JP3327643B2 - Recording apparatus and recording control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus for recording an image by forming dots on a recording medium and a recording control method, and more particularly to a recording apparatus for realizing high quality output images. And a recording control method.

[0002]

2. Description of the Related Art Recording devices such as printers, copiers, and facsimile machines are configured to record an image formed of a dot pattern on a recording material such as paper or a thin resin plate based on image information. . According to the recording method, the recording apparatus includes a wire dot method, a thermal transfer method, a thermal recording method,
It can be classified into an ink jet system, an electrophotographic system, and the like. Among them, the ink jet system has been used in many recording apparatuses in recent years because it can realize high resolution at low cost.

The recording apparatus records dots (a to h) by a recording head 1 in which a plurality of image forming elements (A to H) are arranged as shown in FIG. Then, by repeating the recording while moving the recording head 1 in the main scanning direction, dots are recorded as in (1) to (5), and an image is formed.

However, since a plurality of printing elements are used, there is a variation in the area and formation position between dots formed for each printing element. For this reason, when image information having a uniform dot arrangement is recorded, streaky unevenness may occur in the formed image. This phenomenon will be described with reference to FIGS.

FIG. 13 is a diagram showing a 50% halftone recorded image when recording is performed with dots having a uniform area and a correct position, and high-quality image recording without unevenness is realized. . On the other hand, FIG. 14 is a diagram illustrating an example of a 50% halftone print image when the sizes of dots formed by the print elements vary. In this example, the area of the dot c recorded by the recording element C of the recording head 1 is larger than the reference, and the area of the dot f recorded by the recording element F is smaller than the reference. When printing is performed using a print head having a variation in the area of the dots formed in this manner, a phenomenon in which black tends to occur near the dot c and white tends to occur near the dot f occurs continuously. It is recognized as streak-like unevenness.

FIG. 15 is a diagram showing an example of a 50% halftone print image when dots formed by print elements vary in position. In this example, the area of the dots recorded by the recording elements (A to H) is uniform, but the dots b recorded by the recording element B and the dots d recorded by the recording element D are recorded by the recording element C. This shows a case where recording is performed using a head which is shifted to the side of the dot c to be printed. In this case, since the intervals between the dots b and c and between the dots c and d are smaller than those in the normal case, the dots tend to be black. Similarly, since the dot intervals between the dots a and b and between the dots d and e are wider than those in a normal case, the image tends to be white. Since the above-mentioned black-colored portion and white-colored portion appear continuously, streak-like unevenness is conspicuous.

[0007]

As described above, the streak-like unevenness that degrades the image quality is caused by the continuous occurrence of "white-ish" and "black-ish" images in the recorded image. are doing. Therefore, by controlling the dot area formed by using the same recording element irregularly and changing the area of each dot, there is a variation in individual dot diameter, but a control method (random dot Control) has been proposed.

However, the above-described method of forming the dot area by changing the dot area irregularly has the following problems.

First, as a first problem, the CPU of the recording apparatus
However, there is a problem that the processing capacity required for such a method is increased. For example, in a serial printer in which a carriage scans and prints one line at a time, a print head often has more nozzles than the number of nozzles necessary to print one line.
For example, a print head of 360 DPI has more than 60 nozzles. In such a print head, if the ejection drive speed is 6 KHz, 36
000 heats (discharge operation) are performed.
Therefore, in order to change the dot area irregularly,
At least 360,000 random numbers must be generated per second, and control must be performed to switch the heating pulse applied to each nozzle according to the random number value.

Further, in response to recent demands for a higher printing speed, a serial printer capable of simultaneously printing several lines in one scan and a printing head capable of driving at a higher driving cycle have been developed. Therefore, the processing capacity of the CPU required for the random number control is further increased.

[0011] As a second problem, there is a problem relating to the adverse effect of an image. By randomly changing the dot diameter,
It is possible to reduce the occurrence of regular unevenness (for example, unevenness of the white streak / black streak described above) which is patterned and conspicuous to the human eye. However, depending on the pattern, there may be a case where the whole image has a rough feeling. It has been known that this feeling of roughness depends on the modulation width in random dot diameter modulation, which is one of the adverse effects of random control.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a recording apparatus and a recording control method that reduce the load on the CPU in performing random dot control.

It is still another object of the present invention to provide a recording control device and a recording control method which reduce the occurrence of a feeling of rattling while reducing the load applied to the CPU in the execution of random dot control.

[0014]

A recording apparatus according to the present invention for achieving the above object has the following arrangement.
That is, a printing apparatus for forming a print image using a print head having a plurality of print elements for forming dots on a print medium, wherein a first storage for storing a random number generated in advance to specify a dot diameter to be printed. Means for storing pulse formation information for generating dots with a plurality of types of dot diameters and table information corresponding to the pulse formation information; and
Control means for setting table information to be a central value of a change in dot diameter according to temperature; a random number stored in the first storage means; and a center of change in the dot diameter set by the control means. An acquisition unit that acquires pulse forming information from the second storage unit based on table information to be set as a value; and a driving unit that drives the recording head based on the pulse forming information acquired by the acquisition unit. .

[0015] The recording control method according to the present invention for achieving the above object has the following configuration. That is,
A recording head having a plurality of recording elements for forming dots on a recording medium, first storage means for storing a random number generated in advance to specify a dot diameter to be recorded, and generating dots with a plurality of types of dot diameters Control method for forming a print image using pulse forming information for storing the information and table information corresponding to the pulse forming information, wherein each time a trigger pulse is input,
A control step of setting table information to be a center value of a change in dot diameter according to a temperature; a random number stored in the first storage means; and a center of change in the dot diameter set in the control step. wherein based on the table information to be a value
An acquisition step of acquiring pulse formation information from the second storage means ; and a recording step of driving the recording head based on the pulse formation information acquired in the acquisition step to form dots on a recording medium.

