JP2002040724A - Printing system, printing device, and method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform calibration more speedily with a satisfactory picture quality in a printing system. SOLUTION: In the printing, the picture pattern being printed by printing means is read by a reading means and is kept to be registered. Then, the printing device is made to print the image pattern by printing means, and to read-out the image pattern being printed by the reading means. The device is made to respectively compare these reading image patterns with reference data, and to select a means for performing accurate calibration or a simple calibration among plural calibration means for calibrating the image quality of output images, based on those comparison result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a printing system including an image reading section and a printing section.

[0002]

2. Description of the Related Art In a simple printing system including a scanner and a printer, calibration is performed automatically to obtain a constant image quality when the power is turned on or when a certain period of time has elapsed. This calibration includes a hardware calibration and a software calibration. The hardware calibration is a function usually installed in a printer or the like. In hardware calibration, the settings of the developing bias voltage, the charging potential of the photoconductor, the output intensity of the laser, the irradiation time, and the like are switched to optimal values while sequentially switching the process of each engine. further,
This calibration process is performed for each color of yellow, magenta, cyan, and black. In software proofreading, print data is corrected without setting a print engine.

[0003]

When a color printer or the like is used, a calibration mode is usually entered after the power is turned on. However, in hardware calibration, since the process is adjusted to the optimum value while sequentially changing the process settings on the engine side, it takes too much time before the user can use it. In addition, even when calibration is unnecessary, the calibration is performed every time, which is inefficient. In addition, such a calibration has high accuracy but takes a very long time, and is considerably delayed until the user can use it. In addition, such calibration that changes the process setting of the engine is necessary when the density range where output is impossible is wide, but when only the density of the halftone is shifted, Although hardware calibration alone can quickly produce sufficient images, hardware calibration wastes only waiting time.

[0004] It is an object of the present invention to provide a printing system and a printing method capable of appropriately performing proofing in a printing system.

[0005]

A printing system according to the present invention comprises: printing means for printing an image; reading means for reading the image; a plurality of calibrating means for calibrating the image quality of the image printed by the printing means; A comparing unit that compares image data obtained by reading an image pattern printed by a printing unit based on image data of a predetermined image pattern with a reading unit with reference data; and performing the calibration based on a comparison result by the comparing unit. Of the means, the first calibration means or the first
And selecting a second calibration means for performing a simpler calibration than the calibration means. Preferably, in the printing system, the reference data is image data obtained by reading the image pattern by the reading unit before the image pattern is printed by the printing unit.
Preferably, in the printing system, when the maximum output density of the image pattern read by the reading means is lower than a predetermined density, the selecting means may output the second pattern.
And when the maximum output density of the image pattern is equal to or higher than a predetermined density, the first calibration means is selected. Preferably, in the printing system,
The printing unit and the reading unit are configured as an integrated device (printing device).

In a printing method according to the present invention, in a printing system including a printing unit for printing an image and a reading unit for reading an image, a plurality of calibration units for correcting the image quality of an image printed by the printing unit are provided. A predetermined image pattern printed by the printing unit is read and registered as reference data. Then, the image pattern is printed by a printing unit based on the image data of the image pattern, the image pattern printed by the printing unit is read by a reading unit, and the image data of the read image pattern is compared with reference data. . Then, based on the comparison result, the first calibration unit or the second calibration unit that performs simpler calibration than the first calibration unit is selected from the plurality of calibration units.

