JPS6031424B2 - Color facsimile signal transmission system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color facsimile signal transmission system for documents having patterns such as characters in two colors such as black and red.

A method for efficiently transmitting black and white two-color facsimile signals is to cyclically allocate N carrier waves with a certain phase difference each time a black signal appears, and create a signal in which the carrier waves are amplitude-modulated. The transmission method is well known.

In recent years, there has been an increasing demand for technology to easily and efficiently transmit office documents containing red and black characters, such as corrections written in red ink and red stamps. As a transmission method for documents containing such color information, a method in which amplitude information is increased and transmitted by multi-value conversion can be applied. However, this method has the disadvantage that it is easily affected by level fluctuations and noise in the transmission path, and generally requires a means for converting multilevel information, making the reception and reproduction process complicated. Furthermore, there is a drawback that compatibility with transmission systems that do not perform such special conversion is poor. An object of the present invention is to provide a color facsimile signal transmission system that can transmit facsimile signals for documents containing two colors such as red and black with a simple configuration, and that can also be used as a modem for black and white binary facsimile signals. It's about doing.

According to this invention, when a color signal of the same color is generated, a carrier wave with a fixed phase shift is amplitude-modulated by the color signal every time the color signal is generated, and when a color signal of a different color is generated, the color signal immediately before it is modulated. Amplitude modulates and transmits a carrier wave with the same phase as .

On the receiving side, the phase of the received signal carrier wave is detected, the color signal is separated and identified, and recording density information is obtained from the amplitude value. For example, as shown in FIG. 1, black signals and red signals as shown in FIG. 2 A and B are supplied from input terminals 11 and 12 by a facsimile document, separated by a color filter, etc., to an image signal circuit 13. They are synthesized as shown in Figure 2C.

The synthesized signal amplitude modulates the carrier wave by the phase selection circuit 15 in the amplitude modulation circuit 14. One terminal 1
The color signals 1 and 12 are input to the phase control circuit 16, and the flip-flop 17 is reset by the black signal and set by the red signal, for example.

Therefore, the output of the flip-flop 17 becomes as shown in FIG. 2D, and its state is transferred to the D-type flip-flop 18 by the output of the image signal circuit 13, and after a delay of one signal, the output becomes as shown in FIG. 2E. It changes like this. The outputs of these flip-flops 17 and 18 are supplied to a match circuit 19, which outputs a high level when both inputs match, and a low level when they do not match, and the output is as shown in FIG. 2F. When the color signal repeats the same color, a high level signal is obtained, and when it changes from a black signal to a red signal or vice versa, a low level signal is obtained. The output of the matching circuit 19 is supplied to the enable terminal E of the flip-flop 21, and when the signal is at a high level, the output of the image signal circuit 13 is supplied to the enable terminal E of the flip-flop 21.
Each time the signal is applied to the clock terminal 1, the state of the output of the flip-flop 21 is inverted, and the output becomes as shown in FIG. 2G.

When this world power is applied to the phase selection circuit 15 and the output of the flip-flop 21 is at a high level, the carrier wave generation circuit 22
When the 0-phase carrier wave output from the 0-phase carrier wave is at a low level, the n-phase carrier wave is selected and supplied to the amplitude modulator 14. Therefore, in the output of the amplitude modulator 14, as shown in FIG. 2, the phase of the carrier wave is inverted every time a color signal of the same color appears, but when the color signals differ, the phase of the previous carrier wave is output. Note that the 0-phase carrier wave is shown in FIG. Amplitude modulator 14
The output of is transmitted to the transmission line 23.

On the receiving side, the received signal from the terminal 24 is supplied to an initial signal detection circuit 25 and a reception interface circuit 26. In the interference circuit 26, unnecessary waves are removed by a furnace wave generator, and the amplitude is made constant by automatic gain control, and the signal is supplied to a synchronous detection circuit 27 and a carrier wave regeneration circuit 28. The carrier wave regeneration circuit 28 regenerates the 0-phase carrier wave, thereby controlling the synchronous detection circuit 27. Therefore, the output is a positive pulse when the received carrier wave is 0 phase, as shown in Figure 2 J.
Each becomes a negative pulse in the n phase. The output is sent to a distributor 31 through a full-wave rectifier circuit 29. On the other hand, the output of the initial signal detection circuit 25 resets the flip-flop 32.

Further, the output of the synchronous detection circuit 27 is separated into a positive pulse and a negative pulse by a positive/negative separation circuit 33, and the flip-flop 34 is set by the positive pulse and reset by the negative pulse. The output of the flip-flop 34 is as shown in FIG. 2K, and the output is reduced to a D-type flip-flop by the output of the full-wave rectifier circuit 29, and an output delayed by one signal is obtained as shown in FIG. 2L. . Matching of the outputs of these flip-flops 34 and 35 is detected, and when they match, a low level is output as shown in FIG. 2M, and when they do not match, a high level is output. Its output is flip-flop 3
It is supplied to the enable terminal EN of No. 2. Therefore, when the enable terminal is at a high level, the state is reversed every time a pulse from the full-wave rectifier circuit 29 is generated in the flip-flop 32, and the output shown in FIG. 20 is obtained. This controls the distributor 31 so that the output of the full-wave rectifier circuit 29 is switched to the output terminal 37 at the low level and to the output terminal 38 at the high level. In this way, a black signal is reproduced at the terminal 37 and a red signal is reproduced at the terminal 38. In the embodiments described above, there are two types of carrier wave phases (0 phase and shore phase).
By providing the phase selection circuit 15 shown in the figure with a function of shifting the phase at regular intervals, it is possible to transmit data with many types of phases.

Further, by assigning various types of phases to color signals, it becomes possible to transmit various types of color signals, although the transmission efficiency does not improve. Furthermore, in this invention, since the amplitude value includes the density information of the color signal, halftones can also be transmitted. In addition, in the present invention, when the same color continues, the phase of the carrier wave is sequentially changed by a constant phase difference, so that transmission efficiency can be improved. As explained above, the color facsimile signal transmission system according to the present invention does not require a special modulator/demodulator for color signals, but can be easily implemented by simply adding some additional circuits to a monochrome binary AM-PM modulator/demodulator. It has the advantage of being able to configure a modem.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a color facsimile signal transmission system according to the present invention, and FIG. 2 is a waveform diagram for explaining its operation. 11, 12: Color signal input terminal, 13: Image signal circuit, 14
: amplitude modulator, 15: phase selection circuit, I6: phase control circuit, 22: carrier wave generation circuit, 23: transmission line, 25: initial signal detection circuit, 26: reception interference circuit, 27
: Synchronous detection circuit, 28: Carrier regeneration circuit, 29: Full wave rectifier circuit, 31: Distributor, 33: Positive/negative separation circuit, 37, 3
8: Output terminal. Figure 1 Figure 2

Claims (1)

[Claims] 1 In a color facsimile signal transmission system for originals with two-color characters, etc., for consecutive signals of the same color, a carrier wave with a certain phase difference is amplitude-modulated every time the signal appears, and the color signal is transmitted immediately before the same color signal. If the color differs from the previous color signal, a carrier wave having the same phase as the previous color signal is amplitude-modulated and transmitted, and the receiving side detects the phase of the received signal, separates and identifies the color signal, and records the amplitude value. A color facsimile signal transmission method characterized by obtaining density information.