JPS60230623A - Led array - Google Patents

Abstract

PURPOSE:To illuminate a photodetection surface over a wide area to high illuminance by using a distributed index lens as a condenser lens for the LED array which includes the condenser lens arranged adjacently to a substrate. CONSTITUTION:This invented LED array uses the prismatic distributed index lens as the condenser lens 6 differently from a conventional lens. The refractive index of this condenser lens 6 is uniform in the optical axis direction of the LED array and in its lengthwise direction and a square-law distribution in obtained at right angles to said two directions. Then, light beams emitted by LED chips 2 travel zigzag in the distributed index lens 3 and form an erect image of unmagnification on a photodetection surface 5. In this case, the LED chips and photodetection surface bear a relation of an erect image and unmagnification conjugate surface, so even if the distributed index lens 3 shifts in position finely by DELTA during the assembly, there is no shift in illuminated position and high illuminance is obtained on the photodetection surface over a wide area.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an LED array used for illuminating the document surface of an image reading device such as a facsimile machine or a copying machine, and particularly relates to an LED array used for illuminating the document surface of an image reading device such as a facsimile machine or a copying machine. irradiated surface)
The present invention relates to an LED array that can illuminate a wide area with high illuminance.

[Prior Art] In recent years, there has been an increasing demand for miniaturization of facsimile machines, copying machines, and similar image reading devices. LED made up of multiple pieces of
Arrays are increasingly being used. LED arrays have the advantage of being smaller and more durable than fluorescent lamps, but on the other hand, the absolute amount of light is small, making it difficult to obtain a sufficient amount of light for reading documents.

Referring to Fig. 1.2.3, the conventional LED array shown here includes an elongated substrate 1, LED chips 2 arranged on the substrate in a row in the longitudinal direction, and LED chips 2 arranged in parallel above the substrate l. It consists of a cylindrical condensing lens 3 supported by a support 4.

As can be seen from FIG. 4, which explains the light beam path and the illuminance on the light receiving surface, the light beam emitted from the LED chip 2 that passes near the center of the condenser lens 3 is directed to the center of the light receiving surface 5. It focuses the light and forms a peak in the illuminance distribution. The light beam that has passed through the periphery of the condenser lens 3 is caused by aberrations, so that the light beam passes through the light-receiving surface 5.
The light is not concentrated in the center of the area, but is diffused around it to form the base of the illuminance distribution. The light beam emitted laterally from the LED chip 2 does not directly enter the condenser lens 3, but instead enters the support 4. Usually, the support body 4 is made of white plastic, and the incident light beam is scattered, and a portion thereof passes through the condenser lens 3 and reaches the light-receiving surface 5.

When such an LED array is used to illuminate a document on an image reading device, the area of the document surface that serves as the light-receiving surface that is to be read must coincide with the central portion of the document surface where the highest illuminance can be obtained. .

When assembling the image reading device, if you want to avoid complicating the process by making fine adjustments to match the center of the light-receiving surface with the position you are trying to read on the document, L
High precision is required in the positional relationship between the LED chips of the ED array and the condensing lens. This is because, as shown in FIGS. 4A and 4B, in the conventional LED array, even if the positional relationship between the LED chip 2 and the condensing lens 3 shifts by a minute amount Δ, the illuminance peak on the light receiving surface will shift. This is because it causes

[Object of the Invention] The present invention has been made in view of these problems, and its purpose is to prevent the illuminance peak on the light receiving surface from shifting even if the positional relationship between the LED chip and the condensing lens is slightly shifted. The object of the present invention is to provide an LED array that does not cause

[Summary of the Invention] To achieve this object, the present invention provides an LED array including a substrate, LED chips arranged on the substrate, and a condensing lens arranged adjacent to the substrate. Provided is an LED array characterized in that the condenser lens is a gradient index lens.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described specifically and in detail based on the drawings.

With reference to Figure 5.6.7, the LED of the invention shown here
Similar parts of the array to those of FIGS. 1-4 are designated with like reference numerals. In the LED array according to the present invention, the condenser lens 6 is a rectangular bar-shaped gradient index lens, unlike the conventional one. The refractive index of the condensing lens 6 is uniform in the optical axis direction of the LED array and in the longitudinal direction of the array, and has a square distribution in the direction orthogonal to the first two.

8A and 8B are similar to FIGS. 4A and 4B, respectively, in which the light rays emitted from the LED chip 2 meander through the gradient index lens 3, and then stand upright on the light receiving surface 5. Forms an image at the same size.

In such an LED array, the LED chip and the light-receiving surface are in the same direction as long as we look at the luminous flux in a cross section perpendicular to the longitudinal direction of the array, such as the cross section taken along the line ■-■ in Figure 6. Since there is a conjugate plane relationship of vertical equal magnification, there is an advantage that even if the gradient index lens 3 is misaligned by a minute amount Δ during assembly, the illuminated position with respect to the light receiving surface will not change.

In addition, although a rectangular bar-shaped lens is shown as a gradient index lens in FIGS. 5 to 8, a flat plate-shaped lens may also be used.

[Effects of the Invention] Therefore, if the LED array according to the present invention is used, highly accurate positioning of the gradient index lens 3 is not required when assembling the LED array, and costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a conventional LED array. FIG. 2 is a front view of the LED array of FIG. 1. FIG. 3 is a sectional view taken along the line ■-■ in FIG. 2. Fig. 4 is a diagram explaining the luminous flux traveling within the cross section of Fig. 3 and the illuminance distribution on the light receiving surface, and Fig. 4A shows the case where the condenser lens is provided at the correct position with respect to the LED chip. FIG. 4B is a diagram showing a case where the condenser lens is misaligned with respect to the LED chip. FIG. 5 is a top view of an LED array according to the present invention. 6 is a front view of the LED array of FIG. 5. FIG. FIG. 7 is a sectional view taken along the line ■-■ in FIG. 6. Fig. 8 is a diagram explaining the luminous flux traveling within the cross section of Fig. 7 and the illuminance distribution on the light receiving surface, and Fig. 8A shows the case where the condenser lens is provided at the correct position with respect to the LED chip. FIG. 8B is a diagram showing a case where the condenser lens is misaligned with respect to the LED chip. In the drawings, lee/substrate, 2... LED chip,
3...-Condensing lens, 4... Support, 5... Light-receiving surface, 6... Gradient index condensing lens. 1B1 figure rod 5 figure 11 BA I! i! III BB diagram

Claims (1)

[Claims] (1) A substrate, LED chips arranged on this substrate,
An LED array including a condenser lens disposed adjacent to the substrate, wherein the condenser lens is a gradient index lens. (2. In the LED array according to claim 1, the refractive index distribution type lens has a rectangular bar shape, and the refractive index distribution type lens has a refractive index distribution only in a direction perpendicular to the optical axis of the LED array and the main direction of the array. (3) In the LED array according to claim 1, the gradient index lens has a flat plate shape, and
An LED array characterized in that it has a refractive index distribution only in a direction perpendicular to the optical axis of the array and the main direction of the array. (4) LE described in claim 2 or 3
In the D array, when considering a light flux traveling in a plane perpendicular to the main direction of the array, the light emitting surface of the LED chip and the illuminated surface to be illuminated by the LED array are on the conjugate plane of erect image formation. An LED array characterized by being in a relationship.