JP7455557B2 - Recording device and recording method - Google Patents

Description

The present invention relates to a recording device and a recording method.

2. Description of the Related Art A printing apparatus is known in which printing is performed by ejecting ink onto a printing medium while a printing head scans and conveying the printing medium in a direction intersecting the scanning direction. Furthermore, in order to convey the recording medium to a position where recording is performed by the recording head in such a recording apparatus, it is known that conveyance rollers are provided on the upstream and downstream sides in the conveyance direction of the recording medium with the recording head in between. There is.

Patent Document 1 discloses that in order to prevent the recording medium from bending at the position where recording is performed, tension is applied to the recording medium by rotating a conveying roller on the downstream side at a slightly higher speed than the conveying roller on the upstream side. Disclosed. It is also disclosed that the conveyance amount deviates due to the difference in rotational speed when the conveyance progresses and the upstream conveyance roller is removed.

Patent Document 2 discloses increasing the cluster size of a mask pattern and printing a plurality of adjacent dots in the same scan in order to suppress density unevenness due to deviations in the conveyance amount of a printing medium.

Japanese Patent Application Publication No. 2002-321412 Japanese Patent Application Publication No. 2008-229864

However, in the method of Patent Document 2, a plurality of dots are collected and recorded at once, so it is conceivable that graininess may become noticeable depending on the image.

The present invention has been made in view of the above problems, and it is an object of the present invention to control density unevenness and graininess in a well-balanced manner depending on the situation even when there is a deviation in the conveyance amount.

The present invention provides a print head that has a plurality of ejection ports arranged in a predetermined direction and ejects ink from the ejection ports onto a recording medium based on image data, and a print head that has a plurality of ejection ports arranged in a direction that intersects with the predetermined direction. a plurality of rollers that convey the recording medium in the predetermined direction; and an operation of discharging ink onto the recording medium while moving the recording head by the moving means; An image is formed on the recording medium by alternately carrying out the operation of conveying the recording medium a predetermined distance using the two rollers, and ejecting ink into the same area on the recording medium multiple times to form dots. Acquire image data of a predetermined area of a part of the recording medium, which is a recording apparatus that records, and includes an area recorded during movement of a recording head after conveyance in which the combination of the rollers that convey the recording medium changes. and recording an image in a first mode when the value of the image data corresponds to a halftone based on the image data acquired by the acquisition means; The method further comprises a determining means for determining a mode in which recording is performed according to the image data from among a plurality of modes, so that the image is recorded in the second mode when the image corresponds to a gradation higher than the intermediate tone; The plurality of modes include at least a first mode and a second mode, and when compared assuming that the input data is the same, the first mode is more sensitive to the recording head than the second mode. The average value of the number of consecutive dots recorded in the predetermined direction by recording in one movement of is large, the recording head is capable of ejecting ink of a plurality of colors, and the determining means is configured to The method is characterized in that the mode is determined based on the sum of dot ratios for each of the plurality of ink colors in the image data of the predetermined area acquired by the means .

According to the present invention, by changing the image processing method depending on the image to be recorded in the area to be printed after a deviation in the transport amount has occurred, density unevenness and graininess can be reduced even when there is a deviation in the transport amount. The purpose is to control the amount in a well-balanced manner depending on the situation.

FIG. 1 is a perspective view showing the configuration of a recording apparatus according to a first embodiment. FIG. 3 is a diagram showing the configuration of a discharge port in the first embodiment. FIG. 3 is a diagram illustrating conveyance of a recording medium in the first embodiment. FIG. 2 is a diagram showing a block configuration of a control system of a recording apparatus in a first embodiment. It is a flowchart of image processing in a 1st embodiment. It is a figure showing a mask pattern in a 1st embodiment. FIG. 6 is a diagram for explaining the printing state depending on the presence or absence of conveyance deviation in the first embodiment. FIG. 6 is a diagram for explaining the printing state depending on the presence or absence of conveyance deviation in the first embodiment. FIG. 6 is a diagram for explaining the printing state depending on the presence or absence of conveyance deviation in the first embodiment. FIG. 6 is a diagram showing positions where conveyance deviation may occur in the first embodiment. FIG. 3 is a diagram showing a determination area in the first embodiment. 11 is a table showing the relationship between density unevenness and the total printing rate in the first embodiment. It is a flowchart which shows mask pattern determination processing in a 1st embodiment. It is a figure which shows the mask pattern in 2nd Embodiment. 7 is a table showing the relationship between density unevenness and the total recording rate in the second embodiment. It is a flowchart which shows mask pattern determination processing in a 2nd embodiment. It is a figure which shows the quantization pattern in 3rd Embodiment.

(First embodiment)
[Recording device configuration]
FIG. 1 is a perspective view showing the configuration of a recording apparatus 100, in which casters and a paper ejecting basket are attached. FIG. 1(a) shows the overall appearance, and FIG. 1(b) shows the internal structure visible by opening the top cover. The recording apparatus 100 in this embodiment performs recording by applying ink droplets as a recording material onto a recording medium using an inkjet recording method. The recording medium P is transported with the Y direction as the transport direction. Next, an ink jet printing apparatus including a so-called serial type print head in which a carriage 101 carrying a print head 102 performs printing by reciprocating in the X direction intersecting the Y direction will be described. The recording head is capable of ejecting ink of multiple colors. Furthermore, it may be a multi-function peripheral device (MFP) that integrates not only a recording function but also a scanning function, a FAX function, a sending function, and the like. Alternatively, an electrophotographic recording apparatus using powder toner as a recording material may be used. In this embodiment, the recording device 100 is equipped with an information processing device function for determining a recording medium to be used, which will be described later.

