JP2012126016A - Inkjet recording apparatus - Google Patents

Abstract

In an ink jet recording apparatus, a connecting stripe caused by a variation in a conveyance amount of a recording medium is appropriately suppressed.
The conveyance deviation condition is determined (S4), and when the conveyance deviation amount indicated by the conveyance deviation condition is smaller than when there is almost no, that is, when the recording medium is conveyed less than the specified amount, recording between adjacent bands is performed. The amount of overlapping areas increases, and the density of connecting stripes increases accordingly. For this reason, the thinning amount is relatively increased as compared with the case where there is almost no conveyance deviation amount. On the contrary, when the conveyance deviation condition is smaller than when there is almost no conveyance deviation, the thinning amount is reduced. In this way, by setting the thinning amount according to the conveyance deviation amount, it is possible to appropriately reduce the connecting streaks caused by the deviation in the conveyance amount due to the variation in the driving roller diameter and the thickness of the sheet-like conveyance body. .
[Selection] Figure 7

Description

  The present invention relates to an ink jet recording apparatus, and more particularly to a technique for reducing a connecting stripe that may occur at a connecting portion of a band that is an area recorded by scanning of a recording head.

  Conventionally, what was described in patent document 1 as this kind of technique is known. That is, in the ink jet recording apparatus, when the recording head repeatedly scans in the main scanning direction and records images one band at a time, it is a connection region that is a recording region near the boundary between bands due to ink bleeding between the bands. In some cases, streaky density unevenness may occur in the portion. Patent Document 1 describes a method of correcting recording data so as to reduce the connecting stripe.

  Specifically, in Patent Document 1, the amount of ink of each color to be printed is acquired for each unit region obtained by dividing the band connecting portion into a plurality of portions. Then, the relative relationship between the ink amounts for each ink color and the total ink amount information are calculated, and the ink reduction rate for reducing the ink amount to be driven into the joint portion is determined based on the calculated relationship. Furthermore, based on the ink reduction rate, the recording data in the recording area corresponding to the joint portion is corrected to reduce the amount of ink that is driven into the joint portion. By this method, it is possible to reduce the connecting streak regardless of the print hue and the ink shot amount.

Japanese Patent No. 4006198

  However, although the conventional method as described in Patent Document 1 can reduce the degree of joint streaks, there is a problem that the joint streaks due to variations in the conveyance amount of the recording medium cannot be reduced.

  That is, as a cause of variation in the conveyance amount, in a conveyance mechanism that nipping and conveying a recording medium with a conveyance roller, variation in the conveyance roller diameter, slippage of the recording medium with respect to the conveyance roller, and the like vary depending on the type and temperature of the recording medium. Conceivable. Further, in a transport mechanism that drives a sheet-like transport body such as a belt with a driving roller, and attracts and transports a recording medium to the transport body with an electrostatic force or the like, variations in the driving roller diameter or the thickness of the sheet-shaped transport body There is variation. For these reasons, when the conveyance amount of the recording medium is less than the prescribed amount, the above-described bands are overlapped and black stripes are generated. On the other hand, when the carry amount exceeds the specified amount, the overlapping of the bands decreases or disappears, and white stripes are likely to occur.

  As described above, when the amount of overlapping bands differs due to the variation in the conveyance amount of the recording medium, even if the correction method described in Patent Document 1 is simply applied, the connecting stripe cannot be reduced appropriately. This is because the density of connecting stripes or the degree of recognition as stripes varies depending on the amount of overlapping bands. For example, when the overlapping amount is doubled, the density of the connecting stripe may not be doubled, but may be more than that. In this case, even if the correction method described in Patent Document 1 is applied, the connecting stripe is appropriately displayed. It cannot be reduced.

  An object of the present invention is to provide an ink jet recording apparatus that can appropriately suppress a connecting stripe caused by a variation in the conveyance amount of a recording medium.

  Therefore, in the present invention, an inkjet recording apparatus that records on a recording medium by moving the recording medium relative to the recording head by a transport unit and discharging ink from the recording head based on recording data. A measurement unit that measures the conveyance amount of the recording medium when the conveyance unit conveys the recording medium by a predetermined conveyance amount, and a conveyance deviation that acquires a conveyance deviation amount that is a difference between the conveyance amount measured by the measurement unit and the predetermined conveyance amount. An amount of ink to be ejected on the basis of print data in a first predetermined area in the vicinity of a boundary between adjacent print areas in a plurality of print areas defined by performing the predetermined amount of feed a plurality of times; An ink amount acquisition unit to acquire, a conveyance deviation amount acquired by the conveyance deviation amount measurement unit, and an ink amount acquisition unit. Based on the ink amount, a determining unit that determines a reduction rate for reducing the amount of ink ejected to the second predetermined region in the vicinity of the boundary between the adjacent recording regions, and a reduction rate determined by the determining unit, And a reduction means for performing a process for reducing the amount of ink ejected to the second predetermined area.

