Patent US3454929A successfully refreshed from Google Patents.
US3827808A
Expired / Lapsed
US
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Method and apparatus for measuring the opacity of sheet material in which the transmittance signal is compensated for the reflectivity of the material
Assignee: Industrial Nucleonics Corp
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Filing: 1973-05-09
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Granted: 1974-08-06
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Expires: 1993-05-09
Abstract
Abstract Specifically disclosed is a method and apparatus for measuring the opacity of sheet material, more particularly for measuring the opacity of paper according to the TAPPI contrast ratio definition. A moving sheet of paper from a paper making machine or coater is passed through the gap between a light source and a photodetector. The light transmitted through the paper is passed through a window of opal glass and a bandpass filter before it is received by the photodetector. The opal glass window constitutes a partial reflector having an effective reflectivity between about 20 and 70 percent. This produces multiple reflections between the opal glass and the paper next to it, with sufficient magnitude to compensate the transmittance measurement for the reflectivity of the paper, and thereby automatically corrects the instrument for changes in the composition of the paper. Because of the bandpass filter, the photodetector responds substantially only to light in the visible portion of the spectrum. According to another disclosed arrangement wherein the opal glass window is not used, the instrument is compensated by the use of a second photodetector responsive to light reflected from the side of the paper where the light source is located. Signals from the two detectors are then combined in a simple computer arrangement to obtain a signal which is compensated for the reflectivity of the paper. The compensated signal provided by either of the disclosed arrangements is correlated with opacity in conformance with the TAPPI standard.
Inventors
- 👤 B Cho
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 13:35
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/84; G01N21/86; G01N33/00; G01N33/34; G01N33/346
Claims Analysis
Total Claims: 37
Claim 1
Independent Claim
110 words
The method of measuring the visual opacity of a moving sheet of paper or the like, which comprises directing a beam of visible light through the sheet from one side thereof, detecting said beam on the other side of the sheet to produce a response indicative of the intensity of the light transmitted through the sheet, modifying said response according to the reflectivity of said sheet by additionally detecting a substantial amount of light which has been reflected from said sheet, and correlating said modified response with the visual opacity of said sheet to provide an opacity measurement which is substantially independent of variations in the composition of said sheet.
Claim 2
Independent Claim
110 words
The method of measuring the visual opacity of a moving sheet of paper or the like, which comprises directing a beam of visible light through the sheet from one side thereof, detecting said beam on the other side of the sheet to produce a response indicative of the intensity of the light transmitted through the sheet, modifying said response according to the reflectivity of said sheet by additionally detecting a substantial amount of light which has been reflected from said sheet, and correlating said modified response with the visual opacity of said sheet to provide an opacity measurement which is substantially independent of variations in the composition of said sheet.
Claim 3
Dependent Claim
46 words
The method of claim 1 wherein said response modifying step comprises reflecting a substantial portion of the light transmitted through said sheet back toward said sheet so that it can be rereflected by the sheet, and additionally detecting at least a portion of said rereflected light.
Claim 4
Dependent Claim
34 words
The method of claim 1 wherein said response modifying step comprises detecting on said one side of the sheet a portion of the light from said directed beam which is reflected from the sheet.
Claim 5
Independent Claim
103 words
The method of measuring the visual opacity of a sheet of paper or the like, which comprises passing thE sheet between a light source and a visible light detector so as to derive from the detector a response indicative of the intensity of the light transmitted through the sheet, augmenting said response according to the reflectivity of the sheet by additionally detecting a substantial amount of light which has been reflected from said sheet, and correlating said augmented response with the visual opacity of said sheet to provide an opacity measurement which is substantially independent of variations in the reflectivity of said sheet.
Claim 6
Independent Claim
103 words
The method of measuring the visual opacity of a sheet of paper or the like, which comprises passing thE sheet between a light source and a visible light detector so as to derive from the detector a response indicative of the intensity of the light transmitted through the sheet, augmenting said response according to the reflectivity of the sheet by additionally detecting a substantial amount of light which has been reflected from said sheet, and correlating said augmented response with the visual opacity of said sheet to provide an opacity measurement which is substantially independent of variations in the reflectivity of said sheet.
Claim 7
Dependent Claim
42 words
The method of claim 4 which comprises reflecting a substantial portion of said light transmitted through the sheet back toward said sheet, and wherein said light reflected from said sheet is detected on the side of said sheet opposite said light source.
Claim 8
Dependent Claim
25 words
The method of claim 4 wherein said light reflected from said sheet is detected on the same side of said sheet as said light source.
