Princeton Instruments PhotonMAX System, Manual, Page: 63 / 98

Chapter 6 Advanced Topics 63
In multiple trigger mode, each “exposure-shift” cycle is triggered independently. This
mode is useful when each subframe needs to be synchronized with a pulsed external light
source such as a laser.
ß à t
exp
#1
ß à t
s
#1
ß à t
exp
#2
ß à t
exp
#n
ß à t
s
#2
ß à t
s
#n
Exposure/
Subframe
Vertical Shift
Readout
~500 msec @1 MHz readout
Trigger In
#1 #2 #3
Figure 54. Example showing Kinetics Operation using “Multiple Trigger”
Note:
It is particularly important to keep ambient light to a minimum while multiple
trigger mode is used. In the case of this mode, automatic cleaning of the CCD only occurs
until the first trigger arrives. Once the series of "exposure-shift" cycles begins, cleaning
does not occur and, at the end of a cycle, ambient light will be collected through the
window until the next trigger arrives. Depending on the time between triggers and the
amount of ambient light, some subframes may appear brighter than others.
Cleaning the CCD
Since kinetics is most often used in asynchronous, single-shot experiments, it is important
that CCD be cleared of accumulating background or dark charge while it is waiting for an
external trigger. To take care of this, PhotonMAX automatically cleans the CCD “one
row at a time” before the arrival of the first trigger. This keeps the charge buildup on the
CCD to a minimum at the same time minimizing the timing jitter (determined by vertical
shift time of a single row). If desired, the number of cleans can be set to zero for the best
jitter performance. However, the camera must be in dark environment to minimize the
background.