JP6798129B2 - Inkjet recording device and imaging adjustment method - Google Patents

Description

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

There is an inkjet recording device that ejects ink onto a recording medium and records an image on the recording medium. Further, conventionally, some inkjet recording devices are provided with a reading unit that captures and reads a recorded image, and can detect defects in ink ejection operation and perform various calibrations.

The reading unit is usually provided with an imaging lens and a sensor having an image sensor, and a configuration in which an image reduced and imaged by the imaging lens is read by the sensor is often used. Further, when color imaging is performed, a filter that selectively passes each RGB color is used, and an image of each color that has passed through these filters is imaged (for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2014-216874

In recent years, with the configuration related to ink ejection and the improvement of the accuracy of recorded images, the improvement of the accuracy of image reading is also required. However, in the conventional inkjet recording device, the focal position of the image pickup by the image sensor is fixedly set, and depending on the reading color and the type of recording medium, it may not be possible to read at an appropriate resolution or the required resolution. There is a problem that the configuration of the optical system becomes large in order to obtain the above.

An object of the present invention is to provide an inkjet recording device and an image pickup adjusting method capable of easily reading an image formed on a recording medium with higher accuracy.

In order to achieve the above object, the invention according to claim 1 is
An inkjet recording device including a recording means that ejects ink from a nozzle to perform a recording operation on a recording medium.
An optical unit that forms an image of the imaging target range at the set focal position,
A detection unit that detects an image in the imaging target range via the optical unit,
An imaging adjustment operation is performed in which at least a part 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 focal position by the detection unit. Imaging adjustment unit to be performed and
And an imaging means for imaging the surface of a recording medium,
Of the test image according to the judgment of the normal discharge state of ink, in the case where the a test image formed on the surface of the recording medium by said recording means is imaged by the imaging means, the detection position and the focus by the detection unit At least one of the positions is changed to a position corresponding to the reading type of the test image, the content read from the test image, and at least a part of the thickness of the recording medium including the thickness of the recording medium. An adjustment control means for causing the image formation adjustment unit to perform an image formation adjustment operation,
It is characterized by having.

The invention according to claim 2 is the invention according to claim 1 in the inkjet recording apparatus according to claim 1 .
It is characterized by including a storage means for storing information related to the adjustment content in the imaging adjustment operation in association with each of the predetermined reading types.

The invention according to claim 3 is the invention according to claim 1 or 2 .
The adjustment content in the imaging adjustment operation is characterized in that the modulation transfer function obtained from the structure read from the imaged data of the test image is optimized.

The invention according to claim 4 is the inkjet recording apparatus according to any one of claims 1 to 3 .
The reading type includes at least one of a color type read from the test image and a type of the test image.

The invention according to claim 5 is the invention according to claim 1 in the inkjet recording apparatus according to claim 1.
A transport means for relatively moving the ink ejection range of the recording means, the imaging target range of the imaging means, and the recording medium is provided.
The recording means records according to the length of the recording medium in the width direction in a predetermined relative movement direction of the recording medium by the transport means and a predetermined width direction intersecting in a plane parallel to the recording medium. Having a line head having the ink ejection range over the possible width,
The detection unit has a line sensor and
The imaging means is characterized in that it captures a one-dimensional image over the recordable width.

Further, the invention according to claim 6 is in the inkjet recording apparatus according to any one of claims 1 to 4 .
A transport means for relatively moving the ink ejection range of the recording means, the imaging target range of the imaging means, and the recording medium is provided.
The recording means records according to the length of the recording medium in the width direction in a predetermined relative movement direction of the recording medium by the transport means and a predetermined width direction intersecting in a plane parallel to the recording medium. Having a line head having the ink ejection range over the possible width,
The detection unit has a line sensor and
The imaging means captures a one-dimensional image over the recordable width.
The reading type is characterized in that the recording range of the test image in the width direction is included.

Further, the invention according to claim 7 is in the inkjet recording apparatus according to any one of claims 1 to 6 .
Before while different adjustments according to Kiyuizo adjust operating the imaging adjustment operation was performed by the imaging adjustment section, a modulation transmitted respectively by imaging the setting image having a predetermined spatial periodic structure by the image pickup means the value of the function is calculated, comprise adjusting setting acquiring means for acquiring the adjustment contents the value of the modulation transfer function is optimized for one of the reading type as adjustments corresponding to the one reading type It is characterized by.

The invention according to claim 8 is the invention according to claim 7 in the inkjet recording apparatus according to claim 7 .
The setting image is characterized by having a stripe pattern at predetermined intervals.

