JP3818105B2 - Document reader - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a document reading apparatus suitable for use as an image input unit of an image processing apparatus such as a copying machine or a facsimile machine, and more particularly to a document reading apparatus that reads an image while moving the document.
[0002]
[Prior art]
Document reading devices used for the image input unit in image processing apparatuses such as copiers and facsimile machines are those that fix the original while reading the original image while moving the reading unit, and the reading unit. On the other hand, there is a method of reading a document image while moving the document. In general, the former method is called a platen method, and the latter method is called a CVT (Constant Velocity Transport) method.
[0003]
A platen-type document reading device includes, for example, a platen glass on which a document is placed, a platen cover that is attached to the upper side of the platen glass so as to be freely opened and closed, and an illumination lamp that is movably provided below the platen glass. And a reading sensor in which a large number of photoelectric conversion elements are arranged, and an optical element such as a mirror for guiding reflected light from the original based on the illumination light of the illumination lamp to the reading surface of the read sensor, and moving the illumination lamp However, the image of the document in the fixed state is read by the reading sensor.
[0004]
On the other hand, the CVT-type document reading device is, for example, a document placement tray on which a document is placed, a document discharge tray from which a document is discharged, and a document that conveys documents one by one from the document placement tray to the document discharge tray. A conveyance path, a reading glass disposed along the document conveyance path, an illumination lamp disposed on the opposite side of the reading glass from the document conveyance path, and a reading sensor provided in parallel with the illumination lamp. The image is read by a reading sensor in a fixed state while moving the document.
[0005]
Hereinafter, an image read by the document reading apparatus of each type is referred to as a read image. In these document readers, in order to reliably read the document image, the document surface of the fixed document or the moving document is arranged so that the reflected light from the document forms an image on the reading surface of the reading sensor. Needs to match the focal position of the reading sensor. The platen glass and the reading glass function as a reference plate for that purpose. In the following description, a surface on the side of the document conveyance path, such as a reading glass, and a portion through which irradiation light from an illumination lamp or reflected light from the document is transmitted is referred to as a reading surface such as a reading glass.
[0006]
By the way, in each of the above-described document reading apparatuses, when the original is set with the correction liquid or the ink of the ballpoint pen unfixed and the reading is started, the unfixed material is read on the reading glass or the like. It will stick to the surface. In this state, since the reading light is blocked by the unfixed material attached to the reading surface, black spots and white spots are generated in the read image.
[0007]
In particular, in a CVT type document reading apparatus, if an unfixed material adheres to the reading surface, it becomes impossible to read an image of a corresponding portion along the sub-scanning direction. As a result, black streaks and line-shaped image omissions occur, so deterioration of the read image due to adhesion of unfixed material to the reading surface cannot be ignored. In particular, in the CVT type document reading apparatus, since the image is read while the document is moved without being fixed, the mutual positional relationship between the document surface and the focus position of the reading sensor can be sufficiently stabilized. The document image could not be read with sufficient image quality because the document feed speed at the focal position could not be stabilized sufficiently. Note that these problems occur due to, for example, dirty documents.
[0008]
In order to prevent the deterioration of the read image due to the adhesion of the unfixed material to the reading surface as described above, as shown in FIG. 8, the step forming member 101 is disposed on the upstream side of the document reading position R. The present applicant has proposed a document reading apparatus having a configuration in which the document Ps is not brought into contact with the document reading surface of the reading reference member 102 through which reading light from an illumination lamp (not shown) or reflected light from the document Ps passes. (See JP-A-9-307695).
[0009]
[Problems to be solved by the invention]
In the document reading apparatus according to the conventional example having the above configuration, in order to prevent the document Ps from coming into contact with the document reading surface, the height of the step forming member 101 from the document reading surface must be secured to some extent. However, if the height is too high, when the original Ps passes through the step forming member 101, the original Ps that is curved to some extent due to the presence of the step forming member 101 is instantaneously caused by the action of the force to return to the original state. The trailing edge of the document Ps falls on the document reading surface by the height of the step forming member 101.
[0010]
Then, due to this, the read image is disturbed, or the magnification is changed by changing the focal length of the reading optical system. In particular, in the case of a high-speed color original reading apparatus whose demand has been greatly increasing in recent years, the change in the focal length of the reading optical system greatly affects the image quality of the read image. Furthermore, since the rear end portion of the document Ps comes into contact with the reading surface, there is a concern that the foreign matter such as the unfixed material described above adheres to the rear end portion of the document. is there.
