JPS6164466A - Recording density control system - Google Patents

Abstract

PURPOSE:To make it possible to always perform recording at predetermined recording density without receiving the effect of the variation in the temp. of a head, by detecting the variation in the temp. of the head by a temp. detection means and controlling the temp. of a heat generating element. CONSTITUTION:A thermal head 1 is provided so as to be moved in opposed relation to a drum 2 and the drum 2 is rotated by a drive mechanism 3 controlled by a drive signal S1 and a position detection signal S2. A temp. sensor 5 such as a thermistor is provided to the thermal head 1 and temp. data S3 is outputted. When the image data S4 showing the density of an image to be recorded and temp. data S3 are supplied to a control circuit 6, the voltage apply time data S5 corresponding thereto is read from ROM7 to be supplied to a pulse generation circuit 8 where a gradation pulse S6 with a corresponding pulse width is formed to be supplied to the thermal head 1 and a current supply circuit is operated to alloy a predetermined heat generating element to generate heat.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] Akira Kigane relates to thermal image recording devices with multiple gradations, such as Sendumba thermal printers, and in particular to methods for reducing fluctuations in recording density. The present invention relates to a suitable recording density control system.

[Background of the invention]

Conventionally, an image recording device of this virtue has
As described in No. 82, recording densities of multiple gradations can be obtained by controlling the application time of the voltage applied to the heat generating element of the thermal head. A read-only memory (hereinafter referred to as ROM) is used to control this application time, and data on the voltage application time corresponding to the recording density is written in advance into the OM, and the density of the ghost image to be recorded is stored in advance. The application time was controlled by reading out data corresponding to the current.

The advantage of this recording density control means is that if the recording density characteristics change depending on the recording paper, a dedicated OM that stores data on the voltage application time specific to each recording paper is used.
The point is that you can obtain a certain record once by simply replacing it.

Here, temperature control of the heat generating element is particularly important because the temperature of the heat generating element needs to correspond to the recorded animal.

However, in the conventional example described above, the heat generating element is simply controlled using the data of the voltage application time read from the ROM. Generally, when the recording operation starts, the heat generated by the heat generating element is accumulated on the substrate of the thermal head, and the average temperature of the thermal head (hereinafter referred to as head temperature) gradually increases.As a result, the head temperature increases in the heat generating element. In addition, there was a drawback that the recording density was higher than that specified by the voltage application time data in the ROM.

Nine, when recording with transfer paper using a sublimable dye with a maximum recording density of 1.25, experimental results have been obtained that show that if the head temperature fluctuates by 10°C, the recording temperature will change by a maximum of 0.1. However, the influence of the head temperature was large.

As described above, in the past, even if the temperature of the thermal head varied, the voltage applied to the heat generating element and the voltage application time remained constant, so it was not possible to eliminate variations in recording density.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above and provide a recording once control system that is not affected by fluctuations in head temperature and can always record at a predetermined recording density by controlling the temperature of a heat generating element. be.

[Summary of the invention]

In order to achieve this object, the present invention detects fluctuations in the head temperature appropriately using a temperature detection means, and controls the mental force supplied to the heat generating element based on the detected result, thereby obtaining a predetermined recording degree. It is characterized by being made to be able to be used.

The present invention will now be described in detail based on FIG.

The figure shows the results when using transfer paper coated with sublimation dye.
It is a characteristic curve diagram showing the relationship between recording density and voltage application time with respect to changes in head temperature, in which the vertical axis shows the recording degree and the horizontal axis shows the voltage application time.
c is the head temperature force θl + θf + θ, (however,
θ, 〉θ, 〉θ, ).

From this figure, it can be seen that when the head temperature differs, the recording density characteristics change, and in order to record at a certain recording density, the voltage application time is changed to TI, Tt according to this difference in head temperature.
, Ts (however, TI < TI < Ts).

The present invention focuses on such recording density characteristics. First, the voltage application time corresponding to the recording density is determined by the head temperature (
θ1. θ! , θ1, etc.), and data representing this voltage application time is written in the ROM in advance. Then, data on the voltage application time is read from the ROM in accordance with the head temperature detected by the temperature detection means, and the power supplied to the heat generating element is controlled based on this data.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the recording density control system according to the present invention, in which 1 is a thermal head, 2 is a drum, 3 is a drive mechanism, 4 is a position sensor, 5 is a temperature sensor, and 6
is a gradation control circuit, and 7 is a ROM.