Further, the invention according to claim 9 is
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, and at least a part of the optical unit and the detecting unit. The recording medium has an image forming adjustment unit that performs an image forming adjustment operation of changing at least one of the detection position and the focal position by the detection unit by moving the optical unit in a direction along the optical axis of the optical unit. An image pickup control method for an inkjet recording apparatus including an image pickup means for photographing the surface of an optical axis and a recording means for ejecting ink from a nozzle to perform a recording operation on a recording medium.
An adjustment step in which the imaging adjustment unit performs the imaging adjustment operation .
Of the test image according to the judgment of the normal discharge state of ink, in the case where the a test image formed on the surface of the recording medium by said recording means is imaged by the imaging means, the detection position and the focus by the detection unit At least one of the positions is changed to a position corresponding to the reading type of the test image, the content read from the test image, and at least a part of the thickness of the recording medium including the thickness of the recording medium. An adjustment control step that causes the image formation adjustment operation to be performed in the adjustment step,
It is characterized by including.

The invention according to claim 10 is the imaging adjustment method according to claim 9 .
Before while different adjustments according to Kiyuizo adjustment operation to perform the image adjustment operation in the adjustment step, the modulation transfer function each by capturing an image for setting having a predetermined spatial periodic structure by the image pickup means It calculates the value respectively, characterized in that it comprises adjustment setting acquisition step of acquiring the adjustment contents the value of the modulation transfer function is optimized for one of the reading type as adjustments corresponding to the one reading type It is said.

According to the present invention, the inkjet recording apparatus has an effect that the image formed on the recording medium can be easily read with higher accuracy.

It is an overall perspective view which shows the inkjet recording apparatus. It is a bottom view which shows the surface which faces the transport surface of a head unit. It is a block diagram which shows the internal structure of an inkjet recording apparatus. It is a schematic diagram which shows the internal structure when the image reading part is seen from the front. It is a figure which schematically explains the focal position and the detection position with respect to an optical mechanism. It is a figure which shows the example of the deviation of the reading position according to the color type to be read, and the arrangement direction of the structure to be read. It is a flowchart which shows the control procedure of a discharge adjustment process. It is a flowchart which shows the control procedure of the reference table 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 inkjet recording device 1 according to an embodiment of the present invention.

The inkjet recording device 1 includes a transport unit 10 (transport means), an image forming unit 20 (recording means), an image reading unit 30 (imaging means), a control unit 40 (adjustment control means, adjustment setting acquisition means), and the like. To be equipped.

The transport unit 10 has a transport motor 11, a transport belt 12, and the like, and by using the outer peripheral surface of the transport belt 12 as a transport surface and relatively moving the image forming unit 20 in a predetermined transport direction (relative movement direction). The recording medium P placed on the transport surface is moved in the transport direction.

The image reading unit 30 is provided downstream of the image forming unit 20 in the transport direction of the recording medium P, and the image forming unit 20 captures and captures an image formed on the recording surface of the recording medium P. Output as data. The image reading unit 30 is, for example, a recording medium having a predetermined size (maximum width size capable of forming an image by the inkjet recording device 1) by the head unit 21 in width directions intersecting (here, orthogonal to each other) with respect to the transport direction. It has a line sensor in which image pickup elements are arranged over a width (recordable width, ink ejection range) at which ink can be ejected on P. While the recording medium P is relatively moved in the transport direction with respect to the image reading section 30 by the transport unit 10, 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. By going on, a two-dimensional image on the recording medium P can be obtained.

The control unit 40 controls the operation of each unit of the inkjet recording device 1 in an integrated manner.

The image forming unit 20 performs a recording operation of forming an image by ejecting ink from a nozzle and landing it 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 head units 21), and yellow, magenta, and magenta, which are supplied from ink storage units (not shown), respectively. Discharges cyan and black inks. All of these head units 21 are 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 in a plane parallel to the transport surface, and ink can be ejected. It has become.

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

The head unit 21K is provided with 16 discharge heads 211 in which nozzle openings are arranged at predetermined intervals on the bottom surface. By arranging the pair of the two discharge heads 211 in a houndstooth pattern, the line heads are formed in which the nozzle openings are arranged over the above-mentioned recordable width at uniform intervals in the width direction. That is, the head unit 21K is fixed during image formation, and ink is sequentially ejected to different positions in the transport direction according to the transport of the recording medium P to form an image in a one-pass manner.

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

The inkjet recording device 1 includes a control unit 40, a transfer motor 11, a head drive unit 22, an image pickup drive unit 31, an image formation adjustment drive unit 32, a communication unit 50, and a storage unit 60 (storage means). , The operation display unit 70, the bus 80, and the like are provided.

