JP2003231247A - Dot recording method and apparatus, and recording medium with program therefor recorded - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce generation of banding. <P>SOLUTION: Sub scanning feeding is executed with a constant F dot feeding amount. With the nozzle pitch defined as k dots (k is an integer of 3 or more), the number of nozzles used in one time main scanning N (N is an integer of 3 or more), and parameters Na, Nb, m, L satisfy the following formulae (1)-(4): N=Na+Nb...(1), Na=m×k±1...(2), Nb=Rd[L×Na÷k]...(3), F=Na...(4). Here, m is an integer of 1 or more, and L is an integer satisfying 1≤L<k, respectively. The operator Rd [] represents the calculation of rounding the decimal part of the value in the brackets. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for recording dots on the surface of a print medium using a dot recording head.

[0002]

2. Description of the Related Art As a recording apparatus for recording by using a dot recording head while scanning in a main scanning direction and a sub scanning direction, there is an ink jet recording apparatus such as a serial scan type printer or a drum scan type printer. The inkjet recording apparatus forms characters and images on a print medium by ejecting ink from a plurality of nozzles of a print head. That is, each nozzle of the print head is provided with a pressure chamber filled with ink and an electromechanical conversion element. When an electric signal is applied to this electromechanical conversion element, pressure is generated in the pressure chamber, Ink droplets are ejected from the.

As one of techniques for improving image quality in an ink jet recording apparatus, US Pat. No. 4,198,6
There is a technique called "interlace system" disclosed in No. 42. FIG. 16 is an explanatory diagram of a conventional interlaced recording method. The print head 1 has the numbers # 1 to # 1.
It has 11 nozzles indicated by 1. The pitch k of the nozzles in the sub-scanning direction is 4 dots. Here, the unit [dot] means a minimum pitch P [inch] in the sub-scanning direction of dots recorded on the print medium, and k
The dots correspond to k × P inches. In FIG. 16, the positions of the print head 1 described as pass 1, pass 2, ... Show the positions in the sub-scanning direction during main scanning.
Here, the "pass" means one main scan. After each main scan, sub-scan feed is executed at a constant feed amount F of 11 dots.

In the conventional interlaced recording method, the following two conditions are set in order to perform recording so that there are no missing or overlapping main scanning lines (hereinafter also referred to as "raster"). [Condition 1] The number of used nozzles N and the nozzle pitch k are integers that are relatively prime. (Here, “relatively prime” means that there is no common divisor other than 1.) [Condition 2] The sub-scan feed amount F is equal to the number of used nozzles N.

[0005]

There are two requirements for the ink jet recording apparatus, that is, improvement of printing speed and improvement of image quality. In order to improve the printing speed, the number of nozzles in the print head may be increased. However, in the interlaced recording method, the sub-scan feed amount F is the number of used nozzles N.
Since the number of nozzles is increased, the sub-scan feed amount is also increased.

However, since the mechanical sub-scan feed accuracy deteriorates almost in proportion to the increase in the sub-scan feed amount, increasing the number of nozzles deteriorates the sub-scan feed accuracy. In particular, when the sub-scan feed is performed a plurality of times during the recording of the adjacent rasters, the error of the sub-scan feeds for the plurality of times is accumulated, and the pitch between the adjacent rasters may deviate considerably from the correct pitch. is there. For example, the sub-scan feed is performed three times between the main scan at the time of recording the second raster and the main scan at the time of recording the third raster in FIG. Therefore, the pitch between these two rasters contains the accumulated sub-scan feed error.

FIG. 17 is an explanatory diagram showing the dots recorded in FIG. 16 in more detail. The pitches of the second and third rasters are enlarged due to the accumulated sub-scan feed error, and as a result, a streak-like image quality deterioration portion that is easily noticeable is generated. Such a striped image quality deterioration portion is called "banding". Since banding deteriorates the image quality, there has conventionally been a demand to reduce banding as much as possible.

The present invention has been made to solve the above-mentioned problems in the prior art, and an object thereof is to provide a dot recording technique capable of reducing the occurrence of banding.

[0009]

In order to solve at least a part of the above-mentioned problems, the apparatus of the present invention is a dot recording apparatus for recording dots on the surface of a print medium using a dot recording head. In the device, a plurality of dot forming elements for forming a plurality of dots of the same color are arranged at a position facing the print medium of the dot recording head at a substantially constant pitch along the sub-scanning direction. An array of dot-forming elements, a main-scanning drive unit that drives at least one of the dot recording head and the print medium to perform main-scanning, and at least one of the plurality of dot-forming elements during the main-scanning. Drive means for forming dots by using a section, and each time the main scanning ends, at least one of the dot recording head and the print medium is driven to perform sub-scanning. It includes a sub-scan drive means. The sub-scanning drive unit executes the sub-scanning feed at a constant feed amount F × P (P is the minimum pitch of dots in the sub-scanning direction, F is an integer). When the pitch of the plurality of dot forming elements in the sub-scanning direction is k × P (k is an integer of 3 or more),
The number N of dot forming elements used during one main scan
(N is an integer of 3 or more) and parameters Na, Nb, m, L
And satisfy the following expressions (1) to (4).

N = Na + Nb (1) Na = m × k ± 1 (2) Nb = Rd [L × Na ÷ k] (3) F = Na (4) Here, m is 1 or more. An integer and L are integers satisfying 1 ≦ L <k, respectively, and an operator Rd [] indicates an operation of rounding a fractional part of a value in parentheses.

In this dot recording apparatus, regarding the recording of dots of one color, the first type main scanning line in which recording is completed by one nozzle and the second type main scanning line in which recording is completed by two nozzles. Each main scan line is recorded so that and are arranged almost regularly. The second of these
Since the main scanning line of the type is recorded by two nozzles, it is possible to reduce the occurrence of banding. However, since the second type main scanning line requires twice as long scanning time as the first type main scanning line, the recording speed is 1 /
It becomes 2. However, if the above conditions (1) to (4) are satisfied, some of the main scanning lines become the first type main scanning lines, so that all the main scanning lines become the second type main scanning lines. It is possible to reduce the decrease in recording speed as compared with the case.

