JPS62152763A - Heat sensitive head drive circuit of video printer - Google Patents

Abstract

PURPOSE:To make the accurate representation of gradation possible, by possessing the gradation counter counting each one at each gradation, the comparator connected to the counter, the shift register connected to the comparator, the switches connected to the above-mentioned shift registers and a current application pulse generating circuit and the heat sensitive heads connected to the switches. CONSTITUTION:The picture data of one line contents are inputted to a comparator 1 from a line memory. On the other hand, the gradation data is inputted from a gradation counter. Both data are compared herein: the data judged to be one or zero is transferred to a shift register 4 and the data inputted herein is transferred to a heat sensitive head 5. Then, the gradation data from the gradation data 2 is sent to a current application pulse generating circuit 3 and the current application pulse controlling ON or OFF of the heat sensitive head 5 is generated herein. The current application pulse controls the switch provided between the shift register 4 and the heat sensitive head 5 and the application of current is controlled thereby. The heat sensitive head 5 is heated to carry out printing according to the contents of the data in the shift register 4 and ON or OFF state of the switch. Thereby, the picture of accurate gradation can be printed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video printer, and particularly to a thermal head drive circuit for a video printer suitable for expressing images with accurate gradation.

[Conventional technology]

As shown in Japanese Patent Application Laid-Open No. 58-196784, in the conventional apparatus, as a driving method of the thermal head, the thermal head is made to generate heat depending on the content of data to express gradation.

[Problems to be solved by the invention] The above-mentioned conventional technology does not take into consideration the thermal head drive circuit, and in particular, in order to express accurate gradation, the current pulse width is varied depending on the gradation data. There was a problem in that no consideration was given to this point, and it was difficult to express accurate gradations.

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermal head drive circuit for a video printer that is capable of expressing correct gradation.

[Means for solving problems]

The above purpose is to provide a gradation counter that counts one by one for each gradation, a comparator connected to the gradation counter, a shift register connected to the comparator, and a gradation counter and comparator that This is achieved by providing an energization pulse generation circuit connected to the energization pulse generation circuit, a switch connected to the shift register and the energization pulse generation circuit Km, and a thermal head connected to the switch.

[Effect]

The gradation counter counts the number of gradations and sends gradation data to the comparator and the energization pulse generation circuit.

The comparator compares the input data and the gradation data, and sends comparison data to the shift register.

On the other hand, the energization pulse generation circuit receives the gradation data, generates energization pulses, and controls the switch.

Thereby, the switch turns on and off data from the shift register to the thermal head, and controls the energization time of the thermal head.

This makes it possible to realize a thermal head drive circuit that enables accurate gradation expression.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, 1 is a comparator, 2 is a gradation counter, 3 is an energizing pulse generation circuit, 4 is a shift register, 5 is a thermal head, 2
0 is a switch, and 21 is a head assembly.

Next, the operation of this embodiment will be explained with reference to FIGS. 1 and 2. One line of image data is input to the comparator 1 from the line memory. On the other hand, gradation data is input from the gradation counter. Here, both data are compared, and the data determined to be 1 or 0 is transferred to the shift register 4. Next, the data input to the shift register 4 is transferred to the thermal head 5. Next, the gradation data from the gradation counter is sent to the energizing pulse generation circuit 3, where the thermal head 5 is turned on.
, generates an energization pulse that controls OFF. The energization pulse controls the switch 2° provided between the shift register 4 and the thermal head 50, thereby controlling the energization.

Data contents in shift register 4 and switch 0N
10FF causes the thermal head 5 to generate heat and print. As described above, data of the first gradation is transferred and printed. Similarly, data of the second gradation, third gradation, . . . mth gradation is printed. FIG. 2 is a timing chart showing the operation of FIG. 1. In this embodiment, as shown in Figure 2, the data of the first gradation and the data of the second gradation are transferred to the j-th order, and printed after each transfer. rIL in this way
Prints up to gradation.

The internal structure of the head assembly in FIG. 1 is shown in FIG. 16. In Figure 16, 8 and 4 are shift registers.

20 is a switch, 21 is a head assembly, 22 is a heating element array, 23 is a heating element, 24 is a melon circuit, and 25 is a transistor.

Next, the operation shown in FIG. 16 will be explained. Input data to shift register 4. Next, the data in the shift register 4 is sent in parallel to the AND gate 24, and at the same time an energizing pulse is sent to the Φ gate 24. At the gate of M, shift register 4
Only when the data from energizing Hals comes, current flows through the transistor 25 through the resistor, turns the transistor ONt, and current flows through the heating element 23. As a result, the heating element generates heat, and a glint operation is performed.

