JPS5919166A - Formation of image - Google Patents

Abstract

PURPOSE:To enable to produce a natural gradation image free from coarse and rough feeling, by changing sequentially the gradation in accordance with its level expressing the arrangement pitch and area of an image formation element. CONSTITUTION:An image formation element (for example, a dot pin and an ink dot) is actuated to produce an image by means of an image producing signal 6 corresponding to an image signal (a) to be expressed. The image producing signal 6 is a time series arrangement of pulse signals S1-S10 all having an equal pulse width at non-quantized pitch. Namely, when P1=P2=P3<P5=P6<P4<P7< P8<P9, the arrangement pitch is made not by integral multiples of the minimum pitch P1 but a sequentially changing value. The area of image formation element E is changed in accordance with the gradation level and arranged to be, for example, E(1)=E(2)=E(3)=E(4)>E(5)=E(6)=E(7)>E(8)=E(9)=E(10).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming method that expresses so-called image information in a visually perceptible state, which has a two-dimensional spread such as a character, a graphic, a graph, an image, etc. This invention relates to an image forming method that expresses unique image information.

Image information with gradation, Rlj, intermediate tone (/--7)-
For example, in the image information recording field, there is a method for displaying information in a perceivable state in the image information recording field, which includes the following information: 81t: provided within (hereinafter referred to as cell),
A conventional example involves controlling the number of image forming elements having a constant optical density and a constant area and the arrangement state within the pixel.

That is, the prior art example may be used, for example, to divide a pixel into a plurality of cells that can be occupied by only one of the imaging elements.
Lax-like subdivision (hereinafter referred to as cell matrix),
A desired level of gradation is expressed according to the number of cells occupied by image forming elements among the cells constituting the cell matrix and the arrangement state of the image forming elements occupying the cells. .

The image forming elements are arranged so that the arrangement pitch is an integral multiple of the minimum arrangement pitch determined by the cell size (hereinafter referred to as standard arrangement pitch P8). (expressed as the image forming elements are arranged under the specified arrangement pitch).

According to this method, if you want to improve the gradation, you can either increase the area of each pixel itself (pixel area) or reduce the area of the image forming element as much as possible to make the cells that make up one pixel as small as possible. However, in the former case, the company,
It is an undeniable fact that the larger the pixel area is, the further the sharpness and resolution will be reduced and the image will become rougher, which is not desirable from a practical point of view.

In the latter case, if we try to increase the number of cells constituting one pixel while maintaining a certain degree of sharpness and resolution, there is a limit to reducing the area of the image forming element, so there is a limit. is.

Therefore, when trying to express a wide range of gradations from gradation levels with higher optical density to 14 levels of lower optical density, the gradation expression becomes finer due to the lack of the number of gradation levels that can be expressed. Chips [roughness] or “roughness”
The result is an impressive image. Furthermore, if you try to express the gradation in fine wood grain, the range of gradation expression cannot be wide enough, so either the highlights or the dark areas cannot be fully expressed, and the resulting image will not be able to fully express the dark areas, for example. If you try to express the gradation well enough, it will give a ``glaring'' feeling to the illumination area, which is irritating to the eyes. In any case, if you try to express fine gradation, the gradation expression area will be biased, resulting in an unnatural image.

In particular, in the case of photographic images, naturalness is outstanding in the reproduction of light areas and human skin areas, and it is difficult to smoothly and continuously express a wide range of intermediate tones.

On the other hand, for example, flying ink droplets are formed and the ink droplets are deposited on a recording medium (eg, paper, plastics, etc.).

In the inkjet recording method, which records images by forming ink dots (one of the image forming elements) on a sheet material (such as ceramics), in order to express gradation, Different color densities (color Me
In the case of recording, it has already been proposed to use liquid or solid ink (for each color) and to use these separately for recording. When expressing an image part with equal optical reflection density (hereinafter referred to as "average reflection density"), a high density (
There are two possible expressions: one is to form small-area dots with high-density (high color density) ink, and the other is to form large-area dots with low-density (low color density) ink. , the case of using two types of ink, high density and low density, will be explained below, but the use of ink with different density will be explained below.
(It is not limited to fi11, and the same can be said if two or more types or multiple colors are used). Even if the average reflection densities of the two displayed images are approximately the same, when viewing the resulting images, the human eye will notice a large difference in image quality. It appears as if there is. Of course, this will vary depending on the color density of the ink and the dot pitch, but in general, images expressed using high-density ink and forming small-area dots will have an accentuated "roughness." In addition, the expression of the lowest optical density (lowest gradation level) in image expression is If you try to express it by not forming dots, there will be white areas on the screen, and the tone of the image will obviously be different from the areas where other dots have been formed, which will reduce the image quality. The present invention was created in view of the above meaning, and it is possible to improve wood grain in a wide gradation expression range from a gradation level with a higher optical density to a gradation level with a lower optical density. The main purpose is to propose an image forming method that can express fine gradation.

