JPH0832463B2 - Printer device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to temperature correction of recording characteristics of a printer device for performing halftone recording using a thermal head,
It can be widely applied to T hard copy devices.

2. Description of the Related Art A thermal printer that performs halftone recording has a thermal head in which a plurality of heating elements are integrated. By selectively energizing each heating element to generate heat, an image is transferred from a thermal paper or thermal transfer paper to an image receiver. The halftone recording is performed by controlling the recording pulse width and changing the effective energy, but since the relationship between the recording pulse width and the recording density is non-linear, faithful halftone recording is performed. In general, it is necessary to perform a correction generally called γ correction.

Further, since the recording density when using the thermal head depends on the temperature, it is necessary to correct the temperature.

Conventionally, there have been proposed one in which γ correction and temperature correction are independently performed, and one in which the output of a ROM table group for γ correction at a plurality of temperatures is selected (Japanese Patent Laid-Open No. 58-164368).

FIG. 5 is a block diagram of a conventional example. Temperature n RO
A ROM table group 51 composed of M tables 511, 512 ... 51n is configured. 54 is a temperature detector for detecting the temperature of the thermal head, 53 is an A / D converter for converting the output voltage of the temperature detector 54 into a digital signal, and 52 is the temperature indicated by the output of the A / D converter 53. ROM table each ROM table 511,512 ... 51n
Is a table selection circuit for selecting and outputting from the outputs of the. each
In the ROM table, the relationship between the gradation level and the pulse width for energizing the thermal head to obtain the recording density corresponding to the gradation level is set at that temperature,
The gradation level signal is input as an address to each ROM table. Therefore, when the gradation level signal a is input, the γ-corrected recording pulse width data of each temperature is output from each ROM table, and based on the temperature data b detected by the temperature detector 54, the table selection circuit operates as described above. The γ correction and the temperature correction were performed by selecting the output corresponding to the temperature from the output of each ROM table.

Problems to be Solved by the Invention In the conventional example, a plurality of ROs corresponding to the temperature of the thermal head are used.
The output of the M table was selected by the table selection means, but when trying to perform highly accurate temperature correction, A /
It is necessary to increase not only the number of bits of the D converter but also the number of ROM tables, and it has been difficult to perform accurate temperature correction in terms of circuit scale and cost.

The present invention has been made in view of the above points, and an object thereof is to provide a printer device having a simple configuration and capable of performing highly accurate temperature correction.

Means for Solving the Problems The present invention relates to a thermal head, a head driving means for applying electric power to a heating element of the thermal head, a pulse generating means for applying a recording pulse to the head driving means, and a temperature of the thermal head. A temperature detecting means for detecting the temperature, an A / D converting means for A / D converting the output of the temperature detecting means, and a table showing the relationship between the input density data and the recording pulse width at the reference temperature of the thermal head. Or a γ correction table of the reference temperature set in RAM, a correction coefficient setting generation means for giving a correction value expressed by a table or a mathematical expression for each temperature of the thermal head, the output of the A / D conversion means and the γ correction table And a table creating means for creating a new table from the γ correction table correcting means, and the input density according to the temperature of the thermal head. The temperature is corrected by obtaining the recording pulse width for the data.

Action When the temperature of the thermal head rises or falls, the recording density for the same recording pulse width generally changes, but the present invention is conversely the same as the recording density at a certain predetermined temperature for a change in the temperature of the thermal head. The relationship between the recording pulse widths is expressed as a table or a mathematical expression, and the recording pulse width for the input density data corresponding to the output of the temperature detecting means is obtained, so that the temperature of the thermal head is accurate over the entire halftone range at any temperature. Corrections can be made.

