JPH0939220A - Image recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high quality image record without giving a discontinuous impression to person since gradation control near a linear form is made possible by a method wherein a control means which controls variably a head angle made by a direction of a discharge opening line and a main scan direction, is provided. SOLUTION: A scan unit 12 of a carriage or the like mounts a recording head 10, and scans by transfer in a main scan direction S. A motor gear 15 is meshed with a rotary gear 14, and the scan unit 12 is driven with a controlling motor 16. The controlling motor 16 is driven following instruction from a control part (controller) 17 and driven by control so as to obtain a head angle calculated by an angle calculating part. Then, an image recorder capable of controlling gradation by controllability of the head angle can be embodied. Thereby, continuous gradation control near a linear form which is different from a form wherein a size and a shape of a recording dot itself are varied, can be carried out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus, and more particularly to an image recording apparatus suitable for an ink jet type printer or the like in which dots are recorded by ejecting ink and gradation is required.

[0002]

2. Description of the Related Art Conventionally, as a gradation control in an ink jet recording apparatus for recording a binary image, the following method has been mainly adopted.

The first type is called a halftone dot type. Originally, the dot interval of recording pixels recorded by this type of image recording apparatus is the ink ejection element (hereinafter referred to as recording element) arranged in the recording head. Called) is constant because the interval is constant. Therefore, in such a halftone dot type, the size of the ink dots ejected for recording is changed sequentially as shown in FIGS. 7A, 7B, and 7C to obtain the gradation, that is, the image. By changing the ratio of the density of each dot to the area, the low gradation shown in (A) to the high gradation shown in (C) can be obtained.
This is called halftone gradation.

The second type is called a density matrix type, and in this case, the size of the ink dot does not change, but the recording density per area is controlled to change. A specific example thereof will be described with reference to FIG.
To this end, first, as shown in (A), a table is prepared in which thresholds 1 to 9 corresponding to gradations are matrixed.
Then, after determining which gradation is to be used for recording based on the original, if the gradation 1 is judged according to the gradation table shown in FIG. 9A, then the dot density shown in FIG. When the gradation is 5 or 9, the drive of the recording element is controlled so that recording is performed with the dot density as shown in (C) or (D), respectively.

Among the above-mentioned conventional techniques, the one based on halftone dot gradation is widely used in image recording apparatuses of the form for forming and transferring plates such as printing, and is also called density matrix type. Since the structure of the recording head itself including the recording element and the driving means for the recording element is relatively simple, the inkjet head has been used in relatively inexpensive ink jet printers.

[0006]

When the former halftone dot gradation method is adopted in a relatively inexpensive ink jet type image recording apparatus, as shown in FIG. There is no problem if the dots 1A to 1C for each gradation recorded on the recording material (hereinafter referred to as a recording sheet) P are penetrated into the recording sheet P while keeping the same thickness. However, in actuality, as shown in FIG. 9B, the permeation thickness varies depending on the dots 1A to 1C as indicated by 1A 'to 1C', and therefore it depends on the coverage of the coloring material contained in the ink. The linearity of gradation control is impaired, which hinders accurate gradation realization.

When an image or print is recorded using the latter density matrix, an asymmetric pattern of the recording dots 1 is generated as shown in FIG. 9C, or a high-ride portion is expressed. An isolated point due to the dot 1 is generated, and the discontinuity of the dot is recognized by the human eye, which gives the impression that the image quality is deteriorated.

Furthermore, as another point, there is a problem of moiré which occurs when an image is formed by multi-color superimposition recording. That is, it is known that a regular pattern that gives a smooth impression to the human eye, on the other hand, causes a pattern different from the original image due to moire caused by interference between different colors. Has been. Therefore, in order to suppress the occurrence of such moiré in the halftone dot recording up to now, in the case of color recording, different angles θ called so-called screen angles are used for different color plates.
_As shown in FIG. 10 (A), _S is kept in the recording head 10 and is scanned. In this way, the scanning direction S
By setting, in the main scanning direction S _H, the head 1
Ink dots 1 obtained by ejecting from each ink ejection port 0 of 0 can be gradually shifted in the sub-scanning direction S _S with respect to the main scanning direction as shown in FIG. 10B. The ink ejection ports 11 are provided in the recording head 10 at equal intervals corresponding to individual recording elements (the ink ejection port, the liquid path, and the ejection energy generating element are collectively referred to as a recording element). .

However, screen printing head 10 by adjusting the ratio of the speed of the speed and the sub-scanning direction in the main scanning direction S _H of the recording head 10 as shown in (A) of FIG. 10 (sheet feeding direction) When the recording sheet P is scanned in the oblique direction S so that the angle θ _S is maintained,
Since the arrangement direction of the ink ejection ports 11 matches the sub-scanning direction S _S , even if the regularity of the dots 1 with respect to the main scanning direction S _H changes, the regularity of the sub-scanning direction does not change. Therefore, the occurrence of moire in the sub-scanning direction remains unsolved. Note that a combination of the scanning direction of the recording head 10 and the sheet feeding of the recording sheet P in an oblique direction may be considered here, but this may lead to an increase in the size of the conveying device.

It is an object of the present invention to pay attention to the above-mentioned conventional problems and to solve the problems, gradation control close to linear can be performed, and high quality can be achieved without giving a discontinuous impression to the human eye. SUMMARY OF THE INVENTION It is an object of the present invention to provide an image recording apparatus capable of achieving the image recording of (3) with a relatively inexpensive structure.

[0011]

In order to achieve such an object, a first embodiment of the present invention uses a recording head having an ejection port array composed of a plurality of ink ejection ports for forming recording dots, An image recording apparatus for performing recording by relatively moving the recording head in a main scanning direction which forms an angle with a direction of the ejection port array and a sub scanning direction which is orthogonal to the main scanning direction with respect to a recording material facing the recording head. , A control means for variably controlling a head angle formed by the direction of the ejection port array and the main scanning direction.

According to a second aspect of the present invention, a plurality of recording heads each having an ejection port array composed of a plurality of ink ejection ports are arranged in the main scanning direction and the sub-scanning direction, and at the same time as the ejection port array. In the state where the head angle formed with the main scanning direction is simultaneously changed in each of the recording heads, the head angle is limited to an angle of 90 ° to a threshold angle larger than 0 °, and the threshold angle is set to the threshold angle. It is characterized in that the formation of recording dots by a plurality of recording heads does not overlap and is maintained at equal intervals.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The embodiment of the present invention is based on each of the above-mentioned modes.
(A), the head angle is kept at 90 °, and the recording head 10 is scanned in a direction perpendicular to the arrangement of the recording elements so that image recording can be obtained by the two-dimensional arrangement of the recording dots 1. Was there. Therefore, in this case, the vertical and horizontal arrangement of the recording dots 1 is the distance between the recording elements in the recording head,
That is, the image recording is limited to the square lattice-shaped dot density maintained at the arrangement interval d of the ink ejection ports 11.

On the other hand, according to the embodiment of the present invention, as shown in FIG. 3B, the head angle θ in the recording head is
_By keeping _H at 0 <θ _H <90 °, it becomes possible to set the recording dot interval d ′ <d in the sub-scanning direction, and the scanning speed in the main scanning direction becomes the dot interval d ′ in that direction. By controlling in this manner, it is possible to obtain an image record having a higher dot density than that of FIG. From this, it is possible to change only the dot density without changing the size or shape of the recording dots, and also to keep the arrangement interval of the recording elements as it is, and continuous gradation control becomes possible.

As an example of application to multicolor image recording,
As shown in FIG. 4B, the screen angle θ _S is maintained and the head angle θ _H (here, θ _S + θ _H
= 90 °) by scanning the maintained so the scanning direction S and while utilizing the feature which gave the original screen angle theta _S, in the main scanning direction S _H and the sub-scanning direction on the recording sheet P S _S
For both of the above, high-quality image recording can be obtained without the risk of moire.

Embodiments of the present invention will be described below in detail and specifically with reference to the drawings. Prior to the description, the basic structure according to the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 shows a main circuit configuration for carrying out the present invention in accordance with its control operation procedure. The present invention can control the recording head 10 to incline with respect to the sheet feeding direction (sub-scanning direction) as described as the embodiment, and the head angle described below means recording. The tilt angle of the head 10, that is, the angle formed by the recording element array direction of the recording head 10 and the main scanning direction. The head angle during the normal recording operation is 90 °.

In FIG. 1, reference numeral 111 denotes a head angle calculation unit for calculating an appropriate head angle for image recording at the time of recording, and reference numeral 112 tilts the recording head to the head angle calculated by the head angle calculation unit 111. A head angle control unit 113 for controlling the print head controls the print head in a predetermined scanning direction while keeping the head angle set by the head angle control unit 112, and selectively ejects ink from the ink ejection port to perform recording. This is a recording unit. In the image recording apparatus having such a configuration, first, image information including gradation data is sent from the host side (not shown) to the head angle calculation unit 111 each time scanning is performed.

Therefore, the head angle calculation unit 111 calculates the head angle based on the recording area ratio and the dot spacing based on the gradation data, and outputs the calculated head angle value to the head angle control unit 112. .

A calculation example is shown below. In the calculation, an example in which the gradation data is 0 to 255, the dot diameter is 100 μm, and the distance between the recording elements is 500 μm will be described.

Now, assuming that the gradation data is 127, the area ratio can be calculated from the ratio with the maximum value 255.

[0022]

[Equation 1]

It becomes

Next, regarding the dot interval, the recording area ratio is determined by the ratio between the square value of the dot interval and the dot area. The dot area in this example is

[0025]

(2) 3.14 × 100 μm × 100 μm = 3140
Since it is 0 (μm) ² , the required dot spacing is

[0026]

(Equation 3)

## EQU1 ##

Since the dot spacing, the spacing between recording elements, and the head angle have a trigonometric function relationship, an inverse trigonometric function is used.

[0029]

(Equation 4)

The head angle θ _H can be obtained as (3).

If the relationship between the gradation and the area ratio needs to be corrected from the characteristics of the printer, it is possible to add the correction appropriately.

As described above, the head angle calculator 111 can calculate the head angle θ _H based on the gradation data.

The head angle value output from the head angle calculation unit 111 is input to the head angle control unit 112, and a configuration example of the head angle control unit 112 will be described with reference to FIG.

In FIG. 2, reference numeral 12 denotes a scanning unit (for example, a carriage) on which the recording head 10 is mounted and which moves and scans in the main scanning direction S _H , and 13 is supported by the scanning unit 12 and has the recording head 10 at its center ( A shaft (hereinafter, referred to as a head angle variable shaft) that is rotatable around an ink ejection port array), 14 is a head rotation gear fixed to the head angle variable shaft 13, and 15 is a head rotation gear 14. Mesh with
The motor gear is driven by the control motor 16. The control motor 16 is driven according to an instruction from the control unit (controller) 17, and is controlled and driven so as to obtain the head angle calculated by the head angle calculation unit 111 shown in FIG. A pulse motor can be cited as a suitable example of such a control motor, but any form of actuator may be used as long as it can be controlled accurately.

With the configuration described above, the gradation is adjusted to the head angle θ _H.
It is possible to embody an image recording device that can be controlled by changing the above. Then, in the image recording apparatus having such a configuration,
Unlike the form in which the size or shape of the recording dot 1 itself is changed, it is possible to perform continuous gradation control that is almost linear.
Further, since the regular arrangement of the recording dots 1 is always leaned against regardless of the change of the head angle θ _H , it is possible to obtain a high-quality and high-quality image recording without giving the impression of visually discontinuous image recording. You can

Next, another embodiment to which the above-mentioned basic structure is applied will be described.

