posted on 2009-05-22, 14:04authored byNeil Brown, Michael Jackson, Robert M. Parkin
This paper describes the development of a non-contact system for measuring the colour of printed material at web speeds, in addition to gravure-printed dot feature recognition. The system proposed uses a non-contact spectrophotometer based on a holographic grating, in conjunction with a conventional monochrome area scan camera, from which colour spectral data are extracted, while a xenon flash is used to illuminate colour samples. Dot features are captured by a magnification lens, in conjunction with a progressive scan camera. Software and hardware details of the system are given, together with the underlying mathematics for colour space conversion and measurement. Conversion equations from X, Y, Z chromaticity coordinates to the RGB system are presented, and also equations to convert from the L*a*b* colour space to X, Y, Z chromaticity coordinates. Experimental results are presented whereby the non-contact spectral system is shown to perform to a colour tolerance exceeding that of conventional colour video systems, and where performance of the dot feature system is comparable with traditional static examination methods using a microscope.
History
School
Mechanical, Electrical and Manufacturing Engineering
Citation
BROWN, N., JACKSON, M.R. and PARKIN, R.M., 2003. Automatic gravure print feature determination at production speeds. Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 217(8), pp. 1101-1110.