JP6537022B2 - Image forming apparatus, image forming method, and image forming program - Google Patents

Description

  The present invention relates to an image forming apparatus, an image forming method, and an image forming program.

  In the electrophotographic image forming apparatus, the amount of consumption of toner in each printing is generally calculated based on image data. The toner consumption can be calculated based on the correlation between the toner consumption and the number of dots in the toner image. The calculation result of the toner consumption amount is used, for example, to control toner replenishment to the developing device. As for the calculation method of toner consumption, since the toner consumption differs depending on whether it is character or thin line even if it is data of the same number of dots, the technology to determine the attribute of the image data and improve the accuracy Have also been proposed (Patent Documents 1 and 2).

JP, 2011-048301, A JP, 2015-108772, A

  However, the inventor of the present invention has newly found that the amount of consumed toner fluctuates due to thinning out due to the limitation of the exposure pulse width and calibration of thinning out of the dots themselves. This new problem is that, in the electrophotographic process, toner is superimposed on the drum in a solid area including characters and thin lines, and surplus toner adheres to the drum. Therefore, dot thinning (thinning by limiting the exposure pulse width and thinning of the dots themselves In particular, the present invention has been found focusing on a technique for suppressing the adhesion of excess toner while maintaining the image quality.

  The present invention has been made in view of such a situation, and provides a technique for improving the measurement accuracy of toner consumption in image formation in which dots are thinned while maintaining the image quality of characters and line drawings. To aim.

  The present invention provides an image forming apparatus that forms an image based on image data. The image forming apparatus includes a photosensitive body, an exposure unit that exposes the photosensitive body based on the image data to form an electrostatic latent image, and causes toner to adhere to the photosensitive body based on the electrostatic latent image. An image forming unit having a developing unit, a linear image detecting unit for detecting a specific image based on the image data, and a correspondence between the number of dots on the photosensitive member and the toner consumption amount for the specific image A storage unit for storing a first toner amount table, and a second toner amount table indicating a correspondence between the number of dots on the photosensitive member and the toner consumption amount for images other than the specific image; The toner consumption amount to calculate the toner consumption amount using the first toner amount table for images and calculating the toner consumption amount using the second toner amount table for images other than the specific image Calculation And a plurality of patterns formed by the specific image and having a stepwise difference in thinning rate of the electrostatic latent image are formed in the image forming portion, and determined based on the densities of the plurality of patterns. And an exposure control unit for exposing the exposure unit with a thinning amount, wherein the exposure control portion limits the thinning amount of the electrostatic latent image within a preset range, and the thinning amount reaches an upper limit. The first toner amount table is generated using the density of the pattern having the largest thinning amount among the plurality of patterns and the second toner amount table.

  The present invention provides an image forming method for forming an image based on image data, the image forming method comprising: a photosensitive body; and an exposure for exposing the photosensitive body based on the image data to form an electrostatic latent image Forming an image forming process using an image forming unit and a developing unit for depositing toner on the photosensitive member based on the electrostatic latent image; detecting a line image detecting a specific image based on the image data; The first toner amount table showing the correspondence between the number of dots on the photosensitive member and the amount of consumed toner for the image, and the correspondence between the number of dots on the photosensitive member and the amount of consumed toner for images other than the specific image A storage step of storing a second toner amount table indicating a relationship; and calculating the toner consumption amount using the first toner amount table for the specific image, and calculating an image other than the specific image And a plurality of toner consumption calculation steps for calculating the toner consumption using the second toner amount table, and a plurality of images formed by the specific image, wherein the thinning rate of the electrostatic latent image is stepwise different. An exposure control step of forming a pattern in the image forming step and exposing the exposed portion by a thinning amount determined based on the density of the plurality of patterns, the exposure control step including: The thinning amount is limited within a preset range, and when the thinning amount reaches the upper limit, the density of the pattern having the largest thinning amount among the plurality of patterns is used and the second toner amount table is used. The method includes the step of generating the first toner amount table.

