Abstract: Provided is an optical element including: a liquid crystal cell including a first substrate, a liquid crystal layer, and a second substrate; and a quarter-wave film. The liquid crystal layer contains liquid crystal molecules twist-aligned. The liquid crystal cell includes electrodes. The electrodes are disposed to enable switching between a first state and a second state by application of voltage to the liquid crystal layer. The switching between the first state and the second state controls a polarization state of light incident on the liquid crystal cell. Circularly polarized light incident on the liquid crystal cell is converted to first linearly polarized light in the first state while converted to second linearly polarized light in the second state. Linearly polarized light incident on the liquid crystal cell is converted to first circularly polarized light in the first state while converted to second circularly polarized light in the second state.

Abstract: Provided is an optical element including: a first liquid crystal cell including first liquid crystal molecules and a first electrode; and a second liquid crystal cell including second liquid crystal molecules and a second electrode, the first and second electrodes disposed to enable switching between a first state twist-aligning the second liquid crystal molecules and vertically aligning the first liquid crystal molecules and a second state twist-aligning the first liquid crystal molecules and vertically aligning the second liquid crystal molecules. Alignment directions of the second liquid crystal molecules near a third substrate and the second liquid crystal molecules near a fourth substrate in the first state are respectively at azimuthal angles resulting from a ¼ turn in the same direction of azimuthal angles of alignment directions of the first liquid crystal molecules near the first substrate and the first liquid crystal molecules near the second substrate in the second state.

Abstract: Provided is an optical element including: a first liquid crystal cell including first liquid crystal molecules and a first electrode; and a second liquid crystal cell including second liquid crystal molecules and a second electrode, the first and second electrodes disposed to enable switching between a first state twist-aligning the second liquid crystal molecules and vertically aligning the first liquid crystal molecules and a second state twist-aligning the first liquid crystal molecules and vertically aligning the second liquid crystal molecules. Alignment directions of the second liquid crystal molecules near a third substrate and the second liquid crystal molecules near a fourth substrate in the first state are respectively at azimuthal angles resulting from a ¼ turn in the same direction of azimuthal angles of alignment directions of the first liquid crystal molecules near the first substrate and the first liquid crystal molecules near the second substrate in the second state.

Abstract: Provided is an optical element including: a liquid crystal cell including a first substrate, a liquid crystal layer, and a second substrate; and a quarter-wave film. The liquid crystal layer contains liquid crystal molecules twist-aligned. The liquid crystal cell includes electrodes. The electrodes are disposed to enable switching between a first state and a second state by application of voltage to the liquid crystal layer. The switching between the first state and the second state controls a polarization state of light incident on the liquid crystal cell. Circularly polarized light incident on the liquid crystal cell is converted to first linearly polarized light in the first state while converted to second linearly polarized light in the second state. Linearly polarized light incident on the liquid crystal cell is converted to first circularly polarized light in the first state while converted to second circularly polarized light in the second state.