# Evaluation and Testing System for Automotive LiDAR Sensors
## 3 LiDAR Evaluation and Testing
### Lab Equipment  
_RotGon:_ The RotGon enables tilting/rotating of LiDAR sensors in three distinct angles. The rotation stage permits continuous 360\({}^{\circ}\) motion with a maximum speed of 2\({}^{\circ}\)/s and a minimum incremental motion of 0.01\({}^{\circ}\). The goniometer allows an angular range between \(-\)15\({}^{\circ}\) and 45\({}^{\circ}\) and features a worm mounted rotary encoder for improved accuracy and repeatability. Due to its high precision, the RotGon is highly important for the measurement of the AR and the FoV.  
_Rail System:_ The rail system was designed to enable a base moving that can handle weights of up to 30 kg and can be programmed by external communication. In turn, the base can support several targets with different reflectivity values. The rail system's structure has a length of 25 m and it is installed inside the laboratory. Figure 6 depicts the rail system with the LiDAR sensor installed on top of the RotGon (left side) and the moving platform with a mounted target at the end of the rail structure (right side). The rail system allows the velocity and acceleration/deceleration of the moving target to be controlled with given values (in mm/s for velocity and \(\pm\) mm/s\({}^{2}\) for acceleration/deceleration). Prior to its utilization, the rail system was calibrated with rangefinder equipment used to measure several distances to a target with 95% reflectivity mounted on the rail system. These measurements were used as reference values for the internal position detector sensor.  
_Power Supply:_ This equipment is used to power and monitor the power consumption of the LiDAR sensor under test. The power supply used in the evaluation and testing platform is the N6705C DC Power Analyzer, which includes four independent channels that can be used to power and monitor four different connected modules. The voltage and current levels for each channel can be changed in real time, allowing further testing of the sensor's behaviour under different power source conditions.  
Figure 6: Evaluation and testing platform with the goniometric rotation system, LiDAR sensor, and the rail system.  
_External illumination influence (background and sunlight)_: Ambient light from the sun and artificial sources represents one of the major drawbacks of using LiDAR in outdoor applications. For this reason, we created the setup depicted in Figure 7, which allows the influence of the external illumination to be tested by artificially changing the behaviour of the target's background light.  
Creating a setup with uniform illumination hitting the entire target is not feasible for objects with a larger area, as this would require an extremely strong light source and it would be hard to manipulate which specific area of target should be hit by the light. Therefore, this setup includes a beam splitter between the LiDAR and the target, which can couple the light source in the receiving path coming from the target. This setup makes it particularly easy to simulate different target reflectivities by varying the sending/receiving light signal, and it is possible to specify which region overlays the background light on the receiving path. The distance from the beam splitter to the target is around 5 m, and that from the beam splitter to the LiDAR is 15 cm. The light source used is a MAGIS 650 W lamp from Desisti.  
Figure 8 shows the impact of the background light on LiDAR performance. The validation of this setup was carried out with the Velodyne VLS-128; it can easily be seen that it is possible to blind the LiDAR sensor in such a way that the target is no longer detected on the point cloud. This setup allows for testing of different LiDAR systems in different illumination conditions to evaluate the impact on the collected point cloud.  
Figure 8: Influence of background light.  
Figure 7: Experimental setup for background light influence.