JP7367521B2 - Image forming device, image reading device, and calibration method - Google Patents

Description

The present invention relates to an image forming apparatus, an image reading apparatus, and a calibration method.

Image forming apparatuses that form images on media, particularly those used for commercial applications that require high quality, require highly accurate calibration and prompt abnormality detection. Therefore, there is a technique for detecting density unevenness or poor image quality by capturing a formed image. For imaging, a two-dimensional image is acquired using an imaging sensor in which a plurality of imaging elements are lined up across a width perpendicular to the medium transport direction in a plane parallel to the medium transport direction in a direction intersecting the medium transport direction. Ru.

In such an image forming apparatus, if the length of a single image sensor is increased to match the size of an image to be formed, there are problems in that the cost increases and the yield during manufacturing deteriorates. On the other hand, there is a technique that captures images of the entire width of the medium as a whole by arranging a plurality of image sensors and capturing images in parallel (Patent Document 1). In this case, adjustments are made to match the sensitivity characteristics between the image sensors.

Japanese Patent Application Publication No. 2012-4868

However, as image quality improves, it becomes necessary to adjust absolute values such as hue, and adjustment between image sensors is not sufficient, and conventionally, it is necessary to perform processing outside the image forming device. There is a problem with this.

An object of the present invention is to provide an image forming apparatus, an image reading apparatus, and a calibration method that can more easily and accurately calibrate each image sensor.

In order to achieve the above object, the invention according to claim 1:
a transport unit that moves the medium along a predetermined transport path;
an imaging unit having a plurality of imaging sensors and imaging the surface of the medium on the transport path;
a colorimeter unit that measures the color of the surface of the medium on the transport path;
a control unit;
Equipped with
The imaging range by each of the plurality of image sensors has an overlapping portion between the adjacent image sensors in a width direction perpendicular to the transport direction along the transport route,
The image forming apparatus is characterized in that the control unit performs a calibration operation of the image sensor based on the imaging result of the predetermined inspection image located in the overlapping portion by the imaging unit and the color measurement result by the colorimetric unit. It is.

Further, the invention according to claim 2 provides an image forming apparatus according to claim 1, which includes:
a colorimetry moving unit that moves the colorimetry range by the colorimetry unit in the width direction;
The imaging unit has three or more of the imaging sensors,
The control unit moves the color measurement range to each of the formation positions of the plurality of inspection images, and causes the color measurement unit to perform color measurement for each of the formation positions.

Further, the invention according to claim 3 provides an image forming apparatus according to claim 2, which includes:
comprising a forming operation unit that forms an image on the surface of the medium on the transport path,
The control unit determines a positional shift amount of the plurality of inspection images in the transport direction based on a transport speed of the medium by the transport unit and a movement speed of the colorimetric range by the colorimetric moving unit. The invention is characterized in that the plurality of inspection images are respectively formed by the formation operation section.

Further, the invention according to claim 4 provides an image forming apparatus according to claim 2, which includes:
The control unit is capable of changing the conveyance speed of the medium by the conveyance unit, and is configured to change the speed of movement of the colorimetric range by the colorimetric moving unit and the amount of positional deviation of the plurality of inspection images in the conveyance direction. The method is characterized in that the conveyance speed of the medium by the conveyance section is determined based on the following.

Further, the invention according to claim 5 provides an image forming apparatus according to claim 2, which includes:
The conveyance section is characterized in that it is capable of conveying the medium so that the medium passes through a color measurement range by the color measurement section a plurality of times.

Further, the invention according to claim 6 provides an image forming apparatus according to any one of claims 1, 2, and 5, which includes:
comprising a forming operation unit that forms an image on the surface of the medium on the transport path,
The control unit may cause the formation operation unit to form the inspection image on the overlapping portion.

Further, the invention according to claim 7 provides an image forming apparatus according to any one of claims 1, 2, 5, and 6, which includes:
The control unit is characterized in that it can change the conveyance speed of the medium by the conveyance unit.

Moreover, the invention according to claim 8 is:
a transport unit that moves the medium along a predetermined transport path;
an imaging unit having a plurality of imaging sensors and imaging the surface of the medium on the transport path;
a colorimeter unit that measures the color of the surface of the medium on the transport path;
a control unit;
Equipped with
The imaging range by each of the plurality of image sensors has an overlapping portion between the adjacent image sensors in a width direction perpendicular to the transport direction along the transport route,
The image reading device is characterized in that the control unit performs a calibration operation of the image sensor based on the imaging result of the predetermined inspection image located in the overlapping portion by the imaging unit and the colorimetric result of the colorimetric unit. It is.

Moreover, the invention according to claim 9 is:
A transport unit that moves the medium along a predetermined transport route, and an imaging unit that has a plurality of image sensors and captures an image of the surface of the medium on the transport route, and is perpendicular to the transport direction along the transport route. A method for calibrating the image sensor in an image forming apparatus having an overlapping portion between the image sensors adjacent in the width direction,
The image forming apparatus includes a color measurement unit that measures the color of the surface of the medium on the transport path,
The present invention is characterized in that the method includes a calibration execution step of performing a calibration operation of the image sensor based on the imaging result of the predetermined inspection image located in the overlapping portion by the imaging unit and the color measurement result by the colorimetric unit.

According to the present invention, there is an effect that each image sensor can be calibrated more easily and accurately.

