JP4043542B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus, and in particular, forms a plurality of reference patches having different densities on a non-image portion on a photosensitive member, creates a density conversion table based on the densities of the plurality of formed reference patches, The present invention relates to an image forming apparatus that performs image density control for converting density characteristics of image data based on a created density conversion table.
[0002]
[Prior art]
Conventionally, a plurality of reference patches having different densities are formed on a non-image portion on a photoconductor, a density conversion table is created based on the density of the formed plurality of reference patches, and based on the created density conversion table Many techniques relating to image density control for converting density characteristics of image data have been proposed.
[0003]
The density conversion table created by the image density control by this method is smooth when the entire gradation area is viewed, and the density gradation (for example, the curve K03 in FIG. 8A) corrected by the density conversion table is corrected. The characteristic is closer to the target gradation (curve K02 in FIG. 8A) than the previous density gradation (curve K01 in FIG. 8A), and the apparent density is corrected to approach the target gradation. ing.
[0004]
However, when attention is paid to fine gradation, a jump exists in the density conversion table. FIGS. 13 and 14 show an example of the density conversion table, but even if it looks smooth in FIG. 13 showing the entire area, jumps are seen in places when enlarged as shown in FIG. This jump occurs more prominently when a plurality of conversion tables are combined. The density conversion tables shown in FIGS. 13 and 14 are density conversion tables created by synthesizing the gradation conversion table possessed by the image processing apparatus and the density conversion table for image density control. In general, when forming image data obtained by reading a document image with a scanner or the like, noise is already included in the read image data. The problem is not particularly noticeable.
[0005]
However, image data input from an external image processing apparatus (for example, image data created by computer graphics (CG image data) or image data input from a CD-ROM) contains almost no noise. It has a smooth gradation. When image density control is performed based on the density conversion table in which a jump occurs as described above, particularly for a color image as such image data, a jump occurs in a different density area in each color of YMCK. By overlapping, a subtle color change between the boundary line and the density may occur in the gradation portion, which should originally be a smooth and uniform color.
[0006]
Therefore, a specialized user who is required to output CG image data, CD-ROM image data, etc. as a high-quality image uses, for example, a commercially available image processing software such as Adobe Photoshop as an image output device. Before outputting the image data, the computer adjusts the tone density according to the required level. In addition, professional users can measure a large number of gradation patches using a high-precision densitometer such as X-rite using a commercially available calibration software, and create a more accurate density conversion table. Concentration characteristic conversion is performed.
[0007]
For specialized users who use such commercially available image processing software or calibration software, the density characteristic conversion of the image data using the density conversion table provided in the above-described image forming apparatus is unnecessary and unnecessary. It will be a thing.
[0008]
[Problems to be solved by the invention]
In view of the above-described facts, an object of the present invention is to provide an image forming apparatus capable of performing image density control suitable for the purpose of use of each individual user.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, an image forming apparatus according to claim 1 is an image forming apparatus having a copy function and a printer function, and reads an image of a document by the copy function. At the same time, measure the density of the scanned image A reading unit, an external data input unit for inputting image data from the outside by the printer function, and an image based on the image data read by the reading unit or the image data input by the external data input unit Image forming means for An operation panel provided on an upper surface of the image forming apparatus, and provided on the operation panel; Selection means for selecting whether or not to correct the density characteristics individually for the image data of the image read by the reading means and the image data input by the external data input means; Measured by reading the correction color patch print by the color patch print creating means for creating a correction color patch print made up of a plurality of color patches having different densities and printed with characters indicating the lead edge side. A density conversion table creating means for comparing the gradation based on the measurement result of the density of the color patch with a predetermined target gradation and creating a density conversion table based on the comparison result; When the selection means is selected to correct the density characteristics, In order that the gradation of the image matches the target gradation, The density characteristics of the image data Based on the density conversion table Density characteristic correcting means for correcting.
[0011]
Claims 2 The image forming apparatus described includes a determination unit that determines whether or not there is a problem with the measurement result of the density of the color patch, and displays a warning when the determination unit determines that there is a problem with the measurement result. Processing for performing at least one of processing and processing for canceling creation of density conversion table And means.
Claims 3 In the image forming apparatus described above, the density characteristic correction unit Image line number and color The density characteristics of the image data are corrected based on a density conversion table corresponding to the above.
