Specifications

Version 1.1 rev Jan 2013
Page 100
iXon Ultra
Appendix
A.1.9 - Detection Limit
The Detection Limit is a measure of the smallest signal that can be detected in a single readout. The smallest signal
is dened as the signal whose level is equal to the noise accompanying that signal, i.e. a Signal to Noise ratio (S/N) of
unity. Sources of noise are as shown hereunder:
• Shotnoiseofthesignalitself
• Shotnoiseofanydarksignal
• Readoutnoise
If the signal is small, we can ignore its shot noise. Furthermore, if a suitably low operating temperature and short
exposure time can be achieved, the lowest detection limit will equal the readout noise.
A.1.10 - Exposure Time
The Exposure Time is the period during which the EMCCD collects light prior to readout.
A.1.11 - Frame Transfer
Frame transfer is a special acquisition mode that is only available if your system contains a Frame Transfer (FT) CCD
or EMCCD. The iXon Ultra has an FT EMCCD aquistion mode. An FT CCD or EMCCD differs from a standard CCD or
EMCCD in 2 ways. Firstly, it contains 2 areas of approximately equal size as shown below:
1. The rst area is the Image Area, which is located at the top and farthest from the readout register. This is the light
sensitive area of the CCD.
2. The second section is the Storage Area, and is located between the Image Area and the readout register. This
section is covered by an opaque mask, usually a metal lm, and hence is not sensitive to light.
Figure 45: Frame transfer
The second way in which a FT CCD differs from a standard CCD is that the Image and Storage areas can be shifted
independently of each other. These differences allow FT capable CCD or EMCCD devices to be operated in a unique
mode where one image can be read out while the next image is being acquired. It also allows a them to be used in
imaging mode without a shutter. Note: This is only applicable when the camera is running in Accumulate or Kinetic
mode.