JPH0747318B2 - Thermal transfer gradation control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer gradation control device, in which the size of a print dot is controlled by controlling the energization time of a constant current flowing through a heating resistor of a thermal head to control gradation. The present invention relates to a thermal transfer gradation control device for controlling the temperature.

2. Description of the Related Art There is a problem in that the relationship between the print density and the time for which an electric current is passed through the heating resistor (recording time) in a thermal transfer printing apparatus is not linear as shown by the solid line in FIG. That is, as shown in FIG. 7B, the maximum density obtained at the maximum recording time Dm and the recording times D ₁ , D ₂ and D ₃ shown in FIGS. The relationship with the respective obtained densities is not linear, and, for example, a density difference of Δd occurs between the density obtained at the recording time D ₂ and the originally desired density shown by the broken line in FIG.

Therefore, in order to eliminate this difference in concentration, the present applicant previously disclosed in Japanese Patent Application No. 60-49119 (Japanese Patent Laid-Open No. 61-208366) that the time for applying an electric current to the heating resistor for each unit of concentration. A control device was proposed.

According to this device, it is possible to print without density unevenness, but on the other hand, it becomes necessary to correct the relationship between the recording time and the print density according to the pattern to be printed so as to have a predetermined curve (for example, for a person In the case of printing a face, it is desirable to print skin tone colors in high gradation, while in the case of landscape printing, it is desirable to print in high gradation over all colors). A device has been proposed.
In FIG. 6, the correction circuit 51 is controlled by the control circuit 50.
Depending on the design (correction data is stored for each design, which is composed of a look-up table that converts the number of gradations into recording time data, and that matches the relationship between recording time and print density to a predetermined curve) Gradation correction is performed based on the corrected data, and then the parallel / serial conversion circuit 52 converts the parallel correction data composed of a plurality of parallel bits into the actual recording time (series), shift register 53, latch Circuit 54
Is supplied to the thermal head 55 via the, and printing is performed with the recording time corrected by the correction data corresponding to each pattern.

Problem to be Solved by the Invention When the number of gradations is 256, the recording time is controlled by 1/256 of the maximum recording time Dm. In the conventional apparatus shown in FIG. 6, when the number of gradations is 32, the correction recording time is, for example, 32.5 in the calculated value, and either 32 or 33 is selected and stored in the correction circuit 51. The parallel / series converter 52 at the next stage corrects the density error caused by the error. Here, in the parallel / serial conversion circuit 52, the number of gradations is reduced from 256 to 64 to make the density error inconspicuous. As a result, there is no problem in the case of a pattern that does not require such high resolution. However, when high resolution is required, there is a problem that only unclear printing is possible.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermal transfer gradation control device capable of performing density correction according to a pattern without lowering resolution.

Means for Solving the Problems The present invention comprises a concentration data generation means, a correction data external storage means, a correction data generation circuit, and a means for supplying a current to a heating resistor. The density data generating means compares with the input data to be transferred, and generates density data indicating the time of the current flowing through the plurality of rows of the heating resistors for each unit of density. The correction data external storage means stores the correction data in which the relationship between the recording density and the density data is set to a strict value by calculation according to the pattern to be printed so as to be a straight line or a predetermined curve, The correction data of a predetermined picture is taken out by selecting the picture from the outside.
The correction data generation circuit includes a rewritable internal storage means for storing the correction data extracted from the external storage means,
The input density data is corrected according to the correction data stored in the internal storage means and output. The means for supplying a current to the heating resistor is supplied with the corrected data, and supplies a current to the heating resistor for a time corresponding to the value.

Operation In the present invention, the density data is generated by using the correction data set to the exact value by calculation according to the pattern to be printed, and the density is corrected. This makes it possible to correct the print density according to the pattern to be printed without lowering the resolution of the recording density gradation.

