JPH05188238A - Optical path angle converter of optical fiber - Google Patents

Abstract

PURPOSE:To reduce the size, weight and cost and to facilitate the assembly by forming a reflection type diffraction optical lens, consisting of plural grating zones in an elliptic pattern shape and a reflecting layer, on the oblique surface of a triangular prism. CONSTITUTION:At the center part of the oblique surface of the triangular prism 1 having, for example, a right-angled isosceles triangle shape in section, the reflection type diffraction optical lens 4 of elliptic shape is formed integrally. This reflection type diffraction optical lens 4 consists of a grating zone 2 having saw-tooth wave-shaped in section and the reflecting layer 3 provided on the grating zone 2. The converter in this structure serves also as a collimator lens, a condenser lens, a mirror, and a base and the positioning is facilitated. Light 7 emitted from an input optical fiber 5 is made incident on the reflection type diffraction optical lens 4, reflected and diffracted, emitted and converged at the same projection angle as the incoming angle and coupled with an output optical fiber 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical path angle converter for an optical fiber, and more particularly to a compact, lightweight, low price,
The present invention relates to an optical path angle converter of an optical fiber which is easy to assemble.

[0002]

BACKGROUND OF THE INVENTION Optical fibers are capable of confining light therein and guiding the light relatively freely to any location.
Not only for long-distance optical communication that is often used at present, but for short distances, if optical wiring using an optical fiber as a medium is used instead of electrical wiring, high density is possible because of non-induction, high speed broadband, etc. It can have many features. In such short-distance optical wiring, it is often required to arbitrarily change the direction of light in a short distance. However, when trying to bend while confining light in an optical fiber, the bending strength of the fiber itself increases, and the propagation loss of light increases when strongly bent. Therefore, the radius of curvature of bending increases and the size becomes compact. Is impossible.

For this reason, a method in which light is once emitted, the optical path is changed, and the light is input again is effective. As a conventional optical fiber optical path angle converter, there is one shown in FIG. 2 (cross-sectional view). In the figure, light 7 emitted from the input optical fiber 5 (incident light to the lens 13) is collimated by the collimator lens 13, reflected by the mirror 11, changed in direction by 90 °, and collected by the condenser lens 10. The light is emitted and becomes the emitted light 8, which is coupled to the output optical fiber 6.

[0004]

The conventional optical fiber optical path angle converter shown in FIG. 2 is composed of a total of three parts, that is, two lenses and a mirror, so that the mutual alignment is troublesome and the cost is reduced. It was difficult to make it even smaller and lighter. Further, since the light is once emitted from the optical fiber into the air, it is necessary to perform antireflection coating on the boundary surface between the lens and the mirror with the air in order to eliminate the loss of the light.

The present invention has been made in view of the above problems, and provides an optical path angle converter for an optical fiber which is small, lightweight, inexpensive, and easy to assemble.

[0006]

In order to solve the above-mentioned problems, the present invention comprises a triangular prism and a reflective diffractive optical lens formed on the slope of the prism. An optical fiber optical path angle conversion characterized by comprising a plurality of grating zones and a reflective layer provided on the grating zones, wherein the pattern shape of the grating zones is elliptical, and guides light from the input optical fiber to the output optical fiber. To provide a container.

[0007]

The present invention has a structure in which a reflective elliptical diffractive optical lens composed of a grating is integrated on the inclined surface of a triangular prism, so that it can serve as a collimator lens, a condenser lens, a mirror and a base. , Simplifies the alignment and enables cost reduction. By making the grating pattern shape of the lens elliptical, aberrations caused by oblique incidence are corrected and good condensing characteristics are realized.

[0008]

1 (a) is a side view showing the basic structure of an optical fiber optical path angle converter according to an embodiment of the present invention, showing how light enters and exits. FIG. 1 (b) shows an embodiment of the present invention. It is a block diagram which shows the shape of the reflection type diffractive optical lens seen from the prism slope of an optical fiber optical path angle converter.

In the figure, the cross section is, for example, an isosceles right triangle (eg, hypotenuse length 7.1 mm, length and width 5 m).
m), a triangular prism 1 with a height of 5 mm, for example
At the center of the slope of the, the elliptical reflective diffractive optical lens 4
It has a structure that integrates. The reflective diffractive optical lens 4 has a grating zone 2 (having a groove depth of 0.2 μm, for example) having a saw-tooth cross section, and a metal layer such as Ag, Al, or Au provided on the grating zone 2 or The reflective layer 3 is a multilayered dielectric film. For example, the lens 4 has a size of 0.7 mm in the major axis direction and 0.5 mm in the minor axis direction, and a focal length of 2.5 mm.

In this embodiment, in order to further improve the environment resistance, a protective layer 9 such as A is formed on the reflective layer 3.
1, metal layers such as Cu, Cr, synthetic resins such as UV curable resins and lacquer paints, dielectric multilayer films, SiO, SiO ₂ , M
The structure is such that gF ₂ , SiC, graphite, diamond, etc. are deposited from 1000 Å to several μm.

