Three-dimensional Measurement of Skin Displacement

We propose a method of measuring threedimensional skin displacement when a finger traces a texture. We combine the techniques of index matching and stereoscopy; the former makes the textured plate virtually transparent while the latter allows three-dimensional measurement of markers on the skin. We confirm that the proposed method can observe skin displacement in normal and tangential directions when the pitch of texture is larger than 2 mm. Observation results are reasonable in that the progress of a sinusoidal wave is observed on the skin when the texture is sinusoidal, and a displacement with the same period is observed when the texture is a rectangular linear grating. Moreover, we observe that the skin displacement in the skin normal direction may have a higher resolution or amplitude than that in the tangential direction. Limitations of the proposed method are also discussed.