A New Absolute X, Y, Theta Encoder with Flexible Implementation and Standoff Reading Distance

We present a new position encoder based on pattern imaging and analysis. It provides three absolute coordinates in a snapshot. Two versions of these encoders are presented: one with reading distance adjustable in the 5 to 10 mm range, and another with a larger standoff reading distance adjustable in the 200 to 500 mm range. Depending on the configuration, the noise on orientation angle is in the 10 to 50 murad range, and the noise on position is in the 1 nm to 50 nm range. We present a first application for performance assessment of the repositioning capability of an optical microscopy stage. A second example is motion control of an atomic force microscopy stage. This encoder is easy to implement, and it may be of significant interest to scientists and QC engineers to perform actuator characterization, or to monitor sophisticated motion systems.