JPH0831942B2 - Image reading device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image reading apparatus used in a digital copying machine, an image editing apparatus, and the like, and more particularly, a traveling member including a document image reading unit is moved along a platen. The present invention relates to an image reading apparatus configured so that the distance between the image sensor and the original can be kept constant when the reading is performed.

(Prior Art) In a digital copying machine, an image editing apparatus, etc., an image reading apparatus having a configuration as shown in FIG. 2 has been conventionally used. In the image reading apparatus, the original 1 having the image surface facing downward is placed on the upper surface of the platen 2, the traveling member 3 is moved along the lower surface of the platen 2, and slit exposure is performed. There is. In order to move the traveling member 3, two wires, a drive pulley 9 and 10 provided on the drive shaft 21 and a guide pulley 11 and 12 provided via a tension applying device, are respectively attached to the wire 13, The traveling member 3 having both ends fixed to the respective wires is moved along the guide rail 18 in the sub-scanning direction.

The movement mechanism by the combination of the wire and the pulley is
Compared to the case of an apparatus using a gear member or the like, this method is widely used because the traveling member can be smoothly moved when driving the apparatus. Then, the drive shaft 21 is driven from the drive motor 14 to the timing pulleys 15 and 16 and the timing belt 17.
The driving member 14 is driven in the forward and reverse directions to reciprocate the traveling member 3 in the direction of the arrow to read the image of the original 1 on the upper surface of the platen 2. Further, as shown in FIG. 3, the traveling member 3 is provided with a lamp 4, a light focusing optical system 5, mirrors 6 and 7, and an image sensor 8. The traveling member 3 is moved by the lamp 4 when the traveling member 3 is moved. The document image is irradiated, the reflected image is input to the light focusing optical system 5 via the mirror 6 to form an image, and the reflected image is input to the image sensor 8 via the mirror 7.

In the apparatus having the above-mentioned configuration, the light focusing optical system 5
As for, SELFOC lens (trade name) is used,
Besides, a normal spherical lens can be used, and as the image sensor 8, an image sensor such as CCD which converts optical information into an electric signal can be used.
In the following description of the embodiments of the present invention and the conventional example, the case where a SELFOC lens and an image sensor such as a CCD are used will be described as an example.

The traveling member 3 is guided with respect to the guide rail 18 in a state as shown in FIG. 4, and the guide rail 18 is provided on the lower surface of the platen 2 on which the document 1 is placed in parallel with the platen 2. Is provided. Further, the traveling member 3 is provided with slide pads 19 and 20 on the lower surface of a flange 3a which is provided so as to project to the side of the frame, and the lower surface of the slide pad is moved while sliding on the guide rail 18. By doing so, the distance A between the lower surface of the document 1 and the traveling member 3 can be kept constant.

Apart from the above-mentioned configuration, as a guide method for the traveling member 3, an apparatus as shown in FIG. 5 or 6 is used. For example, in the guide system shown in FIG. 5, slide pads 22 and 23 that are in contact with the upper and lower sides of the guide rail 18 are provided, and the guide rail 18 is sandwiched by the slide pads, so that the traveling member 3 Let them move. In this case, the slide pad on the member such as the flange 3a provided so as to project on the traveling member 3
22 is fixedly provided, and the lower slide pad 23 is provided via a leaf spring 24 so as to be pressed against the lower surface of the guide rail 18, so that the traveling member 3 does not vibrate in the vertical direction when traveling. I am configuring.

Further, in the apparatus shown in FIG. 6, a method of guiding the traveling member 3 by using the slide shaft 25 and the slide bearing 26 is shown. In any of the above-described conventional apparatuses, the scanning reference surface of the traveling member is formed by using a guide rail or a slide shaft whose position is adjusted with respect to the platen 2.

(Problems to be Solved by the Invention) However, in the conventional device as described above, when the platen cover is strongly pressed against the platen 2 or when the weight of the original is large, such as a book-type original. May cause the platen 2 to bend. Then, in that case, the focal length of the SELFOC lens changes, and the quality of the read image deteriorates. That is, in the conventional device,
As shown in FIG. 7a, the SELFOC lens 5 is fixed such that it is positioned in the intermediate portion between the original 1 and the image sensor 8. The conjugate length TC of the SELFOC lens 5 is equal to the original 1 and the image sensor 8
Is fixed to the traveling member 3 in a state of being set to be equal to the optical distance between them and the image sensor 8 is similarly fixed to the traveling member 3 from the center of the SELFOC lens 5 with a distance of 1 / 2TC. To be done.

