A proposed optical-based sensor for assessment of hand movement

The purpose of this research is to evaluate two types of sensor that can be applied to monitor human finger flexion in real time. Currently, flex sensors are the most commonly used resistance sensors in glove-based systems. However, measurements show that current flex sensors have problems associated with hysteresis error, low sensitivity at small angles, and considerable time drift with large bending angles which render them unsuitable for tracking hand motion at low speed. In contrast, the developed optical sensor prototype has good repeatability, sensitivity and low temporal drift, as well as offering the capability of accurate measurements in both clockwise and anticlockwise directions. The sensor is based on the principle of crossed-polarization detection, and consists of one LED, two rotatable polarizers and one photodiode amplifier which enables the detection of changes in polarized light intensity proportional to angular rotation.