JPH05275736A - Optical semiconductor device - Google Patents

Abstract

PURPOSE:To make the title device thin without lowering the transmission efficiency of light from a light-emitting element up to a photodetector, to work a metal mold simply and to manufacture the metal mold easily and at low costs. CONSTITUTION:Composite aspherical Fresnel lenses 11, 12 whose parts 11a, 12a coincide with a light-emitting charactsristic and whose outer circumferential parts 11b, 12b coincide with a photodetection characteristic are used as a lighting lens on the front side of a light-emitting element chip 5 in a light-emitting element 1 and as a photodetection lens on the front side of a photodetection chip 9 in a photodetector 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical semiconductor device having a pair of light emitting and light receiving elements opposed to each other and used as a photo interrupter, a photo isolator, a photo coupler or the like.

[0002]

2. Description of the Related Art As an optical semiconductor device of this type, for example, a photo interrupter shown in FIG. 4 is conventionally known. That is, in FIG. 4, reference numerals 1 and 2 denote a pair of light emitting and light receiving elements which are arranged to face each other with a predetermined interval. Among them, the light emitting element 1 includes an LED (light emitting diode) chip 5 fixed to a predetermined portion of the lead piece 3 and covered with a resin mold 4, and a single spherical projection provided on the front side of the LED chip 5. The light receiving element 2 is composed of an optical lens 6, and the light receiving element 2 is fixed to a predetermined portion of the lead piece 7 and covered with a resin mold 8.
It comprises a single spherical light receiving lens 10 arranged on the front side of the phototransistor chip 9.

In such a configuration, the light from the LED chip 5 in the light emitting element 1 is condensed by the light projecting lens, then emitted to the light receiving element 2 side, taken in by the light receiving lens 10 in the light receiving element 2, and photo The light is received by the transistor chip 9.

[0004]

By the way, in this kind of optical semiconductor device, there is a demand for miniaturization and thinning, and in order to meet this demand, a space between the LED chip 5 and the light projecting lens 6 and the phototransistor 9 is required. The respective distances Th between the light receiving lens 10 and the light receiving lens 10 tend to be reduced, and the radii of curvature of the light projecting and light receiving lenses 6 and 10 also tend to be reduced. Therefore, in the conventional one in which the light projecting and light receiving lenses 6 and 10 are formed of a single spherical lens, an optical mismatch occurs in the light receiving lens 10 and the light transmission efficiency is forced to decrease.

By the way, when the radius of curvature of the light projecting lens 6 is kept constant and the radius of curvature of the light receiving lens 10 is increased, the intensity (light receiving intensity) increases accordingly, as shown in FIG. Therefore, as shown in FIG. 6, by setting the radius of curvature of the light receiving lens 10 to be large, the light transmission efficiency can be improved, but in this case, molding for the light projecting lens 6 and the light receiving lens 10 is performed. Due to the difference in size, a two-sided mold is required, which results in a high production cost.

The present invention has been made in order to solve the above-mentioned conventional problems, and it is possible to reduce the size of the device without lowering the light transmission efficiency, and to manufacture the device easily and at low cost. An object is to provide an optical semiconductor device.

[0007]

In order to achieve the above object, an optical semiconductor device according to the present invention includes a light emitting element having a light projecting lens arranged in front of a light emitting chip and the light emitting element chip. A light-receiving element having a light-receiving lens arranged in front of a light-receiving element chip that is arranged at a predetermined interval and is opposed to the light-receiving element;
The light projecting lens and the light receiving lens are each composed of a compound aspherical Fresnel lens of the same shape whose outer peripheral portion is set to a radius of curvature suitable for the light receiving characteristic.

[0008]

According to the present invention, the light from the light emitting element chip is efficiently collected at the central portion that matches the light projection characteristics of the compound aspherical Fresnel lens on the light emitting side and is received by the compound aspherical Fresnel lens on the light receiving side. Since the light is taken in by the outer peripheral portion that matches the characteristics, even if the radius of curvature of both lenses is made small for thinning, mismatching on the light receiving side does not easily occur, and good light transmission efficiency is maintained. Further, the Fresnel lens facilitates the molding of the one having both the light-projecting and light-receiving characteristics, and can be manufactured at a low cost because the mold having one surface can be used.

