JPH08163320A - Rod shaped lighting device and original reader using it - Google Patents

Abstract

PURPOSE: To attain highly efficient lighting without providing a special reflecting face by using one side of a transparent rod with a specific shaped cross section provided with a light diffusion layer for a light emission face so as to arrange the space efficiently. CONSTITUTION: A light source unit 2 is made up of a LED and a transparent rod 3 has a light diffusion layer on which white paint is printed. A white color 4 covers a side face of the rod 3. The cross section of the rod 3 is shaped to be pentagonal, which is formed by cutting one corner of a rectangle. A face formed by cutting one corner of a transparent rod prism is used for a light emission face 32. Furthermore, e.g. white paint is printed out on one part of one side among faces of the light diffusion layer opposite to the light emission face 32 in a prescribed pattern. When a light source unit is provided at both ends of the transparent rod, the pattern is to be such that the width at both ends of the transparent rod is narrow and the width in the middle of the transparent rod is wide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rod-shaped illuminating device for linearly illuminating a document surface in an image reading device such as a contact type image sensor used in facsimiles, copiers, hand scanners and the like.

[0002]

2. Description of the Related Art Equipment such as a facsimile, a copying machine, and a hand scanner is used as a device for reading a document.
An image reading device such as an image sensor is used. There are various types of image sensors, such as a reduction type, a contact type, and a perfect contact type. Among them, the contact-type image sensor is composed of an illuminating device, an equal-magnification imaging optical device, a sensor, and the like. In addition, such a contact-type image sensor generally has a shorter optical path length than that of a reduction-type image sensor, can downsize the device, and does not require troublesome optical adjustment, and can be easily incorporated into the device. There are some merits, and it has come to be widely used instead of the reduced type.

The illuminating device in such a contact image sensor must illuminate the document surface with an illuminance higher than that which can be read by the sensor. The area to be illuminated by the illuminating device is linear, and may be considerably long in the main scanning direction (hereinafter referred to as "longitudinal direction"), but may be extremely narrow in the sub-scanning direction orthogonal to the main scanning direction. . For example, in the case of A4 size used for facsimile, the length in the longitudinal direction is required to be 216 mm or more. Further, if the illuminance on the document surface is uneven in the longitudinal direction, it causes a reading error. Therefore, it is desirable that the illuminance be as uniform as possible.

As such an illuminating device, as shown in FIG.
A device using, for example, an LED array type light source device as shown in (1) is used by being incorporated in a one-dimensional image reading device such as a contact image sensor (see FIG. 11). This light source device has a large number of LEDs arranged in the longitudinal direction. Specifically, several tens (for example, 30) LEDs are arranged in a row on a printed wiring board by wire bonding or soldering. It is implemented in.

When such a light source device is incorporated in a contact type image sensor as shown in FIG. 11, the light emitted from the light source device passes through a cover glass which also serves as a platen glass, and a document to be read is read. To the SELFOC (registered trademark) lens array (hereinafter referred to as “SL”).
An image of a document is read by a photoelectric conversion element via a rod lens array such as A ”(registered trademark).

By the way, in such a conventional light source device, it cannot be said that the light emitted from the LED is efficiently used. The only light that is actually effective is the light that hits the thin reading line of the document to be read, and the other light is wasted light. There is also a method of bringing the illuminating device as close as possible to the side of the document to be read to make the illuminance of the read document line brighter and reducing the number of LEDs mounted by that amount, but in this case, large illuminance unevenness occurs,
This is an unrealistic method.

Further, in the light source device having such a structure, basically, the light amount unevenness occurs more or less depending on the mounting pitch of the LEDs. In addition, LED between the used LED
Variations in brightness occur due to variations in manufacturing. Therefore, if the number of LEDs mounted on one illuminating device is reduced, the unevenness of the light amount of the brightness of the reading line of the document to be read becomes large, which is extremely difficult to solve. If you want to eliminate such drawbacks, the LED installed
It is possible to reduce the number of devices, which contributes to cost reduction, power consumption reduction, and temperature rise suppression, resulting in a great advantage.