Claim 9
Independent Claim
134 words
The method of measuring the visual contrast ratio opacity of a sheet of paper or the like, which comprises passing the sheet between a light source and a detector, filtering at least the portion of the light from said source which is transmitted through the sheet and incident on said detector, producing a response in accordance with said filtered light incident on said detector which is indicative of the intensity of the visible light transmitted through the sheet, modifying said response according to the reflectivity of said sheet by additionally detecting a substantial amount of visible light which has been reflected from said sheet, and correlating said modified response with the visual contrast ratio of said sheet to provide an opacity measurement which is substantially independent of variations in the reflectivity of said sheet.
Claim 10
Independent Claim
134 words
The method of measuring the visual contrast ratio opacity of a sheet of paper or the like, which comprises passing the sheet between a light source and a detector, filtering at least the portion of the light from said source which is transmitted through the sheet and incident on said detector, producing a response in accordance with said filtered light incident on said detector which is indicative of the intensity of the visible light transmitted through the sheet, modifying said response according to the reflectivity of said sheet by additionally detecting a substantial amount of visible light which has been reflected from said sheet, and correlating said modified response with the visual contrast ratio of said sheet to provide an opacity measurement which is substantially independent of variations in the reflectivity of said sheet.
Claim 11
Dependent Claim
42 words
The method of claim 7 which comprises reflecting a substantial portion of said light transmitted through the sheet back toward said sheet, and wherein said light reflected from said sheet is detected on the side of said sheet opposite said light source.
Claim 12
Dependent Claim
25 words
The method of claim 7 wherein said light reflected from said sheet is detected on the same side of said sheet as said light source.
Claim 13
Independent Claim
117 words
The method of measuring the visual contrast ratio opacity of a moving sheet of paper or the like, which comprises directing a beam of visible light through said sheet from one side thereof, reflecting a substantial portion of the light in said beam which is transmitted through said sheet back toward said sheet whereby said reflected light can be rereflected from said sheet, detecting both said transmitted and said rereflected light, producing a response in accordance with said detected light, and correlating said response with the contrast ratio RO/Rg where RO is the reflectance of said paper as measured over a black backing and Rg is the reflectance of said paper as measured over a white backing.
Claim 14
Independent Claim
117 words
The method of measuring the visual contrast ratio opacity of a moving sheet of paper or the like, which comprises directing a beam of visible light through said sheet from one side thereof, reflecting a substantial portion of the light in said beam which is transmitted through said sheet back toward said sheet whereby said reflected light can be rereflected from said sheet, detecting both said transmitted and said rereflected light, producing a response in accordance with said detected light, and correlating said response with the contrast ratio RO/Rg where RO is the reflectance of said paper as measured over a black backing and Rg is the reflectance of said paper as measured over a white backing.
Claim 15
Dependent Claim
30 words
The method of claim 10 wherein said response is correlated with the contrast ratio RO/R0.89 where R0.89 is the reflectance of the paper as measured over a magnesium carbonate backing.
Claim 16
Dependent Claim
32 words
The method of claim 10 which includes filtering at least the portion of said transmitted and rereflected light which is detected so that said response simulates the response of the human eye.
Claim 17
Dependent Claim
39 words
The method of claim 10 wherein said substantial portion of the transmitted light reflected back toward said sheet is between 20 and 70 percent of at least that portion of the transmitted light which effectively contributes to said response.
Claim 18
Dependent Claim
98 words
Apparatus for measuring the visual opacity of a moving sheet of paper or the like, which comprises a visible light source, a visible light detector, means for supporting said light source and said detector on opposite sides of said sheet, means coupled to said detector for deriving a response indicative of the intensity of thE visible light transmitted through said sheet and detected by the detector, means for substantially modifying said response in accordance with the intensity of visible light reflected from said sheet, and means for correlating said modified response with the visual opacity of said sheet.
Claim 19
Dependent Claim
98 words
Apparatus for measuring the visual opacity of a moving sheet of paper or the like, which comprises a visible light source, a visible light detector, means for supporting said light source and said detector on opposite sides of said sheet, means coupled to said detector for deriving a response indicative of the intensity of thE visible light transmitted through said sheet and detected by the detector, means for substantially modifying said response in accordance with the intensity of visible light reflected from said sheet, and means for correlating said modified response with the visual opacity of said sheet.
Claim 20
Dependent Claim
47 words
Apparatus as in claim 14 wherein said response modifying means comprises means for reflecting back toward said sheet a substantial portion of the visible light transmitted through the sheet so that said transmitted and reflected light can be rereflected by said sheet and detected by said detector.
