JPH0781121A - Device and method for correcting unevenness of recording density of line type thermal head - Google Patents

Abstract

PURPOSE:To correct a density unevenness automatically and in a short period of time at a high precision by a method wherein a thermal conduction uneven ness of a line type thermal head is measured, and a driving signal to drive the line type thermal head is corrected based on the measured thermal conduc tion unevenness information. CONSTITUTION:A thermal conduction unevenness measuring means 102 measures the thermal conduction unevenness of a line type thermal head 101. Also, a memory means 103 stores the thermal conduction unevenness information which is measured by the thermal conduction unevenness measuring means 102. In addition, a correcting means 105 corrects a driving signal to drive the line type thermal head 101, based on the thermal conduction unevenness information which is stored in the memory means 103. As the result, the correction of the density unevenness of a high precision can be automatically performed in a short period of time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording density unevenness correction apparatus for a line type thermal head mounted in a thermal printer and a method therefor.

[0002]

2. Description of the Related Art Conventionally, in a thermal printer equipped with a line type thermal head, recording is performed on a recording paper by applying heat to the ink sheet from the thermal head. This is performed by a heating resistor that is a component of the head.

Usually, when recording is performed without any correction in a thermal printer, there is a drawback that density unevenness occurs. As a solution to this drawback,
For example, Japanese Patent Application Laid-Open No. 62-213370, "Gradation correction device for thermal recording" has been proposed. The correction method in this gradation correction device for thermal recording is generally called "resistance value correction", and the level of the input signal is changed according to the resistance value of the heating resistor, which is a component of the thermal head, Density unevenness due to difference in value (density unevenness due to resistance value variation) is reduced.

However, in the case of Japanese Patent Laid-Open No. 62-213370, although the density unevenness due to the variation in the resistance value is corrected, other factors that cause the density unevenness,
That is, since the density unevenness caused by the unevenness of the surface of the thermal head is not taken into consideration, there is a disadvantage that the density unevenness is not completely solved particularly when the density unevenness caused by the unevenness of the surface of the thermal head is severe.

Therefore, as a means for solving this, for example, Japanese Patent Application Laid-Open No. 1-281960 proposes "a recording density unevenness detecting device, a recording density unevenness correcting device and a recording density unevenness correcting method". The recording density unevenness detection device, the recording density unevenness correction device, and the recording density unevenness correction method of this recording device are generally called "density feedback correction", and the density of a recording medium on which a predetermined pattern is recorded is optically measured. Detection calculation is performed to obtain correction information for uneven recording density,
The recording density unevenness is corrected by correcting the drive signal of the recording head based on the obtained correction information.

By such correction, not only the density unevenness caused by the variation of the resistance value of the heating resistor but also the density unevenness caused by the unevenness of the surface of the thermal head can be solved. The main causes of the density unevenness are the above-mentioned two factors, that is, the variation in the resistance value of the heating resistor and the unevenness of the surface of the thermal head. According to Japanese Patent Laid-Open No. 1-281960, Both of the above two factors have been resolved. In other words, since the correction including the main cause of density unevenness is performed, highly accurate correction can be performed.

Further, as a correction method in Japanese Patent Laid-Open No. 1-281960, there are three steps:
It comprises a step of printing a predetermined pattern in advance, a step of optically detecting recording density unevenness to obtain correction information, and a step of correcting the drive signal of the recording head based on the correction information.

[0008]

However, according to Japanese Unexamined Patent Publication No. 1-281960, the density unevenness sample can be corrected with high accuracy by performing the correction including all the factors causing the density unevenness. Step of printing (printing a predetermined pattern in advance) or measuring the printing result with a density detector (optically detecting recording density unevenness)
Since steps such as steps have to be performed, there are problems that it requires manpower and that correction work takes time.

The present invention has been made in view of the above, and an object thereof is to perform highly accurate density unevenness correction automatically and in a short time.

