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READ NOISE @ 1 to 1000 Hz for a 2.5µm cutoff Teledyne H2RG

READ NOISE @ 1 to 1000 Hz for a 2.5µm cutoff Teledyne H2RG. Roger Smith Caltech 2012-07-03, Tue 10:50am.

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READ NOISE @ 1 to 1000 Hz for a 2.5µm cutoff Teledyne H2RG

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  1. SPIE 8453-35 H2RG noise to 1kHz READ NOISE @ 1 to 1000 Hz for a 2.5µm cutoff Teledyne H2RG Roger Smith Caltech 2012-07-03, Tue 10:50am Slides containing shading such as this box (marked as “Redacted”) contain information concealed by the shading which **may** be ITAR sensitive andif determined as such could incur severe penalties if distributed to non US persons (citizens or Legal Permananent Residents). Therefore it is recommended that this presentation only be distributed to non “US Persons” in PDF format so that the redactions remain in place. Note that the responsibility lies with the person passing the data onwards, not the creator of the information.

  2. The application SPIE 8453-35 H2RG noise to 1kHz Tip tilt sensing for LGS AO on Keck 1, with OSIRIS integral field spectrograph, • Reimage 120 arcsec diameter AO corrected field @ 50 milliarcsec/pixel. • H or K bands; dichroic or annular mirror pickoff. • Multiple guide stars, No moving probes. H2RG For calibrations and acquisition 4ch readout of Band of Interest 105 arcsec For fast tip-tilt correction multiple windows, typically 4x4, read sequentially through 1 ch. Black pixels have low QE 105 arcsec

  3. The Camera SPIE 8453-35 H2RG noise to 1kHz 0.5mm thick fiberglass cylinders cold bench with intermediate stage for floating shields Light tight detector housing, removable through rear hatch Lens barrel, removable through rear hatch Wheel carries pupil stops + filters, and diagnostic apertures Window is tilted to compensate for astigmatism due to dichroic pick off. Articulated fold mirror, manual at present, motorize later.

  4. Simplified block diagram Camera System SPIE 8453-35 H2RG noise to 1kHz For field acquisition & calibration: • Full frame or band of interest readout, only to host. For guiding: • Multiple ROIs, typically 4x4 pixels. • Different visitation rates for each. • Raw data streamed to • 2nd fiber link indefinitely, or • Buffered in host RAM then written as single FITS file = “film strip”. 2nd data link is unidirectional (no handshaking) since timing is slaved to readout. Configuration descriptor packet is sent on video link (2nd fiber) at every reset. Readout configuration commands accepted in real time, but take effect at next reset.

  5. SPIE 8453-35 H2RG noise to 1kHz Optimize for high exposure duty cycle, thus best SNR. Readout modes

  6. Let’s review common readout timing options…. Ignore p scans Reset while idling Correlated Double Sampling SPIE 8453-35 H2RG noise to 1kHz e = 1 = number of exposures to do …. not shown here r = number of reset scans between exposures m = 1 = number of scans to coadd then store. p = 10 = number of dummy scans between coadded groups k = 2 = number of store cycles per exposure • Exposure delay = p dummy reads for constant self heating • Subtract first frame from last frame • Equivalent to Fowler sampling with m = 1 Exposure time Frame time Duty cycle = Frame time Exposure time At least one reset between frames Final scan Initial scan

  7. Coadd m Ignore p scans Coadd m Subtract means Fowler “m” SPIE 8453-35 H2RG noise to 1kHz e = 1 = number of exposures to do …. not shown here r = number of reset scans between exposures m = 3 = number of scans to coadd then store. p = 6 = number of dummy scans between coadded groups k = 2 = number of store cycles per exposure Duty cycle < 1 Exposure delay is multiple of dummy read time but need not be multiple of m. Frame time Exposure time

