KR0150162B1 - Compensating apparatus of image deterioration for sublimation type thermal transfer printer - Google Patents

Abstract

The present invention relates to a sublimation thermal transfer printer, and more particularly, to an apparatus for compensating for deterioration of image quality due to a decrease in concentration due to lack of heat storage at an initial position of a sublimation thermal transfer head. The compensation device includes means for driving the TPH in response to the output of valid image data output from the image memory, and power supply means for generating a voltage corresponding to the first and second control signals and supplying the voltage to the drive voltage of the TPH. And a detection circuit that is enabled in response to the input of a print start signal and detects valid data output from the image memory to detect a printing line to be actually printed, and generates the print start signal and responds to the detected printing line. And maintaining a first control signal to the power supply means for a predetermined printing line and then supplying a second control signal to the power supply means.

Description

Image quality deterioration compensation device of sublimation thermal transfer printer

1 is a block diagram of a thermal transfer printer according to the related art.

2 is a view showing an example of a print image according to the configuration of FIG.

Figure 3 shows a specific circuit diagram of an embodiment of the concentration reduction compensation apparatus according to the present invention.

4 is a view showing the form of the output voltage of the power supply according to the invention.

5 is a timing diagram for explaining the operation of FIG.

6 is a view showing a print image in a sublimation printer having the same configuration as in FIG.

The present invention relates to a sublimation type thermal transfer printer, and more particularly, to an apparatus for compensating for deterioration of image quality due to a decrease in concentration due to lack of heat storage at an initial position of a sublimation thermal transfer head.

The sublimation thermal transfer printer stores image data transmitted from a device such as a computer in a memory, accesses the image data stored in the memory line by line, and transmits the image data to a thermal print head (TPH). Record image data on recording paper. When the recording of one line is completed as described above, the TPH is transferred to the next print position by the operation of the mechanism servo part, and then stopped. The image of one page is printed by printing the image data on the line. Print on the recording sheet.

The TPH used in such a sublimation type thermal transfer printer converts electrical energy into energy of heat to sublimate ink on an ink ribbon, and the sublimated ink is adsorbed on the recording paper to display an image on the recording paper. At this time, the density of the image is expressed on the recording paper in proportion to the amount of ink sublimed according to the electric energy amount. In the TPH as described above, the density of the image is also affected by the temperature of the TPH itself (the temperature around the heating element or the temperature of the TPH heat sink). That is, the sublimation amount of the ink is proportional to the temperature of the TPH. Therefore, even if the same factor data is supplied to the TPH, the concentration is expressed differently according to the temperature of the ambient of the TPH. This phenomenon is severely caused by the heat storage accumulated in the heat sink for adjusting the heat generation amount of the TPH. This is because the heat dissipation plate of the TPH is initially in a low temperature state, and is thermally stored in a high temperature state by continuous heating of the heating element of the TPH. More specifically, it is as follows.

From the first line of recording until the TPH is transferred to the last line, the thermal energy generated from the heating element of the TPH raises the temperature of the TPH itself (accumulated heat of the heat sink of the TPH) due to the remaining heat used for the sublimation of the ink. Therefore, the temperature of the TPH increases gradually toward the last line, so that the density becomes higher even though image data of the same image is represented. This phenomenon of image quality deterioration is more severe when the image data enters the initial line for initial printing, and is also identified by the human eye. Therefore, when the printing is performed without compensating for this phenomenon, the image is initially printed. The density appears lighter than the line of this last printing, causing a serious problem of not being able to represent the correct original image. This deterioration in image quality is referred to as the initial concentration reduction phenomenon of Mars, and the compensation for this is called the initial concentration reduction compensation.

In the conventional compensation method, regardless of the presence or absence of image data (regardless of the size of the image to be printed), the voltage applied to the TPH is slightly higher from the first line of TPH transfer, and the number of lines transferred by the TPH increases. Therefore, a method of printing image data by reducing the voltage and applying a fixed voltage when the TPH is located on a certain line has been used. The construction of a conventional sublimation thermal transfer printer adopting such an initial concentration reduction compensation scheme is shown in FIG. 1.

