JPH0441252A - Image formation device - Google Patents

Abstract

PURPOSE:To record images always favorably by forming first and second dots by driving first and second record heads and controlling driving means such that formation states of the first and second dots coincide with a reference dot state. CONSTITUTION:A CPU 101 constituting a main controlling section controls each section following a procedure. A ROM 102 stores programs and other fixed data corresponding to the procedure. A RAM 219 comprises a temporary retention area of image data and a working area used in process of various controls. A designation input section 106 gives command inputs for an online switch relating to a host device, starting of a recording, and recording of a test pattern for correcting a dot deviation. When the designation input section 106 activates a record dot position correction, the test pattern is printed. The dot record state of each head is corrected to an optimum reference dot state based on a test pattern image obtained by driving each head under a condition corresponding to the reference dot state, so that a printing can be performed on more appropriate record dot position preventing color deviation and degradation of resolution.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to an image forming apparatus such as a color image recording apparatus that forms an image using a plurality of recording heads. The present invention relates to a color inkjet recording device that forms a color inkjet recording device.

[Prior art 1] Conventionally, in this type of device, for example, an inkjet recording device, ink is ejected from a plurality of ink ejection ports formed in a print head based on a data signal, and ink droplets are attached to a print medium to perform printing. It is carried out. This recording method is becoming widely used in, for example, printers, facsimile machines, and copying machines.

Like other systems, inkjet printing devices have a print head mounted on a carriage that moves along the print medium, and print line by line by scanning in the width direction of the print medium. There are a serial type and a line type in which printing is performed using a so-called full multi-head in which ink ejection ports for one line are arranged in a print head.

Incidentally, in recent years in serial printers, the recording head body or the cartridge, which integrates the recording head body and the ink tank that serves as the ink supply source, can be replaced in the event of a malfunction by the recording device user or when there is no remaining ink. The number of people who do this is increasing.

[Problems to be Solved by the Invention] However, in the conventional recording apparatus described above, when the recording head or cartridge is replaced, the position of the recorded dots of each color deviates from the ideal position due to the manufacturing precision of the apparatus main body and the recording head. However, there was a problem in that the quality of the recorded image deteriorated due to color shift or a decrease in resolution.

To prevent this, after replacing the head, the user records an image that allows the recording dot positions of each color to be determined, and while viewing the image, adjust the head fixing position so that the recording dots are printed at the optimal position. The recording dot position has been corrected manually or by changing the ink ejection timing electrically by switching an external selection switch.

However, this method is extremely time consuming, and the higher the resolution of the recording apparatus, the more difficult it becomes for the user to visually determine the optimal recording dot position.

Of course, changes in the landing accuracy etc. may occur due to changes over time, etc., so such problems can be solved by fixed recording heads that are not subject to replacement, full multi-type recording discs, and even other types other than inkjet systems. This also occurs in recording heads based on this method.

SUMMARY OF THE INVENTION An object of the present invention is to solve such problems and provide an image forming apparatus that can always record good images.

[Means for Solving the Problems] To this end, the present invention provides an image apparatus that forms an image according to an image signal using a plurality of recording heads. a driving means for driving the first and second recording heads to form the first and second dots under driving conditions corresponding to the reference dots; and a control means for controlling the driving means so as to match the state.

By correcting the state (for example, the state in which the first and second dots are struck at the same position), printing can be performed at a more optimal recording dot position without the user having to make manual corrections. This makes it possible to prevent color shift and resolution degradation and improve print quality.

(Hereinafter referred to as a margin) [Function] According to the present invention, in an image forming apparatus that forms an image by ejecting ink from a plurality of recording heads according to an image density signal, each head is placed in a reference dot state (for example, the first dot state).
Based on the test pattern image obtained by driving under the conditions corresponding to the state in which the second dots match), the dot recording state (for example, the recorded dot position) of each head is determined to the optimal reference dot shape [Example] The following is a drawing. Examples of the present invention will be described in detail with reference to FIG.

