Patent ID: 8441907

Claim:
A complex objective lens, comprising: a diffraction element; and a refractive lens, wherein the diffraction element includes a first grating, a cross-sectional shape of the first grating is a stepped shape where one step difference is d 1 , the one step difference d 1 is a value between a largest one and a smallest one among multiples of (J×λ1), (K×λ2), and (L×λ3) by a factor of 1/(M×(nc−1)), (J×λ1), (K×λ2), and (L×λ3) are substantially equal, (J, K, L)=(6, 4, 3) and M is 5 where J, K, L, M are natural numbers which meet J>M>K>L, M is a number of step levels in one period of the first grating, and nc is a value between a largest one and a smallest one among refractive indices of a material of the diffraction element for blue light at wavelength λ1, red light at wavelength λ2, and infrared light at wavelength λ3.