JP4604990B2 - Image reader - Google Patents

Description

  The present invention relates to an image reading apparatus, and more particularly, to an original reading type image reading apparatus used as an image input apparatus in a copying machine or a scanner.

  In general, the image reading apparatus reads an image on a reading glass provided at a predetermined reading position while automatically conveying the original one by one so that a large number of originals can be read in a short time. A so-called document panning type is provided. However, this type of image reading apparatus has a problem that streak noise occurs in the read image due to dust or the like adhering to the reading glass. Therefore, a step-through sheet is arranged in front of the reading position, and it is configured to convey the document surface without directly touching the reading glass, so that paper dust and dust are not transferred from the document surface to the reading glass. Has been proposed.

  As a sheet-through method, for example, an image reading apparatus described in Patent Document 1 is known, and the thickness and surface roughness of a document are detected, and image processing characteristics, illumination characteristics, and calibration are detected according to the detection results. By changing the number of times, an image with good image quality can be obtained.

However, generally, the document transport path is curved before and after the reading position. For this reason, in the image reading apparatus described in Patent Document 1, when the original is conveyed, the amount of original floating with respect to the reading glass changes depending on the stiffness of the original due to the thickness of the original. Further, the document floating amount similarly changes depending on whether the read area of the document passing through the reading position is the front end portion, the intermediate portion, or the rear end portion. Therefore, there is a problem that the amount of reflected light from the original incident on the image pickup tube changes, and the gradation reproducibility for the same original density changes depending on the original thickness and original reading position.
JP 2001-326820 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a document panning type image reading apparatus capable of correcting the amount of reflected light from a document incident on an image pickup tube so as not to change depending on the thickness of the document.

  Another object of the present invention is to achieve the above-mentioned object, and to correct the amount of reflected light from the original incident on the image pickup tube so as not to change depending on the read area of the original passing through the reading position. An object of the present invention is to provide an image reading apparatus of the type.

In order to achieve the above object, an image reading apparatus according to the present invention includes a document tray on which a plurality of documents can be placed, a feeding unit that feeds and feeds the documents placed on the document tray one by one, A conveying unit that conveys the document fed from the feeding unit to a paper discharge tray through a predetermined reading position; an image reading unit that reads an image of the conveyed document on the reading position; Document thickness detecting means for detecting the thickness of the document to be fed, and a step sheet disposed upstream of the reading position in the document transport direction so that the document being transported does not directly touch the reading glass . and correcting means for correcting the floating amount of the original at the reading position by changing the thickness or height to control the correction means in accordance with the original thickness which is detected by the original thickness detecting means, the reading position Characterized in that and a control means for correcting the floating amount of the original.

According to the image reading apparatus of the present invention, the amount of floating of the original caused by the original thickness is corrected to be constant by changing the thickness or height of the step sheet . As a result, the gradation reproducibility of the read image with respect to the original density is stabilized.

The image reading apparatus according to the present invention further includes document passing position detecting means for detecting the position of the read area of the document passing through the reading position, and the control means includes the document thickness and the document thickness detected by the document thickness detecting means. The correction unit may be controlled in accordance with the position of the read area of the document detected by the document passing position detection unit to correct the floating amount of the document at the reading position. Thus, in addition to the original floating amount due to the original thickness, the original floating amount due to the position of the read area passing through the reading position can be corrected to be constant. The tone reproducibility is further stabilized.

  Further, in the image reading apparatus according to the present invention, the correction means includes a plurality of step sheets that can be advanced and retracted upstream of the reading position in the document conveying direction, and a step sheet driving member for individually advancing and retracting each step sheet. The control unit may drive the step sheet driving member to change the accumulated thickness of the step sheet according to the detection result of the document thickness detection unit and / or the document passing position detection unit.

  Alternatively, the correcting means includes a step sheet fixed on the reading glass and a height adjusting member of the reading glass, and the control means determines the detection result of the document thickness detecting means and / or the document passing position detecting means. Accordingly, the height adjusting member may be driven to change the height of the reading glass and the step sheet.

  Alternatively, the correction unit includes a step sheet fixed on the reading glass and a driving member that changes an angle with respect to the main scanning direction of the reading glass, and the control unit includes the document thickness detection unit and / or the document. Depending on the detection result of the sheet passing position detecting means, the driving member may be driven to change the angles of the reading glass and the step sheet.

  Embodiments of an image reading apparatus according to the present invention will be described below with reference to the accompanying drawings. In each embodiment, the same parts and the same parts are denoted by the same reference numerals, and redundant description is omitted.

(Refer 1st Example and FIGS. 1-3)
FIG. 1 shows a schematic configuration of an image reading apparatus 1A according to the first embodiment of the present invention. The image reading apparatus 1A generally includes a document tray 2 on which a plurality of documents can be placed, a paper feeding / feeding roller 3 for feeding and feeding documents one by one from the upper side, and a fed document D1 to a reading position A. Conveying rollers 4 and 5 for conveying, step sheets 10, 11, and 12, step sheet driving means 19, reading glass 15, reading glass 15, reading means 14 for reading an original at the reading position A; A scooping guide 6, paper discharge rollers 7 and 8 for discharging a document D 1 whose image has been read to a paper discharge tray 13, a document thickness detection sensor 16, and document passing position detection sensors 17 and 18.

  The reading means 14 is a conventionally well-known one constituted by a light source, a reflecting mirror, an imaging lens, and an imaging tube (for example, a CCD line sensor) (not shown), and detailed description thereof is omitted.

  FIG. 2 schematically shows the configuration of the step sheet driving means 19. The step sheets 10, 11, and 12 are in the form of strips that are elongated in the main scanning direction Y perpendicular to the document transport direction X, and are tensioned by the springs 104 in the document transport direction X from the reading position A. It is located upstream from the reading glass 15. Driving solenoids 100, 101, 102 are attached to the respective step sheets 10, 11, 12. Each solenoid 100, 101, 102 pulls the respective step sheets 10, 11, 12 onto the reading glass 15 against the tension of the spring 104 by an ON signal from the solenoid driving circuit 103.

  FIG. 1 shows a state in which the step sheet 12 has entered the reading glass 15 and the step sheets 10 and 11 have been retracted from the reading glass 15.

  The documents D placed on the document tray 2 are sent out one by one by the separating / feeding rollers 3. The fed document D1 is conveyed onto the reading glass 15 by the conveying rollers 4 and 5, and is further discharged to the discharge tray 13 by the discharge rollers 7 and 8.

  During the conveyance of the document D1, the thickness of the document D1 is detected by the document thickness detection sensor 16, and the thickness detection information is sent to the control unit 20. The control unit 20 drives the step sheets 10, 11, and 12 by the step sheet driving unit 19 according to the detected document thickness, and the step sheets 10, 11, 12 before the reading position A (upstream in the conveyance direction X). The accumulated height of the step sheet is changed by changing the number of stacked sheets.

  Further, the control unit 20 determines which of the leading end, the intermediate portion, and the trailing end of the document D1 is passing the reading position A from the detection timing of the document passing position detection sensor 17 and the document conveyance speed. The number of the stepped sheets 10, 11, 12 determined based on the detection result of the document thickness detection sensor 16 is changed according to the read area.

  More specifically, as shown in FIG. 3A, the document transport path 9 is curved (curved) by the presence of the rollers 4 and 5 and the rollers 7 and 8 before and after the reading position A. Therefore, the conveyed document D1 changes in the document floating amount U (the document height from the upper surface of the reading glass 15 to the image surface of the document D1) at the reading position A depending on the stiffness of the document D1. . That is, when the thickness of the document D1 is thin, the document D1 is easily transported along the transport path 9, and the document floating amount U increases. On the other hand, if the thickness of the document D1 is thick, the document D1 is likely to be transported out of the transport path 9, and the document floating amount U becomes small.

  For this reason, the amount of reflected light from the document D1 incident on the imaging tube changes, and the gradation reproducibility for the same document density basically changes depending on the document thickness. For example, O.D. When the document floating amount U fluctuates by 1.2 mm in the D0.3 chart, the read image changes by about 10 gradations.

  Therefore, according to the document thickness information from the document thickness detection sensor 16, as shown in FIG. 3B, the change in the document floating amount U due to the document thickness at the reading position A is superimposed on the step sheets 10, 11, 12. It was corrected by the number of sheets and kept constant. Thereby, a change in gradation due to a change in the document lifting amount U due to the document thickness can be suppressed.

