JPS63256464A - Thermal recorder - Google Patents

Abstract

PURPOSE:To enable stabilized recording density to be obtained even though high speed recording is carried out, by applying energizing pulses composed of repetition of unit pulse having a short width to a plurality of thermal resistors. CONSTITUTION:A recording control part 52 converts image data to memory data, i.e., binary numeral data corresponding to density of n bits per one picture element, and arranged as memory data of n lines per image data of one line each bit weight of this memory data to be stored in RAM 50. The recording control part 52 commands a pulse control part 53, and makes a pulse emission means 54 apply each number of unit pulses enough to generate density allocated to the weight of each one line data among n lines to corresponding ones of a plurality of heating resistors of a thermal head 51. Thereby, even though high speed recording is carried out by shortening the recording interval, recording density is stabilized. Further, when a frequency of repetition of unit pulses is set at a value capable of generating density in proportion to gradation, an intermediate tone faithful to an original picture can be realized.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a thermal recording device using thermal paper or sublimation ink, and particularly to a thermal recording device that can faithfully reproduce and record halftone levels. It is.

- [Prior Art] Fig. 9 is a block diagram showing the configuration of a conventional thermal recording device disclosed in, for example, Japanese Patent Publication No. 57-14315;
The figures are a signal waveform diagram and a block diagram of the halftone recording means used in the recording section of FIG. 9, and FIG. 11(a).

(b) shows a circuit diagram, a signal waveform diagram, and a first signal waveform diagram of the analog-to-digital conversion circuit used in the signal conversion section in Figure 9.
Figure 2 is an explanatory diagram for explaining conventional energization pulse control;
FIG. 13 is a density characteristic diagram obtained from the process shown in FIG. 12, where the horizontal axis is time and the vertical axis is density. FIG. 14 is a temperature change diagram during conventional high-speed recording, and FIG. 15 is a temperature change diagram during conventional low-speed recording. In Figure 9 (1
) is a signal converter into which the video signal is input, (2) is a recording unit connected to this signal converter (1), and (3) is a recorder for supplying voltage to this recording unit (2). This is the power supply section. In Figure 10, (10a), (10b)
, and (10c) are connection terminals connected to a readout circuit (not shown), respectively; Dt) and (12) are connected to connection terminals (10a) and (Job), respectively, and are shift registers (13a) to (13a) connected to
13h) is a data output terminal of the shift register (12), and (14) is a clock terminal of the shift register (12). In Fig. 11, (21), (22),
and (23) are comparators, respectively, and (25
) is directly connected to the comparator (21) and the inverter (
26) is an AND circuit connected to the comparator (22), and (24) is an OR circuit connected to the comparator (23) and the AND circuit (25).

A conventional thermal recording device is configured as described above, and a video signal is converted by a signal converter (1) to a speed and format suitable for recording and sent to a recording unit (2). In the recording section (2), the recording head (
Current is supplied from the recording power supply unit (3) to the heat generating element (not shown) on the heat generating element (not shown), and an image is recorded on thermal recording paper (not shown) that comes into contact with the heat generating element to obtain a hard copy. Next, the operation of the halftone recording means will be explained in detail.The operation of the halftone recording means will be explained in detail.
) is converted from analog to digital using the circuit shown in Figure 11.
Value signals (C) and (D) are read into shift registers (12) and (11), respectively, by clock pulses CB). The energizing time for one dot (3
During the period T), if the energization to each heat generating element is switched according to the data output signals (13a) to (13h) of the shift register (12), the first period (T) is performed according to the recorded contents of the shift register (12). Electricity is applied. (
When the period T) has elapsed, one clock pulse, for example (E), is input and the contents of the shift register (11) are written to the shift register (12). 11) Energization is performed according to the stored contents.

In addition, in order to convert the four-value gradation image signal (A) into the binary signals (C) and (D), as shown in FIGS. 11(a) and (b), the comparison reference voltage (Ll ).

(L2) and (L3) are connected to comparator (21), (
22) and (23) together with the image signal (A), and the output of the comparator (22) is a binary signal (D>).

Furthermore, the output obtained by inverting this binary signal (D) with the inverter (26) and the output (S> of the comparator (21)) are passed through the AND circuit (25).
By passing the output of 5) and the output (U) of the comparator (23) through the OR circuit (24), a binary signal (C) is generated.
I am getting . As a result, the pulse width of the energizing pulse (F) becomes proportional to the gradation, and halftone recording as shown in (G) can be obtained on the heat-sensitive recording paper.

