JP3253128B2 - Ink jet recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a serial scan type ink jet recording apparatus provided with a recording head having a plurality of discharge ports.

[0002]

2. Description of the Related Art Generally, a recording apparatus such as a printer, a copying machine, a facsimile or the like records an image composed of a dot pattern on a sheet-like recording material such as paper or a thin plastic plate based on image information. It is configured. The recording apparatus can be classified into an ink jet type, a wire dot type, a thermal type, a laser beam type, and the like according to a recording method. Among them, the ink jet type (ink jet recording apparatus) discharges ink onto a recording material to perform recording. Is performed.

The ink jet recording apparatus can record a high-definition image at a high speed and is a non-impact type, so that the noise is small and it is easy to record a color image using multi-color ink. There are advantages such as. The above-described ink jet recording apparatus that performs recording by flying ink from a discharge port of an ink jet recording head onto a recording material based on image information is used in a printer, a facsimile, a copying machine, and the like, where quietness of operation sound is required.
Used favorably. In particular, an ink jet recording apparatus of a system in which ink is locally heated by heat energy from a heating element (heater) and a pressure change is caused inside a discharge port by generated bubbles to discharge ink is performed at a high frequency. Recently, it has been adopted in the recording unit of each model.

In a serial scan type recording apparatus having a recording head having a plurality of ejection ports and capable of high-density recording, ink bleeds at a boundary portion of a scanning line.
In some cases, uneven density and uneven streaks due to non-uniform absorption occur, and the image quality deteriorates due to variations in the amount of ink droplets and landing accuracy.

Therefore, conventionally, the recording medium is conveyed by the width of an area obtained by equally dividing the ejection opening array of the recording head by n, and the number of recording dots formed on the recording medium by the recording head by ink ejection during one scan recording is reduced. By masking the recording signal so as to be 1 / n, and forming a picture by performing n-times scanning and recording the signal of the width of the region equally divided by n with different ejection port arrays, the image is formed. The image quality was improved. This conventional recording method will be described with reference to the drawings.

FIG. 14 shows a mask pattern for masking a recording signal. A hatched portion is a portion for masking a signal, and a blank portion is a recordable portion. The mask pattern is 4 × 4
The image signal is masked by repetition of this pattern both vertically and horizontally. FIG. 15 is a diagram showing an image recording process, and shows a case where the ejection opening array of the recording head is divided into two equal parts (n = 2). In the figure, A is the conveying direction of the recording medium, and B is the scanning direction of the recording head 1.

In printing, first, print data is masked according to the mask pattern shown in FIG. 14A, and an upper half image (a) is printed by one scan printing. Next, the width of the area into which the ejection port array (FIG. 15) is bisected (eight nozzles in the figure)
Is transported in the direction A, the print data is masked according to the mask pattern shown in FIG. 14A (b), and the image (b) is printed while the print head 1 scans in the direction B. The image (c) is formed by the two recording processes described above. In the image (c), the area for the upper eight nozzles (upper half)
An image is completed by two scan recordings using the upper eight nozzles and the lower eight nozzles of the recording head. Thereafter, this recording process is repeated to form one image.

FIG. 16 also shows the ejection port array of the recording head as 2
FIG. 14B is a diagram showing an image recording process when the image is equally divided, and FIG.
The case where the mask pattern of FIG. The operation of transporting the recording head 1 and the recording medium is the same as in the example described above. In the figure, the image (a) is a mask pattern diagram 14b
When (a) is used, the image (b) is a case using the mask pattern diagram 14b (b), and the image (c) is an image formed by two recording processes (a) and (b). is there.

FIG. 17 is a diagram showing a printing process when the ejection port array of the printing head is divided into four equal parts (n = 4). In printing, first, print data is masked according to the mask pattern of FIG. 14C (a), and an image (a) is printed by one scan printing.

Next, an ejection port array of the recording head 1 (FIG. 17)
14A is conveyed in the direction A, the print data is masked according to the mask pattern shown in FIG. 14C (b), and the print head 1 scans in the B direction. Image (b) is recorded. The image (c) is recorded using the mask pattern shown in FIG. 14C (c) and the image (d) is recorded using the mask pattern shown in FIG. The image (e) is formed by the recording process described above. In the area corresponding to the uppermost four nozzles, printing is performed by different discharge port groups obtained by dividing the discharge port array into four equal parts, and an image is formed.

In the printing by these methods, the amount of ink to be printed on a printing medium at one time can be limited.
When recording on a recording medium having poor ink absorbency, particularly for color recording, bleeding can be reduced and high-quality recording can be performed.

[0012]

However, in the above conventional example, when the arrangement pattern of recording dots for forming an image is the same as the mask pattern described above, there is a problem described below.

A case in which print data is masked in accordance with the mask pattern shown in FIG. 14A and a mixed color image of cyan and yellow is printed by the printing method shown in FIG. 15 will be described. At this time, cyan is solid printing, while yellow is a thinned image of the same dot arrangement as in (a) of FIG. 14A.