The control unit 40 performs a control operation that controls the entire operation of the inkjet recording device 1. Further, the control unit 40 is formed by the image forming unit 20, and based on the test image read by the image reading unit 30, the control unit 40 inspects and adjusts the overall image quality and ink ejection from each nozzle opening (ejection adjustment operation). )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 to execute various control-related processes. Control programs related to various controls are stored and stored in the ROM 42. As the ROM 42, a mask ROM or a readable / writable non-volatile memory is used.

The RAM 43 provides the CPU 41 with a working memory space 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 nozzle to be operated at an appropriate timing. These drive signals are output in parallel to each head unit 21 (discharge head 211). Further, this drive signal is output in synchronization with an encoder (not shown) that measures the transport speed (position) of the recording medium P by the transport unit 10. As an ink ejection 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 apply pressure to the ink in the ink flow path in a predetermined pressure pattern. In addition, a piezo type that ejects ink, or a piezo type that generates heat by passing a current through a heating wire, heats the ink in the ink flow path, and vaporizes a part of it to cause a volume change and apply pressure to the ink to eject it. A thermal type or the like is used.

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

The image formation adjustment driving unit 32 is an adjustment mechanism 307 (FIG. 4) for adjusting the focal position and the detection position of the image formed by the optical mechanism by the line sensor during the image reading operation on the recording medium P by the image reading unit 30. Output the drive signal to (see).

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

The storage unit 60 stores image formation data acquired via the communication unit 50, processing data thereof, and the like. Further, the storage unit 60 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. Further, the storage unit 60 may store various execution programs related to image formation, and the CPU 41 reads them out when the execution program is executed and loads them into the RAM 43 for use. As the storage unit 60, for example, an HDD (Hard Disk Drive) or a flash memory may be used, or a RAM or the like may be used in combination.

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

Next, the configuration of the image reading unit 30 will be described.
FIG. 4 is a schematic view showing the internal structure of the image reading unit 30 when viewed from the front.
Here, the lower direction in the figure is shown as the direction of the recording medium P and the transport belt 12 forming the mounting surface thereof.

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 the light-shielding housing 301. A part of the housing 301 is provided with an incident window in which external light is incident through a cover member 302 that transmits light. The housing 301 is arranged 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 transport recording medium P.

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 antifouling treatment, dustproof treatment, or the like to provide an antifouling layer, thereby suppressing adhesion of dust or the like to the outer surface of the cover member 302. As the cover member 302, a well-known transparent member that transmits visible light, for example, a glass plate is used.

The detection unit 308 has the above-mentioned 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 a voltage corresponding to the amount of incident light to each image sensor is output. As a light receiving element that generates an electric charge according to the amount of incident light in each image sensor, for example, a photodiode or a photocoupler is used.

The lens optical unit 306 includes one or more lenses that converge and reduce the image of the incident light (image) at the position of the light receiving element of the detection unit 308, a filter (BPF, LPF) that blocks light having a wavelength other than the measurement target, and the like. Has. An adjustment mechanism 307 is attached to the lens optical unit 306.

The adjustment mechanism 307 is from the focal position of the light incident on the light receiving element of the detection unit 308 by the drive signal from the image formation adjustment drive unit 32, that is, from the lens optical unit 306 (or the first mirror 304) at the imaging target position. The distance between the first adjustment mechanism 307a that changes the distance and the lens optical unit 306 and the detection unit 308 for converging and reducing the light incident from the imaging target position at the position of the light receiving element (position of the detection unit 308; It has a second adjusting mechanism 307b that changes the detection position). The first adjustment mechanism 307a is an optical mechanism including not only the lens optical unit 306 but also 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 mechanism 304 to 306. Further, the adjusting mechanism 307 can integrally move the optical mechanisms 304 to 306 and the detection unit 308 together with the housing 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 related 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 each of them in a predetermined range in the width direction. It may be possible to change the focal position to a different position.
The image formation adjustment unit 32 and the adjustment mechanism 307 form an image formation adjustment unit, and an image formation 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 303a and 303b are provided in the vicinity of the cover member 302 so as not to block the optical path (path of incident light) from the reading surface to the detection unit 308. As the light sources 303a and 303b, various light sources such as LEDs (Light Emitting Diodes) and organic light emitting diodes can be used. The brightness of these light sources 303a and 303b may be appropriately changed, for example, by a predetermined number of steps.