Embodiment FIG. 1 is a block diagram of first and second embodiments of a printer device of the present invention, and FIG. 2 is a block diagram showing the first and second embodiments of the printer device of the present invention more specifically. It is a figure. Reference numeral 1 is a thermal head, 2 is a head driving means for independently driving each heating element of the thermal head 1, 3 is temperature detecting means for detecting the temperature of the base of the thermal head 1, and 4 is temperature detecting means. A / D converting means for converting the output voltage of 3 into a digital value, 5 pulse generating means for generating a recording pulse according to the pulse width data, 6 a power source for applying a voltage to the head driving means 2, 7 for A / D When the output read by the conversion unit 4 decreases, the temperature replacement unit that replaces the output of the A / D conversion unit 4 read last time, and 8 indicates the relationship between the input density data at the reference temperature of the thermal head 1 and the recording pulse width. Γ correction table of the reference temperature, 9 is a γ correction table correction means which represents a correction value for correcting the γ correction table according to the temperature of the thermal head by a table or a mathematical expression, and 10 is a table Is a specified range creating means.

Here, as shown in FIG. 2, the temperature replacing means 7 and the table prescribed range creating means 10 are composed of a microcomputer 20 including a CPU 21, a ROM 22, a RAM 23 and an input / output port 24, and a reference temperature γ correction table 8 The γ correction table correction means 9 is stored in the ROM 22 in advance. Also,
c1 is an address bus and d1 is a data bus. 25 is Y
(Yellow), M (magenta), and C (cyan) ink sheets coated with three colors of ink, 26 is an ink sheet take-up roller that winds the ink sheet 25, and 27 is on the ink sheet 25 due to heat generated by the thermal head 1. Image receiving paper for transferring an image to form an image, 28 is a platen roller for sandwiching the ink sheet 25 and the image receiving paper 27 together with the thermal head 1 and conveying the image receiving paper 27, and 29, 30 are platen rollers 28 for the image receiving paper 27. A roller for conveying the image receiving paper 27 without slipping according to the rotation of the platen roller 28, 31 is an image receiving paper conveying means for rotating the platen roller 28 to convey the image receiving paper 27, and 32 is an ink sheet take-up roller. It is an ink sheet conveying means for conveying the ink sheet 25 that rotates the roller 26.

Here, the recording operation of the printer of this embodiment will be briefly described.

The ink sheet 25 is conveyed by the ink sheet conveying means 32, and the first color Y (yellow) ink is cued.
Then, the thermal head 1 uses the image receiving paper 27 and the ink sheet 25.
And the platen roller 28 is pressed against the platen roller 28 by rotating the platen roller 28 by the image receiving paper conveying means 31 to convey the image receiving paper 27, and the pulse generating means 5 generates a recording pulse according to the pulse width data. The driving means 2 drives each heating element of the thermal head 1 line by line. Due to the heat generated by the thermal head 1, the first color Y (yellow) ink applied on the ink sheet 25 is sequentially transferred to the image receiving paper 27, and a Y (yellow) image is formed on the image receiving paper 27.

Next, when the recording of the Y (yellow) image is completed, the thermal head 1 is separated from the platen roller 28, and the image receiving paper 27 and the ink sheet 25 are opened. Then, the image receiving paper 27 is conveyed to a predetermined initial position by rotating the platen roller 28 by the image receiving paper conveying means 31. Next, for the second color M (magenta) and the third color C (cyan),
Similar to the (yellow) operation, the three colors are superposed and the color image recording is completed.

The first embodiment of the present invention will be described in more detail.

Assuming that the gradation level signal is n bits and the detection accuracy of the temperature output from the A / D conversion means 4 is m bits, the relationship between the temperature of the thermal head 1 and the recording pulse width corresponding to the input density at the reference temperature T0 is shown. The address of the γ correction table for the reference temperature T0 is n bits. In addition to the program, the γ correction table (address n bits, data n bits) of the reference temperature T0 is previously written in the ROM 22, and the input density data of the γ correction table of the reference temperature T0 at the temperature of the thermal head 1 is stored. The relationship between the recording pulse width that makes the density uniform and the recording pulse width of the γ correction table for the reference temperature T0 is γ
Correction Table Correction Unit 9 A = f (T) (1) (where T is temperature data of the thermal head 1 and A is a function f (T) having T as a variable). It is shown and is written in advance in the ROM 22 similarly to the γ correction table of the reference temperature T0.

