JPH0459364A - Video printer print density correction device - Google Patents

Abstract

PURPOSE:To permit the picture parts required of the same density to be printed in the same density by a method wherein the data read out from a memory part and the data based on the enumerated data obtained by a counting part are subjected to an arithmetic process and current is applied to heat-sensitive heads for a time based on the data obtained from the aforesaid arithmetic process. CONSTITUTION:The picture data fed from a memory part 3 to a density and gradient signal converting part 4 is supplied to a counting part 7, whereby the number of the picture data for each line is counted. A control part 8 conducts the arithmetic process of both the data for reference current application time at a first gradation from a memory part 6 and the data for corrected current application time based on the enumerated data obtained by the counting part 7 and produces a time strobe signal based on the data obtained through this arithmetic process. Therefore, although the temperature of a heat-sensitive head is raised by current application at the first gradation, the application voltage is reduced in a line having a high printing density by the impedance of a heating current supply circuit, etc., due to a large amount of the current applied to a gang of the heat-sensitive heads and whereas, a reduction in the application voltage is smaller in a line having a low printing density due to a small amount of the current applied to a gang of the heat-sensitive heads. Therefore, the temperatures of the heatsensitive heads are nearly equall in any of the lines, irrespective, of the number of the picture data.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video printer device, and more particularly to a device for correcting unevenness in print density.

[Prior Art] A video printer device that prints a television image or the like on paper converts the video signal of the television image into digital data, applies current based on the converted digital data to a thermal head of the printer, etc. Some devices sublimate the dye ink on the ink ribbon using the Joule heat generated by the heating resistor of the thermal head, and transfer the dye to paper, etc. (sublimation type thermal transfer printing). depends on the amount of sublimation of the dye ink, that is, the temperature of the thermal head during printing, so in order to print at the appropriate density gradation, the length of time the current is applied to the thermal head must be adjusted to the gradation. It is controlled accordingly to obtain an appropriate print density. However, if the printed image is, for example, as shown in Figure 3, the print density is high throughout the range (■).
In the range of , if there is a part A with high printing density (the range marked with ■ has the same density as this part) and a part with low printing density above and below, the density in the range of Differences may occur in the concentration of the parts. This is because the printing density of almost all pixels is high in the range of
A large heating current flows through almost all of the thermal heads arranged in a row, and the voltage applied to the thermal heads decreases due to the impedance of the current supply circuit, etc., and the amount of heat generated by the thermal heads decreases, resulting in low printing density. On the other hand, in the range ■, there are many mouth parts with low printing density, so there are few thermal heads through which a large heating current flows, and therefore the amount of current supplied to the entire thermal head group is small, and the drop in applied voltage is small. In the range A, the printing density in the area A is higher than in the range ■.To do this, for example, lower the impedance of the heating current supply circuit, etc., or divide the thermal head group into several parts and supply the current separately. It can be improved by doing things like
The former has its limitations due to the need to make the device compact.
The latter has problems such as a decrease in printing speed. Therefore, there is a need for an improvement method that does not increase the size of the apparatus and does not reduce printing time.

[Problems to be Solved by the Invention] The present invention has been made in view of the above points, and includes a method of counting the number of digital data to be read out from the storage unit and transferred to the density gradation signal conversion unit for each line; Print density correction for video printers that controls the application time of heating current to the thermal head in that line according to this count value, so that image parts that should originally have the same density are printed at the same density. It provides equipment.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a video printer that converts an analog video signal into digital data and prints it on paper or the like via a printer, and a storage unit that stores the digital data. , a density gradation signal converter that determines the gradation of the data read from the storage unit and outputs data corresponding to the number of gradations, and a thermal head or the like using a current based on the data from the density gradation signal converter. a printer unit that prints on paper or the like; a memory unit that stores data on a reference time for applying current to the printer unit; a counting unit that counts the number of data read from the storage unit; the storage unit; and a density gradation signal. conversion section,
The control section controls the printer section, memory section, and counting section, and processes the data read from the memory section and the data based on the counting at the counting section, and applies current to the thermal head for a period of time based on this data. The present invention provides a print density correction device for a video printer configured to apply .

[Function] As configured as above, in the print density correction device for a video printer according to the present invention, the number of digital data to be read out from the storage unit and transferred to the density gradation signal conversion unit is counted for each line, The application time data based on this count value and the reference application time data from the memory section are processed, and a heating current is applied to the thermal head of the printer section for a time based on the processed data, and the density gradation signal is Printing is performed based on the data from the converter.

[Embodiment] Hereinafter, an embodiment of a print density correction device for a video printer according to the present invention will be described in detail based on the drawings.

