混合型计算全息图检测低反射率非球面(特邀)

计算全息图被广泛应用于高精度离轴非球面面形检测，为提升低反射率材料检测过程中的条纹对比度，提出了一种混合型计算全息图，对准区域使用反射型全息图，基于衍射效率模型给出了最佳对比度对应的膜层反射率，主区域使用位相型全息图实现衍射效率的提升，从而提升检测区域的条纹对比度。通过多步半导体工艺实现混合全息图的加工，并对某微晶材料离轴非球面进行检测，实验结果表明:该混合型计算全息图可以获得清晰的条纹对比度，最终检测精度优于0.02λ （λ=632.8 nm），该混合型计算全息图可广泛应用于低反射率非球面检测。

Testing of aspheric surface with low reflectivity using hybrid type computer-generated hologram (invited)

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.