Design and alignment of off-axis reflection beam expanding and contracting optical system

There are special requirements for the laser beam diameter and divergence angle in various optical combination systems, so most of the designs add beam expansion and contraction systems. Off-axis reflective systems are more widely used in practical applications because of their nonobstructing characteristics and unaffected by chromatic aberration. This paper designs an optical system with both beam expansion and contraction functions by Zemax optical software according to actual needs. The magnification and reduction are 3×. The mirror surface adopts an aspheric design to overcome system aberrations. The off-axis reflective structure is suitable for lasers of different wavelengths (632.8 nm, 1064 nm, and 1550 nm) without being affected by chromatic aberration. The optical spot diagram shows that the light spot distribution is uniform and meets the magnification and reduction ratio. Besides, combined the dynamic laser interferometer, we install and debug the primary and secondary mirrors of the system and use the laser beam quality analyzer to measure the exit spot of the actual laser beam after passing through the designed optical system. The peak value and root-mean-square value of the system transmission wave front are less than 0.1λ. The beam quality test result of the outgoing spot meets the actual application requirements and image quality requirements.