JP7472525B2 - Image forming apparatus and detection method - Google Patents

Description

The present invention relates to an image forming apparatus and a detection method.

For example, in image forming devices such as inkjet recording devices, it is already known that an in-line reflective sensor detects the width of the recording medium (paper, etc.) to prevent ink from being ejected outside the recording medium.

As a technology for detecting the width of such recording media, an inkjet recording device has been disclosed that can correctly detect the paper width and print on the recording medium, regardless of the position of the image on the recording medium (for example, Patent Document 1). In addition, in order to accommodate various types of recording media with different reflectivities, a technology has been disclosed in which the light receiving threshold of a reflective sensor is changed for each paper type, or the light output value of the light emitting side is changed (for example, Patent Document 2).

However, with conventional technology, if there is only a small difference between the color of the platen, which is the transport path along which the recording medium is transported, the edge of the recording medium cannot be detected, and the width of the recording medium cannot be accurately detected.

The present invention has been made in consideration of the above, and aims to provide an image forming device and a detection method that can accurately detect the edge of a recording medium.

In order to solve the above-mentioned problems and achieve the object, the present invention provides an image forming device that forms an image on a recording medium, comprising: a two-dimensional imaging unit that images the recording medium or the transport path while moving in an orthogonal direction perpendicular to the transport direction on the transport path of the recording medium to obtain an image; a plurality of regions on the transport path that have different reflectivities in the transport direction at a position opposite to the orthogonal movement path of the two-dimensional imaging unit; and a position detection unit that detects the position of an end of the recording medium based on the difference between the output value of the captured image on the recording medium and the output value of the captured image in the plurality of regions, wherein the position detection unit detects the position of the end of the recording medium by using the region corresponding to the largest difference between the output value of the captured image on the recording medium and the output value of the captured image in the plurality of regions, and wherein only one two-dimensional imaging unit is provided, and the imaging range of the two-dimensional imaging unit includes all of the plurality of regions .

The present invention makes it possible to accurately detect the edge of a recording medium.

FIG. 1 is a diagram showing an example of a schematic configuration of an image forming apparatus according to an embodiment. FIG. 2 is a diagram showing an example of a schematic configuration of a main part of a conventional image forming apparatus. FIG. 3 is a diagram showing an example of a schematic configuration of a light detection sensor of a conventional image forming apparatus. FIG. 4 is a diagram illustrating an example of a schematic configuration of a main part of the image forming apparatus according to the embodiment. FIG. 5 is a diagram illustrating an example of a schematic configuration of a two-dimensional sensor of the image forming apparatus according to the embodiment. FIG. 6 is a diagram illustrating an example of a hardware configuration of the image forming apparatus according to the embodiment. FIG. 7 is a diagram illustrating an example of the configuration of functional blocks of the image forming apparatus according to the embodiment. FIG. 8 is a diagram for explaining the operation of detecting an edge of a recording medium in the image forming apparatus according to the embodiment. FIG. 9 is a flowchart showing an example of the flow of a paper width detection process in the image forming apparatus according to the embodiment.

Below, with reference to the drawings, an embodiment of an image forming apparatus and a detection method according to the present invention will be described in detail. Furthermore, the present invention is not limited to the following embodiment, and the components in the following embodiment include those that a person skilled in the art would easily conceive, those that are substantially the same, and those that are within the scope of what is called equivalent. Furthermore, various omissions, substitutions, modifications, and combinations of the components can be made without departing from the spirit of the following embodiment.

(General configuration of image forming apparatus)
Fig. 1 is a diagram showing an example of a schematic configuration of an image forming apparatus according to an embodiment. The schematic configuration of the image forming apparatus 1 according to the embodiment will be described with reference to Fig. 1. Note that in the embodiment, an inkjet recording apparatus will be described as the image forming apparatus 1, but the image forming apparatus 1 is not limited to this, and may be another image forming apparatus such as an MFP (Multifunction Peripheral) or a laser printer.

The image forming device 1 shown in FIG. 1 is an inkjet recording device that forms an image by ejecting ink from a recording head onto recording paper 10. As shown in FIG. 1, the image forming device 1 includes a support frame 2, a guide rod 3, a sub-guide 4, a carriage 5, a maintenance unit 8, a cartridge 9, a main scanning motor 11, a drive pulley 12, a pressure roller 13, a timing belt 14, and a platen 15.

The support frame 2 is a frame that supports the image forming device 1. The guide rod 3 is a rod that supports the carriage 5 as the image forming unit so that it can move in the main scanning direction (arrow AA shown in FIG. 1) (a direction perpendicular to the conveying direction of the recording paper 10). The sub-guide 4 is a guide member that supports the carriage 5 together with the guide rod 3 and guides the carriage 5 so that it can move in the main scanning direction.

The carriage 5 is a unit that has a recording head 6 (described later in FIG. 2) that ejects ink as a liquid to form an image, and causes the recording head 6 to form an image while moving in the main scanning direction along the guide rod 3 and the sub-guide 4.

