JP6819060B2 - Image forming apparatus and its control method - Google Patents

Description

The present disclosure relates to an image forming apparatus and a control method thereof, and more particularly to an image forming apparatus and a method of controlling the transport speed of a recording medium.

Conventionally, an image forming apparatus such as an MFP (Multi-Functional Peripheral) forms an image on a recording medium such as paper. Some image forming devices include an image pickup device that captures an image of a transport path, and specifies the transport speed of a recording medium from an image captured by the image pickup device. For example, Japanese Patent Application Laid-Open No. 2010-134190 (Patent Document 1) provides a technique for specifying the transport speed of a recording medium by processing each of two or more images captured on a certain recording medium using a Fourier transform. It is disclosed.

Japanese Patent Application Laid-Open No. 2011-93242 (Patent Document 2), Japanese Patent Application Laid-Open No. 2011-95162 (Patent Document 3), and Japanese Patent Application Laid-Open No. 2011-96091 (Patent Document 4) describe a recording medium being transported. A technique for specifying a transport speed by pattern matching in captured images at at least two different timings is disclosed.

Of these, in the printer of Patent Document 2, the first image data is generated from the captured image at the first timing, and the second image data is generated from the captured image at the second timing after the first timing. Further, the third image data is generated from the captured image at the third timing after the first timing and after the second timing. The printer cuts out a template pattern from the first image data, obtains the moving state of the object by searching the area having a large correlation with the template pattern in the second image data, and further analyzes the third image data. Change the position to cut out the template pattern using the result.

The printer of Patent Document 3 analyzes the first image data and the second image data in the first image data from the timing when the first image data is acquired to the timing when the second image data is acquired. The movement amount and the movement direction for the template area are acquired, and the position for cutting out the template pattern is set based on the movement amount and the movement direction.

JP-A-2010-134190 Japanese Unexamined Patent Publication No. 2011-93242 Japanese Unexamined Patent Publication No. 2011-95162 Japanese Unexamined Patent Publication No. 2011-96091

In a printer such as Patent Document 1, in two or more captured images, a region other than the overlap region (a region corresponding to the same portion of the recording medium among the two or more captured images) acts as a disturbance in detecting the transport speed. obtain. By increasing the proportion of the overlap region in the analysis target, the detection accuracy of the transport speed can be improved.

The present disclosure has been conceived in view of such circumstances, and an object of the present disclosure is to improve the detection accuracy of the transport speed of a recording medium in an image forming apparatus.

According to a certain aspect of the present disclosure, an image of a transport unit for transporting a recording medium, a first timing, and an image of a transport path of the recording medium by the transport unit at a second timing different from the first timing. Based on the image pickup unit for generating the image, the storage unit for storing the information for specifying the transfer speed of the recording medium by the transfer unit, and the information stored in the storage unit, the captured image of the first timing and the first Ru comprising information processing unit configured to identify as an exclusion portions a portion corresponding to a region that does not correspond to the recording medium in the other one in one of the second timing captured image. The excluded portion is in an area where the recording medium is present at either the first timing and the second timing, but the recording medium is not present at either the first timing and the second timing. Correspond. The information processing unit uses a portion of the captured image of the first timing and the captured image of the second timing other than the excluded portion to determine the amount of movement of the recording medium between the first timing and the second timing. An image forming apparatus is provided that is configured to calculate.

Preferably, the information processing unit calculates the amount of movement by comparing the wave number components of the captured image of the first timing and the captured image of the second timing other than the excluded portion after the discrete Fourier transform. It is configured as follows.

Preferably, the information processing unit is further configured to specify the exclusion portion based on the size of the light receiving element in the imaging unit.

According to another aspect of the present disclosure, the image of the transport path of the recording medium by the transport unit at the transport unit for transporting the recording medium, the first timing, and the second timing different from the first timing. An image pickup unit for generating an image, a storage unit for storing information for specifying the transfer speed of the recording medium by the transfer unit, and an image captured image at the first timing and a first timing based on the information stored in the storage unit. The information processing unit is provided with an information processing unit configured to specify a portion corresponding to a region not corresponding to the recording medium in any one of the captured images at the second timing as an exclusion portion, and the information processing unit is the first. Of the captured image of the timing of and the captured image of the second timing, the portion other than the excluded portion is used to calculate the movement amount of the recording medium between the first timing and the second timing. An image forming apparatus is provided. The information stored in the storage unit is a speed fluctuation value associated with a target value of the transfer speed of the recording medium by the transfer unit, and a correction associated with at least one of the temperature, humidity, and types of the recording medium. Including the value, the information processing unit acquires the target value, and based on the speed fluctuation value associated with the acquired target value and the interval between the first timing and the second timing, the second with respect to the excluded portion. A correction value of 1 is calculated, and at least one of the temperature, humidity, and types of recording media is acquired, and the correction value stored in the storage unit is associated with the acquired value. The second correction value, which is the correction value, is acquired, and the excluded portion is corrected by using the first correction value and the second correction value.

Preferably, the information processing unit is configured to identify the exclusion portion when the temperature, humidity, and at least one of the types of recording media, or the target value, is changed. ..

Preferably, the first timing and the second timing are set so that the lower the target value, the longer the interval between the first timing and the second timing.

Preferably, the interval between the first timing and the second timing is the sampling period in the imaging unit.

According to still another aspect of the present disclosure, at the first timing and the second timing different from the first timing, the step of imaging the transport path for transporting the recording medium and the step of capturing the image in the storage unit are stored. was based on the information specifying the conveying speed of the recording medium, as a negative portion corresponding parts to parts that do not correspond to the recording medium in the other in one of the captured image and the second timing captured image of the first timing The exclusion portion comprises a step to identify, the recording medium was present at either the first timing and the second timing, but was recorded at either the first timing and the second timing. Recording between the first timing and the second timing by using a portion other than the exclusion portion in the captured image of the first timing and the captured image of the second timing corresponding to the region where the medium does not exist. A method of controlling an image forming apparatus is provided, which comprises a step of calculating the amount of movement of the medium.
According to another aspect of the present disclosure, at the first timing and the second timing different from the first timing, the step of imaging the transport path for transporting the recording medium and the step of capturing the image in the storage unit are stored. Based on the information that specifies the transport speed of the recording medium, the portion corresponding to the portion of either the captured image at the first timing or the captured image at the second timing that does not correspond to the recording medium is specified as the excluded portion. The amount of movement of the recording medium between the first timing and the second timing is calculated by using the step to be performed and the portion other than the exclusion portion in the captured image of the first timing and the captured image of the second timing. The information includes a speed variation value associated with a target value of the transport speed of the recording medium and a correction value associated with temperature, humidity, and at least one of the types of recording media. , The step of identifying the exclusion part is based on the acquisition of the target value, the speed fluctuation value associated with the acquired target value, and the interval between the first timing and the second timing. Calculating the first correction value, acquiring at least one of the temperature, humidity, and types of recording media, and associating with the acquired value among the correction values contained in the information. A control method of an image forming apparatus including acquiring a second correction value, which is a correction value, and correcting an excluded portion using a first correction value and a second correction value. Provided.

