| abstract |
A method and apparatus are described for the nondestructive readout of a latent electrostatic image formed on a sheet or layer of insulating material. A sheet or layer (419) of semiconductor material is disposed in relatively close proximity to the insulating material (413, 421). A latent electrostatic image formed on the insulating material (413) (by any known means) causes a surface depletion layer to be produced by induction at the surface of the semiconductor material (419). The location and distribution of the accumulated charges on the semiconductor material are read out as analog electrical signals corresponding to the AC surface photovoltage induced on the semiconductor material as the semiconductor material is scanned with a low intensity modulated light beam of appropriate wavelength, the magnitude of the analog signals depending on the local charge density. The analog electrical signals so obtained are then digitized, processed and stored and/or displayed. |