Some new developments in optical dynamic testing

• Main Authors: Fu, Yu, Phua, Poh Boon
• Other Authors: International Conference on Experimental Mechanics (4th : 2009 : SIngapore)
• Format: Conference or Workshop Item
• Language: English
• Published: 2010
• Subjects: DRNTU::Science::Physics::Optics and light
• Online Access: https://hdl.handle.net/10356/91914; http://hdl.handle.net/10220/6481
• Institution: Nanyang Technological University

In recent years, optical interferometry based on high-speed imaging has been applied to full-field, non-contact measurement of low-frequency vibration or continuous-deformation. Retrieving dynamic phase values from a sequence of interferogram leads to a precise measurement of different kinematic and deformation parameters of the testing object. However, the temporal measurement range of this type of 2-D method is still limited by the imaging rate of the camera. On the other hand, laser Doppler vibrometer (LDV) significantly extend measurement capabilities in time axis, but most of the present vibrometers are based on pointwise measurement. A scanning system is normally employed to generate a 2-D measurement. This will dramatically increase the measurement time and limit the system to study the repeatable events. In this paper, two new optical dynamic testing methods are introduced to increase the measurement range in temporal and spatial axes. One is based on high-speed digital holography from which the instantaneous phase can be retrieved spatially to avoid the phase ambiguity problem in temporal analysis. Another is a double-beam Doppler vibrometer which can measure the vibration on different points simultaneously. The results of these two methods show the trend that the optical interferometry will meet various requirements of dynamic measurement with different temporal and spatial resolutions.