1 is a schematic front view of the overall configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a diagram illustrating a head unit, an imaging section, and a color measurement section. FIG. 1 is a block diagram showing the functional configuration of an image forming apparatus. FIG. 3 is a diagram illustrating generation and reading of a calibration test image. It is a figure explaining the positional relationship of two images for inspection. 7 is a flowchart showing a control procedure of calibration control processing. It is a figure which shows the modification of the formation position of two images for an inspection. It is a flowchart which shows the control procedure of the calibration control process of a modification.

Embodiments of the present invention will be described below based on the drawings.
FIG. 1 is a schematic diagram of the overall configuration of an image forming apparatus 1 according to an embodiment of the present invention, viewed from the front.

The image forming apparatus 1 includes a medium supply section 10, a forming section 20, a medium discharge section 30, a control section 40 (see FIG. 3), and the like. In this image forming apparatus 1, the medium M on which an image is formed is sent from the medium supply section 10 to the formation section 20 based on the control operation by the control section 40, and after the image is formed, it is ejected to the medium discharge section 30. Ru.

The medium supply section 10 includes a medium supply tray 11, a supply conveyance section 12, and the like.
The medium supply tray 11 is a plate-like member on which one or more mediums M can be placed. The medium supply tray 11 moves up and down according to the amount of the medium M placed thereon, and the topmost medium M is held at the conveyance start position by the supply conveyance section 12 .
As the medium M, various media such as printing paper of various thicknesses, cells, films, and fabrics are used. The medium M may have a surface made of a non-absorbent material into which ink does not penetrate.

The supply conveyance unit 12 includes a plurality of (for example, two) rollers 121 and 122, a ring-shaped belt 123 supported by the rollers 121 and 122 on the inner surface, and a conveyor belt for transporting the medium M placed on the medium supply tray 11. It has a supply section (not shown) that delivers the top one to the belt 123. The supply conveyance unit 12 conveys the medium M transferred onto the belt 123 by the supply unit according to the circumferential movement of the belt 123 due to the rotation of the rollers 121 and 122, and sends it to the forming unit 20.

The forming section 20 includes an image forming drum 21, a delivery unit 22, a head unit 23 (forming operation section), a fixing section 24, an imaging section 25, a colorimetric section 26, a delivery section 27, and the like.

The image forming drum 21 has a cylindrical outer peripheral shape, supports the medium M on its outer peripheral surface (conveyance surface), and moves the medium M along a (predetermined) conveyance path according to its rotational movement. A heater is provided on the inner surface of the image forming drum 21, and can heat the conveying surface so that the medium M placed on the conveying surface reaches a predetermined set temperature.

The delivery unit 22 delivers the medium M delivered from the supply conveyance section 12 to the image forming drum 21 . The delivery unit 22 is provided at a position between the supply conveyance section 12 of the medium supply section 10 and the image forming drum 21. The delivery unit 22 includes a claw portion 221 that grips one end of the medium M sent by the supply conveyance section 12, a cylindrical delivery drum 222 that guides the medium M gripped by the claw portion 221, and the like. When the medium M acquired from the supply conveyance section 12 by the claw section 221 is sent to the delivery drum 222, it moves along the outer peripheral surface of the rotating delivery drum 222, and is guided to the outer peripheral surface of the image forming drum 21 and received. passed on.

The head unit 23 is provided on an ink ejection surface facing the medium M at various locations on the surface of the medium M that moves on the conveyance path in accordance with the rotation of the image forming drum 21 carrying the medium M. An image is formed by ejecting ink droplets from a plurality of nozzle openings. In the image forming apparatus 1 of this embodiment, the four head units 23 are spaced apart from the outer peripheral surface of the image forming drum 21 by a predetermined distance and are arranged at predetermined intervals. The four head units 23 each output ink of four colors of CMYK (cyan, magenta, yellow, and black), for example. Here, each color ink of C, M, Y, and K is ejected in order from the upstream side in the transport direction (second direction) of the medium M, but the invention is not limited thereto. Any ink can be used as the ink, but here, it changes phase between a sol state and a gel state depending on the temperature, and can be cured and fixed by irradiation with a predetermined active energy ray, such as ultraviolet rays. Ink is used. When the ink ejected from the head unit 23 in a sol state lands on the medium M, its temperature decreases and it quickly gels, increasing its viscosity, and the ink is fixed on the medium M by ultraviolet rays irradiated from the fixing section 24. .
Each of the head units 23 here has a line head that can form an image at once over the image forming width on the medium M in combination with the rotation of the image forming drum 21.

The fixing unit 24 irradiates the surface of the medium M with predetermined active energy rays, in this case ultraviolet rays as described above. The fixing unit 24 includes, for example, an LED lamp that emits ultraviolet light. The fixing unit 24 is located near the outer peripheral surface of the image forming drum 21, and after ink is ejected from the head unit 23 onto the medium M conveyed by the rotation of the image forming drum 21, the medium M is fixed to the image forming drum 21. The medium M is arranged so as to be able to irradiate the medium M with ultraviolet rays in a range from 21 to the delivery section 27 . The fixing unit 24 includes a shielding member, and sufficiently reduces the amount of ultraviolet rays irradiated to areas other than a predetermined range of the medium M on the transport surface compared to the predetermined range.

