Active compensation research of spatial birefringent filter

The birefringent filter on space solar telescope is sensitive to the change of temperature，however, the precise temperature control of the traditional birefringent filter is difficult to achieve. An active compensation method which added a liquid crystal variable retarder (LCVR) in each single-stage of birefringent filter and introduced an additional retarder to compensate the delay caused by temperature fluctuation was put forward. This allowed the wavelength of the birefringent filter transmission peak to remain stable. The Lyot filter was studied, and the theoretical calculations and simulation proved the feasibility of this method. By applying the method to the spatial birefringent filter, the good performance of the filter could be remained without any temperature control system at the temperature provided by the satellite manufacturer, and the accurate temperature control of spatial birefringent filter was achieved. Since the traditional two-stage temperature control device was abandoned, the volume and weight of the filter were effectively reduced which met the requirements of space payload.