The dot recording is performed so that the dots recorded by the Nb dot forming elements and the dots recorded by the Na dot forming elements have a complementary positional relationship on each main scanning line. The head may be driven.

Alternatively, on each main scanning line, N
The number of dots recorded by b dot forming elements is N
The dot recording head may be driven so as to overlap the dots recorded by a dot forming elements.

The dot recording head has a plurality of dot recording element arrays for recording dots of a plurality of colors, and the plurality of dot recording element arrays have the same main scanning in one main scanning. When each dot recording element is arranged so that line recording can be performed, dot recording may be executed in the forward path and the return path when main scanning is performed bidirectionally in a reciprocating manner. .
By doing so, it is possible to make the color difference of the main scanning lines recorded in the forward and backward passes inconspicuous.

The dot recording method according to the present invention is a dot recording having a dot forming element array in which a plurality of dot forming elements for forming a plurality of dots of the same color are arranged at a substantially constant pitch in the sub-scanning direction. A method of recording dots on the surface of a print medium while performing main scanning along a direction substantially perpendicular to the sub-scanning direction using a head,
The sub-scan feed is executed at a constant feed amount F × P (P is the minimum pitch of the dots in the sub-scan direction, F is an integer), and the pitch of the plurality of dot forming elements in the sub-scan direction is k × P (k: When the number of dot forming elements is N (N is an integer of 3 or more) and the parameters Na, Nb, m, and L are used during one main scanning, the above-mentioned (1) It is characterized in that the expression (4) is satisfied.

Further, the recording medium according to the present invention has a dot having a dot forming element array in which a plurality of dot forming elements for forming a plurality of dots of the same color are arranged at a substantially constant pitch along the sub-scanning direction. A computer-readable recording medium in which a computer program for causing a printing apparatus having a recording head to perform dot scanning on the surface of a printing medium while performing main scanning along a direction substantially perpendicular to the sub-scanning direction is recorded. And a constant feed amount F ×
P (P is the minimum dot pitch in the sub-scanning direction, F is an integer)
And the dot used during one main scanning when the pitch in the sub-scanning direction of the plurality of dot forming elements is k × P (k is an integer of 3 or more). Number of forming elements N (N is an integer of 3 or more) and parameter N
A computer-readable recording medium in which a computer program for causing a computer to execute the function of performing dot recording so that a, Nb, m, and L satisfy the above expressions (1) to (4) Is.

With such a method and recording medium, it is possible to reduce the occurrence of banding as in the above-mentioned apparatus.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION A. Device Configuration: FIG. 1 is a block diagram showing the configuration of a color image processing system as an embodiment of the present invention. The color image processing system includes a scanner 30, a personal computer 90, and an inkjet recording device 22. The personal computer 90 includes a color display 21. The scanner 30 reads color image data from a color original and supplies the computer 90 with original color image data ORG composed of R, G, and B color components.

Inside the computer 90, a CPU, a RAM, a ROM and the like (not shown) are provided, and an application program 95 operates under a predetermined operating system. A video driver 91 and a printer driver 96 are incorporated in the operating system, and the print data FNL which is the final color image data is output from the application program 95 via these drivers. Application program 95 for retouching images
Displays an image on the CRT display 93 via the video driver 91 while reading an image from the scanner and performing a predetermined process on the image. When the application program 95 issues a print command, the printer driver 96 of the computer 90 receives the image information from the application program 95, and the ink jet recording device 22 can print the signal (here, binary values for each color of CMYK). Signal). In the example shown in FIG. 1, inside the printer driver 96, a rasterizer 97 for converting color image data handled by the application program 95 into image data in dot units, and an inkjet recording device for the image data in dot units. Ink color CM used by 22
A color correction module 98 for performing color correction according to Y and color development characteristics, a color correction table CT referred to by the color correction module 98, and an area depending on the presence / absence of ink in dot units from the color-corrected image information. And a halftone module 99 that generates so-called halftone image information that expresses the density in the above.

FIG. 2 is a conceptual diagram showing the structure of the ink jet recording apparatus 22. This inkjet recording device 2
Reference numeral 2 denotes a print head 1, a carriage shaft 2, a carriage belt 3, a main scanning motor 4, a carriage driving circuit 5 for driving the main scanning motor 4, a platen roller 6, a gear 7, and a sub scanning motor 8. A print medium transport control circuit 9 that drives the sub-scanning motor 8 to transport the print medium PM, fixed bases 10 and 11, and a print data control circuit 13. The platen roller 6, the gear 7, the sub-scanning motor 8, and the print medium conveyance control circuit 9 constitute a sub-scanning driving unit. The carriage drive circuit 5, the print medium conveyance control circuit 9, and the print data control circuit 13 may be realized by one control circuit. Further, a control circuit for controlling these circuits 5, 9, and 13 may be separately provided.

The main scanning is realized by the carriage driving circuit 5 driving the main scanning motor 4. That is, when the main scanning motor 4 moves the carriage belt 3, the print head 1 fixed on the carriage belt 3 moves to
A reciprocating operation is performed between two fixed bases 10 and 11. The print head 1 ejects ink droplets onto the print medium PM according to the print data supplied from the print data control circuit 13 during the forward or backward operation. When such one main scan is completed, the print medium conveyance control circuit 9 drives the sub scan motor 8 to move the print medium PM by a predetermined amount.