1 is a block diagram of a thermal transfer printer according to the related art.

Referring to FIG. 1, the sublimation thermal transfer printer 14 receives the image data source 12 transmitted from the outside through the internal interface 16. At this time, the image data source 12 is generated and transmitted from a computer or a still video camera. The interface 16 receives the image data source 12 in response to a reception control signal and supplies it to an image memory 18 connected to an output terminal. The image memory 18 accesses the image data VD to be printed in units of vertical lines, and supplies the image data stored in units of horizontal lines to the TPH controller 20 by supplying a strobe signal ST by controlling data writing and reading. do. The TPH controller 20 converts the electrical energy of the image data VD input by the line sync 'signal LS and the print start signal (Print Start: PS) into data suitable for converting the thermal energy into thermal energy, thereby converting the TPH printer unit. (Here, the TPH printer unit means a TPH print mechanism, and includes a plurality of TPHs that are heating elements and a TPH transfer mechanism for transferring the TPH.) 26. At this time, the reception control signal of the interface 16, the data write and read control of the image memory 18, and the line synchronization signal LS and the print start signal PS input to the TPH controller 20 collectively control the sublimation thermal transfer printer 14. Output from CPU 22 The CPU 22 determines a transfer control signal for transferring the TPH in the TPH printer 26 and the number of transfer lines of the TPH in addition to the control signals, to control the output voltage of a SMPS (swtching mode power supply). Generate a signal.

When the image data source 12 is transferred from a computer, a still video camera, or the like to the circuit constructed as shown in FIG. 1, the CPU 22 controls the interface 16 and the image memory 18 to store the image data source 12 in the image memory 18. The CPU 22 then controls the image memory 18 to transfer the printing data VD of one vertical line back to the TPH controller 20. The TPH controller 20 converts the electrical energy of the input image data VD into data suitable for conversion into thermal energy and inputs the same to the TPH printer 26. The TPH in the TPH printer 26 is moved by one line in the printing direction by the control of the servo unit 24 under the control of the CPU 22 to express the received image on the recording sheet. At this time, the CPU 22 counts the number of transfer lines of the TPH in the TPH printer 26 and outputs a voltage control signal supplied to the SMPS 28 differently according to the increase in the number of transfer lines of the TPH. For example, when the printing is started, the transfer line of TPH is counted, and the voltage control signal is output so that the output voltage of SMPS 28 becomes a voltage VS (VEVS) equal to or higher than the constant voltage VE until the constant transfer line, and the number of constant transfer lines is set. If exceeded, the output voltage of SMPS 28 was again controlled to be a constant voltage VE.

However, the conventional initial concentration reduction compensation method of simply controlling the output of the SMPS 28 by counting the number of transfer lines of the TPH as described above simply transfers the TPH regardless of the presence or absence of image data to be printed due to the limited usefulness. There is a problem that is valid only when the image is full on one screen by compensating as the number of lines. That is, in the case of printing image data in which an image exists only in a portion of one screen display, a problem arises in that the initial density decrease cannot be compensated. This will be described with reference to FIG. 2.

2 is a diagram showing one embodiment of a print image according to the configuration of FIG.

When printing an image transmitted from a computer or still video camera, it is very rare to print the entire maximum printable area 32 with a border (edge) margin on the recording sheet 30 as shown in FIG. In practice, as shown in FIG. 2, it is common to print the actual image 36 with a margin even in the maximum printable area 32 (when the background is white).

However, since the conventional initial density compensation method considers only the maximum printable area 32, it is meaningless to increase the temperature around the TPH by increasing the voltage of the SMPS when image data starts to appear during actual TPH transfer. That is, the conventional initial density compensation control method controls the voltage of SMPS 28 from the first transfer line of the maximum printable area 32 to a constant line, but the image data is activated (effective heating data for driving the heating element: There is no increase in temperature of the heat sink of TPH. Therefore, when printing by the conventional method, there arises a problem that the density of the print start portion 34 of the actual image is lower than the density of the remaining image area.

