Method and apparatus for instantaneous band ratioing in a reflectance radiometer
US4345840A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 8, 1980 |
| Grant date | Aug 24, 1982 |
| Priority date | — |
| Expiry date | Apr 8, 2000 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01J2003/425
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A hand-held instrument is provided to compare information from selected infrared and visible bands in the 0.4 to 2.5 micrometer range, to perform ratioing via a dividing circuit (17) and to directly read out, via a display system (18), ratio values in a continuous digital display. The dual-beam, ratioing radiometer contains two optical trains (10, 12), each having two repeater lenses (L1a, L1b and L2a, L2b) and a cooled lead sulfide detector (D1, D2). One of the trains (10) is pivotal to facilitate measurements at distances ranging from about 1 meter to infinity. The optical trains are intersected by a set of two coaxially-mounted filter wheels (F1, F2), each containing up to five interference filters and slits to pass radiation filtered by the other. Filters with band passes as narrow as 0.01 micrometer are used in the region 0.4 to 2.5 micrometers. The total time for a calibration and measurement is only a few seconds. It is known from previous field studies using prior art devices, that materials, e.g., clay minerals, and carbonate minerals such as limestone, have unique spectral properties in the 2.0 to 2.5 micrometer region. Using properly chosen spectral filters, and ratioing…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.