JPH0632943B2 - Thermal transfer printer - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer printer having a temperature compensating function for keeping a print density constant against a temperature change of a thermal head, and more specifically, a temperature compensating function. In addition to the above, the present invention relates to such a thermal transfer printer capable of performing density correction according to preference.

[Conventional technology]

A conventional thermal transfer printer is disclosed in Japanese Patent Laid-Open No. 58-738.
As shown in Japanese Patent Publication No. 0, a temperature compensation method has been proposed for keeping the print density constant against the temperature change of the thermal head.

Hereinafter, a conventional thermal transfer printer having such a temperature compensation function will be described.

The print density changes depending on the amount of energy applied to the thermal head. As one method of controlling this amount of energy, the applied voltage is kept constant and the energization time is changed to obtain the required print density.

FIG. 4 is an explanatory diagram showing the temperature compensation range of the printer.
In the figure, the lower limit temperature and the upper limit temperature are T _l and T _h , respectively.
, And the two are divided by temperatures T ₁ , T ₂ , ..., T ₇ . Segmented temperature ranges T _{1 to} T ₁ , T _{1 to} T ₂ , ..., T
The ₇ ~T _h, named each temperature level _{t 0, t 1,} and ... _{t 7.} Note that here, T _{1 to} T _h are divided into eight, but the number of divisions is not limited to this.

FIG. 5 is a block diagram showing a conventional thermal transfer printer. In the figure, 1 is an image memory, 2 is a halftone control circuit, 3 is a conduction time data memory, 4 is a thermal head,
Reference numeral 5 is a temperature sensor, 6 is a temperature compensation circuit, and 7 is a print.

Now, suppose that the temperature of the thermal head 4 is in the range of T ₁ to T _h . The temperature sensor 5 detects the temperature of the thermal head 4 and outputs a temperature detection signal to the temperature compensation circuit 6. The temperature sensor 5 is, for example, a thermistor, and in this case, the temperature detection signal is given by the resistance value of the thermistor corresponding to the temperature. In the temperature compensation circuit 6, the temperature detection signal (analog) from the temperature sensor 5 is in the temperature range T _{1 to} T ₁ ,
_{T 1 ~T 2, ..., T} 7 ~T h That is, the temperature level _{t 0,} t 1, ..., determines whether it belongs to any of _{t 7,} the energization time data and the resulting temperature specified number (digital) Output to the memory 3.

FIG. 6 shows a graph as a tone reproduction diagram of the printer. The shape of the graph is slightly different depending on each color in monochrome printing and color printing, but the tendency can be regarded as the same.

In FIG. 6, (a) shows gradation characteristics, and shows what density the gradation level of the image stored in the image memory 1 is printed in the print 7. Here, the density to be expressed is divided into 32 gradations, the lowest density, that is, pure white is set as the gradation level 0, and the highest density is made to correspond to the gradation level 31. The gradation characteristic does not change with temperature, and is set as a characteristic peculiar to this printer (solid line in the figure).

FIG. 6 (b) shows the coloring characteristics, and the thermal head 4
The relationship between the energizing time applied to the print and the print density of the print 7 at that time is shown. The color development characteristic changes depending on the temperature of the thermal head 4. That is, for the same energization time,
When the temperature of the thermal head 4 is high, the print density is high,
The lower the temperature, the thinner the concentration. In the figure, characteristic curves at temperature levels t ₂ , t ₃ and t ₄ are shown.

In this way, the color development characteristics are similar to those of the thermal head 4 and the print 7.
It is unique to the combination of paper and changes with temperature.

FIG. 6C shows the energization time data stored in the energization time data memory 3. The energization time data is uniquely determined as a data string for each temperature level in a printer having gradation characteristics (a) and coloring characteristics (b), and is uniquely determined as a data string for each temperature level. It shows the energization time to be applied to the thermal head 4 in order to obtain a predetermined print density with respect to the gradation level of the image data.

Therefore, the energization time data string γ ₀ , γ ₁ , ..., γ ₇ is set for each temperature level of t ₀ , t ₁ , ..., T ₇ , and the temperature corresponding to the temperature of the thermal head 4 is set. By switching the energization time data string to be used in accordance with the temperature designation signal from the compensation circuit 6, it is possible to perform temperature compensation for keeping the print density constant against temperature changes.