[0016]

[0017]

In the above arrangement, a random number for designating the dot diameter is stored in the first storage means. The second storage unit stores pulse formation information for generating dots with a plurality of types of dot diameters and table information corresponding to the pulse formation information. The control means sets, for each input of the trigger pulse, table information corresponding to the dot diameter to be used as the central value of the change in the dot diameter according to the temperature of the recording head. The stored random numbers are sequentially read out from the first storage means, and the pulse forming information for forming the corresponding dot diameter based on the random numbers and the table information set by the control means is stored in the second storage means.
And drive control of the recording head is performed according to the pulse forming information.

[0018]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

[Embodiment 1] In this embodiment, an ink jet system using thermal energy (hereinafter simply referred to as an ink jet system or an ink jet system) is adopted as a recording system. Hereinafter, the structure of the recording head using this method and the dot area modulation method will be described, and then the image forming method of this embodiment will be described.

(Inkjet Recording Apparatus) FIG. 1 is a schematic view of an inkjet recording apparatus IJRA to which the present invention can be applied. In the figure, a lead screw 5005 rotates via driving force transmission gears 5011 and 5009 in conjunction with forward / reverse rotation of a driving motor 5013. The carriage HC engaging with the spiral groove 5004 of the lead screw 5005 has a pin (not shown) and reciprocates in the directions of arrows a and b. An ink jet cartridge IJC is mounted on the carriage HC. 500
Reference numeral 2 denotes a paper pressing plate, which presses the paper against the platen 5000 in the moving direction of the carriage. 5007,50
Reference numeral 08 denotes a home position detecting means for confirming the presence of the carriage lever 5006 in this area and switching the rotation direction of the motor 5013.

Reference numeral 5016 denotes a member for supporting a cap member 5022 for capping the front surface of the recording head. Reference numeral 5015 denotes suction means for sucking the inside of the cap.
The suction recovery of the recording head is performed via 023. 5017
Reference numeral 5019 denotes a cleaning blade, which is a member that allows the blade to move in the front-rear direction.
These are supported by 18. It goes without saying that the blade is not limited to this form and a known cleaning blade can be applied to this example. Reference numeral 5012 denotes a lever for starting suction for recovery of suction. The lever 5012 moves with the movement of the cam 5020 engaging with the carriage, and the driving force from the drive motor is controlled by known transmission means such as clutch switching. Is done.

The capping, cleaning, and suction recovery are configured so that desired operations can be performed at the corresponding positions by the action of the lead screw 5005 when the carriage comes to the area on the home position side. If a desired operation is performed at a timing, any of the examples can be applied.

Next, a control configuration for executing the recording control of the above-described apparatus will be described with reference to a block diagram shown in FIG. In the figure showing the control circuit, 1700
Is an interface for inputting a recording signal, and 240 is a CP
U and 250 are ROMs for storing control programs and the like executed by the CPU 240, and 1703 is a dynamic ROM for storing various data (the above-mentioned recording signals and recording data supplied to the head). 200 is the recording head 1
Array 1700, CPU 240, RAM
Data transfer control between 1703 is also performed. Reference numeral 1710 denotes a carrier motor for transporting the recording head 1, and reference numeral 1709 denotes a transport motor for transporting the recording paper. Reference numeral 1705 denotes a head driver for driving the head, and reference numerals 1706 and 1707 denote motor drivers for driving the transport motor 1709 and the carrier motor 1710, respectively. Reference numeral 1720 denotes a printer control unit.

The operation of the above control configuration will be described. When a recording signal is input to the interface 1700, the gate array 2
The recording signal is converted between 00 and the CPU 240 into recording data for printing. Then, the motor driver 170
6 and 1707 are driven, and the head driver 17
The print head is driven in accordance with the print data sent to the printer 05, and printing is performed.

(Inkjet Recording Head) Next, the recording head 1 constituting the inkjet cartridge (IJC), that is, the inkjet recording head (IJU) will be described with reference to FIG. Inkjet recording head I
The JU is a recording head of a method of performing recording using an electrothermal converter that generates thermal energy for causing ink to cause film boiling according to an electric signal.

In FIG. 3, reference numeral 100 denotes an electrothermal transducer (discharge heater) arranged in a plurality of rows on a Si substrate, and an electric wiring such as Al (aluminum) for supplying electric power to the heater. Is a heater board formed by: 200
Is a wiring board for the heater board 100, and includes a wiring corresponding to the wiring of the heater board 100 (for example, connected by wire bonding) and a pad 201 located at an end of the wiring and receiving an electric signal from a main body position. Have.

Reference numeral 1300 denotes a grooved top plate provided with a partition for dividing a plurality of ink flow paths, a common liquid chamber, etc., and an ink receiving port 1500 for receiving ink supplied from the ink tank and introducing the ink into the common liquid chamber. An orifice plate 400 having a plurality of discharge ports is integrally formed. Polysulfone is preferred as these integral molding materials, but other molding resin materials may be used.

Reference numeral 300 denotes a support made of, for example, a metal for supporting the rear surface of the wiring board 200 on a plane, and serves as a bottom plate of the ink jet unit. Reference numeral 500 denotes an M-shaped pressing spring, which presses the common liquid chamber at the center of the M-shape, and presses a part of the liquid path by the front drooping part 501 by linear pressure. Heater board 1
00 and the top plate 1300, the foot of the spring is
By engaging with the back side of the support body 300 through the hole 3121 of No. 0, these are engaged with each other while sandwiching them, so that the urging force of the pressing spring 500 and the front sag portion 501 causes the heater board 100 And the top plate 1300 are fixed by crimping.

