Model‐based corrections of geometric errors in multiangle measurements of gonio‐apparent coatings

Abstract

Numerical corrections of colorimetric errors caused by positioning error and irregular geometry in multiangle measurements of gonio-apparent coatings are presented. These corrections use a model function approximating the gonio-reflection characteristics of the coating to convert the angular displacement due to those geometric errors to reflectance factor errors to be corrected as well as to estimate the angular displacement conversely from the reflectance factors. The performance of these corrections was evaluated for 11 different gonioapparent coatings using a multiangle geometry conforming to ASTM E2539 consisting of eight subgeometries to which artificial displacements were applied so as to present typical positioning errors or irregular geometries. The results show that both corrections significantly reduce the colorimetric errors for all specimens in all subgeometries sensitive to geometric errors.

Review of instrumental inter‐agreement study of spectral and colorimetric data of commercial multiangle spectrophotometers

“…This instrument is characterized by a new lateral double illumination system at 45° for minimizing colorimetric errors caused by positioning error in multiangle measurements with an area of measurement of 12 mm. A possible irregular geometry of its optics has been corrected . Therefore, the main purpose of this study is to evaluate the instrumental inter‐model‐agreement of the spectral and colorimetric data of the new multiangle spectrophotometer from Konica Minolta with regard to other current commercial multiangle spectrophotometers available in the market in order to guarantee good performance between instruments.…”

“…A possible irregular geometry of its optics has been corrected. 34 Therefore, the main purpose of this study is to evaluate the instrumental inter-model-agreement of the spectral and colorimetric data of the new multiangle spectrophotometer from Konica Minolta with regard to other current commercial multiangle spectrophotometers available in the market in order to guarantee good performance between instruments.…”