PIN HOLE DETECTOR

摘要

Method and apparatus for inspecting a surface capable of holding electrical charge wherein at least one sensing electrode (14) having an edge (18) is located in close physical proximity to the surface and is disposed so that upon relative movement between the surface and sensing electrode, charge on the surface crosses the edge (18) of the electrode. Electrical charge is applied to the surface (12) and relative movement is provided between the surface and sensing electrode (14) while maintaining a constant distance therebetween. A current signal is induced in the sensing electrode in response to a variation in the surface charge crossing the edge of the electrode, and the signal is detected and electrical parameters thereof are measured to provide information on the charge density of the surface to determine the physical uniformity of the surface.