JPS5834674A - Image reader - Google Patents

Abstract

PURPOSE:To obtain an excellent read image without extending transmitting time, by delaying an image sensor for a fixed time from the readout signal, and driving an original carrying means. CONSTITUTION:Reflected lights from an original 1 are introduced to a lens 6 by a mirror 5 and form an image in an image sensor (CCD) 7. Image information accumulated in the CCD7 is sent to a transmission line through a MODEM10 after it is once stored in a buffer memory 9. At this time, a controller 8 controlls the CCD7, a stepping motor 3, and the buffer memory 9, but, since the driving speed of the stepping motor for the auxiliary scanning is slower than the readout scanning speed of the CCD7, the readout signal of the CCD7 is inputted into a delay circuit (not shown in the figure), and a fixed delay is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image reading device, and more particularly to an image reading device C1 that reads a flat image of a document by dividing it into pixels, such as a facsimile machine.

For example, conventional image reading devices such as facsimile machines have a side scanning line density of 3.85 lines based on the recently established International Tatami Standard (= 3.85 lines), but at this level of sub-scanning line density, Although it can handle general handwritten documents, when transmitting small characters or detailed drawings, the image becomes distorted and becomes unreadable. 7.7/11
Various facsimile machines have also been proposed that have a function of communicating at a high sub-scanning line density. For example, CCITT's 3G standard allows this as an optional feature.

In a device like this facsimile machine (which reads a plane image by dividing it into pixels by scanning), the sub-scanning width (for example, 0.26 at a sub-scanning line density of 3.85 lines/n)
It is common to set the reading slit radius and the element width of the image sensor to correspond to 0m)-1.

Furthermore, in order to obtain good image quality, it is important to use a recording element that is approximately the same size as the pixel width for reading.

However, when a reading operation is performed at a sub-scanning line density of 3.85 lines/M (2) using a matching reader and a sub-scanning line density of 77 lines/M, as shown in Figure 1 (2 adjacent scanning lines (Since the image is read across two lines, each scanning line l,
We obtain a read output such as P, ~P, for ~l. That is, the readout output of the overlapped image portion shows the maximum value, and therefore the readout signals overlap, resulting in the image being distorted and missing.

On the other hand, if the reading operation is performed at a sub-scanning line density of 7.7 lines/- (3.85 lines/eye in total with the reading device), a clear reading output corresponding to each image will be obtained as shown in Figure 2. However, there is a risk that image information between scanning lines may be lost.As a solution to this drawback, the following method has been proposed.In other words, the reading width is adjusted to 3.85 mm/n. (0,260 miscellaneous) and 77 lines/m (: average value (0,1951111) of compatible width (0,130 fins) ≦ 2, or read width and recording element width to 77 lines/1 m A method of increasing the density of a recorded image by recording one main scanning line information twice, or
The book's main scanning line information is scanned twice at a scanning line density of 7.7 lines/- (
A method has been proposed in which the information is read in two parts, the logical sum is taken, and the result is recorded as one main scanning line information.

Among the various methods described above, the third logical sum method can provide the best image quality.

However, with this method, main scanning line information is read twice at a scanning line density of 7.7 lines/fin (because it is read in two parts, if the response of the sub-scanning motor is slow, one scanning line/information is read. It took a long time.

In order to shorten this reading time (by performing sub-scanning at a scanning line density of 23.85 lines/cod and reading twice during that time, the operating speed of the electronic circuit that controls the image sensor is lower than that of the sub-scanning motor. Since the response speed is significantly lower than the response speed of the conventional method, the two scan lines read are too close to each other, resulting in a significant drop in resolution.

The present invention has been made in order to eliminate the above-mentioned conventional drawbacks, and an object of the present invention is to provide an image reading device having two configurations so that a good read image can be obtained without increasing the transmission time. It is said that

In order to achieve the above object, the present invention (second invention) adopts a structure in which a delay means is provided for driving the document conveying means with a certain period of time delay from the signal for reading the image sensor.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 3 is a block diagram illustrating the control circuit of the reading device. In the figure, a document designated by reference numeral 1 is held between upper and lower transport roller groups 2, 2, and is transported by a stepping motor 3 (reference 4). 2 is a light source, and image information, which is reflected light from the original 1, is guided by a mirror 5 (2) to a lens 6 (2), and is imaged on an image sensor (CCD7i), which is a photoelectric conversion element. .

The image information accumulated in the image sensor CCD 7i is temporarily stored in a buffer memory 9, subjected to signal processing, and then sent to a transmission line via a modulator/demodulator 10.

