Image processing method using phase-shifted fringe patterns and curve fitting
US6639685B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Feb 25, 2000 |
| Grant date | Oct 28, 2003 |
| Priority date | — |
| Expiry date | Feb 25, 2020 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06T7/521
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A contour measurement system determines three dimensional surface information of an object using a projection moiré technique to obtain a single fringe pattern that is analyzed using a phase-shift image processing method. A grating is projected onto the object and the reflected fringe pattern is recorded by a camera and stored digitally as an array of pixels. An estimated fringe spacing is then determined for each pixel. Using the estimated fringe spacings, four phase-shifted fringe patterns are generated by correlation integration and then used in a phase calculation to obtain wrapped phase information for the object. This phase information is then unwrapped and normalized, producing a set of data points representative of the unwrapped phase information. Noise suppression using pattern reconstruction and smoothing can be utilized at this point to improve the signal to noise ratio. Thereafter, updated estimated spacings are determined for each data point using a curve fitting function such as a localized least squares fit. The system then performs one or more additional iterations of the correlation integration, phase calculation, unwrapping, noise suppression, and fringe sp…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.