Optical unit

There are two types of optical units. Radial optical units are measured in the image plane, and axial optical units are used to measure distances between the image plane and the observer.

The number of optical units $v$ in a given radial length $r$ is given by:

$v\_\backslash mathrm\{radial\}\; =\; \backslash frac\{2\; \backslash pi\}\{\backslash lambda\}\; \backslash frac\{n\; \backslash sin\; \backslash alpha\}\{M\_\backslash mathrm\{tot\}\}\; r$

where:

• $\backslash lambda$ is the wavelength
• $n\; \backslash sin\; \backslash alpha$ is the numerical aperture
• $M\_\backslash mathrm\{tot\}$ is the total magnification

Axial optical units are more complicated, as there is no simple definition of resolution in the axial direction. There are two forms of the optical unit for the axial direction.

For the case of a system with high numerical aperture, the axial optical units in a distance z are given by:

$u\_z\; =\; \backslash frac\{2\; \backslash pi\}\{\backslash lambda\}\; \backslash frac\{\; (n\; \backslash sin\; \backslash alpha)^2\}\{\backslash eta\}\; z$

where:

• $\backslash eta$ is the index of refraction of the medium above the optical plane.{{cite book |last1=Sandison |first1=D.R. |last2=Piston |first2=D.W. |last3=Webb |first3=W.W. |chapter=Background rejection and optimization of signal-to-noise in confocal microscopy |editor1-last=Stevens |editor1-first=J.K. |editor2-last=Mils |editor2-first=L.R |editor3-last=Trogadis |editor3-first=J.E. |title=Confocal Microscopy: Volume Investigation of Biological Specimens |date=1993 |publisher=Academic Press |location=New York}}

For systems with low numerical aperture, the axial optical unit is:

$u\_z\; =\; \backslash frac\{8\; \backslash pi\; \backslash eta\}\{\backslash lambda\}\; \backslash sin^2(\backslash frac\{\backslash alpha\}\{2\})\; z$

{{reflist}}

Category:Microscopy

Category:Units of length

{{optics-stub}}