JPH0320952B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a thermal recording device used in facsimile machines and the like.

Conventional configuration and problems thereof Recently, facsimile devices that transmit images, etc. using lines have been installed not only in workplaces but also in ordinary homes. A low-noise, high-reliability thermal recording device using a thermal head, which is excellent in high speed and high resolution, is widely used to record images received by this facsimile device. This thermal recording device employs various recording methods. Among these methods, the method in which one line is recorded on recording paper in one drive is the fastest. However, in a thermal recording device using this method, one line is recorded in one drive, so if all the pixels of one line are black pixels, the driving current is applied to all the recording elements of the one line at the same time. In other words, a power supply with a very large capacity is required. However, the proportion of black pixels in most lines of a transmitted original is less than ten percent, and there are cases in which the number of black pixels in a line is extremely small. Therefore, using a large-capacity power source is extremely uneconomical and also increases 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, and if this number of black pixels exceeds the certain value K, the number of black pixels is One line is divided so that the number of lines is less than or equal to K, and the line is divided and recorded as many times as the number of divisions. A so-called constant bit recording method has been proposed.

However, in a thermal recording device using the constant bit recording method described above, the recording time for one line varies depending on the number of black pixels.In other words, although the driving time of each recording element (heating element) is the same, Since the drive timing of the recording element differs depending on the number of recording elements, 1
The greater the number of line divisions, the greater the difference in heat storage between individual recording elements. Therefore, this is a problem in which density differences occur in recorded black pixel portions due to differences in heat storage in individual recording elements, and especially the more lines are divided, the more significant density differences occur.In other words, this problem causes unevenness in the entire recorded image. It was hot.

Purpose of the invention The present invention solves the above-mentioned conventional problems.
Heat-sensitive recording that does not require complicated circuits or controls when driving and recording using a constant bit recording method, and can obtain recorded images with uniform density by changing the driving time of the recording element according to the number of divisions of one line. The purpose is to provide equipment.

Structure of the Invention The thermal recording device of the present invention includes a recording element corresponding to the number of pixels for one line, a storage circuit for storing an image signal for one line, and a recording element corresponding to the number of pixels for one line, and a recording element corresponding to the number of pixels for one line, and a storage circuit for storing an image signal for one line. A recording device comprising: a drive circuit that selectively drives the recording element; and means for detecting the number of black pixels of the image signal stored in the storage circuit; and means for determining a driving time for driving the recording element according to the determined number of divided recordings, and means for determining a driving time for driving the recording element according to the determined number of divided recordings and the driving time. The recording element is driven through a circuit to record on recording paper. The present invention having such a configuration detects the number of black pixels of one line, determines the number of divided recordings of one line based on the number of black pixels, and increases the driving time of the recording element by a predetermined time as the number of divided recordings increases. By doing so, the above purpose can be achieved.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a thermal recording apparatus according to an embodiment of the present invention. In the figure, 1 is a signal input terminal for inputting a transfer clock (hereinafter abbreviated as TCK) for transferring image signals, 2 is a signal input terminal for inputting an image signal (hereinafter abbreviated as PIX), and 3 is 1 line. 4 is a signal input terminal that inputs a recording period signal (hereinafter abbreviated as LINE), 4 is a signal output terminal that outputs a 1-line recording end signal (hereinafter abbreviated as FIN), and 5 is a signal output terminal that outputs a 1-line recording end signal (hereinafter abbreviated as FIN). A signal input terminal for inputting a signal of level “H” (hereinafter abbreviated as TNSO);
6 is a black pixel counter, which counts the number of black pixels in the PIX1 line, and generates a pulse such as a carry (hereinafter referred to as OVR) every time this number exceeds a predetermined value; 7 is a black pixel counter; The transfer pixel counter 8 counts the number of PIX in one line, and inputs the OVR from the black pixel counter 6 and the information on the number of PIX transferred from the transfer pixel counter 7, and calculates the number of pixels necessary to record one line. A batch recording block detection unit 9 determines the division method; a recording block selection unit 9 decodes data (dividing information for one line) from the batch recording block detection unit and selects a block to be recorded based on this data;
11 is a dividing number determining means for counting OVR from a black pixel counter and recording one line, that is, a dividing number counter (hereinafter abbreviated as BDT);
To record one line using the BDT, count the number of outputs of the applied pulse width signal (hereinafter referred to as ENB), which will be described later, and compare this number with the BDT. If the results do not match, the trigger signal (hereinafter referred to as TRIG) is (abbreviated as FIN), and if there is a mismatch, outputs a 1-line recording end signal (hereinafter abbreviated as FIN).
an ENB output number counter; 12 is a drive time determining means that outputs an ENB that is variable according to the BDT from the division number counter 10 and is synchronized with TRIG from the ENB output number counter 11; 13 is an applied pulse width generator; 13 is a TNSO is low level “L”, that is,
While the image signal is not being transferred, a strobe signal (hereinafter referred to as "pixel") for latching PIX temporarily stored in the shift register of the thermal head section 15 to the latch circuit is sent at the output timing of FIN.
A strobe generator that generates STB (abbreviated as STB),
14, in one line recording, ENB1 to ENBN are selected by the signal from the recording block selection section 9 and ENB.
15 is a thermal head section equipped with a shift register, a latch circuit, an AND gate, a driver, etc.

