JP2017183798A - Ink jet recording device and imaging adjustment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording device and an imaging adjustment method that can read an image formed on a recording medium easily and more accurately.SOLUTION: An ink jet recording device comprising recording means that ejects ink from a nozzle to perform recording operation on a recording medium P comprises optical mechanisms 304-306 that form an image within an imaging target range at a set focal position, a detection unit 308 that detects the image within the imaging target range through the optical mechanisms, and an image formation adjustment driving unit 32 and adjustment mechanism 307 that move at least a portion of an optical mechanism and a detection unit in a direction along an optical axis of the optical mechanism, and that perform an image formation adjustment operation which change at least one of a detection position and a focal position by the detection unit, and comprises an image reading unit 30 that images a surface of the recording medium P.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an inkjet recording apparatus and an imaging adjustment method.

  There is an ink jet recording apparatus that records an image on a recording medium by ejecting ink onto the recording medium. Conventionally, some inkjet recording apparatuses include a reading unit that captures and reads a recorded image, and can perform defective detection of ink ejection operations, various calibrations, and the like.

  As the reading unit, generally, a configuration including an imaging lens and a sensor having an imaging element, and an image reduced and imaged by the imaging lens is read by the sensor is often used. Further, when performing color imaging, a filter that selectively passes RGB colors is used, and images of each color that have passed through these filters are respectively captured (for example, Patent Document 1).

JP 2014-216874 A

  In recent years, with the configuration related to ink ejection and the high accuracy of recorded images, high accuracy is also required for image reading. However, in the conventional inkjet recording apparatus, the focus position of imaging by the imaging element is fixedly set, and depending on the reading color, the type of the recording medium, etc., it may not be possible to read at an appropriate resolution, or the necessary resolution Therefore, there is a problem that the configuration of the optical system becomes large.

  An object of the present invention is to provide an inkjet recording apparatus and an imaging adjustment method that can easily read an image formed on a recording medium with higher accuracy.

In order to achieve the above object, the invention according to claim 1
An inkjet recording apparatus including a recording unit that performs recording operation on a recording medium by discharging ink from a nozzle,
An optical unit that forms an image of an imaging target range at a set focal position;
A detection unit that detects an image of the imaging target range via the optical unit;
An imaging adjustment operation in which at least one of the optical unit and the detection unit is moved in a direction along the optical axis of the optical unit to change at least one of the detection position and the focus position by the detection unit. An imaging adjustment unit to perform,
And an imaging means for imaging the surface of the recording medium.

According to a second aspect of the present invention, in the ink jet recording apparatus of the first aspect,
When a predetermined test image formed on the surface of the recording medium by the recording unit is captured by the imaging unit, at least part of the test image, the content read from the test image, and the thickness of the recording medium The image forming apparatus includes an adjustment control unit that causes the image forming adjustment unit to perform the image forming adjustment operation corresponding to the reading type.

According to a third aspect of the present invention, in the ink jet recording apparatus according to the second aspect,
Storage means for storing information relating to the adjustment contents in the imaging adjustment operation in association with each of the predetermined reading types is provided.

According to a fourth aspect of the present invention, in the ink jet recording apparatus according to the second or third aspect,
The adjustment content in the imaging adjustment operation is characterized in that it is determined so as to optimize the modulation transfer function obtained from the structure read from the imaging data of the test image.

The invention according to claim 5 is the ink jet recording apparatus according to any one of claims 2 to 4,
The reading type includes at least one of a color type read from the test image and a type of the test image.

According to a sixth aspect of the present invention, in the ink jet recording apparatus of the first aspect,
A transport unit that relatively moves the ink ejection range of the recording unit, the imaging target range of the imaging unit, and a recording medium;
The recording means has a line head having the ink discharge range over a recordable width corresponding to a length of the recording medium in the width direction in a width direction intersecting a predetermined relative movement direction of the recording medium by the conveying means. Have
The detection unit includes a line sensor,
The image pickup means picks up a one-dimensional image over the recordable width.

The invention according to claim 7 is the ink jet recording apparatus according to any one of claims 2 to 5,
A transport unit that relatively moves the ink ejection range of the recording unit, the imaging target range of the imaging unit, and a recording medium;
The recording means has a line head having the ink discharge range over a recordable width corresponding to a length of the recording medium in the width direction in a width direction intersecting a predetermined relative movement direction of the recording medium by the conveying means. Have
The detection unit includes a line sensor,
The imaging means captures a one-dimensional image over the recordable width,
The reading type includes a recording range in the width direction of the test image.

The invention according to claim 8 is the ink jet recording apparatus according to any one of claims 2 to 5 and 7,
The imaging adjustment operation is performed by the imaging adjustment unit while varying the adjustment content related to the imaging adjustment operation for one reading type, and the imaging unit performs a spatial period corresponding to the one reading type. Adjustment settings for capturing each setting image having a structure and calculating a value of the modulation transfer function, and acquiring the adjustment content with the optimum value of the modulation transfer function as the adjustment content corresponding to the one reading type It is characterized by comprising an acquisition means.

The invention according to claim 9 is the ink jet recording apparatus according to claim 8,
The setting image is a stripe pattern having a predetermined interval.

The invention according to claim 10
An optical unit that forms an image of the imaging target range at the set focal position, a detection unit that detects an image of the imaging target range via the optical unit, and at least a part of the optical unit and the detection unit An imaging adjustment unit that performs an imaging adjustment operation of moving at least one of a detection position by the detection unit and a focus position by moving the optical unit in a direction along the optical axis of the optical unit, and a recording medium An image pickup control method for an ink jet recording apparatus comprising: an image pickup means for picking up an image of the surface of the ink jet recording apparatus; and a recording means for discharging ink from a nozzle to perform a recording operation on a recording medium.
The image forming adjustment unit includes an adjustment step for performing the image forming adjustment operation.

