JP2001111786A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader with a simple configuration at a low cost without the need for any special image data processing or a large-scale revamping and installation of devices that generates no stripe noise information that cannot practically be disregarded even when dust or dirt is deposited on an original platen glass plate for a panning mode or a face of an original image being an object of panning. SOLUTION: In the image reader where an original standstill read mode or an original panning mode can selectively be executed, an image reading focal position F by an image read optical system R in the original standstill read mode is placed onto a face of the original platen glass plate 1, an image read focal position F' in the original panning mode is placed apart from the face of the original platen glass plate 2, and the thickness and (or) the refractive index of the original platen glass plate 2 at the deviated image read focal position F' are selected higher than those of the original platen glass plate 1 for the original standstill mode, and the original S passes through the deviated focal position F' in the original panning mode.

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, and more particularly, to moving an original to a platen glass plate.
The present invention relates to an image reading apparatus capable of executing a document panning mode in which an image reading optical system is fixedly arranged at a fixed position and an image of the moving document is read.

[0002]

2. Description of the Related Art In an image reading apparatus, at least a part of an image reading optical system is moved with respect to a stationary document placed on a platen glass plate to read a document image, thereby executing a document reading mode. An image reading apparatus for moving a document with respect to a platen glass plate while executing a document panning mode in which the image reading optical system is fixedly arranged at a fixed position and reading an image of the moving document; There is an image reading apparatus that can selectively execute both the mode and the original panning mode.

FIG. 7 shows an example of an image reading apparatus which can selectively execute both the original stationary reading mode and the original panning mode. The image reading device shown in FIG.
An original placing glass platen 1 for the original stationary reading mode, and an original platen glass plate 20 adjacent to the original placing glass plate 20 for the panning mode are provided. These glass plates 1, 2
An image reading optical system R is disposed below the image reading optical system R. The glass plates 1 and 20 are made of glass having the same thickness and the same refractive index, and their upper surfaces are in the same plane.

[0004] The optical system R includes a first slider 3, a second slider 4, a lens 5, and a photoelectrically convertible image sensor 6 including a CCD or the like. The first slider 3 is equipped with a lamp 31 for illuminating the original image surface and a first mirror 32 for guiding reflected image light from the original image surface in a predetermined direction.
The second slider 4 is provided with a second mirror 41 and a third mirror 42, which return the image light coming from the first mirror 32 and guide it to the lens 5.

The first slider 3 and the second slider 4 can be moved in a sub-scanning direction X parallel to the platen glass plates 1 and 20 by a slider driving device (not shown) along a guide device (not shown). In any mode, the image reading focal position F of the optical system R is located on the upper surface of the platen glass plate.

In the stationary original reading mode, the first slider 3, the second slider 4, the lens 5, and the image sensor 6
Are located at the initial positions P1 ', P2', P3 'and P4' in this mode, respectively. Then, the original S is placed on the glass plate 1, and the illumination lamp 31 is turned on by the first slider 3, and the first slider 3 is driven at a predetermined speed in the arrow X direction (sub-scanning direction) in the figure. The second slider 4 is driven in the same direction X at half the speed of the first slider 3. Thus, the reflected image light from the original is first,
The light is sequentially reflected by the second and third mirrors 32, 41, and 42, passes through the lens 5, forms an image on the image sensor 6, and the image is read there.

In the panning mode, the first slider 3, the second slider 4, the lens 5 and the image sensor 6 are fixedly arranged at fixed positions P1, P2, P3 and P4 in this mode. The position P1 of the first slider 3 is a position below the glass plate 20. The illumination lamp 31 is turned on in the first slider 3 and the document S is conveyed while the image surface thereof is in contact with the focal position F on the upper surface of the platen glass plate 20. Thus, the reflected image light from the original is first and second.
And are sequentially reflected by the third mirrors 32, 41 and 42,
The light passes through the lens 5 and forms an image on the image sensor 6, where the image is read.

[0008]

However, there are the following problems in the original panning mode. In other words, when the dust or dirt adheres to the original image surface and the dust or dirt adheres to the upper surface of the platen glass plate 2 or when the dirt or dirt adheres to the upper surface of the glass plate 2 from the beginning, the original moves. Since the dust and dirt attached to the glass plate 2 do not move, dust and dirt on the glass plate are continuously read during scanning of the original image reading. As a result, a streak noise such as a black streak is generated in an image displayed on a display or an image formed on a recording medium based on the read image data, and this significantly reduces image quality.

