Institute for Advanced Studies in Basic Sciences, Gavazang, Zanjan, 45195, Iran.
Opt Lett. 2010 Nov 1;35(21):3679-81. doi: 10.1364/OL.35.003679.
A method that utilizes the Fresnel diffraction of light from the phase step formed by a transparent wedge is introduced for measuring the refractive indices of transparent solids, liquids, and solutions. It is shown that, as a transparent wedge of small apex angle is illuminated perpendicular to its surface by a monochromatic parallel beam of light, the Fresnel fringes, caused by abrupt change in refractive index at the wedge lateral boundary, are formed on a screen held perpendicular to the beam propagation direction. The visibility of the fringes varies periodically between zero and 1 in the direction normal to the wedge apex. For a known or measured apex angle, the wedge refractive index is obtained by measuring the period length by a CCD. To measure the refractive index of a transparent liquid or solution, the wedge is installed in a transparent rectangle cell containing the sample. Then, the cell is illuminated perpendicularly and the visibility period is measured. By using modest optics, one can measure the refractive index at a relative uncertainty level of 10(-5). There is no limitation on the refractive index range. The method can be applied easily with no mechanical manipulation. The measuring apparatus can be very compact with low mechanical and optical noises.
介绍了一种利用透明楔形体的相位台阶的菲涅尔衍射来测量透明固体、液体和溶液折射率的方法。结果表明，当单色平行光束垂直于透明楔形体表面照射时，在垂直于光束传播方向的屏幕上会形成由于楔形体侧向边界处折射率突然变化而产生的菲涅尔条纹。在垂直于楔形体顶点的方向上，条纹的可见度在零到 1 之间周期性变化。对于已知或测量的顶点角度，可以通过 CCD 测量条纹的周期长度来获得楔形体的折射率。为了测量透明液体或溶液的折射率，将楔形体安装在包含样品的透明矩形池中。然后，垂直照射池并测量可见度周期。通过使用适度的光学器件，可以在相对不确定度为 10^(-5) 的水平下测量折射率。折射率范围没有限制。该方法易于操作，无需机械操作。测量设备可以非常紧凑，具有低机械和光学噪声。
