Opto-Electronic Engineering 光电工程 Review 2019 年, 第 46 卷, 第 7 期 固态激光雷达研究进展 陈敬业, 时尧成 * 310058 摘要 : 激光雷达可以高精度 高准确度地获取目标的距离 速度等信息或者实现目标成像, 在测绘 导航等领域具有重要作用 本文首先介绍了从机械式向全固态过渡的微机械系统激光雷达解决方案 ; 其次针对激光雷达全固态的发展需求, 介绍了面阵闪光 相控阵激光雷达的基本原理和典型实现方法, 从液晶 光波导材料等研究方向阐述相控阵激光雷达研究现状 ; 最后总结了目前激光雷达存在的问题及不同的解决方案, 并对未来发展趋势进行了展望 关键词 : 激光雷达 ; 微机电系统 ; 闪光 ; 光学相控阵中图分类号 :TN249 文献标志码 :A 引用格式 : 陈敬业, 时尧成. 固态激光雷达研究进展 [J]. 光电工程,2019,46(7): 190218 Research progress in solid-state LiDAR Chen Jingye, Shi Yaocheng * State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou, Zhejiang 310058, China Abstract: Light detection and ranging (LiDAR) system can be used to capture the distances and speeds of the targets with high resolution and high accuracy, and can also form imaging. It is important for the applications such as mapping, and navigation, et al. This paper introduces the LiDAR solution based on micro-electromechanical system (MEMS) is a transitional scheme from mechanical one to solid-state. Meanwhile, in terms of the requirement of solid-state, the principles of Flash and optical phased array LiDAR are introduced in this paper. At the same time, the miniaturization trend of LiDAR is presented with optical phased array based on liquid crystal (LC) and integrated optical waveguides. At last, the performances and open issues of the solutions for LiDAR are concluded and the development trends of LiDAR are summarized with outlook. Keywords: LiDAR; MEMS; Flash; optical phased array Citation: Chen J Y, Shi Y C. Research progress in solid-state LiDAR[J]. Opto-Electronic Engineering, 2019, 46(7): 190218 1 引言 [1-4] (LiDAR) 收稿日期 :2019-05-05; 收到修改稿日期 :2019-06-06 基金项目 :(11861121002) 作者简介 : (1993-) E-mail jingyechen@zju.edu.cn 通信作者 : (1981-) E-mail yaocheng@zju.edu.cn 190218-1
[5-7] (micro-electro-mechanical system, MEMS) (Flash)(optical phased array, OPA) MEMS Flash OPA [8] 2 3 MEMS 4 Flash 5 OPA (liquid crystal LC) (Silicon on insulators SOI) 6 2 基本原理 1 / 3 MEMS 激光雷达 (MEMS) 2 MEMS [9] MEMS [10] 2.3 V 9 12 mw 74 Hz [11] MEMS [12] 3 Laser Scanner Synchronization Computer 图 1 激光雷达工作原理图 Fig. 1 Schematic of the LiDAR system 190218-2
Laser MEMS mirror Synchronization Computer Lens 图 2 MEMS 激光雷达工作原理图 Fig. 2 Schematic of the MEMS LiDAR system MEMS 10 khz (PZT) [13] PZT MEMS [14] 11.2 khz 39 MEMS [15] 10 V 10 KTH [16] 4 MEMS 20 V 5.6 MEMS 7 mm MEMS [17] (time of flight TOF) 0.5 m 80 m 30 550 Hz 5 LiDAR 2 7 [18] 334 mm 80% 60 250 Hz 20 mm [19] 7.2 MEMS 1 khz 100 W MEMS MEMS MEMS [20] Byung-Wook Yoo 6 8 8 MEMS [21] 10 V 1.7π 0.5 MHz 9.14 9.14 Magnet Magnet B x i MEMS comb drive Tunable grating S N S N Coil Moving beam 10 μm Suspension spring (4 ) Waveguide [12] 图 3 电磁驱动 MEMS 结构图 Fig. 3 Schematic of the MEMS based on electromagnetic actuator [12] [16] 图 4 MEMS 驱动光栅电镜图 Fig. 4 SEM image of grating based on MEMS actuator [16] 190218-3
3 5 6 2 1 8 7 PC 4 50 μm [18] 图 5 大孔径 MEMS 激光雷达示意 Fig. 5 Schematic setup of MEMS-based LiDAR with large aperture [18] 4 Flash 激光雷达 20 90 [22] 3D 7 Flash [23] 8 Flash 2010 3D Flash [21] 图 6 8 8 MEMS 光学相控阵芯片扫描电镜图 Fig. 6 SEM image of the 8 8 MEMS optical phased array [21] [24] NASA 3D Flash 9 Flash 256 256 30 Hz 1 km [25] 1064 nm Flash 20 55 Hz [26] Flash PIN [27-28] 10 (avalanche photodetector APD) APD Laser Structure light Computer Synchronization Lens Focal plane detector 图 7 Flash 激光雷达工作原理图 Fig. 7 Schematic of the Flash LiDAR system 190218-4
