JPH0781122A - Device and method to correct recording density unevenness of line type thermal head - Google Patents

Abstract

PURPOSE:To perform the density unevenness correction of a high precision automatically and in a short period of time by a method wherein the pressure unevenness 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 pressure unevenness information. CONSTITUTION:A driving signal to drive a line type thermal head 101 is corrected in response to the resistance value of each heating resistor which is the constituent element of the line type thermal head 101. At this time, a pressure unevenness measuring means 102 measures the pressure unevenness of the line type thermal head 101. Also, a memory means 103 stores the pressure information which is measured by the pressure unevenness measuring means 102. In addition, a correcting means 105 corrects the driving signal to drive the line type thermal head 101, based on the pressure unevenness information which is stored in the memory means 103. As the result, the density unevenness correction 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 thermal printer equipped with a line type thermal head.
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a correction device and method for correcting recording density unevenness of a line type thermal head.

[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. Since it is necessary to perform the steps of printing (printing a predetermined pattern in advance) and measuring the printing result with a density detector (optically detecting recording density unevenness), it is considered to be labor-intensive. There were problems and the correction work took a long 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 is for driving a line type thermal head according to the resistance value of each heating resistor which is a constituent element of the line type thermal head. In a recording density unevenness correction device for a line-type thermal head that corrects a drive signal, pressure unevenness measuring means for measuring pressure unevenness of the line-type thermal head, and storage means for storing pressure unevenness information measured by the pressure unevenness measuring means And a correction unit for correcting the drive signal for driving the line-type thermal head based on pressure unevenness information stored in the storage unit. It is a thing.

The pressure unevenness measuring means measures the pressure unevenness of the line-type thermal head by bringing the pressure-sensitive sensor group in which the surface is processed flat and arranged in a line into contact with the line-type thermal head. It shall be.

In order to achieve the above object, the present invention corrects the drive signal for driving the line type thermal head according to the resistance value of each heating resistor which is a constituent element of the line type thermal head. In the method for correcting uneven recording density of a line-type thermal head, a line for measuring pressure unevenness of the line-type thermal head and correcting the drive signal for driving the line-type thermal head based on the measured pressure unevenness information. The present invention provides a method for correcting uneven recording density of a thermal head.

[0013]

According to the apparatus and method for correcting the recording density unevenness of the line type thermal head of the present invention, the pressure unevenness of the line type thermal head is measured, and the line type thermal head is driven based on the measured pressure unevenness information. Correct the drive signal of.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes the recording density unevenness correction apparatus and method for a line type thermal head according to the present invention in the order of [Example 1] and [Example 2], applied to a thermal printer as an example. Will be described in detail with reference to.

[Embodiment 1] FIG. 1 is a block diagram showing the arrangement of a recording density unevenness correction apparatus according to Embodiment 1, in which recording paper (not shown) is provided by applying heat to an ink sheet (not shown). A thermal head 101 for recording data on a recording medium, a pressure sensitive sensor group 102 for measuring pressure unevenness of the thermal head 101, a ROM (read only memory) or a RAM (random access memory), and the like. A head pressure unevenness information storage unit 103 that stores pressure unevenness information measured at 102, a thermal head applied pulse data sending unit 104 that sends pulse data (thermal head applied pulse data) based on an image to be recorded, a ROM, and the like. The head for correcting the thermal head applied pulse data (calculating the correction data table). The pressure unevenness correction unit 105 includes a pressure unevenness correction unit 105, a data correction table 106 that stores the correction amount calculated by the head pressure unevenness correction unit 105 as a table, a counter, and the like, and is stored in the head pressure unevenness information storage unit 103. It is composed of a control unit 107 that controls the head pressure unevenness correction unit 105 to perform correction based on the information.

In the first embodiment, the head pressure unevenness correction unit 105, the data correction table 106 and the control unit 10 are used.
Although the correction means of the present invention is constituted by 7, the present invention is not particularly limited to this. For example, by using a calculation section for inputting heat conduction unevenness information and thermal head applied pulse data and calculating correction data by calculation. Is also good.

FIG. 2 is an explanatory view showing the positional relationship between the thermal head 101 and the pressure sensitive sensor group 102. As shown in the figure, the pressure-sensitive sensor group 102 is processed into a flat surface and arranged in a line on the pressure-sensitive sensor group substrate 202. In the figure, 201 is a head support material for supporting the thermal head 101. Further, the pressure-sensitive sensor group substrate 202 and the pressure-sensitive 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 pressure sensitive 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 supporting member 201. .

