JPH01239419A - Displacement quantity detector - Google Patents

Abstract

PURPOSE:To accurately measure the quantity of movement of a body to be measured at low cost by making >=2 input-side optical fibers different in length and generating a pulse train which has a time different as projection pulses. CONSTITUTION:Input-side optical fibers 2 and projection-side optical fibers 4 are arranged opposite each other and a light shield body 6 which moves together with the body to be measured is arranged between both fibers. Then the input-side optical fibers 2 are made different in length to obtain delay effect by the difference in optical path length, and light pulses are outputted as the pulse train having the time difference. When the light shield body 6 is at a lower position in this constitution, nine light pulses are detected as a train, but when the shield body 6 moves up, four light pulses, for example, are detected and the movement quantity is converted into the number of pulses. Thus, the movement quantity is accurately measured at low cost without being affected by noises, photodetection sensitivity, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a displacement detector that measures the amount of displacement of an object to be measured using light.

(Prior Art) There have been various methods for measuring the amount of displacement of an object to be measured, one of which is the method shown in FIG. This consists of a secondary coil a, two secondary coils b, b2 connected in opposite directions, a secondary coil a and a secondary coil bl,
b2 and a movable iron piece C disposed between the movable iron piece C. This is done by passing current from an AC power source d through the secondary coil a, and when the iron piece C connected to it moves due to the movement of the object to be measured e, the secondary coils b, , b? The magnitude of the voltage induced in the transformer changes, and the voltage difference is extracted to detect the amount of movement of the object to be measured d as a change in the starting force of the operating transformer. Note that f in FIG. 6 is a voltmeter that displays the starting force of the operating transformer.

However, since the measurement method shown in FIG. 6 uses electricity, it cannot be used in locations where there is electrical or magnetic noise, such as in strong magnetic fields or high electric fields. Therefore, conventionally, optical measurement methods as shown in Figs. 7 and 8 have been developed. In both of these methods, the object to be measured e is connected to a shielding body C, and an input side optical fiber i and an output side optical fiber are connected to each other. A shielding body C is disposed between the optical fiber j and the optical fiber 1.1, and when the object to be measured e moves, the shielding body C shields the space between both optical fibers 1.1 according to the amount of movement of the object e.

Of these, the one in Figure 7 measures the movement of the object e as a change in light intensity using one light source g and one photodetector, and the one in Figure 8 uses one or more photodetectors. light source g
The movement of the object to be measured e is measured by using a large number of photodetectors and a change in the number of light shields of the photodetectors.

(Problems with the prior art) Among the conventional techniques, the measurement method shown in FIG. 7 measures the movement of the object e to be measured as a change in the amount of light. Accurate measurements have been difficult due to the effects of fluctuations in light-receiving sensitivity.

Although the measuring method shown in FIG. 8 allows highly accurate measurements, it requires a large number of photodetectors, which makes the measuring device complicated and large, and has the problem of increasing costs.

(Objective of the Invention) An object of the present invention is to solve the problems of the prior art and to provide a measuring instrument capable of measuring the moving displacement lid of a measured object with high precision and at low cost.

(Means for Solving the Problems) As shown in FIG. Two or more output-side optical fibers 4 that individually receive the optical pulses A from the fibers 2 and transmit them to one photodetector 3 are separated by a predetermined distance and faced to each other, so that the two-party fiber fibers 2
A light shielding body 6 is placed between the input optical fiber 2 and the output optical fiber 4 by moving in accordance with the movement of the object 5 to be measured. In a displacement detector in which the number of fibers is varied, the lengths of the two or more input-side optical fibers 2 are varied so that the optical pulses A emitted from them are pulse trains with a time difference. This is a characteristic feature.

The light @i emits pulsed light having a relatively short emission time (for example, pulse A as shown in FIG. 2).

The input optical fibers 2 have different lengths, and as shown in FIG. 1, the input end 11 is connected to the light source 1, the central part 12 is wound around a cylinder 13, and the output ends 14 are arranged in a line vertically. ing. In this case, the output end 1 of the short input optical fiber 2
4 at the bottom and the output end 14 of the long input optical fiber 2 at the top.

The output side optical fiber 4 has its light receiving end 15 facing the output end 14 of the input side optical fiber with a predetermined separation distance, and its light output end 16 is connected to the photodetector 3.

The light shielding body 6 is arranged between the input side optical fiber 2 and the output side optical fiber 4, and is connected to the object to be measured 5, so that when the object to be measured 5 moves in the direction of the arrow, it follows the movement. They are meant to move in the same direction.

In addition, in FIG. 1, the light from the light source 1 is connected to the input optical fiber 2.
Although it is designed so that the light enters directly into the optical fiber 2, it is also possible to interpose one optical fiber between the light source l and the optical fiber 2. Furthermore, it is also possible to similarly interpose one optical fiber between the photodetector 3 and the output side optical fiber 4. In this way, the displacement detector (both party fiber 2.4
and the light shielding member 6), the light source 1, and the electrical light detection portion (electrical portion) 3 can be installed separately, making it less susceptible to adverse effects from electrical disturbances.