Therefore, in order to solve the above-mentioned problems, the applicant of the present invention has filed Japanese Patent Application No. 5-142427 and Japanese Patent Application No. 5-1.
No. 44908 proposes a rod-shaped illuminating device in which light-emitting elements are provided at both ends of a rod-shaped transparent body and a part of the surface of the transparent body is a light-scattering surface, and a scattering pattern thereof (see FIG. 12).
Furthermore, the inventors of the present invention disclose in Japanese Patent Application No. 5-180906.
The arrangement of the rod-shaped lighting device in the image reading device was proposed (see FIGS. 13 and 14).

In the illuminating device shown in Japanese Patent Application No. 5-180906, the optical axis is arranged substantially parallel to the document surface, and a reflecting surface for reflecting the light emitted from the illuminating device to the document surface is provided. It is provided (see FIGS. 13 and 14). Therefore, in the image reading device, the illumination light from the rod-shaped illuminating device can be effectively used, and the illuminating device can be arranged in a space-efficient manner, so that a compact image reading device can be realized.

[0010]

However, in order to meet the demand for further compactness of the image reading device (especially in the thickness direction), the image reading device using the rod-shaped illumination device of Japanese Patent Application No. 5-180906 discloses: There were inadequacies. That is, in FIGS. 13 and 14, the rod-shaped lighting device is arranged on the document surface side from the end surface of the rod lens array. Therefore, a certain distance is required between the end surface of the rod lens array and the cover glass that also serves as the document table. Further, in order to effectively use the illumination light from the rod-shaped lighting device, it is necessary to use a frame or the like to provide a reflecting surface. When the frame was made of metal, it was possible to utilize its metallic glossy surface. However, if a resin frame is used to reduce the weight, it is necessary to newly provide a reflecting surface.

Therefore, in the present invention, for example, Japanese Patent Application No. 5-18
In the rod-shaped lighting device shown in No. 0906, the rod-shaped lighting device in the image reading device can be arranged in a space-efficient manner, and the rod-shaped lighting device in the image reading device can be illuminated with high efficiency without providing a special reflecting surface. An object is to provide a lighting device.

[0012]

In order to achieve the above object, in the present invention, a rod-shaped lighting device having a long light-transmitting rod and a light source unit arranged near at least one end face of the rod. The rod has a columnar shape having a pentagonal shape in which one corner of a rectangle is removed, or a pillar having a polygonal shape in which two or more corners of a rectangle are removed. One of the resulting planes is a light emitting surface, and a rod-shaped lighting device in which a light diffusion layer is provided on a part of the other side surfaces except the two side surfaces adjacent to the light emitting surface.

In a document reading device composed of an illuminating device for illuminating the document surface, an equal-magnification imaging rod lens array for imaging light from the document surface on a photoelectric conversion element, and a frame, the illuminating device is the above-mentioned device. The rod-shaped lighting device is a document reading device in which one side surface of the transparent rod of the rod-shaped lighting device adjacent to the light emitting surface is close to or bonded to the side surface of the rod lens array.

First, the behavior of light in the transparent rod of the illuminating device is shown in FIGS. 8 and 9. First, when the light source unit and the transparent rod are placed in contact with or close to each other, most of the light generated from the light source unit is incident on the transparent rod. When the refractive index of the transparent rod is 1.5, the critical angle of total reflection at the interface with the outside air in the longitudinal direction of the transparent rod is about 41.8 °, and light with an incident angle θ exceeding 41.8 ° is at the interface. Light that is totally reflected and has an incident angle of 41.8 ° or less is emitted to the outside air.

If the light source unit and the transparent rod are coupled via the air layer, all the light that reaches the interface between the transparent rod and the outside air among the light incident on the transparent rod is totally reflected, and the inside of the transparent rod is the light source unit. And propagates to the other side. Of the light propagating in the transparent rod, the light that hits the light diffusing layer of, for example, white paint provided at the position in FIG. 9 is diffusely reflected by the light diffusing layer of white paint and reaches the light exit surface. Light having an incident angle of 41.8 degrees or less is emitted to the outside air. Light having an incident angle of more than 41.8 degrees propagates in the transparent rod again due to total reflection. Further, most of the light emitted from the interface other than the light emitting surface to the outside air is reflected by the cover covering the transparent rod and returned to the inside of the transparent rod again to realize a rod-shaped lighting device with less loss.

