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摘要: 针对非对称光学系统视场范围和出瞳直径较窄、光学结构复杂、制造成本昂贵、装配调整麻烦等问题,本文采用在系统中加入自由曲面反射镜的设计方法。首先,论述了双反射镜非对称光学系统的设计要求和工作原理。然后,分析了三反射镜非对称光学系统的离轴结构控制方法。最后,采用XY多项式自由曲面反射镜折叠光路、消除遮拦、扩大视场、校正离轴像差,设计出一款适用于头盔显示器的非对称光学系统。设计的双反射镜非对称光学系统的视场为60°×30°,出瞳直径为8 mm。在截止频率52 lp/mm处,全视场的调制传递函数值大于0.25,系统畸变小于5%,单目系统重量约为190 g。设计结果表明,该非对称光学系统的视场大小和成像质量均有所提升,实现了小型轻量化,可应用于头盔显示器。Abstract: In non-symmetric optical systems, the field of view is narrow, the diameter of their exit pupil is narrow, their optical structure is complicated, their cost of manufacturing is high, and assembly adjustment is troublesome. To address these problems, free-form mirror is applied in the system. The design requirements and working principle of the dual mirror non-symmetrical optical system are firstly discussed. Then, the off-axis structure control method of the three-mirror non-symmetric optical system is analyzed. Finally, the XY polynomial free-form mirror is used to fold the optical path, eliminating the obstruction, enlarging the field of view, correcting the off-axis aberration, and a non-symmetrical optical system is designed suitable for Helmet-Mounted Display(HMD). The designed dual mirror non-symmetrical optical system has a field of view of 60° × 30° and a pupil diameter of 8 mm. At a cutoff frequency of 52 lp/mm, the full field of view Modulation Transfer Function(MTF) value is greater than 0.25 and system distortion is less than 5%. This monocular system’s weight is about 190 g. The design results show that the non-symmetrical optical system has an improved field of view and image quality, it is compact and lightweight, and can be applied to a HMD.
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Key words:
- optical design /
- non-symmetrical /
- helmet-mounted display /
- lightweight design /
- free-form surface
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表 1 三反射镜非对称光学系统的结构控制宏语言与注解
Table 1. Control macro language and annotation of non-symmetric optical system structure with three mirror
ZPL annotation !threemirror.zpl ZPLXX.zpl ! nfield=NFLD () Number of fields maxfield=MAXF () Maximum half angle of view IF(Maxfield==0.0)
THEN Maxfield=1.0;Avoid errors that divide by zero ! 面的个数 n==pvhx () Take the value of Hx to n ! field i=pvhy () Take the value of Hy to i ! 子午或弧矢 j=pvpy () Take the value of Py to j hx=FLDX(i)/maxfield Hx= field of view (x direction) / maximum field of view hy=FLDY(i)/Maxfield Hy= field of view (y direction) / maximum field of view PRINT “Field number”, i RAYTRACE hx, hy, 0, j, PWAV () Ray tracing PRINT “X-field angle:”, FLDX(i),
“Y-field angle:”, FLDY(i)PRINT “X-chief ray:”, RAGX(n),
“Y-chief ray:”, RAGY(n),
“Z-chief ray:”, RAGZ(n)Spherical coordinate position at the ray cutoff PRINT OPTRETURN 0, RAGY(n) OPTRETURN 1, RAGZ(n) Return value PRINT “All Done!” 表 2 三反射镜非对称光学系统的部分ZPL调用方式
Table 2. Partial ZPL calling method of three mirror asymmetric optical system
Oper# Op1 Op2 Hx Hy Px Py Target Weight 1 BLNK 1 field of view meridian upper edge of the intersection of light and face 1 2 ZPLM 11 0 1 1 0 1 0 0 3 ZPLM 11 1 4 BLNK 1 field of view meridian upper edge of the intersection of light and face 2 5 ZPLM 12 0 3 1 0 1 0 0 6 ZPLM 12 1 7 BLNK 1 field of view meridian edge light and face 3 intersection 8 ZPLM 12 0 6 1 0 −1 0 0 9 ZPLM 12 1 10 BLNK Solving straight line 11 DIFF 6 3 12 DIFF 5 2 13 BLNK Solving slope k0 14 DIVI 12 11 15 BLNK The distance between the line and the light on the meridian of the field of view 16 PROD 14 9 17 PROD 14 3 18 DIFF 16 17 19 SUMM 2 18 20 DIFF 8 19 21 OPLT 20 250 0.1 22 OPGT 20 25 0.1 表 3 eMagin公司的AMOLED规格参数
Table 3. Specifications of AMOLED produced by eMagin
Item Parameter Pixel size/μm 9.6×9.6 Resolution ratio 1 920×1 200 Visible area/mm 18.7×11.75 (0.856 inch) The white light brightness/(cd·m−2) >150 Contrast >1000:1 Refresh rate/Hz 30~85 Power consumption <350 mW(150 cd/m2) Weight/g <3 -
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