Characterization of Vanilla • Liverpool Physics • 30/1/2007 • Introduction • Vanilla image pixels average, standard deviation • (STD) and common mode (CM) noise depend on • frame number and settings (use Digital Mode). • Change Internal ADC Dark Ref. • Change Row number (regional interest). • Change ADC Clock Period. • Under light illumination.
Output change with ADC dark reference Digital model, device in dark and use default settings. Change ADC dark reference. Mean value increase with ADC ref. and frame number. STD value increase with frame No., but decrease with ADC ref. Fig. 1 Out average and STD change with frame number.
Output change with row number Digital model, device in dark and use default parameters. Change row number from 520 to 100. Mean value and the slope decrease with row No. STD value and the slope decrease with row No. Fig. 2 Out average and STD change with row number.
Average output shift effect Full size image (520 rows) almost linearly increased with increasing frame number (ADC Dark Ref.=3000 mV). Small size image (10 rows) shows non-linear transient depend on frame number due to heating effect. Initial drop could be due to reset effect. Fig. 3 Average output change with frame number.
Average output shift effect ADC Dark Ref. selected for 2800~3200 mV. Recommend for 3000 mV. MEAN<0, when <2750 mV. For full size image (520 rows), the mean value shifts 1.25 DN/frame. This leads to extra CM mode noise with increasing frame number. Fig. 4 Average output and slope change with ADC Dark Ref.
Average common mode noise shift effect In the dark condition. The noise not very sensitive to ADC Dark Ref. The noise increases with increasing row number (integration time). Fig. 5 Average common noise change with ADC Dark Ref.
Change Internal ADC clock period In dark condition. Average output has an initial drop, then almost linearly increase with frame number. Both output and STD increase with increasing ADC clock period (integration time). Fig. 6 Output and STD change with frame number.
Change Internal ADC clock period In dark condition. Pixel count cut off at ~300 DN. FWHM ~180 DN. FWHM increases with Internal ADC clock period. The slope of out put to frame number linearly increases with increasing Internal ADC clock period (integration time). Fig. 7 Mean and slope depend on Internal ADC clock periods.
Noise feature in the dark In dark condition. Some (quite a lot of ) flake spots were seen as well as some weak straps. The noise to output plot shows the distribution relate to PTC feature. Fig. 8 Common mode noise feature in the dark.
Noise changes with ADC clock period In dark condition. Most pixel out put in 300—500 DN region show low noise. Some pixel out put in 500—600 DN region show large noise. The average noise increases with increasing ADC clock period, and the slope is close to that of the average out put. System noise ~2DN (at 12 ADC clock period). Fig. 9 Average and slope depend on Internal ADC clock periods.
Count distributions under illumination Device under illumination. The out put was cut off at ~600 DN (~300 DN in dark). The count distributions shift to low value with decreasing ADC clock period (small integration time). The maximum output (cut off) also reduced with decreasing ADC clock period (small integration time). Fig. 10 Count distributions at various ADC clock periods.
Output and STD change with frame number Device under illumination. Average output increases rapidly in the first a few frames, due to reset effect. The STD (non-uniformity) reaches maximum at frame 2 might due to combination of reset and other (heating) effect. Fig. 11 Frame average output and STD.
Linear fitting of average output Device under illumination. Linear fitting for frames 5—20, at various ADC clock periods. The intersect relate to the average illumination. The slope seems linearly with increasing clock period, but the value is much smaller than that in the dark. Fig. 12 Linear fitting of average output.
Noise and distribution under illumination Under illumination. The noise image corresponds to signal image due to photon noise (PTC) effect. The noise to output plot shows the count distribution and PTC feature. Fig. 13 Noise image and noise to out put plot.
PTC and gain under illumination Under illumination. PTC almost linear in 1500—2500 DN region. The larger slope in 600—1300 ND region might relate to weak light? The PTC not sensitive to ADC clock period. The corresponding gains are ~38 electron/DN (1500—2500 DN) and ~25 electron/DN (700—1100 DN). Fig. 14 Linear fitting of average output.
Conclusion • Average output increased with increasing internal ADC dark ref. (2800--3200 mV), row number (integration time), ADC clock period and frame number (heating effect). The output shift per frame in the dark was bigger than that under illumination. • The CM noise increased with increasing row number (integration time) and ADC clock period, but less significant to internal ADC dark ref. • PTC shows good linearity in 1500—2500 DN region and larger slope in 600—1200 DN region. The gain (slope) fitted from PTC was ~38 electron/DN. ADC readout noise will be dominate at small integration time.