JPS6374025A - Light emitting device - Google Patents

Abstract

PURPOSE:To obtain a desired effective illuminance area without making the overall length longer than required, by forming both end parts of a rod-shaped lens so that its thickness becomes thinner toward its terminal. CONSTITUTION:A rod-shaped lens 11 is cylindrical except both end parts so as to raise a condensing effect of both end parts, and formed so that thickness of both its end parts becomes thinner toward its terminal. As for a shape of one example thereof, both the terminals are provided with a thin end face part 11a containing the diameter of a column being parallel to a substrate, and a slant face part 11b which has been provided so as to slice off the column toward the center part from said part. As for this slant face part 11b, a part of a curved surface or a spherical surface is suitable, and its inclination is provided on 2-3 pieces o LED pellets from an LED array, although there is problem for a design related to an arrangement (interval), etc., of the LED pellets in the LED array. According to such a rod-shaped lens, as for an optical path of an emitted light of the LED pellet of the end part of the LED array, its effect becomes remarkable when a gradient theta of the slant face is within a range of +20 deg. and -10 deg.. In this way, a drop of an illuminance distribution in both end parts of the LED array is reduced remarkably.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention relates to a light emitting device, and particularly relates to an inventive diode array (
(hereinafter abbreviated as LED array).

(Prior Art) An example of a conventional LED array is shown in a partially sectional side view in FIG. 4a. In the figure, 101, 101... are LEDs
The pellets are mounted and wired linearly and at regular intervals on a printed wiring board 102 (hereinafter referred to as the board) made of a glass epoxy base material. In addition, a cylindrical lens 103 (made of acrylic resin, for example) is placed directly above and parallel to these LED pellet groups.
FIG. 4b) shows the lens holding member 10 equipped with a reflector 114.
4, it is fixed to the substrate 102. Note that a light-receiving surface 105 is arranged on one side of the second cylindrical lens 103 at a distance of about 30 mm from it (Fig. 4a,
Figure 5).

The cylindrical lens 103 in the conventional LED array described above is shown in a perspective view in FIG. 4, and as shown in FIG.
The light beam from the D pellet 101 is symmetrical about the LED pellet in the length direction of the cylindrical lens.

Therefore, at the end of the cylindrical lens, the illuminance is the luminous flux of the LED pellet at the edge of the board and the luminous flux incident from one LED pellet on the center side, and the illuminance at the center of the cylindrical lens is the luminous flux of one LIED pellet. Since the illuminance is due to the luminous flux incident from the LED pellets on both sides of this LED pellet and further adjacent LED pellets, the illuminance is low at the edge of the substrate. That is, in this state, as is clear from the illuminance distribution diagram shown in FIG. 6, the illuminance distribution at both ends is noticeably reduced. Figure 6 is an illuminance distribution diagram showing the length direction of the LED array as the horizontal axis and the illuminance at each part as the vertical axis.
There is a Min). In other words, a uniform illuminance distribution area called an effective illuminance area is considerably shorter than the total length of the LED array.

(Problems to be Solved by the Invention) As mentioned above, in the conventional LED array, the illuminance distribution decreases significantly at both ends, and the effective illuminance area is quite narrow relative to the total length of the LED array, that is, the effective illuminance area is wide. In order to obtain this, a longer LED array is required, and it is often difficult to obtain the desired characteristics due to space constraints within equipment such as copying machines and facsimile machines.

An object of the present invention is to provide a structure of an L[ED array that can obtain a desired effective illuminance area without increasing the overall length more than necessary.

[Structure of the invention]

(Means for Solving the Problems) This invention solves the above-mentioned problems of the conventional LED array by increasing the thickness of both ends of the rod-shaped lens so that both ends of the lens have a light focusing effect in the longitudinal direction of the lens. It is characterized by being formed thinly toward the terminal, and the total length of the LED array required to obtain the desired effective illuminance area can be minimized.

(Function) The present invention allows the rod-shaped lenses of the LED array to have a light focusing effect in the longitudinal direction, thereby minimizing the total length of the LED array required to obtain a desired effective illuminance area.

(Example) An example of the present invention will be described below with reference to the drawings. In addition, in the description, parts that are the same as in the prior art are shown in the drawings with the same reference numerals as in the prior art, and the description thereof will be omitted.

FIG. 1a shows a partially cross-sectional side view of an example LED array. In the figure, + 11 is a rod-shaped lens, and as shown in the perspective view in Figure 1, it is cylindrical except for one end, and the thickness of the end is the same as that of the end, so as to ensure the light-condensing effect at both ends. It is thinly formed. For this example shape,
A thin end face portion 11 whose both ends include the diameter of a cylinder parallel to the substrate.
a, and a sloped portion tib provided so as to scrape the cylinder toward the center (Fig. 1b). Although this slope portion 11b is shown as a plane for the purpose of explanation, it is preferable to use a curved surface or a part of a spherical surface. 2 to 3 LEs from the end of
D is provided on the pellet. According to the rod-shaped lens configured in this manner, the optical path of the light emitted from the LED pellet at the end of the LED array is +20 degrees with the slope (0) centered at 25 degrees, as illustrated in FIG. The effect was significant within the range of -10 degrees.

With the above structure, the decrease in illuminance distribution at both ends of the LED array is significantly reduced, and an illuminance distribution diagram is shown in FIG. The method of representing this illuminance distribution is the same as in the conventional example explained with reference to FIG. 6 above.

Incidentally, the material of the rod-shaped lens is not limited to acrylic resin, and other synthetic resins, glass, etc. can also exhibit the same effect.

〔Effect of the invention〕

Although the quantitative effects of this invention vary depending on the system using the LED array, - for example, the irradiation distance is 30 mm.
Let's discuss the case. In FIG. 3 showing the illuminance distribution of LEI) play with the above structure, MAX is the maximum illuminance value in the distribution, MIN is the minimum illuminance value, and the illuminance unevenness is expressed by the following formula.

When the conventional illuminance unevenness shown in FIG. 6 is evaluated using the above equation, it is about 20%, and the illuminance unevenness of the embodiment shown in FIG. 3 is about 10%. In actual applications, a level of about 15% or less is required, so the effects of this invention are very significant.

[Brief explanation of the drawing]

FIG. 1a is a side view showing a part of an LED array according to an embodiment of the present invention in cross section, FIG. 1 is a perspective view of the rod-shaped lens in FIG. 1a, and FIG. 2 is a rod-shaped lens according to the present invention. 3 is a diagram showing the illuminance distribution of the LED array according to the present invention; FIG. 4a is a side view showing a part of the conventional LED array in cross section; Figure 4 is a perspective view of the cylindrical lens in Figure 4a, Figure 5 is a cross-sectional view for explaining the optical path at the end of the cylindrical lens, and Figure 6 is a diagram showing the illuminance distribution of a conventional LED array. It is. 11 ---- One-rod lens 11a---- End view of one-rod lens 11b----
- Slanted part 101 of the cylindrical lens ------- LED pellet 102 ---- One substrate 114 - One reflective plate

Claims (1)

[Claims] A plurality of LED pellets arranged substantially in a straight line on a wiring board, a reflector having a reflective surface corresponding to the LED pellets, and a rod-shaped member arranged above the reflector in parallel with the arrangement of the LED pellets. 1. A light emitting device comprising a lens, wherein the rod-shaped lens has both ends thereof thinner toward the terminal.