JPH04166347A - Thermal recording system - Google Patents

Abstract

PURPOSE:To obtain a high-quality output image independent of the content of image input data by a method wherein a printing pulse width is controlled while the contents of the image input data in a main-scanning direction and a sub-scanning direction are simultaneously considered. CONSTITUTION:Image data are sequentially and serially transmitted to a shift register 2 from image input data DIN in synchronism with a clock signal CK. The data for predetermined number of pixels in the main-scanning direction are stored. When, for example, the three pixels from the beginning of the input out of five pixels stored in the shift register 2 are all black ones, a NAND gate 5 is tuned on, and a counter 6 is actuated. The counter 6 counts the blocks of continuous three black pixels in the main-scanning direction. In this manner, the blocks of continuous black pixels of the predetermined number in the main- scanning direction are counted. In accordance with the count number, the printing pulse width is changed under control in consideration of the contents of image data both in the sub-scanning direction and the main-scanning direction. Therefore, the pulse width is changed in accordance with the type of image data, a proper energy is applied to every printing dot, and a high-speed and high-quality printing is conducted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal recording system, and particularly to a technique for controlling printing energy during thermal recording in a printer device, a facsimile device, or the like.

[Prior art and problems to be solved by the invention]

In the conventional thermal recording method, the content of the image data to be printed (
In other words, recording is performed by changing the printing speed depending on the number of pixels. However, in this control mode that changes the printing speed according to the data content, high-speed printing (for example, 1
There is a problem in that it is not possible to realize (c/line).

For this reason, so-called "history control" is performed in which recording is controlled by keeping the printing speed constant. This history control involves accumulating image data for several lines before the current recording line in the sub-scanning direction (the feeding direction of thermal paper), and then, based on the contents, printing pulses for each print dot on the current recording line. This is a control form in which the printing energy is made variable by changing the width or printing voltage. Note that the line direction perpendicular to the sub-scanning direction is referred to as the "main-scanning direction."

In conventional history control, recording control is performed by focusing only on the previous few lines of image data (image data in the sub-scanning direction), and the image data in the line direction to be recorded (image data in the main scanning direction) is controlled. ), the following inconveniences arise.

For example, if there are many consecutive black pixels in the same recording line, the printing energy becomes excessive and image quality deterioration such as blurring or trailing occurs due to heat accumulation.In other words, if two or more consecutive black pixels When recording black pixels,
Even if you try to record each dot with the same printing energy as one black pixel, unlike recording only one black pixel, it will be affected by heat conduction from the heating elements of other consecutive black pixels, so it will not be possible to print properly. It is larger than the printing energy. As a result, there is a drawback that the above-mentioned image quality deterioration occurs.

The present invention was created in view of the problems in the prior art, and an object of the present invention is to provide a thermal recording method that enables high-speed and high-quality printing.

[Means for solving the problem] Image data can be divided into cases where there are few continuous black pixels in the main scanning direction, such as a vertical line in a line image, and cases where the image data is composed of lines of several dots, such as a character image. It is known that there are cases where there are many consecutive black pixels.

Therefore, in the present invention, we focus on this feature and the feature that different types of image data are rarely mixed in the same area, and count the number of consecutive black pixel blocks on a certain number of bases. Depending on the type of image data, the print pulse width is changed and controlled according to the count value.

Therefore, the thermal recording method of the present invention includes a circuit that responds to image input data and serially holds data for a predetermined number of pixels in the line direction (main scanning direction), and a circuit that serially holds data for predetermined pixels in the line direction (main scanning direction), and A circuit for detecting the presence or absence of consecutive black pixels and counting the number of blocks of a predetermined number of consecutive black pixels, and varying the printing pulse width in accordance with the count value of the number of blocks of black pixels, a control circuit that stops recording and printing when the count value reaches a predetermined value;
and a circuit that responds to the image input data, accumulates image data for several lines before the current recording line in the paper feeding direction (sub-scanning direction), and performs history control based on the accumulated image data. , the printing pulse width is changed based on the contents of both the image data in the paper feeding direction and the image data in the line direction to control printing energy during thermal recording.

