Thermally activated image bar
First Claim
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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Accused Products
Abstract
A thermally activated image bar is disclosed for use in an electrophotographic printer. The image bar comprises at least one transparent prism having a surface closely spaced and parallel with a confronting surface of a transparent member containing an array of transparent heating elements and addressing electrodes thereon to form a gap therebetween. A liquid medium also capable of transmitting light and having an index of refraction matched to that of at least one prism is positioned in the gap. An optical shield bonded to one of the confronting surfaces has at least one aperture aligned with the heating elements to improve optical contrast. This assembly is hermetically sealed within a transparent housing and means are optionally provided to circulate the liquid medium. The heating elements are selectively energized in response to digitized data signals for pulse heating the portions of the liquid medium in the vicinity thereof to form momentary bubbles. The bubbles cause changes in the index of refraction of the medium in the gap, so that selected portions of a sheet of light directed through the prism and into the bubbles are deflected or modulated by the mechanism of total internal reflection. The modulated light may be blocked by a stop or shutter and the unmodulated light may be directed to the precharged photoconductive member of the printer to form latent images or vice versa. Several configurations of the image bar are disclosed for producing latent electrostatic images on a photoconductive member one line of picture elements or pixels at a time. In one embodiment, the optical shield contains a plurality of tunnels which are aligned with the heating elements, so that the bubbles produce a self-pumping action that causes circulation of the liquid medium.
40 Citations
15 Claims
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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:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. 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:
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a transparent prism having a flat surface; a transparent flat substrate having an index of refraction similar to that of the prism and having parallel opposing surfaces, an optical shield with an elongated slit therein being formed on one of the flat substrate surfaces in alignment with an array of transparent heating elements formed on the other flat substrate surface, the heating elements each having an associated addressing electrode, said optical shield and heating elements together with their associated electrodes being formed on the opposing surfaces of the flat substrate prior to said flat substrate being optically bonded to the prism in a manner such that the optical shield is sandwiched between the prism and the flat substrate; a liquid medium having an index of refraction substantially matched to that of the prism and flat substrate; a housing for containing a quantity of the liquid medium, the flat substrate forming one of the housing walls and hermetically sealing the liquid medium therein; a circulating plate having openings at opposing ends and being mounted internally of the housing, so that it is spaced from and parallel to the flat substrate to form a uniform gap between them, the circulating plate openings providing means for circulation of the liquid medium through the uniform gap when the heating elements produce vapor bubbles in the liquid medium; means to direct and focus a sheet of light through the prism, optical shield aperture, and flat substrate as a first focal line of light on the array of heating elements; 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 first focal line of light and passing the modulated portions thereof from the prism by the mechanism of total internal reflection and onto the photoconductive member. - View Dependent Claims (15)
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Specification