JPS5813075B2 - secret communication method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a secret communication system in a still image communication system that divides an image signal into a band and transmits an image signal of one screen.

2. Description of the Related Art As a method of transmitting an image signal through a narrowband transmission path, a method is known in which the image signal is stretched in time and transmitted slowly.

This method includes a method in which image signals from a television camera at a normal scanning speed are temporarily stored in a storage element and read out at a low speed, and a method in which the television camera is scanned at a low speed.

Figure 1 shows a block configuration diagram of a still image communication system that uses a method of reading out image signals once stored in a storage element at a low speed, in which 1 is a television camera, 2 is a scanning speed conversion circuit, and 3 is a scanning speed conversion circuit. 4 is a demodulator, 5 is a display tube, 6 is an image signal baseband transmission line, and 7 is a carrier transmission line.

To operate this, one frame of image signal obtained by the television camera 1 is stored in the scanning speed conversion circuit 2, and read out at a low speed to obtain the baseband signal of the narrowband image signal. is sent to the nearest carrier station through a baseband transmission line 6, modulated by a modulator 3, and transmitted over a long distance through a carrier wave transmission line 7.

On the image receiving side, the signal is demodulated by a demodulator 4 and displayed on a display tube 5 by being refreshed at a normal scanning speed in a scanning speed conversion circuit 2 in order to perform scanning speed conversion opposite to that on the image sending side.

In the conventional system configured in this way, a demodulator 4' branched off from the carrier transmission line 7, a scanning speed conversion circuit 2',
The display tube 5' and the scanning speed conversion circuit 2'' branched from the baseband transmission line 6' and the display tube 5' can be monitored by a third party, and the displayed information can easily become known, which is important. This is inconvenient for transmitting image information.

That is, such conventional still image communication systems have a drawback in that important and confidential image information cannot be easily transmitted.

The present invention provides a secret communication system in which reading by slow scanning is performed in an arbitrary line order in order to eliminate the drawbacks of the conventional example.

Hereinafter, the system of the present invention will be explained in detail with reference to the drawings.

FIG. 2 shows the system of the present invention, and the same reference numerals as in FIG. 11 is a code separation circuit, 12 is a code identification circuit, and 13 is a scan control circuit.

To explain the operation of this system, first, the horizontal scanning order is arbitrarily designated in the scan designation circuit 8, and this is inputted to the scan control circuit 13 as vertical line position information.

As the format of this vertical line position information, pulse amplitude, pulse number, etc. can be used.

The scanning control circuit 13 inputs a control signal corresponding to the line position information to the scanning speed converting circuit 2, and the scanning speed converting circuit 2 scans a corresponding line in the vertical direction based on the control signal of the line position information and scans at a low speed. An image signal is formed and input to the code insertion circuit 10.

Note that the line position is changed during the horizontal planking period.

On the other hand, the line position information is also input to the code generation circuit 9, converted into an electric signal suitable for being superimposed on the low-speed image signal, and inserted into the low-speed image signal by the code insertion circuit 10.

Next, on the image receiving side, the code sent superimposed on the low-speed image signal is separated by a code separation circuit 11, identified by a code identification circuit 12, and line position information is output.

This line position information is input to the scanning control circuit 13, which outputs a control signal corresponding to this position information to the scanning speed conversion circuit 2.

The scanning speed conversion circuit 2 scans the corresponding vertical line in response to the crawl control signal corresponding to the position information and writes the corresponding image signal.

If the above operation is performed for all lines within one screen, one frame image on the image sending side can be directly transferred to the scanning speed conversion circuit 2 on the image receiving side.

Thereafter, by scanning the image receiving side scanning speed conversion circuit 2 at a normal scanning speed, the image can be displayed on the display tube 5.

Although the method of the present invention uses a scanning speed conversion circuit to narrow the image signal, it goes without saying that the method can be applied in the same way if the camera head and scanning section of a low-speed scanning camera are operated separately.

Figure 3 shows the relationship between the scan control signal, code, and image signal in Figure 2. The signal shown in FIG. 3C is a signal obtained by inserting a pulse signal into the front porch of the image signal, and Li means the corresponding line signal.

As can be seen from FIGS. 3A and 3B, the vertical deflection is performed during the horizontal synchronization signal period based on the position information inserted into the back porch of the line before the corresponding line.

In the above description of the method of the present invention, position information is expressed using pulse amplitude, but it is obvious that it can also be applied to other formats such as pulse-coded format using binary pulses, multi-frequency combinations, etc. .

Furthermore, Fig. 4 shows the relationship between the scanning format of the image signal accumulation surface in the scanning speed conversion circuit and the vertical deflection voltage in Fig. 3A. Fig. 5 shows the important components of the present invention. This figure shows a scan designation matrix which is an embodiment of the scan designation circuit, where 14 is a matrix drive pulse input terminal, 15 is a horizontal synchronization pulse input terminal, 16 is a differentiation circuit, 17 is a rectification circuit, 18 is a switch circuit, and 19 is a 20 is a thyristor (SCR); 21 is an amplitude generating circuit; and 22 is a scanning control signal output terminal.

The operation of this embodiment will be explained.

First, each of the thyristors 20 is connected to a vertical line that specifies a scanning line, and its gate terminal is connected to an output terminal of a counting circuit 19 that specifies a scanning order.

Next, the drive pulses input from the input terminal 14 are counted by the counting circuit 19, and the count ranges from 1 to a predetermined number of scanning lines,
For example, go up to 525 and send a trigger pulse to the matrix for each count.

First, the first thyristor 20 is driven by a count of 1, and a predetermined amplitude signal as a scan designation signal is generated in the amplitude generation circuit 21 connected to the vertical line designating the 10th scan line, and the output terminal 22 is output from.

