Capacitive Sensors for Focal Plane Control

Capacitance sensors from MicroSense are widely used in a variety of focal plane control, or nulling, applications in both atmospheric and vacuum environments.

Typically these applications require that system optics be repeatably positioned relative to a part under inspection at the micron or sub-micron level, while the part under inspection is being rapidly moved under the system optics.

 Fig. 1 - Detecting the surface of a silicon wafer - measures position of wafer in Z relative to optics

In focal plane control applications, the position sensor is used either as a feedback sensor for a servo loop, or, as an independent displacement measurement device. It is used to maintain the required offset between the system optics and the part under inspection.