JP6805745B2 - Movement amount detection device and image forming device - Google Patents

Description

This disclosure relates to a technique for detecting the amount of movement of a moving body, and more specifically to a technique for detecting the amount of movement of a moving body from an image.

Conventionally, devices for measuring the velocity of a moving object in a non-contact manner have been used in various products. For example, some image forming devices such as an MFP (Multi-Functional Peripheral) include an image pickup device that images a transport path, and specify 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.

Further, Japanese Patent Application Laid-Open No. 2011-093242 (Patent Document 2), Japanese Patent Application Laid-Open No. 2011-095162 (Patent Document 3), Japanese Patent Application Laid-Open No. 2011-21343 (Patent Document 4), and Japanese Patent Application Laid-Open No. 2015-001407 (Patent Document 4). Patent Document 5) discloses a technique in which two recording media being transported are photographed at different timings, and pattern matching is performed on the two captured images to specify the transport speed.

JP-A-2010-134190 Japanese Unexamined Patent Publication No. 2011-093242 Japanese Unexamined Patent Publication No. 2011-09162 Japanese Unexamined Patent Publication No. 2011-213433 Japanese Unexamined Patent Publication No. 2015-001407

However, the technique of obtaining the transport speed of the recording medium by pattern matching as in Patent Documents 2 to 5 tends to erroneously detect the moving destination because there are many patterns similar to the surface of the recording medium.

The technique disclosed in Patent Document 1 can suppress the false detection of the moving destination of the moving body as described above, but the error of the moving speed of the moving body may be large depending on the arrangement position of the optical system. Therefore, there is a need for a technique that can more accurately determine the amount of movement of a moving body.

The present disclosure has been made to solve the above-mentioned problems, and an object in a certain aspect is to provide a movement amount detecting device capable of obtaining a movement speed of a moving body more accurately than before. Is. An object in another aspect is to provide an image forming apparatus capable of obtaining a transport speed of a recording medium more accurately than before.

A movement amount detection device according to an embodiment includes a transport path for transporting a moving object, a light source, and a two-dimensional sensor, and irradiates light from the light source to detect the reflected light by the moving body during the transport. The imaging unit for generating at least two images including the first image and the second image and the center position of the pattern formed by the reflected light from the moving body on the two-dimensional sensor are detected by using the images at different timings. A detection unit for setting, a setting unit for setting an image analysis range in the first image and the second image based on the center position detected by the detection unit, an image of the image analysis range in the first image, and a first It is provided with a movement amount calculation unit for calculating the movement amount of the moving body between the shooting timings of the first and second images based on the image of the image analysis range in the two images.

Preferably, the movement amount detecting device further includes a noise filter for smoothing the detection result of the two-dimensional sensor.

Preferably, the setting unit is configured to set the image analysis range so that the center position detected by the detection unit is the center of the image analysis range.

Preferably, the detection unit is configured to detect the position having the highest brightness in the pattern formed on the two-dimensional sensor as the center position.

Preferably, the detection unit detects the end portion of the pattern based on the brightness distribution output by the two-dimensional sensor, and detects the end positions of the two points where the distance between the ends in a predetermined direction is the longest. It is configured to detect the middle of the end position of the point as the center position.

Preferably, the detection unit is configured to detect the outer diameter line of the pattern based on the luminance distribution output by the two-dimensional sensor, and to detect the position of the center of gravity of the figure formed by the outer diameter line as the center position.

Preferably, the photographing unit includes a plurality of photoelectric conversion elements arranged in a first direction and a second direction orthogonal to the first direction. The detection unit calculates the brightness distribution that follows one of the first and second directions based on the brightness distribution output by the two-dimensional sensor, and sets the peak position in the brightness distribution that follows one direction as one direction of the center position. It is configured to be detected as a position in.

Preferably, the photographing unit includes a plurality of photoelectric conversion elements arranged in a first direction and a second direction orthogonal to the first direction. The detection unit calculates the brightness distribution according to the first direction based on the brightness distribution output by the two-dimensional sensor, and sets the peak position in the brightness distribution according to the first direction as the position of the center position in the first direction. Detects and calculates the brightness distribution according to the second direction based on the brightness distribution output by the two-dimensional sensor, and detects the peak position in the brightness distribution according to the second direction as the position of the center position in the second direction. It is configured to do.

Preferably, it further includes a displacement sensor that detects the amount of displacement of at least one of the light source and the two-dimensional sensor. The detection unit is configured to detect the center position based on the output of the displacement sensor.

More preferably, the detection unit calculates the brightness distribution that follows one of the first and second directions based on the brightness distribution output by the two-dimensional sensor, and smoothes and smoothes the brightness distribution that follows one direction. When a peak is not detected in the obtained luminance distribution, it is determined that the center position of the pattern does not exist on the two-dimensional sensor.

Preferably, the photographing unit is configured to photograph the moving body and generate a reference image in response to the power being supplied to the movement amount detecting device. The detection unit is configured to detect the center position of the pattern in the reference image. The setting unit is configured to set the image analysis range based on the center position of the pattern in the reference image detected by the detection unit.

More preferably, the detection unit is configured to detect the center position of the pattern in the most recently captured new image according to the elapse of a predetermined time after the reference image is captured. .. The setting unit is configured to update the image analysis range based on the center position of the pattern in the new image detected by the detection unit.

Preferably, it further includes an input device that accepts user input. The setting unit is configured so that the image analysis range can be changed based on the user's input received by the input device.

Preferably, the setting unit determines whether or not the center position detected by the detection unit is separated from the position corresponding to the center of the two-dimensional sensor by a predetermined distance or more, and the center position is from the position corresponding to the center. If it is determined that the distance is more than a predetermined distance, the image analysis range is set based on the center position detected by the detection unit, and the center position must be more than a predetermined distance from the position corresponding to the center. If determined, the image analysis range is configured to be set based on the position corresponding to the center.

Preferably, the two-dimensional sensor includes a transport direction of the transport path and a plurality of photoelectric conversion elements arranged in orthogonal directions orthogonal to the transport direction. The number of photoelectric conversion elements arranged in the transport direction is larger than the number of photoelectric conversion elements arranged in the orthogonal direction.

According to other aspects, the mobile is a recording medium. The image forming apparatus includes the movement amount detecting apparatus according to any one of the above, and an image forming unit for forming an image on a recording medium.

The movement amount detecting device according to a certain embodiment can accurately determine the moving speed of the moving body even when the arrangement position of the optical system changes with time.

The above and other objectives, features, aspects and advantages of the disclosed technical features will become apparent from the following detailed description of the invention as understood in connection with the accompanying drawings.

It is a conceptual diagram which shows typically the method of calculating the transport speed of a moving body according to an embodiment. It is a figure explaining the configuration example of the image forming apparatus according to a certain embodiment. It is a figure explaining the configuration example of a sensor unit. It is a figure which shows two images taken at different timings. It is a figure explaining the calculation method of the movement amount according to the related technique. It is a figure explaining the relationship between the analysis range in a speckle pattern, and the calculated movement amount. It is a figure which shows that the speckle pattern is shifted in the lateral direction. It is a figure which shows that the speckle pattern is shifted in the vertical direction. It is a figure which shows that the speckle pattern protrudes from a two-dimensional sensor. It is a figure which shows that the speckle pattern is larger than a two-dimensional sensor. It is a figure explaining the luminance distribution which follows a horizontal direction, and the luminance distribution which follows a vertical direction. It is a figure (the 1) explaining the control which detects the center position of a speckle pattern. It is a figure (the 2) explaining the control which detects the center position of a speckle pattern. It is a figure (the 1) explaining the control which detects the central position of the speckle pattern according to another embodiment. It is a figure (the 2) explaining the control which detects the center position of the speckle pattern according to another embodiment. It is a figure explaining the control which determines that there is no center position of a speckle pattern on a two-dimensional sensor. It is a figure explaining the calculation method of the movement amount according to embodiment. It is a flowchart explaining the calculation control of the movement amount of the moving body according to a certain embodiment. It is a flowchart explaining the details of the process of step S1815 in FIG. It is a figure explaining the configuration example of the sensor unit included in the image forming apparatus according to another embodiment.

