JPS6255343B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for transmitting and receiving facsimile signals, and more particularly to a method for transmitting and receiving facsimile signals in which the main scanning period is changed depending on the image information value for each line of a document.

FIG. 1a shows a modeled signal waveform of a medium-speed facsimile based on the G2 standard recommended by CCITT. This sending signal is a phase section T _P where there is no document, that is, a phase section where the signal is forcibly made into a white signal.
and an image information section _TV for transmitting the image information of the original. The white signal in the phase interval T _P is used for automatic gain control on the receiving side. Also, the modulation method
Since it is an AMPM method, this white signal is also used to extract carrier waves for synchronous detection. In such a transmission method, a fixed image information section is transmitted regardless of the presence or absence of information on the document, resulting in poor transmission efficiency.

In view of the above-mentioned drawbacks, the present invention provides a facsimile signal transmission/reception method with high transmission efficiency, and includes a pilot signal indicating a certain period of the phase interval and a control signal indicating scan line compression within the phase interval. This is achieved by sequentially inserting transmission signals to compress scanning lines when the amount of image information in the transmitted document is small, and by transmitting a control signal indicating compression to control scanning on the receiving side. It is.

FIG. 1b shows an example of the signal format according to the invention and corresponds to the phase interval in a. The signal format b is used when transmitting image information in the facsimile operation phase, and the normal signal format a is used in other operation phases such as handshake and phase matching.

When transmitting image information, the phase interval is usually
An interval of several percent of the transmission time of one scanning line is allocated. In the present invention, this phase interval is further subdivided. In other words, the first section is the WH section (corresponding to the white signal for two CCITTGs) in which the receiver transmits the carrier for applying AGC and for carrier regeneration synchronization used for synchronous detection, and the second section is A pilot signal period (PL) that gives a fixed period within the phase interval to the receiving side, in which the receiving side constantly monitors the phase relationship with the transmitting side, and the third period is where the transmitting side controls the scanning of the receiving side. Control signal section (CN) for
It is. The control signal section is allocated around 1% of one scanning line. Even in analog transmission, if a signal as large as this is used, it is possible to reduce reception errors, and even if there is a reception error, it is possible to minimize its influence, as will be described later. Furthermore, in facsimile systems using analog transmission, this is not a fatal flaw due to the redundancy of the transmitted signals. It is possible to transmit various control contents using control signals, and if there is no image information to be transmitted or the amount is negligible, information for compressing the scanning line can be inserted by agreement with the receiving side. This control signal can improve transmission efficiency. In addition, the arrangement order of each subdivision of the phase interval is the first
Modifications are possible without being limited to Figure b.

Hereinafter, the present invention will be explained with reference to drawings showing embodiments. FIG. 2 is a block diagram of the transmitting side. 1 is a phase generation circuit, 2 is a photoelectric conversion circuit, 3 is an image signal memory, 4 is an information amount determination circuit, 5 is a signal synthesis circuit, 6
1 is a modulation circuit, 7 is a pulse motor, and 8 is a clock generation circuit.

The phase generation circuit 1 generates timing signals VDST and VDST used in each element based on CLK1 and NVD.
VDWT, QVD, CINP, VDRD, PSIG, MSTEP
Create. VDST is a signal that instructs the photoelectric conversion circuit 2 to read out one line of image information,
VDWT is a signal indicating the period during which image information is read out from the photoelectric conversion circuit, QVD is a signal inquiring whether there is a signal higher than the reference value in one line of image information, and CINP is a signal indicating the period of image information of one line. This is a command to output CSIG indicating this if there is no signal higher than the reference value, and PSIG
is a pilot signal indicating a certain period of the phase interval, VDRD is a command to read the image information written in the image signal memory, and MSTEP is a step pulse that commands the pulse motor 7 to convey the document.

The detailed configuration of the phase generation circuit is shown in FIG. In FIG. 7, a counter 1A and an encoder 1B determine the main scanning period, which is determined by a signal NVD from the information amount determining circuit 4 indicating that there is no signal exceeding a reference value. As a result of outputting QVD, if there is no signal greater than the reference value in one line, NVD will be returned as a response, but if there is a signal greater than the reference value, NVD will not be returned. When NVD returns, set the next main scanning period to T/n (sec), and if it does not return, set it to T.
The counter is loaded with a value such that (sec).
The contents of this counter are decoded by a decoder 1e to create the seven types of outputs.

