Night Vision Technology
M.Raveendra, G.Chaitanya sagar
Abstract - Night has its sorcery quality which many humans missed especially on moonless nights. In comparison to many animals which do their gallivanting in the dark, humans cannot see in the dark because their eyes lack tapetum lucidum. This is a layer of tissues in the eyes which improves vision in low light conditions but is present in the eyes of most animals. Fortuitously human ingenuity popped up with night vision optics that made night vision possible. Night vision technology, by definition, literally allows one to see in the dark. Night vision optics is a device to intensify human sight under very low light conditions. Although more human activities are done during the day than night, the capability to see in the dark is still significant in many occasions. Night vision devices focuses infrared light to objects in the dark; infrared is beyond spectrum visible to the human eyes. A device for night vision was perfected during wartime giving soldiers in the battle field a technical benefit over their enemies. Vision equipment has evolved from bulky optical instruments in to lightweight goggles through the advancement of image intensification technology and thin film technology. 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. Many products have been developed from this technology to enable the man to see even in darkness and serve his needs.
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. [pic]
Fig. 1. Electromagnetic 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.
II. TECHNOLOGIES IN NIGHT VISION
Night vision consists of two major types:
• Thermal imaging
• Image Enhancement
A. Thermal Imaging
Here is how thermal imaging works:
• 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 thermo gram. It only takes about one-thirtieth of a second for the detector array to obtain the temperature information to make the thermo gram. This...
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