为了制作平面变线密度光栅,满足线密度变化的要求,采用两个点光源和辅助透镜对基底曝光。编写了第一代和第二代光路的计算程序,计算出拍摄光路的几何位置参量,依据实际情况选择光路。提出了在线检测波前的方法,将辅助的标准光栅放在基底的位置上,入射光被标准光栅衍射,衍射光在光栅表面的干涉条纹反映了入射光的波前分布。采用数码相机和辅助镜拍摄干涉条纹,编写条纹分析程序,根据条纹调节元件的位置,直到入射波前满足要求后,对涂有光刻胶的基底曝光,制作出了原型的变线密度光栅。波前检测方法也可以用于其他全息光栅的制作中。
To fabricate the varied-line-space gratings and meet the requirements of non-linear line density, two point sources and ellipsoidal mirrors were selected. Some programs were written for the design of optical layout. After aligned the optical elements approximately, the standard gratings, whose density is accurate, replaced the s ubstrate. The interference fringes of diffraction waves are related to the incident wave fronts. To record the interference fringes, some mirrors and digital camera were used. The incident wave fronts could be calculated from the pictures. Adjusting the optic elements carefully, till the wave fronts were suited, and then the substrates replaced the standard gratings. The new gratings were recorded. After exposure and ion beam etching, the line density is assured. The wave fronts measurement can be used in many kinds of holographic gratings.