US Patent 9454001 Toroidal heliostat

A toroidal heliostat and reflector frame for a heliostat are provided which passively adjust the apparent sagittal and/or tangential focal lengths of the reflector. This adjustment is provided by way of passive deflection of the reflector caused by one or more of gravitationally-induced deflection of one or more components of the heliostat; differential thermal expansion of materials of the heliostat; and/or relative movement between two or more components of the heliostat. Careful design of the heliostat enables optimisation of the power delivery profile and/or shape of the reflected image throughout the day.