Detecting the size and shape of bodies

Apparatus for detecting information as to the shape and size of a body, comprising a capacitor, between the plates of which the body is moveable along a fixed path, the electric field of the capacitor plates cutting the path at different points across the breadth of the path along the length of said path, circuit means for determining changes in dielectric constant of the capacitor caused by said movement of the body along the path between the plates, and comparator means for comparing said changes with changes in dielectric constant constant caused by a reference body of known size and shape thereby to determine information as to the size and shape of a body.

Apparatus for use in extracting information concerning a body, comprising means defining a fixed path along which the body moves translationally while rotating about an axis normal to the direction of translation, a capacitor having its plates arranged such that the body moves between the plates as it traverses said path, said plates being elongate and parallel and disposed obliquely to said fixed path such that the electric field of the plates cuts obliquely across said fixed path and intersects the moving body at different points along its said axis as the body traverses said path, and means for detecting changes in dielectric constant of the capacitor caused by movement of the body along said path.