JP4664016B2 - Inkjet recording device - Google Patents

Description

  The present invention relates to an inkjet recording apparatus that can eject ink of a plurality of gradations and performs image recording based on print information.

  Conventionally, an on-demand type ink jet printer is known as an ink jet recording apparatus. The ink jet printer includes an ink jet head having a nozzle for ejecting ink and an ink chamber for storing ink. Ink jet printers cause a volume fluctuation in an ink chamber to eject ink of a predetermined gradation from nozzles, thereby forming an image on a recording medium. As a control method for giving a volume variation in the ink chamber, there are a piezoelectric control method using distortion deformation of a piezoelectric member, a control method using a heating element, and the like. Printing can be performed on demand by giving volume fluctuation to each ink chamber by such a control method.

  An ink jet head used in such an ink jet recording apparatus performs printing using a plurality of nozzles. For this reason, it is ideal that the output characteristics of the ink of each nozzle are uniform, but the ink discharged from the nozzles due to variations in manufacturing and the propagation of pressure fluctuations in the ink chamber during the ink discharge operation, etc. The discharge volume increases or decreases. As the ink ejection volume changes in this way, density unevenness may occur on the recording medium.

In order to prevent such a situation, it is possible to visually reduce density unevenness occurring at the end of each inkjet head of a long inkjet head unit in which a plurality of inkjet heads are arranged. A technique for correcting ink to be ejected (for example, see Patent Document 1) and a technique for processing ink ejected from the end of each inkjet head using an error diffusion method (for example, see Patent Document 2). It has been.
JP 2003-320647 A JP 2003-326747 A

  As described above, an inkjet head has a plurality of nozzles and performs printing by ejecting ink from the nozzles. However, such as manufacturing variations and propagation of pressure fluctuations in the ink chamber during ink ejection operation, etc. The ink discharge volume increases or decreases due to variations. For this reason, each inkjet head has inherent variations in the ejection volume of ink ejected from each nozzle.

  However, in those described in Patent Documents 1 and 2, the density unevenness in the print area printed by the end of each inkjet head can be visually reduced, but the density generated in the area other than the end of the inkjet head. There is no mention of unevenness.

  The present invention has been made in view of the above circumstances, and its purpose is to visually detect density unevenness on a recording medium due to variations in the ejection volume of ink ejected from each nozzle inherent in the inkjet head. It is an object of the present invention to provide an ink jet recording apparatus that can be reduced.

The present invention provides an ink jet having a plurality of ink chambers, a common ink chamber that communicates with each of the plurality of ink chambers to supply ink to the plurality of ink chambers, and a nozzle that discharges ink provided in each ink chamber. By providing a head and selecting an ink chamber for ejecting ink from a plurality of ink chambers based on the input image signal, and causing volume variation in the selected ink chamber, ink of the gradation indicated by the input image signal In an ink jet recording apparatus that discharges ink and forms dots on a recording medium, an area for correcting the density unevenness of the ink ejected from the nozzles, which is obtained in the inspection process of the ink jet head, causes the density unevenness on the recording medium. Nozzle number information indicating the density correction area and the non-density correction area adjacent to the density correction area, and each floor for each recording medium Storage means for storing head information comprising an average dot area information and average dot area information of the non-density correction area for each of the density correction region, when performing printing on the basis of the input image signal, concentration in the head information Ink ejected from nozzles arranged at random positions among the nozzles used for printing in the density correction area so that the sum of the average dot areas of the correction area is equal to the sum of the average dot areas of the non-density correction area Density correction means for increasing or decreasing one gradation .

  According to the present invention, it is possible to provide an ink jet recording apparatus that can visually reduce density unevenness on a recording medium due to variations in the ejection volume of ink ejected from each nozzle inherent in the ink jet head.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram schematically showing the configuration of the inkjet head 1. As shown in FIG. 1, the inkjet head 1 has a plurality of ink chambers 2 arranged side by side, an orifice plate 3 disposed in front of each ink chamber 2, and a common ink chamber 4 disposed behind each ink chamber 2. Formed. In the orifice plate 3, nozzles 5 whose diameter gradually decreases toward the outside corresponding to the respective ink chambers 2 are opened. An ink supply port 6 for supplying ink from the outside to the common ink chamber 4 is provided on the opposite side of the common ink chamber 4 to each ink chamber 2. The inkjet head 1 ejects ink of a predetermined gradation from the nozzle 5 by causing a volume variation in the ink chamber 2 in accordance with a drive signal given from a head drive unit 16 described later.