An operation unit 406 is provided at the top of the recording device 100. The operation unit 406 is an operation panel that displays the amount of remaining ink and candidates for the type of recording medium on the display, and allows the user to select the type of recording medium and make recording settings by operating keys. can.

The carriage 101 includes a recording head 102 having an ejection port surface provided with an ejection port for ejecting ink, and an ink tank 108 for storing ink. The ink tank 108 stores six colors of ink, black (K), cyan (C), magenta (M), yellow (Y), light cyan (Lc), and light magenta (Lm), and each ink is stored in the ink tank 108 from the carriage 101. It is attached in a removable manner. The carriage 101 is configured to be able to reciprocate in the X direction (carriage movement direction) along the shaft 104 via the carriage belt 103 by driving a carriage motor 418 (FIG. 4).

A recording medium P such as a roll paper is conveyed in the Y direction on a platen 106 by a feeding roller 105 (FIG. 3). The recording operation is performed by ejecting ink droplets from the recording head 102 while the carriage 101 moves in the X direction on the recording medium P conveyed onto the platen 106 by the feeding roller 105 and the conveying roller 107 (FIG. 3). be exposed. When the carriage 101 moves to the end of the print area on the print medium P, the feed roller 105 and the conveyance roller 107 transport the print medium P by a certain amount, and move the area for the next print scan to a position where the print head 102 can print. move it to Images are recorded by repeating the above operations. In this embodiment, the feeding roller 105 and the conveying roller 107 rotate at the same conveying speed. In order to prevent the recording medium from sagging on the platen 106, the amount of transportation by the transportation roller 107 may be made slightly larger than the amount of transportation by the feeding roller 105.

FIG. 2 is a schematic diagram of the ejection port surface and ejection ports provided in the recording head 102, viewed from the −Z direction. In the figure, n1 to n768 indicate the respective discharge port numbers. In this embodiment, numbers are assigned sequentially from the upstream side in the transport direction (-Y direction side). A plurality of discharge ports 201 are arranged in the Y direction, and in this embodiment, there are 768 discharge ports arranged so that the distance between the center of one discharge port and the center of the adjacent discharge port is 1/1200 inch. It is provided. The size of the ink droplet from each ink ejection port is about 4 (pl), and the diameter of the dot that lands on the recording medium is about 30 μm. Each ink ejection port is provided with one corresponding heating element. Furthermore, in order to stably eject ink droplets of these ejection amounts, the ejection frequency is 21 KHz, and the ejection speed is approximately 18 m/sec. Furthermore, the speed of the carriage 101 on which such a recording head 102 is mounted in the main scanning direction (X direction) is 17.5 inches/second, so that an image is formed at a recording density of 1200 dpi in the main scanning direction. be done. Further, the recording head 102 has two rows of ejection ports arranged at an interval of 1/600 inch, and the ejection ports are arranged at an interval of 1/1200 inch by arranging them so that they are shifted by 1/1200 inch in the X direction. You can also do this.

FIG. 3 is a schematic cross-sectional view of the inside of the recording apparatus 100 when the recording medium P is conveyed, viewed from the X direction. FIG. 3A is a diagram showing how the recording medium P is conveyed on the platen 106 by the feeding roller 105 in the +Y direction from the left side in the figure. At this time, the recording medium P is being conveyed by the feed roller 105, and the conveyance roller 107 is not used for conveyance. When the recording medium P is conveyed to a position facing the recording head 102, an image is recorded on the recording medium P by ejecting ink onto the recording medium P while the recording head 102 is operated in the X direction. When the recording for one scan is completed, the feeding roller 105 conveys the recording medium P a predetermined distance, and then an image is recorded on the recording medium P by the recording head 102.

FIG. 3(b) is a diagram showing a state in which the recording medium P is further conveyed from FIG. 3(a) and is being conveyed by the feeding roller 105 and the conveying roller 107. 3(c) is a diagram showing a state in which the recording medium P is further conveyed from FIG. 3(b), the rear end of the recording medium P has come off the feeding roller 105, and the recording medium P is being conveyed by the conveying roller 107. It is. From FIG. 3(c) onwards, the recording medium P is transported and discharged only by the transport roller 107. Here, when changing from the state shown in FIG. 3(b) to the state shown in FIG. 3(c), the feeding roller 105 is removed and the paper is transported only by the transport roller 107. Here, it is difficult to make rollers with exactly the same dimensions, and there are some variations. Therefore, from a state in which transport is performed by both the feed roller 105 and the transport roller 107 (FIG. 3(b)), to a state in which the transport roller 105 is removed and transport is performed only by the transport roller 107 (FIG. 3(b)). c)) Conveyance misalignment is likely to occur. Further, in the case of a recording apparatus in which the conveyance roller 107 has a larger conveyance amount, conveyance deviation tends to occur more easily. A band printed in a printing scan immediately after this conveyance deviation occurs may cause density unevenness.

FIG. 4 is a diagram showing a block configuration of the control system of the recording apparatus 100. In the block diagram, it is roughly divided into software processing means and hardware processing means. The software processing means includes an image input section 403 that accesses the main bus line 405, an image signal processing section 404 corresponding thereto, and a CPU 400 that is a central control section. The hardware processing means includes an operation unit 406, a recovery system control circuit 407, a head temperature control circuit 414, a head drive control circuit 415, a carriage drive control circuit 416 in the main scanning direction, and a transport control circuit 417 in the Y direction. The CPU 400 has a ROM 401 and a random memory (RAM) 402. The ROM 401 is a non-volatile memory, and retains, for example, a control program for controlling the recording device 100, a program for realizing the operation of this embodiment, even when the power of the recording device 100 is turned off. The required data is stored. The operation of this embodiment is realized, for example, by the CPU 400 reading a program stored in the ROM 401 into the RAM 402 and executing it. RAM 402 is also used as working memory for CPU 400.