According to the present disclosure, the image forming apparatus uses a portion of the captured image of the first timing and the captured image of the second timing other than the excluded portion, and is between the first timing and the second timing. Calculate the amount of movement of the recording medium.

It is a figure which shows the appearance of the image forming apparatus 1 which is one Embodiment of the image forming apparatus of this disclosure. It is a figure which shows typically the internal structure of the image forming apparatus 1. It is a figure which shows the hardware composition of the image forming apparatus 1. It is a figure which shows the structure of the movement amount detection part 800. It is a figure for demonstrating the irradiation and detection of a laser beam to the surface of a recording paper P2. It is a figure which shows the specific example of the structure of the signal processing unit 808. It is a figure which shows typically the part excluded from the processing target in the captured image. It is a figure which shows typically the part excluded from the processing target in the captured image. It is a figure which shows the fluctuation amount of the transport speed assumed for each of two kinds of transport speeds of the recording paper P2 in the image forming apparatus 1. It is a figure for demonstrating the change of the end part of the detection target area on the rear end side of a moving direction. 6 is a flowchart of processing executed for controlling the transport speed of the recording paper P2 in the image forming apparatus 1. It is a flowchart of the modification of the process of FIG. It is a figure for demonstrating the modification (4). It is a flowchart of another modification of the process of FIG.

Hereinafter, embodiments of the image forming apparatus will be described with reference to the drawings. In the following description, the same parts and components are designated by the same reference numerals. Their names and functions are the same. Therefore, these explanations will not be repeated.

<1. Schematic configuration of image forming apparatus>
FIG. 1 is a diagram showing the appearance of the image forming apparatus 1 which is an embodiment of the image forming apparatus of the present disclosure. FIG. 2 is a diagram schematically showing an internal configuration of the image forming apparatus 1.

As shown in FIGS. 1 and 2, the image forming apparatus 1 includes an image reading unit 3 for reading an image from the original P1 and a paper feed tray 4 for accommodating a recording paper (recording medium) P2 on which an image is formed. The transfer unit 5 that transfers the toner image to the recording paper P2 fed from the paper feed tray 4, the fixing unit 6 that fixes the toner image transferred by the transfer unit 5 to the recording paper P2, and the fixing unit 6 fix the toner image. It includes a paper ejection tray 7 from which the recording paper P2 on which the image is formed is ejected, and an operation panel 9 for receiving an operation on the image forming apparatus 1. In the apparatus main body 2 of the image forming apparatus 1, an image reading unit 3 is provided at the upper part, and a transfer unit 5 is provided at the lower part.

In the image forming apparatus 1, a paper ejection tray 7 is provided on the upper side of the transfer unit 5 in order to receive the recording paper P2 on which the image is recorded and ejected by the transfer unit 5 and the fixing unit 6. The paper feed tray 4 is provided below the transfer unit 5. The paper feed tray 4 can be inserted and removed from the device main body 2. In the image forming apparatus 1, the recording paper P2 stored in the paper feed tray 4 is fed into the apparatus main body 2. By being conveyed upward, the recording paper P2 is sent to the transfer unit 5 arranged at the upper part of the paper feed tray 4, and the image is transferred by the transfer unit 5. The fixing unit 6 fixes the image transferred to the recording paper P2. The recording paper P2 is processed by the fixing unit 6 and then discharged to the paper ejection tray 7. The output tray 7 is provided in a space (recessed space) between the image reading unit 3 and the transfer unit 5.

The image reading unit 3 is provided at the scanner unit 31 that reads the image from the document P1 and the automatic document feeding unit (ADF: Auto Document Feeder) that is provided above the scanner unit 31 and conveys the document P1 to the scanner unit 31 one by one. 32 and is included. An operation panel 9 is provided on the front side (front side) of the apparatus main body 2. By operating the keys while looking at the display screen of the operation panel 9, the user sets the function selected from the various functions of the image forming apparatus 1 or instructs the image forming apparatus 1 to execute the work. You can do it.

The internal structure of the apparatus main body 2 will be described with reference to FIG. The scanner unit 31 of the image reading unit 3 uses the document base 33 having platen glass (not shown) on the upper surface side, the light source unit 34 that irradiates the document P1 with light, and the reflected light from the document P1 as image data. It includes an image sensor 35 that performs photoelectric conversion, an imaging lens 36 that forms an image of reflected light on the image sensor 35, and a mirror group 37 that sequentially reflects the reflected light from the document P1 and causes it to enter the imaging lens 36. The light source unit 34, the image sensor 35, the imaging lens 36, and the mirror group 37 are provided inside the platen 33. The light source unit 34 and the mirror group 37 are configured to be movable in the left-right direction with respect to the platen 33.

An ADF 32 is provided on the upper surface side of the scanner unit 31. The ADF 32 can be opened and closed with respect to the document base 33, and includes a document loading tray 38 and a document ejection tray 39. The ADF 32 can bring the original P1 into close contact with the platen glass (not shown) by covering the original P1 on the platen glass (not shown) of the platen 33.

When the image reading unit 3 reads the document P1 on the platen glass (not shown) of the document table 33, the light source unit 34 moving to the right (secondary scanning direction) irradiates the document P1 with light. The reflected light reflected from the document P1 is sequentially reflected by the mirror group 37 moving to the right like the light source unit 34, incident on the imaging lens 36, and imaged on the image sensor 35. The image sensor 35 executes photoelectric conversion for each pixel according to the intensity of the incident light to generate an image signal (RGB signal) corresponding to the image of the original P1.

On the other hand, when the image sensor 35 reads the document P1 placed on the document loading tray 38, the document P1 is transported to the reading position by the document transport mechanism 40 composed of a plurality of rollers and the like. The light source unit 34 and the mirror group 37 of the scanner unit 31 are fixed at predetermined positions inside the platen 33. The light source unit 34 irradiates the reading position portion of the document P1 with light, and the reflected light is imaged on the image sensor 35 via the mirror group 37 of the scanner unit 31 and the imaging lens 36. After that, the image sensor 35 converts the reflected light into an image signal (RGB signal) corresponding to the image of the document P1. After that, the document P1 is ejected to the document ejection tray 39.