  FIG. 2 is a block diagram showing a schematic control configuration of the inkjet recording apparatus 100 provided with the inkjet head 1 described above. The ink jet recording apparatus 100 includes a control device 11, a control panel control unit 12, a control panel 13, a printer control unit 14, a paper transport unit 15, a head driving unit 16, an ink jet head 1, an image memory 17, a correction processing unit 18, and the like. is doing.

  The control device 11 includes a microprocessor, a memory, and the like. The control device 11 comprehensively controls the control panel control unit 12, the printer control unit 14, and the head drive unit 16 by executing a control program stored in the memory.

  The control panel 13 has a display unit for displaying information necessary for the user and an operation unit for receiving instructions from the user. The control panel control unit 12 controls display on the display unit of the control panel 13 and transmits a user instruction received from the operation unit to the control device 11. The operation unit is provided with various switches such as a recording switch and keys. The recording switch is a switch for instructing the inkjet recording apparatus 100 to start image recording. Further, the user can use the control panel 13 to instruct the type of recording medium used for printing, such as glossy paper or plain paper.

  The head driving unit 16 selects an ink chamber 2 for ejecting ink from each ink chamber 2 on the basis of the input image signal, and gives a driving signal for causing volume variation in the selected ink chamber 2. Thus, ink is ejected from the nozzle 5.

  In the ink jet recording apparatus 100 according to the first embodiment, the discharge volume of ink discharged from each nozzle 5 of the ink jet head 1 varies the voltage t that gives a volume fluctuation to the ink chamber 2 as shown in FIG. By controlling the voltage between t1 and t2 in which the voltage and the discharge volume change in proportion to each other, for example, by dividing into seven, the gradation is controlled from one gradation to seven gradations. The head driving unit 16 can perform printing control of 8 gradations including 0 gradation that does not eject ink. In addition, a mode in which printing control of nine gradations increased by one gradation is possible by slowing the conveyance speed of the sheet conveyed by the sheet conveying unit 15 under the control of the printer control unit 14 is also provided.

  The inkjet head 1 configured as described above is provided with a memory 1a as a storage unit. The memory 1a stores head information. The head information indicates a density correction area where the ink ejected from the nozzle obtained in the inspection process of the inkjet head 1 causes density unevenness on the recording medium, and a non-density correction area adjacent to the density correction area. This is the average dot area information of the density correction area and the non-density correction area for each gradation for each nozzle number information and recording medium.

  The printer control unit 14 controls the sheet conveying operation of the sheet conveying unit 15. The paper transport unit 15 transports the paper stored in a paper feed cassette or the like (not shown) one by one to the lower side of the ink jet head 1 and then discharges the paper to the outside.

  The image memory 17 stores the input image signal that has been input. Here, the input image signal is a gradation value from 0 gradation to 7 gradation after performing pseudo gradation processing (not shown) and input image size (α, β) information.

  An input image signal, a recording medium information signal, and a head information signal stored in the image memory 17 are input to the correction processing unit 18. Here, the recording medium signal is a signal indicating the type of recording medium instructed by the user using the control panel 13 described above, for example, glossy paper or plain paper, via the control panel control unit 12 and the control device 11. Input (recording medium information acquisition means). The correction processing unit 18 corrects the input image signal by creating a correction table from the input image signal and the head information signal and processing for determining the presence / absence of correction from the input image signal and the recording medium signal. Perform the process.

