JPH09127617A - Linear light source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a LED linear light source which is nearly equal in the length of an effective illumination region to the size of a main scanning direction. SOLUTION: A light transparent resin 11 for sealing LED elements 10 is subjected to mirror finishing not only at curved reflection surfaces 12 but at flanks 15 and 16 at both ends as well, by which lateral reflection surfaces are formed. These surfaces are equiv. to the LED elements existing at the mirror image point with respect to the lateral reflection surfaces 15 (or 16) of the LED elements 10. The incident light rays on the lateral reflection surfaces 15, 16 among the light rays emitted from the LED elements 10 existing near the lateral reflection surfaces 15 of the LED wire-shaped light source are reflected at these surfaces and are cast in the final from the radiation surfaces 13 to light receiving surfaces 14. Then, the light rays which are heretofore radiated outside from the flanks at the ends and are not utilized as light sources are effectively utilized by providing the wireshaped light source with the lateral reflection surfaces 15 (or 16).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LED linear light source used as a light source for image reading of a copying machine or a facsimile.

[0002]

2. Description of the Related Art A halogen lamp or the like has been conventionally used as a light source for reading an image in a copying machine or a facsimile. However, when using a halogen lamp etc.,
Generates a large amount of heat. Further, when a color image is read using a halogen lamp as a light source, it is necessary to take out the three primary colors using an optical filter, so there is a problem in that each color cannot be directly electrically adjusted or processed with respect to the light source. is there. For this reason, recently, an LED linear light source in which light emitting diodes (LEDs) having the above-mentioned drawbacks are linearly arranged has been used as a light source for image reading of a copying machine, a facsimile, or the like.

FIG. 7 is a sectional view of a conventional LED linear light source taken along a plane perpendicular to the axis, and FIG. 8 is a sectional view of the same LED linear light source taken along a plane parallel to the axis. Conventional LED
As shown in FIGS. 7 and 8, the linear light source includes a plurality of light emitting elements 71 arranged in a line with their light emitting surfaces facing in the same direction, and a light emitting element provided corresponding to each of the plurality of light emitting elements. A plurality of pairs of leads 72a for supplying electric power to the element 71,
72b, a light-transmissive material 73, a cylindrical reflecting surface 74 having a central axis in the arrangement direction of the plurality of light emitting elements 71, and a radiation surface 75 provided on the back side of the plurality of light emitting elements 71. Have. Each light emitting element 71 is mounted on the corresponding lead 72a via a conductive adhesive (not shown). Also,
Each light emitting element 71 is electrically connected to the corresponding other lead 72b by a wire (not shown). The plurality of pairs of leads 72a and 72b are made of the light transmissive material 73.
Are pulled out alternately in the direction of both sides. The plurality of light emitting elements 71 and the tips of the plurality of pairs of leads 72a and 72b are integrally sealed with a light transmissive material 73. The reflecting surface 74 and the emitting surface 75 are formed on the surface of the light transmissive material 73.

In the conventional light emitting diode having the above-described structure, substantially the entire luminous flux of the light emitted from the plurality of light emitting elements 71 is reflected by the cylindrical reflecting surface 74 and emitted forward from the emitting surface 75. According to the conventional light emitting diode having the above configuration, the light emitting direction is
Since it is controlled by the columnar reflecting surface 74, the light collecting efficiency can be improved when the light emitted from the light emitting element is condensed into a spot shape (here, a linear shape with a narrow line width). Therefore, a high irradiation light quantity density can be obtained. In addition, with a lens surface provided on the light emitting surface side of the light emitting element, a so-called lens type light emitting diode that controls the emission direction of light can also collect the light emitted by the light emitting element in a spot shape.
The light collection efficiency is low, and thus a high irradiation light amount cannot be obtained.

