JP2005234109A - Original illuminating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an original illuminating device being a line illumination system capable of efficiently adapting light emitted from an LED to an original reader in an illumination system surrounding an LED light source and increasing the illuminating light quantity distribution on an original surface more at the peripheral part than at the center part. <P>SOLUTION: In the original illuminating device provided with a light condensing means for condensing light emitted from a plurality of original illuminating light sources arranged in an array state in a main scanning direction, the light condensing means is constituted so that its surface facing the original surface is combined and its surface facing the original illuminating light source has recessed and projecting shape, and the light emitting part of the original illuminating light source is arranged at the projecting part and the side surface of the projecting part is a light reflection surface. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a document illumination device using a light emitting element such as an LED as a document illumination light source of an illumination system of an image reading apparatus.

  More specifically, the present invention relates to a configuration of a document illuminating apparatus suitable for a device such as a digital copying machine or an image reader by efficiently condensing diverging light emitted from a light emitting element such as an LED on a document surface by a condensing member. .

  FIG. 8 is a schematic view of a main part of a conventional document illumination apparatus and image reading apparatus applied to devices such as a digital copying machine and an image reader.

  In the figure, an original 71 placed on an original platen glass 72 is viewed from both sides by indirect illumination light via a reflecting member 74 located at a position opposite to direct illumination light from a light source means 73 which is a bar light source such as a xenon lamp. Illuminated. The reflected light (reflected light beam) based on the image information of the illuminated original 71 is regulated by the slit 75 and is passed through the first mirror 76, the second mirror 77, and the third mirror 78 for scanning by the imaging lens 79. An image is formed on the surface of a solid-state imaging device 80 such as a line-shaped CCD, converted into an electric signal according to the density of the original 71, and an image for one line in the main scanning direction (perpendicular to the paper surface in FIG. 8). Information is read.

  Further, when reading an image in the sub-scanning direction (the direction of arrow A in FIG. 8), the first mirror base 81 including the light source means 73, the reflecting member 74, the slit 75, and the first mirror 76 is read from the original 71 in the sub-scanning direction. And the second mirror base 82 composed of the second mirror 77 and the third mirror 78 is moved in the same direction at half the speed of the first mirror base 81, so that the solid-state imaging device 80 is moved from the original 71 to the solid-state image sensor 80. The image information of the original 71 is read by scanning while keeping the optical path length up to the constant.

  The above-described conventional example is an example in which a document is illuminated from both sides by indirect illumination light through a reflecting member 74 located at a position facing the direct illumination light from the light source means 73 which is a rod-shaped light source such as a xenon lamp. There is also a document illumination device that directly illuminates a document from light source means on both sides without providing a light source means at a position where the light source means is provided.

  As the light source means as described above, fluorescent tubes (lamps) such as fluorescent lamps and xenon lamps are often used because of low power consumption and low calorific value.

  In addition, there is a background that the amount of light emitted from light emitting elements such as LEDs has recently increased as the above light source means. In order to further reduce power consumption and heat generation, light emitting elements such as LEDs (hereinafter referred to as LEDs). An image reading apparatus adopting the above as a document illumination light source has also come out (Patent Document 1).

  However, at present, LEDs are used as the document illumination light source mainly among low-speed image readers among image readers, and relatively high-speed A4 originals such as digital copiers are 20 to 50 sheets / minute, It has not been adopted in an image reading apparatus that reads.

  The reason for this is that although the amount of light emitted by LEDs has increased in recent years, the amount of light emitted is still small for use as a light source for a document illumination device of a relatively high-speed image reading device such as a digital copying machine. For this reason, it is desirable to further increase the amount of light emitted from the LED itself. On the other hand, the diverging light emitted from the LED is condensed on the original surface more efficiently by using the condensing means, and the use efficiency of the light is increased. It is also necessary to increase the amount of illumination light.

  The present applicant has proposed the following configuration as such a highly efficient illumination system.

  The configuration is shown in FIGS. 3A and 3B. FIG. 3A is a sectional view in the sub-scanning direction, and FIG.

