1. An imaging optical lens rotationally symmetric about an optical axis, wherein the imaging operation of the lens renders an incident ray to form an image point on an image plane perpendicular to the optical axis; the incidence angle of the incident ray with respect to the optical axis is δ; the incidence angle ranges from a minimum incidence angle δ 1 to a maximum incidence angle δ 2 (δ 1 ≦δ≦δ 2 ); the image height r defined by a distance from the intersection point between the image plane and the optical axis to the image point is given by Equation 1 for a continuous and monotonic function F(δ) as follows: r ( δ ) = r 2 - r 1 F 2 - F 1 { F ( δ ) - F 1 } + r 1 ( Equation 1 ) F 1 is a functional value corresponding to the minimum incidence angle δ 1 (i.e., F 1 ≡F(δ 1 )); F 2 is a functional value corresponding to the maximum incidence angle δ 2 (i.e., F 2 ≡F(δ 2 )); r 1 is an image height corresponding to the minimum incidence angle δ 1 (i.e., r 1 ≡r(δ 1 )); r 2 is an image height corresponding to the maximum incidence angle δ 2 (i.e., r 2 ≡r(δ 2 )); and the function F(δ) is given by any one among the Equations 2 through 6 as follows: 
 F(δ)=tan δ  (Equation 2) F ( δ ) = tan δ 2 ( Equation 3 ) 
 F(δ)=δ  (Equation 4) 
 F(δ)=sin δ/2  (Equation 5) 
 F(δ)=cot δ  (Equation 6)