  According to the above configuration, it is possible to appropriately suppress the connecting stripe caused by the variation in the conveyance amount of the recording medium.

(A) And (b) is a schematic diagram for demonstrating the principle of a joining stripe generation | occurrence | production and a joining stripe reduction process. 1 is a top view schematically showing an ink jet recording apparatus according to a first embodiment of the present invention. It is a side view of the apparatus shown in FIG. It is a figure which shows the back surface side of the conveyance belt used with the apparatus shown in FIG. It is a schematic diagram for demonstrating the imaging timing of an area sensor and the calculation timing of conveyance deviation | shift amount in the movement amount measuring apparatus for the movement amount measurement in 1st Embodiment. It is a figure explaining acquisition of the conveyance amount by a rotary encoder in a 1st embodiment. 6 is a flowchart showing recording data correction (thinning-out) processing for reducing a connecting stripe according to the first embodiment. (A) And (b) is a figure explaining the area | region which performs the dot count of the recording data in the process shown in FIG. 7, and the area | region which performs a thinning. It is a flowchart which shows the color gamut determination process in the process shown in FIG. It is a figure which shows an example of the result of the said dot count. It is a figure which shows an example of the classification of the color gamut in the said color gamut determination process. It is a figure which shows the table used for determination of the conveyance deviation condition in the process shown in FIG. (A) And (b) is a figure which shows the example of the thinning-out rank graph for determining the thinning-out rank in the process shown in FIG. It is a figure which shows an example of the relationship between the ink reduction rate in a thinning rank, and a counter value. (A)-(f) is a figure which shows the thinning-out rank graph used when the conveyance deviation condition according to the conveyance deviation amount shown in FIG. 12 is "0". (A)-(f) is a figure which shows the thinning-out rank graph used when the conveyance deviation condition according to the conveyance deviation amount shown in FIG. 12 is "-1". (A)-(d) is a figure for demonstrating the thinning-out process of the recording data in 1st Embodiment. (A)-(f) is a figure for demonstrating the process of the recording data in 1st Embodiment. It is a top view which shows the outline of the inkjet recording device which concerns on the 2nd Embodiment of this invention. It is a side view of the apparatus shown in FIG. It is a figure for demonstrating the timing of the measurement of the movement amount in 2nd Embodiment, and the measurement of the conveyance deviation amount.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
An ink jet recording apparatus according to an embodiment of the present invention includes (1) a movement amount measurement unit that measures a conveyance amount of a recording medium when the recording medium is conveyed by a predetermined conveyance amount by a conveyance mechanism. For example, the movement amount measuring unit directly detects the movement amount of the recording medium or the movement amount of the sheet-like conveyance body that sucks and conveys the recording medium. In addition, a conveyance deviation amount acquisition unit is provided that acquires a conveyance deviation amount that is a difference between a conveyance amount measured by the movement amount measurement unit and a predetermined conveyance amount. Further, the ink amount for acquiring the amount of ink ejected to the first predetermined area in the vicinity of the boundary between the adjacent recording areas in the plurality of recording areas defined by performing the predetermined amount of conveyance a plurality of times Includes an acquisition unit. Further, the amount of ink ejected to the second predetermined area near the boundary between the adjacent recording areas is reduced based on the conveyance deviation amount acquired by the conveyance deviation amount measurement unit and the ink amount acquired by the ink amount acquisition unit. A determination unit for determining a reduction rate for Furthermore, a reduction unit is provided that performs processing for reducing the amount of ink ejected to the second predetermined region in accordance with the reduction rate determined by the determination unit. Accordingly, it is possible to reduce the amount of ink to be ejected by a reduction amount corresponding to the density of the connecting stripes according to the conveyance deviation amount.

  An area sensor can be used as the movement amount measuring unit. An area sensor is arranged at a passing position of the recording medium or the sheet-like conveyance body that sucks and conveys the recording medium, and images the surface of the recording medium or the surface of the sheet-like conveyance body at a predetermined timing. The amount of movement of the image captured at a predetermined time interval is calculated by image processing, and the amount of movement of the recording medium or sheet-like conveyance body is calculated. With this configuration, it is possible to directly detect the movement amount of the recording medium that finally forms an image or the movement amount of the movement amount of the sheet-like conveyance body. As a result, the detected movement amount is not affected by variations in the driving roller diameter, slippage between the recording medium and the driving roller, and variations in the thickness of the sheet-like conveyance body, and the deviation amount of the conveyance amount described later is not affected. It can be calculated accurately.

