Automatic print cartridge alignment sensor system

Claim 2

The swath printer of claim 1 wherein said optical sensing means comprises: an illumination source for illuminating a portion of the print media; imaging means for imaging an illuminated portion of the print media; and optical detecting means having an active area and responsive to said imaging means for providing outputs indicative of position in the active area of a line imaged thereon by said imaging means.

Claim 3

The swath printer of claim 2 wherein said optical detecting means comprises four photodiodes.

Claim 4

The swath printer of claim 3 wherein said four photodiodes are positioned in the corners of a square having sides aligned with said carriage scan axis and with said media scan axis.

Claim 5

The swath printer of claim 4 wherein said optical sensing means further includes: first difference amplifier means responsive to the outputs of a first diagonally opposite pair of said photodiodes for providing a first difference signal; and second difference amplifier means responsive to the outputs of a second diagonally opposite pair of said photodiodes for providing a second difference signal; whereby said first and second difference signals are selectively combined to detect the horizontal positions of vertical lines aligned with the media scan axis and to detect the vertical positions of horizontal lines aligned with the carriage scan axis.

Claim 6

In a swath printer having (a) a carriage that is movable along a horizontal carriage scan axis, (b) printing elements supported by the movable carriage for printing onto a print media that is selectively movable along a vertical media scan axis, and (c) an optical sensor for imaging a line aligned with a first one of said axes and providing an output indicative of the position of such line along a second one of said axes within an operating range of the optical sensor along the second axis, a method for calibrating the optical sensor comprising the steps of: (A) printing a series of line serpents aligned with the first axis and offset relative to each other in the same direction by a predetermined distance along the second axis; (B) positioning the optical sensor generally in the center of the series of test lines along the second axis; (F) changing the position of the optical sensor relative to the print media so as to respectively align the optical sensor with each of the test line segments along the first axis while maintaining the position of the sensor relative to the print media constant along the second axis; (G) reading the output of the optical sensor for each of the test lines with which it is aligned; (I) defining the relation between the positions of the test lines along the second axis and the associated sensor values.

Claim 7

A swath type printer comprising: a print carriage movable along a carriage scan axis; means for moving print media along a media scan axis that is substantially orthogonal to said carriage scan axis; a plurality of printheads supported by said print carriage arranged to print rows of dots in a single scan of said print carriage, each printhead including an array of print elements; and optical sensing means carried by said print carriage and configured to detect the positions along a selected one of the carriage and media axes of lines aligned with the other axis; whereby the offset between the nozzle arrays of said plurality of printhead cartridges is determined by optically sensing the positions along the selected axis of test lines printed by each of said plurality of printhead cartridges in alignment with the other axis.

Claim 8

In a swath printer having (a) a carriage that is movable along a horizontal carriage scan axis in first and second carriage scan directions, (b) a printhead cartridge supported by the movable carriage for printing onto a print media that is selectively movable along a vertical media scan axis, the printhead cartridge having a plurality of print elements arranged in one or more columns aligned with the media scan axis, and (c) an optical sensor for imaging a vertical line and providing an output indicative of the horizontal position of such line within a horizontal operating range of the optical sensor, a method for calibrating the optical sensor comprising the steps of: (A) printing with a selected printhead cartridge in a predetermined carriage scan direction a vertical line segment at a selected swath position; (B) advancing the print media by the swath height of the selected printhead cartridge; (C) printing with the selected printhead cartridge in the predetermined carriage scan direction a vertical line segment at a selected swath position displaced a predetermined amount relative to the swath position for the previously printed vertical line; (D) repeating steps (B) and (C) until a predetermined number of vertical line segments have been printed; (E) horizontally positioning the optical sensor generally in the horizontal center of the series of vertical lines printed pursuant to steps (A) through (D); (F) moving the media so as to vertically align the optical sensor with the first vertical line printed at step (A); (G) reading the output of the optical sensor to determine a sensor value for the first vertical line; (H) moving the media so as to vertically align the optical sensor with the next vertical line printed pursuant to step (C); (J) reading the output of the optical sensor to determine a sensor value for the vertical line with which the optical sensor is vertically aligned; (H) repeating steps (H) and (J) until sensor values have been determined for each of the vertical lines printed pursuant to the steps (A) through (D); and (I) defining the relation between the horizontal positions of the vertical lines and the associated sensor values.

Claim 9

In a swath printer having (a) a carriage that is movable along a horizontal carriage scan axis in first and second carriage scan directions, and (b) a printhead supported by the movable carriage for printing onto a print media that is selectively movable along a vertical media scan axis, the printhead having a plurality of print elements arranged in one or more columns aligned with the media scan axis, an optical sensor for detecting the horizontal position of a vertical line and for detecting the vertical position of a horizontal line, comprising: an illumination source for illuminating a portion of the print media containing a line whose position is to be detected; imaging means for imaging a portion of the illuminated portion of the print media; optical detecting means having an active area and responsive to said imaging means for providing outputs indicative of position in the active area of a line image thereon by said imaging means; difference means responsive to said optical detecting means outputs for providing an output indicative of horizontal position in the active area of an imaged vertical line as well as vertical position of in the active area of an imaged horizontal line.

Claim 10

The optical sensor of claim 9 wherein said optical detecting means comprises four photodiodes located at the corners of a square having sides aligned with the carriage scan axis and the media scan axis such that the photodiodes can be grouped into two pairs of vertically aligned photodiodes as well as two pairs of horizontally aligned diodes, whereby the horizontal position in the active area of an imaged vertical line is represented by the difference between (a) the sum of the outputs of one pair of vertically aligned photodiodes and (b) the sum of the outputs of the other pair of vertically aligned photodiodes, and whereby vertical position in the active area of an imaged vertical line is represented by the difference between (a) the sum of the outputs of one pair of horizontally aligned photodiodes and (b) the sum of the outputs of the other pair of horizontally aligned photodiodes.

Claim 11

The optical sensor of claim 10 wherein said difference means comprises: first difference amplifier means responsive to the outputs of a first diagonally opposite pair of said photodiodes for providing a first difference signal; and second difference amplifier means responsive to the outputs of a second diagonally opposite pair of said photodiodes for providing a second difference signal; whereby said first and second difference signals are selectively combined to detect the horizontal positions of vertical lines aligned with the media scan axis and to detect the vertical positions of horizontal lines aligned with the carriage scan axis.