JPH10133026A - Illuminator having light transmission body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly illuminate an irrastrated face with light by forming an area for the reflection/diffusion of a conductor like saw teeth so that teeth are arranged in the longitudinal direction of the rod-like conductor and forming these teeth so that the width of teeth is narrowed in the vicinity of a light source and extended in accordance with separation from the light source. SOLUTION: An area 5 for reflecting/scattering a beam propagated through the inside of the conductor 3 and extracting the beam to the outside of the conductor 3 is constituted so as to form a fine saw tooth-like tooth string on one side face along the longitudinal direction of the conductor 3. The width of the area 5 is set so as to be narrowed in the vicinity of an incident face and extended on a center part separated from any incident face. Since the incident rate of a beam propagated through the inside of the conductor 3 upon the area 5 is reduced on near side of the incident face and increased on the far side, the non-uniformity of illuminance in the longitudinal direction of the conductor 3 is effectively improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illuminating device having a light guide, and more particularly, to an illuminating device used for reading an image such as an information processing device.

[0002]

2. Description of the Related Art Conventionally, facsimile machines, electronic copiers,
Alternatively, as an illumination device of an image reading device of another information processing device, a discharge tube such as a fluorescent tube or an LED chip is used.
Many LED arrays arranged in an array are used. In particular, in recent years, there has been a demand for smaller and less expensive products such as facsimile machines for use at home. For this reason, those using LED arrays are increasing.

In such an LED array, by arranging the LED chips densely, it is possible to obtain a substantially uniform, high illuminance on the document surface. However, because of the large number of LED chips used, it is difficult to achieve a sufficiently low cost in terms of cost.

If the number of LED chips used is reduced for cost reduction, that is, if the LED chips are arranged roughly, the arrangement interval of the LED chips becomes large, so that the illuminance distribution on the surface to be illuminated becomes uneven. As a result, uniform illumination cannot be achieved. Therefore, in order to solve this problem, a light guide is composed of a rod-shaped translucent member, the light of the LED chip is incident from the end face, and the light flux propagating while repeating total internal reflection is applied to one side thereof. A method has been proposed in which a light-diffusing coating applied to the substrate scatters and takes it out.

FIG. 15 shows such an illuminating device. Here, reference numeral 1 denotes an LED chip bonded on a metal lead, and the portion is sealed in a lens shape with a transparent resin. Reference numeral 3 denotes a rod-shaped light guide made of a translucent member such as a quartz rod having a circular cross section, and reference numeral 4 denotes a light flux emitted from the LED lamp 1. Reference numeral 5 denotes an incident surface on which the light enters the light body 3, and a region for reflecting and scattering a light beam propagating inside the light guide 3 and extracting the light outside the light guide 3. The region 5 is formed by roughening one side surface of the light guide 3 or applying a light-diffuse reflective paint thereto.

[0006] The light beam 1 emitted from the LED lamp 1 and incident on the inside of the light guide 3 from the incident surface 4 is repeatedly reflected on the inner surface of the light guide 3 and propagated to the surface on the opposite side of the incident surface 4. Reaches, where it is also reflected and propagates inside the light guide 3. Then, while the reflection is repeated, the area 5
When the light is incident on the area, the light beam is diffused there, and a part of the light 11 is emitted to the outside from the emission surface on the side facing the region 5.

The other part 12 of the diffused light flux is obliquely incident on the exit surface, and is totally reflected.
Again, the light propagates through the light guide 3. Then, the light repeatedly reaches the incident surface 4 at a required angle by repeating the propagation.
From there it is injected outside.

[0008]

However, there has been a reason that such a lighting device has not been widely used while being proposed. That is, in such a configuration, there is a problem that the illuminance distribution of the illuminated surface is bright near the LED lamp 1 as the light source, and becomes darker as the distance from the LED lamp 1 increases.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide an illuminating device capable of linear illumination capable of irradiating an illuminated surface with uniform illuminance.

