| 摘要 |
A portable camera is described by which electrostatic photocopies can be obtained instead of conventional photographs. The camera includes conventional aperture and optical focusing means for producing an image, a surface on which the image is formed, electrode means for electrically charging the surface, an integral EHT generator for producing a high voltage pulse for application to the electrode, a shutter for controlling the passage of light to the surface and a means for applying a printing medium to the surface for retention thereon in dependence on the level of electrical charge remaining at different points over the surface after exposure to the light image. Rollers and a reservoir of a suspension of printing medium particles serve to apply the printing medium to the surface and heated rollers or pressure rollers are used to fix the print. A development electrode may be employed in the form of a grounded conductive plate or roller placed in the immediate vicinity of the electrical image to eliminate edge effect. The surface on which the image is formed may comprise a zinc oxide coated paper or a plate coated with cadmium sulphide or selenium for producing an intermediate electrostatic image. Where zinc oxide coated paper is employed, the optical system must produce an inverted real optical image. Distribution of charge is improved by incorporating a frame electrode at the same potential as the surface. A transparent dotted screen may be inserted in front of the surface prior to image exposure so as to produce a plurality of isolated areas of charge on the surface to reduce charge migration and maintain charge and print density levels. Uniformity of charge is compensated by an aperture in an opaque member which causes a fall-off in light intensity over the surface similar to the fall-off of charge intensity from the electrode.
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