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EP0627319A1 - Verfahren zum Korrigieren der Ungleichmässigkeit in einem Thermodrucksystem - Google Patents

Verfahren zum Korrigieren der Ungleichmässigkeit in einem Thermodrucksystem Download PDF

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Publication number
EP0627319A1
EP0627319A1 EP94201310A EP94201310A EP0627319A1 EP 0627319 A1 EP0627319 A1 EP 0627319A1 EP 94201310 A EP94201310 A EP 94201310A EP 94201310 A EP94201310 A EP 94201310A EP 0627319 A1 EP0627319 A1 EP 0627319A1
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Prior art keywords
heating element
density
power
printing
pixels
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EP94201310A
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English (en)
French (fr)
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EP0627319B1 (de
Inventor
Eric C/O Agfa-Gevaert N.V. Kaerts
Paul C/O Agfa-Gevaert N.V. Verzele
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Agfa Gevaert NV
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Agfa Gevaert NV
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/315—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material
    • B41J2/32—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material using thermal heads
    • B41J2/35—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material using thermal heads providing current or voltage to the thermal head
    • B41J2/355—Control circuits for heating-element selection
    • B41J2/36—Print density control

Definitions

  • the present invention relates to thermal dye diffusion printing, further commonly referred to as sublimation printing, and more particularly to a method for correcting across-the-head uneveness in the printing density of a thermal sublimation print.
  • transistors 29 are selectively turned on by a high state signal (indicated as an "ANDed” STROBE in Fig. 2) applied to their bases and allow current to flow through their associated heating elements 28. In this way a thermal sublimation hardcopy (17 in Fig 1) of the electrical image data is recorded.
  • the image signal matrix to be printed is preferably directed to an electronic lookup table (abbreviated as LUT) which correlates the density to the number of pulses to be used to drive each heating element (H i ) in the thermal print head; this number will further be referred to as input data (I i ).
  • LUT electronic lookup table
  • I i input data
  • FIG. 5 Before the invention is described in further detail, it is useful to illustrate (Fig. 5) the effect of feeding one activation pulse to a resistive heating element 28, showing the temperature on the vertical axis and the time on the horizontal axis.
  • T e the temperature of the resistive heating element
  • the resistive heating element rises from e.g. 20°C to 300°C, rising steeply at first and then more gradually.
  • the resistive heating element cools at an even more gradual rate.
  • said adjusting of the maximum power available for each heating element (P i,u ) to said predetermined power value (P ref ), is followed by equalising the printing power of all heating elements to a same time averaged power value, preferably equal to P ref .
  • an improved eveness in the printing image is attained, which is remarkably better than the state of the art (as e.g. described in U.S. 4,827,279 and in WO-A- 91 14577).
  • the main reason for the attained eveness may be given by the fact that in the present invention only strongly reduced lateral heatflows between neighbouring heating elements exist, because all heating elements are activated with exactly the same time averaged electrical power and so they all have the same temperature.
  • the most important cause of vertical banding is the existing variation in the electrical resistance values of the heating elements.
  • the upper part of Fig 8 illustrates the variance in printing density (D i ) across a page of a flat field printed respectively with uncorrected input data D i,u and relates to the distribution across the thermal head of the "uncorrected" power P i,u available to each individual heating element H i as it may be determined during a preparatory power measurement. That's why, according to the present invention, first a correction will be made for the resistance variation. Therefor, the first step of the method consists of a power compensation calibration of the heating elements of the thermal head, which preferably can be executed according to our pending patent application (with application number 92203816.1, being filed on 09.12.92).
  • the diffusion process for a pixel is a function of its temperature and of its transfertime
  • the printed density is a function of the applied energy.
  • the activation of the heating elements is preferably executed pulsewise, which will be further described in the next paragraphs, and thus the printing density has to be related to a time averaged power.
  • the activation of the heating elements is executed pulsewise in a special manner, further referred to as "duty cycled pulsing", which is indicated in Fig. 7 showing the current pulses applied to a single heating element (refs. Hi and 28 in Fig. 2).
  • the repetition strobe period (t s ) consists of one heating cycle (t son ) and one cooling cycle (t s - t son ) as indicated in the same Fig. 7.
  • the strobe pulse width (t son ) is the time an enable strobe signal (ref "ANDed” STROBE in Fig. 2) is on.
  • the strobe duty cycle of a heating element is the ratio of the pulse width (t son ) to the repetition strobe period (t s ).
