JPH0262252A - Recording controller - Google Patents

Abstract

PURPOSE:To reduce ROM capacity while preventing the unevenness of recording density by changing over quantization or the quantization of a transfer means or transfer characteristics in response to the temperature of a thermal head or the measuring output of a recording period. CONSTITUTION:An analog/digital converter 12a quantizing the measuring output of a temperature sensor 11 measuring the temperature of a thermal head has quantization or transfer characteristics shown in (a), and has resolution at ten steps. An analog/digital converter 12b has quantization or transfer characteristics shown in (b), and has resolution at five steps. An output is turned OFF on V<=Vt and the output is turned ON V>Vt in a comparator 13 comparing the measuring output V of the temperature sensor 11 with reference voltage Vt. A selector 14 selects the output signal of the converter 12a when the output of the comparator 13 is turned OFF, and selects the output signal of the converter 12b when the output of the comparator 13 is turned ON. The converters 12a, 12b and the selector 14 constitute a quantization/transfer means capable of changing over characteristics at two steps as a whole.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a recording control device for controlling recording energy according to the temperature or recording cycle of a thermal head in a thermal recording device.

Conventional Technology In thermal recording devices that thermally record images or characters on recording paper by energizing resistive elements arranged on a thermal head to generate heat, fluctuations in the temperature of the thermal head or the recording cycle can cause problems. Since density unevenness or insufficient density tends to occur, it is necessary to control the recording energy according to the temperature or the recording cycle.

A conventional example of a recording control device that performs such recording energy control is shown in FIG. In FIG. 7, a temperature sensor 31 measures the temperature of a thermal head (not shown), and its output (analog signal) is converted into a digital signal by an analog/digital converter 32 and input to a ROM 33. In addition, the period detection timer detects the previous recording period by counting the number of pulses of the clock CLK within the input interval of the recording trigger signal TRG.
Since the output is a digital signal, it is input directly to the ROM 33. The ROM 33 stores data on recording pulse widths (proportional to recording energy) depending on temperature and recording cycle, and is addressed by input signals from the analog/digital converter 32 and the cycle detection timer.

The flip-flop is sectored by the recording trigger signal TRG, and its output is supplied as a recording node PLS to a thermal head (not shown). The timer counter 36 is used to measure the elapsed time since the recording pulse PLS is turned on, and starts counting the clock CLK after being cleared by the tone of the flip-flop deaf, and starts counting by resetting the flip-flop I. stop. Comparator 37 outputs (records) ROM 33
(pulse width data) and the output of the timer counter 36, and if they match, the reset signal R of the flip-flop 35 is
This turns on 8T.

The operation of this recording control device is as follows.

When the recording trigger signal TRG is input, the flip-flop 35 is turned on and the recording pulse PLS is turned on. As a result, current flows (recording energy is applied) to the resistance element corresponding to the black pixel on the thermal head. Also,
The timer counter 36 and the cycle detection timer start counting clocks, but the cycle detection timer outputs the data of the recording cycle measured last time. ROM3
From 3 onwards, this recording cycle and analog/digital converter 3
Recording pulse width data corresponding to the temperature quantized data input from 2 is output, and this is compared with the output of the timer counter 36 by a comparator 37.

When the time corresponding to the recording pulse width output from the ROM 33 has elapsed, a match is found in the comparator 37, the reset signal R3T is turned on, and the clip-flop 35 is reset.
Therefore, the recording pulse PLS is turned off. With this, the power supply to the heating element on the thermal head is stopped, and one recording is completed.

By repeating such control, the recording pulse width, that is, the recording energy is controlled according to the temperature or the recording cycle, and the recording density is stabilized.

Problems to be Solved by the Invention However, according to such a configuration, in order to enable good image recording without density unevenness or lack of density, it is necessary to increase the number of quantization bits of the analog/digital converter 32 and to increase the number of quantization bits of the analog/digital converter 32, It is not enough to increase the accuracy of temperature or period measurement by increasing the speed of data sampling and increasing the number of bits;
There was a problem that the capacity of 3 had to be increased.

