DE102006021387B4 - Printing system and method for operating a printing system - Google Patents

Abstract

High-pressure printing system comprising a control device (2) for receiving, screening and screening a print data stream,
wherein the control device (2) has a screening device (8) for screening and a screen device (9) which is independent of it for screening,
characterized,
in that a fast data connection (11) for transmitting the screened print data is present between the raster device (8) and the screening device (9), the data connection (11) at the screening device being connected to a screening module, so that the incoming screened print data are screened immediately.

Description

The The invention relates to a printing system. The invention particularly relates a printing system for one High-performance printing system with a standardized print data Supplied pressure data stream and at the different brightness levels by means of a Screening process are generated.

such Printing systems for the high performance printing are known. You have a controller, which is provided with a computing unit that controls both the print data stream into a bitmap file as well as performing the screening process. The Screening method is also called dithering or dithering designated. In "The Printer Book - Technology and Technologies of OPS High-Performance Printer Printing Technologies, "Dr. Gerd Goldmann, Issue 5a, October 2000 (ISBN 3-00-001019-Germany) are in Chapter 6 screening techniques and the print quality achieved here explained in detail. When screening or Dithering, also referred to herein as amplitude modulated screening, the image is scanned point by point with the resolution to be printed and compared with thresholds. The thresholds are in one arranged so-called screening matrix. By means of a comparator and the screening matrix thus becomes a halftone image in a bilevel bitmap image implemented, which can be given directly to the printhead. halftone are bitmaps, where each pixel (pixel) is a grayscale in Form is assigned a number of several bits. Both Halftone images are distinguished between an original image, the contained in the print data stream, and a quantified image, which corresponds to the original image, but in the resolution of the Printing system is implemented. The original picture can be for example a resolution of 50 dpi with 256 brightness levels per pixel, that in one quantified image converted at 300 dpi and 32 grayscale per pixel becomes. The generation of such a quantified image is described in Hereafter referred to as grids. With the grating is thus the local resolution of the picture.

With In the following, the term screening is exclusively used to implement the quantified Image in brightness levels (grayscale or color gradations) from the printhead can be implemented directly, designated. The screening thus indicates the setting of the brightness resolution of Image. Screening is synonymous with dithering.

In a screening method, ordered matrices, such as those from the WO 02 / 51125A1 are known or stochastic matrices are used. Similarly, it is possible to use an error-diffusion method instead of a matrix-based screening method, as it is known, for example, from US Pat US 5,835,687 or the EP 0 545 734 81 is known.

The screened image can be printed directly on the printhead, that is, the brightness levels of the individual pixels directly on a corresponding carrier can be printed. often the so-called bilevel pressure is applied, in which a single Pixel either toner or no toner is applied. But there is also multilevel printing, in which the amount of toner per pixel in several stages changeable is different so by different amounts of toner Brightness values can be generated. For a finer resolution of the To achieve brightness, it is useful, even in a multilevel printing process a screening procedure use.

From the US 5,140,349 go several printing devices ( 20 . 21 . 23 ), each having a means for screening. This means for screening is part of a control device, which may also be provided with means for adjusting the optimum density of the respective image data, whereby the resolution of the image data is changed. For each set resolutions corresponding screening matrices are selected. In another printing system, the image data is supplied from a host computer to the printer along with an image data resolution signal, so that the corresponding screening matrices can be selected based on that signal. Such printing systems are suitable for small office printers with which relatively small amounts of print data are printed, which are already prepared by means of printer drivers on computers in which the print data are generated in suitable for the screening halftone images.

At the Heavy duty printing need Due to the enormous data volumes of the print data corresponding computing capacities for Carry out screening and screening. It is also Known scanning and screening with the help of standard processors and optionally with specially designed hardware coprocessors perform.

Of the Invention is based on the object, a printing system for high-performance printing with which a print data stream is processed more efficiently where the processing of the print data stream is a screening includes.

Farther The object of the invention is an efficient method to create a printing system.

The Task is performed by a printing system with the features of the claim 1 and solved by a method having the features of claim 11. advantageous Embodiments are specified in the respective subclaims.

The Inventive printing system for high performance printing includes a controller for receiving, rasterizing and screening a print data stream on. The printing system is characterized by it in that the control device has a raster device for rasterizing and one of them independent Screening device for screening has.

hereby the screening and screening is decoupled from each other. This leads to considerable advantages across from usual Printing systems, since the inventors have realized that the grating a very lengthy process that is common with that in high-performance printing Data volumes ranging from a few 100 megabytes to a few gigabytes can, one considerable Can take time.

