JP3790738B2 - Composite copier having printer output function - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a composite copying apparatus such as a monochrome copying machine or a color copying machine having a printer output function. The “printer output function” refers to a function that forms and outputs an image corresponding to an image, text, or the like input from the outside in the form of data described in a printer language on paper.
[0002]
[Prior art]
In the copying apparatus, binary image processing is performed in which original image data in which each pixel is expressed in multiple values such as 8 bits is compressed into binary data of 0 and 1 for each pixel and printed. However, since binary images have limitations in terms of gradation and resolution, coupled with the recent demand for higher image quality, it is possible to express more than 3 levels of gradation per pixel. The multi-value dither method has attracted attention. The multilevel dither method is realized by, for example, a PWM (pulse width modulation) method using a laser.
[0003]
In the multi-value dither method, the image density formed as a halftone has a great influence on the image quality, so it is important to accurately express the density corresponding to the dither intermediate value.
Therefore, conventionally, a dither pattern (tone correction patch) having a known gradation as shown in FIG. 6 is experimentally formed on an image carrier such as a transfer belt or a photosensitive drum, and this dither pattern is read. A so-called γ (gamma) correction is performed to correct the density of the entire system including the image forming processing unit.
[0004]
This γ correction condition changes depending on the overall system, especially the climatic conditions such as the number of copies of the image carrier, temperature, and humidity, and so on. Γ correction is performed on the screen. The reason why γ correction is performed during warm-up is to prevent the user from waiting during correction.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-326926 [Patent Document 2]
JP 7-12264 A [0006]
[Problems to be solved by the invention]
However, in a composite copying apparatus having a printer output function, the conditions for screen processing when creating a dither pattern are different between the printer and copying. This is because, in the case of a printer, since input data is known beforehand as image data or text data, the optimum screen processing conditions are individually determined, whereas in the case of copying, the input document is a character document. This is because it is unclear whether it is a photographic manuscript or not, and only general-purpose screen processing conditions can be determined.
[0007]
For example, in the case of a printer, the number of screen lines per inch is 133 lines, the screen angles are set to 0 ° for yellow, 30 ° for magenta, 60 ° for cyan, and 45 ° for black for image data. . In the case of copying, the number of screen lines is set to 175, and the screen angle is set to 15 ° for yellow, 45 ° for magenta, 30 ° for cyan, and 60 ° for black.
Since the screen conditions are different in this way, it is necessary to create a dither pattern for γ correction and perform correction processing. For this reason, it takes time for the correction, and it is difficult to complete the correction during the warm-up.
[0008]
On the other hand, in reality, the frequency of occurrence differs between a copying job and a printer job. Performing correction processing every time the power is turned on in a situation where it is unknown when a printer job will occur will cause the user to wait for the time required for correction processing and generate a dither pattern for printer correction. As a result, there is a problem that excessive toner is consumed.
Therefore, the present invention can reduce the waiting time of the user after power-on or the like in the composite copying apparatus capable of forming images corresponding to the copying process and the printer process by the electrophotographic process, and can reduce the toner consumption. It is an object of the present invention to provide a composite copying apparatus capable of reducing the number.
[0009]
[Means for Solving the Problems]
The composite copying apparatus of the present invention includes a pattern forming unit that forms a dither pattern obtained by performing screen gradation processing on an image carrier, a density sensor that reads the density of the dither pattern formed on the image carrier, and a density sensor. Correction means for correcting the γ correction table based on the read result, and γ correction of the image forming characteristics by referring to the γ correction table at the time of image formation, and forming an image based on the γ corrected characteristics The pattern forming means forms a dither pattern corresponding to the copying process when the power is turned on, and the correcting means reads the γ correction table for copying based on the result of reading the dither pattern. When the printer job from the outside is received for the first time between power on and power off, A dither pattern is formed, and the correction means corrects the γ correction table for the printer based on the result of reading the dither pattern.
[0010]
According to the above configuration, a dither pattern corresponding to the printer process is formed when a printer job from the outside is first received between the time when the power is turned on and the time when the power is turned off, and based on the result of reading the dither pattern. Since the printer γ correction table is corrected, the γ correction table is not necessarily corrected after the power is turned on. Unless the printer job is input from the outside after the power is turned on, the correction of the printer γ correction table is not performed.