In this case, when the traveling member 3 moves up and down or the platen 2 bends, an error of Δl occurs with respect to the conjugate length TC, which causes the position of the image with respect to the SELFOC lens 5 to move from the focal length. As a result, the read image is blurred. Also,
In FIG. 7b, the Selfoc lens 5 and the image sensor 8,
It shows how the response coefficient MTF (Modulation Transfer Function) of the SELFOC lens changes with the relationship with the original 1. The closer the MTF is to 100%, the more faithful the original image is formed. As you can see from this graph, the finer the image information of the original, that is, the more 1p / mm (black and white line pairs per 1mm), the sharpness tends to decrease, and more 1p / mm. The MTF sharply affects the error Δl.

Therefore, as described above, the platen 2 bends or the traveling member 3 vibrates in the vertical direction, and the Δl is between the center of the SELFOC lens 5 and the image surface of the original 1.
If the error occurs, the focal length will be shifted to the left and right of the figure as shown in FIG. 7b, and the resolution will be significantly reduced.

(Object of the Invention) The present invention solves the above-mentioned drawbacks of the conventionally used apparatus. The object of the present invention includes a traveling member and a platen so that the distance between the original image surface and the traveling member can be set constant. It is an object of the present invention to provide an image reading apparatus which is provided with a means for setting an interval and has high scanning accuracy without causing image blur.

(Means and Actions for Solving Problems) According to the present invention, a traveling member including a document image reading means is caused to travel in the sub-scanning direction along a guide rail to display an image of a document set on a platen. , An image reading device for reading from the lower surface of the platen. In the present invention, a flange provided so as to project to both side portions of the frame at right angles to the traveling direction of the traveling member, and an upper sliding member that is disposed on the upper portion of each flange and slides on the lower surface of the platen, Arranged at the bottom of each flange via an elastic body,
A lower sliding member that slides on the guide rail to guide the traveling member, a wire for moving the traveling member in the sub-scanning direction, and a drive device for driving the wire are provided.

With the above-described configuration, in the image reading apparatus of the present invention, even when the platen is bent, the distance between the traveling member and the lower surface of the platen can always be kept constant, and the read image is blurred. Etc. can be prevented.

(Embodiment) The configuration of the image reading apparatus of the present invention will be described with reference to the illustrated embodiment. FIG. 1 is a side view showing only an engaging portion of the traveling member 3 of the present invention with the guide rail 18, and each member is shown in correspondence with the conventional example of FIGS. 2 and 4. There is. As in the case of the conventional device, the traveling member 3 has wires 13 fixed to the front and rear portions in the traveling direction thereof, and the wire 13 is driven by the drive device having the configuration shown in FIG. The original image is moved in the sub-scanning direction and the returning direction.

A flange 3a is provided so as to project from a side portion of the frame of the traveling member 3, and pads as sliding members are provided on upper and lower surfaces of the flange 3a. An upper slide pad as an upper sliding member arranged on the upper surface of the flange 3a.
The upper surfaces of 27 and 28 are brought into contact with the lower surface of the platen 2. Further, for the lower slide pad 29 as a lower sliding member arranged on the lower surface of the flange 3a, an elastic body 30 such as a sponge is provided between the lower slide pad 29 and the flange 3a,
A slide pad 29 that is in contact with the upper surface of the guide rail 18,
It is designed to be pressed downward.

In the image reading apparatus of the present invention, the traveling member can follow the deflection of the platen by providing the slide pads having the above-mentioned configurations on the upper and lower surfaces of the flange 3a of the traveling member 3, respectively. That is, the wire
When the traveling member 3 is moved by 13, the traveling member 3 and the lower surface of the platen 2 are always regulated by the upper slide pads 27 and 28 so that the distance between them is constant. For example,
When the platen 2 is bent for some reason, the elastic body 30 that is provided between the guide rail 18 and the flange 3a and supports the slide pad 29 is expanded and contracted.

Therefore, in the traveling member 3, the position of the scanning member disposed on the traveling member is accurately set in accordance with the state of the unevenness of the platen, and the distance between the image surface of the original and the lens can be prevented from changing. Like In addition to the above configuration, metal, plastic, or other sheet-like material is attached to the lower surface of the platen 2 on which the slide pad is contact-scanned, and the surface is set as a running reference surface, and the slide pad is moved along the reference surface. When the moving means is configured, the running member can be run more smoothly.

