The two-mirror optical system with a small fold mirror

Abstract

A new configuration of two-mirror optical system with a small fold mirror is presented in this paper (Fig. 1). Consisting of a concave (positive power) primary mirror followed by a small flat mirror, a concave (positive power) secondary mirror and four lenses, it gives the excellent image quality. A f/10 1.5-m telescope of the upper configuration is designed over the 4° field angle and 0.50~0.70 µm wavelength range. The aberrations have been highly corrected and the distortion is less than 0.2% over the field. The aberration curves are shown in Fig. 2.