  The present invention provides an image forming program for controlling an image forming apparatus that forms an image based on image data. The image forming apparatus includes a photosensitive body, an exposure unit that exposes the photosensitive body based on the image data to form an electrostatic latent image, and causes toner to adhere to the photosensitive body based on the electrostatic latent image. A linear image detection unit having a developing unit and an image forming unit, wherein the image forming program detects a specific image based on the image data; the number of dots on the photosensitive member and the toner consumption amount for the specific image Storing a first toner amount table indicating a correspondence relationship with the second toner amount table indicating a correspondence relationship between the number of dots on the photosensitive member and toner consumption amount for images other than the specific image The toner consumption amount is calculated using the first toner amount table for the specific image, and the toner consumption amount is calculated using the second toner amount table for images other than the specific image. Forming a plurality of patterns, which are formed by the toner consumption amount calculation unit to be output and the specific image and in which the thinning rate of the electrostatic latent image differs stepwise, in the image forming unit; The image forming apparatus is caused to function as an exposure control unit that exposes the exposure unit with a thinning amount determined based on a density, and the exposure control unit sets the thinning amount of the electrostatic latent image within a preset range. When the thinning amount reaches the upper limit, the first toner amount table is generated using the density of the pattern having the largest thinning amount among the plurality of patterns and the second toner amount table. .

  According to the present invention, there is provided a technique for improving the measurement accuracy of the toner consumption amount in image formation in which dots are thinned while maintaining the image quality of characters and line drawings.

FIG. 1 is a schematic configuration view showing an entire configuration of an image forming apparatus 1 according to an embodiment of the present invention. FIG. 1 is a cross-sectional view showing an entire configuration of an image forming apparatus 1 according to an embodiment. 5 is a flowchart showing the contents of an exposure calibration processing procedure of the image forming apparatus 1 according to an embodiment. FIG. 7 is an explanatory view showing patches P1 to P4 formed on the intermediate transfer belt 27a in the exposure calibration process according to an embodiment. It is a graph which shows the relationship between the exposure pulse width which concerns on one Embodiment, and the output value of a density sensor. It is a graph which shows the relation between the printing rate (thinning rate) of a thin line and the output value of the density sensor according to one embodiment. 5 is a graph showing the relationship between character gradation and toner consumption according to an embodiment. It is a graph which shows the relationship between the character gradation and correction coefficient which concern on one Embodiment. It is a graph which shows the relationship between the printing number between proofreading which concerns on one Embodiment, and the output value of a density sensor.

  Hereinafter, modes for carrying out the present invention (hereinafter, referred to as “embodiments”) will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a functional configuration of an image forming apparatus 1 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the overall configuration of the image forming apparatus 1 according to an embodiment of the present invention. The image forming apparatus 1 includes a control unit 10, an image forming unit 20, an operation display unit 30, a communication interface unit 40, a storage unit 50, a sheet feeding cassette 60, and a housing 70.

  The image forming unit 20 includes an image reading unit 21a, a color conversion processing unit 21b, a halftone processing unit 21c, a calibration density sensor 22, an exposure unit 23, developing units 24c to 24k, and charging units 25c to 25k. have. The image reading unit 21a reads an image from a document and generates image data. The color conversion processing unit 21 b performs color conversion of image data, which is RGB data, into CMYK. The halftone processing unit 21 c performs halftone processing to generate CMYK raster data. The calibration density sensor 22 is used to calibrate the exposure pulse width by the exposure unit 23.

  The control unit 10 includes a main storage unit such as a RAM and a ROM, and a control unit such as an MPU (Micro Processing Unit) and a CPU (Central Processing Unit). The control unit 10 also has a controller function related to interfaces such as various I / Os, USB (Universal Serial Bus), buses, and other hardware, and controls the entire image forming apparatus 1.

  The storage unit 50 is a storage device including a hard disk drive or a flash memory, which is a non-temporary recording medium, and stores control programs and data of processing executed by the control unit 10. In the present embodiment, the storage unit 50 further stores the calibration image data CD and the toner amount table TD.

  The calibration image data CD stores calibration image data CD for forming calibration patches P1 to P4 (also referred to as patterns, the details of which will be described later). The toner amount table TD is also referred to as a toner consumption amount table, and includes a table representing the relationship between the image data value and the toner consumption amount, and a correction coefficient. The toner amount table TD is used to calculate the consumed amount of toner. The toner amount table TD includes a first toner amount table (for example, LUT (Look Up Table)), a second toner amount table (for example, LUT), and a correction table (for example, LUT).

  The first toner amount table indicates the correspondence between the number of dots as a latent image and the amount of consumed toner for images of characters and thin lines. The second toner amount table indicates the correspondence between the number of dots as a latent image and the amount of consumed toner for images other than characters and thin lines. The correction table (for example, LUT) stores correction values when the first toner amount table is used in a state in which the exposure calibration can not control.