The imaging unit 25 images the surface of the medium M on the downstream side of the head unit 23 and the fixing unit 24 in the transport direction on the transport path, and outputs the image to the control unit 40 as read data. The imaging unit 25 has a plurality of line sensors (imaging sensors). The line sensor may be, for example, a CMOS sensor, although it is not particularly limited. The imaging unit 25 measures the amount of incident light at three wavelengths, RGB, and acquires each as a luminance value.

The color measurement unit 26 measures the color of the surface of the medium M downstream of the head unit 23 and the fixing unit 24 in the transport direction on the transport path, here further downstream of the imaging unit 25, and records the color measurement results. It is output to the control section 40. For example, the color measurement position of the color measurement section 26 is not on the image forming drum 21 but on the belt 273 of the delivery section 27, but is not limited thereto. The color space obtained by measurement by the colorimeter 26 may be changeable, and for example, color values can be output in the L*a*b* coordinate system.

The delivery section 27 transports the medium M on which ink has been ejected and fixed from the image forming drum 21 to the medium discharge section 30 . The delivery unit 27 includes a plurality of (for example, two) rollers 271 and 272, a ring-shaped belt 273 supported by the rollers 271 and 272 on the inner surface, a cylindrical delivery roller 274, and the like. The delivery unit 27 guides the medium M on the image forming drum 21 onto the belt 273 using a transfer roller 274, and moves the transferred medium M together with the belt 273, which moves around as the rollers 271 and 272 rotate. The medium is transported and sent out to the medium discharge section 30.

The medium ejecting section 30 stores the image-formed medium M sent out from the forming section 20 until it is taken out by the user. The medium discharge section 30 includes a plate-shaped medium discharge tray 31 on which the medium M conveyed by the delivery section 27 is placed.

FIG. 2 is a bottom view (a) of the head unit 23 seen from the conveying surface side of the image forming drum 21, and a bottom view (b) of the light incident surface of the imaging section 25 seen from the side facing the outer peripheral surface of the image forming drum 21. ) and the colorimeter 26 viewed from above the outer peripheral surface of the belt 273 (c).

As shown in FIG. 2A, the head unit 23 includes a plurality of inkjet heads 231 in which openings of a plurality of nozzles N are arranged within a predetermined range (array range). Here, one head unit 23 has eight inkjet heads 231, but the invention is not limited to this. In the eight inkjet heads 231, two nozzle rows in which the openings of the nozzles N are arranged in the width direction are arranged in two rows in the transport direction, and the opening positions of the nozzles N in these two rows are staggered in the width direction. It is childlike. Note that the size and number of the openings of the nozzle N are shown here to be large and small for the sake of explanation, and are different from the actual number.

As shown in FIG. 2(b), the imaging unit 25 includes a plurality of imaging sensors 251 in which light entrance ports (imaging ranges) for the plurality of imaging elements P are located in a predetermined range in the width direction. Although the imaging unit 25 has a plurality of image sensors 251, four in this case, the present invention is not limited to this. The imaging sensors 251 are arranged in a houndstooth pattern, and the imaging range of each imaging sensor 251 has overlapping portions D1 to D3 between adjacent imaging sensors 251 in the width direction. The position of the light entrance of each image sensor P and the position of each light receiving sensor may be the same in the width direction, or may be arranged by mirrors, lenses, etc. so that the light receiving sensors are collectively located near the center in the width direction. It may also be a reduction optical system. Further, when performing color imaging mainly using RGB, the image pickup elements P of the line sensor do not need to be arranged one-dimensionally only in the width direction. Note that although the light entrance aperture is shown here divided into several large sections for the sake of explanation, in reality it may be connected as one, or it may be divided into more finely divided sections depending on the resolution (number of elements) of the light receiving sensor, etc. Each may be separated. The magnitude relationship between the imaging resolution of the imaging section 25 and the image forming resolution of the head unit 23 is not particularly limited here.

As shown in FIG. 2C, the colorimeter of the colorimeter 26 performs colorimetry in a part of the area (colorimetry range) of the medium M in the width direction. The colorimeter is movable in the width direction along the support member 261. The support member 261 may be provided with, for example, a rail and a belt, and the colorimeter may be able to reciprocate on the rail according to the movement of the belt. The colorimeter is fixed during color measurement and measures color within a color measurement range.

FIG. 3 is a block diagram showing the functional configuration of the image forming apparatus 1 of this embodiment.
In addition to the above-described forming section 20, the image forming apparatus 1 includes a control section 40, a transport drive section 45, an image processing section 46, a storage section 50, a communication section 61, a display section 62, and an operation reception section. 63, a bus 90, etc.

In addition to the above-described imaging section 25, colorimetric section 26, and nozzle N (included in the head unit 23), the forming section 20 includes a head driving section 28 that ejects ink from the nozzle N, and a fixing section that operates the fixing section 24. It has a drive section 29 and the like.

The head driving section 28 operates a mechanism that applies pressure to the ink in an ink flow path that communicates with each nozzle N to supply ink, thereby causing the head unit 23 (inkjet head 231) to perform an image forming operation. For example, the head drive section 28 generates a drive voltage signal for a piezoelectric element that deforms the wall surface of a pressure section (pressure chamber) provided in an ink flow path, and outputs the drive voltage signal to the piezoelectric element. The head drive unit 28 selects a pre-stored voltage waveform pattern based on the control signal from the control unit 40 and generates a power-amplified drive voltage signal, and generates a drive voltage signal according to the image data to be formed inputted from the storage unit 50. to switch whether or not to output a drive voltage signal to each piezoelectric element. The pressure chamber is deformed by the deformation of the piezoelectric element, and pressure fluctuations are applied to the ink in a predetermined pattern, and in response to this, the desired liquid is delivered from the opening of the nozzle N to a predetermined ink landing position (position in plan view). A volume of ink droplets is ejected at a desired speed.

