JPS61227476A - Print method - Google Patents

Abstract

PURPOSE:To improve the picture quality by splitting a dot into plural numbers for printing so as to avoid dots from being remarkable in eyes in the print method where the print time is controlled so as to express the gradation of the dots. CONSTITUTION:A data correction circuit 11 changes a data so as to provide a larger gradation, the corrected data is read from a memory 2 and fed to a comparator 3. A gradation counter 4 consists of two 4-bit counters 4a, 4b, which are connected so as to obtain separately a PWM signal drawing dots corresponding to the odd number order gradation and a PWM signal drawing dots corresponding to the even number order gradation, and the dots representing 15 gradations and the dots representing 128 gradations are split respectively into dots 1011, 1021 corresponding to the odd number order gradation and dots 1012, 1022 corresponding to the even number order gradations.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is capable of expressing dots forming an image by controlling printing time, such as in a sublimation type thermal printer. The present invention relates to a suitable printing method using a printer.

[Summary of the invention]

The present invention improves the image quality by dividing one dot forming an image into a plurality of parts and printing them, thereby narrowing the distance between the dots.

[Conventional technology]

In a sublimation type thermal printer, a dot platen around which recording paper is wound is continuously rotated by a Do motor, and a heating head is pressed against the recording paper f through a thermal ink ribbon to draw an image using dots. 1
It's straining. In this case, the heating time of the head that prints the dot is controlled to express the density of the dot. Therefore, the gradation of shading of a dot is expressed by the length of the dot.

FIG. 7 shows a circuit of a conventional thermal printer.

A video signal consisting of a still image signal is digitized by an A/D converter 1 and then written to a line memory 2.

In this example, one line of the dot row is drawn with 512 dots, and the gradation of one dot for each friend is 7 pitches) (128
gradation). The 512 pieces of data for one line sequentially read out from the memory 2 are applied to a comparator 3 and compared with the data indicating the gradation added from the gradation counter 4. This comparison is performed as follows.

Gradation counter 4 first sends data indicating the lowest gradation "1" to comparator 3#. Comparator 3 sequentially compares the 512 data with the data indicating "1" above,
When it is larger than "1", the rHJ signal is output and "1"
When it is smaller, the rLJ signal is output. This rH
The J or rLJ signal is sequentially sent to the shift register 5.

When the comparison between the gradation level "1" and the 512 pieces of data is completed, the primary f gradation counter 4 sends data indicating the gradation level "2" to the comparator 3. The data and the above 512 pieces of data are sequentially compared, and depending on the comparison result, the 7th number of 9l"HJ or rLJ is sent to the shift register 5#. In this way, 512 pieces of data for one line and 1st '' to the gradation data of r128J are sequentially compared.

As a result, a PWM signal having a pulse width of t according to the gradation is obtained from the shift register 5 for each of the 512 pieces of data. When PWM signals are obtained for all the data on one line, the 512 signals on the next line are
Comparisons are made for each piece of data in the same way as above.

The PWM signal obtained from the shift register 5 is applied to the head driver 41 circuit 7 via the latch circuit 6. Thereby, the heating time of the 512 heads making up the heating head 8 is controlled according to the pulse width of the PWM signal.

The memory 2 is from the 512-decimal counter 9#.

Writing and reading are controlled, and the gradation counter 4 is configured to advance the gradation data by one in response to the carry pulse S of the counter 9.

The counter 4.9 and shift register 5 are driven by a common clock pulse.

Additionally, as a printer using %PWM signals, a patent application filed in 1982-
A pen type printer according to No. 217338 has been proposed by the present applicant.

[Problem that the invention seeks to solve]

As mentioned above, in the printer shown in Figure 7, the head is PWM.
When heating is performed at time t in accordance with the signal, since the recording paper is moving, t dots are printed, the lengths of which vary depending on the gradation, as shown in FIG. 8.

In this column of FIG. 8, a dot 101 indicating the "15" gradation
has a length of 11 and a dot of 102 indicating r128J gradation.
has a length of 12. Therefore, in the case of r15J100, there are approximately 12 points between dot 101 and the adjacent dot (not shown).
A gap with a length of -11 is created. This particular feature makes each dot stand out in low-gradation areas of the screen, degrading the image quality. In the case of color images, multiple ink ribbons of different colors are used for overprinting, so color misregistration may occur, making dots particularly noticeable.

[Means for solving problems]

In the present invention, one conventional dot is divided into a plurality of dots and printed.

