JP2592254B2 - Measuring device for displacement and displacement speed - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is a displacement and displacement speed measuring device for optically detecting the displacement and displacement speed of an object to be measured.

[Conventional technology]

Conventionally, a gas laser such as a He-Ne laser is used as a light source as a method of measuring a displacement amount of sub-micrometer or less, and the laser light is spatially propagated to cause interference between reference light and light reflected from an object to be measured. In general, a method of detecting a signal corresponding to a phase difference is used. One example of the optical system is the third
Shown in the figure. In this case, the light emitted from the laser light source (1) propagates in space, and the one-way light split into two directions in the interferometer (2) is repeatedly reflected in the interferometer as reference light, and is reflected in other directions. The light split in the direction is reflected as a measuring light by a measuring reflecting mirror (3) mounted on an object to be measured, and interferes with a reference light in an interferometer (2). ), And the amount of displacement of the measured object is measured by detecting the phase difference between the reference light and the measurement light.

At the time of actual measurement, the measured value becomes unstable due to relative minute vibration of the interferometer (2) of the laser light source (1) and the measuring reflecting mirror (3), and the measuring accuracy is reduced.

Therefore, it is desirable to carry out the measurement by placing three persons on the same measurement surface plate. This means that a large space is required for disposing a measurement system including a laser light source, an interferometer, a measurement reflecting mirror, and an object to be measured.

[Problems to be solved by the invention]

As described above, the conventional displacement measurement requires a laser light source, an interferometer, and a reflecting mirror for measurement. Also, a laser light source,
The size of the interferometer and the measuring mirror is on the order of hundreds of millimeters to tens of millimeters, and requires a larger space. Further, since light travels straight through the space, it is necessary to devise an arrangement of the optical system, and a wide space is required depending on the arrangement direction.

In addition to the above problems, the optical axis must be aligned in a limited space, and the optical axis alignment requires time. Also,
Since light propagates in the atmosphere, there are many problems such as a decrease in measurement accuracy due to fluctuations of air in the optical path.

[Means for solving the problem]

In order to solve the above-mentioned problems, optical components as components near the front surface of the measuring reflector are connected by an optical fiber,
In this case, even if the laser light source and the interferometer relatively vibrate by splitting, reflecting, changing the polarization state, or interfering with light, the measurement accuracy is not adversely affected. The measuring probe section and the measuring reflecting mirror that emit light to the measuring reflecting mirror are reduced to several tens of millimeters or less to reduce the required space. Further, by connecting the laser light source and the interferometer with an optical fiber, the alignment of the optical axis between the laser light source and the interferometer becomes unnecessary at the time of measurement, and only the alignment of the optical axis between the measuring probe and the measuring mirror is performed.

〔Example〕

 Hereinafter, examples of the present invention will be specifically described.

 FIG. 1 shows the configuration of the displacement measuring device.

The coherent light emitted from the laser light source (1) passes through an optical fiber (8a) and is made parallel by a collimating lens (5a). This parallel light is split into two polarized lights by a beam slitter (7a). One of the split lights is condensed by the condenser lens (6a), passes through the optical fiber (8b), and enters the measurement probe (15). The light is collimated by the collimating lens 5b, passes through the beam splitter (7b), passes through the wave plate (10b), is reflected by the measuring reflector (3) fixed to the object to be measured, and the reflected light is again reflected by the wave plate (10). By passing through 10b), it becomes a polarization orthogonal to that of the incident light, and becomes a beam slitter (7b)
Reflected by the reflecting mirror or prism (16),
The light is focused into the optical fiber (8b) by the focusing lens (6b).
The light that has passed through the optical fiber (8b) enters the interferometer (14).