Farther The inventors have realized that the screening is very printer specific is. Because the screening device is decoupled from the rasterizer is, it can be easier specific to that used in the printing system Printhead adapted to be trained. In case of a change or an exchange The printhead can easily adjust the screening facility accordingly modified or be replaced.

It is from conventional Printing systems known to make the control device scalable, wherein the control device, as needed, one or more raster modules for screening and screening. In the printing system according to the invention Is it possible, only the control device with respect to the grid device be scalable, that is, the control device one or may include multiple grid facilities that are labor-intensive Perform rasters. It is not necessary for provide each screening device with a separate screening device, but for a certain printhead is enough usually a single screening facility. This will the scalability of the printing system to a different Throughput of a print data stream easier and cheaper realizable.

To a preferred embodiment the grid device a data memory for temporarily storing the screened print data. This is the raster where the local resolution of the Printing data is obtained from the screening, in which the resolution in the Achieved in terms of brightness level, temporally decoupled. This data store also allows, if in the printer, a problem should occur, such as by a paper jam or the like., that the rasterized print data that is printer-unspecified out read the data memory and another printer for printing supplied become. Another time-consuming rasterizing of the print data is then not necessary anymore. This represents a significant advantage over the usual Printing systems in which the screening and the screening respectively be carried out in a single unit.

The Invention will be explained in more detail by way of example with reference to the drawing. In The drawing shows schematically:

1 A first embodiment of a printing system according to the invention in a block diagram,

2 A second embodiment of a printing system according to the invention in a block diagram,

3 the structure of a in the printing system according to 1 and 2 used screening device, and

4 the construction of a screening module used in the screening facility.

1 schematically shows the structure of a printing system according to the invention 1 , This printing system 1 is a printing device with a control device 2 for receiving, screening and screening a print data stream. This printing device 1 has an electrographic printhead 3 on, with which approximately circular pressure points in a grid on a paper web 4 to be printed.

The incoming print data stream is via an interface 5 and a data connection 6 from a print server 7 receive.

Of the Print data stream has a standardized format, such as one of the formats IPDS, AFP, PostScript or PCL.

The control device 2 has a raster device 8th and a screening facility 9 on.

The grid device 8th The purpose of this is to convert the print data contained in the print data stream into a quantized image with the resolution with which it is printed on the record carrier 4 should be printed, implement. The raster device thus sets the local resolution of the print data.

The screening facility 9 is designed to screen or dither the quantified pressure data. Thus, with the screening device, the brightness levels are set to be from the print head 3 can be printed. Works the printhead 3 according to the bilevel printing method, only the values 1 or 0 are assigned to the individual pixels, depending on whether the pixel is to be printed or not to be printed. Works the printhead 3 however, according to the multilevel printing method, numerical values are assigned to the individual pixels, which define the brightness levels, that of the print head 3 can be printed. Current printheads 3 Those operating on the multilevel printing method can print the pixels with sixteen different brightness levels so that the numbers defining the brightness levels are each 4-bit-long binary numbers. The screened print data can thus be used directly to control the print head 3 be used.

The printing system according to the invention 1 is characterized by the fact that the grid device 8th and the screening facility 9 are formed of two separate units. In the present embodiment, they are adjacent in the printing system 1 arranged and use the same power supply.

The grid device 8th is in principle similar to the structure in the WO 00/22537 or in the DE 10 2005 062 576 .2 described controller having an I / O module, one or more raster modules and a serializer module. The raster modules described in these documents are designed to perform rastering as well as screening. In this regard, the present invention differs, since here the raster modules are designed only for screening and not for screening. In the present invention, the raster device 8th scaled equally, ie that one or more raster modules are provided as needed. Since enormous amounts of data have to be processed and exchanged while grating, the documents are concerned WO 00/22537 and DE 10 2005 062 576.2 especially with the data connection between the individual modules. These data connections are equally used in the present invention, which is why the WO 00/22537 and the DE 10 2005 062 576.2 incorporated by reference into the present application.

