A two-stage method for measuring the heliostat offset

The conventional method of initial heliostat calibration by sequentially pointing the heliostats one by one onto a target is a very slow process. The use of unmanned airborne vehicles (UAVs) is a possible approach to developing a less time consuming procedure for the initial setup of the field control system and elimination of offset in light beam pointing. This paper presents a UAV based method for measuring the heliostat offset in two stages. The first stage, preliminary and less accurate, creates a three-dimensional model of the mirror facet corners in order to estimate the heliostat orientation. The estimated orientation from the first stage is a prerequisite for the second stage of measurement, in which the highly accurate heliostat orientation is derived from deflectometrically measuring the mirror shape. While work is still ongoing to fully implement the final steps of the second stage, the measuring principles has been demonstrated and partially validated for the first stage.