JP4533000B2 - Image forming apparatus and image density correction method - Google Patents

Description

The present invention relates to an image forming apparatus that visualizes an electrostatic latent image formed on an image carrier as a developer image using a light color developer and a dark color developer of the same hue, and image density correction thereof about the mETHODS.

As the image forming apparatus progresses, the level of user request becomes higher. In an image forming apparatus using an electrophotographic system, four commonly used developers (dark colors) of cyan, magenta, yellow, and black are used. In addition to color toner), it has been proposed to use a light color developer (light color toner) such as light cyan or light magenta (see, for example, Patent Document 1). This is proposed for the purpose of suppressing graininess in a low density region (highlight portion) in each hue and differentiating in terms of image quality.
JP 2002-55500 A

  In the above-described image forming apparatus capable of developing an electrostatic latent image using the light color toner and dark color toner of the same color system and performing image formation, an image in which light color toner and dark color toner are mixed is used. A density region (a light and shade mixed region) occurs, and in this light and shade mixed region, the density characteristic of the corresponding color changes compared to the case where a single toner is used. Therefore, it is necessary to perform gradation correction in a mixed region of light color toner and dark color toner. In addition, when using light color toner and dark color toner, it is desirable not only to perform gradation correction in a mixed region of light color toner and dark color toner but also to perform such gradation correction over all gradations. This can lead to a reduction in device productivity.

The present invention was made in view of the above problems, without causing a significant reduction in productivity, stable density characteristics and image forming apparatus and an image density correction how the gradation characteristics can be obtained a The purpose is to provide.

In order to achieve the above object, the present invention is an image that visualizes an electrostatic latent image formed on an image carrier as a developer image using a light color developer and a dark color developer of the same hue. A forming apparatus that spans both a first density region of an image developed with a light color developer and a second density region of an image developed with a light color developer and a dark color developer of the same hue. A first image density correction unit that performs image density correction; and a part of an area including the first density area and the second density area, wherein the first density area and the second density area a second image density correcting means for performing image image density correction for a given region including the boundary between the density region, according to a preset predetermined condition, the said first image density correcting means first 2 for controlling to perform image density correction by switching between two image density correction means. To provide an image forming apparatus, characterized in that it comprises and.

In order to achieve the above object, the present invention is an image that visualizes an electrostatic latent image formed on an image carrier as a developer image using a light color developer and a dark color developer of the same hue. An image density correction method for a forming apparatus, comprising: a mode switching step for switching between a first image density correction mode and a second image density correction mode according to a predetermined condition set in advance; In the image density correction mode, the first density area of the image developed by the light color developer and the second density area of the image developed by the light color developer and the dark color developer of the same hue are covered. The second image density correction mode is a partial area of the first density area and the second density area, and the first density density correction mode. in a predetermined region including a boundary between the region and the second doped region To provide an image density correction and wherein the to a mode in which images density correction.

  According to the present invention, stable density characteristics and gradation characteristics can be obtained without causing a significant reduction in productivity.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a longitudinal sectional view showing a main part of an image forming apparatus according to an embodiment of the present invention.

  The image forming apparatus 1000 includes a laser beam printer that forms an image on a sheet using an electrophotographic method, and the laser beam printer includes a laser unit 1004 as shown in FIG. The laser unit 1004 drives a laser driver (not shown) based on an image signal from an external device (for example, a reader unit of a copying machine, a network-connected or directly connected computer, a facsimile machine). As a result, the laser driver emits a laser beam E corresponding to the image signal, and this laser beam E passes through the polygon mirror, the lens, and each reflecting mirror (not shown) in the laser unit 1004 and passes through the photosensitive drum 1001. Irradiated onto the exposure position L on the surface.

  The photosensitive drum 1001 is an image carrier that is rotatably supported in the direction of arrow A in the drawing. Around the photosensitive drum 1001, a pre-exposure lamp 1002, a charger 1003, a developing rotary 1005 that is a rotary developing device holding unit, a primary transfer roller 1009, and a cleaning device 1008 are arranged.

  Six developing devices 1006a to 1006f are held inside the developing rotary 1005, and developers of different colors are stored in the developing devices 1006a to 1006f, respectively. Specifically, the developing devices 1006a to 1006f store magenta toner, cyan toner, light magenta toner (hereinafter, light magenta toner), yellow toner, black toner, and light cyan toner (hereinafter, light cyan toner), respectively. ing. Here, magenta toner, cyan toner, yellow toner, and black toner are called dark toners, and light magenta toner and light cyan toners are called light color toners. The light color toner is manufactured by changing the amount of the pigment having the same spectral characteristic as that of the dark color toner. That is, the light magenta toner contains a pigment having the same spectral characteristics as the magenta toner, but its content is less than that of the magenta toner. The light cyan toner contains a pigment having the same spectral characteristics as the cyan toner, but its content is less than that of the cyan toner. Here, the use of dark and light toners for magenta and cyan colors is intended to achieve a reduction in graininess and dramatically improve the reproducibility of light images such as human skin.

  The toner in the developing units 1006a to 1006f is replenished at any time from the toner storage units (hoppers) 1007a to 1007f for each color so that the toner ratio (or toner amount) in the developing unit is kept constant. The

  At the time of image formation, the photosensitive drum 1001 is rotated in the direction of arrow A, and its surface is discharged by the pre-exposure lamp 1002 and then uniformly charged by the charger 1003. The laser unit 1004 irradiates the photosensitive drum 1001 with laser light E for each separated color, and a latent image is formed on the photosensitive drum 1001.

  Next, the developing rotary 1005 is rotated, and the developing device for the corresponding color is moved to the developing surface D on the photosensitive drum 1001. Then, the corresponding developing device is operated (developing bias is applied), and toner is supplied to the photosensitive drum 1001. As a result, a corresponding color toner image is formed on the photosensitive drum 1001.

  The corresponding color toner image formed on the photosensitive drum 1001 is primarily transferred on the primary transfer surface t1 so that the toner images of the respective colors are superimposed on the intermediate transfer belt 1011 as a transfer medium. As described above, the toner images for each color are sequentially superimposed and primarily transferred, whereby a full-color toner image is formed on the intermediate transfer belt 1011. During the primary transfer, a primary transfer bias is applied to the primary transfer roller 1009.

  Thereafter, the full color toner image on the intermediate transfer belt 1011 is secondarily transferred onto the paper P fed from the paper feed roller 1014 on the secondary transfer surface t2. At this time, a secondary transfer bias is applied to the secondary transfer roller 1010. The sheet P is conveyed to the secondary transfer surface t2 at a desired timing, and a full color toner image is transferred onto the sheet P here. The paper P on which the full color toner image is transferred is conveyed to the fixing device 1016 via the conveyance path R. In the fixing device 1016, the full color toner image on the paper P is heat-pressed and fixed on the paper P. Then, the fixed sheet P is discharged onto a discharge tray 1017.

  The intermediate transfer belt 1011 is driven by each of the driving rollers 1012a and 1012b, and a transfer cleaning device configured to be able to contact and separate from the intermediate transfer belt 1011 at a position facing the driving roller 1012a with the intermediate transfer belt 1011 interposed therebetween. 1013 is arranged. After the full color toner image on the intermediate transfer belt 1011 is transferred onto the paper P, the transfer cleaning device 1013 is moved toward the driving roller 1012a so as to come into contact with the intermediate transfer belt 1011. Clean the toner. After cleaning, the transfer cleaning device 1013 is moved away from the intermediate transfer belt 1011.

  A density detection sensor 1015 for detecting the positional deviation and density of the image transferred from the photosensitive drum 1001 is disposed downstream of the primary transfer surface t1 in the moving direction B of the intermediate transfer belt 1011. The output of the density detection sensor 1015 is used for control for correcting image density, toner replenishment amount, image writing timing, image writing start position, and the like.

  In addition, an environment sensor 1103 for detecting an environmental change that changes the characteristics of the image forming apparatus 1000, such as temperature and humidity, is disposed inside the image forming apparatus 1000.

  Next, the control configuration of the image forming apparatus 1000 will be described with reference to FIG. FIG. 2 is a block diagram showing a control configuration of the image forming apparatus of FIG.

  The image forming apparatus 1000 is controlled by a control circuit 1101 shown in FIG. A memory 1102, an environment sensor 1103, a concentration detection sensor 1015, a laser unit 1004, and an external device 1100 are connected to the control circuit 1101.

  A control circuit 1101 controls the entire apparatus according to a control program and data stored in the memory 1102. Further, the control circuit 1101 performs various processes on the image signal (RGB signal) input from the external device 1100. For example, after the input RGB signal is converted into a CMYK signal, the control circuit 1101 performs gamma (γ) correction, image density correction for the signal after gamma correction, binarization for the signal after image density correction, and the like. The binarized signal is output as a drive signal for the laser unit 1004 as will be described later. The memory 1102 stores density correction pattern images (hereinafter referred to as patches) formed on the intermediate transfer belt 1011 and ideal density values Drn (n = 0 to 255). The control circuit 1101 performs switching of an image density correction mode, which will be described later, based on the output of the density detection sensor 1015 or the output of the environment sensor 1103.

  The external device 1100 is, for example, a copier reader unit, a network-connected or directly connected computer, a facsimile machine, and the like, and outputs an image signal (RGB signal) to the control circuit 1101. As described above, the control circuit 1101 generates a drive signal for the laser unit 1004 based on the image signal from the external device 1100 and outputs the drive signal to the laser unit 1004. The laser unit 1004 is driven by the drive signal and emits laser light.

  Next, the relationship between the mixing ratio characteristics of the dark color toner and the light color toner for the image data and the output density characteristics will be described with reference to FIG. FIG. 3 is a diagram showing the relationship between the mixing ratio characteristic of dark color toner and light color toner for the image data and the output density characteristic. In this figure, the horizontal axis represents 8-bit, 256-gradation image data VD for a predetermined color. The left vertical axis represents the toner amount Tn for the image data, and the right vertical axis represents the output density value D.

  As shown in FIG. 3, gradation representation is performed using only the light color toner 301 for the low density area (area from 0 to VDa) of the image data VD, and in this low density area, As the density increases, the amount of light color toner 301 increases. For an area ranging from an intermediate density area to a high density area (toner mixed area 303 with values from VDa to VDmax) of image data VD, gradation expression is performed using light color toner 301 and dark color toner 302. In the toner mixed region 303, the amount of the light color toner 301 is decreased and the amount of the dark color toner 302 is increased as the density increases.

  When the light toner and the dark toner are ideally mixed in the toner mixed region 303 described above, the density characteristic for the image data VD is represented by an ideal curve 304. The ideal curve 304 has a characteristic that the density value Dn is proportional to the image data VDn. Here, Dn is an ideal density value in the patch.

  Next, correction of the light toner input signal for image density correction will be described with reference to FIGS. 4 is a diagram showing output density characteristics with respect to image data when a patch formed on the intermediate transfer belt 1011 is read by the density detection sensor 1015, and FIG. 5 is a diagram showing output density characteristics of the light color toner in FIG. FIG. 6 is a diagram showing an input signal of light toner and an output signal of light toner obtained by correcting the input signal.

  First, output density characteristics for image data when a patch formed on the intermediate transfer belt 1011 is read by the density detection sensor 1015 will be described.

  Here, the patch is specifically formed on the intermediate transfer belt 1011 with a predetermined resolution L (16 in this example) over the entire density region (0 to 255) of the image data of the corresponding color. This is a density detection image. The number of patches at this time is 16, and this patch formation is performed at a preset timing such as when the power is turned on, between jobs, and before and after returning to the energy saving mode.