  The control unit 10 functions as a line image detection unit, and detects images of characters and thin lines based on image data. The control unit 10 calculates the toner consumption amount using the first toner amount table for the detected character and thin line images, and uses the second toner amount table for images other than the characters and thin lines. The amount is calculated and summed to calculate the toner consumption.

  The image forming apparatus 1 of the present embodiment is a tandem type color printer. In the image forming apparatus 1, photosensitive drums (image carriers) 26 m, 26 c, 26 y and 26 k are arranged in a line in a casing 70 corresponding to each color of magenta, cyan, yellow and black. Developing portions 24m, 24c, 24y and 24k are disposed adjacent to the photosensitive drums 26m, 26c, 26y and 26k, respectively.

  The laser beams Lm, Lc, Ly and Lk for respective colors are irradiated from the exposure unit 23 to the photosensitive drums 26m, 26c, 26y and 26k. By this irradiation, electrostatic latent images are formed on the photosensitive drums 26m, 26c, 26y and 26k. The developing units 24m, 24c, 24y and 24k adhere the toner to the electrostatic latent images formed on the surfaces of the photosensitive drums 26m, 26c, 26y and 26k while stirring the toner. Thus, the developing process is completed, and toner images of the respective colors are formed on the surfaces of the photosensitive drums 26m, 26c, 26y and 26k.

  The image forming apparatus 1 has an endless intermediate transfer belt 27a. The intermediate transfer belt 27a is stretched around a tension roller 27c, a drive roller 27b and a driven roller 27d. The intermediate transfer belt 27a is driven to circulate by the rotation of the drive roller 27b.

  For example, the black toner image on the photosensitive drum 26k is primarily transferred to the intermediate transfer belt 27a by holding the intermediate transfer belt 27a between the photosensitive drum 26k and the primary transfer roller 29k and driving the intermediate transfer belt 27a to circulate. Ru. The same applies to the three colors of cyan, yellow and black. A full-color toner image is formed on the surface of the intermediate transfer belt 27a by performing primary transfer so as to be superimposed on each other at a predetermined timing. Thereafter, the full-color toner image is secondarily transferred onto the printing paper P supplied from the paper feed cassette 60, and is fixed on the printing paper P in a known fixing process.

  FIG. 3 is a flowchart showing the contents of the exposure calibration processing procedure of the image forming apparatus 1 according to the embodiment. FIG. 4 is an explanatory view showing patches P1 to P4 formed on the intermediate transfer belt 27a in the exposure calibration process according to one embodiment. This calibration process is performed, for example, at the time of manufacture to suppress individual differences, or is performed at regular intervals to suppress aging. This calibration process may be further executed when requested by the user via the operation display unit 30.

  In step S10, the image forming apparatus 1 forms calibration patches P1 to P4 on the intermediate transfer belt 27a. The patches P1 to P4 are formed of, for example, black toner. The patches P1 to P4 are formed of dots to which any one of four preset exposure pulse width limitations is applied, and a black band area extending in the main scanning direction and an area formed of white pixels are mainly used. White bands extending in the scanning direction are alternately formed in the sub-scanning direction. The number of pixels in the sub scanning direction of the black band area and the white band area is preset for character and line drawing calibration.

  In step S20, the calibration density sensor 22 of the image forming apparatus 1 measures the densities of the four patches P1 to P4. The densities of the four patches P1 to P4 are measured based on the reflected light quantity of the light irradiated by the density sensor 22 for calibration while rotationally driving the intermediate transfer belt 27a. For the measured reflected light quantity, a target value is set in advance by an experiment or other method.

  FIG. 5 is a graph showing the relationship between the exposure pulse width and the output value of the density sensor according to an embodiment. In FIG. 5A, the horizontal axis is the exposure pulse width Ep, and the vertical axis is the output value (density value) of the density sensor 22 for calibration. The target value is an output value for forming dots without gaps as a solid. If the target value is exceeded, it means that the dots are redundantly attached in an overlapping manner.

  FIG. 5B shows four types of pulse width limit values set in the four patches P1 to P4. In the present embodiment, the four patches P1 to P4 are patches having solid regions (also referred to as black band regions) formed by exposure with different percentages of pulse widths of exposure. Specifically, patch P3 is formed of dots formed by 80% exposure in which the proportion of exposure pulse width Ep in the pixel passage period Wp, which is the time for one pixel to pass during main scanning, is 80%. Patch. The patches P1, P2, and P4 are dots formed by 40% exposure, 60% exposure, and 100% exposure, in which the proportion of the exposure pulse width Ep in the pixel passage period Wp is 40%, 60%, and 100%, respectively. It is a configured patch.

