JPS6023063A - Recorder - Google Patents

Abstract

PURPOSE:To obtain uniform recording density even if the performance of recording power source is not so raised, by a method wherein black picture elements or white picture elements in picture signals are counted and the recording time is controlled according to its discrete value. CONSTITUTION:During the period when load current flows through the recording power source 7, the voltage of power source V once decreases lower than a constant value V0 and returns to the constant value V0 again. The length of traditional time from the start of decrease to the completion of returning of the voltage of power source V and the falling width of the voltage of power source V are the larger, as the black rate is the higher. Recording times T1, T2... for keeping the recording electric energy supplied to heating unit constant are calculated as to various black rates and stored in the adress of ROM9 corresponding to the discrete value of black picture element counter 8 at respective black rates. The recording pulse generation part 10 generates the recording pulse of a pulse width corresponding to the output data of ROM9 and supplies it to the thermal head driving part 6.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention has a plurality of recording elements, and by selectively supplying recording power to the recording elements corresponding to black pixels in the image signal, the image signal can be improved. The present invention relates to a recording device that performs recording.

Conventional configuration and its problems A thermal recording device uses a heating element (
The image signal is generated by supplying recording power from the power supply to the recording element (recording element) and coloring the thermal recording paper with the Joule heat generated by the heating element, or by transferring ink or dye from the thermal transfer paper to plain paper. record. Therefore, when the amount of recording power applied to the heating element changes, the recording density changes.

Now, in such a conventional thermal recording device, by using a constant voltage power source as a power source (hereinafter referred to as a recording power source) for supplying recording power to a heating element, recording can be performed while suppressing fluctuations in recording power amount. Efforts are being made to make the concentration uniform.

However, even though it is a constant voltage power supply, transient fluctuations in the power supply voltage occur when the load current changes, and the width of the fluctuation in the power supply voltage and the time during which the power supply voltage fluctuates (hereinafter referred to as the transient time) are the same as the load current. The size varies depending on the number of black pixels recorded simultaneously (in other words, it is proportional to the black ratio of the image signal).

Since such fluctuations in the power supply voltage range and transient time result in fluctuations in the amount of recording power applied to the heating element, there has conventionally been a problem in that the recording density changes depending on the black ratio of the image signal. In particular, in recent high-speed thermal recording devices, since the recording time approaches the transient time, it is no longer possible to ignore recording density unevenness due to transient fluctuations in the power supply voltage.

It is conceivable to deal with such problems by further increasing the voltage stability of the recording power source, suppressing the fluctuation width of the power source voltage, and shortening the transient time. However, this causes a significant increase in the cost of the recording source, resulting in another problem in that the recording device becomes expensive.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned conventional problems, and it is an object of the present invention to provide a recording apparatus that can achieve uniform recording density without increasing the cost of recording power supplies.

Structure of the Invention The present invention provides a means for counting black pixels and white pixels in an image signal to be recorded in a thermal recording apparatus, and a supply time of recording power to a recording element (heating element) according to the counted value of the means; That is, the above object is achieved by providing means for controlling the recording time and suppressing fluctuations in the recording power amount by controlling the recording time.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic block diagram of a thermal recording apparatus according to an embodiment of the present invention. In this figure, 1 to 4 are terminals connected to external circuits (not shown), respectively.

Terminal 1 is the input terminal for the image signal PIX, terminal 2 is the input terminal for the image signal sampling clock (, LOCjK, terminal 3
is the input terminal of the image signal valid interval signal ENABLE, terminal 4
ij: Output terminal for image signal request signal REQUEST.

Reference numeral 6 denotes a thermal head, which has the same number of heating elements (recording elements) as the number of pixels of an image signal recorded in one recording operation. 6 is a thermal head drive unit, 7 is a recording power source, 8 is a black pixel counter, 9 is a ROM (read only memory), and 10 is a recording pulse generator. Reference numeral 11 denotes a control section that controls the entire apparatus.

Next, the operation will be explained. The control unit 11 first resets the black pixel counter 8, and then outputs the image signal request signal RKQUKST.
Turn on. The external circuit uses the image signal request signal RIQUKST.
When it is detected that the image signal valid section signal ENABIF is turned on,
Turn on C. Image signal PI synchronized with Tsuta CLOCK
Start transferring X. When the control unit 11 detects that the image signal valid period signal ENABLE is turned on, the control unit 11 outputs the image signal request signal R.
Turn off EQUEST.

The thermal head driving section 6 has an internal shift register, and the transferred image signals P and X are sequentially taken into this shift register at the timing of the clock CLOCK and stored therein. Further, the black pixel counter 8 operates during the period when the image signal valid period signal ENABLE is on, and the black pixel counter 8 operates while the image signal valid period signal ENABLE is on.
Count the clock GLOCK when IX is 1 (black pixel).

That is, the black pixels in the image signal PIX are counted.

