A military invention, night vision goggles are a device which allows one to literally see in the dark. People usually think that the technology is too complex for them to understand, thus they give up on buying this tool. However, the NV technology can be understood when simplified, which is the purpose of writing this article. You should know everything there is to know before you opt for purchasing them for your personal use.
Original vs. Modern
The first night vision devices (also known as Image Intensifiers) were active Infrared devices, which were ineffective and rather bulky Both sides developed them in World War II. The first passive Image Intensifying devices were developed during the war in Vietnam, because the active ones had one major disadvantage – when the IR source is turned off, both sides could see each other.
Modern night vision goggles, binoculars, bi-oculars and monoculars transform a dark night time scene into a bright one by amplifying available ambient light levels. Thus, we are able to recognize objects and features that would otherwise remain behind the dark curtain of night.
How Does It Work?
The device will work only if there is some light available to be intensified. Light enters the NV device through the objective lens where it is focused onto a phosphor screen. The human eye is particularly sensitive to variances in shades of green, and the phosphor screen translates the image into a green picture.
Under conditions of total darkness (such as a dense forest on a cloudy night, in completely blacked buildings and caves, etc.), night vision scope cannot function properly, unless the user actively supplies some amount of light to assist the scope. This is done with invisible Infrared light which is invisible to the naked eye, unlike ordinary white light. The scope can then generate a clear and bright image, because the IR light illuminates the scene sufficiently. All civilian night vision devices have a built-in IR illuminator to enhance the image clarity or for use in conditions with no light.
Types of NVDs
There are 2 different ways in which light can reach you: it can be emitted directly and can be reflected indirectly. According to this, NVDs are categorized into 2 groups – thermal and enhanced.
Thermal devices utilize heat given off by the observed object. Hotter objects emit more infrared radiation and thermal NVDs can convert that radiation into light. In other words, what they see are extremely precise temperature differences. Thermal devices are used for performing house mold-inspection because one can see the moisture inside of walls (the temperature is relative to the warmer temperature of the wall).
Enhancement devices utilize reflected light from another source. These devices are able to gather small amounts of light and enhance (or multiply) it. For example, the starlight scope is an enhancement device that uses the tiny amount of light (emitted by the stars) that is indirectly reflected off ground, walls and other surfaces. This group of NVDs is where you find night vision goggles for a wide range of budgets.
Optical devices are categorized into Generations 1-4. They rely on optics (lenses) to collect the reflected light, and then enhance it in an intensifier-tube.
Digital devices have the sensitive materials and intensifier-tubes replaced with LCDs and electronics. Impressive advancements have been made in the use of digital computer electronics as enhancement devices, and there is room for future developments and faster breakthroughs.
Before buying night vision goggles, check out some reliable night vision goggles review articles, and consider several factors such as:
Price – the use must justify the expense.
Batteries – the devices are powered by lithium or alkaline batteries, so consider the cost of replacing them.
Size, weight, ease of operation – the device will become more of a burden of it is not easy to operate, not comfortable to hold, or not mobile enough for its purpose.
When selecting night vision goggles, pay attention to:
Gain - the number of times that the device amplifies the level of ambient light.
Magnification – Higher magnification does not always mean better picture. The amount of light is usually reduced when you increase magnification, and your unit’s effective range depends on a combination of magnification, resolution, gain, and available light.
Resolution – the factor that enables us to make out details on objects and distinguish the line and shape of objects that are close to each other. It is expressed in lp/mm (line pairs per millimeter).
The best way to make a right choice is to evaluate your potential night vision goggles under the conditions you plan to use them in and follow these performance factors. Modern NVDs are extremely reliable, provided that they’re not exposed to violent treatment, bright light, or excessive moisture. They’re covered by a minimum of one-year warranty subject to responsible and correct use.