Another object of the present invention is to propose an image forming method that can obtain images with excellent sharpness and resolution. The main purpose of this project is to propose an image forming method that can produce images that are calm, natural, and free from the feeling of "Gasagasa."

In addition, the "image forming element" used in this specification is
For example, in so-called dot recording, in which recording is performed by forming dots in inkjet recording, thermal recording, thermal transfer recording, wire tod recording, electrostatic recording, etc. Also, the "optical reflection density" and the "density (color density)" of the ink, which is frequently used in the following explanations, are the optical reflection density and optical transmission measured with a commercially available densitometer, respectively. Regarding the density, in measuring the reflection density, the value obtained when widely used standard white paper was used as the reference value.

The image forming method of the present invention is an image forming method in which an image is formed by arranging a plurality of image forming elements having different optical densities. The gradation expression area is obtained by modulating the arrangement pitch of the image forming elements under non-quantization, and the gradation is expressed by modulating the area of at least one image forming element among the plurality of image forming elements. An image with gradation can be created by configuring a tonality expression area that can be expressed by all K of the image forming elements in which either the array pitch or the area is modulated. According to the image forming method of the present invention, "roughness" can be expressed.

In addition, it is possible to smoothly and continuously express a wide range of intermediate tones without losing naturalness in reproducing illumination areas and human skin areas.

Furthermore, even when expressing a full-color image, it is possible to obtain a high-quality image with sufficient naturalness.

Furthermore, since it is possible to express fine gradation in a wide range of expression, images with excellent naturalness can be obtained.

Furthermore, the images obtained by the image forming method of the present invention are excellent in sharpness and resolution.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is an explanatory diagram for explaining the basic concept of the present invention. Optical reflection density on one scanning line of the image to be expressed (of course, it may also be expressed as optical transmission density)
Assume that the change in is shown, for example, by the density signal (a) in FIG.

W indicates the lowest gradation level, that is, the level with the lowest optical reflection density, for example, white level, and B indicates the highest gradation level, that is, the level with the highest optical reflection temperature, for example, black. H1+H2+H3 indicate the optical reflection density of their intermediate level, respectively.

(b) shown in FIG. 1 shows an image forming element formed according to the density signal (a) (in the figure, the shape of the image forming element is circular, which is generally used). (as shown)
This is an expression signal for expressing and arranging the
Pulse signals 81 to 810 having the same width and level are arranged in time series under a non-quantized arrangement pitch. The image forming element E for forming an image receives the above expression signal (
gradation that is arranged under a non-quantized arrangement pitch on a recording medium such as paper according to b), and has a density change indicated by a density signal (a) in the arrangement state of the image forming elements E; In other words, in FIG. 1, the arrangement pitch between the image forming elements E1 to Eso arranged in one-to-one correspondence to the pulse signals 81 to 810 is Pl2. P2=P3〈P.

``'' Pg < P4 < Pr < Pg < Pg, and is not an integral multiple of Pl, which is the minimum arrangement pitch. In addition, the area of the image forming element E is also modulated according to the level HIrJ expressed in the present invention, and the area of the image forming element E is modulated according to the level HIrJ expressed in the present invention. The size is g+1+=E(2)
= E (31 = E (4) > E (5)) = E (61
= E(c>E(8J= g(9)=E) There is a clear relationship.

In this way, the present invention continuously modulates the arrangement pitch P and area of the image forming elements E according to the gradation level expressing the naturalness of the image having the desired gradation. It is something that is fully expressed.

In the present invention, the arrangement pitch P is 0 (a state in which two image forming elements are completely overlapped; if the image forming element E is circular as shown in FIG. 1, the center point of one circle is It is continuously modulated within a range of values that can be arbitrarily determined depending on the desired image quality of the image to be formed. Assuming that the area of two successively arranged image forming elements is "'1t82," the upper limit of the modulation area of the array pitch is as follows: Duty ratio D in the arrangement of image forming elements E = (Chang+Chang)/ (,F
-P) (where P is the array pitch).