[0010]

Therefore, in the present invention,
It is rod-shaped as a whole, having a light incident surface at its end, and, with respect to the longitudinal direction of the rod, having a light exit surface for emitting a light beam incident from the light incident surface on one side surface thereof, Illumination having a light guide having a region for reflecting and / or diffusing a light flux incident thereon on a side surface portion facing a light exit surface, and an LED lamp provided near the light incident surface. In the device, the light guide is formed in a saw-tooth shape such that a region for reflection / diffusion is arranged in a bar-shaped longitudinal direction, and the width of the teeth is close to the light source. It is characterized in that it is formed so that its width is wide at narrow and distant places.

In this case, the light guide has at least a part of the surface of the reflection / diffusion region formed in a sawtooth shape.
It is preferable that neither painting nor vapor deposition be performed. Also,
It is preferable that the light guide has a tooth pitch of the sawtooth reflection / diffusion region set in a range of 20 microns to 1 mm. In the LED lamp, the directivity of the luminous flux emitted from the LED lamp is such that the directional _half -value angle?
It is preferable to be set in the range of degrees to 30 degrees, and furthermore, if necessary, the outer periphery of the light guide is a sheath-shaped cover member having at least an inner surface serving as a light reflective surface. Preferably it is covered.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 schematically shows a first embodiment of the present invention.
An LED lamp formed by bonding a chip on a metal lead and sealing the portion with a transparent resin in the form of a lens. Reference numeral 3 has a substantially circular cross section.
A rod-shaped light guide made of a translucent member such as an acrylic resin, reference numeral 4 denotes an incident surface on which a light beam emitted from the LED lamp 1 enters the light guide 3, and reference numeral 5 denotes an inside of the light guide 3. This is an area for reflecting and scattering the propagating light flux and taking it out of the light guide 3. In this embodiment, in this embodiment, a small saw-tooth-shaped tooth row is formed on one side surface along the longitudinal direction of the light guide 5.

The light beam emitted from the LED lamp 1 and incident on the inside of the light guide 3 from the incident surface 4 repeats reflection on the inner surface of the light guide 3 and propagates inside. In the process of repeating this reflection, the region 5
When light enters the light beam, the light beam is diffused there and
Is emitted to the outside from the emission surface on the side opposite to.

On the surface of the region 5, a light-reflective film may be formed in a mirror-like shape by means such as aluminum evaporation, but recently, not by means of evaporation, but by means of painting or printing. However, such a means may be used because a light-reflective coating having a relatively good mirror surface can be obtained. However, in this embodiment, no such light-reflective film is formed on the surface of the region 5. Even in this case, if the surface of the sawtooth is finished to a sufficiently smooth mirror surface, a considerable portion of the light beam incident on the tooth will be reflected by total reflection or Fresnel reflection.
The light is reflected and emitted to the outside from the facing emission surface.

At this time, the light beam incident on the region 5 is not reflected and diffused there, but is specularly reflected on the inclined surface of the minute sawtooth formed at that portion, so that it is efficiently guided to the opposing exit surface. . Therefore, high illuminance can be obtained on the illumination target surface.

However, in the case where the region 5 is formed in a sawtooth shape, there is a problem that is not caused by roughening or applying a light-diffuse reflective paint as in the conventional example, but is caused by the formation of the sawtooth. You have to be careful. In other words, fine unevenness due to the sawtooth pitch P occurs in the illuminance distribution on the illumination target surface.

This problem can be avoided by making the sawtooth pitch P sufficiently small. For example, FIG.
In 4, when the illumination device of the present invention is used as a light source of an image reading device in a form to be described later, the distance from the sawtooth portion to the surface to be illuminated is usually usually between 5 mm and 30 mm. In this embodiment, about 10
mm. In this case, when the pitch P was set to 1 mm or more, the illuminance distribution on the surface to be illuminated became significantly uneven in accordance with the pitch P. Actually, in the embodiment of FIG. 14, the pitch P is set to about 0.6 mm.

If it is desired to further reduce the distance to the surface to be illuminated, or if there is a severe demand for uneven illuminance on the surface to be illuminated, the pitch P must be further reduced. In this embodiment, the pitch P is set to 250 microns in consideration of using the distance to the illuminated surface as 7 mm and aiming at more uniform illuminance on the illuminated surface. I have.

