JPS63314962A - Original illuminator - Google Patents

Abstract

PURPOSE:To realize the precise read of image information by conducting an illumination light outputted by a dot state light source to a cylindrical lens with the aid of an optical fiber and converging the illumination light on an original with a prescribed irradiation angle and in a line state through the cylindrical lens. CONSTITUTION:The illumination light L1 outputted from the light source 12a is made incident on the one edge part of the optical fiber 13a. In this case, a conductive member 22a in a cylindrical state is provided with the one edge part of the optical fiber 13a and the illumination light L1 from the light source 12a is reflected by the internal wall surface of the conductive member 22a and efficiently made incident on the optical fiber 13a to a high degree. Simultaneously to that, the illumination light L1 of uniform quantity is made incident on each optical fiber 13a by random reflecting processing. Then the illumination light L 1 emitted from the edge part of the optical fiber 13a is focused only in the sub-scanning direction of the original S (the direction of an arrow A) by the cylindrical lens 16a and converged on the main scanning line 11 of the original S. As the distance of the focal point of the cylindrical lens 16a is short, an angular aperture can be set big and the original S can be illuminated with the high intensity of illumination.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a document illumination device, and more specifically, it illuminates illumination light emitted from an optical fiber in a line along the main scanning line of a document through a cylindrical lens. The present invention relates to a document illumination device that can effectively illuminate the document by condensing light into a shape.

[Background of the Invention] For example, in the fields of printing and plate-making, image scanning, recording and reproducing is used to electrically process image information carried on a manuscript and create a film master for the purpose of streamlining work processes, improving image quality, etc. The system is widely used.

This image scanning, recording and reproducing system basically consists of an image reading device and an image reproducing device. That is, in the image reading device, image information of a document that is sub-scanned and conveyed in an image reading section is main-scanned by a photoelectric conversion element and converted into an electrical signal. Next, the image information photoelectrically converted by the image reading device is subjected to arithmetic processing such as gradation correction and edge enhancement according to the plate-making conditions in the image reproducing device, and then converted to an optical signal such as a laser beam, etc. The information is recorded and reproduced on a record carrier made of photosensitive material. Note that this recording carrier is developed by a predetermined developing device and used as a film original for printing or the like.

Incidentally, the image reading device uses, for example, a charge-coupled device (hereinafter referred to as CCD) in order to achieve reading of image information carried on a document by high-speed scanning. In this case, in order to read image information using the CCD, it is necessary to illuminate the document with high illuminance along the scanning direction.

Therefore, in order to illuminate the original, there is a method in which an elongated fluorescent lamp or halogen lamp or the like is placed close to the main scanning line of the original.

In this case, the illuminance of the fluorescent lamp tends to decrease near its ends, which may cause unevenness in the image signal read by the CCD.

Further, since a halogen lamp generates a considerable amount of heat, there is a possibility that the document may be bent or deteriorated due to this heat. Therefore, it is necessary to interpose a long heat insulating filter or the like between the halogen lamp and the document, which has the disadvantage of complicating the structure.

On the other hand, there is an illumination device disclosed in Japanese Patent Application Laid-open No. 56-47165 that efficiently illuminates a document with high illuminance.

In this case, the illumination light output from the point light source enters one end of an optical fiber bundle made up of a large number of optical fibers, and then enters the optical fiber bundle arranged in a line along the main scanning line of the document. The light is emitted from the other end of the handle and is focused onto the main scanning line of the document through a cylindrical lens. Therefore, since the illumination light uniformly illuminates the main scanning line of the original by the optical fine 1, the image information carried on the original is effectively photoelectrically converted by the CCD.

By the way, l! is emitted from the end of the optical fiber. Sensitive tips tend to spread at relatively large opening angles, for example about 60 degrees. On the other hand, the cylindrical lens used in the prior art is shaped like a cylinder cut out parallel to the generatrix, and therefore the aperture fi of the lens is
It has been pointed out that the disadvantage is that the illumination light emitted from the end of the optical fiber at a large opening angle cannot be efficiently focused onto the original wall due to the small NA.

[Object of the Invention] The present invention has been made to overcome the above-mentioned disadvantages, and the present invention is to condense illumination light emitted from an optical fiber onto the main scanning line of a document at a predetermined irradiation angle using a cylindrical lens. Accordingly, it is an object of the present invention to provide a document illuminating device that can effectively illuminate the document with an extremely compact configuration.

[Means for Achieving the Object]) In order to achieve the object described in item 1iI, the present invention includes a point light source that outputs illumination light, and a point light source that outputs illumination light, and a line extending along the main scanning line of the original. an optical fiber configured to guide the illumination light to the document; and a cylindrical lens disposed between an end of the optical fiber and the document to focus the illumination light onto a main scanning line of the document. It is characterized by

[Embodiment 1m] Next, preferred embodiments of the document illumination device according to the present invention will be described in detail with reference to the accompanying drawings.

Reference numerals 10a and 10 in FIGS. 1 and 2
b shows the original J and 3 lighting devices according to the present embodiment, respectively. In this case, the document illumination devices 10a and 1Ob illuminate the document S carrying image information and being conveyed in the sub-scanning direction in the direction of the arrow along the main scanning line 11 thereof.

Note that since the original illuminating device 10b is configured in the same manner as the original illuminating device 10a, the reference numeral ``b'' will be added to the corresponding part (e), and a detailed explanation of the configuration will be omitted from FIG. 1 onwards.

Therefore, the document illumination device 10a is constructed by bundling a point-like light source 12a made of a halogen lamp, a xenon lamp, etc., and a large number of optical fibers 13a.
It includes an optical fiber handle 14a that guides the illumination light L1 output from the document S to the document S, and a cylindrical lens 16a that focuses the illumination light L1 in a line shape along the main scanning line 11 of the document S.

The light source 12a is surrounded by a reflecting mirror 18a formed in the shape of an ellipsoid of revolution.
One surface of an infrared absorption filter 20a coated with a reflective coating is disposed to face the opening. Also,
A cylindrical acrylic light guide member 22a is arranged close to the other surface of the infrared absorption filter 20a, and a large number of optical fibers constituting the optical fiber bundle 14a are arranged in the opening of the light guide member 22a. One end of 13a is attached. Note that it is preferable to use a plastic optical fiber as the optical fiber 13a so that the illumination light L1 can be easily guided to a desired location on the document S.

On the other hand, the other end of the optical fiber 13a is arranged at a predetermined distance away from the document S by curving the optical fiber bundle 14a, and the other end is connected to the elongated housing 2.
4a, the illumination light L1 emitted from the end of the optical fiber 13a held by the housing 24a is configured to form a line along the main scanning line 11 of the original S. The direction of the housing 24a is set so that the angle θ between the optical axis of the optical fiber 13a and the perpendicular line erected on the original S is within the range of 20° to 45°. A cylindrical lens 16a is arranged parallel to the main scanning line 11 between the cylindrical lens 16a and the main scanning line 1 of the document S.
1, the distance rd[1 is set to be slightly shorter than the distance between the cylindrical lens 16a and the paraxial image plane.

On the other hand, a CCD 28 is disposed vertically above the main scanning line 11 on the original S with an imaging lens 26 interposed therebetween. In this case, the imaging lens 26 images the reflected light L2 reflected by the image information carried by the document S onto the C0D28,
Further, the CCD 28 photoelectrically converts the reflected light L2 to form an image signal.

The document illumination device according to this embodiment is basically constructed as described above, and its operation and effects will be explained next.

First, the illumination light output from the light source 12a is focused by a reflection mirror 18a formed in the shape of an ellipsoid of revolution.
The light enters one end of the optical fiber 13a constituting the optical fiber bundle 14a via the infrared absorption filter 20a. In this case, a cylindrical light guide member 22a is disposed at one end of the optical fiber 13a, and the illumination light L1 from the light source 12a is reflected by the inner wall surface of the light guide member 22a and is extremely transmitted to the optical fiber 13a. In addition to being efficiently incident, a uniform amount of illumination light is incident on each optical fiber 13a due to the random reflection effect.

n, r<bright light incident from one end of the optical fiber 13a is an optical fiber bundle 14a curved into a predetermined shape.
After being guided to a predetermined location via the optical fiber 13a
The light is emitted from the other end toward the main scanning line 11 of the document S. The illumination light emitted from the end of the optical fiber 13a is focused only in the sub-scanning direction (six arrow directions) of the original S by the cylindrical lens 16a, and is focused onto the main scanning line 11 of the original S. Ru. As a result, the main scanning line 1
1 is illuminated by illumination light L1.

Here, since the cylindrical lens 16a has a shorter focal length than a semicircular cylindrical lens having the same aperture height 2h, the aperture angle α shown in FIG. 3 can be set large. Therefore, the opening angle from the end of the optical fiber 13a is relatively large (approximately 6 mm in the case of a plastic optical fiber).
Most of the illumination light emitted at an angle of about 0°) is focused onto the main scanning line 11 of the document S by the cylindrical lens 16a. As a result, the original S is illuminated with extremely high illuminance.

Further, as shown in FIG. 3, the cylindrical lens 16a has a large spherical aberration in which the focal point of the paraxial ray and the ray that passes through the peripheral portion of the cylindrical lens 16a differ along the optical axis. For this reason, a-a
45. The light intensity distribution in the bb line, C-c line, and dd line is the fourth along the sub-scanning direction (direction of arrow A) of the document S.
The result will be as shown in the figure. Therefore, the document S is
The distance between the cylindrical lens 16a and the original S so that the cylindrical lens 16a and the document S are arranged on the bb line closer to the cylindrical lens 16a than on the paraxial image plane (cc line) of a! By adjusting this, the main scanning line 11 can be illuminated most effectively. In addition, optical fiber 1
The end portions 3a are arranged closely adjacent to each other at γ·a in the main scanning direction (direction of arrow B). In this case, since the cylindrical lens 16a does not focus the illumination light L1 in the main scanning direction (direction of arrow B), the illumination light emitted from each optical fiber 13a is separated from each other as shown in FIG. The light beams are superimposed and irradiated substantially uniformly along the main scanning line 11 of the document S.

In this way, the document S illuminated with high illuminance by the illumination light L1 from the document illumination devices 10a and 10b outputs image information from its main scanning line 11 as reflected light L2.

This reflected light L2 is imaged onto the CCD 28 by the imaging lens 26, and photoelectrically converted to obtain an image signal. Note that since the document S is sub-scanned and conveyed in the direction of the arrow by a conveyance mechanism (not shown), an image signal based on image information carried on the entire surface of the document S is obtained.

Here, it is preferable that the angle θ between the optical axis of the reflected light L2 and the optical axis of the illumination light L1 is set within the range of 20° to 45°. In other words, when the original S is scanned from vertically above using C0D28, the illuminance of the original S generally decreases approximately in proportion to cos θ, and when the angle θ exceeds 45°, the illuminance decreases when the angle θ is 0. It is known that the illumination efficiency is significantly lower than 70% of that in the case of .degree.

Therefore, it is desirable that the upper limit of the angle θ is approximately 15@. Also, the illumination light L irradiated onto the original S.

As shown in FIG. 6, the reflected light 211 consists of diffusely reflected light 30 whose intensity depends on the image information carried on the document S, and specularly reflected light 32 due to the gloss of the surface of the document S. In this case, the diffusely reflected light 30 is necessary as image information, but the specularly reflected light 32 causes noise and decreases the contrast of the image. For example, as shown in FIG. 7, when silk-grain photographic paper with an uneven surface is used as the original S', the specularly reflected light 32 from the original S' spreads over a considerable range, so the angle θ When the angle is approximately 15° or less, the component of the specularly reflected light 32 will be incident on the containing CCD 28. Therefore, it is desirable to set the lower limit of the irradiation angle θ of the illumination light to approximately 20'. After all, the lighting shines,
By setting the irradiation angle 11θ to a 9·n concave circle of about 20° to about 45°, it is possible to obtain the optimal reflected light L2 containing image information from the original S.

[Advantageous Effects of the Invention 1] As described above, according to the present invention, illumination light output from a point light source is guided to a cylindrical lens through an optical fiber, and the illumination light is irradiated onto a document in a predetermined manner through the cylindrical lens. It is configured to focus light into a line at an angle. Therefore, the illumination light illuminates the document extremely effectively through the cylindrical lens, making it possible to read image information accurately.

Furthermore, by optimally setting the irradiation angle of the illumination light on the document, it is possible to obtain image information with little noise and high contrast.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments.
For example, various improvements and design changes may be made without departing from the spirit of the present invention, such as a configuration in which multiple rows of optical fibers are arranged in a line at the ends of the optical fibers that point toward the original. Of course.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a partially omitted configuration of a document 1 (alpha brightness device) according to the present invention, FIG. 2 is an explanatory side view of a document illumination device according to the present invention, and FIG. FIG. 11 is a characteristic diagram of a cylindrical lens in a document 17 (light device) according to the present invention; FIG. 7 is an explanatory diagram of reflected light from a document, and FIG. 7 is an explanatory diagram of reflected light when silk-textured photographic paper is used as the manuscript. 10a, 10b...Document illumination device 11...Main scanning line 12a, 12b...
Light sources 13a, 13b...Optical fibers 14a, 14b...Optical fiber bundles 16a, 16
b...Cylindrical lenses 20a, 20b...Infrared absorption filter 26...Imaging lens 28...CCDLl...Illumination light
L2...Reflected light S...Original

Claims (4)

[Claims] (1) a point light source that outputs illumination light; an optical fiber whose end close to the document is configured in a line along the main scanning line of the document and guides the illumination light to the document; A document illumination device comprising: a cylindrical lens disposed between an end portion and the document to focus illumination light onto a main scanning line of the document. (2) A document illumination device according to claim 1, wherein the distance between the cylindrical lens and the main scanning line is set shorter than the paraxial image plane distance of the cylindrical lens. (3) In the apparatus recited in claim 1, the optical axis of the reading optical system that reads information carried on a document and the optical axis of the illumination light emitted from the end of the optical fiber toward the document A document illumination device having an included angle set in a range of approximately 20° to approximately 45°. (4) An original illumination device according to claim 1, wherein a cylindrical light guiding member having a reflective inner circumferential wall is disposed between the point light source and the end of the optical fiber.