JP2573493B2 - How to measure physical quantities - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a method for measuring physical quantities such as length, angle, and stress.

[Prior art]

Conventionally, a measurement method called a moire method has been known. This is based on the fact that, when two gratings having equal intervals are superposed at a slight angle to each other and illuminated from behind, interference fringes called moire fringes appearing substantially perpendicular to the grating appear. That is, when one grid is fixed and the other grid is moved in a direction parallel to the plane of this grid, the moire fringes also move at the same time, and the amount of movement has a certain relationship with the grid spacing. The amount of displacement of the grating can be known from the amount of movement of the stripes.

Problems to be Solved by the Invention However, in order to perform precise measurement by the above-described moiré method, it is generally necessary to set the lattice spacing to 10 μm or less. Creating a grid is not easy. Also, the optical system becomes complicated,
In addition to lack of versatility, the grid itself also has problems such as environmental resistance and heat resistance. The present invention provides a measurement method that can easily perform precise measurements of physical quantities such as length, angle, and stress using a so-called image fiber and the like, and can perform measurement under a very bad environment. The purpose is to:

[Means for solving the problems]

In the method for measuring a physical quantity according to the present invention, an equidistant grid pattern is provided on the surface of an object to be measured, and a large number of cores are arranged at regular intervals in a direction of 60 ° on the surface of the object on which the lattice pattern is formed. By facing the end face of the correctly arranged multi-core optical fiber and forming an image of the surface of the DUT and the lattice pattern on the end face of the multi-core optical fiber, the image transmitted by the multi-core optical fiber is Moiré fringes are formed, and the relative positional relationship between the lattice pattern and the end face of the multi-core optical fiber is changed in accordance with the physical quantity to be measured. At the other end, observing an image of the surface of the device under test and a change in the moiré fringes caused by a change in a relative positional relationship between the lattice pattern and the end face of the multi-core optical fiber. And it features.

[Action]

A grid pattern is provided at regular intervals on the surface of the device under test, and a large number of cores are regularly arranged at regular intervals in the direction of 60 ° on the surface of the device under test where the grid pattern at regular intervals is formed. When the image of the surface of the object to be measured and the lattice pattern is formed on the end face of the multi-core optical fiber while facing the end face of the core optical fiber, moire fringes are formed in the image transmitted by the multi-core optical fiber. Is done. From the other end of the multi-core optical fiber, an image of the surface of the object to be measured appears. In the image, the portion of the lattice pattern on the surface of the object to be measured becomes moire fringes. Therefore, when observing the output image from the other end, it is possible to qualitatively capture the state of change such as distortion on the surface of the measured object and to capture the state of moire fringes. In this case, since the arrangement of the cores at the end face of the multi-core optical fiber is a hexagonally dense arrangement as described above, the moiré fringe becomes complicated, but the qualitative change in the physical quantity to be measured is caused by a change in the surface image. Since it can be regarded as a change, it is easy to distinguish necessary ones from complicated moire stripes. Therefore, a minute change can be quantitatively and precisely measured by observing the interval of moiré fringes from which only necessary ones are extracted. In other words, instead of considering the downside that the moire fringe becomes complicated when using a multi-core optical fiber with a hexagonal close-packed arrangement for image transmission, the original image can be obtained by using a multi-core optical fiber with a hexagonal close-packed arrangement. Taking advantage of the plus surface that the transmission image can be transmitted better than the image of the surface of the object to be measured because it is for transmission, the physical quantity can be measured by a combination of this transmission image and moiré fringes. By using such a multi-core optical fiber, an ordinary multi-core fiber for image transmission can be used, so that the advantage of simple measurement can be obtained.