FIG. 3 is an explanatory view showing the arrangement of ink jet nozzles in the print head 1. The print head 1 has four nozzle arrays 61 to 6 for four color inks.
4 are provided. That is, the first to fourth nozzle arrays 61 to 64 eject black (K), cyan (C), magenta (M), and yellow (Y) inks, respectively. In addition, each nozzle is provided with a piezo element (not shown) for ejecting ink,
The piezo element is driven according to the print data supplied from the print data control circuit 13, and as a result, ink is ejected from each nozzle.

Each of the four nozzle arrays 61 to 64 has a plurality of nozzles n (for example, 32 or 48) arranged in a staggered pattern at a constant nozzle pitch k along the sub-scanning direction. The plurality of nozzles n included in each nozzle array need not be arranged in a staggered pattern, and may be arranged in a straight line. However, if the nozzles are arranged in a zigzag pattern as shown in FIG.
Has the advantage of being easy to set small.

FIG. 3B shows an array of a plurality of dots formed by one nozzle array. In this embodiment, regardless of whether the arrangement of the ink nozzles is staggered or linear, the plurality of dots formed by one nozzle array are arranged so that the nozzles are arranged in a substantially straight line along the sub-scanning direction. Piezo element (not shown) for driving
Is supplied with a drive signal. For example, when the nozzle arrays are arranged in a zigzag pattern as shown in FIG. 3A, the pitch d between two nozzle rows in the same nozzle array.
[Inch] is divided by the main scanning drive speed v [inch / sec] to shift the timing of the drive signals of the two columns by a time d / v [sec. By doing so, it is possible to arrange a plurality of dots formed by one nozzle array in a straight line along the sub-scanning direction. As will be described later, the plurality of nozzles provided in each of the nozzle arrays 61 to 64 are
Not all of them are always used, and only some of the nozzles may be used depending on the dot recording method.

The plurality of nozzles n of the four nozzle arrays 61 to 64 are arranged in the sub-scanning direction so that dots of four colors can be formed on the same plurality of main scanning lines during one main scanning. They are arranged at the same position as each other.

B. Embodiment of Dot Recording Method: FIG. 4 is an explanatory diagram showing a dot recording method of the first embodiment of the present invention. This dot recording method is reproduced below (1)-
Expression (4) is satisfied.

N = Na + Nb (1) Na = m × k ± 1 (2) Nb = Rd [L × Na ÷ k] (3) F = Na (4) where N is the number of nozzles used , K is a nozzle pitch [dot], m is an integer of 1 or more, L is an integer satisfying 1 ≦ L <k, F is a sub-scan feed amount [dot], and an operator Rd [] is in parentheses. Indicates an operation that rounds the fractional part of a value. Further, the operator ± indicates that either addition or subtraction may be performed.

The values of the respective parameters in the dot recording system of FIG. 4 are N = 14, Na = 11, Nb = 3, k
= 4, F = 11, m = 3, L = 1. here,
Subtraction is used as the operation of ± on the right side of the equation (2), and rounding is used as the rounding operation Rd []. The dot pitch (printing pitch) P in the sub-scanning direction is a value corresponding to a printing resolution of 720 DPI (that is, 1/720 inch).

As shown in the above equation (1), the number of used nozzles N is given by the sum of two integers Na and Nb. Since the first integer Na is equal to the value of the sub-scan feed amount F, this first integer Na corresponds to the number of nozzles in the conventional interlaced recording method shown in FIG. Therefore, in the following, this first integer Na will be referred to as the "basic nozzle number".
The nozzles included in the basic nozzle number Na are referred to as “basic nozzles”. Further, the second integer Nb is referred to as “additional nozzle number”, and the nozzles included in the addition nozzle number Nb are referred to as “additional nozzle”. In the example of FIG. 4, nozzles # 1 to #
Reference numeral 11 is a basic nozzle, and nozzles # 12 to # 14 are additional nozzles. Basic nozzle number Na and additional nozzle number N
The significance of b will be described later.

At the right end of FIG. 4, recording dots formed on the print medium are shown. The range of the raster existing below the raster having the raster number 1 is the range (effective recording area) to be actually recorded.

FIG. 5 is an explanatory diagram showing print data (raster data) assigned to each nozzle in each pass in the first embodiment. In pass 1 (first main scan), print data is supplied to the three additional nozzles # 12, # 13, and # 14, and printing is performed while the print head 1 is moving in the main scan direction. At this time, since the basic nozzles # 1 to # 11 are out of the effective recording area as shown in FIG. 4, the print data control circuit 13 supplies 0 data (non-recording data) to the basic nozzles # 1 to # 11. To do. Similarly, in pass 2, print data is supplied to the six nozzles # 9 to # 14 and recording is performed. At this time,
Since nozzles # 1 to # 8 are out of the effective recording area,
The print data control circuit 13 sets 0 data (non-recorded data)
Are supplied to these nozzles # 1 to # 8.

As can be seen from the pattern of recording dots in FIG. 4, the raster to be recorded by the additional nozzles # 12 to # 14 is also the object to be recorded by the basic nozzles.
In this specification, a raster recorded by both the basic nozzles and the additional nozzles is called an "overlap raster", and a raster recorded by only the basic nozzles is called a "non-overlap raster". In FIG. 4, the raster number is 3,
The rasters 7, 11, ... Are overlap rasters.

FIG. 6 is an explanatory view showing allocation of print data to these three overlapping rasters.
The print data of each pixel on the third raster is 1, 1,
1, 0, 0, 1 ... Here, the value “1” indicates that a dot is recorded at that pixel position, and the value “0” means that a dot is not recorded. In the first embodiment, in the overlap raster, the additional nozzles are in charge of recording even-numbered pixels, and the basic nozzles are in charge of recording even-numbered pixels. Therefore, when the additional nozzle # 12 prints the third raster in pass 1, the print data of the even-numbered pixel positions is supplied to the additional nozzle # 12, and the odd-numbered pixel positions are always 0. (Indicating no recording) is supplied. On the other hand, when the basic nozzle # 1 prints the third raster in pass 5, the print data of the odd-numbered pixel positions is supplied to the basic nozzle # 1, and the even-numbered pixel positions are always 0. Is supplied. That is, the third raster is pass 1
Then, every other pixel is recorded by the additional nozzle # 12,
In pass 5, printing is performed every other pixel so as to be complemented by the basic nozzle # 1.