The present invention has been made in view of the above-mentioned problems, and it is possible to appropriately control recording energy according to temperature or cycle even if the ROM that cannot control recording energy has a relatively small capacity.
It is an object of the present invention to provide a recording control device that enables good image recording without density unevenness.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention quantizes or converts the measured output of the temperature or recording cycle of a thermal head and supplies it as address information to a ROM storing recording pulse width data. The quantization or conversion characteristics of the quantization/conversion means can be switched to two or more stages, and
Providing means for switching the quantization or conversion characteristics of the quantization/conversion means according to the measured output of the temperature or recording period,
Furthermore, the apparatus is provided with means for switching the period of the clock input to the counting means for measuring the elapsed time from the time when the recording pulse is turned on, in accordance with the measurement output.

In action thermosensitive recording, when the relationship between the recording energy required to obtain a predetermined recording density and the temperature or recording cycle of the thermal head is plotted, the characteristic curves Lt and L in Fig. 6 are plotted.
i is obtained. As seen in this characteristic curve, the recording energy required to obtain a given density increases as the temperature is lower or the cycle becomes longer, and decreases as the temperature rises or the cycle becomes shorter, but the characteristic is linear. Rather, it exhibits saturation characteristics in a temperature range exceeding Tt or a period range exceeding rt. That is, the required energy changes sensitively depending on temperature or period in the non-saturated region beyond Tt or It, but in the saturated region, the fluctuation is insensitive.

Conventionally, the idea was to control the recording energy in units of a fixed amount of temperature or period variation for both saturated and non-saturated regions, without considering the existence of such saturation characteristics. In order to perform good image recording, it is necessary to set high measurement accuracy over the entire temperature or cycle range and to increase the capacity of the ROM for storing recording pulse width data.

On the other hand, the present invention has the above-described configuration, takes into account the characteristics of the thermal recording device, and, for example, uses the quantization/conversion means' By switching the conversion or conversion characteristics as shown in FIG. 2(c) or FIG. 5(b), the temperature or cycle unit for controlling the recording energy can be set sufficiently in the non-saturated region as shown in FIG. ΔT or ΔI, and set the measurement accuracy sufficiently high), on the other hand,
In the saturated region, it is recommended to reduce the measurement accuracy by setting the unit to an allowable coarse ΔT2 or Δ■2), and to switch the clock input to the counting means for measuring the on-time of the recording pulse to a long-period one. , ROM than before
By reducing the number of words and even the word length to reduce the ROM capacity, it is possible to achieve the same or better effect of suppressing density unevenness, or to suppress density unevenness that is higher than before with the same ROM capacity. A suppressive effect can be achieved.

In addition, the quantization or conversion characteristics, their switching, and
The relationship between the switching and the ROM capacity will be specifically described in the description of the embodiment.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic configuration of a recording control apparatus according to a first embodiment of the present invention, and 11 is a temperature sensor for measuring thermal and thermal temperatures. 12a and 12b are analog/digital converters for quantizing the measured output of the temperature sensor 11.

One of the analog/digital converters 12a is shown in FIG.
It has quantization or conversion characteristics as shown in a), and 10
It has step resolution. The other analog/digital converter 12b has quantization or conversion characteristics as shown in FIG. 2(b), and has a resolution of 5 steps.

13 is a comparator that compares the measured output V (temperature of the thermal head) of temperature sensor 1 with a reference voltage Vt;
The output is turned off when V≦Vt, and turned on when V>Vt. This reference voltage Vt corresponds to the temperature Tt at the boundary between saturation and non-saturation in FIG. 7(a).

I4 selects the output signal (digital signal) of one analog/digital converter 12a when the output of comparator I3 is off, and selects the output signal (digital signal) of the other analog/digital converter 12b when the output of comparator 13 is on. This is a selector that selects an output signal.

