Goniospectrometric space: identifiable presentation of spectral goniometric data for complex diffractive samples

Abstract

Optical security takes advantage of complex gonioapparent effects of diffractive samples having strong angular and spectral dependence of reflected light. However, resolving the full angular and spectral properties of these kinds of targets might be a tremendous task. Preferably, one would like to measure a more limited number of illumination-viewing directions, using a multiangle goniometer, and still reveal the complex and unique properties of the target. In this study, we use a method for converting the full angular reflection data into reduced goniospectrometric space and further on into an xDNA graph, which we find to show good potential as a fingerprint for gonioapparent surfaces when limited measurement geometries are available. For the evaluation of the xDNA graph, we use two goniometric devices with a 45° incident angle illumination, a high-resolution bidirectional spectrometer, and a portable multiangle goniometer. This study tests the xDNA graph by evaluating the effects of geometry count and spectral resolution in goniometric measurements and further finds that the xDNA graph indeed works best with a reduced count of geometries and is not sensitive to lowered spectral resolution.

Spectroscopic evaluation of the colour play effect of thermochromic liquid crystal printing inks

“…Most likely, the TLC active material inside microcapsules scatters the light in a non‐uniform way so that integrating spheres of smaller diameter cannot integrate it to a good average. However, this interpretation should be studied in more detail, preferably by angular‐resolved measurements such as goniospectrometric measurements .…”