In this embodiment, image information greater than a reference value is a black signal greater than a certain width, and a line containing this black signal is called an information-containing line (hereinafter referred to as a line with information).
PSL), and a line that does not include this black signal is called a no-information line (hereinafter NSL). On the manuscript paper for transmission, squares are drawn with thin lines to make it easier for the writer to write, but it is not necessary to transmit these squares, and it is advantageous to omit them in order to increase speed. be. It also has the effect of removing unnecessary minute dots of developer, which often appear on copied originals. In addition to this, it is possible to set appropriate reference values depending on the application.

The photoelectric conversion circuit 2 uses a high-speed reading element such as a photodiode. From phase generation circuit 1
When VDST arrives, one line of image information is read out.
This output VID goes to the image signal memory 3 and is stored therein, and at the same time goes to the information amount determining circuit 4, where it is determined whether the read line is PSL or NSL.

The image signal memory 3 is a shift register with a capacity to store one line of image information.Writing is performed using a clock CLK2 synchronized with VID, and reading is performed using a clock corresponding to the signal transmission speed.
Read by CLK1.

The detailed configuration of the information amount determination circuit 4 is shown in FIG. The S/R flip-flop (hereinafter referred to as S/RFF) is reset at the rising edge of VDWT, which indicates that image information is being read out from the photoelectric conversion unit 2, and the AND of VDWT and image information VID is performed.
It is connected to the S/RFF set terminal. When the set terminal is “1”, it means PSL. The reason why _R1 and _C1 are inserted between the VID and the AND circuit is that the line containing a black signal of a certain width or more is called "PSL".
This is to make them judge. Black signals below a certain width cannot pass through here. S/RFF output is PSL
Then it will be “0” and even if QVD and CINP come, it will be N.
VD and CSIG are not output. NVD is a signal that transmits NSL to the phase generation circuit, and PSIG is a signal that transmits it to the signal synthesis circuit.

The signal synthesis circuit 5 is a circuit that takes and synthesizes the output VSIG read from the image signal memory 3, the CSIG from the information determination circuit 4, and the R of PSIG from the phase generation circuit 1. The combined output MXDT enters a modulation circuit 6, where AM-PM modulation is performed.

The pulse motor 7 receives MSTEP from the phase generating circuit 1 every time the phase interval is reached and conveys the document.

The clock generation circuit 8 supplies a clock CLK to each element.
1. It is for supplying CLK2, and generally consists of a crystal oscillation circuit and a frequency dividing circuit. This output CLK1 is a low-speed clock according to the transmission speed, and CLK2 is a high-speed clock for reading image information from the photoelectric conversion section 2.

FIG. 3 is a waveform diagram showing the operation on the transmitting side. T
Although _P /T _V is only generated within the phase generation circuit, it is shown for reference as it is a signal representing a phase interval.

At the beginning of the phase interval (TP ₁ , TP ₂ , TP ₃ , . . . ), VDST is output and one line of image information is read out from the photoelectric conversion section. At the same time, VDWT is generated to notify the image signal memory 3 and information amount determination circuit 4 that image information is being read. At the end of the phase interval, a QVD is generated from the phase generation circuit 1, and the information amount determination circuit 4 is inquired as to whether it is PSL or NSL. In the case of TP ₁ , it is PSL, so NVD
won't come back. Therefore, in the phase generation circuit 1, the internal counter 1A is loaded so that the next main scanning period becomes T (sec). Similarly, CINP is output from the phase generation circuit 1, but the information amount determination circuit 4
does not output SCSIG because it is PSL. P.S.I.G.
is a pulse indicating a certain period in the phase interval,
Output unconditionally. These are synthesized
It is MXDT and modulated to become MDDT. Viewed from the beginning of the phase section, the first block at the beginning is the white signal (WH) for automatic gain control and synchronous detection. The second block is the pilot signal (PL),
The third block is a control signal (hereinafter referred to as CN information) indicating whether it is PSL or NSL. The pilot signal is a black signal with white signals at both ends. PSL, NSL
As shown in the figure, the CN information (control information) in the third block indicating PSL corresponds to a white signal (hereinafter referred to as PC) and NSL corresponds to a black signal (hereinafter referred to as NC).