In FIG. 4, assuming that the measurement result for the actually formed patch is represented by a characteristic curve 401, and the density deviation amount with respect to the ideal curve 304 is ΔDn (n = 1 to 16), the density deviation amount ΔDn is
ΔDn = Dn−Dx
It is expressed by the relational expression. Here, Dx is a measured density value.

  Next, a method of calculating a correction value for the light color toner input signal will be described using the density deviation amount ΔDn and the light color toner output density characteristics shown in FIG. Here, the light toner input signal is a signal after gamma (γ) correction.

First, since image formation is performed using only light color toner for image data in the range of 0 to 125, output density deviation amount ΔDn (n = 1 to 8) is equal to the density correction value ΔDpn of the light color toner. Therefore, the density correction value ΔDpn is
ΔDpn = ΔDn (n = 1 to 8)
It is expressed. Then, a correction value ΔXpn (n = 1 to 8) of image data necessary for correcting the output density characteristic of the light color toner shown in FIG. 5 by ΔDpn is obtained from the output density characteristic.

  Then, the obtained correction value ΔXpn is used for correcting the input signal of the light color toner as shown in FIG. Here, in FIG. 6, the input signal of the light toner before correction is represented by a dotted line, and the light toner that is a light toner signal after correction obtained by correcting the input signal using the correction value ΔXpn. The output signal is represented by a solid line.

  Specifically, the value of the corresponding point of the light color toner input signal is corrected with the correction value ΔXpn (n = 1 to 8) obtained as described above. Then, by performing smoothing processing by interpolating between the points obtained by the correction, an output signal of the light toner (corrected light toner input signal) represented by a solid line is obtained. The light toner output signal obtained by this correction is binarized and converted to an analog signal, and this analog signal is transferred to the laser unit 1004 as a drive signal.

  As described above, the density deviation amount ΔDn (n = 1 to 16) with respect to the ideal curve 304 is calculated, and the correction value ΔXpn obtained from the density deviation amount ΔDn is used to correct the input signal of the light color toner. The density of the density portion is corrected and the gradation is improved.

  Next, correction of dark toner input signals for correcting image density will be described with reference to FIGS. 7 is a diagram showing the output density characteristics of the light color toner in FIG. 4, and FIG. 8 is a diagram showing the dark toner input signal and the dark toner output signal obtained by correcting it.

  First, a method for calculating the correction value of the dark toner input signal for correcting the gradation characteristics from the intermediate density region to the high density region will be described. Here, the input signal of dark toner is a signal after gamma (γ) correction.

As shown in FIG. 3, in the present embodiment, the image data of the light color toner 301 is generated not only in the low density area but also in the intermediate density area to the high density area. Therefore, it is necessary to consider the density correction for the input signal of the light color toner described above. As shown in FIG. 3, since the value of the image data of the light color toner 301 is a symmetric value centering on the intermediate value VDa (= 128), the dark color toner density correction value ΔDdm is
ΔDdm = ΔD (7 + m) −ΔD (9−m)
Can be calculated as Here, m is a numerical value in the range of 1 to 9, ΔD (7 + m) is a density correction value ΔDn (n = 8 to 16) for intermediate to high density areas, and ΔD (9−m) is a density correction value for light color toner. It is. Then, by using ΔDdm calculated in this way, the image signal correction value ΔXdm (m = 1 to 9) corresponding to each point can be obtained from the output density characteristics shown in FIG.

  Then, the obtained correction value ΔXpn is used for correcting the input signal of dark toner as shown in FIG. Here, in FIG. 8, the dark toner input signal before correction is represented by a dotted line, and the dark toner signal which is obtained by correcting the dark toner input signal using the correction value ΔXpn. The color toner output signal is represented by a solid line.

  Specifically, the value of the corresponding point of the light color toner input signal is corrected by the correction value ΔXdm (n = 1 to 8) obtained as described above. Then, by interpolating the values between the points obtained by the correction and performing the smoothing process, an output signal (dark toner signal after correction) represented by a solid line is obtained. The dark toner output signal is binarized and converted to an analog signal, and the analog signal is transferred to the laser unit 1004 as a drive signal.

