* NOTE: Non-inverting image intensifiers that use microchannel plates and clear glass for the optics are free of distortion. The 2nd Gen. image intensifiers that Russians make are distortion free, since they do not have fiberoptics twister.
Divergence – is the shifting of an observer's eyes outward.
Electronic Noise – also known as Scintillation, is 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

Emission Point - is 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.

Equivalent Background Illumination (EBI) - is the amount you see in an image tube that is turned on but there is no light at all on the photocathode; it is affected by temperature where the warmer night-vision device, the brighter the background illumination. EBI is measured in lumens per square centimeter (lm/cm2) wherein the lower the value the better. The EBI level determines the lowest light level at which you can detect something. Below this light level, objects will be masked by the EBI.

Eye Relief - is the distance your eyes must be from the last element of the eyepiece in order to achieve the optimal image area.

Eyepiece Lens - focuses the image from the fiber optic inverter on to the eye by adjusting for individual eye acuity. There are two eyepiece lens assemblies in current systems; the 15 mm and the 25 mm eyepiece lens assembly. Tests show the larger eyepiece is more effective. This lens assembly is designed to provide some adjustment for the user to compensate for minor vision deficiencies (i.e. diopter adjustment). However, the assembly does not correct for all eye deficiencies and does not replace the need for wearing prescribed spectacles or contact lenses.

Exit Pupil - in an optical system, the rays of light passing through the system will be limited by either the edges of one of the components such as the eyepiece lens, or by an internal aperture. The image passing through the entrance side of the optical system is the entrance pupil. The image passing out the exit side is the exit pupil. This image forms a small disk containing all of the light collected by the optics from the entire field-of-view.

Field-of-View (FOV) - sometimes called the angle of coverage or angle of view, is the diameter of the imaged area when viewed through an optic. It is the area in the eyepiece of an optical instrument in which the image is visible.

Figure of Merit (FOM) - is an image intensification tube specification designation, calculated on line pair per mm x signal to noise.

Fixed Pattern Noise (FPN) - is a faint hexagonal (honeycomb) pattern throughout the image area that most often occurs under high-light conditions. This pattern is inherent in the structure of the microchannel plate and can be seen in virtually all Gen II and Gen III systems if the light level is high enough.

Focal length - is the distance from the optical center of a lens (or, the secondary principal point for a complex lens like a camera lens) to the focal point (sensor) when the lens is focused on an object at infinity. It's a primary physical characteristic of a lens which can be measured in an optical lab. It remains the same no matter what camera the lens is mounted on. A 7mm focal length lens is always a 7mm focal length lens and a 300mm focal length lens is always a 300mm focal length lens.

Gain - is 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 or system gain. Tube gain is measured as the light output divided by the light input. This figure is usually seen in values of tens of thousands. If tube gain is pushed too high, the tube will be "noisier" and the signal-to-noise ratio may go down. On the other hand system gain is measured as light output divided by the light input and is what the user actually sees. System gain is usually seen in the thousands. In any night vision device, 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.

Gallium Arsenide (GaAs) - is the semiconductor material used in manufacturing of the Gen III photocathode. GaAs photocathodes have a very high photosensitivity in the spectral region of about 450 to 950 nanometers (visible and near-infrared region).

Highlight Shutoff - an image intensifier protection feature incorporating a sensor, microprocessor and circuit breaker. This feature will turn the system off during periods of extreme bright light conditions.

Image Disparity - may exist when there is a difference in brightness between the two image intensifier assemblies within the same binocular.

Infra-Red Illuminators - All Starlight scopes need some light to amplify. This means that if you were in complete darkness you could not see. Due to this AMT corporation built in infra-red illuminator (IRI) on all of their scopes. Basically what an IRI does is throw out a beam of infra-red light that is near invisible to the naked eye but your NVD can see it. Allowing you to use your scope even in total darkness. The IRI works like a flashlight and the distance you can see with it will be limited. AMT corporation uses the most powerful eye-safe illuminator on the market. This allows their IRI to extend to 100 yards. However, because of the power at a short distance the IRI may cover only 40-60% of the viewing area.

Interpupillary Adjustment - is the distance between the user's eyes (pupils) and the adjustment of binocular optics to adjust for differences in individuals. Improperly adjusted binoculars will display a scene that appears egg-shaped or as a reclining figure-8.

Interpupillary Distance (IPD) - is the distance between the user's pupils (eyeball centres). The 95th percentile of US military personnel falls within the 55 to 72mm range of IPD.

IR Laser - are high-power devices providing long-range illumination capability. Ranges of several thousand meters are common. Most are not eye-safe and are restricted in use. Each IR laser should be marked with a warning label.

Light Interface Filter (LIF) - is an optical filter that protects the NVG device and its user from some laser hazards by the LIF. The LIF’s, if installed, are mounted on an adapter attached to the end of the objective lens.