In the above description, the light diffusing layer is formed by printing white paint, but the color is not limited to white, and various colors can be used depending on the wavelength of the light used. be able to. For example, in a fax machine,
Since light with a wavelength of 570 nm is often used, a color with this wavelength may be used. Further, the light diffusing layer may be formed not only by printing a paint but also by adhering a film having a predetermined color.

The light that reaches the end of the transparent rod on the side opposite to the light source unit will fly out of the transparent rod to the outside air. If this end is also covered with a cover, the light reflected by the cover will disappear. It enters the transparent rod again and this time propagates through the transparent rod toward the light source unit side. As described above, covering the transparent rod around the light incident surface from the light source unit and the light emitting surface with a substance having a high light reflectance as much as possible helps to realize a highly efficient rod-shaped lighting device. . Even if only one side is covered with a cover, it is still effective.

Examples of the material of the transparent rod include a resin having a high light transmittance such as acrylic and polycarbonate, or an optical glass having a high light transmittance.

As shown in FIG. 3, the cross-sectional shape of the transparent rod is preferably a pentagonal shape in which the opposite corners of the rectangle are cut. Furthermore, as shown in FIG. 4A, the cross section may be a hexagon in which two opposite corners of a rectangle are cut. In addition, a hexagonal shape in which arbitrary two corners having a rectangular cross section are cut may be considered. In addition, as for the shape of the transparent rod, as long as two sets of side surfaces of the original quadrangular prism facing each other are left, even a hexagonal shape with a rectangular cross section cut from any three corners has all the corners cut. It may be octagonal. Furthermore, the cross section may be a quadrangle as shown in FIG. However, considering the ease of forming the transparent rod and the shape of the cover described later, the pentagonal cross section shown in FIG. 3 is preferable.

As the cover material having a high light reflectance, a white resin prepared by mixing a white colorant having a high reflectance, a member coated with a white paint on the surface, and of course, the color is not limited to white, Similar to the light diffusion layer, various colors can be used depending on the wavelength. In addition, a metal plate having originally high reflectance, such as an aluminum plate or a stainless plate, can be used. Also, it may be configured with a mirror.

The meaning of covering the transparent rod with a cover also has an effect of preventing the surface of the transparent rod from becoming dirty during handling in the assembly process.

[0022]

With the above-described structure, in the rod-shaped illumination device according to the present invention, first, two orthogonal surfaces adjacent to the light emitting surface of the transparent rod are respectively aligned with the optical axis of the equal-magnification imaging rod lens array in the image reading device. Since the light source devices can be arranged in parallel with each other and in parallel with the cover glass serving as a document table, the space efficiency of the light source device can be improved and the arrangement itself is easy.

Further, in the rod-shaped lighting device, the light is directly emitted from the transparent rod in the direction oblique to the object to be illuminated.
Light can be emitted. Therefore, Japanese Patent Application No. 5-18
Unlike the illuminating device shown in No. 0906, it is not necessary to specially provide a reflecting surface for reflecting the light emitted from the illuminating device to the original surface.

In addition, in the document reading apparatus according to the present invention, since one side surface of the transparent rod of the rod-shaped illuminating device which is adjacent to the light emitting surface is close to or adhered to the side surface of the rod lens array, the same magnification is obtained. The space between the imaging rod lens array and the cover glass that also serves as the document table can be reduced. Therefore, if a rod lens array having a space length matching this space is used, it is possible to contribute to miniaturization of the document reading device in the thickness direction. Further, the light emitting surface of the rod-shaped lighting device can be brought close to the illuminated portion of the cover glass, and the illumination light from the rod-shaped lighting device can be effectively utilized.