[Effect]

According to the above-described configuration, the printing pulse width is changed in consideration of not only the image data in the sub-scanning direction but also the content of the image data in the main scanning direction, and print recording control is performed.

Therefore, if there is a lot of vertical line image data, the print pulse width can be kept unchanged, and if there is a lot of character image data, the print pulse width can be controlled to a small value. The width can be changed to give the right amount of energy to each printed dot. This enables high-speed, high-quality printing.

Note that other structural features and details of the operation of the present invention will be explained using the embodiments described below with reference to the accompanying drawings.

〔Example〕

FIG. 1 shows an example of the configuration of a printing pulse width control section applied to the thermal recording method of the present invention.

The printing pulse width control section of this embodiment is based on the image input data DI.
an AND gate 1 that responds to the output of N and a Nant gate 5 (described later); a shift register 2 that serially takes in image input data (output of the AND gate 1) one pixel at a time in response to a clock signal CK; A switch 3 is connected to each bit of a predetermined number (in this example, the first three pixels captured) in the register, and a switch 3 is inserted between each bit and a high potential power supply line VccO on the secondary side of the switch. a Nant gate 5 which responds to each bit signal (3 bits) on the secondary side of the switch 3 and the remaining bit signal (2 bits) in the shift register; A counter 6 receives an inverted output signal in response to a clock signal CK (counting operation) and clears the count contents in response to a clear signal CL; a load signal LD takes in the count value of the counter 6 as an initial value; clock signal CK
A counter 7 that performs a counting operation in response to I, an AND gate 8 that generates a clock signal CKI in response to a clock signal CK and a carry-out (overflow) signal CO from the counter 7, and a carry-out signal CO and a strobe. Strobe signal 5 for print recording in response to signal STB
and an AND gate 9 that generates TBo.

In this configuration, the image data is image input data DI
From N, the data is serially sent to the shift register 2 in response to the clock signal CK, and data for predetermined pixels (5 pixels in the illustrated example) in the main scanning direction is held in the shift register. It is assumed that when the held data is a black pixel, it exhibits an "r level," and when it is a white pixel, it exhibits a "0" level.

In this embodiment, among the data for five pixels held in the shift register 2, when all three input pixels become black pixels, the Nant gate 5 turns on (output "0" level). This causes the counter 6 to operate, and the count number of the counter 6 is added up with the next clock signal CK. As shown in FIG. 2, this counter 6 has three
Count the number of black pixels (number of blocks).

In this example, the case where the number of consecutive black pixels is three is explained, but this is determined by considering the recording density, the structure of the thermal head, the characteristics of the thermal paper, image receiving paper, donor film, etc. By appropriately modifying the configurations of the switch 3 and the resistor unit 4, it is possible to arbitrarily change the set value of the number of consecutive black pixels.

Also, when the Nant gate 5 turns on (output "0" level), the AND gate 1 closes, so the image input data DI
Regardless of the data content from N, a white pixel is automatically inserted into the shift register 2 at the timing of the clock signal CK. This turns off the Nantes gate 5 (output “1”
"level), and the operation of the counter 6 is prohibited again.

The above operations are performed until one line of image data is exhausted.

The counter 7 sets the count value (the number of consecutive black pixel blocks) of the counter 6 as an initial value by the load signal LD, and after loading the number of black pixel blocks into the counter 7, the counter 6 receives a clear signal Clear the contents using CL.

The carry-out signal CO of the counter 7 changes its output timing according to the above-mentioned initial value, and the AND gate 9
Close and turn off the strobe signal 5TBO for print recording (
The timing of the “0” level) is made variable.

FIG. 3 shows the operation timing of each signal in the printing pulse width control section described above.

Next, the configuration and operation of the history control section 10 in FIG. 1 will be explained with reference to FIGS. 4 to 6.

First, referring to FIG. 4, the history control section of this embodiment includes a shift register 20 that serially takes in image input data DIN one pixel at a time in response to a clock signal CK;
A plurality of stages each latches parallel data from a previous stage circuit (shift register or latch circuit) in response to a load signal LD, and sequentially sends the latched data to the next stage circuit (latch circuit or gate circuit).・Sochi circuit 21m~21. and corresponding launch circuits 21. and 21. in response to gate signals G1 to Gm. A gate circuit 22 that selectively outputs parallel data of ~21 m, a driver circuit 23 that outputs data from the gate circuit 22 as a print recording signal PS in response to a strobe signal 5TBO (“H” level), and the driver. The heating element array 24 (heating elements 251 to 25n) is driven by a circuit.

In this configuration, first, the image data to be recorded is
The image input data DIN is sent to the shift register 20 as serial data by the clock signal CK.

Next, the parallel data from the shift register 20 is latched by the load signal LD into the first-stage fake circuit 2bn, and at the same time, each launch circuit sequentially sends the data to the next-stage circuit. Note that the number of stages m of the Usochi circuit is the number of stages for controlling based on the history of (m-1) lines before the current line in the sub-scanning direction, and the first stage launch circuit 21m contains the image data to be printed. is stored, and the image data that has just been printed is stored in the latch circuits of the other stages for use in history control.

FIG. 5 shows an example of the configuration of the gate circuit 22 when the latch circuit has three stages.

The illustrated gate circuit is a latch circuit 21. an inverter 31a each responsive to each bit of parallel data from
1 to 31an and inverters 31b1 to 31b1 to respond to each bit of parallel data from the latch circuit 21□, respectively.
31bn, gate signal G, and inverter 31a,
AND gate 3 that responds to each output of ~31an, respectively.
2a1 to 32an, gate signal G2 and inverter 31
AND gates 32b + ~32bn that respond to each output of b and ~31bn, and gate signals G3 and AND gates -1-52ai and 32bi (i = 1 to n)
ORGATE 33. ~33n and latch circuit 2
Each bit of parallel data from 13 and OR gate 33
．． AND gate 3 that responds to each output of ~33n
4. ~34n.

In this configuration, the image data of the latch circuits 211 and 21□ (image data of the line before the current line) is inputted to the AND gates 32a+ to 32an, 31b to 31bn together with the corresponding gate signals C, C2, respectively. . Here, the image signal of the previous line is black pixel (“1”)
level), each inverter inputs the input with its polarity reversed, so each AND gate closes and outputs “
0" level), the pre-print pulse signals (gate signals C, , Ta and Tb of C2 in FIG. 6(a)) are not output in consideration of heat accumulation. Conversely, the image signal of the previous line “0
” level), each AND gate is open (output “
1” level) and output pre-print pulse signals, respectively.

These Noahrad gates 32a+ to 32an, 31b,
The pre-print pulse output from ~31bn and the main print pulse by gate signal G3 (Tm of gate signal G3 in FIG. 6(a)) are logically added at each OR gate 331-33n to form a print recording signal. do.

In this case, each AND gate 341 to 34n is connected to the corresponding OR gate 34 only when the pixel to be printed is a black pixel.
The print recording signals outputted from 1 to 33n are outputted to the driver circuit 23 for each corresponding dot.

The driver circuit 23 turns on the strobe signal 5TBo (“
During the period (H" level), each heating element 251 to
25n are respectively energized and printed.

FIG. 7 shows the operation timing of each signal in the print pulse width control section of FIG. 1 and the operation timing of each signal in the history control section of FIG. 4.

The print recording signal ps shown in the figure is created by a print pulse signal consisting of the logical sum of gate signals G and -Cm controlled by the history control in the sub-scanning direction, and print pulse width control in the main-scanning direction. It consists of the AND of the strobe signals 5TBo. Here, the pre-print pulse part of the print recording signal ps consists of a combination of gate signals G1 to G, -1 depending on the data content in the sub-scanning direction, but the gate signal G- of the main print pulse part is in the sub-scanning direction. The pulse width can be changed only by main scanning direction control without being affected by history control. In other words, it is possible to simultaneously perform history control in the sub-scanning direction and print pulse width control in the main scanning direction.