  As another example of the moving amount measuring unit, there is a configuration using a sensor that measures a moving speed of an object using a laser Doppler phenomenon. For example, the moving speed is measured every 1 millisecond, and the moving distance is obtained using the measured moving speed. The movement distance measurement in the movement amount measuring unit is performed by integrating the movement distances of the minute unit time. Since the movement distance measurement using the laser Doppler phenomenon is a known technique, it will not be described.

  The deviation amount of the conveyance amount is calculated by taking the difference between the conveyance amount obtained from the driving amount of the driving roller and the more accurate movement amount measured by the movement amount detection unit. For example, the difference between the conveyance target amount for driving the driving roller at the end of conveyance and the movement amount can be obtained. Further, in order to obtain a conveyance deviation amount during conveyance, a difference between the conveyance amount calculated from the driving amount of the driving roller and a more accurate movement amount measured by the movement amount detection unit may be taken. In the latter configuration, since the ink amount reduction rate is determined using the transport deviation amount at the timing before the end of transport, it is possible to correct the print data before the end of transport and avoid a decrease in the throughput of the recording apparatus. be able to. In this case, a deviation in the conveyance amount that occurs during the period from the last area sensor imaging in the conveyance to the completion of the conveyance remains as an error. This can be reduced by performing the imaging timing of the area sensor at a timing close to the end of conveyance.

  On the other hand, when the deviation amount of the conveyance amount is obtained from the difference between the above movement amount at the end of conveyance and the conveyance target amount, the conveyance deviation amount is calculated by using the final conveyance movement amount at the end of conveyance. The amount of conveyance deviation can be obtained accurately. However, since the conveyance deviation amount is obtained after the conveyance is completed and the recording data is corrected, the throughput may be somewhat reduced.

  The connecting stripe reduction process will be described with reference to FIGS. FIGS. 1A and 1B are schematic diagrams for explaining the principle of joint streaks generation and joint streak reduction processing. The recording of the next band is performed when the fixing is promoted in a state where the ink of the previously recorded band is slightly blurred. Therefore, in the process in which the ink in the next band penetrates into the inside or the surface of the paper, the ink newly printed in the next band is drawn into the previously recorded band area. At this time, if no processing is performed on the joint portion, as shown in FIG. 1A, the amount of ink in the joint portion between the bands increases, and the density of the joint portion becomes higher than the other portions. It will be observed as a connecting stripe. Accordingly, in order to reduce the occurrence of such connecting stripes, the recording data of the connecting portions is basically thinned out as shown in FIG. Further, in the present embodiment, the size of the region where the connecting stripe is generated differs depending on the conveyance deviation amount, and the density of the connection stripe varies accordingly, so that the amount of thinning out the recording data differs depending on the conveyance deviation amount. Make it.

(Embodiment 1)
[Configuration of recording device]
FIG. 2 is a top view schematically showing the ink jet recording apparatus according to the embodiment of the present invention. FIG. 3 is a side view thereof. In these drawings, the head cartridge 1 is detachably mounted on the carriage 2. The head cartridge 1 includes a recording head that ejects ink by an ink jet method, and an ink tank that stores ink and supplies the ink to the recording head. The recording head of the present embodiment is a system that ejects ink by generating bubbles in the ink by heating using a heater. Note that this discharge method is not limited to this form, and a known method such as a method using a piezo element, a method using an electrostatic element, or a method using a MEMS element can be used.

  The carriage 2 is guided and supported by a guide shaft 3 and can reciprocate in the main scanning direction (x-axis direction). The carriage 2 is moved by a carriage driving mechanism including a carriage motor 4, a pulley 5, a pulley 6, and a timing belt 7. The sensor 30 and the shielding plate 36 detect that the carriage 2 is at the home position.