The analog/digital converters 12a, 12b and the selector 14 collectively constitute a quantization/conversion means that can switch the characteristics into two stages, and the overall characteristics (l-j: Fig. 2 (C) ).The overall resolution is 8 steps, but below the boundary temperature it has a resolution equivalent to 10 steps, and in a range exceeding the boundary temperature it has a resolution equivalent to 5 steps. The output number is determined by a high-resolution analog/digital converter 1
The number of bits that can express the output value in the range of ■≦Vt of 2a can be set as the number of bits that can express the output value in the range of
It will be less than the number of outputs of b.

A ROM 16 stores recording pulse time data, and is addressed by the output signal of the selector 14, and outputs recording pulse width data from a designated address. This data is applied to one input of comparator 19. This comparator 19 turns on the recent signal RST when the two input values match.

15 is a selector for switching the period of the input clock of the timer counter 18 into two stages;
When the output of comparator 13 is off, the clock CLK1 is selected and input to the timer counter 18, and when the output of the comparator 13 is on, the clock C with twice the cycle of the clock CLKI is selected.
LK2 is selected and input to the timer counter 18.

Reference numeral 17 denotes a flip-flop that generates a recording pulse PLS, which is reset by a recording trigger signal TRG (recording pulse PLS is turned on) and reset by turning on a reset signal R3T (recording pulse PLS is turned off).

A timer counter 8 is used to measure the elapsed time from the time when the recording pulse PLS is turned on.

The output of the flip-flop 17, that is, the recording signal PL
After clearing when S is turned on, counting of clocks input from the selector 15 is started, and when recording pulse PLS is turned off, clock counting is stopped and the counted value is held. This count value is applied to the other input of comparator 19.

The operation of the recording control device configured as described above will be described below. The output of the temperature sensor 11 is analog/
The signals are converted into digital values by digital converters 12a and 12b, respectively.

It is assumed that the measured output V of the temperature sensor 11 is lower than the reference voltage Vt. That is, it is assumed that the temperature T of the thermal head is equal to or lower than the saturation/non-saturation boundary temperature Tt. In this case, the output of the comparator 13 is off, the ROM 16 is addressed by the valid pit signal of the output of the analog/digital converter 12a with a resolution of 10 steps, and the timer counter 18 is addressed via the selector 15. A short-cycle clock CLKl is manually operated.

On the other hand, when v>vt, the output of the comparator 13 is on, so the ROM 16 is addressed by the output signal of the analog/digital converter 1.2b with a resolution of 5 steps (although a certain offset is added). The timer counter 18 also receives a long-cycle clock CLK.
2 enters.

When the recording trigger signal TRG is input, the clip-flop 17 is set and the recording pulse PLS is turned on, and the timer counter 18 starts counting input clocks after being cleared. When the time corresponding to the recording pulse width output from the ROM 16 has elapsed, the reset R8T is turned on, the flip-flop 17 is reset, the recording pulse PLS is turned off, and the timer counter 18 stops counting.

FIG. 3 shows a waveform diagram of the clock and recording pulses. (
a) is the waveform of clock CLKI with short period Twl, (b)
is the waveform of CLK2 with long period Tw2 (= 2 X Tw, ), and (C) is the analog /
Recording pulse P when the output value of the digital converter 12a is 4
LS waveform, (d) is the recording pulse PL when the output value of the analog/digital converter 12b is 4 at a temperature exceeding Tt.
The waveforms of S are shown respectively.

In this manner, at temperatures below Tt where the slope of the characteristic curve shown in FIG. By measuring the recording pulse width using the clock CLK, the recording pulse width (proportional to recording energy) can be controlled with high precision.

On the other hand, in a temperature range exceeding Tt in which the characteristic curve Lt exhibits almost saturation characteristics, the output of the temperature sensor 11 is roughly quantized with a resolution of 5 steps, and the data is used to store the data in the ROM 1.
6, the measurement error increases. Furthermore, the clock period, which is the measurement unit of the recording pulse width, is twice as long as the non-saturation region, and the control error of the recording pulse width increases accordingly.