As means for preventing the generation of noise due to dust or dirt attached to the platen glass plate, for example, Japanese Patent Application Laid-Open Nos. 9-135332 and 9-1353
No. 33 discloses that pixel data read by an image sensor is analyzed to determine whether or not the data is abnormal data. When the pixel data is recognized as abnormal data, the pixel data is replaced with another pixel data or canceled. Is taught.

However, according to this method, when the normal pixel data is erroneously determined to be abnormal data, the normal data is replaced with other pixel data or canceled, so that the image displayed on the display or the recording medium is not displayed. Noise also occurs in the formed image.
For example, when canceling and forming an image on a white recording medium, white stripe noise appears. Further, since the noise generation prevention taught by this publication is performed by processing pixel data to be read, noise due to dust or dirt on the surface of the platen glass plate cannot be sufficiently eliminated.

Accordingly, the present invention provides an image reading apparatus capable of executing an original panning mode in which an original is moved relative to an original platen glass plate while an image reading optical system is fixedly arranged at a fixed position and an image of the moving original is read. Even if dirt or dirt is attached to the platen glass plate for the panning mode, or if dirt or dirt is attached to the original image surface of the panning target, it is difficult to ignore in practical use. Provided is an image reading apparatus that can read the original image without generating streak noise information, and that is simple and inexpensive without requiring special image data processing or major remodeling or installation of equipment. That is the task.

[0012]

In order to solve the above-mentioned problems, the present invention moves an original with respect to a platen glass plate while fixing an image reading optical system at a fixed position to form an image of the moving original. An image reading apparatus capable of executing a panning mode for reading a document, wherein the focal point of image reading by the image reading optical system in the panning mode is shifted from the surface of the platen glass plate used in the panning mode. An image reading device, wherein the thickness and / or refractive index of the platen glass plate is set so that the original passes through the shifted image reading focal position in the panning mode; An original document for reading an original image by moving at least a part of an image reading optical system with respect to a still original placed on a platen glass plate. An image reading apparatus capable of selectively executing a reading mode and a moving original shooting mode in which the original is moved with respect to the original platen glass plate while the image reading optical system is fixedly arranged at a fixed position and an image of the moving original is read. In the original document reading mode, the image reading focal position of the image reading optical system is located on the surface of the platen glass plate used in the original document reading mode, and the image reading optical position is used in the original panning mode. The focal position of the image reading by the system is shifted from the plate surface of the platen glass plate used in the original panning mode, and the shifted image reading focal position of the platen glass plate used in the panning mode. The thickness and / or the refractive index are set to be larger than those of the platen glass plate used in the stationary original reading mode. Yes set, the document in the document panning mode is to provide an image reading apparatus characterized by passing the image reading focal position shifted said.

In any of the above image reading apparatuses according to the present invention, when an original image is read in the panning original mode, the original has an image surface to be read fixed at a fixed position for panning the original. The sheet is conveyed so as to pass through the image reading focal position of the reading optical system, and the image is read. At this time, the image reading focus position of the image reading optical system is shifted from the platen glass plate surface for the original panning mode, so that the document does not contact the glass plate portion through which the optical path of the image reading optical system passes. Conveyed as follows. Therefore, it is possible to prevent dust and dirt that may be attached to the original from being transferred and attached to that portion of the glass plate. Further, even if dust or dirt is attached to the glass plate portion from the beginning, the image reading focal position is not on the glass plate surface, but is located at a position shifted therefrom. Dust and dirt are located at a so-called out-of-focus position, and are not read so clearly as to cause image noise that cannot be ignored. Therefore, even if dirt or dirt is attached to the platen glass plate for the panning mode, or if dirt or dirt is attached to the original image surface of the panning target, a streak that cannot be ignored in practical use The original image can be read without generating noise information, and a high-quality image with reduced noise can be formed. Moreover, it is not necessary to perform any special image data processing or major remodeling or installation of devices, so that the cost can be reduced simply and inexpensively.

