JPH02121467A - Image recording method using a thermal head - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image recording method using a thermal head that performs intermittent recording.

[Prior Art] For example, in a facsimile machine, a recording device that records and outputs received images uses thermal recording paper as the recording paper, and the recording head applies thermal energy to the thermal recording paper to print images line by line. A thermal recording type recording apparatus using a thermal head device for recording is used.

This thermal recording type recording device has a very small number of device elements, is maintenance-free, and can be configured at low cost, so it is widely used in facsimile machines ranging from popular machines to high-end machines.

[Problems to be Solved by the Invention] However, such a thermal recording type recording apparatus has the following disadvantages.

That is, since the image information transmitted by a facsimile machine is run-length encoded on a line-by-line basis with both signals of one element, the amount of image information for one line is .

It varies greatly depending on the content of the original image signal.

Furthermore, since the facsimile device sets the modem speed used for image information transmission according to the line status at the time of transmission, the time interval at which the receiving device obtains one line of image information varies greatly.

Now, the time required for the receiving device to generate an image signal for one line is the time required to receive the image information for one line and the time required to decode the encoded and compressed image information for one line into the original image signal. It is the sum of the time required to do this.

As mentioned above, the reception time of image information and the time required for decoding processing depend on the amount of image information for each line. The time required for this is not constant.

Furthermore, since the amount of information of the image signal for one line generated by the receiving device is constant, the time required for recording the image signal for one line by the recording device is constant.

In this way, while the recording device's one-line recording time is constant, the time interval at which the image signals to be recorded are aligned is not constant, so the time interval at which the image signals are aligned is longer than the recording device's one-line recording time. If this occurs, it is necessary to temporarily stop recording on the recording device.

Therefore, image recording by the recording device is not necessarily performed continuously, but may be performed intermittently.

In this way, when the intermittent recording state is entered, after recording the image signal for one line, the conveyance of the recording paper and the recording operation are stopped until both signals of the next line are manually input, and then,
When the input of the image signal for the next line is completed, conveyance of the recording paper is started again, and the image signal for that one line is recorded.

Therefore, the thermal head that records an image on thermal recording paper will
The temperature drops significantly as most of the accumulated heat is released.

On the other hand, when recording images continuously, 154
Since the time interval between recording the image signal for two minutes and recording the image signal for the next line is very short, both signals for one line are recorded before recording the image signal for the next line. The temperature drop in the thermal head during this period is significantly smaller than in the case of intermittent recording.

By the way, in a thermal recording device, the interval between lines for image recording and the drive pulse width applied to the thermal head are set according to the case of continuous recording, which has the highest recording speed. When recording the first line again, the temperature of the thermal head does not become high enough, as shown in FIG. 10(a).

Note that FIG. 2B shows the driving pulses applied to the thermal head.

Therefore, during intermittent recording, in the first line after resuming recording, the amount of heat applied from the thermal head to the thermal recording paper is not large enough to cause the thermal recording paper to develop sufficient color.
As a result, the heat-sensitive recording paper develops color in a portion smaller than the line spacing, resulting in a disadvantage that the recording density of the line decreases.

For example, if the image information transmission speed is set to a small value and therefore intermittent operation is performed on each line,
The recorded density of the entire image is very small (and as a result,
This causes the inconvenience that the recorded image is partially blurred and difficult to see.

In addition, when intermittent operations are performed at a relatively high frequency,
Since the image density in the intermittent operation portion is lower than that in other portions, there arises a disadvantage that density unevenness occurs in the recorded image.

In order to eliminate this inconvenience, for example, a page memory for storing one page's worth of received image signals is provided, and both received signals are temporarily stored in this page memory and recorded in the recording device. Although it is conceivable to synchronously read out the image signals from the page memory and provide them to the recording device, in that case, the cost of the facsimile device increases by the cost of the page memory, which is not preferable.

An object of the present invention is to provide an image recording method using a thermal head that can solve the problems of the conventional apparatus and improve the image quality.

