JPH09219770A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the change of illuminance on the surface of an original in a scanning mode and to eliminate the uneven reading density by regulating the positions of the original and the carriages by means of the position regulation members. SOLUTION: A 1st carriage 5 is provided with a pair of LED 3a and 3b as the light sources, and a 1st mirror 4 has a slit 11 at its upstream side to transmit the reflected light. Then the rollers (positioning members) 12a and 12b are attached above both ends of the carriage 5 in its traveling (forward and backward) directions, so that a fixed distance is kept between the carriage 5 and the rear side of the contact glass 2. When the carriage 5 is energized from its lower part and held, the carriage 5 is positioned to the glass 2 by the rollers 12a and 12b. These rollers are prepared at both front and inner sides. Thus a fixed distance is always kept between the glass 2 and the original surface by moving the rollers 12a and 12b so as to always make them touch the glass 2.

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 applied to an image forming apparatus, and more particularly to moving a carriage (a single carriage or first and second carriages) to scan a fixed original. The present invention relates to an image reading device for reading by scanning.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram of a general carriage moving type image reading apparatus. This image reading device can read a book original 1, and when reading the book original 1, as shown in the figure, the book original 1 is placed on the contact glass (original table) 2 in a spread state. The light source 3 and the first mirror 4 are mounted on the first carriage 5. The second mirror 6 and the third mirror 7 are mounted on the second carriage 8. An imaging lens 9 and a CCD 10 are arranged on the downstream side of the optical path.

In such a structure, the first carriage 5 and the second carriage 8 are driven by wires or the like,
It is moved while always maintaining the conjugate length. Then, the reflected light of the original is scanned by the carriage, and the reflected light of the original is conveyed to the first carriage 5
The light enters the imaging lens 9 through the carriage 8 and the CCD 10
Imaged above. The imaging light is photoelectrically converted by the CCD 10 and transferred as an electric signal to a system (not shown).

[0004]

Here, in general, the light source 3 is used.
A high-intensity tube light source is used for the recent CCD1
Thanks to the increased sensitivity of 0, it has become possible to use low illuminance LED light sources. However, since the LED light source has a low illuminance, it is necessary to bring the LED light source as close to the document surface as possible, and a change in the illuminance of the document surface due to vertical swing when the traveling body (first carriage 5) is moved becomes a problem.

FIG. 7 is a comparative explanatory view of the illuminance of light sources. L
The illuminance is significantly different (500 lux and 10000 lux) between the case of the ED light source (a) and the case of the tube light source (for example, a fluorescent lamp or a xenon tube) (b) even at the same distance. Since the LED light source has low illuminance, it is greatly affected by changes in distance.

The present invention has been made based on such a background, and provides an image reading apparatus capable of suppressing a change in illuminance of a document even when a light source having a low illuminance such as an LED light source is used. The purpose is to

[0007]

An image reading apparatus according to a first aspect of the present invention is an image reading apparatus that scans and reads an original document placed on an original table by moving a carriage. It is characterized in that a positioning member is provided for keeping a constant distance from the table.

According to a second aspect of the present invention, in the image reading apparatus according to the first aspect, the positioning member is a roller provided at both ends of the carriage in the moving direction.

According to a third aspect of the present invention, in the image reading apparatus according to the first aspect, the intermediate portion of the wire stretched in the traveling direction of the carriage is locked to the carriage below the front and rear end positions thereof. Characterize.

According to a fourth aspect of the present invention, in the image reading apparatus according to the first aspect, a spring member for pressing the carriage against the back surface of the document table is provided.

According to a fifth aspect of the present invention, in the image reading apparatus according to the first aspect, a roller for moving the carriage on the scanner base, and the carriage between the roller and the carriage are provided on the back surface of the document table. It is characterized in that a spring member for pressing against is provided.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. The reference numerals are the same as those in FIG.

FIG. 1 is a block diagram of the essential parts of an image reading apparatus according to the first embodiment. As shown in FIG.
The carriage 5 has a pair of LEDs 3a and 3b as a light source.
And a slit 11 for transmitting reflected light is provided on the upstream side of the first mirror 4.

Then, as shown in FIG. 2B, at the upper portions of both ends of the first carriage 5 in the advancing (forward, backward) direction,
Rollers (positioning members) 12a, 12 for keeping the distance between the first carriage 5 and the back surface of the contact glass 2 constant.
b is attached. When the first carriage 5 is biased and held from below, the first carriage 5 is positioned with respect to the contact glass 2 by the rollers 12a and 12b.
The rollers 12a and 12b are provided on both the front side and the back side.

It should be noted that the member having a small friction coefficient may be used instead of the roller 12. It may also be integrally molded with the carriage. It can also be applied to the second carriage 8. Roller 1
By moving 2a and 12b so that they are always in contact with the contact glass 2, it is possible to keep a constant distance from the document surface and suppress changes in illuminance of the document surface during scanning. Therefore, it is possible to obtain the effect of eliminating unevenness in the reading density of the document.