Next, the processing system No. 9 of the video printer including the thermal head drive circuit explained with reference to FIG. 1 will be explained with reference to FIG. 6th
In the figure, 6 is an analog signal processing section that converts the NTSC video signal into a KGB signal.

7 is an analog/digital converter (hereinafter abbreviated as A/D), 8 is an image memory, 9 is a digital/analog converter (hereinafter abbreviated as D/A), and 10 is an RGB to N
Analog signal processing section for creating TSC video signals, 11
1 is a color selection circuit, and 12 is a line memory. It should be noted that the components indicated by the reference symbols in FIG. 1 have the same functions.

Next, the operation shown in FIG. 3 will be explained. The input image signals are converted into 1g signals for each color of RGB in an analog signal processing section 6. Next, the A/D conversion circuit 7 converts the signal into an RGB digital color signal. The digitized RGB color signals are stored in the image memory 8 at intervals of six colors. The 6-color image data stored in the image memory 6 is read out at the same speed as when it was recorded, and the D/A converter 9 and analog signal processing section 10 are recited and output the same video signal as when it was recorded. is regenerated and sent to the monitor.

On the other hand, during printing operation, the color selection means 11 selects one color from the RGB digital signals, and the line memory 12 selects one color from the RGB digital signals.
to be memorized. Here, the data for one line is the 4th line.
This is data for one vertical line shown in the figure.

One line of image data stored in the line memory is transferred to the next-stage comparator 1, and printing is performed by the operation described at 3 in FIG. 1 below.

When printing of one line is completed, data for the next line is loaded into the line memory 12 and printing for one line is performed again.

Here, as shown in FIG.
It advances from the left edge of the screen to the right, and finishes printing one color at the right edge.In this way, with a video printer,
One sheet of printing is completed by printing in six colors.

Another embodiment of the present invention will be briefly described with reference to FIG. Fifth
The figure is characterized in that a circuit is provided for converting data for determining the energization pulse width to be sent to the energization pulse generation circuit 5 based on the gradation data from the gradation counter 2 shown in FIG.

In FIG. 5, 13 is a data conversion circuit.

In FIG. 5, the same reference numerals as in FIG. 1 operate in the same way. The operation shown in FIG. 5 will be explained below.

After the input data is compared with the gradation data from the gradation counter by the comparator 1, it is transferred to the shift register. On the other hand, the gradation data from the gradation counter 2 is input to the data conversion circuit 13, where it is converted into data including the energization pulse width appropriate for each gradation, and sent to the energization pulse generation circuit 5. The energizing pulse generating circuit 3 generates energizing pulses having a width suitable for each gradation based on the data indicating the energizing width, and transfers them to the switch 20 provided between the shift register 4 and the thermal head 50. Then, the same operation as shown in FIG. 1 is performed to print. FIG. 6 is a timing chart showing the operation of FIG. As shown in FIG. 6, data of the first gradation.

Performs transfer and energizes the head. Transfer the second gradation data and energize the head. The operations 6, 4, . . . are repeated m times to print data up to m gradations. Here, the print width of each gradation can be freely varied.

FIG. 7 shows the relationship Y between travel time/a degree that can be printed with the configuration shown in FIG.

Normally, there is no proportional relationship between concentration and current application time.

However, in this embodiment, since the energization time can be set to express each gradation once, accurate gradation can be expressed.

Next, another embodiment of the present invention will be described with reference to FIG.

In FIG. 8, 14 is a read-only memory (hereinafter abbreviated as ROM). Components with the same symbols as in FIG. 5 operate in the same way.

The difference between this embodiment and the embodiment explained in FIG.
The data conversion circuit shown in the figure is a ROM.

Before explaining this operation, the operation within the energizing pulse generating means will be explained using FIG. 15.

14 is a ROM 126.30 is a gate, 27 is a decoder, 28 is an energizing pulse width counter, 29 is an SR latch, 31 is an image data counter, and 32 is a decoder.

Image data is input to the image data counter 61, the output of the image data counter 31 is decoded into a certain number by the decoder 31, and the decoded signal is sent to the gate 30.

At the same time, the gradation data is transferred to Tomoe (14) and the load data is sent from the ROM 14 to the energization pulse width counter.The energization pulse width counter counts the reference clock of the energization pulse from the number of load data and outputs it to the decoder 27. The decoder 27 decodes a certain number, outputs a decode signal, resets the S-R latch 29, and stops the energizing pulse.The decode signal is also closed by the gate 26.

