Patent ID: 8553220

Claim:
An optical device comprising: a first projection group and a second projection group that are electrically conductive projections and that are arranged along a direction parallel to a virtual plane, wherein the first projection group is provided in a first area, and the second projection group is provided in a second area adjacent to the first area, the first projection group is arranged at a first period, and the second projection group is arranged at a second period different from the first period, the first period and the second period are shorter than a wavelength λ 1 of an incident light, the incident light includes a first light that is incident on the first projection group at a first angle with respect to a vertical line directed to the virtual plane and a second light that is incident on the second projection group at a second angle different from the first angle with respect to the vertical line, and a material of the first and second projection groups, the first and second periods, and the first and second angles are determined so as to make both a first resonant wavelength of first surface plasmon resonance at the first projection group and a second resonant wavelength of second surface plasmon resonance at the second projection group the wavelength λ 1 .