
Sweatt model
The Sweatt model is a way to describe diffractive optics like gratings, kinoforms, or holographic surfaces, using only standard refractive surfaces like planes, spheres, and aspheres. The idea is to replace the diffracting surface with a very thin lens of a material of very high refractive index, to achieve the same ray deflection and phase shift.
For example, consider a grating that diffracts light of d wavelength (587.56nm) through an angle of 5 degrees. This grating can be modelled as a thin prism whose refractive index is 10001 and whose apex angle is 0.0005 degrees. The large value of the refractive index ensures that large ray deflections result from even small thickness variations. Because the prism is nearly zero thickness, the ray enters and leaves the prism with negligible change in position.
Discussion of the Sweatt model can be found in [Smith2005].
See also
- Optics
- Tutorial - Sweatt model prism (links to www.ripplon.com)
- Kinoform surface