JP2013050612A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that ensures time when the amount of light from a light source is stable in an optical sensor without increasing time required for color shift correction, and prevents a decrease in productivity of the image forming apparatus caused by an operation of color shift correction.SOLUTION: A toner pattern is formed in such a way that width of a K toner patch is formed smaller than widths of color patches other than the K toner patch, and an interval between the K toner patch and a color patch adjacent to the K toner patch is larger than intervals between respective color patches.

Description

  The present invention relates to a technique for forming a color misregistration correction pattern in an image forming apparatus such as a copying machine, a printer, or a facsimile machine that forms a color image.

  2. Description of the Related Art Conventionally, image forming apparatuses such as copying machines, printers, and facsimiles that perform color image formation form a color image by superimposing a plurality of basic colors (for example, yellow, magenta, cyan, and black) by a tandem method. is there. In such an image forming apparatus, a color misregistration correction pattern is formed on an intermediate transfer body by a plurality of image forming units, and the intermediate transfer body or the color misregistration correction pattern is read by a reflective optical sensor to calculate a color misregistration amount. Color misregistration correction. As an optical sensor, for example, a sensor that detects regular reflection light and irregular reflection light with one light receiving unit has been proposed (see Patent Document 1).

JP 2001-1000048 A1

  In the case of detecting a color misregistration correction pattern using the above-described conventional optical sensor that detects regular reflection light and irregular reflection light by a single light receiving unit, in order to increase the detection accuracy of the color misregistration correction pattern, It is necessary to secure time until the light quantity of the light source is stabilized. As a result, the time required for color misregistration correction increases. For this reason, when color misregistration correction is performed at a high frequency such as performing color misregistration correction every sheet, the time required for color misregistration correction increases, which may reduce the productivity of the image forming apparatus. .

  In view of the above problems, the present invention can secure a time for stabilizing the light amount of the light source in the optical sensor without increasing the time required for color misregistration correction, and decrease the productivity of the image forming apparatus due to the color misregistration correction operation. An object of the present invention is to provide an image forming apparatus capable of preventing the above-described problem.

  In order to achieve the above object, an image forming apparatus of the present invention is an image forming apparatus having a plurality of image forming means, wherein the plurality of toner patterns are formed on the intermediate transfer member so as to form a toner pattern composed of a plurality of toner patches. A control unit that controls the image forming unit, two light sources, and one light receiving element are provided, and the light emitted from the two light sources is switched to irradiate the intermediate transfer member with light, and the reflected light is received by the light receiving element. Thus, a detection unit that detects a toner pattern formed on the intermediate transfer member, a color shift calculation unit that calculates a color shift amount based on a signal output from the detection unit, and a color shift calculation unit. A color misregistration correction unit that corrects the timing of writing toner images by the plurality of image forming units, and a switching unit that switches light emission of the light source. The toner pattern is formed such that the width of the K toner patch is narrower than the width of the color patch other than the K toner patch, and the interval between the K toner patch and the adjacent color patch is wider than the interval between the color patches. It is formed in this.

  According to the present invention, it is possible to secure a time during which the light amount of the light source in the optical sensor is stabilized without increasing the time required for color misregistration correction, and to prevent a decrease in productivity of the image forming apparatus due to the color misregistration correction operation. be able to.

FIG. 2 is a diagram for explaining a schematic configuration of an image forming unit in the image forming apparatus according to the embodiment of the present invention. It is a figure which shows schematic structure of the pattern detection sensor in FIG. FIG. 2 is a block diagram illustrating a schematic configuration of a color misregistration correction unit in the image forming apparatus of FIG. 1. (A) The figure which shows the state of the light receiving element of a pattern detection sensor, and the color misregistration correction pattern on an intermediate transfer belt, (b) The relationship between the state shown to Fig.4 (a) and the waveform of the output signal of a light receiving element is shown. FIG. (A) The figure which shows the waveform of the sensor output at the time of the color misregistration correction pattern reading in each of the regular reflection light and the irregular reflection light in the state where the gloss of the intermediate transfer belt is high, (b) The state where the gloss of the intermediate transfer belt is low It is a figure which shows the waveform of the sensor output at the time of the color misregistration correction pattern reading in each of the regular reflection light and irregular reflection light in FIG. (A) The figure which shows the relationship between the analog output signal of the light receiving element by irregular reflection light, and the digital signal which binarized the said analog output signal with the 2nd threshold voltage, (b) The analog output signal of the light receiving element by regular reflection light FIG. 5 is a diagram illustrating a relationship between a digital signal obtained by binarizing the analog output signal with a first threshold voltage. (A) The figure which shows an example of the conventional color misregistration correction pattern, (b) The figure which shows an example of the signal waveform of the sensor output at the time of reading the conventional color misregistration correction pattern with an optical sensor, (c) This implementation FIG. 6 is a diagram illustrating an example of a color misregistration correction pattern in the embodiment, and FIG. 8D is a diagram illustrating an example of a signal waveform of a sensor output when the color misregistration correction pattern of the present embodiment is read by an optical sensor. FIG. 8 is a timing chart of sensor output signals when the pattern detection sensor 7 detects the color misregistration correction pattern shown in FIG. 2 is a flowchart showing a flow of color misregistration correction processing in the image forming apparatus of FIG. 1.

