Patent ID: 8148705

Claim:
An inspection method for inspecting a hard disk medium, said method comprising the steps of: irradiating a surface of the hard disk medium with a light beam including a plurality of wavelengths, thereby forming pattern elements with regular intervals on the hard disk medium; detecting the intensity, on a wavelength basis, of a light beam reflected from the hard disk medium; calculating a spectral reflectance from the detected intensity of the reflected light beam; detecting a shape of a pattern element formed on the hard disk medium on the basis of the calculated spectral reflectance, including comparing the calculated spectral reflectance with a predetermined spectral reflectance, the predetermined spectral reflectance created by using an effective medium approximation based on the shape of the target to be inspected and the quality of material thereof; and wherein when the effective medium approximation is used, a target pattern element is divided into a plurality of layers as in a multilayer film structure, and each of the plurality of layers is subjected to the effective medium approximation.