JPH0514603A - Image reader - Google Patents

Abstract

(57) [Summary] [Object] To obtain an image reading device capable of reading image information with high accuracy by appropriately setting the array pitch of the LED array and the array pitch of the condenser lens of the optical means. Optical means for illuminating an original surface 4 with a light beam from an illuminating means 3 in which a plurality of light emitting elements are arranged at a pitch PS, and an image 5 on the original surface is provided with a plurality of light collecting lenses arranged at a pitch PL. When the image is formed on the surface of the image reading means 6 by 1, and the image is read, the pitch PS and the pitch PL are as follows when n is a positive integer. Satisfy the following conditions.

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, and more particularly to a plurality of minute light emitting elements, for example, an illuminating means such as an LED array in which LEDs are arranged at a predetermined pitch and a plurality of condensing lenses such as a refractive index distribution. The present invention relates to an image reading apparatus suitable for data communication, facsimile communication, word processor and the like for reading an image on a document surface by using optical means in which mold lenses are arranged at a predetermined pitch.

[0002]

2. Description of the Related Art Conventionally, in an image reading apparatus, a plurality of light emitting elements, for example, a light emitting diode array (LED array) in which light emitting diodes (LEDs) are arranged at high density is used as an illuminating means to illuminate an image on a document surface. The image is read by forming the image on the surface of the image reading means such as a photoconductor or an electrostatic recording body and a CCD using an optical means. Such an image reading device is disclosed in, for example, Japanese Patent Laid-Open No. 1-144771
It is proposed in Japanese Patent Laid-Open Publication No. 1-222562.

FIG. 9 is a schematic view of a main part of a conventional image reading apparatus. In the figure, a plurality of LEDs 92a, 92b, ...
The image 95 on the document surface 94 illuminated by the light flux from the LED array 93 in which the ... Is arranged in one direction is arranged by the optical means 91 in which a plurality of gradient index lenses 97a, 97b, 97c ... Are arranged in one direction. It is formed on the surface of the image reading means 96 such as CCD. The image 95 is read by the image reading means 96.
Is read digitally.

[0004]

In a recent image reading apparatus, a plurality of condensing lenses are arranged as optical means with a certain interval, as proposed in Japanese Patent Laid-Open No. 63-226621. There has been proposed one using an optical means composed of the above lens array. Then, such an optical means is used to reduce the size and simplify the entire apparatus.

FIG. 3 shows such a plurality of condenser lenses 7.
It is a principal part schematic diagram of the optical means which consists of a lens array which arranged a, 7b, ... at fixed pitch PL.

Generally, one-line type optical means 91 in which a plurality of condensing lenses as shown in FIG. 9 are continuously arranged in a line
And an illuminance distribution on the surface of the image reading unit 96 when the image 95 on the document surface 94 is read using the 1-line type illuminating unit 93 in which the light emitting elements are continuously arranged in a line, for example, the curve 101 in FIG. Like

That is, the unevenness of the illuminance distribution occurs depending on the arrangement, diameter, and degree of overlap of each element of the illumination means 93 and the optical means 91, and bright and dark streaks occur in the read image. As a result, the reading accuracy of the image is improved. There was a problem that it decreased.

The bright and dark streaks (unevenness of illuminance distribution) of the read image at this time are shown by a curve 102 in FIG. 10 when the optical means 1 in which a plurality of condenser lenses are arranged at a constant pitch P as shown in FIG. As shown in the figure, there is a problem in that the image reading accuracy is further increased and the image reading accuracy is further reduced.

The present invention uses an illuminating means in which light and dark stripes of a read image are appropriately configured when the whole device is simplified by using an optical means in which a plurality of condenser lenses are arranged at a constant pitch. Therefore, it is an object of the present invention to provide an image reading device which can reduce the number of times and can read images with high accuracy.

[0010]

An image reading apparatus of the present invention illuminates a document surface with a light beam from an illuminating means in which a plurality of light emitting elements are arranged at a pitch PS, and collects a plurality of images on the document surface. When the optical lens is formed on the surface of the image reading means by the optical means arranged at the pitch PL and the image is read, the pitch PS and the pitch PL are such that n is a positive integer.

[0011]

[Equation 2] It is characterized by satisfying the following condition.

Further, in the present invention, the condensing lens is a gradient index lens, and PL is defined as an effective diameter D>
It is characterized by being D.

[0013]

Embodiment 1 FIG. 1 is a perspective view of an essential part of Embodiment 1 of the present invention, and FIG.
FIG. 2 is an explanatory diagram in which the optical path of FIG. 1 is expanded.

In FIG. 1, reference numeral 1 denotes an optical means, which is composed of a plurality of condenser lenses 7a, 7b, 7c ... Arranged in a one-dimensional direction (X direction) at a constant pitch PL. Figure 3
The perspective view of the optical means 1 is shown in FIG. In this embodiment, the condensing lenses 7a, 7b, 7c ... Are composed of gradient index lenses having a diameter D.

Reference numeral 3 denotes an illuminating means, which comprises a liquid crystal shutter array and a plurality of light emitting elements 2a, 2b, 2c ... Arranged in a one-dimensional direction (X direction) at a constant pitch PS. In this embodiment, the light emitting elements 2a, 2b, 2c ...
Is composed of a light emitting diode (LED). Therefore, the illumination unit 3 is also referred to as an LED array hereinafter. Reference numeral 4 denotes an original surface, and 5 denotes an image of an area on the original surface 4 formed by the optical means 1. An image reading unit 6 is composed of a CCD.

In the present embodiment, the image 5 on the document surface 4 is illuminated with the light flux from the illumination means 3. Then, the image 5 is formed on the surface of the image reading means 6 by the optical means 1, and the image 5 is digitally read by the image reading means 6. By moving the document surface 4 in the Y direction at a constant speed, the images on the document surface 4 are sequentially read two-dimensionally by the image reading means 6.

Generally, the illuminance distribution on the image plane when an image of a surface light source with uniform brightness is formed by the fiber element of the condensing lens used in this embodiment is centered on the optical axis (Z axis) as shown in FIG. It becomes a bell shape. Here, for example, regarding the illuminance in the X-axis direction, if the illuminance on the optical axis is E ₀ and the point on the X-axis at the maximum angle of view is X ₀ , the illuminance E (X) at point X is

[0018]

[Equation 3] Becomes

In this embodiment, as shown in FIGS. 1 and 2, the optical means 1 has a plurality of condensing lenses 7a, 7b ... Arranged at a pitch PL so that a constant gap is formed between the condensing lenses. Is configured as follows. That is, when the diameter of the condenser lens is D, PL> D. This reduces the number of condensing lenses, simplifies the structure of optical means,
We are trying to reduce costs.

On the other hand, by reducing the number of condenser lenses, the brightness of the image reading system is lowered and the unevenness of the illuminance distribution on the image reading surface is further increased. Therefore, in this embodiment, the illumination means is configured as described above to reduce the unevenness of the illuminance distribution and prevent the deterioration of the image reading accuracy.

That is, the arrangement pitch PL of the condensing lenses 7a, 7b ... And the arrangement pitch PS of the light emitting elements 2a, 2b ... are PS = PL / n when n is a positive integer. I have to. In this embodiment of FIG. 2, the case of n = 3 is shown. Also, at this time, the LED array is changed to each LE.
When D is arranged so as to be located on the optical axis of the condensing lens, streaky illuminance unevenness may occur on the image reading surface.

Therefore, in the present embodiment, the optical means 1 and the illuminating means 3 are constructed as described above, and the illuminating means 3 is arranged so as to be movable in the X-axis direction so that the illuminance distribution on the surface of the image reading means 6 is as good as possible. It is adjusted to be uniform.

In the present embodiment, with the above configuration, the unevenness of the illuminance distribution on the surface of the image reading means 6 is corrected as shown by the dotted line illuminance distribution 52 from the conventional illuminance distribution 51 shown by the solid line in FIG. .

That is, the unevenness of the light amount pitch of the illuminance distribution ΔI1
Is corrected to be the unevenness ΔI2. As a result, the image 5 on the document surface 4 is read with high accuracy.

FIG. 6 is a schematic view of the essential portions of Embodiment 2 of the present invention, in which the optical path is expanded as in FIG.

In this embodiment, the arrangement pitch PL of the condenser lenses of the optical means and the arrangement pitch PS of the light emitting elements of the illumination means are set to PS = PL / 2. Generally, in the area corresponding to the gap between the condensing lenses (area A in FIG. 2) on the image reading surface, the illuminance is lower than in other areas.

Therefore, in this embodiment, as shown in FIG. 6, the light emitting element of the illuminating means 3 is positioned at a position corresponding to the area A, and the output of the light emitting element is set to another position. It is set to be higher than the output. Thereby, the unevenness of the illuminance distribution on the image reading surface is corrected well.

As the optical means in the present invention, for example, as shown in FIG. 7, a lens array in which a plurality of condensing lenses are arranged at a constant pitch is provided in a plurality of rows (two rows in the figure). May be. Further, in accordance therewith, a plurality of rows of LED arrays may be used in which the light emitting elements of the illumination means are arranged at a constant pitch.

The illuminating means is not limited to one as shown in FIG. 8, but two illuminating means 3a and 3b are used to cover the document surface 4 in two.
You may make it illuminate from the direction.

[0030]

According to the present invention, as described above, the condensing lens of the optical means and the light-emitting element of the illuminating means are arranged in a fixed relationship, thereby simplifying the entire apparatus and improving the image quality. It is possible to achieve an image reading apparatus capable of reading an image with high accuracy by reducing unevenness of the illuminance distribution on the reading surface.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram when the optical path of FIG. 1 is expanded.

FIG. 3 is an enlarged perspective view of a portion of FIG.

FIG. 4 is an explanatory diagram of an illuminance distribution on the image plane of a condensing lens fiber element.

5 is an explanatory diagram of an illuminance distribution on the image reading surface of FIG.

FIG. 6 is a schematic diagram of a second embodiment of the present invention.

FIG. 7 is an explanatory view of another embodiment of the optical means according to the present invention.

FIG. 8 is an explanatory view of another embodiment of the illumination means according to the present invention.

FIG. 9 is a schematic view of a main part of a conventional image reading device.

10 is an explanatory diagram of an illuminance distribution on the image reading surface of FIG.

[Explanation of symbols]

1 Optical means 2a, 2b ... Light emitting element 3 lighting means 4 Original side 5 Image reading part 6 Image reading means 7a, 7b, ... 8 Condensing lens

Claims (3)

[Claims] 1. An optical means for illuminating an original surface with a light beam from an illuminating means in which a plurality of light emitting elements are arranged at a pitch PS, and for displaying an image on the original surface by a plurality of condensing lenses arranged at a pitch PL. , When the image is formed on the surface of the image reading means and the image is read, the pitch PS and the pitch PL are as follows when n is a positive integer: An image reading apparatus which satisfies the following condition. 2. The image reading apparatus according to claim 1, wherein the condensing lens is a gradient index lens, and PL> D when an effective diameter of the lens is D. 3. The image reading apparatus according to claim 2, wherein the light emitting element comprises a light emitting diode.