Similarly, the seventh raster is recorded by the additional nozzle # 13 every other pixel in the pass 1, and is recorded every other pixel in the pass 5 so as to be complemented by the basic nozzle # 2. The 11th raster is also recorded every other pixel in the pass 1 by the additional nozzle # 14, and is recorded in the pass 5 every other pixel so as to be complemented by the basic nozzle # 3.

Thus, the pixels on the overlap raster are intermittently recorded by one additional nozzle during one main scan, and are recorded by one basic nozzle during another main scan. Recording is performed in a complementary manner, which completes recording of all pixels on the overlapping raster. In other words, the overlap raster is recorded complementarily by one additional nozzle and one basic nozzle. Here, “complementary” means that all the pixels on one raster are recorded by the additional nozzle and the basic nozzle without omission or duplication.

The print medium conveyance control circuit 9 (FIG. 2) is arranged so that Na dot (that is, P × N) is generated every time one main scanning is completed.
The print medium PM is conveyed in the sub-scanning direction by a inch), and as a result, the print head 1 moves from the position of pass 1 to the position of pass 2 in FIG. 4, for example. In pass 5, the three basic nozzles #
1 to # 3 are positioned on the rasters (third, seventh and eleventh rasters) already recorded by the additional nozzles # 12 to # 14. Therefore, these basic nozzles # 1 to # 3 print odd-numbered pixels on these overlapping rasters according to the print data shown in FIG. As a result, complementary recording for the three overlapping rasters is completed. By repeating the above operation, characters and images are formed on the print medium PM.

FIG. 7 is an explanatory diagram showing recording dots formed according to the first embodiment. In FIG. 7, white circles indicate dots printed by the basic nozzles, and black circles indicate dots printed by the additional nozzles. In this example,
The positions of the dots recorded by the additional nozzles are slightly shifted in the sub-scanning direction (vertical direction in FIG. 7) from the positions of the dots recorded by the basic nozzles on the same raster.

As described in the prior art, when the sub-scan feed is performed a plurality of times during recording of the adjacent rasters, the errors of the sub-scan feeds for the plurality of times are accumulated, and the pitch between the adjacent rasters is increased. There is a significant deviation from the correct pitch, which results in banding. However, in the first embodiment, even when the sub-scan feed error (conveyance error) is accumulated while two adjacent raster lines are recorded, some dots on one of the raster lines are added nozzles. Since it is recorded, it is difficult to recognize as banding. The reason for this is that, as shown in FIG. 7, the positions of the dots recorded by the additional nozzles are slightly shifted in the sub-scanning direction from the positions of the dots recorded by the basic nozzles on the same raster.

FIG. 8 shows a case where the dots recorded by the basic nozzles # 1 to # 11 and the dots recorded by the additional nozzles # 12 to # 14 are misaligned in the raster direction (main scanning direction). It is a figure. Such positional deviation occurs due to an error in the detection accuracy of the print start position of the print head 1 in the raster direction. As shown in FIG. 8, when misalignment occurs in the raster direction, in a raster recorded with only basic nozzles, adjacent recording dots are regularly overlapped by a certain amount in the raster direction. on the other hand,
In the raster complementarily recorded by the basic nozzles and the additional nozzles, the dot overlap becomes large in units of two recording dots, and the density fluctuates in the raster direction, so that it is easily recognized as banding. However, as shown in FIG. 9, the human visual characteristic has a characteristic that it becomes difficult to recognize the density difference as the spatial frequency increases. Assuming that the dot pitch in the sub-scanning direction is 720 DPI, the banding pitch is 4/720 inch = 0.14 mm for four rasters when the positional deviation occurs in the raster direction as shown in FIG. The spatial frequency (reciprocal of pitch) is about 7 cycles / mm. It can be seen from FIG. 9 that the banding of the spatial frequency of this degree has a characteristic that it is difficult to visually recognize it.

Even if banding occurs in the first embodiment and this banding has substantially the same spatial frequency as the banding formed by the technique of the above-mentioned US Pat. No. 4,198,642, As can be understood by comparing FIG. 7 and FIG. 17, the first embodiment is much more difficult to recognize as banding.

FIG. 10 is an explanatory diagram showing the recording method of the second embodiment of the present invention. The difference from the first embodiment shown in FIG. 4 is that the basic nozzle and the additional nozzle respectively print dots at all pixel positions on the same raster. For example, the basic nozzle # 1 and the additional nozzle # 12 are
The dots at all pixel positions on the third raster are recorded.

FIG. 11 is an explanatory view showing allocation of print data in the second embodiment, and FIG. 6 in the first embodiment.
Is equivalent to. In the second embodiment, since the basic nozzle and the additional nozzle record dots at all pixel positions on the same raster, the basic nozzle (for example, # 1)
All print data on the raster are respectively supplied to and the additional nozzle (for example, # 12).

In this second embodiment, the spatial frequency of banding is relatively short as in the first embodiment, but the grayscale difference is easier to identify than in the first embodiment. If this difference in light and shade is conspicuous, the first embodiment shown in FIG. 4 is preferable in terms of image quality. However, when a print medium having a large contact angle between the surface of the print medium and the ink, for example, overhead projector paper is used, the maximum density (solid print) portion may not be filled with print dots as shown in FIG. When it occurs, this part is easily noticeable. In particular, since overhead projector paper is mainly used for presentation, graphs or relatively large characters are frequently used, and whether or not a solid record is clean is important. In such a case, as in the second embodiment, dot bleeding is caused by recording dots in a multiple manner, and the image quality can be improved by filling a portion that is not normally filled.

