JPH0556235A - Thermosensible recording device - Google Patents

Abstract

PURPOSE:To obtain a recording image without irregular density by changing the driving time of a recording element corresponding to the number of one line division times without requiring a complicated circuit or control when driving and recording in a constant-bit recording system are performed. CONSTITUTION:A black picture element counter 6 counts the number of black picture elements out of image signals to be received, and when a prescribed count value is reached, it outputs an OVR to a division number counter 10. The division number counter 10 determines the number of dividing one line and outputs a BDT to an impressed pulse width generation part 12, and the impressed pulse width generation part 12 sets the driving time of a heating element from the division number, and the heating element performs recording using the set driving time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal recording device used in a facsimile machine or the like.

[0002]

2. Description of the Related Art Recently, facsimile machines for transmitting images and the like using lines have come to be installed not only in the workplace but also in general households. A low-noise, high-reliability heat-sensitive recording apparatus using a thermal head excellent in high speed and high resolution is widely used for recording a received image of this facsimile apparatus. Various recording methods are used in this thermal recording apparatus. Among these methods, the method of recording one line on the recording paper by one disturbance is the fastest. However, since the thermal recording apparatus according to this method records one line to be recorded by driving once, when the pixels of one line are all black pixels, the recording elements of the one line are simultaneously driven by the drive current. A power supply for supplying the power, that is, a power supply having a very large capacity is required. However, the proportion of black pixels in most lines of a transmitted original document is less than 10%,
Moreover, there may be extremely few black pixels in the line. Therefore, using a large-capacity power source is extremely uneconomical and leads to an increase in the cost of the device itself.

Therefore, if the number of black pixels included in one transmitted line is less than a certain value K, one line is recorded at one time. If the number of black pixels exceeds the certain value K,
One line is divided so that the number of black pixels becomes K or less, and the divided number of times is recorded. A so-called constant bit recording method has been proposed.

[0004]

However, in the thermal recording apparatus using the constant bit recording method, the recording time of one line varies depending on the number of black pixels, that is, each recording element (heating element) is driven. Although the times are the same, since the driving timing of the printing elements differs depending on the number of black pixels, the larger the number of divisions per line, the greater the difference in heat storage of the individual printing elements. Therefore, this causes a density difference in a recorded black pixel portion due to a difference in heat storage of individual recording elements, and in particular, a large density difference occurs as the number of line divisions increases, that is, unevenness occurs in the entire recorded image. there were.

The present invention solves the above-mentioned problems of the prior art, and when drive recording is performed by the constant bit recording method, a complicated circuit,
It is an object of the present invention to provide a thermal recording apparatus that can obtain a recorded image without density unevenness by changing the driving time of the recording element according to the number of divisions of one line without requiring control.

[0006]

In order to achieve the above object, a thermal recording apparatus of the present invention comprises a recording element corresponding to the number of pixels for one line, a storage circuit for storing an image signal for one line, A recording device comprising a drive circuit for selectively driving the recording element according to the number of black pixels of the stored image signal, wherein the number of black pixels of the image signal stored in the storage circuit is detected. Means, a means for determining the number of times of divided recording for one line based on the detected number of black pixels, and a means for determining a driving time for driving the recording element according to the determined number of times of divided recording. is doing.

[0007]

According to the present invention having such a configuration, the number of black pixels in one line is detected, and the number of divided recordings in one line is determined based on the number of black pixels. The greater the number of divided recordings, the longer the driving time of the recording element. By extending the time for a predetermined time, the above object can be achieved.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the schematic arrangement of a thermal recording apparatus according to an embodiment of the present invention. In the figure,
1 is a transfer clock (hereinafter TCK) for transferring an image signal
Signal input terminal for inputting an image signal (hereinafter abbreviated as PIX), 3 for 1
A signal input terminal for inputting a line recording period signal (hereinafter abbreviated as LINE), 4 is a signal output terminal for outputting a one line recording end signal (hereinafter abbreviated as FIN), and 5 is a P
A signal input terminal for inputting, for example, a signal (hereinafter abbreviated as TNSO) that becomes a high level “H” during the transfer of IX,
6 counts the number of black pixels on the PIX1 line, and outputs a pulse, for example, carry (OV or less) every time this number exceeds a predetermined value.
R) is generated, that is, a black pixel counter, 7 is a transfer pixel counter for counting the number of transferred PIXs of one line, and 8 is an OVR from the black pixel counter 6 and a transfer pixel counter. Information on the number of PIXs transferred from 7 is input, and a batch recording block detection unit that determines the division method necessary to record one line, and 9 is data from the batch recording block detection unit (division information for one line. ) Is decoded and a block to be recorded is selected based on this data. A recording block selection unit 10 counts the OVR from the black pixel counter and determines a division number for performing one line recording, that is, a division number counter ( The number of output times of an applied pulse width signal (hereinafter, abbreviated as ENB), which will be described later, is counted, and 11 is for recording one line by the BDT. The number of ENB outputs that compares the number with the BDT and outputs a trigger signal (hereinafter abbreviated as TRIG) if they do not match, and outputs a 1-line recording end signal (hereinafter abbreviated as FIN) if they do not match. Counters 12 are variable according to the BDT from the division number counter 10, and TRI from the ENB output number counter 11
The drive time determining means for outputting ENB synchronized with G, that is, the applied pulse width generating portion, 13 is TNSO at a low level “L”, that is, in the state where the image signal is not being transferred,
At the output timing of IN, the thermal head unit 1 described later
Strobe signal (hereinafter STB) for latching the PIX temporarily stored in the shift register 5 in the latch circuit.
And a gate for selecting ENB1 to ENBN by the signal from the recording block selection unit 9 and ENB in 1 line recording, 15 is a shift register, a latch circuit, an AND gate, It is a thermal head part that mounts a driver and the like.