The support 300 also has a hole 320 through which an ink supply pipe 2200 through which ink can be supplied can penetrate. The attachment of the wiring board 200 to the support 300 is performed by sticking with an adhesive or the like. Also, this parallel groove 30
01 is formed in the ink conduit 1600 that is continuous with the ink supply pipe 2200 described above.
Is formed as a fixed cantilever on the supply pipe 2200 side,
A sealing pin 602 for securing a capillary phenomenon between the fixed side of the ink conduit and the ink supply pipe 2200 is inserted.
Since the ink supply member 600 is molded, not only is it inexpensive, has high positional accuracy, and does not eliminate a decrease in precision in forming and manufacturing, but also cantilever the conduit 1600 in mass production by the cantilever conduit 1600. The pressure contact state with the ink receiving port 1500 can be stabilized.

In this embodiment, a complete communication state can be reliably obtained only by pouring the sealing adhesive from the ink supply member side under this pressure contact state. Note that the ink supply member 600 is fixed to the support 300 by using a pin (not shown) on the back side of the ink supply member 600 with respect to the holes 1901 and 1902 of the support 300.
This can be easily performed by projecting through the via hole 902 and heat-sealing the portion of the support 300 projecting to the back surface side.

(Factors of Non-Uniformity between Nozzles) Five typical causes of non-uniformity in a print image in the above-described print head will be described below.

The first factor is a variation in the resistance value of the discharge heater. This variation in the resistance value is directly linked to the variation in the heat generation temperature when the ejection heater is driven. The variation in the heat generation temperature is a variation in the discharge energy, which affects the variation in the foaming length in the ink. The variation in the foaming length results in a variation in the ejection amount and the ejection speed. If an image is formed using a recording head having such a variation, the dot area and the dot shape vary, leading to unevenness in the recorded image.

The second factor is variation in the surface condition of the heater. Fine irregularities occur on the surface of the heater due to the difference in the degree of contamination by foreign matter or the like. The unevenness causes a variation in the foaming start point at the stage of the foaming start of the ink, that is, a variation in the foaming start time, and causes a difference in the dot shape and the like.

The third factor is a variation in the shape and diameter of the discharge port of the nozzle. The difference in the shape of the nozzle causes a variation in the ejection direction and the ejection amount, and causes unevenness on the image.

The fourth factor is a variation between the heater position and the nozzle position. These variations result in a difference between the impedance in the ejection direction and the impedance in the non-ejection direction when bubbles are bubbled. This difference in impedance results in a difference in conversion efficiency for converting thermal energy into discharge energy during the bubble bubbling, and induces a discharge amount and a discharge speed, thereby causing unevenness on an image.

The fifth factor is endurance fluctuation. The recording head causes a change in the wetting property and the energy conversion efficiency between the ink and the component parts constituting the nozzle according to the frequency of use. Such a change causes a difference in the ejection characteristics of each nozzle. That is, there is a time-dependent difference in the dot diameter, the landing position, and the like between the frequently used nozzles and the low-used nozzles.

It is a very difficult task to control and adjust at the time of manufacture or use in order to suppress the above-mentioned typical causes of image unevenness.

(Dot Area Modulation Method) An example of the dot area modulation means will be described below.

The dot area is determined by the amount of ink ejected. Further, the ejection amount can be changed by the foaming volume of the ink, and the foaming volume increases as the number of ink molecules that undergo phase transition by heat increases. As a drive to efficiently increase the number of molecules, a limit energy that does not cause bubbling in the ejection heater is given to the ink on the heater surface (pre-pulse), and a time (off time) in which the heat is diffused to other inks is set, thereby causing a phase transition. Increase the number of ink molecules that are liable to occur. Then, a method of increasing the number of ink molecules that cause phase transition by giving energy (main pulse) to the ink for the next ejection is adopted. In this method, the amount of ink ejected can be changed by changing the off-time to increase or decrease the number of ink molecules that are likely to cause phase transition. FIG. 4 is a diagram showing a correlation between the off time and the ejection amount. As shown in the figure, when the off time is lengthened, the ejection amount increases. FIG. 5 is a diagram for explaining the relationship between the timing between the main pulse and the pre-pulse and the diameter of the formed dot. (A) to (c) in FIG.
As shown in (1), the dot diameter can be controlled to be large (L), medium (M), and small (S) by changing the length of the off time.

In this embodiment, the dot area modulating means is used, but a dot area modulating means using a pre-pulse, an applied voltage, or a combination thereof may be used.

(Logic Configuration of Ink-Jet Recording Head Used in this Embodiment) The recording head used in this embodiment is an ink-jet recording head having a resolution of 360 DPI and having 128 nozzles. The 128 nozzles are allocated to one block every 16 nozzles, and the ejection control is performed for each block. Hereinafter, an outline of a logic configuration in a head chip in the recording head of the present embodiment will be described with reference to FIG. FIG. 6 is a block diagram showing a logical configuration in a head chip in the recording head of this embodiment.

To the logic circuit of the head chip 100, three kinds of signals for recording (recording data signal, block selection signal, heat signal) are inputted. Hereinafter, each signal and its function will be described.

The print data signal (DATA) is a signal for selecting the heater of the nozzle to be driven. The recording data signal DATA is transmitted to the shift register 1 in the head chip 100.
01 is serially input. Shift register 101
When the data for 128 nozzles corresponding to all the nozzles is stored, the data is output to the latch 102 in parallel in synchronization with a latch signal (not shown). The latch 102 has the number of nozzles (1
An image signal is output to each of the (28) distributed AND gates 104.

