Humans have poor ability to see things in darkness. This is definitely because of absence of light in dark or during night time. Absence of light in darkness doesn’t mean complete absence of light but actually it is the absence of visible range of electromagnetic spectrum. Human eyes cannot detect Infrared and ultra violet light resulting in losing proper in darkness. While it is not the same in case of animals. Animals mainly nocturnal ones can see better even in the absence of light. This is due to the presence of more number of rods than the cones, the light sensing receptors in the eyes of animals compared to humans. Where rods can sense even small intensities of light. Another thing adding to their night vision is the tapetum lucidum, a layer behind the retina of eyes which reflects back the available light during night. Lacking proper vision during night time can be overcome with the advances in technology.
Types of night vision devices
As human eyes lack clear night vision it is necessary to develop artificial devices which help us see objects clearly in dark. Application of night vision technology is largely seen in a nations defence forces although it is applied in wildlife, investigation departments and for entertainment. Militaries without these cannot be imagined. As they strive for the nation day and night, these devices become their second eyes useful for efficient target of enemies. History of using night vision devices backs to the world war time where there are no advanced ones except night glasses. Advances in later technology paved way for the development of different night vision devices. The three different types of night vision devices available currently are cameras, night vision scopes, goggles. Night vision cameras can record images in dark and are to be fixed at one place where permanent observation during night times is desired. Scopes are portable hand-held, single eye piece devices. Goggles or binoculars are double eye piece, hand held, devices which can be held on head wearing like helmet.
Theseare broadly classified as different generations.Generation ‘0’ devices are designed to illuminate the target. The infrared source of light is passed on the target and the vacuum tube in the IR sensitive image intensifier accelerates the electrons between anode and cathode. Thus illuminating the object in dark and focuses on it. Generation ‘1’ devices don’t possess their own IR source but they work under moonlight. Generation ‘2’ devices are designed with microchannel plates replacing vacuum tubes. They work efficiently under low moon light. Generation ‘3’ devices are made for high resolution imaging. Generation ‘4’ are improved with auto gated power system. All these are developed using image intensification, illumination and thermal vision technologies.