Airy Disk and Resolving Power

Resolving power is the capacity of an instrument to resolve two points which are close together
Even an ideal lens without any aberrations cannot reproduce an object detail. Diffraction will limit the resolution possible. The smallest achievable spot from a lens is called Airy Disk. The radius r of the spot is given by wavelength λ and numerical aperture NA:
r=0.61λ/N.A.
r=The radius of Airy Disk ＝Resolving Power
The longer wavelength of the illuminating light has larger spot.
ex) A lens with N.A.0.07 at wavelength 550nm
ｒ=0.61×0.55/0.07=4.8μm

Airy Disk and Resolving Power
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