JP2006018180A - Image forming apparatus and density correction data generating method used for it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To continuously secure image quality of a printed image, to suppress excessive consumption of developer, and to prevent shortening of a service life of an image carrier such as a photoreceptor drum. <P>SOLUTION: Density correction data is generated for each of a plurality of printing modes on the basis of the density of a test pattern image corresponding to the plurality of printing modes formed on the image carrier, the density correction data corresponding to one printing mode is generated again after calculating a ratio between the density correction data corresponding to the one printing mode and the density correction data corresponding to another printing mode among the generated density correction data for each of a plurality of generated printing modes and the density correction data corresponding to the other printing modes is newly generated on the basis of the generated density correction data and the calculated ratio. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus that performs a density correction process for correcting a print density corresponding to a plurality of print modes to match the density of an input image, and in particular, based on the density of a test pattern image formed on an image carrier. The present invention relates to an image forming apparatus and a density correction data generation method for generating density correction data for each of the plurality of printing modes used for correction processing.

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, density correction processing is performed on image data read so as to match the density of a printed image that is actually printed out with the density of image data of a document read from a scanner device or the like. Has been done. The density correction processing is generally performed by, for example, adding or subtracting or multiplying the original image data by a correction amount determined based on previously prepared density correction data.
By the way, the sensitivity of the photosensitive drum changes due to various factors such as a change in the photosensitive characteristics of the photosensitive drum over time and a change in environmental temperature, and the density of the printed image printed based on the image data after the density correction processing is changed. Has a problem that it does not conform to the density of an input image (for example, an image of a document). In order to deal with such a problem, it is necessary to update the density correction data used for the density correction processing at an appropriate timing. As an example of the method for updating the density correction data, a plurality of test patterns corresponding to a plurality of gradation processing modes (or print modes) are formed in different regions on one transfer material, and then the plurality of formed patterns are formed. Japanese Patent Application Laid-Open No. 2004-133867 discloses a method of reading a developed test pattern image and obtaining (generating) new density correction data based on the read result.
JP 2002-335401 A

However, in the method described in Patent Document 1, a plurality of test pattern images corresponding to a plurality of gradation processes and printing modes are formed on a transfer material or an image holding body each time new density correction data is generated. Therefore, there is a problem that the liquid developer (developer) or the solid developer (toner) is consumed relatively quickly.
In recent years, there is an extremely strong demand for a device that can always maintain high image quality. To meet this demand, the density correction data must be frequently generated and updated. As a result, the density correction is performed. There is a problem that the consumption of the developer used for generating and updating data increases.
In addition, when the density correction data is frequently generated and updated, and the test pattern image is frequently developed on an image holding member such as a photosensitive drum, a cleaning process is performed to remove the developed test pattern image. Will increase the burden. This increase in the burden of the cleaning process causes problems such as consumption of the photosensitive drum and deterioration of photosensitive characteristics.
Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to continuously ensure the image quality of a printed image, to suppress excessive consumption of the developer, and to provide a photosensitive drum. It is an object of the present invention to provide an image forming apparatus capable of preventing shortening of the life of the image bile body and the density correction data generation method used therefor.

In order to achieve the above object, an image forming apparatus and a density correction data generation method according to the present invention are provided for each of the plurality of print modes based on test pattern image densities corresponding to a plurality of print modes formed on an image carrier. Density correction data is generated, and the ratio of density correction data corresponding to one printing mode and density correction data corresponding to another printing mode is calculated among the generated density correction data for each of the plurality of printing modes. After that, density correction data corresponding to the one printing mode is generated again, and density correction data corresponding to the other printing mode is newly generated based on the generated density correction data and the calculated ratio. Is configured to generate. As a precondition for the establishment of the present invention described above, the above-described ratio between a plurality of printing modes is always substantially constant. This has been learned from the inventor's many years of experimentation and research. Is.
With the present invention configured as described above, when new density correction data is generated for each print mode, it is necessary to develop a test pattern image for each of a plurality of print modes at least once on a photoconductor or the like. Then, when generating new density correction data, the test pattern image corresponding to one printing mode is developed to generate new density correction data corresponding to the one printing mode. With this density correction data as a reference, it is possible to generate density correction data corresponding to another print mode without developing a test pattern image corresponding to the other print mode. As a result, even if new density correction data is frequently generated and updated to ensure high image quality of the printed image, once the correction data corresponding to a plurality of print modes is generated, the above one print If only the mode test pattern is developed, new density correction data corresponding to each printing mode can be generated, so that excessive consumption of the developer such as toner and developer can be suppressed. Further, since the cleaning area of the test pattern image developed on the image holding member such as the photosensitive drum is reduced, consumption and wear of the photosensitive drum and the like are suppressed, and shortening of the life of the photosensitive drum and the like is prevented. The Of course, it is possible to reduce the consumption of the developer and prevent the life of the photosensitive drum and the like from being shortened without frequently generating and updating new density correction data.

