A grating is provided. The grating includes a first substrate and a second substrate opposite the first substrate, a plurality of first transparent electrodes arranged at equal intervals along a surface of the first substrate and between the first substrate and the second substrate, and a plurality of second transparent electrodes each arranged along a surface of the second substrate and opposite to a respective one of the plurality of first transparent electrodes, and a liquid crystal mixture layer arranged between each pair of the first transparent electrodes and respective second transparent electrodes, wherein a liquid crystal mixture in the liquid crystal mixture layer is switchable between a smectic phase and a cholesteric phase such that the liquid crystal mixture is transparent in the smectic phase and black in the cholesteric phase.