Hamamatsu Photonics K.k. · TSE:6965

Hamamatsu Photonics K.k — Technical Presentation (June 2020)

54 slides from Hamamatsu Photonics K.k's technical presentation, Jun 2, 2020

  1. Slide 1: Solid State Automotive LiDAR: Physics Principles, Design Challenges, and New Developments

    Solid State Automotive LiDAR: Physics Principles, Design Challenges, and New Developments Slawomir Piatek New Jersey Institute of Technology & Hamamatsu Photonics, Bridgewater, NJ 06.2. 2020 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 1

  2. Slide 2: Index

    Index ■ LiDAR Concepts: ToF & FMCW ■ Light Sources & Beam Steering ■ Solid State (Flash) LiDAR 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 2

  3. Slide 3: LiDAR Concepts

    LiDAR Concepts 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 3

  4. Slide 4: Basic Layout of Time of Flight LiDAR

    Basic Layout of Time of Flight LiDAR beam steering Measure the time of flight Δ𝑡 system laser start pulse timer stop pulse target photodetector Distance d = Δ𝑡 ∙ 𝑐/2 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 4

  5. Slide 5: FMCW LiDAR: Heterodyne Mixing

    FMCW LiDAR: Heterodyne Mixing M M frequency 𝑓𝐿𝑂 shifter PD 𝑓𝑃𝑂 = 𝑓𝐿𝑂 + 𝑓𝑜𝑓𝑓𝑠𝑒𝑡 to target electronics M M tunable BS laser optical mixing 𝑓𝑎 = 𝑓𝐿𝑂 + 𝑓𝑜𝑓𝑓𝑠𝑒𝑡 + Δ𝑓 occurs on the M detector collimator returned light receiving optics Legend: 𝑓𝐿𝑂 – Local oscillator…

  6. Slide 6: Example of Frequency Modulation: Double Linear Ramp

    Example of Frequency Modulation: Double Linear Ramp 𝑓0 𝑓𝑚𝑎𝑥 𝑓0 𝑓𝑚𝑎𝑥 𝐵 frequency time 0 𝑇 2𝑇 𝑓𝑚𝑎𝑥 frequency 𝑓0 time 0 𝑇 2𝑇 T ~ 10’s μs – 1 ms, B ~ 100’s MHz – 10’s GHz 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 6

  7. Slide 7: Frequency Shift in FMCW LiDAR

    Frequency Shift in FMCW LiDAR local oscillator received wave 𝑓(𝑡) Δ𝑡 𝑓𝑚𝑎𝑥 𝑓𝐵2 𝐵 𝑓𝐵1 𝑓0 𝑓𝐷 𝑇 time 𝑐 𝑓𝐵1 + 𝑓𝐵2 𝑇 𝑐 𝑓𝐵2 − 𝑓𝐵1 𝑑= 𝑣𝑟 = 8𝐵 4𝑓0 𝑐 𝑐 𝛿𝑑 = 𝛿𝑣𝑟 = 2𝐵 𝑓0 𝑇 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 7

  8. Slide 8: Heterodyne Optical Mixing

    Heterodyne Optical Mixing 𝐸𝑡𝑜𝑡 2 = 𝐸𝑎 + 𝐸𝐿𝑂 2 = 𝐴𝑎 cos 2𝜋𝑓𝑎 𝑡 + 𝜑𝑎 + 𝐴𝐿𝑂 cos 2𝜋𝑓𝐿𝑂 + 𝜑𝐿𝑂 2 𝐸𝑡𝑜𝑡 2 = 𝐸𝑎 2 + 𝐸𝐿𝑂 2 + 𝐴𝑎 𝐴𝐿𝑂 cos 2𝜋 𝑓𝑎 − 𝑓𝐿𝑂 𝑡 + 𝜑𝑎 − 𝜑𝐿𝑂 BS 𝑃𝑠𝑖𝑔 = 𝑃𝑎 + 𝑃𝐿𝑂 + 2 𝑃𝑎 𝑃𝐿𝑂 cos 2𝜋 𝑓𝑎 − 𝑓𝐿𝑂 𝑡 + 𝜑𝑎 − 𝜑𝐿𝑂 PD fLO…

  9. Slide 9: Comparison Between ToF & FMCW Concepts

    Comparison Between ToF & FMCW Concepts ToF FMCW Easy optical layout Optical amplification of the returned signal Pros Easy distance calculation Photon shot noise detection possible Any wavelength of light can be used Pros Immunity to background and interference Gives both distance and radial velocit