As described above, which of the first embodiment and the second embodiment is preferable in terms of image quality depends on the print medium. Therefore, high-quality images can be recorded by switching between the recording methods of the first and second embodiments depending on the print medium.

In the first embodiment, the basic nozzle and the additional nozzle complementarily record pixels on the same raster,
Further, in the second embodiment, the basic nozzles and the additional nozzles record dots by overlapping at the pixel positions on the same raster, but it is also possible to adopt a recording method other than this.
For example, printing may be performed complementarily by the basic nozzles and the additional nozzles, and the size of the dot diameter printed by the additional nozzles may be larger than the dot diameter printed by the basic nozzles. By doing so, substantially the same effect as the second embodiment can be obtained.

In addition to the first and second embodiments described above, various dot recording methods that satisfy the above expressions (1) to (4) can be adopted. In FIG. 12, k = 4 and L
It is explanatory drawing which shows the example of the combination of the parameter of the possible recording system in the case of = 1-3. K = in FIG.
4, L = 1, m = 3, Na = 11, Nb = 3, N = 14
The case is equivalent to the first embodiment shown in FIG. FIG.
FIG. 6 is an explanatory diagram showing an example of possible combinations of recording method parameters when k = 6 and L = 1 to 3. In these examples, rounding up is used as the rounding operation Rd [] in Expression (3), but rounding down can also be used.

As can be seen from FIGS. 12 and 13, when the value of the nozzle pitch k is given, the parameters m, L
It is possible to determine the preferable number of basic nozzles Na and the number of additional nozzles Nb by appropriately setting the value of, and the number of used nozzles N is determined from the sum of them. On the contrary, when the number N of nozzles to be used is determined,
It is also possible to determine the preferable basic nozzle number Na and additional nozzle Nb from the used nozzle number N by using FIG. 12 and FIG. In these cases, what values are preferable as the parameters m and L are determined in consideration of the significance of the parameters L, Na and Nb described later.

FIG. 14 shows k = 4 and L = in FIG.
It is explanatory drawing which shows the recording system of 3rd Example corresponded in the case of 2, m = 2, Na = 9, Nb = 5, N = 14. Further, FIG. 15 shows that k = 4, L = 3, and m = in FIG.
It is explanatory drawing which shows the recording system of 4th Example corresponding to the case of 2, Na = 7, Nb = 6, N = 13.

FIG. 14 shows the meaning of each parameter of the above equations (1) to (4). The significance of each parameter in equations (1) to (4) can be considered as follows.

From the above equations (2) and (4), the sub-scan feed amount F is set to a constant value of (m × k ± 1) dots. That is, the sub-scan feed amount F is set to a value obtained by adding or subtracting 1 to the value m × k that is an integral multiple of the nozzle pitch k. If the sub-scan feed amount F is set to an integral multiple m × k of the nozzle pitch k, the position of each nozzle after the sub-scan feed is the periodic position of the nozzle before the sub-scan feed (that is, k). It is placed again at every other dot). Therefore, when the sub-scan feed amount F is (m × k ± 1) dots, the position of each nozzle after the sub-scan feed is +1 dot or −1 from the periodic position of the nozzle before the sub-scan feed. The dots are arranged at positions displaced in the sub-scanning direction. For example, in FIG. 14, the value of the sub-scan feed amount F is (2 ×
Since 4 + 1) = 9 dots, the nozzles after sub-scan feed are
It is arranged at a position shifted by +1 dot from the periodic position of the nozzle before the sub-scan feed in the sub-scan direction.

By the way, the rounding operator Rd in the above equation (3) is used.
By ignoring, and using the equation (4), the equation (3) can be rewritten as the following equation (3a). L = (Nb × k) / Na 2 = (Nb × k) / F (3a)

The numerator (Nb × k) on the right side of the equation (3a) is
The number Nb of additional nozzles is multiplied by the nozzle pitch k, and indicates the range of additional nozzles in the nozzle array. The range of the additional nozzle is nozzle # 1 in the example of FIG.
The range is from the raster position of 0 to the raster position of 3 dots below the nozzle # 14. Parameter L is (Nb × k)
Is approximately equal to a value obtained by dividing by the sub-scan feed amount F, this parameter L is used to determine how many sub-scan feeds a certain nozzle (for example, the uppermost additional nozzle # 10) passes through in the additional nozzle range. It can be considered to be the value shown. By the way, as described above, by one sub-scan feed, each nozzle is arranged at a position shifted by one dot from the periodic position of the immediately preceding nozzle. Therefore, L after a pass
Considering the number of times of sub-scan feed, the additional nozzle # 10 at the uppermost end
Stays within the range of the additional nozzles in the bus during the L times of sub-scanning, and shifts by one dot from the periodic position of the preceding nozzle for each sub-scanning feed. For example, in FIG. 14, in the second sub-scan feed after pass 1, the uppermost additional nozzle # 10 stays within the range of the additional nozzle in pass 1 during the two sub-scans up to pass 3. In addition, each time the sub-scan feed is performed, the dot is displaced by one dot from the periodic position of the nozzle immediately before that. That is, in pass 2, the uppermost additional nozzle # 10
Is positioned one dot after the nozzle # 12 in pass 1 immediately before it within the range of the additional nozzle in pass 1. In pass 3, the additional nozzle #
10 is within the range of the additional nozzle in pass 1,
Positioning is performed one dot after the nozzle # 12 in pass 2 immediately before that.

Considering such movement of the nozzle position,
The parameter L can be considered to be a value indicating “how many overlapping rasters (rasters recorded by the basic nozzles and the additional nozzles) are continuously arranged”. For example, in the third embodiment shown in FIG. 14, L =
Since it is 2, two overlapping rasters are continuous.
(In FIG. 14, there is a portion where three overlapping rasters are continuous, the reason for which will be described later.) Further, since the additional nozzles are arranged at the nozzle pitch k in the nozzle array. , K of continuous rasters, the first L lines are overlap raster lines and the remaining (k−L) lines are non-overlap raster lines. Therefore, the raster arrangement is such that a k raster group composed of L overlapping rasters and (k−L) non-overlapping rasters is repeatedly arranged.

