DESCRIPTION
The optical micro-profilometer realized at INO is composed of a commercial conoscopic probe mounted on two motorized high-precision linear stages. The probe is equipped with a 50 mm lens which sets a quota resolution of nearly 1 μm and a dynamic range of 8 mm at a stand-off distance about 40 mm. The overall accuracy is better than 6 μm. Surface shape is obtained by mechanical, non-contact scanning. The system allows measurement on a maximum area of about 30×30 cm2. The instrument has a maximum transversal resolution of 20 μm, with an acquisition speed ranging from 100 to 400 point/s depending on the set spatial sampling frequency. The whole system is computer-controlled. The micro-profilometer allows measurements on surfaces with almost any reflectivity, with an incident angle up to 85°, that is to say, scanning at very close to grazing incidence is possible. Therefore, the survey of very small details, like holes of u0026lt; 1 mm diameter and 25:1 ratio between quota and diameter, is possible. Besides, the instrument is not sensitive to colour gradients being, therefore, also suitable for the survey of surfaces characterized by high chromatic contrast. These characteristics, combined with co-linearity, allow the measuring of thin grooves and deep holes.
POTENTIAL RESULTS
Quantitative evaluation of flakes, wrinkles and furrows in the paint layer, marks in the preparatory layer and deformations in the painting support; morphology of nearly flat surfaces; relief; 3D mesh.
REFERENCE
A scanning device for VIS–NIR multispectral imaging of paintings, C Bonifazzi et al 2008 J. Opt. A: Pure Appl. Opt. 10
064011, DOI: 10.1088/1464-4258/10/6/064011
