JPH05104768A - Method for correcting printing density - Google Patents

Abstract

PURPOSE:To reduce the cost of an apparatus by sufficiently correcting the irregularity of printing density. CONSTITUTION:A sample is formed by applying printing of predetermined density to a printing material by a thermal head 11 and the printing density of the sample is measured by a density measuring device 14 and the respective objective resistance values of a plurality of elements reducing the irregularity of the respective printing densities of the elements are determined from the measured values of the respective printing densities of the elements and the respective resistance values of the elements by an apply voltage measuring device 15 to reduce the irregularity of the printing densities of the elements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing density correction method for a printing device such as a printer.

[0002]

2. Description of the Related Art Printing devices such as printers include thermal recording devices and thermal transfer recording devices. Generally, a printing material is produced by applying a pulse signal to a plurality of elements in a printing head in accordance with a printing signal. The image is printed on. However, in such a printing apparatus, since the resistance values of the plurality of elements in the printing head vary, the printing densities of the plurality of elements also vary.

Therefore, in the printing apparatus, the data designation R
A gradation correction device for heat-sensitive recording is provided in which an AM is provided and the level of a print signal is changed stepwise according to the resistance value of each element to reduce unevenness in recording density due to a difference in resistance value of each element. No. 62-213370.

Further, in the printing apparatus, a correction value is obtained by measuring a variation in recording density of each element of the printing head which is a thermal head, and a density unevenness correction ROM is created by the correction value to print each element. A method for correcting unevenness in density of a sublimation printer that reduces unevenness in image density is 1990
Annual Conference of the Institute of Electronics, Information and Communication Engineers, D-351, "Density unevenness correction method for sublimation printers".

[0005]

In the printing apparatus, the cause of the print density unevenness is not only due to the variation in the resistance value of each element of the print head, but also the unevenness of the surface of the print head, the glaze layer, etc. Has a large effect. However, in the above-described thermal recording gradation correction device, since the level of the recording signal is only changed stepwise according to the resistance value of each element, uneven printing density cannot be sufficiently corrected.

Further, in the density unevenness correction method of the sublimation type printer, the correction value is obtained by measuring the variation in the printing density of each element of the thermal head, and the density unevenness correction ROM is created by this correction value to create each element. In order to reduce the print density unevenness, the density unevenness correction ROM and other circuits are required, which leads to an increase in the cost of the apparatus.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a printing density correction method which can remedy the above drawbacks, can sufficiently correct printing density unevenness, and can reduce the cost of the apparatus.

[0008]

In order to achieve the above object, the invention of claim 1 provides a printing density correcting method of a printing apparatus for recording an image on a printing material by a printing head having a plurality of elements. , A sample is formed by printing a predetermined density on the printing material by the printing head, and the printing density of the sample is measured to measure the printing density of each of the plurality of elements and the plurality of elements. The target resistance values of the plurality of elements are set so as to reduce the variation of the printing densities of the plurality of elements from the respective resistance values of, and the variations of the printing densities of the plurality of elements are reduced. According to a second aspect of the present invention, in the printing density correction method according to the first aspect, a pulse signal is applied to the plurality of elements so as to approach the target resistance value, and the printing density of each of the plurality of elements is determined. The month to reduce.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of a printing density correcting apparatus used for implementing the present invention, and FIG. 2 shows an operation flow of this apparatus.
This printing density correcting apparatus applies a pulse signal from a drive circuit 12 to an element composed of a plurality of heating resistance elements arranged in a line in a printing head 11 composed of a thermal head, in accordance with a printing signal, thereby recording paper. It is an example of a printing density correction device in a printing device that prints an image on a printing material consisting of, and first, in step S1, the initial resistance value of each element of the thermal head 11 is measured by the resistance value measuring circuit 13. To be done. Next, in step S2, the drive circuit 12 applies a pulse having the same magnitude to each element of the thermal head 11 to print a solid portion on the recording paper to prepare a sample, and in step S3, the sample is prepared. The density of printing by each element of the thermal head 11 is measured by the density measuring device 14. Then, in step S4, the applied voltage calculation device 15 finds the maximum density measurement value max from the measured values of the printing density of each element measured by the density measuring device 14 in step S3, and determines the printing density of each element. Regarding the measured value, the difference ΔOD from the maximum density measured value max is taken, and (1−ΔOD) is multiplied by the initial resistance value measured by the resistance value measurement circuit 13 to obtain the thermal head 11.
The target resistance value of each element of

