Wavefront aberrations measurement of freeform surface based on computer-generated hologram technology

With the development of machine vision, remote sensing, and wearable displays, the applications of optical imaging systems are becoming more and more complex, and the requirements of intelligence, miniaturization and low cost is becoming higher. By breaking the constraint of rotational symmetry or simple aspherical application, and get more degree of surface shape freedom, freeform surfaces have brought new solutions to the optical imaging system. Meanwhile, traditional optical surface testing method is difficult to meet high-efficiency and high-precision at the same time since the non-rational symmetric characteristics. With the aid of modern photolithography, complicated computer generated hologram (CGH) can be produced for the null testing of optical freeform surfaces. Furthermore, CGH can provide references for system alignment while testing. In this paper, a CGH method of measuring freeform surface is presented, and the measurement uncertainty is analyzed. The result shows that for measuring the wavefront of a freeform surface with over 6-inch clear aperture, the measurement accuracy is less than λ/10.