It is important to observe the optical property of crystal of calcium fluoride because it is possible to use for the lense materaial of the lithography apparatus of silicon device. We have measured the scattering substance of calcium fluoride used for the excimer-lithography grade materials by the new type of light scattering topography method. This method is thought to be effective for the observation method which is no need of cutting samples. Some scattered particles have been observed in the matrix of calcium fluoride. The two types of the particles are shown. One is a large spherical particle, which exists independently, and the other is a small gathered particle, which are formed like a line. The latter is speculated to accumulate along the dislocation of the crystal. Additionally the fog-like particles of calcium fluoride which are occurred by annealing at high temperature have been observed by the method. The particles are formed by the small scattering substances which cordinate along the structure of the crystal and the large substances which are disordered. The small one is thought to be related to the structure of crystal of calcium fluoride.

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