That is, as the duty ratio becomes smaller, the naturalness of the formed image is gradually lost, and when the duty ratio decreases below a certain value, the naturalness is rapidly lost.

This tendency becomes more pronounced as the optical reflection density of the image forming element E increases.

In the present invention, if the optical reflection density of the image forming element E is impaired, in order to achieve the objective more effectively, the duty ratio is set to 0.5 or more. Preferably, the pitch is modulated.

In the present invention, by continuously modulating the arrangement pitch P of the image forming element E from 0 to a value appropriately modulated as desired without quantization, the image forming element E is An image forming element E that can be arranged with continuity from a completely overlapping state to a completely separated state.
The area of is modulated continuously from the minimum electric value to the maximum value.

That is, to explain with reference to FIG. 1, at density level B,
Image forming element E(1), g(2), E(3),
E(4) has the same arrangement pitch (Px='Pz ''Ps)
They are arranged so that a partially overlapping area is formed in the occupied area. At the density level H3, the image forming element E (5
), E(6), E(force is arranged at an array pitch (Ps =
Ps).

Between density level B and density level H3, the arrangement pitch P
The areas of the image forming element E(4) and the image forming element E(4) are also switched by reduction modulation from the area value of the image forming element E(4) to the area value of the image forming element E(5). The density level H2 is arranged below the arrangement pitch P8 so as to be spaced apart from each other by a desired distance, and the density level H1 is expressed as one image forming element E (lol). Shibel) 12,
The arrangement pitches Pγ and P9 are used to switch between the M&degree level H and the density levels 1-11, respectively.

FIGS. 2 and 3 show the relationship between the dot pitch and the optical average reflection density when dots each having a dot diameter of 70 μm are formed on recording paper having two dye-containing densities at different array pitches. In FIGS. 2 and 6, the scale on the horizontal axis is indicated by the reciprocal of the dot pitch.

In Figures 4 and 5, the dye content concentration is 93 wt%, respectively.
Using inks C and D of 0.5Wtq6, a dot array was formed on the recording paper by a drop-on-demand inkjet recording method at a dot density of 5PEL (5 dots per 1 yen/meter) by modulating the dot diameter. In case of
The relationship between dot diameter and optical average reflection density is shown.

In the present invention, in addition to modulating the array pitch and area of the image forming elements, by using a plurality of image forming elements having different optical densities, for example, as shown in FIGS. 2 to 5, This makes it possible to continuously express a wide range of gradation areas from highlights to dark areas.

FIG. 4 shows that three types of image forming elements B(1), E(2), and E(3) having different optical reflection temperatures are used to form an image.
An example of such relationships is shown. The horizontal axis represents the reciprocal of the array pitch and the surface area, and the optical average reflection density is represented as a value normalized with the highest level being 1.

That is, in FIG. 4, an image forming element E (1) (optical reflection density a) having the same area S and an image forming element E (
2) By using <yt optical reflection density 7a), the image forming element IC (1) can continuously modulate the array pitch from 4P to υP1 to continuously reach the optical average reflection density. By modulating, the optical average reflection density D4 to υ1
．． The gradation in the range up to 0 can be expressed continuously, and in the image forming element E(3), by modulating the area from 81 to St, the optical reflection density becomes D! It is possible to easily express the gradation range from to D5.

In the above explanation, the case where three types of image forming elements with different optical densities are used has been shown, but the present invention is not limited to this. The elementary body is 2
One or more types may be used, and as the number of types of image forming elements with different optical densities increases, it is possible to express finer gradation in a wide range of areas.

In addition, in the image forming method of the present invention, although there are two types of image forming elements with different optical densities, a sufficiently wide range can be formed by combining the arrangement pitch and the modulation factor of 2ff1i' in area. It is possible to express gradation areas continuously.

For example, an image forming element E(1) having an optical density of Dl and an image forming element E(2) having an optical density of Dl <where Dx-
(1) The gradation expression by the image forming element E (1) is performed by performing both array pitch modulation and area modulation sequentially or simultaneously, and the image forming element E (2 ), the gradation expression is performed by either one array pitch modulation or area modulation. (2) Image forming elements E(1), B(2)
), the desired gradation can be expressed by performing both array pitch modulation and area modulation sequentially or simultaneously.