A computer-readable recording medium according to the present invention includes a plurality of calibration means for controlling the printing means to calibrate the image quality of an image printed by the printing means, and includes an image pattern printed by the printing means. Reading the image pattern and registering it as reference data, a step of causing the printing means to print the image pattern based on the image data of the image pattern, and a step of causing the reading means to read the image pattern printed by the printing means. Comparing the image data obtained by reading the reference image pattern printed by the printing means with the reading means, and the first calibration means or the first calibration means among the plurality of calibration means based on the comparison result. Selecting a second calibration means for performing a simpler calibration than the calibration means; A computer-readable recording medium storing a program comprising the step of performing the calibration using.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the drawings, the same reference symbols indicate the same or equivalent ones. FIG. 1 shows a printing system including a scanner 100 such as a printer and a printing machine 200. Figure 1 shows the printing press and scanner
May be mutually connected to a server (not shown) via a network 300 or the like, or may be integrated as a copier. In this system, an image of a document is read by a scanner 100, and the read image is printed by a printing machine 200. Scanner 1
At 00, the reading unit 102 reads a document on a platen and outputs image data, and a control unit 104 including a CPU.
Controls the reading unit 102. The control unit 104 includes the reading unit 1
02 is provided with a recording medium (ROM or the like) for storing a program for controlling reading by the O.02. In addition, the scanner 10
0 is the network 3 via the interface unit 106
00 is connected. On the other hand, in the printer 200,
The print engine 202 forms an image on paper by an electrophotographic process based on print data. A control unit 204 including a CPU controls the print engine 202. The control unit 204 is a recording medium (ROM) for storing a program for controlling printing in the print engine 202.
Etc.). The printer 200 is connected to the network 300 via the interface unit 206.

FIG. 2 shows the periphery of the photoconductor 210 of the printing machine 200. The charger 212 rotates the rotating photoconductor 21.
0 is charged to a constant charging potential. A laser beam 214 irradiates the photoconductor 210 from a light source (not shown) corresponding to the image data to form an electrostatic latent image on the photoconductor 210. The electrostatic latent images are yellow, magenta, cyan and black developing units 216Y, 216M, 216C and 216K.
Is visualized as a toner image. In the figure, a test patch 218 is shown as an example of a toner image. The density of the toner image can be detected by the photo sensor 220. The toner image is transferred to a sheet by a transfer unit (not shown). By repeating this for four colors, a color image is formed on the paper.

In this printing system, when the power is turned on or when a certain period of time has elapsed, the printer 200 is automatically calibrated to obtain a constant output image quality. In calibration, software calibration and hardware calibration are used together,
Which to use is automatically selected. The hardware calibration changes a set value of each engine unit of the electrophotographic process. In the present embodiment, the developing voltage and the charging potential are set. The software proofreading simply corrects print data by software processing. In the present embodiment, the gamma table is modified.

In particular, a printing machine of an electrophotographic system or the like is very easily influenced by the environment, so that very detailed process settings are required. Therefore, hardware calibration requires more time than software calibration. Therefore,
When calibrating the printing press 200, the automatic selection of the calibration mode is performed as follows. The test pattern is read, and an original (sample) image is registered as a reference image.
When performing proofreading from the next time, first print the image with a printing machine without any correction, read the printed image, compare the scan data with the original image, and if necessary, Switch to calibration method. When the difference between the scan data and the original image is large, the time required takes a long time but the hardware calibration is selected. When the difference is small, the software calibration with the short required time is selected.

Hereinafter, the calibration will be described more specifically. FIG. 3 shows a gradation chart (reference image) used as a test pattern for calibration. This gradation chart is composed of patches of eight levels of density from low density to high density for the four basic colors of yellow, magenta, cyan and black. The test pattern is printed at the time of new installation in which the state of the engine of the printing press is normal. However, the test pattern may be prepared using a commercial print prepared in advance by a manufacturer or the like.

FIG. 4 is a diagram for explaining comparison with a reference image. At the time of calibration, printing is performed by the printing machine 200 based on the input data (0 to 255) which is a registered reference image, and read data (0 to 255) obtained by reading the obtained copy by the scanner 100 is obtained. Where Dtarget is
The read data is expected when the input data is 255, and Dmax is the actual read data. Dtarget
Density between Dmax and Dmax cannot be printed. The first reference line indicated by the solid line has changed to the second reference line located at the position indicated by the broken line. In the hardware calibration, the setting of each engine of the printing press 100 is switched, and Dmax
Close to Dtarget. In software calibration,
The halftone density is expressed by software processing based on the second reference line. In FIG. 4, the dotted line indicates the output line of the conversion by the gamma table for the first reference line. In this example, since only the halftone density is deviated, it may be possible to deal with only the software calibration without performing the hardware calibration.

