DE102012101207A1 - Method for checking print head arrangement in e.g. electro-graphical printing system, involves assigning certain areas of printed test pattern to certain areas of print head arrangement spatially by coding information - Google Patents

Abstract

The method involves printing test pattern on print head arrangement (10-17) and sensing printed image of test pattern with an opto-electronic sweep device. The identified scanning values are used for review. The test pattern comprising coding information through which certain areas of printed test pattern are spatially assigned to certain areas of print head arrangement. Independent claims are included for the following: (1) a device for checking print head arrangement; (2) a computer for checking print head arrangement; and (3) a computer program product for checking print head arrangement.

Description

The invention relates to a method and apparatus for checking a printhead assembly in a printing system.

Digital high-performance printing devices are able to individually print line by line and in particular pixel-by-pixel information. Such printing devices are based, for example, on electrographic or magnetographic printing techniques or on inkjet techniques. Nowadays, printing speeds of hundreds to several thousand A4 pages per minute can be achieved.

From the US 7,545,523 B2 is a high-performance digital printing system known.

To check the print quality, it is customary to print test patterns and to evaluate them metrologically. In color printing in particular, a number of quality criteria are to be checked, for example color values, density values or the registration of color separations. In the US 2011/0166019 A1 describes a system in which regular patterns are printed, metrologically recorded and the measurement results are used to synchronize the printing process.

From the US 6,474,768 B1 It is known to print colored test patterns and to evaluate the printed image for color deviations.

From the WO 2011/054815 A1 It is known to adjust by means of a test pattern imaging elements of a print head.

The aforementioned publications are hereby incorporated by reference into the present specification.

It is an object of the invention to check a printhead assembly in a printing system in terms of the print quality achieved with it.

This object is achieved by the invention specified in the independent claims. Advantageous embodiments of the invention are specified in the subclaims.

According to the invention, it is provided to print a test pattern with the printhead assembly and to scan the printed image of the test pattern with an optoelectronic scanning device and to use the scanning values determined during the scanning for the verification. In this case, the test pattern comprises an encoding information, by means of which specific areas in printed test patterns can be spatially assigned to specific parts of the print head arrangement. The coding information is arranged spatially in the test pattern in particular. As a result, the spatial allocation to the parts of the printhead assembly is relatively easy.

On the basis of the determined measured values, control values can be adapted for the printhead arrangement or an adjustment of electrical setting values of the printing apparatus can take place in order to optimize the print quality. By means of the measured values, it is also possible to carry out a mechanical adjustment of the printhead arrangement, in particular individual printhead parts assigned to the areas in the test pattern.

The invention is based on the recognition that with the printing of such a test pattern two goals can be pursued in one go. On the one hand, measured values can be recorded by the printed test pattern which provide information about the print quality that can be achieved with the print head arrangement. On the other hand, the test pattern can be used to assign the respective measurement results exactly to a specific part of the print head arrangement, in particular spatially. In particular, the coding information enables automated detection and evaluation of the measuring signals and the printed coding information.

The invention can be used particularly advantageously wherever structurally identical parts are provided at several points in a printing system. For example, it may be provided in an inkjet printing system that a plurality of physically, chemically, mechanically and / or electronically identical printheads are arranged linearly in a so-called pressure bar. By such a modular arrangement can be printed with a corresponding pressure in the printing device statically arranged pressure bar on a principle arbitrarily large print width, this is in each case a multiple of the width of a print head. With the invention, the test pattern areas printed by the respective printheads can then be identified within the printing bar on the basis of printhead-specific coding information.

With the invention can also be advantageously achieved that measurement samples or printed test patterns can be selectively measured from two sides (left / right) with a manually guided scanner freely, ergonomically, easily and user-friendly. As a result, corresponding measurements can be made in a production environment, for example by an operator or user of a printing device, or else as part of a service on-site. No provision needs to be made internally so that a single measuring system can be used on a mobile basis for a variety of pressure equipment, locations or applications. The measuring process can be done in Easily automated, so that the operator does not have to make any inputs during the measurement. The measured value recording can thus be carried out quickly and hardly any errors can be made in the operation of the system.

