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Thermally activated image bar

  • US 4,701,772 A
  • Filed: 11/26/1986
  • Issued: 10/20/1987
  • Est. Priority Date: 11/26/1986
  • Status: Expired due to Fees
First Claim
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1. A thermally activated image bar for use in an electrophotographic printer to form latent electrostatic images on a photoconductive member of the printer one line of pixels at a time, comprising:

  • at least one transparent prism having a flat surface;

    a transparent member having an index of refraction similar to that of the prism and having at least one flat surface;

    means to maintain the prism and the member in fixed relationship to each other, so that their respective surfaces confront and are spaced parallel with each other to form a uniformly thick gap therebetween;

    a liquid medium hermetically sealed between the confronting surfaces of the prism and member, the liquid medium having an index of refraction substantially matched to that of the prism and the member;

    an optical shield being formed on the prism surface having at least one aperture therein for the passage of light therethrough;

    a linear array of transparent heating elements and associated addressing electrodes therefor being formed on the member flat surface, the heating elements being aligned with said at least one aperture;

    means to direct a sheet of light to the photoconductive member through the image bar, so that the sheet of light passes through the prism, optical shield aperture, and the liquid medium in the gap before it strikes the array of heating elements and exits from the member; and

    means for selectively applying current pulses to the heating elements in response to digitized data signals to form momentary vapor bubbles in the liquid medium, the bubbles providing an index of refraction different from the liquid medium, thereby modulating portions of the sheet of light passing therethrough by the mechanism of total internal reflection.

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