JP2010160203A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively improve deterioration of image quality caused by unevenness of one rotation cycle of an electric motor for driving in an image forming apparatus. <P>SOLUTION: A test pattern for detecting a density variation amount (reflected light variation amount) of an image in one rotation cycle of the electric motor for rotating or moving an image carrier is formed while changing a motor control constant, and the density variation amounts of the respective test patterns are compared, whereby the appropriate motor control constant is set. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer that forms electrophotography.

  In an electrophotographic image forming apparatus, an electrostatic latent image is formed on a photosensitive drum, a visible image is formed with a developer by a developing device, and the visible image is transferred onto a recording material to form an image. It has been known.

  In such an image forming apparatus, there is a problem that image density unevenness occurs in an image on which an image is formed, and image quality is deteriorated. As one of the causes of image density unevenness, the rotational speed of the photosensitive drum is not constant, that is, the fluctuation of the rotational speed of the photosensitive drum. In addition to the photosensitive drum, fluctuations in the rotational speed (moving speed) of the intermediate transfer belt and the like can be cited as one factor.

  Under such circumstances, for example, Patent Document 1 proposes to detect a color misregistration detection pattern regarding the rotational speed fluctuation of the photosensitive drum, obtain the speed fluctuation from the detection result, and perform the rotational control of the photosensitive drum. . Thereby, color misregistration between colors can be reduced, density unevenness such as banding can be suppressed, and deterioration in image quality can be suppressed.

On the other hand, fluctuations in the rotation / movement speed of the image carrier such as the photosensitive drum and the intermediate transfer belt are also caused by the electric motor for moving the driven body. Specifically, there is unevenness of one rotation cycle of the electric motor, such as shaft unevenness of the electric motor and eccentricity of the pinion gear of the electric motor. In addition, the unevenness of one rotation cycle of the electric motor may cause banding and the like, leading to a decrease in image quality. However, this cannot be sufficiently solved even with the technique of Patent Document 1.
JP 2006-47920 A

  In response to the above problems related to the electric motor, it is possible to reduce image quality deterioration related to the electric motor by improving the mechanical accuracy with respect to the full pitch meshing error of the pinion gear attached to the electric motor, the shaft runout of the motor shaft, etc. .

  However, the cost increases in improving the mechanical accuracy. Further, even if mechanical accuracy is improved, it is actually a problem and difficult to reduce the unevenness of the rotation cycle of the electric motor that affects the rotation / movement speed of the photosensitive drum, the intermediate transfer belt, and the like. There is also an aspect.

  That is, it is desired to improve the image quality deterioration due to unevenness of one rotation cycle of the electric motor at low cost.

The present invention has been made based on the above request, and an image forming apparatus according to the present invention includes an electric motor for rotating or moving the image carrier and a speed of the electric motor based on an electric motor control constant. Motor speed control means for performing control, and a plurality of the electric motor control constants are set, and the image carrier is rotated or moved by the electric motor driven by the motor speed control means based on each electric motor control constant. Test pattern forming means for forming a test pattern, detection means for detecting reflected light when the formed test pattern is irradiated with light, and the electric motor in the reflected light detected for each electric motor control constant Based on the fluctuation of one rotation cycle of the motor, the motor speed control means has an electric motor control constant for normal print image formation. A control constant setting means for setting,
It is characterized by having.

  According to the present invention, it is possible to inexpensively improve image quality degradation caused by unevenness of one rotation cycle of an electric motor.

Example 1
The image forming apparatus according to the first embodiment will be described below with reference to FIG.

[General outline sectional view of image forming apparatus]
FIG. 1 shows four-color visible image forming means (laser) of yellow (hereinafter referred to as Y), magenta (hereinafter referred to as M), cyan (hereinafter referred to as C), and black (hereinafter referred to as K). 1 shows a color image forming apparatus 1 provided with exposure units 2a, 2b, 2c, 2d).

  First, each exposure unit 3 emits a laser beam, that is, a laser, based on image information obtained by reading a document by a scanner unit (not shown) and image information (print data) transmitted from a host computer or the like. Beam exposure is performed.

  Each exposure unit 3 performs exposure according to the sent image information, and each photosensitive drum 5 (a, b, c, d is Y, M, which is an image carrier driven by each electric motor 4). , C, and K)). Based on the electrostatic latent image, the visible image is developed with toner supplied from a developing device (not shown). The photosensitive drums 5 (5a, 5b, 5c, 5d) receive driving force from the electric motor 4 (4a, 4b, 4c, 4d) and are connected via a pinion gear (not shown).

  The LEDs 15 (15a, 15b, 15c, 15d) emit light, and the density detection sensors 10 (10a, 10b, 10c, 10d) receive the reflected light from the photosensitive drum 5. A detailed configuration will be described later with reference to FIG.

  Further, the recording material S is sequentially conveyed from the recording material cassette 6 on which the recording material is placed by the conveying means 7 so as to coincide with the timing at which a visible image is formed on the photosensitive drum, and visible by the transfer means 8. The image is transferred. The transport unit 7 may be any unit that transports the recording material S, and may be a belt, a roller, or the like.

  In the figure, images are sequentially formed in the order of Y, M, C, and K. Thereafter, the recording material S is separated from the conveying means 7 and thermally fixed by the fixing device 9, and the visible image is thermally fixed on the recording material S and discharged to the outside.

[Functional block diagram of image forming apparatus]
A functional block diagram of the image forming apparatus is shown in FIG.

  The pattern generation unit 11 that controls the test pattern generation generates information on the test pattern 12 that is a pattern for detecting the density fluctuation amount. Note that the density here substantially corresponds to reflected light detected from the test pattern, as will be described later in the density detector 17. Therefore, the density signal, density fluctuation, density unevenness, and the like can be replaced with reflected light signal detected from the test pattern 12, reflected light fluctuation, and reflected light unevenness. This is the same in any embodiment.

  The execution determination unit 22 determines whether to change the electric motor control constant according to the state of the image forming apparatus 1. For example, when the power source of the image forming apparatus 1 is turned on, when the amount of use environment fluctuation of the image forming apparatus 1 exceeds a threshold value, when the cumulative number of printed sheets exceeds the threshold value, or when the cumulative energization time of the image forming apparatus 1 is a threshold value. When the value exceeds, the execution determination unit 22 determines that the change setting of the electric motor control constant is necessary. Further, although a form using a cartridge containing a recording agent (toner) is generally known, the execution determination unit 22 determines whether or not the cartridge has been replaced. It may be determined that the change setting of the motor control constant is necessary.

