High speed D.C. non-contacting electrostatic voltage follower

Claim 1

In a probe for an electrostatic voltmeter including a detector electrode adapted to be disposed toward a test surface bearing an electrostatic quantity to be measure, modulator means operatively associated with said detector electrode for modulating the capacitive coupling between said electrode and said surface, and means defining a path for radiation onto said surface for irradiating a region of said surface in registry with said electrode, the improvement comprising; (a) a carrier element of material transparent to said radiation having a first surface adapted to be disposed toward said test surface; (b) a first film of conductive material transparent to said radiation on said first surface of said carrier element, said first film occupying less than the total area of said first surface of said carrier element and defining said detector electrode; (c) a second film of conductive material transparent to said radiation on the remainder of said first surface of said carrier element and spaced from said first film; (d) said carrier element being operatively associated with said modulator means for modulating the capacitive coupling between said detector electrode and said surface; and (e) said carrier element being disposed in said path for radiation such that radiation passes through said element onto said test surface and such that compensation is made for capacitive fringing effects by allowing for radiation of the fringing areas of the test surface coupled to said detector electrode by fringing capacitance.