[Means for Solving the Problems] The present invention records the image of the first line to be recorded multiple times until the recording paper is moved in the transport direction by the first line after restarting image recording. This is how it was done. Further, the pulse width when recording multiple times is set according to the heat generation rise characteristics of the thermal head.

[Function] Therefore, during intermittent recording, the first line after resuming recording, which generates less heat, is recorded multiple times, so a sufficient amount of heat is supplied to the thermal recording paper, and as a result, the line has the same density as other lines. An image is recorded, and density reduction and density unevenness can be prevented.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a facsimile machine according to an embodiment of the present invention.

In the figure, a control unit 1 performs control processing of each part of the facsimile machine and facsimile transmission control procedure processing, and a system memory 2 stores control processing programs and processing programs executed by the control unit 1. It stores various data needed when executing.

The scanner 3 is for reading an original image at a predetermined resolution, and the plotter 4 is for recording and outputting an image at a predetermined resolution, and is a thermal recording type recording device. Further, the line buffer 5 stores image signals recorded by the plotter 4 for a plurality of lines. Moreover, this line buffer 5 is a FIFO (First
It is controlled as an In First Out) type memory.

The operation display section 6 includes various operation keys and various displays for operating the facsimile machine.

The encoding/decoding unit 7 encodes and compresses the image signal, and also decodes the encoded and compressed image information into the original image signal. This is for storing a large amount of image information in a different state.

The modem 9 performs modulation and demodulation processing in order to transmit digital data using the public telephone line network, which is an analog line, and the network control device 10 is used to connect this facsimile device to the public telephone line network. be. Additionally, this network control bag @10 is equipped with an automatic call/receive function.

These control unit 1, system memory 2. scanner 3,
The plotter 4, line buffer 5, operation display section 6, encoding/decoding section 7, image storage device 8, modem 9, and network control device 10 are connected to the system bus 11, and the Data exchange is performed via this system bus 12.

FIG. 2 shows an example of the configuration of the plotter 4. As shown in FIG.

This plotter 4 includes a thermal head device 21 that constitutes a recording head for recording an image line by line on thermal recording paper (not shown), a step motor 22 that constitutes a drive source of a conveying device that conveys the thermal recording paper, step motor 22
A motor opening circuit 23 for driving the plotter 4, a recording control section 24 for controlling the operation of the plotter 4, and a pulse signal PA serving as a reference for operation timing in the recording control section 24.
It consists of a timer circuit 25 that provides PB and PC.

In the thermal head device 22, the shift register 21
a stores the recording data SD for one line transferred from the line buffer 5, and the latch circuit 2
1b is a latch signal S that outputs the recording data SD stored in the shift register 21a from the recording control unit 24.
When the strobe signal (print pulse signal) SB is output from the recording control section 24, the driver 21c causes the heating resistor array 21d to store the data at the rising timing of L, according to the stored data of the latch circuit 21b. The heating resistor array 21d supplies a driving current, and generates heat when the driving current is supplied, thereby coloring the thermal recording paper.

Further, the thermistor 21e is for detecting the temperature of the 1 heating resistor array 21d, and its temperature detection subtitle T
S is output to the recording control section 24.

Pulse signals PA and PB output from the timer circuit 25.

As shown in FIGS. 3(a) to 3(C), PC is a pulse signal whose output timings are shifted from each other by a cycle TA of the l-line recording interval time.

Here, the pulse signal PA sets the start timing of data transfer from the line buffer 5 to the shift register 21a, and the pulse signal PB sets the output start timing of the strobe signal SB. The PC sets the timing for driving the step motor 22 one step.

The time interval TB from when the pulse signal PC is output to when the pulse signal PB is output is equal to the step pulse signal SP.
The setting corresponds to the time delay from when is output to when the thermal recording paper conveyance system starts conveying the thermal recording paper.

Further, the timing of the pulse signal P8 is set at an appropriate timing after the transfer of one line of recording data SD to the shift register 21a is completed until the transfer of the next line of recording data SD starts. There is.

Further, when the step pulse signal SP is output from the recording control section 24, the motor opening circuit 23 starts the step motor 2.
2 by one step.

