1984 年 40 巻 6 号 p. 420-423
A Michelson interferometer with an arm of flexible optical fiber has been proposed for the vibration amplitude measurement. If a micro lens is attached at the end of the fiber, the interferometer becomes more useful. Up to now only lenses which radiate a collimated laser light are used and the test objects used for the measurement are almost specular ones. The actual vibration objects are optically diffuse ones and it is not clear whether such a lens is best for diffuse objects or not. From the point of view optical fiber probes with a collimating and a focusing lenses are constructed. Using several test objects with various surface roughness, their performances are compared with each other. As the results the optical probe with a focusing lens is proved to be better for actual diffuse objects. This probe is successfully used also for the vibration amplitude measurement of a transducer in the water.