Patent ID: 7961396

Claim:
A diffractive optical system including a diffractive optical element, the diffractive optical system being characterized in that: the diffractive optical element has a concave lens component having a first diffractive optical surface, and an optical member having a second diffractive optical surface; the concave lens component and the optical member are arranged so that the first diffractive optical surface and the second diffractive optical surface face each other; the conditional expression 0.003<t/f<0.3 is satisfied, where t is a thickness of the concave lens component on an optical axis of the diffractive optical system, and f is a focal length of the diffractive optical system, and further characterized in that the following conditional expression is satisfied: −8.5< fN/f<− 0.3, where fN is a focal length of the concave lens component and is less than 0.