JPH0332935B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to an image signal transmission system in which an interference signal is superimposed on an image signal to provide sufficient secrecy.

(2) Background of the technology In recent years, it has become common for video conferences and the like to use wireless technology to transmit not only audio signals but also image signals. However, when transmitting information that is desired to be kept secret, such as confidential information from a certain company, it is necessary to prevent others from reproducing the image signal from the received signal.

(3) Prior Art and Problems Various methods have been studied and are being put into practical use that create disturbances in conventional image signals on the wireless transmitting side for secret communication. One method is to generate several interference waves on the baseband image signal, and a simple sine wave without modulation is used as the interference waves. In this case, on the predetermined receiving side, processing can be easily performed by simply using a band elimination filter that removes the frequency of the interference wave. However, if a third party uses a frequency analyzer, he or she can easily detect the frequency of the interference waves, so secrecy cannot be maintained unless the frequency is changed from time to time. Another method is to utilize the properties of the image signal and perform waveform processing on the image signal itself, but since the audio is in a different band from the image signal, it is possible to interfere with the audio at the same time. The drawback was that it was too complicated to send.

(4) Object of the Invention The object of the present invention is to improve the above-mentioned drawbacks, and to provide an image processing method that easily performs signal processing in the baseband band of an image signal, and in which superimposed interference signals are difficult to decipher from the outside. Our goal is to provide the following.

(5) Structure of the Invention According to the present invention, the above object is to superimpose an interfering signal on an image signal and transmitting it on the transmitting side, and to reproduce the interfering signal on the receiving side and remove the interfering signal from the received signal. In an image signal transmission method for obtaining an original image signal, the transmitting side superimposes a digital signal that repeats a predetermined pattern as an interference signal on the image signal, and also superimposes the fundamental frequency component of the clock of the digital signal and the repetition period of the digital signal. The synchronization signal shown in FIG.
A subcarrier created by multiplying by N is inserted and transmitted, and the receiving side extracts the clock signal from the received signal and creates a subcarrier by multiplying the frequency by M/N from the clock signal. The synchronization signal is extracted from the received signal using the subcarrier, the clock signal and the synchronization signal are used to generate a digital signal having the same pattern as the transmitting side, and the digital signal is superimposed on the received signal with the opposite polarity. This is achieved by providing an image signal transmission method characterized by the following.

(6) Examples of the invention Examples of the present invention will be described below.

The basic operation of the present invention is to superimpose a predetermined digital pattern on an image signal and insert its clock signal and synchronization signal, and on the receiving side, extract the clock signal and synchronization signal, generate the digital pattern, and receive the image signal. Remove from signal.

FIG. 1 is a block diagram of the transmitting side in the basic operation of the present invention. In the figure, 1 is a digital signal pattern generator, 2 is a band pass filter, and 3 is a block diagram of the transmitting side.
is a first synthesizer, 4 is a band-removal filter, 5 is a second synthesizer, 6 is a modulator, 7 is a third synthesizer, VD is an image signal, CLK is a clock signal, SYC is a synchronization signal,
SCR indicates a synchronization signal subcarrier, and BB indicates a baseband signal.

In FIG. 1, a digital signal pattern generator 1 receives a clock signal CLK and a synchronization signal SYC, generates a digital signal pattern with CLK as a bit period, and SYC as a pattern period, and outputs it to a first synthesizer 3. The bandpass filter 2 limits the band of CLK and outputs it to the first synthesizer 3. A first combiner 3 combines the output with the output of the digital signal pattern generator 1 and outputs the result to a band-elimination filter 4 . The band-elimination filter 4 inputs the output, reduces the spectrum of the frequency in which synchronization information will be inserted later, and outputs it to the second synthesizer 5. The second synthesizer synthesizes the output and the image signal VD and outputs it to the third synthesizer 7. Modulator 6 uses the synchronization signal SYC to convert the subcarrier
The SCR is modulated and output to the third synthesizer 7. The third combiner 7 combines the output with the output of the second combiner 5 and outputs it as a baseband signal BB. The baseband signal is then modulated onto the main carrier and transmitted.

FIG. 2 is a diagram showing the point spectrum distribution of FIGS. 1 a to c, in which Y is a luminance signal, C is a color signal, VCE is an audio signal, CLK is a clock signal,
SCR indicates the frequency of the synchronization signal subcarrier, and SYC indicates the subcarrier modulated by the synchronization signal.

The image signal VD inputted in Fig. 1a usually includes a luminance signal Y, a color signal C, and an audio signal as shown in Fig. 2a.
VCE is synthesized.

The signal in Figure 1b is as shown in Figure 2,
The spectrum due to the digital signal pattern is widely distributed, and the clock signal CLK is synthesized.
The spectral power near the frequency SCR where synchronization information is later inserted is reduced. For this reason,
It is becoming easier to extract synchronization information on the receiving side.

As shown in FIG. 2c, the baseband signal BB outputted in FIG. 1c has the spectrum of the digital signal pattern superimposed on the spectrum of the image signal, and synchronization information is further inserted. Since the digital signal pattern is superimposed, it is extremely difficult for someone who does not know the digital signal pattern to extract the original image information even if the baseband signal is received and demodulated.

FIG. 3 is a block configuration diagram of the receiving side related to FIG. 1, in which 1 is a digital signal pattern generator, 8 is a clock signal extraction circuit, 9 is a subcarrier extraction circuit, and 10 is a synchronization signal extraction circuit. , 11
12 is a polarity inversion circuit, 12 is a fourth synthesizer, BB is a baseband signal, VD is an image signal, CLK is a clock signal, SCY is a synchronization signal, and SCR is a subcarrier.

