Glossary
Automatic Brightness Control (ABC)
- An electronic feature that automatically reduces voltages to the Microchannel Plate (MCP) to keep the image intensifier’s brightness within optimal limits and protects the tube.
- The viewing a scene through two eyepieces.
- Cosmetic blemishes found in image intensifiers. Black spots in the image intensifier do not affect the performance or reliability of the device and are inherent in the manufacturing process.
- The momentary loss of the night vision image due to intensifier tube saturation by a bright light source. When bright light enters an I2 , the entire scene becomes much brighter, "whiting out" objects within the Field of View (FOV).
Bright-Source Protection (BSP) – Highlight Cut-Off
- The electronic function that reduces the voltage to the photocathode when an I2 device is exposed to bright light sources. Protects the image tube from damage and enhances its life.
- An inherent pattern which under proper lighting conditions, can be seen as an evenly spread hexagonal pattern.
Collimation
- The process in which light rays are made parallel through optical devices so that diverging/converging rays don't affect image perceptibility at further distances.
- C-mount lenses have a 1-inch mount diameter with a thread pitch of 32 threads per inch and focus 17.5 millimeters behind the rear lens element.
Commercial Specification (COMSPEC)
- Term used to describe image tube quality, testing, and inspection performed by the original equipment manufacturer (OEM).
- The lens cover, usually made of soft plastic or rubber, with a pinhole that allows a small amount of light to enter the objective lens of a night vision device.
- The glass filter assembly designed to fit over the objective lens of a night vision device. The filter reduces light input to a safe level, and allows safe extended daytime use of the night vision device for training purposes
Diopter
- The unit of measurement used to define eye correction or the refractive power of a lens. Adjustments to an optical eyepiece accommodate for differences in individual eyesight.
Distortion
- The undesirable change in the shape of an image resulting from imperfections in the optical or electronic components.
- A defective glow near the outside of the image intensifier FOV.
Emissivity
- The physical property of a material to absorb and release heat energy. Emissivity is a dimensionless quantity between 0 and 1. High emitting surfaces are also good radiators and absorbers.
Equivalent Background Illumination (EBI)
- The amount of light, measured in lumens per square centimeter, as seen when an I2 device is operating with no external light input. EBI varies with the temperature of an I2 ; the warmer the I2 , the brighter the background illumination.
- The distance between the user’s eye and the eyepiece lens of an optical device at which the viewed scene can be clearly seen.
Eye Box
- The distance which a user can move left/right or up/down when looking through an optical device in which the viewed scene can be clearly seen.
- The size of the area that can be seen while looking through an optical device.
- An Image Intensifier specification calculation which is the product of line pair per mm x signal to noise ratio. One measurement of an imaging tubes efficacy.
- The amount of times a night vision device amplifies environmental light. Gain control is available on some night vision devices that enables the user adjust this setting based on the amount of available light.
- Material used in the Gen 3 night vision devices.
- Occurs when looking at lights through night vision devices. A bright ring around the light further obscuring the perceptible image.
- An image intensifier protection feature that turns the system off during periods of extreme bright light conditions.
Image Intensification (l²)
- A vacuum tube that amplifies the amount of light from the objective lens (input) that creates a perceptible image at the ocular lens (output).
Infrared (IR)
- Light just outside the visible range that is imperceptible by the human eye due to its longer wavelength.
- The equivalent of a flashlight build into IR devices that produces light in the infrared range in order to break through photonic barriers that would otherwise make objective unidentifiable.
- Used in conjunction with a Infrared Illuminator as the actually Point of Aim (POA) for ballistic impacts.
- The distance when measuring two central points between eyes.
Light-Secure Eyeguard (Shuttered Eyeguard)
- The 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, thus preventing face glow that can compromise the user’s location.
Lux
- A derived unit based on lumen, and lumen is a derived unit based on candela. One lux is roughly equivalent to a totally overcast day and 0.00001 lux is roughly equivalent to a totally overcast night with no moonlight
Microchannel Plate (MCP)
- The metal-coated glass disk that multiplies the electrons produced by the photocathode. Found only in Gen 2 and Gen 3 image intensifier systems, the MCP typically has between 2 and 6 million holes (or channels).
Military Specifications (MILSPEC)
- The minimum acceptable requirements for products procured by the U.S. Department of Defense. Use of the term MILSPEC indicates that the product meets applicable military specifications
- A device consisting of a single-eyepiece. Image intensifier monoculars are also known as pocket scopes.
- The input surface of an image intensifier tube that absorbs light energy (photons) and in turn releases electrical energy (electrons) in the form of an image.
- The photocathode sensitivity is a measure of how well the image intensifier tube converts light into an electronic signal so it can be amplified.
- The term resolution is used to express the level of detail that can be captured by a sensor, camera imager, or camera, or displayed by a video monitor. Resolution applies to the horizontal, vertical, and color characteristics of the details in an image.
- The faint, random, sparkling effect throughout the image area, also known as electronic noise. Scintillation is a normal characteristic of an image intensifier device.
- A measurable level of the signal versus the background noise. The strength of the signal carrying circuit, expressed in decibels.