  The motor control constant setting unit 13 that controls the control constant of the electric motor can set the control constant of the electric motor 4 that drives the photosensitive drum 5 during normal print image formation. The motor control constant setting unit 13 is configured to change and set a plurality of electric motor control constants. In this case, the normal print image formation does not refer to the image formation of the test pattern 12 shown in FIG. 5, for example, but to image information (print data) input from an external host computer or the like. Image formation based on

  Here, the electric motor control constant is obtained by multiplying the difference between the target value for rotating the electric motor 4 at a predetermined rotational speed (speed) and the actual rotational speed (speed) of the motor by a coefficient to obtain a motor FB (FEED). BACK) is a control coefficient when performing control. For example, in the case of proportional control, the electric motor control constant corresponds to a proportional gain, and in the case of PID control, the electric motor control constant corresponds to an integral gain and a differential gain.

  The motor speed control unit 14 calculates a speed control amount based on a target value for rotating the electric motor 4 set in advance in the CPU 20 at a predetermined rotation speed (speed) and speed information obtained from the electric motor 4. The calculation at this time is based on the electric motor control constant. Based on the calculated speed calculation amount, drive control is performed so that the electric motor 4 approaches the target predetermined rotation speed (speed). The motor speed control unit 14 is configured to be able to change (switchable) the actually used electric motor control constant in accordance with an instruction from the motor control constant setting unit 13.

  The calculation of the speed control amount by the motor control constant setting unit 14 here is realized by the CPU 20 executing a preset calculation processing program. Further, the speed control amount may be calculated by an integrated circuit (IC) as an arithmetic circuit or an application specific integrated circuit (ASIC) integrated circuit.

  After the electric motor control constant is changed, the exposure unit 3 forms an electrostatic latent image on the photosensitive drum 5 at regular intervals based on the information of the test pattern 12, and a visible image test is performed by a developing unit (not shown). A pattern 12 is formed. The formed test pattern 12 is output as an electrical signal as a density signal by the density detection unit 17 including the density detection sensors 10R and 10L, the LED 15, and the IV conversion circuit 16.

  FIG. 3 shows an example of the concentration detection sensor. According to the density detection sensor of FIG. 3, the LED 15 is caused to emit light, and the light emitted from the LED 15 is irradiated toward the test pattern 12. The light applied to the test pattern 12 is reflected, and the reflected light is received by the density detection sensors 10R and 10L. A current corresponding to the density of the test pattern 12 is detected from the density detection sensors 10R and 10L, and is converted into a voltage by the IV conversion circuit 16.

  As described above, the concentration detection sensor shown in FIG. 3 detects reflected light characteristics when the test pattern 12 is irradiated with light, and includes an optical characteristic detection sensor, a light detection sensor, It can also be called an optical sensor or the like. Further, the density signal in the present embodiment is a signal representing the reflected light characteristic from the test pattern 12, and is not limited to a signal representing the density according to a specific density conversion method. This is also true for any of the following examples.

  The density signal of the test pattern 12 obtained by the density detector 17 is a sine of the representative density (DC component) of the test pattern 12 such as the rotational speed unevenness of the electric motor 4 and the drum rotational speed unevenness due to the shake of the motor shaft. It is an electric signal obtained by superposing wavy signals.

  In order to obtain the density fluctuation amount of one rotation period of the electric motor 4 from the detected density signal of the test pattern 12, the density fluctuation amount calculation unit 18 calculates the density fluctuation amount of one rotation period of the electric motor 4 from the density signal. This can be realized by calculating and extracting.

  More specifically, the concentration fluctuation amount in one rotation cycle of the electric motor 4 is extracted by the sampling theorem. In order to extract the concentration fluctuation amount of one rotation cycle of the electric motor 4, a sampling cycle that is at least twice as long as the rotation cycle of the motor is required. In order to obtain the density fluctuation amount of one rotation cycle of the electric motor 4 more reliably, it is sufficient to perform sampling at least five times the one rotation cycle of the electric motor 4. For example, when the frequency of the rotation speed of the electric motor 4 is 50 Hz, the sampling frequency is 500 Hz or more, and the density signal of the test pattern 12 is sampled.

  The density fluctuation amount comparison unit 19 stores the density fluctuation amount in one rotation cycle of the electric motor 4 obtained by the density fluctuation amount calculation unit 18 in a memory 21 in a CPU (one-chip microcomputer) 20. The memory 21 functions as a volatile storage unit and also functions as a nonvolatile storage unit. The memory 21 stores information on density variation corresponding to a plurality of motor control constants. The information on the plurality of density fluctuation amounts is the density fluctuation amount of one rotation period of the electric motor 4 corresponding to each motor control constant, obtained by a test pattern formed by a plurality of motor control constants.

  Then, the density fluctuation amount comparison unit 19 compares the information of each density fluctuation amount. Based on the comparison result, the motor control constant of the test pattern having the smallest density fluctuation amount in one rotation cycle of the electric motor 4 is set by the motor control constant setting unit 13 as the electric motor control constant for normal print image formation.

[Relationship between motor control constant and density unevenness]
FIG. 4 actually sets a plurality of different motor control constants, creates a test pattern 12, performs an FFT analysis by the concentration variation calculation unit 18 based on the measurement information obtained by the concentration detection unit 17, The density fluctuation amount of one rotation period of the electric motor 4 is calculated and compared. Note that FFT (Fast Fourier Transform) analysis is fast Fourier transform.

  4A and 4B show the results of measurement using different motors as the electric motor 4. The motor control constant on the horizontal axis represents a control constant for controlling the speed of the motor. The unit of the vertical axis is a voltage value, and this voltage value represents density unevenness in one rotation cycle of the electric motor 4. As described above, in this embodiment, it is possible to deal with the influence on the density unevenness in one rotation cycle of each electric motor 4 having individual differences depending on how the electric motor control constant is set. Further, even when attention is paid to one electric motor 4, its characteristics can be changed with time, and in this embodiment, such a case can be dealt with.

  In the following description, it is assumed that the FFT analysis is performed, but another method can be considered in order to further simplify the system. For example, it is possible to cause the density fluctuation amount calculation unit 18 to perform soft filtering calculation processing for extracting density unevenness in one rotation cycle of the electric motor 4 from the density signal obtained by sampling. Alternatively, a band pass filter circuit for extracting a density signal of one rotation cycle of the electric motor 4 is incorporated in the density fluctuation amount calculation unit 18 and one rotation of the electric motor 4 is performed based on the output of the band pass filter circuit. Periodic density unevenness may be obtained.

