Patent ID: 6146031
Filing Date: 2000-11-14
Classification: B41J

Abstract:
A method for controlling a thermal printer head, wherein a color image is printed on a recording medium by heating the recording medium from one line to another and from one color to another using a plurality of heating units arranged in a line and supplied with a constant heating power, comprising the steps of:receiving image data of the color image from a computer;sensing a temperature of the recording medium;determining a preheat time based on a relationship between a color to be printed and a temperature of the recording medium;applying said constant heating power to preheat the plurality of heating units for the preheat time;selectively heating the plurality of heating units for a plurality of heating cycles to form on the line of the color image, each of the plurality of heating cycles comprising the steps of:sensing a temperature of the recording medium;determining a heating parameter based on a relationship between the color to be printed, the temperature of the recording medium, and the ordinal number of the current heating cycle;determining a heating time based on the heating parameter; andapplying said constant heating power to selectively, according to said image data, heat the plurality of heating units for said heating time according to the image data so as to cause a color density of corresponding dots on said one line of the color image to rise by one color level during each heating cycle,whereby said thermal printer head controls the color density by adjusting the heating time during each cycle head based on changes in the relationship between the change in the color level and the heating time which occur as a result of changes in the recording medium indicated by the sensed temperature of the recording medium, so that the dots in a line of the image are changed by one color level during each cycle.