[0009]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a block diagram showing an example in which the optical semiconductor device according to the present invention is applied to a photo interrupter. The same parts as those of the conventional one shown in FIGS. Is omitted.

In FIG. 1, a compound aspherical Fresnel lens 1 having the same shape is used as a light projecting lens and a light receiving lens, respectively.
1 and 12 are used. That is, as shown in FIGS. 2 and 3, the composite aspherical Fresnel lens 11 (12) has a central portion 11a (12a) and an outer peripheral portion 11b (12b).
And, the central portion 11a (12a) has a relatively small radius of curvature so as to match the light emitting characteristics, and the outer peripheral portion 11b (12b) has a light receiving characteristic. The radius of curvature is set to be relatively large so as to match.

In such a structure, the light from the LED chip 5 of the light emitting element 1 is condensed at the central portion 11a of the composite aspherical Fresnel lens 11 which matches the light projecting characteristics, and then irradiated to the light receiving element 2 side. .. On the side of the light receiving element 2, since the outer peripheral portion 12b of the composite aspherical Fresnel lens 12 matches the light receiving characteristic, the irradiated light is mainly efficiently absorbed by the outer peripheral portion 12b and is received by the phototransistor chip 9. And converted into an electric signal.

Since the central portion 11a having a small radius of curvature of the composite non-contact Fresnel lens 11 plays a role on the light emitting side and the outer peripheral portion 12b having a large radius of curvature of the composite non-contact Fresnel lens 12 plays a role on the light receiving side. Even when the radius of curvature of each of the lenses 11 and 12 is reduced in order to reduce the thickness of the photo interrupter, it is less likely that mismatch will occur in the optical system, especially on the light receiving side. For this reason, it is possible to achieve a thin and compact structure without causing a reduction in light transmission efficiency. Further, the central portion 11a (12a) suitable for the above-mentioned light emitting characteristic is provided with the outer peripheral portion 11b suitable for the light receiving characteristic.
By adopting the Fresnel lens as the lens having (12b), its molding is facilitated, and since it is sufficient to prepare the composite non-contact Fresnel lenses 11 and 12 having the same shape, it is only necessary to use the one-sided mold. It is possible to manufacture it at low cost.

In the above-mentioned embodiment, the description has been made by using the chatter interrupter as an example, but the same effect can be obtained even if another optical semiconductor device such as a photo coupler is applied.

[0014]

As described above, according to the present invention, the light-projecting lens on the front side of the light-emitting element chip and the light-receiving lens on the front side of the light-receiving element chip are provided with the outer periphery having a radius of curvature that matches the light-projecting characteristics. Since each part is composed of a compound non-contact Fresnel lens of the same shape with a radius of curvature that matches the light receiving characteristics, it is possible to promote compactness while maintaining high light transmission efficiency, and it is easy to manufacture. And cost reduction can be achieved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an example in which an optical semiconductor device according to the present invention is applied to a photo interrupter.

FIG. 2 is a diagram showing a side surface shape of a composite non-contact Fresnel lens on the light emitting and light receiving element side in the photo interrupter of the same example.

FIG. 3 is a view showing a sectional shape of the composite non-contact Fresnel lens.

FIG. 4 is a configuration diagram showing a conventional optical semiconductor device.

FIG. 5 is a characteristic diagram showing a relationship between a radius of curvature of a light-receiving side lens and intensity.

FIG. 6 is a configuration diagram showing another conventional optical semiconductor device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light emitting element 2 Light receiving element 5 Light emitting element chip 9 Light receiving element chip 11,12 Composite non-contact Fresnel lens 11a, 12a Central part 11b, 12b Outer peripheral part

Claims (1)

[Claims] 1. A light emitting element having a light projecting lens arranged on the front side of the light emitting element chip, and a light receiving lens arranged on the front side of a light receiving element chip facing the light emitting element chip at a predetermined interval. And a light receiving element formed of the same, the central portion is set to a radius of curvature that matches the light emitting characteristics, and the outer periphery is set to a radius of curvature that matches the light receiving characteristics. An optical semiconductor device comprising a light receiving lens.