Color electrophotography using encoded multicolor information

Claim 1

A method comprising: focusing light from a multicolor object field to be photographed through a color-encoding spatial filter and transparent conductive layer onto a single adjacent photoconductive insulating layer, forming a color-encoded image corresponding to the multicolor object field thereon, said spatial filter comprised of a plurality of at least three gratings, each grating including spaced lines of the same color, three of the gratings being of different primary subtractive colors thereby encoding the object color information in the formed image in the form of a plurality of sets of fine lines corresponding to the respective gratings of the spatial filter; positioning a single film of transparent dielectric material adjacent the surface of the photoconductive layer opposite the transparent conductive layer; pressure biasing the film against the photoconductive surface by means of a conductive pressure plate; applying a voltage pulse between the transparent conductive layer and the conductive pressure plate during the aforesaid step of focusing light from the multicolor object field onto the photoconductive layer thereby forming a color-encoded electrostatic latent image corresponding to the multicolor object field on the film; developing said electrostatic latent image to form a black and white transparency having the object multicolor information encoded therein in the form of a plurality of sets of fine lines; illuminating said transparency with coherent light; focusing the light passing through said transparency onto a mask positioned in the Fourier transform plane of the light passing through the transparency, said mask having at least one aperture disposed in the position of the diffraction pattern formed by a first one of the sets of fine lines encoded in the image transparency, corresponding to a first one of the gratings of the color-encoding spatial filter; imaging the light passing through said mask at an electrostatic printing station to provide a first image component; developing said first image component on a print receiving medium with marking particles of a first color; changing said mask to provide at least one aperture at a second position being the diffraction pattern formed by a second one of the sets of fine lines encoded in the image transparency corresponding to a second one of the gratings of the color-encoding spatial filter; imaging the light passing through said mask at said electrostatic printing station to provide a second image component; developing said second image component on said print receiving medium over the first image component with marking particles of a second color; changing said mask to provide at least one aperture at a third position being the diffraction pattern formed by a third one of the sets of fine lines encoded in the image transparency corresponding to a third one of the gratings of the color-encoding spatial filter; imaging the light passing through said mask at said electrostatic printing station to provide a third image component; and developing said third image component on said print receiving medium over the first and second image components with marking particles of a third color; wherein the steps of imaging at an electrostatic printing station comprise imaging the light passing through said mask onto a multi-layered apertured screen comprising at least a photoconductive insulating layer and a conductive layer, said apertured screen positioned at a printing station having a source of charged particles disposed on one side thereof and a print-receiving medium and back electrode disposed on the other side thereof, forming an electrostatic latent image of the image component across said screen, the electrostatic latent image comprised of fringing fields in the apertures of the apertured screen, and directing a flow of charged particles through said screen thereby to modulate the flow in accordance with the electrostatic latent image component pattern.

Claim 2

A method comprising: focusing light from a multicolor object field to be photographed through a color-encoding spatial filter and transparent conductive layer onto a single adjacent photoconductive insulating layer, forming a color-encoded image corresponding to the multicolor object field thereon, said spatial filter comprised of a plurality of at least three gratings, each grating including spaced lines of the same color, three of the gratings being of different primary subtractive colors thereby encoding the object color information in the formed image in the form of a plurality of sets of fine lines corresponding to the respective gratings of the spatial filter; positioning a single film of transparent dielectric material adjacent the surface of the photoconductive layer opposite the transparent conductive layer; pressure biasing the film against the photoconductive surface by means of a conductive pressure plate; applying a voltage pulse between the transparent conductive layer and the conductive pressure plate during the aforesaid step of focusing light from the multicolor object field onto the photoconductive layer thereby forming a color-encoded electrostatic latent image corresponding to the multicolor object field on the film; developing said electrostatic latent image to form a black and white transparency having the object multicolor information encoded therein in the form of a plurality of sets of fine lines; illuminating said transparency with coherent light; focusing the light passing through said transparency onto a mask positioned in the Fourier transform plane of the light passing through the transparency, said mask having at least one aperture disposed in the position of the diffraction pattern formed by a first one of the sets of fine lines encoded in the image transparency, corresponding to a first one of the gratings of the color-encoding spatial filter; imaging the light passing through said mask at an electrostatic printing station to provide a first image component; developing said first image component on a print receiving medium with marking particles of a first color; changing said mask to provide at least one aperture at a second position being the diffraction pattern formed by a second one of the sets of fine lines encoded in the image transparency corresponding to a second one of the gratings of the color-encoding spatial filter; imaging the light passing through said mask at said electrostatic printing station to provide a second image component; developing said second image component on said print receiving medium over the first image component with marking particles of a second color; changing said mask to provide at least one aperture at a third position being the diffraction pattern formed by a third one of the sets of fine lines encoded in the image transparency corresponding to a third one of the gratings of the color-encoding spatial filter; imaging the light passing through said mask at said electrostatic printing station to provide a third image component; and developing said third image component on said print receiving medium over the first and second image components with marking particles of a third color; wherein the steps of imaging at an electrostatic printing station comprise imaging the light passing through said mask onto a multi-layered apertured screen comprising at least a photoconductive insulating layer and a conductive layer, said apertured screen positioned at a printing station having a source of charged particles disposed on one side thereof and a print-receiving medium and back electrode disposed on the other side thereof, forming an electrostatic latent image of the image component across said screen, the electrostatic latent image comprised of fringing fields in the apertures of the apertured screen, and directing a flow of charged particles through said screen thereby to modulate the flow in accordance with the electrostatic latent image component pattern.