Hereinafter, embodiments of this technical idea will be described in detail with reference to the drawings. In the following description, the same parts are designated by the same reference numerals. Their names and functions are the same. Therefore, the detailed description of them will not be repeated. In addition, each embodiment and each configuration described below may be selectively combined as appropriate.

(Technical thought)
FIG. 1 is a conceptual diagram schematically showing a method of calculating a transport speed of a moving body according to an embodiment. The image forming apparatus 100 according to an embodiment with reference to FIG. 1 includes a transport path R1, a photographing unit 70, and an FPGA (Field-Programmable Gate Array) 86. The sheet S, which is a recording medium, is transported on the transport path R1. In other words, the sheet S is a moving body.

The photographing unit 70 includes a light source 81 and a two-dimensional sensor 84. The light source 81 irradiates light toward the transport path R1. The two-dimensional sensor 84 comprises a plurality of photoelectric conversion elements arranged in the transport direction of the sheet S (hereinafter, also referred to as “horizontal direction”) and in the orthogonal direction (hereinafter, also referred to as “vertical direction”) orthogonal to the transport direction. Have. The two-dimensional sensor 84 detects the reflected light from the sheet S being conveyed by the photoelectric conversion element. In other words, the two-dimensional sensor 84 takes a picture of the sheet S being conveyed and generates an image. The two-dimensional sensor 84 transmits the generated image to the FPGA 86.

In a certain aspect, the photographing unit 70 outputs the first image and the second image taken at different timings to the FPGA 86. The movement amount calculation unit 90 included in the FPGA 86 calculates the movement amount of the sheet S between the shooting timings of the first and second images based on the first image and the second image.

More specifically, the movement amount calculation unit 90 cuts out an image in the analysis range from the first image and the second image, and calculates the movement amount of the sheet S based on the two cut-out images. The reason is that when the movement amount is calculated by using the first image and the second image as they are, the processing amount is large and the time required for calculating the movement amount becomes long.

In the manufacturing stage of the image forming apparatus 100, the positional relationship between the light source 81 and the two-dimensional sensor 84 is set so that the optical axis of the light emitted by the light source 81 penetrates the center of the two-dimensional sensor 84. In this state, the light source 81 irradiates light according to the optical path 110. The two-dimensional sensor 84 detects the pattern 110-A formed by the light reflected by the sheet S. The center position 110-C of the pattern 110-A is the center of the two-dimensional sensor 84. The movement amount calculation unit 90 uses the range 110-L centered on the center of the two-dimensional sensor 84 as the analysis range. That is, the movement amount calculation unit 90 calculates the movement amount using the image corresponding to the range 110-L in the pattern 110-A. The reason is that the analysis range is closer to the center of the pattern (speckle pattern) formed by the reflected light of the sheet S, the smaller the error in the amount of movement is.

However, the positional relationship between the light source 81 and the two-dimensional sensor 84 may change with the durability of the image forming apparatus 100. For example, the sheet metal for fixing the light source 81 and the two-dimensional sensor 84 changes due to thermal expansion or the like.

In a certain situation, it is assumed that the light source 81 is tilted from a preset position. In this state, the light source 81 irradiates light according to the optical path 120. The two-dimensional sensor 84 detects the pattern 120-A formed by the light reflected by the sheet S. The center position 120-C of the pattern 120-A is laterally deviated from the center of the two-dimensional sensor 84. In this state, when the movement amount calculation unit 90 calculates the movement amount using the image corresponding to the range 110-L in the pattern 120-A, the error of the movement amount becomes large. An image forming apparatus 100 according to an embodiment can solve such a problem.

The FPGA 86 of the image forming apparatus 100 further includes a detection unit 88 and a setting unit 89. The detection unit 88 detects the center position of the pattern formed on the two-dimensional sensor 84 by the light reflected by the sheet S. For example, in response to the pattern 120-A being formed on the two-dimensional sensor 84, the detection unit 88 detects the center position 120-C of the pattern 120-A. The setting unit 89 sets an analysis range in which the movement amount calculation unit 90 performs image analysis based on the center position detected by the detection unit. For example, the setting unit 89 sets the range 120-L in which the center position 120-C is the center as the analysis range.

The movement amount calculation unit 90 calculates the movement amount of the sheet S between the shooting timings of the first and second images based on the image of the analysis range in the first image and the image of the analysis range in the second image. The FPGA 86 outputs the moving speed (conveying speed) of the sheet S to the control unit 6 described later based on the moving amount calculated by the moving amount calculation unit 90. The control unit 6 executes various controls of the image forming apparatus based on the transfer speed.

According to the above, the image forming apparatus 100 according to a certain embodiment can accurately detect the transport speed of the sheet S even when the positional relationship between the light source 81 and the two-dimensional sensor 84 changes. The specific configuration and control of the image forming apparatus 100 capable of realizing such control will be described below.

(Structure of image forming apparatus 100)
FIG. 2 is a diagram illustrating a configuration example of an image forming apparatus 100 according to a certain embodiment. FIG. 2 shows an image forming apparatus 100 as a color printer. Hereinafter, the image forming apparatus 100 as a color printer will be described, but the image forming apparatus 100 is not limited to the color printer. For example, the image forming apparatus 100 may be a monochrome printer, or may be a monochrome printer, a color printer, and a multi-function peripheral (MFP).

As shown in FIG. 2, the image forming apparatus 100 includes an image forming unit 1, an intermediate transfer unit 2, a sheet supply unit 3, a fixing device 4, a sheet winding unit 5, a control unit 6, and the like. .. The image forming apparatus 100 is connected to a network (for example, LAN: Local Area Network), and when it receives an instruction to execute a print job from an external terminal apparatus (not shown), it is yellow (Y) based on the instruction. , Magenta (M), cyan (C) and black (K) to perform color image formation.

The image forming unit 1 includes image forming units 10Y to 10K corresponding to each of the Y to K colors. The image forming unit 10Y charges the surface of the photoconductor drum 11Y rotating at a constant speed, and when an electrostatic latent image is formed on the charged photoconductor drum 11Y by exposure scanning of an exposed portion, the electrostatic latent image is formed. The latent image is developed with Y-color toner, and the developed Y-color toner image is electrostatically first-transferred to the intermediate transfer belt 21.

The other image forming units 10M, 10C, and 10K also perform the same charging, exposure, development, and primary transfer steps as the image forming unit 10Y, and perform the M color toner image on the photoconductor drum 11M and the photoconductor drum 11C. The C-color toner image and the K-color toner image on the photoconductor drum 11K are primarily transferred to the intermediate transfer belt 21. In FIG. 2, the formation timing of the Y to K color toner images is predetermined so that the Y to K color toner images representing the original image on one page are multiple-transferred on the intermediate transfer belt 21. When there are a plurality of pages of the original, toner images corresponding to one page of the original image are sequentially formed on the intermediate transfer belt 21 at regular intervals in the belt circumferential direction for each page of the original.

The intermediate transfer unit 2 includes an intermediate transfer belt 21, a drive roller 22 for tensioning the intermediate transfer belt 21, driven rollers 23, 24, 25, a secondary transfer roller 26, and the like.

The drive roller 22 is rotated by the rotational driving force of the belt motor 71 to orbit the intermediate transfer belt 21 in the direction indicated by the arrow in the figure. The belt motor 71 includes, for example, a DC (Direct Current) brushless motor. The driven rollers 23, 24, and 25 rotate driven as the intermediate transfer belt 21 orbits.

During the rotation of the intermediate transfer belt 21, the Y to K color toner images by the image forming units 10Y to 10K are multiplex transferred to the peripheral surface of the intermediate transfer belt 21.

The Y to K color toner images multiple-transferred on the intermediate transfer belt 21 are directed to the secondary transfer roller 26 which is arranged to face the drive roller 22 with the intermediate transfer belt 21 sandwiched by the orbital running of the intermediate transfer belt 21. Will be transported.

The secondary transfer roller 26 is in contact with the peripheral surface of the intermediate transfer belt 21 at the secondary transfer position 261 of the intermediate transfer belt 21, and is driven to rotate as the intermediate transfer belt 21 orbits.

The sheet supply unit 3 sends a long sheet S from the roll paper 33 wound around the rotating shaft 31 to the paper feed adjusting unit 34 via the supply roller 32. The paper feed adjusting unit 34 conveys the sheet S from the supply roller 32 toward the transfer roller 35 of the main body 9 of the image forming apparatus 100, and the transfer speed of the sheet S sent out from the roll paper 33 in the sheet supply unit 3 In order to absorb the speed difference between the sheet S and the transport speed of the sheet S in the main body 9, the long sheet S is loosened and held, and the paper feeding of the sheet S to the main body 9 is adjusted. As the sheet S, not only plain paper but also label paper or the like may be used.

The sheet S supplied to the transfer roller 35 is wound by the take-up roller 51 via the secondary transfer position 261, the fixing device 4, the discharge roller 46, the paper discharge adjustment unit 53 of the sheet winding unit 5, and the transfer roller 52. Be done. In order to absorb the speed difference between the transfer speed of the sheet S in the main body 9 and the transfer speed of the sheet S by the take-up roller 51 of the sheet take-up unit 5, the paper discharge adjusting unit 53 uses a long sheet S. Loosen and hold, and adjust the output of the sheet S from the main body 9.

During the winding of the sheet S, the Y to K colors that are multiple-transferred on the intermediate transfer belt 21 on the front side (that is, the side in contact with the intermediate transfer belt 21) of the sheet S that passes through the secondary transfer position 261. The toner image is electrostatically collectively secondarily transferred by the secondary transfer roller 26. When a plurality of pages of toner images are formed on the intermediate transfer belt 21 at regular intervals in the belt circumferential direction, the toner images of each page are formed while the elongated sheet S passes through the secondary transfer position 261. Are secondarily transferred onto the sheet S one by one. The toner image of each page secondarily transferred onto the sheet S is conveyed to the fixing device 4 together with the sheet S to be wound.

The fixing device 4 is pressed against the fixing roller 41 at a predetermined pressure at the nip portion 45 of the tubular heating roller 40 in which the heater 43 is inserted, the tubular fixing roller 41, and the fixing roller 41. It is provided with a pressure roller 42. The fixing device 4 heats the heating roller 40 by heating the heater 43 to a predetermined temperature. As the heating roller 40 rotates, heat is transferred to the nip portion 45 between the fixing roller 41 and the pressure roller 42. The fixing device 4 maintains the temperature of the nip portion 45 at a temperature required for fixing the toner (for example, 150 ° C.).

The fixing roller 41 is driven in the direction of the arrow in FIG. 2 by a fixing motor 72 composed of a DC brushless motor, and rotates about a rotation shaft 47. The heating roller 40 may be rotationally driven instead of the fixing roller 41. The pressure roller 42 is driven to rotate by the fixing roller 41. The fixing roller 41 and the pressurizing roller 42 heat and pressurize the toner image after the secondary transfer onto the sheet S when the toner image passes through the nip portion 45 while sandwiching and transporting the sheet S. Heat-fixed on the front side of the sheet S.

The sheet S being wound is conveyed across the fixing roller 41 and the secondary transfer roller 26. If the sheet portion Sd existing between the fixing roller 41 and the secondary transfer roller 26 of the sheet S is loosened during this transfer, the sheet S may be wrinkled at the nip portion 45.

Therefore, in order to prevent the occurrence of wrinkles on the sheet S, a certain amount of tension acts on the sheet portion Sd in the sheet transport direction. This tension is generated, for example, by driving the rotation speed of the fixing roller 41 by a constant value with respect to the rotation speed of the secondary transfer roller 26.

The transport speed of the sheet S is detected by the sensor unit 44. The sensor unit 44 is located upstream of the nip portion 45 in the sheet transport direction and below the position P of the seat S in the transport path R1 and is located near the nip portion 45. The sensor unit 44 measures the transport speed of the surface on the back side (that is, the side on which the toner image is not transferred) of the sheet S that is sandwiched and transported by the fixing roller 41 and the pressure roller 42. The sensor unit 44 measures the transfer speed of the sheet surface at regular intervals (for example, several milliseconds) during the transfer of the sheet S, and sends the measurement result to the control unit 6.

(Configuration of sensor unit 44)
FIG. 3 is a diagram illustrating a configuration example of the sensor unit 44. In the example shown in FIG. 3, the sheet S is conveyed to the fixing device 4.

The sensor unit 44 includes a photographing unit 70, an ADC (Analog-to-Digital Converter) 85, an FPGA 86, and a ROM 92. The sensor unit 44 functions as a movement amount detection device for calculating the movement amount of the sheet S during transportation in a certain period by utilizing the speckle pattern formed on the two-dimensional sensor 84 by the reflected light from the sheet S. .. In other words, the sensor unit 44 is a non-contact type sensor that measures the transport speed of the sheet S.

The photographing unit 70 includes a light source 81 including a laser device, a lens 82 and a lens 83 which are collimator lenses, and a two-dimensional sensor 84.

The two-dimensional sensor 84 has a plurality of photoelectric conversion elements arranged in the horizontal direction and the vertical direction. In one embodiment, the number of photoelectric conversion elements arranged in the horizontal direction is larger than the number of photoelectric conversion elements arranged in the vertical direction, whereby the movement amount calculation unit 90 moves the sheet S more accurately. The amount can be calculated.

In the manufacturing stage of the image forming apparatus 100, the light source 81 is set to emit laser light toward a predetermined irradiation position Sp on the transport path R1. The laser beam emitted from the light source 81 passes through the lens 82 and irradiates the surface Sa of the sheet S being conveyed.

The angle θ2 formed by the laser beam incident on the surface Sa of the sheet S and the surface Sa of the sheet S is 45 ° in FIG. The angle θ2 is not limited to 45 °, and may be any angle in the range of, for example, 20 ° to 45 °.