[0011]
Therefore, the waiting time of the user is reduced as compared to the case where the printer gamma correction table is corrected regardless of whether the printer receives a job after the power is turned on. In addition, since a dither pattern for a printer is not formed, toner consumption can be reduced.
The pattern forming means forms a dither pattern corresponding to the copying process when the power is turned on, and the correcting means corrects the γ correction table for copying based on the result of reading the dither pattern. Since the copying process is executed more frequently than the printer process, it is desirable that the copying process be performed during warm-up when the power is turned on. This makes it possible to always perform stable image quality copying without causing the user to wait after completion of warm-up.
The pattern forming means forms a dither pattern corresponding to the printer process if there is a change in the in-machine environment even when a printer job is received after the second time from power-on to power-off. The correction means may correct the printer gamma correction table based on the result of reading the dither pattern.
[0012]
After the first correction of the printer γ correction table, if there is a change in the internal environment, for example, the internal temperature, the internal humidity, or the output of a predetermined number of sheets, the second and subsequent corrections in the printer γ correction table May be performed. Thereby, it is possible to always obtain a stable printer image quality .
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings, taking an electrophotographic color copying machine having a printer output function as an example.
FIG. 1 is a side sectional view of the color copying machine 1.
The color copier 1 receives (1) an image signal transmitted from an external host computer in the form of data corresponding to an image, text, etc. described in a printer language, and performs multi-value dither processing as a laser beam. A printer function for irradiating the photosensitive drum to form an image. (2) A document reading signal from a scanner (not shown) arranged on the upper portion of the color copying machine 1 is used as a laser beam on the photosensitive drum. It has two functions of a copying function for forming an image by irradiating the light.
[0015]
The laser beam L is oscillated from a laser diode (not shown), modulated by the polygon mirror 2, and irradiated onto the photosensitive drum 5 through the lens 3 and the mirror 4. A charger 6 for uniformly charging the photosensitive drum and a cleaning unit 7 for removing residual toner from the photosensitive drum 5 are disposed upstream of the irradiation point in the rotation direction of the photosensitive drum 5. Yes. The developing unit 8 corresponding to the yellow component, the developing unit 9 corresponding to the magenta component, the developing unit 10 corresponding to the cyan component, and the developing corresponding to the black component are located downstream of the irradiation point in the rotation direction of the photosensitive drum. Units 11 are arranged. A toner tank 11a accumulates black toner.
[0016]
Further, a drum-shaped intermediate transfer body 12 to which a toner image formed on the photosensitive drum 5 is transferred is disposed in contact with the photosensitive drum 5. On the downstream side of the intermediate transfer body 12 in the rotation direction, a density sensor 13 serving as a density detection means for detecting the density of the dither pattern, a transfer roller 14 for transferring a toner image onto a sheet, and residual toner are removed from the intermediate transfer body. A cleaning unit 15 is disposed.
Further, a paper transport unit for transporting paper is disposed below the intermediate transfer body 12. The paper transport unit feeds paper from a paper feed cassette (not shown) at the bottom of the color copying machine 1 and feeds the paper by stopping the paper just before the transfer position of the intermediate transfer member. Registration roller 17 for adjusting the time point, transfer roller 14 described above, transport belt 18 for transporting the transferred paper, fixing device 19 for heating and fixing the toner image on the paper, paper discharge for discharging the paper after fixing Road 20, etc. are provided. The paper discharged from the paper discharge path 20 is loaded and held on either the paper holding unit 21 at the top of the color copying machine 1 or the paper holding unit opened on the left side of the color copying machine 1.
