Displacement sensor based on pyroelectric thick films and contactless light-spot cursor

A sensor is presented to measure translational displacement exploiting the position-dependent signals generated by pyroelectric films when excited by a movable light-emitting diode that works as a contactless light-spot cursor. The pyroelectric films are made of lead zirconate titanate (PZT) screen-printed on alumina substrate by the thick-film technology. The sensor employs a differential configuration which minimizes the sensitivity toward mechanical vibrations and microphonics caused by the piezoelectric response of PZT. An electronic circuit based on excitation modulation and synchronous rectification rejects the interference from thermal and light background. The sensor principle, design, and manufacturing are described, and experimental results from the device characterization are reported.