  • the strobe period (t s ) preferably is a constant, but the pulse width (t son ) may be adjustable, according to a precise rule which will be explained later on; so the strobe duty cycle may be varied accordingly.
  • the line time (t l ) is divided in a number (N) of strobe pulses each with repetition strobe periods t s as indicated on Fig. 7.
  • N number of strobe pulses each with repetition strobe periods t s as indicated on Fig. 7.
  • the maximal diffusion time would be reached after 1024 sequential strobe periods.
  • the maximum time averaged power available for each heating element has to be restricted below a physical upper bound (P limit ) defined by the physical constraints of the printing system as regarding lifetime of the heating element, type of consumables to be used, melting or burning of the carrier or the receiver and loss of glossiness of the printing material.
  • P ref 65 mW
  • said power P min may be adjusted to equal the predetermined power value P ref retrieved from the initial configuration settings of the printer (MEM_0).
  • this adjustment of the power preferably is executed by adjusting the pulse duration of the strobe pulses (t son ) and thus adjusting the strobe duty cycle (being t son : t s ) accordingly (cf. Fig. 7).
  • All heating elements may now be activated with a reduced, but common duty cycle and preferably such that P min equals the above mentioned predetermined power value P ref , stored in a memory means of the printer (MEM_0).
  • P min the above mentioned predetermined power value P ref
  • MEM_0 a memory means of the printer
  • said eventually increased power of the actual reference element has nevertheless to be kept constant and equal to the predetermined power value (P ref ), which, according to the present invention, can be obtained by adjusting the pulse duration of the strobe pulses (t son in Fig.7 ) and thus adjusting the strobe duty cycle and the time averaged power accordingly.
  • P ref predetermined power value
  • the maximum power available for each heating element (P i,u ) is already limited to said predetermined power value (P ref ), but said power is not yet necessarily equal for all heating elements (H i ), which thus leaves some banding in the printing image.
  • the method of the present invention prevents such uneveness by a successive step of equalising the available printing power over all heating elements to a same time averaged power value, preferably P ref .
  • P ref time averaged power value
  • This equalising aim may preferably be attained by ommitting an apt number of heating pulses and applies as well in duty cycled pulse systems as in non duty cycled pulse systems, as e.g. pulsewidth or pulsecount systems.
  • the further and individual reduction of the power of said other elements may preferably be done by equidistant skipping a number of heating pulses (see Fig. 9 and Fig. 17.2).
  • equidistant skipping a number of heating cycles of those heating elements that generate too much instantaneous power namely where P i,u > P min
  • a pulsetrain is drawn as activating the reference heating element (with P min ).
  • a corrected pulsetrain is drawn as activating another heating element which in the abscence of the present invention, would dissipate e.g. 25 percent of power above said reference, thus dissipating 125% P ref .
  • every fifth strobe pulse may be skipped.
  • the available time averaged power (P ave ) for every heating element may be made equal and preferably equal to the power of the heating element actually having the lowest time averaged power (P min ).
  • the wording "equidistant skipping” thus mainly excludes the skipping cases wherein all skipped pulses are grouped, as it is often, in the present state of the art, at the end of the line time; but other possible cases of “grouped skipping” are also excluded, as e.g. grouped skipping at the start or (nearly) in the midde of the line time.
  • Figs. 10 and 11 Both figures, showing the temperature on the vertical axis (indicated as T e in °C) and the time on the horizontal axis (indicated as t in ms), are graphs of the heating and cooling curves of two distinctive heating elements heated by heating pulses corresponding to one line-time and including duty cycle activation with time equidistant skipping.
  • the left parts of said Figs. 10 and 11 give the temperature evolution during a complete line time of e.g. 16 milliseconds; the right parts of said Figs. 10 and 11 give a detailed view of the temperature evolution during a small interval within said line time, e.g. from 2 to 4 milliseconds.
  • the upper curves represent the temperature evolution for a heating element with an electrical resistance of e.g. 2000 ⁇ .
  • the lower part of said Figs. 10 and 11 comprises two curves, wherein the smoother curve of the lower curves represents the temperature evolution for a heating element with an electrical resistance of e.g. 2500 ⁇ , and wherein the dented curve of the lower curves represents the temperature evolution for a heating element with an electrical resistance of e.g. 2000 ⁇ but now corrected by equidistant skipping in order to equalise the available power to P min .
  • the upper curve and the smoother curve of the lower curves of Fig. 10 may also be interpreted as representing the temperature evolution if a conventional breaking off LUT would be used; the dented curve of said lower curves relating to a skipping LUT being used. From this Fig. 10 it is seen very clearly that the state of the art with a conventional LUT breaks off the consecutive heating pulses at the end of a number of pulses required to reach a predetermined optical density.
