The multi-component laser receiver is capable of simultaneously measuring two components of the surface displacement, the out-of-plane and the in-plane motions, using a single laser probe and a single collecting optic. The detection of the in-plane component allows efficient detection of shear waves, particularly when the direction of ultrasounds propagation is normal to the surface of inspection. The TEMPO 2D was born of a research and development grant awarded by the National Science Foundation. The optical setup is based on the TEMPO 1D but with a customized linear array photo-detector capable of detecting both the in-plane and out-of-plane contributions of the surface displacement. The system is capable of reconstructing the complete ultrasonic field.

FEATURES

Multi-Component Receiver
The Tempo 2D can simultaneously measure two components of the surface displacement — the out-of-plane and the in-plane motions — using a single laser probe and a single collecting optic at high frequencies with high sensitivity. The detection of the in-plane component allows for efficient detection of shear waves, particularly when the direction of ultrasounds propagation is normal to the surface of inspection.

High Efficiency Optical Design
The system is optimized to process highly speckled beams. It does not require a single speckle (reflection on mirror-like surface) like classical coherent laser ultrasonic receiver. It also includes a large, 2-inch aperture for high collection-efficiency, ensuring high sensitivity on light-scattering surfaces.

Measurement Precision
The Tempo produces an analog signal that is directly proportional to surface displacements at frequencies above the cutoff. The 2D configuration of the system takes advantage of the
large optical etendue of the Tempo two-wave mixing technology to simultaneously measure in-plane and out-of-plane ultrasonic displacements. When measuring only the out-of-plane displacement, the 2D exhibits the same sensitivity than an optimized single-component interferometer. The in-plane component is obtained without reducing the sensitivity for the out-of-plane component.

Unaffected by Low Frequency Acoustic Noise
Performance is unaffected by low frequency acoustic noise caused by optical components or turbulence in the beam path (Below the cut-off frequency ~ 75Hz without compensation, and up to 10kHz with compensation). The Tempo 1D has an integrated electronic feedback loop that compensates for low frequency acoustic noise up to 10 kHz.

Signal Indicators
Incorporated within the system are visual and audible signal indicators designed to help the user optimize their measurement setup. For absolute calibration, the Tempo 2D also includes an internal calibration signal at 10 kHz.