JP2003060854A - Line illuminator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a line illuminator, which can be made compact and light in weight, especially, can be made thin, improves efficiency in the utilization of light and further can emit the light of uniform illuminance. SOLUTION: In a light illuminator 1 composed of a light transmission body 2, a cover for housing the light transmission body 2 and a light source, the light transmission body 2 is composed of a transparent rod having a light incident plane on one end at least, has a projecting wire 9 on one face parallel to the lengthwise direction of the rod and has a light scattered area 10 on the face opposed to the face having the projecting wire 9, and the upper face of the projecting wire 9 is a line-shaped light emission plane 6. In the cover, an inner face confronted to the light transmission body 2 is a plane for reflecting light, a side face 13 of the projecting wire 9 is covered while having a slit 12 to fit the projecting wire 9 and the light source is located on the light incident plane 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line illuminator used when reading an image. In particular, the present invention relates to a line illumination device that allows light from a light source to enter a transparent light guide body and to emit the light uniformly in a line shape.

[0002]

2. Description of the Related Art Image sensors are used as image reading devices in devices such as facsimiles, copiers and scanners. Among them, the contact image sensor is composed of an illuminating device, a unity-magnification imaging optical device, a line sensor, and the like, and has a short optical path length and can be downsized. A line illumination device is usually used for such a contact image sensor. The line illumination device is a device that is long in the main scanning direction (longitudinal direction) and can illuminate narrowly in the sub scanning direction orthogonal to the main scanning direction.
Such a line illumination device can be used not only for reading an image but also for an image writing device such as a printer.

As a line lighting device, an LED array lighting device is known in which a large number of LEDs are mounted on a printed wiring board in a line by wire bonding or soldering. However, in a lighting device in which a large number of such LEDs are arranged, the portion other than the necessary line is also illuminated, and the light utilization efficiency is not high. Also, a large number of L
Since the ED is used, the power consumption is large.

Further, in JP-A-8-163320 and JP-A-8-172512, a line illumination is provided in which a light emitting element (LED) is provided at one end of a rod-shaped transparent body and a part of the transparent body surface is used as a light scattering surface. The device is described. The line lighting devices disclosed in these publications aim to reduce the cost by disposing the light emitting element only on one end of the rod-shaped transparent body,
The shape of the light-scattering pattern formed on the surface of the rod-shaped transparent body in order to obtain a uniform illuminance along the longitudinal direction, the area of the light-scattering pattern is gradually increased from one end where light is incident from the light emitting element to the other end. Is supposed to expand.

Further, in Japanese Patent Laid-Open No. 2000-307808, a plurality of LEs that can be independently lit are provided at one end of a transparent light guide.
There is described a line illuminator in which a light source unit made of D is provided and a light scattering pattern is formed on a surface of the light guide body which faces the light emission surface. The line illuminator is described as being useful for reading color images.

[0006]

The above-mentioned conventional line lighting device can be mounted on various office equipment such as a facsimile, a copying machine, and a scanner, and contributes to downsizing thereof. However, in recent years, various information communication devices have become portable. For example, mobile phone, PD
Small devices such as A (Personal Digital Assistance), digital cameras, and game consoles that can be easily carried by individuals are widely used.

[0007] In such small portable information communication devices, it has been desired to have a function of reading and writing images. However, since the above-mentioned conventional line lighting device is rather intended mainly for use in office equipment for indoor installation, the degree of miniaturization is not always sufficient. Further reduction in size and weight is desired so that it can be incorporated in a small portable information communication device.

Further, since these devices are driven by batteries, power saving is indispensable, and therefore further improvement in light utilization efficiency is required. And at this time,
It is desired not only to increase the amount of emitted light, but also to provide an illumination device with a uniform irradiation width and a uniform emission direction of light. By doing so, the compatibility with the device to be illuminated becomes good, and the device can be easily incorporated into various devices.

The present invention has been made in order to solve such problems, and it is possible to reduce the size and weight of the device, in particular to reduce the thickness thereof, and to use the light with high efficiency and to emit the light of uniform illuminance. The present invention provides a possible line lighting device.

