JPH07125291A - Multi-gradation thermal recorder - Google Patents

Abstract

PURPOSE:To execute an accurate density correction even in the case of a multi- gradation print by providing detecting means for detecting a time from start of printing or number of lines and drive signal generating means for generating a correction drive signal preset in response to gradation information incoming as its detected result of the detecting means. CONSTITUTION:A multi-gradation thermal recorder uses a thermal head 13, for a color printer, etc., obtains line information to be supplied from an address generator 16 and a gradation select signal BSEL to be supplied from a gradation counter in a head driver 12 in a conducting data table 17, and distinctly uses a correction value in response to print gradation. Density from a start of drawing to an end of drawing is maintained constantly in all the gradations to obtain preferable image. Particularly, in the case of multi-gradation print, density unevenness is eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal recording apparatus which prints by using a thermal head such as a thermal head used in a color printer or the like, and more particularly to correction of multi-tone density.

[0002]

2. Description of the Related Art When a thermal head such as a thermal head is used for printing, even if the gradation data is the same as shown in FIG. 5, the heat of the thermal head is accumulated at the beginning of the line (called heat accumulation). However, the print density is extremely low because of a small amount, but as the number of lines increases, the amount of heat stored in the thermal head increases, and the density increases, resulting in uneven density. As a method of solving this, there is known a method of measuring the temperature of the thermal head with a thermistor or the like and adjusting drive energy based on the temperature information. Also,
A method of estimating the heat storage amount from the history of print data and adjusting the print density has also been proposed. Further, as shown in FIG. 6, a method has been proposed in which density correction at the start of printing is made constant by reducing energization energy as the number of lines advances (JP-A-61-29560).

[0003]

However, in the method of measuring the temperature of the thermal head with a thermistor or the like to adjust the driving energy, the response of the thermistor is poor,
Moreover, there is a problem that the temperature of the heating element itself cannot be measured and accurate correction cannot be performed. Further, the method of estimating the heat storage amount from the history of the print data and adjusting the print density requires a memory for at least several lines or requires a heat storage amount calculation circuit, which complicates the circuit,
The cost will be high.

Further, the method of making the printing density constant by reducing the energizing energy as the number of lines progresses the density correction at the start of printing has a certain effect in the case of binary gradation printing. In the case of gradation printing, even if the driving energy is uniformly reduced for all gradation data, it is impossible to keep the density constant at all gradations.

For example, as shown in FIG. 7, the density energy curve is different between the case of high gradation density and the case of low gradation density, and even if uniform energy is subtracted from these different curves, it is constant. There is a problem that the concentration cannot be maintained. Therefore, it is an object of the present invention to provide a multi-tone thermal recording apparatus capable of performing accurate density correction particularly in the case of multi-tone printing.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide a heat-sensitive device including the following means. That is, in order to prevent the print densities of the same gradation from being different between lines, a correction drive signal that is temporarily reduced from the initial line at the start of printing is supplied to the thermal head, and the recording medium that moves relatively to this thermal head. A multi-gradation thermal recording apparatus capable of performing multi-gradation printing for each line, and a detection means for detecting the time from the start of printing or the number of lines, and the detection result and the incoming floor. A heat-sensitive recording apparatus, comprising: a drive signal generation unit for generating a correction drive signal preset according to the key information.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Particularly, according to the present invention, as shown in FIG. 3, a correction amount for low gradation and a correction amount for high gradation are set in advance, and the correction amount set in advance according to the number of lines at printing and gradation information is set. A drive signal containing the same is supplied to the thermal head so as to correct the drive energy to the thermal head so that the same gradation does not become non-uniform density between lines. One example is shown in FIG. 1 shows a schematic block diagram of a multi-tone thermal device.

In the figure, the heat-sensitive device of this embodiment comprises memories 10 and 11 for storing print data PDATA, a line synchronization signal HSYNC, a signal STB indicating a valid period of the data, and a system clock SCLK. Memory controller 18 for controlling reading and writing of memories 10 and 11, and print pulse data from print data and current data table 17 in memories 10 and 11. TDAT
A head driver 12 that generates a drive signal for the thermal head from A, a thermal head 13 that prints based on the drive signal from the head driver 12, and a line synchronization signal HS.
A motor driver 1 for driving a motor according to YNC
4, a motor 15 for relatively moving the thermal head 13 and the recording medium, an address generator 16 initialized by a print start signal PSTART and generating a predetermined address by a line synchronization signal HSYNC, and this address An energization data table 17 for supplying energization pulse width data to the head driver 12 by the address signal TADRS from the generator 16 and the gradation bit selection signal BSEL from the head driver 12 is roughly configured. There is.

