JP2001080103A - Color printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To print in a constant density irrespective of the dividing number in terms of a dividing number variable type color printer wherein printing is executed by the diving number corresponding to the number of pixels to be printed. SOLUTION: This color printer comprises a gradation counter 5 for counting the number of times of gradation printing, a data counter 7 for counting the number of pixels to be printed by each gradation and a printing times determining section 8 that determines the number of times of divisional printing in the present gradation printing on the basis of the output of the data counter 7 and a predetermined maximum concurrent printable pixel number. When the dividing number obtained by the printing times determining section 8 is great, an energizing time period of a line thermal head 12 is set to be long corresponding to the dividing number.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color printer for printing multi-value image data on recording paper.

[0002]

2. Description of the Related Art A color printer receives, from a host, still image data in which the gradation value of each pixel is described by multi-valued data, sequentially prints the data for each line, and finally records one still image. What you get on paper. First, the principle of printing by the line thermal head will be described. FIG.
FIG. 2 is a schematic block diagram of a line thermal head. The figure shows an example in which only six pixels are used for simplicity.

In a line thermal head, a shift register for storing binary data of printing or non-printing of each pixel constituting one line is masked by a strobe signal (STB), and the value of each shift register (SR1 to SR6) is changed. Gate circuits (G1 to G) transmitted to the transistors (Tr1 to Tr6)
6), and composed of heating resistors (R1 to R6) that are energized by the transistors (Tr1 to Tr6) and generate heat. In this figure, after the print data and the synchronous clock are input to the DATA and CLK terminals, respectively, for the number of print pixels, the STB terminal is activated to cause a current to flow through the heating resistors (R1 to R6) and generate heat.

On the other hand, the line thermal head is in contact with a recording paper on which an image is recorded, and an ink sheet which is sublimated and transferred to the recording paper by heat is interposed between the line thermal head and the recording paper. As described above, the heat generated by the line thermal head causes the ink on the ink sheet to be sublimated and transferred to the recording paper, and printing is performed on the recording paper.
As described above, the line thermal head can perform only binary printing on whether or not sublimation transfer of ink is performed in one printing.

[0005] Therefore, as a multi-gradation printing method using a line thermal head, a method of realizing density modulation by performing printing a number of times corresponding to a gradation value during one-line image formation is general. Briefly, printing is performed five times for data with a gradation value of 5, and 20 times for data with a gradation value of 20. The processing includes a certain gradation printing cycle.
(L time; L = 0, 1, 2, 3,...), If the print data is larger than L, the data is sent to the line thermal head as a non-print otherwise, and the print is performed. Repeat several times for the expression gradation.

[0006] On the other hand, in a line thermal head, the number of printing pixels greatly affects power consumption, and therefore, depending on the power supply capacity, it may not be possible to simultaneously print all printing pixels in one line. In this case, the number obtained by dividing the total number of pixels of the line thermal head by the number of pixels that can be printed simultaneously (if there is a surplus, the above value +
1) (the number of blocks is K), and printing of each block is performed in a time-division manner (hereinafter, referred to as divided printing). In this case, the time required for image formation is as follows. This is simply K times larger than the case where all pixels of the line thermal head are printed collectively.

However, in the case of the multi-tone printing method described above,
For an image input in which the gradation value of a pixel exists from a low gradation to a high gradation such as in a natural scenery, the number of pixels to be printed tends to decrease as the number of times of gradation printing increases (as the gradation increases). In other words, under the limitation of the number of simultaneous printing pixels,
In low tone printing, the number of simultaneous printing pixels is large, so even if it is necessary to divide and print multiple times, the number of simultaneous printing pixels decreases as the number of gradation printing advances, so the number of times of division printing is smaller than before I can do it.

[0008] By utilizing this property, in a certain gradation printing cycle,
With a configuration in which the number of print divisions can be changed in accordance with the number of pixels to be printed, it is possible to suppress an increase in printing time while clearing the limitation on the number of pixels to be simultaneously printed. This printing method is hereinafter referred to as a variable division number printing method.

As described above, in a certain number of gradation printing, printing is performed with a print division number corresponding to the number of pixels to be printed.
FIG. 2 shows the configuration of the division number variable printing method. A two-dimensional image to be printed on the host 1 is stored. Image data of the host 1 is written to the line memory 2 line by line in an exchange between the host and the timing controller 3.

When printing of one line is started, the gradation counter 5 is reset. Then, the print data from the line memory 2 is read out for one line in dot sequence, and is compared with the output of the gradation counter 5 and the comparator 4 to obtain binary data of print or non-print. Stored. The data counter 7 receives the output of the comparator 4 and counts the number of pixels to be printed.

