Suvarna Garge (Editor)

Optical unit

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The Optical Unit is a dimensionless units of length used in optical microscopy. Because every diffraction limited system have their resolution proportional to wavelength / NA, it is convenient for comparison to use this unit. There are actually 2 units, one "axial" (along the optical axis of the objective) and one "radial".

Equation

u a x i a l = 8 π n λ sin 2 ⁡ ( α 2 ) z

v r a d i a l = 2 π λ n sin ⁡ α M t o t r

where :

  • n is the refractive index
  • λ is the wavelength
  • α the beam conus angle
  • M t o t is the total magnification ( M is 1 if you want the size in the sample)

    • Note : n ∗ sin ⁡ α = numerical aperture

    References

    Optical unit Wikipedia
    (Text) CC BY-SA