  In this way, the density from the intermediate density area to the high density area is corrected, and the gradation is improved.

  Next, the procedure of the image density correction process in the image forming apparatus 1000 of the present embodiment will be described with reference to FIGS. FIG. 9 is a diagram showing density characteristics with respect to image data indicating a density detection correction area in the simple image density correction mode, and FIG. 10 is a flowchart showing a procedure of image density correction processing by the control circuit 1101 in FIG. Here, the procedure shown in FIG. 10 is executed by the control circuit 1101 executing a program stored in the memory 1102.

  The image forming apparatus 1000 according to the present embodiment has two image density correction modes, a full image density correction mode and a simple image density correction mode, and two image density corrections, a full image density correction mode and a simple image density correction mode. The mode is switched according to whether or not the detected condition satisfies a predetermined condition set in advance.

  Here, in the full image density correction mode, patches of a specific pattern are formed on the intermediate transfer belt 1101 with a predetermined resolution in all density regions (image data VD0 to VD255) in the same hue. In this mode, the density of the patch is detected, and image density correction is performed based on the detected density value. The correction at this time is performed according to the method described above.

  The simple image density correction mode is a predetermined density region in which dark toner and light color toner in the same hue are mixed (image data value shown in FIG. 9 = density detection region in the simple image density correction mode near 128). In this mode, patch formation and density detection (ΔD6 to ΔD10) with a small number of samplings are performed with respect to the full image density correction mode, and image density correction is performed based on the detected density value. For example, when the detection samples ΔD6, ΔD7, and ΔD8 in the light color toner density region are obtained, the above-described image density correction processing is performed only for the density.

  When performing the image density correction, the control circuit 1101 first determines whether or not the detected condition matches a predetermined condition stored in advance in the memory 1102 as shown in FIG. 10 (step S101). . If the detected condition matches the predetermined condition, the control circuit 1101 executes the full image density correction mode (step S102). That is, since the full image density correction mode requires a relatively long time for correction, it is executed only when the detected condition matches the predetermined condition. On the other hand, if the detected condition does not match the predetermined condition, the control circuit 1101 executes the simple image density correction mode (step S103).

  Next, FIG. 11 shows a case where, as a condition for switching between the full image density correction mode and the simple image density correction mode, whether the density deviation amount with respect to the preset image density ideal table exceeds a predetermined amount A or not. The description will be given with reference. FIG. 11 shows a processing procedure when the density deviation amount with respect to a preset image density ideal table exceeds a predetermined amount A as a condition for switching between the full image density correction mode and the simple image density correction mode. It is a flowchart to show.

  In this case, as shown in FIG. 11, the control circuit 1101 first performs control to form a patch of a predetermined pattern on the intermediate transfer belt 1011 based on a preset density detection region (step S201). Next, the control circuit 1101 takes in the density value of the patch on the intermediate transfer belt 1011 detected by the density detection sensor 1015, and calculates a density deviation amount ΔDn between the detected density value and the ideal density value (step S202). ). For example, as shown in FIG. 9, if an actual characteristic curve a is obtained as a patch density measurement result, the value indicated by the characteristic curve a at the corresponding point in the preset density region and the value indicated by the ideal density curve Are calculated as the density deviation amount ΔDn.

  Then, the control circuit 1101 determines whether or not the calculated density deviation amount ΔDn is greater than a preset threshold value A (step S203). Here, when the calculated density deviation amount ΔDn is larger than the preset threshold value A, the control circuit CPU 1101 determines that accurate gradation expression is difficult in the apparatus main body, and performs full image density correction. Is executed (step S204). On the other hand, when the calculated density deviation amount ΔDn is equal to or less than the threshold value A, the control circuit 1101 executes the simple image density correction mode (step S205).

  In addition, the condition for switching between the full image density correction mode and the simple image density correction mode may be a condition as to whether or not the environment change value inside the apparatus exceeds a preset value. This case will be described with reference to FIG. FIG. 12 is a flowchart showing a processing procedure in a case where, as a condition for switching between the full image density correction mode and the simple image density correction mode, whether or not the environmental change value inside the apparatus exceeds a preset value. .

