JPH0361045A - Ink jet recorder - Google Patents

Abstract

PURPOSE:To conduct recording with a more correct density by a method wherein matrixes each corresponding to the gradation, or color and gradation of a pixel to be recorded are stored in a memory part, and a recording head is driven based on the data of an optimum matrix in accordance with inputted gradation data, or gradation data and color data. CONSTITUTION:Data Di is inputted to a latch circuit 2. The input data Di is the number of a matrix for a density nearest to original input data. The appropriate matrix is selected by a controller. The required matrix is selected by an address signal from the latch circuit 2. A line Y of the selected matrix is selected by an address signal from a counter 5, and a position X on the appropriate line Y is sequentially selected by an address signal from a counter 4. The selected data in the matrix is sequentially outputted from a memory part 13, synchronized by a synchronizing circuit 14, and inputted to a recording head drive circuit 16. A recording head 15 is driven in accordance with the inputted data.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inkjet recording apparatus that records a desired image or the like by colliding ink particles onto a recording sheet.

[Prior Art] An inkjet recording device applies ink particles (dots) onto recording paper stretched over a rotating drum from a recording head that faces the drum and moves in a direction along the drum axis. This is a device that draws images etc. by making jets collide. In the case of monochrome recording, one recording head is used, and in the case of multicolor recording, usually cyan and cyan, respectively, are used.
Four recording heads are used that eject magenta, yellow, and black dots.

By the way, an image recorded on recording paper can be seen as a collection of many "points", and this "point J" is called a pixel. Pixels can be selected to have various sizes, but one example is The size is selected as 0.5 mm x 0.511111.A predetermined number of inkjet particles (dots) can be recorded in one pixel. It is possible to record 64 dots (8 x 8) in a space of mn + In the example, 1
It is possible to produce 64 kinds of 'a' shades for each color. The dot recording signal for each color is given in the form of the above-mentioned gray level.

On the other hand, when the number of dots (shade of color) to be recorded in one pixel is determined, there is the problem of how to distribute those dots within the pixel. for example,
In the above example, if it is determined that the density is exactly in the middle of the 64 types of shading, the number of dots will be 32. Therefore, a problem arises as to where to allocate the 32 dots among the dot recordable positions 64.

This distribution method is usually determined in advance,
Dot records are distributed according to this decision.

Such distribution of dot recording and driving means for driving the recording head in accordance with this distribution are disclosed in, for example, Japanese Patent Laid-Open No. 63-1.
This is proposed in JP No. 02950. This will be explained using a diagram.

FIGS. 4(a) to 4(d) are diagrams showing conventional matrices for performing driver l-recording allocation. In order to avoid the complexity of the matrix shown in the figure, the number of dots that can be recorded in one pixel is set to 16 (
4×4) (Of course, the actual number will be many, such as 16×16). The numbers in the matrix indicate the density level (darkness value), and a dot will be output at a darkness value below the manually entered density data. Mo indicates the basic matrix of darkness values. M,,M2. M, is the first
．． A second and a third matrix are shown, each having a different arrangement of dark values. That is, the first matrix M1 is the basic matrix M. The threshold values in the first column Y, of the basic matrix MO are moved to the fourth column Y4 without changing their order, and the second column Y2 of the basic matrix MO is moved to the first column Y1, the third column Y3 is transferred to the second column Y2, and the 4th row Y4 as 3rd
The array has been moved to column Y3.

Similarly, the second matrix M2 is an array obtained by sequentially shifting the arrangement of the first column Y1 to the fourth column Y4 of the first matrix M to the left one column at a time, and the third matrix M3 is the arrangement of the first matrix M.
The arrangement of the first column Y to the fourth column Y4 of 2 is sequentially shifted to the left one column at a time.

These matrices M. -M3 is stored in the subsequent memory section, in this case the basic matrix M;

The address of each dark value is (Xo+・Y,) ~ (X04・Y
4), the first matrix M+, the 27th matrix M
z, the at L/s of each darkness value of the third matrix M3 is (X,, -Yl) ~ (X,, ・Y4) (X21
・Yl) ~ (X24・Ya), (X31' Yl)
It is represented by ~(X34·'i'4). However, numerical values are used for the actual addresses of these addresses, and the numerical values correspond to the subscripts of the characters X and Y mentioned above. For example, the address (X23・Y4) of matrix M2 is the number “2J
r3'''4J.