FIG. 1 shows the main structure of a serial printer type color inkjet recording apparatus according to an embodiment of the present invention. A recording head la that discharges yellow Y color ink, a recording head 1b that discharges magenta M color ink, a recording head IC1 that discharges cyan C color ink, and black B.
Recording heads 1d that eject color ink of color k are installed on the carriage 2 at distances apart as shown in FIG. Note that FIG. 2 is a plan view of the ejection ports 8 of each recording head viewed from the front, and they are arranged side by side for Bk, C, M, and Y from the left. An element (for example, an electrothermal converter) that generates energy (for example, thermal energy) used for ink discharge is arranged in the liquid path inside each discharge port.

In FIG. 1, the carriage 2 moves left and right along the guide shaft 3 at a speed of . Further, the recording medium 4 is kept parallel to the ink ejection orifice forming surface of the recording head by a pair of transport rollers 5 installed above and below. And black Bk, cyan C.

Ink droplets of magenta M and yellow Y are deposited on the recording medium 4 in this order, forming a multicolor image. Reference numeral 6 denotes an encoder, which is read by an optical sensor provided in the carriage 2, and controls the ink ejection timing according to the scanning position of the recording head. Numeral 7 is a reflective optical sensor mounted on the carriage 2 like the recording head, and is used to detect the position of a recording dot.

Reference numeral 10 denotes a recovery device, which includes a cap that is placed at the home position of the recording heads 1a to 1d and can cover the ejection port forming surface of the head, and a pump that is placed behind the cap.
Alternatively, it may further include a member for cleaning the discharge port forming surface. Using such a recovery device,
For example, the following recovery process for stabilizing the ejection state can be performed. That is, if dust or air bubbles enter the liquid path inside the ejection port, or if the ink in the liquid path thickens and becomes unsuitable for ejection, the cap is brought into contact with the recording head. By applying a suction force using the pump, the ink is forcibly discharged from the ejection port, and the cause of the ejection failure can be removed together with the ink. Further, ink ejection (preliminary ejection) can also be performed by driving the print head in the same manner as during normal driving with the cap facing the print head. Further, after these treatments, the discharge port forming surface can be cleaned by engaging the cleaning member with the discharge port forming surface. In addition, by keeping a cap in contact with the ejection port forming surface during non-recording, the ejection port formation surface can be protected.

Next, the control system of this example device will be explained.

FIG. 3 shows an example of the configuration of the control system. Here, H is a host device that supplies image data and various commands related to recording to the apparatus of this example, and has the form of a computer, image league, or other form. Reference numeral 101 denotes a CPU that constitutes the main control section of the apparatus of this example, and has the form of a microcomputer, and controls each section according to processing procedures etc. to be described later. 102
219 is a ROM that stores programs and other fixed data corresponding to the processing procedure, and 219 is a RAM that has a temporary storage area for image data and an area used for work in various control processes.

106 is an online switch with the host device.

This is an instruction input unit for inputting commands such as manual command to start recording, test pattern recording for dot misalignment correction, and the like. Sensors 108 detect the presence or absence of a recording medium, its conveyance state, the presence or absence of a remaining amount of ink, and other operating states.

Reference numeral 110 denotes a display unit, which is used to notify the operating status and setting status of the device, and whether or not an abnormality has occurred. 111 performs logarithmic transformation, masking, L
This is an image processing unit for performing ICR and color balance adjustment.

Reference numeral 112 denotes a head driver for driving the ink ejection energy generating elements of the recording head 1 (the above-mentioned heads 18 to 1d are collectively shown). Reference numeral 120 denotes a head control section which will be described later with reference to FIG. Reference numeral 113 denotes a temperature adjustment section for adjusting the temperature of the recording head 1, and specifically, it can include, for example, a heating heater and a cooling fan provided for the head 1. 111 is a drive mechanism of the recovery device; 115 is a mechanism including a motor for scanning the print head and reading unit; and 116 is a drive unit for the motor that drives the print medium conveyance system.

FIG. 4 shows an example of the configuration of the head control section 120.

Here, lla is a print head and driver that ejects yellow Y color ink, llb is a print head and driver that ejects magenta M color ink, llc is a print head and driver that ejects cyan C color ink, and l
id is a print head and driver that ejects black Bk color ink.

