Michelson Interferometer - Interference Fringes

The intensity of the interference fringes for a Michelson interferometer is given by
 

where I₁ and I₂ are the intensities of the two beams, λ is the wavelength, and d is the path length difference between the two interferometer arms.  x and y are coordinates in the focal plane of a lens of focal length f.

The fringes for wavelengths λ = 632.8 nm and 420 nm are shown below.  Note that as the magnitude of the path difference increases the fringes move outward while as the magnitude of the path difference decreases the fringes move inward.
 

Thanks to
José Antonio Díaz Navas
Catedrático de Escuela Universitaria
Departamento de Óptica
Facultad de Ciencias
Avda. Severo Ochoa S/N
18071-Granada Spain
email: jadiaz@ugr.es
web: www.ugr.es/~jadiaz