Abstract: In order to determine the difference between the ideal imaging and the real imaging produced by the object point on the axis passing through the biconvex symmetric spherical lens, and to verify whether the imaging device can meet the requirements of practical imaging application, the boundary equation of the imaging region of the object point on the axis passing through the biconvex symmetric spherical lens is derived by using the analytical geometry method, and the influence of the Angle of incident ray and the lens parameters on the imaging region is calculated and analyzed. The results show that when the object point position on the axis and the radius of curvature of the lens are determined, for example, the object distance is 30.0 cm, the radius of curvature is 15.0 cm and the half thickness of the lens L≤0.300 cm, the deviation on the axis representing the degree of deviation from the ideal imaging point on the boundary axis of the imaging region is less than or equal to 2.02%; when the object point position on the axis and the lens parameter are determined, for example, the object distance is 30.0 cm, the lens half-aperture h=3.00 cm and the angle of incident ray α≤4.85 °, the off-axis deviation representing the off-axis degree of imaging points at the boundary of the imaging region is less than or equal to 10%. This method can also analyze other aberrations. The theoretical derivation and calculation results provide theoretical support and technical reference for the subsequent research.

Key words: geometrical optics, biconvex spherical lens, ideal imaging, imaging region