JPS601584A - Optical switch - Google Patents

Abstract

PURPOSE:To prevent flaws and damages to the detection surface while dispensing with a reflection preventing film by providing a transparent protective film with a specified thickness against light used on the detection surface of an optical head forming a optical switch. CONSTITUTION:A transparent protective layer 9 against light used is provided on the detection surface 4 of an optical head forming an optical switch which detects the presence of an object 6 to be inspected with a projecting optical fiber 1, a receiving optical fiber 2 and the like retained on a support holder 5. When the thickness of the layer 9 is selected to be below (NoxT)/2NA, the maximum emission angle of light from the surface 4 of the fiber 1 meets a specified requirement and no reflected light from the end face 9a of the layer 9 is incident into the fiber 2. This can prevents flaws and damages to the detection surface while dispensing with a reflection preventing film or the like. In the formula, T: distance between cores of both the optical fibers on the detection surface, NA: the number of openings of optical fibers and No: refractive index of the protective layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a reciprocal optical switch using an optical fiber, and can be used, for example, as a proximity switch.

[Technical back pressure of the invention and its problems] Figure 1 shows the conventional configuration of a reflective optical switch.
2 is a light-emitting optical fiber; 3 is an optical head formed by the light-emitting end of the light-emitting optical fiber 1 and the light-receiving end of the light-receiving optical fiber 2; 4 is a light-emitting optical fiber; The detection surface of the optical head is formed by the light emitting end surface of the optical fiber 1 for use and the receiving end surface of the light receiving optical fiber 2; 5 is an optical spatula I;
A holder 6 supports the objects C to 3, and 6 is the object C to be detected facing the detection surface 4 of the optical head. The light emitting optical fiber 1 has an end face opposite to the light emitting end face forming the detection surface 4 coupled to a light emitting means (not shown), and guides light from the light emitting means to the detection surface 4J and the other end face. The light is emitted toward the object 6 to be detected. The light-receiving optical fiber 2 has an end face opposite to the light-receiving end face forming the detection surface 4 coupled to a light-receiving means (not shown), and receives reflected light from the object to be detected 6 and directs it toward the light-receiving means. and waveguide.

According to the above configuration, the output light of the light emitting optical fiber 1 is reflected by the detected object 6 and then enters the light receiving optical fiber 2, so the presence or absence of the C detected object 6 is determined based on this incident light. and displacement can be detected. However, as is clear from FIG. 1, an optical switch with such a configuration has
Since the light-emitting end face of the light-emitting optical fiber 1 and the light-receiving end face of the light-receiving optical fiber 2, which form the detection surface 4 of the optical head, are exposed, J3 becomes inoperable due to scratches or damage to the detection surface.
There it was.

Figure 2 shows another conventional configuration of a reciprocating optical switch, in which 7 is a protective layer on the detection surface (transparent against the applied light), 8 is a light emitting optical fiber 2; The anti-reflection film for preventing the emitted light from being reflected by the end face 7a of the protective layer 7 and entering the light-receiving optical fiber 2, and the same reference numerals as those in the thin tube 1 in FIG.

According to the above structure, the drawbacks described in FIG. 1 are improved, but since it is necessary to further provide an antireflection film 8 on the protective layer 7, the manufacturing process becomes complicated and the manufacturing cost increases. I have a problem with that.

[Object of the Invention] The present invention is intended to improve the above-mentioned problems of the conventional technology, and its purpose is to prevent scratches and damage to the detection surface,
Moreover, it is an object of the present invention to provide an optical switch having a structure that does not require an antireflection film.

[Summary of the Invention] A feature of the present invention for achieving the above object is that the present invention includes at least one optical fiber for transmitting light and one optical fiber for receiving light,
In an optical switch in which an optical head is formed by a light-emitting end face of a light-emitting optical fiber and a light-receiving end face of a light-receiving optical fiber, a protective layer transparent to the light used is provided on the detection surface of the optical head, and the protective layer The thickness of NoxT/2NA (
(T is the distance factor between each core of the light emitting optical fiber and the light receiving optical fiber on the detection surface 1, N△ is the numerical aperture of the optical fiber used, and NO is the refractive index of the protective layer). be.

[Embodiments of the Invention] Fig. 3 is a block diagram showing an embodiment of an optical switch according to the invention, Fig. 4 is a diagram showing input/output characteristics of the optical switch used in the invention, and Fig. 5 is a diagram showing a protective layer. FIG. 3 is an explanatory diagram of thickness determination.

