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Gustafsson Coppel, Ludovic
Alternative names
Publications (10 of 25) Show all publications
Namedanian, M., Gustafsson Coppel, L., Neuman, M., Gooran, S., Edström, P., Kolseth, P. & Koh, W. (2013). Analysis of Optical and Physical Dot Gain by Microscale Image Histogram and Modulation Transfer Functions. Journal of Imaging Science and Technology, 57(2), 020504-1-020504-5
Open this publication in new window or tab >>Analysis of Optical and Physical Dot Gain by Microscale Image Histogram and Modulation Transfer Functions
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2013 (English)In: Journal of Imaging Science and Technology, ISSN 1062-3701, E-ISSN 1943-3522, Vol. 57, no 2, p. 020504-1-020504-5Article in journal (Refereed) Published
Abstract [en]

The color of a print is affected by ink spreading and lateral light scattering in the substrate, making printed dots appear larger. Characterization of physical and optical dot gain is crucial for the graphic arts and paper industries. We propose a novel approach to separate physical from optical dot gain by use of a high-resolution camera. This approach is based on the histogram of microscale images captured by the camera. Having determined the actual physical dot shape, we estimate the modulation transfer function (MTF) of the paper substrate. The proposed method is validated by comparing the estimated MTF of 11 offset printed coated papers to the MTF obtained from the unprinted papers using measured and Monte Carlo simulated edge responses.

National Category
Media Engineering
Identifiers
urn:nbn:se:miun:diva-20432 (URN)10.2352/J.ImagingSci.Technol.2013.57.2.020504 (DOI)000344138900004 ()2-s2.0-84886047298 (Scopus ID)
Available from: 2013-12-03 Created: 2013-12-03 Last updated: 2017-12-06Bibliographically approved
Gustafsson Coppel, L., Andersson, M., Norberg, O. & Lindberg, S. (2013). Impact of illumination spectral power distribution on radiance factor of fluorescing materials. In: 2013 Colour and Visual Computing Symposium, CVCS 2013: . Paper presented at 2013 Colour and Visual Computing Symposium, CVCS 2013; Gjovik; Norway; 5 September 2013 through 6 September 2013; Category numberCFP1330V-ART; Code 101069 (pp. Art. no. 6626275).
Open this publication in new window or tab >>Impact of illumination spectral power distribution on radiance factor of fluorescing materials
2013 (English)In: 2013 Colour and Visual Computing Symposium, CVCS 2013, 2013, p. Art. no. 6626275-Conference paper, Published paper (Refereed)
Abstract [en]

The spectral radiance factor and thereby the appearance of fluorescing material is known to depend strongly on the spectral power distribution (SPD) of the illumination in the fluorophore's excitation wavelength band. The present work demonstrates the impact of the SPD in the fluorescence emission band on the total radiance factor. The total radiance factor of a fluorescing paper is measured in three different illuminations. The presence of peaks in the SPD of fluorescent light tubes dramatically decreases the luminescent radiance factor. This effect will impact the appearance of fluorescing media under illuminations with large variation in SPD, which includes recent LED illuminations. © 2013 IEEE.

Keywords
Fluorescence, Illumination, Luminescent radiance factor, Paper, Spectral Power Distribution, Whiteness
National Category
Materials Engineering
Identifiers
urn:nbn:se:miun:diva-20996 (URN)10.1109/CVCS.2013.6626275 (DOI)2-s2.0-84889074759 (Scopus ID)9781479906091 (ISBN)
Conference
2013 Colour and Visual Computing Symposium, CVCS 2013; Gjovik; Norway; 5 September 2013 through 6 September 2013; Category numberCFP1330V-ART; Code 101069
Note

Art. No.: 6626275

Available from: 2014-01-14 Created: 2014-01-09 Last updated: 2015-07-01Bibliographically approved
Linder, T., Löfqvist, T., Gustafsson Coppel, L., Neuman, M. & Edström, P. (2013). Lateral light scattering in fibrous media. Optics Express, 21(6), 7835-7840
Open this publication in new window or tab >>Lateral light scattering in fibrous media
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2013 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 21, no 6, p. 7835-7840Article in journal (Refereed) Published
Abstract [en]

Lateral light scattering in fibrous media is investigated by computing the modulation transfer function (MTF) of 22 paper samples using a Monte Carlo model. The simulation tool uses phase functions from infinitely long homogenous cylinders and the directional inhomogeneity of paper is achieved by aligning the cylinders in the plane. The inverse frequency at half maximum of the MTF is compared to both measurements and previous simulations with isotropic and strongly forward single scattering phase functions. It is found that the conical scattering by cylinders enhances the lateral scattering and therefore predicts a larger extent of lateral light scattering than models using rotationally invariant single scattering phase functions. However, it does not fully reach the levels of lateral scattering observed in measurements. It is argued that the hollow lumen of a wood fiber or dependent scattering effects must be considered for a complete description of lateral light scattering in paper.

