JPS6271812A - Optical fiber sensor - Google Patents

Abstract

PURPOSE:To measure the quantity of displacement precisely even when the surface of a body to be measured is curved by arranging plural photodetection elements symmetrically about at least one projection element. CONSTITUTION:An optical fiber sensor 1 is formed of, for example, seven elements in one body. The projection element 5 is arranged at its center part and the photodetection elements 6 are arranged at the periphery adjacently and symmetrically about the projection element 5. Light emitted by the element 5 is projected on a curved-surface target 2 while having a constant spread 5', and its reflected light is photodetected by the photodetection element while having a constant spread 6' similarly. Consequently, the light emitted by the element 5 is photodetected by the photodetection elements nearly by the total quantity, so variation of the output to the distance to the target surface becomes gentle. Consequently, the distance to the target surface is measured precisely.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an optical fiber sensor that is a non-contact measurement sensor, and in particular, when the surface shape of the object to be measured is a curved surface, the distance to the object to be measured is measured. This invention relates to an optical fiber sensor suitable for measuring.

[Background of the invention]

The optical fiber sensor calculates this νIl meter a+ from the amount of reflected light projected onto the surface of the object to be measured using an optical fiber
The amount of displacement (distance) to the surface of the object (target) to be
q is fixed. There are various types of optical fiber sensors, examples of which are shown in FIG. In FIG. 2, an optical fiber sensor 1 is formed by alternately arranging a light projecting element that projects light to a target and a light receiving element that receives the projected reflected light (5+j).
Optical Technology 1985, 111-6, published by the Optical Industry Technology Association, p. 32).

Note that the light projecting element is equipped with a light emitting element for supplying light, and the light receiving element is equipped with a photoelectric element that converts the received light M into a home/air signal.

Light 3 emitted from the light emitting element of the optical fiber sensor is reflected by the target 2, and the reflected light 4 enters the light receiving element, where the reflected light is converted into an electrical signal by an optical rIi element such as a phototransistor. Ru. As a result, a curve as shown in FIG. 3 is obtained depending on the distance (displacement amount) between the sensor 1 and the target 2. When measuring, the straight portion of the back slope is used for measurement because of the increased amount of light received and the possibility of improving the i++ constant accuracy.

However, in the above-mentioned optical fiber sensor, when the surface of the target is the )P plane, it is possible to perform the accuracy < flllll determination, but when the surface of the target laser 1 becomes a curved surface, the 1lll11 constant accuracy decreases significantly. was there.

[Purpose of the invention]

The purpose of the present invention is to use the wave meter 811 to accurately measure displacement even when the surface of an object is curved. An object of the present invention is to provide an optical fiber sensor that can easily measure the amount of displacement regardless of the surface form of an object to be measured.

[Summary of the invention]

The relationship between light emission and light reception of the conventional optical fiber sensor is schematically explained in FIG. 4.6 In FIG. 4(a),
The exchange of light between the light emitting element 5 and the light receiving element 6 of the optical fiber sensor is shown three-dimensionally. Floodlight 1
The light 5' emitted from the noment 5 exhibits a certain spread depending on the optical characteristics and tip shape of the optical fiber. - The light-receiving elements i and 6 can receive light. Since the light-receiving space also shows a similar spread 6', the sight of the diagonally shaded area 7 where the two overlap is the total amount of light II+ in the optical fiber sensor.

This amount of light is correlated with the amount of displacement of the target.

Accordingly, as shown in C1 Fig. 4 (b), when the target 2 is a flat surface, the arrangement of the light emitting and light receiving amount elements is j
It is possible to always measure a constant scene regardless of the situation. However, if the surface of the target is curved as shown in Figure 4 (Hough), the amount of light entering the center light receiving element will be different for the right and left light emitting elements.Especially the right light emitting element. The light reflected from the element is not received by the light-receiving element.If the surface of the target is curved, the amount of light received is insufficient, so the displacement to the target is 41 degrees f+1 degrees. decline is unavoidable.

The present invention was made based on such knowledge, and its configuration includes a light projecting element, a light emitting element that supplies light to the light projecting element, and a light emitting element that receives light projected by the light projecting element. In an optical fiber sensor comprising a light-receiving element and a photoelectric element that outputs an electrical signal according to the amount of light received by the light-receiving element, at least one light-emitting element is disposed at the center, and the light-emitting element This is an optical fiber sensor characterized in that a plurality of light receiving elements are arranged symmetrically around the circumference.