[Problems to be Solved by the Invention] In the conventional thermal recording apparatus as described above, firstly, when the image pattern to be recorded is continuous, for example, the image pattern shown in FIG.
When the energization time for each line reaches (3T) as shown in a), the next recording pulse is input before the temperature has completely decreased to the level before the energization pulse was applied, as shown in (b) of the same figure, causing heat generation in the recording head. As the temperature of the element increases, the recording density differs depending on the number of lines from the beginning, and this phenomenon occurs when the recording period (PRD
There was a problem that the shorter the 2'), the more it would become a leap.

Second, when thermal paper or sublimation thermal transfer ink is heated with a recording head, the density-current-conducting time characteristic on the thermal paper is shown in Figure 12.If the zero-conducting time is shorter than the period (To), then If the thermal paper does not develop color or the ink does not transfer to the paper, recording becomes possible only after the period (To) has elapsed. This means that the minimum color development temperature of thermal paper or the melting point of sublimation thermal transfer ink is set at a temperature higher than room temperature, and the heating period (To) is required to raise the thermal paper or sublimation thermal transfer ink to this temperature. This is because it becomes necessary.

Therefore, as in the conventional example, the energizing pulse width is changed to (T) and (2T).
), the gradation level is 4 from O to 3.
When recording in gradation, the density characteristic becomes irregular as shown in Figure 13.
For T), it is not possible to obtain a density of (201), and the value becomes D2 (>201). Therefore, as shown in Figure 13, there is no density change between gradation levels 0 and 1. small, and there is a large change between level 1 and level 2,
There is a problem in that when an image is recorded with this density characteristic, in which the change becomes small between level 2 and level 3, the halftone reproduction will be different from the original image.

This invention was made to solve these problems, and it is possible to obtain a stable recording density even when recording at high speed by shortening the recording interval, and to thermally record with linear halftone density characteristics. The purpose is to obtain a thermal recording device.

[Means for Solving the Problems] In the thermal recording device according to the present invention, the recording control unit converts image data into storage data that is n bits per pixel and is binary data corresponding to the density. Then, for each bit weight of this stored data, n is calculated for one line of image data.
The recording control unit instructs the pulse control means to generate the density assigned to the weight for each line of data among the n lines. The heat generating resistor is energized with unit pulses of the same number as the number of unit pulses.

[Function] In the present invention, the recording control section causes the pulse generating means to send an energizing pulse consisting of repeating short unit pulses to the plurality of heat generating resistors by the pulse control means.
The current is applied in accordance with the number of unit pulses assigned to each weight of one line of stored data among the n lines stored in the memory.

[Example] Fig. 1 is a block diagram showing a schematic configuration of an embodiment of the thermal recording device of the present invention, Fig. 2 is a flow chart diagram explaining the operation of the thermal recording device of Fig. 1, and Fig. 3 is a block diagram showing the schematic configuration of an embodiment of the thermal recording device of the present invention. 4 is an explanatory diagram illustrating the energization pulse control of an embodiment of the present invention, and FIG. 5 is an explanatory diagram illustrating the principle of sublimation thermal transfer recording. It is a diagram. FIG. 6 is an explanatory diagram illustrating a method of setting unit pulses, where the horizontal axis represents the number of pulses and the vertical axis represents the density.

FIG. 7 is a density characteristic diagram obtained from the processing according to FIG. 6, where the horizontal and vertical axes indicate gradation level and density, respectively. FIG. 8 explains temperature changes during halftone recording according to the present invention. This is an explanatory diagram, and the horizontal axis of FIG. 8(b) is time, and the vertical axis is temperature.

In FIG. 1, (50) is a RAM for storing image data as recording data, (51) is a thermal head for printing the stored data stored in this RAM (50),
(52) is a recording control section for controlling the operation of the entire apparatus; (53) is a pulse control means;
), the pulse generating means (54) is controlled to generate an energizing pulse consisting of a unit pulse whose width is narrower than the energizing time of each heating resistor corresponding to one dot. In FIG. 3, (57) is a shift register (58) in which stored data for one line out of n lines stored in the RAM (50) is sequentially shifted by a clock.
) is sequentially shifted to the shift register (57) by the latch signal.
) is a latch circuit in which stored data is held; (55) is a switching circuit connected to this latch circuit (58);
(56) is a driver circuit connected to this switching circuit (55). Note that (R, , ) are a plurality of heating resistors connected to the collector terminals of individual transistors of this driver circuit (56), and one end of each is connected to a power source.