[Test pattern formation]
FIG. 5 shows a specific configuration of the test pattern 12. It consists of a plurality of test patterns 12 of the same gradation.

  The test pattern 12 for detecting the density fluctuation amount includes a pattern for each color in order to adjust the control constant for each electric motor 4 that drives each photosensitive drum 5. In FIG. 5, patterns 12 y (Y) and 12 m (M) are shown. However, not only the Y and M patterns but also the C and K patches are actually included in the test pattern 12. When the electric motor that drives the photosensitive drum is shared by a plurality of photosensitive drums, the patch only needs to correspond to each electric motor. For example, if the electric motors of the C, M, and Y photosensitive drums are common, the test pattern 12 may include any one of the C, M, and Y patches and the K patch. This also applies to FIG. 14 described later.

  In this embodiment, the pattern generation unit 11 forms the test pattern 12 on the photosensitive drum 5, and density detection sensors 10 </ b> R and 10 </ b> L are provided at both ends with respect to the rotation direction, and the test pattern 12 is detected on the photosensitive drum 5. The case will be described.

[Motor control constant setting flowchart]
FIG. 6 is a flowchart showing the flow until the motor control constant of this embodiment is set. The flowchart of FIG. 6 is executed for each photosensitive drum of each color.

  First, the power supply of the image forming apparatus 1 is input (S101). Next, the execution determination unit 22 determines whether to change the motor control constant according to the state of the image forming apparatus 1 (S102). The determination as to whether or not the motor control constant of the execution determination unit 22 needs to be changed is as described in the functional block diagram of the image forming apparatus 1 in FIG. This also applies to flowcharts described later.

  When the execution determination unit 22 determines not to change the electric motor control constant, the operation for determining the motor control constant ends (S111).

  On the other hand, when the execution determination unit 22 determines to change the electric motor control constant, the pattern generation unit 11 generates information on the test pattern 12 (S103).

  Next, the motor control constant setting unit 13 sets the motor speed control constant of the motor speed control unit 14 (S104). In step S104, a plurality of different motor control constants are sequentially set. More specifically, the motor control constant is sequentially changed in accordance with the timing of forming the next patch.

  Then, the motor speed control unit 14 controls the driving of the electric motor 4 by the motor control constant according to the setting of the motor control constant setting unit 13, and drives the photosensitive drum 5 by the electric motor 4 (S105).

  In step S105, the image information of the test pattern 12 generated by the pattern generation unit 11 is sent to the exposure unit 3 while a certain motor control constant is set, and the electrostatic latent image of the test pattern 12 is transferred to the photosensitive drum. 5 is formed. Then, a visible image of the test pattern 12 is formed by a developing device (not shown) (S106).

  Note that the processing in step S105 and step S106 is executed for each of a plurality of different motor control constants set in step S104.

  On the other hand, it waits until the timing at which the reflected light from the surface of the photosensitive drum 5 before the first test pattern 12 can be read. The reading timing of the density detection sensors 10R and 10L is calculated and controlled by the CPU 20 from the pattern formation timing. When it is time to read the reflected light from the surface of the photosensitive drum 5, the LED 15 is caused to emit light, and the reflected light from the photosensitive drum 5 is received by the density detection sensors 10R and 10L (S107).

  The detected currents from the concentration detection sensors 10R and 10L are converted into voltages by IV conversion. The voltage is input to the CPU 20 shown in FIG. The photosensitive drum 5 is rotated by the electric motor 4 and the density signal of the test pattern 12 is detected (S107).

  The density fluctuation amount calculation unit 18 performs FFT analysis based on the detected density signal, and calculates the density fluctuation amount of one rotation cycle of the electric motor 4 (S108).

  The CPU 20 (density variation non-each unit 19) compares the density variation in one rotation cycle of the electric motor 4 corresponding to each motor control constant stored in the memory 21 (S109).

  Then, the electric motor control constant corresponding to the pattern having the smallest density fluctuation amount is set as the electric motor control constant when the print image is formed on the photosensitive drum 5 (S110).

  In the description of S110 according to FIG. 6, the electric motor control constant having the smallest density fluctuation amount among the actually set electric motor control constants has been described. However, the present invention is not necessarily limited thereto. Referring to FIG. 4A as an example, as another method, an approximation is performed with an N-order function based on the measurement points actually plotted on the graph of FIG. An electric motor control constant that is predicted to decrease may be set. According to this method, a more ideal electric motor control constant can be set. In addition, it is the same also about other Examples that it is not limited to setting the electric motor control constant with the smallest density fluctuation | variation amount among the actually set electric motor control constants. However, for the sake of explanation, it is assumed that the electric motor control constant having the smallest amount of density fluctuation among the actually set electric motor control constants is set. The same can be said for S211, S311, S411, S504, and S611 described later.

  With the above operation, the setting of the motor control constant is completed (S111).

  As described above, in the first embodiment, a test pattern is drawn for each electric motor 4 and each electric motor control constant, and the density signal of the pattern obtained by the density detection sensors 10R and 10L is subjected to FFT analysis, whereby the electric motor 4 The amount of density fluctuation in one rotation cycle is extracted. Then, by comparing the extracted density fluctuation amount of each electric motor 4 in one rotation cycle, the photosensitive drum 5 performs normal print image formation with the electric motor control constant when the test pattern having the smallest density fluctuation amount is formed. Set when performing.

  As described above, according to the first embodiment, with the conventional configuration, the rotation speed of the electric motor 4 generated by the rotation fluctuation of the rotation speed of the electric motor 4, the shaft shake of the motor shaft, the eccentricity of the pinion gear, and the like. Concentration fluctuation can be suppressed. Accordingly, it is possible to improve the image quality deterioration due to the unevenness of one rotation cycle of the electric motor at a low cost. Further, it is not necessary to provide an encoder or the like for the control of the electric motor 4, the cost can be reduced, and the density unevenness of one rotation cycle of the electric motor 4 can be suppressed without increasing the size of the apparatus.

  In the first embodiment, the color image forming apparatus including the four color image forming units of yellow, magenta, cyan, and black has been described. However, the present invention is not limited to these four colors. It may be. Further, the photosensitive drum may be a four-cycle image forming apparatus using a single color image forming system.

