High-Speed Single-Photon SPAD Camera
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This document discusses the development of a high-speed single-photon camera. It motivates the need for cameras with both extreme sensitivity and high speeds to enable applications like fluorescence correlation spectroscopy (FCS). The camera uses an array of single-photon avalanche diode (SPAD) detectors integrated on a CMOS chip. Each pixel contains circuitry to independently count and time photons with microsecond resolution at frame rates over 100,000 frames per second. The camera has been used for applications demonstrating sub-Rayleigh imaging and high-throughput FCS.
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High-Speed Single-Photon SPAD Camera
- 1. “Say cheese....” High-Speed Single-Photon Camera Fabrizio Guerrieri Advisor: Prof. Franco Zappa Co-advisor: Dr. Simone Tisa Tutor: Prof. Angelo Geraci
- 2. “Say cheese....” What am I going to talk about? MOTIVATIONS THE MAKING OF FROM THE DEVICE... & IDEAS THE SPAD CAMERA ... TO THE APPLICATIONS (3)
- 3. MOTIVATIONS Demanding imaging applications require Extreme sensitivity AND high-speed
- 4. MOTIVATIONS Demanding imaging applications require Extreme sensitivity AND high-speed HIGH-SENSITIVITY HIGH-SPEED EM-CCD EB-CCD I-CCD RR AYS PA DA S CMOS APS Standard CCD
- 5. IMAGER SPECIFICATIONS REQUIREMENT PROPOSED SOLUTION RISK Single-Photon sensitivity SPAD detector High-speed Completely independent pixels ( > 10 kframe/s ) High pixel number > 100 Compactness Use of HV-CMOS compatible tech Additional features Global shutter, programmability... Increasing risk:
- 6. SPAD ARRAYS HIGH PERFORMANCE ARRAY • Large pixel diameter • Moderate number of pixels • Limited by the ext. Electronics CUSTOM TECH DENSE ARRAY • Small pixel diameter • Large number of pixels • Possibility of smart pixels STANDARD CMOS TECH
- 7. ACTIVE QUENCHING CIRCUIT Group’s State-of-the-Art VLQC
- 8. ARRAY ARCHITECTURE INTEGRATED QUENCHING CIRCUIT CMOS SPAD (20µm) 8 BIT COUNTER GLOBAL SIGNALS INTERNAL BUFFER MEMORY
- 10. ARRAY OPERATIONS
- 11. ARRAY OPERATIONS
- 12. ARRAY OPERATIONS
- 13. PIXEL LAYOUT 20 μm 100 μm 100 μm
- 14. SPAD ARRAYS VLQC SMART PIXEL LINEAR 32x1 ARRAY 32x32 SPAD IMAGER 32 counting and timing channels 1,024 parallel counting channels Single-photon sensitivity Single-photon sensitivity Up to 312.5 kframe/s Up to 100 kframe/s
- 15. SPAD IMAGER • 1024 parallel channels • Programmable to read-out any pixel sub- • Global shutter portion to increase max frame-rate • Up to 100 kframe/s
- 16. SPAD IMAGER Experimental measurements Up to 45% Single-Photon Det. Efficiency 75% DCR < 4 kcps at room temperature Negligible crosstalk probability
- 17. IMAGER SPECIFICATIONS REQUIREMENT IMPLEMENTED SOLUTION Single-Photon sensitivity CMOS SPAD detector ✔ High-speed “Smart” pixel comprising everything ( > 10 kframe/s ) necessary to count photons ✔ High pixel number 32x32 CMOS imager ✔ Compactness 100x100 μm pixel dimension ✔ Additional features Global shutter, programmability... ✔
- 18. SPAD CAMERA
- 19. SPAD CAMERA • FPGA-based high-speed electronics • Requires only USB cable to work: Plug’n’Play • Developed cross-platform software
- 20. SPAD CAMERA 770 μs • Easy to use • 40 kframe/s • Low light level at such a high speed
- 21. SUB-RAYLEIGH IMAGING @ MIT Conventional imaging with non-diffraction limited optics
- 22. SUB-RAYLEIGH IMAGING @ MIT Conventional imaging with diffraction limited optics Rayleigh bound Stripe size
- 23. SUB-RAYLEIGH IMAGING @ MIT Setup modi cations to apply the Sub-Rayleight technique 2 1 Movable N-Photon focused Detection laser beam ? Rayleigh bound Stripe size
- 24. SUB-RAYLEIGH IMAGING @ MIT Sub-Rayleigh imaging with diffraction limited optics Movable N-Photon focused Detection laser beam Rayleigh bound Stripe size Sub-Rayleigh bound
- 25. SUB-RAYLEIGH IMAGING @ MIT Good optics Bad optics Bad optics + + + Conventional imaging Conventional imaging Sub-Rayleigh imaging Imaging beyond the Rayleigh limit is possible by •Scanning the object by a focused light spot •Employing N-Photon detection strategy Improvement goes as about the square root of N
- 26. HIGH THROUGHPUT FCS @ UCLA Fluorescent analyte ows or diffuses through a small excitation volume emitting uorescence bursts Fluorescence Correlation Spectroscopy (FCS) analyses the uorescence intensity uctuations using temporal autocorrelation
- 27. HIGH THROUGHPUT FCS @ UCLA To work well only PROBLEM! SOLUTION! Need faster one particle at time Long Multi-spot parallel acquisition should enter the acquisition FCS acquisitions of FCS data excitation volume times!