FIG. 18 shows a recording dot pattern recorded by being masked with the mask patterns (a) and (b) of FIG. 14a. In the figure, A represents a yellow recording dot, and B represents a yellow recording dot.
Indicates cyan recording dots, and (1) indicates each of FIG.
When masked by the mask pattern (a) in (a),
(2) shows recording dots when masked by the mask pattern (b) of FIG. 14A. (1) of FIG. 18A
No print dots are shown for yellow, because the print dot arrangement and the mask pattern are the same, and the data of all print dots has been masked.

FIG. 19 shows an image recorded by the recording method shown in FIG. 18A (1) and B in the first scan recording
(1) is recorded. Next, after the recording medium is conveyed by eight nozzles, the second scan recording is performed to print the data shown in FIGS. The ink recording order during the scanning is cyan → yellow, and the recording dot placed at the top in the figure indicates the dot of the ink color recorded last. Thereafter, FIG. 18A (1) and B (1)
18A (2) and B in FIG.
(2) is recorded. In FIG. 19, in the Y area, the yellow dot is recorded last, but in the C area, the cyan dot is recorded last, and the Y area and the C area are recorded. Are different in the ink recording order.

In the case of ink jet recording, the hue of the recorded image changes when the recording order of the ink colors is different due to the influence of the spread and bleeding of the recording dots on the recording medium and the permeation of the ink into the recording medium. In FIG. 19 as well, the hues of the images in the Y area and the C area are different, and as a result, stripe-like unevenness of different hues with an 8-nozzle width occurs, and there is a disadvantage that the image quality is significantly deteriorated.

Further, there are the following problems depending on the head driving method and mounting accuracy.

In a print head in which a plurality of ink ejection ports are mounted at a high density, a type in which pressure change is used by thermal energy, the crosstalk in which ink ejection becomes unstable due to pressure waves from adjacent ejection ports or thermal diffusion. Therefore, the group of ink ejection ports is divided into a plurality of groups and driven to prevent this phenomenon.

FIGS. 20 and 21 are block diagrams of a conventional electric circuit for driving a print head, and FIG. 22 is a timing chart of signal waveforms of respective parts. Here, a description will be given of a case where the driving for performing the ink discharge of the recording head is performed by dividing into four. The recording head 1 has 16 heaters 101, and each heater 101 corresponds to an ejection port for ejecting ink. The recording head 1 sets print data Si in a 16-bit shift register 102 with a print data synchronous clock CLKi, and enables enable BEi1 ^* and BEi2.
^* , BEi3 ^* , and BEi4 ^* signals are turned on to drive the transistor array 103 of the head.
The heater 101 generates heat for each unit to perform printing. B above
The Ei1 ^* , BEi2 ^* , BEi3 ^* , BEi4 ^* signals are generated by the decoder 104. In addition, LATC
The H ^* signal is a control signal for latching print data in a 16-bit latch 105, and the CARESi ^* signal is a latch 105.
Is a reset signal for clearing the signal. The signal ^* indicates that the signal is low active.

[0020] One heat operation is a Heat Start.
The signal (FIG. 22B) is started, and the Heat Enable signal (FIG. 22C) is changed to Hi during the print head driving period.
gh. Heat Enable signal is Heat
Start signal and HeatClock (FIG. 22 (a))
Is made by the input flip-flop. Hea
During a period in which the t Enable signal is High, the counter 106 and the counter 107 are set to the Heat Clock.
Count up by signal. The value of the counter 106 is a signal He for driving the head 1 via the comparison circuit 108.
at Pulse ^* (FIG. 22D) is generated. The comparison circuit 108 keeps H until the pulse width set by the CPU (not shown) in the register 110 becomes equal to the count value.
EatPulse ^* signal is generated, drop becomes the same as the set value Heat Pulse ^* signal to Low. The counter 107 is incremented every time the counter 106 makes a round, and the comparison circuit 109 selects a divided block of the print head.
1 and 2 signals (FIGS. 22 (e) and 22 (f)) are generated.
Nozzle Select 1 and 2 signals are passed through the decoder 104 to BEi1 ^* , BE
i2 ^* , BEi3 ^* , BEi4 ^* (FIG. 22 (h)-
Select (k)). After the comparison circuit 109 switches the head division signal four times, the heat end signal Heat End
^* (FIG. 22 (g)) is generated and Heat Enable is generated.
The e signal is dropped to Low to end the heating operation. In this circuit, all signals operate in synchronization with the Heat Clock signal. Heat indicating the heat period
The Enable signal starts with a Heat Start signal and ends with a Heat End ^* signal. The Heat Pulse ^* signal for actually heating the head 1 is a divided block selection signal Nozzle Select1, N
Ozle Select 2 BEi1 by each signal
^* , BEi2 ^* , BEi3 ^* , and BEi4 ^* .

FIG. 25 shows the image of FIG. 23 recorded by the recording method shown in FIG. 15 by dividing the discharge ports shown in FIG. 25A shows a case where the head is not tilted, and FIG. 25B shows a case where the head is tilted due to a head mounting error or the like. In the drawing, indicates dots formed by the first, second, and third scans, respectively, and subscripts indicate divided blocks.