By the way, when printing a text image in the text mode (also called printer mode), even if there is a slight density difference between the input image and the printed output image, it cannot be clearly distinguished visually. However, since the printed image is text (sentence), it is not a big problem. For this reason, the density correction data used in the text mode is allowed even if the above-described density difference can occur. However, when printing a photographic image in photographic mode (also called copier mode), the density difference affects the image quality of the printed output image even if the density difference between the input image and the printed output image is very small. To do. Therefore, in order to obtain a high-quality photographic image, the density correction data used in the photographic mode must be of a level that can maintain the sameness between the density of the input image and the density of the print output image.
As described above, the present invention has been made by paying attention to the fact that the ratio between the density correction data corresponding to one printing mode and the density correction data corresponding to another printing mode is always substantially constant. That is, since it is “substantially constant”, the ratio is not always constant, and there may be a slight deviation. Accordingly, the density correction data corresponding to the other printing mode obtained from the ratio may be data corresponding to a printing mode such as the text mode that does not cause a big problem even if a slight density difference occurs. preferable. In other words, the density correction data serving as a reference for generating density correction data according to another print mode is density correction data according to a photo mode that cannot be permitted even if there is a minute density difference. Is desirable.
Of course, the one print mode is not limited to the photo mode. For example, the present invention may be configured to set a print mode selected from the plurality of print modes as desired by the user to the one print mode.

  Here, the process of generating the density correction data for each of the plurality of print modes based on the density of the test pattern image corresponding to the plurality of print modes is performed when the manufactured image forming apparatus is shipped from the factory or sold. It is desirable to generate density correction data for each print mode as default data. Thus, by generating density correction data for each print mode based on each test pattern image in advance at the time of shipment of the apparatus, the user can use the image forming apparatus immediately after purchase.

On the other hand, the ratio between the density correction data corresponding to the one print mode and the density correction data corresponding to another print mode may vary with time due to changes in the photosensitive characteristics and environment of the photosensitive drum. For this reason, it is necessary to regenerate density correction data corresponding to the one printing mode and density correction data corresponding to another printing mode based on each test pattern image regularly or irregularly. This regeneration can be performed, for example, by turning on the power of the image forming apparatus, outputting a predetermined number of prints, changing the developing conditions of the developing device included in the image forming apparatus, or by the image forming apparatus. It is desirable that the processing is executed on condition that a photosensitive drum or the like, which is an example of the image holding member, is replaced.
In addition, the present invention may be configured to execute the process of generating density correction data corresponding to the one printing mode again when each of the above conditions is satisfied.
Of course, the process of generating the density correction data for each of the plurality of print modes based on the density of the test pattern image corresponding to the plurality of print modes, or the process of generating the density correction data corresponding to the one print mode again is as follows. , It may be executed under conditions and timing arbitrarily set by the user.

  As described above, according to the present invention, the density correction data for each of the plurality of printing modes is generated based on the density of the test pattern image corresponding to the plurality of printing modes formed on the image carrier, Of the generated density correction data for each of the plurality of print modes, after calculating the ratio between the density correction data corresponding to one print mode and the density correction data corresponding to another print mode, the one print mode is again displayed. Is generated, and density correction data corresponding to the other print mode is newly generated based on the generated density correction data and the calculated ratio. When new density correction data is generated for each printing mode, it is necessary to develop a test pattern image for each of the plurality of printing modes at least once on a photoconductor. When generating the correct density correction data, the test pattern image corresponding to the one print mode is developed to generate new density correction data corresponding to the one print mode, and the generated new density correction data. As a reference, it is possible to generate density correction data corresponding to another print mode without developing the test pattern image. As a result, even if new density correction data is frequently generated and updated to ensure high image quality of the printed image, excessive consumption of the developer such as toner and developer can be suppressed. Further, since the area for cleaning the test pattern image developed on the image bearing member such as the photosensitive drum is reduced, the consumption and wear of the photosensitive drum are suppressed, and the life of the photosensitive drum is shortened. Is prevented.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
FIG. 1 is a block diagram showing a schematic configuration and control system of a color copying machine X according to an embodiment of the present invention. FIG. 2 is a schematic sectional view of an image forming unit 10 of the color copying machine X. FIG. FIG. 4 is a schematic diagram showing an example of a test pattern, FIG. 4 is a graph showing an example of density correction data used in the density correction process, and FIG. 5 is a flowchart of density correction data generation processing executed by the CPU of the color copier X. It is a flowchart which shows an example.

