JPS632398B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a demodulation method, and more particularly to a demodulation method suitable for use in a white block skip method in analog facsimile and the like.

(2) Background of the technology The white block skip method is known as one of the compression methods for data transmitted in facsimile. When transmitting image data to a destination, data in an area that is clearly composed of only white is simply notified using a control code that it is white, but the data is compressed without being transmitted as image data. This is the method that we are trying to achieve. This is done by dividing an area corresponding to one scanning line length into n small areas (blocks) as a pre-arranged agreement during transmission and reception. The image signal is not included in the image signal data slot to be transmitted, and blocks that are always black are assembled into the slot and transmitted, and the block is usually displayed at the beginning of the slot of the image signal to be transmitted. A code slot is added to this part, and a data slot is added with an index indicating which area's image signal was sent (in other words, it was removed because it is white), and the image data is sent one scanning line at a time. On the receiving side, the transmitted data is compressed by performing demodulation that inserts white blocks between the received image data corresponding to the received blocks according to the table of contents.

Therefore, a data slot for one scanning line used in this method is composed of a code data part and an image data part, and in the received data slot, the code signal and the image signal appear alternately in chronological order. This is distributed from the beginning of the data by synchronous time division (division based on timing) and used as individual signals for demodulation.

In the white block skip method of analog facsimile, if the signal in the code section, which is the table of contents section, is disturbed by billing pulses or noise, malfunctions or significant deterioration in image quality may occur, making it impossible to use the white block system. Therefore, there is a need for a demodulation method that can apply the white block skip method without being affected by noise or the like.

(3) Prior art and problems FIG. 1A is a block diagram of a conventional demodulation system. In FIG. 1A, a demodulator 1 converts the input modulated signal as shown in FIG. After demodulating into a value signal, it is converted into a binary signal by a ternary/binary conversion circuit 2, which is compared with a reference level by a comparator circuit 3, and converted into a digital signal, which is recorded as an image signal and converted into an image as a code signal. It was sent to a signal processing circuit and used as an image signal processing signal.

However, in the method shown in FIG. 1A, if the demodulated signal contains many noise components as shown in FIG.
With this method, the white block skip method of analog facsimile may not be available.

(4) Purpose of the Invention In view of the above-mentioned drawbacks of the conventional art, it is an object of the present invention to provide a demodulation method to which the white block skip method of analog facsimile can be applied and which does not cause malfunctions or deterioration of image quality.

(5) Structure of the Invention According to the present invention, the above object is to receive one data slot's worth of transmission data, which is composed of one scanning line's worth of code data and image data, transmitted by the transmitting side, and to generate a demodulated ternary signal. The code signal forming circuit forming the code signal extraction side includes a filter circuit for removing noise components of the input ternary signal, and a filter circuit for full-wave rectification of the output of the filter circuit. 1 full-wave rectifier circuit, and a first comparison circuit that compares the output of the first full-wave rectifier circuit with a first reference voltage to generate a code signal, and forms the image signal extraction side. The image signal forming circuit includes a second full-wave rectifier circuit that full-wave rectifies the demodulated ternary signal, and a second full-wave rectifier circuit that generates an image signal by comparing the output of the second full-wave rectifier circuit with a second reference voltage. and a delay time correction circuit that corrects the delay time of the output of the second comparison circuit with respect to the output of the first comparison circuit, and processes the image signal using the code signal. This is achieved by providing a demodulation method characterized by the following.

(6) Embodiments of the invention Examples according to the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a block diagram showing an embodiment of the demodulation system according to the present invention, and FIG. 3 is a diagram showing operating waveforms of each part of the block diagram of FIG. 2. In FIG. 2, 11 is an offset correction circuit, 12 is a filter circuit, 13 is a first full-wave rectifier circuit, and 14 is a first full-wave rectifier circuit.
15 indicates a first comparison circuit, 15 indicates a second full-wave rectification circuit, 16 indicates a second comparison circuit, and 17 indicates a delay time correction circuit, respectively.

The operation of the block diagram of FIG. 2 will be explained with reference to the waveform diagram of FIG. 3. The offset of the demodulated ternary signal as shown in FIG. 3a is corrected by the offset correction circuit 11, resulting in a waveform as shown in FIG. It becomes like this. The filter circuit 12 is, for example, a 500Hz low frequency filter.
The three-value output of the filter circuit 12 is a full-wave rectifier circuit 13
The output of the circuit 13 is compared with a reference voltage in the comparison circuit 14 to become a digital signal as shown in FIG. 3e, which is input as a code signal to the image signal processing circuit. On the other hand, the output of the offset correction circuit 11 is applied to the full-wave rectifier circuit 15, where it is converted into a binary signal as shown in FIG. The output of the circuit 16 is input to the delay time correction circuit, and the delay to the first comparator circuit 14 is corrected, resulting in an output as shown in Fig. 3h. This output is used as an image signal. recorded. FIG. 3h shows a signal that is not passed through a filter, and shows that the portion corresponding to the code signal is disturbed by noise. Therefore, e is selected as the period of the code signal, and h is selected as the period of the image signal.

(7) Effects of the Invention As explained in detail above, in the present invention, an input ternary analog signal is separated into a code signal and an image signal, and since the code signal has noise components removed, it is completely unaffected by noise. Therefore, it is possible to prevent malfunctions and significant deterioration of quality of received images.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a conventional demodulation method, FIG. 2 is a block diagram of an embodiment of the demodulation method according to the present invention, and FIG. 3 shows operating waveforms at each part of the block diagram of FIG. FIG. In the figure, 11 is an offset correction circuit;
2 is a filter circuit, 13 is a first full-wave rectifier circuit, 14 is a first comparison circuit, 15 is a second full-wave rectifier circuit, 16 is a second comparison circuit, and 17 is a delay time. The correction circuits are shown respectively.

Claims (1)

[Claims] 1. Receive one data slot's worth of transmission data composed of one scanning line's worth of code data and image data transmitted by the transmitting side, and divide the demodulated ternary signal into code signal extraction and image signal extraction, and extract the code signal. The code signal forming circuit forming the extraction side includes a filter circuit for removing noise components of the input ternary signal, a first full-wave rectifier circuit for full-wave rectifying the output of the filter circuit, and the first full-wave rectifier. The image signal forming circuit, which includes a first comparison circuit that compares the output of the circuit with a first reference voltage to generate a code signal, and forms the image signal extraction side performs full-wave rectification of the demodulated ternary signal. a second full-wave rectifier circuit; a second comparator circuit that compares the output of the second full-wave rectifier circuit with a second reference voltage to generate an image signal; A demodulation system comprising a delay time correction circuit for correcting a delay time with respect to the output of the first comparison circuit, and processing the image signal using the code signal.