FIG. 2 is a schematic block diagram of the head driver 12. The head driver 12 is initialized by a line synchronization signal HSYNC, and a memory controller 18 is provided.
A grayscale counter 12a for counting a read synchronization signal MEMOUT from the same, a grayscale bit of print data is selected by a bit selection signal BSEL from the grayscale counter 12a, and print dot address information is output to the thermal head 13. The selector 12b and the pulse generator 12c for determining the pulse width from the energizing pulse width data TDATA from the energizing data table 17 and outputting the energizing pulse to the thermal head are roughly constituted.

Next, FIG. 4 is a timing chart of the drive pulse of the initial line applied to the apparatus of this embodiment. In this embodiment, for convenience of description, an example in which four gradations are printed and these gradations are represented by 2 bits will be described. FIG. 4A shows a memory read start signal MEMOUT output from the memory controller 18, which is a start signal for reading 2-bit grayscale information and subsequent correction information. The figure (b) is the energization pulse HENB, the figure (c) is the drive pulse for expressing the gradation 1, the gradation of "1" is shown by the first pulse width, and the second The pulse width indicates the correction amount on this line. FIG. 6D shows a driving pulse for expressing the gradation 2. The first pulse width shows the gradation of "2", and the second pulse width shows the correction amount. Similarly, (e) of the figure shows a drive pulse for expressing gradation 3, and shows a gradation of "3" in the first and second pulse widths,
The third pulse width shows the correction amount.

As the correction amount in this example, for example, as shown in FIG. 3, gradation 1 and gradation 2 are the same correction amount according to the correction curve for low gradation, and gradation 3 is correction for high gradation. The correction amount is set according to the curve. The pulse width indicating the correction amount of each gradation shown in FIG. 4 indicates the pulse width of the initial line, but the correction amount is temporarily reduced as the number of lines in the energization data table 17 increases. Pre-correlated data is stored so that the width can be generated by the pulse generator 12c.

Next, the operation of the apparatus of this embodiment will be described.
When printing is started, the address generator 16 is initialized (for example, set to "0") by the print start signal PSTART.
At the same time, the head driver 12 enters the energization start state. In addition, the memory controller 18 has a line synchronization signal H.
When the SYNC and the signal STB indicating the valid period of the data come in, first, the print data PDA coming in to the memory 10.
Write one line of TA. Then, when the next line synchronizing signal HSYNC comes in, this time the print data PDATA of the next line is written in the memory 11, and at the same time the print data previously written from the memory 10 is written.
Data is transferred to the head driver 12. Memory 10, 1
In 1, the writing and reading of PDATA for one line are alternately performed every time the line synchronization signal HSYNC comes in.

The memories 10 and 11 are written only once each time the line synchronization signal HSYNC comes in, but at the time of reading, the gradation data is read until the next line synchronization signal HSYNC comes in. The memory controller 18 reads out the signal MEMOUT synchronized with the read out by the number of times equal to or more than the number of data bits + the number of correction pulses.
Output to. At this time, the motor driver 14 sets the HSYN
The motor 15 is moved by a predetermined amount in synchronization with C.

On the other hand, the gradation counter 12a in the head driver 12 initialized by the synchronizing signal HSYNC counts the memory read start signal MEMOUT, and first outputs the signal BSEL for selecting the first bit of the print data. To do. The selector 12b receives this signal, selects the first bit of the gradation of the print data, and outputs the signal HADRS indicating the resistor to generate heat for one line to the thermal head 13.
Supply to.