First Embodiment FIG. 1 shows a block system diagram of a first embodiment of the device of the present invention. In the figure, the analog video signal supplied from the TV signal generator 8 is converted into a digital signal by the A / D converter 9 and sent to the data storage device 10 for storage. On the other hand, the address counter 11 is supplied with the reference clock signal from the terminal 12 and the start pulse from the terminal 13, and
The address of the second time is sent to the data storage device 10. The data storage device 10 sends the first data (the first data of the image data from the A / D conversion device 9) corresponding to the first address to the grayscale data comparison circuit 14. At this time, the count of the data counter 15 is set to, for example, "1", and the reference density data c (hereinafter, referred to as "second data") that sequentially increases according to the count number is output from the data counter 15 as grayscale data. It is supplied to the comparison circuit 14. The density data comparison circuit 14 compares the first data with the second data "1" indicating the minimum color density, and if the first data is equal to or larger than the second data "1", the shift register Control data “1” is sent to 16, and if smaller, control data “0” is sent to the shift register 16.

In this way, when the processing at the first address is completed, the address counter 11 sequentially sends the addresses of the 2, 3, ..., Nth times to the data storage device 10, and the data storage device 10 receives the second to nth addresses each time. The first data corresponding to each address is sequentially sent to the grayscale data comparison circuit 14. Where 1 ~
The first data from the n-th address corresponds to the image data printed by the heating resistors R _{1 to} R _n of the thermal head 6, respectively. The grayscale data comparison circuit 14 uses the above 2 to n.
The first data and the second data "1" respectively corresponding to the addresses of the second time are compared, and the control data "0" or "1" similar to the above is sent to the shift register 16. The n-stage shift register 16 sequentially fetches n-bit control data corresponding to the 1st to n-th addresses supplied from the grayscale data comparison circuit 14 and sends it to the latch circuit 17.

When the address counter 11 finishes counting the 1st to nth addresses, it sends a data transfer pulse to the correction circuit 18, which is a main part of the present invention, via the data counter 15, the latch circuit 17, and the terminal 19. At the same time as the data transfer pulse is sent to the data counter 15, the heating pulse is supplied to the correction circuit 18, the address counter 11 and the AND circuit 21 via the terminal 20, and the second data which has been "1" until then. From the smaller value to the value "2" indicating the second color density. On the other hand, a reference clock signal is supplied from one terminal 12 to one end of the AND circuit 21, and at the same time when the heating pulse comes in, a pulse is output to the shift register 16 and the address counter 11 receives the 1st to nth address. The n-bit control data corresponding to is transferred from the shift register 16 to the latch circuit 17. When the data transfer pulse comes in, the latch circuit 17 latches the control data supplied from the shift register 16 and sends it to each one of the input terminals of the gate circuits G _{1 to} G _n .

Next, the address counter 11 is reset by the input of the heating pulse, and sequentially counts 1 to n addresses again, and the n first data is the second data of the value "2". Then, the grayscale data comparison circuit 14 sequentially compares the sizes. Even when the second data is “2”, the data counter 15, shift register 16, latch circuit 17, AND circuit 21
Etc. perform the same operation as described above, and send the latched control data to each of the gate circuits G _{1 to} G _n . Gate circuit
A heating pulse is applied to each local input terminal of G _{1 to} G _n by a terminal 28 of the correction circuit 18 described later, and each output signal thereof is applied to the bases of the corresponding NPN type transistors T _{1 to} T _n .
This is switching-controlled. Among the transistors T _{1 to} T _n , current is flowed only through the heating resistor connected to the collector side of the turned-on transistor to generate heat. The above configuration is the same as that described in FIG. 1 of the above-mentioned proposal of the present applicant.

The present embodiment is characterized in that the gradation control device shown in FIG. 1 is provided with a pattern selection section 35, a correction data memory 36, an interface 32, and a correction circuit 18 having the configuration shown in FIG. One example will be described below. Second
In the figure, the correction circuit 18 is a pulse generator 24 and a latch circuit.
25, a correction table storage memory 26, an AND circuit 27, and interlocking switches S ₁ and S ₂ . Here, a case where the correction data corresponding to the design is written in the correction circuit 18 will be described. First, the pattern selection section 35 shown in FIG. 1 selects a pattern to be printed, and selects correction data corresponding to each pattern stored in the correction data memory 36 (correct values stored by calculation are stored). . The pattern selection unit 35 allows the user to freely select a pattern from the outside, and the correction data of a strict value corresponding to the pattern is read by the designation from the pattern selection unit 35, and this correction data can be rewritten. It is something.

