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 .To study about night vision technology we should first know about light .The amount of light energy is related to wavelength .Shorter wavelength have higher energy . Of visible light,violet has the most energy , and red has the least .Night vision technology consists of two major types: light amplification(or identification) and thermal(infrared) .Most consumer night vision products are light amplifying devices
Night vision is a spy or action movie you've seen, in which someone straps on a pair of night-vision goggles to find someone else in a dark building on a moonless night. With the proper night-vision equipment, you can see a person standing over 200 yards (183 m) away on a moonless, cloudy night. Night vision can work in two very different ways, depending on the technology used.
• 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.
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 is a small part of the light 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.
The key difference between thermal-IR and the other two is that thermal-IR is emitted by an object instead of reflected off it. Infrared light is emitted by an object because of what is happening at the atomic level.
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