【Example】

FIG. 1 shows an embodiment in which the measuring method of the present invention is applied to a system for measuring the strain of a sample 10 which is placed in a liquid helium 11 placed in a container 12 and is kept at a very low temperature. . In this figure, a black-and-white stripe pattern 1 on a lattice is formed on the surface of a sample 10 by any method such as direct drawing or sticking of a seal. This stripe pattern 1
Is positioned so as to face the end face of the image fiber 3, and an image of the stripe pattern 1 is formed on the end face of the image fiber 3 by the objective lens 2.
Since the end surface of the image fiber 3 faces the stripe pattern 1 and forms an image with the objective lens 2 in this manner, not only the image of the stripe pattern 1 but also the sample
An image of the surface of the sample 10 is also formed, and a surface image of the sample 10 including the image of the stripe pattern 1 is transmitted by the image fiber 3. The image fiber 3 is composed of one quartz-based integrated image fiber, and both end surfaces thereof are polished. A television camera 5 is arranged on the other end face of the image fiber 3 via an eyepiece range 4, converts an image output from the end face into a video signal, and sends it to a television monitor 6 and an image processing device 7. As shown in FIG. 2, the end face of the image fiber 3 has a large number of cores 21 arranged in a common clad 22 in a hexagonal close-packed manner, that is, in an orderly and regularly spaced manner at intervals of 60 °. Are arranged. Thus, the arrangement of the core portions 21 functions as a grid at equal intervals. for that reason,
When the image of the stripe pattern 1 is formed on the end face of the image fiber 3, the magnification of the objective lens 2 is adjusted so that the interval between the stripe patterns in the formed image is equal to the arrangement interval of the cores on the end face of the image fiber 3. By setting
Moiré fringes can be generated in the image transmitted by the image fiber 3 and the image emitted from the other end face. This moiré fringe pattern is complicated because the arrangement of a large number of cores 21 on the end face of the image fiber 3 is hexagonally dense.
By observing the surface image of the sample 10 on the screen, it is possible to qualitatively understand how the distortion is generated, and based on this, distinguish what is necessary from complex moiré stripe patterns Is easy. Therefore, a necessary pattern is discriminated from among the stripe patterns 1 that change when the sample 10 generates or deforms at an extremely low temperature, and is measured on the screen of the television monitor 6,
Alternatively, if the image is automatically detected by the image processing device 7, the sample 10
The distortion of can be known. That is, the distortion amount ε and the moiré fringe have a relationship of ε = (N / Md) a + k. Here, N is the moiré fringe order, Md is the moiré fringe interval, a is the lattice (core) interval, and k is a constant. Therefore, if the moiré fringe order and the moiré fringe interval can be measured, distortion can be measured. In the measurement system of this embodiment, a core arrangement at the end face of the image fiber 3 is used instead of the grating, and this type of silica-based image fiber 3 is extremely excellent in environmental resistance. Moreover, the stripe pattern 1 provided on the surface of the object to be measured
However, it is easy to achieve high environmental resistance. Therefore, for example, it is particularly effective for strain measurement under a severe environment such as an extremely low temperature or high temperature atmosphere as described above, or measurement of the amount of movement of an object.

【The invention's effect】

According to the measurement method of the present invention, precise measurement of physical quantities such as length, angle, and stress can be easily performed using a multi-core optical fiber such as a normal image fiber in which cores are arranged in a hexagonal close-packed manner. It is possible to perform measurement under severe environment of various physical quantities because of its excellent environmental resistance. That is, by making the end face itself of a multi-core optical fiber such as a normal image fiber function as one of the lattices for forming the moire fringes, a complicated multi-core optical fiber and a special multi-core optical fiber are separately prepared. The complexity has been eliminated. In addition, even if a multi-core optical fiber such as an image fiber is a normal one, a precise measurement can be performed because the core interval is generally extremely small. In addition, multi-core optical fibers such as image fibers generally have explosion-proof properties, insulation properties, and also have excellent environmental resistance and heat resistance. It also acts as a transmitter of the image of the surface of the object to be measured.On the other hand, the grating pattern that pairs with the end face of the multi-core optical fiber that functions as a grating must be one that has excellent environmental resistance, heat resistance, etc. Since the lattice pattern is simply attached to an object to be measured or the like, it is suitable for measurement of physical quantities under an extremely severe environment. In addition, since not only moire fringes but also images of the surface of the object to be measured are transmitted using a multi-core optical fiber such as a normal image fiber, image observation can be performed well in accordance with the original use of image transmission. Therefore, it is easy to qualitatively grasp the state of the change of the surface of the object to be measured, thereby covering a minus surface where moire fringes are complicated when using a multi-core optical fiber having cores arranged in a hexagonal close-packed manner. Thus, only necessary moiré fringes can be captured, and the observation of the surface image can also be useful for positioning and grasping the state of the object to be measured.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a measuring system for executing a method for measuring a physical quantity according to an embodiment of the present invention, and FIG. 2 is a partially enlarged view of an end face of an image fiber used in the embodiment. 1 ... stripe pattern, 2 ... objective lens, 3 ... image fiber, 4 ... eyepiece, 5 ... TV camera, 6
... TV monitor, 7 ... Image processing device, 10 ... Sample, 11 ... Liquid helium, 12 ... Container, 21 ... Core part,
22 …… Clad part.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Tanaka 1440 Mutsuzaki, Sakura-shi, Chiba Pref. 195406 (JP, A) JP-A-52-20051 (JP, A)

Claims (1)

(57) [Claims] An object in which a grid pattern is provided at regular intervals on the surface of an object to be measured, and a large number of cores are regularly arranged at regular intervals in directions of 60 ° on the surface of the object to be measured on which the lattice pattern is formed. Moire fringes in the image transmitted by this multi-core optical fiber by facing the end surface of the multi-core optical fiber, and forming an image of the surface of the DUT and the lattice pattern on the end surface of the multi-core optical fiber. To be formed,
And the relative positional relationship between the lattice pattern and the end face of the multi-core optical fiber is changed corresponding to the physical quantity to be measured, and at the other end of the multi-core optical fiber,
A method for measuring a physical quantity, characterized by observing a change in the moiré fringes generated based on a change in the relative position relationship between the image of the surface of the object and the lattice pattern and the end face of the multi-core optical fiber. .