JPH0435943B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal recording method in which main scanning is performed in a facsimile device or the like by heating heating elements arranged in a row in the main scanning direction by applying electricity in accordance with an image signal.

In this type of conventional thermal recording method, one scanning line (hereinafter simply referred to as a "line") is divided into a plurality of sections, and in each of these sections, all heating elements corresponding to black pixels are By energizing only once, batch printing was performed for each of the divided sections.

Therefore, regardless of the total number N of black pixels in one line, the time required to print one line is:
Since the time required to print one divided section is multiplied by the total number of divided sections, there was a drawback that high-speed printing could not be performed.

In addition, the power supply that supplies power to the heating elements must have enough capacity to simultaneously supply power to all the heating elements in one divided section, but in a typical manuscript, the ratio of black pixels present on one page is is on average 30
%, it also had the disadvantage of poor utilization of power supply capacity.

Furthermore, a method has been used that improves the conventional method and attempts to speed up printing by skipping the printing operation for all-white divided sections. If a black pixel exists, the above-mentioned skipping is not performed, which has the disadvantage that it can only slightly contribute to speeding up.

The present invention has been made in order to eliminate the above-mentioned conventional drawbacks, and an object of the present invention is to provide a heat-sensitive recording method that can improve the utilization efficiency of power supply capacity and speed up printing.

That is, the thermal recording method according to the present invention simultaneously prints the entire section of one line, and
Before printing a line, count the total number of black pixels in one line to be printed, compare this total number of black pixels with a predetermined number (the total number of heating elements divided by 3), and The gist is to determine the number of times the heating element is energized and the energization time based on the comparison results.

The present invention will be described in more detail below based on embodiments shown in the drawings.

1 and 3 show an embodiment of the present invention, and FIGS. 2 and 4 show timing charts thereof. In FIG. 1, A ₁ to _{A 3n} are 3 m heating elements of a thermal head arranged in a row in the main scanning direction.

In this example, as mentioned above, in a typical document, the ratio of black pixels in one page is 30%.
Therefore, the capacity of the power supply that supplies power to each heating element A ₁ to _{A 3n} is 1/3 of all pixels in one line,
In other words, the current application time is 1 for up to m heating elements.
The capacitance is set to be enough to simultaneously energize the printer for the time required to print at the required density with only one energization.

In this embodiment, regardless of the total number N of black pixels in one line, the heating elements A corresponding to all the black pixels in one line are simultaneously energized.

In this case, if N becomes larger than m, the capacity of the power supply will naturally become insufficient if the current supply time is left unchanged. Therefore, in this embodiment, N
In accordance with the value of , the number of times the heating element A corresponding to the black pixel is energized in one line of printing and the energization time of each of these energization times are changed as follows. That is, when () 0≦N≦m, one line of printing is performed by simultaneously energizing the heating elements A corresponding to one line of black pixels only once.

() When m+1≦N≦2m, one line is printed by simultaneously energizing the heating elements A corresponding to all the black pixels of one line twice.
However, the energization time for each time is shorter than in case (), and an appropriate length of energization suspension period is provided between each energization.

() When 2m+1≦N≦3m, one line is printed by simultaneously energizing the heating elements A corresponding to all the black pixels of one line three times. However, the time period for each energization is shorter than that in case (), and an appropriate length of energization suspension period is provided between each energization.

By doing as in () and () above, overload on the power supply can be prevented. Also, the above (), ()
In the case of , the required printing density cannot be obtained with one energization because the time for one energization is short, but by energizing the same heating element A multiple times on the same line, the final density The required print density can be obtained.

As mentioned above, in a typical document, the ratio of black pixels is about 30%, so in many lines, 0≦
N≦m, and in these sections, the entire section of one line can be printed all at once with only one energization, so the printing speed can be significantly increased.

Also, on the line m+1≦N≦3m,
Although energization is performed multiple times as in () and () above,
Rather than printing for each divided section as in the past,
The time required to print one line can be shortened.

Therefore, according to this method, the overall printing speed can be significantly increased.

Next, the circuit shown in FIG. 1 will be explained in more detail.