The transfer unit 5 that transfers the toner image to the recording paper P2 includes an image forming unit 51 that generates toner images of each color of Y (Yellow), M (Magenta), C (Cyan), and K (Key tone), and an image forming unit. An exposure section 52 provided below each of the 51, an intermediate transfer belt 53 for transferring a toner image of each color from the image forming section 51 by abutting against the image forming section 51 of each color arranged in the horizontal direction, and an image drawing. A primary transfer roller 54 provided at a position facing upward with respect to each of the image forming portions 51 of each color so as to sandwich the portion 51 and the intermediate transfer belt 53, and a drive roller 55 for rotating the intermediate transfer belt 53. A driven roller 56 that rotates by transmitting the rotation of the drive roller 55 through the intermediate transfer belt 53, a secondary transfer roller 57 installed at a position facing the drive roller 55 across the intermediate transfer belt 53, and an intermediate transfer belt. A cleaner portion 58 installed at a position facing the driven roller 56 with the 53 in between is included.

The image forming unit 51 uses a photoconductor drum 61 that comes into contact with the outer peripheral surface of the intermediate transfer belt 53, a charger 62 that charges the outer peripheral surface of the photoconductor drum 61 by corona discharge, and a toner charged by stirring. It includes a developing device 63 that adheres to the outer peripheral surface of the drum 61, and a cleaner unit 64 that removes the toner remaining on the outer peripheral surface of the photoconductor drum 61 after transferring the toner image to the intermediate transfer belt 53. At this time, the photoconductor drum 61 is installed at a position facing the primary transfer roller 54 with the intermediate transfer belt 53 interposed therebetween, and rotates in the clockwise direction in FIG. A primary transfer roller 54, a cleaner unit 64, a charger 62, and a developing device 63 are arranged in order around the photoconductor drum 61 along the rotation direction of the photoconductor drum 61.

The intermediate transfer belt 53 is composed of, for example, a conductive endless belt member. The intermediate transfer belt 53 is wound around the drive roller 55 and the driven roller 56 without any looseness, so that the intermediate transfer belt 53 rotates in the counterclockwise direction of FIG. 2 according to the rotation of the drive roller 55. Around the intermediate transfer belt 53, a secondary transfer roller 57, a cleaner portion 58, and an image forming portion 51 of each color of YMCK are arranged in order along the rotation direction of the intermediate transfer belt 53.

The fixing unit 6 fixes the toner image transferred to the recording paper P2. The fixing unit 6 includes a heating roller 59 provided with a halogen lamp or the like that heats the toner image on the recording paper P2, and a pressure roller that presses the recording paper P2 by sandwiching the recording paper P2 together with the heating roller 59. Includes 60 and. The heating roller 59 may heat the surface of the heating roller 59 by generating an eddy current on the surface thereof by electromagnetic induction.

The transport device for transporting the recording paper P2 further feeds the recording paper P2 stored in the paper feed tray 4 from the uppermost layer to the paper feed path R1 and the fed recording paper P2 to the paper feed path R1. The paper feed roller pair 82, the transport roller pair 83 that vertically transports the recording paper P2 fed by the paper feed roller pair 82 on the main transport path R0, and the transport roller pair 83 on the main transport path R0 are arranged on the downstream side of the transport roller pair 83. A timing roller pair 84 for transporting the recording paper P2 toward the transfer unit 5 is included. The main transport path R0 is the main transport path of the recording paper P2 in the process of image formation (printing). The paper feed path R1 is provided for each paper feed tray 4. Each paper feed path R1 joins the main transport path R0. The paper feed path R1 is an example of a transport path.

The recording paper P2 in each paper feed tray 4 is fed one by one from the top layer to the paper feed path R1 by the rotational drive of the corresponding feeding roller 81, and then is fed to the paper feed path R1 by the paper feed roller pair 82 to the main transport path. It is sent out toward R0. In the main transport path R0, the recording paper P2 conveyed from the paper feed roller pair 82 is conveyed toward the timing roller pair 84 arranged in front of the transfer unit 5 by the rotational drive of the transfer roller pair 83. In order for the timing roller pair 84 to normally transfer the toner image to the recording paper P2 at the transfer unit 5, the timing roller pair 84 conveys the recording paper P2 to the transfer unit 5 in synchronization with the formation timing of the toner image at the transfer unit 5. That is, when the recording paper is conveyed to the timing roller vs. 84 by the conveying roller pair 83, the recording paper P2 is loosened to form a loop by stopping the timing roller pair 84, and the paper skew is corrected by the loop. Is conveyed to the secondary transfer roller 57.

In the main transport path R0, a transport sensor (movement amount detection unit) 85 for detecting the recording paper P2 vertically transported by the transport roller pair 83 is installed above the transport roller pair 83 (downstream side in the transport direction). To. Below the timing roller vs. 84 (upstream in the transport direction), a pre-timing sensor (recording paper detection unit) 86 for detecting the tip of the recording paper P2 that has reached the front of the timing roller vs. 84 is installed. Paper transport and loop control in the main transport path R0 are executed based on the detection signals of the transport sensor 85 and the pre-timing sensor 86, respectively.

A paper ejection roller pair 91 that discharges the printed recording paper P2 is arranged at the terminal portion that is the most downstream of the main transport path R0. The printed recording paper P2 is ejected to the output tray 7 by the rotational drive of the output roller pair 91. In the main transport path R0, a paper discharge sensor 90 that detects the rear end of the recording paper P2 is arranged below the paper discharge roller pair 91 (upstream side in the transport direction). As a result, it can be confirmed that the recording paper P2 is normally ejected from the paper ejection roller pair 91 to the paper ejection tray 7 by detecting the rear end of the recording paper P2 by the paper ejection sensor 90.

<2. Hardware configuration of image forming device>
FIG. 3 is a diagram showing a hardware configuration of the image forming apparatus 1. The image forming apparatus 1 includes a main body control unit 10 having the configuration shown in FIG. The main body control unit 10 controls each unit constituting the image forming apparatus 1. As a result, various operations in the image forming apparatus 1 (printing operation on the recording paper P2, image reading operation from the document P1, etc.) are executed.

The main body control unit 10 includes a CPU (Central Processing Unit) 101 that executes various arithmetic processes and controls, a ROM (Read Only Memory) 102 that stores control programs, and a RAM (Random Access) that temporarily stores arithmetic data. Memory) 103, an image processing unit 104 that generates image data that is the basis of the toner image formed by the transfer unit 5, an image memory 105 that temporarily stores the image data obtained by the image processing unit 104, and an image. It includes an input / output interface 106 for transmitting and receiving signals to and from each unit constituting the forming device 1, and a serial interface 107.