The first mirror 304 and the second mirror 305 pass through the cover member 302, reflect the light incident from the incident window, and guide the light to the lens optical unit 306. Here, the first mirror 304 and the second mirror 305 are plane mirrors, but one or both of them may be a concave mirror for condensing light, if necessary.

With these configurations, the image reading unit 30 focuses on the recording medium P facing the incident window and acquires imaging data on a predetermined line extending in the width direction on the recording medium P.

Next, adjustment of the recording operation of the head unit 21 in the inkjet recording device 1 will be described.
In an inkjet recording device, ink ejection defects such that the ink ejection direction and the ejection amount from the nozzle deviate from the normal direction and the value due to clogging of the nozzle, and the ink is not ejected at all occur. Further, even when the ink is ejected normally, the shade and color tone of the entire recorded image may deviate from the originally expected level due to the deviation of the drive voltage and the like. Therefore, in the inkjet recording device, a test image for determining whether or not the ink is normally ejected at a desired level is formed on the recording medium on a regular basis or under predetermined conditions, and the test image is captured. By performing the analysis, the necessity of the 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 a focal position and a detection position with respect to the optical mechanisms 304 to 306.
When the test image is formed and imaged in this way, the focal position changes depending on the type (thickness) of the recording medium and the recording range in the width direction of the test image to be detected. Further, the optical mechanisms 304 to 306 have the same settings because of the difference in the color type (RGB) to be read and the difference in the refractive index of the lens optical unit 306 (lens or filter) according to the angle of the lens with respect to the optical axis. The reduced imaging position from the lens optical unit 306 depending 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 detection content (read content) from the test image. The distance to is different. Therefore, in the inkjet recording device 1 of the present embodiment, depending on the type of the test image to be read, the content detected from the test image, the recording range of the test image, the type of the recording medium, and a part or all (reading type) of the reading color. The focal position and / or the detection position is changed along the direction of the optical axis L.

FIG. 6 is a diagram showing an example of deviation of the reading position 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 amount of deviation of the reading position and the reading resolution when reading the structure in the width direction, and FIG. 6B shows the deviation of the reading position when reading the structure in the transport direction. The relationship between the amount and the reading resolution is shown. Here, as the reading resolution when a 5.5 lp / mm stripe pattern image is captured, the value of the modulation transfer function (MTF) is the amount of deviation (defocus amount) of the reading position from the reference position. On the other hand, each is shown. As for the stripe pattern, an image sensor formed of Y, M, and K inks is imaged using an image sensor that reads G color and B color, and an image sensor formed of C color ink reads R color. It is imaged using.

The MTF is a value used as an index showing the resolution characteristics in the spatial region. For example, a periodic binary image (usually, a stripe pattern at a predetermined interval as described above) is Fourier transformed with respect to the spatial frequency. In some cases, it is obtained as the value of the amplitude intensity with respect to the frequency. In the above-mentioned scanned image of the stripe pattern, there is no blur between the line portion (colored portion) and the non-line portion (background portion), and the more clearly separated at the boundary, the larger the MTF value and the greater the degree of blur. Indeed, the MTF value becomes smaller. Here, the MTF value is displayed by "%" with respect to the difference (amplitude intensity) of the brightness values between the completely separated line portion and the non-line portion.

As shown in FIG. 6A, when reading the structure in the width direction, 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 amount of defocus corresponding to the maximum value of MTF related to color (Green) imaging is about +0.5 mm. Further, the defocus amount corresponding to the maximum value of the MTF related to the R color (Red) imaging is larger than +3.0 mm. In this way, the defocus amount is different depending on the color type to be read, and the defocus amount is adjusted to an appropriate amount according 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. The amount of defocus corresponding to the maximum value of MTF related to 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 differs depending on whether 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 when 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 the direction in which the defocus amount is negative as compared with the case where the structure in the width direction is read 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.

This reading position, that is, the change of the focal position and the detection position is performed by referring to the reference table 61 stored in the storage unit 60 in advance by the control unit 40 as the adjustment control means. That is, by acquiring the parameters (information indicating the reading type) necessary for setting the focal position and the detection position, and reading the information related to the adjustment contents according to the parameters (imaging adjustment setting information) from the reference table 61, Appropriate positions of each part of the optical mechanism 304 to 306 (here, the lens optical part 306) and the detection part 308 are determined.

FIG. 7 is a flowchart showing a control procedure by the control unit 40 of the ejection adjustment process executed by the inkjet recording device 1 of the present embodiment.