The invention according to claim 11 is the imaging adjustment method according to claim 10,
When a predetermined test image formed on the surface of the recording medium by the recording unit is captured by the imaging unit, at least part of the test image, the content read from the test image, and the thickness of the recording medium The image forming apparatus includes an adjustment control step in which the image forming adjustment operation corresponding to the reading type is performed in the adjustment step.

According to a twelfth aspect of the present invention, in the imaging adjustment method of the eleventh aspect,
The imaging adjustment operation is performed in the adjustment step while changing the adjustment contents related to the imaging adjustment operation with respect to one reading type, and the spatial periodic structure corresponding to the one reading type is set by the imaging unit. An adjustment setting acquisition step of calculating the value of the modulation transfer function by capturing each of the setting images, and acquiring the adjustment content that optimizes the value of the modulation transfer function as the adjustment content corresponding to the one reading type It is characterized by including.

  According to the present invention, there is an effect that an image formed on a recording medium can be easily read with high accuracy in the ink jet recording apparatus.

1 is an overall perspective view showing an ink jet recording apparatus. It is a bottom view which shows the surface facing the conveyance surface of a head unit. It is a block diagram which shows the internal structure of an inkjet recording device. It is a schematic diagram which shows an internal structure at the time of seeing an image reading part from the front. It is a figure which illustrates typically the focal position and detection position with respect to an optical mechanism. It is a figure which shows the example of the shift | offset | difference of the reading position according to the color classification to be read and the arrangement direction of the structure of reading object. It is a flowchart which shows the control procedure of a discharge adjustment process. It is a flowchart which shows the control procedure of a reference table production | generation process.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall perspective view showing an ink jet recording apparatus 1 according to an embodiment of the present invention.

  The inkjet recording apparatus 1 includes a conveyance unit 10 (conveyance unit), an image forming unit 20 (recording unit), an image reading unit 30 (imaging unit), a control unit 40 (adjustment control unit, adjustment setting acquisition unit), and the like. Is provided.

  The conveyance unit 10 includes a conveyance motor 11 and a conveyance belt 12. The conveyance unit 10 is moved relative to the image forming unit 20 in a predetermined conveyance direction (relative movement direction) with the outer peripheral surface of the conveyance belt 12 as a conveyance surface. The recording medium P placed on the transport surface is moved in the transport direction.

  The image reading unit 30 is provided on the downstream side in the transport direction of the recording medium P with respect to the image forming unit 20, and captures an image formed on the recording surface of the recording medium P by the image forming unit 20. Output as data. The image reading unit 30 is, for example, a recording medium having a predetermined size (maximum width size capable of image formation by the inkjet recording apparatus 1) by the head unit 21 in the width direction that intersects (herein, intersects) the transport direction. On P, there is a line sensor in which imaging elements are arranged over a width in which ink can be ejected (recordable width, ink ejection range). One-dimensional image data within the imaging target range corresponding to the ink ejection range extending in the width direction is sequentially acquired by the line sensor while the recording unit P is moved relative to the image reading unit 30 by the transport unit 10 in the transport direction. By doing so, a two-dimensional image on the recording medium P can be obtained.

  The control unit 40 performs overall control of the operation of each unit of the inkjet recording apparatus 1.

  The image forming unit 20 performs a recording operation of forming an image by ejecting ink from nozzles and landing on the upper surface of the recording medium P. Here, the image forming unit 20 has four head units 21Y, 21M, 21C, and 21K (hereinafter collectively referred to as a head unit 21), and yellow, magenta, and magenta are supplied from an ink storage unit (not shown), respectively. Cyan and black ink are ejected. Each of these head units 21 is provided with nozzles over the recordable width of the recording medium P having a predetermined size (the above-mentioned maximum width size) in the width direction within a plane parallel to the transport surface, and can eject ink. It has become.

FIG. 2 is a bottom view showing a surface facing the transport surface of the head unit 21K.
Since the head units 21C, 21M, and 21Y have the same configuration, description thereof will be omitted.

  The head unit 21K is provided with 16 ejection heads 211 having nozzle openings arranged on the bottom surface at predetermined intervals. By arranging a set of two ejection heads 211 in a staggered pattern, a line head in which nozzle openings are arranged over the above-described recordable width at uniform intervals in the width direction is configured. That is, the head unit 21K is fixed during image formation, and forms an image by a one-pass method by sequentially ejecting ink to different positions in the transport direction according to the transport of the recording medium P.

  FIG. 3 is a block diagram showing a functional configuration of the inkjet recording apparatus 1 of the present embodiment.

  The inkjet recording apparatus 1 includes a control unit 40, a transport motor 11, a head driving unit 22, an imaging driving unit 31, an imaging adjustment driving unit 32, a communication unit 50, and a storage unit 60 (storage means). , An operation display unit 70, a bus 80, and the like.

  The control unit 40 performs a control operation that comprehensively controls the overall operation of the inkjet recording apparatus 1. The control unit 40 also performs inspection and adjustment (discharge adjustment operation) related to overall image quality and ink discharge from each nozzle opening, based on the test image formed by the image forming unit 20 and read by the image reading unit 30. )I do.

  The control unit 40 includes a CPU 41 (Central Processing Unit), a ROM 42 (Read Only Memory), a RAM 43 (Random Access Memory), and the like. The CPU 41 performs various arithmetic processes and executes processes related to various controls. The ROM 42 stores and saves control programs related to various controls. As the ROM 42, a mask ROM or a readable / writable nonvolatile memory is used.

  The RAM 43 provides a working memory space to the CPU 41 and stores temporary data and various settings. As the RAM 43, various volatile memories such as SRAM and DRAM are used.

