Abstract: Under the paraxial rays condition, the Gaussian equation and light path method can be used to analyze the relationship between object and image of the thin lens or spherical mirror. The Nomorgraph, introduced here, uses the Cartesian coordinate system as the medium to analyze object-image relation. The schematic method of this kind is simple and intuitive. We can quickly estimate the character of the real or visual image as well as obtain their exact position. It is a great supplementary to the traditional method.

Key words: paraxial ray, Nomorgraph, thin lens, spherical mirror