The present invention provides a spatial light modulator, comprising: a plurality of pixel units configured as a two dimensional array extending in a vertical direction and a horizontal direction; a plurality of row lines each comprises a word line and a plate line connected to a plurality of the pixel units along a row in the horizontal direction; a first address decoder for selecting the word line; a second address decoder for selecting the plate line; and a level retention circuit interconnected between the plate line and second address decoder to retain a voltage level of the plate line.