FIG. 1 is a block diagram of essential parts of an embodiment of a print density correction device for a video printer according to the present invention.

In the figure, 1 is a video signal processing unit that adjusts an input analog video signal such as a television image to a predetermined signal level. 2 is an A/D converter that converts the analog video signal from the video signal processor 1 into digital image data. 3 is a storage unit that writes the digital image data from the A/D converter 2 to a frame memory that can record the IN side using, for example, DRAM (dynamic random access memory); 4 is a density gradation unit; In the signal conversion section,
The gradation of the image data read line by line from the storage unit 3 is determined, and depending on the gradation, for example, the printer
If gradation printing is to be performed, data for each density gradation is generated and output a maximum of 64 times. Reference numeral 5 denotes a printer section, which writes the data of each density gradation from the density gradation signal converter 4 into a built-in shift register, etc., one gradation at a time, and then uses the data read out from this shift register to perform the control described later. A strobe signal (a signal for instructing the thermal head to conduct electricity) from the section 8 is subjected to AND processing, and a current based on the processed data is applied to a group of thermal heads arranged in one line, and each heating resistor is energizes to generate Joule heat. Then, this heat is applied to a heat-sensitive sublimation ink ribbon to sublimate the dye ink to develop color, and the dye is transferred to paper or the like for printing.

Reference numeral 6 denotes a memory unit that stores a program for controlling the apparatus, data on reference strobe times set for each gradation, and the like. A counting section 7 counts the number of image data transferred from the storage section 3 to the density gradation signal conversion section 4 for each line. Reference numeral 8 denotes a control unit which controls each part of the device and outputs a strobe signal for instructing the printer unit 5 to energize. The data on the corrected application time and the data on the reference application time for the first gradation aperture read from the memory section 6 are processed, and a strobe signal is output based on the processed data. The strobe signals after the second gradation opening are outputted to the memory section 6 based only on the data corresponding to each number of gradations stored.

FIG. 2 is a block diagram of essential parts of an embodiment of the thermal head of the printer section 5. As shown in FIG. In the figure, reference numeral 11 denotes a shift register, which records image data inputted from the density gradation signal converter 4 through a terminal 16 for each gradation. 12 is a latch circuit consisting of a flip-flop circuit, etc., and shift register 1
Every time data for one gradation is written to 1, the latch is opened by a latch signal applied from the control unit 8 via the terminal 17, and the data from the shift register 11 is ANDed.
Transfer to circuit 13. The AND circuit 13 performs AND processing on the transferred data and a strobe signal applied from the control section 8 via the terminal 8. I4 is the drive circuit, A
A current from the heating power source is applied to the heating resistor 15 via the terminal I9 by the signal input on the NDN0 circuit 3. Note that the shift register 11 records the image data from the terminal 16 for each gradation, for example, in 480 M proportions,
Then, the same <480 heating resistors 15 are energized through the 480 latch circuits I2, the AND circuit circuit board 3, and the drive circuit 14, respectively, and each generates Joule heat.

Next, the operation of the print density correction device for a video printer according to the present invention will be explained. Video signals such as television images are
For example, the signal is input to the video signal processing section l by operating the "memory" key, etc., the signal is adjusted to a predetermined signal level, and the signal is input to the A/D conversion section 2.
and converted into digital image data. A/D
The digital image data converted by the conversion unit 2 is stored in the storage unit 3.
, and write the image data for the IN side into a frame memory or the like. Note that this written data will be erased by inputting the next image data or operating the clear key.

The data recorded in the storage unit 3 is, for example, “Princess I-
Each line is sequentially read out in response to a command signal from the control section 8 based on the operation of the J key, etc., and inputted to the density gradation signal conversion section 4. The density gradation signal converter 4 determines the gradation of the input image data, and if the printer prints, for example, 64 gradations, the density gradation signal converter 4 determines the gradation of the input image data. (If there is a tone) Data for each density gradation is generated sequentially and transferred to the printer section 5. In the printer section 5, the data of each density gradation input from the density gradation signal converting section 4 via the terminal 16 is written into the shift register 11.

After writing the data for the first gradation, a latch signal applied from the control section 8 via the terminal 17 opens the latch of the latch circuit 12, and the data from the shift register 11 is transferred to the AND circuit 13. At this time, AND circuit 13
In this case, a strobe signal via the control section 8 (to be described later) is input from the terminal 18, and the data input via the latch circuit 12 and this strobe signal are subjected to AND processing, and the processed data is applied to the drive circuit 14. do. The drive circuit 14 applies a heating current from the terminal 19 to the heating resistor 15 in response to this data input. After the first gradation data processing is completed, data from the second gradation level up to the 64th gradation level is processed in the same way, and data from the second line onward is also processed in the same way. In this way, these processes are repeated for all lines of one image, for example, 640 lines. The Joule heat generated in the heating resistor 15 by the applied current is
For example, it is added to a heat-sensitive sublimation type ink ribbon to sublimate dye ink and transfer the dye to paper or the like for printing.