  • each heating element enforces for each heating element a same "temperature profile", meaning that independent from possible variations in the individual characteristics of the distinctive heating elements, each heating element will have a same temperature rise during the heating time.
  • a same optical density meaning that independent from possible variations in the individual characteristics of the distinctive heating elements, each heating element will have a same temperature rise during the heating time.
  • the heating power available for heating elements with different electrical resistances are made equal to a same time averaged power, indicated as P min .
  • P min a time averaged power
  • said calibration can be executed in one of several ways, the common data flow of which is given in Fig. 13.
  • a first embodiment incorporates an adjusting of the power P min by adjusting the duty cycle and a consequential equalising of the power P i,u of each heating element H i to a predetermined power value P ref by equidistant skipping an apt number of heating pulses.
  • a third embodiment incorporates said adjusting of the power P i,u not by adjusting the duty cycle, but replaces said common reduction of the duty cycle by a correspondingly enlarged individual equidistant skipping, such that adjusting and equalising of the power P i,u of each heating element H i to a predetermined power value are obtained both together by equidistant skipping an individual apt number of heating pulses via the datapath and related to each individual heating element.
  • an array of power corrections 121 may be obtained, also referred to as "power map", to obtain power corrected image signals.
  • This array gives for each heating element (H i ) and for each uncorrected input data (I i,u ), the "power corrections" R i,p (as illustrated schematically in Fig. 17.1) intended for equidistant skipping of the strobe pulses according to the present invention.
  • This thus guarantees an equal time averaged power available to the heating elements (H i ), although their individual characteristics, as resistance value (Ref. 28 in Fig. 2) and time delay in the switching circuit (Ref. 29 in Fig. 2), may be different. So, eventual heat flows between neighbouring heating elements are principally eliminated, or at least reduced significantly, which is a great advantage above the prior art of the field and is probably the cause of an improved eveness in the print image.
  • Such power map 121 may be implemented in the form of a lookup table, as it is in some preferred embodiments of the present invention.
  • a power compensation R i,p is memorised, comprising pro density level a row of binary 0 's and 1 's such that te heating element with the highest resistance and which, per consequence, could only dissipate a rather low power, is allowed to dissipate fully naturally, in order to attain the above mentioned P ref , and hence all R i,p 's (with i having a fixed value) equal 1.
  • the power map will present a R i,p value consisting of 1024 times 1 (thus 111...111).
  • the power map will present a R i,p value 11101110.... All other heating elements will have R i,p values in between them, as e.g. 10101010...
  • FIG. 14 shows a clock pulsed strobe path (indicated as STROBE), a main data path (from the uncorrected input data I i,u to the final input data I i,h supplied to the heating elements), a power map 121 resulting from the power compensation calibration, and density correction means M i,d , comprising density correction rows R i,d (ref 141) or density correction factors C i,d (ref 142).
  • the optical transmission (indicated by the symbol T) of a print is the ratio of the light intensity of the transmitted light through the print to the light intensity of the incident light
  • the optical density (indicated by the symbol D) equals the logarithm to the base 10 of the reciprocal of the transmission
  • the next step in the density compensation calibration makes a flat field on a receiver, preferably a transparent receiver.
  • a flat field comprises at least a heigth, e.g. 50 mm, which can be measured correctly by a transmission or reflection densitometer or microdensitometer, the transmittance or a relative transmittance of the transparent receiver versus the position accross the head direction may be measured by said densitometer or microdensitometer.
  • the deviation ( ⁇ i ) of the printing density in relation to a printing density intensionally aimed at by the power applied to each heating element may now be calculated for each heating element in one of following ways.
  • the above mentioned determining for each heating element of the deviation in printing density ( ⁇ i ) may be represented by the difference to a desired density, or calculated relative to D min,p and/or to D max,p or calculated relative to the ratio (D i,p -D min,p )/(D max,p -D min,p ).
  • D i,p is the individual pixel related optical density realised by activating the heating elements with power compensated input data I i,p
  • D min,p is the minimum of all D i,p on a printline
  • D max,p is the maximum of all D i,p on same said printline.