The operation of the above configuration will be described.
First, by using the pressure-sensitive sensor group 102, the thermal head 10
The pressure unevenness of 1 is measured. Here, a method for measuring the pressure unevenness will be specifically described. As shown in FIG. 2, the thermal head 101 is pressed by the pressure-sensitive sensor group 102 on the pressure-sensitive sensor group substrate 202 by the operation of the head support member 201, and when the thermal head 101 comes into close contact with the pressure-sensitive sensor group 102. The pressure unevenness transmitted to the pressure sensitive sensor group 102 can be measured. In other words, it is possible to measure pressure unevenness that is approximately equal to the pressure unevenness that occurs during actual printing.

As shown in FIG. 3, the pressure-sensitive sensor group 1
When the pressure 02 is installed on the platen roller 301, when the pressure unevenness is measured, the pressure sensitive sensor group 102 is moved to the contact surface with the thermal head 101 by the rotation of the platen roller 301, and then stopped. In this state, the thermal head 101 is pressed by the pressure-sensitive sensor group 102 by the operation of the head support member 201, and when the thermal head 101 is in close contact with the pressure-sensitive sensor group 102, as in FIG. It is possible to measure the pressure unevenness transmitted to.

In the first embodiment, the pressure unevenness is automatically measured when the thermal printer is started up. However, it is not particularly limited to this, and a dedicated switch for pressure unevenness measurement is provided and the switch is turned on.
When the predetermined number of images have been formed, it may be performed periodically.

When the pressure sensor group 102 finishes measuring the pressure unevenness of the thermal head 101, the pressure sensor group 1
The pressure unevenness information measured in 02 is temporarily stored in the head pressure unevenness information storage unit 103.

When all the pressure unevenness information (for one line) is stored in the head pressure unevenness information storage unit 103, the control unit 10
7, a control signal is sent to the head pressure unevenness information storage unit 103 and the head pressure unevenness correction unit 105.

When the control signal is input, the head pressure unevenness correction unit 105 corrects the thermal head applied pulse data based on the pressure unevenness information stored in the head pressure unevenness information storage unit 103. To create. In the first embodiment, the correction data table is calculated. The correction data table is created corresponding to the number of heating resistors (not shown) 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 pressure unevenness. The thermal head 101 is corrected by the corrected thermal head application pulse data.
By driving, it is possible to solve the density unevenness caused by the pressure 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 pressure-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.

The thermal head 101 is connected to the pressure sensitive sensor group 10
When it is pressed against and closely contacted with 2, the unevenness of the surface of the thermal head 101 causes unevenness in the pressure transmitted to the pressure-sensitive sensor group 102. At this time, it is necessary to reduce the number of pulses because the concentration is high at the place where high pressure is detected, and to increase the number of pulses because the concentration is low at the place where low pressure is detected.

As shown in FIG. 4 (a), assuming that each heat-sensitive sensor measures the pressure of P1 to P5, first, the average pressure P = (P1 + P2 + P3 + P4 + P5) / 5 is applied to each heating resistor. Correct the number of pulses. That is, as shown in FIG. 4B, correction pulse = A * P / P
? 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.

When the same number of pulses are applied to all the heating resistors, the pressure unevenness disappears and the thermal head 10
1 Since the data correction table 106 is created so that uniform heat generation is generated on the entire surface, the data correction table 10
By correcting the pulse applied to the thermal head according to 6, the pressure unevenness of the thermal head 101 is corrected,
It is possible to perform recording without density unevenness due to pressure unevenness of the thermal head 101. Therefore, it is possible to perform recording without density unevenness due to the unevenness of the surface of the thermal head 101.

In the first embodiment, the recording density unevenness correction device is described as being built in the thermal printer. However, the invention is not 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 the first embodiment, the pressure unevenness of the thermal head 101 is measured, and the pressure unevenness is corrected according to the measured pressure unevenness information. It is possible to perform recording without density unevenness. Further, since the predetermined sample data and the like are not printed in advance, the correction time can be shortened. Further, since the pressure sensitive sensor group 102 is brought into contact with the thermal head 101 to measure the pressure unevenness, the pressure unevenness can be measured with a simple configuration. Therefore, it is possible to correct the recording density unevenness due to the pressure unevenness with a simple configuration.

[Second Embodiment] A second embodiment is an apparatus for correcting a drive signal for driving a thermal head according to a resistance value of a heating resistor (not shown) which is a constituent element of the thermal head in the prior art. In the case of correcting the drive signal for driving the thermal head, in addition to the resistance value of the heating resistor, the correction is performed according to the pressure unevenness of the thermal head. In other words, the second embodiment has a function of correcting the drive signal for driving the thermal head according to the resistance value of the heating resistor which is a constituent element of the thermal head, in addition to the configuration of the first embodiment. is there. Therefore, the second embodiment is
Basically, like in the first embodiment, different parts (a drive signal correcting operation according to the resistance value) will be described.

