© 2011 Thorlabs
77Operating the Beam Profiler
A default value of 50 % indicates that only images with a half scale maximum
brightness are triggered, captured and interrogated afterwards. Dark images taken
by the camera with a maximum brightness lower than the selected ‘Min. AD
Saturation’ level will be ignored and not displayed. Only the detected ‘AD Saturation’
level in % will be displayed within the Exposure Control field.
As soon as ‘Software Trigger’ is selected the ‘Auto Exposure Control’ is switched off
automatically and the desired ‘Exposure Time’ and the ‘Gain Factor’ must be
entered manually.
Adjust both controls so that a low ‘AD Saturation’ (in % of full scale brightness)
results when no laser pulse is captured. Increase ‘Exposure Time’ and ‘Gain Factor’
so that a detected laser pulse exceeds the ‘Min. AD Saturation’ threshold. Decrease
both controls in case the detected pulse reaches the limiting 100% saturation
because its real intensity may be considerably higher.
The status bar informs you about the activated software trigger function.
The Beam Profiler is waiting for an image reaching the selected saturation
threshold. In case the actual AD saturation level is below the threshold, the status bar
informs you about a waiting software trigger event.
For frequently occurring pulses it is recommended to adjust the Exposure Time
slightly shorter than the pulse period so that only a single pulse is captured.
Prevent ambient light from entering the input aperture and use one of the neutral
density filters for its attenuation.
Note that the image brightness of a captured single optical pulse isn’t adjustable by
the ‘Exposure Time’ control in case the single optical pulse is shorter than the
adjusted exposure duration. Use the supplied ND filters of the filter wheel and the
‘Gain Factor’ control to adjust image brightness. In order to ensure a minimum noise
level it is recommended to keep the gain value as low as possible.
You also may activate the Beam Profiler’s single shot measurement mode by
clicking in the toolbar in combination with this Software Trigger. Although a
continuous image capturing is performed in the background, the first image fulfilling
the software trigger condition will stop this process and the appropriate image is
displayed and interrogated.
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