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P. Feautrier - OCam and CCD220
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F: excess noise factor
F = 1.4
M: mean gain
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P. Feautrier - OCam and CCD220
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Strehl
ratio
EMCCD
RON=0
Strehl
ratio
EMCCD
RON=0
Thick CCD
RON=2
Thick CCD
RON=2
RON=3
RON=3
RON=5
RON=5
GS Magnitude.
GS Magnitude.

Low read noise of EMCCD is clearly better for white-yellow guide star

and better even for red GS if RON of Thick CCD > 2e.

Conclusion low RON (~ 0.1e-) is better than higher red response.

Reason e2v-EMCCD was chosen.
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P. Feautrier - OCam and CCD220
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240 x 240 pixels with 24 µm pitch
8 EMCCD outputs split frame transfer
Nominal frame rate: 1500 frames/sec
Peltier cooled @ - 45 °C
P. Feautrier - OCam and CCD220
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Reset drain current (e/pixel/frame)
8 10
4
7 10
4
6 10
4
5 10
4
4 10
4
3 10
4
2 10
4
1 10
4
System Gain =
Reset current/
frame rate/charge of e =
20 adu/e
Multiplication x1
Use of reset drain
(per frame) current
measurement
embedded in OCam
0
0
500 1000 1500 2000 2500 3000 3500 4000
Mean signal (adu)
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100
Peak 94% at 650 nm
QE measured (%)
80
60
QE measured
QE specified
40
20
0
500 550 600 650 700 750 800 850 900
Wavelength (nm)
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Ln( N d (T ))  Ln( S dark )  T
G
Statistics from 1000 dark images
Sdark : dark signal
T : threshold
G : multiplication gain
N : fraction of pixels above T
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Standard Si CCD220
Temperature: -40°C
Frame rate: 1300 fps
0123
7654
HV
Clock
(Volt)
Amp 0
43.5
Amp 1
Amp 2
43.4
Amp 3
Amp 4
44.9
Amp 5
Amp 6
43.9
Amp 7
Mean
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43.9
Multiplication
Dark
Noise (e-)
Gain x
(e-/pixel/frame)
1742
1676
1568
1558
1292
1356
956
881
1379
0.0093
0.0094
0.0084
0.0089
0.0088
0.0066
0.0080
0.0097
0.0086
P. Feautrier - OCam and CCD220
870
486
439
698
994
443
525
864
665
Input
referred
noise (e-)
0.50
0.29
0.28
0.45
0.77
0.33
0.55
0.98
0.52
12
ESO WFS camera based on the
Ocam technology.
29/06/2010
OCam2: WFS camera for Grantecan
Delivery of 2 systems Nov 2010
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OCam I

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OCam2 is the commercial version of Ocam I
Improved reliability
Improved performances
Improved environmental conditions (can work
with air and water temperature up to 40°C)
Detector safety (over-illumination)
More compact for integration on telescope
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Civil aviation
DROP = OCAM + TELESCOPE
+ ROBOT + Image Analysis
Runway survey
from control
tower at 2-3 km
Avoid again Concorde crash…
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Test measurement
Mean readout noise
Dark signal at 1300 fps
Result
~ 0.52
< 0.01
Unit
ee-/pix/
frame
Dark signal at 25 fps
~ 0.05 e-/pix/
frame
Detector operating temperature
-40
°C
Peak Quantum Efficiency at 650 nm
94
%
Linearity at gain x1000 from 10 to 150 ke
<3
%
Image area Full Well Capacity at gain x1, 1300 fps
30
KeParallel CTE at gain x1, 1300 fps
>0.99995 N/A
Serial CTE at gain x1, 1300 fps
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0.99994
N/A
17
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