  In this case, the change value ΔT is detected from the environmental value T in the environment around the photosensitive drum 1001 or the intermediate transfer belt 1011 detected by the environmental sensor 1103. Here, the environmental value T detected by the environmental sensor 1103 is temperature or humidity.

  As shown in FIG. 12, the control circuit 1101 first detects the environmental change value ΔT from the environmental value T detected by the environmental sensor 1103 (step S1201). This detection is performed in a preset state such as when the power is turned on, between jobs, and before and after returning to the energy saving mode.

  Next, the control circuit 1101 determines whether or not the detected environment change value ΔT has exceeded a preset threshold value B (step S1202). If the environmental change value ΔT exceeds the threshold value B, the control circuit 1101 determines that accurate gradation expression is difficult, and performs full image density correction (step S1203). On the other hand, when the environmental change value ΔT is equal to or less than the threshold value B, the control circuit 1101 continues to execute the simple correction mode (step S1204).

  In addition, the condition for switching between the full image density correction mode and the simple image density correction mode may be a condition as to whether or not the number of image forming operations (number of prints) exceeds a threshold value C. This case will be described with reference to FIG. FIG. 13 is a flowchart showing a processing procedure when the condition for switching between the full image density correction mode and the simple image density correction mode is whether or not the number of image forming operations (number of prints) exceeds a threshold value C.

  The image forming apparatus 1000 has a counter (not shown) that counts the number of image forming operations (number of printed sheets) N, and the control circuit 1101 takes in the output of the counter at a preset timing.

  As shown in FIG. 13, the control circuit 1101 first takes in the output of the counter, that is, the number N of image forming operations (step S1301), and determines whether or not the number N of image forming operations exceeds a preset threshold C. (Step S1302). If the number N of image forming operations exceeds the predetermined value C, the control circuit 1101 determines that accurate gradation expression is difficult, and performs full image density correction (step S1303). On the other hand, when the number N of image forming operations is equal to or less than the threshold value C, the control circuit 1101 continuously executes the simple correction mode (step S1304).

  As described above, according to the present embodiment, it is possible to provide the image forming apparatus 1000 with stable density characteristics and gradation characteristics without causing a significant decrease in productivity of the apparatus main body.

  An object of the present invention is to supply a storage medium (or recording medium) in which a program code of software that realizes the functions of the above-described embodiments is recorded to a system or apparatus, and the computer (or CPU or CPU) of the system or apparatus. Needless to say, this can also be achieved when the MPU) reads and executes the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.

  Examples of the storage medium for supplying the program code include a floppy (registered trademark) disk, a hard disk, a magneto-optical disk, a CD-ROM, a CD-R, a CD-RW, a DVD-ROM, a DVD-RAM, and a DVD. -RW, DVD + RW, magnetic tape, nonvolatile memory card, ROM, etc. can be used. Alternatively, the program code may be downloaded via a network.

  Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an operating system (OS) running on the computer based on the instruction of the program code. A case where part or all of the actual processing is performed and the functions of the above-described embodiments are realized by the processing is also included.

  Furthermore, after the program code read from the storage medium is written into a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, the function is determined based on the instruction of the program code. The case where the CPU of the expansion card or the function expansion unit performs part or all of the actual processing and the functions of the above-described embodiments are realized by the processing is also included.

1 is a longitudinal sectional view showing a main part of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating a control configuration of the image forming apparatus in FIG. 1. It is a figure which shows the relationship between the mixing amount ratio characteristic of the dark color toner and light color toner with respect to image data, and an output density characteristic. 6 is a diagram illustrating output density characteristics with respect to image data when a patch formed on the intermediate transfer belt 1011 is read by the density detection sensor 1015. FIG. FIG. 5 is a diagram illustrating output density characteristics of light color toner in FIG. 4. FIG. 4 is a diagram illustrating a light toner input signal and a light toner output signal obtained by correcting the light toner input signal. FIG. 5 is a diagram illustrating output density characteristics of light color toner in FIG. 4. FIG. 5 is a diagram illustrating an input signal of dark toner and an output signal of dark toner obtained by correcting the dark toner input signal. It is a figure which shows the density characteristic with respect to the image data which showed the density | concentration detection correction area | region at the time of simple image density correction mode. 3 is a flowchart illustrating a procedure of image density correction processing by a control circuit 1101 in FIG. 2. 6 is a flowchart showing a processing procedure when a condition for whether or not a density deviation amount with respect to a preset image density ideal table exceeds a predetermined amount A as a condition for switching between the full image density correction mode and the simple image density correction mode. is there. It is a flowchart which shows the process sequence in the case of setting as a condition whether the environmental change value inside an apparatus exceeded the preset value as conditions for switching between full image density correction mode and simple image density correction mode. 10 is a flowchart showing a processing procedure when a condition for determining whether or not the number of image forming operations (number of prints) exceeds a threshold value C as a condition for switching between the full image density correction mode and the simple image density correction mode.

Explanation of symbols

1000 Image forming apparatus 1001 Photosensitive drum 1004 Laser unit 1005 Development rotary 1006a to f Developer 1011 Intermediate transfer belt 1015 Density detection sensor 1101 Controller 1102 Memory 1103 Environment sensor P Paper

Claims (6)

An image forming apparatus that visualizes an electrostatic latent image formed on an image carrier as a developer image using a light color developer and a dark color developer of the same hue,
The image density correction is performed for both the first density region of the image developed by the light color developer and the second density region of the image developed by the light color developer and the dark color developer of the same hue . 1 image density correction means;
A part of the area of the region made of the first doped region and the second doped region, the field with respect to a predetermined region including a boundary between the first doped region and the second doped region A second image density correction means for performing image density correction;
And a control means for controlling the image density correction by switching between the first image density correction means and the second image density correction means in accordance with a predetermined condition set in advance. Image forming apparatus. A density detection pattern forming means for forming a developer image as a density detection pattern; and a density detection means for detecting the density of the developer image formed by the density detection pattern formation means,
The control means includes the first image density correction means and the first image density correction means depending on whether or not the density deviation amount between the density value detected by the density detection means and the ideal density value exceeds a preset deviation amount. 2. The image forming apparatus according to claim 1, wherein the second image density correcting unit is switched. A counting means for counting the number of image forming operations;
The control unit includes the first image density correction unit and the second image density correction unit depending on whether the number of image forming operations counted by the counting unit exceeds a predetermined number set in advance. The image forming apparatus according to claim 1, wherein the image forming apparatus is switched. An image density correction method for an image forming apparatus that visualizes an electrostatic latent image formed on an image carrier as a developer image using a light color developer and a dark color developer of the same hue,
A mode switching step of switching between the first image density correction mode and the second image density correction mode according to a predetermined condition set in advance;
The first image density correction mode includes a first density area of an image developed with a light color developer and a second density area of an image developed with a light color developer and a dark color developer of the same hue. It is a mode that performs image density correction over both ,
The second image density correction mode is a partial area of the first density area and the second density area, and includes the first density area and the second density area. image density correction wherein the by for a given region including the boundary is a mode in which images density correction. The image forming apparatus includes: a density detection pattern forming unit that forms a developer image as a density detection pattern; and a density detection unit that detects the density of the developer image formed by the density detection pattern formation unit. Have
In the mode switching step, the first image density correction mode and the first image density correction mode depend on whether or not the density deviation amount between the density value detected by the density detection means and the ideal density value exceeds a preset deviation amount. 5. The image density correction method according to claim 4, wherein the second image density correction mode is switched. The image forming apparatus includes a counting unit that counts the number of image forming operations.
In the mode switching step, the first image density correction mode and the second image density correction mode are set according to whether or not the number of image forming operations counted by the counting means exceeds a predetermined number set in advance. 5. The image density correction method according to claim 4, wherein:

Images