[0011]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to prevent the reading surface from being soiled by the unfixed material of the original, and to disturb the read image or to adjust the focal length of the reading optical system. It is an object of the present invention to provide a document reading apparatus capable of reading a document image without changing the above.
[0012]
[Means for Solving the Problems]
A document reading apparatus according to the present invention includes a transparent member provided in a document conveyance path, a document feeding unit that feeds a document onto the transparent member, and a document that is fed by the document feeding unit and passes over the transparent member. A reading unit that reads an image of a document to be read through the transparent member, and a document that is passing at least above the reading position by the reading unit so as to be substantially parallel to the upper surface of the transparent member with a predetermined gap. A pair of steps provided on the upstream side and the downstream side of the reading position on the transparent member and having a thickness corresponding to the predetermined interval. The apparatus includes a member and a pair of rollers that press the document against each of the pair of step members and apply a conveying force to the document .
[0013]
In the document reading apparatus configured as described above, the document fed onto the transmissive member by the document feeding unit is prevented from contacting the upper surface of the transmissive member, that is, the reading reference surface at least above the reading position by the document regulating unit. The running state is regulated so as to be substantially parallel to the reading reference surface. Thus, even if the original is set with the correction liquid or the ink of the ballpoint pen not fixed and the reading is started, the reading reference surface is not stained with the unfixed material. A pair of step members are used as means for regulating the height of the document, and a pair of rollers are used as means for pressing the document against these step members, thereby ensuring that the document is substantially parallel to the reading reference plane. In addition, since the pair of rollers have a function as a document feeding means, it is possible to ensure good document running performance.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a configuration example of an image processing apparatus, for example, a digital copying machine, in which a document reading apparatus according to the present invention is mounted as an image input unit. The document reading apparatus according to the present invention is not limited to application to an image input unit of a digital copying machine, but can be applied to all image input units in an image processing apparatus such as a facsimile machine.
[0015]
As shown in FIG. 1, a digital copying machine according to this application example includes a document reading unit 10 that reads an image of a document Ps by a platen method or a CVT method, and an image that processes image information output from the document reading unit 10. The image forming apparatus includes a processing unit 20 and an image forming unit 30 that forms an image on the recording paper Po based on image information processed by the image processing unit 20. In this digital copying machine, the present invention is characterized by a specific configuration of a CVT type reading unit in the document reading unit 10. Details thereof will be described later.
[0016]
The document reading unit 10 includes a reading optical system that is provided in the copying machine body and reads an image of the document Ps, and an automatic document feeding unit that can be opened and closed with respect to the upper surface of the copying machine body. .
[0017]
First, a specific configuration of the reading optical system will be described. The reading optical system includes a platen glass 11 disposed on the upper surface of the copying machine main body, a reading glass 12 provided on one end side of the platen glass 11, and a bottom position of the reading glass 12 as a home position. 11, a first carriage 13 movably provided to the other end, a second carriage 14 that moves in conjunction with the first carriage 13, and a CCD line disposed below the home position of the first carriage 13. It has a configuration having a reading sensor 15 such as a sensor.
[0018]
The first carriage 13 has an illumination lamp 13A and a reflector 13B that irradiates illumination light from the illumination lamp 13A onto the document surface of the document Ps, and further, reflected light from the document Ps based on the illumination light on the platen glass 11. A first mirror 13C that reflects in a parallel direction is mounted. The second carriage 14 is equipped with second and third mirrors 14A and 14B that change the optical path of the reflected light from the first mirror 13C and make it incident on the light receiving surface of the reading sensor 15.
[0019]
Next, a specific configuration of the automatic document feeder will be described. The automatic document feeder includes a frame 16 attached to the copying machine main body so as to be freely opened and closed, a platen glass cover 17 having a white surface disposed at a position facing the platen glass 11 of the frame 16, a frame, 16 is disposed on the upper surface side of the document 16 and can carry a plurality of documents Ps, and the documents Ps on the document stacking tray 18 are carried one by one while passing over the reading glass 12. Then, the document feeding section 19 is provided on the upper surface of the frame 16 after being discharged.
[0020]
Original feeding unit 19 includes a peak click up roll 21 from the document input tray 18 pulling the document Ps, a registration roll 22 to feed on the glass 12 reads the original Ps drawn by this pin click up roll 21, and the register roller 22 and the reading glass 12 An upstream chute 23 positioned between the reading glass 12, a discharge roll 24 that discharges the document Ps that has passed over the reading glass 12 onto the frame 16, and a downstream chute 25 positioned between the reading glass 12 and the discharge roll 24. It is composed of
[0021]
When the document Ps is placed on the platen glass 11 in the document reading unit 10 having the above-described configuration, the above-described reading optical system moves the image of the document Ps while moving in the sub-scanning direction (left-right direction in FIG. 1). When the original Ps is placed on the original placement tray 18 while the reading operation is performed, the original Ps is fed onto the reading glass 12 by the above-described original feeding unit 19 and the image is read optically at the home position. The reading operation is performed by the system. Hereinafter, the former reading mode is referred to as a platen mode, and the latter reading mode is referred to as a CVT mode.