(Example 2)
An image forming apparatus of this embodiment is shown in FIG. Regarding the configuration, mechanism, shape, and relative arrangement of the invention of the present embodiment, the description common to the first embodiment will be omitted, and differences from the first embodiment will be described.

  In this embodiment, unlike the first embodiment, the transfer means 8 and the transfer means 7 for transferring the test pattern 12 formed on the photosensitive drum 5 are movable transfer bodies for transferring the recording material S to the transfer means 8. The conveyor belt 23 is provided.

  As shown in the flowchart of FIG. 8, a description will be given of a case where the test pattern 12 for detecting the density fluctuation amount is transferred onto the transport belt 23 and the density signal is detected on the transport belt 23 on the movable transport body. .

  It should be noted that the density detection sensors 10R and 10L and the LED 15 are arranged on the conveyance belt 23 at locations where density signals can be detected.

[Motor control constant setting flowchart]
FIG. 8 shows a flowchart of the operation of this embodiment. The flowchart in FIG. 8 is executed for each photosensitive drum of each color.

  First, the power supply of the image forming apparatus 1 is input (S201). Next, the execution determination unit 22 determines whether to adjust the motor control constant according to the state of the image forming apparatus 1 (S202).

  When the execution determination unit 22 determines not to change the electric motor control constant, the operation for determining the motor control constant ends (S212).

  If the execution determination unit 22 determines to change the electric motor control constant, the pattern generation unit 11 generates information on the test pattern 12 (S203).

  Next, the motor control constant setting unit 13 sets the motor speed control constant of the motor speed control unit 14 (S204). In step S204, a plurality of different motor control constants are sequentially set. More specifically, the motor control constant is sequentially changed in accordance with the timing of forming the next patch.

  Then, the motor speed control unit 14 controls the driving of the electric motor 4 by the motor control constant according to the setting of the motor control constant setting unit 13, and drives the photosensitive drum 5 by the electric motor 4 (S205).

  In step S205, in a state where a certain motor control constant is set, the image information of the test pattern 12 generated by the pattern generation unit 11 is sent to the exposure unit 3, and the electrostatic latent image of the test pattern 12 is transferred to the photosensitive drum. 5 is formed. Then, a visible image of the test pattern 12 is formed by a developing device (not shown) (S206).

  Note that the processing in step S205 and step S206 is executed for each of a plurality of different motor control constants set in step S204.

  Then, the conveyance belt 23 is driven by an electric motor 24 that drives a conveyance belt 23 that is a movable conveyance body that carries and conveys a recording material. The transfer unit 8 forms the photosensitive drum 5 on the conveyance belt 23 in step S206. The test pattern 12 is transferred (S207).

  Then, when it is time to read the reflected light from the surface of the conveyor belt 23, the LED 15 is caused to emit light, and the reflected light from the conveyor belt 23 is received by the density detection sensors 10R and 10L, and each patch included in the test pattern 12 is received. A density signal is detected (S208).

  An FFT analysis is performed based on the detected concentration signal, and the concentration fluctuation amount in one rotation cycle of the electric motor 4 is calculated (S209).

  The CPU 20 (density variation non-each unit 19) compares the density variation in one rotation cycle of the electric motor 4 corresponding to each motor control constant stored in the memory 21 (S210).

  Then, a motor control constant corresponding to the pattern having the smallest density fluctuation amount is set as a motor control constant at the time of image formation on the photosensitive drum 5 (S211).

  With the above operation, the setting of the motor control constant is completed (S212).

  In this embodiment, the transport belt is used as the movable transport body. However, the present invention is not limited to this, and it is possible to carry a recording material and transfer a test pattern onto the movable transport body through the transfer means. It ’s fine.

(Example 3)
The configuration of the image forming apparatus of this embodiment is shown in FIG. Regarding the configuration, mechanism, shape, and relative arrangement of the invention, description common to the first embodiment will be omitted, and differences from the first embodiment will be described.

  In this embodiment, a test pattern 12 is formed on a movable image carrier that can carry a visible image formed on the photosensitive drum 5, and a density signal is detected on the movable image carrier.

  In this embodiment, unlike the above-described embodiment, an intermediate transfer belt 25 as a movable image carrier, a first transfer means 8a for transferring a visible image formed on the photosensitive drum 5 to the intermediate transfer belt 25, and a visible image. Second transfer means 8b for transferring the image to the recording material S is provided.

  With the above configuration, the test pattern 12 formed on the photosensitive drum 5 is transferred onto the intermediate transfer belt 25, and a density signal is detected on the intermediate transfer belt 25. At this time, the density detection sensors 10 </ b> R and 10 </ b> L and the LED 15 are arranged on the intermediate transfer belt 25 where the density signal can be detected.

  A case where the test pattern 12 for detecting the density fluctuation amount is formed on the intermediate transfer belt 25 and the test pattern 12 is detected on the intermediate transfer belt 25 as shown in the flowchart of FIG.

[Motor control constant setting flowchart]
First, the power of the image forming apparatus 1 is input (S301). Next, the execution determination unit 22 determines whether to adjust the motor control constant according to the state of the image forming apparatus 1 (S302).

  When the execution determination unit 22 determines not to change the electric motor control constant, the operation for determining the motor control constant ends (S312).

  On the other hand, when the execution determination unit 22 determines to change the electric motor control constant, the pattern generation unit 11 generates information on the test pattern 12 (S303).

  Next, the motor control constant setting unit 13 sets the motor speed control constant of the motor speed control unit 14 (S304). In step S304, a plurality of different motor control constants are sequentially set. More specifically, the motor control constant is sequentially changed in accordance with the timing of forming the next patch.

  Then, the motor speed control unit 14 controls the driving of the electric motor 4 by the motor control constant according to the setting of the motor control constant setting unit 13, and drives the photosensitive drum 5 by the electric motor 4 (S305).

  In step S305, the image information of the test pattern 12 generated by the pattern generation unit 11 is sent to the exposure unit 3 while a certain motor control constant is set, and the electrostatic latent image of the test pattern 12 is transferred to the photosensitive drum. 5 is formed. Then, a visible image of the test pattern 12 is formed by a developing device (not shown) (S306).

  Note that the processing in step S305 and step S306 is executed for each of a plurality of different motor control constants set in step S104.

  On the other hand, the intermediate transfer belt 25 is driven by a drive motor (not shown), and the test pattern 12 formed on the photosensitive drum 5 is transferred onto the intermediate transfer belt 25 by the first transfer unit 8a (S307).

