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Measuring joint angles is an important task for therapists to monitor and evaluate a patient's recovery progress. A fiber-optic goniometer with modified fiber tips was developed and employed to measure joint angles. The effects of the fiber tip's angle in various off-center positions of the detector on the output beam pattern were investigated. The proper combination of these variables increased the measuring range of joint angles with asymmetric light signals from the modified fiber tips. With inverse mathematical models and LabVIEW computer program, the joint angle was obtained and displayed in real time. The reference joint angle correlated well with the calculated output angle over the test range. This method can be used not only in hospitals and laboratories, but also at home, with a simple and cost-effective optical sensor. This method can be applied in the field of rehabilitation and sports science. [ABSTRACT FROM AUTHOR]

For diagnostic and therapeutic purposes, the joint angle measurement of a patient after an accident or a surgical operation is significant for monitoring and evaluating the recovering process. This paper proposed an optical fiber sensor for the measurement of angular displacement. The effect of beveled fiber angle on the detected light signal was investigated to find an appropriate mathematical model. Beveled fiber tips redirected the light over a range of angles away from the fiber axis. Inverse polynomial models were applied to directly obtain and display the joint angle change in real time with the Lab-VIEW program. The actual joint angle correlated well with the calculated LabVIEW output angle over the test range. The proposed optical sensor is simple, cost effective, small in size, and can evaluate the joint angle in real time. This method is expected to be useful in the field of rehabilitation and sport science. [ABSTRACT FROM AUTHOR]