Princeton Instruments PhotonMAX System, Manual, Page: 40 / 98

40 PhotonMAX System Manual Version 1.B
Exposure and Signal
Exposure Time
Exposure time (set on the
Experiment
Setup|Main
tab page) is the time between
commands sent by the application software to
start and stop signal accumulation on the CCD.
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.
If smearing or other factors require a shutter,
the
SHUTTER OUT
signal from the I/O cable
can be used to control a customer-supplied
external shutter.
The effective exposure time of the array
depends on the active Exposure-Readout mode
(Overlapped or Non-Overlapped).
Overlapped:
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
Figure 23. Setting the Exposure Time
(Experiment Setup|Main tab page)
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.
Non-Overlapped:
In this mode, the effective exposure time is the set exposure
time.
For detailed information on these modes, see Exposure-Readout Modes , page 48.