JPS58124370A - Intermediate tone transmission system for facsimile - Google Patents

Abstract

PURPOSE:To reduce the transmission time remarkably and to cope with a code error in sufficient way, by compressing and coding each digit of a binary signal obtained by applying A-D conversion to an analog picture signal, and transmitting each digit. CONSTITUTION:Upper, middle and lower-order digit signals B, C, D introduced from an A/D conversion circuit 1 to the analog picture signal are given to line memories 3a, 4a, 5a respectively through a switching circuit 2. In this case, each memory is in write state and then, the signals B, C, D are stored over one line's share of each memory. Other line memories 3b, 4b, 5b are in readout state, and the signals B, C, D of each digit before one line written in each memory already are selectively introduced to a compression coding circuit 8 with a multiplexer 7 through a switching circuit 6.

Description

[Detailed description of the invention]

The present invention relates to a facsimile halftone transmission system, and in particular aims to shorten the transmission time.Recently, a transmission system for multi-gradation 71xE/IJ image signals including halftones has been studied. However, many of the methods that have already been proposed simply convert multi-gradation analog image signals into digital signals and transmit them, so they have the disadvantage of requiring a relatively long time to transmit. Therefore, the present invention was made with these points in mind, and the details thereof will be explained below with reference to the drawings. In Fig. 1, (1) is an analog image obtained by reading a manuscript etc. This is an A/D conversion circuit that introduces the signal (Figure 2 (A)), and this circuit samples the above image signal for each unit pixel and then compares it with the eight levels shown in Figure 2 (A). By doing this, the values of the 8 steps are quantized into 8 steps and the values of the 8 steps are derived as a 5-digit parallel binary signal.
Depending on the comparison level between ■ and ■, the image signal represents black.

It is converted into a parallel 6-bit binary signal that changes from [000] to [111] representing white. Therefore, the A/D
The upper digit, middle digit, and lower digit signals derived from the conversion circuit (1) are as shown in Figure 2 (B) and (C), respectively.The signals are derived from the A/D conversion circuit (1). The signals (B), (C), and (Ni) of each digit are guided to the line memories (3a), (4a, and 5a) through the first switching circuit (2), respectively. is in a packed state, and therefore, each of the above-mentioned evens (b), (c), and the like are stored in each memory for one line. At this time, the other line memo IJ (5b) (4b) (5b) is in the shape of a bladder, and the signal (b) of each digit of 1 line 11■ that has already been written in each memory is )) passes through the second switching path (6) and then is selectively sent to the compression encoding circuit (8) by the multiplexer (7). In addition, - the above memories (3a) (3b), (4a) (4b
The input and (5a) and (5b) are alternately switched between the writing system and the reading system (11) for each line by the control circuit (9), and the first and second switching circuits (2) and (6) are It is designed to be switched alternately accordingly.IfJ encoding time 1g (8), first memo IJ (3b
) is introduced, the encoding circuit (8) counts the number of run lengths of this signal during the no-low level period 1+i and the low-level period, and calculates the run length. A number is compressed and encoded into a MH (Modified Hoffman) code. Next is the above encoding circuit (
The signals for one line each from the memories (3b) and (4b) are led to 8), so that the middle digit signal from the memory (4b) is transferred to the upper digit 48 from the memory IJ (31)). MR (Modified Read) using the No. as a reference line.
It is compressed and encoded into a code. Furthermore, the following memo IJ (5b)
The signal for one line of the lower digits from is compressed and encoded into an MR code in the same way using the signal of the middle digits of that moe as a reference line.This operation is under the control of the control circuit (9). Therefore, from the encoding circuit (8), each
A serial (serial) sequential signal is derived at around j of the MH code of the upper digit, the MR code of the middle digit, and the MR code of the lower digit for the line, and this sequential signal is sent to the next modulation circuit 0.
0) and sent out to the line. The reason why the signals of each digit derived from the memories (3b) to (5b) are encoded as described above is as follows. In other words, if all of these signals are compressed and encoded into MR codes, the compression effect will be the greatest, but on the other hand, code errors will occur even once, and it will not be possible to correctly reproduce the original digital image signal. As explained above in 1-1, according to the transmission method of the present invention, an analog image signal is converted into a digital signal representing halftones and sent to the transmitter, and the analog image is converted into a signal AA/D. Since each digit of the obtained binary signal is transmitted by compression encoding 1-, the transmission time can be significantly shortened. In this case, especially when specific digits of the binary signal are compressed and encoded into MH code and other digits are compressed and encoded into MR code, the transmission time can be further reduced and it is possible to prevent code errors etc. It also has the advantage of being able to effectively deal with France.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the general configuration when the transmission system of the present invention is implemented, and Fig. 2 is a signal waveform diagram for explaining its operation.

Claims (2)

[Claims] (1) Analog image signals obtained by reading a manuscript, etc. are A/D converted into 8-digit parallel binary signals, each digit of this binary signal is converted into a compression code, and each compression A facsimile halftone transmission method that transmits encoded codes in sequential format for each digit. (2) A facsimile halftone according to claim 1, wherein a specific digit of the 8-digit binary signal is encoded into an MH code, and the other digits are encoded into an MR code and transmitted. Transmission method.