  As shown in FIG. 3A, the side surface 3a of the light collecting member 3 is a parabolic surface, and the divergent light from the LED is collimated to the optical axis L of the illumination system in the sub-scanning direction by total reflection, and is collimated. The light is refracted on the exit surface 3 b of the light condensing member 3 to be condensed on the document surface. FIG. 4A illustrates the light beam. By doing so, divergent light from the LED can be efficiently collected on the original surface, and the original can be illuminated brightly.

  Further, the main scanning direction is configured as shown in FIG. 3B, and the parabolic reflecting surface 3a and the emitting surface 3b extend in the same shape in the main scanning direction, but end portions in the main scanning direction. The side surface 3c is formed to be inclined in the main scanning direction. As shown in FIG. 4B, the role of the end side surface 3c is to return the luminous flux that is emitted from the LED and spreads at a large angle in the main scanning direction to the N-axis direction (center direction). In order to make this easier to understand, FIG. 4C shows a diagram viewed from another angle.

  With this configuration, the light reflected from the side surface 3c returns to the central portion, and the amount of illumination light increases. Further, it is possible to prevent light that spreads at a large angle in the main scanning direction and is totally reflected by the emission surface 3b and cannot be emitted from the light collecting member 3 and cannot illuminate the original.

  For example, the light quantity distribution on the document placement surface of the illumination system as described above is as shown in FIG. 5A in the sub-scanning direction, and the light quantity distribution in the main scanning direction is as shown in FIG. The light quantity distribution is as follows. The vertical axis of the two light quantity distribution data indicates a relative light quantity because a certain value in the simulation is 1. Thus, a line illumination system suitable for the document illumination system of the image reading apparatus having a width of several mm in the sub-scanning direction and a width of about 30 mm in the main scanning direction can be realized from one LED.

  In order to explain the above illumination, the LED and the light collecting member are representatively shown as a single unit, but the illumination system units are arranged in an array in the main scanning direction so as to match the image reading apparatus. As an illumination system, an original illuminating apparatus that illuminates a width in the main scanning direction, for example, a short side of 297 mm + α when an A3 original is used. It is also conceivable that the illumination system is provided at a position facing the optical axis M in FIG. 4A to illuminate from both sides to increase the amount of illumination light.

By configuring the illumination system as described above, it becomes possible to provide a line illumination system in which the light emitted from the LED in the illumination system employing the LED light source is efficiently adapted to the document reading apparatus.
Japanese Patent Laid-Open No. 10-190953

  However, in the conventional example as described above, the illumination system units are arranged in an array in the main scanning direction to obtain a substantially flat illumination light amount distribution in the image effective area in the main scanning direction on the document surface as shown in FIG. However, if the peripheral light quantity is increased to further improve the illumination light quantity distribution, there are the following problems.

  First, the necessity of increasing the peripheral light amount of the illumination light amount distribution will be described. In an optical system in which a reflected light beam from an original is imaged on a solid-state image sensor such as a CCD by an imaging lens, for example, and the image information of the original is read, the light quantity on the solid-state image sensor such as a CCD is determined by the COS4 law of the imaging lens. Decreases at the periphery with respect to the center. For this reason, in a document illumination light amount distribution that is substantially flat in the image effective area in the main scanning direction, the peripheral light output of the solid-state image pickup device such as a CCD is reduced due to a decrease in the peripheral light amount due to the imaging lens, and the influence of noise increases. For this reason, the image quality deteriorates due to the influence of noise, and in particular, the quality of image information near the edge has been lowered.

  In the above conventional example, the image reading apparatus having a 1: 2 mirror scanning optical system has been described. For example, in the integrated (flat bed type) image reading apparatus shown in FIG. The image information of the document 51 is illuminated with the reflected light beam, and the reflected light beam from the document 51 is routed in the carriage 61 through the first, second, third and fourth reflecting mirrors 55, 56, 57 and 58. The image is formed on the surface of a solid-state image sensor such as a one-dimensional CCD by bending and imaging lens 59. Then, the image information of the original 51 is read by moving the carriage 61 in the direction of arrow R (sub-scanning direction) shown in the drawing by a sub-scanning motor (not shown).

  In the integrated (flatbed type) image reading apparatus as described above, the imaging lens has been increased in angle of view due to the miniaturization thereof, and the influence of the decrease in the amount of peripheral light due to the imaging lens has increased. Yes. For example, in an optical system in which the half angle of view of the imaging lens is 30 degrees, the decrease at the extreme end of the light amount distribution on a solid-state image sensor such as a CCD according to the COS 4 law is 44%, and the problem has become remarkable.

  Therefore, in order not to supplement the COS fourth power law of the imaging lens, the distribution of the original illumination light quantity distribution in the main scanning direction is obtained such that the peripheral light quantity is higher than the center.

  For this purpose, in the illumination system employing the above-described LED light source, it is conceivable that a larger number of illumination system units are arranged in the peripheral part than in the central part in the main scanning direction to irradiate the original with many LEDs to increase the peripheral light amount. .

  However, in the conventional example as described above, since the illumination system unit is configured as shown in FIG. 3, the width of the illumination system unit in the main scanning direction is wide on the exit side. The pitch to be arranged was limited, and it could not be arranged closer than this width.

In the present invention, there is provided a document illuminating device used in an image reading apparatus provided with a condensing means for condensing light emitted from a plurality of document illuminating light sources arranged in an array in the main scanning direction,
The condensing means has a surface facing the document surface coupled to it, and a surface facing the document illumination light source is uneven, and the light emitting portion of the document illumination light source is disposed on the projection, the projection The side surface is a light reflecting surface.

  As described above, by implementing the present invention, the illumination system surrounding the document illumination light source is a line illumination system that efficiently adapts the light emitted from the document illumination light source to the document reader, and the illumination light amount distribution on the document surface is centered. It becomes possible to increase the peripheral part rather than the part.

  In the present invention, when a condensing member is combined with a package in which an LED is enclosed to constitute an illumination system of a document illuminating device, the shape of the condensing member is changed in the main scanning direction in order to increase the degree of freedom of the LED pitch. The peripheral light quantity is increased to improve the illumination light quantity distribution.

  FIG. 1 is a schematic view of a main part of a document illumination device in an image reading apparatus according to an embodiment of the present invention. FIG. 1A shows an illumination system from a direction orthogonal to the sub-scanning direction. A view seen from another angle is shown in FIG.

  In the figure, the illumination system unit 5 at the center is a representative example, 1 is an LED, 2 is a package in which the LED is enclosed, and 3 is a condensing member coupled to the package in which the LED is enclosed. For example, it is made of a transparent resin material such as acrylic. Then, the package 2 in which the LED is enclosed and the light collecting member 3 are bonded by, for example, an ultraviolet curing adhesive.

  Reference numeral 4 denotes an original table glass on which an original is placed. The document placed on the surface of the document table glass 4 is illuminated with light emitted from the LED 1 via the light collecting member 3, and reflected light (reflected light beam) based on the image information is regulated by the slit and is used for scanning. An image is formed on the surface of a solid-state image sensor as a light receiving means such as a line CCD by an imaging lens through the first mirror, the second mirror, and the third mirror, and is converted into an electric signal according to the density of the original. In FIG. 1A, image information for one line in the direction parallel to the paper surface (main scanning direction) is read (not shown).

  Further, in the image reading in the sub-scanning direction orthogonal to FIG. 1A, the first mirror base including the illumination system, the slit, and the first mirror is moved in the sub-scanning direction with respect to the original, and the second By moving the second mirror base composed of the mirror and the third mirror in the same direction at half the speed of the first mirror base, scanning is performed while keeping the optical path length from the original to the solid-state image sensor constant. Image information of the original is read (not shown).

  As shown in FIG. 3A, the illumination system unit 5 at the center of the above embodiment illuminates the side 3a of the light collecting member 3 as a paraboloid in the sub-scanning direction by total reflection of divergent light from the LED. The light is collimated to the optical axis L of the system, and the collimated light is refracted by the exit surface 3b of the condensing member 3 to be condensed on the document surface.

  Further, the main scanning direction is configured as shown in FIG. 3B, and the parabolic reflecting surface 3a and the emitting surface 3b extend in the same shape in the main scanning direction, but end portions in the main scanning direction. The side surface 3c is formed to be inclined in the main scanning direction.

  With this configuration, the light reflected from the side surface 3c returns to the central portion, and the amount of illumination light increases. Further, it is possible to prevent light that spreads at a large angle in the main scanning direction and is totally reflected by the emission surface 3b and cannot be emitted from the light collecting member 3 and cannot illuminate the original.

