(19)
(11) EP 0 541 064 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
21.07.1993 Bulletin 1993/29

(43) Date of publication A2:
12.05.1993 Bulletin 1993/19

(21) Application number: 92118896.7

(22) Date of filing: 04.11.1992
(51) International Patent Classification (IPC)5: B41J 2/36
(84) Designated Contracting States:
DE FR GB

(30) Priority: 04.11.1991 US 787810

(71) Applicant: EASTMAN KODAK COMPANY
Rochester, New York 14650-2201 (US)

(72) Inventors:
  • Sasson, Steven J., c/o EASTMAN KODAK COMPANY
    Rochester, New York 14650-2201 (US)
  • Hodge, Donald J., c/o EASTMAN KODAK COMPANY
    Rochester, New York 14650-2201 (US)

(74) Representative: Wagner, Karl H., Dipl.-Ing. 
WAGNER & GEYER Patentanwälte Gewürzmühlstrasse 5
80538 München
80538 München (DE)


(56) References cited: : 
   
       


    (54) Thermal print head unit


    (57) The invention provides a thermal printer with a removable print head unit (14) having a multitude of very small resistance heating elements (34-1...,34-n) for printing small dots or pixels (e.g., 300 pixels per inch) of an image. Minor variations in the printing characteristics of the multitude of individual head elements are electronically compensated for to achieve uniform print densities for that head unit (14). Print compensation data in the form of correction numbers respective to each resistance element of the print head are permanently stored in a low cost device, such as an electronically erasable programmable read only memory (EEPROM), which is furnished as an integral part of the removable head unit (14). Each such head unit is uniquely calibrated by its permanently stored correction numbers to achieve uniform printing action so that for all intents and purposes all such head units perform the same in any printer. Any head unit may be operated in a given thermal printer without further adjustment to the printer. When the printer is powered-up, the correction numbers unique to the head unit (14) then installed in the printer are automatically loaded into the high speed memory and compensation circuits of the printer. This arrangement greatly simplifies the replacement of the head unit of a printer in the field.






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