The thermal recording apparatus of the present invention is constructed as described above, and its operation will now be explained according to the flowchart of FIG. However, the image data per pixel is n bits (2
In the following explanation, it is assumed that the number of recorded gradations is 2n.

First, in step (SPI), image data for the first line of the original image is read. This is a binary image consisting of n bits per pixel, which corresponds to the density.
It is converted to memory data which is base number data, and each bit of this memory data is arranged for one line of each image data and summarized to make 0942 worth of data. ), RAI4 is used as data for 0942 minutes of step (SPI).
(4). In addition, in step (SF3), the number of lines (i) is initialized as (i←0). In step (SF3), one line of data (9) is stored for each bit of the stored data. It is transferred to the thermal head (51). In step (SF3), energizing pulses corresponding to each dot of the heating resistor (Rt) are sent to the thermal head (51), and recording is performed on the recording paper according to the number of unit pulses. In step (SF3), in order to send out the next line, (i + - i + 1) is set, step (5P6
In a), it is determined whether the stored data for all lines, that is, n lines, has been read, and if not, the process returns to step (S!"4) and the same process is repeated.
If it has been read, the process advances to step (5P7) to read the next line of the original image. Step (S
At F3), the recording paper is advanced by one line. In step (S!'7a), it is determined whether storage data for all lines of the original picture have been recorded. If so, the process ends. If not, return to step (SPI) and repeat the same process. 0 As above, transfer and energize one line of stored data for each bit, and repeat this process n times to transfer one line of the original image. Recording is completed and the recording paper is fed forward by one line.

Furthermore, similar operations are repeated for the number of lines of the original image, and recording of one image is completed.

Next, the internal operation of the thermal head (51) will be explained in detail with reference to FIG. One line of stored data of each bit is sent bit by bit to the shift register (57). At this time, the timing of data input is controlled by the clock. Then, when one line of memory data is stored in the shift register (57), the shift register (57) is transferred to the latch circuit (58) activated by the latch signal.
5)) The content of 0 is taken in and temporarily stored.Next, the stored data is set to 1 for the period when the energizing pulse is a high level signal, and the content of this high level signal and the stored data is 1.
The logical AND with the weight bit is the switching circuit (5
5), and when the ^ND condition is satisfied, the switching circuit (55) drives the corresponding transistor of the driver circuit (56). In this way, the corresponding one of the heating resistors (Rt, ) connected to the driven transistor generates heat. As a result, in the case of thermal paper recording, color is developed, and in the case of sublimation type thermal transfer recording, as shown in Figure 5, inksee) (6G)
is heated, and the sublimation ink applied to its surface is sublimated and transferred to the recording paper (61).

Next, the control process of the energization pulse will be explained. Figure 4 shows 1
FIG. 4 is an explanatory diagram of energization pulse control processing in the case of 3 bits per pixel (n=3). As explained above, in this case, the heating resistor (R) for each bit is energized three times. Each energization is performed by repeating narrow unit pulses instead of using a single wide pulse as in the conventional case. The number of repetitions of unit pulses is set so as to generate a density according to the weight of each digit. By combining energization corresponding to bits with a value of 1, it is possible to record in a range of 8 gradations from 0 to 7.
Each bit is energized by repeating unit pulses, and the method of setting the number of unit pulses is shown in FIG.

For simplicity, in Figure 6, which is explained using an example of 4-gradation recording with n = 2 bits, in order to make the maximum density be (301) in the linear region lower than the saturation region, the bit 0 The number of pulses is set to 4, which gives a density of (Dl), and the number of pulses for bit 1 is set to 6, which gives a density of (201). Under these conditions, four gradations can be recorded by combining two types of energization. As shown in FIG. 7, linear density characteristics can be obtained. In this way, the second conventional problem can be solved.

Next, a solution to the first problem will be described. In this invention, the concentration is controlled by repeating all narrow unit pulses without using any wide energization pulses.