[Effect]

It is possible to prevent dots from standing out even in low-gradation areas of the screen or in cases where color shift occurs.

〔Example〕

I try to print it separately. In the column of Fig. 1, there are dots of r128J gradation (represented by two dots 102t and 1022 in Fig. 8).
The gradation 04 dot (dot 101 in Figure 8) is represented by two dots) 1 (hl, 1012).

For example, the maximum heating time T is 32.5ms! There is c't'',
The length 12 for this is approximately 0.2111 m't'6.

In order to divide one dot into two, in this implementation column, dots 10 corresponding to odd-numbered gradations f are divided as shown in the figure.
11. Dot 1 corresponding to 1021 and even numbered gradation scale
012, 1022, and 5F.

FIG. 2 shows an embodiment of a companion circuit implementing the above-mentioned division method, and the same parts as in FIG. 7 are given the same reference numerals.

In this embodiment, the A/D converted data is corrected by the data correction circuit 11 before being written into the memory 2#ζ. If you divide the dots as described above, for example, dots 10n, 1012 yIr- When printing, first print dot 1011 and then print.

The dot 1012 will be printed once after the printing has stopped, but during the above-mentioned pause period, the heat from the head will escape and the density of the next dot 1012 will be printed at a low density. This method is similar to the conventional one.

The density of the dot itself becomes thinner than when printing a single dot 101 by heating the dot continuously. To solve this problem, the data correction circuit 11
I'll change the data to 5 with a larger gradation of E. 5+
It's straining. This corrected data is read out from the memory 2 and added to the comparator 3.

The gradation counter 4 includes two 4-bit counters 4a.

The constitutive formula is 4b. The terminal of the most significant bit of this counter 4 (the C terminal of the counter 4b) is connected to the terminal of the least significant bit of the comparator 3.
Connect the least significant bit terminal (A terminal of counter 4a) to the second bit terminal of comparator 3, and then
The second to sixth bit terminals of the comparator 3 are connected to the third to T bit terminals of the comparator 3, respectively. When connected in this way, the PWM signal draws dots corresponding to odd-numbered gradations, and the dots corresponding to even-numbered gradations (
PWM signals can be obtained separately.

As described above, in the first embodiment, one dot is divided into two, or may be divided into three or more, and may be divided into an arbitrary number depending on percentage or gradation.

FIG. 3 shows a second embodiment of the present invention, in which one dot is divided into four parts, r15J gradation and r124J gradation.
Gradation is shown as an example.

FIG. 4 shows an implementation sequence of the method of connecting the counter 4 and the comparator 3 when implementing the method according to the second implementation sequence.

The fifth factor shows the third implementation project of the present invention, in which the number of divisions is arbitrarily varied depending on the gradation. In this row, the dots of "15" gradation are divided into 15, and r
A dot with 124J gradation is divided into four.

FIG. 6 shows an example of a method for connecting the counter 4 and the comparator 3 when implementing the third example method.

〔Effect of the invention〕

The dots forming the image gR become less noticeable.

Even if color shift occurs when printing multiple colors one on top of the other, dots will not stand out and the image quality can be improved. The present invention can be effectively applied to thermal printers, pen-type printers, and other printers whose printing time is controlled by PWM signals.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a first implementation row of the present invention, and FIG.
3 is a block diagram showing an embodiment of a circuit for implementing the embodiment of the present invention, FIG. 3 is a diagram showing a second embodiment of the present invention, and FIG. 4 is a block diagram showing an embodiment of a circuit for implementing the second embodiment A block diagram showing an example, FIG. 5 is a diagram showing a third embodiment of the present invention, and FIG.
The figure is a block diagram showing an embodiment of a circuit for implementing the third real MfI sequence, FIG. 7 is a block diagram of a conventional printer, and FIG. 8 is a diagram showing a conventional printing method. Please note the symbols used in the drawings. 1011・1012, 1021.1022...
・・・・・・Divided and next dot 2 ・・・・・・・・・
・・・Memory 3 ・・・・・・・・・Comparator 4 ・・・
...... Gradation counter 8 ......
...It is a heating head. Honkamei's example of Kino 2 Practical example Fig. 3 The second Uradenretsu rotation of the present invention Fig. 4 Fig. 5 Fig. 6

Claims (1)

[Claims] While moving the recording paper and the print head relatively, the head prints dots on the recording paper, and at this time, by controlling the printing time, the gradation of the dots is expressed. In the printing method according to the invention, the dots are divided into a plurality of parts and printed.