- 28. HIGH THROUGHPUT FCS @ UCLA To work well only PROBLEM! SOLUTION! Need faster one particle at time Long Multi-spot parallel acquisition should enter the acquisition FCS acquisitions of FCS data excitation volume times! A very sensitive and high-speed device is required! SPAD arrays as enabling technology
- 29. HIGH THROUGHPUT FCS @ UCLA LCOS-SLM and SPAD array enabling technologies
- 30. HIGH THROUGHPUT FCS @ UCLA 8x8 ACF with rescaling 100 nm beads in H2O Curves overlap and can be tted
- 31. 3D IMAGING Indirect-ToF •Modulated light illuminates the scene •A very sensitive detector measure the re ected light •Depth information can be extracted calculating the waveform phase shift: Δt L= c 2 €
- 32. 3D IMAGING How did a 2D camera become “3D capable”? Light source + driver + waveform generator + new FPGA rmware
- 33. 3D IMAGING Depth resolution: 3 – 9 mm Scene depth: 30 cm Measurement time: 10 s Good results but need to speed the acquisition up to get movie-like 3D imaging
- 34. CONCLUSIONS Group SoA My work VLQC 3D Pixel Imaging FCS 32x32 SPAD Sub-Rayleigh Array Camera Imaging
- 35. CONCLUSIONS Novel SPAD quenching circuit •Small footprint •Small parasitic capacitance •Compatible with CMOS SPAD technology •Reduced afterpulsing and good timing VLQC 3D Pixel Imaging FCS 32x32 SPAD Sub-Rayleigh Array Camera Imaging
- 36. CONCLUSIONS Smart pixel architecture •20-μm CMOS SPAD detector •Front-end electronics (VLQC) •Counting and buffer digital logic VLQC 3D Pixel Imaging FCS 32x32 SPAD Sub-Rayleigh Array Camera Imaging
- 37. CONCLUSIONS 32x32 CMOS SPAD imager •1,024 indipendent photon counting channels •Single-photon sensitivity •Up to 100 kframe/s VLQC 3D Pixel Imaging FCS 32x32 SPAD Sub-Rayleigh Array Camera Imaging
- 38. CONCLUSIONS SPAD camera •High-speed digital FPGA-based system electronics •Plug’n’play device. Power supplies from USB •Cross-platform user-friendly user interface •Optics VLQC 3D Pixel Imaging FCS 32x32 SPAD Sub-Rayleigh Array Camera Imaging
- 39. CONCLUSIONS Sub-Rayleigh imaging @ •Experimentally demonstrated and developed novel imaging technique •Full project responsability •SPAD camera as enabling technology VLQC 3D Pixel Imaging FCS 32x32 SPAD Sub-Rayleigh Array Camera Imaging
- 40. CONCLUSIONS Fluorescence Correlation Spectroscopy @ •Proof of concept for high-troughput FCS on 1,024 parallel channels •Customization of SPAD camera for FCS •Promising preliminary experimental results VLQC 3D Pixel Imaging FCS 32x32 SPAD Sub-Rayleigh Array Camera Imaging
- 41. CONCLUSIONS 3D imaging @ Polimi •Developed and conceived technique to use SPAD camera in 3D imaging •Very good preliminary experiments VLQC 3D Pixel Imaging FCS 32x32 SPAD Sub-Rayleigh Array Camera Imaging
- 42. PHD FACTS Achievements/Awards PhD doctoral school • Physical Review Letters as rst author Courses’ grade: all A (8 courses) (IF=7.33) Attended extra non-mandatory courses • Progetto Rocca fellowship Publications • My research helped the group to submit and win an European grant. Total papers: 29 Conference talks: 6 • Laser Focus World Award “Commendation for excellence in Other technical communications” Magazine • Co-author of 2 invited conference papers Conf. co-author • ESSDERC08: special congratulation by Conf. 1st author conference committee Journal • PhDay 2008 1° year student award 0 3 5 8 10