A variety of technologies to improve optical performance in photolithography are surveyed. The technologies are classified according to which component of the optics they work on: the source, the mask, the pupil, or the image. Emphasis is put on, first, the advantages and disadvantages of annular illumination, which are studied by lithography simulation. Second, a polarized mask is proposed. The effect of polarization on imaging, which has not been explored yet, is studied and the result is that TE polarization produces images of the best quality. Third, as a part of pupil function, aberration optimization is discussed. The conclusion is that positive spherical aberration is suitable for projection optics.