- Automatic Brightness Control (ABC)
An electronic function that protects the tube and intensifier and automatically reduces voltages to the microchannel plate to maintain the brightness of the image intensifier within optimal limits. - Diopter
A unit of measurement used to define the correction of the eye or the refractive power of a lens. Most night vision/thermal vision systems provide a range of diopters from +2 to -6. - Electronic Noise
A weak, random, flickering effect throughout the image area. Flicker is a normal characteristic of microchannel plate image intensifiers and is more pronounced in low-light conditions. - Field of View (FOV)
The spatial angle of the scene that can be viewed through the intensifier tubes and measured laterally and vertically. - Gain (in thermal vision) Used to optimize the device’s performance based on environmental conditions. Environments where all objects have a similar temperature require higher gain to produce the best image quality.
- Infrared (IR) Illuminators IR
illuminators provide additional infrared illumination of appropriate wavelength, typically in a range of wavelengths (e.g., 730 nm, 830 nm, 920 nm), and eliminate the instability of available ambient light, allowing the observer to illuminate only areas of interest. - Infrared (IR)
Laser High-power devices that provide long-range illumination capabilities. - Interpupillary Distance (IPD)
The distance between the observer’s pupils. It typically ranges from 55 to 72 mm. - IR Screen
A very thin layer of phosphor applied to the fiber optic output system that emits light when struck by electrons. The purpose of the phosphor screen is to convert electrons into photons. - Lp/mm (Line Pairs per Millimeter)
Units used to measure the resolution of the image intensifier. The target is a series of patterns of different sizes 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. Generally, the higher the line pairs, the better the image resolution. - Microchannel Plate (MCP)
A glass disc coated with metal that multiplies the electrons produced by the photocathode. An MCP is only found in Gen 2 or Gen 3 systems. MCPs eliminate the characteristic distortion of Gen 0 and Gen 1 systems. The number of holes (channels) in an MCP is an important factor in determining resolution (typical channel range is between 3 and 10 million). - Non-Uniformity Correction (NUC)
One of the less desirable characteristics of modern FPA detectors is their relative non-uniformity from detector to detector. To correct this issue, all thermal vision systems have the NUC system. The methods for correcting this issue vary significantly from manufacturer to manufacturer. - Photocathode
The input surface of an image intensifier tube that absorbs light energy (photons) and in turn releases electrical energy (electrons) as an image. The type of material used is a distinguishing feature of different generations. - Pixel
The smallest resolvable area in which an average brightness value is determined and used to represent that portion of the image. Pixels are arranged in a rectangular matrix to form a complete image. - Resolution (of an image intensifier tube)
The ability of a night vision system to distinguish between closely spaced objects. The resolution of the image intensifier is measured in line pairs per millimeter (lp/mm), while the system’s resolution is measured in cycles per milliradian. - Signal-to-Noise Ratio (SNR)
A measure of the light signal reaching the eye divided by the perceived noise as seen by the eye. The SNR of a tube determines the resolution under low light conditions of the image tube; therefore, the higher the SNR, the better the tube’s ability to resolve objects with good contrast in low light conditions. - Thermal Sensitivity
The quantitative description of how well a thermal device distinguishes temperature differences. It is expressed in mK (milliKelvin or one-thousandth of a Kelvin). The typical value for FPA sensitivity is 50 mK, which means the detector can differentiate objects if the difference in their surface temperatures is 50 mK or greater, for example, 11.95°C and 12°C. - Unifomity Correction (NUC)
One of the less desirable characteristics of modern FPA detectors is their relative non-uniformity from detector to detector. To correct this issue, all thermal vision systems have the NUC system. The methods for correcting this issue vary significantly from manufacturer to manufacturer. - Zoom (Optical and Digital)
Optical zoom is directly related to the focal length of the lens. Magnification with optical zoom results in a smaller field of view while maintaining image quality. Digital zoom, on the other hand, is purely pixel-based. When digital zoom is used, it digitally enlarges the pixels of an image. This results in a more blurred image (also known as more “pixelated”) compared to optical zoom.