Claim 21
Dependent Claim
20 words
Apparatus as in claim 15 wherein said reflecting means comprises means for reflecting a variable portion of said transmitted light.
Claim 22
Dependent Claim
34 words
Apparatus as in claim 16 wherein said variable portion reflecting means comprises a plurality of discrete, partially reflecting bodies and means for selecting one of said bodies in order to determine said variable portion.
Claim 23
Dependent Claim
17 words
Apparatus as in claim 16 comprising means for providing a continuously variable adjustment of said variable portion.
Claim 24
Dependent Claim
29 words
Apparatus as in claim 18 comprising a partially reflecting body adapted to be spaced from said sheet and means for adjusting the spacing between said body and said sheet.
Claim 25
Dependent Claim
17 words
Apparatus as in claim 19 wherein said spacing adjusting means comprises a servomechanism responsive to said detector.
Claim 26
Dependent Claim
61 words
Apparatus as in claim 14 wherein said response modifying means comprises a second detector supported on the same side of said sheet as said light source for providing a second response indicative of the intensity of the light from said source which is reflected from the sheet, and means for modifying said transmitted light-indicative response in accordance with said second response.
Claim 27
Dependent Claim
31 words
Apparatus as in claim 21 wherein said modifying means comprises computer means connected to said transmitted light and second detectors for computing an output signal indicative of a contrast ratio opacity.
Claim 28
Dependent Claim
42 words
Apparatus as in claim 22 wherein said computer means comprises means for computing the opacity defined by RO/Rg where RO is the reflectance of the sheet with a black backing and Rg is the reflectance of the sheet with a white backing.
Claim 29
Dependent Claim
45 words
Apparatus as in claim 21 wherein said light source comprises an integrating sphere having a light input, a light exit adjacent said sheet, and a further light passage diametrically opposite said light exit, and wherein said second detector is mounted in said further light passage.
Claim 30
Dependent Claim
41 words
Apparatus as in claim 21, further comprising a black cavity having said transmitted light detector mounted therein, wherein said second detector is mounted in a position to receive reflected light from a portion of said sheet adjacent to said black cavity.
Claim 31
Dependent Claim
119 words
Apparatus for measuring the visual contrast ratio opacity of a moving sheet of paper or the like, which comprises means for directing a beam of visible light through said sheet from one side thereof, means on the other side of said sheet for reflecting one substantial portion of the light in said beam which is transmitted through the sheet back toward the sheet whereby it can be rereflected by the sheet, means for detecting another portion of said light transmitted through said sheet to derive a signal and for detecting said rereflected light to compensate said signal for the reflectivity of said sheet, and means for correlating said compensated signal with the visual contrast ratio opacity of said sheet.
Claim 32
Dependent Claim
119 words
Apparatus for measuring the visual contrast ratio opacity of a moving sheet of paper or the like, which comprises means for directing a beam of visible light through said sheet from one side thereof, means on the other side of said sheet for reflecting one substantial portion of the light in said beam which is transmitted through the sheet back toward the sheet whereby it can be rereflected by the sheet, means for detecting another portion of said light transmitted through said sheet to derive a signal and for detecting said rereflected light to compensate said signal for the reflectivity of said sheet, and means for correlating said compensated signal with the visual contrast ratio opacity of said sheet.
Claim 33
Dependent Claim
39 words
Apparatus as in claim 26 wherein said reflecting means comprises a partially reflecting member between said sheet and said detecting means for reflecting said one substantial portion of the light while transmitting said another portion of said detecting means.
Claim 34
Dependent Claim
27 words
Apparatus as in claim 27 wherein said partially reflecting member comprises a translucent window Having an effective reflectivity in the range of about 20 to 70 percent.
Claim 35
Dependent Claim
24 words
Apparatus as in claim 27 wherein said partially reflecting member comprises a window of opal glass having a reflective side adjacent to said sheet.
Claim 36
Dependent Claim
56 words
Apparatus as in claim 26 comprising a window on said other side of the sheet for transmitting at least said another portion of said light transmitted by said sheet which is detected by said detecting means, and means for maintaining said moving sheet substantially in a fixed plane closely spaced from and adjacent to said window.
Claim 37
Dependent Claim
34 words
Apparatus as in claim 30 comprising air pressure means for removing foreign matter from the vicinity of the sheet adjacent to said window, thereby to minimize collection of said foreign matter on the window.
References Cited (Backward Citations)
US3455637A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-08-05 | 1978-02-04 | 1978-08-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-08-05 | 1982-02-04 | 1982-08-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-08-05 | 1986-02-04 | 1986-08-06 | $7700.00 | Window Closed / Lapsed |