Method for on-line thickness monitoring of a transparent film
US4748329A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 17, 1987 |
| Grant date | May 31, 1988 |
| Priority date | — |
| Expiry date | Feb 17, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B11/0691
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An optical system is described for monitoring the thickness of a translucent film either free-standing or coated on a reflective substrate. A polychromatic light beam is projected onto the surface of the sheet, and the transmitted light is detected at, at least, three wavelengths of which only one corresponds to an absorption band of the film material. By properly processing the three or more detected signals, an accurate evaluation of the film thickness is obtained irrespective of the presence of colored pigments in the material or of wavelength-dependent attenuation due to scattering at the film interfaces. Optical configurations are also described which avoid errors produced by interference fringes or front-surface reflections while simplifying the scanning of the sheet surface.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.