基于相位偏折术的天文光学镜面面形检测技术

The free-form mirrors widely used in the advanced astronomic telescope are usually rotational asymmetrical or highly aspherical, therefore their surface shapes are hard to measure by the traditional methods. The phase measuring deflection (PMD) technology is suitable for the free-form testing due to its flexibility, efficiency and accuracy, which is based on the deformation detection of the reflection image of the standard fringes by the test mirror. However, its accuracy and application is affected by the difficulties of the Gamma distortion correction, the imaging distortion correction and the shape retrieving from the slope data. To solve these problems, the PMD will be researched in the project, and the carrier squeezing interferometry is introduced to suppress the gamma distortion, while the virtual compensation method is proposed to reserve more valid information with high frequency. The stitching aperture method is proposed to generate standard markers to construct the distortion model so the imaging distortion can be corrected, which is especially useful when measuring the large mirror. Besides, the phase expanding method is proposed to improve the zonal reconstruction algorithm when retrieving the shape from the slope data so that the serious error around the aperture edge can be evaded. These theories and techniques of PMD will be studied by measuring different types of mirrors, and the demands on the accuracy, efficiency and flexibility in the astronomic optics can be satisfied.

先进天文望远镜中广泛使用的自由曲面镜面具有非旋转对称或高非球面度的特点，难以采用传统检测手段测量面形。相位偏折术是一种通过探测标准条纹经过被测镜面反射后的变形量进行面形检测的技术，因兼具灵活性、测量效率和测量精度，可用于自由曲面的测量。然而，该技术尚存在Gamma畸变、成像畸变校正以及从梯度恢复原始相位等难点，严重限制了其测试精度和应用范围。为此，本课题以相位偏折术为研究对象，引入载频交叠重构术抑制Gamma畸变，并提出虚拟补偿法以保留更多的高频有效信息；提出以合成孔径投影法为大口径在线标定提供标靶，以建立相机畸变模型，从而校正系统成像畸变；提出以相位延拓法对区域重构法进行改进，解决由梯度恢复原始面形时孔径边缘误差较大的问题。基于以上方案，通过对不同面形镜面的测量研究，完善相位偏折术的理论和技术，以满足天文光学镜面检测对于灵活性、精度和效率的要求。

先进天文望远镜中广泛使用的自由曲面镜面具有非旋转对称或高非球面度的特点，难以采用传统检测手段直接测量面形。相位偏折术是一种通过探测标准条纹经过被测镜面反射后的变形量进行面形检测的技术，因兼具灵活性、测量效率和精度的特点，适用于自由曲面的测量。然而，该技术尚存在Gamma畸变、成像畸变校正以及从梯度恢复原始相位等难点，限制了其测试精度和应用范围。为此，本课题以相位偏折术为研究对象，满足天文光学镜面检测对于测量灵活性、精度和效率的需求。在课题研究中，搭建了基于相位偏折检测的实验装置，研究了结构参数标定算法，对不同实验镜面进行测量并得到面形结果。研究在相位偏折测量术中的部分关键技术环节取得了具有一定学术和应用价值的原创成果，其中包括：1、提出了一种能够大幅提升条纹反射系统测量效率的方法，正交条纹法。相比于传统移相法，该方法对于特定空间频率的只需投射和采集一幅正交四进制灰度条纹图即可，而传统方法则需要6~8幅图。2、提出并完善了能够抑制条纹反射测量中的Gamma畸变误差的载频交叠重构技术，可省去传统校正方法中复杂的Gamma参数预标定过程；并通过完善相关理论使条纹图数量从3幅缩减为2幅，仍然能够保持相位重构精度和Gamma畸变抑制能力。3、提出了一种改进的从测量梯度数据重构面形的算法，能够兼顾计算效率和可靠性，且能适应不同被测件的孔径形状，并将之拓展应用于空域相位解包。4、设计了一种将条纹投影测量与相位偏折测量结合的镜面检测结构，相比于经典的相位偏折法，该结构使用投影仪向接收屏投射标准条纹图像，能够大幅扩展标准条纹区域，适用于大口径镜面面形检测。