12a, 12b, 12c and 12d are yellow Y, magenta M, cyan C and black B, respectively.
The image density signals 14a, 14b, 14c and 14d of k are yellow Y, respectively, which are binarized by the binarization processing section 13.

These are magenta M, cyan C, and black Bk signals.

15a, 15b, 15c and 15d are buffers for controlling ink ejection timing. 17a
, 17b.

17c and 17d are shift registers 16a, 16b
, yellow Y, which is distributed by 16c and 16d to elements for ejecting ink from each recording head;
These are magenta M, cyan C, and black Bk signals. In addition, shift registers 16a, 16b, 1[)C
, 16d, the number of stages of each shift register is the same as the number of heads. 18 is a recording dot position detection circuit, and the ejection timing is controlled by the ejection timing setting/control circuit 19 based on a signal from this circuit.

An outline of the correction method in this example is shown below.

When recording dot position correction is activated by the instruction input section 106 of the apparatus, a test pattern shown in FIG. 5 is printed. The test pattern is printed in combinations of Bk+C, Bk+M, and Bk+Y, with the black Bk recording dot position as a reference. Here, the case of Bk+C is shown.

FIG. 5(A) shows the case where the recorded dot positions of black Bk and cyan C completely match, and FIG. 5(B) shows the case where the ejection timing of cyan C is later than that of black Bk, and the ejection timing of cyan C is slower than that of black Bk. This shows a case in which there is a deviation in the position of the recorded dots, and FIG. 5C shows a case in which the ejection timing of cyan C is faster than that of black Bk, and a deviation occurs in the positions of the two recorded dots.

FIG. 6 shows the output signal waveform when the optical sensor 7 reads the test pattern.

In this example, the test pattern on the surface of the recording medium is read by the optical sensor 7, and the accuracy of recording dot position matching is determined based on changes in the intensity of reflected light. In this example, it is desirable that the optical sensor 7 has no spectral sensitivity to each color.

The reflected light intensity change is output as a voltage or current value change. FIG. 6(A) shows the case where the recorded dot positions completely match as in FIG. 5(A), and FIG. 6(B)
5(B) shows a case where the ejection timing of other colors is delayed with respect to the reference color black Bk, and there is a deviation in the recorded dot positions of the two, and FIG. (C
), the ejection timing of other colors is faster than the reference color black Bk.

This shows a case where there is a deviation between the positions of the recorded dots.

In this embodiment, a detection method based on a change in current value will be described. The matching accuracy of the recorded dot positions is determined by the time t in FIG. 6, and the shorter the time t, the higher the matching accuracy. Therefore, by controlling the ejection timing of other heads relative to the black Bk head in accordance with this time t, the positional deviation of the recording dots can be corrected.

FIG. 7 shows an example of an ejection timing correction processing procedure according to this example.

When this procedure is started, first, in step S1, the temperature of each head is adjusted. This is due to the following reasons.

In an inkjet recording apparatus, the recording head is usually maintained within a predetermined temperature range (for example, about 40° C., which is the first temperature adjustment standard) in order to suppress fluctuations in image density, stabilize ejection, and the like.

On the other hand, when actually recording images continuously, the temperature of the head increases, and recording may be performed at a maximum temperature of 50° C., which is the second temperature adjustment standard.

Therefore, when this procedure is started immediately after image formation, if there are variations in the usage amount of each recording head depending on the content of the image being formed, the ink viscosity changes depending on the temperature, so each head Variations occur in the amount of ink ejection, that is, the diameter of the dots, and in this example, in which the overlapping state of the dots is determined based on the time t, there is a possibility that positional deviation cannot be accurately detected. Additionally, even when the recording head is not yet controlled within the temperature range that is normally adjusted during recording, such as immediately after the device is powered on or in a bad environment, accurate detection of positional deviation may not be possible. .

Therefore, as in this example, the temperature of each head is adjusted in advance.
By controlling each head within the temperature adjustment range used during normal printing, forming a test pattern, and performing correction based on this, it is possible to prevent dot position deviation during normal printing.

