# US 2018/0022131 A1 · Printing system and method

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- Number: US 2018/0022131 A1
- Document ID: US20180022131A1
- Status: Published application
- Kind: A1
- Application number: 15/541,478
- Filed: 2006-01-14
- Published: 2018-01-25
- Earliest claimed: 2006-01-14
- Assignees: Landa Corporation Ltd.
- Applicants: Landa Corporation Ltd.
- Inventors: Shahar KLINGER; David TAL; Alon SIMAN-TOV
- Web page: https://patentgrep.com/patent/US20180022131A1

## CPC

- B41J 29/393: Devices for controlling or analysing the entire machine {; Controlling or analysing mechanical parameters involving printing of test patterns}
- G06T 7/0004: {Industrial image inspection}
- H04N 1/4015: {of the reproducing head}
- H04N 1/6041: {for controlling uniformity of color across image area}
- G06T 2207/30144: Printing quality
- B41J: TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

Some embodiments relate to a digital printing system and method for depositing ink droplets onto a target surface in dependence upon a received electrical printing signal containing data indicating the desired image to be printed while improving the uniformity of intended tone reproduction of the printed image.

## Claims

### Claim 1

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 are dividable into alternating single-print-head slices and interlace slices; B. within the single-print-head slices, the ICF is derived primarily from region-internal DOCI data; and iii. within the interlace slices, the ICF is derived primarily from extrapolation of region external DOCI data.

### Claim 2

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.

### Claim 3

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

### Claim 4

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.

### Claim 5

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.

### Claim 6

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.

### Claim 7 (depends on 6)

The method of claim 6, wherein:
i. the printing system is configured so that images produced by the print-bar thereof are dividable into alternating single-print-head slices and interlace slices;
ii. within the single-print-head slices, the ICF is derived primarily from region-internal DOCI data; and
iii. within the interlace slices, the ICF is derived primarily from extrapolation of region external DOCI data.

### Claim 8 (depends on 6, 7)

The method of any one of claims 6-7, wherein:
i. 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;
ii. 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;
iii. 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.

### Claim 9 (depends on 6, 7)

The method of any one of claims 6-7, wherein:
i. 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;
ii. 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
iii. 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.

### Claim 10 (depends on 6, 7, 8, 9)

The method of any of claims 6-9, wherein:
i. 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;
ii. 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;
iii. 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. 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.

### Claim 11

The method of any preceding claim, wherein the target surface is a surface of an intermediate transfer member (ITM) of the printing system and the ink images formed on the ITM surface by the droplet deposition are subsequently transferred from the ITM to a printing substrate.

### Claim 12 (depends on 11)

The method of claim 11 wherein the ITM is a drum.

### Claim 13 (depends on 11)

The method of claim 11 wherein the ITM is a belt.

### Claim 14

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.

### Claim 15

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.

### Claim 16

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.

### Claim 17

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.

### Claim 18 (depends on 14, 15, 16, 17)

The digital printing system of any of claims 14-17 wherein:
i. the computing system is further configured to perform the calibration, by 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 computing system is further configured to derive the 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.

### Claim 19

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.

### Claim 20 (depends on 14, 15, 16, 17, 18, 19)

The system of any of claims 14-19, further comprising:
c. an intermediate transfer member (ITM); and
d. an impression station,
wherein:
(i) the target surface on which the ink-images are formed by the print bar is a surface of the ITM;
(ii) the ITM is guided so that ink images formed on the ITM surface are subsequently to the impression station; and
(iii) the ink images are transferred, at the impression station, from the ITM to substrate.

### Claim 21 (depends on 20)

The system of claim 20 wherein the ITM is a drum.

### Claim 22 (depends on 20)

The system of claim 20 wherein the ITM is a belt.