[0022]
In the platen mode, the document reading unit 10 operates the illumination lamp 13A and the reading sensor 15 in the reading optical system and then moves the two carriages 13 and 14 to move the document Ps on the platen glass 11 to the illumination lamp 13. The reflected light from the original Ps based on the illumination light is incident on the light receiving surface of the reading sensor 15 via the first to third mirrors 13C, 14A, and 14B. As a result, the image of the document Ps is read, and the image information is output from the reading sensor 15.
[0023]
In the CVT mode, the document reading section 10 operates the document feeding section 19 after operating the illumination lamp 13A and the reading sensor 15 in the reading optical system, thereby reading the document Ps on the document placement tray 18 with the reading glass 12. , And passes through the reading glass 12 and is then discharged onto the frame 16. When the original Ps passes over the reading glass 12, the reflected light from the original Ps based on the illumination light from the illumination lamp 13 positioned below the reading glass 12 is read via the mirrors 13C, 14A, and 14B. The light is incident on the light receiving surface of the sensor 15. As a result, the image of the document Ps is read, and the image information is output from the reading sensor 15.
[0024]
Image information output from the reading sensor 15 by the image reading operation in the document reading unit 10 is supplied to the image forming unit 30 after predetermined image processing is performed in the image processing unit 20.
[0025]
The image forming unit 30 includes a recording paper storage tray 31 that stores a large number of recording papers Po, a toner image transfer unit 32 that transfers a toner image corresponding to the image information passed through the image processing unit 20 to the recording paper Po, and the toner The fixing device 33 that fixes the toner image transferred by the image transfer unit 32 to the recording paper Po, the recording paper discharge tray 34 that stores the recording paper Po after image formation, and the toner image transfer unit 32 from the recording paper storage tray 31. And a recording paper transport path 35 for transporting the recording paper Po to the recording paper discharge tray 34 via the fixing device 33.
[0026]
In the image forming unit 30 having the above-described configuration, the toner image transfer unit 32 includes a photoconductive drum 36 that can be opened and closed so as to face the recording paper conveyance path 35, and the photoconductive drum 36 is uniformly charged corotron. 37 is charged to a uniform potential, and the laser exposure unit 38 exposes the photosensitive drum 36 in accordance with image information from the image processing unit 20 to form an electrostatic latent image. The image is developed to form a toner image, and the toner image is transferred to the recording paper Po by the transfer corotron 40, whereby a toner image corresponding to the image information from the image processing unit 20 is formed on the recording paper Po.
[0027]
Then, the recording paper Po onto which the toner image has been transferred in the image forming unit 30 is sent to the fixing device 33 through the recording paper conveyance path 35. The fixing device 33 fixes the toner image transferred to the recording paper Ps to the recording paper Po. Thus, the image of the original Ps is formed on the recording paper Po as it is. The recording paper Po on which the image is formed is discharged to the recording paper discharge tray 34.
[0028]
Next, the configuration of the document reading unit 10, that is, the CVT reading unit, which is a characteristic part of the present invention, will be described. FIG. 2 is a block diagram showing the main part of the original reading unit 10, specifically, the peripheral part of the reading glass 12 of FIG. 1. In FIG. 2, the same parts as those in FIG. Yes.
[0029]
In FIG. 2, the upper surface of the reading glass 12 becomes the reading reference surface S of the original Ps. Further, the substantially central portion of the reading glass 12 is the reading position R, that is, the optical axis position of the reflected light (reading light) from the original Ps based on the illumination light from the illumination lamp 13A of FIG. Here, the member having the reading reference surface S is not limited to the glass member, and may be a transmissive member (transparent or translucent member). On the reading glass 12, the document Ps is fed from the document placing tray 18 by the document feeding unit 19 through the upstream chute 23. The fed document Ps passes over the reading position R of the reading glass 12 and is discharged through the downstream chute 25.
