JPH01200973A - Heat correction device of thermal printer - Google Patents

Abstract

PURPOSE:To correct a heat history, by a method wherein a first and a second calculation means for calculating an influence amount on a following line of a gradation data and a history data of a present printing line, an addition means for composing both calculation means, and a means by which a value calculated thereby is made the history data of the following line are established. CONSTITUTION:A gradation data from a line buffer 4 is respectively inputted to a multiplier and an adder. The gradation data is multiplied by a coefficient of 1/4 with the multiplier 5. The coefficient of 1/4 represents a cooling effect of one line content. Besides, the gradation data takes occasion to be inputted to a multiplier 8 and a multiplier 11 from a history data buffer 7. Outputs from the multiplier 11 and the line buffer 4 are added by the adder 12 to show heating effect. Then. the heating gradation data from the adder 12 is PMW converted, and is transferred to a thermal head 14 to perform printing. Besides, cooling effect is considered for the signal inputted to the multiplier 8, and outputs of the multiplier 8 and a multiplier 5 are added by an adder 9 to be written in a buffer 7 as a history data for a following line.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a thermal correction device for a thermal printer.

(Prior art) Conventionally, one pixel has been expressed in multiple gradations by bringing a thermal print head with heating elements arranged into contact with a thermal recording medium, and adjusting the energization time or applied voltage to heat each heating element. A heat-sensitive type so-called thermal printer is known.

This thermal printer is often used because it does not require any development processing, the paper is relatively inexpensive, and the printer head and paper feeding mechanism are simple.

By the way, in the above-mentioned conventional thermal printer, when the same element is continuously energized, the element gradually heats up, and when the energization is removed, the element gradually cools down, so that the printing density is not uniform. There is a problem in that it is necessary to incorporate data from thermal history to make the print density uniform. Japanese Patent Application Laid-Open No. 57-34986 is known as a thermal printer that performs correction taking into consideration the influence of thermal history. The thermal printer disclosed in this document refers to the dot data of several times in the past and makes corrections taking into account the degree of influence of each, but as the number of reference dot data increases, the circuit configuration becomes more complex. There are some problems.

(Objective) An object of the present invention is to provide a thermal correction device for a thermal printer that can correct the thermal history of a thermal print head with a simple configuration.

(Structure) In order to achieve the above object, the thermal correction device for a thermal printer of the present invention includes a first calculation means for calculating the amount of influence of the gradation data of the current printing line on the next line; a second calculation means for calculating the amount of influence exerted on the next line of historical data of the printing line; an addition means for combining the first and second calculation means; The present invention is characterized in that it includes a means for generating historical data of the line.

Embodiments of the present invention will be described below with reference to the drawings. The figure is a block diagram of a color video printer to which a thermal printer thermal correction device according to an embodiment of the present invention is applied.

1 is the RGB decoder, 2 and 6 are the selectors, and 3 is the A/
D converter, 4 is a line buffer, 5, 8.11 is a multiplier, 7 is a history data buffer, 9, 12 is an adder,
IO is a latch, 13 is a PWM converter, 14 is a thermal printer head, 15 is an NTSC signal output terminal, 16 is 1
10 is a pp level data output terminal, 17 is a color selection signal output terminal, and 18 is a clear designation signal output terminal.

First, when an NTSC signal, which is the standard color television system used in Japan, the United States, etc., is output from the output terminal 15, the output signal is separated into three color luminance signals of red, green, and blue by the RGB decoder 1. be done. When an image is actually formed using a color video printer, three-sided sequential transfer is performed using a thermal sublimation transfer method, so the selector 2 sequentially selects the luminance signals based on the output signal from the color selection signal output terminal 17. Start. The selected signal is converted into a digital value by an analog-to-digital converter 3, and the digital signal is stored in a line buffer 4 for only one line to be transferred. This line buffer 4 is used to compensate for differences in data flow speed between components of a data processing system, and is well known.

The gradation data from the line buffer 4 is input to a multiplier 5 and an adder 12, which are first calculating means, respectively.

Here, the gradation data is multiplied by a coefficient 1/4 by the multiplier 5, but this coefficient 1/4 represents the cooling effect for one line, and the influence of cooling after one line is multiplied by the coefficient 1/4. This is approximated by 1/l, and n=2.

Incidentally, the multiplier 8, which is a second calculation means to be described later, also multiplies by a coefficient 1/4 for the same reason.

On the other hand, in the line on the history data buffer 7 side, "O" level data is initially input to the selector 6 based on the output signal from the clear designation signal output terminal 18. This is because there is no need to consider the influence of thermal history at first. This value is stored in a history data buffer 7, which is a means for using the value calculated by the addition means as history data for the next line, and is inputted to a multiplier 8 and a multiplier 11 according to the timing. The input signal is multiplied by (-1), and the outputs from this multiplier 11 and the aforementioned line buffer 4 are input to an adder 12 and added. This subtracts the register data of the history data buffer 7 at the present time from the gradation data of the line buffer 4 at the present time to produce a heating effect, resulting in one heat generation gradation.

The heat generation gradation data outputted from the adder 12 is then subjected to PVM conversion by the PWM converter 13, and transferred to the thermal head printer 14 for printing.

On the other hand, the signal input to the multiplier 8 is multiplied by a coefficient of 1/4 in consideration of the cooling effect, and the output from the multiplier 8 and the output from the multiplier 5 are as follows. The signal is input to an adder 9 which is an adding means.

The signal added by the adder 9 is input to the latch 10 that temporarily stores the data, and then transferred to the aforementioned selector 6, and this transferred output value is stored in the history data buffer 7 for the history of the next line. It is used as data.

Next, this embodiment will be explained using specific numerical values.

First of all, if the initial value A of the gradation data Ai in the case of 64 gradations (data is O to 63) is set to "32", there is no need to consider the influence of thermal history at first, so The initial value B of the register data Bi of the history data buffer 7 is set to '0''.Then, the heat generation gradation (print) data Ci becomes C1=Ai-Bi, so the initial value C of Ci becomes '0''.
1 is set as 32-0=“32”. By the way, as mentioned above, since the influence amount of the gradation data of the current printing line on the next line is expressed by the first calculation means as X1=1/4XAi, x1=1/4xA1=1/4x32=8 becomes.

On the other hand, since the influence amount of the history data of the current printing line on the next line is expressed by the second calculating means as Yi=1/4xBi, Yuni1/4xB,=1/4xO=O.

Here, the output value of the first calculation means and the second
is added to the output value of the calculation means, and the value Zi is expressed as Zi+f=Xi+Yi, so Z,=X engineering+Y
i=8+O=8.

Then, the value "8" calculated by this addition means is stored in the history data buffer 7 as the history data B□ of the next line.
It is said that

Next, when the gradation data A2 is set to 27'', the register data B2 of the history data buffer 7 is set to ``8'' as described above, so the heat generation gradation (print) data C2 becomes C□
=A2-B, so 27-8 = "19". And X, = 1/4XA, = 1/4X27 = 6.75 = 6 (
From then on, all numbers below the decimal point are rounded down), Y2 = 1/4XB, = 1/4X8 = 2, Z, = x2
+Y2=6+2=8.

Then, the value u 8 JP calculated by this addition means
is set as the next line's history data B by the history data buffer 7.

Incidentally, i here represents a natural number.

If the same calculation is repeated after setting each gradation data Ai in this way, the register data Bi of the history data buffer 7 and the print data (heat generation gradation data outputted from the adder 12) Cj will be lower. It will look like a table.

Here, in the case of printing at i=7, C,=A,-
B, =2-3=-1, but in this case it is assumed that the correction cannot be completed and the heat generation gradation data is set to 0.

In this way, according to this embodiment, the data in which the cooling effect has been taken into account is taken into the history data buffer 7 as the next register data, and the register data is rewritten line by line, so that the apparatus can be extremely simplified. . Furthermore, since the printing data (heat generation gradation data outputted from the adder 12) is obtained by subtracting the register data of the history data buffer 7 obtained above from the gradation data at the present time, the heating effect is taken into account. It is an impression.

It goes without saying that the present invention is not limited to the embodiments described above, and can be modified in various ways without departing from the gist of the invention. In order to achieve this, the coefficients representing the cooling effect in multipliers 5 and 8 are both set to 1/4 for convenience, but the coefficients are not limited to 1/4, and the coefficients of multiplier 5 and multiplier 8 are It does not matter if the coefficients do not match.

(Effects) As described above, according to the present invention, the thermal correction device of the thermal printer is configured to include the first calculation means for calculating the amount of influence exerted on the next line of the gradation data of the current printing line, and the current printing line. a second calculating means for calculating the amount of influence exerted on the next line of the history data of the photographed line; an adding means for combining the first and second calculating means; and a value calculated by the adding means for Since it is configured to include a means for generating line history data,
It is now necessary to hold only one line of data representing the influence of the entire past thermal history on the current transfer, making it possible to greatly simplify the correction device.

[Brief explanation of the drawing]

The figure is a block diagram of a color video printer to which a thermal printer thermal correction device according to an embodiment of the present invention is applied. 4... line buffer, 5... first calculation means, 7
. . . Means for using the value calculated by the addition means as history data for the next line, 8 . . . Second calculation means, 9 . . .
Adding means, 14... thermal print head.

Claims (1)

[Claims] A thermal printer that expresses one pixel in multiple gradations by bringing a thermal print head arranged with heat-generating elements into contact with a thermal recording medium and adjusting the energization time or applied voltage to heat each heat-generating element. a first calculation means for calculating the amount of influence exerted on the next line by the gradation data of the printing line; a second calculation means for calculating the amount of influence exerted on the next line of the historical data of the current printing line; A thermal correction device for a thermal printer, comprising an addition means for combining the first and second calculation means, and means for using the value calculated by the addition means as history data for the next line.