JPH0758906A - Image reader - Google Patents

Abstract

PURPOSE:To suppress the flapping of an original and to correctly detect the tip part of the original, etc., by providing an elastic piece being in press-contact with the original whose tip part is carried at the carrier path of the original to be read. CONSTITUTION:The original 1 sent out from an ADF 7 is carried between contact glass 2 and a platen 4 by a carrier roller 5. The original 1 arriving at the tip part of the contact glass 2 and the platen 4 is sent out between the contact glass 2 and the platen 4 as being pressed on the upper plane of the contact glass 2 by a synthetic resin piece 14 provided at the tip part of the platen 4. The original 1 sent out between the contact glass 2 and the platen 4 is pressed by the synthetic resin piece 14 at a position near to a scanning line 3. When the tip part of the original 1 passes between the contact glass 2 and the platen 4, the original 1 is pressed on the upper plane of the contact glass 2 by a synthetic resin piece 15 provided at the rear terminal of the platen 4. In this way, the flatting of the original 1 on the scanning line 3 can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus such as a copying machine or a facsimile apparatus, and more particularly to prevention of fluttering of a document on a scan line for reading an image.

[0002]

2. Description of the Related Art Image reading devices such as facsimile machines
As shown in FIG. 9, a contact glass 2 on which an original 1 to be read is placed, and a pressure plate 4 for pressing the original 1 against the contact glass 2 to regulate the position of the original 1 on the scan line 3.
It has transport rollers 5 and 6 for transporting the document 1, an ADF 7 for feeding the document 1, a document detection sensor 8 for detecting the front and rear ends of the document 1, and a reading optical system 9. The pressure plate 4 is the original 1
The surface pressing the contact glass 2 against the contact glass 2 is formed in white. The reading optical system 9 has a light source 10, a mirror 11, a lens 12, and an image sensor, such as a CCD 13.

When the document 1 is read, the position of the document 1 to be read with respect to the contact glass 2 is regulated by the pressure plate 4, and the document is fed by the transport rollers 5, 6 provided in front of and behind the contact glass 2 in the document transport path. 1 is given tension (Japanese Patent Laid-Open No. 2-305170).

[0004]

As described above, when the original 1 is read, tension is applied to the original 1 by the transport rollers 5 and 6 provided in front of and behind the contact glass 2. Since the document detection sensor 8 is provided between the front and the front conveyance roller 5, the distance between the contact glass 1 and the conveyance roller 5 cannot be shortened by a certain distance or more, and the conveyance roller 5 cannot be shortened. Even if tension is applied to the document 1 by the rollers 5 and 6, the document 1 is likely to flap as shown in FIG.
Document 1 between contact glass 2 and pressure plate 4
The flapping is particularly caused when the front end of the document 1 sent by the front transport roller 5 has not reached the rear transport roller 6, or when the rear end of the document 1 is the front transport roller 5. It occurs remarkably when passing by. For this reason, there is a disadvantage that the image read by the reading optical system 9 is distorted vertically and the density is varied, and the image quality is deteriorated.

Further, when the original 1 flutters as described above, chattering occurs in the output of the original detection sensor 8 when the original detection sensor 8 detects the front end portion or the rear end portion of the original 1, and the original 1 There is a risk that the front end portion and the rear end portion cannot be accurately detected, and the reading start position is displaced.

The present invention has been made to solve the above disadvantages, and provides an image reading apparatus capable of suppressing the fluttering of a document in a scan line for reading the document and accurately detecting the leading end of the document. The purpose is to obtain.

[0007]

SUMMARY OF THE INVENTION An image reading apparatus according to the present invention includes one of a front end portion and a rear end portion of a pressure plate which is provided in a conveyance path of a document to be read and which regulates the position of the document with respect to a reading unit, or It is characterized in that both of them are provided with elastic pieces whose tip portions are brought into pressure contact with a document being conveyed.

Further, there is provided a static elimination brush which is provided on a conveyance path of the document to be read and which suppresses the document conveyed to one or both of a front end portion and a rear end portion of a pressure plate which regulates the position of the document with respect to the reading section. Is also good.

Further, the pressure plate for restricting the position of the original with respect to the reading unit has a black sheet and a white sheet which are divided into front and rear in the original conveying direction, and the sheet is arranged in the original conveying direction. When the original is read, the black sheet of the pressure plate is moved to the reading line of the reading section by the pressure plate moving means when the original is read, and the black sheet of the reading section and the original are read by the front and rear edge detection section of the original. It is preferable to detect the leading edge and the trailing edge of the document from the output signal of the reading unit. Further, it is preferable that the above-mentioned black sheet is formed of an elastic member so as to suppress a document to be conveyed.