  The head drive unit 22 outputs a drive signal for operating the ink discharge mechanism in the discharge head 211 of each head unit 21, and discharges ink from the opening of the operation target nozzle at an appropriate timing. These drive signals are output in parallel to each head unit 21 (discharge head 211). The drive signal is output in synchronization with an encoder (not shown) that measures the conveyance speed (position) of the recording medium P by the conveyance unit 10. As an ink discharge mechanism, for example, a voltage is applied to a piezoelectric element provided along an ink flow path communicating with a nozzle to deform the piezoelectric element, and pressure is applied to the ink in the ink flow path with a predetermined pressure pattern. In addition, a piezo type that ejects ink, or heat is generated by flowing current through a heating wire, and the ink in the ink flow path is heated and partly vaporized, causing a volume change and ejecting by applying pressure to the ink. A thermal type is used.

  The imaging drive unit 31 causes the image reading unit 30 to perform various operations related to reading an image on the recording medium P. The imaging drive unit 31 performs an operation of generating imaging data from incident light amount data detected by operating the line sensor of the detection unit 308 (see FIG. 4) and outputting the imaging data to the control unit 40 (RAM 43) or the storage unit 60. . The imaging data may be directly output to the RAM 43 or the storage unit 60 by DMA (Direct Memory Access) without being controlled by the CPU 41. Further, a predetermined calibration operation may be performed at the time of conversion from incident light amount data to imaging data.

  The image formation adjustment drive unit 32 adjusts the focus position and the detection position by the line sensor of the image formed by the optical mechanism during the image reading operation on the recording medium P by the image reading unit 30 (FIG. 4). Drive signal).

  The communication unit 50 acquires image formation data and a print job from an external computer terminal or a print server, and outputs a status signal related to image formation.

  The storage unit 60 stores image formation data acquired through the communication unit 50 and processing data thereof. The storage unit 60 also stores a reference table 61 for determining the focal position of the sensor during the reading (imaging) operation by the image reading unit 30. The reference table 61 will be described later. The storage unit 60 may store various execution programs related to image formation, and the CPU 41 reads out and loads the execution program into the RAM 43 when the execution program is executed. As the storage unit 60, for example, a hard disk drive (HDD) or a flash memory is used, and a RAM or the like may be used in combination.

  The operation display unit 70 displays a user input operation reception screen and status information, receives a user input operation, and outputs an operation signal to the control unit 40. Here, the operation display unit 70 includes, for example, a liquid crystal screen provided with a touch sensor and its driver. Alternatively, a display screen according to another display method such as an organic EL display may be used for display, or an LED lamp for status display may be used in combination. In addition, a push button switch, a rotation switch, or the like may be provided for accepting the operation instead of or in addition to the touch panel.

  The bus 80 is a path for transmitting and receiving signals between the control unit 40 and other components.

Next, the configuration of the image reading unit 30 will be described.
FIG. 4 is a schematic diagram illustrating an internal structure when the image reading unit 30 is viewed from the front.
Here, the downward direction in the figure is shown as the direction of the recording medium P and the conveying belt 12 forming the mounting surface.

  The image reading unit 30 includes light sources 303a and 303b, a first mirror 304, a second mirror 305, a lens optical unit 306, an adjustment mechanism 307, a detection unit 308, and the like inside a light-shielding casing 301. In addition, an incident window through which external light enters through a cover member 302 that transmits light is provided in part of the housing 301. The housing 301 is disposed at a position and orientation in which the incident window faces the outer peripheral surface of the transport belt 12, that is, the surface of the recording medium P to be transported.

  The cover member 302 transmits light (visible light) and prevents dust and ink mist from entering the housing 301. Further, the outer surface of the cover member 302 may be subjected to an antifouling process, a dustproof process, or the like to be provided with an antifouling layer, whereby adhesion of dust or the like to the outer surface of the cover member 302 may be suppressed. As the cover member 302, a known transparent member that transmits visible light, for example, a glass plate is used.

  The detection unit 308 includes the above-described line sensor. As the line sensor, for example, a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor is used, and an electric charge or voltage corresponding to the amount of light incident on each image sensor is output. For example, a photodiode or a photocoupler is used as a light receiving element that generates a charge corresponding to the amount of incident light in each imaging element.

  The lens optical unit 306 converges incident light (image) at the position of the light receiving element of the detection unit 308 and forms a reduced image, a filter (BPF, LPF) that blocks light having a wavelength outside the measurement target, or the like. Have An adjustment mechanism 307 is attached to the lens optical unit 306.

The adjustment mechanism 307 is a focal position of light incident on the light receiving element of the detection unit 308 by the drive signal from the imaging adjustment drive unit 32, that is, the lens optical unit 306 (or the first mirror 304) at the imaging target position. The first adjustment mechanism 307a that changes the distance, and the distance between the lens optical unit 306 and the detection unit 308 (the position of the detection unit 308; the light that is incident from the imaging target position is converged at the position of the light receiving element and reduced and focused) And a second adjustment mechanism 307b for changing the detection position). The first adjustment mechanism 307a is not only the lens optical unit 306, but also an optical mechanism including the lens optical unit 306, the first mirror 304, and the second mirror 305 (optical unit, hereinafter collectively referred to as optical mechanisms 304 to 306). A part or the whole may be moved in a direction along the optical axis of the optical mechanisms 304 to 306. Further, the adjustment mechanism 307 can move the optical mechanisms 304 to 306 and the detection unit 308 together with the casing 301 to change the position (reading position) with respect to the recording medium P.
When the first mirror 304 and the second mirror 305 move relative to the lens optical unit 306 to change the focal length, the first mirror 304 and the second mirror 305 are incident on the first mirror 304, respectively. The light and the reflected light of the second mirror 305 are moved and rotated along the optical axis, and the optical axes of the incident light and the emitted light according to the combination of the first mirror 304 and the second mirror 305 are not changed. Alternatively, the adjustment mechanism 307 may perform adjustment by fixing one of the lens optical unit 306 and the detection unit 308 and moving only the other. The adjustment mechanism 307 may be configured to uniformly change the focal position of the lens optical unit 306 (optical mechanism) and / or the detection position of the detection unit 308 in the width direction, or for each predetermined range in the width direction. The focus position may be changeable to a different position.
The imaging adjustment drive unit 32 and the adjustment mechanism 307 constitute an imaging adjustment unit, and an imaging adjustment operation for changing the focal position and / or the detection position is performed.

