1 / 48

High Speed Image Acquisition System for Focal-Plane-Arrays

High Speed Image Acquisition System for Focal-Plane-Arrays. Doctoral Dissertation Presentation by Youngjoong Joo School of Electrical and Computer Engineering Georgia Institute of Technology February 12, 1999. Outlines. Introduction Background Readout system architectures

danil
Download Presentation

High Speed Image Acquisition System for Focal-Plane-Arrays

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. High Speed Image Acquisition System for Focal-Plane-Arrays Doctoral Dissertation Presentation by Youngjoong Joo School of Electrical and Computer Engineering Georgia Institute of Technology February 12, 1999 HSSPG Georgia Tech

  2. Outlines • Introduction • Background • Readout system architectures • Compact ovrsampling conversion • Photodetectors • Test • Conclusion and future work HSSPG Georgia Tech

  3. Introduction • MotivationConventional focal-plane-arrays (FPAs) readout methods are not suitable for some scientific and engineering applications. • Low readout speed 1MHz 1000X1000 14 bit images 62THz • Not scalable depending on the readout architecture • Noise sensitive HSSPG Georgia Tech

  4. Introduction • ObjectiveDesign a new high speed scalable image acquisition system for FPAs. • High frame rates (> 100kfps) • Scalable • Low noise HSSPG Georgia Tech

  5. Readout Systems A/D Converters DSP Photo detectors Background • Block diagram HSSPG Georgia Tech

  6. Photo detectors • Generate electronic signals and are located at the front end of the image acquisition system. • Hybrid integration • High responsivity • High fill factor • Substrate must be transparent • Higher fabrication cost HSSPG Georgia Tech

  7. Photo detectors • Monomaterial integration • Compatibility with integration on-chip electronics • Low cost • Low absorption coefficient HSSPG Georgia Tech

  8. A/D converters • What is important for the focal-plane-applications?Size, robustness, variable resolution • Conventional A/D convertersFlash ADC , Successive Approximation ADC Single slope ADC, Cyclic ADC, Oversampling ADC HSSPG Georgia Tech

  9. A/D converters *) modulator only HSSPG Georgia Tech

  10. Readout systems • Support an optimum interface between the detectors and the following signal processing stage. HSSPG Georgia Tech

  11. Readout systems • Serial readout system • Noise reduction • Not scalable • Slow readout speed • Semi-parallel readout system • Increase the readout speed • Less sensitive to noise at the analog signal path HSSPG Georgia Tech

  12. Readout system architecture • Fully parallel readout system was designed as a scalable FPA readout system HSSPG Georgia Tech

  13. Emitter driver 01010010 Emitter 01010010 01010010 Detector 01010010 SIMPil processor Comparator Receiver Readout system architecture • Signal path from image detector to signal processor HSSPG Georgia Tech

  14. Readout system architecture • Two layer FPA system photomicrograph HSSPG Georgia Tech

  15. Readout system architecture • Readout speed comparison with same ADCs 64 HSSPG Georgia Tech

  16. Readout system architecture • Readout speed comparison with different ADCs 15bits 4GHz 288 X 288 168MHz HSSPG Georgia Tech

  17. Oversampling clock fS Nyquist clock fN 1-bit stream Analog input Noise shaping modulator Decimator and Digital LPF PCM Compact oversampling conversion • Oversampling ADC Oversampling converters trade speed for accuracy HSSPG Georgia Tech

  18. Signal Signal PSD PSD In band quantization noise Removed by low pass filtering Quantization noise f0 f0 fS/2 fS/2 Freq. Freq. Compact oversampling conversion • Quantization noise of oversampling modulator Each doubling of the sampling frequency decreases the in-band noise by 3 dB. HSSPG Georgia Tech

  19. PSD 1st order quantization noise 2nd order quantization noise Modulation noise f0 fS/2 Freq. Compact oversampling conversion • Modulation noise of higher order oversampling modulator Each doubling of the sampling frequency decreases the in-band noise by (3+6n) dB. HSSPG Georgia Tech

  20. Compact oversampling conversion • Current input oversampling modulator • Oversampling loop linearity is improved. • Amplifiers are removed from the feedback. • Linear D/A conversion is available. HSSPG Georgia Tech

  21. Compact oversampling conversion • Current buffer • Low input impedance • Stabilize the detector bias voltage HSSPG Georgia Tech

  22. Metal 3 Current in Metal 2 Metal 1 GND Current in Integrator Compact oversampling conversion • Current D/A converter • Integrator HSSPG Georgia Tech

  23. Output signal Input signal Compact oversampling conversion • Comparator (G. M. Yin) Sampling rate : 100MHz, Input signal : 0.1V 10MHz HSSPG Georgia Tech