Advantageously, it can be provided to assign individual parts of the printhead arrangement each individual coding information in the test pattern. If, for example, a plurality of pressure bars are provided within a printing device, which are each provided for printing the same, similar or different inks, then with the invention based on a coding information for the pressure bar a distinction of the printed images of the pressure bolt done. Possibly. In addition, by means of the coding information of the individual print heads within a print bar, a correct assignment of a printed test pattern area to the respective print head can be effected which has printed this test pattern area.

If a plurality of printing devices cooperate in a printing system, for example, a paper web is successively printed by a first printing device on the front and is printed by a second printing device on the back, it can also be distinguished within the test pattern on a pressure device-specific coding information, from which printing device which area of the test pattern was printed. The distinction can then be made advantageously in a test phase based on the printed test pattern, even if it can no longer be determined otherwise during the test phase, which of the two printed pages is the respective front or back of the printed record carrier.

In an advantageous embodiment of the invention, the coding information comprises a barcode. Within a test pattern, the coding information or the barcode can advantageously be integrated into regions of the test pattern in which measuring fields for assessing the print quality are also located. The coding information can be arranged in the test pattern, in particular nested with the measuring fields.

In particular, the invention may be used to advantage in a printing system comprising a plurality of printing devices each having a plurality of printhead assemblies, each printhead assembly being each provided for printing in a given ink and each printhead assembly having a plurality of printheads. It is advantageous in each case to provide coding information for a printing device, for a print head arrangement and / or for a print head.

The invention also relates to a method according to the invention corresponding test device. It comprises an opto-electronic scanning device with which a test pattern printed by a printhead arrangement can be scanned, which comprises coding information for specific parts of the printhead arrangement. For this purpose, samples determined during scanning are used for the check. In the device, a spatial association is made between certain areas in the printed test pattern and the parts of the printhead assembly by means of the coding information.

The invention also relates to a computer according to the invention corresponding to the method, which may be part of the test device in particular. The computer comprises in particular comparison means and storage means for comparing sampled data of a printed image of a test pattern with stored values. It further comprises checking means using sample scanning samples detected for scanning, the test pattern comprising coding information by which certain areas in the printed test pattern are spatially assignable to particular parts of the printhead assembly.

The invention also relates to a computer program product for verifying a printhead assembly in a printing system comprising a comparison program module for comparing sampled data of a printed image of a stored value test pattern. There is also provided a validation program module that utilizes sampled samples for scanning the printhead assembly, wherein it is configured to use encode information of the test pattern by which particular regions in the printed test pattern are spatially assignable to particular portions of the printhead assembly.

Further advantages and embodiments of the invention will be described below with reference to figures.

Show it:

1 : a printing system

2 : an inkjet pressure bar

3 : a measuring and adjustment system for a pressure device

4 : an adjustment process

5 : a scan on a test pattern and

6 : a test pattern

In 1 is a printing system 1 shown, the two pressure equipment 2 . 3 having. The pressure equipment 2 . 3 can be operated independently of each other or together as a so-called twin-pressure system. In individual operation, a paper web 4 each of a unwinding device 5a respectively. 5b unrolled, the pressure device 2 respectively. 3 fed for printing in the direction A or B and then by means of a reel-up 5c respectively. 5d again wound up into a roll. The print data is from a print data source 9 a data controller and raster processor 8th (Raster Image Processor, RIP) and then to the respective printhead control 7a respectively. 7b of the printing device 2 respectively. 3 output.

In twin mode, the paper web becomes 4 in the pressure device 2 printed on its front, then by means of a turning unit 6 turned and then the pressure device 3 supplied for printing on the back. For a full color printing there is printing device 2 a Y-pressure latch 10 for yellow, an M-pressure bolt 11 for magenta, a C-pressure bar 12 for cyan and a K-pressure bar 13 for black on. Corresponding pressure bar 14 for Y, 15 for M, 16 for C and 17 for K has the pressure device 3 on. The pressure equipment 2 . 3 can have more pressure bars, eg for spot colors or for MICR printing. MICR stands for Magnetic Ink Character Recognition. This corresponds to a printing process which uses printed matter which is magnetizable and whose printed characters are automatically readable by magnetic reading devices.

