A Noncontact Velocimeter Using Sensing Arrays

A method for measuring the velocity of a surface moving relative to two area-sensing arrays is described. The arrays are separated by a known distance and are driven by a common clock so that their outputs can be correlated element for element. The velocity of the surface in the direction of the center line between the arrays is measured by determining the transit time required for a portion of the surface imaged onto the leading array to move to the trailing array. This is accomplished by exposing the leading array for one frame scan, and after some adjustable time delay, exposing the trailing array and correlating its output with the leading-array output. The time delay which gives the best correlation is the transit time. Experimental results from a laboratory model are presented.