Claims 4 The image forming apparatus according to claim 1. To any one of claims 3 In the image forming apparatus described above, if the recognition unit recognizes whether image data is input from the reading unit or the external data input unit, and the recognition unit recognizes that the input is input from the reading unit, the selection Selection control means for causing the selection means to select to correct the density characteristic, and when the recognition means recognizes input from the external data input means, the selection means to select not to correct the density characteristic. It is characterized by.
[0012]
In the image forming apparatus according to claim 1, Image data of image read by reading means or image data input by external data input means An image based on the above is formed by the image forming means.
[0013]
Here, in the image forming apparatus according to the first aspect, the selection means for selecting whether or not to correct the density characteristic of the image data. On the operation panel provided on the upper surface of the image forming device Is provided. When the user selects to correct the density characteristic by the selection means, the density characteristic of the image data is corrected by the density characteristic correction means. On the other hand, if the user selects not to correct the density characteristic by the selection means, the density characteristic of the image data is not corrected.
[0014]
In this way, the user can select whether or not to correct the density characteristic by the selection means, so that it is possible to perform image density control suitable for the user's purpose of use. For example, a user who uses external image processing software or calibration software can select not to perform image density control that may cause noise, and perform user-specific image density adjustment.
[0015]
The image forming apparatus according to claim 1. Is Image read by reading means by selecting means Image data In addition, it is possible to individually select whether or not to correct the density characteristic for the image data input by the external data input means. . The external data input means corresponds to, for example, a floppy (registered trademark) disk reading device, a CD-ROM reading device, a communication processing device for receiving data from an external image processing device via a network, and the like. To do.
[0016]
As described above, generally, image data obtained by reading a document image with a reading unit already includes noise of the document or the reading unit, and the noise due to the correction is conspicuous even if the density characteristics of the image data are corrected. Because there is not, it is desirable to choose to correct.
[0017]
On the other hand, since image data from outside (for example, CG image data, etc.) contains almost no noise, when the density characteristics of the image data are corrected, the overall density approaches the target. It will stand out. Therefore, it is desirable to use external image processing software or calibration software if necessary in this case.
[0018]
Therefore, the claim 4 As in the described invention, the image forming apparatus is further provided with a recognition unit and a selection control unit, and when the selection control unit recognizes that the input has been input from the reading unit, the selection unit corrects the density characteristic. When the recognition unit recognizes that the data is input from the external data input unit, it is desirable that the selection unit select the correction so as not to correct the density characteristic.
[0019]
Accordingly, it is possible to appropriately select whether or not to correct the density characteristic according to the type of target image data. In other words, when forming an image read by the reading means, it is possible to realize stable density reproduction by correcting the density characteristic, and when using external image processing software or calibration software, the density characteristic is not corrected. This makes it possible to adjust the image density unique to the user.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments according to the present invention will be described below with reference to the drawings.
[0021]
[Overall configuration of color copier]
FIG. 1 is an overall configuration diagram of a color copying machine to which the present invention is applied, and FIG. 2 is a block diagram of the color copying machine to which the present invention is applied.
[0022]
As shown in FIGS. 1 and 2, a color copying machine 10 includes a reading unit 20 that reads a document, an image processing unit 30 that processes the read image data, and a laser beam that drives the light beam on the photosensitive member according to the processed image data. The ROS optical unit 40 for irradiating and the image forming unit 60 for forming an image.
[0023]
As shown in FIG. 2, in the reading unit 20, a document G placed at a predetermined position on the placement table 12 (see FIG. 1) is irradiated by an exposure lamp 22 and the reflected light is a CCD image sensor (hereinafter abbreviated as CCD). ) 24. The image signal read by the CCD 24 is amplified to an appropriate level by the amplifier 26, and the amplified image signal is converted into 8-bit digital image data by the A / D converter 28. This digital image data is subjected to shading correction and gap correction in this order. The digital image data subjected to these corrections is converted into density data by the density converter 29 and sent to the image processing unit 30.