  The recording medium 8 is stacked on the sheet feeder 32. When there is a recording command, the pickup roller 31 is rotated by the supply motor 35 and the stacked recording media 8 are separated and supplied one by one. The sheet detector 33 is a sensor that detects the recording medium, and determines whether the supply of the recording medium 8 is normal. The recording medium 8 is conveyed in the conveying direction (y-axis) by the rotation of the conveying belt 1009 that is a sheet-like conveying member wound around the driving roller 9 and the driven roller 1010, and faces the recording head of the head cartridge 1. It is sent to the position to do. Here, the recording medium is attracted to the transport belt by, for example, electrostatic attracting force, and the driving force is transmitted without loss. The electrostatic attraction is realized by mounting a neutralizing roller (not shown) for controlling the charge state in addition to a power supply roller (not shown) for applying a charge to the conveying belt. The conveyance amount of the conveyance belt 1009 can be detected by a rotary encoder 1013 attached to the rotation shaft of the drive roller 9. A controller (not shown) controls the rotation of the carry motor 1008 based on the detected amount. Each of the pinch roller 1012 and the spur roller 1011 is a driven roller for performing stable conveyance with a recording medium sandwiched between the conveyance belt 1009. The movement amount measuring apparatus 700 includes an area sensor, and is arranged inside the belt rotation area in a form fixed to a platen portion 1014 for stabilizing the conveyance surface of the conveyance belt as shown in FIG. Thereby, the movement amount measuring apparatus 700 can image the back surface of the belt at a position substantially opposite to the recording position of the recording head. FIG. 4 is a diagram illustrating the back side of the conveyor belt. Patterning 801 is applied to the surface imaged by the area sensor mounted on the movement measuring apparatus 700, and the amount of movement can be obtained by imaging the surface with the area sensor. The patterning can be performed by drawing with a paint, applying a patterning seal, forming a physical unevenness by surface treatment, and laser marking after putting a laser coloring material on the belt material.

  In the above configuration, the formation of an image on the recording medium 8 is performed by alternately conveying the recording medium 8 by the conveying belt 1009 driven by the driving roller 9 and scanning the recording head by moving the carriage 2 by the carriage driving mechanism. Do by repeating. During the scanning of the recording head, ink is ejected from the recording head to record an image on the recording medium.

[Obtain transport amount deviation]
FIG. 5 is a schematic diagram for explaining the imaging timing (D0 to D2) of the area sensor and the calculation timing (F) of the conveyance deviation amount in the movement amount measuring apparatus 700 for measuring the movement amount. The imaging described below and the calculation of the conveyance deviation amount based on the imaging are performed in the conveyance of the recording medium corresponding to one band.

  First, imaging by the area sensor is performed before starting the conveyance of the recording medium (D0). And as mentioned above, based on the measurement by a rotary encoder, the motor which drives a drive roller is controlled using a conveyance amount and conveyance speed, and conveyance is started. After this start, the conveyance speed increases and becomes substantially constant at a predetermined timing (high speed region in the figure). At a predetermined timing D1 in the low speed section, imaging by the area sensor and calculation of the movement amount are performed. At this time, the movement amount measuring apparatus 700 performs a known image processing calculation such as a cross-correlation process on the image captured at the timing D0 and the image captured at the timing D1, and calculates the transport amount.

  In the present embodiment, imaging (D2) by the area sensor, calculation of the movement amount, and calculation of the conveyance deviation amount (F) are performed in the second half of the conveyance. Image processing such as cross-correlation processing is performed on the image captured at timing D1 and the image captured at timing D2, and the amount of movement from timing D1 to D2 is calculated. Then, by taking the sum of the two movement amounts calculated so far, the movement amount from the start (D0) of conveyance to the timing D2 is obtained. Further, at the same timing (F), the conveyance amount by the rotary encoder 1013 is obtained as described later, and the conveyance deviation amount is calculated by taking the difference.

  In the present embodiment, the conveyance deviation that occurs from timing D2 to the end of conveyance is not corrected. Therefore, in order to further reduce the joint streaks due to conveyance deviation, it is desirable that the timing D2 is as far as possible in the conveyance. On the other hand, in order to avoid the decrease in throughput due to the connecting stripe reduction process by calculating the amount of transfer deviation before the end of the transfer and perform the connecting stripe reduction process described later, the timing D2 may ensure a certain time from the end of the transfer. is necessary. The timing D2 is determined from these points.

  FIG. 6 is a diagram for explaining acquisition of the conveyance amount by the rotary encoder 1013. The conveyance amount measuring unit having the rotary encoder is provided with a count unit that counts the slit passing signal of the rotary encoder, and the count unit obtains a count value at a predetermined timing (E1) to (E7). Ask for. FIG. 6 shows the above-described imaging timings (D1) and (D2) by the area sensor of the conveyance amount measuring apparatus 700, along with the conveyance amount acquisition timing by the rotary encoder.

