Methods are apparatus for monitoring the diffuse reflectivity of a surface
US4988206A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 26, 1988 |
| Grant date | Jan 29, 1991 |
| Priority date | — |
| Expiry date | Apr 26, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N21/94
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method and apparatus for monitoring the diffuse reflectivity of a portion of a surface. The method is particularly applicable to soil detection of banknotes. The method comprises exposing the surface portion (3) to a beam of radiation from a source (2). At least one part of the diffuse radiation reflected by the surface portion (3) is sensed by a sensor (6) located closely behind an aperture (7) such that the aperture (7) defines, in effect, a sensing position situated such that the intensity of the diffusely reflected radiation sensed is substantially invariant within a working range of distances (D) between the aperture (7) and the surface portion (3). A value representative of the diffuse reflectivity of the surface portion (3) is then determined from the sensed intensities.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.