3D sensing using laser beam triangulation
The novel 3D perception solution is a serialized triangulation system. Instead of searching for features that may be hard to see or even nonexistent (passive & active stereo), or inferring depth from the deformations of a complex light pattern by stereo matching (structured light), the depth reconstruction is as simple as triangulating corresponding events between sensors by matching the timestamps. This simplicity greatly reduces the latency and power required during the computing step.
- a) a Laser Beam Scanner (LBS) uses a scanning device (e.g., a bi-axial MEMS mirror) to project a laser beam dot in a continuous pattern, such as a raster scan or Lissajous pattern.
- b) two AES sensors capture the position of the laser dot up to every 10ns and output the location of the active dot in their respective image planes in an address event representation format (AER).
- c) based on the two continuous AES position streams, a simple triangulation algorithm computes the corresponding 3D point and outputs its position in world coordinates in the 3D space.
The output of this laser beam triangulation system is a stream of serialized 3D points, or voxels, with a new voxel added up to every 10ns. The dynamic nature of the data stream unlocks new possibilities in computer vision, allowing for pipelined processing and customized perception schemes.
Benefits and Breakthrough
The sensing and perception technology of VoxelSensors disrupts the sensorial status quo with the development of a new AES sensors enabling low power and low latency 3D active sensing using laser beam triangulation:
- Low Power Consumption: By concentrating the optical power in a single laser dot and designing AES sensors such that only the pixels actively detecting the illumination consume energy, the LBS-based perception system achieves up to 10x lower power consumption than existing 3D solutions in similar operating modes. This makes them well-suited for use in devices where battery life is critical.
- Low Latency: VoxelSensors‘ laser beam triangulation system offers unprecedented low latency compared to frame-based systems because the AES sensors capture and output only the laser dot position at a very fast rate rather than capturing a complete image at regular intervals. With a simple pipelined triangulation algorithm, a 3D point is computed based on the AER data after only hundreds of nanoseconds. As a result, the latency from optical sampling to depth measurement is very low. This means that this LBS system can provide a more up-to-date representation of the scanned scene.
- Immunity: Thanks to their high sensitivity and their smart operation, the AES sensors need a minimum photonic budget of ten photons and can therefore distinguish the active laser light from other sources such as indoor lights and sunlight. The same principles, and key patented technologies brought by the Single Photon, provide immunity to concurrent systems and other 3D systems.
- Data Scalability & Versatility: Thanks to its fully serialized data stream, the system provides a new way to look at perception data. Frames are not needed anymore to get information on the scene content. 3D points are created at a very high rate (up to every 10ns) as the laser dot scans the scene, and this incoming data stream comes with a fully flexible operation: one can decide to aggregate data over different time window sizes. In other words, the acquisition rate and the way information can be used are fully scalable. The natural trade-off offered by this novel system is speed versus density. In a limited time frame (e.g., 1ms), a coarse scan of the scene is acquired allowing for fast actionable decisions and updates.
- Spatial and Temporal Precision: This LBS perception system relies on the continuous sweep of a laser dot to ensure high density 3D points along the scan lines. Thanks to key patented technologies, the system takes advantage of the continuous nature of the scanning pattern to enable super-resolution data, thus providing depth data with 4x greater precision than what can be achieved with pixel-level sampling. In addition to the spatial resolution, each depth point carries a sub-microsecond timestamp, eliminating artifacts such as motion blur, and simplifying object tracking and other motion-sensitive applications.
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