Light-Secure Eyeguard (Shuttered Eyeguard) - is a rubber eyecup fitted to an eyepiece of a night vision device that incorporates a shutter that closes when not depressed by the user's eye. Prevents face glow that can compromise the user's location

Line Pairs per Millimetre (lp/mm) - are units used to measure image intensifier resolution. Usually determined from a 1951 Air Force Resolving Power test target. The target is a series of different sized patterns composed of three horizontal and three vertical lines. The lines and spacing between lines in each of the different patterns differ in width; the narrower the width, the greater the resolution is needed to distinguish the lines in a given pattern. Human test subjects must be able to clearly distinguish all the horizontal and vertical lines of a particular pattern in order for an image intensifier to achieve the resolution represented by that pattern.

Luminance Gain - is the ability of a tube or a system to amplify the light it detects. The higher number will be the better the luminance gain.

Magnification - is the magnifying power of the lens. Four power (4X) indicates that the image will appear four times larger than if viewed with a 1X lens.

Microchannel Plate (MCP) - is a metal-coated glass disk that multiplies the electrons produced by the photocathode. An MCP is found only in Gen II and Gen III systems. These devices normally have anywhere from 2 to 6 million holes (or channels) in them. Electrons entering a channel strike the wall and knock off additional electrons which in turn knock off more electrons producing a cascading effect. MCP's eliminate the distortion characteristic of Gen 0 and Gen I systems. The number of holes in an MCP is a major factor in determining resolution.

MILSPEC - is a term for Military Specification. It is the minimum acceptable requirements for products procured by the US Department of Defense. Use of the term MILSPEC indicates that the product meets applicable military specifications.

Minute of Angle (M.O.A) - is angular unit of measurement which is approximately 1.1" at 100 yards. 1/60th part of a degree, the unit of measure used in defining the click adjustments on a rifle scope. Minute of angle translates almost exactly to one inch at 100 yards, to two inches at 200 yards and three inches at 300 yards.

Near-Infrared - is the shortest wavelengths of the infrared region, normally 750 to 2,500 nanometers (nm). GEN II operates from around 440 to 950 nanometers.

Objective Lens - the objective lens assembly collects the available light energy and focuses it on the photocathode (front end of the image intensifier tube). It is housed in
an assembly that is used for distance focusing. A coating is placed on the inside portion of the lens that filters out specific wavelengths, thus allowing the use of properly
modified interior lighting.

Optical coatings - reduce reflection both internally and externally and thereby increase the amount of light that reaches the eye which improves brightness and contrast. Below are the types of coatings:

Output Brightness Variation - This condition is evidenced by areas of varying brightness in or across the image area. The lower contrasts do not exhibit distinct lines of
demarcation nor do they degrade image quality. This condition should not be confused with shading.

Photocathode - is the input surface to an image intensifier that absorbs light energy and in turn releases electrical energy in the form of an electron image. The type of material used in a distinguishing characteristic of the different generations of image intensifiers.

Photocathode Response - also called photosensitivity, is the ability of the image tube to detect light under very dark conditions and convert that low light level into an image that you can see. The higher the numerical value, the better the ability to produce a visible image under darker conditions.

Resolution - is the ability of an image intensifier or night vision system to distinguish between objects close together. Image intensifier resolution is measured in line pairs per millimiter (lp/mm) while system resolution is measured in cycles per miliradian. For any particular night vision system, the image intensifier resolution will remain constant while the system resolution can be affected by altering the objective or eyepiece optics by adding magnification or relay lenses. Often the resolution in the same night vision device is very different when measured at the center of the image and at the periphery of the image. This is especially important for devices selected for photograph or video where the entire image resolution is important.

Reticle (Reticle Pattern) - is an adjustable aiming point or pattern (i.e. crosshair) located within an optical weapon sight

Signal-to-Noise Ratio - is the computed ratio of measured data from photosensitivity, gain, and resolution. The higher the ratio, the better the ability of the tube to produce a clear image under very dark conditions.

Scintillation - also known as electronic noise, is 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

Screen- is the image tube output that produces the viewable image. Phosphor (P) is used on the inside surface of the screen to produce the glow, thus producing the picture. Different phosphors are used in image intensifier tubes, depending on manufacturer and tube generation. P-20 phosphor is used in the systems offered in this catalogue

System Gain- is equal to tube gain minus losses induced by system components such as lenses, beam splitters and filter.

Weaver Mounting System - is a US weapon mounting system used for attaching sighting devices to weapons. A Weaver Rail is a weapon-unique notched metal rail designed to receive a mating throw-lever or Weaver Squeezer attached to the sighting device.

Windage - The left to right adjustment on the reticle.

Zeroing - is a method of boresighting an aiming device to a weapon and adjusting to compensate for projectile characteristics at known distances.