JPS63303309A - Optical fiber unit - Google Patents

Abstract

PURPOSE:To reduce the number of parts and the cost of a product by forming the end part of an optical fiber to an inverted circular cone shape to expand the diameter, forming the largest diameter part corresponding to the base of the circular cone shape as a lens face and focusing the lens face to the vertex of the circular cone shape. CONSTITUTION:A coating member 11c at the end of the optical fiber 11 is stripped and the core 11a is worked by increasing the diameter of the end face forward to have the inverted circular cone shape and is held by a support 12. The core 11a is so worked at this time that the thickness of a clad 11b enclosing the core 11 is equal to the thickness of the part protected by the member 11c. The largest diameter part of the end face is formed as a convex lens in this case and is so formed that the focal point Q of the convex lens is formed at the position corresponding to the vertex of the circular cone shape. The ray R past the point Q is thereby paralleled with the central axis of the fiber at the end face part of the fiber. The state as if a light source exists at the vertex point position Q of the circular conical shape in appearance is attained by such constitution. The detection distance by the ray R is thus extended. The ray from the light source is made into the parallel ray if the lens face is formed as an aspherical face.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of an optical fiber end of an optical fiber unit used in a photoelectric switch or the like.

[Conventional technology]

This type of optical fiber unit is designed to increase the detection distance from the light receiving and transmitting tip of the optical fiber.
A method is adopted in which a lens is attached to the light emitting end. FIG. 2 is a sectional view of the light-receiving and light-emitting ends of an optical fiber having such a structure.

That is, the optical fiber 1 has a central core 1a wrapped in a cladding 1b, and its outer periphery is protected by covering it with a covering member IC such as nylon. At the end of the optical fiber 1,
A convex lens 4 is attached to a lens holder 3 via a lens 2.

The convex lens 4 is installed vertically so that its focal point is connected to the point P on the distal end surface of the core 1a, so that light traveling from the right to the left of the core 1a of the optical fiber 1 enters the convex lens 4 from the point P. However, the light is refracted here and becomes parallel light rays, which are emitted from the lens surface. Further, light that enters the lens surface from the left side of the convex lens 4 is refracted by the convex lens 4, is condensed, enters the core 1a of the optical fiber 1 from point P, and travels to the right in the axial direction of the core 1a.

[Problem that the invention seeks to solve]

According to the above-mentioned structure, attachments in addition to the lens holder are required to attach the convex lens for condensing light to the tip of the optical fiber, resulting in a complicated structure and high manufacturing costs. .

In view of the above-mentioned problems, it is an object of the present invention to reduce the number of components for condensing light installed at the tip of an optical fiber, thereby reducing product costs.

[Means for solving problems]

In order to achieve the above-mentioned object, in the present invention, the structure for condensing light at the end of the optical fiber is as follows. That is, the end of the optical fiber is formed into a conical shape to increase its diameter, and the maximum diameter portion corresponding to the bottom of the conical shape is formed as a lens surface, and the focal point of the lens surface is made to correspond to the apex of the conical shape. It is configured to be tied in place.

[Effect]

The end of the optical fiber is shaped like an inverted cone and the diameter is expanded, making it easier to throw and
The light-receiving area is increased, and since the end of the optical fiber is formed as a lens surface, the light rays emitted from the optical fiber can be made into parallel rays, and the light condensing property is good.

〔Example〕

FIG. 1 is a longitudinal cross-sectional view of an optical fiber end showing an embodiment of the present invention. In this embodiment, first, the optical fiber 1
] The covering member 11C at the end of the core 11 is peeled off, and the core 11a is processed so that the diameter of the end face becomes larger toward the front so that it becomes an inverted conical shape, and is held by a support 12.

At this time, it is important that the thickness of the cladding 11b surrounding the cores 11, 1 is the same as that of the portion protected by the covering member 1]C. In the embodiment, the maximum diameter portion of the end face is formed as a convex lens, and the focal point Q of the convex lens is arranged to be connected to a position corresponding to the apex of the conical shape. As a result, the light ray R passing through the focal point Q at the apex position of the cone becomes parallel to the central axis of the fiber at the fiber end face.

This means that the light source appears to exist at the apex position of the conical shape, and the detection distance by this light beam becomes longer. By making the lens surface an aspherical surface, the light from the light source can be made into parallel rays.

〔Effect of the invention〕

According to this invention, since the end of the optical fiber is formed into an inverted conical shape, the light receiving area is increased, and the end surface corresponding to the bottom of the inverted conical shape is formed as a lens surface, and the focal point of the lens surface is set at the apex position of the conical shape. Since the optical fiber is configured to be tied together, a lens effect can be obtained and the light beam emitted from the optical fiber can be made into parallel light beams, which has the advantage of eliminating the need for a lens or lens holder and reducing the number of parts.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an optical fiber end showing an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view of an optical fiber end showing a conventional example. l]: optical fiber, 1] a: core, llbl dunnid. 11c: Covering member. ll Jihin Abno 1°゛Figure 1Figure 2

Claims (1)

[Claims] 1) In an optical fiber whose outer periphery is coated with a coating member,
forming the end of the optical fiber into an inverted conical shape to increase its diameter, and forming the maximum diameter portion at the bottom of the conical shape as a lens surface;
An optical fiber unit characterized in that the lens surface is configured to focus at a position corresponding to the apex of the conical shape.