JPH09266516A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate unevenness in the quantity of light in a read horizontal scanning direction and to read a document image with high quality without causing an increase in cost as to the image reader which reads the document surface by irradiation with light from light emitting diodes provided at intervals in the read horizontal scanning direction. SOLUTION: A diffusion member 25 is provided between the light emitting diodes 21 and a condenser rod lens 23. The diffusion member 25 is formed of a slender plate material so that the light from the light emitting diodes 21 is diffused in the read horizontal scanning direction. Light from each light emitting diode 21 is made to strike on the diffusion member 25, diffused along the length of the rod lens 23, i.e., in the read horizontal scanning direction, and converged by the rod lens 23 to irradiates the document surface uniformly in the read horizontal scanning direction.

Description

Detailed Description of the Invention

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image reading apparatus such as a scanner, a facsimile, and a copying machine. In particular, the present invention relates to an image reading apparatus that uses a light emitting diode as a light source and irradiates a document with the light emitting diode to read the surface of the document.

[0002]

2. Description of the Related Art Conventionally, in an image reading apparatus of this type, as shown in FIG. 6, for example, an optical unit 2 can be freely moved in the left-right direction (reading sub-scanning direction) below a document placing glass 1. In preparation for this, the printed circuit board 3 is supported by the frame 2a of the optical unit 2 and the light emitting diode 4 is provided thereon, and the rod lens 5 for condensing light is provided between the light emitting diode 4 and the document mounting glass 1. There is something.

As shown in FIG. 7, the printed circuit board 3 is long in the reading main scanning direction and has a plurality of light emitting diodes 4 arranged at equal intervals in the main scanning direction. The rod lens 5
It is composed of a round rod-shaped lens, and is supported by a lens holder 6 standing on the printed circuit board 3 and arranged in the main scanning direction for reading, as shown in FIG.

Then, the light emitted from the light emitting diode 4 is condensed by the rod lens 5 and irradiated on the original surface of the original 7 set on the original placing glass 1, while the optical unit 2 is moved in the reading sub-scanning direction. The reflected light from the document surface is further reflected by the mirror 8 and, though not shown, an image is formed on the photoelectric conversion element through an imaging lens to read the document surface.

However, in the prior art, at the time of this reading, the irradiation light of the light emitting diode 4 is condensed by the rod lens 5, and as can be seen from the light amount distribution in the reading sub-scanning direction shown by the curve A in FIG. The spread in the reading sub-scanning direction is prevented.
This is because if the spread of the irradiation light is not prevented as described above, the reading line of the document 7 will have insufficient light amount and the document image cannot be read accurately.

[0006]

However, conventionally, the individual light emitting diodes 4 have variations in the light amount characteristics and are arranged at intervals in the main scanning direction for reading. 7. As can be seen from the light amount distribution in the reading main scanning direction indicated by the medium waveform curve B, light amount unevenness occurs in the main scanning direction. As a result, conventionally, the reading quality of the original image is deteriorated due to the uneven light amount.

[0007] Conventionally, in order to prevent the occurrence of such uneven light quantity, it is possible to select and use the light emitting diodes 4 having a uniform light quantity characteristic, and install a large number of them at narrow intervals. There is a problem that will be high.

Therefore, an object of the present invention is to eliminate the unevenness of the light amount in the reading main scanning direction and to read the original image with high quality without incurring such high cost.

[0009]

Therefore, according to the invention described in claim 1, a plurality of light emitting diodes 21 are arranged at intervals in the main scanning direction for reading as in the embodiment shown in FIGS. 1 to 3 below. In an image reading apparatus provided with a rod lens 23 which is provided separately and collects the light emitted from the light emitting diodes 21 and irradiates the original surface with the light, the light emitting diodes 21 are provided between the rod lens 23 and the light emitting diodes 21. It is characterized in that it is provided with a diffusing member 25 for diffusing the light from the main scanning direction.

At the time of reading, the light emitted from the light emitting diode 21 is diffused by the diffusing member 25 in the reading main scanning direction, and then the light is condensed by the rod lens 23 and applied to the document surface.