[0014] In the image reading apparatus according to the present invention, the apparatus capable of executing the above-mentioned original still reading mode is also provided.
When executing the mode, an original is placed on a platen glass plate for the mode, and at least a part of the image reading optical system is moved with respect to the stationary original to scan the image surface of the original. Can be read. In any of the image reading apparatuses according to the present invention, the following can be typically mentioned as an image reading optical system. A mirror group, a lens, and an image sensor that guide image light reflected from a document image surface in a predetermined direction, wherein the image light arriving from the mirror group is imaged on the image sensor by the lens, reflection from the document image surface A self-occurring lens including a mirror group for guiding image light in a predetermined direction, and a lens for forming an image on the electrostatic latent image carrier (photoreceptor) via a turning mirror or the like as required, via a mirror or the like; An image reading optical system unit that includes an array and an image sensor, and forms an image of reflected image light from a document image surface on the image sensor by the self-occurring lens array.

The image reading apparatus provided with the image reading optical system can be used as a scanner dedicated to image reading or a document image reading section in a digital copying machine.
The image reading apparatus provided with the above image reading optical system can be used as a document image reading section in an analog copying machine. The optical systems are fixedly arranged at a fixed position for reading an image with respect to a platen glass plate for executing the mode in the original panning mode.

An image reading apparatus capable of executing the stationary original reading mode employs an image reading optical system, and when executing the stationary original reading mode, for example, a mirror group is constituted by first, second and third mirrors. ,
The first mirror is mounted on a first slider movable in the sub-scanning direction parallel to the original platen glass plate for the original stationary reading mode, and the second and third mirrors are movable in the same direction as the first slider. A stationary original image is scanned by moving the first slider at a predetermined speed in the sub-scanning direction and moving the second slider in the same direction at half the speed of the first slider. The reflected image light from the first, second and third
The light is sequentially reflected by a mirror and can be focused on an image sensor or an electrostatic latent image carrier through a lens. When the image reading optical system unit is employed to execute the original stationary reading mode, the unit can be moved in the sub-scanning direction parallel to the original platen glass plate for the original stationary reading mode to read the image.

When an optical system unit using the selfoc lens array is adopted as the image reading optical system, the selfoc lens is a lens having a small depth of focus. The attached dust and dirt are sufficiently out of focus even if the image reading focal position of the optical system unit is slightly shifted from the glass plate surface, so that the generation of streak noise information due to dust and dirt is easily suppressed. . In other words, it is sufficient to make the platen glass plate slightly thicker and / or have a higher refractive index than the glass plate for the original stationary reading mode, so that the image reading focal position is slightly shifted from the glass plate surface. Since the focus is defocused, the generation of streak noise information due to dust or dirt is easily suppressed.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of an example of an image reading apparatus according to the present invention. The image reading apparatus shown in FIG. 1 includes an original placing glass platen 1 for an original stationary reading mode and an original placing glass plate 2 adjacent to the original placing glass mode for a panning original photographing mode. An image reading optical system R is disposed below the glass plates 1 and 2.

The glass plate 1 is covered with a document cover CV that can be opened and closed, and the glass plate 2 is provided with an automatic document feeder ADF. The optical system R is the same as in the conventional apparatus shown in FIG.
A second slider 4, a lens 5, and a photoelectrically convertible image sensor 6 including a CCD and the like are included. The first slider 3 includes a document illumination lamp 31 and a first mirror 32, and the second slider 4 includes a second mirror 41 and a third mirror 4.
2 is provided.

The first slider 3 and the second slider 4 can be moved in a sub-scanning direction X parallel to the platen glass plates 1 and 2 by a slider driving device (not shown). The image reading focal position F of the optical system R in the original stationary reading mode is located on the upper surface of the original platen glass plate 1. The image reading focal position F ′ of the optical system R in the moving original shooting mode is shifted from the upper surface of the original platen glass plate 2 and is located slightly above the same. Here, the glass plate 2 is formed of glass of the same material as the glass plate 1, but the thickness t2 is larger than the thickness t1 of the glass plate 1 so as to obtain the focal position F 'at the aforementioned position. The upper surfaces of the glass plates 1 and 2 are on the same plane. The direction of increasing the thickness of the glass plate 2 may be below the lower surface position of the glass plate 1, above the upper surface of the glass plate 1, or both. However, the focal position F ′ is located above the upper surface of the glass plate 2.

