为了精确地检测非旋转对称的非球面面形质量,将衍射补偿元件计算全息图(CGH)应用到非球面透射式检测光学系统中。利用计算全息图(CGH)可以生成任意形状的波前这一特点,对由三次面形和双曲面叠加而成的集成式波前编码器件进行检测,详细地给出了从检测系统的设计、计算全息图数学模型的建立,到CGH的制作和制作误差分析的过程。以口径33.84 mm的波前编码器件为例,检测系统的模拟残余波像差的峰谷值是0.037 3λ,均方根为0.006 3λ。利用激光直写技术,加工制作了口径为56 mm的计算全息板,计算全息图的制作误差为0.086λ,验证了计算全息图在检测自由曲面中的可行性。

In order to test the aspheric surface with non-rotationally symmetric precisely, the computed graphic holograph (CGH) has been used as a diffraction compensator to test the integrated wave-front coding unit which is integrated with hyperboloid and cubic surface. In this paper, the design of testing system, the mathematical model of the CGH and making error analysis of the CGH are obtained in detail. Testing integrated wave-front coding unit with diameter of 33.84 mm as a practical design example shows that the root mean square (RMS) of remnant wave-front error is 0.006 3λ, the peak to valley (PV) is 0.037 3λ. According to laser direct writer, a CGH with diameter of 56 mm was fabricated. The making error of the CGH is 0.086λ. The results show that the CGH testing method for testing the integrated wave-front coding unit is realized.