numerical aperture

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numerical aperture

[nü′mer·i·kəl ′ap·ə·chər]
(optics)
A measure of the resolving power of a microscope objective, equal to the product of the refractive index of the medium in front of the objective and the sine of the angle between the outermost ray entering the objective and the optical axis. Abbreviated N.A.

numerical aperture

The measurement of the acceptance angle of an optical fiber, which is the maximum angle at which the core of the fiber will take in light that will be contained within the core. Taken from the fiber core axis (center of core), the measurement is the square root of the squared refractive index of the core minus the squared refractive index of the cladding. See critical angle and fiber optics glossary.


The Acceptance Angle
The numerical aperture measures the acceptance angle of a fiber.
References in periodicals archive ?
Within solar CPC PV systems, any radiation within the collector acceptance angle enters through the aperture and finds its way to the absorber surface by multiple internal reflections.
As shown in Figure 1, increasing the launch angle (0) of incident light converts the guided light into an ever-thinning ring beyond the acceptance angle for the fiber.
An interference filter characteristic that needs to be considered for designs is the sensor acceptance angle. As the illuminance source incident angle increases, the interference filter characteristics will change.
With an acceptance angle of [+ or -] 30 degrees, the probe can measure difficult-to-access features at a scanning speed of 1,000 points per second for rapid throughput.
Such low spatial frequencies are preferable when devices with larger acceptance angle (broad angular and wavelength selectivity operation ranges) are sought.
where [C.sub.max] represents the maximum concentration of optical flux (unitless); n is the real component of the refractive index (unitless); and [theta] (acceptance angle along the plane of the azimuth) and [psi] (the acceptance angle of the altitude) are the acceptance angles.
The data taken for the sample outside the IS in the region 300 nm to 800 nm was fitted to the L-M scattering cross section with the parameters: microsphere diameter, real part of the index of refraction, microsphere concentration, and the instrument acceptance angle.
In addition, the sensor incorporates wide acceptance angle pixel technology, helping to maintain corner performance while ensuring a minimum module height.
The system features a high diffraction acceptance angle, which makes it suitable for weak beam, tilting and other analytical experiments.
The signal-to-noise ratio (and thus achievable communications rate) depends on the data rate, contrast ratio, acceptance angle, and spectral bandwidth of the modulator.
The sensor's three transmission and receiver units have an acceptance angle of three degrees and, from about 100 yards away, scan the entire width of a three-lane motorway, detecting any vehicles ahead.
Alex Clarke, global alliance manager with Coventry, UK-based OAS said the antenna can provide an acceptance angle of over 25% off center before the connection between devices fails while still achieving considerable performance benefits over current IR technologies.