In the original stationary reading mode, the first slider 3, the second slider 4, the lens 5, and the image sensor 6
Are arranged at initial positions P1 ′, P2 ′, P3 ′ and P4 ′ in this mode, respectively. Then, cover the original S with the cover CV
Is opened, placed on the glass plate 1, and the cover CV is closed again. Next, the illumination lamp 31 is turned on in the first slider 3, and the first slider 3 is driven at a predetermined speed in the arrow X direction (sub-scanning direction) in the figure by a slider driving device (not shown). In the same direction X at half the speed of the first slider 3. Thus manuscript S
Reflected image light from the first, second and third mirrors 32, 4
The light is sequentially reflected by 1 and 42, passes through the lens 5, and forms an image on the image sensor 6, where the image is read.

In the panning mode, the first slider 3, the second slider 4, the lens 5 and the image sensor 6 are fixedly arranged at fixed positions P1, P2, P3 and P4 in this mode. The position P1 of the first slider 3 is a position below the glass plate 2. The illumination lamp 31 is turned on in the first slider 3 and the original S is transported by the automatic document transporter ADF such that the image surface passes through the focal position F ′ above the platen glass plate 2. Thus, the reflected image light from the original is first, second and third mirrors 32, 41 and 4
The light is sequentially reflected by the lens 2 and passes through the lens 5 to form an image on the image sensor 6, where the image is read.

In this image reading apparatus, when an original image is read in the original panning mode, the image of the original S is read by the image reading optical system R in which the image surface to be read is fixed at a fixed position for the original panning. The sheet is transported so as to pass through the focal position F ′, and an image is read. At this time, the image reading focal position F ′ of the image reading optical system R is located at a position deviated upward from the upper surface of the glass plate 2 for the original follow-up mode, so that the original S passes through the optical path of the image reading optical system R. It is transported so as not to contact the glass plate portion. Therefore, it is possible to prevent dust and dirt that may have adhered to the document S from being transferred and adhered to that portion of the glass plate 2. Even if dust or dirt is attached to the glass plate portion from the beginning, the image reading focal position F 'is not located on the surface of the glass plate 2 and is located at a position shifted therefrom. The dust and dirt on the two surfaces are located at a so-called out-of-focus position, and therefore are not read so clearly as to cause image noise that is not negligible. Accordingly, even if dust or dirt is attached to the platen glass plate 2 for the panning mode, or if dust or dirt is attached to the original image surface of the panning target,
The original image can be read without generating streak-like noise information that is practically insignificant, and a high-quality image with reduced noise can be formed. Moreover, it is not necessary to perform any special image data processing or major remodeling or installation of devices, so that the cost can be reduced simply and inexpensively.

The read image data is sent to, for example, an image processing unit, where it is subjected to necessary processing, and further sent to an image memory unit for image formation. The automatic document feeder ADF includes a document tray 701 for setting a plurality of documents, a roller 702 for taking out and feeding the documents on the tray 701 one by one, an auxiliary tray 704 for manually inserting the documents, and a tray 704. A roller pair 705 for feeding the inserted document, and a tray 701
From the roller 702 facing the document feed roller pair 703,
The original S sent through the 720 or the original S sent from the original feed roller pair 705 facing the tray 704 is moved to the image reading focal position F ′ of the optical system R (slightly above the upper surface of the glass plate 2). (A shifted position), a pair of document transport rollers 706 and 707, a document discharge roller pair 708 for discharging the document S sent from the document transport roller pairs 706 and 707 onto the cover CV, and the document transport roller A document reversing switching claw 711 for guiding the document S sent from the pair 706 and 707 to a document reversing path 713 and a pair of document reversing rollers 710 that can be rotated forward and reverse.
And a roller pair 722 for feeding out the document S again from the path 713 to the document conveying roller pair 706, 707, and a document page for guiding the document S sent out from the document conveying roller pair 706, 707 to the document page alignment path 714. An alignment switching claw 712 and an original page alignment roller pair 709 that can be rotated forward and backward are provided.

When the original S is set on the original tray 701, the image forming surface is set upward. When a document is set on the manual document tray 704, the image surface is set downward. When reading the original image, the optical system R is fixedly arranged at a fixed position for executing the above-mentioned original panning mode, and then the originals S are taken out one by one by the roller 702.
One pair of rollers 706,
The document is conveyed to the sheet 707 by the pair of rollers 706 and 707 such that the document image surface passes through the focal position F ′.

