Patent ID: 6494629
Filing Date: 2002-12-17
Classification: B41J

Abstract:
A data processing method for correcting heating data for a thermal head to eliminate influence of heat accumulation in the thermal head on recording density, the thermal head having an array of heating elements arranged in a line and first to Nth heat accumulating layers disposed under the heating elements in this order from the side of heating elements, the heating elements being driven in accordance with corrected heating data, to print one line after another on a recording sheet, one pixel of each line corresponding to one heating element of the array in regular sequence, wherein a drive voltage to be applied across the heating elements is determined according to a temperature of said Nth heat accumulating layer and an environmental temperature around the thermal head, the method comprising the steps of:A. determining first to (Nâˆ’1)th coefficients for said first to (Nâˆ’1)th heat accumulating layers based on heat transmission properties between said first to Nth heat accumulating layers, and a Nth coefficient for said Nth heat accumulating layer based on the drive voltage for the thermal head and on the heat transmission properties between said first to Nth heat accumulating layers; B. obtaining first to Nth correction data for each pixel of a subject line to print, by multiplying first to Nth heat accumulation data by said first to Nth coefficients respectively, said first to Nth heat accumulation data being representative of heat accumulation amounts in said first to Nth heat accumulation layers respectively, and previously stored in relation to each heating element of the array; C. obtaining corrected heating data for each pixel of said subject line, from basic heating data representative of a heat energy value to be applied to said recording sheet for recording said pixel and said first to Nth correction data for said pixel; D. obtaining a new series of first heat accumulation data by multiplying said corrected heating data of said subject line by a coefficient, multiplying said previously stored first heat accumulation data by a coefficient, and adding multiplication results in pixel-to-pixel correspondence; E. obtaining a new series of Jth heat accumulation data, J being 2 to N, by multiplying said previously stored (Jâˆ’1)th heat accumulation data by a coefficient, multiplying said previously stored Jth heat accumulation data by a coefficient, and adding multiplication results in pixel-to-pixel correspondence; F. storing said new series of first to Nth heat accumulation data in place of said previously stored first to Nth heat accumulation data, while said subject line is printed in accordance with said corrected heating data; and G. repeating the above steps B to F for each line to print.