JPH02289364A - Thermal head heat accumulation correction circuit - Google Patents

Abstract

PURPOSE:To accurately apply a thermal head heat accumulation correction so that printing can be correctly performed with a predetermined printing density as indicated by input printing data by mounting a data correction circuit issuing a correction output to an input printing data signal on the basis of a heat accumulation distribution state calculated by a heat accumulation distribution calculation circuit. CONSTITUTION:A data correction circuit conducts a heat accumulation correction in a main scanning direction on the basis of a heat accumulation distribution state of a thermal head in the main scanning direction as an output of an addition circuit 18 using a predetermined correction factor (e.g. the heat accumulation distribution state of the thermal head in the main scanning direction is multiplied by the predetermined correction factor for conducting the heat accumulation correction in the main scanning direction to an input printing data signal), furthermore performing the heat accumulation correction of the thermal head in a conventional printing direction (a sub scanning direction). The data correction circuit issues heat accumulation outputs (corrected input printing data signals) to the input printing data signal in the main scanning direction and the sub scanning direction (printing direction) of the thermal head. The corrected input printing data signals are supplied to the thermal head (heating elements thereof), whereby printing is correctly applied on a printing surface with a predetermined printing density indicated by original input printing data.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat storage correction circuit for a thermal head used in a recording device using a thermal head, such as a facsimile or a thermal transfer printer.

[Prior Art] A thermal head is used in a printer that uses an ink ribbon coated with thermal transfer ink or thermal sublimation ink. Thermal heads are also used in printers that use thermal paper. Thermal heads are also widely used in facsimiles that perform thermal recording.

For example, when the above-mentioned printer prints using the same certain print data signal, the print screen has different print densities at the beginning and end of the print.9 - For boat fishing, the print density is darker at the end of the print.

This is due to the heat storage effect of the thermal head in the printing direction (sub-scanning direction).

A conventional heat storage correction circuit for a thermal head corrects the heat storage effect in the printing direction of the thermal head as described above.

[Problem to be solved by the invention]

However, the heat storage effect of the thermal head is limited in the printing direction (
They exist not only in the sub-scanning direction (sub-scanning direction) but also in the main-scanning direction.

Therefore, the conventional thermal head heat storage correction circuit described above only corrects the heat storage effect in the printing direction (sub-scanning direction) of the thermal head. Therefore, an error occurs in the correction of the input print data signal for each dot printed by the thermal head, which impairs the print quality.

Next, an explanation will be given using an actual screen as an example.

For example, as shown in Fig. 7, if a screen 3 is printed where the central area 1 (the area indicated by narrow diagonal lines) has a high density and the peripheral area 2 (the area indicated by wide diagonal lines) has a low density. I will explain about it.

If this screen 3 is printed without any correction, the result will be as shown in FIG. That is, the adjacent portions 48 to 4c (portions indicated by horizontal lines) of the central portion 1' (the portion where central portion l in Fig. 7 is printed) are exposed to the peripheral portion 2 due to the heat storage effect of the thermal head.
' (the printed area of the peripheral area 2 in FIG. 7).

Therefore, when the screen 3 is printed by correcting only the printing direction (sub-scanning direction) using the heat storage correction circuit of the conventional thermal head, as shown in FIG.
Adjacent part 4b (the part where central part 1 in Fig. 7 is printed)
, 4c (the area indicated by the horizontal line) is darker than the peripheral area 2' (the area where peripheral area 2 in Figure 7 is printed) (same as in Figure 8), and furthermore, both ends of the central area 1' Adjacent portions 4d and 4e that are more protruding in the printing direction are overcorrected and have a lighter density than the surrounding area, making the boundary line between them clearly visible.

In this way, it is not possible to correctly print at a density that corresponds to the actual screen 3. That is, since the heat storage correction of the thermal head is inaccurate, there is a drawback that printing cannot be performed correctly at a predetermined print density according to manual printing data.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a heat storage correction circuit for a thermal head that performs heat storage correction in a thermal head more accurately than before so that printing can be performed correctly at a predetermined print density according to input print data.