  The light sources 303a and 303b illuminate the reading range on the recording medium P. The light sources 303 a and 303 b are provided in the vicinity of the cover member 302 so as not to block the optical path from the reading surface to the detection unit 308 (incident light path). As the light sources 303a and 303b, various types such as an LED (Light Emitting Diode) and an organic light emitting diode can be used. The luminances of these light sources 303a and 303b may be configured to be appropriately changeable, for example, with a predetermined number of steps.

  The first mirror 304 and the second mirror 305 reflect the light that has passed through the cover member 302 and entered from the incident window, and guides it to the lens optical unit 306. Here, although the 1st mirror 304 and the 2nd mirror 305 are plane mirrors, the concave mirror for performing condensing as needed may be used for one or both.

  With these configurations, the image reading unit 30 obtains imaging data on a predetermined line extending in the width direction on the recording medium P while focusing on the recording medium P facing the entrance window.

Next, adjustment of the recording operation of the head unit 21 in the inkjet recording apparatus 1 will be described.
In an ink jet recording apparatus, an ink ejection failure such as an ink ejection direction or ejection amount from a nozzle often deviating from a normal direction or value due to clogging of the nozzle or the like, and further, no ink is ejected at all occurs. Even when ink is ejected normally, the density and color tone of the entire recorded image may deviate from the originally assumed level in accordance with a drive voltage shift or the like. Therefore, in an inkjet recording apparatus, a test image for determining whether or not ink is normally ejected at a desired level is formed on a recording medium periodically or under predetermined conditions, and the test image is captured. By performing the analysis, the necessity of adjustment related to the recording operation and the content of the adjustment are determined, and the discharge adjustment operation for performing the adjustment is performed.

FIG. 5 is a diagram schematically illustrating the focal position and the detection position with respect to the optical mechanisms 304 to 306.
When test images are formed and imaged in this way, the focal position changes depending on the type (thickness) of the recording medium, the recording range in the width direction of the test image to be detected, and the like. Further, the optical mechanisms 304 to 306 have the same setting due to the difference in the color type (RGB) to be read and the difference in the refractive index of the lens optical unit 306 (lens and filter) according to the angle with respect to the optical axis of the lens. Also, the reduced imaging position from the lens optical unit 306 depends on the ink type (that is, the color type to be read) and the arrangement direction of the structure to be read in the test image, that is, the type of the test image and the detected content (read content) from the test image. The distance to will be different. Therefore, in the ink jet recording apparatus 1 according to the present embodiment, the test image to be read, the detection content from the test image, the test image recording range, the type of the recording medium, and part or all of the reading color (reading type). The focal position and / or the detection position are changed along the direction of the optical axis L.

  FIG. 6 is a diagram showing an example of the reading position shift according to the color type to be read and the arrangement direction of the structure to be read. FIG. 6A shows the relationship between the reading position deviation amount and the reading resolution when reading the structure in the width direction, and FIG. 6B shows the reading position deviation when reading the structure in the transport direction. The relationship between the quantity and the reading resolution is shown. Here, as a reading resolution when a 5.5 lp / mm stripe pattern image is captured, the value of a modulation transfer function (MTF) is a deviation amount (defocus amount) of the reading position from the reference position. Each is shown. The stripe pattern is an image sensor that is formed using Y, M, and K inks and is imaged using an image sensor that reads G and B colors, and an image sensor that is formed of C color inks and reads R color. It is imaged using.

  The MTF is a value used as an index indicating the resolution characteristics in the spatial domain. For example, a periodic binary image (usually a stripe pattern having a predetermined interval as described above) is subjected to Fourier transform with respect to the spatial frequency. In some cases, it is obtained as a value of amplitude intensity with respect to frequency. In the read image of the stripe pattern described above, there is no blur between the line part (colored part) and the non-line part (background part), and the MTF value increases as the image is clearly separated at the boundary, and the degree of blur increases. The MTF value becomes smaller. Here, the MTF value is displayed in “%” with respect to the difference (amplitude intensity) of the luminance value between the line portion and the non-line portion that are completely separated.

  As shown in FIG. 6A, when the structure in the width direction is read, the defocus amount corresponding to the maximum value of the MTF related to the imaging of B color (Blue) is about +0.2 mm, and G The defocus amount corresponding to the maximum value of the MTF related to the imaging of the color (Green) is about +0.5 mm. In addition, the defocus amount corresponding to the maximum value of the MTF related to the imaging of the R color (Red) is larger than +3.0 mm. As described above, the defocus amount varies depending on the color type to be read, and is adjusted to an appropriate defocus amount corresponding to the color type.

  Further, as shown in FIG. 6B, when reading the structure in the transport direction, the defocus amount corresponding to the maximum value of the MTF related to the imaging of the B color and the G color is about −1.7 mm. Further, the defocus amount corresponding to the maximum value of the MTF related to the R color imaging is about +0.7 mm. As described above, the defocus amount differs depending on the color type to be read in both the transport direction and the structure, and the defocus amount changes when the structure in the width direction is read for each color. Therefore, when reading the structure in the width direction, the reading position is moved so that the defocus amount is larger in the positive direction than in the case of reading the structure in the width direction as a whole, and the structure in the transport direction is read. In this case, the reading position is moved in a direction in which the defocus amount is negative compared to the case of reading the structure in the width direction as a whole. When the thickness of the recording medium P is different, the defocus amount is further changed according to the thickness of the recording medium P.