In this way, in this embodiment, the number of blocks of a predetermined number of consecutive black pixels in the main scanning direction is counted, and according to the counted number, the blocks in the main scanning direction are stored together with the image data in the sub scanning direction during thermal recording. The print pulse width is controlled by taking into consideration the content of the image data. For example, the printing speed is l m5
In the case of dividing into four by ec/line, the main printing pulse width is changed and set to 0.125m5ec to 0.075IIsec.

Therefore, the pulse width is changed depending on the type of image data,
Appropriate energy can be applied to each printed dot. As a result, it becomes possible to print at high speed and with high quality.

In addition, in order to improve the accuracy of image data and the position (main scanning direction) where printing energy corresponding to the image data is applied, if the above-mentioned printing pulse width control section is assigned to each division part of the thermal recording with multi-division input, It will be obvious to those skilled in the art that line images and character images can be more precisely separated.

〔Effect of the invention〕

As explained above, according to the present invention, by controlling the printing pulse width while simultaneously considering the contents of image input data in the main scanning direction and the sub-scanning direction, high-quality output can be achieved regardless of the contents of the image input data. You can get the image. Furthermore, since it has the advantage of being less susceptible to heat accumulation than the conventional history control method, high-speed, high-quality printing can be performed, which is extremely effective.

[Brief explanation of the drawing]

1 is a circuit diagram showing an example of the configuration of a printing pulse width control section applied to the thermal recording method of the present invention; FIG. 2 is a diagram for explaining the action of the counter 6 in FIG. 1; The figure is an operation timing diagram of the printing pulse width control section in FIG. 1. FIG. 4 is a block diagram showing the configuration of the history control section in FIG. 1. FIG. 5 shows an example of the configuration of the gate circuit in FIG. 4. The circuit diagram, Fig. 6 axis) and (b) are the operation timing diagram of the circuit in Fig. 5, and Fig. 7 is the operation timing diagram of the printing pulse width control section of Fig. 1 and the history control section of Fig. 4. . (Explanation of symbols) 1...AND gate, 2...Shift register, 3...
...Switch, 4...Resistance unit, 5...Nant gate, 6.7...Counter, 8.9...And gate, 10...History control section, 20...Shift register, 21,~21m+...Latch circuit, 22...Gate circuit, 23...Driver circuit, 24...Heating element array, 251~25n-Heating element, 31a+, 31b+
~31an, 31bn - inverter, 32a+, 32
b+~32an, 32bn -and gate, 33. ~
33n...Orgate, 34. ~34n...AND gate, DIN...image input data, CK...clock signal, LD...load signal, CL...clear signal, STB, 5TBo- strobe signal, G+ ~G
II-gate signal, ps...Print recording signal.

Claims (1)

[Claims] 1. A circuit (2) that responds to image input data (D_I_N) and serially holds data for a predetermined number of pixels in the line direction.
), and a black pixel detection circuit (3 to 6) that detects the presence or absence of continuous black pixels in the line direction based on the held image data and counts the number of blocks of a predetermined number of continuous black pixels.
and a control circuit (7 to 9) that varies the printing pulse width according to the count value of the number of blocks of black pixels and stops recording printing when the count value reaches a predetermined value. a circuit (10) that responds to input data, accumulates image data for several lines before the current recording line in the paper feed direction, and performs history control based on the accumulated image data; 1. A thermal recording method, characterized in that printing energy during thermal recording is controlled by changing a printing pulse width based on the contents of both the image data in the direction and the image data in the line direction. 2. The thermal recording method according to claim 1, wherein the black pixel detection circuit includes means (3, 4, Vcc) for making it possible to change the setting of the number of consecutive black pixels.