  In the example of FIG. 5A, the states of three cases C1 to C3 representing individual differences of the image forming apparatus 1 are shown. Case C1 is the case where the output value (that is, the concentration is high) is the largest among the three cases C1 to C3. In case C1, the target value is reached at point R1 between the 60% exposure and the 80% exposure. In case C2, similarly to case C1, the target value is reached at point R2 between the 60% exposure and the 80% exposure. In case C3, the target value is reached at point R3 between the 80% exposure and the 100% exposure.

  In step S30, the image forming apparatus 1 determines the exposure pulse width. In the present embodiment, the determination of the exposure pulse width is determined as the minimum exposure pulse width reaching the target value among the four types of pulse width limitations. Specifically, in cases C1 and C2, 80% exposure is determined as the exposure pulse width, and in case C3, 100% exposure is determined as the exposure pulse width. The control unit 10 functions as an exposure control unit, and causes the exposure unit 23 to perform exposure with the determined exposure pulse width.

  The pulse width limitation does not have to be determined to one of the four pulse width limitations, and may be determined by interpolation. Specifically, for example, the case C1 may be exposed at 65%, the case C2 may be exposed at 76%, and the case C3 may be exposed at 88%.

  In step S40, the control unit 10 determines whether control by exposure calibration is possible. That is, the control unit 10 determines whether control of the toner amount is possible in the exposure calibration process. The control of the toner amount is intended to control so that toner does not overlap and adhere to the drum excessively in a solid area including characters and thin lines. The first toner amount table is a table set on the assumption that it is used in a controllable state by exposure calibration.

  Control unit 10 advances the process to step S80 if the control is possible by exposure calibration (possible state), and advances the process to step S50 if the control is not possible by exposure calibration (non-controllable state). The case where the exposure calibration can not be controlled means that the patch density exceeds the target density even in the preset maximum thinning state (minimum exposure pulse width).

FIG. 6A is a graph showing the relationship between the printing rate (thinning rate) of a thin line and the output value of the density sensor according to one embodiment. The character gradation means the gradation of an image of a character or a thin line. In this example, the image forming apparatus 1 is in a state where the chargeability is reduced in a high temperature and high humidity environment.

  The printing rate (decimation rate) indicates the printing rate in a state in which the exposure pulse width is limited and the dots themselves are thinned out. In this example, it is shown that the output value of the density sensor is higher by the difference value D than the density of the target value when the printing rate is 40% (60% thinning rate).

  In this case, the control of the toner amount by the exposure calibration can not be controlled so that the toner is not superimposed on the image area of characters and thin lines and excessively attached to the drum. That is, this state means that toner is excessively attached to the drum and consumed. The control of the toner amount by the exposure calibration is previously limited as the thinning rate restriction so that the uniform restriction is within the range in which the image quality of characters and thin lines does not deteriorate.

  As described above, since the control of the toner amount by the exposure calibration is limited in advance to a range in which the image quality of the characters and thin lines does not deteriorate, an uncontrollable state may occur. On the other hand, in the uncontrollable state, the consumption amount of toner increases, and therefore, the prediction accuracy of the toner consumption amount is maintained by the following correction.

FIG. 6 (b) shows a formula for calculating the amount of consumed toner in consideration of the amount of toner adhering to the drum and consumed in excess. The equation (1) is a calculation equation for calculating the difference value D (see FIG. 6A) representing the difference between the lower limit (corresponding to the upper limit of the amount of thinning) of the density sensor output value and the target value. Expression (1) is a calculation expression for calculating the correction coefficient from the difference value D. The correction coefficient is calculated to be 1.1 times in this example.

  FIG. 7 shows the relationship between character gradation and toner consumption according to one embodiment. As can be seen from FIG. 7, according to the present inventor, it was found that the amount of toner adhering to the drum excessively increases in the region (75% to 100%) where the character gradation is high.

  The toner amount may be controlled also by thinning the dots themselves. In such a case, the uncontrollable state is a state in which the toner is excessively attached to the drum due to at least one of the limitation of the control of the toner amount by exposure calibration and the control of the toner amount by thinning of the dots themselves. Means. The thinning of dots has a broad meaning, and includes thinning of dots themselves as well as thinning due to exposure pulse width limitations.