This ejection adjustment process is automatically called and executed periodically and / or when a predetermined condition is satisfied, for example, when the power of the inkjet recording device 1 is turned on, when the recording medium P or the ink is replaced, or the like. Alternatively, it may be executed in response to 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 the reading type related to the discharge adjustment (step S101). Specific types of ejection adjustment include poor ink ejection from a nozzle that ejects ink of a predetermined color, density in a specific recording medium type, and adjustment of color tone and color unevenness, and tests corresponding to each of these are included. 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 according to the type of these discharge adjustments is acquired directly or based on the table data for associating the type of discharge adjustment with the reading type.
The control unit 40 refers to the reference table 61 and acquires the image formation adjustment setting information according to the acquired reading type (step S102).

The control unit 40 outputs a control signal to the image formation adjustment drive unit 32, and operates the adjustment mechanism 307 on the image formation adjustment drive unit 32 according to the acquired image formation adjustment setting information to operate the lens optical unit 306 and the detection unit 40. The position of the unit 308 is adjusted (step S103; adjustment step in the imaging adjustment method, adjustment control step). Then, the control unit 40 outputs a control signal to the transfer motor 11, mounts the recording medium P on the transfer surface, moves the recording medium P in the transfer direction at a predetermined speed, 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 image pickup drive unit 31 to read a test image in a reading range according to the content of the discharge adjustment (step S105). The control unit 40 acquires the read test image, analyzes it according to the content of the discharge adjustment, and obtains the necessity of the adjustment and the adjustment amount when the adjustment is necessary (step S106). When adjustment is required, 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 focal positions or detection positions that cannot be executed at the same time, such as adjustments related to a plurality of ink types, the processes of steps S103 and S105 (and, if necessary, step S104). Process) may be repeated multiple 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 when assembling and adjusting the inkjet recording device 1 in a factory or when inspecting after assembling.

The image formation adjustment setting information to be set is determined based on the actual measurement data in the inkjet recording device 1. Here, for each of the reading types according to the contents of various discharge adjustments, a striped pattern at predetermined intervals, that is, a predetermined spatial period structure is formed while moving the focal position and / or the detection position in a predetermined step. Have the image (setting image) read. Then, the MTF value in each reading result is calculated, and the distance at which the highest (optimal) MTF value is obtained is determined as the optimum focal position and detection position for the combination of the parameters.

The predetermined stripe pattern used here is not limited to the one recorded on the recording medium P by the inkjet recording device 1 as long as it corresponds to the type of the recording medium P and the type of ink used in the inkjet recording device 1. However, in the following, it will be described as assuming that the image is normally recorded by the inkjet recording device 1. For the MTF obtained by combining the same parameters, it is only necessary to know the relative magnitude relationship, and it is not always necessary to consider the effects of absolute value deviation and local concentration unevenness.

When the information including the reading type contains a plurality of parameters, the highest MTF value may be different for each. In such a case, optimization is performed by selecting a combination of a plurality of parameters having the highest value representing the value of MTF for the plurality of parameters. Representative values include, for example, an average value, a median value, and a minimum value. Further, even when the average value or the median value is used in selecting the optimum combination of a plurality of parameters, the minimum value of the MTF value or all the MTF values is a predetermined reference, not determined only by the maximum value of the average value or the median value. When satisfying, for example, it may be limited to a value of a predetermined ratio or more with respect to the average value.

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 by the inkjet recording device 1.
This reference table generation process is activated, for example, in response to a predetermined input operation to the operation display unit 70 by a user (here, a person in charge of adjustment or inspection of the inkjet recording device 1).

When the reference table generation process is started, the control unit 40 (CPU 41) as the adjustment setting acquisition means changes the thickness setting of the recording medium within a predetermined setting range (step S201). The control unit 40 outputs a control signal to the image formation adjustment drive unit 32 of the image reading unit 30 and operates the adjustment mechanism 307 to move 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 transfer motor 11 and the head drive unit 22, and operates each head unit 21 with ink of each color while transporting the recording medium P having a set thickness at a predetermined speed. Predetermined stripe patterns are recorded in order (step S203). The control unit 40 outputs a control signal to the image pickup drive unit 31 to capture and read the recorded stripe pattern image (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 (for each color to be read) (step S205). The control unit 40 determines whether or not the image is read and the MTF is calculated by setting the combination of the positions of all the lens optical units 306 and the detection unit 308 that can be set (step S206). If it is determined that reading has not been performed in all the position combination settings (“NO” in step S206), the control unit 40 changes the position settings of the lens optical unit 306 and / or the detection unit 308. The control signal is output to the imaging adjustment driving 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.
The control unit 40 outputs a control signal to the transfer motor 11, moves the recording medium P in the direction opposite to the normal transfer direction, and returns the recording medium P to the upstream side of the reading range by the image reading unit 30 to step once. 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 setting the combination of the positions of all the lens optical units 306 and the positions of the detection unit 308 that can be set (“YES” in step S206), the control unit 40 extracts the highest MTF for each predetermined range and each ink type (color) for the set thickness, and sets the positions of the lens optical unit 306 and the detection unit 308 from which the MTF is obtained to adjust the image formation. The information is written in the reference table 61 in association with the reading type (step S211).