Further, when it is desired to eliminate the influence of the pitch, the reading resolution of the image reading device is determined by the pitch of the pixels of the photoelectric conversion elements formed on the sensor chip used in combination with the illumination device. Or,
The pitch P of the sawtooth portion may be reduced to less than that. Normally, the reading resolution is about 125 microns for a low-resolution low-cost image reading apparatus, and about 30 to 60 microns for a high-resolution high-quality image reading apparatus.

However, on the other hand, if the pitch is too small, it is extremely difficult to manufacture the sawtooth in an accurate shape. When the saw-tooth portion is formed by a method such as injection molding, a portion of the mold corresponding to the saw-tooth portion is manufactured by, for example, manufacturing a saw-tooth shape by electric discharge machining and, if necessary, further polishing the surface. Or, there is a method of preparing a piece of soft metal such as phosphor bronze, and directly grinding this piece with a diamond bite made by polishing a diamond chip, but in the former case, If the pitch P is not more than 100 microns, and even in the latter case, if the pitch P is not more than 20 microns, it is difficult to accurately obtain the sawtooth shape.

The pitch of the saw teeth does not necessarily have to be the same over the entire area where the saw teeth are formed. In particular, in the embodiment of the present invention (described later with reference to FIG. 2), the width of the teeth of the region 5 in which the sawtooth is formed differs depending on the location.
In some cases, changing the pitch of the sawtooth is more convenient for mold production. In other circumstances, even when the pitch of the sawtooth is not the same, the above-mentioned consideration is taken into account at least in a portion corresponding to the pitch of the sawtooth, where illumination unevenness on the surface to be illuminated becomes a problem. It is desirable.

The serrated region 5 does not necessarily have to be formed so as to protrude from the surface of the light guide as in the embodiment of FIG. For example, as shown in FIG.
May be formed slightly intruding from the surface of the light guide 3 having a substantially circular cross section, or as shown in FIGS. However, depending on the location, the light guide 3 may be formed so as to slightly enter the inside thereof, or may be formed so as to protrude from the surface of the light guide 3.

FIG. 2 is a schematic view of the light guide in the embodiment shown in FIG. 1 when viewed from one side (hereinafter referred to as a lower surface) on the side where the region 5 in FIG. 1 is provided. It is a block diagram. In this embodiment, the width of the region 5 is small in a portion near the incident surface 4-1 or 4-2, and
It is set so as to be wider at the center portion, far from any of 1, 4-2. For this reason, the rate at which the luminous flux propagating inside the light guide enters the region 5 is small on the side near the incident surface 4 and increases on the far side, so that the illuminance unevenness in the longitudinal direction of the light guide is reduced. It is effective to improve.

The directivity of the luminous flux emitted from the LED lamp can be concentrated in the direction of the optical axis by appropriately designing the shape of the lens portion of the LED lamp, and the illuminance distribution on the surface to be illuminated can be improved. Contribute. If the luminous flux emitted from the LED lamp has a sharp directivity in the direction of the optical axis, when the luminous flux is incident on the light guide, the luminous flux incident on the reflection / diffusion area 5 near the incident surface is reduced. , LED
In the vicinity of the lamp, the illuminated surface can be prevented from being over-illuminated (too bright).

FIG. 3 specifically shows the directional characteristics of the luminous flux emitted from the LED lamp used in the embodiment shown in FIG. As is clear from FIG. 3, the luminous intensity of the LED lamp rapidly decreases as the LED lamp deviates from the optical axis direction. The angle at which the luminous intensity becomes half the luminous intensity in the optical axis direction, that is, the directional half-value angle of the radiation intensity with respect to the optical axis direction of the LED lamp is set in the range of θ _half = 5 degrees to 30 degrees. In this embodiment, it is set to about 10 degrees.

If θ _half is not sufficiently small, for example, if it is 30 ° or more, the illuminated surface is too brightly lit near the LED lamp, and the illuminance distribution on the illuminated surface as a whole is sufficiently improved. Not done. On the other hand, when θ _half is extremely small, for example, when it is several degrees or less, conversely, the illuminated surface is not sufficiently illuminated near the LED lamp, and instead, it becomes darker, or the entire illuminated surface becomes darker. Inconveniences such as not being illuminated occur.

FIG. 4 is a view showing a second embodiment of the illumination device of the present invention. In this embodiment, a holding portion 7 for holding and positioning the light guide is provided on the surface of the light guide. The holding portion also functions as a gate portion when the light guide is injection-molded.

