  Here we present a computational tool for optical tweezers which calculates
the particle tracking signal measured with a quadrant detector and the
shot-noise limit to position resolution. The tool is a piece of Matlab code
which functions within the freely available Optical Tweezers Toolbox. It allows
the measurements performed in most optical tweezers experiments to be
theoretically characterized in a fast and easy manner. The code supports
particles with arbitrary size, any optical fields and any combination of
objective and condenser, and performs a full vector calculation of the relevant
fields. Example calculations are presented which show the tracking signals for
different particles, and the shot noise limit to position sensitivity as a
function of the effective condenser NA.