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

As described above, the inkjet recording device 1 of the present embodiment is an inkjet recording device 1 including an image forming unit 20 (head unit 21) that ejects ink from a nozzle and performs a recording operation on the recording medium P. The image of the imaging target range is detected via 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 optical mechanisms 304 to 306. At least a part of the detection unit 308, the optical mechanisms 304 to 306, and the detection unit 308 is 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. It includes an image formation adjustment drive unit 32 and an adjustment mechanism 307 as an image formation adjustment unit that performs an image formation adjustment operation for changing at least one of them, and includes an image reading unit 30 that images 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 changed so as to prevent blurring of the image appropriately according to the type and use of the test image. Therefore, the inkjet recording device 1 can easily read the image formed on the recording medium P with higher accuracy. Further, conventionally, the depth of the subject is deepened in order not to reduce the accuracy with a single focus, and the amount of irradiation light of the illumination unit 303 is increased or the size is increased in response to this, but these are no longer necessary. Further, by providing such an adjustment mechanism for the focal position and the detection position in the sensor of a printer such as the inkjet recording device 1 in which the thickness of the recording medium P can change significantly, the stability is stable regardless of the type of the recording medium P. It is possible to capture and acquire a highly accurate image.

Further, 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 means, the control unit 40 reads the test image and the test image. The adjustment mechanism 307 is driven by the image formation adjustment drive unit 32 to perform an image formation adjustment operation according to the reading type relating to at least a part of the content and the thickness of the recording medium P.
In this way, the reading type such as the test image type and usage information is acquired, and the focal position and 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 content, it is possible to easily and appropriately read the test image and adjust the ejection with high accuracy without bothering the user.

Further, the storage unit 60 is provided to store information related to the adjustment content in the imaging adjustment operation in association with each of the predetermined reading types. By holding the reference table 61 in the storage unit 60 in advance in this way, information on the focal position and the detection position suitable for the configuration of the image reading unit 30 in the inkjet recording device 1 can be read from the reference table 61. It can be easily acquired and made appropriate adjustments.

Further, the adjustment content in the imaging adjustment operation is defined so as to optimize the modulation transfer function (MTF) obtained from the structure read from the imaging data of the test image. That is, since the inkjet recording apparatus 1 of the present embodiment is adjusted so as to appropriately obtain the best resolution with an objective value, high-precision imaging is surely performed according to the reading type, and necessary ink ejection adjustment is performed. Information can be obtained.

Further, the reading type includes at least one of the color type RGB read from the test image and the type of the test image. Therefore, the focal 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 image imaging and the difference in the refractive index according to the arrangement direction of the structure characteristic of the test image. Therefore, it is possible to perform imaging with the optimum accuracy for the necessary information. Further, by dealing with the difference in the refractive index of the lens optical unit 306 in this way, it is not necessary to increase the cost by making the optical component of the lens optical unit 306 deal with chromatic aberration and the like, and it is appropriate in consideration of the chromatic aberration. It is possible to read various images.

Further, the image forming unit 20 includes an ink ejection range of the image forming unit 20, an imaging target range of the image reading unit 30, and a conveying unit 10 for relatively moving the recording medium P, and the image forming unit 20 is a predetermined recording medium P by the conveying unit 10. The detection unit 308 has 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 image. The image reading unit 30 captures a one-dimensional image over the recordable width.
Therefore, by the relative movement of the recording medium P and the sequential operation of the line sensor, it is possible to acquire an image of a desired area in the two-dimensional plane, particularly an area image, with a simple configuration and processing. Further, since each image sensor 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 a nozzle ejection defect or the like.

Further, in the above-mentioned inkjet recording device 1 having a line sensor and a line head, the reading type can include a recording range in the width direction of the test image. Therefore, it is possible to take a test image with an appropriate resolution according to the difference in characteristics depending on the position of the line sensor in the width direction.