  8. Sample Up the Ramp (SUR) SPIE 8453-35 H2RG noise to 1kHz • Store every scan (no real time coadd) • Use post facto least squares fit to measure slope with best S/N • Effective exposure duty cycle due to weighting of shot noise by least squares ~ 90%; reduce this to include effect of the reset overhead. • Equivalent MultiAccumulate with m=1. e = 1 = number of exposures to do …. not shown here r = number of reset scans between exposures m = 1 = number of scans to coadd then store. p = 0 = number of dummy scans between coadded groups k = 12 = number of stores per exposure

  9. Coadd m Coadd m Coadd m Coadd m Coadd m Reset r scans Coadd m Multi-Accumulate (JWST terminology, variant of SUR) SPIE 8453-35 H2RG noise to 1kHz e = number of exposures to do …. not shown here r = 2 = number of reset scans between exposures m = 3 = number of scans to coadd then store. p = 0 = number of dummy scans between coadded groups k = 4 = number of stores per exposure • Coadd in real time, store every m scans, total exposure duration is multiple of m scan times. • Least squares fit of stored (coadded) scans is used to estimate noise. • Advantage of coadd over single samples with gaps is lower noise and better cosmic ray detection ( which appears as jump in ramp). • One or more reset scans between exposures.

  10. Coadd m Coadd m Coadd m Coadd m Coadd m Coadd m Readout mode used in the noise tests presented hereafterDifferential Multi-Accumulate SPIE 8453-35 H2RG noise to 1kHz • Sparse reset allows us to use end of previous frame as baseline for next soduty cycle ~100%, except for a gap when reset occurs. • For tip-tilt control interpolating over this data gap is ok since sample rate is typically ten times servo’s closed loop bandwidth. • Can use global reset (least overhead) or line by line (least thermal transient). Exposure time Reset Difference = frame 4 Occasional gap ! Difference = frame 1 Difference = frame 2 Difference = frame 3

  11. Pixel timing optimization for ARC Inc. 8ch IR video card SPIE 8453-35 H2RG noise to 1kHz • 10 µs/pixel is standard but can go faster with no penalty. • …by reducing overheads to 2.16µs, and overlapped this with signal settling. • For 3µs dwell, pixel time is halved sample twice as often with same noise BW.

  12. Pixel Time Optimization 22 SPIE 8453-35 H2RG noise to 1kHz • Is SNR improved more by: • increasing settling time above 2µs, or • adding more dwell time (noise BW limiting), or • coadding more frames ? Moderately small window for fast readout RMS noise (temporal per pixel) mean in 16x16 window(e-) Conventional 10µs pixel 10 More dwell time is better at high frequency, with most gain by 4us 6 5 4 At low frequency, more coadds are better than more dwell time. 3 Choose 2µs settle + 4µs dwell = 6µs/pixel 2

  13. SPIE 8453-35 H2RG noise to 1kHz MEAN NOISE AT DIFFERENT TEMPERATURES Speed-noise CURVES • Skip through slides to animate.

  14. T=80K SPIE 8453-35 H2RG noise to 1kHz 100 Mean in window for per pixel RMS (temporal) noise (e-) 10 1 0.1 1 10 100 1000 10,000 Synthesized frame rate (Hz)

  15. T=90K SPIE 8453-35 H2RG noise to 1kHz 100 Mean in window for per pixel RMS (temporal) noise (e-) 10 1 0.1 1 10 100 1000 10,000 Synthesized frame rate (Hz)

  16. T=100K SPIE 8453-35 H2RG noise to 1kHz 100 Mean in window for per pixel RMS (temporal) noise (e-) 10 1 0.1 1 10 100 1000 10,000 Synthesized frame rate (Hz)

  17. T=110K SPIE 8453-35 H2RG noise to 1kHz 100 Mean in window for per pixel RMS (temporal) noise (e-) 10 1 0.1 1 10 100 1000 10,000 Synthesized frame rate (Hz)

  18. T=120K SPIE 8453-35 H2RG noise to 1kHz 100 Mean in window for per pixel RMS (temporal) noise (e-) 10 1 0.1 1 10 100 1000 10,000 Synthesized frame rate (Hz)

