Design and Realization of an Optical Rotary Sensor

The traditional optical rotary sensors measured the absolute angular position of a rotating object by sensing the current position of a coded disk using the optical trans-receiver. Due to the small air gap in between the optical trans-receiver and the disk, the sensor cannot withstand the effect of vibration. Also, its fabrication cost is correlated with the disk coding pattern. Thus, in order to overcome such issues a simple, coding free optical rotary sensor is presented in this paper. Instead of binary patterns, here an opaque shaft coupled disk having a single window is used as a positional pointer over a light sensitive circular track. The track has four equal spaces of hollow channels and each one consists of a single photo detector (PD). The PD is placed at the end of the channel wall. Thus, in the presence of a light source, the position of the disk window is determined by measuring the diffused light intensity variation of each channel surface. In order to prove this concept, an experimental prototype has been designed, developed, and tested, where satisfactory performance is achieved in the measured range of 0-360°.