[0010]

In order to achieve the above-mentioned object, the present invention provides a heat conduction unevenness measuring means for measuring heat conduction unevenness of a line type thermal head, and a heat conduction measured by the heat conduction unevenness measuring means. A line-type thermal head including a storage unit that stores unevenness information and a correction unit that corrects a drive signal for driving the line-type thermal head based on the heat conduction unevenness information stored in the storage unit. A recording density unevenness correction device is provided.

The heat conduction unevenness measuring means measures the heat conduction unevenness by contacting a line type thermal head with a group of heat-sensitive sensors whose surfaces are processed flat and arranged in a line.

In order to achieve the above object, the present invention measures the thermal conduction unevenness of the line type thermal head, and drives the line type thermal head based on the measured thermal conduction unevenness information. A method for correcting uneven recording density of a line-type thermal head that corrects a signal is provided.

[0013]

The apparatus and method for correcting the recording density unevenness of the line-type thermal head according to the present invention measures the heat-transfer unevenness of the line-type thermal head and drives the line-type thermal head based on the measured heat-transfer unevenness information. The drive signal for performing the correction is corrected.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The recording density unevenness correction apparatus and method for a line type thermal head according to the present invention will be described in detail below with reference to the drawings, taking the case of application to a thermal printer as an example.

FIG. 1 is a block diagram showing the arrangement of a recording density unevenness correcting apparatus of this embodiment, in which heat is applied to an ink sheet (not shown) to perform recording on a recording paper (not shown). Thermal head 101 and thermal head 1
Thermal sensor group 102 for measuring the heat conduction unevenness of No. 01
And a heat conduction unevenness information storage unit 103 configured to store heat conduction unevenness information measured by the thermal sensor group 102, and a ROM (read only memory) or a RAM (random access memory). A thermal head applied pulse data transmission unit 104 for transmitting pulse data (thermal head applied pulse data);
A correction unit 105 configured to correct the thermal head applied pulse data (calculates a correction data table) and a data correction table 106 that stores the correction amount calculated by the correction unit 105 as a table.
And a counter etc., the heat conduction unevenness information storage unit 1
Control unit 107 that controls the correction unit 105 to perform correction based on the heat conduction unevenness information stored in 03.
It consists of and.

In this embodiment, the correction unit 105, the data correction table 106, and the control unit 107 constitute the correction means of the present invention, but the invention is not limited to this. It is also possible to use a calculation unit that inputs the head applied pulse data and calculates correction data by calculation.

FIG. 2 is an explanatory view showing the positional relationship between the thermal head 101 and the thermal sensor group 102. As shown in the figure, the thermal sensor group 102 has a flat surface and is arranged in a line on the thermal sensor group substrate 202. In the figure, 201 is a head support material for supporting the thermal head 101. Further, the thermal sensor group substrate 202 and the thermal sensor group 102 may be inserted from the outside or may be built in the thermal printer.

FIG. 3 is an explanatory view showing an example in which the thermal sensor group 102 is installed on the platen roller 301 in the thermal printer. As in FIG. 2, the thermal head 101 is supported by the head support member 201.

The operation of the above configuration will be described.
First, the thermal head 10 is set by the thermal sensor group 102.
The heat conduction unevenness of 1 is measured. Here, the method of measuring the heat conduction unevenness will be specifically described. As shown in FIG. 2, the thermal head 101 includes the thermal sensor group 10 on the thermal sensor group substrate 202 by the operation of the head support member 201.
2 is pressed, the thermal head 101 is moved to the thermal sensor group 1
When it comes into close contact with 02, by applying the same number of pulses to all the heating resistors (not shown) in the thermal head 101 to generate heat, it is possible to measure the heat conduction unevenness transmitted to the thermal sensor group 102. In other words, it is possible to measure the heat conduction unevenness that is substantially equal to the heat conduction unevenness that occurs during actual printing.