[Means for Solving the Problems] The present invention provides a heat storage correction circuit for a thermal head used in a thermal transfer printer, etc., in which the main scanning of the thermal head is determined from an input print data signal corresponding to each dot printed by the thermal head. A heat storage distribution state calculation circuit that calculates a heat storage distribution state in a direction, and a data correction circuit that sends out a correction output for the input print data signal based on the heat storage distribution state calculated by the heat storage distribution state calculation circuit. It is.

[Operation] Therefore, the heat storage distribution state calculation circuit calculates the heat storage distribution state in the main scanning direction of the thermal head from the input print data signal, and the data correction circuit calculates the heat storage distribution state in the main scanning direction (heat storage correction data in the main scanning direction). Based on this, a predetermined correction is performed and a corrected output (corrected input print data signal) for the input print data signal is sent out. With this, it is possible to perform heat storage correction in the main scanning direction in addition to the conventional heat storage correction only in the sub-scanning direction, so that it is possible to perform heat storage correction of the thermal head more accurately than in the past. Therefore,
It is possible to correctly print at a predetermined print density according to the input print data.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a main part showing an embodiment of a heat storage correction circuit for a thermal head according to the present invention, and FIG. A calculation circuit is shown.

In the figure, 11 is an address generation circuit, and clock input terminals ckl, ck of this address generation circuit 11 are
2 is supplied with a data clock signal and a line clock signal. The address generation circuit 11 includes a first memory 12 using RAM and a second memory 13 using RAM.
The counting direction for generating the address signal is reversed for each energized line (every time the line to be printed changes). That is, the address in the main scanning direction is reversed. This address has a one-to-one correspondence with the dot address of the thermal head. Here, "the counting direction is reversed" means that when printing a certain line, for example, if you count in the direction O-4096, the next line will be counted 4096-0, etc. This means that the count up and count down are repeated in sequence, and the address signal is inverted and output for each line.

The output (address signal) of the address generation circuit 1 is supplied to the first and second memories 12 and 13. The first and second memories 12 and 13 have a capacity that can store one line of image data.

Further, 14 and 15 are first and second signal processing circuits, respectively, and these first and second signal processing circuits 14 and 15 are constructed using low-pass filters (LPFs) as shown in FIG.
The structure is as follows. That is, the first and second signal processing circuits 14 and 15 are connected to the ROM 16 and the R
The latch circuit 17 inputs the output of the OM 16 and supplies the output to the ROM 16. Therefore, the input of the first and second signal processing circuits 14.15, ie, ROM1
When input data as shown in FIG. 3(a) is supplied as input to the first and second signal processing circuits 14.1
5, that is, the output of the ROM 16, output data as shown in FIG. 5(b) is obtained. The time constant of this output data can be arbitrarily set depending on the contents written in the ROM 16, and the curve can also be made linear rather than exponential. The input print data signal is supplied to a first memory 12 and a first signal processing circuit 14 . first memory 1
The output of 2 is supplied to the second signal processing circuit 15. Second
The output of the signal processing circuit 15 is supplied to an adder circuit 18. Further, the output of the first signal processing circuit 14 is supplied to the second memory 13. Further, the data read by the output of the second memory 13, ie, the output (address) of the address generation circuit 11, is supplied to the addition circuit 18. The adder circuit 18 inputs the output of the second signal processing circuit 15 and the output of the second memory 13, adds these inputs, and further divides the result by 2 and sends out an output. Here, the addition circuit 18
The adder circuit 18 uses the output of the second memory 13 and the output of the second signal processing circuit 15 as input addresses, and calculates a predetermined output from a pre-stored table (by adding the power of both hands, The result is 1/). The output of the adder circuit 18 is determined when the input print data signal is supplied to the thermal head as it is without performing heat accumulation correction in the thermal head (without going through the heat accumulation correction circuit of the thermal head) and is printed (when the heat accumulation in the thermal head is It shows the state of heat storage distribution in the thermal head when printing is continued using the print data signal until it reaches a saturated state. Therefore, in the heat storage correction circuit of the thermal head of the present invention, the first
A data correction circuit receives the output of the heat storage distribution state calculation circuit of the thermal head shown in the figure, that is, the output of the adder circuit 18, performs a predetermined correction based on the input heat storage distribution state, and sends out a correction output for the input print data signal. has been established. Here, the data correction circuit corrects the heat storage in the main scanning direction using a predetermined correction coefficient based on the heat storage distribution state of the thermal head in the main scanning direction calculated by the heat storage distribution state calculation circuit of the thermal head shown in FIG. At the same time, the printing direction of the thermal head (sub-scanning direction) as before
It also performs heat storage correction and sends out a correction output (corrected input print data signal) for the input print data signal.

