JPH0628659Y2 - Photoelasticity measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial field of application) The present invention is an apparatus for measuring stress existing in a transparent object to be inspected by utilizing a photoelastic phenomenon. The measurement can be switched between the used measurement and the transmitted light measurement.

(Prior Art) When a transparent body such as a glass product or a plastic product has internal strain or an external force is applied, stress is generated. A measuring device to which the principle of photoelasticity is applied is generally used in order to measure the presence or absence of stress, its location, or its magnitude in such a transparent inspection object.

For example, when stress is present in the transparent inspection object, when polarized light is transmitted through the transparent inspection object, the polarization characteristics change due to the photoelastic effect, and when observed through a polarizing plate, an interference fringe pattern is seen. From the observation result, it is possible to know the presence or absence of stress in the transparent inspection object, its location or its size. Although such a measuring device is convenient for measuring an object to be inspected that is entirely transparent, when the object to be inspected is a transparent envelope and has a non-translucent member inside, such as a valve of an electron tube. Has the drawback that it cannot be used.

On the other hand, there is known a measuring device which projects polarized light on a transparent inspection object and observes the reflected light through a polarizing plate to know the presence or absence of stress existing in the transparent inspection object and its location or its size. ing. In this device, the light reflected from the surface of the transparent object to be inspected does not undergo the photoelastic effect even if stress is present in the object to be inspected, so that the reflected polarized light is absorbed by the polarizing plate and cannot be seen. On the other hand, the light reflected from the inner surface of the object to be inspected undergoes a photoelastic effect when it reciprocates in the object to be inspected, so the polarization characteristics change when stress is present, and the interference fringe pattern is visible when observed through a polarizing plate. From this observation result, it is possible to know the presence or absence of stress in the body to be inspected, its location or its magnitude. Moreover, in this measurement, as described above, there is an advantage that the light reflected from the surface of the inspection object does not interfere with the measurement.

(Problems to be solved by the invention) As described above, conventionally, both a device that transmits the measurement light to measure the stress in the test object and a device that reflects the measurement light to measure the stress in the test object are used. It was necessary to prepare and use both depending on the structure of the object to be inspected. This is extremely uneconomical.

Therefore, an object of the present invention is to provide a photoelasticity measuring device which can be used for both a measurement for observing a photoelastic effect by using transmitted light and a measurement for reflected light by a slight operation even though it is a single device. It is to be.

[Constitution of device]

(Means for Solving the Problem) The present invention provides a transparent light source for projecting a polarization system measurement light on the front side and the back side of a transparent object to be selectively operated so that a desired light source can be selectively operated. Provided is a photoelasticity measuring device for observing a change due to a photoelastic effect of measurement light reflected or transmitted from an inspection body to measure a stress existing in the inspection body.

(Operation) If the light sources for projecting the polarization measurement light are respectively arranged on the front side and the back side of the transparent object to be inspected and the desired light sources are selectively operated, the two light sources can be measured by simply switching the light sources. Can be performed at any time, and since the light source that is not used is not a hindrance, the equipment is simple and extremely convenient, and it is particularly advantageous when performing measurements of both types at random.

(Embodiment) Hereinafter, the details of the present invention will be described with reference to the illustrated embodiments. FIG. 1 shows an apparatus for measuring the photoelastic effect as interference fringes using linearly polarized light. In the figure, (1) blocks external light,
And the outer box whose inner surface is made light-absorbing, (2) is a transparent support table provided in the center of this outer box (1), and (3) is supported by this support table (2) and is positioned almost horizontally. For example, a plate-shaped inspected object made of glass, plastics, or the like, (4) is provided obliquely above the inspected object (3), that is, on the front side, and the measurement light is projected from the oblique direction onto the inspected object (3) A first light source, (5) is a second light source which is provided obliquely below the inspected body (3), that is, on the back side, and projects measurement light from this oblique direction onto this inspected body (3), (6)
Is a power source for supplying power to both light sources (4) and (5), and (7) is interposed between the power source (6) and both light sources (4) and (5), and both light sources (4),
A switching device for selectively activating any one of (5), for example, a changeover switch, (8) faces each other on the front side of the inspection object (3), and is connected to the inspection object (3) from both light sources (4) and (5). ) Is an observation device for observing the measurement light incident through

Both of the light sources (4) and (5) are incandescent light bulbs (41) and (51) combined with the first linear polarization plates (42) and (52).
Ordinary light emitted from (41) and (51) is applied to the first linear polarization plate (42),
It transmits the light (52), converts it into linearly polarized light, and projects it on the inspection object (3).

The observation device (8) has a second linear polarizing plate (81) as a light-shielding hood.
It is a device that is covered with (82) and measures the change due to the photoelastic effect in the outside body to be inspected (3) by observing the measurement light reflected or transmitted through the transparent inspected body (3). .

Next, the operation of the measuring apparatus of this embodiment will be described. First, the device under test (3) is placed on the support base (2), the power source (6) is turned on, the switching device (7) is operated to operate the first light source (4), and the second light source (4) is activated.
The light source (5) is kept stopped. Then the first light source
The measurement light, which is linearly polarized light, is projected from the (4) onto the transparent inspection object (3), is reflected, and enters the observation device (8). At this time, part of the incident light is reflected from the surface of the transparent inspection object (3) and enters the observation device (8). However, since the reflected light does not pass through the transparent inspection object (3) at all, the stress does not exist in the transparent inspection object (3) even if it does not exist.
Therefore, when the two linear polarization plates (42) and (81) are rotated so that the two polarization axes are orthogonal to each other, the light in the second linear polarization plate (81) disappears. On the other hand, the light reflected from the inner surface of the transparent inspection object (3) and incident on the observation device (8) reciprocally passes through the transparent inspection object (3). When stress is present in the transparent inspection object (3), the transmitted linearly polarized light has an optical path difference between the component linearly polarized light vibrating in two directions orthogonal to each other due to the photoelastic effect. As a result, when linearly polarized light is made incident on the transparent inspection object (3) in which stress is present, the next development occurs.

(1) Linearly polarized light changes to elliptical or circularly polarized light.

(2) In the situation of being orthogonal, the optical path difference is 0 times the light source wavelength, ± 1
Double, ± 2 times ... part looks dark.

(3) The part where the stress acts is parallel to the incident linearly polarized light vibration axis also appears dark.

(4) The direction of the vibration axis of polarized light does not change.

Due to the existence of this light-dark distribution, an interference fringe pattern is visible on the second linear polarizing plate (81). Moreover, as described above, the transparent inspection object
The light reflected on the surface of (3) does not interfere with this observation.

Next, in this embodiment, the switching device (7) is switched to stop the first light source (4) and activate the second light source (5). Then, the measurement light, which is linearly polarized light, is transmitted to the transparent inspection object (3).
Through the observation device (8). (However, in the figure, the object to be inspected (3) is made hollow so that there is no hindrance to the transmission of the measurement light.) If stress is present in the object to be inspected (3), the photoelastic effect is the same as described above. Therefore, an optical path difference is generated between the component linearly polarized lights in two directions in which the linearly polarized lights are orthogonal to each other, and as a result, an interference fringe pattern is visible on the second linearly polarizing plate (81) of the observation device (8).

Then, in the photoelasticity measurement by such reflected light or transmitted light, since the density ratio of the observed interference fringe pattern is related to the magnitude of the stress existing in the inspection object (3), from the interference fringe pattern, It is also possible to know the magnitude of the stress in the inspected body (3) and its location.

Further, in the measuring apparatus of the present embodiment, since the light sources (4) and (5) are arranged on both the front side and the back side of the object to be inspected (3) to selectively operate the desired one, Observation with reflected light and observation with transmitted light can be freely performed with one device.

Next, another embodiment of the photoelasticity measuring device is shown in FIG.
This is a device that allows observation of changes in polarization characteristics due to the photoelastic effect as changes in color.
Each of the linear polarizing plates (42) and (52) of (4) and (5) and the transparent inspection object (3)
And a quarter-wave plate (4
3) and (53) are inserted, and the device under test (3) and observation device (8)
Second quarter-wave plate between the second linear polarizing plate (81)
It is an insertion of (83). This is a light source (4), (5)
The linearly polarized light transformed by the linear polarizing plates (42), (52) of the above is transformed into circularly polarized light by the quarter-wave plates (43), (53), and the circularly polarized light is transmitted inside the transparent inspection object (3). Due to the photoelastic effect of, the optical path difference is generated in both directions components of the vibration axis, and when viewed through the second quarter wavelength plate (83) and the second linear polarizing plate (81), the optical path difference is generated for each color. 0 times the wavelength, ± 1
Double, ± 2 times ... become darker, and a blue or orange-yellow color pattern can be observed in the area where the stress exists depending on the magnitude of the stress. The part to be inspected and the shade of this color pattern
(3) Presence / absence of stress, its magnitude, and its location can be measured. Thus, also in this other embodiment, by operating the switching device, it is possible to perform observation by reflected light and observation by transmitted light at the same time with one device. In addition, each quarter wave plate (43),
The (53) and (83) may be configured to be detachable, and may be attached and used as needed.

In addition, in each of the above-described embodiments, the linearly polarized light used for the measurement was obtained by transmitting the light of the incandescent lamp through the linearly polarizing plate, but in the present invention, other means, for example, a gas laser that generates linearly polarized light is used. And a method using linearly polarized light generated by synchrotron radiation may be used.
However, circularly polarized light may be converted into circularly polarized light by first generating linearly polarized light and then transmitting the linearly polarized light through a quarter-wave plate or by being transmitted through a Fresnel prism.

[Effect of device]

As described above, the photoelasticity measuring device of the present invention has a pair of light sources for projecting the polarization measuring light from the front side and the back side of the transparent object to be inspected, and these light sources are arbitrarily switched to operate. However, it can be used for both the measurement using reflected light and the measurement using transmitted light, especially when inspecting an inspected object that is entirely transparent and a transparent inspected object that includes a non-translucent member in a random order. Is extremely advantageous to

[Brief description of drawings]

FIG. 1 is an explanatory view of an embodiment of the photoelasticity measuring device of the present invention,
FIG. 2 is an explanatory diagram of another embodiment. (3) …… Inspected object, (4), (5) …… Light source (41), (51) …… Incandescent lamp, (42), (52) …… Linear polarizing plate (43), (53) , (83) ...... Quarter wave plate (7) ... Switching device, (8) ... Observation device (81) ... Linear polarizing plate

Claims (1)

[Scope of utility model registration request] 1. A plurality of light sources arranged on the front side and the back side of a transparent object to be inspected and projecting polarization system measurement light onto the object to be inspected, and one of these light sources, the front side or the back side, is selected. Equipped with a switching device that operates
A photoelasticity measuring device characterized by observing a change due to a photoelastic effect of the measurement light reflected or transmitted from the object to be inspected to measure a stress existing in the object to be inspected.