An optical method for quantifiable three-component LDA/LDV/PDA laser alignment

Abstract Aligning measurement volumes in three component phase Doppler anemometry (3D PDA) and three component laser Doppler anemometry/velocimetry (3D LDA/LDV) remains one of the most challenging aspects of these otherwise relatively plug-and-play techniques. Existing alignment methods often suffer from limited precision and accuracy. Furthermore, they do not allow for accurate quantification of the overlap measurement volume. We present a novel method based entirely on optical observations using conventional cameras. The approach employs a new clustering technique to parameterize the laser beams from captured images, allowing precise determination of the 3D positions of the measurement volumes. The method identifies the position at which the measurement volumes should meet for a perfect alignment. These positions are expressed in the camera reference frame, allowing visual adjustment of the positions of the transmitters. The method also quantifies the effective overlap volume relative to the smallest measurement volume, providing a meaningful metric of alignment accuracy. Calibration using this method demonstrates a significant improvement over traditional approaches.