Optical Profilometer Training

Optical Resolution

Optical resolution: the Airy disk

Diffraction of light through a circular aperture (like a lens) limits the resolution of any optical system. The best focus of a point source of light from a lens system will form an Airy disk due to this diffraction, rather than the idealized point source.

Airy disk
Airy disk

Optical resolution is usually defined as the ability to distinguish two objects which are close together, which is difficult due to the overlap of the Airy disks.

Common criteria for the resolution R:

  • The Rayleigh Criterion: R = 0.61λ/NA
  • The Sparrow Criterion: R = 0.5λ/NA (used by Zygo)

The effect of diffraction will be a smoothing of features which are too small to resolve sharply.

Note: This resolution is in the lateral (parallel to the focal plane) direction – it is not related to the vertical resolution of the Nexview's measurements.

Optical lateral resolution
Optical lateral resolution

Optical Resolution of our Objectives

  • 2.75x~ 3.563μm
  • 10x ~ 950 nm
  • 20x ~ 713 nm
  • 50x ~ 518 nm