When the TP ₁ period ends, image information is subsequently read out from the image signal memory 3 since it is PSL.
When it ends, it becomes phase interval TP ₂ , and VDST,
VDWT occurs and one line of image information is read again. In the figure, it is NSL. Therefore,
When QVD occurs in phase generation circuit 1, NVD
is returned as a response, and the next main scanning period is T/
The counter 1A is loaded so that n (sec). Similarly, when CINP occurs, CSIG is output from the information amount determination circuit. Since PSIG is output unconditionally, a signal obtained by combining these three types of signals is sent out as MDDT. Once this phase interval TP ₂ ends, no meaningful signals are sent until the next phase interval TP ₃ . Time passes again and the phase interval
When TP ₃ enters, VDST occurs again, and so on. In this way, PSL is transmitted over T (sec), and NSL is transmitted after being shortened to T/n (sec).

FIG. 4 is a block diagram of the receiving side. 11 is a demodulation circuit, 12 is a phase generation circuit, 13 is a pilot signal detection circuit, 14 is a CN information detection circuit, 15 is a recording amplification circuit for supplying sufficient energy to the recording means, and 16 is a transport for receiving recording paper. 17 is a clock generation circuit for supplying clocks to each element.

The demodulation circuit 11 receives AM input from the telephone line.
- It is for demodulating PM modulated signals and its output is DMDT.

The phase generation circuit 12 generates timing signals PGT, CGT, QPC, and MSTEP used by each element. PGT is the timing when the pilot signal comes in, so it is a command to check. CGT is a command to check since it is the timing when CN information is received. QPC is a signal that inquires whether a pilot signal has been detected, and is sent to the CN information detection circuit 14.
This is a signal that inquires whether an NC representing NSL has been detected. Pilot signal detection circuit 13
If the pilot signal is detected in
Outputs P as a response to QPC.

If NC is detected, the CN information detection circuit 14 returns a signal CNT indicating that NC has been detected as a response to QPC. The detailed configuration of the phase generation circuit is shown in FIG.

In FIG. 9, a counter and an encoder determine the main scanning period. The load input (L) of the counter contains QPC, and when QPC is output, this counter is loaded. The value loaded is determined by the output of the encoder, which is
It changes depending on the state of CNT and PK. QPC
If CNT returns after outputting QPC, the main scanning period (time until the next QPC appears) is T/n (sec)
If CNT is not obtained, T(sec)
becomes. Pilot signal is detected and NC
is not detected (CNT="0", PK=
Only “1”) is the main scanning period of T (sec).

PGT, CGT, and QPC are created by decoding the contents of this counter using a decoder.

The detailed configuration of the pilot signal detection circuit is described in the first section.
As shown in Figure 0. This is a circuit that stores DMDT when PGT is coming in a shift register and checks that both ends of this pattern are white and the center is black.If the check passes, QPC comes. It outputs PK at times. FIG. 10B shows the conditions.

The detailed configuration of the CN information detection circuit is shown in FIG. Check the DMDT when the CGT is coming, and if there is a black signal over a certain amount, the counter will
When Qn becomes 1 and QPC comes, CNT is output.

FIG. 5 is a waveform diagram showing the operation on the receiving side of this embodiment. In facsimile, the phase matching procedure, which is performed at the beginning of communication and which matches the phase intervals of both transmitting and receiving signals, will be described as having already been completed.

T _P /T _V represents the phase interval on the receiving side.
Looking at the TP ₁ section, the pilot signal is coming to the center of the PGT, so it is normal. When QPC occurs, PK will be returned. Since DMDT is a white signal (“0”) when CGT occurs, it is determined that it is PC, and CNT is not returned even if QPC occurs. That is, in this case, the phase generation circuit is PK
="1" and CNT="0", the next main scanning period will be T (sec).

When the phase interval TP ₁ has passed, this is the interval in which image information is sent, so it is recorded. When both signal periods end, phase period TP ₂ is entered and PGT and CGT are activated again.
occurs, and the pilot signal and CN information are checked. The pilot signal is coming normally, so when QPC occurs, PK will be output. A black signal "1" is coming to the CGT section in TP ₂ .
Then, NC was detected and QPC occurred, resulting in C
NT is returned. PK="1", CNT="1"
Therefore, the next main scanning period is T/n (sec). This is not because the phase interval is shortened, but because the image information interval is shortened. When the shortened image information section passes, the phase section becomes TP ₃ , and if NC is detected, the main scanning period is changed to T/n.
(sec), and if NC is not detected, that is, if PC is detected, the main scanning period is set to T (sec).

In FIG. 5, a case has been described in which the CN information is transmitted without error, but this CN information may be received incorrectly due to line noise or the like.

FIG. 6 shows what happens when a reception error in CN information occurs. Up to point A, the transmitter and receiver are operating normally without any phase shift. At point A, the transmitting side sends NC indicating NSL, and the next main scanning period is set to T/n (sec). If this NC is overlooked on the receiving side, the next main scanning period will be T (sec), and point B will be the next phase interval. As is clear from the figure, on the transmitting side, point B is not in the phase interval. In other words, a phase shift has occurred. However, when reaching point B, the receiving side is in the phase interval, but the transmitting side is not in the phase interval, so no pilot signal is detected. At this time, PK is “0” (not detected), so the receiving side knows that the next main scanning period is T/
n (sec), the phase interval on the transmitting side is caught at point C, and the phase interval on the transmitting side is tracked from then on. At point D
This is a case where an NC is mistakenly sent even though it has not been sent. Since it is PSL on the sending side
NC is not output, and the main scanning period is T (sec). On the receiving side, it is mistakenly assumed that NC has arrived, so the next phase interval will be point E. Since the pilot signal cannot be detected at point E, point F becomes the phase section.

At points E to G, no pilot signal is detected,
It catches the pilot signal at point H and then follows the transmitting side. Points I to K are NSL and NC is normally received.

According to this embodiment, as explained above,
The control signal (CN information) indicating NSL and PSL is inserted into the phase interval, and its presence or absence is expressed by white and black signals, which simplifies the device configuration and uses the same modulator as before. Not only is this possible, but the control signal and the image information can be clearly and simply separated during reception and recording, so problems such as recording the control signal will not occur. Further, in this embodiment, since the CN information does not protrude into the image signal section, there is an advantage that no image signal memory is required on the receiving side.
In addition, by setting the main scanning period of PSL and NSL to 1:1/n and by inserting a pilot signal within the phase interval, even if there is an error in sending and receiving CN information and a phase shift occurs, the receiving side It is possible to easily return to the normal position by making an operation to catch the pilot signal at a cycle of T/n (T=PSL).

As explained above, according to the present invention, it is possible to exchange information for controlling scanning within a phase interval, and it is possible to perform efficient transmission without polluting received images. . In addition, since the control signal is expressed by the presence or absence of a carrier (white signal, black signal) and no special signal is transmitted, it can be realized with a simple configuration with almost no changes to the conventional transmission circuit. Furthermore, even if a control signal is received incorrectly, normality can be easily restored.

It should be noted that the present invention can be implemented without being limited to the embodiments, and can be applied even to cases where it is determined that image information across multiple scanning lines is minute. It is also possible to transmit other control information (for example, 1/n×i n≧3, 1≦i<n) using the control signal to perform more complex control. Of course, in this case, it is natural to allocate a section to reduce reception errors of the control signal.

[Brief explanation of the drawing]

FIG. 1a shows a model of the transmission signal waveform of a medium-speed facsimile based on the G2 standard recommended by CCITT, and FIG. 1b shows a model of the transmission signal waveform according to the present invention. FIG. 2 is an example of an electrical circuit diagram of a facsimile transmitter according to the present invention, and FIG. 3 is an operational waveform diagram thereof. FIG. 4 is an example of an electric circuit diagram of a facsimile receiving device according to the present invention, and FIG. 5 is an operational waveform diagram thereof.
Further, FIG. 6 shows an operational waveform diagram until the normal phase is restored when a reception error of CN information occurs on the receiving side. 7 is an electric circuit diagram of the phase generation circuit 1, FIG. 8 is an electric circuit diagram of the information determination circuit 4, FIG. 9 is an electric circuit diagram of the phase generation circuit 12, and FIG. 10a is an electric circuit diagram of the pilot signal detection circuit 13. FIG. 10B is a diagram for explaining its operation, and FIG. 11 is an electric circuit diagram of the CN information detection circuit 13. 1, 12... Phase signal generation circuit, 2... Photoelectric conversion circuit, 3... Image signal memory, 4... Information amount determination circuit, 5... Signal synthesis circuit, 6... Modulation circuit,
7, 16... Pulse motor, 8, 17... Clock generation circuit, 11... Demodulation circuit, 13... Pilot signal detection circuit, 14... CN information detection circuit,
15...recording amplification circuit.

Claims (1)

[Claims] 1 Compare the amount of image information for each main scan with a certain reference value, and if the amount of image information is less than the reference value, set the main scanning period T of the transmission signal to 1/n (n≧2, integer), A control signal consisting of a pilot signal indicating a certain period and at least one of a white signal and a black signal containing information on the periodic change is inserted into a phase signal interval, and the receiving side detects the pilot signal, and A facsimile signal transmission/reception method in which the main scanning period is T/n when the control signal includes the period change information and when the pilot signal is not detected.