The reference numeral 8 is a stiffening device for the entire reading device, and the stepping motor 3. Controls the CCD 7 or buffer memory 9.

FIG. 4 is a detailed explanation of the control device 8 and buffer memory 9 shown in FIG. 3, and FIG. 5' is a time chart showing a part of the operation of FIG.

CCD' which is an image sensor? The read clock a from the controller 11 (see FIG. 5 (3)) (=Therefore, the image signal accumulated by C2 is sent every accumulation time τ. That is, first, the OR buffer write signal b (see FIG. 5 (Bl)
is sent out from the control unit 12, the changeover switch 13 is switched, and the readout taro clock a (see FIG. 5(C)
(As shown in Figure 2, image information A from CCD 7 is OR
Buffer 14 (2 stored; and image buffer 1
7 to 19, for example, if the image information written in the image buffer 17 is electronically transmitted and the image buffer 11 is stored, the control unit 12 outputs the write signal d at the timing shown in FIG. 5(D). and selector switch 1.
3 and causes the image buffer control unit 16 to set the image buffer 17 to the write state.

Also, at this time, the OR buffer 14 (2 stored image information A) is read out, and the image information A2 and O from the CCD 7 are read out.
The R gate 15 performs a logical sum (FIG. 5(C)).

(E)) is stored in the image buffer 17. At this time, the control unit 12 outputs the driving signal f shown in FIG. 5 to the stepping motor 3 to transport the original 1 by one scanning line pitch.

On the other hand, since the OR buffer 14 becomes empty at the time when the image buffer 17 (the image information obtained by performing the two-wheel summation) is stored, the control unit 12 outputs the OR buffer write signal S again.
The CCD 7 receives the readout clock (image signal A3 in two synchronizations).
is output, and the OR buffer (second-side image information A) is written.

By the way, the movement of the document 1 during this time is offset by the error due to mechanical play in the movement of the rotor of the sub-scanning stepping motor 3, but it is approximated (2 is as shown in Fig. 5 (G)). This can be considered as the movement m of the rotor of the stepping motor 3.

The information written to the OR buffer 14 (2) is A3, but the stepping motor 3 is still barely moving at this point due to a delay due to inertia.

Therefore, the scan lines of information written to the OR buffer 14 are two adjacent scan lines, and the image information A3 is almost the same as the image information A2.

This is a scanning line that is the logical sum of image information A and A2,
This means that the scanning lines obtained by calculating the logical sum of image information A3 and A4' have almost the same content, and the image is distorted.

The embodiments shown in FIGS. 6 and 7 solve this problem.

In FIGS. 6 and 7 (=, the same parts or corresponding parts as in FIGS. 3 to 5, and 4 parts are denoted by the same reference numerals.

In this embodiment, an OR gate 15 (a black information detector 20 for detecting whether black information is included in the logical sum of the image information) is connected to That's it.

The operation in such a structure is exactly the same as that described above until the image information A2 is stored in the image buffer 17 (2) and the write signal d to the empty OR buffer 14 is issued.

Image buffer 17 (when image information obtained by calculating the sum of two wheels is written): A black information detector 20 such as a D flip-flop (-Thus, the presence or absence of black information is checked.And,
As shown in FIG. 7(F) (2) When the two-point information g is detected, the two-point information signal is output as shown in FIG. a1
However, when the black information signal is output (-The OR buffer write signal sent out is OR depending on the CCD 7 read signal a that is output immediately after that)
Since the buffer 14 is not driven, writing is started by the next CCD read signal a2. That is, the image information written in the OR buffer 14 (2) is not A, but A
It is 4. Therefore, as is clear from the movement m of the rotor of the stepping motor 3, the image information of the scanning line that is sufficiently (1) away from the scanning line of the image information A2 is
Since the image is written in the same area, the image is less likely to be distorted and the number of missing images is also reduced.

Incidentally, the response of the rotor of the motor is greatly influenced by the inertial mass of the rotor itself, and the inertial mass and frictional loads of reading mechanism parts such as conveyance rollers and speed reducers. That is, when the frictional load is large, the damping characteristics of the stepping motor are improved, but the start of rotation of the rotor is delayed and the response frequency is reduced.

In addition, if the inertial mass is large (second), not only will the start-up of the rotor's rotation be delayed, but the damping characteristics will also deteriorate.

Therefore, depending on the characteristics of the stepping motor used and the characteristics of the drive circuit, the document is transported a predetermined amount after the sub-scanning drive signal is applied (the required time varies. The response of the rotor differs not only due to the motor but also due to variations in the dimensions and materials of the mechanical parts.

When the response of the motor is fast, that is, when the time constant of the sub-scanning drive system is small (2 is the timing chart in Figure 7) (2 is the timing chart in Figure 7). , image information may be lost.

FIG. 8 shows a control circuit of an embodiment for eliminating such drawbacks, and FIG. 9 shows a timing chart of the operation.

That is, the readout signal (RCL
K) (- synchronously and during the image signal (DATA) (-
Whether black information is included (OR determined by two)
Figure 9 shows the write timing to the buffer and image buffer (two-point information BLp, cK, oR buffer write signal 0).
RBBSY and image buffer write signal TBBSY.

First, the driving signal SMCL of the sub-scanning stepping motor is
If ζ= is configured so that K is synchronized with the rising edge of image buffer write signal TBBSY (2), in the case of a sub-scanning drive system with a small time constant, the rotor will move like the curve shown by the two-dashed line m' in FIG. 2 rise, OR/< The scanning line to be written on the sofa will be very close to the next scanning line. To eliminate this, the delay circuit 21 shown in FIG. 8 (2) is used. CCD7 read signal RCLK
-2 A device that causes a certain delay, and its output DELA
Using Y, the Noculus generator 22 obtains signals pt and YCLK with appropriate pulse widths.

The reference numeral 23 is a latch circuit, which outputs the mode drive signal SMCLK only during one read period when the image buffer write signal TBBSY is output;
It is set by RCLK and reset by RCLK.

The output 5TPEND of the latch circuit 23 is connected to the AND gate circuit 24i, and the output DLYCL of the pulse generator 22
Ki is applied to obtain the motor drive signal SMCLK.

FIG. 10 shows a delay circuit 21 and a Noculus generator 22;
This shows an example using a one-shot monomulti variable resistor 25°27.
6 is connected to compensate for variations in the mechanical load of the sub-scanning system (-and thus different motor responses), and the delay time is varied (2).

Figure 11 also shows a mechanism whose load changes depending on usage conditions, such as when an automatic paper feeder is added to the reading and conveying system C unit (
On the other hand, for example, a central processing unit CPU (not shown)
(This shows an example of a delay circuit that can automatically set the delay time C2.

That is, data representing the delay time from the data bus DB from the CPU is latched into the flip-flop 31, and the counter 29 counts a predetermined time. Then, the flip-flop 31 (the set delay data is set in the counter 29 by the reading ratio signal RCLK of the CCD 7. At this time, 'the highest value of the counter 29 becomes a high level;
:Set the data as a negative binary number.

A clock with a short period, for example, a 3-cycle clock used in a CPU, is gated by the value of the most significant digit of the counter 29 (
30), which is divided by a binary counter 28.

When the frequency-divided clock is counted up by the counter 29 (two people), the signal from the CPU (two people) counts the set number of pulses and outputs a carry. If this carry is used as the delay signal DLYCLK, it can be used as a delay circuit. It can be used as a circuit that combines pulse generators.

As is clear from the above description, the present invention (according to Part 2) employs a configuration including a delay circuit for driving the document conveying means with a certain period of time delay from the image sensor read-out signal. Even when the response speed of the stepping motor changes or the load on the transport mechanism section changes (-), it is possible to obtain an image reading device that can obtain high-quality images by determining the reading timing appropriately.

[Brief explanation of the drawing]

FIGS. 1 and 2 are explanatory diagrams showing image distortion and missing states in the conventional method, FIG. 3 is a block diagram of a control circuit of a facsimile image reading device to which the present invention is applied, and FIG. 5 is a block diagram showing the details of the control circuit shown in FIG. 3, FIGS. 5(A) to 5(G) are timing charts showing the operation of the control circuit shown in FIG. A block diagram of the control circuit shown in Fig. 6 is shown in Fig. 7.
8 is a block circuit diagram illustrating an embodiment of the present invention, and FIG. 9 is a timing chart diagram illustrating the operation of the circuit shown in FIG. 10 and 11 are block diagrams of a delay circuit and a pulse generation circuit to which the present invention is applied. 1... Manuscript paper 3... Stepping motor 7... Image sensor 14... OR buffer 17-19... Image buffer 21... Delay circuit 22... Pulse generator 31... Flip-flop.

Claims (2)

[Claims] (1) An image reading device equipped with an image sensor consisting of a multi-bit photoelectric conversion element and means for conveying a document in a direction perpendicular to the scanning direction of the image sensor (
2. An image reading device characterized in that a delay means is provided for driving the document conveying means with a predetermined delay from the signal for reading the image sensor. (2) The image reading device according to claim 1, wherein the delay means has a C2 configuration so that the delay time can be adjusted.