The surface Sa of the sheet S can be said to be a rough surface having minute irregularities when viewed microscopically, and when the rough surface is irradiated with laser light (coherent light), a granular pattern called speckle is generated. The speckle is generated because light having a different phase overlaps due to the superposition of scattered light due to diffused reflection of laser light from each place on the rough surface.

Of the laser light generated by the speckle, the reflected light reflected at an angle θ1 (for example, 90 °) with respect to the surface Sa of the sheet S is received through the lens 83 provided directly below the irradiation position Sp. The light is focused on the detection surface of the two-dimensional sensor 84 as a unit. As a result, on the detection surface of the two-dimensional sensor 84, the speckle pattern generated on the surface Sa of the sheet S located directly above the detection surface can be detected.

The speckle does not change unless the seat S moves, but changes when the seat S moves. This is because the uneven portion of the rough surface passing through the laser beam irradiation position Sp changes at each time point due to the transfer of the sheet S, and the state of superimposition of the diffusely reflected light of the laser also changes at each time point.

The rate of change of the speckle depends on the transport speed of the sheet S, and the amount of laser light received on the detection surface of the two-dimensional sensor 84 also changes due to the change of the speckle. Therefore, the moving speed of the surface of the sheet S can be measured by detecting the time change of the amount of received laser light on the detection surface of the two-dimensional sensor 84. Therefore, it can be said that the irradiation position Sp of the laser light on the sheet S is the measurement position of the moving speed of the sheet surface.

The two-dimensional sensor 84 outputs an analog voltage signal corresponding to the amount of received laser light focused on the detection surface to the ADC (Analog to Digital Converter) 85 at regular intervals, for example, every few milliseconds.

The ADC 85 converts the analog voltage signal from the two-dimensional sensor 84 into a digital signal every time it is received at a fixed cycle, and outputs the converted digital signal to the FPGA 86.

The FPGA 86 includes a noise filter 87, a detection unit 88, a setting unit 89, and a movement amount calculation unit 90.

The noise filter 87 includes, for example, a smoothing filter and a median filter for reducing high-sensitivity noise.

The detection unit 88 receives the image processed by the noise filter 87. The detection unit 88 detects the center position of the speckle pattern formed by the reflected light from the sheet S from this image. Details of this process will be described later with reference to FIGS. 12 to 16.

The setting unit 89 calculates the analysis range so that the center position detected by the detection unit 88 is in the center. The setting unit 89 stores the calculated analysis range 94 in the ROM 92.

The movement amount calculation unit 90 cuts out an analysis image from each of the two images taken at different timings according to the analysis range 94 stored in the ROM 92. The movement amount calculation unit 90 calculates the movement amount of the sheet S between the shooting timings of the two images based on the two analysis images. The movement amount calculation unit 90 calculates the transport speed of the sheet S based on the shooting timing interval of the two images and the calculated movement amount. The movement amount calculation unit 90 outputs the calculated transfer speed of the sheet S to the control unit 6. The control unit 6 may be configured by, for example, a CPU (Central Processing Unit).

The control unit 6 acquires the transport speed of the sheet S being transported from the sensor unit 44. The control unit 6 controls the rotation speed of the fixing motor 72 that drives the fixing roller 41 based on the conveying speed of the sheet S, and sets the conveying speed of the sheet S to a predetermined target speed. As a result, the control unit 6 can prevent the sheet S from being wrinkled at the nip unit 45, for example.

The control unit 6 may further control the rotation speed of the secondary transfer motor 73 that drives the drive roller 22 based on the transfer speed of the sheet S acquired from the sensor unit 44. At this time, the control unit 6 controls the secondary transfer motor 73 so that the rotation speed of the fixing motor 72 is faster than the rotation speed of the secondary transfer motor 73. As a result, the sheet S can be pulled by the fixing device 4 to prevent the sheet S from wrinkling at the nip portion 45.

(Movement of sheet S)
FIG. 4 is a diagram showing two images taken at different timings. The image shown in FIG. 4 represents an image obtained by cutting out an analysis range from a captured image of a speckle pattern of laser light focused on the detection surface of the two-dimensional sensor 84.

The image 410 represents an image taken on the first image, and the image 420 represents an image taken after the image 410 (an image taken on the second image). The sheet S when the image 420 is photographed is moving in the transport direction by the action of the fixing motor 72 or the like as compared with the sheet S when the image 410 is photographed. In the example shown in FIG. 4, the sheet S when the image 420 is photographed is moved in the transport direction from the sheet S position when the image 410 is photographed by the movement amount ΔL.

(Calculation of movement amount according to related technology)
FIG. 5 is a diagram illustrating a method of calculating a movement amount according to a related technique. The movement amount calculation unit 90R according to the related technique includes a cutting unit 510, a discrete Fourier transform unit 520, a normalization processing unit 530, a synthesis unit 540, and an inverse discrete Fourier transform unit 550.

Data indicating the first image and the second image, which are two images taken at different timings, are input to the cutting unit 510 of the movement amount calculation unit 90R.

The cutting unit 510 cuts out a first analysis image and a second analysis image, which are images in a predetermined range from the first image and the second image. As an example, it is assumed that the predetermined range is a range centered on the center of the input image.

The discrete Fourier transform unit 520 decomposes the data into each wave number component by executing the discrete Fourier transform process on the data showing the first analysis image and the second analysis image input from the cutout unit 510. The discrete Fourier transform unit 520 outputs the data decomposed for each wave number component to the normalization processing unit 530.

The normalization processing unit 530 multiplies the amplitude corresponding to the first analysis image and the amplitude corresponding to the second analysis image for each wave number component. As a result, the standardization processing unit 530 standardizes the magnitude of the amplitude for each wave number and extracts the phase information for each wave number. The normalization processing unit 530 outputs the extracted phase information to the synthesis unit 540.

The synthesis unit 540 synthesizes the phase information extracted for each wave number. The synthesis unit 540 derives the phase difference between the first analysis image and the second analysis image by calculating the peak shift amount based on the synthesized phase information. The synthesis unit 540 outputs the derived phase difference to the inverse discrete Fourier transform unit 550.

The reciprocal discrete Fourier transform unit 550 performs the reciprocal discrete Fourier transform process on the phase difference in the derived wave number space, so that this phase difference is the distance in the real space, that is, two images, the first image and the second image. It is converted into the movement amount of the sheet S between the shooting timings of the image of.

As described above, the movement amount calculation unit 90R according to the related technology calculates the movement amount of the sheet S with the predetermined range in the speckle pattern as the analysis range. The problem of the movement amount calculation unit 90 according to this related technique will be described with reference to FIG. 6 below.

FIG. 6 is a diagram for explaining the relationship between the analysis range in the speckle pattern and the calculated movement amount.

With reference to the image 600 of FIG. 6, it can be read that the amount of light is larger (higher brightness) toward the central portion of the speckle pattern (the pattern in which the light reflected by the sheet S is formed on the two-dimensional sensor 84). Ideally, by combining a light source 81 that irradiates almost parallel light with a lens 82 that is a collimated lens, the brightness in the central portion and the brightness in the peripheral portion should be equal to each other, but the effect of slight diffusion. As a result, the brightness of the peripheral portion is lower than the brightness of the central portion.

In such a situation, the movement amount calculated when the range 610, which is the central part of the speckle pattern, is set as the cutting range (that is, the analysis range) by the cutting unit 510 is defined as the ideal movement amount. To do. The amount of movement calculated when the range 620 slightly laterally deviated from the center of the speckle pattern is used as the analysis range by the cutting unit 510 is 0.025% different from the ideal amount of movement. The amount of movement calculated when the range 630, which is largely laterally deviated from the center of the speckle pattern, is used as the analysis range by the cutting unit 510 is 0.15% different from the ideal amount of movement.

