JP3514416B2 - Image reading device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an image reading apparatus, and more particularly, to an image reading apparatus by moving a planar table in a sub-scanning direction. The present invention relates to a flat-scanning and original-moving-type image reading apparatus (hereinafter, original-moving-type flat scanner) that sequentially reads one line of an image on a placed original in a main scanning direction. 2. Description of the Related Art FIG. 5 is a perspective view showing an original moving flat scanner according to a conventional example. In FIG.
On the upper surface of the rail 5 along one long side thereof
The table 50 is provided with a block 5 that slides on the rail 53 near one end of one long side thereof.
1 is provided. The table 50 is supported on the housing 52 via the block 51 and the rail 53 so as to be movable along the sub-scanning direction X (long side direction). At the center of the table 50, there is provided a transparent glass plate 54 of the size of a document.
An original (transparent original) is placed on top. A strip-shaped reading opening 55 is provided on the upper surface of the housing 52 along one short side thereof, and a light source (not shown) is provided above the reading opening 55. Below the reading opening 55, an optical system (not shown) including a mirror and a lens and a CCD are provided, and light emitted from a light source is placed on the table 50 (on the glass plate 54). After passing through the read original, the original enters the housing 52 through the reading opening 55. Then, the light enters the CCD via the optical system. The CCD reads the original for one line in the main scanning direction, performs photoelectric conversion, and outputs an image signal of the original. In the scanner of FIG. 5 configured as described above, the table 50 is driven by a motor (not shown) and moves in the sub-scanning direction X, thereby causing the image of the original placed on the table 50 to be moved. Is on a vertical plane passing through the midpoint of the short side of the reading opening 55 (hereinafter referred to as a reading position).
The CD sequentially reads one line in the main scanning direction Y (short side direction). In the scanner shown in FIG. 5, a table 50 is provided near one end of one long side thereof.
Since the table 50 is supported by the two blocks 51, if the rigidity of the table 50 is low, the table 50 may hang down (warp due to its own weight). The warp due to its own weight includes a warp in the sub-scanning direction X and a warp in the main scanning direction Y. The warpage in the main scanning direction Y is smaller than the warpage in the sub-scanning direction X.
For example, another rail is further provided along the other long side of the upper surface of the housing 52, and another block is further provided at a position corresponding to the block 51 on the other long side of the table 50, or the other rail of the table 50 is provided. By providing a support for supporting the other long side of the table 50, such as providing a roller or the like for supporting the table 50 at a position corresponding to the block 51 on the long side, the magnitude of the warpage can be sufficiently reduced. It does not matter in the following. In the table 50, a block 51
It is not preferable to provide a support for supporting an end different from that provided with to reduce the warpage in the sub-scanning direction X for the following reasons. That is, for example, in the longer side of the table 50 where the block 51 is provided, the block 5
In the case where another block is further provided at a position near the end on the opposite side to the position where No. 1 is provided, the stroke of the table 50 is shortened by the distance between the block 51 and the other block. In addition, the scanner becomes large. Block 5
The same can be said of the above even if the size of 1 is increased. FIG. 6 shows a case where the table 50 is warped in the sub-scanning direction X by its own weight in the scanner of FIG.
FIG. 10 is a diagram (side view) illustrating a state in which a table 50 moves in the sub-scanning direction X. The dashed line in the figure indicates the reading position. In FIG. 6, the table 50 having the warp in the sub-scanning direction X is (1)-
When moving as shown in (3), the height of the table 50 at the reading position increases with the movement. The CCD is moved from the position of the original placed on the table
The optical path length increases, and as a result, a change in magnification and a focus shift occur. Therefore, conventionally, in the scanner shown in FIG.