[0030]
On the upper surface of the reading glass 12, a step member 51 is disposed at the upstream end of the reading position R, and a step member 52 is disposed at the downstream end, avoiding the reading position R. These step members 51 and 52 are formed of plastic or the like so as to have a length corresponding to the maximum width of the original Ps, and the upper surfaces of both of them are substantially the same. Further, the downstream step member 52 has a tapered shape in which the upstream end face 52A gradually rises from the upstream side toward the downstream side.
[0031]
Rollers 53 and 54 are disposed on the step members 51 and 52 as document pressing members that press the document Ps against the step members 51 and 52 so that the passing document Ps does not float up. The rollers 53 and 54 are provided so as to be rotatable around the shafts 55 and 56 with a predetermined gap, preferably about 0.3 mm, between the upper surfaces of the step members 51 and 52. Here, the reason why the gaps are provided between the rollers 53 and 54 and the upper surfaces of the step members 51 and 52 is that the rollers 53 and 54 also have a length corresponding to the maximum width of the document Ps. , 56 to allow attachment errors between both ends.
[0032]
The rollers 53 and 54 have a function as a pressing member for the document Ps, and apply conveying force to the document Ps by rotating the shafts 55 and 56 in conjunction with the feeding operation of the document feeding unit 19 (see FIG. 1). It also has a function as a document feeding means. Accordingly, these rollers 53 and 54 are formed of a viscous elastic body such as rubber so that the friction coefficient between the original Ps is larger than the friction coefficient between the step members 51 and 52 and the original Ps. Yes.
[0033]
The step member 51 and the roller 53 and the step member 52 and the roller 54 make the running state of the document Ps passing over the reading glass 12 at least on the reading position R, the upper surface of the reading glass 12, that is, the reading reference surface S. On the other hand, a document restricting means for restricting the sheet to be substantially parallel to the reading reference surface S at a predetermined interval, specifically, an interval corresponding to the thickness of the step members 51 and 52 is configured.
[0034]
Next, the operation of the document reading unit 10 having the above configuration will be described with reference to the state diagrams of FIGS.
[0035]
FIG. 3 shows a state immediately before starting document reading. In the state immediately before the start of reading, the document Ps fed from the document feeder 19 (see FIG. 1) through the upstream chute 23 has its tip abutted against the roller 53 , so that the step member 51 is brought about by the conveying force of the roller 53. It is sent to the downstream side while being pressed against. At this time, the leading end portion of the document Ps is conveyed from the gap between the step member 51 and the roller 53 substantially parallel to the reading reference surface S with an interval corresponding to the height of the step member 51 with respect to the reading reference surface S.
[0036]
Thereby, since the image of the original Ps is reliably read at the reading position R, a good read image can be obtained. After the leading end of the document Ps passes the reading position R, the upstream end surface 52A of the step member 52 has a tapered shape, so that the leading end of the document Ps is in contact with the step member 52 by the guide of the tapered surface. Therefore, the conveyance of the original Ps is not hindered by the presence of the step member 52 on the downstream side.
[0037]
FIG. 4 shows a state where the central portion of the document is being read. In the reading state of the central portion, the original Ps is separated from the reading reference surface S by the step member 51 and the roller 53 and the step member 52 and the roller 54 with an interval corresponding to the height of the step members 51 and 52 with respect to the reading reference surface S. It is transported while being regulated to be substantially parallel. Therefore, a good read image can be obtained following the state immediately before the start of reading.
[0038]
FIG. 5 shows a state immediately after the rear end portion of the document Ps passes through the step member 51. In a state immediately after passing through the step member 51, the document Ps is conveyed while being regulated by the step member 52 and the roller 54 . Therefore, the rear end portion of the original Ps is not affected by the influence of the curved portion (the roller 54 portion) of the original Ps already guided downstream, that is, the influence of the force to return the original bent portion. Since the sheet S is conveyed substantially parallel to the reading reference surface S with an interval corresponding to the height of the step member 52 with respect to S, a good read image can be continuously obtained even at the rear end portion of the document Ps.
[0039]
As described above, the reading optical system including the reading sensor 15 is fixed, and in the CVT-type document reading apparatus that reads the image while moving the document Ps, the document Ps passing through the reading glass 12 is read from the reading glass. The original Ps is set while the correction liquid, the ink of the ballpoint pen, etc. are not fixed, by being conveyed while being regulated so as to be substantially parallel with a predetermined gap with respect to the upper surface of 12, that is, the reading reference surface S. Even if the reading is started, the reading reference surface S is not soiled by the unfixed material, and the original image can be read without causing the reading image to be disturbed.