The shift shown in FIG. 25A is caused by the division signals BEi1,
The shift is caused by a shift in the ejection timing of BEi2, BEi3, and BEi4, and the shift amount L ₀ is represented by L ₀ = ΔTv.
ΔT is the time difference between the generation of the heat signal of the divided blocks BEi1 and BEi4, and v is the scanning speed of the recording head.
When the head is tilted as shown in FIG. 3B, the ejection reference position varies depending on whether the upper or lower head is used due to the time difference between the generation of the heat signal of each divided block and the tilt of the head. As a result, the displacement amounts have a relationship of L ₂ <L ₁ . In this case, the recording dots are scattered in the region of the upper eight nozzles, while the recording dots are concentrated in the region of the lower eight nozzles. When the head 1 is tilted in the direction opposite to the direction shown in FIG. 2B, the recording dots in the upper region are concentrated and the recording dots in the lower region are scattered.

FIG. 26 shows the image of FIG. 23 recorded by the recording method shown in FIG. 15 by dividing the discharge ports shown in FIG. 26A shows a case where the head is not tilted, and FIG. 26B shows a case where the head is tilted. FIG.
Similarly, the shift amount L _{0 in} (a) is represented by L ₀ = ΔTv, ΔT is the time difference between the generation of the heat signal of the divided blocks BEi1 and BEi4, and v is the scanning speed of the recording head. When the head is tilted as shown in FIG. 26B, the shift amount is L ₂ <L due to the time difference of the generation of the heat signal of each divided block and the variation of the ejection reference position due to the head tilt.
₁ relationship. In this case as well, the recording dots are scattered in the area for eight nozzles as in the previous recording method, whereas the recording dots are concentrated in the area for the lower eight nozzles.

FIG. 27 shows an image obtained by recording the image of FIG. 23 in a mixed color of cyan and yellow by the recording method shown in FIG. At this time, the driving of the head is performed by dividing the ejection openings shown in FIG. 24B, and the recording head that ejects cyan ink has no inclination, and the recording head that ejects yellow ink is inclined. In FIG. 27, hatched dots indicate cyan recording dots, and blank dots indicate yellow recording dots. In the figure, the overlapping of the recording dots of each color is different between the area for the upper eight nozzles and the area for the lower eight nozzles.

The image recorded by such a method has not only stripe-like unevenness due to a dense / dense pattern of dots that occurs in each of n equally divided regions (in the above example, a region for eight nozzles).
The hue difference caused by the difference in the overlapping of the recording dots of each color further deteriorates the unevenness, and has a disadvantage that the image quality is remarkably deteriorated.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to always print a good image even when the print head is conveyed by the width of an area equally divided into n and an image is formed by n print scans. It is an object of the present invention to provide a recording device which can perform the recording.

[0027]

In order to achieve the above object, a recording apparatus according to the present invention is an ink jet recording apparatus capable of changing the number of recording dots per unit area in accordance with an input image signal and capable of expressing halftone. In the apparatus, a recording head having a plurality of ejection units for ejecting ink, and conveying means for relatively conveying the recording head and a recording medium by the width of a region obtained by dividing an ejection unit row of the recording head into n, In order to form an image by n times of scan recording with the width of the region divided into n,
Thinning means for thinning out the recording dots formed on the recording medium by the recording head during one scan recording by using a mask pattern;
An image forming unit that enables an image to be formed by n times of scanning and printing by different ejection unit arrays in which the recording of the width of the n divided areas is divided into n, and an arrangement pattern different from the recording dot arrangement expressing halftone. It is characterized by having generating means for generating the mask pattern.

[0028]

According to the above arrangement, the recording signal can be masked with an arrangement pattern different from the arrangement of the recording dots constituting the image. By using a signal of a conditional decision-type dither method such as an error diffusion method, the mask can be masked. By adding variability to this pattern, it is possible to reduce image quality deterioration factors such as color unevenness.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is a perspective view showing a main part of a serial scan type color ink jet recording apparatus according to an embodiment of the present invention. In the figure, a carriage 2 includes a recording head 1Y for ejecting yellow color ink, a recording head 1M for ejecting magenta color ink, a recording head 1C for ejecting cyan color ink, and a recording head 1K for ejecting black color ink. It is installed at a predetermined distance. A recording medium made of a sheet or a thin plastic plate is sandwiched between sheet discharging rollers 3 and 4 via a conveying roller (not shown), and is sent in the direction of arrow A by driving a not-shown conveying motor.

The carriage 2 is guided and supported by the guide shaft 5 and the encoder 6. The carriage 2 is reciprocated along the guide shaft 5 by driving a carriage motor 9 via drive belts 7 and 8. A plurality of ejection ports are provided on a surface (ejection port forming surface) of the recording head 1 facing the recording medium, and heat is generated inside each ejection port (flow path) to generate thermal energy for ink ejection. An element (electric / thermal energy converter) is provided. According to the reading timing of the encoder 6,
The heating element is driven based on a recording signal, and black,
An image can be formed by flying and attaching ink droplets onto a recording medium in the order of cyan, magenta, and yellow.