Upon receiving the signal corresponding to the operation received by the operation panel 9, the CPU 101 identifies the operation corresponding to the operation received by the operation panel 9. Similarly, when the main body control unit 10 receives a signal transmitted from an external terminal or the like via a communication network 110 such as a LAN (Local Area Network) by the input / output interface 106, the main body control unit 10 identifies an operation specified by the external terminal. To do. As a result, the CPU 101 reads a control program based on the designated operation from the ROM 102 via the operation panel 9 or the external terminal, and the CPU 101 operates based on the control program.

The CPU 101 drives and controls each of the image reading unit 3, the exposure unit 52, the transfer unit 5, the fixing unit 6, and the paper feeding device 8 based on the control program read from the ROM 102, and the image reading control unit 113 and the exposure control unit 114. , A signal is output to each of the transfer control unit 115, the fixing control unit 116, and the transfer control unit 118. Therefore, the image forming apparatus 1 receives signals from the main body control unit 10 to the image reading control unit 113, the transfer control unit 115, and the fixing control unit 116, respectively, so that the image reading unit 1 responds to the designated operation. 3. Drive each of the exposure unit 52, the transfer unit 5, and the fixing unit 6. When a signal is given from the main body control unit 10 to the transfer control unit 118, the image forming apparatus 1 rotationally drives the feeding roller 81 and the roller pairs 82 to 84, 90 in the transfer device.

The image forming apparatus 1 further includes a movement amount detection unit 800 for detecting the movement amount (or transfer speed) of the recording paper. The CPU 101 is connected to the movement amount detection unit 800 via the serial interface 107. The detailed configuration of the movement amount detection unit 800 will be described later with reference to FIG.
<3. Printing operation of image forming apparatus>
Next, the printing operation by the image forming apparatus 1 will be described below. When the image forming apparatus 1 receives an instruction from the operation panel 9 or an external terminal to perform a printing operation, the CPU 101 reads a control program for the printing operation from the ROM 102 in the main body control unit 10 for the printing operation. Start the control operation of. First, the CPU 101 drives and controls the transport device through the transport control unit 118 to feed out the top-layer recording paper P2 from the paper feed tray 4 and send it to the main transport path R0.

The CPU 101 gives a control signal to the exposure control unit 114 and the transfer control unit 115 in order to transfer the toner image to the recording paper P2 sent to the main transport path R1, and drives and controls the exposure unit 52 and the transfer unit 5. At this time, the CPU 101 gives the image signal read from the document P1 by the image reading unit 3 through the image reading control unit 113 or the image signal received from the external terminal through the input / output interface 106 to the image processing unit 103.

As a result, the image processing unit 103 generates image data for forming toner images of Y, M, C, and K colors based on the given image signal, and stores the image data in the image memory 105. The image data of each color of Y, M, C, and K stored in the image memory 105 is read out from the CPU 101 and given to the exposure control unit 114. Therefore, the exposure control unit 114 drives a light emitting element (not shown) in the exposure unit 52 based on the image data of each color of Y, M, C, and K, thereby sensitizing each color of Y, M, C, and K. An electrostatic latent image is formed on the body drum 61. That is, since the transfer control unit 115 drives the transfer unit 5, laser light is emitted from the exposure unit 52 on the surface of the photoconductor drum 61 charged by the charger 62 in the image forming unit 51 of each of the Y, M, C, and K colors. Is irradiated, and an electrostatic latent image corresponding to each color of Y, M, C, and K is formed.

The toner charged by the developing device 63 is transferred to the surface of the photoconductor drum 61 on which the electrostatic latent image is formed, and a toner image is formed on the photoconductor drum 61 serving as the first image carrier. Then, when the toner image carried on the surface of the photoconductor drum 61 comes into contact with the intermediate transfer belt 53, it is transferred to the intermediate transfer belt 53 by the electrostatic force of the primary transfer roller 54, so that the second image carrier A toner image in which Y, M, C, and K colors are superimposed is formed on the surface of the intermediate transfer belt 53. On the other hand, the untransferred toner remaining on the photoconductor drum 61 on which the toner image is transferred to the intermediate transfer belt 53 is scraped off by the cleaner unit 64 and removed from the photoconductor drum 61.

When the tip of the recording paper P2 conveyed to the main transport path R0 is detected by the pre-timing sensor 86, the detection result is given to the transfer control unit 115, so that the recording paper P2 reaches the timing roller pair 84. The transfer control unit 115 recognizes that. The transfer control unit 115 operates the timing roller pair 84 in accordance with the timing at which the toner image is transferred to the intermediate transfer belt 53. At this time, the toner image transferred to the intermediate transfer belt 53 moves to the transfer position where the intermediate transfer belt 53 abuts on the secondary transfer roller 57 by rotating the intermediate transfer belt 53 by the driving roller 55 and the driven roller 56, and the main transfer path. It is transferred to the recording paper P2 which is conveyed to the transfer position on R0. The untransferred toner remaining on the intermediate transfer belt 53 on which the toner image is transferred to the recording paper P2 is scraped off by the cleaner unit 58 and removed from the intermediate transfer belt 53.

The recording paper P2 on which the toner image is transferred at the contact position with the secondary transfer roller 57 is conveyed to the fixing portion 6 by the heating roller 59 and the pressure roller 60. At this time, the CPU 101 drives and controls the fixing unit 6 through the fixing control unit 116 in order to fix the toner image on the recording paper P2 conveyed to the fixing unit 6 (STEP123). That is, the fixing control unit 116 controls the rotational operation of the heating roller 59 and the pressure roller 60, and at the same time controls the heating operation of the heating roller 59.

As a result, the recording paper P2 on which the unfixed toner image is placed is heated by the heating roller 59 and pressed by the pressurizing roller 60 when passing through the fixing nip portion of the fixing portion 6, and the unfixed toner image is applied. Is fixed on the paper. Then, when the recording paper P2 after fixing the toner image (after single-sided printing) is conveyed to the paper ejection roller pair 91, it is ejected to the paper ejection tray 7 by the paper ejection roller pair 91. At this time, the paper ejection sensor 90 detects the rear end of the recording paper P2, and the detection result is given to the main body control unit 10. As a result, the main body control unit 10 confirms that the recording paper P2 has been normally ejected to the output tray 7.

<4. Configuration of movement amount detection unit>
As shown in FIG. 3, the image forming apparatus 1 further includes a movement amount detection unit 800 for detecting the transfer speed and the like of the recording paper P2 in the transfer path. The CPU 101 of the main body control unit 10 specifies a transport mode such as a transport speed based on the detection output of the movement amount detection unit 800, and controls the transport mode by the transport control unit 118 based on the specified mode. FIG. 4 is a diagram showing the configuration of the movement amount detection unit 800.