The fixing drive unit 29 outputs a drive signal to the fixing unit 24 to cause it to emit (light-emit) a predetermined active energy ray (here, ultraviolet rays).

The control unit 40 controls the overall operation of the image forming apparatus 1 and controls the operation of each unit. The control unit 40 includes a CPU 41 (Central Processing Unit), a RAM 42 (Random Access Memory), and the like.

The CPU 41 performs various calculation processes, and controls the transportation of the medium M, the supply of ink, temperature management and ejection, imaging, color measurement, maintenance operations, etc. in the image forming apparatus 1 . Further, the CPU 41 performs various processes related to image formation based on image data, status signals of each section, clock signals, etc. according to the program read from the storage section 50.

The RAM 42 provides a working memory space for the CPU 41 and stores temporary data. The RAM 42 may include a nonvolatile memory, and the data stored in this nonvolatile memory and the data stored in the storage unit 50 are allocated as appropriate.

The image processing unit 46 performs processing related to calibration of the image sensor 251 based on the measurement results of the imaging unit 25 and the color measurement unit 26. The image processing unit 46 may include a CPU and a RAM, or may include a dedicated hardware circuit in addition to or in place of these. Furthermore, the hardware configuration of the image processing section 46 may be one in which the CPU 41 and the RAM 42 of the control section 40 are also used.

When a normal image formed on the medium M is captured by the imaging unit 25, the image processing unit 46 connects the images obtained by the plurality of imaging sensors 251 to generate one image data. . In the overlapping parts D1 to D3 shown in FIG. 2, a boundary position is determined in advance to determine which of the two adjacent image sensors 251 should use data, and images on both ends of the boundary position are The data obtained by the element is discarded.

The storage unit 50 stores job data 52 related to image formation acquired from the outside via the communication unit 61, control programs and setting data related to various control operations of the control unit 40 and the image processing unit 46, and the like. A DRAM is mainly used as a structure for temporarily storing job data 52 and its processing data, and an HDD (Hard Disk Drive) or non-volatile memory is used as a structure for storing control programs and setting data. It is not limited to this. For example, the job data 52 may be stored in a non-volatile memory, and the initial program, initial setting data, etc. may be stored in a mask ROM that cannot be rewritten or updated. In addition, data of a specific image such as for inspection instead of a normal image, setting data for forming the specific image, etc. may be stored in a nonvolatile memory. The control program includes a calibration program 51 that adjusts the sensitivity between the image sensors 251.

Further, the data stored in the storage unit 50 includes calibration data 53 obtained by executing the program 51. For example, the image data captured by the image capture unit 25 is calibrated using the calibration data 53 and then subjected to analysis processing.

The conveyance drive section 45 includes a medium conveyance section 71 that operates each section that conveys the medium M, such as the supply conveyance section 12, the image forming drum 21, the transfer unit 22, and the delivery section 27, and a color measurement range by the color measurement section 26. (a colorimeter).

The medium conveyance section 71 includes a motor that rotates each roller, drum, etc., and that causes the claw section 221 to operate. Of these, at least the image forming drum 21 and the transport drive section 45 constitute the transport section in the image forming apparatus 1 of this embodiment.

The colorimetric moving unit 72 moves the colorimeter (colorimetric range) of the colorimetric unit 26 in the width direction. For example, when the support member 261 is provided with a rail and a belt as described above, the colorimetric moving unit 72 moves the belt a desired distance at a predetermined speed, thereby moving the colorimeter fixed to the belt. Move the range the same distance.

The communication unit 61 is a communication interface that controls communication operations with external devices. The communication interface includes one or more interfaces compatible with various communication protocols, such as a LAN card. The communication unit 61 acquires original image data to be formed and setting data (job data) related to image formation from an external device under the control of the control unit 40, and also transmits status information and the like to the external device. be able to.

The display unit 62 displays the status of the image forming apparatus 1, an operation menu, etc. in response to a control signal from the control unit 40. The display unit 62 has a display screen such as a liquid crystal screen. Further, the display section 62 may include an LED or the like used for notification operation.

Further, the operation accepting unit 63 accepts a user's operation and outputs it to the control unit 40 . The operation reception unit 63 includes, for example, a touch sensor provided overlapping the display screen. The control unit 40 associates information on the content and position of the menu displayed on the display screen with information on the type and position of the user's touch operation received by the operation reception unit 63, and performs processing according to the operation as an image. Control operations to be performed by each part of the forming apparatus 1 are performed. The operation reception unit 63 may include a push button switch, a numeric keypad, or the like.

The bus 90 is a signal transmission path that electrically connects the control unit 40 and each of the above components to exchange signals.
Among the above components, the image reading device of this embodiment is composed of the transport section, the imaging section 25, the colorimetric section 26, and the control section 40. Further, the image reading device of this embodiment may include a colorimetric moving section 72.

