| 摘要 |
PURPOSE:To measure vibration strain which varies at a high speed by projecting a laser beam and extracting vibrations detected from a speckle pattern formed by the beam nearby a peak and a bottom. CONSTITUTION:While the speckle of red laser light is recorded, reflected light from a half-mirror 14 is passed through the 2nd filter 13 to extract only blue light and the light intensity distribution of the speckle pattern of the blue laser light is detected, and transmitted to and stored in a computer 4. The speckle pattern in this case is denoted as I1(X). The 1st image sensor 10 stores the computer 4 with the speckle pattern I2(X) of red laser light after a test-piece deforms. A shutter driving device 17 opens shutters 15 and 16 only when the quantity of vibration of the test-piece has a crest value. The computer computes a mutual correlation function by using speckle patterns I1(X) and I1(X)', and I2(X) and I2(X)' before and after the test-piece deform, finds speckle movements Ax(theta) and Ax(-theta) from its peak value, and further computes the difference DELTAAx of movement and a strain value epsilonxx, so that the result is displayed on an input/output device 5.
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