JP2005234108A - Original illuminating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide 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. <P>SOLUTION: The illuminating device is constituted so that a direction orthogonal to a direction where an electrode arranged proximately to an LED element and the LED element itself are arrayed is set as the subscanning direction of an image reader. <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. 10 is a schematic diagram 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 image sensor 80 such as a line 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. 10). Information is read.

  Further, when reading an image in the sub-scanning direction (the direction of arrow A in FIG. 10), 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, as the above light source means, the amount of light emitted from light emitting elements such as LEDs has recently increased, and 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 that employs a document illumination light source as a document illumination light source has also come out (Patent Document 1).
Japanese Patent Laid-Open No. 10-190953

  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 documents such as digital copying machines are 20 to 50 sheets / minute, It is not adapted to an image reading apparatus that reads.

  The cause of this is that the amount of light emitted by the LED has increased, but 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.

  Therefore, various optical systems for condensing light emitted from the LED have been considered. For example, a system for condensing light by placing a lens in front of the LED and an illumination system for improving the illumination efficiency by combining the reflective surface of the LED have been considered. However, since LEDs are conventionally treated like point light sources (micro-light sources), consideration and design philosophy regarding the influence of electrodes arranged on both sides of the LEDs are lacking as described later.

  In addition, a manufacturer that manufactures an LED simply prepares a limited number of types of packages, and the manufacturer on the side of developing and manufacturing the image reading apparatus starts from the package in which the limited LED is enclosed. It is conceivable to select a material suitable for use in the process and to combine a light collecting member (illumination system) with the package. As described above, the image reading apparatus reads the image information of the document with a solid-state image sensor such as a line-shaped CCD, so that the diverging light from the LED is also condensed in the sub-scanning direction as illumination light. The illumination efficiency of the line-shaped illumination system with a wider width is better. For this reason, when a light condensing member (illumination system) is combined with a package in which LEDs are encapsulated to form a module, it is desired to obtain line-shaped illumination light. However, there was a lack of consideration and design philosophy regarding the combination of a package enclosing an LED and a light collecting member.

  In the present invention, when a light-collecting member is combined with a package in which LEDs are encapsulated to form a module to constitute an illumination system of a document illuminating device, the package in which the LEDs are encapsulated and the light-condensing member are efficiently configured to diverge from the LEDs. Clarify the arrangement for making the light into a line illumination system.

  In the present invention, the reflecting surface shape of the sub-scanning of the illumination system surrounding the LED light source is, for example, an LED in a system that illuminates the document surface using a reflecting surface such as a quadratic surface of a parabolic (elliptical, hyperbolic) surface. Line illumination that efficiently adapts the light emitted from the LED to the document reading device by arranging the short side (short side) direction of the enclosed package in the sub-scanning direction and the long side (longitudinal) direction in the main scanning direction. System.

  As described above, by implementing the present invention, it becomes possible to provide a line illumination system that efficiently adapts the light emitted from the LED to the document reading apparatus in the illumination system surrounding the LED light source.

(Example 1)
1A and 1B are schematic views of a main part of a document illumination device in an image reading apparatus according to an embodiment of the present invention. FIG. 1A is a sectional view in the sub-scanning direction, and FIG.

  In the figure, 1 is an LED, 2 is a package in which the LED is enclosed, 3 is a light collecting member coupled to the package in which the LED is enclosed, and is made of a transparent resin material such as acrylic. Yes. 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. Through the first mirror, the second mirror, and the third mirror, an image is formed on the surface of a solid-state image pickup device such as a linear CCD by an imaging lens, and is converted into an electric signal according to the density of the original. In A), image information for one line in the direction perpendicular to the paper surface (main scanning direction) is read (not shown).

  Further, in the image scanning in the sub-scanning direction in the direction of arrow F in FIG. 1A, the first mirror base composed of the illumination systems 1, 2, 3 and the slit and the first mirror is placed in the sub-scanning direction on the document. The optical path length from the original to the solid-state image sensor is made constant by moving the second mirror base composed of the second mirror and the third mirror in the same direction at half the speed of the first mirror base. The image information of the document is read by scanning while keeping (not shown).

  In the above embodiment, as shown in FIG. 1A, the side surface 3a of the light condensing 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. The collimated light is refracted by the exit surface 3 b of the light condensing member 3 to be condensed on the document surface. FIG. 2A shows 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. As for the light condensing, as shown in FIG. 2A, the reading position by the CCD in the sub scanning direction, in other words, several mm in the sub scanning direction around the optical axis M of the image reading system (imaging system). Condensed with a width of.

  The reason for this will be described below.

