Lidar is an important component of collision avoidance sensors in autonomous vehicles. It measures the distance of obstacles by scanning and sensing the light reflected back from the surface of the obstacle through laser. In the state of driverless, like the eyes of the auto drive system, the laser radar can detect the road traffic lights, road width, oncoming cars, pedestrians crossing the road or other emergencies, and accurately obtain the three-dimensional information of the target. It has the characteristics of high resolution, strong resistance and wide detection range.

Laser radar sensor of auto drive system

The angle of view of the laser radar anti-collision sensor is an important performance parameter. When the laser radar is installed in the car, the angle of view needs to be as large as possible to cover a wider area in front of the car, so that the auto drive system has better obstacle avoidance performance.

Schematic diagram of laser radar anti-collision sensor for autonomous vehicle

The wavelength range and intensity of the laser penetrating the sensor protective cover will change with the angle of incident light and the position of the sensor installation. Therefore, it is necessary to characterize and evaluate the transmittance spectra at different incident angles.

Loading variable angle reflection/transmission accessories on the Shimadzu UV-3600i Plus UV visible near-infrared spectrophotometer can perform angle related testing on the protective cover of radar sensors, providing important reference for the selection of laser wavelengths used in laser radar sensors.

Shimadzu UV-3600i Plus UV Visible Near Infrared Spectrophotometer

By rotating and adjusting the sample stage with a graduated variable angle attachment, different angles of incident light can be obtained. As shown in the figure below, the incident light angles are 35 °, 45 °, and 55 °, respectively.

Transmittance curves at different incident light angles

As shown in the figure, when the incident light angle changes, the wavelength and intensity of the transmitted light through the protective cover will change, and a peak shaped blue shift will occur with the increase of the incident angle. In order to avoid the influence of changes in the angle of incident light, the laser wavelength used in the laser radar collision avoidance sensor should be around 960nm, which is the intersection of the flat areas of the three spectral lines in the figure above. At this time, the incident light passing through the protective cover will not have significant intensity fluctuations due to changes in angle, thus ensuring the accuracy of imaging.