离轴回转对称棱镜式头戴显示器目镜的研制

针对大曲率自由曲面棱镜在加工中存在表面粗糙度差的问题,本文采用离轴非球面面型研制了棱镜式虚拟显示目镜.目镜的3个光学表面都采用了回转对称的非球面面型,其加工精度比自由曲面高且加工难度大大降低.通过控制棱镜各表面的曲率、倾斜角度来实现短焦距和大视场并通过优化高次非球面系数校正像差.实验结果显示:研制的目镜其光瞳大小为6 mm,视场大小为55°;在30 lp/mm处,轴上视场的调制传递函数(MTF)值高于0.2,轴外视场的MTF值高于0.1,目镜的最大畸变量为-5.37％.棱镜的检测和试验结果表明:与自由曲面棱镜相比,采用非球面面型能够显著降低棱镜表面的粗糙度,避免图像重影现象,成像更为清晰,虚拟成像的目视效果得到了明显改善.

Development of HMD eyepiece with prism of decentered rotationally symmetrical surfaces

To solve the problem of poor roughnesses for heavy curved freeform surfaces in prism processing,a Head Mount Display(HMD) prism with decentered aspheric surfaces was developed.All the optical surfaces of the prism were rotationally symmetrical aspherics,which showed a better processing property as compared with freeform surfaces.A short focal length and a large field of view were obtained by controlling the surface curvatures and tilt angles,and the aberration was corrected by optimizing aspheric coefficients.Experiments show that the HMD prism has an exit pupil of 6 mm and a field of view of 55°.At the frequency of 30 lp/mm,the axial Modulation Transfer Function(MTF) is over 0.2,the off-axial MTF is over 0.1,and the maximum distortion is-5.37%.The test and experiment on the prism demonstrate that the surface roughness has been greatly improved to a lower level for the aspheric surfaces,which avoids the image blurring and improves the performance of visualization.