[0005]

By the way, when an LED linear light source is used, not only the light from the LED element closest to that point, but also from the LED elements in the vicinity of this point, is generated at an arbitrary position on the light receiving surface. Light is also emitted. Therefore, the L
At the end of the LED linear light source where the number of ED elements is small, the illuminance is lower than at the center. FIG. 9 is a diagram showing how the illuminance at the end of the LED linear light source decreases.
In the figure, the vertical axis represents the illuminance and the horizontal axis represents the position of the LED linear light source in the main scanning direction x. In order to perform good image reading with a copying machine, a facsimile or the like, it is desirable to use the illuminance within a range (effective illuminance area) m in which the illuminance is about 90% or more of the maximum illuminance Lmax in the central portion. Due to such a decrease in illuminance at both ends, the length of the effective illuminance region of the LED linear light source becomes shorter than the dimension a of the LED linear light source in the main scanning direction. In other words, in order to obtain the effective illuminance area m having a predetermined length, the main scanning direction x of the LED linear light source is obtained.
The dimension a at must be longer than its effective illumination area. This is not desirable in copying machines, facsimiles, etc., where there is a strong demand for downsizing and weight reduction.

The present invention has been made under the above circumstances, and an object thereof is to provide an LED linear light source in which the length of the effective illuminance area is substantially equal to the dimension in the main scanning direction.

[0007]

According to a first aspect of the present invention for solving the above-mentioned problems, a plurality of light-emitting elements linearly arranged at a predetermined interval and a plurality of the light-emitting elements are sealed inside. The light-transmitting resin that stops and the light emitted from the plurality of light-emitting elements are reflected, and the plurality of light-transmitting resins are provided on the surface of the light-transmitting resin so as to be converged on the external light-receiving surface through the emission surface. It is characterized in that it has a cylindrical reflecting surface formed in parallel with the arrangement direction of the light emitting elements and side reflecting surfaces formed on end side surfaces on both sides perpendicular to the arrangement direction of the light emitting elements. .

According to a second aspect of the invention, in the first aspect of the invention, the plurality of light emitting elements are arranged at equal intervals. A third aspect of the present invention is characterized in that, in the first aspect of the invention, the plurality of light emitting elements are arranged such that an interval between end portions is smaller than an interval between central portions.

According to a fourth aspect of the invention, in the first aspect of the invention, the radiation surface is a flat surface, and the cylindrical reflecting surface is designed in consideration of interface refraction on the radiation surface. It is characterized by being a thing.

[0010]

As described above, according to the present invention, by forming the side reflection surfaces on the end side surfaces on both sides of the light-transmitting resin of the linear light source, when these are not provided, the end portions are left unused. The light emitted from the side surface to the outside is reflected by the side surface reflecting surface and returned to the inside of the light transmissive resin.
This light then reaches the external light receiving surface through the emitting surface, or after passing through the emitting surface after being reflected by the cylindrical reflecting surface. Therefore, most of the light emitted from the light emitting element is finally emitted from the emission surface, and the light is effectively used.

Further, by making the distance between the light emitting elements in the vicinity of the end portion smaller than that in the central portion, it is possible to reduce a decrease in illuminance at the end portion due to the reflectance of the side reflection surface not reaching 100%.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic front view of the LED linear light source according to the first embodiment as seen from a radiation surface side,
FIG. 2 is a schematic end side view of this LED linear light source, and FIG.
FIG. 3 is a schematic longitudinal side view of this LED linear light source. The LED linear light source shown in FIGS. 1 to 3 has a total length b of about 150 mm, and has a large number of linearly arranged LED elements 1.
0 is about 0.3 mm square, and the distance d between the respective LED elements is 2.54 mm (0.1 inch). Each LED
The element 10 is mounted on the lead 10a which also serves as an electrode.

The cylindrical reflecting surface 12 and the emitting surface 13 have a shape in which approximately half of them are cut out along the central axis in the longitudinal direction when viewed from the front. In addition, the LED element 1
0 is arranged such that its light emitting surface faces the top of the reflecting surface 12 having a columnar shape. Reflective surface 1 of light transmitting resin 11
2 has a reflecting surface formed by mirror finishing by metal deposition. With this columnar reflecting surface 12, LE
The light emitted from the D element 10 is reflected and emitted from the emission surface 13. Predetermined distance from the emitting surface 13 (eg 1 cm)
A light receiving surface 14 of the read document is arranged so as to face the radiation surface at a position spaced apart from each other. The curved surface shape of the cylindrical reflecting surface 12 is designed so that the light emitted on the light receiving surface 14 converges in a substantially linear shape. For example, the cylindrical reflecting surface 12
The cross section perpendicular to the axial direction of the
The element 10 can be arranged. However, in the case of such an elliptical shape, the converged light cannot be made into a perfect spot due to the interface refraction at the interface between the radiation surface and the outside world. Therefore, in applications where it is necessary to converge light in a spot shape, it is desirable that the cross-sectional shape be a multi-dimensional curved surface in consideration of interface refraction. In this way, the cylindrical reflecting surface 12
Since the light can be converged by appropriately designing the curved surface shape, there is an advantage that it is not necessary to provide a cylindrical lens between the LED element 10 and the light receiving surface 14.

In the present embodiment, the light transmissive resin 11 is further added.
The side surfaces 15 and 16 at both ends are also subjected to the same mirror finishing as the cylindrical reflection surface 12 to form side reflection surfaces. The diagonal lines shown in FIGS. 2 and 3 indicate that the cylindrical reflecting surface 12 and the side reflecting surfaces 15 and 16 are mirror-finished. Next, a method for manufacturing the LED linear light source of this embodiment will be described. First, the lead 10a also serving as one of the electrodes
A large number of LED elements 10 which are mounted on and fixed to the other electrode and wire-bonded to the other electrode 10b are arranged linearly in the main scanning direction, and their relative positions are fixed. This is set in a predetermined mold, the upper mold and the lower mold are closed, and a thermosetting resin having light transparency is filled. 160 with this pressed
Mold by heating to about ° C and heating for several minutes. After that, the cured resin inside is taken out of the mold from the side of the radiation surface 13. At this time, at the end of the mold, in order to make it easier to take out the resin after molding from the mold,
A taper of about 3 to 5 ° is attached. Then, the tapered portion is cut, both end surfaces 15 and 16 are processed so as to be perpendicular to the axis, and further polished and smoothed. Finally, L
A metal thin film is vapor-deposited on the curved surface facing the light emitting surface of the ED element 10 and the smoothed end surface to form a mirror surface, and the columnar reflecting surface 12
And side reflection surfaces 15 and 16 are formed. Therefore, no special process is required to form the side reflection surfaces 15 and 16, and the number of working processes does not increase.

FIG. 4 is a diagram for explaining the effect of providing the side surface reflecting surfaces 15 (and 16) in the LED linear light source of this embodiment. Side reflection surface 1 of LED linear light source
Of the light emitted from the LED element 10 located in the vicinity of 5, the light traveling in the direction indicated by the arrow in FIG. 4A is reflected by the columnar reflecting surface 12 and then travels to the side reflecting surface 15. Here it is further reflected and emitted from the emitting surface 13,
It reaches the light receiving surface 14. On the other hand, of the light emitted from the LED element 10, the light traveling in the direction indicated by the arrow in FIG. 4B is reflected by the side reflection surface 15 and then the cylindrical reflection surface 1
2 where it is further reflected and emitted from the emitting surface 13 to reach the light receiving surface 14. This is equivalent to the presence of the LED element 10 'at the mirror image point of the side reflection surface 15 (or 16) of the LED element 10. As described above, conventionally, the light emitted from the end side surface to the outside and not used as the light source is the side reflection surface 15 (or 1).
By providing 6), the light finally reaches the light receiving surface 14 from the emitting surface 13 and is effectively used as light for irradiating the light receiving surface.

FIG. 5 is a diagram schematically showing the illuminance distribution at both ends of the LED linear light source. The solid line shows the case where the side reflecting surfaces 15 and 16 are provided as in the present embodiment, and the dotted line shows. This is the case where the side reflection surface is not provided. In each case, the effective illuminance area m is shown to be the same. In the conventional LED linear light source, in order to set the effective illuminance region to m, the illuminance gradually decreases at the end, so the dimension in the main scanning direction must be increased to a in the same figure. On the other hand, as in this embodiment, the side reflection surface 15
By providing 16 and 16, almost all of the light emitted from the LED elements provided near the ends is emitted from the emitting surface 13.
Since the light is radiated from the light receiving surface 14 to the light receiving surface 14, the illuminance distribution becomes substantially uniform up to the end as shown by the solid line in FIG.
As a result, the length m of the effective illuminance area and the length b of the LED linear light source in the main scanning direction become substantially equal to each other. Therefore,
It is possible to reduce the size and weight of various devices using this.

FIG. 6 shows an LED according to the second embodiment of the present invention.
It is a schematic longitudinal side view which shows a linear light source, and is a figure corresponding to FIG. 2 which shows 1st embodiment. In this embodiment,
The LED elements 10 at the end portions are arranged closer to each other than the central portion. As in the first embodiment shown in FIGS. 2 and 3, by providing the side surface reflecting surfaces 15 and 16 at both ends of the LED linear light source, the light to be emitted to the side surface is returned to the inside and the light is effectively used. It becomes possible to do. But,
Even in this case, the illuminance at the edge may not be sufficient. In this case, by arranging the LED elements 10 at the ends densely, it is possible to compensate for the decrease in illuminance at the ends.

The present invention is not limited to the above-mentioned embodiments, and various modifications can be made within the scope of the gist thereof. For example, in the above embodiment, the LED linear light source including the monochromatic LED element has been described.
A linear light source that facilitates the reading of a color image may be obtained by sequentially arranging red (R), green (G), and blue (B) LEDs in order with the LED elements arranged at intervals of about 1 mm. It is possible. In the above embodiment, the LED linear light source used as the reading light source of the copying machine or the facsimile has been described.
Other than this, for example, it can be used as an eraser for an EPROM that erases stored contents by irradiating light.

[0019]

As described above, according to the present invention,
In addition to the columnar reflecting surface facing the light emitting surface of the linearly arranged LED elements, side reflecting surfaces are also provided at both ends of the light transmissive resin. The light that has been emitted and has not been used is reflected by the side reflection surface and returned to the inside, and finally emitted from the original emission surface and reaches the light receiving surface. As a result, a decrease in illuminance at the end is suppressed, the effective illuminance region extends to the end of the LED linear light source, and as a result, the dimension in the main scanning direction can be shortened to the same extent as the effective illuminance region. Miniaturization of the size of various devices using such LED linear light source
The weight can be reduced.

Further, according to the present invention, the LE at the end is
By making the arrangement interval of the D elements smaller than that in the central portion, it is possible to further reduce the decrease in the illuminance at the end portion, and thus it is possible to provide the LED linear light source that can maintain the illuminance at the end portion more uniform.

[Brief description of the drawings]

FIG. 1 is a schematic front view of an LED linear light source that is a first embodiment of the present invention as seen from a radiation surface side.

FIG. 2 is a schematic end side view of the LED linear light source that is the first embodiment of the present invention.

FIG. 3 is a schematic longitudinal side view of the LED linear light source that is the first embodiment of the present invention.

FIG. 4 is a diagram for explaining an effect obtained by providing a side surface reflecting surface on the LED linear light source.

FIG. 5 is a diagram showing an illuminance distribution at both ends of an LED linear light source.

FIG. 6 is a schematic longitudinal side view of an LED linear light source that is a second embodiment of the present invention.

FIG. 7 is a schematic lateral sectional view of a conventional LED linear light source.

FIG. 8 is a schematic vertical sectional view of a conventional LED linear light source.

FIG. 9 is a diagram showing how the illuminance at the end of the LED linear light source decreases.

[Explanation of symbols]

 10,71 LED element 10a, 10b, 72a, 72b Lead 11,73 Light transmissive resin 12,52 Columnar reflecting surface 13,75 Radiating surface 14 Light receiving surface 15,16 Side reflecting surface 74 Reflecting surface m Effective illuminance area

Claims (4)

[Claims] 1. A plurality of light emitting elements linearly arranged at a predetermined interval, a light-transmissive resin that seals the plurality of light emitting elements inside, and reflects light emitted from the plurality of light emitting elements. Then, a columnar reflecting surface formed on the surface of the light transmissive resin parallel to the arrangement direction of the plurality of light emitting elements so as to converge on the external light receiving surface through the emission surface, and the light emission. A linear light source having: a side reflection surface formed on both end side surfaces perpendicular to the element array direction; 2. The linear light source according to claim 1, wherein the plurality of light emitting elements are arranged at equal intervals. 3. The linear light source according to claim 1, wherein the plurality of light emitting elements are arranged so that an interval between end portions is smaller than an interval between central portions. 4. The linear surface according to claim 1, wherein the emitting surface is a flat surface, and the cylindrical reflecting surface is designed in consideration of interface refraction on the emitting surface. light source.