The maintenance unit 8 is positioned at a position where the carriage 5 is retracted, and is a unit that performs maintenance on the nozzles of the carriage 5 by cleaning and capping the recording head 6 to prevent nozzle clogging, etc.

The cartridge 9 is an ink cartridge that supplies ink to the recording head 6 mounted on the carriage 5.

The main scanning motor 11 is a motor that rotates the drive pulley 12 to rotate the timing belt 14 stretched between the drive pulley 12 and the pressure roller 13, thereby moving the carriage 5 back and forth in the main scanning direction (scanning operation). The drive pulley 12 is a pulley that is rotated by the main scanning motor 11 and rotates the timing belt 14 stretched between the drive pulley 12 and the pressure roller 13. The pressure roller 13 is a roller that applies a constant tension to the timing belt 14 stretched between the drive pulley 12. The timing belt 14 is a belt that is stretched between the drive pulley 12 and the pressure roller 13 and fixes the carriage 5. The timing belt 14 rotates due to the rotation of the drive pulley 12 by the main scanning motor 11, and moves the carriage 5 in the main scanning direction.

The platen 15 is a member that supports the recording paper 10 from below and serves as a transport path for the recording paper 10 when the recording paper 10 is transported in the sub-scanning direction (arrow B in FIG. 1) by a sub-scanning motor 19, which will be described later in FIG. 6. The platen 15 is formed with a multi-color display section 15a that includes multiple colored areas formed along the main scanning direction.

The recording medium, recording paper 10, is supported from below by a platen 15 and transported intermittently in the sub-scanning direction by a sub-scanning motor 19 under a carriage 5 that reciprocates in the main scanning direction. A recording head 6 mounted on the carriage 5 ejects ink based on image data input to the image forming device 1 onto the recording paper 10 transported over the platen 15 to form an image. Note that while FIG. 1 illustrates the recording paper 10, which is paper, as a recording medium, this is not limited to this, and the recording medium may be, for example, cloth or the like.

(Main configuration of a conventional image forming apparatus)
2 is a diagram showing an example of a schematic configuration of a main part of a conventional image forming apparatus 500. Here, the main part configuration of a conventional image forming apparatus 500 will be described with reference to FIG.

The conventional image forming device 500 shown in FIG. 2 includes, as its main components, a guide rod 3, a carriage 5, a recording head 6, a main scanning motor 11, a drive pulley 12, a pressure roller 13, a timing belt 14, a platen 15, a main scanning encoder 16, an encoder sheet 17, and a light detection sensor 18. Of these, the configurations and roles of the guide rod 3, the carriage 5, the main scanning motor 11, the drive pulley 12, the pressure roller 13, and the timing belt 14 are the same as those described for the image forming device 1 shown in FIG. 1 above. In addition, the platen 15 of the image forming device 500 does not have the multi-color display section 15a shown in FIG. 1 above.

The carriage 5 carries the recording head 6, which is made up of multiple heads for ejecting ink of different colors. The recording head 6 has multiple nozzles formed on the surface facing the recording paper 10 for ejecting ink, and ejects ink from the nozzles when the liquid chamber inside is pressurized by a piezoelectric element or the like. As shown in FIG. 2, the recording head 6 includes a recording head 6k for ejecting black (K) ink, a recording head 6y for ejecting yellow (Y) ink, a recording head 6c for ejecting cyan (C) ink, and a recording head 6m for ejecting magenta (M) ink.

The main scanning encoder 16 is a sensor that is fixed to the carriage 5 and detects the position of the carriage 5 by reading an encoder sheet 17 that is provided along the main scanning direction and has slits at regular intervals when the carriage 5 moves back and forth in the main scanning direction. Generally, among the positions in the main scanning direction that can be read by the encoder sheet 17, the end position on the right side as viewed from the paper surface of FIG. 2 is called the home position.

The light detection sensor 18 is fixed to the carriage 5 and detects the edge of the recording paper 10 by receiving the reflected light of the emitted light when the carriage 5 moves in the main scanning direction and detecting the difference in reflectance between the recording paper 10 and the platen 15.

As shown in FIG. 2, the recording paper 10 is transported in the sub-scanning direction (arrow B) on the platen 15 by the sub-scanning motor 19. Then, an image is formed on the recording paper 10 by alternating between the reciprocating movement of the carriage 5 in the main scanning direction by the main scanning motor 11 and the transport of the recording paper 10 in the sub-scanning direction.

Figure 3 is a diagram showing an example of the schematic configuration of a light detection sensor in a conventional image forming device. The schematic configuration of the light detection sensor 18 will be described with reference to Figure 3.

As shown in FIG. 3, the light detection sensor 18 has a light emitting diode 18a and a phototransistor 18b.