[0010]

[Means for Solving the Problems] The above problems include a light guide,
A line lighting device comprising a cover for accommodating the light guide and a light source, wherein the light guide comprises a transparent rod having a light incident surface at least at one end thereof and is parallel to a longitudinal direction of the rod. A ridge is formed on one surface, a light-scattering region is provided on a surface facing the surface having the ridge, and an upper surface of the ridge is a linear light emitting surface, and the cover is a light guide. An inner surface facing the light is a surface that reflects light, has a slit in which the projection is fitted to cover the side surface of the projection, and the light source is arranged on the light incident surface. This is accomplished by providing a lighting device.

By emitting the light from the upper surface of the convex stripe formed on the light guide, the irradiation width can be made uniform.
In particular, even if the width of the light scattering region is not uniform along the longitudinal direction of the transparent rod as described below, the width of the emitted light can be made uniform. Further, by arranging the light scattering region on the surface facing the surface having the ridge,
It is also possible to reduce variations in the light emission direction.

Further, when the light entering the light guide from the light source is emitted from the upper surface of the convex stripe, it is preferable that the side surface of the convex stripe is covered with a cover whose inner surface reflects the light.
By doing so, light can be efficiently emitted from the upper surface of the ridge, and the proportion of light having an excessively large emission angle can be reduced.

At this time, the rod is flat, and the projection is provided on the wide surface of the rod, so that the light guide can be made thin in the light emission direction. Since many portable information communication devices are thin, it is important to be able to provide a thin lighting device. In addition, it is preferable that the cross-sectional shape of the ridge is substantially quadrangular because the side surface of the ridge can be easily covered with a cover.

Further, since the cover covers all portions except the light incident surface and the light emitting surface, light can be efficiently emitted only from the upper surface of the ridge, and unnecessary light is emitted to other portions. This is preferable because it does not occur.

The light-scattering region formed on the surface opposite to the surface having the convex stripe is a continuous strip along the longitudinal direction of the rod, and the width of the region near the light source is narrow, and the light scattering region is separated from the light source. According to this, it is preferable that the width of the region is widened so that the illuminance distribution along the longitudinal direction of the linear light emitting surface can be made uniform.

It is preferable that the light source is composed of a light source unit composed of a plurality of point light sources that can be turned on independently, and emits light in a direction substantially perpendicular to the direction in which the plurality of point light sources are arranged. By individually turning on a plurality of point light sources having different wavelengths, it is possible to read and write a color image. Further, by making the arrangement direction of the plurality of point light sources substantially perpendicular to the light emission direction, the lighting device can be made thin.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below with reference to the drawings. FIG. 1 is an exploded perspective view of a line lighting device that is an example of an embodiment of the present invention. FIG. 2 is a plan view of the assembled line lighting device. 3 is a front view (a back view is symmetrical with the front view), FIG. 4 is a left side view thereof, FIG. 5 is a right side view thereof, and FIG. 6 is a bottom view thereof. FIG. 7 is a plan view of a light guide incorporated in the above line illuminating device, FIG. 8 is a front view thereof (a back view is symmetrical with the front view), and FIG. 9 is a left side view thereof (right side view is a left side view). FIG. 10 is a bottom view of the same. 11 is a sectional view taken along the line AA ′ in FIG. 2, and FIG. 12 is a sectional view at a position equivalent to that in FIG. 11 showing another embodiment of the present invention.
FIG. 3 is a sectional view at a position equivalent to that of FIG. 11 showing still another embodiment. FIG. 14 shows an example to be compared with the present invention shown in FIG.
It is sectional drawing in a position equivalent to. Further, FIG. 15 is a view of the light source unit viewed from the light incident surface side. FIG. 16 shows FIG.
It is a BB 'sectional view of.

As shown in FIG. 1, the line lighting device 1 includes:
The light guide 2 is covered with the upper cover 3 and the lower cover 4, and the light incident surface 5 and the light emitting surface 6 are exposed from both the covers. The light source unit 7 is arranged. The total length of the device is about 60 mm and its width is about 9 mm. The light generated by the light source unit 7 enters the light guide 2 through the light incident surface 5 and is emitted upward through the light emitting surface 6. The thickness of the assembled line illuminator 1 at the light emitting portion is about 2.3 mm. While many conventional line illuminators have a thickness of about 4 to 5 mm, the line illuminator 1 of this example has a thickness of 3 mm or less, which is extremely useful for mounting on a portable device.

