激光超声与皮肤的作用机理及其振动检测系统

为了探索激光超声在生物组织无损探测方面的应用，用有限元方法研究脉冲激光激发皮肤产生超声波的机理，并构建一个具有较高检测灵敏度的光学干涉系统。首先，在建立由表皮、真皮和皮下脂肪构成的皮肤模型的基础上，研究脉冲激光激发皮肤产生超声波机理的数值分析技术；其次，用解析的方法论述光学外差干涉法检测微弱超声振动的基本原理；最后，构建一种线偏振光外差干涉实验系统。结果显示．用主频为62．42KHz、幅值为74V的方波信号激励超声探头作为振动信号源，测得振动信号频率和幅值分别为62．38KHz和76．4mV。表明有限元方法是研究激光超声机理的一个有效手段，所构建的干涉系统可用于微弱超声振动检测的实验研究。切形

Interaction mechanism between laser ultrasonic and skin and an experimental system for ultrasonic vibration detection

In order to explore applieatian of laser uhrasonie in non - destructive evaluation of biological tissues,finite element method （FEM） was adopted to investigate mechanisms of ultrasound waves induced by a pulsed laser in human skin, and a high- sensitivity optical interferometer was developed. Firstly, based on the skin model, composed of epidermis, dermis and subeutaneons, numerical method was accordingly investigated to simulate ultrasound waves generated by a pulsed laser in the skin. Then, analytical method was used to analyze the fundamental principle of optical heterodyne interferometry for weak vibration detection. Finally, an optieal heterodyne interferometer system was designed with high sensitivity. When a square wave was used to excite an ultrasonic probe with 62.42KHz central frequency and 74V amplitude, the measured vibration signal freclueney and amplitude were 62.38KHz and 76.4mV respectively. Therefore, FEM was proved to be an effective method for investigation of laser ultrasonic, and the proposed optical experimental system can be used to detect the weak ultrasonic vibration induced by a pulsed laser.