  Further, depending on which of the leading end, the intermediate portion, and the trailing end of the document D1 passes through the reading position A, the document floating amount U similarly changes. That is, the leading edge and the trailing edge of the document D1 (each of which means an area of 10 mm from the edge) are easily removed from the conveyance path 9, and the document floating amount U is small. On the contrary, since the intermediate portion of the document D1 (intermediate portion between the front end portion and the rear end portion) is easy to follow along the conveyance path 9, the document floating amount U increases.

  Therefore, the number of overlapped step sheets 10, 11, and 12 is further corrected according to the read area information based on the detection signals of the leading edge and the trailing edge of the document D1 from the document passing position detection sensor 17. For example, when reading the leading edge and the trailing edge of the document D1, since the document floating amount U is small, the number of overlapping step sheets 10, 11, 12 is set to two, and the intermediate portion of the document D1 is read. In such a case, since the document floating amount U is large, the number of the stepped sheets 10, 11, 12 is reduced to one and the change in the document floating amount U is kept constant. Thereby, it is possible to suppress a gradation change due to a change in the document floating amount U at the reading position A due to the document thickness or the read area.

  Table 1 shown below is a list of the control of the number of stacked sheets of stepped sheets 10, 11, and 12 according to the document thickness and the read area. In Table 1, the document thickness is expressed in basis weight, and the larger the value, the thicker.

  Thus, the document D1 is conveyed in a non-contact manner with the reading glass 15 by the step sheets 10, 11, and 12 drawn on the upper surface of the reading glass 15, and an image is read by the imaging tube through the reading glass 15 at the reading position A. Since a desired gap exists between the image surface of the document and the reading glass 15, unnecessary materials such as paper dust and correction liquid do not adhere to the reading glass 15, and the occurrence of sliding scratches is prevented. .

  The document image read by the image pickup tube is formed as a toner image on the photosensitive member by a well-known electrophotographic process in a printer unit (not shown), and is transferred and fixed on a transfer material.

  The image reading apparatus 1 </ b> A having the above configuration can reliably make the change of the document floating amount U due to the document thickness and the read area by controlling the advance and retreat of the step sheets 10, 11, and 12. As a result, the gradation reproducibility of the read image with respect to the original density is stabilized.

(Refer to the second embodiment, FIG. 4)
FIG. 4 shows a main part of an image reading apparatus 1B according to the second embodiment of the present invention. In this image reading apparatus 1B, the step sheet 31 is fixed on the reading glass 15, and the height of the reading glass 15 and the step sheet 31 can be adjusted integrally. Other configurations are the same as those of the first embodiment.

  Then, the height H of the reading glass 15 and the step sheet 31 is controlled by the reading glass height driving means (not shown) according to the detection results of the document thickness detection sensor 16 and the document passing position detection sensor 17, and at the reading position A. Align the height of the original D1. Thereby, there exists an effect similar to the said 1st Example.

(Refer to the third embodiment, FIG. 5)
FIG. 5 shows a main part of an image reading apparatus 1C according to the third embodiment of the present invention. In this image reading apparatus 1C, the step sheet 41 is fixed on the reading glass 15, and the reading glass 15 and the step sheet 41 are integrated in the main scanning direction Y (direction perpendicular to the document conveying direction X, see FIG. 2). The angle can be adjusted as an axis. Other configurations are the same as those of the first embodiment.

  Then, the angle α of the reading glass 15 and the step sheet 41 is controlled by a reading glass angle driving means (not shown) according to the detection results of the document thickness detection sensor 16 and the document passing position detection sensor 17, and the document at the reading position A is controlled. Align the height of D1. Thereby, there exists an effect similar to the said 1st Example.

(Other examples)
The image reading apparatus according to the present invention is not limited to the above-described embodiments, and can be variously modified within the scope of the gist thereof.

  For example, the configuration of the document feeding unit, the conveying unit, the document thickness detecting unit, and the document passing position detecting unit is arbitrary.