  In the present embodiment, the time difference between the imaging timing (D1) by the transport amount measuring device 700 and the measured value income timings (E1) and (E2) of the rotary encoder is based on the clock signal (B) shown in FIG. Get. Then, using the amount of time shift, internal division calculation is performed based on the measured value (count value) by the rotary encoder at the timings (E1) and (E2), and the measured value by the rotary encoder at the timing (D1) is calculated. calculate. Similarly, the measurement value by the rotary encoder at the timing (D2) can be acquired. When the difference between the value measured by the rotary encoder at the timing (D2) and the value measured by the rotary encoder at the timing (D1) is taken, the conveyance amount by the rotary encoder between the timings (D1) and (D2) can be obtained. .

  The conveyance amount by the rotary encoder may include a deviation from the actual conveyance amount of the recording medium due to variations in the roller diameter of the drive roller 9 and variations in the thickness of the sheet-like conveyance body. On the other hand, the movement amount measured by the movement amount measuring apparatus 700 described above is not affected by variations in the roller diameter of the driving roller 9 or thickness variations of the sheet-like conveyance body, and reflects the actual conveyance amount with higher accuracy. Transported amount. In this embodiment, the difference between the conveyance amount by the rotary encoder and the conveyance amount measured by the movement amount measuring device 700 is taken to obtain the conveyance deviation amount.

  In addition, the acquisition method of the conveyance amount by a rotary encoder is not restricted to the method demonstrated above. It is only necessary to obtain the transport amount by the rotary encoder at the timing close to the imaging by the area sensor in the movement amount measuring unit. For example, when the conveyance amount acquisition timing by the rotary encoder is sufficiently fast, the conveyance amount acquisition timing value of the rotary encoder closest to the imaging timing from timing (D0) to (D1) may be used.

[Connecting stripe reduction processing]
FIG. 7 is a flowchart showing recording data correction (thinning-out) processing for reducing stitching lines according to the present embodiment. This process is activated when print data for one scan is received, and is performed for each scan (one band).

  In the processing for reducing the stripe streaking in this embodiment, the reception of the printing data for one scan in step S1 shown in FIG. 7 is performed without waiting for the conveyance deviation amount acquisition timing (F) described in FIG. Immediately after acquiring the quantity, the processing from step S2 is started.

<Reception of printing data for one scan>
In step S1, an amount of print data necessary for printing for one scan corresponding to each color ink is received. In order to perform recording for one scan, in addition to recording data for one band of the scanning, recording data for a dot count area described later in an adjacent band is required. Here, one band is a recording area formed in one carriage scan.

<Dot count>
The dot count in step S2 is performed as follows. In this embodiment, the area where dot count is performed is a 16 raster (pixel) × 16 pixel area straddling the boundary between bands as shown in FIG. By making the area larger than the thinning area and counting the dots (binary data) of both bands across the boundary, it is possible to appropriately grasp the state of bleeding at the joint portion.

  The dot count is performed on all the inks mounted on the recording apparatus used in the present embodiment, that is, binary recording data of each color of cyan, magenta, and yellow. Then, the sum of the dot count numbers obtained from each is used as a dot count value (or total dot count value) as a result of the dot count.

<Color Gamut Determination>
In step S3, color gamut determination is performed. FIG. 9 is a flowchart showing color gamut determination processing. First, in step S2, the dot count of each color is performed as described above. FIG. 10 is a diagram illustrating an example of the dot count result, and FIG. 11 is a diagram illustrating the color gamut division used in the present embodiment.

  In the example shown in FIG. 10, magenta, cyan, and yellow are arranged in descending order of the number of dots. Here, the smallest yellow portion of cyan, magenta, and yellow is a portion generally called UC (Under Color), and hereinafter, the number of dots in this color gamut will be expressed as UC. The portion with the second most cyan minus UC is the secondary color (blue in this example), and the number of dots in this color gamut is denoted as D2. The primary color (magenta in this example) is obtained by subtracting the second most cyan from the most magenta, and the number of dots in this color gamut is expressed as D1. In step S31, D1, D2 and UC are obtained.

  Next, by determining which of these D1, D2, and UC takes the largest value, it is determined which color gamut is within the color gamut shown in FIG. (Step S32). In this example, since D1 is the largest of the three, it is determined that the dot count area is in magenta (step S33).

  When two or three of the largest D1, D2, and UC exist, the color gamuts are in the order of UC, D2, and D1 (if UC and D2 are the same, UC, D1 and D2 are If they are equal, D2 is used, and D1 is not actually used.)

<Conveyance deviation condition judgment>
Referring to FIG. 7 again, in the conveyance deviation condition determination in step S4, the conveyance deviation condition is determined from the conveyance deviation amount obtained as described above with reference to FIGS.