  In the present invention, by arranging a large number of illumination system units as described above in an array in the main scanning direction, an image effective area having a width in the main scanning direction as an illumination system adapted to the image reading apparatus, for example, 297 mm + α for an A3 document. As shown in FIG. 1, the condensing member 6 is configured so that the emission side is coupled at the periphery, and the LED side of the light source is provided with a side surface corresponding to each illumination system unit. is there.

  By configuring in this way, the width of the illumination system unit in the main scanning direction becomes wider on the exit side, that is, the pitch at which the illumination system units are arranged due to interference due to this width is limited. It is possible to solve the problem that it cannot be arranged closer.

  Therefore, it is possible to arrange the pitches of the illumination system units in the peripheral portion in the main scanning direction more closely than the central portion, and the illumination light amount distribution on the document surface increases as it goes from the central portion to the peripheral portion as shown in FIG. It becomes possible. Thereby, the COS4 law of the imaging lens can be supplemented.

  As shown in FIG. 1, the illumination system unit is configured to combine the emission side at the peripheral portion, and the LED side of the light source is provided with a side surface corresponding to each illumination system unit. With this configuration, it is possible to effectively use light from the LED while providing a degree of freedom in the pitch of the illumination units in the main scanning direction.

  For example, if a condensing member having a reflecting surface that condenses light in the sub-scanning direction and extending in the same shape in the main scanning direction has a degree of freedom in arranging the LEDs themselves, such an illumination system is shown in FIG. As described above, the light emitted from the LED 1 in the main scanning direction H at a large angle α is totally reflected on the exit surface of the light collecting member 13 and cannot be used effectively for the original illumination light. For example, if the refractive index n of the light collecting member is 1.5, total reflection occurs when the angle α exceeds 42 degrees.

  In the present invention, on the LED side, the condensing member is configured to have side surfaces corresponding to the respective LEDs, so that light emitted at a large angle α in the main scanning direction H as described above is reflected by the side surfaces. Therefore, it has a configuration that does not totally reflect.

  Therefore, the light from the LED can be used effectively.

  The above-described embodiment shows an example of the shape in which the light collecting member 6 is coupled to the emission side at the peripheral part of the main scanning.

  As another embodiment, it is conceivable to configure the illumination system as a shape in which the exit side of the light condensing member is also combined in the vicinity of the central portion. By adopting such a configuration, the pitch in which the LEDs are arranged can be made dense even in the vicinity of the central portion, so that the amount of illumination light can be increased over the entire area in the main scanning direction.

  As described above, by implementing the present invention, in the illumination system surrounding the LED light source, the line illumination system that efficiently adapts the light emitted from the LED to the document reading apparatus, and the illumination light amount distribution on the document surface from the center to the periphery The number of parts can be increased.

Schematic diagram of the main part of an embodiment of the present invention Document surface light amount distribution according to an embodiment of the present invention The principal part schematic of the illumination unit of the Example of this invention Illumination path diagram of illumination system unit Illumination distribution on the original surface of the lighting system unit Conventional document surface illumination distribution Example of total reflection Example of conventional image reading apparatus Example of conventional image reading apparatus

Explanation of symbols

1 LED
2 Package in which LED is enclosed 3 Condensing member 4 Original glass 5 Illumination system unit 6 Combined condensing member

Claims (5)

A document illuminating device used in an image reading apparatus provided with condensing means for condensing light emitted from a plurality of document illuminating light sources arranged in an array in the main scanning direction,
The condensing means has a surface facing the document surface coupled to it, and a surface facing the document illumination light source is uneven, and the light emitting portion of the document illumination light source is disposed on the projection, the projection An original illuminating device characterized in that the side surface of the document is a light reflecting surface.   The document illumination device according to claim 1, wherein the document illumination light source is an LED element.   The document illumination device according to claim 1 or 2, wherein the document illumination light source has a narrower interval from the center to the periphery in the main scanning direction.   4. The document illuminating device according to claim 1, wherein the light collecting means is made of a transparent resin material and is bonded to a package in which an LED element is enclosed with an ultraviolet curable adhesive. .   An image reading apparatus comprising: the document illumination device according to claim 1; an imaging lens; and a light receiving unit.

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