Next, under the control of the system control circuit 37, the switch S ₁ is turned off and the switch S ₂ is turned on in FIG. As a result, the data transfer pulse b from the address counter 11 coming into the terminal 19 is not supplied to the latch circuit 25, the terminal 30 is connected to the correction table storage memory 26, and the correction data memory 36 from the correction data memory 36 shown in FIG. For example, correction data for 256 gradations is supplied to the correction table storage memory 26 via the interface 32. On the other hand, under the control of the system control circuit 37, a write control signal is output from the interface 32 and the terminal 31
Is supplied to the correction table storage memory 26, and the correction data of strict values for 256 gradations are thereby written in the correction table storage memory 26. In this way, if the correction data according to a certain pattern is written in the correction table storage memory 26, this pattern can be left as it is.

When the writing of the correction data to the correction table storage memory 26 is completed, the switch S ₁ is turned on and the switch S ₂ is turned off,
On the other hand, a read control signal is supplied to the terminal 31. As a result, the data transfer pulse b from the terminal 19 is transmitted to the latch circuit 25,
The second data c supplied from the data counter 15 to the pulse generator 24 is corrected based on the correction data stored in the correction table storage memory 26 based on the correction data and read out. The corrected data for 256 gradations thus obtained is latched by the latch circuit 25. The subsequent operation is the same as the operation of the circuit shown in FIG. 1 which was previously proposed by the present applicant.

That is, the latch circuit 25 latches the corrected second data at the pulse rise time of the data transfer pulse b coming from the terminal 19. The output correction data of the latch circuit 25 is output to the pulse generator 24. The pulse generator 24 is cleared by the pulse b at the beginning of one grayscale data time, and the clock signal a is supplied to receive the incoming data. The transfer pulse b and the correction data d generate a pulse e having a pulse width that rises at the pulse falling times t ₁ , t _{2 and the} like of the data transfer pulse b and changes according to the content of the correction data d. Output to one input terminal of the circuit 27. AND circuit 27
A high-level heating pulse f is supplied from the data counter 15 to the other input terminal via the terminal 20. Therefore, the pulse e passes through the AND circuit 27 as it is and is output to the output terminal 28 as a pulse g obtained by ANDing the pulse e and the pulse f.

Here, the data transfer pulse d always falls at a constant time interval (one gradation data time), while the pulse g (pulse width ΔH) rises at the pulse falling of the data transfer pulse b, and the data of the correction data d. Depending on the content, its pulse width Δ
For example, H increases sequentially.

The pulse g is supplied as a heating pulse to each of the local input terminals of the gate circuits G _{1 to} G _n via the terminal 28. Each of the gate circuits G _{1 to} G _n has this pulse g and the latch circuit 17
A gate signal obtained by performing gate processing on the control data supplied from the device is supplied to the bases of the NPN transistors T _{1 to} T _n . The transistor T ₁ through T _n are turned on during the gate signal has a high level applied to its base, the voltage applied to the terminal 29, a heating current heating resistor R ₁ to R _n
Of these, only the heating resistor connected to the collector of the turned-on transistor is made to flow.

In this way, to some heating resistors among the heating resistors R _{1 to} R _n corresponding to the portion to be recorded, the change of the energization time according to the correction data according to the coloring density and the pattern Recording is performed by applying a heating current to the recording medium. Therefore,
The relationship between the recording time and the density becomes a straight line or a curve depending on the design. Each time the data counter 15 finishes counting 1 to m times (m is the value of the maximum color density), one line is recorded on the recording paper 4, and after the recording of one line is completed, the data is again recorded. The counter starts counting 1 to m times.

The analog video signal supplied from the TV signal generator 8 may be an information signal such as another character or figure.

As described above, according to the present invention, since the gradation correction is performed by controlling the energization time to the heating resistor by using the correction data having the strict calculation value, the pattern can be obtained without lowering the resolution unlike the conventional device. The print density can be corrected according to the above, and the correction amount of the print density can be easily changed by rewriting the correction data memory 36.

FIG. 3 shows a block system diagram of a second embodiment of the device of the present invention. In FIG. 3, the same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. The second embodiment is characterized in that the correction circuit is the correction circuit 18a having the configuration shown in FIG.

