Patent ID: 8634068

Claim:
A method of determining the wavelength of radiation which may be used to automatically inspect an ophthalmic lens of a maximum thickness for missing material of an amount between about zero and about a certain thickness, comprising: (a) measuring a % transmittance of radiation of several different wavelengths through multiple ophthalmic lenses of several different known thicknesses; (b) calculating the k value for each wavelength of the several different wavelengths and confirming that transmission of light through the multiple ophthalmic lenses follows Beers' Law; (c) subtracting the % transmittance at said known thickness from the % transmittance in the absence of an ophthalmic lens at said several different wavelengths to generate first contrast values; (d) subtracting the % transmittance at said maximum thickness from the % transmittance at said known lens thickness at said several different wavelengths to give second contrast values; (e) comparing the first contrast values with the second contrast values at each wavelength and selecting lowest contrast values at each wavelength and the plotting such lowest contrast values against wavelength; and (f) selecting the wavelength from the plot of step (e) at a highest peak for inspection of missing material defects.