JPH0573097B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Description of the Field> The present invention relates to a document reading device in a copying machine, a facsimile machine, etc., and relates to a scanning method and a control method thereof.

<Prior Art> Normally, in a document reading device such as a copying machine, a document reading operation is performed as follows. That is, when reading the original 2 placed on the original platen 1 as shown in FIG. The scanning unit is located at the point , and at the same time as the document reading starts, the illumination lamp 4 is turned on and the scanning unit moves in the direction of arrow A.
Near the point, it retreats in the direction of arrow B and stops at the new point. For example, when reading a large document whose size reaches a point, the document is reversed near the point and returns to the position. On the other hand, recently,
The position where the document is placed is automatically determined during preliminary scanning prior to the reading operation, and only the image area is scanned.
A printing type copying system has been proposed.
Even in the document reading operation in such a copying system, the home position, that is, the normal stopping position is determined. For example, in FIG. Accordingly, scanning is started, reversed near the rear end of the document, retreated in the direction of arrow B, and stopped again at a point to complete one exposure scan. However,
In these cases, for example, between - and A4 width,
If the document is placed as shown in Figure 1 b when the space between - is set to A3 width, the document must be scanned by the width between -, that is, A3 width, even though the document size is A4 (or smaller). First of all, the time taken to travel to - is completely wasteful and significantly reduces the throughput of the copying system. In particular, in the case of a color copying system, the reduction in throughput is even more significant because each copy requires three or four document reading operations. In addition, in such a color copying system, when a color LBP using an electrophotographic method is used, if the same original 2 is placed differently as shown in Figure 1 a and b,
The disadvantages are that the sequence control is different and the control is complicated. Further, the extra power consumption due to exposure lighting during this time cannot be ignored.

<Object of the Invention> The present invention has been made in view of the above points, and an object of the present invention is to scan a document efficiently and without waste, no matter where the document is placed on the document table. be.

<Example> An example of the present invention will be described in detail below with reference to the drawings.

FIG. 2 shows a driving mechanism of a color image reading device according to an embodiment of the present invention. The exposure scanning table 106 includes a fluorescent lamp 107 for illuminating the document exposure, a rod array lens 108 that collects reflected and scattered light from the document, and a solid-state image sensor 109 that converts a light image corresponding to the document into an electrical signal. including,
It is pulled by the drive wire 211 and moves forward or backward in the direction of the arrow. 110 is a solid-state image sensor 10
9 drive signal and image signal transmission line,
It is supplied from a circuit not shown. 113 is an actuator attached to one end of the scanning table 106, and at the home position, the sensor 112
Detected at Reference numeral 100 denotes a scanning table drive motor, which drives the drive shaft 1 through gears 101 and 102.
05, and the drive wire 211 is driven by the pulleys 103 and 104. Figures 3 and 4
The figure shows a drive circuit for a motor 100, and a stepping motor is used to drive the main scanning table. The control circuit 111 is a circuit that controls the entire device.
The oscillator 115 generates a pulse train for generating pulses for driving the motor 100, and the frequency divider 116 generates a pulse train to generate pulses for driving the motor 100.
The frequency is divided into a predetermined frequency. The frequency division ratio is the control circuit 1
This value determines the rotational speed of the motor 100 and, therefore, the scanning speed of the exposure scanning stage. The frequency-divided pulse train is passed through a JK flip-flop 11.
7, gated to gate 119 and provided as shift pulse 208 to shift registers 120-123. The shift pulse 208 is the control circuit 111
The flip-flop 118 is set by the motor drive signal 201 outputted from the motor drive signal 201, which causes the gate 119 to open and is generated.
When is reset, gate 119 closes and shift pulse 208 stops. That is, the motor is driven only during the period in which this shift pulse is generated. From the shift registers 120 to 123, in synchronization with the aforementioned shift pulse 208, for example, the string of "1" and "0" shown in the same figure is output as shown in FIG. 3b,
The signal is input to the motor drive circuit 127 at the subsequent stage. Setting “1” and “0” to each shift register 120 to 123 is performed by the control circuit 111,
When the settings are made as shown in the figure, the shift clock 2 whose frequency is divided to a predetermined speed by the frequency divider 116 as shown in FIG.
120 → 121 → 1 as shown in figure b in synchronization with 08
Since the pulses appear in the order of 22 → 123, and therefore the motor windings L ₁ → L ₂ → L ₃ → L ₄ are excited in the order,
The rotor rotates counterclockwise, forward (FW), and the "1" and "0" settings in the shift register are set to 120 for 1000, 121 for 0100, 122 for 0010, 1
23 is set to "0001" and the motor is driven in the same way, the winding becomes L ₄ →L ₃ →L ₂ →L ₁ as shown in c in the same figure.
When excited, the rotor rotates clockwise, that is, reverse (RV), and when the motor starts, the frequency divider 1
The frequency division ratio of 16 is increased to lower the drive frequency at startup. This will be explained with reference to FIG. The figure shows the internal circuit of the motor drive circuit 127. For example, when a ₁ = “1” and a ₂ to a ₄ = “0”, T _r1 is turned on and the power supply +V → R ₁ → L ₁ → T _r1 Current flows through the motor windings
Energize L ₁ . Next, a ₂ = “1”, a ₁ , a ₃ , a ₄ = “0”
Then, T _r2 turns ON and current flows from +V → R ₁ → L ₂ → T _r2 , exciting L ₂ and rotating the motor by one step. In the following, forward movement (FW) and reverse movement (RV) are performed according to the set values of shift registers 120 to 123. However, when the pulse motor rotates at high speed, the accuracy of start-up, time, etc. is questioned, but I will not focus on that here. I can't touch it until now.

