JP2560110Y2 - Image reading device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus, and more particularly to an image reading apparatus that optically reads an image on a document in line units.

2. Description of the Related Art An image reading apparatus, such as a copying machine, that reads image information written on a document in units of lines is provided with an image reading head that reads the image information written on the document and converts it into an electric signal.

The image reading head includes a light source for irradiating the original with light, a mirror for determining an optical path of light reflected by the original, a lens for condensing light passing through the optical path, and a line sensor for converting the condensed light into an electric signal.

Conventionally, light from the light source 2 is directly transmitted to the original as shown in FIG.
The reflected light was converted into an electric signal by a line sensor.

Problems to be Solved by the Invention However, since the conventional image reading apparatus directly irradiates light from a linear light source to a document, as shown in FIG. Light enters from both sides of the light source 2 at the portion 11a, light enters from only one direction at the end 11b, the central portion 11a is bright, and the end 11b
Is dark, the read image is dark at the end of the light source,
There was a problem that the image became bright at the center and that accurate image reading could not be performed.

The present invention has been made in view of the above points, and has as its object to provide an image reading apparatus that can accurately read an image by adjusting the amount of light from a light source.

Means for Solving the Problems The present invention illuminates a document on which image information is written from a linear light source, and detects reflected light from the document by a linear sensor to obtain the image information from the document. An image reading device that is provided between the light source and the document, has a cross-sectional shape formed into an L shape so as to surround a longitudinal direction of the light source, and a central portion in the longitudinal direction of the light source. And a light source cover that covers a portion of the light source other than the portion facing the lens. The sensor is fixed, and the light source, the lens, and the light source cover are fixed. And a frame that is integrally held.

According to the present invention, the lens is formed such that the central part is thin and the end part is thick in the longitudinal direction of the light source, so that the focal length at the central part of the lens is long, and the focal length at the end part is short. Therefore, the light condensing at the center portion in the longitudinal direction of the light source on the document can be reduced and the light condensing at the end portion can be increased, and therefore, the irradiation of the light from the light source onto the document can be made uniform.

Further, since the portion of the light source other than the portion facing the lens is covered with the light source cover, light from the light source does not leak to unnecessary portions.

Furthermore, since the sensor, the light source, the lens, and the light source cover can be integrally held by the frame, the sensor, the light source,
The positional relationship between the lens and the light source cover can be accurately maintained with a simple configuration, and the image information written on the document can always be read in a constant light state.

In addition, since the lens has an L-shaped cross section and is arranged so as to surround the light source, the lens can be mounted in a space-saving manner, the lens can be easily mounted on the frame, and the lens can be positioned with respect to the light source. It becomes easy and the assembling property can be improved.

Embodiment FIG. 1 is a schematic structural view of an embodiment of the present invention.

An image reading head 1 mainly includes a light source 2, a shading correction lens 3, reflection mirrors 4a to 4d, a condenser lens 5, and a line sensor 6, and these are fixed to a frame 10. The image reading head 1 is provided below a glass plate 7 on which a document 11 on which an image to be read is written is placed, and is moved in the direction of arrow A by a driving mechanism 8.

As the light source 2, a direct fluorescent lamp is used, and the light source 2 is arranged so that the direction of arrow B perpendicular to the moving direction A of the image reading head 1 is the longitudinal direction. The light source 2 is covered with a light source cover 9 so that unnecessary light does not leak outside.

The light emitted from the light source 2 enters the document 11 via the shading correction lens 3. Since the light source 2 emits light approximately uniformly over the entire longitudinal direction, if the light source 2 is directly applied to the document 11, light is applied from both ends at the center portion of the document 11 and light is emitted from only one direction at the end portion. The light is bright at the center and dark at the end, and a difference in brightness occurs between the end and the center on the line sensor 6 by the condenser lens 5. For this reason, shading correction is required.

