Two-Mirror Telescope Optical Axis Alignment by Additive Color Mixing Method

Abstract

In this paper, the two wavelength laser color alignment device, the additive color mixing method and the CCD camera is used to rapidly and accurately align the optical axis of a two-mirror telescope (TMT). In this method the optical axis of a TMT is made parallel to the “five incident parallel laser beams” in the plane of incidence, by checking direction of these five reflected laser beams and changing the height and orientation of the Two-mirror telescope. The two wavelength laser color alignment device emit five laser beams at two different visible wavelengths, including blue lasers with 405 nm at horizontal axis and the other red lasers with 645 nm at vertical axis. The combined dot will become magenta once parallel laser beams focus on focus point of two-mirror telescope and their beams overlap. The blue laser beam and red laser beam are added to the magenta light by the additive color mixing. The additive color mixing method uses to find the best focus and get minimum spot diameter of the TMT. This fast aligning method for finding the optical axis of a two-mirror telescope can measure the effective focal length deviation to an accuracy of 0.9 %.