JPS6022546B2 - Scanning method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a scanning method in a facsimile machine or the like.

Conventionally, in order to shorten transmission time, facsimile machines have used a method of binarizing the read signal and encoding the binarized signal to reduce redundancy before transmitting it. There is.

Therefore, the time from reading one line's worth of signals to transmitting them differs from line to line. Therefore, it is necessary to make the reading sub-scanning speed variable. Conventionally, an roller that feeds a document is driven by a pulse motor, and the input interval of a drive pulse signal input to the pulse motor is varied to convey the document at a variable speed.

However, if the document is transported at variable speed in this way,
When a mechanical load such as a roller driven by a pulse motor is large, an inertial force acts, and the response of the drive system to a signal input to the stepping motor becomes poor.

For this reason, there are drawbacks such as the document not stopping at the regular scanning position or the scanning conditions being different, such as scanning being performed when the document is stopped or moving, and the scanning position being uncertain. The present invention has been made in view of the above drawbacks, and an object of the present invention is to provide a scanning method that enables accurate scanning.

The present invention will be explained below with reference to the drawings.

FIG. 1 is a block diagram of a main part of a scanning device in a facsimile transmitter showing an embodiment of the present invention.

In Figure 1, 1 is a manuscript, and 2 and 3 are manuscripts! This is the drive roller that conveys the 4 and 5 are pinch rollers.

Note that 44 is a document feeding guide plate. 13 is a motor that rotates the drive rollers 2 and 3; 14 is a motor 13;
This is the drive circuit.

This motor 13 may be a hysteresis motor. 15 is a main scanning unit, in which crab light lamps 6a, 6b, a lens 7, and an image sensor 8 are fixed.

16 is a threaded shaft that engages with the main scanning unit 15.

That is, by rotating the shaft 16 in the forward or reverse direction, the main scanning unit 15 moves in the direction of the arrow Y or Y'. 22 is a pulse motor that rotates the shaft 16 forward or reverse.

Reference numeral 9 denotes a conversion circuit, which includes means for amplifying the output signal of the image sensor 8 and means for binarizing the amplified signal.

105 is a 1-line memory and can store 200 million video signals for one line.

11 is a compression encoding circuit.

Reference numeral 23 denotes a timing circuit, which synchronizes the operations of the image pickup device 8, the timing circuit 9, and the one-line memory 10.

12 is a modulation circuit that modulates the box signal and sends it to a telephone line or the like.

Reference numeral 17 denotes a control circuit that controls the operations of the one-line memory 10, the compression encoding circuit 11, and the read timing circuit 23.

18 is a force counter, 19 is a latch, and 20 is a ROM.

25 is an input terminal for a clock pulse signal of an appropriate frequency. Control circuit 17 also controls the operation of counter 18 and latch 19. Reference numeral 21 denotes a drive circuit for the pulse motor 22, which is controlled by an output signal from the ROM 20.

The riddle-taking timing circuit 23 also controls the counting start operation of the counter turtle 8. Items 1 to 1 show the output signals of each component. The operation of the chain running device having the above configuration will be explained below using FIGS. 2 and 3.

FIG. 2 is a timing waveform diagram of input/output signals of each component shown in FIG. 1, and FIG. 3 is an explanatory diagram of the operation of this embodiment.
In Fig. 2 A to E, the /. level portion indicates when each signal is output. First, unlike the conventional case, the document 1 is conveyed at a constant speed. In other words, the drive circuit 1
Reference numeral 4 inputs pulse signals to the motor 13 at regular intervals from when the scanning device of the present invention starts its operation to when it ends.
The constant rotational speed of this motor 31 is
The conveyance speed of the document 1 is set to fall between the maximum value and the minimum value of conventional variable width scanning. In this invention,
The conveyance speed of the document 21 by the motor 13 is set to the average value of the conventional variable sub-scanning speed. Note that the direction of the arrow Z is original 1.
The conveyance direction is shown. Next, in the reading operation of the original 1, the backlights 6a and Sb are always turned on to illuminate the original 1, and the reflected light is collected by the lens 7 and enters the image sensor 8.

The image element 8 converts this light into an electrical signal. This bran image element 8 has minute photodiodes (not shown) lined up in the same number as a predetermined number of main scanning pixels in a direction perpendicular to the transport direction (arrow Z direction). When the image sensor 8 receives the timing pulse signal A output from the timing circuit 26, it continuously outputs a photoelectrically converted signal pixel by pixel according to a predetermined clock pulse signal (not shown). At the same time, the necessary electrical signals are selected and output to the circuit 9 using the gate signal port output from the same discussion timing circuit 25. That is, in this embodiment, the driving of the image sensor takes the following two steps in order to equalize the level of its output signal.

'1} First, input one first timing pulse signal 27a in signal A in FIG.

At this time, the gate signal port is not output. (2) Next, after being phototransferred for a certain period of time B, the second timing signal 2sb in signal A in FIG. 2 is output to cause the image pickup device 8 to output an electrical signal. At this time, since the gate signal port is being output, the output signal 2 of the image sensor 8 is input to the reading circuit 9 as an image signal. This image signal 2 is amplified in consideration of the background density in a reading circuit, binarized, and stored in one line memory 10'. Note that the gate signal port also inputs the input circuit 9 and the 1-line memory 1O', so that it operates only for image signals. Then, while the control circuit 17' reads out the image signal stored in the one-line memory 10, the compression encoding circuit 11 encodes it using a predetermined algorithm.

For example, in the CCITT G standard, the MH method is adopted as the one-dimensional compressed signal method. Note that the time required for converting into a compressed signal differs depending on the content of this binary signal. As described above, the compressed signal H output from the compression encoding circuit 11 is modulated by the modulation circuit and sent to a telephone circuit or the like.