The light-emitting diode 18a is an LED (Light Emitting Diode) that emits light to detect the reflectance of the recording paper 10 and the platen 15. The phototransistor 18b is a transistor that receives the light emitted from the light-emitting diode 18a and reflected by the recording paper 10 or the platen 15, and a current (collector current) flows as a sensor output value according to the amount of the reflected light. Therefore, the reflectance of the recording paper 10 or the platen 15 can be detected by reading the sensor output value (collector current of the phototransistor 18b) by the light detection sensor 18. Therefore, the difference in reflectance between the recording paper 10 and the platen 15 can be detected by the output of the light detection sensor 18, and the paper width of the recording paper 10 can be detected and the recordable range (image formable range) can be determined. Here, reflectance is not limited to the ratio of the amount of reflected light received by the phototransistor 18b to the amount of light emitted by the light-emitting diode 18a, but may simply be considered as the intensity of the amount of reflected light, since the amount of light emitted by the light-emitting diode 18a toward the recording paper 10 and the platen 15 is constant.

However, there are many recording media, including recording paper 10, in the world today that come in a variety of colors and materials. Therefore, if the reflectance of recording paper 10 is close to the reflectance of platen 15, optical detection sensor 18 will not be able to detect the edge of recording paper 10, and therefore will not be able to detect the paper width accurately. To solve this problem, the configuration and operation of image forming device 1 according to this embodiment will be described in detail below.

(Main configuration of image forming apparatus)
4 is a diagram showing an example of a schematic configuration of a main part of an image forming apparatus according to an embodiment of the present invention, with reference to which the main part configuration of the image forming apparatus 1 according to the present embodiment will be described.

As shown in FIG. 4, the image forming apparatus 1 according to this embodiment includes, as its main components, a guide rod 3, a carriage 5, a recording head 6, a main scanning motor 11, a drive pulley 12, a pressure roller 13, a timing belt 14, a platen 15, a main scanning encoder 16, an encoder sheet 17, and a two-dimensional sensor 20 (an example of a two-dimensional imaging unit). Of these, the configurations and roles of the guide rod 3, carriage 5, main scanning motor 11, drive pulley 12, pressure roller 13, timing belt 14, main scanning encoder 16, and encoder sheet 17 are the same as those described for the image forming apparatus 500 shown in FIG. 2 above.

As shown in FIG. 4, the image forming device 1 according to this embodiment has a two-dimensional sensor 20 instead of the light detection sensor 18 provided in the image forming device 500 described above. As shown in FIG. 4, the two-dimensional sensor 20 is fixed to the carriage 5, and when the carriage 5 moves in the main scanning direction, the two-dimensional sensor 20 is a sensor that irradiates light from an internal light source onto an object to be imaged (recording paper 10, multi-color display section 15a, etc.) and receives the reflected light with an image sensor to obtain two-dimensional image data (captured image).

In the image forming apparatus 1 according to the present embodiment, a multi-color display section 15a is formed on the upper surface of the platen 15 at a position facing the main scanning direction movement path of the two-dimensional sensor 20 that moves in accordance with the movement of the carriage 5 in the main scanning direction. The multi-color display section 15a is formed on the platen 15 along the main scanning direction and includes a first color display section 15a-1, a second color display section 15a-2, and a third color display section 15a-3, which are multiple areas that are different in color (different reflectance) in the sub-scanning direction (transport direction). That is, the multi-color display section 15a is formed on the platen 15 so that all of the areas of the multi-color display section 15a are included in the imaging range of the two-dimensional sensor 20. The first color display section 15a-1, the second color display section 15a-2, and the third color display section 15a-3 are each different in color. By making them different colors, the ratio of the amount of reflected light (reflectance) when light is irradiated from a specific light source to the recording paper 10 will be different.

The two-dimensional sensor 20 is fixed to the carriage 5 and configured to move in the main scanning direction together with the carriage 5, but this is not limited thereto, and the mounting position is not limited as long as the sensor is configured to be movable in the main scanning direction and capable of detecting the edge of the recording paper 10.

In the example shown in FIG. 4, the regions of the multi-color display unit 15a are three regions of different colors, but this is not limited thereto, and they may be two regions of different colors, or four or more regions of different colors. In addition, the multiple regions of the multi-color display unit 15a are formed as regions of different colors with different reflectance, but this is not limited thereto, and for example, regions of different materials may be formed as regions with different reflectance.

(Schematic configuration of two-dimensional sensor)
5 is a diagram showing an example of a schematic configuration of a two-dimensional sensor of an image forming apparatus according to an embodiment of the present invention. The schematic configuration of two-dimensional sensor 20 of image forming apparatus 1 according to the present embodiment will be described with reference to FIG.

As shown in FIG. 5, the two-dimensional sensor 20 has a frame 51, an image sensor board 52, an image sensor 53, a lens 54, a support 55, a two-dimensional sensor CPU (Central Processing Unit) 56, a light-emitting diode 57, a reference chart 58, and a mist-preventing transparent member 59.