Outside the recording area, a recovery unit 11 having a cap 10 at the home position of the carriage 2 and capable of performing an ejection recovery operation is provided. 1
Reference numeral 2 denotes a cleaning blade for cleaning the ejection port forming surface of the recording head 1. The ink is supplied to the recording head 1 from an ink tank 14 through an ink supply tube 13 via a sub-tank (not shown) on the carriage 2.

FIG. 2 is a block diagram showing the configuration of the recording apparatus according to the embodiment of the present invention.

Reference numeral 21 denotes a recording device, and 22 denotes R,
G, B image signals of three colors (8 bits for each color) or C,
An image input unit 23 for inputting image signals of four colors of M, Y, and K (one bit for each color), and a CPU 23 that controls the entire recording device 21 based on various programs in a ROM 24. In the CPU 23, reference numeral 24 denotes a ROM storing a control program, an error processing program, a program for operating the CPU 23, and the like. Reference numeral 25 denotes a work area for various programs in the ROM 24 and a temporary save area for error processing. 3 shows a RAM to be used. Reference numeral 26 denotes an image signal processing unit that performs signal processing on the input image signal obtained by the image input unit 22.
Reference numeral 7 denotes an operation unit for performing operations such as printing start. The operation unit 27 has a simple display function of an error message or the like. Reference numeral 28 denotes an input signal form detection unit for observing the signal form of the input image signal, and 29 denotes C, M,
A recording unit that forms an image by ejecting ink onto a recording material by recording heads of four colors Y and K is illustrated. Reference numeral 20 denotes a bus line for transmitting an address signal, a control signal, and data inside the recording device 21.

FIG. 3 is a block diagram showing an image signal processing circuit in this embodiment, FIG. 4 is a block diagram showing a binarization circuit in FIG. 3, and FIG. 5 is a diagram showing an error diffusion method used in the binarization processing in FIG. FIG.

In FIG. 4, an input signal of 8 bits for each color of R, G, B is input-corrected by an input corrector 42, and then converted from a luminance signal to an image density signal by a complementary color converter 43, and a complementary color c is input. , M, y signals. Next, the k signal is generated from the c, m, and y signals in the black generation 44, and the U signal is generated.
The CR45 performs UCR (under color removal) in which c, m, and y components corresponding to the k signal are removed. Next, the masking 46 corrects the color characteristics of the input system and the spectral characteristics of the ink to perform color correction for obtaining faithful color reproduction, and the output correction 47 corrects the gamma characteristics of the four colors k, c, m, and y. After that, the multi-level signal is binarized by a binarization processing unit 48, and K, C,
A binary signal of M and Y is obtained.

Next, the error diffusion method used in the binarization processing section 48 of the present invention will be described with reference to FIG.

In the error diffusion method, an integrated error between an input pixel and an output pixel is two-dimensionally settled. In FIG. 5, the binarization error E _xy generated around the input pixel I _xy (multi-level signal) is weighted by the error allocator 53 multiplied by an error distribution coefficient K _kl based on an error diffusion matrix.
The integration error S _xy of the following equation is obtained.

The error distribution coefficient K _kl is

[0040]

[Outside 1] (Where X is the pixel of interest).

[0041] _{S xy = (1 / ΣK kl} ) Σ kl · E xk, yl ( however, k, l the coordinates of the diffusion matrix)

Next, the integrated error S _xy is added to I _xy by the input correction means of 49 to obtain a correction value I ′ _xy .

The correction value _I'xy is _I'xy = _Ixy + _Sxy .

Next, _I'xy is converted to a threshold signal T by 50 comparators.
, And outputs a binary signal _Pxy .

The error E _{xy at} this time is obtained by 51 difference calculation means, and it becomes E _xy = I ′ _xy −P _xy .

Next, image signal processing in this embodiment will be described with reference to FIG. Here, a case will be described in which the ejection port array of the recording head is divided into two equal parts, the recording medium is conveyed by the width of the equally divided region, and an image having the width of the region is formed by two scan recordings.

When the input image signal is a binary signal, the signal is supplied to the buffer 33 by the selector 30 according to the selection signal S _1.
Fit in. On the other hand, the multi-level signal generation circuit 39 is selected by the selector 41 according to the selection signal S ₁ , and a specified multi-level signal is input to the binarization circuit 31. By inputting the specified multi-level signal at a value of 128 levels out of 255 (8-bit) levels, a binary signal in which the number of dots recorded per unit area is 1/2 is output from the binarization circuit 31. Is done. The output binary signal is stored in the buffer 34 by the selector 32 and used as a mask signal. Buffer 33-2
The arithmetic circuit 37 performs an AND process on the value image data and the binary data (mask data) in the buffer 34 to create thinned image data. After inputting the thinned image data to the output buffer 38, the signal is transmitted to the head 1 and the first data is transmitted. Make a record.