1 is an operation start signal input terminal, into which an operation start signal _S1 is input. Reference numeral 2 denotes an image signal period signal input terminal, into which an image signal period signal _S2 indicating the image signal period of one line is input.

3 is a clock input terminal that inputs synchronized clock b of image signal a, 4 is an image signal input terminal that inputs image signal a for each line, and 5 is a two-input OR gate that receives operation start signal S ₁ as one input. , 6 is a flip-flop which takes the output of the OR gate 5 as a set input and the image signal period signal _S3 as a reset input, and the Q output of this flip-flop 6 is outputted to the image signal request signal output terminal ₇ as an image signal request signal S2. be done. While this image signal request signal _S2 is at a high level (hereinafter, high level is abbreviated as H and low level is abbreviated as L), the image signal period input terminal 2, The image signal period signal S ₃ is input to the clock input terminal 3 and the image signal input terminal 4, respectively.
This is a signal requesting the supply of clock b and image signal a. Note that the image signal a is a black signal of H,
The white signal is set to L.

8 is a two-input AND gate to which the picture signal period signal _S3 and clock b are input; 9 is a two-input AND gate to which clock b and picture signal a are input. 10 is a black pixel counter, which counts the clock b input through the AND gate 9 only while the picture signal period signal _S3 is at H level, and when the signal _S3 becomes low level, it becomes 1 by going into a clear state.
Count the total number N of black pixels in the line.

Reference numeral 11 denotes a one-shot multivibrator (hereinafter abbreviated as OSM) which receives the image signal period signal _S3 as a trigger input, and outputs a trigger pulse _S4 when the image signal period signal _S3 falls. 12 is an egister, with the trigger pulse _S4 as the timing,
The count result of the number of black pixels in one line of the counter 10 is loaded. 13 is a decoder, which analyzes from the contents of the register 12 whether the total number N of black pixels in one line applies to the above (), (), or (), and selects the corresponding one of the three outputs. Only the output is set to H.

Specifically _, 14 is a print _control signal generation circuit having a circuit configuration as shown in FIG. When you complete
A next line picture signal request signal _S6 requesting the picture signal of the next line is output.

As will be explained in detail later, the print control signal _S5 includes the number of times the heating elements _A1 to _A3n corresponding to black pixels are energized when printing one line, the energization time of each time, and the number of times of energization of each time. This is a signal that controls the energization pause time between energization. Further, the next line image signal request signal _S6 becomes the other input of the OR gate 5.

15 is a serial input parallel output shift register, and clock b input through AND gate 8.
is used as a write clock, and one line of image signal a is input in series from the image signal input terminal 4. _B1 ～ _B3n
are the 3m outputs Q ₁ to _{Q 3n} of the shift register 15
It is a two-input AND gate that has one input as each input and a print control signal _S5 as the other input.

The outputs of the AND gates B ₁ to B _3n are respectively connected to the bases of transistors D ₁ to _{D 3n} whose emitters are grounded. One end of each of the heating elements A ₁ to _{A 3n} is a heating element power input terminal 1 connected to the power source.
6 in common, while the other end is connected to the transistor
Connected to the collectors of D ₁ to D _3n , respectively.

Next, the operation of the embodiment shown in FIG. 1 will be explained.

First, at the start of printing the first line, the operation start signal _S1 is input to the operation start signal input terminal 1.
Then, the fall of the operation start signal _S1 passes through the OR gate 5 and sets the flip-flop 6.

Therefore, the picture signal request signal _S2 becomes H, and the picture signal period signal for one line is sent from the picture signal source side circuit.
S ₃ , clock b and picture signal a are supplied to picture signal period signal input terminal 2, clock input terminal 3 and picture signal input terminal 4, respectively.

Then, when the image signal period signal _S3 becomes H, the flip-flop 6 is reset, and the image signal request signal _S2 becomes L. Therefore, the image signal a, etc. for two or more lines are continuously transmitted to the image signal. It is not supplied to the input terminal 4 or the like.

The clock b supplied to the clock input terminal 3 is input as a write clock to the shift register 15 via the AND gate 8 only while the image signal period signal _S3 is H.
An image signal a for one line inputted from the image signal input terminal 4 is written into.