The frame 51 is a member that constitutes the outer casing of the two-dimensional sensor 20. The upper surface of the frame 51 opposite the recording paper 10 is open, and the opening is closed by the image sensor board 52. In addition, an opening 51a is provided on the lower surface of the frame 51 on the recording paper 10 side, for irradiating light from the light emitting diode 57 onto the recording paper 10 and detecting the reflected light by the image sensor 53. The opening 51a only needs to be large enough to capture an image of at least the area (imaging area) required as the imaging target. In addition, the frame 51 is arranged with a gap d between it and the recording paper 10, and can move in the main scanning direction while maintaining the gap d between it and the recording paper 10. However, because of this gap d, a shadow is generated around the opening 51a, so the opening 51a is formed slightly larger in advance, taking into consideration the area where the shadow is generated. On the other hand, a reference chart 58 is fixed inside the frame 51 in the portion of the opening 51a other than the imaging area, so that the imaging area and the reference chart 58 can be imaged simultaneously by the image sensor 53.

The image sensor board 52 is a board on which various components are mounted, and is fixed to the frame 51 in such a manner that it covers the opening on the top surface of the frame 51. An image sensor 53, a two-dimensional sensor CPU 56, and a light-emitting diode 57 are mounted on the bottom surface of the image sensor board 52, i.e., on the inner surface of the frame 51.

The image sensor 53 is a solid-state imaging element that converts the light incident through the lens 54 into an electrical signal to capture a two-dimensional image (captured image). As the solid-state imaging element, a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor, etc., is used.

The lens 54 is an optical system component for focusing the light reflected from the subject, which is emitted from the light emitting diode 57, onto the image sensor 53. The lens 54 also functions as an optical path changing component (e.g., a transparent component with a refractive index n) because the above-mentioned gap d causes an optical path difference between the optical path from the imaging subject, such as the recording paper 10, to the image sensor 53 and the optical path from the reference chart 58 to the image sensor 53.

The support 55 is a member that maintains a distance from the image sensor 53 and supports the lens 54.

The two-dimensional sensor CPU 56 is a calculation device for controlling the operation of the two-dimensional sensor 20.

The light-emitting diode 57 is a light source that irradiates light onto the imaging subject, such as the recording paper 10, and the reference chart 58. The light-emitting diode 57 does not need to be mounted on the image sensor board 52, and may be fixed, for example, to any part inside the frame 51.

The reference chart 58 is a color chart used for color correction, etc., of the captured image obtained by the image sensor 53 from the subject to be imaged.

The mist-preventing transparent member 59 is a cover member that covers the opening 51a provided in the frame body 51 to prevent the image sensor 53, lens 54, light-emitting diode 57, etc. from becoming dirty due to mist or the like entering through the opening 51a. A replacement port 51b is provided on the lower side of the frame body 51 so that the mist-preventing transparent member 59 can be removed for cleaning or replacement as necessary.

In the above-mentioned two-dimensional sensor 20, when the light from the outside is inserted around the frame 51, it is necessary to make the illumination conditions of the imaging area in the opening 51a and the reference chart 58 as identical as possible. Specifically, it is necessary to make the imaging area not exposed to light from the outside of the two-dimensional sensor 20, so that only the light irradiated by the light emitting diode 57 fixed in the frame 51 is used as much as possible. To achieve this, it is preferable that the gap d between the bottom surface of the frame 51 where the opening 51a is provided and the recording paper 10 is as small as possible, but it is necessary to ensure a size that does not allow the frame 51 and the recording paper 10 to come into contact with each other, taking into consideration the flatness of the recording paper 10. For this reason, the gap d is usually configured to be about 1 to 2 mm, for example, but if the recording paper 10 is stiff, floating may occur, and it is preferable to have a mechanism for moving the two-dimensional sensor 20 up and down so as not to damage the recording paper 10, and to variably adjust the gap d. This mechanism makes it possible to handle thick recording paper 10.

(Hardware configuration of image forming apparatus)
6 is a diagram showing an example of a hardware configuration of the image forming apparatus according to the embodiment, the hardware configuration of the image forming apparatus 1 according to the embodiment will be described with reference to FIG.

As shown in FIG. 6, the image forming device 1 has a control unit 100, a carriage 5 including a recording head 6, a main scanning encoder 16, and a two-dimensional sensor 20, a main scanning motor 11, a sub-scanning encoder 16a, a sub-scanning motor 19, a paper feed motor 30, a paper discharge motor 31, and an operation display unit 32.

The control unit 100 is a control unit that is responsible for the overall control of the image forming apparatus 1. As shown in FIG. 6, the control unit 100 has an external I/F 110, a main control unit 120, a sensor control unit 130, a head drive control unit 140, a main scanning drive unit 150 (drive unit), a sub-scanning drive unit 160, a paper feed drive unit 170, and a paper discharge drive unit 180.

The external I/F 110 is an interface for communicating with external devices connected via a network such as a LAN (Local Area Network) or a WAN (Wide Area Network) constructed using a wired or wireless data transmission path.