  The CCD reading line on the document surface is usually relative to the reference sub-scanning position, usually the center of the slit, due to displacement caused by optical adjustment of mirrors, lenses, etc., and displacement caused when scanning from the leading edge to the trailing edge of the document. There is a possibility of moving in the sub-scanning direction by about 0.2 to 1.0 mm. Therefore, in order to prevent the illumination light quantity from changing even when such a deviation occurs, a wider illumination light quantity distribution having a width of several mm in the sub-scanning direction is required.

  Further, the main scanning direction is configured as shown in FIG. 1B, and the paraboloid 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. 2B, 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). FIG. 2C shows a diagram viewed from another angle in order to make this easier to understand.

  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 embodiment of the present invention as described above, for example, the light amount distribution in the sub-scanning direction is as shown in FIG. 3A, and the light amount distribution in the main scanning direction is as shown in FIG. The light quantity distribution is as shown in (B). 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.

  Further, in order to explain in the above-mentioned embodiments, the configuration of the illumination system is shown as one representative, but illumination according to the image reading apparatus is arranged by arranging a large number of the above-mentioned illumination systems in the main scanning direction. An original illuminating apparatus that illuminates a width in the main scanning direction as a system, for example, a width 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. 2A to illuminate from both sides to increase the amount of illumination light.

  Here, the package 2 in which the LED is encapsulated has a configuration as shown in FIG. 4, for example, and has a rectangular parallelepiped shape. Further, there is an electrical wiring portion such as a lead wire for supplying electric power from the outside outside the package 2, but it is omitted here.

  As described above, the package 2 has a rectangular parallelepiped shape because the LED 1 itself is arranged on a pedestal as shown in FIG. 5 to supply power to the LED 1 even if it is a small element. Since the bonding wire 5 is disposed from there, the package shape is long (longitudinal) in the direction in which the electrode 6 is disposed and short (short) in the direction perpendicular thereto. Moreover, an epoxy resin is often used as a material for the package as described above.

  By the way, there is a cylindrical package in which the LED is enclosed, but the arrangement of the electrodes is not changed as described above, so it has a diameter that sufficiently surrounds the longitudinal direction in which the electrodes are arranged, and as a whole is in space. It has a large package shape with a margin.

  As shown in FIG. 6, when the condensing member 3 is combined with the package 2 in which the LEDs having a rectangular parallelepiped shape as described above are enclosed, in the embodiment of FIG. 1, the short side of the package 2 is sub-scanned. The longitudinal direction is arranged in the main scanning direction. By arranging in this way, it is possible to increase the efficiency of light emitted from the LED.

  The reason why the arrangement as described above is necessary for effective use of light from the LED will be described below.

  The reason is that light can be used more effectively if the width of the position corresponding to the focal point of the reflecting surface on which the LEDs are arranged is narrowed in order to efficiently use the light collecting member and increase the amount of illumination of the original.

  This will be described with reference to FIGS. 7 and 8.

  FIG. 7 shows an example of an illumination system in which a package 12 in which LEDs are enclosed is arranged in the sub-scanning direction and the longitudinal direction is arranged in the main scanning direction as in the present invention, and FIG. It is an example of the illumination system arrange | positioned in the scanning direction and has arrange | positioned the transversal in the main scanning direction.

  In these two examples, the shape of the package in FIG. 4 is X = 3.5 mm, Y = 3.0 mm, and Z = 2.0 mm.

  As described above, the short side of the package is Z = 2.0 mm and the long side is X = 3.5 mm. Accordingly, the width in the sub-scanning direction at the focal position of the paraboloid is 2.0 mm in the illumination system of FIG. 7 and 3.5 mm in the illumination system of FIG.

  Here, the width in the sub-scanning direction refers to the width in the direction orthogonal to the optical axis of the illumination system.

  Also, the reason why the width of the package and the width in the sub-scanning direction at the focal point position of the paraboloid are the same as described above is to effectively use all the light emitted upward from the LED. This is to prevent light from escaping from the connecting portion of the members 13 and 15.

  Further, the shape of each exit surface is circular, and the radius of curvature R is the same as R = 7 mm, and the example is created, and the heights (lengths) of the light collecting members 13 and 15 in the optical axis direction are the same. It has become. Here, as can be seen by comparing the examples of FIGS. 7 and 8, the illumination system of FIG. 8 is less concentrated in the light of the LED than the illumination system of FIG. I understand that.