Next, a calibration operation of the image sensor 251 in the image forming apparatus 1 of this embodiment will be described.
As described above, in the calibration operation, a test image of a predetermined color is read by the image sensor 251 and the color measurement section 26, and each image sensor 251 is calibrated by the image processing section 46 based on the difference between the image capture result and the color measurement result. This is done by determining the amount. For example, the image processing unit 46 converts the luminance values of each RBG wavelength measured by the image sensor 251 into color values of the L*a*b* coordinate system, and the L*a Compare with the color value in the *b* coordinate system. Calculation of the calibration amount based on the comparison results may be performed using any of the conventionally known methods.

FIG. 4 is a diagram illustrating generation and reading of a calibration test image.
The head unit 23 generates an inspection image It (inspection image) on the medium M so as to include an overlapping portion of the imaging areas of adjacent imaging sensors 251. The inspection image It is, for example, an image in which patch images of each color are sequentially arranged in the transport direction. First, as shown in FIG. 4A, the inspection image It1 is generated so as to include the overlapping portion D1, and is imaged by both the image sensors 2511 and 2512 related to the overlapping portion D1. The color measurement range by the color measurement unit 26 is positioned to match this overlapping portion D1, and the color measurement of the inspection image It1 is performed. The two image sensors 2511 and 2512 can be calibrated by generating and reading one inspection image It1 once.

Next, as shown in FIG. 4(b), an inspection image It2 that is the same as the inspection image It1 is formed so as to include the overlapping portion D3 of the image sensors 2513 and 2514, and is imaged by the image sensors 2513 and 2514. . During this time, the color measurement range of the color measurement section 26 is moved in the width direction by the color measurement moving section 72, and changed to perform color measurement of the overlapping portion D3.

When the colorimetric range moves, the colorimeter performs colorimetry on the inspection image It2, and compares it with the imaging results of the imaging sensors 2513 and 2514, respectively, to determine the calibration amount of each imaging sensor 2513 and 2514.
Note that, regarding the overlapping portion D2, since the overlapping portions D1 and D3 are imaged by the imaging sensors 2512 and 2513, respectively, generation of the inspection image, imaging, and color measurement may be omitted.

FIG. 5 is a diagram illustrating the positional relationship between the inspection images It1 and It2.
Since the moving speed V2 of the colorimetric moving section 72 is fixed, there is a gap between the upstream end of the inspection image It1 in the transportation direction and the downstream end of the inspection image It2 in the transportation direction. A distance dt12 in the conveyance direction that depends on (based on) a speed V1 (conveyance speed), a movement speed V2 of the colorimetric moving unit 72, and a distance dw13 in the width direction between the overlapping portions D1 and D3 is required. That is, the distance dt12 is determined as dt12≧dw13×(V1/V2), and during image formation, the inspection image It2 is the sum of the length of the inspection image It1 and the length of the distance dt12 (shift amount) in the transport direction. The inspection image It1 is formed shifted from the position of the inspection image It1. In reality, the distance dt12 is set to be somewhat larger than the right side of the above equation because time is required for speed changes at the start and end of the movement of the colorimetric moving unit 72 and for stabilization of the colorimeter. If it is too large, it will not fit in one medium M, and the medium M will be wasted, so it is not necessary to make it larger than necessary. Note that when performing this calibration operation, the distance dt12 can be made smaller by lowering the moving speed V1 than during normal image formation. The medium transport unit 71 may be able to change the moving speed V1, that is, the transport speed of the medium, and may determine the transport speed according to the distance dt12.

FIG. 6 is a flowchart showing a control procedure by the control unit 40 of the calibration control process executed in the image forming apparatus 1 of this embodiment. This calibration control process constitutes a calibration execution step according to the calibration method of the present embodiment, and is started, for example, when a predetermined activation command by a user or the like is obtained from the communication unit 61 or the operation reception unit 63.

When the calibration control process is started, the control unit 40 outputs a control signal to the color measurement moving unit 72 to adjust the color measurement range to the position of the overlapping portion D1 (step S101). The control unit 40 sets the conveyance speed (the speed may be lower than that during normal image formation), and sends out the medium M by the medium conveyance unit 71. While conveying the medium M at the set speed, the inspection images It1, The head driving unit 28 is operated based on the image data of It2, and an operation for forming inspection images It1 and It2 on the medium M is started (step S102).

The control unit 40 adjusts the period in which the medium M moves and the inspection image It1 reaches the imaging position of the imaging sensors 2511 and 2512, and the period in which the inspection image It2 reaches the imaging position of the imaging sensors 2513 and 2514, respectively. to perform an imaging operation (step S103). Further, after the medium M moves further and the inspection image It1 reaches the color measurement range, the control unit 40 causes each patch image to be measured (step S104).

The control unit 40 outputs a control signal to the colorimetric moving unit 72 to move the colorimetric range to the position of the overlapping portion D2 (step S105). After the color measurement range reaches a predetermined position of the test image It2, the control unit 40 causes each patch image of the test image It2 to undergo color measurement (step S106).

The control unit 40 converts the RGB format image data output from each image sensor 251 to the image processing unit 46 into color space data, for example, each component of the L*a*b* coordinate system ( brightness, saturation, hue, etc.) (step S107). The control unit 40 causes the image processing unit 46 to compare the conversion result of the imaging result and the color measurement result, and calculate the amount of correction of the measurement value of each image sensor 251 based on the difference (step S108). The control unit 40 causes the image processing unit 46 to determine a calibration setting based on the calculated correction amount and stores it in the calibration data 53 (step S109). The control unit 40 then ends the calibration control process.