  The reading position, that is, the focus position and the detection position are changed by referring to the reference table 61 stored in advance in the storage unit 60 by the control unit 40 as an adjustment control unit. That is, by acquiring a parameter (information indicating the reading type) necessary for setting the focus position and the detection position, and reading information (imaging adjustment setting information) related to the adjustment content according to the parameter from the reference table 61, Appropriate positions of the optical mechanisms 304 to 306 (here, the lens optical unit 306) and the detection unit 308 are determined.

  FIG. 7 is a flowchart illustrating a control procedure by the control unit 40 of the discharge adjustment process executed in the inkjet recording apparatus 1 of the present embodiment.

  This discharge adjustment process is automatically called and executed periodically and / or when a predetermined condition is satisfied, for example, when the inkjet recording apparatus 1 is turned on, or when the recording medium P or ink is replaced. Alternatively, it may be executed in accordance with a predetermined input operation to the operation display unit 70 by the user.

When the discharge adjustment process is started, the control unit 40 (CPU 41) acquires a reading type related to the discharge adjustment (step S101). Specific types of ejection adjustment include ink ejection failure from nozzles that eject ink of a predetermined color, density, color tone, and color unevenness adjustment in specific recording medium types, and tests corresponding to these respectively. Examples of the image include an image in which lines are formed in a ladder shape from each nozzle, and a halftone image at various densities. The reading type of the test image corresponding to the type of ejection adjustment is acquired directly or based on table data that associates the type of ejection adjustment with the reading type.
The control unit 40 refers to the reference table 61 and acquires imaging adjustment setting information corresponding to the acquired reading type (step S102).

  The control unit 40 outputs a control signal to the imaging adjustment driving unit 32 and operates the adjustment mechanism 307 in the imaging adjustment driving unit 32 according to the acquired imaging adjustment setting information to detect the lens optical unit 306 and the detection. The position of the unit 308 is adjusted (step S103; adjustment step and adjustment control step in the imaging adjustment method). Then, the control unit 40 outputs a control signal to the transport motor 11, places the recording medium P on the transport surface, moves the recording medium P at a predetermined speed in the transport direction, and controls the head drive unit 22. A signal is output, and ink is ejected from each nozzle of the head unit 21 so that an appropriate test image is formed on the recording medium P according to the setting (step S104).

The control unit 40 outputs a control signal to the imaging drive unit 31 to read a test image in the reading range corresponding to the content of the discharge adjustment (step S105). The control unit 40 acquires the read test image, performs analysis according to the content of the discharge adjustment, and obtains the necessity of adjustment and the adjustment amount when adjustment is necessary (step S106). When adjustment is necessary, the control unit 40 performs various adjustment operations with the obtained adjustment amount (step S107). Then, the control unit 40 ends the discharge adjustment process.
If there are reading operations at a plurality of focus positions and detection positions that cannot be executed at the same time, such as adjustments related to a plurality of ink types, the processing of steps S103 and S105 (and step S104 as necessary). This process may be repeated several times.

Next, the setting operation of the reference table 61 will be described.
The reference table 61 is inspected, set and stored in the storage unit 60 before shipment or start of use by the user, such as at the time of assembly adjustment of the inkjet recording apparatus 1 in the factory or at the time of inspection after assembly.

  The imaging adjustment setting information to be set is determined based on actually measured data in the inkjet recording apparatus 1. Here, for each of the reading types corresponding to the contents of various ejection adjustments, a stripe pattern with a predetermined interval, that is, a predetermined spatial periodic structure is formed while moving the focal position and / or the detection position in a predetermined step. The image (setting image) is read. Then, the MTF value in each reading result is calculated, and the distance at which the highest (optimum) MTF value is obtained is determined as the optimum focus position and detection position for the parameter combination.

  The predetermined stripe pattern used here is not limited to those recorded on the recording medium P by the inkjet recording apparatus 1 as long as it corresponds to the type of the recording medium P and the type of ink used in the inkjet recording apparatus 1. However, in the following description, it is assumed that the ink jet recording apparatus 1 performs normal recording. The MTFs obtained by combining the same parameters only need to know the relative magnitude relationship, and it is not always necessary to consider the influences such as deviation of absolute values and local density unevenness.

  When the information including the reading type includes a plurality of parameters, the maximum MTF value may be different for each. In such a case, optimization is performed by selecting a combination of a plurality of parameters in which the value representative of the MTF value for the plurality of parameters is the highest value. Examples of the representative value include an average value, a median value, and a minimum value. Further, even when using an average value or median value in selecting an optimal combination of a plurality of parameters, the minimum value of all MTF values or all MTF values are not determined based on only the maximum value of the average value or median value. When satisfy | filling, you may limit to the value more than a predetermined ratio with respect to an average value, for example.

FIG. 8 is a flowchart showing a control procedure by the control unit 40 of the reference table generation process (adjustment setting acquisition step) executed in the inkjet recording apparatus 1.
This reference table generation process is started in response to, for example, a predetermined input operation on the operation display unit 70 by a user (in this case, a person in charge of adjustment or inspection of the inkjet recording apparatus 1).

  When the reference table generation process is started, the control unit 40 (CPU 41) as the adjustment setting acquisition unit changes the recording medium thickness setting within a predetermined setting range (step S201). The control unit 40 outputs a control signal to the image formation adjustment driving unit 32 of the image reading unit 30, operates the adjustment mechanism 307, and moves the lens optical unit 306 and the detection unit 308 to the initial setting positions (step S202).