  In step S50, the control unit 10 calculates a correction coefficient. The correction coefficient is a correction coefficient for compensating for the increase in consumption of toner caused by the adhesion of the excess toner to the photosensitive drum 26k, which is generated when an image representing a thin line is reproduced.

FIG. 8 is a graph showing the relationship between the character gradation and the correction coefficient according to an embodiment. The horizontal axis is character gradation, and the vertical axis is a correction coefficient . In this example, the correction coefficient changes linearly along the correction straight line L in the range of 1 to 1.1 times in the range of 75% of the character gradation to 100% of the developing portion. Specifically, when the character gradation is 85%, the correction coefficient is 1.04. The correction coefficient is 1 when the character gradation is 0% to 75%.

In step S60, the control unit 10 executes table creation processing. In the table creation process, the control unit 10 is a process for creating a correction table from the correction coefficient which linearly changes along the correction straight line L.

  In step S70, the control unit 10 performs correction using the first toner amount table and the correction table to create a first toner amount correction table. The first toner amount correction table is a table used to calculate the consumption amount of toner consumed for printing characters and thin lines in the uncontrollable state. The control unit 10 stores the first toner amount correction table in the storage unit 50.

  In step S80, the control unit 10 acquires calibration data. The calibration data includes a calibration value of exposure pulse width limitation, a first toner amount correction table (in the uncontrollable state), and data representing whether it is in the controllable state or the uncontrollable state. There is.

  FIG. 9 is a graph showing the relationship between the number of sheets printed during calibration and the output value of the density sensor according to one embodiment. If the calibration data includes data indicating that the control is in an uncontrollable state, the control unit 10 causes the image forming unit 20 to use a patch for monitoring the toner consumption amount between print images for every 100 sheets of the print medium, for example. As a result, a patch P1 (40% exposure with an upper limit of thinning amount) is formed on the intermediate transfer belt 27a.

The control unit 10 updates the difference value D every 100 sheets, and calculates the toner consumption amount using, for example, the correction coefficient based on the difference value D1 between 401 sheets and 500 sheets (or 351 sheets and 450 sheets). The toner consumption amount is calculated using the correction coefficient based on the difference value D2 between 501 sheets and 600 sheets (or 451 sheets and 550 sheets). Thus, the toner consumption can be accurately calculated in accordance with environmental changes such as changes in temperature and humidity.

  As described above, according to the image forming apparatus 1 according to the embodiment, the adjustment of the printing rate (thinning rate) is limited to maintain the image quality of characters and thin lines, and at the time of reproducing an image showing characters and thin lines. The toner consumption can be estimated in consideration of the consumption of the toner resulting from the adhesion of the generated excess toner to the photosensitive member. As a result, the display of the amount of remaining toner and the toner replenishment can be made appropriate.

  The present invention can be implemented not only in the above embodiment but also in the following modifications.

  Modification 1: In the above embodiment, the adjustment of the printing rate (thinning rate) of the image including at least one of the character and the line drawing is limited, but the adjustment to the printing rate (thinning rate) is not limited to the line image. It is also applicable to solid images and their outlines that affect The present invention is applicable to images in which the adjustment of the printing rate (decimation rate) is limited (such an image is called a specific image).

  Modified Example 2 In the above embodiment, a patch for calibration is formed on the intermediate transfer belt, and the density is measured by the calibration density sensor, but the method is not limited to such a method. Specifically, for example, a patch for calibration may be formed on a print medium, and measurement may be performed using an image reading unit.

  Modification 3: In the above embodiment, processing is performed on the area of the image of the thin line formed of black toner, but the invention is not limited to this, the area of the image of the thin line formed of toner of a plurality of colors The present invention may be applied to

Reference Signs List 1 image forming apparatus 10 control unit 20 image forming unit 21a image reading unit 21b color conversion processing unit 21c halftone processing unit 22 density sensor 23 for calibration exposure unit 24c to 24k development unit 25c to 25k charging unit 27a intermediate transfer belt 50 storage unit 60 paper cassette 70 case

Claims (5)

