Traceable characterization of cMUT membrane motion

Silicon micromachining permits tailoring, for optimal device performance, the active membranes of capacitive micromachined ultrasound transducers (cMUTs). The membrane motion determines much of the transducer performance. In a thrust towards traceable characterization of cMUT membrane movement we compared a full field 3D imaging technique with a raster scan laser doppler vibrometry (LDV) technique. The 3D profiles of a moving cMUT membrane oscillating at 2.72 MHz were measured using stroboscopic scanning white light interferometry (SSWLI). In SSWLI pulsed illumination is synchronized with the sample oscillation. This method can characterize both in-plane and out-of-plane sample motion. A broadband, rapidly switchable and stable, light source is essential for the technique. Such sources can't be bought.