Block selection signals (BENB1-BENB)
(3 bits of 3) is a signal for designating which block of the heater is to be driven. As described above, this recording head has 128 nozzles, and has an eight-block configuration for every 16 nozzles. Then, drive control is performed in time series for each block. Therefore, a function of selecting blocks (16 nozzles) to be simultaneously driven in a time-series manner is required. A 3-bit block selection signal for selecting eight blocks is input to the decoder 103.
The decoder 103 decodes the block selection signal, and
The corresponding signal among the eight signals from to B8 is turned on. Since the block division of this recording head is divided into 16 nozzles from the top, the B1 signal is connected to 16 AND gates from nozzle 1 to nozzle 16, and the B2 signal is 16 nozzles from nozzle 17 to nozzle 32 Are connected in the same manner.

The heat signals (16 signals H1 to H16) are signals for determining the drive time of each discharge heater 105. Sixteen signal lines corresponding to the number of nozzles in one block are arranged (however, four signal lines are omitted in the figure). The heat signal lines are connected every 16 lines from the upper part of the nozzle. That is, the first heat signal line H1 is connected to the AND gates 104-1, 17, 33,..., And H2 is connected to the AND gates 104-2, 18, 3.
4,..., H16 are AND gates 104-16, 32,
.. 128 are respectively connected.

As can be seen from FIG. 6, the discharge heater 105-1 of the nozzle 1 is turned on because the nozzle 105-
1, the data signal L1, the block selection signal B1, and the heat signal H1, which are connected to the AND gate 104-1.
The three signals are turned on.

(Random dot diameter modulation means for improving image quality) The dot diameter modulation means is performed by modulating the pulse width of heat as described above. That is, the pulse pattern of the heat pulse (single pulse, double pulse, etc.) and the heat signal lines H1 to H1 for controlling the pulse width are controlled.
6 (FIG. 6), random pulse diameter control is realized by randomly controlling the pulse signal for each heat dot. The details of the random dot diameter control will be described below with reference to FIG. FIG. 7 is a block diagram showing a control configuration for realizing random dot control.

In FIG. 7, reference numeral 240 denotes the CP of the recording apparatus.
U, and data is transferred from the address specified by the address bus indicated by the solid arrow in the drawing via the data bus indicated by the broken arrow in the drawing. Here, the minimum recording cycle of the recording apparatus is 6 KHz, and the 128 nozzles are divided into eight blocks every 16 nozzles and drive-controlled. The block interval is 10 μs. When printing, CP
U240 applies a 6 KHz trigger pulse to the gate array 200
Transfer to Upon receiving this trigger pulse, the gate array 200 is controlled to input the signal to the recording head so that the block selection signal is turned on at block intervals of 10 μs.

At this time, a data signal (DATA) for selecting a nozzle to be driven is inputted in advance from the data signal line to the shift register 101 of the recording head. Are latched, and the print data that has already been latched is input to each AND gate 104 connected to each discharge heater. In this way, the block to be selected and the nozzle to be turned on (driven) in the block are determined. In this state, by inputting the heat signals (H1 to H16) for determining the heat conditions to the print head, energy is applied to the discharge heater of each nozzle.

The gate array 200 includes a register group 210 for setting various conditions and a PWM table 228. The register group 210 stores a basic drive table NO. Setting register 227, H for storing the pulse pattern of each heat signal
1 to H16 table NO. Setting registers 211 to 226
There is. Further, in the PWM table 228, various pulse patterns having different ejection amounts are registered.

In the first embodiment, the dot diameter of the ink to be ejected is randomly modulated in order to improve the image quality, and is applied to the ejection heater in order to minimize the total control time for the randomization. The determination control of the heat pattern for determining the energy will be described with reference to FIG. FIG. 8 is a flowchart illustrating a procedure for determining a heat pattern according to the first embodiment.

First, when the trigger pulse generated every 6 KHz is input to the gate array 200, the gate array 2
The basic drive pulse at that time is set to 00 (steps S11 and S12). In the present embodiment, the optimum basic drive pulse is determined by the CPU according to the temperature of the printhead.
240, the basic drive table NO. It is stored in the setting register 227. The basic drive pulse may be set to a fixed value by the recording head. The basic drive table NO. The setting register 227 does not store the ON / OFF pulse width itself, but a PWM table 228 in which various pulse patterns are registered in advance.
Is stored.

In the PWM table 228, 16 types of pulses from table numbers 1 to 16 are registered, and pulses are set such that the smaller the table number, the smaller the discharge amount. Specifically, the set value is such that if the table number is different by one, the ejection amount is increased or decreased by 1 ng. For example, immediately after high-duty printing is performed continuously, the temperature of the recording head is raised, so that the ejection amount becomes large. To correct this, the CPU 240 sets a basic drive pulse so as to reduce the ejection amount.

In addition, various correction control of the ejection amount according to the temperature of the recording head has been developed in addition to the above, and in this embodiment, any correction means may be used. Further, a recording head in which the correction control is not performed may be used.

Next, a description will be given of a method of setting heat conditions to be applied to each heat signal. The heating conditions to be applied to each heat signal, that is, the ejection amount of each nozzle are set to drive pulses that vary on average with respect to the ejection amount when driven by the basic drive pulse. As described above, the PWM table 228 is set so that the ejection amount is modulated at equal intervals. Setting register 22
It is only necessary to apply a pulse to each heat signal line by moving the table number back and forth with a uniform occurrence probability with respect to the table number set to 7. In order to cause the corresponding basic table number to be evenly shifted back and forth, it is possible to generate a random number centering on zero, add the random number to the relevant basic table number, and generate a heat signal to each heat signal line.

