JP3002948B2 - Printing control device for thermal head type printing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing control apparatus for a thermal head type printing apparatus used for a video printer, a facsimile or the like.

[0002]

2. Description of the Related Art A thermal head type printing apparatus which performs printing and printing using a thermal head can adjust the degree of color development on thermal paper, and therefore, performs gradation expression and high image quality like a video printer. It is suitable for display devices that require printing at a resolution.

Usually, in a thermal head type printing apparatus, a thermal head in which hundreds to thousands of heating elements are arranged in a line form performs a printing operation sequentially for each line (for each raster).

[0004]

Therefore, the residual heat generated by the printing of the previous raster affects the printing of the next raster, and it has been difficult to accurately express the gradation.

It is an object of the present invention to provide a printing control apparatus capable of accurately expressing the gradation of a thermal head type printing apparatus.

[0006]

According to the present invention, there is provided a printing control apparatus for a thermal head type printing apparatus, comprising: a gradation data generating means for generating gradation data; ―
A preheating pulse and a plurality of driving pulses following the preheating pulse are applied to the mulling head, and the preheating pulse is one line.
Print signal supplying means for supplying a print signal for performing gradation expression, which is the same for each pixel for one line, and the print signal for the next one line based on the average gradation value for one line of having all equally amendments modifying means a pulse width of the preheat pulse.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As a method of performing gradation display in a thermal head type printing apparatus, a method of applying a driving pulse train corresponding to the gradation of each pixel to a heating element of a thermal head for each pixel (hereinafter referred to as a "multi-pulse method"). "). In this multi-pulse thermal head type printing apparatus, gradation is expressed by a normal preheating pulse and a plurality of driving pulses following the preheating pulse. Hereinafter, the embodiment will be described by taking the multi-pulse thermal head type printing apparatus as an example.

FIG. 1 is a block diagram showing the configuration of a multi-pulse type thermal head type printing apparatus.

The thermal head section 11 is composed of a head section in which hundreds to thousands of heating elements are arranged in a line, a drive circuit for controlling each heating element with data for turning on / off each heating element, and the like. I have.

The CPU unit 12 includes an I / O port in addition to the CPU. The system ROM 13 stores a program of the entire system, and also stores ON / OFF pattern data of each heating element, data of a drive pulse width described later, data of a start point of generation of a drive pulse, and the like.

The head transfer control circuit 14 includes a CPU 12
Receives a print request signal "PRQ" for each raster from the printer, and outputs a print control signal (a signal for instructing the start and end of data transfer to the thermal head). The memory controller 15 includes a head transfer controller 14
The image memory 16 is controlled in response to a signal from the image memory 16. The image memory 16 stores gradation data of a print pattern printed by the thermal head 11. The pulse number counter 17 receives the data stored in the system ROM 13, presets the total number of pulses of each driving pulse train in one raster, and counts down. The number of pulses of the driving pulse train in one raster is about 8 to 16, and the first one or two are preheating pulses for preheating, and 7 to 15 following this preheating pulse (when there is one preheating pulse) ) Or 6 to 14 (when there are two preheating pulses) are driving pulses for gradation expression.

A two-port memory 18 for pattern development (dual-port memory) reads out gradation data from the image memory 16 and develops the data into on / off data. The bit selection circuit 19 performs bit selection based on the pattern development data from the two-port memory 18.

The two-port memory 20 (dual-port memory) reads the start point data (data of the start position) of each drive pulse of the drive pulse train. Starting point date
The data is determined by the type of thermal paper and the characteristics of the thermal head, and is set in advance by software. For example,
If the thermal head is to be slowly heated, the starting point data is increased to increase the interval between adjacent drive pulses. The start point counter 21 presets start point data from the two-port memory 20 and counts down by a reference clock. As the reference clock, a clock having a constant frequency, such as a system clock or a frequency-divided version thereof, is used.

The two-port memory 22 (dual-port memory) reads a pulse width of a driving pulse. The pulse width counter 23 presets the pulse width data from the two-port memory 22 and outputs the VCO 24 (voltage)
This is to count down by the clock from the control oscillator. Since the frequency of the clock output from the VCO 24 is variable, the pulse width output from the pulse width counter 23 is output from the VCO 24 even if data having the same pulse width is preset in the pulse width counter 23. It fluctuates according to the fluctuation of the clock.

