OIG's CCDs
Quantum Efficiency
The CCD quantum efficiency (QE) was measured in the wavelength interval 2000 10500 Å in incremental steps of 500 Å. The CCD was illuminated using monochromatic light obtained through a Xenon lamp, a series of filters and a monochromator. The signal integrated on the CCD is then compared to the response of a calibrated photodiode.
Dark current
The dark current is measured taking a short dark exposure and a long dark exposure. The signal level in the two exposures is then compared. The frame is divided in 10×10 pixel sub-frames and the dark current is computed for each of them.
Charge Transfer Efficiency
The charge transfer efficiency (CTE) is measured using the X-ray stimulation method. In particular, the parallel CTE is obtained exposing the CCD to the Fe55 source for a given amount of time. After integration, the columns are stacked together and the signal is plotted versus the number of pixel transfers. The CTE is then given by CTE= 1- (Charge loss)/1620 e-/N
CTE = 1 - ( s(0) - s(4095) ) / ( s(0) * 4096)
The EEV chips exhibit a CTE of 0.99999.
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CCD Image
The structure of the CCD EEV4280 is showed in the following figure:
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The image area of the CCD is 2048×4100 pixel, while the length of the output register
is 2148 pixel. The dimension of the image produced by the acquisition system is 2148×4200 pixels
(without binning). This means that the prescan and overscan zones depends by the readout mode and by
the binning utilised.
The User Interface allows different acquisition modes and different binning on chip. In Table 1 and
in Table 2, the overscan and prescan zones for the different kind of acquisitions are showed.
| Readout Mode | Binning | Image Size | X prescan | X image | X Overscan | Y overscan |
| Left | 1 X 1 | 2148 X 4200 | 0 - 49 | 50 - 2097 | 2098 - 2147 | 4100-4199 |
| Right | 1 X 1 | 2148 X 4200 | 2098 - 2147 | 50 - 2097 | 0 - 49 | 4100-4199 |
| Two outs | 1 X 1 | 2148 X 4200 | 0 - 49
2098 - 2147 |
50 - 2097 | NO | 4100-4199 |
| Left | 2 X 2 | 1074 X 2100 | 0 - 24 | 25 - 1048 | 1049 - 1073 | 2050 - 2099 |
| Right | 2 X 2 | 1074 X 2100 | 1049 - 1073 | 25 - 1048 | 0 - 24 | 2050 - 2099 |
| Two outs | 2 X 2 | 1074 X 2100 | 0 - 24
1049 - 1073 |
25 - 1048 | NO | 2050 - 2099 |
| Left | 3 X 3 | 716 X 1400 | 0 - 15 | 16*- 698 | 699*- 715 | 1367 - 1399 |
| Right | 3 X 3 | 716 X 1400 | 699*- 715 | 16*- 698 | 0 - 15 | 1367 - 1399 |
| Two outs | 3 X 3 | 716 X 1400 | 0 - 15
699*-715 |
16*-698 | NO | 1367 - 1399 |
| * The value of this pixel is a mean of overscan and image area. | ||||||
| Readout Mode | Binning | Image Size | X prescan | X image | X Overscan | Y overscan |
| Left | 1 X 1 | 2148 X 4200 | 2148 - 2197 | 2198 - 4245 | 4246 - 4295 | 4100 - 4199 |
| Right | 1 X 1 | 2148 X 4200 | 4246 - 4295 | 2198 - 4245 | 2148 - 2197 | 4100 - 4199 |
| Two outs | 1 X 1 | 2148 X 4200 | 2148 - 2197
4246 - 4295 |
2198 - 4245 | NO | 4100 - 4199 |
| Left | 2 X 2 | 1074 X 2100 | 1074 - 1098 | 1099 - 2122 | 2123 - 2147 | 2050 - 2099 |
| Right | 2 X 2 | 1074 X 2100 | 2123 - 2147 | 1099 - 2122 | 1074 - 1098 | 2050 - 2099 |
| Two outs | 2 X 2 | 1074 X 2100 | 1074 - 1098
2123 - 2147 |
1099 - 2122 | NO | 2050 - 2099 |
| Left | 3 X 3 | 716 X 1400 | 716 - 731 | 732*- 1414 | 1415*- 1431 | 1367 - 1399 |
| Right | 3 X 3 | 716 X 1400 | 1415*- 1431 | 732*- 1414 | 716 - 731 | 1367 -1399 |
| Two outs | 3 X 3 | 716 X 1400 | 716 - 731
1415*- 1431 |
732*- 1414 | NO | 1367 - 1399 |
| * The value of this pixel is a mean of overscan and image area. | ||||||
For any comments please contact Rosario Cosentino.