  19. T=130K SPIE 8453-35 H2RG noise to 1kHz 100 Mean in window for per pixel RMS (temporal) noise (e-) 10 1 0.1 1 10 100 1000 10,000 Synthesized frame rate (Hz)

  20. T=140K SPIE 8453-35 H2RG noise to 1kHz 100 Mean in window for per pixel RMS (temporal) noise (e-) 10 1 0.1 1 10 100 1000 10,000 Synthesized frame rate (Hz)

  21. SPIE 8453-35 H2RG noise to 1kHz Deliberately left blank.

  22. SPIE 8453-35 H2RG noise to 1kHz Same plots again but now identify effects of dark current, RTS, 1/f, white NOISE mechanisms

  23. T=80K SPIE 8453-35 H2RG noise to 1kHz 100 Mean in window for per pixel RMS (temporal) noise (e-) Mux glow, not dark current since depends on # reads not frame rate CDS noise, i.e. no coadds 10 Smaller ROI = more coadd at given frame rate 1 0.1 1 10 100 1000 10,000 Synthesized frame rate (Hz)

  24. T=90K SPIE 8453-35 H2RG noise to 1kHz 100 Mean in window for per pixel RMS (temporal) noise (e-) Hot pixels included 10 Mux glow dominates when hot pixels excluded 1 0.1 1 10 100 1000 10,000 Synthesized frame rate (Hz)

  25. T=100K SPIE 8453-35 H2RG noise to 1kHz 100 Mean in window for per pixel RMS (temporal) noise (e-) Hot pixels? climbing as T increases 10 Mux glow not increasing with T 1 0.1 1 10 100 1000 10,000 Synthesized frame rate (Hz)

  26. T=110K SPIE 8453-35 H2RG noise to 1kHz 100 Must be RTS noise Since rises and falls again with T as characteristic frequency changes. Mean in window for per pixel RMS (temporal) noise (e-) At high frequency noise is white, so scales as ~1/√(coadds) 10 Prevent this turn up at low frame rates by putting time delay between samples instead of reading more often 1 0.1 1 10 100 1000 10,000 Synthesized frame rate (Hz)

  27. T=120K SPIE 8453-35 H2RG noise to 1kHz 100 Mean in window for per pixel RMS (temporal) noise (e-) RTS noise kink 10 1 0.1 1 10 100 1000 10,000 Synthesized frame rate (Hz)

  28. T=130K SPIE 8453-35 H2RG noise to 1kHz 100 Mean in window for per pixel RMS (temporal) noise (e-) Dark current starts to manifest itself at longer exposure times White noise drops very slightly at higher temperature 10 1 0.1 1 10 100 1000 10,000 Synthesized frame rate (Hz)

  29. T=140K SPIE 8453-35 H2RG noise to 1kHz Dark current dominates: Depends mostly on frame rate not # reads 100 Scales faster than 1/√(frame_time) …why? Mean in window for per pixel RMS (temporal) noise (e-) 10 1 0.1 1 10 100 1000 10,000 Synthesized frame rate (Hz)

  30. Mux glow 2.5µm H2RG-220 @ 80K 40 SPIE 8453-35 H2RG noise to 1kHz Idark= 0.004 e-/s (SUR at 2s/sample) Greater for fast read of small windows due to self heating … see next slide. Mux glow= 0.0034e-/read at 6µs/pixel. 4x4 8x8 Change x axis 16x16 32x32 Time (s) Frame number

  31. Self-heating can masquerade as mux glow SPIE 8453-35 H2RG noise to 1kHz As window size is reduced same power is concentrated in smaller area so temperature rises: dark current increases with number of reads rather like mux glow, but more steeply than mux glow. 8x8 window After160,000 frame SUR in 75s 5e-/s or 0.0025 e-/read 8x8 Hot spot in next readout 32x32 window After 10,000 frame SUR in 75s …weaker since thermal footprint of previous 8x8 window is decaying. Glow ~0.0035e-/read

  32. Noise model SPIE 8453-35 H2RG noise to 1kHz Low noise ground based astronomy recipe At 80K, for pixels with negligible RTS Model parameters XX* 10.9*(coadds)-0.47 1/f floor=2.4e- 0.0034e-/read

