A pattern generator includes a minor array plate having a mirror, at least one electrode plate disposed over the minor array plate, a lens let disposed over the minor, and at least one insulator layer sandwiched between the mirror array plate and the electrode plate. The electrode plate includes a first conducting layer and a second conducting layer. The lens let has a non-straight sidewall formed in the electrode plate. The pattern generator further includes at least one insulator sandwiched between two electrode plates. The non-straight sidewall can be a U-shaped sidewall or an L-shaped sidewall.