Patent ID: 8259290

Claim:
A pupil filter-formation diffractive optical device comprising: a dipole pupil filter having two light transmissive areas, wherein said two light transmissive areas are in a fan-like shape symmetric about a given distance from a center of said pupil filter, an area of low light transmittance is provided between and connecting said two light transmissive areas with a width at least equal to that of the poles, and there is a light block area outside said two light transmissive areas and said area of low light transmittance, wherein said area of low light transmittance is in a substantially oval shape characterized in that parameters σi, σo and θ are within the following ranges, and parameters ci and R/r are within the following ranges: 0.65 <σi< 0.75 0.8 <σo< 0.9 40°<θ<50° 5%< ci< 10% 1.5< R/r< 1.9 where σi and σo are the inner and outer diameters of each of said two light transmissive areas; θ is the angular aperture at which said two light transmissive areas subtend the center of said pupil filter; 1 is the radius of said pupil filter; ci is the intensity of light having transmitted through said area of low light transmittance provided that the intensity of light having transmitted through said two light transmissive areas is 100%; and R and r are the major and minor axes of said area of low light transmittance in a substantially oval shape.