This output signal is input to the scanning speed conversion circuit 2 and also to the code generation circuit 9.
Then, low-speed scanning is performed based on this amplitude signal and the horizontal synchronization signal, and an image signal is sent out.

When one scanning line is completed, the next synchronizing signal is inputted from the input terminal 15, differentiated by the differentiating circuit 16, rectified, and the edge spike pulse is inputted to the switch circuit 18.

This switch circuit 18 uses a spike pulse to generate a voltage Ve.
is momentarily interrupted to shut off the first cyrisk 201.

Next, by counting the driving pulses, the counting circuit 19 counts 2.
is sent as a trigger pulse to the second line of the matrix, the second thyristor 202 is driven, and a predetermined scan designation signal is sent to the amplitude generating circuit 21 connected to the vertical line designating the second scan line. An amplitude signal is generated, a predetermined line in the vertical direction is scanned by the scanning speed conversion circuit 2, this position signal is inserted into the image signal, and the thyristor 202 is reset after scanning one line.

The above operations are performed for a predetermined number of scanning lines,
All scans for one screen are performed in the order specified by this matrix.

FIG. 6 is a diagram showing the signal form of each part in FIG.
Figure A shows the thyristor driving pulse, Figure 6 shows the horizontal synchronizing signal and scan control pulse signal, and Figure 6 C shows the thyristor reset pulse.

Next, FIG. 7 shows another method of the present invention, in which the same reference numerals as in FIG. 2 indicate the same things.
3 is a signal baseband transmission line for scan control, and 24 is a signal transmission line for scan control.The operation of the method of the present invention is as follows: First, the vertical line position information of the image signal produced by the scan designation circuit 8 is generated as a code. The signal is encoded in the circuit 9 and sent out via the scan control signal baseband transmission line 23 modulator 3 and the scan control signal carrier transmission line 24 separately from the image signal.

On the image receiving side, a code identification circuit 12 identifies the sent code, controls a scanning speed conversion circuit 2 using an output signal from a scanning control circuit 13, and writes a low corner image signal into this circuit.

The low-speed image signal written in the scanning speed conversion circuit 2 is read out by normal unidirectional vertical scanning, and the same image as the original image on the image sending side is displayed on the display tube.

In this system, the scanning control transmission lines are completely independent as shown in FIG. 7, but it is clear that the same effect can be achieved even if the image signal band is used.

Although each of the above-mentioned systems according to the present invention has been described assuming that the transmitted image signal is in analog form, it goes without saying that even in digital transmission, the same effect can be obtained if the signal is digitized after the operation of the present invention.

As explained above, according to the present invention, line scanning of the screen to be transmitted is performed in an arbitrarily determined order in the vertical direction, and the image signals obtained in this way are sent to the transmission path. Even if a normal low-speed image signal receiver is used to monitor the image along the route, only image signals randomized on a line-by-line basis can be obtained, and information from the monitor cannot be obtained, so confidential and important image signals cannot be transmitted. The present invention has the advantage that it cannot be watched by a third party in cases such as situations, and therefore, the present invention can provide a very effective secret communication method.

[Brief explanation of the drawing]

FIG. 1 is a basic block diagram of the narrowband still image communication system, FIG. 2 is a block diagram of the system of the present invention, and FIG. 3 shows signal waveforms of the main parts in FIG. FIG. 4 is a diagram showing the relationship between the image signal accumulation plane in the scanning speed conversion circuit of FIG. 2 and the vertical deflection voltage in FIG. 6 is a diagram showing an embodiment of the scan designation circuit, and FIG.
FIG. 7 is a diagram showing signal waveforms in each part of the diagram, and FIG. 7 is a block configuration diagram of another method of the present invention. 1...Television camera, 2...Scanning speed conversion circuit, 3...Modulator, 4...Demodulator, 5...Display tube , 6... Image signal baseband transmission line, 7... Image signal carrier transmission line, 8.
... Scanning designation circuit, 9... Code generation circuit,
10... Code insertion circuit, 11... Code separation circuit, 12... Code identification circuit, 13
... Scanning control circuit, 14 ... Matrix drive pulse input terminal, 15 ... Horizontal synchronization pulse input terminal, 16 ... Differentiation circuit, 17 ...・
... Rectifier circuit, 18... Switch circuit, 19.
... Counting circuit, 20 ... Thyristor, 21.
... Amplitude generation circuit, 22 ... Scan control signal output terminal, 23 ... Scan control signal baseband transmission path, 24 ... Scan control signal Transport transmission line.

Claims (1)

[Claims] 1. In a narrowband still image communication system that narrowbands an image signal and transmits and receives the image signal using a narrowband transmission path,
Consisting of a scan designation circuit and a scan control circuit, the image sending side scans in the order of arbitrarily specified lines and sends out an image signal, and the position information of this arbitrarily specified line is transmitted at the same timing as the image signal, and the image receiving side A secret communication method characterized in that line signals constituting one screen image are transmitted in an arbitrary order by writing a predetermined one line image signal in a line of a storage element based on the line position information. 2. The secret communication system according to claim 1, wherein the position information of the specified line is encoded and inserted into a blanking part of an image signal for transmission. 3 In a still image communication system that narrowbands the image signal and transmits and receives the image signal using a narrowband transmission path, the system is composed of a scan designation circuit and a scan control circuit, and transmits the image signal in the line order arbitrarily specified on the image sending side. The image signal is sent out by scanning, this arbitrarily specified line position information is transmitted through a line other than the image signal transmission line, and the image receiving side writes a predetermined line image signal on the line of the storage element based on the line position information. A secret communication method characterized by transmitting line signals that make up one screen image in an arbitrary order.