An image pickup device comprising: an optical filter including a first birefringent member; a second birefringent member; a liquid crystal layer disposed between the first and second birefringent members and configured to control polarization; and an electrode (12, 14) configured to apply an electric field to the liquid crystal layer; and a drive circuit configured to apply an intermediate voltage of constant frequency or an intermediate frequency of constant voltage to the electrode; wherein the intermediate voltage is a voltage between a first voltage of a maximum polarization efficiency and a second voltage of a minimum polarization efficiency on a polarization conversion efficiency curve of the liquid crystal layer, and the intermediate frequency is a frequency between a first frequency of a maximum polarization efficiency and a second frequency of a minimum polarization efficiency on a polarization conversion efficiency curve of the liquid crystal layer; and the first and second birefringent members and the liquid crystal layer are configured to generate a plurality of peaks in a point image intensity distribution of light transmitted through the optical filter when the intermediate voltage or the intermediate frequency is applied to the electrode, wherein a magnitude of the intermediate voltage or the intermediate frequency is changeable so as to vary the values of the plurality of peaks in the point image intensity distribution of light transmitted through the optical filter; and wherein the magnitude of the intermediate voltage or intermediate frequency is set at a value corresponding to a desired cut-off frequency. an optical filter including a first birefringent member; a second birefringent member; a liquid crystal layer disposed between the first and second birefringent members and configured to control polarization; and an electrode (12, 14) configured to apply an electric field to the liquid crystal layer; and a first birefringent member; a second birefringent member; a liquid crystal layer disposed between the first and second birefringent members and configured to control polarization; and an electrode (12, 14) configured to apply an electric field to the liquid crystal layer; and a drive circuit configured to apply an intermediate voltage of constant frequency or an intermediate frequency of constant voltage to the electrode; wherein the intermediate voltage is a voltage between a first voltage of a maximum polarization efficiency and a second voltage of a minimum polarization efficiency on a polarization conversion efficiency curve of the liquid crystal layer, and the intermediate frequency is a frequency between a first frequency of a maximum polarization efficiency and a second frequency of a minimum polarization efficiency on a polarization conversion efficiency curve of the liquid crystal layer; and the first and second birefringent members and the liquid crystal layer are configured to generate a plurality of peaks in a point image intensity distribution of light transmitted through the optical filter when the intermediate voltage or the intermediate frequency is applied to the electrode, wherein a magnitude of the intermediate voltage or the intermediate frequency is changeable so as to vary the values of the plurality of peaks in the point image intensity distribution of light transmitted through the optical filter; and wherein the magnitude of the intermediate voltage or intermediate frequency is set at a value corresponding to a desired cut-off frequency.