[0024]
The image processing unit 30 performs basic image processing as a color copying machine, that is, color signal conversion, black reproduction (UCR), MTF processing, and the like, and is converted into image data of four colors of yellow, magenta, cyan, and black. The The converted image data of each color is subjected to gradation conversion in accordance with the gradation characteristics of the reading unit 20 and the image forming unit 60. In addition, image data from an external image processing device or the like (for example, image data created by computer graphics (CG image data) or image data stored in a CD-ROM) is input to the image processing unit 30. An external data input unit 33 for generating the image data, and an image density control unit 31 for creating a density conversion table for converting the density characteristics of the image data. The image density control unit 31 performs the tone conversion. The image data or the external image data is subjected to density conversion based on the density conversion table. The external data input means 33 can be constituted by, for example, a floppy disk reader, a CD-ROM reader, or a communication processor for receiving data from an external image processor via a network. .
[0025]
The image data subjected to the density conversion is converted into analog image data by the D / A converter 32 and sent to the comparator 39 via the selector 34. The comparator 39 performs pulse width modulation by comparing the sent analog image data with the signal of a predetermined period output from the triangular wave generator 38, and the analog image data is converted into binary image data. Converted. In this pulse width modulation, for example, as shown in FIG. 3, the input analog image data A is compared with the triangular wave B from the triangular wave generator 38, and the portion where the analog image data A is larger than the triangular wave B is “ Binary image data in which “0” (laser off) and analog image data A smaller than the triangular wave B is “1” (laser on) is generated and sent from the comparator 39 to the ROS optical unit 40.
[0026]
Further, the image processing unit 30 is provided with patch signal generating means 36 that generates image signals (hereinafter referred to as patch image signals) of a plurality of image density control patches (reference patches) having different densities. The selector 34 selects analog image data from the D / A converter 32 during normal copying, and when receiving a reference patch creation instruction from the arithmetic unit 84 of the image forming unit 60 described later, a patch signal generating means The patch image signal from 36 is selected and sent to the comparator 39, and binarized by pulse width modulation as described above.
[0027]
The ROS optical unit 40 includes a laser drive circuit 42 that controls on / off of the laser 46 based on the binary image data sent from the comparator 39 and a laser light amount under the control of the arithmetic unit 84 of the image forming unit 60 described later. And a laser light quantity variable device 44 for variably controlling the above. The laser beam is deflected by the polygon mirror 48 and guided to the photosensitive member 62 of the image forming unit 60 through the fθ lens 50 and the reflection mirror 52.
[0028]
As shown in FIGS. 1 and 2, the image forming unit 60 is provided with a photoconductor 62. Around the photoconductor 62, there are a charging device 68 and a photoconductor for performing photoconductor potential control. An electrometer 70 for measuring the potential of the toner, a rotary developing device 72, an optical sensor 74 for measuring the patch density on the photosensitive member for toner dispensing control, a transfer device 80, a cleaner device 64, and a static elimination lamp 66 are installed. Yes. The image forming unit 60 is also provided with a toner dispensing device 76 that supplies toner to each color developing device of the rotary developing device 72, a fixing device 88, and a paper conveying device 92.
[0029]
Further, the image forming unit 60 controls the entire image formation and controls the image forming conditions according to the output of the electrometer 70 and the optical sensor 74, and the charge amount of the charging device 68 under the control of the computing device 84. A charge amount variable device 82 to be changed and a development bias variable device 78 to change the development bias under the control of the arithmetic device 84 are provided. Among these, the arithmetic unit 84 instructs the patch signal generation unit 36 and the selector 34 to create a reference patch.
[0030]
In the present embodiment, an operation panel 97 is provided on the upper surface of the color copying machine 10 for selecting whether or not to perform density characteristic conversion of image data as shown in FIG. The selection information selected by the operation panel 97 is sent to the calculation device 84. The calculation device 84 controls the image density control means 31, and responds to the selection information when using the copy function and when using the printer function. Concentration characteristic conversion is executed.
[0031]
[Outline of image forming process]
Next, an outline of the image forming process executed by the image forming unit 60 will be described. In the image forming unit 60, the following image forming process is executed according to a known xerographic process. That is, the photosensitive member 62 that rotates clockwise in FIG. 1 is uniformly negatively charged by the charging device 68, and a black latent image of the first color is first formed on the photosensitive member 62 by the laser light from the ROS optical unit 40. Is done. This latent image is developed with black toner by the black developing device of the rotary developing device 72. The developed black toner image is transferred by a transfer corotron 80A onto a sheet (not shown) that is conveyed from a sheet tray 90 by a sheet conveying device 92 and wound around a transfer drum 80. The toner image remaining without being transferred onto the photosensitive member 62 is removed by the cleaner device 64, and the photosensitive member 62 is discharged by the discharging lamp 66.
