JPS62285576A - Half tone recording method - Google Patents

Abstract

PURPOSE:To obtain a linear density characteristic without losing the regularity of a gradation pattern by selecting and recording a heat pattern increasing the recording density monotonously among the heat patterns having same number of dots but different arrangement. CONSTITUTION:Recording densities A, D among the recording densities A<B<C<D are expressed by heat patterns comprising organic area gradation method such as centralized type or decentralized type and the recording densities B, C are expressed by heat patterns of different dot arrangement through the use of the heat storage operation due to the effect of simultaneous heating of plural dots by a thermal head and of continuous heating in the direction of sub scanning. A heat pattern whose recording density is increased monotonously is selected from the densities. Thus, the gradation characteristic whose recording density changes linearly is obtained. Since different densities are expressed by changing dot arrangement even with same dot number, the number of gradations over the dot number (NXM) constituting a matrix is obtained and the picture quality is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an image recording method using area gradation in a heat-sensitive, thermal transfer recording device, etc., and particularly relates to a high-speed, multi-gradation,
The present invention relates to a halftone recording method suitable for obtaining high resolution images.

[Conventional technology]

In general, it can be said that the dot density of heat-sensitive and thermal transfer recording devices is relatively low resolution compared to electronic plate making. In such a recording device, special measures are required in order to maintain resolution and obtain multiple gradations.

By the way, in a halftone recording method using an area gradation method in which halftones are expressed by the number of recording dots in a unit pixel or a pattern, when the pixel unit is increased in order to increase the number of gradations, the resolution decreases.

In the conventional area gradation method, picture elements are expressed as an N×M matrix, and systematic heating patterns are created, such as concentrated type and distributed type, so that the number of heating dots increases one by one and the recording density level increases monotonically. It composes to create midtones. (For example, see Electrophotographic Society Journal, Vol. 24, No. 1) For example, in a 4 x 4 matrix halftone gradation pattern (screen angle 06), the printed gradations shown in Figure 10 range from 0 to 16. A gradation pattern (FIG. 11) is obtained. Furthermore, a method is known in which the pitch width in the sub-scanning direction is made smaller than the pitch width of dots to increase the number of recorded dots without increasing the size of pixels, thereby obtaining multiple gradations.

For example, if the recording paper feed (sub-scan feed) is set to P/2 with respect to the heating element pitch P of a line-shaped thermal head, an 8x4 matrix gradation pattern will be created as shown in Figure 12. can get.

[Problem that the invention seeks to solve]

However, in high-density recording where the number of heat-generating dots is concentrated during high-speed recording using a high-definition head, the recording area relative to the area of the heat-generating dots becomes larger due to the heat storage effect of the thermal head, and as shown in Figure 13, the number of heat-generating dots increases. On the other hand, there was a problem in that a linear recording density could not be obtained.

SUMMARY OF THE INVENTION An object of the present invention is to provide a halftone recording method using a heating pattern in which dots do not connect due to the heat storage effect of a thermal head in high-density recording where the number of heating dots is concentrated.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention provides that the number of recorded dots included in an NxM matrix is (N
In a halftone recording method that expresses shading with a number of gradations of X M) + 1, (the recording density A-D corresponds to the above (N x M) + 1 and It K lj is defined). A heating pattern is formed with (K-1) dots and a density of 2. At the same time, densities B and C are different dot arrangements from the heating pattern of the density A, and the heating pattern of the density is When surrounded by dots on all sides or when the dots are continuous in the sub-scanning direction, one dot is removed from the heating pattern of the density to form a heating pattern with (K-1) dots; The heating pattern in which the recording density monotonically increases is selected from among the densities and recorded.

[Effect]

According to the above configuration, among the recording densities A<B<C<D, the recording densities A and D are expressed by a heat generation pattern constructed by the conventional concentrated type 1-distributed type systematic area gradation method, etc. Recording densities B and C are still expressed by heat generation patterns with different dot arrangements that utilize the heat storage effect caused by the simultaneous heat generation of multiple dots in the thermal head and the effect of continuous heat generation in the sub-scanning direction. By selecting a heating pattern in which the recording density increases monotonically, it is possible to obtain a gradation characteristic in which the recording density changes linearly.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 2 shows a gradation pattern created by changing the arrangement of dots at gradations 8, 10, and 12 of the conventional gradation pattern (FIG. 11). Note that each pattern is printed by simultaneously heating each dot one row at a time from the top. Here, gradations 7, 8...
Let the densities obtained in step 9 be A, B, and D, respectively, and in group 1 shown in FIG. 3, the relationship is A<B...D.

An example of how to determine the concentration will be explained.

In FIG. 4, densities A and D are - 1 and Kth, and densities B and C have the same number of recording dots as density A (K-1
The pattern is made up of different dot arrangements. Here, this method can be applied to K when there are 3 consecutive dots vertically or 3 dots horizontally.

Therefore, the range of is 3≦to≦(N×M) It is.

Further, each specific concentration will be explained. In FIG. 3, when the density of the pattern of gradation 7 is the density A of group 1, and the density of the pattern of gradation 9 is the density of group 1, density A is a heating pattern composed of 8 dots. The density is a heating pattern made up of nine dots. These are heat generation patterns of gradation 8 and gradation 9 constructed using the conventional halftone dot type shown in FIG. Density B corresponds to the density obtained by the pattern of gradation 8 shown in FIG. 2, and is a heating pattern composed of eight dots, which constitutes a heating pattern with a dot arrangement different from the heating pattern of density A. are doing.

Similarly, the concentrations A of other groups 2 and 3 in FIG.

The relationship between B...D is also constructed in the same manner as described above.

In either case, as a method for obtaining density B, when the dense heating pattern is surrounded by dots on all sides, or when dots are printed continuously in the sub-scanning direction, It consists of a heating pattern with one dot removed.

Next, the device configuration of this embodiment will be explained.

FIG. 1 shows the basic configuration of a thermal transfer recording apparatus.

FIG. 5 shows a heat generation drive circuit for a thermal head in which 2048 heat generating elements are arranged in a line. continue.

The basic operation of halftone recording will be explained.

The ink sheet 18 is made of a base material (polyester etc.) 14 coated with pigment ink 13, and is overlapped with the recording paper 12, and is held between the thermal head 5 and the platen roller 9 by a spring 16.
Pressure is applied. The thermal head 5 has a heating element 17 and a driving circuit shown in FIG. 5 formed on an insulating material (ceramic) 19, and is fixed to a heat sink 15. A current is passed through the heating element 17 to generate heat, and the ink sheet is heated. Melt the ink 13,
It is attached to the recording paper 12. Ink sheet 18.

The recording paper 12 is conveyed by rotation of the platen roller 9. The platen roller 9 is composed of a core metal 11, rubber 10, and the like.

The thermal head 5 inputs recording information to a data input terminal 1 and transfers it to a shift register 100 using a clock pulse 2. The transferred recording information is stored in the latch circuit ILO by the latch signal 3. The recorded information of the latch circuit is DS
T (1 to 8) The heating element 120 is energized by the applied pulse input to the terminal 4, and the heating element where the information is '1' generates heat.

In this method, as shown in FIG. 3, a linear gradation characteristic in which the recording density shifts in the direction of the arrow can be obtained compared to the conventional method.

Note that density B without an arrow is the recording density according to the present invention.

According to this embodiment, heat is accumulated in the glaze (not shown) under the heating element due to simultaneous or continuous heating of multiple if and tr units,
Even if the number of heat-generating dots is the same, the density level can be controlled by the arrangement of the dots, so even if the recording speed becomes faster, density saturation does not occur at high gradation levels.

(Second Embodiment) FIG. 6 shows one gradation 4 of the conventional gradation pattern (FIG. 12). -5.7,9,12,13,15°17~22,2
This is a gradation pattern created by changing the dot arrangement of 4, 25, and 27. Here, the densities obtained at one gradation level of 3.4 and 5.6 are A, B, and C, respectively.

D, and the relationship is A<B<C<D in each group. The pattern of gradation 3, which obtains the density A, is composed of four dots, and the pattern of gradation 6, which obtains the density, is composed of five dots.

These are the same gradation patterns as the conventional gradations u4 and u5 shown in FIG. The densities B and C are the gradations 4 and 4 shown in FIG.
This is a pattern composed of four dots with the density obtained in pattern No. 5, and constitutes a heating pattern with a dot arrangement different from that of the gradation pattern from which the density A was obtained.

