# A Long-Range Lidar Optical Collimation System Based on a Shaped Laser Source
## 1 Introduction  
Light detection and ranging (lidar) is an active modern optical device that uses lasers as the emitting signal. Taking laser as the signal source, the pulsed laser emitted by the laser hits the target object, causing scattering, and a part of the light wave is reflected to the receiver of the lidar, and after comparing the detected signal with the received signal and making appropriate processing, the relevant information of the target can be obtained [1]. Given the rapid development of lidar technology over the last few decades, it has broad application prospects in the fields of resource exploration [2; 3; 4; 5], urban planning [6; 7; 8; 9], environmental monitoring [10; 11; 12; 13], and traffic communication [14; 15; 16; 17]. Especially in the era of driverless technology and navigation intelligence technology, it is becoming more and more important to realize better recognition of elements of the road using lidar, making people pay more attention to research on lidar in road detection. [PERSON] et al. introduced a novel lidar adaptive-assisted road detection (PLARD) method, which combines lidar information with visual image-based road detection in order to improve detection performances [18]. [PERSON] et al. used a lidar-based method to detect obstacles in front of the vehicle by clustering the lidar data using an improved curing method. This method could calculate the width and length of the obstacles and identify the vehicle more accurately [19]. [PERSON] et al. describe the use of lidar to detect moving obstacles in a road environment. According to an object's shape and motion, lidar provides information to classify and detect velocity, acceleration, and motion without being limited to shape [20]. Currently, conventional lidar optical systems [21; 22] are designed to meet the detection needs of roads, but as the distance increases, is it not only difficult to ensure the compression and collimation effect of the beam [23; 24; 25], but the requirements for the imaging system alsobecome more stringent. [PERSON] et al. designed a lightweight, compact and non-thermalized four-piece all-glass telephoto lens, combining the telephoto lens with a line-array detector, to significantly improve the detection resolution of lidar systems through local image-level imaging and satisfy the temperature adaptability of vehicle-mounted lidar in complex environments [26]. [PERSON] et al. designed a four-element, three-group, tensile-type vehicle lens to meet the requirements of intelligent vehicles in terms of recognition accuracy and imaging quality for close-range targets in front of them by varying the distance and curvature of the lens [27]. [PERSON] et al. proposed a method of optical design parameter optimization to design a matching aspherical surface shape structure to improve the laser echo signal detection capability. The contradiction between the optical system size and the collimation and focusing effect was solved for the near-field conditions and the on-board state interference [28]. All of the above studies can prove that the optical design system of vehicle-mounted lidar at close range has good imaging capability and image quality, but there are still relatively few studies on the imaging system at long range. For example, Figure 1 shows the display of the lidar signal on the main control screen of an existing car from a car manufacturer for autonomous driving. It is observed that in the application of the actual scene, the distant target vehicle outline at the opposite lane is incomplete and the imaging effect is not ideal. This proves that the overall performance in long-range imaging needs to be further improved. This paper presents a long-range lidar optical collimation system based on shaped lasers. The shaped laser refers to the compression of the light source in two different directions, x and y, in the design of the optical system.