The CPU 21 reads the temperature Ts of the thermal head 1 at the start of recording according to the flowchart showing the sequence for temperature correction shown in FIG. 3, and calculates A from the equation (1) and the recording start temperature Ts. Then, from the equation (2), the γ correction table P (Di, T0) (i is 0 to 2 ⁿ −1) for the reference temperature T0.
Data), and a new γ correction table P ′ (Di, Ts) for the recording start temperature Ts is created in the RAM 23.

P ′ = A * P (2) (where P is the recording pulse width data of the γ correction table at the reference temperature T0, P ′ is the recording pulse width data of the newly corrected γ correction table) Temperature Ts of thermal head 1 at the start of recording
To a new γ correction table P ′ (Di, Ts + j * ta) (j is a positive integer) for each predetermined temperature interval ta (the smallest flaw in the detection accuracy of the temperature detected by the A / D conversion means 4) Create up to the maximum temperature Tmax of head 1 in RAM23. The temperature rise (Tmas-Ts) of the thermal head 1 is obtained by allowing a slight margin to the rise amount when one color is recorded with the maximum pulse width, and this value is written in the ROM 22 in advance. That is, no matter what image is printed, the temperature of the thermal head 1 does not rise from the storage start temperature Ts to (Tmax-Ts) or more in one-color printing.

Thereafter, the recording for each line is processed for each pixel in the following sequence.

The temperature data T of the thermal head 1 detected and converted by the temperature detecting means 3 and the A / D converting means 4 is read from the input / output port 24. Here, if the read value is T ≧ Ts, the read value is unchanged, and if the read value is T <Ts, the read value is T = Ts.

For example, if the read value is T = Td (Td ≧ Ts),
A γ correction table P ′ (Di, Td) for the temperature data Td of the thermal head 1 is obtained, and this γ correction table P ′ (Di, T
An address with the input density data a as a parameter is given to d) to obtain pulse width data, which is output from the input / output port 24 to the pulse generating means 5. The pulse generating means 5 generates a recording pulse according to the pulse width data, and the head driving means 2 drives each heating element of the thermal head 1. Although the flowchart of FIG. 3A shows only the end of the recording of the first color, the recording of the second and third colors after B in FIG. 3B is performed in the same manner as the sequence of the first color.

Next, the second embodiment of the present invention will be further described. The configuration is similar to that of the first embodiment.

Assuming that the gradation level signal is n bits and the temperature detection accuracy output from the A / D conversion means 4 is m bits, the relationship of the recording pulse width corresponding to the input density when the temperature of the thermal head 1 is a predetermined temperature is shown. The address of the γ correction table for the reference temperature T0 shown is n bits. In addition to the program, the γ correction table (address n bits, data n bits) of the reference temperature T0 indicating the relationship of the recording pulse width corresponding to the input density when the temperature of the thermal head 1 is a predetermined temperature is stored in the ROM 22.
And the recording pulse width corresponding to the input density data in the γ correction table of the reference temperature T0 and the recording width for making the density equal to this density other than the reference temperature T0. Correction coefficient table C (Tk)
(K is an integer of 0 to 2 ⁿ -1, address 1 bit, data k bit, m> 1) are written in advance.

The CPU 21 follows the temperature detecting means 3 and the A / D in accordance with the flowchart showing the sequence for performing the temperature correction of FIG.
The temperature Ts of the thermal head 1 at the start of recording detected and converted by the conversion means 4 is read from the input / output port 24. here,
Based on the upper 1 bit which is the integer part of the temperature data Ts of the m-bit thermal head 1, the data C (Tk) of the kth correction coefficient table and the k + 1th C (Tk + 1) (Tk ≦ Ts <
Each of Tk + 1 (k is a natural number) 1
The linear interpolation is performed based on the lower (m-1) bit which is a decimal part of the temperature data T of the temperature data T to obtain the correction coefficient C (Ts) for the temperature data Ts of the thermal head 1 at the start of recording, and the correction coefficient C (Ts ) Is calculated for the data of the γ correction table P (Di, T0) of the reference temperature T0 to obtain a new γ for the temperature data Ts.
The correction table P '(Di, Ts) is created in the RAM 23. Then, as in the first embodiment, a new γ correction table P ′ (Di is set for each predetermined temperature interval ta (minimum flaw in the temperature detection accuracy detected by the A / D conversion means 4) from the recording start temperature Ts. , Ts
+ J * ta) (j is a positive integer) is created in the RAM 23 up to the maximum temperature Tmax of the thermal head 1, and recording is performed for each line. Although the flow chart of FIG. 4A shows only the end of the recording of the first color, the recording of the second and third colors after B in FIG. 4B is performed in the same manner as the sequence of the first color.