First, referring to FIG. 1 and FIG. 2, a tandem color copier X (an example of an image forming apparatus) to which the density correction data generation processing (density correction data generation method) according to the embodiment of the present invention is applied. A schematic configuration will be described. FIG. 1 is a block diagram showing a schematic configuration and control system of the color copying machine X, and FIG. 2 is a schematic sectional view of the image forming unit 10 of the color copying machine X. The color copying machine X has a function for setting a print mode, and image data subjected to image processing (halftone processing, etc.) according to a print mode preset by the user or automatically set by the user. Is printed out. As a specific example of the print mode, for example, text to be printed out by executing gradation processing according to the type of document image (text image, photo image, mixed image of text and photo, FAX image such as G3) Mode, photo mode, text / photo mixed mode, FAX mode, etc.
The color copying machine X is merely an example of an image forming apparatus. As another example, for example, a monochrome copying machine, a printer apparatus, a facsimile apparatus, or a multifunction machine (MFP) having functions of a copying function, a printer function, and a facsimile function. ) Is applicable. Note that the print mode in the case of the multifunction machine refers to the text mode, the photo mode, and the text / photo mixed mode in the copying function and the printer function, and the FAX mode in the facsimile function.

  As shown in FIG. 1, the color copying machine X is roughly a document reading unit 40 that reads an image of a document, an image processing unit 41, an image data storage unit 43, and an image transferred from an external device. An external image data input unit 47 for inputting data, a density sensor signal input unit 46, an operation display unit 49 having an operation unit such as a numeric keypad and a display unit such as a touch panel, an image editing unit 45, an external interface (external I / F) 48, an image forming unit 10 (see FIG. 2) having a laser scanner unit (LSU) 104, and the like, and drive control of each drive system device of the color copier X including the image forming unit 10 The engine control unit 50, test patterns 30a and 30b (see FIG. 3) used for density correction data generation processing described later, and density correction data (see FIG. 3) used for density correction processing described later. Data storage section 30 (an example of density correction data storage means) for storing various data such as a reference) and a CPU (central processing unit) 44 that controls each of the above-described components based on a predetermined sequence program. These components are connected to the data bus 42 so that data communication is possible.

  The document reading unit 40 reads a monochrome document or color document image and outputs line data obtained by color separation into RGB color components, and a line of each color of RGB of the document image read by the color CCD 40a. A shading correction unit (shading correction circuit) 40b for correcting the line image level of the data, a line matching unit 40c such as a line buffer for correcting a shift of the line data of each color, and each hue (color data) of the line data of each color. ) Sensor color correction unit (sensor color correction circuit) 40d, MTF correction unit (MTF correction circuit) 40e for correcting the change of the signal of each pixel so as to have an emphasis, and correcting the brightness of the image. And a gamma correction unit (gamma correction circuit) 40f that performs visibility correction.

The image processing unit 41 includes a monochrome data generation unit 41a that generates monochrome data from RGB signals that are color image signals input from the image reading unit 40 in the monochrome copy mode, and an RGB signal input in the full color copy mode. Is converted into a YMC signal applicable to the process units 11 (11b to 11d) (see FIG. 2) corresponding to the respective colors of YMC (yellow, magenta, cyan) included in the image forming unit 10 and clock conversion is performed. A unit 41b, a region separation unit 41c, a black generation unit 41d, a color correction unit (color correction circuit) 41e, a zoom processing unit (zoom processing circuit) 41f, a space filter 41g, a halftone processing unit 41h, At least a semiconductor processor (not shown) such as a DSP that executes each process in each of the above components . Hereinafter, an image processing procedure performed by the image processing unit 41 in the full color copy mode will be briefly described.
The image data converted from the RGB signal to the YMC signal in the input processing unit 41b is then transferred to the region separation unit 41c. In this area separation unit 41c, after the type of image included in the image data (for example, character, halftone dot photograph, drawing paper photograph, etc.) is determined, the image data is converted into a character area (text area), halftone dot photograph. The image is divided into areas for each type of image, such as areas and photographic paper photograph areas. Subsequently, the background color removal processing is performed on the image data separated into the respective areas by the black generation unit 41d. At this time, a K (black) signal is generated based on the YMC signal of the image data (black generation processing).

