JP2725650B2 - LED array light source - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a facsimile machine,
Regarding linear light sources for originals used in scanners, etc., especially LEDs with strong directional characteristics as light sources for contact image sensors
(Light Emitting Diode) The present invention relates to an LED array light source using elements arranged in a straight line.

[0002]

2. Description of the Related Art In recent years, in an image reading apparatus such as a facsimile apparatus and a scanner, for example, a contact type image sensor, an LED array light source having many linearly arranged LED elements as a linear light source for illuminating a document surface is widely used. It's being used.

One LED element itself is a spot-shaped light source having high directivity. Therefore, in order to obtain uniform linear illumination, it is necessary to arrange a large number of LEDs in a straight line. For example, if the LEDs are arranged at a pitch of 6.5 mm, the illuminance distribution on the document surface becomes substantially uniform, and uniform linear illumination can be obtained.

However, the use of a large number of LED elements to obtain uniform illumination leads to a significant increase in cost. Therefore, as far as possible, there is no problem in the uniformity of the illuminance distribution for reading a document. Is desirably reduced. However, if the number of LED elements is reduced and, for example, the LED elements are arranged at a pitch of 16 mm, the illuminance distribution on the document surface becomes non-uniform. As means for solving this problem, Japanese Patent Application Laid-Open No. 4-29379 discloses an LED.
There has been proposed an LED array light source capable of obtaining uniform linear illumination even when the number of used LED elements is reduced.

[0005] That is, as shown in FIGS. 5A and 5B, a large number of LED elements 52 are arranged in a row on an elongated printed wiring board 51, and the front surface of the LED elements 52 is sealed with a transparent resin 53. ing. Further, a light amount adjustment mask 55 is provided on the front surface of the sealing resin 53. The light quantity adjusting mask 55 is made of a transparent thin film, and a concentric light shielding pattern 54 is formed on the surface of the light quantity adjusting mask 55. The light shielding pattern 54 allows the LED element 52
The illumination light from the camera is intermittently blocked to block a portion having a large amount of illumination light, thereby suppressing unevenness in the amount of light.

[0006]

However, the light-shielding pattern 54 reduces the high illuminance portion and attempts to maintain uniformity in accordance with the low illuminance portion, so that the illuminance is greatly reduced and the illumination light from the LED element is reduced. There is a problem that the use efficiency of the device is low. In addition, there is a problem that the light-shielding portion is shaded and reflected in the illuminance distribution, and a sufficient effect cannot be obtained to make the illuminance distribution uniform.

An object of the present invention is to provide an LED array light source that reduces the number of LED elements used, increases the utilization efficiency of illumination light, and achieves uniform illumination distribution.

[0008]

The LED array light source according to the present invention is characterized in that reflectors are formed on both the light incident surface and the light exit surface of the light guide member disposed above the LED array. The first reflector formed on the emission surface side is formed in a striped pattern having a central reflection region facing each light emitting region of the LED and a peripheral reflection region thereof. The first reflector is provided corresponding to each LED so as to reflect a part of the output light from the LED to the incident surface side. On the other hand, a second reflector is provided on the incident surface side so as to reflect light reflected by the first reflector back to the emission surface side.

In the present invention, since the reflectors are formed on both surfaces of the light guide member, a part of the illumination light from the LED element is transmitted, and the rest is caused by the action of the reflector to a valley portion of the illuminance distribution. Since the illuminance is increased by guiding the illuminance, the illuminance distribution can be made uniform.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention, in which LED elements 2 are arranged in a straight line on an elongated printed wiring board 1, and are arranged on the upper surface of the LED element 2. Is provided with a prismatic light guide 3 for guiding illumination light from the LED element 2 to the document surface. On the upper surface (original surface side) of the light guide 3, a stripe-shaped upper reflector 4a and a lower surface (LE
A lower surface reflector 4b is formed on the side of the D element 2).
As shown in FIG. 1A, the upper reflector 4a formed on the upper surface of the light guide 3 is formed on the upper surface of the LED element 2 in a stripe shape in a direction orthogonal to the direction in which the LED elements are arranged. ing. On the other hand, the lower surface reflector 4b formed on the lower surface of the light guide 3 is formed on the entire surface except for the upper surface of the LED element, as shown in FIG.

