Why Optical Phased Arrays Are the Future of LiDAR for Autonomous Vehicles

As OPA-based lidar continues to evolve and mature, it will become a cost-effective, high-performance technology with advanced situational awareness for AV navigation and collision avoidance—one that can be manufactured at scale. This choice of target architecture is evidenced by the proliferation of automotive phased array radars over the past two decades, as the industry has embraced the phased array architecture, with annual shipments exceeding 20 million units.

While OPA-based LiDAR is still relatively new compared to traditional mechanical LiDAR, it is making such rapid progress that solid-state LiDAR with OPA technology will start to become relevant to the transportation industry by 2022. Figure 1 explains Quanergy’s high-level architectural philosophy for automotive LiDAR. While performance specifications are important, the most critical aspects of deploying LiDAR in the transportation industry are low cost and high reliability.

A conscious architectural choice was to use (Si CMOS) processes for all key components in OPA-based solid-state LiDARs. The motivation was to leverage mature semiconductor processes to support a low-cost, high-volume manufacturing cost structure. This technology development path for Quanergy will be more challenging and time-consuming; however, the company took this route to avoid any shortcuts that could compromise long-term cost and reliability metrics - the ultimate determinant of LiDAR mass production.

In this article, we will explain what OPA is and why it is the technology of choice for self-driving cars.

3D LiDAR can be achieved through solid-state scanning or mechanical motion. Although many LiDAR vendors claim solid-state capabilities, most LiDAR sensors on the market today operate using micro- or macro-mechanical motion. These LiDAR sensors typically use rotational or vibrating mechanisms, or MEMS (micro-electromechanical systems) mirrors to achieve mechanical scanning capabilities.

While mechanically moving lidar sensors are used in certain industries and applications, they have their limitations in the automotive market. For example, rotating or oscillating lidar sensors are relatively large and bulky to accommodate the scanning mechanism. In addition, mechanical lidar sensors are more expensive to manufacture than new lidars. Both of these factors make widespread deployment of mechanical lidars in autonomous consumer vehicles impractical.

Mechanical scanning also means there are many moving parts that are more likely to wear out prematurely or become misaligned when subjected to shock or vibration. Mechanical scanning also limits the sensor's ability to respond adaptively to rapidly changing situations, such as driving. Significant engineering efforts are being invested in bringing macro or micro-mechanical lidars to automotive-grade compliance.

OPA is the optical analog of phased array radar. A phased array has multiple antenna elements that receive coherent signals of equal strength and use variable phase or delay control at each element to generate an arbitrary far-field radiation pattern and scan it in space.

Quanergy's OPA solid-state LiDAR is manufactured using a CMOS-compatible silicon photonic integrated circuit (PIC) process. The laser beam is electronically controlled to scan the sensor's field of view without moving parts. Solid-state LiDAR further reduces costs through silicon CMOS detector solutions, providing a path to commercialization of LiDAR sensors.

Common Misconceptions About OPA

While OPA lidar technology sounds new, it is based on decades of research. In addition, the electronics and software solutions developed for spinning lidar products are also applicable to solid-state lidar. This helps to accelerate the pace of commercialization. However, as with any emerging technology, there are still important developments in OPA-based lidar that will continue to improve the technology and make it more widely applicable and cost-effective in the coming years. For example, while the first commercial products have been released for short-range traffic management applications, Quanergy OPA-based sensors are now rapidly extending their performance levels to higher scan rates and longer detection ranges of 100 meters or more in sunny outdoor conditions and 10% reflectivity targets.

Unique features enabled by OPA

OPA technology offers many advantages that cannot be achieved with other lidar scanning methods, including intelligent and adaptive situational awareness, high reliability for everyday use in consumer vehicles, a low-profile form factor that integrates seamlessly with vehicle design, and low-cost production at high volumes.

As is the case in many industries (e.g., communications, computers, medical sensors), hardware has typically been commoditized over time by semiconductor technology on the one hand and software technology on the other. The OPA architecture inherits the semiconductor cost trajectory and software scaling and follows this natural trend to enable scalable mass deployment.

1. Adaptive smart zoom

Electronic scanning allows for a more adaptive approach to scanning and zooming in on areas of interest. Sensors can dynamically adjust their laser beam movement based on changing conditions. For example, Quanergy’s solid-state lidar sensors feature intelligent zooming that dynamically zooms in and out to provide a coarse or fine view (Figure 2) without losing the broader field of view. This software-controlled beam forming and steering brings intelligence to the sensor hardware and places the beam precisely where light is needed.

2. Unparalleled Reliability

OPA-based LiDARs are true 100% solid-state LiDARs with zero moving parts. This provides resistance to shock and vibration, with a mean time between failures (MTBF) of more than 100,000 hours. The unmatched reliability and longevity of these sensors make them ideal for consumer vehicles.

3. Low cost and mass production

Quanergy's OPA-based solid-state LiDAR uses mature CMOS silicon production processes, which can support extremely high-volume production at a significantly lower cost compared to competing LiDAR sensors.

4. Seamless integration of vehicle design

Compact and lightweight OPA-based lidar sensors can be seamlessly integrated into vehicle designs, providing rich data for object detection, tracking and classification, and supporting a variety of functions including truck platooning, ADAS functions (lane departure/change warning and forward/rear collision warning), automatic valet parking and self-navigation in geo-fenced areas.

in conclusion

After years of perfecting lidar, OPA technology is rapidly accelerating to meet the automotive industry’s growing demand for smart sensing. This is yet another way lidar is improving the quality of life for people around the world, ultimately making our world safer, better, and more efficient.

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