Teledyne ProEM Series, System Manual

Page: 95 / 162

Chapter 6 Advanced Topics 95
6.2 Fast and Safe Modes
The ProEM has been designed to allow the greatest possible flexibility when
synchronizing data collection with an experiment. The fundamental difference between
the Fast and Safe modes is how often the acquisition start and acquisition stop
commands are sent by the computer for a data collection sequence. With Safe Mode,
the computer sends a start and a stop command for each frame of a data sequence.
With Fast Mode, the computer sends only one start and one stop command for each
data sequence. Once the start command is sent, the selected timing mode and the
shutter condition determine when charge will be allowed to fall on the CCD array.
In WinX, the choice of Fast or Safe data collection is made on the Experiment
Setup
►
Timing tab. Figure 6-8 shows flowcharts that illustrate the differences between
the two modes. In LightField, Fast data collections is always used.
6.2.1 Fast Mode (WinX and LightField)
In Fast operation, the ProEM runs according to the timing of the experiment, with no
interruptions from the computer. Fast operation is primarily for collecting "real-time"
sequences of experimental data, where timing is critical and events cannot be missed.
Once the ProEM is sent the start command by the computer, all frames are collected
without further intervention from the computer. The advantage of this timing mode is
that timing is controlled completely through hardware. A drawback to this mode is that
the computer will only display frames when it is not performing other tasks. Image
display has a lower priority, so the image on the screen may lag several images behind.
A second drawback is that a data overrun may occur if the number of images collected
exceeds the amount of allocated RAM or if the computer cannot keep up with the data
rate.
NOTE:
LightField always uses Fast Mode.
6.2.2 Safe Mode (WinX)
In Safe Mode operation, the computer processes each frame as it is received: the ProEM
cannot collect the next frame until the previous frame has been completely processed.
Safe Mode operation is useful when the camera is operated from a slower computer
that cannot process the incoming data fast enough. It is also useful when data
collection must be coordinated with external devices such as external shutters and filter
wheels. As seen in
Figure 6-8 , in Safe Mode operation, the computer controls when
each frame is taken. After each frame is received, the camera sends the stop command
to the camera, instructing it to stop acquisition. Once that frame is completely
processed and displayed, another start command is sent from the computer to the
camera, allowing it to take the next frame. Display is therefore, at most, only one frame
behind the actual data collection. One disadvantage of the Safe mode is that events
may be missed during the experiment, since the camera is disabled for a short time after
each frame.
NOTE:
When running WinX/32, Safe Mode must be used whenever
the system is set up for the optional Kinetics Readout Mode.
Refer to
Section 6.4, Kinetics Mode , on page 98 for more
information about this type of image acquisition and
readout.