JPH0444368A - Light emitting diode array - Google Patents

Abstract

PURPOSE:To enlarge the width of an incoming beam without lowering illuminance by arranging two sets of lens, which are to be provided at the ceiling board of a case, such that, for one set, the axes of the lenses line up in parallel with the array directions of light emitting diodes, and that, for the other set, the axes line up perpendicularly to them. CONSTITUTION:LED elements 2 are surrounded by the case 5, whose ceiling board 3 are provided, at both surface and rear, with convex lens 4a and 4b semicircular in cross section. The lens 4a are arranged so that the center axes may line up in parallel with the array direction of the LED elements 2. The convex lens 4b on the side opposite to the elements 2 are arranged, so that each projection end may come right above each element 2, in the direction that the center axes cross the center axes of the lenses 4a at right angles and in plural rows extending in the width direction of the case 5. Each lens 4b absorbs light efficiently in the array direction of the elements 2, and takes it into the lens 4b, and the lens 4a condenses it further in the width direction of a wiring board 1, so the quantity of emission as an array increases, and even if one uses a convex lens of such small curvature that the luminous beam width widens, the illuminance never falls.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a light emitting diode (hereinafter referred to as LED) array used in a light source for reading a document in a copying machine or a FAX.

(Prior Art) Generally, as shown in FIGS. 4 and 5, the LED array described above has LED elements 2 arranged substantially linearly on the surface of a rectangular flat wiring board 1 along its long direction. By surrounding the LED element 2 with a case 5 with a lens, which has convex lenses 4'a and 4'b each having a semi-cylindrical cross section on both the front and back surfaces of the ceiling plate 3 that covers the upper part of the LED element 2. It was configured.

Here, the biconvex lenses 4'a and 4'b are arranged on the front and back surfaces of the ceiling plate 3 so that their central axes extend parallel to the arrangement direction of the LED elements 2, that is, the biconvex lenses 4'a4'
In b, both surfaces formed a double-sided convex lens that protruded in an arc shape in opposite directions.

As a result, as shown in FIGS. 6 and 7, the light beam 6 emitted from the LED element 2 is directed through the two convex lenses 4'.
Due to the lens effect of a, 4' b, the receiving beam width of the receiving system is 7
FA
Sufficient brightness (illuminance) to read X or copy machine originals
I wanted to get it.

(Problem to be Solved by the Invention) However, in order to achieve high illuminance, convex lenses 4/a formed on both the front and back surfaces of the ceiling plate 3 of the case 2 are required.
, 4/b increases the curvature to produce a sharp emission beam 6
However, in order to meet this requirement, the center 6 of the emitted beam 6 may be distorted due to minute positional deviations of the LED elements 2, etc., as shown in FIG.
' is meandering from the straight line 9 connecting each LED element 2,
When incorporated into an actual machine such as a FAX, the problem is that the illuminance distribution curve 10 within the effective illuminance area becomes an uneven curve, resulting in large unevenness in illuminance on the document surface, as shown in FIG. there were.

In order to solve this problem, lens 4'a.

4' b It is conceivable to reduce the curvature and widen the beam width, but the illuminance will be lowered by the amount of the reduced curvature.

In this way, there is a contradictory relationship between high illuminance and wide beam width, which are two important characteristics required for LED arrays, and it is currently difficult to achieve both at the same time. .

In view of the above, an object of the present invention is to provide a device that can widen the width of the received light beam without lowering the illuminance.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above, the light emitting diode array according to the present invention includes a wiring board, light emitting diode elements arranged linearly on the wiring board, and an upper part of the light emitting diode elements. In a light-emitting diode array comprising a lens-equipped case having a pair of convex lenses each having a semi-cylindrical cross section on both the front and back surfaces of a covering ceiling plate, one of the lenses provided on the ceiling plate of the case has its central axis aligned with the light-emitting diode element. are arranged so as to extend linearly along the arrangement direction, and
The other lens is arranged with its central axis perpendicular to the central axis of the lens.

(Function) According to the present invention having the above configuration, the light emitted from the LED (light emitting diode) element is first focused by the convex lens formed on the back surface of the ceiling plate of the case, and then further focused on the surface of the ceiling plate. The light is further focused by the formed convex lens, but at this time, since the biconvex lenses are arranged so that their central axes are orthogonal to each other, the light in directions orthogonal to each other is efficiently focused and the LED Even if a convex lens with a small curvature is used, which efficiently captures the light emitted from the element into the lens, thereby increasing the amount of light emitted by the light emitting diode array and widening the emitted beam width, the illuminance will still be low. It can be prevented.

(Example) An example of the present invention will be described below with reference to FIGS. 1 and 2.

That is, similar to the conventional example, the LED elements 2 are arranged substantially linearly on the surface of the rectangular flat wiring board 1 along the longitudinal direction of the wiring board 1.
Around the D element 2 is a ceiling plate 3 that covers the upper part of the LED element 2.
It is surrounded by a case 5 with a lens provided with convex lenses 4g and 4b each having a semi-cylindrical cross section on both the front and back sides.

Here, one of the convex lenses 4a located on the front surface side of the ceiling plate 3 is arranged so that its central axis extends parallel to the arrangement direction of the LED elements 2, similarly to the conventional example.

The radius of curvature R1 of the second convex lens 4a is, for example, about 2 degrees (
R1-2mm). As shown in FIGS. 10 and 11, a convex lens 4'a is provided only on the back side of the ceiling plate 3.
This is because there is a track record of an emitted beam width of about 5 m1 m1 in an LED array configured with a so-called one-side convex lens.

Further, the convex lens 4b on the back side of the ceiling plate 3, that is, the side facing each LED element 2, has its central axis aligned with the convex lens 4a.
The LED elements 2 are arranged in multiple rows extending in a direction perpendicular to the central axis of the case 5, that is, in the width direction of the case 5, with each protruding end positioned directly above each LED element 2.

In this way, by arranging the biconvex lenses 4a and 4b so that their central axes are perpendicular to each other, the emitted light beam 6 emitted from the LED element 2 first reaches the ceiling plate 3 of the case 5.
At this time, as shown in FIG. 2, each convex lens 4
b is the arrangement direction of the LED elements 2 (longitudinal direction of the wiring board 1)
The light is efficiently absorbed along the lines and taken into the lens 4b, and then the convex lens 4a formed on the surface of the ceiling board 3
The light is further focused in the width direction of the wiring board 1, thereby increasing the amount of light emitted by the LED array.

Here, a convex lens 4b formed on the back side of the ceiling plate 3
The radius of curvature R2 is, for example, 1.5N (R2
= 1.5 degrees).

FIG. 3 shows the LED in this embodiment configured as described above.
The data obtained by measuring the width of the emitted light beams of three types of LED arrays: an LED array with convex lenses on both sides in the conventional example shown in FIGS. 4 to 9, and an LED array with a convex lens on one side shown in FIGS. No. 11 (this example), No. 12
(bilaterally convex lens) and 13 (unilaterally convex lens). Note that in each of the above LED arrays, the same members are used except for the lens.

The vertical axis (X-axis) of this graph indicates the bit position of the light receiving system (CCD), and the horizontal axis (y-axis) indicates the brightness at each bit position. Therefore, the waveform of each graph represents the brightness distribution by measuring the brightness at several points in the direction perpendicular to the longitudinal direction of each LED array, and the higher the peak of the waveform, the brighter it is. The angle of the crest of the waveform, that is, the more obtuse the included angle between the three points where a straight line is drawn from the apex to the lowest part of the ridgeline on either side of the apex and the 0 brightness line, the wider the emission beam width.

As is clear from this graph, LE in this example
D array is L of conventional double-convex lens and single-sided convex lens.
It can be seen that compared to the ED array, this has both increased brightness and increased width of the emitted beam.

〔Effect of the invention〕

Since the present invention has the above configuration, it is possible to efficiently capture the light emitted from the light emitting diode elements into the lens and increase the amount of light emitted by the light emitting diode array, thereby widening the emitted beam width. Even if a lens with such a small curvature is used, since the amount of light taken into the lens increases as described above, it is possible to prevent a decrease in illuminance.

Figure 3 is a graph showing the measurement results of the emission beam width in this embodiment and the conventional example, and Figures 4 to 9 are sectional views taken along the line ■-■.
The figures show a conventional example, FIG. 4 is a perspective view, FIG. 5 is a cross-sectional view of FIG. 4, and FIG. 6 is a view equivalent to FIG. 5 showing the state of light irradiation.
FIG. 7 is a cross-sectional view taken along the line ■-■ in FIG. 11th
The figures show an LED array with a convex lens on one side, FIG. 10 is a cross-sectional view, and FIG. 11 is a cross-sectional view taken along the line XI-XI in FIG. 10.

1... Wiring board, 2... Light emitting diode (L E
D) Element, 3...Ceiling plate, 4a, 4b...Convex lens, 5...Case, 6...Emission beam, 7...Reception beam width.

[Brief explanation of drawings]

Claims (1)

[Claims] A case with a lens that includes a wiring board, light emitting diode elements linearly arranged on the wiring board, and a pair of convex lenses each having a semi-cylindrical cross section on both the front and back sides of a ceiling plate that covers above the light emitting diode elements. In the light emitting diode array, one of the lenses provided on the ceiling plate of the case is arranged so that its central axis extends linearly along the arrangement direction of the light emitting diode elements, and the other lens is arranged so that its central axis extends linearly along the arrangement direction of the light emitting diode elements. A light emitting diode array, characterized in that the light emitting diode array is arranged in a direction perpendicular to the central axis of the lens.