Electric shielding for kinestatic charge detector

Claim 1

In an appartus for detecting propagating energy including means defining a space upon which propagating energy is incident, a medium disposed within the space for interacting with the incident energy to produce secondary energy and means for directing the secondary energy toward a planar detector within the space, said directing mens comprising an electric field across the medium generated by a first electric field across the medium generted by a first electric potential at the detector substantially different from a second electric potential at a side of the space opposite the detector, the improvement comprising: a planar grid positioed adjacent to and spaced from the detector in a plane parallel to a plane of the detector for preventing the secondary energy from being detected by the detector prior to passage through the grid, the grid being formed of three bonded layers comprising a first electrically insulative layer of relatively stiff sheet material electrically separating second and third conductive layers on opposed surfaces of the first layer, said grid including a pluraity of uniformly spaced holes being formed therethrough, each conductive layer being substantially coextensive with the detector; and means for coupling a different voltage to each of said second and third conductive layers for creating a differential electric field through said grid, the voltages applied to each of said conductive layers being intermediate the first and second electric potentials across the medium.