基于透过式低相干光学干涉系统,提出了一种精密调节光程的方法,以测量透镜的中心厚度。利用一对楔形棱镜,将接近垂直于光轴方向的低精度直线移动转化为沿光轴方向的高精度直线移动,实现了高精度的光程调节。楔形棱镜的楔角角度决定了光程差的调节精度,楔角角度越小,光程差调节精度越高。使用5°30'的楔角棱镜组和精度为5 μm的直线移动装置,实现了光轴方向精度小于0.5 μm的移动调节,测量透镜中心厚度的精度在0.9 μm以内。所提方法提高了干涉条纹的对比度,可以测量各种类型透镜的中心厚度,也便于扩大测量厚度范围。

A method for precision-adjustable optical paths is proposed to measure the central thickness of a lens based on low-coherence interference with transmitted illumination. A pair of wedge prisms are used to translate the movement that is nearly perpendicular to the optical axis with low accuracy into movement along the optical axis with high accuracy, and thus the optical path along the optical axis can be precisely adjusted. The accuracy for adjusting the optical-path difference (OPD) is related to the wedge angle. The smaller the wedge angle, the more accurate the adjustable OPD. A pair of prisms with a wedge angle of 5°30' and a linear stage with 5 μm accuracy are used to realize the movement along the optical axis with an accuracy below 0.5 μm, and the central thickness accuracy of the tested lens is less than 0.9 μm. The proposed method is employed to improve the contrast of interference fringes. Moreover, the central thicknesses of lenses with different shapes can be measured by the proposed method and the thickness-measuring scope can be extended easily.