Infrared vision for the nondestructive inspection of the historic Dery Bridge toll panel

The Dery Gorge holds one of the first toll bridges in Quebec that was in effect from the construction of the bridge in 1804 to be finally abolished in 1910. The toll pricing was indicated on a wooden panel, which was originally installed on the bridge's toll keeper's house, In its present condition this panel shows the toll rates in French and English corresponding to the last period during which the toll was in operation (c.1860-1870), Nevertheless, some indications of older inscriptions can also be partially seen. The main goal of this work was to improve the visibility of the hidden inscriptions by exploring two infrared vision techniques: infrared reflectography and infrared thermography. (author)