JP2999680B2 - Rod illumination device and document reading device using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Devices such as facsimile machines, copiers, hand scanners, etc.
An image reading device such as an image sensor is used. There are various types of image sensors, such as a reduced type, a contact type, and a complete contact type. Among them, the contact-type image sensor includes an illumination device, an equal-magnification image forming optical device, a sensor, and the like. In general, such a contact type image sensor has a shorter optical path length, can be downsized, and has no troublesome optical adjustment as compared with a reduced type image sensor. There are certain advantages, and it has been increasingly used instead of the reduced type.

The illuminating device in such a contact type image sensor must illuminate the document surface with an illuminance higher than the illuminance that can be read by the sensor. The range to be illuminated by the illuminating device is linear, and is considerably long in the main scanning direction (hereinafter, referred to as “longitudinal direction”), and 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 of the document surface is uneven in the longitudinal direction, a reading error is caused. Therefore, it is desirable that the illuminance is as uniform as possible.

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

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 And the reflected light is transmitted to a SELFOC (registered trademark) lens array (hereinafter referred to as “SL”).
A (registered trademark)), the image of the original is read by the photoelectric conversion element via a rod lens array.

However, it cannot be said that such a conventional light source device efficiently uses light emitted from an LED. The only effective light is the light that hits the thin reading line of the document to be read, and the other light is useless light. There is also a method in which the illuminating device is brought as close as possible to the original to be read, so that the illuminance of the read original line is increased and the number of mounted LEDs is reduced accordingly, but in this case, large uneven illuminance occurs.
It is an unrealistic way.

Further, in the light source device having such a configuration, the light amount unevenness occurs more or less basically at the mounting pitch of the LEDs. Furthermore, the LED between the used LED
Brightness variations occur due to manufacturing variations of the device itself. Therefore, if the number of LEDs mounted on one illuminating device is reduced, the unevenness in the brightness of the read line of the document to be read becomes large, and the solution is extremely difficult. If you want to solve such disadvantages,
Can be reduced, which is useful for cost reduction, reduction of power consumption and suppression of temperature rise, and a great merit arises.

In order to solve the above-mentioned problems, the present applicant has proposed Japanese Patent Application Nos. 5-142427 and 5-1.
No. 44908 proposes a rod-shaped lighting 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).
Further, the present inventors have disclosed in Japanese Patent Application No. 5-180906,
The arrangement of the rod-shaped illumination device in the image reading device was proposed (see FIGS. 13 and 14).

In the illuminating device disclosed in Japanese Patent Application No. 5-180906, the optical axis of the illuminating device is substantially parallel to the original surface, and a reflecting surface for reflecting light emitted from the illuminating device to the original surface is provided. (See FIGS. 13 and 14). For this reason, in the image reading device, the illumination light from the rod-shaped illumination device can be used effectively, and the illumination device can be arranged with a good space efficiency, so that a compact image reading device can be realized.

[0010]

However, in order to further reduce the size of the image reading device (particularly in the thickness direction), the image reading device using the rod-shaped illumination device disclosed in Japanese Patent Application No. 5-180906 is disclosed. There were insufficient points. That is, in FIGS. 13 and 14, the rod-shaped illumination device is arranged closer to the document surface than the end surface of the rod lens array. For this reason, a certain distance is required between the end surface of the rod lens array and the cover glass also serving as the document table. Further, in order to effectively use the illumination light from the rod-shaped illumination device, a reflection surface must be provided using a frame or the like. When the frame was made of metal, it was possible to use the metallic glossy surface. However, when a resin frame is employed for weight reduction, it is necessary to newly provide a reflection surface.

Therefore, in the present invention, for example, Japanese Patent Application No. Hei.
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 capable of high-efficiency lighting without providing a special reflecting surface. An object is to provide a lighting device.

[0012]

In order to achieve the above object, according to the present invention, there is provided a rod-shaped illuminating device having a long light-transmitting rod and a light source unit disposed near at least one end face of the rod. Wherein the rod has a columnar shape having a pentagonal shape with one corner of a rectangle removed, or a columnar shape having a polygonal shape with a cross-section having two or more rectangles removed. One of the resulting flat surfaces is a light emitting surface, and the rod-shaped lighting device has a light diffusing layer provided on a part of another side surface except two side surfaces adjacent to the light emitting surface.

[0013] In a document reading apparatus comprising an illumination device for illuminating the original surface, a 1: 1 imaging rod lens array for forming an image of light from the original surface on a photoelectric conversion element, and a frame, the illumination device may be configured as described above. An original reading device is a rod-shaped illumination device, wherein one side surface of the transparent rod of the rod-shaped illumination device adjacent to the light emitting surface is close to or adhered to a side surface of the rod lens array.

First, the behavior of light in the transparent rod of the lighting device is shown in FIGS. 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 enters the transparent rod. Assuming that the refractive index of the transparent rod is 1.5, the critical angle of total reflection at the interface between the transparent rod and the outside air in the longitudinal direction is about 41.8 °, and light having an incident angle θ exceeding 41.8 ° is reflected 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 connected via an air layer, of the light incident on the transparent rod, all the light that reaches the interface between the transparent rod and the outside air is totally reflected, and the light source unit passes through the inside of the transparent rod. And propagate toward the opposite side. Among the light propagating in the transparent rod, the light that hits the light diffusion layer of, for example, white paint provided at the position in FIG. 9 is irregularly reflected by the light diffusion layer of white paint and reaches the light exit surface. Of the light, light having an incident angle of 41.8 degrees or less is emitted to the outside air. Light having an incident angle exceeding 41.8 degrees propagates again through the transparent rod by total reflection. Most of the light emitted from the interface other than the light exit surface to the outside air is reflected by the cover covering the transparent rod and returned to the inside of the transparent rod again, thereby realizing a rod-shaped lighting device with less loss.

In the above description, the light diffusion layer is formed by printing a white paint. However, the color is not limited to white, and various colors may be used according to the wavelength of light to be used. be able to. For example, in facsimile
Since light having a wavelength of 570 nm is often used, a color having this wavelength may be used. The light diffusion layer may be formed not only by printing a paint but also by sticking a film having a predetermined color.

The light that reaches the end of the transparent rod opposite to the light source unit jumps out of the transparent rod to the outside air. If this end is also covered with the cover, the light reflected by the cover will not be reflected. It again enters the transparent rod, and then propagates through the transparent rod toward the light source unit. As described above, it is useful to realize a more efficient rod-shaped lighting device by covering the periphery of the transparent rod with a substance having the highest possible light reflectance except for the light incident surface from the light source unit and the light emitting surface. . Covering only one side with a cover has some effect.

As the material of the transparent rod, for example, a resin having a high light transmittance such as acrylic or polycarbonate, or an optical glass having a high light transmittance can be used.

As shown in FIG. 3, the cross-sectional shape of the transparent rod is preferably a pentagonal shape in which a cross section of the rectangular shape is formed by cutting opposite corners. Further, 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 hexagon whose cross section is formed by cutting arbitrary two corners of a rectangle is also conceivable. In addition, as for the shape of the transparent rod, all the corners were cut, even if the cross section of the original quadrangular prism was a hexagon in which any three corners of the rectangle were cut as long as two opposing side faces of the prism were left. It may be octagonal. Further, 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 preferably shaped.

Examples of the cover material having a high light reflectance include a white resin prepared by mixing a white coloring material having a high reflectance, and a member having a surface coated with a white paint. Needless to say, the color is not limited to white. As with the light diffusion layer, various colors can be used according to the wavelength. In addition, a metal plate having a high reflectivity, such as an aluminum plate or a stainless steel plate, may be used. Moreover, it is good also as comprising a mirror.

Further, covering the transparent rod with a cover also has the effect of preventing the surface of the transparent rod from being stained during handling in the assembly process.

[0022]

With the above arrangement, the rod-shaped illumination device according to the present invention firstly sets two orthogonal surfaces adjacent to the light exit surface of the transparent rod with respect to the optical axis of the same-magnification imaging rod lens array in the image reading device. The light source device can be arranged in parallel with the cover glass serving as the document table, so that the space efficiency of the arrangement of the light source device is good and the arrangement itself is easy.

Further, the rod-shaped lighting device is provided so that the rod-shaped lighting device is directly oblique to the object to be illuminated from the light emitting surface of the transparent rod.
Light can be emitted. For this reason, Japanese Patent Application 5-18
There is no need to specially provide a reflecting surface for reflecting light emitted from the illuminating device to the document surface as in the illuminating device disclosed in No. 0906.

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

[0025]

【Example】

(Embodiment of the rod-shaped lighting device) FIG. 1 is a perspective view of an embodiment of the bar-shaped lighting device according to the present invention. In FIG.
The light source unit 2 is composed of an LED, and the transparent rod 3 has a light diffusion layer printed with white paint. The white cover 4 covers three sides of the transparent rod. FIG. 2 shows an exploded view of the rod-shaped lighting device.

FIG. 3 is a perspective view of the transparent rod. Here, the cross section of the transparent rod has a pentagonal shape obtained by cutting one corner of a rectangle. One of these prismatic transparent rods
The light-emitting surface 32 is formed by cutting the corner at the C-plane. The surface serving as 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 area.

Further, the light diffusion layer 31 is provided on the light exit surface 32.
For example, a white paint is printed on a part of one of the surfaces opposed to the above in the pattern shown in FIG. This pattern is an example in which a light source unit is provided at one end of a 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 the width is large at the center of the transparent rod. See FIG. As described above, by forming the pattern of the light scattering layer in accordance with the distance from the light source unit, it is possible to eliminate illuminance unevenness in the main scanning direction.

Further, in this figure, the light diffusion layer is provided on one of the surfaces facing the light exit surface 32. However, the light diffusion layer may be provided on both of the two surfaces facing the light exit surface. . Further, it is preferable that the light diffusion layer is provided at a position on one side surface of the transparent rod on the extension of the light receiving position and the light emitting surface.

FIG. 6 shows a structural example of a light source unit composed of four LEDs. Here, four LEDs 2
1 is mounted on a printed circuit board 22 by wire bonding, and is coated and protected with a transparent epoxy resin 24 thereon. Epoxy resin flow stopper and L
In order to prevent the light emitted from the ED from diverging and to guide the light into the transparent rod 3 as much as possible, a white resin frame 23 is provided by an insert injection molding method.

(Embodiment of Contact Image Sensor) FIG. 7
FIG. 7 is a cross-sectional view of a contact image sensor equipped with the bar-shaped lighting device described in the above embodiment. As can be seen from this figure, the light exit surface 32 of the transparent rod is located forward of the document surface side end surface 61 of the rod lens array. Further, most of the rod-shaped illumination device shown in the above embodiment can be disposed behind the end surface 61 of the rod lens array on the document surface side. 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 which is in contact with the light emitting surface 32 and is not covered with the cover 4 is also covered with the cover, so that the light use efficiency is increased. However, if the surface is covered with a thick cover, the original reading position 7
The distance between the light emitting surface 2 and the light exit surface 32 is increased, and the brightness of the reading position is reduced. Therefore, it is not advisable to cover with a thick cover. In order to increase the light use 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 which is much more efficient than the conventional method and has a high uniformity of light illuminance is realized.
The number of EDs can be reduced, the illuminance can be made more uniform, the cost can be reduced, the size can be reduced, and the power consumption can be reduced.

[Brief description of the drawings]

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

FIG. 2 is an exploded perspective view showing the structure of a rod-shaped lighting device according to an embodiment 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 illumination 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 an example of the structure of a contact image sensor equipped with the bar-shaped illumination 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 view 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.

FIG. 11 is an explanatory sectional view of a document reading apparatus using the LED shown in FIG. 8;

FIG. 12 is a view for explaining a rod-shaped illumination body disclosed in Japanese Patent Application No. 5-142427.

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

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

[Explanation of symbols]

1: Illumination device 11: Document 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 26: LED array 3: Transparent Rod 31: Light diffusing layer 32: Light emitting surface 33: Light source unit mounting surface of transparent rod 4: Cover 41: Inner surface of cover 5: Photoelectric conversion element 6: Rod lens array 61: Document lens side end 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

──────────────────────────────────────────────────続 き Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H04N 1/04 101 G02B 6/00-6/00 346

Claims (9)

(57) [Claims] 1. A rod-shaped lighting device comprising: a long transparent rod made of resin or glass; and a light source unit disposed near at least one end face of the rod, wherein the rod is A cross-sectional shape of a column having a pentagon with one corner of a rectangle removed, or a cross-sectional shape of a column having a polygon with two or more corners of a rectangle removed,
One of the planes formed by the removal is a light emitting surface,
Illuminated position and position of rod side surface on extension of the light exit surface
The light diffusion layer is provided on the location, a cover for covering at least one side surface other than the light emitting surface of the rod is provided, the rod-side surface of the mosquito <br/> bar reflects light which the light source unit emits A bar-shaped lighting device characterized by having a surface. 2. The rod-shaped lighting device according to claim 1, wherein a thin air layer is provided between the cover and the light-emitting surface of the rod and at least one surface other than an end surface on which the light source unit is disposed. . 3. The rod-shaped lighting device according to claim 1, wherein the light source unit includes one or a plurality of LEDs. 4. The light diffusion layer is made of a paint or a film that diffuses light emitted from the light source unit.
2. The rod-shaped lighting device according to 1. 5. The light-diffusing layer is band-shaped along the longitudinal direction of the transparent rod, and the width of the light-diffusion layer near the light source unit side is small, and the light-diffusion layer becomes more distant from the light source unit. The rod-shaped lighting device according to claim 4, wherein the width of the layer is large. 6. The rod-shaped lighting device according to claim 1, wherein the cover has a surface on the rod side made of a white resin, or made of an aluminum plate or a stainless steel plate. 7. The rod-shape according to claim 6, wherein the cover covers the light emission surface, the end surface on the light source unit side, and all other surfaces except one side surface adjacent to the light emission surface. Lighting equipment. 8. A document reading device comprising: an illuminating device for illuminating a document surface; a 1 × image forming rod lens array for imaging light from the document surface onto a photoelectric conversion element; and a frame. The rod-shaped lighting device according to any one of claims 1 to 7, wherein the transparent rod of the rod-shaped lighting device has a light emitting surface that irradiates the document surface obliquely.
Of the two orthogonal side surfaces adjacent to the light exit surface
Place the larger side horizontally so that it is parallel to the original
The rod lens has an optical axis with respect to the document surface.
The transparent rod has a light exit surface that is a rod lens
The relationship between the position of the array closer to the original side than the original side
It has been, the document reading apparatus characterized by being close to or adhered to the side of one side surface Gallo head lens array adjacent to the light emitting surface. 9. The document reading apparatus according to claim 8, wherein a reflection layer is provided on the one side surface of the transparent rod.