JP3405883B2 - Optical device of 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 that converts character or graphic information written on a sheet medium such as paper into an electric signal and reads the same. In particular, the present invention relates to a technique for reducing the size of an optical device used for forming an image on a document on a light receiving surface of a photoelectric conversion element (image sensor). 2. Description of the Related Art FIG. 3 shows an example of an optical device of a conventional image reading apparatus of a document feeding type. In this type of apparatus, the one-dimensional image sensor 4 scans the document A in the main scanning direction, and scans the document A in the sub-scanning direction by feeding the document by the feed roller 5. Therefore, the document A is read linearly, and the read line L is at a fixed position. There are two types of optical devices of an image reading apparatus: an upright unity type and an inverted reduction type shown in FIG.
The erect equal-magnification type has a short optical path length and can be miniaturized, but requires high-precision assembly due to high component costs and a small depth of focus, and is expensive. On the other hand, the inverted reduced type is inexpensive and has stable performance, but the optical device becomes large due to a long optical path length. Accordingly, in an inverted reduction type optical apparatus, as shown in FIG. 3, a plurality of (normally three or more) reflecting mirrors 11,
The optical path K is folded using 12, 13, and 14, thereby reducing the size of the optical device 1, particularly the size in the document feed direction (the left-right direction in FIG. 3). The size of the optical device 1 in the document feeding direction directly affects the size of the installation area of the document feeding type image reading device, and also greatly affects the operability when the optical device 1 is used as a handy scanner. is there. In FIG. 3, reference numeral 6 denotes a contact glass for holding down a reading portion of a document, 7 denotes a light source arranged in parallel with a reading line L to illuminate the reading portion, 3 denotes an image forming lens, and 4 denotes an image sensor. And four reflecting mirrors 11,
The reflection surfaces 12, 13, and 14 are parallel to the reading line L. On the other hand, an optical device in which the reflecting surface of a reflecting mirror is arranged at an angle to the reading line is disclosed in
There is a structure disclosed in 147354. FIG. 4 shows the structure, in which the optical path K is folded back by one reflecting mirror 11, and this one reflecting mirror 11 is perpendicular to the plane including the reading line L and orthogonal to the document A. It has become. [0007] In an optical device of an image reading apparatus, an imaging lens 3 and an image sensor 4 are indispensable, and these must be arranged on the same optical axis. Although it is theoretically possible to place a reflecting mirror between the imaging lens 3 and the image sensor 4 to fold the optical path,
In addition to the small space, the accuracy of the reflecting surface and the mounting accuracy of the reflecting mirror require extremely high precision, which increases the cost and also causes thermal expansion and distortion of the frame to greatly affect the quality of the read image. In reality, it is extremely difficult due to lack of stability. For this purpose, the imaging lens 3 and the image sensor 4
That is, even if the number of reflecting mirrors is increased and the optical path K is finely folded by increasing the number of reflecting mirrors, the dimension b from the front surface of the imaging lens 3 (the surface on the original side) to the back of the image sensor can be obtained. It is impossible to further reduce the size of the optical device.
4 is indispensable, the actual device size is the size b
It had to be a few extra dimensions. In the conventional structure shown in FIG. 4, the size of the optical device (the size in the horizontal direction or the height direction in FIG. 3) is larger than that of the structure shown in FIG. Since it is outside the line L, the dimension in the reading line direction becomes large, and there is an advantage that only one reflecting mirror is required, but it is not suitable for the purpose of reducing the size of the optical device. An object of the present invention is to further reduce the size of an optical device of an image reading apparatus. An optical device of an image reading apparatus according to the present invention comprises a plurality of parallel reflecting mirrors 11, 12, 13, and 14 having a reflecting surface parallel to a reading line L of a document A. When,
One inclined reflecting mirror 2 having a reflecting surface intersecting with the reading line L is provided. The inclined reflecting mirror 2 is disposed between the last-stage parallel reflecting mirror 14 and the imaging lens 3. The reflecting surface of the inclined reflecting mirror 2 is connected to the optical axis N of the imaging lens 3 and the last-stage parallel reflecting mirror. It is arranged at a right angle to a plane including the optical axis M of the reflected light and at an angle close to 45 degrees with respect to the reading line L. The imaging lens 3 and the image sensor 4 are disposed outside the optical path width W of the reflected light from the parallel reflection mirror 14 at the final stage, and the inclined reflection mirror 2, the imaging lens 3, and the image sensor 4
Are arranged within the maximum opposing arrangement dimension d of the parallel reflecting mirrors 11, 12, 13, 14. The reading light from the reading line L passes through the optical path K folded by the plurality of parallel reflecting mirrors 11, 12, 13, and 14, while its optical path width is reduced and is sufficiently narrow. Since the light is reflected by the inclined reflecting mirror 2 between the parallel reflecting mirror 14 of the final stage having the optical path width W and the imaging lens 3, the length S of the inclined reflecting mirror 2 can be shortened. Therefore, the inclined reflecting mirror 2 is
Even when the mirror is inclined at an angle close to 5 degrees, Ssin α when the length of the inclined reflecting mirror is S and the inclination angle is α can be kept small, and the size of the apparatus can be reduced. Further, since the inclined reflecting mirror 2 can be provided to be inclined at an angle close to 45 degrees, the optical axis N of the imaging lens 3 can be swung to an angle nearly parallel to the reading line L. The distance b from the front surface of the image lens to the back surface of the image sensor can be set in the reading line direction, and a portion where the imaging lens 3 is disposed by providing a plurality of parallel reflecting mirrors 11, 12, 13, and 14 Can be made sufficiently smaller than the length of the read line L (the optical path width on the read line), so that the image forming lens 3 and the image sensor 4 are reflected by the last-stage parallel reflecting mirror 14. The imaging lens 3 and the image sensor 4 can be accommodated within the length range of the reading line L even if they are arranged outside the optical path width W of the light, and the device size in the reading line L direction can be increased. No. Further, the inclined reflecting mirror 2, the imaging lens 3 and the image sensor 4 are connected to the parallel reflecting mirrors 11, 12, 13, and 14.
Since the distance between the original A and the imaging lens 3 is finely folded by using an imaging lens with a short focal length and increasing the number of parallel reflecting mirrors,
Since the maximum facing distance d between the parallel reflecting mirrors can be reduced, and the length of the inclined reflecting mirror 2 and the size of the image sensor 4 can also be reduced, the optical device of the image reading apparatus using the inverted reduction type optical system can be significantly reduced. The size can be reduced. FIG. 1 and FIG. 2 show an embodiment of the present invention. In the drawing, the inclined reflecting mirror 2 is provided between the final-stage reflecting mirror 14 and the imaging lens 3 of the optical device having the conventional structure shown in FIG. Figure 1,
2, the same members as those in the apparatus of FIG. 3 are denoted by the same reference numerals. Four parallel reflecting mirrors 11, 12, 13, 14
Are the same as the reflecting mirror of FIG. 3 and the members themselves are arranged in the same positional relationship.
As much as the optical path length in the later stage can be slightly lengthened,
The maximum facing distance dimension d of the parallel reflecting mirror is smaller than that of FIG. The light source 7 and the contact glass 6 are shown in FIG.
There is no difference from the conventional roller, and the feed roller 5 may of course have the same structure as the conventional roller. The imaging lens 3 and the image sensor 4 are the same as those in FIG. 3, but the arrangement directions are different.
The optical axis K is in a direction substantially parallel to the reading line L.
Between the final parallel reflecting mirror 14 and the imaging lens 3, the inclined reflecting mirror 2 inclined about 40 degrees with respect to the reading line L in plan view is provided. The reflecting surface of the inclined reflecting mirror 2 is orthogonal to a plane including the optical axis N of the imaging lens 3 and the optical axis M of the reflected light of the parallel reflecting mirror 14 at the last stage. The imaging lens 3 and the image sensor 4 have their optical axes N coincident with the optical axis of the reflected light of the inclined reflecting mirror 2,
It is arranged outside the optical path width W of the reflected light of the last-stage parallel reflecting mirror. With such an arrangement, the inclined reflecting mirror 2, the imaging lens 3, and the image sensor 4 are smaller than the maximum facing distance d between the plurality of parallel reflecting mirrors 11, 12, 13, and 14 and smaller than the length of the reading line. It can fit in the area within the range. According to the present invention described above, it is possible to reduce the size of the optical device of the image reading apparatus provided with the inverted reduction type optical device, and to reduce the installation area and inexpensive document feeding. Type image reading device can be provided. In addition, by using this optical device as an optical device of a handy scanner, a smaller (elongated) handy scanner can be obtained, and operability at the time of image reading can be improved.