An image forming apparatus for forming an image based on image data, comprising:
An image comprising a photosensitive member, an exposure unit that exposes the photosensitive member based on the image data to form an electrostatic latent image, and a developing unit that adheres toner to the photosensitive member based on the electrostatic latent image The formation part,
A line image detection unit that detects a specific image based on the image data;
A first toner amount table indicating the correspondence between the number of dots on the photosensitive member and the amount of consumed toner for the specific image, and the number of dots on the photosensitive member and the amount of consumed toner for images other than the specific image A storage unit that stores a second toner amount table indicating a correspondence relationship between
The toner consumption amount is calculated using the first toner amount table for the specific image, and the toner consumption amount is calculated using the second toner amount table for images other than the specific image. A toner consumption calculation unit;
A plurality of patterns which are formed by the specific image and in which the thinning rate of the electrostatic latent image is stepwise different due to the limitation of the exposure pulse width are formed in the image forming portion, based on the density of the plurality of patterns. an exposure control unit for exposing the exposed portion at the thinning rate determined Te,
Equipped with
The exposure control unit limits within the ranges set pre SL between pulling rate in advance,
The toner consumption calculation unit, when the thinning rate reaches the upper limit, the for specific images of the plurality most the thinning rate is large pattern density and the first of the pattern toner amount table and the toner An image forming apparatus for calculating the toner consumption amount using a correction coefficient for compensating for an increase in consumption . The image forming apparatus according to claim 1,
The image forming unit includes an intermediate transfer belt for transferring a toner image from the photosensitive member, and a density sensor for measuring the density of the plurality of patterns formed on the intermediate transfer belt.
The exposure control unit, when forming an image on a print medium by the image forming unit, sets the thinning rate to an upper limit among the plurality of patterns among a plurality of toner images formed on the print medium. An image forming apparatus which forms a closest pattern and updates the second toner amount table based on the density of the pattern measured by the density sensor. An image forming apparatus according to claim 1 or 2, wherein
The image forming apparatus, wherein the specific image is an image including at least one of a character and a line drawing. An image forming method for forming an image based on image data, comprising:
A photosensitive member, an exposure unit that exposes the photosensitive member based on the image data to form an electrostatic latent image, and a developing unit that adheres toner to the photosensitive member based on the electrostatic latent image are used. An image forming process,
A line image detection step of detecting a specific image based on the image data;
A first toner amount table indicating the correspondence between the number of dots on the photosensitive member and the amount of consumed toner for the specific image, and the number of dots on the photosensitive member and the amount of consumed toner for images other than the specific image A storage step of storing a second toner amount table indicating a correspondence relationship of
The toner consumption amount is calculated using the first toner amount table for the specific image, and the toner consumption amount is calculated using the second toner amount table for images other than the specific image. Toner consumption calculation step;
A plurality of patterns which are formed by the specific image and in which the thinning rate of the electrostatic latent image differs stepwise due to the limitation of the exposure pulse width are formed in the image forming step, and based on the density of the plurality of patterns an exposure control step of exposing the exposed portion at the thinning rate determined Te,
Equipped with
The exposure control step limits the previous SL between pulling rate in advance in the set range,
The toner consumption calculation process, when the thinning rate reaches the upper limit, the for specific images of the plurality most the thinning rate is large pattern density and the first of the pattern toner amount table and the toner An image forming method including the step of calculating the toner consumption amount using a correction coefficient for compensating for an increase in consumption . An image forming program for controlling an image forming apparatus for forming an image based on image data, comprising:
The image forming apparatus includes a photosensitive body, an exposure unit that exposes the photosensitive body based on the image data to form an electrostatic latent image, and causes toner to adhere to the photosensitive body based on the electrostatic latent image. and an image forming unit and a developing unit,
The image forming program is
A line image detection unit that detects a specific image based on the image data;
A first toner amount table indicating the correspondence between the number of dots on the photosensitive member and the amount of consumed toner for the specific image, and the number of dots on the photosensitive member and the amount of consumed toner for images other than the specific image A storage unit that stores a second toner amount table indicating the correspondence relationship between
The toner consumption amount is calculated using the first toner amount table for the specific image, and the toner consumption amount is calculated using the second toner amount table for images other than the specific image. Forming a plurality of patterns formed by the toner consumption calculation unit, the specific image, and in which the thinning rate of the electrostatic latent image is stepwise different due to the limitation of the exposure pulse width in the image forming unit; to function the image forming apparatus as an exposure control unit for exposing the exposed portion at the thinning rate determined based on the concentration of a plurality of patterns,
The exposure control unit limits within the ranges set pre SL between pulling rate in advance,
The toner consumption calculation unit, when the thinning rate reaches the upper limit, the for specific images of the plurality most the thinning rate is large pattern density and the first of the pattern toner amount table and the toner An image forming program for calculating the toner consumption amount using a correction coefficient for compensating for an increase in consumption .