2 shows an ink jet print bar 20 , which is constructed of several parts modular. For example, this pressure bar could 20 the pressure bolt 13 (K, black) the 1 be. The pressure latches of all colors CMYK are basically the same structure, so that the illustrated pressure bar 20 could also be provided for a different color. When the pressure bar 20 installed in the printing device, moves the paper web 4 transverse to the pressure bar longitudinal direction in direction C. The paper web 4 then runs first on three printheads 21 . 23 . 25 past and then to two offset to the other printheads 23 arranged printheads 22 . 24 , Due to the staggered arrangement of the printheads 21 ... 25 can be achieved that the paper web 4 in large width, eg to 30 inches, is printable, because each offset to the other printheads 21 . 23 . 24 . 25 arranged printheads 22 . 24 can print in paper web areas where the other printheads 21 . 23 . 24 . 25 contain no ink nozzles or lie between these other printheads, such as in the areas 26 . 27 ,

Each of the printheads contains four trapezoidal modules, such as in the printhead 22 , the modules 22a . 22b . 22c and 22d , Each of these trapezoidal modules has a multiplicity of printing nozzles, which are arranged in a high-resolution raster, for example in a 600 dpi raster, and eject the printing ink, for example by means of a piezo technique during the printing process. The appropriate control of the piezo elements via the print head control 7a respectively. 7b and optionally further, in particular provided directly on the respective print head electronic components.

In 3 is illustrated as on a printing system 31 checking a printhead assembly and possibly adjusting drive values of the printhead controller 7 he follows. This will be data of a test pattern 37 in the printhead control 7 held, for example, by a volatile or non-volatile memory of the service computer 32 via a data connection 38 in the printing system 31 be recorded. With the printing system 31 becomes the test pattern 37 then on the paper web running in direction D. 4 printed. In the service computer 32 are the data of a computer program 32b stored, for example in a non-volatile memory (ROM, hard disk), which controls the local process. To do this, the data is stored in an electronic volatile memory 32a , eg a RAM loaded.

The printed test pattern 37 contains in the example shown 4 test bars for each of the four Duck colors, namely the test bar 39a in yellow, the test bar 39b in magenta, the test bar 39c in cyan and the test bars 39d in black. Each of the test bars was printed with a corresponding color bar and is assigned accordingly.

The printed test pattern 37 is at a measuring station 36 by means of a scanner 34 moving freely and by means of a cable 34a on a measuring computer 33 is connected, opto-electronically recorded and the recorded measurement data, if necessary, from the measuring computer 33 preprocessed, in a transfer process E, for example via a network connection or a data carrier to the service computer 32 transfer. In the measuring computer 33 are the data of a computer program 33b stored, which controls the local process flow. For this, the data is stored in an electronic main memory 33a loaded.

In another embodiment, the function of the measuring computer 33 in the service computer 32 integrated, that is the scanner 34 directly connected to the service computer, whereby the measurement data transfer E can be omitted.

As a scanner 34 For example, a conventional reflection spectral scanner can be used for graphic arts applications in the printing industry. It can, for example, have a ring light source which diffuses with a defined spectrum and with which the printed test pattern 37 is illuminated, and a corresponding spectrally sensitive light detector with a hologram grid and a light-sensitive diode array for receiving the test pattern 37 reflected light.

The printing system 31 can be a single print device, as shown with four YMCK color bars, or a twin print system as shown in 1 is shown. In the case of the twin printing system is a print job, which is the test pattern 37 contains, so constructed, a first part of the test pattern 37 is printed by the first printing device and a second part of the test pattern 37 from the second pressure device. The test pattern may then comprise a total of 8 test bars, namely four test bars (YMCK) printed with pressure bars of the first pressure device and four test bars (YMCK) printed with pressure bars of the first pressure device, each of the test bars associated with exactly one of the eight pressure bars and in the test pattern a corresponding coding information is provided, with which this unique assignment can be made.

It may also be advantageous to have a corresponding print data controller 8th provide and print the job using the test pattern from the service computer 32 to the print data controller 8th which in turn then distributes the print data to the two printing devices 2 . 3 takes over. The region of the test pattern which is printed in the first printing device in this case contains a barcode coding which is assigned to the first printing device and the second region of the test pattern contains a barcode coding which is assigned to the second printing device.