Further, in the second embodiment of the present invention, linear interpolation has been described as an example, but it does not depend on the type of interpolation for the purpose of this patent.

As described above, the temperature of the thermal head 1 is read line by line during recording. If the read value is smaller than the temperature value of the thermal head 1 of the previous line, the read value is set to the line value. By doing so, the main flapping of the A / D conversion means 4 due to noise can be absorbed. In addition, the recording start temperature is read before recording one color, and the γ correction table P ′ (Di, T) for each predetermined temperature interval ta is read.
By setting in advance and creating only within the range of temperature rise, the temperature correction for each line during recording reads the temperature for each line and refers to the γ correction table at the read temperature according to the pulse width data. It is only necessary to do so, and it is not necessary to create a new γ correction table for each line.

As described above, in the thermal printer that performs halftone recording, one γ correction table at a predetermined temperature in advance,
By expressing the correction coefficient, which shows the relationship between the recording density and the recording density at a certain predetermined temperature with respect to the change in the temperature of the thermal head, with a table or a mathematical expression, the intermediate value can be obtained at any temperature. It is possible to perform highly accurate temperature correction with a small number of tables over the entire adjustment range.
Specifically, if the correction coefficients are combined, the γ correction table 2
It is enough to prepare only about one piece in advance. That is, an image recorded at a predetermined temperature can be reproduced with a simple structure and at low cost without being affected by temperature.

In addition, a range in which the temperature of the thermal head becomes the maximum temperature from the temperature of the thermal head at the start, that is, a new γ correction table that is a range necessary for recording is created in advance before recording, At the time of recording, it is only necessary to switch a new γ correction table according to the temperature and refer to the input density data as a parameter, so that the recording speed can be increased.

Further, it is extremely difficult to provide the temperature detecting means (for example, a thermistor) on the heating element, and since it is usually unavoidable to provide it on the base of the thermal head, a delay occurs between the temperature of the heating element and the detected temperature. Although the detected temperature may decrease even if the temperature rises, it may be due to the delay between the temperature of the heating element and the detected temperature, or the noise of the A / D converter that converts the temperature of the thermal head into A / D. It is possible to prevent the deterioration of the recorded image due to the fluttering of the output due to.

[Brief description of drawings]

FIG. 1 is a block diagram of a printer apparatus according to the first and second embodiments of the present invention, FIG. 2 is a block diagram showing the apparatus more specifically, and FIG. 3 is a first embodiment of the present invention. FIG. 4 is a flowchart showing a sequence for performing temperature correction of the printer device, FIG. 4 is a flowchart showing a sequence for performing temperature correction of the printer device according to the second embodiment of the present invention, and FIG. It is a block diagram of an apparatus. 1 ... Thermal head, 2 ... Head driving means, 3 ...
Temperature detecting means, 4 ... A / D converting means, 5 ... Pulse generating means, 6 ... Power supply, 7 ... Temperature replacing means, 8 ... Reference temperature gamma correction table, 9 ... Gamma correction table correcting means ,
10 …… Table prescribed range creation means, 20 …… Microcomputer.

Claims (6)

[Claims] 1. A thermal head, head driving means for applying electric power to a heating element of the thermal head, pulse generating means for applying a recording pulse to the head driving means, and temperature detecting means for detecting the temperature of the thermal head. And an A / D conversion means for A / D converting the output of the temperature detection means, and a γ correction table of the reference temperature which sets the relationship between the input density data and the recording pulse width at the reference temperature of the thermal head as a table. A stored ROM or RAM, a γ correction table correction unit that represents a correction value for correcting the γ correction table according to the temperature of the thermal head by a table or a mathematical expression, and the output according to the output of the A / D conversion unit. The table is provided with a γ correction table and a table creating means for creating a new table from the γ correction table correcting means. A printer device for obtaining a recording pulse width for the same input density data. 2. The table creating means comprises a microcomputer including a CPU, RAM, ROM, and an input / output port,
A / D conversion read from the input / output port by allocating the γ correction table of the reference temperature constituted by the table using the ROM or the RAM and the γ correction table correction means expressed by the formula as the memory of the microcomputer A new γ correction table is created from the γ correction table and the formula of the γ correction table correction means according to the output of the means,
With the input concentration data read from the input / output port,
The printer device according to claim 1, wherein the new γ correction table according to the output of the A / D conversion unit is referred to. 3. The table creating means comprises a microcomputer comprising a CPU, RAM, ROM, and input / output port,
The γ correction table of the reference temperature and the γ correction table correction means configured by the table using the ROM or the RAM are assigned as the memory of the microcomputer, and the output of the A / D conversion means read from the input / output port is assigned. The γ-correction-table correction means, the data in the table is interpolated, a new γ-correction table is created from the γ-correction table and the interpolated data, and the input density data read from the input / output port is read. 2. The printer apparatus according to claim 1, wherein the new [gamma] correction table according to the output of the A / D conversion unit is referred to. 4. A thermal head, a head driving means for applying electric power to a heating element of the thermal head, a pulse generating means for applying a recording pulse to the head driving means, and a temperature detecting means for detecting the temperature of the thermal head. And A / D conversion means for A / D converting the output of the temperature detection means, and if the temperature of the thermal head indicated by the output read by the A / D conversion means decreases, the previously read A / D A temperature replacing means for replacing the temperature of the thermal head indicated by the output of the converting means, a γ correction table in which the relationship between the recording pulse width and the input density data at the reference temperature of the thermal head is set in the ROM or RAM as a table, and the thermal A γ-correction-table correcting unit that expresses a correction value for correcting the γ-correction table according to the head temperature by a table or a mathematical expression; A recording pulse width corresponding to the output of the temperature detecting means, the γ correction table, and a table creating means for creating a new table from the γ correction table correcting means is provided, and the recording pulse width for the input density data according to the output of the temperature detecting means is obtained. A printer device characterized by the above. 5. A thermal head, head driving means for applying electric power to a heating element of the thermal head, pulse generating means for applying a recording pulse to the head driving means, and temperature detecting means for detecting the temperature of the thermal head. And A / D converting means for A / D converting the output of the temperature detecting means, and ROM or R as a table showing the relationship between the recording pulse width and the input density data at the reference temperature of the thermal head.
The γ correction table set to AM, the γ correction table correction means that represents the correction value for correcting the γ correction table according to the temperature of the thermal head by a table or a mathematical expression, and the thermal head temperature at the start of recording from the thermal head temperature in advance. The A / D conversion is provided with a table prescribed range creating means for creating a new table from the output of the A / D converting means, the γ correction table, and the γ correction table correcting means only within the set temperature rise range. A printer device for obtaining a recording pulse width for input density data according to the output of the means. 6. A thermal head, a head driving means for applying electric power to a heating element of the thermal head, a pulse generating means for applying a recording pulse to the head driving means, and a temperature detecting means for detecting the temperature of the thermal head. And A / D conversion means for A / D converting the output of the temperature detection means, and if the temperature of the thermal head indicated by the output read by the A / D conversion means decreases, the previously read A / D A temperature determining means for replacing the temperature of the thermal head indicated by the output of the converting means, a γ correction table in which the relationship between the recording pulse width and the input density data at the reference temperature of the thermal head is set in the ROM or RAM as a table, and the thermal A γ correction table correction means that expresses a correction value for correcting the γ correction table according to the head temperature by a table or a mathematical expression. A table prescribed range creating means for creating a new table from the output of the temperature determining means, the γ correction table, and the correction coefficient generating means only within a preset temperature rise range from the temperature of the thermal head at the start. A printer device, comprising: a recording pulse width for input density data according to an output of the temperature detecting means.