As shown in FIG. 3, the thermal sensor group 1
02 is installed on the platen roller 301, the thermal sensor group 102 is rotated by the rotation of the platen roller 301 when measuring the heat conduction unevenness.
The thermal head 101 is pressed against the thermal sensor group 102 by the operation of the head support member 201 in the stopped state by moving the thermal head 101 to the contact surface of the thermal head 101. By applying the same number of pulses to all the heat generating resistors (not shown) in the thermal head 101 when they are in close contact with each other to generate heat,
It is possible to measure the unevenness of thermal conduction transmitted to the thermal sensor group 102.

In this embodiment, the unevenness of heat conduction is automatically measured when the thermal printer is started up. However, it is not particularly limited to this,
A dedicated switch for measuring unevenness of heat conduction may be provided so that it is performed when the switch is turned on, or it may be periodically performed after a predetermined number of images are formed.

When the measurement of the heat conduction unevenness of the thermal head 101 by the heat sensitive sensor group 102 is completed, the heat conduction unevenness information measured by the heat sensitive sensor group 102 is temporarily stored in the heat conduction unevenness information storage unit 103.

When all the heat conduction unevenness information (for one line) is stored in the heat conduction unevenness information storage unit 103, the control unit 107
From the heat conduction unevenness information storage unit 103 and the correction unit 105
A control signal is sent to.

When the control signal is input to the correction unit 105,
Based on the heat conduction unevenness information stored in the heat conduction unevenness information storage unit 103, correction data for correcting the thermal head applied pulse data is created. In this embodiment, a correction data table is created. The correction data table is created corresponding to the number of heating resistors in the thermal head 101, and the created correction data table is stored in the data correction table 106.

Thermal head applied pulse data transmission unit 1
When the thermal head 101 is driven by the applied pulse data sent from 04, the sequence is constructed so as to refer to the data correction table 106 without fail.
Each time the thermal head 101 is driven, the thermal head applied pulse data is corrected by the data correction table 106. In other words, the thermal head applied pulse data is corrected according to the uneven heat conduction. The thermal head 10 is applied with the corrected thermal head application pulse data.
By driving No. 1, it is possible to solve the density unevenness caused by the heat conduction unevenness, and perform recording without density unevenness.

Next, with reference to FIG. 4, a specific example of a method of correcting the thermal head applied pulse data will be described. Here, as a model, a thermal head 1 with five heating resistors is used.
Consider 01. Further, the heat-sensitive sensor group 102 is considered to be composed of five sensors, which is the same number as the number of heating resistors of the thermal head 101, for the sake of simplicity.

In order to measure the heat conduction unevenness, FIG.
As shown in, first, the pulse number = A is uniformly applied to each heating resistor. Since the same number of pulses are applied, ideally, the heat generation of each heating resistor is equal. However,
Due to variations in the resistance value of each heating resistor and unevenness of the surface of the thermal head 101, the heat transferred to the thermal sensor group 102 becomes uneven. At this time, since the concentration becomes high at the place where a high temperature is detected, the number of pulses is reduced,
It is necessary to increase the number of pulses because the concentration becomes low at the location where low temperature is detected.

As shown in FIG. 4B, assuming that each of the heat-sensitive sensors measures the temperature of T1 to T5, first, the average temperature T = (T1 + T2 + T3 + T4 + T5) / 5 is applied to each heating resistor. Correct the number of pulses. That is, as shown in FIG. 4C, correction pulse = A * T / T
? The data correction table 106 is created according to the correction formula of (? = 1 to 5: corresponding to each heating resistor), and the pulse corrected according to the created data correction table 106 is applied to the thermal head 101.

Since the recording density of the line type thermal head is controlled by the amount of heat transferred to the ink sheet and the recording paper, the unevenness of recording density can be corrected by correcting the unevenness of heat conduction. Further, in the present embodiment, since the thermal sensor group 102 is brought into contact with the thermal head 101 to measure the heat conduction unevenness, in other words, the heat conduction unevenness is directly measured from the thermal head 101, so that the heat generation is not generated. It is possible to measure the unevenness of heat conduction including two factors of the variation of the resistance value of the resistor and the unevenness of the surface of the thermal head 101, and it is possible to correct the uneven density with high accuracy.