When the transfer of the image signal PIX recorded in one recording operation is completed, the external circuit turns off the image signal valid period signal ENABLE. The thermal head driving section 6 causes the internal latch circuit to latch the contents of the internal shift register all at once when the image signal valid period signal ENABLE is off. The dimension control unit 11 outputs an image signal valid period signal ENABLE.
When detecting the off state, a trigger signal is supplied to the recording pulse generator 10. When the recording pulse generating section 1o receives this trigger signal, it generates a recording pulse RP having a pulse width corresponding to the output data of the ROM 9 at that time. At this time RO
The output data of M9 indicates the recording time corresponding to the count value of the black pixel counter 8. That is, a recording pulse RP having a width corresponding to the number of black pixels in the image signal to be recorded, or in other words, a recording time corresponding to the black ratio of the image signal, is supplied to the thermal head driving section 6.

The thermal head 6 is installed inside the thermal head drive unit 6.
A switching element is provided corresponding to each heating element. Then, the thermal head drive unit 6 conducts the switching element corresponding to 1 bit of the internal launch circuit for the ON period (recording time) of the recording pulse RP,
The corresponding heating element and the recording power source 7 are connected through the switching element. In this way, recording power is supplied from the recording power source 7 only to the heating element corresponding to the black pixel of the image signal during the ON period of the recording pulse RP.

Thereafter, when the control section 11 detects that the recording pulse RP is turned off, it resets the black pixel counter 8 and also turns on the image signal request signal REQUEST to prepare for the transfer of the next image signal.

Next, the contents stored in the ROM 9 will be explained with reference to FIGS. 2 to 4.

FIG. 2 is a waveform diagram of the power supply voltage V of the recording power source 7 and the recording pulse RP when the black ratio is 100%, that is, when the entire image collection records pixel signals of black pixels. Also, in Figure 3, the black rate is 60
Power supply voltage V and recording pulse RP when recording the picture signal of
FIG. FIG. 4 is a diagram in which the waveform of the power supply voltage V in FIG. 2 and the waveform of the power supply voltage V in FIG. 3 are superimposed.

As shown in FIGS. 2 and 3, during the ON period of the recording pulse RP, that is, the period when the load current flows through the recording power source 7,
The power supply voltage vI'i drops from the steady-state value vo, and then returns to the steady-state value VO. The length of the transient time from the start of the drop in the power supply voltage V to the completion of recovery and the width of the drop in the power supply voltage V become larger as the load current value becomes larger, that is, as the black ratio becomes higher. On the other hand, in order to obtain uniform recording density, it is necessary to keep the amount of recording power supplied to the heating element and the area of the shaded area of the power supply voltage waveforms in Figures 2 and 3 constant. be. Therefore, in this embodiment, the recording time (corresponding to T1 and T2 in FIGS. 2 and 3) required to satisfy the above conditions for various black rates is calculated in advance, and the black pixel counter at each black rate is calculated in advance. It is stored in the address of the ROM 9 corresponding to the count value of 8. Therefore, irrespective of the black rate, the recording time (2) is appropriately controlled, the amount of recording power supplied to the heating element is made constant, and uniform recording density can be obtained. By the way, if the recording time is constant, the black rate is 100.
% and 6o%, there is a difference in the amount of recording power corresponding to the area of the shaded area in FIG. 4, and a corresponding unevenness in recording density occurs.

In this embodiment, the black pixel counter 8 detects the number of black pixels (black ratio) in the image signal, but the number of white pixels (Japan) may also be detected.

However, in this case, the recording time data according to the number of white pixels is
It is necessary to store it in OM9 in advance. Further, in this embodiment, the thermal head drive section is independent from the thermal head, but it goes without saying that the thermal head drive section may be integrated with the thermal head.

Further, in this embodiment, the recording time is not controlled by the ambient temperature of the thermal head, but the recording time can also be controlled by the ambient temperature.

Furthermore, the present invention can be appropriately applied to recording devices other than thermal recording devices.

Effects of the Invention As described above, the present invention has a means for counting black pixels or white pixels in an image signal to be recorded, and a means for controlling recording time according to the counted value of this means (ROM 9 and recording pulse of the above embodiment). (corresponding to the generating section 10) is provided to keep the amount of recording power supplied to the recording element constant, so it is possible to obtain uniform recording density without significantly increasing the performance of the recording power source, and the recording image quality is improved. The effect is that an excellent recording device can be realized at a relatively low cost.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a thermal recording device according to an embodiment of the present invention, FIG. 2 is a waveform diagram of power supply voltage and recording pulses when recording an image signal with a black rate of 100%, and FIG. 3 is a waveform diagram of a recording pulse with a black rate of 6o. FIG. 4 is a waveform diagram showing the power supply voltage waveform of FIG. 2 and the power supply voltage waveform of FIG. 3 superimposed on each other. 6... Thermal head, 6... Thermal head drive unit, 7... Recording power supply, 8...
...Black pixel counter, 9...l (OM, 10...
. . . Recording pulse generation section, 11 . . . Control section.

Claims (1)

[Claims] a plurality of recording elements, a power supply, means for supplying recording power from the power supply to the recording elements corresponding to black pixels in the image signal to be recorded, and means for counting black pixels or white pixels in the image signal. and means for controlling the supply time of recording power to the recording element according to the counted value of the means.