Based on non-contact three-dimensional measuring principle of computer vision and light refraction principle, a new theoretical method of visual measurement in multi-medium was proposed.

We study the beam paths in uniaxial crystal with arbitarily oriented optical axis in general conditions, by it′s plane and ellipsoid of refraction index and Fresnel law.

This paper, based on the straight-line transmitting law and refraction law of light, analysed the conditions that the image of object in water will be clearly observed.