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

  FIG. 1 is a diagram for explaining a schematic configuration of an image forming unit in an image forming apparatus according to an embodiment of the present invention.

  In FIG. 1, an image forming apparatus 100 is a tandem image forming apparatus including a plurality of image forming units. The image forming apparatus 100 includes laser writing units 15a, 15b, 15c, and 15d arranged in the order of yellow (Y), magenta (M), cyan (C), and black (K), and photosensitive drums 1a, 1b, 1c, 1d and developing devices 16a, 16b, 16c, 16d. The latent image is formed on the photosensitive drums 1a to 1d by the laser writing means 15a to 15d. The formed latent image is developed by the developing devices 16a to 16d. The toner images formed on the photosensitive drums 1a to 1d are sequentially transferred onto the intermediate transfer belt 5 which is an intermediate transfer body, thereby forming a color toner image 6.

  The color toner image 6 is transferred onto a sheet at a joint portion (transfer position) between the belt support roller 3 and the transfer roller 4 and is sent to a fixing unit (not shown) by the transport belt 12. Then, the toner image is fixed on the sheet by the fixing unit and is discharged outside the apparatus.

  The pattern detection sensor 7 is a reflective optical sensor that is disposed in the vicinity of the intermediate transfer belt 5 and detects a toner pattern (color shift correction pattern) formed on the intermediate transfer belt 5. The color misregistration correction pattern is also transferred onto the intermediate transfer belt 5 in the same manner as the color toner image 6.

  FIG. 2 is a diagram showing a schematic configuration of the pattern detection sensor 7 in FIG.

  In FIG. 2, the pattern detection sensor 7 includes a regular reflection light emitting element 201, a diffuse reflection light emitting element 202, and a light receiving element 204. The regular reflection light emitting element is at a position where the incident angle and the reflection angle are equal so that the regular reflection light of the light irradiated from the regular reflection light emitting element 201 (first light emitting element) to the intermediate transfer belt 5 enters the light receiving element 204. 201 is arranged. Furthermore, the irregular reflection light emitting element 202 is disposed at a position where the incident angle and the reflection angle of the light emitted from the irregular reflection light emitting element 202 (second light emitting element) are not equal.

  FIG. 3 is a block diagram illustrating a schematic configuration of a color misregistration correction unit in the image forming apparatus 100 of FIG.

  The light receiving element 204 in the pattern detection sensor 7 is connected to the CPU 109 via the A / D converter 205. The light receiving element 204 is connected to the ASIC 101 which is a digital integrated circuit via the comparator 203. The regular reflection light emitting element 201 and the irregular reflection light emitting element 202 are connected to the light source switching unit 111 in the ASIC 101.

  The ASIC 101 includes a pattern generation unit 102 that generates image data of a color misregistration correction pattern, and a pattern reading control unit 103 that reads an output signal from the binarized light receiving element 204 and temporarily stores the data. Further, the ASIC 101 corrects the toner image writing timing based on the color misregistration calculation unit 104 that calculates the color misregistration amount based on the read pattern data and the color misregistration amount calculated by the color misregistration calculation unit 104. And a color misregistration correction unit 105. Further, the ASIC 101 includes a light source switching unit 111 that switches a light source that irradiates the color misregistration correction pattern to either the regular reflection light emitting element 201 or the irregular reflection light emitting element 202. Furthermore, the threshold value control part 112 which sets the 1st threshold value which adapts to regular reflection light, or the 2nd threshold value which adapts to irregular reflection light emission to the comparator 203 is provided.