On the other hand, in this apparatus, the upper limit (the maximum number of simultaneously printable pixels) is determined for the number of pixels that can be printed at one time.
The number of times the printing should be divided is determined, and an instruction is issued to the head controller 10 to divide the number of printings of the gradation into the determined number of times and print.

Thereafter, the head controller 10 reads one line of print data from the line buffer 6 to the AND circuit 9, transfers the print data to the line thermal head 12 via the AND circuit 9, and transfers one line of data. After the end, printing is performed by the STB signal from the STB signal generation unit 11. The operation from the reading of the data in the line buffer 6 to the printing is performed before the division number determination unit 8
Simultaneously, the head controller 10 sends a print pixel mask signal to the AND circuit 9 to mask pixels other than pixels to be printed in each division print. In this way, printing for one gradation is completed.

Next, by incrementing the gradation counter 5 and repeating the above operation, printing for two gradations is completed. If this is repeated until the gradation counter 5 becomes equal to the total number of gradations to be printed, one line gradation printing is completed,
Timing controller 3 to motor controller 13
And the motor 14 is driven to move the recording paper and the line thermal head 12 by one line relatively. Thereafter, printing of the next line is started, and thereafter, this is repeated to print a two-dimensional image.

[0014]

However, the printing method described above has the following problems. For example, even when the gradations of the print data are all the same, when the number of print pixels in one line is large and when the number of print pixels in one line is small, the print density becomes lower with more print pixels. Would. This is because, when there are many printing pixels in one line, the number of divisions in printing of each gradation increases, so that the heating interval in each pixel becomes longer, the temperature of the heating element decreases, and the printing density decreases. It is.

FIG. 3 shows an example of the temperature of a certain pixel of the line thermal head 12 in a case where printing of a certain gradation is performed by dividing into three, and FIG. 4 shows a case in which printing is performed by dividing into one. At the start of n-gradation printing, it is assumed that the temperature of the pixels of the line thermal head is the same in one-division printing and three-division printing, and the target pixel is printed in the first division during three-division printing. Shall be.

[0016] Regardless of whether power is supplied or heat is generated during the same time STB, the power supply interval is longer in three-division printing than in one-division printing. The temperature will be low. Therefore, at the same gradation, the temperature reached is lower than at the time of one-division printing, and the print density is reduced.

[0017] Then, in the case of one-part printing, the cooling time may be lengthened to make the temperature reached at the same gradation the same as that in the three-part printing. In this case, the advantage of the variable division number printing, which is to reduce the printing time by reducing the number of prints, disappears.

[0018]

Means for Solving the Problems The present invention has been made in view of the above-mentioned problems, and the invention according to claim 1 is that “each pixel receives digital image data having multi-gradation data, By controlling the presence / absence of ink transfer for each gradation, a line image composed of print pixels having a multi-gradation density difference is obtained on recording paper by a line thermal head, and at the same time, In a color printer that prints a two-dimensional image by recording a plurality of lines on a recording paper, a gradation number counting unit that counts the number of gradations to be printed, and counts the number of pixels to be printed for each gradation printing The current number of divided prints of gradation printing from the output of the print pixel number counting means and the output of the print pixel number count means and a predetermined maximum simultaneous printable pixel number. A print number dividing means for setting the number of divisions by the print number dividing means, and when the number of divisions is large, the energizing time of the line thermal head is set longer according to the number of divisions. Printer. "
Is provided.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a block diagram showing a configuration of a variable division number printing system according to the embodiment of the present invention. FIG. 6 shows an example of the relationship between the number of divisions and the active time of the STB signal in the STB signal generation unit 11. It is a table shown. FIG. 7 is a diagram illustrating an example of a temperature of a certain pixel of the line thermal head 12 of the color printer according to the embodiment of the present invention in a case where printing of a certain gradation is performed by dividing into three. FIG. 8 is a diagram showing a case where the division is performed by one division.

In FIG. 5, a two-dimensional image to be printed on the host 1 is stored, and image data of the host 1 is written to the line memory 2 line by line between the timing controller 3 and the two-dimensional image. When printing of one line is started, the gradation counter 5 is reset. Then, the print data from the line memory 2 is read out for one line in dot sequence, and is compared with the output of the gradation counter 5 and the comparator 4 to obtain binary data of print or non-print. Stored. The data counter 7 receives the output of the comparator 4 and counts the number of pixels to be printed.

On the other hand, in this apparatus, the upper limit is set for the number of pixels that can be printed at one time, and the division number determination unit 8 receives the output of the data counter 7 and determines how many times the printing should be divided. Then, an instruction is issued to the head controller 10 so as to divide the printing of the gradation into the determined number of times and perform printing.