Further, as an adjustment setting acquisition means, the control unit 40 is an adjustment mechanism 307 in which the image formation adjustment drive unit 32 drives the image formation adjustment operation while making the adjustment content related to the image formation adjustment operation different for one reading type. The image reading unit 30 images each of the stripe patterns, which are setting images having a spatial period structure corresponding to one of the above-mentioned reading types, to calculate the MTF value, and the MTF value is optimal. The adjustment content is acquired as the adjustment content corresponding to this one reading type.
In this way, by actually measuring and obtaining the adjustment contents corresponding to the reading type in advance, especially at the time of inspection before shipment, each device of the inkjet recording device 1 has been used since the start of use of the inkjet recording device 1. It is possible to quickly read the test image with high accuracy with an appropriate value according to the variation of the optical mechanisms 304 to 306 of the above. This makes it possible to easily and accurately adjust the ink ejection.

Further, since the stripe pattern at predetermined intervals is used as the setting image, the MTF can be easily calculated, and the reference table 61 can be easily and surely generated in a short time.

Further, the imaging adjustment method of the present embodiment includes an optical mechanism (lens optical unit 306, first mirror 304 and second mirror 305) for forming an image of an imaging target range at a set focal position, and optical mechanisms 304 to. The detection unit 308 that detects an image in the imaging target range via the 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 for detection. An image reading unit 30 that has an adjustment mechanism 307 that performs an imaging adjustment operation that changes at least one of the detection position by the unit 308 and the focal position of the optical mechanisms 304 to 306, and an image reading unit 30 that images the surface of the recording medium P, and a nozzle. This is an image pickup adjustment method of the inkjet recording apparatus 1 including an image forming unit 20 that ejects ink from the optical axis and performs a recording operation on the recording medium P, and includes an adjustment step of causing the adjustment mechanism 307 to perform the image formation adjustment operation. ..
In this way, 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. Therefore, in this inkjet recording device 1, a test image is obtained. It is possible to easily read the image formed on the recording medium P with higher accuracy than before in the portion required for the above application.

Further, 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, a test image, reading contents and recording from the test image are recorded. The adjustment control step is included in which the image formation adjustment operation according to the reading type relating to at least a part of the thickness of the medium P is performed in the above-mentioned adjustment step.
In this way, the focal position and detection position are adjusted so that the imaging data can be obtained with an appropriate resolution according to the reading type such as the test image type and usage information, so that the test image can be read and ejected with appropriate accuracy. You can make adjustments.

Further, in the image pickup adjustment method, the adjustment content related to the image formation adjustment operation is made different for one reading type in advance before actually controlling the image formation adjustment operation according to the reading type in the adjustment control step. However, the imaging adjustment operation is performed in the adjustment step, and the image reading unit 30 captures an image of a stripe pattern having a direction and a period corresponding to the above-mentioned one reading type, calculates the MTF value, and calculates the MTF value of the MTF. The adjustment setting acquisition step of acquiring the adjustment content having the optimum value as the adjustment content corresponding to the above-mentioned one reading type is included.
In this way, by actually measuring and obtaining the adjustment contents corresponding to the reading type in advance, especially at the time of inspection before shipment, each device of the inkjet recording device 1 has been used since the start of use of the inkjet recording device 1. It is possible to quickly read the test image with high accuracy with an appropriate value according to the variation of the optical mechanisms 304 to 306 of the above. This makes it possible to easily and accurately adjust the ink ejection.

The present invention is not limited to the above 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, but the image reading unit 30 is connected to an external computer to generate the reference table 61, and the generated reference table 61 is generated. It may be stored in the storage unit 60 by copying or moving it to the storage unit 60.

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

Further, in the above embodiment, the first mirror 304, the second mirror 305, and the lens optical unit 306 are provided as the optical mechanism, but the number of mirrors is not limited to this, and the refraction optical system such as a prism Further configurations may 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 be independently moved or may be interlocked to move differently.

Further, in the above embodiment, the quality of the resolution is quantitatively evaluated using MTF, but a value other than MTF may be used.

Further, in the above-described embodiment, the inkjet recording device 1 having a line head has been described as an example, but the inkjet recording device 1 having a scanning type head that forms an image on the recording medium P while operating the head. Even if there is, the present invention can be applied in the same manner.

Further, even when an area sensor is used instead of the line sensor, the focal position and the detection position can be similarly adjusted according to the reading type of the test image.

Further, 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, but the required reading direction and the other direction are separated even if the pattern is not a simple stripe pattern. Any image can be evaluated.
In addition, specific details such as the configuration, structure, and control procedure shown in the above embodiment can be appropriately changed without departing from the spirit of the present invention.