The image data for each color of YMCK generated in this way is transferred to a color correction unit (color correction circuit) 41e provided in the subsequent stage. The color correction unit 41e adjusts the print density to the density of the input image input from the document reading unit 40, the external image data input unit 47, or the external interface 48 based on the density correction data prepared for each print mode. Processing for correction (hereinafter referred to as density correction processing) is performed. The density correction process is performed for each color of YMCK. Therefore, the density correction data for one printing mode includes density correction data for each color corresponding to each color of YMCK of an image printed in the printing mode. An example of the density correction data is shown in FIG. A1 and A2 in the figure indicate Y color density correction data (density correction curve) used for density correction processing of the photographic image read in the photographic mode, and B1 and B2 in the figure indicate the text read in the text mode. The density correction data of Y color used for the density correction process of an image is shown. Although omitted in FIG. 4, the density correction data of other colors (MCK) are of course present in the same manner as the Y color density correction data. Such density correction data is stored in the data storage unit 30 as an example of density correction data storage means.
The density correction data stored in the data storage unit 30 is updated (corrected) at an appropriate timing. That is, a process for generating new density correction data and updating the density correction data stored in the data storage unit 30 to the newly generated density correction data is performed. This is because printing is performed based on the image data after the density correction processing due to various factors such as a change in photosensitive characteristics of the photosensitive drum 101 (see FIG. 2) of the image forming unit 10 with time or a change in environmental temperature. This is performed in order to cope with a problem that the density of the printed image does not match the density of the input image (for example, an original image). The new density correction data is generated using the reference test pattern 31 (FIG. 3 (a)) stored in the data storage unit 30, and the generation process (density correction data generation process) is as follows. This will be described later (see FIG. 5).
The image data that has been subjected to density correction processing by the color correction unit 41e is then subjected to magnification conversion processing in accordance with a magnification set in advance by the user in a subsequent zoom processing unit (zoom processing circuit) 41f. After the filter processing by the filter 41g is performed, halftone processing for expressing gradation properties such as multilevel error diffusion processing and multilevel dither processing is performed in the halftone processing unit 41h.

Image data that has been subjected to various processes by the above-described components in the image processing unit 41 is stored in the image data storage unit 43. The image data storage unit 43 sequentially receives image data of 8 bits (total 32 bits) for each color of YMCK serially output from the image processing unit 41 and temporarily stores it in a buffer (not shown). The 32-bit image data primarily stored in the buffer is read out in the order in which it was stored, converted into 8-bit 4-color image data, and then four hard disks (rotary storage media) provided for each color. 43a, 43b, 43c, and 43d, respectively.
When the 8-bit four-color image data stored in the hard disks 43a to 43d is output to the LSU 104 (see FIG. 2) of the image forming unit 10 described later, the image data for each color is stored in the buffer memory 43e (semiconductor Are temporarily stored in the memory) and output to the LSUs 104 (104a to 104d) corresponding to the respective colors of YMCK after the output timing is shifted. As a result, the deviation of the output timing due to the disposition positions of the image process units 11a to 11d is corrected, and the deviation of the images sequentially transferred onto the intermediate transfer belt 12 is prevented.

The external interface (external I / F) 48 is a communication interface means for receiving image data from an image input processing device such as a communication portable terminal, a digital camera, a digital video camera, etc., connected to the color copying machine X. The image data input from the external I / F 48 is also input to the image processing unit 41 and subjected to the above-described density correction processing, halftone processing, and the like, so that the image data is processed in the process unit 11 of the color copying machine X. It is converted to a data level that can be formed.
The external image data input unit 47 is a printer interface or a FAX interface for inputting image data created in an information processing apparatus such as a personal computer or a facsimile apparatus externally connected to the color copying machine X via a network or the like. Since the image data input from the external image data input unit 47 has already been converted into a YMCK signal that has been subjected to the above-described density correction processing, magnification conversion processing, filter processing, and the like, only the halftone processing unit 41h has been passed through. Later, it is stored and managed in the hard disks 43a, 43b, 43c, and 43d of the image data storage unit 43.
The image editing unit 45 is transferred (or input) to the image data storage unit 43 via the external image data input unit 47, the image processing unit 41 or the external I / F 48, and stored in the hard disks 43a to 43d. A predetermined image editing process is performed on the processed image data. This image editing process is performed in a virtual drawing area on an image composition memory (not shown). The buffer memory 43e of the image data storage unit 43 may be used as an image composition memory.

Next, the image forming unit 10 will be described with reference to FIGS. 1 and 2.
As shown in the schematic cross-sectional view of FIG. 2, the image forming unit 10 includes four process units 11 (11 a to 11 d) and a laser scanner unit (LSU) 104 that form full-color images using YMCK color developers. (104a to 104d), an intermediate transfer belt 12, an intermediate transfer roller 13 (13a to 13d), a fixing device 14 and the like. Further, the process unit 11 is a photoconductor as an example of an image carrier. Drum 101 (101a to 101d), density sensor 15 (15a to 15d) as an example of image density detection means, developing unit (corresponding to developing device) 102 (102a to 102d), charging device 103 (103a to 103d), illustrated It is generally configured with a cleaning unit that does not.