FIG. 5 is a block diagram of a drive circuit of a conventional inkjet recording apparatus. In the figure, ■ is the level signal of the image shading (
2 is a latch circuit that latches the signal output from the level signal generation circuit 1.

3 is a clock signal generating circuit which outputs one pulse every time a dot is generated. A counter 4 inputs a clock pulse from the clock signal generation circuit 3 and counts the number of dots that can be recorded in one row (line) of one pixel (four in the example using the above matrix). 5 is a counter that counts the number of dots that can be recorded in one line in one rotation of the drum (4×number of pixels in the example of 7 tricks).

Reference numeral 6 denotes a memory section that stores the seven trixes shown in FIGS. 4(a) to (d), and 7 a comparison section that compares the level signal output from the level signal generation circuit 1 and the dark value output from the memory section 6. It is a circuit.

The operation of the above drive circuit will be explained with reference to FIG.

FIG. 6 is an enlarged plan view of the - section of the recording paper, and the matrices M shown in FIGS. 4(a) to 4(d) are virtually shown on the recording paper 10. -M3 is applied. The clock signal generation circuit 3 outputs a clock pulse in synchronization with the generation of dots. From the counter 4, the numerical values "1" to "4" are sequentially and repeatedly outputted as the address signal a for each clock pulse, and the numerical value "0" is output as the address signal a.
-1 to "3" are sequentially and repeatedly output every four clock pulses. On the other hand, the counter 5 outputs the numerical values "1" to "4".
'' is repeated in sequence every rotation of the drum.

The dark values of the memory section 6 are sequentially taken out by such address signals from each counter 4.5. The extraction of this dark value will be explained with reference to FIG.

During the first rotation of the drum, the counter 5 outputs the value “1”.
" is output. Also, initially, the address signal a of the counter 4 has a numerical value of "1", and the address signal S has a numerical value of "0". Therefore, the address signal input to the memory section 6 is rollj, and the corresponding address signal is shown in FIG.
) is not shown in the basic matrix M0 address (XO, -Yl
). Therefore, the memory unit 6 outputs the dark value "16" at the address. This dark value "16" is compared with the level signal latched in the latch circuit 2 in the comparator circuit 7, and when the dark value "16" is less than the level signal, the comparator circuit 7 records a dot on the recording head. A command signal to be executed is output.

By the next clock pulse, only the address signal a is changed to the numerical value "2", the address signal becomes r0211, and the corresponding dark value "4" of the basic matrix M0 is output. Thus, the basic matrix M. The threshold values belonging to the first column Y1 are sequentially output, and when this is completed, the address signal a becomes the numerical value "1" by the next clock pulse, and the address signal a becomes the numerical value r1. will be changed to This results in
l of the address (X11・Yl) of the first matrix M1
111 value "8" is output. Thus, each matrix M. - When all the threshold values of the first column Y of M3 are output,
At the next clock pulse, address signal a changes to the numerical value "1",
The address signal S is changed to the numerical value "0" and the basic matrix M is changed again. The threshold value "16" in the first column Y1 is extracted.

In this way, during one revolution of the drum, the matrix M. −
The dark values in the first column Y1 of M3 are repeatedly taken out in sequence.

When one rotation of the drum is completed, the address signal of the counter 5 becomes "2" by the next clock pulse, and from there, each of 7 trixes M is generated. The dark values in the second column Y2 of ~M3 are sequentially and repeatedly taken out. By continuing such operations, an image of light and shade corresponding to the manually input density data is recorded on the recording paper 10'2.

Note that the reason why a plurality of 7-trixes are used is to prevent the shading patterns of each pixel from being the same, thereby preventing diagonal stripes from occurring in the image.