Further, when an image is read while moving the traveling member 3, if an external force that tends to vibrate vertically is applied, or if the guide rail has irregularities, the flange 3a Since the upper and lower sides of the plate are regulated by the slide pad, vibration does not occur, and the traveling member 3 is moved in a state in which the platen 2 is kept in contact with and separated from the platen 2. Become. Therefore, since the SELFOC lens 5 and the image sensor 8 provided inside the traveling member 3 are provided at fixed positions within the frame, the platen 2
While the distance between the traveling member 3 and the traveling member 3 is kept constant, the focal length of the SELFOC lens 5 does not change, and a clear image without blurring can be read.

Further, in the above embodiment, an example in which the slide pad is provided on the traveling member 3 has been described, but the image reading apparatus of the present invention is not necessarily limited to the slide pad, and a platen using rollers is used. It is also possible to contact with. Furthermore, the elastic body is not limited to a member such as a sponge, and it is naturally possible to use a leaf spring, a spring or the like to press the roller or the slide pad.

As described above, in the conventional apparatus, the guide rail or the like whose position has been adjusted with respect to the platen is used to set the traveling reference plane of the traveling member. In the apparatus, the plane of the platen can be used to set the reference plane. Therefore, in the apparatus of the present invention, even if the platen is distorted, the traveling member can accurately follow the distorted platen surface, so that the image surface of the original document pressed by the platen and the SELFOC lens The interval between and can be always maintained constant. Further, the above-described embodiment of the present invention can be applied to other image information automatic reading devices and the like in addition to the digital copying machine, the image editing device, and the like. It can be applied to a general image input device in which the Fock lens is moved.

(Advantages of the Invention) The image reading apparatus of the present invention has the above-mentioned configuration, and the reference surface for guiding the traveling member is set on the back surface of the document pressing member such as the platen. It is possible to always maintain a constant distance from the optical member, and it is possible to set the image surface within the focus range of the light focusing optical system or the like. Then, in the image reading apparatus of the present invention, it is possible to set the reference plane by using the surface of the platen. Therefore, in the device of the present invention, even if distortion or the like occurs in the platen, since the traveling member can accurately follow the distorted platen surface, the image surface of the document pressed by the platen,
The distance from the SELFOC lens can always be kept constant. Further, in the apparatus of the present invention, it is possible to prevent vibration or the like from occurring in the traveling member or the like during the movement of the image reading means, and even if the pressing member such as the platen is bent, It is possible to accurately follow the deflected surface, and thereby
This makes it possible to prevent changes in the respective intervals between the document image surface and the SELFOC lens and the image sensor. Further, in the apparatus of the present invention, it is possible to prevent an error in the image surface of the original with respect to the focal length of the SELFOC lens, so that the read image information is always clear and blurring occurs. Disappears.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view showing a relationship between a guide rail and a platen in an image reading apparatus of the present invention, and FIG. 2 shows a configuration of a main part of an image reading apparatus conventionally used. FIG. 3 is a perspective view, FIG. 3 is a cross-sectional view of the traveling member, FIG. 4 is a side view showing the relationship between the platen and the traveling member in the case of FIG. 2, and FIGS. 5 and 6 correspond to FIG. 4, respectively. FIG. 7A is a front view and a perspective view showing the configuration of another conventional example, FIG. 7a is an explanatory view showing the relationship between the Selfoc lens, the image sensor, and the platen, and FIG. 7b is a view showing the relationship between the MTF and the focal length. It is a graph. Reference numerals in the figure 1 ... manuscript, 2 ... platen, 3 ... running member, 4 ...
Lamp, 5 ... Optical focusing optical system, 6 ... Mirror, 8 ... Image sensor, 9 ... Drive pulley, 11 ... Guide pulley, 13 ... Wire, 14 ... Drive motor, 15 ... Timing pulley, 17 …… Timing belt, 18 …… Guide rail, 19 …… Slide pad, 21 …… Drive shaft, 22 …… Slide pad, 24 …… Flat spring, 25 …… Slide shaft, 26 …… Slide bearing, 30… … Elastic body.

Claims (1)

[Claims] 1. An image reading device for reading an image of a document set on a platen from a lower surface of the platen by causing a running member having a built-in document image reading means to run along a guide rail in the sub-scanning direction. A flange provided so as to project from both sides of the frame at right angles to the traveling direction of the traveling member, an upper sliding member that is disposed on the upper side of each flange and slides on the lower surface of the platen, A lower sliding member that is disposed below the elastic member and slides on a guide rail to guide the traveling member; a wire for moving the traveling member in the sub-scanning direction; and a wire for driving the wire. An image reading device comprising: a driving device.