[0032]
Then, the photosensitive member 62 is uniformly negatively charged again by the charging device 68, and the second color yellow image formation is continued. In this way, a total of four color toner images from the third color magenta to the fourth color cyan are sequentially transferred onto the paper wound around the transfer drum 80. The paper on which the four color toner images have been transferred is peeled off from the transfer drum 80 by the peeling corotron 80B, and the four color toner images are fixed on the paper by the fixing device 88 to form a color copy. After the transfer of each color or after the paper is peeled off, excess charges on the paper and the transfer drum 80 are removed by the static eliminating corotron 80C.
[0033]
[Outline of photoreceptor potential control]
Next, the photoreceptor potential control by the charge amount varying device 82, the developing bias varying device 78, and the laser light amount varying device 44 by the electrometer 70 for measuring the potential on the photoreceptor 62 will be briefly described.
[0034]
In the present embodiment, before the start of copying immediately after the color copying machine 10 is turned on and before the start of copying after every 30 minutes, the arithmetic unit 84 of the image forming unit 60 controls the photoreceptor potential according to the flowchart of FIG. Is done. In the memory of the arithmetic unit 84, the target dark potential VHS, the target exposure partial potential VLS, and the anti-fogging potential difference VC from the target dark potential VHS to the developing bias potential VB are stored in advance.
[0035]
First, at step 152 of FIG. 5, the electrometer 70 detects the dark potential VH1 when the grid voltage of the charging device 68 is changed to the voltage VG1 by the charge amount variable device 82 and the dark potential VH2 when the voltage VG2 is set. . In the next step 154, the grid voltage VGS for obtaining the target dark potential VHS is calculated using the following equation (1).
[0036]
VGS = VG1 + ((VG2-VG1) * (VHS-VH1) / (VH2-VH1)) (1)
In the next step 156, the photosensitive member 62 is charged with the grid voltage VGS obtained in step 154. Then, the laser drive circuit 42 is driven by the laser light quantity variable device 44 with the two laser light quantities LD 1 and LD 2 to form a reference patch by the two laser light quantities LD 1 and LD 2 on the photosensitive member 62. Further, the exposure partial potentials VL1 and VL2 of the two formed reference patches are measured by the electrometer 70. In the next step 158, the laser light quantity LDS for obtaining the target exposure partial potential VLS is calculated using the following equation (2).
[0037]
LDS = LD2-((LD2-LD1) * (VLS-VL2) / (VL1-VL2)) (2)
In the next step 160, the developing bias potential VB is calculated using the following equation (3). Note that VC represents a fog prevention potential difference.
[0038]
VB = VHS-VC (3)
In the next step 162, the grid voltage VGS obtained as described above is set in the charge amount variable device 82, the laser light amount LDS is set in the laser light amount variable device 44, and the development bias potential VB is set in the development bias variable device 78. To finish.
[0039]
[Overview of toner dispensing control]
Next, dispense control of each color toner for the rotary developing device 72 will be described. This toner dispensing control is realized by measuring the patch density for controlling toner dispensing on the photosensitive member 62 with the optical sensor 74 and drivingly controlling the toner dispensing apparatus 76 by the arithmetic unit 84 based on the measured patch density. To do. The toner dispensing control patch is instructed to be created by the arithmetic unit 84.
[0040]
When a patch creation instruction is issued from the arithmetic unit 84, the selector 34 selects a patch image signal for each color for toner dispensing control with an image area ratio of 50% from the patch signal generating means 36, and sends it to the comparator 39. A reference patch for each color having an image area ratio of 50% is formed on a non-image portion on the photoreceptor 62 in the same procedure as the image forming process of the color copying machine described above.
[0041]
As shown in FIG. 4, the optical sensor 74 for measuring the patch density on the photosensitive member 62 irradiates the reference patch P on the photosensitive member 62 with the light from the LED 74A, and the reflected light is measured by the photodiode 74B. The patch density is measured based on the reflected light amount.
[0042]
If the measured patch density is lower than the target value, the arithmetic device 84 drives the toner dispensing device 76 to increase the toner density and bring the patch density closer to the target value. On the other hand, when the measured patch density is higher than the target value, the arithmetic unit 84 stops the toner dispensing apparatus 76 and brings the patch density close to the target value.
