JPS587108B2 - Image signal erasure method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention eliminates black signals generated in areas where there is no original when a facsimile device sends an original narrower than the main scanning width, thereby preventing unnecessary black recording from being recorded on the received image. Related to image signal processing methods.

Regardless of whether the transmitted original is new or old, white level clamping is generally performed in the photoelectric conversion circuit of the transmitter in order to obtain a sufficiently usable received image even with a dirty original.

That is, the white level of the transmitted original paper is always clamped to a constant potential regardless of the white density of the paper, and the density difference of an image such as a character with respect to the white level of the original paper is extracted as an image signal.

For this reason, even if the white density of the original paper has changed due to dirt or the like, a received image that is no inferior in photoelectric conversion output to that of a pure white original paper can be obtained.

As shown in Fig. 1, the most common optical head part of an optical fiber type transmitter has a configuration in which a transmitted document 2 is pressed against an optical fiber head 3 by a document pressing roller 1 to maintain resolution. There is.

The effective main scanning width that can be transmitted by a facsimile device is unique to each device, and the size of the original to be sent does not always match the main scanning width, and in many cases the original size is narrower than the main scanning width. it is conceivable that.

In such a case, the document holding roller contacts the portion of the optical fiber head where there is no document.

In the white clamp method circuit, the white level in the main scanning period is detected and clamped, but if this original holding roller is whiter than the sending original paper, the white level of the holding roller is changed without clamping the white level of the original paper. is clamped to a constant potential.

Therefore, in the case of a dirty original, the original paper portion will be photoelectrically converted to a considerably black level, and in the worst case, it will be impossible to distinguish between images such as text and the original paper portion in the received image, which will defeat the purpose of white level clamping. Completely lost.

For the above reasons, even in the case of documents narrower than the main scanning width, the document holding roller must be It turns out that black is preferable.

However, if the document holding roller is black, it is possible to obtain good records by clamping the ground level of the document paper to a certain level even for bad documents, but on the other hand, the main scanning area where there is no document naturally Since the black color of the presser roller is photoelectrically converted, there is a drawback that the areas where there is no document are recorded in black in the reception record.

The presence of black bands on the side of the received image is not desirable as a recorded image, and it takes time and effort to cut it off with a knife, and in electrostatic recording reception methods, developing toner is wasted on this black band. Since it consumes a large amount, problems such as toner replenishment become a major problem.

The present invention has been made in order to eliminate the above-mentioned disadvantages inherent in the conventional technology. Therefore, an object of the present invention is to reduce the black signal generated in the area where there is no document when transmitting a document narrower than the main scanning width. To provide a new facsimile communication system which eliminates unnecessary black recording on received images.

According to the present invention, it is possible to obtain an image signal erasing method characterized by erasing a black image signal included in each main scan from the start of each main scan until the first self-portrait signal is detected. can.

Next, a preferred embodiment of the present invention will be specifically explained with reference to the drawings.

FIG. 2A shows the phase signal of the transmitter, and T indicates one main scanning period (main scanning width).

The opening is a photoelectric conversion output waveform diagram when a document having a width from B to C, which is narrower than the main scanning width, is photoelectrically converted using a black document pressing roller.

In the figure, from main scanning starting point A to B shows the black level due to the document holding roller protruding from the document, and from B to C
The figures up to this point are the screen signal waveform diagrams of the original, furthermore, C to D are the black levels caused by the original holding roller that has protruded from the original again, and D to E are the black levels generated by the continuous flow of the optical head. It shows.

The photoelectric conversion output when the document is moved all the way to the end of the main scan in this state is shown in FIG.

That is, from F to G is the black part caused by the roller, from G to H is the screen signal of the original, and from H to ■ is the black signal from the seam of the optical fiber head. , in the main scanning direction, a white margin exists before an image such as a character appears.

Therefore, when the original is set as shown in 8, the starting point of the original can be considered to be the white level position that first appears from the start of main scanning, as shown by G, and from F to G.
It is necessary to ensure that the black level up to this point does not appear black in the received record.

FIG. 3 shows an example of a circuit for erasing the black signal present from the start of main scanning until the first white screen signal appears for each main scanning.

FIG. 3 is a diagram showing an embodiment of the image signal erasing method according to the present invention.

Reference numeral 11 is a memory-configured flip-flop, and in this embodiment a JK master-slave flip-flop is used.

The CP input of the flip-flop 11 receives a clock signal S1 with a frequency much higher than the main scanning frequency, the J input receives a photoelectric conversion output S2 through an inverter 12, the K input receives an inverted output Q, and the CL input receives an inverter. A phase signal S3 is applied through 13, respectively.

The output Q of the flip-flop 11 and the photoelectric conversion output S2 are coupled to an AND circuit, which outputs a screen signal.

With this configuration, when a white level potential is generated in the photoelectric conversion output S2, the output of the flip-flop 11 is inverted by the clock signal S3, as shown in FIG. 2, until the flip-flop 11 is reset by the phase signal S1. This inverted state is maintained.

To explain this operation in more detail, the flip-flop 11 shown in FIG. 3 is the most common JK master-slave flip-flop that operates according to the truth table shown in FIG.