  When it is time to read the reflected light from the surface of the intermediate transfer belt 25, the LED 15 emits light, and the reflected light from the intermediate transfer belt 25 is received by the density detection sensors 10R and 10L. Detection is performed (S308).

  The density fluctuation amount calculation unit 18 performs FFT analysis based on the detected density signal, and calculates the density fluctuation amount of one rotation cycle of the electric motor 4 (S309).

  The CPU 20 (density variation non-each unit 19) compares the density variation in one rotation cycle of the electric motor 4 corresponding to each motor control constant stored in the memory 21 (S310).

  Then, a motor control constant corresponding to the pattern having the smallest density fluctuation amount is set as a motor control constant at the time of image formation on the photosensitive drum 5 (S311).

  With the above operation, the setting of the motor control constant is completed (S312).

Example 4
In this embodiment, in the image forming apparatus as shown in FIGS. 5 and 7, the recording material S is transported to the transfer means 8 by the transport belt 23 of the second embodiment or the transport means 7 of the third embodiment. This is a case where the test pattern 12 is transferred onto the material S and the density signal is detected on the recording material S.

  Regarding the configuration, mechanism, shape and relative arrangement of the invention of this embodiment, the description common to the above embodiment will be omitted, and differences from the embodiment will be described. In the present embodiment, unlike the first embodiment, the density detection sensors 10R, 10L and the LED 15 are arranged on the recording material S at locations where a density signal can be detected.

[Motor control constant setting flowchart]
This will be described below as shown in the flowchart of FIG.

  First, the power of the image forming apparatus 1 is input (S401). Next, the execution determination unit 22 determines whether to adjust the motor control constant according to the state of the image forming apparatus 1 (S402).

  When the execution determination unit 22 determines not to change the electric motor control constant, the operation for determining the motor control constant ends (S412).

  On the other hand, when the execution determination unit 22 determines to change the electric motor control constant, the pattern generation unit 11 generates information on the test pattern 12 (S403).

  Next, the motor control constant setting unit 13 sets the motor speed control constant of the motor speed control unit 14 (S404). In step S404, a plurality of different motor control constants are sequentially set. More specifically, the motor control constant is sequentially changed in accordance with the timing of forming the next patch.

  Then, the motor speed control unit 14 controls the driving of the electric motor 4 by the motor control constant according to the setting of the motor control constant setting unit 13, and drives the photosensitive drum 5 by the electric motor 4 (S405).

  In step S405, in a state where a certain motor control constant is set, the image information of the test pattern 12 generated by the pattern generation unit 11 is sent to the exposure unit 3, and the electrostatic latent image of the test pattern 12 is transferred to the photosensitive drum. 5 is formed. Then, a visible image of the test pattern 12 is formed by a developing device (not shown) (S406).

  Note that the processing in step S405 and step S406 is executed for each of a plurality of different motor control constants set in step S104.

  On the other hand, the recording material S is conveyed to the transfer means 8 by the conveying means 7, and the test pattern 12 formed on the photosensitive drum 5 is transferred onto the recording material S (S407).

  When it is time to read the reflected light from the surface of the recording material S, the LED 15 is caused to emit light, and the reflected light from the recording material S is received by the density detection sensors 10R and 10L to detect the density signal of the test pattern 12 ( S408).

  The density fluctuation amount calculation unit 18 performs FFT analysis based on the detected density signal, and calculates the density fluctuation amount of one rotation cycle of the electric motor 4 (S409).

  The CPU 20 (density variation non-each unit 19) compares the density variation in one rotation cycle of the electric motor 4 corresponding to each motor control constant stored in the memory 21 (S410).

  Then, the motor control constant corresponding to the pattern with the smallest density fluctuation amount is set as the motor control constant at the time of image formation on the photosensitive drum 5 (S411).

  With the above operation, the setting of the motor control constant is completed (S412).

  Note that the length of the test pattern 12 in the sub-scanning direction is longer than the distance that the recording material S moves per rotation of the electric motor 4 in order to extract the density fluctuation amount in one rotation cycle of the electric motor 4. There is a need. This is the same in any of the above-described embodiments.

(Example 5)
In the present embodiment, as shown in the flowchart of FIG. 12, an operation for setting an independent electric motor control constant for each image forming process speed (image forming mode) will be described. Here, the image forming process speed corresponds to, for example, a reduction in the transport speed of the transport means, the transfer speed of the transfer means, and the fixing speed of the fixing device in thick paper printing. Since the switching of the image forming process speed itself is already well known, detailed description thereof is omitted.

  Regarding the configuration, mechanism, shape, and relative arrangement of the invention, the description common to the above-described embodiments is omitted, and different points will be described.

[Motor control constant setting flowchart]
First, the power source of the image forming apparatus 1 is input (S501).

  Next, the execution determination unit 22 determines whether to change the motor control constant according to the state of the image forming apparatus 1 (S502).

  When the execution determination unit 22 determines not to change the electric motor control constant, the operation for determining the motor control constant ends (S506).

  On the other hand, when the execution determination unit 22 determines to change the electric motor control constant, the motor control constant corresponding to the test pattern 12 having the smallest density fluctuation amount is printed as the normal print on the photosensitive drum 5 as in the first to fourth embodiments. The electric motor control constant at the time of image formation is set (S503). In step S503, for example, the processing in steps S103 to S110 described in FIG. 6 and the electric motor control constant setting processing during normal print image formation in another flowchart are performed. The image forming process speed is assumed to be performed by an image forming process switching unit (not shown).

  The control constant switching unit 26 of the motor speed control unit 14 repeats S503 for each image forming process speed in order to set an electric motor control constant for each image forming process speed (S504).

  Finally, motor control constants are set for each image forming process speed and electric motor 4 (S505).

  With the above operation, the setting of the motor control constant is completed (S506).

  By setting each electric motor control constant for each image forming process speed, it is possible to further suppress the amount of density fluctuation in one rotation cycle of the electric motor 4 that drives the photosensitive drum 5. The degree of density unevenness caused by one rotation cycle of the electric motor 4 depends not only on individual differences in mechanical accuracy of the electric motor 4 that drives the photosensitive drum 5, but also at what rotational speed the electric motor 4 is driven. I'm concerned. In the image forming apparatus, for example, in the case of printing on thick paper, the photosensitive drum may be rotated at a low speed and the image forming process speed may be controlled to be low. However, in this embodiment, such a case is also dealt with. May be.

