Study On Medical Periodic Long-pulse Nd:YAG Laser

Clinical researches indicate that Nd:YAG 1064nm long-pulse laser is effectiveto treat skin & vascular disease and for cosmetic dermatology. For example,1ms~10ms Nd:YAG 532nm long-pulse is suitable for vacular disease treatment[1];30ms~40ms Nd:YAG 532nm long-pulse is effective to treat the acne disease;and1ms~100ms Nd:YAG 1064nm long-pulse is safe and efficient for permanent hairremoval for dark-skinned patients, especially for Chinese patients. We select the hairremoval as this paper's topic. In order to resolve the problems of the traditionalconstant amplitude long-pulse chopper technology in Nd:YAG laser, we used theperiodic long-pulse chopper technology and achieved this long-pulse which durationcan be adjusted from 1ms to 99ms freely. Some important research results wereachieved in this thesis as followings:1. The foundation of laser-assisted hair removal and the accomplishments of itsresearch in recent years were expatiated in the first chapter. And we select thelong-pulse Nd:YAG 1064nm laser as our research object.2. In order to solve the disadvantages of the traditional constant amplitudelong-pulse chopper technology in Nd:YAG laser, firstly we introduce the periodiclong-pulse chopper technology. Basing on the accomplishments of laser-assistedhair removal in recent years, we define the parameters of the sub-pulse of periodiclong-pulse basing on the medical theory: duty cycle is 50%, frequency is 500Hz.3. We design a periodic long-pulse Nd:YAG laser, especially the chopper circuit.And we mainly design the new IGBT driver with HCPL316J, better the driveability and protect the IGBT with "soft turn-off" process when the IGBT is in theshort circuit state.4. We accomplish the periodic long-pulse experiments, and confirm the advantagesof periodic long-pulse chopper technology. The maximum long-pulse duration weachieved is 99ms and the maximum energy can be up to 50J when the laser waspumped by two Xe-lamps. So our experiment is successful.5. We design an IGBT control circuit with a micro-controller, which can output1~99ms periodic long-pulse signal adjustably and deal with the fault condition.And we also design a water temperature control circuit, which is suitable for ourlaser.