The table 50 may be made of a material that is lightweight and has high rigidity so that the table 50 does not warp due to its own weight. Had been adjusted to correct. [0011] However, a lightweight and highly rigid material is expensive, and it takes time and effort to perform an adjustment operation for correcting warpage due to its own weight. Therefore, the price of the conventional original moving type flat scanner is high. In the above, for the sake of simplicity, the table 50
Is limited to that caused by its own weight in the sub-scanning direction X,
In reality, for example, the material of the table 50 is not uniform, and the warpage of a complicated shape due to the low processing accuracy is further added. Therefore, the uniformity of the material and the processing accuracy are increased, and more complicated adjustment work is performed. You need to do it. Therefore, an object of the present invention is to prevent a change in magnification and a focus shift caused by warpage in the sub-scanning direction on a table on which a document is placed and moved in the sub-scanning direction. It is an object of the present invention to provide an inexpensive original moving flat scanner that does not require the use of an expensive material that does not cause warpage and does not require a complicated adjustment operation for correcting warpage. According to a first aspect of the present invention, a table for placing a document is placed on the table by moving along a sub-scanning direction. A flat-scanning-type and document-moving-type image reading apparatus for sequentially reading one line of an image written on a document in a main scanning direction perpendicular to the sub-scanning direction at a predetermined reading position, The table is movable along the sub-scanning direction on the housing via a guide member extending along the predetermined direction for guiding the table in a predetermined direction and a guide piece sliding on the guide member. The guide piece and the guide member are engaged with each other so that the guide piece is supported at a predetermined distance from the housing in the vertical direction perpendicular to the main scanning direction and the sub-scanning direction. Department The material is provided on the table, and the guide piece is provided only near the position corresponding to the reading position of the housing. As described above, in the first aspect, since the guide piece is provided near the position corresponding to the reading position of the housing, the guide is placed on the table which is placed and moved in the sub-scanning direction. Even when warpage in the scanning direction occurs, the height of the table at the reading position does not change with the movement of the table, or the amount of change can be made sufficiently small, so that a change in magnification or defocusing occurs. Never happen. Therefore, it is not necessary to adopt an expensive material that does not cause the table to be warped or to perform a complicated adjustment to correct the warp, and as a result, the price of the scanner is reduced. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an original moving flat scanner according to an embodiment of the present invention,
FIG. 2 is a cross-sectional view (along the sub-scanning direction X) of the scanner of FIG. 1 and 2, the table 10 is provided with a rail 11 along one long side thereof, and on the upper surface of the housing 12, a reading position (described later) of the one long side is provided. A block 13 that slides on the rail 11 is provided near the end. FIG. 3 is a perspective view showing the shapes of the rail 11 and the block 13 employed in the scanner shown in FIG.
In FIG. 3, a plurality of small balls (not shown) for improving the slip are provided in the concave portion 13a of the block 13, and the concave portion 13a and the convex portion 11a of the rail 11 are engaged with each other. , Rail 11 and block 13 can slide relative to each other along the longitudinal direction of rail 11.
The table 10 includes the rail 11 and the block 13
Are supported on the housing 12 so as to be movable along the sub-scanning direction X. The shapes of the rail 11 and the block 13 are not limited to those shown in FIG. Further, a shaft and a bearing may be provided in place of the rail 11 and the block 13, and furthermore, any parts may be provided as long as the rod guides the table 10 in a predetermined direction and small pieces that slide on the rod. Good. Referring again to FIGS. 1 and 2, table 10
An original-sized transparent glass plate 14 is provided at the center of the document, and an original (a transparent original or a reflective original) is placed on the glass plate 14. A strip-shaped reading opening 15 is provided on the upper surface of the housing 12 along one short side thereof, and a light source 16 (for example, a fluorescent tube) for a transparent original is provided above the reading opening 15. Immediately below, a pair of light sources 17 for a reflective original are provided. Below the reading opening 15, a folding mirror 1 is provided.
Further, a lens 19 and a CCD 20 are provided on a straight line passing through the folding mirror 18 and having a direction perpendicular to the direction from the light source 16 to the folding mirror 18. The lens 19 and the CCD 20 are driven by a motor (not shown) to move back and forth along the straight line, thereby adjusting the magnification and the focus. The light emitted from the light source 16 is
After passing through a document (in this case, a transparent document) placed on (the glass plate 14 of), the document enters the housing 12 through the reading opening 15. Then, the traveling direction is changed by the folding mirror 18, and the light enters the CCD 20 via the lens 19.
When a reflective document is placed on the table 10, light emitted from the pair of light sources 17 passes through the reading opening 15 through the housing 1.
2 and is reflected by the original, and then enters the housing 12 again. Then, the traveling direction is changed by the folding mirror 18, and the light enters the CCD 20 via the lens 19. The CCD reads the original for one line in the main scanning direction, performs photoelectric conversion, and outputs an image signal of the original. In the scanner of FIG. 1 configured as described above, the table 10 is driven by a motor (not shown) and moves in the sub-scanning direction X, so that the document on the document placed on the table 10 On a vertical plane where the image passes through the midpoint of the short side of the reading opening 15 (hereinafter, reading position),
The CCD 20 sequentially reads one line in the main scanning direction Y. In the scanner shown in FIG. 1, similarly to the scanner shown in FIG. 5, since the table 10 is supported via one block 13, if the rigidity of the table 10 is low, the table 10 is placed in the sub-scanning direction by its own weight. X warpage may occur. FIG. 4 shows a case where the table 10 is warped in the sub-scanning direction X by its own weight in the scanner of FIG.