In 4 the procedure is shown, with which a test pressure is created and measured and the measurement result is evaluated, whereby also a readjustment can be made for the print heads. After the process start S1, the printing system is prepared for the test print in a step S2. In this case, for example, the printheads are mechanically adjusted and cleaned, a certain paper type inserted into the printing device and set other reference conditions in the printing system. It may be necessary to change the settings made in the previous printing operation to reference settings.

In step S3, the test print is created, that is, printed on the paper web. The phase of the two steps S2 and S3 is also referred to as the pressure phase. This is followed by a measurement phase with steps S4, S5, wherein in step S4 with the scanner 34 the printed test pattern 37 is measured. At the same time, it is checked whether coding information which can be assigned to the respective printhead parts of the printhead arrangements is unambiguously contained in the recorded measured values. Otherwise, an error message is output and scan S4 is aborted. After completing the scanning process S4, in the measuring computer in step S5 33 or in the service computer 32 checks whether the measured values are within specified tolerance ranges. If this is confirmed, then in step S6, the changes made in the printing system settings in step S2 are reversed and the test procedure is ended therewith. The printing system will then be ready for regular printing with the previous device settings. If a measurement is found to be out of order in step S5, the printheads are aligned in step S5, that is, electronic printhead drive adjustment parameters are changed, and then a step S3 of creating the test print is initiated again.

In 5 are the three test bars 39b . 39c and 39d of the printed test pattern 37 shown. Each test bar can be divided into five sections 40a . 40b . 40c . 40d and 40e be divided, which were printed by each associated printheads. For example, the printhead area became 40a of the test bar 39d from the printhead 21 ( 2 ) of a black printing printing bar. Above each test bar is a corresponding, continuous color bar 41b . 41c . 41d For example, it is possible to check the homogeneity of the color saturation or density values within a print bar, ie the accuracy of the adjustment of the print heads and / or the trapezoidal modules installed in them.

To measure the test pattern 37 becomes the scanner 34 Freehand starting from point F in direction G, first over the K-measuring bar 39d in direction G along a measuring path 42 guided and then meandering continued over the other two test bars 39c (cyan) and 39b (magenda) until reaching the target point H. During the movement, the scanner takes 34 the recorded printed measuring fields and sends the corresponding measurement data to the measuring computer 33 , For example, color values, greyscale values, scan speed values and / or measurement times are recorded as measurement data. Within each printhead area 40a ... 40e There are four measuring fields each, each one a trapezoidal module of a printhead according to the trapezoidal modules 22a ... 22d of the 2 assigned. For example, within the printhead area 40b of the test bar 39b in the measuring field area M the four measuring fields 43a . 43b . 43c . 43d intended. For example, the first measuring field corresponds to this 43a the field of view group 43a ... 43d the first trapezoidal module 22a of the second printhead 22 in 2 , The respective measuring field is arranged substantially centrally in the respective trapezoidal module or is printed by the corresponding inkjet nozzles which lie in the central region of the trapezoidal module. On a pixel-accurate printing is not important. In order to capture suitable measured values of trapezoidal modules, it is not necessary to print on the edge of the respective trapezoids. Areas in the test pattern, which are assigned to the respective edges or the overlapping areas of trapezoidal modules are therefore unprinted as in the area 45 between the printhead areas 40c and 40d exemplified.

At the measuring fields 43a ... 43d In each case, measurement data for assessing the print quality of the respective trapezoid module are recorded, for example color density values or brightness values. In the measuring computer 33 or in the service computer 32 ( 3 ), these values can be stored there with reference values stored in an electronic memory for the test pattern 37 and, if appropriate, values derived therefrom are determined, for example a so-called delta-E value which indicates the color distance of a color measurement field from a desired color value in the Lab color space. From such values, corresponding correction values or setting values for adjusting the respective print head or trapezoidal module can be calculated. The memory operations and comparison processes are doing with a corresponding, in the measuring computer 33 or in the service computer 32 controlled and executed computer program controlled. The computer program can for this purpose be of modular construction with corresponding computer program modules which in each case carry out specific control comparison and / or calculation tasks.

