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16.3
Appendix C: Measuring pulsed irradiation
16.3.1
Trigger operation
The dynamic range of the CCD sensor in the camera housing is extended by means of a variable integration
time control. The integration time can be freely determined in the range between 6 µs and 225 ms, or it can
be set automatically (for this purpose, activate the Autom. exposure option in the Settings tab of the Single
planes measuring mode.
If the automatic exposure is enabled, then the software will automatically – using a series of pre-measu-
rements – set the integration time at which the output signal of a pixel in the array is too high. The optimal
integration time will then be a little below that.
By means of the variable integration time control, not only cw laser beams but also a multitude of pulsed
beams can be measured in quasi-cw operation. An exception are, for example, laser beams with a very
low pulse frequency. For measuring such beams, the trigger operation is available in the measuring modes
Single planes / Manual caustic / Automatic caustic. If this is enabled, the device only measures within de-
fined time periods. The laser pulse or the corresponding trigger signal marks the beginning of such a period
and the (freely adjustable) integration time marks its end.
Fig. 16.2 shows that in addition to the trigger signal and the integration time, a further variable intervenes in
the sequential control of the CCD sensor: the trigger delay. It indicates the time period between the trigger
signal and the start of the integration time.
Trigger
level
Fig. 16.2:
Options for affecting the sequence control of the CCD sensor
A measurement can be triggered internally or externally. Internal signals are triggered by the photodiode inte-
grated in the device. Externally triggered signals enter the device via a BNC socket. You can freely determine
the threshold value of the internal trigger signal (trigger level).
Every measurement consists of a dark measurement and a measurement with photo transfer. This applies
for trigger operation as well as cw / quasi-cw operation. This means that each measurement requires at least
two trigger signals.
The following time constants apply:
Timeout:
Minimum integration time:
Maximum integration time:
Minimum delay:
Maximum delay:
110
Trigger
2 sec (Standard)
6 µs
225 ms
12 µs
400 ms
Delay time
Sequential -control camera
Integration time
Revision 00 EN - 02/2022
MSM+ HB
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