As shown in FIG. 4, the movement amount detection unit 800 includes a light emitting unit 801 that irradiates the recording paper P2 with light, and a light receiving unit 802 that photoelectrically converts the reflected light from the recording paper P2 into an electric signal. .. The movement amount detection unit 800 includes a control unit 810 for controlling the operation of the light emitting unit 801. The control unit 810 receives the electric signal output from the light receiving unit 802 and outputs it to the CPU 101. The CPU 101 can detect the transport speed of the recording paper P2 and the like by processing the signal input from the light receiving unit 802. The sampling period in the light receiving unit 802 is, for example, 1 ms.

The light emitting unit 801 is installed at a predetermined distance (for example, 5 to 10 mm) and a predetermined angle from the recording paper P2 in the transport path, and irradiates the recording paper P2 with the light from the built-in light source 803 via the lens 804. To do. The light receiving unit 802 is arranged at a predetermined distance (example: 7 to 12 mm) from the recording paper P2 in the transport path so that the built-in image sensor 805 is substantially parallel to the recording paper P2. The arranged light is received by the image sensor 805 via the lens 806 from the surface of the recording paper P2.

FIG. 5 is a diagram for explaining irradiation and detection of laser light on the surface of the recording paper P2. On the surface of the recording paper P2, a region to be an image formed by the image sensor 805 of the light receiving unit 802 is formed inside the region irradiated with the light from the light emitting unit 801.

The light source 803 irradiates the recording paper P2 with a laser beam having an angle θ2 (for example, 45 °) with respect to the surface of the recording paper P2. The image sensor 805 receives reflected light at an angle θ1 (for example, 90 °) from the surface of the recording paper P2 with respect to the surface of the recording paper P2. The image sensor is realized by, for example, a two-dimensional sensor, but may be realized by another type of image sensor such as a one-dimensional sensor.

When the movement amount detection unit 800 is realized by an LED sensor, the light emitting unit 801 incorporates a light emitting diode (LED) as a light source 803, and the light receiving unit 802 receives a light / dark pattern due to unevenness on the surface of the recording paper P2. .. In the light receiving unit 802, a light / dark pattern is formed on the surface of the image sensor 805 via the lens 806. The image sensor 805 outputs an electric signal (image signal) based on the imaged light / dark pattern as a detection signal. The light-dark pattern is formed not only by the characters or patterns drawn on the surface of the recording paper P2, but also by the unevenness of the surface, the pattern of the paper fibers, the unevenness of the paper, etc., which are also present in ordinary white paper.

The image sensor 805 is configured by arranging pixels provided with photoelectric conversion elements in a matrix. The detection cycle is set to, for example, 100 μs. The detection cycle of the image sensor 805 can be appropriately changed according to the type of paper and the like, and can be changed up to, for example, about 80 μsec. The number of pixels of the image sensor 805 is, for example, 900 pixels (30 × 30: 1 pixel = 1/800 inch). The arrangement of the optical conversion elements in the image sensor 805 does not have to be in a matrix shape, and may be a rectangular arrangement such as “30 × 120”.

The reflected light from the recording paper P2 can be classified into a specular reflection component and a scattered reflection component. From this, the irradiation direction of the light by the light emitting unit 801 to the recording paper P2 is inclined by the incident angle θ2 with respect to the normal direction of the recording paper P2, and the light receiving direction by the light receiving unit 802 is the normal direction of the recording paper P2. By matching to, the light receiving unit 802 can receive the scattered reflection component.

The control unit 810 includes an AD (Analogue Digital) converter 807 and a signal processing unit 808. The AD converter 807 is realized, for example, by the processor executing a predetermined program. The signal processing unit 808 is realized, for example, by the processor executing a predetermined program. The AD converter 807 converts the analog signal generated by the photoelectric conversion by the image sensor into a digital signal. The signal processing unit 808 calculates the moving distance of the recording paper P2 by processing the digital signal generated by the AD converter 807 for the images of the recording paper P2 captured at different timings.

FIG. 6 is a diagram showing a specific example of the configuration of the signal processing unit 808. As shown in FIG. 6, the signal processing unit 808 decomposes the digital signal generated by the AD converter 807 into each wave number component by the discrete Fourier transform unit 808A, for example. After that, the signal processing unit 808 is a standardization processing unit 808B, and each wave number component is standardized. After that, the signal processing unit 808 uses the phase difference calculation module 808C to perform a predetermined calculation on the waveform of the wave number component after normalization, so that the position of the image captured before the movement and the image captured after the movement are performed. Derivation of phase difference. After that, the signal processing unit 808 calculates the moving distance of the recording paper P2 by converting the derived phase difference into real space data by the inverse Fourier transform in the inverse Fourier transform module 808D.

In the signal processing unit 808, each of the discrete Fourier transform unit 808A, the standardization processing unit 808B, the phase difference calculation module 808C, and the inverse Fourier transform module 808D may be realized by a dedicated circuit or by a program module. May be done.

<5. Target of image processing in detecting the amount of movement>
In the image forming apparatus 1, the signal processing unit 808 detects the movement amount of the recording paper P2 by processing the data of two or more images captured at different timings of the recording paper P2. The signal processing unit 808 excludes a part of two or more captured images from the processing target according to a predetermined condition. 7 and 8 are diagrams schematically showing a portion of the captured image that is excluded from the processing target. In the example shown in FIG. 7, the movement amount of the recording paper P2 is detected from the two captured images of the recording paper P2.

In FIG. 7, the portion of the first captured image corresponding to the recording paper P2 is shown as the image ST1. The portion of the second captured image corresponding to the recording paper P2 is shown as the image ST2. The second captured image is taken after the first captured image. Further, in FIG. 7, the moving direction of the recording paper P2 (the transporting direction of the recording paper P2) is shown as an arrow D1. The recording paper P2 when the image ST2 is captured moves along the direction indicated by the arrow D1 by being conveyed by the conveying device. Correspondingly, the image ST2 is moving with respect to the image ST1 along the direction indicated by the arrow D1.

In FIG. 7, lines L1, L2, and L3 indicate three positions in the direction indicated by arrow D1. The line L1 indicates the position of the tip of the image ST1. The line L2 indicates the position of the rear end of the image ST2. The line L3 indicates the position of the rear end of the image ST1.

The hatched region AR1 in FIG. 7 is located on the side opposite to the direction indicated by the arrow D1 from the rear end of the image ST2. In the region AR1, the recording paper P2 was present at the time when the first captured image was taken in the captured image, but the recording paper P2 was not present at the time when the second captured image was taken. Corresponds to the area.

