Spectral imaging system for non-contact colour measurement

This paper describes the development of a non-contact system for measuring colour of printed material at web speeds. The system proposed uses a non-co ntact spectrophotometer based on a holographic grating, in conjunction with a conventional monochrome area scan camera. from which colour spectral dat a is extracted, whilst a xenon flash is used to illuminate colour samples. Software and hardware details of the system are given, along with the under lying mathematics fur colour space conversion and measurement. Conversion e quations from X, Y, Z chromaticity co-ordinates to the RGB system are prese nted, and also equations to convert from the L*a*b* colour space to X, Y, Z chromaticity co-ordinates. Experimental results are presented whereby the non-contact spectral system is shown to perform to a colour tolerance excee ding that of conventional colour video systems. (C) 2001 Eisevier Science L td. All rights reserved.