Next, the processing flow of the correction processing unit 18 when an input image signal and a recording medium signal are input will be described with reference to FIG.
First, the input image signal is stored in the image memory 17. The image signal stored in the image memory 17 is input to the correction processing unit 18. The correction processing unit 18 determines whether or not to perform density correction based on the input image signal and the recording medium signal. When correcting density, a correction table (to be described later) is created and corrected using the above-described head information signal sent to the control unit 182 of the correction processing unit 18 when the inkjet head 1 is attached and the input image signal. The input image signal in the power region is corrected, and when the correction is not performed, the input image signal is transmitted to the head driving unit 16 as it is. At the same time, a predetermined signal is transmitted to the control device 11. In response to this predetermined signal, the control device 11 transmits a signal for instructing the start of printing to the control panel control unit 12, the printer control unit 14, and the head drive unit 16. Then, in synchronization with the printer controller 14 controlling the paper transport unit 15 to transport the paper, the head drive unit 16 gives a drive signal to each nozzle 5 selected by the ink jet head 1 to generate ink of a predetermined gradation. Printing is performed by discharging the ink.

  Next, the configuration of the correction processing unit 18 will be described with reference to FIG. In the following, it is assumed that the input image signal has a constant gradation value. As shown in FIG. 4, the correction processing unit 18 includes a determination unit 181 as a determination unit and a control unit 182 as a density correction unit.

  In the correction processing unit 18, first, the determination unit 181 determines whether or not to perform density correction with reference to the determination table Ta shown in FIG. 5. The determination table 5a shown in FIG. 5 is predetermined to determine whether or not to perform correction from the relationship between the gradation value (dot area) of the input image signal and the recording medium signal (type of recording medium). is there. A method for creating the determination table Ta will be described below.

  As shown in FIG. 6, when the dots formed on the recording medium are completely covered by the ink ejected from the nozzle 5 (FIG. 6A) (FIG. 6B), the density unevenness On the other hand, the dots formed on the recording medium by the ink ejected from the nozzle 5 (FIG. 7A) do not completely cover the recording medium, as shown in FIG. In this case (FIG. 7B), the density unevenness becomes conspicuous, and thus the density correction is performed.

  Even when high gradation printing is performed, if printing is performed on a recording medium with large blurring (large dot diameter), the dots completely cover the recording medium, and thus no correction for density is performed (for example, on the seventh floor of plain paper). Key). On the other hand, in a recording medium with little blurring (small dot diameter), the dots do not completely cover the recording medium, and thus correction regarding density is performed (for example, seven gradations of glossy paper). Further, when printing with low gradation and halftone, since the dot diameter is small and the recording medium is not completely covered, correction relating to density is performed.

  Accordingly, the determination table Ta shown in FIG. 5 has a density correction from 1 to 7 for glossy paper, and a density correction from 1 to 5 for plain paper. In the case of gradation and 7 gradation, the determination unit 181 determines that there is no correction regarding density.

  Further, the determination unit 181 operates the changeover switch 181a to output the input image signal to the control unit 182 when it is determined that there is a correction related to density, and when it is determined that there is no correction, the input image signal is directly used as the correction processing unit 18. Output to the outside (head drive unit 16).

  Next, the processing of the correction processing unit 18 will be specifically described by taking as an example a case where glossy paper is set in the paper transport unit 15 and uniform printing with 7 gradations is performed. In this case, as described above, the determination unit 181 determines to perform density correction from the gradation value indicating the seven gradations of the recording medium signal indicating glossy paper and the input image signal based on the determination table Ta. .

  Further, the ink jet recording apparatus 100 is provided with the ink jet head 1 in which the density unevenness of the characteristic shown in FIG. 8 occurs in the image formed on the recording medium due to the change in the ejection volume of the ink ejected from the nozzle 5 or the like. And In FIG. 8, the vertical axis indicates the density, and the horizontal axis indicates the arrangement of the nozzles 5 of the inkjet head 1. As shown in the figure, the density change in the region B corresponding to the nozzles B1 to Bn is gradual, but the density change in the region A corresponding to the nozzles A1 to An is steep. FIG. 9 is a diagram showing a recorded image on a recording medium when an image signal having seven gradations is printed by the inkjet recording apparatus 100 provided with the inkjet head 1. The density of the area A is lower than the hatched area (area other than the area A) in FIG. FIG. 10 is an enlarged view of the region A and the region B adjacent to the region A, that is, a diagram showing dots formed by ink ejected from the nozzles B1,..., Bn, A1,. . Since the inkjet head 1 has the density unevenness characteristic shown in FIG. 8 even though an image signal having seven uniform gradations is input, the dot diameter printed in the area A is larger than the dot diameter printed in the area B. Is getting smaller. Hereinafter, the area A is referred to as a density reduction area A, and the area B adjacent to the density reduction area A is referred to as a non-density reduction area B. In this embodiment, the non-density reduction region B is set so that the number of nozzles corresponding to the density reduction region A and the number of nozzles corresponding to the non-density reduction region B are equal. The density reduction area A and the non-density reduction area B are determined from the head information signal (nozzle number) and the image size (α, β) of the input image signal.