Stop picking 1. The signal is input to the static gate 30, the next load signal is sent, the S-R latch 29 is set, and an energizing pulse is generated.

This series of operations is repeated the same number of times as the number of gradations, and the output of the melon gate 60 is returned to the line memory as the end signal of one line, thereby handshaking with the line memory and shortening the overall print time. .

In the operation shown in FIG. 8, gradation data 1'' representing the gradation is first input to the ROM 14 as an address.

The ROM 14 contains data for reducing the energization pulse width for the first gradation, and upon receiving the address "11" outputs the data that determines the energization pulse width and loads the energization pulse generation circuit 15. .

In the ROM 14, the energizing pulse generating circuit, which sequentially stores data of the second gradation at address 2 and data of the 5th gradation at address 3, generates an energizing pulse having a pulse width based on this load value. Thereafter, as described above, energizing pulses for the second and sixth gradations are sequentially generated, and a printing operation is performed as in the embodiment shown in FIG.

Here, a major feature of this embodiment is that a ROM is used as the data conversion circuit.

By adopting this method, it is possible to easily change the pulse width even if the ambient temperature changes or the paper or ink paper is changed.

Next, another embodiment of the present invention is shown in FIG. FIG. 10 is a timing chart showing the operation of FIG. 9.

In FIG. 9, 16 is a latch. Note that the same reference numerals as in FIG. 5 have the same operations.

In this embodiment shown in FIG. 9, a latch 16 is provided after the shift register 4, so that the data input to the shift register 4 is sent to the latch 16, and the next data is simultaneously shifted while the thermal head 5 is operating. It can be entered into the register.

Next, the operation shown in FIG. 11 will be explained. Input data is comparator 1
The data is input to the shift register 4, compared with the gradation data from the gradation counter 2, and input to the shift register 4. The contents of the shift register are then transferred to latch 16. First, the value of gradation counter 2 is input to comparator 1, and data equal to or higher than this value is input to comparator 1.
．． Shift register 4 sets data smaller than this value to 0.
Enter. Next, the gradation data from the gradation counter 2 is transferred to the data conversion circuit 13, which outputs data for determining the energization pulse width, and then transferred to the energization pulse generation circuit 3. The energizing pulse generating circuit 3 generates an energizing pulse that controls the switch between the latch 16 and the thermal head 50, and
The thermal head generates heat only during the period when 0 is closed.

In this way, the next data is sent during the printing period.

Next, in FIG. 9, if the data conversion circuit 13 is considered as a ROM', the first gradation data to be input into the ROM is
By dividing the output data into fewer bits,
The components of this embodiment, which shows an embodiment that can be expressed in terms of number of characters, are the same as those shown in FIG. 9.

FIG. 10 is a timing chart showing this operation.

As shown in FIG. 10, data for the second gradation is sent when printing the first gradation, and data for the third gradation is transferred when printing the second gradation.

In this embodiment, the next data is transferred during the print operation, so the current flow can be output without any interruption as shown in Figure 12.Therefore, the data transfer between each gradation is There is no need for the thermal head to turn off and get cold during the time.
Being able to accurately express the degree of busyness is effective. Also, since the printing operation is performed at the same time as the transfer of the next data, it has the effect of shortening the overall printing time.

The method will be explained below. As shown in Figure 5, energizing time and color development! The I degree has a proportional characteristic, especially the low gradation part of the degree C.0 is shown in FIG. In FIG. 13, 0.1.2.3 on the density axis represents gradation, and 1.3 on the energization time axis represents gradation. ,
1! , 13 respectively represent the energization time required to develop one gradation density, the energization time required to develop two gradation densities, and the energization time required to develop three gradation densities. .

Generally, thermal printers require a considerable amount of time to be energized before color develops. The current application time required to print the density of one gradation is Δt1. If the current application time required to print the density of the second gradation from the density of the first gradation is Δt, then 7t, >> Δt, (Δ ”s/It, 〉10
) holds true.

Here, as a means of converting the energizing pulse width from the gradation data, R
When considering OM, since Δt is very long, it is necessary to set the pulse width after Δt2 in a very rough step-like manner. The time relationship is shown in FIG.

In this embodiment, the above Δt is divided into Δt8+Δt1.

Next, the specific method of this example is shown in FIG.