Note that the processing contents of steps S102 to S107 may be performed in parallel and/or with the timing of processing the inspection image It1 and the timing of processing the inspection image It2 appropriately, and may be performed in parallel. This does not mean that everything is done in series.

[Modified example]
FIG. 7 is a diagram showing a modification of the formation positions of the inspection images It1 and It2.
In the above embodiment, the inspection images It1 and It2 are formed at different positions in the conveyance direction as the medium M is conveyed. When the medium transport unit 71 can be operated so that the medium M passes through the color measurement range multiple times, the inspection images It1 and It2 may be formed at the same position in the transport direction of the medium M. Alternatively, the medium M is peeled off from the image forming drum 21 by locating the color measuring section 26 facing the outer peripheral surface of the image forming drum 21 so that the image on the medium M can be measured on the image forming drum 21. Alternatively, the inspection images It1 and It2 at the same position in the transport direction of the medium M may be color-measured in each revolution while the medium M is rotated a plurality of times.

FIG. 8 is a flowchart showing a control procedure by the control unit 40 of the calibration control process regarding the inspection images It1 and It2 in this modification. This calibration control process is the same as the calibration control process of the above embodiment, except that steps S111 and S112 are added, and step S103 is replaced with step S103a. The same processing contents are given the same reference numerals and detailed explanations will be omitted.

After starting to form the inspection images It1 and It2 on the medium M in the process of step S102, the control unit 40 outputs a control signal to the imaging unit 25 during a period when the medium M reaches the imaging position of the imaging sensor 251. Then, inspection images It1 and It2 are captured in parallel (step S103a). Then, the process of the control unit 40 moves to step S104.

In the process of step S104, after the colorimetry of the inspection image It1 is completed, and before the upstream end of the medium M leaves the transfer roller 274 (and the outer peripheral surface of the image forming drum 21), the control unit 40 controls the medium transport unit 71 is stopped in the normal transport direction, and the medium M is transported backwards until the downstream end (head) of the inspection image It2 returns to the upstream side in the transport direction relative to the color measurement range of the color measurement unit 26. (Step S111). Then, the process of the control unit 40 moves to the process of step S105. Note that the processes in steps S111 and S105 may be performed in parallel. After that, the control unit 40 causes the medium transport unit 71 to restart the transport operation of the medium M in the transport direction (step S112). Then, the process of the control unit 40 moves to step S106.

As described above, the image forming apparatus 1 of this embodiment includes the medium transport section 71 and the image forming drum 21 as a transport section that moves the medium M along a predetermined transport path, and a plurality of image sensors 2511 to 2514. , an imaging unit 25 that captures an image of the surface of the medium M on the transport path, a colorimeter 26 that measures the color of the surface of the medium M on the transport path, and a control unit 40. The imaging range of each of the plurality of image sensors 251 (2511 to 2514) overlaps between adjacent image sensors in the width direction perpendicular to the transport direction along the transport path (usually in a plane parallel to the transport surface). The control unit 40 controls the imaging sensor based on the imaging results by the imaging unit 25 and the color measurement results by the colorimetry unit 26 of predetermined inspection images It1 and It2 located in the overlapping parts D1 and D3. 251 calibration operation is performed.
In this way, since the image forming apparatus 1 includes the color measurement section 26, the image sensor can be calibrated more easily and with high precision. Therefore, the color of the image formed by the head unit 23 can be more appropriately monitored and adjusted using this image sensor. In addition, at this time, by forming an inspection image in accordance with the overlapped area of the two image sensors and calibrating the two image sensors at once, the accuracy of calibration can be improved more efficiently and easily. can be done.

The image forming apparatus 1 also includes a colorimetric moving unit 72 that moves the colorimetric range by the colorimetric unit 26 in the width direction. The imaging unit 25 has three or more imaging sensors 251, and the control unit 40 causes the colorimetry unit 26 to perform colorimetry by moving the colorimetric range to each of the formation positions of a plurality of inspection images. A colorimeter does not measure color over a wide range at once like an image sensor, and is not used as frequently as an image sensor, so by making it movable, calibration can be performed efficiently.

The image forming apparatus 1 also includes a head unit 23 that forms an image on the surface of the medium M on the transport path. The control unit 40 determines the amount of positional deviation (in particular, The distance dt12) is determined, and the head unit 23 forms a plurality of inspection images, respectively. Thereby, it is possible to carry out colorimetry of a plurality of inspection images without much effort while transporting them in the normal direction using the single colorimeter 26.

Further, the control unit 40 can change the conveyance speed of the medium M by the conveyance unit, and can change the movement speed V2 of the colorimetric range by the colorimetric movement unit 72 and the position of the plurality of inspection images It1 and It2 in the conveyance direction. The moving speed V1 (transporting speed) of the medium M by the transporting unit is determined based on the amount of deviation (distance dt12 may be sufficient). Therefore, when the inspection images It1 and It2 are determined in advance according to the size of the medium M, etc., the conveyance speed can be adjusted to the arrangement of the inspection images It1 and It2.