  As described above, the memory 1a of the ink jet head 1 stores the density correction area, which is an area where the ink discharged from the nozzle causes density unevenness on the recording medium, and the nozzle number of the non-density correction area adjacent to the density correction area. Head information indicating the average dot area information of the density correction area and the non-density correction area for each gradation is stored for each information and recording medium. That is, it is stored in the memory 1a that the nozzle numbers B1, B2,..., Bn are non-density reduction regions B, A1, A2,. Yes. When the ink jet head 1 is attached to the ink jet recording apparatus 100, head information is read from the memory 1a of the ink jet head 1 and input to the correction processing unit 18 as a head information signal. Here, the number of nozzles A1 to An is equal to the number of nozzles B1 to Bn. Thus, the density reduction area A is (nozzles A1 to A4) × 4 = 4 × 4 = 16, and the non-density reduction area B is (nozzles B1 to B4) × 4 = 4 × 4 = 16, each having 16 pixels. .

Next, processing of the correction table generation unit 182a in the control unit 182 will be described.
As a correction processing method for correcting the density, using the average dot area information, the first floor of the density reduction area A is set so that the sum of the dot areas of the density reduction area A and the sum of the dot areas of the non-density reduction area B are substantially equal. It is assumed that processing for inserting a large dot is performed.

Therefore, first, it is necessary to obtain the number P of pixels in the density-reduced region A that can contain dots that are one gradation larger. As a method for obtaining the number of pixels P, average dot area information at 7 gradations and 8 gradations in glossy paper included in the head information signal is used. The average dot areas of the density reduction area A and the non-density reduction area B are X and Y. Let T be the average dot area of dots that are one gradation larger (eight gradations) in the density reduction region A. Assuming that the number of pixels in the density reduction area A and the non-density reduction area B is n and the number of pixels to be corrected by adding one large gradation dot is P, the sum of the dot areas in the density reduction area A and the sum of the non-density density areas is To be approximately equal

It is expressed by the relationship shown in The number of pixels P to be corrected is obtained by the equation (1).

  In the case described with reference to FIG. 10, the average dot areas of the density reduction area A and the non-density reduction area B are X (= 98) and Y (= 100), respectively. The area is T (= 102) (X: average value of dot area when the ink ejected from the A1, A2, A3, and A4 nozzles has 7 gradations, Y: ejected from the B1, B2, B3, and B4 nozzles Average value of dot area when ink is gradation). When the number of pixels P is obtained from this numerical value, P = 8 because the number of pixels is 16 in the density reduction area A and the non-density reduction area B. That is, the number of pixels whose density is corrected is 8 for 4 × 4 (= 16) pixels.

  Next, the obtained eight pixel numbers to be corrected are arranged at random positions of 16 pixels in the density reduction region A. This random position arrangement generates a random number and determines the position based on the random number. In this way, the correction table Th1 for the density reduction region A is generated as shown in FIG. In FIG. 11, “0” indicates a pixel that is not corrected, and “1” indicates a pixel that is corrected.

  The table value of the correction table Ti1 generated by the correction table generation unit 182a is added to the input image signal Ti having uniform seven gradations shown in FIG. 12 by the adder 182b, and the gradation of the pixel corresponding to the density reduction region A is added. Correct the value. That is, after the correction, in the density reduction area A, as shown in the table Tj1 of FIG. 13, 8 pixels out of the 16 pixels in the density reduction area A are corrected so as to be printed with one larger 8 gradations. . Therefore, the ink jet recording apparatus 100 corrects the density decrease region A inherent to the ink jet head 1 as shown in the table Tj1 shown in FIG. It can be visually reduced.

  In the first embodiment, the case where uniform printing is performed on glossy paper with 7 gradations has been described. However, if the table described with reference to FIG. For other types of recording media and gradations, correction relating to density can be similarly performed.

