- 千歲Lv 51 十年前最愛解答
Night Vision Monocular is created under biological and physical concepts
Night vision is the ability to see, whether through biological or technological means, in a dark environment. Most instances, whether biological or technological, use a combination of two approaches: enhanced spectral range, and enhanced intensity range.
Enhanced spectral range
Enhanced spectral range techniques make the viewer sensitive to types of light that would be invisible to a human observer. Human vision is confined to a small portion of the electromagnetic spectrum called visible light. Enhanced spectral range allows the viewer to take advantage of non-visible sources of electromagnetic radiation (such as near-infrared or UV radiation).
Enhanced intensity range
Enhanced intensity range is simply the ability to see with very small quantities of light. Although the human visual system can, in theory, detect single photons under ideal conditions, the neurological noise filters limit sensitivity to a few tens of photons, even in ideal conditions. Some animals have evolved better night vision through the use of a larger optical aperture, improved retina composition that can detect weaker light over a larger spectral range, more photoefficient optics in the eye, and improved neurological filtering which is more tolerant of noise. Enhanced intensity range is achieved via technological means through the use of an image intensifier, gain multiplication CCD, or other very low-noise and high-sensitivity array of photodetectors.
Biological night vision
In biological night vision, molecules of rhodopsin in the rods of the eye undergo a change in shape as light is absorbed by them. The peak rhodopsin build-up time for optimal night vision in humans is 30 minutes. Rhodopsin in the human rods is insensitive to the longer red wavelengths of light, so many people use red light to preserve night vision as it will not deplete the eye's rhodopsin stores in the rods and instead is viewed by the cones.
Night glasses are telescopes or binoculars with a large diameter objective. Large lenses can gather and concentrate light, thus intensifying light with purely optical means and enabling the user to see better in the dark than with naked eye alone. Often night glasses also have a fairly large exit pupil of 7 mm or more to let all gathered light into the user's eye. However, many people can't take advantage of this because of the limited dilation of the human pupil. To overcome this, soldiers were sometimes issued atropine eyedrops to dilate pupils. Before the introduction of image intensifiers, night glasses were the only method of night vision, and thus were widely utilised, especially at sea.
Far infrared, or thermal, sensing is generally not considered night vision because it is constructed with mechanisms substantially different from the methods used to sense visible light. It is possible to construct an imaging device with microwave energy, sound, or any other signal that is reflected or radiated by objects and can be focused and sensed, but these are also not generally considered night-vision.
Night vision goggles
Night vision goggles typically use an image intensifier to convert weak light from the visible and near-infrared spectrum to visible light. Most night vision goggles display a green image, because the peak sensitivity of human color vision is around 555 nm. Some however, may use a black and white image.