JPH10257236A - Image reading device - Google Patents

Abstract

(57) [PROBLEMS] To provide an image reading apparatus that reads a self-propelled reading unit having a reduction type optical system using an image forming lens to stabilize an optical path length and eliminate out-of-focus in original scanning. , Even if the entire device is twisted, misalignment (skew) between the reading start position and the reading end position
To provide an image reading apparatus capable of solving the problem. The flatbed unit includes a reading unit having a contact member that comes into contact with a document placing table of the flatbed unit, and a pressing element that presses between the reading unit and the document placing table. Further, it is preferable that the reading unit includes a contact member that presses and contacts the driven rail of the flat bed unit.

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 for reading a self-propelled reading unit having a reduction type optical system using an imaging lens.

[0002]

2. Description of the Related Art An image reading apparatus (hereinafter, referred to as a scanner) for reading character information and graphic information on a medium such as paper as image information includes a reading unit having a reduction type optical system using an imaging lens. 2. Description of the Related Art Flatbed scanners that scan and read are generally known.

FIG. 7 shows a diagram of the prior art. 1A and 1B, the flatbed scanner includes a flatbed unit 51 and a reading unit 52.

The flat bed unit 51 has a document table 61, a driven rail 62, and a reference shaft 71.

The reading unit 52 comprises a light source 75, a reflecting mirror 76, an image forming lens 77, and a CCD 78 to constitute a reduced optical system, and further comprises a contact member comprising a sliding member and a rolling member opposed to the driven rail 62. It has a member 53.

When scanning a document, the reading unit 52 is driven by a drive belt (not shown) to run on a reference shaft 71. The driven rail 62 side of the reading unit 52 slides on the surface of the driven rail 62 whose flatness is increased.

[0007] For this reason, in the conventional scanner shown in FIG. 7, due to the flatness and mounting accuracy of the driven rail 62, the twist of the entire scanner device including the flat bed unit 51 and the reading unit 52, etc., it is shown in FIG. As described above, an error δ may occur in the position between the document table 61 and the reading unit 52. For this reason, from the document table 61 to the CCD 7
The optical path length up to 8 becomes unstable.

On the other hand, in a recent scanner, a reading unit provided with a reduction type optical system using an image forming lens includes:
As the resolution has been increased, it has been necessary to use an imaging lens having a small depth of field and a small depth of focus as shown in FIG.

[0009]

As described above, the conventional scanner has the following problems.

1) When the optical path length is unstable, the reading accuracy is deteriorated.

2) If the depth of field is exceeded, focusing is not achieved.

3) When the entire apparatus is twisted, a misalignment (skew) occurs between the reading start position and the reading end position.
Occurs.

[0013]

In order to solve the above problems, the present invention takes the following measures.

When scanning a document, the reading unit is always brought into contact with the document table of the flatbed unit and slid.

By taking the above measures, the distance between the reading unit and the document table is always kept constant.
When scanning a document, the optical path length from the document table to the CCD is stabilized.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention adopts the following embodiments.

In an image reading apparatus in which a reading unit having an optical system of a reduction type using an image forming lens is made to run by itself and read, an original placing table 1 of a flat bed unit 1 is provided.
Reading unit 2 having a contact member 21 abutting on
And a pressing element 30 for pressing between the reading unit 2 and the document table 11.

Further, as shown in FIG. 2, the reading unit 2 is a driven rail 1 of the flatbed unit 1.
It is preferable to include a contact member 22 that presses and contacts the second member 2.

Further, as shown in FIGS. 2 and 3, it is also effective to press a contact member 22a slidably mounted on the reading unit 2 toward the driven rail 12 with a spring member 23. .

Further, as shown in FIG. 4, it is preferable to mount the contact member 22b on a spring member 24 for pressing the driven rail side of the reading unit 2.

Further, as shown in FIG. 5, it is preferable to press a contact member 25 made of an elastic synthetic resin material forming the frame 26 of the reading unit 2 against the driven rail 12.

Also, as shown in FIG.
Bed 1
It is preferable to attach to.

Further, as shown in FIG. 6, the flatbed unit 1 has a column 13 for regulating the position of the document table 11 in the main scanning direction and the sub scanning direction.
It is also effective to attach the document table 11 to the document table 3.

By employing the above-described embodiment, the following operation works.

Since the reading unit scans the original in a state where the reading unit is always in contact with the original placing table by the pressing element, the distance between the reading unit and the original placing table is always kept constant.
Therefore, the optical path length from the document table to the CCD is stable,
Out-of-focus in document scanning is eliminated. Further, even if the entire apparatus is twisted, the positional deviation (skew) between the reading start position and the reading end position is eliminated.

