Printing system and method

A method of digital printing by a printing system that (i) comprises a multi-nozzle and multi-head print bar that defines print and cross-print directions and (ii) is configured to convert digital input images into ink images by droplet deposition onto a target surface, the method comprising:

• a. performing a calibration by:
• i. printing on the target surface a digital input-calibration-image DICI by the print-bar of the printing system so as to generate an ink calibration-image;
• ii. optically imaging the ink calibration-image to obtain a digital output-calibration-image DOCI;
• iii. computing from the digital output-calibration-image DOCI a representative print-bar tone-reproduction-function trf(bar) for the entire print bar;
• iv. for each slice slicei(DOCI) of a plurality {slice1(DOCI), slice2(DOCI) . . . sliceN(DOCI)} of slices of the digital output-calibration-image DOCI, computing a respective slice-specific tone-reproduction-function trf(slicei(DOCI));
• and
• v. deriving a print-bar-spanning image-correction-function ICF (cross-print-direction-location, tone-value) from the slice-specific and/or print-bar tone reproduction function(s);
• b. applying the image-correction-function ICF to a uncorrected digital image UDI so as to compute a corrected digital image CDI;
• and
• c. printing the corrected digital image CDI by the printing system,
• wherein:
• A. the printing system is configured so that images produced by the print-bar thereof comprise first and second distinct single-print-head slices and a mediating slice therebetween, the first and second single-print-head slices being respectively exclusive for first and second print-heads of the multi-head print bar;
• B. the mediating slice includes first and second sets of positions interlaced therein, positions of the first and second set respectively corresponding to nozzle positions for nozzles of the first and second print heads;
• C. the deriving of the ICF includes computing first and second extrapolation functions respectively describing extrapolation from the first and second single-print-head slices into the mediating region of DOCI data, or a derivative thereof;
• and iv. within the mediating region, (A) at positions of the first set, the ICF is derived primarily from the first extrapolation function and (B) at positions of the second set, the ICF is derived primarily from the second extrapolation function.

A method of digital printing by a printing system that (i) comprises a multi-nozzle and multi-head print bar that defines print and cross-print directions and (ii) is configured to convert digital input images into ink images by droplet deposition onto a target surface, the method comprising:

• a. performing a calibration by:
• i. printing on the target surface a digital input-calibration-image DICI by the print-bar of the printing system so as to generate an ink calibration-image;
• ii. optically imaging the ink calibration-image to obtain a digital output-calibration-image DOCI;
• iii. computing from the digital output-calibration-image DOCI a representative print-bar tone-reproduction-function trf(bar) for the entire print bar;
• iv. for each slice slicei(DOCI) of a plurality {slice1(DOCI), slice2(DOCI) . . . sliceN(DOCI)} of slices of the digital output-calibration-image DOCI, computing a respective slice-specific tone-reproduction-function trf(slicei(DOCI));
• and
• v. deriving a print-bar-spanning image-correction-function ICF (cross-print-direction-location, tone-value) from the slice-specific and/or print-bar tone reproduction function(s);
• b. applying the image-correction-function ICF to a uncorrected digital image UDI so as to compute a corrected digital image CDI;
• and
• c. printing the corrected digital image CDI by the printing system,
• wherein A. the printing system is configured so that images produced by the print-bar thereof comprise first and second of distinct single-print-head slices and a interlace slice therebetween, the first and second single-print-head slices being respectively exclusive for first and second print-heads;
• B. the interlace slice includes first and second sets of positions interlaced therein, positions of the first and second set respectively corresponding to nozzle positions for nozzles of the first and second print heads;
• and C. within the interlace region, the ICF is computed by determining if a position in the mediating region corresponds to a nozzle position of the first print-head or the second print-head, and the ICF is computed according to the results of the determining

A method of digital printing by a printing system that (i) comprises a multi-nozzle and multi-head print bar that defines print and cross-print directions and (ii) is configured to convert digital input images into ink images by droplet deposition onto a target surface, the method comprising:

• a. performing a calibration by:
• i. printing on the target surface a digital input-calibration-image DICI by the print-bar of the printing system so as to generate an ink calibration-image;
• ii. optically imaging the ink calibration-image to obtain a digital output-calibration-image DOCI;
• iii. computing from the digital output-calibration-image DOCI a representative print-bar tone-reproduction-function trf(bar) for the entire print bar;
• iv. for each slice slicei(DOCI) of a plurality {slice1(DOCI), slice2(DOCI) . . . sliceN(DOCI)} of slices of the digital output-calibration-image DOCI, computing a respective slice-specific tone-reproduction-function trf(slicei(DOCI));
• and
• v. deriving a print-bar-spanning image-correction-function ICF (cross-print-direction-location, tone-value) from the slice-specific and/or print-bar tone reproduction function(s);
• b. applying the image-correction-function ICF to a uncorrected digital image UDI so as to compute a corrected digital image CDI;
• and
• c. printing the corrected digital image CDI by the printing system,
• wherein:
• A. the printing system is configured so that images produced by the print-bar thereof comprise first and second of distinct single-print-head slices and a mediating slice therebetween, the first and second single-print-head slices being respectively exclusive for first and second print-heads;
• B. the mediating region includes first P1 and second P2 positions, the first position P1 being closer to the first single-print-head slice than the second P2 position is to the first single-print-head slice, the second position P2 being closer to the second single-print-head slice than the first position P1 is to the second single-print-head slice;
• C. the deriving of the ICF includes computing first and second extrapolation functions respectively describing extrapolation from the first and second single-print-head slices into the mediating region of DOCI data, or a derivative thereof;
• and D. when computing ICF for the first position, a greater weight is assigned to the second extrapolation function than to the first extrapolation function;
• and v. when computing ICF for the second position, a greater weight is assigned to the first extrapolation function than to the second extrapolation function.

The method of any preceding claim wherein:

• i. the calibration further comprises:
• for each of slice slicei(DOCI) of the slice plurality, applying a respective inverse of a respective slice-specific tone-reproduction-function to the representative print-bar tone-reproduction-function trf(bar) to yield a tone-shift-function-set tsfs(DOCI)={tsf_slice1(DOCI)(tone-value), tsf_slice2(DOCI)(tone-value), . . . tsf_sliceN(DOCI)(tone-value)} of slice-specific tone-shift functions;
• and
• ii. the print-bar-spanning image-correction-function ICF (cross-print-direction-location, tone-value) is derived from the tone-shift-function-set tsfs(DOCI) of slice-specific tone-shift functions.

A method of digital printing by a printing system configured to convert digital input images into ink images by droplet deposition onto a target surface, the printing system comprising a multi-nozzle and multi-head print bar that defines print and cross-print directions, the method comprising:

• a. performing a calibration by:
• i. printing on the target surface a digital input-calibration-image DICI by the print-bar of the printing system so as to generate an ink calibration-image;
• ii. optically imaging the ink calibration-image to obtain a digital output-calibration-image DOCI;
• iii. computing from the digital output-calibration-image DOCI a representative print-bar tone-reproduction-function trf(bar) for the entire print bar;
• iv. for each slice slicei(DOCI) of a plurality {slice1(DOCI), slice2(DOCI) . . . sliceN(DOCI)} of slices of the digital output-calibration-image DOCI, computing a respective slice-specific tone-reproduction-function trf(slicei(DOCI));
• and
• v. for each of slice slicei(DOCI) of the slice-plurality, applying a respective inverse of a respective slice-specific tone-reproduction-function to the representative print-bar tone-reproduction-function trf(bar) to yield a tone-shift-function-set tsfs(DOCI)={tsf_slice1(DOCI)(tone-value), tsf_slice2(DOCI)(tone-value), . . . tsf_sliceN(DOCI)(tone-value)} of slice-specific tone-shift functions;
• and
• vi. deriving a print-bar-spanning image-correction-function ICF (cross-print-direction-location, tone-value) from the tone-shift-function-set tsfs(DOCI) of slice-specific tone-shift functions;
• b. applying the image-correction-function ICF to a uncorrected digital image UDI so as to compute a corrected digital image CDI;
• and
• c. printing the corrected digital image CDI by the printing system.

A digital printing system comprising:

• a. a multi-nozzle and multi-head print bar for depositing ink-droplets on a target surface in dependence to received electrical printing signals to form ink-images on the target surface, the multi-nozzle and multi-head print bar defining print and cross-print directions and being configured so that ink-images produced by the multi-head print-bar are dividable into alternating single-print-head slices and interlace slices;
• and
• b. a computing system for data-processing and for generating the electrical printing signals so as to control the print bar, the computer system configured to:
• i. perform a calibration by:
• A. causing the print bar to print a digital input-calibration-image DICI onto the target surface as to generate an ink calibration-image;
• B. after the DICI is optically imaged into a digital output-calibration-image DOCI representing the ink-calibration image, processing the DOCI to compute therefrom a representative print-bar tone-reproduction-function trf(bar) for the entire print bar;
• C. for each slice slicei(DOCI) of a plurality {slice1(DOCI), slice2(DOCI) . . . sliceN(DOCI)} of slices of the digital output-calibration-image DOCI, computing a respective slice-specific tone-reproduction-function trf(slicei(DOCI));
• and
• D. deriving a print-bar-spanning image-correction-function ICF (cross-print-direction-location, tone-value) from the slice-specific and/or print-bar tone reproduction function(s) such that within the single-print-head slices, the ICF is derived primarily from region-internal DOCI data and within the interlace slices, the ICF is derived primarily from extrapolation of region external DOCI data;
• and
• ii. apply the image-correction-function ICF to a uncorrected digital image UDI so as to compute a corrected digital image CDI;
• and
• iii. cause the print bar to print the corrected digital image CDI onto the target surface.

A digital printing system comprising:

• a. a multi-nozzle and multi-head print bar for depositing ink-droplets on a target surface in dependence to received electrical printing signals to form ink-images on the target surface, the multi-nozzle and multi-head print bar defining print and cross-print directions and being configured so that ink-images produced by the multi-head print-bar comprise first and second distinct single-print-head slices and a mediating slice therebetween, the first and second single-print-head slices being respectively exclusive for first and second print-heads of the multi-head print bar, the mediating slice including first and second sets of positions interlaced therein, positions of the first and second set respectively corresponding to nozzle positions for nozzles of the first and second print heads;
• and
• b. a computing system for data-processing and for generating the electrical printing signals so as to control the print bar, the computer system configured to:
• i. perform a calibration by:
• A. causing the print bar to print a digital input-calibration-image DICI onto the target surface as to generate an ink calibration-image;
• B. after the DICI is optically imaged into a digital output-calibration-image DOCI representing the ink-calibration image, processing the DOCI to compute therefrom a representative print-bar tone-reproduction-function trf(bar) for the entire print bar;
• C. for each slice slicei(DOCI) of a plurality {slice1(DOCI), slice2(DOCI) . . . sliceN(DOCI)} of slices of the digital output-calibration-image DOCI, computing a respective slice-specific tone-reproduction-function trf(slicei(DOCI));
• and
• D. deriving a print-bar-spanning image-correction-function ICF (cross-print-direction-location, tone-value) from the slice-specific and/or print-bar tone reproduction function(s) such that the deriving of the ICF includes computing first and second extrapolation functions respectively describing extrapolation from the first and second single-print-head slices into the mediating region of DOCI data, or a derivative thereof;
• and within the mediating region, (I) at positions of the first set, the ICF is derived primarily from the first extrapolation function and (II) at positions of the second set, the ICF is derived primarily from the second extrapolation function;
• and
• ii. apply the image-correction-function ICF to a uncorrected digital image UDI so as to compute a corrected digital image CDI;
• and
• iii. cause the print bar to print the corrected digital image CDI onto the target surface.

A digital printing system comprising:

• a. a multi-nozzle and multi-head print bar for depositing ink-droplets on a target surface in dependence to received electrical printing signals to form ink-images on the target surface, the multi-nozzle and multi-head print bar defining print and cross-print directions and being configured so that ink-images produced by the multi-head print-bar comprise first and second of distinct single-print-head slices and a mediating slice therebetween, the first and second single-print-head slices being respectively exclusive for first and second of the print-heads of the multi-head print bar, the interlace slice including first and second sets of positions interlaced therein, positions of the first and second set respectively corresponding to nozzle positions for nozzles of the first and second print heads;
• and
• b. a computing system for data-processing and for generating the electrical printing signals so as to control the print bar, the computer system configured to:
• i. perform a calibration by:
• A. causing the print bar to print a digital input-calibration-image DICI onto the target surface as to generate an ink calibration-image;
• B. after the DICI is optically imaged into a digital output-calibration-image DOCI representing the ink-calibration image, processing the DOCI to compute therefrom a representative print-bar tone-reproduction-function trf(bar) for the entire print bar;
• C. for each slice slicei(DOCI) of a plurality {slice9(DOCI), slice2(DOCI) . . . sliceN(DOCI)} of slices of the digital output-calibration-image DOCI, computing a respective slice-specific tone-reproduction-function trf(slicei(DOCI));
• and
• D. deriving a print-bar-spanning image-correction-function ICF (cross-print-direction-location, tone-value) from the slice-specific and/or print-bar tone reproduction function(s) such that within the interlace region, the ICF is computed by determining if a position in the mediating region corresponds to a nozzle position of the first print-head or the second print-head, and the ICF is computed according to the results of the determining;
• and
• ii. apply the image-correction-function ICF to a uncorrected digital image UDI so as to compute a corrected digital image CDI;
• and
• iii. cause the print bar to print the corrected digital image CDI onto the target surface.

A digital printing system comprising:

• a. a multi-nozzle and multi-head print bar for depositing ink-droplets on a target surface in dependence to received electrical printing signals to form ink-images on the target surface, the multi-nozzle and multi-head print bar defining print and cross-print directions and being configured so that ink-images produced by the multi-head print-bar comprise first and second of distinct single-print-head slices and a mediating slice therebetween, the first and second single-print-head slices being respectively exclusive for first and second print-heads, the mediating region includes first P1 and second P2 positions, the first position P1 being closer to the first single-print-head slice than the second P2 position is to the first single-print-head slice, the second position P2 being closer to the second single-print-head slice than the first position P1 is to the second single-print-head slice;
• and
• b. a computing system for data-processing and for generating the electrical printing signals so as to control the print bar, the computer system configured to:
• i. perform a calibration by:
• A. causing the print bar to print a digital input-calibration-image DICI onto the target surface as to generate an ink calibration-image;
• B. after the DICI is optically imaged into a digital output-calibration-image DOCI representing the ink-calibration image, processing the DOCI to compute therefrom a representative print-bar tone-reproduction-function trf(bar) for the entire print bar;
• C. for each slice slicei(DOCI) of a plurality {slice1(DOCI), slice2(DOCI) . . . sliceN(DOCI)} of slices of the digital output-calibration-image DOCI, computing a respective slice-specific tone-reproduction-function trf(slicei(DOCI));
• and
• D. deriving a print-bar-spanning image-correction-function ICF (cross-print-direction-location, tone-value) from the slice-specific and/or print-bar tone reproduction function(s) such that (i) the deriving of the ICF includes computing first and second extrapolation functions respectively describing extrapolation from the first and second single-print-head slices into the mediating region of DOCI data, or a derivative thereof;
• and (ii) when computing ICF for the first position, a greater weight is assigned to the second extrapolation function than to the first extrapolation function;
• and when computing ICF for the second position, a greater weight is assigned to the first extrapolation function than to the second extrapolation function;
• and
• ii. apply the image-correction-function ICF to a uncorrected digital image UDI so as to compute a corrected digital image CDI;
• and
• iii. cause the print bar to print the corrected digital image CDI onto the target surface.

A digital printing system comprising:

• a. a multi-nozzle and multi-head print bar for depositing ink-droplets on a target surface in dependence to received electrical printing signals to form ink-images on the target surface, the multi-nozzle and multi-head print bar defining print and cross-print directions;
• and
• b. a computing system for data-processing and for generating the electrical printing signals so as to control the print bar, the computer system configured to:
• i. perform a calibration by:
• A. causing the print bar to print a digital input-calibration-image DICI onto the target surface as to generate an ink calibration-image;
• B. after the DICI is optically imaged into a digital output-calibration-image DOCI representing the ink-calibration image, processing the DOCI to compute therefrom a representative print-bar tone-reproduction-function trf(bar) for the entire print bar;
• C. for each slice slicei(DOCI) of a plurality {slice1(DOCI), slice2(DOCI) sliceN(DOCI)} of slices of the digital output-calibration-image DOCI, computing a respective slice-specific tone-reproduction-function trf(slicei(DOCI));
• and
• D. for each of slice slicei(DOCI) of the slice-plurality, applying a respective inverse of a respective slice-specific tone-reproduction-function to the representative print-bar tone-reproduction-function trf(bar) to yield a tone-shift-function-set tsfs(DOCI)={tsf_slicei(DOCI)(tone-value), tsf_slice2(DOCI)(tone-value), . . . tsf_sliceN(DOCI)(tone-value)} of slice-specific tone-shift functions;
• and
• E. deriving a print-bar-spanning image-correction-function ICF (cross-print-direction-location, tone-value) from the tone-shift-function-set tsfs(DOCI) of slice-specific tone-shift functions;
• ii. apply the image-correction-function ICF to a uncorrected digital image UDI so as to compute a corrected digital image CDI;
• and
• iii. cause the print bar to print the corrected digital image CDI onto the target surface.