| 摘要 |
PURPOSE:To make it possible to measure the speed of moving matter with high accuracy, by arranging moving matter to the waist region of coherent light to irradiate the moving matter with coherent light and arranging a light receiving element so as to leave a specific distance from the moving matter. CONSTITUTION:A numeral 11 is a coherent laser beam source and anumeral 12 is a projection optical system for converting laser beam to a converging region, a waist region and a diffusion region and a numeral 13 is pervious moving matter which is arranged to the converging region and moves at a speed V and a numeral 14 is a photoelectric converter element which is arranged to a laser beam region. Because the photoelectric converter element 14 is arranged at a position spaced apart by R>=(piW0)/lambda from the moving matter 13, a speckle is brought to a boiling state on the surface of a perforated plate 16 and the highly accurate measurement of a speed is enabled. Herein, lambda is the wavelength of laser beam and w0 is a waist radius.
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