Dithering unit for multi-segment printhead

• US 20040239710A1
• Filed: 07/06/2004
• Published: 12/02/2004
• Est. Priority Date: 05/23/2000
• Status: Abandoned Application

• Current Assignee: Silverbrook Research Pty Limited
• Original Assignee: Silverbrook Research Pty Limited
• Inventors: Silverbrook, Kia, Lapstun, Paul, Walmsley, Simon Robert
• Application Number:
  US10/884,881
• Publication Number:
  US 20040239710A1
• Time in Patent Office: Days
• US Class Current: 347/15
• CPC Class Codes: B41J 2/2132 Print quality control characterised by dot disposition, e.g. for reducing white stripes or banding methods for local corrections by dot omission, image edge enhancement, or multi-pass mask selection G06K15/102; colour conversion H04N1/40
• CPC Class Codes: H04N 1/3871 the composed originals being of different kinds, e.g. low- and high-resolution originals
• CPC Class Codes: H04N 1/405 Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels
• CPC Class Codes: H04N 1/4051 producing a dispersed dots halftone pattern, the dots having substantially the same size different sizes H04N1/4057

Abstract

A dithering unit for a multi-segment printhead having a plurality of printhead segments that are positioned in a printhead to span a print area so that portions of consecutive printhead segments overlap in common print areas, with each printhead segment defining a lead-in area in one common print area and a lead-out area in a consecutive common print area, the dithering unit being configured to communicate with an interface to receive image data from the interface and a memory device to receive data relating to the characteristics of the multi-segment printhead, the dithering unit being configured to generate a set of dither matrices for each printhead segment so that each set has at least a lead-in dither matrix associated with the lead-in area and a lead-out dither matrix associated with the lead-out area, to generate lead-in/lead-out dither matrices for each common print area based on characteristics of the printhead segments of each common print area, to generate a variable probability value that is dependent on a scalar value that corresponds to a position along a line spanning each common print area and to interpolate the lead-in/lead-out dither matrices with the variable probability value to generate interpolated lead-in/lead-out dither matrices.

Claims

1. A dithering unit for a multi-segment printhead having a plurality of printhead segments that are positioned in a printhead to span a print area so that portions of consecutive printhead segments overlap in common print areas, with each printhead segment defining a lead-in area in one common print area and a lead-out area in a consecutive common print area, the dithering unit being configured to communicate with an interface to receive image data from the interface and a memory device to receive data relating to the characteristics of the multi-segment printhead, the dithering unit being configured to generate a set of dither matrices for each printhead segment so that each set has at least a lead-in dither matrix associated with the lead-in area and a lead-out dither matrix associated with the lead-out area, to generate lead-in/lead-out dither matrices for each common print area based on characteristics of the printhead segments of each common print area, to generate a variable probability value that is dependent on a scalar value that corresponds to a position along a line spanning each common print area and to interpolate the lead-in/lead-out dither matrices with the variable probability value to generate interpolated lead-in/lead-out dither matrices.

2. A dithering unit according to claim 1 further configured to generate a dither matrix for each non-overlapping area of the printhead segments.

3. An inkjet printer that comprises

a printhead that includes a number of printhead segments that span a print area, the printhead segments being positioned so that portions of consecutive printhead segments overlap in common print areas, with each printhead segment defining a lead-in area in one common print area and a lead-out area in a consecutive common print area;

an interface which is configured to receive image data;

a memory device that is capable of storing data relating to characteristics of the printhead;

a dithering unit according to claim;

a compositor that communicates with the dithering unit to receive data representing the interpolated lead-in/lead-out dither matrices and to composite the data into print data; and

a printhead interface that communicates with the compositor to receive the print data, the printhead interface being in communication with the printhead to provide the printhead with the print data.

4. A printer as claimed in claim 3 wherein each common print area defined by consecutive printhead segments has a width of at least 1 mm.