To measure a refractive index readily without depending on the refractive index and the phase (solid/liquid/gas) of a material to be measured.
Pulse laser light A, which is outputted from a pulse-laser light source 3 in synchronization with the synchronous signal outputted from a synchronous-signal generating part 4 is transmitted through a material to be measured filled in the inside of a sample cell 2. The scattered light generated at this time appears at the outside of the sample cell 2, and the image is formed on a gate 7 by a lens 6. The gate 7 is opened at respective times t1 and t2 in accordance with the timing signal generated in a timing-signal generating part 5 in synchronization with the synchronous signal. The image of the scattered light at this time is obtained in a photodetector 9. An operating part 10 obtains the optical speed of the pulse laser light A in the material to be measured 1, based on the scattered-light generating positions at the respective times t1 and t2 and the time difference of the time t1 and the time t2, and obtains the refractive index of the material to be measured 1.
SHIROSHITA MASAHISA
ISHIDA MASAYUKI