The operation unit 406 receives instructions from the user to turn on the power, execute recording, and set various functions. The output unit displays various device information such as power saving mode and setting screens for various functions executable by the recording device 100. In this embodiment, the operation unit 406 is an operation panel provided in the recording apparatus 100, and is connected to the main bus line 405 so that data can be transmitted and received. Information input by the user by operating the operation unit 406 is input to the RAM 402 via the main bus line 405, and settings etc. are changed by the CPU 400.

Alternatively, the information may be input using the keyboard of an external host computer, or instructions from the user may be accepted from the external host computer. The panel that notifies the user of information may be an LED display, an LCD display, or a display connected to a host device. Further, when the operation unit 406 is a touch panel, instructions from the user can be accepted using software keys. Further, the operation unit 406 may include a speaker and a microphone, and input from the user may be input by voice, and notifications to the user may be output by voice.

An image input unit 403 stores image data transmitted from a host device such as a computer. The image signal processing unit 404 receives the image data stored in the image input unit 403 by the CPU 400, and performs various image processing on the input data to convert it into recording data that can be recorded by the recording head 102. .

The head drive control circuit 415 supplies a drive signal according to print data to a nozzle drive circuit that is mounted on the print head 102 and includes a selector and a switch, and controls the print operation of the print head 102 such as the nozzle drive order. I do. For example, the print head 102 is driven based on print data converted by the image signal processing unit 404. At this time, the conveyance control circuit 417 drives each motor based on the band width of the recording data, etc., and rotates the rollers connected to each motor, such as the feeding roller 105 and the conveying roller 107, thereby moving the recording medium. transport. The carriage drive control circuit 416 causes the carriage 101 to scan via the carriage belt 103 by driving a carriage motor connected to the carriage belt 103 .

The recovery system control circuit 407 is controlled by the CPU 400 according to a recovery program stored in the ROM 401. A recovery system control circuit 407 drives a recovery system motor 408 and performs a recovery operation to restore the ejection performance of the print head 102 by driving a blade 409, a cap 410, and a pump 411 connected to each recovery system motor 408. .

The heat-retaining heater 413 is provided in the print head 102 and can heat the ink inside the print head 102 . A thermistor 412 measures the temperature of the print head 102. The head temperature control circuit 414 controls the driving of the heat-retaining heater 413 based on the control by the CPU 400 and the temperature measured by the thermistor 412. The thermistor 412 may be provided within the print head 102 or may be provided outside the print head 102.

FIG. 5 is a flowchart showing the flow of image processing performed by the image signal processing unit 404. The image signal processing unit 404 reads out the RGB 8-bit data stored in the image input unit 403, and first performs color adjustment processing (step S501). Multi-value RGB data for recording is obtained from RGB data for the host device through color adjustment processing.

Next, in step S502, a color conversion process (S502) is performed to convert the image data into ink color data corresponding to each amount of ink used for printing on the print medium. In this embodiment, data is for six CMYKLcLm colors, but data for other numbers of ink colors may be used. Through the color conversion process, ink color data composed of 8 bits of information for each CMYKLcLm value is generated from the input original image data composed of 8 bits of information for each RGB value. The ink color data indicates one of 256 values from 0 to 255 for each pixel with a data resolution of 1200 dpi x 1200 dpi. The color conversion process uses a method using a three-dimensional lookup table or an arithmetic expression, and the process is performed using what is stored in the ROM 401 in advance.

Next, in step S503, gamma correction processing is performed to adjust the amount of each ink applied to the recording medium. Outputs converted data for data input for a certain color. In this embodiment, gamma correction processing is performed using a one-dimensional lookup table, and the lookup table data is stored in the ROM 401 in advance.

In step S504, quantization processing is performed to obtain binary data. Quantization processing is performed using a quantization pattern. A quantization pattern is a pattern in which a threshold value is set for each pixel, and if the value of the input data exceeds the threshold value, it is decided to record a dot, and if the value of the input data does not exceed the threshold value, it is determined to not record a dot. .

Then, in step S505, mask processing is performed using a mask pattern in order to obtain data that corresponds to multiple scans.

Through the above processing, the image data input from the host device is converted into print data that can be printed by the print head 102.

The printing method of this embodiment is multi-pass printing in which ink is ejected multiple times to the same area to print an image. In the following description, two-pass printing is used in which an image is printed by ejecting ink in two scans. The two-pass printing of this embodiment will be explained below. First, ink is ejected onto the recording medium from the ejection ports n1 to n384, which are half of the 768 ejection ports. When the ejection is completed, the ink is conveyed the distance recorded at n1 to n384, and then ink is ejected onto the recording medium from the ejection ports n385 to n768, thereby completing the recording of the image in that area.

FIG. 6 shows a mask pattern corresponding to an 8 pixel×8 pixel size used in this embodiment. The mask pattern is a pattern for determining whether recording of dots is permitted or not. FIG. 6A shows a mask pattern with emphasis on graininess. If the cluster size is large and the dispersion is low, individual clusters will become visually recognizable and the graininess of the image will worsen. Therefore, FIG. 6A shows a mask pattern (first mask pattern) in which the cluster size that allows recording of dots is 1 pixel×1 pixel so that the dispersibility is high. FIG. 6(a-1) and FIG. 6(a-2) have a complementary relationship. FIG. 6B shows a mask pattern that focuses on suppressing density unevenness due to conveyance error of the recording medium. This mask pattern (second mask pattern) is configured such that the cluster size that allows recording of dots is 1 pixel (X direction) x 4 pixels (Y direction), and the cluster size increases in the Y direction. FIG. 6(b-1) and FIG. 6(b-2) have a complementary relationship.

