Measurement of fiber diameters with high precision
US5309221A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 31, 1991 |
| Grant date | May 3, 1994 |
| Priority date | — |
| Expiry date | Dec 31, 2011 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B11/105
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Methods for measuring the diameters of transparent filaments with high precision, e.g., RMS standard deviations of less than 0.02 microns, are provided. The methods involve determining the average spatial frequency .omega. of the far-field interference pattern produced by illuminating the filament with a beam of laser light. The average spatial frequency is determined by performing a fast Fourier transform (FFT) on the interference data to obtain a coarse estimate for the average and then performing a set of discrete sequence Fourier transforms (DSFTs) in the region of the coarse estimate to obtain the desired high precision estimate of the average. Efficient on-line processing procedures are provided so that real time measurements can be performed on, for example, a moving optical waveguide fiber, at rates of 500 measurements/second and above.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.