MesaPhotonics VideoFROG FROGscan, Руководство пользователя

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Chapter 3. Program Panels
Page 20 FROGSCAN USER’S MANUAL 09/07/2018 Vs 003
3.2 Left Control Panel
Remember to activate popup windows containing more detailed information by clicking on the desired
heading.
Video FROGscan data is displayed in eight different Panels. Each of these Panels displays a panel on
the left in which the following parameters can be set:
Time Center ̶ Controls the steps the servo motor must complete in order to achieve temporal overlap of
the beams. This number was determined in the factory, but can be adjusted so that the raw FROG Trace
is exactly centered in the Summary Panel (Section 3.3).
Recenter ̶ Returns the Time Center to the previous number.
Offset ̶ Displays the number of pixels the center of the FROG trace is from the correct location. This
value should never be more than 2X the Time Delay Spacing.
Time Delay Spacing ̶ Determines the duration of the temporal scan and the amount of frequency space
used in the FROG Trace retrieval. The number can be changed by clicking the stepper control or by
sliding the toggle. Each step is nominally 1 fs. As the time spacing increases, the amount of frequency
data decreases; therefore, setting the time delay spacing requires deciding on the trade-off between time
and frequency information.
Crystal Tilt ̶ Not applicable for instrument without the Crystal Autotilt function. For instruments with the
Autotilt function, see the Data Acquisition Panel, Section 3.4.
Center Wavelength ̶ Center of the FROG Trace area used by the algorithm.
This number should be set to correspond to the center of the Live FROG Trace in the Summary Panel,
Section 3.3.
Integration Time ̶ The length of time that the spectrometer detector is allowed to collect photons before
passing the accumulated charge to the A/D converter for processing. This is the only spectrometer setting
that can be controlled using the FROGscan Interface. Short exposure times decrease the sensitivity
whereas long exposure times increase dark levels and noise. Do not decrease the integration time below
the minimum for a given spectrometer; this will cause a software hang-up (see Chapter 8). The minimum
times are 1000
µ
s for an Ocean Optics Flame and HR series spectrometers, 7200
µ
s for the MayaPro,
and 8000
µ
s for the QEPro spectrometers.
Images to Average ̶ The number of raw FROG images averaged between retrievals. This setting allows
extracting small signals from the noise background. However, increasing the number of images to
average will increase the acquisition time.
Use Background Subtraction – Activating this features (can be activated only in the Summary Panel)
activates different types of background subtraction options that can be entered in the Data Acquisition
Panel (see Section 3.4). Because the background of spectrometers is high, activating this feature is
recommended.
Save Data ̶ Saves the measured FROGscan Trace and retrieved pulses in a set of time-stamped files to
the directory selected in the Program Information Panel, Section 3.8.
Warnings ̶ See Chapter 8 for different types of warnings.