Apparatus for inspecting defects in a periodic pattern
US4360269A · kind A · utility
22Cited by
2References
9Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Oct 30, 1980 |
| Grant date | Nov 23, 1982 |
| Priority date | — |
| Expiry date | Oct 30, 2000 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B27/46
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The apparatus of this invention is used for inspecting defects in a periodic pattern. The apparatus comprises a device for forming a Fourier transformed pattern of the periodic pattern and a filter for passing predetermined spatial frequency ranges of the Fourier transformed pattern. The predetermined spatial frequency ranges are lower than a spatial frequency which coincides with a first order diffraction of the Fourier transformed pattern.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.