JP2883116B2 - Optical image reading device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus, and more particularly to an optical image reading apparatus used for reading image information from a document in a facsimile apparatus or the like.

(Prior Art) Conventionally, as an image reading apparatus using a one-dimensional line sensor as a light source, an equal-magnification optical system having a long one-dimensional line sensor having the same length as the width of a document has been used to simplify the optical system. Has been adopted. Here, in addition to the method using a converging fiber or a contact lens array as the 1 × optical system, a completely close contact method in which the original is read while moving the original on the one-dimensional line sensor without using these at all (See JP-A-55-74262, JP-A-55-75271, JP-A-56-45084, JP-A-56-122172, etc.)
It has been known.

The principle configuration of such an image reading apparatus is as shown in FIG. That is, the original 3 is conveyed between the backup roller 2 and the image reading device 1 by the rotation of the roller 2 (or another conveying system). At this time, in the image reading device 1, FIG. As shown in the figure, the light sensor 6 receives reflected light of a light beam emitted from an LED or Xe glow lamp 9 as a light source onto the surface of the document 3 and performs photoelectric conversion. In this case, the optical sensor 6 is configured to receive the reflected light from the converging optical fiber 13 via the transparent glass plate 14 which is in close contact with the document 3 in FIG. 6, and in FIG. The light receiving unit 7 is formed on a transparent substrate 17, a transparent protective film 16 is provided thereon, and the light receiving unit 7 is provided with an illumination window 15 through which a light beam directed from a light source to a document is provided. In this case, the optical sensor 6 is directly located at the position of the transparent glass plate 14 described above. In this case, the roller 2 has a white surface. This is because the color of the roller affects the image when reading a narrow original, or when reading a transparent original or a thin paper original.

(Problems to be Solved by the Invention) However, in recent image reading apparatuses, “gradation reading” has been required from “binary reading” of white and black to “multi-color reading”. The following problems have been highlighted.

That is, unevenness of illuminance of light rays hitting the original from the light source, unevenness of sensitivity of the optical sensor, and contamination of the white roller were not regarded as problems in the “binary reading”, but the output processing was high in the “gradation reading”. Since the resolution becomes higher, the image quality is reduced.

For this reason, for “illuminance unevenness” and “sensitivity unevenness of the optical sensor”, a method of storing the output in units of bits with reference to the reflectance of the white roller has been adopted, and is electrically corrected. However, sufficient measures have not been taken against "dirty white rollers".

Note that the document conveying means may be changed according to another configuration, and the white roller itself may be separated from the document, for example, 0.05 to 1 nm.
It is conceivable to place the paper so that the dirt does not directly adhere to the white roller, but in this case, the document flaps in the gap between the roller and the reading device, and the resolution is degraded. In particular, in the perfect contact type, the tendency is greater because the depth of focus is shallower than that of an optical system using an imaging system. Similarly, since the flatness of the reading device itself is not absorbed, there is a disadvantage that the resolution is deteriorated.

(Object of the Invention) The present invention has been made based on the above circumstances, and is not affected by dirt on the backup roller, maintains uniformity in reflectance due to white, and provides correction values such as illuminance unevenness and optical sensor sensitivity unevenness. The backup roller is configured to be driven while maintaining the contact pressure with the original so that the roller can be taken out electrically, and it is intended to provide an optical image reading apparatus capable of increasing the resolution and maintaining the high quality of the image. Is what you do.

(Means for Solving the Problems) For this reason, in the present invention, light emitted from a light source is reflected by a document passing through the surface of a backup roller, and the image is read by detecting an optical sensor facing the backup roller. In a typical image reading apparatus, a white reference member is disposed near the backup roller, and when the backup roller is rotated in a direction in which the document is fed, the white reference member is moved to a position where the optical sensor reads the document. The members are configured to operate.

(Operation) Therefore, even if the original is passed in close contact with the backup roller, dirt may adhere thereto.
For example, when performing gradation reading, illuminance non-uniformity, output signal non-uniformity correction for optical sensor non-uniformity, etc. can be achieved by irradiating a separately prepared white reference member with light rays and receiving reflected light therefrom. Since the white reference member does not touch the document, it is not stained, and accurate correction can be maintained. Therefore, it is possible to obtain a high-resolution image with high resolution.

