A universal 3D imaging sensor on a silicon photonics platform (2008.02411v3)

Abstract: Accurate 3D imaging is essential for machines to map and interact with the physical world. While numerous 3D imaging technologies exist, each addressing niche applications with varying degrees of success, none have achieved the breadth of applicability and impact that digital image sensors have achieved in the 2D imaging world. A large-scale two-dimensional array of coherent detector pixels operating as a light detection and ranging (LiDAR) system could serve as a universal 3D imaging platform. Such a system would offer high depth accuracy and immunity to interference from sunlight, as well as the ability to directly measure the velocity of moving objects. However, due to difficulties in providing electrical and photonic connections to every pixel, previous systems have been restricted to fewer than 20 pixels. Here, we demonstrate the first large-scale coherent detector array consisting of 512 ($32 \times 16$) pixels, and its operation in a 3D imaging system. Leveraging recent advances in the monolithic integration of photonic and electronic circuits, a dense array of optical heterodyne detectors is combined with an integrated electronic readout architecture, enabling straightforward scaling to arbitrarily large arrays. Meanwhile, two-axis solid-state beam steering eliminates any tradeoff between field of view and range. Operating at the quantum noise limit, our system achieves an accuracy of $3.1~\mathrm{mm}$ at a distance of 75 metres using only $4~\mathrm{mW}$ of light, an order of magnitude more accurate than existing solid-state systems at such ranges. Future reductions of pixel size using state-of-the-art components could yield resolutions in excess of 20 megapixels for arrays the size of a consumer camera sensor. This result paves the way for the development and proliferation of low cost, compact, and high performance 3D imaging cameras.

Universal 3D Imaging Sensor on a Silicon Photonics Platform

The paper presents a comprehensive exploration of an innovative 3D imaging sensor developed on a silicon photonics platform. This technology leverages the focal plane array (FPA) concept used in 2D CMOS image sensors to establish a scalable and cost-efficient approach for 3D imaging. This research addresses the existing gap in 3D imaging technology, wherein numerous technologies cater to niche demands but lack universal applicability.

The authors demonstrate a large-scale coherent detector array comprising 512 pixels, a significant leap from previous systems limited to fewer than 20 pixels. This array is integrated into a LiDAR-based 3D imaging system operating at the quantum noise limit, a state where sensitivity is constrained by the fundamental quantum limit rather than technical imperfections such as thermal noise. The reported performance includes a distance measurement accuracy of 3.1mm at a range of 75 meters using merely 4mW of light, portraying the system as exceedingly efficient compared to existing technologies.

Key Achievements and Design

1. Integration of Photonic and Electronic Circuits: A major contribution of this paper is the successful monolithic integration of photonic and electronic circuits, facilitating the creation of dense optical heterodyne detector arrays with an integrated electronic readout. This enables straightforward scaling for arrays, a critical component for achieving the high resolution necessary for various 3D imaging applications.
2. Field of View and Range Without Trade-Offs: The integration of two-axis solid-state beam steering within the system avoids the conventional trade-off between field of view and range. This is vital for applications like autonomous navigation where both wide coverage and long range are essential.
3. Scalable Architecture: The architecture devised by the researchers supports expansion to large arrays, hinting at future developments that could reach above 20 megapixels, comparable to consumer camera sensors. This scalability is made possible by a combination of high multiplexing and integration on silicon photonics processes.

Implications and Future Directions

The impact of this scalable 3D imaging technology is multifold, comprising both practical and theoretical implications:

• Theoretical Implications: The successful minimization of the pixel size using state-of-the-art integrated circuits exemplifies an ideal combination of microelectronics and photonics. Future enhancements could revolve around further reducing pixel dimensions, thereby significantly increasing the resolution of 3D imaging sensors.
• Practical Applications: This technology provides a pathway for the high precision and low-cost production of 3D cameras for applications spanning from autonomous vehicles and robotics to healthcare and augmented reality. Enhancements in LiDAR systems meeting long-range requirements of up to a kilometer, as proposed in the paper, would significantly enhance their utility in autonomous systems and detailed mapping tasks.
• Future of 3D Imaging: The universality of this 3D imaging framework propels the field towards achieving a level of ubiquity akin to that of CMOS sensors in 2D imaging. This adoption could foster a broad range of applications previously deemed impractical due to cost or technical limitations.

In conclusion, this paper highlights the transformative potential of integrating photonics and electronics for 3D imaging, presenting a robust solution adaptable to diverse applications. As the technology matures, its promise in delivering highly precise 3D data at reduced costs could prove instrumental in various domains, raising the standard for future 3D imaging developments.