On the other hand, the black pixel counter 10 counts the total number N of black pixels in one line as described above. The total number N of black pixels in one line obtained in this way is:
The signal is loaded from the counter 10 to the register 12 using the trigger pulse S ₄ outputted from the OSM 11 as a timing.

The decoder 13 selects the first one from the contents of the register 12.
The total number N of black pixels in the line is (), (),
Analyze which of the equations () applies, and set only the corresponding one of the three outputs to be H. Then, the print control signal generation circuit 14 ANDs the print control signal _S5 corresponding to the output of the decoder.
Output to gates B ₁ to B _3n . Then, from the shift register 15 of each AND gate B ₁ to _{B 3n}
The input of the output is the print control signal _S5
is open while the corresponding transistor is high.
Turn on D ₁ to D _3n . This allows the heating element A ₁ ~
The heating elements corresponding to the black pixels of A _3n are energized in the manner of (), (), or () above, depending on the value of the total number N of black pixels in the first line.

Further, the print control signal generation circuit 14 outputs the next line supply signal S ₆ after finishing sending out the print control signal S ₅ . And this falling edge of S ₆ is OR
The flip-flop 6 is set again via the gate 5. Therefore, the image signal request signal _S2 goes high again.
Therefore, the image signal a of the second line and the image signal period signal _S3 are supplied to the image signal input terminal 4 and the image signal period signal input terminal 2, respectively.

As a result, the same operation as in the case of the first line is performed, and the second line is printed. Further, the same operation is performed for the third line and the subsequent lines.

Next, a specific configuration of the print control signal generation circuit 14 shown in FIG. 1 will be explained with reference to FIG.

17 is a trigger pulse input terminal for inputting trigger pulse _S4 from OSM11, 18, 19, 20 are:
These are decoder output input terminals that input the three outputs of the decoder 13, and these input terminals 1
The outputs of the decoder 13 input to 8, 19, and 20 are H in the case of (), (), and (), respectively.
becomes. 21 is a two-input AND gate which inputs the trigger pulse S ₄ from the trigger pulse input terminal 17 to one input, and inputs one of the outputs of the decoder 3 from the decoder output input terminal 18 to the other input.
22 is an OSM whose trigger input is the output of the AND gate 21, and the time width during which the output S ₅ a becomes H.
_T1 determines the energization time in the case () above. 23 is an OSM which uses the output S ₅ a of the OSM 22 as a trigger input. 24 receives the trigger pulse S ₄ from the trigger pulse input terminal 17 to one input;
The other input is inputted with another one of the outputs of the decoder 13 from the decoder output input terminal 19.
The input AND gate 26 is a two-input OR gate that takes the output of the AND gate 24 as one input. 2
6 is an OSM that inputs the output of OR gate 25 as a trigger
The energization time in the above case () is determined by the time width T ₂ during which the output S ₅ b becomes H. Furthermore, T ₂
= T ₁ /2. 27 is an OSM whose trigger input is the output _S5b of OSM28, and this
The time width _T5 during which the output _S7 of the OSM 28 becomes H determines the energization pause time between each energization in the above case ().

28 is a flip-flop, and the output S ₅ b of OSM 26 is used as a set input. 29 is a counter, and when the flip-flop 28 is set,
In the operating state, the rising edge of the output S ₇ of the OSM 27 is counted, and when the same rising edge is counted twice, the signal S ₆ b, which should be the next line image signal request signal S ₆ in the case () above, is output. This S ₆ b becomes a reset input for the flip-flop 28. 30 is the Q output of flip-flop 28 and the output of OSM 27
It is a two-input AND gate with _S7 as input, and this
The output of the AND gate 30 becomes the other input of the OR gate 25.

31 is the trigger pulse input terminal 1 for one input.
It is a two-input AND gate which inputs the trigger pulse S ₄ from 7 and the remaining output of the decoder 13 from the decoder output input terminal 20 to the other input. 32
is 2 with the output of AND gate 31 as one input.
It is an input OR gate. 33 is an OSM that receives the output of the OR gate 32 as a trigger input, and its output S ₅ c
The energization time in the above case () is determined by the time width T ₂ in which the voltage becomes H. Note that T ₃ is set to T ₁ /3. 34 is an OSM which uses the output _S5c of OSM33 as a trigger input, and the length of the energization pause time between each energization in the above case () is determined by the time width during which the output _S8 of this OSM34 becomes H. be done. 3
5 is a flip-flop, and the output of OSM33
S ₅ c is set input. 36 is a counter;
When the flip-flop 35 is set, it becomes operational and counts the rising edge of the output _S8 of the OSM34.
When the same rising edge is counted three times, the signal S ₆ c which should become the next line image signal request signal S ₆ in the above case () is output. Further, this S ₆ c becomes a reset input for the flip-flop 35. A 2-input AND gate 37 receives the Q output of the flip-flop 35 and the output _S8 of the OSM 34, and the output of this AND gate 37 becomes the other input of the OR gate 32. 38 is the output S ₅ a of OSM22, OSM2
This is a 3-input OR gate that receives the output S ₅ b of OSM33 and the output S ₅ c of OSM33.
The output of 8 becomes the print control signal _S5 . 39 is
3 inputs with output S ₆ a of OSM 23, output S ₆ b of counter 29, and output S ₆ c of counter 36
This is an OR gate, and the output of this OR gate 39 becomes the next line image signal request signal _S6 .

Next, the print control signal generation circuit 14 shown in FIG.
Explain the operation. First, when N of the black pixels of the next line to be printed is 0≦N≦m, the one input to the decoder output input terminal 18 out of the three outputs of the decoder 13 is H as described above. Therefore, the trigger pulse S ₄ triggers the OSM 22 via the AND gate 21. Then, the output of the OSM 22 becomes H only for time _T1 . And this S ₅ a is
The print control signal _S5 is input via the OR gate 38 to one input of each AND gate _B1 to _B3n in FIG.

Therefore, in this case, all the heating elements corresponding to the black pixels among the heating elements A ₁ to _{A 3n} of one line are energized at the same time only once during the energization time T ₁ as described in () above, This completes printing of one line.

Also, at the fall of the output S ₅ a of OSM22, OSM
23 is triggered, the output S ₆ a of the same OSM23
becomes H during T ₄ after the fall of S ₅ a. Then, the next line image signal request signal S ₆ is outputted from the print control signal generation circuit 14 via this S ₆ aOR gate 39, and the next line image signal a is output as described above.
etc. are requested.

Furthermore, if the total number N of black pixels in one line to be printed next is m+1≦N≦2m, the one input to the decoder output input terminal 19 among the three outputs of the decoder 13 is H as described above. Become. Therefore, trigger pulse S ₄ is connected to AND gate 24 and OR
Trigger OSM 26 via gate 25.

Then, the output S ₅ b of this OSM 26 becomes H for a time T ₂ . As a result, flip-flop 28 is set. Also, the output of OSM26
₅ The OSM27 is triggered at the falling edge of b, and the OSM2
The output S ₇ of 7 becomes H for a time T ₅ after the fall of S ₅ b.

Then, this fall of S ₇ triggers the OSM 26 again via the AND gate 30 and the OR gate 25, so that the output S ₅ b of the OSM 26 becomes H again for the time T ₂ . In addition, OSM27 is also triggered again at the second falling edge of S ₅ b, and from then on the same
The output S ₇ of the OSM 27 also becomes H again for a time T ₅ .

On the other hand, the counter 29 is in the operating state from the time when the flip-flop 28 is set, and the OSM 2
Output S of 7 If you count the rising edge of ₇ twice, the output
Let S ₆ b be H for a certain period of time. This resets the flip-flop 28 and closes the AND gate 30, thereby closing the OSMs 26 and 27.
is not triggered more than three times.

By performing the above operations,
The output S ₆ b of OSM26 is H twice with an interval T ₅ .
This S ₅ b is input as the print control signal S ₅ to one input of the AND gates B ₁ to _{B 3n} via the OR gate 38. Therefore, this m+1≦
When N≦2m, all the heating elements A corresponding to the black pixels of one line are energized twice at the same time, as shown in () above, and one line of printing is performed by these two energizations. Here, the energization time of each energization is T ₂ =T ₁ /2, and the energization suspension period between each energization is T ₅ .

