| 摘要 |
PURPOSE:To enhance measuring accuracy, by providing a correction circuit for detecting the thickness of moving object, when laser beam is allowed to irradiate to calculate the speed of the object by Doppler effect, to reduce a speed measuring error on the basis of the change of a thickness. CONSTITUTION:Laser beam emitted from a laser beam source 2 is divided into two beams by a splitter 13 to irradiate an object 1 moving to the direction shown by an arrow at a speed V from transmission optical systems 5a, 5b through glass fibers 4a, 4b. The optical axes of the optical systems 5a, 5b form an angle phi and, while a distance (l) is held from the object 1, one of them moves against an advance direction and the other one directs to the advance direction. The reflected wave from the intersecting point O of both optical axes is detected by a light detector 7 through a light receiving optical system 6 and amplified by an amplifier 8 and Doppler frequency is tracked by a frequency tracking device 9 to operate a speed by a speed operator 10. The change in the thickness of the object 1 is detected by a thickness meter 11 and a thickness correction circuit 12 corrects the speed calculated by the operator 10 corresponding to the thickness of the object 1. By this method, a speed measuring error due to the variation of the measuring distance (l) accompanied by the change in the thickness of the object is reduced. |
