JPH06143652A - Printer - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a printer having a correction mechanism capable of appropriately correcting the heat generation amount at both ends of the thermal head by performing heat influence on the thermal head from portions other than the thermal head by data setting. thing. [Structure] Pixel data input from a data input unit 1 is stored in an input data holding unit 2. On the other hand, the virtual data holding means 3 is preliminarily set with data (minus value) that virtualizes the heat quantity at both ends of the thermal head. The contents of the input data holding means 2 and the contents of the virtual data holding means 3 are one data string and the thermal history correction data creating means 4
And is stored in the correction data holding means 5. Therefore, the contents of the correction data holding means 5 are transferred to the printing means and printing is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal correction method for a printer having a thermal head.

[0002]

2. Description of the Related Art In a printing apparatus having a thermal head, a number of methods have been proposed in the prior art for performing thermal correction in consideration of thermal influence from adjacent heating elements. These are based on the premise that the heat generating elements in the thermal head are thermally affected by the adjacent left and right heat generating elements.

However, since the heat generating elements at both ends of the thermal head have the heat generating elements adjacent to each other on only one side, it is not necessary to consider the heat effect from the side having no adjacent heat generating element, which is a condition for the other heat generating elements. Is different.

Therefore, Japanese Patent Laid-Open No. 2-305658 discloses an apparatus in which thermal correction is performed in consideration of the thermal influence on the heating elements at both ends of the thermal head.

In the above invention, a correction data memory corresponding to the number of heat generating elements and a memory for supporting the portions without heat generating elements on both sides of the thermal head are provided, and more heat generating elements than the number of heat generating elements actually existing are provided. The feature is that the thermal history correction is performed as if it exists, and printing is performed.

[0006]

However, in the invention of Japanese Patent Application Laid-Open No. 2-305658, there is no specific disclosure regarding the data setting in the memory for dealing with the portions without the heating elements on both sides of the thermal head. Therefore, FIG. 6 shows how such a virtual heating element behaves. Reference numerals 1, 2, and 3 are real heating elements, and 0, -1, and -2 are virtual heating elements.

In FIG. 6, the arrow indicates the path through which the pixel formed at position 1 at time t has a thermal effect on the pixel formed at position 1 at time t + 3. . Also, from the heating element at the end of the thermal head to the virtual heating element located outside,
The thermal effect of the portion that is fed back to the heating element at the end of the thermal head is indicated by a thick arrow.

In this figure, non-printing data (= 0) is set as the initial data setting value of the virtual heating element,
If correction is performed using this, it is considered that a larger amount of heat than the amount of heat actually fed back is fed back, and the energy input is set low, resulting in a decrease in concentration. This is because the heat generating elements at both ends of the thermal head are open on one side, so that the heat amount is not only maintained but rather diffused to be actively cooled.

Therefore, it is inappropriate to set the non-printing data as the initial data setting value of the virtual heating element. In particular, a serial thermal printer that prints one page by scanning a thermal head having heating elements arranged in the sub-scanning direction a plurality of times in the main scanning direction. In the sub-scanning direction), the density between the serial prints (one print scan in the main scan direction) becomes thin and the image appears white, which causes deterioration of the image quality.

The present invention has been made in view of the above problems, and an object of the present invention is to make the thermal influence of a virtual heating element on a heating element inside the thermal head by setting data more accurately. The purpose is to correct the heat generation amount at both ends, and as a result, to improve the printing quality of the printer.

[0011]

In order to solve such a problem, the printer of the present invention corresponds to the data input means for taking in the data to be printed and the input data obtained by the data input means in correspondence with the number of heating elements. Input data holding means for holding in a form, virtual data holding means for holding virtual data of virtual heating elements at both ends of the thermal head,
The thermal history correction data creating means for creating correction data considering the thermal history using the input data and the virtual data, and the correction data created by the thermal history correction data creating means correspond to the number of heating elements. A correction data holding unit that holds the data in a shape, and a printing unit that prints with a thermal head having a plurality of heating elements, and print with the correction data obtained by the thermal history correction data creating unit as printing data. Is characterized by.

[0012]

EXAMPLE The dot density of the thermal head of the serial printer produced by using the present invention is 360 dpi, and the number of printing dots is 48 dots. The density of the recording screen is the main scanning direction,
The sub-scanning direction is 360 dpi, the number of recording dots is 2880 in the main scanning direction, 3984 in the sub-scanning direction, and the recording screen size is about 200 mm × 280 mm, and all pages are printed by serial printing 83 times.

