Method and apparatus for measuring small displacement
US7457721B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Apr 22, 2005 |
| Grant date | Nov 25, 2008 |
| Priority date | — |
| Expiry date | Apr 22, 2025 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06T2207/30164
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
Without using an interferometer, small displacement and/or three-dimensional shape of an object is detected in a noncontact way with high accuracy using pseudo-phase information calculated from e.g., a speckle pattern having a spatially random structure. A speckle image of the test object of the before displacement is obtained, and a spatial frequency spectrum is calculated by executing an N-dimensional Fourier transform for this. The complex analytic signal is obtained by setting the amplitude of frequency spectrum in the half plane including zero frequency in this amplitude distribution to zero, and executing the frequency spectrum amplitude in the half plane of the remainder in the inverse Fourier transform. And then, the amplitude value of this complex analytic signal is replaced with the constant value, a part of the obtained analytic signal domain is clipped, the phase information is calculated by the phase-only correlation function, and the cross-correlation peak in N-dimension is obtained. The displacement magnitude can be obtained by executing the above-mentioned method to the after displacement of the test object, and obtaining the difference of the cross-correlation peak…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.