The light detection and ranging (LiDAR) technology is getting traction beyond level 2+ and above autonomous vehicles, and analog design breakthroughs are at the heart of this sensing and vision technology uptake. Intel, for instance, has built a LiDAR system for industrial applications like robotic arms for bin picking, volumetric measurements, logistics, and 3D scanning.
The blog outlines three major analog and mixed-signal design breakthroughs that are expected to significantly lower the size and cost of LiDARs and take them to new realms such as drones, facial recognition, and holographic displays.
- Micro-mirror scanning
Intel’s LiDAR depth camera is built around a tiny MEMS mirror that enables continuous laser scanning across the entire field of view to provide high-resolution scanning. This micro-mirror, developed by STMicroelectronics, is combined with a custom photodiode sensor to create a LiDAR camera based on Intel’s RealSense depth sensor technology.
Figure 1 The micro-mirror facilitates continuous laser scanning across the entire field of view in a depth sensor design. Source: STMicroelectronics
The MEMS mirror operates at 30 frames per second and provides a field-of-view of 70° by 55° while delivering high-resolution depth with no interpolated pixels. The high-resolution LiDAR depth camera—L515—is of hockey-puck size and ensures close-to-zero pixel blur.
- Photomultiplier arrays
A monolithic 1×12 array of silicon photomultiplier (SiPM) pixels claims to bring sensitivity to near-infrared (NIR) light, achieving photon detection efficiency (PDE) of 18.5%. The SiPM technology, which delivers high signal-to-noise performance for longer distances in bright sunlight conditions, is becoming popular in depth-sensing applications.
Figure 2 The SiPM devices lower the supply biases and sensitivity to temperature changes than legacy avalanche photodiodes (APDs). Source: ON Semiconductor
ON Semiconductor has unveiled an automotive-qualified SiPM array device—ArrayRDM-0112A20-QFN—that enables detecting the faintest return signals and expands the range to greater distances even with low reflective targets. That, in turn, leads to lower-cost and longer-range LiDAR solutions.
- Optical phase arrays
Another array technology—optical phased arrays (OPAs)—claims to improve scanning speed, power efficiency, and resolution compared to the heavy, power-hungry, and expensive mechanical beam-steering systems used in current LiDARs. CEA-Leti reported the calibration and characterization results of high-channel-count OPAs at Photonics West 2021 Digital Forum.
OPAs, optical antennas spaced at around 1 µm, radiate coherent light in a broad angular range. Next, the interference pattern can be changed by adjusting the relative phase of the light emitted by each antenna. If the phase gradient between the antennas is linear, a directional beam will be formed. This direction of the beam can be controlled by changing the slope of the linear gradient.
LiDAR, a key enabling technology for next-generation sensing and vision applications, must accurately resolve a scene. And, for that, technologies like high-channel-count OPAs and MEMS micro-mirrors are going to be crucial. These analog and mixed-signal building blocks are likely to bridge the gap between experimentation and massive commercial deployment in automotive and beyond.
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