[0017]
The operation of the color copying machine 1 will be described. Corresponding to one color, the laser beam L scans the photosensitive drum 5 uniformly charged by the charger 6 through the polygon mirror 2, the lens 3, and the mirror 4. Thereby, an electrostatic latent image is formed on the photosensitive drum 5. Next, the formed electrostatic latent image is developed by the developing units 8 to 11 of the color, and a toner image is formed on the surface. The toner image is transferred onto the intermediate transfer member 12 that is in contact with the photosensitive drum 5. Thereafter, the photosensitive drum 5 is cleaned by the cleaning unit 7, and an electrostatic latent image corresponding to the next color is formed on the photosensitive drum 5. This electrostatic latent image is developed by developing units 8 to 11 of the next color, and a toner image is formed on the surface. The toner image is displaced on the intermediate transfer body 12 in contact with the photosensitive drum 5. Transcribed so that there is no. By performing such a process four times in total for yellow, magenta, cyan, and black, a color toner image can be formed on the intermediate transfer member 12.
[0018]
On the other hand, a sheet is fed at a predetermined timing, and immediately before the leading edge reaches the transfer start position, a transfer bias voltage having a polarity opposite to that of the toner formed on the intermediate transfer body 12 is applied to the transfer roller 14, The color toner image on the transfer body 12 is transferred to a sheet. Thereafter, the residual toner is removed from the intermediate transfer body 12 by the cleaner 15.
The sheet on which the image has been transferred as described above passes through the conveying belt 18 and passes through the fixing roller 19 to fix the image. Finally, the paper is discharged from the paper discharge path 20, and the discharged paper is stacked on the paper holding unit.
[0019]
FIG. 2 is a control function block diagram showing a flow of processing for performing correction processing of the γ correction table. Reference numeral 30 denotes a scanner control unit for outputting a scanner image signal, which is arranged inside a scanner arranged at the upper part of the color copier 1, and 40 is a printer arranged inside the color copier 1. 1 shows a printer control unit for outputting an image signal. Reference numeral 50 denotes an image formation control unit for setting a timing for correcting the γ correction table of the present invention.
[0020]
The scanner control unit 30 performs A / D conversion on the signal from the CCD 31 for reading the density information of the original image by the A / D converter 32 and supplies the signal to the image input unit 33. An output signal from the image input unit 33 is input to the selector 35. On the other hand, a dither pattern signal formed on the intermediate transfer body 12 is input to the selector 35 from the pattern generator 34. The selector 35 normally selects the path of the output signal from the image input unit 33, but switches to the path for selecting the output signal from the pattern generation unit 34 when correcting the γ correction table. The γ correction processing unit 36 performs γ correction processing on the image signal obtained from the selector 35 using the γ correction table. The screen processing unit 37 generates a multi-value dither image signal based on a predetermined screen condition for the image signal subjected to the γ correction by the γ correction processing unit 36. The multi-value dither image signal is sent to the image formation control unit 50 through the image output unit 38.
[0021]
On the other hand, when the printer control unit 40 receives data described in a printer language such as an image or text from an external personal computer PC or the like, the code analysis unit 41 decodes the code. The decoded data is input to the image data generation unit 42, and an image signal corresponding to the decoded data is generated. An output signal of the image data generation unit 42 is input to the selector 44. On the other hand, a dither pattern signal formed on the intermediate transfer body 12 is input to the selector 44 from the pattern generation unit 43. The selector 44 normally selects the path of the output signal from the image data generation unit 42, but switches to the path for selecting the output signal from the pattern generation unit 43 when correcting the γ correction table. The γ correction processing unit 45 performs γ correction processing on the image signal obtained from the selector 44 using the γ correction table. The screen processing unit 46 generates a multi-value dither image signal for the image signal that has been γ corrected by the γ correction processing unit 45 under a predetermined screen condition. The multi-value dither image signal is sent to the image formation control unit 50 through the image output unit 47.
[0022]
The image formation control unit 50 selects either an image signal from the scanner control unit 30 or an image signal from the printer control unit 40 by a selector 51, and a laser diode control unit 52 that drives the laser diode LD with the image signal. To supply. The laser diode drive signal from the laser diode control unit 52 is supplied to the laser diode LD, from which the laser beam is applied to the polygon mirror 2 described above.
[0023]
On the other hand, the dither pattern reading signal on the intermediate transfer body 12 from the density sensor 13 is supplied to the density detection unit 53 in the image formation control unit 50, and density correction control for managing the progress of the entire process from the density detection unit 53. Input to the unit 54. The density correction control unit 54 forms a printer job reception signal indicating that the color copying machine 1 has received a printer job, a copy job reception signal indicating that a copy job has been received, and a predetermined number of images on the photosensitive drum 5. And a signal indicating the temperature and humidity in the machine obtained from the environmental sensor. The “certain number” is set to a multiple of a certain number N, such as N, 2N, and 3N. The constant N is, for example, 1000 sheets.
[0024]
The read dither pattern density information is sent from the density correction control unit 54 to the γ table correction calculation unit 55, where correction processing of the γ correction table drawn from the γ correction processing units 36 and 45, that is, table rewriting is performed. The rewritten γ correction table is sent to the γ correction processing units 36 and 45.
The “pattern forming unit” of the present invention corresponds to the pattern generation units 34 and 43, and the “correction unit for correcting the γ correction table” corresponds to the density correction control unit 54 and the γ table correction calculation unit 55.
[0025]
FIG. 3 shows that a dither pattern corresponding to the copying process is formed at the time of turning on the power, performing γ correction, and a dither pattern corresponding to the printer process is formed when the printer job is received for the first time after the power is turned on. It is a flowchart which shows the process of this invention which performs (gamma) correction corresponding to it.
When the operator turns on the power (step S1), the color copying machine 1 starts warming up. During this time, operations such as heating of the fixing roller in the fixing device 19 are performed. During this warm-up, the image formation control unit 50 sets a screen condition corresponding to the copying process (step S3), and scans the laser beam to place a dither pattern corresponding to the screen condition on the intermediate transfer body 12. Let it form. Then, the dither pattern formed on the intermediate transfer body 12 is read using the density sensor 13 to correct the γ correction table. When this correction is completed, the warm-up is completed and the copying operation is possible (step S5).
[0026]
Then, it is determined whether or not a copy job has been received (step S6). If a copy job has been received, screen conditions such as the number of lines and angle for copying are set (step S7). Then, with reference to the corrected γ correction table, the gradation of the input image is corrected based on the γ correction table, and the copying operation is executed (step S8).
When a printer job is received (YES in step S9), the image forming control unit 50 determines whether or not it is the first printer job after power-on (step S10), and if it is the first printer job, sets a printer screen. (Step S11), the correction of the γ table is executed (step S12). The γ table correction process will be described later with reference to FIG.
[0027]
If it is not the first printer job after the power is turned on (NO in step S10), refer to the detected value of the environmental sensor, etc., and whether the environmental conditions such as the machine temperature, the machine humidity, and the number of copies have changed since the power was turned on. Determination is made (step S13). This determination is made based on whether the in-machine temperature, the in-machine humidity, etc. fluctuate beyond a certain threshold. Alternatively, the determination is made based on whether the number of copies exceeds a set value (for example, the N sheets, 2N sheets, 3N sheets,...).
[0028]
If there is an environmental change, a correction process for the γ table is executed. This correction process will be described later with reference to FIG.
If there is no environmental change, printer processing is performed using the correction value of the previous γ table as it is. That is, with reference to the γ correction table, tone correction of the image density is performed, screen conditions corresponding to the printer process are set (step S14), and the printer operation is executed (step S15).
[0029]
FIG. 4 is a graph for explaining the γ correction method. Input and output levels are normalized to 0-255, respectively. Graph A in the upper right shows the γ characteristic of the color copying machine. Graph B in the upper left shows the target input / output relationship. As shown in graph B, it is assumed that the target output level is i when the input level such as the document density is j. However, it is assumed that the input level i ′ is necessary to obtain the output level i due to the γ characteristic of the color copying machine. A graph showing the relationship between the input level i ′ and the input level j is the lower left γ correction curve C. The γ correction table is a table that stores numerical values of the γ correction curve C.
[0030]
The γ characteristic of a color copying machine changes over time depending on copying conditions such as temperature, humidity, or the number of copies of a photoreceptor. Therefore, the contents of the γ correction table must be updated, for example, every day.
Here, correction processing of the γ table related to printer processing will be described. FIG. 5 is a flowchart for explaining the correction process of the γ table.