Next, the operation of the thermal recording apparatus of the present invention will be explained based on the timing chart of FIG. First of all,
PIX, TCK, TNSO in synchronization with the rise of LINE
enters. Here, the first line of 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, so the corresponding black pixels are distributed. When this PIX is transferred to the thermal head section 15, the previous line that has already been transferred to the shift register is latched by the latch circuit, and the next line is
Recording starts when LINE starts up.

At this time, using the data already detected by the black pixel counter 6 and the transfer pixel counter 7, the batch recording block detection section 8 calculates the data of the recording block for collectively recording the previous line. Then, the black pixel counter 6 sends a pulse signal (hereinafter referred to as
(abbreviated as OVR). That is, if one line needs to be divided into n parts and recorded, n-1 OVRs are output. Then, the batch recording block detection unit 8 inputs this OVR, detects the data from the pixel counter 7, and transfers the data.
Decide how to divide the PIX1 line. Also, at the same time,
From the division number counter 10 that inputs this OVR, the BDT (in this example, the number of divisions is 0, 1, 2,
3rd class data) is output. The ENB output number counter 11 that inputs this BDT presets the number of divisions, and outputs it from the applied pulse width generator 12.
Generates a TRIG that outputs ENB. Also, this
The applied pulse width generator 12 that receives the BDT determines the pulse width according to the number of divisions and outputs the ENB in synchronization with the TRIG. The pulse width of this ENB is
The width increases as the number of divisions increases. Therefore, in this example, the ENB pulse width has a relationship of T _A < T _B < T _C. In other words, the applied pulse width can be varied according to the number of times one line is divided. At this time, the batch recording block detection unit 8, which has input this ENB, determines the method of dividing one line, and outputs the data of the block to be batch recorded to the recording block selection unit 9. Here, the data of the block is decoded by the recording block selection section 9,
ENB was selected via AND gate 14
Thermal head section 15 as ENB1 to ENBN
is applied to At this time, the more times the ENB is divided, the more the pulse width (T _A , T _B , T _C ) becomes sufficient to correct the degree of heat accumulation between the recording elements.
In addition, the ENB output count counter 11 to which this ENB is input continues until it matches the preset value (BDT).
Continuously outputs TRIG every time ENB output ends.
In other words, the number of pulses corresponding to the number of divisions is output. Then, when the preset width and the number of END outputs match and the 1-line recording end signal FIN is output, the strobe generator 13 detects this FIN and the low level of TNSO from the outside and starts the next line to be recorded on the thermal head. The STB to be latched to the latch circuit of section 15 is output. One page is recorded by sequentially repeating the above operations. Furthermore, LINE is
It performs handshake with FIN, and after detecting the output of FIN, it is input to signal input terminal 3. In other words, a high level signal is input to this input terminal 3. Also, the timing chart in Fig. 2 shows whether one line is driven all at once, divided into two, or three.
Although the case of divided driving is shown, even if the number of divisions of one line increases, the recording operation can be performed at the same timing as above.

On the other hand, the recording paper is fed in the sub-scanning direction by generating a predetermined drive current by a stepping motor driver (not shown) and rotationally driving the stepping motor in synchronization with the rising edge of LINE.

Effects of the Invention According to the present invention, the drive time (current supply time to the recording elements) can be adjusted according to the number of divided recordings of one line without using complicated circuits or controls so as to eliminate the influence of heat storage difference between the recording elements. ) can be varied, so even in the constant bit recording method, density unevenness does not occur in the recorded image, and a high quality image can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a thermal recording apparatus showing an embodiment of the present invention, and FIG. 2 is an operation timing chart of the thermal recording apparatus shown in FIG. 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 unit, 10...Division number counter (division recording number determination means), 11...
. . . ENB output number counter, 12 . . . Applied pulse width generation section (driving time determining means), 13 . . . Strobe generation section, 14 . . . AND gate, 15 .

Claims (1)

[Claims] 1 Recording elements equivalent to the number of pixels for one line,
A recording device comprising: a storage circuit that stores one line of image signals; and a drive circuit that selectively drives the recording element according to the number of black pixels of the stored image signal, means for detecting the number of black pixels of the image signal stored in the storage circuit; means for determining the number of divided recordings of one line based on the detected number of black pixels; and driving the recording element according to the determined number of divided recordings. the recording element is driven via the drive circuit according to the number of divided recordings and the drive time to record on recording paper. Heat-sensitive recording device.