[0040]
Further, since the height position of the original Ps does not change on the reading position R, the focal length of the reading optical system does not change, so that a good read image can be obtained, particularly in a high-speed color original reading apparatus. The effect is extremely great when used as the image input unit. This is because in a high-speed color original reading apparatus, a 3-line or 4-line CCD line sensor (linear sensor) is used as the reading sensor 15, and therefore, when the focal length of the reading optical system changes, the same reading position. On the other hand, the focal length differs between the lines, which greatly affects the image quality of the read image.
[0041]
Further, step members 51 and 52 whose upper surfaces are substantially the same are used as means for regulating the height position of the document Ps, and rollers 53 and 54 are used as document pressing members for pressing the document Ps against the step members 51 and 52. , The original Ps can be reliably regulated to be substantially parallel to the reading reference surface S, and the original pressing member also has a function as the original feeding means (rollers 53 and 54), so that an excellent original running can be performed. It is possible to secure the sex.
[0042]
In the above embodiment, the rollers 53 and 54 are used as the document pressing members that press the document Ps against the step members 51 and 52. However, the present invention is not limited to this, and as shown in FIG. It is also possible to use a guide member 57 arranged with a gap of about 0.3 mm between the upper surfaces of 51 and 52. However, from the viewpoint of ensuring good document travelability, it is preferable to use rollers 53 and 54 that can impart a conveying force to the document Ps.
[0043]
Furthermore, it is possible to adopt a configuration in which a roller is disposed on one side of the step members 51 and 52 and a guide member is disposed on the other side. For example, as shown in FIG. 7, the guide member 58 is disposed on the step member 51 side with a gap of about 0.3 mm between the upper surface of the step member 51 and the roller 54 is disposed on the step member 52 side. Can be considered.
[0044]
【The invention's effect】
As described above, according to the present invention, in the CVT type document reading apparatus, the running state of the document passing through the document reference surface with a predetermined gap with respect to the upper surface (reading reference surface) of the transmissive member. Even if the original is set with the correction liquid or ballpoint pen ink unfixed and scanning is activated, the document is scanned with the unfixed material. The reference surface is not soiled, and the original image can be read satisfactorily without causing any disturbance in the read image. In addition, a pair of step members are used as means for regulating the height of the original, and a pair of rollers are used as means for pressing the original against these step members, thereby ensuring that the original is substantially parallel to the reading reference plane. In addition, since the pair of rollers have a function as a document feeding means, it is possible to ensure good document running performance.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram illustrating a configuration example of a digital copier equipped with an original reading apparatus according to the present invention as an image input unit.
FIG. 2 is a configuration diagram illustrating a specific configuration example of a document reading unit.
FIG. 3 is a state diagram immediately before starting document reading for explaining the operation of the document reading unit;
FIG. 4 is a state diagram during reading of the central portion of a document for explaining the operation of the document reading unit.
FIG. 5 is a state diagram immediately after the document trailing edge for passing through the step member for explaining the operation of the document reading unit;
FIG. 6 is a configuration diagram illustrating a modified example of a document reading unit.
FIG. 7 is a configuration diagram illustrating another modification of the document reading unit.
FIG. 8 is a configuration diagram illustrating a document reading apparatus according to a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Document reading part, 11 ... Platen glass, 12 ... Reading glass, 15 ... Reading sensor, 19 ... Document feeding part, 20 ... Image processing part, 30 ... Image forming part, 32 ... Toner transfer part, 33 ... Fixing device, 36: photosensitive drum, 51, 52: step member, 53, 54: roller, 57, 58 ... guide member, R: reading position, S: reading reference surface

Claims (4)

A transmissive member provided in the document conveyance path;
Document feeding means for feeding a document onto the transparent member;
A reading unit that reads an image of a document that is fed by the document feeding unit and passes through the transparent member, through the transparent member;
Document regulating means for regulating a document passing at least above the reading position by the reading means so as to be substantially parallel to the upper surface of the transparent member with a predetermined gap ;
The document regulating means is
A pair of step members provided on the upstream side and the downstream side of the reading position on the transparent member and having a thickness corresponding to the predetermined interval;
An original reading apparatus, comprising: a pair of rollers that press the original against each of the pair of step members and apply a conveying force to the original. The pair of step members, a document reading apparatus according to claim 1, wherein each top surface, characterized in that it is substantially flush. Of the pair of step members, the step member located on the downstream side of the reading position has a tapered shape in which the end surface on the upstream side gradually rises from the upstream side toward the downstream side. The document reading device according to claim 1 . The document reading apparatus according to claim 1, wherein the pair of rollers is set so that a friction coefficient between the pair of rollers and a document is larger than a friction coefficient between the step member and the document.

Images