1 is a schematic configuration diagram illustrating a first embodiment of an image reading apparatus according to the present invention. It is a typical top view of the level | step difference sheet drive means shown in FIG. It is a principal part block diagram for demonstrating the effect of the said level | step difference sheet | seat. It is a principal part block diagram which shows 2nd Example of the image reader which concerns on this invention. It is a principal part block diagram which shows 3rd Example of the image reader which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1A, 1B, 1C ... Image reading device 2 ... Document tray 3 ... Separation / feed roller 4, 5 ... Conveyance roller 10, 11, 12, 31, 41 ... Step sheet 13 ... Paper discharge tray 14 ... Reading means 15 ... Reading Glass 16 ... Document thickness detection sensor 17 ... Document passing position detection sensor 19 ... Step sheet driving means 20 ... Control unit A ... Reading position U ... Document floating amount X ... Conveyance direction

Claims (8)

A document tray on which a plurality of documents can be placed;
A feeding unit that feeds and feeds the documents placed on the document tray one by one;
Conveying means for conveying the document sent from the feeding means to a paper discharge tray through a predetermined reading position;
Image reading means for reading an image of a document being conveyed on the reading position;
Document thickness detecting means for detecting the thickness of the document fed from the document tray;
A step sheet disposed upstream of the reading position in the document transport direction so that the document being conveyed does not directly touch the reading glass, and the thickness or height of the step sheet is changed to change the thickness of the document at the reading position. Correction means for correcting the floating amount;
Control means for controlling the correction means in accordance with the document thickness detected by the document thickness detection means and correcting the floating amount of the document at the reading position;
An image reading apparatus comprising: The correction means includes a plurality of step sheets that can be advanced and retracted upstream of the reading position in the document conveying direction, and a step sheet driving member for individually advancing and retracting each step sheet,
The control unit drives the step sheet driving member to change the accumulated thickness of the step sheet according to the detection result of the document thickness detection unit;
The image reading apparatus according to claim 1. The correction means includes a step sheet fixed on the reading glass, and a height adjusting member of the reading glass,
The control means drives the height adjusting member to change the height of the reading glass and the step sheet according to the detection result of the document thickness detection means,
The image reading apparatus according to claim 1. The correction means includes a step sheet fixed on the reading glass, and a driving member that changes an angle about the main scanning direction of the reading glass,
The control unit drives the driving member to change the angles of the reading glass and the step sheet in accordance with a detection result of the document thickness detection unit;
The image reading apparatus according to claim 1. A document tray on which a plurality of documents can be placed;
A feeding unit that feeds and feeds the documents placed on the document tray one by one;
Conveying means for conveying the document sent from the feeding means to a paper discharge tray through a predetermined reading position;
Image reading means for reading an image of a document being conveyed on the reading position;
Document thickness detecting means for detecting the thickness of the document fed from the document tray;
Document passing position detecting means for detecting the position of the read area of the document passing through the reading position;
A step sheet disposed upstream of the reading position in the document transport direction so that the document being conveyed does not directly touch the reading glass, and the thickness or height of the step sheet is changed to change the thickness of the document at the reading position. Correction means for correcting the floating amount;
Control for correcting the amount of floating of the document at the reading position by controlling the correction unit according to the thickness of the document detected by the document thickness detecting unit and the position of the read area of the document detected by the document passing position detecting unit. Means,
An image reading apparatus comprising: The correction means includes a plurality of step sheets that can be advanced and retracted upstream of the reading position in the document conveying direction, and a step sheet driving member for individually advancing and retracting each step sheet,
The control unit drives the step sheet driving member to change the accumulated thickness of the step sheet according to detection results of the document thickness detection unit and the document passing position detection unit;
The image reading apparatus according to claim 5. The correction means includes a step sheet fixed on the reading glass, and a height adjusting member of the reading glass,
The control means drives the height adjusting member to change the height of the reading glass and the step sheet according to the detection results of the original thickness detecting means and the original passing position detecting means;
The image reading apparatus according to claim 5. The correction means includes a step sheet fixed on the reading glass, and a driving member that changes an angle about the main scanning direction of the reading glass,
The control means drives the driving member to change the angles of the reading glass and the step sheet according to the detection results of the original thickness detecting means and the original passing position detecting means;
The image reading apparatus according to claim 5.

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