High-Speed Single-Photon SPAD Camera
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My PhD thesis at Politecnico di Milano
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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