Timing Modes - Princeton Instruments PhotonMAX System Manual

54
provide TTL output for the timing of an external shutter driver. This signal is high during
Shutter Open Compensation Time (t
The Shutter Output connector does not provide power to drive the shutter directly, so
an external shutter drive controller is required.
Figure 39 shows the relationships between the action of a mechanical shutter and the
Shutter Out and Expose Out levels. The values of t
Mechanical Shutter
SHUTTER OUT
EXPOSE OUT
Since most shutters behave like an iris, the opening and closing of the shutter will cause
the center of the CCD to be exposed slightly longer than the edges. It is important to
realize this physical limitation, particularly when using short exposures.
The shutter signal options available in WinView and WinSpec include Normal, Disable
Opened or Disable Closed. Disable simply means that the shutter will not operate during
the experiment. Disable closed is useful for making dark charge measurements, or when
no shutter is present in the camera.
Caution
Electromechanical shutters typically have a lifetime of about a million cycles. Avoid
running the shutter unnecessarily. Also avoid using shorter exposure times and higher
repetition rates than are required.

Timing Modes

The basic PhotonMAX timing modes are Free Run, External Sync, Bulb Trigger, and
Single Trigger. These modes are combined with the Shutter options (see previous topic)
to provide the widest variety of modes for precision experiment synchronization.
PhotonMAX cameras offer several methods of integration with external trigger sources,
such as delay generators or laser pre-triggers. Each camera has a 26-pin, high-density I/O
connector (pinout functions are described on page 84) on the back for trigger-in/out and
various TTL input and output operations. The I/O cable supplied with the PhotonMAX
provides access to primary signals such as "Trigger-in," "Trigger-invert," "Expose out,"
"Frame readout," and "Shutter out." In the default mode, the camera triggers on the rising
edge of a TTL signal. To invert the triggering polarity, the "Trigger-invert" must be
grounded, which can be done with a 50-ohm terminator. PhotonMAX cameras support the
timing modes described in the next sections.
PhotonMAX System Manual
) and the Exposure Time (t
o
Open
Exposure
t t
exp
o
t = Shutter Open Compensation Time
O
t = Exposure Time
exp
t = Shutter Close Compensation Time
C
t = Readout Time
R
Figure 39. External Shutter Timing Diagram
).
exp
and t are shutter-type dependent.
c
o
Closed
Readout
t t
c R
Version 1.B