Patent Document ID: 4158564
Application ID: 05868098
Patent Status: 1

Claim One:
1. The method of limiting the gray scale response of an electrostatic printer having a multilayered apertured screen comprising a photoconductive layer and at least two electrically conductive layers separated by an insulator for receiving an electrostatic latent image of a source image, a source for projecting charged particles toward said screen for modulated transmission therethrough towards a copy medium in accordance with said latent image, a voltage supply for providing an internal bias voltage said first and second conductive layers of said screen and means for controlling the magnitude of said bias voltage, said method comprising the steps of: (a) impressing an electrostatic latent image on said screen; thereafter (b) adjusting said control means to provide a bias voltage of a first magnitude V.sub.S corresponding to a first image density limit; thereafter (c) altering said latent electrostatic image by directing charged particles toward said screen for an interval sufficient to limit the density producible by said latent electrostatic image to said first limit; thereafter (d) adjusting said bias voltage control means to provide an internal bias voltage of a second magnitude V.sub.P corresponding to a second image density limit; and thereafter (e) directing charged particles toward said screen for duplication interval, the passage of said charged particles during said duplication interval through the screen apertures in areas of image density ranging beyond one of said first and second limits being blocked by the corresponding one of said bias voltages V.sub.P, V.sub.S and the passage of charge particles through the screen apertures in areas of image density corresponding to the other of said first and second limits being substantially uniform over the screen image area.