FIG. 5 is a block diagram showing the arrangement of a recording density unevenness correction apparatus according to the second embodiment. The same reference numerals as those in FIG. 50
The thermal head 1 is composed of an analog circuit and the like.
Reference numeral 502 denotes a head resistance value measuring unit for measuring the resistance value of the heating resistor which is a component of 01, and 502 is composed of a ROM or the like and corrects the thermal head applied pulse data (calculates a data table for correction). Resistance value unevenness correction unit 503, and 503 is a head pressure unevenness correction unit 1.
05 and a data correction table that stores the correction amount calculated by the resistance value unevenness correction unit 502 as a table. Reference numeral 504 includes a CPU, a counter, and the like.
Based on the pressure unevenness information stored in the head pressure unevenness information storage unit 103, the head pressure unevenness correction unit 105 is made to perform correction, and the resistance value is measured based on the resistance value measured by the head resistance value measuring unit 501. The control unit that causes the unevenness correction unit 502 to perform correction is illustrated.

In the second embodiment, the head pressure unevenness correction unit 105, the resistance value unevenness correction unit 502, the data correction table 503, and the control unit 504 constitute the correction means of the present invention, but the present invention is not limited to this. Instead of this, for example, a calculation unit that inputs pressure unevenness information and resistance value unevenness and thermal head applied pulse data and obtains correction data by calculation may be used.

The operation of the above configuration will be described.
First, in parallel with the correction according to the pressure unevenness of the thermal head 101 in the first embodiment, the correction according to the resistance value of the heating resistor is performed. First, a control signal is sent from the control unit 504 to the head resistance value measurement unit 501 and the resistance value unevenness correction unit 502.

When the control signal is input, the head resistance value measuring unit 501 measures the resistance value of each heating resistor, and the resistance value unevenness correcting unit 502 determines the resistance value based on the resistance value measured by the head resistance value measuring unit 501. Then, the pulse data applied to the thermal head is corrected. In the second embodiment, a correction data table is created. The correction data table created by the resistance value unevenness correction unit 502 is stored in the data correction table 503 together with the correction data table created by the head pressure unevenness correction unit 105. In the data correction table 503, the correction data table created by the resistance value unevenness correction unit 502 and the correction data table created by the head pressure unevenness correction unit 105 are combined for each heating resistor. To store.

Thermal head applied pulse data transmission unit 1
When the thermal head 101 is driven by the applied pulse data transmitted from 04, the sequence is constructed so as to always refer to the data correction table 503.
Each time the thermal head 101 is driven, the thermal head applied pulse data is corrected by the data correction table 503. In other words, the thermal head applied pulse data is corrected according to the pressure unevenness and the resistance value unevenness.
By driving the thermal head 101 with the corrected thermal head application pulse data, it is possible to solve the density unevenness caused by the pressure unevenness and the resistance value unevenness.

Next, with reference to FIG. 6, a specific example of the method of correcting the thermal head applied pulse data will be described. Here, as a model, a thermal head 1 with three heating resistors is used.
Consider 01. Further, the pressure-sensitive sensor group 102 is considered to be composed of three sensors in the same number as the number of heating resistors of the thermal head 101, for the sake of simplicity.

The thermal head 101 is connected to the pressure sensor group 10
When pressed to 2 and brought into close contact, as in the first embodiment, the pressure transmitted to the pressure-sensitive sensor group 102 becomes uneven, and the concentration becomes high at the location where high pressure is detected, so the number of pulses is reduced and low pressure is Since the concentration becomes low at the detected location, it is necessary to increase the number of pulses. Further, when the resistance value of each heating resistor measured by the head resistance value measuring unit 501 is large, the heat generation amount becomes small, so the number of pulses is increased, and when the resistance value is small, the heat generation amount becomes large. Therefore, it is necessary to reduce the number of pulses.

As shown in FIGS. 6 (a) and 6 (b), assuming that the pressure-sensitive sensors measure the pressures P1 to P3 and the resistance values of the heating resistors are R1 to R3, first, Average pressure P = (P1 + P2 + P3) / 3 and average resistance value R =
The number of pulses applied to each heating resistor is corrected by using (R1 + R2 + R3) / 3. That is, as shown in FIG. 6C, correction pulse = A * (P / P?) * (R? / R)
The data correction table 503 is created according to the correction formula (? = 1 to 5: corresponding to each heating resistor), and the pulse corrected according to the created data correction table 503 is applied to the thermal head 101.