As shown in FIG. 6, as the position of the analysis range moves away from the center of the speckle pattern, the error in the amount of movement increases.

As described above, the cutout unit 510 of the movement amount calculation unit 90R according to the related technique is configured to cut out a predetermined range as an analysis image with respect to the input image. Therefore, when the positional relationship between the light source 81 and the two-dimensional sensor 84 changes with the use of the image forming apparatus 100, the position of the speckle pattern formed on the two-dimensional sensor 84 changes. As a result, the predetermined analysis range deviates from the central position of the speckle pattern. In this case, the movement amount calculation unit 90R according to the related technique cannot accurately detect the movement speed of the moving body.

(How to shift the speckle pattern)
Next, how to shift the position of the speckle pattern formed on the two-dimensional sensor 84 will be described with reference to FIGS. 7 to 10.

FIG. 7 is a diagram showing that the speckle pattern is laterally displaced. When the angle θ2 formed by the light emitted by the light source 81 and the sheet S is 45 ° and the sheet S and the two-dimensional sensor 84 are parallel, the speckle pattern 110-A is formed on the two-dimensional sensor 84. Shall be. It is assumed that the center position of the speckle pattern 110-A coincides with the center of the two-dimensional sensor 84.

From here, it is assumed that the positional relationship between the light source 81 and the two-dimensional sensor 84 is changed, and the angle θ2 becomes less than 45 °, for example. As a result, the speckle pattern 700 formed on the two-dimensional sensor 84 moves in the lateral direction (opposite to the transport direction) as compared with the speckle pattern 110-A. In this case, the analysis range used for calculating the movement amount should be changed from the analysis range 110-L to the analysis range 700-L deviated in the lateral direction.

FIG. 8 is a diagram showing that the speckle pattern is displaced in the vertical direction. It is assumed that the positional relationship between the light source 81 and the two-dimensional sensor 84 is changed so that the angle formed by the optical axis of the light emitted by the light source 81 and the vertical direction orthogonal to the transport direction becomes non-90 °. As a result, the speckle pattern 800 formed on the two-dimensional sensor 84 moves in the vertical direction as compared with the speckle pattern 110-A. In this case, the analysis range used for calculating the movement amount should be changed from the analysis range 110-L to the analysis range 800-L deviated in the vertical direction.

FIG. 9 is a diagram showing that the speckle pattern protrudes from the two-dimensional sensor 84. It is assumed that the positional relationship between the light source 81 and the two-dimensional sensor 84 is changed so that the angle θ2 becomes less than 40 °, for example. As a result, the two-dimensional sensor 84 detects only a part of the light reflected by the sheet S (that is, the speckle pattern 900). In this case, the analysis range used for calculating the movement amount should be changed from the analysis range 110-L to the analysis range 900-L deviated in the lateral direction.

FIG. 10 is a diagram showing that the speckle pattern is larger than that of the two-dimensional sensor 84. The size of the speckle pattern depends on the aperture of the aperture of the light source 81. Therefore, in a certain aspect, the speckle pattern 1010-A formed when the angle θ2 formed by the light emitted by the light source 81 and the sheet S is 45 ° and the sheet S and the two-dimensional sensor 84 are parallel is formed. It can be larger than the two-dimensional sensor 84. In the present disclosure, the aperture of the light source 81 is elliptical (that is, the speckle pattern is elliptical), but in other aspects, the shape of the aperture of the light source 81 is not limited to an ellipse, but is a quadrangle or the like. The shape can be adopted.

In the example of FIG. 10, it is assumed that the positional relationship between the light source 81 and the two-dimensional sensor 84 is changed and the angle θ2 becomes less than 45 °. As a result, the speckle pattern 1020-A formed on the two-dimensional sensor 84 moves in the lateral direction (opposite to the transport direction) as compared with the speckle pattern 1010-A. In this case, the analysis range used for calculating the movement amount should be changed from the analysis range 1010-L to the analysis range 1020-L deviated in the lateral direction.

(Brightness distribution according to the horizontal direction, brightness distribution according to the vertical direction)
FIG. 11 is a diagram for explaining the luminance distribution in the horizontal direction and the luminance distribution in the vertical direction. In the segmentation diagram (A), the center of the two-dimensional sensor 84 and the center position of the speckle pattern coincide with each other. In the segmentation diagram (B), the center position of the speckle pattern is laterally displaced with respect to the center of the two-dimensional sensor 84.

The segment diagram (C) is a diagram for explaining the luminance distribution according to the lateral direction of the speckle pattern. The distribution 1110 is a luminance distribution that follows the lateral direction of the speckle pattern shown in the fractional diagram (A). The distribution 1120 is a luminance distribution that follows the lateral direction of the speckle pattern shown in the fractional diagram (B). The luminance distribution according to the horizontal direction represents the luminance distribution obtained by adding the luminance (light intensity) detected by the plurality of photoelectric conversion elements arranged in the vertical direction among the plurality of photoelectric conversion elements constituting the two-dimensional sensor 84. .. In the example shown in the fraction (C), the luminance according to the lateral direction of the pixel position 100pixel is 1024 photoelectrics arranged at the horizontal pixel position 100pixel among the plurality of photoelectric conversion elements constituting the two-dimensional sensor 84. The brightness obtained by adding the brightness detected by the conversion element is shown.

As shown in the fraction (C), the peak position 1110-P of the distribution 1110 appears at the lateral center position (680pixel) of the two-dimensional sensor 84. On the other hand, the peak position 1120-P of the distribution 1120 is deviated from the lateral center position of the two-dimensional sensor 84.

The fractional diagram (D) is a diagram for explaining the luminance distribution according to the vertical direction of the speckle pattern. The distribution 1130 is a luminance distribution that follows the vertical direction of the speckle pattern shown in the fractional diagram (A). Distribution 1140 is a luminance distribution that follows the vertical direction of the speckle pattern shown in the segment (B). The luminance distribution according to the vertical direction represents the luminance distribution obtained by adding the luminance (light intensity) detected by the plurality of photoelectric conversion elements arranged in the horizontal direction among the plurality of photoelectric conversion elements constituting the two-dimensional sensor 84. .. In the example shown in the fraction (D), the luminance according to the vertical direction of the pixel position 100pixel is 1360 photoelectrics arranged at the vertical pixel position 100pixel among the plurality of photoelectric conversion elements constituting the two-dimensional sensor 84. The brightness obtained by adding the brightness detected by the conversion element is shown.

As shown in the fraction (D), the peak position 1130-P of the distribution 1130 appears at the lateral center position (512pixel) of the two-dimensional sensor 84. The peak position 1140-P of the distribution 1140 also appears at the lateral center position (512pixel) of the two-dimensional sensor 84. This is because the center position of the speckle pattern shown in the fraction (A) and the segment (B) is located at the center of the two-dimensional sensor 84 in the vertical direction.

(Detection of the center position of the speckle pattern)
Next, the detection control of the center position of the speckle pattern by the detection unit 88 will be described with reference to FIGS. 12 to 16.

FIG. 12 is a diagram (No. 1) for explaining the control for detecting the center position of the speckle pattern. In a certain aspect, the detection unit 88 converts the luminance distribution detected by the two-dimensional sensor 84 into a luminance distribution 1200 that follows the lateral direction as shown in the segment diagram (C) of FIG.

The detection unit 88 detects the edge of the speckle pattern from the luminance distribution 1200. As an example, the detection unit 88 detects as an edge a pixel position in which the vertical relationship with the threshold brightness Cth is reversed in the brightness distribution 1200.

In the example shown in FIG. 12, the detection unit 88 detects two edges 1200-L and 1200-R from the luminance distribution 1200. As a result, the detection unit 88 determines that the two-dimensional sensor 84 includes all speckle patterns that follow the lateral direction (for example, the states of FIGS. 7 and 8).

The detection unit 88 sets the pixel position 1200-C, which is intermediate between the edge 1200-L and the edge 1200-R, at the center position of the speckle pattern (for example, in response to detecting two edges from the luminance distribution 1200). , (X, Y)), it is determined to be the position (X) in the lateral direction.

FIG. 13 is a diagram (No. 2) for explaining the control for detecting the center position of the speckle pattern. Similar to FIG. 12, the detection unit 88 converts the luminance distribution detected by the two-dimensional sensor 84 into the luminance distribution 1300 that follows the lateral direction.

The detection unit 88 detects the edge of the speckle pattern from the luminance distribution 1300. In the example shown in FIG. 13, the detection unit 88 detects one edge 1300-L from the luminance distribution 1300. The detection unit 88 determines whether or not there is a peak in the luminance distribution 1300 according to the fact that two edges could not be detected from the luminance distribution 1300.

In the example shown in FIG. 13, the detection unit 88 detects the peak position 1300-P in the luminance distribution 1300. In response to this determination, the detection unit 88 determines that the peak position 1300-P is a position in the lateral direction among the center positions of the speckle pattern.

In the above examples of FIGS. 12 and 13, the detection unit 88 specifies the position (X) in the lateral direction at the center position (for example, (X, Y)) of the speckle pattern, but the same applies. The position (Y) in the vertical direction at the center position can also be obtained by the algorithm.

According to the above, the detection unit 88 according to a certain embodiment converts the luminance distribution detected by the two-dimensional sensor 84 into a luminance distribution according to the horizontal direction and a luminance distribution according to the vertical direction, thereby performing the central position of the speckle pattern ( X, Y) can be specified.

FIG. 14 is a diagram (No. 1) for explaining the control for detecting the center position of the speckle pattern according to another embodiment. In another embodiment, the detection unit 88 can identify the edge 1400 of the speckle pattern based on the luminance distribution output by the two-dimensional sensor 84. As an example, the detection unit 88 scans the luminance distribution output by the two-dimensional sensor 84 in the horizontal direction or the vertical direction. At this time, the detection unit 88 identifies the position where the upper limit relationship between the luminance and the threshold luminance Cth in the luminance distribution is inverted is the edge 1400 of the speckle pattern.

Next, the detection unit 88 calculates the distance between the edges that follow the predetermined direction 1410. The detection unit 88 identifies the position of the end portion where the distance between the edges is the longest. In the example shown in FIG. 14, the detection unit 88 identifies two points, the edge 1420 and the edge 1430. The detection unit 88 specifies the intermediate 1450 of the specified two edge positions as the center position of the speckle pattern.

FIG. 15 is a diagram (No. 2) for explaining the control for detecting the center position of the speckle pattern according to another embodiment. The detection unit 88 according to the other embodiment identifies the edge 1500 of the speckle pattern, as in FIG.

In the example shown in FIG. 15, the detection unit 88 determines that all of the edges 1500 are not included on the two-dimensional sensor 84 (for example, the state of FIG. 10). In response to this determination, the detection unit 88 estimates a figure (in other words, a speckle pattern) formed by the outer diameter based on the outer diameter line formed by the plurality of detected edges 1500. The detection unit 88 can specify the center of gravity 1510 of the estimated figure as the center position of the speckle pattern.

FIG. 16 is a diagram illustrating a control for determining that the center position of the speckle pattern does not exist on the two-dimensional sensor 84.

In the example shown in the fraction (A), the center position 1610 of the speckle pattern 1600 is not on the two-dimensional sensor 84. In this state, the detection unit 88 converts the brightness distribution detected by the two-dimensional sensor 84 into a brightness distribution that follows the horizontal direction and / or the vertical direction. In the example shown in the segment (B), the detection unit 88 converts the luminance distribution detected by the two-dimensional sensor 84 into a luminance distribution 1620 that follows the lateral direction.

The detection unit 88 performs a smoothing process on the converted luminance distribution 1620 to obtain a luminance distribution 1630. The detection unit 88 determines whether or not a peak (inflection point) is present in the luminance distribution 1630. As an example, the detection unit 88 calculates the average value of the slope for each predetermined distance (for example, 20 pixels), and when the average value of the slope switches from positive to negative, it can be determined that a peak exists.

When the detection unit 88 determines that the peak does not exist in the luminance distribution 1630, it determines that the center 1610 of the speckle pattern 1600 does not exist on the two-dimensional sensor 84. The detection unit 88 may notify the control unit 6 to that effect. For example, when the control unit 6 receives the notification from the detection unit 88, the control unit 6 uses a voltage applied to the fixing motor 72 or the secondary transfer motor 73 rather than the transfer speed of the sheet S calculated by the movement amount calculation unit 90. The transfer speed (system speed) of the determined sheet S can be prioritized. The reason is that, as described with reference to FIG. 6, the movement amount error increases as the position of the analysis range moves away from the center of the speckle pattern.

(Structure of movement amount calculation unit 90)
FIG. 17 is a diagram illustrating a method of calculating a movement amount according to an embodiment. Since the parts having the same reference numerals as those in FIG. 5 are the same, the description of the parts will not be repeated.

With reference to FIG. 17, the movement amount calculation unit 90 differs from the movement amount calculation unit 90R according to the related technique described with reference to FIG. 5 in that it has the cutout unit 1700 instead of the cutout unit 510.

The cutting unit 1700 cuts out the first analysis image and the second analysis image from the input first image and second image according to the analysis range 94 stored in the ROM 92. The analysis range 94 is set by the setting unit 89 based on the center position of the speckle pattern detected by the detection unit 88. More specifically, the setting unit 89 sets the analysis range 94 so that the center position of the speckle pattern detected by the detection unit 88 is at the center of the analysis range 94.

As described above, the movement amount calculation unit 90 according to the embodiment does not cut out the input image in a predetermined range, but cuts out in an analysis range based on the center position of the speckle pattern. As a result, the movement amount calculation unit 90 can calculate the movement amount of the moving body with high accuracy even when the positional relationship of the optical system constituting the photographing unit 70 changes.

(Specific control flow)
FIG. 18 is a flowchart illustrating calculation control of the movement amount of the moving body according to a certain embodiment. The process shown in FIG. 18 can be realized by the FPGA 86. In other aspects, part or all of the processing may be implemented by the control unit 6 (CPU) or by other hardware.

In step S1810, the FPGA 86 receives a notification from the control unit 6 that the power is turned on to the image forming apparatus 100.

In step S1815, the FPGA 86 sets the analysis range 94 (image cropping range) as the detection unit 88 and the setting unit 89. Details of this process will be described later in FIG.

In step S1820, the FPGA 86 determines whether or not a print job has been input to the image forming apparatus 100. For example, when a print job is input to the image forming apparatus 100, the control unit 6 notifies the FPGA 86 to that effect. Thereby, the FPGA 86 can make this judgment.