  FIG. 12 is a diagram illustrating a table used for determining the conveyance deviation condition. Based on the conveyance deviation amount, the conveyance deviation condition is selected with reference to the table shown in FIG. As described above, the conveyance deviation amount is obtained by subtracting the conveyance amount by the rotary encoder from the actual movement amount of the recording medium. From this, a positive conveyance deviation indicates that the actual conveyance amount is larger than the target conveyance amount, and a negative conveyance deviation indicates that the actual conveyance amount is smaller than the target conveyance amount. Indicates. For example, when the conveyance deviation amount is −10 μm or less, that is, a negative value and the absolute value is 10 μm or more, the conveyance deviation condition “−1” is selected.

<Decimation rank determination>
Referring to FIG. 7 again, in the next step S5, a thinning rank is determined.

  FIG. 13A is a diagram illustrating an example of a thinning rank graph for determining a thinning rank. In the thinning rank graph, the vertical axis represents the thinning rank (corresponding to the ink amount reduction rate), and the horizontal axis represents the total dot count value. That is, the ink amount reduction rate (thinning rate) corresponding to the total dot count value obtained by dot count is obtained according to the relationship of the thinning rank graph.

  Specifically, in the thinning rank graph, the number of start dots means a total dot count value when starting to use a thinning rate of 12.5% (thinning rank 1). The dot interval means a dot count number until the next thinning rate (25% if 12.5% is followed), that is, a dot count range using the same thinning rate. The MAX rank is the maximum thinning rate. That is, when the thinning rate reaches the MAX rank without selecting a thinning rate exceeding this, even if the dot count value for the dot interval is obtained thereafter, the thinning rate is not increased, and the MAX rank is not increased. This means that the thinning rate is maintained.

  In this embodiment, the ink amount reduction rate (thinning rate) is 0%, 12.5%, 25%, 37.5%, 50%, 62.5%, 75%, 87.5%, 100%. Set 9 levels. FIG. 14 is a diagram illustrating an example of the relationship between the ink reduction rate and the counter value.

  In the present embodiment, the example in which the thinning rank graph is specified by the three parameters (the number of start dots, the thinning interval, and the MAX rank) as described above is shown, but it is not necessary to limit to this method. In the specific case of the thinning rank graph as in the present embodiment, the relationship between the total dot count and the ink amount reduction rate can only be linear, whereas as shown in FIG. 13B, the thinning rank graph. You may make it prescribe | regulate the shape of itself. Further, the ink amount reduction rate does not need to be limited to nine levels as in the above example, and the ink amount reduction rate may be increased or decreased as necessary.

  FIGS. 15A to 15F and FIGS. 16A to 16F are used when the conveyance deviation conditions corresponding to the conveyance deviation amounts shown in FIG. 12 are “0” and “−1”, respectively. It is a figure which shows a thinning rank graph.

  When the conveyance deviation condition is “0”, the conveyance deviation amount is not so large as shown in FIG. In accordance with this condition, the thinning rank graph (table) shown in FIGS. 15A to 15F is set. The thinning rank graph is set for each color gamut shown in FIG. In addition, in this embodiment, a thinning rank is set for each different ink (cyan, magenta, yellow). In addition, regarding this thinning rank setting, a thinning area described later is divided into two in the recording medium conveyance direction (sub-scanning direction), and an independent thinning rank graph is set for each area. Therefore, as shown in FIGS. 15A to 15F, six thinning rank graphs (cyan upper, cyan lower, magenta upper, magenta lower, yellow upper, and yellow lower) are set.

  In contrast to the decimation rank graph when the conveyance deviation condition is “0” shown in FIGS. 15A to 15F, when the conveyance deviation condition is “−1”, the decimation shown in FIGS. A rank graph is set. That is, when the transport deviation amount is small, that is, when the recording medium is transported less than the specified amount, the amount of overlapping of the recording areas between adjacent bands increases, and the density of the connecting stripes increases accordingly. For this reason, the thinning amount is relatively increased as compared with the case of the conveyance deviation condition “0”. Specifically, in this embodiment, as shown in FIGS. 16A to 16F, the number of start dots is set to be smaller than that in the case of the conveyance deviation condition “0”. Conversely, in the case of the conveyance deviation condition “+1”, the number of start dots is set to be larger than that in the case of the conveyance deviation condition “0”.

  As described above, by setting the thinning amount in accordance with the conveyance deviation amount, it is possible to appropriately reduce the connecting stripe caused by the deviation in the conveyance amount due to the variation in the driving roller diameter and the thickness of the sheet-like conveyance body. it can.

