Apparatus having a multiple angle transparent rotating element for measuring the thickness of transparent objects
US6144456A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 4, 1997 |
| Grant date | Nov 7, 2000 |
| Priority date | — |
| Expiry date | Nov 4, 2017 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B2290/35
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The apparatus for measuring the thickness of transparent objects (1) has a radiation source (3) of short coherence length and a Michelson interferometer (5), wherein the object (1) to be measured can be arranged in its measuring arm (11), and path length variation element (15), which has an optical path length that changes periodically due to its own rotation, is arranged in the reference arm (13). The cross-sectional surface (34) of the element (15) wherein the reference beam comes to rest has at least four corners so that the reference radiation path in the element (15) has at least two reflections on the inner surfaces of the element. The reference beam (41e) coming out of the element (15) is reflected back by means of a fixed reflector (30) into the element (15), preferably into itself. The measurements of the side surfaces of the element (15), the beam entry location therein, as well as the index of refraction of the element material can be selected in such a way that the path length difference obtained by means of the rotating element (15) runs approximately linearly to the rotation angle in a preferred embodiment. This linearity results in a reduced bandwidth of the Doppler …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.