FIG. 13 shows data in the ROM, the upper part of FIG. 16 corresponds to FIG. 11 explained above, and the lower part of FIG. 13 shows data in the ROM corresponding to FIG. 12. Here, in the figure below, Dt in the above figure is divided into Dt'o and Dtl and R
OM is input, then Dt, and the following are input in sequence.

Therefore, the accuracy of the pulse width after Δt is approximately twice as high as that of the pulse width setting method shown in FIG.

Next, another embodiment of the present invention is shown in FIG.

In the figure, 4-1 and 4-2 are the shift register 4 in FIG. 11 divided into two, 16-1 and 16-2 are the latch 16 in FIG. −
2C The thermal head shown in FIG. 11 is divided into two blocks.

The operation of this embodiment will be explained in detail. First, input data is input to the comparator. A comparator compares the data with the gradation data from the gradation counter 2 and transfers it to the next stage, 2-dividing means 17. The two-part dividing means 17 divides the data into data to be transferred to the thermal heads of the upper block and data to be transferred to the thermal heads of the lower block, and transfers them to shift registers 4-1 and 4-2, respectively. The data transferred to the shift registers 4-1 and 4-2 are transferred to the latches 16-1 and L6-2, respectively, and the switch 20 is opened and closed under the control of the energization pulse from the energization pulse generation circuit 5 to thermally transfer the data. Head 5-1
, 5-2 and print.

In this embodiment, by dividing each of the shift register, latch, and thermal head into two parts, there is an effect that the transfer speed for sending data to the shift register can be reduced to 1/2 compared to the input speed of input data.

〔Effect of the invention〕

According to the present invention, it has become possible to correctly control the time of the head necessary for gradation expression, and it has become possible to print images with accurate gradation.

In addition, the number of comparators required for each line of pixels was reduced to one, reducing the cost of the circuit.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a timing chart showing the operation of Fig. 1, Fig. 3 is a block diagram showing the entire video printer, and Fig. IIGJ shows the printing operation. A schematic diagram, FIG. 5 is a block diagram showing another embodiment, FIG. 6 is a timing chart showing the operation of FIG. 5, FIG. 7 is a graph showing color density characteristics, and FIG. FIG. 10 is a timing chart showing the operation of FIG. 9, FIG. 11 is a block diagram showing the embodiment of FIG.
FIG. 12 is a diagram showing color density characteristics. Figure 13 is a schematic diagram of the arrangement of ROM data, Figure 14 is a block diagram showing another embodiment, Figure 15 is a block diagram of the energizing pulse generation circuit, and Figure 16 is a circuit diagram of the head assembly. be. 1... Comparator, 2... Gradation counter,
3... Current pulse generation means, 4... Shift register, 5... Thermal head, 1
5...Data conversion circuit, 14...ROM, 16...
...Latch, 20...Switch. Fig. 1 Fig. 2 Yong 4- Fig. 7 Fig. 7 High 8 Fig. Genus 9 Fig. Name Io Fig. N Fig. 12 (α) Fig. 3 Flower ts Fig.

Claims (1)

[Claims] 1. A video printer that prints input data using a thermal head, comprising: a gradation counter that counts one for each gradation; a comparator connected to the gradation counter; A shift register connected to a comparator, an energizing pulse generating circuit connected to the gradation counter and the comparator, and a switch connected to the shift register and the energizing pulse generating circuit connected to the switch. A thermal head drive circuit for a video printer characterized by being equipped with a thermal head. 2. A thermal head drive circuit for a video printer according to claim 1, characterized in that a data conversion circuit is provided between the gradation counter and the energization pulse generation circuit. . 3. A thermal head drive circuit for a video printer according to claim 2, wherein the data conversion circuit is a read-only memory. 4. A thermal head drive circuit for a video printer according to claim 1, characterized in that a latch is provided between the shift register and the thermal head. 5. In the thermal head drive circuit for a video printer as set forth in claim 3, data giving a pulse width close to the time required to start coloring is input as the first gradation data of the read-on memory. A thermal head drive circuit for a video printer characterized by: 6. A thermal head driving circuit for a video printer according to claim 1, wherein the shift register, the switch, and the thermal head are each divided into two parts. 7. A thermal head drive circuit for a video printer according to claim 1, which comprises: an energizing pulse width counter as energizing pulse generating means; an energizing pulse width decoder connected to the energizing pulse width counter; an image data counter; and the image data counter. 1. A thermal head drive circuit for a video printer, comprising an image data decoder connected to a data counter, and an AND circuit for outputting an AND of the energizing pulse width decoder and the image data decoder.