Further, in FIG. 7, at a position ahead of the line L1 in the moving direction, the recording paper P2 is present at the time when the second captured image is taken in the captured image, but the first image is captured. It corresponds to the area where the recording paper P2 does not exist at the time when the image is taken.

Therefore, in order to calculate the movement amount of the recording paper P2, the signal processing unit 808 displays the image data in the range shown as the “detection target area” in FIG. 7 in each of the image ST1 and the image ST2, such as FIG. Perform the process described with reference to. The “detection target area” represents a range from the line L2 to the line L1.

The region excluded in the calculation of the movement amount will be described in more detail with reference to FIG. In FIG. 8, the image ST2 of FIG. 7 is shown by a solid line, and the image ST1 of FIG. 7 is shown by a broken line. The line LX1 and the line LX2 are the positions of the ends of the image ST1 which are assumed by the shaking assumed at the conveying speed of the recording paper P2.

FIG. 9 is a diagram showing a fluctuation amount of the transport speed assumed for each of the two types of transport speeds of the recording paper P2 in the image forming apparatus 1. In FIG. 9, the target speed V1 is an example of the set value of the transport speed in the image forming apparatus 1. The target speed V2 is another example of the set value of the transport speed in the image forming apparatus 1.

The horizontal axis of the graph of FIG. 9 indicates the time T. In the graph of FIG. 9, an example of the time change of the actual transport speed under the target speed V1 is shown by the line LV1. The speed fluctuation Vd1 represents the amount of fluctuation of the actual speed at the target speed V1. Further, in the graph of FIG. 9, an example of the time change of the actual transfer speed under the target speed V2 is shown by the line LV2. The speed fluctuation Vd2 represents the actual speed fluctuation amount at the target speed V2.

In the transfer device of the image forming apparatus 1, the speed at which the recording paper P2 is actually conveyed, as indicated by the lines LV1 and LV2, varies according to the change in time. The value of the speed fluctuation Vd1 is larger than the value of the speed fluctuation Vd1. That is, the amount of fluctuation in the transport speed increases as the set value of the transport speed increases.

Returning to FIG. 8, considering the fluctuation of the transport speed, the position of the captured image that is supposed to correspond to the recording paper P2 may fluctuate. Lines LX1 and LX2 in FIG. 8 represent the position of the tip of the image ST1 according to the fluctuation of the transport speed. The line LX1 indicates the position of the tip when the transport speed reaches the maximum within the expected range. The line LX2 indicates the position of the tip when the transport speed is minimized within the expected range.

The signal processing unit 808 may specify the detection target region in consideration of the fluctuation of the transport speed. That is, first, as described with reference to FIG. 7, the signal processing unit 808 uses recording paper for both the first image and the second image based on the set value of the transport speed. The area where P2 is expected to be included is specified as the detection target area. After that, as described with reference to FIGS. 8 and 9, the signal processing unit 808 sets the detection target region with fluctuation amounts (speed fluctuations Vd1 and Vd2 in FIG. 9) corresponding to the set value of the transport speed. Use to correct. As a result, the end portion of the detection target region is changed from the line L1 to the line LX1 on the tip side in the moving direction. The distance between the line LX1 and the line L1 is determined by, for example, the following equation (1) using the fluctuation amount Vd associated with the transport speed and the length Td of the time from the first timing to the second timing. It is calculated according to.

[Distance between line LX1 and line L1] = (Vd × Td) ÷ 2 ... (1)
Similarly, on the rear end side in the moving direction, the end of the detection target area can also be changed according to the amount of variation associated with the transport speed. FIG. 10 is a diagram for explaining a change in the end portion of the detection target region on the rear end side in the moving direction.

As shown in FIG. 10, the end of the detection target region on the rear end side indicated by the line L2 can fluctuate from the line LY1 to the line LY2. The signal processing unit 808 can change the end of the detection target region to the line LY2 on the rear end side in the moving direction. The distance between the line L2 and the line LY2 is determined by, for example, the following equation (2) using the fluctuation amount Vd associated with the transport speed and the length Td of the time from the first timing to the second timing. It is calculated according to.

[Distance between line L2 and line LY2] = (Vd × Td) ÷ 2 ... (2)
The signal processing unit 808 may include a memory. The amount of variation associated with the transport speed may be stored in the memory. The memory may store two or more types of fluctuation amounts associated with each of the two or more types of transport speeds.

As described with reference to FIG. 9, the amount of variation can change in response to changes in the target speed of the transport speed. Therefore, the correction amount at the end of the detection target region may change depending on the transport speed.

As described above, the signal processing unit 808 excludes a region other than the region specified as the detection target region from the processing target in the processing of the captured image (FIG. 6 and the like). As a result, the area that is likely not to correspond to the recording paper P2 is excluded from the processing target. Therefore, the processing speed of the signal processing unit 808 can be improved, and the detection accuracy of the movement amount can be improved.

<6. Process flow>
FIG. 11 is a flowchart of processing executed for controlling the transport speed of the recording paper P2 in the image forming apparatus 1. The flowchart is realized, for example, by the control unit 810, the signal processing unit 808, and the CPU 101 executing a given program. The control by the control unit 810 and the control by the signal processing unit 808 in the following description may be executed by the same processor or may be executed by different processors.

With reference to FIG. 11, in step S10, the control unit 810 identifies the image forming mode designated by the image forming apparatus 1, thereby acquiring the system speed (set value of the conveying speed, etc.). The image formation mode is specified, for example, by inputting to the operation panel 9. After that, the control proceeds to step S20.

In step S20, the control unit 810 specifies the detection target area (FIG. 7, etc.) of the Nth captured image and the N + 1st captured image from the set speed (set value of the transport speed) and the planned speed fluctuation amount. .. After that, the control proceeds to step S30.

In step S30, the CPU 101 executes a printing operation (image forming operation) by driving the transfer unit 5, the fixing unit 6, and the like. After that, the control proceeds to step S40.

In step S40, the control unit 810 captures the Nth image of the recording paper P2. After that, the control proceeds to step S50.

In step S50, the signal processing unit 808 cuts out a detection target area as an image before movement from the Nth captured image. After that, the control proceeds to step S60.

In step S60, the signal processing unit 808 performs a discrete Fourier transform process on the image cut out in step S50, and executes a normalization process by removing high frequencies with the above-mentioned filter value. After that, the control proceeds to step S70.

In step S70, the control unit 810 captures the N + 1th image of the recording paper P2. After that, the control proceeds to step S80.

In step S80, the signal processing unit 808 cuts out a detection target area as a moved image from the N + 1th captured image. After that, the control proceeds to step S90.