By the way, among the Na rasters recorded by one main scan by the Na basic nozzles, the Nb rasters recorded by the Nb additional nozzles are overlap rasters, and the rest. (Na-Nb) rasters are non-overlapping rasters. That is, Na
Within the range of the book raster, a k raster group composed of L overlapping rasters and (k−L) non-overlapping rasters is repeatedly arranged, and as a result, among the Na books, Nb lines are overlap rasters,
The remaining (Nb-Na) lines are non-overlapping rasters. For example, in the third embodiment shown in FIG. 14, k = 4, N
Since a = 9 and Nb = 5, within the range of 9 rasters, 2
A raster group composed of two overlapping rasters and two non-overlapping rasters is repeatedly arranged. As a result, five of the nine rasters are overlapping rasters, and the remaining four are non-overlapping rasters. Has become.

The rightmost diagram in FIG. 14 shows the division of rasters for each Na lines. In this example, the last raster in a set of Na rasters is an overlap raster, and the next set of first L (= 2) rasters is also an overlap raster. Therefore, three overlapping rasters are adjacent to each other at the boundary of each Na raster. However, basically, the array of rasters in FIG.
It can be seen that a k raster group consisting of L overlapping rasters and (k−L) non-overlapping rasters is repeatedly arranged.

The parameters k, L, N as described above
It can be understood from FIGS. 4, 10 and 15 that the relationship between a and Nb and the arrangement of the overlapping rasters and the non-overlapping rasters holds in the other embodiments.

As described above, in each of the above-described embodiments, the overlapping rasters and the non-overlapping rasters are arranged almost regularly according to the parameters k, L, Na, and Nb. That is, since the overlapping rasters, each of which is approximately L in number, are arranged substantially regularly with the non-overlapping rasters of approximately (k−L), banding is less noticeable by these overlapping rasters. There are advantages.

In the case of bidirectional printing in which main scanning is performed bidirectionally, the above-mentioned recording overlap raster arrangement also exhibits the following effects. That is, as shown in FIG. 3, when nozzle arrays of four colors of Y, M, C, and K inks are arranged to record the same raster, each color is sequentially printed on each raster in the order of K, C, M, and Y on the forward path. Dots are formed. On the other hand, in the return path, on the contrary, dots of each color are formed in the order of Y, M, C, K on each raster. Therefore, there is a possibility that the rasters recorded in the forward pass and the rasters recorded in the return pass may appear slightly different in color. At this time, if dots are recorded by the conventional interlace recording method without forming the overlapping raster, the color difference between the raster recorded in the forward pass and the raster recorded in the return pass becomes conspicuous, which is recognized as image quality deterioration. To be done. Therefore,
If the overlapping rasters and the non-overlapping rasters are arranged almost regularly as in each of the above-described embodiments, there is an advantage that such a difference in raster color between the forward pass and the return pass becomes inconspicuous.

In order to make the banding inconspicuous, it is also conceivable that all the rasters are overlap rasters (that is, recorded by two nozzles). However, if all the rasters are overlapped rasters, the main scanning time is about twice as long as in the case where all rasters are non-overlapping rasters, and therefore the recording speed becomes about 1/2. On the other hand, in each of the above-described embodiments, since the overlapping raster and the non-overlapping raster are mixed, it is possible to reduce the decrease in the recording speed as compared with the case where all the overlapping rasters are used. There is an advantage.

In an actual dot recording apparatus, it is possible to determine preferable values for the number of used nozzles N, the number of basic nozzles Na, and the number of additional nozzles Nb according to the following procedure. Here, assuming that the nozzle pitch k is 6 dots, it is 1
It is assumed that the total number of nozzles included in the color nozzle array is 48. At this time, the number N of used nozzles is 48 or less, and it is feasible that the number N of used nozzles is 48 or less in FIGS. 13A to 13C. From the viewpoint of printing speed, it is preferable that the number of used nozzles N is as large as possible. Therefore, for example, when L = 1, N = 48, Na = 41. It is understood that Nb = 7 is preferable. Further, when L = 2, N = 4 from FIG.
7, Na = 35. Nb = 12 is preferable, and when L = 3, N = 47, Na = 31. Nb = 1
6 is preferred. A preferable value of the parameter L is, for example, L
It can be determined by actually recording an image by using the recording method corresponding to each value of and comparing the image qualities thereof. As described above, when the conditions of the above equations (1) to (4) are used, the preferable values of the number of used nozzles N, the number of basic nozzles Na, and the number of additional nozzles Nb are set in consideration of the hardware constraint of the nozzle array. It is possible to decide.

The present invention is not limited to the above-described examples and embodiments, but can be carried out in various modes without departing from the scope of the invention.
For example, the following modifications are possible.

The present invention can be applied not only to bidirectional printing but also to unidirectional printing in which dots are recorded only in a fixed main scanning direction (for example, only in the forward path).

The present invention can be applied to monochrome printing as well as color printing. It can also be applied to printing in which multiple gradations are expressed by expressing one pixel with a plurality of dots. It can also be applied to a drum scan printer.
In the drum scan printer, the drum rotation direction is the main scanning direction and the carriage traveling direction is the sub scanning direction. Further, the present invention is not limited to the inkjet recording device,
In general, it can be applied to a dot recording apparatus that records on the surface of a print medium using a recording head having a plurality of dot forming element arrays. Where "dot formation element"
Means a constituent element for forming dots, such as an ink nozzle in an inkjet printer.