  33. SPIE 8453-35 H2RG noise to 1kHz AT DIFFERENT TEMPERATURES noise MAPS

  34. Noise Maps, sparsely sampled 4x4 windows evenly spaced across detector • 128 pixels in from edge • 256 pixel inter-ROI separation. Packed into 32x32 pixel array

  35. Noise maps vs. Frame rate and Temperature SPIE 8453-35 H2RG noise to 1kHz 1kHz 100Hz Redacted 10Hz 80K 110K 130K 140K

  36. Histograms vs. Frame rate and Temperature SPIE 8453-35 H2RG noise to 1kHz 1kHz 100Hz 10Hz 80K 110K 130K 140K

  37. Using data from noise maps on previous slide:Noise Histograms vs. Frame rate and Temperature SPIE 8453-35 H2RG noise to 1kHz 80K Redacted 10Hz 100Hz 1kHz

  38. Using data from noise maps on previous slide:Noise Histograms vs. Frame rate and Temperature SPIE 8453-35 H2RG noise to 1kHz 110K Redacted 10Hz 100Hz 1kHz

  39. Using data from noise maps on previous slide:Noise Histograms vs. Frame rate and Temperature SPIE 8453-35 H2RG noise to 1kHz 130K Redacted 10Hz 100Hz 1kHz

  40. Using data from noise maps on previous slide:Noise Histograms vs. Frame rate and Temperature SPIE 8453-35 H2RG noise to 1kHz 140K Redacted 10Hz 100Hz 1kHz

  41. SPIE 8453-35 H2RG noise to 1kHz AT DIFFERENT TEMPERATURES Speed-noise CURVESFOR SELECTED PIXELS • Differentiate RTS and hot pixels.

  42. 16x16 ROI, single pixel speed-noise curves SPIE 8453-35 H2RG noise to 1kHz Column 1 pixels 1000e- 120K 100e- 10e- 1e- Redacted 1000e- 110K 100e- 10e- 1e- Noise@10Hz Noise@100Hz Speed-noise curve

  43. Random Telegraph Signal SPIE 8453-35 H2RG noise to 1kHz • Gain of the pixel buffer MOSFET is bistable when there is a single electron trap located in or near the channel.

  44. RTS frequency vs. T SPIE 8453-35 H2RG noise to 1kHz Same pixels 80 K 110 K Normal RTS

  45. Fixed patterns SPIE 8453-35 H2RG noise to 1kHz • Dominated by self heating • Power dissipation (only) when pixel addressed. • Addressing one pixel continuously when idle creates hot spot. • Starting up at a new window location, • setup overheads exceed thermal settling time. • Settling is benign provided that you idle the way you read! • Effect of moving window • Must move window • to compensate for atmospheric dispersion differential w.r.t. science target, • or for non-sidereal science target. • Self heating profile across window changes….

  46. Jog 4x4 window 2 pixels to left 100Hz synth frame Repeats Time last frame before move First frame after move

  47. Jog 4x4 window 2 pixels to left exponential decay 1kHz synthesized frame rate Repeats Time last frame before move First frame after move

  48. Transients settle in 6 milliseconds 1kHz synthesized frame rate 6 ms Column 2 Column 1 Columns 3 and 4

  49. SPIE 8453-35 H2RG noise to 1kHz These may be skipped due to lack of time. Anomalies

  50. Line skip fault in engineering grade mux SPIE 8453-35 H2RG noise to 1kHz Line advances two or more lines per vertical clock pulse when a particular range of lines is addressed. Which lines are affected depends on temperature, supply voltages and number of channels being read out. Pixels in windows not overlapping with affected bands are addressed correctly so the band of ~100 lines can be treated as bad pixels for window mode but in full frame all trailing lines are effectively lost. Scan bottom to top, H2RG-222 Scan top to bottom, H2RG-222 Pinhole grid imaged onto detector with 15.25 pixel pitch in X and Y No change when clocking direction is reversed Vertical skips occur whenaddressing these lines

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