It is therefore an object of the present invention to provide an apparatus for compensating for a decrease in density due to lack of heat storage at an initial position of a TPH for printing an image in a sublimation thermal transfer printer for printing an image.

Another object of the present invention is to provide an apparatus for compensating for the initial density decrease such that the density of the entirety of the printed image is uniform even when printing image data occupying only a part of the total area of the recording paper.

Still another object of the present invention is to provide an image deterioration compensation device of a sublimation type thermal transfer printer capable of preventing the phenomenon of initial concentration decrease by detecting the actual printing start line of an image and controlling the heat storage of TPH.

The present invention for achieving the above object is a first and second control signal in the image quality degradation compensation apparatus of a sublimation thermal transfer printer having a means for driving the TPH in response to the output of the effective image data output from the image memory Power supply means for generating a voltage corresponding to and supplying the driving voltage of the TPH, and valid data which is enabled in response to an input of a print start signal and detects valid data output from the image memory to detect a printing line to be actually printed. A control circuit for generating a print start signal and maintaining the first control signal to the power supply means for a predetermined printing line in response to the detected printing line, and supplying a second control signal to the power supply means. It is characterized by including.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings of the embodiments of the present invention, those having substantially the same configuration and function as those in the above-described drawings will use the same reference numerals.

3 is a detailed circuit diagram of an embodiment of the concentration reduction compensator according to the present invention, which generates voltages corresponding to the image memory 18, the TPH controller 20, the first and second control signals, SMPS 28 for supplying a driving voltage, a detection circuit 40 that is enabled in response to the input of the print start signal PS, and detects valid data output from the SMPS 28 to detect a printing line to be actually printed, and the print start signal PS And a controller 22 which maintains a first control signal in the SMPS 28 for a predetermined printing line and changes it into a second control signal in response to the detected printing line.

In the above configuration, the detection circuit 40 includes a plurality of inverters 42 to 58 which invert image data respectively output from the least significant bit line from the most significant bit of the image memory 18, and from the output terminals of the plurality of inverters 42 to 58. OR gate 72 generating a detection signal for a printing line on which the actual printing image data is located by logically combining the outputs of the plurality of latch circuits 60 to 74 and the outputs of the plurality of latch circuits 60 to 74 respectively. Consists of The controller 22 includes a voltage controller 38.

The voltage controller 38 has a function of outputting the first control signal for a predetermined time in response to the activation of the printing line detection signal PLD to be actually printed (state transitioned to logic 1), and then outputting the second control signal. . The voltage controller 38 may be implemented by a program, and may be configured using a discrete device. The embodiment of the present invention shows an example of the configuration of the control unit 22 and the voltage control unit 38 using a one-chip microprocessor.

Figure 4 is a view showing the form of the output voltage of the power supply according to the present invention, the line shown by the solid line shows the level of the voltage output from the SMPS 28 in a conventional manner, the line indicated by the dotted line is The level of the voltage output from SMPS 28 by the control according to the invention is shown. Where N is the total number of lines printed, M is the actual print (factor) time line, TL is the reprint time, and NxTL is the page print time (transfer time of the entire line of TPH).

FIG. 5 is a timing diagram for explaining the operation of FIG. 4, which illustrates the printing start signal PS and the printing line detection signal output from the OR gate 72 shown in FIG.

FIG. 6 is a view showing a print image in a sublimation printer having the configuration as shown in FIG.

Now, when an operation for printing a page on a circuit as shown in FIG. 3 is started, the controller 22 generates a printing start signal PS transitioned to logic 1 as shown in FIG. The clearing of the plurality of latch circuits 60 to 74 in the detection circuit 40 is released by the printing start signal PS as shown in FIG. 5 to be in an enabled state.

In this state, when the image data VD and the strobe signal ST to be printed from the image memory 18 are output, they are supplied to the TPH controller 20 as described above. Here, the image data VD is assumed to be R, G, and B color data, and each of the R, G, and B data is assumed to be 8 bits.