Note that the other gradation patterns mentioned above are also created by the above-described method.

Furthermore, the gradation pattern 12°13 shown in FIG.
The number of dots is one dot less than that of the gradation pattern 9 shown in the figure, and the dot arrangement is different from that of the gradation pattern 8. Similarly,
The gradation patterns 15°24 and 25.27 have one dot less than the gradation patterns IQ, 13 and 14 shown in FIG.
The dot arrangement is different from the one shown below.

With this method, as shown in FIG. 7, gradation characteristics with improved linearity can be obtained compared to the conventional method.

According to this embodiment, when the heat generating resistors are arranged at a distance P, it is effective even if the length of the heat generating resistors is P/2 or more. In addition, by selecting a gradation pattern so that the shape of the recorded dot area is not discontinuous with the pattern before and after the 1st gradation pattern, contour line-like contours ( false contours) can be prevented from appearing.

Note that FIGS. 8 and 9 are embodiments of the second embodiment of the present invention, and show different gradation patterns.

Although the embodiments of the present invention have been described with respect to thermal transfer recording, it can also be applied to thermal recording using thermal paper.

〔Effect of the invention〕

As described above, according to the present invention, heating patterns having the same number of dots but different arrangement are formed in the matrix, and a heating pattern that monotonically increases the a'a degree is selected from among the heating patterns including the heating pattern. Since the recording is performed in such a manner that the texture of the gradation pattern is not lost, a linear density characteristic can be obtained. Further, a gradation pattern that takes heat accumulation in the head into consideration can be applied to high-speed recording, and a gradation pattern that does not cause false contours can be selected, so that high-speed recording and improved image quality can be achieved. and.

Even if the number of dots is the same, different densities can be expressed by changing the arrangement of the dots, so that the number of gradations greater than the number of dots (N×M) constituting the matrix is obtained, and the quality of one image is improved.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of an apparatus configuration for implementing the halftone recording method of the present invention. Fig. 2 is a diagram showing a gradation pattern of a 4 x 4 matrix according to the first embodiment of the present invention, Fig. 3 is a density characteristic diagram of the first embodiment, and Fig. 4 is a diagram showing the conventional density characteristic. This is a diagram explaining how to determine the number of recording dots to obtain the density characteristics of the method.
a) is a conventional density characteristic diagram, (+)) is a density characteristic diagram of this method, FIG. 5 is a diagram showing a drive circuit of a line type thermal head, and FIG. 6 is a diagram showing a second embodiment of the present invention. FIG. 7 is a diagram showing the gradation pattern of a certain 8×4 matrix, and FIG. 7 is a density characteristic diagram of the second embodiment. FIGS. Figure 10 shows the conventional 4
Halftone dot type consisting of ×4 matrix (screen angle 0°
11 is a diagram showing the gradation pattern in numbers, FIG. 11 is a diagram showing the gradation pattern in FIG. , Figure 13. It is a conventional halftone type density characteristic diagram.

Claims (3)

[Claims] (1) Heat-sensitive and thermal transfer recording in which characters and images are recorded by heating a heating element according to an input signal, and the number of recorded dots (N×M) included in a matrix of N rows and M columns is )+1 tone number created using the known systematic area gradation method (N
Among the xM) heating patterns, the (K-1)th recording density A is formed by (K-1) dots, the Kth density D is formed by K dots, and the densities B and C is formed with a different dot arrangement from the heating pattern of the density A, and when the heating pattern of the density D is surrounded by dots on all sides, or when the dots are continuous in the sub-scanning direction, the density D A halftone recording method in which a heating pattern is formed by (K-1) dots, one dot removed from the heating pattern, and the heating pattern in which the recording density monotonically increases is selected from among the densities and recorded. (2) Set the above densities B and C to 1 dot near the center or inside of the heating pattern when the heating pattern of density D is surrounded by dots on all sides or when the dots are continuous in the sub-scanning direction. 2. The halftone recording method according to claim 1, wherein the halftone recording method is obtained using a removed heating pattern. (3) It is characterized by using a recording means in which the movement of the recording paper or the thermal head is P/n with respect to the heating element pitch P of the thermal head, and the matrix is made up of (N × n) rows × M columns. A halftone recording method according to any one of claims 1 and 2.