FIG. 7 shows a printing situation using a mask pattern depending on whether or not conveyance deviation of the printing medium occurs.

FIG. 7A shows a printing situation with print data with a printing rate of 100% and no conveyance deviation. In this embodiment, 100% recording rate means that the size of the area corresponding to one pixel is 1/1200 inch x 1/1200 inch, and one dot of 4 pl ink droplets is recorded in every pixel of the area. Refers to the state. In this embodiment, the recording rate is 200% when all input values of image data are at the maximum gradation. If no conveyance error occurs, no matter which mask pattern is used, one dot is recorded in one pixel range, and an image with uniform density is recorded.

FIG. 7(b) shows the recording situation when the first mask patterns of FIGS. 6(a-1) and 6(a-2) are used and are shifted by 1/2 pixel in the +Y direction, which is the transport direction. . FIG. 7(c) shows the recording situation with a 1/2 pixel shift in the +Y direction, which is the transport direction, when using the second mask pattern of FIGS. 6(b-1) and 6(b-2). . In contrast to FIG. 7(b), which uses the first mask pattern that emphasizes graininess in FIG. 6(a), the diagram uses the second mask pattern that emphasizes suppression of density unevenness, as shown in FIG. 6(b). 7(c) has fewer blank areas and overlapping areas, and is closer to the recording situation where no conveyance deviation occurs. Therefore, it can be seen that density unevenness due to transport misalignment is less likely to occur when the second mask pattern shown in FIG. 6(c) is used than the first mask pattern shown in FIG. 6(a).

FIG. 8 is a diagram for explaining a case in which print data with a print rate of 25% is printed on a print medium using the first mask pattern.

FIG. 8A shows print data when data with a print rate of 25% is divided into two passes using the first mask pattern. FIG. 8(a-1) is the data recorded in the first pass, and FIG. 8(a-2) is the data recorded in the second pass. FIG. 8(b) shows a recording situation when recording is performed on a recording medium without conveyance deviation. FIG. 8C shows a printing situation when printing is performed with the conveyance shifted by 1/2 pixel in the +Y direction. In FIGS. 8(b) and 8(c), there are no overlapping dots, and density unevenness due to conveyance deviation of the recording medium does not occur. As described above, it can be seen that when recording data with a low recording rate is recorded, density unevenness due to conveyance deviation of the recording medium is less likely to occur.

FIG. 9 is a diagram for explaining a case in which print data with a print rate of 175% on a print medium is printed using the first mask pattern.

FIG. 9A shows print data when data with a print rate of 175% is divided into two passes using the first mask pattern. FIG. 9(a-1) is the data recorded in the first pass, and FIG. 9(a-2) is the data recorded in the second pass. FIG. 9(b) shows the recording situation when the recording medium is placed in a state where there is no conveyance shift. FIG. 9C shows a printing situation when printing is performed with the conveyance shifted by 1/2 pixel in the +Y direction. In FIG. 9B and FIG. 9C, since the number of overlapping locations is the same, density unevenness due to conveyance deviation of the recording medium does not occur. As described above, it can be seen that when recording data with a high recording rate is recorded, density unevenness due to conveyance deviation of the recording medium is less likely to occur.

As explained using FIGS. 7 to 9, density unevenness occurs more when recording data with a recording rate of 25% and 175% than when recording data with a recording rate of 100% due to conveyance deviation of the recording medium. It's difficult. This is because density unevenness is likely to occur at intermediate gradations where the number of overlapping dots changes greatly due to a deviation in the transport amount, but at low and high gradations where the number of overlapping dots does not change significantly due to a deviation in the transport amount. This means that density unevenness is less likely to occur. Therefore, in this embodiment, when the total recording rate of all colors of print data to be printed in a predetermined area of a print medium is 40% or more and less than 150%, a second mask pattern is used that emphasizes suppression of density unevenness. to generate recorded data. Furthermore, when the total recording rate is less than 40% or more than 150%, print data is generated using the first mask pattern that emphasizes graininess. The predetermined area is a position where density unevenness in a recorded image is likely to occur due to transport misalignment of the recording medium. As explained using FIG. 3, the position where density unevenness is likely to occur is when the sheet comes off the feeding roller 105. The mask pattern to be used is determined based on the recording rate of print data to be printed in an area where printing may be performed when the feed roller 105 is removed.

FIG. 10 is a diagram showing a position where the recording medium P is removed from the feeding roller 105 during conveyance. In FIG. 10, the distance D from the leading edge of the recording medium P on the +Y side to the position Y3 is such that when the area up to the distance D is at a position facing the recording head 102, the recording medium P is conveyed by the feeding roller 105. This is the distance. In this embodiment, the recording medium P is conveyed by 384 pixels, which is the recording distance, by 384 ejection ports. Therefore, when the area from position Y1 to Y3 on the 384-pixel + Y side from position Y3 faces the recording head 102, the recording medium P is at a position immediately before it leaves the feeding roller 105. Further, when the area from position Y2 to Y3 on the 384-pixel Y side from position Y3 is located at a position facing the recording head 102, it is located at a position immediately after coming off the feeding roller 105. Therefore, the area of the recording medium P corresponding to 768 pixels from the position Y1 to the position Y2 is an area where density unevenness in the recorded image is likely to occur due to conveyance misalignment. The recording rate of this area is set as the area used for determining the mask pattern.

