JPS60117979A - Picture signal transmission system - Google Patents

Abstract

PURPOSE:To avoid easy detection of picture signals and to keep satisfactorily the privacy with a system where the variation amount of a certain time difference from the picture signal, by controlling optionally said time difference. CONSTITUTION:A horizontal/vertical synchronizing signal detecting part 1 detects both horizontal and vertical synchronizing signals for some of the picture signals applied to an input terminal 5. A delay time control circuit 2 detects the order of the input horizontal synchronizing signal based on the vertical synchronizing signal. While the delay amount of a variable delay circuit 3 is previously decided in response to each horizontal synchronizing signal, and the circuit 3 is controlled to obtain the prescribed delay time. The rest picture signals supplied to the terminal 5 receive the delay from the circuit 3 and are supplied to another terminal of a differential amplification part 4 to be scrambled and delivered through a terminal 6 after the difference calculated from the picture signals supplied directly. At the reception side some of the reception signals supplied to a terminal 13 undergoes detection for both horizontal and vertical synchronizing signals through a horizontal/vertical synchronizing signal detecting part 7. Then the control exactly equal to the transmission side is given to a variable delay circuit 10 by means of said detected horizontal and vertical synchronizing signals.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an image signal transmission system, and more particularly to an image transmission system in which images are scrambled to provide sufficient secrecy.

(b) Prior Art and Problems Conventionally, various means have been studied and put into practical use for creating a disturbance in the image signal on the transmitting side of a wireless device for secret communication.

One of them is to generate a plurality of sine waves as interference waves in the baseband image signal, and this interference can be easily removed on the receiving side.

However, there is a problem in that if a third party uses a frequency analyzer or the like, the frequency of the interference wave can be easily detected and the original image can be easily removed by removing it.

(C) Purpose of the Invention The present invention has been made in view of the above-mentioned problems of the prior art.In a method of transmitting a change amount of a certain time difference from an image signal, it is possible to easily control the time difference by arbitrarily controlling it. It is an object of the present invention to provide an image transmission method in which the original image signal cannot be extracted.

(dl Structure of the Invention The object of the invention is to divide an image signal into two and transmit the difference between the first part of the image signal and the remaining part of the image signal that has passed through a delay circuit. Then, the delay time of the delay circuit is controlled and timing information indicating the control standard is transmitted, and the receiving side uses the received signal and the detected timing information to control the delay time to be the same as the delay time of the delay circuit. This is achieved by providing an image signal transmission system characterized in that an image signal is extracted from the received signal by calculating the sum of the received signal that has passed through the received signal and the received signal that has passed through the received delay circuit.

(e) Embodiment of the invention FIG. 1 is an example of a block connection diagram for carrying out the present invention, and FIG. 1(a) shows the transmitting side scramble circuit.
1 indicates a descrambling circuit on the receiving side.

In the figure, 1 and 7 are horizontal and vertical synchronization signal detection units, and 2 and 8 are horizontal and vertical synchronization signal detection units.
3 and 10 are variable delay circuits; 4 is a delay time control section; 3 and 10 are variable delay circuits;
9 is a differential amplifier section, 9 is a hybrid circuit, 12 is a video amplifier section, 11 is a high-pass filter, 5.6.13 and 1
4 each indicate a terminal.

These elements are connected as follows.

First, in FIG. 1, the terminal (11) of the variable delay circuit 3 is
is connected to terminal 6 via differential amplifier section 4, terminal (2) is connected to terminal 5 via delay time control section 2 and horizontal/vertical synchronization signal detection section 1, and terminal (3) is connected to another terminal of differential amplifier section 4. terminal and terminal 5
are connected to each other.

In FIG. 1 (bl), the terminal (1) of the variable delay circuit 10 is connected to the terminal 14 via the hybrid circuit 9 and the video amplifier 12, and the terminal (2) is connected to the terminal 14 via the high-pass filter 11. Terminal 14 and terminal (3) are connected to terminal 13 and another terminal of hybrid circuit 9 via delay time control section 8 and horizontal/vertical synchronization signal detection section 7, respectively.

Figure 2 (a) and Figure 2 (bl are respectively Figure 1 (a)
This is a diagram for explaining the operation of FIG. 1(b), and the operation of FIG.

Note that the numbers on the left side of FIG. 2 indicate the waveforms of the portions with the same numbers in FIG.

The image signal applied to the input terminal 5 (irrespective of the presence or absence of an audio signal) is divided into two parts, one part is directly applied to the differential amplification section 4, and the rest is applied to the horizontal and vertical synchronization signal detection section 1 (see Fig. 2). T
a)-■).

A horizontal/vertical synchronizing signal detection section 1 detects a horizontal synchronizing signal and a vertical synchronizing signal from this image signal using a known method. These two synchronization signals are input to the delay time control section 2,
This is to use the detected horizontal synchronization signal and vertical synchronization signal as reference timing. Incidentally, the reference timing can also be externally used without using the horizontal and vertical synchronization signals.