The recording control unit 24 receives the pulse signal PA from the timer circuit 25.
When is output, other processes being executed at that time are temporarily interrupted and the process shown in FIG. 4 is executed.

That is, the recording data S is stored in the line buffer 5 at that time.
It is checked whether D is not stored and is in an empty state (determination 101).

When the result of judgment 101 is NO, it is checked whether a pause flag FD, which indicates that image recording should be paused, is set (judgment 102).

When the result of judgment 102 is NO, it means that continuous recording is being performed, so one line of recording data SD is read out from the storage area of line buffer 5 indicated by the read pointer and transferred to shift register 21a (process 103).
, when the transfer is completed, outputs a latch signal SL to store the transferred recorded data SD in the latch circuit 21b, and sets a latch flag FL to indicate that the recorded data So is recorded in the latch circuit 21b. (Process 104).

Then, the continuation pointer indicating the read position of the line buffer 5 is advanced by one (process 105), and the process returns to the original process that was interrupted.

When the result of judgment 102 becomes YES, intermittent recording is being performed, and the data of the first line after restarting recording is to be recorded for the first time, so one line is saved from the storage area of the line buffer 5 indicated by the continuous pointer. Process 106) to read the recorded data SD and transfer it to the shift register 21a, and when the transfer is completed, output the latch signal SL and transfer the transferred recorded data SD to the latch circuit 21.
The latch flag F indicates that the recording data SD is recorded in the latch circuit 21b.
At this time, the read pointer is not advanced and the original process that was interrupted is returned to.

As a result, when the pulse signal PA is generated next time, the recording data SD of the same line is read out from the line buffer 5 and set in the latch circuit 21b.

If the result of the judgment 101 is YES, the suspension flag FD is set in the process 108), and this process is immediately ended and the original process that was interrupted is returned to.

Further, when the pulse signal PB is output from the timer circuit 25, the recording control section 24 temporarily suspends other processes being executed at that time and executes the process shown in FIG. 5.

First, it is checked whether the latch flag F is set (decision 201), and when the result of determination 201 is YES, it is checked whether the pause flag FD is set (decision 202).

When the result of the judgment 202 is NO, it means that image recording is to be performed continuously and the recording data SD is stored in the latch circuit 21b, so strobe signal output processing for outputting the strobe signal S8 is started. 203), this process ends and returns to the original process that was interrupted.

When the result of the judgment 202 is YES, it means that intermittent recording is being performed and the image of the first line is to be recorded to restart the image recording, so the process 204) starts the restart strobe signal output process and resets the pause flag FD. (process 205), this process is ended, and the original process that was interrupted is returned to.

When the result of judgment 201 is NO, latch circuit 2
Since the recording data SD is not stored in 1b, this process is immediately terminated and the original process that was interrupted is returned to.

Note that the strobe signal output processing is as follows.

That is, the amount of heat storage in the heating resistor array 21d is determined based on the temperature detection signal TS output from the thermistor 21e, and the well-known heat storage control process is performed based on the determination result and a preset reference pulse width. Then, the pulse width of the strobe signal SB is determined. and,
When the calculation of the pulse width is completed, the strobe signal SB is raised and this state is maintained for the period of the calculated pulse width.

Further, the restart strobe signal output processing is the same as the strobe signal output processing described above, except that the reference pulse width of the strobe signal SB is set to a value corresponding to the heat generation rise characteristic of the thermal radar device 21. The reference pulse width in that case is basically set to a smaller value in the case of a thermal head device 21 with good heat generation rise characteristics, but in reality it is determined through experiments.

Further, when the pulse signal PC is output from the timer circuit 25, the recording control unit 24 temporarily suspends other processes being executed at that time and executes the process shown in FIG. 6.

First, it is checked whether the latch flag FL is set (decision 301), and when the result of determination 301 is YES, it is checked whether the pause flag FD is reset (decision 302).