  The charging device 103 is a contact-type charger that uniformly charges the surface of the photosensitive drum 101 to a predetermined potential. When the surface of the photosensitive drum 101 charged to a uniform potential by the charging device 103 is irradiated with the laser beam emitted from the LSU 104, an electrostatic latent image corresponding to the image data included in the laser beam is generated. Formed on the photosensitive drum 101. The electrostatic latent image formed on the surface of the photosensitive drum 101 is visualized as a toner image by the developing unit 102. When density correction data generation processing described later is executed, a toner image (test pattern image) corresponding to the test patterns 30a and 30b (see FIG. 3) stored in the data storage unit 30 is stored in each of the photosensitive drums. It is visualized on the surface of 101.

  The toner image formed on the surface of the photosensitive drum 101 by the developing unit 102 is transferred to a density sensor 15 (see FIG. 2) located downstream of the developing unit 102 in the rotation direction of the photosensitive drum 101. The concentration is detected. As a specific example of such a density sensor 15, there is, for example, a diffuse reflection type or specular reflection type optical sensor that detects the density of the toner image by measuring the amount of reflected light of the light irradiated on the toner image. Conceivable. When reflected light is received by the density sensor 15, a voltage signal corresponding to the reflected light amount is generated and sent to the density sensor signal input unit 46.

  The intermediate transfer belt 12 disposed below the photosensitive drum 101 is a loop-like endless belt stretched between a driving roller 12a and a driven roller 12b. Intermediate transfer rollers 13 (13a to 13d) corresponding to the respective photosensitive drums 101 are arranged at positions facing the respective photosensitive drums 101 with the intermediate transfer belt 12 interposed therebetween. In order to transfer the toner image carried on the surface of the photosensitive drum 101 onto the intermediate transfer belt 12, a transfer bias having a polarity opposite to the charging polarity of the toner is applied to the intermediate transfer roller 13. As a result, the YMCK color toner images formed on the photosensitive drum 101 (101a to 101d) are sequentially transferred onto the outer peripheral surface of the intermediate transfer belt 12, and a full color toner image is formed on the outer peripheral surface of the intermediate transfer belt 12. Is done.

Here, the test patterns 30a and 30b stored in the data storage unit 30 will be described with reference to FIG.
The test patterns 30a and 30b are used for density correction data generation processing, which will be described later. The test pattern 30a (FIG. 3A) is a test pattern corresponding to the photographic mode, and the test pattern 30b (FIG. 3 (b)) is a test pattern corresponding to the text mode. As shown in FIG. 3, each of the test pattern 30a, 30b is made of density patterns determined in accordance with the density value D ₁ ~ ₁₆ of 16 stages predetermined. Here, the density pattern refers to an image in which a plurality of rectangular images having a uniform density are arranged in series and the density of each rectangular image is changed stepwise as shown in FIG. That is, such a density pattern is used as a test pattern.
Among a plurality of density patterns of the test pattern 30a, for example, the concentration pattern of concentration D _15, as shown in FIG. 3 (a), the gradation representation of the image formed by the photographic mode (printing process in the photographic mode Is represented by a gradation expression 31a composed of 8 dot arrays scattered in a 6 × 6 matrix as gradation expression per pixel. ing. Further, as shown in FIG. 3B, the density pattern of the density D ₁₅ of the test pattern 30b is a gradation expression of a text image formed in the text mode (intermediate processing performed when printing processing is performed in the text mode). Gradation representation of gradation processing), and is represented by gradation representation 31b including four dot arrays scattered in a 3 × 3 matrix as gradation representation per pixel. In any gradation expression, the density D ₁₅ can be expressed, but the gradation expression 31a can express the most natural halftone than the gradation expression 31b. The gradation expression 31a is suitable for halftone printing. In contrast, the gradation expression 31b is unnaturally expressed as a halftone, but is suitable for halftone printing performed in the text mode because the edge portion of the image is emphasized.

  Next, an example of the procedure of density correction data generation processing executed by the CPU 44 (FIG. 1) of the color copying machine X will be described with reference to FIGS. In the figure, S10, S20,... Indicate process procedure (step) numbers, and the process starts from step S10. In order to simplify the explanation here, Y included in the image data of the original read in the photo mode (corresponding to one print mode) and the text mode (corresponding to another print mode) provided in the color copying machine X. The generation process of Y color density correction data used for the density correction process of color image data will be described, and the process for the Y image data will be described for the image data of other colors and the density correction data generation process of other print modes. Since it is the same as the procedure, the description is omitted. FIG. 4A shows density correction data generated on condition that the main power supply (not shown) of the color copier X is turned on, and FIG. 4B shows that 1000 sheets have been printed. Shows the density correction data generated.

  First, in step S10, it is determined whether the color copying machine X is turned on. Such determination is made, for example, based on whether an ON signal of a main power switch provided in the color copying machine X is input, or whether a predetermined input voltage is established after the ON signal is input. The determination result in step S10 is used as a starting condition for density correction data generation processing (hereinafter referred to as first generation processing) performed in steps S20 to S40 described later. Starting conditions include, for example, that a predetermined number of print outputs have been made, and development conditions (development state of toner particles, development bias, remaining amount of toner, etc.) of the development unit 102 provided in the color copying machine X have been changed. Alternatively, the condition may be that the photosensitive drum 101 provided in the color copying machine X has been replaced. The first generation process may be executed under conditions and timing arbitrarily set by the user. Further, the density correction data for each of the plurality of printing modes (photo mode, text mode) is generated as default data when the color copying machine X is shipped after the color copying machine X is manufactured. Is preferred. The determination in step S10 is repeated until it is determined that the power is turned on.

  If it is determined in step S10 that the color copying machine X has been powered on (Yes side of S10), then the CPU 44 sends test patterns 30a and 30b (FIG. 3) to the image forming unit 10 on the photoreceptor. Development is performed on the drum 101 (S20). That is, the test patterns 30a and 30b stored in the data storage unit 30 are read out by the CPU 44, and the read test patterns 30a and 30b are temporarily stored in the buffer memory 43e. Based on this, the image is transferred to the image forming unit 10.

In the image forming unit 10, when the toner images (test pattern images) of the respective colors of the test patterns 30a and 30b are developed on the photosensitive drum 101 (101a to 101d) by the developing unit 102 (102a to 102d), Thereafter, the density values of the density patterns corresponding to the plurality of density values D ₁ to ₁₆ included in the test patterns 30 a and 30 b are arranged at the density downstream of the developing unit 102. It is detected by the sensor 15 (15a to 15d) (S30).

Subsequently, in step S40, based on the detected density values E ₁ to ₁₆ (A1) and F ₁ to ₁₆ (B1) detected by the density sensor 15, the density correction process for the Y color image data in the photo mode is performed. Y-color density correction data A1 used in the above-described process and Y-color density correction data B1 (see FIG. 4A) used in the density correction process of the Y-color image data in the text mode are generated. Of course, density correction data for each color of MCK corresponding to each of the photo mode and the text mode is also generated by performing the same processing as the processing in steps S20 to S40. In this embodiment, only the photo mode and the text mode will be described. In other print modes, the density correction data for each color is generated by performing the same process as the process of steps S20 to S40. can do.
Note that the detected density values E ₁ to ₁₆ (A1) of the Y color of the test pattern image of the test pattern 30a (for photographic mode) corresponding to the input density values D ₁ to ₁₆ (horizontal axis in FIG. 4) in a plurality of stages (4 vertical axis) and Y color detected density values F ₁ to ₁₆ (B1) (FIG. 4 vertical axis) of the test pattern image of the test pattern 30b (for text mode) are plotted, respectively, to obtain the graph of FIG.
The generated density correction data A1 and B1 are then stored in the data storage unit 30 (S50).
The plurality of prints based on the processing of steps S20 to S40, that is, based on the density of the test pattern images of the test patterns 30a and 30b corresponding to the plurality of print modes of the photographic mode and the text mode formed on the photosensitive drum 101. The CPU 44 for executing the process (first generation process) for generating the density correction data A1 and B1 used for the density correction process corresponding to the mode corresponds to the first density correction data generation unit.

When the density correction data A1 and B1 are stored in the data storage unit 30 in step S50, the density correction data A1 corresponding to the photo mode stored in the data storage unit 30 and the density corresponding to the text mode are subsequently stored. A process of calculating a ratio with the correction data B1 (density ratio calculation process) is executed by the CPU 44, and then stored in the data storage unit 30 (S60). The CPU 44 when executing this density ratio calculation process corresponds to the density ratio calculation means. In the process of step S60, for example, each detected density values E ₁ ~ ₁₆ corresponding to each density value D ₁ ~ ₁₆ of the density correction data A1 (A1), the density values D ₁ ~ ₁₆ of the density correction data B1 A ratio with each corresponding detected density value F ₁ to ₁₆ (B1) is calculated. That is, the ratio k _n is calculated as shown by the following formula (1). In addition, n in Formula (1) shows the natural number of 1-16.