In addition, after the two energizations are completed, the output S ₆ b of the counter 29 becomes H as described above.
S ₆ b is output as the next line image signal request signal S ₆ via the OR gate 39, thereby requesting the supply of the image signal a, etc. of the next line.

Furthermore, if the total number N of black pixels in one line to be printed next is 2m+1≦N≦3m, the one input to the decoder output input terminal 22 out of the three outputs of the decoder 13 is H as described above. becomes. Therefore, the trigger pulse S ₄ is connected to the AND gate 31 and
Trigger OSM 33 via OR gate 32. Thereafter, the OSMs 33, 34, flip-flop 35, counter 36, etc.
By performing the same operation as in the case of ≦N≦2m, the output S ₅ c of the OSM 33 becomes H three times, and this S ₅ c becomes the print control signal via the OR gate 38.
It is input as _S5 to one input of AND gates _B1 to _B3n .

Therefore, in this case, all the heating elements A corresponding to the black pixels of one line are energized simultaneously three times as shown in () above, thereby printing one line. Here, the energization time of each time is set as time T ₃ =T ₁ /3, and the energization pause time between each time of energization is set as T ₆ .

Furthermore, after the three energizations are completed, the output S ₆ c of the counter 36 becomes H for a certain period of time, and this S ₆ c
It is outputted as the next line picture signal request signal _S6 via the OR gate 39, requesting the supply of the next line picture signal a, etc.

In addition, in any case of (), () or () above, after energization to heating element A is completed, S ₆ a, S ₇ or S ₈ becomes H for a certain period of time, and when these fall, When the flip-flop 6 is set, the image signal request signal _S2 becomes H for the first time, so by appropriately setting the periods in which _S6a , _S7 , and _S8 are H, it is possible to print a certain line. An appropriate heat dissipation period can be given to the heating elements A ₁ to A _3n between the end of printing and the printing of the next line.

In addition, in the above embodiment, T ₂ =T ₁ /2, T ₃ =
It is said that T ₁ /3, T ₄ = T ₅ = T ₆ , but T ₂ ≦
It is also possible to set T ₁ /2, T ₃ ≦T ₁ /3, T ₅ ≦T ₄ and T ₆ ≦T ₄ due to the accumulation effect of the residual temperature of the thermal head.

As is clear from the above explanation, the thermal recording method according to the present invention prints the entire section of one line at the same time, and before printing one line,
Count the total number of black pixels in one line to be printed, and combine this total number of black pixels with a predetermined number (the total number of heating elements is 3).
By comparing the number divided by It is possible to obtain the desired effect. In addition, since the present invention controls printing of one line at once, only one printing control signal _S5 is required to control printing of the entire one line, and for this purpose, an interface is used. It can be simplified.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment to which the thermal recording method according to the present invention is applied, FIG. 2 is a timing chart of the same, and FIG. 3 is a block diagram showing a specific configuration example of the print control signal generation circuit in the embodiment. figure,
Figure 4 is the same timing chart. 1...Operation start signal input terminal, 2...Picture signal period signal input terminal, 3...Clock input terminal, 4...
...Picture signal input terminal, 10...Black pixel counter, 1
1...OSM, 12...Register, 13...Decoder, 14...Print control signal generation circuit, 15...
Shift register, 16... heating element power input terminal,
17...Trigger pulse input terminal, 18-20...
Decoder output input terminal, 22, 23, 26, 27
...OSM, 29...Counter, 33, 34...
OSM, 36...Counter.

Claims (1)

[Claims] 1. In a thermal recording method in which recording is performed by simultaneously heating heating elements arranged in the scanning direction in one scanning line section in accordance with an image signal, black in one scanning line to be printed. Count the total number N of pixels, compare whether this total number N of black pixels is larger than a predetermined number m (the number obtained by dividing the total number of heating elements by 3), and (1) The comparison result is 0≦N≦ When m, the heating elements corresponding to all black pixels of one line are energized at the same time for T ₁ hour, (2) When m+1≦N≦2m, the heating elements corresponding to all black pixels of one line are energized simultaneously. (3) When 2m+ ₁ ≦N≦ _3m , the above T ₂ is applied to the heating elements corresponding to all black pixels in one line. A thermal recording method characterized by simultaneously applying electricity _three times for a time shorter than T3 hours.