FIGS. 5A to 5C show the arrangement of the recording heads and the recording operation as the second embodiment. In this example, the recording heads are arranged in two rows as shown in FIG. 5A. In this example, the five heads 10A to 10D are arranged in a dispersed manner. Note that in FIGS. 5A, 5B, and 5C, the head angles θ _H of the recording heads 10A to 10D are 90 degrees, respectively.
Rotational states are shown in three cases of 90 °, 90 ° to θmin, and θmin. And the head angle θ _H is θ
In the state of (C) where min occurs, the recording heads 10A and 10
B, 10C, and 10D maintain the same head angle, and the recording elements 11 are arranged on the same line at equal intervals. Then, like this (C)
In this state, the image recording with the width D ₁ is obtained in the sub-scanning direction.

In the structure having such a head arrangement, the recording areas shown by hatching in FIGS. 5A and 5B extend or overlap the recording width D ₁ shown in FIG. 5C. Therefore, by suspending the recording element related to such a recording area in each of the recording heads 10A to 10E, a constant recording width D can be obtained without overlapping the image recording.
_You can keep ₁ for recording. Thus, by operating the recording heads 10A to 10E according to the present embodiment as shown in FIG. 3 or 4, it is possible to continuously change the gradation and contribute to the prevention of moire during color recording. The reason why the print heads are dispersed into a plurality of print heads 10A to 10E as in the present embodiment is that the print heads 10 are now as shown in FIGS.
When the recording head 10 is integrated, the length of the recording head 10 in the sub-scanning direction becomes long and the scanning unit 12 (see FIG. 2) becomes large accordingly. On the other hand, in the present embodiment, the scanning unit can be made compact. There is a point that can be done.

Next, the recording head arrangement according to the third embodiment of the present invention will be described with reference to FIG.

In this embodiment, the screen angle θ _S is set so that a desired gradation can be obtained, and the screen angle θ _S
Head angle θ _H according to

[0041]

[Mathematical formula-see original document] [theta] _H = 90 [deg.]-[Theta] _S (4) After controlling the rotation of the recording head 10 so that this head angle [theta] _H is maintained, the recording head 10 is rotated in the main scanning direction. Screen angle θ depending on the ratio with the speed in the sub-scanning direction
_The recording is performed on the recording sheet P by scanning in the S direction S so that the image recordings by the scanning do not overlap each other. In FIG. 6, the screen angle θ _S is 30 °.
The following shows an example in which recording is performed while keeping at.

According to the present embodiment, by simply selecting the screen angle freely, the density of the dot pattern remains the same, the generation of moire is prevented, and high quality image recording can be obtained.

The present invention is not limited to the above-described embodiments, and it goes without saying that the circuit configuration and mechanism can be appropriately changed without departing from the gist of the invention.

[0044]

As described above, according to the present invention, a recording head having an ejection port array composed of a plurality of ink ejection ports for forming recording dots is used, and the recording head facing the recording head is used. An image recording apparatus for performing relative recording in a main scanning direction which forms an angle with a direction of the ejection port array with respect to a material and a sub scanning direction which is orthogonal to the main scanning direction,
Since the control means for variably controlling the head angle formed by the direction of the ejection port array and the main scanning direction is provided, gradation control close to linear is possible, and a discontinuous image is visually recognized in the obtained image recording. It is possible to provide an image recording apparatus that gives a high quality image with a relatively inexpensive structure without giving an impression.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic circuit configuration for control according to the present invention together with a flow.

FIG. 2 is an explanatory diagram schematically showing a configuration example of a head angle control section according to the present invention.

FIG. 3 is a conventional example of dot recording by a recording head (A).
It is explanatory drawing shown in comparison with the example (B) by this invention.

FIG. 4 is an explanatory view showing a recording operation and a relationship between a screen angle and a head angle according to the present invention by (A) and (B).