Further, the conveyance section can convey the medium M so that the medium M passes through the color measurement range by the color measurement section 26 multiple times. That is, the transport unit can perform colorimetry of the inspection image at a different position in the width direction each time the medium M is sent backwards or around the circuit route a plurality of times. This eliminates the need to form a plurality of inspection images at different positions in the conveyance direction as described above, so that the length in the conveyance direction necessary for forming the inspection images can be shortened.

The image forming apparatus 1 also includes a head unit 23 that forms an image on the surface of the medium M on the conveyance path, and the control unit 40 causes the head unit 23 to apply predetermined inspection images It1 and It2 to the overlapping portions D1 and D3. to form. In this way, by forming the inspection images It1 and It2 by the image forming apparatus 1 itself, it is easy to adjust the positional relationship of the inspection images It1 and It2 to match the image forming apparatus 1.

Further, the control unit 40 can change the moving speed V1 of the medium M by the transport unit. Therefore, not only when the distance dt12 is predetermined as described above, but also by decelerating the conveyance speed or reducing the speed according to the time required for color measurement by the color measurement section 26, the distance dt12 can be reduced. Accordingly, the length of the medium M in the transport direction required for inspection can be reduced.

Further, even in the image reading device having the above configuration in which the head unit 23 is separated, the image sensor can be calibrated more easily and with high accuracy by having the color measurement section 26. Therefore, the color of the image formed by the head unit 23 can be more appropriately monitored and adjusted using this image sensor. In addition, at this time, by forming an inspection image in accordance with the overlapped area of the two image sensors and calibrating the two image sensors at once, the accuracy of calibration can be improved more efficiently and easily. can be done.

In addition, in the image sensor calibration method of the present embodiment, the image forming apparatus 1 includes the color measurement section 26, and the imaging results and measurement results obtained by the imaging section 25 of predetermined inspection images It1 and It2 located in the overlapping portions D1 and D3 are used. It includes a calibration execution step of performing a calibration operation of the image sensors 2511 and 2512 based on the color measurement results by the color unit 26. Thereby, the image sensor in the image forming apparatus 1 can be calibrated more easily and with high precision. Therefore, the color of the image formed by the head unit 23 can be more appropriately monitored and adjusted using this image sensor. In addition, at this time, by forming an inspection image in accordance with the overlapped area of the two image sensors and calibrating the two image sensors at once, the accuracy of calibration can be improved more efficiently and easily. can be done.

Note that the present invention is not limited to the embodiments described above, and various changes are possible.
For example, although the plurality of image sensors 251 have been described as being arranged in a houndstooth pattern, the arrangement is not particularly limited as long as the arrangement has overlapping portions in the width direction.

Further, in the above embodiment, the image sensor is described as a line sensor, but it may be a two-dimensional sensor that can collectively take images in a predetermined width also in the transport direction. Further, the number of colorimeter is not limited to one, and each colorimeter may be provided corresponding to a plurality of overlapping parts.

Further, in the above embodiment, the moving speed V2 by the colorimetric moving unit 72 is described as being constant, but it may be such that the speed gradually increases at the start of the movement and gradually decreases at the end of the movement. . On the other hand, the moving speed V1 of the medium M by the medium transport section 71 does not need to be variable. Variable here refers to something that can be selectively conveyed at any one of a plurality of speeds, and does not take into account the portion where the speed is gradually increased/decreased at the start and end of conveyance.

Further, in the above embodiment, the inspection images are formed only in the overlapping parts D1 and D3, but they may be formed continuously in the width direction as long as these parts are included. In this case, images of portions that are not colorimetrically measured are not used for calibration. Alternatively, an inspection image used for inspection for other purposes that does not require colorimetry is formed in areas other than the overlapping areas D1 and D3, or even in areas that are not within the colorimetric range. may be done. Since the imaging itself can be performed entirely at once using an imaging sensor, various inspections can be performed efficiently by performing image formation and imaging at the same time.

In addition, in the above embodiment, the four line sensors are calibrated by forming the inspection images It1 and It2 at the two overlapping parts D1 and D3, and by imaging and colorimetrically measuring the images. Although the operation has been performed, if the number of line sensors is different, inspection images of the number of locations corresponding to the number may be formed and used for calibration. When there are two line sensors, only one inspection image is required, so if it is not used for other purposes, it is not necessary to provide the colorimetric moving unit 72, and the colorimeter can be measured according to a single overlapping area. The color measurement range of section 26 is fixed.

Furthermore, in the above embodiment, the inspection images It1 and It2 are formed at one location in each of the overlapping portions D1 and D3, respectively, and the configuration is performed using the imaging result of each location and the color measurement result of the corresponding portion. However, depending on the widths of the overlapping portions D1 and D3, the present invention is not limited to this. For example, color measurement may be performed at two different locations within the overlapping portions D1 and D3, and a representative value (for example, an average value) of the obtained results may be obtained.

Furthermore, in the above modification, the second and subsequent color measurements are performed while the medium M is transported in the reverse direction and is transported in the forward direction again; however, the color measurements may be performed during the reverse transport. . In particular, when colorimetry is performed three or more times, the number of round trips can be reduced by allowing colorimetry to be performed on both the forward and return trips.

Furthermore, the inspection images It1 and It2 are not limited to those formed by the image forming apparatus 1 itself. If alignment with the overlapping parts D1 and D3 is possible properly, the inspection images It1 and It2 on the inspection paper prepared in advance may be imaged and color measured, and the inspection paper once formed may be May be reused multiple times.