When the FPGA 86 determines that the print job has been input to the image forming apparatus 100 (YES in step S1820), the FPGA 86 proceeds to the process in step S1825. If not (NO in step S1820), the FPGA 86 returns the process to step S1820.

In step S1825, the FPGA 86 initializes the variable N (eg, sets it to 1). This variable N can be stored in, for example, a RAM (Random Access Memory) (not shown).

In step S1830, the FPGA 86 photographs the sheet S being conveyed by the photographing unit 70 to generate the Nth image.

In step S1835, the FPGA 86 cuts out a portion corresponding to the analysis range 94 from the generated Nth image as the cutout unit 1700 to generate the Nth analysis image.

In step S1840, the FPGA 86 photographs the sheet S being conveyed by the photographing unit 70 to generate the N + 1th image.

In step S1845, the FPGA 86 cuts out a portion corresponding to the analysis range 94 from the generated N + 1th image to generate the N + 1th analysis image.

In step S1850, the FPGA 86 calculates the movement amount of the sheet S based on the Nth analysis image and the N + 1th analysis image as the movement amount calculation unit 90.

In step S1855, the FPGA 86 determines whether or not the print job has been completed. For example, when the print job is completed, the control unit 6 notifies the FPGA 86 to that effect. Thereby, the FPGA 86 can make this judgment.

When the FPGA 86 determines that the print job has been completed (YES in step S1855), the FPGA 86 ends a series of processes. If not (NO in step S1855), the FPGA 86 proceeds to step S1860.

In step S1860, the FPGA 86 increments the variable N and then returns the process to step S1840.

FIG. 19 is a flowchart illustrating details of the process of step S1815 in FIG.

In step S1910, the FPGA 86 irradiates a laser beam from the light source 81 toward the moving sheet S.

In step S1915, the FPGA 86 generates a reference image (speckle pattern) formed on the two-dimensional sensor 84 by the reflected light from the sheet S.

In step S1920, the FPGA 86 acquires a luminance distribution that follows the lateral direction of the reference image.

In step S1925, the FPGA 86 acts as a noise filter 87 to remove noise components from the acquired luminance distribution.

In step S1930, the FPGA 86 determines whether or not there are two edges (edges of the speckle pattern) in the luminance distribution following the lateral direction. As an example, the FPGA 86 determines whether or not there are two positions where the upper limit relationship between the luminance and the threshold luminance Cth in the luminance distribution is inverted.

When the FPGA 86 determines that there are two edges in the luminance distribution following the lateral direction (YES in step S1930), the processing proceeds to step S1935. If not (NO in step S1935), the FPGA 86 proceeds to step S1940.

In step S1935, the FPGA 86 sets the middle of the detected two edge positions as a position in the lateral direction among the center positions of the speckle pattern, and proceeds to the process in step S1950.

In step S1940, the FPGA 86 determines whether or not a peak is present in the luminance distribution following the lateral direction. When the FPGA 86 determines that a peak exists (YES in step S1940), the processing proceeds to step S1945. If not (NO in step S1940), the FPGA 86 proceeds to step S1960.

In step S1945, the FPGA 86 sets the detected peak position as a position in the lateral direction among the center positions of the speckle pattern, and proceeds to the process in step S1950.

In step S1950, the FPGA 86 performs the same processing as in steps S1920 to S1945 in the vertical direction, and sets a position in the vertical direction among the center positions of the speckle pattern.

In step S1955, the FPGA 86 sets the analysis range 94 as the setting unit 89 so that the center position of the detected speckle pattern is at the center of the analysis range.

According to the above series of controls, the sensor unit 44 as the movement amount detecting device accurately detects the conveying speed of the sheet S even when the positional relationship of the optical system constituting the photographing unit 70 changes. Can be done. In addition, this movement amount detecting device can detect the movement amount of the moving body with higher accuracy than the conventional one by using the same hardware configuration as the conventional one. Therefore, this technique can suppress an increase in the production cost of the sensor unit 44.

(Other configurations-Detection of center position)
The sensor unit 44 (movement amount detecting device) according to the above embodiment has a configuration of detecting the center position of the speckle pattern based on the image captured by the photographing unit 70. The image forming apparatus 100A according to another embodiment can physically measure the displacement amount of the arrangement position of the light source 81 and the two-dimensional sensor 84, and detect the central position of the speckle pattern based on the measurement result.

FIG. 20 is a diagram illustrating a configuration example of the sensor unit 44A included in the image forming apparatus 100A according to another embodiment. The sensor unit 2000 is different from the sensor unit 44 described with reference to FIG. 3 in that it further includes distance measuring sensors 2010 and 2020, and includes a detection unit 88A instead of the detection unit 88.

The distance measuring sensors 2010 and 2020 measure the distance to an object in a non-contact manner using, for example, light or ultrasonic waves. In another aspect, these sensors may be configured to measure the displacement of the object by a contact method (for example, a differential transformer method).

The distance measuring sensor 2010 measures the distance between the distance measuring sensor 2010 and the light source 81. In a certain aspect, the light source 81 is arranged so that the angle θ2 is 45 °. In this case, for example, when the light source 81 is tilted and the angle θ2 becomes larger than 45 °, the distance measured by the distance measuring sensor 2010 becomes shorter. On the other hand, when the light source 81 is tilted and the angle θ2 is smaller than 45 °, the distance measured by the distance measuring sensor 2010 becomes long.

The detection unit 88A receives the measurement results of the distance measuring sensors 2010 and 2020. The detection unit 88A identifies the angle θ2 based on the measurement result of the distance measuring sensor 2010. Similarly, the detection unit 88A identifies the angle θ1 formed by the vertical line with respect to the two-dimensional sensor 84 and the sheet S based on the measurement result of the distance measuring sensor 2020.

The detection unit 88A specifies the center position of the speckle pattern on the two-dimensional sensor 84 based on the specified angle θ1 and angle θ2.

According to the above, the sensor unit 2000 according to another embodiment can detect the center position of the speckle pattern by the distance measuring sensor. Even with such a configuration, the sensor unit 2000 can accurately calculate the moving speed of the moving body even when the positional relationship of the optical system constituting the photographing unit 70 changes.

(Other configurations-update center position)
In the above example, the sensor unit 44 is configured to detect the center position of the speckle pattern when the power of the image forming apparatus 100 is turned on and to set the analysis range 94. In another aspect, the sensor unit 44 may be configured to update (change) the analysis range 94 after the power is turned on to the image forming apparatus 100. In the example of FIG. 19, the FPGA 86 is a new image taken most recently by the photographing unit 70 at the time when a predetermined time (for example, 10 minutes) has elapsed since the reference image was taken. The analysis range 94 may be updated based on this.

(Other configurations-manual setting of analysis range)
In the above example, the sensor unit 44 automatically sets the analysis range 94. In a certain situation, as shown in FIG. 16, the center position of the speckle pattern may not exist on the two-dimensional sensor 84. In such a case, the setting unit 89 can update (change) the analysis range 94 based on the user input received by the input device (not shown) provided in the image forming apparatus 100. The input device can be, for example, a touch panel, a hard key, or the like.

(Other configurations-Analysis range setting (update) conditions)
In the above example, the sensor unit 44 is configured to detect the center position of the speckle pattern and set the analysis range 94 so that the center position is the center of the analysis range. In another embodiment, the sensor unit 44 has an analysis range set with the center of the two-dimensional sensor 84 as the center position in the initial state, and analyzes the center position of the speckle pattern when a predetermined condition is satisfied. The analysis range 94 may be updated so that it is in the center of the range. The predetermined condition may be, for example, a case where the center position of the speckle pattern is separated from the center of the two-dimensional sensor 84 by a predetermined distance (number of pixels) or more.

The various processes shown above are supposed to be realized by one FPGA 86, but are not limited thereto. These various functions include at least one processor-like semiconductor integrated circuit, at least one application specific integrated circuit (ASIC), at least one DSP (Digital Signal Processor), at least one FPGA, and /. Alternatively, it may be implemented by a circuit including a circuit having other arithmetic functions.

These circuits can realize the various functions shown above by reading one or more instructions from at least one tangible readable medium.

Such media take the form of magnetic media (eg, hard disks), optical media (eg, compact discs (CDs), DVDs), volatile memory, non-volatile memory of any type, and the like. It is not limited to the form.

Volatile memory may include DRAM (Dynamic Random Access Memory) and SRAM (Static Random Access Memory). The non-volatile memory may include a ROM and an NVRAM. A semiconductor memory can be a part of a semiconductor circuit along with at least one processor.

It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the scope of claims, and it is intended that all modifications within the meaning and scope equivalent to the scope of claims are included.

1 Image forming unit, 2 Intermediate transfer unit, 3 Sheet supply unit, 4 Fixing device, 5 Sheet winding unit, 6 Control unit, 10K, 10M, 10Y image drawing unit, 11C, 11K, 11M, 11Y Photoreceptor drum, 21 Intermediate transfer belt, 32 supply roller, 33 roll paper, 34 paper feed adjustment unit, 35, 52 transfer roller, 40 heating roller, 41 fixing roller, 42 pressure roller, 43 heater, 44, 44A, 2000 sensor unit, 45 nip Unit, 46 Ejection roller, 51 Winding roller, 53 Emission adjustment unit, 70 Imaging unit, 84 Two-dimensional sensor, 87 Noise filter, 88,88A detection unit, 89 Setting unit, 90, 90R Movement amount calculation unit, 100, 100A image forming apparatus, 510, 1700 cutting unit, 520 discrete Fourier transform unit, 530 standardization processing unit, 540 synthesis unit, 550 inverse discrete Fourier transform unit.

Claims (16)

A transport route for transporting a moving body and
A light source and a two-dimensional sensor are included, and the light reflected by the moving body that is being conveyed by irradiating light from the light source is photographed at different timings by using the two-dimensional sensor, and at least the first image and the second image are included. A shooting unit for generating two images, and
A detection unit for detecting the center position of a pattern formed on the two-dimensional sensor by the reflected light from the moving body, and a detection unit.
A setting unit for setting an image analysis range in the first image and the second image based on the center position detected by the detection unit, and a setting unit.
The amount of movement of the moving body between the shooting timings of the first and second images is calculated based on the image of the image analysis range in the first image and the image of the image analysis range in the second image. A movement amount detection device provided with a movement amount calculation unit for the purpose. The movement amount detecting device according to claim 1, further comprising a noise filter for smoothing the detection result of the two-dimensional sensor. The movement amount detecting device according to claim 1 or 2, wherein the setting unit is configured to set the image analysis range so that the center position detected by the detection unit becomes the center of the image analysis range. .. The movement amount detection according to any one of claims 1 to 3, wherein the detection unit is configured to detect the position having the highest brightness in the pattern formed on the two-dimensional sensor as the center position. apparatus. The detection unit
Based on the brightness distribution output by the two-dimensional sensor, the end of the pattern is detected.
Detects the end positions of the two points where the distance between the ends in the predetermined direction is the longest,
The movement amount detecting device according to any one of claims 1 to 3, which is configured to detect the middle of the end positions of the two points as the center position. The detection unit
The outer diameter line of the pattern is detected based on the luminance distribution output by the two-dimensional sensor.
The movement amount detecting device according to any one of claims 1 to 3, which is configured to detect the position of the center of gravity of the figure formed by the outer diameter line as the center position. The photographing unit includes a plurality of photoelectric conversion elements arranged in a first direction and a second direction orthogonal to the first direction.
The detection unit calculates a luminance distribution that follows one of the first and second directions based on the luminance distribution output by the two-dimensional sensor, and determines the peak position in the luminance distribution that follows the one direction. The movement amount detecting device according to any one of claims 1 to 3, which is configured to detect the center position as a position in the one direction. The photographing unit includes a plurality of photoelectric conversion elements arranged in a first direction and a second direction orthogonal to the first direction.
The detection unit
Based on the brightness distribution output by the two-dimensional sensor, the brightness distribution according to the first direction is calculated, and the peak position in the brightness distribution following the first direction is set as the position of the center position in the first direction. Detect and
Based on the brightness distribution output by the two-dimensional sensor, the brightness distribution according to the second direction is calculated, and the peak position in the brightness distribution following the second direction is set as the position of the center position in the second direction. The movement amount detecting device according to any one of claims 1 to 3, which is configured to detect. A displacement sensor that detects the amount of displacement of at least one of the light source and the two-dimensional sensor is further provided.
The movement amount detection device according to any one of claims 1 to 3, wherein the detection unit is configured to detect the center position based on the output of the displacement sensor. The detection unit
Based on the brightness distribution output by the two-dimensional sensor, the brightness distribution according to any one of the first and second directions is calculated.
Smooth the luminance distribution according to the one direction,
The movement amount detecting device according to claim 7 or 8, which is configured to determine that the center position of the pattern does not exist on the two-dimensional sensor when no peak is detected in the smoothed luminance distribution. .. The photographing unit is configured to photograph the moving body in response to the power being supplied to the movement amount detecting device and generate a reference image.
The detection unit is configured to detect the center position of the pattern in the reference image.
The setting unit according to any one of claims 1 to 10, wherein the setting unit is configured to set the image analysis range based on the center position of the pattern in the reference image detected by the detection unit. Movement amount detection device. The detection unit is configured to detect the center position of the pattern in a new image captured most recently by the imaging unit according to the elapse of a predetermined time after the reference image is captured.
The movement amount detecting device according to claim 11, wherein the setting unit is configured to update the image analysis range based on the center position of the pattern in the new image detected by the detection unit. It also has an input device that accepts user input.
The movement amount detecting device according to any one of claims 1 to 12, wherein the setting unit is configured so that the image analysis range can be changed based on the input of the user received by the input device. The setting unit
It is determined whether or not the center position detected by the detection unit is separated from the position corresponding to the center of the two-dimensional sensor by a predetermined distance or more.
When it is determined that the center position is separated from the position corresponding to the center by a predetermined distance or more, the image analysis range is set based on the center position detected by the detection unit.
Claim 1 is configured to set the image analysis range based on the position corresponding to the center when it is determined that the center position is not separated from the position corresponding to the center by a predetermined distance or more. The movement amount detecting device according to any one of 13 to 13. The two-dimensional sensor includes a plurality of photoelectric conversion elements arranged in a transport direction of the transport path and in an orthogonal direction orthogonal to the transport direction.
The movement amount detecting device according to any one of claims 1 to 6, wherein the number of photoelectric conversion elements arranged in the transport direction is larger than the number of photoelectric conversion elements arranged in the orthogonal direction. The moving body is a recording medium and
The movement amount detection device according to any one of claims 1 to 15,
An image forming apparatus including an image forming unit for forming an image on the recording medium.