Optics: measuring and testing – By shade or color – With sample responsive to plural colors applied simultaneously
Patent
1980-04-08
1982-08-24
Evans, F. L.
Optics: measuring and testing
By shade or color
With sample responsive to plural colors applied simultaneously
250339, 250340, 350315, 356 51, 356418, G01J 350, G01N 2125
Patent
active
043458408
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 the signals to remove the effect of topography on the brightness measured, the instrument can be used for real-time analysis of reflecting materials in the field. Other materials in the broader range of 0.4 to 2.5 micrometers (and even beyond) could be similarly identified once the reflectance spectrum of the material is established by any means.
REFERENCES:
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patent: 3519816 (1970-07-01), Bartz et al.
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patent: 3960452 (1976-06-01), Huebner
patent: 4043668 (1977-08-01), Goetz et al.
patent: 4134683 (1979-01-01), Goetz et al.
patent: 4266878 (1981-05-01), Auer
Goetz Alexander F. H.
Machida Richard A.
California Institute of Technology
Evans F. L.
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