Analysis of the effect of retro-reflective tape during laser Doppler vibrometry measurements

Laser Doppler vibrometry (LDV) is a non-contact optical measurement technique used to determine the velocity of a vibrating surface. LDV is highly valued for its non-contact, non-invasive approach which captures target vibration without physically altering test article dynamics. Historically hardware limitations required the application of retro-reflective tape to measurement surfaces to support reflection levels for accurate measurements. However, improvements in photodetector technology have supported tape-free LDV measurements for more reflective surfaces in newer LDV measurement systems. Currently, in many situations, tape is still required for non-reflective surfaces. The study is an examination of the effectiveness of retro-reflective tape across different materials and surface roughness to improve measurement quality. Comparative measurements were conducted using the Texas Christian University (TCU) Polytec VibroGo LDV system. Frequency response functions (FRFs) were collected for test samples with both untreated surfaces and surfaces coated with retro-reflective tape. The reflected signal strength, measurement precision, and noise levels are compared across these configurations. For instances where both cases were successfully tested, the effect of the tape introducing unwanted surface dynamics or the effect of additional weight on the test article dynamics is explored.