Surface characteristic determining apparatus
US8077324B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jun 14, 2007 |
| Grant date | Dec 13, 2011 |
| Priority date | — |
| Expiry date | Jul 23, 2027 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B2290/70
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Light from the first and second different wavelength light sources is combined and supplied to a director that directs zeroth order light to a reference surface and other order, generally first order diffracted light to on a location of the sample surface which is dependent upon wavelength. Light reflected by the sample and reference surfaces interfere. A characteristic of a sample surface is determined from interference light of the first wavelength. Interference light of the second wavelength is used to enable phase-locking by adjusting the path length difference by moving the reference surface or changing the refractive index of a path portion to compensate for phase variation due to environmental effects. Non-mechanical scanning is used to scan the sample surface by using a variable wavelength source and a director providing different first order diffraction angles for different wavelengths or an acousto-optical device that provides a variable pitch acoustic diffraction grating.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.