  The light receiving element 204 receives reflected light from the color misregistration correction pattern formed on the surface of the intermediate transfer belt 5 or on the intermediate transfer belt 5, and converts the light amount into a voltage for output. The voltage signal that the light receiving element 204 receives and outputs the specularly reflected light is input to the comparator 203 in which the first threshold voltage Vth1 corresponding to the specularly reflected light is set. On the other hand, the voltage signal output by the light receiving element 204 receiving the irregularly reflected light is input to the comparator 203 in which the second threshold voltage Vth2 corresponding to the irregularly reflected light is set.

  A voltage signal (analog signal) output from the light receiving element 204 is also input to the A / D converter 205, converted into a digital signal by the A / D converter 205, and output to the ASIC 101 and the CPU 109.

  As described above, the comparator 203 binarizes the analog signal input from the pattern detection sensor 7 with the set first threshold voltage Vth1 or the second threshold voltage Vth2, and outputs it as a digital signal. The binarized digital signal is temporarily stored in the pattern reading control unit 103 in the ASIC 101 and used by the color misregistration calculation unit 104 and the color misregistration correction unit 105.

  A CPU 109 is connected to the ROM 110, the ASIC 101, and the like, and controls the entire image forming apparatus 100. The CPU 109 performs various controls by executing program data stored in the ROM 110.

  FIG. 4A is a diagram showing the state of the color misregistration correction pattern on the light receiving element 204 of the pattern detection sensor 7 and the intermediate transfer belt 5, and FIG. 4B is the state shown in FIG. 4A and the light receiving element. It is a figure which shows the relationship with the waveform of the output signal of 204. FIG. In the illustrated example, the case where the light receiving element 204 receives the irregularly reflected light from the patch using the irregularly reflected light emitting element 202 will be described. The point that the level changes in accordance with the area that can be detected by the light receiving element 204 is the same when the regular reflection light emitting element 201 is used.

  In FIG. 4A, as the color misregistration correction pattern approaches the light receiving element 204, the area in which the light receiving element 204 can detect irregularly reflected light from the color misregistration correction pattern increases. Level increases (state (1) to state (2) in FIG. 4B). When irregularly reflected light from the color misregistration correction pattern can be detected on the entire surface of the light receiving element 204, the level of the output signal of the light receiving element is maximized (state (3) in FIG. 4B), and output is performed as the detectable area decreases. The level of the signal decreases (state (4) to state (5) in FIG. 4B).

  FIG. 5A is a diagram illustrating a waveform of a sensor output at the time of reading a color misregistration correction pattern in each of regular reflection light and irregular reflection light when the gloss of the intermediate transfer belt 5 is high. In this embodiment, the intermediate transfer belt is assumed to use a black glossy polyimide sheet.

  As indicated by the waveform 501, since the regular reflection light from the intermediate transfer belt 5 is larger than the regular reflection light from the color misregistration correction pattern formed by each YMCK toner, the intermediate transfer belt 5 has YMCK. The sensor output is higher than the color misregistration correction pattern.

  On the other hand, as shown by the waveform 502, the irregularly reflected light from the intermediate transfer belt 5 is less than the irregularly reflected light from the color misregistration correction pattern formed with each YMC toner, and the intermediate transfer belt 5 has the YMC color misregistration. The sensor output is lower than the correction pattern. The sensor output is low because there is little diffusely reflected light from the color misregistration correction pattern formed with K toner, which is almost the same as the sensor output of the intermediate transfer belt 5.

  FIG. 5B is a diagram illustrating a waveform of a sensor output at the time of reading a color misregistration correction pattern in each of regular reflection light and irregular reflection light in a state where the gloss of the intermediate transfer belt 5 is low.

  As indicated by a waveform 503, since the regular reflection light from the intermediate transfer belt 5 is low when the gloss is low, the sensor output of the intermediate transfer belt 5 is low when the gloss is low. Therefore, the sensor output of the intermediate transfer belt 5 in a state where the gloss is low is at the same level as the sensor output of the color misregistration correction pattern formed by each YMC toner. The sensor output for the K toner color misregistration correction pattern is lower than the sensor output of the specularly reflected light on the surface of the intermediate transfer belt 5 when the gloss is low.