  10. Slide 10: Light Sources & Beam Steering

    Light Sources & Beam Steering 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 10

  11. Slide 11: Light Sources

    Light Sources ToF FMCW Short-duration pulses: ~ few ns Tunable output frequency High peak power: ~ 100 W Coherence length 𝐿 > 2𝑑𝑚𝑎𝑥 Repetition period: ~ ms - μs Stable phase Wavelength: NIR, e.g., 905 nm, 1550 nm some light source offerings by Hamamatsu 🄫 Hamamatsu Photonics K.K. and its…

  12. Slide 12: 905 or 1550 nm? Solar irradiance

    905 or 1550? Solar irradiance at sea level Spectral irradiance μW cm-2 nm-1 𝑃𝐵 @ 905 nm > 𝑃𝐵 @ 1550 nm Figure from Matson et al. 1983 905 nm 1550 nm Wavelength [nm] Solar background at 905 nm is higher than at 1550 nm 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 12

  13. Slide 13: 905 or 1550 nm? Water absorption

    905 or 1550? Absorption coefficient of water [cm-1] From Wojtanowski et al. 2014 Wavelength [nm] H2O absorption @ 1550 nm > (100×) @ 905 nm Reference: “Comparison of 905 nm and 1550 nm semiconductor laser rangefinders’ performance deterioration due to adverse environmental conditions,” Wojtanowski e

  14. Slide 14: 905 or 1550 nm?

    905 or 1550? 905 nm + Better transmission in atmosphere + Silicon-based photodetector 1550 nm + Best eye safety + Lower background 𝜆2 + Coherence length 𝐿 ∝ 𝐵 - Requires IR (non-silicon) photodetectors 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 14

  15. Slide 15: Mechanical Beam Steering: Rotating Platform

    Mechanical Beam Steering: Rotating Platform Vertical sweep 𝜔 Horizontal sweep Each laser is matched with its own detector Scan direction 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 15

  16. Slide 16: Mechanical Beam Steering: Galvo Mirrors

    Mechanical Beam Steering: Galvo Mirrors ω 𝑥 − 𝑦 scan ω Laser Rotating Galvo mirrors are another example of a mechanical beam steering. 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 16

  17. Slide 17: Beam Steering: Optical Phase Array

    Beam Steering: Optical Phase Array Amplitude & phase control unit Beam in the far field Laser Amplitude and phase of the light emitted by each pixel (emitter) can be controlled electronically. Optical phased array is an example of a solid state or ”no moving parts” beam steering. 🄫 Hamamatsu…

  18. Slide 18: OPA Emitter and Receiver

    OPA Emitter and Receiver emitted beam detected beam Current output Light feed for Local oscillator emission light for optical amplification Control unit 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 18

  19. Slide 19: LiDAR Based on OPA Emitter and Receiver

    LiDAR Based on OPA Emitter and Receiver First prototype of a FMCW LiDAR that uses optical phased arrays for beam steering and light detection. The figure is from “Coherent solid-state LIDAR with silicon photonic optical phased arrays” by Poulton et al. 2017 🄫 Hamamatsu Photonics K.K. and its…

  20. Slide 20: Beam Steering: Flash and Structured Light

    Beam Steering: Flash and Structured Light ■ Wider the angle, smaller the surface brightness ■ For a Gaussian beam, the surface brightness is not uniform Laser and pulse expander ■ Lateral resolution limited by the 2D sensor Divergent pulse of light ■ Beams have the same intensity ■ Lateral resolutio

  21. Slide 21: Solid State (Flash) LiDAR

    Solid State (Flash) LiDAR 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 21

  22. Slide 22: Basic Layout of ToF Flash LiDAR

    Basic Layout of ToF Flash LiDAR to the target 𝜃𝑒 projector control unit 𝜃𝑑 2D detector 𝑓 focal plane array The emission FOV, 𝜃𝑒 , should be matched with the detection FOV, 𝜃𝑑 . 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 22

  23. Slide 23: Focal Plane Distance Measurement

    Focal Plane Distance Measurement image of the scene Focal plane detector array A single “pixel” in the 2D detector determines distance to a single element of the scene. 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 23