When writing correction data to the correction table storage memory 26, the switch S ₁ is turned off and the switch S ₃ is turned on under the control of the system control circuit 37a. As a result, the write control signal h is supplied from the arithmetic unit 33 to the correction table storage memory 26, and the standard correction data from the standard correction data table 34 and the correction data according to the pattern from the correction data memory 36a (first The correction data that does not have to be strictly calculated as in the embodiment) is calculated as optimum correction data (same as the calculated exact value), and the correction table storage memory is generated by the write control signal h. Written on 26.

By using the standard correction table 34 and the arithmetic circuit 33 in this manner, the correction data in the correction data memory 36a does not have to be the correction data that has been subjected to the strict calculation as in the first embodiment, and the calculation by hand becomes relatively easy. .

At the time of reading, the switch S ₁ is turned on and the switch S ₃ is turned off, and the read control signal h ′ is output from the arithmetic circuit 33. Since the other operations are the same as those shown in FIGS. 1 and 2, the description thereof will be omitted.

1 and 3, the system control circuits 37, 37a,
The interfaces 32 and 32a may be configured to directly exchange data as a CPU.

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to correct the print density according to the design (person's face, landscape, etc.) to be printed without lowering the resolution of the recording density gradation.

[Brief description of drawings]

FIG. 1 and FIG. 2 are a block system diagram of a first embodiment of the device of the present invention and a circuit system diagram of its main part, FIG. 3 and FIG.
FIG. 4 is a block system diagram of a second embodiment of the device of the present invention and a circuit system diagram of the main part thereof, FIG. 5 is a diagram for explaining density vs. recording time characteristics of the conventional device, and FIG. 6 is an example of the conventional device. It is a block system diagram. 6 ... Thermal head, 10 ... Data storage device, 12 ... Reference clock signal input terminal, 14 ... Gray data comparison circuit, 15
…… Data counter, 16 …… Shift register, 17,25…
… Latch circuit, 18,18a …… Correction circuit, 19 …… Data transfer pulse input terminal, 20 …… Heating pulse input terminal, 21,27…
… AND circuit, 22 …… Clock signal input terminal, 23 …… Reference concentration data input terminal, 24 …… Pulse generator, 26 …… Correction table memory, 30 …… Correction data input terminal, 31…
… Write / read control signal input terminal, 33 …… Computing device,
34: Standard correction data table, 35: Design selection section, 3
6,36a …… Correction data memory, 37,37a …… System control circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Toshinori Takahashi, 3-12 Moriya-cho, Kanagawa-ku, Yokohama, Kanagawa, Japan Victor Company of Japan, Ltd. (56) Reference JP-A-63-176162 (JP, A) JP Sho 60-90779 (JP, A) JP 62-284360 (JP, A)

Claims (2)

[Claims] 1. A thermal transfer gradation control device for individually controlling the time of an electric current to be individually passed through a plurality of heating resistors arranged in a line according to the density, and comparing the input data to be transferred. A means for generating density data indicating the time of the current flowing through a plurality of rows of the heating resistors for each unit of density, and the relationship between the recording density and the density data is a straight line or a predetermined curve. Correction data set to exact values by calculation according to the pattern to be printed are stored,
The input density data is stored in the internal storage unit including a storage unit that can retrieve correction data of a predetermined design by selecting a design from the outside, and a rewritable internal storage unit that stores the correction data retrieved from the external storage unit. It is characterized by comprising a correction data generation circuit for correcting and outputting according to the correction data of the storage means, and means for supplying the corrected data and for supplying a current to the heating resistor for a time corresponding to the value. Thermal transfer gradation control device. 2. A heat-sensitive transfer gradation control device for individually controlling the time of each current flowing through a plurality of heating resistors arranged in a line according to the density, and comparing with input data to be transferred. And a standard correction data for correcting the relationship between the recording density and the density data, for generating the density data indicating the time of the current flowing through the plurality of rows of the heating resistors for each unit of density. Compensation data for calculation used for computation with the internal storage means that stores therein and the standard correction data according to the pattern to be printed so that the relationship between the recording density and the density data becomes a straight line or a predetermined curve External storage means capable of taking out the calculation correction data of a predetermined pattern by selecting a pattern from the outside, the calculation correction data extracted from the external storage means and the internal storage means. Calculating means for calculating optimum correction data by calculating the standard correction data, a correction data generating circuit for correcting and outputting the input density data according to the optimum correction data, and the correction data And a means for supplying a current to the heating resistor for a time corresponding to the value thereof.