In step S90, the signal processing unit 808 performs a discrete Fourier transform process on the image cut out in step S80, and executes a normalization process by removing high frequencies with the above filter value. After that, the control proceeds to step S100.

In step S100, the signal processing unit 808 calculates the phase difference between the wave numbers of the data standardized in step S60 and the data standardized in step S90. After that, the control proceeds to step S110.

In step S110, the signal processing unit 808 performs an inverse discrete Fourier transform on the phase difference data derived in step S100. After that, the control proceeds to step S120.

In step S120, the signal processing unit 808 calculates the moving distance by obtaining the real space data sum of the phase difference of each wave number and dividing by the number of wave numbers. The moving distance is the moving distance of the recording paper P2 conveyed by the conveying device from the acquisition of the Nth image to the acquisition of the N + 1th image. After that, the control proceeds to step S130.

In step S130, the signal processing unit 808 converts the moving distance calculated in step S120 into an actually measured value (speed data) of the transport speed, and transfers the speed data to the CPU 101 mounted on the main body control board of the image forming apparatus 1. Forward. The velocity data is derived, for example, by dividing the moving distance calculated in step S120 by the time from the time when the Nth image is captured to the time when the N + 1th image is captured. After that, the control proceeds to step S140.

In step S140, the CPU 101 adjusts the operation of the transfer device based on the speed data received from the signal processing unit 808. The CPU 101 derives, for example, a difference between the speed data and the set value of the transfer speed, and changes the control of the transfer device so as to eliminate the difference. After that, the control proceeds to step S150.

In step S150, the CPU 101 determines whether or not the printing operation in the image forming apparatus 1 may be terminated. For example, the CPU 101 determines whether or not the printing of the already scheduled number of recording papers P2 has been completed, and if it determines that the printing of the number of recording papers P2 has been completed, the CPU 101 terminates the printing operation. Judge that it is good.

When the CPU 101 determines that the printing operation may be terminated, the processing of FIG. 11 is terminated. On the other hand, when the CPU 101 determines that the print operation should not be terminated yet, it proceeds to the control in step S160.

In step S160, the CPU 101 adds 1 to update the number of recording papers P2 for which the printing operation has been completed. After that, the control proceeds to step S40.

<7. Summary of embodiments>
In the image forming apparatus 1 of the first embodiment described above, the transport device is an example of a transport unit for transporting the recording medium.

The light receiving unit 802 is an example of an imaging unit for generating an captured image of the transport path at the first timing and the second timing different from the first timing.

The memory provided in the signal processing unit 808 is an example of a storage unit for storing information that specifies the transfer speed of the recording medium by the transfer unit. An example of the stored information is a fluctuation amount (speed fluctuation Ld1, Ld2, etc.) associated with the transport speed.

Based on the information stored in the storage unit, the control unit 810 provides a portion of either the image captured at the first timing or the image captured at the second timing corresponding to a region corresponding to the recording medium in the other. This is an example of an information processing unit configured to be specified as an exclusion part. The control unit 810 includes a signal processing unit 808.

The signal processing unit 808 of the control unit 810 uses a portion other than the excluded portion of the captured image of the first timing and the captured image of the second timing to record between the first timing and the second timing. It is configured to calculate the amount of movement of the medium.

<8. Modification example (1)>
In the image forming apparatus 1, when the set value of the conveying speed is changed during the execution of the printing operation, the detection target area can be changed. FIG. 12 is a flowchart of a modified example of the process of FIG.

In the process of FIG. 12, as compared with the process of FIG. 11, the control of step S12 is executed after the control of step S10, and then the control proceeds to step S20.

In step S12, the movement amount detection unit 800 switches between the set value of the transfer speed and the planned speed fluctuation amount according to the transfer information. The transport information is, for example, a print mode set in the image forming apparatus 1. The movement amount detection unit 800 includes a memory, and the transfer speed associated with the print mode is stored in the memory. After that, the control proceeds to step S20.

In step S20, the movement amount detection unit 800 detects the Nth captured image and the N + 1th captured image from the set speed (set value of the transport speed) and the planned speed fluctuation amount after being switched in step S12. Specify the target area (Fig. 7, etc.). After that, the control proceeds to step S30.

In the process of FIG. 12, as compared with the process of FIG. 11, the control of step S170 is further executed after the control of step S160.

In step S170, the movement amount detection unit 800 determines whether or not there is any change in the transfer information in the image forming apparatus 1. For example, if there is no change in the print mode setting after the control in step S12, the movement amount detection unit 800 determines that there is no change in the transfer information, and returns the control to step S40. For example, when the print mode setting is changed after the control in step S12, the movement amount detection unit 800 determines that the transfer information has changed, and proceeds to the control in step S180.

In step S180, the movement amount detection unit 800 switches between the set value of the transfer speed and the planned speed fluctuation amount according to the transfer information. After that, the control proceeds to step S190.

In step S190, the movement amount detection unit 800 sets the detection target area based on the set value of the transport speed and the planned speed fluctuation amount after being switched in step S180. After that, the control proceeds to step S40.

<9. Modification example (2)>
The detection target region can be corrected based on the amount of speed fluctuation associated with the target speed (target speeds V1, V2, etc. in FIG. 9). The detection target region may also be corrected according to the temperature inside the image forming apparatus 1, the humidity inside the image forming apparatus 1, and / or the type of paper of the recording paper P2.

The transport speed of the recording paper P2 can be changed according to the temperature inside the image forming apparatus 1. The friction between the recording paper P2 and the transfer roller can be changed according to the humidity inside the image forming apparatus 1, whereby the transfer speed of the recording paper P2 can be changed.

When the transport speed increases, for example, the detection target area is corrected so that the detection target area expands. When the transport speed decreases, the detection target area is corrected so that the detection target area is narrowed, for example. In the memory of the movement amount detection unit 800, for example, correction values of the detection target area associated with each of the two or more types of temperatures are stored. In the memory of the movement amount detection unit 800, for example, correction values of the detection target area associated with each of two or more types of humidity are stored. In the memory of the movement amount detection unit 800, for example, correction values of the detection target area associated with each of two or more types of paper are stored. The movement amount detection unit 800 corrects the detection target area by using the correction value.

<10. Modification example (3)>
The detection target region may be further corrected according to the size of the light receiving element of the image sensor 805.

For example, even if it is determined that the part is included in the first image (FIG. 7) but not included in the second image (FIG. 7) based on the set value of the transport speed, the first image is included. The detection target region can be corrected so that the portion detected by the same light receiving element as the portion determined to be included in both the image of the above image and the second image is included in the detection target region.