In the thus configured LED array light source, the illumination light from the LED element 2 enters the light guide 3 from the lower surface of the light guide 3 and is formed on the upper surface of the light guide 3. The light reflected by the reflector 4a and the upper reflector 4
The light is directly illuminated from the slit portion where a is not formed to illuminate the original. The light reflected by the upper surface reflector 4a formed on the upper surface of the light guide 3 is directed to the lower surface side of the light guide 3 and is reflected again by the lower surface reflector 4b formed on the lower surface of the light guide 3. Then, the document surface is illuminated.

It can be seen from the drawing that the upper reflector and the lower reflector have the following positional relationship.

A part of the output light deviated from the emission center of the LED element is transmitted through a gap between the central reflection area and the peripheral reflection area of the top reflector, and the light reflected by the peripheral reflection area is transmitted. They are arranged so as to be reflected by the lower reflector and emitted from a region between adjacent upper reflectors.

Next, the operation of the upper reflector 4a and the lower reflector 4b thus configured will be described. FIG. 2 shows an example in which the number of used LED elements is reduced to 16
The simulation result about the illuminance distribution at the time of arrange | positioning by a mm pitch is shown.

FIG. 2A shows an illuminance distribution on the original 6 when the light guide 3 of the present invention is not used. Fig. 2 (a)
When the number of used LED elements is reduced, the illuminance is large immediately above the LEDs, but the illuminance is greatly reduced between the LED elements, and the illuminance distribution has a very large variation as shown by.

FIG. 2B shows a case where three stripe-shaped upper reflectors 4a are formed on the upper surface of the light guide 3 in correspondence with the respective LED elements. The illumination light reflected by the upper surface reflector 4a formed on the upper surface of the light guide 3 is then reflected by the lower surface reflector 4b formed on the lower surface of the light guide 3.
Reflected by the light source, a portion farther from the optical axis of the LED element 2,
That is, the light is guided to a portion between the adjacent LED elements and a valley of the illuminance distribution in FIG. Then, since the illumination light reflected by the reflector 4 contributes to the valley portion of the illuminance distribution, the illuminance of the valley portion of the illuminance distribution, which is greatly reduced in FIG.
As a result, as shown in FIG. 2B, the uniformity is improved from about ± 60% to about ± 30% in the ripple width as compared with the case where the light guide plate 3 is not used, while reducing the light amount reduction. Can be.

The ripple width is an index indicating the degree of uniformity, and is a numerical value defined by ripple width = (MAX−MIN) / (MAX + MIN). The smaller the ripple width, the higher the uniformity.

FIG. 2 (c) shows a case where the upper reflector 4a is further added to make the illuminance distribution shown in FIG. 2 (b) uniform. By the action of the newly formed top reflector 4a, the illumination light reflected by this top reflector 4a is guided between the adjacent LED elements and to the valley of the illuminance distribution in FIG. 2B. This contributes to an increase in the illuminance of this portion. As a result, as compared with the case of FIG.
→ It can be improved to about ± 10%, and uniform illumination distribution can be achieved.

As the upper reflector 4a and the lower reflector 4b, it is desirable to select a material having a high reflectivity. For example, a metal such as aluminum has a high reflectivity (about 0.9 by vapor deposition). It is optimal because it can be inexpensive. Of course, the present invention is not limited to aluminum as long as it follows the gist of the present invention.

