Lateral-scanning interferometer with tilted optical axis
US6449048B1 · kind B1 · utility
Assignee
Inventor
Key dates
| Filing date | May 11, 2000 |
| Grant date | Sep 10, 2002 |
| Priority date | — |
| Expiry date | May 11, 2020 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B11/2441
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An interferometer scans the sample surface laterally with respect to the optical axis of the interferometric objective. The objective is tilted, so that the sample surface is placed at an angle with respect to the maximum coherence plane of the instrument. By moving the sample stage laterally, at an angle, through a point at a set distance from the objective on the objective's optical axis, rather than vertically along the optical axis, different parts of the object intersect the maximum coherence plane at different times as the surface passes through the coherence plane, the precise time depending on the profile of the surface. When the OPD of a point on the object's surface is greater than the coherence length of the light source, the intensity of light reflected from this point does not produce interference fringes. Therefore, the intensity registered by the detector is approximately constant. However, when the object point enters the zone of coherence, the interference effects modulate the intensity the same way as in a regular VSI procedure. As the object moves along the scanning direction, it also has a relative vertical speed with respect to the objective because of the tilt…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.