Next, the prescribed multi-level signal is input to a binarization circuit 31, and the output binary signal is supplied to a buffer 34 by a selector 32.
After that, the binary data (mask data) of the buffer 34 and the binary image data of the buffer 33 inverted by the inverting circuit 36 by the selector 35 are AND-processed by the arithmetic circuit 37 to generate thinned image data. Is input to the output buffer 38, and a signal is transmitted to the head 1 to perform the second scan recording. When the ejection openings of the recording head 1 have 16 nozzles, the memory capacity of the buffers 33 and 34 is (maximum number of print pixels in the scanning direction / 8 × 4 colors × 16 nozzles).
Byte is required.

After performing the first scanning recording in which the number of recording dots is reduced to 1/2, the recording medium is conveyed by eight nozzles, and then the recording is performed by reversing the thinning pattern in the first scanning recording. The second scan printing is performed with the number of dots thinned out to 1/2, and the data in the buffer is successively printed for each scan print except for the image area (for 8 nozzles) that overlaps in the first and second scan prints. Is input into the buffer.
Thereafter, one image is formed by repeatedly performing the first and second scan recordings including the transport operation of the recording medium.

When the input signal is a multi-level signal, the selection signal S ₁
The signal is input to the binarization circuit by the selector 30 according to the formula (1), binarized, and then stored in the buffer 33 through the selector 32. On the other hand, the mask pattern table 40 is selected by the selector 41 in accordance with a selection signal S _1,
The mask pattern data is input to the buffer 34. The pattern in the mask pattern table is as shown in FIG. 6, in which the hatched portion indicates that the bit is “1” and the blank portion indicates “0”.

The binary image data in the buffer 33 and the binary data (mask data) in the buffer 34 are processed by an arithmetic circuit 37.
Then, an AND process is performed to create thinned image data, which is input to the output buffer 38, and then a signal is transmitted to the head 1 to perform first printing. After the recording medium is conveyed (for eight nozzles), the data in the buffer and the data in the buffer are exchanged.
The binary data (mask data) of the buffer 34 inverted by the above is subjected to an AND process in the arithmetic circuit 37 to create thinned-out image data, which is input to the output buffer 38 and then transmitted to the head for second recording. I do. Thereafter, one image is formed by repeatedly performing the first and second scanning recordings including the operation of transporting the recording medium. Selection signals S ₁ may be subjected to switching by the image data the head of the header signal.

When printing is performed with this configuration, since the arrangement pattern of the recording dots and the arrangement pattern of the signals of the mask pattern are different, it is possible to reduce color unevenness caused by a hue difference.

Further, since the arrangement pattern of the mask pattern signal has an arrangement having a certain degree of randomness by using an error diffusion method, there is a specificity in how the color dots overlap each other due to the accuracy of the head inclination and the like. Without concentration,
Color unevenness can be reduced.

When the error diffusion method is used for the binarization processing of the image signal, the dot arrangement of the binarized image signal is irregular. The same effect can be obtained, and the image quality can be improved.

If the pattern signal generating means of the mask pattern can be arbitrarily selected regardless of the input image signal form, the input binary image signal is the same as the binarization processing method in the printing apparatus. Even in this case, it is possible to prevent the arrangement pattern of the recording dots from overlapping the arrangement pattern of the pattern signals of the mask pattern.

(Embodiment 2) Next, FIG. 7 shows a block diagram of image signal processing according to Embodiment 2 of the present invention.

In FIG. 7, the binarization circuit is the same as that shown in the block diagram of FIG.
Here, the description is omitted. The binarization circuit 55 uses the error diffusion method shown in FIG. On the other hand, in the binarization processing of the binarization circuit 56, an independent decision type dither method is used in which a multi-level signal of a corresponding pixel is binarized according to a threshold of a dither matrix as shown in FIG.

Hereinafter, the ejection port array of the recording head having 16 ejection ports is divided into two equal parts, the recording medium is conveyed by the width of the bisected area, and the image having the width of the area is scanned twice. The case of forming by recording will be described.

An input image signal (multi-valued) according to the selection signal S ₁
To be binarized by the binarization circuit 55 or the binarization circuit 56 is selected.

Assuming that the binarization processing is performed by the binarization circuit 55, the input image signal (multi-valued) is binarized by the binarization circuit 55 and stored in the buffer 70. Binarization circuit 5
6 receives a specified multi-level signal from a multi-level signal generation circuit 74. By inputting the specified multi-level signal at this time into a value of 128 levels among 255 (8 bits) levels, a binary signal in which the number of dots recorded per unit area is １ ／ is output from the binarization circuit 56. You. This output binary signal is supplied to selector 57
And is used as a mask signal in the buffer 58. The memory capacity of the buffer 70 and the buffer 58 is (Maximum number of print pixels in the scanning direction / 8 × 4 colors × 16 nozzles) Byte.

