JP2547234B2 - Displacement detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a displacement amount detector adapted to measure a moving displacement amount of an object to be measured using light.

(Prior Art) There have been various conventional methods for measuring the amount of displacement of an object to be measured, and one of them is shown in FIG. This is composed of a primary coil a, two secondary coils b ₁ and b ₂ connected in opposite directions, and a movable iron piece c arranged between the primary coil a and the secondary coils b ₁ and b _2. It uses a working transformer. This is because power is supplied from the AC power supply d to the primary coil a, and the iron pieces c connected to them are moved by the movement of the object e to be measured, the secondary coils b ₁ and b ₂ are moved according to the amount of movement. The magnitude of the induced voltage changes, the voltage difference is taken out, and the amount of movement of the object d to be measured is detected as a change in the starting force of the working transformer. In addition, f of FIG. 6 is a voltmeter which displays the starting force of the working transformer.

However, since the measuring method of FIG. 6 uses electricity, it cannot be used in locations where there is electrical or magnetic noise, such as in a strong magnetic field or in a high electric field. Therefore, conventionally, optical measurement methods as shown in FIGS. 7 and 8 have been developed. In all of these, the object e to be measured is connected to the shield c, the shield c is arranged between the input side optical fiber i and the output side optical fiber j that face each other, and the amount of movement of the object to be measured e moves. According to the above, the shield c shields between the optical fibers i and j. Of these, the one shown in FIG. 7 measures the movement of the object e to be measured as a change in the amount of light using one light source g and one photodetector h, and the one shown in FIG. The light source g and a large number of photodetectors h are used to measure the movement of the object e to be measured as a change in the number of light shields of the photodetectors h.

(Problems of Prior Art) Since the measuring method of FIG. 7 of the prior art measures the movement of the object e to be measured as a change in the light amount, the output fluctuation (light amount fluctuation) of the light source g and the photodetector h It was difficult to perform accurate measurement due to the influence of fluctuations in light receiving sensitivity.

Although the measuring method shown in FIG. 8 can perform accurate measurement, it has a problem that the measuring device becomes complicated and large in size and the cost becomes high because a large number of photodetectors h are required.

(Object 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 accurately and inexpensively measuring the moving displacement amount of an object to be measured.

(Means for Solving Problems) As shown in FIG. 1, the displacement detector of the present invention has two or more input side optical fibers 2 for transmitting the optical pulse A from the light source 1.
And two or more output-side optical fibers 4 which individually receive the optical pulse A from each input-side optical fiber 2 and transmit it to one photodetector 3, are separated by a predetermined distance and face each other.
A light-shielding body 6 for blocking the optical coupling between the two is arranged between 4 and 4, and the light-shielding body 6 moves in accordance with the movement of the DUT 5 to shield the input side optical fiber 2 and the output side optical fiber 4. In the displacement detector in which the number is changed, the lengths of the two or more input side optical fibers 2 are changed so that the optical pulse A emitted from them becomes a pulse train with a time difference. It is a feature.

The light source 1 emits pulsed light having a relatively short emission time (for example, pulse A as shown in FIG. 2).

The input side optical fibers have different lengths, and as shown in FIG. 1, the input end 11 is connected to the light source 1 and the central part 12 is a cylinder.
It is wound around 13, and the output ends 14 are arranged in a line in the vertical direction.
In this case, the output end 14 of the short input side optical fiber 2 goes down,
The long input optical fiber 2 is arranged with the output end 14 facing upward.

The output side optical fiber 4 has its light receiving end portion 15 separated by a predetermined distance so as to face the output end 14 of the input side optical fiber.
16 is connected to the photodetector 3.

The light shield 6 includes an input side optical fiber 2 and an output side optical fiber 4.
And is connected to the object to be measured 5, and when the object to be measured 5 moves in the direction of the arrow, it follows the movement and moves in the same direction.

Although the light from the light source 1 is directly incident on the input side optical fiber 2 in FIG. 1, it is also possible to interpose one optical fiber between the light source 1 and the optical fiber 2. Is. Further, similarly, the photodetector 3 and the output side optical fiber 4
It is also possible to interpose one optical fiber between and. By doing so, the displacement amount detecting section (both optical fibers 2,
4 and the portion of the light shield 6), the light source 1, and the electrical light detection portion (electrical portion) 3 can be installed separately, so that they are less likely to be adversely affected by electrical interference.

Further, although the one shown in FIG. 1 measures the movement amount of the DUT 5 which moves linearly, the movement amount (rotation angle) of the DUT 5 which changes in rotation may be measured. .
In this case, the input side optical fiber and the output side optical fiber,
Arrange it on the circumference of the rotating shaft of the rotating DUT, and attach the shield to the rotating shaft. With this configuration, when the DUT rotates, the shield also rotates, and the number of both optical fibers shielded thereby changes. Therefore, the rotation angle of the light shield (the rotation angle of the DUT) can be detected. it can. That is, it can be a rotary encoder.