  On the other hand, as shown in the waveform 504, the diffusely reflected light is the same as in the state where the gloss is high as in the waveform 502 shown in FIG.

  FIG. 6A is a diagram illustrating a relationship between an analog output signal of the light receiving element 204 by irregularly reflected light and a digital signal obtained by binarizing the analog output signal with the second threshold voltage Vth2. FIG. 6B is a diagram showing a relationship between an analog output signal of the light receiving element 204 by regular reflection light and a digital signal obtained by binarizing the analog output signal with the first threshold voltage Vth1.

  The analog output signal of the light receiving element 204 due to the irregularly reflected light becomes a triangular wave 601 shown in FIG. 6A. The triangular wave exceeds the second threshold voltage Vth2, and “1” indicates that the triangular wave exceeds the second threshold voltage Vth2. When converted into a value, it becomes a digital signal of a rectangular wave 602 shown in FIG.

  The analog output signal of the light receiving element 204 due to the specularly reflected light becomes a triangular wave 603 shown in FIG. 6B. This triangular wave is “0” when it exceeds the first threshold voltage Vth1, and “1” when it does not exceed the first threshold voltage Vth1. When binarized, it becomes a digital signal of a rectangular wave 604 shown in FIG.

  FIG. 7A is a diagram illustrating an example of a conventional color misregistration correction pattern.

  A conventional color misregistration correction pattern detects and corrects a relative shift amount of each color with respect to a reference color, and a toner patch of a reference color and a toner patch other than the reference color (hereinafter simply referred to as “patch”). Are alternately formed at intervals c. In the illustrated example, the reference color is M, and M toner patch (M patch), Y toner patch (Y patch), M patch, C toner patch (C patch), M patch, K toner patch (K patch), and M patch. Are formed in this order. The intervals between the patches are unified at an interval c.

  FIG. 7B shows an output signal when the pattern detection sensor 7 detects the color misregistration correction pattern shown in FIG. 7A, and the sensor output is the second threshold for the YMC patch, and for the K patch. FIG. 4 is a diagram showing a signal binarized with a first threshold value.

  The pattern detection sensor 7 receives irregularly reflected light by the light receiving element 204 and detects YMC toner patches other than the K toner patch, while detecting only the K patch with regular reflected light. When the K patch 702 is detected, the light source is switched from the irregularly reflected light emitting element 202 to the regular reflected light emitting element 201 between the M patch 701 and the K patch 702 (hereinafter abbreviated as “between MKs”). Then, between the K patch 702 and the M patch 703 (hereinafter abbreviated as “between KM”), the light source is switched from the regular reflection light emitting element 201 to the irregular reflection light emitting element 202. The light source is switched by the light source switching unit 111 during the detection of the color misregistration correction pattern by the pattern detection sensor 7.

  FIG. 7C is a diagram illustrating an example of a color misregistration correction pattern in the present embodiment.

  In the illustrated color misregistration correction pattern, the width g of the K patch 704 is narrower than the width h of the color (MYC) patch as compared to the color misregistration correction pattern shown in FIG. Note that the width of the patch in the present embodiment is a width in the direction perpendicular to the moving direction of the intermediate transfer belt 5 (the arrow direction in the drawing). In the illustrated color misregistration correction pattern, since the width g of the K patch 704 is narrowed, the distances a and b between the K patch 704 and the adjacent M patches 701 and 703 are between MYC color patches. It is wider than the interval c. As described above, since the light source is switched between the MK and the KM as described above, the interval a, which is longer than the interval c between the color patches in order to secure time until the light quantity of the light source is stabilized. b is set.

  FIG. 7D shows an output signal when the pattern detection sensor 7 detects the color misregistration correction pattern shown in FIG. 7C, and the sensor output is the second threshold value for the YMC patch, and the K patch. FIG. 4 is a diagram showing a signal binarized with a first threshold value.

  As shown in the figure, the detection of the K patch by the specularly reflected light can be easily performed as compared with the color patch regardless of whether the gloss of the intermediate transfer belt 5 is high or low. Therefore, it is easy to reduce the width g of the K patch. Can be detected. In this way, the color patch is formed at regular intervals with the reference color, while the width of the K patch is narrowed. As a result, the distances a and b between the K patch and the adjacent M patch can be made wider than the distance c between the color patches, and it is possible to secure a stable time of the light amount when the light source is switched.