8 is a pulse generating circuit.

In the figure, a thermal head 1 is provided to move opposite a drum 2, and the drum 2 is rotated by a drive mechanism 3 controlled by a drive signal SI and a position detection signal S. The position sensor 4 is provided adjacent to the drum 21C and outputs a position detection signal St representing the position of the recording paper conveyed between the drum 2 and the thermal head 1. The thermal head 1 is provided with a temperature sensor 5 such as a thermistor, and outputs temperature data S representing the head temperature.

In the gradation control circuit 6, data on the voltage application time corresponding to the recording density is written according to the difference in head temperature.
OM7 is connected. This gradation control circuit 6 receives thiI#!, which indicates the density of the image to be recorded. When data S4 and temperature data S, are supplied, those data S, , S
Voltage application time data corresponding to 4 S! is read out from the ROM 7 and supplied to the pulse generation circuit 8.

In the pulse generation circuit 8, voltage application time data S.

A gradation pulse S having a pulse width corresponding to , is formed and supplied to the thermal head 1 .

Furthermore, although not shown, the thermal head 1 is provided with a supply circuit for supplying power to each heat generating element.
controlled by.

Then, the power supply circuit is activated by the gradation pulse S, so that a predetermined heating element generates heat.

FIG. 2 is a recording density characteristic diagram for explaining the voltage application time data written in the 80M7, and is for recording in 64 gray levels. Corresponding voltage application time data Ss is shown, and the horizontal axis shows artist data S4 representing recording density in gradations.

In the same figure, K, , K, , ..., Kf
i indicates head temperature of 01. θ2. ......, θ
This is a characteristic curve showing the case where n(θ, θ2... where θn is an integer).

Generally speaking, the narrower the interval between the two temperatures, the more accurate the control becomes.
A 64-step characteristic curve is taken for each test.

The dtl data S4 is the recording density converted into a 6-bit digital signal, and is the recording density Dma
The maximum value of x is 63, and 64 levels of recording performance are expressed.

The voltage application time data S is obtained by converting the voltage application time into an 8-bit digital signal, with the maximum voltage application time Tmax being 255 and representing 256 levels of voltage application time.

Then, in the general OM7, voltage application time data S corresponding to the ML having the smallest value of m@data S4 are written in the order of the head temperature from the lowest to the lowest. In other words, the head temperatures of the m1 numbers in descending order of head temperature are θ
i (1≦i≦n), voltage application time data S5. j is 64 (i
-1) Written at address 10j.

Therefore, as explained in FIG. 1, tI111ts
When data S and temperature data S are supplied to the floor control circuit 6, a predetermined address signal corresponding to each data S, S4 is formed, and this address signal compensates for fluctuations in head temperature. The obtained voltage application time data S is 0
1'V17.

Note that the temperature data S is digitized within the gradation control circuit 6, and the number of bits thereof is determined according to the number of divisions of the head temperature. For example, the head temperature can be represented by 64 levels.

FIG. 3 is a timing chart of each signal shown in the block of FIG. 2, and the operation of the system will be described below based on each signal.

When the drive signal SI is supplied to the drive wJ mechanism 3, Tanabata etc. inside the drive mechanism rotates the drum 2, and the recording paper between the drum 2 and the thermal head 1 is fed. When the recording paper is thus fed to the recording start position, the position sensor 4 outputs a position detection signal S, and the drum 2 stops.

Then, temperature data S is taken into the gradation control circuit 6 in synchronization with this position detection signal S.

On the other hand, as explained above, the gradation control circuit 6
! 11 Voltage application time data Ss corresponding to the recording density at a predetermined at density is read from the OM 7 from the temperature data S4 and the temperature data S. In the figure, corresponding to image data 84-1...84-m (m is an integer greater than or equal to 1 and equal to the number of heat generating elements), voltage application time data 5S-t... ... Indicates that 55-0 is read.