First, the structure of the light guide 2 will be described.
The light guide 2 is made of a transparent rod whose one end is a light incident surface 5, and has a ridge 9 on one surface 8 parallel to the longitudinal direction of the rod, and the upper surface of this ridge 9 is a line. The light emitting surface 6 is shaped like a circle. The cross-sectional shape of the light guide 2 perpendicular to the longitudinal direction is a flat rectangle except for the portion of the ridge 9. By making the cross section of the light guide 2 a flat shape in the vertical direction and disposing the ridges 9 on the wide surface thereof, a thin lighting device can be obtained, and in response to the demand for thinning of the equipment used. To be The sectional shape is not limited to a rectangle, and the corners may be chamfered appropriately,
There may be a curved part. The cross-sectional shape of the ridge 9 in this example is trapezoidal. The light emitting surface 6 formed on the upper surface has a length of about 53 mm and a width of 0.5 mm, and can emit narrow line-shaped light.

As the material of the light guide body 2, resin or optical glass having high light transmittance can be used. Since it is low in cost and lightweight, it is preferably made of transparent resin, and acrylic resin or polycarbonate resin is preferably used. The surface of the light guide 2 is a smooth surface that does not scatter light, except for a light scattering region 10 described later.

The light incident from the light incident surface 5 travels in the longitudinal direction of the light guide 2. At this time, the light reaching the interface between the light guide 2 and the air is refracted at the interface and emitted to the air, and the light reflected at the interface and traveling inside the light guide 2. Divided into Assuming that the refractive index of the transparent body forming the light guide 2 is 1.5, the critical angle at the interface with the outside (air having a refractive index of 1) is 41.8 degrees, and thus the incident angle is larger than this. The light is totally reflected and propagates in the light guide 2.

A light-scattering region 10 is formed on the surface of the light guide 2 facing the surface having the ridges 9, that is, the lower surface 11. The light-scattering region 10 has a strip shape continuous along the longitudinal direction of the transparent rod, and the width of the region near the light source unit 7 is narrow, and the width of the region increases as the distance from the light source unit 7 increases. . This light scattering area 1
0 is formed by screen-printing a white paint. The color of the light scattering region 10 is not limited to white, and various colors can be used depending on the wavelength of light used, but it is preferably white when handling a color image. The light scattering region 10 may be formed not only by a method of printing a paint on the lower surface 11 of the light guide 2 but also by adhering a white film, or by forming unevenness on the lower surface 11 of the light guide 2 capable of light scattering. It may be provided and formed. In this example, since the lower surface 11 of the light guide 2 is flat, printing and pasting are easy.

The light propagating in the light guide 2 has the light scattering region 1
By scattering and reflecting at 0, the traveling direction is changed toward the ridge 9 on the opposite surface, and the light emitting surface 6 on the upper surface of the ridge 9 is changed.
Can emit light. Since the width of the light scattering region 10 near the light source unit 7 is narrow and the width of the light scattering region 10 increases as the distance from the light source unit 7 increases, the area contributing to scattering is small at a position close to the light source. At a position distant from, the area contributing to scattering becomes large, and as a result, the illuminance in the longitudinal direction can be made uniform. In this example, the area of the light-scattering region 10 increases linearly, but the increase rate can be appropriately adjusted to obtain a uniform illuminance distribution. The shape of the light-scattering region 10 is not limited to the band shape as in this example, and it is also possible to form a discontinuous dot shape such that the arrangement density is low near the light source and high in the distance from the light source. In the present invention, since the light guide 2 is extremely thin, local unevenness of illuminance is more likely to occur in the dot shape when compared with the conventional thickness, so that the light guide 2 has a continuous strip shape. Is preferred.

The light guide 2 includes an upper cover 3 and a lower cover 4.
It is covered with and. The upper cover 3 is a ridge 9 of the light guide 2.
Has a slit 12 for fitting with, and covers the side surface 13 of the ridge 9 of the light guide 2, the surface 8 having the ridge, and the three sides of the light guide except the light incident surface 5. The upper cover 3 is formed by injection molding a resin containing a white pigment. The lower cover 4 is a film containing a white pigment and having a thickness of 188 μm.

The cover preferably has an inner surface facing the light guide 2 that reflects light. As the material for the cover, a resin containing a white pigment having a high reflectance, a material having a surface coated with white paint, or the like is used. The color is not limited to white, and other colors may be used depending on the wavelength of light used, but white is preferable when handling a color image. It is also possible to use a metal plate having a high reflectance, such as an aluminum plate or a stainless plate,
A mirror may be placed on the inner surface. With such a configuration, most of the light emitted from the light guide 2 into the air and reaching the inner surface of the cover can be reflected and enter the inside of the light guide 2 again. Therefore, the light guide 2 of the cover
To increase the reflectance of the inner surface facing the
This helps realize a more efficient lighting device. Further, since the cover covers substantially all the portions except the light incident surface 5 and the light emitting surface 6, the light formed on the upper surface 8 of the ridge 9 does not emit unnecessary light from other portions. This is preferable because light can be efficiently emitted from only the emission surface 6. However, the small gaps that can occur during assembly are rarely a problem.

An air layer is preferably provided between the cover and the light guide 2. This is because the critical angle at the interface between the light guide 2 and the air becomes smaller due to the difference between the refractive index of the light guide 2 and the refractive index of air, and the proportion of light that is totally reflected can be increased. When the cover and the light guide 2 are completely in close contact with each other, the light cannot be totally reflected, which is not preferable in terms of light utilization efficiency. However, in the case of an ordinary plastic molded product containing a white pigment, the molded product is flat at the wavelength level of visible light due to molding shrinkage and fine surface irregularities derived from the pigment contained inside. Therefore, there is no need to make any special efforts during molding. However, it is not preferable to press-fit the light guide 2 and the cover unnecessarily because the proportion of the light totally reflected may be reduced. Therefore, for example, the ridge 9 of the upper cover 3
The size of the slit 12 into which is fitted is designed to be slightly larger than the size of the ridge 9, for example, about 0.1 mm.

Further, it is not preferable that the light guide 2 is directly contacted with the adhesive or the like at the time of assembly because the interface between the light guide 2 and the air layer is destroyed at that portion. Therefore, only the upper cover 3 and the lower cover 4 are bonded with an adhesive, and the light guide 2 is held between them. In this example, in the lower cover 4, a pressure sensitive adhesive application region 14 is formed in a portion in contact with the upper cover 3, and the upper and lower covers are bonded via this. Since the adhesive has an appropriate elasticity, it is preferable because the cover and the light guide body are not unnecessarily strongly pressed against each other. Such an adhesive may be formed by cutting out from a so-called double-sided adhesive tape and adhering it, or may be formed by printing an adhesive. Also, other types of adhesives having appropriate elasticity may be used.

The light guide 2 and the light source unit 7 covered by the cover are provided with two protrusions 15 provided at one end of the upper cover 3.
Is inserted into the projection insertion hole 16 provided in the light source unit 7, the hot plate is pressed against the penetrating projection 15 to be softened and deformed, and the assembly is accurately assembled by caulking. After assembly, the caulking portion 17 is formed on the outer surface of the light source unit 7.

The light source unit 7 of this example has four LED light emitting elements. The LED light emitting element chip is mounted on the printed circuit board so as to be connected to the wiring portion 18 via a bonding wire 19, and is further protected by a transparent epoxy resin 20. When viewed from the side of the light guide 2, the yellowish green color L
ED21 (center wavelength; 574 nm), yellow-green LED22
(Same), the red LED 23 (center wavelength; 655 nm), and the blue LED 24 (center wavelength; 470 nm) are arranged in this order in the horizontal direction from the right. These LEDs can be turned on individually for each color, and by illuminating each color, it is possible to read or write a color image. The reason why there are two yellow-green LEDs is to improve the illuminance in this wavelength range in accordance with the sensitivity of the light receiving portion, and even if there is only one LED, there is no problem in handling a color image depending on the specifications. For example, instead of using the two yellow-green LEDs above, a green LED (525
(nm) is also exemplified.

In this example, the red LEDs 23 are displaced downward from the LEDs of other colors due to the wiring layout requirement, but they are basically arranged side by side in the horizontal direction. In this way, by generating light from a plurality of point light sources arranged in the horizontal direction, guiding the light into the flat light guide body 2 in the horizontal direction, and emitting the light in the substantially vertical direction, a color image is read or written. It is possible to provide a thin lighting device that can be used even for a device that can perform the above.

The light emitted from the LED enters the light guide 2 through the light incident surface 5. The light that has entered the light guide body 2 is totally reflected at the interface between the light guide body 2 and the surrounding air, and
Propagate inside. At that time, the light reaching the light scattering region 10 is scattered and reflected there, and travels in various directions in the light guide 2. Of these lights, most of the light that has traveled into the ridge 9 provided on the surface facing the light scattering region 10 is emitted from the light emitting surface 6 on the upper surface of the ridge 9, and most of it is the light. It can be used as effective light traveling in the direction perpendicular to the emission surface 6. In this example, the width of the light scattering region 10 is not uniform along the longitudinal direction of the transparent rod, but even in such a case, the light is emitted from the light emitting surface 6 on the upper surface of the ridge 9 so as to emit light. The width of the emitted light can be made uniform.

Of the light traveling in a direction other than the light emitting surface 6, the light that reaches the interface between the light guide 2 and the air at an incident angle larger than the critical angle is totally reflected at the interface and is guided again. Since it propagates in the body 2, there is no light loss at this stage. On the other hand, what is incident on the interface at an incident angle smaller than the critical angle is partly reflected at the interface and returned to the inside of the light guide 2, but most of it is emitted into the air. This light is reflected on the inner surface of the cover that covers the periphery of the light guide 2 and is again reflected.
Will return to inside. Therefore, the higher the reflectance of the inner surface of the cover, the smaller the amount of light loss, which is preferable.

Even if light is emitted from the entire upper surface of the light guide 2 without providing the ridges 9, the width of the light receiving portion that is actually required to be irradiated is extremely narrow, so that the light is wasted. Will be released. On the other hand, as described above, in order to make light from the light source unit 7 composed of a plurality of LEDs incident and to make a thin irradiation device, it is preferable to make the light guide body wide to some extent in the horizontal direction. Therefore, like the light guide 2 of the present invention, it is preferable to emit light from only a part of the upper surface of the light guide 2 from the viewpoint of light utilization efficiency.

However, at this time, as shown in FIG. 14, if the ridge 9 is not formed on the light guide 2 and it is simply covered with a cover having an opening, the light is emitted from the light guide 2 into the air. Most of the light reaching the side surface 25 of the slit 12 formed in the cover is lost, and the proportion of light having an excessively large emission angle increases. Since the light emitted from the light guide 2 into the air has a large emission angle due to refraction, even if the height of the side surface 25 of the slit 12 of the cover is not so high, the proportion of the light impinging there is not small. .

On the other hand, in the present invention, as shown in FIG. 11, for example, the ridge 9 is formed on the upper surface of the light guide 2, and the ridge 9 is formed.
The side surface 13 is covered with the upper cover 3. As a result, the light reaching the side surface of the ridge 9 is totally reflected and reaches the light emitting surface 6 on the upper surface of the ridge 9 when the incident angle is equal to or greater than the critical angle, and the incident angle is equal to or less than the critical angle. Also in this case, the light once emitted into the air can be reflected on the inner surface of the cover and returned to the inside of the light guide 2. That is, according to the present invention, all the light emitted from the portion other than the narrow light emitting surface 6 to the outside of the light guide 2 reaches the inner surface of the cover and is reflected there.
Light loss is low.

In this example, since the ridge 9 has a trapezoidal cross-section, light is emitted from the light emitting surface 6 having a narrow width of 0.5 mm while taking in more light into the ridge 9. be able to. When the illuminance distribution of the light emitted from each LED was measured over the entire width of the line irradiation device thus obtained, over the entire width in the longitudinal direction,
The illuminance distribution was within ± 10%.

The cross-sectional shape of the ridge 9 may be rectangular as shown in FIG. In this way, although the illuminance is slightly reduced by widening the line width of the light emitting surface 6,
It is possible to increase the uniformity of the illuminance distribution and the allowable range of dimensional error incorporated in the device. On the other hand, as shown in FIG. 13, if the light emitting surface 6 on the upper surface of the convex strip 9 has a curvature and acts as a convex lens, it is possible to supply light of higher illuminance to a narrower width. However, in this case, the uniformity of the illuminance distribution in the longitudinal direction may be slightly deteriorated, and the allowable range of the dimensional error incorporated in the apparatus may be reduced. The shape of the cross section of the ridge 9 is optimized by appropriately changing it according to the requirements of the reading device and the writing device used.

The line illumination device thus obtained is incorporated into various image processing devices and used as illumination for reading or writing an image, particularly a color image. In particular, since the line lighting device of the present invention is thin,
It is suitable for use in small portable devices.

[0039]

The line illuminator according to the present invention can be reduced in size and weight, in particular, can be made thin, have high light utilization efficiency, and can emit light with uniform illuminance.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a line lighting device that is an example of an embodiment of the present invention.

FIG. 2 is a plan view of a line lighting device that is an example of an embodiment of the present invention.

3 is a front view of the line lighting device of FIG. 2. FIG.

FIG. 4 is a left side view of the line lighting device of FIG.

FIG. 5 is a right side view of the line lighting device of FIG.

6 is a bottom view of the line lighting device of FIG. 2. FIG.

FIG. 7 is a plan view of a light guide incorporated in a line lighting device that is an example of an embodiment of the present invention.

FIG. 8 is a front view of the light guide body of FIG.

9 is a left side view of the light guide body of FIG. 7. FIG.

FIG. 10 is a bottom view of the light guide body of FIG. 7.

11 is a cross-sectional view taken along the line A-A ′ of FIG.

FIG. 12 is a sectional view at a position equivalent to that of FIG. 11 showing another embodiment of the present invention.

FIG. 13 is a sectional view at a position equivalent to that of FIG. 11 showing still another embodiment.

FIG. 14 is a cross-sectional view at the same position as in FIG. 11 of an example to be compared with the present invention.

FIG. 15 is a diagram of the light source unit viewed from the light incident surface side.

16 is a cross-sectional view taken along the line B-B ′ of FIG.

[Explanation of symbols]

1 line lighting device 2 Light guide 3 Upper cover 4 Lower cover 5 Light incident surface 6 Light exit surface 7 Light source unit 9 convex stripes 10 Light scattering area 12 slits

Claims (6)

[Claims] 1. A line lighting device comprising a light guide, a cover for housing the light guide, and a light source, wherein the light guide comprises a transparent rod having a light incident surface at least at one end thereof. And has a ridge on one surface parallel to the longitudinal direction of the rod, and has a light-scattering region on the surface opposite to the surface having the ridge, and the upper surface of the ridge has a linear light emission surface. The cover is a surface where the inner surface facing the light guide reflects light, has a slit in which the ridge is fitted, and covers the side surface of the ridge, and the light source is the light incident surface. A line lighting device characterized in that the line lighting device is arranged in. 2. The line lighting device according to claim 1, wherein the rod is flat, and the convex strip is provided on a wide surface thereof. 3. The line lighting device according to claim 1, wherein the cross-sectional shape of the ridge is substantially quadrangular. 4. The line lighting device according to claim 1, wherein the cover covers all portions except the light incident surface and the light emitting surface. 5. The light-scattering region is in the form of a strip continuous along the longitudinal direction of the rod, the width of the region near the light source is narrow, and the width of the region increases as the distance from the light source increases. 1. The line lighting device according to 1. 6. A light source unit comprising a plurality of point light sources each of which can be turned on independently, and emits light in a direction substantially perpendicular to a direction in which the plurality of point light sources are arranged. Line lighting equipment.