  24. Slide 24: Distance Resolution

    Distance Resolution 𝛿𝑑 𝑐 𝛿𝑑 = (distance resolution) 2𝐵 1 𝐵~ 𝑇 − pulse duration 𝑇 For 𝑇 = 5 ns, 𝛿𝑑 ≈ 0.75 m → 𝐵 ≈ 200 MHz Better distance resolution requires pulses of even shorter duration. The limitation is in the laser technology (parasitic inductance). 🄫 Hamamatsu Photonics K.K…

  25. Slide 25: Distance Uncertainty

    Distance Uncertainty 𝜎𝑑 𝑑 𝑑 𝛿𝑑 2 𝑐 2 𝜎𝑑2 ~ = (distance uncertainty) 𝑆/𝑁 4𝐵2 𝑆/𝑁 𝑆 1. The larger the , the smaller the uncertainty, all else being the same 𝑁 2. Photodetector and electronic time jitters also contribute to the uncertainty. 🄫 Hamamatsu Photonics K.K. and its…

  26. Slide 26: Photon Budget: Single Photodetector

    Photon Budget: Single Photodetector Assumptions: TX Lambertian reflection Laser spot smaller than the target Normal incidence 𝛾 is constant 𝐴0 𝑃 𝑑 = 𝑃0 𝜌 2 𝜂0 𝑒 −2𝛾𝑑 𝜋𝑑 𝑃 𝑑 − Peak power received 𝐴0 − Aperture area of the receiver 𝑃0 − Peak power transmitted 𝜂0 − Receiving optics…

  27. Slide 27: Photon Budget: Single Photodetector

    Photon Budget: Single Photodetector 𝐴0 𝑃 𝑑 = 𝑃0 𝜌 2 𝜂0 𝑒 −2𝛾𝑑 𝜋𝑑 Example: 𝑃0 = 100 W, 𝜌 = 0.1, 𝐴0 = 3.14 × 10−4 m2, 𝜂0 = 0.5, 𝛾 = 0.5 km-1 for 𝒅 = 𝟏𝟎𝟎 m, 𝑷 = 𝟒𝟓 nW 1. Atmospheric extinction 𝛾 depends on weather conditions and wavelength. Its value can range from about 4 km-1…

  28. Slide 28: Photon Budget: Flash

    Photon Budget: Flash 𝐴 TX RX 𝑆 There is a tradeoff between spatial resolution and . 𝑁 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 28

  29. Slide 29: Photon Budget: Flash

    Photon Budget: Flash 𝜃𝑝2 𝐴0 𝑃 𝑑 = 𝑃0 𝜌 2 2 𝜂0 𝑒 −2𝑑𝛾 (received peak power per pixel) Θ 𝜋𝑑 𝜃𝑝 − angular subtense (field of view) of a pixel Θ − angular field of view of the pulse projector (pulse divergence) Note that 𝜃𝑝 ≪ Θ, so if the pulse peak power is the same, the amount of…

  30. Slide 30: Photodetection (Single Element)

    Photodetection (Single Element) Optical bandpass filter Pulse of light To timer Trigger FOV circuit TIA PD Focal plane ■ Active area of the photodetector, focal length of the lens, and placement of the optical bandpass filter determine the photodetector’s field of view. ■ Avalanche photodiode or sil

  31. Slide 31: Noise in Transimpedance Amplifier

    Noise in Transimpedance Amplifier 𝐶𝑓 𝐶𝑇 = 𝐶𝑡 + 𝐶𝑓 + 𝐶𝑜𝑝 + 𝐶𝑠 (total capacitance) 𝑖𝐽 𝑖𝑇 = 𝑖𝑛2 + 𝑖𝐽2 + 𝑖𝑑2 + 𝑖𝑝ℎ 2 𝑅𝐹 𝑒𝑛 − 𝑖𝑝ℎ 𝑖𝑑 𝑖𝑛 𝐶𝑡 + 𝐶𝑆 𝐶𝑜𝑝 𝑣𝑛 𝑅 noise output + 𝑅 = 𝑅𝑆𝑖𝑃𝑀 ||𝑅𝑜𝑝 2 1/2 𝑅𝐹 4𝜋 2 𝑣𝑛 = 𝑒𝑛2 1+ + Δ𝑓 2 𝐶𝑇2 𝑅𝑓2 + 𝑅𝑓2 𝑖…

  32. Slide 32: Bandwidth and Stability of Transimpedance Amplifier

    Bandwidth and Stability of Transimpedance Amplifier 𝑅𝐹 −𝑅𝑓 1 1 𝑣𝑜𝑢𝑡 = 𝐼 𝛽 𝑗𝜔 = = 1 + 𝑗𝜔𝑅𝐹 𝐶𝑖 1 1 + 𝑗𝜔𝑅𝐹 𝐶𝑖 𝛽(𝑗𝜔) 1+ 𝐴𝑜𝑙 𝛽 where 𝐶𝑖 = 𝐶𝑗 + 𝐶𝑜𝑝 𝐴𝑜𝑙 − Open loop gain of TIA − 𝑣𝑜𝑢𝑡 𝐶𝑗 Gain peaking and + oscillations occur around 𝐼 this frequency…

  33. Slide 33: Bandwidth and Stability of Transimpedance Amplifier

    Bandwidth and Stability of Transimpedance Amplifier 𝐶𝐹 1 + 𝑗𝜔𝑅𝐹 𝐶𝐹 𝛽 𝑗𝜔 = 1 + 𝑗𝜔𝑅𝐹 (𝐶𝑖 +𝐶𝐹 ) 𝑅𝐹 − 𝑣𝑜𝑢𝑡 𝑓𝐹 𝑓𝑖 𝑓𝐺𝐵𝑊𝑃 𝐶𝑗 + 𝐼 1 1 𝑓𝐹 = 𝑓𝑖 = 2𝜋𝑅𝐹 𝐶𝑖 + 𝐶𝐹 2𝜋𝑅𝐹 𝐶𝐹 1 Simplified equivalent circuit of a compensated 𝐶𝐹 = 1+ 1 + 8𝜋𝑅𝐹 𝐶𝑖 𝑓𝐺𝐵𝑊𝑃…

  34. Slide 34: Importance of Noise and Bandwidth

    Importance of Noise and Bandwidth High bandwidth → higher noise but high fidelity trigger level time trigger time Low bandwidth → lower noise and lower fidelity trigger level flat top time trigger time 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 34

  35. Slide 35: Importance of Excess Noise (F)

    Importance of Excess Noise (F) Signal Waveform 1 Fixed trigger level Constant fraction trigger Waveform 2 time Δ𝑡1 Δ𝑡2 Δ𝑡1 = Δ𝑡2 Fixed trigger level gives different round-trip-times, Δ𝑡1 ≠ Δ𝑡2 ✖ Constant-fraction trigger gives the same round-trip-times, Δ𝑡1 = Δ𝑡2 ✔ 🄫 Hamamatsu Photonics…

  36. Slide 36: Takeaway

    Takeaway Analog photodetection in ToF LiDAR, especially in flash LiDAR, is very challenging. Is there anything else we can do? What about a statistical measurement using SPAD? 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 36

  37. Slide 37: Single-Photon Avalanche Photodiode (SPAD)

    Single-Photon Avalanche Photodiode (SPAD) 𝑉𝐵𝐼𝐴𝑆 𝐼𝑆𝑃𝐴𝐷 steady state 𝑅𝑄 (Quench resistor) transient 𝑣𝑜 𝑆𝑃𝐴𝐷 𝑉𝐵𝐼𝐴𝑆 quench 𝑅𝑄 quasi-stable “ready” state 𝑅𝑙 (Load resistor) 𝑉𝐵𝐷 𝑉𝐵𝐼𝐴𝑆 𝑉𝑆𝑃𝐴𝐷 recharge 𝑅𝑄 ≫ 𝑅𝑙 𝑅𝑄 must be large enough to ensure quenching 🄫…

  38. Slide 38: Measuring Distance with a Single SPAD

    Measuring Distance with a Single SPAD t=0 𝑡=𝑇 Pulse emission 2𝑑 time Δ𝑡 = 𝑐 laser timer target SPAD 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 38

  39. Slide 39: Measuring Distance with a Single SPAD

    Measuring Distance with a Single SPAD Histogram of trigger times time 𝑡=0 2𝑑 𝑡=𝑇 Δ𝑡 = 𝑐 Multiple pulse illumination provides distance information to the target. The information comes from a histogram of trigger times. 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 39

  40. Slide 40: SPAD Arrays

    SPAD Arrays Photodetector array Micro-bumps ASIC (application-specific integrated circuit) 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 40

  41. Slide 41: Detection Techniques with a SPAD Array

    Detection Techniques with a SPAD Array Time gating: Pixel 1 Pixel 2 Pixel 3 𝑡=0 𝑡=𝑇 Time window Only the events in the pre-defined time window are counted. The choice of the time window depends on the expected knowledge of the target distance. 🄫 Hamamatsu Photonics K.K. and its affiliates. All…