The application rate counter 25 includes a bit selection circuit 1
Based on the on / off data from step 9, the application rate (the ratio of the heating element to which the driving pulse is applied to the heating element of the thermal head and the heating element to which the driving pulse is not applied) is determined. D / A
The converter 26 receives the thermal head 1 from the CPU 12.
The temperature correction data of No. 1 and data relating to the variation of the thermal head are applied from the application rate counter 25 to the application rate data.
And performs a D / A conversion operation to send a voltage control signal to the VCO 24.

The average gradation calculating circuit 27 is provided in the image memory 16
, The average gradation value of one raster (the value obtained by adding the gradation of each pixel in one raster divided by the number of pixels) is obtained, and the average gradation value is determined by the CPU. Part 12
To send to. In the CPU section 12, this one raster
The temperature rise of the thermal head 11 is predicted on the basis of the average gradation value for one minute, and the prediction result is calculated based on the preheat pulse of the next raster (the first one or two pulses in the drive pulse train in one raster). This is reflected in the pulse width. Specifically, when the average gradation value is large, the temperature rise is predicted to be large, so the pulse width of the preheating pulse is narrowed. When the average gradation value is small, the temperature rise is predicted to be small. Increase the pulse width of the preheating pulse. Since the preheating pulse is common to each pixel in one raster, it is not necessary to correct different preheating pulse data for each pixel, and correction can be performed easily.

The constant voltage source 28 supplies a predetermined constant voltage to the head of the thermal head 11.

Next, the operation of the thermal head type printing apparatus of FIG. 1 will be described with reference to the timing chart of FIG. 2 and the flowchart of FIG.

The calculation is performed in consideration of the setting for use of thermal paper, image gamma, etc., the head temperature, the variation of the thermal head, and the like.
Data, the starting point data of the driving pulse and the pulse width data of the driving pulse are obtained, and the two-port memory 18 for pattern development, the two-port memory 20 for setting the starting point of the driving pulse, and the driving, respectively. The pulse width is set in the two-port memory 22 for setting the pulse width (a).

It is determined whether there is a change in the setting for use or a change in the environment (b). If there is a change in the setting or a change in the environment, the setting operation to the two-port memory is performed again in the process of "a". If there is no setting change or environmental change, it is determined whether to perform the printing operation (c).

When printing is performed, the number of pulses of the driving pulse train in one raster is set in the pulse number counter 17 (d). The number of normal drive pulses is about 8 to 16 in total, and the first one or two are preheating pulses for preheating,
7 to 15 (when there is one preheating pulse) or 6 to 14 (when there are two preheating pulses) following this preheating pulse
Are drive pulses for gradation expression. I of the CPU unit 12
A signal "P" requesting the start of printing of one raster from the / O unit
RQ "is output to the head transfer control circuit 14 (e).

The gradation data is read from the image memory 16,
The two-port memory 18 for pattern development develops on / off data for each heating element. The developed data is sequentially transferred to the drive circuit of the thermal head 11 through the bit selection circuit 19 (f). 2 for setting start point of drive pulse
The starting point data from the port memory 20 is preset in the starting point counter 21. The start point counter 21 sequentially counts down by a reference clock having a constant frequency (g).

Turning on / off each heating element to the thermal head 11
It is determined whether the transfer of the off data has been completed and the start point of the drive pulse has been reached. ON / OFF date of each heating element
Whether the transfer of the data has been completed is determined by a signal “TRNS” indicating whether the transfer from the head transfer control circuit 14 has been completed.
The determination is made based on the logical state of the signal "TRGRDY" indicating whether or not the start point of the drive pulse has been counted (h). ).

When the transfer of the on / off data of each heating element is completed and the start point of the drive pulse is reached, the pulse width data from the two-port memory 22 for setting the pulse width of the drive pulse is used. Preset in the pulse width counter 23. The pulse width counter 23 sequentially counts down by the clock from the VCO 26 (i). VCO
The clock from the D / A converter 26 is used for various data (temperature correction data of the thermal head from the CPU 12 and variation data of the thermal head).
, The pulse width output from the pulse width counter 23 is also variable. The pulse counter 17 is counted down by one count (j), and it is determined whether a borrow occurs (k).