A set value TCNT 206 is set by the control circuit 111 for the down counter 124 in FIG. 3, and this set value determines the driving time of the motor as described above.

Next, a method of detecting the document position will be explained.
FIG. 5 is an external view of the color document reading device according to the embodiment, in which reference numeral 136 is a document table on which a document is placed, 137 is a document cover, and a reflection plate 135 that totally reflects incident light on the inner surface. is attached, all the light from the fluorescent lamp 107 is reflected in the direction of the arrow, as shown in FIG. 5b, and the photoelectric conversion element 10
It does not enter 9. That is, it is read as a "black" image. On the other hand, in the example shown in FIG. 6, most of the originals are usually painted with a color other than white or black within the required reading width, and are distinguished from the "black" color of the original cover. Therefore, by knowing the _X1 coordinate of line AB and line CD _of the original ABCD in figure a, the _X2 coordinate of line CD, and the _X1 coordinate of line A′ and the You can decide. FIG. 7 shows a circuit for determining X ₁ and X ₂ for determining the above-mentioned required scanning width. In this embodiment, first, in order to obtain X ₁ and X ₂ , prior to the original reading operation by the CCD 109, exposure illumination is performed and preliminary scanning by the CCD 109 is performed once. Line Cautan 128 is
It is cleared once by VSYNC213, which is generated once before preliminary scanning, and then HSYNC21 is generated every time during scanning.
2, count the number of lines.

Since the signals of VSYNC213 and HSYNC212 are well known, they will not be described here. After starting preliminary scanning, the first signal other than the black signal
BLACK 214, that is, when preliminary scanning reaches the edge of the document, BLACK 214 sets F/F 130, latches the number of lines from VSYNC 213 at that time in latch 129, and at the same time, the number of lines at this time is also latched in latch 131. However, latch 1
The output of latch 132 is connected to one input of comparator 133, while the input of latch 132 is cleared to zero by VSYNC 213.
3, and when the latch output of 131 is greater than the latch output of latch 132, the comparator generates an output such that A>B, and latches the new latch output of 131 at this time to latch 132. After that, this operation is repeated until the preliminary scanning is completed.

Therefore, once _the trailing edge of _the document, that is, The exposure scanning stage is returned to the detected document leading edge point. In order to realize this control, the comparator 152, AND gate 151, and counter 150 shown in FIG. 7 are used to ensure that even if there is a black line in the main scanning direction, as in the original shown in FIG. 9, this will not be mistakenly detected as the trailing edge of the original. I have to. In other words, the number of lines where the final non-black signal BLACK was detected continues to be not updated. Therefore, the black part is the value set by the counter 150 (the counter 150 can be set to a predetermined value by the preset 155). Continuing above, the output of comparator 152, gated to 160,
HSYNC212 counts the counter, and when it counts down, RETURN215 controls the control circuit 11.
1, and in response to RETURN 215, the control circuit 111 outputs a STOP signal 207 to stop driving the motor. Further, in the case of a special type of original, for example, an almost black original, a changeover switch may be provided to perform full scanning.

FIG. 10 is a flow diagram of the preliminary scan, which flow is programmed into the program memory of the control circuit 111. The preliminary scanning will be explained below based on FIG. 10.

In step S1, PRS200 is the control circuit 1.
11, the frequency divider 116 is set,
In S2, the shift registers 120 to 12 are controlled by the control circuit 111 via the signal lines 202 to 205.
3 is set as FW. The down counter is fully set in S3, but this is because the down counter is operated no matter where the document is placed on the document table. Next, DRV201 is output, the motor is driven,
The positions of X ₁ and X ₂ are detected as described above. S5
When the document position is detected in , RETURN21
5 is input to the control circuit 111, and in S6,
The motor drive is stopped, and in S7, the number of lines at the _X1 position latched in the latch 129 is input to the control circuit 111, and then in S8,
The number of lines at the _X2 position latched in latch 132 is input to control circuit 111. In S9, the number of pulses of K(X ₂ −X ₁ +α) is TCNT20
6 is output to the down counter 124, and the down counter 124 is set. α is the amount by which the scanning unit moves to read a predetermined number of black information after detecting the trailing edge CD of the document, and when performing main scanning, Front edge AB of the document for stable scanning
This is the number of lines to stop the scanning unit a little earlier than , and the reason why it is multiplied by K is to obtain the number of pulses corresponding to the moving distance. At S10, the shift register 120 is controlled by the control circuit 111 via the signal lines 202 to 205.
~123 is set to RV, and in S11, DRV
201 is output, the motor is driven, the scanning unit moves backward, and the down count is 124 in S12.
is counted down, and the scanning unit moves until the countdown is completed. When the countdown is completed, the motor is stopped in S13 and the preliminary scanning is completed.

As mentioned above, the scanning unit will be reversed at the position shown in FIG. 8 and will stop at the position shown in FIG.

FIG. 11 is a flowchart of document scanning, and the flow is programmed into the program memory of the control circuit 111. Document scanning will be explained below based on FIG. 11.

In step S15, PRS 200 is output from control circuit 111 and frequency divider 116 is set. In S16, as TCNT206, K×
The number of pulses of (X ₂ −X ₁ +β) is down counter 12
Set to 4. At this time, the scanning unit is at the position where preliminary scanning has been completed, that is, the position shown in Figure 8.
β is an amount to allow a little margin for stable scanning when scanning the original. At S17, the control circuit 11 is connected via signal lines 202 to 205.
FW of shift registers 120 to 123 by 1
When set to , the DRV 201 is outputted from the control circuit 111 in S18 to drive the motor, and the scanning unit moves forward. In S19, the down counter 124 counts down, and when the countdown is completed, the process advances to S20 and the motor is stopped. Forward scanning stops. In S21, a countdown of a predetermined number of scans is determined, and if the predetermined number of originals have been scanned, the process advances to S26, and if the predetermined number of originals have not been scanned, the process advances to S22. The predetermined number of scans can be set because, for example, in the case of color copying, the document is often scanned several times.

In step S22, the signal lines 202 to 205
The shift registers 120 to 123 are set to RV by the control circuit 111 via the control circuit 111, and in S23,
When the DRV 201 is output from the control circuit 111, the motor is driven and the scanning unit moves backward. S24
At this point, the down counter 124 counts down, and when the countdown is completed, the motor stops at S25, and the backward movement of the scanning unit is stopped. This S17, S18, S19, S20, S21, S22,
S23, S24, and S25 are repeated until the document is scanned a predetermined number of times.

When the document has been scanned a predetermined number of times, the process advances to S26.
In S26, shift registers 120 to 123
RV is set, and in S27, the number of pulses _of K x
The down counter 124 is set, and the control circuit 111 outputs the DRV 201 in S28.
is output, the motor is driven, the scanning unit moves backwards, the down counter 124 counts down in S29, and when the countdown is completed, the scanning unit moves backward.
At this point, scanning of the original is completed.

In addition, in this embodiment, the AB edge and CD edge of the document are detected, but it is also possible to detect the document size, and it is also possible to correct a document placed at an angle so that it can be read. This is possible using well-known techniques.

In this embodiment, the case where the entire document is read has been described, but it goes without saying that the required reading width may be further narrowed due to partial trimming of the document, and the effect is even more remarkable.
Further, the motor to be used is not limited to a stepping motor, but any motor may be used as long as the position can be controlled with high precision.

Further, in this embodiment, a fixed document type reading device has been described, but a document platen moving type reading device can be similarly applied.

Alternatively, it may be possible to control either the document scanning start position or the end position.

<Description of Effects> As explained above, according to the present invention, the document is pre-scanned from the home position, the position of the leading edge of the document is detected, and the position of the leading edge of the document is detected without returning the scanning means to the home position. By controlling the motor to move the document to the leading edge position and start scanning the document from there, even if the document is not placed at the standard placement position on the document table and is placed shifted in the scanning direction,
It is possible to prevent unnecessary scanning of a portion where there is no document between the home position and the leading edge of the document, and to efficiently scan the necessary portion.

In particular, when the same original is repeatedly scanned, the time required for scanning the original can be shortened, and throughput can be improved.

Further, it is possible to scan a document of a size other than the standard size from the leading edge position of the document.

[Brief explanation of the drawing]

1A and 1B are diagrams showing the conventional scanning method, FIG. 2 is a drive mechanism diagram of the color image reading device of the embodiment, FIGS. 3 and 4 are motor drive circuit diagrams, and FIG. The figure is an external view of the color document reading device.
Figure 6 is a diagram showing an example of a document placed on the document table, Figure 7 is a scanning position detection circuit diagram, Figure 8 is a diagram showing the movement of the scanning unit, and Figure 9 is a diagram showing an example of a manuscript. , FIG. 10 is a preliminary scanning flowchart, and FIG. 11 is a document scanning flowchart. 1 is an original table, 2 and 6 are originals, 3 is a self-occurrence lens, 4 is an exposure illumination lamp, 5 is a single-magnification solid-state image sensor, 100 is a pulse motor, 111 is a control circuit, 115 is an oscillator, and 116 is a frequency divider. vessel, 117 is
JK flip-flop, 118 is a flip-flop, 119 and 199 are gates, 120 to 123 are shift registers, 124 is a down counter, 12
8 is a line counter, 129, 131, 132 are latches, 130 is a flip-flop, 133, 1
52 is a comparator, 150 is a counter, 151
is a gate, and 155 is a preset.

Claims (1)

[Scope of Claims] 1. A mounting table on which a document is placed, a scanning means for scanning the document placed on the mounting table, a motor for moving the scanning means, and a document scanned by the scanning means. a reading means for reading an image of the original; a detecting means for detecting a placement position of the original on the placing table based on an image signal from the reading means; and a predetermined scanning means for detecting the placement position of the original. perform preliminary scanning from the home position of the document, move the scanning means to the leading edge position of the original to the detected document placement position without returning to the home position, and move the scanning means from the leading edge position to scan the original. A document reading device comprising: control means for controlling the operation of the motor so as to move the motor.