JP2897709B2 - Print density control device for thermal printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer, and more particularly, to a print density control device for adjusting print density.

[0002]

2. Description of the Related Art A thermal printer generates Joule heat by selectively energizing a large number of heating resistors.
By transmitting the Joule heat to the thermal paper or the transfer film, pictures, characters, and the like are printed as an aggregate of dots.

A conventional print density control device detects the optical print density of previously printed data (hereinafter referred to as "first data") on a sheet of paper, and based on this print density, the next print data (hereinafter referred to as "data"). , "Next data") by changing the dot density. For example, if the print density of the previous data is lower than the set value, the print density of the next data is increased by increasing the amount of power to the heating resistor. Conversely, if the print density of the previous data is higher than the set value, the print density of the next data is reduced by reducing the amount of power to the heating resistor.

[0004] It is technically difficult to detect the optical density of only one dot with an ordinary optical sensor. Therefore, the print density here refers to an area that is considerably larger than the area of one dot. The dot density is literally the density of one dot.

[0005]

However, the conventional print density control apparatus has a problem that the uniformity of print density is insufficient.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a print density control device having improved print density uniformity.

[0007]

Means for Solving the Problems The present inventor has repeatedly studied the causes of the inability to obtain sufficient print density uniformity with the conventional print density control device. As a result, it has been found that the dot configuration of the characters is not always the same between the preceding data and the following data, and this affects the print density. Regarding the dot configuration of characters, for example, between Mincho and Gothic, the Mincho font has sparse dots, and the Gothic font has dense dots. That is, even if the same dot density is set, if the dots are dense, it looks dark, and if the dots are sparse, it looks light. The present invention has been made based on this finding. Note that “dense or sparse dots” means that the number of dots per unit area (which is considerably larger than one dot) is large or small when the area of one dot is fixed.

That is, a print density control device according to the present invention comprises: a data storage means for storing first data printed first and next data to be printed next; and a first data and a second data stored in the data storage means. Data comparison means for comparing the dot configuration with the data, density detection means for detecting the optical print density on the paper of the preceding data, and the print density detected by the density detection means compared with the data comparison means. Density adjusting means for changing the dot density or font in the next data based on the result.

[0009]

FIG. 1 is a functional block diagram showing an embodiment of a print density control device according to the present invention. Hereinafter, description will be made based on this drawing.

The print density control device 10 includes a data storage unit 12 for storing first data a printed first and next data b printed next, and a first data a and a next data b stored in the data storage unit 12. A data comparing means 14 for comparing the dot configuration of the data, a density detecting means 16 for detecting an optical print density on the paper of the preceding data a, and a density detecting means 16
In the detected print density and dot density or off in the following data b based on the result of the comparison by the data comparing means 14
And a density adjusting means 18 for changing the font .

The thermal printer includes a print controller 20, a print head 22, and the like. The print control unit 20 receives the previous data a and the next data b from the host device 24 and outputs them to the data storage unit 12. In addition, the print control unit 20 supplies a power supply amount corresponding to the dot density adjusted by the density adjusting unit 18 to a heating resistor (not shown) of the print head 22.

FIG. 2 is a flowchart showing an example of the operation of the print density control device of FIG. Hereinafter, FIGS. 1 and 2
It will be described based on.

When the print head 22 prints the preceding data a (step 101), the density detecting means 16 detects the printing density of the preceding data a (step 102). The density adjusting means 18 determines the density of the print density (step 10).
3). As a result, when the print density is high, the dot density of the next data b is set low by reducing the amount of power (step 104). If the print density is appropriate, the amount of power is not changed (step 105). If the print density is light,
By increasing the energization amount, the dot density of the next data b is set to be high (step 106).

On the other hand, the data comparison means 14
And the dot configuration of the next data b are compared (step 10
7). As a result, if the dots of the next data b are dense, the dot density set in steps 104 to 106 will appear dark. Conversely, if the dots of the next data b are less sparse, the dots appear lighter with the dot density set in steps 104 to 106. Therefore, if the next data b is dense, the density adjusting unit 18 sets the dot density of the next data b to be low by reducing the amount of current (step 108). If the dot configurations are equal, the amount of current is not changed (step 109). If the next data b is sparse, the dot density of the next data b is set to be high by increasing the amount of energization (step 110). Finally, the print head 22 prints the next data b in accordance with the amount of current thus obtained (step 111).

FIG. 3 is a functional block diagram showing an example of a more specific configuration of the print density control device 10 of FIG.
Hereinafter will be described with reference to FIGS.

