The Research For Measuring Vibration Of Loudspeaker Membrane Using Fringe Projection

China has a big loudspeaker output in the world. Compared with some developed countries, the quality of the loudspeakers is not so good. So improving the quality of the loudspeaker is becoming a serious problem. The quality of reproduced sound of loudspeaker highly depends on the vibration and radiation properties of the membrane. The characteristics of the vibration of the membrane of the loudspeaker are important in studying the acoustic characteristic and improving the manufacture technique of the loudspeaker. With the development of the static optical 3D measurement as well as electronic technology, photoelectron technology, optical technology, dynamic optical 3D measurement has become a research focus. Dynamic high speed 3D optical measurement has the advantages of full field measurement, high resolution, high speed, high precision characteristics. So we proposed the method for measuring vibration of loudspeaker membrane using fringe projection.The project is divided into the following parts:1) Introduce the typical methods of loudspeaker vibration measurement, analyzes its advantages and disadvantages.2) We discuss the basic principle of 3D measurement technology using fringe projection.3) We proposed a cost-effective and full-field method for measuring vibration of loudspeaker using general industrial camera, including the structure of the system, working process, the external trigger timing analysis, the design of trigger generation circuit.4) To test verification system, we used general industrial camera and high-speed camera to measure the vibration of loudspeaker at the same time, and compare the results between them. Finally, we analyze the error and precision of experimental results.5) The summary and prospect.The innovations of the project include:Firstly, we can achieve real-time and full-field measurement of loudspeaker vibration and phase by using fringe projection. Secondly, the cost of the system is saved by using low-speed camera. At last, a trigger generation circuit is designed to control the camera, and we can automatically get the real-time images.