As in 6 is shown in the test pattern 37 between each two of the measuring fields 43a ... 43d one more field each, which is provided for encoding purposes, these three coding fields for each one printhead area 40a ... 40e form a digital three-digit code. As for the printhead area 40b shown by way of example are the measuring fields 43a ... 43d and the coding fields 44a . 44b . 44c nested inside each other. This makes it possible to both the measuring fields 43a ... 43d as well as the coding fields 44a . 44b . 44c to print together in one go with the respective same printhead or trapezoidal module and to capture and evaluate both types of field, namely measuring fields and coding fields, together in a scanning process.

The coding fields are each printed in digital form, ie either with white (density value = 0) or with the highest density value, eg as with bars 39b shown with magenta in the highest density level. The printed code can then be viewed as a barcode and evaluated. This code can be recorded in the course of the measured value acquisition and evaluated in areas, for example, printhead area, test bar or test pattern. Thus, for example, the respective print heads can be assigned within a test bar. As such, the barcodes are color-independent, ie with them the respective parts of the printhead arrangements can be identified independently of the respective color in which the barcode is printed.

Furthermore, the test bars can thus be identified and detected, for example, within a twin-printing system, which test bar was generated by which of the two pressure devices. Finally, it can be detected in the course of the measured value recording on the basis of the bar code information in which direction the measured value recording takes place, for example, whether the movement is within a measuring bar 39b ... 39d from left to right or from right to left ( 5 ). A fully insbes. Black printed barcode field 44a In addition, it can act as a trigger to initiate a measuring process or also to sort successively recorded measured values and correctly assign them to the respective parts of the print head arrangement. Therefore, the respective user of the manually guided scan system does not have to pay attention to start the measured value recording at the first printhead of a bar, but can begin measuring at the beginning of the bar or also at the end of the bar. The identification via the barcode also allows the meandering recording of the measured values and nevertheless correct assignment of the measured values to the respective pressure bars, printheads and / or trapezoidal modules.

The invention has been described with reference to a printing system in which is printed on a web-shaped recording medium. However, it can equally well be used for printing systems in which sheet-like recording media such as paper sheets are printed.

Computer programs according to the invention can be mounted on a physical support such as a computer. CD, DVD, ROM, RAM can be stored and exchanged or transmitted via appropriate server, and network technologies as a file, file collection or data stream.

LIST OF REFERENCE NUMBERS

1

printing system

2

First printing device

3

Second pressure device

4

paper web

5a, 5b

dispensers

5c, 5d

retractor

6

turning device

7, 7a, 7b

 Printhead control

8th

Print Data Controller (RIP)

9

Data Source

10

first Y-pressure bolt

11

first M-pressure bolt

12

first C-push bar

13

first K-pressure bolt

14

second Y-pressure bolt

15

second M-pressure bolt

16

second C-pressure bolt

17

second K-pressure bolt

20

pressure lock

21

first printhead

22

second printhead

22a ... 22d

 Trapezoid modules of the second printhead

23

third printhead

24

fourth printhead

25

fifth printhead

26

Pressure bar area without ink nozzles

27

Pressure bar area without ink nozzles

30

Measuring and adjustment system

31

printing system

32

Service computer

32a

random access memory

32b

Computer program data

33

Measuring computer

33a

random access memory

33b

Computer program data

34

scanner

34a

Scanner Cable

35

Service software

36

measuring Station

37

test pattern

38

Data Connection

39a ... 39d

 Test Bar (YMCK)

40a ... 40e

 Printhead area

41b ... 41d

 continuous color bars

42

Measuring path

43a ... 43d

 measuring field

44a ... 44c

 Coding field

45

unprinted area

A, B, C, D

Paper Grain

e

Measurement data transfer

F

starting point

G

start direction

H

endpoint

M

Measurement field area

S1

begin

S2

Prepare printing system

S3

Create test print

S4

Measure test pressure

S5

exam

S6

reset

S7

Adjust heads

S8

The End

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 7545523 B2 [0003]
• US 2011/0166019 A1 [0004]
• US 6474768 B1 [0005]
• WO 2011/054815 A1 [0006]

Claims (12)