Here, since the recording head has 128 nozzles and is driven at 6 KHz, it must repeat at least 128 random number generation calculations and 128 PWM value settings within 166 μs. . Normally, the CPU has both a function of controlling the printer engine, such as an interrupt process for heating and an interrupt process for driving the motor during printing, and a function as a controller for analyzing a print command and expanding the print command into recording data. Is processed in time division. With the recent increase in the speed of recording apparatuses, the amount of processing per unit time of the CPU has increased dramatically.

If the processing overflows during printing in which processing is concentrated on the CPU most, the engine function cannot be neglected because the recording apparatus is operating.
Therefore, the division processing is controlled so that the controller function is temporarily stopped and the recording apparatus does not malfunction. However, stopping the controller function is to temporarily suspend the development of the print data of the next line. Therefore,
After the line is printed, the operation of the recording apparatus waits until the development of the next line print data is completed. Therefore, even if the printing speed per line is extremely high,
There was a problem that the printing time per page was not so fast.

It is obvious that the recording apparatus will be further speeded up in the future, and how to speed up the basic function of the recording apparatus and how to reduce the CPU occupation rate in the additional processing will be described. This can be said to be one of the most important issues in responding to future high speeds.

Random dot control that modulates the dot diameter for each print dot is effective in improving image quality. However, by analogy with the future development of recording apparatuses, it is easily assumed that it is difficult to realize random dot control due to processing time restrictions. In this embodiment, as described below, the processing time of the random dot control is reduced.

In the random dot control according to the first embodiment, random numbers for randomly modulating the dot diameter are calculated in advance, and stored in the RAM 230 in the form of a table (random number table 231). Then, a random value is extracted from the RAM 230 to the gate array as needed (step S13).
Note that the extraction of the random value is achieved by a DMA (Direct Memory Access) function of the gate array 200. In the normal random dot control, the random number value must be further processed to generate a heat pulse. In this embodiment, the heat pulse is generated using the PWM table 228 provided in the gate array 200. The PWM table 228 is set so that the discharge amount changes by a fixed amount for each table number.
By adding the random number value drawn from the random number table 231 to the basic drive table number preset by the CPU 240, the table NO. Is obtained, and random dot diameter control can be performed (step S14). Then, step S14
Table NO. The PWM table 228
To generate a heat pulse (step S15).

In this embodiment, the random number table is 0
It is a numerical table randomized between ± 3 with the center as the center. That is, control is performed such that the dot diameter is randomly modulated with a modulation width of ± 3 ng of the ejection amount around the basic drive pulse that provides the optimum ejection amount in the state of the recording head in consideration of the current temperature rise and the like. . Further, as described above, since the configuration of the recording head is a 16-nozzle configuration per block, it is necessary to read 16 random numbers to print one block.

Since the width of the random number in the first embodiment is ± 3 and the range is 7 as described above, one random value is stored in 3 bits. Therefore, a value of 48 bits (3 bits × 16 nozzles) per block printing, that is, a value of 3 words is extracted. Here, if the CPU 240 used in the present embodiment is, for example, a 16-bit CPU, three accesses make
It is possible to obtain random numbers for the nozzles. Further, the gate array 200 has a function of accessing the RAM 230 while the gate array 200 itself creates necessary addresses while the CPU 240 accesses the ROM 250. Therefore, the occupancy of the CPU required to pull out the random numbers onto the gate array can be set to substantially zero. Further, after the random number value is input to the gate array 200, the pulse to be applied to the heat signal line can be set only by the easy addition processing as described above. In this manner, random dot diameter modulation control can be performed with extremely little processing.

The random number table may be a sequence table of numerical values having no regularity, or may have a periodicity within a range in which the printed matter subjected to the present control does not have a visually incongruent periodicity. It may be a random number table.

In this embodiment, the random number table stored in the ROM 250 is developed in the RAM 230 for control, but the present invention is not limited to this. For example, a random number table is provided in the ROM 250 in advance, and the gate array 200
May be configured to directly access the ROM 250.

In this embodiment, the PWM table 228 is set so that the discharge amount is modulated at equal intervals.
The setting is not necessarily limited to equal intervals, and may be, for example, a setting that increases proportionately, or a setting that has an increasing tendency with less rigor within a range that does not cause discomfort.

According to the first embodiment, the random number table 23 for holding the random numbers obtained in advance in the form of a table.
1. While using a PWM table 228 that holds a drive pulse pattern in the form of a table in advance, the gate array 200 creates an address for accessing the random number table 230 and obtains data of the random number table 230 without passing through the CPU 240. (DMA) function. Further, the random number value and the basic drive table NO. Is also performed in the gate array 200. Therefore, the CPU 240 sets the basic drive table NO. Of the table No. to be used for each heat signal only by setting That is, a randomized heat pulse is obtained. As described above, in realizing the random dot control, the load applied to the CPU is significantly reduced.

As described above, according to the first embodiment, an increase in processing capacity, which is an adverse effect of random dot control, while maintaining the effect of reducing density unevenness such as white streaks and black streaks of a recorded image, that is, It is possible to reduce an increase in the load on the CPU.

In the above embodiment, the dot diameter is modulated for each nozzle in each block. However, the dot diameter may be modulated in block units or in units of one row of recording heads (column units). Good. However, when the dot diameter is modulated for each nozzle in the same block as in the present embodiment, deterioration of a recorded image (for example, a sense of discomfort due to regularity in texture) can be reduced. FIG.
FIG. 7 is a schematic diagram showing a result of executing the above irregular dot diameter modulation on a column basis. On the other hand, FIG. 17 is a schematic diagram illustrating a result of executing dot diameter modulation for each nozzle according to the present embodiment. As can be seen from FIGS. 16 and 17, it is understood that the image obtained by performing the dot diameter modulation for each dot has a more uniform image and improved image quality than the case where the dot diameter modulation is performed for each column. .