On the other hand, the selection signal BSEL is supplied to the energization data table 17, and the selection signal BSEL is supplied.
At the same time, the selection signal B supplied from the address generator 16
Address signal TADR indicating the number of lines synchronized with SEL
Conduction time data TDA corresponding to the first bit by S
The TA is supplied to the pulse generator 12c. Pulse generator 1
In 2c, the energizing pulse HENB is supplied to the thermal head 13 based on this data. As a result, in the thermal head 13, the signal HAD indicating the resistor that should generate heat earlier is generated.
The first bit of the print data for one line is printed by the drive signal based on the logical sum of RS and the energization pulse HENB.

Next, when the memory read signal MEMOUT for the second time enters the gradation counter 12a, the signal BSEL for selecting the second bit of the gradation of the print data is output to the selector 12b, and thereafter. Similarly to the first bit, the second bit drive signal is supplied to a predetermined heating element in the thermal head 13.

Next, when the memory read signal MEMOUT for the third time is input to the gradation counter 12a, the signal BSEL for selecting the gradation 2 or less of the print data is output, and the selector 12b outputs the print data. A pixel corresponding to the gradation 2 or less of the data is selected, and a signal HADRS indicating a resistor to generate heat for one line is supplied to the thermal head 13. At the same time, this signal BSEL is transmitted to the energizing data table 1
7 is selected, and here, for example, data indicating a predetermined correction amount on the correction curve for low gradation as shown in FIG. 4 is selected. This predetermined correction amount is determined by the address signal TADRS from the address generator 16 coming from the other side at the same time, and the time data TDATA having a pulse width corresponding to the number of lines at that time is supplied to the pulse generator 12c. Supplied. In the pulse generator 12c, an energizing pulse HEN having a predetermined width that is associated in advance based on this data.
B is output to the thermal head 13, and the thermal head 1
It is applied as driving energy for correction to the heating element in 3.

Furthermore, when the memory read signal MEMOUT for the fourth time is input to the gradation counter 12a, the print data is output.
The signal BSEL for selecting the gradation 3 or more of the data is output, the selector 12b selects the pixel corresponding to the gradation 3 or more of the printing data, and the signal H indicating the resistor which should generate heat for one line.
ADRS is supplied to the thermal head 13. At this time, similarly to the above, the selection signal BSEL is set to the energization data.
The data supplied to the bull 17, and the signal BSEL and the address signal coming from the other side select data indicating a predetermined correction amount on the correction curve for high gradation shown in FIG.

Data TDAT indicating the correction amount
A is supplied to the pulse generator 12c, an energizing pulse HENB corresponding to this data is supplied to the thermal head 13, and thereafter, in the same manner as described above, the driving energy for correction is supplied to a predetermined heating resistor. Is applied to the electrode to maintain a constant concentration. In this way, since the correct driving energy for correction is applied to the heating resistor according to each gradation, the density from the beginning of drawing to the end of drawing is constant in all gradations. Can be kept.

In this embodiment, the case of four gradations has been described, but the present invention can be applied to other gradation expression. Further, the correction amount used is one on two curves, but it is set to 3 depending on the difference in density energy between gradations.
You may prepare one or more. Further, one original correction curve may be prepared, and a plurality of correction curves may be derived and used by calculation. Furthermore, in the present embodiment, the number of lines is detected and the correction amount is changed.
The correction amount may be changed by detecting the elapsed time from the start of printing.

[0021]

According to the multi-body thermosensitive recording apparatus of the present invention,
Since the correction amount corresponding to the number of lines is supplied according to the gradation, the density from the beginning of drawing to the end of drawing can be kept constant in all gradations.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a multi-tone thermosensitive device according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a head driver 12.

FIG. 3 is a diagram showing a correction amount for low gradation and a correction amount for high gradation.

FIG. 4 is a timing chart of drive pulses.

FIG. 5 is a diagram showing the number of lines and changes in the amount of heat stored in the thermal head.

FIG. 6 is a diagram showing a relationship between the number of lines and a correction amount.

FIG. 7 is a comparison diagram of energy curves of high gradation density and low gradation density.