In the above embodiment, a part of the configuration realized by hardware may be replaced by software, and conversely, a part of the configuration realized by software may be replaced by hardware. Good. For example, the computer 90 may execute the control functions of the print data control circuit 13, the carriage drive circuit 5, and the print medium conveyance control circuit 9 shown in FIG. In this case, the printer driver 9
A computer program such as 6 realizes the same control function as these circuits.

The computer program for realizing such a function is provided in a form recorded on a computer-readable recording medium such as a floppy disk or a CD-ROM. The computer system 90 reads the computer program from the recording medium and transfers the computer program to an internal storage device or an external storage device. Alternatively, the computer program may be supplied from the program supply device to the computer system 90 via a communication path. When realizing the functions of the computer program, the computer program stored in the internal storage device is executed by the microprocessor of the computer system 90. Further, the computer system 90 may directly execute the computer program recorded in the recording medium.

In this specification, the computer system is a concept including a hardware device and an operating system, and means a hardware device operating under the control of the operating system. The computer program causes such a computer system to realize the functions of the circuits described above. Note that some of the functions described above may be realized by the operating system instead of the application program.

In the present invention, the "computer-readable recording medium" is not limited to a portable recording medium such as a flexible disk or a CD-ROM, and various internal memories such as RAM and ROM in the computer. The device and an external storage device fixed to the computer such as a hard disk are also included.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an image processing system of the present invention.

FIG. 2 is a conceptual diagram showing an embodiment of an inkjet recording apparatus according to the present invention.

FIG. 3 is an explanatory diagram showing an arrangement of inkjet nozzles in the print head 1.

FIG. 4 is an explanatory diagram showing a dot recording method of the first embodiment.

FIG. 5 is an explanatory diagram showing print data assigned to each nozzle in the first embodiment.

FIG. 6 is an explanatory diagram showing allocation of print data to nozzles in the first embodiment.

FIG. 7 is an explanatory diagram showing a state of recording dots formed in the first embodiment.

FIG. 8 is an explanatory diagram showing a state of recording dots when the start position of the raster is displaced.

FIG. 9 is a graph showing the relationship between the spatial frequency and the number of distinguishable gradations in human visual characteristics.

FIG. 10 is an explanatory diagram showing a recording method of a second embodiment.

FIG. 11 is an explanatory diagram showing print data assigned to each nozzle in the second embodiment.

FIG. 12 is an explanatory diagram showing an example of possible combinations of recording method parameters when k = 4 and L = 1 to 3.

FIG. 13 is an explanatory diagram showing an example of possible combinations of recording method parameters when k = 6 and L = 1 and 2.

FIG. 14 is an explanatory diagram showing a recording method of a third embodiment.

FIG. 15 is an explanatory diagram showing a recording method of a fourth embodiment.

FIG. 16 is an explanatory diagram showing a conventional recording method.

FIG. 17 is an explanatory diagram showing an example of banding.

[Explanation of symbols]

1 ... Print head 2 ... Carriage axis 3 ... Carriage belt 4 ... Motor 5 ... Carriage drive circuit 6 ... Platen roller 7 ... Gear 8 ... Motor 9 ... Print medium conveyance control circuit 10 ... Fixed stand 11 ... Fixed stand 13 ... Print data control circuit 20 ... Image output device 21 ... Color display 22 ... Inkjet recording apparatus 30 ... Scanner 90 ... Computer 91 ... Video driver 93 ... CRT display 95 ... Application program 96 ... Printer driver 97 ... rasterizer 98 ... Color correction module 99 ... Halftone module

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[Procedure amendment]

[Submission date] December 13, 2002 (2002.12.
13)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

[0009]

Means for Solving the Problem and Its Action / Effect According to the present invention , in order to solve at least a part of the above problems .
The same method is used with a substantially constant pitch along the sub-scanning direction.
Multiple dot formation required to form multiple dots of color
By using a dot recording head having a dot forming element array in which elements are arranged, a line is formed in a direction substantially perpendicular to the sub-scanning direction.
Method for selecting dot recording method for dot recording apparatus for recording dots on surface of print medium while performing main scanning
In the dot recording method, (a) constant feed
Amount F × P (P is the minimum dot pitch in the sub-scanning direction, and F is
(Integer) to perform sub-scan feed, and (b)
The pitch of the plurality of dot forming elements in the sub-scanning direction is k × P
Used for dot recording when (k is an integer of 3 or more)
The number of dot forming elements N (N is an integer of 3 or more)
Parameters Na, Nb, m, and L are the following (1) to
The number of used dot forming elements so that expression (4) is satisfied.
The number N is selected.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

N = Na + Nb (1) Na = m × k ± 1 (2) Nb = Rd [L × Na ÷ k] (3) F = Na (4) Here, m is 1 or more. An integer and L are integers satisfying 1 ≦ L <k, respectively, and an operator Rd [] indicates an operation of rounding a fractional part of a value in parentheses.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

In the first selection method of the dot recording method,
Is the total number of dot forming elements in the dot recording device.
Based on, the number N of used dot forming elements is the largest.
For each parameter k, Na, Nb, m, L, N
A set is determined for each possible value of L, and the determined parameters
Images according to the set of, and compare the quality of the recorded images.
By comparing the above parameters k, Na, Nb,
Determine the values of m, L, N.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

In the second selection method of the dot recording method
Is a hardware limitation of the dot recording device.
In consideration of the above, a plurality of notations satisfying the above formulas (1) to (4)
The image is recorded using the recording method, and the image quality of the recorded image is adjusted.
By comparing, the parameters k, Na, Nb,
Determine the values of m, L, N.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

The number N of used dot forming elements is
In consideration of hardware restrictions in
And satisfying the above formulas (1) to (4).
It may be set to a large value.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

Further, the hardware in the dot recording apparatus is
The total number of dot forming elements and the
Consider the value of the parameter k that represents the pitch of the dot formation element.
In consideration of this, the values of the parameters m and L should be set appropriately.
Determine the values of other parameters Na, Nb, N by and
At this time, the value of the parameter L is
Images are recorded using multiple recording methods corresponding to each value,
Determined by comparing the quality of the recorded images
You may do it.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