[Embodiment 2] Next, a description will be given of a recording apparatus for further improving the image quality in the random dot control of the embodiment 1.

In the first embodiment, one random number table is used as the dot diameter modulation means. In the second embodiment, a plurality of random number tables are used. In the first embodiment, by calculating the random numbers in advance and storing them in a table, the processing time is significantly reduced as compared with the case where the random numbers are calculated every time. However, periodicity caused by repeatedly using this random number table appears in a recorded image, which may cause unevenness. To solve this problem, it can be improved by making the memory for storing the random number table large enough, but it is often difficult to implement such measures because of the cost (see one example). For example, in order for a recording device having a resolution of 360 DPI to have a random number of 5 lines as 3 bits of one information as in the above, a memory capacity of about 2.6 M bits is required.)

The second embodiment solves the above-mentioned problem, and solves the above-mentioned regularity by randomly selecting and using a plurality of random number tables. To give a specific example, a 200K-bit random number table (a resolution of 360 DPI and a recording apparatus of 3 bits of information, about 4/1
(Corresponding to a random number value of 0 line), and the five random number tables are randomly selected and used.

By performing control as described above, the periodicity of the random number table can be theoretically eliminated. As a result, even if the above random control is executed by the random number table generating means having a small control load, it is possible to suppress the occurrence of periodic unevenness in the recorded image, to improve the quality of the output image, and to greatly increase the processing speed and the memory capacity. It is possible to realize a recording apparatus in which the adverse effect of the increase is suppressed.

The random dot control in the second embodiment will be described with reference to FIG. FIG. 9 is a block diagram illustrating a control configuration for implementing random dot control according to the second embodiment. In FIG. 9, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will not be repeated. Further, similarly to the first embodiment, a configuration is provided for randomly modulating the dot diameter of the ejected ink in order to improve the image quality, and for minimizing the total control time for the randomization. The configuration for shortening the time of the random dot control is the same as in the first embodiment. That is, it includes a random number table that holds a table of previously calculated random number values and holds the same, and a PWM table that holds drive pulse patterns in a table format in advance. In the pulse pattern set in the PWM table, the ejection amount is set for each predetermined change amount. Also, the gate array has a DMA function for creating an address for accessing the random number table and acquiring random number data without going through the CPU.

In the second embodiment, a plurality of random number tables 232-1 to 232-n are stored in the RAM 230. Reference numeral 229 denotes a random number table designation register, which stores information on which of the random number tables stored in the RAM 230 is to be used.

FIG. 10 is a flowchart showing a characteristic procedure of the random dot control of the second embodiment, and shows a process executed between steps S12 and S13 of the flowchart of the first embodiment. That is, in step S21, it is determined whether it is time to switch the random number table. If it is time to switch, the process proceeds to step S22, and the random number table to be used is switched. As an example of a method of randomly selecting a random number table, the CPU 240 or the gate array 200 may be switched at the timing of switching the random number table (for example, the timing at which the currently used random number table ends).
A random number for selecting a random number table, and storing the result in a random number table designation register 229. Also in this case, with the setting according to the present embodiment, the calculation is performed once every hundred and several tens of msec.
It does not impose a large processing load. Alternatively, a random number table selection table for randomly selecting a random number table may be prepared, and information on the next random number table to be selected from the random number table selection table may be obtained at the timing when the random number table is changed.

As described above, by providing a plurality of random number tables and randomly selecting and using the plurality of random number tables, it is possible to further reduce density unevenness such as white streaks and black streaks of a recorded image. It is possible to realize a recording apparatus having an effect and suppressing an increase in processing time and an increase in required memory capacity, which are adverse effects of random dot control.

The configuration and control other than the random number table selection means are the same as those of the above-described embodiment, and a detailed description thereof will be omitted.

[Embodiment 3] In Embodiment 3, a configuration for controlling a modulation width of a dot diameter to be randomized in random dot control will be described.

In the above embodiments, the modulation width of the randomized dot diameter is fixed by the recording apparatus. However, as described above, in the case of random dot control, an image may have a feeling of roughness. Also, this feeling of roughness has the property of increasing almost in proportion to the modulation width of the randomized dot diameter. Conversely, it has been found that the feeling of [white streaks] and [black streaks] in the image decreases in inverse proportion to the modulation width. Therefore, the modulation width of the dot diameter in the randomization is set to the maximum modulation width at a level at which a normal feeling of roughness is not considered. However, the feeling of rattling is greatly affected by the user's preference, and some users do not mind the feeling of rattling, and there are rarely users who are sensitive to disgust.

The third embodiment eliminates the difference in the user's preference. The control configuration in the third embodiment is the same as that in the second embodiment, and thus the description is omitted here. However, the plurality of random number tables have different levels of variation, and the random number tables are configured such that the modulation width of the dot diameter is regulated according to the selected random number table. Further, the random number table designation register stores information for designating a random number table determined to be used based on the set modulation width.

As a specific example, the third embodiment has five types of random number tables, and the variation range of each random number is ± 1, ± 2, ± 3, ± 4, ± 5. It is configured as follows. That is, the values of 0, 1, and 2 are randomly arranged in the random number table having a variation range of ± 1. Here, the PWM selected by the center value 1
The table number is a PWM table number stored in the basic drive table number setting register, and its drive signal is applied. If the value is 0, the basic drive table number is reduced by 1, and the drive is performed under the condition of the PWM table that is one unit less. Conversely, with random number 2, the basic drive table number is increased by one, and drive is performed under the condition of a PWM table that is one unit larger.

