JP5220174B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus having a colorimetric function.

  Image quality (hereinafter referred to as image quality) of the image forming apparatus includes graininess, in-plane uniformity, character quality, color reproducibility (including color stability), and the like. In today's widespread use of multicolor image forming apparatuses, the most important image quality is sometimes referred to as color reproducibility.

  Humans have a memory of expected colors (especially human skin, blue sky, metal, etc.) based on experience, and feel uncomfortable when the tolerance is exceeded. These colors are called memory colors, and their reproducibility is often asked when outputting photographs.

  Not only for photographic images but also for document images, color reproducibility (stable) for image forming devices, such as office user groups who feel uncomfortable with the color difference from the monitor, and graphic arts user groups who pursue color reproducibility of CG images. (Including sex) is increasing.

  Therefore, an image forming apparatus that reads a measurement image (patch image) formed on a recording sheet by a color sensor provided in the conveyance path of the recording sheet has been proposed in order to satisfy the user's color reproducibility requirement ( For example, see Patent Document 1).

  This image forming apparatus forms a colorimetric image on recording paper with toner, and applies feedback to process conditions such as exposure amount and development bias based on the result of reading the colorimetric image by a color sensor. It is possible to reproduce the density, gradation, and color tone.

JP 2004-086013 A

However, in the invention of Patent Document 1, since a color sensor is arranged in the conveyance path in the vicinity of the fixing device, a phenomenon called “thermochromism” in which the color of the patch image to be measured changes with temperature becomes a problem. . This is a phenomenon caused by a change in the molecular structure forming a color material such as toner or ink due to “heat”.

  Here, in order to measure the color of the patch image inside the image forming apparatus, it is necessary that the color mixture is completed after the color material is placed on the recording paper. In an image forming apparatus that uses ink as a color material, it is necessary to perform color measurement after drying by heating with a drying device. In an image forming apparatus using toner as a color material, it is necessary to measure the color after the toner is heated and melted and mixed by a fixing device. Therefore, the color sensor needs to be disposed downstream of the drying device and the fixing device in the recording paper conveyance direction.

  On the other hand, in order to make the image forming apparatus compact, the length of the conveyance path from the drying device or the fixing device to the color sensor needs to be kept to the minimum necessary. Therefore, the recording paper and the color material heated by the drying device or the fixing device are conveyed to the color sensor without being cooled to room temperature. Further, the temperature of the recording paper becomes higher than the normal temperature also due to the temperature rise of the members inside the image forming apparatus such as the recording paper conveyance guide and the atmosphere inside.

As described above, in an image forming apparatus including a color sensor therein, a color measurement result different from a color under a normal environment (a room temperature environment) may be obtained under the influence of thermochromism.

SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that can reduce color variation due to the effect of thermochromism and accurately detect the color of a patch image.

To achieve the above object, an image forming apparatus according to the present invention includes an image forming means for forming a measurement image on a recording sheet, a fixing unit for fixing on the recording paper by heating the measurement image, the recording A measuring unit that is provided downstream of the fixing unit in the paper conveyance direction and measures the color of the measurement image fixed on the recording paper; and a setting unit for setting the paper type of the recording paper; based on the setting contents of the setting unit, so as to reduce the effect of thermochromism, and a control means for the recording sheet to control the time until the measure by the measurement means after passing through the fixing means It is characterized by having.

According to the image forming apparatus of the present invention, it is possible to reduce color variation due to the influence of thermochromism and to accurately detect the color of the measurement image.

2 is a cross-sectional view showing the structure of the image forming apparatus 100. FIG. 2 is a diagram illustrating a structure of a color sensor 200. FIG. 1 is a block diagram showing a system configuration of an image forming apparatus 100. FIG. 2 is a diagram illustrating a control block of the image forming apparatus 100. FIG. It is a figure which shows the tendency of the color change for every coloring material. 3 is a flowchart showing the operation of the image forming apparatus 100. It is a flowchart which shows multi-order color correction processing. It is a figure explaining a recording paper setting screen.

(Image forming device)
In this embodiment, a solution to the above problem will be described using an electrophotographic laser beam printer. Here, as an example, an electrophotographic system is adopted as an image forming system. However, the present invention can also be applied to an ink jet method and a sublimation method. This is because the present invention is effective in an image forming apparatus in which the thermochromism phenomenon that the color of the measurement object changes with temperature can occur. In the ink jet system, an image forming unit that forms an image on recording paper by discharging ink and a fixing unit (drying unit) that dries the ink are used.

  FIG. 1 is a cross-sectional view illustrating the structure of the image forming apparatus 100. The image forming apparatus 100 includes a housing 101. The casing 101 is provided with various mechanisms for configuring the engine unit and a control board storage unit 104. The control board storage unit 104 stores an engine control unit 102 that performs control related to each printing process process (for example, a paper feed process) by each mechanism, and a printer controller 103.

  As shown in FIG. 1, the engine unit is provided with four stations 120, 121, 122, and 124 corresponding to YMCK. Stations 120, 121, 122, and 124 are image forming units that transfer toner onto the recording paper 110 to form an image. Here, YMCK is an abbreviation for yellow, magenta, cyan, and black. Each station is composed of almost common parts. The photosensitive drum 105 is a kind of image carrier and is charged to a uniform surface potential by a primary charger 111. A latent image is formed on the photosensitive drum 105 by the laser light output from the laser 108. The developing device 112 develops the latent image using a color material (toner) to form a toner image. The toner image (visible image) is transferred onto the intermediate transfer member 106. The visible image formed on the intermediate transfer member 106 is transferred to the recording paper 110 conveyed from the storage 113 by the transfer roller 114.

  The fixing processing mechanism of this embodiment includes a first fixing device 150 and a second fixing device 160 that heat and press the toner image transferred to the recording paper 110 and fix the toner image on the recording paper 110. The first fixing device 150 includes a fixing roller 151 for applying heat to the recording paper 110, a pressure belt 152 for pressing the recording paper 110 against the fixing roller 151, and a first post-fixing sensor for detecting completion of fixing. 153. These rollers are hollow rollers and each have a heater inside.

  The second fixing device 160 is arranged downstream of the first fixing device 150 in the conveyance direction of the recording paper 110. The second fixing device 160 imparts gloss (gloss) to the toner image on the recording paper 110 fixed by the first fixing device 150 or secures the fixing property. Similar to the first fixing device 150, the second fixing device 160 also has a fixing roller 161, a pressure roller 162, and a second post-fixing sensor 163. Depending on the type of recording paper 110, it is not necessary to pass through the second fixing device 160. In this case, the recording paper 110 passes through the transport path 130 without going through the second fixing device 160 for the purpose of reducing energy consumption.

  For example, when the setting is made to add a lot of gloss to the image on the recording paper 110, or when the recording paper 110 requires a large amount of heat for fixing like a thick paper, it passes through the first fixing device 150. The recording paper 110 is also conveyed to the second fixing device 160. On the other hand, when the recording paper 110 is plain paper or thin paper and the setting for adding a lot of gloss is not made, the recording paper 110 is transported through a transport path 130 that bypasses the second fixing device 160. Whether the recording paper 110 is conveyed to the second fixing device 160 or whether the recording paper 110 is conveyed bypassing the second fixing device 160 is controlled by switching the flapper 131.

  The conveyance path switching flapper 132 is a guide member that guides the recording paper 110 to the discharge path 135 or guides the recording paper 110 to the discharge path 139 to the outside. The leading edge of the recording paper 110 guided to the discharge path 135 passes through the reversal sensor 137 and is conveyed to the reversing unit 136. When the reverse sensor 137 detects the trailing edge of the recording paper 110, the conveyance direction of the recording paper 110 is switched. The transport path switching flapper 133 is a guide member that guides the recording paper 110 to the transport path 138 for forming a double-sided image or guides the recording paper 110 to the discharge path 135.

  A color sensor 200 that detects a patch image on the recording paper 110 is disposed in the discharge path 135. Four color sensors 200 are arranged side by side in a direction orthogonal to the conveyance direction of the recording paper 110, and can detect four rows of patch images. When color detection is instructed by an instruction from the operation unit 180, the engine control unit 102 executes density adjustment, gradation adjustment, multi-order color adjustment, and the like.

  The conveyance path switching flapper 134 is a guide member that guides the recording paper 110 to the discharge path 139 to the outside. The recording paper 110 conveyed through the discharge path 139 is discharged outside the image forming apparatus 100.

(Color sensor)
FIG. 2 is a diagram illustrating the structure of the color sensor 200. Inside the color sensor 200, a white LED 201, a diffraction grating 202, a line sensor 203, a calculation unit 204, and a memory 205 are provided. The white LED 201 is a light emitting element that irradiates the patch image 220 (measurement image) on the recording paper 110 with light. The diffraction grating 202 separates the light reflected from the patch image 220 for each wavelength. The line sensor 203 is a light detection element that includes n light receiving elements that detect light decomposed for each wavelength by the diffraction grating 202. The calculation unit 204 performs various calculations from the light intensity value of each pixel detected by the line sensor 203.

  The memory 205 stores various data used by the calculation unit 204. The calculation unit 204 includes, for example, a spectral calculation unit that performs a spectral calculation from a light intensity value, a Lab calculation unit that calculates a Lab value, and the like. Further, a lens 206 for condensing the light emitted from the white LED 201 onto the patch image 220 on the recording paper 110 or condensing the light reflected from the patch image 220 onto the diffraction grating 202 may be further provided. .

(Profile)
The image forming apparatus 100 creates a profile from the detection result of the patch image, converts the input image using the profile, and forms an output image. Here, an ICC profile accepted in the market in recent years is used as a profile for realizing excellent color reproducibility. However, the present invention is not an invention that can be applied only to an ICC profile. The present invention can also be applied to CRD (Color Rendering Dictionary) adopted from Level 2 of PostScript proposed by Adobe, or a color separation table in Photoshop.

  When replacing parts by a customer engineer, before a job that requires color matching accuracy, or when you want to know the color of the final output at the design concept stage, the user operates the operation unit 180 to perform color Instructs the profile creation process.

  The profile creation process is performed in the printer controller 103 shown in the block diagram of FIG. The printer controller 103 has a CPU, and reads a program for executing a flowchart described later from the storage unit 350 and executes it. In FIG. 3, the inside of the printer controller 103 is represented by blocks in order to make the processing performed by the printer controller 103 easier to understand.

  When the operation unit 180 receives a profile creation instruction, the profile creation unit 301 outputs the CMYK color chart 210, which is an ISO12642 test form, to the engine control unit 102 without passing through the profile. The profile creation unit 301 sends a color measurement instruction to the color sensor control unit 302. The engine control unit 102 controls the image forming apparatus 100 to execute processes such as charging, exposure, development, transfer, and fixing. As a result, an ISO 12642 test form is formed on the recording paper 110. The color sensor control unit 302 controls the color sensor 200 to measure the color of the ISO12642 test form. The color sensor 200 outputs spectral reflectance data, which is a color measurement result, to the Lab calculation unit 303 of the printer controller 103. The Lab calculation unit 303 converts the spectral reflectance data into L * a * b * data and outputs it to the profile creation unit 301. Note that the Lab calculation unit 303 may convert the spectral reflectance data into the CIE 1931XYZ color system that is a color space signal independent of the device.

  The profile creation unit 301 creates an output ICC profile from the relationship between the CMYK color signal output to the engine control unit 102 and the L * a * b * data input from the Lab calculation unit 303. The profile creation unit 301 stores the created output ICC profile instead of the output ICC profile stored in the output ICC profile storage unit 305.

  The ISO12642 test form includes patches of CMYK color signals that cover a color reproduction range that can be output by a general copying machine. Therefore, the profile creation unit 301 creates a color conversion table from the relationship between each color signal value and the measured L * a * b * value. That is, a conversion table of CMYK → Lab is created. Based on this conversion table, an inverse conversion table is created.

  Upon receiving a profile creation command from the host computer via the I / F 308, the profile creation unit 301 outputs the created output ICC profile to the host computer via the I / F 308. The host computer can execute color conversion corresponding to the ICC profile with an application program.

(Color conversion processing)
In color conversion in normal color output, an image signal input assuming an RGB signal value input from the scanner unit via the I / F 308 or a standard print CMYK signal value such as Japan Color is an input for external input. It is sent to the ICC profile storage unit 307. The input ICC profile storage unit 307 performs RGB → L * a * b * or CMYK → L * a * b * conversion according to the image signal input from the I / F 308. The input ICC profile stored in the input ICC profile storage unit 307 includes a plurality of LUTs (lookup tables).

  These LUTs are, for example, a one-dimensional LUT that controls the gamma of the input signal, a multi-order color LUT called direct mapping, and a one-dimensional LUT that controls the gamma of the generated conversion data. The input image signal is converted from device-dependent color space to device-independent L * a * b * data using these LUTs.

L * a * b * seat converted image signals to the target is input to the CMM 306. CMM is an abbreviation for color management module. The CMM 306 performs various color conversions. For example, the CMM 306 executes GAMUT conversion for mapping a mismatch between a reading color space such as a scanner unit as an input device and an output color reproduction range of the image forming apparatus 100 as an output device. In addition, the CMM 306 performs color conversion that adjusts a mismatch between a light source type at the time of input and a light source type when observing an output (also referred to as a color temperature setting mismatch).

  In this way, the CMM 306 converts the L * a * b * data into L ′ * a ′ * b ′ * data and outputs the data to the output ICC profile storage unit 305. A profile created by colorimetry is stored in the output ICC profile storage unit 305. Therefore, the output ICC profile storage unit 305 performs color conversion on the L ′ * a ′ * b ′ * data using the newly created ICC profile, converts the data into CMYK signals depending on the output device, and outputs the CMYK signal to the engine control unit 102. To do.

  In FIG. 3, the CMM 306 is separated from the input ICC profile storage unit 307 and the output ICC profile storage unit 305. However, as shown in FIG. 4, the CMM 306 is a module that manages color management, and performs color conversion using an input profile (print ICC profile 501) and an output profile (printer ICC profile 502).

(Thermochromism color characteristics)
Next, thermochromism characteristics for each color will be described. When the molecular structure forming the color material such as toner or ink is changed by heat, the light reflection / absorption characteristic is changed to change the color . As a result of experimentation and verification, it was found that the tendency of color change differs for each color material as shown in FIG. In this figure, the horizontal axis indicates the temperature of the patch image, and the vertical axis indicates the color change ΔE with 15 ° C. as a reference.

  ΔE can be expressed by the following three-dimensional distance between two points (L1, a1, b1) and (L2, a2, b2) in the L * a * b * color space defined by CIE. .

In FIG. 5, C: cyan 100%, M: magenta 100%, Y: yellow 100%, K: black 100%, W: paper white. As shown in this figure, as the temperature of the patch image increases, the color change of the patch image increases and an error occurs in the ICC profile to be created.

  As an index for color matching accuracy and color stability, in the color matching accuracy standard described in ISO 12647-7 (IT 8.7 / 4 (ISO 12642: 1617 patch) [4.2.2]), ΔE average is 4 .0. Further, reproducibility [4.2.3], which is a stability standard, defines that ΔE ≦ 1.5 of each patch. In order to satisfy this condition, the detection accuracy of the color sensor 200 is desirably ΔE ≦ 1.0.

  As shown in FIG. 5, in order to realize ΔE ≦ 1.0 for all colors of YMCK, it is necessary to dissipate the temperature of the patch image to 34 ° C. or lower. Therefore, in this embodiment, after the recording paper 110 heated by the fixing device is radiated, color measurement by the color sensor 200 is performed. Hereinafter, this control will be described in detail.

(Thermochromism technology)
FIG. 6 is a flowchart showing the operation of the image forming apparatus 100. This flowchart is executed by the printer controller 103. First, the printer controller 103 determines whether there is an image formation request from the operation unit 180 and whether there is an image formation request from the host computer via the I / F 308 (S601).

  If there is no image formation request, the printer controller 103 determines whether there is a multi-order color correction instruction from the operation unit 180 (S602). When there is a multi-order color correction instruction, multi-order color correction processing described later with reference to FIG. 7 is performed (S603). If there is no multi-order color correction instruction, the process returns to step S601.

  If it is determined in step S601 that there is an image formation request, the printer controller 103 feeds the recording paper 110 from the storage 113 (S604), and forms a toner image on the recording paper 110 (S605). Then, the printer controller 103 determines whether or not image formation for all pages has been completed (S606). If image formation for all pages has been completed, the process returns to step S601. If not, the process returns to step S604 to perform image formation for the next page.

  FIG. 7 is a flowchart showing multi-order color correction processing. This flowchart is executed by the printer controller 103. Note that the control of the image forming apparatus 100 is executed by the engine control unit 102 according to an instruction from the printer controller 103.

  First, the printer controller 103 feeds the recording paper 110 from the storage 113 (S701), and forms a patch image on the recording paper 110 (S702). Next, the printer controller 103 waits until the reverse sensor 137 detects the trailing edge of the recording paper 110 (S703).

