JPH0250857A - Printer - Google Patents

Abstract

PURPOSE:To perform the dot printing of a character, a line drawing and a medium contrast image with high-grade image quality by controlling the printing of the character and the line drawing on the basis of the size of the first dot while controlling that of the medium contrast image on the basis of the second dot. CONSTITUTION:In printing a character and a line drawing, a character/line drawing mode is indicated from an operator panel 3 and change-over switches SW1, SW2 are connected to a character/line drawing data control part 2d to make the energy applied to a heating unit large and current supply history is controlled to obtain the sharpness of a line. In the case of a medium contrast image, a medium contrast image mode is indicated from the operator panel 3 and the change-over switches SW1, SW2 are connected to a medium contrast image data control part 2e to make the energy applied to the heating unit small and the estimation control of heat accumulation is performed because of a high printing rate to obtain uniform printing. Herein, the change-over is performed on the basis of the operator panel but may be executed according to the indication from a host by a control part 2a and, not only in the case of one page unit but also in such a case that the character and the medium contrast image are mixed within one page, printing can be realized by the change-over within a page.

Description

[Detailed description of the invention] [Table of contents] Overview Industrial field of application Conventional technology Problems to be solved by the invention (Fig. 5) Means for solving the problems (Fig. 1) Functional example (a) 1 Description of Embodiments (Figures 2 to 4) (b) Explanation of Other Embodiments Effects of the Invention [Summary] Regarding a printer that prints with dots and is capable of expressing halftones, it is possible to print characters, line drawings, and halftone images in high quality. The purpose of this printer is to print dots with high quality image quality, and includes a dot printing unit that prints dots, and a print control unit that controls printing in maximum density for characters and line drawings and in halftone expression for images. The control unit has a first print control mode in which printing is controlled for the text or line drawing using a first dot size, and a second print control mode for controlling printing for the image using a second dot size. It has a

[Industrial application field]

The present invention relates to a printer that prints with dots and is capable of expressing halftones.

Printers, which are widely used as output devices for computers, word processors, etc., have developed as devices for printing characters. Initially, only alphabets and katakana were printed, but with the development of printers that print dots, they can print characters such as kanji and figures. Those that can print (line drawings) are the best.

On the other hand, with the development of graphic processing, the demand for image printing including halftones is increasing, and this has been realized by thermal transfer printers, laser printers, and inkjet printers.

Halftone printing is broadly divided into area gradation method and density gradation method, but in either case, gradation reproducibility greatly affects image quality.
Color printers also allow full color printing.

In printers that print with such dots,
What is desired is something that can print both characters, line drawings, and halftone images with good image quality.

[Conventional technology]

Conventional printers that print both text and line drawings and halftone images generally print the text and line drawings at the highest density and the images at halftone.

For example, in a thermal transfer printer that expresses halftones by area gradation, the basic principle is to melt and transfer the ink of the ink sort by the heat generated by the normal hand.

In the area gradation method (for example, the density pattern method), one pixel is expressed by an MXM dot matrix, and halftones are expressed by determining how many dots out of each 7 links are printed.

For example, when expressing one pixel with a 2 x 2 matrix, five gradations from 0 to 4 are possible, and in order to guarantee gradation, the area ratio of printed dots and non-printed dots must be adjusted. must be printed correctly.

In conventional printers, the basic size of the dots is uniquely designed and adjusted.

[Problem to be solved by the invention]

FIG. 5 is a diagram illustrating problems in the prior art.

Conventionally, the size of the dot is uniquely determined, so if you design and adjust the dot to match the character, the size shown in Figure 5 (A
) to (C), characters and line drawings are continuous and can be printed clearly, but in halftone images, dots blur, overlap, and thicken, affecting adjacent dots, and as shown in Figure 5 (B). )
As shown in the image, the white part is crushed and the gradation cannot be expressed well,
There was a problem that the gradation quality deteriorated.

On the other hand, if dots are designed and adjusted with emphasis on halftone images, as shown in FIGS. 5(D) to (E), in halftone images,
Although it is possible to express good gradation without overlapping dots or the influence of adjacent dots, there is a problem that the characters and line drawings are discontinuous or thin, and the quality of the characters and line drawings deteriorates.

This tendency is particularly strong in printers that perform area gradation, and is particularly noticeable in thermal transfer printers that use wax ink.

Although there are differences in printing methods, this may be due to text,
For line drawings, the printing rate is low and lines with a certain thickness are required, and it is better for each dot to blur or overlap a little, whereas for halftone images, the printing rate is high (white This is because the dots tend to have a small number of dots), and each dot has a lot of staining, thickening, and overlapping (easily occurring), which causes problems in terms of gradation.

In this way, with the conventional technology, if dots are designed and adjusted to match characters and line drawings, the gradation is distorted, and if dots are designed and tuned with emphasis on gradation, the quality of the characters and line drawings deteriorates. Therefore, it has been difficult to achieve both the image quality of characters, line drawings, and halftone images.

