US 5,473,351 A · Method and apparatus for regulating print density in an ink-jet printer

Abstract

Method and apparatus for regulating print density in a printer of the type of an ink-jet printer having a print cartridge including nozzles which each fire ink therefrom responsive to a voltage pulse applied to a resistor in the nozzle. An optical sensor senses line width printed by the nozzles. Circuitry determines the difference between a predetermined optimum line width and the printed line width. Look-up tables relate the line width to the energy of a pulse applied to each resistor and use this signal to control ink drop volume, and therefore printed dot size. In another embodiment, a nozzle includes 2400 addressable nozzles per inch. Sensed line width is used to vary the dpi by selecting different ones of the nozzles for firing thereby maintaining appropriate relative positioning of the dots when their size varies from the predetermined line width. In the direction of paper movement, the speed of a paper carrier is varied to match the printing frequency of the X-axis to produce square images.

Claims18

Dependent claims

A method for regulating print density in a printer having a plurality of nozzles which are each associated with a resistor that causes an ink drop to be fired from an associated nozzle responsive to voltage applied thereto, said method comprising the steps of:

selecting a predetermined line width;
positioning print media opposite said nozzles;
applying energy to the resistor associated with each of said nozzles in increasing predetermined increments during a calibration run so as to produce a plurality of calibration lines having correspondingly increasing line widths;
sensing widths of the calibration lines;
calculating a relationship between the widths of the calibration lines and ink-drop volume;
storing the relationship in the printer;
printing a line on the print media by applying a voltage pulse to the resistor of selected ones of each of said nozzles;
sensing a width of the printed line;
determining a difference between the predetermined line width and the printed line width;
and
varying, in response to the difference determination, a density of ink printed on the print media in accordance with the stored relationship so as to maintain resolution.

8 more elements

Apparatus for regulating printer density in a printer comprising:

a plurality of nozzles arranged to print rows of dots;
a resistor associated with each nozzle, said resistor causing an ink drop to be fired from an associated nozzle responsive to voltage applied to the resistor;
means for moving print media along a media scan axis beneath said nozzles;
means for selecting a predetermined line width;
means for applying energy to the resistor of selected ones of each of said nozzles in increasing predetermined increments during a calibration run so as to produce a plurality of calibration lines having correspondingly increasing line widths;
a sensor for sensing widths of the calibration lines printed on the print media;
means for calculating a relationship between the widths of the calibration lines and ink-drop volume;
means for storing the relationship in the printer;
means for printing a line on the print media;
means for determining a difference between the predetermined line width and the width of such a printed line;
and
means for varying a density of ink printed on the print media responsive to the difference determined by the means for determining and in accordance with the stored relationship so as to maintain resolution.

9 more elements

Dependencies are inferred from the claim text.

Method and apparatus for regulating print density in an ink-jet printer

Life of this patent

Method and apparatus for regulating print density in an ink-jet printer

Life of this patent

Abstract

Claims18