1 Inkjet recording device 10 Conveying unit 11 Conveying motor 12 Conveying belt 20 Image forming unit 21, 21C, 21M, 21K, 21Y Head unit 211 Discharge head 22 Head drive unit 30 Image reading unit 31 Imaging drive unit 32 Image adjustment drive unit 301 Housing 302 Cover member 303a, 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 (10)

An inkjet recording device including a recording means that ejects ink from a nozzle to perform a recording operation on a recording medium.
An optical unit that forms an image of the imaging target range at the set focal position,
A detection unit that detects an image in the imaging target range via the optical unit,
An imaging adjustment operation is performed in which at least a part 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 focal position by the detection unit. Imaging adjustment unit to be performed and
And an imaging means for imaging the surface of a recording medium,
Of the test image according to the judgment of the normal discharge state of ink, in the case where the a test image formed on the surface of the recording medium by said recording means is imaged by the imaging means, the detection position and the focus by the detection unit At least one of the positions is changed to a position corresponding to the reading type of the test image, the content read from the test image, and at least a part of the thickness of the recording medium including the thickness of the recording medium. An adjustment control means for causing the image formation adjustment unit to perform an image formation adjustment operation,
An inkjet recording device characterized by comprising. The inkjet recording apparatus according to claim 1, further comprising a storage means for storing information related to the adjustment content in the imaging adjustment operation in association with each of the predetermined reading types. The inkjet recording apparatus according to claim 1 or 2, wherein the adjustment content in the imaging adjustment operation is defined so as to optimize the modulation transfer function obtained from the structure read from the imaging data of the test image. The inkjet recording apparatus according to any one of claims 1 to 3, 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 means for relatively moving the ink ejection range of the recording means, the imaging target range of the imaging means, and the recording medium is provided.
The recording means records according to the length of the recording medium in the width direction in a predetermined relative movement direction of the recording medium by the transport means and a predetermined width direction intersecting in a plane parallel to the recording medium. Having a line head having the ink ejection range over the possible width,
The detection unit has a line sensor and
The inkjet recording apparatus according to claim 1, wherein the imaging means captures a one-dimensional image over the recordable width. A transport means for relatively moving the ink ejection range of the recording means, the imaging target range of the imaging means, and the recording medium is provided.
The recording means records according to the length of the recording medium in the width direction in a predetermined relative movement direction of the recording medium by the transport means and a predetermined width direction intersecting in a plane parallel to the recording medium. Having a line head having the ink ejection range over the possible width,
The detection unit has a line sensor and
The imaging means captures a one-dimensional image over the recordable width.
The inkjet recording apparatus according to any one of claims 1 to 5, wherein the reading type includes a recording range in the width direction of the test image. The imaging adjustment operation is performed by the imaging adjustment unit while different the adjustment contents related to the imaging adjustment operation, and the imaging means is used to image a setting image having a predetermined spatial period structure, respectively, and a modulation transfer function is used. Each of the values of is calculated, and the adjustment setting acquisition means for acquiring the adjustment content for which the value of the modulation transfer function is optimal for one reading type is provided as the adjustment content corresponding to the one reading type. The inkjet recording apparatus according to any one of claims 1 to 6. The inkjet recording apparatus according to claim 7, wherein the setting image has a striped pattern at predetermined intervals. 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, and at least a part of the optical unit and the detecting unit. The recording medium has an image forming adjustment unit that performs an image forming adjustment operation of changing at least one of the detection position and the focal position by the detection unit by moving the optical unit in a direction along the optical axis of the optical unit. An image pickup control method for an inkjet recording apparatus including an image pickup means for imaging the surface of an optical axis and a recording means for ejecting ink from a nozzle to perform a recording operation on a recording medium.
An adjustment step in which the imaging adjustment unit performs the imaging adjustment operation.
Of the test image according to the judgment of the normal discharge state of ink, in the case where the a test image formed on the surface of the recording medium by said recording means is imaged by the imaging means, the detection position and the focus by the detection unit wherein at least one of the previous SL test image in the position is changed to a position corresponding to at least a portion reading according type including a thickness of the recording medium of the thickness of the read contents and the recording medium from the test image An adjustment control step that causes the image formation adjustment operation to be performed in the adjustment step,
An imaging adjustment method comprising. The image formation adjustment operation is performed in the adjustment step while the adjustment contents related to the image formation adjustment operation are different, and the setting image having a predetermined spatial period structure is imaged by the imaging means to obtain the value of the modulation transfer function. Is included, and the adjustment setting acquisition step of acquiring the adjustment content for which the value of the modulation transfer function is optimal for one reading type as the adjustment content corresponding to the one reading type is included. 9. The imaging adjustment method according to claim 9.

Images