[0010]

According to the present invention, the elastic piece or the static elimination brush is directly attached to the front end or the rear end of the pressure plate for restricting the position of the document to be read with respect to the reading unit, and the document conveyed at the front and rear ends of the pressure plate is set to the reading unit. Against this, the fluttering of the original on the scan line is suppressed.

Further, the pressure plate is divided into a black sheet and a white sheet with respect to the front and rear of the original conveying direction, and when the original is read, the black sheet of the pressure plate is read by the reading section by the pressure plate moving means. Move to the line and directly detect the leading edge or trailing edge of the document with the document front / rear edge detection unit from the change in the output signal of the scanning unit when reading the black sheet and the output signal of the scanning unit when scanning the document. . The black sheet of the pressure plate is formed of an elastic member to suppress the document to be conveyed, thereby suppressing the fluttering of the document on the scan line.

[0012]

1 is a block diagram of an embodiment of the present invention.
As shown in the figure, the image reading apparatus includes a contact glass 2 on which a document 1 to be read is placed, a pressure plate 4 for pressing the document 1 against the contact glass 2 to regulate the position of the document 1 on a scan line 3, and a document 1. It has transport rollers 5 and 6 for transporting, an ADF 7 for sending out the original 1, an original detection sensor 8 for detecting the front end and the rear end of the original 1, and a reading optical system 9. The pressure plate 4 has a white surface on which the original 1 is pressed against the contact glass 2. The front and rear ends of the pressure plate 4 with respect to the document transport direction are provided with synthetic resin pieces 14 and 15 which are elastic and have their leading ends pressed against the upper surface of the document 1 to be transported. The reading optical system 9 includes a light source 10, a mirror 11, and a lens 12.
And an image sensor such as CCD 13.

In the image reading apparatus constructed as described above,
The original 1 sent from the DF 7 is conveyed between the contact glass 2 and the pressure plate 4 by the conveying roller 5. The manuscript 1 reaching the tip of the contact glass 2 and the pressure plate 4 is pressed by the pressure plate 4
It is sent between the contact glass 2 and the pressure plate 4 while being pressed against the upper surface of the contact glass 2 by the synthetic resin piece 14 provided at the tip of the. The original 1 sent between the contact glass 2 and the pressure plate 4 is held by the synthetic resin piece 14 at a position close to the scan line 3, so that when the leading end of the original 1 passes the position of the scan line 3. Flapping is very small.

The front end of the original 1 is the contact glass 2
After passing between the pressure plate 4 and the pressure plate 4, the original 1 is pressed against the upper surface of the contact glass 2 by the synthetic resin piece 15 provided at the rear end of the pressure plate 4. In this way, since the original 1 being conveyed is suppressed by the synthetic resin pieces 14 and 15 provided at the front and rear ends of the pressure plate 4, the original 1 is placed at the position closest to the scan line 3.
Document 1 in scan line 3
Flapping can be made smaller.

Even if the original 1 is further conveyed and the rear end of the original 1 comes off the front synthetic resin piece 14, the original 1 is held by the rear synthetic resin piece 15, so the original 1 on the scan line 3 is held. Flapping can be kept very small. In this way, the original 1 on the scan line 3
By suppressing the fluttering, it is possible to prevent the image of the original 1 read by the reading optical system 9 from being distorted in the vertical direction and the density is varied, and an image of high quality can be obtained.

In the above embodiment, the case where the original 1 being conveyed is directly held by the synthetic resin pieces 14 and 15 provided at the front and rear ends of the pressure plate 4 has been described, but as shown in FIG. Static elimination brushes 16 and 17 are attached to the front and rear ends of the pressure plate 4.
May be provided, and the original 1 conveyed between the contact glass 2 and the pressure plate 4 may be suppressed by the static elimination brushes 16 and 17. When the original 1 is suppressed by the static elimination brushes 16 and 17 in this manner, static electricity can be removed from the original 1, and the fluttering of the original 1 on the scan line 3 can be further suppressed.

In each of the above embodiments, the description has been given of the case where the synthetic resin pieces 14 and 15 and the static eliminating brushes 16 and 17 are provided at the front end and the rear end of the pressure plate 4, but the front end and the rear end of the pressure plate 4 are described. Even if a synthetic resin piece or a static elimination brush is provided on either one of them, the fluttering of the original 1 on the scan line 3 can be suppressed to a small level.

Further, when the synthetic resin pieces 14 and 15 and the static elimination brushes 16 and 17 provided at the front and rear ends of the pressure plate 4 are made of a material having a low reflectance, irregular reflection in the vicinity of the pressure plate 4 can be prevented. , You can get a better image.

