Design of an array collimating system based on VCSEL light source

In lidar system, the laser has a divergence angle due to its Gaussian distribution which limits the detection distance. The improvement of lidar detection range is mainly based on the receiver and transmitter. Vertical Cavity Surface Emitting Laser (VCSEL) can form a two-dimensional (2D) array light source, which can realize direct detection without using a single laser for scanning. The structure of the lidar can therefore be simplified and the performance can also be improved. This paper aims to enhance the detection range of lidar by reducing the divergence angle of laser light source through designing an array collimator lens. The collimating lens unit designed is composed of a freeform surface lens and a standard lens, which is arranged in the same way as the light source. The aperture of the lens needs to be less than the distance between each adjacent light source unit, which makes direct calculation difficult. The design process is realized by nonsequential mode simulation by ZEMAX software, and the final design is obtained through the combination of calculation and software optimization. The design result shows that the initial divergence angle of the laser after passing through the lens array is compressed from 24.4° to about 0.7° theoretically, and the overall collimation keeps the energy loss within 20%. Simulation results indicate the design can initially achieve the detection range in a few of kilometers. The research work provides new solutions for light collimation and is helpful for advancing the development of lidar detection.