Beyond 2, 2005 - Innventia.com

Have you changedaddress?Please let us know by sendingan e-mail to info@stfi.se.BWhere hasthe light gone,Grace?Ludovic Coppel, Hjalmar Granberg and Marie-Claude Béland are the people behind Grace, anSTFI-Packforsk optical modelling tool for simulatingwhere light goes when it hits paper.“The user interface assists the user in building up a paper structure and in visualisingthe simulation results,” say Ludovic Coppel and Marie-Claude Béland.“Grace allows us to show many differenteffects,” says Marie-Claude Béland. “Togive some examples, this tool shows howlight is reflected, transmitted or absorbedin all the strata of the paper.”Flexible modelling tool“Since this tool is so flexible and offers somany simulation variations, it can be usedto predict paper characteristics before thepaper has been made,” continues Marie-Claude Béland.On a paper machine, it is not so easyGrace simulates a three dimensional structuremodel of the paper, consisting of different layerswith varying optical properties and calliper variations.Incoming light spreads inside the paper andis detected by sensors that simulate a camera, forexample.to control all the parameters and to knowexactly how they will influence the propertiesof a paper. Yet, with the help of awell developed optical modelling tool, itis possible to identify the trends and thecharacteristics that will have an effect onthe finished paper. With Grace, this canbe done by artificially building up thepaper in a computer model and then, ina controlled mode, altering the variousparameters.Optical interplay betweenpaper and lightThe changes made in the model can thenbe visualised in the programme. It showsthe optical interplay between the paperand light in the different strata of thepaper.“We have developed Grace over thecourse of about 10 years. Improvementshave been made to it year after year,” saysLudovic Coppel.There is another interesting applicationfield for Grace. It can be used foranalysing printed paper products. It ispossible to study the connection betweenthe physical parameters and how oneperceives a printed product.“Now we have even developed a modelfor how the eye sees the light comingfrom paper products,” adds Marie-ClaudeBéland.Grace uses the measured paper propertiesto be able to simulate the effectof changes in the paper structure on theappearance of the paper and its opticalproperties. Some of the properties thathave been studied are mottling, glossand gloss variation, fluorescence as wellas colour reproduction. Grace is also capableof generating a paper structure withcertain properties that can then be easilyvisualised.•CONTACT: marieclaude.beland@stfi.seGrace är ett optiskt modellerings-och simuleringsverktyg som visar varljuset tar vägen när det träffar pappersytan.Bland annat kan verktyget visa hur ljusetreflekteras, transmitteras och absorberas ipapperets alla skikt.Grace är flexibelt och erbjuder mångaolika simuleringsvarianter och kan ävenanvändas till att förutse ett pappers egenskaperinnan det är tillverkat.I en pappersmaskin är det inte så lättatt kontrollera alla parametrar och exaktveta vilka parametrar som påverkar papperetsegenskaper. Men med hjälp avGrace går det att identifiera trender ochvilka egenskaper som påverkar det utveckladepapperet. De förändringar som görs imodellen kan programmet visualisera ochvisa det optiska samspelet mellan papperoch ljus i papperets olika skikt.Beyond is published by STFI-Packforsk ABLegally responsible for the publication: Thomas Johannesson (thomas.johannesson@stfi.se)Editor: Veronica Rudheim (veronica.rudheim@stfi.se)Layout: Marianne Lockner (marianne.lockner@stfi.se)Translations: Kevin Austin, BizTech English ABISSN: 1652-6503Print: SIB-Tryck, NorsborgSTFI-Packforsk ABBox 5604, SE-114 86 Stockholm, SwedenPhone: +46 8 676 70 00Fax: +46 8 411 55 18info@stfi.sewww.stfi-packforsk.se– turning science into reality –