Thermal Management for LiDAR Systems
With high-powered lasers and the need for long-distance transmission, LiDAR systems are notorious for overheating. Lasers are not very efficient because approximately only 10% of the input gets converted to output, and the rest of that energy gets turned into heat. Solar loading is also a problem with LiDAR systems that are outside.
Solar Loading
Solar loading will be a significant factor if your device is living in the sun, like a car-mounted device, drone, radio, or an antenna. Solar loading adds about 1000 Watts of additional heat per square meter. Compounding these issues is that with many devices, the internal heat load is generated by the device’s operation. This solar exposure is added to the heat generated by the components within. Effective management of both heat sources is required for outside LiDAR systems.
Mitigation Techniques
There are two methods to mitigate heat. The first is to prevent the heat in the first place. Best practices for preventing heat include enclosure covers, paint, and material selection. The second is to transfer heat from the hot source to another cooler part. Best practices for moving heat from where it is generated to external surfaces start with board layout and conductive thermal path design.
Heat Management with Three Major Techniques: Conductive, Convective, Radiant Cooling
Conduction cooling is the transfer of heat from one hot part to another cooler part by direct contact. For example, most lasers use heat sinks that make contact with the device housing components via a thermal conductive paste or pad to conduct away the heat. The heatsinks, in turn, depend upon convection cooling to transfer their conducted heat to the cooler surrounding air.
Convection cooling involves transferring heat from a device by the action of the natural airflow. The advantage of convection cooling is that no fans are required. Due to their mechanical components, fans tend to reduce the mean-time-between-failures (MTBF) ratings of electronic systems. Convection cooling works best when the products have a natural circulating source of air. For enclosed applications, to ensure a natural exchange of air, a number of vents should be provided at various locations in the case or enclosure.
Radiant cooling is the transfer of heat utilizing energy waves that flow from a hot object to a cooler object. Painting the device, a dark color is an example of radiant cooling as long as it is not exposed to the sun. Your back will get hot if you are out in the sun and have a black shirt on. Balancing radiant surfaces with solar-exposed surfaces is the trick to optimum heat dissipation.
LiDAR Systems
In the case of LiDAR systems, the heat generated from the components is conducted, convected, and radiated to the external enclosure surfaces. Heat is moved from the components to the outside of the metal enclosure with heat-sinking fins, gap pads, and other conduction paths.
Image Source: Dllu - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=63450446
Image Source: https://ouster.com
Mitigation Starts with Best Practices
Best practices for dissipating heat include metal enclosure covers, strategically placed paint, and large surface area fins. Best practices for moving heat from where it is generated to external surfaces start with board layout and conductive thermal path design.
Optimize
We use thermal analysis tools such as ANSYS and SolidWorks to run heat flow simulations from source to destination to optimize system performance. For example, fin sizing can be optimized for the right amount of material usage, reducing cost and weight.
Image Sourde: ANSYS (https://www.technet-alliance.com/software/software-product/ansys-multiphysics/ on 9/2/2020)
Conclusion - Thermal Management for LiDAR Systems
As LiDAR technology continues to evolve and find applications in various industries, thermal management remains critical to its performance and reliability. Effective cooling strategies ensure accurate data capture and reliable system operation and contribute to the safety and success of LiDAR-enabled applications. As engineers and researchers continue to innovate in thermal management, LiDAR systems will be able to maintain their cool, providing clearer and more detailed 3D visions of the world around us.