In the third lens 1, the detection surface 4 formed by the light-emitting end face of the light-emitting optical fiber 1 and the light-receiving end face of the light-receiving optical fiber 2 is provided with b optical heads 3. It is no different from the conventional 4J4 configuration shown in Figure 1 and Figure 2. The difference from the conventional structure of the present invention is that the thickness of the transparent 4-domain control layer 9 is changed by changing the thickness of the transparent 4-domain control layer 9 to the used light that is also received on the detection surface 4 of the optical system 1-3. The thickness of the emitted light (r/: 1) is selected to be below that which prevents the emitted light from being reflected by the end face 9a of the layer 9 and entering the light-receiving optical fiber 2.

The input/output characteristics of this type of anti-fouling optical switch are shown in Figure 4.
Ipa 2 input 0 = 1 light However, the horizontal axis is the detection surface 4 and the detected object 6
When the distance between the detecting object 14 and the detected object G is longer than 1, the reflected light leaks into the light receiving optical fiber 2. Therefore, the guarantee A'5 PA 9
It is clear that if the thickness is set to less than 1, the reflected light will not enter the light receiving optical fiber 2 from the end face 9a.

Determine Ifj of Ai 1 above using Figure 5.

In FIG. 5, at J3, 1a and 1b are the cladding and core of the light-emitting optical fiber 1, and 2a and 211 are the cladding and core of the light-receiving optical fiber 2.

Reference numeral 10 denotes a virtual image of the light emitting optical fiber 1 relative to the nonconforming surface 6a of the object 6, ioa and 10b represent the cladding and core of the virtual image 10, and 20 indicates the receiving optical fiber 13 of the light receiving optical fiber 1 relative to the nonconforming surface 6a of the detected object 6. statues, 20a and 201
+ is the cladding 63 and core of 1120. A 1b of the light emitting optical fiber 1 and the core 2 of the light receiving optical fiber 2
Let the separation distance between the detection surface 4 and the detection surface 40 be T, and the separation distance between the detection surface 4 and the detection surface 40 of the virtual image be 29-.

The distance between the detection surface 4 and the object to be measured 6 is nl, which means that 2!11, and the light emitted from the point A of the core 1b of the optical fiber 1 for light emission is the one for light reception. This means reaching point B of the core 20b of the f8 image 20 of the optical fiber 2.

Therefore, if the maximum angle of emission from the detection surface 4 of the light projecting optical fiber 1 is 0nlaX, then the following equation holds true between A1 and T.

T=21+tanθmax On the other hand, if the numerical aperture of the optical fiber used is NA, then NA
has the following relationship between Omax and the refractive index No of the protective layer.

NA=sinθmax/N.

Using the near linear equation sin θ-tan o when θ is small, fLIL is as follows.

Eden-NoxT/2NA Therefore, the thickness L of the protective layer 9 is set to t<1l-NoxT/
If 2NΔ is selected, the reflected light from the end surface 9a of the protective layer 9 will not enter the light-receiving optical fiber 2. For example, N.A.
=0.2. If T=O', 5mm No.=1.5 then L
= 1.875 mm, so the thickness t of the protective layer 9 is 1.
, 875 mm or less.

Figure 6 (Δ) a5 and Figure 6 (B) show front views of the detection surface of the optical head, and Figure 6 (A) is composed of one optical fiber for light emission and one for light reception. In this case, Figure 6 (B)
1 and 2 show cases in which each of them is composed of a plurality of optical fibers. T1
indicates the distance between the cores when one optical fiber is used, and T2 indicates the distance between the cores when multiple optical fibers are used. I5 [Effects of the Invention] As explained in 1-1, according to the present invention, the thickness of the protective layer is selected to a value that prevents reflected light from the end face of the protective layer from entering the light-receiving optical fiber I. Therefore, the anti-reflection coating is already applied (
It is possible to provide a light switch that does not need to be turned on.

[Brief explanation of the drawing]

Fig. 1 shows a conventional example of an optical switch, Fig. 2 shows a configuration diagram of another conventional example of an optical switch, and Fig. 3 shows an embodiment of an optical switch according to the present invention. FIG. 4 is a diagram showing the input/output characteristics of the optical switch used in the present invention, FIG. 5 is an explanatory diagram of determining the thickness of the protective layer, and FIGS. 6(A) and 6(B) shows a front view of the detection surface of the optical head. 1... Optical fiber for light emission 1b, 211... Core 2... Optical fiber for light reception 3... Optical head 4... Detection surface 6... Object to be detected 9... Maintenance Leopard-C%C

Claims (1)

[Scope of Claims] An optical head comprising at least one light-emitting optical fiber and one light-receiving optical fiber, and the light-emitting end face of the light-emitting optical fiber and the light-receiving end face of the light-receiving optical fiber. In the switch, a protective layer that is transparent to the light used is provided on the detection surface of the optical head, and the thickness of the protective layer is
T/2NA (T is the distance between the cores of the light emitting optical fiber and the light receiving optical fiber on the detection surface, NA is the number of openings of the optical fiber used, and NO is the refractive index of the protective layer). and a light switch that covers.