When the result of judgment 302 is YES, either image recording is being performed continuously, or in the case of intermittent recording, this is the second recording of the first line after restarting recording, so one step pulse signal SP is output. The step motor 22 is driven one step to convey the thermal recording paper at one line interval (
Process 303), the latch flag FL is reset (process 304), this process is ended, and the process returns to the original process that was interrupted.

When the result of the judgment 301 is NO, the latch circuit 21
Since the recording data SD is not recorded in b, the process returns immediately to the original process that was interrupted.Also, when the result of judgment 302 is NO, in the case of intermittent recording, the first line 1 after resuming recording Since it is the time of recording the first time, process 304
to move to.

With the above configuration, the operation when one or more lines of recording data SD are stored in the line buffer 5 and continuous recording is performed will be described.

That is, first, when the pulse signal PA is output (the third
(see figure (a)), the recording control unit 24 has a line buffer 5
Check the status of F, and if it is not empty, then set the pause flag F
Check whether or not D is set, and if it is not set, read one line of recording data SD from the line buffer 5 and sequentially transfer it to the shift register 21a of the thermal head device 21. , when the transfer is completed, outputs the latch signal SL (as shown in the figure (
(see e)), one line of recording data SD transferred to the shift register 21a is stored in the latch circuit 21b.

Further, the read pointer indicating the data read area from the line buffer 5 is advanced by one, and the setting is made so that the recording data SD of the next line will be read out in the next processing cycle.

On the other hand, when the pulse signal pc is output during the transfer of the recording data SD (see (c) in the same figure), the transfer process is temporarily interrupted and the states of the latch flag FL and the pause flag FD are checked (see (h) in the same figure). , see (i)).

At this time, in the process of the previous line, the latch circuit 21a
, the recording data SD is stored, the latch flag FL is set, and the pause flag FD is reset, the recording control unit 24 outputs the step pulse signal S.
Output one P (see (g) in the same figure).

The step motor 22 is operated one step and the latch flag FL is reset.

When the output of the step pulse signal SP is finished, the transfer process of the recording data SO is continued.

Then, when the pulse signal PR is output (see (b) in the same figure), the recording control section 24 checks the states of the latch flag FL and the pause flag FL.

At this point, the latch flag FL is set,
Furthermore, since the pause flag FD has been reset, the recording control unit 24 starts strobe signal output processing and outputs a strobe signal S8 with a pulse width PW corresponding to the temperature of the heating resistor array 21d at that time. Start.

As a result, the heating resistor array 21d generates heat according to the contents of the recording data SD stored in the latch circuit 21b, and thereby one line of heat is generated according to the contents of the recording data SD stored in the latch circuit 21b. A recorded image is recorded on thermal recording paper.

Thereafter, the same process is repeated to record an image line by line on the thermal recording paper.

Next, the operation when performing one intermittent recording will be explained.

Assume that processing of the last line of recording data SD stored in the line buffer 5 is started in the same manner as described above by the pulse signal PA output at time T1.

At this time, when the transfer of the recording data SD to the shift register 21a is completed and the last line of recording data SD is latched by the latch circuit 21b, the latch flag FL is set.

Further, when the pulse signal PC is output immediately after time TI, the latch flag FL is set, and.

Since the pause flag FD has been reset, the step pulse signal SP is output and the thermal recording paper is fed to the last line.

When the pulse signal P8 is output immediately thereafter, the latch flag FL is set and the pause flag FD is reset, so the strobe signal SB for recording the last line is output.

Next, when the pulse signal PA is output at time T2 following time T1, the line buffer 5 is in an empty state, so the pause flag FD is set.

Furthermore, the latch flag FL is not set in this processing cycle.

Then, when the pulse signal PC is output immediately after time T2, the pause flag FD is set, so the recording control unit 24 does not output the step pulse SP.
Reset the latch flag FL.

Therefore, when the pulse signal PB is output after that, the pause flag FD is set and the latch flag FL is reset, so the strobe signal S8
is not output.

In this way, the last recording data SD of the line buffer 5
When the recording is completed, the thermal head device 21 does not record data, and the step motor 22 does not transport the thermal recording paper.