(Operation) In the displacement detector of FIG. 1, one light source 1 emits a light pulse (FIG. 2A) having a relatively short light emission time,
Two or more light pulses with different lengths (9 in FIG. 1)
Input) to the input side optical fiber 2, the same optical pulse A
Is delayed by the delay effect due to the difference in the optical path lengths of the respective optical fibers 2 and is output, resulting in an optical pulse train in which nine optical pulses are aligned in a line as shown in FIG. When it is completely out of the space between the input side optical fiber 2 and the output side optical fiber 4, it is transmitted to the photodetector 3 through the output side optical fiber 4 as it is, and is detected as the same optical pulse train by the photodetector 3. It

Next, the DUT 5 moves upward in FIG.
Is the lower 5 of the input side fiber 2 and the output side fiber 4.
When the light transmission of the book is blocked, the light is transmitted only between the upper four fibers which are not blocked, and only the optical pulse input from the four output side fibers 4 to the photodetector 3 is as shown in FIG. The pulse train has a time difference. That is, the amount of movement of the DUT 5 is converted into a change in the number of pulses and detected.

(Embodiment) FIG. 1 shows an embodiment of a displacement amount detector of the present invention. This uses a laser diode having a light wavelength of 1.3 μm as the light source 1, and can generate a pulse A having a pulse width of 3 × 10 ⁻⁸ sec and a pulse interval of 1 × 10 ⁻⁶ sec by electric modulation.

The input side optical fiber 2 has a core diameter of 50 μm and a cladding diameter of 12
Using 20 GI type optical fibers with 5μm and coating diameter of 400μm,
Set them every 5m to 10m with lengths of 5, 15, 25 ... 185, 195m, and use them as a plastic round bar with a diameter of 200mm 13
Each of the input ends 11 was connected to the laser diode of the light source 1, and the output ends 14 were arranged at 0.5 mm intervals. At this time, the output end of the short input-side optical fiber was set to the bottom, and the output end of the long input-side optical fiber was set to the top, and they were sequentially arranged.

The output side optical fiber 4 is similar to the input side optical fiber 2.
Twenty GI type optical fibers are prepared, each having a length of 5 m, and the light receiving end 15 thereof is opposed to the output end 14 of the input side optical fiber 2 by a predetermined distance, and the light emitting end 16 is provided as a photodetector. 3 is connected to the photodiode, the output of which is led to the arithmetic unit 17.

When the object 5 to be measured is moved in FIG. 1, the amount of change is obtained by the arithmetic unit 17 as a change of a 20-digit binary number. FIG. 5 shows the relationship between the movement amount of the DUT 5 and the result of converting the binary number obtained by the arithmetic unit 17 into a decimal number. From this, it can be seen that the movement amount of the DUT 5 was measured.

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

(1) It is possible to measure the moving displacement amount with high accuracy by the pair of the light source 1 and the photodetector 4.

(2) Since the number of the optical fibers 2 and 4 is at most one, the number of the light sources 1 and the number of the photodetectors 4 may be one, so that the configuration can be simplified and a low cost displacement detector can be provided.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of a displacement amount detector of the present invention, FIG. 2 is an explanatory view showing an example of an optical pulse generated from a light source of the displacement amount detector, and FIG. 3 is a light shield. Fig. 4 is an explanatory view of a pulse train when it is not shielded from light by Fig. 4, Fig. 4 is an explanatory diagram of a pulse train in which the lower five input side optical fibers and output side optical fibers are blocked by a light shield, and Fig. 5 is an output of the arithmetic unit Explanatory diagram showing the relationship between the movement amount of the object to be measured, FIG.
FIG. 8 is an explanatory view of a different example of the conventional displacement amount detecting device. A is an optical pulse 1 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 shield

Claims (1)

(57) [Claims] 1. Two or more input side optical fibers 2 for transmitting an optical pulse A from a light source 1, and an optical pulse A from each input side optical fiber 2 are individually received and transmitted to one photodetector 3. The two or more output-side optical fibers 4 are separated by a predetermined distance and face each other, and a light-shielding body 6 for blocking the optical coupling between the two is set between the two optical firers 2 and 4, and the light-shielding body 6 is to be measured. In the displacement detector in which the number of light-shielding lines of the input side optical fiber 2 and the output side optical fiber 4 is changed by moving according to the movement of the object 5, the lengths of the two or more input side optical fibers 2 are
A displacement amount detector characterized in that light pulses A emitted from them are different so as to form a pulse train having a time difference.