JPH0690328A - Picture reader - Google Patents

Abstract

PURPOSE:To form only an accurate original information light onto a CCD by extracting only a reflecting light from an original face in the vicinity of a line state read position so as to prevent flair due to an excess reflected light from an original white background part around the original face. CONSTITUTION:Two plate members 11, 12 whose edge is arranged along a line-shaped read position respectively so as to introduce a reflected light from an original face at the line-shaped read position R, opposite to each other via a prescribed short interval (w) in the carrying direction of an original 1 and made of opaque members whose outer face is a non-reflecting face are provided to the picture reader using a reduction optical system. Thus, only the light radiating from a light source 6 and reflected in the original face in the vicinity of the line-shaped read position R is extracted.

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 mounted on a facsimile machine or the like and capable of reading high quality images.

[0002]

2. Description of the Related Art An original image is printed on a line C using a reduction optical system.
There is an image reading device which forms an image on a CD and photoelectrically converts it to read an original image.

FIG. 6 shows an image reading apparatus of this type. Reference numeral 1 is a document, 2 is a paper feed roller, 3 is a discharge roller, and the document 1 is conveyed in the direction of the arrow. Reference numeral 4 is a contact glass, and a line-shaped reading position R in a direction perpendicular to the document conveying direction is set in this portion. Reference numeral 6 denotes a rod-shaped light source which is long in a direction perpendicular to the document conveying direction and illuminates the document surface with the light. Reference numeral 7 denotes a plurality of mirrors that guide the reflected light from the document surface at the line-shaped reading position, and bends the optical path so as to obtain a required optical path length for downsizing the entire apparatus. Reference numeral 8 denotes an imaging lens for forming reflected light (that is, an original image) on the reading sensor, and 9 denotes a line CCD as the reading sensor.
Is.

In the image reading apparatus thus constructed,
The original 1 is conveyed in the direction of the arrow by the paper feed roller 2 (sub-scanning), the light from the light source 6 is applied to the original surface, and a plurality of reflected lights from the original surface passing through the set linear reading position R are generated. The light is guided by the mirror 7, and an image is formed on the line CCD 9 by the image forming lens 8. The CCD 9 scans (main-scans) the light receiving elements arranged in a line, and converts the optical information into an electric signal.

By the way, the resolution of a facsimile apparatus equipped with an image reading apparatus using this type of reduction optical system is 8 lines / mm in the main scanning direction and about 3.85 lines in the sub scanning direction, and 7.7.
This is 1 book or 15.4 books / mm. Since this resolution is lower than that of copying machines and scanners, the output image is much degraded compared to the original image. Since the output image of the facsimile has a binary value of white or black, unless the faithful reading with respect to the document reflectance is performed, "line breakage" of the character portion, which is the head of the image deterioration phenomenon, frequently occurs.

The cause of this "line break" may be the factors of the image processing unit, plotter unit, etc., but the largest cause is the reading error occurring in the reading system. The causes of the thin line reading error include factors related to document transportation, lens performance, and problems of the illumination system, and the influence of the illumination system is particularly serious.

FIG. 7 shows such a situation. Although the output of the black background portion B is originally low as shown in FIG. 7A, the output of the reflectance as shown in FIG. When the black area B having a low reflectance surrounded by the high white background W is read by the conventional reduction optical system, the output tends to be high. This is because the light reflected by the white background portion other than the reading point of the document is repeatedly reflected by an object close to the document or the surface of the light source tube and is read as document information. Due to the influence of the flare light component, the document information at the reading point does not form an image faithfully on the CCD light receiving portion, which has a great influence particularly when reading a thin line document, and "line breaks" frequently occur. Further, not only the binary image but also the reading of an original having gradation such as a photographic image has the same problem, so that the halftone cannot be accurately reproduced in the output image.

On the other hand, a transparent shield member (contact glass) is masked with an opaque material,
It has been proposed that the transparent portion has a slit shape parallel to the document conveying direction (Japanese Patent Laid-Open No. 3-36875).
Issue). Alternatively, it is also proposed that a slit is provided in the lens array that focuses the light of the light source to increase the amount of light applied to the document and to eliminate the deterioration phenomenon of contrast due to the wraparound of the illumination light.
(JP-A-1-265660).

[0009]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art by suppressing the effects of flare light components and causing "line breaks" and deterioration of halftones due to reading errors that are frequently occurring at present. It is an object of the present invention to provide an image reading apparatus that suppresses the above-mentioned problem.

[0010]

In order to achieve the above object, the present invention provides an image reading apparatus using a reduction optical system so as to guide the reflected light from the document surface at the linear reading position. Two plate-like members made of an opaque member, each end edge of which is arranged along a line-shaped reading position, face each other with a predetermined short distance in the document transport direction, and whose outer surface is a non-reflective surface A member is provided.

Further, an illumination light guide member is provided between the long light source and the linear reading position so that the opening width becomes narrower as it approaches the reading position. In this case, the inner surface of the illumination light guide member may be a mirror.

Further, the illumination light from the light source is once reflected by a long mirror and the reflected light is applied to the document surface at the reading position, or the light source is arranged far from the reading position. Light is guided by an optical fiber to irradiate the document surface at the reading position.

[0013]

In any of the above configurations, flare due to the reflection component of the white background of the document other than the linear reading position is suppressed, and only accurate document information light is imaged on the CCD. As a result, high-quality document reading can be obtained.

[0014]

Embodiments will be described in detail below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention, in which the same reference numerals as those in FIG. 6 represent the same things (hereinafter the same), and 11 and 12 indicate the linear reading position R. Two plate-like members, each edge of which is arranged along the linear reading position so as to guide the reflected light from the document surface, and which face each other with a predetermined short distance w in the document transport direction. It is a member. The plate-like members 11 and 12 are made of an opaque member that does not transmit the light from the light source 6, and the outer surface (the surfaces facing each other are the inner surface) is subjected to, for example, black processing to be a non-reflective surface.

The upper edge of the plate-like member 11 on the light source 6 side is cut out so that the light from the light source 6 is applied to the reading position R. The distance w between the plate-like members 11 and 12 is such that the light from the light source 6 is diffusely reflected on the document surface, and among the reflected light, only the reflected light in the vicinity of the reading position R is transmitted, and the excess reflected light around it is not transmitted. So, it is set appropriately narrow.

In this embodiment having such a configuration, only the reflected light from the document surface at the line-shaped reading position R is guided, and the direct light from the light source 6 and the extra reflected light around the reading position R are generated. Since it does not enter the reading light information, only the correct document information is imaged on the CCD, and therefore, faithful reading is possible.

FIG. 2 shows a second embodiment of the present invention, in which 13 and 14 are provided between the light source 6 and the line-shaped reading position R, and the opening width becomes narrower toward the reading position. Such an illumination light guide member. In the vicinity of the light source 6, the illumination light guide members 13 and 14 cover the light source tube surface so that light does not leak in other directions, and the outer surface is subjected to, for example, black processing so as to be a non-reflective surface. I am trying.

In this embodiment having such a configuration, the light from the light source 6 is narrowed down by the illumination light guide members 13 and 14, and only the vicinity of the line-shaped reading position R is illuminated, so that the extra light is the reading light information. I can't come in. Therefore, only the correct document information is imaged on the CCD.

FIG. 3 shows a third embodiment of the present invention. Here, although the illumination light guide members 15 and 16 similar to those of the second embodiment are provided, this illumination light guide member 1
The difference is that the inner surfaces of 5 and 16 are mirrors. In this way, when the inner surface is a mirror, the light P2 emitted from the light source 6 and hitting the inner surface is reflected by the mirror and directly added to the light P1. As it is illuminated, there is no loss of light. It should be noted that at least the outer surface of the illumination light guide member 16 is subjected to black processing as in the second embodiment to form a non-reflective surface.

FIG. 4 shows a fourth embodiment of the present invention, which is arranged so that the direct light from the light source 6 does not reach the linear reading position R, and the light emitted from the light source 6 is A long mirror 18 parallel to the light source is once totally reflected, and the reflected light reaches the linear reading position R. Therefore,
It is possible to prevent the light from the light source 6 from spreading around the linear reading position R.

FIG. 5 shows a fifth embodiment of the present invention. In this case as well, the light source 6 is arranged at a position sufficiently distant so that the direct light thereof does not reach the linear reading position R, and the light source 6 is provided. The light emitted from is condensed by a condenser lens 19 and guided to near the reading position by an optical fiber 20 such as a lens array. This can prevent the light from the light source 6 from spreading around the linear reading position R.

[0022]

As described above, according to the present invention, (1) the two plate-shaped members are provided so as to guide the reflected light from the document surface at the line-shaped reading position, It is possible to prevent flare due to the reflected light of the white background of the document other than the reading position, and only the accurate document information light is imaged on the CCD, and high-quality image reading becomes possible.

(2) The one provided with the illumination light guide member in which the opening near the line-shaped reading position is narrowed so that the light from the light source is narrowed, since the extra light radiated to the original is cut, the original white background Flare caused by reflected light from the part is also suppressed, enabling high-quality image reading.

(3) In the configuration of (2), the illumination light guide member having the inner surface as a mirror allows efficient image reading with high quality without loss of light quantity.

(4) The one in which the light from the light source is once reflected by the mirror to irradiate the linear reading position can prevent the illumination of a wide range around the reading position by the direct light from the light source, and thus the linear reading position can be prevented. It is possible to prevent flare due to the reflected light from the white background of the document other than the reading position.

(5) Even in the case where the light from the light source is guided by the optical fiber to irradiate it to the linear reading position, it is possible to prevent the illumination of a wide range around the reading position by the direct light from the light source. The same effect as 4) can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a main part of a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a main part of a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a main part of a third embodiment of the present invention.

FIG. 4 is a configuration diagram of a main part of a fourth embodiment of the present invention.

FIG. 5 is a configuration diagram of a main part of a fifth embodiment of the present invention.

FIG. 6 is a schematic configuration diagram of an image reading apparatus using a reduction optical system to which the present invention is applied.

FIG. 7 is a diagram showing an output level of black background detection according to a conventional example.

[Explanation of symbols]

1 ... manuscript, 4 ... contact glass, 6 ... light source,
9 ... Line CCD, 11, 12 ... Plate-shaped member, 13, 14, 15,
16… Illumination light guide member, 18… Mirror, 20… Optical fiber.

Claims (5)

[Claims] 1. A document surface is illuminated with light from a light source that is long in a direction perpendicular to the document transport direction, and reflected light from the document surface at a line-shaped reading position parallel to the light source is guided by an imaging lens. In an image reading apparatus using a reduction optical system for forming an image on a line CCD and reading an original image, each edge has the linear reading so as to guide reflected light from the original surface at the linear reading position. An opaque member that is arranged along each position and faces each other with a predetermined short interval in the document transport direction, and has an outer surface that is a non-reflective surface.
An image reading apparatus having a sheet-shaped member. 2. A document surface is illuminated with light from a light source that is long in a direction perpendicular to the document transport direction, and reflected light from the document surface at a line-shaped reading position parallel to the light source is guided by an imaging lens. In an image reading apparatus using a reduction optical system for forming an image on a line CCD and reading an original image, an illumination light whose opening width becomes narrower between the long light source and the line reading position as the reading position is approached. An image reading apparatus provided with a guide member. 3. The image reading device according to claim 2, wherein the inner surface of the illumination light guide member is a mirror. 4. An image forming lens illuminates a document surface with light from a light source long in a direction perpendicular to a document conveying direction, guides reflected light from the document surface at a line-shaped reading position parallel to the light source, and uses an imaging lens. In an image reading apparatus using a reduction optical system for forming an image on a line CCD and reading an original image, the illumination light from the light source is once reflected by a long mirror, and the reflected light is applied to the original surface at the reading position. An image reading apparatus characterized by: 5. An image forming lens illuminates a document surface with light from a light source long in a direction perpendicular to the document conveying direction, guides reflected light from the document surface at a line-shaped reading position parallel to the light source, and forms an image by an imaging lens. In an image reading apparatus using a reduction optical system for forming an image on a line CCD and reading an original image, the light source is arranged far enough from the reading position, and the light from the light source is guided by an optical fiber to read the original surface at the reading position. An image reading device, which irradiates the image with the image.