Dear Sridhar,

A transparent coating is a thin film coating of any transparent material (in vis region) like MgF2,Ta2O5, SiO2, SiO etc whose refractive index and thickness can any desired value. But for an antireflection coating we have to choose a transparent material which has a refractive index, that is sqr. root of the index of the substrate. For example for glass substrate ( r.i ~1.5) the coating material is generally MgF2 (r.i ~ 1.37, which is the nearest available value to the ideal 1.22). More over optical thickness (ie. r.i x physical thickness) of a single layer AR coating should be one fourth of the design wavelength so as to allow destructive interference to take place between the beams reflected from the surfaces of the glass and the film.

Dear Sridhar,

A transparent coating is a thin film coating of any transparent material (in vis region) like MgF2,Ta2O5, SiO2, SiO etc whose refractive index and thickness can any desired value. But for an antireflection coating we have to choose a transparent material which has a refractive index, that is sqr. root of the index of the substrate. For example for glass substrate ( r.i ~1.5) the coating material is generally MgF2 (r.i ~ 1.37, which is the nearest available value to the ideal 1.22). More over optical thickness (ie. r.i x physical thickness) of a single layer AR coating should be one fourth of the design wavelength so as to allow destructive interference to take place between the beams reflected from the surfaces of the glass and the film.

Now I can understand the difference.

Thank you very much sir .

Absolutely agree with Rajeev Kumar. The difference is that each antireflective coating is transparent coating but the transparency is not the only parameter that AR coating should fulfill