[Problem to be solved by the invention]

Here, the dots actually recorded on the recording paper 10 will be considered with reference to FIG. In the figure, A is recording paper 1
Indicates a region on 0. Area A is each matrix M. -M
The area is the same size as the area 3, and the areas separated by broken lines are the same size as the areas of each darkness value. Now, 1
If the density of area A when one area is filled is "l", density data "16" is output from level signal generation circuit 1.
When is output, area A will be completely filled in. This is true when the shape of the dots recorded on the recording paper 10 exactly matches the shape of the area, as shown by Dl in the figure.

However, in general, the shape of the dot is approximately circular, and is not square like the dots. If the driver 1- is adopted as a circular dot that fits exactly into the division shown by the symbol D2, a space S will be created at the four corners of each division, so even if the density data "16" is output. It is not possible to completely paint over the entire area A, and therefore, the recorded image has a lower density than the original image.

In order to avoid this, the size of the dot is usually selected to cover the entire size of the section, as shown by reference numeral D3.

When such dots D3 are used, considering the number of dots, the adjacency of these dots, etc., the number of dots and the area A
is no longer proportional to the concentration of This will be explained with reference to FIG. FIG. 7 is a characteristic diagram showing the relationship between the number of dots D and the density when dots D and D are used. In the figure, the horizontal axis shows the number of dots, and the vertical axis shows the density. F is a straight line representing the characteristics when it is assumed that the dots D shown in FIG. 6 are used;
F2 is the characteristic curve of dot D3. Further, n indicates the total number of dots in a pixel, and N indicates the density at that time (density when all pixels are filled in), and in the example of area A, n - N = 1.6. .

It is clear that when dot D is used, the characteristic becomes straight line F. Also, when dots D are used, one dot has a larger area than one section, so the overall density is a That is, when the rate of increase in density is large and the number of dots is high, the remaining margin becomes small and the rate of increase in density becomes small.

Note that the curve F2 is drawn in a slightly exaggerated manner, and the shape of the curve differs depending on the distribution of the dark values of the 7 trix. In addition, although the straight line F1 and the curve F2 actually have a staircase shape,
In the figure, the staircase shape is shown in a leveled state.

As is clear from the above, conventional inkjet recording apparatuses have a problem in that the density linearity is poor, and as a result, the recorded image does not have a density that matches the input data.

Furthermore, in the case of color inkjet recording apparatuses, in addition to the negative problems, there are also problems specific to color.

That is, in a color inkjet recording apparatus, when a composite color is created using a plurality of colors, it may not be possible to obtain an arbitrary composite color depending on the density of each color. This problem becomes noticeable when black (BK) is used. For example, when expressing a "bluish black", cyan and black dots are recorded in the pixel;
When the density of is large, cyan and black dots overlap more often. Since the cyan that falls under the black color does not develop color, the "bluish black" actually expressed on the recording paper 10-hi is blacker than the hue expected from the human data. Regarding other colors as well, when black is involved, it may not be possible to obtain the desired hue, although this is not particularly noticeable.

The purpose of the present invention is to solve the problems in the above-mentioned prior art,
It is necessary to provide an inkjet recording apparatus that can perform recording with even more accurate density and, in the case of color recording, can also express the desired color tone.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an inkjet recording apparatus that performs recording by outputting ink dots onto a recording medium stretched over a rotating drum from a recording pad provided opposite to the recording medium. a storage unit that stores matrices configured to correspond to the gradations of pixels to be recorded, or gradations and colors; and a matrix corresponding to the manually generated gradation data or gradation data and color data among the matrices; a counter circuit that sequentially specifies the addresses of the matrix in synchronization with the ink dot generation signal; and a counter circuit that sequentially specifies the data of the matrix in synchronization with the generation signal. It is characterized by having the following.

do.

[For production]

The storage unit stores respective matrices corresponding to the gradations of pixels to be recorded, or colors and gradations. and,
An optimal matrix is selected according to the manually inputted gradation data or the manually inputted gradation data and color data, and the recording head is driven based on the data of this matrix to record dots.