Note that the temperature to be adjusted may be the same for each head, or may be determined for each head depending on the ejection conditions and frequency of use of each head, but the temperature may be adjusted at an appropriate temperature for normal recording. Preferably, a pattern is recorded.

Next, in this example, a discharge stabilization operation is performed in step 5100B. This means that if the print head does not have normal ejection characteristics due to ink thickening, dust, air bubbles, etc., if you continue to form a test pattern, you will be able to accurately recognize the characteristics of the head. This is because there is a risk that it will not be possible to do so.

During the ejection stabilization process, the recording heads la to 1d and the recovery device 220 can be placed opposite each other, and the above-described suction process can be performed to forcibly eject ink from the ejection ports. Further, the ejection port forming surface may be cleaned by bringing an ink absorber that can be disposed in the cap unit into contact with the ejection port forming surface, or by blowing air, wiping, or the like. It is also possible to perform preliminary ejection by driving the print head in the same way as during normal printing (however, the driving energy during preliminary ejection does not necessarily have to be the same as during printing). That is, a process similar to the so-called ejection 8 recovery operation performed in an inkjet recording apparatus may be performed.

In addition, instead of or after the above processing,
A pattern for ejection stabilization can also be recorded on the recording medium. After that, a test pattern or the like for correcting density unevenness may be recorded.

Next, in step 5IO1, the test pattern shown in FIG. 5 is printed, in step 5102 the test pattern is read by the optical sensor 7, and in step 5103, time t in the waveform shown in FIG. 6 is stored as to.

In step 5104, the ejection timing of the controlled head is made one step faster than the reference color head (Bk head in this example), the test pattern is printed again in step 5105, and the test pattern is read in step 3106. At 5107, time t in the waveform shown in FIG. 6 is set to 1. be memorized as .

In step 5108, the times to and tl are compared, and if the time 1+ after changing the ejection timing is shorter, the time t1 is changed to t in step 5116. In step 5117, the ejection timing of the controlled head is set to 1 again.
Step faster, steps 5118, 5l19, 512
At 0, the test pattern is printed, read, and the time t of the waveform change portion is stored as tl.

In step 5121, time t is compared with tl, and t is t.
If tl is shorter than to, the ejection timing of the controlled head is delayed by one step in step 5122, and the correction is finished as the state before re-correction.On the other hand, if tl is shorter than to in step 5121, the ejection timing of the controlled head is delayed by one step. The operations from step 3116 to step 5121 are carried out until 1.>1° is satisfied (unsuccessful.

If the time t is longer than to in step 5108, the ejection timing of the controlled head is delayed by one step in step 5109, and steps 5ilo and 5il are performed.
l.

In step 5112, the time t of printing, reading, and reading waveform change portion of the test pattern is stored as tl.

In step 5113, to and tl are compared, and the ejection timing of the controlled head is accelerated by one step, and the correction is completed as the state before re-correction. In step 5113, t,
If is shorter than to, steps 5109 to 5113 are repeated until t+>jo is satisfied.

Note that it is desirable that the one-step correction amount of the ejection timing can be corrected by an amount that is equal to or less than the recording dot pitch.

As shown in Figure 8 (A), if the recorded dot positions of the reference head and the controlled head are separated by more than the recording dot pitch, there will be two waveform changes in the output depending on the reading light intensity. .

In this case, refer to the counter pulse with the same pulse waveform as the black Bk ejection timing in Figure 7 CB), and if there are two changes in the test pattern reading waveform between each pulse, change the change time t to the False detection can be avoided by setting as shown in FIG. 7(A).

The above sequence for determining and correcting the recording dot position accuracy is performed for each combination of black Bk vs. cyan C, black Bk vs. magenta M, and black Bk vs. yellow Y, and is continued until correction for all combinations is completed. .

In addition, the ejection timing correction conditions after correction are set to non-volatile RA.
It is possible to write the information to M, etc., so that it is stored even when the device power is turned off, unless correction is performed again.