  In addition to the case where the end portion of the inkjet head 1 has density unevenness (density reduction region A) characteristics as shown in FIG. 8, as shown in FIG. Similarly, the density-related correction can be performed in the case of having the lowered region A) characteristic. In the case of the inkjet head 1 having the density unevenness characteristic at the center, it may be determined in advance which side of the non-density reduction area B used for correction is adjacent to the density reduction area A.

  Furthermore, although the case where there is one inkjet head 1 is described, even when a long head in which a plurality of inkjet heads 1 are arranged side by side is used, the density reduction region A can be similarly corrected, and density unevenness is visually reduced. can do.

(Second Embodiment)
Next, a second embodiment will be described.
In the first embodiment described above, the average dot area information of the density correction area and the non-density correction area for each gradation is added to the memory 1a of the inkjet head 1 as head information for each recording medium. In this embodiment, instead of the average dot area information, the dot area information of each nozzle 5 of each gradation is added for each recording medium.

  The configuration of the ink jet head 1 shown in FIG. 1 and the control configuration of the ink jet recording apparatus 100 shown in FIG. 2 are the same as those in the first embodiment, and thus the description thereof will be omitted. A case will be described where uniform printing of seven gradations is performed on glossy paper by the inkjet head 1 described with reference to FIGS. Accordingly, the determination unit 181 determines to perform density correction based on the table illustrated in FIG. The method for determining the density reduction area A and the non-density reduction area B is also the same as that in the first embodiment, and thus the description thereof is omitted. The density reduction area A is (nozzles A1 to A4) × 4 = 4 × 4. = 16, the non-density reduction region B is (nozzles B1 to B4) × 4 = 4 × 4 = 16, each having 16 pixels.

Next, processing of the control unit 182 correction table generation unit 182a will be described.
As a correction processing method for correcting the density, by using the dot area information of each nozzle 5, the density reduction region A is set so that the sum of the dot areas of the density reduction region A and the sum of the dot areas of the non-density reduction region B are substantially equal. It is assumed that a process of putting a dot larger by one gradation is performed.

Therefore, first, it is necessary to obtain the number P of pixels in the density-reduced region A that can contain dots that are one gradation larger. As a method for obtaining the pixel number P, the dot area information of each nozzle 5 in the 7th gradation and the 8th gradation on the glossy paper included in the head information signal is used. XA1, XA2, XA3, and XA4 represent dot areas of seven gradations formed by ink ejected from the nozzles A1, A2, A3, and A4 in the density reduction region A, and the nozzles B1, B2, and B3 in the non-density reduction region B. , B4, the dot area of 7 gradations formed by the ink ejected from B4 is YB1, YB2, YB3, YB4. Let TA1, TA2, TA3, and TA4 be the dot areas of dots that are one gradation larger (eight gradations) in the density reduction region A. The image size β of the density reduction area A and the non-density reduction area B = 4, and the number of pixels to be corrected by adding one large gradation dot is P (P = P1 + P2 + P3 + P4) (P1, P2, P3, P4 are TA1, respectively. Number of TA2, TA3 and TA4.) In this case, the sum of the dot areas of the density reduction region A and the sum of the dot areas of the non-density reduction region B are substantially equal.

It is expressed by the relationship shown in

  At this time, as shown in FIG. 8, since the density of the region formed by the ink ejected from the nozzle A4 is the lowest, the number of 8 gradation dots is P1 ≦ P2 ≦ P3 ≦ P4.

  Next, the obtained pixel number P is arranged at a random position in the density reduction region A. This position arrangement generates a random number and determines the position based on the random number. In this way, the correction table Th2 for the density reduction region A is created as shown in FIG. In FIG. 15, “0” indicates a pixel that is not corrected, and “1” indicates a pixel that is corrected.