Further, the contact glass 2 is formed by the roller 12.
Since it is possible to keep the distance between and the LED 3 constant, it becomes possible to bring the LEDs 3 as close as possible in terms of layout, and the effect of increasing the illuminance on the document surface can be obtained. Thereby, C
Since the CD video output is improved, the S / N is improved, and the first carriage 5 can be thinned, the scanner unit is also thinned, and the merit of further miniaturization comes out.

As described above, since the LED 3 can be used as the light source, various effects such as miniaturization, weighing, cost reduction, noise generation due to non-use of the lighting device, and immediate lighting can be obtained.

FIG. 2 is a block diagram of the essential parts of an image reading apparatus according to the second embodiment. In this embodiment, the first carriage 5 having the rollers 12a and 12b is attached to the wire 1
It is configured such that it is urged upward by No. 4.

The intermediate portion of the wire (which may be a belt) 14 stretched in the traveling direction of the first carriage 5 is locked to the first carriage 5 below the front and rear end positions thereof (locking portions 13a, 13a,
13b), the upward biasing force is applied to the first carriage 5. The wire 14 is a wire for moving the carriage.

FIG. 3 is a perspective view of an essential part of an image reading apparatus according to the third embodiment. In this embodiment, fixed shafts 15 are provided on the front side and the back side of the first carriage 5 (only the front side is shown in the drawing), and the fixed shafts 15 are provided between the pedestal 16 and the back surface of the first carriage 5. The coil spring 17 is compressed and intervened in 15. The coil spring 17 biases the first carriage 5 upward. The pedestal 16 is pulled by the wire 14 and moves on the fixed stay 18.

In the second embodiment, if the carriage is heavy, it is difficult to push it up only by the tension of the wire 14, but this problem is solved in the present embodiment.

FIG. 4 is a block diagram of the image reading apparatus according to the fourth embodiment, and FIG. 5 shows the configuration of the drive system [FIG. (A)] and the locus of the conveying roller [FIG. (B)]. FIG. In FIG. 4, the transport roller 21 for moving the first carriage 5 on the scanner base 27 is attached to the tip of a leaf spring 24 provided in the lower portion of the first carriage 5. The first carriage 5 is urged upward by the leaf spring 24 with the transport roller 21 in contact with the scanner base 27.

Similarly, the second carriage 8 is also provided with rollers 22a and 22b for position regulation and transportation with the scanner base 27, and the transportation roller 2 rolling on the back surface of the contact glass 2.
Three. The transport roller 23 is attached to the tip of a leaf spring 25 provided on the upper portion of the second carriage 8, and the leaf carriage 25 presses the second carriage 8 against the scanner base 27. Lens 9, CCD
10 is housed in the lens block 26.

As shown in FIG. 5A, the first and second carriages 5 and 8 have the wire 1 having a spring 28 locked at one end.
It is multiplied by 4 and moves at a speed ratio of 2: 1. Further, the movement loci 29, 30 of the transport roller 21 (and the roller 22) are as shown in FIG.

[0025]

According to the present invention, since the positions of the original and the carriage are restricted by the position restricting member, the change in the illuminance of the original surface during scanning (when the carriage is moved) is suppressed, and the unevenness in reading density of the original image is eliminated. be able to. Also,
Since the carriage is forcibly pressed against the document table by the wire (claim 3) or the spring member (claims 4 and 5), the reliability of the position regulation can be enhanced.

[Brief description of drawings]

FIG. 1 is a configuration diagram of main parts of an image reading apparatus according to a first embodiment of the present invention.

FIG. 2 is a main part configuration diagram of an image reading apparatus according to a second embodiment of the present invention.

FIG. 3 is a main part configuration diagram of an image reading apparatus according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram of an image reading apparatus according to a fourth embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of a drive system and a locus of a conveyance roller of the same.

FIG. 6 is a configuration diagram of a general carriage moving type image reading device.

FIG. 7 is a comparative explanatory diagram of illuminance of light sources.

[Explanation of symbols]

 2 Contact Glasses 3a, 3b LED 5 First Carriage 8 Second Carriage 12a, 12b Rollers (position regulating member)

Claims (5)

[Claims] 1. An image reading apparatus for scanning a document placed on a document table by scanning a carriage to move the carriage, and the carriage is provided with a positioning member for keeping a constant distance from the document table. An image reading device characterized by the above. 2. The image reading device according to claim 1, wherein the positioning member is a roller provided at each end of the carriage in the moving direction. 3. The image reading device according to claim 1, wherein an intermediate portion of a wire stretched in a traveling direction of the carriage is locked to the carriage below a front / rear end position thereof. 4. The image reading apparatus according to claim 1, further comprising a spring member that presses the carriage against the back surface of the document table. 5. The roller according to claim 1, further comprising a roller for moving the carriage on the scanner base, and a spring member interposed between the roller and the carriage for pressing the carriage against the back surface of the document table. An image reading device characterized by.