The binary image data in the buffer 70 and the binary data (mask data) in the buffer 58 are processed by an arithmetic circuit 72.
Performs AND processing to create thinned image data, inputs this to the output buffer 73, and transmits a signal to the head 1 to perform first printing. After the recording medium is conveyed (for eight nozzles), the data in the buffer is replaced with new data as needed, and then the binary image data in the buffer 70 and the binary data in the buffer 58 inverted by the inversion circuit 71. The (mask data) is subjected to an AND process in the arithmetic circuit 37 to create thinned-out image data. After inputting this to the output buffer 73, a signal is transmitted to the head 1 to perform second printing.
Thereafter, one image is formed by repeatedly performing the first and second scanning recordings including the operation of transporting the recording medium.

An input image signal (multi-value) according to the selection signal S ₁
Is selected to be performed by the binarization circuit 56, the binarization circuit 55 is used as a mask signal generation circuit.

Also in this embodiment, since the arrangement pattern of the recording dots and the arrangement pattern of the mask pattern signals are different,
Color unevenness caused by a hue difference can be reduced.

(Embodiment 3) Next, Embodiment 3 of the present invention.
FIG. 9 is a block diagram of the image signal processing of FIG. In FIG. 9, the binarization circuit is the same as that shown in the block diagram of FIG. 4 of the previous embodiment, and the description is omitted here.

An error diffusion method as shown in FIG. 10 is used for the binarization processing. Description of the error diffusion method is omitted mentioned earlier, in FIG. 10 is adapted to select the error distribution coefficient by the selection signal S _3, optionally 2
Value parameters can be changed. The error distribution coefficients include the coefficients shown in FIG.

Hereinafter, the ejection port array of the recording head having 16 ejection ports is divided into two equal parts, the recording medium is conveyed by the width of the equally divided area, and the image having the width of the area is scanned twice. The case of forming by recording will be described.

An input image signal (multi-value) according to the selection signal S ₃
Of which of the error distribution coefficients 85 and 86 is to be used for the binarization processing. Now, the error distribution coefficient 85
, The input image signal (multi-valued) is first divided by eight nozzle lines (8 rasters) by an error distribution coefficient.
The value is processed and the data is stored in the buffer 80. Then 2
The error distribution coefficient of the binarizing circuit is switched to 86, and the specified multi-level signal from the multi-level signal generating circuit is binarized. By inputting a 128-level value among the 255 (8-bit) levels of the specified multi-level signal at this time, a binary signal value in which the number of recorded dots per unit area is １ ／ is output. The output binary signal is stored in the buffer 78 by the selector 77 and used as a mask signal. Buffer 80 and buffer 7
8 is (maximum number of print pixels in the scanning direction / 8 × 4
(Color × 16 nozzles) Byte.

The binary image data in the buffer 80 and the binary data (mask data) in the buffer 78 are calculated by an arithmetic circuit 82.
Performs AND processing to create thinned image data, inputs this to the output buffer 73, and transmits a signal to the head 1 to perform first printing. After the recording medium is conveyed (for eight nozzles), the data in the buffer is replaced with a new one as needed, and then the binary image data in the buffer 80 and the binary data in the buffer 78 inverted by the inverting circuit 81. The (mask data) is AND-processed by the arithmetic circuit 82 to create thinned-out image data, which is input to the output buffer 83 and then transmitted to the head 1 for second printing.
Thereafter, one image is formed by repeatedly performing the first and second scanning recordings including the operation of transporting the recording medium. When the binarization processing of the input image signal (multilevel) selected to perform the error distribution coefficient by the selection signal S ₃ is a binary signal by an error distribution coefficient is used as a mask pattern signal.

Also in this embodiment, since the arrangement pattern of the recording dots and the arrangement pattern of the signals of the mask pattern are different, the color unevenness caused by the hue difference can be reduced.

(Embodiment 4) FIG. 12 is an explanatory diagram of the error diffusion method used for the binarization processing of Embodiment 4 in this embodiment. This embodiment also performs signal processing by arbitrarily changing a binarization processing parameter by a selection signal as in the third embodiment, and a detailed description thereof will be omitted, and only different points will be described.

The error diffusion method shown in FIG. 12 has two error buffer memories having different diffusion matrices and corresponding error distribution coefficients. The error distribution coefficients include the coefficients shown in FIG. Select error buffer memory, and the error distribution coefficient, the the selection signal S _3, performs generation of binarization processing and the mask pattern signal of the image signal. According to this method, the binarization processing parameters other than those described in the first and third embodiments may be varied, and the same effect can be obtained by varying the threshold signal in the second embodiment.

(Embodiment 5) In the preceding embodiment, the ejection port array of the recording head having 16 ejection ports is divided into four equal parts, and the recording medium is conveyed by the width of the equally divided area. A case in which an image having a width of? Is formed by four scan recordings will be described.

In the printing of the first scan, a binary image signal corresponding to an even nozzle in the buffer (even raster) and a binary signal for mask in the buffer are AND-processed by an arithmetic circuit to create thinned image data. And record the image. The binary image signal (odd raster) corresponding to the odd nozzle is “00”.
(Hex) ".

In the recording of the second scan, the binary image signal of the odd raster in the buffer and the binary signal for mask in the buffer are AND-processed by an arithmetic circuit to generate thinned-out image data and record the image. . “00 (Hex)” is assigned to the binary image signal of the even raster.