The upper reflector 4a and the lower reflector 4b can be easily formed by a method such as vapor deposition or printing. The size and number of the upper reflector 4a and the lower reflector 4b to be formed may be arbitrarily formed so as to obtain a desired illuminance distribution. Of course, at this time, it is effective to form the upper reflector 4a and the lower reflector 4b so that the illumination light of the high illuminance portion can be guided to the low illuminance portion, which is effective in achieving uniform illumination distribution. Needless to say,

According to the embodiment, the upper surface reflector 4a
As shown in FIG. 1, the illumination light reflected from the upper surface reflector 4 a formed on the upper surface of the light guide 3 is formed on both the upper surface and the lower surface of the light guide 3. The lower reflector 4b formed on the lower surface of the light guide 3 again
To illuminate the original surface by reflecting the light. Moreover, since such reflected light can be arbitrarily guided to a valley portion in the illuminance distribution of FIG.
Even if the number of ED elements 2 used is reduced, the reduction in illuminance can be reduced and uniform illuminance distribution can be achieved. Specifically, in this embodiment, when the light guide 3 is not used, 42 LED elements 2 of B4 size are required to maintain uniformity in a range where there is no problem in reading a document. However, by using the light guide 3 as in the present embodiment, the number of the LED elements 2 may be 16 and the number of the LED elements 2 used can be reduced to about 1/3 to achieve uniformity. .

As described above, for example, in the case of using 16 LED elements of B4 size, in the above-mentioned conventional example, about ±
In contrast to an increase in the ripple width of 30%, in the embodiment, the ripple width can be reduced to about ± 10% to achieve uniformity. there is no problem.

The positional relationship between the upper reflector and the lower reflector is as follows.
As shown in the drawing, the light is selected so as to satisfy the relationship that the light reflected from the stripe-shaped top reflector is re-reflected to the emission surface side. That is, if at least an opening through which the output light from the LED element is transmitted is secured, the lower surface reflector can be provided on the entire incident surface of the light guide member.

Although the example of the stripe pattern is shown as the stripe pattern in the embodiment, the stripe pattern may be a concentric circle as shown in the conventional example. However, from the viewpoints of a linear light source and ease of manufacturing, it is more preferable to use a stripe as in the embodiment of the present invention.

The light guide member may be made of glass or plastic as long as it is transparent to the output light of the LED element. Further, the cross section is not limited to a square cross section, and may be a plate shape or another shape as shown in the following embodiment.

Next, a second embodiment of the present invention will be described with reference to FIG.

In FIG. 3A, LED elements 32 are arranged in a straight line on a long and narrow printed wiring board 31, and the illumination light from the LED elements 32 is placed on the upper surface of the LED elements 32 on the document surface. FIG. 3 as a light-transmitting member for guiding
A light guide lens 3 having a circular column shape as shown in FIG.
3 are provided. On the upper surface (original surface side) of the light guide lens 33, a striped upper reflector 34a is formed, and on the lower surface (on the side of the LED element 32), a lower reflector 34b is formed. The upper surface reflector 34a formed on the upper surface of the light guide lens 33 includes:
On the upper surface of the LED element 32, a stripe is formed in a direction orthogonal to the direction in which the LED elements are arranged. On the other hand, a lower surface reflector 34 formed on the lower surface of the light guide lens 33
b is formed on the entire surface except for the upper surface of the LED element. Since the translucent member has a columnar shape, it is possible to collect illumination light in a direction perpendicular to the arrangement direction of the LED elements.

In the thus configured LED array light source, in the arrangement direction of the LED elements,
By the same reflection, the illuminance of the portion where the illuminance distribution is greatly reduced can be increased as compared with the case where the light guide lens 33 is not provided, the ripple width becomes about ± 10%, and L
The illuminance distribution in the arrangement direction of the ED elements can be made uniform.

Further, in the direction orthogonal to the arrangement direction of the LED elements, a higher illuminance on the original surface can be obtained by the light condensing effect of the cylindrical light guide lens 33.

In the above embodiment, the case where the stripe width of each of the top reflectors is different has been described. However, a desired original irradiation light distribution can be obtained even with the same stripe width.
An example in that case will be described below.

[0032]

FIG. 4 is a partially enlarged sectional view showing a preferred embodiment of the present invention.

