非全对称五面镜单视点折反射红外周视系统

Objective Infrared omnidirectional imaging system can provide 360° image of the surrounding environment, enhancing vehicle safety and autonomous driving ability in low visibility and nighttime conditions. Recent developments in uncooled infrared focal plane detectors have paved the way for large-scale application of low-cost infrared imaging modules in vehicles. Therefore, an aperture-divided non-symmetrical five-sided mirrors based single viewpoint constraint catadioptric omnidirectional infrared imaging system is proposed, which combines the strengths of both multi-viewpoint omnidirectional imaging system and single-viewpoint catadioptric omnidirectional imaging system, taking advantages of the high spatial resolution of the former and the direct imaging without splicing of the latter. Methods To solve the problem that the requirement for detection distances of pedestrian in the front and lateral view, such as 200 m, is generally higher than that in the rear view, such as 145 m (Fig.4). Three sets of infrared imaging modules with focal length of 5.8 mm, two sets with focal length of 4.1 mm (Tab.1), and structure based on stitching multi-mirror are used to construct prototype. The structure of the non-symmetrical five-sided mirrors and the spatial position of the infrared imaging modules (Fig.7) are adjusted so that the virtual viewpoints formed by multiple infrared imaging modules with different focal lengths are overlapped at the same point (Fig.6). Results and Discussions The design process of single viewpoint constraint non-symmetrical five-sided mirror structure is established (Fig.9). The imaging model of the planar projection converted into omnidirectional image by cylindrical projection is analyzed (Fig.10). A mechanical structure scheme that can be adjusted and aligned with the viewpoint is proposed (Fig.11). The prototype system is processed and assembled (Fig.12), which can provide 360° horizontal azimuth and ±29° elevation field of view (Fig.13). Conclusion To address the different requirements for pedestrian detection distances in different direction, a non-symmetrical five-sided mirrors based single viewpoint constraint catadioptric omnidirectional infrared imaging system which has 64° FOV for the front view, left and right lateral view respectively and two 84° FOV for the rear view is proposed. According to the spatial resolution and distance, the appropriate infrared imaging modules are selected, and the specific size of the non-symmetric mirror is determined with the constraint of the single viewpoint. Then the system structure is further optimized with the imaging analysis until the system has small structure size and can image without occlusion. After successfully processing and installing the system, a series of omnidirectional image processing steps including cylindrical projection, scaling, center alignment, redundant part cutting, grayscale balance are also proposed. This system has the potential to serve all-round, large-pitch vehicle-mounted infrared imaging information, which can provide theoretical basis and technical support for applications in military and civilian fields such as intelligent transportation, automatic driving, and military reconnaissance.