Specifications

Version 1.1 rev Jan 2013
Page 65
iXon Ultra
, Features and Functionality
3.5 - TRIGGERING OPTIONS
The iXon Ultra camera has several different triggering modes. These include Internal, External (and Fast External),
External Start, External Exposure and Software Trigger. Note also that many of these features require iCam
technology within the camera, fuller details of which can be viewed through www.andor.com
• InInternal Trigger the camera determines the exact time when an exposure happens, based on the acquisition
settings entered by the user. This is the most basic trigger mode and requires no external intervention
• InExternal Trigger, once an acquisition has been started, the camera is placed into a special cleaning cycle
called “External Keep Clean Cycle”, which ensures that charge built up on the EMCCD is kept to a minimum
while waiting for the external trigger event. The External Keep Clean Cycle consists of a continuous sequence
of one vertical shift followed by one horizontal shift. Once the External Trigger is received the current Keep
Clean Cycle is completed and the exposure phase initiated. The exact nature of the acquisition will depend on
the user settings and is explained in more detail in a subsequent section. The external trigger is fed via the Ext
Trig input on the camera head
• Fast External Trigger is for the most part identical to External Trigger. It differs in only one key aspect. In Fast
External Trigger the camera will not wait for a sufcient number of Keep Clean Cycles to have been completed
to ensure the image area is completely clean of charge before accepting an external trigger event but, instead,
will allow a trigger event to immediately start the acquisition process. As a result, Fast External trigger allows a
higher frame rate than standard External Trigger.
NOTE: Once a “sufcient” number of Keep Cleans Cycles have been performed, External and Fast
External Trigger are identical
• External Start is a mixture of External and Internal Trigger. In this mode the camera will perform a sequence
of External Keep Clean Cycles while waiting for one external trigger event to occur and will then start the
acquisition process. Once this external trigger event has occurred, the camera will switch to internal trigger and
the acquisition will progress as if the camera was in Internal Trigger mode
• External Exposure Trigger is a mode of operation where the exposure time is fully controlled by the external
trigger input. While the trigger input is high, the EMCCD is accumulating charge in the Image area. When the
External Trigger goes low, the accumulated charge is quickly shifted into the Storage area and then read out in
the normal manner
• Software Trigger is a mode whereby the camera and software are in a high state of readiness and can react
extremely quickly to a trigger event issued via software. This mode is particularly useful when the user needs
to control other equipment between each exposure, and does not know in advance how long such control will
take, or if the time taken changes randomly
These modes are explained and illustrated in more detail in the following sections.