Study On The Measuring System For Artificial Joint Based Laser And CCD

With the development of economy and level of modern medicine, artificial joint replacement is applied widely in the field of orthopaedics. Before the replacement, proper artificial joint need to be ordered for the patient. The artificial joint used to be replaced must keep with the original joint of patient in size and shape at all parts. Therefore, during the procedure of making artificial joint, the surface of artificial joint having been made need to be measured, then to be compared with the X-ray or CT image of patient's joint. If the error is large, the artificial joint should be modified. Usually the dimension of artificial joint may satisfy requirement after times of measuring and modifying.The contact-measuring tool is usually used to mesure the dimension of each cross section of artificial joint. But precision of this way is not high, and it's not convinient. Further, it may hurt the measuring surface of artificial joint. Another, it is very expensive to measure the artificial joint by the X-ray or CT image every time. The laser-CCD sensor has the characteristic of high speed, high resolving power, high sensitivity and non-wound, especially in measuring the artificial joint whose surface is not rule. So it's a economy and feasible method to measure artificial joint. This thesis have developed an allpurpose and multifunctional non-contact measuring system based laser and CCD, whose speed and response time is quick, precision and resolving power is high. This system can satisfy the requirement of measuring artificial joint well.The paper described a measuring system for artificial joint, which uses the principle of laser triangulation. The contects need to be researched include optical path design, mechanical probe design, system hardware design and sofrware design. Each part of circuit, signal processing and controlling software were described in detail, including driving circuit of laser-diode, driving module of linear-CCD, pre-processing and acquaring circuit for CCD signal, interface circuit of DSP, signal processing and controlling software based DSP and PC software. The measuring equipment designed comprises three parts, including probe, main controller and displaying board.The characteristics of this system are these: satisfy the requirement of measuring in different environment by adjusting the laser automaticly; advance the speed of data acquisition and processing in use of high-speed CCD, high-speed ADC, high-speed FIFO and special processing method, in the result, advance the speed of measuring of artificial joint; advance the resolving power and precision in use of high-elements CCD sensor and effective algorithm; the dimention data of artificial joint can be transmitted to PC by RS232, and then be processed and analysised by the PC software.In the experiment, a pig bone with joint was made to be artificial joint. After the measurement, 5040 data had been acquired. All data were transmitted to PC, and then 3D image of pig bone was reconstructed, which showed the surface circument of pig bone. It is showed that, the target of constructing 3D image using two-dimention data was realized by proper method.