FIG. 11 shows an area where the recording rate explained in FIG. 10 is used to determine a mask pattern. This region of 768 pixels in the Y direction is divided into 384 pixels each in the X direction into determination region 1, determination region 2, . . . determination region n. Obtain the recording rate for each divided judgment area, and check whether the sum of the recording rates of all colors in each judgment area is greater than or equal to the first proportion and less than the second proportion at which density unevenness becomes more visible. Determine. In this embodiment, the first ratio is 40% and the second ratio is less than 150%. If there is one or more determination areas where the total recording rate is 40% or more and less than 150%, it is determined that density unevenness is easily recognized, and a second mask pattern that focuses on suppressing density unevenness is used. Determine. This is because the areas where density unevenness is noticeable due to transport misalignment vary depending on the amount of transport misalignment, the characteristics of the recording medium, the size of the recording medium, the characteristics of the ink, the combination of ink colors, etc. The determination area is not limited to 384 pixels x 768 pixels. For example, an area divided into pixels in the X direction may be set as the determination area.

FIG. 12 shows a table showing the recording rate in which density unevenness is not noticeable and the recording rate in which density unevenness is noticeable for an image size of 384 pixels x 768 pixels in a determination area at 1200 dpi in an area where density unevenness is likely to occur. As described above, when the total recording rate of all colors in the determination area is 40% or more and less than 150%, density unevenness is noticeable, and when it is less than 40% or 150% or more, density unevenness is not noticeable. In the present embodiment, the recording rate where density unevenness is noticeable is set to 40% or more and less than 150%, but is not limited to this. The printing rate on a printing medium with noticeable density unevenness varies depending on the amount of conveyance deviation, the ejection amount, the characteristics of the ink, the characteristics of the printing medium, the combination of ink colors, etc. Therefore, it is preferable to set the recording rate according to the ink used.

FIG. 13 is a flowchart of mask pattern determination processing for determining a mask pattern used to generate print data. The mask pattern determination process is performed, for example, by the CPU 400 reading out a program stored in the ROM 401 into the RAM 402 and executing it. The process in FIG. 13 starts when a recording instruction and image data are sent from the host device to the recording device 100. The host device also transmits recording information such as size information of a recording medium to be recorded along with the image data, and the image input unit 403 stores the recording information along with the image data.

First, in step S901, the length of the recording medium in the conveyance direction is acquired. The length is acquired by the CPU 400 reading out the size information of the recording medium from the image input unit 403.

Next, in step S902, from the size information acquired in step S901, a position Y1 in the Y direction at which the conveyance position of the recording medium becomes as shown in FIG. calculate. As described above, the positions Y1 and Y2 are positions corresponding to 384 pixels in the Y direction from Y3, which is the position where the rear end of the recording medium leaves the feeding roller 105.

In step S903, image data corresponding to the determination area used to determine the mask pattern to be used is acquired from the image input unit 403, color adjustment processing is performed in the image signal processing unit 404, and 8-bit RGB data for recording is obtained. Get data.

In step S904, the average value of each of the R data, G data, and B data in the determination area is calculated. Then, in step S905, color conversion processing is performed on the average values of the R data, G data, and B data calculated in step S904, and each ink color (in this embodiment, K, C, M, Y, Lc , Lm), 256-value ink color data is calculated. Gamma processing and quantization processing are performed on the assumption that the ink color data is uniform for the determination area. As a result, binary data is generated for each color. Based on the generated binary data, a recording rate for the number of pixels in the determination area is calculated.

Next, in step S906, first, the total recording rate is calculated by summing up the recording rate of each ink color in the determination area calculated in step S905. Next, it is determined whether the total recording rate is greater than or equal to 40% and less than 150%. If the total recording rate on the recording medium is 40% or more and less than 150%, the process advances to step S909, which is a mode that emphasizes suppression of density unevenness, and the image data of the same page is converted into the image data of FIG. 5 using the second mask pattern. Decide to perform the image processing shown. On the other hand, if the total recording rate on the recording medium is less than 40% or more than 150%, the process advances to step S907, and it is determined whether determination of all determination areas has been completed. If the determination of all determination areas has not been completed, the determination target is shifted to the next determination area, and the process starts from step S903. If all the determination areas have been determined, the process proceeds to step S908, which is a mode that emphasizes graininess, and it is determined that the image data of the same page is subjected to the image processing shown in FIG. 5 using the first mask pattern. do.

As explained above, if the data to be recorded in an area where density unevenness due to transport misalignment is likely to occur is data where the density unevenness is not noticeable, a highly dispersive mask pattern that emphasizes graininess is used. Graininess can be suppressed even in areas where density unevenness may occur. In addition, in the case of data with noticeable density unevenness, density unevenness is unlikely to occur. By using a mask pattern with a large cluster size in the Y direction, density unevenness can be suppressed even in areas where density unevenness may occur. I can do it. Note that the average value of the allowable number of dots in the Y direction of the first mask pattern that emphasizes graininess is the average value of the allowable number of dots in the Y direction that the second mask pattern that emphasizes suppression of density unevenness has. It should be smaller than .

In this embodiment, conveyance deviation occurs when switching from conveyance using both the feed roller 105, which is an upstream roller, and the conveyance roller 107, which is a downstream roller, to conveyance using only the downstream roller in the conveyance direction. Although it is said that it is easy, it is not limited to this. For example, conveyance deviation may easily occur when the recording medium is switched from being conveyed by an upstream roller to being conveyed by both upstream and downstream rollers. The position at which conveyance deviation occurs varies depending on the configuration of the recording apparatus. If it is an area where density unevenness due to transport misalignment is likely to occur, a suitable image can be obtained by determining the mode. Furthermore, if there is a region where density unevenness occurs due to a plurality of transport deviations, the print mode is determined for each region. If it is determined to use the second mask pattern, which is a mode emphasizing suppression of density unevenness in any region, image processing is performed using the second mask pattern.