Next, the operation of the thermal recording apparatus of the present invention will be described in a second step.
A description will be given based on the timing chart in the figure. First, L
In synchronization with the rising edge of INE, PIX, TCK, TNSO
To enter. Here, the first line of the PIX does not need to be divided, the second line needs to be divided into two, and the third line needs to be divided into three.
The black pixels corresponding to each are distributed. When this PIX is transferred to the thermal head unit 15, the previous line already transferred to the shift register is latched by the latch circuit, and recording is started at the rising edge of LINE of the next line.

At this time, the collective recording block detection unit 8 calculates the data of the recording block for collectively recording the previous line, using the data already detected by the black pixel counter 6 and the transfer pixel counter 7. Then, the black pixel counter 6 outputs a pulse signal (hereinafter abbreviated as OVR) each time the number of black pixels which is the detected data exceeds a preset value. That is, when it is necessary to record one line by dividing it into n, n-1 OVRs are output. Then, the collective recording block detection unit 8 inputs this OVR, detects the data from the transfer pixel counter 7, and transfers the PIX.
Decide how to divide one line. At the same time, this OV
The BDT (data in which the number of divisions is 0, 1, 2, 3, etc.) is output from the division number counter 10 to which R is input. The ENB output number counter 11 to which this BDT is input presets the number of divisions and generates TRIG to output ENB from the applied pulse width generation unit 12. In addition, the applied pulse width generation unit 12 to which this BDT is input
Determines the pulse width according to the number of divisions and outputs ENB in synchronization with TRIG. The pulse width of this ENB becomes larger as the number of divisions increases. Therefore, in this example, the pulse width of ENB has a relation of TA <TB <TC. In other words, this can change the applied pulse width according to the number of divisions of one line. At this time, this E
The collective recording block detection unit 8 that has input NB determines the method of dividing one line, and outputs the data of the block to be collectively recorded to the recording block selection unit 9. Here, the recording block selector 9 decodes the block data, and the ENB 1 is selected via the AND gate 14.
~ ENBN is applied to the thermal head unit 15. At this time, the larger the number of divisions of this ENB, the more sufficient the pulse width (T
A, TB, TC). In addition, E which input this ENB
The NB output counter 11 has a preset value (BDT).
TRI is continuously output after each ENB output until
Output G. That is, the number of pulses corresponding to the number of divisions is output. When the preset width and the number of ENB outputs match and the 1-line recording end signal FIN is output, the strobe generator 13 that detects this FIN and the low level of TNSO from the outside detects the line to be recorded next with the thermal head. The STB to be latched is output to the latch circuit of the section 15. The above operation is sequentially repeated to record one page. In addition, LINE is a handshake with FIN.
ke) and the FIN output is detected and then input to the signal input terminal 3. That is, a high level signal is input to the signal input terminal 3. The timing chart of FIG. 2 shows the case of simultaneous driving of one line, two-division driving, and three-division driving, but the recording operation is performed at the same timing as above even when the number of divisions of one line increases. It is possible.

On the other hand, the sub-scan feed of the recording paper is performed by rotating a stepping motor by generating a predetermined driving current by a stepping motor driver (not shown) in synchronization with the rise of LINE.

[0013]

According to the present invention, according to the number of divided recordings of one line, the driving time (recording element recording time) can be adjusted without using a complicated circuit or control so as to eliminate the influence of the heat storage difference between the recording elements. Since the energization time) can be varied, density unevenness does not occur in the recorded image even with the constant bit recording method, and an effect of obtaining a high quality image is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a thermal recording apparatus showing an embodiment of the present invention.

FIG. 2 is an operation timing chart of the thermal recording apparatus shown in FIG.

[Explanation of symbols]

 1 TCK signal input terminal 2 PIX signal input terminal 3 LINE signal input terminal 4 FIN signal output terminal 5 TNSO signal input terminal 6 Black pixel counter (black pixel number detection means) 7 Transfer pixel counter 8 Batch recording block detection unit 9 Recording block selection Section 10 division number counter (division recording number determination means) 11 ENB output number counter 12 applied pulse width generation section (driving time determination means) 13 strobe generation section 14 AND gate 15 thermal head section

Claims (1)

[Claims] 1. A recording element corresponding to the number of pixels for one line, a memory circuit for storing an image signal for one line, and the recording element is selectively selected according to the number of black pixels of the stored image signal. A recording device comprising a driving circuit for driving to a black circuit, which sequentially counts the number of black pixels of an image signal transferred to the storage circuit for each predetermined value, and outputs a counting end signal at each count end. Pixel counting means, means for counting the number of times the count end signal is output for each line, and determining the number of divided recordings for one line in accordance with the output result, and responding to an increase in the number of divided recordings for the one line Means for determining a driving time for driving the recording element so that the driving time also gradually increases, and the recording element while increasing the number of divided recordings of one line and the recording element driving time according to the increase of the black ratio. Drive the The end of one line is determined by detecting the coincidence between the number of divided recordings of the print data and the number of outputs of the drive time signal sent by the means for determining the drive time,
A heat-sensitive recording apparatus, comprising: a control unit that controls to shift to a recording process of an image signal of the next line.