In this example, the above sequence is performed in response to an instruction input by the operator, but it can also be started at an appropriate timing, such as every predetermined period, or when the device is powered on.

FIG. 9 shows an enlarged view of a test pattern for detecting the position of recorded dots according to another embodiment of the present invention.

Each color is printed with one or two dots thinned out, and Figure 9 (A) shows the reference color head (black Bk
) and the recording dot position of the controlled head (cyan C in this case) are the same. Further, FIG. 9(8) shows that the recording dot positions of the reference color head and the control target color head are misaligned.

The optical sensor used in this embodiment has lower resolution than the sensor shown in the previous embodiment, and can measure the area within the dotted line in FIG. 9(A) on average.

FIG. 1O shows the output current value from the optical sensor according to this example.

When the recorded dots of the reference head and the controlled head match, the output current value indicates Io, and when there is a discrepancy in the recorded dot position between the reference color and the output color of the controlled head, the output current value shows Io. Engineering, becomes. Here L<I. The reason for this is that if there is a misalignment in the position of the recording dot, the amount of ink covered per unit area is large, and the whiteness of the paper decreases, in other words, the amount of reflected light decreases, and the output current from the optical sensor decreases. (To become.

When performing actual correction, the initial output current value is compared with the output current value when the ejection timing of the controlled color is corrected, using a method similar to the sequence shown in FIG.
The ejection timing can be corrected so that the output current value from the sensor becomes maximum. Note that in this case, since the value of Io may differ depending on the combination of colors, the reference value I is determined depending on the combination. It is preferable to change the value of .

Additionally, when recording a test pattern using a recording head, depending on the type of recording medium, the ink recorded from each recording head may not be absorbed instantly, and the state of the test pattern recorded on the recording medium may not stabilize immediately. If there is a risk that accurate dot positional deviation may not be detected, wait processing is performed until the test pattern recorded by each recording head has stabilized, and reading of the test pattern is not performed. be able to.

In addition, in the above explanation, the case where correction is performed to obtain a state in which there is no positional deviation of the recording dots between the recording heads as the reference dot state to be formed is described, and furthermore, the test pattern used for the correction is used as the reference dot state. Although it has been described that the recording dots are formed under driving conditions such that the recording dots of the controlled recording head overlap the recording dots of the recording head, the present invention is not necessarily limited to such embodiments.

For example, dots may be formed simultaneously on the reference recording head and the control target head at a certain scanning position of the carriage, instead of forming the test pattern under driving conditions such that the test pattern is overprinted. In this case, the distance between both heads is obtained based on the output obtained by scanning these with a reading sensor (for example, by measuring between peaks), and this is determined as a predetermined distance # (i.e., determined for the head to be controlled). If the distance is not a standard distance that would not cause a dot position shift when driving is performed using the ejection timing adjustment value, the correction may be performed on the assumption that a dot position shift will occur.

In addition, by comparing the density distribution pattern obtained by reading and scanning such a test pattern with the density distribution pattern that serves as a standard in terms of shape and size, the density of the recorded dots, that is, the amount of ink ejected, can also be controlled. The density may be corrected not only by correcting the recording dot position as the reference dot state to be applied, but also by adjusting the ejection amount between the heads.

Furthermore, the reference dot state specifically means that the dots recorded by multiple heads overlap, but the state of overlap is that the centers of the dots match, or that the radii (sizes) also match. The state can be determined to obtain an optimal formed image.

(Others) The present invention is applicable not only to inkjet recording methods but also to recording apparatuses using various recording methods such as thermal printers, but when applied to inkjet recording methods,
Among these, it brings about excellent effects in bubble jet type recording heads and recording apparatuses. This is because such a system can achieve higher recording density and higher definition.