(Example) Hereinafter, an example of the present invention will be specifically described with reference to FIG. 1 to FIG. In the embodiment shown in FIGS. 1 to 3, the document 103 is passed between the backup roller 102 (preferably, the surface is white) and the reading device 101 in a close contact state. And the backup roller 10
In the vicinity of 2, a white reference member 104 having a white outer surface is prepared. When the backup roller 102 rotates in the counterclockwise direction (see FIG. 1) to feed the original 103, The backup roller 102 is retracted backward from the document reading position P, and the backup roller 102 rotates clockwise (see FIG. 2) so that the document 103 is moved into the document reading position P when the document 103 is not fed. You do it.
For this purpose, for example, the white reference member 104 has a drive mechanism as shown in FIG. Here, the white reference member 104 is provided with shaft portions 102a at both ends of the backup roller 102.
And arms 104a, 104a 'that are rotatably supported, and are held by a spring 110 in a counterclockwise direction. A gear 108 is provided on the shaft 102a.
Are attached and connected to a drive source (not shown). A twisted coil spring 105 is provided between the gear 108 and the arm 104a. When the roller 102 is rotated clockwise, the twisted coil spring 105 is squeezed, and the The reference member 104 is operated clockwise. When the roller 102 is rotated counterclockwise, the twisted coil spring 105
The white reference member 104 is moved to the original reading position P as shown in FIG.
Evacuated from When the backup roller 102 is also used as a document conveying means, one end of the twisted coil spring 105 is not directly attached to the gear 108, but is interlocked with the gear 108 in the clockwise direction and the gear in the counterclockwise direction. It may be attached to a one-way clutch (not shown) that releases the link with the gear 108, and only the clockwise driving force of the gear 108 may be used as the operating force of the white reference member 104 via the clutch.

In such a configuration, since the document 103 is closely attached to the backup roller 102, dirt may adhere to the surface (this may be removed periodically). Original 10
Before the introduction of 3, the correction value can be accurately obtained based on the reflectance of the white reference member (there is no dirt and uniformity is secured as a whole), and high-quality images, especially gradation reading The obtained high-quality image can be obtained. Moreover,
Due to the close contact between the backup roller 102 and the document 103, stable high resolution is also maintained.

In another embodiment shown in FIGS. 4 and 5, the white reference member 17 is moved in a horizontal direction by appropriate means so that it can enter and exit the reading position P. The other components are the same as those of the conventional example shown in FIG. 6, and thus the same reference numerals are given and the description is omitted.

The white color on the surface of the white reference member 17 is printed,
Adhesion of a white sheet may be used. Further, the driving means of the white reference member 17 in the second embodiment (FIGS. 4 and 5) may use the frictional contact force with the document. It is preferable to return (enter) the reading position P by using a spring force, a frictional force with a roller, and the like when the frictional force does not work after being retracted from the reading position P.

(Effects of the Invention) The present invention has been described above. Since the white reference member does not come into direct contact with the document, the white reference member does not become soiled and always serves as a uniform and constant white reference, uneven illuminance, and sensitivity of the optical sensor. Correction of unevenness and the like can be correctly realized, a high-quality image can be reproduced, and the backup roller can be used in close contact with the document, so that a stable resolution is maintained. In addition, the white reference member is retracted when reading the document, and does not hinder the document transport.

[Brief description of the drawings]

1 and 2 are end views for explaining the operation of the basic structure of one embodiment of the present invention, FIG. 3 is an exploded perspective view of an image portion, and FIGS. 4 and 5 are diagrams of another embodiment. End view for operation explanation,
6 and 7 are end views of a conventional example, and FIG. 8 is a perspective view showing a basic configuration of a general optical image reading apparatus. 102 Backup roller 103 Original 104,17 White reference member 105 Twisted coil spring 110 Spring 101 Image reading device

Claims (1)

(57) [Claims] An optical image reading apparatus for reflecting a light beam emitted from a light source to a document passing through a surface of a backup roller and detecting an image by an optical sensor opposed to the backup roller to read an image. A white reference member is arranged at the position, and when the backup roller is rotated in the direction of feeding the document, it is retracted from the reading position of the document by the optical sensor and enters the reading position when the backup roller rotates in the reverse direction. An optical image reading apparatus wherein the white reference member is operated as described above.