Since the amount of toner carried on the photosensitive drum 101 varies due to variations in the photosensitive characteristics of the photosensitive drum 101 and environmental temperatures, for example, the above steps S20 to S40 (first generation processing) are performed at different times. When the density correction data is generated in the above, the contents of the generated density correction data do not coincide with each other, but it has been found that the ratio k _n is always substantially constant by the inventor's many years of experiments and research. Yes. Therefore, when new density correction data is generated later by determining the ratio k _n after generating the respective density correction data based on the test pattern image density in the photo mode and text mode. In addition, only the density correction data corresponding to the photo mode is generated, and the processing described below (S90 to S120) is performed without developing the test pattern 30b corresponding to the text mode, thereby corresponding to the text mode. It is possible to generate density correction data.

When the ratio k _n is calculated in step S60, followed in step S70, the number of printed sheets of the first generation process is performed the color copying machine from X is a predetermined number of steps S20～S40 (e.g. 1000) Is reached by monitoring a count value such as a counter (not shown). If it is determined that the predetermined number has been reached, the process proceeds to step S90. If it is determined that the predetermined number has not been reached, it is then determined whether an instruction to update density correction data stored in the data storage unit 30 (FIG. 1) has been input (S80). This determination is made based on, for example, whether or not a predetermined key input has been made from the operation display unit 49 of the color copying machine X. If it is determined that the update instruction is input, the process proceeds to step S90. If it is determined that the update instruction is not input, the process returns to step S70, and the processes of steps S70 to S80 are repeated. Done.
The determination results in steps S70 and S80 are both density correction data generation processing (hereinafter referred to as second generation processing) in steps S90 to S110, which will be described later, and density correction data generation processing in step S120 (hereinafter referred to as third processing). The start conditions of the second and third generation processes are, for example, that the color copying machine X is turned on and the color copying machine X has the following starting conditions. The development conditions of the developing unit 102 (the charged state of toner particles, the development bias, the remaining amount of toner, etc.) have been changed, or the photosensitive drum 101 provided in the color copying machine X has been replaced. There may be. Further, the second and third generation processes may be executed under conditions and timing arbitrarily set by the user. In this case, as a matter of course, it is necessary to set the determination condition in step S70 so as not to overlap with the determination condition in step S10. For example, when the determination in step S10 is based on the number of printed output sheets, the determination in step S70 needs to be set to a condition smaller than the number of printed output sheets.

When the process proceeds to step S90, the test pattern image of the test pattern 30a (FIG. 3) is developed on the photosensitive drum 101 in the same manner as the process of step S20. Here, only the test pattern image of the test pattern 30a corresponding to the photo mode is developed, and the test pattern image of the test pattern 30b corresponding to the text mode is not developed.
When the test pattern image is developed on the photosensitive drum 101, followed by similarly to the processing in step S30, the concentration of the above-described density pattern corresponding to the plurality of density values D ₁ ~ ₁₆ contained in the test pattern 30a Values E ₁ to ₁₆ (A2) (see FIG. 4B) are detected by the density sensor 15 (15a to 15d) (S100), and then the detected density values E ₁ to ₁₆ detected by the density sensor 15 are detected. Based on (A2), new Y color density correction data A2 (FIG. 4B) used for the density correction processing of the Y color image data in the photo mode is generated (S110). Of course, also in this case, new density correction data for each color of MCK and new density correction data for each color in other printing modes are generated by performing the same processing as the processing in steps S90 to S130.
As described above, the density correction data A1 and B1 corresponding to a plurality of printing modes (photo mode and text mode) are generated by the processing of steps S90 to S130, that is, the first generation processing of steps S20 to S40. The CPU 44 that executes the second generation process for generating the density correction data A2 corresponding to the photographic mode again after that corresponds to the second density correction data generation means.

このようにして濃度値Ｆ₁〜₁₆（Ｂ１）が求められるため，図４（ｂ）に示す濃度補正データＢ１が生成される。もちろん，このような処理例に限らず，例えば，上記係数ｋ_nから求められる濃度値の差分を，上記既知の濃度値Ｅ_n（Ａ１）に加減算することにより上記濃度値Ｆ₁〜₁₆（Ｂ１）を求めて上記濃度補正データＢ１を生成する処理例であってもよい。 When the density correction data A2 is generated in step S120, subsequently, in step S130, the ratio k _{n represented} by the above equation (1) and the density generated by the second generation process of steps S90 to S110 are performed. The CPU 44 executes a process (third generation process) for generating density correction data B2 (see FIG. 4B) corresponding to the text mode based on the correction data A1. The CPU 44 when executing the third generation process corresponds to a third density correction data generation unit.
As a specific example of the processing in step S120, for example, the detected density values E ₁ to ₁₆ (A2) corresponding to the density values D ₁ to ₁₆ of the density correction data A2, that is, the detection detected by the density sensor 15 is performed. There is an example of processing for obtaining density values F ₁ to ₁₆ (B1) corresponding to the density values D ₁ to ₁₆ by multiplying the density values E ₁ to ₁₆ (A2) by the ratios k ₁ to ₁₆ . That is, the density values F ₁ to ₁₆ (B1) are obtained based on the following equation (2).