In the pulse generation circuit 8, these tE application time data 5
S-t,...8. -mK - gradation pulses 56-1, . Then, the applied signal S
, while each gradation pulse 5S-t,...
..., 8. -ffi causes each heating element to generate heat.

The 8 applied signals are signals with a pulse width equal to the voltage application time to obtain the maximum recording density, and the gradation pulse 56-1
...... It is now possible to control the supply and non-supply of Ss-, .

By pressing the recording paper through the transfer paper against the heating element that generates heat in this way, one-time elaboration is performed at a predetermined concentration.

, y et al 1 E diagonal vertical +', #! The driving force is supplied to the main body 1's3, and the above-described operation (
(range B in the aga diagram) is repeated over and over again.

By the way, in order to record one image, it is necessary to record a large number of lines (for example, 640 lines). In this case, the head temperature during recording and the head temperature during long recording are:
A difference of about lθ℃ may occur, and this difference is approximately 64
In the case of gradation recording, there is an extreme m difference of 5 gradations.

In order to prevent such errors from occurring, for example, the head temperature from 10C to 73C can be divided into 128 steps at 0.5C increments. As shown in range B in Figure 3, it is preferable to detect the head temperature every line feed and perform direct compensation.

On the other hand, even at the expense of some deterioration of the documentary artist, 90M7
For example, in order to reduce the amount of heat generated or to shorten the recording time, it is necessary to
The head temperature interval t is divided into 16 steps for each °C.
- In addition, the head temperature is detected only in the -1 proverbial break 01 line, as shown in range B in Figure 3, and the rest of the recording is performed using the head temperature as shown in range A of the same opening. It is better to record without detecting the temperature.

In any case, since the head temperature is detected and fluctuations in recording density characteristics are compensated for based on the detected head temperature, a good recording image can be obtained.

FIG. 4 is a block diagram showing another embodiment of the recording magnetism control system according to the present invention, in which 10 is an offset circuit, and parts corresponding to those in FIG. 1 are given the same reference numerals.

This allows an offset input signal to be applied to the temperature signal S output by the temperature sensor 5 by the offset circuit 10, and can be adjusted from the outside.

Here, if the offset input signal is set to zero, this recording density control system operates in the same way as the embodiment described above (FIG. 1).

On the other hand, if the heat-generating element of the thermal head 10 deteriorates or the desired recording density cannot be obtained when a different recording paper is used, the desired recording density can be achieved by appropriately adjusting the offset input signal. You can record with .

Another advantage is that a desired recording performance can be obtained by adjusting the offset input signal.

〔Effect of the invention〕

As explained above, according to the present invention, since the power supplied to the heat generating element is controlled according to the fluctuation in the head temperature, changes in the recording density characteristics due to the fluctuation in the head temperature are compensated for.
It is possible to always perform stable recording at one time, and to provide a recording density-based system with excellent functions, except for the drawbacks of the above-mentioned conventional techniques.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the operation of the recording density control system according to the present invention, and FIG. 2 is a block diagram showing the operation of the recording density control system according to the present invention.
FIG. 3 is a characteristic curve diagram showing the contents of the EE application time data, FIG. 3 is a timing chart of each signal in this embodiment, FIG. 4 is a block diagram showing another embodiment of the recording density characteristic system according to the present invention, and FIG. Plan. l...Thermal head, 5. Song/temperature sensor, 6.
- Grayscale control circuit, 7...ROM, 8...
...Pulse generation circuit. Boat Figure 1 Figure 2 Figure 2 East data (54) Figure 3 Figure 4

Claims (1)

[Claims] a thermal head comprising one or more groups of recording elements;
In a recording density control system, the recording density control system is provided with a power supply means for energizing the recording element for a time indicated by voltage application time data, and is configured to obtain a recording density according to the temperature of the recording element. Temperature detection means detects and outputs temperature data representing the head temperature, and voltage application time data corresponding to the recording density for each different head temperature is stored in advance in the recording element, and when the temperature data is supplied, it is handled accordingly. A recording density control system comprising: a control means for supplying the voltage application time data to the power supply means to compensate for temperature fluctuations of a heat generating element due to head temperature fluctuations.