The gradation expression method based on the combination of the type of image forming element E and the modulation factor is shown in Table 1 below, especially when there are two types of image forming element E.

Table 1 In Table 1, when a type of image forming element has two modulation factors, those modulation factors may be modulated for each region in the gradation expression region, Alternatively, the expression areas may be modulated simultaneously without distinction.

In Table 1, when it is stated that neither the array pitch nor the area is modulated, other modulation factors, such as the number of image forming elements occupying one pixel, are changed (P
gradation is expressed by (modulation).

FIG. 7 shows a block diagram when the present invention is applied to an on-demand inkjet type monochrome printer.

Signal 5(a) with gradation such as a video signal at the input terminal
is input. The grayscale signal 8 (a) is amplified by the amplifier section AMP and input to the frequency modulation section FMOD.

Frequency modulation section 1" M OD grayscale signal 5 (a) V
The signal is frequency modulated and input to the filter part FIL.

The frequency modulated signal s (b) is controlled by the controller C0NT in the filter section FIL to remove frequency components higher than the maximum response frequency of the inkjet head, and is inputted as the signal S (c) to the dot pitch diameter control section DCON. For the dot pitch diameter control unit DCON (ff No. 8 (c)), the controller C0NT
By this control, a voltage applied to the head corresponding to the gradation is obtained, and a dot pitch is given based on the density threshold given by the controller 9-CONT. Dot pitch diameter control unit 1) The head applied voltage signal outputted from CON is input to the head applied voltage control unit voL, head application II, pressure is set, and the image forming pulse generation unit PGE
Supplied to N. In the image forming pulse generation section PGDN, the head applied voltage control section V01. Switching the current from the inkjet head 1'J 111. IJ
1-12 drive pulses are generated. This driving pulse causes inkjet head 1JIIl, I
JI12tjON-OFPMIJ9 is combed back to form flying ink droplets. In synchronization with the ejection of the ink liquid, the controller C0NT outputs a control signal to the carriage control section C and the paper feed control section PF', thereby causing the inkjet head to scan the recording paper.

FIG. 8 shows signals of various parts in the first embodiment of the present invention. (G)+ is a timing pulse for generating a driving pulse for the dark ink nozzle, and the applied voltage at that time is given by (1)).

A driving pulse (E) for the inkjet head for ink A is generated by (C) and (port), and the inkjet head for dark ink is operated repeatedly from ON to OFF according to this signal. An array state is formed.

In (F), the pitch between the dots and the diameter of the dots change according to the level 1, and there are areas where the dots overlap each other in the dark part. As for the signals that drive the inkjet head for light ink, the above-mentioned FIG. 9 is a block diagram of the second embodiment of the present invention, which is an on-demand inkjet system and uses six colors of ink: yellow, magenta, and cyan. This is a case where it is used for a color printer that prints in color.

First, the color video signal or lMo (red), G (green).

B (%D (1) 4n number k 7 y 7” R
Ah4P, GAMP, BAMP vc , ): are amplified and input to the color signal generating section CGEN, respectively. The controller C0NT performs image processing on this input signal and sends the resulting output signal to the frequency modulation unit YFM.
Supplies to 1M, 12M and CFM respectively. Frequency modulation section YF
M, ~IF'M, CFM changes the frequency of each input signal w
After ~, the output signal is filtered by YIi'LL
.

MFIL, CI"IIL, \1 manual labor. Filter part YFIL.

In MFIL and CFIL, controller C0NT cuts frequency components higher than the maximum response frequency of the inkjet head, resulting in dot pitch.

It is output to the diameter control units YCON, MC0N, and CC0N, respectively. Dot pitch, diameter control section YCON, MC0N
, from the signal input to CC0N, controller C0N
TK provides a dot timing signal and a head applied voltage signal corresponding to the gradation change.

The dot timing signal is generated by the image forming pulse generator YGEN.
, MGhiN, and CGEN, respectively. Further, the head applied voltage signal is transmitted to the head applied voltage control unit YVOL.
.

The voltage value of the drive signal that is output to the MVOL and CVOL and applied to each head is set.

Image forming pulse generator YGF! N, M (3EN, CG
In each of EN, pitch/diameter control parts YCON, MC0
The head applied voltage control unit YVOL is controlled by input signals from each of N and CC0N.