According to a second aspect of the present invention, a plurality of light emitting diodes 21 are provided at intervals in the reading main scanning direction as in the embodiment shown in FIG. 4 and FIG. In an image reading apparatus including a rod lens 23 that collects the light emitted by 21 and irradiates the surface of the document, the outer peripheral surface of the rod lens 23 on the side of the light emitting diode 21 is formed into a rough surface 23a.
It is characterized by the following.

At the time of reading, the light emitted from the light emitting diode 21 is diffused in the reading main scanning direction by the rough surface 23a, and then the light is condensed by the rod lens 23 and applied to the original surface.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of a document reading unit of a copying machine according to the first aspect of the invention.

Reference numeral 10 in the drawing denotes a case of the document reading unit. A document placing glass 11 is fitted on the upper surface of the case 10. A document 12 is set on the document mounting glass 11 with the document surface facing down, as shown in the figure.

In the case 10, the original placing glass 1 is placed.
1, an optical unit 15 is provided so as to be movable in the left-right direction (reading sub-scanning direction) in the drawing.

The optical unit 15 has its frame 13
A light source kit 14, an imaging lens 16, a photoelectric conversion element (CCD) 17, and a reading circuit board 18 to which the photoelectric conversion element 17 is attached are mounted on each of them.

The light source kit 14 includes the fixed frame 1
An elongated printed circuit board 20 is mounted on the bottom of 9, and a plurality of light emitting diodes 21 are mounted on the printed circuit board 20. Then, the light emitting diodes 21 are arranged at equal intervals in the reading main scanning direction to form a so-called LED array. Further, on the printed circuit board 20, a pair of holding plates 22 are set up on both sides with the light emitting diode 21 interposed therebetween. The holding plates 22 and 22 have their lower ends fixed on the printed circuit board 20 and hold the rod lens 23 between their upper ends. A diffusing member 25 is held between the rod lens 23 and the light emitting diode 21.

The rod lens 23 is a round rod-shaped condenser lens. The diffusing member 25 is made of, for example, a milky white resin plate material, and is formed in an elongated plate shape having a width substantially the same as the diameter of the rod lens 23.

When the original 12 is copied, the original 12 is set on the original placing glass 11, a start switch (not shown) is pressed, a reading drive motor (not shown) is driven, and the light emitting diode 21 is driven. Lights up. Then, the light emitted from the light emitting diodes 21 is diffused by the respective diffusing members 25, and then the light is condensed by the rod lens 23 and applied to the original surface of the original 12, while the optical unit 15 is read in the sub-scanning direction. Move to.
Then, the reflected light reflected from the document surface is introduced into the photoelectric conversion element 17 through the imaging lens 16 and the photoelectric conversion element 17
Then, the reflected light is converted into an electric signal to read the original image.

In this embodiment, as described above, the individual irradiation light emitted from the light emitting diode 21 is applied to the diffusing member 25 to be diffused. At that time, the diffusing member 25 has a width substantially the same as the diameter of the rod lens 23. Since it is an elongated diffusion plate, the irradiation light is scattered at a wide angle in the length direction of the rod lens 23, that is, mainly diffused in the reading main scanning direction.

Therefore, when the light thus diffused is condensed by the rod lens 23, the spread of the light in the sub-scanning direction is small as can be seen from the light amount distribution in the reading sub-scanning direction shown by the curve C in FIG. It can be suppressed. On the other hand, in the reading main scanning direction, the individual irradiation light is diffused at a wide angle and the rod lens 2
3, the original surface is evenly irradiated in the reading main scanning direction, and as can be seen from the light amount distribution in the reading main scanning direction indicated by the line D in FIG. 3, there is almost no unevenness in the reading main scanning direction.

By the way, in the invention described in claim 1 described above, the diffusion member 25 is provided for diffusing the light from the light emitting diode 21, but as described in the following embodiments, for example, it is described in claim 2. In the invention of (1), the light from the light emitting diode is diffused in the reading main scanning direction without using such a diffusion member.

For example, as shown in FIG. 4, nothing is interposed between the light emitting diode 21 and the rod lens 23 thereon, and the outer peripheral surface of the rod lens 23 on the light emitting diode 21 side is subjected to, for example, sandblasting. The rough surface 23a is formed.

At the time of reading, the light emitted from the light emitting diode 21 is diffused by the rough surface 23a, and then the diffused light is condensed by the rod lens 23 and applied to the original surface of the original 12.

At this time, since the outer peripheral surface of the rod lens 23 on the side of the light emitting diode 21 is formed as a rough surface 23a in the length direction, the irradiation light is the rough surface 23a and the length of the rod lens 23. In a wide angle direction, that is, mainly diffuses in the reading main scanning direction.

The light thus diffused is used as the rod lens 23.
When the light is condensed at 2, the spread of the light in the sub-scanning direction is suppressed to be small, as can be seen from the light amount distribution in the reading sub-scanning direction shown by the curve E in FIG. 5, as in the case shown in FIG.
On the other hand, in the reading main scanning direction, the individual irradiation light diffuses at a wide angle, so that the original surface is evenly irradiated in the reading main scanning direction, and is indicated by the center line F in FIG. 4 as in the case shown in FIG. As can be seen from the light amount distribution in the reading main scanning direction, there is almost no unevenness in the light amount in the reading main scanning direction.

[0027]

Therefore, according to the first and second aspects of the present invention, the light from the light emitting diode is diffused in the reading main scanning direction, and then is condensed by the rod lens to irradiate the original surface. Therefore, even if light-emitting diodes with some variations in light quantity characteristics are provided at intervals in the reading main scanning direction, the spread of light in the reading sub-scanning direction is reduced while the light quantity unevenness in the reading main scanning direction is reduced. Can be prevented, and as a result, it is possible to prevent the reading quality of the original image from being deteriorated due to insufficient light amount or uneven light amount. In addition, in order to prevent the occurrence of uneven light quantity,
It is not necessary to select and use light emitting diodes having uniform light quantity characteristics and to install a large number of them at narrow intervals, and as a result, it is possible to prevent an unnecessarily high cost.

According to the second aspect of the present invention, the light from the light emitting diode is diffused in the reading main scanning direction by the rough surface of the rod lens itself without using a separate diffusion member. The number of parts can be reduced.

[Brief description of drawings]

FIG. 1 shows an embodiment of the invention described in claim 1,
FIG. 3 is a schematic configuration diagram of a document reading unit of the copying machine.

FIG. 2 is an explanatory diagram illustrating a light amount distribution of light in a reading sub-scanning direction when light is emitted from a light emitting diode of the document reading unit toward a document.

FIG. 3 is an explanatory diagram illustrating a light amount distribution of the light in a reading main scanning direction.

FIG. 4 shows an embodiment of the invention described in claim 2,
FIG. 8 is an explanatory diagram illustrating a light amount distribution of the light in a reading main scanning direction when light is emitted from a light emitting diode of the document reading unit toward a document.

FIG. 5 is an explanatory diagram illustrating a light amount distribution of the light in the reading sub-scanning direction.

FIG. 6 is a schematic configuration diagram of a document reading unit of a conventional image reading apparatus.

FIG. 7 is an explanatory diagram illustrating a light amount distribution of the light in a reading main scanning direction when light is emitted from a light emitting diode of the document reading unit toward a document.

FIG. 8 is an explanatory diagram illustrating a light amount distribution of the light in a reading sub-scanning direction.

[Explanation of symbols]

 12 manuscript 21 light emitting diode 23 rod lens 23a rough surface 25 diffusing member

Claims (2)

[Claims] 1. An image reading apparatus comprising: a plurality of light emitting diodes provided at intervals in a main scanning direction for reading; and a rod lens which collects light emitted by the light emitting diodes and irradiates the original surface with the rod lens. An image reading apparatus comprising a diffusion member for diffusing light from the light emitting diodes in the reading main scanning direction between the light emitting diodes and the light emitting diodes. 2. An image reading apparatus comprising: a plurality of light emitting diodes provided at intervals in a main scanning direction for reading; and a rod lens which collects light emitted from the light emitting diodes and irradiates the original surface with a rod lens. The outer peripheral surface of the light emitting diode side of
An image reading device formed on a rough surface.