As for typical configurations and principles thereof, it is preferable to use the basic principles disclosed in, for example, US Pat. No. 4,723,129 and US Pat. No. 4,740,796. This method can be applied to both the so-called on-demand type and continuous type, but especially in the case of the on-demand type, it is necessary to arrange the liquid (ink) in accordance with the sheet and liquid path that hold it. The electrothermal converter that is
By applying a single drive signal that corresponds to the recorded information and causes a rapid temperature rise exceeding nucleate boiling, the electrothermal transducer generates thermal energy, causing film boiling on the heat-active surface of the recording head. This is effective because it causes bubbles in the liquid (ink) that correspond one-to-one to this drive signal.The growth and contraction of these bubbles causes the liquid (ink) to flow through the ejection opening. It is ejected to form at least one drop.If this drive signal is in a pulse shape, bubble growth and contraction will occur immediately and appropriately.
Particularly responsive liquid (ink) ejection can be achieved,
More preferred. This pulse-shaped drive signal is described in U.S. Pat. Nos. 4,463,359 and 4,345,262.
Those described in the specification are suitable. Furthermore, if the conditions described in US Pat. No. 4,313,124 concerning the invention regarding the temperature increase rate of the heat acting surface are adopted, even more excellent recording can be performed.

The configuration of the recording head includes, in addition to the combination configuration of ejection ports, liquid paths, and electrothermal converters (straight liquid flow path or right-angled liquid flow path) as disclosed in the above-mentioned specifications, a heat acting section. The present invention also includes configurations using US Pat. No. 4,558,333 and US Pat. No. 4,459,600, which disclose configurations in which the wafer is placed in a bending region. In addition, Japanese Patent Application Laid-Open No. 1989-5 discloses a configuration in which a common slit is used as a discharge part of a plurality of electrothermal converters.
No. 9-123670 and Japanese Patent Application Laid-Open No. 59/1989 which discloses a configuration in which a discharge portion is made to correspond to an opening that absorbs pressure waves of thermal energy.
The effects of the present invention are also effective even if the structure is based on the publication No.-138461. That is, regardless of the form of the recording head, according to the present invention, recording can be performed reliably and efficiently.

Furthermore, even for full-line type recording heads whose length corresponds to the maximum width of the recording medium that can be recorded by the recording device, dot position deviations occur due to changes over time in the head itself and the mounting members around it. can occur, so the present invention can be effectively applied. Such recording heads include configurations that satisfy the length by combining multiple recording heads,
Any configuration as a single recording head formed between them may be used.

In addition, both a serial type as shown above and a recording head fixed to the main body of the apparatus are effective in dealing with the above-mentioned changes over time. In addition, there are also replaceable chip-type recording heads that can be attached to the device body to enable electrical connection to the device body and supply of ink from the device body, or an ink tank integrated into the recording head itself. When a cartridge type recording head is used, it is particularly effective in dealing with dimensional errors, etc. in addition to the above-mentioned changes over time.

Further, it is preferable to add recovery means for the recording head, preliminary auxiliary means, etc., which are provided as a configuration of the recording apparatus, to the present invention, because the effects of the present invention can be further stabilized. Specifically, these include capping means for the recording head, cleaning means, pressure or suction means, preheating means using an electrothermal transducer or another heating element, or a combination thereof; It is also effective to perform a preliminary ejection mode in which ejection is performed separately from printing in order to perform stable printing.

In addition, regarding the types and number of print heads to be mounted, a plurality of print heads may be provided to correspond to a plurality of inks having different densities as well as those having different print colors. That is, for example, the recording mode of the recording apparatus is a recording mode using dark and light ink of only a mainstream color such as black, a multi-color recording mode in which the recording head is configured integrally or in a combination of two or more different colors, The present invention is also extremely effective for devices equipped with at least one full color by color mixture.

Additionally, in the embodiments of the present invention described above,
Although ink is described as a liquid, it is an ink that solidifies at room temperature or below, but softens or liquefies at room temperature, or in an inkjet method, the ink itself is
Generally, the temperature is adjusted within the range of 0°C or more and 70°C or less so that the viscosity of the ink is within the stable ejection range, so even if the ink is in a liquid state when the recording signal is applied. Bye. In addition, the temperature increase caused by thermal energy can be actively prevented by using the energy to change the state of the ink from a solid state to a liquid state, or ink that solidifies when left standing is used to prevent ink evaporation. In any case, the ink is liquefied by applying thermal energy in accordance with the recording signal, and the liquid ink is ejected, or the ink has already begun to solidify by the time it reaches the recording medium. The present invention is also applicable when using ink that is liquefied only by energy. The ink used in this case is
Publication No. 4-56847 or JP-A-60-71260
As described in the above publication, the porous sheet may be held in a liquid or solid state in the recesses or through-holes of the porous sheet, facing the electrothermal converter. In the present invention, the most effective method for each of the above-mentioned inks is to implement the above-mentioned film boiling method.