By configuring so that the optimum table can be selected from the random number tables configured as described above, the optimum variation range depending on the user's preference and the type of output image can be controlled to a desired range. Becomes possible.

FIG. 11 is a flowchart showing a characteristic procedure of the random dot control of the third embodiment, and shows a procedure executed between steps S12 and S13 in the flowchart of FIG. In step S31, a random number table to be used is determined with reference to the random number table designation register 229.

As a method of setting a desired random number variation range, a setting by a command from an external device such as a host computer, a setting by a switch such as a panel switch or a dip switch, or a recording device by a combination of these methods It should just be able to communicate to. Means for transmitting information to the recording device is a very rudimentary known technique, and a detailed description thereof will be omitted.

The configuration and control other than the selection control means for the desired random number table are the same as those of the above-described embodiment, so that the detailed description will be omitted.

As described above, according to the third embodiment, the modulation width of the dot diameter in the random dot control can be set. For this reason, the modulation width of the dot diameter can be designated according to individual differences in the feeling of the roughness, the degree of conspicuousness of the roughness depending on the image, and the like, and the roughness can be suppressed efficiently.

The present invention brings about an excellent effect particularly in an ink jet recording head and a recording apparatus in which a flying droplet is formed by utilizing thermal energy and recording is performed among the ink jet recording methods.

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 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 the nucleate boiling to an electrothermal transducer arranged corresponding to the sheet or the liquid path holding the Since thermal energy is generated in the electrothermal transducer and film boiling occurs on the heat-acting surface of the recording head, bubbles in the liquid (ink) corresponding to this drive signal on a one-to-one basis can be formed. It is valid. By discharging the liquid (ink) through the discharge opening by the growth and contraction of the bubble, at least one droplet is formed. 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.

As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. When the conditions described in US Pat. No. 4,313,124 of the invention relating to the temperature rise rate of the heat acting surface are adopted, excellent recording can be performed.

The configuration of the recording head is not limited to the combination of a discharge port, a liquid path, and an electrothermal converter (a linear liquid flow path or a right-angled liquid flow path) as disclosed in the above-mentioned specifications. A configuration using U.S. Pat. No. 4,558,333 or U.S. Pat. No. 4,459,600 which discloses a configuration in which the heat acting surface is arranged in a bent region may be used.

In addition, JP-A-59-123670 which discloses a configuration in which a common slit is used as a discharge portion of an electrothermal converter for a plurality of electrothermal converters or absorbs pressure waves of thermal energy. A configuration based on JP-A-59-138461, which discloses a configuration in which an opening corresponds to a discharge unit, may also be employed.

Further, as a full-line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by the recording apparatus, the length is determined by a combination of a plurality of recording heads as disclosed in the above specification. This may be either a configuration satisfying the above requirements or a configuration as a single recording head formed integrally.

In addition, the print head is replaceable with a print head of a replaceable chip type, which can be electrically connected to the main body of the apparatus or supplied with ink from the main body of the apparatus, or is integrated with the print head itself. Alternatively, a cartridge type recording head provided with an ink tank may be used.

It is preferable to add recovery means for the printhead, preliminary auxiliary means, and the like provided as components of the printing apparatus of the present invention since the effects of the present invention can be further stabilized. . If these are specifically mentioned, capping means for the recording head, cleaning means, pressurizing or suction means, preheating means using an electrothermal transducer or another heating element or a combination thereof, and printing Performing a preliminary ejection mode for performing another ejection is also effective for performing stable printing.

Further, the printing mode of the printing apparatus is not limited to the printing mode of only the mainstream color such as black, but may be a single printing head or a combination of a plurality of printing heads. Alternatively, the apparatus may be provided with at least one of full colors by color mixture.

In the embodiments of the present invention described above, the ink is described as a liquid. However, an ink which solidifies at room temperature or below and which softens at room temperature, or which is liquid, In general, in the ink jet system, the temperature of the ink itself is controlled within a range of 30 ° C. or more and 70 ° C. or less to control the temperature so that the viscosity of the ink is in a stable ejection range. It is sufficient if the ink is in a liquid state.

In addition, the temperature rise due to thermal energy can be positively prevented by using it as energy for changing the state of the ink from a solid state to a liquid state, or solidified in a standing state for the purpose of preventing evaporation of the ink. Either ink may be used, or in any case, the ink may be liquefied by application of heat energy according to the recording signal and ejected as a liquid ink, or may already start to solidify when reaching the recording medium. The use of an ink having a property of being liquefied for the first time by thermal energy is also applicable to the present invention. In such a case, the ink is disclosed in JP-A-54-5684.
No. 7 or Japanese Patent Application Laid-Open No. 60-71260, in which the porous sheet is opposed to the electrothermal converter while being held in a liquid or solid state in the concave portions or through holes of the porous sheet. It may be. In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

In addition to the above, the recording apparatus according to the present invention may be provided as a single or separate image output terminal of an information processing apparatus such as a word processor or a computer, a copying apparatus combined with a reader, and the like. May take the form of a facsimile machine having a transmission / reception function.

In each of the embodiments described above, the recording head of the ink jet system using thermal energy has been described. However, the present invention can be applied to a recording apparatus of another ink jet system or a thermal transfer system. In particular, in the thermal transfer method, the “size of recording dots” in each of the above embodiments is “density of recording dots”, but the basic operations and effects are the same as those of the ink jet method.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of one device. In addition, it is needless to say that the present invention can be applied to a case where the present invention is achieved by supplying a system or an apparatus with a program for executing the processing specified by the present invention.