  • said correction of the applied energy is made in reference to the number and the time spread of the strobe pulses, e.g. by additional skipping an apt number of pulses; said skipping being preferably distributed over the total number of strobe pulses (which Sach was already explained above in reference to Fig. 9)
  • the density deviation factor ⁇ i may adapt the contents of the abovementioned power map 121 (Fig. 12 & Fig. 13). More practically, from said ⁇ i may result pro heating element H i a row vector consisting of logical 0's and 1's, as e.g. [11111111001111101 ...], called "density correction row" R i,d . It is stated that this correction row R i,d not necessarily has to be time equidistant, as it may be illustrated by a power map 121 intended for maximal 1024 density levels relating to a heating element with index i and to a density level d.
  • further steps include calculating for each heating element a density correction row R i,d taking into account said deviation ( ⁇ i ) in printing density, and storing each of said density correction rows R i,d individually to each heating element (H i ) into a memory means (POWER MAP_D, ref. 151).
  • further steps may include transforming the input data (I i,u ) to each heating element taking into account said deviation ( ⁇ i ) in printing density, the thus transformed data further being indicated as "density-corrected input data" I i,d , and storing each of said density corrected input data (I i,d ) individually to each heating element (H i ) into a memory means (LUT_D, ref 161).
  • each of said transformed input data (I i,d ) or of each of said density correction factors (Ci,d), both individually related to each heating element can preferably be implemented in the form of a look up table (indicated as LUT_D, ref 161).
  • LUT_D look up table
  • the use of a specific LUT embodiment brings an additional advantage. While such a table consists of an ordered pair of input and output values, the LUT is very efficient in performing repetitive operations. Indeed, rather than calculating every time the density corrected input data I i,d from the power compensated input data I i,p , these power and density corrected data I i,d are directly retrieved from said LUT. Especially when dealing with large size images, this can save a significant amount of time.
  • each heating element is activated by power and density corrected signals available at the output of the ENABLE AND gate 131 (see Fig. 15 and 16), which thus guarantees an equal density printed by the heating elements 29, although their individual characteristics, as e.g. resistance value and mechanical or thermal contacts, may be different.
  • Said fitting parameter ⁇ is generally not a constant over the entire density range.
  • said fitting parameter ⁇ may be defined (see Fig. 18) empirically by the following method:
  • Fig. 17 there is illustrated a principal flow chart of all main steps of the method of the present invention according to a preferred embodiment, including as well the power compensation calibration (see Fig. 17.1) as the density compensation calibration (see Fig. 17.2).
  • Fig. 18 there is illustrated a principal flow chart of all steps of the method for the experimental defining of the fitting parameter ( ⁇ ) according to a preferred embodiment of the present invention. Because the arrangements of Fig. 17 and of Fig. 18 are similar in structure and operation to the above identified steps in the full description, they do not need to be described once again. As already mentioned above, some of these steps may be modified or even omitted, within the same scope of the present invention.
  • the printing system is ready to perform the steps of correcting an input image. While printing, said correction may be carried out by replacing each initially uncorrected input data signal (I i,u ) by its power and density corrected input data signal (I i,d ) .
  • a method for correcting across-the-head uneveness in the printing density (D i ) of a thermal sublimation printer containing a head having a plurality of heating elements (H i ) and containing storing means for holding density corrected values I i,d or density correction factors C i,d or density correction row R i,d for each heating element I i,d so that while printing said density corrected values I i,d or said density correction factors C i,d or said density correction row R i,d can be used to print input image data, characterised in that said density corrected values I i,d or said density correction factors C i,d or said density correction row R i,d are obtained according to the method described hereabove.
  • figure 8 illustrates the variance in printing density (D i ) across a page of a flat field printed respectively with uncorrected input data D i,u , with power corrected input data D i,p and with power and density corrected input data D i,pd .
  • the illustrated curves may progressively be obtained by the consecutive steps of the present invention, which steps were hereabove described one by one. Note that for the density corrected values the same densities are achieved for many more heating elements than for uncorrected values of input data.
  • the method for printing an image by thermal sublimation is characterised in that the pixels wherefrom the printing density in a flat field print is measured, correspond to individual pixels.
  • Such embodiment is schematically illustrated in Figs. 19.1 to 19.5.
  • the method for printing an image by thermal sublimation is characterised in that the initial pixel on a line wherefrom the printing density in a flat field print is measured, is located either in a fixed position (see Figs. 19.1 and 19.2), or in a (phase-) shifted position (see Figs. 19.3 to 19.5)
  • the method for printing an image by thermal sublimation is characterised in that the pixels wherefrom the printing density in a flat field print is measured, correspond to individual pixels which are distant pixels, either periodically distant (see Figs. 19.1 and 19.2) or variably distant (see Figs. 19.3 to 19.5), It may be clear that in case all individual pixels are measured, the highest accuracy may result. It also follows that in case distant pixels are measured, the capacity of the memory may be reduced economically; and that in case of variably distant pixels, possible sytematic faults also may be reduced.