When reading only one side of the image of the original S set on the tray 701, as shown in FIG.
Discharge onto V. At this time, the switching claws 711 and 712 are located at positions where the document S passes through this path. Tray 7
When reading images on both sides of each document set at 01, one side of each document S is read, and then, as shown in FIG.
Is guided to the document reversing path 713 by forward rotation of the pawl 711 and the document reversing roller pair 710 switched to the document reversing position by a pawl drive solenoid (not shown), and then the roller pair 710 is reversed as shown in FIG. Then, the image is again sent to a pair of rollers 706 and 707 for image reading by the roller pair 722 to read the image on the back surface. Thereafter, the pawl 712 switched to the original page aligning position by a nail driving solenoid (not shown) and the original page aligning roller pair 709 are forwardly guided to the original page aligning path 714, and then the roller pair 709 is inverted and discharged. The sheet is discharged from the roller pair 708 to the cover CV. Thus, the page alignment of the original is executed.

When a document is inserted from the tray 704, the document is discharged onto the cover CV as it is after reading the image. In the image reading apparatus shown in FIG. 1, the thickness of the original platen glass plate 2 for panning the original is made larger than the glass plate 1 for the stationary original reading mode, so that the image reading focal position F 'above the glass plate 2 as described above. However, by setting the thickness of the glass plate 2 to be t1 as in the case of the glass plate 1 and making the refractive index of the glass plate 2 larger than that of the glass plate 1, the similarly shifted focal position F ′ is obtained. You can also get.

FIG. 5 shows an image reading apparatus employing a glass plate 2 'for taking a panning shot of an original having such a large refractive index. Except for the point of the glass plate 2 ', it is the same as the image reading apparatus shown in FIG. The image reading apparatus described above includes, as the image reading optical system R, mirror groups 31, 41 that guide image light reflected from the original image surface in a predetermined direction;
Although the one comprising the lens 42, the lens 5 and the image sensor 6 is employed, an image reading optical system unit U shown in FIG. 6 may be employed instead. The image reading apparatus shown in FIG. 6 employs an optical system unit U instead of the optical system R in the image reading apparatus shown in FIG.
Other points are the same as those of the apparatus shown in FIG.

The optical system unit U includes a self-occurring lens array SL in which selfoc lenses are arranged in the main scanning direction, and an image sensor 6 'comprising a CCD or the like.
Is to form an image on the image sensor 6 '. The unit U can be driven in the sub-scanning direction by a drive device (not shown) along a guide device (not shown).

In the panning mode, the platen glass plate 2
It is fixedly arranged at the lower fixed position P1s. In the original stationary reading mode, the initial position P for executing this mode is initially set.
1's, from which it is driven to read a document image. In the image reading apparatus shown in FIG. 5, this optical system unit U can be used instead of the optical system R.

When such an optical system unit U is employed, since the SELFOC lens is a lens having a small depth of focus,
The dust and dirt adhering to the upper surface of the original platen glass plate 2 (or 2 ') for the original panning mode can be sufficiently removed by slightly shifting the image reading focal position F' of the optical system unit U from the glass plate surface. Defocus occurs, and the generation of streak noise information due to dust or dirt is easily suppressed. In other words, the platen glass plate 2 (or 2 ') has a slightly larger thickness (or refractive index) than the glass plate 1 for the original stationary reading mode, so that the image reading focal position is shifted from the glass plate surface. Even a slight shift causes sufficient defocusing, so that the generation of streak noise information due to dust or dirt is easily suppressed.

The original platen glass plate for executing the original panning mode is the same as the original platen glass plate for stationary original reading mode, even if both the thickness and the refractive index are increased so as to obtain desired focal positions. Good. 1, 5 and 6 described above.
In the apparatus shown in FIG.
The distance at which the focal position when there is no platen glass plate is shifted due to the presence of the platen glass plate is a, the shifted distance is a, the thickness of the glass plate is t, and the refractive index of the glass plate is n. a = t (1-1 / n).

Therefore, in each of the above apparatuses, for example, the platen glass plate 1 for the document stationary reading mode has a thickness t.
= 3 mm, using a glass plate with a refractive index n = 1.52,
a = 1.02 mm, and the focal position F of the optical system is set on the upper surface of the glass plate 1 by taking this deviation into account. Then, for example, the original platen glass plate 2 for the original panning mode,
When 2 ′ is used having a thickness of t = 4 mm and a refractive index of n = 1.89, a = 1.88 mm, and a difference of 0.86 mm from a = 1.02 mm in the glass plate 1 is reduced by 0.86 mm. The focal position F 'can be shifted upward from the upper surfaces of the glass plates 2, 2'.