Therefore, as shown in Fig. 8, in the heat generating resistor (R,,), heat storage ('r, period) and heat radiation (Torr period) are reversed, and large heat storage does not occur. Stable recording density can be obtained without providing a recording interval.

In addition, although the above embodiment shows the case of monochrome recording,
This invention can also be applied to color recording. In this case, the above embodiment may be applied to each of yellow, magenta, and cyan, for example.

[Effects of the Invention] As explained above, in the present invention, the recording control unit converts image data into storage data that is n bits per pixel and is binary data corresponding to density, and converts the storage data into storage data. n for one line of image data for each bit weight
The memory data for the life is compiled and stored in the RAM, and the recording control section instructs the pulse control means to generate the density assigned to the weight for each line of data among the n lines. Since the number of unit pulses corresponding to the number of heating resistors is energized to the corresponding number of heating resistors, a large amount of heat is not accumulated in each heating resistor, and temperature control is easy. Therefore, the recording interval can be shortened and high-speed recording can be achieved. By setting the number of unit pulse repetitions to a value that produces a density proportional to FJillJ, the density characteristics of halftones become linear, reproducing halftones that are faithful to the original image. It has the effect of being able to do it.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of the present invention, FIG. 2 is a flowchart explaining the operation of the device shown in FIG. 1, and FIG. 3 is an internal configuration of a thermal head used in the present invention. A circuit diagram showing. FIG. 4 is an explanatory diagram for explaining energization pulse control in an embodiment of the present invention, FIG. 5 is an explanatory diagram for explaining the principle of sublimation type thermal transfer recording, and FIG. 6 is an explanatory diagram for explaining the method of setting unit pulses. 7 is a density characteristic diagram obtained from the processing shown in FIG. 6, FIG. 8 is an explanatory diagram illustrating temperature changes during halftone recording according to the present invention, and FIG. 9 is a configuration of a conventional thermal recording device. FIG. 10 is a signal waveform diagram and block diagram of the halftone recording means used in the recording section of FIG. 9, and FIGS. A circuit diagram and a signal waveform diagram of the analog-to-digital conversion circuit used, FIG. 12 is an explanatory diagram for explaining conventional energization pulse control, FIG. 13 is a concentration characteristic diagram obtained from the processing in FIG. 12, FIG. 14 is a temperature change diagram during conventional high-speed recording, and FIG. 15 is a temperature change diagram during conventional low-speed recording. In the figure, (50) is a RAM, (51) is a thermal head, (R, , ) is a heating resistor, (52) is a recording control section, (53) is a pulse control means, (54) is a pulse generation means, (55) is a switching circuit, (56) is a driver circuit, (57) is a shift register, (58) is a latch circuit, (SO) is an ink sheet, and (61) is a recording paper. In each figure, the same reference numerals indicate the same or corresponding parts.萬 4 fig. 51 - Sun-maruhe・γ doro 0: Ishikut 61: R Feng Xiangshi 昂 6 fig.! Ajri 7 figure 1o figure [) (BA 14 figure 15 procedural amendment document October-9, 1986)

Claims (3)

[Claims] (1) A RAM that stores image data as storage data; A thermal head connected to this RAM and including a plurality of heat generating resistors placed side by side; This thermal head has the plurality of heat generating elements necessary for recording one dot. A thermosensitive recording comprising a pulse generating means for sending out a unit pulse having a pulse width narrower than the energization time of the resistor, a pulse controlling means for controlling the pulse generating means, and a recording control section connected to the pulse controlling means and the RAM. In the apparatus, the recording control unit converts the image data into the storage data which is n bits per pixel and is binary data according to the density, and converts the image data into the storage data which is binary data according to the density, and converts the image data into the storage data for each bit weight of the storage data. n for one line of the image data
The above-mentioned storage data for the line is collected, and this is
AM, the recording control section instructs the pulse control means to cause the pulse generation means to select one of the n lines.
A heat-sensitive recording device characterized in that a heating resistor is energized with a number of unit pulses sufficient to generate a density assigned to the weight for each line of stored data. (2) The thermal recording device according to claim 1, wherein the number of unit pulses is set so that the density corresponding to each bit weight becomes linear. (3) One pixel is composed of 3 bits, and the number of unit pulses for each weight of bit 0, bit 1, and bit 2 is set to 4, 6, and 8, respectively. Or the thermal recording device according to item 2.