In this article, propagation characteristics of light rays in glass plates with parabolic distributions of refractive index on the thickness are discussed. The central refractive index higher than that of the two big surfaces and the central refractive index lower than that of the two big surfaces are discussed respectively. The former is called glass plates with positively directional distribution of refractive index and the latter is called glass plates with negatively directional distribution of refractive index, and also, propagation of light rays in two perpendicularly intersected glass plates with positively direotional parabolic distribution of refractive index is discussed. Glass plates with positively directional parabolic distribution of refractive index are obtained by using Tl+ ions from the thallium lead silicate glasses is exchanged by K+ ions from the melt. And also, the interference ring is observed by double light ray interferometer. It is obtained from the above discussion that two perpendicularly intersected glass plates with positively directional distribution of refractive index are provided with an imaging property, and a glass plate with negatively directional parabolic distribution of refractive index is provided with a divergent property. In this article, their applications are considered.