The main control unit 120 is a control board having a calculation function and a storage function for controlling the entire image forming apparatus 1. The main control unit 120 has a CPU 301, a ROM (Read Only Memory) 302, a RAM (Random Access Memory) 303, a NVRAM (Non-Volatile RAM) 304, an ASIC (Application Specific Integrated Circuit) 305, and an FPGA (Field-Programmable Gate Array) 306. The main control unit 120 also inputs position information in the main scanning direction of the carriage 5 detected by reading the encoder sheet 17 by the encoder 16. The main control unit 120 also inputs position information of the carriage 5 in the sub-scanning direction detected by the sub-scanning encoder 16a.

The CPU 301 is a computing device that loads various programs stored in the ROM 302 into the RAM 303 used as a work area to realize various functions. The NVRAM 304 is a non-volatile storage device that stores various setting information, etc.

The ASIC 305 is an integrated circuit for performing various signal processing and image processing on image data. The FPGA 306 is an integrated circuit for performing input/output signal processing and the like for controlling the operation of the entire control unit 100.

The sensor control unit 130 is a control circuit that controls the operation of the two-dimensional sensor 20 provided on the carriage 5. The head drive control unit 140 is a control circuit that controls the ejection operation of the recording head 6 mounted on the carriage 5 based on image data.

The main scanning drive unit 150 is a drive circuit that controls the rotational operation of the main scanning motor 11 to control the movement and position of the carriage 5 fixed to the timing belt 14 in the main scanning direction. The sub-scanning drive unit 160 is a drive circuit that controls the rotational operation of the sub-scanning motor 19 to control the transport amount and transport timing of the recording paper 10 in the sub-scanning direction (transport direction).

The paper feed drive unit 170 is a drive circuit that drives the paper feed motor 30 to rotate so that the recording paper 10 is fed at a predetermined timing. The paper discharge drive unit 180 is a drive circuit that controls the rotation operation of the paper discharge motor 31 so that the recording paper 10 on which an image has been formed is discharged.

The operation display unit 32 is, for example, a touch panel configured with a liquid crystal panel or the like, and is a device that has an input function such as buttons for receiving input from the user, and a display function for displaying the operating status and setting values of the image forming device 1, etc.

Note that the hardware configuration of the image forming device 1 shown in FIG. 5 is an example, and other components may be included. Also, for example, if the function of the ASIC 305 or FPGA 306 can be replaced by a function realized by the CPU 301 executing a program, the ASIC 305 or FPGA 306 may not be provided.

(Functional block configuration of image forming apparatus)
7 is a diagram showing an example of a functional block configuration of an image forming apparatus according to an embodiment. The functional block configuration of a main control unit 120 and a two-dimensional sensor 20 of an image forming apparatus 1 according to the present embodiment will be described with reference to FIG.

As shown in FIG. 7, the two-dimensional sensor 20 includes an image sensor 53 and a two-dimensional sensor CPU 56. The two-dimensional sensor CPU 56 includes a position detection unit 201 and an actual distance calculation unit 202.

The position detection unit 201 is a functional unit that detects the boundary position between the recording paper 10 and the platen 15 (i.e., the edge of the recording paper 10) in the captured image of the object (the recording paper 10 and the multi-color display unit 15a, etc.) captured by the image sensor 53.

The actual distance calculation unit 202 is a functional unit that calculates the actual distance in the main scanning direction that the recording paper 10 occupies in the captured image based on the boundary position between the recording paper 10 and the platen 15 detected by the position detection unit 201.

The position detection unit 201 and the actual distance calculation unit 202 described above are realized by the two-dimensional sensor CPU 56 executing a program. At least one of the position detection unit 201 and the actual distance calculation unit 202 may be realized by a hardware circuit such as an integrated circuit.

As shown in FIG. 7, the main control unit 120 includes a two-dimensional sensor command unit 101, a carriage position identification unit 102, an end position calculation unit 103, a platen end position determination unit 104, and a width calculation unit 105.

The two-dimensional sensor command unit 101 is a functional unit for controlling the operation of the two-dimensional sensor 20.

The carriage position identification unit 102 is a functional unit that identifies the absolute position of the carriage 5 in the main scanning direction when the edge of the recording paper 10 is detected in the image captured by the two-dimensional sensor 20.

The end position calculation unit 103 is a functional unit that calculates the absolute position in the main scanning direction of the end of the recording paper 10 from the actual distance in the main scanning direction of the recording paper 10 on the image captured by the two-dimensional sensor 20 calculated by the actual distance calculation unit 202 and the absolute position in the main scanning direction of the carriage 5 identified by the carriage position identification unit 102.

The platen end position determination unit 104 is a functional unit that determines whether the platen 15 is at the end position when the carriage 5 moves in the main scanning direction during the paper width detection process in Figure 9, which will be described later.