  In the present embodiment, as described above, the thinning rank tables shown in FIGS. 15A to 15F and FIGS. 16A to 16F are transported with the color gamut (cyan, magenta, yellow, UC). Twelve sets are set for combinations of deviation conditions (condition-1, condition 0, condition + 1).

<Thinning processing area>
As shown in FIG. 8A, the thinning-out area is adjacent to the band on which recording has already been performed, and the discharge side of the band recorded after conveyance of one band of the recording medium (downstream side in the conveyance direction). Set to . Further, as shown in FIG. 8B, the four rasters to be thinned are further divided into two areas, namely, a discharge side 2 raster (also expressed as upper) and a paper feed side 2 raster (also expressed as lower). For each of them, the thinning rank is determined as described above.

  In this embodiment, the thinning area and the dot count area are not the same area, and a part of the dot count area is a thinning area. In addition, since the thinning area is not the paper feeding side but the paper discharging side, the recording data is corrected (thinning) after the conveyance deviation amount is calculated, so the recording data to be corrected corresponds to the band for recording after the conveyance. This is because it is recorded data.

<Thinning processing>
Referring to FIG. 7 again, in the next step S6, the thinning process is performed on the recording data in the thinning area determined in step S5 by the thinning rank determined in step S5.

  In the thinning-out process of this embodiment, whenever there is recording data, the count value (specific bit, MSB in this case) designated by the counter (register) is read. Move (shift) one by one. When the counter value is 0, the recording data is thinned and the counter is moved to the right by one. When the counter moves to the right, it returns to the left again. By repeating this process every time recording data comes, thinning dots are determined.

  The thinning process will be described more specifically with reference to FIGS. 17A to 17D and FIGS. 18A to 18F. In these drawings, among the recorded data, the recorded data is indicated by ◯, and the place where there is no data to be recorded is indicated by ×. The data of interest is shown in bold. As for the counter value, 1 is used for recording, 0 is used for thinning out recorded data, and the counter value designated by the counter is shown in bold.

  In FIG. 17A, since the first recording data is ◯ and the counter value is 0, the first data is thinned out. For this reason, the first recorded data after processing becomes “x”, and the counter moves one to the right ((b) in the figure). Since the next data is not recorded, it is left as it is, and the counter remains in the same position without moving ((c) in the figure). In the third recording data, since the counter value is 1, the recording data remains as it is, and the counter is moved to the right by one. In this way, the recording data is thinned out at a rate of 1 in 4 ((d) in the figure).

  FIGS. 18A to 18F show an example in which the thinning-out processing area is 4 rasters, and data before and after thinning-out processing of 8 dots in the main scanning direction and 4 rasters in the paper discharge direction. Is shown. Further, the figure shows the case where the thinning rank is the paper discharge side 2 and the paper supply side 4. For the sake of explanation, as shown in FIG. 18A, they are called the first raster, the second raster, the third raster, and the fourth raster from the paper discharge side. Here, the thinning process is performed for each raster from the raster on the paper discharge side, and when one raster is processed, the process proceeds to the next raster. At this time, the counter does not return to the initial position even if the thinning level changes. In the present embodiment, the counter does not return to the initial position even if the thinning-out processing area moves to an adjacent area within one band, and the counter position is stored within one band. In addition, when the process moves to a different band, the counter position is returned to the initial position. The initial position of the counter in the first processing area of one band is specified at random. As a result, the first raster to the fourth raster are processed as shown in FIGS. 18B to 18E, and the whole is as shown in FIG. 18F.

  As described above, according to the present embodiment, it is possible to reduce the connecting stripe due to the variation in the transport distance.

  In the above-described embodiment, the thinning rank graph is set for each color gamut and conveyance deviation condition as the thinning rank determination method, and the ink reduction rate is determined from the thinning rank graph and the total count amount. However, the present invention is not limited to this form. In order to realize the present invention, it is preferable that the reduction rate for reducing the amount of ink to be struck into the joint portion based on the conveyance deviation amount can be adjusted. For example, a three-dimensional lookup table for the relative relationship between the ink amounts calculated for each ink color, the total ink amount information, and the conveyance deviation amount may be created, and the thinning table number may be determined using the table.

(Embodiment 2)
In the first embodiment described above, the configuration in which the recording medium is electrostatically attracted to the conveyance belt to convey the recording medium, and the back surface of the conveyance belt is imaged by the area sensor as the movement amount measurement unit has been described. Further, the configuration has been described in which the conveyance deviation amount is calculated before the end of conveyance of the recording medium and the joint stripe reduction process is started. In the second embodiment of the present invention, a configuration in which a recording medium is conveyed by a driving roller and the surface of the recording medium is directly imaged by an area sensor as a movement amount measuring unit will be described. In addition, the conveyance deviation amount is calculated after the conveyance of the recording medium is completed, and the connecting stripe reduction process is started.

  FIG. 19 is a diagram showing a schematic configuration of the ink jet recording apparatus according to the present embodiment, and FIG. 20 is a side view thereof. The recording medium 8 is directly conveyed by the driving roller 9. Further, the discharge roller 2301 has a gear attached to its shaft to obtain a driving force from a gear attached to the drive roller via a transmission gear 2302.

  The movement amount detection device 700 is supported by the platen unit 1014 and is provided at a position facing the recording head, and images the fibers on the back surface of the medium passing through the recording head, the unevenness created in advance, and the like by an area sensor. As a cause of the conveyance deviation in this configuration, there are variations in the driving roller diameter and variations in the amount of slip between the recording medium and the driving roller.

[Obtain transport amount deviation]
FIG. 21 is a diagram for explaining movement amount measurement and conveyance deviation amount calculation timing according to the present embodiment. The difference from the first embodiment described above is that, at the end of conveyance (D3), the area sensor is imaged and the amount of movement based on it is calculated, and the sum of the amount of movement calculated so far is taken, Get the amount of movement for the entire transport. At this time, the conveyance deviation amount is calculated (F). The conveyance deviation amount is calculated by subtracting the target conveyance amount from the obtained movement amount of the entire conveyance. Of course, the conveyance amount measured by the rotary encoder may be used instead of the target conveyance amount.

  The connecting stripe reduction process is the same as the process of the first embodiment described above. A thinning rank is determined using the measured conveyance deviation amount, total dot count, and color gamut information, and thinning processing is performed. In the first embodiment, the amount of conveyance deviation is obtained before the end of conveyance, and the connecting stripe reduction process is started, which is advantageous in improving the throughput of the recording apparatus. However, it is not possible to correct a transport deviation newly generated from the measurement of the transport deviation amount to the end of the transport. Since the configuration of the present embodiment measures the amount of conveyance deviation after the conveyance is completed, by correcting the conveyance deviation amount of the entire conveyance, the connection streaks are reduced by correcting the conveyance variation with higher accuracy than the first embodiment. Processing can be performed.

DESCRIPTION OF SYMBOLS 1 Head cartridge 8 Recording medium 9 Drive roller 1009 Conveyance belt (sheet-like conveyance body)
1013 Rotary encoder 700 Movement measuring device 801 Patterning

Claims (5)

An inkjet recording apparatus that records on a recording medium by moving the recording medium relative to the recording head by a conveying unit and discharging ink from the recording head based on recording data,
Measuring means for measuring the transport amount of the recording medium when transporting the recording medium by a predetermined transport amount by the transport means;
A conveyance deviation amount acquisition unit that acquires a conveyance deviation amount that is a difference between a conveyance amount measured by the measurement unit and a predetermined conveyance amount; and
Ink amount acquisition for acquiring the amount of ink ejected based on print data in a first predetermined area in the vicinity of the boundary of adjacent print areas in a plurality of print areas defined by carrying the predetermined carry quantity a plurality of times Means,
Based on the conveyance deviation amount acquired by the conveyance deviation amount measuring unit and the ink amount acquired by the ink amount acquisition unit, the amount of ink ejected to the second predetermined area near the boundary of the adjacent recording areas is reduced. A determination means for determining a reduction rate for
Reduction means for performing a process for reducing the amount of ink ejected to the second predetermined area according to the reduction rate determined by the determination means;
An ink jet recording apparatus comprising:   The inkjet recording apparatus according to claim 1, wherein the conveyance deviation amount acquisition unit acquires the conveyance deviation amount from a difference between a movement amount measured by the measurement unit and a driving amount by the conveyance unit. .   The inkjet recording apparatus according to claim 1, wherein the conveyance deviation amount acquisition unit acquires the conveyance deviation amount from a difference between a movement amount measured by the measurement unit and a target conveyance amount.   The inkjet recording apparatus according to claim 1, wherein the conveyance deviation amount acquisition unit acquires the conveyance deviation amount before completion of conveyance of the predetermined conveyance amount of the recording medium. The ink amount acquisition means acquires the amount of ink ejected to the first predetermined area by counting the number of binary data corresponding to the ink,
The determining means determines a thinning rate of binary data as the reduction rate,
The inkjet recording apparatus according to claim 1, wherein the reducing unit thins out binary data based on the thinning rate.

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