  24. Integrator Current buffer & Photo detector Integrator & Current DAC Comparator Compact oversampling conversion • Overall system HSSPG Georgia Tech

  25. Integrator output voltage PDF [dB] 50 kHz input signal Modulator output Modulation noise Freq. Compact oversampling conversion • Overall system simulation results HSSPG Georgia Tech

  26. edi eci + xi + wi yi Delay - Compact oversampling conversion • Circuit noise attenuation where, edi= detector, current buffer, and current D/A converter noise and eci= quantization and comparator noise. HSSPG Georgia Tech

  27. Compact oversampling conversion • Layouts • To make a large detector, all the effort were applied to design a compact circuit. • Input parts of the circuits were carefully designed not to overlapped with digital lines. • To reduce the offset and improve the switching time of the comparator, all the components were carefully layout to make a matched comparator. • When the capacitor was laid-out, metal 1 and metal 3 layers were connected to the GND to prevent the metal-substrate capacitor. • The latch transistor size was optimized to drive a high capacitor load which is connected to several pixels through a long data line. HSSPG Georgia Tech

  28. Circuits Circuits Detector Capacitor Pad Capacitor Compact oversampling conversion • Photomicrographs HSSPG Georgia Tech

  29. Photodetectors • Hybrid detectors 8X8 detectors top contact HSSPG Georgia Tech

  30. GND Vbias p+ n+ p+ n+ p+ p Vbias n+ p+ Photodetectors • Monomaterial detectors HSSPG Georgia Tech

  31. 8X8 detectors test structures emitter driver Photodetectors • Monomaterial detectors HSSPG Georgia Tech

  32. Test • Test setup • Arbitrary waveform generator (AWG2041) • DC current sources (Keithley SMU 236) • Sampling oscilloscope (Tektronix 11403A) • Transient capture oscilloscope (Tektronix • Multi-function optical meter (Newport 1835-c) • Digital data acquisition card (CYDIO 192T) • 50MHz 486 processor • 233MHz Pentium processor • Newport coated ND filters HSSPG Georgia Tech

  33. Oscilloscope DC current source 1.000uA 2.013V Test • Electrical testing • Verify the functionality of the circuit HSSPG Georgia Tech

  34. Test • Electrical testing results Input = 0.03A Input = 0.06A HSSPG Georgia Tech

  35. 1 1 2 11 8 6 4 1 1 2 5 8 11 11 5 1 1 4 16 10 16 16 16 2 5 4 10 16 16 16 16 1 3 5 16 16 16 16 16 1 3 3 8 16 16 16 10 0 1 2 2 10 16 11 11 1 1 0 2 2 6 4 4 1 Test • Slow speed testing setup HSSPG Georgia Tech

  36. Test • Slow speed testing : sampling rate=1MHz HSSPG Georgia Tech

  37. Test • Uniformity Low light intensity High light intensity HSSPG Georgia Tech

  38. Saturation 6 bit range Test • Linearity 64 pixels data 6 bits linearity HSSPG Georgia Tech

  39. Measured data Test data Test • Nonlinearity • The nonlinearity of the small light intensity was not coming from the FPA system but the optical filter. • The nonlinearity of the high light intensity was coming from the saturation of the system HSSPG Georgia Tech

  40. Test • System noise The system noise is over than 8 bits. HSSPG Georgia Tech

  41. Test • High speed testing To obtain a 8 bit 100kfps image : • oversampling ratio : 26 • modulator bandwidth : 2.6 MHz • System bandwidth : 167 MHz HSSPG Georgia Tech

  42. Test • Modulator 2 MHz 4 MHz HSSPG Georgia Tech

  43. Test • Output with 2.5MHz system frequency. Room light Microscope light HSSPG Georgia Tech

  44. Test • Output with 40MHz system frequency. Room light Microscope light HSSPG Georgia Tech

  45. Test • Output with 100MHz system frequency. Room light Microscope light HSSPG Georgia Tech

  46. Conclusion and future works • A new high speed readout system for FPAs were designed and tested. • A new readout architecture was designed. • A new current input first-order sigma-delta A/D modulator was designed. • Two kinds of photo detectors were utilized. • Several tests had been done to verify the proposed system. HSSPG Georgia Tech

  47. Conclusion and future works • To complete the fully parallel readout system for FPAs, two things need to be tested and verified. • Test the speed of the through-wafer optical communication. • Test with a microprocessor. • The focal-plane-array chip and the microprocessor chip need to be stacked and test together. HSSPG Georgia Tech

  48. Whole system HSSPG Georgia Tech

More Related