| 摘要 |
PROBLEM TO BE SOLVED: To simplify an apparatus and to detect sped information on a moving body with high accuracy by a method wherein an electro-optical crystal whose refractive index is changed by applying a voltage and whose phase modulation state is different according to the difference in the passage region of a luminous flux is used and a frequency difference is given between two luminous fluxes. SOLUTION: Parallel luminous fluxes 3 which are radiated from a collimating lens 2 are incident on a frequency shifter 20 which is composed of an electro- optical crystal 10 which uses, e.g. LiNbO3 . Then, by a drive circuit 101, an electrode 11a and an electrode 11b apply electric fields to only one luminous flux part out of two luminous flux parts in the transmission part of the crystal 10. Then, two luminous fluxes which have a prescribed frequency difference are obtained at the end part of the crystal 10. The luminous fluxes are polarized by a polarization means 21 as a prism, and an object 7 to be measured is irradiated from two directions at prescribed angles. Then, scattered light due to the object 7 to be measured is detected by a light detecting means 9 via a condensing lens 8, and a Doppler frequency is computed. Thereby, an apparatus can be simplified as a whole, and speed information on a moving object can be detected with high accuracy. |