  FIG. 8 is a diagram showing a timing chart when the color misregistration correction pattern shown in FIG. 7C is formed.

  As shown in FIG. 7 (d), in order to form the reference M patch and the other color patches alternately with an interval c, the CPU 109 causes the pattern generation unit 102 to perform an arbitrary timing at the time of color misregistration correction. The image data for generating the M patch is transmitted to the image forming unit. Subsequently, the image data of the Y patch, M patch, C patch, and M patch are sequentially transmitted to the image forming unit at intervals of time t. The time t can be calculated from the distance X between the photosensitive drums 1a to 1d and the speed Y of the intermediate transfer belt 5, and the time t = X / Y.

  The CPU 109 transmits the image data of the third M patch 801 to the image forming unit by the pattern generation unit 102, and then transmits the image data of the K patch 802 to the image forming unit after a time ta. Here, the patch formation start timing of the K patch 802 is delayed by time e and the patch formation end timing is advanced by time f with respect to the timing at the time of forming the Y patch and C patch, thereby shortening the width of the K patch 802. To do. Then, after the K patch is formed, the image data of the M patch 803 is transmitted to the image forming unit at a time tb.

  Therefore, the light quantity stabilization times ta and tb are as follows.

Light amount stabilization time ta = time t + time e
Light amount stabilization time tb = time t + time f
Next, the flow of color misregistration correction processing in the image forming apparatus 100 will be described with reference to FIG.

  FIG. 9 is a flowchart showing the flow of color misregistration correction processing in the image forming apparatus 100. This process is a process that is executed mainly by the CPU 109 executing the control program stored in the ROM 110 to control the ASIC 101 and the like.

  The CPU 109 determines whether or not a print job has been received (or received) in the print standby state (step S600) (step S601). If it is determined that the print job has been received (or received), the print operation is performed. Start (step S602).

  Next, the CPU 109 determines whether or not the counted number of printed sheets has exceeded a predetermined value (step S603). The counted number of printed sheets is the number of printed sheets counted after printing is started in step S602, but is not limited to this.

  If it is determined in step S603 that the number of prints does not exceed the predetermined value, the CPU 109 determines whether or not the print job has ended (step S611). If it is determined that the print job has not ended, the process returns to step S602. On the other hand, if it is determined that the process has been completed, the process proceeds to step S612.

  In step S612, the CPU 109 determines whether or not the power is turned off. If it is determined that the power is not turned off, the process returns to step S600. If it is determined that the power is turned off, the process ends. .

  If it is determined in step S603 that the number of prints has exceeded a predetermined value, the color misregistration correction operation in steps S604 to S610 is executed.

  First, the CPU 109 controls the pattern generation unit 102 to form a color misregistration correction pattern on the intermediate transfer belt 5 (step S604).

  Next, the CPU 109 controls the light source switching unit 111 to cause the irregularly reflected light emitting element 202 to emit light, and also controls the pattern reading control unit 103 so that the pattern detection sensor 7 generates a color misregistration correction pattern on the intermediate transfer belt. It is detected (step S605). At this time, the YMC color patch in the color misregistration correction pattern is detected by the pattern detection sensor 7. The analog signal output from the light receiving element 204 that has received the irregularly reflected light is binarized by the comparator 203 based on the second threshold voltage Vth2 set in the comparator 203 by the threshold control unit 112 and is then input to the pattern reading control unit 103. Stored temporarily.

  Next, the CPU 109 controls the light source switching unit 111 to switch the light source from the irregularly reflected light emitting element 202 to the regular reflected light emitting element 201 (step S606). The switching timing is immediately after (falling) the signal waveform of the M patch in FIG.

  Next, the CPU 109 controls the pattern reading control unit 103 to cause the pattern detection sensor 7 to detect a color misregistration correction pattern on the intermediate transfer belt (step S607). At this time, only the K patch in the color misregistration correction pattern is detected by the pattern detection sensor. The analog signal output from the light receiving element 204 that has received the specularly reflected light is binarized by the comparator 203 based on the first threshold voltage Vth1 set in the comparator 203 by the threshold control unit 112, and is read by the pattern reading control unit 103. Temporarily stored.

  Next, the CPU 109 controls the color misregistration calculation unit 104 to calculate a relative color misregistration amount between the respective colors based on the signal (pattern data) stored in the pattern reading control unit 103 (step S608). . Next, the CPU 109 controls the color misregistration correction unit 105 to correct the image writing timing based on the color misregistration amount calculated in step S608 (step S609), and performs color misregistration correction. After the color misregistration correction is completed, the CPU 109 clears the counted number of prints (step S610) and proceeds to step S611.