[Explanation of symbols]

 10, 11 memory 12 head driver 12a gradation counter 12b selector 12c pulse generator 13 thermal head 14 motor driver 15 motor 16 address generator 17 energization data table 18 memory controller

[Procedure amendment]

[Submission date] May 31, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

For example, FIG. 7 is a diagram showing the print densities in the line direction from high gradation to low gradation when multi-gradation printing is performed without performing density correction, but all levels are shown. When the density correction is performed by uniformly adding the energization for the time represented by one kind of correction amount corresponding to the line as shown in FIG. 6 to the tonal print, as shown in FIG. 7, high gradation and low gradation are obtained. There is a problem that the tone of correction differs depending on the tones, and it is not possible to maintain a constant density even if uniform correction is performed for each gradation. Therefore, it is an object of the present invention to provide a multi-tone thermal recording apparatus capable of performing accurate density correction particularly in the case of multi-tone printing.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide a heat-sensitive device including the following means. That is, in order to prevent the print densities of the same gradation from being different between lines, a correction drive signal that is temporarily reduced from the initial line at the start of printing is supplied to the thermal head, and the recording medium that moves relatively to this thermal head. A multi-gradation thermal recording apparatus capable of performing multi-gradation printing for each line, including a detection unit for detecting the time or the number of lines from the start of printing, and the time or the number of lines from the start of printing. Holds multiple correction data of corresponding energization time,
Correction amount generating means for selectively outputting the correction data corresponding to the gradation information of the print signal from these correction data, the gradation information of the incoming print signal, and the correction data supplied from the correction amount generating means. And a head drive means for generating a signal for driving a thermal head according to the above.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

[0021]

According to the multi-gradation thermal recording apparatus of the present invention,
Since there is a plurality of correction data corresponding to the number of lines and the density correction is performed by selecting the correction data corresponding to the gradation from the plurality of correction data, it is possible to perform the density correction from the beginning of drawing to the end of drawing at all gradations. The concentration can be kept constant.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a multi-tone thermosensitive device according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a head driver 12.

FIG. 3 is a diagram showing a correction amount for low gradation and a correction amount for high gradation.

FIG. 4 is a timing chart of drive pulses.

FIG. 5 is a diagram showing the print density in the line direction when density correction is not performed.

FIG. 6 is a diagram showing a relationship between the number of lines and a correction amount.

FIG. 7 is a diagram showing the print densities in the line direction of each gradation when density correction is not performed in multi-gradation printing.

[Explanation of reference numerals] 10,11 memory 12 head driver 12a gradation counter 12b selector 12c pulse generator 13 thermal head 14 motor driver 15 motor 16 address generator 17 energization data table 18 memory controller

[Procedure correction 6]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 7

[Correction method] Change

[Correction content]

[Figure 7] ─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] August 30, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

For example, when density correction is performed by uniformly adding energization for a time represented by one type of correction amount corresponding to a line as shown in FIG. 6 to prints of all gradations,
As shown in FIG. 7, the degree of correction differs between high gradation and low gradation, and there is a problem in that even if uniform correction is performed for each gradation, a constant density cannot be maintained. Therefore, it is an object of the present invention to provide a multi-tone thermal recording apparatus capable of performing accurate density correction particularly in the case of multi-tone printing.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a multi-tone thermosensitive device according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a head driver 12.

FIG. 3 is a diagram showing a correction amount for low gradation and a correction amount for high gradation.

FIG. 4 is a timing chart of drive pulses.

FIG. 5 is a diagram showing the print density in the line direction when density correction is not performed.

FIG. 6 is a diagram showing a relationship between the number of lines and a correction amount.

FIG. 7 is a diagram showing the print densities in the line direction of each gradation when correction is performed with one type of density correction amount in multi-gradation printing.

[Explanation of reference numerals] 10,11 memory 12 head driver 12a gradation counter 12b selector 12c pulse generator 13 thermal head 14 motor driver 15 motor 16 address generator 17 energization data table 18 memory controller

Claims (1)

[Claims] 1. A driving signal for correction, which is temporarily decreased from an initial line at the start of printing, is supplied to the thermal head so that the printing density of the same gradation does not differ between the lines, and the thermal head moves relative to the thermal head. A multi-gradation thermal recording apparatus capable of performing multi-gradation printing for each line on a recording medium to be recorded, the detection means for detecting the time from the start of printing or the number of lines, and the detection result by this. A thermal recording device, comprising: a drive signal generating unit for generating a drive signal for correction that is preset according to the coming gradation information.