| vascular disease do not harm to person health,but seriously influence the qualityof patient's lives. Basing on the theory of selective photothemolysis, the best methodto treat vascular disease is long-pulsed double frequency Nd:YAG laser.The directorof Willman medical laser lab, Rox Andersons, who is a well-known scientist in thelaser therapy circle, pointed out in his papers which published in 1995 that treating thevascular disease needs the laser whose pulse width is adjustable and from 1 to 10ms ismost suitable for treating[7].A new medical laser is designed for treating the vasculardisease. Some important research results were achieved in this thesis as followings:1,The foundation of skin-therapy with lasers and the demand of laser parameter wereexplicated in the first chapter. And we put forword the idea of many-pulse long pulselaser.2,A passive Q-switching by Cr4+:YAG crystal is used in our laser. In the thesis, we dosome theoretical deduceing and the study of experimental technique for its saturableabsorption and figure out the best initial transmittivity. Through the passive Q-switchrate equation, the peak power,pulse enengy and pulse width are deduced , we analyseand compare the theoretical value and experiment value . Then some useful results areobtained .3,We introduces a current-stabilized Xenon-lamp simmer circuit. The circuitstabilizes the current in Xenon-lamp by stabilizing the current-limiting resistance tostalilize the voltage of Xenon-lamp and solves the question of Xenon-lamp crushingout after the long-pulse laser. The circuit has the characters of small capacity, highefficiengy and the adjustion of electric network.4,A IGBT chopper is developed to adjust laser energy and pulse width,which has thecharacters of switching controlled hign-current high-frequency impulse, includingdrive circuit which uses slig M57962L, sequential control circuit and a currentfoldback circuit and cushion circuit using for rejection transient voltage.
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