JPH0431479B2 - - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a video image processing apparatus for obtaining high-quality color separations for printing of arbitrarily selected video images from a video signal.

[Prior art and its problems]

In recent years, with the rise of television broadcasting in the mass media and the development and spread of video technology, there has been an increasing demand for recording and mass-producing desired images from video images on printed matter.

Conventionally, when making video images into printed matter, there is a method of photographing the cathode ray tube surface of a color monitor with a still camera and making a plate of the resulting color film using a plate-making scanner. B. A method of making a color film obtained by multiple exposure through a color filter using a plate-making scanner, and furthermore, JP-A-55-
There was a method for making a plate by directly inputting the R, G, and B video signals in the 74545 as electrical signals to a plate making scanner.

However, with the method of photographing on a color monitor, the color tone and gradation of the video image cannot be satisfactorily reproduced due to the mismatch between the spectral radiation characteristics and density range of the R, G, and B phosphors of the cathode ray tube and the spectral sensitivity and density range of the color film. , R, G, and B phosphor dots and the halftone dots of the printed matter interfere with each other, causing moiré. Furthermore, even with the method of multiple exposure on a black and white monitor, the running lines of the video image and the halftone dots of the printed matter interfere with each other, causing moiré, and the addition of the process of creating a color film and then platemaking degrades the resolution of the video image. There were flaws.

In the method of directly inputting the R, G, and B video signals to a plate-making scanner as described in JP-A-55-74545, the color tone, gradation, and resolution representing the video signal are reproduced almost as they are, but the original image quality of the video image is not suitable for printing. It is often not sufficient as a manuscript.

The reason for this is that the video signal follows the standard system for color television broadcasting, and among several standard systems, Japan has adopted NTSC, but the NCSC video signal is similar to the earlier black-and-white television broadcasting system. This is due to the fact that the amount of information in the image is compressed, taking into consideration the compatibility of the images. The image information compression method utilizes the characteristics of the human eye when it comes to moving images, so even if the image quality appears to be sufficient for a moving image on a monitor TV, the image quality may not be satisfactory for printed matter (i.e., a still image) from a TV image. No.
Further, processing performed on video signals by various devices to make the video images more visible to the human eye as a moving image, noise added in the video signal recording and transmission system, etc. are factors that deteriorate the image quality of still images.

One of the causes of this deterioration is subcarrier leakage. To transmit the color components of a television signal, the color signal is superimposed on a black and white signal. That is, within the 42MHz luminance signal band, the color subcarrier is selected at 3.58MHz, and the signal and Q signal are modulated in two phases at right angles and transmitted. The reason why we chose the frequency of 3.58 MHz to create the color subcarrier is because the color subcarrier is transmitted over the luminance signal, so we can minimize the interference of both signals and the occurrence of interference fringes on the screen. be. Looking at the energy distribution of the luminance signal, the horizontal scanning frequency is 15.75K.
3M, which is mostly distributed around frequencies that are integral multiples of Hz
Above Hz, the energy becomes weaker.
Therefore, it is sufficient to transmit the subcarrier signal by inserting it into a portion where the luminance signal energy distribution is small. Even so, both signals still interfere with each other, causing dotted brightness and darkness in the raster. Therefore, by setting the relationship between the horizontal scanning frequency fh and the color subcarrier s as s = (h/2) × 455, the points where brightness and darkness are created will shift for each raster scanning line, and the scanner of the next frame will The points of light and darkness are reversed.

As a result, when a television signal is viewed through a CRT tube, it can be seen that the CRT tube itself is emitting light.
Since the synchronization of brightness and darkness is minute, the brightness and darkness points are visually canceled out and become less noticeable.

However, in printed matter (i.e., still images) from television images, because the image is expressed using reflected light and the image is printed at a large magnification, each line has a clear cycle of brightness and darkness, resulting in checkerboard-like noise. appears and the print quality becomes insufficient.

<Object of the Invention> The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to have a means for removing checkered pattern noise caused by subcarrier leakage in printed matter created from video images. An object of the present invention is to provide a video image processing device having the following characteristics.

<Summary of the Invention> The present invention provides a video image processing device for obtaining a high-quality color separation plate for printing with respect to a video image arbitrarily selected from a video signal, in which the video signal is A/D converted, The stored image data is converted into a digital signal and stored in a frame memory, etc., and the approximate image data is Fourier-transformed to remove checkered noise caused by subcarrier leakage. This video plate making apparatus comprises an output means for performing inverse Fourier transform after adjusting the above, color converting the image data after the above calculation into separation plate creation data for printing, and outputting the color converted data.

<Embodiment of the Invention> An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a system configuration diagram of the present invention. There are a TV tuner 1, a VTR 2, etc. as video signal sources representing video images.
After recording an image on a frame, etc., a video signal of a video image for plate making is input to the frame buffer section 4. The video signal is A/D in the frame buffer section 4.
The converted video image information becomes digital data and is stored in the frame buffer 3. The computer section 5 performs digital image processing on the video image stored in the frame buffer section 4 to improve the image quality of the video image for printing, and outputs the processed video image information to the prepress scanner 6 to color the video image. Get the disassembled version.