  The table value of the correction table Th2 generated by the correction table generation unit 182a is added to the input image signal Ti having uniform seven gradations shown in FIG. 12 by the adder 182b, and the gradation of the pixel corresponding to the density reduction region A is added. Correct the value. That is, after correction, in the density reduction area A, as shown in the table Tj2 of FIG. 16, among the 16 pixels of the density reduction area A, 4 pixels of nozzle A4, 2 pixels of nozzle A3, 1 pixel of nozzle A2, and nozzle The correction is performed so that one pixel of A1 is printed with one larger eight gradations. Therefore, in the ink jet recording apparatus 100, as shown in the table Tj2 shown in FIG. 16, the density reduction region A unique to the ink jet head 1 has the highest density on the end side (nozzle A4 side) where the density is the lowest. After the correction is performed, output to the head driving unit 16 and printing are performed, whereby density unevenness can be visually reduced further than in the first embodiment.

(Third embodiment)
Next, a third embodiment will be described. Unlike the above-described first and second embodiments, the third embodiment is not a region where the concentration decreases, but the concentration of the region A is higher than that of the region B as shown in FIG. The case of the inkjet head 1 having density unevenness characteristics in which regions are generated will be described.

  The configuration of the inkjet head 1 shown in FIG. 1 and the control configuration of the inkjet recording apparatus 100 shown in FIG. In the third embodiment, as a correction processing method for correcting the density, the area in which the sum of the dot areas of the area A ′ where the density is high and the sum of the dot areas of the area B ′ where the density is not high is substantially equal. It is assumed that a process of putting a dot one gradation smaller in A ′ is performed.

  That is, similarly to the first embodiment, the number of pixels P to be corrected when the area A ′ and the area B ′ are each 16 pixels is obtained using the expression (1). For example, if the number of pixels P is 8, these 8 pixels are randomly arranged in the region A ′. In this way, the correction table Th3 for the area A ′ shown in FIG. 18 is generated. In FIG. 18, “0” indicates a pixel that is not corrected, and “−1” indicates a pixel that is corrected.

  The table value of the correction table Th3 generated by the correction table generation unit 182a is added by the adder 182b to the input image signal Ti having uniform seven gradations shown in FIG. 12, and the gradation value of the pixel corresponding to the region A is added. to correct. That is, after the correction, in the area A ′, as shown in the table Tj3 of FIG. 19, 8 pixels out of the 16 pixels in the area A are corrected so as to be printed with one smaller 6 gradations. Accordingly, the ink jet recording apparatus 100 corrects the region A ′ where the density specific to the ink jet head 1 is increased as shown in the table Tj3 shown in FIG. 19, and then outputs it to the head driving unit 16 to perform printing. The density unevenness can be visually reduced.

  Further, in each of the above embodiments, the head information is stored in the memory 1a of the ink jet head 1. Therefore, the ink jet head 1 is automatically attached to the ink jet recording apparatus 100 when it is newly attached or replaced. In particular, the head information specific to the ink jet head can be output to the correction processing unit 18 in the ink jet recording apparatus 100. Instead of storing the head information in the memory 1a of the inkjet head 1, the control device 11 of the inkjet recording apparatus 100 may be configured to store the head information of the inkjet head 1 to be attached.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying constituent elements without departing from the scope of the invention in the implementation stage, and is disclosed in the embodiment. Various inventions can be modified by appropriately combining a plurality of components.

1 is a diagram illustrating a schematic configuration of an ink jet head according to a first embodiment of the present invention. The figure which shows the control structure of the inkjet recording device in the embodiment. The figure which shows the relationship between the voltage and discharge volume in the embodiment. The figure which shows the structure of the correction | amendment process part in the embodiment. FIG. 6 is a diagram illustrating a determination table in which a relationship between a gradation value (dot area) of an input image signal and a recording medium signal (type of recording medium) is obtained in advance in the embodiment. The figure which shows the example which does not perform correction | amendment in the embodiment. The figure which shows the example which correct | amends in the same embodiment. The figure which shows the density nonuniformity characteristic of the inkjet head in the embodiment. The figure which shows the density | concentration unevenness in the embodiment. The figure which shows a dot when the density nonuniformity in the same embodiment generate | occur | produces. The figure which shows the correction table in the embodiment. The figure which shows the image signal with 7 gradation uniform in the embodiment. The figure which shows the image signal after correction | amendment in the embodiment. The figure which shows the density nonuniformity characteristic of the other inkjet head in the embodiment. The figure which shows the correction table in 2nd Embodiment in the embodiment. The figure which shows the image signal after correction | amendment in the embodiment. The figure which shows the density nonuniformity characteristic of the inkjet head in the 3rd Embodiment of this invention. The figure which shows the correction table in the embodiment. The figure which shows the image signal after correction | amendment in the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Inkjet head, 1a ... Memory, 2 ... Ink chamber, 3 ... Orifice plate, 4 ... Common ink chamber, 5 ... Nozzle, 11 ... Control device, 13 ... Control panel, 17 ... Image memory, 18 ... Correction processing part, 181 ... determination unit, 182 ... control unit, 182a ... correction table generation unit, Ta ... determination table, Th1, Th2, Th3 ... correction table