Method for checking a printhead assembly ( 10 ... 17 ) in a printing system ( 1 . 2 . 3 . 31 ), with the printhead assembly ( 10 ... 17 . 20 ) a test pattern ( 37 ) and the printed image of the test pattern ( 37 ) with an optoelectronic scanning device ( 34 ) and sampling probes are used for the scan, whereby the test pattern ( 37 ) an encoding information ( 44a ... 44c ) through which certain areas in the printed test pattern ( 37 ) certain parts of the printhead assembly ( 10 ... 17 . 20 ) are spatially assignable. Method according to claim 1, wherein the coding information ( 44a ... 44c ) in the test pattern ( 37 ) is arranged spatially. Method according to claim 1 or 2, wherein the coding information ( 44a ... 44c ) comprises a barcode. Method according to one of the preceding claims, wherein several parts of the printhead assembly ( 10 ... 17 . 20 ) each individual coding information ( 44a ... 44c ) in the test pattern ( 37 ). Method according to one of the preceding claims, wherein the printhead arrangement ( 10 ... 17 . 20 ) several print heads ( 21 ... 25 ) and in the test pattern ( 37 ) each printhead ( 21 ... 25 ) a print head-specific coding information ( 44a ... 44c ) assigned. Method according to one of the preceding claims, wherein the printing system ( 1 . 2 . 3 . 31 ) several pressure devices ( 2 . 3 ) with a plurality of printhead arrangements ( 10 ... 17 . 20 ), each printhead assembly ( 10 ... 17 . 20 ) is provided for printing in a given ink and each printhead assembly ( 10 ... 17 . 20 ) several print heads ( 21 ... 25 ) and wherein in each case coding information ( 44a ... 44c ) are provided for a printing device, for a printhead assembly and / or for a printhead. Method according to one of the preceding claims, wherein the test pattern ( 37 ) additional measuring fields ( 43a ... 43d ) to assess the print quality and with the scanning device ( 34 ) both the coding information ( 44a ... 44c ) as well as measured values for the printed measuring fields ( 43a ... 43d ) and wherein the respective measured values of the respective coding information ( 44a ... 44c ) and thus the respective parts of the printhead assembly ( 10 ... 17 . 20 ) are assigned spatially. Method according to one of the preceding claims, wherein as optoelectronic scanning device ( 34 ) a manually operable scanner is used, preferably in a scanning direction over the printed test pattern ( 37 ), the coding information ( 44a ... 44c ) and wherein in an evaluation unit the detected coding information ( 44a ... 44c ) the respective part of the printhead assembly ( 10 ... 17 . 20 ). Device for checking a printhead assembly ( 10 ... 17 . 20 ) in a printing system ( 1 . 2 . 3 . 31 ) comprising an optoelectronic scanning device ( 34 ), with which one of a printhead assembly ( 10 ... 17 . 20 ) printed test pattern ( 37 ) is scannable, the coding information ( 44a ... 44c ) for certain parts of the printhead assembly ( 10 ... 17 . 20 ), wherein samples determined during the scanning are used for the checking and by means of the coding information ( 44a ... 44c ) a spatial association between certain areas in the printed test pattern ( 37 ) and the parts of the printhead assembly ( 10 ... 17 . 20 ) he follows. Apparatus according to claim 9, wherein the optoelectronic scanning device ( 34 ) is a manually executable scanner. Computer for checking a printhead assembly ( 10 ... 17 . 20 ) in a printing system ( 1 . 2 . 3 . 31 ) comprising comparison means and memory means for comparing sampled data of a printed image of a test pattern ( 37 ) with stored values as well as checking means, the sampling values for the scanning of the printhead arrangement ( 10 ... 17 . 20 ), the test pattern ( 37 ) an encoding information ( 44a ... 44c ) through which certain areas in the printed test pattern ( 37 ) certain parts of the printhead assembly ( 10 ... 17 . 20 ) are spatially assignable. Computer program product for checking a printhead assembly ( 10 ... 17 . 20 ) in a printing system ( 1 . 2 . 3 . 31 ) comprising a comparison program module and for comparing sampled data of a printed image of a test pattern ( 37 ) with stored values, and a check program module, the samples for scanning the printhead assembly ( 10 ... 17 . 20 ), the test pattern ( 37 ) an encoding information ( 44a ... 44c ) through which certain areas in the printed test pattern ( 37 ) certain parts of the printhead assembly ( 10 ... 17 . 20 ) are spatially assignable.

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