In each of the above-mentioned embodiments, the case where the leading edge or the trailing edge of the document 1 conveyed by using the document detection sensor 8 is detected has been described. However, the leading edge of the document 1 is detected without using the document detection sensor 8. Alternatively, the trailing edge may be detected, and the distance between the transport rollers 6 provided in front of and behind the contact glass 2 may be shortened to suppress the fluttering of the document 1 on the scan line 3.

FIG. 3 shows a structure for detecting the leading edge and the trailing edge of the document 1 without using the document detection sensor 8. As shown in the figure, the pressure plate 4 that regulates the position of the original 1 with respect to the contact glass 2 has a white sheet 4a and a black sheet 4b that are divided in the front-back direction of the original 1 in the conveying direction. The pressure plate 4 can be moved forward and backward in the conveyance direction of the document 1 by the pressure plate moving means 21. CC of the reading optical system 9
The image processing unit 22 to which the output signal from D13 is input,
As shown in the block diagram of FIG. 4, an AD conversion unit 23 that converts an analog signal that is an output signal of the CCD 13 into a digital signal, a shading correction unit 24 that performs shading correction, a RAM 25, and a binarization unit 26. Besides CCD13
And a document front / rear edge detection unit 27 for detecting the front and rear edges of the document from the output signal from the document. The RAM 25 has a shading correction data storage unit 25a and a black sheet data storage unit 25b.

The operation of reading the original 1 in the image reading apparatus configured as described above will be described with reference to the flow chart of the drawing and the waveform chart of FIG.

When the original 1 to be read is set and the reading of the original 1 is started (step S1), first, as shown in FIG. 3, the white sheet of the pressure plate 4 is placed at the position of the scan line 3.
The sheet 4a is set, and the white sheet 4a is read by the CCD 13. CCD when this white sheet 4a is read
As shown in FIG. 6A, the output 13 of the main scanning direction is white waveform data of a high output level which is substantially uniform between the reading start position and the reading end position A. The image processing unit 22 uses the white waveform data as the shading correction data in the RAM 25.
(Step S2). Next, the pressure plate 4 is moved by the pressure plate moving means 21, the black sheet 4b is set at the position of the scan line 3 as shown in FIG. 7, and the black sheet 4b is read by the CCD 13 (step S3). When the black sheet 4b is read, the output of the CCD 13 in the main scanning direction is black waveform data of a low output level which is substantially uniform between the reading start position and the reading end position A as shown in FIG. 6B. become. The image processing unit 22 converts this black waveform data into black
The data is fetched as data and stored in the RAM 25 (step S4).

Then, the conveyance of the original 1 is started (step S5). When the conveyance of the document 1 is started, the document front / rear end detection unit 27 sequentially reads the read data output from the CCD 13.
It is compared with the black sheet data stored in AM25 (step S6). Then, the read data output from the CCD 13
While the data matches the black sheet data, it is determined that the leading edge of the document 1 has not reached the scan line 3. When the leading edge of the original 1 reaches the scan line 3, the waveform of the read data output from the CCD 13 in the main scanning direction is shown in FIG.
As shown in FIG. 3C, the original sheet data between the both side edges B of the original sheet 1 suddenly rises to a high level from the black sheet data. Therefore, the document front / rear edge detection unit 27 outputs document data output from the CCD 13 different from the black sheet data.
When it is detected that the data has become the input data, the document leading edge detection signal is sent to the binarization unit 26 and the CP is sent via the system bus 28.
Send to U etc. Upon receiving the document leading edge detection signal, the binarizing unit 26 binarizes the read data output from the CCD 13 and transfers it as image information (step S7). Thereafter, the read data output from the CCD 13 is detected by the document front / rear edge detection unit 27.
While detecting the original data whose data is different from the black sheet data, the binarizing unit 26 binarizes the read data output from the CCD 13 and transfers it as image information. When the document front / rear end detection unit 27 detects that the rear end of the document 1 has passed the scan line 3 and the read data output from the CCD 13 has become black sheet data, the document front / rear detection unit 27 27 sends the document trailing edge detection signal to the binarization unit 26 (step S
8). When the binarizing section 26 receives the document trailing edge detection signal, it stops binarizing the read data and transferring the image information (step S).
9). Then, the leading edge detection, the image reading, and the trailing edge detection of all the originals 1 are repeated in the same manner as described above (steps S6 to S9),
When the reading of the original 1 on the last page is completed (step S1
0), the pressure plate 4 is moved by the pressure plate moving means 21, and the black sheet 4b is returned to the initial position at the position of the scan line 3 as shown in FIG. 3 (step S11).

As described above, since the black sheet 4b is provided on the pressure plate 4 and the leading and trailing edges of the document are directly detected from the read data output from the CCD 13, the leading and trailing edges of the document can be accurately detected. Further, since it is not necessary to provide a document detection sensor in the conveyance path of the document 1, the interval between the scan line 3 and the front conveyance roller 5 can be shortened, and the document between the contact glass 2 and the pressure plate 4 can be reduced. It is possible to suppress the fluttering of the document 1 and to convey the document 1 having a plurality of pages with a short interval between the pages, so that high-speed reading can be performed.

In the above embodiment, the black sheet 4b is used only for detecting the leading and trailing edges of the original 1, but the black sheet 4b is made of a synthetic resin material having elasticity, as shown in FIG. Part of the surface is in contact with the contact glass 2,
The original 1 to be read may be held on the surface of the contact glass 2. By thus suppressing the original 1 with the black sheet 4b, it is possible to completely eliminate the fluttering of the original 1 on the scan line 3.

[0026]

As described above, according to the present invention, an elastic piece or a static eliminating brush is directly attached to the front end or the rear end of the pressure plate that regulates the position of the document to be read with respect to the reading unit, and the sheet is conveyed at the front and rear ends of the pressure plate. The originals to be scanned against the scanning section to prevent the originals from fluttering on the scan line.
It is possible to prevent vertical distortion and density variation in the read original image, and it is possible to obtain a high-quality image.

Further, by attaching a static eliminating brush to the front end portion or the rear end portion of the pressure plate, it is possible to eliminate static electricity from the original to be read, and to suppress the fluttering of the original on the scan line.

Further, the pressure plate is divided into a black sheet and a white sheet in the front and rear of the original conveying direction, and when the original is read, the black sheet of the pressure plate is read by the reading section by the pressure plate moving means. Move to the line and directly detect the leading edge or trailing edge of the document with the document front / rear edge detection unit from the change in the output signal of the scanning unit when reading the black sheet and the output signal of the scanning unit when scanning the document. As a result, it is possible to accurately detect the leading and trailing edges of the document.

Further, by directly detecting the leading edge or the trailing edge of the document, it is not necessary to provide a document detecting sensor in the document transport path, so that the interval between the scan line and the transport roller can be shortened. Flapping of a document on a scan line can be suppressed.

Further, by shortening the interval between the scan line and the transport roller, it is possible to transport the document having a plurality of pages with a short interval between each page, and high-speed reading can be performed.

Further, by forming the black sheet of the pressure plate by the elastic member and suppressing the original document to be conveyed, the fluttering of the original document on the scan line can be completely eliminated.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a second embodiment.

FIG. 3 is a configuration diagram showing a third embodiment.

FIG. 4 is a block diagram showing an image processing unit of a third embodiment.

FIG. 5 is a flowchart showing the operation of the third embodiment.

FIG. 6 is a waveform chart showing the operation of the third embodiment.

FIG. 7 is a configuration diagram showing an operating state of the third embodiment.

FIG. 8 is a configuration diagram showing a fourth embodiment.

FIG. 9 is a configuration diagram showing a conventional example.

[Explanation of symbols]

 1 Original 2 Contact Glass 3 Scan Line 4 Pressure Plate 4a White Sheet 4b Black Sheet 8 Original Detection Sensor 9 Reading Optical System 13 CCD 14 Synthetic Resin Piece 15 Synthetic Resin Piece 16 Static Erasing Brush 17 Static Erasing Brush 21 Pressure Plate Moving Means 22 Image Processing unit 25 RAM 27 Document front and rear edge detection unit

Claims (4)

[Claims] 1. A front end portion of one or both of a front end portion and a rear end portion of a pressure plate, which is provided in a conveyance path of a document to be read and regulates the position of the document with respect to the reading unit, is brought into pressure contact with the conveyed document. An image reading apparatus comprising an elastic piece. 2. A static eliminator brush for suppressing an original conveyed to either or both of a front end portion and a rear end portion of a pressure plate which is provided in a conveying path of an original to be read and regulates the position of the original with respect to the reading unit. An image reading device characterized by the above. 3. An original having a black sheet and a white sheet divided in the front and rear of the original conveying direction, movably provided in the front and rear of the original conveying direction, with respect to the reading unit. Of the pressure plate, the pressure plate moving means for moving the black sheet of the pressure plate to the reading line of the reading section when reading the original, and the output of the black sheet of the reading section and the reading section which has read the original. An image reading apparatus, comprising: a document front / rear edge detection unit that detects a front edge and a rear edge of a document from a signal. 4. The image reading apparatus according to claim 3, wherein the black sheet is formed of an elastic member to suppress a document being conveyed.