Night vision devices gather existing ambient light (starlight, moonlight or infra-red light) through the front lens. This light, which is made up of photons goes into a photocathode tube that changes the photons to electrons. The electrons are then amplified to a much greater number through an electrical and chemical process. The electrons are then hurled against a phosphorus screen that changes the amplified electrons back into visible light that you see through the eyepiece. The image will now be a clear green-hued amplified re-creation of the scene you were observing. FIRST, SECOND, THIRD AND FOURTH GENERATION A Night Vision Device can be either a 1st, 2nd, 3rd or 4th generation unit. What this stands for is what type of light intensifier tube is used for that particular device The light intensifier tube is the heart and soul of an NVD. 1st generation is currently the most popular type of night vision in the world. Utilizing the basic principles described earlier, a 1st generation will amplify the existing light several thousand times letting you clearly see in the dark. These units provide a bright and sharp image at a low cost, which is perfect, whether you are boating, observing wildlife, or providing security for your home. You may notice the following when you are looking through a 1st gen unit A slight high-pitched whine when the unit is on. The image you see may be slightly blurry around the edges. This is known as Geometric Distortion. When you turn a 1st gen off it may glow green for some time. These are inherent characteristics of a 1st gen and are normal. 2nd generation is primarily used by law enforcement or for professional applications. This is because the cost of a 2nd gen unit is approximately $500.00 to $1000.00 more then a 1st gen. The main difference between a 1st and a 2nd generation unit is the addition of a micro-channel plate, commonly referred to as a MCP. The MCP works as an electron amplifier and is placed directly behind the photocathode. The MCP consists of millions of short parallel glass tubes. When the electrons pass through these short tubes, thousands more electrons are released. This extra process allows 2nd generation units to amplify the light many more times then 1st generation giving you a brighter and sharper image. 3rd generation By adding a sensitive chemical, gallium arsenide to the photocathode a brighter and sharper image was achieved over 2nd generation. An ion barrier film was also added to increase tube life. Gen. 3 provides the user with good to excellent low light performance. 4th Generation / Gated Filmless tubes: 4th generation / Gated Filmless technology represents the biggest technological breakthrough in image intensification of the past 10 years. By removing the ion barrier film and Gating the system Gen 4 demonstrates substantial increases in target detection range and resolution, particularly at extremely low light levels. The use of filmless technology and auto-gated power supply in 4th generation image intensifiers result in: Up to 100% improvement in photoresponse. Superb performance in extremely low light level (better S/N and EBI) At least triple high light level resolution (a minimum of 36 lp/mm compared to 12 lp/mm) With significant improvement in contrast level and in performance under all light conditions, 4th generation represents the top of the line performance in the night vision market. Note: The term 4th generation is used/accepted among Night Vision manufactures to describe gated filmless tubes. However, this designation is widely debated and is currently referred to as Filmless & Gated image intensifiers by the US Military. Gen 4 technology improves night operational effectiveness for military users of night vision goggles and other night vision devices. The filmless MCP provides a higher signal-to-noise ratio than Gen 3, resulting in better image quality (less scintillation) under low-light conditions. The gated power supply further improves image resolution under high light conditions, and the reduced halo minimizes interference from bright light sources. These improvements also substantially increase the detection range of the systems.

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