Optical 3-D dynamic measurement system and its application to polymer membrane inflation tests

An optical surface measurement system, which is capable of measuring transient surface shape, has been developed by using a high-speed digital camera. The system is based on the grating projection and Fourier transform technique. A calibration procedure is developed to allow the system to generate Cartesian coordinates directly, which are with respect to a fixed coordinate system in 3-D space. The measurement accuracy( +/- 50 mum) is defined and verified as the maximum error between measured values and the known values of standard objects both flat and curved. The camera and a grating projector are mounted into a portable sensor head to allow in situ measurements, In addition, external force or pressure signals can be correlated with each measurement through a device called the multi-channel data link. The system is capable of digitizing a 3-D curved surface into an array of points with known xyz coordinates at a sampling rate from 30 to 1000 Hz. As an application, the system is used to measure the transient surface shape during a polymer membrane inflation test. The measurement results along with the pressure information provide an approach to determine the material parameters used in different material models. (C) 2000 Elsevier Science Ltd. All rights reserved.