[Brief description of the drawings] FIG. 1 is a plan view showing a reading optical path of the present invention. FIG. 2 is a side view of the embodiment. FIG. 3 is a side view of the first conventional example. FIG. 4 is a front view showing an optical path of a second conventional example. [Explanation of symbols] 2 Inclined reflector 3 Imaging lens 4 Image sensor A Manuscript d Maximum facing distance L reading line M optical axis N optical axis W Optical path width

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Claims (1)

(57) [Claims] [Claim 1] A plurality of parallel reflecting mirrors (11, 12, 13, 14) having a reflecting surface parallel to a reading line (L) of a document (A), and reading One inclined reflector with a reflective surface crossing the line (L)
(2), and the inclined mirror (2) is the last parallel mirror (1).
4) and the imaging lens (3), and the reflecting surface of the inclined reflecting mirror (2) is reflected by the optical axis (N) of the imaging lens (3) and the reflected light of the last-stage parallel reflecting mirror. Is arranged at a right angle to the plane including the optical axis (M) and at an angle of about 45 degrees with respect to the reading line (L), and the imaging lens (3) and the image sensor (4) are reflected at the last stage by parallel reflection. It is arranged outside the optical path width (W) of the reflected light of the mirror (14), and the inclined reflecting mirror (2), the imaging lens (3) and the image sensor (4) are connected to the parallel reflecting mirrors (11, 12, 13, 14) The optical device of the image reading device, wherein the optical device is arranged within the maximum opposing arrangement dimension (d).