Next, the applied voltage calculation device 15 determines in step S
In FIG. 5, the thermal head 11 is calculated by using the relationship between the resistance value change rate of the element of the thermal head 11 and the pulse voltage applied to each element of the thermal head 11 and the target resistance value of each element as shown in FIG. For each element, the amount of applied voltage to be applied to each element is calculated, that is, the applied pulse voltage to each element corresponding to the change rate of the target resistance value of each element is calculated from the relationship of FIG. Calculate how much applied voltage should be applied. Then, the applied voltage calculation device 15 applies the pulse of the applied voltage for each element calculated above in step S6 to each element of the thermal head 11, and in step S7, the resistance value of each element of the thermal head 11 changes to the resistance value. It is measured by the measurement circuit 13. Next, the applied voltage calculation device 15 compares the resistance value of each element measured in step S7 by the resistance value measuring circuit 13 in step S8 with the target resistance value of each element obtained in step S4. If the resistance value of the element is less than or equal to (target resistance value +20) Ω, the process ends, but if the resistance value of each element is not less than or equal to (target resistance value + 20) Ω, go to step S5. The process is returned and the above process is repeated until the resistance value of each element becomes a value equal to or less than (target resistance value + 20) Ω, and then the process ends.

According to the above-mentioned example, since the print density unevenness by the thermal head 11 is measured and the print density unevenness is corrected by feeding back to the thermal head 11 itself, the resistance value of each element of the thermal head 11 is corrected. It is possible to correct not only the print density unevenness due to the variation of the print head, but also the print density unevenness due to the influence of the unevenness of the surface of the thermal head 11 and the glaze layer, and the print density unevenness can be sufficiently corrected. And thermal head 11
It is not necessary to provide a circuit for correcting the unevenness of the printing density in the printing apparatus using, and the cost can be reduced.

The present invention is not limited to the above-mentioned example, and it is necessary to change the above (target resistance value + 20) Ω depending on the thermal head 11, and the value of (1-ΔOD) in step S4 is further added. It needs to be multiplied by some factor. Further, there is no problem even if the order of the steps S1, S2 and S3 is changed to the order of steps S2, S3 and S1.

[0013]

As described above, according to the present invention, a printing head is used to print a predetermined density on a printing material to form a sample, and the printing density of this sample is measured to measure a plurality of elements. The target resistance value of each of the plurality of elements is determined from the measured value of each print density and the resistance value of each of the plurality of elements, and each target resistance value of each of the plurality of elements is determined to reduce each print resistance of each of the plurality of elements. Since the unevenness of the density is reduced, the unevenness of the printing density can be sufficiently corrected and the cost of the apparatus can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a printing density correction apparatus used for implementing the present invention.

FIG. 2 is a flowchart showing an operation flow of the printing density correction apparatus.

FIG. 3 is a characteristic curve diagram showing a relationship between a resistance change rate of an element of the thermal head and a pulse voltage applied to each element of the thermal head.

[Explanation of symbols]

 11 Thermal Head 12 Drive Circuit 13 Resistance Measurement Circuit 14 Concentration Measurement Device 15 Applied Voltage Calculation Device

Claims (2)

[Claims] 1. A printing density correction method of a printing apparatus for recording an image on a printing material by a printing head having a plurality of elements, wherein the printing head prints a predetermined density on the printing material. A sample is formed, the print density of the sample is measured, and the variation in the print density of each of the plurality of elements is calculated from the measured value of each print density of the plurality of elements and each resistance value of the plurality of elements. A printing density correction method, characterized in that a target resistance value of each of the plurality of elements is set to be small to reduce variations in printing density of each of the plurality of elements. 2. The printing density correction method according to claim 1, wherein a pulse signal is applied to the plurality of elements so as to approach the target resistance value to reduce variations in printing density of the plurality of elements. A printing density correction method characterized by the above.