Velocity detecting apparatus

摘要

Noise signals from a relatively moving object, such as those caused by eddies in a fluid or by protrusions and recesses or gradation on the surface of paper or an iron plate, are sensed at two or more points spaced in the direction of the motion. A difference signal is then obtained from the resulting two noise signals. The relative velocity of the object is detected from the difference signal by utilizing the autocorrelation function or the frequency spectrum of the difference signal.