Description
This paper presents selected surface measurement enhancement techniques while using a three-dimensional vibration measurement optical system. In this case, the 3D scanning Laser Doppler Vibrometer (3D LDV) is used to obtain the frequency response function of the investigated objects. The 3D LDV system allows for contactless measurements of complicated objects and is ideal for cultural heritage objects where, in most cases, it is not permitted to mount sophisticated sensors or use contact methods for the excitation of vibrations. This approach can incorporate sound pressure to input the energy into the system and a laser Doppler vibrometer as sensing technology. In this way, the whole measurement procedure is performed in a completely non-contact way. Additionally, a high number of scan points can be obtained in a very short time. In the case of many objects, especially heritage ones, the additional problem is the lack of visibility of some surfaces from the place where the 3D LDV system is mounted or/and the lack of sufficient signal strength for proper signal acquisition. This paper presents some typical problems and solutions to those issues. Some solutions include the advanced use of mirrors, stitching of measurement planes, and the use of enhancement surface techniques to improve signal strength during the measurement of particular surfaces or for particular difficult environmental conditions. This last element is especially worth evaluating in the case of the measurement of cultural objects in dark and dusty locations. The results demonstrate the feasibility of applying selected methods for 3D vibration measurement by the LDV system for specific objects.