The raster device according to the invention 8th has a data store 10 in which the rastered print data is stored. This data store 10 can be distributed to the individual raster modules. Preferably, a large-volume memory unit for the entire raster device 8th with a storage volume of at least 1 gigabyte, preferably at least 4 to 50 gigabytes. This data memory can be designed as a semiconductor memory or in the form of a hard disk. The advantage of a hard disk is that it can cost-effectively provide a storage capacity of a few 10 gigabytes, so that an entire print job can be cached. Of course, data access to a hard disk is slower than to a corresponding semiconductor memory.

Between the grid device 8th and the screening facility 9 for transmitting the print data, is a high-speed serial data connection 11 provided that may include several high-speed links. Furthermore, between the grid device 8th and the screening facility 9 a data bus 12 arranged, which serves to transmit control data. These data connections 11 . 12 correspond to those in the DE 10 2005 062 576.2 For this reason, reference is made to this document in this regard.

The structure of the screening facility 9 is schematic in 3 shown. The screening device is controlled by a programmable logic device (FPGA = Field Programmable Gate Array) 13 and a data storage independent thereof 14 analyzed. The data store 14 is a semiconductor memory and includes several DDR-SDRAM dimming modules with a storage volume of at least one gigabyte and preferably at least 4 gigabytes.

The screening facility 9 has a bus interface 15 that with the data bus 12 connected, and a data interface 16 on that with the serial data connection 11 connected is. The main element of the screening facility 9 is a screening module 17 which will be explained in more detail below. The screening module 17 is in connection with the bus interface 15 , the data interface 16 and a memory manager 18 , The memory management 18 controls the data stream within the screening facility 9 from and to the screening module 17 , the bus interface 15 , a memory controller 19 and a printhead interface 20 ,

The screening module 17 performs a screening with ordered matrices, as for example from the WO 02 / 51125A1 is known. In this case, threshold values arranged on matrices are compared with the brightness values of the pixels of the quantified pressure data, and based on the comparison with the threshold values, the brightness values are used to control the printhead 3 determined. In the present exemplary embodiment, the quantified image data has 8-bit brightness values (256 brightness levels), which are reduced to 4-bit brightness values (16 brightness levels) using the screening process. This reduction of the quantified print data to the screened print data represents a compression by a factor of 1: 2. The thus compressed screened print data are provided by the screening module 17 about the memory management 18 the memory controller 19 in the data store 14 cached.

The screening module 17 of the present embodiment has a threshold interface 21 and a comparator unit 22 on. The comparator unit 22 is designed for the simultaneous parallel comparison of brightness values of four pixels. The threshold interface 21 performs the comparator unit thresholds needed to compare 22 to. The threshold interface 21 is designed so that there are four thresholds at the same time to the comparator unit 22 can pass. The threshold interface 21 reads the appropriate thresholds using memory management 18 and the memory controller 19 from the store 14 out. The memory 14 thus serves both for storing the threshold values and for storing the screened print data.

The data volume of thresholds required for a screening procedure is very extensive and can range from 1 to several megabytes. The transmission of such large amounts of data over the data bus 12 would take a lot of time. That's why the screening module points 17 a bypass data connection 23 to bypass the comparator unit 22 on. About this bypass data connection 23 can be a set of new thresholds from the grid facility 8th via the serial data connection 11 past the comparator unit 22 about memory management, the memory controller 19 in the data store 14 be registered. This makes it possible to rapidly replace the existing thresholds with a set of new thresholds, which allows the screening method to be adapted to the current printing parameters. For example, it may be convenient to adjust the thresholds accordingly to the new type of paper when replacing the type of paper to be printed.

The data store 14 Screened print data is sent through the memory controller 19 , about memory management 18 and the printhead interface 20 read out and the printhead 3 transmitted for driving the printing process.

In a high-performance printer, the printing process should always be possible without interruption. By providing the large volume data store for the screened print data 14 Screening is temporally decoupled from printing, ensuring that printing can be done continuously.

2 shows an alternative embodiment of the printing system according to the invention 1 , which is a printing device with a screening device 9 a printhead 3 that covers on a paper web 4 circular pixels prints. The grid device 8th is formed separately from this printing device and via a high-speed data connection 24 connected to the printing device. The grid device 8th again has a data memory 10 for temporarily storing the latched or quantified print data. The grid device 8th and the screening facility 9 in turn form the control device 2 the pressure system, but they are locally separated from each other. The raster device 8th may also communicate with one or more printing devices via the high speed data link 24 be connected and thus provide several printing devices with quantified print data.

The structure of the grid device 8th otherwise corresponds exactly to the structure of the corresponding grid device of in 1 shown embodiment.

• – Das Rastern der Druckdaten ist bei gleicher Auflösung unabhängig von der verwendeten Druckvorrichtung. Die gerasterten und im Datenspeicher 10 abgespeicherten Druckdaten können bei Problemen an der Druckvorrichtung an eine weitere Druckvorrichtung entweder direkt von der Raster-Einrichtung (Ausführungsform gemäß 2) oder über den Server 7 (Ausführungsform gemäß 1 und 2) übermittelt werden. Dadurch geht die bereits aufgebrachte erhebliche Leistung durch das Rastern der Druckdaten nicht verloren.
• – Durch das Trennen des Rasterns und des Screenens kann eine speziell zum Screenen dedizierte Hardware-Lösung vorgesehen werden, die die Druckdaten „on the fly" screent, d.h., dass die über die serielle Hochgeschwindigkeitsdatenverbindung 11 zugeführten Druckdaten ohne Verzögerung gescreent werden. Es genügt somit ein einziges Screening-Modul 17, unabhängig davon, ob die skalierbare Raster-Einrichtung 8 mit einem oder mehreren Raster-Modulen versehen ist. Bei dem vorliegenden Ausführungsbeispiel können bis zu zwölf Raster-Module in der Raster-Einrichtung 8 vorgesehen werden.
• – Bei bisherigen Drucksystemen wurden in der Steuereinrichtung nach dem Rastern der Daten diese in einem Datenspeicher zwischengespeichert, von dem Datenspeicher wieder zum Screenen ausgelesen und wieder auf dem Datenspeicher in der Steuereinrichtung zwischengespeichert. Es sind somit wesentlich mehr Zugriffe auf den Datenspeicher notwendig. Bei Verwendung einer Festplatte als Datenspeicher verzögert dies die gesamte Datenverarbeitung erheblich. Werden hingegen alle Daten in einem Halbleiterspeicher abgelegt, so muss dieser entweder eine enorme Speicherkapazität aufweisen oder man muss sich mit einem abschnittsweisen Speichern der Datenmenge behelfen, was das gesamte Verfahren kompliziert macht.
• – Da bei der Erfindung das Screenen „on the fly" erfolgt, wird ein weiterer Schreib- und Lesevorgang der zu scannenden Druckdaten eingespart. Dies bewirkt eine weitere Effizienzsteigerung.
• – Da die Screening-Einrichtung 9 unabhängig von der Raster-Einrichtung 8 ausgebildet ist, kann sie kostengünstiger und einfacher an Änderungen an der Druckvorrichtung angepasst werden. Da das Screening im Gegensatz zum Rastern sehr druckerspezifisch ist, kann beim erfindungsgemäßen Drucksystem einfacher und präziser auf Änderungen im Druckvorgang reagiert werden.

Equally, whether the grid device 8th regardless of the printing device ( 2 ) or as part of the printing device ( 1 ), the independent design of the raster device by the screening device provides the following advantages:

• - The screening of the print data is the same resolution regardless of the printing device used. The rasterized and in the data store 10 stored print data can in case of problems on the printing device to another printing device either directly from the raster device (embodiment according to 2 ) or via the server 7 (Embodiment according to 1 and 2 ). As a result, the already applied considerable power is not lost by rasterizing the print data.
• - By separating the screening and the screening, a dedicated dedicated hardware solution can be provided which scans the print data "on the fly", that is, via the high speed serial data link 11 supplied print data without delay be screened. Thus, a single screening module is sufficient 17 , regardless of whether the scalable grid device 8th is provided with one or more raster modules. In the present embodiment, up to twelve raster modules in the grid Einrich tung 8th be provided.
• - In previous printing systems were in the control device after rasterizing the data stored in a data memory, read from the data memory again for screening and cached again on the data memory in the control device. There are thus much more accesses to the data storage necessary. Using a hard disk as a data store significantly delays all data processing. If, on the other hand, all the data are stored in a semiconductor memory, then this must either have an enormous storage capacity or one must manage to store the amount of data in sections, which complicates the entire process.
• Since the screening is done "on the fly" in the invention, a further writing and reading operation of the print data to be scanned is saved, resulting in a further increase in efficiency.
• - because the screening facility 9 regardless of the grid setup 8th is formed, it can be more cost-effective and easier to adapt to changes to the printing device. Since the screening is very printer-specific, in contrast to screening, the printing system according to the invention can react more easily and precisely to changes in the printing process.

The inventive method is especially for provided the monochrome printing and the highlight color printing, provided when highlight color printing the colors are not mixed together, that is, they are independent be printed from each other. When multicolor printing is a complete separation Rasterization and Screening is not always possible because of the printing Image when screening printer-specific in the individual inks must be disconnected. For single-color printing and highlight color printing Thus, the advantages achieved by the invention more pronounced than Multicolor printing.

at the embodiments described above Screening is performed using ordered matrices. in the Within the scope of the invention, it is also possible to use the screening by means of stochastic matrices or by means of the error diffusion method.

The embodiments described above each have a single printhead. However, in multi-color printing, it may be convenient to provide multiple printheads. The plurality of print heads are preferably supplied with print data by a single screening device. When screening the different colors, different sets or matrices of thresholds should be used. These are in memory 14 deposited.

The invention can be briefly summarized as follows:
According to the invention, the print data are screened with a raster device and screened by a screening device independent thereof. The very printer-specific screening device can thus be arranged close to the print head and designed specifically for the print head. The printer-unspecified rasterizer can be located remotely from the printhead, and both devices can be independently optimized for the particular requirements of the printing process.

1

printing system

2

control device

3

printhead

4

paper web

5

interface

6

data line

7

server

8th

Raster device

9

Screening device

10

data storage

11

serial Data Connection

12

bus

13

programmable logic module

14

data storage

15

Bus Interface

16

Data interface

17

Screening Module

18

memory management

19

Memory controller

20

Printhead Interface

21

Thresholds interface

22

comparator unit

23

Bypass data connection

24

Data Connection

Claims (12)

Printing system for high-performance printing with a control device ( 2 ) for receiving, screening and screening a print data stream, wherein the control device ( 2 ) a raster device ( 8th ) and an independent screening device ( 9 ) for screening, characterized in that between the raster device ( 8th ) and the screening facility ( 9 ) a fast data connection ( 11 ) for transmitting the rasterized print data, the data connection ( 11 ) at the screening device is connected to a screening module so that the incoming rasterized print data is immediately screened. Printing system according to claim 1, characterized ge indicates that the grid device ( 8th ) a data memory ( 10 ) for temporarily storing the screened print data. Printing system according to claim 2, characterized in that the printing system ( 1 ) an interface ( 5 ) to a print server ( 7 ), via which the rastered print data to the print server ( 7 ) can be transmitted for printing on another printing system. Printing system according to one of claims 1 to 3, characterized in that the screening device ( 9 ) for storing screened print data and for storing thresholds for screening a data memory ( 14 ) having. Printing system according to claim 1, characterized in that in the screening device a bypass data connection ( 23 ) for bypassing a comparator unit ( 22 ) of the screening module ( 17 ) is adapted to threshold values for the screening process via the fast data connection ( 11 ) into the data memory ( 14 ) of the screening facility ( 9 ). Printing system according to one of claims 1 to 5, characterized the print data stream is a standardized format, e.g. IPDS, AFP, PostScript or PCL. Printing system according to one of claims 1 to 6, characterized in that the printing system ( 1 ) a printhead ( 3 ), with which approximately circular pressure points in a grid on a recording medium ( 4 ) are printed by a bilevel printing method or a multilevel printing method. Printing system according to one of claims 1 to 7, characterized in that the raster device ( 8th ) is scalable and includes one or more raster modules. Printing system according to one of Claims 1 to 8, characterized in that the screening device ( 9 ) from a programmable logic device ( 13 ) and a data memory ( 14 ) consists. Printing system according to one of claims 1 to 9, characterized that the printing system for single-color printing or highlight color printing is trained. A method of operating a printing system, comprising the following steps: - receiving a print data stream, - screening the print data stream with a raster device ( 8th ), - screening the print data stream with a screening device ( 9 ) independent of the grid device ( 8th ), and - transmitting the scanned print data to a print head ( 3 ) for printing on a record carrier, characterized in that between the raster device ( 8th ) and the screening facility ( 9 ) a fast data connection ( 11 ) is used to transmit the screened print data, the data connection ( 11 ) at the screening device is connected to a screening module so that the incoming screened print data is immediately screened. Method according to claim 11, characterized in that that to perform the method of a printing system according to one of claims 1 to 10 is used.