Specifications

Version 1.1 rev Jan 2013
Page 81
iXon Ultra
, Features and Functionality
3.9 - PUSHING FRAME RATES WITH CROPPED SENSOR MODE
The iXon Ultra offers Cropped Sensor Mode, which provides the following advantages:
• Specializedreadoutmodeforachievingveryfastframerates(sub-millisecondexposures)from‘standard’
cameras
• Continuousrapidspoolingofimages/spectratoharddisk
• Userselectablecroppedsensorsize–highlyintuitivesoftwaredenition
• TheiXonUltraisnowavailablewiththecomplementaryOptoMaskaccessory,whichcanbeusedtoshieldthe
region of the sensor outside of the cropped area
If an experiment demands fast temporal resolution but cannot be constrained by the maximum storage size of the
sensor (as is the case for ‘Fast Kinetics Mode’ of readout), then it is possible to readout the iXon Ultra in ‘Cropped
Sensor Mode’. In this mode, the user denes a ‘sub-array’ size from within the full image sensor area, such that it
encompasses the region of the image where change is rapidly occurring (e.g. a ‘calcium spark’ within a cell). The sensor
subsequently “imagines” that it is of this smaller dened array size, achieved through software executing special readout
patterns, and reads out at a proportionally faster frame rate. The smaller the dened array size, the faster the frame rate
achievable.
In order to use Cropped Sensor mode, one has to ensure that no light is falling on the light sensitive area outside of the
dened region. Any light collected outside the cropped area could corrupt the images which were acquired in this mode.
For microscopy set-ups this is now aided with an accessory called OptoMask, which is available from Andor.
Cropped Sensor Mode has the end result of achieving a much faster frame rate than that obtainable in a conventional
‘sub-array’ / ROI readout (during which we would still have to vertically shift the unwanted rows). The frame rate increase
is achieved by not reading out (i.e. discarding) the unwanted pixels.
Figure 36: Cropped Sensor Mode.
The active imaging area of the sensor is dened in such a way that only a small section of the entire chip is used for
imaging. The remaining area has to be optically masked to prevent light leakage and charge spill-over that would
compromise the signal from the imaging area. By cropping the sensor one achieves faster frame rates because the
temporal resolution will be set by the time it requires to read out the small section of the sensor.