In addition, the one in Fig. 1 measures the movement g of the object to be measured 5 that moves linearly, but the object to be measured 5 that changes rotationally.
In this case, the input optical fiber and the output optical fiber are placed on the circumference of the rotation axis of the rotating object, and a shield is placed Attach to the same rotating shaft. In this way, when the object to be measured rotates, the shielding body also rotates, which changes the number of both optical fibers that are shielded, so it is possible to detect the rotation angle of the shielding body (the rotation angle plane of the object to be measured). Can be done. In other words, it can be used as a rotary encoder (function) In the displacement detector shown in FIG. Two or more pieces of different lengths (nine pieces in Figure 1)
When input to the input optical fiber 2, the same optical pulse A is delayed and outputted due to the delay effect due to the difference in optical path length of each optical fiber 2. As shown in Fig. 3, the nine optical pulses are combined at the same time. When the light shield 6 is completely removed from between the input optical fiber 82 and the output optical fiber 4, this optical pulse train, which becomes an aligned optical pulse train, is directly transmitted to the photodetector 3 through the output optical fiber 4. The light is transmitted and detected by the photodetector 3 as an optical pulse train as it is.

Next, the object to be measured 5 moves upward in FIG. Light passes only between the fibers, and only the optical pulses input from these four output side fibers 4 to the photodetector 3 form a pulse train with a time difference as shown in FIG. In other words, the amount of movement of the object to be measured 5 is converted into a change in the number of pulses and detected.

(Example) FIG. 1 shows an example of the displacement amount detector of the present invention. A laser diode with an optical wavelength of 1.3 gm is used as the light source I, and a pulse A having a pulse width of 3 x 10-8 sec and a pulse interval I x 10-6 sec can be generated by electrical modulation.

The input optical fiber 2 has a core diameter of 50Bm and a cladding diameter of 1.
2 to GI type optical fiber with 25 tiles m and coating diameter 400 lm
0 pieces, and 5.15.
25---185,195m in length, with a diameter of 2
It was wound around nine plastic rods 13 with a diameter of 0.00 mm≠, each input end 11 was connected to the laser diode of the light source 1, and the output ends 14 were arranged at intervals of 0.5 mm. At this time, the output ends of the short input optical fibers were placed at the bottom, and the output ends of the long input polarizing fibers were placed at the top.

The output optical fiber 4 has the same G as the input optical fiber 2.
Prepare 20 II optical fibers, each with a length of 5
m, its light-receiving end 15 faces the output end 14 of the input-side optical fiber 2 with a predetermined distance apart, the light-emitting end 16 is connected to the photodiode of the photodetector 3, and its output is sent to the arithmetic unit 17. It is guidance.

When the object to be measured 5 was moved in FIG. 1, the amount of displacement was obtained as a change in a 20-digit binary number using the oil calculation system 17. The relationship between the amount of movement of the object to be measured 5 and the result of converting the binary number obtained by the arithmetic unit 17 into a decimal number is shown in FIG. 5, from which it can be seen that the amount of movement of the object to be measured 5 has been measured. .

(Effects of the Invention) Since the displacement detector of the present invention uses two or more input-side optical fibers 2 of different lengths as a delay circuit, it has the following effects.

(1) The combination of light source 1 and photodetector 4 makes it possible to measure the amount of displacement with high accuracy.

(2) Although the number of optical fibers 2.4 is large, only one light source 1 and one photodetector 4 are required, so the configuration is simple and an inexpensive displacement detector can be provided.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing one embodiment of the displacement detector of the present invention, Fig. 2 is an explanatory diagram showing an example of a light pulse generated from the light source of the displacement detector, and Fig. 3 is an explanatory diagram showing an example of the light pulse generated from the light source of the displacement detector. Figure 4 is an explanatory diagram of the pulse train when the light is not blocked by the input optical fiber and the output side of the lower five trees. An explanatory diagram of a 7g pulse train in which the optical fiber is blocked by a light shielding body. FIG. 5 is an explanatory diagram showing the relationship between the output of the arithmetic unit and the amount of movement of the object to be measured. FIGS. 6 to 81; i4 is It is an explanatory view of a different example of a conventional displacement amount detector. A is a light pulse ■ is a light source 2 is an input side optical fiber 3 is a photodetector 4 is an output side optical fiber 5 is an object to be measured 6 is a light shielding body

Claims (1)

[Claims] Two or more input optical fibers 2 that transmit optical pulses A from a light source 1, and optical pulses A from each input optical fiber 2.
Two or more output-side optical fibers 4 that individually receive and transmit the signals to one photodetector 3 are separated by a predetermined distance and face each other, and a light shielding device is provided between both optical fibers 2 and 4 to block optical coupling between them. In the displacement detector, the light shielding body 6 is arranged in such a manner that the light shielding body 6 moves in accordance with the movement of the object to be measured 5 to change the number of light shielded optical fibers 2 and 4 on the input side. A displacement detector characterized in that the lengths of the input optical fibers 2 are made different so that the optical pulses A emitted from the input optical fibers 2 form a pulse train with a time difference.