[0043]
[Overview of image density control]
Next, an image density control unit that forms a plurality of reference patches having different densities, creates a density conversion table based on the density measurement results, and converts density characteristics of the image data based on the created density conversion table. 6 will be described with reference to a flowchart of density conversion table creation processing 6 and a schematic diagram of image density control in FIG.
[0044]
As shown in FIGS. 6 and 7, when the density conversion table is created, the arithmetic unit 84 sends a correction color patch creation signal to the patch signal generation means 36, and each color selector 34 corrects the correction from the patch signal generation means 36. The color patch image signal is selected and sent to the comparator 39, and the correction color patch is printed on the paper and output in the same image forming procedure as the color copying machine described above (step S1). Here, for example, as shown in FIGS. 12 and 14, a color patch print for correction composed of 24 gradation patches having different densities for each color of yellow, magenta, cyan, and black is output. In FIGS. 12 and 14, Y at the top is yellow, M is magenta, C is cyan, and K is black.
[0045]
Next, in order to use the reading unit 20 of the color copying machine 10 as a correction color patch print density measuring device, the operator sets the correction color patch print on the mounting table (platen) 12 (step S2). It should be noted that the density measuring device for the correction color patch print may use a densitometer other than the reading unit 20 of the color copying machine 10.
[0046]
Next, the reading unit 20 measures the density of 24 color patches for each color to obtain the current gradation (step S3). Further, the density measurement result here is sent to the image density control means 31, and it is determined whether or not there is a problem in the measurement result (step S4). If there is no problem, the image density control means 31 compares the current gradation with a predetermined target gradation, creates a density conversion table based on the comparison result, and stores it in the memory (step S5). On the other hand, if there is a problem in the measurement result in step S4, there is a possibility that the color patch print for correction is placed in a wrong position, so a warning is displayed to the operator and the process is stopped (step S6).
[0047]
The density conversion table is created as described above, and at the time of image output, as shown in FIG. 7, the original image data sent from the reading unit 20 is subjected to color conversion and gradation conversion by the image processing unit 30. After the processing, the density of the image is converted based on the created density conversion table so that the gradation of the image matches the target gradation. Similarly, when printing image data transmitted from the outside, an external input is made based on the created density conversion table so that the gradation of the image matches the target gradation. Density conversion is performed on the image data.
[0048]
[Results of image density control]
The execution results of the above-described image density control will be described with reference to FIGS. In FIG. 8B, the measurement results of 24 patches with different densities for black (curve K11), the target value of 24 patches (curve K12), and the measurement results of 24 patches are created to match the target values. The density conversion table (curve K13) is shown. FIG. 8A shows a density gradation (curve K01) before density control for black, a target value of the gradation gradation (curve K02), and the density conversion table (curve K13 in FIG. 8B). ) Shows density gradation (curve K03) after density control. Obviously, the curve K03 is closer to the curve K02 than the curve K01. That is, the density gradation can be brought close to the target value by performing the density control.
[0049]
Similarly, for yellow, the measurement results of 24 patches having different densities (curve Y11), the target value of 24 patches (curve Y12), and the measurement results of 24 patches in FIG. A density conversion table (curve Y13) is shown. In order to bring the density gradation (curve Y01) before density control shown in FIG. 9A closer to the target value (curve Y02), the density conversion table (FIG. 9) is shown. The density control is performed based on the curve Y13) of (B), and the density gradation after the density control (curve Y03) can be obtained.
[0050]
Also for magenta, the measurement result of 24 patches with different densities (curve M11), the target value of 24 patches (curve M12), and the density for matching the measurement results of 24 patches with the target values are shown in FIG. A conversion table (curve M13) is shown. In order to bring the density gradation (curve M01) before density control shown in FIG. 10A closer to the target value (curve M02), the density conversion table (FIG. The density control is performed based on the curve M13) of B), and the density gradation after the density control (curve M03) can be obtained.
[0051]
Further, for cyan, the measurement results of 24 patches having different densities (curve C11), the target value of 24 patches (curve C12), and the density for matching the measurement results of 24 patches with the target values are shown in FIG. A conversion table (curve C13) is shown. In order to bring the density gradation (curve C01) before density control shown in FIG. 11A closer to the target value (curve C02), the density conversion table (FIG. The density control is performed based on the curve C13) of B), and the density gradation after the density control (curve C03) can be obtained.