(Example 6)
In the sixth embodiment, in the image forming apparatus shown in the first embodiment, an average value calculation is further performed on the density fluctuation amount of the test pattern 27 of the present embodiment, a gradation correction table is created, and image gradation control is performed. To obtain a stable image. In addition, as an average value calculation method here, you may use various average methods, such as a simple average and a weighted average.

  Regarding the configuration, mechanism, shape, and relative arrangement of the invention, the description common to the above-described embodiments is omitted, and different points will be described.

[Functional block diagram of image forming apparatus]
The configuration of this embodiment of the image forming apparatus is shown in FIG.

  Unlike the first embodiment, a density average value calculation unit 28, a density variation percentage calculation unit 29, and an image gradation control unit 30 are provided. The other configurations are the same as those in the first embodiment. Yes. The calculation by the density average value calculation unit 28 is to calculate the average value (DC component value) of the density signal obtained from the detected reflected light of the test pattern 27. Therefore, the calculation by the density fluctuation amount calculation unit 18 can be distinguished as the first calculation, and the calculation by the density average value calculation unit 28 can be distinguished as the second calculation.

  The density fluctuation percentage calculation unit 29 manages the normalization process and calculates the ratio of the density fluctuation amount of the electric motor 4 to the density signal average value. The image gradation control unit 30 is a part that performs conventionally known gradation input / output control, that is, density control.

[Test pattern formation]
A specific configuration of the test pattern 27 of this embodiment will be described with reference to FIG. The pattern 27 is for simultaneously performing control constant adjustment and image gradation control for each electric motor 4 that drives each photosensitive drum 5, and includes test patterns 27y (Y) and 27m (M) on the photosensitive drum 5. It is. Of course, the test pattern 27 is not limited to a test pattern including only yellow and magenta patches, as in FIG. 5 described above. Patches of the necessary colors can be included as appropriate.

  In order to detect the concentration fluctuation amount in one rotation cycle of the electric motor 4, for example, when the frequency of the motor rotation speed is 50 Hz, the sampling frequency for concentration detection needs to be 500 Hz or more from the sampling theorem, as in the first embodiment. is there. Further, the pattern length needs to be longer than the distance that the photosensitive drum 5 moves per rotation of the electric motor 4.

  In addition, since the motor control constant is set and the image gradation control is performed using the same pattern, a total of 36 patterns are obtained by changing the motor control constant and the density gradation degree (image printing rate) for each color in nine stages. It is formed. Here, the gradation (printing rate) of each of the Y and M test patterns 27y and 27m is set to 9 levels in steps of 10% from 10% to 90%. Also, C and K draw the same pattern.

  The density average value calculation unit 28 calculates a density average value signal of the detected test pattern 27 in order to perform image gradation control. The image gradation control unit 30 is for obtaining a gradation correction table in order to obtain target gradation characteristics when performing image gradation control, and will be described with reference to FIG.

  The test pattern 27 used in this embodiment performs image gradation control simultaneously with motor speed control. For this reason, since the gradation is different for each test pattern 27, even if the speed fluctuation of the photosensitive drum 5 is the same, the density fluctuation amount (magnitude) of one rotation cycle of the electric motor 4 obtained from the density detection sensor 10 is different. It becomes a thing.

  As described above, in this embodiment, the density fluctuation amount in one rotation cycle of the electric motor 4 corresponding to each motor control constant is not compared as it is. In the present embodiment, the ratio of the density fluctuation amount in one rotation cycle of the electric motor 4 with respect to the density average value signal as the detected density of each test pattern 27 is obtained (normalization is performed), and even if the gradation degree is different, the influence is exerted. Compare with the value you don't receive.

  The density fluctuation amount comparison unit 19 obtains the ratio of the density fluctuation amount of one rotation cycle of the electric motor 4 to the density average value signal obtained by the density average value calculation unit 28 for each motor control constant, and stores the memory in the CPU 20. 21 is stored. Then, the normalized values corresponding to each motor control constant are relatively compared, and the test pattern 27 having the smallest density variation amount is determined.

  The image gradation control unit 30 is for obtaining a gradation correction table in order to obtain target gradation characteristics when performing image gradation control, and will be described with reference to FIG. Although only Y gradation correction will be described here, correction is performed in the same way for M, C, and K.

  In FIG. 15, the horizontal axis indicates the gradation of the image information, and the vertical axis indicates the density signal itself of the density detector 17 or the density value obtained by converting the detection result by a specific density conversion method. Further, the ♦ marks in the figure are plots of the density signal of the test pattern 27 after the average value calculation is performed by the density average value calculation unit 28.

  A straight line T represents a density gradation characteristic which is a target of image density control. In this embodiment, the target density gradation characteristic T is determined so that the relationship between the image information and the density is proportional. A curve γ represents a density gradation characteristic in a state where image density control is not performed. It should be noted that the gradation density where the test pattern 27 is not formed is calculated by performing spline interpolation so as to pass through the origin and the asterisk.

  A curve D represents a gradation correction table calculated by this control. The curve D is calculated by obtaining a target point with respect to the target gradation characteristic T of the gradation characteristic γ before correction, and the gradation correction table D is used. Thus, the target gradation characteristic can be obtained.

  The algorithm of the present embodiment will be described with reference to the flowchart of FIG. The feature of this embodiment is that the same test pattern 27 is used to determine a motor control constant corresponding to the smallest density fluctuation amount and to execute image gradation control (density control).

[Motor control constant setting flowchart]
Hereinafter, description will be made according to the flowchart of FIG.

  First, the power of the image forming apparatus 1 is input (S601). Next, the execution determination unit 22 determines whether to adjust the motor control constant according to the state of the image forming apparatus 1 (S602).

  When the execution determination unit 22 determines not to change the electric motor control constant, the operation for determining the motor control constant ends (S612).

  If the execution determination unit 22 determines to change the electric motor control constant, the pattern generation unit 11 generates information on the test pattern 27 (S603).

  Next, the motor control constant setting unit 13 sets the motor control constant so that the electric motor control constant is changed for each gradation in the test pattern 27 (S604). For example, when a test pattern including patches of each gradation such as 100%, 90%... 10% at 10% intervals, different motor control constants are set for each gradation. It is done sequentially.

  Then, the motor speed control unit 14 controls the driving of the electric motor 4 by the motor control constant according to the setting of the motor control constant setting unit 13, and drives the photosensitive drum 5 by the electric motor 4 (S605).

