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冰洲石就是无色透明的方解石,它具有很强的双折射现象,是一种理想的双折射晶体材料。冰洲石晶体的加工方法与一般的光学玻璃有着很多相似之处,但由于冰洲石具有各向异性的性质,因此晶轴定向是一个很重要的特殊工作。冰洲石属于三方晶系,为棱形六面体,具有三个钝角(101°55′)隅棱角(图1)。从微观晶格结构看,它具有一个高次对称轴L_6~3,也就是它的光轴;从宏观上看,晶体的光轴位于隅棱角所组成的三角锥的角平分线上。如果沿此角锥方向研磨出正三角形截面,光轴就垂直于这个截面(图2)。以前常用偏光显微镜等偏光仪器进行定轴。我们感到,当晶体的尺寸较大时,这种方法很难保证定轴精度。
Icelandic stone is a colorless and transparent calcite, it has a strong birefringence phenomenon, is an ideal birefringent crystal material. The processing methods of Icelandic stone crystal have many similarities with the general optical glass. However, because of the anisotropic nature of Icelandic stone, crystal axis orientation is an important special task. Icelandic stone belongs to the tripartite crystal system, is a prismatic hexahedron, with three obtuse angles (101 ° 55 ’) corner (Figure 1). From the microscopic lattice structure, it has a high-order symmetry axis L_6 ~ 3, which is its optical axis; from the macroscopic point of view, the optical axis of the crystal is located on the corner bisector formed by the corner bisector of the bisector. If an equilateral triangle is ground along this pyramid, the optical axis is perpendicular to this section (Figure 2). Polarizers such as polarizing microscopes were previously used to set the axis. We feel that when the crystal size is large, this method is difficult to ensure the accuracy of the shaft.