FIG. 1 is a block diagram of a portion that performs image processing in a video image processing apparatus according to the present invention. The video signal generated from the video signal source is converted into an RGB video signal and a synchronization signal by a decoder (not shown)
After being converted by, for example, the data is input to the frame buffer section 4. In the frame buffer unit 4, the RGB video signal is converted into digital data by an A/D converter 10 and stored in a frame memory 12. The video image data stored in the frame memory 12 is transferred to the interfaces 14 and 2 of the frame buffer section 4 and computer section 5, respectively.
3 to the RAM 21 of the computer unit 5 and subjected to image processing by the CPU 20. The processed video image data is stored in the frame memory 12 from the RAM 21 via the interfaces 23 and 14 again, and the state of the processed video image is stored in the D/A converter (not shown) connected to the frame memory 12. This can be confirmed as an RGB video signal on a color monitor (not shown). It is also possible to perform interactive processing using the digitizer 16 while viewing the color monitor. Next, the means for removing checkered pattern noise will be explained in more detail.

As described above, image deterioration due to subcarrier leakage appears in a checkered pattern. As shown in Figure 5, the signal f(x) of any one line in the horizontal direction of the image is the original image signal g(x) plus a noise signal h(x) due to subcarrier leakage. The original image signal is g(x)=f(x)-h(x)-(1).

Checkered noise signal h due to subcarrier leakage
Since (x) is a regular repetition of light and dark, using trigonometric functions, if A is the amplitude and α is the phase, then g(x) = f(x) - A x { cos (x + α) } −(2). Utilizing this, the noise signal h(x) is subtracted from any one-line signal f(x) in the form of a trigonometric function to obtain the original signal g(x).

Furthermore, there is a means for removing frequency components including the noise signal h(x) in the frequency domain using Fourier transform.

The present invention will be mainly described with reference to checkerboard noise removal means using Fourier transform. In this method, in order to obtain the original image signal g(x), the signal f(x) of any one line is Fourier transformed, and the frequency components including the checkered noise signal h(x) are deleted in the frequency domain. After that, the original image g(x) is obtained by performing inverse Fourier transform. By repeating this for multiple lines, checkerboard noise is removed from the entire image. FIG. 4 is a waveform diagram for explaining the means for removing the checkered noise.

FIG. 4A shows an arbitrary line of signal f(x) containing checkerboard noise. FIG. 4B shows the frequency distribution of F(f) after Fourier transform of f(x).

In Figure 4C, there are three types of parameters: fc, f _w , D
Applying a trap with a certain frequency to a specific frequency range,
A waveform diagram is shown for removing checkered noise.

The method of applying the trap described above, in which F(f) is a Fourier-transformed arbitrary line signal f(x), is as follows.
It is shown by the calculation formula shown in equation (3).

In equation (3), D, fc, and _fw need to be set as parameters. A desired signal can be obtained by subjecting F'(f) obtained here to inverse Fourier transform.

FIG. 3 shows a flowchart for performing the image processing. For the image to be processed, select the parameters fc and _fw in equation (3) in step S1, then specify the portion and several lines to be processed, and in step S2, select the parameters fc and fw in equation (3). Apply processing. Next, in step S3, the image stored in the frame memory before processing is outputted on the monitor in real time interspersed with the processed image, and a comparison is made in step S4 to see if it is appropriate. If it is determined that it is appropriate after the comparison, the above process is applied to the entire surface in step S5, and if it is inappropriate, the process returns to step S1 and the parameters are selected again.

Here, better processing can be obtained by setting parameters interactively with the monitor. As a result of the above processing, the image data has checkerboard noise removed.

In this embodiment, a plate-making scanner is used as the output means, but this may be any other plate-making device such as a cylinder engraving machine. Although the video signal is input to the frame buffer through a 1-inch VTR, any other device may be used as long as it is capable of outputting a video signal.

The separated printing plates produced according to the present invention are processed into printed matter through conventional practical plate processes and printing processes.

<Effects of the Invention> As described above, according to the present invention, data representing a video image can be directly converted into separation plate creation data for printing without using a hard copy as an intermediate medium such as a color film or a color print. This not only prevents image deterioration, but also
By removing the checkered noise caused by subcarrier leakage, the present invention becomes an extremely superior video image processing device that can obtain higher quality printed matter.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, FIG. 2 is an explanatory diagram showing the system mechanism of an embodiment of the video image processing device of the present invention, and FIG. 1 shows the image processing in the system of the present invention. Fig. 3 is a flowchart of processing for removing checkered pattern noise from a video image, and Fig. 4 shows a process of Fourier transforming a video signal and extracting frequency components containing noise signals in the frequency domain. This is a waveform diagram for explanation, and FIG. 5 is a waveform diagram showing the principle of checkerboard pattern noise generation. 4...Frame buffer, 5...Mini computer, 10...A/D converter, 12...Frame memory, 14, 23...Interface,
16...Digitizer, 20...CPU, 24...
Terminal.

Claims (1)

[Claims] 1. A video image processing device for creating still images such as separated plates for printing from video images without using intermediate media such as films,
A/D conversion means for converting an NTSC video signal into a digital signal; a storage means for storing the converted signal; and a Fourier transform for the stored image data, and a specific frequency of the Fourier transformed image data. 1. A video image processing apparatus, comprising: a means for removing noise caused by subcarrier leakage by adjusting a frequency range and performing an inverse Fourier transform on the image data after the adjustment; 2. The video image processing apparatus according to claim 1, wherein the adjustment of the specific frequency range includes parameter setting means for setting parameters in an interactive manner.