  In step S605, the image information of the test pattern 12 generated by the pattern generation unit 11 is sent to the exposure unit 3 while a certain motor control constant is set. Then, an electrostatic latent image of the test pattern 27 is formed on the photosensitive drum 5, and a visible image of the test pattern 27 is formed by a developing device (not shown) (S606).

  Note that the processing in step S605 and step S606 is executed for each of a plurality of different motor control constants set in step S604.

  Wait until the timing at which the reflected light from the surface of the photosensitive drum 5 before the first test pattern 27 can be read. The reading timing of the density detection sensors 10R and 10L is calculated and controlled by the CPU 20 from the pattern formation timing. When it is time to read the reflected light from the surface of the photosensitive drum 5, the LED 15 is caused to emit light, and the reflected light from the photosensitive drum 5 is received by the density detection sensors 10R and 10L.

  The detected currents from the concentration detection sensors 10R and 10L are converted into voltages by IV conversion. The voltage is input to the CPU 20 shown in FIG.

  The photosensitive drum 5 is rotated by the electric motor 4 and the density signal of the test pattern 27 is detected (S607).

  The density fluctuation amount calculation unit 18 performs FFT analysis on the detected density signal, calculates the density fluctuation amount of one rotation period of the electric motor 4, and the density average value calculation unit 28 calculates the density average value signal ( DC component) is calculated (S608).

  The density fluctuation percentage calculation unit 29 obtains the ratio of the density fluctuation amount to the density average value signal of the test pattern 27 obtained by the density average value calculation unit 28. The CPU 20 stores the density variation ratio and compares the density gradation characteristic γ obtained by plotting the obtained density average value signal with the target density gradation characteristic T, and the image gradation control unit 30 compares the density gradation characteristic γ. A gradation correction table D is created and stored in the memory 21 of the CPU 20 (S609).

  The CPU 20 (density variation comparison unit 19) compares the density variation ratios of one rotation period of the electric motor 4 corresponding to the motor control constants stored in the memory 21 (S610). Then, the motor control constant corresponding to the test pattern 27 having the smallest density variation amount is set as the motor control constant at the time of image formation on the photosensitive drum 5 (S611).

  With the above operation, the setting of the motor control constant is completed (S612).

  As described above, in the sixth embodiment, the pattern 27 is drawn intermittently while changing the motor control constants and the gradation, the density signal is detected by the density detection sensors 10R and 10L, and the density average value of the test pattern 27 is obtained. The signal and the concentration fluctuation amount of one rotation cycle of the electric motor 4 are calculated.

  The motor control constant having the smallest density fluctuation in one rotation cycle of the electric motor 4 is obtained by relatively comparing the density fluctuation ratio in one rotation period of the electric motor 4 with respect to the density average value signal calculated from each test pattern 27. Can be determined.

  In this embodiment, the density fluctuation amount of one rotation cycle of the density electric motor 4 indicating the amount of density fluctuation is detected. However, the test pattern 27 detects the density itself of one rotation cycle of the electric motor 4. There may be.

  Even if the density itself of one rotation cycle of the electric motor 4 is detected by the test pattern 27, it can be carried out in the same manner as the case of detecting the density fluctuation amount.

  The length of the test pattern 27 in the sub-scanning direction is longer than the distance that the photosensitive drum 5 moves per rotation of the electric motor 4 in order to extract the density fluctuation amount of one rotation cycle of the electric motor 4. There is a need.

  In this embodiment, the density signal is detected by the density detection sensors 10R and 10L on the photosensitive drum 5 from the test pattern 27 formed on the photosensitive drum 5. However, the present invention is not limited to this. You may use the detection method of a density | concentration signal as shown to 1-4.

  Further, by performing the operation of setting the motor control constant of the electric motor 4 for each image forming process speed in the fifth embodiment, the image information is corrected by the gradation correction table D for each image forming process speed. The target gradation characteristics can be obtained.

  Further, a gradation correction table is created by comparing the density gradation characteristic γ not subjected to image gradation control obtained from the density average value signal of each pattern with the target density gradation characteristic T.

  In the above description, the density control is performed by correcting the gradation correction table D. Instead, the density control can be performed by correcting the developing bias, the charging bias, etc. It is possible to obtain a high-quality color image with reduced image quality.

  In the sixth embodiment, the average value is calculated for the density fluctuation amount of the test pattern 27, so that normalization is performed in order to make a comparison that is not affected by even different image gradation levels.

  More specifically, the density average value calculation unit 28 obtains the density average value signal of the test pattern 27, and the density fluctuation amount percentage calculation unit 29 obtains the ratio of the density fluctuation amount with respect to the density average value signal of the test pattern 27 and normalizes it. Do. Then, the optimum motor control constant of the electric motor 4 is set based on comparing the normalized values.

  However, the processing of the density average value calculation unit 28 for normalization can be replaced with filter processing such as using a low-pass filter. That is, a low-pass filter having a frequency characteristic that sufficiently attenuates density unevenness in one rotation cycle of the electric motor 4 can be applied.

  In addition, the test pattern 27 has a rectangular shape in this embodiment. However, any test pattern width can be used as long as the test pattern width in the sub-scanning and main scanning directions is larger than the spot diameter of the LED 15 and the density of the test pattern 27 can be detected. Such a shape may be used. Further, the test pattern 27 may be divided separately for different gradation levels.

  Further, in the example of FIG. 14, the test patterns 27 having different gradation levels are formed so as to be separated from each other. However, for example, one test is continuously performed like a gradation without leaving a gap between the test patterns 27. The test pattern 27 may be formed.

  Further, if the width of the test pattern 27 in the sub-scanning direction corresponds to a plurality of rotations of the electric motor 4, the following application examples can be considered. Specifically, the number of electric motor control constants assigned to the test pattern 27 is m, the first test pattern 27 is formed by changing the n electric motor control constants, and the next test pattern 27 is the remaining ( It may be formed by changing (mn) electric motor control constants. It will be apparent to those skilled in the art that the same effect can be obtained even if the electric motor control constant determination process is performed on the test pattern formed as described above.

  As described above, according to the sixth embodiment, the optimum control constant of the electric motor 4 can be determined together with the well-known image gradation control (image density control), and the electric motor control constant is determined. It is possible to eliminate the need only for calibration processing. That is, usability can be improved without making the down time of the image forming apparatus longer than necessary.