First, screen conditions such as the number of lines and angle for the printer are set (step T1),
Dither patterns for yellow, magenta, cyan and black are generated on the intermediate transfer body 12 (step T2). The dither pattern has a density corresponding to a plurality of predetermined input levels. Next, the dither pattern is read by the density sensor 13 (step T3). Based on the read value, the contents of the γ correction table are updated so that a target output level is obtained (step T4).
[0031]
As described above, after the power is turned on, the contents of the printer γ correction table are updated when the printer job is received for the first time. Therefore, after the power is turned on regardless of whether the printer receives a job, the printer γ correction table is updated. Compared with the case where correction is performed, the waiting time of the user is reduced. In addition, since a dither pattern for a printer is not formed, toner consumption can be reduced.
Although the embodiments of the present invention have been described above, the embodiments of the present invention are not limited to the above-described embodiments. For example, in the above embodiment, a color copying machine having a printer output function has been described as an example, but a monochrome copying machine having a printer output function may be used. In addition, various modifications can be made within the scope of the present invention.
[0032]
【The invention's effect】
As described above, according to the present invention, the correction time of the γ correction table for the printer is limited in view of the fact that the job of the printer is less frequently generated than the copy job. The waiting time of the user is reduced as compared with the case of correcting the gamma correction table for the printer regardless of whether or not it is received. In addition, the number of printer dither patterns can be reduced, and the amount of toner consumed can be reduced.
[Brief description of the drawings]
FIG. 1 is a side sectional view of a color copying machine 1 according to an embodiment of the present invention.
FIG. 2 is a control function block diagram showing a flow of processing for performing correction processing of a γ correction table.
FIG. 3 forms a dither pattern corresponding to the copying process when the power is turned on, performs γ correction, and forms a dither pattern corresponding to the printer process when the printer job is first received after the power is turned on. It is a flowchart which shows the process of this invention which performs (gamma) correction corresponding to it.
FIG. 4 is a graph for explaining a γ correction method.
FIG. 5 is a flowchart for explaining γ table correction processing related to printer processing;
FIG. 6 is a diagram illustrating an example of a dither pattern (tone correction patch) formed on the image carrier on a trial basis.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Color copier 2 Polygon mirror 3 Lens 4 Mirror 5 Photoconductor drum 6 Charger 7 Cleaning unit 8-11 Developing unit 12 Intermediate transfer body 13 Density sensor 14 Transfer roller 15 Cleaning unit 16 Paper feed roller 17 Registration roller 18 Conveyor belt 19 Fixing device 20 Paper discharge path 21 Paper holding unit 30 Scanner control unit 31 CCD
32 A / D converter 33 Image input unit 35 Selector 34 Pattern generation unit 36 γ correction processing unit 37 Screen processing unit 38 Image output unit 40 Printer control unit 41 Code analysis unit 42 Image data generation unit 44 Selector 43 Pattern generation unit 45 γ Correction processing unit 46 Screen processing unit 47 Image output unit 50 Image formation control unit 51 Selector 52 Laser diode control unit 53 Density detection unit 54 Density correction control unit 55 γ table correction calculation unit L Laser beam LD Laser diode

Claims (2)

In a composite copying apparatus capable of forming images corresponding to copy processing and printer processing by an electrophotographic process,
Pattern forming means for forming a dither pattern obtained by subjecting the image carrier to screen gradation processing, a density sensor for reading the density of the dither pattern formed on the image carrier, and γ based on the result read by the density sensor A correction unit that corrects the correction table, and an image processing unit that can γ-correct the image formation characteristics by referring to the γ correction table at the time of image formation and can form an image based on the γ-corrected characteristics. ,
The pattern forming means forms a dither pattern corresponding to a copying process when the power is turned on, and the correcting means corrects a γ correction table for copying based on a result of reading the dither pattern,
The pattern forming means forms a dither pattern corresponding to the printer process when the first external printer job is received between power-on and power-off, and the correction means reads the dither pattern. A composite copying apparatus having a printer output function, wherein the gamma correction table for a printer is corrected based on the result.   The pattern forming means forms a dither pattern corresponding to the printer process if there is a change in the in-machine environment even when a printer job is received after the second time from power-on to power-off. 2. The composite copying apparatus having a printer output function according to claim 1, wherein the correction means corrects a gamma correction table for a printer based on a result of reading the dither pattern.

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