Since the density values F ₁ to ₁₆ (B1) are obtained in this way, density correction data B1 shown in FIG. 4B is generated. Of course, the present invention is not limited to such a processing example. For example, the density values F ₁ to ₁₆ (B ₁ ) are obtained by adding or subtracting the density value difference obtained from the coefficient k _n to the known density value E _n (A 1). ) To generate the density correction data B1.

In the description of the processing procedure of the flowchart of FIG. 5 described above, has been described an example of generating the density correction data B2 corresponding to the text mode on the basis of the density correction data A2 corresponding to the photo mode and the ratio k _n. However, the present invention is not limited to such processing examples. For example, one print mode arbitrarily selected by the user by operating the operation unit of the operation display unit 49 (FIG. 1) from a plurality of print modes is replaced with the density correction data of other print modes instead of the photo mode. By configuring the color copying machine X so as to set the print mode corresponding to the density correction data to be generated as a reference, other color correction data corresponding to the print mode arbitrarily selected and set by the user can be set. It is possible to generate density correction data for the print mode. It may be preferable for the user to generate density correction data for other printing modes in this way.

1 is a block diagram showing a schematic configuration and a control system of a color copying machine X according to an embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of the image forming unit 10 of the color copying machine X. The schematic diagram which shows an example of a test pattern. The graph which shows an example of the density correction data used for density correction processing. 6 is a flowchart showing an example of a procedure of density correction data generation processing executed by the CPU of the color copying machine X.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Image forming part 30 ... Data storage part 30a, 30b ... Test pattern 40 ... Original reading part 41 ... Image processing part 42 ... Data bus 43 ... Image data storage part 46 ... Temperature sensor signal input part 47 ... External image data input part 48 ... External interface 49 ... Operation display unit 50 ... Engine control unit

Claims (8)

Based on the density of the test pattern image according to the plurality of printing modes formed on the image carrier, the plurality of printing modes used for the density correction processing for correcting the printing density according to the plurality of printing modes. First density correction data generating means for generating density correction data;
Density correction data storage means for storing density correction data for each of the plurality of printing modes generated by the first density correction data generation means;
Density ratio calculating means for calculating a ratio between density correction data corresponding to one print mode stored in the density correction data storage means and density correction data corresponding to another print mode;
Second density correction data generating means for generating density correction data corresponding to the one printing mode again after the density correction data is generated by the first density correction data generating means;
Third density correction data generation for generating density correction data corresponding to the other print mode based on the calculation result by the density ratio calculation means and the density correction data generated by the second density correction data generation means. Means,
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the one printing mode is a photographic mode.   The image forming apparatus according to claim 1, further comprising a print mode selection setting unit that selects and sets the one print mode from the plurality of print modes.   The first density correction data generation unit generates density correction data for each of the plurality of printing modes as default data when the manufactured image forming apparatus is shipped. Image forming apparatus.   The first density correction data generating means is that the image forming apparatus is powered on, a predetermined number of prints are output, the developing conditions of the developing device included in the image forming apparatus are changed, or 5. The image forming apparatus according to claim 1, wherein density correction data for each of the plurality of printing modes is generated on condition that an image carrier included in the image forming apparatus is replaced.   The second density correction data generation means that the image forming apparatus has been turned on, a predetermined number of prints have been output, the developing conditions of the developing device provided in the image forming apparatus have been changed, or the image 6. The image forming apparatus according to claim 1, wherein density correction data corresponding to the one printing mode is generated again on condition that the image carrier included in the forming apparatus is replaced.   Timing for generating density correction data for each of the plurality of printing modes by the first density correction data generating means, or density correction data corresponding to the one printing mode again by the second density correction data generating means. The image forming apparatus according to claim 1, further comprising a timing setting unit that sets a generation timing. In a density correction data generation method for generating density correction data used in density correction processing for correcting print density according to the plurality of print modes,
Density correction data for each of the plurality of printing modes is generated based on the density of the test pattern image corresponding to the plurality of printing modes formed on the image carrier, and the generated density correction data for the plurality of printing modes is generated Is stored in the density correction data storage means, and among the density correction data for each of the plurality of print modes stored in the density correction data storage means, the density correction data corresponding to one print mode and the other print modes are supported. After calculating the ratio with the density correction data to be generated, density correction data corresponding to the one print mode is generated again, and the other print mode is changed based on the generated density correction data and the calculated ratio. A density correction data generation method characterized by newly generating corresponding density correction data.

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