Next, the operation will be explained using FIG. 4. In addition, the fourth
The figure is a timing chart showing the operating waveforms of each part in Figure 1, and the horizontal axis indicates the head address (the address for each heat generating element of a thermal head in which heat generating elements are arranged in a row in the direction perpendicular to the printing direction). , hereinafter abbreviated as head address), and time is taken in the direction of the arrow in the figure.

An input print data signal as shown in FIG. 4(a) is supplied to the first memory 12 and the first signal processing circuit 14.

The first memory 12 stores the input print data signal. Further, the output of the first signal processing circuit 14 is passed through a low-pass filter in the same figure (b) from the above explanation.
) is stored in the second memory 13.

Here, when the line to be printed becomes the next line, the output (address signal) of the address generation circuit 11 is reversed. Therefore, the data read from the first and second memories 12 and 13 in the address direction opposite to that at the time of writing is shown in FIG.
C) and (d). Also, after reading,
The data of the immediately next line is written in the first and second memories 12 and 13.

The data signal shown in FIG. 2C read out from the first memory 12 is input to the second signal processing circuit 15. Second
The output of the signal processing circuit 15 is input to the adding circuit 18. The output of the second signal processing circuit 15 is similar to that of the first signal processing circuit 14, as shown in FIG. The output of this second signal processing circuit 15 is
is input. The data signal shown in FIG. 4D, which is read out from the second memory 13 in the address direction opposite to that at the time of writing, is input to the adder circuit 18. Then, as the output of the adder circuit 18, an output as shown in FIG. 2(f) is obtained.

The output of this adder circuit 18 corresponds to the order of the input print data in a reverse order. Therefore, if a problem arises because the output of the adder circuit 18 corresponds in the opposite order to the order of the input print data, it is necessary to provide another memory using RAM and input the input print data to this memory first. is manually stored, read out by the output of the address generation circuit 11, and the memory output is stored in the first memory 12 in FIG.
And if it is supplied to the first signal processing circuit 14,
The output of the adder circuit 18 corresponds to the same order as the manually printed data, and the above-mentioned inconvenience is eliminated. In this case, the address input to the separately provided memory is performed using the first memory 12 . It is connected in the same way as the second memory 13.

The screen to be printed now is screen 3 as shown in Figure 7.
think of.

The print data signals sent to the thermal head in the direction of arrows A-F on screen 3 are shown in FIGS. 5(a) to 5(f).
It is indicated by. In addition, in FIGS. 5(a) to (f), A
-F indicates a print data signal in the arrow direction A-F on the screen 3 in FIG. 1, with the head address taken in the horizontal axis direction and the time (data sending time) taken in the arrow direction.

When the print data signals for the screen 3 shown in FIGS. 5(a) to 5(f) are manually inputted to the heat storage distribution state calculation circuit of the thermal head shown in FIG. 1, the outputs are as shown in FIGS. ). Here, Fig. 6 (b), (e), (f)
The output data shown in (a) of the same figure is the same output data, and the output data shown in (d) of the same figure is the same output data as (C) of the same figure.

The output of the heat storage distribution state calculation circuit of the thermal head (Fig. 6) shown in Fig. 1 is obtained when the manual printing data signal is printed without performing heat storage correction of the thermal head (until the heat storage of the thermal head reaches a saturated state). It shows the heat storage distribution state of the thermal head when printing is continued based on the print data signal.

