Patent ID: 6057924
Filing Date: 2000-05-02
Classification: G01B

Abstract:
A system for characterizing a partially transparent substrate by using electromagnetic radiation, comprising:a sample holder having a support surface operable to support a substrate which has a first surface and a second opposite surface;a radiation source, disposed relative to said sample holder and configured to produce a first substantially monochromatic probe beam at a first discrete wavelength to illuminate the first surface of the substrate, wherein said first discrete wavelength is one at which said probe beam is partially absorbed by the substrate and partially passes through the substrate as a transmitted probe beam;a sensing array configured to have a plurality of sensing pixels and disposed relative to said sample holder to receive said transmitted probe beam, said sensing array operable to produce an electrical signal indicative of an intensity distribution of said transmitted probe beam;an analog-to-digital converting device, connected to said sensing array and configured to convert said electrical signal into a digital data array corresponding to said intensity distribution of said transmitted probe beam; andan electronic processing device, connected to said analog-to-digital converting device to receive said digital data array and configured to determine an amount of attenuation by said substrate at said first discrete wavelength to produce a thickness map of the substrate,wherein said electronic processing device is programmed to digitally remove noise and selected signal components from said digital data array to improve a quality of said thickness map.