Furthermore, the image formation in the above embodiments is not limited to a flat image using colored ink. The ink may contain colorless ink or transparent (light-transmitting) ink, or may have a three-dimensional structure. The medium M does not need to be conveyed by the cylindrical image forming drum 21, and a belt member or the like that conveys the medium M along a plane may be used.

Further, in the embodiment described above, an image forming apparatus having a line head has been described as an example, but an image forming apparatus that forms an image while scanning the medium M with the head unit 23 may also be used. , the content of the above disclosure can be applied to the calibration of an elongated imaging section 25 configured by connecting a plurality of imaging sensors.

Further, in the above embodiments, an inkjet type image forming apparatus (inkjet recording apparatus) is used as an example of the image forming apparatus, but an image forming apparatus using other types, such as an electrophotographic type image forming apparatus, may also be used. good. Further, the ink ejection method may be any method such as a piezo type using a piezoelectric element or a thermal type using a heating element.
In addition, the specific configuration, contents and procedures of processing operations, etc. shown in the above embodiments can be changed as appropriate without departing from the spirit of the present invention. The scope of the present invention includes the scope of the invention described in the claims and its equivalents.

1 Image forming apparatus 10 Medium supply section 11 Medium supply tray 12 Supply conveyance section 20 Forming section 21 Image forming drum 22 Delivery unit 23 Head unit 231 Inkjet head 24 Fixing section 25 Imaging section 251, 2511 to 2514 Imaging sensor 26 Color measurement section 261 Support member 27 Delivery section 28 Head drive section 29 Fixing drive section 30 Media discharge section 31 Media discharge tray 40 Control section 41 CPU
42 RAM
45 Conveyance drive section 46 Image processing section 50 Storage section 51 Program 52 Job data 53 Calibration data 61 Communication section 62 Display section 63 Operation reception section 71 Media conveyance section 72 Color measurement moving section 90 Buses D1, D3 Overlapping parts It, It1, It2 Inspection image M Medium N Nozzle

Claims (9)

a transport unit that moves the medium along a predetermined transport path;
an imaging unit having a plurality of imaging sensors and imaging the surface of the medium on the transport path;
a colorimeter unit that measures the color of the surface of the medium on the transport path;
a control unit;
Equipped with
The imaging range by each of the plurality of image sensors has an overlapping portion between the adjacent image sensors in a width direction perpendicular to the transport direction along the transport route,
The image forming apparatus is characterized in that the control unit performs a calibration operation of the image sensor based on the imaging result of the predetermined inspection image located in the overlapping portion by the imaging unit and the color measurement result by the colorimetric unit. . a colorimetry moving unit that moves the colorimetry range by the colorimetry unit in the width direction;
The imaging unit has three or more of the imaging sensors,
The image forming apparatus according to claim 1, wherein the control section moves the color measurement range to each of the formation positions of the plurality of inspection images, and causes the color measurement section to perform color measurement on each of the formation positions. comprising a forming operation unit that forms an image on the surface of the medium on the transport path,
The control unit determines a positional shift amount of the plurality of inspection images in the transport direction based on a transport speed of the medium by the transport unit and a movement speed of the colorimetric range by the colorimetric moving unit. 3. The image forming apparatus according to claim 2, wherein each of the plurality of inspection images is formed by the forming operation section. The control unit is capable of changing the conveyance speed of the medium by the conveyance unit, and is configured to change the speed of movement of the colorimetric range by the colorimetric moving unit and the amount of positional deviation of the plurality of inspection images in the conveyance direction. 3. The image forming apparatus according to claim 2, wherein the conveyance speed of the medium by the conveyance section is determined based on the following. 3. The image forming apparatus according to claim 2, wherein the conveyance section is capable of conveying the medium so that the medium passes through a color measurement range by the color measurement section a plurality of times. comprising a forming operation unit that forms an image on the surface of the medium on the transport path,
The image forming apparatus according to any one of claims 1, 2, and 5, wherein the control unit causes the forming operation unit to form the inspection image on the overlapping portion. The image forming apparatus according to any one of claims 1, 2, 5, and 6, wherein the control unit is capable of changing the conveyance speed of the medium by the conveyance unit. a transport unit that moves the medium along a predetermined transport path;
an imaging unit having a plurality of imaging sensors and imaging the surface of the medium on the transport path;
a colorimeter unit that measures the color of the surface of the medium on the transport path;
a control unit;
Equipped with
The imaging range by each of the plurality of image sensors has an overlapping portion between the adjacent image sensors in a width direction perpendicular to the transport direction along the transport route,
The image reading device is characterized in that the control unit performs a calibration operation of the image sensor based on the imaging result of the predetermined inspection image located in the overlapping portion by the imaging unit and the colorimetric result of the colorimetric unit. . A transport unit that moves the medium along a predetermined transport route, and an imaging unit that has a plurality of image sensors and captures an image of the surface of the medium on the transport route, and is perpendicular to the transport direction along the transport route. A method for calibrating the image sensor in an image forming apparatus having an overlapping portion between the image sensors adjacent in the width direction,
The image forming apparatus includes a color measurement unit that measures the color of the surface of the medium on the transport path,
A calibration method comprising: performing a calibration operation of the imaging sensor based on the imaging result of the predetermined inspection image located in the overlapping portion by the imaging unit and the colorimetric result by the colorimetric unit.

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