Spatial Filtering Velocimetry Without Tracer Substance Using linear CCD

Velocity is undoubtedly a fundamental parameter in daily life. Previous studies revealed that the optical velocimetry has the features of non-interfering, non-contact and high accuracy, which make this method welcomed. An optical spatial filtering velocimetry (SFV) will be introduced in this paper. It measures in-plane velocity by measuring signal frequency instead of getting the displacement per unit time. In order to set up an experimental device, we discussed this velocimetry theoretically and obtained the requirements for spatial filter (SF) such as the transmission function. Furthermore, an experiment which is based on taking a linear CCD as a combine of SF and photodetector (PD) is performed, and a lens is also needed for imaging. Analysis of the signal frequency shows that SFV is effective even without a tracer substance to gain the objective displacement, which promises SFV extensive applications. Another attraction of SFV is that a laser as light source is not necessary, which means a cheap broad-spectrum light source can meet the requirement. Thanks to advantages mentioned above, we applied this velocimetry to a specific industrial condition where a small object moves in a plane, and we tested this velocimetry when the velocity is 2.5m/s below and the error of maximum velocity is around 3%-7%.