High resolution lenses for machine vision — standard and custom lens design
How Does Night Vision Work?
High Resolution Lenses for machine vision, instrumentation, inspection and vibration-sensitive applications. Standard and custom hi-res lens assemblies.
Night vision telescopes or binoculars allow the wearer to see items at night in low light conditions. The lenses in night vision binoculars or telescopes gather and intensify the ambient light and concentrate it with optics that allow the wearer to see better in the dark than they can with the naked eye. The exit lenses of night vision eyewear are usually large, sometimes 7 mm or more, as this allows all the area ambient light to be gathered and concentrated for sight.
There are three different types of infrared light:
- Mid-infrared (mid-IR) which gathers wavelengths that range from 1.3 to 3 microns. mid-IR wavelengths are utilized in devices such as remote controls.
- Near-infrared (near-IR) is the closest to visible light and its wavelengths range from 0.7 to 1.3 microns. near-IR is also used in remote control devices.
- Thermal-infrared (thermal-IR) takes up the most space on the infrared spectrum. The wavelengths on thermal-IR range from 3 microns to more than 30 microns.
One of the main differences between thermal-IR and near- and mid-IR are that with thermal-IR, light is emitted from an object rather than being reflected off of it. In thermal-IR the light is emitted because of the atoms in the object that are in continual motion. These atoms emit the light because of the energy they create. Because the atoms emit energy they also emit heat, which makes them show up on thermal imaging.
The heat generated by the energy excites the atoms and they fire photos in the thermal-infrared spectrum and the hotter the object becomes, the shorter the infrared wavelength it emits. The photons emitted by the heated atom show up in the color spectrum as a glowing red, orange, yellow, blue and finally white. When using night vision through thermal imaging the infrared emissions are collected and dispersed.
The way thermal imaging night vision works is this:
- Through the use of a special lens, the infrared light is gathered from objects in the vicinity.
- The light gathered is focused, scanned by a phased array of infrared elements in a detector. The detector creates a detailed temperature array that is known as a thermogram. This information is gathered and disseminated in less than one-thirtieth of a second.
- The newly created thermogram is then translated into electric impulses and then sent to a unit that processes the impulses and the data is then visible for display
- After all of this information is gathered then translated it is sent to a display (which could be through night vision goggles or binoculars) and it appears as colors, which vary, depending on the heat intensity of the infrared emissions.
There are many types of thermal imaging devices scanning at a rate of 30 times a second, interpreting temperature changes that vary in range from -4 degrees Fahrenheit to 3,600 Fahrenheit. Temperature fluctuations as little as 0.4 degrees can be collected.
There are two common thermal-imaging technologies on the market: uncooled and cryogenically cooled. The uncooled device is the most commonly used and operates at room temperature. This technology is silent and activates as soon as darkness descends. Cryogenically cooled devices are susceptible to damage and are considerably more expensive. In a cryogenically cooled device, the internal elements are sealed in a container that keeps them at 32 degrees Fahrenheit. Cryogenically cooled night vision technology can sense differences as small as 0.2 degrees Fahrenheit from a distance of more than 1,000 feet away. They also have crystal clear resolution.
While thermal imaging is a useful and potentially lifesaving tool for use in detecting people or when having to work in absolute darkness, the night vision equipment on the market continues to utilize image-enhancement technology.