US4345840A
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US
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Method and apparatus for instantaneous band ratioing in a reflectance radiometer
Assignee: California Institute of Technology
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Filing: 1980-04-08
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Granted: 1982-08-24
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Expires: 2000-04-08
Abstract
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.
Inventors
- 👤 Alexander F. H. Goetz
- 👤 Richard A. Machida
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 00:51
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/17; G01N21/25; G01N21/31; G01N21/314; G01J; G01J3/00; G01J3/02; G01J3/0205; G01J3/0232; G01J3/0272; G01J3/0286; G01J3/0294; G01J3/04; G01J3/28; G01J3/30; G01J3/36; G01J3/12; G01J2003/1213; G01J2003/1217; G01J2003/1226; G01J2003/123; G01J2003/283; G01J2003/2833; G01J3/42; G01J2003/425; G01J3/2803
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
170 words
A method for providing instantaneous identification of particular reflecting materials by ratioing reflectance measurements at selected pairs of wavelength bands, each band of a pair being chosen for a particular spectral characteristic of a material of interest selected from a group consisting of spectral peaks and band wings on either side of spectral peaks for each band reflected from a particular material, comprising the steps of selecting a plurality of different paired bands, one pair at a time, for instantaneous band ratioing, simultaneously detecting the intensity of radiation reflected by materials under investigation into said plurality of predetermined bands centered on spectral characteristics of the different materials, determining the ratio of radiation intensity in at least one band to the radiation intensity in other bands, and displaying the band ratio thus determined to provide a ratio display indicative of the particular material, whereby a reflecting body can be checked for the presence of a plurality of different materials identified by at least one particular band ratio value for each material.
Claim 2
Independent Claim
170 words
A method for providing instantaneous identification of particular reflecting materials by ratioing reflectance measurements at selected pairs of wavelength bands, each band of a pair being chosen for a particular spectral characteristic of a material of interest selected from a group consisting of spectral peaks and band wings on either side of spectral peaks for each band reflected from a particular material, comprising the steps of selecting a plurality of different paired bands, one pair at a time, for instantaneous band ratioing, simultaneously detecting the intensity of radiation reflected by materials under investigation into said plurality of predetermined bands centered on spectral characteristics of the different materials, determining the ratio of radiation intensity in at least one band to the radiation intensity in other bands, and displaying the band ratio thus determined to provide a ratio display indicative of the particular material, whereby a reflecting body can be checked for the presence of a plurality of different materials identified by at least one particular band ratio value for each material.
Claim 3
Dependent Claim
17 words
A method as defined in claim 1, wherein said spectral characteristics of said materials are spectral peaks.
Claim 4
Dependent Claim
33 words
A method as defined in claim 1 wherein said spectral characteristics of said material are band wings consisting of a measurement of intensity measurements on either side of spectral peaks characterizing said material.
Claim 5
Dependent Claim
137 words
Apparatus for identifying an unknown material in a target area that reflects radiation within predetermined selected bands comprising two optical trains directed independently at the same target area, each train having a detector for measuring the intensity of radiation reflected from the same target area, and each train having a suitable filter for passing a different one of a set of selected bands of reflecting radiation, each one being selected to be centered on different spectral characteristics of the material, means for producing the ratio of reflected radiation intensity detected through the detector of one optical train to the reflected radiation intensity detected through the detector of the other optical train for each set of selected bands, and means for displaying the value of said ratios, whereby said particular material is identified by a particular ratio value.
Claim 6
Dependent Claim
137 words
Apparatus for identifying an unknown material in a target area that reflects radiation within predetermined selected bands comprising two optical trains directed independently at the same target area, each train having a detector for measuring the intensity of radiation reflected from the same target area, and each train having a suitable filter for passing a different one of a set of selected bands of reflecting radiation, each one being selected to be centered on different spectral characteristics of the material, means for producing the ratio of reflected radiation intensity detected through the detector of one optical train to the reflected radiation intensity detected through the detector of the other optical train for each set of selected bands, and means for displaying the value of said ratios, whereby said particular material is identified by a particular ratio value.
Claim 7
Dependent Claim
29 words
Apparatus as defined in claim 4 including means for adjusting said two optical trains to receive radiation from the same target area for different distances from the target area.
Claim 8
Dependent Claim
47 words
Apparatus as defined in claims 4 or 5 including means for selectively positioning one of a plurality of filters on the optical axis of each of said optical trains for each of a plurality of materials to be identified, each material by a unique band ratio displayed.
Claim 9
Dependent Claim
119 words
Apparatus as defined in claim 4 or 5 including two coaxial filter wheels positioned with their axes between and parallel to the optical axes of said optical trains, said filter wheels having spaced slits and filters arranged so that a slit in one wheel and a filter in the other wheel will be aligned with the axis of one optical train, and a filter in said one wheel and a slit in the other wheel will be aligned with the axis of the other optical train, whereby one of a plurality of filters is selected in each of said optical trains for each of a plurality of materials to be identified, each material by a unique band ratio displayed.
Claim 10
Dependent Claim
18 words
Apparatus as defined in claim 4 or 5 wherein said spectral characteristics of said material are spectral peaks.
Claim 11
Dependent Claim
34 words
Apparatus as defined in claim 1 or 5 wherein said spectral characteristics of said material are band wings consisting of a measurement of intensity measurements on either side of spectral peaks characterizing said material.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1985-08-23 | 1986-02-22 | 1986-08-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-08-23 | 1990-02-22 | 1990-08-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-08-23 | 1994-02-22 | 1994-08-24 | $7700.00 | Window Closed / Lapsed |