Now, when a phase signal S3 whose waveform and polarity are shown in FIG. Added.

A general JK master-slave flip-flop such as the flip-flop 11 is reset when the reset terminal CL is at the L (logic low) level, and the output Q is set at the L level.

Therefore, this flip-flop 11 is reset every time the phase signal S3 is input, so that the output Q is reset to L level and the inverted output Q is reset to H (logic high) level.

Also, as is clear from the truth table in FIG. 4, after the flip-flop 11 is reset and the output Q is set to L level, while the J terminal is at L level, the clock terminal CP is
No matter how much clock signal is applied, the output Q remains high, the inverted output Q continues to be at H level, and it is not until the J terminal becomes H level that the clock pulse inverts the output Q to H and the inverted output q to L. .

In the truth table of FIG. 4, n is the number of clock pulses.

Therefore, the photoelectric conversion output signal S with the polarity shown at 8 in FIG.
2 is inverted by the inverter 12 and applied to the J terminal of the flip-flop 11, when the signal S2 is at the black level, the J terminal is at the L level, so the flip-flop 11 is not inverted and the signal S2 is at the white level. Only then will the flip-flop 11 be inverted by the clock pulse S, and the output Q will be at the - level.

Furthermore, since the inverting output Q terminal of the flip-flop 11 is connected to the K terminal, as can be understood from the truth table in FIG. Once the level is reached, no matter how much the clock signal is applied to the CP terminal after that, the output Q will hold H and Q will hold L until it is reset by the reset signal of the phase signal S3.

Therefore, as is clear from the above explanation, the output Q of the flip-flop 11 is first reset by the phase signal S3, as shown in FIG. 2, and the output Q is brought to the L level.

Next, while the photoelectric conversion output S2 is input to the terminal 16 and a black signal is applied to the J terminal, the clock signal is at the L level, but when it becomes a white signal, the H level is applied and the clock signal is input from the terminal 15. The output Q is inverted to H level.

Thereafter, the output Q maintains the H level until it is reset by the phase signal S3 input to the terminal 17.

As the frequency of the clock signal is selected to be sufficiently high compared to the image signal frequency, the delay time from when the J terminal of the flip-flop 11 becomes H level to when the output Q is inverted to H level can be ignored. The flip-flop can be reliably inverted even for a short white signal.

The signal at the Q terminal of this flip-flop 11 (Fig. 2 2)
and the photoelectric conversion output signal S2 (Fig. 2, 8) are connected to the AND circuit 1.
4, and a screen signal output S4 as shown in FIG. 2E is obtained from the terminal 18 in which the extra roller black signal from F to G in FIG.

That is, with this circuit configuration, the completely redundant black signal of the roller up to F+G of the image signal shown in FIG. 28 is completely erased.

In Fig. 3, inverters 12 and 13 may be unnecessary depending on the polarity of each signal, and the flip-flop circuit 11 can be modified in various ways. Trigger flip-flop, D-type flip-flop,
Almost the same purpose can be achieved by using a shift register or the like.

The circuit shown in FIG. 3 can be applied not only to facsimiles but also to televisions and the like.

As described above, according to the present invention, with a very simple circuit configuration, the black signal appearing in the final output signal S4 is only the screen signal, and the black signal of the portion of the document holding roller protruding from the document is completely erased. Because of this, no extra black band is generated in the received record, and therefore it has a very advantageous feature in terms of replenishment of developing toner.

Further, it is not necessary to erase this extra black signal at the transmitter, and the same result can be obtained even if it is carried out at the receiver.

Furthermore, if this erasure is performed in the transmitter,
In this embodiment, during the phase signal period, the flip-flop 11
Since the optical head is reset, the joint signal of the optical head is also erased, but it is also natural that the output signal S4 can be further processed to make the phase signal a black level and sent out at the same time as the image signal.

Although the present invention has been described above with respect to preferred embodiments, these are merely illustrative, and it goes without saying that the scope of the claims of the present invention is not limited only by the embodiments described herein. be.

[Brief explanation of the drawing]

Figure 1 is the most general schematic diagram of the head portion of an optical fiber type transmitter, and Figure 2 is a waveform diagram for explaining the method according to the present invention, of which A is a phase signal waveform of the transmitter. , A is the photoelectric conversion output waveform when a transmission document narrower than the main scanning width in the main scanning direction is placed in the center, and C is the photoelectric conversion output waveform when the transmission document narrower than the main scanning width in the main scanning direction is placed at the end of the main scanning. 2 shows the signal waveform for erasing the extra black signal, E shows the output image signal waveform from which the extra black signal has been erased, and Figure 3 shows the photoelectric conversion output waveform when placed side by side in the same direction. FIG. 4 is a circuit configuration diagram showing one embodiment, and FIG. 4 is a diagram showing a truth table of the circuit of FIG. 3. 1. ．． ．． Original holding roller, 2... Original to be sent, 3...
Head, 11...J-K master-slave flip-flop, 12, 13... Inverter, 14... AND circuit.

Claims (1)

[Claims] 1. An image signal erasing method for erasing a black image signal included in an image signal of a facsimile machine from the start of each main scan to when the first white image signal is detected for each main scan.