Probe measurement apparatus using a curved grating displacement interferometer
US5517307A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 30, 1993 |
| Grant date | May 14, 1996 |
| Priority date | — |
| Expiry date | Nov 30, 2013 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B2290/70
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Apparatus for surface measurement has a grating interferometer with a curved diffraction grating carried on a pivotal support arm of a probe for contacting a surface. The probe is biased into contact with a surface by an electromagnetic coil acting on an armature, or a pair of such biasing arrangements. A laser diode illuminates the grating to produce a pair of first order diffracted beams of opposite sign which are reflected from internal faces of a prism, and combined by a diachronic central layer of the prism and a pair of beam splitters. Output signals from the beam splitters are supplied to a signal processing circuit having a fringe counter and an interpolator. The fringe counter detects zero crossings of the signals and the interpolator maintains a digital estimate of the phase of the signals and updates the estimate when the phase difference between the estimate and the input signals exceeds a predetermined threshold. The interpolator has a digital counter for providing low order bits of the digital output signal. The output of the fringe counter provides the high order bits.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.