Next, a data correction circuit (not shown) receives the output of the heat storage distribution state calculation circuit of the thermal head (the output of the addition circuit 18) shown in FIG. . Here, the data correction circuit performs heat storage correction in the main scanning direction using a predetermined correction coefficient based on the heat storage distribution state in the main scanning direction of the thermal head, which is the output of the addition circuit 18 in FIG. , the heat storage distribution state in the main scanning direction of the thermal head is multiplied by a predetermined correction coefficient to perform heat storage correction in the main scanning direction on the input print data signal), as well as the conventional thermal head printing direction (sub-scanning direction). It also performs heat accumulation correction and sends out heat accumulation correction outputs (corrected input print data signals) in the main scanning direction and sub-scanning direction (printing direction) of the thermal head with respect to the input print data signal. This corrected input print data signal is supplied to the thermal head (its heating element), and the print screen is correctly printed at a predetermined print density according to the original input print data.

In addition, in the present invention, when calculating the heat storage distribution state of the thermal head in the main scanning direction, 1
Since the heat storage distribution state in the main scanning direction is calculated by manually inputting the entire print data for the line into the circuit shown in FIG. 1, the heat storage distribution state in the main scanning direction can be calculated accurately. This kind of thing has never been done before. The heat storage correction of the thermal head according to the present invention is performed by taking into consideration the conventional heat storage distribution state in the sub-scanning direction in addition to the heat storage distribution state in the main scanning direction. It is possible to perform a more accurate heat accumulation correction of the thermal head than that of the thermal head, which is based on the heat accumulation distribution state only in the scanning direction (printing direction). Therefore, the data correction circuit can accurately correct heat accumulation in the thermal head.

As can be seen from the above description, in the present invention, the heat storage effect in the main scanning direction of the thermal head is taken into consideration in advance, and the heat storage effect in the printing direction (sub-scanning direction) of the conventional thermal head is also taken into consideration in advance. As a result, it is possible to perform more accurate heat accumulation correction of the thermal head than in the past.

From the data correction circuit, accurate corrected input print data is obtained as simulation data that allows printing with the correct print density as the original input print data.

Therefore, it is possible to print with the correct print density corresponding to the original input print data.

Note that the present invention is not limited to this embodiment, and various applications and modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As described above, according to the present invention, in performing heat accumulation correction of the thermal head so that printing can be performed correctly at a predetermined print density according to input print data, in addition to the conventional heat accumulation correction only in the sub-scanning direction. Since the heat storage correction in the main scanning direction is also performed, it is possible to perform the heat storage correction of the thermal head more accurately than before.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a main part showing an embodiment of a heat storage correction circuit for a thermal head according to the present invention, FIG. 2 is a block diagram showing an embodiment of the signal processing circuit 14 and 15 of FIG. 1, and FIG. is a diagram showing the input/output relationship of the signal processing circuits 14 and 15 in FIG. 2, FIG. 4 is an operation waveform diagram of each part in FIG. 1, and FIG. FIG. 6 is a diagram showing the output data for each line when the print data in FIG. 5 is used as input data for the heat storage distribution state calculation circuit of the thermal head in FIG. 1, and FIG. 8 is a diagram showing an example of a screen to be printed, FIG. 8 is a diagram showing a printing screen when printing is performed on a screen like that shown in FIG. 7 without correcting heat accumulation in the thermal head, and FIG.
FIG. 6 is a diagram showing a print screen when printing is performed after performing heat accumulation correction in the main scanning direction of the thermal head on the screen as shown in the figure. DESCRIPTION OF SYMBOLS 11... Address generation circuit, 12... First memory, 13... Second memory, 14... First signal processing circuit, 15... Second signal processing circuit, 18. ...Addition circuit. Patent Applicant: Victor Company of Japan Co., Ltd. Figure 2 Figure 3 □ Time Figure 5 1--Head of time 1 hour (time during which data is sent)

Claims (1)

[Claims] In a heat storage correction circuit for a thermal head used in a thermal transfer printer, etc., a heat storage distribution state calculation circuit that calculates the heat storage distribution state in the main scanning direction of the thermal head from an input print data signal corresponding to each dot printed by the thermal head. and a data correction circuit that sends out a correction output for the input print data signal based on the heat storage distribution state calculated by the heat storage distribution state calculation circuit.