  42. Slide 42: Detection Techniques with a SPAD Array

    Detection Techniques with a SPAD Array Temporal and spatial correlation: 𝑡 = 𝑡1 Pixel 1 𝑡 = 𝑡1 Pixel 2 Event not counted: temporal correlation but no spatial 𝑡=0 𝑡 = 𝑡1 𝑡=𝑇 correlation. 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 42

  43. Slide 43: Detection Techniques with a SPAD Array

    Detection Techniques with a SPAD Array Temporal and spatial correlation: 𝑡 = 𝑡1 𝑡 = 𝑡2 Pixel 1 Event not counted: spatial correlation but Pixel 2 no temporal correlation. 𝑡=0 𝑡 = 𝑡1 𝑡 = 𝑡2 𝑡=𝑇 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 43

  44. Slide 44: Detection Techniques with a SPAD Array

    Detection Techniques with a SPAD Array Temporal and spatial correlation: 𝑡 = 𝑡1 𝑡 = 𝑡1 Pixel 1 Event counted: spatial correlation but Pixel 2 no temporal correlation. 𝑡=0 𝑡 = 𝑡1 𝑡=𝑇 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 44

  45. Slide 45: SPAD Pixel for Correlated Detection

    SPAD Pixel for Correlated Detection 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 45

  46. Slide 46: SPAD Pixel for Correlated Detection

    SPAD Pixel for Correlated Detection coincidence detection Pulse Signal photon Background photon 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 46

  47. Slide 47: Comments

    Comments 1. This technique can be used both in a scanning and flash LiDAR. 2. In a scanning LiDAR, an OPA array is well-suited for beam steering. 3. The greatest advantage is a reduced sensitivity to the background light. 4. Additional advantages: less affected by gain variations, sensitivity in IR

  48. Slide 48: Hamamatsu Assists LiDAR Companies

    Hamamatsu Assists LiDAR Companies  Photodetectors (Silicon or InGaAs, PIN, APD, SiPM, SPAD and more) for all LiDAR concepts  Light sources (PLDs or VCSELs) for selected LiDAR concepts  Custom integrated optical assemblies, from front-end electronics to complete ASICs  Support automotive grade qu

  49. Slide 49: Photodetectors for LiDARS (850 nm – 940 nm)

    Photodetectors for LiDARS (850 nm – 940 nm) Si PIN photodiode Si APD SPPC (or SPAD) MPPC (or SiPM) High Photosensitivity; High Photosensitivity; Low Photosensitivity; Low Photosensitivity; Internal Gain = 1 Internal Gain ~ 100 Internal Gain ~ 105 to 106 Internal Gain ~ 105 to 106 🄫 Hamamatsu…

  50. Slide 50: Photodetectors for LiDARS (1550 nm)

    Photodetectors for LiDARS (1550 nm) InGaAs PIN PD InGaAs APD Photosensitivity [A/W] Photosensitivity [A/W] Wavelength [nm] Wavelength [nm] High Photosensitivity; High Photosensitivity; Internal Gain – 1 Internal Gain ~10-20 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 50

  51. Slide 51: Closing Remarks

    Closing Remarks 1. Two distinct LiDAR systems, ToF and FMCW, are actively researched 2. Each system presents a unique set of engineering challenges 3. Beam steering and photodetection are the two most outstanding challenges 4. Flash LiDAR together with a SPAD-based statistical detection is a new ave

  52. Slide 52: Thank you for listening

    Thank you Thank you for listening Contact information: piatek@njit.edu 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 52

  53. Slide 53: Join Us for Weeks of FREE Photonics Webinars (17 Topics)

    Join Us for 10 Weeks of FREE Photonics Webinars (17 Topics) Week # Weekly Topics # of Talks Talk #1 Date Talk #2 Date 1 Introduction to Photodetectors 2 26-May-20 28-May-20 2 Emerging Applications - LiDAR & Flow Cytometry 2 2-Jun-20 4-Jun-20 3 Understanding Spectrometer 2 9-Jun-20 11-Jun-20 1 Weeks

  54. Slide 54: 🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved.

    🄫 Hamamatsu Photonics K.K. and its affiliates. All Rights Reserved. 54

Hamamatsu Photonics K.K. — Technical Presentation (June 2020) on 6ix