Prismatic, viewfinder, monocular, glasses, what is the Night Vision device that best suits my needs?
We measure the intensity of light in a place in lux. On a sunny day, you can measure 10,000 lux, in an office 500 lux, a clear sunset 100 lux and the lighting of the population drops to a mere 10 lux. With this light, it is already difficult to see colours well. A full moon goes down to 0.1 lux (there are no more colours), and a starry night is just 0.001 lux. In developed countries, only the most remote places have less light. With the use of the thermal scope for rifle recently, the options are coming with the best choices for the hunters.
The Channeling of Lights
Light is tiny particles of energy called photons. The less is the light. The less are the photons. The human eye can adapt to very low light conditions if it gets used to it, even if it takes more than half an hour. A person from the city, who always lives, surrounded by artificial light, can lose that ability.
When it gets dark, there comes a time when the eye needs help. In developed areas with large populations nearby, good quality binoculars and large optics, such as 7 × 50 or 8 × 56, enlarge objects and make them visible.
Below this, a night viewer is necessary
Equipment with an intensifier tube can capture those few photons that are no longer useful to the eye, including those of infrared light that constitute 70% of that of stars.
It is advisable to carry some type of IR illuminator to help the equipment if the light that remains is not enough. However, most of the time, the valuable range of Gen 1 / Super Gen 1+ and Gen 2 devices will barely reach 50 meters with near-infrared (800-850nm) and look like a red dot when viewed from the front.
The Intensifying Tube
The night vision goggles are (optical and electronic boards) “optoelectronic” devices that intensify or amplify light. The “soul” of the equipment is the Image Intensifier, a high vacuum tube.
The front optics collects light and concentrates it in the front part of the tube where a photocathode converts photons (light energy) into electrons (electrically charged particles) that are amplified and projected onto a phosphor screen at the back that emits the visible light that we see. The projected image corresponds to the input image.
The phosphor used is green because it is the colour in which the human eye distinguishes more different shades and tires less than with other colours. Grey tubes are an expensive fad.The number of times the equipment amplifies the light is called gain and depends on the ability of the photocathode to convert the weakest photons into electrons and on the ability to accelerate these electrons against the phosphor screen. With a given photocathode, more sensitivity means brighter but not necessarily better seeing. Too much gain usually means more “noise”, lower contrast.The buyer of night vision equipment should look at the total profit. Bad optics can ruin the best tube.