In this embodiment, the data storage unit 12, the data comparison unit 14, the density adjustment unit 18 and the print control unit 20
It comprises a CPU 30, a ROM 32, a RAM 34, an interface 36, a density setting device 38, a print head driver 40, a motor driver 42 and the like. The density detecting means 16 includes the image sensor 44 and the A / D converter 4.
6. The CPU 30 has a ROM 3
2. Based on the programs and data stored in the RAM 34 and the like, each processing as the data storage unit 12, the data comparison unit 14, the density adjustment unit 18 and the print control unit 20 is executed. Further, the CPU 30 serves as the print control unit 20
The print head 22, carriage motor 48, and line feed motor 50 are controlled via the print head driver 40 and the motor driver 42. The density setting device 38 is, for example, a digital switch or a variable resistor, and is used by an operator to set a desired print density.

Note that the density adjusting means 18 may change the font in the next data b instead of changing the dot density in the next data b. In this case, in FIG. 2, in steps 104 and 108, “reduce the amount of energization” is replaced with “change to a lower density font”.
In steps 105 and 109, “the current amount is not changed” is changed to “the font is changed”, and steps 106 and 11 are changed.
The phrase "increase the amount of energization" in 0 is replaced with "change to a higher density font". At this time, only steps 104, 105, 106, or steps 108,
Only 109 and 110 may be replaced as described above.

The density adjusting means 18 changes the font in the next data b instead of changing the dot density in the next data b only when the amount of current to the heating resistor reaches the upper limit or the lower limit. you. In this case, a wider range of print densities can be realized as compared with a case where either the dot density or the font is changed.

[0019]

According to the print density control device of the present invention, the dot density or font in the next data is changed by comparing the dot configuration of the previous data and the next data. The influence on the print density can be eliminated, thereby improving the uniformity of the print density.

When the font in the next data is changed instead of changing the dot density in the next data only when the amount of electricity to the heating resistor reaches the upper limit or the lower limit, A wider range of print density can be realized as compared with the case where either the density or the font is changed.

[Brief description of the drawings]

FIG. 1 is a functional block diagram illustrating an embodiment of a print density control device according to the present invention.

FIG. 2 is a flowchart illustrating an example of an operation of the print density control device of FIG. 1;

FIG. 3 is a functional block diagram showing an example of a more specific configuration of the print density control device of FIG. 1;

[Explanation of symbols]

 Reference Signs List 10 print density control device 12 data storage means 14 data comparison means 16 density detection means 18 density adjustment means a preceding data b next data

Claims (4)

(57) [Claims] 1. Data storage means for storing previously printed previous data and next data to be printed next, and data comparing means for comparing the dot configuration of the previous data and the next data stored in the data storage means. Density detection means for detecting an optical print density on the paper of the preceding data; and a format for the next data based on a print density detected by the density detection means and a result of comparison by the data comparison means.
Print density control device for a thermal printer that includes a concentration adjusting means for changing the cement. 2. The data to be printed first and the next data to be printed next.
Data storage means for storing data and the data storage means
The dot configuration of the previous data and the next data stored in the means
Data comparing means for comparison, and
Density detection means for detecting the optical print density
Print density detected by the degree detecting means and the data comparing means
Docking in the next data based on the results compared in
Density adjusting means for changing the dot density or font, the density adjusting means, if the print density detected by the density detecting means is high, by reducing the amount of electricity to the heating resistor, the dot density If the print density is low, if the print density is low, the energization amount is increased to set the dot density high. As a result of comparison by the data comparing means, the dot of the next data is compared with the dot of the next data. If the density is high, the energization amount is set to be low by reducing the amount of energization to the heating resistor, and if the dots of the next data are sparser than the previous data, the energization amount is increased. by the addition to set darker dot density, only when the energization amount has reached the upper or lower limit, the following
Instead of changing the dot density in the data,
A print density control device for thermal printers that changes fonts in serial data . 3. The density adjusting means, if the print density detected by the density detection means is high, changes the font in the next data to a lower density dot, and if the print density is light, The font is changed to a higher density dot, and as a result of the comparison by the data comparing means, if the dots of the next data are denser than the preceding data, the font in the next data is changed to a lower density dot. It was changed to the long the destination the next person dots are sparse data than is changed to the higher density dot the font, print density control unit of the thermal printer of claim 1, wherein. 4. The density adjustment unit, when changing the font in the next data, if the print density detected by the density detection unit is high, changes the font in the next data to a lower density dot. If the print density is low, the font is changed to a high-density dot, and as a result of comparison by the data comparing means, if the dots of the next data are denser than the preceding data, Changing the font in the next data to a lower density dot, and changing the font to a higher density dot if the dots in the next data are sparser than the preceding data. 2. A print density control device for a thermal printer according to item 2 .