| 摘要 |
PURPOSE:To extend a dinamic range with the simple constitution and to improve an SN ratio by detecting optically Karman's vortex street. CONSTITUTION:Karman's vortex street generating members 3, 3a are provided at an engine sucking passage 1, thereby the Karman's vortex stree 5 are generated by the members 3, 3a at the downstream side. A photoelastic element 4 is provided at the downstream side further from the members 3, 3a. In the signal system for detecting the Karman's vortex street at first the light is generated by an optical transmitter 6 and a light emitting diode 7, and the light is transferred by an optical fiber 8, allowed to have the directivity by a mircolense 9, furthermore polarized by a polarizer 10, and then supplied to the element 4. In such a way, the light supplied to the element 4 generates the phase variation having the information by Karman's vortex street 5, and changes to the elliptic polarization. But the light is converted to the light intensity (light quantity) by a lambda/4 plate 11 and an analyzer 12, then condensed by a microlense 13, transferred by an optical fiber 14, and converted to the voltage or the current by a photodetecting element 15 and a photodetector 16. |