[0025]

【Example】

(Example of Rod-Shaped Lighting Device) FIG. 1 shows a perspective view of an embodiment of the rod-shaped lighting device according to the present invention. In FIG.
The light source unit 2 is composed of LEDs, and the transparent rod 3 has a light diffusion layer on which white paint is printed. The white cover 4 covers the three sides of the transparent rod. FIG. 2 shows an exploded view of the rod-shaped lighting device.

FIG. 3 shows a perspective view of the transparent rod. Here, the transparent rod has a pentagonal shape in which one corner of the rectangle is cut. 1 of this prismatic transparent rod
A surface obtained by cutting the corner by the C surface is used as the light emitting surface 32. The surface that becomes the light emitting surface may be a flat surface, or may be a convex surface or a concave surface depending on the shape of the illuminated region.

Further, the light diffusion layer 31 has the light emitting surface 32.
A white paint, for example, is printed in a pattern shown in FIG. 3 on a part of one of the surfaces facing each other. This pattern is an example of the case where the light source unit is provided at one end of the transparent rod. When the light source units are provided at both ends of the transparent rod, the pattern may be such that the width is narrow at both ends of the transparent rod and wide at the center of the transparent rod. See FIG. As described above, the pattern of the light scattering layer is formed according to the distance from the light source unit, so that the uneven illuminance in the main scanning direction is eliminated.

Further, in this drawing, the light diffusing layer is provided on one of the surfaces facing the light emitting surface 32, but the light diffusing layer may be provided on both of the two surfaces facing the light emitting surface. . Further, the position where the light diffusion layer is provided is preferably provided at a position on one side surface of the transparent rod on the extension line of the illuminated position and the light emitting surface.

FIG. 6 shows a structural example of a light source unit composed of four LEDs. Here, 4 LEDs2
1 is mounted on a printed circuit board 22 by wire bonding, and is coated and protected by a transparent epoxy resin 24 thereon. Epoxy resin flow stop and L
In order to prevent divergence of the light emitted from the ED and guide the light into the transparent rod 3 as much as possible, a white resin frame 23 formed by insert injection molding is provided.

(Example of Contact Image Sensor) FIG. 7
FIG. 9 shows a sectional view of a contact image sensor equipped with the rod-shaped lighting device shown in the above embodiment. As can be seen from this figure, the light emitting surface 32 of the transparent rod is located in front of the document surface side end surface 61 of the rod lens array. Furthermore, most of the rod-shaped lighting device shown in the above-mentioned embodiment can be arranged behind the document surface side end surface 61 of the rod lens array. Therefore, the space between the document surface side end surface 61 of the lens array and the cover glass back surface 72 can be reduced.

Therefore, if the space length of the lens array is appropriately selected, the length of the contact type image sensor in the thickness direction can be made as small as possible.

The surface of the transparent rod 3 that is in contact with the light emitting surface 32 and is not covered with the cover 4 is covered with the cover to improve the light utilization efficiency. However, if the cover is covered with a certain thickness, the document reading position 7
The distance between the light emitting surface 32 and the light emitting surface 32 is increased, and the brightness at the reading position is reduced. Therefore, covering with a thick cover is not a good idea. In order to improve the light utilization efficiency, it is desirable to provide a thin reflective layer or the like on this surface.

[0033]

According to the present invention configured as described above, a rod-shaped lighting device having significantly higher efficiency than that of the conventional system and having high uniformity of light illuminance is realized, and as a result, L
The number of EDs can be reduced, the illuminance is highly uniform, and cost reduction, compactness, and low power consumption are realized, and the effect is extremely large.

[Brief description of drawings]

FIG. 1 is a structural perspective view showing an embodiment of a rod-shaped lighting device of the present invention.

FIG. 2 is a structural exploded perspective view of an embodiment of the rod-shaped lighting device of the present invention.

FIG. 3 is a structural perspective view illustrating a light diffusion layer of a transparent rod when a light source unit is provided on one side in the rod-shaped lighting device of the present invention.

FIG. 4 is a diagram illustrating a cross-sectional shape of a transparent rod in the rod-shaped lighting device of the present invention.

FIG. 5 is a structural perspective view illustrating a light diffusion layer of a transparent rod when light source units are provided on both sides in the rod-shaped lighting device of the present invention.

FIG. 6 is an explanatory diagram of a structural example of a light source unit used in the rod-shaped lighting device of the present invention.

FIG. 7 is a cross-sectional view of a structural example of a contact image sensor equipped with the rod-shaped lighting device of the present invention.

FIG. 8 is a view for explaining the behavior of light in the length direction of the transparent rod of the rod-shaped lighting device of the present invention.

FIG. 9 is a diagram for explaining the behavior of light in the cross-sectional direction of the transparent rod of the rod-shaped lighting device of the present invention.

FIG. 10 is a diagram illustrating a conventional LED array.

11 is a cross-sectional explanatory diagram of a document reading device using the LED shown in FIG.

FIG. 12 is a diagram illustrating a rod-shaped illumination body disclosed in Japanese Patent Application No. 5-142427.

FIG. 13 is an explanatory view (1) of a document illumination device in the image reading device disclosed in Japanese Patent Application No. 5-180906.

FIG. 14 is an explanatory view (2) of the document illuminating device in the image reading device disclosed in Japanese Patent Application No. 5-180906.

[Explanation of symbols]

1: Illumination device 11: Original illumination device disclosed in Japanese Patent Application No. 5-180906 2: Light source unit 21: LED 22: Printed circuit board 23: Resin frame 24: Transparent resin 25: Terminal part 26: LED array 3: Transparent Rod 31: Light diffusion layer 32: Light emitting surface 33: Transparent light source unit mounting surface 4: Cover 41: Inner surface of cover 5: Photoelectric conversion element 6: Rod lens array 61: End surface of original surface of rod lens array 7: Cover glass 71: Original surface (of cover glass) 72: Back surface of cover glass 73: Original reading position 8: Frame 81: Reflective surface

Claims (10)

[Claims] 1. A rod-shaped lighting device having a long light-transmitting rod and a light source unit arranged near at least one end face of the rod, wherein the rod has a rectangular cross section. Is a columnar shape having a pentagon removed, or a columnar shape having a polygonal cross-sectional shape in which two or more corners of a rectangle are removed,
One of the planes formed by the removal is a light emitting surface,
A rod-shaped lighting device, wherein a light diffusing layer is provided on a part of the other side surfaces except the two side surfaces adjacent to the light emitting surface. 2. The rod-shaped lighting device according to claim 1, wherein at least one surface other than the end surface on which the light emitting unit and the light source unit are arranged has a cover provided with a thin air layer therebetween. 3. The rod-shaped lighting device according to claim 1, wherein the light source unit includes one or a plurality of LEDs. 4. The rod-shaped lighting device in a document reading device according to claim 1, wherein the light diffusion layer is made of a paint or a film that diffuses the light emitted from the light source unit. 5. The light diffusing layer is a strip along the longitudinal direction of the transparent rod, and the width of the diffusing layer near the light source unit side is narrow, and the light diffusing layer becomes closer to the light source unit. The rod-shaped lighting device according to claim 4, wherein the width is wide. 6. The rod-shaped lighting device according to claim 1, wherein the rod-side surface of the cover is a surface that reflects light emitted from the light source unit. 7. The rod-shaped lighting device according to claim 6, wherein the surface of the cover on the rod side is made of a white resin, or an aluminum plate or a stainless plate. 8. The rod shape according to claim 7, wherein the cover has a shape that covers the light emitting surface, the end surface on the light source unit side, and all the surfaces except one side surface adjacent to the light emitting surface. Lighting equipment. 9. An original reading device comprising an illuminating device for illuminating a document surface, an equal-magnification imaging rod lens array for imaging light from the document surface on a photoelectric conversion element, and a frame, wherein the illuminating device comprises: The rod-shaped lighting device according to any one of claims 1 to 8, wherein one side surface of the transparent rod of the rod-shaped lighting device that is adjacent to the light emitting surface is adjacent to or bonded to a side surface of the rod lens array. Document reading device. 10. The document reading device according to claim 9, wherein a reflective layer is provided on the one side surface of the transparent rod.