The image reading apparatus described above can be used as a scanner dedicated to reading an image or as a document image reading section in a digital copying machine. In the image reading apparatus shown in FIGS.
Alternatively, if the image light passing through the lens 5 is guided to the photoconductor by using a folding mirror (not shown) as necessary, it can be used as an image reading unit of an analog copying machine.

[0035]

As described above, according to the present invention, the original is moved relative to the original platen glass plate, while the image reading optical system is fixedly arranged at a fixed position to read the image of the moving original. An image reading apparatus capable of executing the mode, wherein even if dust or dirt is attached to the platen glass plate for the panning mode, dust or dirt is attached to the original image surface of the panning target. Also, the original image can be read without generating streak noise information that is hard to ignore in practical use, and it is simple and inexpensive without requiring special image data processing or extensive remodeling and installation of equipment. It is possible to provide an image reading device that can be completed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an example of an image reading apparatus according to the present invention.

FIG. 2 is a diagram illustrating a document reversing operation in the automatic document feeder.

FIG. 3 is a diagram illustrating a part of a document page alignment operation in the automatic document feeder.

FIG. 4 is a diagram illustrating the rest of the document page alignment operation in the automatic document feeder.

FIG. 5 is a diagram illustrating a schematic configuration of another example of the image reading apparatus according to the present invention.

FIG. 6 is a diagram showing a schematic configuration of still another example of the image reading apparatus according to the present invention.

FIG. 7 is a diagram showing a schematic configuration of a conventional example.

[Explanation of symbols]

1 Original platen glass plate for placing document for stationary original reading mode 2, 2 ', 20 Platen glass plate for original panning mode t1 Thickness of glass plate 1 t2 Thickness of glass plate 2 R Image reading Optical system 3 First slider 31 Illumination lamp 32 First mirror 4 Second slider 41 Second mirror 42 Third mirror 5 Lens 6 Image sensor X Sub-scanning direction P1 ', P2', P3 'and P4' In original stationary reading mode First slider 3, second slider 4, lens 5
And the initial position of the image sensor 6 P1, P2, P3, and P4 The first slider 3, the second slider 4, the lens 5, and the fixed position of the image sensor 6 in the original follow-up mode U Image reading optical system unit SL Selfoc lens array 6 'Image sensor CV Document holding openable / closable cover F, F' Image reading focal position S Document ADF Automatic document feeder 701, 704 Document tray 702 Document take-out supply roller 705 Document feed roller pair 703, 720 Document feed roller pair 706 , 707 A pair of document feed roller pair for image reading 708 Document discharge roller pair 709 Document page alignment roller pair 710 Document inversion roller pair 711 Document inversion switching claw 712 Document page alignment switching claw 713 Document inversion path 714 Document Page matching Use passage 722 document reversing feed roller pair

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroyuki Nagamine 2-13-13 Azuchicho, Chuo-ku, Osaka City International Building Minolta Co., Ltd. F-term (reference) 2H012 CA11 CA15 CA27 CC11 2H108 AA19 BA02 CB01 5C072 AA01 BA02 BA20 LA02 LA18 MB01 MB06 NA01 RA11

Claims (2)

[Claims] An image reading apparatus capable of executing an original panning mode in which an original is moved with respect to an original platen glass plate while an image reading optical system is fixedly arranged at a fixed position and an image of the moving original is read. The thickness of the platen glass plate and / or the thickness of the platen glass plate so that the image reading focal position by the image reading optical system in the document panning mode is shifted from the plate surface of the platen glass plate used in the document panning mode. An image reading apparatus, wherein a refractive index is set, and an original is passed through the shifted image reading focal position in the original panning mode. 2. An original stationary reading mode for reading an original image by moving at least a part of an image reading optical system with respect to a stationary original placed on an original platen glass plate, and moving the original with respect to the original platen glass plate On the other hand, in the image reading apparatus, the image reading optical system is fixedly arranged at a fixed position, and the image reading optical system can selectively execute a document panning mode for reading an image of the moving document. The image reading focal position by the system is located on the surface of the platen glass plate used in the original stationary reading mode, and in the original panning mode, the image reading focal position by the image reading optical system is in the original panning mode. The position of the platen glass plate to be used is shifted from the plate surface, and the shifted image reading focal position is The thickness and / or refractive index of the platen glass plate used in the mode is set to be larger than that of the platen glass plate used in the stationary document reading mode. An image reading apparatus, wherein the image reading apparatus passes a reading focus position.