According to the above configuration of the present invention, since the light emitting element is disposed in the center, the light emitted from the light emitting element is
Even if the surface of the target is curved, all of the reflected light will be received by the light receiving element. the result,
This will result in a 1llllllllll surface polishing of the amount of change to the target surface.

[Embodiments of the invention]

Next, embodiments of the optical fiber sensor according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a diagram showing the tip portion We of an optical fiber sensor, and the optical fiber sensor 1 is formed by seven elements integrated together. A light projecting element 5 is disposed at the center, and light receiving elements 6 are disposed adjacently and symmetrically to each other on the periphery. The light projected from the light projecting element 5 is projected onto the curved target 2 with a certain spread 5', and the reflected light is similarly received by the light receiving element with a certain spread 6'.

When such a sensor is moved from side to side, the distance between the sensor and the target 2 becomes longer due to the curved surface, and the corresponding change in the amount of light received is measured as an electrical signal.

FIG. 5 shows the relationship between the distance (displacement amount) to the surface of the target 2 and the electrical output signal (11i pressure) according to the amount of received light.

Graph A in FIG. 5 is a graph measured using the optical fiber sensor described in Section J[・4, and graph B in FIG. These are measurement results obtained using a conventional optical fiber sensor with a light emitting element arranged around it.

Note that the curvature of the curved surface of the target 2 surface is bilaterally symmetrical.

In both optical fiber sensors, the curvature of the surface of the target 2 is uniform, so the graphs are symmetrical as shown in Figure 5 Δ and B. It can be seen that with conventional optical fiber sensors, the output of the receiving star changes suddenly with respect to displacement, making it impractical.

This is because the light-receiving element is arranged in the center and the light-emitting element is arranged around the light-receiving element, so the light-receiving element cannot receive a sufficient amount of light emitted by the light-emitting element. . On the other hand, in the optical fiber sensor shown in Fig. 1, which has a light emitting element in the center, almost all of the light emitted from the light emitting element can be received by the light receiving element, so that the output relative to the distance to the target surface is Changes will be gradual. As a result, it becomes possible to accurately measure the distance to the target surface by 811 in total.

In addition to the structure shown in Fig. 1, the structure of the tip of the optical fiber sensor is as shown in Fig. 6, in which a light-emitting element is arranged in the center and two light-receiving elements are arranged in pairs. ! (61A(Δ)), in which a PT optical element is arranged in the center and four light receiving elements are arranged symmetrically around it (Fig. 6 ( B)). These idiots believe that if the light emitting element is placed in the center and the light receiving elements are placed symmetrically, it will always be safe regardless of the number and orientation of the light receiving elements. It has been experimentally confirmed that output in the range can be obtained.

〔Effect of the invention〕

As explained below, according to the optical fiber sensor according to the present invention, even if the surface of the target array 1 is a curved surface, the amount of displacement to the target can be measured with high accuracy. As a result, it becomes possible to always accurately measure the amount of displacement to the target regardless of the surface form of the wave meter t111 object.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the tip structure of the optical fiber sensor according to the present invention and the state of measurement up to the target surface distance;
Figure 2 is a diagram showing the tip structure of a conventional optical fiber sensor and measurement of target displacement, Figure 3 is a graph showing the relationship between displacement and electrical output, and Figure 4 is a diagram showing the projection of a conventional optical fiber sensor. A schematic diagram of the relationship between light and light reception, FIG. 5 is a graph showing the relationship between the displacement amount to the target and the electric signal of the optical fiber sensor according to the present invention and the conventional optical fiber sensor, and FIG. 6 is the optical fiber sensor according to the present invention. A cross-sectional view showing the sensor tip groove jt in another embodiment of
FIG. 7 is a sectional view showing the tip structure of a conventional optical fiber sensor. 1. Optical fiber sensor, 2. Receiving object, 3.
・Projected light, 4... reflected 1st. 5. Light emitting element, 6. Light receiving element.

Claims (1)

[Claims] 1. A light emitting element, a light emitting element that supplies light to the light emitting element, a light receiving element that receives the light emitted by the light emitting element, and an electric signal according to the amount of light received by the light receiving element. In an optical fiber sensor comprising a photoelectric element that outputs a An optical fiber sensor characterized by: