Exposure And Signal; Exposure Time; Avalanche Gain {Em Gain - Princeton Instruments ProEM+ EMCCD User Manual

62
Acquiring Data
1. After you have achieved focus, you can stop running in Alignment mode.
2. Make any required changes to your experiment setup and software parameters.
3. Begin running Acquire mode. Data will be acquired and displayed/stored based
4. If you have completed data collection, you can leave the camera power on so the
Shutdown
1. Close LightField.
2. Turn off the light source and the spectrograph.
3. Turn off the camera power.

Exposure and Signal

Exposure Time

Exposure time, which is set on the Experiment Setup|Main tab { Common
Acquisition Settings expander}, is the time between commands sent by the application
software to start and stop signal accumulation on the sensor. In combination with
triggers, these commands control when continuous cleaning of the CCD stops and when
the accumulated signal will be read out. Cleaning prevents buildup of dark current and
unwanted signal before the start of the exposure time. At the end of the exposure time,
the CCD is readout and cleaning starts again.
The effective exposure time of the array depends on the active readout mode (frame
transfer or full frame).


For detailed information on these modes, see "Exposure-Readout Modes" (page 71).

Avalanche Gain {EM Gain}

As explained previously, the ProEM+ uses a unique EMCCD capable of multiplying the
charge (electrons) generated in the pixels. When the multiplication is sufficiently high, it
is possible to see extremely low-light events. The amount of multiplication is controlled
by the voltage applied to multiplication register clocks.
When Multiplication Gain {Electron Multiplied} is selected on the Experiment Setup|ADC
tab { Analog to Digital Conversion expander}, the Avalanche {EM Gain} can be set by
entering the desired gain value on the Experiment Setup|Main tab { Analog to Digital
Conversion expander}. A Gain setting of one (1) refers to a no-gain state where the camera
behaves like a standard high speed CCD (with rather high read noise). As the result of EM
ProEM
Changes might include adjusting the exposure time, setting up an entrance slit
shutter, changing the timing mode to External Sync, or lowering the temperature.
on the experiment settings.
array temperature will remain locked or you can shut down the system.
Frame Transfer: In this mode, the effective exposure time depends on the
frame readout time. When the set exposure time is greater than or equal to the
frame readout time, the effective exposure time is the set exposure time.
However, if the set exposure time is less than the frame readout time, the first
exposure will be the set exposure time and subsequent exposures in a sequence
will be exposed for the frame readout time.
Full Frame: In this mode, the effective exposure time is the set exposure time.
®
+ System Manual Version 1.B