Agfa-gevaert

Agfa Gevaert Nv

Eric Kaerts

Dirk Meeussen

Geert H Defieuw

Ivan Hoogmartens

Luc Horemans

Stefaan DeMeutter

Bartholom&auml;us Herrmann-Biber

Paul Verzele

A thermal head printer with image-invariant printing speeds for printing a substantially light-insensitive thermographic material having a print density-driving power level characteristic, the thermal head printer comprising a transport means, one or more thermal heads each having an array of heating elements, a thermal print head drive system capable of supplying power to each of the printing elements, and a calibration means based on the print density-driving power level characteristic of the thermographic material; a process for calibrating a thermal head printer with image-invariant printing speeds, the thermal head printer comprising one or more thermal heads each having an array of heating elements connected to a power supply capable of supplying a given number of heating element driving power levels from 0 to a maximum driving power level number, corresponding to P, to each heating element for printing a substantially light-insensitive thermographic material by image-wise heating the thermographic material with the heating elements, the process comprising the steps of: (i) putting the printer into a calibration mode; (ii) printing one or more step-wedges of print densities by heating the thermographic material with the heating elements at different DPLN'S; (iii) determining the optical density of each step of the step-wedge(s) of print densities with a densitometer thereby obtaining the dependence of the print density upon DPLN; (iv) deriving from the dependence, or all the dependences of the print density upon DPLN, a single smoothed dependence of the rate of change of print density, D, with DPLN, &#x394;D/&#x394;DPLN, as a function of DPLN for the thermographic material; (v) establishing a threshold rate of print density change per DPLN for the specific thermographic material being printed; and (vi) setting up the thermal head printer so that the threshold rate of print density increase per DPLN cannot be undercut; and a process for printing a substantially light-insensitive thermographic material with a thermal head printer comprising one or more thermal heads each having an array of heating elements connected to a power supply capable of supplying a given number of heating element driving power levels from 0 to a maximum driving power level number, corresponding to P, the process comprising the steps of: calibrating the thermal head printer according to the above-described calibration process, transporting the substantially light-insensitive thermographic material past the thermal head, and image-wise heating of the substantially light-insensitive thermographic material by means of the heating elements.

Thermal head printer and process for printing substantially light-insensitive recording materials

A thermal head printer for printing but not perforating a substantially light-insensitive thermographic material, the thermal printer comprising: a transport system having a transport direction, n thermal heads, where n is an integer, each of the thermal heads comprising an array of substantially rectangular energizable heating elements, the heating elements having a length Lin the transport direction and a pitch Pbetween adjacent heating elements, and a means for supplying electrical energy to each of the substantially rectangular energizable heating elements in at least one of the thermal heads, the transport system being capable of transporting the light-insensitive thermographic material in contact or proximity with at least one of the thermal heads, wherein at least one of the thermal heads comprises heating elements for which L/Pis between 0.25 and 0.88; a first process for printing a substantially light-insensitive thermographic material with the above-described thermal head printer; a second process for printing a substantially light-insensitive thermographic material at different printing speeds with a thermal head comprising heating elements without significant variation in image tone, wherein the length of the heating elements in the transport direction of the substantially light-insensitive thermographic material decreases with decreasing printing speed; and a third process for printing a substantially light-insensitive thermographic material at different printing speeds with a different thermal head at each printing speed without significant variation in image tone, wherein each of said different thermal heads comprises heating elements with a different length in the transport direction of the substantially light-insensitive thermographic material and the length of the heating elements in the transport direction of the substantially light-insensitive thermographic material decreases with decreasing printing speed.

Thermal head printer and process for printing substantially light-insensitive recording material

A method for calibrating a thermal printer, having a thermal head incorporating a plurality of energisable heating elements, comprises the step of supplying to the thermal printer a thermographic material m, a plurality of printer data P each intended to be recorded as a pixel having a density Di, and default reference values for printing parameters comprising a value Pref for a reference printing power; and the step of printing a calibration pattern for the plurality of printer data P , the calibration pattern comprising a multiple step density wedge such that a whole range of a relation Di(P ) between the printer data P and the density Di is covered. Further steps comprise measuring a density Dexp for each patch of the density wedge of the calibration pattern in relation to the plurality of printer data P and storing a first set S &equals;(Pref, P , Dexp ) in a first memory M ; calculating, for a desired density Dwant , a corresponding value Prefnew for the reference printing power and storing a second set S &equals;(Dwant , Prefnew ) in a second memory M ; calculating, for the desired density Dwant , for each printer data P a corresponding density Di and storing a third set S &equals;(Dwant , Prefnew , P , Di) in a third memory M

Method for calibrating a thermal printer

A method for printing by thermal sublimation is provided, comprising the steps of: 1) supplying uncorrected input data I.sub.i,u to a processing unit of a printer having a head with a plurality of heating elements; 2) obtaining density correction means M.sub.i,d for improving across-the-head uneveness according to the steps of: a) activating each heating element with power compensated input data, so that a same time-averaged power is generated in each heating element; b) measuring the printing density of pixels; c) estimating for each heating element the deviation .delta..sub.i of the density from a density aimed at by applying said power; d) calculating for each heating element a density correction means M.sub.i,d taking into account said deviation .delta..sub.i ; e) storing each of said density correction means M.sub.i,d ; 3) combining the respective uncorrected input data I.sub.i,u with the respective density correction means M.sub.i,d ; 4) providing the thus corrected data to the thermal head.

Method for correcting across-the-head uneveness in a thermal printing

Thermal recording comprising the steps of supplying input data I.sub.u to a processing unit (23) of a printer having a thermal head with a plurality of heating elements; storing input data of a line into a buffer memory (24), further called input line data I.sub.l ; converting (25) the data I.sub.l into serial configurated data I.sub.s ; mapping (32) the data I.sub.s with resistance compensation data into power mapped data I.sub.m ; shifting the data I.sub.m into a shift buffer memory (26), further called shifted power mapped data I.sub.m' ; counting (33) a number N.sub.s,on of simultaneously activated heating elements; adapting (34) a strobe duty cycle .delta. (35) in accordance with N.sub.s,on, further called voltage corrected strobe duty cycle .delta..sub.v ; providing (36) the .delta..sub.v and the data I.sub.m' to the heating elements for reproducing the line of an image.

Method and apparatus for thermal printing with voltage-drop compensation

A thermal dye transfer printing process for making transparent prints, which comprises bringing a dye-bearing donor ribbon (17) in contact with a dye-receiving polymer print sheet (15) at a print zone, supporting both materials on a backing support (14) in said zone and contacting the donor ribbon with a print head (18) for image-wise heating the ribbon and cause dye transfer to the print sheet, wherein the rear side of the print sheet is uniformly heated on a drum (30) after removal of the sheet from the backing support, thereby to reduce curling of the sheet caused by the image-wise heating of its front side.

Thermal dye transfer printing process for reducing curling of a print

A thermal sublimation printer comprises means for counting at periodic observation times the number (N.sub.h) of activated heating elements; means for measuring at periodic observation times the temperature (T.sub.d) of the drum and the temperature (T.sub.h) of the heatsink; means for digitising the measured temperature of the drum and the measured temperature of the heatsink; means for transferring the number of activated heating elements and the digitised temperature values T.sub.d and T.sub.h ; a device for estimating the temperature (T.sub.e) of the heating elements based on the values of N.sub.h, T.sub.d and T.sub.h ; memory means for storing the estimate of the temperature of the heating elements; the printer operating to adjust the applied energy as a function of the estimate of the temperature of the heating elements and of the required temperature of the heating elements.

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Melsele, Belgium

Eric Kaerts