Research On The Frequency Tracking Technology In Phacoemulsification Instrument

Cataract is the major cause of blindness around the world. Especially in recent years, with the acceleration of population aging, the number of cataracts is growing in worldwide. Treatment of cataract is also developing from the traditional cataract extraction to the current phacoemulsification. Phacoemulsification with its advantages of small incision, quick healing, small astigmatism, fast postoperative visual acuity and small surgical damage, has become an important surgical treatment of cataract. But phacoemulsification is not perfect, it also has many shortcomings, such as corneal astigmatism, corneal thermal damage caused by ultrasonic vibration and so on. During these years, people have been committed to the improvement and perfection of phacoemulsification and its instrument to enhance emulsifying efficiency, shorten operation time and reduce intraoperative ineffective energy release, in case of cornea injury and incision thermal burns. For the purpose, this paper researches a new frequency tracking program about the resonant problem of vibration system in phacoemulsification instrument.Firstly, the development of phacoemulsification was introduced in the paper. Next the composition of phacoemulsification instrument, functions of each part and its working principle were described in detail. Then frequency tracking technologies of the vibration system in phacoemulsification instrument were analyzed and studied, and last the amplitude-frequency characteristic of the resonant network equivalent circuit was analyzed deeply in theory. On this basis, according to the amplitude-frequency characteristic of the resonant network, a frequency tracking system has been realized based on the IP soft-core FPGA embedded SOPC system development platform, and by using Quaruts Ⅱ and Nios Ⅱ development tools, which has a set of functions such as ultrasound occurred, driving and voltage detection. In the design process, the system was divided into several independent hardware and software modules. The purpose of tracking the resonant frequency was achieved by detecting the voltage across the resonant network and real-time adjusting the frequency of the stimulating signal. Finally, the frequency tracking system has been tested and verified from three different experiments. The experimental results show that the frequency tracking system designed in this paper not only has the merits of simple principle and easy operation, but also has a good frequency tracking performance.