MVOL, 1 from CVOL “Switching the flow,
Inkjet head YIJH1, YIJH2, MI
JHI, MIJH2.

It generates drive pulses for CIJHl and CIJH2. This drive pulse causes the inkjet head YI
JH1, YIJH2, MIJHl, MIJH2, CI
JHl and CIJH2 are repeatedly turned on and off, and flying ink droplets are formed each time. In synchronization with the ejection of ink droplets, the controller C0NT outputs a control signal to the carriage control section C and paper feed control section PF, thereby causing the inkjet head to scan the recording paper.

FIG. 10 is a block diagram showing a sixth embodiment of the present invention.
This is the case when applied to a color printer that prints in color using four color inks: magenta, cyan, and black. The circuit block is a modulation unit BFM for processing signals for black ink in the six-color printer shown in Figure 9.
, filter part DFIL, dot pitch, diameter control section 1
3CON, head applied voltage control section BVOL, and image forming pulse generation section BGEN.

Inkjet heads BIJHI and BIJI12 are added, and the basic signal processing contents are as shown in Fig. 9. Fig. 11 is a block diagram showing the fourth embodiment of the present invention. When applied to an on-demand inkjet type monochrome printing device equipped with a reading unit for reading the image, the result is C.

The reading main scanning control section NC and the reading sub-scanning control section RPF are controlled by a control signal from the controller C0NT, and the reading section RIN scans the original image to obtain a gradation signal. The process subsequent to the processing of the gradation signal is the same as in the embodiment shown in FIG. Note that the symbols used are the same as those in FIG. 7.

FIG. 12 shows a block diagram of the fifth embodiment of the present invention, which is an on-demand inkjet system equipped with a reading section for reading the original image, and prints ink in six colors of yellow, magenta, and cyan. This is a case where it is applied to a color printing device that prints in color.

The control signal from the controller C0NT controls the reading main scanning control section RcrL and the reading sub-scanning control section RPF, and the reading section IN scans the original image to obtain gradation signals of each color. The processing of each gradation signal after each amplifier is the same as in the embodiment shown in FIG. The symbol used is the 9th
The same parts as shown in the figure indicate the same parts as shown in FIG.

FIG. 13 shows a sixth embodiment of the present invention, which is an on-demand inkjet system equipped with a reading section for reading the original image, and uses four colors of ink: yellow, magenta, cyan, and black. This is a case where the present invention is applied to a color printing device for printing.

The reading main scanning control section ℃ and the reading sub-scanning control section PF are controlled by the control signal from the controller C0NT, and the reading section ILIN scans the original image and determines the level of each color. A JI4 signal is obtained. The processing after each amplifier of the gradation signal of each color is done in the first step.
This is the same as in the embodiment example shown in FIG.

Note that the same symbols used in FIG. 10 indicate the same symbols as shown in FIG. 10.

In the above description, an on-demand inkjet type inkjet head is used as the inkjet head, but the present invention is not limited to this and can be applied to other printers, such as a thermal transfer printer, a wire tod printer, and a 1FL photo printer. .

[Brief explanation of drawings]

FIG. 1 is a schematic illustration for explaining the basic concept of the present invention, FIGS. 2 and 3 are graphs showing the relationship between dot pitch and optical average reflection density, respectively, and FIGS. 5 is a graph showing the relationship between dot diameter and optical reflection density, FIG. 6 is a graph for explaining the relationship between the gradation expression area and modulation factor according to the present invention, and FIGS. FIG. 8 is a block diagram and timing chart for explaining the first embodiment of the present invention, and FIGS. 9 to 16 are
Block diagrams of second to sixth embodiments are shown below. (Dora Tobi Sochi) -1 (Dora Tobi 1 Suzudo F゛tsu L direct (/l, 1) 50 100 150 Zoo
: 150 Do, F direct

Claims (1)

[Claims] In an image forming method in which an image is formed by arranging a plurality of image forming elements having different optical densities, the image forming element in at least one of the arranging directions of at least one of the image forming elements is Variation 1 under childization of non-1 array pitch
4, and the gradation expression area by modulating the area of at least one image forming element of the plurality of image forming elements, one of which is modulated in the array pitch or area. An image forming method characterized by forming an image with gradation by configuring a gradation expression area that can be expressed by all of the image forming elements.