| 摘要 |
PROBLEM TO BE SOLVED: To allow ultrasonic excitation even for a transparent specimen using a laser beam, and to remarkably enhance excitation efficiency compared with a method using thermal-elastic effect. SOLUTION: In this ultrasonic excitation method, a material having electrostriction effect is coated on a surface portion of a specimen, the coated surface portion of the specimen is irradiated by two parallel laser beams to allow interference and having different frequencies each other to generate interference fringes scanned in a single direction, a strain distribution having the same intervals as the interference fringes is formed in the material having electrostriction effect coated on the surface of the specimen by electrostriction effect of the interference fringes to serve as a sound source, and an ultrasonic wave is efficiently excited by the sound source, when a phase speed of a wave front which the ultrasonic wave excited in the specimen by the sound source forms on the surface of the specimen coated with the material having the electrostriction effect is equal to a phase speed of the interference fringes.
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