Claims (5)

An ink jet head having a plurality of ink chambers, a common ink chamber communicating with each of the plurality of ink chambers for supplying ink to the plurality of ink chambers, and a nozzle for discharging ink provided for each ink chamber; The ink of the gradation indicated by the input image signal is provided by selecting an ink chamber from which the ink is ejected from the plurality of ink chambers based on the input image signal, and causing volume variation in the selected ink chamber. In an inkjet recording apparatus that forms dots on a recording medium
The density correction area, which is an area for correcting the density unevenness in the ink ejected from the nozzles, is obtained in the ink jet head inspection process, and the density correction area adjacent to the density correction area. Storage means for storing head information including nozzle number information indicating a region, average dot area information of the density correction region for each gradation for each recording medium, and average dot area information of the non-density correction region;
When performing printing based on the input image signal, the sum of the average dot areas of the density correction regions included in the head information is equal to the sum of the average dot areas of the non-density correction regions. Density correction means for increasing or decreasing one gradation of ink ejected from nozzles arranged at random positions among nozzles used for printing in the density correction area ;
An ink jet recording apparatus comprising: The density correction means includes
Recording medium information acquisition means for acquiring recording medium information indicating the type of the recording medium;
A determination unit that determines whether or not correction is necessary based on the relationship between the type of the recording medium indicated by the recording medium information acquired by the acquisition unit and the gradation indicated by the input image signal;
When the determination unit determines that correction is necessary, the head information is referred to, and the relationship between the average dot area of the density correction region and the average dot area of the non-density correction region included in the head information A control unit that generates a correction table from the image and performs gradation correction;
The inkjet recording apparatus according to claim 1, further comprising: An ink jet head having a plurality of ink chambers, a common ink chamber communicating with each of the plurality of ink chambers for supplying ink to the plurality of ink chambers, and a nozzle for discharging ink provided for each ink chamber; The ink of the gradation indicated by the input image signal is provided by selecting an ink chamber from which the ink is ejected from the plurality of ink chambers based on the input image signal, and causing a volume variation in the selected ink chamber. In an inkjet recording apparatus that forms dots on a recording medium
The density correction area, which is an area for correcting the density unevenness in the ink ejected from the nozzles, is obtained in the inspection process of the inkjet head, and the density correction area adjacent to the density correction area. A storage for storing head information including nozzle number information indicating a region, dot area information of each nozzle in the density correction region for each gradation for each recording medium, and dot area information of each nozzle in the non-density correction region Means,
When printing is performed based on the input image signal, the total dot area of each nozzle in the density correction area included in the head information is equal to the total dot area of each nozzle in the non-density correction area. As described above, density correction means for increasing or decreasing the ink discharged from the nozzles arranged at random positions among the nozzles used for printing in the density correction area ,
An ink jet recording apparatus comprising: The density correction means includes
Recording medium information acquisition means for acquiring recording medium information indicating the type of the recording medium;
A determination unit that determines whether or not correction is necessary based on the relationship between the type of the recording medium indicated by the recording medium information acquired by the acquisition unit and the gradation indicated by the input image signal;
When the determination unit determines that correction is necessary, the head information is referred to, and the dot area of each nozzle in the density correction area and the dot of each nozzle in the non-density correction area included in the head information. A control unit that generates a correction table from the relationship with the area and performs gradation correction;
The inkjet recording apparatus according to claim 3 , comprising: Wherein the storage unit, an ink jet recording apparatus according to any one of claims 1 to 4, characterized in that provided in the ink jet head.

Images