Rack mounted system 1998 3D portable video camera 2005 Compact TigerEye July 2009 [23] 图 8 Flash 激光雷达小型化发展过程 Fig. 8 Miniaturization evolution of Flash LiDAR [23] Flash LiDAR Laser altimeter Aft port window Ribbon cable down loads 3D data to laptop Hand held 3D camera under development at ASCs Receiver aperture Laser transmitter aperture Laptop processes and displays 3D images Controls camera functions [25] 图 9 Flash 激光雷达框架图 Fig. 9 Configuration of Flash LiDAR [25] APD (linear mode avalanche photodiode LMAPD) (Geiger mode avalanche photodiode GMAPD) Lincoln 32 32 GMAPD 500 MHz 5000 10000 15 cm [29] 256 256 GMAPD 11 CMOS 30 ms 3.5 km [30] Raytheon (HgCdTe) LMAPD 3D 256 256 [31] [27] 图 10 Flash 激光雷达系统 Fig. 10 System of Flash LiDAR [27] Flash (APD) [32] Flash KAIST (polarization modulating Pockels cell, PMPC) (micro-polarizer charge-coupled device, MCCD) CMOS readout Silica substrate [30] 图 11 混合集成成像器截面图 Fig. 11 Cross section of hybridized imager [30] APDs 190218-5
[33] MCCD 1024 1024 MCCD APD 0.12 mrad 16 m 5.2 mm 5 OPA 激光雷达 12 [8] 5.1 液晶 (LC) 相控阵 McManamon [34] 13 (spatial light modulator SLM) Phase modulator LO Laser Phase modulator LO Computer 图 12 OPA 激光雷达工作原理图 Fig. 12 Schematic of the OPA LiDAR system Polarization Optical beam Off 360 Phase shift/( ) On V 0 0 V t 5 RMS voltage/v [34] 图 13 液晶光学相控阵结构原理 Fig. 13 Schematic of the LC optical phased array [34] 190218-6
±10 David Engström [35] 200 μs ±3.4 V ±9 ( khz ) ( ) 5.2 集成光波导型相控阵 1972 Meyer (LiTaO 3 ) 46 [36] 2π 32 V CMOS (silicon-on- insulator SOI) SungWon Chung 1024 [37] 180 nm SOI 45 0.03 136 66 μs MIT 14 [38] π 8.5 mw 24 1.6 19 db LiDAR LiDAR [39] (frequency modulated continuous wave FMCW) 15 L mn y Column phase control Unit cell ϕ mn Row phase control SMF Intrinsic Si n-si n * -Si Contact Metal 2 Metal 1 x Input 300 μm [38] 图 14 二维硅基光学相控阵结构示意图 Fig. 14 Schematic of 2D silicon optical phased array [38] Ge PDs Control pads 10% LO tap RX TX [39] 图 15 硅基光学相控阵收发芯片显微镜图 Fig. 15 Optical microscope image of the silicon optical phased array transceiver chip [39] 190218-7
46 36 0.85 0.18 2 m 20 mm [40] FMCW 5 mw 60 m 9 mm 9 mm 8 8 [41] 16 MIT 27.2 mw 2π 12 db, 6 总结与展望 OPA 1 20 90 Flash 3D 21 MEMS MEMS LiDAR MEMS Calibration GC z o y x Output GC Input GC T/R switch Poly-Si(p+) Poly-Si(p-) Si(p-) Metal layer 2 Metal layer 1 Via Si(p+) Top metal Metal layer 3 Amplitude control line Phase control line Active cell 8 8 active OPA Dimensions are not scaled [41] 图 16 单片集成 8 8 光学相控阵收发器示意图 Fig. 16 Schematic of the 8 8 monolithic optical phased array transceiver [41] 表 1 不同类型的激光雷达芯片性能对比 Table 1 Performances comparison of different LiDAR chips Type Scanning angle/( ) Resolution/( ) Speed/Hz Voltage/V MEMS [21] 9.14 9.14 NA 0.5 M 10 Flash [26] 20 NA 55 NA LC [35] 18 0.025 5 k ±3.4 Silicon OPA [39] 46 36 0.85 0.18 NA 12 190218-8