Further, the cost is reduced because the surface accuracy and the mounting accuracy of the driven rail are not required. Furthermore, even if the follower rail surface is twisted, the optical path length from the document table to the CCD is stable and does not require the strength of the device itself, so that the device can be formed with inexpensive materials.

Furthermore, the contact member provides a stable contact between the reading unit and the flatbed unit, and the reading unit travels stably in scanning the original, thereby preventing transmission of vibration from the motor which causes jitter and the like. I do.

Further, by integrally molding the contact member and the pressing element, it is not necessary to add a special part, and the number of parts is reduced.

When scanning a document, the document table is always in contact with the reading unit by its own weight, and the distance between the reading unit and the document table is always kept constant. Therefore, the optical path length from the document table to the CCD is stabilized, and blurring in document scanning is eliminated. Further, even if the entire apparatus is twisted, the positional deviation (skew) between the reading start position and the reading end position is eliminated.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A typical embodiment according to the present invention will be described with reference to FIGS. In the following, the same portions are denoted by the same reference numerals, and detailed description may be omitted.

FIG. 1 is a diagram showing the principle structure of the present invention.

Referring to FIG. 1, the flatbed scanner includes a flatbed unit 1 and a reading unit 2. The flatbed unit 1 has a document table 11, a driven rail 12, and a reference shaft 35. The reading unit 2 includes a light source (not shown), a reflecting mirror, an imaging lens, and a CCD to constitute a reduction optical system. The optical system of the reading unit 2 is the same as that of the reading unit 52 having the reduction type optical system of the prior art shown in FIG.

The reading unit 2 has a contact member 21 made of, for example, a rolling member, which comes into contact with the original placing table 11 in contact therewith. Further, the flatbed scanner includes a pressing element 30 that presses between the reading unit 2 and the document table 11. The pressing element 30 may be provided on the reading unit 2 side or on the flat bed unit 1 side.

When scanning a document, the reading unit 2 is driven by a drive belt (not shown) to run on the reference shaft 35. The reading unit 2 is slid between the upper surface of the driven rail 12 and the lower surface of the document table 11.

The sliding of the upper surface of the driven rail 12 is caused by the pressing element 3
The reading unit 2 slides the reading unit 2 while keeping the reading unit 2 in contact with the lower surface of the document table 11.

FIG. 2 is a schematic view of an embodiment of the present invention (part 1).
It is.

In the figure, the reading unit 2 is provided with a contact member 22a made of, for example, a rolling member, which presses and contacts the driven rail 12 of the flatbed unit. The contact member 22a has a shaft 27 slidably mounted in a groove 28 formed in a frame 26 constituting the reading unit 2.

The contact member 22a is pressed toward the driven rail 12 by attaching a spring member 23 made of, for example, a leaf spring to the frame 26 at a substantially central portion of the shaft 27.

FIG. 3 is a schematic view of an embodiment of the present invention (part 2).
It is.

In the figure, the spring member for pressing the contact member 22a toward the driven rail 12 may be a torsion coil spring 31 as shown in FIG. 5A or a tension spring as shown in FIG. A compression spring 33 may be provided between the fixed plate 34 attached to the frame 26 and the shaft 27 as shown in FIG.

FIG. 4 is a schematic view of an embodiment of the present invention (part 3).
It is.

In the figure, a spring member 24 made of, for example, a leaf spring, which presses the driven rail 12 on the lower surface of the reading unit 2 facing the driven rail 12, is attached. further,
This spring member 24 is provided with a contact member 22b. The contact member 22b may be a sliding member as shown in FIG. 7A or a rolling member as shown in FIG.

FIG. 5 is a schematic view of an embodiment of the present invention (part 4).
It is.

In the figure, the frame 26 of the reading unit 2 is formed of an elastic resin material. The frame 26 has a spring property at a portion facing the driven rail 12 so as to press the driven rail 12, and
The tip portion is formed by integral molding including the contact member 25.

FIG. 6 is a schematic view of an embodiment of the present invention (part 5).
It is.

In the figure, the original placing table 11 is slidable up and down so as to come into contact with a contact member 21 of the reading unit 2 and is mounted on the flat bed unit 1.

The flatbed unit 1 has a column 13 for regulating the positions of the document table 11 in the main scanning direction and the sub-scanning direction, and mounts a fixed frame 37 to which the document table 11 is fixed. Note that the document table 11 is
It may be directly attached to. On the other hand, a contact member 38 made of, for example, a sliding member is provided on the lower surface of the reading unit 2 and is in contact with the driven rail 12 of the flatbed unit 1.

[0048]

As described above, according to the present invention, the following effects can be obtained.

In an image reading apparatus for reading a self-propelled reading unit having a reduction type optical system using an image forming lens, a reading unit having a contact member abutting on a document table of a flatbed unit, and a reading unit Since the reading unit always scans the original in a state in which the reading unit is in contact with the original placing table by the pressing element, the reading unit is provided with a pressing element for pressing between the reading unit and the original placing table. The distance is always kept constant. Therefore, the optical path length from the document table to the CCD is stabilized, and blurring in document scanning can be eliminated. Further, even when the entire apparatus is twisted, a position shift (skew) between the reading start position and the reading end position can be eliminated.

Further, since the reading unit is provided with the contact member which presses and abuts the driven rail of the flatbed unit, it does not require the surface accuracy and the mounting accuracy of the driven rail, so that the cost can be reduced. Furthermore, even if the follower rail surface is twisted, the optical path length from the document table to the CCD is stable and does not require the strength of the device itself, so that the device can be formed with inexpensive materials.

Further, a contact member slidably mounted on the reading unit is pressed against the driven rail by a spring member. Alternatively, since the contact member is attached to the spring member that presses the driven rail side of the reading unit, stable contact between the reading unit and the flatbed unit is obtained by the contact member, and the traveling of the reading unit in document scanning is stabilized. Therefore, transmission of vibration from the motor that causes jitter or the like can be prevented.

Since the contact member made of an elastic resin material for forming the frame of the reading unit is pressed against the driven rail, the pressing element is formed without adding any special parts, thereby reducing the number of parts. Can be.

Further, the original placing surface is slidable in the vertical direction and is mounted on the flat bed unit. Further, the flatbed unit has a column for regulating the position of the document placing surface in the main scanning direction and the sub-scanning direction, and the document placing table is attached to the column. As a result, the reading unit is always in contact with the reading unit, and the distance between the reading unit and the document table is always kept constant. Therefore, the optical path length from the document table to the CCD is stabilized, and blurring in document scanning can be eliminated. Further, even when the entire apparatus is twisted, a position shift (skew) between the reading start position and the reading end position can be eliminated.

[Brief description of the drawings]

FIG. 1 is a principle structural diagram of the present invention.

FIG. 2 is a schematic diagram (part 1) of an embodiment of the present invention.

FIG. 3 is a schematic diagram (part 2) of the embodiment of the present invention.

FIG. 4 is a schematic diagram (part 3) of the embodiment of the present invention.

FIG. 5 is a schematic diagram (part 4) of the embodiment of the present invention.

FIG. 6 is a schematic diagram (part 5) of the embodiment of the present invention.

FIG. 7 is a diagram of the prior art.

FIG. 8 is an explanatory diagram of a depth of field and a depth of focus.

[Explanation of symbols]

 1: Flat bed unit 2: Reading unit 11: Document mounting table 12: Follower rail 13: Post 21: Contact member 22: Contact member 22a: Contact member 22b: Contact member 23: Spring member 24: Spring member 25: Contact member 26 : Frame 27: Shaft 28: Groove 38: Contact member

Claims (7)

[Claims] An image reading apparatus for reading a self-propelled reading unit having a reduction type optical system using an image forming lens, comprising: a document table (1) provided in a flat bed unit (1);
A reading unit (2) provided with a contact member (21) that comes into contact with the reading unit (1); a reading unit (2);
An image reading device comprising: a pressing element (30) for pressing between the image reading device and the image reading device. 2. The reading unit according to claim 1, wherein the reading unit includes a contact member which presses and abuts a driven rail of the flat bed unit. Image reader. 3. A contact member (22a) slidably mounted on a reading unit (2) is pressed against a driven rail (12) by a spring member (23). Image reading device. 4. The image reading device according to claim 2, wherein the contact member is mounted on a spring member that presses the driven rail side of the reading unit. 5. The frame (26) of the reading unit (2).
Contact member made of an elastic resin material (2)
3. The image reading device according to claim 2, wherein 5) is pressed against the driven rail. 6. The image reading apparatus according to claim 1, wherein the document table is slidable in a vertical direction and mounted on the flatbed unit. 7. The flat bed unit (1) has a column (13) for regulating the positions of the document table (11) in the main scanning direction and the sub-scanning direction, and the document table (11) is mounted on the column (13). The image reading device according to claim 6, wherein the image reading device is mounted.