Design of Shaping Optical System for Double- Cone Lens Antenna

Objective Communication systems always expect high transmit power from the aspect of energy transmission. However, the traditional Cassegrain antenna system suffers significant central energy loss when transmitting solid beams, which greatly reduces the transmission efficiency of optical antenna systems in space optical communications. To resolve the issue of low transmission efficiency caused by secondary mirror obstruction in the Cassegrain antenna system, we propose a shaping optical system based on double- cone lenses. The main principle is to achieve solid beam- hollow beam interconversion by symmetrically placing the double- cone lenses. Compared with other Cassegrain antenna beam shaping systems, our system has a simple structure, is easy to install and adjust, and offers improved transmission efficiency. Methods We first analyze the factors affecting transmission efficiency in the Cassegrain antenna system and exploit the beam deflection properties of conical lenses. Two conical lenses are placed symmetrically; the first lens performs beam splitting, while the second lens restores the beam angle based on the principle of optical path reversibility. The recovered spot is a circular beam of a certain size. One advantage of this system is its applicability to various spectral ranges of antenna systems, as the relative distance between components can be adjusted without changing the beam's imaging angle. We also analyze the effects of lens tilting, off- axis displacement, and axial offset on laser transmission efficiency. Theoretical results show a transmission efficiency of 96.21 degrees o, influenced by the chamfering of the conical lens's top angle. When the axial displacement is-0.050 mm, transmission efficiency decreases to 95.02 degrees o, and at +0.050 mm, it drops to 90.65 degrees o. By controlling mounting errors, we maintain an overall transmission efficiency of more than 94 degrees o. The system's simplicity and versatility make it highly advantageous in engineering applications. Results and Discussions We set up a test platform consisting of a 1550 nm laser light source, a collimated beam expanding system, a double- cone lens shaping system, a focusing lens, and an illuminometer. The test results show that the laser transmission efficiency of the mounted double- cone lens system is 95.85 degrees o. This is slightly lower than the ideal 96.21 degrees o due to unavoidable mounting errors. After analyzing the effects of offset, off- axis alignment, and axial displacement, the transmission efficiency of the system remains above 92 degrees o. Conclusions Our research analyzes the factors affecting transmission efficiency in the Cassegrain antenna system. Based on this analysis, we propose a shaping optical system using double- cone lenses and provide the design method for this system. We investigate the factors influencing transmission efficiency, including the effects of conical lens top angle chamfering, tilting, off- axis displacement, and axial deviation. This research offers technical support for the mounting and machining of double- cone lens shaping systems in practical engineering, effectively improving the transmission efficiency of Cassegrain antenna systems.