  The control unit 40 outputs a control signal to the transport motor 11 and the head drive unit 22 and operates each head unit 21 with each color ink while transporting the recording medium P having a set thickness at a predetermined speed. A predetermined stripe pattern is recorded in order (step S203). The control unit 40 outputs a control signal to the imaging drive unit 31, and causes the recorded stripe pattern image to be captured and read (step S204).

The control unit 40 divides the read image into predetermined ranges in the width direction, and calculates the MTF for each predetermined range and each ink type (each reading target color) (step S205). The control unit 40 determines whether image reading and MTF calculation have been performed with the combination setting of the positions of all the settable lens optical units 306 and the detection unit 308 (step S206). If it is determined that reading has not been performed for all combinations of positions (“NO” in step S206), the control unit 40 changes the position settings of the lens optical unit 306 and / or the detection unit 308. Then, a control signal is output to the imaging adjustment drive unit 32, and the lens optical unit 306 and / or the detection unit 308 are moved (step S207). Then, the process of the control unit 40 returns to step S203.
Note that the control unit 40 outputs a control signal to the transport motor 11, moves the recording medium P in the direction opposite to the normal transport direction, and returns it to the upstream side from the reading range by the image reading unit 30, thereby once stepping is performed. The stripe pattern recorded in the process of S203 may be reused.

  When it is determined that the reading of the stripe pattern and the calculation of the MTF have been completed by the combination setting of the positions of all the lens optical units 306 and the positions of the detection unit 308 ("YES" in step S206), the control unit For the set thickness, the highest MTF is extracted for each predetermined range and for each ink type (color), and the positions of the lens optical unit 306 and the detection unit 308 from which the MTF is obtained are set to image adjustment. Information is written in the reference table 61 in association with the reading type (step S211).

  The controller 40 determines whether or not the imaging adjustment setting information has been written in the reference table 61 for all thicknesses within the setting range (step S212). If it is determined that writing has not been performed for all thicknesses ("NO" in step S212), the process of the control unit 40 returns to step S201. When it is determined that the imaging adjustment setting information has been written for all the thicknesses (“YES” in step S212), the control unit 40 ends the reference table generation process.

As described above, the ink jet recording apparatus 1 of the present embodiment is an ink jet recording apparatus 1 including the image forming unit 20 (head unit 21) that performs the recording operation on the recording medium P by discharging ink from the nozzles. The lens optical unit 306, the first mirror 304 and the second mirror 305, which form an optical mechanism for forming an image of the imaging target range at the set focal position, and the imaging target range image are detected via the optical mechanisms 304 to 306. The detection unit 308, and at least a part of the optical mechanisms 304 to 306 and the detection unit 308 are moved in the direction along the optical axis of the optical mechanism (lens optical unit 306), and the detection position and the focal position by the detection unit 308 are detected. An image adjustment drive unit 32 and an adjustment mechanism 307 as an image adjustment unit that performs an image adjustment operation to change at least one of And an image reading unit 30 for imaging the surface of the recording medium P.
In this way, by adjusting the focal position of the optical mechanisms 304 to 306 of the image reading unit 30 and the detection position by the detection unit 308 (line sensor) of the image to be imaged reduced by the optical mechanisms 304 to 306. The adjustment can be appropriately adjusted to prevent the image from blurring according to the type and application of the test image. Therefore, the ink jet recording apparatus 1 can easily read an image formed on the recording medium P with higher accuracy. Conventionally, in order to prevent a reduction in accuracy with a single focal point, the depth of the subject is increased, and the illumination light amount of the illumination unit 303 is increased or the size is increased correspondingly, but these are unnecessary. Further, by providing such a focus position and detection position adjusting mechanism with a printer sensor that can change the thickness of the recording medium P as in the case of the ink jet recording apparatus 1, it is stable regardless of the type of the recording medium P. Thus, it is possible to capture and acquire a highly accurate image.

In addition, when the image reading unit 30 captures a predetermined test image formed on the surface of the recording medium P by the image forming unit 20 as the adjustment control unit, the control unit 40 reads the test image from the test image. The adjustment mechanism 307 is caused to perform an imaging adjustment operation according to the reading type related to at least a part of the contents and the thickness of the recording medium P by driving the imaging adjustment driving unit 32.
As described above, the reading type such as the type of the test image and the usage information is acquired, and the focus position and the detection position are adjusted so that the imaging data can be obtained with an appropriate resolution according to the acquired reading type. With regard to the contents, it is possible to easily and appropriately perform highly accurate test image reading and discharge adjustment without bothering the user.

  In addition, a storage unit 60 is provided that stores information related to the adjustment contents in the imaging adjustment operation in association with each predetermined reading type. In this way, by storing in advance as the reference table 61 in the storage unit 60, information on the focal position and detection position appropriate for the configuration of the image reading unit 30 in the inkjet recording apparatus 1 is read from the reference table 61. It can be easily acquired and adjusted appropriately.

  Further, the adjustment contents in the imaging adjustment operation are determined so as to optimize the modulation transfer function (MTF) obtained from the structure read from the imaging data of the test image. In other words, since the inkjet recording apparatus 1 of the present embodiment is adjusted so that the best resolution can be appropriately obtained with an objective value, high-accuracy imaging is reliably performed according to the reading type, and necessary ink ejection adjustment is performed. Information can be acquired.

  The reading type includes at least one of the color type RGB and the test image type read from the test image. Therefore, the focus position and the detection position are adjusted to appropriate positions according to the difference in the refractive index of the lens optical unit 306 related to the image capturing and the difference in the refractive index according to the arrangement direction of the structure characteristic of the test image. As a result, it is possible to perform imaging with the optimum accuracy for the necessary information. In addition, by dealing with the difference in the refractive index of the lens optical unit 306 in this way, it is unnecessary to increase the cost by dealing with chromatic aberration or the like in the optical component of the lens optical unit 306, and appropriate in consideration of the chromatic aberration. Can be read.