On the other hand, the image data sent from the storage section 3 to the density gradation signal conversion section 4 is also input to the counting section 7, and the counting section 7 counts the number of image data for each line. Then, the control section 8 performs arithmetic processing on the reference application time data for the first gradation from the memory section 6 and the data on the corrected application time based on the count of the counting section 7, and calculates the time based on the arithmetic processed data. Outputs a strobe signal. In other words, the counting section 7
For example, there is data for all gradations II (64 gradations) of all pixels (480 pixels) in a line, and therefore, The count value by the counting unit 7 is 480 x64=3
0,720, set the correction application time data to +40, or set each thermal head to a predetermined temperature when printing the primary gradation in which all pixels are energized for only one gradation. (The energization time is set within a range in which the dye ink on the ink ribbon hardly sublimes), so that the count value by the counting unit 7 is 480
In the case of 1 = 480, the data of the correction application time is set to O, etc.

As a result, the first gradation strobe signal output from the control unit 8 is set to 1 if the image data of that line is all black.
The data of the reference application time of the gradation, for example, 120
The corrected application time data +40 based on the count value of the counting unit 7 is added to 160, and this data is multiplied by the reference strobe time value of 12.5 microseconds (μS),
Output a 2.000 μs strobe signal (if the line is all white, calculate as above and get 120 +
O-120, so 12.5x 120 = 1.5
00 μs, etc.), the temperature of the thermal head increases due to the energization of the first gradation, but in lines with high printing density, the amount of energization to the thermal head group is large, so the applied voltage decreases due to the impedance of the heating current supply circuit, etc. On the other hand, in lines with low printing density, the amount of current supplied to the thermal head group is small, so the applied voltage decreases little. Therefore, between lines with high print density and lines with low print density, the temperature of each thermal head is relatively lower in the line with high print density. For this reason, in lines with high printing density, the energization time for the first gradation is slightly longer, thereby bringing each thermal head to a predetermined temperature. Note that when printing the second and subsequent gradations, each thermal head reaches the required temperature due to the residual heat generated by the energization for the first gradation, so there is no need to adjust the energization time.

[Effects of the Invention] As explained above, in the print density correction device for a video printer according to the present invention, the number of image data is counted for each line to be printed, and the thermal head is adjusted for that line according to the counted value. Since it controls the energization time, the temperature of each thermal head will be the same for any line regardless of the number of image data, and therefore, an image that should have the same density will be printed anywhere in the image with the density between the lines. This makes it possible to print high-quality images with little density unevenness.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a main part of an embodiment of a print density correction device for a video printer according to the present invention, and FIG. FIG. 3 is a diagram for explaining print density unevenness of a conventional video printer device. In the figure, 1 is a video signal processing circuit, 2 is an A/D conversion section, 3 is a storage section, 4 is a density gradation signal conversion section, 5 is a printer section, and 6
1 is a memory section, 7 is a counting section, 8 is a control section, 11 is a shift register, 12 is a latch circuit, 13 is an AND circuit, 14 is a drive circuit, 15 is a heating resistor, 16 is an image data input terminal, 18 is a strobe The signal input terminal 19 is a heating power supply terminal. Patent applicant Fujitsu General Ltd. Figure 1 Figure 2 Figure 3 ■ ■ Printing direction

Claims (2)

[Claims] (1) In a video printer that converts analog video signals into digital data and prints it on paper etc. via a printer,
a storage unit that stores the digital data; a density gradation signal converter that determines the gradation of the data read from the storage unit and outputs data corresponding to the number of gradations; a printer section that prints on paper or the like with a thermal head or the like using a current based on the current, a memory section that stores data on a reference time for applying current to the printer section, and a counter section that counts the number of data read from the storage section; The control unit controls the storage unit, the density gradation signal conversion unit, the printer unit, the memory unit, and the counting unit, and performs arithmetic processing on the data read from the memory unit and the data based on the count in the counting unit. , a print density correction device for a video printer, characterized in that a current is applied to the thermal head for a period of time based on this data. (2) Claim (1) characterized in that the arithmetic processing with the data based on the count of the counting section is performed only for a predetermined gradation of the data from the density gradation signal converting section.
Print density correction device for the video printer described.