  • the estimating for each heating element of the individual deviation ( ⁇ i ) of the printing density from a printing density aimed at by said power applied to each heating element (H i ) may preferably be carried out by curve fitting.
  • this technique is well known to the people skilled in the art, it does not require any additional description.
  • the method for printing an image by thermal sublimation is characterised in that the distant pixels wherefrom the printing density in a flat field print is measured are variably distant in one direction, e.g. in either horizontal direction (see Fig. 19.4) either in vertical direction (see Fig. 19.3), or are variably distant in two perpendicular directions, preferably in horizontal and in vertical direction (see Fig. 19.5).
  • the method is characterised in that the pixels wherefrom the printing density in a flat field print is measured, correspond to clustered pixels _comprising individual pixels aggregated or clinged together (see Fig. 20)_, having either a fixed number (see Fig. 20.1 to 20.3, 20.5 to 20.7) of pixels or a variable number (see Fig. 20.4) of pixels.
  • a more conventional densitometer _e.g. with a conventional circular spot of a diametre 3 to 5 mm_ may be used and that the capacity of the memory may be reduced economically. It also may be clear that in case all individual pixels are measured, the highest accuracy may result. It also follows that in case distant clusters are measured, the capacity of the memory further may be reduced even more economically; and that in case of variably distant clusters, possible sytematic faults also may be reduced.
  • the method is characterised in that the clustered pixels are aggregated into a rectangular or a quasi-rectangular spot (see Figs. 20.1 to 20.6) or into a circular spot (see Fig. 20.7).
  • the method for printing an image by thermal sublimation is characterised in that the initial cluster on a line wherefrom the printing density in a flat field print is measured, is located either in a fixed position (see Figs. 20.1 and 20.2; 20.4 to 20.7), either in a (phase) shifted position (see Figs. 20.3)
  • the method is characterised in that consecutive sets of clustered pixels are distant, either periodically distant (see Figs. 20.1 and 20.2, 20.4 or 20.5) or variably distant (see Fig. 20.3 and 20.6).
  • the consecutive sets of clustered pixels are variably distant in one direction, e.g. in horizontal direction (see Fig. 20.3) or in vertical direction, or are variably distant in two perpendicular directions, preferably in horizontal and in vertical direction.
  • the method is characterised in that consecutive sets of clustered pixels are partly overlapping (see Figs. 20.6 and 20.7).
  • the method for printing an image by thermal sublimation is characterised in that a memory means (MEM_C) for holding a density correction means M i,d comprises a floppy disk drive fitted for cooperating with a floppy disk for holding a density correction means M i,d for each heating element H i to be used to correct the input image data while printing.
  • a memory means (MEM_C) for holding a density correction means M i,d comprises a floppy disk drive fitted for cooperating with a floppy disk for holding a density correction means M i,d for each heating element H i to be used to correct the input image data while printing.
  • the method for printing an image by thermal sublimation is characterised by the step of storing the estimates for each heating element of the deviation ( ⁇ i ) of the printing density (D i,p ) from a printing density D i,t aimed at by said power applied to each heating element in a memory means that comprises a floppy disk.
  • the method for printing an image by thermal sublimation is characterised by the step of storing the values (e.g. 2000 ⁇ , 2500 ⁇ ) of the electrical resistances of the (e.g. 2880) different heating elements in a memory means that comprises a floppy disk.
  • Both last mentioned embodiments have the specific advantage that, if the thermal head is accurately measured while leaving the manufactury, it may be dispatchied with a floppy disk holding only a moderate number of measured values (e.g. 2880).
  • this floppy disk has to be introduced in a floppy disk drive of the printer, and preferably copied on a hard disk of the printer.
  • said moderate number of measured values e.g. 2880
  • said moderate number of measured values may be read on the hard disk of the printer and may be followed by an automatically generating of the density correction means M i,d described hereabove.
  • the method of the present invention provides a remarkable eveness in the printing density across the headwidth, said method is very well suited to be used in medical diagnosis.
  • the printing may be applied in graphic representations, in facsimile transmission of documents etc.
  • This invention may be used as well for greyscale thermal sublimation printing as well as for colour thermal sublimation printing.