Then, at time T3, when one or more lines of recording data SD are stored in the line buffer 5, the recording control unit 24
Immediately after that, at time T4 when the pulse signal PA is output, data accumulation in the line buffer 5 is detected, and data transfer to the shift register 21a of the first line of the accumulated recording data SD is started. When the data transfer is completed, a latch signal SL is output to cause the transferred recording data SD to be stored in the latch circuit 21b.

Also, at this time, since the pause flag FD is set, the read pointer is not advanced, and the same recorded data 5D (81) is set to be read out in the next processing cycle.

At the time when the pulse signal PC is output during the transfer of the recording data SD, the latch flag FL is reset and the pause flag FD is set, so the step pulse signal SP is not output.

After time T4, when the first recording data SD (#1) is stored in the latch circuit 21b and the latch flag FL is set, immediately after the setting, when the pulse signal PB is generated, the recording control unit 24 detects a state in which the latch flag FL is set and the pause flag FD is reset.

Thereby, the recording control unit 24 starts the restart strobe signal output process and resets the pause flag FD.

As a result, a strobe signal SB having a maximum pulse l1lPva smaller than the maximum pulse width Pw of the strobe signal SB during continuous recording is output.

When the pulse signal PA is output after time T4, the pause flag FD has been reset at this time.

The recording control unit 24 performs the same processing as in the case of continuous recording.

That is, in this case, the same recorded data 5o(si) as previously transferred is transferred to the shift register 21a, the latch signal SL is outputted, and the transferred recorded data SD(
#1) is stored in the latch f1921b, the read pointer is advanced by one, and the next recording data SD (#2) is set to be read out in the next processing cycle.

Therefore, from then on, the next recording data SD is sequentially read out, transferred to the shift register 21a, stored in the latch circuit 21b, and an image is recorded line by line on the thermal recording paper by the heating resistor array 21d. .

In this way, during intermittent recording, when recording is restarted after stopping the recording operation, the first two recording operations
The recording data SD of the same line is recorded.

Therefore, the heating resistor array 21d of the thermal head device 21, which has cooled down after the recording operation has stopped, records the data of the first line twice when recording is resumed.

By the way, as shown in FIGS. 8(a)-(C), when recording is resumed and the first step pulse signal SP is applied, the thermal sensor, which had completely stopped due to mechanical play, etc. There is a slight time delay before the recording paper conveyance system starts conveying the thermal recording paper, and when the second and subsequent step pulse signals SP are applied, the conveyance system conveys the thermal recording paper accordingly. .

In this case, recording is stopped again after recording four lines of images, but the thermal recording paper hardly moves with the first step pulse signal SP, and with the second and subsequent step pulse signals SP. , move one line at a time.

In FIG. 8(a), the ideal movement mode of the thermal recording paper is shown by a broken line, and the actual movement mode is shown by a solid line. Also, the symbols PI, P2. P3. P4 shows the time course of image recording for the 1st, 2nd, 3.4th lines, respectively.

Further, during continuous recording, the output timing of the strobe signal SB is set in synchronization with the timing when the thermal recording paper that has been moved after outputting the step pulse signal SP reaches the next line.

Therefore, after outputting the first two step pulse signals SP, recording is resumed and the second strobe signal S8 is output.
At the timing of outputting, the recording position on the thermal recording paper is
Move approximately one line from the initial stop position.

On the other hand, as described above, the recording control unit 24 uses the same recording data SD as that for the first line as the recording data SD for the second line immediately after resuming recording.

Therefore, while the thermal recording paper moves a distance of one line, the thermal head device 21 records the same recording data SD twice.
recorded.

In addition, as shown in FIGS. 9(a) and 9(b), when recording data SD of the first line after restarting recording for the first time, the heating resistor array 21d of the thermal head device 21
The temperature of the heat generating resistor array 21d (head temperature) does not rise much because the heat generating resistor array 21d has completely cooled down, but when recording the same recording data SD for the second time, the heat generating resistor array 21d generates heat again before it is completely cooled down. Therefore, at this time, the head temperature rises to about the same temperature as during continuous recording.