Furthermore, in the present embodiment, it is preferable to send image data of a determination area, which is an area where density unevenness due to transport misalignment may occur, before image data of a normal area.

In this embodiment, it is determined whether density unevenness is conspicuous or not conspicuous for image data of a determination area of 1200 dpi and an image size of 384 pixels by 768 pixels, and an image processing mode is selected. However, it is not necessary to decide on a mode that emphasizes suppression of density unevenness just because it is determined that it is noticeable once. For example, it is determined whether density unevenness is noticeable or not, and a 1-bit flag is prepared, which is 1 if it is noticeable and 0 if it is not. The mode may be determined based on the ratio or number of 1 flags and 0 flags when all determination areas are determined.

Although RGB data that has been subjected to color adjustment processing is obtained in step S903, it is also possible to obtain RGB data stored in the image input unit 403 and perform subsequent processing. Further, ink color data that has been subjected to color conversion processing or ink color data that has been subjected to gamma correction processing may be acquired and subsequent processing may be performed.

In steps S904 and S905, the printing rate of each ink color on the printing medium was calculated from the respective average values of the RGB data in the determination area. For example, for each pixel of the image size of 384 pixels x 768 pixels in the determination area, it is determined whether or not to place emphasis on suppressing density unevenness for RGB data. Prepare a 1-bit flag of 0. The mode may be determined based on the ratio or number of 1s and 0s within the determination area.

(Second embodiment)
In the first embodiment, we will explain how to select two types of mask patterns: a first mask pattern with high dispersion that emphasizes graininess, and a second mask pattern with a large cluster size in the Y direction that emphasizes suppression of density unevenness. did. In this embodiment, a method of selecting a mask pattern from three types of mask patterns including a third mask pattern whose cluster size in the Y direction is between the first mask pattern and the second mask pattern will be described. Portions similar to those in the first embodiment will be omitted.

FIG. 14 shows a third mask pattern corresponding to the 8 pixel×8 pixel size used in this embodiment. FIG. 14(c) shows a mask pattern (third mask pattern) composed of 1 pixel x 2 pixels, which has an intermediate size and has N=2 consecutive clusters in the Y direction. FIG. 14(a-1) and FIG. 14(a-2) have a complementary relationship.

FIG. 15 shows a table showing the recording rate where density unevenness is not noticeable and the recording rate where density unevenness is noticeable for an image size of 384 pixels x 768 pixels in a determination area at 1200 dpi in an area where conveyance misalignment is likely to occur. In this embodiment, it is assumed that density unevenness is noticeable when the recording rate of the determination area is 60% or more and less than 120%. Therefore, image processing is performed using a second mask pattern that emphasizes suppression of density unevenness. Further, if the recording rate of the determination area is 40% or more and less than 60%, or 120% or more and less than 150%, density unevenness is considered to be somewhat noticeable. Therefore, image processing is performed using the third mask pattern in the intermediate mode, which puts a little emphasis on suppressing density unevenness. If the recording rate of the determination area is less than 40% or more than 150%, it is assumed that the density unevenness is not noticeable. Therefore, image processing is performed using the first mask pattern that emphasizes graininess.

FIG. 16 is a flowchart of mask pattern determination processing for determining a mask pattern used to generate print data. The mask pattern determination process is performed, for example, by the CPU 400 reading out a program stored in the ROM 401 into the RAM 402 and executing it. The process in FIG. 16 starts when a recording instruction and image data are sent from the host device to the recording device 100. The host device also transmits recording information such as size information of a recording medium to be recorded along with the image data, and the image input unit 403 stores the recording information along with the image data.

Steps S1701 to S1705 perform the same processing as steps S901 to S905 in FIG. 13 of the first embodiment.

In step S1706, it is determined whether the total printing rate of each ink color in the determination area on the recording medium is greater than or equal to 40% and less than 150%. If the total recording rate on the recording medium is 40% or more and less than 150%, the process advances to step S1707. On the other hand, if the total recording rate on the recording medium is less than 40% or more than 150%, the process advances to step S1708 and the non-uniformity flag is set. If there is no unevenness flag, "absence" is stored in the RAM 402.

If the process advances to step S1707, it is determined whether the total recording rate of each ink color in the determination area on the recording medium is greater than or equal to 60% and less than 120%. If the total recording rate is 60% or more and less than 120%, the process advances to step S1714, which is a mode that emphasizes suppression of density unevenness, and the image data of the same page is subjected to image processing shown in FIG. 5 using the second mask pattern. The process is then terminated. If the total recording rate is less than 60% or more than 120%, an unevenness flag is set in step S1709. If the unevenness flag is present, the fact that it is "present" is stored in the RAM 402.

When steps S1708 and S1709 are completed, the process advances to step S1710, and it is determined whether or not all determination areas have been determined. If the determination of all determination areas has not been completed, the determination target is shifted to the next determination area and the process starts from step S1703. When all the determination areas have been determined, in step S1711, it is determined whether the unevenness flags of all the determination areas are "absent". If all of them are "none", the process proceeds to step S1712, which is a mode that emphasizes graininess, and it is determined that the image data of the same page is subjected to the image processing shown in FIG. 5 using the first mask pattern. If the unevenness flag is "present", the process advances to step S1713, which is an intermediate mode, and it is determined that the image data of the same page is subjected to the image processing shown in FIG. 5 using the third mask pattern.

As explained above, in the case of image data with inconspicuous density unevenness in areas where there is a risk of transport misalignment, a highly dispersive mask pattern that emphasizes graininess is used to suppress graininess. can be recorded. Furthermore, in the case of image data with noticeable density unevenness, it is possible to record an image in which the density unevenness is not noticeable by using a mask pattern with a large cluster size in the Y direction that focuses on suppressing density unevenness. In addition, in the case of image data with somewhat noticeable density unevenness, we can suppress density unevenness and graininess by using a mask pattern with an intermediate cluster size in the Y direction, which can slightly suppress density unevenness and graininess. can be recorded.

In this embodiment, a method for selecting three types of mask patterns has been described, but three or more types of mask patterns may be prepared.

(Third embodiment)
In the first embodiment and the second embodiment, a method for determining a mask pattern was shown, but in this embodiment, a method for determining a quantization pattern will be described. Contents similar to those in the above-described embodiments will be omitted.

FIG. 17 shows a quantization pattern corresponding to a 4 pixel×4 pixel size of 1200 dpi used in this embodiment.

FIG. 17(a-1) is a first quantization pattern that emphasizes graininess. FIG. 17(b-1) shows a second quantization pattern emphasizing suppression of density unevenness. FIGS. 17(a-1) and (b-1) show threshold values for input signal values in 8-bit, 256-value image data of each ink color. If the input signal value of the image data exceeds the threshold, recording is determined, and if it does not, non-recording is determined. Figures 17(a-2) and (b-2) are diagrams showing recording and non-recording of each pixel when quantizing using each quantization pattern when the input signal value of image data is 127. be. (a-2) is composed of 1 pixel x 1 pixel with high dispersion, and (b-2) is composed of 1 pixel x 4 pixels clustered in N=4 pieces in the recording medium transport direction. . Therefore, it can be seen that the quantization pattern of FIG. 17(b-1) can suppress the occurrence of density unevenness better than that of FIG. 17(a-1).

If the quantization pattern is determined based on the table in FIG. 12, density unevenness will be noticeable if the total recording rate of all colors in the determination area is 40% or more and less than 150%. Perform image processing using the quantization pattern. In addition, if the total recording rate of all colors in the determination area is less than 40% or more than 150%, density unevenness is not noticeable, so image processing is performed using the first quantization pattern shown in FIG. 17(a). I do.

As described above, by switching the quantization pattern, density unevenness can be suppressed when density unevenness is noticeable, and graininess can be suppressed when density unevenness is not noticeable.

(Other embodiments)
Although the ink droplet used in this embodiment was 4 pl, the larger the ink droplet, the less noticeable the image deterioration due to density unevenness even in areas where the conveyance error of the recording medium is large. Therefore, if it is determined that density unevenness is noticeable, large ink droplets may be ejected, and a highly dispersive mask pattern or quantization pattern that emphasizes graininess may be used. For example, the first printing mode has ejection ports capable of ejecting 4 pl and 8 pl ink droplets, and if the density unevenness is not noticeable, the first printing mode prints with the 4 pl ejection port, which emphasizes graininess, and if it is noticeable, it prints with the 4 pl ejection port. A second printing mode in which printing is performed using an 8 pl ejection port may be selected.

In the case of an ejection amount of 8 pl, the number of recording ink ejections may be set to half the number of recording ink ejections for an ejection amount of 4 pl to match the ejection amount recorded on the recording medium.

With ink such as yellow or light ink (e.g. light cyan, light magenta), which has a low ink density, the amount of variation in density is suppressed to a small level even when misalignment occurs due to conveyance error of the recording medium, and the ink density Density unevenness is less likely to occur than with dark, dark ink. Therefore, the recording rate of ink with a low ink density may not be included in the total recording rate when determining a mask pattern or a quantization pattern. For example, the total recording rate may be the total of black, magenta, and cyan recording rates.

The size of the mask pattern or quantization pattern applied to this embodiment has been described for the case where a mask pattern of 8 pixels x 8 pixels size is repeatedly applied, but it is not limited to this. A larger size different from the 8 pixel x 8 pixel size may be used, such as 384 pixels or 192 pixels, which is the same as the conveyance amount of the print medium during multi-pass printing.

Further, in step S905 of the mask pattern determination process in FIG. 13, the recording rate is calculated based on binary data generated from RGB data, but the recording rate may be calculated from multivalued ink color data. By storing a table or formula representing the correspondence between multivalued ink color data and recording rate, it is possible to determine the recording rate from the ink color data.

100 Recording device 102 Recording head 105 Feeding roller 107 Conveyance roller 400 CPU
401 ROM
402 RAM
P Recording medium

Claims (12)

