POWER CONTROLS Panel
The POWER CONTROLS panel pertains to the (optional) control of a Pockels cell (or other light modulater) supported by ScanImage, allowing the power level used during image acquisition to be controlled. See the ScanImage Hardware Reference for the latest information on supported/recommended hardware.
The POWER CONTROLS panel only appears on ScanImage startup if pockelsOn is enabled in the INI File. In addition, at least 1 (and up to 3) Beams must be configured in the INI File, as described therein.
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This menu selects among the (up to 3) Beams that have been configured (and named) in the INI File. The
level and
value displayed and controlled in this panel pertain to the selected Beam. In addition, the actions initiated via the Calibration >> Calibrate... menu items also pertain to the selected Beam.
Unknown macro: {blue} Level">Unknown macro: {blue} Level
The value displayed and controlled, either by direct numeric input or with the slider control, represents the power level ScanImage should use during subsequently initiated image acquisitions.
The
level is stored/loaded as part of the ScanImage Configuration (CFG file)
KEY POINTS:
- The power is adjusted to the specified level immediately upon each [_trigger_] initiating an acquisition.
In ScanImage, triggers arrive to initiate each FOCUS or GRAB acquisition, each LOOP Repeat, and each Slice within an Image Stack.
- In between such acquisitions (i.e., in between triggers), the
Unknown macro: {blue}level is adjusted to the minimum power determined during Pockels calibration for the Beam – i.e. the Beam is 'OFF'
- The
Unknown macro: {blue}level can be specified either:
- as a percentage (
Unknown macro: {blue}) of the maximum power determined during Pockels calibration for the Beam, OR
- directly in milliwatts (
Unknown macro: {blue}), provided the powerConversion value is set in the INI File for the particular Beam
- as a percentage (
- If Flyback Blanking is enabled (
Unknown macro: {blue}in the Configuration panel), then the command signal generated by ScanImage for the particular Beam will alternate between the specifiedUnknown macro: {blue}level and the minimum power (during beam flyback or turnaround).
- The initial value of the
Unknown macro: {blue}level is specified in the INI File for each Beam as maxPowerN (for Beam N). This will be overridden when/if a ScanImage Configuration is loaded.
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Normally, during
acquisitions, the slider control of the
level is inactive. Selecting
overrides this behavior for all Beams, allowing slider adjustment during FOCUS.
As soon as the slider control is adjusted during a FOCUS acquisition, flyback blanking (if enabled in the Configuration panel), is disabled for remainder of FOCUS acquisition.
Note that it is always possible to type in a power value on the
panel during FOCUS. Doing so will result in a brief stop of scanning, and then a restart of scanning. Flyback blanking, if specified, remains in effect. The stop & restart is required to recompute the periodic command waveform to generate on the Pockels AO channel(s)
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Normally, changes to
while not acquiring have no immediate effect. For optical measurement & testing purposes, the
option can be selected. This causes changes to the
level to take immediate effect. This mode applies to all Beams.
Note that following any image acquisition (including with
, the Pockels/EOM power for each beam is set to the minimum value measured during the last Pockels calibration. The
level must be changed, with slider or text entry, to re-enable transmission.
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The
value simply determines the maximum value to allow for the
level setting, for the specified
. This is useful for preventing the value from accidentally being set too high.
The initial value of
is specified in the INI File for each Beam as maxLimitN (for Beam N). This is useful for assigning a Beam power limit for a particular 'rig' (i.e. shared by all users). However, ScanImage allows this limit to be overridden during operation.
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When collecting image stacks in scattering tissue, the power level required at each slice in the stack generally increases with depth in order to maintain a fixed signal. ScanImage can adjust the power automatically during stacks.
: Checkbox enables/disables automatic 'P vs z' adjustment feature for all beams
: Specifies the exponential length constant for the currently selected beam. Power is increased with depth according to P = P0 * exp^((z-z0)/Lz).
A value of Inf implies no power adjustment should occur for the selected beam.
Value of Lz must be positive
- The
Unknown macro: {vi-statevar}value in the INI file must be set correctly, specifying whether larger Z values on the motor controller corresponds to deeper imaging (true by default).
- In general, the user will experiment to identify the Lz value suited for their preparation, which is typically fairly constant from acquisition to acquisition.
- Note the power level only adjusts in integer increments of the percentage value.
The P/z Adjust and Lz controls are User Settings. These values are thus typically loaded on ScanImage startup and apply to all stack configurations/acquisitions during a session.
ScanImage also provides a facility to measure, rather than enter, the
value for the current specimen/stack. See
for more information.
Power Box
The
panel can be shown/hidden using the
control.
Calibration Menu
The items on this menu are explained further in the section on Pockels Calibration.
- Unknown macro: {blue}This causes the Pockels Calibration for the currently selectedUnknown macro: {blue}to be remeasured.
- Unknown macro: {blue}This displays a Matlab figure showing the results of the most recent Pockels Calibration obtained for the currently selectedUnknown macro: {blue}.