Keywords
Radiative transfer, Halftone image reproduction, Multiple scattering, Turbid media
National Category
Other Physics Topics Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-18657 (URN)10.1364/OE.21.007835 (DOI)000316796000119 ()2-s2.0-84875750991 (Scopus ID)
Projects
PaperOpt
Funder
VinnovaThe Knowledge Foundation
Available from: 2013-03-28 Created: 2013-03-28 Last updated: 2017-12-06Bibliographically approved
Neuman, M., Gustafsson Coppel, L. & Edström, P. (2012). A partial explanation of the dependence between light scattering and light absorption in the Kubelka-Munk model. Nordic Pulp & Paper Research Journal, 27(2), 426-430
Open this publication in new window or tab >>A partial explanation of the dependence between light scattering and light absorption in the Kubelka-Munk model
2012 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, no 2, p. 426-430Article in journal (Refereed) Published
Abstract [en]

The Kubelka-Munk scattering and absorption coefficients of a set of paper samples are assessed using reflectance measurements in d/0 geometry. The coefficients display the widely studied dependence between light scattering and light absorption, since the light scattering coefficient decreases in regions of high absorption. It is shown using general radiative transfer theory that part of this dependence can be explained and eliminated by taking into account the geometry of the d/0 instrument and the single scattering anisotropy, thus capturing the angular variations of the light reflected from the samples. These findings allow the papermaker to better predict the reflectance from mixtures of pulps, fillers, dye, and FWA, and to better evaluate bleaching efforts. 

Keywords
Anisotropic reflectance; Kubelka-Munk; Paper optics; Parameter dependence; Reflectance measurements
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-16873 (URN)10.3183/NPPRJ-2012-27-02-p426-430 (DOI)000315696000035 ()2-s2.0-84865251384 (Scopus ID)
Available from: 2013-04-04 Created: 2012-08-28 Last updated: 2017-12-07Bibliographically approved
Granberg, H., Gustafsson Coppel, L., Eita, M., de Mayolo, E. A., Arwin, H. & Wågberg, L. (2012). Dynamics of moisture interaction with polyelectrolyte multilayers containing nanofibrillated cellulose. Nordic Pulp & Paper Research Journal, 27(2), 496-499
Open this publication in new window or tab >>Dynamics of moisture interaction with polyelectrolyte multilayers containing nanofibrillated cellulose
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2012 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, no 2, p. 496-499Article in journal (Refereed) Published
Abstract [en]

Recent findings have shown that it is possible to use the Layer-by-Layer technique to create nanofibrillated cellulose / polyethyleneimine interference films whose colour change with relative humidity. This study uses different optical models to describe spectral ellipsometry measurements data of interference films and how the film properties alter in dry and humid environments. The results indicate that water condensation initially is filling the surface pores within seconds whereas relaxation of the film to adjust to the added water is a slower process that reaches a steady state after ≈20 min. The maximum swelling ratio of the LbL films is almost independent of the number of layers within the film, but decreases considerably by crosslinking via heat treatment. The films show a distinct birefringence with optical axis perpendicular to the surface. Analysis of the moisture response with different optical models indicates that the films swell uniformly in the thickness direction with no separate water film on top. The results provide important understanding for the design of NFC based LbL films for visual moisture sensors and interactive security paper. 

Keywords
Colour; Interference; Layer-by-Layer; Nanofibrillated cellulose; Optics
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-16872 (URN)10.3183/NPPRJ-2012-27-02-p496-499 (DOI)2-s2.0-84865218419 (Scopus ID)
Available from: 2012-08-28 Created: 2012-08-28 Last updated: 2017-12-07Bibliographically approved
Gustafsson Coppel, L., Neuman, M. & Edström, P. (2012). Extension of the Stokes equation for layered constructions to fluorescent turbid media. Journal of the Optical Society of America A, 29(4), 574-578
Open this publication in new window or tab >>Extension of the Stokes equation for layered constructions to fluorescent turbid media
2012 (English)In: Journal of the Optical Society of America A, ISSN 1084-7529, Vol. 29, no 4, p. 574-578Article in journal (Refereed) Published
Abstract [en]

Expressions relating the bispectral reflectance of a stack of n fluorescinglayers to each individual layer's reflectance and transmittance arederived. This theoretical framework is used together with recentlyproposed extensions of the Kubelka--Munk model to study the fluorescencefrom layered turbid media. For one layer over a reflecting background,the model is shown to give the same results as a previous model.The extension to n layers with different optical properties allowssimulating the bispectral reflectance from a pad of layered turbidmedia. The applicability of the model is exemplified with an optimizationof fluorophore distribution in layered turbid media.

Place, publisher, year, edition, pages
Optical Society of America, 2012
Keywords
Fluorescence; Multiple scattering; Turbid media; Color
National Category
Physical Sciences
Identifiers
urn:nbn:se:miun:diva-16015 (URN)000302561500025 ()2-s2.0-84873472513 (Scopus ID)
Projects
PaperOpt
Available from: 2012-03-23 Created: 2012-03-23 Last updated: 2018-02-13Bibliographically approved
Gustafsson Coppel, L., Andersson, M., Neuman, M. & Edström, P. (2012). Fluorescence model for multi-layer papers using conventional spectrophotometers. Nordic Pulp & Paper Research Journal, 27(2), 418-425
Open this publication in new window or tab >>Fluorescence model for multi-layer papers using conventional spectrophotometers
2012 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, no 2, p. 418-425Article in journal (Refereed) Published
Abstract [en]

We present an extension of a Kubelka-Munk based fluorescence model in which we introduce an apparent scattering (SUV) and absorption (KUV) coefficient for all wavelengths below 400 nm. We describe a method for modelling the total radiance factor of multi-layer papers and for estimating the optical parameters (S, K and Q) of each layer. Assuming that the fluorescent whitening agent only absorbs below 400 nm, we are able to determine SUV, KUV and the apparent quantum efficiency, Q(UV,l) for 400 nm<l<700 nm, from spectral radiance measurements in the visual part of the electromagnetic spectrum. We test the proposed method on different layered constructions made of three individual pilot paper layers. The proposed method allows the papermaker to determine the illumination independent fluorescence characteristics of single- and multilayer paper layers using a conventional single-monochromator spectrophotometer operating in the visible part of the electromagnetic spectrum, and also to predict the radiance factor of fluorescing layered papers.

Keywords
Whiteness, Kubelka-Munk, Multi-layer, Fluorescence, Fluorescent whitening agents
National Category
Physical Sciences
Identifiers
urn:nbn:se:miun:diva-16016 (URN)10.3183/NPPRJ-2012-27-02-p418-425 (DOI)000315696000034 ()2-s2.0-84865261999 (Scopus ID)
Projects
PaperOpt
Available from: 2013-04-04 Created: 2012-03-23 Last updated: 2017-12-07Bibliographically approved
Gustafsson Coppel, L. (2012). Whiteness and Fluorescence in Layered Paper and Board: Perception and Optical Modelling. (Doctoral dissertation). Sundsvall: annat förlag
Open this publication in new window or tab >>Whiteness and Fluorescence in Layered Paper and Board: Perception and Optical Modelling
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is about modelling and predicting the perceived whiteness of plain paper from the paper composition, including fluorescent whitening agents. This involves psychophysical modelling of perceived whiteness from measurable light reflectance properties, and physical modelling of light scattering and fluorescence from the paper composition.

Existing models are first tested and improvements are suggested and evaluated. A colour appearance model including simultaneous contrast effects (CIECAM02-m2), earlier tested on coloured surfaces, is successfully applied to perceived whiteness. An extension of the Kubelka-Munk light scattering model including fluorescence for turbid media of finite thickness is successfully tested for the first time on real papers. It is extended to layered constructions with different layer optical properties and modified to enable parameter estimation with conventional d/0° spectrophotometers used in the paper industry. Lateral light scattering is studied to enable simulating the spatially resolved radiance factor from layered constructions, and angle-resolved radiance factor simulations are performed to study angular variation of whiteness.

It is shown that the linear CIE whiteness equation fails to predict the perceived whiteness of highly white papers with distinct bluish tint. This equation is applicable only in a defined region of the colour space, a condition that is shown to be not fulfilled by many commercial office papers, although they appear white to most observers. The proposed non-linear whiteness equations give to these papers a whiteness value that correlates with their perceived whiteness, while application of the CIE whiteness equation outside its region of validity overestimates perceived whiteness.

It is shown that the fluorescence efficiency of FWA is essentially dependent only on the ability of the FWA to absorb light in its absorption band. Increased FWA concentration leads accordingly to increased whiteness. However, since FWA absorbs light in the violet-blue region of the electromagnetic spectrum, the reflectance factor decreases in that region with increasing FWA amount. This violet-blue absorption tends to give a greener shade to the paper and explains most of the observed greening and whiteness saturation at larger FWA concentrations. A red-ward shift of the quantum efficiency is observed with increasing FWA concentration, but this is shown to have a negligible effect on the whiteness value. The results are directly applicable to industrial applications for better instrumental measurement of whiteness and thereby optimising the use of FWA with the goal to improve the perceived whiteness.

Place, publisher, year, edition, pages
Sundsvall: annat förlag, 2012. p. 158
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 138
Keywords
Whiteness, Perception, Colour Appearance Modelling, Paper Optics, Light Scattering, Fluorescence, Lateral Light Scattering, White-Top Mottle, Kubelka-Munk, Radiative Transfer
National Category
Paper, Pulp and Fiber Technology Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:miun:diva-17782 (URN)978-91-87103-50-6 (ISBN)
Public defence
2013-01-23, Sal 0111, Mittuniversitetet, Holmgatan 10, Sundsvall, 10:31 (English)
Opponent
Supervisors
Projects
PaperOpt
Funder
The Knowledge FoundationVinnova
Available from: 2012-12-20 Created: 2012-12-17 Last updated: 2012-12-20Bibliographically approved
Neuman, M., G. Coppel, L. & Edström, P. (2011). Angle resolved color of bulk scattering media. Applied Optics, 50(36), 6555-6563
Open this publication in new window or tab >>Angle resolved color of bulk scattering media
2011 (English)In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 50, no 36, p. 6555-6563Article in journal (Refereed) Published
Abstract [en]

The angle resolved reflectance factor of matte samples is measured with a goniophotometer and simulated using radiative transfer theory. Both measurements and simulations display the same characteristic dependence of the reflectance factor on the observation angle. The angle resolved reflectance spectra are translated to CIELAB color coordinates and the angular color differences are found to be surprisingly large. A chromatic adaptation that is dependent on the observation angle is suggested, in which a nonabsorbing opaque medium is used as the reference white, and the angular color differences are then reduced. Furthermore, the use of an undyed paper as the reference white is evaluated. The angular lightness differences are then reduced further, but the angular differences in chroma are still large. It is suggested that smaller variations in perceived color could be explained by angle dependent chromatic adaptation and a limited sensitivity of the human visual system to changes in chroma.

Keywords
Angle resolved color; bulk scattering media
National Category
Other Physics Topics
Identifiers
urn:nbn:se:miun:diva-15157 (URN)10.1364/AO.50.006555 (DOI)000299166700002 ()2-s2.0-84255190004 (Scopus ID)
Projects
PaperOptOptics of paper and print: continuous models
Available from: 2011-12-12 Created: 2011-12-12 Last updated: 2017-12-08Bibliographically approved
Gustafsson Coppel, L., Andersson, M. & Edström, P. (2011). Determination of quantum efficiency in fluorescing turbid media. Applied Optics, 50(17), 2784-2792
Open this publication in new window or tab >>Determination of quantum efficiency in fluorescing turbid media
2011 (English)In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 50, no 17, p. 2784-2792Article in journal (Refereed) Published
Abstract [en]

A method is proposed to estimate the optical parameters in a fluorescing turbid medium with strong absorption for which traditional Kubelka–Munk theory is not applicable, using a model for the radiative properties of optically thick fluorescent turbid media of finite thickness proposed in 2009[J. Opt. Soc. Am. A26, 1896 (2009)JOAOD60740-323210.1364/JOSAA.26.001896]. The method is successfully applied to uncoated papers with different thicknesses. It is found that the quantum efficiency of fluorescent whitening agents (FWAs) is nearly independent of the fiber type, FWA type, FWA concentration, and filler additive concentration used in this study. The results enable an estimation of the model parameters as function of the FWA concentration and substrate composition. This is necessary in order to use the model for optimizing fluorescence in the paper and textile industries.

Keywords
fluorescence, turbid media, quantum efficiency, scattering, paper
National Category
Engineering and Technology
Identifiers
urn:nbn:se:miun:diva-15704 (URN)10.1364/AO.50.002784 (DOI)000291872800036 ()2-s2.0-79958796672 (Scopus ID)
Projects
PaperOpt
Available from: 2012-01-13 Created: 2012-01-13 Last updated: 2017-12-08Bibliographically approved
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