Further, the number N of used dot forming elements is determined.
Set of parameters that satisfy the above equations (1) to (4)
From among the above, it is preferable to achieve the number N of dot forming elements used.
Determine the values of favorable parameters Na and Nb.
The values of the parameters Na and Nb are expressed by the equations (1) to (4) above.
Image recording using multiple recording methods that satisfy
As determined by comparing the quality of the captured images
You may

[Procedure Amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Delete

[Procedure Amendment 10]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Delete

Claims (9)

[Claims] 1. A dot recording apparatus for recording dots on a surface of a print medium using a dot recording head, wherein a dot having a substantially constant pitch along a sub-scanning direction is provided at a portion of the dot recording head facing the print medium. A dot forming element array in which a plurality of dot forming elements for forming a plurality of dots of the same color are arranged, and main scanning drive for driving at least one of the dot recording head and the print medium to perform main scanning. Means, a head driving means for forming dots by using at least a part of the plurality of dot forming elements during the main scanning, the dot recording head and the dot recording head each time the main scanning ends. And a sub-scanning driving means for driving at least one of the print media to perform sub-scanning, wherein the sub-scanning driving means is a constant feed amount F × P (P is a dot sub-scanning method). Minimum pitch, F is running scanning feed an integer), the sub-scanning direction pitch of said plurality of dot-forming elements k × of
When P (k is an integer of 3 or more), the number N (N is an integer of 3 or more) of dot forming elements used in one main scan and the parameters Na, Nb, m and L are A dot recording apparatus characterized by satisfying the following expressions (1) to (4). N = Na + Nb (1) Na = m × k ± 1 (2) Nb = Rd [L × Na ÷ k] (3) F = Na (4) where m is an integer of 1 or more, L Indicates an integer satisfying 1 ≦ L <k, and the operator Rd [] indicates an operation for rounding the fractional part of the value in parentheses. 2. The dot recording apparatus according to claim 1, wherein the head driving unit is N on each main scanning line.
dots recorded by b dot forming elements, N
A dot recording apparatus for driving the dot recording head so that the dots recorded by a dot forming elements have a complementary positional relationship. 3. The dot recording apparatus according to claim 1, wherein the head driving unit is N on each main scanning line.
The number of dots recorded by b dot forming elements is N
A dot recording device for driving the dot recording head so as to overlap the dots recorded by a dot forming elements. 4. The dot recording apparatus according to claim 1, wherein the dot recording head has a plurality of dot recording element arrays for recording dots of a plurality of colors, In the plurality of dot recording element arrays, the respective dot recording elements are arranged so that the same main scanning line can be recorded in one main scanning. A dot recording apparatus that executes dot recording on the forward path and the reverse path when performed in the opposite direction. 5. A dot recording head having a dot forming element array in which a plurality of dot forming elements for forming a plurality of dots of the same color are formed at a substantially constant pitch along the sub-scanning direction. In a method of recording dots on the surface of a print medium while performing main scanning along a direction substantially perpendicular to the scanning direction, a constant feed amount F × P (P is the minimum pitch of dots in the sub-scanning direction, F is an integer). ), The sub-scan feed is performed, and the pitch in the sub-scanning direction of the plurality of dot forming elements is k ×
When P (k is an integer of 3 or more), the number N (N is an integer of 3 or more) of dot forming elements used in one main scan and the parameters Na, Nb, m and L are A dot recording method characterized by satisfying the following expressions (1) to (4). N = Na + Nb (1) Na = m × k ± 1 (2) Nb = Rd [L × Na ÷ k] (3) F = Na (4) where m is an integer of 1 or more, L Indicates an integer satisfying 1 ≦ L <k, and the operator Rd [] indicates an operation for rounding the fractional part of the value in parentheses. 6. The dot recording method according to claim 5, wherein dots recorded by Nb dot forming elements and dots recorded by Na dot forming elements are provided on each main scanning line. A dot recording method, wherein the dot recording head is driven so as to have a complementary positional relationship. 7. The dot recording method according to claim 5, wherein the dots recorded by the Nb dot forming elements overlap the dots recorded by the Na dot forming elements on each main scanning line. A dot recording method in which the dot recording head is driven as described above. 8. The dot recording method according to claim 5, wherein the dot recording head has a plurality of dot recording element arrays for recording dots of a plurality of colors, In the plurality of dot recording element arrays, the respective dot recording elements are arranged so that the same main scanning line can be recorded in one main scanning, and when the main scanning is performed bidirectionally in both directions. A dot recording method in which dot recording is performed in each of the forward and backward passes. 9. A printing apparatus including a dot recording head having a dot forming element array in which a plurality of dot forming elements for forming a plurality of dots of the same color are formed at a substantially constant pitch along the sub-scanning direction. Is a computer-readable recording medium in which a computer program for recording dots on the surface of the printing medium is recorded while performing main scanning along a direction substantially perpendicular to the sub-scanning direction, A function of executing sub-scan feed with an amount F × P (P is the minimum pitch of dots in the sub-scan direction, F is an integer), and the pitch of the plurality of dot forming elements in the sub-scan direction is k ×
When P (k is an integer of 3 or more), the number N (N is an integer of 3 or more) of dot forming elements used in one main scan and the parameters Na, Nb, m and L are A computer-readable recording medium recording a computer program for causing a computer to execute the function of recording dots so as to satisfy the following expressions (1) to (4). N = Na + Nb (1) Na = m × k ± 1 (2) Nb = Rd [L × Na ÷ k] (3) F = Na (4) where m is an integer of 1 or more, L Indicates an integer satisfying 1 ≦ L <k, and the operator Rd [] indicates an operation for rounding the fractional part of the value in parentheses.