(Example 7)
In the first to sixth embodiments, the density fluctuation amount (density unevenness amplitude) in one rotation cycle of the electric motor 4 has been described. However, in order to extract the density component corresponding to one rotation cycle of the electric motor 4, this density fluctuation amount is used. It is not limited to. For example, the same effect can be obtained by obtaining an average value of density peak values generated in one rotation cycle of the electric motor 4 corresponding to a certain electric motor control constant, and replacing the peak average value with the first to sixth density fluctuation amounts. be able to.

  In this case, the process for obtaining the minimum value of the density fluctuation amount in the first to sixth can be a process for obtaining the minimum value of the peak average value. Further, the processing for obtaining the ratio of the density fluctuation amount of one rotation cycle of the electric motor 4 to the concentration average value signal in the embodiment 6 is processing for obtaining the ratio of the peak average value of one rotation cycle of the electric motor 4 to the concentration average value signal. Can be replaced.

  In other words, in the present invention, it is only necessary to be able to extract the influence of density unevenness in one rotation cycle of the electric motor 4, and in order to extract the density unevenness, various density components are used in various cases. Is applicable.

(Example 8)
In the first to seventh embodiments described above, the electric motor 4 for driving the photosensitive drum 5 has been described as an example of the electric motor. However, the present invention is not limited to the electric motor 4 for driving the photosensitive drum 5. For example, the present invention can be applied to an electric motor that drives the conveyance belt 23 and the intermediate transfer belt 25. Further, it can be applied to both the photosensitive drum 5 and the intermediate transfer belt 25.

  In this case, in addition to the processing of the first to seventh embodiments, an electric motor control constant for transferring the test pattern to the transport belt 23 and the intermediate transfer belt 25 may be set variably. As described above, the present invention is not limited to the photosensitive drum, and can be applied to various image carriers (first image carrier, second image carrier,...).

1 is a diagram illustrating an embodiment of a cross-sectional view of an image forming apparatus. 1 is a diagram illustrating an embodiment of a functional block diagram of an image forming apparatus. It is a figure which shows an example of a density | concentration detection sensor (optical characteristic detection sensor). It is a graph which shows an example of the relationship between a motor control constant and an image density fluctuation amount. It is a figure which shows an example of the formation mode of a test pattern. It is a flowchart of a motor control constant setting. 1 is a diagram illustrating an embodiment of a cross-sectional view of an image forming apparatus. It is a flowchart of a motor control constant setting. 1 is a diagram illustrating an embodiment of a cross-sectional view of an image forming apparatus. It is a flowchart of a motor control constant setting. It is a flowchart of a motor control constant setting. It is a flowchart of the motor control constant setting for every image formation process speed. 1 is a diagram illustrating an embodiment of a functional block diagram of an image forming apparatus. It is a figure which shows an example of the formation mode of a test pattern. It is a graph which shows the characteristic of a density and a gradation. It is a flowchart of a motor control constant setting.

DESCRIPTION OF SYMBOLS 4 Electric motor 5 Photosensitive drum 7 Conveying means 8 Transfer means 10 Density detection sensor 11 Pattern generation part 12 Test pattern 1
13 Motor control constant setting part 14 Motor speed control part 15 LED
16 IV Conversion Circuit 17 Density Detection Unit 18 Density Variation Calculation Unit 19 Density Variation Comparison Unit 20 CPU
21 Memory 22 Execution Judgment Unit 23 Conveyor Belt 25 Intermediate Transfer Belt 26 Control Constant Switching Unit 27 Test Pattern 2
28 Density Average Value Calculation Unit 29 Density Variation Percentage Calculation Unit 30 Image Density Control Unit

Claims (8)

An image carrier;
An electric motor for rotating or moving the image carrier;
Motor speed control means for controlling the speed of the electric motor based on an electric motor control constant;
A test pattern for setting a plurality of electric motor control constants and forming a test pattern on the image carrier that is rotated or moved by the electric motor driven by the motor speed control means based on each electric motor control constant Forming means;
Detecting means for detecting reflected light when the formed test pattern is irradiated with light;
Control constant setting means for setting an electric motor control constant for normal print image formation in the motor speed control means based on a fluctuation of one rotation period of the electric motor in reflected light detected for each electric motor control constant;
An image forming apparatus comprising:   Comparing means for comparing fluctuations of one rotation period of the electric motor of reflected light detected by the detecting means in correspondence with the electric motor control constants, the control constant setting means is a comparison of the comparing means 2. The image forming apparatus according to claim 1, wherein an electric motor control constant for forming the normal print image is set based on the result.   The detection unit detects reflected light from a test pattern on a photosensitive drum as the image carrier or reflected light from a test pattern transferred to a recording material. Image forming apparatus. Transfer means for transferring a visible image formed on the image carrier to a recording material;
A movable carrier that carries and conveys the recording material,
The image forming apparatus according to claim 1, wherein the detection unit detects a density of the test pattern transferred onto the movable carrier by the transfer unit. The image carrier is a first image carrier,
A first transfer means for transferring a visible image on the first image carrier to a second image carrier; a second transfer means for transferring the visible image transferred to the second image carrier to a recording material; Have
The image forming apparatus according to claim 1, wherein the detection unit detects reflected light from a test pattern transferred onto the second image carrier by the first transfer unit. A process speed switching means for switching an image forming process speed;
The image forming apparatus according to claim 1, wherein the control constant setting unit sets an electric motor control constant for each switched image forming process speed. The test pattern forming means has, as the test pattern, a plurality of different gradations on the image carrier that is rotated or moved by the electric motor driven by the motor speed control means based on each electric motor control constant. A test pattern including
7. The apparatus according to claim 1, further comprising density control means for performing image density control based on a detection result of the reflected light of the test pattern including the plurality of different gradations formed by the detection means. The image forming apparatus according to claim 1. Computation means for computing fluctuation of one rotation period of the electric motor based on the detection result by the detection means,
The detection means detects each detected reflected light corresponding to each of the plurality of gradations from the reflected light from the test pattern including the plurality of gradations,
The calculation means obtains a fluctuation of one rotation cycle of the electric motor of each detected reflected light,
Normalizing means for normalizing fluctuations of one rotation period of the electric motor of each reflected light by a DC component based on each detected reflected light;
8. The image forming apparatus according to claim 7, wherein the control constant setting unit sets an electric motor control constant for normal print image formation based on each variation after normalization by the normalization unit.

Images