Returning to FIG. 5, an example of the temperature compensation operation is shown. It is assumed that the temperature of the thermal head 4 is in the range of T _{3 to} T ₄ . This is detected by the temperature sensor 5 and the temperature detection signal is sent to the temperature compensation circuit 6
Output to. Further, the temperature compensating circuit 6 has a temperature range of T ₃ to.
Since the temperature level t ₃ corresponding to T ₄ is output to the energization time data memory 3 as a temperature designation signal, the energization time data string γ ₃ corresponding to this is selected, and the halftone control circuit 2
Uses the color gradation designation data given along with the image data to be printed read out from the image memory 1, obtains the energization time required to obtain a predetermined print density, and instructs the thermal head 4 to print.

Similarly, when the temperature of the thermal head 4 rises to T _{4 to} T ₅ (temperature level t ₄ ), the energization time data string γ ₄
Is selected and the energizing time is obtained by the operation of the halftone control circuit 2 and the thermal head 4 is instructed.
_The same print density as in case ₃ is finally obtained.

If the energization time data string γ ₃ is used as it is even if the temperature level becomes t ₄ , printing is performed for the same gradation level as shown by the dashed line in FIG. The concentration becomes high.

[Problems to be solved by the invention]

As described above, in the conventional thermal transfer printer as described above,
Although it is considered that the print density is constant, that is, it is kept at the standard density, density correction is performed to make the print density darker or lighter than the standard density depending on the condition of the input image and user preference. Was not considered.

An object of the present invention is to provide a thermal transfer printer capable of maintaining a print density at a constant standard density by temperature compensation, and making the print density darker or lighter based on the standard density, and performing density correction according to preference. Especially.

[Means for solving problems]

The above object can be achieved by providing a density correction unit so that the user can perform the density correction.

[Action]

The density correction unit includes a density correction input unit and a density correction circuit. The density correction input unit outputs a density correction signal according to the density correction level set by the user. The concentration correction circuit corrects the temperature designation signal from the temperature compensation circuit according to the concentration correction signal from the concentration correction input section, and outputs it as a corrected temperature designation signal to the energization time data memory,
Select the required energization time data. In this manner, the temperature compensation makes it possible to maintain the print density at a constant standard density, and to perform density correction for making the print density darker or lighter using the temperature-compensated energization time data.

〔Example〕

 Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, the same components as those in FIG. 5 are designated by the same reference numerals. Besides, 8 is a density correction input unit, and 9 is a density correction circuit.

Please refer to FIG. The density correction input section 8 is a section in which the user of the printer specifies and inputs the density level of the print density as necessary. Here, as a simple example,
At each temperature level, three types of density levels can be set: darker, standard (without correction), and lighter.
Represented as +, 0,-. The density correction input section 8 corresponds to the density level set by the user, and outputs the density correction signals (+, 0,-).
Is output to the density correction circuit 9.

The concentration correction circuit 9 outputs a correction temperature designation signal for designating the energization time data sequence to be selected at that time from the temperature designation signal from the temperature compensation circuit 6 and the concentration correction signal from the concentration correction input unit 8 to the energization time data memory 3 Output to.

FIG. 2 shows a gradation reproduction diagram at a temperature level t ₃ as an example. (A) of FIG. 2 represents the gradation characteristic, and +,
Curves marked with 0 and-indicate dark, standard, and light print densities, respectively.

The curve marked with 0 is the same as the characteristic curve (solid line) in FIG. 6A in which only temperature compensation is performed.

FIG. 2 (b) shows a coloring characteristic, which is uniquely given to the temperature level t ₃ . (C) of FIG. 2 is energization time data, and as shown by the broken line, from the three types of gradation characteristics +, 0, − set in (a) and (b) the coloring characteristics at t ₃ , respectively, γ _{3 ^{+, γ 3 0, γ 3}} - is determined. Therefore, at the temperature level t ₃ , the energization time data string is γ _{3
^{+, Γ 3 0, γ 3}} - By selecting one from among a print density, respectively, it is possible to select darker, standard, either thinner.

As described above, in order to satisfy both the two functions of temperature compensation and concentration correction, at each temperature level of t ₀ to t ₇ ,
If the density levels of +, 0, and − are individually set, 8 × 3 =
Twenty-four energization time data strings are required.

However, comparing FIG. 6 (c) with FIG. 2 (c), at temperature level t ₃ , in FIG. 2 (c), γ ₃ ⁰
On the other hand, selecting γ ₃ ⁺ in FIG. 6 (c) means selecting γ ₂ corresponding to a temperature level lower than t ₃ , for example, t ₂ instead of γ _{3 which} should be originally selected. You can see that they are equivalent. The same applies to γ ₃ ⁻ and γ ₄ .