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EP19940201310 1993-05-28 1994-05-10 Verfahren zum Korrigieren der Ungleichmässigkeit in einem Thermodrucksystem Expired - Lifetime EP0627319B1 (de)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0714780A1 (de) * 1994-11-29 1996-06-05 Agfa-Gevaert N.V. Verfahren und Vorrichtung zum Wärmedrucken mit Spannungsabfallkompensation
EP0835760A1 (de) * 1996-10-09 1998-04-15 Agfa-Gevaert N.V. Korrektur der streifenförmigen Druckunregelmässigkeiten in einem thermischen Drucksystem
EP1104700A1 (de) 1999-12-01 2001-06-06 Agfa-Gevaert naamloze vennootschap Thermokopf

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6256161A (ja) * 1985-09-06 1987-03-11 Sharp Corp 印字装置
US4801948A (en) * 1986-04-30 1989-01-31 Fuji Xerox Co., Ltd. Thermal recording apparatus with resistance compensation
US4827279A (en) * 1988-06-16 1989-05-02 Eastman Kodak Company Process for correcting across-the-head nonuniformity in thermal printers
JPH01192561A (ja) * 1988-01-29 1989-08-02 Toshiba Corp 画情報処理方式
JPH01310971A (ja) * 1988-06-08 1989-12-15 Eastman Kodatsuku Japan Kk サーマルプリンタの濃度ムラ補正方法
EP0375073A1 (de) * 1988-12-23 1990-06-27 Koninklijke Philips Electronics N.V. Prädiktive Kodier- und Dekodierschaltung für Bildelementwerte
EP0375921A1 (de) * 1988-12-27 1990-07-04 International Business Machines Corporation Steuerungssystem für eine automatische Läppmaschine
WO1991014577A1 (en) * 1990-03-29 1991-10-03 Dowty Maritime Limited Thermal recording apparatus
US5160941A (en) * 1990-04-26 1992-11-03 Sanyo Electric Co., Ltd. Method for driving thermal print head to maintain more constant print density

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6256161A (ja) * 1985-09-06 1987-03-11 Sharp Corp 印字装置
US4801948A (en) * 1986-04-30 1989-01-31 Fuji Xerox Co., Ltd. Thermal recording apparatus with resistance compensation
JPH01192561A (ja) * 1988-01-29 1989-08-02 Toshiba Corp 画情報処理方式
JPH01310971A (ja) * 1988-06-08 1989-12-15 Eastman Kodatsuku Japan Kk サーマルプリンタの濃度ムラ補正方法
US4827279A (en) * 1988-06-16 1989-05-02 Eastman Kodak Company Process for correcting across-the-head nonuniformity in thermal printers
EP0375073A1 (de) * 1988-12-23 1990-06-27 Koninklijke Philips Electronics N.V. Prädiktive Kodier- und Dekodierschaltung für Bildelementwerte
EP0375921A1 (de) * 1988-12-27 1990-07-04 International Business Machines Corporation Steuerungssystem für eine automatische Läppmaschine
WO1991014577A1 (en) * 1990-03-29 1991-10-03 Dowty Maritime Limited Thermal recording apparatus
US5160941A (en) * 1990-04-26 1992-11-03 Sanyo Electric Co., Ltd. Method for driving thermal print head to maintain more constant print density

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 11, no. 247 (M - 615)<2694> 12 August 1987 (1987-08-12) *
PATENT ABSTRACTS OF JAPAN vol. 13, no. 485 (M - 887)<3833> 6 November 1989 (1989-11-06) *
PATENT ABSTRACTS OF JAPAN vol. 14, no. 110 (M - 943)<4053> 28 February 1990 (1990-02-28) *
SASAKI, E. ET AL.: "HIGH QUALITY RECORDING IN THERMAL DYE TRANSFER PRINTING", THE FIFTH INTERNATIONAL CONGRESS ON ADVANCES IN NON-IMPACT PRINTING TECHNOLOGIES, November 1989 (1989-11-01), HOLIDAY INN ON THE BAY, SAN DIEGO, CALIFORNIA, pages 477 - 484, XP000138923 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0714780A1 (de) * 1994-11-29 1996-06-05 Agfa-Gevaert N.V. Verfahren und Vorrichtung zum Wärmedrucken mit Spannungsabfallkompensation
EP0835760A1 (de) * 1996-10-09 1998-04-15 Agfa-Gevaert N.V. Korrektur der streifenförmigen Druckunregelmässigkeiten in einem thermischen Drucksystem
EP1104700A1 (de) 1999-12-01 2001-06-06 Agfa-Gevaert naamloze vennootschap Thermokopf

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