Photoacoustic study of printed samples

Photoacoustics and photoacoustic spectroscopy are presented as methods for the non-destructive study of the optical and thermal properties at different depths beneath the sample surface, together with physical principles of indirect photoacoustic effect and its applications in the field of graphic arts. Capabilities for photoacoustic evaluation of printed samples quality in terms of thickness and uniformity of individual ink layers, ink trapping and real tone value regardless of printed substrate characteristics are summarized. Recently the possibilities of photoacoustic investigation of ink trapping on two-colour overprinted solids were tested and compared with results obtained from optical density spectra and CIE L*C*h* coordinates. In this paper a model for dot area determination was proposed and experimentally verified on sets of one-colour prints on paper and good correlation with densitometry results was found. This model was further used for evaluating halftone images printed over solids and photoacoustic approach was compared with another alternative method for dot area determination -- image analysis.