When the reverse sensor 137 detects the trailing edge of the recording paper 110, the printer controller 103 controls the transport roller drive motor 311 to stop the transport of the recording paper 110 (S704). Next, the printer controller 103 waits until the time T elapses after the conveyance of the recording paper 110 is stopped (S705). Thus, while the recording paper 110 is temporarily stopped by the reversing unit 136, the patch image on the recording paper 110 is radiated. As a result, the color change due to the influence of thermochromism can be reduced. The time T is set according to the basis weight, surface property, and glossiness setting of the recording paper 110. Details of this point will be described later.

  When the stop time T elapses, the printer controller 103 controls the conveyance roller drive motor 311 to resume conveyance of the recording paper 110 (S706). At this time, the printer controller 103 conveys the recording sheet 110 toward the color sensor 200 with the conveying direction of the recording sheet 110 reversed.

  When the recording paper 110 reaches the color sensor 200, the printer controller 103 causes the color sensor 200 to measure a patch image (S707). Thereafter, the printer controller 103 creates an ICC profile by the above-described processing based on the color measurement result of the color sensor 200 (S708), and stores it in the output ICC profile storage unit 305 (S709).

(Setting of heat dissipation time)
The image forming apparatus 100 has seven fixing modes as shown in Table 1. The reason for preparing a plurality of modes in this way is that it is necessary to change the fixing conditions in accordance with the basis weight, surface property, and glossiness setting of the recording paper 110.

  FIG. 8 is a diagram for explaining a recording sheet setting screen. The screens shown in FIGS. 8A and 8B are displayed on a touch panel display provided in the operation unit 180. The user selects which cassette to set in the storage box 113 from the screen of FIG. For example, when the cassette 1 is selected, the screen is switched to the screen of FIG. 8B, and the basis weight, surface property, and glossiness of the recording paper 110 stored in the cassette 1 can be set.

  It is necessary to change the amount of heat necessary for fixing according to the basis weight, surface property, and glossiness setting of the recording paper 110. This is because when the toner image formed on the recording paper 110 is heat-fixed, the amount of heat taken by the recording paper 110 differs according to the basis weight of the recording paper 110. Further, when a large amount of heat is applied to a paper having a rough surface such as recycled paper, this is to cope with a phenomenon in which the toner penetrates into the fiber of the paper and the quality deteriorates. Furthermore, it is necessary to prepare a plurality of fixing modes in order to meet the user's demand for gloss level.

  Table 2 shows the setting of the fixing mode when the recording paper 110 is recycled paper, Table 3 shows the setting when the recording paper 110 is high-quality paper, and Table 4 shows the setting of the fixing mode when the recording paper 110 is coated paper. The engine control unit 102 applies the first fixing heater 312 provided in the first fixing device 150 and the second fixing device 160 according to the basis weight, surface property, and glossiness set by the operation unit 180. The second fixing heater 313 provided is controlled.

As shown in Table 3, when the glossiness is changed from standard to −1, for example, on fine paper and basis weight 80 g / m ² , the temperature of the first fixing device 150 is changed from 180 ° C. to 165 ° C. Become. Further, for example, when a glossy of +1 is selected on fine paper and a basis weight of 80 g / m ² , not only the first fixing device 150 but also the second fixing device 160 is set to be used.

  In this way, when the fixing conditions are different, the temperature of the recording paper 110 when the color sensor 200 performs color measurement is different. Therefore, it is necessary to set the standby time T when the recording paper 110 is stopped and dissipated by the reversing unit 136 in step S705 of FIG. 7 according to the settings of the basis weight, surface property, and glossiness.

  In determining the waiting time T for heat dissipation, it is necessary to consider (1) the distance from the last fixing unit to the reversing unit 136, (2) the fixing temperature, and (3) the heat dissipation characteristics of the recording paper 110 itself. There is.

  (1) The distance from the second fixing device 160 to the reversing unit 136 is shorter than the distance from the first fixing device 150 to the reversing unit 136. For this reason, until the recording paper 110 that passes through both the first fixing device 150 and the second fixing device 160 reaches the reversing unit 136 than the recording paper 110 that passes through only the first fixing device 150. Therefore, the waiting time T in the reversing unit 136 is increased.

  (2) The higher the fixing temperature, the more heat the recording paper 110 holds. Therefore, it is necessary to lengthen the standby time T in the reversing unit 136 as the fixing temperature increases.

  (3) The heat dissipation characteristics of the recording paper 110 itself include a characteristic that heat is easily released in the order of recycled paper, high-quality paper, and coated paper. In addition, the smaller the basis weight of the recording paper 110, the easier it is to dissipate heat.

  In consideration of the above (1) to (3), the present applicant conducted an experiment using the image forming apparatus 100 to obtain an appropriate waiting time T. Table 5 shows the waiting time T in the reversing unit 136 when the recording paper 110 is recycled paper, Table 6 shows when the recording paper 110 is high quality paper, and Table 7 shows when the recording paper 110 is coated paper.

  As shown in Tables 5 to 7, the waiting time T is changed according to the basis weight, surface property, and glossiness of the recording paper 110, and the color measurement start time by the color sensor 200 is changed. As a result, the temperature of the patch image can be radiated to 34 ° C. or lower before the start of color measurement by the color sensor 200, and ΔE ≦ 1.0 can be achieved.

As described above, in the present embodiment, the time from when the recording paper 110 passes through the fixing device until the color sensor 200 performs color measurement is controlled based on the setting type of the recording paper 110. I did it. As a result, in this embodiment, it is possible to reduce the color variation due to the effect of thermochromism and detect the color of the patch image with high accuracy.

  In this embodiment, the waiting time T of the recording paper 110 in the reversing unit 136 is optimized. However, as long as the time until the recording paper 110 passes through the fixing device and reaches the color sensor 200 can be adjusted. The configuration is not limited to this. For example, the time until the recording paper 110 reaches the color sensor 200 after passing through the fixing device may be adjusted by decelerating the recording paper 110 and controlling the deceleration time.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 102 Engine control part (control means)
103 Printer controller (control means)
110 Recording paper 150 First fixing device (fixing means)
160 Second fixing device (fixing means)
180 operation unit (setting means)
200 Color sensor (colorimetric means)

Claims (9)

Image forming means for forming an image for measurement on recording paper ;
Fixing means for heating and fixing the measurement image to the recording paper;
A measuring unit that is provided downstream of the fixing unit in the conveyance direction of the recording paper and measures the color of the measurement image fixed on the recording sheet;
Setting means for setting the paper type of the recording paper;
Based on the setting contents of the setting unit, so as to reduce the effect of thermochromism, and a control means for the recording sheet to control the time until the measure by the measurement means after passing through the fixing means ,
An image forming apparatus comprising: Wherein, the recording paper is temporarily stopped and the recording paper to measure by is performed the measurement means after passing through the fixing means, said recording sheet by controlling the stop time the image forming apparatus according to claim 1, wherein the controlling the time until the measure by the measurement means after passing through the fixing means. Said control means, said recording paper slows down the recording paper to reach the measurement means after passing through the fixing unit, the recording paper by controlling the deceleration time is passed through the fixing means the image forming apparatus according to claim 1, wherein the controlling the time until the measure by the measurement means from. Wherein, claims wherein the higher fixing temperature by a high fixing means, the recording paper is equal to or up to the amount of time Kusuru is measure by the measurement means after passing through the fixing means The image forming apparatus according to 1. The fixing unit includes a first fixing device and a second fixing device provided downstream of the first fixing device,
The control unit passes both the first fixing device and the second fixing device after passing the recording paper through the first fixing device, rather than not passing the recording paper through the second fixing device. who If the recording paper is an image forming apparatus according to claim 1, wherein the up to a time length Kusuru is measure by the measurement means after passing through the fixing means. The control means, as the rough surface of the recording paper that has been set by said setting means, said recording sheet to reduce the time until it is measurement by said measurement means after passing through the fixing means The image forming apparatus according to claim 1. It said control means, wherein the greater the amount of gloss to be imparted to the measurement image, the recording paper is the time until the measurement that the length Kusuru by said measurement means after passing through the fixing means The image forming apparatus according to claim 1. The image forming means is means for transferring the toner onto the recording paper to form the image;
The image forming apparatus according to claim 1, wherein the fixing unit is a unit that heats and fixes the toner to the recording paper. The image forming means is means for discharging the ink to form the image on the recording paper;
The image forming apparatus according to claim 1, wherein the fixing unit is a drying unit that dries the ink.

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