Therefore, an object of the present invention is to provide a printer capable of dot printing both characters, line drawings, and halftone images with high image quality.

[Failure to solve the problem] FIG. 1 is a diagram showing the principle of the present invention.

As shown in the 11th RI (A), the present invention includes a dot printing section 1 that performs dot printing, and a print control section 2 that controls printing in maximum density for characters and line drawings and halftone expression for images. In the printer including the printer, the print control unit 2 operates in a first print control mode in which the characters and line drawings are controlled in a first dot size, and in a first print control mode in which the images are controlled in a second dot size. and a second print control mode.

[Effect]

In the present invention, since the printer has a first control mode for text and line drawings and a second control mode for halftone images, the printer has a first control mode for text and line drawings. Optimal printing control is possible with one dot size, and for halftone images, the second dot size
Since printing can be controlled optimally depending on the size of the dots, text, line drawings, and halftone images can be printed with optimal image quality by using different print control modes.

〔Example〕

(a) Description of an Embodiment FIG. 2 is a block diagram of an embodiment of the present invention, showing a thermal transfer printer capable of expressing halftones.

In the figure, the same components as those shown in FIG. The head 1 is driven by a plug and a strobe signal.

2a is a control unit that controls the interface with the host and also controls the expansion of characters, diagrams, etc.; 2b is a pattern generator that converts code data such as characters, diagrams, etc. into patterns; Reference numeral 2c is a memory in which image data from the control section 2a and patterns generated using the pattern generation section 2b are developed page by page.

2d is a character and line drawing data control unit, which generates a large amount of energizing energy to print in large dots, and also controls the energizing history of several lines for heat accumulation correction on the order of milliseconds, as shown in Figure 3. 2e is a halftone image data control unit, which generates a small amount of energizing energy to print small dots, and also prints several tens of lines to hundreds of lines to perform heat accumulation correction on a second-by-second basis as shown in Figure 4. It performs heat storage prediction control based on the line's energization history.

Reference numeral 3 designates an operator panel, which instructs to switch printing modes for text, line drawings, and halftone images; SW1 and SW2 are mode changeover switches, respectively, and control sections for character and line drawing data control section 2d, memo 'J2c, and head; drive circuit 1b,
The connections between the halftone image data control section 2e, the memory 2C, and the head drive circuit 1b are switched according to instructions from the operator panel 3.

In this embodiment, in the case of character and line drawing printing, the printing rate is low and the transfer efficiency is poor, so energization history control is performed to increase the energy applied to each heating element and obtain sharp lines.

On the other hand, when printing halftone images, less energy is applied to each heating element than in the former case, and the printing rate is high, so heat storage predictive control is performed.

FIG. 3 is a diagram showing the main part of the configuration shown in FIG. 2, showing the character and line drawing data control section 2d.

In the figure, 20 is a shift register, which stores the data for one line to be printed this time, and 21 is a shift register, in which the data of the shift register 20 is set in parallel, and the data for one previous line is stored. 22 is a shift register, in which the data of the shift register 21 is set in parallel, and data for one line from the previous time is stored.

NOR is a NOR gate, and shift register 21.2
The one that inverts the logical sum (OR) of 2 and outputs it, AD is an AND gate, and the output of the shift register 20 and NO
R game) Something that takes the logical product (AND) of the output of NOR,
SW is a changeover switch, which is switched to the a side when the first half is energized and to the b side when the second half is energized.

In this configuration, the shift register 20 stores the 1 to be printed this time.
The data for the line is stored, and the shift register 2
1.22 stores the line data of the previous time and the time before the previous time.

For printing one line, the changeover switch SW is first connected to the a side, and the shift register 21 is connected to the thermal head 1a.
．． The NOR outputs of 22 are transferred, and at this time shift registers 20, 21, and 22 are shifted to the right one dot at a time.

At this time, a first half energization pulse (strobe) is outputted to the thermal head 1a from an energization pulse generation circuit (not shown).

Next, the changeover switch SW is connected to the b side, and while the shift register 20 is shifted to the right one dot at a time, the thermal head 1a serially transfers the bone pig to be printed this time.

The second half energizing pulse (strobe) at this time is output to the thermal head 1aL.

Therefore, as shown in Fig. 3 (B), if one line is to be printed but the current has not been energized either the previous time or the time before the previous one, the single mode energization is applied for a long time, and either the previous time or the time before the previous time is used. When it is energized, it is energized for a short time in continuous mode.

Therefore, as shown in Fig. 3 (B), the energizing pulse has a first half that depends on the data from the previous time and the time before the previous, and a second half that depends only on the current data. The changeover switch SW switches between the a side and the b side,
Transfer data twice.

After this data transfer, the data in the shift register 21 is transferred to the shift register 22, the data in the shift register 20 is transferred to the shift register 21, and the data of the next line is input to the shift register 20.

In this way, the heat storage and heat dissipation characteristics of the thermal head in ms
High-speed heat storage correction is performed to make it possible to print characters and line drawings with a large diameter, thick, and sharp.

FIG. 4 is a diagram showing the main part of the configuration shown in FIG. 2, showing a halftone image data control section.

In the figure, 23 is a shift register in which print data for one line is stored, and 24 is an addition plane, which calculates the number of dots to be printed in one line transferred to the shift register 23 or the thermal head 1a. The counting circuit 25 is a conversion circuit, which is composed of ROM (read only memory) or RAM (random access memory), and depending on medium-speed heat storage characteristics, adds or subtracts the value of the adder circuit 24 to an addition/subtraction counter (described later). It is used to convert the value into the desired value.

26 is an addition/subtraction counter that adds or subtracts the converted value of the conversion circuit 25 to numerically indicate the medium-speed heat storage state of the thermal head la; 27 is a conversion control circuit that performs conversion based on the output value of the addition/subtraction counter 26; 28 is an energization pulse generation circuit that changes the conversion of the circuit 25, which controls the energization pulse (strobe) width according to the value of the addition/subtraction counter 26 (medium-speed heat storage state), and also controls the low-speed heat storage correction. Therefore, the energization pulse width is also controlled depending on the temperature of the thermal head 1a.

This circuit predicts heat accumulation within a page and controls the energization pulse width to achieve uniform printing.

1947 worth of print data is input to the shift register 23, and the data is serially transferred to the thermal head 1a.

At this time, the addition circuit 24 counts the number of dots to be printed in the line (1), this value is converted by the conversion circuit 25, and added or subtracted by the addition/subtraction counter 26.

The energization pulse generation circuit 28 controls the energization pulse width according to the value of the addition/subtraction counter 26 and the temperature of the thermal head.

On the other hand, even if the number of printed dots in one line is the same, the amount of heat storage and heat radiation differs depending on the heat storage state (value of the addition/subtraction counter) at that time. In other words, since the medium-speed heat storage characteristic is a nonlinear saturation curve, the addition/subtraction counter 2 is adjusted according to this nonlinear characteristic.
In order to count 6, the conversion value of the conversion circuit 25 is changed by the value of the addition/subtraction counter 26 by the conversion control circuit 27.

The addition circuit 24 also operates an addition/subtraction counter 26 for each line.
is cleared every page.

In this way, the thermal head performs medium-speed heat storage correction on the order of seconds and low-speed heat storage correction on the order of minutes, making it possible to print uniformly on halftone images with small dot diameters and no interference between dots. .

As described above, when printing text and line drawings, specify the text and line drawing mode from the operator panel 3, connect the selector switches SWI and SW2 to the text and line drawing data control section 2d, and increase the energy applied to the heating element. Then, the energization history is controlled to obtain the sharpness of the line.

On the other hand, in the case of a halftone image, specify the halftone image mode from the operator panel 3, and select switch SWI, SW2.
is connected to the halftone image data control section 2e, the energy applied to the heating element is reduced, and the printing rate is high, so heat accumulation prediction control is performed to obtain uniform printing.

(b) Description of other embodiments In the embodiments described above, switching is performed using the operator panel 3, but it may also be performed by the control unit 2a in response to instructions from the host. First, even when characters and halftone images coexist within one page, this can be realized by switching within the page.

Further, although the description has been made using an example of a thermal transfer printer, the present invention can also be applied to a direct thermal printer, an inkjet printer, and an electrophotographic printer.

In the case of an electrophotographic printer, the power of the laser beam can be made stronger when printing text and weaker when printing halftone images.For example, the power of the laser beam can be changed by changing the current value flowing through the laser diode or by using a filter. All you have to do is control it.

Furthermore, the dot diameter may be changed by changing the aperture of the laser beam diameter, and this can be achieved by controlling the optical system, such as controlling the position of a lens, for example.

Furthermore, the intensity of the laser beam and the size of the beam diameter may be controlled in combination.

Although the present invention has been described above using examples, the present invention can be modified in various ways according to the gist of the present invention, and these are not excluded from the present invention.

〔Effect of the invention〕

As explained above, the present invention has printing control modes for both text, line drawings, and halftone images, so it is possible to print dots with high image quality for both text, line drawings, and halftone images. This will contribute to the realization of a printer that can print various types of data in high quality.

[Brief explanation of the drawing]

Fig. 1 is a diagram of the principle of the present invention, Fig. 2 is a block diagram of an embodiment of the present invention, Figs. 3 and 4 are block diagrams of main parts of the structure shown in Fig. 2, and Fig. 5 is an explanation of problems with the prior art. It is a diagram. In the figure, 1-dot printing section, 2-printing control section.

Claims (1)

[Claims] (1) In a printer that includes a dot printing section (1) that prints in dots, and a print control section (2) that controls printing in maximum density for characters and line drawings and in halftone expression for images, the print control section ( 2) is a first print control mode in which printing of the text or line drawing is controlled using a first dot size, and a second print control mode in which printing is controlled for the image using a second dot size. A printer comprising: