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reworked lidar figure caption

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Jan Kowalczyk
2025-09-28 14:47:43 +02:00
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@@ -320,7 +320,8 @@ LiDAR (Light Detection and Ranging) measures distance by emitting short laser pu
Because the speed of light in air is effectively constant, multiplying half the round‐trip time by that speed gives the distance between the lidar sensor and the reflecting object, as can be seen visualized in figure~\ref{fig:lidar_working_principle}. Modern spinning multi‐beam LiDAR systems emit millions of these pulses every second. Each pulse is sent at a known combination of horizontal and vertical angles, creating a regular grid of measurements: for example, 32 vertical channels swept through 360° horizontally at a fixed angular spacing. While newer solid-state designs (flash, MEMS, phased-array) are emerging, spinning multi-beam LiDAR remains the most commonly seen type in autonomous vehicles and robotics because of its proven range, reliability, and mature manufacturing base. Because the speed of light in air is effectively constant, multiplying half the round‐trip time by that speed gives the distance between the lidar sensor and the reflecting object, as can be seen visualized in figure~\ref{fig:lidar_working_principle}. Modern spinning multi‐beam LiDAR systems emit millions of these pulses every second. Each pulse is sent at a known combination of horizontal and vertical angles, creating a regular grid of measurements: for example, 32 vertical channels swept through 360° horizontally at a fixed angular spacing. While newer solid-state designs (flash, MEMS, phased-array) are emerging, spinning multi-beam LiDAR remains the most commonly seen type in autonomous vehicles and robotics because of its proven range, reliability, and mature manufacturing base.
\figc{lidar_working_principle}{figures/bg_lidar_principle.png}{An illustration of lidar sensors' working principle. Reproduced from~\cite{bg_lidar_figure_source}}{width=.8\textwidth} \figc{lidar_working_principle}{figures/bg_lidar_principle.png}{Illustration of the working principle of a lidar sensor. The emitter sends out an optical signal that is reflected by objects in the scene and captured by the receiver. The system controller measures the time delay $\Delta t$ between emission and reception to calculate distance using $d = c \cdot \Delta t / 2$. By repeating this process across many directions—either with multiple emitter/receiver pairs or sequentially in a spinning lidar—the sensor obtains a dense set of distances that, combined with their emission angles, form a 3D point cloud of the environment. Reproduced from~\cite{bg_lidar_figure_source}.
}{width=.8\textwidth}
Each instance a lidar emits and receives a laser pulse, it can use the ray's direction and the calculated distance to produce a single three-dimensional point. By collecting millions of such points each second, the sensor constructs a “point cloud”—a dense set of 3D coordinates relative to the LiDAR’s own position. In addition to X, Y, and Z, many LiDARs also record the intensity or reflectivity of each return, providing extra information about the surface properties of the object hit by the pulse. Each instance a lidar emits and receives a laser pulse, it can use the ray's direction and the calculated distance to produce a single three-dimensional point. By collecting millions of such points each second, the sensor constructs a “point cloud”—a dense set of 3D coordinates relative to the LiDAR’s own position. In addition to X, Y, and Z, many LiDARs also record the intensity or reflectivity of each return, providing extra information about the surface properties of the object hit by the pulse.