FIG. 1 shows a conceptual diagram of processing in the present invention. 1 is data input means, 2 is input data holding means, 3
Are virtual data holding means located outside both ends of the thermal head, 4 is thermal history correction data creating means, 5 is correction data holding means, and 6 is printing means. The thermal head having a heating element is a constituent element of the printing unit 6.

The concept of processing will be described with reference to FIG. The pixel data input from the data input means 1 is temporarily stored in the input data holding means 2.

On the other hand, the virtual data holding means 3 is preliminarily set with virtual heat amounts on both outer sides of the thermal head.
In this case, since the outside of both ends of the thermal head generally acts as a cooling source for the thermal head, the virtual heat quantity is set to a value lower than the non-printing data (= 0), that is, negative data.

The contents of the virtual data holding means 3 are input to the heat history correction data creating means 4 in a form added before and after the input data holding means 2. The thermal history correction data creating means 4 performs thermal history correction on the input data (a correction method will be described later), and the corrected data is held in the correction data holding means 5. The data of the correction data holding means 5 is transferred to the printing means 6 and printing is performed.

By thus assuming the virtual heating elements outside the both ends of the thermal head, it is possible to consider the thermal influence from the outside on the thermal head, so that the density at both ends of the thermal head can be appropriately corrected. It is possible.

FIG. 2 shows a schematic diagram of the system of the first embodiment according to the present invention. 101 is a data input unit, 102 is an 8-bit data bus, 103 is a central control unit (CPU), 104 is a thermal history processing unit, 105 is an address control unit, 106 is a serial thermal head having a drive circuit, and 107 is a printing mechanism. is there. The serial thermal head 106 and the printing mechanism 107 are connected to the printing means 6 by the data input unit 101.
Corresponds to the data input unit 1, and the heat history processing unit 104 corresponds to the input data holding unit 2, the virtual data holding unit 3, the heat history correction data creating unit 4, and the correction data holding unit 5.

FIG. 3 shows an internal block diagram of the thermal history correction unit 104. 1041 is an input data part, 1042 is an input data buffer, 1043 and 1044 are virtual data, 1
Reference numeral 045 is an output data creation unit, 1046 is a correction term data buffer, 1047 is a correction term creation unit, and 1048 is an output data buffer. The sizes of the virtual data 1043 and 1044 are provided for three pixels, respectively.

Generally, a recursive filter refers to one that calls itself, but a recursive filter according to the present invention means that the correction of input data at time t is output at time t-j (j is a natural number). It has a configuration that is corrected by the data value. The simplest form is Qo [n, t] = Qi [n, t] -P [n, t] (1) P [n, t] = αQo [n, t-1] (2) ( α is a thermal history correction coefficient) (Qi [n, t] is input data, Qo [n, t] is output data, P
[n, t] is a correction term). This is a format in which correction is performed only by the output data at time t-1. The configuration of the recursive filter adopted in the thermal history correction unit 104 of this embodiment is more complicated, and the input data at the time t is corrected by the output data value at the time t-1 and the value of the correction term at the time t-1. I am doing it. When this is expressed by an equation, Qo [n, t] = Qi [n, t] -P [n, t] (3) P [n, t] = k0 * Qo [n, t-1] + k1 * P [n, t-1] (4) (k0 and k1 are thermal history correction coefficients). Expressions (3) and (4) are equivalent to Expression 1 below.

[0021]

[Equation 1]

Equation (5) shows that the correction of the input data at the time t is corrected by the output data value at the time t-j.

Further, the thermal history processing unit 104 of this embodiment has a form that can take into consideration the influence from the adjacent pixels. The processing of the heat history processing unit 104 is expressed by the following equation.

Qo [n, t] = Qi [n, t] −P [n, t] −c (Qi [n-1, t] + Qi [n + 1, t]) (6) P [n , t] = k0 * (a0 * Qo [n, t-1] + a1 * (Qo [n-1, t-1] + Qo [n + 1, t-1]) + k1 * (b0 * P [n, t-1] + b1 * (P [n-1, t-1] + P [n + 1, t-1]) (7) where a0, a1, b0, b1 and c are from adjacent pixels This is a coefficient for correcting the thermal effect, and is hereinafter referred to as a distribution correction coefficient.The origin (1, 1) where n and t are both 1 is the printing start position (printing is started from the upper left of the image receiving paper. In addition, n represents the dot arrangement position in the thermal head, t represents the dot printing position in the main scanning direction, and the printing speed of the thermal head is xdot / sec.
Then, t is also the time in units of 1 / x. When n and t are associated with the serial printer of this embodiment, n is the number of heating elements on the thermal head (48 dots).
In correspondence with + the number of virtual data (3 dots) × 2 and the actual print portion is set to 1 or more, an integer of −2 ≦ n ≦ 51. Since t corresponds to the number of main scanning dots, it is an integer of 1 ≦ t ≦ 2880. Hereinafter, the process corresponding to Expression (6) will be referred to as “output data creation process”, and the process corresponding to Expression (7) will be referred to as “correction term creation process”.

When the heating element shown in FIG. 5 forms a pixel,
The manner in which the pixel is affected by heat from the pixels formed by the surrounding heating elements is shown. In FIG. 5, the heat effect indicated by A is from the adjacent heating element that generates heat at the same time t, and the heat effect indicated by B and C is from the pixel formed at time t-1 ( B is from the adjacent heating element and C is from itself). From the figure, it can be seen that pixels are formed while mutually exerting a thermal influence on each other.

However, the heating element at the end of the thermal head is as shown in FIG. 6, unlike FIG. In FIG. 6, reference numerals 1, 2, and 3 represent existing heating elements, and 0, -1, and -2 represent virtual heating elements. The pixel formed at the position 1 at the time t has a thermal effect on the pixel formed at the position 1 at the time t + 3 in the path as shown by the arrow in FIG. The path indicated by the thick arrow indicates the thermal effect in the virtual region. Since the outside of the thermal head behaves as a cooling source with respect to the end of the thermal head, the data of the virtual area provided assuming the outside of the thermal head is set to a negative value. This makes it possible to appropriately correct the diffusion and feedback of heat generation.

Further, in the present embodiment, since a plurality of pixels are assigned to the virtual area (three pixels in the present embodiment), the virtual area is diffused in a wider range compared to one pixel. It is possible to consider the feedback of the calorific value. This makes it possible to more accurately correct the thermal effect on the end of the thermal head.

Furthermore, when there is a temperature difference around the thermal head due to the shape and environment of the thermal head,
By changing the setting data for the heating elements in a plurality of virtual areas depending on the distance from the heating element of the thermal head, there is also an effect that the thermal influence at the end of the thermal head can be accurately corrected.

FIG. 4 shows a one-page printing algorithm according to the first embodiment. A detailed description will be given with reference to FIGS. 2, 3, and 4. The number of main scanning dots is H (= 2880), the number of data for the thermal head is v (= 49), the number of virtual data is k (= 3), and the number of repetitions in the sub-scanning direction is N (= 8).
3).

Upon receiving the print command for one page, {procedure 1} The CPU 103 initializes the print mechanism 107 and clears the contents of the correction term data buffer 1046 in the thermal history processing unit 104. The virtual cooling heat data (negative value) is input to the virtual data 1043 and 1044. (Since this value is a fixed value, the virtual data 1043 and 1044 are stored in the read-only memory (R
OM)).

{Procedure 2} The printing start positions of the paper and the thermal head are set.

{Procedure 3} The following procedure is repeated N times,
Print one page.

-Procedure 3-1: For printing one serial line, the following procedure is repeated H times.

Procedure 3-1-1: Data for v dots is input from the data input unit 101 and stored in the input data buffer 1042 in the thermal history correction unit.

Procedure 3-1-2 The data (Qi) of the input data section 1041 and the data (P) of the correction term data buffer 1046 are sequentially read out within the range of −2 ≦ n ≦ v + k × 2, and the output data creating section 1045. The output data is created at and is sequentially stored in the output data buffer 1048 (Q
o).

Procedure 3-1-3 Correction term data buffer 1
046 and the contents of the output data buffer 1047 in sequence-2
The correction term creating unit 10 reads out within the range of ≦ n ≦ v + k × 2.
The correction term creation processing is performed at 47, and the correction term data buffer 10
Sequentially store in 46.

Procedure 3-1-4 The contents of the short cycle correction data buffer 1047 are transferred to the drive circuit and printing is performed.

Step 3-2: Return the thermal head to the printing start position, and feed the paper by the length of the thermal head.

{Procedure 4} The paper is ejected and the printing is completed.

With the above, printing of one page is completed.

