The School of Electrical, Information and Media Engineering of the University of Wuppertal (BUW) had issued an invitation to the 55th Scientific Colloquium for Print and Media Technology, on the subject of “Specialties of Spectral Color Measurement”, on February 11, 2016. More than 40 guests attended the event, at which results of the successful cooperation between BST eltromat International and the BUW were presented under the title “Results in the Context of Industrial Inline Spectral Color Measurement”. The speakers were Daniel Bohn M.Sc., who has been working at this school of the BUW as a PhD student since 2012 and was responsible for the joint research project, and Dr.-Ing. Dipl.-Math. Michael Dattner, who is in charge of innovation management at BST eltromat. Together with moderator Prof. Ulrich Jung, representative of this school of the BUW, the two speakers guaranteed the high scientific standard of the colloquium.
Industry and science have been meeting at the university for an intensive dialog in the framework of the Scientific Colloquium since 1999. The event is designed to encourage a lively exchange of information between members of the university, business enterprises, students and interested representatives of the print and media industry, regarding current topics, expert knowledge, news and trends.
The 55th Scientific Colloquium mainly focused on two key topics of research: the design of an inline measurement backing, and a model for compensating for varying backing colors.
The backing for the inline measurements is designed to eliminate the air layer between substrate and backing at web speeds up to 1,000 m/min and to obtain a standard-compliant surface (Fig. 1). The industrial capability of the solution was demonstrated on the basis of comprehensive studies, which showed that the reproducibility of an inline system is superior to that of a hand-held device for certain materials. It was also shown in this context, how large the fluctuations can become, if identical samples are measured manually without electrostatic assistance, compared to the inline system (Fig. 2). With electrostatic assistance, the results of the inline system vs. the hand-held device are virtually identical, with an identified mean value of 0.4 DeltaE00.
The physically based model for spectral compensation for different backing colors particularly meets a demand from customers who have individualized backings that deviate from the standard (Fig. 3). The model, derived from Kubelka and Munk, uses the Fresnel equation in the Saunderson correction. In combination, this takes the internal and external reflection processes into account, specifically for film substrates. In this way, the spectral data determined on a white backing can be transformed for backings of any color.
To validate the method, results were presented that had been obtained in connection with an ECI 2002 test chart with 1,504 color patches, printed on films with different opacities. It was demonstrated that a color deviation of up to 11.27 DeltaE00 (mean: 4.48 DeltaE00) is to be expected in the event of changing the backing from white to black. The compensation reduces this color deviation to a maximum of 2.15 DeltaE00 (95% quantile: 1.83 DeltaE00), with a mean of 1.22 DeltaE00, for all 1,504 CIE Lab coordinates (Fig. 4 clearly visualizes this result). Even better results can be expected in the case of colored or slightly deviating backings.
The response from the audience was entirely positive, underlining the great interest of the participants. The key point were presented comprehensibly and vividly – and in sufficient scientific depth to provide an excellent basis for further discussions and personal meetings during the subsequent come-together. “This research cooperation is an ideal example of how productive collaboration between industry and science can be,” said Dr. Dattner, commenting on the successful event. Alongside the aspects dealt with during the Colloquium, the range of topics covered by the research project also included, among other things: Examining the influence of different measuring geometries; RGB image-based homogeneity testing of the measuring position; Development of a concept for parametrizing contrast sensors.
Industry and science have been meeting at the university for an intensive dialog in the framework of the Scientific Colloquium since 1999. The event is designed to encourage a lively exchange of information between members of the university, business enterprises, students and interested representatives of the print and media industry, regarding current topics, expert knowledge, news and trends.
The 55th Scientific Colloquium mainly focused on two key topics of research: the design of an inline measurement backing, and a model for compensating for varying backing colors.
The backing for the inline measurements is designed to eliminate the air layer between substrate and backing at web speeds up to 1,000 m/min and to obtain a standard-compliant surface (Fig. 1). The industrial capability of the solution was demonstrated on the basis of comprehensive studies, which showed that the reproducibility of an inline system is superior to that of a hand-held device for certain materials. It was also shown in this context, how large the fluctuations can become, if identical samples are measured manually without electrostatic assistance, compared to the inline system (Fig. 2). With electrostatic assistance, the results of the inline system vs. the hand-held device are virtually identical, with an identified mean value of 0.4 DeltaE00.
The physically based model for spectral compensation for different backing colors particularly meets a demand from customers who have individualized backings that deviate from the standard (Fig. 3). The model, derived from Kubelka and Munk, uses the Fresnel equation in the Saunderson correction. In combination, this takes the internal and external reflection processes into account, specifically for film substrates. In this way, the spectral data determined on a white backing can be transformed for backings of any color.
To validate the method, results were presented that had been obtained in connection with an ECI 2002 test chart with 1,504 color patches, printed on films with different opacities. It was demonstrated that a color deviation of up to 11.27 DeltaE00 (mean: 4.48 DeltaE00) is to be expected in the event of changing the backing from white to black. The compensation reduces this color deviation to a maximum of 2.15 DeltaE00 (95% quantile: 1.83 DeltaE00), with a mean of 1.22 DeltaE00, for all 1,504 CIE Lab coordinates (Fig. 4 clearly visualizes this result). Even better results can be expected in the case of colored or slightly deviating backings.
The response from the audience was entirely positive, underlining the great interest of the participants. The key point were presented comprehensibly and vividly – and in sufficient scientific depth to provide an excellent basis for further discussions and personal meetings during the subsequent come-together. “This research cooperation is an ideal example of how productive collaboration between industry and science can be,” said Dr. Dattner, commenting on the successful event. Alongside the aspects dealt with during the Colloquium, the range of topics covered by the research project also included, among other things: Examining the influence of different measuring geometries; RGB image-based homogeneity testing of the measuring position; Development of a concept for parametrizing contrast sensors.