The delay time control circuit 2 detects the number of the input horizontal synchronizing signal with respect to the vertical synchronizing signal. On the other hand, the delay amount of the variable delay circuit 3 is determined in advance corresponding to each horizontal synchronization signal, and this correspondence table is stored in a storage device (
(not shown). Therefore, the delay time control section 2 reads the delay time corresponding to the input horizontal synchronizing signal from the storage device, and controls the variable delay circuit 3 so that the predetermined delay time is achieved.

Therefore, the remaining part of the image signal input to the terminal 5 is delayed by the above-mentioned time in the variable delay circuit 3, and is then delayed by the differential amplifier 4.
is input to another terminal (Figure 2 +8)-〇).

Here, the difference between the directly input image signal and the delayed image signal is taken, scrambled, and output from terminal 6 (
Figure 2 Ta)-■).

Next, on the receiving side, the received signal (second
The signal shown in (b)-◯) is divided into two parts, and one part is directly input to the video amplifier 12 through the hybrid circuit 9. A part of the amplified output passes through a high-pass filter 11 and is input to a variable delay circuit 10.

On the other hand, the horizontal and vertical synchronization signal detection section 7 detects the horizontal synchronization signal and the vertical synchronization signal from the rest of the input received signal, and uses these two synchronization signals to perform the processing performed by the delay time control section 2 on the transmitting side. Exactly the same control is performed on the variable delay circuit 10.

Therefore, the two variable delay circuits have exactly the same delay time for the same horizontal synchronizing signal.

The received signal that has passed through the variable delay circuit 10 controlled in this way is added to the above-mentioned received signal in the high print circuit 9, so that the scrambled received signal is descrambled and the original image signal can be extracted (see Figure 2). (bl-■).

FIG. 3 Ta) is a diagram showing an example of the configuration of a horizontal/vertical synchronizing signal detection section, in which 15, 18 and 19 are comparators, 16 is an integrating circuit, and 17 is a differentiating circuit.

FIG. 3 (bl is a diagram for explaining the operation of FIG. 3 (al), and the numbers on the left side indicate the waveforms of the portions with the same numbers in FIG. 3(a).

The horizontal/vertical synchronizing signal detection section shown in FIG. 3(al) operates as shown in FIG.
A vertical synchronizing signal is output from terminal 6, and a horizontal synchronizing signal is output from terminal 37, which are applied to terminals 54 and 53 in FIG. 5, respectively.

FIG. 4 is a diagram showing an example of the configuration of a variable delay circuit, in which 20 to 24 are coils, 30 to 34 are variable capacitance diodes, 35 is a resistor, 40 is an input terminal, 41 is an output terminal, and 42 is a resistor. indicate control bias terminals, respectively.

In the figure, the capacitance values of the variable capacitance diodes 30 to 34 are controlled by the DC control voltage applied from the delay time control section 8 to the terminal 42, and the delay time of the line between the terminals 40 and 41 is set to a required value. do.

The delay time τ of the delay circuit shown in FIG. 4 can be calculated from the following equation.

τ-(1-(1/nte・(ω/ωd))/Here, L-
C=1/ω, MC=1/ω2, ωa-(1/n
) ・ωb, L indicates the inductance of the coil, C indicates the capacitance value of the capacitor, and M indicates the mutual inductance of the coil.

FIG. 5 is a diagram without showing an example of the configuration of the delay time control section, in which 50 is a counter, 51 is a code converter, and 52 is a digital/digital converter.
Each analog converter is shown.

In the figure, a counter 50 counts the number of horizontal synchronizing signals inputted from a terminal 53, and is reset by a vertical synchronizing signal inputted from a terminal 54.

Code converter 51 to which the output from the counter 50 is input
reads out a preset and digitized delay amount corresponding to the input data from, for example, a storage device (not shown) and converts it into a digital/analog converter 52.
It converts it into an analog quantity, outputs it from terminal 55, and adds it to terminal 42 in FIG.

(f) As described in detail, according to the present invention, the image signal is scrambled by taking the difference between the image signals and varying the time amount of the difference. - Since the amount of time is set arbitrarily and the amount of time is changed depending on the time, detection of the image signal becomes difficult and confidentiality is sufficiently maintained.

[Brief explanation of the drawing]

FIG. 1 shows an example for implementing the present invention, FIG. 2 is a diagram for explaining the operation of FIG. 1, and FIG. The diagram for the 4th
The figure shows an example of the configuration of the variable delay circuit, and FIG. 5 shows an example of the configuration of the delay time control section. In the figure, 1 and 7 are horizontal and vertical synchronization signal detection sections, 2
and 8 are delay time control sections, 3 and 10 are variable delay circuits, 4 is a differential amplifier section, 9 is a hybrid circuit, 11
12 indicates a high-pass filter, and 12 indicates a video amplifier.寥 3 Diagram (a) ■ -mouth side ■- Answer 4 Diagram

Claims (1)

[Claims] In an image signal transmission method that divides an image signal into two and transmits the difference between the image signal of the first part and the image signal of the remaining part after passing through a delay circuit, the transmitting side controls the delay time of the delay circuit. At the same time, timing information indicating the control standard is transmitted, and on the receiving side, using the received signal and the detected timing information, a reception delay circuit is controlled so that the delay time is the same as the delay time of the delay circuit. An image signal transmission method characterized in that an image signal is extracted from the received signal by calculating the sum with the passed received signal.