As described above, by providing the virtual area other than the thermal head portion and setting the virtual heat quantity (minus data), the end of the thermal head can be properly corrected. According to the present invention, white spots due to a decrease in density between one serial print and one serial print are alleviated,
The image quality is improved.

In this embodiment, the size of the virtual area is 3
Although it is used for pixels, it has been confirmed that one pixel is effective. It is also possible to have more than 3 pixels.

FIG. 7 shows a system schematic diagram of the second embodiment according to the present invention. 101 is a data input unit, 102 is an 8-bit data bus, 103 is a central control unit (CPU), 104 is a thermal history processing unit, 106 is a printing mechanism, 107 is a serial thermal head having a drive circuit, and 108 is a temperature sensor. . The configuration of the thermal history correction unit 104 is the same as that in FIG.

The data set in the virtual data 1043, 1044 is a numerical representation of the thermal effect on the thermal head from the parts other than the thermal head, but this state differs depending on the atmosphere inside the printer housing. That is, it is conceivable that the temperature inside the casing is rising due to the surrounding environmental temperature or continuous printing. The temperature sensor 108 is installed near the thermal head and measures the temperature around the thermal head by C
It informs PU 103. The CPU 103 changes and sets the virtual data values of the virtual data 1043 and 1044 according to the temperature inside the housing. The state of this data setting is shown in FIG. After setting the virtual data value in this way, printing is performed in the same manner as the algorithm of the first embodiment. There are two setting methods: one has virtual data 1043 and 1044 as RAM, and the CUP 103 directly rewrites the contents, and the other is because the virtual data value is a fixed value, the virtual data 1043 and 1044 are used as ROM. Have, CUP
103 is a method of designating the address value.

Since the virtual heat quantity can be set according to the ambient temperature by adopting such a configuration and procedure, it is possible to more appropriately correct the heat quantity of the thermal head.

Although this embodiment refers to a serial printer, it can be easily applied as a method of correcting both ends of a line printer and has the same effect.

[0047]

As described above, the virtual data holding means is provided in addition to the portion for holding the input data, and the virtual heat quantity at both ends of the thermal head is set in the virtual data holding means, so that the thermal head from the thermal head end to the thermal head is changed. It has become possible to provide a printer that can appropriately correct the amount of heat generated at both ends of the thermal head in consideration of thermal effects. As a result, the print quality of the thermal printer has improved significantly compared to the past.

[Brief description of drawings]

FIG. 1 is a diagram showing a concept of processing of the present invention.

FIG. 2 is a diagram showing an outline of a system according to the first embodiment.

FIG. 3 is a block diagram of a heat history processing unit according to the first and second embodiments.

FIG. 4 is a diagram showing a processing algorithm of the first embodiment.

FIG. 5 is a diagram for explaining the influence of heat on a portion other than the end of the thermal head in the present invention.

FIG. 6 is a diagram for explaining the influence of heat at the end of the thermal head in the present invention.

FIG. 7 is a diagram showing an outline of a system according to a second embodiment.

FIG. 8 is an explanatory diagram of the second embodiment.

[Explanation of symbols]

 1 data input means 2 input data holding means 3 virtual data holding means 4 thermal history correction data creation means 5 correction data holding means 6 printing means 101 data input section 102 8-bit data bus 103 central control section (CPU) 104 thermal history processing section 1041 input data unit 1042 input data buffer 1043 virtual data 1044 virtual data 1045 output data creation unit 1046 correction term data buffer 1047 correction term creation unit 1048 output data buffer 105 address control unit 106 serial thermal head 107 having a driving circuit printing mechanism 108 temperature Sensor

Claims (3)

[Claims] 1. Data input means for taking in data to be printed, input data holding means for holding the input data obtained by the data input means in a form corresponding to the number of heating elements, and virtual heating elements at both ends of the thermal head. Virtual data holding means for holding the virtual data, thermal history correction data creating means for creating correction data in consideration of thermal history using the input data and the virtual data, and the thermal history correction data creation The thermal history correction data creating means includes a correction data holding means for holding the correction data created by the means in a form corresponding to the number of heating elements, and a printing means for printing with a thermal head having a plurality of heating elements. A printer which prints using the correction data obtained by the above as print data. 2. The printer according to claim 1, wherein the thermal history correction data creating means is configured by using a recursive filter. 3. The printer according to claim 1, wherein the data of the second data holding unit is set according to the environmental temperature.