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待检测非球面是微晶材料离轴抛物面,具体参数如表1所示。
Parameter Value/mm Radius of curvature R
Rex
Rey
X axis decenter
Y axis decenter3803.552
300
300
0
500Table 1. Parameters of off-axis aspheric surface
使用Zernike标准面型对计算全息图进行优化,图1为计算全息图的设计光路,标准镜采用4D 4 in(1 in=2.54 cm)F#3.3镜头,干涉仪焦点距离CGH前表面640 mm,CGH后表面距离待检测微晶反射镜中心3170 mm。
主区域设计波像差残差RMS优于0.0028λ,见图2。
Testing of aspheric surface with low reflectivity using hybrid type computer-generated hologram (invited)
doi: 10.3788/IRLA20220547
- Received Date: 2022-08-03
- Rev Recd Date: 2022-08-31
- Publish Date: 2022-09-28
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Key words:
- CGH /
- low reflectivity /
- diffraction efficiency /
- fringe contrast
Abstract: Computer-generated hologram (CGH) is widely used in high-precision off-axis aspheric surface testing. In order to improve the fringe contrast in the testing process of materials with low reflectivity, a hybrid type computer-generated hologram is proposed. The alignment area uses a reflective hologram, the optimal contrast corresponding to the film reflectivity is derived based on diffraction efficiency model, the main area applies phase type CGH to achieve diffraction efficiency improvement, thereby improving the fringe contrast of the detection area. The processing of hybrid hologram is realized by multi-step photo lithography process, and the off-axis aspheric surface of glass-ceramics material is tested using the fabricated CGH. The experimental results show that the hybrid type CGH can obtain clear fringe contrast, and the final detection accuracy is better than 0.02λ(λ=632.8 nm). The proposed hybrid type CGH can be widely used in the testing of aspheric surfaces with low reflectivity material.