Nanometer: One billionth of a meter (10-9 m), often written as nm.
Nanosecond: One billionth of a second (10-9 s), often written as ns.
Narcissus Effect: The effect where the detector images itself through reflection off a window in front of it.
NEP: Acronym for Noise Equivalent Power, this is a system performance metric that combines all noise sources in the system into one value that would yield a signal to noise ratio of one.
NFOV: Acronym for Narrow Field of View, this describes the lens position in a multi-field of view system that gives the narrowest field of view, and therefore, the highest magnification.
NIR: Acronym for Near Infrared, the spectral region from about 0.8 to 2.5 microns where some imaging systems operate. Most systems operating in this spectral range need either some ambient light or active illumination to operate effectively.
NRTD: Acronym for Noise Equivalent Temperature Difference, a measure of the minimum difference in energy (expressed in units of blackbody temperature) required to thermally discriminate a target from the background.
NTSC: Acronym for National Television Standards Committee, which developed a set of video standards that are still in use in the U.S. and Japan. The term “NTSC video” refers to the typical analog video standards that are commonly seen in the U.S. today. Modern standards have been developed for digital video, but the NTSC standards for analog video are still widely in service, and will be for the foreseeable future. Standard NTSC video contains 640 x 480 visible pixels (there are additional pixel spaces that are not viewable), and is presented at a frame rate of 29.97 Hz.
NVTherm: Acronym for Night Vision Thermal Model, a sophisticated infrared imaging model developed by the Night Vision and Electronic Sensors Directorate of the U.S. Army’s Communication and Electronics Command. NVTherm is used to model the performance of a complete, end-to-end thermal imaging system, including many factors such as target characteristics, weather, background, the type of monitor used, and even some human factors.
Nyquist Frequency: Sometimes called the Nyquist Criteria, this is highest frequency that can be accurately reproduced by a system, and is generally equal to twice the system resolution.