[0052]
[Operation and effect of this embodiment]
Next, functions and effects of this embodiment will be described. When the button 97A is operated on the operation panel 97 of FIG. 15 provided on the upper surface of the color copying machine 10, density characteristic conversion is performed both when using the copy function of the color copying machine 10 and when using the printer function. You can choose. If the button 97B is operated, it can be selected that density characteristic conversion is performed only when the copy function of the color copier 10 is used. If the button 97C is operated, the density characteristic conversion is performed only when the printer function of the color copier 10 is used. Can be selected. Further, if the button 97D is operated, it can be selected that density characteristic conversion is not performed in either of the case where the copy function of the color copier 10 is used or the case where the printer function is used.
[0053]
As shown in FIG. 2, the selection information on the operation panel 97 is sent to the arithmetic device 84, and the arithmetic device 84 controls the image density control means 31 to use the copy function and the printer function, respectively. The density characteristic conversion according to the selection information is executed.
[0054]
FIG. 16 shows the flow of processing at this time. As shown in FIG. 16, a selector 98 (the above-described arithmetic device 84 and image data) is selected for image data read by the reading unit 20 when the copy function is used or image data received from the outside when the printer function is used. Whether the density characteristic conversion is to be executed or not is selected according to the selection information on the operation panel 97.
[0055]
If it is selected not to execute the density characteristic conversion, the density characteristic conversion is not performed on the image data, and the image output unit 99 (corresponding to the ROS optical unit 40 and the image forming unit 60 in FIG. 2) is sent as it is. The image is output.
[0056]
On the other hand, when it is selected to execute density characteristic conversion, density characteristic conversion based on the density conversion table corresponding to the number of image lines (for example, 200 lines or 400 lines) and the color is executed for the image data. Then, it is sent to the image output means 99 and output as an image.
[0057]
As described above, according to the present embodiment, it is possible to select whether or not to perform density characteristic conversion of image data for each of the case where the copy function is used and the case where the printer function is used, and according to the selection result. In addition, appropriate execution control of density characteristic conversion is realized.
[0058]
By the way, as described above, generally, noise already exists in the image data read by the reading unit 20, and even if the density characteristics of the image data are corrected, the noise due to the correction is not noticeable. It is desirable to choose.
[0059]
On the other hand, since image data from outside (for example, CG image data, etc.) contains almost no noise, when the density characteristics of the image data are corrected, the overall density approaches the target. It will stand out. That is, it is desirable to select not to correct external image data.
[0060]
Therefore, for example, as shown in FIG. 17, a recognition unit 192 that recognizes the input source of the input image data (whether it is the reading unit 20 or the outside), and selection information is determined based on the recognition result by the recognition unit 192. It is desirable to newly provide the color copying machine 10 with a selection control means 194 that transmits selection information to the selector 98 to control the selection operation, and performs the following control.
[0061]
That is, when the recognition unit 192 recognizes that the image data has been input from the reading unit 20, the selection control unit 194 transmits selection information for correcting the density characteristics of the image data to the selector 98 and transmits the density of the image data. Correct the characteristics. On the other hand, when the recognition unit 192 recognizes that the image data is input from the outside, the selection control unit 194 transmits selection information indicating that the density characteristic of the image data is not corrected to the selector 98 so that the density characteristic of the image data is obtained. Control not to correct.
[0062]
As a result, when forming an image read by the reading unit 20, it is possible to realize stable density reproduction by correcting the density characteristics of the image data, and not correcting the density characteristics of image data from the outside. Enables user-specific image density adjustment.
[0063]
In the above embodiment, an example is shown in which a plurality of reference patches having different densities are formed on a sheet, and a density conversion table is created based on these density measurement results, but not on a sheet but on a photoreceptor or transfer belt body. Alternatively, a plurality of reference patches having different densities may be formed, and these densities may be measured to create a density conversion table from the measurement results. Thus, even when the reference patch is formed on the photosensitive member or the transfer belt member, the same effect can be obtained.
[0064]
【The invention's effect】
Book According to the invention, since the user can select whether or not to correct the density characteristics of the image data, it is possible to perform image density control suitable for the purpose of use of the user.