First, it becomes parallel light by the collimator lens (5c), other polarized light is removed by the polarizer (9b), is converted to circularly polarized light by the wave plate (10c), and is phase-detected by the beam splitter or half mirror (12). )to go into. On the other hand, the other light split by the beam splitter (7a) passes through the polarizer (9a),
After being converted into circularly polarized light in the opposite direction to the above-mentioned circularly polarized light by the wave plate (10a) and adjusting the light intensity level by the optical attenuator (11), the interference light that has interfered with the circularly polarized light is converted into a phase detector ( 13) Enter. Light passing through the measuring mirror is a measuring probe (15)
The phase changes due to the change in the distance between the end face and the measuring mirror (3), and the interference light changes the angle of the polarization plane in accordance with the change in the phase. The phase is detected by measuring this angle by phase detection, and the displacement between the measuring mirror (3) and the measuring probe (15) is measured. The size of the measuring prog (15) and the measuring reflecting mirror (3) should be several tens of millimeters or less.

FIG. 2 shows a laser light source (1), an interferometer (14) and a measuring probe (15) connected by the above-mentioned optical fiber,
Using a measuring reflector (3) attached to the device under test, the phase detector is replaced with a polarizer (9c) and an optical pulse counter (17).
The displacement velocity of the object to be measured can be obtained from the following relational expression, in which each optical path is constituted by an optical fiber.

υ: Displacement velocity of the object to be measured λ: Wavelength of light used T: Time counted light pulse P: Number of light pulse within T time [Effect of the invention] Connecting laser light source and interferometer by optical fiber Therefore, even if the laser light source and the interferometer are relatively slightly vibrated, the measurement accuracy is not affected. The required space can be narrowed by reducing the size of the measuring probe and the measuring reflecting mirror to several tens of millimeters or less. Also, by connecting the laser light source and the interferometer with an optical fiber, the alignment of the optical axis between the laser light source and the interferometer is not required at the time of measurement, and only the alignment of the optical axis between the measuring probe and the measuring mirror can be performed. Further, since the distance over which the light propagates in the space is short, it is possible to prevent a decrease in measurement accuracy due to the fluctuation of air. Since the measurement probe can be fixed to a narrow place, the displacement can be measured even for a complexly-measured object, and a wider object can be measured with higher accuracy than the conventional method.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a displacement amount measuring device according to an embodiment of the present invention, FIG. 2 is a block diagram showing a configuration of a displacement speed measuring device according to an embodiment of the present invention,
FIG. 3 is a block diagram showing the configuration of a conventional displacement measuring device. 1: Laser light source 2: Interferometer 3: Measurement mirror 4: Optical detector 5a, 5b, 5c: Collimating lens 6a, 6b: Condensing lens 7a, 7b: Beam slitter 8a, 8b: Optical fiber 9a, 9b: Polarizer 10a, 10b: Wave plate 11: Optical attenuator 13: Phase detector 14: Interferometer 15: Probe for measurement

Claims (2)

(57) [Claims] A light source, an interferometer and a measuring probe,
The coherent light from the light source is split into two orthogonally polarized lights by an interferometer, one of which is used as a reference light, and the other is used as a measurement light. The reflected light and the reference light are converted into circularly polarized light or elliptically polarized light, which rotate in opposite directions, and interfere with each other. The displacement of the measured object is measured by the angle of the main polarization plane of the obtained interference light. In the apparatus, the coherent light of the light source is guided to the interferometer, the measurement light is guided to the measurement probe from the interferometer, and the reflected light is guided to the interferometer from the measurement probe. A displacement measuring device, wherein an optical path is constituted by an optical fiber. 2. A light source, an interferometer and a measuring probe,
The coherent light from the light source is split into two orthogonally polarized lights by an interferometer, one of which is used as a reference light, and the other is used as a measurement light. The reflected light and the reference light are converted into circularly polarized light or elliptically polarized light that rotate in opposite directions to interfere with each other, and the rotation angle of the main polarization plane of the obtained interference light is detected to detect the rotation angle of the measured object. In a device adapted to measure the displacement velocity, while deriving the coherent light of the light source to the interferometer,
A displacement velocity measuring device, wherein each optical path is formed by an optical fiber while a measuring light is led out to an interferometer from a measuring probe and a reflected light is led out to the interferometer from the measuring probe.