JPS6319982A - Gradation control system for video printer - Google Patents

Abstract

PURPOSE:To easily obtain a data string of double gradation by inserting one-bit data obtained by using a comparing logical circuit into ordinary data. CONSTITUTION:A video signal is inputted from a terminal 1, processing such as amplification and shaping filter clamping is executed in an input circuit 2 and data removing a synchronizing signal are converted into digital data by an A/D converter 3. Each unit data are temporarily stored in a VRAM 6 under control by a memory control circuit 5. A repeating signal of '1' and '0' is generated from a dither signal generator 11 by using a clock generated from a clock generating circuit 7. The comparing logical circuit 12 compares a data string read out from the storage or its partially processed data string with the dither signal. The compared result is processed by a microprocessor 8 sent to an output buffer 9 and inserted into the LSB of the data read out from the VRAM 6, so that a signal of 2n gradation can be obtained from a signal of (n) gradation.

Description

[Detailed Description of the Invention] [Summary] In a video printer that stores and reproduces n-gradation video signals and prints them on predetermined thermal paper, a dither signal generator and a comparison logic circuit are installed on the output side of a signal output stage. By using the calculated result as the least significant bit of the signal,
This is a gradation control method for video printers that can display 2n gradations.

[Industrial Field of Application] The present invention relates to a control method for doubling the gradation of a conventional device when printing and recording signals on a video printer using thermal paper.

Conventionally, thermal video printers print and record data with 16 gradations, but false contours sometimes occur, so there is a demand for doubling the gradations and recording with high quality. ing.

[Prior Art] A video signal such as a TV broadcast is temporarily stored in a storage device, and then
Research has been done on making hard copies of its contents. At that time, thermal recording printers have been realized that use self-coloring thermal recording paper (Unetsu Mashitsutsu Paper) coated with or impregnated with an organic compound that develops color when heated.

At this time, the gradation of the recorded image is conventionally up to about 16\. When recording on heat-sensitive plain paper, the gradation expression may ``bleed'' and the storage stability is also poor.

Therefore, heat-sensitive synthetic paper is being researched. This is made by coating polyethylene on the surface of thermal recording paper.
The gradation reproducibility is better than that of 9 thermal paper sheets, and the storage stability is also good.

[Problems to be solved by the invention] When recording and reproducing video signals using the operating circuit of a conventional thermal video printer as is, the conventional circuit is
If the paper has gradations, false contours may occur when using heat-sensitive synthetic paper. This is exactly the phenomenon where stripes appear in the contour lines when recording a person's face.

When research into synthetic paper progressed, conventional printers had the disadvantage of not being able to be used as-is due to their circuitry.

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned drawbacks, improve the circuitry of a conventional video printer, and provide a gradation control system for a printer that enables good recording up to 2n gradations.

[Means for Solving the Problems] FIG. 1 is a diagram showing the basic configuration of the present invention. In FIG. 1, ■ is a video signal input terminal, 2 is a video signal input circuit, 3 is an A/D conversion circuit (for example, for 4 bits), 4 is a synchronization separation circuit, 5 is a memory control circuit, and 6 is a video storage device. (video random memory VRAM), 7 is a clock generation circuit, 8 is a microprocessor (MPU), 9 is an output sofa to the print head, and 10 is a video signal output terminal, that is, a signal terminal to the printer. The present invention provides a gradation control method for a video printer in which the above is connected and configured to temporarily store an n-gradation video signal in the video storage device 6, and then reproduce it again and record it in an unillustrated manner. is characterized by having the following configuration. That is, 11 is a dither signal orderer, 12 is a comparison logic circuit, and V RA
The output of M6 and the output of the dither signal generator 11 are calculated in the comparison logic circuit 12, and the output is calculated by the microprocessor 8.
Under the control of , the arithmetic operation output is inserted as the least significant bit of the output of the VRAM 6, and is used as an output for printing.

[Function] When thermal recording is performed using a video printer, a video signal is input from terminal 1, is amplified, shaped filtered, clamped, etc. in input circuit 2, and the data excluding the synchronization signal is sent to A/D conversion circuit 3. It is converted into digital data at The output of the clock generation circuit 7 is used for this operation. When converted as 4-bit data as shown in FIG. 2A, the gradation level of each unit data is as shown in FIG. 2B. These data are temporarily stored in the VRAM 6 under the control of the memory control circuit 5. The dither signal generator 11 uses the clock of the clock generation circuit 7.
Then, a comparison logic circuit 12 performs a comparison operation between the stored data string, or a partially processed data string, and the dither signal. The calculation result is processed by the microprocessor 8 and sent to the output buffer 9, and inserted into the LSB of the data read from the VRAM 6, thereby obtaining a data string as shown in FIG. It is a diagram showing levels. When an input video signal is A/D converted in this way, for example, a signal with a 4-bit configuration and 16 gradations is converted into a 5-bit, 32-level signal with the least significant bit inserted. This signal is obtained from the terminal 10 and printed by a printer (not shown).

Generally, by inserting it into the least significant bit of a digital signal, a signal with n gray levels can be converted into a signal with 2n gray levels.

At this time, as a result of experiments, it was found that an image without false contours could be obtained.

[Example: When the A/D converter 3 shown in FIG. 1 has a 4-bit configuration, the data shown in FIG. 2A is obtained, and the lowest significant bit (LSB)
For example, when the bit string is, the comparison logic circuit 12 for adjacent bits
, first perform an exclusive OR operation to obtain .

Next, the signal from the dither signal generator and the bit string are operated by an AND operation circuit in the comparison logic circuit 12 to obtain the following, which is inserted into the A/D converter bit string as a new LSB bit.

Initially using an EXOR circuit in the comparison logic circuit 12 and performing an AND operation with a dither signal are examples of the present invention, and other logic circuits other than these circuits may be used. It is also possible.

[Effects of the Invention] As described above, according to the present invention, a double gradation data string can be easily generated by inserting 1-bit data obtained using a comparison logic circuit into conventional data. can be obtained. It was confirmed that when a video signal was printed using heat-sensitive synthetic paper, no suspicious contours were generated in the image.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle configuration of the present invention, FIG. 2 is a diagram for explaining the operation of FIG. 1. 1---Video signal input terminal 2.-Video signal input terminal 3.-.A/D conversion circuit 5--Memory control circuit 6-・VRAM 8-M P U 9.--Output buffer 10 --- Video printer signal terminal 11-Dither signal generator 12--Comparison logic circuit

Claims (1)

[Claims] In a gradation control method for a video printer when an n-gradation video signal is temporarily stored in a video storage device (6) and then reproduced again to be recorded on thermal paper, a dither signal generator is used. (11), a signal comparison logic circuit (12), a video signal readout output, and the dither signal generator (11).
The output is compared with the output in the comparison logic circuit (12), and the resulting output is inserted as the least significant bit of the video signal and applied to a video printer to print a 2n gradation video signal. Printer gradation control method.