- Conference date: 27–29 June 2012
- Location: Ancona, Italy
In a previous work, the authors presented preliminary data showing how noise can be mapped as a function of beam focus and standoff distance. This analysis builds on the previous work, but presents a method of mapping laser Dopopler vibrometer (LDV) noise which can be broadly generalized. The apparatus used in the experiments is a Polytec OFV505 with a custom servo-actuated attachment to the focus ring, which is mounted to linear positioning stages to control standoff distance and dither location. A high resolution grid of measurement locations is generated to create a map of signal strength as a function of both standoff distance and "focus error" - a description of the degree to which the beam is defocused, expressed in terms of how the standoff would need to be adjusted in order to move the beam into focus. Using this approach, the particular optics of the LDV system are no longer directly a factor, as determining the relationship between the focus adjustment and standoff distance should be possible with any system. Further noise maps from experiments which dither the horizontal location of the measurement beam show how the signal field can change for nearby measurement locations on a rough surface and highlight the importance of averaging LDV measurements.
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