When a glass plate having a thickness of 4 mm is used as the glass plate 3, a lower reflector is entirely provided on the lower surface of the glass plate 3 except for an opening having a width of 1.5 mm for receiving the output light of the LED element 2. Is formed. The top reflector corresponding to each LED element 2 has one central reflection area 41a facing the opening and a pair of peripheral reflection areas 42a arranged on both sides thereof. In one top reflector, the length of the LED element 2 in the array direction is 3.0 mm, the width of each stripe reflector is 0.05 mm, and the interval between adjacent stripe reflectors is 0.1 mm. With this configuration, even if the pitch of the LED array is widened to 14.5 mm, the output light from the adjacent LED element 2 is also reflected on the output surface of the glass plate 3 corresponding to the central area of the adjacent LED element 2. The light is guided sufficiently by the reflection effect of the body and the lower reflector, and a desired original irradiation light distribution can be obtained.

[0034]

As described above, according to the present invention,
The illumination light from the LED element is reflected by the light guide plate or the reflector formed on the upper surface and the lower surface of the light guide lens, and the light not reflected by the reflector illuminates the original as it is, and the light reflected by the reflector has reduced illuminance. LE can be guided to the part where
It is possible to obtain an effect that uniformization of the illuminance distribution in the main scanning direction can be achieved by effectively using almost all of the illumination light from the D element.

Further, by using a light guide lens as a member for guiding the illumination light from the LED element, the illumination light from the LED element can be condensed in the sub-scanning direction by the function as the lens. The effect that a lighting device with high illuminance can be obtained by the light effect can be obtained.

[Brief description of the drawings]

FIG. 1A is a plan view of an upper surface of a light guide plate of an LED array light source according to a first embodiment of the present invention. FIG. 1B is a sectional view taken along the line AA in FIG. (C) A plan view of the lower surface of the light guide plate in FIG.

FIG. 2 is a view for explaining the function of a reflector formed on the light guide plate in FIG. 1;

FIG. 3A is a sectional view of an LED array light source according to a second embodiment of the present invention, taken along the array direction. FIG. 3B is a sectional view taken along line BB in FIG.

FIG. 4 is a sectional view of an LED array light source according to an embodiment of the present invention, taken along an array direction.

FIG. 5A is a plan view of a conventional light amount adjustment mask of an LED array light source. FIG. 5B is a sectional view taken along line LL of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printed wiring board 2 LED element 3 Light guide plate 4a Upper surface reflector 4b Lower surface reflector 31 Printed wiring board 32 LED element 33 Light guide lens 34a Upper surface reflector 34b Lower surface reflector 35 Supporter 41a Central reflection area 42a Peripheral reflection area 52 LED Element 53 Sealing resin 54 Light-shielding pattern 54a, 54b, 54c Light-shielding portion 55 Light intensity adjustment mask 6 Original

Claims (8)

(57) [Claims] An LED in which a plurality of LEDs are arranged in a line
An array, and a light guide member disposed above the LED array, wherein the light guide member has an incident surface on which output light from the LED array is incident, and an exit surface facing the incident surface. A first reflector having a striped pattern having a central opposite region facing each light emitting region of the LED and a peripheral reflection region on the emission surface, receives a part of the output light from the LED; A plurality of light-reflecting elements are provided so as to reflect the light toward the surface, and the light-incident surface is provided with a second light-reflecting body that reflects the light reflected by the first light-reflecting body toward the light-emitting surface. Characteristic LED array light source. 2. A light emitting device according to claim 1, wherein the light reflected by the peripheral reflection region is reflected by the second reflector and emitted from a region between the adjacent first reflectors. The LED array light source according to claim 1, wherein 3. The LED array light source according to claim 1, wherein said first reflector has a parallel stripe shape extending in a direction orthogonal to an arrangement direction of said LEDs. 4. The LED array light source according to claim 3, wherein a stripe width of the region opposite to the periphery of the first reflector is smaller than a stripe width of the central reflection region. 5. The LED array light source according to claim 3, wherein each stripe width of said first reflector is all the same. 6. The LED array light source according to claim 1, wherein the light guide member is a cylindrical member having a long column axis in the arrangement direction of the LEDs. 7. The LED according to claim 5, wherein a width of the stripe pattern is smaller than a stripe interval.
Array light source. 8. The LED array light source according to claim 3, wherein the number of stripes in the stripe pattern is an odd number of at least three or more, and the width of each stripe decreases from the center toward both sides. .