A computer generated hologram for forming a light intensity distribution on a predetermined plane by giving a phase distribution to a wavefront of incident light, said hologram comprising: a plurality of anisotropic cells (110a, 110b) each including an anisotropic medium configured to change, in use, a polarization state of the incident light; and a plurality of isotropic cells (110c, 110d) each including an isotropic medium configured not to change, in use, a polarization state of the incident light, said hologram being configured such that, in use, a light component of the incident light, linearly polarized in a first direction, diffractively forms a first predetermined light intensity distribution of the linearly polarized light component in the first direction on the predetermined plane, and a light component of the incident light, linearly polarized in a second direction perpendicular to the first direction, diffractively forms a second predetermined light intensity distribution of the linearly polarized light component in the second direction on the predetermined plane, characterized in that dimensions and arrangements of said plurality of anisotropic cells and said plurality of isotropic cells are set such that a region is formed on the predetermined plane, in which the first light intensity distribution and the second light intensity distribution are superposed on each other, and in which the linearly polarized light component in the first direction of the first light intensity distribution is in phase with or π out of phase from the linearly polarized light component in the second direction of the second light intensity distribution and in which a light intensity ratio between the linearly polarized light component in the first direction of the first light intensity distribution and the linearly polarized light component in the second direction of the second light intensity distribution is a predetermined ratio, to form polarized light of a predetermined polarization direction in the region. a plurality of anisotropic cells (110a, 110b) each including an anisotropic medium configured to change, in use, a polarization state of the incident light; and a plurality of isotropic cells (110c, 110d) each including an isotropic medium configured not to change, in use, a polarization state of the incident light, said hologram being configured such that, in use, a light component of the incident light, linearly polarized in a first direction, diffractively forms a first predetermined light intensity distribution of the linearly polarized light component in the first direction on the predetermined plane, and a light component of the incident light, linearly polarized in a second direction perpendicular to the first direction, diffractively forms a second predetermined light intensity distribution of the linearly polarized light component in the second direction on the predetermined plane, characterized in that dimensions and arrangements of said plurality of anisotropic cells and said plurality of isotropic cells are set such that a region is formed on the predetermined plane, in which the first light intensity distribution and the second light intensity distribution are superposed on each other, and in which the linearly polarized light component in the first direction of the first light intensity distribution is in phase with or π out of phase from the linearly polarized light component in the second direction of the second light intensity distribution and in which a light intensity ratio between the linearly polarized light component in the first direction of the first light intensity distribution and the linearly polarized light component in the second direction of the second light intensity distribution is a predetermined ratio, to form polarized light of a predetermined polarization direction in the region.