FIG. 5 is a recording operation (A) according to a second embodiment of the present invention,
(B) and (C) are recording operations according to another example (D),
It is explanatory drawing shown in comparison with (E) and (F).

FIG. 6 is an explanatory diagram showing the configuration according to the third embodiment of the present invention together with the operation thereof.

FIG. 7A shows an example of dot change due to halftone dot gradation (A),
It is explanatory drawing shown in 3 steps of (B) and (C).

FIG. 8 is a matrix table example (A) of threshold values for density matrix gradation and three examples (B) for each gradation;
It is explanatory drawing shown by (C), (D).

FIG. 9 is an explanatory diagram showing a recording example by a conventional halftone dot gradation method in an ideal state (A) and a state in which it actually occurs (B), and a recording example by a density matrix gradation method in (C). Is.

FIG. 10 is an explanatory diagram showing inconveniences in the case of gradation recording by conventional screen angle control by a recording operation (A) and a recording example (B).

[Explanation of symbols]

1, 1A to 1C (ink or recording) dots 10, 10A to 10E recording head 11 ink ejection port 12 scanning unit 13 head angle variable shaft 14, 15 gear 16 control motor 17 control unit (controller) 111 head angle calculation unit 112 Head angle control unit 113 Recording unit S Scanning direction _SH (Recording head) Main scanning direction S _S (Sheet feeding) Sub-scanning direction θ _S Screen angle θ _H Head angle P Recording sheet d Discharging port arrangement interval d ′ Dot interval

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[Procedure amendment]

[Submission date] November 21, 1995

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Fig. 5

[Correction method] Change

[Correction contents]

FIG. 5 is an explanatory diagram of a recording operation according to a second embodiment of the present invention.

Claims (10)

[Claims] 1. A recording head comprising an ejection port array comprising a plurality of ink ejection ports for forming recording dots, wherein the recording head makes an angle with the direction of the ejection port array with respect to a recording material facing the recording head. An image recording device for performing recording by relatively moving in a main scanning direction and a sub scanning direction orthogonal to the main scanning direction, wherein a head angle formed by the direction of the ejection port array and the main scanning direction is variable. An image recording apparatus comprising control means for controlling. 2. The image recording apparatus according to claim 1, wherein the head angle is variably controlled according to a gradation required when the recording dots are formed. 3. The image recording apparatus according to claim 1, wherein the timing of ink ejection from the plurality of ink ejection ports is variably controlled according to the head angle. 4. The range of the ink ejection port for ejecting ink among the plurality of ink ejection ports is regulated according to the head angle, according to any one of claims 1 to 3. Image recording device. 5. A plurality of recording heads each having an ejection port array including a plurality of ink ejection ports are arranged in the main scanning direction and the sub-scanning direction, and a head angle formed by the ejection port array and the main scanning direction. Is simultaneously changed by each of the recording heads, the head angle is limited to an angle of 90 ° to a threshold angle larger than 0 °, and the recording dots of a plurality of the recording heads are set to the threshold angle. An image recording apparatus, characterized in that formation is not overlapped and is kept at equal intervals. 6. The image recording according to claim 5, wherein a plurality of the recording heads have mutually overlapping recording areas in a state where the head angle is maintained at a displacement angle larger than the threshold angle. apparatus. 7. The control is performed such that the ink ejection from the corresponding ink ejection port of any one of the recording heads of the overlapping recording regions is stopped. Item 7. The image recording device according to item 6. 8. The image according to claim 5, wherein a range of ejection ports for ejecting ink among the ejection ports of the plurality of recording heads is regulated according to the head angle. Recording device. 9. The image recording apparatus according to claim 1, wherein a scanning direction for relative movement of the recording head with respect to the recording material is variably controlled according to the head angle. 10. The image recording apparatus according to claim 1, wherein the control unit controls the head angle according to a gradation of an image recorded on the recording material.