Further, when the same number of pulses are applied to all the heating resistors, the thermal conduction unevenness disappears and the thermal head 1
01 Since the data correction table 106 is created so that uniform heat is generated over the entire surface, the data correction table 1
By correcting the thermal head application pulse in accordance with 06, the thermal conduction unevenness of the thermal head 101 is corrected, and clear recording without density unevenness can be performed.

In this embodiment, the recording density unevenness correction device has been described as being built in the thermal printer, but the invention is not particularly limited to this, and the recording density unevenness correction device and the thermal printer are separately provided. It may be configured.

As described above, according to this embodiment, the heat conduction unevenness of the thermal head 101 is measured, and the heat conduction unevenness is corrected according to the measured heat conduction unevenness information. It is possible to correct recording density unevenness without printing in advance. Further, since the predetermined sample data and the like are not printed in advance, the correction time can be shortened. Furthermore, since the thermal sensor group 102 is brought into contact with the thermal head 101 to measure the unevenness of heat conduction,
It is possible to measure heat conduction unevenness with a simple configuration. Therefore, it is possible to correct the recording density unevenness with a simple configuration.

[0033]

As is apparent from the above, according to the recording density unevenness correction apparatus for the line type thermal head of the present invention, the heat transfer unevenness measuring means for measuring the heat transfer unevenness of the line type thermal head and the heat transfer unevenness are provided. Storage means for storing the heat conduction unevenness information measured by the measuring means, and correction means for correcting the drive signal for driving the line type thermal head based on the heat conduction unevenness information stored in the storage means. Since it is equipped, highly accurate density unevenness correction is automatically performed.
And it can be done in a short time.

Further, according to the recording density unevenness correcting apparatus for the line type thermal head of the present invention, the heat conduction unevenness measuring means comprises a line type thermal sensor having a group of thermal sensors having a flat surface processed and arranged in a line. Since the heat conduction unevenness is measured by contacting with the head, it is possible to perform highly accurate density unevenness correction with a simple configuration.

Further, according to the recording density unevenness correction method of the line-type thermal head of the present invention, the thermal conduction unevenness of the line-type thermal head is measured, and the line-type thermal head is measured based on the measured thermal conduction unevenness information. Since the drive signal for driving is corrected, highly accurate density unevenness correction can be performed automatically and in a short time.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a recording density unevenness correction apparatus of this embodiment.

FIG. 2 is an explanatory diagram showing a positional relationship between a thermal head and a thermal sensor group.

FIG. 3 is an explanatory diagram showing an example in which a thermal sensor group is installed on a platen roller.

FIG. 4 is an explanatory diagram showing a specific example of a method of correcting a pulse applied to a thermal head.

[Explanation of symbols]

 101 Thermal Head 102 Thermal Sensor Group 103 Thermal Conduction Nonuniformity Information Storage Unit 104 Thermal Head Applied Pulse Data Transmission Unit 105 Correction Unit 106 Data Correction Table 107 Control Unit

Claims (3)

[Claims] 1. A heat conduction unevenness measuring unit for measuring heat conduction unevenness of a line type thermal head, a storage unit for storing heat conduction unevenness information measured by the heat conduction unevenness measuring unit, and a memory unit stored in the storage unit. A recording density unevenness correction device for a line type thermal head, comprising: a correction unit that corrects a drive signal for driving the line thermal head based on information on uneven heat conduction. 2. The heat conduction unevenness measuring means measures the heat conduction unevenness by bringing a group of thermal sensors whose surfaces are processed flat and arranged in a line into contact with a line type thermal head. The recording density unevenness correction device for a line-type thermal head according to claim 1. 3. A line-type thermal head characterized by measuring heat conduction unevenness of a line-type thermal head and correcting a drive signal for driving the line-type thermal head based on the measured heat-conduction unevenness information. Method for correcting recording density unevenness of the head.