Kinetics Timing Modes And Shutter Control; Triggered Operation; Figure 52. Experiment Setup| Timing Tab - Princeton Instruments ProEM+ EMCCD User Manual

Chapter 6 Advanced Topics 89

Kinetics Timing Modes and Shutter Control

For Kinetics, the timing modes are Free Run {No Response}, Single Trigger {Readout
Per Trigger}, and Multiple Trigger {Shift Per Trigger}. Free run {No Response} mode is
used for experiments that do not require any synchronization with the experiments. The
other two modes (single trigger and multiple trigger) require that an external TTL pulse be
applied to the camera via the Trigger In connector on the I/O cable. The camera can be
triggered either on +ve {Positive} or -ve {Negative}edge of the incoming TTL pulse.
In the Free Run Kinetics mode, the ProEM+ takes a series of images, each with the Exposure
time set through the software (in WinX, the exposure time is set on the Experiment
Setup|Main tab). The time between image frames, which may be as short as a few
microseconds, is limited by the time required to shift an image under the mask: this
interimage time equals the Vertical Shift rate (specified in ns/row) multiplied by the Window
Size (the number of rows allocated for an image frame). The exact number of frames depends
on the selected Window Size and is equal to the number of pixels perpendicular to the shift
register divided by the Window Size. Integrate signals (SHUTTER) or Readout signals
(READ OUT) are provided at the LOGIC OUT connector for timing measurements.
The Shutter Control options are Normal, PreOpen {Open Before Trigger}, Disabled Open
{Always Open} and Disabled Closed {Always Closed}. Normal means that the Shutter opens
at the beginning of the first exposure-shift kinetics cycle and closes at the end of the last
exposure-shift cycle. Disabled simply means that the shutter will not operate during the
experiment. Disabled closed is useful for making dark charge measurements. PreOpen {Open
Before Trigger}, available in the External Sync and External Sync with Continuous Cleans
{Clean Until Trigger} modes, opens the shutter as soon as the ProEM+ is ready to receive an
External Sync pulse. This is required if the time between the External Sync pulse and the
event is less than a few milliseconds, the time it takes the shutter to open.

Triggered Operation

In Single Trigger {Readout Per Trigger} mode, the
camera requires only one trigger to initiate an entire
Select the Trigger
series of "exposure-shift" cycles as shown in the
Mode: Single or
Multiple.
timing diagram below. Here, the camera uses the
exposure time as entered into the software. The
trigger is applied at the Ext Sync connector on the
rear of the ProEM+.
In multiple trigger {Shift Per Trigger} mode, each
"exposure-shift" cycle is triggered independently by a
pulse applied at the Ext. Sync connector. This mode is
useful when each subframe needs to be synchronized
with a pulsed external light source such as a laser.
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,
Figure 52. Experiment Setup|
ambient light will be collected through the window
Timing tab
until the next trigger arrives. Depending on the time
between triggers and the amount of ambient light,
some subframes may appear brighter than others.
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