In addition, in addition to being used as an image output terminal for information processing equipment such as a computer, the inkjet recording apparatus of the present invention may also take the form of a copying machine combined with a league, etc., or a facsimile machine having a transmission/reception function. It may also be something.

[Effects of the Invention] As described above, according to the present invention, in an image forming apparatus that forms an image by ejecting ink from a plurality of recording heads according to an image density signal, each head is set to a reference dot state (for example, The dot recording state of each head (for example, the recorded dot position) is adjusted to the optimum reference dot state (for example, the first By correcting the condition in which the second dot is placed in the same position), it is possible to print at a more optimal recording dot position without the user having to make manual corrections, and the color This makes it possible to prevent misalignment and resolution degradation and improve print quality.

Furthermore, since the recording dot positions of the other heads are corrected using one of the heads as a reference, positional deviations between the heads can be corrected reliably and easily.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of main parts of a serial printer type color inkjet recording device according to an embodiment of the present invention, FIG. 2 is a front view showing an example of the head configuration in the color inkjet recording device shown in FIG. 1, and FIG. Figure 1 is a block diagram showing an example of the configuration of the control system of the apparatus shown in Figure 1. Figure 4 is a block diagram showing an example of the configuration of the dot position deviation correction section in this example. Figures 5 (A) to (C) are An explanatory diagram showing test pattern images used in the example; FIGS. 6(A) to (C) are waveform diagrams showing output signal waveforms obtained by reading the test pattern images of FIGS. 5(A) to (C) with an optical sensor; FIG. 7 is a flowchart showing an example of a sequence for determining and correcting the recording dot position in this embodiment, and FIGS. 8 (A) and (B) show output signal waveforms obtained by reading the test pattern image with an optical sensor, respectively. FIG. 10 is an explanatory diagram showing an output current value when the test pattern image of FIG. 9 is read by an optical sensor. . 1.1a-ld... Recording head, 2... Carriage, 3... Guide shaft, 4... Recording paper, 5... Conveyance roller, 6... Encoder, 7... Optical sensor , 8... Ink discharge port, 10... Recovery device. 11... Recording head and driver, 12... Image density signal, 13... Binarization processing section, 14... Binarized signal, 15... Buffer, 16... Shift register . (A) (B) Figure (A) (B) Figure Figure Figure

Claims (1)

[Scope of Claims] 1) In an image device that forms an image according to an image signal using a plurality of recording heads, the above-described method is performed under driving conditions corresponding to a reference dot state to be formed by the first and second recording heads. 1st and 2nd
a driving means for driving the recording head of the recording head to form first and second dots; and control for controlling the driving means so that the formation state of the formed first and second dots matches the reference dot state. An image forming apparatus comprising: means. 2) The control means has a reading means for reading the formation state of the first and second dots, and a determination means for determining whether the formation state corresponds to the reference dot state. 1. The image forming apparatus according to 1. 3) The image forming apparatus according to claim 1, wherein the reference dot state is a state in which the first and second dots are recorded so as to be overlapped at the same position. 4) The image forming apparatus according to claim 3, wherein the control means controls the driving means according to a positional shift of the second dot with reference to the first dot position. 5) Image formation according to any one of claims 1 to 4, characterized in that a plurality of recording heads are provided corresponding to recording materials of different colors in order to perform multicolor recording. Device. 6) The recording head has the form of an inkjet recording head, and the inkjet recording head is characterized in that the recording element includes an electrothermal conversion element that is used to cause film boiling in the ink to eject the ink. The image forming apparatus according to any one of claims 1 to 5.