Patent ID: 10732327

Abstract:
A Fresnel lens includes a Fresnel surface that includes effective Fresnel surfaces allowing imaging rays to pass through. Two adjacent effective Fresnel surfaces are connected through a non-effective Fresnel surface. On a cross-section including an optical axis of the Fresnel lens, a draft angle is between a reference line and a connecting straight line between one end of each non-effective Fresnel surface located at a tooth peak of the Fresnel lens and the other end of each non-effective Fresnel surface located at a tooth valley of the Fresnel lens. The optical axis coincides with the cross-section. The reference line is parallel to the optical axis and passes through the end of the effective Fresnel surface located at the tooth peak of the Fresnel lens. The draft angles each smaller than 90 degrees include first, second, third, fourth, and fifth draft angles which gradually increase radially outward from the optical axis.