〔Example〕

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 1 is a block diagram of a drive circuit of an inkjet recording apparatus according to an embodiment of the present invention. In the figure, parts that are the same as or equivalent to those shown in FIG. b, only one address data is output.T1 is a drum rotation timing signal or line update timing signal, T1 is a drum rotation timing signal or a line update timing signal;
2 indicates a dot generation clock signal. 12 is a synchronization circuit that synchronizes the signal T1 with the signal T2. Reference numeral 13 denotes a memory section, into which signals from the latch circuit 2 and counter circuits 4-45 are input as address signals. The contents stored in the memory section will be described later. 14 is a synchronization circuit that synchronizes the recording signal output from the memory section 13 with the signal T2;
15 is a recording head, 16 is a recording head according to a recording signal]
This is a recording head drive circuit that outputs dots from the recording head 5.

Here, regarding the data stored in the memory section 13, the second
This will be explained with reference to Figures (a) to (p). Figure 2(a)~
(p) is an explanatory diagram of data in the memory section. First, FIG. 2(a) will be explained. Figure 2 (a) is Figure 4 (a)
It is a 4×4 matrix similar to that shown in ~(d). Mo, indicates this matrix, and X1 to X4. Y
l to Y4 are matrix M. 1 row and column are shown. This matrix M. 1 is each matrix M shown in FIGS. 4(a) to 4(d). -M3 is different from each matrix M in the latter.

- This matrix M while the contents of M3 are dark value data. The content of 1 is binary data 'OJ, rl'. In this example, matrix M. The contents of I become the recording signal as is. That is, data r□ is a signal that does not output a dot, and data "1" is a signal that outputs a dot. This matrix M.

is used, one pixel (4 pixels) on the recording paper 10
x4 dot), one dot is recorded at the position (χ3.Yl). Now, following the previous example, if the density of dot D shown in Figure 6 is "1", then
Since the dot actually used is dot D3, the density recorded when matrix M61 is used is "
1". Therefore, this matrix M.

, 'M o + J represents the concentration of the matrix, and X1 to X4. Y+ to Y4 represent addresses of matrix data. The same applies to each matrix shown in FIGS. 2(b) to 2(p). For example, the matrix M shown in FIG. 2(c). 3, the concentration M6
3 is the position (X2. Yl ), (X3. Y
Since data "1" of matrix M 61 exists adjacently, the density is not three times that of matrix M 61, but is lower than that. In this way, the storage unit 13 stores the matrix M with the determined density. 1 to M16 are stored. and,
The address signals for each matrix data include M,
, Y subscripts are used.

Next, the operation of this embodiment will be explained. In the latch circuit 2,
Human power data D is input. This human data D, is
This is the number of the matrix whose density is closest to the original human power data (density data of the original image), and the selection of this matrix is made by a control device (not shown). For example, if the human power data indicates the minimum concentration,
Human power data D.

is matrix M. It becomes "01" which specifies 1. The latch circuit 2 latches this data and outputs it as an address signal. On the other hand, the counter 4 sequentially outputs address signals rl to "4" in synchronization with the signal T2, and the counter 5 outputs address signals rl to "4" in synchronization with the signal TI, changing every rotation of the drum or every update of the line. An address signal is output.

A desired matrix is selected by the address signal of the latch circuit 2, and then, by the address signal of the counter 5,
The line Y of the selected matrix is selected, and the position X on the line Y is sequentially selected by the address signal 7 of the counter 4. The selected data in the matrix is sequentially output from the memory section 13, synchronized by the synchronization circuit 14, and then manually inputted to the recording head drive circuit 16.
5 is driven. That is, every time the clock signal T2 is output, data at the address specified by the counter 4.5 in the matrix selected by the input data D3 is output from the memory section 13. For example, the output of latch circuit 2 is "02" (Di = 02), and the output of counter 5 is "3".
”, and when the output of the counter 4 is “1”, the matrix M is stored from the storage unit 13. Data “0” at position 2 (X+, Y3) is output, and the next signal T2 outputs the data “0” at position (X2Y3).
) data “1” is output. At this time, when the human power data D is changed to "03" and the next signal ``2'' is output, the matrix M03 is selected in the storage unit 13 and the matrix M is selected. 3, the data "1" of the position (X3.Y3) next to the previous position (χ2.Y3) is output, and then, if there is no change in the input data D, the data "1" of the position (X4. .Y3) data "O" is output. According to the above example, the data r
o', '1', '1', and 'O' are output in sequence, and on the recording paper 10, there are records of no dots, with dots, with dots, and without dots along the rotation direction of the drum. will be done.

It should be noted that the matrix shown in the description of the above embodiment is merely one example, and various positions for arranging "1" or "0" in each of the seven matrices can be selected in advance. In particular, in the matrix of a low concentration region, it is possible to reduce the concentration by placing the positions of "1" adjacent to each other, and the input D
8, it is possible to improve the linearity especially in the low concentration region even if the original human power data is used as is. Further, when recording in multiple colors, the above-mentioned circuit is used for each color.

In this way, in this example, a matrix is created for each density rather than a darkness value, and the matrix is selected based on the manual data of the density, so it is possible to record with a density that is more faithful to the original image. can be done. Also, when memorizing multiple colors, it is recommended to create a bottom color.
By constructing a matrix of each color by #, it is possible to reduce the overlap of dots of each color, and it is possible to make a desired hue appear. Furthermore, when there is a change in the human power data, the 7 trix corresponding to the human power data is selected, and the changed Since data on the position of the matrix is output, it is possible to better respond to human input data and obtain more precise images.

FIG. 3 is a block diagram of a drive circuit for a color ink jet recording apparatus according to another embodiment of the present invention. In the figure, the first
Parts that are the same as or equivalent to those shown in the figures are given the same reference numerals, and their explanations will be omitted. Human power data C of latch circuit 2]]
, indicates the density data of each color, and each data of field (B+<), cyan (C), magenta (M), and yellow (Y) is input in this order. C-3 is color type data indicating the type of color, and data specifying each color is given in advance to each of the colors. 17 is a selector circuit that selects a color based on the input of data C-3.

13' is a memory section corresponding to the memory section 13 of the circuit shown in FIG. This memory section 13' stores matrices as shown in FIGS. 2(a) to 2(p), which are created for each color. Note that the 71-trix may be a common matrix for each color instead of a matrix for each color. 158, 15C, 15M, and 15Y are black, cyan, magenta, and yellow recording heads, respectively; 168, 16C, 16
188 to 18Y are latch circuits that latch the matrix data ("1" or "0") output from the memory section 13'. 19C, 19M, 19Y
are shift registers with different numbers of stages. 2
0 indicates a drum on which recording paper is stretched. T2' is the first
This is a clock signal obtained by dividing the clock signal T2 shown in the figure by four, and one clock signal T2' is output when the generation of dots in the four colors of BK, C, M, and Y is completed.

Next, the operation of this embodiment will be explained. Now, for example, 1 latch circuit 2 has black density data, and selector circuit 1
Assuming that color-specific data indicating black in 7 is input manually, the matrix with the density closest to the corresponding density data is selected from among the 71-risks for black stored in the memory unit 13' based on the color-specific data and density data. be done. Then, the counter circuits 4 and 5 designate the address at that time for the selected matrix. For example, if the address immediately before that point is X3-Y2, the address at that point is X4 Y2. Memory section 13'
outputs the matrix data corresponding to the specified address. Furthermore, since the selector circuit 17 has already selected the black latch circuit 188K based on the input color data, the data output from the memory section 13' is latched into the latch circuit 188K via the synchronization circuit 14. Ru.

On the other hand, the latch circuit 2 and the selector circuit 17 are manually input with cyan density data and color data following the input of black data. As a result, as in the case of black,
The memory unit 13' outputs data at the next address (same address as the address in the black matrix) of the previously specified address in the matrix closest to the density data in the cyan 2 matrix, and the data is manually input to the latch circuit 18C. Ru.

This manually entered data is then manually entered into the shift register 19C. In exactly the same way, magenta and yellow data are latched into latch circuits 18M and 18Y, respectively.