  There are two reasons for this. First, the shape of the paraboloid is determined by the width orthogonal to the optical axis at the focal position. However, as the width becomes wider at the focal position, as shown in FIG. 7 and FIG. The exit (outgoing surface side) also has an expanded shape. For this reason, the ratio (angle) of light that goes in the direction reflected by the paraboloid in the light emitted from the LED decreases. When the decreasing rate is graphed for the illumination system as shown in FIGS. 7 and 8, the solid line in FIG. 9 is obtained. Here, the light reflected by the paraboloid when the width in the sub-scanning direction at the position of the focal point of the paraboloid is 2.0 mm is graph data comparing with 1. Further, the above graph assumes that light is emitted like complete diffusion using an LED as a point light source.

  Another reason is that the light emitted from the LED is collimated to the optical axis L of the illumination system at the parabolic reflection surface, and the collimated light is refracted at the exit surfaces of the light collecting members 13 and 15. If the parabolic surface is concentrating on the original surface, the angle from the optical axis gradually becomes parallel to the optical axis as the exit surface goes to the end, causing total reflection, and light from the condensing member. It is because it becomes impossible to go out. The situation appears at 16 in FIG. The ratio of the amount of illumination light considering the decrease in the amount of illumination light due to the total reflection is represented by a dotted line graph in FIG.

  As described above, when the light from the LED is condensed on the document surface by using the paraboloid as described in the above example, the LED is disposed at the focal position of the paraboloid. It can be seen that divergent light from the LED can be used more efficiently when the width in the sub-scanning direction is smaller. In other words, if the LED is a minute light source such as a point light source, the light emitted very efficiently can be used as the original illumination light. However, the LED itself has a size, and when considering a package that includes electrodes, even if the package is downsized, it becomes a package having a short side and a long side as in the above example, and the size is also 2 mm short and long. It becomes about 3.5 mm.

  Therefore, as described above, when the package and the light collecting member are combined, it is very important to improve the illumination efficiency by setting the short side direction of the package to the sub-scanning direction as in the present invention.

  In the above-described embodiment, the reflecting surface is described as a parabolic surface. However, the short direction of the package is also set to the sub-scanning direction for other secondary curved surfaces and condensing surfaces such as an elliptical reflecting surface. However, it will improve the lighting efficiency.

(Example 2)
In the above-described embodiment, the illumination system combining the package and the light collecting member has been described. However, as described above, the contents of the present invention can also be applied to the case where the LED is provided with an illumination system having a light collecting action directly. The divergent light from the LED can be used more effectively as document illumination light when the illumination system is configured with the short direction of the LED system used for illuminating the document, that is, the direction orthogonal to the direction in which the electrodes are arranged, as the sub-scanning direction. become.

Schematic diagram of the main part of an embodiment of the present invention Illumination optical path diagram of an embodiment of the present invention Document surface illumination distribution in an embodiment of the present invention Example of LED package Example in LED package Example of LED package and condensing member Example of the present invention Example of the present invention Example graph of the present invention 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 Bonding wire 6 Electrode

Claims (8)

An illumination means provided with means for condensing emitted light surrounding the LED element using an LED element as a document illumination light source of the image reading apparatus,
An original illuminating apparatus characterized in that a direction orthogonal to a direction in which the electrodes arranged close to the LED elements and the LED elements themselves are arranged is set as a sub-scanning direction of the image reading apparatus.   2. A document illuminating apparatus according to claim 1, wherein a reflecting surface is used as a condensing means surrounding the LED element, and a reflecting surface shape in the sub-scanning direction is a parabolic secondary curved surface.   2. The document illumination device according to claim 1, wherein the LED element and a plurality of means for condensing light emitted from the LED element are arranged in the main scanning direction of the document reading device.   In an illuminating means combining a package in which an LED element is enclosed as a document illumination light source of an image reading apparatus and a means for concentrating emitted light surrounding the package, the transverse direction of the package is the sub-scanning direction and the longitudinal direction is the main scanning. A document illumination device characterized by being arranged as a direction.   5. The document illuminating apparatus according to claim 4, wherein a reflecting surface is used as a condensing means surrounding the package in which the LED element is enclosed, and a reflecting surface shape in the sub-scanning direction is a parabolic second curved surface.   5. The original illumination according to claim 4, wherein a plurality of light collecting means surrounding the package enclosing the LED element and the package enclosing the LED or the like are arranged in the main scanning direction of the original reading apparatus. apparatus.   The document illumination device according to any one of claims 4 to 6, wherein the package in which the LED element is enclosed has a rectangular parallelepiped shape made of an epoxy resin.   8. The document illuminating device according to claim 4, wherein the light collecting means is made of a resin material such as acrylic and is bonded to the package by an ultraviolet curing adhesive.

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