Before revision: This difference is called the optical path difference, the difference in distance between the top and bottom reflection paths, which can be calculated with equation 2: OPD = 2nd cos(θ) (2) OPD = mλ (3) Where is the refractive index of the absorptive material, is the thickness of the absorptive film, and is the angle of reflection.
After revision: This difference is called the optical path difference, the difference in distance between the top and bottom reflection paths, which can be calculated with equation 2: Where is the refractive index of the absorptive material, is the thickness of the absorptive film, and is the angle of reflection.