Thereafter, the print data for one line is read out from the line buffer 6 to the AND circuit 9 by the head controller 10 and transferred to the line thermal head 12 via the AND circuit 9 to transfer the data for one line. After the end, printing is performed by the STB signal from the STB signal generation unit 11. The operation from the reading of the data in the line buffer 6 to the printing is performed before the division number determination unit 8
Simultaneously, the head controller 10 sends a print pixel mask signal to the AND circuit 9 to mask pixels other than pixels to be printed in each division print.

Here, in the present invention, the STB signal generated by the STB signal generator 11 is controlled by the division number information determined by the division number determiner 8, and the active time of the STB signal is changed. For example, when the number of divisions determined by the division number determination unit 8 is large, the active time of the STB signal is extended to increase the heat generation temperature, thereby compensating for the temperature decrease during the non-energization time. FIG. 6 shows an example of the relationship between the number of divisions and the active time of the STB signal in the STB signal generator 11. In this way, printing for one gradation is performed.

Next, the gradation counter 5 is advanced, and the above operation is repeated to finish printing for two gradations. If this is repeated until the gradation counter 5 becomes equal to the total number of gradations to be printed, the gradation printing of one line is completed, and a command is issued from the timing controller 3 to the motor controller 13.
The motor 14 is driven to relatively move the recording paper and the line print head by one line. Thereafter, printing of the next line is started, and thereafter, this is repeated to print a two-dimensional image.

FIG. 7 shows an example of the temperature of a certain pixel of the line thermal head 12 in the present embodiment when printing of a certain gradation is performed by dividing into three parts. As shown in FIG.

At the start of n-gradation printing, one division printing and three
It is assumed that the temperature of the pixel of the line thermal head 12 is the same between the division printing and the target pixel is printed at the first division in the three division printing.

Since the active time of the STB signal at the time of three-division printing is extended to increase the heat generation time, the temperature at the end of printing of each gradation in one-division printing and three-division printing becomes the same. , The maximum temperature reached at each gradation printing is almost the same. As a result, it is possible to suppress a change in density caused by a change in the number of divisions.

[0028]

As described above, the color printer according to the present invention has the advantage of the variable division number printing even in the variable division number printing in which the division number of the printing is changed according to the number of simultaneous printing pixels at each gradation printing. The change in density caused by the change in the number of divisions can be suppressed while shortening the printing time.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a line thermal head.

FIG. 2 is a block diagram showing a configuration of a conventional division number variable printing system.

FIG. 3 is a diagram illustrating an example of a temperature of a certain pixel of a line thermal head of a conventional color printer in a case where printing of a certain gradation is performed by dividing into three.

FIG. 4 is a diagram illustrating an example of a temperature of a certain pixel of a line thermal head of a conventional color printer in a case where printing of a certain gradation is performed by dividing into one.

FIG. 5 is a block diagram illustrating a configuration of a division number variable printing method according to the embodiment of the present invention.

FIG. 6 is a table showing an example of a relationship between the number of divisions and an active time of an STB signal in an STB signal generation unit.

FIG. 7 is a diagram illustrating an example of a temperature of a certain pixel of the line thermal head of the color printer according to the embodiment of the present invention in a case where printing of a certain gradation is performed by dividing into three.

FIG. 8 is a diagram illustrating an example of a temperature of a certain pixel of the line thermal head of the color printer according to the embodiment of the present invention in a case where printing of a certain gradation is performed by dividing into one;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Host 2 Line memory 3 Timing controller 4 Comparator 5 Gradation counter 6 Line buffer 7 Data counter 8 Division number decision part 9 AND circuit 10 Head controller 11 STB signal generation part 12 Thermal print head 13 Motor controller 14 Motor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C066 AA03 AB03 AB09 AC01 AD03 CD03 CD06 CD14 CD15 CD19 CD23 CD27 5C077 LL04 LL18 MP08 NP09 PP41 PP61 PP78 PQ08 PQ17 TT04 TT06 5C079 KA13 LA31 NA11 PA02 PA03

Claims (1)

[Claims] 1. Each pixel receives digital image data having multi-gradation data and controls the presence or absence of ink transfer for each gradation by using a line thermal head to reduce the multi-gradation density difference. In a color printer that prints a two-dimensional image by recording a plurality of lines on recording paper by sub-scanning of the line thermal head at the same time as obtaining a line image composed of print pixels on a recording paper, Means for counting the number of gradations to be counted; means for counting the number of pixels to be printed for each gradation printing; means for counting the number of pixels to be printed; and the output of the means for counting the number of printed pixels and the predetermined maximum number of simultaneously printable pixels And a print frequency dividing means for determining the number of divided prints of the current gradation printing from the above. When the number of divisions divided by the print frequency A color printer, wherein the energizing time of the line thermal head is set longer according to the number of divisions.