However, since the required recording energy is insensitive to temperature in the saturated region, the influence of such errors is small and does not cause density unevenness or insufficient density, so that good images can be obtained.

Now, the quantization or conversion characteristic of the output of the temperature sensor 11 over the entire temperature range is as shown in Figure 2 (C), and the resolution can be regarded as 8 steps, so the resolution over the entire temperature range is assumed to be 10 steps. The number of words in the ROM 16 can be reduced compared to the case.

To give another example, the quantization precision of the analog/digital converter 12a is 8 bits (=256 stenops), and the quantization precision of the analog/digital converter 13b is 6 bits (=64 bits).
step), Vt is set to 66% of full scale, and in the non-saturation region, the output pitch of the analog/digital converter 12a is D. , ]D+1...Most significant bit D of LD7
Using the 7 bits excluding 7, the output signal D of the analog/digital converter 12b is used in the saturation region. ,Dl,...l
The ROM 16 can be addressed using 7 bits obtained by shifting D5 up by one pin and adding a "1" bit to the lowest order. In this case, the number of words in the ROM 16 can be reduced by reducing the number of address bits from 8 bits to 7 bits.

Further, in the non-saturated region, the short-cycle clock CLKI is used because it is necessary to finely control the recording pulse width, but in the saturated region, where there is no problem even if the control unit is coarsened, the double-cycle clock CLKI is used. Therefore, the recording pulse width data for the non-saturated region is stored in the ROM 16 as a half value of the value when using the short period clock CLKI.
can be stored in That is, ROM 16 in the saturation region
The recording pulse width data length to be stored in ROM1
6 word length can be reduced.

As described above, according to this embodiment, even if the capacity is reduced by reducing the number of words and the word length of the ROM 16, it is possible to obtain an effect of preventing density unevenness and insufficient density that is equal to or greater than that of the conventional method.

Alternatively, better image recording than before can be achieved without increasing the capacity of the ROM 16.

Note that it is also possible to achieve similar quantization or conversion characteristics by using a single analog/digital converter and switching the number of output bits and bit positions used for addressing between the saturated and non-saturated regions. .

FIG. 4 is a schematic configuration diagram of a recording control device according to a second embodiment of the present invention, and the same reference numerals as those in FIG. 1 indicate equivalent parts.

In this embodiment, an analog/digital converter 12c with a reference voltage input terminal is used, and the positive and negative reference voltages applied to the reference voltage input terminal are switched by a switch circuit 21 according to the output of a comparator 13. , at temperatures below Tt, the quantization steps are made fine, and at temperatures above Tt, the quantization steps are made coarse. By doing this,
As in the past, the number of bits of the analog/digital converter 12c is reduced, and as a result, the capacity of the ROM 16 is reduced, thereby achieving the same or greater effect of preventing density unevenness. Alternatively, analog/digital converter 1
The number of bits of 2c is kept the same as before, and the effect of suppressing density unevenness etc. is enhanced more than before without increasing the capacity of the ROM 16.

The characteristics of the analog/digital converter 12c will be explained with reference to FIG. As shown in Figure 5(a), when the temperature is below Tt, +V1 and -v3 are applied to the reference voltage input terminal and the full scale is set to FSI, but when the temperature exceeds Tt, +V2 and -v3 are applied to the reference voltage input terminal and the full scale is set to FSI. Apply -V4 to the reference voltage input terminal and set full scale to FS2. Thus, the characteristics of the analog/digital converter 12c are as shown in FIG. 5(b).
It has a nonlinear characteristic of the broken line approximation type as shown in , and the required accuracy can be secured even if the number of bits is reduced compared to the linear characteristic.

The above embodiments are examples in which the quantization or conversion characteristics of the measured output are switched in accordance with the temperature of the thermal head, but the same applies to the case where the recording pulse width is controlled in accordance with the recording period.

In other words, the recording period and required recording energy are shown in Figure 7 (b
), the measured output of the recording cycle is finely quantized at the recording cycle below It, which is the saturation/non-saturation boundary, and the precision is coarsened at the recording cycle exceeding It. A digital conversion means (when the measured output of the recording cycle is an analog value) or a conversion means using ROM (when the measured output is a digital value) is used as a means for measuring the recording cycle (for example, the cycle detection timer 3 in FIG. 7). and the recording pulse width storage ROM. The clock of the timer counter 18 is switched so that the clock cycle is lengthened in the saturation region, since the slope of the characteristic curve Li regarding the recording cycle is opposite to the characteristic curve Lt of temperature.

In the embodiments described above, the quantization or conversion characteristics and the clock period are set to 2 at the saturation-unsaturation boundary of temperature or period.
Although the non-saturated region is divided into two or more regions, the non-saturated region may be divided into two or more regions, and the number may be changed to three or more stages at each boundary thereof and at the boundary between the saturated and non-saturated regions, or it may be changed continuously. Further, the clock cycle may not be switched, the clock cycle may be switched to three or more stages, or the clock cycle switching magnification may be increased or decreased.

Effects of the Invention As is clear from the above description, the present invention provides a quantizer that quantizes or converts the measured output of the temperature or recording cycle of a thermal head and supplies it as an address input to a ROM storing recording pulse width data. The quantization or conversion characteristic of the quantization/conversion means can be switched to two or more stages, and the quantization or conversion characteristic of the quantization/conversion means can be changed, and furthermore, the elapsed time from the ON point of the recording pulse can be measured. By providing means for switching the cycle of the clock input to the counting means according to the measured output of the temperature or recording cycle, the characteristics between the thermal head temperature or recording cycle and the required recording energy can be effectively utilized, and The effect of reducing the ROM capacity required to achieve the same effect of preventing uneven recording density, etc., or achieving a higher preventing effect of preventing uneven recording density etc. than before without increasing the ROM capacity. It has the following.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a recording control device according to a first embodiment of the present invention, FIG. 2 is an explanatory diagram of quantization characteristics of temperature measurement output in the first embodiment, and FIG. 3 is a diagram of the first embodiment. FIG. 4 is a schematic configuration diagram of a recording control device according to a second embodiment of the present invention, FIG. 5 is an explanatory diagram of quantization characteristics of temperature measurement output in the second embodiment, FIG. 6 is a characteristic diagram showing the relationship between recording energy required to obtain a predetermined density, thermal head temperature, and recording cycle, and FIG. 7 is a schematic diagram of a conventional recording control device. 11... Temperature sensor, 12a, 12b, 12c.
...Analog/digital converter, 13...Comparator, 14.15...Selector, 16...ROM, 1
7...Flip-flop, I8...Timer counter, 19...Comparator, 21...Switch circuit. Name of agent: Patent attorney Shigetaka Awano and one other person Fig. 1 (α) Fig. (b) Δka (Aaro γ) Fig. (Q)

Claims (2)

[Claims] (1) Means for measuring the temperature or recording cycle of the thermal head, and quantization/conversion for quantizing or converting the measurement output of the means.
a converting means, a ROM that outputs recording pulse width data by using the quantization or conversion output of the means as an address input, a clock counting means, and a comparing means that compares the counted value of the means with the output data of the ROM. , means for turning on the recording pulse in response to input of a recording trigger signal and turning off the recording pulse in response to a coincidence output of the comparison means, and the counting means counts clocks during the on period of the recording pulse. The quantization/conversion means is capable of switching the quantization or conversion characteristics to two or more stages, and the quantization/conversion means includes means for switching the quantization or conversion characteristics of the quantization/conversion means in accordance with the measurement output of the measurement means. A recording control device comprising: (2) The recording control device according to claim (1), further comprising means for switching the cycle of the clock input to the counting means in accordance with the measurement output of the measuring means.