Next, calibration will be described. FIG. 5 shows a flow of reference image registration. The image data of the test pattern as shown in FIG. 3 is built in the printing press 200 or received from a server via a network as data. The printing machine 200 prints the test pattern based on this. The scanner 100 reads the printed test pattern (S10), and registers the read data as a data file (S12). The registration destination may be the scanner 100 itself, or a server (not shown) via the printing machine 200 or the network 300. Basically, this image is stored in a file as reference image data. This is, for example, data as shown by the solid line in FIG.

FIG. 6 is a flowchart at the time of calibration.
For example, when it is necessary to perform calibration or when the power is turned on, a test pattern is printed from the registered reference image data by the printing machine 200 in a state where printing has been performed before (S20). Subsequently, the output image is read by the scanner 10.
By reading 0, the image is read in the same manner as the reference image (S22), and the read data is compared with the reference image data in the data file (S24). The module for performing the comparison may be provided in the scanner 100 or may be provided in the server via the printing machine 200 or the network 300.

According to the result of comparing the output image data,
The normal mode is roughly divided into two. For example, as shown in FIG.
Corresponding to output line A (dotted line) and output line B (dotted line).
D _maxIf yes, perform software calibration
And ΔD = Dtarget to Dmax is a non-printable area
Become. Therefore, the threshold density Dth is determined by experiments and the like.
I will decide. In the flow of FIG. 5, the value of Dth and the current printing
The relationship between the maximum density Dmax that can be obtained depending on the machine status
So select software calibration or hardware calibration
(S26). That is, if Dmax <Dth (in printing
Hardware calibration is performed when the concentration range is not large)
(S28), if Dmax ≧ Dth, software calibration
Is performed (S30). In other words, the density area that cannot be printed
If it is narrow, perform software calibration and
Eliminate unnecessary time loss due to justification.

Next, hardware calibration will be described.
In the hardware calibration, the settings of the engines of the printing press 10 are switched while sequentially switching the processes of the engines. FIG. 8 shows an example flow of hardware calibration. First, a 100% density patch is written on the photoreceptor 20 (S100), and this is detected by the photo sensor 28 or the like (S102), and the bias potential of the developing device 26 is adjusted to an optimum value so that the density becomes constant. Yes (S10
4). This means, for example, that Dmax in FIG. 4 is set to Dtarget. Subsequently, a patch having a halftone density is written on the photoconductor 20 (S106), and the patch is similarly read by the photosensor 28 (S108), and is applied to the photoconductor 20, for example, so that it can be adjusted to the target density. The charging potential is set (S110). This means that the predetermined halftone density is adjusted to the first reference line in FIG. Although not shown, the settings of the laser output intensity and the irradiation time may be changed. This calibration process is performed for each color of yellow, magenta, cyan, and black.

Next, software calibration will be described.
FIG. 9 shows the concept of software calibration. Software calibration can generally be performed by changing the gamma table. Specifically, in FIG. 7, ΔD = Dtarg
Since the output of et-Dmax cannot be actually output, the target reproduction curve is changed from the reference line 1 to the reference line 2 as shown in FIG. The input data is internally converted so that the density indicated by the reference line (broken line) can be output. For example, assuming that a target density for input data Xin is D (Xin), a target density for any input Xin is calculated as D ′ (Xin) by the following equation. D '(Xin) = D (Xin) * Dmax / Dtarget

FIG. 10 shows an example of gamma table conversion in software calibration. When Xin = 65, the target density is once converted from 65 (first reference line) to 62 (second reference line). Then, calibration data Xout = 68 is output so that the density 62 can be output when Xin = 65. That is, as described above with reference to FIG.
Is converted to the second reference line, and the gamma table is converted so as to maintain the halftone for the second reference line.