The width calculation unit 105 is a functional unit that calculates the width of the recording paper 10 from the absolute positions of both ends of the recording paper 10 in the main scanning direction calculated by the end position calculation unit 103.

The above-mentioned two-dimensional sensor command unit 101, carriage position identification unit 102, end position calculation unit 103, platen end position determination unit 104, and width calculation unit 105 are realized by a program executed by the CPU 301 shown in FIG. 6. At least one of the two-dimensional sensor command unit 101, carriage position identification unit 102, end position calculation unit 103, platen end position determination unit 104, and width calculation unit 105 may be realized by a hardware circuit such as an ASIC 305 or an FPGA 306.

Note that the position detection unit 201 and actual distance calculation unit 202 of the two-dimensional sensor CPU 56, and the two-dimensional sensor command unit 101, carriage position identification unit 102, end position calculation unit 103, platen end position determination unit 104, and width calculation unit 105 of the main control unit 120 shown in FIG. 7 are conceptual representations of functions, and are not limited to such configurations. For example, multiple functional units illustrated as independent functional units in FIG. 7 may be configured as a single functional unit. On the other hand, the function of one functional unit shown in FIG. 7 may be divided into multiple parts and configured as multiple functional units.

In addition, while FIG. 7 shows a configuration in which the two-dimensional sensor 20 has a position detection unit 201 and an actual distance calculation unit 202, for example, at least one of the functions of the position detection unit 201 and the actual distance calculation unit 202 may be provided by the main control unit 120. Furthermore, the functions of the position detection unit 201 and the actual distance calculation unit 202 may be provided by the main control unit 120, and the two-dimensional sensor 20 may only have an imaging function using the image sensor 53 and transmit the captured image to the main control unit 120.

(Example of operation for detecting the edge of recording paper)
8 is a diagram for explaining an operation of detecting an edge of a recording medium in the image forming apparatus 1 according to the embodiment. With reference to FIG. 8, an operation of detecting an edge of a recording sheet 10 in the image forming apparatus 1 according to the embodiment will be explained.

The captured image IM shown in FIG. 8 is an example of an image captured by the image sensor 53 through the opening 51a. As shown in the captured image IM, the multi-color display section 15a of the platen 15 is composed of a first color display section 15a-1 with the highest reflectance, a second color display section 15a-2 with an intermediate reflectance, and a third color display section 15a-3 with the lowest reflectance. Furthermore, in the example shown in FIG. 8, the detection operation when a recording paper 10 with a high reflectance is set will be described.

As shown in the graph of FIG. 8, the sensor output value of each area of the multiple color display section 15a (the brightness value of the portion of each area of the multiple color display section 15a in the captured image IM) and the sensor output value of the recording paper 10 (the brightness value of the portion of the recording paper 10 in the captured image IM) are detected as differences D1 to D3, respectively. In the example shown in FIG. 8, recording paper 10 with a high reflectance is set, so the difference D1 between the sensor output value of the first color display section 15a-1 and the sensor output value of the recording paper 10 is small, whereas the difference D3 between the sensor output value of the third color display section 15a-3 and the sensor output value of the recording paper 10 is large. Furthermore, if the recording paper 10 has a low reflectance, the magnitude relationship between the difference D1 and the difference D3 will be reversed. In other words, if the reflectance of the recording paper 10 is constant, by providing multiple areas of different reflectance (different colors) on the multi-color display section 15a, it is possible to find an area on the multi-color display section 15a where the difference with the sensor output value of the recording paper 10 becomes large (the third color display section 15a-3 in the example shown in FIG. 8).

Specifically, the position detection unit 201 detects the position of the end of the recording paper 10 by using the area corresponding to the largest difference between the sensor output value of each area of the multi-color display unit 15a and the sensor output value of the recording paper 10. In this case, the position detection unit 201 may detect, for example, the position where the sensor output value has changed by 1/2 the difference D3 from the smaller value of the sensor output values of the third color display unit 15a-3 and the recording paper 10 (the sensor output value of the third color display unit 15a-3 in the example shown in FIG. 8) as the position of the end of the recording paper 10. Then, the actual distance calculation unit 202 calculates the actual distance X in the main scanning direction occupied by the recording paper 10 in the captured image IM based on the boundary position between the recording paper 10 detected by the position detection unit 201 and the multi-color display unit 15a (here, the third color display unit 15a-3). Note that the method of detecting the position of the end of the recording paper 10 by the position detection unit 201 is not limited to the above-mentioned operation.

(Flow of paper width detection process of image forming device)
Fig. 9 is a flow chart showing an example of the flow of paper width detection processing of the image forming apparatus 1 according to the embodiment. The flow of paper width detection processing of the image forming apparatus 1 according to the embodiment will be described with reference to Fig. 9. Note that, before the paper width detection processing is started, the carriage 5 of the image forming apparatus 1 is assumed to be in the home position (the right end as viewed from the paper surface in Fig. 4).

