Patent ID: 7352678

Claim:
A laminated wave plate, comprising a first wave plate with a phase difference α and a second wave plate with a phase difference β both with respect to monochromatic light having a wavelength λ, said wave plates being laminated together in such a way that directions of optical axes of said wave plates intersect each other, so that the laminated wave plate, as a whole, functions as a quarter-wave plate with respect to lights having two or more different wavelengths, wherein: said first wave plate satisfies the following formula: (3/2)×π≠α−2 ×π×m said second wave plate satisfies the following formula: π≠β−2 ×π×n a relationship between said α and β satisfies the following formula: β−2 ×π×n <α−2 ×π×m; said α and β respectively satisfy the following formulas: α>2 ×π×m , and β>2 ×π×n wherein each of m and n is a positive integer; and said optical axes of said first and second wave plates cross each other at an angle not equal to 90°.