand night vision, it is important to understand something about light.
The amount of energy in a light wave is related to its wavelength: Shorter wavelengths have higher energy.
Of visible light, violet has the most energy, and red has the least. Just next to the visible light spectrum is the infrared spectrum.
Infrared light can be split into three categories
Near-infrared (near-IR) - Closest to visible light, near-IR has wavelengths that range from 0.7 to 1.3 microns, or 700 billionths to 1,300 billionths of a meter.
Mid-infrared (mid-IR) - Mid-IR has wavelengths ranging from 1.3 to 3 microns. Both near-IR and mid-IR are used by a variety of electronic devices, including remote controls.
Thermal-infrared (thermal-IR) - Occupying the largest part of the infrared spectrum, thermal-IR has wavelengths ranging from 3 microns to over 30 microns.
Thermal Imaging
Thermal imaging works as
A special lens focuses the infrared light emitted by all of the objects in view.
The focused light is scanned by a phased array of infrared-detector elements. The detector elements create a very detailed temperature pattern called a thermogram.
The thermogram created by the detector elements is translated into electric impulses.
The impulses are sent to a signal-processing unit, a circuit board with a dedicated chip that translates the information from the elements into data for the display.
The signal-processing unit sends the information to the display, where it appears as various colors depending on the intensity of the infrared emission. The combination of all the impulses from all of the elements creates the image.