At this time, the 8-bit image data VDs output from the image memory 18 are connected to the input terminals of the inverters 42 to 58 that are individually connected from each bit line, that is, the line of the most significant bit MSB to the least significant bit line LSB. Accordingly, the outputs of the inverters 42 to 58 are distributed to the clock terminals and the data input terminals of the plurality of latch circuits 60 to 74. In this case, the inverters 42 to 58 invert the actual image data having the state of logic 0 to logic 1 to generate the complementary value. In the case of a sublimation thermal transfer printer having the logic of the effective heat generation data as 1, Please note that inverters may be omitted.

Therefore, when at least one bit of 8-bit data output from the image memory 18 is output as valid data 0 to be actually printed, one data is received from at least one latch circuit of the plurality of latch circuits 60 to 74. Is output. At this time, the OR gate 72, which logically sums the outputs of the plurality of latch circuits 60 to 74, activates the printing line detection signal PLD as logic 1 and transmits to the controller 22 that the actual line to be printed is detected. That is, the output of logic 0 data from the image memory 18 means that the transfer of the TPH has detected a printing line located at the beginning of the image area 36 to be actually printed past the margin section of FIG.

The control unit 22 supplies the SMPS 28 with a first control signal as shown in FIG. 5 in response to the printing line detection signal PLD in the logic 1 state. At this time, the SMPS 28 maintains and outputs the voltage supplied to the TPH by the first control signal at the VS level of FIG. 4, and the state of the SMPS 28 is controlled by the operation of the voltage controller 38 in the controller 22. It is maintained until it is transferred to (TS2 of FIG. 4).

When the transfer of TPH in the TPH printer unit is transferred to the position of TS, the controller 22 outputs a second control signal as shown in FIG. 5 to the SMPS 28 through the voltage controller 38. At this time, the SMPS 28 converts the output voltage to the level of VE of FIG. 4 according to the second control signal and outputs the same, thereby suppressing a temperature rise due to heat storage of the heat sink of TPH. Of course, in order to prevent deterioration of image quality due to the rise of heat storage as described above, the controller 22 controls a fan motor (not shown) by sensing a temperature around the TPH like a general-purpose printer. The output of the VE voltage as described above is maintained until the printing of one page of image data is completed.

That is, the compensating circuit according to the present invention uses the logic that the print (factor) data of the white margin is 0, and the print data (effective heat generation data) of the actual image is 1, starting from the line containing the image data including the logic 1 It can be seen that the voltage of VS is maintained for a predetermined time and then reduced to the level of VE to generate a voltage to compensate for the initial concentration drop phenomenon. By the operation as described above, density reduction compensation is performed from the first line actually printed regardless of the size and shape of the image.

As described above, the present invention is not the first line of the maximum printable area, but the density of one image in the size and shape of the image by controlling the voltage from the line on which the image data to be actually printed is carried out to compensate for the initial density. Can be made uniform.

Claims (3)

An apparatus for compensating for image quality deterioration of a sublimation thermal transfer printer having means for driving a TPH in response to an output of valid image data output from an image memory, comprising: generating a voltage corresponding to a first control signal and a second control signal to generate a TPH; A power supply means for supplying a driving voltage, a detection circuit that is enabled in response to the input of a print start signal, detects valid data output from the image memory, and detects a printing line to be actually printed, and generates the print start signal And a control unit which maintains a first control signal to the power supply unit for a predetermined printing line in response to the detected printing line and supplies a second control signal to the power supply unit. Image quality deterioration compensation device. 2. The apparatus of claim 1, wherein the detection circuit comprises a plurality of latch means for latching image data respectively output from the least significant bit line from the most significant bit of the image memory, wherein at least one of the plurality of latch means is actually And a means for generating a printing line detection signal in response to the case of image data. 2. The apparatus of claim 1, wherein the detection circuit comprises a plurality of inverters for inverting image data respectively output from the least significant bit line from the most significant bit of the image memory, and image data respectively output from output terminals of the plurality of inverters. Image quality of a sublimation thermal transfer printer characterized in that a plurality of latch circuits for latching and outputting and the output of the plurality of latch circuits are ORed together so that a printing line on which actual printed image data is located is configured as a gate for generating a detection signal. Deterioration Compensation Device.