If no borrow occurs, the start point data from the two-port memory 20 for setting the start point of the drive pulse is preset in the start point counter 21 in order to determine the start point of the next drive pulse. In the start point counter 21,
It is sequentially counted down by a reference clock having a constant frequency (l).

It is determined whether or not a borrow has occurred from the pulse width counter 23, that is, whether or not the output of the drive pulse has been completed (m). When a borrow occurs, the same gradation data is read out again from the image memory 16 and developed into on / off data by the 2-port memory 18 for pattern development. The developed data is sequentially transferred to the drive circuit of the thermal head 11 through the bit selection circuit 19 (n). Since the bit selection is determined by the pulse number counter 17, different bits are selected from the read pattern development data.

In the process of "k", when a borrow occurs from the pulse number counter 17, that is, when printing for one raster is completed, it is determined whether or not printing for one screen is completed (see FIG. 6). o). Normally, one screen is composed of 480 to 512 rasters. If printing for one screen has not been completed, the average gradation calculation circuit 27 outputs the previous one.
An average gradation value for the raster is calculated (p). The average gradation value for one raster is sent to the CPU unit 12 and
The unit 12 appropriately changes and changes the pulse width of the preheating pulse of the next raster (the first one or two pulses in the driving pulse train in one raster) based on the average gradation value for one raster. The data of the pulse width is stored in the pulse width memory 22.
(Q). That is, when the average gradation value is large, the set value of the pulse width memory 22 is changed so that the pulse width of the pre-heating pulse of the next raster becomes narrow, and when the average gradation value is small, the pre-heating of the next raster is performed. The set value of the pulse width memory 22 is changed so that the pulse width of the pulse becomes narrow.

It is determined whether or not it is the timing of the printing of the next raster (r). If it is the timing of printing of the next raster, the process proceeds to "d".

As described above, the operation of the thermal head type printing apparatus of FIG. 1 is performed.

In the above embodiment, the memories 18, 2
Although a two-port memory is used for 0 and 22, it is also possible to use an output port unit instead of the two-port memory.

In general, the thermal storage (remaining heat) of the thermal head gradually increases as printing proceeds. Therefore, in the above embodiment, the average gradation calculation circuit 27 is omitted, and for example, even if the pulse width of the preheating pulse gradually decreases as the printing progresses (for example, the data of the pulse width of the preheating pulse for one screen). In advance in the system ROM1
3 is stored. It is possible to achieve some effect. However, in such a method, since fine correction based on gradation data for one line is not performed unlike the above-described embodiment, it is difficult to perform accurate gradation expression.

[0032]

According to the present invention, the preheating pulse is set to 1
There as identical with respect to each pixel of the line, provided all equally amendments modifying means the pulse width of the preheat pulse for one line of the printing signal following on the basis of the average gradation value of one line is there. Therefore, when the average gradation of one line or the gradation data of one line is small, the pulse width of the preheating pulse of the printing signal of the next one line is increased, and the average gradation of one line is increased. When the tone data for one line or one line is large, the correction can be easily made by changing the pulse width, such as reducing the pulse width of the preheating pulse of the printing signal for the next one line. Thus, it is possible to accurately express the gradation of the thermal head type printing apparatus. Moreover, 1 the pulse width of the preheat pulse line of printing signals are Tadashisa all equal Osamu, there is no need to correct for each pixel, it is possible to easily correct.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment according to the present application.

FIG. 2 is a time chart for explaining the operation of FIG. 1;

FIG. 3 is a flowchart for explaining the operation of FIG. 1;

[Explanation of symbols]

 12 CPU (correction means) 16 image memory (gradation data generation means) 18 pattern development memory (print signal supply means) 19 bit selection circuit (print signal supply means) 20 start point memory (Print signal supply means) 21 ... Start point counter (Print signal supply means) 22 ... Pulse width memory (Print signal supply means) 23 ... Pulse width counter (Print signal supply means)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 2/36-2/38

Claims (1)

(57) [Claims] 1. A Kaichode - tone de generates data - and data generating means, the tone de - based on the data service - to the thermal head portion, a plurality of driving pulse following the preheat pulse and the warming pulse identical or Rannahli, the warming pulse for each pixel of one line
, And the a printing signal supply means for supplying a printing signal for gradation expression, all equally Osamu forward the pulse width of the preheat pulse for one line of the following on the basis of average gray value of one line A printing control apparatus for a thermal head type printing apparatus having a correction unit.