Therefore, at each temperature level, instead of individually setting the energization time data string of each concentration level, only the energization time data string of the standard concentration for temperature compensation (γ ₀ , ..., γ ₇ of 8 types) is set. In the case of + or one density correction, the temperature level given by the temperature specifying signal is converted to a lower or higher temperature level in the density correcting circuit 9 as a correction temperature specifying signal, and the energizing time is set. By sending the data to the data memory 3, both temperature compensation and density correction are possible.

As described above, the characteristic point of the present invention is that the energization time data string for temperature compensation is also used for density correction.

An operation example is shown. The temperature level is set to 8 levels of t ₀ , ..., T ₇ ,
Assuming that the concentration levels are three levels of +, 0, and-, eight kinds of energization time data strings γ ₀ , ..., γ ₇ are required. As shown in FIG. 3, the energization time data string converted into a one-step low temperature level in the case of + correction (dark) and one-step high temperature level in the case of one correction (thin) select.

Since γ ₀ , ..., γ ₇ originally do not correspond to the + correction at the temperature level t ₀ and the one correction at t _7, the energization time data strings γ ₀₀ and γ ₈ are individually set. Yes (in this case, a total of 10 data strings are required), or there is a method of substituting γ ₀ and γ ₇ for substantially no correction (in this case, 8
seed).

For example, if the temperature designation signal from the temperature compensation circuit 6 is t ₃ and the density correction signal from the density correction input unit 8 is 0, the density correction circuit 9 applies t ₃ as it is as the correction temperature designation signal to energize. The data is sent to the time data memory 3 and the energization time data string γ ₃ is selected. If the density correction signal is +, the correction temperature designation signal is converted to t ₂ , and the energization time data string γ
Select ₂ . If the density correction signal is −, the correction temperature designation signal is converted into t ₄ and the energization time data string γ ₄ is selected.

The numbers of temperature levels, density levels, and gradation levels are not limited to the numerical values shown here, and can be set arbitrarily. In the case of a color printer that uses three colors, for example, if the same correction is performed for all three colors, the overall density of the print changes, and if the correction is changed for each color, the specific color is emphasized. It becomes possible to do.

As described above, according to the present embodiment, it is possible to easily add the density correction function to the thermal transfer printer having the temperature compensation function, and accordingly, most of the required energization time data is Since it can be shared with the one for temperature compensation, there is an effect that a small amount of data is newly set.

〔The invention's effect〕

According to the present invention, since the energization time data for temperature compensation is stored in the memory in advance, it is possible to newly add a print density correction function in the thermal transfer printer which performs temperature compensation. If needed,
This has the effect of increasing the number of functions by which print density can be corrected. In addition, at this time, it is possible to minimize the number of energization time data newly required.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a gradation reproduction diagram in density correction, FIG. 3 is an explanatory view of a density correction conversion table, and FIG. 4 is an explanatory view of a temperature compensation range. Fifth
FIG. 6 is a block diagram showing a conventional thermal transfer printer, and FIG. 6 is a gradation reproduction diagram in temperature compensation. Explanation of symbols 1 ... Image memory, 2 ... Halftone control circuit, 3 ... Energization time data memory, 4 ... Thermal head, 5 ... Temperature sensor, 6 ... Temperature compensation circuit, 7 ... Print, 8 ......
Density correction input section, 9 ... Density correction circuit

Claims (1)

[Claims] 1. An image memory for storing image data, a thermal head for generating heat when energized to print, and an energization time vs. density characteristic data showing a relationship between energization time and print density in the thermal head, An energization time data memory for separately storing the temperature of the head, a temperature sensor of the thermal head, and one characteristic of energization time vs. concentration characteristic data in the energization time data memory according to the temperature of the thermal head sensed by the sensor. When a temperature compensation circuit for selecting and designating data and color gradation designating data for designating the color gradation to be printed are provided along with the image data to be printed read from the image memory, Using the energization time vs. density characteristic data selected and specified by the temperature compensation circuit, the color gradation specification data Image data read from the image memory regardless of the temperature of the thermal head. In a thermal transfer printer that prints with the thermal head at a constant color gradation specified by the adjustment specification data (this is the color gradation with standard density), the print density is darker or lighter than the standard density. According to the density correction input section in which the user sets and inputs the density correction level for density correction, and the density correction level input by the input section, according to the temperature of the thermal head, the energization time vs. density in the energization time data memory From the characteristic data, select the specified characteristic data as a reference Further comprising a density correction circuit for specifying-option, the halftone control circuit, a thermal transfer printer is characterized in that so as to obtain the required energization time by using the characteristic data selected and designated by the density correction circuit.