Automatic Brightness Contract (ABC)
An Electronic feature which automatically reduces voltages to the micro channel plate to keep the image intensifier’s brightness within optimal limits, and protects the tube. The effect of this can be seen when rapidly changing from low light to high light conditions. The image gets brighter and then, after a momentary delay, suddenly dims to a constant level.
Auto Gated Power Supply
When you have a power supply that is Auto Gated, it means that the unit is turning itself off and on at a rapid rate.
Black spots are blemishes in the image intensifier. These can also be dirt, or dust between the lenses. If your image intensifier has black spots they do not affect the performance or reliability of your device. Black spots are apart of the manufacturing process. Every tube is different.
When you are looking at a bright light source the image of your night vision device will be loss. This is also known as “Halo”.
Bright Source Protection (BSP)
When your night vision device is exposed to a bright light source the BSP protects the intensifier from damage and enhances its lifespan.
The alignment of weapon-aiming device to the bore of the weapon.
Commercial spec tubes are tested and inspected by the OEM.
An patter of dark thin lines in the FOV either throughout the image area or in parts of the image area. Under worst case conditions, these lines will form hexagonal or square wave lines.
Equivalent Background Illumination (EBI)
This is the amount of light you see through a night vision device when an image tube is turned on but no light is on the photocathode. EBI is affected by temperature; the warmer the night vision device, the brighter the background illumination. EBI is measured in lumens per square centimeter (lm/cm2). The lower the value the better. The EBI level determines the lowest light level at which an image can be detected. Below this light level, objects will be masked by the EBI.
A steady or fluctuating pinpoint of bright light in the image area that does not go away when all light is blocked from the objective lens. The position of an emission point within the field of view will not move. If an emission point disappears or is only faintly visible when viewing under brighter nighttime conditions, it is not indicative of a problem. If the emission point remains bright under all lighting conditions, the system needs to be repaired. Do not confuse an emission point with a point of light source in the scene being viewed.
Field Of View
The diameter of the imaged area when viewed through an optic
Figure Of Merit
Image Intensification tube specification designation, calculated on line pair per mm x signal to noise.
Also called brightness gain or luminance gain. This is the number of times a night vision device amplifies light input. It is usually measured as tube gain and system gain. Tube gain is measured as the light output (in fL) divided by the light input (in fc). This figure is usually expressed in values of tens of thousands. If tube gain is pushed too high, the tube will be “noisier” and the signal-to-noise ration many go down. U.S. military Gen 3 image tubes operate at gains of between 20,000 and 45,000. On the other hand, system gain is measured as the light output (fL) divided by the light input (also fL) and is what the user actually sees. System gain is usually seen in the thousands. U.S. military systems operate at 2,000 to 3,000. In any night vision system, the tube gain is reduced by the system’s lenses and is affected by the quality of the optics or any filters. Therefore, system gain is a more important measurement to the user.
The semiconductor material used in manufacturing the Gen 3 photocathode. GaAs photocathodes have a very high photosensitivity in the spectral region of about 450 to 950 nanometers (visible and near-infrared region).
Two technologies are referenced as night vision; image intensification and thermal imaging (see definitions). Because of cost and the fact that image intensifier scenes are easier to interpret than thermal (thermal images show targets as black or white – depending upon temperature – making it more difficult to recognize objects), the most widely used night vision aid in law enforcement is image intensification (l²) equipment. To date, there have been four generations of l² devices, identified as Gen 0, Gen 1, Gen 2, and Gen 3. Developmental laboratory work is on going, and the U.S. military may designate the resulting as Gen 4. However, no definition for Gen 4 presently exists.
Halo is the circular region around a bright light that appears “brighter” – It’s caused by elastic collisions of electrons with the MCP surface which subsequently then bounce off and down another hole. Halo’s are the same size all over the screen and the size is dictated by the distance between the photocathode and the MCP. Basically, it’s the round circle around lights when you look at them with Night Vision and it’s generally used as an indication that you’re looking at something that’s too bright.
The distance between the user’s pupils (eyeball centers). The 95th percentile of US military personnel falls within the 55 to 72mm range of IPD.
Many night vision devices incorporate a built-in infrared (IR) diode that emits invisible light or the illuminator can be mounted on to it as a separate component. The unaided eye cannot see IR light; therefore, a night vision device is necessary to see this light. IR Illuminators provide supplemental infrared illumination of an appropriate wavelength, typically in a range of wavelengths (e.g. 730nm, 830nm, 920nm), and eliminate the variability of available ambient light, but also allow the observer to illuminate only specific areas of interest while eliminating shadows and enhancing image contrast.
ITAR represents a set of US Government regulations that control the export of defense-related materials, articles, and services on the United States Munitions List. These regulations implement the provisions of the Arms Export Control Act, and are described in Title 22 (Foreign Relations), Chapter I (Department of State), Subchapter M of the Code of Federal Regulations. The Department of State Interprets and enforces ITAR. Its goal is to safeguard US National Security and further US Foreign Policy objectives. Basically, ITAR dictates that any defense related items (including Night Vision Equipment and IR Equipment) cannot be exported from the United States in any way, without express permission from the US Department of State. Failing to follow ITAR will result in felony charges which can lead to heavy fines and/or prison sentences.
Units used to measure image intensifier resolution. Usually determined from a 1951 U.S. Air Force Resolving Power Test Target. The target is a series of different-sized patterns composed of three horizontal and three vertical lines. A user must be able to distinguish all the horizontal and vertical lines and the spaces between them. Typically, the higher the line pair, the better the image resolution. Generation 3 tubes generally have a range of 64 – 72 lp/mm, although line pair measurement does not indicate the generation of the tube. Some Generation 2+ tubes measure 28-38 lp/mm, (Gen 2 SHP at 54-59 lp/mm typically), while a Generation 1+ tube may have measure at 40 lp/mm.
A metal-coated glass disk that multiplies the electrons produced by the photocathode. An MCP is found only in Gen 2 or Gen 3 systems. MCPs eliminate the distortion characteristic of Gen 0 and Gen 1 systems. The number of holes (channels) in an MCP is a major factor in determining resolution. ITT Industries’ MCPs have 10.6 million holes or channels compared to the previous standard of 3.14 million
Signal To Noise Ratio
A measure of the light signal reaching the eye divided by the perceived noise as seen by the eye. A tube’s SNR determines the low light resolution of the image tube; therefore, the higher the SNR, the better the ability of the tube to resolve objects with good contrast under low-light conditions. Because SNR is directly related to the photocathode’s sensitivity and also accounts for phosphor efficiency and MCP operating voltage, it is the best single indicator of an image intensifier’s performance
Also known as electronic noise. A faint, random, sparkling effect throughout the image area. Scintillation is a normal characteristic of Microchannel plate image intensifiers and is more pronounced under low-light-level conditions
Variable Gain Control
Allows the user to manually adjust the gain control ( basically like a dim control ) in varying light conditions. This feature sets the PVS-14 apart from other popular monoculars that do not offer this feature.