In FIG. 3, a clock signal extraction circuit 8 extracts a clock signal from the received and demodulated baseband signal BB and outputs it to the digital signal pattern generator 1. The subcarrier extraction circuit 9 extracts the subcarrier SCR from the baseband signal, and the synchronous signal extraction circuit 1 extracts the subcarrier SCR from the baseband signal.
Output to 0. A synchronization signal extraction circuit 10 extracts a synchronization signal SYC from BB using the subcarrier SCR and outputs it to the digital signal pattern generator 1. The digital signal pattern generator 1 generates the same digital signal pattern from CLK and SYC as that on the transmitting side and outputs it to the polarity inversion circuit 11. Polarity reversal circuit 1
1 inverts the polarity of the digital signal pattern and outputs it to the fourth synthesizer 12. The fourth synthesizer 12 synthesizes the signal and the baseband signal, removes the spectrum due to the digital signal pattern from the baseband signal, and extracts the original image signal VD. Although the clock signal and synchronization information still remain in the original image signal, by removing the frequency of these signals from the video signal and audio signal bands as shown in FIG. 2, there will be no effect.

The fourth part is a block configuration diagram of the transmitting side according to the embodiment of the present invention, in which 1 is a digital signal pattern generator, 2 is a band pass filter, and 3 is a first filter.
a combiner; 4 is a band-reject filter; 5 is a second combiner;
6 is a modulator, 7 is a third combiner, 13 is an M/N multiplier, VD is an image signal, CLK is a clock signal, SYC
indicates a synchronization signal, and BB indicates a baseband signal.

In FIG. 4, an M/N multiplier 13 multiplies the frequency of the clock signal CLK by M/N to create a synchronization signal subcarrier SCR. This eliminates the need for an oscillator for SCR. At this time, synchronization signal SYC
The phase of the synchronization signal subcarrier is synchronized with SYC. This is to align the phases of subcarriers between transmitting and receiving.

The rest is the same as the basic configuration.

FIG. 5 is a block configuration diagram of the receiving side related to FIG. 4, in which 1 is a digital signal pattern generator, 8 is a clock signal extraction circuit, and 10
11 is a synchronous signal extraction circuit, 11 is a polarity inversion circuit, and 12 is a synchronous signal extraction circuit.
13 is a fourth synthesizer, 13 is an M/N multiplier, BB is a baseband signal, CLK is a clock signal, SCR is a subcarrier, SYC is a synchronization signal, and VD is an image signal.

In FIG. 5, the M/N multiplier 13 converts the frequency by M/N from the clock signal CLK extracted from the baseband signal BB by the clock signal extraction circuit 8.
The subcarrier SCR for synchronization signal is created by multiplying it.
At this time, a reset is applied using the synchronization signal SYC,
Synchronize the phase of the subcarrier with the synchronization signal to align the phase with the carrier on the transmitting side. The subcarrier in the baseband signal is modulated by the synchronization signal,
Because CLK is not modulated, subcarriers created from CLK are more stable than subcarriers extracted from the baseband signal.

The rest is the same as the basic configuration.

Next, a third embodiment of the present invention will be described.

(7) Effects of the Invention According to the present invention, as described above, a digital signal is superimposed on an image signal as an interfering signal, and the image signal is transmitted in a confidential manner, so that it is effective as a secret communication. Furthermore, it has the effect of simultaneously concealing the voice. It also has the effect that the device on the receiving side does not become too complicated.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram of the transmitting side according to the first embodiment of the present invention, FIG. 2 is a spectrum distribution diagram at each point a to c in FIG. 1, and FIG. 3 is a receiving side related to FIG. 1. FIG. 4 is a block diagram of the transmitting side according to an embodiment of the present invention, and FIG. 5 is a block diagram of the receiving side related to FIG. 4. In the drawing, 1 is a digital signal pattern generator, 2 is a bandpass filter, 3 is a first synthesizer, and 4 is a digital signal pattern generator.
5 is a band-elimination filter, 5 is a second synthesizer, 6 is a modulator, 7 is a third synthesizer, 8 is a clock extraction circuit, 9
is a subcarrier extraction circuit, 10 is a synchronization signal extraction circuit, 1
1 is a polarity inversion circuit, 12 is a fourth synthesizer, 13 is an M/N multiplier, VD is an image signal, CLK is a clock signal, SCR is a subcarrier, SYC is a synchronization signal, and BB is a baseband signal.

Claims (1)

[Claims] 1. Image signal concealment in which a transmitting side superimposes an interference signal on an image signal and transmits the image signal, and a receiving side reproduces the interference signal and removes the interference signal from the received signal to obtain an original image signal. In this method, the transmitting side superimposes a digital signal that repeats a predetermined pattern as an interference signal on the image signal, and further superimposes the clock signal by using the fundamental frequency component of the clock of the digital signal and a synchronization signal indicating the repetition period of the digital signal. A signal modulated with a subcarrier created by multiplying the frequency by M/N is inserted and transmitted, and on the receiving side, the clock signal is extracted from the received signal, and the frequency is multiplied by M/N from the clock signal. A subcarrier is created using the subcarrier, a synchronization signal is extracted from the received signal using the subcarrier, a digital signal having the same pattern as that on the transmitting side is generated using the clock signal and the synchronization signal, and the digital signal is inverted to the received signal. An image signal transmission method characterized by adding polarized signals and removing superimposed digital signals.