[0101]

As described above, according to the present invention,
It is possible to reduce the load applied to the CPU in performing the random dot control.

Furthermore, according to another configuration, it is possible to reduce the load applied to the CPU in the execution of the random dot control and to reduce the feeling of roughness caused by the random dot control.

[0103]

[Brief description of the drawings]

FIG. 1 is an inkjet recording apparatus I to which the present invention can be applied.
FIG. 2 is a schematic view of JRA.

FIG. 2 is a block diagram illustrating a control configuration for executing printing control of the printing apparatus of FIG.

FIG. 3 is a diagram illustrating a configuration of an inkjet recording head.

FIG. 4 is a diagram showing a correlation between an off time and a discharge amount.

FIG. 5 is a diagram illustrating the relationship between the timing between a main pulse and a pre-pulse and the diameter of a formed dot.

FIG. 6 is a block diagram illustrating a logical configuration in a head chip in the recording head of the present embodiment.

FIG. 7 is a block diagram showing a control configuration for realizing random dot control.

FIG. 8 is a flowchart illustrating a procedure for determining a heat pattern according to the first embodiment.

FIG. 9 is a block diagram illustrating a control configuration for realizing random dot control according to a second embodiment.

FIG. 10 is a flowchart illustrating a characteristic procedure of random dot control according to the second embodiment.

FIG. 11 is a flowchart illustrating a characteristic procedure of random dot control in the third embodiment.

FIG. 12 is a diagram illustrating an image forming operation performed by a recording head in which a plurality of image forming elements are arranged.

FIG. 13 is a diagram illustrating a 50% halftone print image when printing is performed with dots having a uniform area and accurate positions.

FIG. 14 is a diagram illustrating an example of a 50% halftone print image when dots formed by print elements vary in size.

FIG. 15 is a diagram illustrating an example of a 50% halftone print image when dots are formed at different positions.

FIG. 16 is a schematic diagram of a recorded image when irregular dot diameter modulation is performed for each column.

FIG. 17 is a schematic diagram of a recorded image when irregular dot diameter modulation is performed for each nozzle.

[Explanation of symbols]

 200 Gate Array 210 Register Group 228 PWM Table 230 RAM 231 Random Number Table 240 CPU 250 ROM

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kiichiro Takahashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Osamu Iwasaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Daigoro Kanematsu 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 2/52 B41J 2/205 B41J 2/51

Claims (12)

(57) [Claims] 1. A printing apparatus for forming a print image using a print head having a plurality of print elements for forming dots on a print medium, wherein a random number generated in advance to specify a dot diameter to be printed is stored. First storage means; second storage means for storing pulse formation information for generating dots with a plurality of types of dot diameters and table information corresponding to the pulse formation information; Control means for setting table information to be the central value of the change in dot diameter according to the temperature of the recording head; random numbers stored in the first storage means; Acquiring means for acquiring pulse forming information from the second storage means based on table information to be a center value of a change; and acquiring the pulse forming information based on the pulse forming information acquired by the acquiring means. Recording apparatus comprising: a driving means for driving the recording head. 2. The recording apparatus according to claim 1, wherein the second storage unit has a plurality of pieces of the pulse forming information. 3. The recording head forms dots by discharging ink from the plurality of recording elements, and the pulse formation information stored in the second storage means controls the discharge amount of the recording elements. 2. The recording apparatus according to claim 1, wherein the information is information to be recorded. 4. The recording apparatus according to claim 1, wherein the acquisition unit acquires the pulse forming information corresponding to each of the plurality of recording elements. 5. The method according to claim 1, wherein the first storing means has a plurality of random number tables storing a plurality of random numbers generated in advance, and the control means has a selecting means for selecting one of the plurality of random number tables. The recording device according to claim 1, wherein 6. The method according to claim 1, wherein the selection unit has a selection table for storing selection information for randomly selecting the random number table, and selects the random number table based on the selection information. The recording device according to claim 5, wherein 7. The method according to claim 5 , wherein the selection unit selects the random number table when all the random numbers stored in the random number table are read by the acquisition unit. Recording device. 8. The control unit selects one of the plurality of random number tables included in the first storage unit based on a change unit specified by the change unit specified by the change unit. 6. The recording apparatus according to claim 5 , further comprising a selection unit that performs the selection. 9. The recording head according to claim 1, wherein the recording head is an inkjet recording head that performs recording by discharging ink.
9. The recording device according to any one of 8 . 10. The recording head, which ejects ink by using thermal energy, is an ink jet recording head including a thermal energy converter for generating thermal energy to be applied to the ink. Term
10. The recording device according to 9 . 11. The recording head according to claim 10 , wherein a state change is caused in the ink by thermal energy applied by the thermal energy converter, and the ink is ejected from an ejection port based on the state change. The recording device according to any one of the preceding claims. 12. A recording head having a plurality of recording elements for forming dots on a recording medium, first storage means for storing a random number generated in advance for designating a dot diameter to be recorded, and a plurality of types of dot diameters. A recording control method of forming a recording image using pulse forming information for generating dots by using a second storage unit for storing table information corresponding to the pulse forming information, the method comprising: A control step of setting table information to be a center value of a change in dot diameter according to the temperature of the recording head; a random number stored in the first storage means; and the dot set in the control step. and acquisition step of acquiring a pulse forming information from the second storing means based on the center value and the table information to be changes in diameter, to the pulse forming information acquired in said acquisition step Recording control method characterized by comprising a recording step of forming dots on a recording medium by driving the recording head Zui.