| 摘要 |
PURPOSE:To obtain a microphone excellent in the transient characteristics, by using a member reflecting light as a diaphragm, arranging the diaphragm at a focus of a condenser lens, and outputting the shift in the focus when the diaphragm is dislocated with the sound pressure as an electric signal. CONSTITUTION:As the diaphragm 6 vibrated with sound waves 7, a diaphragm reflecting light is used, and this diaphragm 6 is arranged at the focus of an optical system comprising a laser 1, a polarized prism 2, a collimeter lens 3, a 1/4 wavelength plate 4 and a condenser lens 5. When this diaphragm 6 is dislocated at the sound waves 7, the shift in the focus of the optical system produced with the dislocation is applied to 4-split photodetector 9 via a deflection lens 2 and a cylindrical lens 8. The change in the distribution of strength of laser light of the detector 9 is converted into the electric signal at current- voltage converters 10-13, adders 14, 15 and a subtractor 16 to detect the sound waves 7 with excellent transient characteristics. |