<Step S11>
Next, the main scanning drive unit 150 rotates the main scanning motor 11 under control of the main control unit 120 to move the carriage 5 in the main scanning direction to the start position of scanning the recording paper 10 and the platen 15. Then, the process proceeds to step S12.

<Step S12>
Then, the main scanning drive unit 150 rotates the main scanning motor 11 under the control of the main control unit 120 to start scanning the carriage 5 in the main scanning direction relative to the recording paper 10 and the platen 15. Then, the process proceeds to step S13.

<Step S13>
The two-dimensional sensor command unit 101 causes the image sensor 53 to start capturing an image of the target (such as the recording paper 10 and the multi-color display unit 15a) when the carriage 5 starts scanning. The position detection unit 201 then reads out the image captured by the image sensor 53 as a sensor output. Then, the process proceeds to step S14.

<Step S14>
Position detection unit 201 detects the position of the edge of recording paper 10 by using the area corresponding to the largest difference among the differences between the sensor output values of each area of multi-color display unit 15a and the sensor output value of recording paper 10. If the edge position of recording paper 10 is detected (step S14: Yes), the process proceeds to step S15, and if not detected (step S14: No), the process proceeds to step S18.

<Step S15>
The actual distance calculation unit 202 calculates the actual distance in the main scanning direction occupied by the recording paper 10 in the image captured by the image sensor 53, based on the boundary position (the edge position of the recording paper 10) between the recording paper 10 and the multiple color display unit 15a detected by the position detection unit 201. Then, the actual distance calculation unit 202 transmits information on the calculated actual distance to the main control unit 120 via the sensor control unit 130.

Then, the carriage position identification unit 102 of the main control unit 120 identifies the absolute position of the carriage 5 in the main scanning direction. Then, the process proceeds to step S16.

<Step S16>
The edge position calculation unit 103 calculates the absolute position in the main scanning direction of the edge of the recording paper 10 from the actual distance in the main scanning direction of the recording paper 10 on the captured image received from the actual distance calculation unit 202 and the absolute position in the main scanning direction of the carriage 5 identified by the carriage position identification unit 102. Then, the process proceeds to step S17.

<Step S17>
The edge position calculation unit 103 stores information on the calculated absolute positions of the edges of the recording paper 10 in the main scanning direction in the RAM 303 or the NVRAM 304. Then, the process proceeds to step S18.

<Step S18>
The platen end position determination unit 104 determines whether or not the position of the carriage 5 in the main scanning direction has reached the end position of the platen 15. If the position of the carriage 5 has reached the end position of the platen 15 (step S18: Yes), the process proceeds to step S19, and if the position has not reached the end position (step S18: No), the process returns to step S12.

<Step S19>
The width calculation unit 105 reads out from the RAM 303 or the NVRAM 304 information on the absolute positions of both ends in the main scanning direction of the recording paper 10 calculated by the end position calculation unit 103, and calculates the width in the main scanning direction of the recording paper 10. Then, the paper width detection process ends.

As described above, in the image forming device 1 according to this embodiment, a multi-color display section 15a is formed on the upper surface of the platen 15 at a position facing the main scanning direction movement path of the two-dimensional sensor 20 that moves in accordance with the movement of the carriage 5 in the main scanning direction, and the multi-color display section 15a has multiple areas each having a different color, and the position detection section 201 detects the position of the edge of the recording paper 10 by using the area corresponding to the largest difference between the sensor output value of each area of the multi-color display section 15a and the sensor output value of the recording paper 10. This makes it possible to accurately detect the edge of the recording medium, the recording paper 10, and to prevent ink from being ejected outside the recording paper 10.

In the above embodiment, when at least one of the functional units of the main control unit 120 and the two-dimensional sensor CPU 56 of the image forming device 1 is realized by the execution of a program, the program is provided by being pre-installed in a ROM or the like. The program executed by the main control unit 120 and the two-dimensional sensor CPU 56 of the image forming device 1 according to the above embodiment may be provided by being recorded in a computer-readable recording medium such as a CD-ROM (Compact Disc Read Only Memory), a flexible disk (FD), a CD-R (Compact Disk-Recordable), or a DVD in an installable or executable format. The program executed by the main control unit 120 and the two-dimensional sensor CPU 56 of the image forming device 1 according to the above embodiment may be provided by being stored on a computer connected to a network such as the Internet and downloaded via the network. The program executed by the main control unit 120 and the two-dimensional sensor CPU 56 of the image forming device 1 according to the above embodiment may be provided or distributed via a network such as the Internet. In addition, the programs executed by the main control unit 120 and the two-dimensional sensor CPU 56 of the image forming device 1 according to the above embodiment are modularized to include at least one of the functional units described above, and in terms of actual hardware, the CPU reads the programs from the above storage device and executes them, causing each of the above functional units to be loaded and generated on the main storage device.

In addition, each function in the above-mentioned embodiment can be realized by one or more processing circuits. Here, "processing circuit" includes a processor programmed to execute each function by software, such as a processor implemented by an electronic circuit, and devices such as an ASIC (Application Specific Integrated Circuit), DSP (Digital Signal Processor), FPGA (Field Programmable Gate Array), and conventional circuit modules designed to execute each of the above-mentioned functions.

LIST OF SYMBOLS 1 Image forming device 2 Support frame 3 Guide rod 4 Sub-guide 5 Carriage 6, 6c, 6k, 6m, 6y Recording head 8 Maintenance unit 9 Cartridge 10 Recording paper 11 Main scanning motor 12 Drive pulley 13 Pressure roller 14 Timing belt 15 Platen 15a Multiple color display unit 15a-1 First color display unit 15a-2 Second color display unit 15a-3 Third color display unit 16 Main scanning encoder 16a Sub-scanning encoder 17 Encoder sheet 18 Light detection sensor 18a Light emitting diode 18b Phototransistor 19 Sub-scanning motor 20 Two-dimensional sensor 30 Paper feed motor 31 Paper discharge motor 32 Operation display unit 51 Frame 51a Opening 51b Replacement port 52 Image sensor board 53 Image sensor 54 Lens 55 Support 56 CPU for two-dimensional sensor
57 Light emitting diode 58 Reference chart 59 Mist prevention transparent member 100 Control unit 101 Two-dimensional sensor command unit 102 Carriage position identification unit 103 End position calculation unit 104 Platen end position determination unit 105 Width calculation unit 110 External I/F
120 Main control unit 130 Sensor control unit 140 Head drive control unit 150 Main scanning drive unit 160 Sub-scanning drive unit 170 Paper feed drive unit 180 Paper discharge drive unit 201 Position detection unit 202 Actual distance calculation unit 301 CPU
302 ROM
303 RAM
304 NVRAM
305 ASIC
306 FPGA
500 Image forming device IM Captured image

JP 2014-097582 A Japanese Patent Application Laid-Open No. 07-179248

Claims (9)

An image forming apparatus for forming an image on a recording medium,
a two-dimensional imaging unit that captures an image of the recording medium or the transport path while moving in a direction perpendicular to a transport direction of the recording medium on the transport path;
a plurality of regions having different reflectances in the conveying direction, the regions being disposed on the conveying path and facing a moving path of the two-dimensional imaging unit in the orthogonal direction;
a position detection unit that detects a position of an edge of the recording medium based on a difference between an output value of the captured image on the recording medium and an output value of the captured image in the plurality of regions;
Equipped with
the position detection unit detects a position of an end of the recording medium by utilizing an area corresponding to a largest difference among differences between an output value of the captured image on the recording medium and an output value of the captured image in the plurality of areas , and only one two-dimensional imaging unit is provided;
An image forming apparatus , wherein each of the plurality of regions is included in the imaging range of the two-dimensional imaging section . an actual distance calculation unit that calculates an actual distance in the perpendicular direction that the recording medium occupies in the captured image based on the position of the end of the recording medium detected by the position detection unit;
an edge position calculation unit that calculates an absolute position of the edge of the recording medium in the perpendicular direction based on the actual distance calculated by the actual distance calculation unit;
The image forming apparatus according to claim 1 , further comprising: The image forming apparatus according to claim 2, further comprising a width calculation unit that calculates the width of the recording medium in the orthogonal direction from the absolute positions of the ends on both sides of the recording medium in the orthogonal direction calculated by the end position calculation unit. The image forming device according to claim 3, wherein the two-dimensional imaging unit includes the position detection unit and the actual distance calculation unit. The image forming device according to any one of claims 1 to 4, wherein the multiple regions are each a different color. The image forming device according to any one of claims 1 to 4, wherein the multiple regions are made of different materials. a carriage having a recording head that ejects ink onto the recording medium and to which the two-dimensional imaging unit is fixed;
a drive unit that moves the carriage in the perpendicular direction;
7. The image forming apparatus according to claim 1, further comprising: The image forming device according to any one of claims 1 to 7, wherein the plurality of regions include a first color display section having the highest reflectance, a third color display section having a reflectance lower than that of the first color display section, and a second color display section having a reflectance intermediate between that of the first color display section and the third color display section. A method for detecting an image forming apparatus that forms an image on a recording medium, comprising the steps of:
an imaging step in which a two-dimensional imaging unit captures an image of the recording medium or the transport path while moving in an orthogonal direction perpendicular to a transport direction on the transport path of the recording medium to obtain an image;
a position detection step of detecting a position of an end of the recording medium by using an area corresponding to the largest difference among output values of the captured image in a plurality of areas having different reflectances in the conveying direction, the area being located on the conveying path opposite to a moving path of the two-dimensional imaging unit in the orthogonal direction, and the output value of the captured image on the recording medium;
and only one two-dimensional imaging unit is provided;
A detection method in which each of the plurality of regions is included in the imaging range of the two-dimensional imaging unit .

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