Light 7 emitted from the input optical fiber 5
Is incident on the reflection type diffractive optical lens 4 by, for example, an incident angle θ = 45.
Incident at 4 °, reflected and diffracted, and emitted at the same exit angle (4
It is emitted and condensed at 5 ° and is coupled to the output optical fiber 6. The output optical fiber 6 is the input optical fiber 5
In contrast, they are arranged with their directions changed by 90 °, and the direction of the optical path can be changed by 90 °. The input optical fiber 5 and the output optical fiber 6 are optical bonds made of synthetic resin or the like (refractive index is almost the same as the core of the fiber),
It is attached to the triangular prism 1, and the direction of the optical path can be changed without ever letting the light propagating through the optical fiber into the air. Therefore, it is possible to eliminate the Fresnel reflection at the boundary surface, resulting in low loss,
Stabilization can be achieved without the influence of disturbance.

The present inventor has determined that the shape of the grating zone 2 is such that the ratio of the major axis to the minor axis (major axis / minor axis) with respect to the incident angle (θ) of light to the reflective diffractive optical lens 4. 1 / cos
It has been discovered that the elliptical shape of θ eliminates the aberration that occurs when the incident light 7 is obliquely incident on the lens 4 and can satisfactorily focus light. In particular, when the optical path length from the input optical fiber 5 to the reflection type diffractive optical lens 4 is equal to the optical path length from the output optical fiber 6 to the reflection type diffractive optical lens 4 (each optical path length is equal to the focal length of the lens 4 is 2). (When doubled), the condensing characteristic of this lens 4 is the best, and at this time, the same light distribution as the light distribution on the end face of the core of the optical fiber 5 is obtained.
It was found that the coupling efficiency with the optical fiber 6 is good because it is realized by the core end surface of.

A known electron beam was used as a method for manufacturing the reflection type diffractive optical lens of the present invention. That is, a synthetic resin coated on the substrate 1, for example, an electron beam resist such as PMMA or CMS, which is sensitive to an electron beam is irradiated with the electron beam, and at that time, the same shape as the grating zone 2 of the lens 4 to be manufactured is used. Adjust the irradiation amount on the curve (ellipse) so that it becomes a sawtooth shape, gradually increase the size of the ellipse until it becomes the size of the lens,
Repeated irradiation. After that, a development process is performed to change the film thickness, and then a reflective layer 3 of, for example, Ag is deposited, for example, 4000 Å.
Was deposited as 1000 Å to form the lens 4. The reflection efficiency could be increased by making the thickness of the reflective layer 3 larger than the maximum thickness of the grating zone 2.

In mass production, the lens element 4 before the reflection layer 3 is deposited is used as a master to make a mold by, for example, a nickel electroforming method. For example, a UV curable resin is used to reproduce from the mold and the reflection is performed. If the layer 3 is deposited, the same lens element as that of the master can be manufactured at low cost. In particular, when it is desired to manufacture an optical fiber optical path angle converter that converts the optical path of the fiber array by arraying the diffractive optical lenses 4 on the prism slope, this method can be used to form the lenses with the same characteristics at a high accuracy. The effect is great because it can be done.

The triangular prism 1 need only be transparent with respect to the wavelength used, and for example, a glass prism is stable with respect to temperature, and is lightweight when a prism made of synthetic resin is used.

In this embodiment, the converter for changing the direction of the optical path by 90 ° has been described. However, by changing the angle of the prism, it is possible to manufacture converters with various angles. Further, as the prism, a triangular prism has been described, but it goes without saying that the shape of the portion through which light does not pass is not a problem and, for example, a shape obtained by cutting the portion may be used.

[0017]

As described above, according to the present invention, there is an effect that it is possible to realize an optical path angle converter of an optical fiber which is small, lightweight, low in cost, and easy to assemble.

[Brief description of drawings]

FIG. 1A is a side view showing a basic configuration of an optical fiber optical path angle converter according to an embodiment of the present invention, and a state of entering and exiting light. FIG. 1B is an optical fiber optical path angle converter according to an embodiment of the present invention. Configuration view from the prism slope of

FIG. 2 is a block diagram of a conventional optical fiber optical path angle converter.

[Explanation of symbols]

 1 Triangular prism 2 Grating zone 3 Reflective layer 4 Reflective diffractive optical lens 5 Optical fiber for input 6 Optical fiber for output 7 Incident light 8 Emission light 9 Protective layer

Claims (4)

[Claims] 1. A triangular prism and a reflective diffractive optical lens formed on the slope of the prism, wherein the reflective diffractive optical lens includes a plurality of grating zones.
Consisting of a reflective layer provided on the grating zone,
An optical fiber optical path angle converter characterized in that the pattern shape of the grating zone is elliptical and guides light from the input optical fiber to the output optical fiber. 2. The optical path angle of an optical fiber according to claim 1, wherein the optical path length from the input optical fiber to the reflection type diffractive optical lens is equal to the optical path length from the output optical fiber to the reflection type diffractive optical lens. converter. 3. The ratio of the major axis to the minor axis (major axis / minor axis) of the elliptical grating zone is 1 / cos θ with respect to the incident angle (θ) of light to the reflective diffractive optical lens. The optical fiber optical path angle converter according to claim 1, wherein: 4. The optical path angle converter according to claim 1, wherein a protective layer is provided on the reflective layer.