Long range and nanometric resolution sensor for non-contact position measurement

Miniature high resolution sensors are required in integrated systems. In the field of high resolution sensor, available sensors can be separated into two categories : small size sensor but having a limited range and high range sensor but with prohibitive size. This paper describes a miniature position sensor (2 mm diameter, 10 mm length). Used in a common way, this optical sensor have a 1 nm rms resolution but a linear range less than 200 pm (linearity criterion 1%). We propose to use two optical probes in front of a grating in order to increase the range to few millimeters while keeping a 15 nm resolution. We propose to describe the sizing method for the grating in order to optimize the sensor performances. Then actual performances are verified on experimental results and compared to simulations.