FIG. 4 is a diagram (side view) showing a state in which a table moves in a sub-scanning direction X. The dashed line in the figure indicates the reading position. In FIG. 4, when the table 10 is at the position shown in (1), one end of the table 10 (the end opposite to the side supported by the block 13) hangs down by its own weight. When it is in the position (2), both ends hang down slightly. When it is in the position (3), the other end side (the end side opposite to the side supported by the block 13) hangs down. ing. That is, the scanner of FIG. 1 differs from the scanner of FIG. 5 in that the shape and size of the warp change depending on the position of the table 10. But,
The most important difference is that FIGS. 4 (1) to (3) and FIG. 6 (1)
As can be understood by comparing (3) to (3), in the scanner of FIG. 1, since the block 13 is provided near the position corresponding to the reading position on the upper surface of the housing 12, the table 10 Is that the height of the table 10 at the reading position does not change with the movement of the table 10 even when the table 10 is warped. Further, in addition to (simple) warpage due to its own weight as shown in FIG. 4, even if warpage of a complicated shape due to non-uniform material or low processing accuracy is added, the table 10 Obviously, the height of the table 10 at the reading position does not change with the movement. Further, when an external vibration is applied, the scanner shown in FIG.
Vibration is amplified on the end side opposite to the position where the table 50 is provided. Therefore, particularly when the table 50 is at the position shown in FIG. In contrast, in the scanner of FIG.
Is provided in the vicinity of the position corresponding to the reading position on the upper surface of the housing 12, so that the table 10 does not move up and down near the reading position regardless of the position of the table 10. As described above, in the scanner of FIG. 1, since the block 13 is provided near the position corresponding to the reading position on the upper surface of the housing 12, the original is placed and moved in the sub-scanning direction X. Even when the table 10 is warped in the sub-scanning direction X, the height of the table 10 at the reading position does not change with the movement of the table 10 or the amount of change can be made sufficiently small. There is no change in magnification or out of focus. Therefore, table 10
It is not necessary to adopt an expensive material that does not cause warpage or to perform a complicated adjustment for correcting the warpage, and as a result, the price of the scanner can be reduced. In the scanner shown in FIG.
A glass plate 14 is provided at the center of the document, and an original (a transparent original or a reflective original) is placed on the glass plate 14. However, another detachable glass plate is further provided,
An original may be sandwiched between the glass plate 14 and another glass plate. As a result, the document is not slackened or floated, and fluctuations in magnification and out-of-focus caused by the loosening and floating can be eliminated. In the scanner shown in FIG. 1, the load on the block 13 is increased because the rail 11 is provided on the table 10 side, and the service life of the scanner is expected to be shortened due to wear of the block 13. . Therefore, if a lightweight synthetic resin plate is provided instead of the glass plate 14, the load on the block 13 can be reduced. Alternatively, instead of the glass plate 14, a frame (document holder) for holding the document by gripping only the peripheral portion thereof may be provided. Thus, the load on the block 13 can be significantly reduced while the slack of the document is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing an original moving flat scanner according to an embodiment of the present invention. FIG. 2 is a sectional view (along a sub-scanning direction X) of the scanner of FIG. 1; FIG. 3 is a perspective view showing shapes of a rail 11 and a block 13 employed in the scanner of FIG. FIG. 4 is a diagram showing a case where the table 10 is warped in the sub-scanning direction X by its own weight in the scanner of FIG.
(Side view) showing the state of moving in the sub-scanning direction X
It is. FIG. 5 is a perspective view showing an original moving flat scanner according to a conventional example. FIG. 6 is a diagram showing an example of a configuration of the scanner shown in FIG.
FIG. 7 is a diagram (side view) showing a state of moving along the sub-scanning direction X. [Description of Signs] 10 Table 11 Rail 12 Housing 13 Block 14 Glass plate 15 Reading apertures 16, 17 Light source 18 Folding mirror 19 Lens 20 CCD

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-116170 (JP, U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) H04N 1/00-1/00 108 H04N 1 / 04-1/027

Claims (1)

(57) [Claim 1] By moving a table for placing a document along the sub-scanning direction, an image written on the document placed on the table is moved. A flat-scanning-type and original-moving-type image reading apparatus that sequentially reads one line at a predetermined reading position in a main scanning direction perpendicular to the sub-scanning direction. A guide member extending along the predetermined direction for guiding in the direction of and a guide piece sliding on the guide member so as to be movable along the sub-scanning direction on the housing, and And the guide member are engaged with each other so as to be fixed at a predetermined distance from the housing in a vertical direction perpendicular to the main scanning direction and the sub-scanning direction, and are supported by the guide member. table Provided, the guide piece, of the housing, in the vicinity of a position corresponding to the reading position
An image reading device, comprising: