Optics 101

Night Vision Goggles - How Night Vision Goggles Work

Night vision devices or NVDs provides an individual the ability to maneuver and see at night and during times when the visibility is poor.

Types of Night Vision Devices
What is Night Vision Goggles and How Does it Work
Night Vision Goggles - The Phosphor Screen
The Evolution of Night Vision Industry

Types of Night Vision Devices

Two different types of night vision devices are currently available. The first type of night vision devices relies on a difference in temperature between the surrounding environment and the object. These types of devices are commonly referred to as Forward-Looking Infrared (FLIR) and they are currently installed on various combat aircrafts. The second type of night vision devices use light amplification and must rely on the presence of a small amount of light. Night vision goggles are a common example of night vision devices that uses light amplification.

What is Night Vision Goggles and How Does it Work

Night vision goggles are a type of electro-optical devices which amplifies existing light rather than using its own light source. Ambient light such as the moon and stars are captured with the use of an image intensifier and using electronic means, the light is then intensified thousands of times to generate an image which is then displayed on a phosphor display similar to those used in night vision goggles.

As the ambient light travels through the objective lens of the night vision goggles, it encounters a photo cathode driven by a high energy charge. This energy charged light then speed across a vacuum situated inside the intensifier where it comes into contact with a phosphor screen to produce a focused image. This image then gets magnified by the eyepiece.

Night Vision Goggles

Night Vision Goggles - The Phosphor Screen

The phosphor screen inside the night vision goggles is intentionally designed to be colored green, given that the human eye can distinguish larger variations of green than other phosphor colors.

Through Night Vision Goggles

The Evolution of Night Vision Industry

Over the past 40 years, the night vision industry has undergone three generations of development. As a result of the evolution in the night vision industry, an improvement in the life expectancy of the intensifier tubes as well as the amplification power has been achieved.

Generation I – Generation I night vision devices does not have the required light amplification and sensitivity to see below full moonlight. The light amplification power is approximately 1000. Consequently, these systems were relatively poor low light imagers. Generation I image intensifier tubes has an operating life expectancy of about 2000 hours.

Generation II – The birth of Generation II night vision devices was the result of the development of Microchannel Plate. The operating life expectancy of Generation II image intensifier tubes has increased to a maximum of 4000 hours. The light amplification power has also increased from 1000 to 20,000.

Generation III - The state-of-the-art night vision devices with a light amplification power of 30,000 times. Generation III night vision devices utilizes a Gallium Arsenide photocathode that stretches into the near-infrared region. Ongoing advancements in the night vision industry have increased the operating life expectancy of Generation III image intensifier tubes to 10,000 hours.

Source: AZoOptics

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