FIG. 5 is a diagram showing a third embodiment of the illumination device of the present invention. In this embodiment, the light guide has a white, light yellow,
A sheath-like cover member 8 made of a reflective material such as light gray
Is coated. A slit 9 is provided on a surface of the cover member facing the surface to be illuminated, and a light beam emitted from the light guide passes through the slit 9 and is directed toward the surface to be illuminated. ing. Note that the width of the slit 9 may have a wide portion and a narrow portion on the surface to be illuminated in accordance with a required illuminance distribution shape.

The cover member guides the light via an air layer having a thickness larger than the main emission wavelength of at least the luminous flux emitted from the LED lamps 1-1 or 1-2 between the cover member and the outer peripheral surface of the light guide. Surrounding the body. For this reason, the presence of the cover member hardly affects the luminous flux propagating while repeating total internal reflection inside the light guide, but the surface of the light guide,
Alternatively, the light flux leaking from the sawtooth-shaped region is reflected on the inner surface of the cover member, returned to the inside of the light guide again, or irradiated toward the surface to be illuminated. Therefore, such a function is particularly effective when no light reflecting film is formed on the surface of the sawtooth formed in the reflection / diffusion region 5.

FIG. 10 is a diagram showing a fourth embodiment of the illumination device of the present invention. In this embodiment, the LED lamp as a light source is provided only on one end side (incident surface side) of the light guide. In addition, a reflection surface 6 is provided at the terminal end of the light guide 3 opposite to the incident surface side instead of the LED lamp. The reflective surface is formed by depositing a metal such as aluminum on the surface of the terminal end of the light guide 3 itself, applying a light-diffusing reflective paint, or providing another member.

FIG. 11 is a schematic configuration diagram of the light guide according to the embodiment shown in FIG. 10 when viewed from below. Here, the width of the region 5 is narrow at a portion near the incident surface 4 and is wide at a portion far from the incident surface 4. For this reason, the ratio of the luminous flux propagating inside the light guide to the region 5 is small on the side close to the incident surface 4 and increases on the far side, so that the uneven illuminance on the irradiated surface is improved. It is effective.

FIG. 12 is a diagram showing a fifth embodiment of the illumination device of the present invention. In this embodiment, the LED lamp used as the light source
As shown in FIG. 1, LED chips having different emission wavelengths are mounted together in one package. In this case, reference numeral 1a in the drawing denotes a red light emitting LED chip having a peak light emission wavelength of 600 nm or more,
1b is its peak emission wavelength: 500 nm to 600 n
m, and 1c is a blue light emitting LED chip having a peak light emission wavelength of 500 nm or less. And these different emission wavelength LEDs
Color reading can be performed by switching the chips simultaneously or sequentially to emit light.

As described above, when a light source is provided only at one end of the light guide, or when an LED lamp used as a light source is provided with L
Even in the case where the ED chip is mounted together, as described above with respect to the first to third embodiments of the present invention, the light guide is provided with the holding portion or the LED lamp is provided. It is all effective to make the directivity sharp or provide a sheath-shaped cover member.

Next, FIG. 14 schematically shows an image reading apparatus using the illumination device of the present invention. In the figure, reference numeral 100
Is a lighting device already described in the third embodiment of the present invention, and 200 is a document carrying an image to be read,
300 is a lens array, 400 is a sensor chip, 50
Reference numeral 0 denotes a substrate on which an electric circuit is formed by printing or the like, and a sensor chip is mounted thereon.

The luminous flux emitted from the illumination device 100 is
Illuminate 00. The light beam reflected in accordance with the density of the image on the document 200 is imaged on the sensor chip by the lens array 300. The light flux is converted into an electric signal by a photoelectric conversion element formed in an array on the sensor chip, and an image is read.

In this case, if the lighting device of the present invention is used,
Since the document surface can be uniformly illuminated with high illuminance with a small number of LEDs, an inexpensive and high-performance image reading apparatus can be realized.

