| 摘要 |
PURPOSE:To detect moving speed of a moving object highly accurately by preventing deviation of spot crossing position of two refraction beams on the moving object by using an optical system which is appropriately set forth. CONSTITUTION:Laser beam of wave length lambda turns into parallel beam flux I0 and comes into a diffraction grid 10 vertically, to a grid arrangement direction and then comes out therefrom as diffraction beam I1 of diffraction angle theta1. The beam flux I1 is refracted and comes out as beam flux I2 when coming into the first lens 11 of which focal distance is f. The beam flux I2 comes out again as parallel beam I3 when coming into the second lens 12 of which position is departed by 2f from the first lens, and then comes into a measuring point M of object 7 to be measured, by an angle theta2 which is similar to the diffraction angle theta1 from the diffraction grid 10. On the other hand, from the grid 10, another diffraction beam differing from the diffraction beam I1, comes into the measuring point M via a symmetrical optical path to an optical axis L and, at that moment, the two diffraction beams cross one another at the measuring point M to form a fringe thereby. Then, scattered beam of the object to be measured, from the measuring point M, is detected by an optical detector, and optical signal containing Doppler signal can be obtained. |
