"Development of Scanning Laser Micro-polariscope and its Applications for Stress Evaluation"

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We have developed an optical equipment that possesses high detection sensitivity for measuring the small optical retardation induced by small stress by means of laser photoelasticity. A He-Ne laser is used as a light source to measure small stress in transparent materials. We worked on the theory and process of the measurement of optical retardation in the materials. The magnitudes of principal stress difference and the directions of the principal stress are obtained simultaneously and quantitatively using our equipment. To evaluate the validity of the measurement results of the equiment, the stress distribution of a pulled rectangular glass plate with notches at both sides is measured using the equipment. The experimental results of stress distribution agree well with the analytical results of FEM.The stress distribution can be determined quickly by using the equipment and scanning stress distribution measurement has been realized. The features of the developed optical equipment and future applications are as follows,(1)This optical equipment has high resolution power of measurement less than 1 nm retardation and this technology can be applicable to the static and dynamic force evaluations in bio-membrane, bio-cell and several kinds of thin layrs,(2)This method can achieve the spatial-resolution of about 12 micrometer and has possibility of higher spatial-resolution up to 1 micrometer with the lens system like a microscope.