Optical system design and measurement of freeform surface

The use of sparse aperture can reduce the size and weight of the large aperture telescope. The sphere or aspheric surface commonly used is difficult to increase the field of view of the system and improve the image quality. Compared with spherical or aspherical surfaces, optical freeform surface has more design freedoms. This paper designs a two-mirror sparse aperture telescope. The primary mirror is made of three sub-mirrors arranged in the Golay3 configuration while the primary is a freeform surface defined by Zernike polynomials. The results show that the full field of view increases up to 0.32° in the optical system when the primary mirror uses a freeform surface. The image quality meets the requirements form its modulation transfer function.