The invention provides a light incoming surface and a light emitting surface, which are located on the two sides away from each other of the lens and are symmetric with respect to the central axis of the lens. The light incoming surface and the light emitting surface are located in the same coordinate
system. The light incoming surface meets a formula 1 (shown in the description), wherein C1 is the curvature of the light incoming surface, r1 is the distance between the center of the lens and the intersecting point between the light incoming surface and the
radius perpendicular to the central axis of the lens, u1 is the normalized
radius of the light incoming surface, am is the non-spherical coefficient, and Qm is an m polynomial representing that the sum of the am in the formula 1 is equal to the sum of the
mean square root of the slope of the light incoming surface. The light emitting surface meets a formula 2 (shown in the description), wherein C2 is the curvature of the light emitting surface, r2 is the distance between the center of the lens and the intersecting point between the light emitting surface and the
radius perpendicular to the central axis of the lens, u2 is the normalized radius of the light emitting surface, am is the non-spherical coefficient, Qm is an m polynomial representing that the sum of the am in the formula 2 is equal to the sum of the
mean square root of the slope of the light emitting surface.