[0037]

As described above, according to the present invention, according to the present invention, the rod-like structure is provided as a whole, and has a light incident surface at an end thereof. A light guide having a light exit surface for emitting the light beam incident from the incident surface, and having, on a side surface portion facing the light exit surface, a region for reflecting and / or diffusing the light beam incident inside; In a lighting device having an LED lamp provided in the vicinity of the light incident surface, the light guide has a sawtooth shape such that a region for reflection / diffusion is arranged in a bar-shaped longitudinal direction. The teeth are formed such that the width of the teeth is small near the light source and wide at the distance.

Therefore, the light beam incident from the light incident surface at the end of the light guide is reflected / reflected on the side surface along the longitudinal direction.
In the case where the surface to be illuminated is linearly illuminated by being reflected / diffused in the diffusion region and emitted from one side surface facing the same, the surface to be illuminated can be uniformly illuminated. Further, by using such a lighting device of the present invention, an inexpensive and high-performance image reading device or the like can be easily realized.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a lighting device according to a first embodiment of the present invention when viewed from a side.

FIG. 2 is a schematic configuration diagram when the light guide in FIG. 1 is viewed from below.

FIG. 3 is a diagram showing emission directivity characteristics of the LED lamp in FIG. 1;

FIG. 4 is a diagram showing a second embodiment of the lighting device of the present invention.

FIG. 5 is a diagram showing a third embodiment of the lighting device of the present invention.

FIG. 6 is a diagram showing another example in which a sawtooth portion is formed on a side surface of a light guide in the first embodiment of the lighting device of the present invention.

FIG. 7 is a diagram showing still another example in which a sawtooth portion is formed on a side surface of a light guide in the first embodiment of the lighting device of the present invention.

FIG. 8 is a diagram showing another example in which a sawtooth portion is formed on a side surface of a light guide in the first embodiment of the lighting device of the present invention.

FIG. 9 is a diagram showing a fourth example in which a sawtooth portion is formed on a plane on a side surface of a light guide in the first embodiment of the lighting device of the present invention.

FIG. 10 is a diagram showing a fourth embodiment of the lighting device of the present invention.

11 is a schematic configuration diagram when the light guide in FIG. 10 is viewed from below.

FIG. 12 is a view showing a fifth embodiment of the lighting device of the present invention.

FIG. 13 is a view showing the LED lamp in FIG. 12;

FIG. 14 is a diagram of an image reading device using the illumination device of the present invention.

FIG. 15 is a diagram illustrating an example of a conventional lighting device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 1-1-1, 1-2 LED lamp 3 Light guide (transparent member) 4, 4--1, 4-2 Incident surface 5 Area 6 Reflective surface 7 Holding part 8 Cover member 9 Slit 11 Light 12 Light 100 Illumination Apparatus 200 Original 300 Lens array 400 Sensor chip 500 Substrate

Claims (5)

[Claims] 1. A light emitting device which has a rod shape as a whole, has a light incident surface at an end thereof, and emits a light beam incident from the light incident surface to one side surface of the rod in the longitudinal direction. With a surface, on the side surface facing the light exit surface,
In a lighting device including a light guide having a region for reflecting and / or diffusing a light beam incident therein and an LED lamp provided near the light incident surface, the light guide is provided by The area for reflection / diffusion is formed in a saw-tooth shape such that the teeth are arranged in the longitudinal direction of the rod, and the width of the teeth is small near the light source and wide at the distance. A lighting device having a light guide, wherein the lighting device is formed. 2. The light guide according to claim 1, wherein at least a part of a surface of the reflection / diffusion region formed in a saw-tooth shape is in a state of being neither coated nor deposited. An illumination device having a light guide. 3. The light guide according to claim 1, wherein a pitch of teeth of the reflection / diffusion region formed in a sawtooth shape is set in a range of 20 μm to 1 mm. An illumination device having a light guide. 4. The LED lamp according to claim 1, wherein a directivity of a luminous flux emitted from the LED lamp is set in a range of a _half value angle θ _half = 5 degrees to 30 degrees of radiation intensity with respect to an optical axis direction of the LED lamp. The lighting device according to claim 1, comprising the light guide. 5. The light guide according to claim 1, wherein an outer peripheral portion of the light guide is covered with a sheath-shaped cover member having at least an inner surface serving as a light reflective surface. A lighting device having a light guide.