The data correction table 503 is prepared so that when the same number of pulses are applied to all the heating resistors, the pressure unevenness and the resistance unevenness are eliminated and uniform heat generation is generated on the entire surface of the thermal head 101. Therefore, by correcting the thermal head applied pulse according to the data correction table 503, the pressure unevenness and the resistance value unevenness of the thermal head 101 are corrected, and the thermal head 10 is corrected.
It is possible to perform recording without density unevenness due to pressure unevenness and resistance value unevenness of No. 1. Therefore, it is possible to perform recording without density unevenness due to resistance value unevenness and density unevenness due to unevenness of the surface of the thermal head 101.

The causes of density unevenness during printing are mainly variations in the resistance value of the heating resistor and unevenness of the surface of the thermal head. In the second embodiment, both of the above two causes are solved. In other words, since the correction including the main cause of density unevenness is performed, it is possible to perform highly accurate correction and perform clear recording without density unevenness.

As described above, according to the second embodiment, the pressure unevenness and the resistance unevenness of the thermal head 101 are measured,
Since the pressure unevenness and the resistance value unevenness are corrected according to the measured pressure unevenness and resistance value unevenness information, it is possible to perform clear recording without density unevenness. Further, since the predetermined sample data and the like are not printed in advance, the correction time can be shortened. Further, since the pressure sensitive sensor group 102 is brought into contact with the thermal head 101 to measure pressure unevenness,
Pressure unevenness can be measured with a simple configuration. Therefore, it is possible to correct the recording density unevenness due to the pressure unevenness with a simple configuration.

[0044]

As is apparent from the above, according to the recording density unevenness correction apparatus for a line-type thermal head of the present invention, the line-type thermal head is constructed in accordance with the resistance value of each heating resistor which is a constituent element of the line-type thermal head. In a recording density unevenness correction device for a line-type thermal head that corrects a drive signal for driving the thermal head, pressure unevenness measuring means for measuring pressure unevenness of the line-type thermal head, and pressure unevenness measured by the pressure unevenness measuring means Since the storage means for storing information and the correction means for correcting the drive signal for driving the line-type thermal head based on the pressure unevenness information stored in the storage means are provided, highly accurate density unevenness is provided. Correction can be performed automatically and in a short time.

Further, according to the recording density unevenness correcting apparatus for the line type thermal head of the present invention, the pressure unevenness measuring means includes a line type thermal pressure sensor group in which the surface is processed flat and arranged in a line. Since the pressure unevenness of the line-type thermal head is measured by bringing the head into contact with the head, it is possible to perform highly accurate density unevenness correction with a simple configuration.

In addition, according to the recording density unevenness correction method of the line type thermal head of the present invention, the line type thermal head is driven according to the resistance value of each heating resistor which is a constituent element of the line type thermal head. In the recording density unevenness correction method of the line-type thermal head that corrects the drive signal of, the pressure unevenness of the line-type thermal head is measured,
In order to correct the drive signal for driving the line type thermal head based on the measured pressure unevenness information,
High-precision density unevenness correction can be performed automatically and in a short time.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a configuration of a recording density unevenness correction apparatus according to a first exemplary embodiment.

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

FIG. 3 is an explanatory diagram showing an example in which a pressure 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.

FIG. 5 is a block diagram illustrating a configuration of a recording density unevenness correction device according to a second embodiment.

FIG. 6 is an explanatory diagram showing a specific example of a method of correcting a pulse applied to a thermal head.

[Explanation of symbols]

 Reference Signs List 101 thermal head 102 pressure sensor group 103 head pressure unevenness information storage unit 104 thermal head applied pulse data transmission unit 105 head pressure unevenness correction unit 106 data correction table 107 control unit 501 head resistance value measurement unit 502 resistance value unevenness correction unit 503 data Correction table 504 control unit

Claims (3)

[Claims] 1. A recording density unevenness correction device for a line-type thermal head, which corrects a drive signal for driving the line-type thermal head according to the resistance value of each heating resistor which is a constituent element of the line-type thermal head. A pressure unevenness measuring means for measuring pressure unevenness of the line-type thermal head, a storage means for storing pressure unevenness information measured by the pressure unevenness measuring means, and pressure unevenness information stored in the storage means, A recording density unevenness correction apparatus for a line-type thermal head, comprising: a correction unit that corrects the drive signal for driving the line-type thermal head. 2. The pressure unevenness measuring means measures pressure unevenness of the line-type thermal head by bringing a pressure-sensitive sensor group whose surface is flattened and arranged in a line into contact with the line-type thermal head. The recording density unevenness correction device for a line-type thermal head according to claim 1, wherein: 3. A recording density unevenness correction method for a line-type thermal head, which corrects a drive signal for driving the line-type thermal head according to the resistance value of each heating resistor that is a component of the line-type thermal head. The recording density unevenness of the line-type thermal head is characterized by measuring the pressure unevenness of the line-type thermal head and correcting the drive signal for driving the line-type thermal head based on the measured pressure unevenness information. Correction method.