Automatic processing in Moiré deflectometry by local fringe direction calculation
An algorithm for accurately extracting the local fringe direction is presented. The algorithm estimates, in the neighborhood of n × n points, the direction of the gradient that points normal to the local fringe direction. The performance of four different derivative kernels is also compared. Since t...
| Authors: | , , |
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| Format: | article |
| Publication Date: | 1998 |
| Country: | España |
| Institution: | Universidad Complutense de Madrid (UCM) |
| Repository: | Docta Complutense |
| Language: | English |
| OAI Identifier: | oai:docta.ucm.es:20.500.14352/58796 |
| Online Access: | https://hdl.handle.net/20.500.14352/58796 |
| Access Level: | Open access |
| Keyword: | 535 Patterns Maps Óptica (Física) 2209.19 Óptica Física |
| Summary: | An algorithm for accurately extracting the local fringe direction is presented. The algorithm estimates, in the neighborhood of n × n points, the direction of the gradient that points normal to the local fringe direction. The performance of four different derivative kernels is also compared. Since this method is sensitive to noise and variations in background and amplitude, a preprocessing step is used to limit these error sources. The method has been applied to the moiré deflectogram of a spherical and a progressive addition ophthalmic lens, resulting in a map of the refractive power of these lenses. The results are compared with the data obtained with a commercial focimeter. This technique is useful for analyzing the fringe patterns where the fringe direction is variable and must be obtained locally. |
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