Apparatus for optically measuring the distance between two grating-like structures and the size of periodic pattern elements forming one of the grating-like structures
US4560280A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 17, 1983 |
| Grant date | Dec 24, 1985 |
| Priority date | — |
| Expiry date | Aug 17, 2003 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B11/14
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The distance between first and second grating-like structures such as a shadow mask and a faceplate of a color picture tube or the size of pattern elements of the second grating-like structure such as black stripes formed on the inner surface of the faceplate is optically measured. The shadow mask has a periodic pattern of apertures or slots and the faceplate has a periodic pattern of the black stripes. An optical system located between a light source and an assembly of the first and second grating-like structures applies parallel rays of light to the assembly and is arranged to vary an incident angle of the parallel rays to the assembly. A photodetector detects the quantity of light passed through the assembly to produce an electric signal whose amplitude periodically varies with variation in the incident angle of the parallel rays to the assembly. A signal processing unit evaluates the distance between the first and second grating-like structures or the size of pattern elements forming the second grating-like structure on the basis of the electric signal from the photodetector.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.