[0065]
Further, according to the present invention, it is possible to appropriately select whether or not to correct the density characteristic according to the type of target image data. Claim 4 When forming an image read by the reading unit as described in the invention, it is possible to realize stable density reproduction by correcting the density characteristics, and when using external image processing software or calibration software. By not correcting the density characteristics, it is possible to make user-specific image density adjustments.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a color copying machine according to an embodiment.
FIG. 2 is a block diagram of the color copying machine of FIG.
FIG. 3 is a diagram illustrating binarization of image data by pulse width modulation.
FIG. 4 is a diagram illustrating a configuration of an optical sensor.
FIG. 5 is a flowchart showing a processing routine of photoreceptor potential control.
FIG. 6 is a flowchart showing a procedure for creating a density conversion table.
FIG. 7 is a diagram for explaining an outline of image density control;
8A is a graph showing density gradation before density control for black, density gradation target value, and density gradation after density control, and FIG. 8B is a density of 24 patches for black; It is a graph which shows a measured value, a target value of 24 patches, and a density conversion table.
9A is a graph showing a density gradation before density control for yellow, a target value of density gradation, and a density gradation after density control; FIG. 9B is a density of 24 patches for yellow; It is a graph which shows a measured value, a target value of 24 patches, and a density conversion table.
10A is a graph showing a density gradation before density control, a target value of density gradation, and a density gradation after density control for magenta, and FIG. 10B is a density of 24 patches for magenta. It is a graph which shows a measured value, a target value of 24 patches, and a density conversion table.
11A is a graph showing a density gradation before density control for cyan, a target value of density gradation, and a density gradation after density control, and FIG. 11B is a density of 24 patches for cyan. It is a graph which shows a measured value, a target value of 24 patches, and a density conversion table.
FIG. 12 is a diagram showing a plurality of reference patches in the present embodiment.
FIG. 13 is a graph showing an example of a density conversion table.
14 is an enlarged view of the density conversion table of FIG.
FIG. 15 is a diagram illustrating an example of a panel for selecting whether or not to perform gradation correction.
FIG. 16 is a diagram showing a flow of processing in the present embodiment.
FIG. 17 is a diagram showing a flow of processing when a selection control unit and a recognition unit are further provided.
[Explanation of symbols]
10 Color copier (image forming device)
20 Reading unit
30 Image processing unit
31 Image density control means
60 Image forming unit
62 photoconductor
84 Arithmetic unit
97 Operation panel
98 selector
192 recognition means
194 Selection control means

Claims (4)

An image forming apparatus having a copy function and a printer function,
Reading means for reading an image of a document by the copy function and measuring the density of the read image ;
External data input means for inputting image data from the outside by the printer function;
Image forming means for forming an image based on image data of the image read by the reading means or image data input by the external data input means;
An operation panel provided on an upper surface of the image forming apparatus;
Selection means provided on the operation panel, for selecting whether or not to correct the density characteristics individually for the image data of the image read by the reading means and the image data input by the external data input means When,
A color patch print creating means for creating a correction color patch print that is composed of a plurality of color patches of different densities and printed with characters indicating the lead edge side;
The gradation based on the measurement result of the density of the color patch measured by reading the color patch print for correction by the reading unit is compared with a predetermined target gradation, and the density conversion table based on the comparison result Density conversion table creation means for creating
Density for correcting the density characteristic of the image data based on the density conversion table so that the gradation characteristic of the image matches the target gradation characteristic when the selection unit is selected to correct the density characteristic. Characteristic correction means;
An image forming apparatus. Determination means for determining whether there is a problem in the measurement result of the density of the color patch;
A processing unit that performs at least one of a process of displaying a warning when the determination unit determines that there is a problem with the measurement result and a process of canceling the creation of the density conversion table ;
The image forming apparatus according to claim 1, further comprising: 3. The image according to claim 1, wherein the density characteristic correcting unit corrects the density characteristic of the image data based on a density conversion table corresponding to the number of image lines and the color of the image data. Forming equipment. Recognizing means for recognizing whether image data is input from the reading means or the external data input means;
When the recognition means recognizes that it has been input from the reading means, the selection means selects to correct the density characteristic, and when the recognition means recognizes that it has been input from the external data input means, the selection means Selection control means for selecting not to correct the density characteristics by,
The image forming apparatus according to any one of claims 1 to 3 further comprising a.

Images