The image forming unit 20 includes a transport unit 10 that relatively moves the ink ejection range of the image forming unit 20 and the imaging target range of the image reading unit 30 and the recording medium P. A line head capable of ejecting ink over a recordable width corresponding to the length of the recording medium P in the width direction intersecting the relative movement direction of the recording medium P, and the detection unit 308 includes a line sensor The image reading unit 30 captures a one-dimensional image over the recordable width.
Therefore, an image of a desired area in the two-dimensional plane, particularly an area image, can be acquired with a simple configuration and processing by relative movement of the recording medium P and sequential operation of the line sensor. In addition, since each imaging element of the line sensor and each nozzle of the line head correspond to each other in a fixed manner, it is possible to easily and appropriately detect nozzle ejection defects and the like.

  In the inkjet recording apparatus 1 having the above-described line sensor and line head, the reading type can include a recording range in the width direction of the test image. Therefore, it is possible to capture a test image with an appropriate resolution according to the difference in characteristics according to the position of the line sensor in the width direction.

In addition, the control unit 40 serves as an adjustment setting acquisition unit, and an adjustment mechanism 307 that drives the imaging adjustment driving unit 32 while changing the adjustment contents related to the imaging adjustment operation for one reading type. The MTF value is calculated by causing the image reading unit 30 to capture each of the stripe patterns that are setting images having the spatial periodic structure corresponding to the one reading type described above, and the MTF value is optimal. Is obtained as the adjustment content corresponding to this one reading type.
As described above, the adjustment content corresponding to the reading type is actually measured and obtained in advance, for example, at the time of inspection before shipment, so that each apparatus of the ink jet recording apparatus 1 is started after the use of the ink jet recording apparatus 1 is started. It is possible to quickly read a test image with an appropriate value according to variations in the optical mechanisms 304 to 306. This makes it possible to easily and accurately adjust ink ejection.

  In addition, since a stripe pattern with a predetermined interval is used as the setting image, the MTF can be easily calculated, and the reference table 61 can be generated easily and reliably in a short time.

In addition, the imaging adjustment method of the present embodiment includes an optical mechanism (a lens optical unit 306, a first mirror 304, and a second mirror 305) that forms an image of an imaging target range at a set focal position, and optical mechanisms 304 to. A detection unit 308 that detects an image in the imaging target range via 306, and at least a part of the optical mechanisms 304 to 306 and the detection unit 308 are moved in a direction along the optical axis of the optical mechanisms 304 to 306 to detect the image. An image reading unit 30 that has an adjustment mechanism 307 that performs an image forming adjustment operation that changes at least one of the detection position by the unit 308 and the focal positions of the optical mechanisms 304 to 306; And an image forming unit 20 that performs a recording operation on a recording medium P by ejecting ink from the inkjet recording apparatus 1 and an adjustment mechanism 07 by including an adjustment step of causing the imaging adjustment operation.
As described above, at least a part of the optical mechanisms 304 to 306 and the detection unit 308 of the image reading unit 30 can be moved to a suitable focal position and / or detection position. It is possible to easily read an image formed on the recording medium P with a higher accuracy than in the prior art.

In this imaging adjustment method, when a predetermined test image formed on the surface of the recording medium P by the image forming unit 20 is imaged by the image reading unit 30, the test image, the content read from the test image, and the recording are recorded. An adjustment control step is included in which an image forming adjustment operation according to the reading type relating to at least a part of the thickness of the medium P is performed in the adjustment step described above.
As described above, the focus position and the detection position are adjusted so that the imaging data can be obtained with an appropriate resolution according to the reading type such as the type of the test image and the usage information. Adjustments can be made.

Also, in the imaging adjustment method, before the image forming adjustment operation is actually controlled in accordance with the reading type in the adjustment control step, the adjustment contents related to the image forming adjusting operation are made different for one reading type in advance. However, the image forming adjustment operation is performed in the adjustment step, and the image reading unit 30 causes the image of the stripe pattern having the direction and the period according to the one reading type to be captured to calculate the MTF value. An adjustment setting acquisition step of acquiring the adjustment content with the optimum value as the adjustment content corresponding to the one reading type;
As described above, the adjustment content corresponding to the reading type is actually measured and obtained in advance, for example, at the time of inspection before shipment, so that each apparatus of the ink jet recording apparatus 1 is started after the use of the ink jet recording apparatus 1 is started. It is possible to quickly read a test image with an appropriate value according to variations in the optical mechanisms 304 to 306. This makes it possible to easily and accurately adjust ink ejection.

The present invention is not limited to the above-described embodiment, and various modifications can be made.
For example, in the above embodiment, the reference table generation process is performed by the operation of the control unit 40. However, the reference table 61 is generated by connecting the image reading unit 30 to an external computer, and the generated reference table 61 is displayed. The data may be stored in the storage unit 60 by being copied or moved to the storage unit 60.

  Further, the reference table 61 itself may be acquired from the outside without being held inside the inkjet recording apparatus 1. For example, it may be acquired from an external computer connected to the network. Alternatively, the user may input the set value from the operation display unit 70 while looking at the quick reference table.

  In the above embodiment, the first mirror 304, the second mirror 305, and the lens optical unit 306 are provided as an optical mechanism. However, the number of mirrors is not limited to this, and a refractive optical system such as a prism is used. A configuration may further be included. Further, the lens optical unit 306 may be configured by a combination of a plurality of lenses, and a part of the plurality of lenses may move independently, or may move differently in conjunction with each other.

  Moreover, in the said embodiment, although the quality of the resolution was quantitatively evaluated using MTF, values other than MTF may be used.

  In the above embodiment, the inkjet recording apparatus 1 having a line head has been described as an example. However, in the inkjet recording apparatus 1 having a scan type head that forms an image on the recording medium P while operating the head. Even if it exists, this invention can be applied similarly.

  Even when an area sensor is used instead of a line sensor, the focus position and the detection position can be adjusted in accordance with the test image reading type.

In the above embodiment, the MTF is calculated using the stripe pattern, and the correspondence between the reading type and the adjustment content is determined. However, the necessary reading direction and other directions are separated even in cases other than the simple stripe pattern. Any image that can be evaluated can be used.
In addition, specific details such as the configuration, structure, and control procedure shown in the above embodiment can be changed as appropriate without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 10 Conveyance part 11 Conveyance motor 12 Conveyance belt 20 Image formation part 21, 21C, 21M, 21K, 21Y Head unit 211 Discharge head 22 Head drive part 30 Image reading part 31 Imaging drive part 32 Imaging adjustment drive part 301 Case 302 Cover members 303a and 303b Light source 304 First mirror 305 Second mirror 306 Lens optical unit 307 Adjustment mechanism 307a First adjustment mechanism 307b Second adjustment mechanism 308 Detection unit 40 Control unit 41 CPU
42 ROM
43 RAM
50 Communication Unit 60 Storage Unit 61 Reference Table 70 Operation Display Unit 80 Bus L Optical Axis P Recording Medium

Claims (12)

An inkjet recording apparatus including a recording unit that performs recording operation on a recording medium by discharging ink from a nozzle,
An optical unit that forms an image of an imaging target range at a set focal position;
A detection unit that detects an image of the imaging target range via the optical unit;
An imaging adjustment operation in which at least one of the optical unit and the detection unit is moved in a direction along the optical axis of the optical unit to change at least one of the detection position and the focus position by the detection unit. An imaging adjustment unit to perform,
An inkjet recording apparatus, comprising: an imaging unit that images the surface of the recording medium.   When a predetermined test image formed on the surface of the recording medium by the recording unit is captured by the imaging unit, at least part of the test image, the content read from the test image, and the thickness of the recording medium The inkjet recording apparatus according to claim 1, further comprising an adjustment control unit that causes the imaging adjustment unit to perform the imaging adjustment operation according to the reading type.   3. An ink jet recording apparatus according to claim 2, further comprising storage means for storing information relating to adjustment contents in the image forming adjustment operation in association with each of the predetermined reading types.   4. The ink jet recording apparatus according to claim 2, wherein the adjustment contents in the imaging adjustment operation are determined so as to optimize a modulation transfer function obtained from a structure read from imaging data of the test image.   The ink jet recording apparatus according to claim 2, wherein the reading type includes at least one of a color type read from the test image and a type of the test image. A transport unit that relatively moves the ink ejection range of the recording unit, the imaging target range of the imaging unit, and a recording medium;
The recording means has a line head having the ink discharge range over a recordable width corresponding to a length of the recording medium in the width direction in a width direction intersecting a predetermined relative movement direction of the recording medium by the conveying means. Have
The detection unit includes a line sensor,
The inkjet recording apparatus according to claim 1, wherein the imaging unit captures a one-dimensional image over the recordable width. A transport unit that relatively moves the ink ejection range of the recording unit, the imaging target range of the imaging unit, and a recording medium;
The recording means has a line head having the ink discharge range over a recordable width corresponding to a length of the recording medium in the width direction in a width direction intersecting a predetermined relative movement direction of the recording medium by the conveying means. Have
The detection unit includes a line sensor,
The imaging means captures a one-dimensional image over the recordable width,
The ink jet recording apparatus according to claim 2, wherein the reading type includes a recording range of the test image in the width direction.   The imaging adjustment operation is performed by the imaging adjustment unit while varying the adjustment content related to the imaging adjustment operation for one reading type, and the imaging unit performs a spatial period corresponding to the one reading type. Adjustment settings for capturing each setting image having a structure and calculating a value of the modulation transfer function, and acquiring the adjustment content with the optimum value of the modulation transfer function as the adjustment content corresponding to the one reading type The inkjet recording apparatus according to claim 2, further comprising an acquisition unit.   9. The ink jet recording apparatus according to claim 8, wherein the setting image is a stripe pattern having a predetermined interval. An optical unit that forms an image of the imaging target range at the set focal position, a detection unit that detects an image of the imaging target range via the optical unit, and at least a part of the optical unit and the detection unit An imaging adjustment unit that performs an imaging adjustment operation of moving at least one of a detection position by the detection unit and a focus position by moving the optical unit in a direction along the optical axis of the optical unit, and a recording medium An image pickup control method for an ink jet recording apparatus comprising: an image pickup means for picking up an image of the surface of the ink jet recording apparatus; and a recording means for discharging ink from a nozzle to perform a recording operation on a recording medium.
An imaging adjustment method, comprising: an adjustment step of causing the imaging adjustment unit to perform the imaging adjustment operation.   When a predetermined test image formed on the surface of the recording medium by the recording unit is captured by the imaging unit, at least part of the test image, the content read from the test image, and the thickness of the recording medium The imaging adjustment method according to claim 10, further comprising an adjustment control step for performing the imaging adjustment operation in accordance with the reading type in the adjustment step.   The imaging adjustment operation is performed in the adjustment step while changing the adjustment contents related to the imaging adjustment operation with respect to one reading type, and the spatial periodic structure corresponding to the one reading type is set by the imaging unit. An adjustment setting acquisition step of calculating the value of the modulation transfer function by capturing each of the setting images, and acquiring the adjustment content that optimizes the value of the modulation transfer function as the adjustment content corresponding to the one reading type The imaging adjustment method according to claim 11, further comprising:

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