Vibration visualization element including optical member

1. A vibration visualization element comprising an optical member that retroreflects light or electromagnetic wave in a static state, the optical member including:

a fixed section, relative positional relationship of which with respect to a measurement object is fixed; and

a movable section movably supported by the fixed section to allow relative positional relationship with the fixed section to be changed by application of an acceleration to the fixed section in a predetermined direction, wherein

the fixed section and the movable section are configured such that, according to the change in the relative positional relationship between the fixed section and the movable section, a reflection direction of the light or the electromagnetic wave is changed to change a luminance of reflected light in a retroreflection direction or an amount of reflected electromagnetic wave in the retroreflection direction.

2. The vibration visualization element according to claim 1 ,

wherein the optical member includes a first mirror, a second mirror, and a third mirror having specular surfaces perpendicular to each other,

the first mirror is included in the fixed section,

the second mirror is included in the movable section, and

the first and second mirrors are configured to allow an angle of the second mirror with respect to the first mirror to be changed by the application of the acceleration to the fixed section in the predetermined direction.

3. The vibration visualization element according to claim 2 ,

wherein the optical member further includes an elastic member, and

the second mirror is connected to the fixed section via the elastic member.

4. The vibration visualization element according to claim 2 ,

wherein the optical member includes an elastic member,

the fixed section includes a shaft, and

the second mirror is supported by the shaft as a center to turn, and is connected to the fixed section via the elastic member.

5. The vibration visualization element according to claim 2 ,

wherein the optical member includes a weight and an elastic member,

the second mirror includes a plurality of fourth parallel mirrors having specular surfaces parallel to each other,

the fixed section includes a plurality of shafts, and

each of the fourth mirrors is supported by a corresponding one of the shafts as a center to turn, and is connected to the fixed section via the weight and the elastic member in common.

6. The vibration visualization element according to claim 2 ,

wherein the optical member retroreflects the light or the electromagnetic wave in a range of a predetermined dispersion angle, and

a range of variation in the angle of the second mirror with respect to the first mirror is smaller than the dispersion angle.

7. The vibration visualization element according to claim 1 ,

wherein the optical member includes a spherical lens and a concave reflector positioned behind the spherical lens,

one selected from the group consisting of the spherical lens and the concave reflector is included in the fixed section,

the other selected from the group is included in the movable section, and

the other selected from the group is supported by the fixed section to allow relative positional relationship with the one selected from the group to be changed by application of an acceleration to the fixed section in a predetermined direction.

8. The vibration visualization element according to claim 7 ,

wherein the optical member includes an elastic member,

the spherical lens is one of a plurality of spherical lenses connected each other,

the concave reflector is one of a plurality of concave reflectors each positioned behind corresponding one of the spherical lenses,

the concave reflectors are included in the fixed section,

the spherical lenses are included in the movable section, and

the spherical lenses are connected to the fixed section via the elastic member.

9. The vibration visualization element according to claim 1 ,

wherein the optical member includes a corner cube having three reflection surfaces perpendicular to each other, and a deformation member in contact with the corner cube,

at least part of the corner cube is included in the fixed section,

the deformation member is included in the movable section, and

the deformation member is supported by the fixed section to cause at least one of the three reflection surfaces of the corner cube to be deformed by application of an acceleration to the fixed section in a predetermined direction.

10. A vibration measurement system comprising:

a first vibration visualization element and a second vibration visualization element that are fixed to a measurement object,

a light source that emits light or electromagnetic wave to the first vibration visualization element and the second vibration visualization element, and

an imaging device that captures an image including the measurement object, the first vibration visualization element and the second vibration visualization element, wherein:

each of the first and second vibration visualization elements comprises an optical member that retroreflects the light or the electromagnetic wave in a static state, the optical member including:

a fixed section, relative positional relationship of which with respect to the measurement object is fixed; and

a movable section movably supported by the fixed section to allow relative positional relationship with the fixed section to be changed by application of an acceleration to the fixed section in a predetermined direction, and

the fixed section and the movable section are configured such that, according to the change in the relative positional relationship between the fixed section and the movable section, a reflection direction of the light or the electromagnetic wave is changed to change a luminance of reflected light in a retroreflection direction or an amount of reflected electromagnetic wave in the retroreflection direction.

11. The vibration measurement system according to claim 10 , further comprising a vibration measurement device that measures change in the relative positional relationship between the fixed section and the movable section in each of the first vibration visualization element and the second vibration visualization element, based on change in the luminance of the reflected light or the amount of the reflected electromagnetic wave from each of the first vibration visualization element and the second vibration visualization element in the image captured by the imaging device.

12. The vibration measurement system according to claim 10 ,

wherein a natural frequency of the movable section of the first vibration visualization element is different from a natural frequency of the movable section of the second vibration visualization element.

13. The vibration measurement system according to claim 10 ,

wherein a vibration direction of the movable section of the first vibration visualization element is different from a vibration direction of the movable section of the second vibration visualization element in a state where the vibration visualization elements are fixed to the measurement object.

14. The vibration measurement system according to claim 12 , further comprising

first and second color filters with different transmission wavelength bands,

wherein the first color filter is disposed at least on an optical path of the light or the electromagnetic wave incident on the first vibration visualization element, or on an optical path of the reflected light or the reflected electromagnetic wave emitted from the first vibration visualization element, and

the second color filter is disposed at least on an optical path of the light or the electromagnetic wave incident on the second vibration visualization element, or on an optical path of the reflected light or the reflected electromagnetic wave emitted from the first vibration visualization element.

15. The vibration measurement system according to claim 13 , further comprising

first and second color filters with different transmission wavelength bands,

wherein the first color filter is disposed at least on an optical path of the light or the electromagnetic wave incident on the first vibration visualization element, or on an optical path of the reflected light or the reflected electromagnetic wave emitted from the first vibration visualization element, and

the second color filter is disposed at least on an optical path of the light or the electromagnetic wave incident on the second vibration visualization element, or on an optical path of the reflected light or the reflected electromagnetic wave emitted from the first vibration visualization element.

16. The vibration measurement system according to claim 11 ,

wherein the light source intermittently emits light or electromagnetic wave to the first vibration visualization element and the second vibration visualization element, and

the vibration measurement device identifies a position of the vibration visualization element in the image by detecting a portion in the image, the portion changing in synchronization with the intermittent emission of the light source.

17. The vibration measurement system according to claim 10 ,

wherein the light source has an irradiation angle which allows the first vibration visualization element and the second vibration visualization element to be irradiated.

18. A vibration measurement method using a vibration visualization element fixed to a measurement object, wherein:

the vibration visualization element retroreflects light or electromagnetic wave in a static state, and changes a reflection direction of the light or the electromagnetic wave to change a luminance of reflected light in a retroreflection direction or an amount of reflected electromagnetic wave in the retroreflection direction due to application of an acceleration to the visualization element in a predetermined direction, and

the method comprises:

emitting the light or the electromagnetic wave to the vibration visualization element;

capturing an image including the measurement object and the vibration visualization element; and

measuring vibration of the measurement object based on the change in a luminance of the reflected light or an amount of the reflected electromagnetic wave from the vibration visualization element in the image.