The proofreading by the scanner 100 can process all colors of yellow, magenta, cyan, and black at the same time and can be processed in a very short time. As a result, although the total number of output data associated with the table conversion is actually slightly reduced, there is an advantage that unnecessary time loss due to hardware calibration of the engine is eliminated.
Especially for general office documents, such software proofing is often sufficient.

In the present embodiment, the calibration mode is switched according to the maximum density and the halftone density. However, the threshold density can be similarly determined to switch the mode even with the minimum density, that is, the fog margin of Xin = 0. It is.

[0022]

According to the present invention, the optimum calibration means is automatically selected from a plurality of calibration means according to the state of the image. This eliminates time loss due to unnecessary hardware calibration.

[Brief description of the drawings]

FIG. 1 is a diagram of a printing system.

FIG. 2 is a diagram around a photoconductor of a printing press.

FIG. 3 is a diagram of a test pattern (gradation chart)

FIG. 4 is a diagram showing a comparison with a reference image.

FIG. 5 is a flowchart for registering an image.

FIG. 6 is a flowchart for calibration.

FIG. 7 is a diagram for explaining switching of a concentration calibration mode;

FIG. 8 is a flowchart of hardware calibration.

FIG. 9 is a diagram for explaining the concept of software calibration;

FIG. 10 is a diagram of a software calibration table conversion.

[Explanation of symbols]

100 scanner, 104 control unit, 200
Printing press, 204 control unit, 300 network.

Continued on front page F-term (reference) 2C061 AP01 AQ06 AR01 KK13 KK26 KK28 KK32 2H027 DA09 DE02 DE07 EA01 EA05 EB03 EC03 EC06 EC20 5C062 AA05 AB05 AB42 AB46 AC02 AC04 AC21 AC22 AC55 AC61 5C072 AA05 BA15 RA18 RA20

Claims (6)

[Claims] A printing means for printing an image; a reading means for reading the image; a plurality of calibrating means for calibrating the image quality of the image printed by the printing means; and a printing means based on image data of a predetermined image pattern. Comparing means for comparing the image data obtained by reading the image pattern printed by the reading means with the reference data, based on the comparison result by the comparing means, the first calibrating means, or A selection method for selecting a second calibration unit that performs simpler calibration than the first calibration unit. 2. The apparatus according to claim 1, wherein the reference data is image data obtained by reading the predetermined image pattern by the reading unit before the image pattern is printed by the printing unit. 2. The printing system according to 1. 3. The method according to claim 1, wherein the selecting unit selects the second calibration unit when a maximum output density of the image pattern read by the reading unit is lower than a predetermined density. 3. The printing system according to claim 1, wherein when the output density is equal to or higher than a predetermined density, the first calibration unit is selected. 4. The apparatus according to claim 1, wherein the printing unit and the reading unit are configured as an integrated device.
4. The printing system according to any one of claims 1 to 3. 5. A printing system comprising a printing unit for printing an image and a reading unit for reading the image, comprising: a plurality of calibration units for correcting the image quality of the image printed by the printing unit, wherein the printing unit prints the image. The image pattern is read and registered as reference data, the image pattern is printed by printing means based on the image data of the image pattern, the image pattern printed by the printing means is read by reading means, and the reading means A second calibration for comparing the image data of the read image pattern with the reference data, and performing a simpler calibration than the first calibration unit or the first calibration unit among the plurality of calibration units based on the comparison result. A printing method that selects a means and performs proofreading. 6. A printing apparatus, comprising: a plurality of calibrating units for calibrating the image quality of an image printed by the printing unit by controlling the printing unit. The image pattern printed by the printing unit is read and registered as reference data. A step of causing the printing means to print the image pattern based on image data of the image pattern; a step of causing the reading means to read the image pattern printed by the printing means; and a reference image pattern printed by the printing means. Comparing the image data obtained by reading the image data with the reference data with the reference data; and performing a simpler calibration than the first calibration means or the first calibration means among the plurality of calibration means based on the comparison result. 2. A program comprising a step of selecting a calibration means and a step of performing calibration using the selected calibration means. A computer-readable recording medium that records a computer system.