Development of a new velocity calibration method for laser velocimetry using multiple scattering points on a single slit aperture

We developed a new calibration method for minimizing the uncertainty and for establishing the uncertainty traceability of laser velocimetry, especially for laser Doppler velocimetry (LDV). While former calibration methods had uncertainties larger than the lower uncertainty limit of an LDV, the new method has an uncertainty smaller than that of an LDV. In the new method, the radial uncertainty of a calibration object was reduced by using a combination of a linear precision stage and multiple scattering points placed on a rotating disk. The working principle is based on the linear relationship between the orbit radii and the resulting output signals. A linear regression provides a promising estimate of the true orbit radius and hence the calibration constant of the velocimetry. In the present work, we used multiple scattering points along a single slit aperture located on a rotating disk. The feasibility was confirmed in a series of experiments using a prototype setup of the calibration system. With the new method, the resulting calibration uncertainty is reduced down to 0.2 %, which is smaller than the general uncertainty of an LDV.