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Due to Snell's law, the numerical aperture remains the same: NA = n 1 sin θ 1 = n 2 sin θ 2. In optics, the numerical aperture (NA) of an optical system is a dimensionless number that characterizes the range of angles over which the system can accept or emit light.
Diagram of decreasing apertures, that is, increasing f-numbers, in one-stop increments; each aperture has half the light-gathering area of the previous one.. An f-number is a measure of the light-gathering ability of an optical system such as a camera lens.
A standard format for tag data in digital camera files. [10] f: f-number, f-stop. The numerical value of a lens aperture. The ratio of the focal length of the lens divided by its effective aperture diameter. [4] FF: Full frame, where the image sensor is approximately the same size as a 35 mm film: 36 × 24 mm. FP: Focal plane.
Optical units are dimensionless units of length used in optical microscopy. They are used to express distances in terms of the numerical aperture of the system and the wavelength of the light used for observation. Using these units allows comparison of the properties of different microscopes. [1]
The angular aperture of a thin lens with focal point at F and an aperture of diameter . The angular aperture of a lens is the angular size of the lens aperture as seen from the focal point: = (/) = where
In an optical fiber, the normalized frequency, V (also called the V number), is given by = =, where a is the core radius, λ is the wavelength in vacuum, n 1 is the maximum refractive index of the core, n 2 is the refractive index of the homogeneous cladding, and applying the usual definition of the numerical aperture NA.
The digital analysis of a set of holograms recorded from different directions or with different direction of the reference wave allows the numerical emulation of an objective with large numerical aperture, leading to corresponding enhancement of the resolution. [22] [23] [24] This technique is called interferometric microscopy.
Here, λ 0 is the wavelength in vacuum; NA is the numerical aperture for the optical component (maximum 1.3–1.4 for modern objectives with a very high magnification factor). Thus, the resolution limit is usually around λ 0 /2 for conventional optical microscopy. [17]