In the printing of the third scan, the binary image signal of the even raster in the buffer and the binary signal for mask in the buffer inverted by the inverting circuit are AND-processed by the arithmetic circuit to create thinned image data. To record the image. “00 (Hex)” is assigned to the binary image signal of the odd raster.

In the recording of the fourth scan, the binary image signal of the odd raster in the buffer and the binary signal for mask in the buffer inverted by the inverting circuit are subjected to AND processing by the arithmetic circuit to create thinned image data. Record the image. “00 (Hex)” is assigned to the binary image signal of the even raster.
Thereafter, one image is formed by repeatedly performing the first to fourth scans including the operation of transporting the recording medium.

Also in this embodiment, since the arrangement pattern of the recording dots and the arrangement pattern of the signals of the mask pattern are different, the color unevenness caused by the hue difference can be reduced.

The conditional decision dither method applied to the present invention includes, in addition to the error diffusion method (average error minimization method) described in each of the above embodiments, a pixel distribution method within a mesh, a multi-stage division quantization method, a CAPIX method. A method or the like may be used.

The present invention provides an excellent effect particularly in a recording head and a recording apparatus of a type utilizing thermal energy among ink jet recording types.

The typical configuration and principle are described in, for example, US Pat. Nos. 4,723,129 and 4,740.
It is preferable to use the basic principle disclosed in the specification of Japanese Patent No. 796. This method can be applied to both the so-called on-demand type and the continuous type. In particular, in the case of the on-demand type, liquid (ink)
By applying at least one drive signal corresponding to the recorded information and providing a rapid temperature rise exceeding nucleate boiling, to the electrothermal transducer disposed corresponding to the sheet or the liquid path in which is held, This is effective because thermal energy is generated in the electrothermal transducer, and the film is boiled on the heat-acting surface of the recording head. As a result, bubbles in the liquid (ink) can be formed in one-to-one correspondence with the drive signal. The liquid (ink) is ejected through the ejection opening by the growth and contraction of the bubble to form at least one droplet. When the drive signal is formed into a pulse shape, the growth and shrinkage of the bubble are performed immediately and appropriately, so that the ejection of liquid (ink) having particularly excellent responsiveness can be achieved, which is more preferable. Examples of the drive signal in the form of a pulse include those described in U.S. Pat.
Suitable are those described in US Pat. No. 45,262. If the conditions described in U.S. Pat. No. 4,313,124 relating to the temperature rise rate of the heat acting surface are adopted, more excellent recording can be performed.

As the configuration of the recording head, in addition to the combination of the discharge port, the liquid path, and the electrothermal converter (linear liquid flow path or right-angled liquid flow path) as disclosed in the above-mentioned respective specifications, U.S. Pat. No. 4,558,333 and U.S. Pat. No. 4,558,333 which disclose a configuration in which a heat acting portion is arranged in a bending region.
A configuration using the specification of Japanese Patent No. 459600 is also included in the present invention. In addition, Japanese Unexamined Patent Publication (Kokai) No. 123670/1984 discloses a configuration in which a common slit is used as a discharge portion of an electrothermal converter for a plurality of electrothermal converters, and an aperture for absorbing pressure waves of thermal energy. The present invention is also effective as a configuration based on JP-A-59-138461 which discloses a configuration corresponding to a discharge unit.

[0082]

As described above, according to the present invention, a recording signal can be masked with an arrangement pattern different from the recording dot arrangement constituting an image, and a conditional decision type dither method such as an error diffusion method can be used. By using the signal, variability is added to the pattern of the mask, so that image quality deterioration factors such as color unevenness can be reduced, and good image recording can be performed.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a main configuration of a serial scan type color inkjet recording apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a recording apparatus according to an embodiment of the present invention.

FIG. 3 is a block diagram illustrating an image signal processing circuit according to an embodiment of the present invention.

FIG. 4 is a block diagram showing a binarizing circuit according to one embodiment of the present invention.

FIG. 5 is an explanatory diagram of an error diffusion method used in one embodiment of the present invention.

FIG. 6 is a diagram showing a mask pattern in a mask pattern table according to one embodiment of the present invention.

FIG. 7 is a block diagram illustrating an image signal processing circuit according to a second embodiment of the present invention.

FIG. 8 is a threshold value matrix used for a binarization process according to the second embodiment of the present invention.

FIG. 9 is a block diagram illustrating an image signal processing circuit according to a third embodiment of the present invention.

FIG. 10 is an explanatory diagram of an error diffusion method used in Embodiment 3 of the present invention.

11 is used for the binarization processing of the error diffusion method of FIG.
It is a figure showing an error distribution coefficient.

FIG. 12 is an explanatory diagram of an error diffusion method used in Embodiment 4 of the present invention.

FIG. 13 is a diagram showing an error distribution coefficient used in the binarization processing of the error diffusion method in FIG.

FIG. 14 is a mask pattern for masking a recording signal.

FIG. 15 is a diagram illustrating a method of performing printing by dividing an ejection port array of a print head into two equal parts.

FIG. 16 is a diagram illustrating another method of performing printing by dividing the ejection port array of the print head into two equal parts.

FIG. 17 is a diagram illustrating a method of performing printing by dividing an ejection port array of a print head into four equal parts.

FIG. 18 is a diagram showing an image recorded by masking using the mask pattern of FIG. 14;

19 is a diagram showing an image obtained by recording the image of FIG. 18 by the method of FIG. 15;

FIG. 20 is a configuration diagram of a conventional electric circuit including a head unit.

FIG. 21 is a configuration diagram of a conventional electric circuit including a signal processing system.

FIG. 22 is a timing chart in a conventional electric circuit.

FIG. 23 is a diagram showing a pattern of a recorded image.

FIG. 24 is a diagram illustrating a divided state of a recording head.

FIG. 25 is a diagram showing a conventional image recorded by the recording method of FIG.

FIG. 26 is a diagram showing another conventional image recorded by the recording method of FIG.

FIG. 27 is a diagram illustrating a mixed-color image recorded by the same recording method as in FIG. 25;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Recording head 2 Carriage 22 Image input part 23 CPU 26 Image signal processing part 28 Input signal form detection part 29 Recording part 30, 32, 35, 41 Selector 31 Binarization circuit 33, 34 Buffer 36 Inversion circuit 37 Arithmetic circuit 38 Output Buffer 39 Multi-level signal generation circuit 40 Mask pattern table 55, 56 Binarization circuit 74 Multi-level signal generation circuit 76 Binarization circuit 84 Multi-level signal generation circuit 85, 86 Error distribution coefficient 88, 89 Error distribution coefficient 91, 92 Error buffer memory 101 Heater 200 Discharge port

Claims (7)

(57) [Claims] 1. An ink jet recording apparatus capable of changing the number of recording dots per unit area in accordance with an input image signal and capable of expressing a halftone, comprising: a recording head having a plurality of ejection sections for ejecting ink; Transport means for transporting the print head and the print medium relative to each other by the width of an area obtained by dividing the ejection portion array of the print head by n; and forming an image by n times of scan printing using the width of the n-divided area. Thinning means for thinning out the recording dots formed on the recording medium by the recording head during one scanning recording by using a mask pattern; and recording the width of the n-divided area by n different scanning sections by n different scanning sections. Image forming means for forming an image, and generating means for generating, as the mask pattern, an array pattern different from the recording dot array expressing halftones. Ink jet recording apparatus. 2. The image processing apparatus according to claim 1, wherein said generating means has a pattern table for storing a pattern, and a multi-level signal generating means for generating a prescribed multi-level signal, and selectively selects a binary or multi-level input image signal as said input image signal. Input means for inputting the multi-valued input signal; binarization processing means for converting the multi-valued input signal into a binary output signal by a conditional decision-type dither method such as an error diffusion method; Output means for selectively outputting the multi-valued input image signal and the specified multi-valued signal. When the input means inputs a binary input image signal as the input image signal, The specified multi-level signal generated by the multi-level signal generating means is input to the value processing means,
2. A pattern stored in the pattern table is used as the mask pattern when a value signal is used as the mask pattern and the input unit inputs a multi-value input image signal as the input image signal. 3. The ink jet recording apparatus according to claim 1. 3. The multi-level signal generating means for generating a specified multi-level signal, the multi-level signal input means for inputting a multi-level input image signal as the input image signal; A plurality of types of binarization processing means for converting to an output signal; and an output means for selectively outputting the multilevel input image signal and the specified multilevel signal as a multilevel input signal of the binarization processing means. Further comprising: inputting a specified multi-level signal generated by the multi-level signal generation means to the binarization processing means different from the binarization processing means to which the multi-level input image signal is input; 2. The ink jet recording apparatus according to claim 1, wherein a binary signal is used as the mask pattern. 4. The multi-level signal generating means for generating a prescribed multi-level signal, the multi-level input image signal being input as the input image signal; Binarization processing means for converting a binarization processing parameter into a binary output signal by a conditional decision-type dither method such as an error diffusion method capable of selectively changing the binarization processing parameter; Output means for selectively outputting a signal and the prescribed multi-level signal, wherein the binarization processing parameter different from the binarization processing parameter selected for the multi-level input image signal is selected. 2. The ink-jet printing method according to claim 1, wherein a prescribed multi-level signal generated by said multi-level signal generation section is input to said binarization processing section, and the obtained binary signal is used as said mask pattern. apparatus. 5. The ink jet recording apparatus according to claim 2, wherein said generating means is capable of arbitrarily selecting a pattern from said pattern table regardless of an input image signal form as said mask pattern. 6. An ink jet recording apparatus according to claim 3, wherein at least one of said plurality of binarization processing means is a conditional decision type dither method such as an error diffusion method. 7. The recording head is provided for each of the plurality of ejection units corresponding to the plurality of ejection units, and causes a state change of the ink due to heat, and ejects the ink from the ejection unit based on the state change to fly. The ink jet recording apparatus according to any one of claims 1 to 6, further comprising a thermal energy generating means for forming a droplet.