Therefore, the recorded data SD of the l-th line that has resumed recording
When recording for the first time, the thermal recording paper is mostly not moving, so in this case, the thermal head device 21
Although the temperature does not rise sufficiently, the amount of heat supplied per unit area becomes large enough to color the thermal recording paper.

The required concentration can be obtained.

Furthermore, when the recording data SD of the 1st line is recorded for the second time, the same amount of heat as in the case of continuous recording is supplied, so that the heat-sensitive recording paper is sufficiently colored and the necessary density can be obtained.

Since the recording position of the first recording and the recording position of the second recording of the recording data SD of the first line are consecutive, the image of the 1st line, which has restarted recording, has a sufficient density over a period of 1912 minutes, and the image of the previous line The connection with the image also improves.

Therefore, during intermittent recording, when recording is restarted, the recording density of the first line will be about the same as the recording density of other lines, which can suppress the decrease in image density during intermittent recording. The image quality will be significantly improved.

Note that such double writing control during intermittent recording can be prohibited as appropriate depending on the content of the image to be recorded and the image reading mode of the partner device.

For example, if the other device that has read the halftone image has set the reading density to be dark in advance in anticipation of intermittent recording on the receiving side, the recording can be performed even if the double writing control during intermittent recording is not performed. In such a case, double writing control is prohibited since uneven density of the image does not occur.

Incidentally, in the above embodiment, the present invention is applied to a plotter of a facsimile machine, but the present invention can be applied to other apparatuses that perform intermittent recording.

Further, in the above embodiment, the same recording data is recorded twice when resuming recording during one intermittent recording, but the number of times of recording is not limited to this.

[Effects of the Invention] As described above, according to the present invention, the image of the first line to be recorded is recorded between the time when image recording is restarted and the recording paper moves in the transport direction by the first line. Since recording is performed multiple times, during intermittent recording, the first line after resuming recording, where the amount of heat generated is small, is recorded multiple times, so a sufficient amount of heat is supplied to the thermal recording paper, and as a result,
An image is recorded with the same density as other lines, and density reduction and density unevenness can be prevented.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a facsimile apparatus according to an embodiment of the present invention, FIG. 2 is a block diagram showing an example of a plotter, FIG. 3 is a waveform diagram for explaining operations during continuous recording, and FIG. 4 is a block diagram showing an example of a plotter. FIG. 5 is a flowchart showing an example of processing when pulse signal PA is output, FIG. 5 is a flowchart showing an example of processing when pulse signal PB is output, and FIG. 6 is processing when pulse signal PC is output. A flowchart showing an example; FIG. 7 is a waveform diagram for explaining the operation during intermittent recording; FIG. 8 is a schematic diagram for explaining the relationship between the movement of the thermal recording paper and the timing of the step pulse signal and the strobe signal; FIG. 9 is a schematic diagram for explaining the head temperature, and FIG. 10 is a schematic diagram for explaining the disadvantages of the conventional device. 21... Thermal head device, 21a... Shift register, 21b... Latch circuit, 22c... Driver, 22d... Heat generating resistor array, 21e... Thermistor, 22... Step motor, 23... Motor opening circuit, 24... Recording control section, 25... Timer circuit. Figure (Co (J 0-0) CL J OQ-CL
CL t/) t/') t/'1
The capital of LLLr...＼; Figure Figure Figure C3D Figure Figure Figure

Claims (2)

[Claims] (1) In an image recording method using a thermal head that temporarily stops image recording when the generation of recording data is interrupted, image recording is restarted and the recording paper is moved in the transport direction by the first line. An image recording method using a thermal head, characterized in that an image of the first line to be recorded is recorded multiple times. (2) In an image recording method using a thermal head that temporarily stops image recording when the generation of recording data is interrupted, image recording is restarted and the recording paper is moved in the transport direction by the first line. An image recording method using a thermal head, characterized in that an image of the first line to be recorded is recorded multiple times with a pulse width depending on the heat generation rise characteristic of the thermal head device.