The optical lens 3 has an L-shape as shown in FIG.
The light source lens 3 fixed to the lens is thicker toward the end in the longitudinal direction and thinner toward the center, and the focal point at the end is closer to the center.
The lens 3 is arranged so that the focal point of the end is on the surface of the document 11.

For this reason, the light from the light source 2 is poorly condensed at the central portion 11a of the document 11, and the light is well condensed toward the end 11b. 11a
It is corrected to be brighter.

Light incident on the original 11 is reflected by the original 11 and is reflected by a reflection mirror.
It is incident on 4a. The reflection mirror 4a bends the incident light at a right angle. In the reflection mirror 4b, the bent light from the reflection mirror 4a is further bent at a right angle. The light from the reflection mirror 4b is further bent at a right angle by the reflection mirror 4c, and is incident on the reflection mirror 4d. The reflection mirror 4d bends the light from the reflection mirror 4c at a right angle and enters the light receiving unit.

The light from the reflection mirror 4d is condensed by the lens 6 and then enters the line sensor 5. The line sensor 5 is a CCD (Cha
rge Coupled Devices) are arranged in a line, and generate an electric signal according to incident light.

When reading an image from the document 11, the image reading head 1 is moved in the direction of arrow A while the light source 2 emits light. At this time, the line sensor 5 scans the document every certain clock.
The light from the light source 2 reflected at 11 is read. In this way, the image can be read line by line.

Thus, the light source lens 3 having different focal points at the center and the end between the document 11 and the light source 2 is provided, and the center of the document 11 is darker at the center than at the end, and darker at the end than at the center. The shading correction can be performed to make the document brighter, and there is no inconvenience such that the read image information is bright at the center or dark at the edges, and the document is more accurately
The image on 11 can be read. Further, since the light from the light source 2 is condensed by the lens 3 and hits the document 11, the light from the light source 2 can be used effectively without waste. Further, in this embodiment, the image reading apparatus is used for an original reading type image reading apparatus. However, the present invention can be used for an apparatus which reads an image by moving an original.

Effect of the Invention As described above, according to the present invention, the lens is formed such that the central portion is thin and the end portion is thick in the longitudinal direction of the light source.
Since the focal length at the center of the lens is longer and the focal length at the end is shorter, the light condensing at the center in the longitudinal direction of the light source on the document is small, and the light condensing at the end is large. Therefore, light irradiation from the light source onto the document can be made uniform, and the portion of the light source other than the portion facing the lens is covered with the light source cover, so that light from the light source may leak to unnecessary portions. In addition, the sensor, the light source, the lens, and the light source cover can be integrally held by the frame, so that the positional relationship between the sensor, the light source, the lens, and the light source cover can be accurately maintained with a simple configuration, and the constant light In this state, the image information written on the document can be read, and since the lens has an L-shaped cross section and is arranged so as to surround the light source, the lens can be mounted in a space-saving manner. It makes it easier to attachment to's frame, the positioning of the lens with respect to the light source can be easily, have a feature, such as it is possible to improve the assemblability.

[Brief description of the drawings]

FIG. 1 is a schematic structural view of an embodiment of the present invention, FIG. 2 is a front view and a sectional view of a main part of an embodiment of the present invention, and FIG. 1 image reading head, 2 light source, 3 shading correction lens, 5 line sensor, 8 driving mechanism.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-53-81010 (JP, A) JP-A-59-111464 (JP, A) JP-A-59-126526 (JP, A)

Claims (1)

(57) [Scope of request for utility model registration] An image read from a document in line units by irradiating a document on which image information is described with light from a linear light source and detecting reflected light from the document by a linear sensor. In the reading device, the light source is provided between the light source and the document, a cross-sectional shape is formed in an L shape so as to surround the longitudinal direction of the light source, and a central portion is thin in a longitudinal direction of the light source, and an end portion is formed. A thickly formed lens, a light source cover that covers a portion of the light source other than the portion facing the lens, a frame in which the sensor is fixed, and the light source, the lens, and the light source cover are integrally held. An image reading device comprising: