衍射光学器件光线追迹公式的实验验证

Experimental verification of the formulae for ray tracing through diffractive optical elements

本文介绍了一种衍射光学器件光线追迹的方法，并给出了计算公式。作为验证，在实验室里制作了具有连续相位的体全息器件，将其实际再现光斑与计算点列图进行比较。构造透射体全息片的物光为离轴的球面波，始于轴外点Ａ（０，１３２ｓｉｎ８°，－１３２ｃｏｓ８°），参考光为平面光束，其与Ｚ轴夹角为１７°。激光器采用氩离子激光器（Ｓｐｅｃｔｒａ－ｐｈｙｓｉｃｓＭｏｄｅｌ２０２０），波长４８８ｎｍ；干板感光胶为重铬酸明胶（ＤＣＧ），胶层厚为１５μｍ；通光口径３０ｎｍ。测试时把全息片放在干板的位置。挡住物光，让再现光以和参考光路相同的路径平行入射到全息片上，在全息片后垂直光轴放置毛玻璃片，平行光轴移动毛玻璃片，可观察到－１级衍射光的变化。在距离原点的距离分别为（ａ）４０ｍｍ，（ｂ）７０ｍｍ，（ｃ）８７ｍｍ，（ｄ）９５ｍｍ的地方用ＣＣＤ拍摄了衍射光的形状。

This paper introduces a method for ray tracing through diffractive optical elements (DOEs), and give out computational equations. As an verification an off axis volume phase transmission holographic lens is recorded in dichromated gelatin, and the diffracted beam are compared with computer generated spot diagrams. The construction spherical wave origins from an off axis point source A(0,132sin8°,-132cos8°),and the reference beam is an off axis plane wave, which has an interangel 17° with the axis. The model of laser is spectral physics, Model 2020. The thickness of dichromated gelatin in film glass 15μm. The aperture is 30mm. The reconstruction beam is the same as the reference beam. Behind the holographic lens, put a frosted glass plate which is vertical to the axis, move the plate along the axis, the variation of -1 order diffraction, which has rays diffracted at a rather sharp angel forming a highly aberrated focus can be observed. Both the shape and size of the -1 order diffracted beam are found to agree very well with computer generated spot diagrams.