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Research progress in solid-state LiDAR Chen Jingye, Shi Yaocheng * State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou, Zhejiang 310058, China Laser Scanner Synchronization Computer Schematic of the LiDAR system Overview: Radar is utilized as the eyes to have the sense of the world for human, which has the ability to detect the target in dead zone and long distance. It plays a significant role in the military and civilian domains. Light detection and ranging (LiDAR) system has the shorter wavelength than that of the traditional radar. Thus, LiDAR systems have higher resolutions of distance, angle, and speed compared with the radar system. Due to the high direction and high coherence of laser, LiDAR systems can realize detection and ranging of the remote targets without external interference. The information of distance and speed can be obtained with coherent detection of LiDAR, which can be used in the fields such as missile guidance, mapping, driverless technology and so on. LiDAR can be classified as three types: mechanical, mixed solid-state, and solid-state. The mechanical LiDAR systems utilize the mechanically rotating parts to realize beam steering, of which the field of view is large but the assembly is complexed and the scanning speed is low. The solid-state LiDAR systems are without mechanical scanners and can be realized by the micro-electromechanical system (MEMS), Flash and optical phased array (OPA) technologies. MEMS based LiDAR realizes the beam scanning with micro mirror. The MEMS mirrors can be actuated by electrostatic method, electromagnetic method, piezoelectric method, and electrothermal method. The integration of the MEMS system is relatively high but the field of view is limited by the displacement of the micro mirror. Flash based solid-state LiDAR is proposed in 1990s, the techniques of which are relatively mature and have commercial applications. However, the detection range and field of view are limited. OPA emerged in 1970s is a novel optical beam scanning technology, which is based on principles and techniques of the microwave phased array. The OPAs realize beam steering based on the principle of changing the optical phase in the array unit, which will modulate the wavefronts of the emission beam. The OPA beam scanners are non-inertia, precision, accurate and have the potential to be utilized in the LiDAR field. The technique is emerging with liquid crystal (LC) and integrated optical waveguides and so on. The OPAs with high integration can satisfy the requirements of the miniaturization trends in some driverless fields. In the future, the LiDAR will develop on the way to the solid state and miniaturization trend. In this paper, we review the recent research of OPA LiDAR systems in Section 2, the basic working principle of Li- DAR system is introduced. In Section 3, the technique researches of MEMS based LiDAR are introduced. In Section 4, the principle and research of Flash LiDAR are introduced. The LC OPA and integrated waveguide OPAs for LiDAR, including the electro-optic materials, silicon-on-insulator (SOI) platform and so on, are introduced in Section 5. The performances of the techniques are compared and the open issues and outlook are given in the Section 6. Citation: Chen J Y, Shi Y C. Research progress in solid-state LiDAR[J]. Opto-Electronic Engineering, 2019, 46(7): 190218 Supported by National Natural Science Foundation of China (11861121002) * E-mail: yaocheng@zju.edu.cn 190218-11