KR960010406B1 - Image color converting device in cvp - Google Patents

Abstract

The printer is provided for printing video signals with fine quality by finding out the temperature of a TPH(Thermal Print Head) to convert the tone according to the temperature, and there for includes a level detector for decting the level size of the luminance signal separated, an A/D converter for setting the deteced luminance signal as a base to convert for decoded analog chrominance signals into digital ones, a memory control gate array for storing the converted signals to a frame memory, a temperature data selector for converting the tone according to a loop-up table for the temperature detected from the TPH, a thermister equipped on the TPH to detect its temperature to output it into the selector.

Description

Gradation Converter of Color Video Printer

1 is a configuration diagram of a gradation converter of a conventional color video printer.

2 is a block diagram of a gradation conversion device of a color video printer of the present invention;

* Explanation of symbols for main parts of the drawings

1, 21: luminance (Y) / color (C) signal separation unit 2, 22: decoder

3, 23: analog (A) / digital (D) converter 4, 24: gate array for memory control

5, 25: memory 6, 26: tone array gate array

8, 28: thermal printer head 10, 30: digital (D) / analog (A) converter

11, 31: encoder 12, 32: mixing section

33: temperature data selector 34: lockup table

35: Dummyster

The present invention relates to gradation conversion of a color video printer. In particular, the reference value of an analog / digital converter is automatically adjusted according to an input level, the temperature of the thermal print head (TPH) is detected, and then the thermal print head applied voltage is adjusted. The present invention relates to a gradation converting device of a color video printer capable of printing a constant quality image regardless of an input signal.

As shown in FIG. 1, the gray level conversion of the conventional color video printer is composed of a luminance / calibration signal that is divided into a luminance signal Y and a color signal C from a composite image signal input through the video input terminal Vin. A decoder 2 which decodes the luminance signal and the color signal separated from the luminance / color signal separator 1 to produce R, G, and B signals, and the decoder 2 The analog (A) / digital (D) converter 3 for converting the analog signals of R, G, and B into digital signals and the digital values of the analog / digital converter 3 are sequentially stored in the frame memory 5. The thermal print head, which reads the values stored in the memory array gate array 4 and the frame memory 5 in succession, and is grayscale-converted by a look-up table (LUT) value of the ROM 7. Sends data to (TPH) and controls to receive and print the voltage of the voltage supply unit 9 The tone array gate array 6, the digital (D) / analog converter 10 for converting the digital signal of the analog / digital converter 3 back to an analog signal, the analog R of the converter 10, The encoder 11 combines G and B signals to produce luminance and chroma signals, and a mixing unit 12 that mixes the luminance signals and chroma signals from the encoder 11 and sends them to the monitor.

In the conventional circuit configured as described above, when the composite video signal is input to the video input terminal Vin, the luminance signal Y and the color signal are passed through a digital comb filter (not shown) of the luminance / color signal separator 1. The signal is separated into (C), and the separated signal is separated into R, G, and B signals through the decoder 2 and input to the analog (A) / digital (D) converter 3. Then, the memory control gate array 4 stores the digital R, G, and B values digitally converted by the predetermined reference value in the frame memory 5.

After that, the values memorized by the tone control gate array 6 are sequentially read and input to the ROM 7, and the values converted by the look-up table LUT of the ROM 7 are sent to the thermal print head TPH. The image is printed by receiving the voltage from the supply unit 9.

At this time, the R, G, B digitalized through the analog / digital converter 3 is analog-converted again through the digital / analog converter 10 and the R, G, B signals are synthesized by the encoder 11 to synthesize the luminance signal and the chromaticity signal. After mixing, the mixing unit 12 mixes the luminance signal and the chroma signal and sends them to the monitor.

However, the conventional gradation conversion device prints by analog / digital conversion as it is, so the printer prints it as it is even when the input signal is low or high, resulting in a dark or bright shape and adopting a single look up table Therefore, since the recording density changes according to the residual heat of the thermal print head (TPH), there is a problem that a high quality print image cannot be obtained.

Therefore, in order to solve the conventional problems, the present invention finely adjusts the reference voltage of the analog / digital converter according to the magnitude of the input signal, detects the temperature change of the thermal print head (TPH), and adjusts the applied voltage of the thermal print head. The gradation converting apparatus of the color video printer which adjusts the printing to an appropriate density is made. The following description will be given in detail with reference to the accompanying drawings.

2 is a configuration diagram of a gradation conversion device of a color video printer. As shown in FIG. 2, a level detection unit 36 for detecting a level of luminance and color signals separated from the luminance / calibration signal separation unit 21, The decoder 22 which receives luminance and color signals from the level detector 36 and generates R, G, and B signals, and the analog detector R, G, and B signals received through the decoder 22, respectively. The analog / digital converter 23 for converting into digital R, G, and B using the luminance signal level of?) As a reference value, and the memory for controlling the digital value converted by the converter 23 to be stored in the frame memory 25. The control gate array 24 and the control gate array 26 and the thermal print head TPH which sequentially output the digital values of R, G, and B stored in the frame memory 25 to perform gray level conversion. The dummyster 35 which is attached and detects the temperature, and this further Temperature data selection unit for inputting temperature data from the MRS 35 and selecting from a lookup table ROM 34 composed of a plurality of lookup tables (LUTs) corresponding to the temperature data. (33), the digital converter 30, the encoder 31, and the mixing unit 32.

Referring to the operation and effect of the present invention configured as described above in detail.

When the composite image signal is input to the luminance / calibration signal separator 21 through the video input terminal Vin, the luminance signal Y and the color signal are separated through a digital comb filter (not shown). The level of the separated luminance signal Y is detected by the level detecting section 36 and outputted so as to be the reference value Ref of the analog / digital converter 23.

The R, G, and B signals separated through the decoder 22 are converted into digital R, G, and B signals based on the voltage of the luminance signal detected by the level detector 36 in the analog / digital converter 23. It is stored in the frame memory 25 by the control of the control gate array 24.

In order to print the stored data, the tone control gate array 26 sequentially sends data from the frame memory 25 to the temperature data selecting section 33. Then, the temperature data selecting section 33 uses the current thermal print head ( A lookup against the current temperature in the plurality of lockup tables (LUT ₁ -LUT _n ) of the ROM 34 determined to the detected temperature value by checking the temperature of the thermal print head 28 from the dummyster 35 installed in the 28). The R, G, and B signals are gray-scaled according to the table values.

When the grayscale value is sent to the thermal print head 28 as described above, it is printed by the head 28.

As described in detail above, the present invention finds the temperature of the thermal print head irrespective of the input signal and varies the gradation conversion according to the temperature, so that printing of a good concentration is possible. There is.

Claims (2)

The level detector 36 detects the level of the luminance signal separated by the luminance / color signal separator 21, and receives the luminance and color signals from the level detector 36 to receive the color signals R, G, and B. An analog / digital converter 23 for converting the analog color signals R, G, and B produced by the decoder 22 to be generated into digital values based on the luminance signal level detected by the level detector 36 as a reference value; A memory control gate array 24 for controlling the digital value converted by the analog / digital converter 23 to be stored in the frame memory 25 and color signals R, G, and B stored in the frame memory 25. Temperature data selector 33 for converting the digital values of the < RTI ID = 0.0 >) < / RTI > to the lookup table value of lookup table ROM 34 according to the temperature detected from thermal print head 28, ) To detect its temperature And a dummyster (35) for outputting the sensed temperature to the temperature data selecting unit (33). The gradation converting apparatus of claim 1, wherein the lookup table ROM (34) has one or more lookup tables.