When the data of f error is latched into the latch circuit 18Y, the data of -18Y are simultaneously output to each latch circuit 188. Then, the black data of the latch circuit 18BK is immediately input to the drive circuit 168K, and if the data is "1", a black dot is struck on the recording paper on the drum 20 by the recording head 158K; Badots are not hit. On the other hand, latch circuits 18C, 18M, 1
The data latched in 8Y are input to shift registers 19C, 19M and 19Y, respectively.

Here, each of the shift registers 19C, 19M and 19Y will be explained. Now, the recording head 158 and the recording spatula I"15C are simultaneously recording on the recording paper on the drum 20.
The distance between the two dots when the dot is hit is T, 1, and the distance between the dots of the recording heads 15C and 15M is L2,
Similarly, if the distance between the dots of the recording heads 15M and 15Y is 1.3, the dot pitch is Δd, the drum rotational speed is N, and the dot generation clock period is T2, then the dot pitch Δd is expressed by the following equation.

2 Each shift register has 1 count per dot generation clock.
Assuming that the shift is performed one by one, the number of stages of each shift I register 19C, 19M, and 19Y is nc.

n, , nY are determined by the following equation.

1 4 Since the number of stages of the shift registers 19C, 19M, and 19Y is determined as in equations (2), (3), and (4) above, the latch circuit 188 ends up with 18C, 18M, and
The data of each color latched in 18Y is made to correspond to the same point on the recording paper. In this way,
A color image will be recorded on the recording paper.

The effects of this embodiment are also the same as those of the previous embodiment.

In the explanation of each of the above embodiments, an example was explained in which one bit is outputted from the corresponding matrix, but the invention is not limited to this. For example, four bits are simultaneously outputted from the corresponding matrix, and they are sequentially outputted one by one. You can also output it.

In this case, the 4 bits have two addresses X and two Y, for example, addresses (L, Yl), (L, Y2) (X2
．． Y1) and (X2.Y2) are selected, and recording is performed on two lines on the recording paper at an angle of 54 degrees. Note that in this case, a shift register that performs parallel-to-serial conversion of data is appropriately used. Further, selection of two lines on the recording paper is performed by changing the amount of charge of particles for each line. When 4 bits are used as a unit in this way, it is also possible to perform an image recording trial by coarsening the resolution of the input data through circuit processing.

〔Effect of the invention〕

As described above, in the present invention, a matrix corresponding to gradation data or gradation data and color data is created, so that printing can be performed with even more accurate density. Furthermore, when recording in color, a desired color tone can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a drive circuit of an inkjet recording apparatus according to an embodiment of the present invention, and FIGS.
3 is a block diagram of a drive circuit of an inkjet recording apparatus according to another embodiment of the present invention, and FIGS. 4(a) to 6(d) show a conventional matrix. 5 is a block diagram of a drive circuit of a conventional inkjet recording apparatus, FIG. 6 is a partially enlarged plan view of a recording sheet, and FIG. 7 is a characteristic diagram of density versus number of dots. 2.188, 18C, 18M, 18Y...Latch circuit, 4.5...Counter circuit, 13.13'...Memory section, 15.158, 15C, 15M, 15Y...
- Recording head, 17... Selector circuit 7 2nd (a) (b) YI Y2 Y3 Y4 (C) (d) (i) (j) (k) (L) (a) (b) 1 2 3 4 1 2 3 4 Figure (C) (d) 1 2 3 4 1 2 3 4

Claims (1)

[Claims] In an inkjet recording device that performs recording by outputting ink dots onto a recording medium stretched over a rotating drum from a recording head installed opposite to the recording medium, the gradation or gradation and color of pixels to be recorded are a storage unit that stores each matrix configured in a corresponding manner; a selection unit that selects a matrix corresponding to input gradation data or gradation data and color data from among the matrices; and a generation signal of the ink dots. An inkjet recording apparatus comprising: a counter circuit that sequentially designates addresses in the matrix in synchronization with the inkjet recording device; and an output means that outputs data at the address designated by the counter circuit to the recording head.