Furthermore, when the compression signal conversion operation of the compression signal conversion circuit is completed, the control circuit outputs the control signal C to the read timing circuit 23. outputs the first timing pulse signal 28a.The above operations are repeated thereafter.By the way, in a facsimile transmitter, the scanning line density is fixed, and scanning is performed at predetermined intervals.

In FIG. 3, solid line arrows V and .about.V5 with respect to the document 1 indicate the pick-up positions, and the pick-up positions V and .about.V5 are equally spaced. In the present invention, the document 1 is moved at a constant speed in the direction of the arrow Z, so if the time required to convert it into a compressed signal is average, the scanning position will be directly below the image sensor 8. If the time required to compress and encode the binary image signal read at position V3 is short, the next reading position will be at broken line V4.
The scanning operation is performed even though the position is .

Therefore, in this case, the image pickup device is moved in the direction of the lost line Y' to the position indicated by the broken line V4'. Conversely, reading position V3
If the time required to convert the read binary image signal into a compressed signal is long, the next reading position will pass under the image sensor 8 and arrive at the position indicated by the broken line V4''. The green image element 8 is moved in the direction of the arrow Y to the position. In this way, the operation of moving the moat image element 8 by a predetermined length and in a predetermined direction according to the time required to convert the binarized image signal of the previous scan line into a compressed signal is performed by the force counter 8 and the latch 19. ,
This is performed by the ROM 20, the pulse motor drive circuit, and the pulse motor 22. That is, the counter 18 starts counting the clock pulse signal input from the input terminal 25 when the gate signal port of the read timing circuit 23 is input, and is cleared when the control signal C from the control circuit 17 is input. This control signal C is also input to the latch 19, and the latch 19 stores the count value of the counter 18 before it is cleared at the arrival timing of this control signal C.
The memory contents are transferred to and from the ROM 20. The contents of the address indicated by the output signal of the ROM2 river latch 19 are output to the pulse motor drive circuit 21. That is, since the traveling speed of the document 1 is known in advance, and the time required for the binary image signal of the previous scan line is known, it is possible to know in advance where the next scan line will be. Therefore, depending on the output content of the latch 19, the moving direction and moving distance of the image pickup device 8, that is, the scanning unit 15 can be calculated. Further, in the pulse motor 22, the moving distance can be converted into the number of drive pulses. From the above, the address indicated by the latch 19 in the ROM 20 stores therein the direction of rotation and the number of drive pulses indicating the moving distance according to the output content of the latch 19. Therefore, if the output signal of the ROM 20 is n bits, 1 bit indicates the rotation direction of the pulse motor 22, and the remaining (n-1) bits indicate the number of drive pulses input to the pulse motor 22. It turns out. The drive circuit 21 receives the output signal of the ROM 20 and outputs two signals. A predetermined number of drive pulses are output in series to one output signal, and a signal indicating normal rotation or reverse rotation as "1" or "0" is output to the other output signal.

This causes the pulse motor 22 to rotate in a predetermined direction by a predetermined amount. The main scanning unit 15 then moves by a predetermined amount in the arrow Y or Y direction. 26 in signal C in FIG. 2 indicates an arbitrary control signal, and after a certain period A has elapsed since this control signal 26 was output, the first timing pulse signal 28a is output from the read timing circuit 23. be done. This fixed period A is the scanning unit 1
It is provided for the movement of 5. In this way, according to this embodiment, even if the original 1 is moved at a constant low speed, the scanning unit 15 with a small inertial force can be moved with high precision, so that the original 1 can be stopped or moved. This is not necessary; the scanning conditions remain unchanged and accurate scanning is possible.

Note that the present invention is not only applied to variable sub-scanning as described above, but also increases the line density in areas where there is a lot of black information or where there are many transition points between white and black, and vice versa. It goes without saying that it can also be applied to an automatic line density switching operation in which parts are made sparse, and a skip operation in which all white lines omit or simplify field signals.

Furthermore, this embodiment can also be applied to a recording apparatus by using a recording paper instead of a transmission document and a recording head instead of a main scanning unit.

As described above, according to the present invention, a scanning method in a facsimile machine or the like includes a means for moving a sheet at a constant speed, a main scanning means, and a means for moving the main scanning means, and a sub-scanning speed and a means for moving the main scanning means. By moving the main scanning means by the difference from the sheet feeding speed, the main scanning means can perform scanning under the same conditions and can read at an accurate position.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the main parts of a scanning device for a facsimile transmitter to which an embodiment of the present invention is applied, FIG. 2 is a timing waveform diagram of output signals of each component in the turtle diagram, and FIG. 3 is a diagram of the present invention. FIG. 1... Original, 2, 3... Drive roller,
6a, 6b...Fluorescent lamp, 7...Lens, 8...Image sensor, 9...Kendori circuit, 10
...1 line memory, 11 ... compression encoding circuit, 12 ... modulation circuit, 13 ... motor, 14 ... motor drive circuit, 15・・・・・・
・Main scanning unit, 16...Threaded shaft, 1
7... Control circuit, 18... Counter, 19
...1 foot, 20. 、． ．． 、． ROM, 21...
... Pulse motor drive circuit, 22..." pulse motor, 23... Read timing circuit. Fig. 1 Fig. 2 Fig. 3

Claims (1)

[Claims] 1. A means for conveying the sheet at a constant speed, a main scanning means for optically reading the writing surface of the sheet, a moving means for moving the main scanning means in the conveying direction of the sheet or the opposite direction, and a drive for the moving means. 1. A scanning system comprising: a control means for controlling a driving means of the moving means based on difference information between a scanning speed and a sheet conveyance speed.