a recording head having a plurality of ejection ports arranged in a predetermined direction and ejecting ink from the ejection ports onto a recording medium based on image data;
moving means for moving the recording head in a direction crossing the predetermined direction;
a plurality of rollers that transport the recording medium in the predetermined direction;
The recording medium is configured to alternately perform an operation of ejecting ink onto the recording medium while moving the recording head by the moving means, and an operation of conveying the recording medium a predetermined distance by at least one of the rollers, A recording device that records an image on the recording medium by ejecting ink multiple times to the same area on the recording medium to form dots, the recording device comprising:
acquisition means for acquiring image data of a predetermined area of a part of the recording medium, including an area recorded during movement of the recording head after conveyance in which the combination of the rollers that convey the recording medium is changed;
Based on the image data acquired by the acquisition means, an image is recorded in a first mode if the value of the image data corresponds to a halftone, and the value of the image data is higher than the halftone. determining means for determining a mode in which recording is performed according to the image data from among a plurality of modes, such that when the image corresponds to gradation, the image is recorded in the second mode;
Furthermore,
The plurality of modes include at least a first mode and a second mode, and when compared assuming that the input data is the same, the first mode is more effective than the second mode. The average value of the number of consecutive dots recorded in the predetermined direction by recording in one movement of the head is large;
The recording head is capable of ejecting ink of a plurality of colors,
The recording device is characterized in that the determining unit determines the mode based on a total of dot ratios for each of the plurality of ink colors in the image data of the predetermined area acquired by the acquiring unit. The plurality of rollers include a roller upstream of the recording head and a roller downstream of the recording head in the conveyance direction of the recording medium,
The area recorded after the conveyance changes the combination of the rollers that convey the recording medium, from the conveyance performed using the upstream roller and not the downstream roller to the area where the combination of the rollers conveying the recording medium changes. The recording apparatus according to claim 1, wherein the area is recorded after switching to conveyance by the downstream roller. The plurality of rollers include a roller upstream of the recording head and a roller downstream of the recording head in the conveyance direction of the recording medium,
The area to be recorded after the conveyance in which the combination of the rollers conveying the recording medium changes, from conveyance by the upstream roller and the downstream roller to conveyance by the downstream roller without using the upstream roller. 2. The recording apparatus according to claim 1, wherein the area is recorded after switching to conveyance using rollers. The plurality of color inks are inks of a plurality of colors having different concentrations,
4. The total dot ratio for each of the plurality of ink colors is the sum of the dot ratios of ink having a dark color among the plurality of color inks. The recording device according to item 1 . 5. The determining means determines to record the image in the second mode when the value of the image data corresponds to a gradation lower than the intermediate tone. The recording device according to any one of the items. processing means for generating print data for the print head to eject ink by processing the image data;
The processing means is configured to perform the recording processing for dividing the image data to be recorded in the same area of the recording medium into data to be recorded by moving the recording head a plurality of times according to the mode determined by the determining means. processing the image data by switching a mask pattern in which dot recording is permitted or not permitted for each pixel to be recorded on the medium;
6. Any one of claims 1 to 5 , wherein the average value of the number of consecutive dots allowed to be recorded in the predetermined direction of the mask pattern used is larger in the first mode than in the second mode. The recording device according to item 1. By processing the multi-valued image data using a quantization pattern in which a threshold value is set for each pixel of the multi-valued image data, binary data is generated for the recording head to eject ink. has a processing means for generating recorded data of
The processing means performs processing by switching the quantization pattern according to the mode determined by the determining means, and records dots when the value of the image data exceeds the threshold value of the pixel of the corresponding quantization pattern. and generating binary data by determining non-recording of dots if the threshold value is not exceeded;
6. The threshold value of the quantization pattern in the first mode is set to a continuously lower value in the predetermined direction than in the second mode. The recording device according to item 1. the plurality of modes has a third mode;
If the value of the image data is higher than the halftone and lower than the halftone higher than the halftone, recording the image in the third mode;
When compared assuming that the input data is the same, the first mode has a higher number of dots recorded in the predetermined direction by one movement of the recording head than the third mode. The average value of the number of consecutive dots is larger, and the average value of the number of consecutive dots recorded in the predetermined direction by recording in one movement of the recording head is higher in the third mode than in the second mode. 8. The recording device according to claim 1, wherein the recording device has a large value. a recording head having a plurality of ejection ports arranged in a predetermined direction and capable of ejecting ink from the ejection ports onto a recording medium based on image data and ejecting ink droplets of a plurality of sizes;
moving means for moving the recording head in a direction crossing the predetermined direction;
a plurality of rollers that transport the recording medium in the predetermined direction;
The recording medium is configured to alternately perform an operation of ejecting ink onto the recording medium while moving the recording head by the moving means, and an operation of conveying the recording medium a predetermined distance by at least one of the rollers, A recording device that records an image on the recording medium by ejecting ink multiple times to the same area on the recording medium to form dots, the recording device comprising:
acquisition means for acquiring image data of a predetermined area of the recording medium, including an area recorded after conveyance in which the combination of the rollers that convey the recording medium is changed;
Based on the image data acquired by the acquisition means, an image is recorded in a first mode if the value of the image data corresponds to a halftone, and the value of the image data is higher than the halftone. determining means for determining a mode in which recording is performed according to the image data from among a plurality of modes, such that when the image corresponds to gradation, the image is recorded in the second mode;
Furthermore,
A printing apparatus characterized in that printing is performed using larger ink droplets in the first mode than in the second mode. 10. The determining means determines to record the image in the second mode when the value of the image data corresponds to a gradation lower than the intermediate tone. Recording device. A recording head having a plurality of ejection ports arranged in a predetermined direction and capable of ejecting ink of a plurality of colors is moved in a direction crossing the predetermined direction from the ejection ports based on image data. The operation of ejecting ink onto a recording medium and the operation of transporting the recording medium a predetermined distance by at least one roller are performed alternately, and the ink is ejected into the same area on the recording medium in multiple steps to form dots. A recording method for recording an image on the recording medium by forming an image, the recording method comprising:
an acquisition step of acquiring image data of a predetermined area of the recording medium, including an area recorded after conveyance in which the combination of the rollers conveying the recording medium changes;
Based on the image data acquired in the acquisition step, an image is recorded in a first mode if the value of the image data corresponds to a halftone, and the value of the image data is higher than the halftone. a determining step of determining a mode for recording in accordance with the image data from among a plurality of modes, such that when the image corresponds to gradation, the image is recorded in a second mode;
has
The plurality of modes include at least the first mode and the second mode, and when compared assuming that the input data is the same, the first mode is better than the second mode. The average value of the number of consecutive dots recorded in the predetermined direction by recording in one movement of the recording head is large;
A recording method characterized in that, in the determining step, the mode is determined based on the total dot ratio for each of the plurality of ink colors in the image data of the predetermined area acquired in the acquiring step. 12. The determining step determines to record the image in the second mode if the value of the image data corresponds to a tone lower than the intermediate tone. How to record.

Images