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iXon 3

Features & Functionality

3.5 - TRIGGERING OPTIONS

The iXon3 range of cameras have several different triggering modes. These include Internal, External (and Fast

External), External Start, External Exposure and Software Trigger. It should be noted that not all the triggering

options are available on all cameras. 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buildupontheCCDiskepttoaminimum

while waiting for the external trigger event. The external keep clean consists of a continuous sequence of

oneverticalshiftfollowedbyonehorizontalshift.OncetheExternalTriggerisreceivedthecurrentkeepclean

sequence 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 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 then start the acquisition

processgoing.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 CCD 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.

Andor Technology iXon3 Series User Manual

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