The localized fringes are obtained in Michelson interferometer, irrespective of coherence of sources, if the two mirrors are tilted with respect to each other. ... The fringe formation and localization also depends upon coherence of optical waves, interfering medium, polarization etc.

What is meant by localized fringes?

When coherent light rays mix together they create fringes in some areas and they are called localized fringes. If the fringes are seen in the whole area of observation then it is called non-localized fringes. Coherence is spatial and temporal symmetry.

What do you mean by non localized fringes?

Interference fringes can be found on a screen placed anywhere in front of the coherent sources. Thus interference pattern is not loclised in a region and hence these are called non - localised fringes.