Agfa Gevaert Nv

Agfa-Gevaert

Texas Instruments Corporation

Agfa Corporation

Xeikon Manufacturing N.v.

Punch Graphix International N.v.

Frank A Deschuytere

Dirk K Broddin

Paul A Delabastita

Chris Tuijn

William E Nelson

Robert F Janssens

Herman Van De Straete

Venkat V Easwar

Vadlamannati Venkateswar

Werner F Heirbaut

Jean-Pierre J Slabbaert

Danny Smolders

Eric Soulliaert

Werner Willemsens

Erik Van Waverberg

Romain Van Der Gucht

A light emitting head for use in copiers or printers, the light emitting head having an illuminated length, e.g. a print width or copy width, and including a rigid carrier structure provided from a bulk material that spans at least the illuminated length of the head, the bulk material having a coefficient of thermal conduction larger than 100 W/mK and a coefficient of thermal expansion; a plurality of blocks of light elements arranged in a longitudinal array, the blocks having a coefficient of thermal expansion, each of the blocks of light elements having a first and a second surface, each of the blocks of light elements including a plurality of light-emitting elements exposed on a first surface on the block, the plurality of blocks being physically attached to the carrier structure by a conductive adhesive at substantially the second surfaces, and wherein the bulk material has a coefficient of thermal expansion that differs from the thermal expansion coefficient of the block material by a maximum of 5*10/K.

Light emitting array for printing or copying

The present invention provides improved electrostatographic single-pass multiple station printers as well as methods of operating the same being able to avoid displacement of different color images by effects of the toner coverage of the printed pages. To obtain this, a main encoder means () and a printing medium advancement measurement means () are provided, the main encoder means () for producing a first signal () indicative of printing medium displacement and the printing medium advancement measurement means () for providing a second signal () representative of printing medium advancement. The printing medium advancement measurement means () is adapted to co-operate with the main encoder means () for automatic adjustment of said first signal () using said second signal ().

Electrostatographic single-pass multiple station printer with improved colour registration

A frequency-modulation halftone screen and method for making same, utilizing local randomization of a deterministic screen. The deterministic screen optimizes uniformity of the halftone dot distribution, while the local randomization suppresses artifacts due to subject moir&eacute;.

Frequency modulation halfstone screen and method for making the same

A frequency-modulation halftone screen and method that enable the use of relatively large frequency-modulation halftone dots, which have desirable reprographic characteristics, in combination with high resolution rendering of text, graphics, and boundary information in general.

Frequency-modulation halftone screen and method for making same

An apparatus and a method are disclosed for digitizing a color negative picture and correcting the image signals in a way that they are linearly related to the luminance of the photographed scene for grey tones in the scene. A second embodiment allows obtaining on the basis of the color-corrected image signals a reproduction of true color of the scene on a color display unit. For determining the correction, use is made of the characteristic system curve indicating for each of the color components the relation between the luminance of a neutral color swatch in the scene and the density sensed by the scan system. Several methods for drafting said system curve are described. Furthermore, the way of obtaining the color-corrected image signals by means of a color transformation and the way of determining the transformation are explained.

Color negative scanning and transforming into colors of original scene

Color negative scanning and transforming into colors of original

A method is described to control the maximum density and the pixel profile of microdots produced by a binary or multilevel electrophotographic device. In various embodiments, from the maximum development potential. The working point of the device is established by imposing a relation between charge level, discharge level and saturation voltage level of the photosensitive element. This allows to achieve consistent output densities, irrespective of the environmental parameters, such as relative humidity and temperature.

Process control of electrophotographic device

In classic optical rendering systems, the spot, illuminating a microdot on the photosensitive medium, is designed to overlap with neighboring microdots, typically having an overlap of 1.7 times the pitch of the microdots, for a luminous intensity of 1/e.sup.2 the highest intensity. A 'sharp' photosensitive medium, such as a photographic film used in graphical applications, generates a binary circle, obtainable by thresholding. The area of such a circle is too large, which results in higher dot gain. Many systems, such as electrographic systems, do not behave as a 'sharp' medium. If intermediate energy levels are used, in order to obtain continuous tone or multiple density levels, thresholding behavior may be avoided by appropriate choice of energy levels. Such a different sensitometry results in specific requirements for the energy distribution for each microdot. A square shaped uniform energy distribution within the space allotted to each microdot, allows for multiple density levels, without severe sensitometric requirements.

Uniform exposure of photosensitive medium by square intensity profiles

A method is disclosed for rendering monochrome or colored continuous tone images by a system having restricted continuous tone rendering capabilities, such as electrographic printers capable of printing more than two density levels on each addressable micro dot. A method for preferred halftone dot growth is described, starting from isolated dots arranged along base lines and auxiliary lines, evolving to high density lines along the base lines and approximating full continuous tone rendition for high density regions. Preferred arrangements for the orientation, spacing and absolute location of the base lines and auxiliary lines are disclosed and a method to generate preferred arrangements. A moire free combination of three halftone images is described for the reproduction of color images. A method to select a restricted set of energy levels to obtain linear reflectance response is disclosed. Halftone cells are arranged in supercells to improve the density resolution of the system.

Clustered dot and line multilevel halftoning for electrographic color

Clustered dot and line multilevel halftoning for electrographic colour

A halftone screen and method for generating halftones representing a continuous tone image, wherein the number of halftone dots per unit area varies non-proportionally with the tone values utilized as inputs to the screening process. The method incorporates an implicit gradation compensation as part of the frequency modulation halftoning itself to correct for the additional tone gain due to recording, plate processing and/or printing, as well as aesthetic corrections. This implicit compensation has the advantage that no external compensation is required, thereby maintaining the number of tone values which can be rendered on a digital system. Finally, the implicit gradation compensation enables the combination of page elements rendered according to either 'conventional' or 'frequency-modulated' halftoning techniques with appropriate tone-matching.

High precision gradation compensation for stochastic screening

Digital input commands defined in a page description language are separated in two types of instructions: first instructions resulting in solid regions on the printed output and second instructions resulting in halftoned regions. The first instructions generate a binary bitmap indicating a high or low density of the solid regions and a binary bitmask indicating whether recorder elements belong to a solid or screened region. The bitmap and bitmask are preferentially compressed by a lossless compression method. The second type of instructions generate a contone map, representing images having contone levels and graphics having intermediate levels. The contone map is preferentially compressed by a lossy compression method, stored on a storage medium and retrieved once the output device must render the rasterized image. The rasterized image is constructed on the fly from the compressed bitmap, bitmask and contone map, which is halftoned before combination with the bitmap. A serious amount of memory can be saved, while keeping up with the speed of the rendering process in the output devise and without deteriorating the quality of the reproduction.

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Beveren, Belgium

Frank A Deschuytere