Night vision report page 3 of 7

There are two common types of thermal-imaging devices:

• Un-cooled - This is the most common type of thermal-imaging device. The infrared-detector elements are contained in a unit that operates at room temperature. This type of system is completely quiet, activates immediately and has the battery built right in.

• Cryogenically cooled - More expensive and more susceptible to damage from rugged use, these systems have the elements sealed inside a container that cools them to below 32 F (zero C). The advantage of such a system is the incredible resolution and sensitivity that result from cooling the elements. Cryogenically-cooled systems can "see" a difference as small as 0.2 F

(0.1 C) from more than 1,000 ft (300 m) away, which is enough to tell if a person is

holding a gun at that distance! While thermal imaging is great for detecting people or working in near-absolute

Generations

NVD Evolved from bulky optical instruments in lightweight goggles through the advancement of image intensification technology. Types of night vision Categorized by generations each substantial change NVT establishes a new generation Categorized into:

Generations	Invention Time	Uses
Generation 0	The earliest (1950's)	Created by US Army Uses active infrared.
Generation 1	1960's (Vietnam Era)	Uses passive infrared Uses ambient light provided by the moon and the stars.
Generation 2	late 1970s and early 1980s	Offer improved resolution and performance over Generation-1 devices.
Generation 3	1990	Uses the gallium arsenide (GaAs) photocathode and the ion-barrier Film on the MCP.
Generation 4	2000	Known as filmless and gated technology Shows significant improvement in both high- and low-level light environments.

Generation 0 - The earliest (1950's) night vision products were based on image conversion, rather than intensification. They required a source of invisible infrared (IR) light mounted on or near the device to illuminate the target area.

Generation 1 - The "starlight scopes" of the 1960's (Vietnam Era) have three image Intensifier tubes connected in a series. These systems are larger and heavier than Gen 2 and Gen 3. The Gen 1 image is clear at the center but may be distorted around the edges. (Low-cost Gen 1 imports are often mislabeled as a higher generation. Figure illustrates first-generation night vision. Incoming light is collimated by fiber optic plates before impacting a photocathode t which releases electrons, which in turn impact a phosphor screen. The excited screen emits green light into a second fiber optic plate, and the process is repeated. The complete process is repeated three times providing an overall gain of 10,000.