  According to the present embodiment, the toner pattern is formed such that the width of the K toner patch is narrower than the width of the color patch other than the K toner patch, and the interval between the K toner patch and the adjacent color patch is the interval between the color patches. It is formed to be wider. As a result, it is possible to secure a time during which the light amount of the light source in the optical sensor is stabilized without increasing the time required for color misregistration correction. As a result, it is possible to prevent a decrease in productivity of the image forming apparatus due to the color misregistration correction operation.

  In the present embodiment, a method for correcting color misregistration by forming a color misregistration correction pattern on the intermediate transfer belt 5 has been described. In addition to this, the present invention can also be applied to a method of forming a color misregistration correction pattern on a continuous sheet or a method of forming a color misregistration correction pattern on a sheet conveyed by a sheet conveying belt.

  In this embodiment, the image forming apparatus that performs printing using the electrophotographic process has been described. However, the present invention is not limited to this, and can be applied to, for example, an ink jet printing apparatus. .

  Furthermore, in the present embodiment, the configuration for detecting the color misregistration correction pattern by the regular reflection light emitting element 201 and the irregular reflection light emitting element 202 is used, but a configuration for detecting the density of the color misregistration correction pattern may be used. That is, the density detection is performed by detecting the density of the YMC patch by the amount of light incident on the irregularly reflected light emitting element 202, and detecting the density of the K patch by the amount of light incident on the regular reflected light emitting element 201. It becomes possible.

  In the present embodiment, as shown in FIG. 6A and FIG. 6B, a pulse signal is obtained by comparing signal waveforms in light amounts detected by emitting two light sources based on two threshold values. And auto-registration is performed by calculating the center position of the pulse. However, the present invention is not limited to this, and the auto-registration may be performed by detecting the peak value of the signal waveform and generating a pulse signal.

  The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

DESCRIPTION OF SYMBOLS 102 Pattern generation part 103 Pattern reading control part 104 Color shift calculation part 105 Color shift correction part 111 Light source switching part 112 Threshold control part 201 Regular reflection light light emitting element 202 Diffuse reflection light light emitting element 203 Comparator 204 Light receiving element

Claims (4)

In an image forming apparatus having a plurality of image forming means,
Control means for controlling the plurality of image forming means so as to form a toner pattern composed of a plurality of toner patches on the intermediate transfer member;
Two light sources and one light receiving element are provided, and the intermediate transfer body is formed by switching light emission of the two light sources, irradiating the intermediate transfer body with light, and receiving the reflected light by the light receiving element. Detection means for detecting a toner pattern;
Color misregistration calculating means for calculating a color misregistration amount based on a signal output from the detection means;
A color misregistration correction unit that corrects writing timing of toner images by the plurality of image forming units based on the color misregistration amount calculated by the color misregistration calculation unit;
Switching means for switching the light emission of the light source,
The toner pattern is formed such that the width of the K toner patch is narrower than the width of the color patch other than the K toner patch, and the interval between the K toner patch and the adjacent color patch is wider than the interval between the color patches. An image forming apparatus formed.   The image forming apparatus according to claim 1, wherein the switching unit switches light emission of the light source during detection of the toner pattern by the detection unit. The detection means includes a first light emitting element for irradiating the intermediate transfer body on which the toner pattern is formed with regular reflection light, and a second light emitting element for irradiating the intermediate transfer body on which the toner pattern is formed with irregular reflection light. A light emitting element and a light receiving element that receives regular reflection light or irregular reflection light;
The switching unit causes the second light emission to the Y toner patch, the M toner patch, and the C toner patch so that the first light emitting element emits light to the K toner patch during the detection of the toner pattern by the detection unit. The image forming apparatus according to claim 1, wherein light emission of the first light emitting element and the second light emitting element is switched so that light is emitted from the element. Threshold control means for setting a first threshold value for binarizing the output signal of the light receiving element by the regular reflection light and a second threshold value for binarizing the output signal of the light receiving element by the irregular reflection light,
The threshold value control means switches the setting of the first threshold value and the second threshold value when the light emission of the first light emitting element and the second light emitting element is switched by the switching means. The image forming apparatus described.

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