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

我们研制了一种探测灵敏度高的光学装置，用激光光弹性法测量小应力引起的微小光延迟。用He-Ne激光器作为光源，测量透明材料中的微小应力。我们研究了材料中光延迟测量的理论和过程。利用本装置可以同时定量地获得主应力差的大小和主应力的方向。为了验证该装置测量结果的正确性，利用该装置测量了拉制的带缺口的矩形玻璃板的应力分布。应力分布的实验结果与有限元分析结果吻合较好，利用该装置可以快速确定应力分布，并实现了扫描应力分布的测量。所研制的光学设备的特点和应用前景如下：(1)该光学设备具有小于1 nm延迟的高分辨率测量能力，该技术可适用于生物膜、生物细胞和几种薄层的静力和动态力的评估。(2)该方法可达到约12微米的空间分辨率，并有可能与显微镜等透镜系统一起实现高达1微米的空间分辨率。

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.