<11. Modification example (4)>
The movement amount detection unit 800 can set the first timing and the second timing. The time interval between the first timing and the second timing can be changed according to the transport speed. For example, the slower the transport speed, the longer the time interval between the first timing and the second timing can be. The change of the time interval between the first timing and the second timing can be realized by, for example, changing the sampling cycle in the movement amount detection unit 800. More specifically, each region of the recording paper P2 is detected by a light receiving element different from the light receiving element in which the captured image of the first timing is detected in the captured image of the second timing (same light receiving). The time interval can be adjusted (so that it is not detected by the element).

FIG. 13 is a diagram for explaining a modification (4). In FIG. 13, each of the regions C1, C2, and C3 corresponds to different light receiving elements. In the first time interval, the pixel P1 in the first image moves to the pixel P2 in the second image. Pixel P1 and pixel P2 are included in the region C1 corresponding to the same light receiving element. In the second time interval, pixel P1 in the first image moves to pixel P3 in the second image. Pixels P1 and P3 are included in regions (regions C1 and C2) corresponding to light receiving elements different from each other. In the modification (4), as the time interval between the first timing and the second timing, a second time interval may be set instead of the first time interval.

<12. Modification example (5)>
In the image forming apparatus 1 of the modification (5), a detection target area is set for each sampling cycle. FIG. 14 is a flowchart of another modification of the process of FIG. As shown in FIG. 14, after the number of sheets of recording paper P2 for which the printing operation has been completed is updated by 1 in step S160, the control proceeds to step S162.

In step S162, the movement amount detection unit 800 resets the detection target area based on the speed obtained in step S120 for the latest sampling cycle. After that, the control proceeds to step S40.

It should be considered that each embodiment disclosed this time is exemplary in all respects and is not restrictive. The scope of the present invention is shown not by the above description but by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims. In addition, the inventions described in the embodiments and the modifications are intended to be implemented, either alone or in combination, wherever possible.

1 Image forming apparatus, 101 CPU, 800 movement amount detection unit, 805 image sensor, 808 signal processing unit.

Claims (9)

A transport unit for transporting the recording medium and
At the first timing and at a second timing different from the first timing, an imaging unit for generating an image of the transport path of the recording medium by the transport unit, and an imaging unit.
A storage unit for storing information for specifying the transfer speed of the recording medium by the transfer unit, and a storage unit.
Based on the information stored in the storage unit, a portion of either one of the captured image of the first timing and the captured image of the second timing corresponds to a region corresponding to the recording medium in the other. It has an information processing unit that is configured to be specified as an exclusion part.
In the excluded portion, the recording medium was present at either the first timing or the second timing, but the recording medium was present at either the first timing or the second timing. Corresponds to areas that are not
The information processing unit uses a portion other than the exclusion portion of the captured image of the first timing and the captured image of the second timing between the first timing and the second timing. An image forming apparatus configured to calculate the amount of movement of a recording medium. The information processing unit determines the amount of movement by comparing the wave number components of the captured image of the first timing and the captured image of the second timing other than the excluded portion after the discrete Fourier transform. The image forming apparatus according to claim 1, which is configured to calculate. The image forming apparatus according to claim 1 or 2, wherein the information processing unit is further configured to specify the excluded portion based on the size of the light receiving element in the imaging unit. A transport unit for transporting the recording medium and
At the first timing and at a second timing different from the first timing, an imaging unit for generating an image of the transport path of the recording medium by the transport unit, and an imaging unit.
A storage unit for storing information for specifying the transfer speed of the recording medium by the transfer unit, and a storage unit.
Based on the information stored in the storage unit, a portion of either one of the captured image of the first timing and the captured image of the second timing corresponds to a region corresponding to the recording medium in the other. It has an information processing unit that is configured to be specified as an exclusion part.
The information processing unit uses a portion other than the exclusion portion of the captured image of the first timing and the captured image of the second timing between the first timing and the second timing. It is configured to calculate the amount of movement of the recording medium.
The information stored in the storage unit is associated with a speed fluctuation value associated with a target value of a recording medium transport speed by the transport unit, and at least one of temperature, humidity, and a type of recording medium. Including the corrected value
The information processing unit
Obtain the target value and
A first correction value for the excluded portion is calculated based on the acquired speed fluctuation value associated with the target value and the interval between the first timing and the second timing.
Get at least one of the temperature, humidity, and recording medium types,
Of the correction values stored in the storage unit, a second correction value, which is a correction value associated with the acquired value, is acquired.
An image forming apparatus configured to correct the excluded portion using the first correction value and the second correction value. The information processing unit is configured to identify the exclusion portion when the temperature, humidity, and at least one value among the types of recording media, or the target value is changed. , The image forming apparatus according to claim 4. The first timing and the second timing are set according to claim 4 or 5, wherein the lower the target value, the longer the interval between the first timing and the second timing. Image forming device. The image forming apparatus according to any one of claims 1 to 6, wherein the interval between the first timing and the second timing is a sampling cycle in the imaging unit. A step of imaging a transport path for transporting a recording medium at a first timing and a second timing different from the first timing.
Based on the information that identifies the transport speed of the recording medium stored in the storage unit, the portion of either the image captured at the first timing or the image captured at the second timing that does not correspond to the recording medium at the other. and a step of identifying the corresponding portion as an exclusion section,
In the excluded portion, the recording medium was present at either the first timing or the second timing, but the recording medium was present at either the first timing or the second timing. Corresponds to areas that are not
The amount of movement of the recording medium between the first timing and the second timing is calculated by using the captured image of the first timing and the portion other than the excluded portion in the captured image of the second timing. A method of controlling an image forming apparatus, further comprising steps to perform. A step of imaging a transport path for transporting a recording medium at a first timing and a second timing different from the first timing.
Based on the information that identifies the transport speed of the recording medium stored in the storage unit, the portion of either the image captured at the first timing or the image captured at the second timing that does not correspond to the recording medium at the other. identifying a corresponding portion as an exclusion section,
The amount of movement of the recording medium between the first timing and the second timing is calculated by using the captured image of the first timing and the portion other than the excluded portion in the captured image of the second timing. With steps to do
The information includes a rate variation value associated with a target value for the transport rate of the recording medium and a correction value associated with temperature, humidity, and at least one of the recording medium types.
The step of identifying the exclusion part is
Obtaining the target value and
To calculate the first correction value for the excluded portion based on the acquired speed fluctuation value associated with the target value and the interval between the first timing and the second timing.
Obtaining values for temperature, humidity, and at least one of the types of recording media,
Of the correction values included in the information, the acquisition of the second correction value, which is the correction value associated with the acquired value,
A method for controlling an image forming apparatus, which comprises correcting the excluded portion by using the first correction value and the second correction value.

Images