Monitoring microclimate-induced deformations on hygroscopic materials using conoscopic holography sensors

摘要

Changes of temperature and relative humidity of the environment where the artefact is stored can cause deformationsof the surface that can harm the object or aect the repeatability of the measurement. Currently, thereare very few techniques and approaches that allow studying non-invasively the surface deformations of objects ofdierent sizes maintaining accuracy of the order of micrometres. To address this problem, three dierent systemsbased on a conoscopic holography sensors have been tested on hygroscopic samples. Moreover, we implementeda low-cost apparatus for controlling relative humidity. Eventually, we investigated procedures that use referencestandards, insensitive to thermal and hygrometric variations with the scope to assess short and long-term driftsof the instrumental set-up. We tested the approach on samples of paper and lambskin parchment and on awooden icon.